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Dexamethasone and zinc loaded polymeric nanoparticles reinforce and remineralize coronal dentin. A morpho-histological and dynamic-biomechanical study. Dent Mater 2023; 39:41-56. [PMID: 36460577 DOI: 10.1016/j.dental.2022.11.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 11/18/2022] [Accepted: 11/25/2022] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To investigate the effect of novel polymeric nanoparticles (NPs) doped with dexamethasone (Dex) on viscoelasticity, crystallinity and ultra-nanostructure of the formed hydroxyapatite after NPs dentin infiltration. METHODS Undoped-NPs, Dex-doped NPs (Dex-NPs) and zinc-doped-Dex-NPs (Zn-Dex-NPs) were tested at dentin, after 24 h and 21 d. A control group without NPs was included. Coronal dentin surfaces were studied by nano-dynamic mechanical analysis measurements, atomic force microscopy, X-ray diffraction and transmission electron microscopy. Mean and standard deviation were analyzed by ANOVA and Student-Newman-Keuls multiple comparisons (p < 0.05). RESULTS At 21 d of storage time, both groups doped with Dex exhibited the highest complex, storage and loss moduli among groups. Zn-Dex-NPs and Dex-NPs promoted the highest and lowest tan delta values, respectively. Dex-NPs contributed to increase the fibril diameters of dentin collagen over time. Dentin surfaces treated with Zn-Dex-NPs attained the lowest nano-roughness values, provoked the highest crystallinity, and produced the longest and shortest crystallite and grain size. These new crystals organized with randomly oriented lattices. Dex-NPs induced the highest microstrain. Crystalline and amorphous matter was present in the mineral precipitates of all groups, but Zn and Dex loaded NPs helped to increase crystallinity. SIGNIFICANCE Dentin treated with Zn-Dex-NPs improved crystallographic and atomic order, providing structural stability, high mechanical performance and tissue maturation. Amorphous content was also present, so high hydroxyapatite solubility, bioactivity and remineralizing activity due to the high ion-rich environment took place in the infiltrated dentin.
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Tichy A, Brabec M, Bradna P, Hosaka K, Chiba A, Tagami J. Influence of central and peripheral dentin on micro-tensile bond strength estimated using a competing risk model. J Mech Behav Biomed Mater 2020; 115:104295. [PMID: 33412405 DOI: 10.1016/j.jmbbm.2020.104295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 12/17/2020] [Accepted: 12/21/2020] [Indexed: 10/22/2022]
Abstract
The bonding performance of dental adhesives is most frequently evaluated using the micro-tensile bond strength (μTBS) test. Despite lacking evidence, peripheral specimens are often discarded to avoid regional variability. This study, therefore, examined whether μTBS to central and peripheral dentin differed. Dentin surfaces of extracted human molars were bonded with various self-etch adhesives, built up with a resin composite, cut into beams, and stressed in tension. Failure mode was classified as adhesive, cohesive in dentin, or other using scanning electron microscopy. Since cohesive failures in dentin were frequent and could confound μTBS results, the data from central/peripheral dentin were analyzed using a Weibull competing risk (CR) model distinguishing failure modes, and its outcomes were compared to a conventional failure mode non-distinguishing Weibull model. Based on the strength data of cohesively failed specimens, the CR model also estimated the strength of dentin. For comparison, the ultimate tensile strength (UTS) of dentin was measured in both regions. The conventional model suggested that peripheral μTBS was higher than central μTBS. Conversely, the CR model disclosed no significant difference in μTBS between the regions but indicated a higher strength of peripheral dentin. This finding was confirmed by UTS measurements, and further supported by the significantly higher incidence of cohesive failures in central dentin. Therefore, peripheral specimens can be used in the μTBS test as well as central ones, but a CR model should be used for statistical analysis if cohesive failures in dentin are frequent, as the strength of peripheral dentin is higher.
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Affiliation(s)
- Antonin Tichy
- Institute of Dental Medicine, First Faculty of Medicine of the Charles University and General University Hospital in Prague, Karlovo Namesti 32, Prague, 121 11, Czech Republic; Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan.
| | - Marek Brabec
- Department of Statistical Modelling, Institute of Computer Science of the Czech Academy of Sciences, Pod Vodarenskou vezi 271/2, Prague, 182 00, Czech Republic
| | - Pavel Bradna
- Institute of Dental Medicine, First Faculty of Medicine of the Charles University and General University Hospital in Prague, Karlovo Namesti 32, Prague, 121 11, Czech Republic
| | - Keiichi Hosaka
- Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Ayaka Chiba
- Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Junji Tagami
- Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
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Enrich-Essvein T, Benavides-Reyes C, Álvarez-Lloret P, Bolaños-Carmona MV, Rodríguez-Navarro AB, González-López S. Influence of de-remineralization process on chemical, microstructural, and mechanical properties of human and bovine dentin. Clin Oral Investig 2020; 25:841-849. [PMID: 32462276 DOI: 10.1007/s00784-020-03371-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 05/21/2020] [Indexed: 11/25/2022]
Abstract
OBJECTIVES This study compared the chemical composition, microstructural, and mechanical properties of human and bovine dentin subjected to a demineralization/remineralization process. MATERIALS AND METHODS Human and bovine incisors were sectioned to obtain 120 coronal dentin beams (6 × 1 × 1 mm3) that were randomly allocated into 4 subgroups (n = 15) according to the time of treatment (sound, pH-cycling for 3, 7, and 14 days). Three-point bending mechanical test, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), thermogravimetric (TG), and X-ray diffraction (XRD) techniques were employed to characterize the dentin samples. RESULTS Regarding chemical composition at the molecular level, bovine sound dentin showed significantly lower values in organic and inorganic content (collagen cross-linking, CO3/amide I, and CO3/PO4; p = 0.002, p = 0.026, and p = 0.002, respectively) compared to humans. Employing XRD analyses, a higher mineral crystallinity in human dentin than in bovines at 7 and 14 days (p = 0.003 and p = 0.009, respectively) was observed. At the end of the pH-cycling, CI (ATR-FTIR) and CO3/PO4 ratios (ATR-FTIR) increased, while CO3/amide I (ATR-FTIR), PO4/amide I (ATR-FTIR), and %mineral (TG) ratios decreased. The extension by compression values increased over exposure time with significant differences between dentin types (p < 0.001, in all cases), reaching higher values in bovine dentin. However, flexural strength (MPa) did not show differences between groups. We also observed the correlation between compositional variables (i.e., PO4/amide I, CI, and %mineral) and the extension by compression. CONCLUSIONS Human and bovine dentin are different in terms of microstructure, chemical composition, mechanical strength, and in their response to the demineralization/remineralization process by pH-cycling. CLINICAL RELEVANCE These dissimilarities may constitute a potential limitation when replacing human teeth with bovines in in vitro studies.
