Originl Article Stbility of nterior crossbite correction: A rndomized controlled tril with 2-yer follow-up Ann-Pulin Wiedel ; Lrs Bondemrk b ABSTRACT Objective: To compre nd evlute the stbility of correction of nterior crossbite in the mixed dentition by fixed or removble pplince therpy. Mteril nd Methods: The subjects were 64 consecutive ptients who met the following inclusion criteri: erly to lte mixed dentition, nterior crossbite ffecting one or more incisors, no inherent skeletl Clss III discrepncy, moderte spce deficiency, nonextrction tretment pln, nd no previous orthodontic tretment. The study ws designed s rndomized controlled tril with two prllel rms. The ptients were rndomized for tretment with removble pplince with protruding springs or with fixed pplince with multibrckets. The outcome mesures were success rtes for crossbite correction, overjet, overbite, nd rch length. Mesurements were mde on study csts before tretment (T0), t the end of the retention period (T1), nd 2 yers fter retention (T2). Results: At T1 the nterior crossbite hd been corrected in ll ptients in the fixed pplince group nd ll except one in the removble pplince group. At T2, lmost ll tretment results remined stble nd equl in both groups. From T0 to T1, minor differences were observed between the fixed nd removble pplince groups with respect to chnges in overjet, overbite, nd rch length mesurements. These chnges hd no clinicl implictions nd remined unltered t T2. Conclusions: In the mixed dentition, nterior crossbite ffecting one or more incisors cn be successfully corrected by either fixed or removble pplinces with similr long-term stbility; thus, either type of pplince cn be recommended. (Angle Orthod. 2015;85:189 195.) KEY WORDS: Orthodontics; Anterior crossbite; Stbility; Rndomized controlled tril INTRODUCTION The reported prevlence of nterior crossbites vries between 2.2% nd 12%, depending on the ge of the subjects, whether n edge-to-edge reltionship is included in the dt, nd the ethnicity of the children studied. 1 5 It hs lso been reported tht 36% of subjects with nterior crossbite exhibit functionl shift; tht is, interincisl contct is possible when the mndible is in centric reltionship, implying pseudo Reserch Fellow, Deprtment of Orl nd Mxillofcil Surgery, Skne University Hospitl, Mlmö, Sweden. b Professor nd Hed, Deprtment of Orthodontics, School of Dentistry, University of Mlmö, Sweden. Corresponding uthor: Dr Ann-Pulin Wiedel, Deprtment of Orl nd Mxillofcil Surgery, Jn Wldenströmsg. 18, Skne University Hospitl, SE-205 02 Mlmö, Sweden (e-mil: nn-pulin.wiedel@mh.se) Accepted: My 2014. Submitted: April 2014. Published Online: July 8, 2014 G 2015 by The EH Angle Eduction nd Reserch Foundtion, Inc. Clss III mlocclusion with no inherent skeletl Clss III discrepncy. 5 Anterior crossbite is estblished in the mixed dentition. Erly intervention is therefore recommended to prevent dverse effects on growth nd development of the jws nd disturbnce of temporl nd msseter muscle ctivity, which would increse the risk of crniomndibulr disorders during dolescence. 2,4,6 8 Moreover, erly tretment improves mxillry lip posture nd fcil ppernce. 9 A recent systemtic review 10 disclosed wide vriety of tretment modlities, more thn 12 methods, in use for nterior crossbite correction. However, strong evidence in support of ny one technique ws lcking. Thus, the review highlighted the need for high-qulity clinicl trils to identify the most effective intervention for correcting nterior crossbites. The fundmentl gol of orthodontic tretment is to chieve norml occlusion tht is morphologiclly stble in the long term nd functionlly nd estheticlly cceptble. As erly correction of nterior crossbite is DOI: 10.2319/041114-266.1 189
