Veneers And RBBs

Question 1

Discuss the indications for the provision of veneers

Answer 1

Masking discolouration/intrinsic staining
Enamel hypoplasia
Changing shape of teeth
Reduce spacing/diastemas between teeth

Question 2

Veneers can be made out of

Answer 2

porcelain or laboratory cured (indirect) composite resin.

Question 3

Features of a veneer

Answer 3

Constructed in thin sections
Rely entirely on bonding to enamel for retention.
Heavily restored teeth, or where no enamel is available for bonding, are not suitable for porcelain veneering techniques.
Where there is extensive intrinsic staining, it is a good idea to undertake a vital bleaching procedure in the first instance to optomise the final cosmetic outcome.

Question 4

Clinical technique for preparing veneers

Answer 4

Very smooth preparation – rough edges act as stress concentration areas and may result in veneer fracture
Avoid guiding contacts on the incisal edge of the veneer. This can be achieved by finishing the veneer at the incisal edge.
Keep the margin supra-gingival
Prepare the mesial and distal margins to the contact point area such that the veneer can slide onto the tooth when bonded.
Use a try-in paste to check veneer fit. These are water soluble and can be washed off.
Isolate the teeth with rubber dam, place retraction cord in the gingival crevice (this will reduce the risk of the gingival crevicular fluid contaminating the bonding resin and marginal discolouration).
Etch and silanate the veneer fitting surface; etch, prime and bond the tooth; apply resin luting cement to the veneer.
Place cellulose strips between teeth, apply the veneer, remove excess resin, light cure.
When the resin has cured, use a hand scaler to remove excess set cement, polish the veneers with rubber composite polishing cones.

Question 5

Preparation guidelines/vital points/ key points for prepping veneers

Answer 5

The depth of preparation should be 0.5-0.75mm maximum.
Do not prepare into dentine.
It is vital to assess the quality of the bonding surface area.
Check the amount of enamel available for bonding.

Question 6

What materials can we use for constructing veneers

Answer 6

Composite resin:
Porcelain
IPSe.max

Question 7

About composite resin used for construction veneers

Answer 7

direct or indirect technique. Often used in younger patients when gingival margins have not fully matured.

Question 8

About porcelain used for constructing veneers

Answer 8

Feldspathic porcelain: ceramic material that is predominantly glassy. Excellent aesthetics that can mimic enamel and dentin. Low strength.
Pressed ceramics: restorations are formed into the desired shape by a process called heat pressing where molten ceramic flows in a mould and then solidifies. Material then stained and characterised to provide excellent aesthetics. Stronger materials than traditional porcelains.

Question 9

Not on LO: bonding veneers

Answer 9

Veneers must be bonded into place
Bonding of restorations allows a chemical bond between the fitting surface of the restoration and the tooth.
This will require suitable chemical treatment of both surfaces.
Bonding materials are resin based (e.g., Rely X, Panavia, Nexus)
It is essential that you follow the exact steps for the bonding process set out in the manufacturer’s instructions.
These materials are technique sensitive, and its vital that the exact materials and sequence of steps are flowed to ensure success.

Question 10

Recognise the features of a successful or failed treatment with veneers

Answer 10

-Assessment of the abutment tooth

-Occlusion

Question 11

About assessment of abutment tooth

Answer 11

Enamel is the key to success (bonding substrate)
Lack of enamel = lack of bonding

Question 12

About assessment of occlusion

Answer 12

Even contacts in ICP
Veneers cannot be involved in guidance movements
Check dynamic occlusion: before and after placing veneers
Use articulating paper

Question 13

A bit about resin bonded bridges: not in the LO

Answer 13

Simple yet effective option when considering the replacement of missing teeth.
Minimally invasive.
A cantilever design is favoured to reduce the amount of tooth preparation and to produce a more retrievable and successful restoration.
Current bridge designs use sandblasted, non-precious metal cemented with chemically active resin
Evidence illustrates that RBB placed using current techniques can achieve high success rates with survival of up to 87.7% reported after 5 years

Question 14

Indications for RBBs

Answer 14

Resin bonded bridges are indicated for short spans (single tooth)
The abutment teeth must be unrestored or very minimally restored
Rely almost entirely on bonding to enamel for retention.
Heavily restored teeth, or where no enamel is available for bonding, are not suitable for RBB.
Commonly used to manage hypodontia and restoration to a shortened dental arch (SDA).

Question 15

Case selection for RBBs not in LO just have a read

Answer 15

Restoration of missing teeth aims to improve oral function, aesthetics and restore occlusal stability.

However, intervention should be considered carefully it will always require a biological price

All patients should still be dentally motivated and caries and periodontal disease should be under control before embarking on any sort of fixed prosthodontics.

In addition, managing expectations with regard to aesthetic outcome and longevity should be considered an important part of treatment planning.

