Aob correct by le fort i or bssoDocument Transcript
Oral Maxillofacial Surg Clin N Am 19 (2007) 321–338 Anterior Open Bite Correction by Le Fort I or Bilateral Sagittal Split Osteotomy Johan P. Reyneke, BChD, MChD, FCMFOS (SA), PhDa,b,*, Carlo Ferretti, BDS, MDent (MFOS), FCD (SA) MFOSa,c a Department of Maxillofacial and Oral Surgery, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa b Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Oklahoma, Oklahoma City, OK, USA c Department of Maxillofacial and Oral Surgery, Chris Hani Baragwanath Hospital, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa Some of the most challenging dentofacial de- causative mechanisms, and the question remainsformities facing surgeons and orthodontists are incompletely answered.anterior open bite malocclusions. Determining the Nonnutritive sucking is a normal developmen-cause of an anterior open bite and formulating tal phenomenon whose frequency decreases witha diagnosis are complicated by the role of age. Persistence of the habit beyond the age of 6neuromuscular and genetic inﬂuences. Long-term years is strongly associated with open bite maloc-skeletal and dental stability are a concern because clusion . Complicating the issue is the fact thatof the inﬂuence that the neuromusculature has on there is a wide racial variation in the incidence ofthe repositioned jaws and stability of teeth after anterior open bite, which suggests a modulating ef-vertical orthodontic mechanics required for clos- fect of genetic control of skeletal proportions [2,3].ing open bites. Nasopharyngeal and oropharyngeal obstruction as a result of one of several possible conditions, such as allergic rhinitis, enlarged adenoids, and enlargedEtiology tonsils, has been associated with development of Mechanistic insights on the development of the anterior open bite deformity .anterior open bite malocclusion remain subject to It is proposed that obstruction to normal nasaldebate and discussion. Patently, two philosophies breathing triggers an adaptive neuromuscularmay concur with research ﬁndings: the morpho- response that results in open rotation of thegenetic theory and the adaptive theory. The mandible, inferior and anterior repositioning ofanterior open bite may be the result of aberrant the tongue, and extended head posture giving risegenetic control of morphology via growth pat- to the classical ‘‘adenoidal facies.’’ There areterns, or a malformation secondary to functional several implications of these functional adapta-aberrations of the naso-oropharyngeal apparatus. tions to nasal breathing. First, a change in theIt has proven diﬃcult to separate these two direction of mandibular growth from horizontal to vertical results in increased lower facial height. Second, inferior and anterior repositioning of the tongue has several dental eﬀects, including * Corresponding author. Centre for Orthognathic narrowing of the maxillary dental arch causedSurgery and Implantology, Sunninghill Hospital, PO by the unopposed action of the buccinator muscle,BOX 5386, Rivonia, South Africa. retroclination of the upper incisors caused by E-mail address: email@example.com (J.P. Reyneke). the unopposed actions of orbicularis oris, and1042-3699/07/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved.doi:10.1016/j.coms.2007.04.004 oralmaxsurgery.theclinics.com
322 REYNEKE & FERRETTIproclination of the lower incisors caused by open bite. Because vertical problems (in particularincreased tongue pressure. The case for this in patients with anterior open bite) can result frommechanism has been strengthened by the ﬁnding habits, environmental inﬂuences, or vertical skel-that early removal of the obstruction and return etal growth problems, the diagnosis has twoto nasal breathing often results in normalization important components: the speciﬁc anatomicof anterior height. Finally, chronic mouth breath- location of the discrepancy (eg, maxilla, mandible,ing can cause alterations in head posture, most or both) and identiﬁcation of a cause. In youngcommonly extension or upward rotation of the growing individuals, the major cause of anteriorhead, in an attempt to improve oropharyngeal open bite is sucking habits and environmentalpatency. This altered posture has been associated inﬂuences. The open bite as a result of thumbwith several disturbances in craniofacial morphol- sucking is usually limited to the anterior region,ogy, including increased lower facial height, with a narrow palate, often posterior cross bites,mandibular and maxillary retrognathism, and and relatively normal facial proportions. Thesteep mandibular plane. most important step in the treatment is to stop Increased vertical development of the maxilla the habit. For this purpose a removable appliancealso has been associated with several muscle with a crib is used. The sucking habit stopsweakness syndromes. Weakness of the mandibu- immediately in approximately 50% of patientslar elevators and decreased biting force allow the and the open bite