Alveolar corticotomies

International Orthodontics 2008 ; 6 : 343-354 343

2008. CEO.dit par / Published by Elsevier Masson SAS.

Tous droits rservs/All rights reservedArticle originalOriginal article

Les corticotomies alvolaires : principes et applications cliniques

Alveolar corticotomies: principles and clinical applications

Marc THIERRY1, Jean-Baptiste CHARRIER2

1 Facult de chirurgie dentaire Paris V, Dpartement dorthodontie, 1 rue Maurice Arnoux, 92120 Montrouge.2 Service dORL et de Chirurgie de la face et du cou, CHU de Bictre, AP-HP, Universit Paris Sud-11.

Correspondance et tirs part / Correspondence and reprints:M THIERRY, Facult de chirurgie dentaire Paris V, Dpartement dorthodontie, 1 rue Maurice Arnoux, 92120 [email protected]

RsumLa dure dun traitement dorthodontie est denviron deux ans, ce quia conduit au dveloppement de nouvelles techniques, comme les cor-ticotomies, qui permettent dacclrer le dplacement dentaire ortho-dontique. Cette technique consiste en une intervention chirurgicalesur la corticale osseuse autour des dents dplacer. Elle provoqueune diminution de la densit de los mdullaire et une augmentationdu remodelage osseux (turn-over). Ces processus biologiques sont lorigine de lacclration du dplacement dentaire, mais permettentaussi dobtenir des dplacements qui dpassent les limites classiquesdun traitement dorthodontie, permettant parfois de surseoir lachirurgie orthognathique. Cette technique ouvre de nouvelles pers-pectives dans le traitement orthodontique de ladulte.

Mots-cls Corticotomie alvolaire. Dplacement dentaire. Acclration du traitement.

SummaryOrthodontic treatment typically lasts about two years. This hasled to the development of new techniques, such as corticotomies,which help speed up orthodontic tooth displacement. The cortico-tomy technique consists of a surgical procedure on the corticalbone surrounding the teeth needing to be moved. The result isdecreased medullary bone density and increased bone turnover.These biological processes trigger acceleration of the bone dis-placement while also enabling displacements which exceed theusual limits of orthodontic treatment and even, on occasion, helpavoid orthognathic surgery. Corticotomy opens up new prospectsfor adult orthodontic treatment.

Key-words Alveolar corticotomy. Displacement tooth. Treatment acceleration.

Marc THIERRY, Jean-Baptiste CHARRIER

344 International Orthodontics 2008 ; 6 : 343-354

Introduction

Les facteurs biologiques sont les principales limitations au tempsde traitement en orthodontie. Il a t montr que le rythme bio-logique de dplacement dentaire dpend de plusieurs facteurs :le turn-over osseux [1, 2], la densit osseuse [3], la raction duligament alvolo-dentaire et sa dure de hyalinisation [4]. Ladure dun traitement orthodontique classique est denvirondeux ans. Cette dure peut tre un obstacle chez les adultes, deplus en plus nombreux dsirer un traitement, sans compterlincidence des problmes carieux et parodontaux qui augmenteavec la dure du traitement. Ds lors, diverses techniques ont tproposes pour acclrer le dplacement orthodontique.

Techniques non chirurgicalespour acclrer le traitement

Ladministration de drogues telles que les prostaglandines [5-8],interleukines [9], leucotrines [10], adnosine monophosphate[11], ou de vitamine D [12, 13] a t exprimente. Ces mol-cules dclenchent ou augmentent linflammation, et peuventacclrer la rgnration ligamentaire en augmentant le nom-bre dostoclastes forms, ou en augmentant la permabilitcapillaire. Cependant, leur utilisation est limite par lexistencedeffets secondaires gnraux.Des sollicitations mcaniques ou physiques, telles que lapplica-tion de champs lectriques ou magntiques ont t proposes,mais ont aussi des effets indsirables [14-16].

Techniques chirurgicales pour acclrer le traitement

La fibrotomie supracrestale consiste en une section des fibresgingivo-dentaires. Il a t montr que la pratique dune fibroto-mie supra-crestale sur une dent dplacer acclrait la vitessede dplacement, mais dans de faibles proportions [17].Les techniques de distraction ont pour ambition de raccourcir laphase de recul canin dans les cas avec extraction de premiresprmolaires. Cette tape passe alors dune dure de 6-8 mois 10 jours. Les distractions dento-alvolaires consistent faire uneostotomie autour de la dent dplacer, de faon individualiserun bloc osseux comprenant la dent et son os alvolaire, et mobi-liser par la suite ce bloc osseux par le biais de vrins [18, 19].Concrtement, lextraction des premires prmolaires est imm-diatement suivie dune ostotomie autour de la canine. Le blocosseux est dplac par lintermdiaire du vrin qui prend appuisur une bague scelle sur la canine raison de 0,8 mm par jour.Le chirurgien doit veiller ce quil ny ait pas dobstacle audplacement du bloc osseux alvolaire. Tout obstacle osseuxventuel en distal de la canine doit tre limin. Les distractions ligamentaires ou dentaires consistent en unrecul de la canine avec un vrin, raison de 0,5 1 mm par jour,aprs avoir affaibli la paroi dos interdentaire [20-22] . Dans cecas, le ligament est considr comme une suture entre los et la

Introduction

Biological factors are the main limitations on orthodontic treat-ment time. It has been demonstrated that the biological rate oftooth displacement is dependent upon several conditions: boneturnover [1, 2], bone density [3], the response of the periodontalligament and its speed of hyalinization [4]. Orthodontic treatmenttypically lasts about two years. This duration can discourageadults, many more of whom are now seeking treatment. In addi-tion, there is the incidence of caries- and periodontium-relatedproblems which increases the longer treatment lasts. As a result,various techniques have been suggested to speed up orthodonticdisplacement.

