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The European Journal of Orthodontics Advance Access originally published online on October 18, 2007
The European Journal of Orthodontics 2008 30(1):73-79; doi:10.1093/ejo/cjm083
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© The Author 2007. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oxfordjournals.org.

Three-dimensional bimetric maxillary distalization arches compared with a modified Begg intraoral distalization system

Ayse Tuba Altug-Atac, Dilek Erdem and Züleyha Mirzen Arat

Department of Orthodontics, School of Dentistry, University of Ankara, Turkey

Address for correspondence, Ayse Tuba Altug-Atac, Ankara Universitesi, Dis Hekimligi Fakultesi, Ortodonti Anabilim Dali, 06500 Besevler, Ankara, Turkey, E-mail: aysealtug{at}yahoo.com


   Summary
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 Summary
Introduction
 Subjects and methods
 Results
 Discussion
 Conclusions
 Funding
 References
 
The purpose of this study was to compare the dentofacial effects of two intraoral molar distalization techniques [three-dimensional bimetric maxillary distalization arches (3D-BMDA) and a modified Begg intraoral distalization system (MBIDS)] in subjects requiring maxillary molar distalization. Twenty-one patients (12 females and 9 males, mean age pre-treatment: 14.7 ± 1.50 years) were treated with the 3D-BMDA and 17 (14 females and 3 males, mean age pre-treatment: 14.4 ± 1.43 years) with the MBIDS. Measurements were recorded from lateral cephalometric radiographs taken at two different points in time: at the start of treatment for the MBIDS group and prior to distalization for the 3D-BMDA group (T1) and post-distalization (T2). Student's t- and paired t-tests were used to determine differences between and within the groups.

The total amount of distalization for the 3D-BMDA and MBIDS groups was similar (3.55 and 3.27 mm, respectively). However, there were statistically significant differences in the length of the distalization period (3.4 and 6.5 months, respectively) and the amount monthly of distalization (1.11 and 0.54 mm, respectively). The most significant differences were observed in the mandibular dental arches and vertical facial dimensions. Anchorage loss in the mandible was greater in the 3D-BMDA group, whereas increases in facial dimensions were greater in the MBIDS group. Both 3D-BMDA and MBIDS techniques were found to be effective to obtain distal movement of the maxillary molars. In order to achieve successful results, the side-effects of each treatment modality on dentofacial structures need to be taken into consideration.


   Introduction
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 Summary
 Introduction
Subjects and methods
 Results
 Discussion
 Conclusions
 Funding
 References
 
Three-dimensional bimetric maxillary distalization arches (3D-BMDA) was introduced for the correction of Class II malocclusions by Wilson (1978)Go and Wilson and Wilson (1980Go, 1984Go, 1987Go, 1988Go). With this system, the maxillary molars are distalized using an open coil spring and Class II elastics (Wilson and Wilson, 1987Go, 1988Go).

The dental and skeletal effects of the 3D-BMDA have been previously evaluated (Muse et al., 1993Go; Yuksel et al., 1996Go; Rana and Becher, 2000Go; Ucem et al., 2000Go; Altug-Atac and Erdem, 2007Go); however, there are no publications evaluating the effects of the ‘modified Begg intraoral distalization system (MBIDS)’. The purpose of this study was to introduce a MBIDS and compare the effects of the 3D-BMDA and the MBIDS on dentofacial structures in subjects requiring maxillary molar distalization.


   Subjects and methods
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 Summary
 Introduction
 Subjects and methods
Results
 Discussion
 Conclusions
 Funding
 References
 
The subjects were randomly selected from among those referred to the Department of Orthodontics of Ankara University. Informed consent was obtained from each patient or his/her parent prior to treatment.

The inclusion criteria were as follows:

  1. Skeletal Class I or Class II malocclusion and a dental Class II relationship on both sides;
  2. Non-extraction treatment plan;
  3. SN/GoGn angle less than 40 degrees;
  4. No/minimal crowding in the mandibular dental arch;
  5. Erupted maxillary and mandibular second molars in occlusion.

