A bivariate multi-level model, which avoids mathematical coupling in the study of change and initial periodontal attachment level after therapy

Order in the absence of an effect: Identifying rate-dependent relationships

The heterogeneity of group data can obscure a significant effect of an intervention due to differential baseline scores. Instead of discarding the seemingly heterogeneous response set, an orderly lawful relationship could be present. Rate dependence describes a pattern between a baseline and the change in that baseline following some intervention. To highlight the importance of analyzing data from a rate-dependent perspective, we (1) briefly review research illustrating that rate-dependent effects can be observed in response to both drug and non-drug interventions in varied schedules of reinforcement in clinical and preclinical populations; (2) observe that the process of rate-dependence likely requires multiple parts of a system operating simultaneously to evoke differential responding as a function of baseline; and (3) describe several statistical methods for consideration and posit that Oldham's correlation is the most appropriate for rate-dependent analyses. Finally, we propose future applications for these analyses in which the level of baseline behavior exhibited prior to an intervention may determine the magnitude and direction of behavior change and can lead to the identification of subpopulations that would be benefitted. In sum, rate dependence is an invaluable perspective to examine data following any intervention in order to identify previously overlooked results.

Clinical and microbiological effects of an essential-oil-containing mouth rinse applied in the "one-stage full-mouth disinfection" protocol--a randomized doubled-blinded preliminary study

The aim of this randomized double-blinded preliminary study was to evaluate the clinical and microbiological long-term effects of an essential-oil-containing mouth rinse as the active agent utilized in the "one-stage full-mouth disinfection protocol." Probing pocket depth and plaque and gingival indices were evaluated by the same calibrated examiner in all teeth of 20 moderate chronic periodontitis subjects. Presence of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis were determined by polymerase chain reaction in nonstimulated saliva, tongue dorsum, and pooled subgingival samples. The subjects were randomized into two groups: full-mouth disinfection plus essential oils (Listerine) or full-mouth disinfection plus placebo. Clinical and microbial parameters were evaluated at baseline (T0), 45 (T1) and 180 (T2) days after therapy and analyzed using analysis of variance, Student t, and Wilcoxon tests (p < 0.05). No significant differences were observed between groups regarding clinical measurements at baseline. However, in the later examinations, T1 and T2, the test group always presented higher reductions of pocket depth, plaque index, and gingival index compared to the control group. The essential-oils group revealed significant reduction on occurrence of P. gingivalis in saliva comparing baseline and 45 days; this difference still remain at 180 days. The essential-oil-containing mouth rinse demonstrated beneficial effects on clinical parameters. Microbiological findings were less consistent. The results of this preliminary study suggest further investigations.

Repeatability of ultrasonic determination of gingival thickness

The aim of the present study was to assess the degree of disagreement of ultrasonic measurements of gingival thickness at different teeth. Gingival thickness was determined in 33 volunteers with plaque-induced gingivitis. Facial/buccal gingiva was measured at the level of the gingival sulcus depth. Measurements were repeated after 2 and 4 weeks. A repeated measures, two-level (occasion, subject), variance components model revealed a within-subject variance of 0.187 mm(2) resulting in a repeatability coefficient of 1.20 mm. When modeling level 1 (occasion) variance as a function of tooth type, respective error terms were used for calculating 95% repeatability coefficients for different teeth. Unreliable measurements were largely confined to upper and lower second and third molars. Error terms were lowest (0.03-0.05) at upper canines and first premolars as well as lower anterior teeth and premolars, where repeatability coefficients of 0.5 to 0.6 mm could be estimated. It was concluded that performance of the device was best at certain tooth types with rather thin gingiva. The present resolution and rather high degree of disagreement may preclude, however, detection of minute increases in thickness in the micrometer range, which seem to occur during gingivitis.