For most of 19th

century caries was

treated using surgical

approach(Black

principles)----removal

diseased portion and

extension to areas

presumed to be caries

resistant

Father of dentistry

The reasons for this approachwere

A) Lack of Understanding the caries process.

Caries was thought irreversible sequence of events begin

with enamel demineralization followed by protein

(collagen)degradation…..now recognized there is

demineralizatio-remineralization cycle in which tooth

alternatly lose and gain calcium and phosphate depend on

microenviroment

C) Poor physical properties of available restorative

SURGICAL MODEL OF TREATMENT

Black’s principle of extension for prevention:

This principle sacrifices sound enamel and dentin for the sake of placement of cavity margins into self- cleansing areas or caries- immune sites, via food excursion thus preventing caries recurrence.

It also dictates the extension of preparations through fissures to allow cavosurface margins to terminate on non-fissured enamel.

Satisfy the resistance and retention forms required to prevent amalgam restorations failures.

Recently, the extension for prevention concept is substituted by the theory of ‘prevention rather than extension” via implementing risk assessment, prevention and remineralization of demineralized non-cavitated tooth structure as the basis of daily practice.

Consequences of Black’s principle of extension for prevention

1.Gross weakening of the remaining tooth substance:

The loss of the bulk of cusps and ridges loss

in the structural continuity,

Creation of stress concentration

Fracture of the restorative system.

2.Structural and marginal failure of the restorations:

Increased amount of restoration,

increased functional load.

Larger preparations, increased

marginal leakage.

3. Increased potential to pulpal irritation:

Cutting of extra amount of sound viable virgin dentin and more dentinal tubules will be opened for convey of more stimuli to the pulp.

Overextension will maximize the chemical, electrical, thermal, bacterial, osmotic and evaporative stimuli.

4.Increased gingival and periodontal irritation: Subgingival cavity margins leads to change of The

secretion of the normal gingiva which is alkaline tends to turn acidic in nature and thus negating its immunizing potential.

Plaque accumulation on the rough surfaced restorations.

Irritational constituents of the restorative materials could also aid in causing this condition.

5.Increased restorative display Certain unaesthetic restoratives could become objectionable when present in larger restorations.

6.More time, money and effort consumption

7.Difficult maintenance of restorative system Less controllable procedures due to extended

margins.

On failure of restoration, less tooth tissues will be

available to allow restoration replacement.

This conservative concept includes the following principles

1.Control of causative factor or cariogenicity to eliminate further demineralization. Prevention

2.Remineralization of early lesions.

3.Minimal surgical intervention for cavitated lesions.

4.Repair rather than replace for defective restorations.

Several contributing factors are to be sharing in order to allow the conservative equation

These could be dependent on:

1. The operator.

2. The tools used.

3. The restorative materials employed.

4. The oral environment conditions.

5. The socioeconomic conditions of the patient.

Essentials to allow conservation

1. THE OPERATOR

1. Decide the line of treatment.

2. The nature of the disease affecting the hard tooth structure. At one time, it was thought that caries is an irreversible condition caused by enamel demineralization followed by organic part degradation. Thus, the logical treatment was surgical excision.

3. Now, it’s evident that tooth structure is subjected to a demineralization/ remineralization cycle in which it loses and/ or gains calcium and phosphate ions according to the environment and bathing conditions.

Allowing remineralization to occur more than demineralization:

1- Elimination of microorganisms 2- IS the saturation of saliva with fluorides, calcium and phosphates to drive them inside the tooth, thus enhancing remineralization.

These changes in concepts thus require that the knowledge, experience and skill of the operator should be synchronized to outline the treatment

strategy to be followed.

2. THE TOOLS USED:

Microdentistry replaced macrodentistry to allow microscopic removal of diseased tissue.

It was found essential for this ultraconservative approach to utilize:

1. Magnification tools.

2. Advanced diagnostic tools.

3. Non-invasive cutting tools.

MAGNIFICATION:

Using the naked eye to perform a restorative

procedure sometimes limits its accuracy.

This triggered the profession to magnify the field of operation using loupes or microscopes.

