Treatment of a malocclusion characterized

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1 CONTINUING EDUCATION ARTICLE Cephalometric evaluation of open bite treatment with NiTi arch wires and anterior elastics Nazan Küçükkeleș, DDS, PhD, a Ahu Acar, DDS, PhD, b Arzu A. Demirkaya, DDS, c Berna Evrenol, DDS, c and Ayhan Enacar, DDS, PhD d Istanbul and Ankara, Turkey The aim of this study was to evaluate cephalometrically the effects of open bite treatment with NiTi arch wires and anterior elastics. The study group comprised of 17 patients who displayed a high angle skeletal pattern, along with an anterior open bite. After initial leveling, inch upper accentuated-curve and lower reverse-curve arch wires were placed, with anterior elastics applied in the canine regions. Cephalometric assessment was carried out on lateral head films taken at the beginning of treatment and on average 2.8 months after open bite closure was obtained. The results of this study indicated that open bite closure had been achieved mainly by extrusion of the lower incisors and uprighting of the upper incisors. The functional occlusal plane was leveled by extrusion of lower premolars and uprighting of lower molars. Lateral cephalograms obtained from 10 patients who had been available after 1 year postretention were used to evaluate relapse changes. During the follow-up period, position of the upper and lower incisors and the inclination of the occlusal plane were maintained. However, extrusion of upper and lower molar teeth resulted in a reduction in overbite. (Am J Orthod Dentofacial Orthop 1999;116:555-62) a Associate professor, Department of Orthodontics, Marmara University, Faculty of Dentistry, Istanbul. b Assistant professor, Department of Orthodontics, Marmara University, Faculty of Dentistry, Istanbul. c Research Assistant, Department of Orthodontics, Marmara University, Faculty of Dentistry, Istanbul. d Professor, Department of Orthodontics, Hacettepe University, Faculty of Dentistry, Ankara. Reprint requests to: Dr Ahu Acar, Marmara Üniversitesi, Diș Hekimliǧi Fakültesi, Ortodonti Anabilim Dalı, Büyükçiftlik Sok. No: 6 Nișantașı İstanbul Türkiye; , erverdi@turk.net Copyright 1999 by the American Association of Orthodontists /99/$ /1/97248 Treatment of a malocclusion characterized by open bite can be a difficult task for the orthodontist because such a malocclusion develops as a result of the interplay of many different etiologic factors. 1-3 Skeletal open bite cases are usually characterized by an increase in the vertical growth of the maxillary posterior dentoalveolar segments. 3,4 As intrusion of posterior teeth becomes more difficult with older age, mechanical treatment options are limited in adult patients. Orthognathic surgery is indicated in adult patients with severe open bite and unesthetic facial proportions. For the treatment of borderline cases, and those individuals who are reluctant to undergo surgery, the search for effective treatment modalities continues. One of the methods available for the treatment of open bite is the multiloop edgewise arch wire technique developed by Kim. 5 This technique involves the use of multiloop gable bend arch wires with vertical elastics in the canine regions. The goals of this technique include correction of the inclination of the occlusal planes, alignment of the maxillary incisors relative to the lip line, and uprighting of the axial inclinations of the posterior teeth. Using this technique, Goto et al 6 and Sato 7 reported successful treatment outcomes. Enacar et al 8 modified Kim s 5 technique by using inch upper accentuated-curve and lower reverse-curve nickel titanium arch wires instead of multiloop gable bend arch wires, with the intermaxillary elastics applied in the canine regions. They suggested that upper accentuated-curve and lower reversecurve nickel titanium arch wires were simpler and more hygienic compared to multiloop arch wires, they reduced chairtime, and did not irritate the soft tissues. Enacar et al 8 reported that their results were similar to those obtained by the multiloop edgewise arch wire system. The aim of the present study was to evaluate the changes in dentofacial structures of open bite patients treated with upper accentuated-curve and lower reversecurve NiTi arch wires and intermaxillary elastics. SUBJECTS AND METHODS The sample consisted of 17 patients (12 females and 5 males). Mean ages for females and males were 19.5 years and 19 years, respectively. All of the cases presented with a high angle skeletal pattern (SN-Go- Me > 37 ) and an anterior open bite that ranged between 2 and 11 mm with the average being

