Article
Reference
Skeletal and dental stability of segmental distraction of the anterior mandibular alveolar process. A 5.5-year follow-up
JOSS, C U, et al.
Abstract
17 patients (14 female; 3 male) were analysed retrospectively for skeletal and dental relapse before distraction osteogenesis (DO) of the mandibular anterior alveolar process at T1 (17.0 days), after DO at T2 (mean 6.5 days), at T3 (mean 24.4 days), at T4 (mean 2.0 years), and at T5 (mean 5.5 years). Lateral cephalograms were traced by hand, digitized, superimposed, and evaluated. Skeletal correction (T5-T1) was mainly achieved through the distraction of the anterior alveolar segment in a rotational manner where the incisors were more proclined. The horizontal backward relapse (T5-T3) measured -0.3mm or 8.3% at point B (non-significant) and -1.8mm or 29.0% at incision inferior (p
JOSS, C U, et al . Skeletal and dental stability of segmental distraction of the anterior mandibular alveolar process. A 5.5-year follow-up. International Journal of Oral and Maxillofacial Surgery , 2013, vol. 42, no. 3, p. 337-44
DOI : 10.1016/j.ijom.2012.10.019 PMID : 23153785
Available at:
http://archive-ouverte.unige.ch/unige:29121
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1 / 1
Clinical Paper Orthognathic Surgery
Skeletal and dental stability of segmental distraction of the anterior mandibular alveolar process. A 5.5-year follow-up
C. U. JossA. Triaca,M. Antonini,S. Kiliaridis,A.M. Kuijpers-Jagtman:Skeletal anddentalstabilityofsegmentaldistractionoftheanteriormandibularalveolar process.A5.5-yearfollow-up. Int.J.OralMaxillofac.Surg.2013;42:337–344.
#2012InternationalAssociationofOralandMaxillofacialSurgeons.Publishedby ElsevierLtd.Allrightsreserved.
C.U.Joss1,2,A.Triaca3, M.Antonini3,S.Kiliaridis2, A.M.Kuijpers-Jagtman1
1DepartmentofOrthodonticsandCraniofacial Biology,RadboudUniversityNijmegen MedicalCentre,Nijmegen,TheNetherlands;
2DepartmentofOrthodontics,Universityof Geneva,Geneva,Switzerland;3Pyramide Klinik,Zu¨rich,Switzerland
Abstract. 17patients(14female;3male)wereanalysedretrospectivelyforskeletal anddentalrelapsebeforedistractionosteogenesis(DO)ofthemandibularanterior alveolarprocessatT1(17.0days),afterDOatT2(mean6.5days),atT3(mean24.4 days),atT4(mean2.0years),andatT5(mean5.5years).Lateralcephalograms weretracedbyhand,digitized,superimposed, andevaluated.Skeletalcorrection (T5–T1)wasmainlyachievedthroughthedistractionoftheanterior alveolar segment inarotationalmannerwheretheincisorsweremoreproclined.The horizontalbackwardrelapse(T5–T3)measured0.3mmor8.3%atpointB(non- significant)and1.8mmor29.0%atincisioninferior(p<0.01).Age,gender, amountandtype(rotationalvs.translational)ofadvancementwerenotcorrelated withthe amountofrelapse.Highanglepatients(NL/ML0;p<0.01)showed significantsmallerrelapseratesatpointB.Overcorrectionoftheoverjetachieved bythedistractioncouldbeareasonfordentalrelapse.Consideringtheamountof long-termskeletalrelapsetheDOcouldbeanalternativetobilateralsagittalsplit osteotomyformandibularadvancementinselectedcases.
Key words: distraction osteogenesis; skeletal stability; dental stability; relapse; cephalo- metrics.
Acceptedforpublication11October2012 Availableonline12November2012
Theprinciplesofdistractionosteogenesis (DO)1anditsclinicalapplicationinmax- illofacial surgery2haveopenednewhor- izonsinthetreatmentoffacialandskeletal disharmonies. Mandibular DO is still mainly used in patients with syndromes andcongenitalanomaliesandlessinnon- syndromicadultpatients.3Manysurgeons stillprefertoadvancethemandibleinone step bybilateral sagittal split osteotomy
(BSSO)innormalpatientsthaninseveral steps by DO. Mandibular DO seems to show similar risk factors for skeletal relapse when compared with BSSO for mandibularadvancement.4
Today there are new surgical approaches to correct mandibular defi- ciency.DOoftheanterioralveolarman- dibular process5 and mandibular wing osteotomy for the correction of the
mandibularplane6aretwoofthem.Triaca etal.5reportedthatDOofthemandibular alveolarprocesscanbeappliedinseveral specificcases:inskeletalClassIIpatients with crowding to reduce the required sagittal distance to be achieved by an advancement BSSO;inskeletalClassIII patientstocreatespaceforthedecompen- sationofthelowerincisorinclination;in skeletalClassIpatientswithadentalClass
http://dx.doi.org/10.1016/j.ijom.2012.10.019,availableonlineathttp://www.sciencedirect.com
0901-5027/030337+08$36.00/0 #2012InternationalAssociationofOralandMaxillofacialSurgeons.PublishedbyElsevierLtd.Allrightsreserved.
II tocreatespaceofonepremolarwidth andoverjetnormalization,andinskeletal anddentalClassIpatientswithcrowding toavoidextractionandtheresultingunfa- vorableprofilethatoftenresults.
