All-ceramic premolar guiding plate retains resin-bonded fixed partial dentures / 华西口腔医学杂志

OBJECTIVE@#This study aims to investigate the fracture resistance and short-term restorative effects of resin-bonded fixed partial dentures (RBFPDs) made from heat-pressed lithium-disilicate-based glass-ceramic (IPS e.max press) and zirconia ceramic (WIELAND) and retained by all-ceramic guiding plates when used to restore missing mandibular second premolars.@*METHODS@#A total of 64 human mandibular first premolars and first molars were prepared as abutments, then were randomly divided into 4 groups (n=8): E0, heat-pressed ceramic RBFPDs, no cyclic loading; E1, heat-pressed ceramic RBFPDs exposed to 300 000 cycles of dynamic loading; W0, zirconia ceramic RBFPDs, no cyclic loading; and W1, zirconia ceramic RBFPDs exposed to 300 000 cycles of dynamic loading. Fracture strength was tested in a universal testing machine.@*RESULTS@#The medians of fracture strength were 1 242.85 N±260.11 N (E0), 1 650.85 N±206.77 N (W0), 1 062.60 N±179.98 N (E1), and 1 167.61 N±265.50 N (W1). Statistical analysis showed that all the groups exhibited significantly higher fracture strength compared with the maximum bite force in the premolar region (360 N; P0.05). Significant statistical differences were found between the zirconia ceramic groups (W0 and W1, P0.05) after dynamic loading.@*CONCLUSIONS@#The RBFPDs retained by all-ceramic guiding plates exhibited promising fracture properties and optimal short-term restorative effects when used to restore missing mandibular second premolars.

The effect of coloring liquid dipping time on the fracture load and color of zirconia ceramics

PURPOSE: The aims of the study were to evaluate the fracture load of zirconia core material after dipping in coloring liquid at different time intervals and to compare the color of dipped blocks with that of prefabricated shaded blocks. MATERIALS AND METHODS: 3-unit bridge frameworks were designed digitally. Sixty frameworks were fabricated using uncolored zirconia blocks by CAD/CAM and divided into 4 groups randomly (n = 15). Group 2 (G2) was subjected to coloring liquids for 2 minutes, Group 4 (G4) for 4 minutes, and Group 6 (G6) for 6 minutes. CFS group was not subjected to any coloring procedure. After coloring, color differences between the test groups and a prefabricated shaded zirconia group (CPZ, n = 15) were evaluated by using a spectrophotometer. Fracture test was conducted immediately after shade evaluation with a Testometric test device at a cross-head speed of 1 mm/sec. Statistical analysis for evaluating color and fracture load was performed by using one way ANOVA followed by Tukey HSD test (P ≤ .05). Weibull analysis was conducted for distribution of fracture load. RESULTS: There was no difference in terms of fracture load and color between CFS (1176.681 N) and G2 (985.638 N) group and between CPZ (81.340) and G2 (81.140) group, respectively. Fracture load values of G4 (779.340 N) and G6 (935.491 N) groups were statistically significantly lower than that of CFS group (P ≤ .005). The color values of G4 (79.340) and G6 (79.673) groups were statistically different than that of CPZ group (P ≤ .005). CONCLUSION: Prolonged immersion of zirconia in coloring liquid not only negatively affected the fracture load of the zirconia being tested in the current study but also deteriorated the desired shade of the restoration.

Fracture load and survival of anatomically representative monolithic lithium disilicate crowns with reduced tooth preparation and ceramic thickness

PURPOSE: To investigate the effect of reducing tooth preparation and ceramic thickness on fracture resistance of lithium disilicate crowns. MATERIALS AND METHODS: Specimen preparation included a standard complete crown preparation of a typodont mandibular left first molar with an occlusal reduction of 2 mm, proximal/axial wall reduction of 1.5 mm, and 1.0 mm deep chamfer (Group A). Another typodont mandibular first molar was prepared with less tooth reduction: 1 mm occlusal and proximal/axial wall reduction and 0.8 mm chamfer (Group B). Twenty crowns were milled from each preparation corresponding to control group (n=5) and conditioned group of simultaneous thermal and mechanical loading in aqueous environment (n=15). All crowns were then loaded until fracture to determine the fracture load. RESULTS: The mean (SD) fracture load values (in Newton) for Group A were 2340 (83) and 2149 (649), and for Group B, 1752 (134) and 1054 (249) without and with fatigue, respectively. Reducing tooth preparation thickness significantly decreased fracture load of the crowns at baseline and after fatigue application. After fatigue, the mean fracture load statistically significantly decreased (P .05) in Group A. CONCLUSION: Reducing the amount of tooth preparation by 0.5 mm on the occlusal and proximal/axial wall with a 0.8 mm chamfer significantly reduced fracture load of the restoration. Tooth reduction required for lithium disilicate crowns is a crucial factor for a long-term successful application of this all-ceramic system.

Fracture load and fracture modes of prefabricated fiber post restoration in different tilted mandible premolars:A pilot study / 实用口腔医学杂志

80 extracted human mandible premolars were divided into 10 groups(n =8)based on the post with different tilted angles(0°, buccal 15°and 30°,ligual 15°and 30°).The samples in experiment group were restored with fiber post while in the control group with cast post.Then all the teeth were restored with cast crown and bonded by glass ionomer.Compressive load with the speed of 1.0 mm/min was ap-plied to the restored teeth with a universal material testing machine until failure and the fracture modes were observed.The fracture load of fi-ber post and cast post restoration with the same tilted angles was similar(P >0.05).The main fracture mode of the teeth in all groups was unfavorable tooth fracture.No significant interaction was observed(P =0.217)between the 2 kinds of post and angulation of tilted teeth.

