Using digital photographs as a tool to assess the clinical color stability of lithium disilicate veneers: A clinical trial.

STATEMENT OF PROBLEM: Clinical information regarding the color stability of lithium disilicate veneers by using different methods of evaluation is scarce. PURPOSE: This clinical trial aimed to evaluate whether digital photographs are a reliable method of clinically assessing the color stability of lithium disilicate veneers. Standardized digital photographs (ELAB) were compared with the VITA Easyshade spectrophotometer (ES) at baseline and at a 6-month follow-up. MATERIAL AND METHODS: A split-mouth model was used in this randomized clinical trial to assess the performance of ceramic veneers (N=162), which were produced by either the CAD (IPS e.max CAD; n=81) or PRESS technique by heat pressing (IPS e.max PRESS; n=81), including the color dimension assessment. The ELAB evaluation was performed by making digital photographs with polarized light and a white balance (WhiBal) card. These data were transferred to the Adobe Lightroom CC2015 software program in RAW extension. The Digital Color Meter App (Apple) was used to measure L∗, a∗, and b∗ coordinates in this method. The ES color evaluation was performed with a spectrophotometer (Easy Shade) (control group) in the CIELab system. Measurements were performed 1 week after cementation (baseline) and at a 6-month follow-up. Data collected by the ELAB and ES methods were analyzed by a blinded calibrated operator to calculate ΔE by using the Mann-Whitney-Wilcoxon test (α=.05). RESULTS: For all periods, the comparison among ELAB and ES methods (P=.331), CAD×PRESS by ELAB (P=.658), and CAD×PRESS by ES (P=.833) showed no statistically significant differences. CONCLUSIONS: Standardized digital photographs (ELAB) were shown to be a straightforward and available resource for evaluating the color stability of lithium disilicate veneers, manufactured by CAD or PRESS.

Marginal adaptation of CAD-CAM onlays: Influence of preparation design and impression technique.

STATEMENT OF PROBLEM: Factors that may affect the marginal adaptation of computer-aided design and computer-aided manufacturing (CAD-CAM) restorations include preparation design, impression technique, and CAD-CAM system. The influence of impression technique and preparation design on CAD-CAM partial coverage restorations has not been fully addressed. PURPOSE: The purpose of this in vitro study was to investigate the influence of direct and indirect digital scanning techniques and 2 preparation designs on the marginal adaptation of CAD-CAM onlays. MATERIAL AND METHODS: Two mesio-occlusal buccal onlay preparations with reduction of the mesiobuccal cusp were made: conventional preparation (CP) with a 1.2-mm modified shoulder margin and modified preparation (MP) flat cuspal reduction without shoulder. Virtual models were generated from each preparation by using a digital scanner (BlueCam; Dentsply Sirona) from the plastic teeth (direct digital scan) or from the stone dies (indirect digital scan). Onlays were designed using a CAD-CAM system (CEREC 4.0; Dentsply Sirona), and nanoceramic resin blocks (Lava Ultimate Restorative; 3M ESPE) were milled using the CEREC MCX milling machine. Marginal discrepancy was evaluated using an optical stereomicroscope at ×25 magnification in 18 locations distributed along the margins of the preparation. The data were analyzed by using 3-way ANOVA followed by the Tukey HSD test (α=.05). RESULTS: CP presented a statistically significant reduced average marginal adaptation (59 ±50 µm) than did MP (69 ±58 µm) (P<.001). The Tukey HSD test showed the presence of a significantly larger marginal discrepancy in the mesial and buccal locations of MP when compared with CP. Regarding impression techniques, the buccal location presented the smallest average marginal discrepancy in restorations fabricated with indirect impression when compared with direct impression (42 ±33 µm and 60 ±39 µm) (P<.001). CONCLUSIONS: The results showed that conventional preparation with a modified shoulder margin presented improved marginal adaptation compared with modified preparation with flat cuspal reduction. Direct and indirect digital scanning techniques produced restorations within a clinically acceptable range; however, the indirect scanning technique resulted in the fabrication of restorations with superior marginal adaptation on the buccal location.

Effect of surface treatments on the bond strength of self-etching adhesive agents to dentin.

