dental caries
degredative pathological process that causes defect (cavity) in enamel or in enamel adn dentin; disease that attacks tooth
4 objectives of cavity prep
- remove caries
- meet bio reqs of tooth
- preserve max natural tooth
- meet mech/phys reqs of restorative material
father of dentistry
GV Black
cavity prep classification, general
class 1 to class 6
- structural defect origin
- posterior proximal surface
- anterior proximal surface – no incisal edge
- anterior proximal surface – yes incisal edge
- gingival (cervical) third of F/L surface of any tooth (if M or D, not class 2)
- incisal or occlusal edges due to wear/chewing/grinding
class I
- originate in structural defects (pits in fossae, fissures in grooves)
- not just occlusal surfaces, also in lingual pits
- MD walls of this prep diverge; BL walls converge
class II
- originate on proximal surfaces of PM and molars
- smooth surface caries usually – food traps/poor flossing
- box in prep; use occlusal surface for retention
- if M or D involved on a posterior tooth – it class II (except when cervical 1/3 involved and then class V)
class III
- originate on proximal surfaces of anteriors
- does NOT involved loss/removal of incisal edge (that is IV)
- usually smooth surface caries
class IV
- proximal surface of anteriors and DOES involve incisal edge
- can be due to trauma
- same as 3 but with incisal edge
class V
- gingival/cervical third of F or L crown surface of ANY tooth
- smooth surface caries
- can extend to M or D – in this case, proximal surface caries is NOT class II
- might have to cut a class II to get to it
- might connect to cementum
class VI
- incisal edge of incisors or cusp of canine/PM/molar
- forms from wear–patient chewing/grinding
cavosurface angle vs margin
- cavosurface angle = angle of tooth structure formed by jxn of prepared wall and external surface of tooth
- cavosurface margin = actual jxn of the 2 walls
line angle vs point angle
line angle = 2 walls meet (ex: buccal cavosurface angle or mesiopulpal angle)
point angle = corner where 3 walls meet
7 steps in cavity prep
- outline form
- resistance form
- retention form
- convenience form
- removal of caries
- finish prep walls
- cleanse
strongest enamel margin
- full length enamel rods
2. buttressed by progressively shorter rods whose outer ends are cur but inner ends are on sound dentin
outline form
- clean DEJ, smooth, no sharp angles
- do not remove healthy tooth unless indicated
- remove unsup.enamel
- be conservative – has less of an effect on inter/intra arch relationships and esthetics and strength of tooth
- strongest enamel margin has to do with dentin supported enamel
resistance form
- prevent fracture of remaining tooth and/or restoration
- round sharp angles
- wall angulation: floors are perpindicular to long axis of tooth (gingival adn pulpal walls) and walls (including axial) are parallel to long axis
- depth is just within dentin for amalgam (need bulk for resistance)
- if too wide, decrease strength
- internal line angles: slightly round to decrease stress concentration, help with uniform depth, delineate prep walls, prevent rotation of restoration (increase retention)
depth, width, wall angles of resistance forn
- depth for amalgam - just within dentin, need bulk
- width can’t be too great or decrease resistance
- walls parallel to long axis, floors perpindicular
retention form
prevents dislodgement of restoration.
occlusal convergence.
retentive grooves adn points
finish cav.prep walls
- remove unsup.enamel
- smooth cavosurface margins (bevel)