starts to close rapidly. In theposterior teeth to overerupt and the mandible to remaining children the thumb sucking may persistrotate downward. It has been reported that the for a few weeks; however, the device is usuallybiting forces of patients with long faces are below eﬀective in 85% to 90% of cases . At this stage,normal, although the bite force of preadolescent orthodontic correction of the cross bites solves thepatients with long face characteristics is normal transverse and anterior open bites. The long-term[5,6]. The role of decreased bite force as an etio- prognosis depends on the growth pattern, how-logic factor in the development of vertical maxil- ever, and a poor response to treatment suggestslary excess and anterior open bite is not clear, persistent excessive vertical growth. These patientshowever. most probably develop vertical maxillary excess In the past, tongue thrust or abnormal tongue and an anterior open bite malocclusion.activity during speech has been blamed for the Not all children who are thumb suckers de-development of anterior open bite malocclusion velop anterior open bites. In children with chronicand poor stability after treatment. Various at- mouth breathing, one, or all, of three neuromus-tempts to change patients’ swallowing patterns, cular responses must be present for an anteriorsuch as speech therapy and removable appliance open bite malocclusion and altered skeletal re-with a crib, have been used to control anterior sponse to develop: (1) altered mandibular posture,open bite problems. Contemporary research has (2) altered tongue posture, (3) extended headshown, however, that tongue thrust swallow is posture . Several studies have shown that ana physiologic adaptation to an anterior open bite obstructed upper airwaydassociated with alteredrather than the cause of it. An abnormally large mandibular posturedis related to increased lowertongue or true macroglossia should ﬁrst be facial height [8,9]. Removal of the cause of the na-diﬀerentiated from pseudomacroglossia and only sopharyngeal obstruction (eg, enlarged adenoidsthen considered as an etiologic factor in the or tonsils, allergic rhinitis) has been reported todevelopment of an anterior open bite. A large decrease the open bite . Upper airway obstruc-tongue also may be the cause of poor stability tion may be one factor in the multifactorial etio-after treatment . logic complex that inﬂuences the dentition and It seems that an anterior open bite is pre- morphogenetic facial pattern.dominantly the result of alterations in mandibular In young individuals in whom vertical growthgrowth patterns, and more attention is required persists and in patients who have reached adoles-for treatment philosophies that address this fact. cence, environmental causes for anterior open bite become less important than skeletal factors. Skel- etal anterior open bite malocclusion in adults is basically a vertical dentofacial problem caused byDiagnosis excessive vertical development of the maxilla, As with the diagnosis of all malocclusion, it is shortening of the mandibular ramus, or a combina-important to identify the cause of the anterior tion of both. It is important to distinguish between
ANTERIOR OPEN BITE CORRECTION 323Fig. 1. An anterior open bite (A) in an 8-year-old patient was treated by orthodontic expansion of the maxillary dental archcombined with habit control (thumb sucking) (B). The arrow indicates the ‘‘gate’’ incorporated into a removable appliance.A stable posttreatment result was achieved (C). (Courtesy of T. McCollum, BDS, MDent, Johannesburg, South Africa.)the two skeletal deformities because it ultimately headgear and class III elastics , titanium screwdetermines the surgical treatment plan. anchorage , a rapid molar intruder appliance , reverse headgear combined with class IIITreatment of growing individuals Box 1. Clinical, dental, and Anterior open bites in children with mixed cephalometric ﬁndings of patientsdentition and good facial proportions are usually with anterior open bite deformitycaused by prolonged thumb sucking (beyond theage of 6 years) or other environmental inﬂuences, Aesthetic featuresand the most important corrective measure in Lower third of the face almost alwaysthese patients is cessation of the habit. Posterior elongatedcross bites are usually the result of narrowing of Excessive incisor exposure under thethe maxilla. Removable and ﬁxed appliances can upper lipbe eﬀective in the correction. Maxillary dental Increased interlabial gapexpansion not only corrects the cross bites but Gummy smilealso assists in closing the anterior open bite and Obtuse nasolabial angleshould be combined with habit control (Fig. 1). Retrusive chinBy the time adolescence is reached, environmental Dental characteristicscauses become less important. Skeletal factors Open bites may be associated with allshould be considered after poor response to habit types of malocclusion; however,control and maxillary expansion . relative or absolute mandibular