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Zhou Z, Guo D, Watts DC, Fischer NG, Fu J. Application and limitations of configuration factor (C-factor) in stress analysis of dental restorations. Dent Mater 2023; 39:1137-1149. [PMID: 37838610 DOI: 10.1016/j.dental.2023.10.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 10/06/2023] [Accepted: 10/06/2023] [Indexed: 10/16/2023]
Abstract
OBJECTIVE The configuration factor (C-factor) is an index used to evaluate the relationship between cavity configuration and the development of polymerization shrinkage stress in dental restorations. Although C-factor has been widely researched, its correlation with stress analysis in dental restorations remains controversial. This review aims to discuss the application and limitations of C-factor and define the restricted conditions under which the C-factor "rule of thumb" is applicable. METHODS A thorough literature review was conducted on the application and limitations of C-factor in stress analysis of dental restorations. This was principally based on MEDLINE/PubMed and Web of Science databases and a review of the relevant studies and publications in scientific papers in international peer-reviewed journals for the specific topic of C-factor and polymerization shrinkage. RESULTS The C-factor alone cannot provide an accurate prediction of the shrinkage stress of restorations and the mechanical behavior of material-tooth interfaces. C-factor is only applicable under one condition not typically seen in clinical practice: low, near-rigid compliance. SIGNIFICANCE Conditions for the application of C-factor have been explicitly defined. A more accurate and precise understanding and utilization of the C-factor is of benefit as it contributes to better understanding of polymerization shrinkage behavior of restorations.
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Affiliation(s)
- Zixuan Zhou
- Department of Prosthodontics, The Affiliated Hospital of Qingdao University, 266000 Qingdao, China; School of Stomatology of Qingdao University, 266003 Qingdao, China
| | - Di Guo
- Department of Prosthodontics, The Affiliated Hospital of Qingdao University, 266000 Qingdao, China; School of Stomatology of Qingdao University, 266003 Qingdao, China
| | - David C Watts
- University of Manchester, School of Medical Sciences, Oxford Road, M13 9PL Manchester, UK
| | - Nicholas G Fischer
- Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Jing Fu
- Department of Prosthodontics, The Affiliated Hospital of Qingdao University, 266000 Qingdao, China; School of Stomatology of Qingdao University, 266003 Qingdao, China.
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Aminoroaya A, Esmaeely Neisiany R, Nouri Khorasani S, Panahi P, Das O, Ramakrishna S. A Review of Dental Composites: Methods of Characterizations. ACS Biomater Sci Eng 2020; 6:3713-3744. [DOI: 10.1021/acsbiomaterials.0c00051] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alireza Aminoroaya
- Department of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - Rasoul Esmaeely Neisiany
- Department of Materials and Polymer Engineering, Faculty of Engineering, Hakim Sabzevari University, Sabzevar 9617976487, Iran
| | - Saied Nouri Khorasani
- Department of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - Parisa Panahi
- Department of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - Oisik Das
- Material Science Division, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå 97187, Sweden
| | - Seeram Ramakrishna
- Centre for Nanofibers and Nanotechnology, Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore
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Han SH, Park SH. Incremental and Bulk-fill Techniques With Bulk-fill Resin Composite in Different Cavity Configurations. Oper Dent 2018; 43:631-641. [PMID: 29630486 DOI: 10.2341/17-279-lr] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
PURPOSE: To compare the microtensile bond strengths of incremental and bulk-fill techniques under different C-factor and compliance conditions. METHODS AND MATERIALS: Extracted human third molars were divided into three experimental groups. For group I, Class I cavities were prepared. For group II, MOD cavities of the same size were prepared. For group III, the cavities were prepared the same way as group II only with high compliance cavity walls. The cavity wall compliance of the specimens was evaluated. Each of these groups was divided into four subgroups. The teeth were restored using two different materials: TB (Tetric N-Ceram Bulk Fill; Ivoclar Vivadent, Hanau, Germany) and VB (Venus Bulk Fill; Heraeus Kulzer, Armonk, NY, USA), and two methods, either an incremental or bulk-fill technique. Then, the microtensile bond strengths (μ-TBSs) were measured and compared. The polymerization stresses of the composites were calculated using a custom-made device. The results were statistically analyzed using the Kruskal-Wallis test and Weibull analysis. RESULTS: In group I, the μ-TBS obtained using the incremental technique was significantly higher than that obtained by the bulk-fill technique ( p<0.05). In contrast, no difference of the μ-TBS value was observed between the two techniques in groups II and III. The μ-TBS value of group I was significantly lower than those of groups II and III ( p<0.05). No statistical difference in the μ-TBS was observed when the cavities were filled with either TB or VB ( p>0.05). CONCLUSIONS: The incremental technique showed higher bond strength than did the bulk-fill technique in high C-factor cavities. However, no difference was found between the two techniques in the low C-factor cavities. The bond strength in the high C-factor cavities was significantly lower than that of the low C-factor cavities.
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Algamaiah H, Sampaio CS, Rigo LC, Janal MN, Giannini M, Bonfante EA, Coelho PG, Reis AF, Hirata R. Microcomputed Tomography Evaluation of Volumetric Shrinkage of Bulk-Fill Composites in Class II Cavities. J ESTHET RESTOR DENT 2016; 29:118-127. [PMID: 27925387 DOI: 10.1111/jerd.12275] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE This study aimed to quantify polymerization shrinkage of one conventional and three bulk-fill composites, under bonded and unbonded conditions, in Class II preparations using 3D microcomputed tomography (μCT) and report its location. MATERIALS AND METHODS Preparations (2.5 mm occlusal depth × 4 mm wide × 4 mm mesial box and 1 mm beyond the CEJ distal box depth) were made in 48 human extracted molars (n = 6). Four composites were tested, one regular (Vitalescence/VIT) and three bulk-fill: SureFil SDR Flow (SDR), Tetric EvoCeram Bulk Fill (TET), and Filtek flowable Bulk Fill (FIL). Teeth were divided into four groups according to restorative material used and subdivided into two subgroups, according to the presence of an adhesive system (XP Bond) application (bonded [-B]) or its absence (unbonded [-U]). Each tooth was scanned three times: (1) after cavity preparation, (2) before and (3) after composite light-curing. Acquired μCT images were imported into 2D and 3D software for analysis. RESULTS Significantly different volumetric shrinkage between bonded and unbonded conditions was observed only for TET group (p < 0.05), unbonded presenting significantly higher volumetric shrinkage. Among the bonded groups, TET-B presented significantly lower shrinkage than both SDR-B and FIL-B but not significantly different from VIT-B. Generally, shrinkage occurred at occlusal and distal surfaces. CONCLUSIONS When applied to bonded Class II cavities, TET exhibited significantly lower volumetric shrinkage compared to the other bulk-fill composites. However, it also exhibited the highest difference of volumetric shrinkage values between unbonded and bonded cavities. CLINICAL SIGNIFICANCE Volumetric polymerization shrinkage occurred with all composites tested, regardless of material type (conventional or bulk-fill) or presence or absence of bonding. However, volumetric shrinkage has been reduced or at least maintained when bulk-fill composites were used compared to a conventional composite resin, which makes them a potential time saving alternative for clinicians. (J Esthet Restor Dent 29:118-127, 2017).
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Affiliation(s)
- Hamad Algamaiah
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA.,Department of Restorative Dental Science, King Saud University, Riyadh, Saudi Arabia
| | - Camila S Sampaio
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA.,Research Professor, Department of Biomaterials, Universidad de Los Andes, Santiago, Chile.,Department of Restorative Dentistry, Piracicaba Dental School, UNICAMP, Piracicaba, SP, Brazil
| | - Lindiane C Rigo
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA
| | - Malvin N Janal
- Department of Epidemiology and Health Promotion, New York University College of Dentistry, New York, NY, USA
| | - Marcelo Giannini
- Associate Professor, Department of Restorative Dentistry, State University of Campinas, Piracicaba Dental School, Piracicaba, SP, Brazil
| | - Estevam A Bonfante
- Assistant Professor, Department of Phosthodontics, University of São Paulo, Bauru School of Dentistry, Bauru, SP, Brazil
| | - Paulo G Coelho
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA
| | - Andre F Reis
- Associate Professor, Department of Operative Dentistry, Guarulhos University, Guarulhos, SP, Brazil
| | - Ronaldo Hirata
- Assistant Professor, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA
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5
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Polymerization shrinkage assessment of dental resin composites: a literature review. Odontology 2016; 104:257-70. [DOI: 10.1007/s10266-016-0264-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 07/15/2016] [Indexed: 10/21/2022]
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6
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Hao W, Chen X, Yuan Y, Ma Y. Experimental Investigation on Curing Stress in Polymer Composite Using Digital Gradient Sensing Technique. INT POLYM PROC 2016. [DOI: 10.3139/217.3140] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
The curing stress and deformation of epoxy resin and aramid fiber/epoxy composites was measured using Digital Gradient Sensing (DGS) technique. First, the working principle of the DGS method was explained, and the governing equations were derived based on angular deflections of light rays. Then the angle deflection of light rays due to curing stress of epoxy resin was measured, and the effect of the fiber bundle and aramid fiber fabric on the stress distribution during formation was analyzed. The experimental results show that angular deflections of light rays can be related to nonuniform distribution of curing stress in epoxy. The fiber bundles and fabric style have important effects on the curing stress distribution. These results play an important role for predicting curing stress and deformation of fiber reinforced composites.
