The effects of space closure of the mandibular first molar area in adults.

There is little information regarding the orthodontic closure of remodeled, edentulous spaces in the posterior area of the mandible. The present study was undertaken to determine the dental and periodontal changes that occur when mandibular first molar areas are closed in adults. Fourteen adult patients were selected from private orthodontic practices. Pre- and posttreatment study models were used to measure the mesiodistal length of the edentulous space and the buccolingual width of the alveolar ridge. The amount of crown and root movement of the second molar and premolar was measured from lateral cephalometric radiographs. From pre- and posttreatment panoramic or periapical radiographs, the anatomic changes of the second molar and adjacent periodontium were also measured. Every case showed significant space closure (x = 6.2 mm) ranging from 2.7 to 11.5 mm. There was crestal bone loss (x = 1.3 mm) mesial to the second molar in all but five cases. These latter cases showed bone addition. As the molar moved mesially , the alveolar ridge increased in width an average of 1.2 mm. The adult patient who showed the greatest amount of space closure and the least amount of molar bone loss had (1) mesiodistal space of 6.0 mm, (2) buccolingual ridge width of 7.0 mm, and (3) mesial molar bone level 1.0 mm apical to the cementoenamel junction. The results of this study indicate that space closure is not only possible but may aid the treatment of certain cases. Space closure should be considered as a potential solution to the absence of mandibular first permanent molars.