52. Preparation junctions’ types. Partial crown – definition, types.

whats in it

require,ets of a prep junction/finishing line

types of finishing line

MARGIN finish

partial crown

types of partial crowns

advantages/disadvangtages

additional: CREATING ¾ CROWNS FOR INCISORS VS PREMOLARS/MOLARS (study on second round of essays)

require,ets of a prep junction/finishing line

• must be clear, smooth, well defined

• must lie on healthy tooth structure

types of finishing line

Types of finishing line:

1. Feathered edge – knife or chisel edge

2. Chamfer (quarter of a sphere or quarter of an ellipse): Chamfer with bevel

3. Shoulder:

• -  Butt shoulder

• -  Shoulder with bevel

• -  Radial shoulder. (BE SO REAL)

4. 135dc preparation junctio

margin finish

SBHC

SOME BALLS HAVE COME

adv and disadv

advantages:

:

- Saving tooth structure -

- Easy for finishing and polishing by the dentist and easy for cleaning by the patient.

- Safe for the periodontal tissue

- Easy for luting (cementing)

- Easy to adapt, because of the

visibility of the margins

- There is always an opportunity to

check the tooth vitality if necessary

Disadvantages

Poor retention in comparison to the

full anatomic crown, but still can be

used as a single crown, or as a

retainer for small FPD.

- It is not recommended as a retainer

for long FPDs, especially in the

distal area.

- Usually, there is a need of additional

retentive elements.

what is a partial crown. and types?

•  3⁄4 crown: is a partial coverage restoration that restores the occlusal surface(or incisal

  edge), and three axial surface of the clinical crown where the buccal or facial surface

  is not included

• -  Reversed 3⁄4 crown : is a partial coverage restoration that restores the occlusal

  surface(or incisal edge), and three axial surface of the clinical crown where the lingual

  surface is not included.

• -  Mesial 1⁄2 crown : is a partial coverage restoration that restores the occlusal

  surface(or incisal edge), the mesial surface and a portion of the facial or lingual

  surfaces.

• -  7/8 crown : is a partial coverage restoration that restores all surfaces of the clinical

  crown except the mesiobuccal cusp - used only for the maxillary first molar teeth.

¾ partial crown for premolars/molars prep as well as incisors

(unnecessary actually don’t learn)

🦷 3/4 Crown Prep – Premolars & Molars

1. Functional cusp reduction – 1.5 mm
2. Non-functional cusp reduction – 1.0 mm
3. Occlusal reduction – with a 45° phase using a conical bur
4. Axial reduction – start from lingual with a torpedo bur
5. Proximal surfaces – reduce with short needle bur, finish with torpedo bur
6. Create approximal chutes – toward the buccal side, parallel to long axis
7. Connect chutes with occlusal ditch
8. Finishing – smooth all surfaces with a carbide bur, light pressure

1. Lingual surface groove – use a small spherical bur (~0.7 mm)
2. Incisal edge reduction – with the same spherical bur
3. Lingual axial wall – shaped with a torpedo bur
4. Proximal walls – use short needle bur, avoid contact points
  ⤷ Finish later with enamel knife and torpedo bur
5. Create approximal chutes – toward facial (vestibular) side, parallel to facial axis
6. Connect chutes with occlusal ditch
7. Finishing – use a carbide bur, gentle strokes