2 556 Küçükkeleș et al American Journal of Orthodontics and Dentofacial Orthopedics November 1999 A B Fig 1. A, Intrusive effect of upper accentuated-curve and lower reverse-curve NiTi arch wires on anterior teeth. B, Intrusive force and uprighting moment is created in posterior teeth. mm. Skeletal relationship in the sagittal direction was Class I, and the dental relationship was Class I or mild Class II. Treatment Procedure After the placement of bands and inch slot brackets, treatment was initiated with inch coaxial arch wires. The leveling phase was continued with inch round stainless steel arch wires. After leveling was finished, inch upper accentuated-curve and lower reverse-curve nickel titanium arch wires were placed. The biomechanical basis of the appliances is shown in Fig 1. When used without anterior elastics, upper accentuated-curve and lower Fig 2. Intrusive effect of arch wires is counteracted by elastics applied in canine regions. reverse-curve arch wires create an intrusive effect on the upper and lower incisors. With the addition of vertical elastics in the canine regions, the intrusive forces that act on the anterior region are canceled, while those that act on the posterior teeth are allowed. The intrusive force of the wires on the anterior teeth was counteracted with two 3 16 inch, 6 oz elastics placed between upper and lower canines on both sides. The patients were instructed to renew their elastics once a day (Fig 2). Once the open bite in the canine region was eliminated, the elastics were applied in box form until 3 months after incisal overlap was fully achieved. After removal of the NiTi arch wires, inch stainless steel arch wires were inserted and kept in place for a period of 3 months, during which box elastics were continued to be worn. Average treatment time with fixed appliances was 16 months. After debonding, positioners were inserted for 3 months, followed by Hawley retainers which were worn for 6 months (Figs 3-5). Cephalometric evaluation of the treatment changes was conducted on lateral cephalograms from 17 patients, taken at the beginning and on average 2.8 months after an overbite of 1 to 2 mm was obtained (Figs 6-8). Follow-up changes were assessed on lateral cephalograms obtained from 10 patients who were available at our clinic at the end of 1 year postretention period. Twenty randomly selected cephalograms were retraced 1 week after the original tracing session. The error between duplicate determinations was assessed using Dahlberg s 9 formula. The error ranged between 0.13 and 0.76 mm for the linear measurements and 0.17 and 0.87 for the angular measurements. The coefficient of reliability exceeded 90% for all the measurements. 10

3 American Journal of Orthodontics and Dentofacial Orthopedics Küçükkeleș et al 557 Volume 116, Number 5 Fig 3. Pretreatment extraoral and intraoral photographs. The statistical package NCSS (Number Cruncher Statistical System) was used for statistical evaluation of the data. Cephalometric changes from pretreatment to posttreatment films and from posttreatment to postretention films were evaluated by paired t test. RESULTS Posttreatment cephalometric changes attained with this treatment are shown in Tables I and II. Skeletal Changes The two skeletal parameters that were altered significantly at the end of therapy were N-Me and ANS- Me. N-Me increased by 2.29 mm (P <.01) and ANS- ME by 2.50 mm (P <.001). Dental Changes Upper incisors were both uprighted and extruded as shown by the 6.41 decrease in U1-PP (P <.01) and 3.15 mm increase in U1-PP (mm) (P <.001). The upper first molar was extruded by 1.11 mm (P <.01). L1-MP (mm), L4-MP (mm), and L6-MP (mm) parameters increased by 3.35 mm (P <.001), 2.59 mm (P <.001), and 1.39 mm (P <.01), respectively, indicating extrusion of lower incisors, first premolars and first molars. In addition, the lower first molar was uprighted by 8.35 (P <.001). There was a 1.79 mm decrease in overjet (P <.05), and a 5.37 mm increase in overbite (P <.001). SN-FOP decreased by 2.09 (P <.01) and FOP/MP increased by 2.38 (P <.001). Skeletal Changes at the End of 1 Year Follow-up Period (Table III) N-Me and ANS-Me increased by 2.20 mm and 2.30 mm, respectively. The rest of the skeletal parameters showed no significant change. Dental Changes at the End of 1 Year Follow-up Period (Table IV) Upper first molar and lower first molar were extruded by 1.05 mm and 1.70 mm, respectively (P <

