Class i cavity preparation

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CLASS I CAVITY PREPARATION

GUIDED BY- DONE BY-

Dr. SANDEEP METGUD Dr. RAMSUNDAR HAZRA

Dr. DEEPALI AGRAWAL (1ST YEAR PG)

DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS

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CONTENTS- INTRODUCTION DEFINITION FACTORS TO CONSIDER BEFORE TOOTH PREPARATION CLINICAL TECHNIQUE FOR CLASS I AMALGAM

a) CONSERVATIVE CLASS I

b) EXTENSIVE CLASS I

c) OCCLUSOLINGUAL CLASS I

d) OCCLUSOFACIAL CLASS I CLASS I COMPOSITE RESTORATION TOOTH PREPARATION:AMALGAM V/S COMPOSITE REFERENCES

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INTRODUCTION- In the past, most restorative treatment was

due to Caries(decay).

A breach in the surface integrity was referred to as Cavity.

Now many indications for treatment for teeth are not due to caries, and the preparation of the tooth no longer referred as Cavity preparation, but as Tooth preparation.

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Tooth preparation is the mechanical alteration of a defective, injured, or diseased tooth to receive a restorative material that re-establishes a healthy state for the tooth, including esthetic corrections where indicated and normal form and function. (By Sturdevant)

Cavity preparation is the mechanical removal of caries and shaping the remaining tooth tissue in such a way so that after restoration it can withstand masticatory forces and will be able to prevent subsequent caries.

(By Vimal K Sikri)

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CLASSIFICATIONS OF TOOTH PREPARATION-

According to Anatomic areas involved and by associated type of treatment was presented by Black.

Designated as Class I, II, III, IV, V. Class VI – additional Classification.

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DEFINITION- Class I Restoration-All pit and fissure

restorations are Class I, and they are assigned to three groups.

A)Restorations on Occlusal Surface of Premolars and Molars.

B)Restorations on Occlusal Two-Thirds of the Facial and Lingual Surfaces of Molars.

C)Restorations on lingual Surface of Maxillary Incisors.

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Class I could be – a) Simple Occlusal Cavity b) Compound Occlusal

Cavity -OcclusoBuccal -Occluso

Palatal/Lingual c) Complex Occlusal

Cavity d) Buccal Pit e) Anterior Palatal Pit

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TOOTH PREPARATION WALLS:

f:facial; d:distal; l:lingual; m:mesial; p:pulpal

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CLASS I LINE ANGLES AND POINT ANGLES

LINE ANGLES- fp:faciopulpal; df:distofacial; dp:distopulpal; dl:distolingual; lp:linguopulpal; ml:mesiolingual: mp:mesiopulpal; mf:mesiofacial.POINT ANGLES- dfp:distofaciopulpal; dlp:distolinguopulpal; mlp:mesiolinguopulpal; mfp:mesiofaciopulpal.

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FACTORS TO CONSIDER BEFORE TOOTH PREPARATION-

Extent of caries Occlusion Pulpal Involvement Esthetics Patient’s Age Patient’s Home care Gingival Status Anesthesia Bone support Patient’s Desires Material Limitations Operator Skill Enamel rod direction

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FACTORS TO CONSIDER BEFORE TOOTH PREPARATION-

Extent of old restorative material Extent of defect Pulpal protection Contours Economics Patient’s Risk status Bur design Radiographic assessment Patient cooperation Fracture Lines Tooth anatomy Ability to isolate area

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CLASS I AMALGAM RESTORATION- Amalgam is used for the restoration of many

carious and fractured posterior teeth and in the replacement of failed restoration.

If properly placed it provides many years of service.

Understanding the physical properties of amalgam and the principles of tooth preparation.

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TOOTH PREPARATION CLASS I

CONSERVATIVE CLASS I AMALGAM RESTORATION

It is recommended to protect the pulp. Preserve strength of the tooth. To reduce deterioration of the amalgam

restoration.TOOTH PREPARATION

INITIAL TOOTH PREPARATION

FINAL TOOTH PREPARATION

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CLINICAL TECHNIQUE OF CLASS I AMALGAM-

INITIAL CLINICAL PROCEDURES Isolation with Rubber dam-when removing deep

caries less than 1mm from the pulp. For single Maxillary tooth, caries is not extensive,

moisture control is achieved with cotton rolls and profound anesthesia.

