1-s2.0-S1073874600800213-main

An Evaluation of the Pendulum Distalizing Appliance Abu A. Joseph and Chris J. Butchart

Interest in nonextraction therapy has accelerated the use and development of several molar distalizing appliances requiring minimal patient compliance. The Pendulum appliance, developed by Hilgers, has become one of the more popular designs. This study attempts to evaluate the performance of the Pendulum appliance in correcting Class II malocclusions via molar distaliza- tion. Seven patients were treated using this appliance. Lateral cephalo- graphs were taken before treatment and immediately after removal of the appliance. Measurements were taken to evaluate molar movement and changes in angulation. Anchorage loss was measured by evaluating mesial incisor movement and angular changes. Changes in vertical dimension were also noted. Distalization occurred quite rapidly with overcorrection beyond a Class I molar relationship completed in an average time of 3.4 months. Mean distal movement of the upper first molars was 5.1 mm. This movement was accompanied by a mean change in angulation of 15.7 °. Anchorage loss was evident with a mean increase in incisor angulation of 4.9 ° and an average advancement at the incisal edge of 3.7 mm. Vertical dimension was virtually unaffected. This appliance was an effective means of distalizing molars into a Class I relationship with little patient cooperation. Some side effects were evident such as anchorage loss in the form of increased overjet and molar tipping. These side effects must be taken into account for when considering the use of this appliance. (Semin Orthod 2000;6:129-135.) Copyright © 2000 by W.B. Saunders Company

T he correction of a Class II malocclusion has always been a challenge in orthodontics.

Many treatment methodologies have been used to correct such conditions including extraction, headgear, 1 and functional appliance therapy, as well as o ther distalizing mechanisms such as the Wilson bimetric distalizing arch (Rocky Moun- tain Orthodontics, Denver, CO), 2 the Jones jig, the acrylic cervical occipital appliance (ACCO),3 and Class II elastics. A significant problem with these approaches is that they require patient cooperation.

'To diminish cooperation, various distalizing

From St. Louis, MO; and Montefiore Medical Cent~ Bronx, NY.. Address correspondence to Abu A. Joseph, BDS, MDS, DMD,

16267Port of Nantucket Dr, Ca'ov~ MO 63040. Copyright © 2000 by W.B. Saunders Company 1073-8746/00/0602-0007510:00/0 doi: l O. 1053/od. 2000.5901

systems have been developed that require less patient cooperation. Most of these appliances have used fixed Nance buttons with ei ther open coil springs 4 or repelling magnets. 5,6 One such appliance, the Pendulum, was int roduced by Hilgers in 1992. v As is the case with similar appliances, the Pendulum appliance consists of a palatal Nance componen t with rests that are bonded to the occlusal surface of the first a n d / o r second premolar teeth. The distalizing mechanism consists of bilateral helical springs composed of titanium molybdenum alloy (Fig 1). The springs of the appl iance p roduce 200 to 250 g of force in a swinging arc move- rnent, hence the name pendulum. A modification of this appliance, called the Pendex, incorporates an expansion screw to allow for palatal expan- sion.

In this study, the authors examined the effects of the Pendulum appliance on molar distaliza-

Seminars in Orthodontics, Vol 6, No 2 (June), 2000: pp 129-135 129

130 Joseph and Butchart

Figure 1. The Pendulum appliance used in the pre- sent study.

tion, vertical dimension, and anchorage loss measured at the incisor and molar teeth.

Materials and Methods

Seven patients in the late mixed and early perma- nent dentit ion with Class II malocdusions were selected. The characteristics of each patient is shown in Table 1. The patients had an age range of 9 years, 3 months to 13 years, 4 months. The patients varied in skeletal pat tern as defined by the ANB angle with a range of 2 ° to 6 °, but all patients had a Class II dental relationship. Three patients had a full-cusp Class II molar relation- ship whereas the remaining four had an end on molar relationship. In 3 of the patients, the second molar teeth had erupted before the commencement of treatment.