190 WIEDEL, BONDEMARK undertken in the growing child, it is lso importnt to evlute posttretment chnges in long-term perspective. Very few studies, however, hve nlyzed the posttretment effects of nterior crossbite correction nd most re retrospective in design. 11,12 Also lcking re prospective studies compring the long-term effects of fixed or removble pplince therpy for correcting nterior crossbite in the mixed dentition. 10 The im of the present study, in the form of rndomized controlled tril (RCT), ws to compre nd evlute the stbility of outcome in ptients who hd undergone fixed or removble pplince therpy t the mixed dentition stge to correct crossbites ffecting one or more incisors. The null hypothesis ws tht the two tretment methods chieve similr long-term outcomes. MATERIALS AND METHODS The originl study smple comprised 62 subjects (25 girls nd 37 boys) with one or more incisors in nterior crossbite with functionl shift. The study ws pproved by the Ethics Committee of Lund University, Lund, Sweden (Dnr: 334/2004). All ptients nd prents were informed of the purpose of the tril. Written, informed consent ws required before enrolment. The ptients were consecutively recruited between 2004 nd 2009 from the Deprtment of Orthodontics, Fculty of Odontology, Mlmö University, Mlmö, Sweden, nd from one public dentl helth service clinic in Mlmö, Skåne County Council, Sweden. All ptients met the following inclusion criteri: erly to lte mixed dentition; nterior crossbite ffecting one or more incisors; nterior crossbite with functionl shift, tht is, interincisl contct is possible when the mndibulr is in the centric reltion (1 to 3 mm sliding from centric reltion to centric occlusion), no inherent skeletl Clss III discrepncy (ANB ngle. 0u), moderte spce deficiency in the mxill (up to 4 mm), nonextrction tretment pln, nd no previous orthodontic tretment. Hlf of the subjects were rndomly llocted to removble therpy nd hlf to fixed pplince therpy. Two orthodontists nd one postgrdute student undergoing specilist trining in orthodontics nd under the supervision of n orthodontist then treted the ptients ccording to pre-set concept. Study csts were mde t pretretment, tht is, t bseline (T0); t postretention, tht is, fter tretment, including the retention period (T1); nd t follow-up, tht is, 2 yers postretention (T2). One subject in the removble pplince group withdrew from the study fter noncomplince between T0 nd T1. Another subject in the removble pplince Figure 1. Flow chrt of the ptients in the study. group hd relpse between T1 nd T2 nd ws retreted with fixed pplince. Moreover, four subjects, two from ech group, were excluded becuse they could not be contcted for the two-yer follow-up. Thus, the study comprised 57 subjects, 28 treted with removble pplinces nd 29 with fixed pplinces. The ptient flow is illustrted in Figure 1. Tble 1 presents the smple size, gender, nd ge distribution of the subjects t pretretment/bseline (T0), t postretention (T1), nd t follow-up 2 yers postretention (T2). The following outcome mesures were ssessed: N Success rte of nterior crossbite correction (yes or no); N Tretment durtion in months, from insertion to dte of pplince removl; N Overjet nd overbite in millimeters; N Arch length incisl: distnce in millimeters from the incisl edge of the mxillry incisor in nterior crossbite to tngents of the mesiobuccl cusp tips of the mxillry first molr (Figure 2); N Arch length gingivl: distnce in millimeters from the gingivl mrgin of the mxillry incisor in nterior crossbite to tngents of the mesiobuccl cusp tips of the mxillry first molr (Figure 2);