Non-surgical techniques for speeding up treatment

Experiments have been performed with the administration of variousdrugs including prostaglandins [5-8], interleukins [9], leukotrienes[10], adenosin monophosphate [11], and vitamin D [12, 13].These molecules trigger or exacerbate inflammation and canaccelerate ligament regeneration by increasing the number ofosteoclasts or by increasing capillary permeability. However, theiruse is limited by the advent ofgeneral side effects.

Mechanical and physical forces involving, for instance, electricalor magnetic fields have been proposed. However, these havealso been shown to have undesirable side effects [14-16].

Surgical techniques for speeding up treatment

Supracrestal fibrotomy consists in sectioninggingivo-dental fibers.It has been shown that performing supracrestal fibrotomy on atooth requiring to be moved accelerates the rate of displacement,although only moderately [17]. The aim of distraction techniques is to shorten the canine retrac-tion phase in cases involving first premolar extractions. This stagethen takes only 10 days as opposed to 6-8 months.

Dentoalveolar distractions consist in performing an osteotomyaround the tooth to be displaced in order to create an individual-ized bone block comprising the tooth and its alveolar bone andthen to use jack-screws in order to move the bone block [18, 19].In concrete terms, extraction of the first premolars is immediatelyfollowed by osteotomy around the canine. The bone block is dis-placed by 0.8mm per day using a jackscrew fixed to a band whichis cemented to the canine. The surgeon needs to ensure thatthere is no obstacle in the path of the displaced alveolar boneblock. Any potential obstacle distal to the canine needs to beremoved. Ligament or tooth distractions consist of jackscrew-assistedcanine retraction by between 0.5 and 1mm per day after firstweakening the interdental wall [20-22]. In this instance, the liga-ment is considered to be a stretchable suture between the bone

Les corticotomies alvolaires : principes et applications cliniquesAlveolar corticotomies: principles and clinical applications


dent, que lon peut tirer. Le ligament peut se dchirer, mais il sergnre par les mmes principes biologiques que pour la dis-jonction de la suture palatine mdiane.Les corticotomies consistent en la ralisation de traits ou de per-forations concernant uniquement la corticale, autour des dents dplacer. Cette technique nest donc pas limite au recul canin,et peut concerner toute larcade ou au contraire tre segmentaire.Cest une technique gnralement rserve ladulte, qui permetde rendre le dplacement dentaire et le traitement orthodontiquedans son ensemble deux quatre fois plus rapide quun traite-ment dorthodontie conventionnel. Les corticotomies peuvent tre employes uniquement dans unbut dacclration du traitement, puisque les dures de traite-ment rapportes vont de quatre sept mois. Elles peuvent gale-ment, dans certains cas de dcalage des bases modr, treemployes comme alternative la chirurgie orthognathique,puisque les corticotomies permettent dobtenir des dplacementsdentaires qui permettent de dpasser les limites dun traitementorthodontique classique, et donc daugmenter les possibilits detraitement. Les techniques de distraction et les corticotomies font donc appel des processus physiologiques diffrents pour obtenir un dpla-cement dentaire acclr :Les distractions font appel des forces lourdes, appliques par lebiais de vrins du type de ceux employs sur les disjoncteurs.Ces techniques permettent de saffranchir de la limitation physio-logique du ligament dento-alvolaire, puisque dans un cas ondplace la totalit du bloc osseux alvolaire sans le solliciter, etdans lautre cas, le ligament est dchir.Les corticotomies mettent en jeu des mcanismes biologiquesplus physiologiques.

Historique des corticotomies

Le premier introduire le concept de mouvement dentaire acc-lr par la chirurgie est Kle en 1959 [23]. Il dcrit une techni-que qui est lanctre des corticotomies. Il pratique des incisionsverticales entre les racines intressant la totalit de la corticale,et ne concernant que superficiellement los mdullaire. Ces inci-sions sont relies entre elles au niveau apical par un trait dosto-tomie horizontal concernant la totalit de los alvolaire, corticaleet os mdullaire, crant ainsi des blocs osseux relis entre euxuniquement par de los mdullaire de moindre densit. Klepense ainsi pouvoir mobiliser les blocs osseux plus facilement.Les rsultats sont bons puisque les dplacements dentaires sonteffectivement plus rapides, mais les pertes de vitalit pulpaire nesont pas rares.En 1978, Generson supprime lostotomie sous-apicale pour ra-liser uniquement des traits de corticotomie limits la corticale[24].Les publications au sujet des corticotomies deviennent ensuiteplus nombreuses dans les annes 2000.

and the tooth. The ligament may tear but will regenerate. Theprinciple is the same as for disjunction of the mid-palatal suture.

Corticotomies consist in creating bone-cuts or perforations exclu-sively in the cortical bone surrounding the teeth to be displaced.This technique, therefore, is not reserved for canine retractionalone and can involve the entire arch or can be performed in seg-ments. The technique isgenerally performed only on adults andmakes tooth displacement and the overall orthodontic treatmentbetween two and four times shorter than conventional orthodontictreatment. Corticotomies can be used exclusively with a view to acceleratingtreatment as the treatment times reported in the literature rangefrom four to seven months. They can also be used in some casesinvolving a moderate discrepancy of the base as an alternative toorthognathic results obtained using classic orthodontic treatmentand thus broadens the range of treatment alternatives.

