Dr. Mahmoud Ramadan

Rem. Prosthodontics502

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Dr. Mahmoud Ramadan

Precision Attachments Used for Over-denture

♥ The shape& size of the inner copings or root surface preparations will decide the retention& stability to be gained by Over-denture.

♥ Preparations depend on the vertical& bucco-lingual space available with loads that can be safely withstood by the roots.

→ 3 categories of preparation may be considered -: 1 -The thimble-shaped coping.

2 -The domed coping.3 -The use of attachments.

1 -Thimble-shaped copings-:→ It may be placed on vital abutments.

→ Miller termed these abutment preparations "biologic stabilizers". He pointed out that even if the short life of the teeth, they might lend in helping the pt. become accustomed to denture wearing.

→ There is an evidence of lessened resorption of the ridge tissues as none of the dentures had required refitting.

→ The technique required preparation for Full jacket crowns-:a- shoulder finish line.b- occlusal portion should be rounded or parabolic in form.

→ The basic principals in Full crown preparation-:a- Occluso-gingival reduction of clinical crown to provide advantage of periodontal support.b- Reduction of the axial surfaces to provide sufficient space for esthetic placement of denture teeth of proper size& contour.

→ the occlusal surface is covered with gold casting so that, the loads of occlusion would only be directed along the long axis of the abutment teeth.

→ In case of restricted space, it is wiser to limit height of preparations to around 4mm. (the walls of preparation must be parallel sided, otherwise a retaining post will be required).

→ Inner copings cemented to the teeth need to be made of gold.

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Dr. Mahmoud Ramadan

→ The outer copings forming part of the denture can be constructed in metal or resin.

→ Schweitzer has claimed the advantages for resien outer copings-:a) The degree of stabilization& retention can be controlled by the operator during denture insertion.b) Closely spaced teeth may interfere with placement of two layers of metal copings.c) Occlusal difficulties arise in seating the denture in the mouth over the inner coping.

→ Resien copings should not be used without a labial flange due to strength& retention considerations .

☺ Disadvantages-:1 -Space considerations often require devitalization of the abutment teeth. (root

canal treatment allows for great flexibility of treatment).2 -occupy considerable vertical& bucco-lingual space.

3 -coping must be covered with an adequate thickness of denture base material& facing to-:

a) Withstand loads& prevent breakage.b) Provide a satisfactory appearance.

4 -The retention obtained from Over-denture will vary inversely with the taper of the coping.

☺ Indications-:1 -Pt. with partial anodontia.

2 -Enough inter-ridge space is available.

2 -Dome-shaped copings-: *Indications-:

1 -Relatively small lateral loads applied to the roots.2 -Where the root support nor vertical space permits the use of thimble copings or

attachments.

→ Cutting root filled teeth down& preparing dome-shaped copings to extend only 1 or 2mm above the ridge crest will produce-:

a) Very significant improvement in the crown-root ratio.b) Lateral load are reduced.c) The space occupied is at a minimum.

→ The roots are being used to give support against vertical loads, their contribution to retention will be negligible.

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Dr. Mahmoud Ramadan

→ Denture stability depends on-:a) Number& distribution of the roots.b) The adaptation of the denture to the root preparation.

→ Silver amalgam restorations are placed to seal the occlusal surface of the root canal and the tooth surface& restoration polished.

→ A gold coping with short retaining post is applied only when the acceptable contour of the tooth surface can't be obtained.

→ The absence of a coping simplifies the construction but topical application of a 2% sodium fluoride containing solution is recommended.

3 -The use of attachment-:

→ Like Stud attachments, magnets, bar attachments.→ Attachments provide considerable retention& stability.

→ the space required is normally midway between the thimble copings& the extremely short dome shaped preparations.

→ the design& shape of attachments provide a significant measure of retention& stability of over-denture.

→ Adequate level of bone around the root is required to say nothing of sufficient space within the over-denture to accommodate he opposite section of the attachment and still provide enough strength for the denture base.

→ Warren& Caputo felt that load distribution to the abutments might not be so favorable when applied through attachments as with tapered copings.

→ Attachments not only require precise location between the various components but may place additional forces on their retaining posts.

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Dr. Mahmoud Ramadan

Diagram to show the vertical space requirements for the 3 types of root preparation

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