Noéli Boscato

Cast metal vs. glass fibre posts: A randomized controlled trial with up to 3 years of follow up

OBJECTIVE This randomized controlled trial compared the survival of glass fibre and cast metal dental posts used to restore endodontically treated teeth with no remaining coronal wall. METHODS Fifty-four participants (45 women) and 72 teeth were evaluated during a follow-up period of up to 3 years. Teeth were randomly allocated to the glass-fibre and cast-metal post groups. All teeth were restored with single metal-ceramic crowns. Survival probabilities were analyzed using Kaplan-Meier statistics (p≤0.05). RESULTS The 3-year recall rate was 92.3% and the survival rates of glass fibre and cast metal posts were similar (97.1% and 91.9%, respectively; p=0.682). Four failures were observed: two glass fibre posts in a premolar and anterior tooth debonded, one glass fibre post in a premolar debonded in association with root fracture, and one root fracture occurred in a molar with a cast metal post. CONCLUSIONS Glass fibre and cast metal posts showed similar clinical performance in teeth with no remaining coronal wall after 3 years. CLINICAL SIGNIFICANCE Posts are used to restore most endodontically treated teeth with no remaining coronal wall. This randomized controlled trial, one of few to compare glass fibre and cast metal posts in such teeth, showed that post type did not significantly influence the survival of restorations. These results can help dentists respond to the important question of how best to rehabilitate endodontically treated teeth with no remaining coronal wall.

Biofilm formation of Candida albicans on the surface of a soft denture-lining material

BACKGROUND Soft denture lining-materials are more susceptible to microbial adhesion than hard denture base acrylic resin. Poor oral hygiene and Candida albicans infection are common among elderly denture wearers as these patients usually have difficulty in keeping them clean. PURPOSE To evaluate the influence of the oral hygiene methods on the formation of a biofilm over a soft denture-lining material. MATERIAL AND METHODS Twenty volunteers were randomly separated into two groups: G1 and G2. Ten volunteers performed daily hygiene of the prostheses with a soft toothbrush and toothpaste. The G2 performed a treatment identical to G1 but also immersed the prostheses in sodium hypochlorite 0.5% for 20 min, once a week. Quantification of the mean score values of biofilm formation at different times were statistically analysed using analysis of variance and Tukeys test (alpha = 0.05). RESULTS G1 (0.65 +/- 0.52) showed the lowest mean score values of biofilm formation. There was statistical difference between G1 and G2. The highest mean score values were found at 6 weeks (1.3 +/- 1.08) and were statistically different from other times. CONCLUSION The oral hygiene methods had a significant effect in the formation of the biofilm over a soft denture-lining material.

Resin-based luting agents and color stability of bonded ceramic veneers

STATEMENT OF PROBLEM The type of resin-based luting agent might influence the color stability of ceramic veneers. PURPOSE The purpose of this study was to investigate the effects of resin-based agents and aging on the color stability of ceramic veneers bonded to enamel. MATERIAL AND METHODS Ceramic disks were cemented to bovine enamel disks with 4 resin-based luting agents (n=10): dual-polymerizing cement (RelyX ARC), light-polymerizing cement (RelyX Veneer), flowable composite resin (Filtek Z350 Flow), or composite resin preheated for 30 minutes at 60°C (Filtek Z350 XT). CIE L*, a*, and b* color coordinates were measured 24 hours after cementation (baseline) with a color spectrophotometer and reevaluated after 10,000 and 20,000 thermal cycles. Color variation was calculated by using CIELab (ΔE*(ab)) and CIEDE2000 (ΔE00) methods. Then 95% confidence intervals were calculated for color variation means between baseline and 10,000 thermal cycles and between 10,000 and 20,000 thermal cycles. The 95% confidence intervals were also calculated for the means of individual color coordinates (L*, a*, and b*). RESULTS The dual-polymerizing cement had the highest color variation among all luting agents. No significant differences were found in color variation among the light-polymerizing materials. All agents showed ΔE*(ab)>3.46 and ΔE00>2.25 after 20,000 thermal cycles. Variations in L*, a*, and b* coordinates were material dependent. The dual-polymerizing agent was yellowish and reddish after aging. CONCLUSIONS The dual-polymerizing cement had higher color variation than the light-polymerized materials when used for bonding ceramic veneers to enamel. Flowable and preheated composite resins had similar color stability to that of light-polymerizing resin-based cement.

