Dental adhesives and strategies for displacement of water/solvents from collagen fibrils.

OBJECTIVES: To evaluate the influence of temperature of evaporation in adhesive systems with different solvents on the apparent modulus of elasticity and mass change of macro-hybrid layers modified by proanthocyanidins (PACs). METHODS: Adhesive resin beams (A) from Single Bond Plus (SB), Excite (EX) and One Step Plus (OS) were prepared after solvent evaporation at 23°C or 40°C (n=12). Macro-hybrid layers (M) (n=12) were prepared using demineralized dentin beams sectioned from extracted human third molars. The demineralized dentin specimens were infiltrated with each one of the three adhesive systems at 23°C or 40°C; with or without prior dentin treatment with PACs for 10min. The apparent modulus of elasticity (E) and mass change (Wmc, %) of adhesives beams and resin-infiltrated specimens were assessed in dry and wet conditions after immersion in water (24h, 1, 3 and 6 months). The E was statistically analyzed by Tukey-Kramer test and the Wmc, % by Kruskal Wallis, and Dunn (α=0.05). RESULTS: Solvent evaporation at 40°C resulted in higher E values for adhesive resin beams at all storage conditions, regardless of the adhesive system (p<0.05). Increased mass loss (3 months: -0.01%; 6 months: -0.05%) was observed in One Step resin beams (p≤0.05). In the macro-hybrid layer models the pretreatment with PACs along with solvent evaporation at 40°C increased E and decreased the Wmc, % (3 months: -2.5; 6 months: 2.75%) for adhesives evaluated over time (p<0.05). No significant differences in ratio (resin/dentin) were found for the macro-hybrid layers (p>0.05). SIGNIFICANCE: Improved solvent evaporation at higher temperature, and increased collagen cross-linking induced by PACs, enhanced the mechanical properties resulting in highly stable macro-hybrid layers over 6 months storage.

Nanomechanical properties, SEM, and EDS microanalysis of dentin treated with 2.5% titanium tetrafluoride, before and after an erosive challenge.

The aim was to assess the nanohardness (H) and the reduced modulus of elasticity (Er ) of 2.5% titanium tetrafluoride (TiF4 ) modified dentin, before and after an erosive challenge with 0.3% citric acid (CA). Exposed dentin surfaces were divided into two groups (n = 5): (1) Control-no dentin pretreatment with TiF4 prior to etching with CA, and (2) Experimental-dentin pretreatment with TiF4 + CA. The H and the Er of intertubular dentin were measured using a triboindenter at different time points: baseline for both groups, after using 2.5% TiF4 for the experimental group, and after using CA for both the experimental and the control groups. Scanning electron microscope and energy dispersive X-ray spectroscopy (EDS) analysis of the dentin surfaces were undertaken at the same time points for both groups. Two-way ANOVA for randomized block design was applied. There was significant interaction between the application of the TiF4 solution and different time points (p = 0.001 for H and p < 0.001 for Er ), identified by Tukey's test. Erosive challenge provided a significant decrease in H and Er mean values. The TiF4 solution caused a significant increase in H and Er values, but no significant differences were found between post-TiF4 and post-CA application. TiF4 application produced a precipitate surface layer on intertubular and intratubular dentin. EDS analysis indicated the presence of titanium. The H and Er of the dentin surface were greatly increased after application of 2.5% TiF4 . TiF4 may modify the micromorphology of the dentin surface and produces an erosive resistance surface.

Distance and protective barrier effects on the composite resin degree of conversion.

CONTEXT: The food wrap films are used to cover the tip of curing light units in order to avoid contamination and prevent damage to the light guide. However, their effects on resin polymerization are not fully known. AIMS: We investigated the effects on restoration efficiency of a food wrap protective barrier used on the tip of curing light units. MATERIALS AND METHODS: For each treatment, five replications were performed, a total of 60 bovine incisor. The degree of conversion (%DC) of restorations with the composite resin Opallis EA2 was evaluated using 3 curing light devices (Optilux 501, Optilight and Ultra LED) and 2 curing distances (0 and 5 mm). The composite resin was tested for restoration of cavities in bovine crowns. %DC values were measured by the Fourier transform infrared spectroscopy-attenuated total reflectance technique. STATISTICAL ANALYSIS USED: The data were analyzed using 3-way ANOVA and Tukey's test. RESULTS: Use of the protective film lowered %DC (F = 4.13; P = 0.05), and the effects of curing distance were associated to the curing light device (F = 3.61; P = 0.03). CONCLUSIONS: The distance from the light curing tip and use of a translucent protective barrier on the light-cure device can both impair composite resin %DC.

Effects of silane application on luting fiber posts using self-adhesive resin cement.

