Patterns of permanent incisor, canine and molar development in modern humans, great apes and early fossil hominins.

OBJECTIVE: The objectives of this study were to quantify the variation in coincident stages of incisor, canine and molar eruption and tooth formation in modern humans and great apes and then to ask if any early fossil hominins showed a dental development pattern beyond the human range and/or clearly typical of great apes. DESIGN: Four stages of eruption and 18 stages of tooth development were defined and then scored for each developing tooth on radiographs of 159 once-free-living subadult great apes and on orthopantomographs of 4091 dental patients aged 1-23 years. From original observations, and from published images of eleven early fossil hominins, we then scored formation stages of permanent incisors when M1 was at root formation stage R»-R½ and R¾-RC. RESULTS: Incisor and canine eruption/development was delayed in great apes relative to molar development when compared with humans but there was overlap in almost all anterior tooth stages observed. Molar crown initiation was generally advanced in great apes and delayed in humans but again, we observed overlap in all stages in both samples. Only two fossil hominin specimens (L.H.-3 from Laetoli, Tanzania and KNM-KP 34725 from Kanapoi, Kenya) showed delayed incisor development relative to M1 beyond any individuals observed in the human sample. CONCLUSIONS: For certain tooth types, the distribution of formation stages in our samples showed evidence of generally advanced or delayed development between taxa. However, it would rarely if ever be possible to allocate an individual to one taxon or another on this basis.

Associations of nutritional status, sugar and second-hand smoke exposure with dental caries among 3- to 6-year old Malaysian pre-schoolers: a cross-sectional study.

BACKGROUND: Dental caries in primary teeth is a serious oral health concern among children. It can lead to detrimental impacts on a child's growth, development, and quality of life. Therefore, this cross-sectional study aimed to examine the prevalence of dental caries and its associations with nutritional status, sugar and second-hand smoke exposure among pre-schoolers. METHODS: A total of 26 pre-schools in Seremban, Malaysia were randomly selected using the probability proportional to size sampling. Dental examination was performed by a dentist to record the number of decayed teeth (dt). Weight and height of the pre-schoolers were measured. The mother-administered questionnaire was used to gather information pertaining to the sociodemographic characteristics and second-hand smoke exposure. Total sugar exposure was calculated from a 3-day food record. RESULTS: Among the 396 participating pre-schoolers, 63.4% of them had at least one untreated caries, with a mean ± SD dt score of 3.56 ± 4.57. Negative binomial regression analysis revealed that being a boy (adjusted mean ratio = 1.42, 95% CI = 0.005-0.698, p = 0.047), exposed to second-hand smoke (adjusted mean ratio = 1.67, 95% CI = 0.168-0.857, p = 0.004) and those who had more than 6 times of daily total sugar exposure (adjusted mean ratio = 1.93, 95% CI = 0.138-0.857, p = 0.013) were significantly associated with dental caries among pre-schoolers. CONCLUSION: A high prevalence of dental caries was reported in this study. This study highlights the need to reduce exposure to second-hand smoke and practice healthy eating behaviours in reducing the risk of dental caries among pre-schoolers.