Fatigue and Stress Distribution Analyses of Ceramic-Reinforced PEEK Abutments Restored with Monolithic Zirconia Crowns as an Alternative to Conventional Esthetic Abutments.

PURPOSE: To determine the fracture strength and stress distribution of esthetic dental implant abutments. MATERIALS AND METHODS: Fifty specimens were prepared. Four hybrid abutment groups with titanium bases (zirconia [Z], lithium disilicate [L], ceramic-reinforced polymer [B] and [BC]) and a custom titanium abutment control group (T) were restored with monolithic zirconia crowns except BC, which was crowned with layered composite. Ceramic abutments were cemented on Ti bases with a self-curing resin cement. Polymer abutments were cemented on Ti bases with an adhesive resin cement. All crowns for T, Z, and L were cemented with another self-adhesive resin cement, while the B and BC groups were cemented with the same adhesive resin cement for the polymer. Fatigue testing was performed by a chewing simulator (CS-4.2, SD, 50 N, 240,000 cycles) followed by fracture strength testing (0.5 mm/min, 5,000 N). Failure type analysis was made by a stereomicroscope. Statistical analyses were made (SPSS 25.0, analysis of variance [ANOVA], Tukey honestly significant difference [HSD], 95% CI). Complementary finite element analyses (FEAs) were performed (Algor Fempro). RESULTS: Mean ± SD fracture strengths for T, Z, L, B, and BC were 1,522.67 ± 190.77, 1,207.76 ± 89.03, 818.81 ± 109.96, 1,126.23 ± 142.23, and 899.08 ± 60.36, respectively (P < .05). Abutment screw flexure and/or cracks or crown material fractures for T, Z, L, and B occurred, while no implant and/or abutment fractures were observed for BC except for crown fracture and Ti base flexure. FEA exhibited similar stress concentrations. CONCLUSION: Monolithic zirconia crowns on titanium abutments and hybrid zirconia abutments exhibited the highest fracture strengths. Lithium disilicate and BioHPP abutments had the lowest fracture strength, while no fractures were observed on the implant, abutment, or screw.

Replacement of maxillary lateral incisors with digitally manufactured single tooth retained all-ceramic pontics: a clinical report / Reabilitação da região de incisivo lateral superior ausente por pôntico modelo cantiléver em cerâmica pura fabricado digitalmente: relato de caso clínico

Several treatment options for replacement of anterior missing teeth exist, varying from no-prep (no preparation) adhesive restorations to implants. Patients' biological, psychological, economic conditions or age have an effect on the treatment choice. It is important to perform the most conservative and beneficial treatment option considering the patient based factors. The aim of this case report was to demonstrate a single session, minimally invasive, cantilevered 2-unit all-ceramic restorations replacing anterior missing teeth combined with the advantages of CAD/CAM technology and materials. (AU)

Existem várias opções de tratamento para reabilitação de dentes anteriores ausentes, variando de restaurações adesivas sem preparo (sem preparação) até implantes. As condições biológicas, psicológicas, econômicas ou a idade dos pacientes têm um efeito na escolha do tratamento. É importante realizar a opção de tratamento mais conservadora e benéfica, considerando os fatores baseados no paciente. O objetivo deste relato de caso foi demonstrar em sessão única, minimamente invasiva, um cantiléver de restaurações de cerâmica pura de 2 unidades, reabilitando a região de dentes anteriores ausentes combinadas com as vantagens da tecnologia CAD/CAM.(AU)

Detection of the hybrid layer biodegradation initiation factor with a scanning electron microscope.

The purpose of this study was to elucidate the origin of initiation of hybrid layer biodegradation. Ninety caries-free human third molars were divided into three surface groups: enamel, dentin, and NaOCl-treated dentin. (n = 30/group) Each group was divided into three subgroups (n = 10/group) of luting resin materials with etch-and-rinse; self-etch and self-adhesive systems. Resin composite blocks and sticks were fabricated and adhered onto dentin and enamel surfaces. The bond strength values were evaluated with micro shear test and statistical analysis were made. On the other hand, teeth were sectioned with a slow-speed saw into multiple beams. After thermocycling, samples were kept in 50% silver nitrate solution. Samples were analyzed with SEM in back-scattered mode. According to the micro-shear bond tests, higher bond strength values were observed in etch-and-rinse system. Bond strength values in self-adhesive and etch-and-rinse groups were significantly higher than self-etch groups in dentin surface and dentin surface treatment with NaOCl. Back-scattered scanning electron microscope results showed that, different degradation mechanism was observed. The present study indicates that, due to the acid etching in dentin, collagen biodegradation was observed within the hybrid layer. On the enamel surfaces, resin degradation was related with resin monomers in adhesive systems.

In vivo wear determination of novel CAD/CAM ceramic crowns by using 3D alignment.

