Abstract
For the purpose of investigating the thickness of the dental structure in the mandibular first deciduous molars, the distance between the pulp cavities and the external boundaries of the teeth were measured. The materials used were 42 teeth, some without caries and some with caries localized in the enamel. The classification of the specimens and the methods of the investigation applied were similar to those applied to the maxillary molars reported previously.
The observational regions used for these measurements consisted of the occulusal aspest, the mesio-distal aspects divided on the buccal groove in the mesiodistal diameter and the bucco-lingual aspects divided on the center of the transverse ridge in the bucco-lingual diameter, adding the cross sections of the central fossa, the center of the transverse ridge and the horns of the pulp chamber.
Result:
1. The smallest measurement for the distance from the pulp horns to the occlusal surface was 2.0 mm at the disto-lingual horn in the cross section of its horn.
2. For the measurements of the distance from the bucco-lingual grooves and the lingual trigonid notch to the pulp chamber, the distance of the buccal groove was 3.0 mm, greater than the other ones.
3. The smallest measurement of the distance from the pulp horns to the buccolingual and the interproximal surfaces was 2.1 mm. This phenomenon was observed on the mesial side in the lingual aspect and type I of the lingual side in the cross section of the mesio-lingual horn.
4. The smallest measurement of the distance from the maximum bulge of the pulp chamber to the bucco-lingual and the interproximal surfaces was 1.7 mm at all regions except for the mesio-buccal angle.
5. The smallest measurement at the maximum depression of the pulp chamber and cervical regions was 1.4 mm.
6. As for the measurement of the distance from the central fossa and the center of the transverse ridge to the pulp chamber, the former was 2.4 mm, the latter 2.8 mm.
7. The mesio-lingual horn existed closest to the summit of the cusp holizontally and the disto-lingual pulp horn was at the inner most part from the summit of the cusp.
8. According to the degree of the resorption, type II was greater than the other types when measuring the distance from the pulp chamber to the occulusal surface. Appropriate attention must be given to the occasion of the cavity preparation because the thickness of the dental structure in the mandibular first molars was thin at the portions of the central fossa, distal maximum bulge of the pulp cavity and mesio-buccal horn.