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Affiliation(s)
- W. Hao
- Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation , Beijing Institute of Aeronautical Materials, Beijing , PRC
| | - X. Chen
- Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation , Beijing Institute of Aeronautical Materials, Beijing , PRC
| | - Y. Yuan
- Department of Engineering Mechanics , Applied Mechanics Lab, Tsinghua University, Beijing , PRC
| | - Y. Ma
- Department of Engineering Mechanics , Applied Mechanics Lab, Tsinghua University, Beijing , PRC
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7
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Milosevic M. Polymerization Mechanics of Dental Composites – Advantages and Disadvantages. ACTA ACUST UNITED AC 2016. [DOI: 10.1016/j.proeng.2016.06.672] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Tauböck TT, Feilzer AJ, Buchalla W, Kleverlaan CJ, Krejci I, Attin T. Effect of modulated photo-activation on polymerization shrinkage behavior of dental restorative resin composites. Eur J Oral Sci 2015; 122:293-302. [PMID: 25039287 DOI: 10.1111/eos.12139] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2014] [Indexed: 11/30/2022]
Abstract
This study investigated the influence of modulated photo-activation on axial polymerization shrinkage, shrinkage force, and hardening of light- and dual-curing resin-based composites. Three light-curing resin composites (SDR bulk-fill, Esthet X flow, and Esthet X HD) and one dual-curing material (Rebilda DC) were subjected to different irradiation protocols with identical energy density (27 J cm(-2) ): high-intensity continuous light (HIC), low-intensity continuous light (LIC), soft-start (SS), and pulse-delay curing (PD). Axial shrinkage and shrinkage force of 1.5-mm-thick specimens were recorded in real time for 15 min using custom-made devices. Knoop hardness was determined at the end of the observation period. Statistical analysis revealed no significant differences among the curing protocols for both Knoop hardness and axial shrinkage, irrespective of the composite material. Pulse-delay curing generated the significantly lowest shrinkage forces within the three light-curing materials SDR bulk-fill, Esthet X flow, and Esthet X HD. High-intensity continuous light created the significantly highest shrinkage forces within Esthet X HD and Rebilda DC, and caused significantly higher forces than LIC within Esthet X flow. In conclusion, both the composite material and the applied curing protocol control shrinkage force formation. Pulse-delay curing decreases shrinkage forces compared with high-intensity continuous irradiation without affecting hardening and axial polymerization shrinkage.
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Affiliation(s)
- Tobias T Tauböck
- Department of Preventive Dentistry, Periodontology and Cariology, Center for Dental Medicine, University of Zurich, Zurich, Switzerland
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Dietschi D, Argente A, Krejci I, Mandikos M. In Vitro Performance of Class I and II Composite Restorations: A Literature review on Nondestructive Laboratory Trials—Part II. Oper Dent 2013; 38:E182-200. [PMID: 23725090 DOI: 10.2341/12-020b-lit] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
ABSTRACT
A literature review was conducted on adhesive Class I and II restorations and nondestructive in vitro tests using the PubMed/Medline database for the 1995-2010 period. The first part of this review has presented and critically appraised selected literature dealing with the quality and in vitro behavior of adhesive Class II restorations using photoelasticity, finite element analysis, and microleakage study protocols. This second part reviews additional parameters, which are deformation and fracture resistance to cyclic loading, shrinkage stress and tooth deformation following restoration placement, bond strength (microtensile, tensile, and shear tests), and marginal and internal adaptation. In addition, a “relevance score” has been proposed that aims to classify the different study protocols according, firstly, to the resulting quality, quantity, and consistency of the evidence and then, secondly, to their potential clinical relevance, as estimated by their ability to simulate oral and biomechanical strains. The highest clinical relevance was attributed to marginal and internal adaptation studies, following cyclic loading in a moist environement. However, a combination of in vitro protocols will have an even greater predictive potential and has to be considered as a crucial preclinical research approach with which to investigate the numerous restorative configurations that cannot be efficiently and rapidly tested in vivo.
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Affiliation(s)
- D Dietschi
- Didier Dietschi, DMD, PhD, privat-docent, School of Dentistry, University of Geneva, Cariology & Endodontics, Geneva, Geneva CH 1205, Switzerland
| | - A Argente
- Ana Argente, DMD, School of Dentistry, University of Geneva, Cariology & Endodontics, Geneva, Geneva CH 1205, Switzerland
| | - I Krejci
- Ivo Krejci, Geneva School of Dentistry, Department of Cariology and Endodontology, Geneva, 1205, Switzerland
| | - M Mandikos
- Michael Mandikos, Brisbane Prosthodontics, Graceville, Queensland 4075, Australia
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Dietschi D, Argente A, Krejci I, Mandikos M. In Vitro Performance of Class I and II Composite Restorations: A Literature Review on Nondestructive Laboratory Trials—Part I. Oper Dent 2013; 38:E166-81. [DOI: 10.2341/12-020a-lit] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
ABSTRACT
Posterior adhesive restorations are a basic procedure in general dental practices, but their application remains poorly standardized as a result of the number of available options. An abundant number of study hypotheses corresponding to almost unlimited combinations of preparation techniques, adhesive procedures, restorative options, and materials have been described in the literature and submitted to various evaluation protocols. A literature review was thus conducted on adhesive Class I and II restorations and nondestructive in vitro tests using the PubMed/Medline database for the 1995-2010 period. The first part of this review discusses the selected literature related to photoelasticity, finite element analysis (FEM), and microleakage protocols. Based on the aforementioned evaluation methods, the following parameters proved influential: cavity dimensions and design, activation mode (light or chemical), type of curing light, layering technique, and composite structure or physical characteristics. Photoelasticity has various limitations and has been largely (and advantageously) replaced by the FEM technique. The results of microleakage studies proved to be highly inconsistent, and the further use of this technique should be strictly limited. Other study protocols for adhesive Class II restorations were also reviewed and will be addressed in part II of this article, together with a tentative relevance hierarchy of selected in vitro methods.
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Affiliation(s)
- D Dietschi
- Didier Dietschi, DMD, PhD, privat-docent, School of Dentistry, University of Geneva, Cariology & Endodontics, Geneva, Geneva CH 1205, Switzerland
| | - A Argente
- Ana Argente, DMD, School of Dentistry, University of Geneva, Cariology & Endodontics, Geneva, Geneva CH 1205, Switzerland
| | - I Krejci
- Ivo Krejci, Geneva School of Dentistry, Department of Cariology and Endodontology, Geneva, 1205, Switzerland
| | - M Mandikos
- Michael Mandikos, Brisbane Prosthodontics, Graceville, Queensland 4075, Australia
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Abstract
Polymerization contraction stress of dental composites is often associated with marginal and interfacial failure of bonded restorations. The magnitude of the stress depends on the composite's composition (filler content and matrix composition) and its ability to flow before gelation, which is related to the cavity configuration and curing characteristics of the composite. This article reviews the variations found among studies regarding the contraction stress testing method, contraction stress values of current composites, and discusses the validity of contraction stress studies in relation to results from microleakage tests. The effect of lower curing rates and alternative curing routines on contraction stress values is also discussed, as well as the use of low elastic modulus liners. Moreover, studies with experimental Bis-GMA-based composites and recent developments in low-shrinkage monomers are described.
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Affiliation(s)
- Roberto R Braga
- Departament of Dental Materials, School of Dentistry, University of São Paulo
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Pecie R, Onisor I, Krejci I, Bortolotto T. Marginal adaptation of direct class II composite restorations with different cavity liners. Oper Dent 2013; 38:E210-20. [PMID: 23713806 DOI: 10.2341/12-229-l] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
UNLABELLED The aim of this study was to evaluate how cavity linings with different elastic modulus can influence the marginal adaptation (MA) of Class II composite restorations before and after thermo-mechanical loading. MATERIALS AND METHODS Forty Class II cavities with margins extending 1 mm below the cement-enamel junction were prepared in extracted human third molars. In each group except the control group, a lining material of 1-mm thickness was applied to the bottom of the cavity and polymerized before placing the resin composite Herculite XRV Ultra (group A: control; group B: Premise Flowable lining; group C: Herculite XRV Ultra lining; and group D: Optibond FL lining). MA was evaluated (with a scanning electron microscope) before and after loading (200,000 loading cycles). Statistical analysis was done using the Shapiro-Wilks test, the analysis of variance test, and Duncan post hoc test at p<0.05. RESULTS Before loading, the percentages of continuous margins in dentin were superior (p<0.05) for groups C and D (71.1% and 87.2%, respectively) compared to groups A and B (55.7% and 48.3%, respectively). After loading, group D (79.8%) was statistically superior in dentin compared to all of the other groups (43.6%, 35.9%, and 54.4%, respectively). In occlusal enamel, no significant difference was found between groups. The percentage of enamel fractures and the percentage of noncontinuous margins in proximal enamel were high, with no significant difference between liners. It can be concluded that for the materials used in this study, a 1-mm-thick lining with an extremely low elastic modulus (2-3 GPa) could redistribute shrinkage stress. The use of a flowable composite did not significantly improve MA.
