To determine the skeletal and dentoalveolar effects produced by the MARA and the AdvanSync functional appliances in the treatment of growing patients with Class II malocclusion.
A retrospective study was conducted using lateral cephalograms of patients consecutively treated with MARA (n = 40) and AdvanSync (n = 30) during their skeletal growth spurt as evaluated by the improved cervical vertebral maturation method. A comparison was made with 24 untreated Class II control subjects obtained from the University of Michigan growth study and matched with the experimental groups for skeletal age, sex, and craniofacial morphology. Cephalograms were taken at three time points: (T1) pretreatment, (T2) postfunctional appliance treatment, and (T3) fixed orthodontic treatment completion. Treatment changes were evaluated between the time points using 35 variables. Data were analyzed using one-way analysis of variance and Scheffe's post hoc test.
At the postfunctional appliances' phase (T2–T1), both appliances showed significant increases in total mandibular length, ramus height, and anterior/posterior facial height. The AdvanSync resulted in significant restriction of maxillary growth, 1° more than MARA. This effect continued during the fixed orthodontic treatment stage (T3–T2). The net changes (T3–T1) revealed significant mandibular growth enhancement with MARA (+2.7mm) and significant headgear effect with AdvanSync. Both appliances caused 5° flaring in mandibular incisors as well as significant decreases in overjet and overbite. The treatment time for AdvanSync was 1 year less than MARA.
The MARA and the AdvanSync resulted in normalization of the Class II malocclusion. The AdvanSync showed more headgear effect but less mandibular length enhancement than MARA did. Both appliances showed similar dentoalveolar changes.
Of the fixed functional appliances available to the orthodontist today for the correction of Class II dentoskeletal malocclusion are the mandibular anterior repositioning appliance (MARA)1 (AOA, Sturtevant, Wis) and the AdvanSync2 (also known as Molar to Molar appliance; Ormco Co, Glendora, Calif), in addition to others. Both the MARA and the AdvanSync are fixed tooth-born functional appliances consisting of crowns cemented on maxillary and mandibular permanent first molars, a position where orthopedic forces are applied. They have the advantage of allowing concurrent treatment with preadjusted edgewise appliances and therefore efficient normalization of the occlusion.
The efficacy of the MARA in correcting Class II malocclusions has been evaluated in a few studies.3–7 A recent study3 of 23 consecutively treated MARA patients concluded that the appliance resulted in significant elongation of the mandible and headgear effect of the maxilla compared with untreated controls. The study did not report sex differences nor did it compare its effects with other functional appliances. Pangrazio-Kulbersh et al.5 compared the treatment effects of the MARA with untreated controls and with banded Herbst and Frankel appliances' effects reported in previous studies. They found similar effects of the MARA to the Herbst but with less headgear effect on the maxilla and less mandibular incisor flaring. It also produced greater dentoalveolar changes than the Frankel II appliance. Their study, however, lacked a concurrent comparative treatment group to MARA. The effects of the AdvanSync are still not known.
No published studies were found comparing the MARA and the AdvanSync appliances. The aim of this retrospective cephalometric study is to evaluate the skeletal and dentoalveolar changes produced by the MARA and the AdvanSync during active treatment with the appliances and during follow-up including edgewise fixed orthodontic treatment.
MATERIALS AND METHODS
A retrospective study was conducted using lateral cephalograms in habitual occlusion of adolescent patients who received treatment for their Class II skeletal malocclusions using the MARA or the AdvanSync functional appliances. Measurements on cephalograms were made at three time points: (T1) pretreatment, (T2) at functional appliance treatment completion, and (T3) at fixed orthodontic treatment completion. Approval for this study was obtained from the Health Sciences Institutional Research Board of the University at Buffalo.
The inclusion criteria were: white healthy boys and girls presenting with Class II malocclusion with the molars in at least an end-to-end relationship, presenting during the peak growth spurt as indicated by the improved version of the cervical vertebral maturation (CVM) method,8 retrognathic mandible (SNB ≤77°), ANB angle ≥4°, normal Frankfort to Mandibular plane angle (FMA° = 25 ± 5°), overjet <10 mm, no missing teeth, a nonextraction treatment approach, crowns cemented on permanent maxillary and mandibular first molars, and the appliance maintained for at least 6 months.