All patients had their maxillary molar teeth distalized using a Pendulum appliance (Fig 1). The appliances were activated only one time by bending the springs 90 ° to the base of the

Table 1. Patient Characteristics

Treatment Time 2nd Molars Molar Pret~atment

Patient (114o) Present Classification Age

1 1.5 N o E n d o n 11 y I m o 2 5 N o Ful l Class II 9 y 3 m o 3 5 Yes E n d o n 13 y 4 m o 4 2 N o E n d o n 11 y 2 m o 5 3 N o E n d o n 9 y 3 m o 6 3 Yes Ful l Class II 13 y 2 m o 7 4 Yes Ful l Class II 11 y 10 m o

appliance, and were maintained in the mouth until all the molars were overcorrected to a super Class I relationship. Cephalometric radiographs were taken before t reatment and immediately after removal of the appliance.

The radiographs were then traced. A custom analysis was used to determine the changes that occurred and that were unique to this appliance. The points and lines used were upper incisor long axis (U1), upper incisor edge (U1E), upper incisor apex (U1A), upper first molar long axis (U6), upper first molar mesial buccal cusp (U6MB), upper first molar distal root apex (U6A), Gonion, Gnathion (GoGn), and a verti- cal plane (Y). The vertical plane (Y) used the points SE and inferior point of PM as described by Enlow. s

The following angular and linear measure- ments (Fig 2) were then constructed using these reference points:

Anchorage Loss:

1. Upper central incisor long axis (U1) to pala- tal plane (PP) (angular);

2. Upper central incisor edge (U1 E) to Y (linear);

3. Upper central incisor apex (U1A) to Y (lin- ear) ;

Molar Movement:

4. Upper first molar long axis (U6) to palatal plane (PP) (angular) ;

5. Upper first molar mesial buccal (U6MB) cusp to Y (linear);

7. Upper first molar distal buccal root apex (U6A) to Y (linear);

Vertical Changes:

8. Upper first molar mesial buccal cusp (U6MB) to palatal plane (PP) (linear);

9. GoGn to Sn (angular).

Results

As previously stated, all patients had their maxil- lary first molar teeth sufficiently distally moved so that overcorrection of the molars into a Class I molar relationship was achieved. An example of the distalization can be seen in Figures 3 and 4. Treatment time ranged from 1.5 to 5 months (Table 1).

An Evaluation of the Pendulum Distalizing Appliance 131

Figure 2. The cephalomet- ric analysis used in the study. The points and lines used were upper incisor long axis (U1), upper incisor edge (U1E), upper incisor apex (U1A), upper molar long axis (U6), upper molar me- sial buccal cusp (U6MB), upper molar apex (U6A), Gonion, Gnathion, and a vertical plane (Y). Angular measurements were GoGn- SN, U6-PE and U1-PP. Lin- ear measurements includ- ing UIA-Y, U6A-Y, U1E-Y, and U6MB-Y are repre- sented by the various dashed lines.

SN

GoGn

U6

U1

. . . . . . . . . . . . U 1A-Y 1 GoGn-Sn (Angle)

.. . . . . . . . . . . . . . . . . . . . . U6A-Y 2 U6-PP (Angle)

............................................. U1E-Y

. . . . . . . . U6MB-Y 3 U1-PP (Angle) 4 ANB (Angle)

T h e average max i l l a ry m o l a r d i s ta l iza t ion was 5.1 m m with a r ange o f 3 to 7 m m when m e a s u r e d at the mesia l bucca l cusp t ip (Table 2). M o v e m e n t at the r o o t apex , however, was mini - mal . T h e max i l l a ry m o l a r crowns t i p p e d distal ly an average o f 15.7 ° with a r a n g e o f 3 ° to 28 °. General ly , t i p p i n g i n c r e a s e d as m o v e m e n t in- c r ea sed (Fig 5). In add i t i on , t h e r e was a r ec ip ro - cal effect on the incisors in tha t the max i l l a ry incisors p r o c l i n e d an average o f 4.9 ° with a r a n g e o f 1 ° to 10 °. T h e incisors were a d v a n c e d an average o f 3.7 m m at the incisal edge ( r ange 2 to 6 m m ) , a n d 1.7 m m at the apex ( r ange 1 to 3 m m ) . Vert ical d i m e n s i o n r e m a i n e d vir tual ly un- c h a n g e d with a m e a n c h a n g e at G o G n to Sn o f only 0.14 ° . T h e average effects o f the a p p l i a n c e on the d is ta l iza t ion o f the t ee th a n d the anchor - age loss a re r e p r e s e n t e d in F igure 6.