Fewstudieshavebeenpublishedonthe results of DO on the anterior alveolar mandibular process.5 Recently, the soft tissue, skeletal and dental stability, neu- rosensory and function after DO of the anterior alveolar process were examined 2.0 years postoperatively.7–9 Skeletal relapse at point B was found in 19%.
No correlation between the amount of skeletal relapse and the amount of advancement, patient’s age or gender could be demonstrated.7 Studies on the long-term results of DO of the anterior alveolarprocessarestilllacking.Theaims ofthepresentstudyweretoevaluate the amount of skeletal changes and dental changes5yearsaftertreatmentinpatients treatedwithDOofthemandibularanterior alveolar process, and to identify factors relatedtoskeletalanddentalstability.
Materialsandmethods
This study reports the follow-up of an initial sample of 33 patients published previously.7,8 Of the 33 patients, 17 patients were available for re-examina- tion.Thefollow-upgroup(T1)consisted of17Caucasianpatients(14femalesand3 males); aged 16.5–56.0years (meanage 29.8years,SD11.9).
Theywerealltreatedorthodonticallyby oneorthodontist(MA)andunderwentDO of the mandibular anterior alveolar pro- cesstocorrectaskeletalClassIIandlarge overjetwithorwithoutincisorcrowdingat the Pyramide Clinic in Zu¨rich, Switzer- landintheyears1998–2004.Thefemale patientsinthefollow-upgrouphadamean age of 31.7 years (17.1–56.0 years, SD 12.0 years) and the male patients 21.5 years (16.5–31.4years, SD8.6years) at T1.Thesurgicalprocedurewasperformed byoneexperiencedmaxillofacialsurgeon (AT)andthetechniquehasbeenpublished previously.5,10 Patients receiving other surgical procedures simultaneously on themandibleandmaxillasuch asgenio- plasty,BSSO,andLeFortwereexcluded.
Syndromic or medically compromised patientswereexcluded.
Fivecephalogramsweretaken:thefirst onaverage17.0daysbeforesurgery(T1);
andthesecond(T2)between0and12days (mean6.5 days)after theosteotomyand beforeanydistractionwascarriedout.The third(T3)cephalogramwastakenbetween 13and92days(mean24.4days)whenthe distractionwascompleted;thefourth(T4)
between0.9and3.7years(mean2.0years) attheendoforthodontictreatment;andthe fifth(T5)between2.7and8.3years(mean 5.5years)afterdistractionofthemandib- ularanterioralveolarprocess.Lowerinci- sorswereretainedwithabondedcanineto canineretainer.TheDOprocedurehasbeen describedpreviously.5,10
EthicalapprovalwasgivenbytheEthic CommitteeoftheKantonZu¨rich,Switzer- land, number 593. All subjects signed written,informedconsent.
Cephalometricanalysis
Skeletalchangeswereevaluatedonprofile cephalogramstaken withtheteethinthe intercuspal position, including a linear enlargement of1.2%.The cephalograms were taken with the subject standing upright in the natural head position and with relaxed lips. The same X-ray machineandthesamesettingswereused forallcephalograms.
Thelateralcephalogramswerescanned andevaluatedwiththeprogramViewbox 3.11 (dHal software, Kifissia, Greece).
The cephalometric analysis for T1, T2, T3, T4 and T5 was carried out by one author (CUJ) andincludedthe reference
pointsandlinesshowninFig.1.Horizon- tal(X-values)andvertical(Y-values)lin- ear measurements were obtained by superimposingthetracingsofthedifferent stages (T2, T3, T4 and T5) on the first radiograph (T1), and the reference lines weretransferredtoeach consecutivetra- cing. During superimposition, particular attentionwasgiventofittingthetracings of the cribriform plate and the anterior wall of the sella turcica which undergo minimalremodelling.11Atemplateofthe outlineofthemandibleofthepreoperative cephalogram(T1)wasmadetominimize errors for superimposing on subsequent radiographs.
Conventional cephalometric variables aswellasthecoordinatesofthereference points (Table 1) were calculated by the computerprogram.Thecoordinatesystem haditsoriginatpointS(sella),anditsX- axisformedanangleof78withtherefer- encelineNSL(Fig.1).Overjetandover- bitewerecalculatedfromthecoordinates ofthepointsIs(incision superior)andIi (incisioninferior).
The lateral cephalograms of T2 were only used to locate the cephalometric point alveolar surgical anterior base (Asab) before postoperative distraction 338 Jossetal.
Fig.1. Referencepointsandlinesusedinthecephalometricanalysis.Thecoordinatesystem haditsoriginatpointS(sella),anditsX-axisformedanangleof78withthereferencelineNSL.
S,sella;NSL,nasion-sella-line;N,nasion;X,horizontalreferenceplane;NL,nasalline;ILs, upperincisalline;Ar,articulare;RL;ramusline;Ans,anteriornasalspine;Pns,posteriornasal spine;As,apexsuperior;pointA;Ii,incisioninferior;Is,incisionsuperior;Go,gonion;Go0, gonionprime;ML0,mandibularlineprime;ML,mandibularline;Ai,apexinferior;pointB;Pg, pogonion;Me,menton;and y,vertical referenceplane.TheHoldewayratio isthedistance betweenIiverticaltoN-B-lineminusdistancePgverticaltoN-B-lineandtheJarabakratioisthe distancefromStoGo0/distanceNtoMe.
of the alveolar process was carried out.
