Cavity Preparation Terminology and Concepts

primary etiologic factors

agent (bacteria)

environment (diet)

host (tooth)

additional etiologic factors

time (demin and remin)

fluoride

saliva

social and demographic factors

primary organism in caries initiation

streptococcus mutans

bacteria that initiates root surface lesions

actinomyces

what bacteria is still considered the primary organsim in root caries?

strep mutans

bacteria that contributes to caries progression

lactobacillus acidoophilus

common sites of origin

pit and fissure

smooth enamel

root surfaces

teeth must be both ___ and ___ for caries detection

clean

dry

what surface is most susceptible to caries

root surface

what smooth surface has the highest caries incidence amongst smooth surfaces?

proximal surfaces

what is the most likely area to exhibit caires?

pit and fissure enamel surfaces

how to detect pit and fissure lesions

visual inspection (best)

bitewing radiograph

tactile exam

how to detect proximal surface lesions

bitewing radiograph (most accurate in posterior teeth)

periapical radiograph/ visual/ fiber optic transillumination (anterior teeth)

how to detect smooth surface lesions

visual

who created the common caries and cavity preparation classification system used in dentistry?

GV Black

is GV Black's classification and preparation system still used today?

yes

class 1 lesion

caries affecting pit and fissure, on occlusal, buccal, and lingual surfaces of posterior teeth, and lingual of anterior teeth

class 2 lesion

caries affecting proximal surfaces of molars and premolars

class 3 lesion

caries affecting proximal surfaces of central incisors, lateral incisors, and cuspids NOT involving the incisal edge

class 4 lesion

caries affecting proximal INCLUDING incisal edges of anterior teeth

class 5

caries affecting gingival 1/3 of facial or lingual surfaces of anterior or posterior teeth

class 6

caries affecting cusp tips of molars, premolars, and cuspids

2 other types of classification systems

number of surfaces involved

type of surface involved

number of surfaces involved classification

simple = 1 surface

compound = 2 surfaces

complex = 3+ surfaces

type of surfaces involved classification

smooth surface = sides of teeth

pit and fissure = occlusal surfaces, grooves, and pits

tooth preparation

mechanical alteration of a tooth to receive a restorative material which will return the tooth to proper form, function, and esthetics

what significantly increases restoration longevity?

achieving proper outline form

preparation walls can be

external or internal (no connection to prep)

external preparation walls

buccal, distal, mesial, lingual, gingival

internal preparation walls

axial and pulpal

axial internal wall

parallels long axis of tooth, vertical plane of the tooth adjacent to pulp

pulpal internal wall

perpendicular to long axis of tooth closest to the pulp in the horizontal plane

when are the terms floors/ seats used instead of walls?

when the wall exists perpendicular to the long axis of the tooth

pulpal floor

gingival seat

line angles

junction of 2 walls; named based on the two walls

ex. lingual-gingival line angle

axial-pulpal line angle

point angles

junction of 3 walls; named based on the 3 walls

ex. axial-facial-gingival point angle

margin

junction of a cavity wall + external tooth surface

cavosurface margin

margins follow the entire preparation circumferentially

cavosurface angle

angle of tooth structure formed by the junction of a prepared wall + external surface of tooth (90º)

steps for a cavity preparation

1. outline form

2. resistance and retention form

3. convenience form

4. removal of remaining carious dentin

5. finishing enamel walls

6. cleansing the preparation

step 1 outline form

process of placing the cavity margins (cavosurface) in the tooth

should be visualized BEFORE any tooth reduction... measure twice, cut once

factors influencing outline form

1. location of the carious lesion

2. size of the carious lesion!!!

3. tooth anatomy

4. type of restorative material

5. esthetics

6. positioning of adjacent structures

7. functional requirements

8. retentive factors

step 1

outline form

what is the primary determinant in outline form?

lateral spread of decay in dentinal layer

aka SIZE of lesion (lateral)

what aspect of carious lesion size is not considered for outline form

lesion depth

final outline is not established until

carious dentin and overlying enamel have been removed

unsupported enamel

enamel not supported by dentin

when is the final outline form established?

when you have a DEJ free of carious tooth structure and no unsupported enamel

step 2

resistance and retention form

resistance form

shape/ placement of the preparation walls that enable both the restoration and the tooth to withstand, without fracture, masticatory forces delivered principally in the long axis of the tooth

resistance form 4 requirements

1. flat floors perpendicular to masticatory forces

2. restriction of preparation extensions to allow strong cuspal/ marginal ridges (conserve unaffected tooth) (keep marginal ridges)

3. inclusion of weakened tooth structure in the preparation design to prevent tooth fracture (cap a compromised cusp)

4. consideration of restorative materials: amalgam should have 90 degree cavosurface angle

retention form

shape/ form of preparation that resists displacement of the restoration from tipping/lifting forces

___ considers what is holding the material in the cavity preparation?

retention form

retention form 7 requirements

1. dovetails

2. convergent walls

3. grooves / slots

4. pins (large preps only)

5. frictional resistance of walls (nearly parallel, vertical or minimally tapered)

6. acid etch with bonding systems

7. mutually divergent rounded areas*

what type of retention does acid etch help with?

composite resin micromechanical retention

retention divots

divergent rounded area

purpose of dovetails in retention form

proper position maintains width and strength of marginal ridges

step 3 convenience form

shape/ form of preparation that provides the easiest way to operate/ restore the tooth

inadequate convenience form

prevents proper instrumentation

3 factors that influence convenience form

1. extension of the preparation

2. changing the direction of approach

3. changing the instrumentation utilized

why is preservation of unaffected structure crucial?

it helps resistance form

step 4

removal of remaining carious dentin

when is the remaining carious dentin/ infectious structure removed?

after basic cavity design has been completed

incipient lesion

dentin penetration by carious process 0.5mm or less

extensive lesion

advanced dentin penetration by the carious process

what is the ideal preparation depth?

0.5mm inside the DEJ after steps I, II and III have been completed

what step does not apply with incipient lesions?

step 4, removal of remaining carious dentin

technique for removing carious tooth structure and why

remove it ONLY from the affected area to avoid pulpal involvement and maintain resistance form

step 5

finishing enamel walls

what do you smooth and refine to finish enamel walls (step 5)?

walls of cavity prep + cavosurface angles

3 purposes of finishing preparation walls

1. good seal between restorative material + tooth

2. good marginal junction

3. max strength to at margin

why is a good marginal junction important?

it is less noticeable to the patient and facilitates cleansing (less plaque retentive)

factors to consider during wall finishing 4

- direction of enamel rods

- dentinal support for enamel rods

- restorative material that will be used

- location of preparation margins

when does the angulation of enamel rods vary?

varies with location of tooth structure and between primary vs. permanent teeth

fissured surfaces enamel rods (occlusal surfaces)

rods converge from DEJ to surface in areas of pits and grooves

rods diverge from DEJ to surface in areas of cusps and ridges

smooth surfaces enamel rods (proximal, facial, lingual)

- perpendicular to long axis of the tooth in the middle 1/3

- incline occlusally in the occlusal 1/3

- incline gingivally in the gingival 1/3

for proper enamel support, we want to finish our enamel walls so that enamel rods that form cavosurface have their inner ends...

resting on sound dentin

full length rods from DEJ to cavosurface are preferred

where do full length enamel rods receive support from?

DEJ + shorter rods w/ inner end resting on dentin

step 6

cleansing the preparation

cleansing the preparation entails

1. removing all debris from cavity preparation

2. dry and inspect for any remaining weakened structure (carious dentin and unsupported enamel)

caries on mesial aspect of secnd premolar is classified as what?

smooth surface caries