Principles of tooth preparation Flashcards

1
Q

What is an indirect restoration? ๐Ÿงฑ๐Ÿฆท

A

An indirect restoration is a dental restoration thatโ€™s fabricated outside the mouth ๐Ÿ› ๏ธ โ€” either in a dental lab or via CAD/CAM โ€” and then cemented or bonded to the tooth. Examples include:

Crowns ๐Ÿ‘‘
Veneers ๐Ÿ’…
Inlays/Onlays ๐Ÿงฉ
Implant-retained restorations โš™๏ธ

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2
Q

What are the steps involved in providing an indirect restoration? ๐Ÿ”„

A

Tooth preparation to create space ๐Ÿฆทโœ‚๏ธ
Impressions or scans ๐Ÿ“ธ
Lab work โ€“ cast models, wax-ups, fabrication ๐Ÿ—๏ธ
Try-in of the restoration ๐Ÿค“
Final cementation ๐Ÿช„

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3
Q

What are the advantages of indirect restorations? ๐Ÿ’Ž

A

โœ… Aesthetics โ€“ perfect shape, color, and alignment โœจ
โœ… Cuspal coverage โ€“ protects fractured/weakened teeth ๐Ÿ’ช
โœ… Restores function โ€“ chewing, speaking, occlusion ๐Ÿ—ฃ๏ธ๐Ÿฝ๏ธ
โœ… Stability โ€“ prevents drifting or over-eruption โš–๏ธ
โœ… Comfort โ€“ better fit, less irritation ๐Ÿ˜Š
โœ… Implants โ€“ essential for restoring implants ๐Ÿ› ๏ธ๐Ÿฆท

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4
Q

What are the disadvantages of indirect restorations? ๐Ÿ˜ฉ

A

โš ๏ธ Multiple appointments ๐Ÿ—“๏ธ
โš ๏ธ Higher cost ๐Ÿ’ธ
โš ๏ธ Longer chair time โฐ
โš ๏ธ Involves more professionals ๐Ÿ‘ฉโ€โš•๏ธ๐Ÿ‘จโ€๐Ÿ”ฌ
โš ๏ธ Technically sensitive ๐Ÿ”ฌ

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5
Q

Why do we prepare the tooth before an indirect restoration? ๐Ÿ”ง

A

To create space for the material (ceramic, metal, etc.) โœ‚๏ธ
To conform to the patientโ€™s occlusion ๐Ÿ‘„
To ensure path of insertion (no undercuts) ๐Ÿšช
To give the crown its ideal shape and fit ๐Ÿ“
To prevent high spots or occlusal interference โš™๏ธ

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6
Q

What happens if we donโ€™t prepare the tooth properly? ๐Ÿ˜ฌ

A

Crown will be too high ๐Ÿ”๏ธ
Patient may experience pain when biting ๐Ÿ˜ฃ
Crown may fracture ๐Ÿ’ฅ
Impression errors due to undercuts ๐Ÿ“‰
Risk of pulpal exposure if overprepared ๐Ÿ˜ฑ

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7
Q

What is the ideal taper or TOC (Total Occlusal Convergence) for a prep? ๐ŸงŠ๐Ÿ“

A

๐Ÿ”น 6โ€“12ยฐ is optimal
๐Ÿ”น Maintains retention and resistance
๐Ÿ”น Too much taper = less retention ๐Ÿ˜“
๐Ÿ”น Achieved by holding the bur parallel to the long axis of the tooth ๐Ÿชฅ

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8
Q

Why is retention and resistance important in indirect restorations? ๐ŸŽฏ

A

๐Ÿ”’ Retention = resists pulling off along path of insertion
๐Ÿ” Resistance = resists tipping or lateral forces
Both are crucial for keeping the crown securely seated during function!