Distraction techniques and corticotomies thus call on differentphysiological processes in order to achieve accelerated tooth dis-placement. Distractions require high forces applied by jackscrews of the typeused in palatal expansion screws. Using these techniques, it ispossible to overcome the physiological limitations of the peri-odontal ligament since, in one instance, the entire alveolar boneblock is displaced without applying a force and, in the other, theligament is torn. Corticotomies involve more physiological biological mechanisms.

A background to corticotomies

The first person to introduce the notion of surgically-acceleratedtooth movement was Kle in 1959 [23] when he described a tech-nique which is the forerunner of the corticotomy. He made verticalincisions between the roots involving the entire cortex and pene-trating the medullary bone only superficially. These incisions wereconnected to one another at apical level by a horizontal osteo-tomy line taking in the entire alveolar bone, cortex and medullarybone, thus creating bone blocks connected to one another onlyby less dense medullary bone. Kle maintained that this permit-ted easier movement of the bone blocks. The results aregoodsince tooth displacement effectively occurs more rapidly, but pul-par devitalization is not an unusual occurrence.

In 1978, Generson dispensed with the subapical osteotomy andperformed corticotomy lines on the cortex alone [24].

A larger number of publications regarding corticotomies hasbegun to appear since 2000.



Protocole actuel des corticotomies

On peut rsumer le protocole actuellement utilis de la maniresuivante : Selon les quipes, lanesthsie est locale avec prmdication,ou gnrale. Incision sulculaire classique, et leve dun lambeau muco-priost incluant les papilles en vestibulaire et en lingual. Il fautprotger les paquets vasculo-nerveux issus des foramens palatinset mentonniers. En gnral, on ralise les corticotomies en vesti-bulaire et en palatin lors de la mme intervention, mais certainsauteurs prfrent le faire lors de deux interventions distinctespour limiter linconfort post-opratoire. Ralisation de saignes corticales verticales entre les dents enprenant soin dviter les racines, traversant la totalit de la corti-cale, mais ne pntrant pas los mdullaire. Il est possible decombiner des traits de section osseuse ponctuels et linaires cir-conscrivant les racines, qui pour certains auteurs doivent rester 2-3 mm en de de la crte alvolaire [25] (fig. 1, 2). Certains auteurs pratiquent une greffe complmentaire dosbovin [25]. Cela permettrait potentiellement daugmenter lpais-seur dos cortical, permettant une meilleure stabilit des traite-ments. Le bnfice rel de ces greffes nest pas encore clairementtabli.Les corticotomies ne doivent concerner que les dents dplacer.Les dents dont les secteurs nont pas reu de corticotomie bnfi-cient alors dune valeur dancrage relative plus importante, ce quipermet de raliser les mouvements dsirs avec un meilleurcontrle mcanique.Les rendez-vous orthodontiques postopratoires doivent tre fr-quents, en gnral espacs de deux semaines. Cela permet deprofiter au maximum de cette priode de mouvement dentaire

Fig. 1 : Aspect peropratoire de lintervention au maxillaire.Fig. 1: Peri-operative view of the maxillary procedure.

Fig. 2 : Aspect peropratoire de lintervention la mandibule.Fig. 2: Peri-operative view of the mandibular procedure.

Current corticotomy protocols

Current corticotomy protocols can be summarized as follows:

Depending on the team, the anesthetic will be either local, withpremedication, orgeneral. A classic sulcular incision is made and a mucoperiosteal flap islifted including the lingual and buccal papillae. The vascular-nerve bundles emerging from the palatal and mental foramensmust be protected. Generally, corticotomies are performed on thebuccal and palatal sides during a single procedure although someauthors prefer two separate interventions in order to reduce post-operative discomfort. Vertical incisions are made in the cortex between the teeth takingcare to avoid the roots. The incision crosses the entire corticalbone but does not penetrate the medullary bone. It is possible tocombine pin-point and linear bone cuts in the areas encircling theroots. Some authors maintain that these cuts should be made atleast 2-3mm from the alveolar ridge [25] (fig 1, 2). Some authors also perform a bovine bonegraft [25]. In principle,this should help thicken the cortical plate and enhance treatmentstability. The real benefit of thesegrafts has not yet been clearlyestablished.

Corticotomies should only be performed on the teeth to be moved.The teeth in segments which have not received a corticotomy canthen provide relativelygood anchorage, thus permitting the desiredmovements withgreater mechanical control.

Post-operative appointments should be quite frequent, every twoweeks or so. The practitioner can make maximum use of thisperiod of accelerated tooth movement, or even prolong the phe-



acclr, voire dentretenir ce phnomne. La priode postopra-toire o il est possible dobtenir les dplacement dentaires lesplus importants dbute la fin du premier mois.

Thories explicatives et mcanismes mis en jeu

La thorie des blocs osseux

Initialement, la physiopathognie propose pour expliquer larapidit et lamplitude des mouvements dentaires avec corticoto-mies a t la thorie des blocs osseux . Kle en effet suggreque la corticale est un obstacle majeur aux dplacements dentai-res, et que les corticotomies permettent dindividualiser des blocsosseux relis entre eux uniquement par de los mdullaire demoindre densit. Les dents servent alors de support dancragepour mobiliser ces supports osseux les uns par rapport auxautres. Afin de mobiliser ces blocs osseux, il faut employer desforces relativement lourdes. Pendant de nombreuses annes, tou-tes les tudes dcrivant des corticotomies se sont rfres cettethorie des blocs osseux [24, 26-30].

