CURRENT CONCEPTS IN CLASSIFICATION, INDICATION, PRINCIPLES AND PROCEDURES OF CAVITY PREPARATION WITH RESPECT TO ADHESIVE RESTORATIONS

IntroductionMacrodentistry is the density that has been practiced for centuries with the

conventional concept of “Extension for prevention” or cutting for immunity. A patient who has been assessed as having a high caries risk is immediately worked on and preventive restorations have been given.

MicrodentistryIn the past few years the emerging techniques of operative density dedicated to

minimal invasion and minimal sacrifice of sound tooth structure have been explored and documented and they have become part of the mainstream dentistry. As new techniques emerge and are adapted into dental disciplines, the usual intent and purpose of the original technology often change in the course of adaptation.

Microdentistry, the dental science of diagnosing, intercepting and treating dental decay on the microscopic level is now emerging as an operative tool in science-based microdentistry. The ultimate goal is prevention of extension and restriction with conviction.

Historical aspects1. Historical aspects of G.V. Blacks – Concept of cavity preparation

a. Introduction

When Black defined the parameters for his classification, the cavity designs were controlled by a number of factors, many of which no longer apply. Caries was rampant and the significance of fluoride was not understood. There were limitations in the available instruments for cavity preparation as well as in the selection of restorative materials. The five categories of carious lesion were related to the site of the lesion and to the nature of the intended restoration, but they did not take into account the increasing dimensions of a cavity nor the complexity of the method of restoration.

b. G. V. Black’s classification

Class IAll pit and fissure restorations are class I and they are assigned to the three groups

as follows

1. Restorations on occlusal surface of premolars and molars.2. Restorations on occlusal two thirds of facial and lingual surfaces of molars.3. Restorations on lingual surface of maxillary incisions.

Class IIRestorations on proximal surfaces of posterior teeth

Class IIIRestorations on proximal surface of class III which do not involve the incision angle

Class IVRestorations on proximal surface of anterior teeth which involve incisal edge

Class VRestorations on gingival third of the facial or lingual surfaces of all teeth

Class VIRestorations on the incisal edge of anterior teeth or the occlusal cusp heights of

posterior teeth

c. Materials

Amalgam, Direct filling gold, Cast metal

d. Principles

To remove tooth structure to gain access and visibility. To remove all trace of affected dentine from the floor of the cavity. To make room for the insertion of the restorative material itself. To provide mechanical interlocking retentive designs. To extend the cavity to self-cleansing areas to avoid recurrent caries.

The result was that, by today’s standards, all such restorations were large. In his designs, Black showed commendable respect for remaining tooth structure as well as occlusal and proximal anatomy but it was necessary to sacrifice relatively extensive areas of enamel to achieve his goals.

e. Earlier concepts of conservation

1. Occlusal convergence

It aids in retention as well as conversation of occlusal tooth structure. This design of cavity preparation exposes minimal amount of restorative material to occlusal loading.

2. Reverse curve

3. Double pulpal floor

Here one level of pulpal floor is at ideal depth (1.5mm for amalgam) and others will be at a deeper level as dictated by the pulpal extent of decay. The deeper part of pulpal floor is called ledge. It can be circumferential, interrupted or opposing.

iv. Preservation of oblique ridge

Oblique ridge is included in cavity preparation only when (i) undermined by caries, (ii) directly affected by caries and (iii) when less than 0.5mm.

v. Enameloplasty

If less than one third of enamel depth is involved by carried the fissure may be removed by enamel plaster without extending the tooth preparation. Enamel is reshaped into a saucer form so that the area becomes cleanable, finishable and allows conservative placement of preparation margins.

vi. Prophylactic odontotomy

Proposed by Hyart in 1924. It is characterized by minimally preparing and filling with amalgam, developmental, structural, imperfections of the enamel, such as pits and fissures, to prevent caries originating in these sites.

The demineralization and remineralization cycle

Demineralization The mineral component of enamel, dentine and cementum is hydroxyapatite,

Ca10(PO4)6(OH)4 in a neutral environment, hydroxyapatite is in equilibrium with the local aqueous environment, which is saturated with Ca2+ and PO4

3 ions.

Hydroxyapatite is reactive to hydrogen ions at pH 5.5 (the critical pH for hydroxyapatite) and below. Hydrogen preferentially with the phosphate groups in the aqueous environment immediately adjacent to the crystal surface. The process can be thought of as conversion of PO4

3 to HPO42 by the addition of

hydrogen and the hydrogen being buffered at the same time. The HPO4

2 ions is then not able to contribute to the normal hydroxyapatite equilibrium because it contains PO4, not HPO4 and the hydroxyapatite crystal therefore dissolves. This is termed demineralization.

Remineralization The demineralization process can be severed if the pH is neutral and there are

sufficient Ca2+ and PO43 ions in the immediate environment.

Either the apatite dissolution products can reach neutrality by buffering or the Ca2+ and PO4

3 ions in saliva can inhibit the process of dissolution through the common ion effect.

This enables rebuilding of partly dissolved apatite crystals and is termed remineralization.

This interaction can be greatly enhanced by the presence of fluoride ion at the reaction site.

