Abstract
The aim of this present study was to measure the occlusal angles of the buccal grooves in the mandibular deciduous molars and to reveal the difference of the angles between mandibular first deciduous molar and second deciduous molar. Dental casts of the deciduous dentition were obtained from children aged from three years to just under three years and one month, and caries free with hardly any attrition and with normal occlusion. The occlusal angles of the buccal grooves in the mandibular first deciduous molar and second deciduous molar were measured. The tangents were drawn at the disto-internal oblique plane of the mesio-buccal cusp and the mesio-internal oblique plane of the disto-buccal cusp. The occlusal angle of the buccal groove was defined as the interior angle which intersected these tangents.
The results were as follows.
1. The mean occlusal angle of the buccal groove of the third near the mesio central pit was 119.71° at the mandlbular first declduous molar and was 123.46°at the mandibular second deciduous molar. The mean occlusal angle of the baccal groove of the third near the buccal margin was 125.69° at the mandibular first decidaous molar and was 125.67° at the mandibular second deciduous molar.
2. The mean occlusal angles of the buccal groove of the mandibular first deciduous molar approximated that of the mandibular second deciduous molar, and indicated a tendency for the angles to stabilite from the central pit toward the buccal margin.
3. According to reseach regarding whether the buccal groove was included in the outline form of cavity on the mandibular deciduous molars, the cases of first deciduous molars which included the buccal groove accounted for 48%, and those excluding the buccal groove accounted for 52%. On the other hand, the buccal groove was included in the outline form of cavity on the second deciduous molars in all the cases.
