Third molar agenesis in Down syndrome

Abstract

The frequency, gender, and maxillary/mandibular occurrences of third molar agenesis have been studied in a Danish population of Down syndrome individuals (39 F and 31 M). The study was based on radiological examination and compared with 2 control groups of normal Caucasian populations. We found that the occurrence of third molar agenesis in Down syndrome individuals was around 4 times greater than in a normal population and higher than in corresponding previous studies. The agenesis occurred more often in the maxilla than in the mandible, and the frequency was not significantly higher in females than in males. The present study stresses the importance of focusing on the dental germs in the phenotypic discussion, as different genes are involved in tooth formation. The absence of teeth can contribute to an understanding of the interaction between genotype and phenotype.

Prevalence and patterns of permanent tooth agenesis in Down syndrome and their association with craniofacial morphology

“…40 The reported prevalence of third molar agenesis in DS is much higher. It was noted in 88% of our sample, similar to the 84.4% reported by Lomholt et al 20 from Denmark but greater than the 74% reported by Shapira et al 19 from Israel. Agenesis of all third molars was seen in 52% of our sample, similar to the 55% reported by Shapira et al 19 Because of the frequent agenesis of all third molars in our sample, we explored whether this occurrence was associated with any specific craniofacial features.…”

“…Most studies report that mandibular second premolars, maxillary lateral incisors, maxillary second premolars, and mandibular central incisors are the teeth most often affected (in decreasing order). 35 In DS, the prevalence of hypodontia is much greater and more severe [12][13][14][15][16][17][18][19][20][21][22] and is recognized as a characteristic phenotypical feature of the syndrome.…”

“…Similarly, measurements of subjects exhibiting absence of all third molars were compared with those without this presentation. Since dental agenesis is frequently observed in both jaws in DS, [12][13][14][15][16][17][18][19][20][21][22] ANCOVA tests were additionally adjusted for the proportion of other missing teeth (vs in the regions of interest) in the total number of missing teeth. Statistical tests were conducted using SAS (version 9.1; SAS Institute Inc, Cary, NC).…”

“…2 Cephalometric analyses of subjects with DS have described platybasia, reduced maxillary and mandibular alveolar heights, short teeth, reduced maxillary and mandibular dimensions, and forward rotation of the maxillary and mandibular planes, which collectively lead to overclosure and relative mandibular prognathism. [3][4][5][6][7][8][9][10][11][12] Hypodontia in DS is well known, [12][13][14][15][16][17][18][19][20][21][22] with prevalence documented at about 90% 12,19,20 if the third molars are considered and between 30% 13 and 60% 22 when the third molars are not considered in the analysis. A very high prevalence of total agenesis of all third molars has also been described.…”

Health Supervision for Children With Down Syndrome

“…22 • Reassure parents that delayed and irregular dental eruption patterns are common and that hypodontia occurs with increased frequency (23%). 77,78 • Encourage and model use of accurate terms for genitalia and other private body parts (penis, vulva) any time these body parts are discussed or examined. Model respect for body rights by reminding patients that their body is their own and explain to the child what you will do before moving into child's personal space or performing a procedure.…”