ORIGINAL ARTICLE
Apical root resorption comparison between Fränkel and eruption guidance appliances Guilherme Janson,a Alexandre Nakamura,b Marcos Roberto de Freitas,a José Fernando Castanha Henriques,a and Arnaldo Pinzanc Bauru, São Paulo, Brazil Introduction: The objectives of this study were to compare the amounts of apical root resorption that occur after treatment with 2 removable appliances—the Fränkel function regulator and the eruption guidance appliance (EGA)—in an untreated control group, and to determine the prevalence of root resorption in the maxillary and mandibular incisors and the dental arches. Methods: After treatment, periapical radiographs were obtained of the maxillary and mandibular incisors with the long-cone paralleling technique from 72 patients divided into 3 groups. Group 1 included 24 patients treated with the Fränkel appliance, group 2 consisted of 24 patients treated with the EGA, and group 3 comprised 24 untreated subjects. Some patients in groups 1 and 2 were also treated with fixed appliances. Subgroups of patients who had used exclusively 1 functional appliance were also formed and evaluated. Root resorption was scored according to the method of Levander and Malmgren. Results: Results of the Kruskal-Wallis tests showed significantly greater resorption in the Fränkel group, the EGA group, and the EGA subgroup in relation to the control group. However, there were no statistically significant differences between the Fränkel and the EGA groups and the subgroups. The amounts of resorption were predominantly small and similar in the experimental groups and the subgroups. The prevalence of resorption for the incisors was greatest for the maxillary central, followed by the maxillary lateral, mandibular central, and mandibular lateral. Conclusions: It was concluded that the Fränkel group, the EGA group, and the EGA subgroup had significantly greater resorption than the control group. There was no difference in the amount of resorption between the Fränkel and the EGA groups. (Am J Orthod Dentofacial Orthop 2007;131:729-35)
T
he function regulator (FR) was developed by Fränkel1 for use during the mixed or early permanent dentition. It differs from other functional appliances by protruding the mandible, ideally without contacting any mandibular and maxillary teeth. The stimulus for mandibular repositioning is provided by the inferior border of the vestibular shield, the lower labial pads that touch the labial mucosa, and, mainly, the lingual shield that touches the lingual mucosa.2 Studies of the effects of the FR in the treatment of Class II malocclusions demonstrated greater mandibular growth development, absence of maxillary growth changes, increase in lower anterior face height, palatal From the Department of Orthodontics, Bauru Dental School, University of São Paulo, São Paulo, Brazil. a Professor. b Associate professor. c Professor. Based on research by Alexandre Nakamura in partial fulfillment of the requirements for the degree of Master of Science in orthodontics at Bauru Dental School, University of São Paulo. Reprint requests to: Guilherme Janson, Department of Orthodontics, Bauru Dental School, University of São Paulo, Alameda Octávio Pinheiro Brisolla 9-75, Bauru, SP, 17012-901, Brazil; e-mail,
[email protected]. Submitted, March 2005; revised and accepted, June 2005. 0889-5406/$32.00 Copyright © 2007 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2005.06.038
tipping of maxillary incisors, labial tipping of mandibular incisors, and greater vertical development of mandibular molars compared with control samples.3-6 Other investigators found no increase in mandibular growth from the FR in the treatment of Class II malocclusions.7,8 On the other hand, eruption guidance appliances (EGAs) (Occlus-o-Guide, Ortho-Tain, Bayamon Gardens, Puerto Rico) are constructed of an elastomeric material with intercuspation for the maxillary and mandibular teeth in normal occlusion. These prefabricated appliances advance the mandible to correct Class II sagittal discrepancies, simultaneously producing anterior opening that allows greater vertical development of the posterior teeth, while producing minor tooth movement like a positioner.9-11 In general, Class II malocclusion correction with the EGA produces the following statistically significant changes: increases in mandibular growth and degree of mandibular protrusion, increases in lower anterior and total anterior face height, lingual tipping and retrusion of maxillary incisors and protrusion of mandibular incisors, increased mandibular molar mesial drifting and mandibular posterior dentoalveolar height, improvements in maxillomandibular and molar relationships, decreases in over729
730 Janson et al