Preoperative assessment of occlusal relationship of involved and adjacent teeth.

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INITIAL TOOTH PREPARATION

It is defined as establishing the outline form by extension of the external walls to sound tooth structure, while maintaining a specified, limited depth and providing resistance and retention forms.

The Outline form for Class I should include only the faulty, defective occlusal pits and fissures.

Occasionally the marginal outline for Maxillary premolars is Butterfly shaped.

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IDEAL OUTLINE FORM

Ideal outline form incorporates the following resistance form principles-

Extending around the cusps to conserve tooth structure and prevent the internal line angles from approaching the pulp horns too closely.

Keeping the facial and lingual margin extensions as minimal as possible between the central groove and the cusp tips.

Extending the outline to include fissures, placing the margins on relatively smooth, sound structure.

Minimally extending into the marginal ridges without removing dentinal support.

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IDEAL OUTLINE FORM

Eliminating a weak wall of enamel by joining two outlines that come close together i.e. <0.5mm apart.

Extending the outline form to include enamel undermined by caries.

Using enameloplasty on the terminal ends of shallow fissures to conserve tooth structure.

Establishing an optimal, conservative depth of the pulpal wall.

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ARMAMENTARIUM

1. BURS- Nos 245 Bur Nos 330 Bur

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2. HAND INSTRUMENTS- Excavators Enamel Hatchets Binangle Chisels Curved Wedelstaedt Chisels

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SEQUENCE OF PREPARATIONINITIAL TOOTH PREPARATION

Enter the deepest or most carious pit with a punch cut using No. 245 carbide bur

As the bur enters the pit, the proper depth of 1.5mm should be established

Depth of external walls is 1.5 to 2mm;Pulpal depth is 0.1 to 0.2mm into dentin

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SEQUENCE OF PREPARATION

Incline bur distally to establish proper occlusal divergence to distal wall

For Premolars, distance from the margin of extension to the proximal surface should not be

less than 1.6mm; For Molars, the minimal distance is 2mm

While maintaining the bur’s orientation and depth, the preparation is extended distofacially or distolingually

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Maintain the bur’s orientation and depth and, with intermittent pressure extend along the central

fissure towards the mesial pit, following DEJ

The pulpal floor should follow the DEJ,Maintain a uniform flat pulpal floor depth

Ideally, the width of the isthmus should be just wider than the diameter of the bur;

Minimal Faciolingual width and Minimal Occlusal convergence are desired

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Remainder of any occlusal enamel defects is included, facial and lingual walls are extended if necessary

Conservative preparation should have an outline form with gently flowing curves and distinct cavosurface

margins

For Initial tooth preparation pulpal floor should remain at the initilal ideal depth, even if restorative material or

caries remains,Remaining caries is removed in final tooth preparation

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PRIMARY RESISTANCE FORM Sufficient area of relatively flat pulpal floor in

sound tooth structure. Minimal extension of external walls. Strong, ideal enamel margins. Sufficient Depth(1.5mm)

PRIMARY RETENTION FORM

Parallelism or slight occlusal convergence of two or more opposing, external walls.

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Removal of remaining defective enamel and infected dentin on the pulpal floor.

Pulp protection, where indicated. Procedures for finishing external walls. Final procedures of cleaning and inspecting

the prepared tooth.

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Enamel pit and fissure remnants in the pulpal floor should be removed

If pit and fissure remnants are few and small, they can be removed with a suitably sized, round

carbide bur or spoon excavators

When removing infected dentin, the excavation should be stopped when tooth structure feels hard

or firm;A sharp explorer is more reliable than a rotating bur in judging the adequacy of removal of

infected dentin

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If the tooth preparation is of ideal or shallow depth, no liner or base is indicated.

In deeper carious excavations-remaining dentin thickness is 0.5-1mm-Place a thin layer(0.5-0.75mm) of a light cured RMGI Base.

It should be placed only over the deepest portion of the excavation.

The entire dentin surface should not be covered.

Every completed tooth preparation should be inspected and cleaned before restoration.

Tooth preparation should be free of debris after rinsing tooth with air-water syringe.

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An occlusal cavosurface bevel is contraindicated in an amalgam cavity preparation.

