Size, ultrastructure, and microhardness of natal teeth with agenesis of permanent successors.

OBJECTIVE: Natal and neonatal teeth may occur in conjunction with other oral anomalies, including anomalous development of succedaneous teeth. Our purpose was to examine the size, ultrastructure, and microhardness of two natal teeth without permanent successor germs, and compare them with the characteristics of normal primary teeth. DESIGN: The dimensions of two natal mandibular incisors extracted from a healthy 7-year-old child were measured with a digital sliding caliper. The crown dimensions of normal primary mandibular central incisors were established from dental casts of 102 children. Since the natal teeth were nearly completely devoid of enamel, the average enamel thickness determined on a sample of 19 normal primary mandibular incisors was added to the values measured. External surfaces and transverse sections of the natal teeth were examined under a scanning electron microscope. Vickers microhardness of radicular dentine was assessed for the natal teeth and for 11 normal primary mandibular incisors. RESULTS: Only remnants of enamel were present. All crown dimensions corrected for enamel loss were within the normal range. The ultrastructure of hard dental tissues was normal. The radicular dentine hardness of the natal teeth was similar to that of the normal primary mandibular incisors. CONCLUSIONS: The results indicate that the natal teeth were prematurely erupted regular primary mandibular central incisors. In our case, the occurrence of natal teeth associated with agenesis of their primary successors appears to be related to an accelerated or premature pattern of dental development, rather than to superficial positioning of the tooth germs.

Cementum thickness in multirooted human molars: a histometric study by light microscopy.

Cementum distribution was studied on transversely sectioned roots of 33 three-rooted maxillary and 33 two-rooted mandibular permanent molars. The roots were sectioned at a level midway between furcation and apical region. Cementum thickness was measured at the midpoint of each of the four root surfaces and at a site exhibiting maximal cementum thickness. A reflected light microscope was used. Midpoint cementum thickness ranged between 5 and 800 microm in maxillary molars and between 5 and 700 microm in mandibular molars. Maximal cementum thickness ranged between 25 and 1140 microm in maxillary molars and between 20 and 700 microm in mandibular molars. The results indicate that cementum tends to accumulate along interradicular surfaces of multirooted molars. In addition, a tendency was noted for more cementum to occur orally than vestibularly in roots of mandibular molars as well as in buccal roots of maxillary molars. Furthermore, this study indicates that cementum accumulates in root concavities (developmental depressions), although the exact mechanism still awaits a clear explanation. Previous studies have suggested that tensile forces stimulate cementum apposition. It may be assumed, however, that masticatory function and continuing eruption of the teeth exert no discernible effect on cementum thickness in the examined region of the root. In conclusion, the observed cementum distribution could be attributed to at least two factors: one is buccal drift and the second may be the effect of root concavities. From a clinical viewpoint, the established pattern of cementum distribution in multirooted molars should be considered in endodontic and periodontal treatment.

Unusual variant of type 3 dens invaginatus in a maxillary canine: a rare case report.

A 13-year-old boy presented with clinical symptoms of periapical inflammation related to the right maxillary canine. A bizarre radiographic appearance of the root was considered suggestive of a compound odontome. Histological examination of the surgically extracted canine revealed a very rare variant of Oehlers' type 3 invagination. The invagination originated in a pit above the cingulum as a narrow coronal channel that opened into a large cavity inside the dilated root. The radicular part of the invagination contained all components of the attachment apparatus. The root canal and its apical foramen were slit-like and circular. Radiographic appearance of two roots separated by a wide interradicular area in a normally single-rooted tooth is indicative of this variant of type 3 invagination. Timely prophylactic treatment and follow-up or early endodontic treatment confined to the coronal channel are crucial to prevent pulp necrosis and consequent loss of the tooth.

Carabelli's trait in contemporary Slovenes and inhabitants of a medieval settlement (Sredisce by the Drava River).

The objectives of this study were to determine the total frequency, expression and asymmetry of Carabelli's trait in permanent dentitions of contemporary Slovenes and a medieval skeletal population from northeastern Slovenia. A total of 254 dental casts from contemporary Slovene children were examined. The population of a medieval settlement (10th-15th centuries), was represented by 94 skeletons. A modification of the method of Alvesalo and associates was used to classify Carabelli's trait on a five-grade scale. The trait was expressed on the upper first molars of 79.7% of the contemporary subjects and 75.8% of the medieval sample. Positive expressions of the trait were found in 10.1% of the contemporary subjects and 15.2% of the medieval sample. While the observed total frequency of the trait in both samples is characteristic of Europeans, the rates of positive expressions are surprisingly low but consistent with data from a recently published worldwide literature survey. Both populations showed a low rate of left-right fluctuating asymmetry of the trait. This finding might reflect a pronounced ability of individuals in the medieval population to buffer unfavourable influences from the environment and a relatively low level of environmental stress in the contemporary population.