Asabisthemostanteriorandinferiorpoint of the lower anterior segment resulting from thesurgicalosteotomy(Figs 2and 3). This cephalometric point was intro- ducedtoevaluatethemovement(rotation vs.translation)oftheloweranteriorseg- ment base in comparison to the lower incisors as the ratio (Ii [X-value; T3–
T2]/Asab[X-value;T3–T2]).
Errorofthemethod
Todeterminetheerrorofthemethod,21 randomlyselectedcephalogramswerere-
traced and re-analysed after a 2-week interval.Horizontal (X-values)andverti- cal (Y-values) linearmeasurements were re-obtainedbysuperimposingthetracings ofthedifferentstages(T2,T3,T4,andT5) onthefirstradiograph(T1).Theerrorof the method(Si) was calculated withthe formula
Si¼
ffiffiffiffiffiffiffiffiffiffiffi Pd2 2n s
where d is the difference between the repeatedmeasurementsandnisthenum- berofduplicatedeterminations.12
The random errors are presented in Table1.Nosystematicerrorswerefound when the values were evaluated with a paired t-test. The drop-out analysis included the unpaired t-test to compare drop-outs with the remaining patients for age and cephalometric features at T1, T2, T3 and T4, and the x2 test for sex.Drop-outanalysisshowedthatthere were no significant differences between the drop-out and the remaining patients forageandcephalometricfeaturesatT1, T2,T3andT4.
Statisticalanalysis
Statisticalanalyseswereconductedusing SPSSsoftware(version 19.0,SPSSInc., Chicago, IL, USA). Normal distribution was confirmed with the Kolmogorov–
Smirnov test. The effect of treatment, i.e.thedifferencesbetweenthevariables andco-ordinatesatT3andT1(T3andT2 for Asab), T5 and T1 (T5 and T2 for Asab),T5andT4weretestedwithapaired ttest.Therelationshipsbetweenskeletal variables,age,andgenderwereanalysed withthePearson’sproductmomentcorre- lationcoefficient.
Results
Table 2 shows the selected variables before surgery (T1) and at 5.5-year fol- low-up(T5).Themeanchanges,standard deviations, and ranges for the selected cephalometric parametersbefore surgery and during the subsequent observation periodsaregiveninTables3and4.
Negativevaluesimplyabackwardand positivevaluesaforwardmovementofthe pointinthehorizontal plane.Inthever- tical plane, negative values imply an upward and positivevalues a downward movementofthepoint.
Horizontalchanges
The mean advancement of the anterior alveolar process immediately following DO (T3–T1) was 3.6mm at point B, 2.2mmatAsab(T3–T2),and6.2mmat incision inferior (all p=.000). Mean relapse (T5–T3) was 0.3mm or 8.3%
at pointB, 1.0mmor 45.5% at Asab (T5–T2),and1.8mmor29.0%atinci- sion inferior of the initial surgical advancement. Figures 3 and 4 show the surgicalchanges(T3–T1)andtheamount ofrelapse(T5–T3)ofpointBandoverjet.
Figure5showsthechangesofpointBand incisioninferiorovertimefromT1toT5.
RegardingtheratioIi[X-value;T3-T2]/
Asab [X-value; T3–T2], the alveolar Skeletalanddentalstabilityofsegmentaldistraction
Table1. Randomerrors(Si)inmmordegreesofthecephalometricvariables.
Si(mm)
Variable Si Variable Si Referencepoint X Y
SNA(8) 1.14 IiL-N-pointB(8) 1.14 Incisionsup. 0.48 0.21 SNB(8) 0.82 IiL-N-pointB(mm) 0.24 Incisioninf. 0.58 0.55
ANB(8) 0.48 IiL-A-Pg(8) 1.29 Apexinf. 0.54 0.18
NSL/NL(8) 0.86 IiL-A-Pg(mm) 0.49 PointB 0.28 0.45
NSL/ML0(8) 1.01 Holdawayratio 0.47 Asab 0.35 0.25
NL/ML0(8) 0.84 IsL/IiL(8) 1.63 Pogonion 0.37 1.19
Jarabakratio 1.15 Overjet 0.36 Menton 0.89 0.45
IsL/NSL(8) 1.52 Overbite 0.53 Gonion0 2.48 1.14
IsL/NL(8) 1.31 IiL/ML0(8) 1.39
SeeFig.1fordetailsofthevariables.
Fig.2. ReferencepointsusedinthecephalometricanalysisofthelowerapicalbaseinDO patients.Ii,incisioninferior;pointB;Ai,apexinferior;Asab,apicalsurgicalanteriorbase;Pg, pogonion;andMe,menton.Asabisthemostanteriorandinferiorpointoftheloweranterior segmentformedbythesurgicalosteotomy.Thiscephalometricpointwasintroducedtoevaluate themovement(rotationvs.translation)oftheloweranteriorsegmentbaseincomparisontothe lowerincisors(Ii)astheratioIi(X-value)/Asab(X-value).
Fig.3. Surgicalchange(T3–T1)andamountofrelapse(T5–T3)ofpointB(X-valueinmm)in individualpatients(n=17).
segmentmovedasaresultoftheDOina rotationalwayinallbutonepatientifthe ratio between 0.8 and 1.2 was taken as translationalmovement.That means that in13patientstheincisaledgesofthelower incisors(Ii)weremoreadvancedthantheir Asab.Inthreepatientstheratiowasnega- tive;thatmeansthatpointAsabwaseven set backwhilepointIi wasadvanced by theDO.