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Oliveira KMC, Lancellotti ACRA, Ccahuana-Vásquez RA, Consani S. Influence of filling techniques on shrinkage stress in dental composite restorations. J Dent Sci 2013. [DOI: 10.1016/j.jds.2012.01.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Fakhouri SF, Zamarioli A, Shimano MM, Defino HLA, Araujo CA, Shimano AC. Photoelastic analisys in the lower region of vertebral body L4. ACTA ORTOPEDICA BRASILEIRA 2012; 20:17-20. [PMID: 24453574 PMCID: PMC3718409 DOI: 10.1590/s1413-78522012000100003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Accepted: 11/12/2010] [Indexed: 11/22/2022]
Abstract
Objective To analyze the shear forces on the vertebral body L4 when submitted to a compression
force by means of transmission photoelasticity. Methods Twelve photoelastic models were divided into three groups, with four models per group,
according to the positioning of the sagittal section vertebrae L4-L5 (sections A, B and
C). The simulation was performed using a 15N compression force, and the fringe orders
were evaluated in the vertebral body L4 by the Tardy compensation method. Results Photoelastic analysis showed, in general, a homogeneous distribution in the vertebral
bodies. The shear forces were higher in section C than B, and higher in B than A. Conclusion The posterior area of L4, mainly in section C, showed higher shear concentrations,
corresponding to a more susceptible area for bone fracture and spondylolisthesis.
Economic and Decision Analyses - Development of an Economic or Decision Model.
Level I
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Affiliation(s)
- Sarah Fakher Fakhouri
- Department of Biomechanics, Medicine and Rehabilitation of the Musculoskeletal System of the Faculdade de Medicina de RibeirãoPreto da Universidade de São Paulo - RibeirãoPreto, SP, Brazil
| | - Ariane Zamarioli
- Department of Biomechanics, Medicine and Rehabilitation of the Musculoskeletal System of the Faculdade de Medicina de RibeirãoPreto da Universidade de São Paulo - RibeirãoPreto, SP, Brazil
| | - Marcos Massao Shimano
- Department of Mechanical Engineering of Universidade Federal doTriânguloMineiro MG, Brazil
| | - Helton Luiz Aparecido Defino
- Department of Biomechanics, Medicine and Rehabilitation of the Musculoskeletal System of the Faculdade de Medicina de RibeirãoPreto da Universidade de São Paulo - RibeirãoPreto, SP, Brazil
| | - Cleudmar Amaral Araujo
- Laboratório de Projetos Mecânicos Professor Henner Alberto Gomide of the Mechanical Engineering School of Universidade Federal de Uberlândia, MG, Brazil
| | - Antonio Carlos Shimano
- Department of Biomechanics, Medicine and Rehabilitation of the Musculoskeletal System of the Faculdade de Medicina de RibeirãoPreto da Universidade de São Paulo - RibeirãoPreto, SP, Brazil
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Borges AFS, Simonato LE, Pascon FM, Kantowitz KR, Rontani RMP. Effects of resin luting agents and 1% NaOCl on the marginal fit of indirect composite restorations in primary teeth. J Appl Oral Sci 2011; 19:455-61. [PMID: 21986649 PMCID: PMC3984190 DOI: 10.1590/s1678-77572011000500004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2006] [Accepted: 10/26/2010] [Indexed: 11/21/2022] Open
Abstract
Objective The purpose of this study was to provide information regarding the marginal
adaptation of composite resin onlays in primary teeth previously treated with 1%
sodium hypochlorite (NaOCl) (pulp irrigant) using two different resin luting
agents. Material and Methods Forty extracted sound primary molars had their crowns prepared in a standardized
machine and were randomly divided into 4 groups (n=10): G1 (1% NaOCl
irrigation+EnForce); G2 (EnForce); G3 (1% NaOCl irrigation+Rely X); G4 (Rely X).
The onlays were made with Z250 composite resin on plaster models. After luting,
the tooth/restoration set was stored in 100% relative humidity at 37ºC for
24 h and finished with Soflex discs. Caries Detector solution was applied at the
tooth/restoration interface for 5 s. The specimens were washed and four digital
photos of each tooth were then taken. The extents of the gaps were measured with
Image Tool 3.0 software. The percentage data were submitted to a Kruskal-Wallis
test (α=0.05). The Relative Risk test analyzed the chance of a gap
presence correlated to each group. Results There were no statistically significant differences (p>0.05) among the groups.
The relative risk test revealed that some groups were more apt to have a presence
of gaps than others. Conclusion Neither the 1% NaOCl treatment nor the resin luting agents caused any alterations
in the dental substrate that could have influenced the marginal adaptation of
composite onlays in primary teeth.
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Affiliation(s)
- Ana Flávia Sanches Borges
- Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil
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Lopes MB, Valarini N, Moura SK, Guiraldo RD, Gonini Júnior A. Photoelastic analysis of stress generated by a silorane-based restoration system. Braz Oral Res 2011; 25:302-6. [DOI: 10.1590/s1806-83242011000400004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 06/16/2011] [Indexed: 11/22/2022] Open
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Takahashi H, Finger WJ, Wegner K, Utterodt A, Komatsu M, Wöstmann B, Balkenhol M. Factors influencing marginal cavity adaptation of nanofiller containing resin composite restorations. Dent Mater 2010; 26:1166-75. [DOI: 10.1016/j.dental.2010.08.189] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 02/01/2010] [Accepted: 08/27/2010] [Indexed: 11/17/2022]
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Formation of gaps at the filler–resin interface induced by polymerization contraction stress. Dent Mater 2010; 26:719-29. [DOI: 10.1016/j.dental.2010.03.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 01/07/2010] [Accepted: 03/05/2010] [Indexed: 11/20/2022]
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Fróes-Salgado NR, Silva LM, Kawano Y, Francci C, Reis A, Loguercio AD. Composite pre-heating: effects on marginal adaptation, degree of conversion and mechanical properties. Dent Mater 2010; 26:908-14. [PMID: 20557926 DOI: 10.1016/j.dental.2010.03.023] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 03/04/2010] [Accepted: 03/16/2010] [Indexed: 11/25/2022]
Abstract
OBJECTIVES This study evaluated the effect of composite pre-polymerization temperature and energy density on the marginal adaptation (MA), degree of conversion (DC), flexural strength (FS), and polymer cross-linking (PCL) of a resin composite (Filtek Z350, 3M/ESPE). METHODS For MA, class V cavities (4 mm x 2 mm x 2 mm) were prepared in 40 bovine incisors. The adhesive system Adper Single Bond 2 (3M/ESPE) was applied. Before being placed in the cavities, the resin composite was either kept at room-temperature (25 degrees C) or previously pre-heated to 68 degrees C in the Calset device (AdDent Inc., Danbury, CT, USA). The composite was then light polymerized for 20 or 40s at 600 mW/cm(2) (12 or 24 J/cm(2), respectively). The percentage of gaps was analyzed by scanning electron microscopy, after sectioning the restorations and preparing epoxy resin replicas. DC (n=3) was obtained by FT-Raman spectroscopy on irradiated and non-irradiated composite surfaces. FS (n=10) was measured by the three-point-bending test. KHN (n=6) was measured after 24 h dry storage and again after immersion in 100% ethanol solution for 24h, to calculate PCL density. Data were analyzed by appropriate statistical analyses. RESULTS The pre-heated composite showed better MA than the room-temperature groups. A higher number of gaps were observed in the room-temperature groups, irrespective of the energy density, mainly in the axial wall (p<0.05). Composite pre-heating and energy density did not affect the DC, FS and PCL (p>0.05). SIGNIFICANCE Pre-heating the composite prior to light polymerization similar in a clinical situation did not alter the mechanical properties and monomer conversion of the composite, but provided enhanced composite adaptation to cavity walls.
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Affiliation(s)
- Nívea Regina Fróes-Salgado
- Department of Biomaterials and Oral Biochemistry, School of Dentistry, University of Sao Paulo, Sao Paulo, Brazil
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Blažić L, Pantelić D, Savić-Šević S, Murić B, Belić I, Panić B. Modulated photoactivation of composite restoration: measurement of cuspal movement using holographic interferometry. Lasers Med Sci 2010; 26:179-86. [DOI: 10.1007/s10103-010-0774-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Indexed: 11/25/2022]
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de Camargo EJ, Moreschi E, Baseggio W, Cury JA, Pascotto RC. Composite depth of cure using four polymerization techniques. J Appl Oral Sci 2010; 17:446-50. [PMID: 19936524 PMCID: PMC4327672 DOI: 10.1590/s1678-77572009000500018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Accepted: 05/19/2009] [Indexed: 11/22/2022] Open
Abstract
The light-curing technique is relevant to reduce the degree of polymerization shrinkage, improving clinical and esthetic success of composite resin restorations.