PURPOSE: To evaluate the effects of different glass-fiber post surface treatments on the bond strength to root dentin. MATERIALS AND METHODS: Fifty bovine incisors were used in this study. After removing the crowns, the teeth were endodontically treated. The roots were randomly divided into five groups according to post surface treatment. The groups were as follows: CO (Control) - no treatment; G1 - RelyX Ceramic Primer (silane) only; G2 - silane and Solobond M; G3 - silane and Scotchbond Adhesive; G4 - silane and Excite. For post cementation, RelyX Unicem was used according to the manufacturer's recommendation and the roots were stored in a light-proof container with 100% relative humidity for 24 h. The specimens were transversally sectioned. Subsequently, the cervical, middle, and apical regions of the root were positioned in a push-out device and tested at 0.5 mm/min using a universal testing machine (Instron). The data were statistically analyzed with two-way ANOVA and Tukey's post-hoc test. The fractured specimens were then observed under a stereoscopic loupe at 60X magnification. RESULTS: No significant difference in bond strength was found among the groups that received a silane or silane plus an adhesive system (p > 0.05). However, the CO (no silane) showed the lowest bond strength. Regarding G1, G2, G3, and G4, the cervical region of the root canal attained better bond strengths than did the middle or apical regions. The most frequent failure mode occurred at the cement/dentin interface. CONCLUSION: Silane application may be necessary to improve the adhesion of fiber posts luted with the self-adhesive resin cement evaluated here. The application of an adhesive layer between the fiber post and resin cement did not have any influence on the bond strength when the silane coupling was previously used.

Adaptação à dentina de materiais forradores sob restauração de resina composta / Liner adaptation to dentin under composite resin restoration

Introdução: Um dos principais problemas na utilização de resina composta é a sua contração de polimerização e consequente tensão transmitida às paredes aderidas e ao material forrador. Foi analisada a adaptação de agentes protetores à dentina associadosà restauração de resina composta fotopolimerizável. Material e Métodos - CavidadesClasse I oclusal foram confeccionadas com profundidade 1,5 mm, em molares humanos hígidos (n=40). Os dentes foram divididos em 4 grupos, segundo o material de forramento utilizado: FF - resina de baixa viscosidade (Fill Magic Flow), HP - cimento de hidróxidode cálcio fotopolimerizável (Hi-Cal Photo), VLC: cimento de ionômero de vidro fotopolimerizável (Vitro Fill LC), VB: cimento de ionômero de vidro fotopolimerizável(Vitrebond). As cavidades foram restauradas com resina composta (Adper Single Bond2/Filtek Z250), inserida em incrementos oblíquos. Após armazenamento em ambiente úmido a 37°C por 7 dias, os molares foram seccionados no longo eixo do dente e obtidas réplicas em negativo de polivinilsiloxana Adsil e em positivo com resina epóxica. Foi utilizada microscopia óptica para mensuração da porcentagem de adaptação linear domaterial forrador e a parede pulpar. Resultados - Os testes de Kruskal-Wallis e Dunnapontaram diferença estatisticamente significante (p<0,05) entre VB (97,7±1,30) e FF(59,3±33,7), e entre HP (5,3±4,9) e VLC (44,3±24,2). Conclusões - A tensão de contração da resina composta causada à interface adesiva durante sua fotoativação provoca fendas entre o material forrador e a parede pulpar, em magnitudes distintas, mesmo quando ainserção da resina se dá por incrementos. O cimento de ionômero de vidro fotoativado Vitrebond obteve a melhor adaptação.

Introduction: One of the main problems when using composite resin is its polymerization shrinkage and resultant stress transmitted to the adhered walls and to the cavity lining material. This work analyzed the adaptation of protective agents to the dentin associated to the composite resin restoration. Material and Methods - Class I occlusalcavities − 1.5 mm deep − were performed in healthy human molars (n=40). The teethwere divided into four groups according to the lining material used: FF – flowable resin(Fill-Magic Flow); HP – light-cured calcium hydroxide cement (Hi-Cal Photo); VLC –resin-modified glass-ionomer liner (Vitro Fill LC); and VB – resin-modified glass-ionomer liner (Vitrebond). The cavities were restored with composite resin (Adper Single Bond2/Filtek Z250) inserted into oblique increments. After storage in a humid environmentat 37°C for seven days, the molars were sectioned to the long axis of the tooth. Negative replicas were obtained through polyvinyl siloxane (Adsil), and positive ones by epoxyresin. Optical microscopy was used for measuring the percentage of linear adaptationof the cavity liner to the pulp wall. Results - Kruskal-Wallis and Dunn tests showed a statistically significant difference (p<0,05) between VB (97,7 ± 1,30) and FF (59,3 ±33,7), and between HP (5,3 ± 4,9) and VLC (44,3 ± 24,2).Conclusions - The shrinkage stress of the composite resin polymerization causes gaps between the cavity liner and the pulp wall even when restored in increments, in distinct magnitude. The resin-modified glass-ionomer liner Vitrebond proved to have the best adaptability.