Abstract: Delamination of the veneering composite is frequently encountered with fibre-reinforced composite (FRC) fixed dental prosthesis (FDPs). The aim of this study is to evaluate the influence of framework design on the load-bearing capacity of laboratory-made three-unit inlay-retained FRC-FDPs. Inlay-retained FRC-FDPs replacing a lower first molar were constructed. Seven framework designs were evaluated: PFC, made of particulate filler composite (PFC) without fibre-reinforcement; FRC1, one bundle of unidirectional FRC; FRC2, two bundles of unidirectional FRC; FRC3, two bundles of unidirectional FRC covered by two pieces of short unidirectional FRC placed perpendicular to the main framework; SFRC1, two bundles of unidirectional FRC covered by new experimental short random-orientated FRC (S-FRC) and veneered with 1.5mm of PFC; SFRC2, completely made of S-FRC; SFRC3, two bundles of unidirectional FRC covered by S-FRC. Load-bearing capacity was determined for two loading conditions (n=6): central fossa loading and buccal cusp loading. FRC-FDPs with a modified framework design made of unidirectional FRC and S-FRC exhibited a significant higher load-bearing capacity (p<0.05) (927+/-74N) than FRC-FDPs with a conventional framework design (609+/-119N) and PFC-FDPs (702+/-86N). Central fossa loading allowed significant higher load-bearing capacities than buccal cusp loading. This study revealed that all S-FRC frameworks exhibited comparable or higher load-bearing capacity in comparison to an already established improved framework design. So S-FRC seems to be a viable material for improving the framework of FRC-FDPs. Highest load-bearing capacity was observed with FRC frameworks made of a combination of unidirectional FRC and S-FRC.

Abstract: OBJECTIVES: Ormocer composites, consisting of a silicon-based polymer, have been developed recently as a tooth-colored restorative material. The purpose of this prospective randomized clinical trial was to evaluate the performance of two small-particle hybrid ormocer-based restorative systems (AD, Admira/Admira Bond, VOCO; DE, Definite/Etch & Prime 3.0, Dentsply) and one small-particle hybrid bis-GMA-based composite restorative system (TC, Tetric-Ceram/Syntac, Ivoclar-Vivadent) in class II cavities. METHODS: From 128 occlusal-proximal restorations (44 AD, 43 DE and 41 TC) placed in 32 adult patients, eventually 77 (22 AD, 29 DE and 26 TC) remained available for evaluation after 5 years. Their clinical performance was scored according to the USPHS criteria and evaluation of bite-wing radiographs. RESULTS: After 5 years, eight AD, six DE and seven TC restorations had failed (p=0.10, log-rank test). The main reason was fracture or marginal gap formation, while secondary caries accounted for four failures. In all restorations the quality of surface, margins and contact point decreased significantly compared to baseline. DE had a significant poorer color match (p<0.01). Statistical evaluation using the KW test showed that failures were concentrated on specific patients. CONCLUSIONS: In a group of class II restorations, there was no significant difference in failures after 5 years between ormocer-based and bis-GMA-based restorative systems.

Abstract: PURPOSE: The aim of this study was to evaluate in vitro the influence of retainer design on the strength of two-unit cantilever resin-bonded glass fiber-reinforced composite (FRC) fixed dental prostheses (FDP). MATERIALS AND METHODS: Four retainer designs were tested: a proximal box, a step-box, a dual wing, and a step-box-wing. Of each design on 8 human mandibular molars, FRC-FDPs of a premolar size were produced. The FRC framework was made of resin impregnated unidirectional glass fibers (Estenia C&B EG Fiber, Kuraray) and veneered with hybrid resin composite (Estenia C&B, Kuraray). Panavia F 2.0 (Kuraray) was used as resin luting cement. FRC-FDPs were loaded to failure in a universal testing machine. One-way ANOVA and Tukey's post-hoc test were used to evaluate the data. The four designs were analyzed with finite element analysis (FEA) to reveal the stress distribution within the tooth/restoration complex. RESULTS: Significantly lower fracture strengths were observed with inlay-retained FDPs (proximal box: 300 +/- 65 N; step-box: 309 +/- 37 N) compared to wing-retained FDPs (p < 0.05) (step-box-wing: 662 +/- 99 N; dual wing: 697 +/- 67 N). Proximal-box-, step-box-, and step-box-wing-retained FDPs mainly failed with catastrophic cusp fracture (proximal box 100%, step-box 100%, and step-box-wing 75%), while dual-wing-retained FDPs mainly failed at the adhesive interface and/or due to pontic failure (75%). FEA showed more favorable stress distributions within the tooth/restoration complex for dual wing retainers. CONCLUSION: A dual-wing retainer is the optimal design for replacement of a single premolar by means of a two-unit cantilever FRC-FDPs.

Abstract: OBJECTIVES: Ormocer composites, consisting of a silicon-based polymer, have been developed recently as a tooth-coloured restorative material. The purpose of this prospective randomised clinical trial was to evaluate the performance of two small-particle hybrid ormocer-based restorative systems (AD, Admira/Admira Bond, VOCO; DE, Definite/Etch & Prime 3.0, Dentsply) and one small-particle hybrid bis-GMA-based composite restorative system (TC, Tetric-Ceram/Syntac, Ivoclar-Vivadent) in occlusal stress-bearing restorations. METHODS: One hundred and twenty-eight occlusal-proximal restorations (44 AD, 43 DE and 41 TC) were placed according to the manufacturer's instructions in thirty-two adult patients. Their clinical performance was scored according to the USPHS criteria and evaluation of bite-wing radiographs. RESULTS: After 3 years, four AD, five DE and four TC restorations had failed due to fracture or marginal gap formation. Surface roughness improved significantly when compared to the baseline in AD and TC (Friedman test, p<0.05) during the first year but returned to baseline values after 3 years. DE had a significant tendency towards discolouration (p<0.05). Bite-wing radiographs showed two AD and one TC restorations with internal porosities. ANOVA showed that larger restorations (> or = 3 surfaces) showed significantly more degradation than smaller ones. CONCLUSIONS: In a group of class II restorations, there was no significant difference in failures after 3 years between ormocer-based and bis-GMA-based restorative systems.