jet and overbite, and inhibition of the vertical development of the maxillary incisors.10,12,13 There is good agreement that the FR and the EGA cause favorable anteroposterior apical base, molar relationship, and overjet changes.3,5,11,13-15 It has also been shown that the 2 appliances have similar efficacy in producing occlusal changes, regardless of treatment time.16 Root resorption with removable and functional appliances is mild.17-22 Resorption with the FR is also mild, as shown in a case report.23 However, root resorption investigations with the FR and the EGA have not been conducted so far. Therefore, the primary objective of this study was to evaluate the amount of root resorption after treatment with the FR and the EGA in relation to a control group and comparatively between the 2 appliances. We also determined the prevalence of root resorption in the maxillary and mandibular incisors and the dental arches. MATERIAL AND METHODS
Our sample consisted of patients who had completed treatment in the Orthodontic Graduate Clinic, Bauru Dental School, University of Säo Paulo, Brazil. Group 1 comprised 24 patients (14 boys, 10 girls) with an initial mean age of 9.69 years (range, 6.31-12.00 years) treated with the FR during a mean period of 3.59 years (range, 1.93-7.30 years). Twenty-one had Class II Division 1 malocclusions with at least an end-to-end Class II molar relationship (one half Class II), and 3 had mild Class III malocclusions. They were treated according to the methods of Fränkel and Fränkel2 and McNamara.24 A maximum initial mandibular advancement of 6 mm was performed in patients with overjet equal to or larger than this for the Class II patients.24 In patients with overjet greater than 6 mm, a second advancement was needed. The patients were instructed to use the appliance 18 hours a day. Fixed appliances were placed in 12 patients to align and detail their occlusions. The mean treatment time with fixed appliances was 1.67 years (range, 0.67-4.10 years). Group 2 consisted of 24 patients (11 boys, 13 girls) with an initial mean age of 9.13 years (range, 8.1811.05 years), treated with the G-series EGA9,25 for a mean time of 4.25 years (range, 0.84-7.72 years). Twenty-one had Class II Division 1 malocclusions with at least an end-to-end molar relationship, and 3 were Class I with excessive overbite. The appliance was recommended to be used while sleeping and for a minimum of 4 hours during the day. These 4 hours were divided into 4 periods of 1 hour each. In each 1-hour period, the patient was to bite into the appliance heavily for 1 minute and gently for the next minute for the first half hour. In the next half hour, the patient was
American Journal of Orthodontics and Dentofacial Orthopedics June 2007
only to bite gently into the appliance, always keeping the lips in contact.9,13,25 Once in the permanent dentition, multibracket appliances in both jaws, often combined with Class II elastics, were used in 9 patients for final adjustments. The mean treatment time of fixed appliances was 1.81 years (range, 0.55-3.83 years). To investigate whether complementary treatment with fixed appliances influenced the results, subgroups of patients who had been treated exclusively with removable appliances were formed and similarly compared. Periapical radiographs of 24 subjects were used as controls. All had Class II Division 1 malocclusions and mild anterior crowding. The controls were subjected to the same criteria applied to the treatment samples, except for the parameters for the treated patients. The selection criteria excluded patients with history of trauma at the pretreatment stage, endodontic treatment, nail-biting26 and other habits,27 and radiographic pathologic signs.28 Patients whose treatment had not been completed, regardless of compliance level, or whose treatment plans had changed either at the beginning of or during treatment, were not included. Patients with apical root resorption and those whose orthodontic records were incomplete were also excluded. Poor quality radiographs were also eliminated. None of the patients was being retreated. The orthodontic records were used to determine each patient’s sex and age at the beginning of therapy, type of treatment, removable appliance used, and treatment time. To quantify resorption, posttreatment periapical radiographs of the maxillary and mandibular incisors, totaling 576 teeth, were examined. The incisors were selected to represent root resorption because they are considered the most prone to root resorption during treatment.29 The posttreatment periapical radiographs were obtained with the DABI 70 Spectro 1070X x-ray machine (Dabi Atlante, Ribeirão Preto, Brazil), set up for 70 kV, 10 mA, and an exposure time of 1 second, with the long-cone paralleling technique. Kodak Ektaspeed EP 21 films (Eastman Kodak, Rochester, NY) were used, and the angles were obtained by an intraoral XCP positioner (Rinn-Dentisply, Elgin, Ill).30 All radiographs were processed automatically. All films were scanned, and the images were displayed and analyzed on a large computer monitor at 4-times magnification. Sources of variance inherent in research with dental radiographs (eg, different angulations, development times, operators) were not a concern because resorption was evaluated by the subjective score system of Levander and Malmgren,31 classifying
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Table I.