deﬁciency and class II malocclusion are most commonTreatment of nongrowing individuals Tendency for the maxillary arch to be V-shaped and the mandibular arch toOrthodontic correction of anterior open bite be U-shaped Posterior cross bites The treatment of patients with anterior open Flat or reverse mandibular occlusal planebite by means of orthodontic treatment alone curveusually focuses on three areas: (1) extrusion of Stepped maxillary occlusal planeupper and lower incisor teeth, (2) intrusion ofmolar teeth, and (3) expansion of the maxillary Cephalometric featuresdental arch. This orthodontic treatment requires Increased anterior facial heightalmost exclusively the use of vertical mechanics. Steep mandibular and occlusal planeExtrusion of incisor teeth can be accomplished in anglethree ways: (1) the use of anterior elastics, (2) Normal mandibular ramus heightusing a continuous arch wire from molar to molar Saddle cranial baseto level an excessive occlusal curve in the maxil- Increased distance from tooth apices tolary arch, and (3) leveling a reverse curve of Spee the nasal ﬂoorin the lower arch in the same manner. The Palatal plane is tipped up anteriorly andmechanics to intrude the molars include intrusion down posteriorlyof molars with miniplate anchorage , high-pull
324 REYNEKE & FERRETTIFig. 2. This 17-year-old patient developed an anterior open bite as a result of excessive vertical growth of her maxilla.The mandible rotated clockwise, which resulted in a class II anterior open bite malocclusion (A–F). The maxillary dentalarch was aligned in two segments (11 to 17 and 21 to 27) (G–L). The open bite was surgically corrected by superiorrepositioning of the maxilla (more in the posterior area than anterior) and expanded, which allowed the mandible toautorotate (O). A balanced aesthetic result and functional occlusion were achieved (M–R).and anterior box elastics , zygomatic anchor- Most of the reports in the literature regardingage , and bite blocks with repelling magnets orthodontic correction of skeletal anterior open. Expansion of the maxillary posterior teeth bite are case reports that discuss speciﬁc ortho-in adult individuals with skeletal transverse dontic techniques or introduce new orthodonticdeﬁciency usually results in dental tipping and mechanics. There is, however, a paucity of studiesquestionable stability [18,19]. regarding results after orthodontic correction of
ANTERIOR OPEN BITE CORRECTION 325 Fig. 2 (continued)anterior open bite malocclusions to draw any problems have questionable long-term stabilityevidence-based conclusions [20–22]. Few studies and may build relapse into the surgical result. Thehave reported on the pretreatment aesthetic con- basic goal of presurgical orthodontic treatmentsiderations and facial aesthetic outcomes. Regard- should be to align the maxillary teeth (either inless of the speciﬁc mechanism used to achieve the segments or in one piece) and avoid any mechanicstooth movements, stability is unpredictable and in that are intended to close the bite. Segmentalmany cases results in compromised aesthetics surgery is indicated when the maxillary dental[23,24]. In cases in which the anterior open bite arch has a tendency to natural segments or to levelis associated with increased incisor angulation the occlusal curves surgically. This does not mean(as may be found in cases with bimaxillary that individual teeth within a segment should not beprotrusion), correction of the incisor angulation leveled; intrusion of the incisors or maintainingby tipping the incisors has a relative extrusion their pretreatment height is recommended. Open-eﬀect, thus closing the bite. ing the bite before surgery improves stability because relapse of incisor intrusion serves to furtherCombined orthodontic and surgical treatment close the bite after surgery. Orthodontic alignmentAnterior open bite secondary to vertical maxillary of the maxilla in segments can be done with orexcess: Le Fort I maxillary osteotomy with or without extractions. The need for extractions inwithout mandibular surgery these cases is dictated by the amount of crowding The common but variable clinical, dental, and and the dental movements necessary to place thecephalometric ﬁndings of patients with skeletal upper and lower incisors in their desired angulationanterior open bite deformity as a result of vertical and in the central trough of bone. Keep in mind thatmaxillary excess are as shown in Box 1 (Fig. 2): the angulation of the incisor and posterior teeth can be altered with segmental surgery. In cases in whichPresurgical orthodontic treatment segmental surgery is contemplated, care should be Presurgical orthodontic mechanics should not taken to coordinate the arch form of the maxillarybe directed toward correcting vertical, transverse, segments with the mandibular arch and deviate theor anteroposterior skeletal problems. Orthodontic roots of the teeth adjacent to the intended in-tooth movements for the correction of these terdental osteotomy sites.
