1
|
Lehmann A, Nijakowski K, Drożdżyńska A, Przybylak M, Woś P, Surdacka A. Influence of the Polymerization Modes on the Methacrylic Acid Release from Dental Light-Cured Materials-In Vitro Study. MATERIALS (BASEL, SWITZERLAND) 2022; 15:ma15248976. [PMID: 36556780 PMCID: PMC9786925 DOI: 10.3390/ma15248976] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 12/12/2022] [Accepted: 12/12/2022] [Indexed: 05/14/2023]
Abstract
The study focuses on the problem of lowering the pH around a composite filling concerning the polymerization modes and methacrylic acid release, which may affect not only the oral health but also the whole organism. A total of 90 specimens (30 of each: Filtek Bulk Fill, Evetric and Riva LC) were placed in 90 sterile hermetic polyethene containers with saline and incubated at 37 °C. Ten samples of each material were light-cured for 40 s with one of the three curing modes: full power mode (FPM), ramping mode (RM) and pulse mode (PM). The pH and methacrylic acid release evaluation were performed at the following time points: after 2 h and after 3, 7, 21 and 42 days from the specimen preparation. Regardless of light-curing mode, all used materials were characterized by a gradual elevation in methacrylic acid concentration. Only for Filtek Bulk Fill, increased methacrylic acid release was closely associated with lower pH. The choice of the polymerization mode has no significant influence on the methacrylic acid release. However, further research about composite light-curing is necessary to create the procedure algorithm, reducing the local and systemic complications associated with composite fillings.
Collapse
Affiliation(s)
- Anna Lehmann
- Department of Conservative Dentistry and Endodontics, Poznan University of Medical Sciences, 60-812 Poznan, Poland
| | - Kacper Nijakowski
- Department of Conservative Dentistry and Endodontics, Poznan University of Medical Sciences, 60-812 Poznan, Poland
- Correspondence:
| | - Agnieszka Drożdżyńska
- Department of Biotechnology and Food Microbiology, Poznan University of Life Sciences, 60-627 Poznan, Poland
| | - Martyna Przybylak
- Department of Biotechnology and Food Microbiology, Poznan University of Life Sciences, 60-627 Poznan, Poland
| | - Patryk Woś
- Student’s Scientific Group in Department of Conservative Dentistry and Endodontics, Poznan University of Medical Sciences, 60-812 Poznan, Poland
| | - Anna Surdacka
- Department of Conservative Dentistry and Endodontics, Poznan University of Medical Sciences, 60-812 Poznan, Poland
| |
Collapse
|
2
|
Şişman R, Aksoy A, Yalçın M, Karaöz E. Cytotoxic effects of bulk fill composite resins on human dental pulp stem cells. J Oral Sci 2016; 58:299-305. [DOI: 10.2334/josnusd.15-0603] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Affiliation(s)
- Reyhan Şişman
- Department of Restorative Dentistry, Faculty of Dentistry, University of Inonu
| | - Ayça Aksoy
- Faculty of Bioengineering, Institute of Science, Yildiz Technical University
| | - Muhammet Yalçın
- Department of Restorative Dentistry, Faculty of Dentistry, University of Inonu
| | - Erdal Karaöz
- Liv Hospital, Center for Regenerative Medicine and Stem Cell Research and Manufacturing
| |
Collapse
|
3
|
Aguirre-Soto A, Hwang AT, Glugla D, Wydra JW, McLeod RR, Bowman CN, Stansbury JW. Coupled UV–Vis/FT–NIR Spectroscopy for Kinetic Analysis of Multiple Reaction Steps in Polymerizations. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b01685] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Alan Aguirre-Soto
- Department
of Chemical and Biological Engineering, University of Colorado Boulder, 3415 Colorado Ave., Boulder, Colorado 80303, United States
| | - Albert T. Hwang
- Department
of Chemical and Biological Engineering, University of Colorado Boulder, 3415 Colorado Ave., Boulder, Colorado 80303, United States
| | - David Glugla
- Department
of Electrical, Computer, and Energy Engineering, University of Colorado Boulder, 425 UCB, Boulder, Colorado 80303, United States
| | - James W. Wydra
- Department
of Chemical and Biological Engineering, University of Colorado Boulder, 3415 Colorado Ave., Boulder, Colorado 80303, United States
