prosthodontic management of acquired defects of mandible /certified fixed orthodontic courses by Indian dental academy

PROSTHODONTIC
MANAGEMENT OF
ACQUIRED DEFECTS
OF MANDIBLE
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INDIAN DENTAL ACADEMY
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Table of content
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Introduction
Review of literature
Definitions
Classification of mandibular defects
Physiology of oral function following
resection
• Diagnostic Consideration for
Prosthodontic rehabilitation

• Prosthodontic management
Mandibular guidance prosthesis
Partially edentulous patient
Completely edentulous patient
• Role of implants in rehabilitation
• Summary
• Conclusion

Partially edentulous patient
• Lateral discontinuity defect
• Anterior continuity defect
• Lateral continuity defect


Lateral discontinuity defect


Impression
• Preliminary impression are made with
modified stock tray.
• Cast poured
• Surveyed
• RPD design

Partial denture design
All principles of designing a conventional
partial denture should be followed.
• Major connector- rigid
• Occlusal rest- direct forces along long axis
• Direct retainer- engage several teeth


Factors To consider
• Closure is angular rather than vertical
• Forces of occlusion confined to
unresected side
• fulcrum line difficult to determine due to
frontal plane rotation making it difficult to
predict movement pattern of prosthesis
during function

Forces of occlusion

Frontal plane rotation


• Once framework is fabricated it is tried in
the patient’s mouth


Altered cast impression
• Altered cast impression of edentulous
area is taken
• Special care on lingual extension of
unresected side should be taken as it
provides additional retention and stability
• Maximum soft tissue coverage
• Coverage of buccal shelf on unresected
side is important

• On resected side tissue bed is unyielding
hence to mold this area manipulate the
cheek and ask patient to move tongue
from side to side.
• After altered cast impression is obtained,
master cast is segmented.
• Impression placed on the sectioned cast,
boxed and poured

• Occlusal rim are made.
• Jaw relation recorded by softening the
wax and gently guiding the mandible.
• Excessive force to be avoided

• Select teeth depending on opposing
dentition
• After jaw relation are verified at try-in,
denture is acrylized
• Partial denture is delivered


Defect with mandibular continuity
maintained or reestablished


Anterior defect


• These patients have posterior teeth and
extensive edentulous area anteriorly
creating a kennedy classIV situation.
• Normal mandibular movement pattern
• Following bony recostruction
vestibuloplasty are indicated

• Design must consider movement of
anterior segment of prosthesis
• Long mesial rest on 2nd molar provide
indirect retention.
• Care taken to relieve proximal plate and
distal aspect of minor connector to allow
for expected movement of prosthesis

• Conventional RPD enhance aesthetic and
provide lip support leading to improved
articulation of speech and salivary control
• In small defects mastication is restored
• In larger defects mastication is
compromised because of length and
movement of anterior edentulous span
hence RPD serves mainly for lip support


Lateral defect


• Lateral defects in which posterior dentition
remains only on one side are difficult to
design.
• Long lever arm and compromised tissue
bed on resected side cause excessive
movement of the prosthesis.


Favorable edentulous extension


Unfavorable edentulous extension


Completely edentulous patient
Compromising factors
• Stability, retention, support reduced due to
resection
• Radiotherapy makes mucosa fragile and
atrophic
• Reduced saliva with altered quality
compromises retention

• Angular pathway of closure induces lateral
forces on denture which tend to dislodge
• Deviation creates abnormal jaw relation
and teeth placement difficult
• Impairment of motor and sensory function
impair ability to control prosthesis.

• Primary impression made with irreversible
hydrocolloid in a modified stock tray
• Particular attention must be paid in
recording areas posterior to the resection.


Swallowing impression
technique


Area supported by bone and free of
muscular activity drawn on diagnostic cast


• Perforated acrylic resin tray constructed
on outlined area
• Modeling compound stops placed on
impression surface for stability and to
provide space for impression material.
• Two lateral columns that extend towards
the maxillary ridge are formed on tray

Conventional technique
• Border molding and secondary impression
can also be used


Maxillomandibular relation
recording
• Acrylic resin base fabricated on this cast
indicates zone of neutralization
• Wax occlusal rim placed within this zone
• Maxillary rim adjusted for lip support and
occlusal plane
• Maxillary rim wider on unresected side to
account for deviation of mandible

