Variability associated with mandibular buccal shelf area width and height in subjects with different growth pattern, sex, and growth status

Abstract

The primary objective of the study was to quantitatively analyze the width and height of the mandibular buccal shelf area (MBS) at 3 different potential locations for mini-implant placement. In addition, we aimed to compare and contrast the bone parameters of the MBS to study the correlation between different growth status (growing or nongrowing), facial types (hypodivergent, normodivergent, and hyperdivergent), and sex differences (male or female). In this retrospective cone-beam computed tomography study, 678 subjects were included. They were divided into groups according to growth status, facial type, and sex. Scans were imported into the reconstruction program and were aligned in 3 different steps. Measurements were made at 6 different coronal sections: mandibular first molar distal root, secondmolar mesial root, and secondmolar distal root (bilaterally). The roots of mandibular molars were used as a reference to measure the width and the roof of the inferior alveolar canal to measure the height of the buccal shelf area. Intraobserver reliability was assessed by measuring the width and height of MBS in 20 randomly selected subjects. No significant difference (P>0.05) was found in the width of MBS between males and females. MBS width increased, and height decreased (P<0.0001) as moved distally from the first molar distal root to the secondmolar distal root in all 3 facial types irrespective of age or sex. The hypodivergent facial type had significantly greater bone width than the hyperdivergent facial type at all the 3 locations in both males and females. The hypodivergent facial type had significantly less (P<0.0001) bone height than the hyperdivergent group at all the 3 locations irrespective of age or sex. The optimal site for MBS mini-implant is the buccal region of the distal root of mandibular secondmolars. Hypodivergent patients have more width and less height of MBS compared with hyperdivergent patients. MBS mini-implants are not advised for growing patients because of proximity to developing roots.