Mandibular prognathism

Mandibular prognathism

1\I h S D 11~u L A R prognathism can best bc described as a noticeable prominence of the lower jaw. Although there have been worthy attempts to define this facial characteristic cephalometrically, anthropometrically, and statistically, I have: not found these descriptions as meaningful as my introductory statement. 8ichcr1” considers prognathism to br present whrn the angle formed hctw~n a lint connecting nasion and prosthion with l+ankfort horizontal is hctwcclal 70.0 and 79.9 degrees. Sanboql in an excellent cephalomctric study ol’ forty-two (“lass 111 adult patients compared to thirty-sis adult cont,rols, classifies the Class III wsw inlo four groups. The breakdown shows 15 per c*cnt>with a normal maxilla and protrusive mandible, 33 per cent with deficient maxilla and normal mandible, !) per cent, with neither maxillary nor mandibular prognathism but a slightl\ larger mandible as compared to the maxilla, and 9 per cent with a deficic~nt maxilla, and protrusive mandible. In mango of’ the prognathic patients, the genial angle was more obtuse, which would make the effective length of the> mandible greater and hcncc> more protrusive. Of grcatcr significance is the t’aet that I 11~ joint angle (S-Art-(!o) is more acute in (-‘lass III cases than in thcl norm;11 face-that is, the smilll(~r joint angle indicates t,hat, thca elntire mandil)l(~. althongll it may not be larger, is shifted f’orwarcl as related to t.hc~cranium, I bus produc*ing mandibular prognathism. Whc~n we consider the many variables described above, as well as those discltssetl l)~- B j6rk” and others, the absence of any real skeletal Class III pattern lcnds me back to my original stattmclnt Ihilt, mandihula to prognathism caan list 1W tltscrihccl as a llOtiCC%ll)l(l promiiic~iic*c~ Of the> loWc~12 ,jaw. The trcatmcnt of Class III malocclllsions in ~(~11(~1~ill. ant1 matltlih~tl;ll~ l)t~)g-

nathism in particular, is a constant challenge to the clinical orthodontist. The indications for a, combination of surgical and orthodontic techniqncs arc many ant1 varietl. Certainly, treatment, with conventional orthodontic appliances must 1)~ considered first. However, the severity of the prognathism may rule out this approach. A1 combination of certain factors-and, indeed, a marked dc~gror 01’ one of thcsc Factor-would place grave limitations on orthodontic therap!-. Those factors arc severe open-bite, extreme promincncc of the lowz~r jan-, disproportion between the size of the mandibular base and the maxillary base, and marked negative ovcrjet (that, is, mandibular incisors 2 mm. or more antt9ior to maxillary incisors, and a definite obtuse angle). The patient should bc highly mot iratrtl from an esthetic and functional point o E view. The treatment usuall> and interrequires a I to 3 hour period of anesthesia, 5 da)-s’ hospitalization, masillal~- fixation for 6 to 8 weeks, necessitating a liquid or semiliquid diet : in some instances it may result in a paresthesia of the lower lip lastng for scrvcral n~onths to a J-car or two. Therefore, a patient should bc very anxious to improve function and/or esthetics to bc millin, 1~ to subject himscl t’ to the ;Ifol,clnc~iitioiicd trcatmcnt. Ol’EK.\TION

The surgical site is primarily the responsibilit>T of the surgeon, although best results are obtained when he consults with the orthodontist. The site ma,v 1~ located in the body of the mandible or in the ascending ramus. The operation 1na.y take the form of an ostcotomy in which the bone is cut and the sections arc repositioned, or it. may be an ostect.omy in which an actual section of bone is removed and the proximal and distal segments are coaptcd. The procedure is most often approached from an cstraoral incision, although many surgical (norrections arc completed entirely from intraoral access. The variety”-” of surgical sites and approaches makes it apparent. that there arc many advantages and disadvantages to each procedure, with no set technique applicable for all SWgeons and patients. Ontcotomies of the ramus arc the more frequent procedures today. They may he vertical or oblique, extending from the subsigmoid notch toward the angle. or the cuts may be made horizontally frorn above the lingnla, or even higher up on the ramus just below the condylc. The osteotomics have the advantage of leaving the dentition intact and usually avoiding incision of the alveolar nerve. In patients with severe obtuseness, of the angle, osteotomy of the ramus allows for rotation of the mandible to correct this facial discrepancy. Incision of the body of the mandible could not bring about this correction. M7hen the preoperative cephalogvam shows the tongue completely filling the oral cavity” and the dorsum contacting the soft and hard palate, then the ramns osteotomy is usually preferable. If a section of the mandibular body mere rcmoved in such a case, then the already crowded tongue would have Eden smaller housing and there would probably be a resultant open-bite following removal of fixation. Therefore, making an incision behind the myeloh;void ridge in the; ramns brings the entire floor of the mouth and the tongue posteriorly, diminishing clinnccs of an open-bite relapse.