326 REYNEKE & FERRETTI
ANTERIOR OPEN BITE CORRECTION 327 Although the mandible may require surgical (3) the need for surgical correction of a transverseadvancement or setback, the lower dental arch discrepancy.serves as the ‘‘template’’ and ultimately dictates The amount of superior repositioning of the max-the symmetry and form of the upper arch. The illa. The amount of superior repositioning of thepresurgical orthodontic treatment goals are to anterior and posterior maxilla is inﬂuenced by twoplace the lower dentition symmetrically in the aspects: (1) The planned ideal maxillary incisor/ideal anteroposterior, vertical, and transverse upper lip relationship determines the amount ofpositions in relation to its supporting bone. In vertical and anteroposterior repositioning of theindividuals with a severe reverse curve of Spee in anterior maxilla. In most cases the incisor teeththe lower arch, consideration should be given to require superior repositioning. In some cases,surgically leveling the mandibular arch by means however, the incisor height may need to beof segmental mandibular surgery. maintained, whereas in other cases the anterior Orthodontic mechanics expressly intended to maxilla may have to be inferiorly repositioned.close the bite should be avoided during the The ﬁnal anteroposterior and vertical positions ofpresurgical orthodontic phase. Bite blocks with the maxillary incisor are the key to treatmentrepelling magnets, high-pull headgear, miniplate planning [25,26]. (2) The ﬁnal occlusal plane isanchorage for molar intrusion, vertical elastics, determined by the mandibular occlusal plane aftermolar expansion beyond its alveolar bone base, or autorotation of the mandible. The amount ofany other device used to close the bite are superior repositioning of the posterior maxilla isinadvisable. Previous attempts to close a skeletal determined by the height of the mandibularanterior open bite orthodontically without con- posterior teeth after autorotation.sidering surgical correction will leave the clinicianwith a dilemma. After orthodontic attempts to The position of the mandible after autorotation.close the bite, pretreatment orthodontic records The anteroposterior position of the lower incisormust be compared with current records to evalu- after autorotation determines whether mandibularate the potential for dental relapse. It is recom- surgery is indicated. Individuals with a class Imended to discontinue all vertical mechanics and molar relation, combined with vertical maxillaryallow vertical relapse by placing light sectional excess and an anterior open bite malocclusion,arch wires to maintain alignment and rotations. end with a class III dental relationship afterOnce no further vertical opening of the bite maxillary superior repositioning. Based on theoccurs, the patient can be re-evaluated for appro- aesthetic requirements of the case, the clinicianpriate surgery and orthodontics. must decide whether the class III dental relation- ship should be corrected by advancement of the maxilla (Fig. 3) or mandibular setback (Fig. 4). The mandible of an individual with verticalSurgery maxillary excess and a class II occlusion rotates The anterior open bite in this group of patients to a class I relation after superior repositioningis caused by excessive vertical growth of the of the maxilla and may not require mandibularmaxilla. The vertical deformity often occurs in surgery. Patients with class III anterior open biteconjunction with either a primary or secondary and vertical maxillary excess end with a class IIIsagittal deformity. During treatment planning occlusion of increased severity after verticalthree factors should be considered: (1) the amount correction of the maxilla and anterior rotationof superior repositioning of the maxilla, (2) the of the mandible. These cases most probably needposition of the mandible after autorotation, and a mandibular setback procedure in conjunction:Fig. 3. The typical clinical signs of vertical maxillary excess (ie, increased lower facial height, the appearance ofmandibular deﬁciency, and convex proﬁle caused by the backward rotation of the mandible). A gummy smile and anincreased interlabial gap are well demonstrated in this 19-year-old patient (A–D). He had a class I open bite malocclusionand a tendency to bilateral posterior cross bites (E). The upper dental arch was orthodontically aligned in one segmentand the lower arch leveled (F). The surgical treatment plan consisted of a three-piece Le Fort I maxillary osteotomy withsuperior repositioning and expansion of the maxilla. The mandible autorotated into a class III dental relation. The facialaesthetics required maxillary advancement rather than mandibular setback. For optimization of facial aesthetics, thechin was advanced by means of a genioplasty (G,H). The posttreatment results (I–M).