Acid reaction with apatite at the tooth surface Following eruption there is a process of continuing mineralization of enamel

from salivary calcium and phosphate. Initially, enamel apatite contains many carbonate and magnesium ions, which

are highly soluble in even mild acidic conditions. However, there is a rapid and extensive exchange of hydroxyl and fluoride ions as the magnesium and carbonate are dissolved, leading to a more mature enamel with a greater resistance to acid ion challenge.

This level of maturity or acid resistance can be greatly enhanced by the presence of fluoride.

As the pH decreases the acid ions react, principally with the phosphates in saliva and plaque (or calculus) until the critical pH for dissolution of hydroxyapatite is reached at approximately pH 5.5 – 5.2.

Further decrease in pH results in progressive interaction of the acid ions with the phosphate groups of hydroxyapatite, causing partial or full dissolution the surface crystallite.

Stored fluoride released in this process reacts with the Ca2+ and HPO42 ion

breakdown products, forming fluorapatite or fluoride – enriched apatite. If the pH decreases further below 4.5, which is critical pH for fluorapatite

dissolution even fluorapatite will then dissolve. If acid ions are neutralized and the Ca2+ and HPO4

2 ions are retained the reverse process of remineralization occur.

Factors contributing to maintenance of de- and remineralization

Saliva with its buffering capacityCa2+ and PO4

levels

Fluoride application

Oral clearance of proteins &Glycoproteins

Buffering andRemineralization potential

Protective factors

Diet + plaque acids

Decreased salivary flow Decreased buffering

capacity and oral

clearance rate

Acidic saliva erosive acids

To detect accurately the prime cause of an imbalance in a particular patient. It is essential to be familiar with the precise nature of each of the factors and the activity that occurs on the tooth surface.

The various factors are:

1. Bacterial flora – Streptococcus mutans2. Plaque retention – contact areas, overhangs, over contours, pits and fissures,

sticky foods. 3. Thickness of plaque4. Salivary buffers5. Fluorides6. Frequency of carbohydrate intake

Effect of plaque on pH of salivaFermentable carbohydrate entering the oral environment go into solution in saliva

and become available to plaque microbes 2 – 4 point drop in pH at tooth surface. Amount of pH drop depends on plaque thickness, number and type of plaque bacteria, efficiency of salivary buffering.

Recovery to normal resting pH takes from 20 minutes average to several hours for those with increased caries susceptibility.

Acids from carbohydrate fermentation are weak organic acids and will cause only chronic low grade caries.

Destabilizing factors

Other sources of acids are from Carbonated drinks Citrous fruits Gastric reflux

Protective factors Natural factors – role of saliva Diet factors

- Increased fat in diet decreased plaque attachment- Milk products like cheese- Fibrous foods increased chewing increased flow of saliva

Saliva and its protective factorsSaliva plays an important role in protecting teeth against acid challenge. Normal

salivary flow = 3ml/min, in xerostomia – it is 0.3ml/min increased caries risk.

Factors decreasing salivary flow Physiologic

- age – decreased secretory cells- sleep

Xerostomia- Sjogren’s syndrome

Radiation therapy - Xerostomia- Cervical caries due to decreased salivary flow

Medications - Anticholinergics- Antihypertensives- Antidepressants

Unstimulated saliva contains little bicarbonate buffer with fewer calcium ions and more phosphate ions.

Reflex stimulation of saliva by chewing or through the presence of acidic foods can increase the flow by a factor of more than 10. Bicarbonate buffer concentration increased 60 times upon stimulation. Calcium ions increased but PO4 ions do not increased in proportion to flow rate reduction of maximum salivary flow to less than 0.7ml/min increased caries risk.

Salivary protective factors1. Ca and PO4 ions

It is usually the saliva is supersasturated when the enamel apatite is at neutral pH. PO4 ions also provides a significant buffering capacity at resting pH and in early stage of acidic challenge.

2. Pellicle

Origin from saliva. Protects against acid challenge. Acts as a barrier to diffusion of acid ions into the tooth. Also may inhibit mineralization of apatite to form supersaturated levels of Ca and PO4 in saliva.

3. In stimulated saliva

Good HCO3 buffering system

4. Salivary flow and oral clearance rate

Influence removal of food debris and microorganisms

5. Fluoride content of saliva is low

0.03 ppm or 1.6 mol/litre but still contribute to protection and repair of tooth minimal.

Effect of fluoride on enamelIn acidic environment, fluoride ion reacts with free Ca++ and HPO4

2 ions forming fluorapatite crystals. Fluoride replaced hydroxyl ions since the ionic radii of fluoride (1.36A0) and OH (1.4A0) are similar. Fluorapatite is less soluble because of better submit stacking. It gets dissolved at pH of 4.5. In tooth structure, its concentration is as high as 2500 – 4000 ppm. Daily consumption of water contain fluoride at 1mg/lit increased caries resistance.

Fluoride Fluorapatite (less soluble) Inhibits bacterial metabolism Decreased demineralization Increased remineralization Decreased plaque formation Decreased wettability of tooth structure

Increased concentration of fluorides stored as CaF2 around apatite crystals heavy remineralization at surface lesions.