4 558 Küçükkeleș et al American Journal of Orthodontics and Dentofacial Orthopedics November 1999 Fig 4. Posttreatment extraoral and intraoral photographs..05, P <.01). Upper first premolar and lower first premolar were extruded by 1.40 mm and 1.85 mm, respectively (P <.01). Overbite decreased by 1.25 mm (P <.01). The rest of the dental parameters, including the parameters related to occlusal plane and upper and lower incisors showed no significant alteration. DISCUSSION The results of this study indicated that bite closure had been achieved to a great extent by extrusion of the lower incisors and uprighting of the upper incisors. Elastics, which were applied to prevent incisor intrusion as a result of NiTi arch wires, caused extrusion and uprighting of the incisors. The 3.15 mm extrusion measured in the upper incisors was in part due to the change in the relative distance of the incisor tip to the palatal plane that took place as the central incisor was being uprighted. Although the configuration of the arch wires in the molar region forced the molars to be both intruded and uprighted, no molar intrusion took place. Instead, the molars were extruded while being uprighted. Extrusion of molars is an undesirable treatment effect in the group of patients that formed our study sample. However, the amount of molar extrusion in the present study was minimal (1 mm), and it may have been related to the selection of mesiobuccal cusp tip of the first molar as a landmark for linear measurements. Mesiobuccal cusps of both upper and lower first molars were elevated as a result of the uprighting movement caused by the upper accentuated-curve and lower reverse-curve arch wires. Extrusion of lower premolars and uprighting of lower molars have led to rotation of the functional occlusal plane in a counterclockwise direction, thus decreasing its steepness. The increase in N-Me and ANS-Me could be attributed to this 1 mm extrusion of upper and lower first molars, which may have caused slight clockwise rotation of the mandible. However, this change was not reflected in mandibular plane angle, which stayed stable throughout treatment. Extrusion of lower incisors, increase in overbite, and uprighting of upper incisors were in accordance with the findings of Goto et al 6 and

5 American Journal of Orthodontics and Dentofacial Orthopedics Küçükkeleș et al 559 Volume 116, Number 5 Fig 5. Photographs of patient after 1 year follow-up period. Enacar et al. 8 Furthermore, uprighting of teeth in the buccal segments and the alteration of the occlusal plane to SN angle were in agreement with the reports of Enacar et al 8 On the other hand, Goto et al 6 reported an increase in SNB angle and a decrease in ANB and mandibular plane angles, while in the present study no significant difference was noted regarding these parameters. Although Goto et al 6 and Enacar et al 8 reported significant lower incisor uprighting, lower incisors were uprighted by 1.26 in the present study, a difference that was not found statistically significant. The uprighting and relative extrusion of the upper incisors during treatment could increase the maxillary gingival display of the patients when smiling. Thus, it is of utmost importance to exclude those individuals who already show a gummy smile at the beginning of the treatment. The effects of this treatment method were similar to those of the multiloop edgewise arch wire system in that the inclination of the occlusal plane was corrected, Fig 6. Skeletal measurements: (1) SN-MP, (2) SN-PP, (3) SNA, (4) SNB, (5) ANB, (6) SN-Pg, (7) N-Me, (8) ANS-Me.

6 560 Küçükkeleș et al American Journal of Orthodontics and Dentofacial Orthopedics November 1999 Fig 7. Dental measurements: (1) SN-functional occlusal plane (FOP), (2) mandibular plane (MP)-FOP, (3) U1-palatal plane (PP), (4) U1-PP (mm), (5) U4-PP (mm), (6) U6-PP, (7) U6-PP (mm), (8) L1-MP, (9) L1-MP (mm), (10) L4-MP (mm), (11) L6-MP, (12) L6-MP (mm), (13) overjet, (14) overbite. Fig 8. Superimposition of pretreatment and posttreatment lateral cephalograms. Table I. Comparison of pretreatment and posttreatment skeletal measurements (N = 17) Pretreatment Posttreatment Mean SD Mean SD Difference SD P SN-MP NS SN-PP NS N-Me ** ANS-Me *** SNA NS SNB NS ANB NS SN-Pg NS NS, Not significant. **P <.01. ***P <.001. open bite was corrected by extrusion of the lower incisors and uprighting of the upper incisors, and axial inclinations of the posterior teeth were uprighted. Working with upper accentuated-curve and lower reverse-curve NiTi arch wires was less time consuming compared with multiloop arch wires. The patients did not have any difficulty in maintaining their oral hygiene, and there was no complaint about oral soft tissue irritations. Stability of treatment effects is probably the most important criterion when deciding on a treatment method for open bite correction. Posterior mandibular rotation resulting from growth after treatment 11 or extrusion of posterior teeth during treatment 12 has been reported as an important factor for open bite relapse. Cephalometric evaluation of 10 patients at the end of 1 year postretention has shown that although upper and lower incisor positions and the inclination of functional occlusal plane had been maintained, there was a decrease in overbite that was due to extrusion of upper and lower first molars. Total anterior and lower anterior face heights were increased, again as a result of upper and lower molar extrusion. Relapse into anterior open bite can occur by depression of the incisors and/or elongation of the