328 REYNEKE & FERRETTIFig. 4. This 22-year-old male patient presented with an increased lower facial height, mandibular prognathism and asym-metry to the left, and a class III anterior open bite malocclusion (A–C). The preoperative orthodontic treatment consisted ofthe aligning the maxillary arch in three segments (the anterior segment, including the four incisor teeth), and leveling thelower dental arch (D–F). The treatment plan consisted of superior repositioning and expanding the posterior maxilla bymeans of a three-piece Le Fort I osteotomy, which allowed the mandible to autorotate and close the open bite. The classIII dental and skeletal relation, however, worsened after autorotation of the mandible, which necessitated mandibular set-back and correction of the mandibular asymmetry at the same time (G, H). The posttreatment results (I–N).with maxillary advancement (see Fig. 4). This Poor midface esthetics are usually the conse-decision is based on the aesthetic requirements quence of maxillary setback procedures (>3 mm).of each case. Individuals who have vertical maxil- A combination of maxillary superior reposition-lary excess and severe class II malocclusion and ing and setback will compromise the esthetics evenanterior open bites end with a class II occlusal re- more and should be avoided. The mandiblelationship after maxillary superior repositioning. should rather be advanced in these cases, andTo establish a class I occlusion, these cases often the maxilla superiorly repositioned and preferablyrequire additional mandibular advancement pro- slightly advanced. The slight advancement (2–3cedures (Fig. 5). mm) has the added technical advantage that the
ANTERIOR OPEN BITE CORRECTION 329 Fig. 4 (continued)posterior maxilla is moved away from the bite. The problem often stems from poor preopera-pterygoid plates, which avoids diﬃculty in re- tive diagnosis, inappropriate presurgical orthodon-moving bone posteriorly to allow for adequate tics, poor surgical management, and poorsuperior repositioning of the posterior maxilla. postsurgical orthodontic control . Initially theBecause of the disproportionate vertical excess clinician should determine whether the discrepancyof the posterior maxilla in open bite deformities, is skeletal or dental in nature and whether it is rel-it often requires more bone removal in this area ative or absolute. Only when the dental casts arethan in correction of non–open bite deformities held in their correct sagittal relationship with thewith vertical maxillary excess. In all of these canines in a class I occlusion can an absolute crosstreatment scenarios the chin contour and posi- bite be revealed. When the cross bite is obviouslytion should be evaluated to enhance the aes- skeletal in nature, compensatory dental expansion,thetic outcome. When considering a genioplasty headgear, arch wires or through-the-bite elasticsprocedure, two important aspects should be kept should be avoided. These dental changes havein mind: (1) genioplasty is not a substitute for a high potential for relapse that may only manifestmandibular surgery and (2) chin shape or long after treatment .contour is more important than chin position Presurgical orthodontic tipping of molar teeth(anteroposterior position of pogonion). that leaves the lingual cusps hanging below the occlusal plane has additional surgical problems.The need for surgical correction of a transverse Hanging palatal cusps of the molars increase thediscrepancy. An individual with an open bite amount of surgical expansion of the palate that ismalocclusion and skeletal vertical maxillary excess required. Surgical palatal expansion in these casesoften has a transverse skeletal deﬁciency of the would involve expansion of the bony base and anmaxillary arch. These cases require surgical expan- element of uprighting of the molar teeth. Thesion of the maxilla by segmental surgery. Surgical increased amount of expansion leads to increasedexpansion of the maxilla has been shown to be one potential for relapse (Fig. 6).of the most unstable orthognathic procedures, Transverse stability can be enhanced byhowever . Transverse relapse is one of the placing a bone graft in the palatal defect.most common postsurgical complications and in- Stabilization of the bone graft can be facilitatedevitably leads to recurrence of the anterior open by performing the palatal osteotomy in the
330 REYNEKE & FERRETTIFig. 5. A 16-year-old female patient with a class II anterior open bite malocclusion (A–C). Her maxilla was verticallyexcessive and mandible anteroposteriorly deﬁcient. Both dental arches were orthodontically leveled, aligned, and coor-dinated before surgery (D). After the superior repositioning of her maxilla, the bite was closed and the mandible rotatedinto a class II occlusion. Her mandible was advanced by means of a bilateral sagittal split osteotomy and her chinaugmented by means of a sliding genioplasty (E, F). The posttreatment results (G–J).mid-palate, where the bone is thickest. The loss of the graft. Performing bilateral osteoto-disadvantage is that the mucosa in this area of mies in the palate facilitates larger expansion;the palate is at its thinnest. A tear in the palatal however, grafting these areas where the bone ismucosa exposes the graft and eventually leads to thin is more diﬃcult.
