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Twenty male volunteers, average age 24 years, participated in this study. Specimens were obtained by enamel biopsy using 5 microliters of 0.5 M HClO4 for 30 s. Using a regression curve, comparisons of fluoride concentrations were made at different depths. The fluoride concentrations (mean +/- SE) at a depth of 5 microns were highest in the distobuccal (1698 +/- 136), high in the mesiobuccal (1343 +/- 122), low in the distolingual (1119 +/- 107), and lowest in the mesiolingual sites (819 +/- 78). Of the interior enamels (or = 10 microns in depth), the distobuccal site (1330 +/- 88 parts/10(6) F at 10 microns) had a higher-concentration than all other sites. The fluoride profiles were steepest to shallowest in the order: distobuccal, mesiobuccal, distolingual and mesiolingual. There were no correlations between the enamel fluoride concentrations and the fluoride concentration in parotid saliva. It was concluded that in vivo fluoride profiles of maxillary first molars reflect the wear of the tooth surface with age and the condition of dental plaque deposition, and, to some extent, the site-specific distribution of saliva between buccal and lingual surfaces.

The mandibular molars typically have two roots placed mesiodistally, but they occasionally have an additional distolingual (DL) root. This study was to determine the morphological characteristics of the crown of such mandibular molars.Radiographic records and study models were collected from a Korean population (n=86 patients). Each molar was assigned to either the experimental group (i.e. with a DL root) or the control group (i.e. without a DL root; n=41 patients) based on the radiographic findings. The intercuspal distances of the first permanent molars (total, n=100; control/experimental, n=50/50) and primary second molars (46, 23/23), and the largest buccolingual/mesiodistal widths of those molars and primary first molars (42, 21/21) were measured for molars with and without a DL root. In addition, the correlation between the existence of a sixth cusp and a DL root was examined.The crowns of first permanent and primary second molars with DL roots had significantly larger intercuspal distances between the distobuccal-distolingual cusp tips and a larger distal-area buccolingual width than those without the DL root (t-test; p0.05). There was no significant correlation between the existence of a sixth cusp and the presence of a DL root.The existence of a DL root was associated with larger buccolingual dimensions, especially in the distal area.

The crown and root morphology, and bilateral occurrence of human deciduous lower first molars that exhibited a triangular occlusal outline, taken from excavated samples of Japanese, Jomonese and Iraqi origin, were investigated. The crowns of triangular teeth had smaller mesiodistal and larger buccolingual diameters than normally shaped deciduous lower first molars. An elongated buccolingual diameter was derived from the buccal projection of the distobuccal cusp and lingual projection of the portion between the metaconid and distolingual cusp. In this analysis, all triangular deciduous lower first molars in which root morphology could be observed were accompanied by additional distolingual roots. Correlation between the right- and left-hand sides of this trait was high.

A description of development of M1 based on thirty-nine specimens dissected from human foetuses. At each stage, the mesiobuccal part of the crown is most advanced, the distolingual part least so; the protocone and metacone develop nearly together. Cusps and ridges, at first rounded, become increasingly acute up to the time of their calcification. Epithelial downgrowths delimiting root openings are formed early in development. The distal part of the crown is at first narrow and increases in relative width during development. The main cusps spread apart and the crown increasingly overhangs the root openings. Comparison is made with molars of lower primates, and the application of the Recapitulation Theory is discussed.