Le regional accelerated phenomenon ou RAP

Toute agression chirurgicale des tissus mous ou osseux provoqueune rorganisation tissulaire importante, que Frost nomme le regional accelerated phenomenon (RAP) [31]. Dans los, cetterorganisation est marque par un turnover cellulaire accru etpar une diminution de la densit et de la calcification osseusesdues une augmentation de lactivit ostoclasique. Cet tattransitoire ostopnique va ensuite laisser la place une cicatri-sation osseuse complte avec un rtablissement de la densitosseuse dorigine. Ce phnomne est dautant plus marqu que lesite chirurgical est proche et que lagression est importante.Le RAP est mis en jeu lors de la consolidation dun foyer de frac-ture pour permettre une noformation dos lorigine de la forma-tion dun cal osseux.Cest plus probablement ce phnomne de RAP qui est lori-gine des dplacements dentaires acclrs. Le principe est lemme que pour la consolidation dun foyer de fracture, mais laconsolidation va ici tre guide par le traitement orthodontique.Cest cette priode de consolidation qui permet de maintenir unemobilit dentaire augmente pendant un certain temps aprslintervention.

Augmentation du turnover

On sait que le turnover osseux est augment par une fracture, uneostotomie, une greffe osseuse [31], ou par le simple fait de rali-ser un lambeau fibromuqueux avec un dcollement sous priost[32]. Il a t montr que le turnover cellulaire au niveau osseux aun impact sur la rapidit des mouvements dentaires [33, 34].Exprimentalement, en augmentant pharmacologiquement chezlanimal le turnover cellulaire au niveau osseux, on constate un

nomenon. The post-operative phase when most tooth displace-ment can be achieved begins at the end of the first month.

Underlying theories and the mechanisms involved

The bone blocks theory

Initially, a bone blocks theory was advanced to describe thephysiopathogenics behind the acceleration and scope of the toothmovements achieved by corticotomy. Kle suggested that thecortical plate constituted a major barrier to tooth displacementand claimed that corticotomies separated bone blocks whichwere then only bound together by less dense medullary bone.The teeth then provide anchorage supports which help movethese supports relative to one another. Relatively high forces areneeded to move these bone blocks. For many years, all the stud-ies describing corticotomies referred to this bone blocks theory[24, 26-30].

The regional accelerated phenomenon or RAP

Any surgical aggression to soft or bony tissue will trigger majortissue reorganization, which Frost termed regional acceleratedphenomenon (RAP) [31]. With bone, this reorganization ismarked by increased cell turnover and by decreased density andbone calcification on account of increased osteoclastic activity.This temporary osteopenic condition will then be followed bycomplete bone healing with restoration of the original bone den-sity. This phenomenon is all the more marked the closer the siteof surgery and thegreater the aggression.

RAP occurs during consolidation of a fracture site enabling newbone to be formed which will create a bony callus.

It is probably this RAP which triggers the accelerated tooth dis-placements. The underlying principle is the same as that underly-ing fracture consolidation although, in this case, consolidation willbeguided by the orthodontic treatment. It is the consolidationphase which makes it possible to maintain increased tooth mobilityfor some time following the procedure.

Increased turnover

It is well known that bone turnover increases following a fracture,osteotomy or bonegraft [31], or by simply lifting a fibromucousflap with subperiosteal elevation [32]. It has been demonstratedthat cell turnover at bone level impacts the speed of tooth move-ments [33, 34]. In experimental conditions in animals, pharmaco-logically increased cell turnover in the bone results in more rapidtooth displacement. In the clinical setting, in periodontal surgery,



dplacement dentaire plus rapide. Cliniquement, en chirurgieparodontale, le simple fait de faire un lambeau daccs provoqueune mobilit dentaire augmente pendant une certaine priodesuivant lacte. Aprs une chirurgie dostotomie, les dents sontaussi plus faciles mobiliser.Les observations histologiques [35, 36] ont confirm que les cor-ticotomies augmentaient le turnover osseux, mesur par le nom-bre dostoclastes activs. Du ct tmoin, deux semaines sontncessaires pour que le nombre de cellules atteigne son niveaumaximal, alors que le recrutement cellulaire atteint tout de suiteun niveau lev qui se maintient du ct de la corticotomie.

Diminution de la densit osseuse

Il a galement t montr que la diminution de la densit osseuserendait le dplacement dentaire plus facile et plus rapide [3]. Les mouvements dentaires facilits seraient donc dus la dimi-nution de la densit osseuse et au turnover cellulaire augment.Ceci explique que les forces optimales appliquer aux dentsaprs lintervention aient beaucoup diminu avec la comprhen-sion des mcanismes mis en jeu lors dune corticotomie. Engnral, les premires publications rapportent lutilisation de for-ces relativement lourdes, car les auteurs se rattachent au conceptde dplacement de blocs osseux [28-30]. Les tudes plus rcen-tes utilisent des forces plus lgres avec autant de succs, carelles sappuient sur des donnes plus physiologiques du dplace-ment dentaire.