Intraexaminer error investigation (kappa statis-
tics) Tooth
Fig. Score system of Levander and Malmgren31 (redrawn): grade 0, no root resorption; grade 1, mild resorption—root with normal length and only irregular contour; grade 2, moderate resorption—small area of root loss with apex having almost straight contour; grade 3, accentuated resorption—loss of almost one third of root length; grade 4, extreme resorption—loss of more than one third of root length.
Percentage of agreement (%)
Coefficient value
Strength of agreement
90.00 83.33 83.33 86.67 86.67 86.67 90.00 83.33
0.84 0.74 0.71 0.80 0.75 0.78 0.83 0.71
Almost perfect Substantial Substantial Substantial Substantial Substantial Almost perfect Substantial
12 11 21 22 42 41 31 32
12, Maxillary right lateral incisor; 11, maxillary right central incisor; 21, maxillary left central incisor; 22, maxillary left lateral incisor; 42, mandibular right lateral incisor; 41, mandibular right central incisor; 31, mandibular left central incisor; 32, mandibular left lateral incisor. Table II.
31
it into 5 grades (Fig). The scores were blindly assigned by a previously calibrated examiner (A.N.). The resorption score was determined for each tooth; there were 8 evaluations per subject. Additionally, a mean resorption score was calculated for each subject. Thereafter, a mean for each group and subgroup, based on the mean for each subject, was calculated and compared between the groups and the subgroups.32 The reproducibility of the measurements was assessed by statistically analyzing the difference between double evaluations made 2 weeks apart on 30 randomly selected periapical radiographs (10 from each group). Agreement was tested with intraclass coefficients generated by kappa statistics.33
Comparison between initial age and treatment time (t test)
Group 1 ⫻ 2 Initial age Treatment time Subgroup 1 ⫻ 2 Initial age Treatment time
FR
EGA
Mean (SD)
Mean (SD)
P
9.69 (1.29) 3.59 (1.22)
9.13 (0.73) 4.25 (2.30)
.070 .226
9.67 (1.06) 3.18 (0.96)
9.18 (0.65) 3.28 (2.15)
.155 .882
Table III.
Comparison between evaluation ages (ANOVA followed by Tukey tests) Group 1 (n ⫽ 24)
Group 2 (n ⫽ 24)
Group 3 (n ⫽ 24)
Statistical analysis
Mean (SD)
Mean (SD)
Mean (SD)
F
P
Student t tests were used to evaluate compatibility of initial ages and treatment times between the experimental groups and the subgroups. Ages at which the radiographs were taken were compared with analysis of variance (ANOVA), followed by Tukey tests, as a second step. The difference in sex percentages in the groups was evaluated with chi-square tests. The amounts of root resorption (dependent variable) between the experimental groups and the control group, as well as between the subgroups and the control group (independent variables), were compared with the Kruskal-Wallis test, followed by Dunn nonparametric tests, as a second step. Results were considered significant at P⬍.05. Descriptive statistics were used to evaluate the prevalence of root resorption grades in each group and subgroup and the prevalence of root resorption in the incisors and the dental arches. Statistical computations
16.97 (3.58)
18.34 (2.04)
17.00 (3.16)
1.645
.200
were performed with Statistica 6.0 for Windows (Statsoft, Tulsa, Okla). RESULTS
Intraexaminer agreement was excellent (Table I). Coefficients demonstrated substantial or almost perfect agreement rates. The experimental groups and subgroups were well matched with respect to initial age, treatment time, evaluation age, and sex percentage in the groups (Tables II-IV). Both experimental groups and the EGA subgroup had more resorption than the control group. However, there were no statistical differences in degree of root resorption
732 Janson et al
American Journal of Orthodontics and Dentofacial Orthopedics June 2007
Table IV.
