Biomechanical consideration in tooth-supported glass-ceramic restorations: A systematic review and meta-analysis of survival rates and irreparable failures.

STATEMENT OF PROBLEM: Knowledge on the biomechanical behavior of glass-ceramics, their survival rate over time, and their potential failures is essential for decision-making in clinical practice. Systematic reviews and meta-analysis of their survival rates and irreparable failures are lacking. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate the survival rates and irreparable failures of various monolithic glass-ceramic dental restorations to help determine biomechanical indications. MATERIAL AND METHODS: A comprehensive literature search was conducted across the PubMed, Scopus, Web of Science, and EMBASE databases based on the population, intervention, comparison, and outcome (PICO) question, risk of bias assessment, data extraction, subgroup analysis, and meta-analysis. Both randomized and nonrandomized clinical trials that reported survival rate and irreparable failure were screened. The risk, with a 95% confidence interval, was calculated by using the Mantel-Haenszel method. RESULTS: A total of 46 articles met the inclusion criteria: 8 for laminate veneers, 20 for partial coverage restorations, 11 for single crowns, and 6 for fixed partial dentures, encompassing 1715 participants rehabilitated with 4209 restorations. The estimated cumulative survival rate for partial coverage restorations was 90% over an average span of 6.2 years, with an irreparable failure occurrence of n=5.9. Laminate veneers had a survival rate of 90.2% over 6.5 years, with an irreparable failure occurrence of n=8.2. Single crowns had a survival rate of 96% over 4.6 years and an irreparable failure of n=2.7. Conversely, fixed partial dentures had a survival rate of 76.1% over 6.5 years with an irreparable failure of n=5.2. CONCLUSIONS: Glass-ceramic materials demonstrate relatively high survival rates, indicating that they provide a safe and reliable option for partial coverage restorations, laminate veneers, and single crowns. However, fixed partial dentures had a higher proportion of irreparable failures and a lower survival rate, and caution is required.

Effect of different beverages and storage period on bis-acryl color stability using two assessment methods.

OBJECTIVE: This study aimed to evaluate the color stability (ΔE00 ) of bis-acryl resins after different immersion solutions and storage time by different evaluation methods. MATERIALS AND METHODS: Sixty specimens (n = 30) were prepared from Protemp 4 and Structur 3. The specimens were divided into three groups (n = 10), according to the immersion solution (artificial saliva, cola beverage, and yerba mate tea) and evaluated at two storage times (7 and 14 days). The ΔE00 of each group was calculated using color coordinates obtained by a spectrophotometer and by a digital method, using the CIEDE2000 color difference formula. Data were analyzed by three-way ANOVA and Tukey test (α = 0.05). RESULTS: The 7-day period presented the lowest ΔE00 values, regardless of the material and solution evaluated for both evaluation methods (ΔE00 < 0.93; ΔE00 < 3.12). The immersion solution with the highest color change was yerba mate tea after 14 days (ΔE00 > 2.11). For digital analyses, all materials and solutions at both times presented ΔE00 values higher than the clinically acceptable (ΔE00 > 1.8), while in spectrophotometer only in yerba mate tea (14 days) Structur was above the clinical acceptability level. CONCLUSIONS: Yerba mate tea was the immersion solution with a higher color change in both materials and assessment methods. The highest values were found after 14 days of immersion, regardless of the solution. The ΔE00 for the digital method was higher than the spectrophotometer analysis. CLINICAL SIGNIFICANCE: It is important to identify the influence of staining beverages on interim materials used in patients requiring temporary rehabilitation. The use of a spectrophotometer seems to be more accurate than the digital method for the evaluation of color parameters of the tested materials.

Long-term stainability of interim prosthetic materials in acidic/staining solutions.

OBJECTIVE: To evaluate the long-term color stainability, translucency, and contrast ratio (CR) of different resins used to fabricate interim prostheses after immersion in acidic/staining solutions. MATERIALS AND METHODS: A total of 160 specimens were divided into 16 groups (n = 10) according to the material (heat-polymerized acrylic resin [HPAR], auto-polymerized acrylic resin [APR], nanoparticulated bis-acrylic resin [BR], and prefabricated poly(methyl methacrylate) block for CAD/CAM [CADR]) and immersion solutions (artificial saliva, cola beverage, coffee, and red wine). A spectrophotometer was used before and after each immersion period (7, 14, 28, 90, and 180 days). Color differences (CIEDE2000 and CIELab) were calculated. A three-way repeated-measures analysis of variance and Bonferroni test (α = .05) were used. RESULTS: After 180 days, the APR presented the highest value for coffee and the CADR presented the smallest value for the cola (P < .001). For the CR, the highest values were obtained at 180 days for BR in coffee (1.35) and wine (1.18) (P < .001). Higher translucency parameters were obtained in the BR and CADR in the initial, 14, 28, and 90 days (P < .001). CONCLUSIONS: From the greatest to the smallest staining potential, the solutions were classified as: wine > coffee > cola beverage > saliva, while for the materials as: APR > BR > HPAR > CADR. CLINICAL SIGNIFICANCE: The knowledge of the long-term optical behavior of interim prosthetic materials is important for clinicians to decide which material to use to match the dietary intake of their patients and their esthetic demands. Prefabricated blocks for CAD/CAM systems have been shown to maintaining their optical characteristics even after a long period of immersion in acidic/staining solutions.

