Long-term Effectiveness and Treatment Timing for Bionator Therapy

Transcription

1 Originl Article Long-term Effectiveness nd Tretment Timing for Biontor Therpy Kurt Fltin Jr, DD, PhD; Rolf M. Fltin, DD, Mc, PhD; b Tizino Bccetti, DD, PhD; c Lorenzo Frnchi, DD, PhD; c Bruno Ghiozzi, DD; d Jmes A. McNmr Jr, DD, PhD e Abstrct: The im of the present investigtion ws to provide informtion bout the long-term effects nd optiml timing for clss-ii tretment with the Biontor pplince. Lterl cephlogrms of 23 clss-ii ptients treted with the Biontor were nlyzed t three time periods: T1, strt of tretment; T2, end of Biontor therpy; nd T3, long-term observtion (fter completion of growth). T3 includes phse with fixed pplinces. The treted smple ws divided into two groups ccording to their skeletl mturity s evluted by the cervicl vertebrl mturtion (CVM) method. The erly-treted group (13 subjects) initited tretment before the pek in mndibulr growth, which occurred fter completion of Biontor therpy. The lte-treted group (10 subjects) received Biontor tretment during the pek. The T1 T2, T2 T3, nd T1 T3 chnges in the treted groups were compred with chnges in control groups of untreted clss-ii subjects by nonprmetric sttistics (P.05). The findings of the present study on Biontor therpy followed by fixed pplinces indicte tht this tretment protocol is more effective nd stble when it is performed during the pubertl growth spurt. Optiml timing to strt tretment with the Biontor is when concvity ppers t the lower borders of the second nd the third cervicl vertebre (CVM II). In the long term, the mount of significnt supplementry elongtion of the mndible in subjects treted during the pubertl pek is 5.1 mm more thn in the controls, nd it is ssocited with bckwrd direction of condylr growth. ignificnt increments in mndibulr rmus height lso were recorded. (Angle Orthod 2003;73: ) Key Words: Clss-II mlocclusion; Functionl jw orthopedics; Cephlometrics; Cervicl vertebrl mturtion INTRODUCTION The Blters Biontor 1,2 is one of the most commonly used pplinces for functionl tretment of clss-ii, division Chir, Deprtment of Orthodontics, chool of Dentistry, University Pulist, ão Pulo, Brzil; Invited Professor, Deprtment of Fcil Orthopedics, University of Ulm, Germny. b Associte Professor, Deprtment of Orthodontics, chool of Dentistry, University Pulist, ão Pulo, Brzil. c Reserch Associte, Deprtment of Orthodontics, The University of Florence, Florence, Itly; Thoms M Grber Visiting cholr, Deprtment of Orthodontics nd Peditric Dentistry, chool of Dentistry, The University of Michign, Ann Arbor, Mich. d PhD progrm in Peditrics nd Preventive Orthodontics, Deprtment of Orthodontics, The University of Florence, Florence, Itly. e Thoms M nd Doris Grber Endowed Professor of Dentistry, Deprtment of Orthodontics nd Peditric Dentistry, chool of Dentistry; Professor of Cell nd Developmentl Biology, chool of Medicine; nd Reserch cientist, Center for Humn Growth nd Development, The University of Michign, Ann Arbor, Mich; Privte prctice, Ann Arbor, Mich. Corresponding uthor: Lorenzo Frnchi, DD, PhD, Universitá degli tudi di Firenze, Vi del Ponte di Mezzo, 46-48, 50127, Firenze, Itly (e-mil: condx@tin.it). Accepted: November ubmitted: August by The EH Angle Eduction nd Reserch Foundtion, Inc. 1 mlocclusions ssocited with mndibulr retrusion. The populrity of this pplince is due in prt to number of fvorble chrcteristics tht include the reltive ese in the construction nd clinicl hndling of the pplince nd the high level of comfort for the ptient, who usully shows positive cceptnce nd complince. The generic term Biontor, s mtter of fct, describes fmily of toothborne pplinces tht produce forwrd positioning of the mndible in ssocition with vrible effects in the verticl plne, ie, open, close, or mintin the bite. 3 After its introduction in 1964, the Biontor hs been the object of severl investigtions imed to identify both the dentolveolr nd skeletl effects of this pplince. Most studies delt with short-term outcomes of Biontor therpy by using vrious types of control groups (untreted clss-i or clss-ii subjects). 