In this procedure,

a s&ion of boric is cut out of the mantliln~lar body in and the anterior scetiorl is brought distall,v. IYhen a. careful technique is used, the alveolar n(‘r~ ma;- bc left intact. T’cr~- oftc>tr, however, the nerve is sovcrcd during the operation and the resultant 1)arestlresia may last from several months to Fears. Ncverthcless, the body ostoctonly has the distinct. advantage of achieving correction wit trout, stretching t Ilo mus~nlar VIIvir*onmcnt. The patient usually remains in the hospital for= :3 to 5 days. At this tirnc antibiotics and wound cwc are given and general precautions a~ taken IO pw vent or control infection. The splint is inspected for stabilization and dirc~ction, and necessary adjustments are made. The patient is taught proper oral h>$rnt rnethods for an oral cavity with splinted uppc~v and lower dentitions. This ma? irivolvc a syringe using a mouthwash under pressure or cotton swabs clippctl in peroxide followed by rinsing. The liquid or scmiliquid diet of soups, l’r~rpp&s. baby foods, etc. can be snpplcnientcd by the nuni~i~ous conimcr~c+l var%tic~s of cnrichcd balanced liquid preparations now on the markrt. tllC

111012l~ 01’ ~JY2lllOlEl~

EtlY’iI,

SPLISTS

The purpose of the splint is to provide a means for immobilizing the jaw following surgical intervention. The splints should bt: placed 3 to 5 days prior to the patient’s admission to the hospital t,o allow time for an,v wcakncsscs or irritations to show up. Since the maxilla is not affected by this proc(~lut~:~ tht‘ maxillary splint is the same for either the osteotomy or the ostrctomy. The maxillary splint. ma:- hc &herb prefabricated or individual 1~ dcs~igncd. The ready-made varirtp (Fig. .1) has the advanta.ge of requiring Icss chair time to apply and is indicated when rnost of the maxillary teet)h are intact. The splint is supplied from the commercial house in straight lengths made of soft metal. It can be ada.pted with thr fingers to conform to t,he masillary tlcntition, although the final adjustment can best lx madr with No. 139 or similar plieras. The adapted splint is ligated individually to the terth with 0.020 or 0.022 inch soft stainless steel mire. It is essential that thr resulting ligation rclnders this splint immobile. When many or all of the maxillary teeth are missing, it is necessary to prcpare an individually designed splint to meet the needs of the particular patient. Fig. 2 shows a patient with a maxillary full denture. Hooks wwe rmhedded in

lq’ig. 1. Maxillary

splint made from prefabricated

E’ig. 2. Maxillary splint made from denture wired to patient’s palate.

patient’s

unit. Mandibular

splint

indiridually

full

denture.

Spurs embedded

Fig. 3. Naxillary splint includes anterior partial tlihlar splint consists of tllrrc separate units.

denture

soldered

Fig.

1

Fig.

2

Fig.

3

~lcsigned.

in acrylic,

to canine

lwl~ls.

and Man-

The surgical approach to mandibular prognathism has been reviewed from an orthodontist’s point of view. Various splinting techniques have been described and illustrated. The importance of occlusion in the fabrication of splints and postoperative immobilization of the jaws has been emphasized. Photographs of treatcld eases have been presented. REFERENCES

