Abstract
For the purpose of investigating the thickness of the dental structure in the maxillary second deciduous molars, the distances between the pulp cavities and the external boundaries of the teeth were measured.
Materials: The materials used were 63 teeth without caries and with caries localized to the enamel.
These specimens were divided into 3 types according to the degree of the root resorption; type I for less than 50% resorption of the root, type II for more than 50% resorption of the root and type III for the crown only.
Methods: For visualization of the pulp cavity, india ink was infused into the cavity using a vacuum pump. After dehydration, a transparent specimen was prepared by dipping the tooth in styren-monomer and embedded in epoxy resin. Markers were notched on the surface of this embedded block parallel to the dental axis.
The block was then sliced mesiodistally into serial sections of 93μ using a microtome (used for cutting hard tissues).
The serial sections were enlarged ten-times and traced. The traces were three-dimentionally reconstructed using a personal computer. The distances from the various points of the crown were measured on the reconstructed stereogram. The cross-sections used for these measurements consisted of the occlusal aspect, the center of the mesio-distal diameter, the center of the bucco-lingual diameter, the centra fossa, mesial and distal pits and the pulp horns.
Results:
1) The smallest measurement for the distance from the pulp cavity to the occlusal surface was 2.5-2.6 mm at the mesio-buccal horn.
2) In the cross-section of the pulp horn, the smallest measurement for the distance from the pulp horns to the bucco-lingual and interproximal surfaces was 2.7 mm at the distance from the mesio-buccal horn to the mesial and buccal surfaces.
3) The smallest measurement of the distance from the maximum bulge of the pulp cavity to the bucco-lingual and the interproximal surfaces was 1.9-2.0mm. This tendency was observed at the mesial side in the bucco-lingual aspect and the central fossa.
4) The smallest measurement in the cervical regions was 1.4-1.7 mm at the mesial side of the buccal aspect.
5) According to the degree of the resorption, a few portions in which the 37thickness of the dental structure varied significantlly was observed. Therefore on the occation of the cavity preparation, it is dengerous that too much reliance is placed on the physiological formation of the secondary dentin.