Table 1 shows the gender and age and the distalization periods of the subjects in each treatment group. Although 50 patients were initially selected for inclusion in the study, 12 were later excluded due to problems of non-cooperation during treatment. The patients were randomly selected and distributed to the treatment groups without regard for gender. As a result of both randomization and dropout, although the number of females in each group were similar (3D-BMDA = 12 and MBIDS = 14), the number of males varied significantly (3D-BMDA = 9 and MBIDS = 3).


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  		Table 1. The mean (X), standard errors (Sx), and minimum (min) and maximum (max) values of the age, gender, and distalization periods of the subjects in the treatment groups.

 
In the 3D-BMDA group, a full-bonded mandibular dental arch was used as an anchorage unit for Class II elastics (Figure 1a–c), with a 0.019 x 0.025 inch lower archwire to increase anchorage. The elastic load reduction principle (Wilson and Wilson, 1988Go) was modified for each patient, with an initial elastic force of approximately 175–185g applied by adjusting the load until the 3D-BMDA was seated inside the 0.022 inch straight wire bracket slot. The patients were examined at 10 day intervals, and the elastic loads were checked and adjusted at each visit.


Figure 1
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  		Figure 1 Three-dimensional bimetric maxillary distalization arches (3D-BMDA); in a 16-year-old female patient treated by 3D-BMDA. (a) Occlusion before maxillary molar distalization, (b) 3D-BMDA in place supported by intermaxillary Class II elastics, and (c) occlusion after 3D-BMDA therapy.

 
In the MBIDS group, both maxillary and mandibular dental arches (including mandibular second molars) were banded and bonded with Begg fixed appliances. The maxillary distalization arch was prepared using a 0.018 inch special plus Australian wire (TP Orthodontics, La Porte, Indiana, USA) consisting of bilateral vertical loops with two helixes resting mesial to the maxillary molar tubes. A plain mandibular archwire (0.018 inch) bent with anchorage bends to reinforce the molar anchorage was used. Uprighting springs were also added to the mandibular first and second premolars to prevent mesial drift of the mandibular molars from the Class II elastics (Figure 2a–d). For each patient, an initial elastic force of approximately 80–85g was applied by adjusting the load until the distalization arch was seated inside the Begg bracket slot.


Figure 2
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  		Figure 2 Modified Begg intraoral distalization system (MBIDS); (a) maxillary 0.018 inch Australian wire distalization arch with bilateral double-twisted single vertical loop; (b) the distalization arch positioned one loop width anterior of the maxillary incisors; (c) the uprighting springs to reinforce the mandibular anchorage and activation of the arch with intermaxillary Class II elastics; and (d) occlusion after MBIDS therapy.

 
Lateral cephalometric radiographs were taken for both groups at two different time points: at the start of treatment for the MBIDS group and just prior to distalization for the 3D-BMDA group (T1) and after molar distalization was complete (T2).

A total of 11 angular and 25 linear parameters were measured in order to determine differences in the effects of the 3D-BMDA and the MBIDS. Total structural superimpositions were used to evaluate craniofacial and soft tissue changes (Björk and Skieller, 1983Go). Reference planes were drawn on T1 and transferred to T2 radiographs, using sella–nasion (S–N) plane as the horizontal reference plane and the perpendicular to SN through point S as the vertical reference plane. Maxillary and mandibular local superimpositions were used to evaluate dentoalveolar changes. Maxillary local superimpositions were established along the palatal plane (ANS–PNS) registered at ANS (Broadbent, 1937Go). Mandibular local superimpositions were performed based on the structural methods of Björk and Skieller (1983)Go. Reference planes were transferred from T1 to T2 radiographs using these superimpositions. Total (Figure 3a,b), maxillary (Figure 4a) and mandibular (Figure 4b) measurements were recorded from the total vertical and horizontal and local vertical and horizontal reference planes.


Figure 3
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  		Figure 3 Angular (a) 1: SNA, 2: SNB, 3: ANB, 4: SN/GoGn, 5: SN/PP, 17: SN/Occ and linear (b) 8: PNS–HR, 9: ANS–HR, 10: N–Me, 11: N–ANS, 12: ANS–Me, 13: S–Go, 14: Co–A, 15: Co–Gn, 16: Co–Go, 23: overjet, 24: overbite, 35: Ls–(Steiner), 36: Li–(Steiner) measurements on total tracings.