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Affiliation(s)
- Tattiana Enrich-Essvein
- Department of Operative Dentistry, School of Dentistry, University of Granada, Campus de Cartuja, Colegio Maximo s/n, 18071, Granada, Spain.
| | - Cristina Benavides-Reyes
- Department of Operative Dentistry, School of Dentistry, University of Granada, Campus de Cartuja, Colegio Maximo s/n, 18071, Granada, Spain
| | - Pedro Álvarez-Lloret
- Department of Geology, Faculty of Geology, University of Oviedo, Jesús Arias de Velasco s/n, 33005, Oviedo, Spain
| | - María Victoria Bolaños-Carmona
- Department of Pediatric Dentistry, School of Dentistry, University of Granada, Campus de Cartuja, Colegio Maximo s/n, 18071, Granada, Spain
| | - Alejandro B Rodríguez-Navarro
- Department of Mineralogy and Petrology, Faculty of Sciences, University of Granada, Avenida de Fuentenueva s/n, 18002, Granada, Spain
| | - Santiago González-López
- Department of Operative Dentistry, School of Dentistry, University of Granada, Campus de Cartuja, Colegio Maximo s/n, 18071, Granada, Spain
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Microtissue Engineering Root Dentin with Photodynamically Cross-linked Nanoparticles Improves Fatigue Resistance of Endodontically Treated Teeth. J Endod 2020; 46:668-674. [DOI: 10.1016/j.joen.2020.01.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 12/28/2019] [Accepted: 01/28/2020] [Indexed: 11/18/2022]
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Kominami N, Shimada Y, Hosaka K, Luong MN, Yoshiyama M, Sadr A, Sumi Y, Tagami J. The effect of flowable composite lining and dentin location on microtensile bond strength and internal fracture formation. Dent Mater J 2019; 38:798-805. [PMID: 31341147 DOI: 10.4012/dmj.2018-232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The objective of this study was to determine the effect of flowable composite lining and dentin location on internal dentin fracture formation in the microtensile bond strength (MTBS) test using swept-source optical coherence tomography (SS-OCT). MTBS test beams (1.0×1.0 mm) were prepared from human superficial and deep dentin, which was bonded with a self-etch adhesive (Clearfil SE Bond) and hybrid composite resin (Clearfil AP-X), with or without flowable lining (Clearfil Majesty ES-Flow). We tested 4 groups according to placement technique (with vs. without flowable liner) and dentin (superficial vs. deep) locations. Cross-sectional 2D images of the bonded interface were obtained before and after the MTBS test. Internal dentin fracture after MTBT was observed as a bright zone in SS-OCT. Flowable lining significantly reduced internal fracture formation in dentin (p<0.05). Dentin location significantly influenced MTBS (p<0.05), and this was reduced by flowable lining usage.
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Affiliation(s)
- Nao Kominami
- Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University
| | - Yasushi Shimada
- Department of Operative Dentistry, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University
| | - Keiichi Hosaka
- Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University
| | - Minh Nguyet Luong
- Department of Restorative Dentistry and Endodontics, Faculty of Odonto-Stomatology, University of Medicine and Pharmacy at Ho Chi Minh City.,Biomimetics Biomaterials Biophotonics & Technology Laboratory, Department of Restorative Dentistry, University of Washington School of Dentistry
| | - Masahiro Yoshiyama
- Department of Operative Dentistry, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University
| | - Alireza Sadr
- Biomimetics Biomaterials Biophotonics & Technology Laboratory, Department of Restorative Dentistry, University of Washington School of Dentistry
| | - Yasunori Sumi
- National Center for Geriatrics and Gerontology, Department of Advanced Dental Research, Center of Advanced Medicine for Dental and Oral Disease
| | - Junji Tagami
- Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University
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Kafantari N, Gulabivala K, Georgiou G, Knowles J, Ng YL. Effect of Heated Sodium Hypochlorite on the Viscoelastic Properties of Dentin Evaluated Using Dynamic Mechanical Analysis. J Endod 2019; 45:1155-1160. [DOI: 10.1016/j.joen.2019.05.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 05/23/2019] [Accepted: 05/26/2019] [Indexed: 11/30/2022]
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Yin R, Jang YS, Lee MH, Bae TS. Comparative Evaluation of Mechanical Properties and Wear Ability of Five CAD/CAM Dental Blocks. MATERIALS 2019; 12:ma12142252. [PMID: 31336968 PMCID: PMC6678169 DOI: 10.3390/ma12142252] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 07/10/2019] [Accepted: 07/11/2019] [Indexed: 11/17/2022]
Abstract
This study compares the mechanical properties and wear ability of five CAD/CAM (computer-aided design/computer-aided manufacturing) millable dental blocks. All the discs, including Amber Mill Hybrid, Vita Enamic, Katana Avencia, Lava Ultimate, and Amber Mill, were cut in dimensions of 1.2 mm in thickness and 12 mm in diameter, polished to a machined surface, and immersed in distilled water for seven days. Vickers hardness was measured and the indentations were observed using microscope. The discs were brushed under a 150 g load. Mean surface roughness (Ra) and topography were determined after 100,000 cycles. Finally the biaxial flexure strength of the discs was measured and the broken surfaces were observed using scanning electron microscopy (SEM). The data was subjected to Weibull analysis. All data were analyzed by one-way analysis (ANOVA). The results of Vickers hardness are shown as: Amber Mill > Vita Enamic > Amber Mill Hybrid > Lava Ultimate > Katana Avencia. Katana Avencia showed the highest volume percentage reduction and the roughest surface after toothbrushing. The biaxial flexural strength is shown as: Amber Mill > Katana Avencia > Lava Ultimate > Amber Mill Hybrid > Vita Enamic. All the tested materials exhibited varying degrees of mass loss and surface roughness. The properties of the composite materials are related to the filler content, filler volume, and polymerization methods.
