ORIGINAL ARTICLE

Treatment effects of a modified palatal anchorage plate for distalization evaluated with cone-beam computed tomography Yoon-Ah Kook,a Mohamed Bayome,b Vu Thi Thu Trang,c Hye-Jin Kim,d Jae Hyun Park,e Ki Beom Kim,f and Rolf G. Behrentsg Seoul, Korea, Asuncion, Paraguay, Hanoi, Vietnam, Mesa, Ariz, and St Louis, Mo

Introduction: The purpose of this study was to evaluate the treatment effects of maxillary posterior tooth distalization performed by a modified palatal anchorage plate appliance with cephalograms derived from cone-beam computed tomography. Methods: The sample consisted of 40 lateral cephalograms obtained from the conebeam computed tomography images of 20 Class II patients (7 men, 13 women; average age, 22.9 years) who underwent bilateral distalization of their maxillary dentition. The lateral cephalograms were derived from the cone-beam computed tomography images taken immediately before placement of a modified palatal anchorage plate appliance and at the end of distalization. Paired t tests were used for comparisons of the changes. Results: The distal movement of the maxillary first molar was 3.3 6 1.8 mm, with distal tipping of 3.4 6 5.8 and intrusion of 1.8 6 1.4 mm. Moreover, the maxillary incisors moved 3.0 6 2.7 mm lingually, with lingual tipping of 6.2 6 7.6 and insignificant extrusion (1.1 mm; P 5 0.06). The occlusal plane angle was increased significantly (P 5 0.0001). Conclusions: The maxillary first molar was distalized by 3.3 mm at the crown and 2.2 mm at root levels, with distal tipping of 3.4 . It is recommended that clinicians should consider using the modified palatal anchorage plate appliance in treatment planning for patients who require maxillary total arch distalization. (Am J Orthod Dentofacial Orthop 2014;146:47-54)

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xtraoral appliances have been prescribed for maxillary molar distalization in nonextraction treatment of Class II malocclusion patients. However, these devices require patient cooperation.1 To effectively overcome this problem, intraoral a Professor, Department of Orthodontics, Seoul St. Mary's Hospital, Catholic University of Korea, Seoul, Korea. b Research assistant professor, Graduate School, Catholic University of Korea, Seoul, Korea; visiting professor, Department of Postgraduate Studies, Universidad Auton oma del Paraguay, Asunci on, Paraguay. c Lecturer, Department of Orthodontics, Hanoi Medical University, Hanoi, Vietnam. d Private practitioner, Yonseijin Dental Clinic, Seoul, Korea. e Associate professor and chair, Postgraduate Orthodontic Program, Arizona School of Dentistry & Oral Health, A. T. Still University, Mesa, Ariz; adjunct professor, Graduate School of Dentistry, Kyung Hee University, Seoul, Korea. f Associate professor, Department of Orthodontics, Center for Advanced Dental Education, Saint Louis University, St Louis, Mo. g Professor, Department of Orthodontics, Center for Advanced Dental Education, Saint Louis University, St Louis, Mo. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Yoon-Ah Kook, Department of Orthodontics, Seoul St. Mary's Hospital, Catholic University of Korea, 505 Banpo-Dong, Seocho-Gu, Seoul, 137-701, Korea; e-mail, [email protected]. Submitted, July 2013; revised and accepted, March 2014. 0889-5406/$36.00 Copyright Ó 2014 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2014.03.023

noncompliance appliances have been developed.2-6 Nevertheless, the negative side effects of these appliances include anchorage loss at the reactive part, distal tipping, and extrusion of molars.7,8 To reduce the drawbacks of noncompliance appliances, temporary skeletal anchorage devices (TSADs) have been applied to the buccal plate of the bone to achieve molar distalization.9-13 However, the buccal approach poses an increased risk of contacting the roots of adjacent teeth, and the range of action might be limited by the interradicular space. Sugawara et al14 placed plates at the zygomatic buttresses for distalization of the maxillary dental arch. However, their method involved surgical procedures and a latency time between the surgery and force application. Recently, palatal bone thickness and density as well as palatal soft-tissue thickness have been evaluated in adults and adolescents.15-18 These studies have provided detailed information for the placement of the TSADs in the palate. In addition, the placement of the TSADs in the palate eliminates the need for reimplanting miniscrews as in the buccal approach.19,20 Several appliances with TSADs have been reported to distalize the maxillary posterior teeth, but some were 47