The aim of this study was to investigate the influence of different surface treatments on the shear bond strength (SBS) of self-etching adhesive systems to dentin. Ninety freshly extracted noncarious human molars were sectioned mesiodistally and embedded in chemically cured resin with the buccal or lingual surfaces facing upward. Superficial dentin was exposed, and specimens were randomly assigned to 3 groups, according to the self-etching adhesive system utilized: Clearfil SE Bond (2-step), Scotchbond Universal (1-step), and Clearfil S³ Bond Plus (1-step). These groups were assigned to 5 subgroups (n = 12), according to the following treatments: G1, distilled water (control); G2, 35% phosphoric acid gel; G3, ultrasonic vibration; G4, sandblasting; G5, pumice slurry. For the 1-step self-etching adhesives, no significant differences in SBS values were observed between the different surface treatment groups and their control subgroup (P > 0.05). For the 2-step adhesive, mean values were significantly higher in the ultrasonic vibration and pumice-treated groups than in the control subgroup (P < 0.05). Overall, the use of vibration resulted in superior mean SBS values to dentin for all adhesives tested, although the values were not always significantly higher.

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.

Current all-ceramic systems in dentistry: a review.

This article describes the ceramic systems and processing techniques available today in dentistry. It aims to help clinicians understand the advantages and disadvantages of a myriad of ceramic materials and technique options. The microstructural components, materials' properties, indications, and names of products are discussed to help clarify their use. Key topics will include ceramics, particle-filled glasses, polycrystalline ceramics, CAD/CAM, and adhesive cementation.

Influence of oral health condition on swallowing and oral intake level for patients affected by chronic stroke.

BACKGROUND: According to the literature, the occurrence of dysphagia is high in cases of stroke, and its severity can be enhanced by loss of teeth and the use of poorly fitting prostheses. OBJECTIVE: To verify that the status of oral health influences the level of oral intake and the degree of swallowing dysfunction in elderly patients with stroke in chronic phase. METHODS: Thirty elderly individuals affected by stroke in chronic phase participated. All subjects underwent assessment of their oral condition, with classification from the Functional Oral Intake Scale (FOIS) and nasoendoscopic swallowing assessment to classify the degree of dysphagia. The statistical analysis examined a heterogeneous group (HG, n=30) and two groups designated by the affected body part, right (RHG, n=8) and left (LHG, n=11), excluding totally dentate or edentulous individuals without rehabilitation with more than one episode of stroke. RESULTS: There was a negative correlation between the need for replacement prostheses and the FOIS scale for the HG (P=0.02) and RHG (P=0.01). Differences in FOIS between types of prostheses of the upper dental arch in the LHG (P=0.01) and lower dental arch in the RHG (P=0.04). A negative correlation was found between the number of teeth present and the degree of dysfunction in swallowing liquid in the LHG (P=0.05). There were differences in the performance in swallowing solids between individuals without prosthesis and those with partial prosthesis in the inferior dental arch (P=0.04) for the HG. CONCLUSION: The need for replacement prostheses, type of prostheses, and the number of teeth of elderly patients poststroke in chronic phase showed an association with the level of oral intake and the degree of oropharyngeal dysphagia.

Effect of preheating on microhardness and viscosity of 4 resin composites.

OBJECTIVE: This study was undertaken to determine the effect of temperature on the microhardness and viscosity of 4 resin composite materials. METHODS: To investigate microhardness, samples of each of the 4 composite materials, prepared by standard insertion of resin into prefabricated moulds, were divided into 2 groups (n = 10 per group). On the first group, the resin composite materials were inserted into the moulds at room temperature and cured. On the second group, the resin composite materials were pre-heated in a heating device, inserted into the moulds and immediately cured. Microhardness after curing (both immediately and after 24 hours of storage) was determined (using a 300 g load applied for 10 seconds) and averaged for 5 randomly selected points on the top and bottom surfaces of each sample. To investigate viscosity, 0.5 g samples of room temperature or preheated resin composite (n = 15 per group) were placed under a 454 g load for 45 seconds before light-curing (40 seconds). After curing, each sample was photographed and the surface area calculated. Data were analyzed by t tests or one-way analysis of variance and Tukey's test. RESULTS: Preheating the resin composites increased the microhardness and decreased the viscosity of the samples. Filtek Supreme Ultra resin composite had the highest mean microhardness, and Vit-l-escence resin composite had the lowest viscosity. CONCLUSIONS: The effects of preheating resin composites may allow easier placement of restorations and greater monomer conversion.