Correlations
No significant correlations were found between the amount of relapse (T5–T3 andT5–T4,X-value)atpointB,Ii,Asab or pogonionwith genderand ageof the patients. Nocorrelations werefound for theamountofadvancement(T3–T1)and long-term relapse(T5–T3) atIi,pointB andAsab.Thetypeofadvancement(rota- tional vs. translational; Ii [X-value;T3–
T2]/Asab[X-value;T3–T2])hadnoinflu- ence on relapse (T5–T3) at point B (X- value)andAsab(X-value).
Alargergonialangle(T1)wassignifi- cantly correlated with a smaller relapse (T5–T3) at the X-values of pogonion (p=0.024;R=0.544).A largerNL/ML0 angle(T1)showedsignificantcorrelations withasmallerrelapse attheX-valuesof pointB(T5–T3:p=0.006;R=0.633;T5- T4: p=0.015; R=0.576) and pogonion (T5–T3: p=0.000; R=0.773; T5–T4:
p=0.013;R=0.588).Thesamewasseen for a larger NSL/ML0 angle (T1) and a smallerrelapse(T5–T3)attheX-valueof point B (p=0.047; R=0.487) and pogonion(p=0.012;R=0.596).Alarger
Jarabakratio(T1)wassignificantlycorre- latedwithalargerrelapse(T5–T3)atthe X-values of point B (p=0.026;
R=0.538) and pogonion (p=0.014;
R=0.586).
No correlation was seen between the advancement of point B (T3–T1) and the verticalrelationsat T1ofNSL/ML0, NL/ML0,and Jarabakratio.Relapseasa puregeometriccorrelationbetweenverti- cal and sagittal relationship was thus excluded.
Discussion
The present study was undertaken to investigate long-termdental andskeletal changesinpatientsundergoingDOofthe mandibularanterioralveolarprocess.Ina previouspaperonskeletalanddentalsta- bility 2 years after DO of the anterior alveolar process the authors reported a 19% amount of relapse at point B.7 To theauthors’knowledge,nootherstudyon DO of the mandibular anterior alveolar processhasbeenpublished,whichmakes a direct comparison of the present data impossible for themoment.For thepre- sentstudyauniformgroupof17patients wasobtainedduetotheexclusionofaddi- tionalsurgicalproceduresonthemandible (genioplasty, BSSO) and maxilla. An examination of alveolar segmental DO withouttheinfluenceofotherconfounding surgicalproceduresonthehardtissuewas thus possible. An inherent problem of long-term studies is the loss ofpatients forfollow-upexaminations.Only17of31 patients initially evaluated7 could be
re-examined. The drop-out analysis showedthattherewasnosignificantdif- ference between the drop-out and the remainingpatientsforcephalometricpara- meters, age and sex. Even though the percentageofskeletalrelapseinthissam- pleis8.3%whichissmallerthanthe19%
reported2yearsafter DOoftheanterior alveolarprocess.Figures6and7illustrate long-term skeletal and dental changes fromT1 toT5 in twodifferentpatients.
The number of re-examined patients is comparable to the 18 patients receiving DOinthelong-termstudybyBaasetal.13 AlthoughtherearenostudiesonDOof themandibular anterior alveolarprocess there are some comparing mandibular advancement with DO or by a BSSO.
Vosetal.14couldnotshowretrospectively anysignificantskeletaldifferencesinnon- syndromicadultpatientstreatedforman- dibular advancement either with DO (BSSOtype)orBSSO10–49monthsafter surgery. Recently, in a follow-up study Baas et al.13 could still not show any difference 46–95 months after surgery onthesame butreducedpatientsamples whilethemeandistance ofadvancement was comparableinboth groups.No dif- ferencein relapsebetween patients with highornormalto lowmandibular plane wasfound.IncontrasttothestudyofBaas et al.,13 high angle patients (NL/ML0) examined in the present study showed significantlysmallerrelapseratesatpoint B (p<0.01) and pogonion (p<0.001).
Thiswasasurprisingfindingwhencom- paredtorelapsepatternsafteraBSSOfor mandibular advancement where a large 340 Jossetal.
Table2. ValuesofselectedcephalometricvariablesatT1(beforesurgery)andT5(5.5yearsaftersurgery).
T1 T5
Mean SD Range Mean SD Range
SNA(8) 80.9 3.7 73.1to85.7 80.0 2.8 74.0to84.4
SNB(8) 76.7 4.2 69.8to83.8 77.3 3.8 70.7to85.5
ANB(8) 4.2 2.2 0.3to7.1 2.7 3.0 2.9to6.3
NSL/NL(8) 7.4 4.1 1.9to15.0 7.6 3.7 0.1to13.0
NSL/ML0(8) 33.6 7.9 21.4to53.7 34.7 7.1 23.9to53.7
NL/ML0(8) 26.2 6.4 16.2to44.8 27.1 5.8 19.8to45.2
Gonionangle(8) 125.9 8.1 115.6to145.8 124.3 8.0 111.0to143.0
Jarabakratio 64.5 6.5 49.2to75.7 63.6 5.4 49.9to72.5
IsL/NSL(8) 109.3 9.8 81.7to120.5 105.0 7.1 91.3to117.0
IsL/NL(8) 116.7 9.4 91.0to126.7 112.6 6.2 99.0to121.8
IiL/ML0(8) 91.0 6.8 77.2to104.6 96.5 6.6 81.5to108.3
IiL-N-pointB(8) 21.2 8.3 6.2to36.3 28.5 6.7 18.1to42.3
IiL-N-pointB(mm) 4.4 3.8 1.0to12.9 7.3 3.7 2.5to15.6
IiL-A-Pg(8) 20.1 6.5 7.6to30.3 26.4 5.7 18.4to39.9
IiL-A-Pg(mm) 0.1 3.7 5.3to9.0 4.8 2.7 1.3to11.9
Holdawayratio 1.0 5.8 6.1to13.6 6.3 4.9 3.4to17.2
IsL/IiL(8) 126.2 14.0 106.9to157.3 123.8 6.6 81.5to108.3
Overjet(mm) 7.7 2.1 4.5to11.9 2.8 0.9 1.3to4.5
Overbite(mm) 4.4 1.7 1.0to7.3 3.0 1.5 0.2to5.5
SeeFig.1fordetailsofthevariables.
