MORPHOLOGY OF ANTERIOR AND POSTERIOR MANDIBULAR RIDGES AND THE PREVELENCE OF LINGUAL CONCAVITY IN THE UNITED STATES DENTAL POPULATION

Abstract

Introduction: Dental implant placement has become an increasingly popular method of tooth replacement. CBCT imaging has revolutionized dental implant planning by providing a three-dimensional view of intra-oral dental structures. The lingual concavity is a concave area located on the lingual surface of the posterior mandible. Perforation of the lingual concavity is associated with floor of the mouth bleeding and upper airway obstruction. A thorough understanding of the mandibular ridge morphology is critical to avoid surgical complications associated with lingual cortex perforations. The objective of this study was to assess the morphology of the anterior and posterior mandibular lingual ridges, determine the prevalence of the posterior lingual concavity, measure the average length and depth of the concavity, and investigate the influence of gender, ethnicity, smoking status, and history of periodontal disease on mandibular ridge morphology. Materials and Methods: The study was a retrospective analysis initially involving 1006 CBCT scans obtained from Temple University – Kornberg School of Dentistry from January 2020 to July 2022. Inclusion criteria included subjects who were above the age of 18. Exclusion criteria included subjects who were under the age of 18, subjects who received limited field of view CBCTs, and scans that were unintelligible due to scatter. 552 CBCT scans met the inclusion criteria and were included in the final analysis. Data was recorded on anterior and posterior mandibular lingual ridge shape, location, length, and depth. Results: The mean age of subjects at the time of CBCT scan acquisition was 55 years. The study included 310 females and 242 males. 545 subjects (99%) presented with a convex mandibular anterior lingual ridge morphology. The average length in millimeters of the anterior lingual convexity was 19.01mm. There was a significant relation between anterior ridge length and smoking status (ANOVA, F=4.819, p=0.016). There was also a significant mean difference in anterior ridge length based on the history of periodontal disease (t-test, t=8.683, p<2.2e-16). The most prominent location of the mandibular lingual anterior convexity was at the central incisor site in 514 subjects. 332 subjects presented with a lingual concavity in the right posterior mandible (60.1%). 330 subjects presented with a lingual concavity in the left posterior mandible (59.8%). The average length in millimeters of the lingual concavity was 12.73mm and 12.35mm for the right and left posterior mandible. The average depth in millimeters of the lingual concavity was 2.03mm and 1.96mm for the right and left posterior mandible respectively. The most common location of the posterior mandible lingual concavity was found at the right first molar site in 184 subjects (52%) followed by right second molar in 165 subjects (46%) and the right second premolar in 6 subjects (2%). Conclusion: CBCT imaging can improve the ability of practitioners to identify the mandibular lingual concavity and pre-plan dental implants of adequate dimensions. This may prevent complications associated with lingual concavity perforations, including potentially life-threatening hemorrhages and airway obstruction. Further research should incorporate a broader range of confounding variables (systemic conditions, medication usage), to better understand their impact on mandibular lingual ridge morphology.