The stability of the arch-expansion effects of Frankel appliance therapy David L. Hime, DDS, MS, and Albert H. Owen III, DDS, MSD Austin, Texas
To assess the long-term stability of the arch expansion effects of the functional regulator, mandibular dental casts were evaluated for treatment and postretention changes in intercanine width, width between first premolars, width between second premolars, intermolar width, incisor irregularity, and arch length. This study was comprised of 11 cases that were treated with the Fr&nkel appliance (~ = 27 mo.) and were and average of 4 years and 4 months out of active treatment. Results showed overall stability to be good, with some variability present in individual responses. Intercanine width, width of first premolars, width of second premolars, and intermolar width all demonstrated maintenance of treatment increases. Correction of incisor irregularity displayed better stability than has been reported in other stability studies. Arch length decreased with treatment and continued to decrease during the postretention period, although to a lesser extent than has been previously reported. The results of this study support the statements of Fr~inkel concerning the stability of this type of arch expansion. (AM J ORTHODDENTOFACORTHOP 1990;98:437-45.)
The treatment of crowding of the dental arches has stirred considerable debate for much of this century. Angle t taught that ideal occlusion requires a full complement of teeth, and that an ideal occlusion provides "such functional efficiency, t h a t . . , it will be sufficient to ensure a permanent result." Thus, arch expansion to such a degree as to accommodate a full complement of teeth was thought to be the only way to ensure treatment stability. In 1923 Lundstrom 2 proposed the concept of malocclusions of the teeth as related to the apical base. He opposed Angle's concept that the size of the dental arches determined the size of the apical base. When tooth mass exceeds the limits of the apical base, two alternatives exist for the resolution of the imbalance. The first is a reduction in tooth mass by extraction of teeth 3 or a reduction in the mesiodistal size of individual teeth. 46 The second alternative is to increase the size of the apical base to allow for alignment of the full dentition. According to Moss and Salentijn, 7 the tooth is the functional matrix for alveolar growth; the growing and erupting tooth is able to induce alveolar growth and hence the formation of an adequate bony scaffold. This is the working hypothesis for the functional regulator appliance as described by Fr/inkel. 8t3 Based on a thesis submitted in partial fulfillment of the requirements for the Master of Science degree. University of Louisville, School of Dentistry. Supported in part by a grant from the Southern Society of Orthodontists, Scientific Affairs Committee. 811116888
Many investigators have sought to evaluate the longterm stability of arch expansion as a means of resolving space deficiency problems. These studies have all demonstrated the futility of mandibular lateral expansion, particularly in the canine region) ~25 Decrease in intercanine width with age has also been observed in untreated patients with normal dentition, 26 the amount being slightly less than the amount reported in retention studies of nonextraction cases. 23,25 The functional regulator appliance offers a method of orthodontic/orthopedic treatment that does not alter occlusion directly but alters the conditions that determine the pattern of occlusal development. The proposed action of the functional regulator appliance is (1) displacement of the attachment of the lips and cheeks at the sulci in an outward direction, followed by (2) development of the apical base (Fig. 1). This muscular adaptation allows for an expansion of the soft tissue capsule and a normalization of a faulty pattern of muscular behavior. According to Fr~inkel, these factors lead to stable treatment results: Expansion of the mandibular arch during functional regulator treatment is well documented in the literature, 27"31 and it could be a particularly effective form of treatment for space deficiencies in the mixed dentition if it proves to be stable over an extended time. The purpose of this study is to evaluate the long-term stability of the arch-expansion effects of the functional regulator appliance.
437
438
Am. J. Orthod.Dentofac.Orthop. November 1990
Hime and Owen
~ " : ~
:::--":'t
"-
~
"
-BICUSPID
VESTIBULAR SHIELD
Fig. 1. Schematic view of the influence of vestibular shields on eruptive path and dentoalveolar development. Small arrows indicate mechanical strain in the inner and outer alveolar walls affected by tongue pressure and the vestibular shield during premolar eruption. Dense stippling shows alveolar apposition prompted by the vestibular shield, whereas lighter stippling shows the more lateral position of the permanent tooth. (Adapted from Fr~,nkel.)
T a b l e I. Patient treatment data
Months elapsed Patient No.
I
1
2 3 4 5 6 7 8 9 10 11 x SD Minimum Maximum
Age At Tt ()'r-too) 6-9 1!-4 10-10 9-6 11-3 9-0 9-9 12-4 11-4 7-8 7-10 9-9 ± !-10 6-9 12-4
MATERIALS AND METHODS This pilot study comprised 11 cases that were treated in the mixed dentition with the Fr~inkel appliance for an average o f 27 months. All o f the cases were selected from the private practice o f the secondary author ( A . H . O . ) , solely on the basis o f the availability o f long-term records and the fact that no other archexpansion appliances had been used. Neither the perceived success or failure o f the treatment, nor longterm stability was a consideration in the selection of these cases. None o f the patients received preFr~inkel orthodontic treatment, although orthodontic correction o f dental compensations is a common treatment approach today. Appliance construction and clinical application o f the appliance have been discussed by Fr~inkel,3:'33 Graber
At T.,-TI 56 9 34 19 15 29 12 21 21 46 29 26.5 ± 14.4 9 56
I
At T4-Tj 42 24 87 77 67 59 42 59 46 30 42 52.3 ± 19.4 24 87
et al., 34 M c N a m a r a , 3537 and Owen. 3s All patients in this study were treated according to the methods described by Owen. 3s All had completed active treatment at least 2 years before the study began. The mean posttreatment period was 4 years 4 months and the range was 2 years to 7 years 3 months. All of the cases selected involved fixed appliance therapy after first-phase Frfinkel treatment, with the exception o f Case 3, in which received Fr~inkel appliance treatment only. Patients 1, 2, 4, and 5 had been given removable retainers and instructions for full-time wear for 6 months, followed by 1 additional year o f nighttime wear only. Patient 3 did not receive any retaining devices at all. Patients 6 through 11 had been given bonded lower 3-3 retainers and were less than 2 years after retention. For this reason, postretention measurements o f intercanine width and incisor
Stability of arch-expansion effects of Friinkel appliance
Voh~rae 98 Number 5
A >
'
-
~
A~
Fig. 2. Locations of points used in measurement of arch width parameters. A-A', Intercanine width; B-B', width between first premolars; C-C', width between second premolars; D-D', intermolar width.