| | - Robert R. McLeod
- Department
of Electrical, Computer, and Energy Engineering, University of Colorado Boulder, 425 UCB, Boulder, Colorado 80303, United States
| | - Christopher N. Bowman
- Department
of Chemical and Biological Engineering, University of Colorado Boulder, 3415 Colorado Ave., Boulder, Colorado 80303, United States
| | - Jeffrey W. Stansbury
- Department
of Chemical and Biological Engineering, University of Colorado Boulder, 3415 Colorado Ave., Boulder, Colorado 80303, United States
- Department
of Craniofacial Biology, School of Dental Medicine, University of Colorado, 12800 East 19th Ave., Aurora, Colorado 80045, United States
| |
Collapse
|
4
|
Abstract
This study evaluated the biocompatibility of contemporary bulk-fill resin-based composites (RBCs) including PRG (pre-reacted glass ionomer) materials based on the International Organization for Standardization 10993. In addition, the effect of composite thickness on cytotoxicity was also assessed. Two standard composites, two bulk-fill PRG RBCs, and three bulk-fill non-PRG RBCs were investigated. Block-shaped specimens of 2-mm and 4-mm thickness were cured with an irradiance of 700 mW/cm(2) for 20 seconds with a light-emitting diode curing light and eluted with culture medium at 37°C for 24 hours. L929 mouse fibroblasts were exposed to extracts at varying dilutions (1:1, 1:2, and 1:10) for 24 hours. Analyses were performed to assess cytotoxicity, phase contrast microscopy, and quantitative cell viability. Among the bulk-fill RBCs, extracts of PRG materials resulted in the lowest cell viability. At 4-mm thickness, undiluted extracts of bulk-fill non-PRG RBCs had significantly higher cell viability than the standard composites. Chemical composition, specimen thickness, and testing concentrations of extracts had significant effects on cell viability and morphology. Cytotoxic effects of composites on cell viability were parallel with cell morphologic changes. Not all bulk-fill RBCs demonstrated high cell viability (>70%) at 4-mm thickness despite manufacturers' recommendations of bulk placement and curing.
Collapse
|
5
|
Sabatini C. Color Stability Behavior of Methacrylate-based Resin Composites Polymerized with Light-emitting Diodes and Quartz-Tungsten-Halogen. Oper Dent 2015; 40:271-81. [DOI: 10.2341/14-080-l] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
SUMMARY
Despite significant developments in improving the optical properties of resin composite materials, their color stability remains a challenge. This study aimed to evaluate the shade stability of light-polymerized, methacrylate-based resin composites with different filler particle composition (microfill, minifill, nanohybrids, and microhybrids) polymerized with quartz-tungsten-halogen (QTH) and light-emitting diodes (LED).
Methods and Materials
Composite discs were fabricated from Tetric EvoCeram, Premise, Artiste, and Beautifil II (nanohybrids); Filtek Supreme Plus and Vit-l-escence (microhybrids); Heliomolar (microfill); and Estelite Sigma Quick (minifill) using a Teflon mold. The specimens were irradiated either with QTH (Elipar 2500; 600 mW/cm2) for 40 seconds or with LED (Bluephase G2; 1200 mW/cm2) for 20 seconds. Color parameters were measured with a colorimeter before and after polymerization and at 24 hours, one week, one month, and three months. Color change was calculated among the different storage periods.
Results
There was a significant effect of the composite, time, and their interaction (p<0.001) but no effect of the polymerization unit on the color stability. Color changes immediately after polymerization and at 24 hours (4.22 and 3.88 for LED; and 4.08 and 3.82 for QTH) were not significantly different from each other but were both significantly higher than changes after one week (0.96 and 0.78), one month (1.12 and 1.02), and three months (1.27 and 1.11) for LED and QTH, respectively (p<0.001).
Conclusions
Color changes were observed for all the materials that were dependent on the type of composite but not on the polymerization unit. These color shifts took place primarily immediately after polymerization and after 24 hours and were additive in nature.
