MANDIBULAR IMPLANT OVERDENTURES

PRESENTERHARISH.V.SFINAL yr PG

CONTENTSINTRODUCTIONTERMINOLOGIESINDICATIONS FOR OVERDENTURECONTRAINDICATIONSADVANTAGES OF OVERDENTUREDISADVANTAGECLASSIFICATION OF IMPLANT OVERDENTUREDIAGNOSISIMPLANT SITE SELECTION IN MANDIBLEATTACHMENTS IN OVERDENTUREPROSTHESIS MOVEMENTTREATMENT OPTIONSREFERENCES

INTRODUCTION

INTRODUCTION

David R. Burns, Mandibular Implant Overdenture Treatment: Consensus and Controversy; J Prosthod 2000;9:37-46.

TERMINOLOGIESOVERDENTURE- Any removable dental prosthesis that

covers and rests on one or more remaining natural teeth, the roots of natural teeth, and/or dental implants; also called overlay denture, overlay prosthesis, superimposed prosthesis

PATRIX - the extension of a dental attachment system that fits into the matrix

MATRIX - the portion of an attachment system that receives the patrix

ATTACHMENT – 1: A mechanical device for the fixation, retention, and

stabilization of a prosthesis 2: A retainer consisting of a metal receptacle and a closely

fitting part

INDICATIONS: To reduces resorption of the ridge Presence of tori which precludes conventional

dentures Unfavourable muscle attachments Young edentulous patients Patient desire for implant treatment. Systemic health status, which permits a minor

surgical procedures. Patient willingness and ability to maintain oral

health status. Patients, who psychologically, cannot tolerate a

full lower denture. Where extremely sharp mylohyoid ridges exist

that cannot be easily and surgically corrected.

CONTRAINDICATIONSResidual ridge dimensions do not accommodate

preferred implant dimensions.General health conditions preclude a minor surgical

intervention. Immunosuppressive therapy, prolonged intake of

antibiotics or corticosteroids, or brittle meta bolic disease history.

Communication with patient is not possible because of his or her compromised cogni tive skills.

ADVANTAGES

Improved aesthetics and stabilityProvides stable occlusionImproves psychological acceptance towards the

treatment.

DISADVANTAGELong-term maintenanceFood impaction

CLASSIFICATION OF IMPLANT SUPPORTED PROSTHESIS

19

89 CARL.E.MISCH

5 TYPES

19

99 CLEPPER

4 TYPES

MISCH’S CLASSIFICATION

FP-1 FP-2 FP-3

RP-4 RP-5

CLEPPER’S CLASSIFICATION

Type I overdentures is a tissue-supported overdentures retaiined by freestanding implants.

The Type II overdentures can be supported by a straight, round bar with clips in the overdentures. The straight, round bar provides an axis of rotation with the type II overdentures.

CLEPPER’S CLASSIFICATIONThe Type III overdentures

are supported by a bar with distal rotational attachments and a midline clip attachment.

The Type IV overdentures are supported completely by the bar and implants.

DIAGNOSISGeorge Bernard Shaw – “worst disease is the wrong

diagnosis”Mandibule – fixed or removable ?With overdenture, support is obatained from both implant

and tissue depending on number of implants,Zitzmann and Marinello described a detail parameters that

need to be evaluated – bone quality & quantity, facial support, mucosa, aesthetic demands etc.

Good facial support –

Poor facial support -

Lip supportShort lip / high smile line –

Long lip / decreased mobilty -

INTRAORAL EXAMINATION MucosaBone

QualityQuantity

Muscle attachmentBony exostosis

BONE QUANTITY AND QUALITYTooth loss – limited bone – far from

original position – biomechanical disadvantage.

Visual examination with and without denture

CT scan

LEKHOLM AND ZARB CLASSIFICATIONShape – five types

A to E – minimal resorption to severeQuality

LINKOW AND CHERCHEVE CLASSIFICATION OF BONE DENSITY3 categories in 1970Class I – ideal bone consisting of evenly spaced

trabeculae with small cancellated spacesClass II – bone has slighty larger cancellated

spaces with less uniformity of trabecular patternClass III – Large marrow-filled spaces exist

between bone trabeculae.