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Affiliation(s)
- Ericson Janolio de Camargo
- Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.
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Oliveira LC, Duarte S, Araujo CA, Abrahão A. Effect of low-elastic modulus liner and base as stress-absorbing layer in composite resin restorations. Dent Mater 2010; 26:e159-69. [DOI: 10.1016/j.dental.2009.11.076] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 10/21/2009] [Accepted: 11/13/2009] [Indexed: 11/28/2022]
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Mcleod ME, Price RBT, Felix CM. Effect of Configuration Factor on Shear Bond Strengths of Self-etch Adhesive Systems to Ground Enamel and Dentin. Oper Dent 2010; 35:84-93. [DOI: 10.2341/09-075-l] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Clinical Relevance
Despite recent improvements in self-etch bonding systems, a two-step etch and rinse system gave consistently higher shear bond strengths to both ground enamel and dentin and would be the best system to use clinically.
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Schneider LFJ, Cavalcante LM, Silikas N. Shrinkage Stresses Generated during Resin-Composite Applications: A Review. JOURNAL OF DENTAL BIOMECHANICS 2009; 2010. [PMID: 20948573 PMCID: PMC2951111 DOI: 10.4061/2010/131630] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Accepted: 07/08/2009] [Indexed: 11/29/2022]
Abstract
Many developments have been made in the field of resin composites for dental applications. However, the manifestation of shrinkage due to the polymerization process continues to be a major problem. The material's shrinkage, associated with dynamic development of elastic modulus, creates stresses within the material and its interface with the tooth structure. As a consequence, marginal failure and subsequent secondary caries, marginal staining, restoration displacement, tooth fracture, and/or post-operative sensitivity are clinical drawbacks of resin-composite applications. The aim of the current paper is to present an overview about the shrinkage stresses created during resin-composite applications, consequences, and advances. The paper is based on results of many researches that are available in the literature.
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Affiliation(s)
- Luis Felipe J Schneider
- Department of Restorative Dentistry, The University of Passo Fundo, Passo Fundo 99001-970, RS, Brazil
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Cabrera E, de la Macorra JC. Effects of polymerization contraction on interface’s µTBS of luting material and dentin. Clin Oral Investig 2009; 14:207-16. [DOI: 10.1007/s00784-009-0284-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 05/05/2009] [Indexed: 10/20/2022]
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Abstract
The objective of the study was to assess the effect of the cavity design factor (C-factor) on polymerization stress development (PSD) in resin composites. An experimental resin (BT resin) was prepared, which contained 2,2-bis[p-(2’-hydroxy-3’-methacryloxypropoxy)phenylene]propane (B) and triethylene glycol dimethacrylate (T) in 1:1 mass ratio, and an activator for visible light polymerization. An experimental composite with demonstrated remineralizing potential was also formulated by inclusion into the BT resin of zirconia-hybridized amorphous calcium phosphate (ACP) filler at a mass fraction of 40 % (BT/ACP composite). A commercial glass-filled composite (TPH) was used as a control. To assess the effect of the test geometry on PSD, C-factor was systematically varied between 0.8 and 6.0 by varying the height of the cylindrical composite specimens. The measured PSD values obtained by cantilever beam tensometry for specimens with variable C-factors were normalized for mass to specimens with a C-factor of 1.33 (h=2.25 mm) as controls to give calculated PSD values. Degrees of vinyl conversions (DC) attained in the TPH control and in the experimental BT/ACP composites were measured by near-infrared spectroscopy. In both the TPH and BT/ACP composite series, PSDcalc increased with the increasing C-factor, confirming the hypothesis that the C-factor value influences PSD values. The higher PSDmeas and PSDcalc values for the experimental BT/ACP composite compared to the commercial TPH composite probably reflect differences in the type and mass of the resin and filler phases in the two types of composite. These differences also account for the observed variation (21 %) in DC attained in a BT/ACP composite 2 h after cure (69.5 %) and in the DC of the TPH composite (57.5 %) having the same C-factor. The cavity design factor seems to play a key role in influencing the PSD of bonded composites, but other factors such as composite mass and composition also must be considered for their effects on PSD.
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Lopes LG, Franco EB, Pereira JC, Mondelli RFL. Effect of light-curing units and activation mode on polymerization shrinkage and shrinkage stress of composite resins. J Appl Oral Sci 2009; 16:35-42. [PMID: 19089287 PMCID: PMC4327278 DOI: 10.1590/s1678-77572008000100008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a LED and a quartz tungsten halogen (QTH) light sources. The LED was used in a conventional mode (CM) and the QTH was used in both conventional and pulse-delay modes (PD). The composite resins used were Z100, A110, SureFil and Bisfil 2B (chemical-cured). Composite deformation upon polymerization was measured by the strain gauge method. The shrinkage stress was measured by photoelastic analysis. The polymerization shrinkage data were analyzed statistically using two-way ANOVA and Tukey test (p≤0.05), and the stress data were analyzed by one-way ANOVA and Tukey's test (p≤0.05). Shrinkage and stress means of Bisfil 2B were statistically significant lower than those of Z100, A110 and SureFil. In general, the PD mode reduced the contraction and the stress values when compared to CM. LED generated the same stress as QTH in conventional mode. Regardless of the activation mode, SureFil produced lower contraction and stress values than the other light-cured resins. Conversely, Z100 and A110 produced the greatest contraction and stress values. As expected, the chemically cured resin generated lower shrinkage and stress than the light-cured resins. In conclusion, The PD mode effectively decreased contraction stress for Z100 and A110. Development of stress in light-cured resins depended on the shrinkage value.
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Affiliation(s)
- Lawrence Gonzaga Lopes
- Department of Preventive and Oral Reabilitation, Dental School, Federal University of Goiás, Goiânia, GO, Brazil
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Fakhouri SF, Siqueira DPPD, Araújo CAD, Defino HLA, Shimano AC. Análise fotoelástica de parafuso de sistema de fixação vertebral. ACTA ORTOPEDICA BRASILEIRA 2009. [DOI: 10.1590/s1413-78522009000400002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
INTRODUÇÃO: A fotoelasticidade é utilizada para avaliar as tensões/deformações produzidas nos materiais fotoelásticos, quando submetidos a determinado carregamento, através da observação de efeitos óticos. O desempenho do parafuso e as funções mecânicas estão diretamente relacionados com a qualidade da fixação dos parafusos nas vértebras. A fotoelasticidade é uma ferramenta importante para realizar estudos comparativos desta natureza. OBJETIVO: O objetivo deste estudo foi comparar por meio da fotoelasticidade, as tensões internas produzidas pelo parafuso com 6 mm de diâmetro externo, quando submetido a duas diferentes forças de arrancamento. MATERIAIS E MÉTODOS: Para isso, foram confeccionados quatro modelos fotoelásticos. A simulação foi realizada utilizando duas forças de arrancamento 0,75 e 1,50 kgf. As tensões cisalhantes foram calculadas nos 19 pontos em torno dos parafusos, utilizando o método de compensação de Tardy. RESULTADOS: Os valores das tensões cisalhantes foram maiores quando utilizada a força de arrancamento de 1,50 kgf. CONCLUSÃO: Assim sendo, o parafuso estará mais suscetível ao arrancamento com a aplicação de força de maior intensidade. De acordo com as análises realizadas verificamos também que o local de maior tensão cisalhante foi observado no pico das cristas, principalmente próxima às pontas dos parafusos, independente da força utilizada.
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Yamamoto T, Ferracane JL, Sakaguchi RL, Swain MV. Calculation of contraction stresses in dental composites by analysis of crack propagation in the matrix surrounding a cavity. Dent Mater 2008; 25:543-50. [PMID: 19100613 DOI: 10.1016/j.dental.2008.10.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Revised: 08/20/2008] [Accepted: 10/30/2008] [Indexed: 11/18/2022]
Abstract
OBJECTIVES Polymerization contraction of dental composite produces a stress field in the bonded surrounding substrate that may be capable of propagating cracks from pre-existing flaws. The objectives of this study were to assess the extent of crack propagation from flaws in the surrounding ceramic substrate caused by composite contraction stresses, and to propose a method to calculate the contraction stress in the ceramic using indentation fracture. METHODS Initial cracks were introduced with a Vickers indenter near a cylindrical hole drilled into a glass-ceramic simulating enamel. Lengths of the radial indentation cracks were measured. Three composites having different contraction stresses were cured within the hole using one- or two-step light-activation methods and the crack lengths were measured. The contraction stress in the ceramic was calculated from the crack length and the fracture toughness of the glass-ceramic. Interfacial gaps between the composite and the ceramic were expressed as the ratio of the gap length to the hole perimeter, as well as the maximum gap width. RESULTS All groups revealed crack propagation and the formation of contraction gaps. The calculated contraction stresses ranged from 4.2 MPa to 7.0 MPa. There was no correlation between the stress values and the contraction gaps. SIGNIFICANCE This method for calculating the stresses produced by composites is a relatively simple technique requiring a conventional hardness tester. The method can investigate two clinical phenomena that may occur during the placement of composite restorations, i.e. simulated enamel cracking near the margins and the formation of contraction gaps.