Effect on established lesions1. Contribute to remineralization of incipient enamel caries.

2. Partly remineralize carious dentin and therefore slows down assets carious process in the cavitated lesion.

3. Remineralize root surface lesions to the extent that they may not need a restoration.

Topical fluoride is more effective in inhibiting smooth surface caries and in aiding remineralization of enamel, dentin and cementum. Less effective in fissures. Daily application of topical fluoride to demineralzie root surfaces over a period of 2 – 4 months leads to significant hardening of exposed dentin. Deep and extensive root caries can be hardened with in the same period of time but required a higher concentration of fluoride.

Level of remineralization

Enamel Till actual cavitation has not occurred. Only if some crystal structure is present.

Dentin Early stages of development of lesion. Till the collagen matrix has not collapsed.

Breakdown within dentin can be divided into two identifiable zones.

1. Infected dentine

Surface layer closest to oral environment. Heavily infected with bacteria. Collagen matrix collapsed. Stain red with basic Fuschindye. Dark brown / black in color Soft consistency can be readily removed with sharp excavator. Not remineralizable.

2. Affected dentine

In the advancing front of caries following course of dentinal tubules. Colorless, relatively soft Basic structure of collagen matrix present and intact Sterile with very few pioneer bacteria Can be remineralized to some degree Regarded as precarious, not removed and left to be healed Also not removed entirely as pulp immediately subjacent to approaching caries

will be initiated and inflamed by presence of bacterial toxins and mechanical exposure will lead to pulpal death.

Potential for remineralizationOnce the cavitation has occurred, the infected layer is removed and the lesion is

completely isolated from the oral environment with an adhesive restoration, which will prevent microleakage. Remaining pioneer bacteria left in the affected dentin will become dormant and pulpal irritation will cease.

The deep affected layer that had been demineralized will be subject to remineralization because collagen matrix is still intact.

In the past zinc oxide and eugenol paste was used as a sealant because of its antibacterial properties, but now glass ionomer is preferred as it completely seals cavity and releases fluoride, Ca++, phosphate ions thus encouraging remineralization and healing of dentin.

Demineralized enamel and dentin can be remineralized but not cavitated lesions.

White spot lesions on the visible surfaces of tooth can be remineralized.

Radiographic assessment Minimal depth of detectable lesion on the radiograph is about 500m. 60% of teeth with proximal radiographic lesion on the outer half of dentin are

non-cavitated and hence should be remineralized than restored.

Classification of approximal radiolucencies assessing caries based on radiographs.

E1 - outer half of enamel

E2 - inner half of enamel

D1 - outer third of dentin

D2 - middle third of dentin

D3 - inner third of dentin

E0 - no carious lesion

Dentin is divided into three zones, as it enables more conservation criteria to be established.

Using this minimally invasive technique, restorations are not indicated until lesion has extended to D2 region.

Disadvantages overlapping proximal contacts lengthening of image wrong idea on depth of lesion 2-D image superficial remineralization not seen fracture of one lingual cusp is seen as radiolucency of proximal cavity.

1. In case of incipient or minimal lesion involving limited pit and fissures preventive resin restoration (sealant alone / sealant and filled resin).

2. Decalcified appearance of pits and fissures indicative of incipient / minimal caries Sandwich preventive resin restoration (Glass ionomer liner, filler resin and sealant).

3. Involvement of adjacent pit and fissure enamel with possible minimal involvement of underlying enamel and dentin glass ionomer PRR (GIC liner, GIC restorative and sealant)

4. No minimal undermining isolated pits and fissured. No radiographic / clinical evidence of interproximal caries but possible radiographic evidence of occlusal caries sealant amalgam PRR (Amalgam in isolated pits and fissures without extension for prevention and sealant).

New cavity classificationThe understanding of the effect of fluoride on the demineralization –

remineralization cycle as well as the advent of true long term, adhesion with restorative materials, has made it possible to reconsider the classification of carious lesions and cavity designs first rationalized by G.V. Black.

Mount’s classification

The three sites of carious lesions

Site 1Pits, fissures and enamel defects on occlusal surfaces of posterior teeth or other

smooth surfaces

Site 2Approximal enamel immediately below areas in contact with adjacent teeth

Site 3The cervical one-third of the crown or following gingival recession, the exposed

root

The four sizes of carious lesionsRegardless of site or origin of lesion

Size 1Minimal involvement of dentin just beyond treatment by remineralization alone

Size 2Moderate involvement of dentin. Following cavity preparation, remaining enamel is

sound, well supported by dentin and not likely to fail under normal occlusal load

Size 3The cavity is enlarged beyond moderate involvement. Remaining tooth structure is

weakened to the extent that cusps or incisal edges are split or are likely to fail if exposed to occlusal load. The cavity needs to be further enlarged so that the restoration can be designed to provide support to remaining tooth structure.

Size 4Extensive caries and bulk loss of tooth structure has already occurred.

Minimal Moderate Enlarged Extensive

Size 1 2 3 4

SitePit/fissure 1.1 1.2 1.3 1.4

1Contact area 2.1 2.2 2.3 2.4

2Cervical 3.1 3.2 3.3 3.4

3

Black’s classification did not allow for size 1 lesion in either site 1 or site 2 because of absence of adhesive restorative materials.

