OVER DENTURES

DEFINITIONDentures which derive support from one

or more abutment teeth by completely enclosing them beneath the fitting

surface i.e. dentures that covers the roots and utilize them for support

The roots of teeth unsuitable for use as abutment for a removable partial denture may be employed

Loss of supporting bone causes the crown: root to become increasingly unfavorable

A dramatic improvement in crown: root ratio is achieved by reducing the crowns to 1 or 2mm above the gingival margins, which vastly reduces the lateral leverage on the remaining root

May be complete or partial

ADVANTAGES Preservation of remaining alveolar

bone around the retained roots Greater retention and stability of the

denture Sensory feedback from periodontal membrane. The sensory and propioceptive feedback from the

retained periodontal membrane is of great importance

It aids in pt`s recognition ofi. Jaw positionii. Food textureiii. Muscle force used in mastication Greater masticatory force is possible Retaining devices can be attached to

the remaining roots by means of a post. The male attachment (patrices) joins female counterpart (matrices) within the body of the denture

Reduction of psychological trauma

DISADVANTAGES More clinical time and expenses Difficult time consuming endodontic

may be necessary Patient must have good oral hygiene

otherwise the roots will be lost due to carries and periodontal diseases

Increased labial or buccal fullness around retained roots due to lack of resorption

To avoid excessive bulk in region of retained tooth, denture base may need to be thinned, which increases the like hood of #

Increased masticatory loads and often smaller inter-ridge distance may predispose to denture #. This problem can be helped by using high impact resins or metal alloys in the denture

More frequent maintenance visits

INDICATIONS A complete denture opposed by natural

teeth b/c alignment of occlusal plane can make occlusal balance difficult

Cleft lip palates Hypodontia Extreme attrition Potentially difficult lower CD Bruxists

PATIENT SELECTION General health e.g. vavular diseases adversely affects the prescription of

endodontic treatment Cooperation of pt Attitude of pt, especially regarding tooth

loss Periodontal state of potential abutment Sufficient inter-arch space, critical if

attachments are used

CHOOSING THE ABUTMENT TEETH Ideally: bilateral, symmetrical with a

minimum of one tooth space b/w them Order of preference: canines ,molars ,

premolars, incisors Healthy attached gingiva, adequate

periodontal support (>1/2 root in bone), and no or limited mobility

Is RCT required or not

PREPARATION OF ABUTMENT TEETH Removal of undercuts Preparation of crown for

thimble/telescopic gold coping RCT, tooth cut to dome shape and

access cavity restored with amalgam RCT and gold coping over root face RCT and precision attachment (bar,

magnets, stud/anchor

CLINICAL METHODS The retained tooth is root treated If carries is unlikely to occur, the root

face is prepared so that 2mm projects from the ging. margin and the root face is left bare, apart from the restoration required to seal off the root canal filling

If carries is likely, a coping is necessary,(made of cast gold)

Often in older pts the root will not need to be devitalized b/c of sec dentine

Two clinical methods are used1) After abutments have been prepared

and stoned to ging. level, impression are taken and denture made using routine procedure

2) The teeth are root treated but not stoned to the level of ging. The denture are then made as for immediate replacement.

The clinician reduces the height of the prospective abutment on the master castto about 4mm above the gingiva.

On completion of the denture, the teeth are reduced in the mouth and denture fitted as accurately as possible.

Cold cure acrylic is then placed on the fitting surface of the denture in the recesses which corresponds to the abutments

Venting holes having been cut right through to the polished surfaces

When set the resin is trimmed away and the final fit of the denture checked with disclosing paste

MAINTAINENCE Abutments are examined at 6 months

interval Pt is instructed to brush over the

abutments twice a day. Topical fluoride in the form of toothpaste should be applied once a day using denture as applicator

Denture must be kept clean. An inter-space brush must be used to clean the recesses on fitting surface

The denture should not be worn at night

THANK YOU