Abstract
ObjectivesThis study investigated the safety of orthodontic anchor screw (OAS) placement by examining the morphology and degree of depression of the maxillary sinus adjacent to the alveolar bone between the maxillary molars.MethodsWe reviewed panoramic and CT imaging data of 25 patients. First, the morphology of the maxillary sinus adjacent to the alveolar bone between the maxillary molars on panoramic images was classified into three types: non-depressed sinus, funnel-like sinus depression, and sawtooth-like sinus depression. Then, the distance from the maxillary buccal bone to the maxillary sinus or to the maxillary lingual bone and the distance between the roots of the maxillary second premolar and first molar at heights of 5, 6.5, and 8 mm from the alveolar crest were measured on CT images and compared between the three sinus morphology groups.ResultsThe sawtooth-like depression group had significantly smaller bone thickness than the other two groups, with mean thickness of < 4 mm at any height from the alveolar crest. The funnel-like depression and non-depression groups had mean bone thickness of > 8 mm at any height from the alveolar crest.ConclusionsSawtooth-like sinus depression had increased risk of maxillary sinus perforation, suggesting that OAS placement in this region should be avoided. In contrast, OAS placement between 6.5 and 8 mm from the alveolar crest is advisable in patients with funnel-like sinus depression and at a site > 8 mm from the alveolar crest in those with a non-depressed sinus.
Highlights
Orthodontic anchor screws (OASs) have been introduced as an absolute source of orthodontic anchorage, enabling intrusion and distal movement of the maxillary molars, which had been considered difficult to achieve previous [1,2,3]
Because an OAS is often placed in the alveolar region between the maxillary second premolar and first molar, we considered it important to evaluate the positional relationship of the alveolar bone between the maxillary molars and the maxillary sinus in order to ensure safe OAS placement
We propose a new classification for the morphology of the maxillary sinus in the maxillary molar alveolar region on panoramic images and closely examined the maxillary sinus on CT images to evaluate the risk of maxillary sinus perforation and contact with adjacent tooth roots during OAS placement
Summary
Orthodontic anchor screws (OASs) have been introduced as an absolute source of orthodontic anchorage, enabling intrusion and distal movement of the maxillary molars, which had been considered difficult to achieve previous [1,2,3]. The risk of tipping and root resorption during distal movement of the maxillary molars has been reported [7, 8]. Given these concerns, the positional relationship between the maxillary molars and the maxillary sinus has been extensively examined [9,10,11]. Because an OAS is often placed in the alveolar region between the maxillary second premolar and first molar, we considered it important to evaluate the positional relationship of the alveolar bone between the maxillary molars and the maxillary sinus in order to ensure safe OAS placement
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