MISCH BONE DENSITY CLASSIFICATION:

AVAILABLE BONEThe available bone is classified into following

divisions:Division ADivision BDivision CDivision D

DIVISION A BONEWidth ≥ 5mmHeight ≥ 12mmLength ≥ 7mmImplant angulation ≤ 30

degrees between occlusal plane and implant long axis

Crown-height ≤ 15mm(high profile attachments like O-ring are contraindicated)

DIVISION B BONEWidth – 2.5-5mm (B+ 4-5mm, B-w

2.5-4mm)Height ≥ 12mm(with

augmentation can be converted to Div-A)

Length ≥ 6mm Implant angulation ≤ 20

degrees(due to smaller dia implant)

Crown-height ≤ 15mm (crestal bone might require osteoplasty to improve crown height)

DIVISION BTREATMENT OPTION:

Grafted ridge wil result in FP-1 or FP-3 prosthesis,

whereas osteoplasty results in FP-2,FP-3 or RP-4.

DIVISION C BONEWidth 0-2.5mm (C-w

bone)Height ≤ 12mm (C- h

bone)Implant angulation ≥ 30

degree (C-a bone)Crown height ≥ 15mm

DIVISION CTREATMENT OPTIONS:

osteoplasty for C-w bone, Sub periosteal implants for (C-h and C-a bone)

and Ramus blade implants/ transosteal implants for

c-h completely edentulous mandible. RP-4 and RP-5 are ideal treatment options, FP-2

or FP-3 incase of partially edentulous.

DIVISION D BONESevere atrophyFlat Maxilla & Pencil thin

mandible≥ 20mm crown height.The only treatment option

for Division D is grafting.

MANDIBULAR IMPLANT SITE SELECTION

OVERDENTURE ATTACHMENTSIntra coronal / Extra coronal attachmentsResilient / Non-Resilient attachments

INTRACORONAL ATTACHMENTSZest anchor locatorsGinta attachments

EXTRACORONAL ATTACHMENTSStud attachmentsBar attchmentsAuxillary attachments

STUD ATTACHMENTSGerberDalabonaCekaRothermanAncrofix

BAR ATTACHMENTHader barDolder barAndrew bar

PROSTHESIS MOVEMENTPM-0 : The prosthesis does not move in

functionPM-2 : A prosthesis with hinge movement, i.e

in two direction facial & lingual.PM-3 : A prosthesis that moves in three

planes, facial, lingual and apical.PM-4 : A prosthesis that moves in four

directions. PM-6 : A prosthesis that moves in all

directions.

OVERDENTURE TREATMENT OPTIONFive optionsImplant retained to Implant supportedTo reduce risk of failures

OD-1: cost is of primary concern if only retention of existing denture is poor. Bone volume should be abundant (Div A or B) Posterior ridge form should be an inverted U shape with high

parallel walls Two independent implants are placed in B & D position with equal

distance from the midline, at the same occlusal height O-ring attachment is used

OD-1

OD-1:Advantage:

Cost effectiveExisting denture can be rebased with the

attachment componentsHygiene maintenance is easy

OD-1Disadvantages:

Poor implant support and stability compared to other options ( rigid connections with bar).

Jemt et al in 1996, demonstrated decrease in occlusal forces in splinted implants with bar attachment)

No reduction in posterior bone loss due to placement of only two implants anteriorly.

Frequent prosthetic maintenance like relining and change of attachments.

If the positioning of independent implants are not proper ,complication of failure of implant or attachment is more likely.

OD-1:Patient selection criteria:

Cost is primary factorGood anatomic factorsPatient’s needs and desire are lessAdditional implant placement in near future

OD-2:Most commonly used option than OD-1Two implants are placed in B and D position

which are splinted together with a metal superstructure without any distal cantilever.

