Objective: Class II malocclusion is associated with the gene FGFR2. Genotyping involved conducting genome linkage scans to identify mutations in various mandibular genes and loci associated with Class II malocclusion. The present study aimed to improve the current understanding of genetic factors involved in the development of a retrognathic mandible and to correlate genetic variations with phenotypic characteristics. Methods: Two hundred patients with class II jaw relation have been examined; twenty patients with a retrognathic mandible and another twenty with normal mandibular size and position have been selected from the population by analyzing their lateral cephalometric radiographs. DNA was extracted from saliva samples collected from 40 individuals. FGFR2-8 and FGFR2-10 genes were amplified using the genomic DNA of patients' saliva by PCR. The results of sequenced samples were analyzed using a phylogenetic tree. Results: Cephalometric readings indicated that patients with class II had a retrognathic mandible, while their maxilla was normally positioned. Genetically, when comparing FGFR2 exon 8 and exon 10, exon 10 is more promising for detecting class I and class II, because it mimics the results of clinical examination by cephalometric radiographs. In FGFR2-10 the controls were in one group of the phylogenetic tree. Conclusions: This study concludes that FGFR2-10 may be promising for detecting class II malocclusion, while FGFR2-8 was not very specific. All found mutations were point mutations and can be considered new SNPs (Single Nucleotide Polymorphisms). FGFR2-10 showed clearer grouping patterns between cases and controls in the phylogenetic tree; these findings may serve as a diagnostic aid and require further validation.
Aram O. Hamad (Tue,) studied this question.