 

Figure 4
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  		Figure 4 (a) Measurements on maxillary 6: A–max.VR, 18: U1/max.HR, 19: U6/max.HR, 20: U7/max.HR, 25: U1i–max.VR, 26: U6t–max.VR, 27: U7t–max.VR, 28: U1i–max.HR, 29: U6t–max.HR, 30: U7t–max.HR and (b) mandibular 7: B–mand.VR, 21: L1/mand.HR, 22: L6/mand.HR, 31: L1i–mand.VR, 32: L6t–mand.VR, 33: L1i–mand.HR, 34: L6t–mand.HR. local tracings.

 

Statistical analysis

The mean and standard error of the mean were calculated for each variable. Student's t-tests were used to compare differences in pre-treatment measurements between the groups (Table 2). Paired t-tests were used to determine significant changes between pre- (T1) and post (T2)-treatment measurements within each group (Table 3). Student's t-tests were also used to compare differences in the amount of change between the groups (Table 3).


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  		Table 2. Comparison of the initial values of three-dimensional biometric maxillary distalization arch (3D-BMDA) prior to molar distalization and the modified Begg intraoral molar distalization group (MBIDS) at the beginning of fixed appliance therapy (X, mean and Sx, standard error of the mean, and Sd, standard error of the differences) by Student's t-test.

 

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  		Table 3. Comparison of the means of differences (D) and standard error of the differences (Sd) between the three-dimensional bimetric maxillary distalization arches (3D-BMDA) and the modified Begg intraoral distalization system (MBIDS) groups by Student's t-test.

 

Error study

Twenty randomly selected cephalograms were retraced by the same author (ATA-A) after a period of 1 month. No significant differences were found between the two series. Reliability coefficients (r) ranged from 0.93 to 0.99.


   Results
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 Summary
 Introduction
 Subjects and methods
 Results
Discussion
 Conclusions
 Funding
 References
 
Cephalometric measurements for the 3D-BMDA group prior to molar distalization and of the MBIDS group at the beginning of fixed appliance therapy are shown in Table 2 and comparison of the treatment changes in Table 3.

A Class I molar relationship was achieved in 3.4 months in the 3D-BMDA group and in 6.5 months in the MBIDS group (Table 1).

Sufficient distalization of the maxillary molars was achieved in both intraoral distalization groups. However, as Table 3 shows, the rate of distal molar movement was significantly greater in the 3D-BMDA group (1.11 ± 0.13 mm/month) than in the MBIDS group (0.54 ± 0.17 mm/month, P < 0.001).

The mean amount of distalization, intrusion, and distal tipping of the maxillary molars was similar in both groups. However, first and second maxillary molar intrusion (U6t–max.HR and U7t–max.HR: P < 0.05) and mandibular molar extrusion were greater in the MBIDS group (L6t–mand.HR: P < 0.01).

Mesial tipping of the mandibular first molars was significantly greater in the 3D-BMDA group (L6/mand.HR), whereas proclination of the mandibular incisors was significantly greater in the MBIDS group (L1/mand.HR and L1i–mand.VR, P < 0.001).

Increases in the occlusal plane angle and decreases in overbite were also significantly greater in the MBIDS group (P < 0.01 and P < 0.001, respectively).

The decrease in ANB was statistically significant (P < 0.05) in the MBIDS group, whereas the increase in SNB was statistically significant (P < 0.05) in the 3D-BMDA group. However, the changes in these angles did not differ significantly between the groups. There were significant differences (P < 0.05) between the groups with respect to changes in A–max.VR, which decreased significantly (P < 0.01) in the 3D-BMDA group, but not in the MBIDS group.

SN/GoGn angle remained stable in the 3D-BMDA group, despite statistically significant changes in the vertical position of the molars, whereas in the MBIDS group this angle significantly increased (P < 0.05). Co–Gn, Co–Go, and S–Go increased significantly in both groups.

N–Me and ANS–Me increased in both the MBIDS and 3D-BMDA groups; however, the increases were significantly greater in the MBIDS group in comparison with the 3D-BMDA group (P < 0.001 and P < 0.01, respectively).

