Renata Corrêa Pascotto

In vivo effect of a resin-modified glass ionomer cement on enamel demineralization around orthodontic brackets

Because the risk of dental caries increases with the use of orthodontic appliances and its control cannot depend only on the patients self-care, this study evaluated the effect of a glass ionomer cement on reducing enamel demineralization around orthodontic brackets. Fourteen orthodontic patients were randomly divided into 2 groups of 7; they received 23 brackets fitted to their premolars, bonded with either Concise (3M Dental Products, St Paul, Minn), a composite resin (control group), or Fuji Ortho LC (GC America, Chicago, Ill), a resin-modified glass ionomer cement (experimental group). The volunteers lived in a city that has fluoridated water, but they did not use fluoridated dentifrices during the study. After 30 days, the teeth were extracted and longitudinally sectioned; in the enamel around the brackets, demineralization was assessed by cross-sectional microhardness. The determinations were made at the bracket edge cementing limits, and at occlusal and cervical points 100 and 200 microm away from them. In all of these positions, indentations were made at depths from 10 to 90 microm from enamel surface. Analysis of variance showed statistically significant effects for position, material, depth, and their interactions (P<.05). The Tukey test showed that the glass ionomer cement was statistically more efficient than the control, reducing enamel demineralization in all analyses (P<.05). The use of glass ionomer cement for bonding can be encouraged because it decreases the development of caries around orthodontic brackets.

Composite depth of cure using four polymerization techniques

The light-curing technique is relevant to reduce the degree of polymerization shrinkage, improving clinical and esthetic success of composite resin restorations. Objective: To evaluate in vitro the effect of four light-curing techniques on depth of cure of a composite resin. Material and Methods: Ten specimens of a composite resin were made in cylindrical cavities prepared in PVC plates (3.0 X 7.0 mm) for each light-curing technique. Four photoactivation methods were investigated: stepped, ramped, pulse-delay and traditional. Specimens were longitudinally sectioned and polished for microhardness measurements (kg/mm2), which were made at 0.1, 1.0, 2.0 and 4.0 mm from the irradiated surface. Data were subjected to ANOVA and Tukeys test. Results: The effect of factors studied (curing method and distance from the surface) and the interaction of these factors was statistically significant (p<0.05). The traditional method of cure provided higher microhardness values (69.6 ± 2.5) than the stepped (63.5 ± 3.1) and pulsed (63.9 ± 3.2) methods at all depths evaluated, but it did not differ from the ramped method (66.7± 4.4) at 0.1 and 1.0 mm of depth. Conclusion: All techniques employed provided satisfactory cure of the composite resin up to the depth of 2.0 mm from the irradiated surface.

LIBERAÇÃO DE FLÚOR DE QUATRO CIMENTOS DE IONÔMERO DE VIDRO RESTAURADORES

A liberacao de fluor de quatro cimentos de ionomero de vidro usados para restauracaox97 Photac Fil (PF), Vitremer (VT), Fuji II LC (F2) e Fuji IX (F9) x97 foi testada durante 14 dias. As leituras do fluor liberado para agua deionizada foram realizadas por um eletrodo especifico para esse ion, acoplado a um analisador de pH/ions. Os dados foram submetidos a analise de variância e teste de Tukey-Kramer. A quantidade de fluor liberada foi significantemente maior para o PF em relacao aos outros materiais (PF > VT > F9 > F2), sendo que VT/F9 e F2/F9 nao apresentaram diferenca significante entre si (p < 0,05).

