DENTAL AND FACIAL CHARACTERISTICS IN DOWN'S SYNDROME (MONGOLISM)

Characteristics of permanent teeth in persons with trisomy G

Tooth size and morphology have been studied in 35 participants with trisomy G. The control material was obtained from 33 dental students. Special attention has been paid to the mean cusp pattern of the upper first and second molars. The classification matrix for the linear discriminant function analysis between participants with trisomy G and controls, based on five selected variables that determine the cusp pattern, showed three misclassifications.

Posteruptive tooth age in children with Down's syndrome and their sibs

The accumulated posteruptive tooth age was calculated for 212 children with Down's syndrome and 124 of their unaffected sibs. Posteruptive tooth age was shown to vary widely with different morphological permanent tooth types at the same chronological age. Girls in both groups had greater accumulated posteruptive tooth age than boys at each age. Sibs of both sexes generally exceeded the exposure experience of the children with Down's syndrome.

Composition of parotid and submandibular saliva and serum in Down's syndrome

Parotid saliva, submandibular saliva, and blood were collected from mongoloid and nonmongoloid populations. Salivary flow rates were determined and fluid samples were analyzed for various electrolytes. Ten samples of parotid saliva and serum were analyzed for total protein, creatinine, amylase, and uric acid. Parotid saliva of mongoloids showed some differences in composition, but serum showed only a higher level of uric acid.

Birth weight and congenital absence of teeth in twins

The relationship between hypodontia and birth weight was investigated in 262 twins from the naval recruit population at Great Lakes. The overall frequency of hypodontia including third molars was 34.8%. Excluding third molars, hypodontia frequency was 11.6%. Anatomic distribution of congenitally missing teeth and frequency of third molar hypodontia were similar to other studies, but hypodontia of teeth other than third molars occurred two-three times as frequently in twins as in the general population.

The frequency of low birth weight (2500 g or less) in the twin sample was 47.7%. Hypodontia occurred more frequently in twins with low birth weight (42.6%) than in twins with birth weights over 2500 g (28.6%). Mean birth weight of twins with hypodontia was 2479 g, and without hypodontia, 2675 g. Twins with missing teeth other than third molars had a mean birth weight of 2357 g.

Mean birth weight was lower and hypodontia frequency was higher in MZ than in DZ twins. Discordances in anatomic location and number of missing teeth occurred in several MZ and DZ twin pairs. Discordances within MZ sets tended to be related to anatomic location rather than number of missing teeth. Six twin pairs (5 MZ and 1 DZ) out of 20 (13 MZ and 7 DZ) having one or more missing teeth had perfect concordance in both number and location of missing teeth. In 28 pairs neither member had hypodontia.

Mean intrapair variance in number of congenitally missing teeth was almost ten times greater in DZ than in MZ pairs, indicating the presence of a strong genetic component in connection with tooth number variability in twins.