Clinical And Genetic Study On Primary Failure Of Eruption

Objectives:To examine the primary failure of eruption(PFE) patients in clinic and gene,and in order to further understand PFE and guide clinical works.Methods: 5 patients with posterior open bite were selected. 3 of them were in permanent dentition and 2 in mixed dentition. The number and the position of the affected teeth was examined in clinic. X-ray was used to assess the following information: eruption passageway, position, ankylosis and skeletal deformity in sagittal and coronal section. The DNA was extracted from the peripheral blood. Then parathyroid hormone receptor1(PTHR1) gene was amplified by polymerase chain reaction(PCR) and sequenced.Results: No obvious mechanical failure of eruption(MFE) was found in all 5 patients. 2of them were bilateral posterior failure and 3 were unilateral failure. The 3 patients in permanent dentition were affected in morals and premolars. Among the 3 patients in permanent dentition, 1 patient was type?, and 2 were mixed type?and ?. In permanent dentition patients 27 teeth were affected totally. 17 teeth of them were vertical impaction.There was a tendency that the impacted teeth were incline to the most serious alveolar defect. In 12 teeth the periodontal ligament were not apparent. The teeth eruption situation and type of patients in mixed dentition were not included. According to the cephalometric analysis, skeletal class?was expressed in 2 patients and ? in the other 3patients. According to the posterior-anterior film, there was mild mandibular deviation in3 patients. The PTHR1 gene detection was examined on 4 of the 5 patients. Exon mutation was found in 1 patient. Intron mutation was found in 1 patient. Single nucleotide polymorphism(SNP) was found in 2 patients.Conclusions: The main clinical manifestation of PFE shows unilateral or bilateral posterior open bite. More than 2 posterior teeth are affected in PFE patients. No obvious mechanical eruption impaction is found. The impacted teeth are most vertical, and the rest tend to be inclined to the severe alveolar defect. Skeletal class ? and mandibular deviation seem to be higher prevalence. Some of affected teeth are companied by ankylosis. PTHR1 gene mutation can not be detected in all PFE patients. It implies that the occurrence of PFE may be associated with other genes or other pathogenesis.