Influence of exposure time to saliva and antioxidant treatment on bond strength to enamel after tooth bleaching: an in situ study

Objectives This study evaluated the influence of different exposure times to saliva in situ in comparison with an antioxidant treatment on composite resin bond strength to human enamel restored after tooth bleaching. Material and Methods Forty human teeth specimens measuring 5x5 mm were prepared and randomly allocated into 5 groups with 8 specimens each: Gct (control group, restored on unbleached enamel); Gbl (restored immediately after bleaching); Gsa (bleached, treated with 10% sodium ascorbate gel for 60 min and restored); G7d (bleached, exposed to saliva in situ for 7 days and restored); and G14d (bleached, exposed to saliva in situ for 14 days and restored). Restored samples were cut into 0.8 mm2 sticks that were tested in microtensile. Specimens were microscopically analyzed and failure modes were classified as adhesive, cohesive, or mixed. Pretest and cohesive failures were not considered in the statistical analysis, which was performed with one-way ANOVA and Tukeys post-hoc test (α=0.05), with the dental specimen considered as the experimental unit. Results Mean bond strength results found for Gbl in comparison with Gct indicated that bleaching significantly reduced enamel adhesiveness (P<0.01). However, no statistically significant differences were found between Gct, Gsa and G7d (P>0.05). Bond strength found for G14d was significantly higher than for Gsa (P<0.01). Fractures modes were predominantly of a mixed type. Conclusions Bonding strength to bleached enamel was immediately restored with the application of sodium ascorbate and exposure to human saliva in situ for at least 7 days. Best results were obtained with exposure to human saliva in situ for 14 days. Treatment with sodium ascorbate gel for 60 min may be recommended in cases patients cannot wait for at least 7 days for adhesive techniques to be performed.

Susceptibility to Coffee Staining during Enamel Remineralization Following the In-Office Bleaching Technique: An In Situ Assessment.

PURPOSEnTo assess in situ the enamel mineralization level and susceptibility to coffee staining after in-office bleaching.nnnMATERIALS AND METHODSnThirty-six human dental fragments assembled into intraoral devices were bleached with 35% hydrogen peroxide and treated as follows: (group 1) no contact with coffee; (group 2) immersion in a coffee solution for 30 minutes daily for 7 days, starting 1 week after bleaching; and (group 3) immersion in a coffee solution for 30 minutes daily for 14 days, starting immediately after bleaching. Enamel mineralization and color were assessed before bleaching (T1), immediately after bleaching (T2), and after 7 (T3) and 14 days (T4). The CIE whiteness index (W*) and closeness to white (ΔW*) following bleaching and/or immersion in coffee were calculated. Data were analyzed with Friedman and Wilcoxon tests or Kruskal-Wallis and Mann-Whitney U-tests (αu2009=u20090.05).nnnRESULTSnSignificant differences in the mineralization levels were observed as a function of time. No significant differences in W* were observed between groups, nor was W* significantly different at T3 and T4. Similar ΔW* was observed between groups after 7 or 14 days.nnnCONCLUSIONSnThe mineral loss after in-office bleaching was progressively reversed by contact with saliva for 14 days. The whiteness index was not affected by contact with coffee during the remineralization period.nnnCLINICAL SIGNIFICANCEnThe results of this in situ study suggest that the mineral loss caused by in-office dental bleaching is minimal and is partly compensated by remineralization due to contact with saliva. Additionally, whiteness was not affected by daily exposition to coffee during the enamel remineralization, which indicates that avoiding the consumption of coffee immediately following in-office bleaching is unnecessary. (J Esthet Restor Dent 28:S23-S31, 2016).

Meta-analysis of the clinical behavior of posterior direct resin restorations: Low polymerization shrinkage resin in comparison to methacrylate composite resin