STABILITY OF ANTERIOR CROSSBITE CORRECTION 191 Tble 1. Gender, Men Ages, nd Stndrd Devitions (SDs) t Bseline (T0), t Posttretment, Including the Retention Period (T1), nd t the 2-Yer Follow-up (T2) Removble Applince Fixed Applince Anlysis n Gender Men Age SD n Gender Men Age SD T0 31 13 girls, 18 boys 9.1 1.19 31 12 girls, 19 boys 10.4 1.52 T1 31 13 girls, 17 boys 9.7 1.09 31 12 girls, 19 boys 10.8 1.50 T2 28 11 girls, 17 boys 11.7 1.02 29 11 girls, 18 boys 12.9 1.54 N Mxillry dentl rch length totl: distnce in millimeters t the lveolr crest between the mesil surfce of the left nd right mxillry first molrs (Figure 2); N Trnsverse mxillry molr distnce: trnsverse distnce in millimeters between the mesiobuccl cusp tips of the mxillry first molrs (Figure 2). Successful tretment ws defined s positive overjet (norml interincisl reltionship) for ll incisors t T1 nd T2. The overjet, overbite, rch length, nd trnsverse mxillry molr distnce were mesured with digitl sliding cliper (Digitl 6, 8M007906, Muser-Messzeug GmbH, Oberndorf/Neckr, Germny). All mesurements were mde to the nerest 0.1 mm by n orthodontist (Dr Wiedel). Chnges in the different mesures were clculted s the difference between T1 nd T0, T2 nd T1, nd T2 nd T0. All study cst mesurements were blinded, tht is, the exminer ws unwre of the group to which the ptient belonged. Furthermore, the T0, T1, nd T2 csts were rndomized for mesurements. Finlly, the durtion of tretment ws registered from the ptient files. The removble pplince (Figure 3A) comprised n crylic plte with protrusion springs for the incisors in nterior crossbite, bilterl occlusl coverge of the posterior teeth, n expnsion screw, stinless steel clsps on either the first deciduous molrs or the first premolrs (if erupted) nd the permnent molrs. The protrusion springs were ctivted once month until norml incisor overjet ws chieved. Lterl occlusl coverge (1 to 2 mm of thickness) ws used to void verticl interlock between the incisors in crossbite nd the mndibulr incisors nd lso to increse the retention of the pplince. The occlusl coverge ws removed s soon s the nterior crossbite ws corrected. An inctive expnsion screw ws inserted into the pplince. The screw ws ctivted during the tretment period only if it ws judged to comply with the nturl trnsverse growth of the jw. The dentist instructed the ptient firmly to wer the pplince dy nd night, except for mels nd toothbrushing, tht is, the pplince ws to be worn t lest 22 hours dy. Progress ws evluted every 4 weeks. The sme pplince then served s pssive retiner for retention period of 3 months. The fixed pplince (Figure 3B) consisted of stinless steel brckets (Victory, slot 0.0220, 3MUnitek, Monrovi, Clif). Usully, eight brckets were bonded to the mxillry incisors, the deciduous cnines, nd either the first deciduous molrs or the first premolrs, if erupted. All ptients were treted ccording to stndrd stright-wire concept designed for light forces. 13 The rchwire sequence ws: 0.016 hetctivted nickel-titnium, 0.019 3 0.0250 hetctivted nickel-titnium, nd finlly 0.019 3 0.0250 stinless steel wire. To rise the bite, composite (Point Four, 3M Unitek) ws bonded to the occlusl surfces of both the mndibulr second deciduous molrs. This prevented verticl interlock between the incisors in crossbite nd the mndibulr incisors. The composite ws removed s soon s the nterior crossbite ws corrected. Progress ws evluted every 4weeks. The sme fixed pplince then served s pssive retiner for retention period of 3months. Sttisticl Anlysis Figure 2. Sgittl nd trnsverse mesurements mde on the mxillry study csts. For definitions of the different vribles, see the list of outcome mesures in the Mterils nd Methods section. SPSS softwre (version 21.0, SPSS Sttistics, Chicgo, IL) ws used for sttisticl nlysis of the dt. For ctegoricl vribles, the x 2 test ws used. Arithmetic mens nd stndrd devitions were clculted for numericl vribles. To compre ctive tretment time nd tretment effects between the