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Affiliation(s)
- Ruizhi Yin
- Department of Dental Biomaterials, School of Dentistry, Chonbuk National University, 664-14, Duckjin-dong, Jeonju-city 561-756, Korea
| | - Yong-Seok Jang
- Department of Dental Biomaterials, School of Dentistry, Chonbuk National University, 664-14, Duckjin-dong, Jeonju-city 561-756, Korea
| | - Min-Ho Lee
- Department of Dental Biomaterials, School of Dentistry, Chonbuk National University, 664-14, Duckjin-dong, Jeonju-city 561-756, Korea
| | - Tae-Sung Bae
- Department of Dental Biomaterials, School of Dentistry, Chonbuk National University, 664-14, Duckjin-dong, Jeonju-city 561-756, Korea.
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Karunanayake G, Ng YL, Knowles JC, Delgado AHS, Young AM, Gulabivala K, Nazhat SN. The effect of NaOCl and heat treatment on static and dynamic mechanical properties and chemical changes of dentine. J Mech Behav Biomed Mater 2019; 97:330-338. [PMID: 31153114 DOI: 10.1016/j.jmbbm.2019.05.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 05/23/2019] [Accepted: 05/27/2019] [Indexed: 11/26/2022]
Abstract
OBJECTIVES To determine the effect of heat on flexural strength (FS), maximum strain (MS), storage modulus (SM), tan delta (TD) and chemical changes through micro-Raman spectroscopy of dentine exposed to 2.5% NaOCl or saline. METHOD ology: Dentine bars were randomly allocated to 8 test groups. Half (groups 2,4,6,8) were treated with NaOCl for 20 min; the rest (groups 1,3,5,7) remained in saline. FS/MS were measured in groups 1-4 (n = 15) (3/4 were also heated to 200 °C & re-hydrated in saline). Micro-Raman spectroscopy was performed on bars from groups 1-4. SM/TD were measured in 5-8: in 5/6 (n = 10), repeated after heating (200 °C), then following re-hydration; in 7/8 (n = 3) after heating to 25-185 °C. RESULTS Increase in MS on heat and FS/MS on heat + NaOCl was not significant (P > 0.05). SM increased (P = 0.06) after heat treatment but reduced to initial state after rehydration (P = 0.03). TD did not change (P = 0.4) after heat (200 °C) treatment but rehydration increased it compared with pre-treatment state (P = 0.001). For dentine bars pre-treated with NaOCl, SM did not change (P = 0.6) after heat (200 °C) treatment or rehydration but TD significantly increased (P = 0.02) upon re-hydration compared with pre- (P=0.007), or post- (P = 0.03) heat-treatment states. SM and TD varied between 25-185 °C with no consistent trend amongst the NaOCl pre-treated bars. Micro-Raman only detected chemical changes following NaOCl treatment in the mineral phase. CONCLUSIONS Exposure of dentine bars to heat and NaOCl produced only moderate changes to quasi-static but marked changes to viscoelastic properties, which may be explained by chemical alterations.
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Affiliation(s)
- G Karunanayake
- Unit of Endodontology, Division of Restorative Dental Science, UCL Eastman Dental Institute, University College London, London, UK
| | - Y-L Ng
- Unit of Endodontology, Division of Restorative Dental Science, UCL Eastman Dental Institute, University College London, London, UK.
| | - J C Knowles
- Biomaterials & Tissue Engineering, UCL Eastman Dental Institute, University College London, London, UK; Institute of Tissue Regeneration Engineering (ITREN) and Department of NanobiomedicalScience and BK21 Plus NBM, Global Research Center for Regenerative Medicine, DankookUniversity, 518-10, Anseo-dong, Dongnam-gu, Cheonan, Chungcheongnam-do, South Korea; The Discoveries Centre for Regenerative and Precision Medicine, UCL Campus, GowerStreet, London, WC1E 6BT, UK
| | - A H S Delgado
- Biomaterials & Tissue Engineering, UCL Eastman Dental Institute, University College London, London, UK
| | - A M Young
- Biomaterials & Tissue Engineering, UCL Eastman Dental Institute, University College London, London, UK
| | - K Gulabivala
- Unit of Endodontology, Division of Restorative Dental Science, UCL Eastman Dental Institute, University College London, London, UK
| | - S N Nazhat
- Department of Mining and Materials Engineering, McGill University, Montreal, Qc, H3A 0C5, Canada
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Toledano M, Muñoz-Soto E, Aguilera FS, Osorio E, Pérez-Álvarez MC, García-Menocal JAD, Toledano-Osorio M, Osorio R. The mineralizing effect of zinc oxide-modified hydroxyapatite-based sealer on radicular dentin. Clin Oral Investig 2019; 24:285-299. [DOI: 10.1007/s00784-019-02938-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 05/02/2019] [Indexed: 11/30/2022]
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Detecting Dentinal Microcracks Using Different Preparation Techniques: An In Situ Study with Cadaver Mandibles. J Endod 2017; 43:2070-2073. [DOI: 10.1016/j.joen.2017.07.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 07/06/2017] [Accepted: 07/09/2017] [Indexed: 12/13/2022]
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Vennat E, Wang W, Genthial R, David B, Dursun E, Gourrier A. Mesoscale porosity at the dentin-enamel junction could affect the biomechanical properties of teeth. Acta Biomater 2017; 51:418-432. [PMID: 28110070 DOI: 10.1016/j.actbio.2017.01.052] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 01/16/2017] [Accepted: 01/17/2017] [Indexed: 10/20/2022]
Abstract
In this paper, the 3D-morphology of the porosity in dentin is investigated within the first 350μm from the dentin-enamel junction (DEJ) by fluorescence confocal laser scanning microscopy (CLSM). We found that the porous microstructure exhibits a much more complex geometry than classically described, which may impact our fundamental understanding of the mechanical behavior of teeth and could have practical consequences for dental surgery. Our 3D observations reveal numerous fine branches stemming from the tubules which may play a role in cellular communication or mechanosensing during the early stages of dentinogenesis. The effect of this highly branched microstructure on the local mechanical properties is investigated by means of numerical simulations. Under simplified assumptions on the surrounding tissue characteristics, we find that the presence of fine branches negatively affects the mechanical properties by creating local stress concentrations. However, this effect is reduced by the presence of peritubular dentin surrounding the tubules. The porosity was also quantified using the CSLM data and compared to this derived from SEM imaging. A bimodal distribution of channel diameters was found near the DEJ with a mean value of 1.5-2μm for the tubules and 0.3-0.5μm for the fine branches which contribute to 30% of the total porosity (∼1.2%). A gradient in the branching density was observed from the DEJ towards the pulp, independently of the anatomical location. Our work constitutes an incentive towards more elaborate multiscale studies of dentin microstructure to better assess the effect of aging and for the design of biomaterials used in dentistry, e.g. to ensure more efficient bonding to dentin. Finally, our analysis of the tubular network structure provides valuable data to improve current numerical models.