Polymerization shrinkage of resin composite can compromise the longevity of restorations. To minimize this problem, the monomeric composition of composites have been modified. The objective of this study was to conduct a meta-analysis to assess the clinical behavior of restorations performed with low polymerization shrinkage resin composite in comparison with traditional methacrylates-based resin composite. This systematic review was registered at Prospero data system (CRD42015023940). Studies were searched in the electronic databases PubMed, Web of Science, Scopus, Lilacs and EMBASE according to a predefined search strategy. The inclusion criteria were as follow: (1) randomized controlled clinical trials with at least six months of follow-up; (2) studies investigating composites with monomers designed to reduce polymerization shrinkage; (3) studies conducted with class I or II restorations in the permanent dentition; and (4) studies that assessed at least one of the following criteria: marginal integrity/adaptation, marginal discoloration, recurent caries, retention of composite restorations, and postoperative sensitivity. Two independent reviewers analyzed the articles to determine inclusion and risk of bias. The search conducted in the databases resulted in a total of 14,217 studies. After reviewing the references and citations, 21 articles remained. The longest clinical follow-up time was 60 months. The meta-analysis of the data in the included studies demonstrated that only one variable (marginal adaptation after 12 months) showed statistically significant outcomes, in which methacrylates-based composites presented significantly better results than resin composites containing modified monomers. The good level of the scientific evidence as well as the overall low risk of bias of the included studies indicate that composites with silorane, ormocer or bulk-fill type modified monomers have a clinical performance similar to conventional resin composites.

Influence of immediate dentin sealing and interim cementation on the adhesion of indirect restorations with dual-polymerizing resin cement

Statement of problem: Dentin surface contamination before the cementation of indirect restorations may impact bonding effectiveness. Purpose: The purpose of this in vitro study was to analyze the influence of immediate dentin sealing (IDS) and interim cementation on the adhesion of indirect restorations with a dual‐polymerizing resin cement. Material and methods: Composite resin inlays were placed in class V cavities prepared in the buccal and lingual surfaces of 30 extracted human molars with a dual‐polymerizing resin cement in 3 different ways (n=10): CG, directly on dentin; PG, after 14 days interim cementation; SG, after IDS and 14 days interim cementation. Buccal restorations were sectioned into sticks and submitted to the microtensile bond strength (&mgr;TBS) test. Lingual restorations were submitted to micro‐Raman spectroscopy (MRS). Data were analyzed with 1‐way ANOVA and the Tukey‐Kramer post hoc test (&agr;=.05). Results: Significantly higher &mgr;TBS results were found for SG (35.7 ±8.2 MPa) when compared with CG (23.1 ±7.1 MPa) and PG (17.0 ±6.0 MPa) (P<.05), but no differences were observed between CG and PG. MRS showed that the diffusion zone in SG (3.7 ±0.5 &mgr;m) was significantly thicker than that of CG (1.8 ±1.2 &mgr;m) or PG (1.5 ±0.3 &mgr;m) (P<.05). Additionally, a new interface peak (at approximately 1330 cm‐1) was found in SG, indicating a chemical interaction. Conclusions: The use of IDS before cementation resulted in a chemical interaction at the interface and significantly higher &mgr;TBS and diffusion zone thickness values. Interim cementation did not interfere with adhesion quality when compared with the control group.

Influence of 10% sodium ascorbate gel application time on composite bond strength to bleached enamel

Abstract Objective To analyze bond strength to bleached enamel following application of 10% sodium ascorbate gel. Material and methods Forty third molars were allocated into five groups (nu2009=u20098): GP – unbleached specimens restored with composite resin; GN – specimens restored immediately after bleaching; and G15; G30 and G60 (test groups) – bleached specimens treated with 10% sodium ascorbate gel for 15, 30 and 60u2009min before restoration. The teeth were sectioned and the buccal and lingual faces were restored. After storage in distilled water (37u2009°C/24u2009h), sticks ofu2009±0.8u2009mm2 were tested in tensile (0.5u2009mm/min). Fractures were observed and classified. Data (in MPa) were analyzed with one-way ANOVA and Tukey tests (αu2009=u20090.05). Results No differences were found among GP (26u2009±u20096.0), G15 (23u2009±u20097.3), G30 (25u2009±u20096.1) and G60 (25u2009±u20095.1), with GN (15u2009±u20095.5) showing the lowest bond strength (pu2009<u20090.0001). Conclusion The application of 10% sodium ascorbate gel for 15u2009min after bleaching with 37.5% hydrogen peroxide restored the bonding to enamel.