Comparison between sex percentages (chisquare tests)
Sex
Group 1 (n ⫽ 24)
Group 2 (n ⫽ 24)
Group 3 (n ⫽ 24)
N (%)
N (%)
N (%)
2
Table VI. Comparison between subgroups and group 3 (Kruskal-Wallis followed by Dunn tests)
P Tooth
Male Female
14 (58.3) 10 (41.7)
11 (45.8) 13 (54.2)
12 (50) 12 (50)
0.778
Subgroup 1 (n ⫽ 12)
Subgroup 2 (n ⫽ 15)
Group 3 (n ⫽ 24)
Median (mean)
Median (mean)
Median (mean)
P
.677
Table V.
Comparison between groups (Kruskal-Wallis followed by Dunn tests) Group 1 (n ⫽ 24)
Group 2 (n ⫽ 24)
Group 3 (n ⫽ 24)
Tooth
Median (mean)
Median (mean)
Median (mean)
P
12 11 21 22 42 41 31 32 Mean
1.00 (1.25)A 1.00 (1.12)A 1.00 (1.12)A 1.00 (1.12)A 1.00 (0.79)A 1.00 (0.83)A,B 1.00 (0.95)A 1.00 (0.70)A,B 0.87 (0.98)A
1.00 (0.91)A,B 1.00 (1.08)A 1.00 (0.95)A 1.00 (0.95)A 1.00 (0.62)A,B 1.00 (1.04)A 1.00 (0.95)A 1.00 (0.83)A 1.00 (0.92)A
0.00 (0.50)B 0.00 (0.41)B 0.00 (0.41)B 0.00 (0.45)B 0.00 (0.25)B 0.00 (0.41)B 0.00 (0.33)B 0.00 (0.25)B 0.31 (0.38)B
.001* .000* .000* .006* .002* .003* .000* .001* .000*
Different letters represent statistically significant differences in Dunn tests. *Statistically significant. 12, Maxillary right lateral incisor; 11, maxillary right central incisor; 21, maxillary left central incisor; 22, maxillary left lateral incisor; 42, mandibular right lateral incisor; 41, mandibular right central incisor; 31, mandibular left central incisor; 32, mandibular left lateral incisor.
between the experimental groups and between the subgroups at the end of treatment (Tables V and VI). The experimental groups and subgroups had a greater prevalence of mild resorption (grade 1). Extreme apical root resorption was not observed, and accentuated resorption was present only in patients treated with the FR, followed by fixed appliances (2 patients,1.82%, Table VII). The prevalence of resorption occurred in decreasing order: maxillary central incisors, maxillary lateral incisors, mandibular central incisors, and mandibular lateral incisors (Table VIII). DISCUSSION
Treatment variables play an important role in external apical root resorption after orthodontic tooth movement.34 It is difficult to obtain large groups treated by 1 operator with 2 appliances. Additionally, other studies had samples from various sources, and their authors stated that this factor would not interfere with the results.27,32,35-37
12 11 21 22 42 41 31 32 Mean
A
1.00 (0.91) 1.00 (0.66)A,B 1.00 (0.75)A,B 0.50 (0.58)A 1.00 (0.58)A 1.00 (0.58)A,B 1.00 (0.91)A,B 0.00 (0.33)A,B 0.68 (0.66)A,B
A
1.00 (0.86) 1.00 (1.00)A 1.00 (0.93)A 1.00 (0.73)A 1.00 (0.53)A 1.00 (1.06)A 1.00 (0.93)A 1.00 (0.73)A 0.87 (0.85)A
A
0.00 (0.50) 0.00 (0.41)B 0.00 (0.41)B 0.00 (0.45)A 0.00 (0.25)A 0.00 (0.41)B 0.00 (0.33)B 0.00 (0.25)B 0.31 (0.38)B
.093 .002* .007* .249 .087 .002* .001* .008* .005*
Different letters represent statistically significant differences in Dunn tests. *Statistically significant. 12, Maxillary right lateral incisor; 11, maxillary right central incisor; 21, maxillary left central incisor; 22, maxillary left lateral incisor; 42, mandibular right lateral incisor; 41, mandibular right central incisor; 31, mandibular left central incisor; 32, mandibular left lateral incisor.