The treatment groups included consecutively treated Class II malocclusion division 1 patients obtained from two orthodontists. Forty (22 males, 18 females) MARA patient records obtained from the cases treated by the developer of the appliance, Dr Douglas Toll, and 30 (13 males, 17 females) AdvanSync obtained from one author (Dr Dischinger) were included. Results were compared with 24 (13 males, 11 females) untreated control individuals obtained from the University of Michigan Growth Study Center and matched with the treatment groups for skeletal age, sex, and craniofacial morphology. Mean ages and treatment/observation durations for each group are listed in Table 1.
The MARA (AOA, Sturtevant, Wis) and the AdvanSync (Ormco Co, Glendora, Calif) were designed to allow simultaneous fixed orthodontic appliance treatment (0.022″ × 0.028″ slot edgewise bracket system in the included samples fully bonded at T1) with the brackets on the mandibular incisors having a built-in labial root torque. Both functional appliances include stainless-steel crowns with single archwire tubes on permanent first molars. The MARA's upper crowns are also attached to 0.062″ square tubes to accommodate 0.060″ upper elbows and lower crowns with soldered lower protruding arms. The crowns are attached to lower lingual holding arches (2–3 mm lingual to mandibular incisors) to prevent mesiolingual rotation of the molars. This side effect can also be prevented by bonding lower anterior brackets. The AdvanSync did not include lower lingual holding arches, and the maxillary and mandibular crowns of this appliance are connected by telescoping rods.
The treatment protocols used by the MARA and the AdvanSync developers include stepwise activation as judged by the severity of the overjet.9,10 The appliances are activated 2 to 4 mm every 3 months over a 12-month (for MARA) and 6- to 12-month (for AdvanSync) duration until slight dental overcorrection is achieved with the MARA and moderate overcorrection with the AdvanSync. The occlusion with the AdvanSync is overcorrected to an anterior crossbite and a Class III canine relationship with the maxillary canine in an end-to-end relationship with the mandibular first premolar or in a full-tooth relationship in the more severe cases. Once the appliances are removed, edgewise fixed orthodontic treatment is continued to achieve correct anterior torque and occlusion and adequate finish.
The lateral cephalograms representing the treatment groups were scanned with an Epson Expression 1680 Pro (Epson USA, Long Beach, Calif) and with the use of Adobe Photoshop 6.0; the scanning resolution was set at 300 dpi and color depth at 16-bit grayscale. All cephalograms were then imported into commercial software (Dolphin Digital Imaging system version 11, Chatsworth, Calif), where they were digitally traced using a customized digitization set that included 58 landmarks and four fiducial markers. Thirty-five variables were produced per x-ray and were chosen from different cephalometric analyses.11–14 Magnifications of x-rays were 8% for the MARA group, 6% and 10% for the AdvanSync group (two different x-ray machines), and 12.9% for the untreated controls. For standardization purposes, the magnification was corrected to 8% for all cephalograms.
The tracings and measurements were carried out by one author and validated by another. Any disagreement was resolved by retracing after discussion. Linear measurements were made to the nearest 0.5 mm and angular measurements to the nearest 0.5°. Superimpositions were conducted manually. The overall craniofacial treatment changes were evaluated by superimposing on the S-N line, registered at Sella. Regional superimpositions in the maxilla were made along the palatal plane and registering on the internal structures of the maxilla above the incisors and the surfaces of the hard palate.12,13 The mandibular regional superimposition was made on the inner contour of the posterior symphysis, the outline of the inferior mandibular canal, and the germ of the third molar prior to root development (if present).12,13 Superimpositions to evaluate sagittal and vertical dentoalveolar changes were conducted using the method described earlier by McNamara.12 All of the registrations were repeated twice to ensure accuracy.