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Degradation in the fatigue crack growth resistance of human dentin by lactic acid. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2016; 73:716-725. [PMID: 28183665 DOI: 10.1016/j.msec.2016.12.065] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/18/2016] [Accepted: 12/13/2016] [Indexed: 01/08/2023]
Abstract
The oral cavity frequently undergoes localized changes in chemistry and level of acidity, which threatens the integrity of the restorative material and supporting hard tissue. The focus of this study was to evaluate the changes in fatigue crack growth resistance of dentin and toughening mechanisms caused by lactic acid exposure. Compact tension specimens of human dentin were prepared from unrestored molars and subjected to Mode I opening mode cyclic loads. Fatigue crack growth was achieved in samples from mid- and outer-coronal dentin immersed in either a lactic acid solution or neutral conditions. An additional evaluation of the influence of sealing the lumens by dental adhesive was also conducted. A hybrid analysis combining experimental results and finite element modeling quantified the contribution of the toughening mechanisms for both environments. The fatigue crack growth responses showed that exposure to lactic acid caused a significant reduction (p≤0.05) of the stress intensity threshold for cyclic crack extension, and a significant increase (p≤0.05) in the incremental fatigue crack growth rate for both regions of coronal dentin. Sealing the lumens had negligible influence on the fatigue resistance. The hybrid analysis showed that the acidic solution was most detrimental to the extrinsic toughening mechanisms, and the magnitude of crack closure stresses operating in the crack wake. Exposing dentin to acidic environments contributes to the development of caries, but it also increases the chance of tooth fractures via fatigue-related failure and at lower mastication forces.
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Franzen R, Kianimanesh N, Marx R, Ahmed A, Gutknecht N. Fracture Forces of Dentin after Surface Treatment with High Speed Drill Compared to Er:YAG and Er,Cr:YSGG Laser Irradiation. Anal Cell Pathol (Amst) 2016; 2016:8517947. [PMID: 26962473 PMCID: PMC4745301 DOI: 10.1155/2016/8517947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 01/12/2016] [Indexed: 11/25/2022] Open
Abstract
Dental tooth restorative procedures may weaken the structural integrity of the tooth, with the possibility of leading to fracture. In this study we present findings of coronal dentin strength after different techniques of surface modification. The fracture strength of dentin beams after superficial material removal with a fine diamond bur high speed drill hand piece, Er:YAG (2.94 μm, 8 J/cm(2)), and Er,Cr:YSGG (2.78 μm, 7.8 J/cm(2)) laser irradiation slightly above the ablation threshold was measured by a four-point bending apparatus. Untreated dentin beams served as a control. A total of 58 dentin beams were manufactured from sterilized human extracted molars using the coronal part of the available dentin. Mean values of fracture strength were calculated as 82.0 ± 27.3 MPa for the control group (n = 10), 104.5 ± 26.3 MPa for high speed drill treatment (n = 10), 96.1 ± 28.1 MPa for Er,Cr:YSGG laser irradiation (n = 20), and 89.1 ± 36.3 MPa for Er:YAG laser irradiation (n = 18). Independent Student's t-tests showed no significant difference between each two groups (p > 0.05). Within the parameter settings and the limits of the experimental setup used in this study, both lasers systems as well as the high speed drill do not significantly weaken coronal dentin after surface treatment.
