MORPHOMETRIC ANALYSIS OF DEVELOPING CROWNS OF MAXILLARY PRIMARY 2ND MOLARS AND PERMANENT FIRST MOLARS IN HUMANS

The purpose of this study was firstly to characterize the changes occu rring in size and form of the mineralizing maxillary second primary mo lar and first permanent molar crowns, and secondly to determine if sim ilar changes in size and form characterize enamel apposition in the cr owns of these teeth. Twenty-five primary second molars and 20 maxillar y permanent first molars at various stages of development, found in ar chaeological excavations in Israel, were examined for a number of meas ured variables using image analyser software. Teeth were divided into two groups according to their stage of development: stage 1 included a ll teeth at an early stage of development in which mesiobuccal-cusp he ight was less than 5 mm for the primary molar and 5.9 mm for the perma nent molar; stage 2 included all teeth in later stages of development where mesiobuccal-cusp height was greater than these values. In the pr imary molar, a significant increase was found between the two stages i n almost all variables. Significant correlations were also found betwe en all intercusp distances and the external variables. Strong correlat ions between height of the mesiobuccal cusp and all external and inter nal variables were noted in stage 1, but fewer in stage 2, In the perm anent tooth, no increase was observed in intercusp distances and very few correlations were found between and among the variables. The resul ts suggest that a change in the shape of the maxillary primary second molar occurs during formation, with the lingual cusp tips moving lingu ally and distally, and the distobuccal cusp tips moving distally. No c hange occurs in the shape of the maxillary permanent first molar durin g crown formation. Growth of the maxillary primary second and permanen t first molar crowns occurs in 'bursts' of development. (C) 1998 Elsev ier Science Ltd. All rights reserved.