1. Sanhorn, Richard T.: Diffwcnce Betwren the Facial Skeletal Patterns of Class III Xalocclusion and Normal Occlusion, angle Orthodontist 25: 208-222, 1955. 2. Monteleone, Louis, and Duvigneaud, J. D.: Prognathism, J. Oral Surg., Anesth. Q%HOSP. D. Serv. 21: 190-195, 1963. Protrusion by Ostectomy and 3. Murphey, P. J., and Walker, R. V.: Correction of Maxillary Orthodontic Therapy, J. Oral Surg., An&h. R- Hosp. 1). Serv. 21: 2i5-290, 1963. 4. IIovell, J. II.: Muscle Patterning Factors in the Surgical Correction of Mandibular Prognathism, J. Oral Surg., Anrsth. & Hosp. D. Serv. 22: 122-126, 1964. 3. nroose, s. htt.: Surgical Correction of Mandibular Prognathism by Intraoral Subcontlylar Osteotomy, J. Oral Surg., Oral Med. 8: Oral Path. 22: 19’i-202, 1964. 6. 13arrow, G. V., and Dingman, R. 0.: Olthodontic Considerations in the Surgical Management of Devclopment,al Deformities of the 1fandible, hr. J. ORTIIOIIONTICS 36: 121-134, 1950. j. Cohen, M. 1.: Ort,ltodontics as an Aid in the Treatment of Mandibular Fractures in Children and in Mandibular Prognathism, AK J. ORTHODOXTICS 44: 358-381, 1958. 8. Alling, C. C.: Mandibular Prognat,hism, Oral Surg., Oral Med. R; Oral Path. 14: 3-0‘7, Supp. I, 1961. 9. Lysell, G., and others: Planning of Corpus Ostectomy in the, Trcatmrnt of JIandibular Protrusion, Acta odont. scandinav. 18: 279-291, 1960. 10. Sicher, H.: Oral Anatomy, St. Louis, 1949, The C. V. Nosh?- Company, p. i9. Il. Bjiirk, A.: In Salzmann, J. A.: Principles of Orthodontics, ~1. 2, I’hiladc~lphia, 1950, J. R. Lippincott Company, p. 505.

Fig. 4. Diagrammatic illustration operakion; H, after operation.

of mandibular

splint

nscvl in body

ostectomy.

~4, Before

the upper dentition so that the best possible occlusion is obtained. When this favored relationship is produced, then, and only then, arc the two loops ligated with soft stainless steel wire and quick-curin g acrylic added to the loop area. Jf it is not feasible to add the a.c.rylic at the time of the operation, then, elastic or wire t,raction between the upper and lower splints is strntcgically placed to maintain this favored occlusion. Acrylic may be addrd on the first or second postoperative day. It is significant that the occlusion is the key to this procedure. If the posterior and anterior segments were stabilized first and t,hen brought up to the maxilla for immobilization, the resulting occlusion would depend on how well this new, inflexible unit fits the maxillary dentition. On the other hand, if the three segments were manipulated to t.he best occlusion possible, any minor ad-

3 71

(‘ohm

In mandibular ostectomy, it is important to establish the cvrrcct amountJ and position of the surgical cut. A satisfactoq- method for this, drscribed 1)~ Barrow and IXngman,” consists of taking casts of 1hc occlusion and mounting them on an articulator. B,v using an oricntcd tcmplatc, trial-and-error cuts (*all he mndr on the plastic casts iintil one arrircs at favol~ablc occlusiolt. il

of postcbrior posit,ioning of the mandible will hc largcl? While the amount dictated by the cstent of the anterior cross-bite, the resulting facial csthrtics must also be anticipat.ed. The amount, of’ posterior movement of thv tiiandiblc

Fig. 6. Schematic text for details.)

illustration

to test for

facial

esthetics

following

surgical

procedure.

(See

necessary to produce a satisfactory orerjct is determined. This is recorded with a divider. Then a tracing of the face in profile is made from the ccphalogram, including the landmarks of the mandible and dentition (Fig. 6). Another tracing of the lower face alone, consisting of only the mandible, teeth, and soft-tissue outline of the lov-cr lip, chin, and upper throat, is made and cut out. This cutout. section of the mandible, teeth, and soft tissue is moved distally along the plane of occlusion by the prcdetcrmined amount recorded with the divider. The resulting correction in soft tissue can then bc inspected. If the cut-out se&ion is outlined in another color, risualizat,ion of the corrected profile is easier. It is possible that the occlusal corrrct,ion has still left the profile too prognathic or has rendered it. too rctrognathic. In these instances, adjustments or compromises in the occlusion may bc required to product hcttclr facial esthetics. The amount of this modification would bc communicated to the surgeon.

Fig.

‘i. Patient

treated

by ostcctomy.

A,

Before

trratmmt;

R, after

treaknent.

A.