A B
439
C D
Fig. 3. Incisor Irregularity Index = A + B + C + D + E.
irregularity were not taken for these cases. No circumferential fiberotomies had been performed on any of the patients. Sample data are presented in Table I. Dental casts had been taken before treatment (T~), after removal of the Fr/inkel appliance (T2), after treatment (T3), and after retention (T4). The following six measurements were made on each mandibular dental case with dial calipers accurate to _ 0.05 mm: 1. Intercanine width, measured from the buccal gingival margin at the most prominent portion of one canine to the same point on the contralateral canine (Fig. 2). If the teeth were not fully erupted, the measurement was made from cusp to cusp. If the teeth were unerupted, no measurement was made. 2. Width between first premolars, measured from the buccal gingival margin at the most prominent portion of one first premolar to the same point on the contralateral tooth (Fig. 2). If the deciduous first molars were still present at T,, the measurement was made at the buccal gingival margin at the prominent mesiobuccal ridge. 3. Width between second premolars, measured from the buccal gingival margin at the most prominent portion of one second premolar to the same point on the contralateral tooth (Fig. 2). If the deciduous second molars are still present at T,, the measurement was made at the buccal gingival margin at the buccal groove. 4. Intermolar width, measured from the buccal gingival margin at the buccal groove of one molar to the same point on the contralateral tooth (Fig. 2). 5. Incisor Irregularity Index, defined as the
Fig. 4. Arch length = A + B.
summed displacement of adjacent anatomic contact points of the mandibular anterior teeth (Fig. 3). 39 6. Arch length, defined as the sum of the right and left distances from the mesial anatomic contact points of the mandibular first permanent molars to the contact point of the central incisors or to the midpoint between the central incisor contacts, if spaced (Fig. 4). 4° Analysis of the data involved the use of means standard deviations for all dental cast parameters. means and standard deviations were rounded to nearest 0.05 mm. Because of the small sample size the retrospective nature of this study, population tistical analytical procedures were not employed.
and All the and sta-
RESULTS The results of the dental cast analysis are presented in Tables II, III, and IV. Changes from T: (pretreatment) to T2 (post-Fr~inkel) are presented in Table II. Changes
440
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Hime and Owen
Table II. Study cast analysis, TI (pretreatment) - T: (post-Fr~inkel)
3-3 [ 4-4 [
Patient No.
c-c (ram)
d-d (mm)
5-5 e-e (mm)
6-6 (ram)
Irregularity (ram)
l 2 3 4 5 6 7 8 9 l0 11 n
+3.75 0.05 * + 1.35 +0.15 +2.90 * +0.80 * * * 6 + 1.50 -+ 1.50 + 0.05 + 3.75
+5.85 +3.40 +6.60 * + 1.05 * +2.95 +0,90 +0.30 +3.05 + 5.70 9 + 3.40 --+2.25 + 0.30 + 6.60
+3.60 +0.15 +3.50 * * +2.60 + 1.80 + 1.60 + 1.20 + 1.10 + 1.55 9 + 1.90 ± 1.15 + 0.15 + 3.60
+2.30 + 1.45 +0.35 + 1.05 +0.60 + 1.25 + 1.40 +i.10 + 1,80 +1.10 +2.50 II + 1.35 -- 0.65 +0.35 +2.50
- 8.65 +0.10 + 1.25 +0.10 - 2.20
SD Minimum Maximum
Arch length (mm) -
0.40
+0.30 +2.35 -
1.50
-
3.40
-
1.55
--2.25 --0.20 -0.55
-
1.85
-
-0.10 +0.15 + 2.45 11 -
1.25
± 2.95 + 1.25 -
1.30
- 2.70 -0.95 - 0.05 11 -0.65 -----1 . 3 5 - 2.70 +2.35
8.65
*Deciduous teeth h a d been lost a n d p e r m a n e n t teeth h a d not yet erupted.
Table Ill. Study cast analysis, T2 (post-Fr~inkel)-T3 (posttreatment) Patient No.
3-3 (turn)
I 2 3 4
4--4 (ram)
5-5 (ram)
6-6 Onm)
Irregularity (ram)
+0.10 + 1.50 0 - 0.95
+0.15 +0.30 0 + 3,00
+0.40 +0.85 0 + 2.45
+O.8O - 0.95 0 +2.85
- 1.35 +0.35 0 - 2.90
- 0.40 +3.85 0 + 3.70
5
*
*
*
6
*
*
*
7
*
*
*
+ 1.25 +0.70 -2.25
+2.60 +0.80 + 1:35
+ 1.15 -0.65 +2.05
-0.05 -0.30 +0,90
-3.25 -2.15 -5.30
+0.10 + 1.05 -2.95
7 +0.45
7 -2.10 ± i .95 +0.35
7 +0.75 __.2 . 4 0 -3.85
-
+ 3.70
8 9 I0 11 n x SD Minimum Maximum
I [
*
*
*
7 +0.05 .4-1.30 -- 2 . 2 5 + 1.50
7 + 1.15 --- 1.20 + 0.15 + 3.00
7 +0.90 .4-1.10 - 0.65 + 2.45
-
1.25
-0,95 + 2.85
5.30
[ [
Arch length (ram)
*Final records were unavailable. Postretention c h a n g e s w e r e calculated f r o m T2 to T,.
from '1"2to T3 (posttreatment) are presented in Table III. The changes observed from "1"3to T4 (postretention) are listed in Table IV. The results for each parameter measured in this study follow: 1. Intercanine width. From Table II it can be seen that the mean intercanine width increase from T~ to T2 was + 1.50 mm. The data, however, demonstrate wide variation in treatment response, with a range of +0.05 mm to +3.75 mm. At T~, five of the patients in this study had
exfoliated deciduous canines and unerupted permanent canines; therefore, treatment changes for these cases could not be measured. Table IV shows changes that occurred from T3 to T4. The mean relapse in intercanine width was - 0 . 3 0 mm, with a range of + 0 . 5 0 to - 0 . 7 5 . Six of the patients had fixed lingual retainers, either still in place or removed within the previous 2 years, so these cases were not included in computation of the means. . Width between first premolars. From Table II it
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Stability of arch-expansion effects of Friinkel appliance 441
Table IV. Study cast analysis, Ta (posttreatment)-T4 (postretention)
,,i,6
Patient No.
(mm)
(mm)
(mm)
(mm)
1 2 3 4 5 6 7 8 9 10 11 n x SD Minimum Maximum
0.00 -0.60 +0.50 --0.75 -0.65 * * * * * * 5 - 0.30 __-0.55 +0.50 -0.75
0.00 +0.35 --0.10 -- 1.80 0.00 -0.25 +0.40 - 1.00 -0.40 +0.30 + 0.50 11 - 0.20 ±0.70 +0.50 - 1.80
+0.65 +0.25 --0.30 --2.60 - 1.05 -0.I0 -0.10 - 2.35 -0.80 +0.20 + 0.65 11 -- 0 . 5 0 ± 1.10 +0.65 -2.60
+0.10 +0.60 +0.05 -- 1.10 + 1.00 +0.75 + 1.75 -0.95 -0.10 +0.35 + 0.25 I1 + 0.25 ---0.80 + 1.75 - 1.10
e'u'or'larch'enth (mm)
(ram)
--0.15 -- 1.10 +2.70 +0.40 +0.25 * * * * * * 5 + 0.40 ± 1.40 - 1.10 +2.70
+0.40 - 1.60 + 1.10 - 1.75 -2.60 -0.65 - 1.15 - 1.45 -0.50 - 1.10 + 2.70 11 - 0.80 ± 1.40 +2.70 -2.60
C a s e s 6 - 1 1 either were still w e a r i n g fixed l o w e r 3-3 retainers, or h a d h a d the retainer r e m o v e d within t w o y e a r s o f the final postretention m o d e l s . F o r this reason, intercanine width a n d incisor irregularity were not measured for these cases.
