R.J.M. Gruythuysen

The Effect of 6-Monthly Application of 40% Chlorhexidine Varnish on the Microflora and Dental Caries Incidence in a Population of Children in Surinam

This study is aimed at determining whether a commercially available varnish, containing 40% chlorhexidine, is able to reduce the numbers of mutans streptococci and lactobacilli in saliva, in a moderately caries-active population in Surinam. 238 children, ages 13–14 years, were selected from different schools in Paramaribo, Surinam. From these children, total dental status was recorded and saliva samples were taken. At baseline and every 6 months, a 40% chlorhexidine varnish (EC40®) was applied. The control group received a neutral gel that did not contain chlorhexidine. The numbers of salivary mutans streptococci and lactobacilli were calculated by standard methods, and the caries status was recorded every 12 months. The study lasted 30 months. The results indicate that chlorhexidine varnish did not decrease the numbers of cariogenic bacteria, nor did it decrease caries progression. Moreover, in this population with a low dental health care, children with lactobacilli present in the saliva above our detection level, the chlorhexidine varnish even tended to increase caries progression, possibly due to selection of aciduric and acidogenic oral bacterial species. We therefore conclude that 40% chlorhexidine varnish is not likely to decrease caries in children in a high-treatment-need population without treatment of the sources of infection.

Replacement risk of amalgam treatment modalities: 15-year results

OBJECTIVES This paper reports on the replacement risk of different treatment modalities for Class II amalgam restorations in a clinical trial of 15 years duration. METHODS The performance of 1117 conventional Class II amalgam restorations in a controlled, longitudinal study were analysed using logistic regression with a random component. Primary variables regarding replacement risk were the treatment modality (cavity wall treatments) and alloy (conventional versus high copper). Secondly, the operator, type of tooth and type of restoration (MO/DO vs MOD) were considered. RESULTS Over 15 years, 17% of the restorations were replaced (true failures). The application of copalite varnish or silver suspension and the type of alloy did not reduce the replacement risk. Reduced risks were observed by providing a 90-degree cavosurface angle combined with a cavity wall finish. The operator and the type of restoration determine replacement risk to a significant extent. CONCLUSIONS Additional treatment modalities do not necessarily reduce replacement risks of Class II amalgam restorations within 15 years, while clinical variables affect the risk of replacement to a certain degree.

THE ANALYSIS OF RESTORATION SURVIVAL DATA IN SPLIT-MOUTH DESIGNS

OBJECTIVE To report methodological difficulties with restoration survival data in controlled clinical trials on Class II amalgam restorations using a split-mouth design. The advantages and disadvantages of different ways of handling these data are described. METHODS Three statistical methods (Kaplan-Meier estimation, logistic regression with random component and Friedmans statistic) are compared using data from a controlled clinical trial in which cavosurface angle (regular or non-standard) and cavity wall finish (applied or not applied) determine four treatment modalities of New True Dentalloy restorations. RESULTS In this study logistic regression with a random component yields the best interpretable results. Cavity wall finish in combination with a regular cavosurface angle is indicated as the worst and cavity wall finish in combination with a non-standard cavosurface angle as the best treatment when the criterion is replacement or not within 15 years. CONCLUSIONS The dependency between restorations within a patient needs to be taken into account. Logistic regression with a random component may be a valuable alternative to very advanced statistical survival modelling when restricting the research question to replacement within a certain time interval is not a major problem.