Collapse
Affiliation(s)
- C Sabatini
- Camila Sabatini, DDS, MS, University at Buffalo, Restorative Dentistry, Buffalo, NY, USA
| |
Collapse
|
6
|
Sabatini C. Comparative study of surface microhardness of methacrylate-based composite resins polymerized with light-emitting diodes and halogen. Eur J Dent 2014; 7:327-335. [PMID: 24926213 PMCID: PMC4053622 DOI: 10.4103/1305-7456.115417] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Objective: The aim of this study was to evaluate the effect of polymerization with quartz-tungsten-halogen (QTH) and light-emitting diodes (LED) on the surface microhardness of eight commercially available light-polymerized, methacrylate-based composite resins, with different filler particle composition (microfill, minifill, nanohybrids, and microhybrids) immediately after polymerization, after 24 hours, and after three months of storage. Materials and Methods: Eighty disk-shaped specimens were prepared using a split Teflon mold (6 × 2 mm) and were irradiated with either the QTH (Elipar 2500; 600 mW/cm2) for 20 seconds or an LED (Bluephase G2; 1,200 mW/cm2) for 40 seconds. The microhardness values were recorded using a Vickers hardness tester at a 300 g load for 15 seconds, immediately after polymerization, after 24 hours, and after three months of dark aging in distilled water at 37°C. Statistical analysis was performed using a two-way analysis of variance (ANOVA) and the Tukey's test. Results: The baseline values demonstrated a significant effect of the composite and the interaction composite-LCU on the microhardness (P < 0.05). At 24 hours, only the composite variable showed a significant effect on the hardness values (P < 0.05). After three months, the composite, LCU, and the interaction composite-LCU all demonstrated a significant effect on the microhardness (P < 0.05). Conclusions: The effectiveness of polymerization, measured in terms of surface hardness, was shown to be dependent not only on the type of light curing unit, but also on the type of composite. Moreover, the choice of composite was shown to affect the performance of the light curing unit.
Collapse
Affiliation(s)
- Camila Sabatini
- Department of Restorative Dentistry, School of Dental Medicine, SUNY at Buffalo, Buffalo, NY, USA
| |
Collapse
|
7
|
Jan YD, Lee BS, Lin CP, Tseng WY. Biocompatibility and cytotoxicity of two novel low-shrinkage dental resin matrices. J Formos Med Assoc 2014; 113:349-55. [DOI: 10.1016/j.jfma.2012.07.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2012] [Revised: 06/11/2012] [Accepted: 07/13/2012] [Indexed: 10/28/2022] Open
|
8
|
Effect of emitted wavelength and light guide type on irradiance discrepancies in hand-held dental curing radiometers. ScientificWorldJournal 2013; 2013:647941. [PMID: 24222744 PMCID: PMC3810486 DOI: 10.1155/2013/647941] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Accepted: 08/28/2013] [Indexed: 12/02/2022] Open
Abstract
The purpose of this study was to determine any discrepancies in the outputs of five commercial dental radiometers and also to evaluate the accuracy of these devices using a laboratory-grade spectroradiometer. The power densities of 12 different curing light sources were repeatedly measured for a total of five times using each radiometer in a random order. The emission spectra of all of the curing light sources were also measured using the spectroradiometer, and the integral value of each spectrum was calculated to determine the genuine power densities, which were then compared to the displayed power densities measured by the dental radiometers. The displayed values of power density were various and were dependent on the brand of radiometer, and this may be because each radiometer has a different wavelength sensitivity. These results cast doubt upon the accuracy of commercially available dental radiometers.
Collapse
|
9
|
Mehdawi IM, Pratten J, Spratt DA, Knowles JC, Young AM. High strength re-mineralizing, antibacterial dental composites with reactive calcium phosphates. Dent Mater 2013; 29:473-84. [PMID: 23434447 DOI: 10.1016/j.dental.2013.01.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 09/12/2012] [Accepted: 01/25/2013] [Indexed: 10/27/2022]
Abstract
OBJECTIVE Development of high strength dental composites with adhesive, antibacterial and re-mineralizing potential. MATERIALS Urethane and triethylene glycol dimethacrylates were combined with HEMA (10 or 20wt%) and 2MP (2 or 10wt%), antibacterial chlorhexidine (2.5wt%) and chemical cure initiators. Reactive mono/tri calcium phosphate (CP) mixed with silica/silicon carbide nanoparticles (S) (CP:S weight ratio 1:2 or 2:1) was added (50wt%). RESULTS Decreasing CP/S ratio and HEMA content reduced monomer conversion at 15min from 93 to 63%. Conversely, decreasing CP/S increased initial "dry" compressive (137-203MPa) and flexural (79-116MPa) strength. With high HEMA content, these decreased by ∼15-20MPa upon 24h water storage. With low HEMA content, average decline was <8MPa due to reduced water sorption. Early water sorption induced mass increase, volume expansion, mono calcium phosphate dissolution and chlorhexidine release, were proportional to the initial calcium phosphate content. Furthermore, they increased ∼1.5 fold upon raising HEMA wt%. These diffusion controlled processes and strength decline slowed after 24h as phosphates reaction bound water within the materials. Increasing 2MP concentration reduced calcium release but did not affect strength. Formulations with high CP/S indicated greater antibacterial activity in agar diffusion and in vitro biofilm tests. SIGNIFICANCE New material use beneath a conventional composite could potentially reduce high failure rates associated with residual caries and bacterial microleakage.