4 8 Dentolveolr chnges consist of mxillry incisor retrction nd uprighting, ssocited with proclintion of the lower incisors (when cpping of these teeth is not used). An increse in mndibulr molr eruption cused by djustments in the eruption fcets of the pplince hs been documented s well. Although no skeletl modifiction hs been found for the mxill, fvorble increse in totl 221

2 222 FALTIN, FALTIN, BACCETTI, FRANCHI, GHIOZZI, MCNAMARA mndibulr length hs been described consistently in ptients treted with the Biontor. The skeletl chnges re ssocited with significnt effects on the soft tissues, minly consisting of chnges in the verticl dimensions of the fce nd position of the lips. 9,10 Recently, the issue of optiml tretment timing for functionl jw orthopedics hs gined the ttention of both reserchers nd clinicins. Cephlometric studies hve shown tht the therpeutic effectiveness of the most functionl pplinces is gretest when these pplinces re used during the scending portion of the individul pubertl growth spurt. Typiclly, ptients treted during the pek period demonstrte significnt skeletl effects induced by the pplince, wheres ptients treted in the prepek period hve the significnt effects confined to the dentolveolr level. The Biontor is no exception to these findings, s documented in the studies by Jnson. 4,5 In her short-term investigtion, Jnson described n insignificnt slight increse in mndibulr size when the Biontor ws used during prepubertl developmentl stges, wheres the mndibulr chnges becme significnt over untreted controls when the pek ws included in the tretment period. To our knowledge, the only long-term study on the crniofcil chnges induced by the Biontor is by Rudzki- Jnson nd Nochtr, 18 who evluted group of ptients treted with the Biontor five yers fter the completion of retention. These ptients showed n increse in the size of the mndible nd decrese in both the distl skeletl jw reltionship nd the gonil ngle. However, the lck of control group of untreted subjects nd the use of tretment outcome s criteri for cse selection re limiting fctors for n dequte pprisl of the effectiveness of Biontor therpy in the long term. Furthermore, no ssessment of idel tretment timing for this type of tretment ws ttempted in the study. The im of the present investigtion is to provide informtion bout the long-term effects of clss-ii mlocclusion tretment with the Biontor nd, concurrently, to nlyze differences in the dentoskeletl response of ptients treted before or during the pek in mndibulr growth. The strengths of the study re the use of group of untreted clss-ii subjects nd the pprisl of stges in individul skeletl mturity by the cervicl vertebrl mturtion (CVM) method. UBJECT AND METHOD The cephlometric records of 30 clss-ii mlocclusion ptients consecutively treted with the Biontor were collected from single orthodontic prctice where this type of therpy ws used. The tretment protocol consisted of clss-ii correction by Biontor constructed without coverge of the lower incisors, followed by pproximtely one yer of fixed pplince therpy to refine occlusion. After FIGURE 1. The new CVM method. the comprehensive phse, ech ptient ws given fixed lower incisor retiner. even ptients were eliminted from the study becuse of the pretretment bsence of full clss-ii molr reltionship or poor film qulity. The remining 23 sets of cephlogrms were nlyzed. Finl successful completion of therpy ws not criterion for cse selection. Lterl cephlogrms were obtined t three time periods: T1, t the strt of tretment; T2, t the end of Biontor therpy; nd T3, t long-term observtion fter completion of growth. Therefore, the effects of ctive tretment with the Biontor were ssessed during the T1 T2 intervl, wheres the nlysis of T2 T3 intervl provided informtion bout the posttretment chnges tht included phse of tretment with fixed pplinces to refine the occlusion. The T1 T3 intervl ws used to describe the overll tretment nd posttretment dentoskeletl modifictions. The treted smple ws divided into two groups ccording to skeletl mturity t the strt of tretment s evluted by recently implemented version of the CVM method. 19,20 This version of the CVM method includes five mturtionl stges (CVM I through CVM V, insted of Cvs 1 through Cvs 6 in the former CVM method; 21 Figure 1). The pek in mndibulr growth occurs between CVM II nd CVM III; the pek hs not been reched without the ttinment of CVM II. CVM V is recorded t lest two yers fter the pek. The dvntges of the new version of the CVM method re tht mndibulr skeletl mturity cn be pprised on single cephlogrm nd tht it involves the nlysis of only the second, third, nd fourth cervicl vertebre, which usully re visible even when protective rdition collr is worn. The erly-treted group (ETG; Tble 1) consisted of 13 subjects (seven femles nd six mles) presenting with CVM I in cervicl vertebre mturtion t T1. The stges in cervicl vertebre mturtion t T2 were either CVM I or CVM II. Therefore, the pek in growth velocity ws not included in the period of tretment with the Biontor for ny of the subjects in the erly group. The stges in cervicl vertebre mturtion t T3 were either CVM IV or CVM V. The lte-treted group (LTG; Tble 1) included 10 subjects (six femles nd four mles) presenting with CVM II in cervicl vertebre mturtion t T1. The stges in cervicl vertebre mturtion t T2 were either CVM

3 LONG-TERM EFFECT OF BIONATOR 223 TABLE 1. Descriptive ttistics for Age nd Observtion Periods Age T1 T2 T3 Observtion Period T1 T2 T2 T3 T1 T3 Erly-treted group (n 13) 9y8mo 1y3mo 11y6mo 1y3mo 17y5mo 2y 1y10mo 7mo 5y10mo 2y2mo 7y8mo 2y5mo Erly control group (n 11) 9y5mo 1y3mo 11y6mo 1y4mo 16y4mo 1y9mo 2y1mo 7mo 4y10mo 1y10mo 6y10mo 1y6mo Lte-treted group (n 10) 10y9mo 1y8mo 13y2mo 2y3mo 19y2mo 2y2mo 2y4mo 1y6mo 6y0mo 10mo 8y4mo 1y8mo Lte control group (n 10) 11y2mo 1y6mo 12y11mo 1y9mo 17y2mo 1y1mo 1y9mo 8mo 4y3mo 2y3mo 6y0mo 1y10mo III or CVM IV. Therefore, the pek in growth velocity ws included in the period of tretment with the Biontor for ll the subjects in the lte group. The stge in cervicl vertebre mturtion t T3 ws CVM V. The treted smple ws compred with smple of 21 subjects with untreted clss-ii mlocclusions (control smple) selected from the University of Michign Elementry nd econdry chool Growth tudy. 22 The control smple lso ws divided into two groups ccording to the stge in CVM. The erly control group (ECG; Tble 1) included 11 subjects (five femles nd six mles), wheres the lte control group (LCG; Tble 1) consisted of 10 subjects (five femles nd five mles). The control groups mtched the corresponding treted groups to the stge in CVM t ech observtion period (T1, T2, nd T3). The reltively shorter T2 T3 intervl of observtion in the LCG when compred with LTG did not ffect the interprettion of the dt becuse ll the subjects in both LCG nd LTG hd completed the ctive phse of skeletl growth t T3 (CVM V). Cephlometric nlysis Lterl cephlogrms of both treted groups nd both control groups t T1, T2, nd T3 were stndrdized to the mgnifiction fctor nd nlyzed by digitizing tblet (Numonics, Lnsdle, Pennsylvni, PA) nd digitizing softwre (Viewbox, ver. ). 23 A cephlometric nlysis derived from both Johnston s 24 nd Pncherz s 25 originl nlyses nd comprising modified reference system for the superimposition procedure ws pplied. The definitions for the lndmrks used in the nlysis hve been provided previously. 