ORIGINAL ARTICLE

Skeletal and dental modifications produced by theBionator III appliance

Giovanna Garattini, MD, DDS,a Luca Levrini, MD,b Paolo Crozzoli, MD, DDS,a andAurelio Levrini, MD, DDSc

Milan, Italy

The therapeutic results of a functional orthopedic treatment with a Balters’ Bionator III appliance wereevaluated. The sample group included 39 white growing subjects with a dentoskeletal Class IIImalocclusion. A 2-year study compared results with a control group. The results showed that theBionator III is effective, especially when the malocclusion is mainly the result of a midfacial deficiencyand when there is a hypodivergent growth pattern. (Am J Orthod Dentofacial Orthop 1998;114:40-4.)

Different therapeutic approaches havebeen proposed for the treatment of skeletal Class IIImalocclusions; some authors assert the benefits ofearly orthopedic therapy, and others believe thatthis type of treatment should be delayed or that itshould be treated surgically.1-5 Such different thera-peutic strategies demonstrate how difficult it is forthe clinician to choose the correct treatment. Dif-ferent appliances may be used both in the orthodon-tic and in the orthopedic treatment of skeletal ClassIII malocclusions. These appliances are used indifferent ways, according to malocclusion patterns,skeletal age, patient compliance, and clinician’s ex-perience in their use. Successful clinical resultsreported by several authors6-13 have led us to verifythe actual skeletal modifications that occur whenusing the Balters’ Bionator III appliance in growingpatients with skeletal Class III malocclusion. Theuse of this appliance seems to cause some skeletalchanges1,14-17 through neuromuscular modifications.In this article the efficacy of Balters’ Bionator III ina group of white growing subjects is longitudinallyevaluated. The present study represents the comple-tion of a previous pilot study.18-21 The data of thesesubjects were compared considering sex and agewith the longitudinal cephalometric data of theLondon King’s College. Unfortunately, it was im-possible to compare our findings with other studiesbecause there was no other analogous research.

MATERIAL AND METHODSSamples examined and selection standards

Bionator III sample group. The sample group included55 selected patients consecutively treated between 1988and 1992, their ages ranged from 5 to 11 years (mean age,8 years). These patients were affected with four or more ofthe following anatomic or functional characteristics at thesame time: angle Class III molar relationship; edge-to-edge incisor position or anterior cross bite; concaveprofile; head hyperextension posture22; static and dynamicClass III neuromuscular attitude4; hypertonic upper lip;low and forward tongue rest position.23 The subjects wereradiographically examined (panoramic and lateral cepha-lometric radiographs taken by the same operator) usingtwo different instruments (Siemens Nanodor II and Sie-mens Ortocef 10). The treatment protocol foresaw theapplication of a modified Balters’ Bionator III (Fig. 1) ineach patient selected. The modified Balters’ Bionator III16

differs from the original24-26 in the following characteris-tics: deeper and wider lingual wings27; acrylic vestibularlateral shields extending deeply into the upper fornix28;upper labial buttons; upper incisor inclined plane.

The construction bite was taken by gently reposition-ing the mandible distally in centric relation. To do this, thepatient must be in a lying position and relaxation of themandible must be obtained for example using the tap-taptechnique. The mandible is thus positioned distally, ap-plying as little force as possible in order to put the condylein centric relation, avoiding compression in the retrodiscalpad. The vertical thickness of the bite, corresponding tothe interocclusal acrylic between upper and lower firstmolar should not exceed 3 to 4 mm, according to Balters’indications.17,26 Patients had to wear this appliance for atleast 22 hours a day. In order to check their complianceparents had to undersign a form on which the dailywearing time was recorded by the patient. Both body andoral muscle gymnastics were prescribed as auxillary ther-apy, according to individual needs.1 At the end of the2-year treatment period, clinical and radiographic exami-nations were repeated to evaluate dental and skeletal

