The Transoral Chin Correction

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The Transoral Chin Correction


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Historical Background

Chin

Anomaly

Retrogenia

Hypergenia

Hypogenia


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Risk for possible infection Submental Scar

Second operation at donor site for the

bone graft

Resorption of the bone graft within a

year

Temporarily produce quite a pleasing chin

prominence

Historical BackgroundRetrogenia Cases

A bone graft was onlayed via a

submental approach.

Often enough the bone graft was justplaced around the cortical surface withsome cancellous bone on the contactarea

+

-

Cortical bone shrinks like a

mushroom in the sun, and

cancellous bone melts awaylike ice cream when used as an

onlay graft for contour

correction. (Principle Nr.18)


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Selections of Material Used Autogenous bone

Autogenous rib cartilage

Alloplastic material :

Titanium mesh (K.H.Thoma 1948)

Acrylic Prefabricated silastic chin

implants


High incidence of infection.

Secondary displacement.

Dehiscence of the suture line.

High incidence of problems. It could

erode into the bone and come to

rest against the roots of the patients

front teeth due to the pressure from

the advanced soft tissues.

The need for a second operation.

The graft quietly disappeared.


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H.Obwegeser 1957)Hyper and/or hyporetrogenia :Slide the lower border of the chin forwards and upwards, leaving it pedicled on

the digastric and geniohyoid muscles.

H. Obwegeser also did chin advancement transorally, using J.M. Converses degloving

technique.



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Steps on doing the chin advancement H. Obwegeser, 1957) Cut off lower border of chin with a

Lindemann bur.

The osteotomy line is from low

posteriorly to higher anteriorly.

Pull the bone forwards by 10 mm,

pedicled on geniohyoid muscles.

Fix the advanced chin horseshoe with

a strong perimandibular Supramidthread on each side over an acrylic

dental splint, so as to permit removal

of the thread after three weeks.



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O. Hofer 1942) Sliding the inferior border of

the chin forwards, from

extraoral approach leavingit muscle pedicled on the

platysma, digastric, and the

geniohyoid muscles.

The operation is performedon cadaver using a rather

large bone saw.



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O. Neuner 1965) Double step advancement

technique.

H. Obwegeser 1974) In appropriate cases, one

can even perform triple-

step advancement. Steps :

Free all the musculature

Trim and shape to the

requirements

Fix it with direct wires

Material used :Deep frozen cancellous cadaver bank bone.

(But even without it he usually found new

bone formation in the step area)


But, in follow up investigations, 50%

resorption occured, however some of it

was transformed into soft tissues,

decreasing the amount of loss of contour.

Later, H. Obwegeser always left the

advanced inferior border muscle-

pedicled again. Follow up study shows on

average 10% resorption and even that

amount often found to be transformed into

soft tissue, thus producing the planned

amount of prominence advancement.


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H. Obwegeser Final Method The vestibular incision is made

approximately 5-8 mm labial to the depth

of vestibulum at a right angle at mucosal

surface only, and then directed

horizontally to the alveolar process.

The periosteum is incised from

underneath the mental foramen as far

back as necessary, from one side to

another.


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The direction of the bone cut has to be determined preoperatively on a tracing of the lateral

cephalogram, on which the desired profile line has been drawn.

According to that planning, the lower border chin has to be moved :

Forwards : for correction of retrogenia

Upwards and if necessary by excision of a strip of bone below the teeth : for correction of

severe hypergenia or in cranially convex curvature for the correction of hypo- and retrogenia.


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The mental nerve must be well protected,

The more soft tissues are left attached to the

piece of bone which is to be moved, the less

resorption of the moved segment will takeplace.

H. Obwegeser Final Method The tracing with the desired profile line

permits the use of transparent foil which is

cut according to the existing shape of the

bony chin to simulate the osteotomy

necessary to achieve the planned result.

If >8 mm advancement is necessarya double-step advancement

should be planned. (On rather larger

steps, soft tissue line will show and

may be fixed into that step).

The more the chin has to be

advanced, the further back the bone

cut will be, in particular when

performing doule or triple-step

advancement.


