Amalgam use and mercury emission in the Netherlands

An overview is presented of the emission of mercury to the environment by restoring teeth with amalgam, extraction, replacement of amalgam, and the final phase of teeth. Important input data were the trade figures of amalgam. The emission of mercury from amalgam fillings are characterized by diffuse spreading. Many small sources are together a substantial source of the leakage of mercury to the environment. Amalgam adhering to cotton-wool and in extracted teeth deliver a relevant contribution to the mercury load in municipal waste. The total mercury emission from dental amalgam to the environment in the Netherlands is at the estimate 500 kg a year, with a worst case maximum of 935 kg.     

Fluoride distribution in human dental calculus obtained from different sites on the tooth surface

We examined the site specificity of fluoride (F) distribution in human dental calculus. Teeth with supra- and subgingival calculus were obtained from patients who resided in non-fluoridated areas in Japan and China. Sequential layers of the dental calculus (30 μm thick) were abraded by an abrasive micro-sampling technique and fluoride and phosphorus in the powdered samples were analyzed. Fluoride concentrations were highest in the outer, lowest in the middle and intermediate in the inner layers of dental calculus in general. In the outermost layers fluoride concentrations were highest in calculus found near the tooth cervix both in supra- and subgingival calculus. Fluoride concentrations decreased markedly toward the apical region in subgingival calculus. while it did not change toward the incisal or occlusal region in supragingival calculus. In the inner layers, fluoride concentrations in both supra- and subgingival calculus were not affected by position on the teeth. Fluoride concentrations in subgingival calculus near the apex were lower than in supragingival calculus near the incisal or occlusal region. It was concluded that the fluoride concentrations differ in different regions of dental calculus, probably due to their different mechanisms of formation.     

Dentin bond durability after three years using a dentin bonding agent with and without priming

Objectives: This three-year study was conducted to evaluate the tensile bond strengths of a dual-cured bonding resin, with and without priming, to bovine dentin.Methods: Superficial bovine dentin was conditioned with 37% phosphoric acid and left unprimed (control) or was primed with 5-NMSA. Clearfil Photobond (Kuraray Co., Japan) was placed and light-cured, a layer of Protect Liner (Kuraray Co.) was applied, cured, then covered with Photo Clearfil Bright (Kurary Co.) resin composite and cured. Bonds were stressed in tension to failure at 1 d, 1 mon, 3 mon, 6 mon, 1 y and 3 y after preparation. Ten specimens were made for each group. Results were analyzed using one-way ANOVA and Duncan's multiple range test. Visual and SEM observations determined mode of failure and were analyzed using the Mann-Whitney U-test. Separate 1 d and 3 y specimens were fractured across the bonded interface and observed using a Field Emission SEM. After observation, the photomicrographs were compared for visual qualitative changes between the two time periods.Results: The control (non-primed) group showed only a small decrease in bond strengths over 3 y, but in the primed group, a significant decrease was observed (p < 0.05). The bond strength of the non-primed group (5.2 MPa) was less than the primed group (10.6 MPa) at 1 d (p < 0.01), but by 3 y, the bonds of both groups were similar, 4.3 MPa and 5.5 MPa, respectively. Fractography indicated that only adhesive failure occurred in the control group. Failure in the primed group was cohesive in dentin initially, but shifted to the base or top of the hybrid layer after 1 y. Field Emission SEM observations showed hybrid layer formation in the primed group, but minimal resin infiltration in the control group.Significance: Initially greater bond strengths were obtained for the primed group compared to the unprimed group (p < 0.01). However, by 3 y, the bond strength had decreased markedly in the primed group (p < 0.01), being almost the same for both groups. It was concluded that priming may only be useful to achieve strong bonding in the short term. These results may have significant implications related to clinical longevity of restorations.     

Inhibition of lipoxygenase of rat dental pulp and human platelets by phenolic dental medicaments

The effects of phenolic dental medicaments on lipoxygenase activities of rat dental pulp and human platelets were studied. The major product derived from [14C] arachidonic acid by the homogenate of rat dental pulp was 12-HETE (15-HETE). Eugenol and p-chlorophenol dose-dependently inhibited HETEs formation. The IC50 values of eugenol and p-chlorophenol were 0.62 and 0.34 mM respectively. The concentrations of these compounds that inhibit lipoxygenase were similar to those required to inhibit cyclooxygenase. These compounds also inhibited 12-lipoxygenase of human platelets with a similar range of concentrations. The results show that phenolic dental medicaments inhibit pulpal and platelet lipoxygenase. Thus, inhibition of arachidonic acid metabolism by phenolic dental medicaments via the lipoxygenase pathway may be involved in the analgesic and anti-inflammatory effects of the medicaments in endodontic therapy.     

An electromyographic observation of the extensional labiobuccal flange lower complete denture

The electromyogram of the buccinator and the myoid muscles in 26 lower full denture patients with severe atrophic alveoli were measured separately in three groups: group one, the conventional dentures: group two, the extension flange dentures in preliminary stage after the denture insertion and group three, the extensional flange denture in forward stage. The main results showed that (1) the functional force, except on mouth opening, exerted by the buccinator muscles increased significantly in group two and three. (2) the functional force exerted by the mylohyoid muscles on mouth opening decreased significantly in group two and increased in group three which was similar to group one. There were no significant difference between these three groups on swallowing. (3) the functional force except on mouth opening, exerted by the buccinator and mylohyoid muscles between these three groups was no significant difference. These observations indicated that there was no significant interference in the physiological activities of the buccinator and the mylohyoid muscles with the extensional flange dentures. In addition, the extensional buccal flange may enhance the denture retention.