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PURPOSE: The purpose of present study was to investigate fracture strength and mode of failure of endodontically treated teeth restored with metal cast post-core system, prefabricated fiber post system, and newly introduced polyetherketoneketone (PEKK) post-core system. MATERIALS AND METHODS: A total of 21 mandibular premolar were randomly grouped into 3 groups of 7 each according to the post material. Group A was for metal cast post core; Group B for prefabricated glass fiber post and resin core; and Group C for milled PEKK post cores. All specimens were restored with metal crown. The fracture strength of each specimen was measured by applying a static load of 135-degree to the tooth at 2 mm/min crosshead speed using a universal testing machine. After the fracture strength measurement, the mode of failure was observed. The results were analyzed using Kruscal-Wallis test and post hoc Mann-Whitney U test at confidence interval α = .05. RESULTS: Fracture resistance of PEKK post core was lower than those of cast metal post and fiber reinforced post with composite resin core. In the aspect of fracture mode most of the root fracture occurred in the metal post core, whereas the post detachment occurred mainly in the fiber reinforced post. In the case of PEKK post core, teeth and post were fractured together. CONCLUSION: It is necessary to select appropriate materials of post for extensively damaged teeth restoration and clinical application of the PEKK post seems to require more research on improvement of strength.
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Bicuspid , Crowns , Glass , Tooth , Tooth, NonvitalABSTRACT
Objective@#To explore the best indication for veneers and to improve the repair success rate by investigating the effects of different types of dentin exposure on the shear bond strength of cast porcelain veneers with two new veneer bonding systems.@*Methods@#Bonding interfaces with 0%, 25%, 50%, 75% and 100% dentin exposure were designed and fabricated. The bonding interfaces were divided into groups A, B, C, D and E. Sixty 4-mm x 4-mm x 2-mm (length x width x thickness) ceramic specimens were bonded by using two bonding systems, The VN-A, VN-B, VN-C, VN-D and VN-E groups were bonded with Variolink bonding system, and the PF-A, PF-B, PF-C, PF-D and PF-E were bonded with Panavia F bonding system (six specimens per group). The bonded specimens were stored in a distilled water bath at (37 + 1)℃ for 24 hours. The fracture load was tested by a universal testing machine, and the fracture type was observed by scanning electron microscopy.@*Results @#The VN-A (25.14 ± 3.40 MPa), VN-B (22.54 ± 4.48 MPa), VN-C (19.59 ± 2.21 MPa), PF-A (20.61 ± 2.42 MPa), PF-B (18.08 ± 4.11 MPa), PF-C (17.06 ± 2.29 MPa) groups’ shear bond strengths were above 17 MPa. The VN-A group had the highest shear bond strength value. There was no statistically significant difference in bond strength between the VN-A group and the VN-B and VN-C groups (P > 0.05) or the PF-A and PF-B groups (P > 0.05); however, the differences between VN-A and the VN-D and VN-E groups (P < 0.05) and between PF-A and the PF-C and PF-D and PF-E groups (P < 0.05) were statistically significant. The differences between the VN-A group and PF-A group (P < 0.05) were statistically significant. The fracture modes of the VN-A, PF-A, VN-B, PF-B, and VN-C groups mainly included resin cement cohesive failure and mixed failure; the VN-D, VN-E, PF-C, PF-D and PF-E groups were dominated by interface failure and mixed failure.@*Conclusion@#When the dentin exposure is greater than 50%, the shear bond strength value of the veneer was significantly affected. To obtain a better clinical effect, the dentin exposure rate should be less than 25%.
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Objective: To investigate the effects of three different types of dentin protective membranes (HyC, SBU and S3) on dentin adhesive properties. Methods: Fresh isolated molar teeth were collected, and smooth dentin surface was obtained after embedding, cutting and polishing. In the control group, dentin protective membrane was not applied, while the remaining three groups were coated with three different types of dentin protective membranes, and the preformed resin prosthesis was cemented with resin cement. A strip dentin-resin sample with a cross-sectional area of 0.9 mm×0.9 mm was obtained by a precision cutting machine. The tensile force was tested at the loading speed of 0.5 mm/min with a universal testing machine until the dentin-resin strip was broken. The maximum tensile force during the loading process was automatically recorded by the computer, and the microstructure and fracture mode of the section were observed by a scanning electron microscope. Results: After coating dentin protective membranes, the tensile strength of each experimental group was significantly increased compared with that of the control group (P<0.05), and the tensile strength of group HyC was significantly smaller than that of group SBU and group S3 (P<0.05). The tensile fracture mode shown by microstructure observation was mainly interfacial failure. Conclusion: Different types of dentin protective membranes can increase the adhesive properties between dentin and resin prosthesis. SBU and S3 can improve the adhesion strength more significantly than HyC.
