Preliminary Considerations in Operative Dentistry

By DR.SELVA

Operator positions

Direct vision

In-Direct vision

Maxillary Dentition working position

Mandibular Dentition working position

Working Position for Phantom Head Exercises

Removal of Single Typhodont tooth

Attachment of Single Typhodont tooth

Attachment of Articulator on the Jaw

Attachment of Gingival simulator on the articulator

Removal of Gingival simulator on the articulator

CLASS I PREPARATIONS

The restorative materials available differ as to their performance characteristics, cost, ease of use, aesthetic appeal, long-term effectiveness and safety.

As a result, their suitability for the different types of clinical situations varies. No single restorative is ideal for all indications.

AMALGAM COMPOSITES

COMPOMERS MODIFIED GIC

Amalgam Class I restorations:

Factors to be considered:a. Extent of pit and fissure caries.b. Incidence of proximal surface caries.c. Esthetics.d. Economics.e. Preventive procedures.

Occlusion:use of articulating paper to register centric holding

cusps and excursive contacts so that these areas can either be excluded or properly restored.

Local anesthesia:given both to reduce pain and also reduction of

salivation.

Conservative cavity preparation:is recommended to preserve the integrity of pulp and

also strength of the tooth.

Isolation of operating site:rubber dam application is mandatory for isolation and

salivary control.

Initial cavity preparation:

Outline form, Resistance form, Retention form:include all pits and fissures and sharp marginal outline

form is avoided.marginal outline form for a maxillary premolar is butterfly

shape.

General principles:a. going around the cusps to conserve the tooth structureb. not extending the facial and lingual margins more than

half-way between central groove and cusp tips.c. extending the outline to include fissures thereby

placing the margins on relatively smooth sound tooth structure.d. minimal extension into the marginal ridges.e. joining two faults when less than 0.5mm apart.f. establishing ideal conservative depth of cavity.

Preparation sequence:No. 245 bur with a head length of 3mm and a diameter of

0.8mm is used to prepare the class I cavity preparation.No. 330 bur (pear shaped) is used for conservative

cavity preparation.beginning of cavity preparation is done by performing a

punch cut over the deepest involved pit or the distal pit.the bur should be rotating when it enters and should not

stop until its removed from tooth.as the bur enters the tooth the depth should be kept as

1.5-2mm (1/2 – 2/3rd the length of cutting portion of bur)distal extension into the marginal ridge to include a

fissure or caries sometimes indicates a slight tilting of the bur distally to prevent undermining of the marginal ridge.

premolars – distance from margin of cavity to proximal surface must not be less than 1.6mm

molars – this distance be minimum of 2mm.

169L bur can be used for extension from pits and fissures facially and lingually.

in larger teeth with steep cuspal inclines floor of the cavity can follow the rise of cusps.

ideally the isthmus width be width of the bur.minimal faciolingual width of the outline and minimal

occlusal convergence is desired.an ideal conservative class I cavity should have a

faciolingual width of no more than 1 - 1.5mm and a depth of 1.5 - 2mm.

Final cavity preparation:includes Removal from pulpal wall of any remaining

defective enamel, Pulp protection, Procedure for finishing external walls, Cleaning and inspection of cavities.

Removal of any defective enamel:No 245 bur can be used to deepen the floor of cavity to

remove caries.a small round carbide bur or spoon excavator can be

used to remove small caries lesions.atleast three seats of sound dentin be there periphery

to the excavated areas.removal caries be stopped once we feel the excavated

dentin hardness is same as that of surrounding dentin.

Pulp protection:in cavities of ideal depth no liners or bases is required.in regions where cavity depth is of moderate zinc oxide

eugenol liner or base is preferred.

Finishing enamel walls:its finished during the earlier steps itself so no special

steps are required.

Cavity preparation for extensive caries:caries is extensive if the distance between infected

dentin and the pulp is judged to be less than 1mm.