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Affiliation(s)
- Rene Franzen
- Department of Conservative Dentistry, Periodontology and Preventive Dentistry, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen, Germany
- AALZ Aachen Dental Laser Center, Center for Biomedical Technology, RWTH Aachen Campus, Pauwelsstrasse 17, 52074 Aachen, Germany
| | - Nasrin Kianimanesh
- AALZ Aachen Dental Laser Center, Center for Biomedical Technology, RWTH Aachen Campus, Pauwelsstrasse 17, 52074 Aachen, Germany
| | - Rudolf Marx
- Medical Material Science, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen, Germany
| | - Asma Ahmed
- AALZ Aachen Dental Laser Center, Center for Biomedical Technology, RWTH Aachen Campus, Pauwelsstrasse 17, 52074 Aachen, Germany
| | - Norbert Gutknecht
- Department of Conservative Dentistry, Periodontology and Preventive Dentistry, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen, Germany
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Zhang Z, Beitzel D, Mutluay M, Tay FR, Pashley DH, Arola D. On the durability of resin-dentin bonds: Identifying the weakest links. Dent Mater 2015; 31:1109-18. [PMID: 26169318 DOI: 10.1016/j.dental.2015.06.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 04/04/2015] [Accepted: 06/19/2015] [Indexed: 10/23/2022]
Abstract
UNLABELLED Fatigue of resin-dentin adhesive bonds is critical to the longevity of resin composite restorations. OBJECTIVES The objectives were to characterize the fatigue and fatigue crack growth resistance of resin-dentin bonds achieved using two different commercial adhesives and to identify apparent "weak-links". METHODS Bonded interface specimens were prepared using Adper Single Bond Plus (SB) or Adper Scotchbond Multi-Purpose (SBMP) adhesives and 3M Z100 resin composite according to the manufacturers' instructions. The stress-life fatigue behavior was evaluated using the twin bonded interface approach and the fatigue crack growth resistance was examined using bonded interface Compact Tension (CT) specimens. Fatigue properties of the interfaces were compared to those of the resin-adhesive, resin composite and coronal dentin. RESULTS The fatigue strength of the SBMP interface was significantly greater than that achieved by SB (p≤0.01). Both bonded interfaces exhibited significantly lower fatigue strength than that of the Z100 and dentin. Regarding the fatigue crack growth resistance, the stress intensity threshold (ΔKth) of the SB interface was significantly greater (p≤0.01) than that of the SBMP, whereas the ΔKth of the interfaces was more than twice that of the parent adhesives. SIGNIFICANCE Collagen fibril reinforcement of the resin adhesive is essential to the fatigue crack growth resistance of resin-dentin bonds. Resin tags that are not well hybridized into the surrounding intertubular dentin and/or poor collagen integrity are detrimental to the bonded interface durability.
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Affiliation(s)
- Zihou Zhang
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Dylan Beitzel
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Mustafa Mutluay
- Adhesive Dentistry Research Group, Department of Cariology, Institute of Dentistry, University of Turku, Turku, Finland
| | - Franklin R Tay
- Department of Oral Biology, College of Dental Medicine, Georgia Regents University, Augusta, GA, USA; Department of Endodontics, College of Dental Medicine, Georgia Regents University, Augusta, GA, USA
| | - David H Pashley
- Department of Oral Biology, College of Dental Medicine, Georgia Regents University, Augusta, GA, USA
| | - Dwayne Arola
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA; Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, WA, USA.
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Awada A, Nathanson D. Mechanical properties of resin-ceramic CAD/CAM restorative materials. J Prosthet Dent 2015; 114:587-93. [PMID: 26141648 DOI: 10.1016/j.prosdent.2015.04.016] [Citation(s) in RCA: 257] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 04/21/2015] [Accepted: 04/22/2015] [Indexed: 11/28/2022]
Abstract
STATEMENT OF PROBLEM The recent development of polymer-based computer-aided design and computer-aided manufactured (CAD/CAM) milling blocks and the limited availability of independent studies on these materials make it pertinent to evaluate their properties and identify potential strengths and limitations. PURPOSE The purpose of this in vitro study was to determine and compare mechanical properties (flexural strength, flexural modulus, modulus of resilience) and compare the margin edge quality of recently introduced polymer-based CAD/CAM materials with some of their commercially available composite resin and ceramic counterparts. MATERIAL AND METHODS The materials studied were Lava Ultimate Restorative (LVU; 3M ESPE), Enamic (ENA; Vita Zahnfabrik), Cerasmart (CES; GC Dental Products), IPS Empress CAD (EMP; Ivoclar Vivadent AG), Vitablocs Mark II (VM2; Vita Zahnfabrik), and Paradigm MZ100 Block (MZ1; 3M ESPE). Polished 4×1×13.5 mm bars (n=25) were prepared from standard-sized milling blocks of each tested material. The bars were subjected to a 3-point flexural test on a 10-mm span with a crosshead speed of 0.5 mm/min. In addition, 42 conventional monolithic crowns (7 per material) were milled. Margin edge quality was observed by means of macrophotography and optical microscopy, providing a qualitative visual assessment and a measurement of existing roughness. The results were analyzed by ANOVA followed by the Tukey HSD test (α=.05). RESULTS The mean flexural strength of the tested materials ranged from 105 ±9 MPa (VM2) to 219 ±20 MPa (CES). The mean flexural modulus ranged from 8 ±0.25 GPa (CES) to 32 ±1.9 GPa (EMP). The mean modulus of resilience ranged from 0.21 ±0.02 MPa (VM2) to 3.07 ±0.45 MPa (CES). The qualitative assessment of margin edge roughness revealed visible differences among the tested materials, with mean roughness measurements ranging from 60 ±16 μm (CES) to 190 ±15 μm (EMP). The material factor had a significant effect on the mean flexural strength (P<.001), flexural modulus (P<.001), modulus of resilience (P<.001), and margin edge roughness (P<.001) of the tested specimens. CONCLUSIONS The new-generation polymer-based materials tested in this study exhibited significantly higher flexural strength and modulus of resilience, along with lower flexural modulus values compared with the tested ceramic or hybrid materials. Crowns milled from the new resin-based blocks seemed to exhibit visibly smoother margins compared with the ceramic materials studied.
