Implant supported fixed bridge for edentulous mandible
Botan Barzan Khafaf
Hawler Medical Universtity
College of Dentistry
*Unlike a maxillary denture, the labial flange of a mandibular
overdenture rarely is required for esthetic.
*The laboratory cost for a hybrid fixed restoration are similar to
those for a fully implant-supported overdenture . So if the fees for
these two restorations were similar, many patients would opt for a
*The chair time required to fabricate an overdenture and bar is
similar to that for an implant supported fixed prosthesis.
Figure -2 : complete arch implant fixed prosthesis may be
hybrid, with denture teeth and acrylic joined to a metal substructure.
* Psychological: "feels like teeth”.
* Less prosthetic maintenance
(e.g., attachments, relines, new overdenture).
*Less food entrapment.
* Posterior mandibular bone gain.
Posterior mandibular bone loss
Nearly all of the bone
during the first year
-Maintenance and even regeneration
of posterior bone in the mandible.
-Because posterior bone loss in this region
may lead to paresthasia and even
mandibular body fracture ..
Cantilevered fixed prostheses from anterior
* Masticatory dynamics.
* Bone density of the implanted regions.
should modify the implant
*Position Implant Number Size Design
Force factors contribute to:
2- Screw loosening.
3- Component fracture .
4- Crestal bone loss.
*F. transmitted to implant fixed prosthesis (IFP)
F.Transmitted to implant supported overdenture(IOD)
*Mandibular Overdenture maybe removed at night
( risk of parafunctional overload ) but at the same time most of
Man. eden. Pts. also have eden. Maxilla.
*parafunctional bruxism and clenching may cause
problems in the implant support system and
So : the number of implants required to restore a fixed prosthesis may
be similar to a fully implant-supported overdenture.
*Medial convergence Masticatory muscles
Stable. Movement toward medline on opening
Distal to foraminae
Attachment of internal
pterygoid muscle on the
medial surface of mandible
Mouth opening, Max.in Protrusive movement
28% or 12 mm mouth opening
*Amount of movement varies Density & volume
Of bone &site of
*Amount of mand. Flexure toward medline :
- 800microM in first molar region .
- 1500 microM at ramus-to-ramus sites .
* Hobkirk stated that :Fixed dental implant prosthesis, medial
convergence up to 41MicroM.
*Parasagittal bending of the human jaw during unilateral biting
(Marx ,1994) .
*Distal to the foraminae.
*Mandible with implant prostheses measured up to
19 degrees of dorsoventral shear. (Hobkirk et al,2000) .
*The torsion during parafunction is caused primarily by forceful
contraction of the masseter muscle attachments.
• Jaw flexure is a primary cause of posterior implant
loss in full arch mandibular prostheses.(Miyamoto et
• Body of the mandible flexes more when the size of the
*Bilateral rigid post. mandibular splinting in a full-arch restoration are
subject to a considerable buccolingual force on opening and during
*Man. Flexure and torsion 10-20% more that tooth movement.
*In complete mandibular subperiosteal implants, pain upon opening
was noted in 25% of the patients at the suture removal appointment
when a rigid bar connected molar-to-molar regions.
* When the connecting bar was cut into two sections between the
forarminae, the pain upon opening was eliminated immediately.
Apical Movements Lateral movements
Tooth 28 56-108
Implant 5 10-60
full-arch splinted restorations joining bilateral molar implants in the
mandible should not be a tx. of choice??
1. Bone loss around the implants.
2. Loss of implant fixation.
3. Material fracture (implant or prosthesis components).
4. Unretained restorations.
5. Discomfort upon opening.
*So to prevent these complications related to the flexure or torsion of
Implants placed in front of the
foraminae and splinted
Implants in one posterior
quadrant joined to anterior
• Why the posterior bone gain in edentulous patients restored
with cantilevered prostheses from anterior implants may be a
consequence of the mandibular flexure and Torsion ?
• Because the bite force may increase 300% with an implant
prosthesis compared with a denture, the increased torsion
may stimulate the posterior Mandibular body to increase in
(Reddy et al, 2002 ; Wright et al , 2002).
*IMPLANT TREATMENT OPTIONS FOR
*Treatment Option 1: The Branemark Approach
The placement of four or six anterior root forms between the mental
foraminae and a distal cantilever off each side to replace the posterior
oResulted in an 80% to 90% implant survival for 5 to 12 years after the
first year of loading.
treatment of choice from 1967 to 1981 with the Branernark system"
*important criteria when four to six implants:
Arch form(square, oval or tapering) .