Initial cavity preparation:here outline, resistance, retention forms are deferred

until the excavation of infected dentin is completed followed by insertion of base.

reason is to protect the pulp as early as possible from insult of cavity preparation.

Final cavity preparation:if pulp exposure occurs during removal of caries direct

pulp capping could be tried.here using a non-pressure flow technique to insert a

0.5-0.75mm of calcium hydroxide cement is used to cover exposures of pulp.

Insertion of amalgam:use an amalgam carrier to transfer amalgam to the

cavity preparation.use a flat faced circular or elliptical condenser to

condense amalgam over the floor.initial condenser be small followed by larger condenser

for overpacking.each condensing stroke should overlap each other.each condensed increment should only fill 1/3rd – 1/2th

cavity depth.condensation of mix be done within 21/2 – 31/2 mins.

Otherwise crystallization of amalgam be over.

Precarve burnishing:is a form of condensation.cavity preparations be overfilled with amalgam.burnisher head be large enough it will contact slopes

not the margins.this is done to remove excess mercury and also adapt

amalgam closely to cavity margins.

Carving procedure:carving can be done immediatelysharp discoid – cleiod instruments are selected.all carving be done with the edge of the blade

perpendicular to margins and moved parallel to margins.part of the edge of carving blade should rest on

unprepared tooth surface adjacent to cavity margins.

after carving the outline of amalgam restoration should reflect the contour and location of the prepared cavosurface margins revealing a regular outline with gentle curves.

Post carve burnishing:is the slight rubbing of the carved surface with a

burnisher of suitable size and shape to improve smoothness and produce a satin appearance.

with precarve burnishing and now postcarve burnishing the polishing of amalgam becomes unnecessary.

Occlusion of restoration:after completion of procedure patient is advised not to

bite because of danger of fracturing of restoration which is weak at this stage.

to ensure occlusion is correct its checked using articulating paper.

while carving its advised to establish stable centric contacts which is perpendicular to direction of occlusal load.

Finishing and Polishing procedures:not all amalgam restorations require these procedures

but some do,a. to complete carving procedureb. refine the restorationsc. enhance surface texture of restorations.

This procedure is not attempted within 24hrs.

finishing and polishing of restoration should not leave a underfilling.

after this procedure an explorer should pass from the tooth surface to restoration without any catch or jump.

a white fused alumina or green carborundum stone is used to correct the discrepancy.

a flame shaped finishing burs may be used to define the grooves and fissures.

polishing procedure is initiated by coarse rubber abrasive point at slow speed.

a high polish may be imparted using series of medium and fine abrasive points.

instead of rubber points rubber cups with pumice could be used.

Occlusolingual cavity preparation and restoration:Initial cavity preparation:on maxillary molars its indicated when the distal pit and

distal oblique ridge and lingual fissures are connected.some special considerations are,

a. cavity should be no wider than necessary.b. when indicated the cavity preparation should

be done more at the expense of oblique ridge rather than centering over the fissure.

c. especially in smaller teeth the occlusal portion can have slight distal tilt.

these features help in strengthening the restoration and tooth.

Preparation procedure:using an mouth mirror indirect vision and no 245 bur

enter the distal pit. Bur should be parallel to long axis of tooth.to preserve distal marginal ridge it may be necessary to

cut more mesial tooth structure.slight distal inclination of bur may be necessary to

preserve the distolingual cusp.next is preparation of the lingual surface. Tip of the bur

should be located at the gingival end of the lingual fissure. Lingual portion should be should have an uniform depth of 1.5mm. Axial wall should follow contour of lingual tooth structure.

mesial and distal walls of lingual portion should converge slightly and axiopulpal line angle be rounded.

Final cavity preparation:Secondary retention and resistance form:

it can be prepared using no.1/4 bur to prepare locks on mesio and disto-axial line angles.

locks should be of depth 0.5mm into dentin.cutting direction is bisector of the line angle.