From the Department of Dentistry and Stomatology, University of Milan,School of Medicine, Milan, Italy.aDepartment of Dentistry and Stomatology, University of Milan.bDepartment of Orthodontics, University of Pavia branch of Varese.cIn private practice.Reprint requests to: Dott.Luca Levrini, Via Recchi, 7, 22100 Como, Italy.Copyright © 1998 by the American Association of Orthodontists.0889-5406/98/$5.00 1 0 8/1/84818

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modifications caused by the treatment. From the original55 patients in the sample group, 4 were excluded as aresult of treatment planning modifications, 4 for poorcompliance, 6 because radiographic examination did notcomply with the expected protocol times at the end of theobservation period (i.e., after 2 years 6 2 months) and 2because they moved to another town. Finally, the Biona-tor sample group, reconsidered at the end of the experi-mental period was composed of 39 patients (average age,94.9 months): 24 females (average age, 90.4 months) and15 males (average age, 102.3 months) (Table I).

Control group. Changes in cephalometric values afterBionator III therapy in the Bionator sample group werecompared with those recorded in a longitudinal study of theLondon King’s College matched according to sex and age.29

Analysis method

Cephalometric analysis. We selected cephalometricmeasurements that in our opinion detected the changesproduced in the jaws by the orthopedic treatment, moreaccurately during the observation period (Fig. 1). All thelateral headplates were traced by the same operator andanalyzed with a computerized system (Orthocad 8.0,Databit, Cernusco sul Naviglio, Milan, Italy). Ten cepha-lograms were selected and traced to evaluate the reliabil-ity of the method. The average total difference betweenthe first and the second measurement was not statisticallysignificant for any landmark (p , 0.01). Consequently, theresulting error could be ignored.

Statistical analysis. A computerized system (Statview4.0, Abacus Concepts Inc, Berkeley, Calif.) was used tostatistically compare the cephalometric data of the pa-tients and the control group. Mean value and standarddeviations were calculated for each measurement, as wellas the differences between the start of treatment and theend of the observation period. The significance of thedifferences between the groups, which were due to bothtreatment and growth, was evaluated using the Wilcoxonsigned rank test. Pearson’s correlation test was also car-ried out. Finally, the ANOVA test was carried out todetermine whether the therapeutical effect depended onthe skeletal pattern.

RESULTS

The homogeneity of the initial conditions ofthe two examined groups was assessed by compar-ing the initial cephalometric measurements. Nostatistically significant difference was found, ex-cept data indicating a skeletal Class III, thus thetwo groups were considered equivalent. Analysisof the therapeutic effects was carried out bymeans of the same variables used to check theinitial conditions; these highlighted a significantincrease in all the measurements indicating thesagittal development of the maxilla. In particular,the mean interspinal increase of 2.9 mm (Table II)

was accompanied by a significant advancement ofpoint A (Ba-A 1 4.2 mm, ANS 1 1.2°, Pns-A 1 3mm [Table II]). Moreover, a significant increasein facial heights was recorded (N-Me 1 5.6 mm,S-Go 1 3.2 mm [Table II]) along with a slightposterior rotation of the palatal plane (N-Ans 1 3mm, S-NˆPns-Ans 1 0.9°, Table II). This poste-rior rotation was associated with a similar changeof the mandibular plane angle (Ans-Me 13.1 mm,S-NˆGo-Gn 1 0.9°, Table II).

Such changes contributed to a statistically signifi-cant change in the anteroposterior relationships be-tween the upper and the lower jaw (Wits 1 2.7 mm,ANB 1 2°, facial convexity 1 1.7 mm, Table II). Inorder to distinguish the modifications produced by thefunctional treatment from growth-linked increases,measurements describing the modifications occurring

Fig. 1. A and B, The modified Bionator III appliance.

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Garattini et al. 41

in both groups during the observation period werereciprocally compared.

