Fundamentals of cavity Preparation - SRM · PDF fileFundamentals of cavity Preparation ....
Transcript of Fundamentals of cavity Preparation - SRM · PDF fileFundamentals of cavity Preparation ....
1
Fundamentals of cavity Preparation
INTRODUCTION
CAVITY: Refers to a defect in enamel, or enamel & dentin, resulting from pathologic process- DENTAL CARIES
Effective treatment for preventing further progress - complete removal of affected area
3
Needs for Restorations
• Caries• Non-carious lesions• Replacement of restorations or repair• Iatrogenic dentistry
CAVITY PREPARATIONdefined as the mechanical alteration of a defective injured or diseased tooth in order to best receive a restorative material which will re-establish a healthy state for the tooth including esthetic corrections, along with normal form and function.
5
Objectives of Tooth Restorations
1. To restore form/function and esthetics, if possible
2. To promote maintenance of integrity of hard and soft tissues of the oral cavity
3. To promote health and welfare of patients
6
Objectives of Cavity Preparation
1. To remove all defects and give necessary protection to the pulp
2. To locate the margins of the restorations as conservatively as possible
3. To form the cavity so that under the masticatory forces the tooth and the restoration will not fracture and the restoration will not be displaced
4. To allow for the esthetic and functional placement of a restorative material
7
Definition of Cavity Preparation
• Mechanical alteration of a tooth to receive a restorative material which will return the tooth and area to proper form, function, and esthetics
• Preparation procedure includes all defective and friable tooth structure
8
What factors do we have to consider in cavity preparation
for successful restorations?• Type of dental restorative material: physical
and biological properties
• Tooth: location vs. masticatory forces
FACTORS AFFECTING CAVITY PREPARATION
GENERAL FACTORS
• diagnosis• prevention• interception• preservation• restoration
PATIENTS FACTOR
• economic status • age• choice of material
G V BLACKS CLASSIFICATION
First classificationuniversally acceptedbased on type of treatment & areas involvedcontrolled by number of factors
• to gain access & visibility• removal of affected dentin from floor• room for restorative material• extension for prevention• mech. Interlocking retentive designs• cavosurface margins self cleaning areas
G V BLACK’S CLASSIFICATION
CLASS I
pit & fissure
occlusal surfaces - premolars & molars
lingual surfaces of maxillary incisors
CLASS II
proximal surfaces of posterior teeth
CLASS III
proximal surfaces of anterior teeth do not involve the incisal edge
CLASS IV
proximal surfaces of anterior teeth involve incisal edge
CLASS V
gingival third of facial or lingual surfaces
CLASS VI
incisal edge of anterior / occlusal cusps heights of posterior teeth
Simon - later added
OPERATING SITE
moist- free environment
isolation
protecting soft tissues
margins limited to supragingival sulcus
Intra-coronal Cavity Preparation
25
Principles of Cavity Preparation1. Outline form2. Resistance form: resistant to tooth and
restoration fracture and displacement of restoration
3. Retention form: prevent from dislodging of restoration
4. Convenience form: access for caries removal, band insertion, etc
5. Remove remaining carious lesions6. Finish margin of enamel walls7. Perform the toilet of the cavity
INITIAL CAVITY PREPARATION
extension & initial design of external walls of preparation at a specific limited depth, provide access to cavity/ defect reach sound tooth structure, resist fracture of restoration/ tooth,forces directed in long axis of tooth & retain restoration
no deeper than 0.2mm into dentin - pit & fissure
0.2mm - 0.8mm - smooth suface
OUTLINE FORM & INITIAL DEPTH
placing cavity margins in positions will occupy in final preparations except enamel walls & margins
preparing initial depth of 0.2 - 0.8mm pulpally of DEJ
PRINCIPLES
friable / weakened enamel removedall faults includedmargins placed in position- good finishing of margins of restorationextension for preventionsufficient enamel & dentin to locate the pulpal & axial walls or prepn.surfaces within 0.5mm from DEJ
extent of carious lesion, defect/ faulty restorations
esthetic considerations
occlusal relationships
adjacent tooth structure
cavosurface margin
FACTORS
FEATURESpreserving cuspal strength
preserving marginal ridge strength
minimizing f-l extensions
enameloplasty
connecting to close faults
restricting depth
31
Principles of Cavity Preparation1. Outline form
1. Cover all carious lesions2. No extension for prevention
PRIMARY RESISTANCE FORM
defined as the shape & placement of the cavity walls best enables both restorations & the tooth to withstand, without fracture , masticatory forces delivered in long axis of tooth architectural form given to a tooth , which enables both restoration & remaining tooth to resist structural failure from occlusal loading stresses
33
Principles of cavity preparation2. Resistance form
1. Depth- 0.5 mm below DEJ (about 1.5 mm from the deepest pit)
2. Flat floor3. No unsupported enamel (undermined)
1. Cavosurface margin: 90 degree2. Angle of departure: 90 degree
4. Slightly-rounded internal line angle5. Preserve marginal ridge if possible
PRINCIPLESutilize box shape with a flat floorrestrict extension of external wallsslight rounding of internal line angles - reduce stresscap weak cusps & envelope / include enough weakened toothprovide enough thickness of restorative material - prevent fracturemajor principle is that restoration should rest on flat sound tooth structure, perpendicular to occlusal forces directed parallel to the long axis of tooth
FEATURESrelatively flat floors box shape includes weakened tooth structurespreservation of cusps & marginal ridgesrounded internal line anglesadequative thickness of restorative materialsseats on sound dentin peripheral to excavation of infected dentinreduction of cusps for capping
36
Flat FloorRelatively parallel to the cusp tips
37
Cavosurface Margin
– amalgam -90 degree– inlay beveled- 20-40 degree– margins located on self-cleansing areas– smooth curves
38
39
Prepared Cavity Walls
1. Cavosurface margin 2. Enamel wall3. Dentinoenamel junction (DEJ)4. Dentin wall
Sharp definitecavosurface
margin
E
DEJ
DDefinite slightly-rounded internal line angle
40
Undermined Enamel or Overhanged Enamel
• Cavity preparation -> walls of cavity should be parallel to directions of enamel rods as much as possible.