Influence of preparation depths on the fracture load of customized zirconia abutments with titanium insert

PURPOSE: This study evaluated the fracture load of customized zirconia abutments with titanium insert according to preparation depths, with or without 5-year artificial aging. MATERIALS AND METHODS: Thirty-six identical lithium disilicate crowns (IPS e.max press) were fabricated to replace a maxillary right central incisor and cemented to the customized zirconia abutment with titanium insert on a 4.5x10 mm titanium fixture. Abutments were fabricated with 3 preparation depths (0.5 mm, 0.7 mm, and 0.9 mm). Half of the samples were then processed using thermocycling (temperature: 5-55degrees C, dwelling time: 120s) and chewing simulation (1,200,000 cycles, 49 N load). All specimens were classified into 6 groups depending on the preparation depth and artificial aging (non-artificial aging groups: N5, N7, N9; artificial aging groups: A5, A7, A9). Static load was applied at 135 degrees to the implant axis in a universal testing machine. Statistical analyses of the results were performed using 1-way ANOVA, 2-way ANOVA, independent t-test and multiple linear regression. RESULTS: The fracture loads were 539.28 +/- 63.11 N (N5), 406.56 +/- 28.94 N (N7), 366.66 +/- 30.19 N (N9), 392.61 +/- 50.57 N (A5), 317.94 +/- 30.05 N (A7), and 292.74 +/- 37.15 N (A9). The fracture load of group N5 was significantly higher than those of group N7 and N9 (P<.017). Consequently, the fracture load of group A5 was also significantly higher than those of group A7 and A9 (P<.05). After artificial aging, the fracture load was significantly decreased in all groups with various preparation depths (P<.05). CONCLUSION: The fracture load of a single anterior implant restored with lithium disilicate crown on zirconia abutment with titanium insert differed depending on the preparation depths. After 5-year artificial aging, the fracture loads of all preparation groups decreased significantly.

Influence of surface treatment and cyclic loading on the durability of repaired all-ceramic crowns

OBJECTIVE: This study investigated the durability of repaired all-ceramic crowns after cyclic loading. MATERIAL AND METHODS: Eighty In-ceram zirconia crowns were fabricated to restore prepared maxillary premolars. Resin cement was used for cementation of crowns. Palatal cusps were removed to simulate fracture of veneering porcelain and divided into 4 groups (n = 20). Fracture site was treated before repair as follows: roughening with diamond bur, (DB); air abrasion using 50 µm Al2O3, (AA) and silica coating using Cojet system followed by silane application, (SC). Control group (CG) 20 specimens were left without fracture. Palatal cusps were repaired using composite resin. Specimens were stored in water bath at 37ºC for one week. Ten specimens of each group were subjected to cyclic loading. Fracture load (N) was recorded for each specimen using a universal testing machine. Two-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) test (a=.05) were used for statistical analysis. RESULTS: There was statistically significant difference between control and tested groups, (p<0.001). Post Hoc analysis with the Tukey HSD test showed that cyclic loading fatigue significantly decreased means fracture load of control and test groups as follows (CG, 950.4±62.6 / 872.3±87.4, P = 0.0004), (DB, 624.2 ±38 / 425.5± 31.7, P <.001), (AA, 711.5 ±15.5 / 490 ± 25.2, p <0.001) and (SC, 788.7 ± 18.1 / 610.2 ± 25.2, P <.001), while silica coating and silane application significantly increased fracture load of repaired crowns (p<0.05). CONCLUSION: Repair of fractured In-ceram zirconia crowns after chairside treatment of the fracture site by silica coating and silane application could improve longevity of repaired In-ceram zirconia crowns.

Comparison of fracture strength and pattern of endodontically treated teeth restored with fiber posts and metal cast post / 대한치과보철학회지

PURPOSE: The purpose of this study is to compare the effect of two fiber post systems and one metal cast post system on the fracture strength and fracture pattern of crowned, endodontically treated teeth with 2 mm-height of the reamining tooth structure. MATERIALS AND METHODS: A total of 36 recently extracted sound human mandibular premolars were selected. Each tooth structure of the crown portion except 2mm-height of the one above the cementoenamel junction was removed. After being endodontically treated, they were randomly distributed into 3 groups: group 1, restored with quarts fiber post(D.T. Light-Post), group 2, with glass fiber post(FRC Postec), and group 3, metal cast post and core. All teeth were fully covered with nonprecious metal crowns. Each specimen was embedded in an acrylic resin block and then secured in a universal load-testing machine. A compressive load was applied at a 130 degree angle to the long axis of the tooth until fractured, at a crosshead speed 20mm/min. The highest fracture loads were measured and recorded as the fracture strength of each specimen. Fracture areas were measured on the mid-buccal and mid-lingual point from the crown margins. One-way analysis of variance and Turkey test were used to determine the statistic significance of the different fracture loads and areas among the groups(p.05). The mean fracture area of the fiber post was closer to the crown margin than that of the metal cast post and core(p<.05). The metal cast post showed unrestorable and catastrophic fracture patterns. CONCLUSION: Within the limitations of this study, fracture loads with any statistically significant difference were not recorded for endodontically treated teeth restored with two fiber posts and the metal cast post. But teeth restored with the fiber posts typically showed the fracture pattern close to the crown margin, which was almost restorable.