In the past, most restorative treatment was due to carries (dacay) and the term cavity was used to describe a carious lesion in a tooth that had progressed to the point that part of the tooth structure had been destroyed. Therefore, when the affected tooth was repaired the cutting or preparation of remaining tooth structure was referred to as a cavity preparation.

Nowadays many indications for treatment for teeth are not due to caries and therefore the preparation of the tooth is no longer referred to as cavity preparation but as tooth preparation.

Tooth preparation is defined as the mechanical alteration of defective, injured or diseased tooth to best receive a restorative material that will reestablish a healthy state for the tooth, including esthetic corrections where indicated, along with normal form and function.

Earlier Black advocated the principle of extension for prevention i.e. in tooth preparations for smooth-surface caries, the restoration should be extended to areas that are normally self-cleansing to prevent reoccurrence of caries and to include full length of enamel fissures in pit and fissure cavities.

This extension for prevention has been reduced to restriction with conviction by treatments that conserve tooth structure, therefore restored teeth are stronger and more resistant to fracture. Such treatments are enameloplasty, pit and fissure sealants, preventive resins and conservative composite restoration.

Earlier preventive measures included prophylactic odontonomy i.e. developmental, structural imperfections of enamel, such as pits and fissures were minimally prepared and filled with amalgam to prevent caries originating in these sites.

Guiding principles of adhesive cavities Black’s concept of extension for prevention is no longer valid. The current

paradigm is rather prevention of extension.

Cavity outline form cavity outline internal and external, is only dictated by the extent of the carried. Once caries dentin is removed, no further removal of tooth substance is required.

Resistance Resistance of both tooth and restorative material to resist fracture. Loose and fragile enamel rods should be moved, but unsupported tooth

structure may conserved and weakened tooth may be reforced by the bonded restoration.

90-degree cavosurface angles are given for GIC. Long level design for composite. If the margin is under functional loading the margin in that area might have a

cavosurface angle that approaches 60 to 80 degrees. Occlusal bevels should not be utilized for posterior composite preparations. After caries removal, the internal cavity features rounded characteristics,

straight internal walls and defined line angles are no longer required for adhesive materials.

Retention Macroretentive interlocking designs have changed to retention by means of

micromechanical (interlocking of resin tags into the retentive pattern of erched tooth tissues), submicromechanical (hybrid layer, horizontal branching between dentin tubules, surface roughness of tubules) and chemical adhesion (ion-exchange layer of glass ionomers).

Placement of a bevel increase by the potential surface area for retention by a more transverse cut of enamel prisms (enhanced etch pattern) and by extending the surface area of the preparation available for bending.

Cervical margins should only be beveled if the margin is well above the cementoenamel junction.

Convenience The concept of convenience continues to apply, as the clinician should have

access to the work area for efficient execution of techniques and manipulation of the materials.

The concept of self cleansing areas has been discarded and removal of all affected dentine from the axial wall of the cavity is strictly contra-indicated because of the potential for remineralization and healing.

Cavity preparations

Site 1 lesions Fissures on occlusal surface of posterior teeth. Pits on lingual of upper anterior teeth Pits on buccal surface of lower molars Pits on lingual extension of distal occlusal groove of upper molars

Size 1Small defect in one section of a pit or fissure, it is of ten combined with placement

of a fissure seal on remainder of the fissure system.

Size 2Moderate size lesion with most fissures involved or replacement of an existing

Black class 1 restoration.

Size 3Larger lesion requiring incorporation of protection for one or more cusps in the

design.

Size 4Extensive lesion with one or more cusps already missing

Size 1 and size 2No equivalent in G.V. Black classification

PreparationExtent limited, most of fissure system free of caries. Other sections of fissures deep

and convoluted and subject to later attack require protection through sealing at this time.

Fine tapered diamond pointEnter fissure till the extent of lesion

Small round bursIt is used to clean walls of infected enamel and dentin. It is unnecessary to remove

the affected, demineralized dentin on the floor of the cavity, but it is essential the walls are completely clean and free of caries. Enamel margins should be sound and free of microcracks and loose enamel rods.

Restoration – advantages

GIC Adhesion fluoride release Use strongest cement High powder liquid ration to ensure optimal physical properties Condition cavity will 10% polyacrylic acid to ensure optimal adhesion Placement of cement with a syringe is desirable to ensure positive adaptation

into the depths of cavity.

Autocure cement Resin modified glass ionomer

cement

Apply positive pressure using lightly

lubricated gloved finger as matrix.

After seating, seal the cement with

resin sealant to maintain water balance

Trim occlusion with round steel bur at

low speed with no air water spray

Seal again

No matrix required. No need to seal

as long as it has been light

activated for 40 secs.

Restoration polished immediately

after light activation at

intermediate high speed under air-

water spray

Erosion, abrasion lesions on occlusal surface of posteriors and incisal edges of anteriors not instruments as free of caries and smooth.