mandibularplaneangle(NL/ML0)isoften correlated with increased horizontal relapse.15Itispossiblethatpatientswith a hyperdivergent facial pattern have a lower perioral muscular tonus and thus fewerrelapse.7
Itcould alsobearguedthatDOofthe mandibular anterior alveolar segment mightbebeneficial toprevent biomecha- nicalsideeffects onthemandibularcon- dyle that can occur after BSSO or mandibularDO.16Thiscouldpreventpro- gressive condylar resorption which is
relatedtolong-termrelapseandimpaired mandibularfunction.Thetargetgroupsfor condylarresorptionareyoungwomenwith ahighmandibularplaneangle.17,18Itwas shownthat7%ofallBSSOadvancement patientsappeartoundergoprogressivecon- dylar resorption.19 Further research is needed to elucidate whether condylar resorption is less in cases treated with DO of the mandibular alveolar process.
Recently, Josset al.9showedthatDOof themandibularanterioralveolarprocessis avaluableandsafemethodwithminorside
effectregardingneurosensoryimpairment andcraniomandibularfunction.Nosignifi- cantdifferenceincraniomandibularfunc- tionandneurosensorystatusbetweenaDO groupandanorthodonticallytreatedcon- trolgroupcouldbefound.
In the present study the amount of advancement (T3–T1) had no influence on the amount of relapse (T5–T3) at point B, at Ii, and Asab. Smaller advancements with DO did not show less relapse than larger advancements even though the mean advancement at Skeletalanddentalstabilityofsegmentaldistraction
Table3. Changes(mmordegree)inthevariablesandcoordinatesofthemandibleandlowerincisorsastheimmediate(T3–T1)andfinal(T5–T1) resultofDOsurgery.
T3–T11 T5–T12
Variableorcoordinate Mean p SD Range Mean p SD Range
Horizontal(X-value[mm])
PointB 3.6 *** 2.0 0.21to7.6 3.2 *** 2.3 0.2to7.3
Asab 2.2 *** 2.1 1.1to5.4 1.2 * 2.1 2.2to4.7
Pogonion 0.1 ns 1.0 1.7to1.8 0.5 * 1.0 0.8to2.4
Go0 0.6 ns 2.4 3.5to2.5 0.4 ns 2.7 5.7to2.8
Incisionsup. 1.1 ** 1.4 1.3to3.2 0.4 ns 1.9 4.1to3.0
Incisioninf. 6.2 *** 2.5 0.5to10.9 4.6 *** 3.2 1.6to11.5
Apexinf. 4.2 *** 1.9 1.7to8.8 3.1 *** 2.2 0.6to6.7
Vertical(Y-value[mm])
PointB 1.4 ** 1.7 1.6to4.8 0.0 ns 1.9 6.0to2.3
Asab 0.4 ns 1.4 4.6to1.0 0.1 ns 1.3 2.5to2.1
Pogonion 0.2 ns 2.4 5.1to4.8 0.3 ns 1.8 2.8to4.8
Menton 0.1 ns 0.5 0.6to1.2 0.0 ns 1.0 1.5to1.5
Go0 0.3 ns 2.4 3.5to2.5 0.6 ns 1.9 3.5to3.2
Incisionsup. 1.8 *** 1.7 6.7to0.4 0.3 ns 1.4 3.3to2.4
Incisioninf. 1.3 ** 1.9 1.8to4.9 1.3 * 1.9 1.7to4.9
Apexinf. 0.2 ns 1.2 2.8to2.0 0.1 ns 1.8 2.8to3.4
Angular(8),linearmeasurements(mm),andratios
SNA(8) 0.4 ns 1.6 3.0to1.7 0.9 * 1.6 3.2to2.2
SNB(8) 0.9 * 1.2 0.6to3.9 0.6 ns 1.6 1.7to3.3
ANB(8) 1.3 *** 1.0 3.9to0.9 1.5 *** 1.2 3.7to0.2
Wits(mm) 3.1 *** 1.5 5.3to0.4 2.9 *** 2.2 7.7to1.3
NSL/NL(8) 0.2 ns 1.3 2.0to2.8 0.2 ns 1.3 2.1to2.1
NSL/ML0(8) 1.3 *** 1.3 0.5to3.5 1.1 * 1.6 2.8to3.8
NL/ML0(8) 1.1 ** 1.5 0.4to3.7 1.0 * 1.4 1.6to3.6
Gonionangle(8) 2.1 ** 2.7 7.0to1.9 1.6 ns 3.7 10.2to4.5
Jarabakratio 0.3 ns 1.6 2.7to2.2 0.9 ns 2.0 4.0to3.4
IsL/NSL(8) 1.3 ns 5.9 5.1to22.0 4.3 ** 6.0 16.7to9.6
IsL/NL(8) 1.5 ns 5.3 4.6to20.1 4.1 ** 5.7 14.7to8.0
IiL/ML0 (8) 7.2 *** 4.9 6.5to15.7 5.5 ** 5.9 5.7to16.1
IiL-N-pointB(8) 9.4 *** 4.6 4.2to16.1 7.2 *** 6.1 4.3to16.5
IiL-N-pointB(mm) 3.4 *** 1.5 1.7to5.2 2.9 ns 2.5 1.4to7.8
IiL-A-Pg(8) 6.2 *** 4.0 4.9to13.4 6.3 *** 5.7 3.1to14.7
IiL-A-Pg(mm) 6.0 *** 1.9 0.5to8.9 4.6 *** 2.7 0.5to11.4
Holdawayratio 7.9 *** 2.7 1.4to12.7 5.4 *** 3.3 1.2to13.3
IsL/IiL(8) 9.7 *** 7.9 31.4to4.9 2.4 ns 9.6 21.9to14.5
Overjet(mm) 5.1 *** 1.7 7.8to1.1 4.9 *** 1.9 9.2to3.0
Overbite(mm) 3.1 *** 1.7 6.4to0.1 1.5 ** 1.7 5.3to1.1
Ii/Asab 1.8 7.5 22.4to9.7
SeeFig.1fordetailsofthevariables.T1,beforesurgery;T3,24.4daysaftersurgery;T5,5.5yearsaftersurgery.