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Affiliation(s)
- Abdallah Awada
- Assistant Professor and Director, Implant Prosthodontics Fellowship Program, Department of Prosthodontics, Louisiana State University School of Dentistry, New Orleans, La.
| | - Dan Nathanson
- Professor and Chair, Department of Restorative Sciences and Biomaterials, Boston University Henry M. Goldman School of Dental Medicine, Boston, Mass
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Orrego S, Romberg E, Arola D. Synergistic degradation of dentin by cyclic stress and buffer agitation. J Mech Behav Biomed Mater 2015; 44:121-32. [PMID: 25637823 PMCID: PMC4499057 DOI: 10.1016/j.jmbbm.2015.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Revised: 01/05/2015] [Accepted: 01/05/2015] [Indexed: 11/30/2022]
Abstract
Secondary caries and non-carious lesions develop in regions of stress concentrations and oral fluid movement. The objective of this study was to evaluate the influence of cyclic stress and fluid movement on material loss and subsurface degradation of dentin within an acidic environment. Rectangular specimens of radicular dentin were prepared from caries-free unrestored 3rd molars. Two groups were subjected to cyclic cantilever loading within a lactic acid solution (pH = 5) to achieve compressive stresses on the inner (pulpal) or outer sides of the specimens. Two additional groups were evaluated in the same solution, one subjected to movement only (no stress) and the second held stagnant (control: no stress or movement). Exterior material loss profiles and subsurface degradation were quantified on the two sides of the specimens. Results showed that under cyclic stress material loss was significantly greater (p ≤ 0.0005) on the pulpal side than on the outer side and significantly greater (p ≤ 0.05) under compression than tension. However, movement only caused significantly greater material loss (p ≤ 0.0005) than cyclic stress. Subsurface degradation was greatest at the location of highest stress, but was not influenced by stress state or movement.
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Affiliation(s)
- Santiago Orrego
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Elaine Romberg
- Department of Endodontics, Prosthodontics, and Operative Dentistry, Dental School, University of Maryland, Baltimore, MD, USA
| | - Dwayne Arola
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA; Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, WA, USA.
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Wang W, Roubier N, Puel G, Allain JM, Infante IC, Attal JP, Vennat E. A New Method Combining Finite Element Analysis and Digital Image Correlation to Assess Macroscopic Mechanical Properties of Dentin. MATERIALS 2015; 8:535-550. [PMID: 28787955 PMCID: PMC5455261 DOI: 10.3390/ma8020535] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 01/19/2015] [Accepted: 01/27/2015] [Indexed: 11/30/2022]
Abstract
A literature review points out a large discrepancy in the results of the mechanical tests on dentin that can be explained by stress and strain assessment during the tests. Errors in these assessments during mechanical tests can lead to inaccurate estimation of the mechanical properties of the tested material. On top of that, using the beam theory to analyze the bending test for thick specimens will increase these experimental errors. After summarizing the results of mechanical tests on dentin in the literature, we focus on bending tests and compare the stress assessment obtained by finite element analysis (FEA) and by beam theory application. We show that the difference between the two methods can be quite large in some cases, leading us to prefer the use of FEA to assess stresses. We then propose a new method based on coupling finite element analysis and digital image correlation (DIC) to more accurately evaluate stress distributions, strain distributions and elastic modulus in the case of a three-point bending test. To illustrate and prove the feasibility of the method, it is applied on a dentinal sample so that mean elastic modulus and maximum tensile stress are obtained (11.9 GPa and 143.9 MPa). Note that the main purpose of this study is to focus on the method itself, and not to provide new mechanical values for dentin. When used in standard mechanical testing of dentin, this kind of method should help to narrow the range of obtained mechanical properties values.
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Affiliation(s)
- Wenlong Wang
- MSSMat, UMR 8579 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, 92295 Chatenay-Malabry Cedex, France.
| | - Nicolas Roubier
- MSSMat, UMR 8579 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, 92295 Chatenay-Malabry Cedex, France.
| | - Guillaume Puel
- MSSMat, UMR 8579 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, 92295 Chatenay-Malabry Cedex, France.
| | - Jean-Marc Allain
- LMS, UMR 7649 CNRS-Ecole Polytechnique, 91128 Palaiseau Cedex, France.
| | - Ingrid C Infante
- SPMS, UMR 8580 CNRS-Ecole Centrale Paris, Grande Voie des Vignes,92295 Chatenay-Malabry Cedex, France.
| | - Jean-Pierre Attal
- URB2i, EA4462 Université Paris Descartes, 1 rue M. Arnoux, 92120 Montrouge, France.
| | - Elsa Vennat
- MSSMat, UMR 8579 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, 92295 Chatenay-Malabry Cedex, France.
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Majd B, Majd H, Porter JA, Romberg E, Arola D. Degradation in the fatigue strength of dentin by diamond bur preparations: Importance of cutting direction. J Biomed Mater Res B Appl Biomater 2015; 104:39-49. [PMID: 25611951 DOI: 10.1002/jbm.b.33348] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 11/16/2014] [Accepted: 12/02/2014] [Indexed: 11/12/2022]
Abstract
The objectives of this investigation were to evaluate the degradation in fatigue strength of dentin by diamond bur preparations and to identify the importance of cutting direction. Three groups of coronal dentin specimens were prepared from unrestored third molars, including a flaw free "control," and two groups that received a diamond bur cutting treatment performed parallel or perpendicular to the specimen length. The specimens were subjected to static or cyclic flexural loading to failure and the results were compared with data for carbide bur cutting. Under static loading diamond bur cutting resulted in significantly lower flexure strength (p ≤ 0.05) than the control for both cutting directions (from 154 to ∼124 MPa). However, there was no significant difference in the strength between the control and carbide bur treated specimens. Similarly, the fatigue strength of the diamond bur treated specimens was significantly lower (p ≤ 0.0001) than that of the control for both cutting directions. Cutting in the perpendicular direction resulted in nearly 60% reduction to the endurance limit (from 44 to 19 MPa). Based on the results, diamond bur cutting of cavity preparations causes a reduction in the fatigue strength of dentin, regardless of the cutting direction. To maintain the durability of dentin, cavity preparations introduced using diamond burs must be performed with appropriate cutting direction and followed by a finishing pass.