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Objective:To compare the bonding strength of 3M Adper Easy One(3AEO),Clearfil S3 Bond(CSB)and Super-Bond C&B(SBCB)in vertical tooth fracture mode.Methods:30 freshly extracted human molars were randomly assigned to three groups(n =10).The teeth were cut along the long axis with low speed cutting machine and were prepared into a unified model of the vertical tooth fracture.The three adhesives were respectively used to adjoin the surface of the fractured teeth.The samples were subjected to thermal cycling for 500 cycles,stored in distilled water at 37 ℃ for 24 h.Then the pillar-like specimens with the bonding area of 1.0 mm × 1.0 mm were prepared.The microtensile bond strength was measured and the fracture mode was observed.Results:The bond strength (MPa)of 3AEO,CSB and SBCB was 18.57 ±4.98,16.93 ±4.70 and 22.75 ±5.18 respectively(P 0.05).Conclusion:The surface bonding of Super-Bond C&B in tooth fracture is stronger than 3MAdper Easy One and Clearfil S3 Bond.
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Objective:To observe the effect of storage period of three experimental dentin self-etching primers on the shear bond strength.Methods:Three experimental primers with 2-hydroxyethyl methacrylate (HEMA)or N-methacryloyl glycine (NMGly)as a hydrophilic monomer and 1 0-methacryloxydecyl dihydrogen phosphate(MDP)or N-methacryloyl-2-aminoethylphosphonic acid (NMEP) as an acid monomer,were designed.Immediately after preparation of the samples of MDP-HEMA,MDP-NMGly and NMEP-NMGly, the primers were stored at 40 ℃for 0,6 and 1 4 weeks.At the end of each storage period,the shear bond strength of resin to dentin(n=1 4)and the pH value of the primers were measured.Results:After storage at 40 ℃ for 1 4 weeks,the shear bond strength of MDP-HEMA decreased from (1 7.61 ±1 .56)MPa to (7.53 ±1 .76)MPa;however the bond strenth of MDP-NMGly and NMEP-NMGly did not decrease;most of the specimens of MDP-HEMA and MDP-NMGly exhibited an interfacial failure of the resin from the dentin sur-face;however NMEP-NMGly exhibited a cohesional failure of the dentin and/or resin.The SEMimages showed a separation of resin and dentin of MDP-HEMA and MDP-NMGly had storaged at 40 ℃for 1 4 weeks;while the interface of NMEP-NMGly did not change.Con-clusion:The NMEP-NMGly primer has noticeably higher hydrolytic stability than the MDP-HEMA and MDP-NMGly primers.
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Objective To explore the influence of different lengths and contents of glass-fiber post on the fracture resistance of teeth, and to investigate the optimal length and content of glass-fiber post used for restorative treatment. Meth-ods Forty-two intact single canal mandibular premolars were collected from orthodontic patients and were divided into three experimental groups (A, B and C). All the teeth were endodontically treated after cut off the crowns from the 2 mm above cemento-enamel junction. The post lengths were10 mm in A group, 8 mm in B group, and 6 mm in C group.There were two subgroups for each experimental group (A1, A2, B1, B2, C1, C2 ), 7 teeth for each subgroup.The 42%glass fiber post was used in A1, B1 and C1 groups. The 75%glass fiber post was used in A2, B2 and C2 groups. All of groups were restored with resin cores and metal crowns. The fracture resistance was measured with universal testing machine and recorded the root frac-ture pressure data and the mode of all the teeth. Results The fracture resistance was significantly higher in group A than that of group B and group C (P<0.05), and the fracture resistance was significantly higher in group B than that of group C (P<0.05). The fracture resistance was significantly higher for 75%glass fiber post than that of 42%glass fiber post (P<0.05). Conclusion Within a certain range, the longer the length of glass fiber post, the greater the tooth fracture resistance. The fracture resistance of fiber content is better for 75%glass fiber post than that of 42%glass fiber post.
