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Background: Although many studies have focused on the association of the MMP-9 promoter -1562 C/T polymorphism with the susceptibility and/or severity of chronic periodontitis (CP), results have been inconsistent. Therefore, a meta-analysis of all eligible studies was performed to derive a more precise estimation of the association between this polymorphism and CP risk., Methods: All relevant studies were identified through a database search in PubMed, Medline, and Web of Science. All the full-text studies with appropriate analytical design, published in English, which evaluated the association of MMP-9 promoter -1562C/T polymorphism with CP risk using validated genotyping methods, and with non-duplicated data were selected for this study. A fixed-effect model was used to calculate pooled ORs in the absence of heterogeneity across included trials (P > 0.1 and I(2) < 50 %), otherwise the random-effect model was applied., Results: In an overall meta-analysis, pooled ORs revealed that T variant in the MMP-9 promoter -1562 C/T polymorphism was associated with a significantly decreased risk for CP under all comparison models. In subgroup analyses by ethnicity, pooled ORs showed that a significant association of the MMP-9 promoter -1562 C/T polymorphism with CP risk was only detected in Caucasians and Asians but not in mixed population. In the subgroup analysis by severity of CP, pooled ORs indicated that T allele of the MMP-9 promoter -1562 C/T polymorphism was associated with decreased susceptibility to severe CP while there was no significant association between this polymorphism and moderate CP., Conclusions: Our meta-analysis showed that T allele in the MMP-9 promoter -1562 C/T polymorphism might be a protective factor for CP, especially in Caucasians and Asians. Moreover, there was a significant association of the MMP-9 promoter -1562 C/T polymorphism with decreased susceptibility to severe CP, while the allelic and/or genotype distributions of this polymorphism were not associated with moderate CP.

Objective: To modify the conventional straight elevator with a unique and innovative design in respect to approach and accessibility during extraction for patients with abrasions around corners of the mouth and with thick buccal mucosa, without causing overstretching of angles of the mouth., Methods: The shank of the straight elevator in the shape of a 'U' was modified, giving it a shape similar to 'P' in the English alphabet hence it is named the P Elevator. The P elevator utilises a 'U' shaped bend in the shank of the conventional straight elevator making space for the buccal soft tissues and the angle of the mouth, to accommodate properly in the 'U' shank. The application of this elevator in the successful removal of third molars is described., Results: Two hundred patients underwent extraction of third molars with the P elevator including 166 patients with disimpaction of all third molars, 23 patients with abrasion around the angle of the mouth, and 11 patients with thick buccal mucosa. Satisfactory results were obtained in all the cases with no postoperative complications., Conclusion: The P elevator permits prudent, meticulous, innovative and proficient extraction of third molars in patients with thick buccal mucosa and abrasions around the angle of the mouth, without overstretching the corners of the mouth. We introduce novel applications of the P elevator in third molar extraction that provide substantial advantages over a conventional straight elevator.