Management of occlusal canting with miniscrews

Case Report Management of occlusal canting with miniscrews Rosa Maria Ya´n˜ ez-Vico a *; Alejandro Iglesias-Linares a *; Maria Cadenas de Llano-Pe´rula b ; Alvaro Solano-Reina a ; Enrique Solano-Reina c ABSTRACT A 14-year-old boy with a skeletal Class II malocclusion and open bite whose chief complaint was a posterior crossbite showed a canted occlusal plane with asymmetric gummy smile and mandibular deviation at clinical examination. The treatment with miniscrews focused on the bilateral intrusion of the maxillary posterior teeth and, after resolving the open bite, a new biomechanical technique involving joined miniscrews was applied for an en masse intrusion of the left side. This treatment strategy achieved optimal occlusion with improvements to the sagittal, vertical, and transverse relationships and achieved a harmonious smile. (Angle Orthod. 2014;84:737–747.) KEY WORDS: Miniscrews; Occlusal plane; Canting INTRODUCTION A skeletal anterior open bite has been long considered one of the most difficult malocclusions to treat. It has multiple etiologies: an unfavorable growth pattern; increased anterior dentoalveolar height 1 ;an increased lower anterior and a decreased posterior facial height; clockwise rotation of the mandibular plane 2 ; increased gonial angle; narrow maxillary arch 3 ; habits, such as thumb sucking or abnormal tongue behavior 4 ; and respiratory problems, such as enlarged adenoids or other airway obstructions. 5 In addition, an open bite is often characterized by excessive growth of maxillary and mandibular posterior dentoalveolar heights, which is difficult to reduce. Orthopedic devices—such as high-pull headgears, 6 vertical elastics, functional appliances to help eliminate habits or bite blocks to stop growth in the posterior sectors—have frequently been used to treat such cases, although their effectiveness is often limited by the absence of patient cooperation. Temporary bone anchorage devices 7–13 may be good treatment alternatives since they obviate the need for the patient’s cooperation. The purpose of this case report is to describe the treatment of a patient using miniscrews with a double purpose: to correct an anterior open bite and as a new approach for treating a canted occlusal plane with asymmetric gummy smile. Diagnosis and Etiology A 14-year-old boy visited the Orthodontic Department of our School of Dentistry (University of Seville, Seville, Spain). The mother’s main complaint was the posterior crossbite and the anterior open bite of her son, which their family dentist had explained to her (Figure 1). The boy was a mouth breather and had a convex profile due to mandibular retrusion accentuated by clockwise mandibular rotation (Figure 1). He had a 7-mm overjet, with bilateral Angle Class I molars and Class II canines. Crowding was not severe and there were no signs of temporomandibular problems. The facial midlines did not coincide at the menton, and the anterior and lateral open bites, as well as the posterior crossbite, suggested that the centric relationship be checked and the first point of contact be determined. Dental casts were mounted in centric relation on an articulator (Figure 2). At this point, the sagittal and vertical relationships worsened, with a fulcrum between the second left molars. The dental midlines and the posterior crossbite were maintained, which indicated that the deviation was not functional. Extraorally, the patient presented a gummy smile, which was accentuated on the left side due to the canted occlusal plane (Figures 1 and 3). A cephalometric * Both authors contributed equally to the clinical case and the case report manuscript. a Associate Professor of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Seville, Seville, Spain. b Postdoctoral student, School of Dentistry, University of Seville, Seville, Spain. c Professor of Orthodontics, Chairman of Orthodontics, School of Dentistry, University of Seville, Seville, Spain. Corresponding author: Professor Rosa-Maria Ya´n˜ez-Vico, School of Dentistry, University of Seville, C/Avicena sn, 41009 Seville, Spain (e-mail: [email protected]) Accepted: November 2013. Submitted: May 2013. Published Online: December 23, 2013 G2014 by The EH Angle Education and Research Foundation, Inc. DOI: 10.2319/051313-369.1 737 Angle