Visual acuity helped accuracy of incipient caries diagnosis and minimization of healthy tooth destruction cutting.

1. Loupes:

Magnification power 2X-5X.

With or without fiberoptic light.

2. Microscopes:

Magnification power of 10X-25X.

MAGNIFICATION TOOLS:

Microscopes are either fixed (wall-mounted or ceiling-mounted) or mobile to serve in several workstations

ADVANCED DIAGNOSTIC TOOLS TO DETECT

INCIPIENT LESIONS:

Probing may

1- Disrupt tooth surface.

2- Predispose to cavitation.

3- May result in misdiagnosis because stickiness may be due to fissure morphology or probe pressure.

The development of several techniques that help the operator to reach an accurate diagnosis. Amongst which is the use of:

Imaging Technology Intraoral camera, Digital radiography,

Laser-based device (DIAGNOdent),

Fiberoptic transillumination

Electric caries monitor.

1- INTRAORAL CAMERA

It’s a camera placed inside the oral cavity to allow

display of intraoral images of exceptional quality on a computer.

It serves to communicate and demonstrate to patients the need for treatment.

THE ADVANTAGES OF DIGITAL RADIOGRAPHY

1. Ease of manipulation to change contrast and density

2. Lower exposure of radiation for patient

3. Absence of dark room

4. It takes less time for image

5. Image storage and communication is easier with digital networking.

6. Diagnose initial approximal caries lesions adequately

BUT It possesses minimal diagnostic value for detection of occlusal enamel caries and superficial dentinal caries

3- LASER-BASED DEVICE (DIAGNODENT)

It utilizes laser fluorescence

that satisfies both sensitivity

and specificity requirements

regarding occlusal caries

diagnosis.

The device works on the fluorescing nature of bacterial (mutans streptococci) metabolic by-products.

The emitted light with a wavelength of 655nm (red

light) penetrates the tooth.

This fluorescence is detected into a numerical

figure.

It thus allows measuring

the level of cariogenic

bacterial activity.

The intensity of the fluorescent

light is displayed as a

number ranging from 0 to 99.

4- DIGITAL IMAGING FIBER OPTIC TRANSILLUMINATION

Its technology is based on the fact

that carious enamel has a lower index of light transmission than sound enamel.

Its mouthpieces enable dentist to

view decay on occlusal surfaces,

around restorations, in addition to both facial and lingual surfaces.

It detects incipient caries as well as fractures.

A high-intensity safe white light is passed through the tooth

and the transilluminated image of the tooth is captured on a

charge coupled device (CCD), then analyzed by computer

software and displayed on a computer screen for diagnosis.

5- ELECTRICAL CARIES MONITOR (ECM)

It’s based on the electrical conductivity differences

between sound and carious tooth structure.

It works effectively for detection of occlusal caries .The resistance should be recorded in the absence of liquid (saliva).

High measurements indicate well-mineralized tissue

low values indicate demineralized tissue.

MINIMAL OR NON-INVASIVE CUTTING TOOLS

The ideal cutting instrument should fulfill certain requirements :

1. Comfortable.

2. Easy and able to remove diseased tissues only.

3. Painless.

4. Silent.

5. Requires minimal pressure for optimal use.

6. No heat generation or vibration during operation .

7. easy to maintain.

I-Air-abrasion Technology:

Allows the flow of

compressed air that carries

aluminium oxide particles

(20- 50μm) which strike the tooth surface.

It is effectively cut sound

enamel, dentin and defective

restorations that are to be

replaced. However, it’s less

effective in achieving caries

removal.

CHEMICO-MECHANICAL REMOVAL OF TOOTH TISSUES:

New methods of caries dissolution allowed the use of

combination of amino acids + a weak solution of sodium hypochloride in a gel form.

procedure for caries removal consists of :

1- Applying gel over diseased tissue for several minutes.

2-Gentle scrapping is done using specially designed instruments that resemble excavators.

Ultrasonic cutting

Use of ultrasonic power that is highly controlled in tooth cutting.

LASER CUTTING

There are several types of lasers that depend on different wavelengths.