Caractristiques histologiques du dplacement dentaire aprs corticotomie

La physiologie du dplacement dentaire a t dcrite par Reitan[37]. La premire phase du dplacement est un mouvementimmdiat caus par la compression du ligament par dformationlastique. La deuxime phase correspond la hyalinisation dudesmodonte. La pression exerce dans certaines localisations duligament provoque des zones vitrifies et acellulaires. Les osto-clastes ne peuvent plus arriver sur le site pour rsorber losalvolaire, le mouvement dentaire est alors interrompu. Cettetape apparat vers 24-48 heures, et peut durer deux semaines. Ilest souhaitable de raccourcir cette priode darrt du dplace-ment, en allgeant les forces par exemple, afin que le mouvementdentaire se fasse avec le plus defficacit. La hyalinisation pr-cde les ventuelles rsorptions radiculaires. Dans les tudeshistologiques, on constate gnralement au microscope des zonesde rsorption radiculaire au voisinage des zones de hyalinisation.Le mouvement ne peut reprendre que lors de la troisime phase,lorsque la rsorption indirecte par voie centripte a rsorb cettezone hyaline. Los alvolaire est ensuite rsorb par voie directe,et le dplacement reprend de faon continue.Une tude animale sur les corticotomies, mene chez le chien,a rcemment t publie afin de mettre en vidence les cons-quences histologiques de cette technique [35]. Lexprience estmene la mandibule, o la msialisation de troisimes pr-molaires est compare entre un ct exprimental qui bnficie

the mere act of making an access flap triggersgreater tooth mobilityover a limited period following the procedure. Following osteotomysurgery, teeth are also easier to move. Histological observations[35, 36] have confirmed that corticotomies increase bone turnovermeasured by the number of activated osteoclasts. In controls, ittook two weeks for the cells to reach their maximum concentra-tion whereas in subjects receiving corticotomies a high level wasobtained immediately.

Decreased bone density

It has also been shown that decreased bone density makes toothdisplacement easier and faster [3]. These easier tooth movements would therefore appear to be theresult of decreased bone density and increased bone turnover. This explains why the optimal force needing to be applied afterthe procedure decreased considerably with understanding of themechanisms produced by a corticotomy. Generally speaking, theearly publications used relatively high forces as the authors werestill attached to the notion of bone block displacement [28-30].More recent studies have used lighter forces with equal successas they are based on more physiological data related to tooth dis-placement.

Histological characteristics of tooth displacement after a corticotomy

The physiology of tooth displacement was described by Reitan[37]. The first phase of displacement is a moment which occursimmediately and isgenerated by compression of the ligament withelastic deformation. The second phase coincides with the hyalin-ization of the periodontal ligament. The pressure built up in cer-tain areas of the ligament causes some zones to become vitrifiedand acellular. Osteoclasts can no longer reach the site to resorbthe alveolar bone and tooth movement comes to a halt. Thisstage occurs after 24-48 hours and can last two weeks. It isadvisable to shorten this period of interrupted displacement, byapplying lighter forces for instance, in order to promote optimumtooth movement. Hyalinization occurs prior to any root resorption.Histological studies havegenerally shown, under microscope, thepresence of patches of root resorption in the proximity of hyalin-ized areas. Movement can only resume during the third phasewhen indirect centripetal resorption has resorbed the hyalinizedarea. The alveolar bone is then resorbed directly and the continuousdisplacement resumes.

An animal study into corticotomies in dogs has recently been pub-lished and shows the histological impact of this technique [35].The experiment was conducted on the mandible in which acomparison is made between mesialization of the third premolarson the experimental corticotomized side and the non-corticotomized



de la corticotomie, et un ct tmoin qui nen bnficie pas.Les secondes prmolaires sont extraites, afin de laisser unespace pour msialer la troisime prmolaire, et un dlai de16 semaines est respect pour obtenir une cicatrisation osseusecomplte. Du ct exprimental, la troisime molaire estmsiale sous laction dun ressort NiTi de 50 grammes imm-diatement aprs la corticotomie. Du ct tmoin, la dent estdplace de la mme manire aprs la ralisation de simpleslambeaux daccs.Les rsultats montrent que le dplacement dentaire est enmoyenne deux fois plus rapide du ct exprimental que du cttmoin (fig. 3). Il est surtout intressant de noter que le dplace-ment dentaire est linaire du ct de la corticotomie tout au longdu dplacement. On ne retrouve pas larrt du dplacement den-taire caractristique de la phase de hyalinisation, qui est iciextrmement rapide et limite.Du ct exprimental, on constate lexistence de rsorptionosseuse indirecte seulement pendant une priode trs limite,tandis que la rsorption directe est demble le processusmajoritaire. On ne note microscopiquement aucun dbut dersorption radiculaire. Classiquement, du ct tmoin, onrelve la prsence de rsorption indirecte et de hyalinisationdu desmodonte de la premire la quatrime semaine, pourlaisser la place de la rsorption directe par la suite. Des pla-ges de rsorption radiculaire sont retrouves sur les observa-tions microscopiques de coupes histologiques la quatrime et la huitime semaine.Les corticotomies semblent donc tre une bonne technique pourlimiter les risques de rsorption radiculaire, et pour obtenir desdplacements dentaires acclrs plus physiologiques.Selon nous, les botiers autoligaturants passifs trouvent ici unintrt particulier. Les techniques orthodontiques permettant dedlivrer de faibles niveaux de forces et les corticotomies relventdun objectif commun, qui est un dplacement dentaire plus phy-siologique et plus rapide. Les deux techniques ne sopposent pas,mais sont selon nous complmentaires.

