Effect of self-etch adhesives on self-sealing ability of high-copper amalgams

Statement of the Problem: Similar to conventional amalgam, high-copper amalgam alloy may also undergo corrosion, but it takes longer time for the resulting products to reduce microleakage by sealing the micro-gap at the tooth/amalgam interface

Purpose: The aim of this study was to evaluate the effect of self-etch adhesives with different pH levels on the interfacial corrosion behavior of high-copper amalgam restoration and its induction potential for self-sealing ability of the micro-gap in the early hours after setting by means of Electro-Chemical Tests [ECTs]

Materials and Method: Thirty cylindrical cavities of 4.5mm x 4.7mm were prepared on intact bicuspids. The samples were divided into five main groups of application of Adhesive Resin [AR]/ liner/ None [No], on the cavity floor. The first main group was left without an AR/ liner [No]. In the other main groups, the types of AR/liner used were I-Bond [IB], Clearfil S[3] [S[3]], Single Bond [SB] and Varnish [V]. Each main group [n=6] was divided into two subgroups [n=3] according to the types of the amalgams used, either admixed ANA 2000 [ANA] or spherical Tytin [Tyt]. The ECTs, Open Circuit Potential [OCP], and the Linear Polarization Resistance [LPR] for each sample were performed and measured 48 hours after the completion of the samples

Results: The Tyt-No and Tyt-IB samples showed the highest and lowest OCP values respectively. In LPR tests, the R[p] values of ANA-V and Tyt-V were the highest [lowest corrosion rate] and contrarily, the ANA-IB and Tyt-IB samples, with the lowest pH levels, represented the lowest R[p] values [highest corrosion rates]

Conclusion: Some self-etch adhesives may increase interfacial corrosion potential and self-sealing ability of high-copper amalgams

Effect of different air-drying time on the microleakage of single-step self-etch adhesives

OBJECTIVES: This study evaluated the effect of three different air-drying times on microleakage of three self-etch adhesive systems. MATERIALS AND METHODS: Class I cavities were prepared for 108 extracted sound human premolars. The teeth were divided into three main groups based on three different adhesives: Opti Bond All in One (OBAO), Clearfil S3 Bond (CSB), Bond Force (BF). Each main group divided into three subgroups regarding the air-drying time: without application of air stream, following the manufacturer's instruction, for 10 sec more than manufacturer's instruction. After completion of restorations, specimens were thermocycled and then connected to a fluid filtration system to evaluate microleakage. The data were statistically analyzed using two-way ANOVA and Tukey-test (alpha = 0.05). RESULTS: The microleakage of all adhesives decreased when the air-drying time increased from 0 sec to manufacturer's instruction (p < 0.001). The microleakage of BF reached its lowest values after increasing the drying time to 10 sec more than the manufacturer's instruction (p < 0.001). Microleakage of OBAO and CSB was significantly lower compared to BF in all three drying time (p < 0.001). CONCLUSIONS: Increasing in air-drying time of adhesive layer in one-step self-etch adhesives caused reduction of microleakage, but the amount of this reduction may be dependent on the adhesive components of self-etch adhesives.

[Comparison of restoration types requirements in dentistry curriculum with the practiced restorations by dentistry students of mashhad dental school during 2007 - 2008]

Background and Objective: Theoretical and clinical teachings in dentistry are not always according to the dentistry curriculum requirements, but they serve as the basis upon which Dentistry graduates start their own practice. The aim of this study was to find the resemblance between dentistry curriculum requirements with clinical experiences in restorative clinics of Mashhad Dental School in the two academic years of 2007 and 2008

Methods: Recorded data related to the teachings devoted to posterior Amalgam and Composite restorations were gathered from the archive of Restorative Department of Mashhad Dental School. Teaching volume was determined by considering the number of lecturers and sessions of preclinical exercises in the operative simulation laboratory during the General Dentistry program. Data available for direct posterior restorations placed by fourth, fifth and sixth year students were gathered from the students' report papers. The collected data were coded and categorized according to the surface number of posterior amalgam fillings [AFS1, AFS2, AFS3] and posterior composite fillings [CFS1, CFS2, CFS3]. These finding were placed on spreadsheets of Excel program and the related bar graphs were constructed for comparison of the devoted teaching volume and practice with the Dentistry curriculum requirements and the number of posterior amalgam and composite restorations

Results: Theoretical and practical teachings of amalgam and composite restorations have been in favor of amalgam with the ratio of 2 to 1. Clinically, practiced posterior composite restorations were 3 times more than the curriculum requirement. For the placement of three surface posterior restorations, amalgam favored over composite

Conclusion: Shift to the placement of posterior composite restorations needs to be addressed within dentistry curriculum, so the newly graduated dentists are prepared to place composite restorations properly