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Fig 1. The palatal plate is connected to the hooks of the palatal wire via power elastics or nickeltitanium closed-coil springs. The direction of force can be changed according to the notches on the arms of the palatal plate (A, B, and C).

bulky and others contributed to distal crown tipping.21,22 Kinzinger et al23 proposed a distal jet appliance supported by dental and skeletal anchorages. Although it reduced the anchorage loss, it prevented movement of the premolars during the distalization period. Kircelli et al24 used a bone-anchored pendulum appliance. A large amount of distal tipping of the first molar (10.9 ) was reported with this appliance; this could have been due to a force vector similar to the conventional appliance. On the other hand, the modified palatal anchorage plate (MPAP) appliance has been reported to effectively distalize the posterior teeth in adults and adolescents.25,26 Finite element analysis suggested that distalization with a palatal plate rather than buccally placed mini-implants provides bodily molar movement without tipping or extrusion.27 However, no clinical evaluation has been performed with the MPAP. So far, most distalization studies have used 2dimensional lateral cephalograms. The disadvantages of this approach include confounded images caused by superimposed anatomic structures, vertical and horizontal magnifications, and a lack of right and left side information.28,29 Although cone-beam computed tomography (CBCT) has disadvantages that include higher doses of radiation, higher cost, and limited availability, these limitations are overcome by the huge amount of data that is provided without distortion or superimposition.30 The degree of difficulty and the prognosis of distalization are affected by the patient's dental and chronologic ages. A high success rate with fewer complications occurs when the maxillary molars are distalized in the mixed dentition stage.31 Hence, most distalization studies have focused on adolescents, and there have been no studies, to the best of our knowledge,

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investigating the distalization effect in adults who have full eruption of their maxillary second molars. Therefore, the purpose of this study was to evaluate the treatment effects of posterior tooth distalization in adults with an MPAP appliance using lateral cephalograms derived from CBCT images. MATERIAL AND METHODS

Forty lateral cephalograms were obtained from CBCT images of 20 consecutively treated Class II adult patients (7 men, 13 women; average age, 22.9 years; range, 17.433 years) who underwent bilateral distalization of their maxillary dentition at the Department of Orthodontics at Seoul St. Mary's Hospital, Catholic University of Korea. Of the 40 lateral cephalograms, 15 sides had one quarter cusp, 12 had one half cusp, 7 had three quarters cusp, and 6 had full cusp Class II molar relationships. The inclusion criteria for this retrospective study were (1) dental Class II relationship, (2) 3-dimensional CBCT images taken immediately before and after distalization, (3) exclusive use of the MPAP appliance for distalization, and (4) age over 17 years. The exclusion criteria were (1) extraction treatment (except for third molars) and (2) unilateral distalization. Approval was obtained from the institutional review board of the Catholic University of Korea (KC11RASI0790), and informed consent was provided according to the Declaration of Helsinki. The MPAP appliance (Fig 1) and its installation method have been described in previous articles.25,26 The MPAP was fitted on the dental cast to the shape of the palate, extending its arms to the area between the first molar and the second premolar and leaving enough space between the arms and the palatal slopes. The transfer from the cast to the patient's mouth was made with a jig by the same operator (Y.-A.K.) using 3