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Affiliation(s)
- Takatsugu Yamamoto
- Department of Operative Dentistry, Tsurumi University School of Dental Medicine, 2-1-3, Tsurumi, Tsurumi-ku, Yokohama, Kanagawa 230-8501, Japan.
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Ferracane JL. Buonocore Lecture. Placing dental composites--a stressful experience. Oper Dent 2008; 33:247-57. [PMID: 18505214 DOI: 10.2341/07-bl2] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The setting of dental composites is accompanied by significant polymerization contraction, resulting in the generation of stresses within the material and at the tooth-restoration interface. These stresses can have a deleterious effect on marginal integrity if they exceed the adhesive strength of the restorative, as well as on the properties of the composite. It has been determined that several factors affect these stresses, including the polymerization rate of the composite, its formulation, including filler and monomer composition and the constraints imposed by the geometry of the cavity preparation. Many strategies have been developed to reduce the effect of these stresses. Changes in the formulation of the composite have included experimentation with a variety of stress relieving additives, modified catalyst compositions and alternative monomer systems. Modifications to the placement techniques have included the use of incremental curing, altered light activation schemes and resilient liners. This manuscript will review many of the important scientific and clinical issues relating to the generation and quantitation of the stresses produced in dental composites during curing.
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Affiliation(s)
- Jack L Ferracane
- Department of Restorative Dentistry, Oregon Health & Science University, Portland, OR, USA.
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Pantelić D, Blazić L, Savić-Sević S, Panić B. Holographic detection of a tooth structure deformation after dental filling polymerization. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:024026. [PMID: 17477741 DOI: 10.1117/1.2714056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
An experimental technique to reveal the effects of dental polymer contraction is established to choose the most appropriate polymerization technique. Tooth deformation following a dental filling polymerization is analyzed using double-exposure holographic interferometry. A caries-free, extracted human molar is mounted in dental gypsum and different cavity preparations and fillings are made on the same tooth. Dental composite fillings are polymerized by an LED light source especially designed for this purpose. Holographic interferograms are made for occlusal (class I), occlusomesial (class II), and mesioocclusodistal (class II MOD) cavities and fillings. Maximum intercuspal deformation ranges from 2 microm for the class I cavity to 14 mum for the MOD class cavity. A finite element method (FEM) is used to calculate von Mises stress on a simplified tooth model, based on experimental results. The stress varies between 50 and 100 MPa, depending on the cavity type.
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Affiliation(s)
- Dejan Pantelić
- Institute of Physics, Pregrevica 118, 11080 Zemun, Belgrade, Serbia.
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Chikawa H, Inai N, Cho E, Kishikawa R, Otsuki M, Foxton RM, Tagami J. Effect of incremental filling technique on adhesion of light-cured resin composite to cavity floor. Dent Mater J 2007; 25:503-8. [PMID: 17076320 DOI: 10.4012/dmj.25.503] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The purpose of this study was to evaluate the effect of various incremental filling techniques on adhesion between composite and cavity floor using light-cured resin composite. Black ABS resin and hybrid resin composite were used as mold materials--instead of dentin--for the preparation of cavities, and standardized to 5x5x5 mm. Each cavity was then treated with a bonding system (Clearfil SE bond). Resin composite (Clearfil Photo Core) was placed on the bonding resin using different incremental filling techniques or in bulk and irradiated for a total of 80 seconds using a halogen light unit. Specimens were subjected to the micro-tensile bond test at a crosshead speed of 1 mm/min. Data were analyzed by two-way ANOVA. The results indicated that an incremental filling technique was more effective in improving adhesion to the cavity floor than a bulk filling technique.
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Affiliation(s)
- Hirokazu Chikawa
- Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, Japan.
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Stoll R, Gente M, Palichleb M, Stachniss V. On the effect of an internal light conductor on the marginal integrity of class-II composite fillings. Dent Mater 2007; 23:145-52. [PMID: 16519928 DOI: 10.1016/j.dental.2006.01.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Accepted: 01/04/2006] [Indexed: 11/22/2022]
Abstract
OBJECTIVES The aim of this study was to examine the marginal behavior of class-II double surface fillings made with newly designed light transmitting inserts. These inserts guide the polymerization light directly into the body of the filling. MATERIAL AND METHODS Sixty standardized two-surface cavities have been prepared into freshly extracted human molars and filled with Herculite XRV. Fifteen cavities were filled using the incremental technique (positive control group), 15 were filled with one single increment (negative control group) and 15 teeth each were filled with light conducting inserts with and without use of the light conducting system. Before and after thermomechanical stressing in a chewing simulator (50,000x50N and 2000 cycles between 5 degrees C and 55 degrees C), the amount of perfect margin was measured by quantitative margin analysis using a SEM. Additionally, following dye penetration (24h, 0.1% methylene blue), all teeth were cut in the mesio-distal direction and the amount of penetration was measured. RESULTS The group with light transmitting inserts showed 79.8% perfect margin, the positive control group 68.0%, the group with inactive inserts 65.4% and the negative control group 57.8%. MANOVA showed a strong effect (p<0.001) on the parameters group and thermocycling. The results from dye penetration were similar. SIGNIFICANCE Light conducting inserts seem to have a positive effect on the marginal integrity of class-II composite fillings. Results show that this effect is produced by the internal light conductor and not volumetric effect alone.
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Affiliation(s)
- Richard Stoll
- Department of Operative Dentistry, Philipps-University of Marburg, Dental School (MZ für ZMK), Georg Voigt Str. 3, 35033 Marburg, Germany.
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Lee SH, Chang J, Ferracane J, Lee IB. Influence of instrument compliance and specimen thickness on the polymerization shrinkage stress measurement of light-cured composites. Dent Mater 2006; 23:1093-100. [PMID: 17112580 DOI: 10.1016/j.dental.2006.10.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 07/07/2006] [Accepted: 10/07/2006] [Indexed: 10/23/2022]
Abstract
OBJECTIVES The aim of our study was to investigate the effects of instrument compliance and specimen geometry on the polymerization shrinkage stress measurements of composites. METHODS A custom designed stress-strain analyzer was made using a linear variable differential transformer probe and a cantilever load cell. A sandblasted glass rod was fixed at the free end of the load cell, and another glass rod was located on a base plate. A composite was placed between the two rods and light cured. The end displacement of the load cell during polymerization was recorded for 10 min. A flowable (Filtek Flow), a universal hybrid (Z100), and a packable (P60) composite were studied. To investigate the effect of specimen geometry and instrument compliance, specimen thickness was varied between 0.5, 1.0, and 2.0 mm, and three load cells with maximum capacities of 20, 100, and 500kgf were used. Ten maxillary premolars were prepared with two sizes of MOD cavities; the bucco-lingual widths and depths of the cavities were 1.5 mm x 2 mm and 3 mm x 2 mm, and the cusp compliance and deflection were measured before and during composite polymerization. RESULTS The measured polymerization stress decreased in the order of Filtek Flow, Z100, and P60 for all measurement conditions. As the specimen thickness was increased, the shrinkage stress per unit thickness (mm) decreased. The measured stress decreased with increasing instrument compliance. The cusp compliance (3.32 microm/N) of the 3 mm x 2 mm cavities was similar to that of instrument with a 20 kgf load cell (3.34 microm/N). SIGNIFICANCE For determining the most clinically relevant values for shrinkage stress of dental composites, the instrument compliance should closely match that of the tooth walls in the cavity geometry to be tested.
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Affiliation(s)
- Sue Hyun Lee
- Department of Conservative Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, 28-2 Yeongeon-Dong, Jongro-Gu, Seoul 110-749, South Korea
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Shinkai K, Suzuki S, Katoh Y. Effect of high light intensity on cavity wall adaptation of a resin composite with a self-etching primer system. J Biomed Mater Res B Appl Biomater 2006; 79:420-4. [PMID: 16637036 DOI: 10.1002/jbm.b.30556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This study evaluated the effect of high light intensity using a plasma arc lamp on the cavity wall adaptation of photo-polymerized composite restorations. Bowl-shaped cavities were prepared on the labial surfaces of extracted bovine teeth. Each cavity was restored with a resin composite restorative system (SE Bond & Clearfil AP-X) and then polymerized using a plasma arc lamp (Arc Light II) with a series of light intensities, including 1100, 1200, 1300, 1400, 1500, and 1600 mW/cm(2), and a halogen lamp (Candilux) with 400 mW/cm(2) light intensity (n = 10). The photo-irradiation time was adjusted for each group to receive a total energy output of approximately 16,000 mJ/cm(2). The specimens were subjected to 2500 cycles of thermal fatigue and sectioned bucco-lingually through the center of the restoration. Contraction gaps on the sections were measured using a replica-SEM observation technique. The degree of gap formation was determined as the ratio of the total length of the contraction gaps to the total length of the cavity wall on each sectioned specimen. The value was converted to a percentage. The data were statistically analyzed with Kruskal-Wallis and Mann-Whitney U tests at a 0.05 level of significance. There were no significant differences (p > 0.05) in the cavity adaptation among the composites polymerized by the plasma arc lamp with high light intensities and the composite polymerized with the halogen lamp with 400 mW/cm(2) light intensity. There were no significant differences (p > 0.05) in the degree of cavity adaptation among the specimens polymerized with light intensities higher than 1100 mW/cm(2).