The groups and subgroups were compatible with respect to initial ages, treatment times, evaluation ages, and sex percentages (Tables II-IV). The inclusion of 3 subjects with Class III and Class I malocclusions in groups 1 and 2, respectively, might be criticized. They were included because the appliances are designed to correct these discrepancies, and they also helped to increase the numbers of evaluated patients. It is unlikely that this interfered with the evaluation.36,37 Root morphology might play an important role in root resorption.31,34,38 Because the groups were not selected according to root morphology, it is reasonable to assume that the various types were evenly distributed in the groups. As shown in Table V, both the FR and the EGA, when followed by fixed appliance treatment, affect the morphology of root apexes similarly. Although the changes were significantly greater in relation to the control group, they were similar between the experimental groups. However, in the subgroups, which were treated with only 1 functional appliance, only the EGA group showed significantly greater resorption than the control group for most of the teeth, despite no difference with the FR subgroup (Table VI). Probably, this is because EGAs are primarily tooth-borne appliances with a vertical effect on the incisors.9,10 These appliances have thicker elastomeric material between the incisors to restrict their vertical development and consequently correct deep overbite and curve of Spee.11,13 During
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Table VII.
Prevalence of root resorption grades in groups and subgroups Grade 0
Group 1 Group 2 Subgroup 1 Subgroup 2 Group 3
1
2
3
4
Prevalence*
%
Prevalence
%
Prevalence
%
Prevalence
%
Prevalence
%
54/192 31/192 40/96 22/120 126/192
28.12 16.15 41.67 18.33 65.62
93/192 145/192 48/96 94/120 59/192
48.44 75.52 50.00 78.33 30.73
38/192 16/192 8/96 4/120 7/192
19.79 8.33 8.33 3.34 3.65
7/192 0/192 0/96 0/120 0/192
3.65 0.00 0.00 0.00 0.00
0/192 0/192 0/96 0/120 0/192
0.00 0.00 0.00 0.00 0.00
*Number of resorbed roots/number of examined roots. Table VIII.
Prevalence of root resorption in incisors and dental arches Group 1 (n ⫽ 24)
Teeth 12, 22 11, 21 32, 42 31, 41 Max arch Mand arch Total
Subgroup 1 (n ⫽ 12)
Group 2 (n ⫽ 24)
Subgroup 2 (n ⫽ 15)
Group 3 (n ⫽ 24)
Prev*
%
Prev
%
Prev
%
Prev
%
Prev
%
37/192 39/192 30/192 32/192 76/192 62/192 138/192
19.27 20.31 15.62 16.67 39.58 32.29 71.87
14/96 15/96 11/96 16/96 29/96 27/96 56/96
14.58 15.63 11.46 16.67 30.21 28.13 58.34
40/192 45/192 34/192 42/192 85/192 76/192 161/192
20.83 23.44 17.70 21.88 44.27 39.58 83.85
23/120 29/120 19/120 27/120 52/120 46/120 98/120
19.16 24.17 15.83 22.50 43.33 38.33 81.66
21/192 16/192 11/192 18/192 37/192 29/192 66/192
10.90 8.30 5.70 9.40 19.20 15.10 34.30
*Number of resorbed roots/number of examined roots. Prev, prevalence; Max, maxilla; Mand, mandible. 12, Maxillary right lateral incisor; 11, maxillary right central incisor; 21, maxillary left central incisor; 22, maxillary left lateral incisor; 42, mandibular right lateral incisor; 41, mandibular right central incisor; 31, mandibular left central incisor; 32, mandibular left lateral incisor.