Fig. Y. Patient treated ly oblique ostcotomy of the ramus. ,1, Refore treatmcd; I{, at”trl t watment

is secured by temporarily wiring the upper and lower splints. Then the surgrorl can proceed to make the holes in both segments of the ramus for interosseous wiring. Some surgeons prefer to depend on the dental splints and muscular housing, eliminating the interosseous wiring. In either case, however, it is dvsirable for the orthodontist. to overset this splinted occlusion. It is desirable also for the orthodontist to anticil)atc, whc~rc possible, an? intcrfcrcnccs that might prevent a satisfactory occlusion. In cases requiring osteotomy thcsc may be not,cd by occluding the upper and lowc~r casts in the corrccttxl position. In eases trcatcd by mandibular ostvctomy, the cut-out mandibular plaster caast can bc held tog:cthcr and occl~~dcd with the maxilla. It ma.~ bc, ncccssary to expand the maxilla, cxt,ract teeth, or modify cusps prior to tht: s~~rgical procedure t,o produce good interdigitation. ll‘ig. 7 shows facial photographs of a paticlnt trcvt,cd by mandibular ostcvtomy. Individually dcsigncd splints wwc used for irrlluol)ilizatio~L. (Fig:. 1 rep-

Fig.

9. Utmtition

of patient

brfore

surgical

procwlu~~

378

(‘ohen

resents the maxillary splint.! Thcl surgical ac~ws for this tr~~atmcnt. was inttw oral, so that no facial sca.r was Ivt’t. ~IOWC~WI~, a paresthesia of the lowc~r 1ip was present for more than a year ant1 ;I haI 1’.

Fig. 9 shows the occlusion prior to surgical interwntion. It is apparent that there is crowding of the maxilla, as well as a constriction of the masillqv arch. Thercforc, one premolar was cstractd and sotnc expansion was instituted OII the maxilla. Fig. 10 S~OMYS the splints 1 wwks following s~~rg!'cry, a1K1 Fig. 11 shows the dentit~ion 3 months ai’tcr winoral of’ the splints.

Fig.

10. Splints

Fig. 11. Drntition

in place 4 weeks following

3 months following

surgical

operation.

procehre.

The surgical approach to mandibular prognathism has been reviewed from an orthodontist’s point of view. Various splinting techniques have been described and illustrated. The importance of occlusion in the fabrication of splints and postoperative immobilization of the jaws has been emphasized. Photographs of treatcld eases have been presented. REFERENCES

1. Sanhorn, Richard T.: Diffwcnce Betwren the Facial Skeletal Patterns of Class III Xalocclusion and Normal Occlusion, angle Orthodontist 25: 208-222, 1955. 2. Monteleone, Louis, and Duvigneaud, J. D.: Prognathism, J. Oral Surg., Anesth. Q%HOSP. D. Serv. 21: 190-195, 1963. Protrusion by Ostectomy and 3. Murphey, P. J., and Walker, R. V.: Correction of Maxillary Orthodontic Therapy, J. Oral Surg., An&h. R- Hosp. 1). Serv. 21: 2i5-290, 1963. 4. IIovell, J. II.: Muscle Patterning Factors in the Surgical Correction of Mandibular Prognathism, J. Oral Surg., Anrsth. & Hosp. D. Serv. 22: 122-126, 1964. 3. nroose, s. htt.: Surgical Correction of Mandibular Prognathism by Intraoral Subcontlylar Osteotomy, J. Oral Surg., Oral Med. 8: Oral Path. 22: 19’i-202, 1964. 6. 13arrow, G. V., and Dingman, R. 0.: Olthodontic Considerations in the Surgical Management of Devclopment,al Deformities of the 1fandible, hr. J. ORTIIOIIONTICS 36: 121-134, 1950. j. Cohen, M. 1.: Ort,ltodontics as an Aid in the Treatment of Mandibular Fractures in Children and in Mandibular Prognathism, AK J. ORTHODOXTICS 44: 358-381, 1958. 8. Alling, C. C.: Mandibular Prognat,hism, Oral Surg., Oral Med. R; Oral Path. 14: 3-0‘7, Supp. I, 1961. 9. Lysell, G., and others: Planning of Corpus Ostectomy in the, Trcatmrnt of JIandibular Protrusion, Acta odont. scandinav. 18: 279-291, 1960. 10. Sicher, H.: Oral Anatomy, St. Louis, 1949, The C. V. Nosh?- Company, p. i9. Il. Bjiirk, A.: In Salzmann, J. A.: Principles of Orthodontics, ~1. 2, I’hiladc~lphia, 1950, J. R. Lippincott Company, p. 505.