The lower lip protruded significantly in both groups; however, protrusion was significantly greater in the MBIDS group (P < 0.01).


   Discussion
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 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
Conclusions
 Funding
 References
 

Anchorage maintenance

Although intraoral molar distalization techniques are looked upon positively because they do not rely on patient co-operation for their effects, they unfortunately result in anchorage loss in different areas of the dental arches. With the use of intramaxillary intraoral techniques, e.g. magnets (Blechman and Smiley, 1978Go), superelastic NiTi coils (Gianelly et al., 1991Go), pendulum (Hilgers, 1992Go), Jones jig (Jones and White, 1992Go), and distal jet (Carano and Testa, 1996Go), anchorage loss is frequently observed in the maxillary anterior region. In intermaxillary intraoral techniques (e.g. 3D-BMDA and MBIDS), significant anchorage loss has been observed in the mandibular dental arch as a result of the intermaxillary Class II elastics used as part of the system (Reddy et al., 2000Go; Ucem et al., 2000Go). In the present study, a Class I molar relationship was successfully achieved using both 3D-BMDA and MBIDS. Although the maxillary molars were distalized significantly in both groups, mesial movement of the mandibular molars due to anchorage loss caused by the intermaxillary Class II elastics affected the final results. These results show that the traditional full-bonded mandibular arch is insufficient for controlling anchorage, even when reinforced by lingual crown torque in the 3D-BMDA group and by uprighting springs in the MBIDS group. A 4.40 mm proclination of the mandibular incisors was observed in the MBIDS group, indicating anchorage loss in the anterior region. However, it should be noted that the elimination of anterior crowding only accounts for part of this anterior movement. There was also less mesial movement of the mandibular molars observed in the MBIDS group in comparison with the 3D-BMDA group. This finding supports the assumption that all facets of anchorage loss in the MBIDS group were lower than in the 3D-BMDA because of the use of uprighting springs on the premolars and the use of the mandibular second molars as anchorage units for intermaxillary elastics.


Mandibular rotation

The posterior rotation of the mandible was not significant in the 3D-BMDA group (mean 0.01 degrees), but was significant (P < 0.01) in the MBIDS group (mean 0.81 degrees). The difference between the groups was also statistically significant (P < 0.05). However, even in the MBIDS group, rotation was less than 1 degree, which is acceptable in patients treated with continuous Class II elastics. Interestingly, in both groups, the relative lack of mandibular rotation was accompanied by significant extrusion of the mandibular molars, which previous reports have shown to cause significant rotation (Reddy et al., 2000Go; Ucem et al., 2000Go). This contradiction may be explained by the compensatory increase in posterior face and ramus heights in both groups occurring as a result of condylar growth, which is indicated by the significant increases in Co–Gn and Co–Go in both groups.


Maxillary changes

A–max.VR remained nearly stable in the MBIDS group, but decreased significantly in the 3D-BMDA group (–0.85 mm, P < 0.01). This posterior movement of point A could be explained by the backward movement of the maxillary incisor roots. While the intermaxillary elastics inhibited protrusion of the incisor crowns (0.06 mm), the incisor roots showed a slight palatal movement, resulting in a –0.85-mm movement of point A.


Maxillary incisor extrusion

Intermaxillary Class II elastics were found to have caused significant maxillary incisor extrusion in both treatment groups. Extrusion of the maxillary incisors is a common finding in studies involving intermaxillary Class II elastics (Muse et al., 1993Go; Doganay, 1996Go; Rana and Becher, 2000Go).


Lower lip

The lower lip protruded in both groups; however, this protrusion was greater in the MBIDS group (P < 0.01). These findings are consistent with the movements of the maxillary and mandibular incisors.


