The effect of shared genetic and environmental factors on periodontal disease parameters in untreated adult siblings in Guatemala.

BACKGROUND: Increasing evidence supports the role of genetic factors in susceptibility to infectious diseases, including chronic periodontitis. The role of genetic factors in phenotypic expression can be estimated from the degree of resemblance between relatives, as compared with that of unrelated members of a population. Heritability is an estimate of the proportion of total phenotypic variation of a quantitative trait, which is attributable to genetic factors, and is based on the variance within versus between family members. The aim of this study was to determine whether there is a familial basis for periodontal disease status in an untreated population in Guatemala using heritability estimates as a measure of familial clustering of disease. METHODS: One-hundred and thirteen adult subjects (including both siblings and spouse pairs), age range 35 to 60 years, participated in this study. Full-mouth periodontal examinations were performed and heritability estimates were calculated for mean plaque score, mean gingival index (GI), probing depth (PD), and clinical attachment level (CAL). Intraclass correlation coefficients (ICCs) were calculated using the same parameters for spouses to determine whether a common family environment in adulthood plays a role in disease expression. RESULTS: Only in the case of mean plaque score and mean recession score were heritability estimates significantly above zero at alpha = 0.05. For spouse pairs, mean GI score, mean PD, and percentage of sites of PD > or = 5 mm showed a statistically significant ICC. CONCLUSIONS: These results lead us to reject the hypothesis that there is substantial heritability for periodontal disease expression in this population. This may be due to an underlying lack of genetic variation within this sample or may indicate that, compared with the role of environmental factors, the genetic contribution to periodontal disease phenotypes is relatively minor.

The applicability of half-mouth examination to periodontal disease assessment in untreated adult populations.

BACKGROUND: Data from whole-mouth examinations are the gold standard for accurate assessment of periodontal disease. Since periodontal destruction exhibits left-right symmetry, however, it is hypothesized that a half-mouth exam provides an appropriate alternative to whole-mouth assessment, with considerable advantage over a more limited partial-mouth assessment of index teeth. METHODS: Data from 2 untreated populations were utilized in the analyses. Half-mouth (random diagonal quadrants) and Ramfjord teeth assessment was compared with whole-mouth assessment as follows. Intraclass correlation coefficients (ICCs) were calculated for mean plaque index (PI), gingival index (GI), probing depth (PD), and clinical attachment level (CAL) and for percentage of sites with PD > or = 4, 5, or 6 mm; CAL > or = 3, 4, 5, or 6 mm; and recession > or = 3 mm to determine the agreement between the whole- and partial-mouth assessment. Disease prevalence was also determined for both whole- and partial-mouth assessments. RESULTS: For mean PI, GI, PD, and CAL, both half-mouth and Ramfjord teeth assessment provided an acceptable alternative to whole-mouth assessment (ICCs > 0.92). For percentage of sites above a specified threshold, ICCs were generally greater than 0.90 in all age cohorts for half-mouth assessment, but consistently lower for Ramfjord teeth assessment. Ramfjord teeth assessment also considerably underestimated disease prevalence compared with half-mouth assessment. CONCLUSIONS: These results support the use of a half-mouth examination procedure, to conserve time, limit cost, and reduce patient and examiner fatigue while providing maximal clinical information. Ramfjord teeth assessment was not as suitable for evaluation of either disease extent or prevalence.