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

Microleakage under orthodontic metal brackets bonded with three different bonding techniques with/without thermocycling

The aim of this study was to compare the microleakage of beneath the orthodontic brackets bonded with 3 different bonding techniques and evaluate the effect of thermocycling. One hundred and twenty premolars were randomly divided into 6 groups, received the following treatment: group 1: 37% phosphoric acid gel+Unite primer+Unite adhesive, group 2: 37% phosphoric acid gel+ Transbond XT primer+Transbond XT adhesive, group 3: Transbond plus Self Etching Primer [TSEP]+Transbond XT adhesive. Groups 4, 5, and 6 were similar to groups 1, 2, and 3, respectively. Evaluation of microleakage was done following to thermocycling test. After bonding, the specimens were sealed with nail varnish except for 1 mm around the brackets and then stained with 0.5% basic fuchsine. The specimens were sectioned at buccolingual direction in 2 parallel planes and evaluated under a stereomicroscope to determine the amount of microleakage at bracket-adhesive and adhesive-enamel interfaces from gingival and occlusal margins. Microleakage was observed in all groups, and increased significantly after thermocycling at some interfaces of Unite adhesive group and conventional etching+Transbond XT adhesive group, but the increase was not significant in any interface of TSEP group. With or without thermocycling, TSEP displayed more microleakage than other groups. In most groups, microleakage at gingival margin was significantly higher than occlusal margin. Thermocycling and type of bonding technique significantly affect the amount of microleakage

Light conduction capability of different light-transmitting FRC posts

Application of light transmitting posts to restore greatly damaged endodontically treated teeth .ias been increased. It is suspected that light intensity decreases as it passes throughout different materials. This can reduce the degree of conversion required for adequate bond strength throughout the length of these posts. The objective of this study was to evaluate the amount of light intensity reduction after passing through different depths of FRC posts. Four groups of fiv extracted human central incisors were prepared to cement four types of FRC posts with Panavia F 2 resin cement. The apical end of the posts were exposed by sectioning with a diamond disk and then polished. The light intensity measurement was performed using a micro-voltmeter in 8 points or depths with 2mm intervals beginning from the apical depth of 16mm up to a coronal depth of 6mm. Two different output light intensities [HIP [High Intensity Program] and LOP [Low Intensity Program]] were evaluated. Statistical analysis showed significant differences in light intensity at various depths between 6 and 16mm in all groups. These reductions were linear in all specimens; however, the rate of reduction was dissimilar among different FRC posts. HIP and LOP light exposure modes had not the same rate of light reduction. Light intensity decreased dramatically after passing through different depths of FRC posts. None of the posts had sufficient enough light transmission for satisfactory polymerization at the apical and middle levels