Influence of ceramic shades on surface hardness of different resin cements.

OBJETIVES: The aim of this study was to evaluate the effect of different ceramic spacer shades on the Knoop hardness (KH) of dual-cure resin cements (RelyX ARC RLX, 3M ESPE; Variolink II VLK, Ivoclar Vivadent) cured for 20 seconds with an LED light-curing unit. MATERIALS: Eight groups (n equals 15) were tested as follows: RelyX Control (light-cured without ceramic spacer); RelyX-2M2 ceramic spacer; RelyX-5M3 ceramic spacer; RelyX self-cured. Similar conditions were used with Variolink II cement. A microhardness tester was used to measure the KH values. Specimens were subjected to five 50 g/15 s indentations following curing at 0, 1, 2, 3, 4, 6, 24, 168, and 336 hours in order to determine the point at which the cements reach the maximum KH values. RESULTS: Control groups exhibited significantly higher KH values than the other groups (P less than 0.001) at 0 h following light curing. The KH values for RelyX-2M2 were not significantly different than the control group (P greater than 0.05) after 336 hours. All groups tested with 5M3 spacers had KH values that were not significantly different from the groups with self-cure mode, P greater than 0.05. The KH values for RelyX self-cure cement were significantly higher than Variolink II self-cure, P equals 0.003. RelyX-2M2 had KH values that were not significantly different from that of Variolink-2M2, P greater than 0.05. CONCLUSIONS: Ceramic spacer shades have tremendous effect on the KH values of RelyX and Variolink II. Darker ceramic shades (5M3 spacers) interfere with the absorption of light by the cements tested. In addition, the chemical portion in the self-cured mode is not sufficient to achieve optimum microhardness.

Evaluation of proximal contacts of posterior composite restorations with 4 placement techniques.

BACKGROUND: Contrary to the situation for amalgam restorations, obtaining acceptable proximal contacts with posterior composite restorations can be difficult. Proximal contacts that are less than ideal may permit food impaction and subsequent caries formation and periodontal problems. PURPOSE: The aim of this study was to assess the quality of proximal contacts of posterior composite restorations placed with 4 restorative techniques. METHODS: Seventy-five mounted ivorine teeth with large, standardized MOD cavities were divided into 5 groups of 15 teeth each. The teeth in 4 of these groups were restored with a resin composite and those in the remaining group were restored with amalgam. The restorative techniques for the 4 composite groups were traditional wedge and matrix (Group 1), use of a light-tip attachment (Group 2), use of the Contact Pro hand instrument (Group 3) and use of Beta Quartz glass-ceramic inserts (Group 4). All restorations were completed under simulated clinical conditions. Standards for evaluating proximal contacts were set by preparing 4 dental study models, each model having one type of proximal contact (open, not tight enough, ideal and too tight). All restored teeth were carefully painted with opaque nail polish, except at the contact areas, to conceal restoration type and hence to ensure unbiased evaluation by assessors. Three experienced clinicians independently assessed the quality of the proximal contacts of all restored teeth (total of 150 contacts) relative to the 4 types of contacts exemplified by the dental study models. In cases of disagreement, the clinicians reassessed the disputed contact collectively. RESULTS: Amalgam restorations had 5 contacts that were not tight enough, 20 that were ideal and 5 that were too tight. The Group 1 composite restorations had a total of 25 open contacts and 5 contacts that were not tight enough; the Group 2 composite restorations had 3 open contacts, 13 contacts that were not tight enough and 14 that were ideal; the Group 3 composite restorations had 11 contacts that were not tight enough and 19 that were ideal; and the Group 4 composite restorations had 3 contacts that were not tight enough and 27 that were ideal. None of the composite contacts was judged too tight. CONCLUSIONS: The use of inserts (Group 4) resulted in a better rate of acceptable proximal contacts in posterior composite restorations than the 3 other techniques (90% vs. 0%, 47% and 63% for Group 1, Group 2 and Group 3, respectively).