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Affiliation(s)
- B Majd
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, Maryland
| | - H Majd
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, Maryland
| | - J A Porter
- Department of Endodontics, Prosthodontics and Operative Dentistry, Dental School, University of Maryland, Baltimore, Maryland
| | - E Romberg
- Department of Endodontics, Prosthodontics and Operative Dentistry, Dental School, University of Maryland, Baltimore, Maryland
| | - D Arola
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington.,Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Washington
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Importance of age on the dynamic mechanical behavior of intertubular and peritubular dentin. J Mech Behav Biomed Mater 2014; 42:229-42. [PMID: 25498296 DOI: 10.1016/j.jmbbm.2014.11.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 11/20/2014] [Accepted: 11/22/2014] [Indexed: 11/23/2022]
Abstract
An experimental evaluation of human coronal dentin was performed using nanoscopic dynamic mechanical analysis (nanoDMA). The primary objectives were to quantify any unique changes in mechanical behavior of intertubular and peritubular dentin with age, and to evaluate the microstructure and mechanical behavior of the mineral deposited within the lumens. Specimens of coronal dentin were evaluated by nanoDMA using single indents and in scanning mode via scanning probe microscopy. Results showed that there were no significant differences in the storage modulus or complex modulus between the two age groups (18-25 versus 54-83 yrs) for either the intertubular or peritubular tissue. However, there were significant differences in the dampening behavior between the young and old dentin, as represented in the loss modulus and tanδ responses. For both the intertubular and peritubular components, the capacity for dampening was significantly lower in the old group. Scanning based nanoDMA showed that the tubules of old dentin exhibit a gradient in elastic behavior, with decrease in elastic modulus from the cuff to the center of tubules filled with newly deposited mineral.
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20
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Degradation in the fatigue strength of dentin by cutting, etching and adhesive bonding. Dent Mater 2014; 30:1061-72. [PMID: 24985539 DOI: 10.1016/j.dental.2014.06.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 06/07/2014] [Accepted: 06/09/2014] [Indexed: 11/20/2022]
Abstract
UNLABELLED The processes involved in placing resin composite restorations may degrade the fatigue strength of dentin and increase the likelihood of fractures in restored teeth. OBJECTIVE The objective of this study was to evaluate the relative changes in strength and fatigue behavior of dentin caused by bur preparation, etching and resin bonding procedures using a 3-step system. METHODS Specimens of dentin were prepared from the crowns of unrestored 3rd molars and subjected to either quasi-static or cyclic flexural loading to failure. Four treated groups were prepared including dentin beams subjected to a bur treatment only with a conventional straight-sided bur, or etching treatment only. An additional treated group received both bur and etching treatments, and the last was treated by bur treatment and etching, followed by application of a commercial resin adhesive. The control group consisted of "as sectioned" dentin specimens. RESULTS Under quasi-static loading to failure there was no significant difference between the strength of the control group and treated groups. Dentin beams receiving only etching or bur cutting treatments exhibited fatigue strengths that were significantly lower (p≤0.0001) than the control; there was no significant difference in the fatigue resistance of these two groups. Similarly, the dentin receiving bur and etching treatments exhibited significantly lower (p≤0.0001) fatigue strength than that of the control, regardless of whether an adhesive was applied. SIGNIFICANCE The individual steps involved in the placement of bonded resin composite restorations significantly decrease the fatigue strength of dentin, and application of a bonding agent does not increase the fatigue strength of dentin.
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Ivancik J, Naranjo M, Correa S, Ossa A, Tay FR, Pashley DH, Arola D. Differences in the microstructure and fatigue properties of dentine between residents of North and South America. Arch Oral Biol 2014; 59:1001-12. [PMID: 24960115 DOI: 10.1016/j.archoralbio.2014.05.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2014] [Revised: 05/08/2014] [Accepted: 05/30/2014] [Indexed: 11/25/2022]
Abstract
UNLABELLED Spatial variations in the microstructure of dentine contribute to its mechanical behaviour. OBJECTIVE The objective of this investigation was to compare the microstructure and fatigue behaviour of dentine from donors of two different countries. METHODS Caries-free third molars were obtained from dental practices in Colombia, South America and the US to assemble two age-matched samples. The microstructure of the coronal dentine was evaluated at three characteristic depths (i.e. deep, middle and superficial dentine) using scanning electron microscopy and image processing techniques. The mechanical behaviour of dentine in these three regions was evaluated by the fatigue crack growth resistance. Cyclic crack growth was achieved in-plane with the dentine tubules and the fatigue crack growth behaviour was characterized in terms of the stress intensity threshold and the Paris Law parameters. RESULTS There was no difference in the tubule density between the dentine of patients from the two countries. However, there were significant differences (p≤0.05) in the tubule lumen diameters between the two groups in the deep and peripheral regions. In regards to the fatigue resistance, there was a significant increase (p≤0.05) in threshold stress intensity range, and a significant decrease in fatigue crack growth coefficient with increasing distance from the pulp in teeth from the US donors. In contrast, these properties were independent of location for the dentine of teeth from the Colombian donors. CONCLUSIONS The microstructure of dentine and its mechanical behaviour appear to be a function of patient background, which may include environmental factors and/or ethnicity.
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Affiliation(s)
- J Ivancik
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD, USA
| | - M Naranjo
- Bioengineering Research Group (GIB), Prosthodontic Department, CES University, Medellín, Colombia
| | - S Correa
- Bioengineering Research Group (GIB), Product Design Engineering Department, EAFIT University, Medellín, Colombia
| | - A Ossa
- School of Engineering, EAFIT University, Medellín, Colombia
| | - F R Tay
- Department of Endodontics, School of Dentistry, Georgia Regents University, Augusta, GA, USA
| | - D H Pashley
- Department of Oral Biology, School of Dentistry, Georgia Regents University, Augusta, GA, USA
| | - D Arola
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA; Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, WA, USA.