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9
Q

What factors affect retention and resistance? ๐Ÿงฎ

A

โœ”๏ธ TOC (Taper)
โœ”๏ธ Height of the prep (minimum 3mm!) ๐Ÿ“
โœ”๏ธ Surface area โ€“ larger tooth = more retention ๐Ÿ”„
โœ”๏ธ Preparation design โ€“ grooves & boxes for extra resistance ๐Ÿงฉ
โœ”๏ธ Cement selection โ€“ active vs passive luting agents ๐Ÿงช

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10
Q

How does tooth height influence retention/resistance? ๐Ÿ“

A

๐Ÿ“ Minimum height = 3mm
๐Ÿฆท Taller teeth = more surface for bonding
๐Ÿงฑ Short preps may require grooves or boxes for stability
๐Ÿ’ฅ Short height = increased risk of crown dislodgement

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11
Q

What is the purpose of grooves or boxes in prep design? ๐Ÿงฉ

A

They increase resistance to torque or lateral forces ๐Ÿ”
๐Ÿ“Œ Grooves should be parallel to the path of insertion
โš ๏ธ Must be at least half a burโ€™s diameter to avoid filling with die spacer

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12
Q

What are the different crown materials used? ๐Ÿช™๐Ÿงฑ๐Ÿ’Ž

A

Metal-ceramic crowns (MCC) โ€“ strong + aesthetic
Gold crowns โ€“ kind to opposing dentition, durable
Non-precious metals โ€“ cheaper, still functional
All-ceramic crowns โ€“ best for aesthetics, but brittle

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13
Q

Why is structural durability important for a restoration? ๐Ÿฆพ

A

๐Ÿฆท It must withstand:

Occlusal forces ๐Ÿ’ช
Temperature changes ๐ŸŒก๏ธ
Moisture, pH & bacteria ๐ŸŒŠ๐Ÿฆ 
Poor durability = cracks, wear, failure ๐Ÿ’ฅ
๐Ÿงฑ Need enough thickness and correct prep to support the material!

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14
Q

What is marginal integrity, and why is it important? ๐Ÿ”

A

๐Ÿงผ A well-fitting margin:
โœ”๏ธ Prevents plaque accumulation
โœ”๏ธ Reduces cement washout ๐Ÿงด
โœ”๏ธ Protects against perio and caries ๐Ÿฆท๐Ÿฆ 
๐Ÿชš Should be placed on sound tooth structure, either supragingival or equigingival

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15
Q

What are the types of prep margins? โœ‚๏ธ

A

๐Ÿ”น Shoulder (horizontal) โ€“ common in MCC, needs โ‰ฅ1.2mm
๐Ÿ”น Knife edge (vertical) โ€“ thin metal, fades into tooth
๐Ÿ“ Finish line should follow the contour of gingiva and be in a healthy position

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16
Q

What are the biological considerations during tooth prep? ๐ŸŒฟ

A

๐Ÿง  Preserve periodontium โ€“ no bulky restorations
๐Ÿงผ Supragingival margins if possible (easier to clean)
๐Ÿฉธ Avoid violating biological width โ€“ can cause recession & inflammation
๐Ÿงฌ 1mm subgingival margins โ†‘ recession risk ร—2.65!
๐Ÿ›‘ Preserve pulp vitality โ€“ 1/5 teeth become non-vital after crown prep!

17
Q

What is biological width and why does it matter? ๐Ÿ“๐Ÿงฌ

A

The space between the base of the sulcus and the alveolar crest, needed for soft tissue health. Violating it can cause:

Chronic inflammation
Recession
Loss of attachment

18
Q

What if thereโ€™s not enough tooth structure above the gingiva? ๐Ÿงฑ

A

You may need crown lengthening surgery ๐Ÿฆท๐Ÿ”ช
๐Ÿ‘‰ Removes bone and repositions the gingiva more apically
๐Ÿ‘‰ Increases the height of clinical crown = better retention/resistance!

19
Q

What is the final principle in tooth preparation? ๐Ÿง‘โ€๐ŸŽจ

A

๐ŸŽจ Aesthetics!

Patient consent is key ๐Ÿ“
Material choice affects how much tooth you need to remove
MCC needs at least 1.2mm to allow for multiple material layers (metal, opaquer, ceramic)
Smooth, natural-looking results = happy patient! ๐Ÿ˜๐Ÿ’•

20
Q

What are the 7 principles of tooth preparation for indirect restorations?

