Bone anchored maxillary protraction

Abstract

The thought-provoking article by Nguyen et al1Nguyen T. Cevidanes L. Cornelis M.A. Heymann G. de Paula L.K. De Clerck H. Three-dimensional assessment of maxillary changes associated with bone anchored maxillary protraction.Am J Orthod Dentofacial Orthop. 2011; 140: 790-798Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar in the December issue reported on an assessment of maxillary protraction with bone anchorage. Comprehensive methods to treat maxillary deficiency are available in the orthodontic literature, but we thank the authors for opening new doors and concepts in the field. We have the following questions regarding their study.1.What about the force vector direction, since the maxillary plates were placed below the center of resistance of the maxilla? This will tend to rotate the maxilla downward in the posterior part and upward in the anterior part; this is not ideal in Class III patients. The mandibular plates were placed between the canines and the lateral incisors, again anterior to the center of resistance of the mandible, which will tend to rotate the mandible in a counterclockwise direction and is contraindicated in Class III patients.2.The authors selected I-type plates, although it is well proven in the 3-dimensional studies by Lee et al2Lee N.K. Baek S.H. Choi D.S. et al.Influence of miniplate shapes as skeletal anchorage for application of orthopedic force: a three-dimensional finite element analysis.J Korean Assoc Maxillofac Plast Reconstr Surg. 2008; 30: 345-352Google Scholar and Cha and Ngan3Cha B.K. Ngan P.W. Skeletal anchorage for orthopedic correction of growing Class III patients.Semin Orthod. 2011; 17: 124-137Abstract Full Text Full Text PDF Scopus (39) Google Scholar that the Y-type of plate has a distinct advantage over the I-type.3.The maximum amount of traction force applied by the authors was 250 g per side, but, for any kind of orthopedic correction, especially protraction of the maxilla, the minimum amount of force should be 400 to 450 g per side.4Vego L. Early orthopedic treatment for Class III skeletal patterns.Am J Orthod. 1976; 70: 59-69Abstract Full Text PDF PubMed Scopus (18) Google Scholar, 5Ritucci R. Nanda R. The effect of chincap therapy on the growth and development of the cranial base and midface.Am J Orthod Dentofacial Orthop. 1986; 90: 475-483Abstract Full Text PDF PubMed Scopus (57) Google Scholar, 6Mitani H. Fukazawa H. Effects of chincap force on the timing and amount of mandibular growth associated with anterior reversed occlusion (Class III malocclusion) during puberty.Am J Orthod Dentofacial Orthop. 1986; 90: 454-463Abstract Full Text PDF PubMed Scopus (63) Google Scholar4.The authors did not have any panoramic radiographs to show the actual position of the plates in the maxilla and the mandible.5.Only the Wits appraisal was used for assessment of the correction. How did the authors determine that the maxilla was protracted or the mandible was retracted, because the traction force is coming from the mandible?6.The authors haven’t considered or discussed the possible effects of opening or loosening of the circummaxillary sutural system, which could facilitate the orthopedic effect.7Haas A.J. Treatment of maxillary deficiency by opening the midpalatal suture.Angle Orthod. 1965; 65: 200-217Google Scholar, 8McNamara Jr., J.A. An orthopedic approach to the treatment of Class III malocclusion in young patients.J Clin Orthod. 1987; 21: 598-608PubMed Google Scholar, 9Gautam P. Valiathan A. Adhikari R. Skeletal response to maxillary protraction with and without maxillary expansion: a finite element study.Am J Orthod Dentofacial Orthop. 2009; 135: 723-728Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar Three-dimensional assessment of maxillary changes associated with bone anchored maxillary protractionAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 140Issue 6PreviewBone-anchored maxillary protraction has been shown to be an effective treatment modality for the correction of Class III malocclusions. The purpose of this study was to evaluate 3-dimensional changes in the maxilla, the surrounding hard and soft tissues, and the circummaxillary sutures after bone-anchored maxillary protraction treatment. Full-Text PDF Author’s responseAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 141Issue 5PreviewWe thank Dr Mathur and his group for their interesting comments regarding in our article. Below are our responses to the questions that were asked. Full-Text PDF