implant treatment options in mandible

8/13/2019 implant treatment options in mandible

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Presented by: Dr. Glareh Eblaghian

Supervised by: Dr. Mansour Rismanchian

and Dr. saied NosouhianDental of Implantology

Dental Implants Research Center

Isfahan university of medical science


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Over the last 15 years, many of completely edentulus mandibular

arches have been treated with implant overdentures

Many of these patients choose to have a removable prosthesis because

of financial consideretions

Advantages of maxillary supported removable prosthesis is:

upper lip support for aesthetic and daily maintanance

Labial flange of mandibular overdenture rarely is requred for aesthetic

For hybrid fix restoration and fully implant supported overdenture (RP4):

labratoary and component cost is simillar Chair time required is similar

But because dentures and partial dentures typically costseveral times less than fixed restorations, the doctor often

chareges half the fee for an implant denture


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1. Feeling and acting simillar to natural teeth2. Removable implant overdentures require greater maintenance and exhibit

more complications than fixed restorationsProblem of IODs in review of litrature by Goodacare:

Retention and adjestement problem(30%)

Clip or attachment fracture(17%)

Fracture of prosthesis (12%)

Reline(19%)

3. Mandibular overdenture often traps food below its flanges

the daily care for bar implant overdenture is similar to that for fixedmandibular restoration ( because ridge lap pontics are not required)4.Important role for the presence of complete implant supported restoration

is the maintenance and regeneration of posterior bone in mandible


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the amount of force transmitted to an implant fixed prosthesis is

similar to RP4 (then the number of implants to support either prosthesis

should be simillar)

For noctural parafunctional overload, patient is willing to remove the

maxillary denture at night

For patient with natural teeth or implants in the maxillary, more

implants usually are indicated for mandibular fix prosthesis

Force factores: parafunction, crown height, masticatory dynamics,bone density of implant region


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increased force factores contribute to

Uncemented restorations, screw loosening, component

fracture, crestal bone loss

Fixed prosthesis may required an improved

biomechanical position


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five different movement have been postulated (medial convergence is most

common):

Mandible between mental foraminae is stable

Distal to the foraminae , mandible exhibits movementtoward the midline on opening ( because of attachment of

internal ptrygoid)

distortion of the mandible occurs early in the opening cycle

maximum changes occure with as little as 28% opening (12mm)

Flexture also occure during protrusive movement

Amount of movement depends on densityand volume of bone and

location of the site


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Mandibular body flexture

to midline:

1500 micron in ramus toramus

800 micron in first molar tofirst molar


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In animal study: mandible twisted on working side and bent on balancingside in the parasagital plan during power stroke

in human study Using strain gauges on screws attached to

cortical bone

Using implant supported prosthesis

the torsion during parafunction is caused by contraction of masseter

muscle attachments

Posterior bone gain in edentulous patients restored with cantileveredprosthesis may be consequence of mandibular flexture and torsion

Becausebite force may increase 300% with an implant prosthesiscompared with denture stimulate posterior mandibular body to

increase size


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most common position of mental foramen is between the first and second

premolar mandibular dynamic should be consider in splinting

teeth distal to the bilateral premolar

The more distal the rigid splint from one side to other , thegreater the risk thet mandiblular dynamics may influencethe prognosis

The body of mandible flexes more when thesize of bone decreases (C-h or D A)


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Difference in movement between an implant and tooth:

natural tooth 28 micron movement apically

56-108 micron movement laterally

rigid implant 5 micron movement apically10-80 micron movement lateraly

Mandibular flexture and torsion may be more than 10-20 times

Flexture and torsion of mandibular body are morecritical

In the past , 4 implant in the mandible is thwarted by the prosthesis but this

introduces lateral stress to the implants


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Molar implants, screws and bone

have increase risk because ofmandibular flexture and torsion

Consequence of cross arch connection of posterior mandibular implants

loss of implant fixation

material fracture (implant or prosthesis)

unretained restorations

discomfort upon opening

JustImplants placed in front of foraminae and splinted together, orimplants in one posterior quadrantjoined to antrior implants have not

shownthese complication


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Therfore all edentulous mandibular patients should be given the

option of having fixed prosthesis

There are five treatment option used to restore a complete

edentulous mandible with fixed prosthesis or RP4 overdenture


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The mandible does not flex or exhibit significant torsion between mental

foraminae, soanterior implants may be splinted together

Branemark approach: placement of 4 or 6 anterior root form implant

between the mental foraminae and distal cantilever offeach side to

replace the posterior teeth

Result: 80% to 90% implant survival for 5 to 12 years after first year

84% success rate for 18 to 23 years

The anterior arch form + foraminae position , affects the position ofthe distal most implants