Dolder in 1961, presented that reduced loading forces are exerted on two anterior implants when splinted with bar compared with individual implants.

Usually splinted implants are not advisable in A and E positions because as the distance increase, the flexibility of the metal bar increases.

OD-2

OD-2:B&D Vs A&E:

Increased flexibility of superstructure (9 times more than B&D positions)

When attachments with retentive clips are used on a curved bar on A & E, the clips are placed in different planes and it prevents movements, which generates more lateral load on implants.

Straight bars cannot be used to splint A & E because it will create excessive lingual projection.

Bite force is higher than for B and D position, because of splinting the forces on posterior region is greater.

OD-2:Patient selection criteria:

Anatomical conditions are good to excellentPosterior ridge form is good providing good

support and stabilityWhen retention is the only problem in old

prosthesis

OD-3:Three implants are placed in

A,C and E positions and are splinted with bar

No distal cantilever is givenThis option reduces the flexure

by 6 folds.Greater surface area of implant

to bone allows better force distribution.

 

OD-3:Advantage of A,C,E splint

Six times less bar flexure compared to A & E positionLess screw looseningLess stress to each implant due to better stress distribution

over greater surface areaHalf the moment force compared to A & E positionsA-P spread between the C-implant and A,E is more which

provides greater biomechanical stability.Rotation of the prosthesis may be more limited compared to

OD-1 and 2.When the patient has poor posterior ridge form Div (C-h),

implants are given in B,C & D position splinted with bar. This option allows greater posterior movement of the prosthesis and reduces load on implants.

OD-3:Patient selection criteria:

Usually the first option Patient needs and desires about retention is more Improved retention, support and stability Anatomic conditions are good Posterior ridge form is good – moderate.

OD-3

OD-4 Here four implants are placed in A,B,D & E positions These implants usually provide sufficient support to include a distal

cantilever upto 10mm on each side if the stress factors are low. Additional implant support, biomechanical advantage and less

undesirable forces. The distal cantilever magnifies the occlusal load which is

proportional to its length The moment forces is resisted by the length of the bar anterior to

the fulcrum.

OD-4:According to the arch form the A-P spread changes, square

form limits the A-P spread and cannot tolerate a distal cantilever. In tapering arch form the A-P spread is usually 10mm and it can withstand 10mm distal cantilever, whereas ovoid is most common, which allows a A-P spread of 8mm hence cantilever may be upto 8mm distally.

OD-4Other factor which influence the length of cantilever is that

as the occlusal forces increases the length of the cantilever decreases.

Under ideal conditions with low occlusal stresses the cantilever may be extended upto 1.5 times the A-P spread for OD-4 overdentures.

OD-4:Patient selection criteria:

Moderate to poor posterior anatomyLack of retention and stabilitySpeech difficultyMore demanding patient type.

OD-5:This is a minimum treatment option for patient with

moderate to severe problems with traditional denture. In this option 5 implants are placed in A,B,C,D & E positions. The superstructure is cantilevered distally a maximum of 2.5

times the A-P spread.Last teeth does not extend beyond the bar/ molar region.Under ideal conditions RP-4 is the treatment option.

REFERENCES:Carl.E.Misch, Dental Implant Prosthetics.Allen A.Brewer, Overdentures, 2nd edition.Treatment planning of the edentulous mandible, W. Chee

and S. Jivraj; British Dental Journal 2006; 201: 337-347George A.Zarb, Implant supported prostheses for

edentulous patients, Prosthodontic Treatment for Edentulous patients, 12th edition.

Steven J. Sadowsky, Mandibular implant-retained overdentures: A literature review, J Prosthet Dent 2001;86:468-73

Alfred H.Greering, Complete and Overdenture Prosthetics,1993.

REFERENCES:Harold.W.Prieskel, Overdentures made easy.David R. Burns Mandibular Implant

Overdenture Treatment:Consensus and Controversy; J Prosthod 2000;9:37-46

Sarah Enright ,Treatment of edentulous patients using implant supported mandibular overdentures improves quality of life, TSMJ vol.8, 2007.