can be seen that the increases in arch width between the first premolars with Fr/inkel treatment averaged + 3.40 mm. Although two o f the cases showed minimal increases, six showed increases of 3 m m or more. Two patients had lost the deciduous first molars and first premolars had not yet erupted; their measurements, therefore, were not averaged with the rest. Table IV shows the dental cast changes from T3 to "1"4. The average relapse in this sample was - 0 . 2 0 mm, with a range from + 0 . 5 0 to - 1.80. . Width between second premolars. The increase in arch width, as measured at the second premolars, averaged + 1.90 mm, with a range o f + 0 . 1 5 to + 3 . 6 0 (Table II). The postretention data (Table IV) demonstrate that the average relapse of this arch width parameter was - 0 . 5 0 mm, with a range of + 0 . 6 5 to - 2 . 6 0 . . Intermolar width. The average increase in the intermolar width in this sample was + 1.35 mm, with a range of + 0 . 3 5 to + 2 . 5 0 (Table II). Postretention records demonstrate excellent stability of this parameter, with a mean postretention increase of + 0 . 2 5 mm. The relapse varied from - 1.10 to + 2.70 (Table IV). . Incisor Irregularity. The change in incisor irregularity observed in Fr~inkel treatment was quite variable (Table II). The mean decrease in irregularity was - 1 . 2 5 mm, but the changes with treatment varied from + 1.25 to - 8 . 6 5 mm. Postretention measurements reveal that, on av-
Table V. Sample incisor irregularity I
PatientNo. 1
2
3 4 5 x Minimum Maximum
I
Tt (ram) 11.65 1.20 0.70 5.10 4.65 4.65 0.70 11.65
T4 (ram) 1.55 0.55 4.65 2.70 2.70 2.40 0.55 4.65
ChangeTrT, (ram) - 10.10 - 1.65 +3.95* - 2.40 - 2.95 - 2.65 + 3.95" - I0.10
*Canines were u n e m p t e d at T~ a n d , therefore, incisor irregularity increased despite a n o b v i o u s decrease in space deficiency. N o fixed appliances o r retaining devices w e r e used (see Fig. 6).
erage, the incisor irregularity increased only + 0 . 4 mm from "1"3to "1"4(Table IV). The data reveal variability: one case had an increase in irregularity o f + 2 . 7 0 mm and another had a further decrease in incisor irregularity of - 1.10 mm after retention. Six of the cases were not included in the calculation o f the mean because fixed lingual retainers either had been recently removed or were still in place. 6. Arch length. The effect o f the Fr/inkel appliance on arch length was variable. The mean effect in this sample was - 0 . 6 5 mm, but this measurement varied from - 2 . 7 0 to + 2 . 3 5 (Table II). Nine of the eleven patients had actual reductions in arch length with treatment. Postretention data
442
Hhne and Owen
Am. J. Orthod. Dentofac. Orthop. November 1990
Fig. 5. Case number 1. A, Pretreatment; B, post-Fr&nkel; C, posttreatment; D, postretention. This case demonstrates excellent stability of atl parameters measured in this study (see Table IV).
reveal a consistent continued loss o f arch length after active treatment (Table IV). The mean decrease was - 0 . 8 0 mm, with a range of + 2 . 7 0 to - 2.60.
DISCUSSION The initial impression supported by the data is one of stability of the arch expansion and arch alignment attained during the Fr/inkel appliance treatment o f this sample, with some variation in individual responses. Although there is no control group sample in this study, comparison of the results of this study with the results o f other stability studies may offer additional insight into the relative indication or contraindication for this type of treatment.l~~'4~43 The inviolability of intercanine width has long been held as one of the "golden rules" o f orthodontic philosophy. This study revealed a mean increase in intercanine width of + 1.50 mm with treatment and a mean postretention decrease of only - 0 . 3 0 ram. None of the patients had a relapse o f more than - 0 . 7 5 mm. Glen
et al., 23 in a study of nonextraction cases with an average postretention time o f nearly 8 years, found a mean decrease of - 1.0 mm; 95% of the cases that had treatment increases in intercanine width showed postretention decreases in this measurement. Similar findings are reported by Gardner and Chaconas 2~ for cases just over 5 years out of retention. Little et al. 35 showed a mean decrease of - 2.02 mm, with some decrease during the 10-year postretention period for 60 of 65 first premolar extraction cases. The mean treatment-induced increase in width between first premolars was + 3 . 4 0 mm, with all cases showing some increase in this dimension. During the postretention period, the mean decrease of - 0 . 2 0 mm is considered to be of negligible clinical importance, although some variation was evident. Two of the patients had relapses of more than 1 mm, while six showed either no relapse or an actual continued increase in this parameter during the postretention period. The increase in width between second premolars during Fr~inkel treatment averaged + 1.90 mm, again
Volume 98 Number 5
Stabifty of arch-expansion effects of Friinkel appliance 443
Fig. 6. Case number 3. A, Pretreatment; El, post-Fr&nkel; C, postretention. This patient had no fixed appliance therapy at all and wore no retention devices. Notice that incisor irregularity increased from T1 to "1"2(+ 1.25 mm) as the permanent canines erupted. This is an example of a case in which incisor irregularity increased during Fr&nkel treatment, although there was an obvious decrease in the space deficiency. This is one of the factors leading to increased variability in the treatment effect on incisor irregularity width during treatment. Also note that this patient had the greatest increase in incisor irregularity from T= to "I-4(+2.70 ram).
with all cases in which measurement could be made at TI showing some increase. During the postretention period, the mean relapse was - 0 . 5 0 ram. Variation was evident in this measurement, also. The increase in intermolar width during treatment = + 1.35) appeared to be quite stable; the mean postretention change was an actual increase of + 0.25 ram. In one case only, a relapse of greater than 1 mm was recorded. Perhaps more important, eight of the cases (73%) actually had postretention increases. Glen et al. 23 reported a mean decrease of - 0 . 5 0 mm, with 75% of the cases which were expanded showing some postretention decrease. Other studies 24"25have held that intermolar width is less susceptible to relapse after expansion; this study found essentially no relapse of the expansion achieved during functional regulator treatment.