Discuss ion

T h e P e n d u l u m a p p l i a n c e eff iciently d is ta l ized the m a x i l l a r y m o l a r t ee th to a Class I re la t ion-

ship. This d i s ta l iza t ion o c c u r r e d wi thou t any c o o p e r a t i o n p r o b l e m s on the pa r t o f any o f the pa t ien ts . F u r t h e r m o r e , only o n e ac t iva t ion pe- r iod was n e e d e d for the process to be successful. T h e s e are the two m a i n advan tages o f the appl i - ance when c o m p a r e d with o t h e r app l i ances re- q u i r i n g p a t i e n t c o m p l i a n c e such as h e a d g e a r a n d Class II elastics.

M o r e d i s ta l iza t ion was n o t e d (5.1 m m ) than has b e e n r e p o r t e d in p rev ious studies. T M How- ever, this inc rease in d i s ta l iza t ion was a t t a ined at the e x p e n s e o f i n c r e a s e d dis ta l m o l a r t i p p i n g ( m e a n 15.7°). Gosh a n d N a n d a 9 a n d Byloff a n d D a r e n d e l i l e r a° f o u n d t i p p i n g as a resul t o f the

132 Joseph and Butchart

Pendulum to range from 8.3 ° and 14.5 ° , respec- tively. Byloff and Darendeliler 1° found a signifi- cant correlation between the amount of distaliza- tion and the degree of distal molar tipping. Increased tipping with increased distalization was also noted in the present study (Fig 5). Byloff and Darendeliler 11 attempted to correct the molar tipping by incorporating an uprighting bend in the pendulum spring after distalization of the molar had been completed. The upright- ing bend in the pendulum spring appeared to be successful in uprighting the roots of the tipped molars.

Figure 3. A patient treated with the pendulum appli- ance. Pretreatment view of maxillary arch (A) and pre- treatment cephalometric ra- diograph (B). Posttreat- ment occlusal view with the pendulum appliance in place (C) and posttreat- ment cephalometric radio- graph (D).

The presence of second molars has been considered to be a hindrance to traditional means of distalization, such as the use of the headgear. However, this was not the case with the pendulum appliance. Distalization seemed to be successfully achieved regardless of the status of the second molar teeth, patient age, or molar classification (Table 1). The three patients who had second molars erupted achieved a correc- tion as quickly as those who did not. Gosh and Nanda 9 also did not find second molars to be a hindrance to distalization. It was reported that the presence of second molar teeth did not

Figure 4. Buccal photo- graphs of the distalization achieved in a typical pa- tient. Pretreatment (A, B) and posttreatment (C, D).

An Evaluation of the Pendulum Distalizing Appliance 133

Table 2. Descriptive Statistics of the Analysis Used in the Study

U1-PP (Angle) U1A-Y U1E-Y (Degrees) (ram) (ram)

U6-PP (Angle) (Degrees)

Patients Pre Post Change Pre Post Change Pre Post Change Pre Post Change

1 100 105 - 5 41 43 - 2 50 52 - 2 74 71 3 2 117 125 - 8 43 46 - 3 57 63 - 6 73 63 10 3 102 112 - 1 0 46 47 - 1 57 60 - 3 73 56 17 4 127 129 - 2 41 42 - 1 53 56 - 3 79 61 18 5 119 125 - 6 43 42 1 55 58 - 3 76 58 18 6 112 114 - 2 44 47 - 3 54 58 - 4 79 63 16 7 114 115 - 1 51 54 - 3 66 71 - 5 88 60 28