To determine accuracy of the method, 15 randomly chosen cephalograms were retraced, remeasured, and superimposed 2 weeks apart by one investigator using the same landmarks and variables included in this study. Measurements were calculated using the intraclass correlation coefficient, and they showed high reliability (between .86 and .98) and were all within 1 mm/1° of the original. The average error did not exceed 0.3 mm/0.30°.
Data were analyzed using SPSS (SPSS version 16 for Windows, Chicago, Ill). Descriptive statistics were conducted initially, and means and standard deviations were calculated. Data were normally distributed; therefore, parametric tests were conducted. A one-way analysis of variance was used to compare differences among the three groups at baseline and to evaluate the changes at each time point. Scheffe's post hoc analysis was used for multiple comparisons. Statistical tests were interpreted at the 5% significance level.
When the initial records of the three groups were compared (T1), the dentoskeletal characteristics of the three groups were generally similar except for four measurements. The MARA group had increased maxillary protrusion (Co-Pt A; P < .001), mandibular corpus length (Go-Gn; P = .002), and Wits appraisal (P = .004) compared with controls. Both the MARA and the AdvanSync groups showed more distally positioned mandibular molars (P < .001) than the controls.
Table 2 illustrates the T2–T1 differences between groups. The AdvanSync restricted maxillary growth “headgear effect” as indicated by SNA° (−2°). Both treatment groups showed significant increases in the total lengths of the mandible (Co-Gn), the ramus height (Co-Go), and the anterior and posterior facial heights. The dentoalveolar measurements revealed significant retroclination of the maxillary incisors relative to Frankfort horizontal in the AdvanSync group in addition to nonsignificant eruption and distalization of maxillary molars. The mandibular incisors proclined 5°, and the mandibular molars moved forward (+2 mm) with MARA and AdvanSync (P < .001) over controls.
The treatment effects at follow-up (T3–T2) are presented in Table 3. The AdvanSync in comparison to controls showed a continued significant restraining in maxillary growth, less increase in ramus height (Co-Go; P < .001), and more relapse in the Wits appraisal and maxillary molars' horizontal position. All interdental measurements were statistically significant for the same group.
The net treatment changes (T3–T1) showed a significant headgear effect in the AdvanSync group (Table 4). The mandibular growth enhancement (Co-Gn) was significant with MARA (+2.7 mm) and not significant with AdvanSync over controls. Figure 1 depicts the changes in the total mandibular length (Co-Gn) between the three time points. Both treatment modalities resulted in reduction in the ANB° and the angle of convexity and an increase in the anterior and posterior facial height over controls. The anterior/posterior facial height of the Advan-Sync group was less than MARA. The mandibular molars erupted and drifted forward more than 3 mm in both groups. Interdentally, significant decreases in overjet and overbite were observed. Sex differences between the groups were analyzed at the three time points, but the small samples did not allow reliable subanalyses.
This is a retrospective cephalometric study of the dentoskeletal treatment effects of the MARA and the AdvanSync functional appliances with edgewise fixed orthodontic treatment in Class II skeletal malocclusion correction of patients treated during their growth spurt. The results showed that the differences between the two treatment modalities are modest with few exceptions.
At the completion of functional appliances treatment (T2–T1), the MARA and the AdvanSync showed significant skeletal increases in total mandibular lengths (+1.9 mm and +1.4 mm, respectively). Similar effects were reported in previous studies of the MARA over untreated controls.3,5 In addition, the AdvanSync showed significant restriction in maxillary growth. These findings confirm a short-term orthopedic effect on the maxilla and the mandible of this appliance. This is similar to the short-term effects documented in multiple studies of the Herbst appliance.15–17 VanLaecken et al.16 in a cephalometric study of 52 consecutively treated patients with the edgewise Herbst appliance found that after 8 months of Herbst treatment, the mandible moved forward 1.7 mm and the maxilla underwent temporary growth restriction of 1.4 mm in addition to other dentoalveolar effects. The MARA in our study did not show a significant headgear effect despite the significant larger maxillary length at starting form. Results of previous studies are inconsistent with respect to this measurement.3,5,6 This could be attributed to the different methodologies used in the studies, and many did not consider skeletal age at case inclusion. Although the mandibular body increased in length with MARA, it underwent a slight decrease in the AdvanSync group when compared with controls.