Orthodontist, Vol 84, No 4, 2014 Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/84/4/737/1396553/051313-369_1.pdf by guest on 05 May 2021 analysis (Table 1) showed that the patient was dolichofacial, with a skeletal Class II malocclusion. There was increased upper and lower dentoalveolar height, so that excessive growth of the posterior sector was considered the cause of the open bite. Treatment Objectives The treatment objectives were to solve the crossbite, create an ideal overbite and overjet, and achieve Angle Class I molars and Class I canines, with coinciding facial and dental midlines. Since there was an occlusal cant in the frontal plane and the patient presented an asymmetric gummy smile, bilateral posterior intrusion and unilateral anterior intrusion were planned. Treatment Alternatives To correct a posterior crossbite, expansion is needed. In children, posterior crossbites are often corrected with slow or rapid maxillary expansion. A removable expansion plate or a fixed appliance, such as the Quad-Helix, provides slow expansion with light forces. 14 Rapid maxillary expansion maximizes orthopedic correction of the transverse dimensions with heavier forces and has also been found to lead to increased nasal cavity and nasopharynx volumes. 15,16 In patients with a hyperdivergent facial pattern, however, rapid maxillary expansion would worsen the vertical dimension. 17–19 Some good recent research, however, has found that rapid maxillary expansion is not a contraindication for the hyperdivergent patient. 20 Since the patient was a mouth breather, we chose rapid maxillary expansion for the first phase of treatment to resolve the maxillary compression and the posterior crossbite, and we used a fixed lingual bar to compress the overexpanded lower arch. 21 Three treatment alternatives were presented to the patient: Figure 1. Pretreatment facial and intraoral photographs. 738 YA ´N ˜EZ-VICO, IGLESIAS-LINARES, DE LLANO-PE ´RULA, SOLANO-REINA, SOLANO-REINA Angle Orthodontist, Vol 84, No 4, 2014 Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/84/4/737/1396553/051313-369_1.pdf by guest on 05 May 2021 (1) A combined surgical and orthodontic treatment to resolve the open bite, gummy smile, and canted occlusal plane. The profile could be harmonized with an advancement genioplasty, while a sagittal split or intraoral vertical ramus osteotomy could help correct the mandibular deviation. The principal disadvantage was the age of the patient, which determined the postponement of surgical treatment. (2) A combined headgear-activator Teuscher appliance, 22 followed by fixed appliance treatment, utilizing growth modification to reduce sagittal and Figure 3. Posteroanterior cephalograms. (A) Pretreatment. (B) After rapid maxillary expansion. (C) Posttreatment. Figure 2. Pretreatment dental casts mounted in centric relation on the articulator. MANAGEMENT OF OCCLUSAL CANTING WITH MINISCREWS 739 Angle Orthodontist, Vol 84, No 4, 2014 Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/84/4/737/1396553/051313-369_1.pdf by guest on 05 May 2021 vertical discrepancies and help correct the gummy smile. However, the results of this treatment option would depend on the patient’s collaboration. (3) Temporary bone anchorage devices, such as miniscrews, combined with a fixed appliance to intrude the maxillary posterior teeth and resolve the open bite. This would create a counterclockwise rotation of the mandible and so help correct the sagittal discrepancy, although it would not correct the profile or the severely retruded mandible. Miniscrews would help resolve the canted occlusal plane and the asymmetric gummy smile. After explaining the treatment alternatives to the patient and his parents, the last option was selected, with the parents’ consent. Treatment Progress A hyrax expander appliance 23 was attached to the first maxillary molars and first premolars to deal with the crossbite and palatal compression. The required expansion was achieved after 27 days of active expansion treatment at one turn per day (0.25 mm/ day), followed by 4 months of expander retention with a lingual arch to compress the lower dental arch (Figure 4). The hyrax expander appliance (Dentaurum, Inc, Newtown, PA) was removed and replaced with two transpalatal bars with bone anchorage for effective intrusion of the first