Prevention of Occupational Hazards Due to Asbestos Exposure in Dentistry. A Proposal from a Panel of Experts.

Asbestos in all its forms is a Group 1 material agent with proven carcinogenic effects in the human being since 1977. Exposure to asbestos can be considered unsafe. The use of asbestos in the field of dentistry had a common use in the manufacture of dental prostheses in the 1960s and 1970s. Taking into account the long induction period of this agent and the plausibility for being a risk factor in dentistry, the objective of this study is to propose a plan for the prevention of occupational risks due to asbestos exposure in dentistry by means of the contribution of a panel of experts. An Expert Panel (EP) approach was used in which a group of nine experts identified and documented the use of asbestos in the dental profession. EP was created and followed the protocol in accordance with the EuropeAid Assessment Guidelines. As a result of this study, EP documented the common use and sources of asbestos in dentistry in prosthetic materials, dental dressings, and in the coating of casting cylinders. EP also created a consensus document on the priority measures for the Plan for the Prevention of Risks from Asbestos in Dentistry, based on previous reports from the European Commission Senior Labour Inspectors' Committee. The document concluded that obtainment of information, receiving specific training on the subject and performing epidemiological studies, and the proper risk assessments were the priority measures to adopt.

Influence of different surface conditioning protocols on microtensile bond strength of self-adhesive resin cements to dentin.

STATEMENT OF PROBLEM: According to manufacturers, bonding with self-adhesive resin cements can be achieved without any pretreatment steps such as etching, priming, or bonding. However, the benefit of saving time with these simplified luting systems may be realized at the expense of compromising the bonding capacity. PURPOSE: The purpose of this study was to assess whether different dentin conditioning protocols influence the bond performance of self-adhesive resin cements to dentin. MATERIAL AND METHODS: Flat dentin surfaces from 48 human molars were divided into 4 groups (n=12): 1) control, no conditioning; 2) H(3)PO(4), etching with 37% H(3)PO(4) for 15 seconds; 3) SEBond, bonding with self-etching primer adhesive (Clearfil SE Bond); and 4) EDTA, etching with 0.1M EDTA for 60 seconds. The specimens from each dentin pre-treatment were bonded using the self-adhesive cements RelyX Unicem, Maxcem or Multilink Sprint (n=4). The resin-cement-dentin specimens were stored in water at 37°C for 7 days, and serially sectioned to produce beam specimens of 1.0 mm(2) cross-sectional area. Microtensile bond strength (µTBS) testing was performed at 1.0 mm/min. Data (MPa) were analyzed by 2-way ANOVA and Tukey multiple comparisons test (α=.05). Fractured specimens were examined with a stereomicroscope (x40) and classified as adhesive, mixed, or cohesive. Additional bonded interfaces were evaluated under a scanning electron microscope (SEM). RESULTS: Cement-dentin µTBS was affected by the dentin conditioning approach (P<.001). RelyX Unicem attained statistically similar bond strengths to all pre-treated dentin surfaces. H(3)PO(4)-etching prior to the application of Maxcem resulted in bond strength values that were significantly higher than the other groups. The lowest µTBS were attained when luting Multilink Sprint per manufacturers' recommendations, while H(3)PO(4)-etching produced the highest values followed by Clearfil SE bonding and EDTA. SEM observations disclosed an enhanced potential of the self-adhesive cements to form a hybrid layer when applied following manufacturer's instructions. CONCLUSIONS: When evaluated self-adhesive resin cements are used, selectively etching dentin with H(3)PO(4) prior to luting results in the most effective bonding.

Effect of two axial wall height preparations on the retentive properties of full crowns using three different cements.

This study evaluated how different tooth preparation heights and luting cements affected the retention of metallic full crowns. Tooth preparations were made on 60 extracted maxillary premolars with occluso-cervical heights of 4.0 or 5.0 mm. The nickel chromium (NiCr) metallic crowns in each group were subdivided randomly into three groups (n = 10); the samples in each group were cemented with either a self-adhesive resin cement, a conventional resin cement, or a zinc phosphate cement. Cementation was performed by applying 5.0 kg pressure in 50% relative humidity. Specimens were stored in 100% humidity at 37 degrees C for seven days, at which time they were subjected to a vertical tensile test with a universal testing machine at 0.5 mm/min. Data (Kgf) were analyzed by two-way ANOVA and Tukey's multiple comparisons tests (alpha = 0.01). There was a significant difference in mean force in the height preparations (P < 0.001) and in tensile strength (P < 0.001) among the resin cements. Regardless of the cement used, 5.0 mm high preparations showed significantly higher mean forces than the 4.0 mm high preparations. The self-adhesive resin cement showed significantly higher mean tensile strength than the conventional resin cement; the zinc phosphate cement displayed the lowest retention values. The self-adhesive resin cement displayed retention rates twice that of the zinc phosphate cement.

Influence of ceramic surface conditioning and resin cements on microtensile bond strength to a glass ceramic.

STATEMENT OF PROBLEM: It is not clear how different glass ceramic surface pretreatments influence the bonding capacity of various luting agents to these surfaces. PURPOSE: The purpose of this study was to evaluate the microtensile bond strength (microTBS) of 3 resin cements to a lithia disilicate-based ceramic submitted to 2 surface conditioning treatments. MATERIAL AND METHODS: Eighteen 5 x 6 x 8-mm ceramic (IPS Empress 2) blocks were fabricated according to manufacturer's instructions and duplicated in composite resin (Tetric Ceram). Ceramic blocks were polished and divided into 2 groups (n=9/treatment): no conditioning (no-conditioning/control), or 5% hydrofluoric acid etching for 20 seconds and silanization for 1 minute (HF + SIL). Ceramic blocks were cemented to the composite resin blocks with 1 self-adhesive universal resin cement (RelyX Unicem) or 1 of 2 resin-based luting agents (Multilink or Panavia F), according to the manufacturer's instructions. The composite resin-ceramic blocks were stored in humidity at 37 degrees C for 7 days and serially sectioned to produce 25 beam specimens per group with a 1.0-mm(2) cross-sectional area. Specimens were thermal cycled (5000 cycles, 5 degrees C-55 degrees C) and tested in tension at 1 mm/min. Microtensile bond strength data (MPa) were analyzed by 2-way analysis of variance and Tukey multiple comparisons tests (alpha=.05). Fractured specimens were examined with a stereomicroscope (x40) and classified as adhesive, mixed, or cohesive. RESULTS: The surface conditioning factor was significant (HF+SIL > no-conditioning) (P<.0001). Considering the unconditioned groups, the microTBS of RelyX Unicem was significantly higher (9.6 +/- 1.9) than that of Multilink (6.2 +/- 1.2) and Panavia F (7.4 +/- 1.9). Previous etching and silanization yielded statistically higher microTBS values for RelyX Unicem (18.8 +/- 3.5) and Multilink (17.4 +/- 3.0) when compared to Panavia F (15.7 +/- 3.8). Spontaneous debonding after thermal cycling was detected when luting agents were applied to untreated ceramic surfaces. CONCLUSION: Etching and silanization treatments appear to be crucial for resin bonding to a lithia disilicate-based ceramic, regardless of the resin cement used.