Comparison of transverse changes during maxillary expansion with 4-point bone-borne and tooth-borne maxillary expanders Mennatallah Ihab Mosleh, a Mohamed Amgad Kaddah, b Fatma Abdou Abd ElSayed, c and Hend Salah ElSayed d Cairo, Egypt Introduction: The purposes of this study were to evaluate and compare the dentoskeletal changes concurrent with 4-point bone-borne and tooth-borne rapid maxillary expanders in growing children. Methods: The study was conducted with 20 growing girls (ages, 12 6 0.6 years) with posterior crossbite. They were divided into 2 equal groups; patients in one group were treated with a tooth-borne maxillary hyrax expander (TBME), and those in the other group received a bone-borne maxillary hyrax expander (BBME) anchored directly to the palatal bone. Changes were assessed using cone-beam computed tomography. Images were taken before and immediately after expansion. Results: Superimpositions of the 3-dimensional palatal images showed significant increases in skeletal widths at the canine, first premolar, and first molar areas in both groups. The TBME group had greater nasal width expansion. Regarding the transverse dentolinear measurements, significant increases were seen in both groups, whereas the TBME group showed a greater increase than the BBME group. Significant increases in the dentoangular measurements were seen in the TBME group only and were significantly greater than in the BBME group at the first premolars. Conclusions: There were sig- nificant increases in facial and maxillary widths for the BBME group and in nasal width for the TBME group. Both expanders produced basal bone expansion at the level of the hard palate. The TBMEs produced more dental expansion, buccal rolling, and a greater increase in nasal width than did the BBMEs. (Am J Orthod Dentofacial Orthop 2015;148:599-607) M axillary constriction is considered one of the most common orthodontic problems that could be accompanied by unilateral or bilateral posterior crossbite, narrow nasal cavity, and dental crowding. 1,2 Transverse maxillary deficiencies may give rise to several clinical manifestations such as maxillary hypoplasia, asymmetrical facial growth, positional and functional mandibular deviations, altered dentofacial esthetics, adverse periodontal responses, unstable dental tipping, and other functional problems. 3 Posterior crossbite is one of the most prevalent mal- occlusions; it is reported to occur in 8% and 22% of patients and requires early intervention to coordinate the maxillary and mandibular arches. 4,5 The main treatment modality was introduced into orthodontics by Derichsweiler 6 and Haas 7 for correction of severe crossbite and improvement of nasal breathing. 8 The pri- mary goal of maxillary expansion was to maximize den- tofacial orthopedics and minimize orthodontic movements of the teeth. In tooth-borne expanders, transmitting the expansion forces throughout the teeth might decrease the amount of force applied to the maxilla and contribute to more undesirable effects to- ward the anchorage teeth. However, applying expansion forces directly toward the palatal bone would provide more parallel displacement of the maxillary shelves with no unwanted tooth movement. Many mechanically rigid fixed rapid maxillary expan- sion appliances have been developed to split the midpa- latal suture. Hyrax (or Biederman) expanders are known for greater hygiene and comfort, minimal interference a Research assistant, Orthodontics and Pediatric Dentistry, National Research Centre, Cairo, Egypt. b Chairman and professor, Department of Orthodontics, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. c Professor, Department of Orthodontics, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. d Researcher, Orthodontics and Pediatric Dentistry, National Research Centre, Cairo, Egypt. All authors have completed and submitted the ICMJE Form for Disclosure of Po- tential Conflicts of Interest, and none were reported. Address correspondence to: Mennatallah Ihab Mosleh, 143 Alhegaz St, Elnozha, Heliopolis, Cairo, Egypt; e-mail, menna_mosleh@hotmail.com. Submitted, February 2015; revised and accepted, April 2015. 0889-5406/$36.00 Copyright Ó 2015 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2015.04.040 599 ORIGINAL ARTICLE