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Objective To analyze the compressive strength and fracture mode between four kinds of dental zirconia CAD/CAM ceramic materials by Hertzian contact test. Methods Four CAD/CAM ceramic materials including Cercon smart, Lava, Porcera, and CEREC 3 were selected. Six zirconia sectioned flat specimens were prepared in each group. The critical load and fracture load as well as the fracture mode for each specimen were analyzed with digital image correlation (DIC) technique. Results It was found that cracks were initiated at the middle level of the veneer below the contact zone and propagating along an arc curve into the core/veneer interface, which eventually caused the debonding of the core/veneer layers. For the four ceramic systems, there were no significant differences in the critical load（P＞0.05）, while there were significant differences in the fracture load（P＜0.05）. Conclusions The compressive strength of the four zirconia CAD/CAM ceramic materials could substantially meet the clinic requirement for oral functions regarding the maximum occlusal load. Crack initiation and complete fracture only occurred in the veneer, which indicated that the strength of the veneer should be further reinforced.
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This study investigated the hypothesis that the dentin bond strength of self-etching adhesive (SEA) might be improved by applying additional layer of bonding resin that might alleviate the pH difference between the SEA and the restorative composite resin. Two SEAs were used in this study; Experimental SEA (Exp, pH: 1.96) and Adper Prompt (AP, 3M ESPE, USA, pH: 1.0). In the control groups, they were applied with two sequential coats. In the experimental groups, after applying the first coat of assigned SEAs, the D/E bonding resin of All-Bond 2 (Bisco Inc., USA, pH: 6.9) was applied as the intermediate adhesive. Z-250 (3M ESPE, USA) composite resin was built-up in order to prepare hourglass-shaped specimens. The microtensile bond strength (MTBS) was measured and the effect of the intermediate layer on the bond strength was analyzed for each SEA using t-test. The fracture mode of each specimen was inspected using stereomicroscope and Field Emission Scanning Electron Microscope (FE-SEM). When D/E bonding resin was applied as the second coat, MTBS was significantly higher than that of the control groups. The incidence of the failure between the adhesive and the composite or between the adhesive and dentin decreased and that of the failure within the adhesive layer increased. According to the results, applying the bonding resin of neutral pH can increase the bond strength of SEAs by alleviating the difference in acidity between the SEA and restorative composite resin.
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Adhesives , Dentin , Hydrogen-Ion Concentration , Incidence , Oceans and SeasABSTRACT
OBJECTIVES: In the unique metal iris method, the developing interfacial gap at the cavity floor resulting from the cavity wall property during polymerizing composite resin might affect the nominal shear bond strength values. The aim of this study is to evaluate that the iris method reduces the cohesive failure in the substrates and the cavity wall property effects on the shear bond strength tests using iris method. MATERIALS AND METHODS: The occlusal dentin of 64 extracted human molars were randomly divided into 4 groups to simulate two different levels of cavity wall property (metal and dentin iris) and two different materials (ONE-STEP(R) and ALL-BOND(R) 2) for each wall property. After positioning the iris on the dentin surface, composite resin was packed and light-cured. After 24 hours the shear bond strength was measured at a crosshead speed of 0.5 mm/min. Fracture analysis was performed using a microscope and SEM. The data was analyzed statistically by a two-way ANOVA and t-test. RESULTS: The shear bond strength with metal iris was significant higher than those with dentin iris (p = 0.034). Using ONE-STEP(R), the shear bond strength with metal iris was significant higher than those with dentin iris (p = 0.005), but not in ALL-BOND(R) 2 (p = 0.774). The incidence of cohesive failure was very lower than other shear bond strength tests that did not use iris method. CONCLUSIONS: The iris method may significantly reduce the cohesive failures in the substrates. According to the bonding agent systems, the shear bond strength was affected by the cavity wall property.
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Humans , Dentin , Incidence , Iris , Molar , PolymersABSTRACT
The purpose of this study was to evaluate the effect of oral environment on the strength of resin bracket wings by comparing fracture mode according to water immersion and thermocycling. Seventy-five resin brackets(Spirit MB, Ormco, California) were divided into three groups and treated for six months as follows; (1) untreated, (2) water immersion in distilled water at 37degrees C, (3) water immersion in distilled water at 37degrees C with total 2,100 times of thermocyeling taken 350 times each month. Fracture mode of the wing was tested on universal testing machine. In addition to resin brackets, 25 metal brackets were used as controls. Through the statistical analyses, following results were obtained. 1. Resin bracket wings showed significantly lower fracture strength than metal brackets(p<0.001). 2. Water immersion and water immersion with thermocycling groups showed significantly lower fracture strength than open air condition group(p<0.001). 3. Water immersion with thermocycling group showed significantly lower fracture strength than water immersion group(p<0.001). The above results sugg est that the mechanical property of resin bracket wing may be influenced by oral environment and further research is needed to improve the strength of the wing in the resin bracket.