7 American Journal of Orthodontics and Dentofacial Orthopedics Küçükkeleș et al 561 Volume 116, Number 5 Table II. Comparison of pretreatment and posttreatment dental measurements (N = 17) Pretreatment Posttreatment Mean SD Mean SD Difference SD P SN-FOP ** MP-FOP *** 1-PP ** 1-PP (mm) *** 4-PP (mm) NS 6-PP NS 6-PP (mm) ** 1-MP NS 1-MP (mm) *** 4-MP (mm) *** 6-MP *** 6-MP (mm) ** Overjet * Overbite *** NS, Not significant. *P <.05. **P <.01. ***P <.001. Table III. Comparison of posttreatment and postretention skeletal measurements (N = 10) Pretreatment Postretention Mean SD Mean SD Difference SD P SN-MP NS SN-PP NS N-Me ** ANS-Me * SNA NS SNB NS ANB NS SN-Pg NS NS, Not significant. *P <.05. **P <.01. Table IV. Comparison of posttreatment and postretention dental measurements (N = 10) Pretreatment Postretention Mean SD Mean SD Difference SD P SN-FOP NS MP-FOP NS 1-PP NS 1-PP (mm) NS 4-PP (mm) ** 6-PP NS 6-PP (mm) * 1-MP NS 1-MP (mm) NS 4-MP(mm) ** 6-MP NS 6-MP(mm) ** Overjet NS Overbite ** NS, Not significant. *P <.05. **P <.01.

8 562 Küçükkeleș et al American Journal of Orthodontics and Dentofacial Orthopedics November 1999 molars. In patients without a habit of placing an object between their front teeth, open bite relapse is usually the result of elongation of the posterior teeth, with no apparent intrusion of incisors. 13 Vertical growth and eruption of posterior teeth may continue until late teen years or early twenties, making the open bite tendency quite difficult to control. Thus, retention in open bite patients should be long term and involve strict control of eruption of the posterior teeth. CONCLUSIONS Treatment changes obtained by using NiTi arch wires and anterior elastics were similar to those reported to be achieved by multiloop edgewise arch wire technique. Although long-term follow-up studies are yet to be done, ease of application and patient comfort provided by this newer method can make it an alternative for multiloop edgewise arch wire technique. REFERENCES 1. Subtelny JD. Openbite: diagnosis and treatment. Am J Orthod 1964;50: Dung DJ, Smith RJ. Cephalometric and clinical dignoses of openbite tendency. Am J Orthod 1988;94: Nielsen IL. Vertical malocclusions: etiology, development, diagnosis and some aspects of treatment. Angle Orthod 1991;61: Proffit WR, White RP. Surgical-orthodontic treatment. St. Louis: Mosby Yearbook; p Kim YH. Anterior openbite and its treatment with multiloop edgewise archwire. Angle Orthod 1987;57: Goto S, Boyd RL, Nielsen IL, Iizuka T. Case report: nonsurgical treatment of an adult with severe anterior open bite. Angle Orthod 1994;64: Sato S. Case report: developmental characterization of skeletal Class III malocclusion. Angle Orthod 1994;64: Enacar A, Ugur T, Toroglu S. A method for correction of open bite. J Clin Orthod 1996;30: Dahlberg G. Statistical methods for medical and biological students. New York: Interscience Publications; Houston WJB. The analysis of errors in orthodontic measurements. Am J Orthod 1983;83: Nemeth RB, Isaacson RJ. Vertical anterior relapse. Am J Orthod 1974;65: Ricketts RM. The influence of orthodontic treatment on facial growth and development. Angle Orthod 1960;30: Proffit WR, Fields HW Jr. Contemporary orthodontics. St Louis: Mosby Year Book Inc; AVAILABILITY OF JOURNAL BACK ISSUES As a service to our subscribers, copies of back issues of the American Journal of Orthodontics and Dentofacial Orthopedics for the preceding 5 years are maintained and are available for purchase from the publisher, Mosby, Inc, at a cost of $13.00 per issue. The following quantity discounts are available: 25% off on quantities of 12 5o 23, and one third off on quantities of 24 or more. Please write to Mosby, Inc, Subscription Services, Westline Industrial Dr, St Louis, MO , or call (800) or (314) for information on availability of particular issues. If unavailable from the publisher, photocopies of complete issues are available from Bell & Howell Information and Learning, 300 N. Zeeb Rd, Ann Arbor, MI (734) or (800)