Biofilm formation on denture liners in a randomised controlled in situ trial

OBJECTIVES This randomised clinical trial assessed how biofilm development and composition is affected by time and denture material type in denture wearers with and without denture stomatitis. METHODS Specimens of acrylic resin (control) and denture liners (silicone-based or acrylic resin based, depending on the experimental phase) were inserted into the surface intaglio of 30 denture wearers. Biofilm was formed in two phases of 21 days, and counts of viable micro-organisms in the accumulating biofilm were determined after 7, 14 and 21 days of biofilm formation. Data were analysed by three-way ANOVA followed by Tukey test to assess differences among health condition (healthy or with denture stomatitis), materials and time point. RESULTS Non-albicans Candida species counts were higher in diseased patients with silicone-based denture liners (p=0.01). Denture stomatitis patients showed higher mutans streptococci counts after 7 days (p=0.0041). CONCLUSIONS Longer biofilm formation time periods did not result in differences on biofilm composition. The denture liners evaluated in this study accumulate greater amount of biofilm, and therefore their use should be carefully planned. CLINICAL SIGNIFICANCE The silicone-based denture liner tested should be used cautiously in patients with denture stomatitis as it showed increased non-albicans species counts, known to be difficult to treat.

Prevalence of temporomandibular disorders in a population of complete denture wearers

BACKGROUND Complete tooth loss among the elderly is still frequent in developing countries and the incidence of temporomandibular disorders (TMD) is a common finding in complete denture wearers. OBJECTIVES The aim of this study was to evaluate the prevalence of temporomandibular disorders (TMD) in a population of complete denture wearers. MATERIALS AND METHODS The data were collected by four examiners for the diagnosis of use and need for complete dentures followed by the World Health Organization standards and interviews for TMD signs and symptoms evaluation. Exploratory variables included demographic, socio-economic status and TMD prevalence. RESULTS The prevalence of TMD among denture wearers was 55.12%. Chi-squared test showed no statistical difference between subjects with or without TMD for gender, geographical location and skin colour (p < 0.05). The number of subjects with TMD increased as the period of complete denture wear increased, although no statistical difference between groups were found (p < 0.05). CONCLUSIONS There is a need of educational programmes aiming at the importance of health care and periodical change of a complete denture, and strategies with a preventive approach to quality general dental care.

Effect of cariogenic challenge on the stability of dentin bonds

Objective The oral environment is subject to biofilm accumulation and cariogenic challenge, and few studies exist on the effect of these factors on the bond strength of adhesive systems. The aim of this study was to test if the exposure of adhesive interfaces to cariogenic challenge under biofilm accumulation could promote higher degradation than the exposure to biofilm accumulation alone. Material And Methods Five molars were ground until exposure of medium dentin and then restored (Single Bond 2 and Z250 3M ESPE). The tooth/resin sets were cut to obtain beam-shaped specimens, which were distributed according to the aging conditions (n=20): water for 24 h (control); biofilm under cariogenic challenge for 3, 5 or 10 days; biofilm without cariogenic challenge for 10 days; and water for 3 months. Microcosm biofilms were formed from human saliva and grown in a saliva analogue medium, supplemented or not with sucrose to promote cariogenic challenge. Specimens were tested for microtensile bond strength, and failure modes were classified using light microscopy. Bond strength data were analyzed using ANOVA and failure modes were analyzed using ANOVA on ranks (α=0.05). Results No significant differences in bond strength were detected among the aging methods (P=0.248). The aging period was associated with an increase in the frequency of adhesive failures for the groups aged for 10 days or longer (P<0.001). Conclusion Aging leads to a higher prevalence of interfacial adhesive failures, although this effect is not associated with cariogenic challenge or reduction in bond strengths.

Effectiveness of Combination of Dentin and Enamel Layers on the Masking Ability of Porcelain

This study evaluated the masking ability of different porcelain thicknesses and combination of enamel and/or dentin porcelain layers over simulated background dental substrates with higher (A2) and lower (C4) color values. Combination of the enamel (E) and dentin (D) monolayer porcelain disks with different thicknesses (0.5 mm, 0.8 mm, and 1 mm) resulted in the following bilayer groups (n=10): D1E1, D1E0.8; D1E0.5; D0.8E0.8; D0.8E0.5, and D0.5E0.5. CIELAB color coordinates were measured with a spectrophotometer. The translucency parameter of mono and bilayer specimens and the masking ability estimated by color variation (ΔE*ab) of bilayer specimens over simulated dental substrates were evaluated. Linear regression analysis was used to investigate the relationships translucency parameter × ΔE*, translucency parameter × porcelain thickness, and ΔE* × porcelain thickness. Data were analyzed statistically (α= 0.05). Thinner porcelain disks were associated with higher translucency. Porcelain monolayers were considerably more translucent than bilayers (enamel + dentin). Dentin porcelain was less translucent than enamel porcelain with same thickness. ΔE* was always lower when measured over A2 background. Higher ΔE* was observed for the C4 background, indicating poorer masking ability. Increased ΔE* was significantly associated with increased translucency for both backgrounds. Decreased translucency and ΔE* were associated with increased total porcelain thickness or increased dentin thickness for both backgrounds. In conclusion, increased porcelain thickness (particularly increased dentin layer) and increased porcelain opacity resulted in better masking ability of the dental backgrounds.