The most commonly used types are Excimers, which are special ultraviolet lasers. CO2 and Nd:YAG lasers have also shown to be promising.

Lasers are used with caution for cavity preparations due to:

1- Inefficient at removing large

amounts of enamel and dentin.

2- Heat generation.

ENZYMES

This approach is still surrounded with extensive researches.

The enzyme preparation pronase successfully disintegrates decayed dentin (digestion of carious dentin). Solubilizes more than 90% of the nitrogen present in carious dentin.

Pronase does not attack sound dentin .

It has no ability to remove sound or carious enamel.

OZONE TECHNOLOGY

Advantages:

•Simple, time saving and effective

approach.

•No cutting is performed.

•It penetrates bacteria and kills them

In their protected niches.

•It used in treatment of root and deep

caries.

It’s supplied through a medical device known as HealOzone. Ozone reaches the lesion via a handpiece covered by a cup that is placed on the lesion for a period of 10 seconds. This results in deactivation of 99% of bacteria, fungi and viruses. This is followed by suction to eliminate any ozone remnants.

ADHESION MICROMECHANICAL BONDING

chemical-based bonding by strong interatomic or intermolecular attraction forces.

relies for retention and sealing on an intermediary joint consisting of a system of numerous resin microtags and resin tooth hybrid created in the top 2-5 µm layer of substrate tooth.

3.The restorative materials

Bondodontics True adhesion does not actually occur to the oral tissues.

It seems essential to substitute the term adhesion by bondodontics.

Bonding thus allows maximum preservation of tooth structure and hence maximum conservation.

The cavities to be cut should be matching with the

properties of the different restorative materials which dictate certain depth, width, walls’ inclinations and finishing of enamel walls.

Shift to direct tooth-colored restoratives rather than metallic and indirect restoratives.

4.THE ORAL ENVIRONMENT CONDITIONS

SALIVARY FLOW AND SALIVARY PH

The rate of salivary flow:

The resting flow rate 0.3-0.4 ml/min.

The stimulated flow rate 1-2 ml/min.

The buffering effect of saliva is an important parameter.

Oral microbes, chemical degradation potentials, masticatory forces and chewing habits, all these parameters should be evaluated.

These factors are important as it can be a contributing

factors in the occurrence of caries and thus modify the

line of treatment for each patient :

5. SOCIOECONOMIC STATUS OF THE PATIENT:

Educated patients that would perform regular dental

check-ups are categorized as being low caries risk

individuals and hence would require conservative

measures for treatment.

On the other hand, the opposite individuals would

require much more surgical approach.

BIOLOGICAL OR MEDICAL MODEL OF

TREATMENT ????

This model deals with caries as a disease that should be treated prior to any restorative procedure.

It includes the following:

1.Diet and habits modification.

2.Salivary flow and buffering capacity adjustment.

3.Mechanical preventive measures (calculus and oral biofilms control) dental office preventive program.

4.Use of antimicrobials home-care preventive program.

5.Remineralization of initial lesions. It can be perofrmed using fluorides, hydroxyapatites, calcium phosphates.

6.Fissure sealing for susceptible sites using low viscosity resinous materials or glass-ionomers.

7.Close follow up to monitor the healing procedure.

8.Perform minimal intervention and preparation for diseased tissues that cannot be remineralized and restore them conservatively.

Concervative cavity

preparation

A conservative cavity is prepared by minimally removing hard tooth structure with maximum preservation of its strength and anatomy followed by its restoration for maximum longevity.

FEATURES OF A CONSERVATIVE CAVITY SHOULD

PROVIDE THE FOLLOWING:

1.Include all defective enamel and dentin.

2.No extension beyond defective areas.

3.Convenient instrumentation and material placement.

4.Freeing of all margins with adjacent surfaces.

5.Necessary resistance and retention forms.

Obtaining the outline form:

According to Black's principle: An extension for prevention concept was performed: •In occlusal surfaces: - It allowed removal of all pits and fissures. - Mesial and distal extension. - Buccal and lingual extension. • In proximal surfaces: - Facial and lingual margins extension. - The gingival margin.