Fig. 3 : Vitesse du dplacement dentaire avec et sans corticotomie.Fig. 3: Rate of tooth displacement with and without corticotomy.

control side. The second premolars were extracted in order toleave space for third premolar mesialization. A period of16 weeks was allowed to ensure complete bone healing. On theexperimental side, the third molar was mesialized using a 50gNiTi spring placed immediately after the corticotomy. On thecontrol side, the tooth was displaced in a similar manner aftersimply lifting access flaps.

The results showed that the mean rate of tooth displacement wastwice as rapid on the experimental side as on the control side(fig. 3). Above all, it is interesting to note that tooth displacementwas linear on the corticotomy side throughout the movement.Investigators observed none of the interrupted tooth displace-ment characteristic of the hyalinization phase, which in this casewas extremely rapid and limited. On the experimental side, they observed indirect boneresorption for a short period only whereas direct resorptionwas immediately seen to be the main process. Microscopicobservation showed no incipient root resorption. Classically,on the control side, one observes the presence of indirectresorption and hyalinization of the periodontal ligamentbetween the first and fourth week, followed thereafter bydirect resorption. Areas of root resorption were found undermicroscopic observation on histological sections at the fourthand eighth week.

Corticotomies would therefore appear to offer agood techniquefor limiting the risks of root resorption and for achieving morephysiological accelerated tooth displacements. In our opinion, passive self-ligating brackets are of particularinterest in this context. The orthodontic techniques delivering lowforce levels and corticotomies share a common objective, whichis to ensure faster and more physiological tooth movement. Thetwo techniques are complementary rather than opposed.



Stabilit des traitements

Il est encore trop tt pour juger si les corticotomies permettent detraiter les cas avec moins de rcidive. Lpaisseur dos corticalserait un des lments influant sur les taux de rcidive. Les tra-vaux de Rothe montrent que les patients prsentant un os corticalfin sont davantage sujets la rcidive [38]. Limpact des cortico-tomies sur lpaisseur dos cortical nest pas encore montr. SelonSebaoun, ce serait la greffe dos bovin associe dans son proto-cole de corticotomie qui permettrait une augmentation dpais-seur de corticale osseuse. Cependant, des travaux mens sur leporc (J.-B. Charrier, M. Steve, rsultats non publis), ainsi queplusieurs tudes laissent penser au potentiel ostognique descorticotomies [39-41]. Selon nous, il est possible que la techni-que des corticotomies en elle-mme suffise induire cette rac-tion dostogense et donc favorise la stabilit du traitement.

Applications cliniques

Intrusion de molaires gresses

Lingression est probablement le mouvement dentaire le plus dif-ficile obtenir. On ne peut pas corriger une gression molaire defaon satisfaisante avec un appareil multiattache seul, puisqueleffet principal est davantage une gression des dents dappuiquune intrusion des dents dplacer.Plusieurs tudes prsentent le cas de patients adultes prsentantune dentation dans un secteur mandibulaire [29, 42]. Lgres-sion des premires et deuximes molaires antagonistes empchetoute reconstruction prothtique. Une corticotomie sous anesth-sie locale concernant les molaires maxillaires ingresser estalors ralise. Les traits passent en msial de la premiremolaire, et 3 mm au-dessus des apex des premires et deuximesmolaires. Une miniplaque en vestibulaire, et deux mini-implantsen palatin constituent le moyen dancrage. Une intrusion denvi-ron 3 mm au moyen de tractions lastiques de 100 150 gram-mes par ct est obtenue en deux mois de traitement, sansgression des dents voisines, ce qui permet de raliser la recons-truction prothtique. Cette intrusion semble stable onze moisaprs lintervention.Une autre tude sest intresse lingression des secteurs post-rieurs, cette fois comme alternative la chirurgie orthognathiquepour traiter une bance antrieure et latrale [43]. Dans les casde bance svre, le traitement classique consiste en une chirur-gie bimaxillaire, avec rotation antihoraire de la mandibule, et uneimpaction maxillaire postrieure.Dans ce cas, le traitement consiste en une impaction importantedes secteurs postrieurs maxillaires laide de corticotomies etde miniplaques et de minivis. Ce mouvement ne serait pas possi-ble dans de telles proportions dans un traitement orthodontiqueclassique. La corticotomie des secteurs postrieurs maxillairesest ralise en deux temps (vestibulaire puis palatin) sous anes-thsie locale. Les miniplaques et les minivis sont poses au coursde lintervention. Le rsultat obtenu est une ingression des sec-

Treatment stability

It is still too early to say whether fewer relapses can be achievedusing corticotomy treatment. The thickness of the cortical plate isthought to be one of the factors most strongly affecting relapserate. Studies by Rothe have shown that patients with thin corticalbone are more inclined to relapse [38]. The impact of corticoto-mies on the thickness of cortical bone has not yet been estab-lished. In Sebaouns view, it is the bovine bonegraft associatedwith his corticotomy protocol which promotesgreater cortical bonethickness. However, work conducted on pigs (J.-B. Charrier,M. Steve, unpublished results) as well as several other studiespoint to the osteogenic potential of corticotomies [39-41]. In ourview, the corticotomy technique alone may suffice to produce thisosteogenic response and thus promote treatment stability.