Effect of triazine derivative added to denture materials on a microcosm biofilm model.

The aim of this study was to assess the effect of triazine incorporation to denture materials on biofilm formation of saliva derived from microcosms of patients who are positive for Candida albicans. Biofilms were formed on microwave-cured acrylic resin, one hard denture liner, and two soft denture liners containing 0, 2.5, 5, and 10% triazine. For experimental subset (n = 10), mechanical properties of the materials and colony-forming unit counts from the biofilms formed on the materials were assessed. Flexural strength and modulus decreased with the addition of 2.5% triazine (p < 0.01). In general, the addition of 5 and 10% triazine leaded to more soluble materials (p < 0.001). Saliva donor with candidiasis resulted in higher counts of total microorganisms (p = 0.0294) and Streptococci (p = 0.0008). Soft denture liners showed the highest counts for total microorganisms, Streptococci, and Candida species (p < 0.001). The addition of triazine directly to denture materials was not beneficial in reducing biofilm formation in a complex biofilm model.

Influence of varnish application on a tissue conditioner: analysis of biofilm adhesion

PURPOSE The aim of this study was to evaluate if the use of a varnish on a tissue conditioner would affect biofilm adhesion. BACKGROUND After the surgery has been performed, before the delivery of a complete denture, it is often necessary to use materials such as tissue conditioners on the surgical wound. However, these materials present deficient physico-mechanical properties, which allow biofilm development. METHODS Forty elderly volunteers wearing complete maxillary dentures were selected. They were randomly allocated into two groups (n = 20), G1 and G2. In both groups, a silicone-based tissue conditioner was placed in a recess created at the base of the denture, according to the manufacturers guidelines. In group G1, a varnish was applied to the tissue conditioner, while in group G2, no treatment was applied. All volunteers performed daily hygiene of the prosthesis with a soft toothbrush, and toothpaste. Quantification of the mean score values of biofilm formed at different time points (baseline, 1 week and 3 weeks) was statistically analysed using anova (alpha = 0.05). RESULTS Group G2 (1.6 +/- 1.2) showed the lowest mean score values of biofilm formation and there was a statistical difference between the groups (p = 0.03). The highest mean score values were found after 3 weeks (2.7 +/- 1.4) and were statistically different from the other time points studied (baseline and 1 week). CONCLUSION The use of a varnish had a detrimental effect on the tissue conditioner studied, allowing higher biofilm formation.

Masking Colored Substrates Using Monolithic and Bilayer CAD-CAM Ceramic Structures

OBJECTIVE  To evaluate the masking ability and translucency of monolithic and bilayer CAD-CAM ceramic structures. METHODS  Discs of high translucency (HT) and low translucency (LT) lithium disilicate-based ceramic (IPS e.max CAD) with different thicknesses (0.7, 1, 1.5, and 2 mm) were evaluated as a monolithic structure or combined (bilayer) with a 0.5-mm-thick zirconia framework (IPS e.max ZirCAD). The masking ability and translucency were calculated based on CIE L*a*b* color coordinates measured with a spectrophotometer (SP60, X-Rite). The translucency parameter (TP) was calculated using color coordinates measured over standard white-and-black backgrounds. The masking ability was calculated by CIEDE2000 color difference metric (ΔE00) for each specimen measured over a tooth-colored substrate (shade A2) compared to three darker backgrounds (shade C4 and two metal substrates). Confidence intervals (CI) for the means (95% CI) were calculated for TP and ΔE00. The Pearson correlation between ΔE00 and TP was investigated for monolithic and bilayer structures over all backgrounds. RESULTS  The thinner the lithium disilicate layer, the greater the translucency and the higher the ΔE00 values. The effect of ceramic thickness on both translucency and masking ability was more pronounced for the monolithic structures. In addition, monolayers always presented a greater color variation than their bilayer counterparts. The metallic background produced greater ΔE00 than the C4-shaded substrate. CONCLUSION  Monolithic veneers were able to mask C4-shaded background but did not mask metallic backgrounds. Bilayer structures showed greater shade masking ability than monolithic structures.