The depth of lock should decrease in depth as it moved towards occlusal surface.

Insertion and carving procedures:a rigid matrix is necessary to prevent land sliding of the

restoration during condensation of lingual portion.a tofflemire retainer is used to retain a matrix band but

this does not allow intimate adaptation of matrix to lingual portion of tooth.

an additional step here is to cut a piece of stainless steel matrix (0.0002 inch thick, 5/16 inch wide) that will be used to fit in space between tooth and matrix band.

break off a round tooth pick holding it in no.110 plier.heat a green stick compound cover this with end of a

tooth pick, now insert the tooth pick with heated compound between tooth and matrix band.

now using a burnisher the matrix band is contoured with firm pressure.

this was suggested by Barton.condensation of amalgam is started from the gingival

end of lingual portion.as the condensation is finished the matrix band is

removed using no.110 plier by slightly moving it lingually and then occlusally.

Additional Class I preparations:

Facial pit of mandibular molar:facial surface of a mandibular molar has often a faulty

pit and not a fissure.cavity preparation is accomplished by a no.245 bur

positioned perpendicular to the tooth surface.when the defect is small a no.330 or no.169L burs may

be used.cavity depth is usually 1.5mm.

Lingual pit in maxillary incisors:usually a no.245 bur is used in direction with orientation

of the pit which is usually apical in direction.since the lingual enamel is thinner its recommended

depth be only 1 – 1.2mm only.sometimes anterior maxillary teeth may develop dens –

in – dente which may also require intervention and restoration.

Occlusal pits of mandibular first premolar:mostly because of presence large facial cusp a central

fissure is absent.a no.245 bur is used to prepare a punch cut of 1.5-2mm

depth.orientation of bur should be parallel to long axis of the

tooth.this orientation preserves the small lingual cusp.sometimes if a central fissure is present its connected by

a conventional outline.

Occlusal pits and fissures in maxillary first molar:leaving the oblique ridge can preserve the strength of the

tooth but if required the oblique fissure must be involved.

Occlusal pit and fissures in mandibular second premolar, molar.if mandibular second premolar has two lingual cusps the

lingual development groove may be restored.often in mandibular molars a facial fissure may involve

the occlusal surface and may require restorations.facial extension preparation is same as that

occlusolingual preparation in maxillary molars.

Class I Upper Premolar Class I Lower First Premolar Class I Lower Second Premolar

Class I Lower Molar Class I Upper Molar

Class I Upper Incisor

Designs of class I preparation (according to Marzouk):a. Class I design I:

Location – occlusal surface of molars and premolars.Indications:

caries cone into dentin no more than 1mm.patient has low caries index.

b. Class I Design 2:Location – occlusal surfaces of premolars and molars.Indications:

caries cone into dentin 1mm or more from DEJ.cavity width is more than 1/4th interproximal width.as a preventive measure in patients with high caries

index.

c. Class I Design 3:Location – occlusal 1/3rd of facial and lingual surfaces of

molars and lingual surfaces of upper anterior teeth.Indications:

a pit in aforementioned location decayed.used as a prophylactic procedure.involved pit in this location not connected with

other surfaces of tooth.used in dens invagintus.

d. Class I Design 4:Location – in molars in addition to involving their

occlusal surfaces the grooved part of facial and lingual surfaces also involved.

Class I Design 5:Location – in molar tooth in addition to occlusal surface

involvement most of the facial or lingual surfaces are also included in the preparation.

Indications:facial and lingual cusps are undermined by

backward cariesoutline is not conducive to retention of

restorationfoundation for cast restoration

Class I Design 6:Location – design included for part of the occlusal surface

of molars or premolars as well as a portion of the facial, proximal or lingual surface in the form of a table of an entire cusp.

Indications:portion or an entire cusp undermined by caries.marginal ridge adjacent to an occlusal

preparation is crossed by a fissure to the facial or lingual embrasures.

foundation for future cast restorations.

