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prostho
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Factors that govern the clinical decision on type of prosthesis
• Dental factors:– Abutment teeth present– No. of teeth lost– Position– Periodontal consideration– Conservation– Toot treatment required– Quality of bone and ridge– Presence of any pathology– Occlusion
• Canine guided-group function• Opposing teeth
Factors that govern the clinical decision on type of prosthesis
• Patients’ factors– Wishes and expectations– Age– Medical conditions– Social factors
• Smoking • Alcohol • cost
Principles of tooth preparation
• Biological:– Conservative– Supra-gingival margins– Correct contours– Tooth protection from fracture
Principles of tooth preparation
• Mechanical:– Retention– Resistance performance– Resistance to deformation
Principles of tooth preparation
• Aesthetic– Adequate thickness of porcelain– No metal– Colour matching
Check list prior to clinical bridge procedure
• All preparatory conservative work completed• Good plaque control /periodontal condition• Abutments tested for vitality• Relevant radiographs• Occlusion assessed• Diagnostic wax up• Selection of abutments• Trial preparations on mounted casts• Design• Integrate design to existing /anticipated treatment
needs
Meta-analysis
• Conventional bridge survival rate• At 5 years recall : 4-5 % failure• 15 years recall : 25-30 %• Loosening-recurrent caries
Fibre – reinforced composite bridge
• Well suited to single visit immediate tooth replacement
• Improved aesthetics• Long term provisional• Suitable for young and elderly• Wear is kind• Low treatment costs• Readily repaired
• Resin bonded bridges• Are the best treatment option for many cases• Meta analysis: 4 years survival rate -> 25% • Appropriate case selection -> 10 years recall ->
90% success rate
Requirements for RBB’s
• Space for aesthetics pontics• Sufficient area of surface enamel -> bonding• Abutments -> unrestored +sound • Occlusion favourable• Rubber dam
Hybrid bridge
• Sound abutment on one end & heavily restored on the other
• Resin bonded retainer + conventional bridge retainer
• Common problem after many years: debonding on the resin retained side and patient ignorance -> caries
Pontics : optimal design• Biological:
– No presurre on the ridge– Tissue surface cleansable– Access to abutments
• Mechanical:– Rigid – Strong– Correct framework design
• Aethetic– Shade matched– Appear to ‘grow out’– Porcelain bulk
Pontics : types
• Saddle X• Modified ridge lap • Mandible: hygienic, wash through or sanitary
pontic(non-ceramic)• Anterior region ->ceramic• Posterior region-> Gold
Occlusal considerations
• Group function• Canine guided• ICP• Retruded contact position• Centric stops
• Functional occlusion: smooth gliding movements without interferences
• Balanced occlusion: contacts on working and non-working side
Ante’s Law
States that the total periodontal membrane area of the abutment teeth should be equal to or exceeds the teeth to be replaced
UK-> Non-applicable
Ante’s law has no specific bases & no longer has place in contemporary bridge work design, it doesn’t take into account that we are dealing with a biological system
As the load is high on the abutment teeth a biological feedback mechanism operates to cause reduction in this load
All ceramic crown
• Inceram• Empress• Procera• Cerec systems
• High strength alumina core ceramic can be used as posterior bridge
Bridge failure
• Most common reasons:– Loss of retention– Mechanical failure # of the casting– Problems with the abutment teeth
Specific design problemsPeriodontally involved abutments
• First control periodontal disease.• Then ? • bridge indicated. Fixed-fixed type of design
preferable to splint teeth together.
Specific design problemsPier abutments
• This is the central abutment in a complex bridge that supports pontics on either side, which are in turn anchored to the terminal abutments.
• pier abutment can act as a fulcrum and when one part of the bridge is loaded the retainer at the other end experiences an unseating force which can lead to cementation failure.
• Solution :stress-breaking element must be introduced, e.g. fixed-movable joint, or avoid pier abutments by simplifying the design.
Specific design problemsTilted abutments
This occurs most commonly following loss of a molar. Solutions:• Orthodontic treatment to upright abutments.• Two-part bridge, e.g. fixed-movable.• Telescopic crowns-placement of individual gold shell crowns
on abutments, over which telescopic sleeves of bridge fit.• Partial veneer preparations in which pins or slots are
prepared to compensate for slight mal-alignment of abutments (least satisfactory).
• Precision attachments-a precision screw and screw tube can be incorporated into a two-part bridge. After cementation the screw is inserted, which effectively converts the bridge to a fixedfixed design.
Specific design problemsCanines
• The canine is often the keystone of the arch, and a very difficult tooth to replace.
• The adjacent teeth are poor in terms of the amount of retention and support that they offer and the canine is often subject to enormous stresses in lateral excursion (in a canine-guided occlusion).
• If a canine is to be replaced with a bridge the occlusal scheme should be designed to provide group function in lateral excursion-never canine guidance.
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