26 The occlusl line (OL) nd the occlusl line perpendiculre (OLp) from the cephlogrm t T1 were used s reference grid. The grid ws trnsferred from the initil trcing to subsequent trcings t T2 nd T3 by superimposing the trcings on the T-FMN line, with T point s the registrtion point. All liner mesurements were performed prllel to OL nd perpendiculr to OLp. The following vribles were mesured (Figure 2). is/olp minus ii/olp overjet; ms/olp minus mi/olp molr reltion ( positive vlue FIGURE 2. Cephlometric nlysis. indictes distl reltion; negtive vlue indictes mesil reltion); A point/olp sgittl position of the mxillry bse; pg/olp sgittl position of the mndibulr bse; co/olp sgittl position of the condylr hed; pg/olp co/olp composite mndibulr length; is/olp minus A point/olp sgittl position of the mxillry centrl incisor within the mxill; ii/olp minus pg/olp sgittl position of the mndibulr centrl incisor within the mndible; ms/olp minus A point/olp sgittl position of the mxillry permnent first molr within the mxill; mi/olp minus pg/olp sgittl position of the mndibulr permnent first molr within the mndible. Additionl mesurements for crnil bse ngultion, mndibulr dimensions, nd skeletl verticl reltionships were obtined on ll cephlogrms t T1, T2, nd T3, independently from the superimposition reference system (Figure 3). liner mesurements co-pg, co-go, go-pg; ngulr mesurements FMN-T-b, FMN-T-r, cl-ml, rgoi-me, nl/t-fmn line, ml/t-fmn line, nl-ml.

4 224 FALTIN, FALTIN, BACCETTI, FRANCHI, GHIOZZI, MCNAMARA mm when compred with growth chnges in the ECG. The min contribution to occlusl correction ws due to smller, though insignificnt, increse in mxillry protrusion in ETG when compred with ECG. No other significnt modifictions were detected in the ETG during ctive therpy. Posttretment chnges in the ETG (Tble 3) No significnt modifiction ws found during the posttretment period in ETG when compred with ECG. Both overjet nd molr reltion remined virtully unchnged fter Biontor therpy. Overll tretment nd posttretment chnges in the ETG (Tble 4) FIGURE 3. Additionl cephlometric mesures. The method error nd the coefficient of relibility for the cephlometric mesurements hve been described previously. 26 ttisticl nlysis The strting forms of ETG nd LTG were compred with those in ECG nd LCG, respectively. Crniofcil modifictions in the treted groups were compred with the growth modifictions occurring in the corresponding control groups. In prticulr, T1 T2 chnges were nlyzed to describe the effects of ctive therpy with the Biontor. T2 T3 chnges indicted posttretment modifictions including phse with fixed pplinces. T1 T3 chnges provided informtion bout the long-term overll effects of both tretment nd posttretment intervls. All sttisticl comprisons were performed by nonprmetric test due to the limited number of subjects in ech group (Mnn-, P.05). The tests were crried out by using commercil sttisticl pckge (P for Windows, relese 1.0, P Inc). REULT Comprison of strting forms No sttisticlly significnt difference ws found in the crniofcil configurtions t T1 in ETG nd LTG when compred with ECG nd LCG, respectively. All groups showed n verge overjet of more thn six mm nd full cusp clss-ii molr reltionship. Tretment effects in the ETG (Tble 2) Tretment with the Biontor pplince before the pubertl pek produced significnt overjet correction of mm nd significnt sgittl correction in molr reltion of At the completion of the overll observtion period, no significnt difference in the dentoskeletl configurtion of the ptients treted before the pubertl growth spurt ws recorded. Tretment produced n overjet correction of mm nd correction in molr reltion of mm when compred with chnges in the ECG. Tretment effects in the LTG (Tble 5) Tretment with the Biontor pplince when the pubertl pek ws included in the ctive tretment period induced significnt overjet correction of 4.4 mm nd correction in molr reltion of mm when compred with chnges in the LCG. A significnt mesil dvncement of the mndibulr dentition t both the molr nd incisor regions occurred in LTG. At the skeletl level, supplementry increses in totl mndibulr length nd in rmus height (of 4.3 mm both), long with significnt opening of the gonil ngle nd of the ngle between the condylr line nd the mndibulr line, were found in LTG when compred with LCG. Posttretment chnges in the LTG (Tble 6) As for ETG vs ECG, no significnt modifiction ws found during the posttretment period in LTG when compred with LCG either. Both overjet nd molr reltion remined lmost unchnged fter Biontor therpy. Overll tretment nd posttretment chnges in the LTG (Tble 7) In the long term, the ptients treted during the pubertl growth spurt showed significnt overjet correction of 4.2 mm nd correction in molr reltion of mm when compred with chnges in the LCG. ignificntly greter increments in totl mndibulr length ( 5.1 mm) nd in rmus height ( 4.8 mm) were ssessed in LTG when compred with LCG. These chnges were ssocited with significntly greter growth increment of the mndibulr condyle in bckwrd direction in LTG, nd with significnt opening of the gonil ngle nd of the ngle be-

5 LONG-TERM EFFECT OF BIONATOR 225 TABLE 2. Chnges T2 T1 in the Erly s Vrible Erly-Treted (ETG) (n 13) D Erly Control (ECG) (n 11) D Mnn- ETG/ECG (Tretment Effect) Cephlometric nlysis (mm) Molr reltion (ms/ol p minus mi/ol p ) Mxillry bse (A point/ol p ) Mndibulr bse (pg/ol p ) Condylr hed (co/ol p ) Composite mndibulr length (pg/ol p co/ol p ) Mxillry incisor (is/ol p minus A point/ol p ) Mndibulr incisor (ii/ol p minus pg/ol p ) Mxillry molr (ms/ol p minus ss/ol p ) Mndibulr molr (mi/ol p minus pg/ol p ) FMN-T point-b ( ) FMN-T point-r ( ) r-goi-me ( ) significnt comprison (P.05); not significnt comprison. TABLE 3. Chnges T3 T2 in the Erly s Vrible Erly-Treted (ETG) (n 13) D Erly Control (ECG) (n 11) D Mnn- ETG/ECG (Posttretment Chnges) Cephlometric nlysis (mm) Molr reltion (ms/ol p minus mi/ol p ) Mxillry bse (A point/ol p ) Mndibulr bse (pg/ol p ) Condylr hed (co/ol p ) Composite mndibulr length (pg/ol p co/ol p ) Mxillry incisor (is/ol p minus A point/ol p ) Mndibulr incisor (ii/ol p minus pg/ol p ) Mxillry molr (ms/ol p minus ss/ol p ) Mndibulr molr (mi/ol p minus pg/ol p ) FMN-T point-b ( ) FMN-T point-r ( ) r-goi-me ( ) significnt comprison (P.05); not significnt comprison.

6 226 FALTIN, FALTIN, BACCETTI, FRANCHI, GHIOZZI, MCNAMARA TABLE 4. Chnges T3 T1 in the Erly s Vrible Erly-Treted (ETG) (n 13) D Erly Control (ECG) (n 11) D Mnn- ETG/ECG (Long-Term Chnges) Cephlometric nlysis (mm) Molr reltion (ms/ol p minus mi/ol p ) Mxillry bse (A point/ol p ) Mndibulr bse (pg/ol p ) Condylr hed (co/ol p ) Composite mndibulr length (pg/ol p co/ol p ) Mxillry incisor (is/ol p minus A point/ol p ) Mndibulr incisor (ii/ol p minus pg/ol p ) Mxillry molr (ms/ol p minus ss/ol p ) Mndibulr molr (mi/ol p minus pg/ol p ) FMN-T point-b ( ) FMN-T point-r ( ) r-goi-me ( ) significnt comprison (P.05); not significnt comprison. TABLE 5. Chnges T2 T1 in the Lte s Vrible Lte-Treted (LTG) (n 10) D Lte Control (LCG) (n 10) D Mnn- LTG/LCG (Tretment Effect) Cephlometric nlysis (mm) Molr reltion (ms/ol p minus mi/ol p ) Mxillry bse (A point/ol p ) Mndibulr bse (pg/ol p ) Condylr hed (co/ol p ) Composite mndibulr length (pg/ol p co/ol p ) Mxillry incisor (is/ol p minus A point/ol p ) Mndibulr incisor (ii/ol p minus pg/ol p ) Mxillry molr (ms/ol p minus ss/ol p ) Mndibulr molr (mi/ol p minus pg/ol p ) FMN-T point-b ( ) FMN-T point-r ( ) r-goi-me ( ) significnt comprison (P.05); not significnt comprison.