Class I Design 7:Location – design usually involves occlusal, facial lingual

surfaces of molars and premolars.

Class I Design 8:Location – used in molars, premolars and incisors.Indication:

designed specifically for endodontically treated tooth

Composite Restorations:

Introduction:search still continues for a tooth colored material to

withstand high occlusal stresses.newer formulation have these general features,

a. Radiopaque fillers.b. Smaller filler particles.c. increased amount of fillers.d, greater strength.e. reduced porosityf. reduced water sorptiong. polymerization with visible light.

Advantages:a. esthetics.b. conservation of tooth structure.c. improved resistance to microleakage.d. strengthening remaining tooth structure.e. low thermal conductivityf. completion in one appointment.g. economics.h. no corrosion.

Disadv:very technique sensitivityhigher coefficient of thermal expansionlow modulus of elasticitybiocompatability issue.limited wear resistance.

Indications:Class I cavities that can be properly isolated.with minimal centric holding involvement.

Contraindications:operating site cannot be isolated.all occlusal contacts will be on the composite.heavy occlusal stresses.deep subgingival areas that are difficult to restore.

Shade matching in posterior teeth is not critical a slight shade mismatch can aid in revaluation of the restoration.

Basic preparation designs:a. Conventional designb. Beveled conventional design.c. Modified design.

Conventional design:these are box like cavities have slightly converging

walls, flat floors, undercuts in dentin (if required).usually this designed is not employed because it do not

strengthen the tooth structure, its employed only when an amalgam restoration is already present or the cavity extends onto the root surface.

Beveled conventional preparation design:bevel is prepared using flame shaped diamonds of

approx 0.5mm width and at an angle of 45deg to external surface.

this design is preferred when there is a requirement for increased resistance form.

this is the preferred design for class II preparation.

More extensive preparations require reverse bevels, skirts, bracings to enhance retention and resistance forms.

Modified design is recommended for class I preparation where ultraconservative preparation be made.

Modified preparation:emphasis here is more on the conserving tooth structure.characterized by,

a. conservative removal of tooth structure.b. establishment of beveled margins on all

cavosurface margins

Class I cavity preparation:when restoring small pits and fissures a ultraconservative

modified preparation is recommended.ultraconservative preparation is done using no.1/2 bur

and bevel by flame shaped diamonds.depth of cavity is done till the caries has been removed.for deep cavities CaOH liner and light cure GIC base is

recommended.no.245 bur and beveled conventional preparation may be

employed when extensive preparation is entitled or a large faulty restoration is present.

an undermined marginal ridge (enamel) can be left in extensive preparation and can be strengthened by composite bonding.

Conventional preparation

Beveled Conventional preparation

Modified preparation

Glass Ionomer Restorations:early GIC lacked physical strength and wear resistance

to be utilized in occlusal restorations. Newer more heavily filled GIC and resin modified GIC have improved strength to be utilized with certain precautions.

they are utilized in,a. in small to medium sized restorations protected from

occlusal forces.b. for patients in perceived need of fluoride release.c. for longer provisional tooth colored restorations.d. for patients in whom restorative procedures cannot be

prolonged.e. atraumatic restorative procedures is to performed.f. when margins of large load bearing restorations needs

to be repaired.

Preparation outline be carefully planned to leave out margins from occlusal contacts and not to bevel the cavosurface margins as it may leave a thin flash of material with insufficient strength.

Minimal Invasive Dentistry (MI):is a conservative opportunity to identify early caries risk

followed by preventive procedures designed to heal early lesions whilst eliminating the bacterial disease.

when lesions have advanced and healing is not possible then a minimal invasive surgical approach should control and eliminate surface cavitation and stimulate remineralization using a biomimetic restorative material.

the philosophy of Minimal Intervention Dentistry combines the current knowledge of prevention, remineralization and ion exchange adhesion.

