Abstract
In exploring the diagnostic criteria for deep overbite in the deciduous dentition, the present study was conducted to investigate the relationship between the amount of vertical overbite of the anterior teeth in deciduous dentition and the size of the teeth, and the dental and apical base arches.
From the serial dental materials kept by the Department of Pediatric densitry, Nippon Dental University, the study used casts of deciduous dentition were obtained from a total of 85 children,42 boys and 43 girls (mean age,3 years and 8months), who had no dental caries and minimal attriction. The size of the teeth and the dental and apical base arches, the morphology of the teeth, and the interdental spaces were investigated in relation to the amount of vertical overbite of the left central deciduous incisor in these casts. The following results were obtained:
1) With respect to the size of the teeth, those subjects with a deeper overbite tended to have a greater coronal length of the maxillary anterior teeth and the maxillary and mandibular second deciduous molars. No significant relationship was found, however, between the depth of the overbite and individual values for or the sum total of the coronal mesicdistal width. The depth of the overbite was related to the longitudinal coronal length of the deciduous canine and second molar teeth.
2) Measurement of the dental and apical base arches showed that those with a deeper overbite had a narrower intercanine dental arch particularly in the mandible. No significant relationship was found, however, between the depth of the overbite and the size of the apical base arch or the dental arch. There was also no relationship between the depth of the overbite and differerences in size between the maxillary and mandibular apical base arches.
3) No significant relationship was found between the occlusal surface area of the deciduous molar and the depth of the overbite.4
) There was an apparent continuous incisal edge-cusp curve even in the deciduous dentition. The curvature became more pronounced as the depth of the overbite increased, indicating a close relationship with the occlusion.
5) In assessing the interdental space, closed denal arshes were frequently found in both the maxilla and mandible of subjects with deep overbite. A closed dental arch of the mandible contributed particularly to a deep overbite.
6) The incidence of morphological variations in the mandibular first deciduous molar was high,63.4%, in those with deep overbite, and their mandibular first deciduous molars, and dental and apical base arches differed in size from normal cases. Morphological variations in the mandibular first deciduous molar appeared to be a factor responsible for deep overbite in deciduous dentition.