• Lower rim adjusted till a tentative occlusal
vertical dmension has been established.
• Vertical dimension of occlusion should be
closed as much as possible in patient with
reduced tongue bulk or mobility to allow
tongue to interact with palatal structure
• Mandible guided by clinician into
unstrained repeatable position for centric
registration
• Maxillary ramp may be made at this stage

• Retention achieved by close adaptation of
the prosthesis with bearing surface and
maximal extension of lingual flange on
unresected side as compatible with
anatomical limitation
• Support obtained from buccal shelf, crest
of ridge retromolar pad and soft tissue bed
posterior to resection

Teeth arrangement
Non- anatomic teeth to be used
• Abnormal jaw relation
• Angular path of closure
• Increased lateral stress
• teeth arranged within the neutral zone

• Due to deviation and retrusion maxillary
anterior teeth are placed lingual to and
mandibular anterior teeth are paced labial
to normal position.


Mandibular posterior teeth
• Posterior teeth on unresected side placed
buccal to crest of ridge.
• With the lingual inclination of residual
mandible and elevation of buccal shelf,
placing posterior teeth buccaly centers he
forces more favorably on supporting tissue
and also is compatible with tongue
position.

On the resected side posterior teeth are
placed lingual to the crest as
• Lips and cheeks pulled medially due to
scarring
• To facilitate occlusal relationship with
maxilla

Resected side, lingual placement of teeth

Unresected side, buccal placement of teeth

Functionally generated palatal
ramp
• Soft occlusal wax is added on to the
posterior and palatal surface of maxillary
rim.
• Mandible guided through opening and
closing movement


Maxillary posterior teeth
• Maxillary posterior teeth are placed
lingualy on unresected side and buccaly
on resected side for favorable occlusal
relation
• Maxillary palatal ramp can be fabricated at
this stage


• Following try- in prosthesis is processed in
conventional manner.
• At the time of insertion disclosing agent
should be used to relieve area of
excessive tissue displacement.


• “ Mastication is confined to non-defect
side and bilateral occlusal contact serve
more as stabilizing force. As muscles of
mastication are no longer present on
resected side bilateral balance of
complete dentures during function in the
classical sense is not possible.”
Beumer

Role of Implants in
rehabilitation


Application of implants has offered a major
improvement in management of mandibular
resection cases. By providing a foundation onto
which fixed prosthodontic treatment is based or
for retention of removable prosthesis, implants
play a role in making rehabilitative efforts
functional rather than mere aesthetic.


The patient receives a stable fixed prosthesis
with an appropriate interocclusal relationship
and occlusal scheme, predetermined by the
guidance-positioning
device.
The
fixed
prosthesis resolves the problems, reduces
mechanical irritation to the tongue and soft
tissue, and allows sufficient space for the tongue
for efficient mastication.


PERI-IMPLANT SOFT TISSUE
CONSIDERATIONS
• Implant abutments that traverse thick, movable,
soft tissue beds before entering the oral cavity,
frequently are plagued with soft tissue
maintenance problems. The cause of these
problems is often related to tissue movement,
plaque accumulation, and ineffective oral
hygiene efforts.
• These factors can affect peri-implant health and
possibly long-term retention of the implant.

TIMING OF IMPLANT PLACEMENT
Placement of osseointegrated implants at the
time of surgical resection and osseous
reconstruction has been reported and promoted
on the basis of eliminating a separate surgical
sitting, avoiding the need for hyperbaric oxygen,
and reducing delays in prosthetic rehabilitation.
However, this approach frequently results in
compromised implant position and orientation
limiting optimal prosthetic rehabilitation.

A better appreciation for tumor prognosis
after definitive (permanent section)
microscopic
evaluation
of
surgical
margins, neck node status lifestyle
(alcohol, tobacco, other drug abuse) of the
patient, and compliance for follow-up
evaluations are all important factors to
consider and are usually


more predictable and apparent when
implant placement is performed in a
delayed manner. Even if indicated, it
would be imprudent from an oncologic
standpoint to place implants when tumor
prognosis is poor and risk for recurrence
is high.

Osteoradionecrosis is the primary concern after
invasive procedures, such as placement of
endosseous implants in irradiated bone.
Evidence suggests that placement of an
endosseous dental implant into irradiated
mandibles does not compromise implant
integration nor reduce survival rate.


Implants placed in irradiated mandibles
show a very high survival rate. Histologic
examination
confirms
implant
osseointegration in irradiated bone. A
minimal interval of 9 to 12 months
between
radiotherapy
and
implant
placement is recommended.