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miniscrews (length, 8 mm; diameter, 2 mm: Jeil, Seoul, Korea). Then a palatal bar with 2 hooks extending along the gingival margins of the teeth was banded to the right and left maxillary first molars. Immediately after placement, distalization can be initiated by engaging elastics or nickel-titanium closed-coil springs between the MPAP arm notches and the hooks on the palatal bar, applying approximately 300 g of force per side. Along with the MPAP appliance, 0.022-in slot brackets and bands (Tomy, Tokyo, Japan) were placed on the maxillary and mandibular teeth including the second molars. The interval between appointments was 3 to 4 weeks. The distalization periods were calculated from the patients' records. CBCT images (before and after distalization) were taken with an iCAT scanner (Imaging Science International, Hatfield, Pa). The scanning parameters were 120 kV, 47.7 mAs, 20 seconds per revolution, 170 3 130 mm field of view, and voxel size of 0.4 mm. Each seated subject's head position was oriented so that the Frankfort plane was parallel to the floor, and the images were taken at the intercuspal position. The CBCT data were exported in a digital imaging and communications in medicine (DICOM) multifile format and imported into InVivo software (version 5.2; Anatomage, San Jose, Calif) for 3-dimensional volume rendering. Reorientation of the head position of each scan was performed as follows. The horizontal plane (x) was defined through the right and left orbitales and the left porion, and the midsagittal plane (y) was defined as the perpendicular plane passing through nasion and anterior nasal spine. The vertical plane (z) was perpendicular to both x and y. Then, using the super-ceph module in the InVivo software, a lateral cephalometric image was created for each right and left side independently and saved in JPG format. Each image was then traced and superimposed using V-Ceph software (version 5.5; Cybermed, Seoul, South Korea) with the manual geometric method.32,33 The horizontal reference line was the Frankfort horizontal plane, and the vertical reference line was the perpendicular at pterygoid. All tracings and digitizations were made by 1 examiner (V.T.T.T.) to minimize operator-generated variation in the measurements. The software calculated the linear and angular dimensions between certain landmarks according to the definitions given in Figures 2 through 4. The maxillary third molar was present in 31 sides and extracted or missing from 9 sides during treatment. Ten randomly selected subjects were reprocessed 4 weeks later to evaluate intraoperator reliability. The

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Fig 2. Cephalometric landmarks and maxillary dental sagittal, vertical, and angular measurements. Landmarks: Or, Orbitale; Po, porion; Pt, pterygoid; ANS, anterior nasal spine; PNS, posterior nasal spine; FH, Frankfort horizontal; VRL, vertical reference line; U1, incisal tip of the maxillary central incisor; U1r, root tip of the maxillary central incisor; U5, cusp tip of the maxillary second premolar; U5r, root tip of the maxillary second premolar; U6, distobuccal cusp of the maxillary first molar; U6r, distobuccal root tip of the maxillary first molar. Measurements: 1, U6-VRL; 2, U6r-VRL; 3, U6-FH; 4, U6r-FH; 5, angle between U6-U6r and FH; 6, U5-VRL; 7, U5r-VRL; 8, U5-FH; 9, U5r-FH; 10, angle between U5-U5r and FH; 11, U1-VRL; 12, U1r-VRL; 13, U1-FH; 14, U1r-FH; 15, angle between U1-U1r and FH.

intraclass correlation coefficient showed that the measurements were reliable (.0.997). Statistical analysis

Statistical evaluation was performed using SPSS software (version 16.0; SPSS, Chicago, Ill). Normal distribution of the parameters was assessed with the Kolmogorov-Smirnov test. The paired t test was used to evaluate the skeletal, dental, and soft-tissue changes from before to after distalization. The comparison between subjects who had third molars during distalization and those with missing or extracted ones was performed by an independent sample t test. The statistical significance was determined at a 5 0.05. RESULTS

Clinically successful distalization was achieved using the MPAP appliance for an average of 12.5 months. There were significant changes in the sagittal and vertical positions (P \0.0001) and angulations (P 5 0.001) of the maxillary first molars after distalization. The mean amount of first molar distalization was 3.30 6 1.80 mm,

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Fig 3. Cephalometric landmarks and mandibular dental sagittal, vertical, and angular measurements. Landmarks: Or, Orbitale; Po, porion; Pt, pterygoid; FH, Frankfort horizontal; VRL, vertical reference line; L1, incisal tip of the mandibular central incisor; L1r, root tip of the mandibular central incisor; L5, cusp tip of the mandibular second premolar; L5r, root tip of the mandibular second premolar; L6, distobuccal cusp of the mandibular first molar; L6r, distal root tip of the mandibular first molar. Measurements: 1, L6-VRL; 2, L6r-VRL; 3, L6-FH; 4, L6r-FH; 5, angle between L6L6r and FH; 6, L5-VRL; 7, L5r-VRL; 8, L5-FH; 9, L5rFH; 10, angle between L5-L5r and FH; 11, L1-VRL; 12, L1r-VRL; 13, L1-FH; 14, L1r-FH; 15, angle between L1-L1r and FH.