Relapse of incisor irregularity is perhaps the greatest concern to the clinical orthodontist because this problem is generally the most common complaint from patients after treatment. Treatment of moderate (3.5 to 6.5 mm) to severe (>6.5 mm) incisor irregularity commonly involves extraction of premolars. Unfortunately, studies from the University of Washington 4~43 have shown that such extractions do not necessarily lead to stability of anterior alignment. Of first premolar extraction cases, 70% at 10 years postretention and 90% at 20 years postretention were found to have moderate-to-severe incisor irregularity. Glen et al. 23 reported a mean postretention increase of + 1.2 mm, even though the initial incisor irregularity was only 2.9 mm. Little 4' reported a mean relapse of + 2.9 mm in extraction cases in which the initial incisor irregularity was 7.3 mm. In the present study, the average incisor irregularity at T~ was 4.65
444
Hime and Owen
mm. The mean decrease in irregularity was - 1.25 mm, although the treatment effect was quite variable Fig. 5. The variability of the treatment effect is due in part to the fact that the lower canines erupted between T1 and Tz in five of the cases, and although space deficiency appeared to decrease with treatment, the irregularity increased with the added contribution o f the erupted canines. During the postretention period, the mean incisor irregularity increased only + 0 . 4 0 mm, with a maximum relapse of + 2 . 7 0 mm (see Fig. 6). The sample size for measurement of incisor irregularity was small (five cases), as six cases still have fixed lingual 3-3 retainers or had recently had them removed. However, the mean irregularity at T4 was 2.40 mm, with minimum irregularity in four o f the five cases and moderate irregularity in one. These cases have maintained an average decrease in irregularity of 2.30 mm (see Table V) compared with an average maintained decrease o f only 0.70 m m reported by Glen et al. 23 Arch length typically decreased in this sample from Tt to T2, with a mean decrease of - 0 . 6 5 mm. In nine o f the eleven cases, arch length decreased during treatment. This finding is not surprising, since all o f the cases involved the mixed dentition, and arch length typically decreases in the transition from the mixed to the permanent dentition. The postretention analysis also revealed a mean decrease in arch length of - 0 . 8 0 n~m. These cases appeared to be more stable than those reported by Glen et al. 23 (~ = - 2 . 4 mm) or by Little et al. 4t ~ = - 2 . 4 8 mm). Close examination o f the data presented in Table IV reveals that patient 4 had much greater elapse of all arch width parameters than any of the other patients. In searching for the reason for this disproportionate amount of relapse, it can be seen that this case involved much greater expansion during fixed appliance therapy (see Table III). This may have contributed to much of the observed relapse, and this case appears to substantiate the concept of intercanine width previously reported. ,4_25 CONCLUSIONS
The functional regulator appliance, as described in this study, has two main treatment effects: Class II correction and arch expansion. Reduction o f crowding during eruption is accomplished through the action of the vestibular shields. Although the stability o f the Class II correction is equally important in determining the viability of functional regulator treatment, and reports are inconclusive as to the mechanism of the Class II correction, 4453 this study is devoted solely to the study of the stability o f the arch expansion effects o f the
Am. J. Orthod. Dentofac. Orthop. November 1990
appliance. A future study will be devoted to investigation of the stability of the Class II correction. This study involves the analysis o f a very small sample and is intended to serve as a pilot study for future research. For this reason, the results should not be projected to the population. Because o f the retrospective nature o f this study, cause and effect conclusions would be invalid in the absence of other similar findings. All but one of the patients in this study wore some type of retention device, and the postretention period was not as long as in other postretention studies. True comparisons can be made only between cases with similar postretention periods. However, the results of this study support the suggestion that the arch expansion gained in this type o f treatment is more stable than expansion seen in fixed appliance treatment. Further investigations involving larger sample sizes and longer postretention periods should be conducted either to suppert or to dispute the findings of this study. Until such a time as there is sufficient evidence that any form of treatment results in acceptable long-term stability, it appears wise to be cautious regarding the retention phase of treatment.
REFERENCES 1. Angle EH. The treatment of malocclusion of the teeth. 7th ed. Philadelphia: SS White Manufacturing, 1907. 2. LundstromA. Malooclusionsof the teeth regarded as a problem in connection with the apical base. I,,,rr J ORTHODORALSURG 1923;I 1:591-602, 933-41, 1109-33. 3. Tweed CH. Clinical Orthodontics, vol 1. St. Louis: CV Mosby, 1966. 4. Sheridan JJ. Air-rotor stripping. J Clin Orthod 1985;19:43-59. 5. Bolton WA. Disharmony of tooth size and its relation to the analysis and treatment of malocclusion. Angle Orthod 1958; 28:113-30. 6. PeckS, Peck H. Crown dimensionsand mandibular incisor alignment. Angle Orthod 1972;42:148-53. 7. Moss ML, Salentijn L. The primary role of functional matrices in craniofacial growth. AM J ORTHOD1959;55:566-77. 8. Fr~nkel R. Decrowding during eruption under the screening influence of vestibular shields. AM J ORraOD 1974;65:372-406. 9. Friinkel R. Biomechanical aspects of the form/function relationship in craniofacial morphogenesis: a clinician's approach. In: McNamara JA Jr, Ribbens KA, Howe RP eds. Clinical alteration of the growing face. Ann Arbor: Center for Human Growth and Development, The University of Michigan, 1983. (Craniofacial growth series; No. 14.) 10. Fff2nkelR. The theoretical conceptunderlyingthe treatment with functional correctors. Trans Eur Orthod Soc 1966;42:233-54. I 1. Frankel R. The practical meaning of the functional matrix in orthodontics. Trans Eur Orthod Soc 1969;45:207-19. 12. Fr/inkel R. The guidance of eruption without extraction. Trans Eur Orthod Soc 1971;47:303-15. 13. Friinkel R. A functional approach to orofacial orthopedics. Br J Orthod 1980;7:41-51.
Volume 98 Number 5 14. Strang R. The fallacy of denture expansion as a treatment procedure. Angle Orthod 1949;19:!2-22. 15. Steadman S. Changes of intermolar and intercuspid distances following orthodontic treatment. Angle Orthod 1961 ;31:207-15. 16. Lombardi A. Mandibular incisor crowding in completed cases. AM J ORTHOD 1972;61:374-83. 17. Peak J. Cuspid stability. AM J ORTIIOD 1956;42:608-14. 18. Riedel RA. A review of the retention problem. Angle Orthod 1960;20:!79-99. 19. Riedel RA. Post-pubertal occlusal changes. In: McNamara JA Jr, ed. The biology of occlusal development. Ann Arbor: Center for Human Growth and Development, The University of Michigan. (Craniofacial growth series; No. 7.) 20. Graber TM. Postmortems in posttreatment adjustment. AM J ORTHOD 1966;42:331-52. 21. Herberger RJ. Stability of mandibular intercuspid width after long periods of retention. Angle Orthod 1981;51:78-83. 22. Bishara SE, Chadha JM, Potter RB. Stability of intercanine width, overbite, and overjet correction. AM J OR'I'HOD 1973; 63:588-95. 23. Glen G, Sinclair PM, Alexander RG. Nonextraction orthodontic therapy: posttreatment dental and skeletal stability. AM J ORTIIOD DENTOFACORTHOP 1987;92:321-8. 24. Johnson K. Cases six years postretention. Angle Orthod 1977 ;47:210-21. 25. Gardner S, Chaconas S. Posttreatment and postretention changes following orthodontic therapy. Angle Orthod 1976;46:i51-61. 26. Sinclair PM, Little RM. Dentofacial maturation of untreated normals. AM J ORTHOD 1985;88:146-56. 27. Fraukel R, Muller M, Falek F. The uprightiag effect of the Fr.~nkel appliance on the mandibular canines and premolars during eruption. AM J OR'rHOI:~DEN'rOFACORTHOP 1987;92:109-16. 28. Owen AH. The morphologic changes in the transverse dimension using the Fr~ankel appliance. AM J ORmoo 1983;83:200-17. 29. McDougall PD, McNamara JA, Dierkes JM. Arch width development in Class II patients treated with the Fr~nkel appliance. Art J ORTHOD 1982;82:10-22. 30. McWade RA, Mamandras AH, Hunter WS. The effects of Fr~nkel II treatment on arch width and arch perimeter. AM J ORTHOD DENTOFACORTHOP 1987;92:313-20. 31. Hamilton SD, Sinclair PM, Hamilton RH. A cephalometric, tomographie, and dental cast evaluation of Fr~inkel therapy. AM J ORTHODDENTOFACORTHOP 1987;92:427-34. 32. Fr~inkelR. Technik und Handhabung der Funktionsregler, Berlin: VEB Verlag Volk und Gesundheit, 1976. 33. Frankel R, FrLrlkel C. Orofacial orthopedics with the function regulator. Basel: S Karger, 1989. 34. Graber TM, Rakoski T, Petrovic AG. Dentofacial orthopedics with functional appliances. St. Louis: CV Mosby, 1985. 35. McNamara JA. On the Fr'finkelappliance. Part I. Biological basis and appliance design. J Clin Orthod 1982;16:320-37. 36. MeNamara JA. On the Fr~nkel appliance. Part I1. Clinical Management. J Clin Orthod 1982;16:391-406.