Collapse
Affiliation(s)
- Idris M Mehdawi
- UCL Eastman Dental Institute, 256 Gray's Inn Road, London, UK
| | | | | | | | | |
Collapse
|
10
|
Reaction of rat subcutaneous connective tissue to resin composites polymerized with different light curing units and different lightening methods. Int J Dent 2012; 2012:156352. [PMID: 22761617 PMCID: PMC3384911 DOI: 10.1155/2012/156352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 03/24/2012] [Accepted: 04/24/2012] [Indexed: 11/17/2022] Open
Abstract
The aim of the study was to determine and compare the reaction of rat subcutaneous connective tissue to resin composites polymerized with different lights curing and lightening methods. In this in vivo study, 20 mature Wister Albino rats were used. The composite discs, 4 mm in diameter and 2 mm thick, were cured by QTH or LED light curing units with 4 different lightning methods (full power QTH, full power LED, pulse LED, and ramp LED). Five resin composite discs were implanted in each rat, so that 4 of 5 discs for implantation of cured composite discs differently and central one as control without implantation. After sacrificing at 7, 14, 30, and 60 days the inflammatory grade, fibrosis, and necrosis were determined. Freedman and Cochran tests were used to analyze the data using SPSS software ver. 15. The results of the study showed significant differences in inflammation grade and fibrosis among control group and 4 experimental groups at day 14 (P < 0.05). In necrosis, there was no significant difference among 4 groups in different times (P > 0.05). In conclusion, neither the type of light curing units (LED or QTH) nor the lightening methods can affect the grade of inflammatory reaction.
Collapse
|
11
|
Sideridou ID, Karabela MM, Micheliou CN, Karagiannidis PG, Logothetidis S. Physical Properties of a Hybrid and a Nanohybrid Dental Light-Cured Resin Composite. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2012; 20:1831-44. [DOI: 10.1163/156856208x386435] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- Irini D. Sideridou
- a Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-5412 Thessaloniki, Greece.
| | - Maria M. Karabela
- b Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-5412 Thessaloniki, Greece
| | - Christina N. Micheliou
- c Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-5412 Thessaloniki, Greece
| | - Panagiotis G. Karagiannidis
- d Lab of Thin Films-Nanosystems and Nanometrology, Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece
| | - Stergios Logothetidis
- e Lab of Thin Films-Nanosystems and Nanometrology, Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece
| |
Collapse
|
12
|
AGUIAR FLÁVIOHENRIQUEBAGGIO, GEORGETTO MATHEUSHENRIQUE, SOARES GIULLIANAPANFIGLIO, CATELAN ANDERSON, DOS SANTOS PAULOHENRIQUE, AMBROSANO GLAUCIAMARIABOVI, FIGUEROBA SIDNEYRAIMUNDO, LOVADINO JOSÉROBERTO. Effect of Different Light-Curing Modes on Degree of Conversion, Staining Susceptibility and Stain's Retention Using Different Beverages in a Nanofilled Composite Resin. J ESTHET RESTOR DENT 2011; 23:106-14. [DOI: 10.1111/j.1708-8240.2011.00406.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
13
|
Bakopoulou A, Papadopoulos T, Garefis P. Molecular toxicology of substances released from resin-based dental restorative materials. Int J Mol Sci 2009; 10:3861-3899. [PMID: 19865523 PMCID: PMC2769064 DOI: 10.3390/ijms10093861] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 08/24/2009] [Accepted: 09/02/2009] [Indexed: 01/22/2023] Open
Abstract
Resin-based dental restorative materials are extensively used today in dentistry. However, significant concerns still remain regarding their biocompatibility. For this reason, significant scientific effort has been focused on the determination of the molecular toxicology of substances released by these biomaterials, using several tools for risk assessment, including exposure assessment, hazard identification and dose-response analysis. These studies have shown that substances released by these materials can cause significant cytotoxic and genotoxic effects, leading to irreversible disturbance of basic cellular functions. The aim of this article is to review current knowledge related to dental composites' molecular toxicology and to give implications for possible improvements concerning their biocompatibility.
