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Principles of cavity preparation presented by DR.rupali
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PRINCIPLES OF CAVITY PREPARATION
Presented By,Rupali Balpande
Guided By,Dr.Sarvesha BhondaveDr.Vishal Mahajan
CONTENTINTRODUCTION CAVITY PREPARATION DEFINITIONHISTORYOBJECTIVES OF CAVITY PREPARATIONFACTORS AFFECTING CAVITY
PREPARATIONCLASSIFICATION STAGES OF CAVITY PREPARATION
Introduction• Dr. G.V. Black
Chicago, Illinois1836-1915
• "The Grand Old Man of Dentistry" • The basic principles governing the design
of cavity and steps in their preparation was first suggested by American Dentist and teacher Dr.G.V.Black in the first decade of last century.
Definition of Cavity preparation
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 where indicated, along with normal form and function.
HISTORY
Archaeological evidence of dental treatment
from 5000 BC1800 early drills by hand1955-Page Chyles handpiece-1st driven angle handpiece9 th century –cavity prepared for inlay19 th century Hamelton Jameson -1st emphasized the
organized cavity preparation.Extension For Prevention- Marshall Ebb & G.V. Black1930-G.V.Black-systemic approach to cavity preparationSimon –sixth classification1998 G.J.Mount classification
OBECTIVES OF TOOTH PREPARATION
• Remove all defects and provide
necessary protection to the pulp.
• Extend the restoration as conservatively as possible .
• Tooth prep such that under mastication both the tooth and restoration will not fracture or displace.
• Allow the functional and esthetic placement of a restorative material.
Factors affecting tooth Preparation
GENERAL
FACTORSDiagnosis Prevention InterceptionPreservationRestoration
PATIENTS
FACTOREconomic statusAgeChoice of Material
Classification G.V. Black Classification
Modification of G.V.Black
Classification
Graham J Mount
V.K. Sikri
G.V.Black ClassificationFirst ClassificationUniversally AcceptedBased on type of treatment and area
involvedControlled by no. of factorsI.To gain access & visibility
II.Removal of affected dentin from floor
III.Room for restorative material
IV.Extension for prevention
V.Retentive designs
VI.Cavosurface margins self cleaning areas
G.J.Mount classification-design to simplify identification of lesions
According to site lesion1.Pits &fissure
2.Contact area
3.Cervical
According to size of lesion1.Minimum
2.Moderate
3.Enlarged
4.Extensive
Sikri classification-classify same as G.V. Black
and then gave division in each class
TOOTH PREPARATION TERMINOLOGY :
• Simple tooth preparation -Only one tooth surface is involved.
• Compound tooth preparation – Only two tooth surface is involved.
• Complex tooth preparation – Involves three or more surfaces.
Terminology in Cavity Preparation
Definition – Cavity-Cavity is defined as a defect in enamel or dentin resulting from pathologic process of dental caries(breach in the continuity of the surface integrity of tooth). The term cavity was used to describe a carious lesion in a tooth that has progressed to the point that part of tooth structure had been destroyed.
Tooth preparation wallsINTERNAL WALL-An internal is prepared surface that does not extend to external tooth surface.
AXIAL WALL – An axial wall is an internal wall parallel with the long axis of the tooth.
PULPAL WALL- A pulpal wall is an internal wall that is perpendicular to the long axis tooth and occlusal of pulp.
External wall – An external wall is prepared surface that extend to the external tooth surface
Floor / seat-A floor is a prepared wall that is reasonably flat and perpendicular to the occlusal forces that are directed occlusogingivally.
Enamel wall –Enamel wall is that portion of a prepared external wall consisting of enamel.
Dentinal wall- The dentinal wall is that portion of a prepared external wall consisting of dentin ,in which mechanical features can be located.
CAVITY PREPARATION ANGLES : Line angle : It is the junction of two planar surfaces of
different orientation along a line. internal line
angle and an external line angle. Internal line angle : Is a line angle whose apex points into
the tooth
e.g. FP. External line angle : Is a line angle whose apex points away
from the tooth e.g. ap. Point angles : A point angle is junction of three planal
surfaces of different orientation.
Cavo surface angle :
The cavo surface angle is the angle of the tooth structure formed by the junction of a prepared cavity wall and the external surface of the tooth.
Line angles & point angles Cavo-surface angle
Classification of cavityClassification of cavity
Class I Class II Class III Class IV Class V Class VI
— G. V. Black
CLASS I CAVITY
1) Pits & fissures2) Occlusal surface of premolars & molars3) Occlusal 2/3 rd of buccal & lingual surface4) Lingual surface of maxillary incisors
CLASS II CAVITY1) Restoration on Proximal surface of posterior teeth
CLASS III CAVITY1)Restoration on the proximal surface of the anterior teeth that do not involve incisal edge.