Mean 113.0 117.9 -4 .9 44.1 45.9 -1 .7 56.0 59.7 -3 .7 77.4 61.7 15.7 Median 114 115 - 5 43 46 - 2 55 58 - 3 76 61 17 SD 8.8 8.0 3.1 3.2 3.9 1.4 4.7 5.6 1.3 4.9 4.5 7.1 Range 100-127 105-129 9 41-51 42-54 - 4 50-66 52-71 4 73-88 5@71 25

Descriptive Statistics of the Analysis Used in the Study

U6MB- Y U6A- Y U6MB-PP GoGn-Sn (ram) (ram) (mm) (Degrees)

Patients Pre Post Change Pre Post Change Pre Post Change Pre Post Change

1 21 18 3 15 17 - 2 20 21 1 38 37 1 2 17 13 4 12 14 - 2 20 20 0 35 35 0 3 21 15 6 17 16 1 23 22 1 36 37 - 1 4 21 15 6 17 17 0 20 20 0 28 28 0 5 15 10 5 12 13 - 1 18 21 - 3 35 38 - 3 6 42 37 5 38 37 1 26 27 - 1 48 48 0 7 31 24 7 23 23 0 19 19 0 33 31 2

Mean 24.0 18.9 5.1 19.1 19.6 -0 .4 20.9 21.4 -0 .6 36.1 36.3 -0.1 Median 21 15 5 17 17 0 20 21 0 35 37 0 SD 8.7 8.4 1.2 8.4 7.7 1.2 2.5 2.4 1.2 5.6 5.8 1.5 Range 15-42 10-37 4 26 24 3 8 8 4 20 20 5

interfere with distalization of the molar teeth when using the Wilson distalizing arch. ~2 The latter is contrary to the findings of Gianelly 5 who found that second molars impeded the distaliza- tion of the first molars when using magnets.

Anchorage loss was clearly shown in the pres- ent study as def ined by the significant maxillary incisor procl inat ion (mean 4.9 °) and increase in overjet that occurred at the end of the move-

Figure 5. Chart represents the tipping of the first molar that occurred when plotted against the move- ment achieved.

m e n t (mean 3.7 mm) . Anchorage loss was also noted by Ghosh and Nanda 9 and Byloff and Darendeliler. 1° However, the authors observed a larger increase in overjet compared with that repor ted by Gosh and Nanda 9 and Byloff and Darendeliler, 1° 3.7 m m versus 1.3 m m and 0.92 ram, respectively. Again, there appears to be some correlat ion to the amoun t of distalization and the extent of side effects, in this instance incisor proclination. The Pendulum appliance may be detr imental for those who should not have their maxillary incisor teeth advanced dur- ing molar distalization. Examples of these pa- tients would be those with thin labial bone, deficient gingival height, or severe incisor procli- nation.

Very little change in vertical dimension was found in the present study. This is especially interesting in view of the pat ient sample. The present sample was composed of a predomi- nately hyperdivergent skeletal pa t te rn pat ient group who had a mean p re t rea tment mandibu- lar plane angle of 36.1 ° . Two patients had man-

134 Joseph and Butchart

5.1ram

(Average linear ~'~" change in U6MB-Y) /"

/ i /

1 5.7 degrees

(Average angular change in U6-PP)

%

3.7 m~

"~\'* '~".i (Average linear c i [ i g e In U1E Y)

4,9 degrees (Average angular changein UI-PP)

Figure 6. The average changes in tooth positions. Pretreatment positions of the maxillary first molar and the maxillary central inci- sor are represented by the solid line. Posttreatment po- sitions of these same teeth are represented by the dashed lines.

