Exploration of the relationship between tooth dimensions, body size, and age is important in paleontology, forensic odontology and aesthetic dentistry. It is reasonable to speculate that tooth length is associated with stature since teeth contribute to facial height. This study aimed to determine whether there was an association between tooth length and stature and age in a sample of Sri Lankan Sinhalese. Extracted teeth of adults, whose age, sex and standing height were known, were used for measurements. The total tooth length (TTL), crown length (CL) and root length (RL) of permanent maxillary central (68) and lateral (67) incisors were measured using a caliper. Statistical analyses were performed with the software MINITAB version 14.0 (Minitab Inc, USA). Mean age and standing height were 47.81 yr and 152.15 cm, respectively. There was no significant correlation between stature and tooth lengths of incisors. However, age was found to have a significant correlation with RL, (r = 0.26, P < 0.05) and CL (r = -0.28, P < 0.05). Absence of an association between tooth length and stature indicated that the genetic linkage between tooth size and stature was weak, suggesting that determination of stature from tooth lengths is unwarranted. The association between tooth length and age indicates the importance of root length in age determination.

The mechanism whereby a region-specific deposition of the two types of cementum (cellular cementum and acellular extrinsic fibre cementum) is regulated on the growing root surface was tested using bisphosphonate-affected teeth of young rats and guinea pigs. The animals were injected subcutaneously with 8 or 10 mg P x kg body weight(-1) x day(-1) of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 1 or 2 weeks. In rat molars, HEBP prevented mineralization of newly formed root dentin matrix and totally inhibited de novo deposition of acellular extrinsic fibre cementum. Instead, thick cellular cementum was induced on the non-mineralized root dentin surface, irrespective of the position of the root. In both animals, cellular cementum was also induced on the non-mineralized surface of root analogue dentin in HEBP-affected incisors, where only acellular extrinsic fibre cementum is deposited under normal conditions. In normal rat molars, dentin sialoprotein (DSP) was concentrated along the dentin-cellular cementum border, but not that of dentin and acellular extrinsic fibre cementum. In HEBP-affected rat incisors, DSP was shown to penetrate through the non-mineralized dentin into the surrounding tissues, but not through the mineralized portions. These data suggest that, at the site of cellular cementum formation, putative inducing factors for cellular cementum might diffuse into the periodontal space through the newly deposited mantle dentin matrix before it is mineralized. At earlier stages of root formation, mantle dentin might mineralize more promptly not to allow such diffusion. The timing of mineralization of mantle dentin matrix might be the key determinant of the types of the cementum deposited on the growing root surface.

This sample of students uses both deep and surface learning approaches with more preference to DA than SA. The correlation between learning approaches and academic performance was inconsistent.

Cementum pearls (CPs) belong to a type of acellular extrinsic fiber cementum (AEFC) that form on the maturing enamel of guinea pig molars. This study aimed to elucidate the forming process of intrinsic matrix of AEFC using the CPs of normal and bisphosphonate-affected guinea pig molars as experimental models. A group of guinea pigs were subjected to continuous administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 2 wk to inhibit mineralization of growing CPs. Fenestration of the enamel organ and migration of periodontal cells on to the exposed surface of maturing enamel appeared to be unaffected by HEBP, whereas de novo formation as well as growth of pre-existing CPs did not proceed under the same conditions. Immunoreactions for osteopontin were located exclusively on the mineralized matrix of preformed CPs, implying the absence of additional deposition or accumulation of putative intrinsic cementum matrix on the affected CPs, where the propagation of mineral phase had been arrested. In both normal and HEBP-treated groups, distinct enzymatic reactions for alkaline phosphatase appeared on the cells of the periodontal ligament associated closely with the sites of CP formation, and along the mineralization front of CPs. These observations suggest that the mineralization process per se plays a central role in the deposition of AEFC matrix and that alkaline phosphatase of periodontal cells penetrating through the enamel organ to the maturing enamel surface plays a key role in the mineralization process of CPs.

This study describes the unique distribution of Ruffini endings (RE) in the periodontal tissues of the guinea pig teeth with special references to their presence in the enamel-related aspects of the continuously growing incisors and molars. In guinea pig incisors, immunohistochemistry for PGP 9.5 and glia specific S-100 protein revealed a condensed distribution of well-developed RE in the bone-related part of the lingual periodontal ligament as has been reported in many other rodents. In most cases, some RE-like nerve elements characterized by dendritic ramification and rounded terminal Schwann cells were found to be located in the labial, enamel-related regions, where no periodontal ligament-like fiber arrangement was established. In the molar periodontal ligament, well-developed RE-like nerve elements were also distributed in the enamel-related part, but in intimate relation to thick periodontal fiber bundles inserted in the cementum pearls grown on the enamel surface. In some cases, few RE were located in the apical region of the alveolar socket, where no periodontal fiber bundles could be identified. Our data provide the first morphological evidence of the presence of RE-like nerve elements in the enamel-related, fibrous connective tissue of continuously erupting rodent incisors. These data indicate that RE in guinea pig periodontal tissues have variable spatial correlation to the surrounding fibers, implicating their diverse mechanoreceptive properties depending on the anatomical location.