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Affiliation(s)
- Koichi Shinkai
- Department of Operative Dentistry, School of Dentistry at Niigata, The Nippon Dental University, 1-8 Hamaura-cho, Niigata 951-8580, Japan.
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Witzel MF, Ballester RY, Meira JBC, Lima RG, Braga RR. Composite shrinkage stress as a function of specimen dimensions and compliance of the testing system. Dent Mater 2006; 23:204-10. [PMID: 16494936 DOI: 10.1016/j.dental.2006.01.016] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2005] [Accepted: 01/11/2006] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Verify the influence of specimen dimensions on composite shrinkage stress in testing systems of known compliance and in situations where axial strain of bonding substrates was suppressed. Stress distribution was evaluated using finite element analysis (FEA). METHODS A chemically activated composite (Bisfill 2B, Bisco) was inserted between the flat surfaces of two glass rods (2, 4 or 6mm diameter, D) attached to a universal testing machine. Specimen height (H) was defined by adjusting the distance between the rods (0.5, 1, 2 or 4mm). An extensometer was used to monitor the distance between them. Maximum force after 30min of polymerization was divided by the cross-sectional area of the rod to obtain nominal stress (sigma(n)). Mathematical equations were employed in order to estimate the 'corrected nominal stress' (sigma(cor)) that would be obtained in ideally rigid systems. Data were analyzed by two-way ANOVA/Tukey test (alpha=0.05) and regression analysis (stress versus 'C factor' and stress versus specimen volume). Axysimetrical 2D models were used to evaluate X-component stress distribution (sigma(x)) in the zero compliance condition. RESULTS The interactions between D and H were significant for sigma(n) and sigma(cor) (p<0.001). For D=2mm, height influenced only sigma(cor) values. A direct correlation was found between stress and C factor (sigma(n):R(2)=0.959; sigma(cor):R(2)=0.923), but not between stress and volume. FEA evidenced the effect of boundary restraints on sigma(x). SIGNIFICANCE Specimen dimensions influenced test results, mostly regarding sigma(cor). Stress values strongly increased with the confinement of the specimen probably due to stress concentration adjacent to the bonded interface.
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Affiliation(s)
- Marcelo F Witzel
- Department of Dental Materials, School of Dentistry, University of São Paulo, São Paulo, Brazil
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da Silva Segalin A, Fernandez DM, de Oliveria Bauer JR, Loguercio AD, Reis A. Marginal adaptation and hardness of resin composite restorations activated with four energies. J ESTHET RESTOR DENT 2005; 17:303-10; discussion 311. [PMID: 16225795 DOI: 10.1111/j.1708-8240.2005.tb00135.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE The purpose of this study was to evaluate the influence of variations in light intensity versus exposure time, under the same energy density, on the marginal adaptation and hardness of resin composites restorations. MATERIALS AND METHODS The occlusal surfaces of 20 third molars were flattened with 180-grit SiC paper and a Class I cavity was prepared (4 mm wide, 4 mm long, and 2 mm deep). The specimens were randomly divided into four groups (n = 5 teeth). The adhesive system was applied according to the manufacturer's directions followed by one increment of Filtek Z250. The resin composite was light activated with 18 J/cm(2) according to one of the following light intensities/exposure times: group 1-100 mW/cm(2)/180 s; group 2-300 mW/cm(2)/60 s; group 3-600 mW/cm(2)/30 s; group 4-1,000 mW/cm(2)/18 s. After 24 hours, the restorations were longitudinally sectioned into two halves. Enamel, bottom, and total mean gap widths (in micrometers) were measured with a stereomicroscope (x200). After that, one of the sections was embedded in acrylic resin and polished up to 4,000-grit SiC for Knoop hardness number (KHN) measurements (100 g/15 s) at the top and bottom surfaces. The data from mean gap widths were analyzed by one-way analysis of variance (ANOVA). The KHN values (kg/mm(2)) were subjected to a two-way, repeated-measures ANOVA (a = .05). Tukey's test was used for pairwise comparisons. RESULTS No significant difference was observed between total and bottom mean gap widths among groups (p > .05). Group 1 showed lower enamel mean gap widths than did groups 3 and 4 (p < .05) but similar to those for group 2 (p > .05). The KHN at the top surface was higher than the bottom hardness (p < .05). For the bottom surface, all groups had similar KHN values (p > .05). CONCLUSIONS The variations in light intensity and exposure times allowed the achievement of adequate mechanical properties. The use of a low light intensity reduces only the enamel mean gap width but has no effect on the overall gap formation along the composite-tooth interface. CLINICAL SIGNIFICANCE As long as an adequate energy density is used to produce adequate mechanical properties in the resin composite, the use of a low light intensity for an increased time does not markedly improve marginal integrity.
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Santos AJS, Lisso MT, Aguiar FHB, França FMG, Lovadino JR. Effect of Stepped Exposure on Quantitative In Vitro Marginal Microleakage. J ESTHET RESTOR DENT 2005; 17:236-42; discussion 243. [PMID: 16231494 DOI: 10.1111/j.1708-8240.2005.tb00120.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE The aim of this in vitro study was to evaluate the effect of a soft-start curing mode on microleakage MATERIALS AND METHODS Standardized Class V cavities were prepared within all the margins in the buccal enamel or dentin surface of sound, freshly extracted inferior bovine incisors. Forty preparations were filled with a restorative system (Single Bond and Filtek Z250, 3M ESPE, St. Paul, MN, USA). Ten restorations of each group were made on both types of substrates and polymerized with a conventional curing technique (600 mW/cm2/40 s) or with a soft-start technique (150 mW/cm2/10 s + 600 mW/cm2/30 s). All specimens were thermocycled 3000 times and then immersed in methylene blue 2% for 12 hours. The specimen microleakage was quantitatively determined in a spectrophotometer. RESULTS The soft-start technique resulted in statistically significant less microleakage for each substrate (p < .05). The conventional groups exhibited 6.1 (dentin) to 15.4% (enamel) more leakage compared with the soft-start groups. When compared with the enamel margins, the dentin margins demonstrated greater microleakage: from 15.5% greater with the conventional light-curing mode to 25.6% greater with the soft-start light-curing mode. CONCLUSIONS The polymerization technique using a very low initial intensity (150 mW/cm2/10 s) decreased the microleakage of composite resin restorations. CLINICAL SIGNIFICANCE A soft-start light-curing approach to resin composite polymerization resulted in less microleakage at enamel and dentin margins in Class V cavities compared with resin composite restorations polymerized using a conventional light-curing approach.
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Sato T, Miyazaki M, Rikuta A. Real-time dimensional change in light-cured composites at various depths using laser speckle contrast analysis. Eur J Oral Sci 2005; 112:538-44. [PMID: 15560838 DOI: 10.1111/j.1600-0722.2004.00179.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Laser speckle contrast analysis is an interferometric technique that is used to measure the displacement of the rough surface of a specimen. The purpose of this study was to present a laser speckle correlation method for monitoring real-time dimensional changes of light-cured composites. Uncured composite was condensed into a glass tube and irradiated for 30 s with 600 or 200 mW cm(-2). The speckle patterns obtained from lateral and bottom composite surfaces were monitored using a speckle analyser. The speckle field is recorded in a digital frame and stored by image processing system as the carrier of information on the displacement of the tested surface. The calculated values were obtained for each pair of adjacent patterns and the changes in speckle contrast as a function time were obtained from five repeated measurements. The overall magnitude of the speckle contrasts decreased soon after the initial light exposure and gradually increased thereafter. The speckle contrasts obtained from the bottom surface were smaller than those obtained from the lateral surface. This tendency was more pronounced when the specimen was irradiated with lower power density. It can be concluded that monitoring differential shrinkage at various levels of depth can be achieved with this new technique.
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Affiliation(s)
- Tomomi Sato
- Department of Operative Dentistry, Nihon University Graduate School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan
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Fano L, Fano V, Ma W, Wang X, Zhu F. Hydrolytic degradation and cracks in resin-modified glass-ionomer cements. J Biomed Mater Res B Appl Biomater 2004; 69:87-93. [PMID: 15015215 DOI: 10.1002/jbm.b.20037] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Water-absorption affects the basic properties of resin-modified glass-ionomer cements (RMGICs). Fick's law is usually invoked to explain the absorption process. The purpose of this study is to show that the absorption in accordance with the Fickian model cannot be extended to the whole of the specimen, and that microcrack formation is the main degradation mechanism for specimens cured in a closed environment. For this purpose, flat disk-shaped paste specimens 1.5 mm thick (aspect ratio 4), irradiated in closed conditions between two glass slides and stored in water for approximately 20 months, were analyzed periodically gravimetrically and under confocal fluorescence microscopy, with absorbed eosin used as the fluorescent probe. At pH 7.0, the specimen surface (10-20 micrometers in depth) absorbed water rapidly, swelled, and disintegrated in 20-40 days. Long-term storage produced isolated cracks and grains, no progress in the swelling, and a slow weight decrease. A lower pH (pH 3.5) produced a significant increase of the number of microcracks. The decrease in the irradiation time (30 s or less) enhanced the erosion process, producing very broad cracks. It was concluded that the prevalent mechanism of long-term hydrolytic degradation was based on the slow formation of cracks, whereas only in the early stage of storage did absorption occur quickly in accordance with the Fickian diffusion.
