principles of tooth prep Flashcards
defn of tooth prep
is the mechanical alteration of a defective, injured or diseased tooth such that placement of restorative material reestablishes normal form (and therefore function)
objectives of tooth prep
1) conserve as much healthy tooth structure as possible
2) remove all defects while simultaneously providing protection of the pulp dentine complex
3) form the tooth prep so that under the forces of mastication, the tooth or resto or both will not fracture, and the restoration will not be displaced
4) allow for aesthetic placement of a restorative material
reasons for tooth prep
1) carious lesion progression to the point that loss of tooth structure requires a restoration
2) tooth fracture compromising form and function
3) congenital malformation or improper position in need of reestablishment of form or function
4) previous resto with inadequate proximal contacts, defective margins or poor aesthetics
class VI of GV black classification
- incisal edges of anterior teeth
- occlusal cusp tips of posterior teeth
requirement of prep walls
due to the nature of enamel formation, prep walls must be at minimum, orientated 90 degrees to the external surface of the enamel to maintain a continuouse connection with essential supporting dentine
what are polycrystalline vs polymeric dental restorative materials
polycrystalline
- amalgam, glass ceramic
- very limited ability to flex without fracturing
polymeric
- CR
- greater ability to flex without fracture
what is convenience form
the shape or form that provides adequate observation, accessibility, and ease in the prep and restoration of the tooth
- sometimes need to extend more to gain adequate access to deeper areas
- one example is extension of proximal walls to clear proximal contacts for better access for finishing, placement
difference between affected and infected dentine
affected dentine is firm, is carious dentine with some mineral loss but not to the point of collagene xposure
- not as hard as normal dentine
- but if isolated from oral envt by a resto, will remineralize
- so should not be removed
infected dentine is soft
- when demin progresses, then degradation of collgen by bacterial proteases changes the 3d structure of collagen such that remin is no longer possible
what is a moderate vs advanced carious lesion
moderate is when caries havent progeess to inner 1/3 of dentine, advanced is when caries progress within inner 1/3 of dentine liao
what is the dimension required between pulp and a metallic resto material
2mm bulk
- can be remaining dentine, liner or base
what are the 2 types of secondary retention and resistance forms
1) mechanical features
- retention grooves
- coves (small retentive indentations used in incisal areas of classIII AR)
- extending prep onto facial/lingual surface
- beveled margins for CR
- steps, slots, pins
2) use of adhesives
- superficially demineralization prep walls (with etch) + subsequent infiltration with resin based adhesives will increase retention
why should desiccation be avoided
because it results in rapid outward tubular fluid movement, leading to stretching of odontoblastic processes with potential for aspiration of odontoblastic cell bodies into dentinal tubules
