Cone beam computed tomographic analyses of alveolar bone anatomy at the maxillary anterior region in Chinese adults

To provide an anatomical basis for clinical implant esthetics,we evaluated the morphology of the nasopalatine canal（NPC） and analyzed labial and interproximal bone anatomy at the maxillary anterior region.We sought to investigate the effect of maxillary protrusion and tooth labiolingual inclination on labial bone anatomy in Chinese adults.Three dimensional（3D） images were reconstructed using cone-beam computed tomography（CBCT） images from 80 Chinese subjects and by SimPlant 11.04.The dimensions of the NPC,the thickness and profile of the labial bone,the width and height of the interproximal bone,angle sella-nasion-subspinale（SNA） and angle upper central incisor-nasion,subspinale（U1-NA） were measured.The incisive foramen of the NPC was markedly wider than its nasal foramen.The dimension of its labial bone wall demonstrated an increasing width from the crestal to apical measurements.The labial bone at the maxillary anterior region was rather thin,especially at 3 mm below the cemento-enamel junction（CEJ） and the mid-root level;the profile of the labial bone was more curved at the central incisor,and the interproximal bone became wider and shorter posteriorly.There were significant relationships between maxillary protrusion and labial bone profile,tooth labiolingual inclination and labial bone thickness（P 〈 0.02）.To achieve optimal esthetic outcome of implant,bone augmentation is necessary at the maxillary anterior region.For immediate or early placement at the maxillary anterior region,the implant should be located palatally to reduce labial bone resorption and marginal recession;its apex should be angulated palatally to avoid labial perforation at the apical region.To protect the NPC,implants at the central incisor region should be placed away from NPC.

Advancement of maxillary anterior segment by distraction osteogenesis for severe maxillary retrusion in cleft lip and palate

Background Maxillary anterior segmental distraction osteogenesis （MASDO） is a recently used method for correction of severe maxillary retrusion in cleft lip and palate （CLP） patients.In this article,we evaluated the feasibility of MASDO using rigid external distraction （RED） and rapid orthodontic tooth movement to correct severe maxillary retrusion in CLP patients.Methods Fourteen male and five female complete CLP patients between the ages of 18 and 22 years （mean age 19.7 years） at the time of distraction,with severe maxillary retrusion,were treated with the rigid external distraction （RED） device after maxillary anterior osteotomy.Rapid orthodontic tooth movement was started one week after the MASDO.Standard profile photographic,cephalometric films were obtained preoperatively and after therapy.Sella-nasion-point A （SNA） and Sella-nasion-point B （SNB） angles were measured to reflect changes in maxillary and mandibular position,and the distance between anterior nasal spine and posterior nasal spine （ANS-PNS） was measured to represent the maxillary dental arch length.Results The SNA angle increased from an average of 74.6° （range 73.0°-78.0°）,preoperatively,to 83.4° （range 78.6°-88.0°） after the RED was removed （P ＜0.01）.All cases of severe maxillary retrusion were improved.Nine patients＇ profiles became harmonious after therapy.One patient had a bimaxillary protrusion deformity and needed further surgery.The regenerate alveolar crest and edentulous space on both segments was almost completely eliminated after rapid orthodontic tooth movement.Conclusion MASDO with the RED system and rapid orthodontic tooth movement is a successful way of correcting severe maxillary retrusion in CLP patients.