treatment, patients should bite heavily into the appliance to generate the forces to restrict vertical development. With these designs and forces, EGAs induce significant palatal tipping, retrusion and restriction of maxillary incisors’ vertical development, and labial tipping of mandibular incisors; these could have caused the significantly greater resorption observed in relation to the control group.9,13 The FR is primarily a tissueborne appliance,2,15 with no acrylic over the maxillary and mandibular incisors to control their vertical development, and the mandibular lingual coil springs should not contact the incisors.2,24 For this reason, less resorption with the FR than the EGA should be expected. However, studies with the FR usually showed many dentoalveolar changes and some adverse effects on the maxillary and mandibular incisors, such as palatal tipping and proclination, respectively.14,15,39,40 Therefore, it is likely that contact of the labial arch with the maxillary incisors and of the lingual coil springs with the mandibular incisors during treatment might have led to the nonsignificantly greater resorption in relation to the control group that was similar to the EGA group (Table VI). More specifically, the FR in many patients of this subgroup caused significant palatal tipping and
retrusion of the maxillary incisors but did not restrict their vertical development and did not labially tip or protrude the mandibular incisors significantly, as reported in a previous study.14 As a consequence of the smaller vertical control on the incisors with the FR, the vertical forces of the fixed appliances used later on these teeth to correct the overbite and the curve of Spee might have contributed to the significantly greater resorption in group 1, as compared with the control group (Table V). Another factor that could have contributed to the smaller tendency of resorption in subgroup 1 was the nonsignificantly shorter treatment time compared with subgroup 2 (Table II), although increased treatment time is a controversial risk factor for apical root resorption.37,41-43 Evidently, the results in these subgroups have limitations because of small subgroup sizes; further investigations with larger samples are necessary for confirmation. Although the group sizes might be considered satisfactory, the subgroups were small. This is because functional appliances usually need complementary fixed appliance treatment to refine the occlusion. The EGAs’ need of fixed appliances to
734 Janson et al
complement treatment is less because of their action as a tooth positioner.16 An interesting finding was the absence of a significant difference between the experimental subgroups and the control group for both maxillary lateral incisors (Table VI). The period of complete root formation of the mandibular central incisor is 9 years of age. Both mandibular lateral and maxillary central incisors have complete root formation by 10 years of age. The maxillary lateral incisors are the last incisors to complete root formation, at 11 years of age. So, at a mean age of 11 years, all permanent incisors have completed root calcification.21,44 Incomplete roots have greater resistance to resorption.45 Therefore, the smaller resorption of the lateral incisors could be consequent to the shorter treatment time that their complete roots were exposed to orthodontic forces. Despite having greater resorption than the control group, the resorption degrees were predominantly mild (grade 1), especially in the subgroups that were treated only with removable appliances (Table VII). In relation to fixed appliances, the findings showed less root resorption for the removable appliances exclusively, as previously reported.18,21 Only 2 patients in the FR group followed by fixed appliance treatment had accentuated resorption. This was probably caused during the fixed appliance treatment phase because the FR subgroup did not have significantly greater resorption than the control group. As in others studies,32,35,46-49 we found greater root resorption in the maxillary arch (Table VIII). In the experimental groups and subgroups, the prevalence of resorption was similar to that reported in the literature,20,27,29,47 which is, in decreasing order, maxillary central incisors, maxillary lateral incisors, mandibular central incisors, and mandibular lateral incisors. Compared with the control group, only the EGA used exclusively showed greater resorption, presumably because it is essentially a tooth-borne appliance, applying more force on the incisors and causing greater tooth displacement during treatment. However, there was no difference in apical root resorption between the 2 appliance systems, and the amount of resorption was predominantly small. CONCLUSIONS
1. Both the FR and the EGA, when followed by fixed appliance treatment, caused significantly greater resorption than that in the control group. 2. When both appliances were used as the only treatment protocol, only the EGA showed significantly greater resorption than the control group.