192 WIEDEL, BONDEMARK Figure 3. Occlusl view of (A) the removble orthodontic pplince nd (B) the fixed orthodontic pplince. The lterl occlusl coverge of the removble pplince hs just been removed becuse the mxillry incisors were the in correct position nd the nterior crossbite ws corrected. Also, the expnsion screw hs been ctivted during the tretment becuse it ws judged to comply with the nturl trnsverse growth of the jw. groups, n independent smple t-test ws used for nlysis of mens. Differences with probbilities of less thn 5% (P,.05) were considered sttisticlly significnt. Ten rndomly selected study csts were mesured on two occsions, t n intervl of t lest 1 month. RESULTS The bseline mesurement vribles before tretment re summrized in Tble 2. No significnt differences were found between the groups, except for ge (P,.05) (Tble 1). There ws no significnt intergroup difference in the number of mxillry incisors in nterior crossbite before tretment. No significnt gender differences were found for ny of the study vribles; hence, the dt for boys nd girls were pooled for nlysis. Pired t-tests disclosed no significnt men differences between the two series of records. The error of the method did not exceed 0.13 mm for ny study vrible. The crossbites of ll ptients in the fixed pplince group, nd ll except one in the removble pplince group, were successfully corrected during the tretment period (T0 T1). Tretment durtion ws significntly shorter (men, 1.4 months; P,.05) in the fixed pplince group (men, 5.5 months; SD, 1.41) thn in the removble group (men, 6.9 months; SD, 2.8). Overjet nd incisl rch length incresed significntly in both groups between T0 nd T1 (Tble 3). The fixed pplince group lso showed significnt increse in gingivl rch length (Tble 3). The increse in overjet fter tretment ws significntly greter in the fixed pplince group (P,.05). This group lso exhibited significntly greter increses in incisl nd gingivl rch lengths fter tretment, s shown in Tble 3. There were no intergroup differences with respect to overbite, totl mxillry dentl rch length nd trnsverse mxillry molr distnce (Tble 3). At the 2-yer follow-up, relpses hd occurred in three subjects. Thus, 27 of 29 ptients in the fixed plince group nd 27 of 28 ptients in the removble pplince group hd mintined norml interincisl reltionships. It ws lso noted tht, t follow-up, trnsition to the permnent dentition hd occurred in most of the subjects in both groups. During the follow-up period (T1 T2), smll but significnt increse in overbite occurred in the removble pplince group nd smll, lbeit significnt, intergroup difference ws found with respect to overjet. There were no other significnt chnges in the outcome vribles (Tble 4). The overll chnges during the study period (T0 T2) re shown in Tble 5. Significnt increses in overjet Tble 2. Bseline Mesurements (T0) (in Millimeters) Group A (N 5 31) Group B (N 5 31) 95% CI for Men 95% CI for Men P Men SD Lower Upper Men SD Lower Upper A Versus B Overjet 21.4 0.47 21.6 21.3 21.4 0.63 21.6 21.2 NS Overbite 2.2 0.84 1.9 2.5 2.0 1.07 1.7 2.4 NS Arch length to incisl edge 26.3 2.95 25.2 27.4 25.1 2.74 24.1 26.1 NS Arch length gingivl 22.8 2.60 21.8 23.7 21.6 2.51 20.7 22.5 NS Arch length totl 75.5 3.79 74.1 76.9 75.4 3.76 74.0 76.8 NS Trnsverse molr distnce 50.9 2.98 49.8 52.0 50.4 2.39 49.3 51.1 NS Group A indictes removble pplince group; group B, fixed pplince group; CI, confidence intervl; SD, stndrd devition; NS, not significnt.
