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
+
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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
Historical Background
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.
Historical Background
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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.
Historical Background
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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.
Historical Background
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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)
Historical Background
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.