1T3–T2forAsab,Ii(X-value,T3–T2)/Asab(X-value,T3–T2)insteadmeanvaluethemedianwastakenforthisratioandnopairedt-testwas possiblebecausemeasuredonasingleoccasion
2T5–T2forAsab.Negativevaluesimplyabackwardandpositivevaluesaforwardmovementofthepointinthehorizontalplane.Inthevertical plane,negativevaluesimplyanupwardandpositivevaluesadownwardmovementofthepoint.
*p0.05.
**p0.01.
***p0.001.
point B (X-value) was rather low with 3.6mm. This is in accordancewith the findings of the authors’ previous study 2.0yearsafterDOoftheanterioralveo- lar segment.7 In contrast, in BSSO a positivecorrelationbetweentheamount ofrelapseandtheamountofmandibular advancement is oftenseen.
Advancementsintherange6–7mmor more predispose to horizontal relapse.15 Only two of 17 of the patients had advancements largerthan 6mmat point B.TheamountofrelapseatpointBwas 8.3% 5.5 years after DOof theanterior alveolar segment. Nevertheless, the amountofrelapseatpointBwas 19.0%
after2.0years.7Reasonsforthisimprove- mentregardingtherelapserateatpointB could be the missing data from the 16 patients whichcouldnotbere-examined forthis5.5yearfollow-up.Thesystematic reviewonBSSOformandibularadvance- mentofJossandVassalli15showedalarge variability from2to50.3%inlong-term relapse(>1.5years)atpointB.
A reason for the amount of dental relapse of 29.0% at incision inferior to the initial surgical advancement could be the overcorrection achieved by the distractionwhereanedge-to-edgeincisal positionornegativeoverjetatT3hadtobe correctedwithClassIIIelasticspostsurgi-
cally.Furthermore,theDOcreatesspace distalofthecanineswhilecrowdingisstill presentintheincisorregion.Incisoralign- mentiscarriedoutinthisnewlygenerated space to prevent further proclination or roundtripping.Forthisreason,itispos- siblethatincision inferiormovesfurther posteriorlybyorthodonticforces.7
The distraction vector (translation vs.
rotational) was defined by the type of distraction appliance chosen, whereas pseudarthrosis at the osteotomy sites occurredinnoneofthe17patientsexam- ined.Thehingeplateallowsamorerota- tional and the base-distractor a more translational movement of the anterior 342 Jossetal.
Table4. Changes(mm,degreeorratio)inthevariablesandcoordinatesofthemandibleandlowerincisorsastherelapse(T5–T3)andthelong- termchange(T5–T4)ofDOsurgery.