and second molars. Two 1.6 38mm ACR-model (H) miniscrews (Jeil Medical Corp, Seoul, South Korea) were inserted on each side, one between the roots of the maxillary second premolar and the first molar, the second between the roots of the first and second maxillary molars. Two closed Sentalloy coil springs (200 gr, GAC International, Bohemia, NY) were tied between the tubes attached to the molars and the miniscrews, and a 0.016 30.022-inch stainless steel segmental archwire was placed (Figure 5). Brackets were not used in the first stages of treatment, although as intrusion developed, they were progressively fitted (0.018-inch slot brackets, MSE, DM-CEOSA, Madrid, Spain) first to the premolars, then the canines and incisors, using round 0.016-inch nickel-titanium archwire. Sequential nickel-titanium archwires were then used for alignment and leveling. Table 1. Cephalometric Data of the Pretreatment, Posttreatment, and 4 Years and 6 Months Retention Period Cephalometric Measurements Spanish Means, SD Pretreatment Clinical Meaning Skeletal analysis Sella angle (N-S-Ar), degrees 122.0 65.0 119.8 Skeletal Class I Articular angle (S-Ar-Go), degrees 143.0 66.0 148.4 Mesofacial Gonial angle (Ar-Go-Gn), degrees 130.0 67.0 138.5 Dolichofacial Sum of angles, degrees 396.0 66.0 406.7 Dolichofacial Upper gonial angle (Ar-Go-N), degrees 63.5 61.5 61.2 Vertical Lower gonial angle (N-Go-Gn), degrees 72.5 62.5 87.3 Vertical Posterior cranial base (S-Ar), mm 37.0 63.0 36.1 Normal Ramus height (Ar-Go), mm 54.5 65.0 45.7 Short Anterior cranial base (N-S), mm 81.5 65.0 72.7 Hypoplasia Mandibular body (Go-Gn), mm 82.6 65.0 72.1 Hypoplasia Posterior facial height (S-Go), mm 77.5 67.5 77.6 Mesofacial Anterior facial height (N-Gn), mm 112.5 67.5 134.4 Brachifacial Posterior facial height/ anterior facial height, mm 63.5 61.5 67.9 Dolichofacial Sella-nasion/point A angle (S-N-A), degrees 82.0 62.0 81.0 Skeletal Class I Sella-nasion/point B angle (S-N-B), degrees 80.0 62.0 74.0 Skeletal Class II Nasion -point A/nasion-point B angle (A-N-B), degrees 2.0 61.0 7.0 Skeletal Class II Dentoalveolar analysis A and B points on the occlusal plane, mm 0.0 61.0 7.4 Dental Class II Antero-superior alveolar height, mm 33.2 62.0 37.8 Increased Antero-inferior alveolar height, mm 48.0 62.0 45.0 Decreased Total anterior alveolar height, mm 60.0 62.0 72.4 Increased Postero-superior alveolar height, mm 26.5 62.0 30.2 Increased Postero-inferior alveolar height, mm 28.0 62.0 31.7 Increased Total posterior alveolar height, mm 60.0 65.0 58.4 Normal Posterior facial height/posterior alveolar height, mm 20.0 65.0 19.4 Normal Occlusal plane analysis Occlusal plane, degrees 89.0 62.0 94.2 Dental Class II Upper incisor angle, degrees 57.0 62.5 56.8 Normal Lower incisor angle, degrees 70.6 62.5 62.7 Bucally inclinated 740 YA ´N ˜EZ-VICO, IGLESIAS-LINARES, DE LLANO-PE ´RULA, SOLANO-REINA, SOLANO-REINA Angle Orthodontist, Vol 84, No 4, 2014 Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/84/4/737/1396553/051313-369_1.pdf by guest on 05 May 2021 When a 2.5-mm overbite had been achieved, posterior intrusion continued on the left side, leaving the right side inactive. To increase the bone anchorage, a 0.017 30.025-inch titanium-molybdenum-alloy (TMA) sectional archwire was passed through the holes of the two left miniscrews together and tied between the left canine and lateral left incisor (Figure 5). The sectional archwire was activated 45uto the occlusal plane to intrude the maxillary left anterior teeth, taking advantage of the increased bone anchorage from the two miniscrews inserted as a single unit, and to correct the canted occlusal plane. The occlusal plane was eventually corrected. The second stage of biomechanics required total bone anchorage to fix the superior left side in the vertical dimension. A 0.0017 30.025-inch TMA archwire was inserted, as before, although bent 90uand tied in an inactive way to the superior dental arch (Figure 5). Furthermore, the hemimaxilla was blocked as a single unit by tying stainless steel ties between the interproximal of each tooth and the 0.017 30.025-inch segmental archwire. Then, inferior extrusion was performed with vertical elastics and the patient’s cooperation. In the lower arch, the lingual bar was removed by the end of the treatment so that the first molars would migrate mesially