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H. Obwegeser personally like to use a

reciprocating saw with thin disposable

blades.

H. Obwegeser Final Method A. Triaca usually use rather use short, hard

steel bur normally used in dental laboratorywork (Maillefer No. 540).

A.Triaca does not free the prominence of thechin from the investing soft tissues completely.

He leaves the inferior part of the mentalismuscle attached to it. He only frees the lowerborder in the area where the osteotomy reachesit. He resects the lingual rim of the detachedchin prominence with the detached musculatureusing the same bur in order to reduce itsbackwards pull when the chin is movedanteriorly.

This seems much better than dissecting theinsertion of the musculature.


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When there is need to correct hypogenia,

again the desired profile line tracing is

used to ascertain whether an upwardly-

curved, almost semicircular bone cut willachieve the planned result or whether the

sandwich technique (J.M. Converse 1964)

has to be used to achieve the necessary

height increase.

The technique for enlarging or reducing

the width of horse-shoe shaped lower

border remains the same as published in

1958.

H. Obwegeser Final Method


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Final MethodH.Sailer (1985)

The asymmetric chin prominence, notonly present in case of hemifacialmicrosomia but also in condylarhyperactivity cases, deserves special

consideration.

H. Sailer (1985) has suggested his so-called chin propeller technique.

Another simple way is to cut the detached

lower border into two unequal segments,using the symphysis as the site of the cut.Then the longer part is shortened so thatfrom medial to lateral both are equal inlength. Both segments are fixed togetherand to the chin.


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Chin reduction is less often necessarythan the correction of lack of its verticalheight or horizontal length. The type ofcorrection of surplus of the bony chindepends on its existing and the desiredshape.

To correct a horizontal surplus bytrimming it off with a bur seems theeasiest way. In my hand that very rarelyproduced a pleasing result. Almost alwaysthe prominence became too rounded. Amuch more pleasing result is achieved bya rather vertical strip excision. If the chin

is too high (deep) in its vertical dimensionpreferably a wedge shaped piece willhave to be excised, as shown in theillustration (H. Kole 1970).

Final Method


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Smith 1985) The soft tissue surplus in the chin region is more difficult to correct than are the bony

abnormalities.

A certain amount of contour reduction can be achieved by reducing the underlying bonychin. But there are cases which definitely need soft tissue excision, skin as well as

subcutaneous tissues and musculature.

Final Method


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Fixation

Fixation

**Nowadays varies from surgeon

to surgeon

Lag screws with 1,5 mm

Designed plates

Wires


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No hydrophilic thread is any good. It absorbs saliva and

conducts infection into and underneath the approximated

edges.

Better not to use toothed forceps to hold the edges.

Fine single hooks do less harm.

When closing the wound, this permits a better bite with the

needle than when mucosal edges only are approximated

permits good adaption of the wound edges

How to prevent Suture Dehiscence

Method of managing and

closing incision line

The knife must cut the mucosa at aright angle to the mucosal surface

With the subsegment vertical cut to the chin area,

quite a bit of musculature remains on the chin

The handling of the edges of the

mucosa

The types of material used


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Suturing MethodSuture

Material Used

Supramid. A suture material which is not as stiff as a

monofilic thread as it consists of a great number of very

fine filaments which are covered by a layer of non-hygroscopic material.

Types of Suturing

Submucosal catgut suturestoo difficult too insert.

H. Subwegeser prefers Continuous sutures, changing

between a vertical mattress type to an ocassionallyordinary continuous sutures.

Post-Operative CareCompress the soft tissues towards the chin, particularly

above the advances part, with some slightly elastic strips.


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Principal Complications, How to Deal with Them and Avoid Themroblems during surgery

Bleeding

The Mental Nerve

Wrong directions of the bone cut

Problems with fixation

Losing a piece of bur or a saw blade

roblems after surgery Infection with slight pus discharge

Suture dehiscence

Relapse

Resorption

Unaesthetic chin-neck contour

Unsightly upward retraction of the

skin behind the advanced

prominence.

The Transoral Chin Correction

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