[ effects of adhesive type and different curing methods on micro leakage and marginal adaptation of composite veneers]

The adhesives type and placement application technique may be important in long term stability and function of composite veneers. This study was conducted to evaluate the influence of dentin adhesive application techniques [pre-curing vs. non-curing] on micro leakage and marginal adaptation of indirect composite veneer restorations. A total etch bonding system, Excite/Variolink II [EXV], and a self-etching primer system, Panavia F 2.0 [PF2] were used in this in-vitro investigation. Forty-eight human central incisors were prepared for composite veneer restoration. These teeth were then divided into two groups [n=24]. Pre-cure adhesive [PC] with light cure technique as well as no pre-cure [NPC] prior to resin cement insertion in half of specimens in each group. By using these methods, we worked with four experimental subgroups [PC+EXV, NPC+EXV, PC+PF2, NPC+PF2]. Composite veneers [Tetric Ceram resin] were cemented using a dual-cured resin luting agents. All specimens were then stored in distilled water at 37°C for 24 hours before checking for marginal leakage. By random sampling, two specimens were selected from each group for SEM observations and evaluation of marginal adaptation at 1050 time magnifications. Data was analyzed by ordinal regression and link function of probit type at alpha

[In-Vitro evaluation of fracture resistance of weakened roots restored with fiber posts and tooth-colored materials]

Restoration of endodontically-treated anterior teeth with weakened roots requires special attention. The purpose of this investigation was to compare the fracture resistance of experimentally weakened anterior roots reinforced with three different methods using tooth-colored materials. Forty human sound maxillary central incisors were used in this in vitro study. The crowns of 30 teeth were removed 2mm above the CEJ. After root-canal therapy, flared canals were simulated. The teeth were filled with D.T. light-post plus resin composite [Clearfil DC Core Automix] in group 1, D.T. light-post plus two accessory posts [Reforpin+Panavia F 2.0] in group 2 and D.T. light-post plus Panavia F 2.0 in group 3. Access cavities in the fourth [control] group were restored after ideal root-canal therapy. Following cementation of the posts and restoration of the crowns with Clearfil Photo-Core composite, the roots were embedded in acrylic resin blocks, 1 mm below the CEJ. After 24h storage, the samples were loaded in an Instron testing machine with a crosshead speed of 0.5 mm/min at a 45° angle to the long axis of the tooth on the palatal surfaces until failure. The data were analyzed using ANOVA and Tukey test [P=0.05]. The lowest [300.17 N] and highest [585.11 N] mean fracture resistance values were observed in the third and fourth groups, respectively [P<0.05]. These values were not significantly different between the first, second and third groups. The results showed that Reforpin could be used as an alternative to resin composite for internal reinforcement of weakened roots

[ effect of filler on microleakage of self-etch adhesives with dentin and SEM interfacial morphology evaluation]

One of the most important disadvantages of using of tooth colored restorations is microleakage. This is more noticeable when there is a cavity with dentinal walls. Despite all improvements in dentin bonding agents, thusfar, no adhesive has been able to overcome microleakage between resin-dentin. The purpose of this survey is investigating the effect of filler on microleakage of self-etch adhesives with dentin and SEM interfacial morphology evaluation. Class V cavities were made on extracted human premolars [n=60]. Then the teeth were randomly divided into 6 groups based on type of adhesives used. Next teeth were grouped as filled adhesive [Xeno III, Clearfil SE Bond, Excite] and three grouped as unfilled adhesive [iBond, Bistite II, Single Bond]. After restoration, specimens were treated by thermocycling and a dye penetration test was done. Then longitudinal sections were made toward the direction of the buccal lingual and were observed carefully under a stereomicroscope for any leakage. From each group, 2 samples were prepared for investigating micromorphology of resin under an SEM electronic mircroscope. Data was analyzed by the Kruskal-Wallis test and Mann-Whitney test with an accuracy level of 0.05%. Using the Mann-Whitney test, it was clear that in the one-step self-etch adhesive, the filled type [Xeno III] had reduction in microleakage compared to the unfilled type [i Bond]. On the two-step self-etch and total etch adhesives, there was no significant difference between filled and unfilled adhesive in reduction of microleakage. In SEM investigations self-etch adhesives make thinner hybrid layers, but there are more resin tags with more regularity in this system and resin is well penetrated in the spaces due to demineralization and was polymerized. The filled type of one-step self-etch adhesive [Xeno III] had more reduction in microleakage than other groups. There was no significant difference between the two types [filled and unfilled] two-step self-etch and total etch adhesives in reduction of microleakage. It was clear that if self-etch adhesive is used carefully give better sealing compared to total etch adhesive. Because they can infiltrate the spaces made due to demineralization and get polymerized

Factors contributing to the incompatibility between new adhesive systems and various composite resin restorations

Although light cured composites are easily accessible, self/dual-cure cements and composite resins also have broad clinical applications. The aim of this study was to evaluate the incompatibility between new adhesives and different types of cement and composite resin restorations and their effects on interface bond strength. All articles and theses on adhesives and cement/composite resin restorations up to June 2005, available at Mashhad dental school library, medline and other internet information banks were collected and evaluated. Some two-step-total-etch and one-step-self-etch adhesives were incompatible with self7dual-cured cements and composite resins. This is due to the large concentration of acidic, ionic and hydrophilic resin monomers that result in adverse chemical interactions and increased permeability of these adhesives. In order to prevent the adverse acid-base chemical interactions between simplified adhesives, light cured cements or composites or dual cured adhesives containing catalysts should be used. For neutralizing the permeability effect of simplified adhesives, light cured composites or a single layer of unfilled resin bonding or flowable composites should be applied over the adhesive layer to induce rapid curing

[Microleakage evaluation of four luting cements in full coverage base metal crowns]

It is thought that the most important factor for pulpal stimulation and necrosis is the microleakage of intracoronal and extracoronal restoration. A luting cement with a favorable seal and the least bacterial leakage should be selected. The purpose of this study was to compare the microleakage of four luting cements: Zinc phoshate, zinc polycarboxylate, glass ionomer and panavia F and also three finishing margins: deep chamfer, shoulder, and shoulder bevel, when been applied with porcelain fused to base metal crowns. In this parallel interventional study, 96 intact human premolars were selected and divided into three groups of 32 based on the type of finishing line. Each group was randomly divided into four subgroups of 8, based on the type of luting cement. After cementation, the specimens were thermocycled. Dye penetration was done by 0.5% fushin. The data were statistically analyzed using Kruskal Wallis and Mann-Whitney test [alpha =0.05]. 1. There was a significant difference among cements in respect to mean rank of microleakage [P<0.05] 2. There was a significant difference in mean rank of cements after two by two comparison. [P<0.05] 3. The least microleakage was observed in Panavi F followed by glass ionomer and zinc polycarboxylate. 4. The greatest microleakage was observed in zinc phosphate cement Panavia F as a luting cement could create suitable seal for base metal crown due to its ability in producing the least microleakage and adhesion to dental tissue