Provide an approximate 90-100 degree cavosurface angle which should result in 80-90 degree amalgam at the margins.

Amalgam is a brittle material with low edge strength and tends to chip under occlusal stress.

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TYPICAL CLASS I TOOTH PREPARATION ON MAXILLARY PREMOLAR

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OTHER CONSERVATIVE CLASS I AMALGAM PREPARATIONS

Facial pit of Mandibular molar Lingual pit of Maxillary lateral incisor Occlusal pits of Mandibular 1st Premolar Occlusal pits and fissures of Maxillary 1st

Molar Occlusal pits and fissures of Mandar 2nd

Premolar

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VARIATIONS IN DESIGN FOR CLASS I MAXILLARY 1ST MOLAR

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VARIATIONS IN DESIGN FOR CLASS I LOWER 1ST MOLAR

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EXTENSIVE CLASS I AMALGAM RESTORATIONS

Caries is considered extensive if the distance between infected dentin and the pulp is judged to be less than 1mm or when the facilolingual extent of the defect is up the cuspal inclines.

Extensive caries requires a more extensive restoration.

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INITIAL CLINICAL PROCEDURESIsolation of the operating site.If caries excavation exposes the

pulp, pulp caping may be more often successful if the site is isolated with a properly applied rubber dam.

Preoperative occlusal assessment and anesthetic administration-factors.

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TOOTH PREPARATION-INITIAL

Using a No. 245 bur at high speed and oriented with its long axis parallel to the long axis of the

tooth crown,prepare the outline, primary resistance, and primary retention form

An initial depth of 1.5-2mm should be maintained

The preparation is extended laterally to remove all enamel undermined by caries by alternatively cutting and examining

the lateral extension of the caries

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TOOTH PREPARATION- FINAL

Removal of remaining infected dentin

If pulp exposure occurs the operator must decide whether to apply a direct pulp cap of calcium

hydroxide or to treat endodontically

For pulpal protection, a thin layer (0.5-0.75mm) of Calcium hydroxide liner may be placed.

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TOOTH PREPARATION- FINAL

A thin base of RMGI should be used over Calcium hydroxide

Usually no Secondary resistance or retention features are necessary

Primary resistance form-Extend the outline of the tooth preparation to include only undermined and defective

structure Primary Retention-Occlusal convergence of enamel

walls

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CLASS I OCCLUSOLINGUAL AMALGAM RESTORATIONS

Occlusolingual amalgam restorations may be used on maxillary molars when a lingual fissure connects with the distal oblique fissure and distal pit on the occlusal surface.

Tooth preparation includes the following- 1) Tooth preparation should be no wider than

necessary. 2) Ideally mesiodistal width of the lingual

extension should not exceed 1mm except for extended caries or undermined enamel.

3) When indicated, the tooth preparation should be cut more at the expense of the oblique ridge rather than centering over the fissure.

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4) Especially on smaller teeth, the occlusal portion may have a slight distal tilt to conserve the dentin support of the distal marginal ridge.

5) The margins should extend as little as possible onto the oblique ridge, distolingual cusp, and distal marginal ridge.

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CLASS I OCCLUSOFACIAL AMALGAM RESTORATIONS-

Occasionally, mandibular molars exhibit fisssures that extend from the occlusal surface through the facial cusp ridge and onto the facial surface.

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CLASS I COMPOSITE RESTORATIONS

In 1959, Skinner wrote, ‘The esthetic quality of a restoration may be as important to the mental health of the patient as the biological and technical qualities of the restoration are to his physical or dental health.’

Composites are presently the most popular tooth-colored materials, having completely replaced silicate cement and acrylic resin.

The ADA indicated the appropriateness of composites for use as pit and fissure sealants, preventive resin restorations, and Class I and II restorations for initial and moderately sized lesions.

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ADA further stated, ‘ When used correctly in the primary and permanent dentition, the expected lifetime of resin-based composites can be comparable to that of amalgam in Class I, Class II, and Class V restorations’.

Composite is a material that has sufficient strength for Class I and II restorations.

Because Composite is bonded to enamel and dentin, tooth preparations for composite can be very conservative.