The anterior arch form (square, oval, tapered) is related to the anterior

most implant position


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The greater the A-P spread, the

further the distal cantilever may be

extended

The most common number of

implants used today in the

Branemark option is five

This number allows as great an A-P spred as six implants with greater

interimplant distance

If bone loss occurs on one implant, the loss whould not automatically

affect the adjacent implant sites

Genaral rule: for five anterior implants in the anterior mandiblebetween the foraminae the cantilever should not exceed 2.5 times the

A-P spread


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oIf the stress factors are high (

parafunction , crown height,

masticatory musculature dynamics,

opposing arch) , cantilevering may be

contraindicated

Length of the posterior cantilever

depends on the specific force factors ofthe patients

oThe area over which the forces are applied from the prosthesis to the

implant can be modified through the number, size, and design of the implant

oA cantilever rarely is indicated on three implants, even with a simillar A-P

spread as five implants

oNarrow implants are not designed to support cantilevers


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treatment option 1 depends greatly on patient force factors,archform, number, size and design of implants

The safest action: reserve this option for patients with low

force factors such as older female, wearing upper denture, abundant

anterior bone, crown height to 15mm , tapered or ovoid mandibular

arches


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A slight variation of the Branemark protocol to

place additional implants above the mental

foraminae


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Bone strain model of

flexture and torsion

in university of

Alabama

A slight variation of the

Branemark protocol isto place additional

implants above the

mental foraminae

Advantages:1. number of implants may be increased to as many as seven 2.A-

P spread for implant placement is greatly increased, even when the totalimplant number is 5

3.The length of the cantilever is reduced dramatically because the distalmost

implant is placed one tooth more distal


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A prerequisite available bone in height and width over theforaminae (because foraminae usually is located 12mm above the

inferior border of the mandible)

themost distal implant bears the greatest load when loads are

placed on the cantilever

A minimum recommended implant height of 9mm and a greater

diammeter of an enhanced surface area recommended

Key implant positions: second premolars, canines, centeralincisor or midline position


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One posterior segment connected to

anterior segment


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Misch has evaluated full-arch fixed prostheses on implants with one

posterior segment connected to the anterior region over the last decade

another treatment option to support a fixed mandibular prosthese

consist of additional implants in the first molar or second premolar,

connected to 4 or 5 implant between the mental foraminae


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The key implant position are: first molar (on one side), bilateral

premolar, bilateral canine

The secondary impalnt position are: second premolar on the same

side as the molar implant, central incisor (midline)

One pice casting can be fabricated and one cantilever to the oppositeside of the molar implant would replace those posterior teeth

When one or two implants are placed distal to the foraminae on one

side and joined to anterior implants, a considrable biomechanical

advantage is gained


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option 3 is a better option than anterior implants with

bilateral cantilevers

TheA-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 first molar

When force factors are greater , 6 or 7 implant may be usedfive implant between foraminae and one or two implant distal on one

side

this option requires available bone in at least one posterior region


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Bilateral implant that they are not splinted

together


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This option is selected :1. When force factors are great or the bone densityis poor

2. When the body of mandible is division C-h and subperiosteal or disc

like implants are used for posterior

Key implant positions: first molars, first premolars, canines

Secondary implant positions: second premolars and/or incisor


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al l implants in the anterior

and one posterior side are

splinted together for a 9-unit

fixed prostheses

The other posterior segment is

restored independently

Most often three implant are used for smaller segment to compensate

for force factores and the alignment of the implants almost in a straight line

advantages:1. Elimination of cantilever

2. risk of uncemented restorations and occlusal overload are reduced

3. prostheses has two segments rather than one


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4. Weaker cements can be used

5. If the prostheses requires repair, the affected segment may beremoved easily

Disadvantages need for abundant bone in both posterior region

additional cost

The restoration should

exhibit posterior disclusion

in excursions to limit lateral

loads, especially to the

prostheses supported by

fewer implants


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Three independent prostheses


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Key implant positions:1. Two first molars, two first premolars, two canines posterior

restoration extend from first molar to first premolar and anterior restoration

replaces the six anterior

Treatment option 4 is better

2. Two first molars , second premolars, first premolars, and both canines

Treatment option 5 is better


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posterior restorations are two independent implant prostheses unit

and anterior prosthesis extend from first premolar to first premolar

Advantages :

Smaller segments for individual restorations

Most flexibility and torsion of the mandible in greater body movement

(in parafunction and decrease in size of the body)

choice option when force factors are sever

Disadvantages:Greater number of implants required

Available bone needs are greatest in this option

Most common scenario for option 5 is when the posterior mandible is

C-H bone volume and a circumferential subperiostealor disc-design

Implant is used as the second premolar and first molar


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implant treatment options in mandible

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