General principles of cavity design:until recent times cavities were designed along surgical

lines without an understanding of the action of fluoride ion and for placement of restorative materials that were difficult to handle, were subject to microleakage, and were often not esthetic.

also in absence of adhesion it was necessary to remove undermined enamel defeating the purpose of preservation of remaining tooth structure.

with better understanding of fluoride properties and adhesion developments its possible to place restorations in limited size cavities retaining much of tooth structure.

by today’s standard cavity design proposed by G.V.Black is large and it was necessary to remove additional tooth structure for ‘extension for prevention’.

New cavity classification:prime objective here is to retain as much as natural tooth

structure as possible. Given by G.J.Mount and Hume

Three sites of carious lesion:site 1 – pits, fissures, and enamel defects on occlusal

surface of posterior teeth and other smooth surfaces. {Class I}site 2 – approximal enamel immediately below areas in

contact with adjacent tooth. {Class II, III, IV}site 3 - cervical one third of crown following gingival

recession in root. {Class V}

Four sizes of carious lesions:size 1 – minimal involvement of dentine just beyond

treatment by remineralization alone.size 2 – moderate involvement of dentine. Following

cavity preparation, remaining enamel is sound, well supported by dentine and not likely to fail under normal occlusal load.

size 3 – cavity is enlarged beyond moderate involvement. Remaining tooth structure is weakened to the extent that cusps or incisal edges are split if exposed to occlusal load. Cavity needs to further enlarged so that the restoration can be designed to provide support to remaining tooth structure.

size 4 – extensive caries and bulk loss of tooth structure has already occurred.

Size 1 lesion is most commonly will be a new lesion ideal for adhesive restorationsSize 2, 3,4 lesions may be lesions progressed to considerable extent or may be breakdown of a earlier restoration.

Use of composite is limited by its polymerization shrinkage.Amalgam limitation is its poor esthetic qualityGIC has excellent adhesion but lacks strength to be utilized in marginal ridges and incisal edge.

Cavity design and preparation:when dealing with new lesion cavity design be very

conservative, because margins can be remineralized, and cavity extent is determined only by the extent of caries cavitaion.

on the other hand replacement of failed restoration cavity outline will be already defined and often will be extensive. And here most of Black’s principles hold good.

Site I , Size I, [1.1]:usually the extent is limited and most of the fissure

system should be free of caries.using very finest tapered diamond point (#200) enter the

fissure in region of caries attack, open the enamel to determine the full extent of caries.

its unnecessary to remove the affected demineralized dentin on floor of cavity but walls of cavity be free of caries.

remaining fissure system are also opened to determine the presence of caries.

small round burs (#008 or #012) can be used to clean walls of infected enamel.

generally there is no need to penetrate the full depth of enamel.

Restoration:Glass ionomer is material of choice because of fluoride

release and adhesion.use strongest GIC available either autocure or self cure.condition the cavity with 10% polyacrylic acid.placement of cement in a syringe is desirable.when using an autocure cement positive pressure with

gloved finger may be required followed by protection with a resin sealant to prevent contamination with moisture.

when using light cure resin mosified GIC there’s no need for finger pressure and restoration can be immediately finished and no resin sealant required.

if the occlusal load is heavy may be lamination with composite (sandwich restoration) can be performed.

Site I, Size 2 [ 1.2 ]:G.V.Black classification – Class I

Preparation:it may be a new cavity or repairing or replacement of an

old restoration.tungsten carbide bur (#140TC) can be used to remove

old restoration, a tapered diamond or straight diamond (#160 Dia or #156 Dia) is then used to explore the lesion.

small round burs can be used to clean the walls of the cavity.

Restoration:GIC is the best choice of material.also lamination technique with composite can be

considered.

Site 1 Size 3 [ 1.3]:when cavity reaches this size there will be extensive

undermining of atleast one cusp. It may be a new lesion of old restoration that may be recurrent.Preparation:

tungsten carbide burs (#140) should be used to remove any remaining old restorations.

a small diamond straight fissure (#156) is used to explore the lesion.