Stability of arch-expansion effects of Friinkel appliance
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37. McNamara JA, Huge SA. The Fr~inkel appliance (FR-2): model preparation and appliance construction. AM J OR'I'HOO 1981; 80:478-95. 38. Owen AH. Clinical management of the Fr'ankel FR II appliance. J Clin Orthod 1983;18:605-18. 39. Little RM. The Irregularity Index: a quantitative score of mandibular anterior alignment. AM J OR'I'ItOD 1975;68:554-63. 40. Shapiro PA. Mandibular dental arch form and dimension. AM J OR'rHOD 1974;66:411-30. 41. Little RM, Wallen TR, Riedel RA. Stability and relapse of mandibular anterior alignment--first premolar extraction cases treated by traditional edgewise orthodontics. AM J ORTHOD 1981;80:349-65. 42. Shields TE, Little RM, Chapko MK. Stability and relapse of mandibular anterior alignment: a cephalometric appraisal of firstpremolar extraction cases treated by traditional edgewise orthodontics. AM J ORTHOO 1985;87:27-38. 43. Little RM, Riedel RA, Artun J. An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention. AM J ORTHODDENTOFACORTHOP 1988;93:423-28. 44. Creekmore TD, Radney LJ. Frankel appliance therapy: orthodontic or orthopedic? AM J OR'roOD 1983;83:89-108. 45. Eirew HL. The functional regulator of Fr'finkel. Br J Orthod 1976;3:67-74. 46. Gianelly AA, Arena SA, Bernstein L. A comparison of Class II treatment changes noted with the light wire, edgewise, and Frankel appliances. AM J OR'rHOD 1984;86:269-76. 47. Gianelly AA, Brosnan P, Martignoni M, Bernstein L. Mandibular growth, condyle position, and Fr~kel appliance therapy. Angle Orthod 1983;53:131-42. 48. McNamara JA, Bookstein FL, Shaughnessy TG. Skeletal and dental changes following functional regulator therapy on Class II patients. AM J ORTHOD 1985;88:91-110. 49. Nielsen IL. Facial growth during treatment with the function regulator appliance. AM J ORTHOD 1984;85:401-10. 50. Remmer KR, Mamandras AH, Hunter WS, Way DC. CephaIometric changes associated with treatment using the activator, the Frankel apliance, and the fixed appliance. AM J OR'I-HOD 1985;88:363-72. 51. Righellis EG. Treatment effects of Fr'~ankel, activator, and extraoral traction appliances. Angle Orthod 1983;53:107-21. 52. Robertson NRE. An examination of treatment changes in children treated with the functional regulator of Fr.~nkel. AM J OR"nlOD 1983;83:299-310. 53. Owen AH. Morphologic changes in the sagittal dimension using the Fr~kel appliance. AM J ORTHOD 1981;80:573-603.
Reprint requests to: Dr. David L. Hime 1500 W. 38th St., Suite 27 Austin, TX 78731
To assess the long-term stability of the arch expansion effects of the functional regulator, mandibular dental casts were evaluated for treatment and postretention changes in intercanine width, width between first premolars, width between second premolars, intermolar width, incisor irregularity, and arch length. This study was comprised of 11 cases that were treated with the Fr&nkel appliance (~ = 27 mo.) and were and average of 4 years and 4 months out of active treatment. Results showed overall stability to be good, with some variability present in individual responses. Intercanine width, width of first premolars, width of second premolars, and intermolar width all demonstrated maintenance of treatment increases. Correction of incisor irregularity displayed better stability than has been reported in other stability studies. Arch length decreased with treatment and continued to decrease during the postretention period, although to a lesser extent than has been previously reported. The results of this study support the statements of Fr~inkel concerning the stability of this type of arch expansion. (AM J ORTHODDENTOFACORTHOP 1990;98:437-45.)
The treatment of crowding of the dental arches has stirred considerable debate for much of this century. Angle t taught that ideal occlusion requires a full complement of teeth, and that an ideal occlusion provides "such functional efficiency, t h a t . . , it will be sufficient to ensure a permanent result." Thus, arch expansion to such a degree as to accommodate a full complement of teeth was thought to be the only way to ensure treatment stability. In 1923 Lundstrom 2 proposed the concept of malocclusions of the teeth as related to the apical base. He opposed Angle's concept that the size of the dental arches determined the size of the apical base. When tooth mass exceeds the limits of the apical base, two alternatives exist for the resolution of the imbalance. The first is a reduction in tooth mass by extraction of teeth 3 or a reduction in the mesiodistal size of individual teeth. 46 The second alternative is to increase the size of the apical base to allow for alignment of the full dentition. According to Moss and Salentijn, 7 the tooth is the functional matrix for alveolar growth; the growing and erupting tooth is able to induce alveolar growth and hence the formation of an adequate bony scaffold. This is the working hypothesis for the functional regulator appliance as described by Fr/inkel. 8t3 Based on a thesis submitted in partial fulfillment of the requirements for the Master of Science degree. University of Louisville, School of Dentistry. Supported in part by a grant from the Southern Society of Orthodontists, Scientific Affairs Committee. 811116888
Many investigators have sought to evaluate the longterm stability of arch expansion as a means of resolving space deficiency problems. These studies have all demonstrated the futility of mandibular lateral expansion, particularly in the canine region) ~25 Decrease in intercanine width with age has also been observed in untreated patients with normal dentition, 26 the amount being slightly less than the amount reported in retention studies of nonextraction cases. 23,25 The functional regulator appliance offers a method of orthodontic/orthopedic treatment that does not alter occlusion directly but alters the conditions that determine the pattern of occlusal development. The proposed action of the functional regulator appliance is (1) displacement of the attachment of the lips and cheeks at the sulci in an outward direction, followed by (2) development of the apical base (Fig. 1). This muscular adaptation allows for an expansion of the soft tissue capsule and a normalization of a faulty pattern of muscular behavior. According to Fr~inkel, these factors lead to stable treatment results: Expansion of the mandibular arch during functional regulator treatment is well documented in the literature, 27"31 and it could be a particularly effective form of treatment for space deficiencies in the mixed dentition if it proves to be stable over an extended time. The purpose of this study is to evaluate the long-term stability of the arch-expansion effects of the functional regulator appliance.
437
438
Am. J. Orthod.Dentofac.Orthop. November 1990
Hime and Owen
~ " : ~
:::--":'t
"-
~
"
-BICUSPID
VESTIBULAR SHIELD
Fig. 1. Schematic view of the influence of vestibular shields on eruptive path and dentoalveolar development. Small arrows indicate mechanical strain in the inner and outer alveolar walls affected by tongue pressure and the vestibular shield during premolar eruption. Dense stippling shows alveolar apposition prompted by the vestibular shield, whereas lighter stippling shows the more lateral position of the permanent tooth. (Adapted from Fr~,nkel.)
T a b l e I. Patient treatment data
Months elapsed Patient No.
