Heat alters colour and crystallinity of teeth by destruction of the organic content and inducing hydroxyapatite crystal growth. The colour and crystallite changes can be quantified using spectrophotometric and x-ray diffraction analyses, however these analyses are not commonly used in combination to evaluate burned dental remains. In this study, thirty-nine teeth were incinerated at 300-1000 °C for 15 and 30 min and then measured using a spectrophotometer and an x-ray diffractometer. Response variables used were lightness, L*, and chromaticity a* and b* and luminance (whiteness and yellowness) for colour, and crystal size for crystallinity. Statistical analysis to determine the attribution of these variables revealed yellowness and crystal size were significantly affected by temperature (p < 0.05), whilst duration of heat-exposure showed no significant effect. This study suggests the inclusion of both spectrophotometric and x-ray diffraction in investigating thermal-heated teeth is useful to accurately estimate the temperature teeth are exposed to.
The aim of this study was to determine the periodontal status in relation to the quality of the adjacent proximal tooth surface. The gingival index (GI) and probable pocket depth (PD) were measured in 144 contra-lateral pairs of sound vs. restored and 95 contra-lateral pairs of sound vs. carious surfaces in 124 patients. The restorations studied were silver amalgams and tooth-coloured filling materials, the margins of which were supragingival or level with the gingival margins. The results showed that the GI and PD were greater for both restored and carious tooth surfaces than for the contra-lateral sound surfaces. When all the teeth were grouped together, the differences in the mean values of GI and PD were statistically significant at the P less than or equal to 0.05 level. A comparison between restored and carious (non-paired) tooth surfaces revealed higher mean values of GI and PD for the latter, which were highly significant at the P less than 0.001 level. Thus the present study shows that proximal tooth surface quality influences the health status of the adjacent periodontium.
The objectives of this study were 1) to provide an estimate of the value of the intraclass correlation coefficient (ICC) for dental caries data at tooth and surface level, 2) to provide an estimate of the design effect (DE) to be used in the determination of sample size estimates for future dental surveys, and 3) to explore the usefulness of multilevel modeling of cross-sectional survey data by comparing the model estimates derived from multilevel and single-level models. Using data from the United Kingdom Adult Dental Health Survey 2009, the ICC and DE were calculated for surfaces within a tooth, teeth within the individual, and surfaces within the individual. Simple and multilevel logistic regression analysis was performed with the outcome variables carious tooth or surface. ICC estimated that 10% of the variance in surface caries is attributable to the individual level and 30% of the variance in surfaces caries is attributable to variation between teeth within individuals. When comparing multilevel with simple logistic models, β values were 4 to 5 times lower and the standard error 2 to 3 times lower in multilevel models. All the fit indices showed multilevel models were a better fit than simple models. The DE was 1.4 for the clustering of carious surfaces within teeth, 6.0 for carious teeth within an individual, and 38.0 for carious surfaces within the individual. The ICC for dental caries data was 0.21 (95% confidence interval [CI], 0.204-0.220) at the tooth level and 0.30 (95% CI, 0.284-0.305) at the surface level. The DE used for sample size calculation for future dental surveys will vary on the level of clustering, which is important in the analysis-the DE is greatest when exploring the clustering of surfaces within individuals. Failure to consider the effect of clustering on the design and analysis of epidemiological trials leads to an overestimation of the impact of interventions and the importance of risk factors in predicting caries outcome.
Thalassaemia is a public health problem in Malaysia. It is known to cause skeletal deformity. The purpose of this study was to compare the skeletal, dentoalveolar, and soft tissue features of Malay transfusion-dependent thalassaemia (TDT) patients with a Malay control group. Lateral cephalometric radiographs of 30 Malay (14 males and 16 females aged 6.4-21.8 years) TDT patients and 60 normal Malays matched for chronological age and gender were analysed and compared using an independent t-test. The TDT group showed a similar sagittal relationship to the control group but with a significantly increased (P < 0.01) mandibular plane inclination. They also showed a significantly shorter (P ≤ 0.001) mandibular body, ramus length, and posterior face height and consequently a smaller ratio of posterior to anterior face height (P < 0.01). The upper and lower lips were significantly procumbent (P < 0.001) in the TDT group together with a significantly smaller nasolabial angle (P < 0.05). Dentoalveolar measurements showed less proclined maxillary teeth in the TDT group compared with the controls (P < 0.05). The cephalometric features of Malay TDT patients were characterized by a mild Class II skeletal pattern, prominent vertical growth direction of the mandible, and protruded upper and lower lips.