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Affiliation(s)
- Luca Fano
- Department of Public Health, Section of Physics, Istituto Nazionale Fisica della Materia, University of Parma, via Volturno 39, Parma, Italy.
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Loguercio AD, Reis A, Schroeder M, Balducci I, Versluis A, Ballester RY. Polymerization shrinkage: effects of boundary conditions and filling technique of resin composite restorations. J Dent 2004; 32:459-70. [PMID: 15240064 DOI: 10.1016/j.jdent.2004.02.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Revised: 02/12/2004] [Accepted: 02/28/2004] [Indexed: 11/25/2022] Open
Abstract
OBJECTIVE To evaluate the linear polymerization shrinkage (LPS) and the effect of polymerization shrinkage of a resin composite and resin-dentin bond strength under different boundary conditions and filling techniques. METHODS Two cavities (4 x 4 x 2 mm3) were prepared in bovine incisors (n=30). The teeth were divided into three groups, according to boundary conditions: In group TE, the total-etch technique was used. In group EE, only enamel was conditioned, and in group NE, none of the walls of the cavities were conditioned. A two-step adhesive system was applied to all cavities. The resin composite was inserted in one (B) or three increments (I) and light-cured with 600 mW/cm2 (80 s). The LPS (%) was measured in the top-bottom direction, by placing a probe in contact with resin composite during curing. Enamel and total mean gap widths were measured (400 x) in three slices obtained after sectioning the restorations. Then, the slices were sectioned again, either to obtain sticks from the adhesive interface from the bottom of the cavity or to obtain resin composite sticks (0.8 mm2) to be tested for tensile strength (Kratos machine, 0.5 mm/min). The data was subjected to a two-way repeated measures ANOVA and Tukey's test for comparison of the means (alpha=0.05). RESULTS The highest percentage of LPS was found for the TE when bulk filled, and the lowest percentage of LPS was found in the EE and NE when incrementally filled. The resin-dentin bond strength was higher and the total mean gap width was lower for TE group; no significant effect was detected for the main factor filling techniques. No difference was detected for the tensile strength of resin composite among the experimental groups. CONCLUSIONS The filling technique is not able to minimize effects of the polymerization shrinkage, and bonding to the cavity walls is necessary to assure reduced mean gap width and high bond strength values.
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Affiliation(s)
- Alessandro Dourado Loguercio
- Dental School, University of Oeste de Santa Catarina, UNOESC, Campus Joaçaba, R. Getúlio Vargas, 2125, Bairro Flor da Serra, CEP 89600-000 Joaçaba, SC, Brazil.
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42
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Abstract
Polymerization contraction stress of dental composites is often associated with marginal and interfacial failures of bonded restorations. The magnitude of stress depends on composite composition (filler content and matrix composition) and its ability to flow before gelation, which is related to the cavity configuration and curing characteristics of the composite. This article reviews variations among studies regarding contraction-stress-testing methods and contraction stress values of current composites, and discusses the validity of contraction stress studies in relation to results from microleakage tests. The effects of lower curing rates and alternative curing routines on contraction stress values are also discussed, as well as the use of low-elastic-modulus liners. Moreover, studies with experimental dimethacrylate-based composites and recent developments in low-shrinkage monomers are described.
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Affiliation(s)
- R R Braga
- University of São Paulo, School of Dentistry, Department of Dental Materials, São Paulo-SP 05508-900, Brazil.
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Price RB, Dérand T, Andreou P, Murphy D. The effect of two configuration factors, time, and thermal cycling on resin to dentin bond strengths. Biomaterials 2003; 24:1013-21. [PMID: 12504523 DOI: 10.1016/s0142-9612(02)00441-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Most in vitro testing of bonding systems is performed using specimens made in a mold with a low configuration (C) factor (ratio of bonded/unbonded surfaces) whereas clinically the C-factor is usually much greater. This study compared the effect of thermal cycling on the measured shear bond strength of 3M Single Bond dental adhesive bonded to dentin using molds with two different C-factors. The hypothesis was that neither C-factor nor thermal cycling would affect measured bond strengths. Resin composite was bonded to human dentin in cylindrical molds with an internal diameter of 3.2mm and either 1mm or 2.5mm deep. The 1mm deep molds had a C-factor of 2.2 and the 2.5mm deep molds had a C-factor of 4.1. Specimens were debonded either 10min after they had been bonded to dentin, or after they had been stored for 7 days in water at 37+/-1 degrees C, or after thermal cycling 5000 times for 7 days. Two-way ANOVA showed that overall both the C-factor and the storage condition had a significant effect on bond strength (p<0.001). There was a significant interaction (p<0.001) between the C-factor and how the specimens had been stored. The GLM/LSMEANS procedure with Sidak's adjustment for multiple comparisons showed that overall the specimens made in the mold with a high C-factor (4.1) had a lower bond strength than those that had been made in the mold with a lower (2.2) C-factor (p<0.001). Thermal cycling had a negative effect on the bond strength only for specimens made in molds with a C-factor of 4.1 (p<0.001).
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Affiliation(s)
- Richard B Price
- Department of Dental Clinical Sciences, Dalhousie University, Nova Scotia, Halifax, Canada B3H 3J5.
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Abstract
The stress that results from the placement of dental composite in a confined setting compromises the integrity of the marginal seal. Dental composites which include nanofiller particles that are not treated with a functional agent to couple them to the resin matrix can result in lower stress levels. Three types of nanofillers were evaluated having either a functional silane coating, a non-functional silane coating. or no coating. These were added at five different vol% levels to a photo-sensitized mixture of three dimethacrylate monomers alone or at three different vol% levels to the same resin filled with mini-filler particles to a clinically realistic level. The stress generated by these materials when cured in a confined setting was measured in a mechanical testing machine. The effect of monomer molecular weight on the stress levels was evaluated by preparing three resin formulations with varied co-monomer levels and filling them with bonded or non-bonded nanofillers. Reductions in polymerization stress of up to 31% were achieved among both the nanofilled resins and the mini-filled composite. The materials which contained a heightened level of diluent monomer produced significantly higher stress levels (ANOVA/Tukey's test, p < 0.05). Significant reductions in polymerization stress can be achieved through minor alterations in composite chemistry.
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Affiliation(s)
- John R Condon
- Department of Biomaterials and Biomechanics, School of Dentistry, Oregon Health and Science University, Portland, USA.
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Braga RR, Ferracane JL, Condon JR. Polymerization contraction stress in dual-cure cements and its effect on interfacial integrity of bonded inlays. J Dent 2002; 30:333-40. [PMID: 12554115 DOI: 10.1016/s0300-5712(02)00047-7] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
OBJECTIVES To compare the polymerization contraction stress of resin cements in dual-cure and self-cure modes, and verify its effect on microleakage and gap formation in class I cavities restored with porcelain inlays. METHODS Dual-cure cements (Calibra, Choice and RelyX ARC) were monitored for contraction stress during 30 min in the tensilometer, in the presence or absence of photo-activation. Microleakage was evaluated in porcelain inlays bonded to cavities prepared in bovine incisors, combining the same adhesive (One-Step) with each of the cements in both activation modes. Epoxy replicas of the sectioned specimens were analyzed in the SEM to determine the percentage of discontinuous margins. RESULTS The stress developed in dual-cure mode was higher than in self-cure mode for all cements. In self-cure mode, no significant difference in stress was found among materials. Choice and RelyX ARC showed higher microleakage in dual-cure mode than in self-cure mode. Calibra did not show a significant difference in microleakage between activation modes. Contraction gap results showed wide variations, and no significant differences were detected among the groups. Gaps occurred more often in dentin, with an overall average of 22 +/- 17.5%. CONCLUSIONS The higher stress generated in dual-cure cements subjected to photo-activation may lead to higher marginal leakage. In the confinement condition represented by the class I inlay, even the lower contraction stress of the cements in self-cure mode had enough magnitude to disrupt the bonding to dentin.
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Affiliation(s)
- Roberto R Braga
- Department of Dental Materials, School of Dentistry, University of São Paulo, Av Prof Lineu Prestes, 2227, São Paulo, SP 00508-900, Brazil.