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3. The amounts of resorption were predominantly small and similar in both experimental groups and subgroups. 4. The prevalence of resorption for each incisor group, in decreasing order, was maxillary central, maxillary lateral, mandibular central, and mandibular lateral. REFERENCES 1. Fränkel R. The theoretical concept underlying the treatment with functional correctors. Eur Orthod Soc Trans 1966;42:233-54. 2. Fränkel R, Fränkel C. Orofacial orthopedics with the function regulator. Basel: Karger; 1989. 3. Falck F, Fränkel R. Clinical relevance of step-by-step mandibular advancement in the treatment of mandibular retrusion using the Fränkel appliance. Am J Orthod Dentofacial Orthop 1989; 96:333-41. 4. McNamara Jr JA, Howe RP, Dischinger TG. A comparison of the Herbst and Fränkel appliances in the treatment of Class II malocclusions. Am J Orthod Dentofacial Orthop 1990;98: 134-44. 5. Perillo L, Johnston LE, Ferro A. Permanence of skeletal changes after function regulator (FR-2) treatment of patients with retrusive Class II malocclusions. Am J Orthod Dentofacial Orthop 1996;109:132-9. 6. Toth LR, McNamara Jr JA. Treatment effects produced by the Twin-block appliance and the FR-2 appliance of Fränkel compared with an untreated Class II sample. Am J Orthod Dentofacial Orthop 1999;116:597-609. 7. Hamilton SD, Sinclair PM, Hamilton RH. A cephalometric, tomographic, and dental cast evaluation of the Fränkel therapy. Am J Orthod Dentofacial Orthop 1987;92:427-36. 8. Nielsen IL. Facial growth during treatment with the function regulator appliance. Am J Orthod 1984;85:401-10. 9. Bergersen EO. The eruption myofunctional appliance: how it works, how to use it. Funct Orthod 1984;1:28-35. 10. Janson GRP, Pereira ACJ, Bergersen EO, Henriques JFC, Pinzan A, Almeida RR. Cephalometric evaluation of the eruption guidance appliance in Class II, division 1 treatment. J Clin Orthod 1997;31:299-306. 11. Methenitou S, Shein B, Ramanathan G, Bergersen EO. Prevention of overbite and overjet development in the 3 to 8 year old by controlled nighttime guidance of incisal eruption: a study of 43 individuals. J Pedod 1990;14:219-30. 12. Pourrahimi P. Cephalometric evaluation of the correction of overbite and overjet with the eruption guidance appliance. Chicago: Northwestern University; 1982. p. 89. 13. Janson GRP, Silva CCA, Bergersen EO, Henriques JFC, Pinzan A. Eruption guidance appliance effects in the treatment of Class II Division 1 malocclusions. Am J Orthod Dentofacial Orthop 2000;117:119-29. 14. Janson G, Toruño JLA, Martins DR, Henriques JFC, Freitas MR. Class II treatment effects of the Fränkel appliance. Eur J Orthod 2003;25:301-9. 15. McNamara Jr JA, Bookstein FL, Shaughnessy TG. Skeletal and dental changes following functional regulator therapy on Class II patients. Am J Orthod 1985;88:91-110. 16. Janson G, Souza JEP, Freitas MR, Henriques JFC, Cavalcanti CT. Occlusal changes of Class II malocclusion treatment between Fränkel and the eruption guidance appliance. Angle Orthod 2004;74:521-5.
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