Collapse
Affiliation(s)
- Athina Bakopoulou
- Department of Fixed & Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece; E-Mails: (B.A.); (G.P.)
| | - Triantafillos Papadopoulos
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, 115 27, Greece
| | - Pavlos Garefis
- Department of Fixed & Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece; E-Mails: (B.A.); (G.P.)
| |
Collapse
|
14
|
Mehdawi I, Neel EAA, Valappil SP, Palmer G, Salih V, Pratten J, Spratt DA, Young AM. Development of remineralizing, antibacterial dental materials. Acta Biomater 2009; 5:2525-39. [PMID: 19410530 DOI: 10.1016/j.actbio.2009.03.030] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2008] [Revised: 03/17/2009] [Accepted: 03/24/2009] [Indexed: 11/28/2022]
Abstract
Light curable methacrylate dental monomers containing reactive calcium phosphate filler (monocalcium phosphate monohydrate (MCPM) with particle diameter of 29 or 90microm) and beta-tricalcium phosphate (beta-TCP) at 1:1 weight ratio in a powder:liquid ratio (PLR) of 1:1 or 3:1 and chlorhexidine diacetate (0 or 5 wt.%), were investigated. Upon light exposure, approximately 90% monomer conversion was gained irrespective of the formulation. Increasing the PLR promoted water sorption by the set material, induced expansion and enhanced calcium, phosphate and chlorhexidine release. Concomitantly, a decline in compressive and biaxial flexural strengths occurred. With a reduction in MCPM particle diameter, however, calcium and phosphate release was reduced and less deterioration in strength observed. After 24h, the remaining MCPM had reacted with water and beta-TCP, forming, within the set materials, brushite of lower solubility. This provided a novel means to control water sorption, component release and strength properties. Measurable chlorhexidine release was observed for 6weeks. Both diffusion rate and total percentage of chlorhexidine release decreased with lowering PLR or by adding buffer to the storage solutions. Higher chlorhexidine release was associated with reduced bacterial growth on agar plates and in a biofilm fermenter. In cell growth media, brushite and hydroxyapatite crystals precipitated on the composite material surfaces. Cells spread on both these crystals and the exposed polymer composite surfaces, indicating their cell compatibility. These formulations could be suitable antibacterial, biocompatible and remineralizing dental adhesives/liners.
Collapse
Affiliation(s)
- Idris Mehdawi
- UCL Eastman Dental Institute, 256 Gray's Inn Road, London WC1X 8LD, UK
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Contemporary Methacrylate Resin–based Root Canal Sealers Exhibit Different Degrees of Ex Vivo Cytotoxicity When Cured in Their Self-cured Mode. J Endod 2009; 35:225-8. [DOI: 10.1016/j.joen.2008.11.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Revised: 11/03/2008] [Accepted: 11/03/2008] [Indexed: 01/21/2023]
|
16
|
Pfeifer CS, Ferracane JL, Sakaguchi RL, Braga RR. Factors affecting photopolymerization stress in dental composites. J Dent Res 2008; 87:1043-7. [PMID: 18946012 DOI: 10.1177/154405910808701114] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Polymerization stress development results from the complex interplay of volumetric shrinkage, reaction kinetics, and viscoelastic properties. The objective of this study was to examine the relationships among volumetric shrinkage, degree of conversion, rate of polymerization (RP(max)), and stress development for 2 model bis-GMA-based composites. Three irradiances were used--220, 400, or 600 mW/cm(2)--with exposure times adjusted to deliver the same radiant energy. Volumetric shrinkage was determined with a mercury dilatometer, degree of conversion and RP(max) by differential scanning calorimetry (DSC), and polymerization stress with a low-compliance device (Sakaguchi et al., 2004b). Results indicated that polymerization reaction rate and shrinkage were not correlated. Irradiance was directly related to polymerization reaction rate and to stress development. The group with the highest stress/degree of conversion exhibited the lowest RP(max), so it can be assumed, within the limitations of this study, that the conversion was most closely related to stress development.
Collapse
Affiliation(s)
- C S Pfeifer
- Department of Biomaterials and Oral Biochemistry, School of Dentistry, University of São Paulo, Av. Prof. Lineu Prestes, 2227 São Paulo, SP, Brazil.
| | | | | | | |
Collapse
|