Fig 4. Cephalometric midsagittal measurements. Landmarks: S, Sella turcica; N, nasion; Or, orbitale; Po, porion; Pt, pterygoid; FH, Frankfort horizontal; ANS, anterior nasal spine; A, A-point; Ls, labrale superior; Li, labrale inferior; B, B-point; Pog’, soft-tissue pogonion; Me, menton; VRL, vertical reference line. Measurements: 1, SNA; 2, ANB; 3, palatal plane angle; 4, occlusal plane angle; 5, mandibular plane angle; 6, ANS-Me; 7, nasolabial angle; 8, mentolabial fold; 9, Ls-VRL; 10, Li-VRL; 11, Pog'-VRL.

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with distal tipping of 3.42 6 5.79 and intrusion of 1.75 6 1.35 mm. The maxillary second molar showed 2.66 6 1.90 mm of distalization, 1.28 6 1.61 mm of intrusion, and 2.03 6 7.49 of distal tipping. The maxillary second premolars moved distally 3.05 6 2.14 mm and tipped distally 8.38 6 6.80 , with no significant change in the crown vertical position. The maxillary central incisors were retracted by 2.99 6 2.73 mm, with a retroclination angle of 6.21 6 7.64 and no significant change in the vertical position (Table I, Fig 5). The occlusal plane angle was significantly (P 5 0.001) increased by 2.81 . However, the palatal plane angle was not changed. The upper and lower lips showed about 1.5 mm of retraction (P 5 0.016 and 0.008, respectively). The nasolabial angle was significantly (P 5 0.008) increased to 101.9 (Table II). There were no significant differences in the amount of the change in position or angulation of teeth between the maxillary third molar extraction (n 5 31) and nonextraction (n 5 9) groups (Table III). DISCUSSION

The aim of this study was to evaluate a newly developed palatal plate appliance designed for molar and total arch distalization using cephalograms derived from CBCT images. A lateral cephalogram of each side was created independently to eliminate the superimposition of anatomic structures. This allowed for accurate root position and evaluation of each side separately. These reconstructed images are accurate and reliable when compared with conventional radiographs.34,35 With the pendulum appliance, Ghosh and Nanda5 had distal tipping of the maxillary first and second molars of 8.4 and 12.0 , respectively, at the end of the distalization period. They stated that the molar relationship could be corrected by a tipping movement, but retention would be doubtful during retraction of the incisors. Other studies showed 8.8 and 10.9 of distal tipping of the maxillary first molars after distalization via miniscrews.24,36 Meanwhile, the bone-anchored pendulum appliance showed 9 of distal tipping.22 In our study, the maxillary first and second molars tipped distally by 3.4 and 2.0 , respectively. This decreased tipping in our study might be due to the ability to adjust the force vector by selecting the most appropriate plate notch that is estimated to result in bodily movement. Although the distal tipping was limited (3.4 ), the standard deviation was 5.8 , which represented wide variability. This might be attributed to the individual

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Table I. Comparisons of predistalization and postdistalization positions of the maxillary dentition (n 5 40) Predistalization Variable Central incisor crown horizontal distance (mm) Central incisor root horizontal distance (mm) Central incisor crown vertical distance (mm) Central incisor root vertical distance (mm) Central incisor inclination ( ) Second premolar crown horizontal distance (mm) Second premolar root horizontal distance (mm) Second premolar crown vertical distance (mm) Second premolar root vertical distance (mm) Second premolar angulation ( ) First molar crown horizontal distance (mm) First molar root horizontal distance (mm) First molar crown vertical distance (mm) First molar root vertical distance (mm) First molar angulation ( ) Second molar crown horizontal distance (mm) Second molar root horizontal distance (mm) Second molar crown vertical distance (mm) Second molar root vertical distance (mm) Second molar angulation ( )