into the space created between them and the second premolars and to obtain a stable Class I molar relationship (Angle). Root position parallelism was checked with a control orthopantomogram, and those brackets that needed replacing were replaced (Figure 6). The mesiodistal size of the maxillary lateral and central incisors was smaller than average, so these were reconstructed using composite materials to avoid spaces or unesthetic black triangles that might lead to relapse or create incorrect contact points. The total length of the second stage of treatment was 20 months. After debonding, a fixed canine-to-canine lingual retainer and a removable superior circumferential retainer were placed. Treatment Results The patient’s treatment ended with the original treatment objectives having been achieved (Figure 7). Functional occlusion and lateral and protrusive jaw movements could be performed effectively and without Posttreatment Clinical Meaning Changes (Pretreatment to Posttreatment) Retention Clinical Meaning Changes (Posttreatment to Retention) 122.9 Skeletal Class I +3.1 120.1 Skeletal Class I 22.8 144.7 Mesofacial 23.7 151.2 Mesofacial +6.5 140.3 Dolichofacial +1.8 145.7 Dolichofacial +5.4 407.9 Dolichofacial +1.2 417 Dolichofacial +10 61.9 Vertical +0.7 58.0 Vertical 23.9 88.3 Vertical +1.0 87.7 Vertical 20.6 35.6 Normal 20.5 36.2 Normal +1.6 47.6 Short +1.9 43.9 Short 23.7 73.7 Hypoplasia +1.0 74.7 Hypoplasia +1.0 72.8 Hypoplasia +0.7 76.7 Hypoplasia +3.9 79.6 Mesofacial +2.0 77.9 Mesofacial 21.7 138.3 Brachifacial +3.9 139.9 Brachifacial +1.6 67.6 Dolichofacial +0.3 62.0 Mesofacial 25.6 80.0 Skeletal Class I 21.0 80.3 Skeletal Class I +0.3 75.0 Skeletal Class II +1.0 75.6 Skeletal Class II +0.6 5.0 Skeletal Class II 22.0 3.8 Skeletal Class II 21.2 1.0 Dental Class I 26.4 1.1 Dental Class II +0.1 38.7 Increased +0.9 40.1 Increased +1.3 46.2 Normal +1.2 48.8 Normal +2.6 73.7 Increased +1.3 76.7 Increased +3.0 28.7 Increased 21.5 29.1 Increased +0.4 34.9 Increased +3.2 36.3 Increased +1.4 61.0 Normal +2.6 64.0 Normal +3.0 18.4 Normal 21.0 18.9 Normal 20.5 87.4 Dental Class I 26.8 88.2 Dental Class I +0.8 58.8 Normal +2.0 58.5 Normal +0.3 67.6 Normal +4.9 67.8 Normal +0.2 Table 1. Extended MANAGEMENT OF OCCLUSAL CANTING WITH MINISCREWS 741 Angle Orthodontist, Vol 84, No 4, 2014 Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/84/4/737/1396553/051313-369_1.pdf by guest on 05 May 2021 improper contact with the rest of the teeth (Figure 8). The smile was fuller and more harmonious than before, equal in gingival height and with no black corridors, and the canted occlusal plane had been resolved (Figure 7). The posttreatment extraoral and intraoral photographs (Figure 7) and the frontal radiograph showed coincidence of the dental and facial midlines, and the slight improvement of the mandibular deviation induced by rapid maxillary expansion was completed after the posterior intrusion and correction of the canted occlusal plane (Figure 3). No complications or complaints from the patient were recorded concerning the miniscrews, and no signs of temporomandibular distress or pain were found. After treatment, a cephalometric analysis and the superimposed pretreatment and posttreatment tracings confirmed the changes. Incisor extrusion was minimal and the maxillary molars were intruded by 1.5 mm (Figure 9; Table 1). The posttreatment orthopantomogram showed the teeth to be parallel and with no root resorption (Figure 7). After a posttreatment period of 4 years and 6 months, the clinical results showed good stability (Figure 10). In addition, the cephalometric results appear substantially stable (Figure 11; Table 1). DISCUSSION Two different points should be discussed concerning the treatment of this patient: the open bite and the canted occlusal plane with asymmetric gummy smile. With respect to the first point, conventional nonsurgical techniques rely on extrusion of the incisors rather than intrusion of the posterior sectors in order to resolve open bites. 24 In this patient, two transpalatal bars and Figure 4. Intraoral photographs of treatment progress. (A) After rapid maxillary expansion. (B) Progressive intrusion of molar and premolars. (C) Full superior and inferior bonding. (D) Correction of canted occlusal plane with joined miniscrew segmental archwire. 