7 LONG-TERM EFFECT OF BIONATOR 227 TABLE 6. Chnges T3 T2 in the Lte s Vrible Lte-Treted (LTG) (N 10) D Lte Control (LCG) (N 10) D Mnn- LTG/LCG (Posttretment Chnges) Cephlometric nlysis (mm) Molr reltion (ms/ol p minus mi/ol p ) Mxillry bse (A point/ol p ) Mndibulr bse (pg/ol p ) Condylr hed (co/ol p ) Composite mndibulr length (pg/ol p co/ol p ) Mxillry incisor (is/ol p minus A point/ol p ) Mndibulr incisor (ii/ol p minus pg/ol p ) Mxillry molr (ms/ol p minus ss/ol p ) Mndibulr molr (mi/ol p minus pg/ol p ) FMN-T point-b ( ) FMN-T point-r ( ) r-goi-me ( ) significnt comprison (P.05); not significnt comprison. TABLE 7. Chnges T3 T1 in the Lte s Vrible Lte-Treted (LTG) (n 10) D Lte Control (LCG) (n 10) D Mnn- LTG/LCG (Long-Term Chnges) Cephlometric nlysis (mm) Molr reltion (ms/ol p minus mi/ol p ) Mxillry bse (A point/ol p ) Mndibulr bse (pg/ol p ) Condylr hed (co/ol p ) Composite mndibulr length (pg/ol p co/ol p ) Mxillry incisor (is/ol p minus A point/ol p ) Mndibulr incisor (ii/ol p minus pg/ol p ) Mxillry molr (ms/ol p minus ss/ol p ) Mndibulr molr (mi/ol p minus pg/ol p ) FMN-T point-b ( ) FMN-T point-r ( ) r-goi-me ( ) significnt comprison (P.05); not significnt comprison.

8 228 FALTIN, FALTIN, BACCETTI, FRANCHI, GHIOZZI, MCNAMARA tween the condylr line nd the mndibulr line in the group tht received tretment during the pubertl growth spurt. DICUION Even though the Biontor hs been prt of routine functionl pplince therpy for nerly four decdes, surprisingly few methodologiclly sound clinicl studies of this tretment pproch, t lest by tody s stndrds, hve ppered in the orthodontic literture. Although severl cephlometric investigtions on the short-term tretment effects of the Biontor pplince in growing subjects with clss-ii mlocclusion hve been published, 4 8 no previous reserch hs delt with the issue of long-term response to this type of therpy. The only contribution tht nlyzed tretment outcomes of the Biontor in the long term is by Rudzki- Jnson nd Nochtr 18 tht does not include n untreted control smple for the pprisl of tretment effectiveness. The need for dequte informtion regrding the longterm dentoskeletl modifictions tht cn be produced by the Biontor ppers compelling becuse the Biontor is one of the most commonly used pplinces for functionl jw orthopedics. Furthermore, the efficiency of given tretment protocol in dentofcil orthopedics hs to be evluted not only on the bsis of tretment effectiveness but lso for the issue of optiml tretment timing to chieve significnt chnges in the crniofcil structures. With these ims in mind, the present study nlyzed the long-term skeletl nd dentolveolr chnges fter Biontor therpy in two different groups of clss-ii individuls t different stges of skeletl mturtion. The pprisl of skeletl mturity in both treted nd untreted clss-ii smples ws performed by the evlution of growth stges in the cervicl vertebre, ccording to recently modified version of the originl CVM method. The originl method hs been used in previous ppers 16,17 to identify idel tretment timing for other functionl pplinces such s the twin-block nd the FR-2. In the present investigtion, the newly developed CVM method 19,20 (bsed on the evlution of the morphologicl fetures of the second, third, nd fourth cervicl vertebre only) ws dopted to discriminte between group of subjects treted before the onset of the pubertl spurt in mndibulr growth (ETG) nd group of subjects who strted tretment during the spurt (LTG). Both groups were reevluted fter the completion of growth (bout six yers fter ctive tretment with the Biontor hd been terminted). The posttretment period in both erly nd lte groups included short phse of therpy with fixed pplinces to refine nd detil the occlusion. The findings of the present study indicte clerly tht significnt long-term chnges in the occlusl reltionships nd mndibulr growth increments cn