The mandibular molars in both treatment groups at the end of T2–T1 moved forward (+2 mm) more than controls, and the findings were significant. Pangrrazio-Kulbresh et al.5 in an earlier study evaluated pretreatment and posttreatment changes in 30 Class II patients treated with MARA and compared them to 21 untreated controls and found that the mandibular molars moved forward a mean distance of 1.2 mm versus 0.5 mm in controls, which accounted for some of the Class II correction. The difference in the forward drift between our study and the previous study can be explained by the increased distal position of the mandibular molars at the starting forms for both treatment groups. The AdvanSync also showed significant clockwise rotation of the functional occlusal plane. This can be explained by the significant proclination of the mandibular incisors. The mandibular incisor to the mandibular plane angle in both appliances showed an increase of 5° over controls. This finding is in agreement with many earlier studies17–19 that evaluated the dentoalveolar effects of functional appliances and is greater with tooth-born appliances than tissue-born ones such as the Frankel appliance.19
The skeletal changes during follow-up (T3–T2) were not significantly different from controls for the MARA group. The patients started treatment during the skeletal growth spurt, and during this follow-up phase, they might have passed the growth spurt. This can explain the stability of the changes during the follow-up phase. The AdvanSync, on the other hand, showed a continued restraining effect on maxillary growth. The mandibular growth enhancement, however, did not remain significant. This finding was reported in studies of the effects of the Twin block appliance on patients treated during the peak growth spurt in which the mandibular elongation does not differ from controls after active treatment with the appliance.20 It is also similar to studies of other appliances such as the Herbst appliance when evaluated during the active treatment phase and during the fixed orthodontic treatment phase.21 In addition, the rebound in the overcorrected Wits appraisal measurements and overjet was significant in the AdvanSync group. This is expected since the treatment protocol includes greater overcorrection at the end of the functional appliance phase (T2–T1) than with the MARA.
The net changes at the completion of fixed orthodontic treatment (T3–T1) revealed different orthopedic effects of the two treatment modalities. A significant restriction in maxillary growth was evident with AdvanSync. The MARA induced a larger mandibular growth enhancement than AdvanSync and controls. This confirms a mandibular growth modification effect of this appliance. This could also be related to the significantly larger mandibular length of MARA group at starting forms. It has to be noted that the effects of the condyle/fossa were not evaluated in this study.
Previous studies of the Herbst appliance have documented significant intrusion of maxillary first molars.16 Our study found slight eruption of maxillary molars with the use of both treatment modalities, but the finding was not significant.
To our knowledge, this is the first study to report on the treatment effects of the AdvanSync appliance. It should be noted that ethical principles precluded the use of a concurrent control group; therefore, a historical control sample was used that might or might not be similar to the experimental group in the growth pattern. This study assumed that the growth pattern of the controls was linear and matched the experimental groups. The clinical effects in this cephalometric study cannot be completely explained by the growth modification effects of the examined appliances. Other factors using different methods of evaluation such as tomographic studies of the temporomandibular joints should be investigated. This warrants the need for longitudinal follow-up comparative studies of patients who received treatment with the appliances after treatment completion and growth cessation.
Both the MARA and AdvanSync affect the skeletal and dentoalveolar craniofacial complex and are effective in normalizing the Class II malocclusion to Class I in patients treated during the skeletal growth spurt.
The MARA produced a significant elongation in the total length of the mandible.
The AdvanSync resulted in significant headgear effect when compared with MARA and controls and maintained the Class I relationship at T3–T1.
Both appliances resulted in similar dentoalveolar findings.
We would like to express our appreciation to Douglas E. Toll for providing the MARA sample for this study and Robert Dunford for his help during the statistical analysis of the data. We also thank James A. McNamara Jr. the curator of the Michigan Growth Study for his help.