Mean 55.22 47.21 54.52 35.17 68.15 33.14 33.61 49.88 33.26 92.11 18.43 22.99 45.51 31.53 109.30 9.23 16.00 42.56 30.97 120.67

Postdistalization

SD 5.32 3.77 4.57 3.46 10.47 5.21 3.87 4.69 5.20 7.22 4.42 3.48 4.08 3.74 6.05 3.93 3.13 4.75 3.91 10.05

Mean 52.23 46.89 55.61 35.72 74.36 30.09 33.26 50.04 32.75 100.49 15.13 20.82 43.76 29.98 112.72 6.57 13.88 41.28 29.67 122.71

SD 5.52 3.97 4.20 3.43 10.34 4.94 4.03 4.13 3.63 8.66 4.17 3.53 4.63 3.78 7.83 3.74 3.19 5.15 4.03 9.36

Change Mean 2.99 0.33 1.09 0.55 6.21 3.05 0.34 0.16 0.51 8.38 3.30 2.17 1.75 1.55 3.42 2.66 2.12 1.28 1.30 2.03

SD 2.73 2.08 3.51 1.92 7.64 2.14 2.21 3.91 3.61 6.80 1.80 1.85 1.35 1.96 5.79 1.90 1.90 1.61 1.45 7.49

P value \0.001 0.327 0.056 0.077 \0.001 \0.001 0.332 0.798 0.381 \0.001 \0.001 \0.001 \0.001 \0.001 0.001 \0.001 \0.001 \0.001 \0.001 0.118

Positive values indicate distal movement, retraction, intrusion, and mesial tipping. P values were obtained by paired t test.

Fig 5. Summary of mean maxillary dental changes after distalization by the MPAP appliance.

variations in the shape and extension of the maxillary sinus and the alveolar arch, which might have affected the distalization, and to the differences in the required amount of distalization in each patient. Recently, a finite element study has suggested that application of force through the most apical notch in the MPAP resulted in bodily movement of the first molar.27 Therefore, in our study, this minimal amount of distal tipping might have resulted from using the occlusal or the middle plate notches in some patients according to their estimated treatment needs (Fig 1).

In addition, a recent modification of this appliance had a fourth notch to provide a better range to control the distal tipping and vertical dimension.26 Since palatal morphology varies widely in its degree of concavity, anteriority, and sharpness, these 4 notches of the MPAP allow for adjusting the force vector according to the estimated center of resistance of the dentition; this might be difficult to achieve in some patients.37 Moreover, these notches might also facilitate the application of various forces on at least 1 tooth according to the required tooth movement. It

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Table II. Skeletal and soft-tissue cephalometric measurements before and after distalization (n 5 20) Predistalization Variable SNA ( ) ANB ( ) Palatal plane angle ( ) Occlusal plane to SN ( ) Mandibular plane angle ( ) ANS-Me (mm) Overjet (mm) Overbite (mm) Nasolabial angle ( ) Mentolabial fold ( ) LS-VRL (mm) LI-VRL (mm) Pog0 -VRL (mm)

Mean 81.18 4.38 5.96 18.78 23.90 67.43 4.71 3.28 98.64 135.53 67.22 63.70 42.38

Postdistalization

SD 3.35 2.11 17.50 6.33 8.96 6.01 1.67 1.44 7.69 9.74 5.04 5.86 9.77

Mean 80.42 3.36 9.31 21.60 24.46 68.62 3.54 3.16 101.90 133.36 66.04 62.16 41.82

Change

SD 3.22 1.80 3.08 5.94 9.00 6.44 0.90 1.15 8.38 9.02 5.01 5.87 9.92

Mean 0.76 1.01 3.35 2.81 0.55 1.19 1.17 0.13 3.26 2.17 1.18 1.54 0.56

SD 1.95 1.46 16.81 3.37 2.58 3.26 1.90 1.64 4.87 6.39 1.99 2.33 2.91

P value 0.097 0.006 0.384 0.001 0.351 0.120 0.013 0.735 0.008 0.145 0.016 0.008 0.398

P values were obtained by paired t test.