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Ausiello P, Apicella A, Davidson CL. Effect of adhesive layer properties on stress distribution in composite restorations--a 3D finite element analysis. Dent Mater 2002; 18:295-303. [PMID: 11992906 DOI: 10.1016/s0109-5641(01)00042-2] [Citation(s) in RCA: 174] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Teeth, adhesively restored with resin-based materials, were modeled by 3D-finite elements analysis that showed a premature failure during polymerization shrinkage and occlusal loading. METHODS Simulation of Class II MOD composite restorations with a resin bonding system revealed a complex biomechanical behavior arising from the simultaneous effects of polymerization shrinkage, composite stiffness and adhesive interface strain. Due to a polymerization contraction, shrinkage stress increases with the rigidity of the composites utilised in the restoration, while the cusp movements under occlusal loading are inversely proportional to the rigidity of the composites. The adhesive layer's strain also plays a relevant role in the attenuation of the polymerization and occlusal loading stresses. RESULTS The choice of an appropriately compliant adhesive layer, able to partially absorb the composite deformation, limits the intensity of the stress transmitted to the remaining natural tooth tissues. For adhesives and composites of different rigidities, FEM analysis allows the determination of the optimal adhesive layer thickness leading to maximum stress release while preserving the interface integrity. Application of a thin layer of a more flexible adhesive (lower elastic modulus) leads to the same stress relief as thick layers of less flexible adhesive (higher elastic modulus).
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Affiliation(s)
- Pietro Ausiello
- Department of Cariology, School of Dentistry, University of Naples 'Federico II', Italy
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Armstrong SR, Keller JC, Boyer DB. The influence of water storage and C-factor on the dentin-resin composite microtensile bond strength and debond pathway utilizing a filled and unfilled adhesive resin. Dent Mater 2001; 17:268-76. [PMID: 11257301 DOI: 10.1016/s0109-5641(00)00081-6] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVE To test the elastic wall concept utilizing adhesive resins of varying stiffness in a low- and high-C-factor cavity design after short- and long-term water storage. METHODS A flat and box-shaped cavity was restored on occlusal dentin with a resin composite using a filled and unfilled adhesive resin from which microtensile specimens with a 0.5mm(2) cross-sectional area were formed. After storage for 30- and 150-days the microtensile bond strength (muTBS) was determined in a Zwick materials testing machine and the subsequent debond pathway was examined under scanning electron microscopy. Fisher's exact test was used to determine differences in joint and substrate failure modes and a Weibull regression model with gamma frailties was used to test for differences between failure distributions. Tests for three-way and two-way interactions were also completed for storage time, C-factor and adhesive. All tests were at 95% confidence levels. RESULTS The characteristic strength (TBS degrees ) for the Optibond FL adhesive applied on a flat cavity was 47.57 and 20.90MPa and a box-shaped cavity was 49.26 and 17.49MPa for short- and long-term storage, respectively, while the corresponding TBS degrees for the unfilled Optibond adhesive on the flat cavity design was 36.93 and 32.68MPa and in a box-shaped cavity was 32.84 and 15.46MPa. Combining all groups according to storage time revealed a three-fold increase in the debond pathway including the bottom of the hybrid layer. SIGNIFICANCE Evidence suggests that the durability of the bonded joint is threatened by hydrolysis and the most susceptible region is the bottom half of the hybrid layer and in low C-factor cavity designs a more flexible adhesive resin liner was more durable.
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Affiliation(s)
- S R Armstrong
- Department of Operative Dentistry, University of Iowa, Iowa City, IA, USA.
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Miguel A, de la Macorra JC. A predictive formula of the contraction stress in restorative and luting materials attending to free and adhered surfaces, volume and deformation. Dent Mater 2001; 17:241-6. [PMID: 11257297 DOI: 10.1016/s0109-5641(00)00077-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVES To find a predictive formula of stress, considering the surfaces (free, adhered) involved, the volume and characteristics of material and the deformation of the measuring system. MATERIALS AND METHODS 231 samples of five chemically cured restoratives (Silar (SIL, 23), Clearfil F2 (CLE, 39), P10 (P10, 33), Concise (CON, 30), Isopast (ISO, 28)) and four luting (3M Experimental 241 (EXM, 20), Variolink II (VAR, 13), Vitremer LC (VTM, 20) and Dyract Cem (DYR, 25)) materials were allowed to polymerize until they reached a maximum tension (T(max), 25 min) between six pairs (null 5.81, 8.5, 11.26, 12.42, 17.02, 23.14 mm) of polished metallic discs (range of distances: 0.02-5.9 mm) mounted in a tension machine. The deformation of the measuring system was measured for the recorded forces. RESULTS A descriptive non-linear formula T(max)=KVol(-3.267)FS(3.283)AS(0.642)Def(0.561) was found that individualizes the material's characteristics (K) that considers volume (Vol), free (FS) and adhered (AS) surfaces and deformation (Def) of the system for each force. This formula renders good correlation (material K (r(2) coefficient)): SIL 0.9998 (0.995), CLE 1.0062 (0.989), P10 1.0224 (0.990), CON 0.9908 (0.992), ISO 0.9648 (0.974), EXM 1.0083 (0.991), VAR 0.9777 (0.996), VTM 0.9925 (0.993), DYR 0.9971 (0.997) between actual T(max) and calculated Tension. There are statistically significant differences (p=0.002) between K values of both (restorative and luting) groups. SIGNIFICANCE Predictive parameters have influence in a different way to what is actually considered, if the system is allowed to have deformation, as occurs naturally and volume and material's characteristics are considered.
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Affiliation(s)
- A Miguel
- Conservative Dentistry Department, Faculty of Odontology, Complutense University, Madrid, Spain
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Kinomoto Y, Torii M, Takeshige F, Ebisu S. Polymerization Contraction Stress of Resin Composite Restorations in a Model Class I Cavity Configuration Using Photoelastic Analysis. J ESTHET RESTOR DENT 2000; 12:309-19. [PMID: 14743526 DOI: 10.1111/j.1708-8240.2000.tb00240.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE An important factor that contributes to deterioration of resin composite restorations is contraction stress that occurs during polymerization. The purpose of this article is to familiarize the clinician with the characteristics of contraction stress by visualizing the stresses associated with this invisible and complex phenomenon. MATERIALS AND METHODS Internal residual stresses generated during polymerization of resin composite restorations were determined using micro-photoelastic analysis. Butt-joint preparations simulating Class I restorations (2.0 mm x 5.0 mm, 2.0 mm in depth) were prepared in three types of substrates (bovine teeth, posterior composite resin, and transparent composite resin) and were used to examine contraction stress in and around the preparations. Three types of composite materials (a posterior composite, a self-cured transparent composite, and a light-cured transparent composite) were used as the restorative materials. The self-cured composite is an experimental material, and the others are commercial products. After treatment of the preparation walls with a bonding system, the preparations were bulk-filled with composite. Specimens for photoelastic analysis were prepared by cutting sections perpendicular to the long axis of the preparation. Fringe patterns for directions and magnitudes of stresses were obtained using transmitted and reflected polarized light with polarizing microscopes. Then, the photoelastic analysis was performed to examine stresses in and around the preparations. RESULTS When cavity preparations in bovine teeth were filled with light-cured composite, a gap was formed between the dentinal wall and the composite restorative material, resulting in very low stress within the restoration. When cavity preparations in the posterior composite models were filled with either self-cured or light-cured composite, the stress distribution in the two composites was similar, but the magnitude of the stress was greater in the light-cured material. When preparations in the transparent composite models were filled with posterior composite and light-cured transparent composite material, significant stress was generated in the preparation models simulating tooth structure, owing to the contraction of both restorative materials. CLINICAL SIGNIFICANCE Polymerization contraction stress is an undesirable and inevitable characteristic of adhesive restorations encountered in clinical dentistry that may compromise restoration success. Clinicians must understand the concept of polymerization contraction stress and realize that the quality of composite resin restorations depends on successful management of these stresses.
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Affiliation(s)
- Y Kinomoto
- Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Osaka, Japan.
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Kinomoto Y, Torii M, Takeshige F, Ebisu S. Comparison of polymerization contraction stresses between self- and light-curing composites. J Dent 1999; 27:383-9. [PMID: 10377614 DOI: 10.1016/s0300-5712(98)00065-7] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
OBJECTIVES The objective of this study was to examine the distributions and the magnitudes of the internal stresses in self- and a light-curing composite restorations resulting from polymerization shrinkage. METHODS Butt-joint box-shaped cavities (5.0 x 2.0 mm2, 2.0 mm in depth) prepared in composite molds were filled with either a self- or light-curing transparent resin composite. The restorations were cross-sectioned perpendicular to the longitudinal axes of the cavities and observed using polarizing microscopes. The principal stresses in the restorations, normal and shear stresses at the cavity wall were evaluated by photoelastic analysis. RESULTS The distributions of the principal stresses and the stresses generated at the cavity wall in both the self- and the light-curing composite restorations were similar. The maximum stress generated at the cavity wall in the light-curing composite restorations was twice as large as that seen in the self-curing restorations. CONCLUSIONS The results of this study indicated that the difference in the magnitude of the internal stresses between self- and light-curing composites was not related to the distribution of the stresses. The velocity of polymerization appeared to be the most important factor contributing to the magnitude of the internal stresses generated in the composite restorations in this study.
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Affiliation(s)
- Y Kinomoto
- Department of Conservative Dentistry, Osaka University Faculty of Dentistry, Japan.
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