According to the conservative approach: •In occlusal surfaces: - Extensions include all contiguous fissures only.

•In proximal surfaces: -Facial and lingual margins are extended just beyond the contact to free it with the approximating tooth with a clearance of 0.5 mm. -The gingival margin is extended just to include the defective lesion.

Modifications in outline form:

•Enameloplasty

•Pit and fissure sealant

•Spot preparation:

•Slot preparation

•Tunnel preparation

•Simple box preparation

II-Obtaining the resistance and retention forms:

Resistance form:

According to Black,

The cavity width is governed by margin placement

midway between the cusp tip and depth of the fissure. The

cavity depth was about 0.5 mm pulpal to the DEJ.

The conservative approach allows the cavity width to be

extended just to provide convenience. The cavity depth is

located just below the DEJ for amalgam while it can be in

dentin or enamel in modified cavities for composite.

II-Obtaining the resistance and retention forms:

Retention form:

According to Black.

The retention was mainly macro-mechanical.

According the conservative approach:

Bonding offers a micromechanical level of attachment

to tooth structure

III. Convenience form:

According to Black:

Cutting of sound tooth

structure was sacrificed to

improve the visibility &

accessibility.

According the conservative approach:

The recent magnification tools, micro-sized

cutting tools & recent cavity designs allow

extreme tooth preservation.

IV- Removal of remaining carious dentin:

According to Black:

All caries must be eliminated completely and if the pulp

becomes exposed (called pathological exposure) & then it

has to be treated endodontically.

According the conservative approach:

• Pulp capping can be made as there is no clinical

manifestation of pulpitis or degeneration; by making secondary

dentin.

• Removing the infected dentin and leaving the affected one.

PREVENTIVE RESIN RESTORATIONS (PRR)

-It’s a technique that allows the removal of fissure caries, including any associated dentinal caries and its restoration with a resin composite material.

SIMPLE BOX PREPARATAION Indication Small proximal lesion without either occlusal fissures. It’s limited to teeth with narrow interproximal contact. Outline Buccal and lingual walls of the box should be almost facing each other to maximize retention. Preparation Proximal retentive grooves. on the expense of facial and lingual walls having of 0.5mm at the gingival point angles and taper to 0.3mm at the occlusal surface are done. Restoration Using amalgam or resin composite.

SLOT PREPARATION Indication Old patients who have gingival recession or with wide embrasures which allow easy access to the proximal lesion.

Outline -The approach is buccally or lingually. - Two retentive grooves could be placed along the occluso-axial and gingivo-axial line angles for non-bonded restoration.

Restorations This could be done using amalgam, resin composite or glass-ionomer and its modifications.

TUNNEL PREPARATION

Allow preservation of the marginal ridge.

The access could be directly on the lesion by trepanning the occlusal enamel in the fossa near the marginal ridge keeping it untouched.

The tunnel preparation and restoration are still until now controversy as no firm data have been given to support its use

unrestrictedly.

Two types: Total and Partial tunnel

CHAPTER 1

CONSERVATIVE APPROACH IN RESTORATIVE

DENTISTRY Introduction

Conservation is becoming a demand in restorative dentistry. There is a

shift to substitute the concept of drilling and filling by a newly introduced

philosophy based on emphasizing prevention and reducing drilling and

filling to a minimum. This trend is due to the increased knowledge of the

healing factors operating in the mouth plus a greater understanding of the

materials properties.

In the past decades, conservatism was just targeting the minimization of

tooth structure cutting whereas in the modern conservative theory there’s an intention to use a medical model and avoid cutting if possible. This would

require the detection and discovery of the lesion in its subclinical stage

before it initiates any defect that would need repair. This initial condition

would thus impose the inclusion of the diagnosis and interception steps in

the conservation theory.

The adoption of the medical model of treatment would thus save money,

effort and time by:

Preventing the development of defects or new cavities.

Preventing gum problems.

Stopping the progress of existing lesions and decay spots.