T5–T3 T5–T4
Variableorcoordinate Mean p SD Range Mean P SD Range
Horizontal(X-value[mm])
PointB 0.3 ns 1.3 2.7to3.3 0.3 ns 0.7 1.0to2.0
Asab 1.0 *** 0.9 2.4to1.1 0.1 ns 0.6 1.1to1.5
Pogonion 0.4 ns 1.0 1.6to2.9 0.1 ns 0.7 1.0to2.0
Go0 0.2 ns 2.7 6.4to4.7 0.4 ns 2.5 7.6to4.1
Incisionsup. 1.5 ** 1.7 5.4to1.2 0.1 ns 0.6 1.6to0.9
Incisioninf. 1.8 *** 1.9 5.4to0.6 0.2 ns 0.6 1.6to1.4
Apexinf. 1.1 * 1.7 3.8to1.6 0.1 ns 1.4 3.5to2.9
Vertical(Y-value[mm])
PointB 1.4 * 2.7 7.9to2.7 0.1 ns 1.7 3.2to3.2
Asab 0.5 ns 1.0 1.1to2.7 0.1 ns 0.6 1.9to0.9
Pogonion 0.1 ns 2.3 3.7to3.3 0.4 ns 1.7 4.6to3.0
Menton 0.2 ns 0.6 1.3to0.9 0.0 ns 0.6 1.0to1.0
Go0 0.3 ns 1.4 2.9to2.4 0.4 ns 1.5 2.9to2.1
Incisionsup. 1.4 *** 1.5 1.2to3.9 0.5 ** 0.8 0.6to1.8
Incisioninf. 0.1 ns 1.6 4.3to2.8 0.1 ns 0.7 1.1to1.4
Apexinf. 0.3 ns 1.7 2.5to3.0 0.6 ns 1.5 4.2to2.9
Angular(8),linearmeasurements(mm),andratios
SNA(8) 0.5 ns 1.3 2.9to2.4 0.2 ns 1.4 2.6to2.4
SNB(8) 0.3 ns 1.1 1.9to1.9 0.4 ns 0.8 1.0to1.8
ANB(8) 0.2 ns 1.0 2.2to1.8 0.2 ns 1.0 2.5to1.4
Wits(mm) 0.2 ns 1.8 3.2to2.8 0.2 ns 1.4 2.1to2.2
NSL/NL(8) 0.0 ns 0.8 1.3to1.4 0.3 ns 0.9 1.7to1.6
NSL/ML0(8) 0.1 ns 1.4 3.5to1.9 0.6 ns 1.3 3.5to1.6
NL/ML0(8) 0.1 ns 1.2 2.2to2.1 0.3 ns 1.1 1.9to1.8
Gonionangle(8) 0.6 ns 3.4 7.3to6.7 1to1 ns 3.6 7.1to4.6
Jarabakratio 0.6 ns 1.7 3.9to2.1 0.6 ns 1.6 2.9to3.5
IsL/NSL(8) 5.5 *** 4.5 12.4to0.1 0.6 ns 2.7 5.7to3.0
IsL/NL(8) 5.5 *** 4.6 12.3to0.3 1.0 ns 2.9 5.4to3.2
IiL/ML0 (8) 1.7 ns 5.4 11.5to9.0 0.0 ns 3.1 5.1to7.8
IiL-N-pointB(8) 2.1 ns 5.3 12.2to10.1 0.3 ns 3.4 5.8to9.0
IiL-N-pointB(mm) 0.5 ns 2.3 4.8to4.0 0.5 * 0.7 2.1to0.7
IiL-A-Pg(8) 0.1 ns 5.9 12.1to11.7 0.2 ns 3.3 5.6to8.1
IiL-A-Pg(mm) 1.4 ** 1.9 5.5to2.5 0.3 ns 1.0 1.8to1.3
Holdawayratio 2.6 *** 2.2 6.0to1.2 0.3 ns 0.9 2.2to1.0
IsL/IiL(8) 7.3 *** 6.3 7.0to18.3 1.3 ns 4.0 5.3to9.3
Overjet(mm) 0.1 ns 1.4 2.6to2.4 0.3 * 0.5 0.4to1.7
Overbite(mm) 1.7 *** 1.7 1.5to3.9 1.0 ** 1.1 0.5to4.0
SeeFig.1fordetailsofthevariables.T3,24.4daysaftersurgery;T4,2.0yearsaftersurgery;T5,5.5yearsaftersurgery.Negativevaluesimplya backwardandpositivevaluesaforwardmovementofthepointinthehorizontalplane.Intheverticalplane,negativevaluesimplyanupwardand positivevaluesadownwardmovementofthepoint.
*p0.05.
**p0.01.
***p0.001.
mandibular alveolar segment.The intro- duction of the newly defined skeletal points (Asab) permits the evaluation of the movementofthesurgicalbaseinde- pendentlyandtheboneremodelingatthe surgicalsite.7Acomparisonbetweenthe movementsofIi,pointB,andlowerinci- sorapexcandeterminewhetherDOcre- ated predominantly a rotation or translationofthe alveolarprocess,espe- cially when considering the ratio Ii (X- value,T3–T2)/Asab(X-value,T3–T2).A ratioof1signifiesthatapuretranslationof thesegment hadtakenplace.Thehigher the ratio over 1 the more the centre of rotationislocatedatthelowerincisorapex oratAsab,respectively,andtheopposite forvaluesbelow1.
Threeofthe 17patientshadanegative ratio indicating a setback of point Asab while point Ii was advanced. Only one patienthadaratiobetween0.8and1.2which couldbedescribedastranslationmovement, thatmeansthat13patientshadamoreorless accentuatedrotationalmovementofthedis- tractedsegment.Someproclinationofthe lowerincisorswasrelatedtotheorthodontic treatment which could have biased the assessmentofthatratio.
Inthis study, therelapse rateat Asab (45.5%)wasquitelarge.Thiscouldbedue toremodelingoftheborderofthesegment to smooththe contour andaspectof the anterior symphysis.The interfaceof the surgical sectionoftheanterior aspectof the symphysis is highly susceptible to resorption and bony remodeling. This hasalsobeenshownatthesurgicalborders ofadvancementgenioplasties whereoss- eousremodelingwashighest.20
Insummary, this long-term follow-up found that no change in further relapse wasseenbetween2.0yearsand5.5years postoperativelyregardingpointBandthe incisionofthelowerincisors.DOofthe mandibular anterior alveolar process resultedinamainlyrotationalratherthan translational advancement of the tooth bearing alveolar segment. 5 years after treatment 8.3% of the original skeletal advancement and 29% of the dental advancement has vanished. Considering the amountoflong-termskeletal relapse the procedure could bean alternative to BSSO for mandibular advancement in selectedcases.
Funding None.
Competinginterests Nonedeclared.
Skeletalanddentalstabilityofsegmentaldistraction
Fig.4. Surgicalchange(T3–T1)andamountofrelapse(T5–T3)ofoverjet(inmm)inindividual patients(n=17).
Fig.5. ChangesofpointBandoverjetfromT1toT5.