   Conclusions
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
 Conclusions
Funding
 References
 

  1. Both 3D-BMDA and MBIDS techniques are effective in distalization of the maxillary molars.
  2. Iny addition to the distalization of the maxillary molars, the mesial movement of the mandibular molars contributed to the achievement of a Class I relationship in both groups of patients.
  3. The rate of distal molar movement was significantly greater in the 3D-BMDA group than in the MBIDS group.
  4. Moderate anchorage loss in the mandibular dental arch was observed in both groups; however, this was less in the MBIDS group.
  5. Full-bonded dental arches are not sufficient for supporting mandibular anchorage.
  6. The effects of treatment modality on dentofacial structures need to be taken into consideration for each individual patient in order to achieve successful results with either of these techniques.


   Funding
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
 Conclusions
 Funding
References
 
Ankara University Research Foundation (Project No: 980200002).


   References
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
 Conclusions
 Funding
 References
 

    Altug-Atac AT, Erdem D. Effects of three-dimensional bimetric maxillary distalizing arches and cervical headgear on dentofacial structures. European Journal of Orthodontics (2007) 29:52–59.[Abstract/Free Full Text]

    Björk A, Skieller V. Normal and abnormal growth of the mandible. A synthesis of longitudinal cephalometric implant studies over a period of 25 years. European Journal of Orthodontics (1983) 5:1–46.[Abstract/Free Full Text]

    Blechman AM, Smiley H. Magnetic force in orthodontics. American Journal of Orthodontics (1978) 74:435–443.[CrossRef][Web of Science][Medline]

    Broadbent BH. Bolton standards and technique in orthodontic practice. Angle Orthodontist (1937) 7:209–233.

    Carano A, Testa M. The distal jet for upper molar distalization. Journal of Clinical Orthodontics (1996) 30:374–380.[Medline]

    Doganay A. The clinical evaluation of bimetric distalizing arches in maxillary first molar distalization. In: Thesis, (1996) Turkey: Marmara University.

    Gianelly A A, Bednar J, Dietz VS, et al. Japanese NiTi coils used to move molars distally. American Journal of Orthodontics and Dentofacial Orthopedics (1991) 99:564–566.[Web of Science][Medline]

    Hilgers JJ. The pendulum appliance for Class II non-compliance therapy. Journal of Clinical Orthodontics (1992) 26:706–714.[Medline]

    Jones RD, White JM. Rapid Class II molar correction with an open coil jig. Journal of Clinical Orthodontics (1992) 16:661–664.

    Muse DS, Fillman MJ, Emmerson WJ, Mitchell RD, et al. Molar and incisor changes with Wilson rapid molar distalization. American Journal of Orthodontics and Dentofacial Orthopedics (1993) 104:556–565.[Web of Science][Medline]

    Rana R, Becher MK. Class II correction using the bimetric distalizing arch. Seminars in Orthodontics (2000) 6:106–118.[CrossRef]

    Reddy P, Kharbanda OP, Duggal R, Parkash H, et al. Skeletal and dental changes with nonextraction Begg mechanotherapy in patients with Class II division 1 malocclusion. American Journal of Orthodontics and Dentofacial Orthopedics (2000) 118:641–648.[CrossRef][Web of Science][Medline]

    Ucem TT, Yuksel S, Okay C, Gulsen A, et al. Effects of a three-dimensional bimetric maxillary distalizing arch. European Journal of Orthodontics (2000) 22:293–298.[Abstract/Free Full Text]

    Wilson WL. Modular orthodontic systems. Part 1. Journal of Clinical Orthodontics (1978) 11:250–278.

    Wilson WL, Wilson RC. New treatment dimensions with first phase sectional and progressive edgewise mechanics. Journal of Clinical Orthodontics (1980) 14:607–627.[Medline]

    Wilson WL, Wilson RC. Modular 3D appliances. Problem solving in edgewise, straight wire and light wire treatment. Journal of Clinical Orthodontics (1984) 8:272–281.

    Wilson WL, Wilson RC. Multidirectional 3D functional Class 2 treatment. Journal of Clinical Orthodontics (1987) 21:186–189.[Medline]

    Wilson WL, Wilson RC. Enhanced orthodontics. Book 1, concept, treatment and case histories (1988) Denver, Colorado: Rocky Mountain Orthodontics.

    Yuksel S, Gulsen A, Ucem TT, et al. Molar distalization with modified 3D bimetric maxillary distalizing arches. Turkish Orthodontic Journal (1996) 9:229–235.


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This Article
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