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Eltit F, Ebacher V, Wang R. Inelastic deformation and microcracking process in human dentin. J Struct Biol 2013; 183:141-8. [DOI: 10.1016/j.jsb.2013.04.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 03/16/2013] [Accepted: 04/01/2013] [Indexed: 11/28/2022]
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Ivancik J, Arola DD. The importance of microstructural variations on the fracture toughness of human dentin. Biomaterials 2012; 34:864-74. [PMID: 23131531 DOI: 10.1016/j.biomaterials.2012.10.032] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 10/10/2012] [Indexed: 11/20/2022]
Abstract
The crack growth resistance of human dentin was characterized as a function of relative distance from the DEJ and the corresponding microstructure. Compact tension specimens were prepared from the coronal dentin of caries-free 3rd molars. The specimens were sectioned from either the outer, middle or inner dentin. Stable crack extension was achieved under Mode I quasi-static loading, with the crack oriented in-plane with the tubules, and the crack growth resistance was characterized in terms of the initiation (K(o)), growth (K(g)) and plateau (K(p)) toughness. A hybrid approach was also used to quantify the contribution of dominant mechanisms to the overall toughness. Results showed that human dentin exhibits increasing crack growth resistance with crack extension in all regions, and that the fracture toughness of inner dentin (2.2 ± 0.5 MPa·m(0.5)) was significantly lower than that of middle (2.7 ± 0.2 MPa·m(0.5)) and outer regions (3.4 ± 0.3 MPa·m(0.5)). Extrinsic toughening, composed mostly of crack bridging, was estimated to cause an average increase in the fracture energy of 26% in all three regions. Based on these findings, dental restorations extended into deep dentin are much more likely to cause tooth fracture due to the greater potential for introduction of flaws and decrease in fracture toughness with depth.
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Affiliation(s)
- Juliana Ivancik
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD 21250, USA
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Majd H, Viray J, Porter JA, Romberg E, Arola D. Degradation in the fatigue resistance of dentin by bur and abrasive air-jet preparations. J Dent Res 2012; 91:894-9. [PMID: 22851284 DOI: 10.1177/0022034512455800] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The objective of this investigation was to distinguish whether the instruments commonly used for cutting dentin cause degradation in strength or fatigue behavior. Beams of coronal dentin were obtained from unrestored 3(rd) molars and subjected to either quasi-static or cyclic flexural loading to failure. The surfaces of selected beams were treated with a conventional straight-sided bur or with an abrasive air jet laden with glass particles. Under monotonic loading, there was no difference in the strength or Weibull parameters obtained for the control or treated beams. However, the fatigue strength of dentin receiving bur and air-jet treatments was significantly lower (p ≤ 0.0001) than that of the control. The bur treatment resulted in the largest overall degree of degradation, with nearly 40% reduction in the endurance limit and even more substantial decrease in the fatigue life. The methods currently used for cavity preparations substantially degrade the durability of dentin.
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Affiliation(s)
- H Majd
- Department of Mechanical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
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Arola D, Ivancik J, Majd H, Fouad A, Bajaj D, Zhang XY, Eidelman N. Microstructure and mechanical behavior of radicular and coronal dentin. ACTA ACUST UNITED AC 2012. [DOI: 10.1111/j.1601-1546.2012.00267.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Ivancik J, Majd H, Bajaj D, Romberg E, Arola D. Contributions of aging to the fatigue crack growth resistance of human dentin. Acta Biomater 2012; 8:2737-46. [PMID: 22484693 DOI: 10.1016/j.actbio.2012.03.046] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 03/21/2012] [Accepted: 03/28/2012] [Indexed: 10/28/2022]
Abstract
An evaluation of the fatigue crack resistance of human dentin was conducted to identify the degree of degradation that arises with aging and the dependency on tubule orientation. Fatigue crack growth was achieved in specimens of coronal dentin through application of Mode I cyclic loading and over clinically relevant lengths (0 ≤ a ≤ 2 mm). The study considered two directions of cyclic crack growth in which the crack was either in-plane (0°) or perpendicular (90°) to the dentin tubules. Results showed that regardless of tubule orientation, aging of dentin is accompanied by a significant reduction in the resistance to the initiation of fatigue crack growth, as well as a significant increase in the rate of incremental extension. Perpendicular to the tubules, the fatigue crack exponent increased significantly (from m=14.2 ± 1.5 to 24.1 ± 5.0), suggesting an increase in brittleness of the tissue with age. For cracks extending in-plane with the tubules, the fatigue crack growth exponent does not change significantly with patient age (from m=25.4 ± 3.03 to 22.9 ± 5.3), but there is a significant increase in the incremental crack growth rate. Regardless of age, coronal dentin exhibits the lowest resistance to fatigue crack growth perpendicular to the tubules. While there are changes in the cyclic crack growth rate and mechanisms of cyclic extension with aging, this tissue maintains its anisotropy.
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Assessment of Vickers hardness, microstructure, and surface roughness of dentin after initial dissolution by acidulated phosphate-fluoride. PEDIATRIC DENTAL JOURNAL 2012. [DOI: 10.1016/s0917-2394(12)70254-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Ryou H, Romberg E, Pashley DH, Tay FR, Arola D. Nanoscopic dynamic mechanical properties of intertubular and peritubular dentin. J Mech Behav Biomed Mater 2011; 7:3-16. [PMID: 22340680 DOI: 10.1016/j.jmbbm.2011.08.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 08/11/2011] [Accepted: 08/17/2011] [Indexed: 10/17/2022]
Abstract
An experimental evaluation of intertubular and peritubular dentin was performed using nanoindentation and Dynamic Mechanical Analysis (DMA). The objective of the investigation was to evaluate the differences in dynamic mechanical behavior of these two constituents and to assess whether their response is frequency dependent. Specimens of hydrated coronal dentin were evaluated by DMA using single indents over a range of parametric conditions and using scanning probe microscopy. The complex (E∗), storage (E') and loss moduli (E″) of the intertubular and peritubular dentin were evaluated as a function of the dynamic loading frequency and static load in the fully hydrated condition. The mean complex E∗ (19.6 GPa) and storage E' (19.2 GPa) moduli of the intertubular dentin were significantly lower than those for peritubular dentin (E∗ = 31.1 GPa, p < 0.05; E' = 30.3 GPa, p < 0.05). There was no significant influence of dynamic loading frequency on these measures. Although there was no significant difference in the loss modulus (E″) between the two materials (p > 0.05), both constituents exhibited a significant increase in E″ with dynamic load frequency and reduction in the quasi-static component of indentation load. The largest difference in dynamic behavior of the two tissues was noted at small quasi-static indentation loads and the highest frequency.
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Affiliation(s)
- Heonjune Ryou
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD 21250, USA
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