be chieved by Biontor therpy only when functionl tretment includes the pubertl growth spurt. According to the new CVM method, these dt indicte tht functionl jw orthopedics with the Biontor should strt not erlier thn CVM II (when concvity is evident t the lower borders of both the second nd third cervicl vertebre). In the long term, the lte-treted subjects, who strted Biontor tretment t the growth spurt, showed significnt improvement in the overjet ( 4.2 mm) nd fvorble chnge in the molr reltion ( mm). The mount of supplementry elongtion of the mndible in the LTG when compred with corresponding controls (5.1 mm) ws two nd hlf times tht of the ETG ( mm), nd it ws produced lmost entirely by Biontor therpy. Posttretment chnges were not significnt. The greter increse in totl mndibulr length (co-pg) ws ssocited with significnt supplementry increses in the height of the mndibulr rmus (cogo, 4.8 mm) in the group treted t the pek when compred with the corresponding control group, wheres only 0.5-mm chnge for this mesurement ws recorded in the ETG. These results hve significnce not only t the sttisticl level but lso re relevnt cliniclly. The significnt supplementry growth of the mndible in the LTG ws concurrent with fvorble chnges in both the nteroposterior position (co-olp) nd the growth direction (cl-ml) of the mndibulr condyle. This growth modifiction hs been described in the pst s posterior mndibulr morphogenetic rottion, 14 biologicl mechnism leding to greter increments in totl mndibulr length nd, thus, efficiently improving the skeletl sgittl reltionships in clss-ii mlocclusion. In fct, the group treted during the pubertl growth spurt presented with ll the cephlometric signs 16 tht demonstrte the effectiveness of functionl tretment of skeletl clss-ii dishrmony (1) increses in totl mndibulr length (co-pg), (2) increses in rmus height (co-go), (3) opening of the gonil ngle (r-goi-me), (4) posterior rottion of the condylr line in reltion to the mndibulr line (cl-ml), nd (5) bckwrd displcement of the condylr hed in reltion to the reference system (co- OLp). Although not sttisticlly significnt, dentoskeletl modifictions during ctive tretment with the Biontor pplince (T1 T2) deserve to be discussed to compre the shortterm results of the present study with those reported by other investigtors. The crniofcil chnges, s evluted in the T1 T2 intervl in the totl treted smple, exmined in this study (23 subjects) pproximte those found by Liviertos nd Johnston 27 in their investigtion of short-term effects of Biontor therpy s the first phse of comprehensive clss-ii correction. When nnulized, increses in mndibulr length in both totl treted nd untreted smples in this study re similr to those reported in the rndomized clinicl tril by Tulloch et l. 28 Illing et l 8 reported two mm/y supplementry elongtion of the mndible in treted subjects with respect to untreted controls, wheres Bolmgren nd Moshiri 6

9 LONG-TERM EFFECT OF BIONATOR found n increse of bout mm/y for the sme mesurement when compred with normtive controls. The results of the present study confirm the possibility of producing bout -mm/y dditionl increments in totl mndibulr length fter Biontor therpy provided tht tretment is initited immeditely before the pubertl growth spurt. Erlier tretment induces cliniclly irrelevnt chnge in mndibulr growth (bout 1 mm/y more thn untreted controls). A significnt dentolveolr dvncement of the lower dentition in mesil direction ws detected in the lte-treted smple in the short term. However, no significnt movement of the dentition persisted in either of the treted groups in the long term. Erlier, 6 cpping of the mndibulr incisors ws recommended to prevent flring of these teeth during therpy. The pplince design used in the present study did not include ny cpping of the lower incisors. In recent times, the nlysis of the effectiveness of the Biontor pplince when compred with the twin-block is becoming the most populr lterntive clinicl option for functionl tretment of clss-ii mlocclusion. The most fvorble time period to strt tretment with the twin-block is during or slightly fter the pek in mndibulr growth. 