Analysis of the results confirmed that the Biona-tor III is effective in producing a statistically signif-icant mean increase in the upper jaw length (Pns-Ans 1 1.4 mm, Pns-A 1 1.6 mm, Table III) togetherwith an advancement of point A (Ba-A 1 1.9 mm,Table III). Besides, palatal and mandibular planeangles widened (S-NˆPns-Ans 1 0.7°, Table IV,S-NˆGo-Gn 1 1.3°, Table III). These changes ac-count for the increase of the anterior facial height

(N-Me 1 1.5 mm, Table III). Reduced anteropos-terior mandibular growth (Go-Me 21.1 mm, S-N/Go-Me 1 1.6, PNSog 21°, Table III) and thevariation of the anteroposterior relationships be-tween the upper and the lower jaw were noticed(Wits 1 2.4 mm, Table III).

The ANOVA test was performed to assess thesignificance of the therapeutic changes according tothe skeletal pattern, determined by the anteriorfacial height/posterior facial height ratio (S-Go/N-Me). This test showed that therapeutical changes

Table I. Initial composition of the Bionator III group and control group

Group

Sex Initial ageObservation period

length Wits index

Male FemaleMean

(months)SD

(months)Mean

(months)SD

(months) Mean SD SE

Bionator 15 24 94.9 20 24.3 1.2 25.3 1.9 0.3Control 15 24 94 20 24 1 1.7 0.9 0.1

SD, Standard deviation.SE, Standard error.

Table II. Comparison of Bionator III group and control group

Bionator III group Control group

Initial Final Difference SD SE Significance Initial Final Difference SD SE

ANS 79.9 81.1 1.2 2.4 0.4 S** 79.6 79.6 20.1 0.2 eSNB 78.5 77.7 20.8 1.7 0.3 S** 76.7 76.6 20.1 2.2 0.4ANB 1.4 3.5 2 2 0.3 S*** 3.6 3.2 20.4 0.3 eS-N 66.3 67.9 1.6 1 0.2 S*** 62.6 64.1 1.6 0.3 ePns-A 41.6 44.6 3 1.8 0.3 S*** 41.2 42.6 1.4 0.6 0.1WITS 25.3 22.5 2.7 1.9 0.3 S*** 1.7 2 0.3 0.9 0.1Convessita 1.2 2.9 1.7 1.5 0.2 S*** 2.7 2.2 20.5 0.2 ePns-Ans 45.9 48.8 2.9 1.2 0.2 S*** 44.9 46.4 1.5 0.1 eGo-Me 66.3 68.6 2.3 1.9 0.3 S*** 58.9 62.3 3.4 0.8 0.1PNSog 78.6 78.4 20.3 1.6 0.3 NS 76.7 77.4 0.8 0.2 eBa-A 85.4 89.6 4.2 1.8 0.3 S*** 81.2 83.5 2.3 0.2 eAr-Pog 96.7 100.5 3.8 2.1 0.3 S*** 87.6 91.7 4 0.3 0.9S-N/Go-Me 99.8 98.2 21.6 4 0.6 S* 106.3 103 23.3 1.3 0.2Ar-Go anat 40.2 41.5 1.4 2 0.3 S*** 36.3 37.7 1.4 0.5 0.1N-Me 107.8 113.4 5.6 2.6 0.4 S*** 98.7 102.7 4 0.5 0.1N-Ans 46.5 49.6 3 2.3 0.4 S*** 44 46.3 2.3 0.4 0.1Ans-Me 62.6 65.7 3.1 1.6 0.3 S*** 56.1 57.7 1.6 0.3 eS-Go 67.1 70.3 3.2 1.4 0.2 S*** 60.9 63.8 2.9 0.3 eS-Go/N-Me 60.8 60.7 20.1 1.7 0.3 NS 61.7 62.1 0.4 0.4 1ArGoMe geo 130.5 129.5 21 2.6 0.4 S* 132.4 131.4 21 0.2 eSom. Jarabak 395.2 396 0.8 2.4 0.4 NS 396.7 396.1 20.5 0.4 0.1S-NˆGo-Gn 35.9 36.8 0.9 2.4 0.4 S* 36.7 36.2 20.5 0.4 0.1Pns-AnsˆGo-Gn 28.9 28.9 e 2.1 0.3 NS 29.7 29 20.6 0.3 0.1S-NˆPns-Ans 7 7.8 0.9 2.5 0.4 S* 7 7.1 0.1 0.2 eIˆS-N 102.3 97.9 24.3 15.2 2.9 NS 101.2 102.2 1.1 1.2 0.2IˆGo-Gn 87.8 84.2 23.6 7.9 1.5 S* 89.1 90.6 1.5 1 0.2EL-Ls Rik 23.4 23.2 0.2 2 0.3 NS 22.2 22.6 20.4 0.2 eEL-Li Rik 21.3 22.2 1 1.6 0.2 S* 21.9 22 20.1 0.2 eCmSnLs 115.3 116 0.7 9 1.4 NS 109.7 110.5 0.8 1.4 0.2

