Assessment of Bone Thickness in the Infra-Zygomatic Crest Region for Determining the Optimal Site and Angle of Orthodontic Bone Screw Insertion: A CBCT Short Study

Abstract

AbstractObjective: To evaluate overall bone thickness (OBT) and cortical bone thickness (CBT) at selected infra-zygomatic crest (IZC) sites at two insertion angulations for determining a favourable site and angle for orthodontic bone screw placement.Materials and Methods: This retrospective cross-sectional CBCT study included pretreatment scans of 20 patients aged 18-30 years with maximum anchorage requirements and fully erupted permanent second molars. OBT and CBT were measured at four posterior maxillary sites: distobuccal root of the maxillary first molar, interdental region between the maxillary first and second molars, mesiobuccal root of the maxillary second molar and distobuccal root of the maxillary second molar. Measurements were made at 50 degrees and 70 degrees from the maxillary occlusal plane using IC Measure software. Descriptive statistics, Student's t-test andpost-hoc comparisons were performed.Results: Overall bone thickness was significantly greater at 70° than at 50° across all four IZC sites: distobuccal root of the maxillary second molar (p = 0.001), mesiobuccal root of the maxillary second molar (p < 0.001), interdental region between the maxillary first and second molars (p < 0.001), and distobuccal root of the maxillary first molar (p = 0.002). Cortical bone thickness was also significantly greater at 70° at the distobuccal root of the maxillary second molar (p = 0.009) and the interdental region between the maxillary first and second molars (p = 0.023). The interdental region showed the highest overall and cortical bone thickness values, with a significant post-hoc difference in cortical bone thickness between the interdental region and the distobuccal root of the maxillary first molar at 70° (p = 0.047.Conclusion: Within the limitations of this small CBCT sample, the interdental region above the roots of the maxillary first and second molars at an insertion angle of 70 degrees appeared to be the most favourable IZC site for orthodontic bone screw placement.