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.

Determination of chemical species of fluoride during uptake mechanism of glass-ionomer cements with NMR spectroscopy.

OBJECTIVE: The aim of the present study was to determine the chemical species formed inside glass-ionomer cements after fluoride uptake and to investigate the depth of penetration of fluoride ions within the cement matrix. METHODS: An experimental fluoride-free glass with composition 2SiO2-AlO3-CaO was produced. The glass powder was mixed with aqueous poly(acrylic acid) (PAA), and allowed to set. The resulting specimens were stored in 20ml KF solution with 1000ppm fluorine for 24h and then placed into the same amount of water as for 24h. A fluoride selective electrode was used to give the F concentration of the respective solutions. 19F MAS-NMR spectra were recorded on powdered cement specimens using a Bruker AVANCE-NEO 600 spectrometer. In addition, SEM observation and EDX chemical analysis were conducted on the cross-section of a carefully fractured specimen. RESULTS: Fluoride was shown to be mainly present in the surface layers of the specimen after placement in the KF solution, and only a small fraction was re-released into water. 19F NMR spectroscopy showed that AlF complexes were formed within the cement. SIGNIFICANCE: The fluoride taken up by a free-fluoride glass ionomer cement mostly occupies surface layers and is retained because it bonds to aluminum within the matrix. This finding explains why the majority of fluoride taken up by conventional glass ionomer cements is retained.

Wettability and pre-osteoblastic behavior evaluations of a dense bovine hydroxyapatite ceramics.

In this study, the wettability, cell viability, and roughness of an experimental dense bovine hydroxyapatite [Ca10(PO4)6(OH)2] ceramic block were evaluated so that, in the future, it could be used as a base material for dental implants. The results to commercial zirconia and a commercially pure titanium (Ti) alloy were compared. The surface roughness and contact angles were measured. An in vitro evaluation was conducted by means of tests in which pre-osteoblastic MC3T3-E1 cells were placed in indirect and direct contact with these materials. For cell viability, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and crystal violet test were conducted. A qualitative analysis was conducted using variable pressure scanning electron microscopy (SEM). No statistically significant differences were observed in wettability and roughness tests among the groups. In both the MTT assay and crystal violet test, all groups demonstrated satisfactory results without cytotoxicity. SEM showed cell adhesion and cell proliferation results on the material surfaces after 24 h and 48 h. In conclusion, this dense Ca10 (PO4)6(OH)2 ceramic can be considered as a potential biocompatible material.

Flexural strength of minimum thickness ceramic veneers manufactured with different techniques.

OBJECTIVE: The objective of the present study was to assess the effect of monolithic and bilayer restorations considering heat-pressed and milled/CAD/CAM reinforced lithium disilicate ceramic veneers, on the flexural strength after cementation. METHOD AND MATERIALS: Thirty-five specimens were divided into five groups (n = 7), according to the restorative solution: 2-mm thickness composite resin (CR2); heat-pressed monolithic ceramic 0.6 mm (HPM), CAD/CAM monolithic ceramics 0.6 mm (CCM); heat-pressed monolithic ceramic 0.4 mm + 0.2 mm glass-ceramic (HPB); CAD/CAM monolithic ceramic 0.4 mm + 0.2 glass-ceramic (CCB). Specimens were cemented on composite resin bars and submitted to a three-point bending test on a Universal Testing Machine, until fracture. Fractured samples were analyzed under stereomicroscope and SEM. Flexural strength data were analyzed by one-way ANOVA and Tukey test. RESULTS: The control group showed the highest flexural strength results (119.57 ± 19.49 MPa), with values similar to groups HPM (98 ± 25.62 MPa) and CCM (96.14 ± 20.60 MPa). Groups HPB and CCB showed lower values when compared with the other groups. Fracture started from the base on monolithic groups and from ceramic on bilayer groups. CONCLUSION: Both ceramic systems (CAD/CAM and heat-pressed) have similar fracture strength, although bilayer restorations present lower strength when compared with monolithic ceramics.

Influence of external energy sources on the dynamic setting process of glass-ionomer cements.

OBJECTIVE: To evaluate the influence of external energy sources on the dynamic setting process of glass-ionomer restorative materials. METHODS: Eighteen brands of GIC were studied: Bioglass R (Biodinâmica; G1), Chemfil Rock (Dentsply; G2), Equia Forte (GC; G3), Gold Label 2 (GC; G4), Gold Label 9 (GC; G5), Glass Ionomer Cement Type II - (Shofu; G6), Ionglass R (Maquira; G7), Ion Z (FGM; G8), Ionomaster (Wilcos; G9), Ionofil Plus (Voco; G10), Ionostar Plus (Voco; G11), Ketac Molar easymix (3M ESPE; G12), Magic Glass R (Vigodent; G13), Maxxion R (FGM; G14), Riva Self Cure (SDI; G15), Vidrion R (SS White; G16), Vitro Fil R (Nova DFL; G17) and Vitro Molar (Nova DFL; G18). LED, halogen light or ultrasound (n=20 for each set) applied for 30s was used to activate setting, and a control group of each material was allowed to set without activation. Samples were analyzed by FTIR spectroscopy using the ratio of intensities of bands at 1637cm-1 (carboxylate) and 1720cm-1 (carbonyl) as a function of time. Means and standard deviations were subjected to ANOVA and Tukey tests (p<0.05). RESULTS: All three activation modes significantly reduced the time at which the carboxylate content became stable in G2, G4, G5, G6, G8, G10, G14, G16, G17 and G18. By contrast, in G1, G7, G12 and G15 no activation source had any significant effect (p>0.05). SIGNIFICANCE: External activation sources, namely LED, halogen light and ultrasound, typically but not always increase the setting rate of restorative GICs.