If expectations are unrealistic, patient satisfaction with the final result is likely to be low.

Question 16

Choosing the abutment teeth…

Answer 16

Clinical (and where necessary radiographic) investigations should be carried out to ensure endodontic and periodontal health.

Periodontal support should be assessed considering bone levels and root configuration.

The use of abutments with active periodontal disease is inappropriate.

It is vital that there is sufficient enamel available for bonding.

Heavily restored abutment teeth are not appropriate for resin bonding and small amalgam restorations should be replaced with resin composite.

The alignment or angulation of teeth also needs to be assessed as this may affect the degree to which a retainer / wing can be extended.

If periodontal support and coronal condition are favourable, any teeth can act as abutments over an appropriate span.

However, anterior teeth with long roots (central incisors and canines) and multi-rooted posterior teeth should be favoured.

Question 17

Discuss occlusion for RBBs not on LO

Answer 17

When planning RBBs, a detailed assessment of both the static and dynamic occlusion is crucial. This can be aided with the use of accurate, mounted study models and a diagnostic wax up.

It is vitally important that any pontic is not involved in guidance movements and simply acts as a light holding contact in ICP

Where there is insufficient interocclusal space the adjustment of opposing teeth could be considered.

Cementing the RBB retainer / wing high in the occlusion does not appear to increase the risk of debonding, however this technique should be used to make only modest and controlled changes to the occlusion.

Parafunctional forces increase the likelihood of restoration failure.

Where bruxism is suspected the prescription of RBB is contraindicated.

Question 18

Preparation for RBBs?
Retainer wing coverage and preparation

Answer 18

The surface area covered by an RBB retainer affects retention.
It is accepted that 180° wraparound retainers constitute the ideal design, but this must be balanced with the demand for aesthetics.
Retainers on posterior teeth may be extended to a proportion of the occlusal surface to increase the surface area and improve retention.
Preparation of the abutment tooth is minimal and confined entirely to enamel with a chamfered finishing line.
The margins should finish at least 1mm above the gingival margin, just short of the proximal contact point and fade out towards the incisal edge.
Occlusal support is gained in the anterior dentition by the placement of an occlusal rest seat in the cingulum area whilst in posterior teeth occlusal rest seats are placed on the mesial and distal marginal ridges.
Reduction of the axial walls of abutment teeth should allow for a single path of draw for the prosthesis.
If teeth are restored, small fillings should be replaced with fresh composite restorations, which will bond more favourably to the resin cement enhancing retention of the bridge.

Question 19

Retainer wing design?…

Answer 19

The metal used for construction of the bridge is Nickel-Chromium (NiCr) which should be sandblasted with 50μm alumina on the fitting surface by the laboratory.
Any flexing of the metal bridge retainer exerts stress on the cement lute that eventually leads to fatigue failure.
Base metal alloys are highly rigid and therefore can be used in thin section without risk of flexing, making them ideally suited for use in RBB retainers.
A minimum thickness of 0.7 mm should be stipulated in the technical prescription.
Maximal coverage of the palatal surface of the abutment tooth should also be stipulated.
A modified ridge lap pontic should be prescribed as this provides good aesthetics and facilitates maintenance of oral hygiene

Question 20

Cementation for RBBs

Answer 20

The bridgework is tried in the patient’s mouth to check fit prior to cementation.
After fit has been deemed satisfactory the fitting surface is again sandblasted chairside with 50μm alumina on the fitting surface.
Following sandblasting, care is taken to avoid contamination and the prosthesis is never retried on the stone model.
Panavia resin cement is used for bridge cementation and should be used strictly according to manufacturer’s instructions.
Rubber dam should be used where possible to provide optimal moisture control.
All excess cement should be removed before setting is complete.
The static and dynamic occlusion should be carefully checked using articulating paper with adjustments made to ensure that the pontic is not involved in guidance movements but instead acts only as a light holding contact in ICP.

Question 21

Dealing with failure

Answer 21

Biological reasons for failure include caries and periodontal disease but these occur relatively rarely.
The most common technical reason for RBB failure is debonding. If a bridge debonds there are two options: remake or recement. If a one off event such as trauma has resulted in decementation, recementing the restoration is appropriate.
However, once a bridge has debonded it is more likely to fail again and recementing for a second time is generally ill advised as replacing the bridge has been found to have a higher success rate. This is probably because in the majority of failed cases, there is an inherent problem with bridge design which may have been present at initial cementation and/or developed since. With this in mind, the restoration itself should be examined and the patient should be reassessed from an occlusal perspective.
If the decision is made to recement a RBB, the metal retainer should be cleaned and any cement residue removed carefully from the tooth using an ultrasonic scaler. The cementation protocol described above should then be used including sandblasting, moisture control and use of resin cement.