Evaluation of ten extra-alveolar temporary anchorage device insertion sites by cone beam volumetric computer tomography: a pilot study

Background/purpose: In order to increase the success rate of temporary anchorage devices (TADs), it is important not to cause root injury or soft-tissue inflammation. The aim of the present study was to evaluate hard- and soft-tissue thicknesses of TAD insertion sites and the perforation ratio with different lengths of TADs by cone beam volumetric computed tomography (CBCT). Materials and methods: The hard- and soft-tissue thicknesses were evaluated on 10 patients (5 males and 5 females) by CBCT. The ages ranged 20-36 years. Ten regions of interest (ROIs) in extra-alveolar bone were selected and based on anchorage requirements. Soft-tissue depths were measured in the premaxillary and mid-palatal regions, while the cortical bone thicknesses were measured in all the other sites. Data were collected and the Wilcoxon rank sum test was used to compare differences, while the Wilcoxon signed rank test was used for paired data. Results: The average bone depth of the jaw was around 10 mm at most of the extra-alveolar ROIs, except for the infrazygomatic crest and midpalatal region. The average cortical bone thickness of the jaw was around 2 mm. The soft-tissue depth in the premaxillary region was thicker than that of the midpalatal region (P < 0.05). The infrazygomatic crest possessed the largest variation of hard-tissue depth. The cortical bone thickness increased from the mesial to the distal in both the buccal and lingual areas of the mandible. Conclusion: CBCT provides better radiographic evaluation than traditional radiographs. TAD insertion at these 10 extra-alveolar sites introduced in the study could be ideal locations. The design of TADs for different ROIs should take hard- and soft-tissue thicknesses into consideration to reduce clinical complications.