Table III. Comparison of amounts of distalization in the maxillary dentition between the third molar extraction and

nonextraction groups Extraction (n 5 31) Variable Central incisor crown horizontal distance (mm) Central incisor root horizontal distance (mm) Central incisor crown vertical distance (mm) Central incisor root vertical distance (mm) Central incisor inclination ( ) Second premolar crown horizontal distance (mm) Second premolar root horizontal distance (mm) Second premolar crown vertical distance (mm) Second premolar root vertical distance (mm) Second premolar angulation ( ) First molar crown horizontal distance (mm) First molar root horizontal distance (mm) First molar crown vertical distance (mm) First molar root vertical distance (mm) First molar angulation ( ) Second molar crown horizontal distance (mm) Second molar root horizontal distance (mm) Second molar crown vertical distance (mm) Second molar root vertical distance (mm) Second molar angulation ( )

Mean 3.12 0.08 0.22 0.32 6.37 3.01 0.19 0.36 1.04 8.69 3.23 2.20 1.75 1.45 3.27 2.52 2.22 1.14 1.44 0.58

SD 2.86 2.05 1.86 1.21 8.01 2.22 2.33 3.59 3.62 7.14 1.89 1.87 1.36 2.11 5.78 2.00 1.98 1.70 1.59 7.51

Nonextraction (n 5 9) Mean 2.55 1.18 0.73 1.34 5.67 3.19 0.87 0.34 0.09 7.31 3.55 2.18 1.73 2.00 3.94 3.05 1.83 1.78 0.79 4.74

SD 2.34 2.08 0.90 3.41 6.60 1.94 1.73 1.07 1.39 5.71 1.54 1.88 1.43 1.14 6.16 1.60 1.74 1.21 0.49 4.10

P value 0.594 0.167 0.488 0.401 0.812 0.824 0.423 0.990 0.503 0.598 0.643 0.976 0.972 0.512 0.765 0.478 0.597 0.357 0.085 0.146

Positive values indicate distal movement, retraction, intrusion, and mesial tipping. P values were obtained by independent sample t test.

might be important to conduct further studies to evaluate the effect of palatal shape on the force system used for distalization. Previous studies showed 3.8 and 3.9 mm of distal movement of the maxillary first molars using TSADs.24,36 However, because of a small amount of distal tipping in our study, the amount of root movement might be more than that in other studies. The maxillary molars were also intruded by 1.8 mm, and the maxillary incisors were extruded by 1.1 mm;

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therefore, the occlusal plane angle was increased by 2.8 . The intrusion of the molars during distal movement could help maintain the anterior facial height; the ANS-Me difference was 1.19 mm (P 5 0.12). This is especially important if the patient has a hyperdivergent growth pattern. The maxillary incisors were retroclined by 6.2 and retracted by 3 mm. In agreement, previous studies showed incisor retroclination in their implantsupported pendulum appliance groups.38,39 The