Clinical applications

Intrusion of extruded molars

Intrusion is probably the most difficult tooth movement to achieve.Molar over-eruption cannot be adequately corrected with a multi-attachment appliance alone since the main effect produced isextrusion of the adjacent teeth rather than intrusion of the teeth tobe moved. Several studies have presented cases showing adult patientswith edentulousness in a segment of the mandible [29, 42]. Over-eruption of the antagonist first and second molars ruled outprosthodontic reconstruction. Corticotomy under local anestheticinvolving the maxillary molars requiring intrusion was then per-formed. The bone-cuts were made mesial to the first molar and3mm above the apices of the first and second molars. A buccalmini-plate and two palatal mini-implants were used for anchor-age. A 3mm intrusion was then obtained over two months using100 to 150g of elastic traction on both sides, without extruding theneighboring teeth, thus permitting prosthodontic treatment to beperformed. The intrusion had a stable appearance 11 monthsafter the procedure.

Another study investigated intrusion in the posterior segments,this time as an alternative to orthognathic surgery in order to treatanterior and lateral open bite [43]. In cases of severe open bite,conventional treatment consists of bimaxillary surgery with anti-clockwise mandibular rotation and posterior maxillary impaction.

In such cases, treatment involves a major impaction of theposterior maxillary segments by means of corticotomies, mini-plates and miniscrews. Such a degree of movement would beunobtainable using conventional orthodontic treatment. Cortic-otomy of the posterior maxillary segments is performed in twosteps, buccal then palatal, with local anesthetic. The mini-plates and miniscrews are placed during the procedure. Theachieved outcome is 7mm of intrusion of the posterior seg-



teurs postrieurs de 7 millimtres en un mois de traction, ce quiprovoque la fermeture de la bance.

Correction orthopdique dune Classe III

Lquipe de Pelo rapporte le cas de deux patients adolescents de15 et 16 ans, prsentant une Classe III par brachygnathie maxil-laire [44]. Chez ces patients, lge est trop avanc pour esprerune correction orthopdique, et la fois trop jeune pour raliserune chirurgie orthognathique. Des corticotomies dont les traitssuivent ceux dune intervention de type Le Fort I est ralise aumaxillaire. Les patients portent ensuite un masque de Delaire24 heures sur 24 pendant deux semaines, puis la nuit seulement,et obtiennent une correction de la Classe III, qui semble stablecinq ans aprs. Un des deux patients prsente en plus une endo-gnathie. La corticotomie maxillaire est alors associe un traitdostotomie palatin parasagittal. Une disjonction maxillaire estensuite ralise avec succs.Lintrt de cette technique est dobtenir des corrections ortho-pdiques chez des patients ayant achev leur croissance.

Acclration de la mise en place dune canine incluse en position palatine

Lquipe de Fischer a tudi lintrt des corticotomies chez sixpatients prsentant des canines incluses bilatrales en positionpalatine [45]. Pour chaque patient, lexposition chirurgicale desdeux couronnes est ralise dans la mme sance. Dun ct, leprotocole standard est utilis, de lautre, une corticotomie estajoute : une srie de perforations limites la corticale, espa-ces de 2 mm, et entourant la position de la couronne de lacanine tracter est effectue. La traction commence simultan-ment pour les deux dents, sans que lorthodontiste sache quel estle ct qui a bnfici de la corticotomie. Les canines ayantbnfici de la corticotomie sont mises en place environ 30 %plus vite que celles du ct tmoin. La vitesse moyenne dvolu-tion de la canine ct tmoin est de 0,75 mm/mois, et la vitessede la canine ayant bnfici des corticotomies est de 1,06 mm/moisenviron. Les auteurs estiment que la diminution de la masse osseusecontribue acclrer le dplacement, mais cest plus probable-ment la diminution de la densit de los mdullaire provoquepar la corticotomie que la diminution de la masse dos cortical enelle-mme qui est responsable de lacclration du dplacement.Dautres techniques visant diminuer la masse osseuse ont djt envisages pour mettre en place les canines plus rapidement.Mais elles se traduisent en fin de traitement par une perte dosimportante, ce qui nest pas le cas pour la corticotomie.

Rtraction incisive

Lquipe de Germe [46] rapporte le cas dune patiente adultetraite pour une Classe III avec encombrement par lextraction dequatre prmolaires. La patiente doit retourner dans son paysdorigine lors du recul incisif, et une corticotomie lui est propose

ments within one month of traction, thus ensuring closure ofthe open bite.

Orthopedic correction of a Class III

Pelos team reported the case of two teenage patients of 15 and16 who presented a Class III due to maxillary brachygnathia [44].These two patients were already too old to benefit from orthope-dic correction and yet too young to undergo orthognathic surgery.Corticotomies using bone-cuts that followed the lines used in aLe Fort 1 type procedure were performed on the maxilla. Thepatients then wore a Delaire mask 24 hours a day for two weeks,then only at night, and achieved a Class III correction whichappears to be stable 5 years post-treatment. In addition, one ofthe patients also presented an endognathy. Maxillary corticotomywas then combined with a parasagittal palatal osteotomy incision.Following this, maxillary disjunction was successfully performed.

The advantage of this technique is that it allows orthopedic cor-rection on patients who have completed theirgrowth.

Accelerated placement of a palatally impacted canine

Fischers team investigated the benefits of corticotomies in sixpatients presenting bilateral palatally impacted canines [45]. Ineach patient, the two crowns were surgically exposed during asingle session. On one side, the standard protocol was used. Onthe other, a corticotomy was also performed involving a series ofperforations spaced 2mm apart restricted to the cortical bone andsurrounding the crown of the canine to be moved. Tractioncommenced simultaneously on the two teeth with the orthodontistunaware of the side on which the corticotomy had been per-formed. The corticotomized canines moved into place roughly30% more quickly than the control teeth. The mean velocity of thecanines on the control side was 0.75mm/month versus approxi-mately 1.06mm/month for the corticotomized canines.