ANTERIOR OPEN BITE CORRECTION 331Fig. 6. With the maxillary posterior teeth in good angulation, a 5-mm expansion of the upper dental arch creates a 5-mmbony defect in the palate (A, B). When the posterior teeth are orthodontically expanded, however, the molar teeth aretipped buccally and the palatal cusps tend to hang. The expansion of the upper arch also needs to include a rotationalmovement to ‘‘tuck’’ the buccal cusps in. A 5-mm dental expansion leads to a 10.5-mm bony defect (C, D). The use of a splint during surgery and Preoperative orthodontic treatmentmaintaining the splint in position for at least 6 In general, avoidance of presurgical bite-closingweeks after surgery allow stabilization during mechanics also applies in these cases. A transversebone healing and may enhance skeletal stability. discrepancy between the upper and lower arch mayObtaining immediate postsurgical orthodontic exist. The absolute or true transverse discrepancycontrol by placing a palatal bar or a strong arch can be measured by holding the models in thewire or both to support the palatal expansion desired class I relation. The potential cross bitesfurther enhances stability of the result. In patients should be corrected orthodontically if the discrep-who have macroglossia, reduction of the tongue ancy falls within the range of stable orthodonticat the time of orthognathic surgery should be movement. When an absolute cross bite existsconsidered. An abnormally large tongue does not because of a transverse maxillary deﬁciency thatadjust to the decreased oral volume after surgical is not the result of dental tipping, three surgicalcorrection and plays an important role in relapse. options should be considered: (1) surgically assistedA normal-sized tongue with forward posturing expansion of the maxillary dental arch , (2) nar-does adjust to the smaller volume after surgery, rowing of the mandibular arch by an osteotomyhowever. Pretreatment tongue thrust swallowing through the symphysis [31,32], and (3) two-jaw sur-disappears after correction of the anterior open gery with surgical expansion of the maxilla bybite because the physiologic necessity for tongue means of segmental surgery .thrust has been eliminated. Surgery Individuals who have anterior open bite asOpen bite secondary to short mandibular ramus a result of short mandibular rami do not have thewith a normal condyle: mandibular surgery typical facial, skeletal, and occlusal features asso- The clinical features of individuals with ciated with patients with vertical maxillary excessanterior open bites as a result of deﬁciency of and open bite. Aesthetic and functional correctionthe mandibular ramus height diﬀer from patients in these cases demands a diﬀerent surgicalwith vertical maxillary excess. Although variable, approach, and consideration should be given tothe clinical features are as shown in Box 2 (Fig. 7). correcting this type of dentofacial deformity by
332 REYNEKE & FERRETTI ramus osteotomy, two muscle groups are Box 2. Features of anterior open bite stretched: the suprahyoid muscles and the medial caused by deﬁciency in mandibular pterygoid and masseter muscle. The suprahyoid ramus height musculature is lengthened when the symphysis of the mandible is rotated superiorly and is further Aesthetic features stretched after mandibular advancement and gen- Normal incisor upper lip relations ioplasty. Although suprahyoid myotomies have Normal paranasal conﬁgurations and been used successfully in animal studies to de- alar base widths crease postsurgical relapse , human studies Sufﬁcient upper lip support and nasal tip have not supported these results . Epker advo- projections cated clinical evaluation of the patient and careful Slightly increased anterior lower facial examination of the cephalometric prediction to height determine the possible need for suprahyoid myot- Convex proﬁle and retrusive chin omies . Measurement of the potential length- Dental characteristics ening of the suprahyoid muscles is made from Class II occlusion is usually present (the the surgical treatment prediction tracing. If the dental relation should be seen in the suprahyoid muscles will lengthen more than context of the horizontal change after 30%, a suprahyoid myotomy is indicated . back and downward rotation of the The amount of suprahyoid muscle stretch would mandible as a result of the short be inﬂuenced directly by the amount of mandibu- mandibular ramus) lar rotation required to close the open bite. The Maxillary and mandibular dental arches authors believe, however, that the role of supra- exhibit normal occlusal curves hyoid muscle stretch in long-term stability needs although the occlusal planes deviate further research. Transverse dimensions of the dental When the sagittal split ramus osteotomy is arches are usually coordinated performed (as described by Trauner and Obwe- geser  and modiﬁed by Dal Pont ) and the Cephalometric features distal segment is rotated counterclockwise, the No posterior vertical maxillary excess posterior mandibular height is increased (Fig. 8). Short mandibular ramus heights, which Downward rotation of the distal segment at the may be associated with mandibular mandibular angle and lengthening of the ramus anteroposterior excess or deﬁciency stretches the pterygomandibular sling and soft tis- Mandible of an individual with class III sue envelope. Postoperative muscular force leads occlusal relation appears excessive to poor proximal segment control and causes skel- with a concave proﬁle; individuals with etal relapse . Splitting the mandibular ramus class II occlusions exhibit convex along the lower border followed by counterclock- proﬁles and retrusive chins wise rotation also stretches the medial pterygoid muscle and the stylomandibular ligament on themeans of mandibular