I
1
2 3 4 5 6 7 8 9 10 11 x SD Minimum Maximum
Age At Tt ()'r-too) 6-9 1!-4 10-10 9-6 11-3 9-0 9-9 12-4 11-4 7-8 7-10 9-9 ± !-10 6-9 12-4
MATERIALS AND METHODS This pilot study comprised 11 cases that were treated in the mixed dentition with the Fr~inkel appliance for an average o f 27 months. All o f the cases were selected from the private practice o f the secondary author ( A . H . O . ) , solely on the basis o f the availability o f long-term records and the fact that no other archexpansion appliances had been used. Neither the perceived success or failure o f the treatment, nor longterm stability was a consideration in the selection of these cases. None o f the patients received preFr~inkel orthodontic treatment, although orthodontic correction o f dental compensations is a common treatment approach today. Appliance construction and clinical application o f the appliance have been discussed by Fr~inkel,3:'33 Graber
At T.,-TI 56 9 34 19 15 29 12 21 21 46 29 26.5 ± 14.4 9 56
I
At T4-Tj 42 24 87 77 67 59 42 59 46 30 42 52.3 ± 19.4 24 87
et al., 34 M c N a m a r a , 3537 and Owen. 3s All patients in this study were treated according to the methods described by Owen. 3s All had completed active treatment at least 2 years before the study began. The mean posttreatment period was 4 years 4 months and the range was 2 years to 7 years 3 months. All of the cases selected involved fixed appliance therapy after first-phase Frfinkel treatment, with the exception o f Case 3, in which received Fr~inkel appliance treatment only. Patients 1, 2, 4, and 5 had been given removable retainers and instructions for full-time wear for 6 months, followed by 1 additional year o f nighttime wear only. Patient 3 did not receive any retaining devices at all. Patients 6 through 11 had been given bonded lower 3-3 retainers and were less than 2 years after retention. For this reason, postretention measurements o f intercanine width and incisor
Stability of arch-expansion effects of Friinkel appliance
Voh~rae 98 Number 5
A >
'
-
~
A~
Fig. 2. Locations of points used in measurement of arch width parameters. A-A', Intercanine width; B-B', width between first premolars; C-C', width between second premolars; D-D', intermolar width.
A B
439
C D
Fig. 3. Incisor Irregularity Index = A + B + C + D + E.
irregularity were not taken for these cases. No circumferential fiberotomies had been performed on any of the patients. Sample data are presented in Table I. Dental casts had been taken before treatment (T~), after removal of the Fr/inkel appliance (T2), after treatment (T3), and after retention (T4). The following six measurements were made on each mandibular dental case with dial calipers accurate to _ 0.05 mm: 1. Intercanine width, measured from the buccal gingival margin at the most prominent portion of one canine to the same point on the contralateral canine (Fig. 2). If the teeth were not fully erupted, the measurement was made from cusp to cusp. If the teeth were unerupted, no measurement was made. 2. Width between first premolars, measured from the buccal gingival margin at the most prominent portion of one first premolar to the same point on the contralateral tooth (Fig. 2). If the deciduous first molars were still present at T,, the measurement was made at the buccal gingival margin at the prominent mesiobuccal ridge. 3. Width between second premolars, measured from the buccal gingival margin at the most prominent portion of one second premolar to the same point on the contralateral tooth (Fig. 2). If the deciduous second molars are still present at T,, the measurement was made at the buccal gingival margin at the buccal groove. 4. Intermolar width, measured from the buccal gingival margin at the buccal groove of one molar to the same point on the contralateral tooth (Fig. 2). 5. Incisor Irregularity Index, defined as the
Fig. 4. Arch length = A + B.
summed displacement of adjacent anatomic contact points of the mandibular anterior teeth (Fig. 3). 39 6. Arch length, defined as the sum of the right and left distances from the mesial anatomic contact points of the mandibular first permanent molars to the contact point of the central incisors or to the midpoint between the central incisor contacts, if spaced (Fig. 4). 4° Analysis of the data involved the use of means standard deviations for all dental cast parameters. means and standard deviations were rounded to nearest 0.05 mm. Because of the small sample size the retrospective nature of this study, population tistical analytical procedures were not employed.
and All the and sta-
RESULTS The results of the dental cast analysis are presented in Tables II, III, and IV. Changes from T: (pretreatment) to T2 (post-Fr~inkel) are presented in Table II. Changes
440
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Hime and Owen
Table II. Study cast analysis, TI (pretreatment) - T: (post-Fr~inkel)
3-3 [ 4-4 [
Patient No.
c-c (ram)
d-d (mm)
5-5 e-e (mm)
6-6 (ram)
Irregularity (ram)
l 2 3 4 5 6 7 8 9 l0 11 n
+3.75 0.05 * + 1.35 +0.15 +2.90 * +0.80 * * * 6 + 1.50 -+ 1.50 + 0.05 + 3.75
+5.85 +3.40 +6.60 * + 1.05 * +2.95 +0,90 +0.30 +3.05 + 5.70 9 + 3.40 --+2.25 + 0.30 + 6.60
+3.60 +0.15 +3.50 * * +2.60 + 1.80 + 1.60 + 1.20 + 1.10 + 1.55 9 + 1.90 ± 1.15 + 0.15 + 3.60
+2.30 + 1.45 +0.35 + 1.05 +0.60 + 1.25 + 1.40 +i.10 + 1,80 +1.10 +2.50 II + 1.35 -- 0.65 +0.35 +2.50
- 8.65 +0.10 + 1.25 +0.10 - 2.20
SD Minimum Maximum
Arch length (mm) -
0.40
+0.30 +2.35 -
1.50
-
3.40
-
1.55
--2.25 --0.20 -0.55
-
1.85
-
-0.10 +0.15 + 2.45 11 -
1.25
± 2.95 + 1.25 -
1.30
- 2.70 -0.95 - 0.05 11 -0.65 -----1 . 3 5 - 2.70 +2.35
8.65
*Deciduous teeth h a d been lost a n d p e r m a n e n t teeth h a d not yet erupted.
Table Ill. Study cast analysis, T2 (post-Fr~inkel)-T3 (posttreatment) Patient No.
3-3 (turn)
I 2 3 4
4--4 (ram)
5-5 (ram)
6-6 Onm)
Irregularity (ram)
+0.10 + 1.50 0 - 0.95
+0.15 +0.30 0 + 3,00
+0.40 +0.85 0 + 2.45
+O.8O - 0.95 0 +2.85
- 1.35 +0.35 0 - 2.90
- 0.40 +3.85 0 + 3.70
5
*
*
*
6
*
*
*
7
*
*
*
+ 1.25 +0.70 -2.25
+2.60 +0.80 + 1:35
+ 1.15 -0.65 +2.05
-0.05 -0.30 +0,90
-3.25 -2.15 -5.30
+0.10 + 1.05 -2.95
7 +0.45
7 -2.10 ± i .95 +0.35
7 +0.75 __.2 . 4 0 -3.85
-
+ 3.70
8 9 I0 11 n x SD Minimum Maximum
I [
*
*
*
7 +0.05 .4-1.30 -- 2 . 2 5 + 1.50
7 + 1.15 --- 1.20 + 0.15 + 3.00
7 +0.90 .4-1.10 - 0.65 + 2.45
-
1.25
-0,95 + 2.85
5.30
[ [
Arch length (ram)
*Final records were unavailable. Postretention c h a n g e s w e r e calculated f r o m T2 to T,.
from '1"2to T3 (posttreatment) are presented in Table III. The changes observed from "1"3to T4 (postretention) are listed in Table IV. The results for each parameter measured in this study follow: 1. Intercanine width. From Table II it can be seen that the mean intercanine width increase from T~ to T2 was + 1.50 mm. The data, however, demonstrate wide variation in treatment response, with a range of +0.05 mm to +3.75 mm. At T~, five of the patients in this study had
exfoliated deciduous canines and unerupted permanent canines; therefore, treatment changes for these cases could not be measured. Table IV shows changes that occurred from T3 to T4. The mean relapse in intercanine width was - 0 . 3 0 mm, with a range of + 0 . 5 0 to - 0 . 7 5 . Six of the patients had fixed lingual retainers, either still in place or removed within the previous 2 years, so these cases were not included in computation of the means. . Width between first premolars. From Table II it
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Stability of arch-expansion effects of Friinkel appliance 441
Table IV. Study cast analysis, Ta (posttreatment)-T4 (postretention)
,,i,6
Patient No.