A
  1. Preservation of tooth structure ๐Ÿ›ก๏ธ
  2. Retention and resistance ๐Ÿ”’
  3. Structural durability ๐Ÿงฑ
  4. Material
  5. Marginal integrity & position ๐ŸŽฏ
  6. Biological considerations: Preservation of the periodontium ๐ŸŒฟ Preservation of pulp tissue ๐Ÿ’“
  7. Aesthetics โœจ
21
Q

Why is preserving tooth structure during prep important?

A

Balances the need for material space with the goal of protecting the pulp and periodontium ๐Ÿง ๐Ÿซ€
Prevents weakening the tooth or exposing pulp โš ๏ธ
Under-preparation = bulbous, unaesthetic crowns or poor material thickness ๐Ÿ˜ฌ
Over-preparation = pulp exposure risk (๐Ÿ‘€ pink hue shining through = danger!)
โœ… Goal: Conserve as much healthy tooth as possible while making room for the restoration

22
Q

What is the difference between retention and resistance form in prep?

A

Retention โžก๏ธ Prevents crown removal along the path of insertion ๐Ÿงฒ
Resistance โžก๏ธ Prevents dislodgement by lateral or apical forces during function ๐Ÿ›‘
Influenced by:
Taper of the walls: ideal 6โ€“12ยฐ convergence ๐Ÿ“
Surface area: More contact = better grip โœŠ
Prep height: โ‰ฅ3mm for good retention โฌ†๏ธ
Prep design: grooves/boxes = more stability ๐Ÿ“ฆ
Cement selection: type & technique matter ๐Ÿงช

23
Q

Why is structural durability critical in indirect restorations?

A

Restoration must survive occlusal forces, temperature, pH changes, and moisture ๐Ÿ’ฅ๐ŸŒก๏ธ
If thereโ€™s inadequate reduction, the material (e.g., ceramic or metal) could be too thin โ†’ cracks or perforation ๐Ÿ˜ต
Need enough bulk in functional areas (e.g., cusps) to ensure long-term survival ๐Ÿ”ง
โœ… Reduce tooth following natural contours & planes = better strength & fit! ๐Ÿฆท๐Ÿงฉ

24
Q

Whatโ€™s the role of margin design and position in prep?

A

Accurate margins = better fit, less cement exposure, fewer plaque traps ๐Ÿ’ฅ
Shoulder margins (horizontal) = great for ceramic/porcelain-fused-to-metal ๐Ÿฆท
Knife-edge/Chamfer (vertical) = good for metal ๐Ÿ’ซ
Margins should be:
On sound tooth ๐Ÿงฑ
Equi-/supra-gingival if possible for hygiene ๐Ÿงผ
Smooth and continuous ๐ŸŽฏ
Incorrect margins = bulky restorations, open margins, or increased caries risk ๐Ÿฆ 

25
Q

How do you protect the periodontium during prep?

A

Aim for supragingival margins when possible ๐ŸŒธ
Avoid bulky restorations that lead to plaque accumulation ๐Ÿฆ 
Consider biological width: distance from sulcus to bone (2-3 mm) โ€“ donโ€™t violate it! ๐Ÿšซ
If crown height is insufficient โžก๏ธ consider crown lengthening surgery โœ‚๏ธ๐Ÿฆท
Soft tissue management (e.g., retraction cords for impressions) is crucial ๐Ÿงต

26
Q

How can prep affect pulp health?

A

Over-prep or excessive heat can cause pulpal trauma ๐Ÿฅต
1 in 5 crowned teeth become non-vital ๐Ÿ˜จ
Follow natural tooth contours and use coolant spray to avoid thermal damage ๐Ÿ’ฆ
Get informed consent from patients โ€” they must know the risk of possible RCT later ๐Ÿ“œ๐Ÿง 

27
Q

What aesthetic factors are considered during tooth prep?

A

Especially important for ceramic restorations in visible areas ๐Ÿ˜
Requires 1.2โ€“2mm reduction to accommodate layering of materials (ceramic, opaquer, metal etc.) ๐ŸŽจ
Contour and translucency of final crown depend on prep accuracy ๐Ÿ”
Margin placement and symmetry affect final look ๐Ÿ”
Discuss shade, material, and limitations with the patient โœ