16 The short-term supplementry mndibulr increment tht cn be obtined with the twin-block t puberty is pproximtely 4.7 mm/y. A similr mount of dditionl mndibulr growth when compred with untreted subjects is found in ptients treted with the Biontor pplince t the pubertl growth spurt. However, in Biontor therpy this clinicl result is chieved in two-yer time intervl, which is twice the durtion of the intervl for ctive twin-block therpy. Regrdless of the differences in both the mode of ction nd the clinicl mngement of the two functionl pplinces, both the Biontor nd the twin-block re effective therpeutic mens for clss-ii tretment ssocited with mndibulr deficiency. Nevertheless, the twin-block ppers to be more efficient in terms of shorter durtion of tretment time intervl (on verge 14 months vs 22 months for the Biontor pplince). Dt regrding the long-term outcomes of twin-block therpy re needed for definitive pprisl of the stbility of the very fvorble short-term dentoskeletl chnges. Posttretment stbility ppers to be feture of Biontor therpy followed by fixed pplinces to refine occlusion, both in prepubertl nd pubertl ptients. None of the skeletl prmeters exhibited ny relpse fter ctive therpy in the present study. This finding is evident prticulrly in the LTG, which still showed smll fvorble chnges even during the retention period. CONCLUIO The findings of the present long-term study on Biontor therpy followed by fixed pplinces in clss-ii ptients indicte tht this tretment protocol is effective nd stble 229 when it is initited immeditely before the pubertl growth spurt. Optiml timing to strt tretment with the Biontor is when concvity is evident t the lower borders of both the second nd the third cervicl vertebre (CVM II). In the long term, the mount of significnt supplementry elongtion of the mndible in subjects treted with the Biontor during the pubertl growth spurt is 5.1 mm more thn tht in untreted subjects with clss-ii mlocclusion. imilr fvorble findings cn be recorded for the significnt increments in mndibulr rmus height nd for significntly more bckwrd direction of condylr growth. ACKNOWLEDGMENT This rticle is dedicted to Professor Wilhelm Blters (in memorim). The uthors express their grtitude to Dr Crlos A. Kessner, Dr Cristin Ortolni-Fltin, nd Dr Mrci A. A. Almeid for their ssistnce in this reserch project. REFERENCE 1. Blters W. Die Technik und Übung der llgemeinen und speziellen Biontor-Therpie. Quintessenz. 1964;Heft 5:77, IV. 2. Blters W. Einführung in die Biontor Heilmethode Ausgewählte, chriften und Vortrnge. 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Angle Orthod. 1995;65: Morris DO, Illing HM, Lee RT. A prospective evlution of Bss, Biontor nd Twin Block pplinces. Prt II The soft tissues. Eur J Orthod. 1998;20: McNmr JA Jr, Bookstein FL, hughnessy TG. keletl nd dentl chnges following functionl regultor therpy on Clss II ptients. Am J Orthod. 1985;88: Mlmgren O, Ömblus J, Hägg U, Pncherz H. Tretment with n pplince system in reltion to tretment intensity nd growth periods. Am J Orthod Dentofcil Orthop. 1987;91: Hägg U, Pncherz H. Dentofcil orthopedics in reltion to chronologicl ge, growth period nd skeletl development. An nlysis of 72 mle ptients with Clss II division 1 mlocclusion treted with the Herbst pplince. Eur J Orthod. 1988;10: Petrovic A, tutzmnn J, Lvergne J. Mechnism of crniofcil growth nd modus operndi of functionl pplinces: cell-level nd cybernetic pproch to orthodontic decision mking. In: Crlson D, ed. Crniofcil Growth Theory nd Orthodontic Tret-

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