implant supported fixed bridge for edentulous mandible

Prepared by:

Botan Barzan Khafaf

MSc. Student

Supervised By:

Dr.Luqman

THE COMPLETELY EDENTULOUS MANDIBLE:TREATMENT PLANS FOR FIXED RESTORATIONS

Hawler Medical UniverstityCollege of DentistryConservative Dep.

*Why Fixed Bridge?

*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 fixed Prosthesis.

*The chair time required to fabricate an overdenture and bar is similar to that for an implant supported fixed prosthesis.

* Figure-1:Implant overdentures with posterior soft tissuesupport lose bone in the posterior regions almost 75% of the time. Fixedprostheses cantilevered from anterior implants gain bone in the posteriorregions more than 80% of the time (right side of graph).

Figure -2 : complete arch implant fixed prosthesis may behybrid, with denture teeth and acrylic joined to a metal substructure.

Advantages

* Psychological: "feels like teeth”.

* Less prosthetic maintenance

(e.g., attachments, relines, new overdenture).

*Less food entrapment.

* Posterior mandibular bone gain.

* (Wright et al ,2002)

Posterior mandibular bone loss

Nearly all of the bone growth occurredduring the first year of function.

The role:-Maintenance and even regenerationof posterior bone in the mandible. -Because posterior bone loss in this region may lead to paresthasia and even mandibular body fracture ..

Implant Overdentures

Cantilevered fixed prostheses from anterior implants

Force factors

Include:

*Parafunction.

*Crown height.

* Masticatory dynamics.

* Bone density of the implanted regions.

should modify the implant

*Position Implant Number Size Design

Force factors contribute to:1-Uncemented restorations. 2- Screw loosening.3- Component fracture . 4- Crestal bone loss.

Force factors

Parafunction

*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 prosthesis.(bilateral splinting).

So : the number of implants required to restore a fixed prosthesis may be similar to a fully implant-supported overdenture.

MANDIBULAR DYNAMICS

*Medial Movement

*Torsion

MANDIBULAR DYNAMICS

MEDIAL MOVEMENT

*Medial convergence Masticatory muscles

Stable. Movement toward medline on opening

Distal to foraminae

Between mental Foraminae

Attachment of internal pterygoid muscle on the medial surface of mandible

*MANDIBULAR DYNAMICS

Medial Movement

Distortion

Mouth opening, Max.in Protrusive movement

28% or 12 mm mouth opening

*Amount of movement varies Density & volume

Of bone &site of

question

*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.

depend on

Medial Movement Distortion

MANDIBULAR DYNAMICS

Torsion*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.

*MANDIBULAR DYNAMICS

• Jaw flexure is a primary cause of posterior implant loss in full arch mandibular prostheses.(Miyamoto et al,2003).

• Body of the mandible flexes more when the size of the bone decreases.

*Bilateral rigid post. mandibular splinting in a full-arch restoration are subject to a considerable buccolingual force on opening and during parafunction.

*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

*Mandibular dynamics

full-arch splinted restorations joining bilateral molar implants in the mandible should not be a tx. of choice??

*Consequences :

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 the mandible:

Implants placed in front of the foraminae and splinted

together

Implants in one posterior quadrant joined to anterior implants

*MANDIBULAR DYNAMICS

• 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 size .

(Reddy et al, 2002 ; Wright et al , 2002).

IMPLANT TREATMENT OPTIONS FOR

FIXED RESTORATIONS

*IMPLANT TREATMENT OPTIONS FOR

FIXED RESTORATIONS

*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 teeth.

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"

Treatment Option 1: The Branemark Approach

*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: The Branemark Approach

*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.

* Treatment Option 1: The Branemark Approach

*Tx. option 1 depends greatly on patient force factors, arch form, and the number, size, and design of the implants.

* indications:

1. Patients with low force factors.

2. Old female wearing an upper denture, with abundant anterior bone.

3. crown height inferior to 15 mm .

4. Tapered or ovoid mandibular arch.

5. Posterior Segments of inadequate height for endosteal implant placement.

IMPLANT TREATMENT OPTIONS FOR

FIXED RESTORATIONS

Treatment Option 2 : Additional implants above the mental foraraminae, because the mandible flexes distal to the foramen.

*Avantages:

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.

IMPLANT TREATMENT OPTIONS FORFIXED RESTORATIONS

Treatment option-3

*Implants in one posterior section may be splinted to anterior implants.(5-7 implants).

*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.

* Treatment option -3

*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.

IMPLANT TREATMENT OPTIONS FORFIXED RESTORATIONS

Treatment option-1 Treatment option-2

Treatment option-3

IMPLANT TREATMENT

OPTIONS FOR FIXED RESTORATIONS

Treatment option-4

*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.

Indications:

*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.

Treatment option-4

Advantages :

*Primary advantage is the elimination of cantilevers.As a result, risks of uncemented restorations and occlusal overload are reduced.

*The prosthesis has two segments .(installation &repair)

Disadvantages:

*Need for abundant bone in both mand. Post. regions .(not like tx 5)

* Additional costs(need of 1-4 add. Implants).

IMPLANT TREATMENT OPTIONS FOR FIXED RESTORATIONS

*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.

IMPLANT TREATMENT OPTIONS FOR FIXED RESTORATIONS

Indications: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.

IMPLANT TREATMENT OPTIONS FOR FIXED RESTORATIONS

*Treatment option -5

*Disadvantages:

*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 .

IMPLANT TREATMENT OPTIONS FOR FIXED RESTORATIONS

IMPLANT TREATMENT OPTIONS FORFIXED RESTORATIONS