Fracture resistance of zirconia-composite veneered crowns in comparison with zirconia-porcelain crowns.

The objectives were to evaluate the fracture resistance and stress concentration in zirconia/composite veneered crowns in comparison to zirconia/porcelain crowns using occlusal fracture resistance and by stress analysis using finite element analysis method. Zirconia substructures were divided into two groups based on the veneering material. A static load was applied occlusally using a ball indenter and the load to fracture was recorded in Newtons (N). The same crown design was used to create 3D crown models and evaluated using FEA. The zirconia/composite crowns subjected to static occlusal load showed comparable results to the zirconia/porcelain crowns. Zirconia/composite crowns showed higher stress on the zirconia substructure at 63.6 and 50.9 MPa on the zirconia substructure veneered with porcelain. In conclusion, zirconia/composite crowns withstood high occlusal loads similar to zirconia/porcelain crowns with no significant difference. However, the zirconia/composite crowns showed higher stress values than the zirconia/porcelain crowns at the zirconia substructure

Class II MOD 직접 복합 레진 수복 시 기저재의 종류와 두께에 따른 응력 분포의 비교: 삼차원 유한 요소 연구

학위논문 (석사) -- 서울대학교 대학원 : 치의학대학원 치의과학과, 2020. 8. 서덕규.1. Purpose The purpose of this study was to investigate and compare the stress distribution of different base materials and thicknesses in posterior direct MOD class II resin restoration. 2. Material and methods Nine 3D models of teeth obtained from CBCT scan data were fabricated and analyzed through 3D CAD software (ABAQUS CAE 2016, Dassault systems, Velizy-Villacoublay, France). The experimental groups of 3D models were categorized as follows: Control: Sound tooth Group A: Composite resin without base material Group B: Lithium disilicate with resin cement layer Group C-tn: Composite resin with glass ionomer cement base 0.5 mm Group C-tk: Composite resin with glass ionomer cement base 1.0 mm Group D-tn: Composite resin with low-viscosity resin base 0.5 mm Group D-tk: Composite resin with low-viscosity resin base 1.0 mm Group E-tn: Composite resin with tricalcium silicate cement base 0.5 mm Group E-tk: Composite resin with tricalcium silicate cement base 1.0 mm Group C, D, E had multi-layer construction consisted of adhesive layer, base and composite resin. Then these groups were further divided into two sub-groups: thin (tn) and thick (tk). Stress distribution of all groups were compared and analyzed by visualizing maximum principal stress of each model after simulation of vertical loading with 600 N on occlusal surface. Polymerization shrinkage effect on resin-based materials was applied in prior to vertical loading. 3. Results Sound tooth showed lowest stress value and its stress propagation was confined on outer enamel surfaces only. Group A showed highest stress distribution along interfaces between tooth and restoration with increased failure risk on marginal area. In contrast, Group B showed the lowest maximum stress value among all groups although the stress was concentrated on resin cement layer. Group C, D, E both in thin and thick subgroups showed reduced stress level compared to Group A. However, differences in stress distribution between base materials and base thicknesses of 0.5 mm and 1.0 mm were not significant. 4. Conclusion Marginal stress caused by polymerization shrinkage of composite resin was reduced by presence of GIC, low-viscosity resin and tricalcium silicate cement bases in class II MOD direct composite resin. However, influence of different base materials and thicknesses of 0.5 mm and 1.0 mm on stress distribution of tooth and composite resin was not observed.1. 목 적 본 연구의 목적은 Class II MOD 직접 복합 레진 수복 시 Base 재료의 종류 및 두께에 따른 응력 분포를 3D 유한 요소 해석법을 통해 비교 분석하는 것이다. 2. 방 법 CBCT-scan 데이터를 기반으로 한 9개의 삼차원 치아 모형을 유한요소 소프트웨어 (Abaqus CAE 2016, Dassault systems, Velizy-Villacoublay, France)를 이용해 제작하였으며 형성된 유한요소 모형의 실험군을 다음과 같이 분류하였다. Control Group: 정상 치아 (Sound tooth) Group A: Base를 적용하지 않은 직접 수복 Composite Resin Group B: Resin luting cement를 적용한 간접 수복 Lithium disilicate Group C-tn: Composite resin 과 Glass ionomer cement base 0.5 mm Group C-tk: Composite resin 과 Glass ionomer cement base 1.0 mm Group D-tn: Composite resin 과 Low-viscosity resin base 0.5 mm Group D-tk: Composite resin 과 Low-viscosity resin base 1.0 mm Group E-tn: Composite resin 과 Tricalcium silicate cement base 0.5 mm Group E-tk: Composite resin 과 Tricalcium silicate cement base 1.0 mm Group C, D, E 는 공통적으로 adhesive layer 와 base 그리고 composite resin 으로 구성된 다층 구조로 형성되었으며, 이 3 개의 그룹을 다시 두께에 따라 thin (Tn, 0.5 mm) 과 thick (Tk, 1.0 mm), 2 개의 세부 그룹으로 나누었다. 레진 재료들의 중합 수축 효과와 함께 600 N 의 수직하중을 교합면에 가하고 모든 실험 모형들의 최대 주 응력 (Maximum principal stress) 분포 데이터를 도표 및 그림으로 시각화 하여 비교 분석하였다. 3. 결 과 대조군에서는 응력 분포가 법랑질에 국한되어 고르게 분산되었으며 모든 실험군 중 가장 낮은 응력 값을 보였다. Group A 에서는 치아와 수복물의 계면을 따라서 가장 높은 응력 분포를 보였으며 특히 변연에서 파절 위험이 증가하였다. Group B의 경우 대조군을 제외한 모든 군에서 가장 낮은 응력 값을 보였으나 Resin cement layer 에 집중된 응력이 관찰되었다. Group C, D, E의 경우 Group A와 비교했을 시 Group C, D, E 모두 중합 수축에 의한 응력을 감소시켰으나, Base의 종류에 따른 응력 분포에 유의미한 차이는 없었으며 0.5 mm 과 1.0 mm의 두께에 따른 응력 분포에 차이는 없었다. 4. 결 론 Class II MOD 직접 레진 수복 시, Base의 적용은 중합 수축으로 인한 응력을 감소시켰으나 Base 재료 종류의 차이 그리고 0.5 mm 과 1.0 mm의 두께 차이가 응력의 분포에 미치는 영향은 없었다.I. Introduction........................................... 1 II. Material and Methods........................... 4 III. Results.................................................. 7 IV. Discussion............................................ 9 V. Conclusion............................................. 12 References................................................. 13 Tables and Figures.................................... 17 Abstract (in Korean)................................. 28Maste