Round burs (#012 or 016) can be used to remove infected dentin from walls of the cavity.

if it’s a new active caries it may be necessary to place an indirect pulp capping agent then review after minimum of 12 weeks.

if cuspal strength is adequate a conventional restoration be attempted.

if cuspal strength is weakened grooves may be placed in cusps to strengthen the cusp with restorations.

Restoration:of plastic direct filling materials amalgam is the choice.most of the time teeth affected will be going in for crown.lamination technique with resins could also be done.

Site I Size 4 [1.4] :this is an extensive cavitated lesion there will be one or

more loss of cusps full restoration with direct restoration is difficult.

preparation is same as for size 3 lesion.amalgam as a restorative material could be used with

mechanical interlocks.a full crown is the most ideal restoration.

Direct Gold Restorations:principles of direct gold restorations must be followed

diligently for proper gold restorations.sharp internal line angles are established for proper

starting convenient form.

Indications and contraindications:small pits and fissures in posterior teeth and lingual

surfaces of anterior teeth.small class V restorations.small class III restorations.small class II lesions in tooth not subjected to heavy

occlusal forces.class VI lesions.repairing of acceptable cast gold restorations.

Contraindications:teeth with large pulp chamber.severely periodontally weakened tooth.handicapped patients not willing to sit for longer periods

of time.root canal treated tooth.

Class I tooth preparation and restoration:Design:

outline is extended to include the lesion on the tooth and also the fissured enamel.

preparation margins are placed beyond the pits and fissures of the tooth.

outline is kept as small as possible with acceptance for condensation and manipulation of restorative material.

pulpal wall is of uniform depth and established at 0.5mm into the dentin.

small undercuts are placed in pulpal floor to aid in beginning of condensation of gold.

a very slight cavosurface bevel is placed about a) 30 – 40 deg of marginal metal to aid in ease of finishing of gold. b) to remove rough remaining enamel.

this bevel is not more than 0.2mm in width.

General shape:outline form is similar to class I cavity preparation for

amalgam with three modifications,a. instead of round corners here its angular corners.b. extensions in facial and lingual grooves will end in

spear shaped form.c. whole outline form will look more angular than

amalgam preparations.

Instrumentation:for description a mandibular premolar is selected.no 330 or 329 bur is used for establishing outline form

and initial depth.a small hoe can be used to establish desired

smoothness in pulpal floor.using a 33½ inverted bur or angle former chisel an

undercut may be given in the pulpal floor.round burs may be used to remove any remaining

caries.angle former or finishing bur (7802) or flame shaped

stone may be used to finish the cavosurface margins.

Restoration:The restorative phase begins with insertion

of a pellet of E-Z Gold or gold foil. The gold is first degassed in the alcohol flame, cooled

momentarily in air, and inserted into the preparation.The gold is pressed to place with the nib of

a small round condenser.Next, compaction of the gold begins with a line of

force directed against the pulpal wall.Hand pressure is used for E-Z Gold; malleting is used

for gold foil.the line of force is changed to a 45-degree angle to the

pulpal and respective external walls (to best compact the goldagainst the internal walls).

If E-Z Gold is to be the final restoration surface, compaction is continued until the restoration is slightly overfilled.

If gold foil is selected to veneer this restoration, thenpellets of suitable size are selected.

The pellet is degassed and carried to the preparation. First, hand pressure compaction is used to secure the pellet against the compacted E-Z Gold and spread it over the surface; then mallet compaction is used.

The first step in the finishing procedure is to burnish the gold.A flat beaver-tail burnisher is used with heavy hand

pressure to harden the surface gold.A cleoid-discoid carver is used to continue the burnishing

process and remove excess gold on the cavosurfacemargin.

After use of the cleoiddiscoid, a small round finishing bur (No. 9004) is used to begin polishing.

It is followed by the application of flour of pumice and tin oxide or white rouge.