O RIGINAL A RTICLE Cephalometric evaluation of vertical and anteroposterior changes associated with the use of bonded rapid maxillary expansion appliance Moara De Rossi*, Maria Bernadete Sasso Stuani**, Léa Assed Bezerra da Silva*** Abstract Introduction: Bonded rapid maxillary expansion appliances have been suggested to control increases in the vertical dimension of the face after rapid maxillary expansion but there is still no consensus in the literature concerning its actual effectiveness. Objective: The purpose of this study was to evaluate the vertical and anteroposterior cephalometric changes associ- ated with maxillary expansion performed using bonded rapid maxillary expansion appliances. Methods: The sample consisted of 25 children of both genders, aged between 6 and 10 years old, with skeletal posterior crossbite. After maxillary expansion, the expansion appliance itself was used for fixed retention. Were analyzed lateral teleradiographs taken prior to treatment onset and after removal of the expansion appliance. Conclusion: Based on the results, it can be concluded that the use of bonded rapid maxillary expansion appliance did not significantly alter the children’s vertical and anteroposterior cephalometric measurements. Keywords: Bonded rapid maxillary expansion appliance. Rapid maxillary expansion. Cephalometry. INTRODUCTion the maxilla, extrusion and inclination of maxil- Rapid maxillary expansion (RME) is a wide- lary and mandibular molars, clockwise rotation ly accepted procedure recommended for the of the mandible, with a resulting increase in fa- correction of maxillary atresia related to poste- cial height and anterior open bite.4,14,15,20,21,26 rior crossbite.7,8 The opening of the midpalatal In 1860, Angell1 reported the first maxillary suture causes increases in maxillary width and expansion case using an appliance with a screw dental arch perimeter, allowing the coordina- placed across the maxilla. Since then, different tion of the upper and lower basal bones and appliances have been suggested for hemi maxil- crossbite correction. As well as the correction of lary separation, all featuring modifications, es- transverse discrepancy, however, RME also pro- pecially in the type of material and anchoring, 5,10,12,14,18,22,23 motes changes such as inferior displacement of and different activation modes. * PhD in Pediatric Dentistry, FOP / UNICAMP. MSc in Pediatric Dentistry, FORP / USP. ** Professor of Orthodontics, FORP / USP. *** Professor and Chair of the Department of Child, Preventive and Social Dentistry, FORP / USP. Dental Press J Orthod 62 2010 May-June;15(3):62-70 Rossi M, Stuani MBS, Silva LAB Bonded rapid maxillary expansion appliance had erupted and were in occlusion. The orth- have been proposed to control the side effects odontic documentation comprised panoramic of RME, which may be associated with adverse and occlusal X-rays, lateral and frontal cepha- increases in anterior facial height, especially lometric radiographs, intraoral photographs in individuals with a predominantly vertical and study models. growth pattern and a tendency towards open bite.2,10,17,18,20,22,24 No consensus has been found Rapid maxillary expansion in the literature, however, concerning the RME- RME was performed using bonded rapid related vertical and anteroposterior effects pro- maxillary expansion appliance, made from col- duced with this type of appliance.2,7,9,13,19,20,24,25 orless acrylic resin covering the posterior teeth The purpose of this study was to evaluate (Jet; Artigos Odontológicos Clássico Ltda, São lateral teleradiographs for possible vertical and Paulo, SP, Brazil) and a palatal expansion screw anteroposterior changes resulting from the use (split screw, 9 mm, code 65.05.011; Dental of bonded rapid maxillary expansion appliance Morelli, Sorocaba, SP, Brazil) positioned on for the correction of skeletal posterior cross- the midpalatine raphe at about 2 mm from the bite in children. palate and between the primary second molars (Fig 1). The appliance was adjusted in the pa- MATERIAL AND METHODS tient’s mouth in order to ensure as many bilat- Sample eral occlusal contacts as possible, and was then The sample comprised 25 children (13 girls attached using dual-curing acrylic resin cement and 12 boys), irrespective of gender, race or adhesive (Rely X: 3M do Brasil Ltda., Produtos social class, with a mean age of 8 years and 5 Dentários, Sumaré, SP, Brazil). months (ranging from 6 years and 11 months to 10 years and 11 months) presenting with maxil- lary atresia and either unilateral or bilateral pos- terior crossbite, indicated for maxillary expan- sion as the first stage of orthodontic treatment. Maxillary atresia was detected based on clini- cal parameters characterized by the presence of