(mm)
(mm)
(mm)
(mm)
1 2 3 4 5 6 7 8 9 10 11 n x SD Minimum Maximum
0.00 -0.60 +0.50 --0.75 -0.65 * * * * * * 5 - 0.30 __-0.55 +0.50 -0.75
0.00 +0.35 --0.10 -- 1.80 0.00 -0.25 +0.40 - 1.00 -0.40 +0.30 + 0.50 11 - 0.20 ±0.70 +0.50 - 1.80
+0.65 +0.25 --0.30 --2.60 - 1.05 -0.I0 -0.10 - 2.35 -0.80 +0.20 + 0.65 11 -- 0 . 5 0 ± 1.10 +0.65 -2.60
+0.10 +0.60 +0.05 -- 1.10 + 1.00 +0.75 + 1.75 -0.95 -0.10 +0.35 + 0.25 I1 + 0.25 ---0.80 + 1.75 - 1.10
e'u'or'larch'enth (mm)
(ram)
--0.15 -- 1.10 +2.70 +0.40 +0.25 * * * * * * 5 + 0.40 ± 1.40 - 1.10 +2.70
+0.40 - 1.60 + 1.10 - 1.75 -2.60 -0.65 - 1.15 - 1.45 -0.50 - 1.10 + 2.70 11 - 0.80 ± 1.40 +2.70 -2.60
C a s e s 6 - 1 1 either were still w e a r i n g fixed l o w e r 3-3 retainers, or h a d h a d the retainer r e m o v e d within t w o y e a r s o f the final postretention m o d e l s . F o r this reason, intercanine width a n d incisor irregularity were not measured for these cases.
can be seen that the increases in arch width between the first premolars with Fr/inkel treatment averaged + 3.40 mm. Although two o f the cases showed minimal increases, six showed increases of 3 m m or more. Two patients had lost the deciduous first molars and first premolars had not yet erupted; their measurements, therefore, were not averaged with the rest. Table IV shows the dental cast changes from T3 to "1"4. The average relapse in this sample was - 0 . 2 0 mm, with a range from + 0 . 5 0 to - 1.80. . Width between second premolars. The increase in arch width, as measured at the second premolars, averaged + 1.90 mm, with a range o f + 0 . 1 5 to + 3 . 6 0 (Table II). The postretention data (Table IV) demonstrate that the average relapse of this arch width parameter was - 0 . 5 0 mm, with a range of + 0 . 6 5 to - 2 . 6 0 . . Intermolar width. The average increase in the intermolar width in this sample was + 1.35 mm, with a range of + 0 . 3 5 to + 2 . 5 0 (Table II). Postretention records demonstrate excellent stability of this parameter, with a mean postretention increase of + 0 . 2 5 mm. The relapse varied from - 1.10 to + 2.70 (Table IV). . Incisor Irregularity. The change in incisor irregularity observed in Fr~inkel treatment was quite variable (Table II). The mean decrease in irregularity was - 1 . 2 5 mm, but the changes with treatment varied from + 1.25 to - 8 . 6 5 mm. Postretention measurements reveal that, on av-
Table V. Sample incisor irregularity I
PatientNo. 1
2
3 4 5 x Minimum Maximum
I
Tt (ram) 11.65 1.20 0.70 5.10 4.65 4.65 0.70 11.65
T4 (ram) 1.55 0.55 4.65 2.70 2.70 2.40 0.55 4.65
ChangeTrT, (ram) - 10.10 - 1.65 +3.95* - 2.40 - 2.95 - 2.65 + 3.95" - I0.10
*Canines were u n e m p t e d at T~ a n d , therefore, incisor irregularity increased despite a n o b v i o u s decrease in space deficiency. N o fixed appliances o r retaining devices w e r e used (see Fig. 6).
erage, the incisor irregularity increased only + 0 . 4 mm from "1"3to "1"4(Table IV). The data reveal variability: one case had an increase in irregularity o f + 2 . 7 0 mm and another had a further decrease in incisor irregularity of - 1.10 mm after retention. Six of the cases were not included in the calculation o f the mean because fixed lingual retainers either had been recently removed or were still in place. 6. Arch length. The effect o f the Fr/inkel appliance on arch length was variable. The mean effect in this sample was - 0 . 6 5 mm, but this measurement varied from - 2 . 7 0 to + 2 . 3 5 (Table II). Nine of the eleven patients had actual reductions in arch length with treatment. Postretention data
442
Hhne and Owen
Am. J. Orthod. Dentofac. Orthop. November 1990
Fig. 5. Case number 1. A, Pretreatment; B, post-Fr&nkel; C, posttreatment; D, postretention. This case demonstrates excellent stability of atl parameters measured in this study (see Table IV).
reveal a consistent continued loss o f arch length after active treatment (Table IV). The mean decrease was - 0 . 8 0 mm, with a range of + 2 . 7 0 to - 2.60.
DISCUSSION The initial impression supported by the data is one of stability of the arch expansion and arch alignment attained during the Fr/inkel appliance treatment o f this sample, with some variation in individual responses. Although there is no control group sample in this study, comparison of the results of this study with the results o f other stability studies may offer additional insight into the relative indication or contraindication for this type of treatment.l~~'4~43 The inviolability of intercanine width has long been held as one of the "golden rules" o f orthodontic philosophy. This study revealed a mean increase in intercanine width of + 1.50 mm with treatment and a mean postretention decrease of only - 0 . 3 0 ram. None of the patients had a relapse o f more than - 0 . 7 5 mm. Glen
et al., 23 in a study of nonextraction cases with an average postretention time o f nearly 8 years, found a mean decrease of - 1.0 mm; 95% of the cases that had treatment increases in intercanine width showed postretention decreases in this measurement. Similar findings are reported by Gardner and Chaconas 2~ for cases just over 5 years out of retention. Little et al. 35 showed a mean decrease of - 2.02 mm, with some decrease during the 10-year postretention period for 60 of 65 first premolar extraction cases. The mean treatment-induced increase in width between first premolars was + 3 . 4 0 mm, with all cases showing some increase in this dimension. During the postretention period, the mean decrease of - 0 . 2 0 mm is considered to be of negligible clinical importance, although some variation was evident. Two of the patients had relapses of more than 1 mm, while six showed either no relapse or an actual continued increase in this parameter during the postretention period. The increase in width between second premolars during Fr~inkel treatment averaged + 1.90 mm, again
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Stabifty of arch-expansion effects of Friinkel appliance 443
Fig. 6. Case number 3. A, Pretreatment; El, post-Fr&nkel; C, postretention. This patient had no fixed appliance therapy at all and wore no retention devices. Notice that incisor irregularity increased from T1 to "1"2(+ 1.25 mm) as the permanent canines erupted. This is an example of a case in which incisor irregularity increased during Fr&nkel treatment, although there was an obvious decrease in the space deficiency. This is one of the factors leading to increased variability in the treatment effect on incisor irregularity width during treatment. Also note that this patient had the greatest increase in incisor irregularity from T= to "I-4(+2.70 ram).