surgery. Surgical closure of medial aspect of the mandibular ramus (Fig. 9).an anterior open bite by mandibular surgery in- When the sagittal split of the mandibularvolves counterclockwise rotation of the mandible ramus is performed according to the modiﬁedat the posterior teeth. Historically this surgical technique suggested by Epker , the mandibu-movement of the mandible has been considered to lar ramus is not lengthened during counterclock-be unstable . Reports in the literature identify wise rotation of the distal segment, and thethree main factors that may inﬂuence the stability pterygomandibular sling is not stretchedafter orthognathic surgical procedures: (1) stretch- (Fig. 10) if the mandible is advanced.ing of soft tissue, (2) neuromuscular adaptation,and (3) alteration of the muscle orientation . Neuromuscular adaptation. The postoperativeThese factors are particularly important when clos- adaptation of the neuromusculature after mosting an open bite by counterclockwise rotation of orthognathic procedures is good. Backward rota-the mandible. tion of the ramus (proximal segment) may stretch the medial pterygoid muscle and stylomandibularStretching of soft tissue. If the mandible is rotated ligament attached at the medial side of the ramus,counterclockwise by means of a bilateral sagittal however (see Figs. 9 and 10). The muscle and
ANTERIOR OPEN BITE CORRECTION 333Fig. 7. This 20-year-old patient had a severe class II anterior open bite as a result of a short mandibular ramus. Thetypical soft tissue, skeletal, and dental characteristics of patients who have open bite and short mandibular rami areexhibited (A–D). The presurgical orthodontic treatment consisted of retraction of the upper and lower incisor teeth, leveland alignment, and coordination of both dental arches (E). A functional occlusion was established by mandibularadvancement, and an aesthetic chin contour was achieved by advancement and slight downgraft of the chin by a genio-plasty (H). The posttreatment results 3 years after debanding (F–I).
334 REYNEKE & FERRETTIFig. 8. The medial side of the mandible demonstrates the sagittal split osteotomy performed through the lower border ofthe body and posterior border of the ramus of the mandible (the so-called ‘‘long split’’) (A). The mandible is advanced by10 mm and rotated counterclockwise by 3.5 mm at the incisor area, which increases the ramus height by 8 mm (B).ligament attachment also interfere with posterior changes in the inclination of the mandibularrepositioning the distal segment and lead to ramus alter the orientation of the mandibularbackward and downward rotation of the proximal elevators. The three masseter muscle bundlesegment. Stripping the attachments of the medial groups and temporalis muscle with their respec-pterygoid muscle and stylomandibular ligament tive attachments and orientations are demon-from the medial side of the angle of the mandible strated in Fig. 11.during surgery is recommended. The length of the There is a paucity of studies in the literaturetemporalis muscle is also inﬂuenced by backward regarding the long-term postoperative stabilityrotation of the ramus, and control of the proximal after surgical closure of anterior open bite dento-segment is important to facilitate neuromuscular facial deformities by surgical counterclockwiseadaptation (Fig. 11). rotation of the mandible. However, skeletal stability after counterclockwise rotation of theMuscle orientation. Muscular adaptation is least mandible as part of the rotation of the maxillo-possible when muscle orientation is changed. The mandibular complex was studied and reported byFig. 9. The medial view of the mandible illustrates the attachments of the medial pterygoid muscle and stylomandibularligament and their relation to the medial aspect of the sagittal osteotomy design, which includes the lower and posteriorborder [37,38]. Counterclockwise rotation of the distal segment increases the height of the ramus and stretches the muscleand ligament (A). When the osteotomy is performed according to the Epker  modiﬁcation, the height of the ramus isnot increased and the muscle and ligament are not stretched (B). The arrow indicates the anterior border of thepterygomandibular sling.
ANTERIOR OPEN BITE CORRECTION 335Fig. 10. The medial side of the mandible illustrates the sagittal osteotomy. The horizontal osteotomy is extended justposterior to the lingula, whereas the vertical osteotomy is performed through the buccal cortex and extended throughthe inferior border to include the medial cortex. This osteotomy design results in the medial osteotomy runningfrom just posterior to the lingula downward to the lingual side of the vertical osteotomy (the so-called ‘‘short split’’)(A). The mandible is advanced by 10 mm and rotated counterclockwise by 3.5 mm at the lower incisor tip. Note thatthere is no increase in the posterior ramus height (B).Reyneke  and Chemello and colleagues, . to be comparable to other mandibular surgicalWith this surgical design, an anterior open bite procedures.is created by surgical counterclockwise rotationof the maxillary occlusal plane. The counterclock- Open bite secondary to a combination of verticalwise rotation of the maxilla is followed by the maxillary excess and short mandibular ramussurgical rotation of the mandible. Long-term Many individuals with anterior open bite maypostoperative stability in both studies was found display a combination of the clinical, dental, andFig. 11. The deep muscle group of the masseter tends to have a vertical orientation, whereas the superﬁcial massetermuscle groups have a more oblique orientation (A). The orientation of the temporalis muscle is more vertical, andany posterior rotation of the proximal segment changes the orientation and length of the muscle (B).