Restoration lamination technique

Conditioning

Autocure GIC on dentin as base

Both enamel resin build up

Conditioning

Resin modified GIC

Only enamel etching

Chemical union between GIC and composite

Site 1 site 2

Preparation

New cavity or replace old restoration Tapered or parallel sided diamond bur to explore extent Round burs to remove caries from walls Affected dentin on floor left Occlusal enamel retained, even though it is unsupported, so long the margin

are sound and there are no microcraks.

Restoration GIC as it can reinforce undermined enamel and it can be laminated as required

with composite resin if occlusal load is excessive. Composite resin should not be used alone because of its shrinkage on curing

with the consequent risk of micro-leakage. Lamination over GIC provides a combination of two materials sufficient to restore the physical properties of tooth very close to original conditions.

Site 1 site 3

PreparationDo not remove all affected dentin from floor of cavity to avoid problems arising

from pulp exposure. Indirect pulp capping may be required, seal with GIC for 12 weeks and then reassess.

Temporary restorationOld New

On affected layer give ZnOE GIC

Advantages

Provide adequate seal.

Eugenol kill residual

bacteria and diffuse through

dentin into pulp space to

inhibit inflammation and

pain.

Advantages

Relatively insoluble

Sufficiently strong to

withstand occlusal load

Easily placed and easy to

remove

Release fluoride which has

potential to kill bacteria in

dentin and promotes

remineralization of adjacent

hard tissues with exchange

of Ca, PO 4 and fluoride ions

between GIC and

demineralized dentin.

Disadvantages

Limited mechanical strength

Limited durability for longer

term as it degrades through

hydrolyses

Advocated by Masster 40 years

ago used ZnOE as provisional

restoration. It was antibacterial

and isolated lesion from

bacterial invasion, pulp

recovered from inflammation but

remineralization did not occur.

GIC adheres to enamel and

dentin through an ion

exchange mechanism, thus

eliminating microleakage.

It adheres to collagen of

demineralized dentin on

cavity floor through either

hydrogen bonding or

metallic-ion bridging. In

absence of bacterial activity

the pulpal inflammation

subsided.

In the presence of water

from the positive dentinal

fluid flow that follows, there

will be Ca, PO 4 and fluoride

ion exchanged between glass

ionomer and demineralized

dentin. Further ions will be

available from pulpal fluid

and dentin will remineralize.

GIC has relatively low

fracture resistance, therefore

provide a layer of 3mm if

soft demineralized dentin

remains on floor.

Reinspected after 3 months

(12 weeks) and laminated

with another material like

composite which as high

strength, satisfactory wear

resistance and adhesion to

sound well supported

enamel.

Next, check the remaining cusps1. If a cusp has a column of sound dentine providing adequate support for enamel

and there is more than one half of medially facing cuspal incline still present, it can remain standing without protection.

2. If a cusp is undermined and medial incline is subject to occlusal load, it requires protection otherwise it will develop a split at the base.

Therefore retentive elements such as grooves and ditches are placed in remaining sound dentin to ensure that a restoration is soundly locked in.

RestorationPlastic material – amalgam

Advantages Easier to build and cause occlusal anatomy Wear factor similar to natural tooth Superior resistance to flexure and is better able to provide positive protection

to weakened tooth structure Make more satisfactory base for crown which will be required at later stage.

GIC liner 0.5mm thick to minimize thermal exchange greater thickness of base will reduce bulk of restorative mat. Carefully modify the length of opposing working cusp to minimize the depth of intercupation between two teeth and reducing splitting stresses on restored tooth and eliminating undesirable contacts during lateral excursions.

Site 1 site 4

PreparationExtensive on molar. Complete loss of one or more cusps. Restorative material

amalgam. Later full or three quarter crown will be required. Preparation same as 1:3 and indirect pulp capping may be required.

Restoration If amalgam used mechanical interlocks like ditches and grooves placed in

gingival area. GIC base 0.5mm thick as thermal barrier. Place matrix to compensate for missing enamel wall. Build up.

Site 2 lesionsProximal surface of anterior or posterior teeth beginning immediately below contact

area

Size 1Minimum dentin involvement which has reached a point beyond healing through

remineralization identified by radiography or transillumination.

Size 2More extensive involvement of dentin with marginal ridge weakened or broken

down but still sufficient tooth structure remaining to support the restoration

Size 3On posterior tooth considerable involvement of dentin with split at the base of

cusp or at least the potential for split – need to protect one or more cuspal inclines from occlusal load.

On anterior tooth extensive proximal caries with loss of support for incisal corner which will be deeply undermined.

Size 4Complete loss of at least one cusp from a posterior teeth or loss of part of incisal

edge of an anterior tooth as a result of either caries or trauma

Site 2 size 1

No equivalent in G.V. Black classification Lesion commences in enamel Extends facially and lingually in elliptical shape controlled by extent of contact

area Does not involve contact area Does not undermine marginal ridge or incisal corner If prism structure of enamel has not collapsed it can be remineralized

a. Internal occlusal fossa (Tunnel) – 1st approach

When enamel lesion is at least 2.5mm apical to crest of marginal ridge Entry through the occlusal fossa just medial to marginal ridge

Preparation

Posterior teeth Enter occlusal fossa just medial to marginal ridge aiming towards expected

carious lesion Lean bur facially and lingually to form funnel shaped access cavity. Triangular

in outline with apex towards central occlusal fossa and base along medial aspect of marginal ridge.