Effects of mouth rehabilitation with removable complete dentures on stimulus perception and the electromyographic activity of the orbicularis oris muscle.

STATEMENT OF PROBLEM: Many elderly individuals are rehabilitated with removable complete dentures, which require an initial adaptation period for both oral perception and the perioral muscles. Studies assessing the changes in stimulus perception and the electromyographic (EMG) activity of the orbicularis oris muscle shortly after conventional complete denture insertion are lacking. PURPOSE: The purpose of this clinical study was to evaluate the effect of mouth rehabilitation with removable complete dentures on stimulus perception and the EMG activity of the orbicularis oris muscle. MATERIAL AND METHODS: This study was approved by the Human Research Ethics Committee of the Araçatuba Dental School (São Paulo State University). Fifteen participants who had worn their removable complete dentures for at least 5 years and needed rehabilitation with new prostheses were enrolled in the study. A perception questionnaire was applied, and surface EMG examinations of the orbicularis oris muscle during rest, suction of water with a straw, and pronunciation of the syllables /bah/, /mah/, /pah/, and the word 'Mississippi' were performed before (T0) and 30 (T1) and 100 (T2) days after insertion of the new prostheses. The data were analyzed with the Cochran Q test, McNemar test, 2-way repeated measures ANOVA, and honestly significant difference (HSD) Tukey test (α=.05). RESULTS: Significant improvement was reported in the perception questionnaire in terms of the oral discomfort sensation in the T2 period. EMG activity decreased during rest and suction after insertion of the new prostheses. A statistical difference between the upper and lower fascicles of the orbicularis oris muscle was detected, with a decrease of EMG activity between the T0 and T1 periods on the lower fascicle, except for when pronouncing the /pah/ syllable. CONCLUSIONS: Mouth rehabilitation with removable complete dentures decreased oral discomfort and, depending on the oral function, decreased or increased EMG activity of the orbicularis oris muscle. In addition, the lower fascicle was more active than the upper fascicle during rest and most functional activities.

Evaluation of Different Polymerisation Methods of Ocular Prosthesis Acrylic Resins on Subcutaneous Tissue Inflammatory Response in Rats.

Objectives: This study aimed to evaluate the influence of different polymerisation methods of acrylic resin for ocular prostheses on the subcutaneous tissue inflammatory response of rats. Methods: The study was conducted at the Basic Sciences Department, Araçatuba Dental School, São Paulo State University (UNESP), Brazil, from 2016 to 2018. The samples were prepared by water bath (WB), microwave energy (MW) or autopolymerisation (AP) (n = 20 samples per group). The inflammatory response (cell count and immunohistochemical analysis of interleukin [IL]-1ß, IL-6, tumour necrosis factor [TNF]-α, IL-17 and macrophage inflammatory protein-3α) was analysed by the implantation of a sample from each group in the subcutaneous tissue of 20 Wistar rats and evaluated after seven, 15, 30 and 60 days. The quantitative and qualitative data were analysed using analysis of variance and Tukey tests (P <0.05) and visual comparison, respectively. Results: There was a moderate inflammatory infiltrate for the MW and AP groups and a light infiltrate for the WB group after seven days. The inflammatory infiltrate and the immunolabeling of tested targets decreased gradually during the 60-day period. The AP group had the highest immunolabeling of TNF-α (seven days), IL-1ß and IL-17 (at 15 and 30 days) and IL-6 (at 30 and 60 days). The WB and MW groups showed greater immunolabeling at 15 and 30 days, while the MW group also had high results at 60 days. Conclusion: Polymerisation by microwave energy and by chemical activation resulted in a higher inflammatory response.

Characterisation of a new plasma-enhanced film to improve shear bond strength between zirconia and veneering ceramic.

The aim of this study was to develop and characterise a new plasma-enhanced chemical vapor deposition (PECVD) film for improving shear bond strength (SBS) between yttria-stabilised tetragonal zirconia (Y-TZP) and veneering ceramic. In total, 192 Y-TZP samples (13 × 5.4 × 5 mm) were divided into 6 groups: control - no treatment (C), airborne-particle abrasion with 27 µm aluminum oxide particles (Al27), 110 µm aluminum oxide particles (Al110), and 250 µm aluminum oxide particles (Al250), application of liner for zirconia (L) and the PECVD film application (P). The Y-TZP surface was characterised by means of Scanning Electronic Microscopy (SEM), Energy-dispersive Spectroscopy (EDS), atomic force microscopy (AFM), surface profilometry and surface-free energy (SFE). SBS between Y-TZP and veneering ceramic was tested before and after thermocycling (20,000 cycles of 5 and 55 °C), and failure mode was also evaluated. Data were analysed by ANOVA and Tukey's HSD test (α = 0.05). Data analysis showed that PECVD film had no effect on surface roughness of Y-TZP (p > 0.05 vs control), whilst the other groups presented higher roughness values (p < 0.05). All treatments increased SFE, except the Al27 group. The highest SBS was presented by the P group (p < 0.05), and values were similar to those of the Al27 group (p = 0.107). Mixed failures were prevalent in all groups, and premature failures were found only in Al groups after thermocycling. Whilst PECVD treatment did not affect Y-TZP surface roughness, high SBS between Y-TZP and the veneering layer was observed. Therefore, PECVD treatment is a promising alternative to improve the performance of bi-layer zirconia-based restorations.