STABILITY OF ANTERIOR CROSSBITE CORRECTION 193 Tble 3. Chnges in different Mesures (in Millimeters) Within nd Between Groups Clculted s the Difference Between T1 (Posttretment, Including the Retention Period) nd T0 (Pretretment) Group A (N 5 31) Group B (N 5 31) 95% CI for Men 95% CI for Men P Men SD Lower Upper Men SD Lower Upper A Versus B Overjet 3.5*** 1.15 3.1 3.9 4.2*** 1.26 3.8 4.7 * Overbite 20.1 0.75 20.4 0.2 0.0 1.07 20.4 0.4 NS Arch length to incisl edge 2.5** 1.04 2.0 2.8 3.7*** 2.06 2.9 4.4 ** Arch length gingivl 0.9 0.85 0.6 1.2 1.7** 1.20 1.2 2.1 ** Arch length totl 1.1 1.10 0.7 1.5 1.8 1.90 1.1 2.5 NS Trnsverse molr distnce 0.6 0.87 0.3 1.0 0.7 0.76 0.4 1.0 NS Group A indictes removble pplince group; group B, fixed pplince group; CI, confidence intervl; SD, stndrd devition; NS, not significnt. * P,.05; ** P,.01; *** P,.001. nd incisl rch length were found in both groups. In the fixed pplince group, incisl rch length nd gingivl rch length incresed significntly more thn in the removble pplince group. No other significnt intrgroup or intergroup differences were observed. DISCUSSION The results of this RCT confirm the initil hypothesis tht t follow-up the outcomes in the two tretment groups were comprble: in the mixed dentition, nterior crossbite ffecting one or more incisors cn be successfully corrected by either fixed or removble pplinces with similr stbility nd eqully fvorble prognoses. Thus, either type of pplince cn be recommended to correct nterior crossbite ffecting one or more incisors in the mixed dentition. The success rte of both tretment methods ws high t completion of tretment nd t the 2-yer follow-up. In the removble pplince group there ws significnt increse in overbite during the follow-up period, which could lso hve contributed to the stble tretment results. In both groups there were minor decreses in rch length t the 2-yer follow-up. These chnges hd no clinicl implictions. In ll, three ptients relpsed over the entire tril period, one in the removble pplince group nd two in the fixed pplince group. Becuse of ethicl regultions, lterl hed rdiogrphs ws not ssessed 2 yers fter retention, nd therefore, we hve no dt to show whether unfvorble growth of the mndible my hve occurred in these ptients. Idelly, the study should hve included n untreted control group of ptients with nterior crossbite to evlute the potentil impct of the condition on long-term growth. However, postponement of needed intervention for 3 yers ws regrded s ethiclly uncceptble. Nevertheless, the RCT design permits the reduction of the risk of norml growth bis between the groups. In generl, stbility fter orthodontic tretment is reported to vry, though most relpses occurring during the first 2 yers fter retention. 14 Consequently, the follow-up period of 2 yers used in this study ws dequte for long-term conclusions, nd t T2, trnsition to the permnent dentition hd occurred in most of the subjects in both groups. Idelly, n even longer follow-up period thn 2 yers would hve been preferble, but s it ws found tht t 2 yers fter retention lmost ll subjects hd good Clss I occlusion with norml overjet nd overbite, the Tble 4. Chnges in Mesures (in Millimeters) Within nd Between Groups Clculted s the Difference Between T2 (2-Yer Follow-up) nd T1 (Posttretment, Including Retention Period) Group A (N 5 27) Group B (N 5 29) 95% CI for Men 95% CI for Men P Men SD Lower Upper Men SD Lower Upper A Versus B Overjet 0.2 0.51 0.0 0.4 20.4 1.39 21.0 0.1 * Overbite 0.7* 0.85 0.4 1.0 0.4 1.18 20.1 0.8 NS Arch length to incisl edge 20.3 0.83 20.7 0.0 20.4 0.81 20.7 20.1 NS Arch length gingivl 20.8 0.86 21.1 20.5 20.8 1.01 21.2 20.4 NS Arch length totl 0.3 1.15 20.1 0.8 20.4 1.82 21.1 0.3 NS Trnsverse molr distnce 0.3 0.85 20.1 0.6 0.2 0.74 20.1 0.5 NS Group A indictes removble pplince group; group B, fixed pplince group; CI, confidence intervl; SD, stndrd devition; NS, not significnt. * P,.05.