Remove carious dentin with round burs

Removal of all affected dentin on axial wall is unnecessary, if there is risk of exposing pulp

If enamel demineralized and not cavitated – it is left alone to be supported and remineralized through cement

If enamel cavitated and needs to be broken down, short length of metal matrix placed interproximally and wedged. Small round burs and hand instruments used to complete cavity.

Anterior teeth Access through labial or lingual (esthetic) side Labial approach only if crowding and overlapping present Enter medial to marginal ridge

Restoration

GIC both anterior and posteriorLamination with composite if the load bearing area of restoration involves occlusal

support against the opposing tooth.

If using type II resin modified GIC should be radioopaque mixed at high P.L ratio use mylar strip as matrix for good proximal contour.

Place cement in 2 increments using a syringe. Tamp the first increment into the depths of the cavity using a small dry plastic

sponge. If enamel cavitated, some excess cement should be extruded between matrix

and tooth. Add the second increment and tamp again to ensure firm adaptation to entire

cavity wall. Light activate the cement from several directions for to see. Trim restoration apply surface glase to seal

If autocure usedIt should be sealed to maintain water balanced as soon as the matrix is removed

because these cements remain susceptible to water loss and water uptake for several hours after placement. Cover restoration with low viscosity, single component, light activated resin bond.

Adjust occlusion with a round bur at slow spread with no air-water spray. Add further resin bond to ensure adequate isolation of the cement form oral environment, finally light activate the resin.

If lamination with composite required Remove GIC to a thickness of 2mm Expose entire enamel wall. Bevel the enamel as required Acid etch for 15 seconds both enamel and autocure GIC Wash, apply enamel bonding agent and build composite.

Site 2 size 1 (slot cavity) – 2nd approach When carious lesion commence high on the proximal surface of posterior teeth

leaving less than 2.5mm of the marginal ridge occluso-gingivlly or its may be cracked or otherwise very seek.

Preparation Lesion approached from marginal ridge and small box shaped cavity prepared

not extending beyond demineralized enamel. Contact may be maintained on adjacent tooth on facial, lingual margin or both. Do not extend medially more than half-way through the marginal ridge.

RestorationResin modified GIC or lamination with composite mylar strip used as matrix.

Size 2 size 1 (Proximal approach) – 3rd approachWhen preparation of a larger site 2 size 3 or 4 cavity will allow good access and

visibility to the proximal surface of an adjacent tooth with a site 2, size 1 lesion no need to involve marginal ridge.

Preparation Entry by small tapered diamond cylinder bur. Access to lesion and entry

angle will be dictated and controlled to some degree by the cavity in the adjacent tooth but as the caries is progressing into the dentine in an apical direction and normally doesn’t undermine marginal ridge at this size, there is no problem removing all infected layer without involving marginal ridge.

Round bur is used to clean along circumference of walls.

RestorationRestorative material should be radiopaque. Restoration not under load and esthetics

not a problem, type II to autocure cement is used. With resin modified GIC, there may be problems with access for activating light.

Site 2, size 2 – G. V. Black – Class II (posterior), Class III (anterior)

Marginal ridge and proximal surface broken down. Sound enamel, particularly fro the gingival floor, is not removed just because it

is undermined following removal of caries. The enamel at the gingival is not under occlusal load and can be retained, thus keeping the restoration margin out of gingival crevice.

No need for dovetail retentive element final proximal outline form will often be curved rather than dovetail and generation of sharp line and point angles is contraindicated because the angles complicate the placement of restorative material and lead to stress concentration.

Weekend enamel around the proximal box, particularly along the gingival floor, can be supported and reinforced with GIC, but facial and lingual enamel must be soundly based on dentine if it is to be a significant factor in retention and prevention of microleakage when placing a composite resin restoration.

In anterior teeth, if no fissure involved, prepare a slot. Do not remove entire contact area.

Unsupported enamel will be maintained through adhesion with restoration.

PreparationBegin just medial to marginal ridge using very fine diamond point (# 200). Remove

caries with small round bur (008 to 012).

Leave affected dentin on axial wall to be remineralized. Walls need no be free of contact with adjacent tooth. Retain as much gingival enamel as possible even if it is undermined and

weekend. Because this enamel is not subjected to occlusal load, it can be supported and reinforced through adhesion with GIC.

Weekend and unsupported enamel should not be involved in adhesion using composite resin with the etching technique because it is likely to fail under setting contraction of resin.

If amalgam is used for restoration, prepare retentive features and involve occlusal fissures.

RestorationIf with amalgam

a. Base of GIV 0.5mm thick as thermal insulators.b. Cavity and lining covered by a single, application of copal varnish which will

wash out over a short period of time and this will allow deposition of corrosion products to seal interface.

c. Resin or GI amalgam bonding agent over lining and cavity which will provide some degree of adhesion between amalgam and tooth structure.

If GIC restoration - used alone or laminated with composite resin in posterior teeth where occlusal load is too great for GIC to remain without support.

