IMF- NEW TECHNIQUE

Introduction:
I n t e rm a x i l l a ry fixation using arch bars is perform e d
for most mandibular and many maxillary fractures
not requiring open reduction or internal fixation.
These are applied to the respective maxillary and
mandibular arches with circumdental stainless steel
wires.
Immobilization is achieved using intermaxillary
wires or elastics. However, there is a possibility of
inadvertent skin puncture and thus contamination
by virus-infected saliva or blood. The number of
p e rsons infected with human immunodeficiency
virus (HIV) has been increasing in the world and is
of great concern to many individuals involved in the
treatment of facial fractures.
It is important to lessen the possibility of the sharp
ends of wires causing skin puncture during maxillofacial
surgery. Therefore, interm a x i l l a ry fixat i o n
needs to be achieved without using circumdental
stainless steel wiring. The authors have applied a
method of intermaxillary fixation using an adhesive
cast splint which was made on working models and
bonded to the tooth enamel with adhesive resin.

Materials and methods:
For six months between May and October 1993,
18 patients with facial fractures were hospitalized in
Komaki City Hospital.
The new technique of adhesive cast splinting was
used for 10 patients who had sufficient molars to
maintain vertical dimension; 7 of these patients had
mandibular fractures, two had maxillary fractures,
and one had multiple fractures. Three patients with
condylar fractures did not undergo open reduction
so intermaxillary fixation with elastics was carried
out. Seven cases underwent open reduction
combined with rigid fixation by miniplates.
It was sufficient to use one cast splint extending
from the first molar to the first premolar in each
quadrant. A dimple was created on the contour
(0.5~1.0 mm) in the enamel (Fig. 1). A rubber base
impression in a small custom tray was obtained to
provide maximal accuracy of the working models
which were then cut and repositioned. A wax pattern
was fabricated on the duplicated cast, and the
pattern was then invested and cast in 12% Au-Ag
palladium alloy (Fig. 2). Before insertion the casting
was adjusted on the model to avoid premature
contact (Fig. 3.) The cast was then disinfected by
immersion in 2% glutaraldehyde solution for 30
minutes. When the fracture line occurs between the
first and second premolars, the splints should not
include the first premolar. If necessary, the bracket
can be applied by the direct bonding system3 (Fig. 4).
The splints were carefully inserted and the fit
checked intraorally. The teeth to which the splint
were bonded were polished to remove the pellicle
and the enamel surfaces were etched, then irrigated
and dried. Grit blasting with alumina was carried
out to obtain firm adhesion. The splints we r e
attached to the teeth by adhesive resin. The resulting
strength was found to be generally superior to that
achieved with arch bars (Fig. 5).

Discussion and conclusion:
Dental arch bars are the most frequently
e m p l oyed fixation method in the treatment of
mandibular fractures,4 and they are also used in
maxillary fractures. They are simple to use, but the
health professional applying the peridental wires is at
risk of acquiring blood-borne diseases through
perforating injuries from sharp wire ends.5 In recent
years, the number of people infected with HIV has
increased. In Europe, Gimeno et al.6 reported that
the incidence of HIV + patients was high (19.8 per
cent) in the mandibular fracture group. Therefore,
skin puncture must pose a danger for the oral and
maxillofacial surgeon.
Recently, the period of intermaxillary fixation has
been reduced by ri gid fixation techniques bu t ,
generally, intermaxillary fixation is indispensable.
Direct bonding of a bracket with adhesive resin3
instead of wires for mandibular and maxillary
fractures to prevent periodontal tissue injury and to
improve oral hygiene was tried by the authors.
H owe ver, this method required complicat e d
procedures and had some disadvantages such as easy
detachment when not properly placed. Therefore,
the authors developed and tested a method of intermaxillary
fixation using an adhesive cast splint. Ten
cases were treated with this technique. The method
reduced the use of wires to a minimum and, therefore,
also reduced the risk of skin puncture. The cast
splints proved to be sufficiently stable without
surgery in three patients when elastic intermaxillary
fixation was applied during the postoperative period.
They also proved to be sufficiently stable during and
after surgery in seven patients who underwent open
reduction with miniplates and rigid intermaxillary
fixation during surgery. To obtain stronger stability
of the splints, a dimple was created in the enamel
using the interdental undercut, and the splints were
bonded to the teeth with adhesive resin containing
4-methacryloxyethyl trimellitate anhydride.
To ensure metal bonding using an adhesive resin,
pretreatment of the metals is essential to obtain firm
adhesion with the resin.7 There are various methods
of pretreatment including an alloy conve rs i o n
method, ion coating surface treatment from a Cu
target, pretreatment with a metal primer, and tin
electroplating.7-9 The authors used the simple metal
surface treatment of grit blasting with alumina.
The use of the cast splints reduced the surgical
time significantly (and may even eliminate the need
for local anaesthesia because the cast splints can be
applied without causing pain due to mouth opening
as is necessary when applying ordinary arch bars).
Other advantages included the ease with which
proper hygiene was maintained, and freedom from
gingival impingement. Oral hygiene was markedly
i m p r oved during the period of interm a x i l l a ry
fixation since no ligatures were present. Therefore,
the gi n gi val health of the patients was not
compromised (Fig. 6).
The major disadvantages of these cast appliances
are that there is little tolerance for err o rs in
fa b ri c ation or surgical positioning, they are expensive ,
and they require a special laboratory facility for
construction. Generally, some limitations in their
application were observed including few interdental
undercuts in young patients and problems in
bonding to teeth with metal crowns. There was a
possibility of causing secondary caries when
p r e p a ring dimples in the teeth. Howe ver, this
technique has proved a useful supplement to
previously used methods, and is useful for avoiding
skin puncture.