PURPOSE: To determine wear amount of single molar crowns, made from four different restoratives, and opposing natural teeth through computerized fabrication techniques using 3D image alignment. MATERIALS AND METHODS: A total of 24 single crowns (N = 24 patients, age range: 18 - 50) were made from lithium disilicate (IPS E-max CAD), lithium silicate and zirconia based (Vita Suprinity CAD), resin matrix ceramic material (Cerasmart, GC), and dual matrix (Vita Enamic CAD) blocks. After digital impressions (Cerec 3D Bluecam, DentsplySirona), the crowns were designed and manufactured (Cerec 3, DentsplySirona). A dual-curing resin cement was used for cementation (Variolink Esthetic DC, Ivoclar). Then, measurement and recording of crowns and the opposing enamel surfaces with the intraoral scanner were made as well as at the third and sixth month follow-ups. All measurements were superimposed with a software (David-Laserscanner, V3.10.4). Volume loss due to wear was calculated from baseline to follow-up periods with Siemens Unigraphics NX 10 software. Statistical analysis was accomplished by Repeated Measures for ANOVA (SPSS 21) at = .05 significance level. RESULTS: After 6 months, insignificant differences of the glass matrix and resin matrix materials for restoration/enamel wear were observed (P>.05). While there were no significant differences between the glass matrix groups (P>.05), significant differences between the resin matrix group materials (P<.05) were obtained. Although Cerasmart and Enamic were both resin matrix based, they exhibited different wear characteristics. CONCLUSION: Glass matrix materials showed less wear both on their own and opposing enamel surfaces than resin matrix ceramic materials.

Evaluation of Different Thickness, Die Color, and Resin Cement Shade for Veneers of Multilayered CAD/CAM Blocks.

PURPOSE: To investigate the effect of resin cement color on the post-cementation shade of thin laminate veneers milled from multilayered glass ceramic blocks for each layer. MATERIALS AND METHODS: Thin slices (N = 180) with two thicknesses (A: 8 × 8×0.55 mm and B: 8×8×0.8 mm; n = 90/group) were obtained from multilayered glass ceramic blocks using a diamond saw. Resin die specimens were prepared (8 × 8 × 4 mm) (n = 180) and divided into two resin cement colors (D: -3. L: +3) and one control group (C: translucent). Each slice was luted to the composite specimens using a dual-curing resin cement under a constant load of 250 g and light-polymerized for 120 seconds. Specimens were placed on a white background and CIELab values for each layer of the blank slices (incisal [In], body [Bo], and cervical [Ce]) were recorded using a dental contact spectrophotometer. The values were calculated as ΔE, and the data were statistically analyzed (one-way ANOVA, Shapiro-Wilk). RESULTS: Mean ΔE values for A and B were significant (p < 0.05) for In (A: 6.2 ± 1.1; B: 6.6 ± 1.2), Bo (A: 5.1 ± 2.6; B: 3.9 ± 1), and Ce (A: 5.3 ± 2.7; B: 3.8 ± 1.2). Mean ΔE values for In for D and L for A and B groups were significantly higher (6.3 ± 1.2; 6.6 ± 1.2) than Bo and Ce for D (4.4 ± 2.4; 4.6 ± 2.6) and L (4.6 ± 1.4; 4.5 ± 1.7) groups (p < 0.05), respectively. Mean differences between Bo and Ce for A and B groups were insignificant (p ≥ 0.05), while for In the differences were significant. Mean differences between Bo and Ce for A (5.1 ± 2.6; 5.3 ± 2.7) and for B (3.9 ± 1; 3.5 ± 1.2) groups were insignificant (p ≥ 0.05), while for In the differences were significant (6.2 ± 1.1 for A and 6.6 ± 1.2 for B). CONCLUSION: The color changes for body and cervical regions of multilayered ceramic veneers were not affected by resin color or ceramic thickness, but the incisal area was affected. The translucency of each layer in ceramic veneer fabricated with multilayered blanks should be considered for clinical situations.

Influence of cervical finish line type on the marginal adaptation of zirconia ceramic crowns.

The current study evaluated the effect of different cervical finish line designs on the marginal adaptation of a zirconia ceramic. Four different marginal finish lines (c: chamfer, mc: mini-chamfer, fe: feather-edge and s: rounded shoulder) were prepared on phantom incisors. Die models for each preparation group (N = 28, n = 7 per finish line design group) were made of epoxy resin. Y-TZP (ICE Zirkon) frameworks were manufactured by a copy-milling system (Zirconzahn) using prefabricated blanks and tried on the master models for initial adaptation of the framework; they were then sintered, followed by veneering (Zirconzahn). The finished crowns were cemented with a polycarboxylate cement (Poly F) under 300 g load and ultrasonically cleaned. The specimens were sliced and the marginal gap was measured, considering absolute marginal opening (AMO) and marginal opening (MO) for each coping under a stereomicroscope with image processing software (Lucia). The measurements were statistically analyzed using the Kruskal Wallis, Mann Whitney and Wilcoxon Signed Ranks tests at a significance level of alpha = 0.01. Means of AMO measurement (microm) for the feather-edge finish line (87 +/- 10) was significantly lower than that of the chamfer (144 +/- 14), shoulder (114 +/- 16) and mini-chamfer finish line types (114 +/- 11) (p < 0.01). Means of MO measurements was the lowest for feather-edge finish line (68 +/- 9) (p < 0.01) and then, in ascending order, shoulder (95 +/- 9), mini-chamfer (97 +/- 12) and chamfer (128 +/- 10). The cervical finish line type had an influence on the marginal adaptation of the tested zirconia ceramic. Although the feather-edge finish line resulted in lower AMO and MO values, with its proven mechanical disadvantage, it cannot be recommended in clinical applications of zirconia crowns. This type of finish line has acted solely as a control group to test the null hypothesis in the current study. For better marginal adaptation, both shoulder and mini-chamfer finish line types could be suggested for zirconia crowns.