Reciprocal actions of Magnetic Resonance Imaging with dental prostheses and oral tissues - awareness among the dentists.

OBJECTIVE: MRI (Magnetic Resonance Imaging) does not use ionizing radiation and provides a comparatively better resolution. It is an important tool for the diagnosis of problems related to the head and neck area. It has various applications in dentistry, including MRI-based planning for implant placement. Previously, studies have been performed to assess its medical use, but very few studies have been conducted on its applications in dentistry. MATERIALS AND METHODS: A pre-validated online questionnaire was distributed through various messenger groups and social media. The questionnaire comprised two sections to collect demographics and assess the knowledge and awareness among dentists about the interactions between dental prostheses and materials with MRI. RESULTS: In the present study, 63.20% of respondents indicated that MRI provided a good view of the implant sites, TMJ and salivary gland tumours, but the majority believed that metallic and titanium implants do not interact or cause artefacts on MRI imaging. CONCLUSIONS: We concluded that dental undergraduates and graduates had limited knowledge of the interactions of dental materials and prostheses with MRI. Dentists should be aware of interactions of MRI with the various dental materials and prostheses and possible image distortion to ensure the safety of the patient.

Peutz-Jeghers syndrome: confirmation of linkage to chromosome 19p13.3 and identification of a potential second locus, on 19q13.4.

Peutz-Jeghers syndrome (PJS) is an autosomal dominant disease with variable expression and incomplete penetrance, characterized by mucocutaneous pigmentation and hamartomatous polyposis. Patients with PJS have increased frequency of gastrointestinal and extraintestinal malignancies (ovaries, testes, and breast). In order to map the locus (or loci) associated with PJS, we performed a genomewide linkage analysis, using DNA polymorphisms in six families (two from Spain, two from India, one from the United States, and one from Portugal) comprising a total of 93 individuals, including 39 affected and 48 unaffected individuals and 6 individuals with unknown status. During this study, localization of a PJS gene to 19p13.3 (around marker D19S886) had been reported elsewhere. For our families, marker D19S886 yielded a maximum LOD score of 4.74 at a recombination fraction (theta) of .045; multipoint linkage analysis resulted in a LOD score of 7.51 for the interval between D19S886 and 19 pter. However, markers on 19q13.4 also showed significant evidence for linkage. For example, D19S880 resulted in a maximum LOD score of 3.8 at theta = .13. Most of this positive linkage was contributed by a single family, PJS07. These results confirm the mapping of a common PJS locus on 19p13.3 but also suggest the existence, in a minority of families, of a potential second PJS locus, on 19q13.4. Positional cloning and characterization of the PJS mutations will clarify the genetics of the syndrome and the implication of the gene(s) in the predisposition to neoplasias.