[Morphological studies on the roots of maxillary premolars in Japanese]

Visual observations were made of 3,202 maxillary first premolars and 3,365 maxillary second premolars from subjects of known sex, age, and side attributes. The material belongs to the Okamoto Research Laboratory of Dentistry. Items observed for each donor included number of dental roots, shapes of root apexes, root grooves, root orientation and curvature, and conditions of the maxillary first and second premolars. Results 1) In 65.7% of all materials (55.4% in males and 76.1% in females), maxillary first premolars had primary single roots. Complete branched roots accounted for 25.5% of the male and 17.6% of the female materials. In both cases, there was significant distinction between the sexes. Triple root teeth were extremely rare in both male- and female-donor teeth, as were double rooted maxillary second premolars. 2) Protruding, circular, and flat root apex types occurred in both maxillary first and second premolars. Circular and flat types were common among males. Branched and double-root maxillary first and second premolars were of either the complete or the incomplete type, both of which were more common in males. 3) About half of the mesial surface grooves in single-root maxillary first premolars were deeper than distal surface grooves in the same teeth: In 1/4-branch double teeth, 28.8% of the mesial surface grooves were deeper than the distal-surface grooves. The corresponding percentage for 1/3-branch double teeth was 38.8%. In 7.6% of 1/4-branch and 17.4% of 1/3-branch double teeth, distal-surface grooves were deeper than mesial-surface grooves. In 36.4% of 1/4-branch double teeth and 28.9% of 1/3-branch double teeth, the lower portion of the root was web shaped. In maxillary first premolars, lingual roots of 1/3-branch double-root teeth were cylindrical, as were 28.9% of buccal roots. Root grooves occurred on the lingual sides of 61.7% of all specimens. For 1/2-branch double root teeth, 18.4% were cylindrical: and 62.7% had grooves on the lingual side. Results are essentially the same in both cases. 4) Straight dental roots occurred in 37.4% of maxillary first and 35.4% of maxillary second premolars. Roots inclined distally in 36.7% of maxillary first premolars and in 18.8% of maxillary second premolars. A variety of inclinations and curvatures was observed. Booth roots were straight in 47.5% of 2-branch maxillary first premolars, whereas 35.1% had 1 straight and 1 inclined root and 84.4% had 2 distally inclined roots.(ABSTRACT TRUNCATED AT 400 WORDS)