SD, Standard deviation.SE, Standard error.*p , 0.05; **p , 0.01; ***p , 0.001.

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42 Garattini et al.

were more significant in hypodivergent rather thanin normodivergent patients (Pns-Ans 1 0.8 mm,Pns-A 1 1.6 mm, Ar-Go 1 1.8 mm, Wits 1 1.8 mm,Table IV).

DISCUSSION

The age of the Bionator III patients ranged from5 to 11 years (mean age, 8 years); during this timethe annual growth rate is reduced in comparisonwith prepubertal growth spurt. As a consequence,although the Bionator III influences the craniofacialskeleton, its efficacy is higher when used during thepubertal growth spurt. Different reasons led to thechoice of patients who were far from the pubertalgrowth spurt. First of all, the choice of an earlytreatment is consistent with studies that show thegrowth potential of the incisive-canine suture de-creases after the age of 7 years.2,30-34 Besides, theprognosis of Class III malocclusions has beenjudged extremely poor by some authors,1,2 whoconsequently assert that early therapy is necessary togrowth. Although in our study the Bionator IIIappeared to be more effective in older patients, thecontrol of the malocclusion is not always predict-able. For this reason, we did not consider theinclusion of older patients in the Bionator III groupethically correct. To assess the effect of the BionatorIII on the craniofacial skeleton, the modifications inthe Bionator III group were compared with those inthe control group. In particular, the increase in themaxillary anteroposterior length and the advancingof point A, explain the significantly greater growthin the Bionator III group (mean value, 10.8 mm/year). At the same time, a decrease in mandibulargrowth (–0.5 mm/year) was noticed. The maxillarylength increase and the decrease of the mandibulargrowth explain the significant change in the antero-posterior relationships between the jaws (11.2 mm/year). These favorable changes make the Class IIImalocclusion treatment easier. This anteroposteriorjaw relationship improvement is mostly due to struc-tural changes and to anterior movements of theupper jaw. The anterior facial height increases whilethe posterior rotation of both jaws takes place. Such

Table III. Comparison of Bionator III group and control group

VariablesMean

difference SD SESignificance of

difference

Cranial and CraniofacialLinear (mm)

SN 20.1 1 0.2 N.S.N-Ans 0.7 2.2 0.4 N.S.Ans-Me 1.5 1.6 0.2 S.***N-Me 1.5 2.5 0.4 S.**S-Go 0.3 1.4 0.2 N.S.

Percentage (%)S-Go/N-Me 20.5 1.7 0.3 N.S.

Angular (°)Jarabak summation 1.3 2.3 0.4 S.**

Upper jawLinear (mm)

Pns-A 1.6 1.7 0.3 S.*Pns-Ans 1.4 1.3 0.2 S.**Ba-A 1.9 1.8 0.3 S.*

Angular (°)ANS 1.3 2.4 0.4 S.**SNˆPns-Ans 20.7 2.5 0.4 N.S.EL-Ls 0.6 2 0.3 N.S.CmSnLs 20.1 2 0.3 N.S.