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CLINICAL INDICATIONS- Small and moderate restorations When esthetics is considered Restorations that does not provide all

of the occlusal contacts Restorations that does not have heavy

occlusal contacts Restorations that can be appropriately

isolated As foundations for crown For economic/interim use reasons

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CONTRAINDICATIONS-When the operating site cannot be isolated

Heavy occlusal stresses are present

All the occlusal contacts are on composite only

Restorations that extend onto the root surface

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ADVANTAGES-EstheticsConservative tooth structure removal

Easier, less complex tooth structure

EconomicsInsulationBonding benefits

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DISADVANTAGES-

1. Material related2. Require more time to place3. More technique sensitive4. More expensive than

amalgam restorations

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CLINICAL TECHNIQUE FOR DIRECT CLASS I COMPOSITE RESTORATION

INITIAL CLINICAL PROCEDURES-

Anesthesia and shade selection

Assessment of the preoperative relationship of the tooth to be restored

Isolation of the operating area

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TOOTH PREPARATION The three typical composite

preparations-Conventional, Beveled conventional and Modified

Beveled Conventional design rarely would be used except for groove extensions.

Conventional-When increased resistance form is needed; for large preparations

Modified- Typically uses more flared cavosurface forms without uniform or flat pulpal or axial walls.

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ARMAMENTARIUMOperator prefer Diamond instrument.

Flat tipped bur or diamondInverted cone cutting instruments with rounded corners

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CONVENTIONAL CLASS I TOOTH PREPRATION

For large Class I, one enters the tooth in the distal pit area of the faulty occlusal surface with inverted cone diamond, positioned parallel to the long axis of the crown.

Pulpal floor-1.5mm initial depth Facial and Lingual measurement-1.75mm depth Initial depth- Approx. 0.2mm inside DEJ Facial and lingual extension and width are

dictated by caries, old restorative material, or fault

Extensions into Marginal ridges should result in approx. 1.6mm of thickness remaining tooth structure for premolars and 2mm for molars

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The occlusal margin does not have a beveled or flared form, it is left as prepared

The inverted cone instrument results in occlusal walls that converge oclusally, enhancing retention form.

The marginal form of a groove extension on the faical or lingual surface may be beveled with a diamond, resulting in a 0.25-0.5mm width bevel at a 45 degree angle to the prepared wall.

A large Class I composite tooth preparation-Conventional design.

If facial or lingual groove included- Combination of Conventional and beveled conventional.

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MODFIED CLASS I TOOTH PREPARATION-

Minimally involved Class I lesions or faults may be restored with composite using modified tooth preparations.

Less specific in form, having a scooped out appearance.

Prepared with a small round or inverted cone diamond or bur.

Initial pulp depth is still 1.5mm or approx 0.2mm inside DEJ, but may not be uniform.

Entire bevel or flare becomes part of the final tooth preparation.

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CONCLUSION-TOOTH PREPARATION: AMALGAM VS

COMPOSITE

FEATURES AMALGAM COMPOSITE

OUTLINE FORM Include faultMay extend to break proximal contactInclude adjacent suspicious area

SameSame

No

PULPAL DEPTH Uniform 1.5mm Remove fault; not usually uniform

AXIAL DEPTH Uniform 0.2-0.5mm inside DEJ

Remove fault; not usually uniform

CAVOSURFACE MARGIN Create 90-degree amalgam margin

> Equal to 90 degrees

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BEVELS None(Except Gingival)

Large preparation, esthetics, and seal

TEXTURE OF PREPARED WALLS

Smoother Rough

CUTTING INSTRUMENT Burs Burs or Diamonds

PRIMARY RETENTION FORM

Convergence Occlusally

None

SECONDARY RETENTION FORM

Grooves, slots, locks, pins

Bonding; grooves for very large or root surface preparation

RESISTANCE FORM Flat floors, rounded angles, box-shaped

Same for large preparations

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BASE INDICATIONS Provide 2mm between pulp and amalgam

Not needed

LINER INDICATIONS Ca(OH)2 over direct or indirect pulp caps

Same

SEALER GLUMA desensitizer when not bonding

Sealed by bonding system used

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REFERENCES-Sturdevant's Art and Science of Operative Dentistry, 5th edition 2006.

Textbook Of Operative Dentistry, By Vimal K Sikri

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Health & Medicine

Class i cavity preparation