The authors consider that reduction of bone mass helps acceler-ate tooth displacement but that the decrease in density of themedullary bone triggered by the corticotomy is probably moreresponsible than the reduction of the cortical bone mass for theaccelerated displacement.Other techniques designed to reduce bone mass have alreadybeen studied to enable quicker canine repositioning. However,they result, post-treatment, in a major loss of bone, which is notthe case for corticotomy.

Incisor retraction

Germecs team [46] reported the case of an adult patient treatedby extraction of the four premolars for a Class III with crowding.The patient had to return to his country of origin during incisorretraction and was offered a corticotomy to speed up the process.



pour acclrer le traitement. Dans ce cas, le protocole est allgpuisque lquipe ne ralise quun abord vestibulaire, et ralisedes corticotomies traversant la totalit de los spongieux et attei-gnant la corticale linguale. Le trait de corticotomie horizontalsous les apex nest ici pas ralis. Le rsultat est moins spectacu-laire puisque les corticotomies ont t pratiques au milieu durecul incisif. La fin du recul obtenu aprs corticotomie a t obte-nue en un mois et demi, portant la dure du traitement seize mois.

Distalisation des premires molaires maxillaires

Une tude rapporte le traitement dune patiente adulte chez quile traitement de la Classe II dentaire est envisag par recul despremires molaires maxillaires, puis des secteurs antrieurs etlatraux par traction intermaxillaire [47]. Des corticotomies sontralises au niveau des premires molaires maxillaires poureffectuer une distalisation plus facile. Les dents antrieures quinont pas reu de corticotomie sont plus difficiles mobiliser etconstituent donc un ancrage plus important par rapport auxmolaires qui ont bnfici dune corticotomie. Huit semainesaprs les corticotomies et le dbut de la distalisation, un reculdenviron 3 mm peut tre constat cliniquement et sur les super-positions. Cependant, les auteurs constatent un retour la posi-tion dorigine de la premire molaire en fin de traitement, ce quiest plutt d la technique employe quaux corticotomies qui,dans ce cas, ont produit les rsultats escompts.

Traitement des dysharmonies dento-maxillaires

Plusieurs tudes ont dmontr lintrt des corticotomies pouracclrer les tapes dalignement-nivellement dans les casdencombrement modr important. Les auteurs utilisent dansce cas des corticotomies tendues toute larcade, de prmolaire prmolaire [25, 48]. Lextension des dcortications jusquauxprmolaires est prconise mme si la dysharmonie ne concerneque la zone antrieure, car cela permet dobtenir un certain degrdexpansion latrale.

Conclusion

De nombreuses tudes ont montr que les corticotomies avaientune place dans notre arsenal thrapeutique pour acclrer lestraitements dorthodontie de ladulte, et pour augmenter lenve-loppe des mouvements dentaires possibles. En modifiant lemtabolisme local, les corticotomies permettent une diminu-tion de la dure de hyalinisation, et donc un dplacement den-taire continu, ainsi quune diminution des risques de rsorptionradiculaire. Lacclration du turnover osseux a peut-tre aussidautres implications qui nont pas encore t mises en videnceaujourdhui. Dautres tudes sont ncessaires, pour prciser les indications decette technique, gagner en recul, et tenter de rpondre la ques-tion de la meilleure stabilit des traitements orthodontiques ra-liss en association des corticotomies.

In this instance, the protocol was slimmed down as the team onlyperformed the procedure from the buccal side making bone cutsthrough the entire cancellous bone to reach the lingual corticalplate. Horizontal bone-cuts beneath the apices were not made inthis case. The result was less spectacular as the corticotomieswere made in the course of the incisor retraction process. Retrac-tion after corticotomy was completed in a month and a half bring-ing total treatment time to 16 months.

Distalization of the maxillary first molars

A study by Spena et al. reported the case of a female adultpatient for whom it was planned to treat her dental Class II byretracting her maxillary first molars and then by retracting heranterior and lateral segments using inter-maxillary traction [47].Corticotomies were performed at the maxillary first molars inorder to facilitate distilization. The non- corticotomized anteriorteeth were less mobile and therefore providedgreater anchorageas opposed to the molars which had been corticotomized. Eightweeks after corticotomization and the onset of distalization,roughly 3mm of retraction could be observed clinically and onsuperimpositions. However, the authors remarked that the firstmolars returned to their original position at the end of treatmentprobably on account of the technique used rather than the cortic-otomies which, in this case, produced the anticipated results.

Treatment of dentomaxillary disharmonies

Several studies have demonstrated the benefits of corticotomiesfor accelerating alignment and levelling in cases of moderate tosevere crowding. In this case, the authors applied corticotomiesto the entire arch, premolar to premolar [25, 48]. It is recom-mended to extend the decortications as far as the premolars evenif the disharmony only affects the anterior segment as this willachieve some degree of lateral expansion.

Conclusion

Numerous studies have shown that corticotomies have theirplace in our armamentarium in order to accelerate adult orthodon-tic treatment and to increase the range of possible tooth move-ments. By modifying the local metabolism, corticotomies reducehyalinization time and thus promote uninterrupted tooth displace-ment as well as a lower risk of root resorption. Speeding up boneturnover possibly offers other advantages which have not yetbeen highlighted. Further research is needed to define more pre-cisely the indications of this technique, to provide further hind-sight, and to provide a solution to the problem of how to obtainoptimum stability for orthodontic treatments conducted in combi-nation with corticotomies.



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Alveolar corticotomies