with all cases in which measurement could be made at TI showing some increase. During the postretention period, the mean relapse was - 0 . 5 0 ram. Variation was evident in this measurement, also. The increase in intermolar width during treatment = + 1.35) appeared to be quite stable; the mean postretention change was an actual increase of + 0.25 ram. In one case only, a relapse of greater than 1 mm was recorded. Perhaps more important, eight of the cases (73%) actually had postretention increases. Glen et al. 23 reported a mean decrease of - 0 . 5 0 mm, with 75% of the cases which were expanded showing some postretention decrease. Other studies 24"25have held that intermolar width is less susceptible to relapse after expansion; this study found essentially no relapse of the expansion achieved during functional regulator treatment.
Relapse of incisor irregularity is perhaps the greatest concern to the clinical orthodontist because this problem is generally the most common complaint from patients after treatment. Treatment of moderate (3.5 to 6.5 mm) to severe (>6.5 mm) incisor irregularity commonly involves extraction of premolars. Unfortunately, studies from the University of Washington 4~43 have shown that such extractions do not necessarily lead to stability of anterior alignment. Of first premolar extraction cases, 70% at 10 years postretention and 90% at 20 years postretention were found to have moderate-to-severe incisor irregularity. Glen et al. 23 reported a mean postretention increase of + 1.2 mm, even though the initial incisor irregularity was only 2.9 mm. Little 4' reported a mean relapse of + 2.9 mm in extraction cases in which the initial incisor irregularity was 7.3 mm. In the present study, the average incisor irregularity at T~ was 4.65
444
Hime and Owen
mm. The mean decrease in irregularity was - 1.25 mm, although the treatment effect was quite variable Fig. 5. The variability of the treatment effect is due in part to the fact that the lower canines erupted between T1 and Tz in five of the cases, and although space deficiency appeared to decrease with treatment, the irregularity increased with the added contribution o f the erupted canines. During the postretention period, the mean incisor irregularity increased only + 0 . 4 0 mm, with a maximum relapse of + 2 . 7 0 mm (see Fig. 6). The sample size for measurement of incisor irregularity was small (five cases), as six cases still have fixed lingual 3-3 retainers or had recently had them removed. However, the mean irregularity at T4 was 2.40 mm, with minimum irregularity in four o f the five cases and moderate irregularity in one. These cases have maintained an average decrease in irregularity of 2.30 mm (see Table V) compared with an average maintained decrease o f only 0.70 m m reported by Glen et al. 23 Arch length typically decreased in this sample from Tt to T2, with a mean decrease of - 0 . 6 5 mm. In nine o f the eleven cases, arch length decreased during treatment. This finding is not surprising, since all o f the cases involved the mixed dentition, and arch length typically decreases in the transition from the mixed to the permanent dentition. The postretention analysis also revealed a mean decrease in arch length of - 0 . 8 0 n~m. These cases appeared to be more stable than those reported by Glen et al. 23 (~ = - 2 . 4 mm) or by Little et al. 4t ~ = - 2 . 4 8 mm). Close examination o f the data presented in Table IV reveals that patient 4 had much greater elapse of all arch width parameters than any of the other patients. In searching for the reason for this disproportionate amount of relapse, it can be seen that this case involved much greater expansion during fixed appliance therapy (see Table III). This may have contributed to much of the observed relapse, and this case appears to substantiate the concept of intercanine width previously reported. ,4_25 CONCLUSIONS
The functional regulator appliance, as described in this study, has two main treatment effects: Class II correction and arch expansion. Reduction o f crowding during eruption is accomplished through the action of the vestibular shields. Although the stability o f the Class II correction is equally important in determining the viability of functional regulator treatment, and reports are inconclusive as to the mechanism of the Class II correction, 4453 this study is devoted solely to the study of the stability o f the arch expansion effects o f the
Am. J. Orthod. Dentofac. Orthop. November 1990
appliance. A future study will be devoted to investigation of the stability of the Class II correction. This study involves the analysis o f a very small sample and is intended to serve as a pilot study for future research. For this reason, the results should not be projected to the population. Because o f the retrospective nature o f this study, cause and effect conclusions would be invalid in the absence of other similar findings. All but one of the patients in this study wore some type of retention device, and the postretention period was not as long as in other postretention studies. True comparisons can be made only between cases with similar postretention periods. However, the results of this study support the suggestion that the arch expansion gained in this type o f treatment is more stable than expansion seen in fixed appliance treatment. Further investigations involving larger sample sizes and longer postretention periods should be conducted either to suppert or to dispute the findings of this study. Until such a time as there is sufficient evidence that any form of treatment results in acceptable long-term stability, it appears wise to be cautious regarding the retention phase of treatment.
REFERENCES 1. Angle EH. The treatment of malocclusion of the teeth. 7th ed. Philadelphia: SS White Manufacturing, 1907. 2. LundstromA. Malooclusionsof the teeth regarded as a problem in connection with the apical base. I,,,rr J ORTHODORALSURG 1923;I 1:591-602, 933-41, 1109-33. 3. Tweed CH. Clinical Orthodontics, vol 1. St. Louis: CV Mosby, 1966. 4. Sheridan JJ. Air-rotor stripping. J Clin Orthod 1985;19:43-59. 5. Bolton WA. Disharmony of tooth size and its relation to the analysis and treatment of malocclusion. Angle Orthod 1958; 28:113-30. 6. PeckS, Peck H. Crown dimensionsand mandibular incisor alignment. Angle Orthod 1972;42:148-53. 7. Moss ML, Salentijn L. The primary role of functional matrices in craniofacial growth. AM J ORTHOD1959;55:566-77. 8. Fr~nkel R. Decrowding during eruption under the screening influence of vestibular shields. AM J ORraOD 1974;65:372-406. 9. Friinkel R. Biomechanical aspects of the form/function relationship in craniofacial morphogenesis: a clinician's approach. In: McNamara JA Jr, Ribbens KA, Howe RP eds. Clinical alteration of the growing face. Ann Arbor: Center for Human Growth and Development, The University of Michigan, 1983. (Craniofacial growth series; No. 14.) 10. Fff2nkelR. The theoretical conceptunderlyingthe treatment with functional correctors. Trans Eur Orthod Soc 1966;42:233-54. I 1. Frankel R. The practical meaning of the functional matrix in orthodontics. Trans Eur Orthod Soc 1969;45:207-19. 12. Fr/inkel R. The guidance of eruption without extraction. Trans Eur Orthod Soc 1971;47:303-15. 13. Friinkel R. A functional approach to orofacial orthopedics. Br J Orthod 1980;7:41-51.
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