posterior crossbite associated with a deep palate, “V”-shaped maxillary arch and reduced transverse maxillary dimensions compared with the mandible. This study was approved by the Research Ethics Committee of the Ribeirão Pre- to School of Dentistry, University of São Paulo (FORP / USP - Case No 2003.1.1067.58.8), and the children’s parents and/or guardians signed a consent form, according to resolution 196/96 of the Brazilian Health Council. The children included in the sample had received no previous orthodontic treatment and exhibited good general and oral health. Their upper and lower first permanent molars FIGURE 1 - Bonded rapid maxillary expansion appliance. Dental Press J Orthod 63 2010 May-June;15(3):62-70 Cephalometric evaluation of vertical and anteroposterior changes associated with the use of bonded rapid maxillary expansion appliance Activation was carried out by the children’s • Posterior Nasal Spine Point (PNS): Locat- parents and/or guardians and amounted to ¼ ed at the posterior end of the maxilla. turn of the screw every 12 hours, starting one • Basion (Ba): Lowest point of the image of week after appliance installation. When cross- the anterior margin of the foramen magnum. bite overcorrection was observed, i.e., when the • Pterygoid Point (Pt): Posterior-most and palatal cusps of the upper posterior teeth were superior-most point in the upper contour occluding on the buccal cusps of the lower pos- of the pterygomaxillary fissure. terior teeth, the expander screw was fixed with • Pogonion (Pg): Anterior-most point of the acrylic resin and a new occlusal adjustment was bony chin. made. The average interval time between acti- • Gnathion (Gn): The anterior-most and vations was 20 days (ranging between 14 and inferior-most point of the mandibular 26 days) and the appliance remained in the pa- symphysis, as determined by bisecting the tients’ mouth as fixed retention for a minimum angle formed by the lower margin of the of 90 days (107 days average, ranging from 90 mandibular body and the facial line (NPg). to 124 days). After this period, the appliance • Menton (Me): Located at the intersection was removed and patients wore a removable re- of the outer contour of the mandibular tainer (acrylic plate with a Hawley labial clasp symphysis and the inferior margin of the and retention clasps) for 6 months. mandibular body. • Gonion (Go): Located in the outer contour Cephalometric evaluation of the gonial angle, determined by bisecting Lateral teleradiographs were taken before the angle between the mandibular ramus and treatment onset (T1) and after removal of the the lower margin of the mandibular body. expansion appliance (T2). The cephalometric radiographs were performed in standardized fashion by a single technician in the Laboratory of Analysis and Control of Dental Radiographic Images (LACIRO), at FORP-USP. N The cephalometric tracings were performed manually by the same experienced and calibrat- S ed examiner. The following cephalometric land- Pt marks were located and marked on the lateral cephalograms (Fig 2): • Sella (S): Virtual point located at the geo- PNS ANS metric center of the sella turcica. A Ba S1 • Nasion (N): The anterior-most point of the frontonasal suture. • Subspinal Point (A): The deepest point of Go the subspinal concavity. • Supramental Point (B): The deepest point B of the supramental concavity. Pg • Anterior Nasal Spine Point (ANS): Lo- Me Gn cated at the anterosuperior end of the maxilla. FIGURE 2 - Lateral cephalogram and location of cephalometric landmarks. Dental Press J Orthod 64 2010 May-June;15(3):62-70 Rossi M, Stuani MBS, Silva LAB • Point S1: Connection point between a line permanent molars and intersecting the drawn from Point S—perpendicularly to upper and lower incisors. the SN line—and the palatal plane (junc- To assess the anteroposterior behavior of the tion of ANS and PNS). apical bases, the following cephalometric mea- After locating and marking the landmarks surements were used (Fig 3): the following lines and planes of orientation • SNA Angle: Formed by intersecting the were traced: SN and NA lines. Measures the position • S-N Line: Connecting S to N. of the maxilla relative to the anterior cra- • N-A Line: Connecting N to A. nial base. • N-B Line: Connecting N to B. • SNB Angle: Formed by intersecting the • S-Gn Line: Connecting S to Gn. SN and NB lines. It measures the position • Ba-N Line: Connecting Ba to N. of the mandible relative to the anterior • Pt-Gn Line: Connecting Pt to Gn. cranial base. • N-ANS Line: Connecting N to ANS. • ANB Angle: Determined by the differ- • ANS-Me Line: Connecting ANS to Me. ence between SNA and SNB. It measures • N-Me Line: Connecting N to Me. the anteroposterior relationship between • Steiner’s mandibular plane (GoGn):