MandibularLinear (mm)

Ar-Pog 20.3 2.1 0.3 N.S.Go-Me 21.1 1.9 0.3 S.**Ar-Go 0.0 2.0 0.3 N.S.

Angular (°)SNB 20.7 2.6 0.4 S*PNSog 21.0 1.5 0.2 S.***ArGoMe 0.0 2.6 0.4 N.S.S-NˆGoGn 1.3 2.2 0.4 S.***

Percentage (%)SN/GoMe 1.6 3.9 0.6 S.**

Anteroposterior jawsLinear (mm)

Wits 2.4 2.1 0.3 S.***Angular (°)

ANB 2.5 2.0 0.3 S.***Convexity 2.2 1.5 0.2 S.***Pns-AnsˆGo-Gn 0.7 2.1 0.3 N.S.

SD, Standard deviation.SE, Standard error.*p , 0.05; **p , 0.01; ***p , 0.001.

Table IV. Analysis of the variance (Anova test) according to skeletal pattern in the Bionator III group

Number ofcases

Difference between the groups

Pns-Ans(mean of thedifferences)

Pns-A(mean of thedifferences)

Ar-Go(mean of thedifferences)

Wits(mean of thedifferences)

F-test 2.3 4.3 3.2 4.3p 5 0.0492 p 5 0.0209 p 5 0.0483 p 5 0.0208

Hypodivergent 19 13.2 13.7 12.2 23.5Normodivergent 14 12.4 12.1 10.2 21.7Hyperdivergent 6 13.1 13.0 11.4 22.8

Fischer’s test PLSDHypodivergent vs Normodivergent

0.8* 1.2* 1.4* 1.3*

*95% significance.

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Garattini et al. 43

a modification may mean that the Bionator III doesnot effectively control the vertical growth, especiallyat mandibular level (1 0.7 mm/year), whereas themaxilla rotates posteriorly in a compensatory way.Some interesting variations were observed whencomparing the hypodivergent group with the nor-modivergent group. In particular the anteroposte-rior maxillary growth in the first group was greater(0.7 mm/year) and the Wits Index improvement (11 mm/year) was bigger.

CONCLUSIONS

Some authors are skeptical about orthopedic treat-ment with functional appliances.4 Unfortunately wecannot compare our results with those reported in theliterature, because previous studies only consideredclinical aspects. The results of our study suggest that theeffects of Balters’ appliance are mainly the result ofdentoalveolar changes in the growing craniofacial skel-eton. Although such changes are statistically significant,they are less evident from a clinical point of view. It wasalso proved in the study that the Balters’ Bionator III isan effective appliance in the treatment of Class IIImalocclusions in growing patients with midfacial defi-ciency. The Bionator III control of the anteroposteriormandibular growth is unpredictable and insignificant.Changes in the anterior facial height should be evalu-ated in a more exhaustive way with a larger study group.This may then explain how the improvement of theanteroposterior jaw relationship is produced. Betterrelationships might follow an increased development ofthe upper jaw as well as a mandible growth limitation.A larger study group could also show how important therole of the posterior rotation of the mandible is inmodifying these cephalometric measures. The BionatorIII failed to show an effective control on verticalgrowth. We feel that the use of this appliance should bepreceded by a careful evaluation of patient skeletal andgrowing patterns as it is not indicated for use in patientswith increased facial height. Therefore, the Bionator IIIis helpful in Class III malocclusion treatment in grow-ing patients with midfacial deficiency, hypodivergentgrowth pattern, and reduced facial height. Finally, theBionator III may also be considered a valid appliance inpatients with favorable skeletal features. In otherwords, a correct diagnosis is necessary to stress facialand skeletal variables and the extent of the malocclu-sion in order to rationally use this appliance. Noncom-pliance with these indications could explain clinicalfailures. We believe this therapy is cheap and quitecomfortable, and it may prove helpful when the diag-nosis is correct and patient compliance is good.

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