336 REYNEKE & FERRETTIcephalometric features of excessive vertical de- cannot be avoided, however, use of rigid ﬁxationvelopment of the maxilla and deﬁcient develop- is not recommended but rather a period of 3 to 4ment of the mandibular rami. In these cases the weeks of intermaxillary ﬁxation. Any orthodontictreatment objectives should be aimed at address- treatment, such as class III elastics, that increasesing the speciﬁc skeletal, soft tissue, and dental the loading of the condyles (and could reinitiateproblems as discussed for each of the two the condylar resorption process) should begroups. avoided. Degenerative joint disease (osteoarthrosis). Osteo-Open bite secondary to short mandibular ramus arthrosis of the temporomandibular joint is not anwith condylar resorption acute entity but rather a progressive degenerative Any process of resorption of the condyle alters disease that alters the position, morphology, andthe morphology of the condyle and its position in physiology of the bony joint structures. It involvesthe glenoid fossa. Resorption of the condyles and the progressive uncontrollable degeneration of theconsequent shortening of the mandibular rami mandibular condyle, and unfortunately, thelead to the development of a class II anterior open diagnosis and treatment selection are complicatedbite malocclusion. When considering correction of by the variability of the rate of progression ofan anterior open bite caused by resorption of the resorption. Patients experience chronic signs ofcondyle, the clinician should diﬀerentiate between joint pain, crepitus, and hypomobility with pe-idiopathic condylar resorption, degenerative joint riods of acute exacerbations. It may be possible todisease, and rheumatic arthritis with destruction obtain short-term relief of the symptoms byof the condyle. conservative partial reconstruction of the joint and orthognathic surgery; however, in mostIdiopathic condylar resorption (condylysis). Al- patients the natural progression of the degenera-though condylysis may occur in any patient tive process leads to recurrence of the open bitepopulation, it often presents in relatively young and increasing joint symptoms. Total joint re-caucasian women with high mandibular and placement combined with orthognathic correctionocclusal plane angles and develops into a class II of the dentofacial deformity is often the ﬁnalanterior open bite malocclusion. The anterior treatment solution.open bite usually develops progressively with no Treatment planning for combined orthog-pain or hypomobility. The process is usually self- nathic surgery and total joint replacement doeslimiting and may last from 6 months to 2 years. It not diﬀer from conventional orthognathic treat-is thought that the resorption may be related to ment planning. There is, however, a limitedchronic excessive loading of the mandibular amount of mandibular advancement that can becondyle, which produces progressive remodeling obtained by the placement of a joint prosthesis.of the condyle. There are two important aspects To maintain satisfactory contact between thewhen planning the correction of the existing implant and the mandibular ramus, the advance-dentofacial deformity: (1) ensuring that the re- ment should be limited to 7 to 8 mm.sorption process is inactive and (2) treating thedeformity in such a way that the loads on thecondyles are not increased. To establish whetherthe condition is still active, the patient’s previous Summarydental records, cephalometric radiographs, andocclusal models can be compared with current Development of an anterior open bite isrecords. An alternative method, such as a radio- predominantly the result of an altered growthisotope bone scan of the temporomandibular pattern that involves excessive vertical growth ofjoints, may help to detect the presence of any the maxilla, lack of vertical mandibular ramusresorptive activity in the condyle. Treatment development, or both. Successful correction ofshould be delayed until the disease becomes anterior open bite dentofacial deformities requiresquiescent. careful assessment of the speciﬁc anatomic Surgical correction should focus on the max- location of the discrepancy and an understandingilla, and mandibular advancement should be of all factors that may inﬂuence the stability ofavoided if possible. Maxillary setback, which results. The ﬂowchart (Fig. 12) summarizes themay compromise the aesthetic outcome, may suggested principles of surgical orthodontic treat-have to be considered. If mandibular surgery ment of anterior open bite dentofacial deformities.
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