Positive correlation between fluoride release and acid erosion of restorative glass-ionomer cements.

OBJECTIVE: The aim of this study was to determine whether there is a correlation between acid erosion and fluoride release of conventional glass ionomer cements. METHODS: Ten specimens for each material were prepared for fluoride release tests and five for acid erosion tests separately. After placed in pH cycling solution, concentration of fluoride was measured by a fluoride-ion selective electrode each day for 15 days. For the acid erosion test, specimens were immersed in a lactic acid solution and their depth measured with a spring-loaded dial gauge. The data were submitted to 3-way ANOVA, followed by Tukey's test (p<0.05) RESULTS: All materials showed ability to elute fluoride in the 15 day period of the test, with the same pattern of high fluoride release at the first 24h. Despite this, the amount of fluoride released was statistically different among the 18 groups, with the highest for Maxxion R and the lowest for Chemfil Rock (p>0.05). The highest acid erosion values were registered for Magic Glass, Ion Z, VitroFil and Maxxion R, which exceeded the maximum stipulated by the relevant ISO test (ISO 9917-1). A positive linear correlation (r2=0.4886) was found for both properties, i.e., higher fluoride release is related to higher acid erosion. SIGNIFICANCE: Acid erosion and fluoride release are related properties of GICs, though factors such as pH and P/L ratio lead to differences between actual values for individual brands of these materials.

Titanium dioxide nanotubes addition to self-adhesive resin cement: Effect on physical and biological properties.

OBJECTIVES: This study has investigated the influence of Titanium dioxide nanotubes (TiO2-nt) addition to self-adhesive resin cement on the degree of conversion, water sorption, and water solubility, mechanical and biological properties. METHODS: A commercially available auto-adhesive resin cement (RelyX U200™, 3M ESPE) was reinforced with varying amounts of nanotubes (0.3, 0.6, 0.9wt%) and evaluated at different curing modes (self- and dual cure). The DC in different times (3, 6, 9, 12 and 15min), water sorption (Ws) and solubility (Sl), 3-point flexural strength (σf), elastic modulus (E), Knoop microhardness (H) and viability of NIH/3T3 fibroblasts were performed to characterize the resin cement. RESULTS: Reinforced self-adhesive resin cement, regardless of concentration, increased the DC for the self- and dual-curing modes at all times studied. The concentration of the TiO2-nt and the curing mode did not influence the Ws and Sl. Regarding σf, concentrations of both 0.3 and 0.9wt% for self-curing mode resulted in data similar to that of dual-curing unreinforced cement. The E increased with the addition of 0.9wt% for self-cure mode and H increased with 0.6 and 0.9wt% for both curing modes. Cytotoxicity assays revealed that reinforced cements were biocompatible. SIGNIFICANCE: TiO2-nt reinforced self-adhesive resin cement are promising materials for use in indirect dental restorations. Taken together, self-adhesive resin cement reinforced with TiO2-nt exhibited physicochemical and mechanical properties superior to those of unreinforced cements, without compromising their cellular viability.

The shear bond strength of self-adhesive resin cements to dentin and enamel: an in vitro study.

STATEMENT OF PROBLEM: Clinicians continue to search for ways to simplify bonding procedures without compromising clinical efficacy. PURPOSE: The purpose of this study was to evaluate the shear strength of self-adhesive cements RelyX U100 and RelyX U200, and conventional resin cement RelyX ARC to enamel and dentin after different surface treatments. MATERIAL AND METHODS: The crowns of 120 bovine incisor teeth were separated from the roots and embedded in epoxy resin in polyvinyl chloride tubes. In each tooth, the area to be cemented was delimited with central holed adhesive tape. The teeth were distributed into 12 groups (n=10) according to the substrate; etched or not with 37% phosphoric acid; and cement type of enamel-U100, enamel-phosphoric acid-U100, enamel-U200, enamel-phosphoric acid-U200, enamel-ARC, enamel-phosphoric acid-ARC, dentin-U100, dentin-phosphoric acid-U100, dentin-U200, dentin-phosphoric acid-U200, dentin-ARC, and dentin-phosphoric acid-ARC. After 7 days of storage in artificial saliva, shear strength tests were performed by using a universal testing machine (0.5 mm/min). The data were analyzed with 3-way ANOVA and the Tukey test (α=.05). Fracture analysis was performed with a light microscope. Two specimens from each group were analyzed with a scanning electron microscope. RESULTS: In enamel, ARC (9.96 MPa) had higher shear strength (P=.038) than U100 (5.14 MPa); however, after surface etching, U100 (17.81 MPa) and U200 (17.52 MPa) had higher shear strength (P<.001). With dentin, no significant differences were observed (P=.999), except for dentin-ARC (0.34 MPa) (P=.001). Most fractures were of the adhesive type. CONCLUSIONS: U200 self-adhesive cement had similar bond strength to the ARC in enamel, but the combination with phosphoric acid had the best bond strength. For dentin, self-adhesive resin cements are equally effective alternatives to conventional resin cement.