41
Undermined Enamel
42
Principles of Cavity Preparation3. Retention form
Retention form : shape / form of prepared cavity that resists displacement / removal of restoration from tipping/ lifting forcesdefined as a form given to tooth prepn.,especially its detailed anatomy & general shape, which enables the restoration, that will accommodate, to avoid being lodged by masticatory loading
intra coronal-inside a cavity prepn,within the tooth
extra coronalon prepn.surface, replacing reduced ext.tooth
43
44
Principles of cavity preparation3. Retention form
1. Box form2. Convergence to occlusal surface (small
undercut)3. Retentive groove4. Pins and slots5. Dovetail6. Acid etching (for resin composite restorations)
45
Retention form
1. Box form 2. Convergence to occlusal surface (small undercut)
AB
46
3. Retention FormDovetail
47
Principles of cavity preparation3. Retention form
Retentive groove
Pins
48
49
50
Retention Slot & Pin
51
Principles of Cavity Preparation4. Convenience form
• Convenience form : shape/ form of cavity that provide adequate observation & accessibility
• ease of operation in preparing & restoring the cavity
FINAL CAVITY PREPARATIONRemoval of any remaining enamel pit / fissure &/ or infected dentin & / old restorative material, if indicated.
it is elimination of any infected carious tooth structure / faulty restoration within the tooth after initial cavity preparation
caries left in pulpal / axial floor excavated
0.75-1mm of dentin cover the pulp
when affects esthetically
weakened tooth- given retention
secondary caries , if present
periphery of old resto.mate. not intact
PULP PROTECTIONpulpal injury, due to
heat generated while cuttingresto.mat.with good thermal conductivitychemicals from resto.mate.Galvanic currentsmicroleakage
placement of cavity liners / bases/varnish–not a stepit is the step in adapting the preparation for receiving the final restorative materialmechanical, chemical & thermal protection of pulp
SECONDARY RESISTANCE & RETENTION FORM
TWO TYPES
MECHANICAL FEATURES
CAVITY WALL CONDITIONING
� Mechanical featuresretention locksgrooves & covesskirtsbeveled enamel marginspins amalgapinsslots
Cavity wall conditioning featuresenamel, dentinal wall conditioningfor bonded restorations
FINISHING THE EXTERNAL WALLS OF CAVITY PREPARATION
further development when indicated, of a specific cavosurface design & degree of smoothness that produces maximum effectiveness of restorative material being usedto create best marginal seal bet.resto.mate.& toothto afford smooth marginal jnprovide maxi.strength of both tooth & resto.
• Features
design of cavosurface margin
degree of smoothness of wall
• cavity preparation for – class I amalgam• outline form
class II cavity preparation for amalgam
Class III Cavity Preparation for Amalgam:
Class V Cavity Preparation for Amalgam:
Enameloplasty
It is the removal of a shallow, enamel developmental fissure or pit to create a smooth, saucer shaped surface that is self cleansing or easily cleaned.
This is mainly used for smooth surface enamel defects.
64
Concepts behind conservative restorations
1. Remove minimum tooth structure required for convenience form
2. Caries removal3. Access, carving and finishing margins4. Retention and resistance form
65
False conservatism
1. Insufficient convenience form2. Leaving unsupported enamel3. Insufficient reduction for restoration
strength
66
Advantages
1. Reduced risk of pulpal and perio involvement
2. Improved esthetics3. Less risk of margin and tooth fracture
67
Class I Amalgam-preparation design
1. Minimize width of isthmus (1/3 intercuspal distance or less) to reduce risk of tooth fracture.
2. Remove contiguous fissures3. Rounded internal line angles to facilitate
condensation and minimize stresses4. Minimal pulpal depth is 0.5 mm into dentin from
DEJ5. No need to cross isthmus unless caries is
present.6. If questionable occlusal pits/fissures, consider
PRR or sealant