Site 2, size 3 – Black’s class III and II

For anterior teeth Extensive proximal caries with loss of support for incisal corner which will be

deeply undermined.

Preparation Retain all possible enamel even though unsupported by dentin. Don’t remove affected dentin from axial wall. Remove friable enamel rods. No dovetail preparation Bevel as required to enhance retention with composite resin. Undermined enamel should be supported with GIC and it will then provide

degree of retention to composite resin. If composite resin alone to be used enamel must be well supported with sound dentin around the full circumferences.

Pins contraindicated as1. Difficult to disguise under esthetic restoration, shadow casted through

restoration.2. Lead to microleakage in future.

Restoration If there is satisfactory enamel margin around full circumference of the cavity,

it will be sufficient to cover and protect the exposed dentine with GIC as dentin substitute. The microchemical attachment of composite resin to enamel through acid etching will then retain restoration.

Cavity extensive and gingival enamel is insufficient or too week, begin restoration with GIC as dentin substitute (strongest GIC with high powder liquid ratio).

As soon as cement is set, cut back to expose enamel margins and make room for composite resin. Rebuild the contact area in composite but leave gingival extension of proximal box in GIC.

For posterior teethConsiderable involvement of dentin with split at base of cusp or at least potential for

splitting.

SplitGenerally the result of frequent loading on sharp angled, medially facing cusp

inclines, often through working side contacts in lateral excursions. Patient will report pain on pressure or possibly following release of pressure.

If 2.2 cavity, there was sufficient strength in both buccal and lingual walls to support the restoration, whereas in 2.3 it is necessary to rely on the restoration to protect the remaining tooth structure.

PreparationMaterial of choice for this type is amalgam due to large size of cavity. Both tooth

structure and most restorative materials, apart from gold are relatively brittle. They are strong enough in bulk to withstand masticatory stress but in their section will fail easily. Therefore modification to cavity design should aim at

1. Provision of restorative material in bulk to provide protection for the tooth structure which is now regarded as weak.

2. Remove weakened tooth structure from undue occlusal load.

The combined effect can be developed by leaving the facial and lingual walls out from the gingival floor, in a straight line to or just beyond the tip of the cusp.

Eliminate the medially facing inclines form the occlusal end of the cusp and at the same time retaining as much as possible of the original cusp height.

A non working cusp does not require great deal of support so it is sufficient to provide approximately 0.5mm of coverage.

Working cusp will be subject to heavy load and therefore required up to 2.01mm of coverage depending on type of occlusion.

By turning the walls outwards in this fashion restorative material can be built over the cusp with a cavosar face margin close to 900 without compromising strength of the cusp at gingival end.

Use # 168 diamond bur for this preparation. Retentive grooves and ditches can be prepared for amalgam.

RestorationAmalgam material of choice with a lining of GIC (low powder content) for thermal

protection shape buccal and lingual contour before carving occlusal surface. Correct occlusion.

If GIC used it is laminated with composite normally not used as GIC is too brittle; composite resin is flexible and the enamel to which it would gain adhesion is unsupported and brittle.

Site 2 size 4 for anterior teeth – G.V. Black’s class IV Incisal half of the crown lost Occlusal load not heavy

PreparationAccess achieved by # 168 or #156 bur unsupported enamel can be supported to

some degree with GIC, so trim the margins to a smooth finish. Remove caries around wall only and leave affected dentin on the axial wall.

In traumatic fracture protect expose dentin with GIC. Bevel enamel margins and place composite restoration.

RestorationGIC laminated with composite.

GIC high powder content reinforced or resin modified.

If gingival margin has no enamel left or is too weak to allow retention with composite resin, let it be covered by GIC.

Bevel the enamel. Begin with hybrid resin on the lingual for optimum strength and laminate with

microfilm resin on the labial to enhance esthetics.

In posterior teeth Entire cusp has failed, either from extensive carious attack or as a result of a

split and it generally leaves at least one margin close to the epithelial attachment.

PreparationThe cusps are undermined or split they should be protected as in the design for a

#2.3 cavity. Retention must be developed in the gingival floor wherever possible using ditches and grooves.

Restoration Amalgam is the material of choice. GIC is not used as it requires support from the

remaining tooth structure. Composite not used as sound enamel for adhesion is not available.

For bicuspids lamination technique can be used as occlusal load is not excessive.

Site 3 size 1Occurring in the gingival one-third of the crown or on the exposed root surface of

any tooth.

G. V. Black classification – Class V

Preparation Remove the carious dentine only, using small round burs (# 008 or #012). Do not remove demineralized enamel If GIC to be used the state of enamel is not important because the continuing

fluoride release will encourage remineralization. If the cavity is to be restored with composite resin, the outline will need to be extended to reach sound, fully mineralized enamel which can be safely etched to provide microchemical attachment.

No instrumentation is required for the restoration of an erosion lesion.

Control of gingival seepage and haemorrhage with an application of trichcoroacetic acid.

Gingival retraction cord.

Restoration The material of choice is a type II.1 restorative aesthetic glass-ionomer, either

autocure or resin modified and a gingival margin in dentine can be laminated with composite resin.

Clean cavity with a brief scrub of pumice and water on a small rubber up to remove the pellicle.