194 WIEDEL, BONDEMARK Tble 5. Overll Chnges in Mesures (in Millimeters) Within nd Between Groups Clculted s the Difference Between T2 (2-Yer Followup) nd T0 (Pretretment) Group A (N 5 27) Group B (N 5 29) 95% CI for Men 95% CI for Men P Men SD Lower Upper Men SD Lower Upper A Versus B Overjet 3.7*** 1.12 3.3 4.2 3.9*** 1.93 3.1 4.6 NS Overbite 0.6* 0.98 0.2 1.0 0.6 1.38 0.0 1.1 NS Arch length to incisl edge 2.0* 1.73 1.4 2.7 3.5*** 1.73 2.8 4.1 ** Arch length gingivl 0.1 0.89 20.2 0.5 0.9 1.13 0.5 1.3 ** Arch length totl 1.4 1.71 0.7 2.0 1.2 1.86 0.5 1.9 NS Trnsverse molr distnce 0.9 0.86 0.5 1.2 0.9 1.12 0.5 1.3 NS Group A indictes removble pplince group; group B, fixed pplince group; CI, confidence intervl; SD, stndrd devition; NS, not significnt. * P,.05; *** P,.001. prognosis ws fvorble for the tretment nd postretention results to be stble in the future. Moreover, nlyses of retrospective dt on ptients with nterior crossbite nd functionl shift treted with 2 3 4 fixed pplinces hve disclosed stble results 5 11 nd 10 yers fter tretment. 12 These studies support fvorble long-term prognosis for correcting nterior crossbite ffecting one or more incisors in the mixed dentition. A recent systemtic review disclosed the lck of RCTs compring the effectiveness of fixed nd removble pplinces in correcting nterior crossbite nd the lck of long-term evlutions. 10 Thus, no comprison cn be mde with previous studies. Although not directly comprble, multicenter RCT 15 of erly Clss III orthopedic tretment with protrction fcemsk versus untreted controls reported successful outcomes in 70% of the subjects. An RCT studying correction of unilterl posterior crossbite in the mixed dentition 16 reported nd confirmed tht fixed pplince (Qud-helix) therpy ws superior to removble pplince (expnsion plte) therpy: one-third of the filures in the removble pplince group were ttributed to poor ptient complince. This is in contrst to the high success rte in the present study. It is likely tht ptients with nterior crossbite re more wre of their mlocclusion: unlike posterior crossbite, it is very obvious nd estheticlly disturbing condition. Hence, our ptients were obviously highly motivted nd keen to comply with tretment. The rtionle for selecting n RCT design ws to reduce the risk of error from such fctors s selection bis, the clinicin s preferred tretment method, nd the differences in the skills of the opertors with respect to the two tretment methods. Furthermore, rndom lloction of subjects reduces bis nd confounding vribles by ensuring tht both known nd unknown determinnts of outcome re evenly distributed mong the subjects. The prospective design lso ensures tht the bseline chrcteristics, tretment progression, nd side effects cn be strictly controlled nd ccurtely observed. A drwbck ws tht significnt men difference in ge ws found between the groups; the explntion for this is uncler, even though the rndomiztion should hve voided the ge difference. In ny event, the ge difference ws regrded to be of minor importnce becuse ll subjects followed ll the inclusion criteri, nd thus, for exmple, were in the sme dentl ge, tht is, erly to lte mixed dentition. Moreover, to reduce the risk of bis, mesurement of the study csts ws blinded; the exminer ws unwre of the ptients groups. Thus, the design nd methodology ensured good externl vlidity of the results. In long-term study, the effect on outcomes of subject dropout during the tril must be considered. However, in the present study the ttrition rte ws smll, ensuring tht the outcomes were not bised by loss of dt. The present study evluted reltively limited number of outcome mesures. The primry im ws to compre long-term success rtes of fixed nd removble pplince therpy, but further im ws to ssess chnges in overjet nd mxillry rch length s well s tipping effects on the mxillry incisors. These outcome mesures re highly relevnt to the clinicin. Hving estblished tht the two tretment strtegies re eqully effective with respect to clinicl outcomes, other spects now wrrnt investigtion. A comprtive study of the cost-effectiveness of the two methods is currently in progress. Another importnt spect of tretment tht wrrnts investigtion is tht of ptient perceptions of tretment by fixed or removble pplinces. CONCLUSIONS N In the mixed dentition, nterior crossbite ffecting one or more incisors cn be successfully corrected
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