Effect of cavity preparation design and ceramic type on the stress distribution, strain and fracture resistance of CAD/CAM onlays in molars

Objective: This study aimed to evaluate the effect of the cavity preparation and ceramic type on the stress distribution, tooth strain, fracture resistance and fracture mode of human molar teeth restored with onlays. Material and Methods: Forty-eight molars were divided into four groups (n=12) with assorted combinations of two study factors: BL- conventional onlay preparation with boxes made from leucite ceramic (IPS-Empress CAD, Ivoclar Vivadent); NBL- conservative onlay preparation without boxes made from leucite ceramic; BD- conventional onlay preparation with boxes made from lithium disilicate glass ceramic (IPS e.max CAD, Ivoclar Vivadent); NBL- conservative onlay preparation with boxes made from lithium disilicate glass ceramic cuspal deformation (µS) was measured at 100 N and at maximum fracture load using strain gauge. Fracture resistance (N) was measured using a compression test, and the fracture mode was recorded. Finite element analysis was used to evaluate the stress distribution by modified von Mises stress criteria. The tooth strain and fracture resistance data were analyzed using the Tukey test and two-way ANOVA, and the fracture mode was analyzed by the chi-square test (α=0.05). Results: The leucite ceramic resulted in higher tooth deformation at 100 N and lower tooth deformation at the maximum fracture load than the lithium disilicate ceramic (P<0.001). The lithium disilicate ceramic exhibited higher fracture resistance than the leucite ceramic (P<0.001). The conservative onlay resulted in higher fracture strength for lithium disilicate ceramic. Finite element analysis results showed the conventional cavity preparation resulted in higher stress concentration in the ceramic restoration and remaining tooth than the conservative onlay preparation. The conservative onlays exhibited increased fracture resistance, reduced stress concentration and more favorable fracture modes. Conclusion: Molars restored with lithium disilicate CAD-CAM ceramic onlays exhibited higher fracture resistance than molars restored with leucite CAD-CAM ceramic onlays

Functional Biomimetic Dental Restoration

Bioinspired functionally graded approach is an innovative material technology, which has rapidly progressed both in terms of materials processing and computational modeling in recent years. Bioinspired functionally graded structure allows the integration of dissimilar materials without formation of severe internal stress and combines diverse properties into a single material system. It is a remarkable example of nature’s ability to engineer functionally graded dental prostheses. Therefore, this novel technology is designed to improve the performance of the materials in medical and dental fields. Thus, this chapter book reviews the current status of the functionally graded dental prostheses and biomimetic process inspired by the human bone, enamel and dentin-enamel junction (DEJ) structures and the linear gradation in Young’s modulus of the human bone, enamel and dentin-enamel junction, as a new material design approach, to improve the performance compared to traditional dental prostheses. Notable research is highlighted regarding application of biomimetic prostheses into various fields in dentistry. The current chapter book will open a new avenue for recent researches aimed at the further development of new dental prostheses for improving their clinical durability