CLASS IV CAVITY1)Restoration on the proximal surface of anterior teeth that do involve the incisal edge .
CLASS V CAVITY1) Restoration on the gingival third of the facial / lingual surfaces of all teeth.
CLASS VI CAVITY
1) Restoration on incisal edge of anterior teeth and occlusal cusp height of posterior teeth.
2) It is given by Simon.
Stages of Cavity Preparation INITIAL STEPS OF CAVITY PREPARATION
FINAL STEPS OF PREPARATION
1. Outline Form and Initial Depth
Definition: placing the cavity margins in the positions they will occupy in the final preparation except for the finishing enamel walls and margins;
preparing an initial depth of 0.2~0.8 mm pulpally of the dentinoenamel junction.
Principles :1.All friable and weakened enamel should be removed.2.All fault should be included3.All margin should be placed in a position to afford good finishing of margins of restoration.
PROCEDURE
Features:1.Preserving cuspal strength.2.Preserving marginal ridge.3.Minimizing facio-lingual extension.4.Using enameloplasty5.Connectiong two close faults of the tooth which are < 0.5 mm apart
6.Restricting depth of penetration into dentin
for pits and fissure-0.2 for smooth surface-0.2 to 0.8
1.Preserving cuspal strength-avoiding termination of the margin on extreme eminence, such as cusp height-if extension of primary groove includes half / > of cusp incline, then CUSP
CAPPING consider.
2. Preserving marginal ridge strength
• Remaining Marginal ridge should be greater than 1.6 mm for premolar & 2mm for molar
• If Remaining Marginal ridge
will be less than 1.6 mm there there may be the chances of
fracture due to undermining
the ridge.
Direction of mesial & distal walls• When >1.6 mm
thickness width is remained at mesial /distal marginal ridge , then mesial / distal wall should be parallel.
• When less than/= 1.6 mm thickness width is remained at mesial /distal marginal ridge , then mesial / distal wall should be divergent.
3. Minimizing facio –lingual Extension
- Minimizing facio –lingual Extension ,which
prevents the weakening of cusp.
- For conservative class I CAVITY
facio-lingual width should be 1 to 1.5 mm
4. Depth of preparation Restricting depth of penetration into dentin
for pits and fissure-0.2
for smooth surface-0.2 to 0.8Because,
1.To avoid the seating
of the restoration on
the very sensitive DEJ.
2.To give the bulk of
restoration.
3.To take advantages of
dentin elasticity during
insertion and function.
5. Enameloplasty• This is the procedure of reshaping the enamel surface by
making it rounded / Saucered ,the area becomes cleansable and finishable.
• It is indicated when remaining fissure is not greater than 1/3 rd of enamel thickness.
Outline form for class I • The outline form varies from one tooth to another .• Premolars-• Upper premolars have “ Dumb- bell “ shape with
their ends triangular.• In lower premolar –are confined to pit only
but if they involve entire occlusal surface ,then they resemble like upper premolar.
• In tricuspid lower premolar it will assume Y-shape
Class I upper premolar
Class I lower premolar
Class I & II Outline form for MOLARS
• Preparation in lower molars have an elongated shape mesio-distally with three lateral extensions.
• In upper molars if cavity involves all the occlusal surfaces ,the preparation elongated mesio-distally .
• If the oblique ridge is not involved the mesial preparation will assume kidney shape & distal will appear as heart shape .
• In class II the shape of proximal box is Inverted Truncated Cone.
Mandibular Maxillary
Class outline formⅠOcclusal view Proximalview
Class II outline form
Position of Gingival floor
• In class II cavity preparation ,gingival margin should be extended apically of proximal contact to provide a minimum of 0.5 mm clearence between the gingival margin and djacent tooth.
Position of Embrassure wallIsthmus –By G.V.Black- Advocate that class II cavity
preparation with isthmus width
equal to 1/3rd of intercuspal distance.
By Vale & Brooner- It should be 1/4th of intercuspal distance.
The axio-pulpal line angle should be beveled to reduce the concentration of stresses and provide grater bulk of material in the isthmus area, which is liable to fracture.
Final location for the facial and lingual Walls of proximal box relative to the contact area
REVERSE CURVE –When viewed from occlusal outline form of class II cavity particularly in max . teeth the proximal contact lies towards the buccal surface whereas the groove line occurs in the central portion of th occlusal table. This disparity necessitates
occlusal outline with a REVERSE CURVE.Advantages1.It preserve the triangular ridge of cusp2.Facilitates formation of 90°angle between proximal wall & the tangent of proximal surface.
Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form
2. 2. Primary Resistance Form Primary Resistance Form
Definition: It is defined as that shape and placement of
the cavity walls that best enable both the restoration and the tooth to withstand, without fracture, when masticatory forces delivered principally in the long axis of the tooth.
Primary Resistance Form Primary Resistance Form
Principles: To utilize the box shape with a relatively flat floor to resist occlusal loading by virtue of being at right angles to mastication force;
To restrict the extension of the external walls (keep as small as possible) to allow strong cusp and ridge areas to remain with sufficient dentin support;
Primary Resistance Form Primary Resistance Form
Principles:To have a slight rounding of internal line angles to reduce stress concentration in tooth structure;
To provide enough thickness of restorative material to prevent its fracture under load.
Primary Resistance Form Primary Resistance Form
Feature: Box shape
Relatively flat floors
Inclusion of weakened tooth structure
Preservation of cusps and marginal ridges
Rounded internal line angles
Adequate thickness of restorative materials
Reduction of cusps for capping if indicated
Flat pulpal floor prevents rocking of the restoration which produce wedging forces
Pulpal wall is flat in all cases except in lower 1st premolar ,where the lingual cusp is very small & buccal cusp is pronounced with very large pulp horn. So in this case we have to make flat pulpal floor which is parallel to imaginary line joining the tips of the and lingual cusp.
Exception
Rounding of line angles prevents stress concentration & provide resistance form
&Shows strongrst enamel margin by full length of enamel rods
Facio-lingual width should be not more than ¼ th the intercuspal distance . As minimum tooth structure is removed, it increases the resistance of tooth.
¼ th intercuspal distance
The type of restorative material also dictates resistance form need
Silver amalgam needs thickness -1.5 mm
Cast metal needs thickness -1to2mm
Porcelain needs thickness - 2 mm
Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form
3. Primary Retention Form Primary Retention Form
Definition: primary retention form is the shape
or form of conventional preparation that resists displacement or removal of the restoration from tipping or lifting forces.
In many respects retention and resistance form are accomplished in the same cutting procedure.
Principal means of retentionFrictional retention -1.Greater surface area (length, width, depth)produces greater frictional component.
2.Parallel walls / convergent wall provide greater frictional retention
3.Proximity –bringing the restorative material closer to tooth structure during insertion provide greater frictional retention component.
4.Elastic deformation of dentin –during condensation within dentin proportional limit can add more gripping action.
4.Inverted truncated cones
-In class II cavity preparation , proximal surface have inverted truncated cones shape
-It prevents the occlusal displacement of restoration in class II Cavity.
6. DovetailIn Class II Cavity
-Dovetail provide retention in class II
cavity .
-It prevents lateral displacement of
restoration in class II cavity.
In Class I Cavity
-In class I ,it is given for the purposeful modification in outline usually for
‘EXTENSION FOR PREVENTION’
Primary Retention Form Primary Retention Form
Principles: For Amalgam restoration: -developing external cavity walls that converge occlusally. -Adhesive system provide retention by micromechanically bonding amalgam to tooth structure.
Primary Retention Form Primary Retention Form
Principles: Composite restoration:
a mechanical bond between the material
and conditioned, prepared tooth structure.
Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form
4 . 4 . Convenience Form Convenience Form
Conception: The shape or form of the cavity that
provides for adequate observation, accessibility, and ease of operation in preparing and restoring the cavity.
Convenience Form Convenience Form
Principles:
Allow access for caries removalAllow access for restoration placementAllow access to margins for finishing,
evaluation and cleaning
Convenience Form
-In class II cast restoration divergence of vertical wall -extending proximal preparation beyond proximal contact -In class III cavity convenience form mainly through lingual side.- In class I & V , divergence of wall of cavity
in INLAY
Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin or old restoration, if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures
6. 6. Removal of any remaining Removal of any remaining infected dentin or old infected dentin or old restoration, if indicatedrestoration, if indicated
Definition: The elimination of any infected carious
tooth structure or faulty restorative material left in the tooth after initial cavity preparation.
Removal of dentinal caries using round burs and spoon excavators
Removal of dentin depends on the two condition
whether it is affected or infected?• Affected dentin
-Does not contain micro-organisms
-can be remineralise by restorative mean.
-it is accepted to allow affected dentin to remain in prepared tooth.
• Infected dentin
-It contain micro-organisms
-can not be remineralise by restorative mean.
-it should be removed during cavity preparation.
-Soft decay can be best removed using spoon excavator by flaking up the caries -Hard decay, heavily discolored should removed using very low speed bur.-care should have to take during removal as pulp may infected by forcing micro- organisms into dentinal tubules through excessive pressure.
Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures
6. 6. Pulp protectionPulp protection - Using liners or bases
- to protect the pulp or
- to aid pulpal recovery or both.LINERS-liners are volitile /aquous
suspension /dispersion of zinc oxide or calcium hydroxide that can be applied to tooth surface in relatively thin film & are used to effect a particular pulpal response.
BASES-Are those cements used in thicker dimensions beneath permanent restoration to provide for mechanical, chemical ,thermal protection of the pulp
-Liners are primarily used to provide a barrier to protect dentin from residual reactants.
-Bases are used to provide thermal protection for the pulp and to supplement mechanical support for the restoration by distributing local stresses from restoration across the underlying dentin surface.
If remaining dentin overlying the pulp is 2mm then no need of liners
But if it is less than 2mm ,pulp protection is mandatory .
Schematic view of needs for pulpal protection below metallic restoration
Schematic examples of liners & bases for amalgam restoration
For shallow tooth preparation
For moderate tooth
preparation
For very deep tooth
preparation
Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures
7. 7. Secondary resistance and Secondary resistance and retention forms retention forms
Most compound and complex cavity preparations require additional resistance and retention form.
The exception being those preparations that are very conservative.
Secondary resistance and Secondary resistance and retention forms retention forms
Mechanical forms
Cavity wall conditioning form
Mechanical form:
Retention locks, grooves, and coves Groove extensionsSkirtsBeveled Enamel MarginsPins, Slots, Steps, Amalgampins
Proximal Grooves for cast restoration
Retention locks for amalgam
Incisal retention coves
Incisal & Gingival retention groove
Groove extensions & skirts
When lingual wall absent or inadequate in proximal preparation, then retention form can be improved by facial skirt extension.
Pins slots steps & amalgampins
Beveled Enamel margins-The bevels for cast metal may improve retention form -Primarily to afford a better junctional relationship-Beveled margins increases the surface area of etchable enamel
Dentin slots Amalgampins
Cavity wall conditioning form
Placement of etchant , Primer , Adhesive on prepared wall
-in addition to mechanical alteration to tooth structure certain bonding agents also provide some extent of retention & resistance form
-such treatment require in bonded restoration like porcelain , composite , or amalgam materials
Micromechanical retention of bonding system to dental enamel
Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Finishing external walls
Step 9 Final procedures
8. 8. Finishing the external walls Finishing the external walls
Definition: is the further development of a
specific cavosurface design and degree of smoothness that produces the maximum effectiveness of the restorative material being used.
Finishing the external walls Finishing the external walls
Objectives: To create the best marginal seal possible
between the restorative material and tooth structure;
To afford a smooth marginal junction; To provide maximum strength of both the
tooth and the restorative material at and near the margin.
The strongest enamel margin is that marginwhich is composed of full-length enamel rodsthat are supported on the cavity side by shorterenamel rods, all of which extend to sound dentin.
Finishing the external walls Finishing the external walls
The design of the cavosurface angle
The degree of smoothness of the wall
The design of the cavosurface angle: depending on the material
amalgam: 90°(Cavosurface margin 90°-Butt joint)
Help to minimize the marginal deterioration of restoration by locating the margins away from the enamel eminence where occlusal forces may be concentrated.composite: beveling 30°~ 40° Is indicated primarily in larger restoration because the potential for retention increased by increasing the surface area of enamel available
for etch.
Occlusal cavosurface
margin
Proximal cavosurface
margin
Vertical section of Class II Tooth preparation-a slight bevel is given to remove unsupported
enamel rods
Gingival Bevel placed with an instrument
Gingival marginal trimmer
Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures
Final proceduresFinal procedures
cleaning
inspecting
Sealing
A .Water, air, or combinations of bothB . Dry cotton pellets are very efficient and safer way to dry preparation .C. Using cavity cleaner (vey low conc. Of citric acid ,ascorbic or acetic acid),dilute sol. Of hydrogen peroxide.D. Scraping preparation walls with sharp hand instrument.E. Irrigate the cavity with saline before drying.F. Inspecting the cavity for any remaining debris G. Sealing the cavityH. Composite requires etching ,priming & bonding before insertion of restoration.
Cavity preparation seen after final procedure
References
1.Sturdevants- Art and Science Of Operative Dentistry
2.Marzouk – Modern Theory and Practice
3.G.V. Black –Work on operative dentistry
3.Vimal Sikri- Textbook of Operative Dentistry
4.Journal of Australia- Conservative Dentistry
5.American Dental Association Document
6.Vale –Cavity preparation
7.www.googleimages.com
8.www.dentalacademy/images/cavity preparation.com