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mechanics of retracting the entire dentition with miniscrews might prevent the round tripping movement of the anterior teeth. Several authors have suggested that the erupted second molars create resistance to distalization.40 Gianelly et al41 recommended that the maxillary third molars should be extracted before distalization of the posterior teeth. However, in our study, the maxillary third molars were sometimes left in position during distalization because the patients did not want extractions. Several studies reported greater distal tipping and higher movement rates of the maxillary first molars when the second molars were at the apical third of the first molars than when the second molars were erupted.2,42,43 In contrast, several authors reported minimal or no significant effect of the second and third molars' eruption status on first-molar movement.3,5,44 However, in these studies, the second or third molars were either erupted or unerupted, but not extracted. Therefore, their effect might have been based on their position inside the alveolar ridge as a fulcrum opposing the movement of the first molar. Our results showed no noticeable difference in the amounts of distalization and tipping between the subjects who had third molars and subjects in whom they had been extracted. However, these results should be approached with caution because of the small sample size of the nonextraction group. Further study evaluating the effect of the presence of the third molar on total arch distalization might be recommended. In this study, the total distalization period was an average of 12.5 months. Sar et al22 reported that the average distalization durations were 8.2 months in the miniscrew-supported distalization system group and 10.2 months in the bone-anchored pendulum appliance group. Chiu et al4 reported 10 months for distalization of the molars. The longer distalization time in our study might have been because the MPAP appliance was placed for total arch distalization, not just Class II dental correction. The MPAP appliance allows for molar distalization simultaneously with leveling and alignment of the maxillary dentition. Therefore, the plate should be installed early in the treatment so that distalization can start with the molars and then expand to include the whole dentition via buccal archwires as soon as the leveling and alignment stage is finished. Moreover, it is advisable to include the second molars in bonding to the archwire to prevent any unwanted tooth movement, such as tip-back caused by distal movement of the first molar, and to provide efficient movement of the second molar during full arch distalization. In our study, the similar degrees of distal tipping of both first and

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second molars confirmed this. The MPAP was left in place after the end of distalization to serve as skeletal anchorage whenever needed and then was removed at debonding. In our study, some of the early subjects, treated when the MPAP had no screw tubes, showed inflammation and overgrowth of palatal soft tissues. However, it resolved soon after removal of the MPAP. In the recent subjects, the screw tubes decreased the micromovements of the MPAP; this reduced the irritation to the soft tissues. Hence, no signs of inflammation were noticed. In addition, the installation of the MPAP resulted in alteration of the pronunciation of some letters in some patients, but this resolved within 2 weeks without any intervention. Further study to evaluate the effect of this appliance in adolescent patients is also recommended. In addition, assessment of long-term stability after the retention period should be considered. CONCLUSIONS

The maxillary first molar was distalized 3.3 mm at the crown and 2.2 mm at the root level, with distal tipping of 3.4 and 1.8 mm of intrusion. The MPAP appliance is effective in minimizing distal tipping and preventing molar extrusion during distalization. Therefore, it is recommended that clinicians consider using the MPAP appliance in treatment planning for patients who require maxillary total arch distalization. REFERENCES 1. Fields HW, Proffit WR. Treatment of skeletal problems in children and preadolescents. In: Proffit WR, Fields HW, Sarver DM, editors. Contemporary orthodontics. St Louis: Mosby Elsevier; 2013. p. 507. 2. Bolla E, Muratore F, Carano A, Bowman SJ. Evaluation of maxillary molar distalization with the distal jet: a comparison with other contemporary methods. Angle Orthod 2002;72:481-94. 3. Bussick TJ, McNamara JA Jr. Dentoalveolar and skeletal changes associated with the pendulum appliance. Am J Orthod Dentofacial Orthop 2000;117:333-43. 4. Chiu PP, McNamara JA Jr, Franchi L. A comparison of two intraoral molar distalization appliances: distal jet versus pendulum. Am J Orthod Dentofacial Orthop 2005;128:353-65. 5. Ghosh J, Nanda RS. Evaluation of an intraoral maxillary molar distalization technique. Am J Orthod Dentofacial Orthop 1996;110: 639-46. 6. Muse DS, Fillman MJ, Emmerson WJ, Mitchell RD. Molar and incisor changes with Wilson rapid molar distalization. Am J Orthod Dentofacial Orthop 1993;104:556-65. 7. Keles A, Sayinsu K. A new approach in maxillary molar distalization: intraoral bodily molar distalizer. Am J Orthod Dentofacial Orthop 2000;117:39-48. 8. Kinzinger GS, Eren M, Diedrich PR. Treatment effects of intraoral appliances with conventional anchorage designs for noncompliance maxillary molar distalization: a literature review. Eur J Orthod 2008;30:558-71.

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American Journal of Orthodontics and Dentofacial Orthopedics

Treatment effects of a modified palatal anchorage plate for distalization evaluated with cone-beam computed tomography.

The purpose of this study was to evaluate the treatment effects of maxillary posterior tooth distalization performed by a modified palatal anchorage p...
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