Implant supported overdenture


Implant supported removable
partial denture


Arrangement of artificial teeth in the neutral zone after
surgical reconstruction of the mandible


Summary
• Rehabilitation of acquired mandibular
defect is a challenging task. Several
problems are encountered during the
rehabilitation.


Physiologic impairment

Degglutition
Salivary control
Speech
Mandibular movement

Psychologic factors

Diagnostic
Consideration
for Prosthodontic
rehabilitation

Location and extent
of mandibular defect

Presence of remaining
natural teeth


Rotation and
deviation of mandible

• Often with lateral resection, frontal plane
rotation, deviation to the resected side is
seen. Hence guidance prosthesis is the
starting point to rehabilitation. Once
appropriate occlusal relationship can be
achieved final removable or fixed
prosthesis can be fabricated


Partially
edentulous patient

Lateral discontinuity
defect

Anterior
continuity defect


Lateral
continuity defect

• For completely edentulous patient the
swallowing technique for impression
recording, to record neutral zone is
recommended. Placement of teeth in
neutral zone stabilizes the prosthesis.
• Use of implants in management of these
cases greatly enhances the functional
outcome. The number, location and time
of placement are important.

Conclusion
Patients operated on for malignant tumors of the
mandible, present a far more difficult
rehabilitation problem, than those patients with
maxillary defects. Recently, advances in the
reconstruction of such defects by means of
microvascular free flaps have allowed the
maxillofacial prosthodontist to rehabilitate these
patients more effectively.

With proper multidisciplinary pretreatment
planning and postoperative treatment,
osseointegrated implants can be strategically
placed in those patients with a reconstructed
mandible to restore occlusal and masticatory
function while also achieving an acceptable
esthetic.


Reference
•

Canter, R. and Curtis, T. A. Prosthetic management of
the edentulous mandibulectomy patient. Part II Clinical
procedures. J Prosthet Dent 25:546-555, 1971.

•

Canter, R. and Curtis, T. A. Prosthetic management of
the edentulous mandibulectomy patient. Part III Clinical
evaluation. J Prosthet Dent 25:670-678, 1971.

• Curtis, T. A. and Canter, R. The forgotten patient in
maxillofacial prosthetics. J Prosthet Dent 31:662-680,
1974.


• Firtell, D. N. and Curtis, T. A. Removable partial denture
design for the mandibular resection patient. J Prosthet
Dent 48:437-443, 1982.
• Moore, D. J. and Mitchell, D. L. Rehabilitating dentulous
hemimandibulectomy patients. J Prosthet Dent 35:202206, 1976.
• Desjardins, R. P. Occlusal considerations for the partial
mandibulectomy patient. J Prosthet Dent 41:308-315,
1979.
• Beumer, J., III, Curtis, T. A. and Firtell, D. N.
Maxillofacial Rehabilitation: Prosthetic and Surgical
Considerations. C. V. Mosby, St. Louis, 1979

• Prosthetic treatment of maxillofacial injuries
• JPD 1955: Lt Colonel Edwin
• Prosthetic reconstruction of a resected
mandible JPD 1962: Adisman
• Use of a guide plane for maintaining the
residual fragment in partial or
hemimandibulectomy JPD 1964: Robinson
and Rubright
• Prosthetic mandible of resected edentulous
mandible JPD 1969: Swoope

• Rehabilitation of an irradiated mandible after
mandibular resection using implant/toothsupported fixed prosthesis: a clinical report.
BArak et al JPD 2004: 91:310
• Arrangement of artificial teeth in the neutral zone
after surgical reconstruction of the mandible: A
clinical report. Kokubo et al JPD 2002:88:125-7
• Titanium osseointegrated implants combined
with hyperbaric oxygen therapy in previously
irradiated mandibles. Arcuri et al JPD
1997;77:177-83

• Functional criteria for mandibular implant
placement post resection and reconstruction for
cancer
Marunik and Roumanas JPD 1999;82:107-13.
• The fabrication of cast metal guidance flange
prostheses for a patient with segmental
mandibulectomy: A clinical report Aslan et al
JPD 2005;93:217-20
• Clinical maxillofacial prosthetics: Thomas Taylor:
quintessence pub.

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prosthodontic management of acquired defects of mandible /certified fixed orthodontic courses by Indian dental academy

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