The impact of restorative material and ceramic thickness on CAD\CAM endocrowns

Endocrown restorations as a conservative approach to restore endodontically treated teeth still need in vitro investigation under fatigue and made in different materials. This study evaluated the effect of restorative material and restoration thickness on the maximum fracture load of endocrowns subjected to cyclic loading. Sixty (60) third molar teeth received an endocrown preparation with three different heights of remaining dental tissue (1.5, 3.0 or 4.5 mm). A leucite-based ceramic (LEU) and a lithium disilicate (LD) based ceramic were selected to manufacture the CAD/CAM endocrown restorations, totaling 6 groups (n=10). The specimens were subjected to fatigue loading (200N, 2 x 106 cycles, water) and then to the single load to failure test (1 mm/min crosshead speed). Data were analyzed by using two-way ANOVA and Tukey tests (p< 0.05). All endocrowns survived the fatigue test. The thickness did not influence the restoration?s fracture load (p=0.548) instead the restorative material (p=0.003). LD showed higher mean values (1714.43 N)A than LEU (1313.47 N)B. Endocrowns manufactured with CAD/CAM lithium disilicate blocks showed superior fracture load than the leucite-based blocks after mechanical fatigue. Nevertheless, both materials presented acceptable survival and fracture load as long as the material?s minimum thickness and the enamel adhesion are respected

Effect of framework type on survival probability of implant-supported temporary crowns : an in vitro study

This in vitro study evaluated the effect of framework type on the survival probability of temporary implant-supported crowns and on the implant platform structure after dynamic fatigue. Thirty (30) external hexagon implants (3.75 x 10 mm) were embedded in acrylic resin following the ISO-14801. Standardized temporary crowns (n=10, N=30) were manufactured in acrylic resin and divided according to the framework type: Total plastic, Plastic with CoCr base and Titanium. The crowns were installed onto the implants (20N.cm) and fatigued (100N, 2 Hz) to determine the crowns? survival probability for missions of 300.000 and 600.000 cycles. Fatigue data were submitted to the Kaplan-Meier test followed by Wilcoxon and Log Rank, all with ? = 5%. The implant platforms were parametrically inspected based on the scanning before and after the fatigue to evaluate the damage. The strain values were analyzed using One-way ANOVA and Tukey test, all with ? = 5%. ANOVA revealed that the Total plastic showed less implant damage (-0.07 ± -0.03 mm) than the Plastic with CoCr base (-0.08 ± -0.04 mm) and the Titanium (-0.10 ± -0.01 mm) frameworks. Therefore, the framework type to manufacture implant-supported temporary crowns influences the fatigue survival of the restoration and the implant platform damage. The Plastic with CoCr base and Titanium frameworks showed superior reliability than the Total plastic framework which could not survive 600,000 cycles. The Plastic with CoCr base and the Titanium framework are suitable for restorations over 3 months in use, without a difference in the implant platform damage

Influence of adhesive technique and thermomechanical fatigue on the fracture strength of minimally invasive CAD/CAM occlusal veneers

With the development of new CAD/CAM restorative dental materials, limited data regarding their survival rate and fracture strength are available when they are used as occlusal veneers. Therfore, These materials could be evaluated under conditions similar to those of the oral environment before being recommended for clinical use . For that reason, the influence of thermomechanical fatigue and adhesive bonding technique (etch-and-rinse and self-etching ) on the survivability and fracture strength for four different CAD/CAM materials were evaluated in this study

Three-dimensional finite element analysis of anterior two-unit cantilever resin-bonded fixed dental prostheses

The aim of this study was to evaluate the influence of different framework materials on biomechanical behaviour of anterior two-unit cantilever resin-bonded fixed dental prostheses (RBFDPs). A three-dimensional finite element model of a two-unit cantilever RBFDP replacing amaxillary lateral incisorwas created. Five frameworkmaterialswere evaluated: direct fibre-reinforced composite (FRC-Z250), indirect fibre-reinforced composite (FRC-ES), gold alloy (M), glass ceramic (GC), and zirconia (ZI). Finite element analysis was performed and stress distribution was evaluated. A similar stress pattern, with stress concentrations in the connector area, was observed in RBFDPs for all materials.Maximal principal stress showed a decreasing order: ZI >M>GC> FRC-ES > FRCZ250. The maximum displacement of RBFDPs was higher for FRC-Z250 and FRC-ES than for M, GC, and ZI. FE analysis depicted differences in location of the maximum stress at the luting cement interface between materials. For FRC-Z250 and FRC-ES, the maximum stress was located in the upper part of the proximal area of the retainer, whereas, for M, GC, and ZI, the maximum stress was located at the cervical outline of the retainer. The present study revealed differences in biomechanical behaviour between all RBFDPs.The general observation was that a RBFDP made of FRC provided a more favourable stress distribution