742 YA ´N ˜EZ-VICO, IGLESIAS-LINARES, DE LLANO-PE ´RULA, SOLANO-REINA, SOLANO-REINA Angle Orthodontist, Vol 84, No 4, 2014 Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/84/4/737/1396553/051313-369_1.pdf by guest on 05 May 2021 two miniscrews were used on each side, placed between the roots of the maxillary second premolar and the first molar, and between the first and second maxillary molars, so that the effect would be spread equally over both molars. Intrusion of the molars has been reported as being more stable over time than extrusion of the incisors, 25 causing occlusal plane change and leading to counterclockwise rotation of the mandible which may improve the profile in skeletal Class II cases. Nevertheless, a conventional orthodontic treatment of an open bite, consisting of vertical elastics which may increase the plane angle 26 and the gummy smile, 27 generally results in extrusion of the incisors. According to a study performed by Deguchi et al., 28 miniscrews were more effective for absolute molar intrusion and the improvement in esthetics than conventional techniques. They also had an effect on the soft tissues, with more obviously reduced facial convexity in the miniscrew group; the extrusion of the molars arising from conventional techniques may cause a clockwise rotation of the mandible, which is not a desirable outcome in a patient with skeletal Class II malocclusion. It has also been reported in the literature that miniscrews may achieve molar intrusion between 1 and 3 mm and a counterclockwise rotation of the mandible position of 3u. Xun et al. 29 reported intrusion of the maxillary and mandibular molars of 1.8 and 1.2 mm, respectively, and a 2.3ucounterclockwise mandibular rotation. In this patient, a 1.5-mm intrusion of the maxillary molars was achieved, enough for a counterclockwise rotation of the occlusal plane from a Class II to a Class I, with a normalized Wits appraisal. Minimal incisor extrusion was observed with this technique. The second key point of treatment was the canted occlusal plane and asymmetric gummy smile. In terms of etiology, the patient was characterized by a hyperdivergent facial pattern, and presented a skeletal 30,31 asymmetric gummy smile, caused by excessive vertical maxillary growth due to a canted occlusal plane. Also, a slight mandibular deviation was Figure 5. Intraoral photographs of miniscrew biomechanics. (A) Molar intrusion with miniscrews and two transpalatal bars. (B) Molar and premolar intrusion. (C) First stage of canted occlusal plane correction (superior intrusion). (D) Second stage of occlusal plane correction (superior anchorage). (E) Second stage of canted occlusal plane correction (inferior extrusion). Figure 6. Control orthopantomogram of treatment. MANAGEMENT OF OCCLUSAL CANTING WITH MINISCREWS 743 Angle Orthodontist, Vol 84, No 4, 2014 Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/84/4/737/1396553/051313-369_1.pdf by guest on 05 May 2021 Figure 8. Functional jaw movements, protrusive, left and right laterally, with complete posterior distocclusion. Figure 7. Posttreatment facial and intraoral photographs. 744 YA ´N ˜EZ-VICO, IGLESIAS-LINARES, DE LLANO-PE ´RULA, SOLANO-REINA, SOLANO-REINA Angle Orthodontist, Vol 84, No 4, 2014 Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/84/4/737/1396553/051313-369_1.pdf by guest on 05 May 2021 found prior to treatment. In adults, this combination of problems generally requires orthognathic surgery, 32,33 which also improves the sagittal position of the mandible. However, since the child was 14 years old—and after carefully balancing the costs and risks—the parents decided not to pursue that option at that time, although they were warned that if the result was not satisfactory, the child would be observed until he had finished growing so that a combined surgical-orthodontic course of treatment could be initiated. The satisfactory outcome of the treatment we selected leads us to think that this will not be necessary. Figure 9. Superimposed pretreatment (blue) and posttreatment (red) tracings. Figure 10. Retention facial and intraoral photographs (4 years and 6 months after treatment). MANAGEMENT OF OCCLUSAL CANTING WITH MINISCREWS 745 Angle Orthodontist, Vol 84, No 4, 2014 Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/84/4/737/1396553/051313-369_1.pdf by guest on 05 May 2021