Methods: As part of a larger study six families affected by DI II underwent complete medical, dental and radiographic examinations. Venous blood samples were collected from 15 affected and 13 unaffected individuals. Genomic DNA was extracted; exons 1 to 4 of DSPP were amplified using PCR, and directly sequenced to identify mutations.
Results: Fifteen DI II positive patients were identified from the six families studied. A broad spectrum of clinical and radiographic features were identified as being characteristic of DI II. In general the primary dentition showed greater discolouration and toothwear than the permanent dentition. Significant intrafamilial variations in clinical severity were also observed. 6 out of 15 DI II patients showed mutations within exons 1 to 4 of DSPP gene, 9 out of 15 DI II patients showed no mutation in exons 1 to 4 of DSPP gene. None of the unaffected family members had DSPP mutations.
Conclusion: A variety of genotypes are associated with DI II including mutations in exons 1 - 4 of the DSPP gene. Individuals without DSPP mutations in exons 1 - 4 may have mutations in exon 5, or mutations in other gene(s). This study will allow genotype-phenotype comparisons which may lead to the development of a system of classification of DI based on genotype.