Then condition with 10% polyacrylic acid for 10 seconds, washed thoroughly and dry lightly when using light activated resin modified cement, contour and polish immediately with a very fine diamonds under an air-water spray. Apply a thin coat of the appropriate glaze to seal any remaining surface porosities and scratches.

When using an autocure glass-ionomer with a high powder: liquid ratio, cover the cement with a layer of a single component, very low viscosity resin enamel bond to stabilize the cement and avoid water uptake or water loss. Complete the contour and polish after 1 week, if after a few days, the aesthetics of the glass-ionomer is unsatisfactory laminate with a composite resin.

Site 3, size 2 More extensive than 3.1, treatment same

Site 3, size 3Approximal lesions that have developed either as primary root surface caries after

gingival recession or recurrent caries at the gingival margin of an existing restoration.

Treatment same.

Site 3, size 4Combination of two or more cavities around the cervical margin of any tooth.

Example lone-standing lower canine where a labial # 3.2 lesion is joined by another # 3.3 lesion on the distal side possibly even another # 3.2 on the lingual side.

Restoration The greatest problem will be to construct suitable matrix to facilitate placement

of the cement. One technique is to cut a soft tin matrix to shape and then cut a small hole in an appropriate to syringe the cement.

An alternative technique is to use a resin-modified cement and build the restoration incrementally with carefully light curing at each stage.

Pit and fissure sealants

DefinitionPit and fissure sealants are cements or resin materials which are introduced into

unprepared occlusal pit and fissures of caries susceptible teeth forming a mechanical and physical protective layer against the action of acid producing bacteria and their substrate.

Mode of action1. Mechanical sealing of pits and fissures with acid resistant material.2. Annulling the preferring habitat of streptococcus mutants and lactobacillus.3. Allowing better cleaning of pits and fissures.

Selection of patientChild with extensive caries on primary teeth is indicated for sealing all the 1st

permanent molars. Medically compromised, physically / mentally retarded children fall under special category for sealant placement.

Tooth selection Child with occlusal caries on one of the 1st permanent molars – seal the rest of

the 1st permanent molars. Child with more than one carious first permanent molar – seal the 2nd

permanent molars as soon as they erupt. Diagnosis – it is important to know which tooth is sealed. Visual and tactile – they still play an important role despite an improvement in

technology.

DrawbacksCavitations can be diagnosed by binding of explorer. Mechanical binding of

explorer in pits and fissures may be due to non-carious causes like

Shape of fissure Sharpness of probe Force of application Injudicious exploring causes cavitations Probing may vary from one operator to other Detecting fissure caries by probing is only 24% efficient (Penning).

Criteria for diagnosis Softening at the base of fissure Opacity surrounding the fissure Softened enamel that may flake away during probing

Treatment plan based on exploringI. Caries free surface (no explorer wedging)

Well coalesced self cleansing Observe and recall 6 months

Stained fissure Observe and recall

Stained minimal opacity Sealant placement

II. Caries free (explorer wedging) sealant placement

Materials1. Resins

The 1st use of sealant was an unfilled resin BIS-GMA but because of its viscous nature it was discontinued. Later diluents like methylmethacrylate made resin effective aw sealants. Two types of polymerization – chemical and light cured.

DifferencesLight cured Chemical cure

1. Working time – 10-20

seconds

2. No mixing is needed, no

voids formation

3. Polymerization starts until

light activated

1. 1 – 2 minutes

2. Voids can be incorporated

3. Starts immediately after

mixing

Sealants differ from restorative resins by the amount of filler added which increase the wear resistance.

Examples

Filled - Kerr sealants

Unfilled - Contact seal

Chemically - Concise white (3M) Delton

Light cured - Prisma shield Helio seal

Light cure resin show better retention rates in comparison to unfilled / filled chemically cure sealants.

Laser curing of sealants was introduced by Powell in 1989. Laser curing of visible light activated sealant shows increased tensile bond

strength of resin material and increased resistance to caries.

Sealants with fluoridesIt was perceived that addition of fluorides to sealants may improve caries resistance.

But no study documented the beneficial effect with fluoride sealants.

Fluoridated sealants release fluoride to the greatest extent in the 1st 24 hours after mixing and the release falls sharply on the 2nd day and slowly decreased later (Garcia Goday) caries reduction of both fluoridated and non-fluoridated sealant are not statistically significant (Koch 1997).

Caries reduction of sealants is mainly due to mechanical sealing of fissures and blocking nutrients for bacteria from oral environment.

Glass ionomer sealants because of its fluoride releasing ability, considered to be effective in reducing

caries. So this cement was tried as sealant, but conventional GIC has very less wear resistance and in a comparative study between GIC and resin as sealants the latter showed better caries reduction than GIC.

Resin modified GIC compomer are also used as sealants nowadays as they have better wear resistance than

conventional GIC.

Ionosit seal compomer pit and fissure sealant Contains an ionomer glass in polymerizable polycarbonic acid.

Opaque appearance, fluoride releasing. Releases zinc ions after set and thus produce antibacterial effect.

Available with fine long tipped nozzles which allows precise application (BDJ 2003).