Revision P.2 Flashcards
Checking the fit of the crown
Visual:
1. Margins
2. Direct or with mirror
3. Magnification
Using instruments:
- Use explorer (Straight probe) – esp. if margins are subgingival
- Use the correct size tip and angle of approach
Where should the crown margins end
- It is better for the gingival health to place a crown margin supragingivally .
- For posterior teeth which are outside the aesthetic zone we aim for supragingival or equigingival margins in order to be able to monitor but also to maintain cleansable .
- In anterior teeth this is not often possible because of aesthetic considerations .
- The exception to this is in patients with low smile line that we may decide to keep the margins equigingival .
- Subgingival margins should only be 0.5mm within the gingival crevice otherwise there may be invasion of the biologic width .
- If we can not achieve parallelism between the abutment teeth we may choose to keep the margins supragingival .
Crown Margins
What is the general rule for anterior vs posterior teeth?
As a general rule for anterior teeth we aim for equigingival or 0.5mm subgingival crown margins, whereas for posterior teeth in the non aesthetic zone we aim for supragingival / equigingival margins. This can vary in patients with low smile lines.
Crown Margins
When would you consider to have a subgingival finish line?
- Improve aesthetics (Especially when preparing for PFM crowns in the aesthetic zones or ceramic veneers). Also important when teeth are discoloured .
- To access and remove root caries
- When there is a fracture that is extending subgingivally but the tooth is considered restorable
- To increase the amount of tooth structure when there is inadequate ferrule above the gingival margin
- To correct the zenith of a tooth
Evaluating the crown prior to cementation
- Proximal Contacts – use floss to check
- Marginal Fit – use an explorer to check
- Aesthetics – Check both shape and shade
- Occlusion – Check using GHM articulating paper
The order is important as if the proximal contacts are too tight then it will be impossible to assess the rest.
Options for replacing teeth
The Strategic Value of a tooth
- Aesthetic Impact
- Medical Impact
- Occlusal Impact
- Prosthodontic Impact
- Functional Impact
- Financial Impact
How would you assess the prognosis of a tooth
If a tooth is to be crowned or used as an abutment to support a bridge it needs to have favourable prognosis.
The following factors need to be considered:
1. Endodontic status – is it Root treated or does it need?/ Is the quality of the RCT adequate?
2. Periodontal status – is there active periodontal disease? / It there sufficient bone
3. Restorative status – Is there caries? Do you need to replace any existing fillings? / Decide if the existing restorations are adequate to be used as foundation restorations / Is there enough tooth structure left? Does it need a post and core?
4. Sometimes even consider the inclination of teeth and their position
The Strategic Value of a tooth
Apical Surgery - Strategically important teeth
- A tooth may be considered of strategic importance when it is an anterior tooth in a patient with a high lip line and thin soft tissues where implant success may be difficult to predict and achieve
- When the tooth is a terminal abutment where extraction would leave the patient with an unbounded saddle particularly if complicating factors for Ol e.g. lack of access, bone or poor anatomy
- financial and time limitations - e.g. NHS funding
Pontic Designs:
Which pontic to use where:
When would you use an ovate pontic?
- Most commonly used pontic.
- Especially used when offering an immediate prosthesis to replace an extracted tooth .
- The ovate pontic will help maintain the papilla .
Which pontic to use where:
When would you use a sanitary / hygienic pontic?
- Especially useful in implant dentistry following implant placement so that the pontic does not apply pressure on the healing cap or cover screw .
- Also allows easier cleaning .
Which pontic to use where:
When would you use a modified-ridge lap design?
When you want the pontic to look longer