dibular plane angles of 38 ° and 48 °, respectively, and their pos t t rea tment outcomes indicated re- markably little change in the vertical dimension. In the study by Ghosh and Nanda, 9 a small backward rotation of the mandible (mean 1.09 ° ) was reported. They divided their patients into three groups based on the Frankfort mandibula r plane angle (FMA). These groups were as fol- lows: less than 20 °, 20 ° to 25 °, and greater than 25 °. In their study, there was a t rend observed after t rea tment toward an increase in the man- dibular plane angle, however, it was not statisti- cally significant. When main tenance of the man- dibular plane angle is the desired objective, the fact that bite opening did not occur with the Pendulum appliance can be a factor worth con- sidering. Perhaps mandibu la r p lane mainte- nance occurs because the appliance appears to tip the molars back in an arc with t ipping occurr ing near the apex of the roots. The fact that cervical headgears have a bi te-opening ef- fect is well known, ~ so any appliance that can distalize molar teeth without opening the bite would be particularly advantageous in the treat- men t of high-angle Class II a n d / o r dentally crowded patients.

The need for minimal pat ient cooperat ion is one of the most desirable qualities of the Pendu- lum appliance when compared with o ther appli- ances such as the headgear, the ACCO, and the Wilson distalizing arch. In addition, because the

Pendulum does not require intermaxil lary elas- tics for anchorage support , as required in the Wilson distalizing system, loss of anchorage in the mandibular arch is not a concern. The Pendulum appliance could prove to be useful in the t rea tment of patients who have prognathic maxillas and ideal lower arches that otherwise would have to be compromised in a system that uses the lower arch for anchorage support .

Also of particular interest to the clinician should be the fact that only one activation per iod was necessary to achieve results. Most distalizing appliances, including headgears, the ACCO, and Wilson mechanics, require some sort of reactiva- tion or titration of forces to effect a change.

This study has shown the propert ies and action of the pendu lum distalizing appliance. Although the authors ' results were remarkably similar to those repor ted in previous studies, 9-n the interpretat ion of their results is understand- ably limited owing to a small sample size. Further- more, the authors ' sample consisted of patients who had essentially hyperdivergent skeletal pat- terns.

Conclusions

The results of the authors ' study are in agree- m e n t with those of past studies 9,1° in that the Pendu lum appliance is an effective me thod for molar distalization requir ing little in the way of

An Evaluation of the Pendulum Distalizing Appliance 135

patient compliance. However, this gain in distal- ization is at the expense of significant side effects including distal molar tipping and anchorage loss at the incisors. Molar distalization occurred without any significant changes to the mandibu- lar plane angle.

References

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2. Wilson RC, Wilson WL. Rapid bilateral molar distaliza- tion. In: Wilson RC, Wilson WL (eds). Enhanced Orth- odontics. Denver: Rocky Mountain/Orthodontics, 1988, pp 113-130.

3. Cetlin NM, Ten Hoeve A. Non extraction treatment. J Clin Orthod 1983;17:396-413.

4. Gianelly AA, BednarJ, Dietz VS.Japanese NiTi coils used to move molars distally. AmJ Orthod 1991;99:546-566.

5. Gianelly AA, Vaitas AS, Thomas WM, et al. Distalization

of molars with repelling magnets.J Clin Orthod 1988;22: 40-44.

6. GianellyAA, Vaitas AS, Thomas WM. The use of magnets to move molars distally. AmJ Orthod 1989;96:161-167.

7. Hilgers~J. The Pendulum appliance for Class II noncom- pliance therapy.J Clin Orthod 1992;26:700-713.

8. Enlow D, Huroda T, Lewis A. The morphological and morphogenetic basis for craniofacial form and function. Angle Orthod 1971;41:161-188.

9. GhoshJ, Nanda RS. Evaluation of an intraoral maxillary molar distalization technique. Am J Orthod 1996;110: 639-646.

10. Byloff FK, Darendeliler MA. Distal molar movement using the pendulum appliance. Part I: Clinical and radiographic evaluation. Angle Orthod 1997;4:249-260.

11. Byloff FK, Darendeliler MA, Clar E, et al. Distal molar movement using the pendulum appliance. Part 2: The erects of maxillary molar root uprighting bends. Angle Orthod 1997;4:261-262.

12. Muse D, Fillman M, Emmerson W, et al. Molar and incisor changes with Wilson rapid molar distalization. AmJ Orthod 1993;104:556-565.