#FIXEDPROS

Planning stages before tooth prep

• study casts
• photographs
• trial preparations
• appearance
• final impression
• temporary crown

Study cast

• good impression with PVS and opposing cast articulated against eachother
  Photograph
• photo prior to prep
• also old photo of patient and how their teeth used to look
  planning tooth prep
• trial prep on study cast
• shows for sufficient length and thickness of different aspects for each type of tooth, and what materials may be indicated from these limitations
• can prep half the tooth to help visualise limtations etc.

Planning appearance

• diagnostic wax up
• shade
  • best to do at start so not done hurriedly, as its most important
  • needs to be correct in both artificial and daylight
    

Impression

• standard, make special acrylic tray with some perforations and stops

temporisation

• typically bisacryl composite resin made from a putty key which is adjusted and cemented with a temp luting cement

Preparation

Posterior

• occlusal
  • follow general shape with contours of cusps
  • cusps that are "functional" (determiend by occluding surfaces and group function etc.) will be prepared more to facilitate greater thickness of material coverage
  • the greater the axial length, the greater the retention, therefore over reduction of occlusal surface reduces retention
  • reduction varies 1mm, 1.5mm depending on PFM or ceramic
• axial
  • care for M and D where contacts are, leave thin wall to break off when prepping
  • keep parallel as possible without undercuts, ideal taper of 10-20 degrees so dont start too angled

ANterior

• incisal and proximal
  • keep the same inclination of tooth
• labial
  • need adequate reduction to give good phonetics and avoid bulky labial surface
• gingivopalatal
  • keep shoulder and wall nearly parallel to buccal gingival surface
• incisalpalatal
  • best for large diameter instrument
  • needs sufficient space, compare regularlyl

Anterior post crown

• remove GP from coronal part and prepare post hole, using whatever method manufacturer instructions advise
• post is cemented in place at an appropriate length to facilitate atleast minimum thickness of core buildup material around post to create the core

Impressions

• putty impression taken and relined to get an accurate impression first of what the original tooth was like
• in addition we must take impression of the actual preparation using 2 retraction cords and allowing plastic deformation of gingiva to create a really ideal impression
• occlusal record taken to articulate against
• lower impression taken to articulate against

Checking crowns

• me must inspect for marginal fit wit probe and eye
  • looking for gaps, overhanging margins and deficiencies
• uniform circumferential gap indicates incomplete seating of the crown
  • first check for retained temp cement, trapped gingival tissue, firmer seating force, check contact points with floss
  • inspect fit surface to inspect where crown is binding and ground lightly with a bur or stone
• retention
  • shouldnt feel tight, shouldnt really rock or pivot, adjust as per necessary
• shade
  • either stain it more and refire if its too bright
  • if its too dark probably need to remake entirely

Cementation

choice of cements

• zinc phosphate
  • long term usage, however there are cases of transient discomfort, or pulpal inflammation and necrosis,
  • very long and controllable working time
  • very thin cemment film (up to 10 um)
• resin based and adhesive
  • 4-meta or phosphonate derivatives are inhibited in oxygen presence
  • havent been used for as long as the other options
  • usually for porcelain veneers or minimum prep bridges

• GI cement