C. Splieth

Polymerization shrinkage-strain and microleakage in dentin-bordered cavities of chemically and light-cured restorative materials.

OBJECTIVES The aim of this study was to evaluate in vitro the relationship between polymerization shrinkage and microleakage in dentin-bordered restorations. METHODS Four light-cured restorative materials in combination with their respective dental bonding agents (DBA) were investigated: Tetric Ceram/Syntac classic (Vivadent), Solitaire/Gluma Solid bond (Heraeus Kulzer), Definite/Etch & Prime 3.0 (Degussa), Solitaire 2/Gluma Solid bond (Heraeus Kulzer). The chemically cured resin Degufill sc microhybrid (Degussa) in combination with ART Bond (Coltène) was also included. Polymerization shrinkage of the restorative materials was measured using three different methods (dilatometer, linometer, buoyancy method) and analyzed with ANOVA. For the determination of microleakage, caries-free human molars were embedded in acrylic resin and subsequently abraded with a wet abrasion machine to produce four level dentin surfaces. One hundred sixty cavities (3 mm diameter/1.5 mm deep) were randomly assigned to four groups of equal size. The groups were restored without (group 1 and 2) and with DBA (group 3 and 4), and either not subjected (group 1 and 3) or subjected (group 2 and 4) to 2000 cycles from 5-55 degrees C. Each group was further divided into five material subgroups of eight cavities each. Microleakage was determined using a dye penetration test assessed at depths of 200, 400 and 600 microm into the fillings. Data were analyzed with the Kruskal-Wallis and the Mann-Whitney test. RESULTS All three methods of measuring polymerization shrinkage (PS) generated the same, statistically secured ranking for the four light-cured restorative materials: PS Definite < PS Tetric Ceram < PS Solitaire 2 < PS Solitaire. In the microleakage study, only a few statistically significant differences were observed. Etch & Prime 3.0/Definite in group 3 and Solid Bond/Solitaire 2 in group 4 tended to exhibit the least microleakage. Correlation coefficients between aggregated shrinkage and microleakage data were 0.3 for group 3 and -0.2 for group 4. SIGNIFICANCE The results do not suggest any correlation between polymerization shrinkage and microleakage in dentin of direct adhesive restorations.

A New in vivo Method for Measuring Caries Activity Using Quantitative Light-Induced Fluorescence

The aim of this in vivo study was to assess the association between caries prevalence and activity parameters and the properties of etched sites measured with quantitative light-induced fluorescence (QLF). In a clinical method, two areas of a deciduous tooth were etched in each of 44 children (mean age 8.23 years ± 1.45) with 36% phosphoric acid gel for 1 min and 4 min, respectively. ΔQ of the etched site was measured immediately after the etching (ΔQ1) and 24 h later (ΔQ2) with QLF. In addition, deft/DMFT, approximal plaque (API), bleeding on probing (mod. PBI), active carious lesions and currently used fluorides were recorded. In a regression analysis for the deft, the use of fluoridated salt (standardized coefficient SC = –0.25) and fluoride gel (SC = –0.37) showed the greatest effect, as did the fluoride gel (SC = –0.26) and gingival bleeding (SC = 0.50) for the number of active carious lesions. The deft and the number of active carious lesions correlated significantly (r = 0.70, p < 0.001). ΔQ1 and ΔQ2 showed a significant statistical correlation with the age-adjusted deft (0.39 < r < 0.52, p < 0.01) and with the number of active lesions (0.42 < r < 0.59, p < 0.01). Correlations between ΔQ and the API, PBI and the fluoride scores were slightly weaker but also statistically significant. In a principal-component analysis, these parameters were approximately identical, indicating a strong relationship between the different variables and ΔQ. This relationship was especially strong for the deft and the active carious lesion scores. In conclusion, these data suggest that the degree of demineralization by etching and its changes with time are associated with caries activity and that this method might be used for the early assessment of caries activity.

Prevalence and distribution of root caries in Pomerania, North-East Germany.

The aim of this study was to assess the prevalence and distribution of root caries in the adult population of Pomerania, Germany. The study sample comprised 6,267 randomly selected subjects who were scheduled for examination from 1997 to 2001 (population-based cross-sectional study, response rate: 69%, age range 20–79 years). 499 edentulous persons were excluded from the dental examination (12%) performed according to WHO guidelines (1997). In the statistical analysis, frequency distributions, means and median values were calculated and subdivided for different age groups. The percentage of exposed and affected root surfaces increased with age (root caries index 4.6–10.6%). The mean number of carious/filled root surfaces (RDFS) rose from 0.4 per person (25–34 years) to 2.3 (55–64 years) and dropped for seniors due to the low number of retained teeth. Fillings comprised the largest proportion of the RDFS (69.5%). Most caries/fillings were found on buccal surfaces, the highest rate in mandibular premolars. With about half of over-45-year-olds having at least one carious/filled root surface and increasing number of retained teeth in seniors, root caries is a relevant and probably growing disease in Pomerania and East Germany.

Effectiveness of Sealants in Adolescents with High and Low Caries Experience

The aim of this 3-year longitudinal study was to analyze caries increment and the caries-preventive effect of sealants in adolescents in the setting of the German national health system. 434 pupils (193 male, 241 female) took part in compulsory school examinations at age 12 (mean 12.3 ± 0.4 years) and 15 (mean 15.6 ± 0.3 years) according to WHO criteria, including the examination of sealants. Mean DMFT increased from 1.78 (± 2.15) to 3.97 (± 3.68), mean DMFS from 2.79 (±4.07) to 6.94 DMFS (± 8.34), respectively. Logistic regression analysis showed that high caries incidence at the individual level was mostly associated with the type of school (’Gymnasium’, RR = 0.3), gender (female, RR = 2.08) and high baseline DMFS (RR = 1.2 per surface), but not with the number of sealants. In an interaction model, adolescents with high baseline DMFS values had an even higher risk of caries increment with an increasing number of sealants compared to adolescents with fewer sealants (p = 0.047). At the tooth level, this effect was detected for first permanent molars, while sealants in premolars and second permanent molars did not result in a statistically significant caries-preventive effect due to the low caries incidence on these surfaces. Thus, sealants on occlusal surfaces of first permanent molars were only protective in individuals with low or moderate caries activity (p = 0.006), which indicates the need for other measures to reduce caries activity in high risk adolescents. In addition, rates of 19% lost sealants and 18% carious or filled surfaces in 3 years suggest a discrepancy between sealant retention under real-life conditions and the results of controlled clinical trials.

Responder and nonresponder analysis for a caries prevention program.

To be able to generalize studies, it is important to know whether responders and nonresponders differ significantly. These data are usually not available. To assess whether responders and nonresponders differed significantly, 319 first and second graders in Greifswald, Germany took part in a compulsory dental school examination. Their parents completed a questionnaire on oral health topics and were asked to decide about their children’s participation in a school-based caries prevention program plus anonymous scientific evaluation. The 91 children who were not allowed to participate (nonresponders) were older (mean 8.5 years) than the 228 responders (mean 8.1 years; p < 0.001), mostly because of a few older children having repeated a grade. In an age-adjusted analysis, nonresponders exhibited in 21 of 30 indices of higher caries and plaque values, less preventive measures and a lower rate of participation. The difference in caries in the permanent dentition and fluorosis reached statistical significance. This study suggests that nonresponders to caries prevention programs might comply less with preventive measures and exhibit poorer oral health than responders: a result which has to be taken into account in research and prevention programs in the community.

51st ORCA Congress

51st Congress of the European Organisation for Caries Research (ORCA), Marburg, Germany. 30 June - 3 July 2004