Position of the mental foraminae
(distal implant position).
*The most common number of implants used today in the Branernark
treatment option is five ??
Allows as great an A-P spread as six implants, so that if bone loss
occurs on one implant , the loss would not automatically affect the
adjacent implant site.
* Treatment Option 1
*Distance from the center of the most anterior implant to a line
joining the distal aspect of the two most distal implants on each side
is called the A-P distance or the A-P spread” .
*When five anterior implants are placed the cantilever should not
exceed 2.5 times the A-P spread, with all other stress factors
(e.g., parafunction, crown height, masticatory musculature
dynamics, opposing arch), being low if not it is contraindicated.
*Tx. option 1 depends greatly on patient force factors, arch form,
and the number, size, and design of the implants.
1. Patients with low force factors.
2. Old female wearing an upper denture, with abundant anterior
3. crown height inferior to 15 mm .
4. Tapered or ovoid mandibular arch.
5. Posterior Segments of inadequate height for endosteal implant
Treatment Option 2 : Additional implants above the mental
foraraminae, because the mandible flexes distal to the foramen.
1- The number of implants may be increased to seven (increases
implant surface area).
2- The A-P spread for implant increased, even when the total implant
number is five.( reduces the Class 1 lever forces generated from
the distal cantilever).
3- The length of the cantilever is reduced dramatically because the
distal most implant is placed one tooth more distal.
Treatment Option 2
Indication: Presence of available bone in height and width over the
foraminae.(usually is located 12 mm above the inferior border of the
mandible) So requires implants of reduced height .
The key implant positions are :
*2PMs,canines and the central incisor or midline position. The two
optional implant sites are 1PMs.
*A minimum recommended implant height of 9 mm and a greater
Diameter or an enhanced surface area design are recommended to
compensate for the reduced length.
*Implants in one posterior section may be splinted to anterior
*The key implant positions are: the 1M (on one side only), the
bilateral 1PM positions, and the bilateral canine. The secondary
implant position is the 2PM on the same side as the molar implant
and the central incisor (midline) position.
*Is a better option than anterior implants with bilateral cantilevers
for several reasons:
When one or two implants are placed distal to the foraminae on one
side and are joined to anterior implants between the foraminae, a
considerable biomechanical advantage is gained.
Number of implants may be the same as opt. 1 or 2, the A-P spread
is 1.5 to 2 times greater, because on one side the distal aspect of the
last implant now corresponds to the distal aspect of the 1M.,but it it
only one cantilever.
*Increased force factors: 6-7 implants indicated.
*Two 1M, two 1PM and two canine sites. Secondary implants may be
added in the 2PM sites and/or the incisor (midline).
*All implants in the anterior and one posterior side are splinted together
for a nine-unit fixed prosthesis. The other posterior segment is
restored independently with an independent three-unit.
*When force factors are great or the bone density is poor.
*When the body of the mandible is Division C-h and subperiosteal or
disk-design implants are used for posterior implant Support.
*Primary advantage is the elimination of cantilevers.As a result,
risks of uncemented restorations and occlusal overload are
*The prosthesis has two segments .(installation &repair)
*Need for abundant bone in both mand. Post. regions .(not like tx 5)
* Additional costs(need of 1-4 add. Implants).
*Treatment option -5
*Three independent prostheses rather than one or two.
*The anterior region of the mandible may have (4-5) implants.
*(8) implants may also have a secondary implant in the midline.
*The key implants are in the two 1M, the two 1PM, and two canine
regions. Secondary positions are the two 2PM and central.
*the posterior restorations extend from first molar to first premolar
and an anterior restoration replaces the six anterior teeth.
When force factors are severe (but it is rarely used).
When the posterior mandible is C-h bone volume and a
circumferential subperiosteal or disk-design implant is used as the
2PM and 1M implant abutment supports.
The decrease in the bone volume of the posterior mandible
increases the flexure and torsion. As a result, three independent
prostheses are warranted.
Greater mandibular body movement is because of parafunction.
Smaller segments for individual restorations in case one should
fracture or become uncemented.
*Treatment option -5
*the greater number of implants required. (8 or add. Central)
*This treatment option has the greatest need for available bone
Rarely are more than nine implants required, regardless of the bone
density or force factors present .