Fig.6. Superpositionofserialtracings(T1,T3,T4,andT5)inamalepatient(number12)with littleskeletalanddentalchangesinlong-term.Legend:T1(24.06.2002),T3(13.08.2002),T4 (28.09.2005),andT5(27.06.2007).
Ethicalapproval
Yes.Ethicalapprovalwasadmittedbythe Ethic Committee of the Kanton Zu¨rich, Switzerland,number593.
References
1. CodivillaA.Onthemeansoflengtheningin the lower limbs, the muscles and tissues which are shortened through deformity.
AmJOrthopSurg1905;2:353–69.
2. McCarthyJG,SchreiberJ,KarpN,Thorne CH,GraysonBH.Lengtheningthehuman mandible by gradual distraction. Plast ReconstrSurg1992;89:1–8.[discussion9–
10].
3. Swennen G, Schliephake H, Dempf R, SchierleH,MalevezC.Craniofacialdistrac- tionosteogenesis:areviewoftheliterature:
Part1:clinicalstudies.IntJOralMaxillofac Surg2001;30:89–103.
4. Ow A,Cheung LK.Skeletalstabilityand complicationsofbilateralsagittalsplitosteo- tomiesandmandibulardistractionosteogen- esis: an evidence-based review. J Oral MaxillofacSurg2009;67:2344–53.
5. Triaca A,AntoniniM,Minoretti R,Merz BR. Segmental distractionosteogenesis of theanterioralveolarprocess.JOralMax- illofacSurg2001;59:26–34.[discussion34–
25].
6. TriacaA,MinorettiR,SaulacicN.Mandi- bula wingosteotomyforcorrectionofthe mandibularplane:acasereport.BrJOral MaxillofacSurg2010;48:182–4.
7. JossCU,TriacaA,AntoniniM,KiliaridisS, Kuijpers-JagtmanAM.Skeletalanddental stabilityinsegmentaldistractionoftheante- rior mandibularalveolarprocess.A2-year follow-up. Int J Oral Maxillofac Surg 2012;41:553–9.
8. JossCU,TriacaA,AntoniniM,KiliaridisS, Kuijpers-JagtmanAM.Softtissuestability insegmentaldistractionoftheanteriorman- dibularalveolarprocess.A2-yearfollow-up.
IntJOralMaxillofacSurg2012;41:560–5.
9. JossCU,TriacaA,AntoniniM,Kuijpers- Jagtman AM, Kiliaridis S. Neurosensory and functional evaluation in distraction osteogenesis of the anterior mandibular alveolarprocess.IntJOralMaxillofacSurg 2012Jul19.
10.TriacaA,MinorettiR,MerzB.Treatmentof mandibular retrusionby distraction osteo- genesis:anewtechnique.BrJOralMax- illofacSurg2004;42:89–95.
11.Bjo¨rkA,SkiellerV.Growthofthemaxillain three dimensionsas revealed radiographi- cally bytheimplantmethod.BrJOrthod 1975;4:53–64.
12.DahlbergG.Statisticalmethodsformedical and biologicalstudents. New York:Inter- sciencePublications;1940.
13.Baas EM,PijpeJ,deLangeJ.Long term stabilityofmandibularadvancementproce- dures:bilateralsagittalsplitosteotomyver- sus distraction osteogenesis. Int J Oral MaxillofacSurg2011;41:137–41.
14.VosMD,BaasEM,deLangeJ,Bierenbrood- spotF.Stabilityofmandibularadvancement procedures:bilateralsagittalsplitosteotomy versus distractionosteogenesis. IntJ Oral MaxillofacSurg2009;38:7–12.
15.JossCU,VassalliIM.Stabilityafterbilateral sagittal split osteotomy advancement sur- gerywithrigidinternalfixation:asystematic review. J Oral Maxillofac Surg 2009;67:301–13.
16.Peltomaki T. Stability, adaptation and growth following distraction osteogenesis inthecraniofacialregion.OrthodCraniofac Res2009;12:187–94.
17.HoppenreijsTJ,FreihoferHP,StoelingaPJ, Tuinzing DB, van’t Hof MA. Condylar remodellingand resorptionafterLeFortI andbimaxillaryosteotomiesinpatientswith anterioropenbite.Aclinicalandradiologi- cal study. Int J Oral Maxillofac Surg 1998;27:81–91.
18.Sesenna E, RaffainiM.Bilateral condylar atrophyaftercombinedosteotomyforcor- rection of mandibular retrusion. A case report.JMaxillofacSurg1985;13:263–6.
19.Scheerlinck JPO,Stoelinga PJW, Blijdorp PA, Brouns JJA, Nijs MLL. Sagittalsplit advancement osteotomies stabilized with miniplates:a2-5-yearfollow-up.IntJOral MaxillofacSurg1994;23:127–31.
20.McDonnell JP, McNeill RW, West RA.
Advancement genioplasty: a retrospective cephalometricanalysisofosseousandsoft tissuechanges.JOralSurg1977;35:640–7.
Address:
ChristofUrsJoss
DepartmentofOrthodonticsandCraniofacial Biology
RadboudUniversityNijmegenMedicalCentre Nijmegen
TheNetherlands Tel:+31243614005
E-mail:[email protected] 344 Jossetal.
Fig.7. Superpositionofserialtracings(T1,T3,T4,andT5)inafemalepatient(number13) with important skeletal and dental changes in long-term. Legend: T1 (24.11.1998), T3 (14.12.1998),T4(28.08.2000),andT5(14.03.2007).