Maintaining existing old restorations

It’s therefore essential to evaluate the surgical model of treatment, which

allows dealing with the defect only and review Black’s principle of extension for prevention to highlight its consequences.

Black’s principle of extension for prevention: This principle sacrifices sound enamel and dentin for the sake of

placement of cavity margins into self- cleansing areas or caries-

immune sites, via food excursion thus preventing caries recurrence.

It also dictates the extension of preparations through fissures to allow

cavosurface margins to terminate on non-fissured enamel.

Justification of this principle was also to satisfy the resistance and

retention forms required to prevent amalgam restorations failures.

Recently, the extension for prevention concept is substituted by the

theory of ‘prevention rather than extension” via implementing risk

assessment, prevention and remineralization of demineralized non-

cavitated tooth structure as the basis of daily practice.

2

Consequences of Black’s principle of extension for prevention

Sticking of the operator to extensive cutting would alter and violate the

biological and mechanical principles that should be followed during

preparation. This can lead to:

1. Gross weakening of the remaining tooth substance. The loss of the bulk of cusps and ridges leads to a loss in the structural

continuity, creation of stress concentration and fracture of the restorative

system.

It’s noteworthy to know that upon removal of 1 micrometer of dentinal

tissues, an exposure of 30,000 to 70,000 dentinal tubules occurs. This allows

the opening of a large number of channels communicating the oral

environment to the pulpal tissues if not adequately obliterated by the

restorative material.

2. Structural and marginal failure of the restorations. Increased amount of restoration will be subject to an increase in the

functional loading.

Larger preparations would also allow increased marginal leakage with all its

deteriorating sequelae on the materials and the tooth.

3. Increased potential to pulpal irritation Sacrifice of sound tooth structure leads to cutting of extra amount of sound

viable virgin dentin and more dentinal tubules will be opened for convey of

more stimuli to the pulp.

Overextension will maximize the chemical, electrical, thermal, bacterial,

osmotic and evaporative stimuli.

4. Increased gingival and periodontal irritation. This could be the result of walls extending gingival to the gum margin. The

secretion of the normal gingiva which is alkaline tends to turn acidic in

nature and thus negating its immunizing potential.

Plaque accumulation on the margins and surfaces of restorations would

increase the gingival irritation and becomes potentiated by the rougher

surface of restorations.

Irritational constituents of the restorative materials could also aid in causing

this condition.

5. Increased restorative display. Certain unaesthetic restoratives could become objectionable when present in

larger restorations.

3

6. More time, money and effort consumption. An increased time is required to perform wider cavities and achieve their

faithful restoration.

More cost due would also be required due to increased material

consumption.

7. Difficult maintenance of the restorative system. Less controllable procedures due to extended margins.

On failure of restoration, less tooth tissues will be available to allow

restoration replacement.

Conservative approach in restoration of hard tooth structure defects

It’s the most minimal intervention to eliminate and restore defects of the

hard tooth structures

It focuses on a minimally invasive dentistry or preservative dentistry,

which allows a shift from the traditional surgical approach to a control of

defects without cutting or if cutting is to be done it has to be restricted as

much as possible.

This concept encompasses the following principles:

1. Control of causative factor or cariogenicity to eliminate further

demineralization.

2. Remineralization of early lesions.

3. Minimal surgical intervention for cavitated lesions.

4. Repair rather than replace for defective restorations.

Essentials to allow conservation:

To achieve this conservative equation, several contributing factors are to be

sharing in order to allow the realization of this required target. These could

be dependent on the operator, the tools used, the restorative materials

employed, the oral environment conditions and the socioeconomic

conditions of the patient receiving the treatment.

1. The operator decide the line of treatment followed.

Another important part is the understanding of the defect or the nature of

the disease affecting the hard tooth structure. At one time, it was thought

that caries is an irreversible condition caused by enamel demineralization

followed by organic part degradation. Now, it’s evident that tooth structure is subjected to a demineralization/ remineralization cycle in

which it loses and/ or gains calcium and phosphate ions according to the

environment and bathing conditions.

This gave the clue to treat caries by allowing remineralization to occur

more than demineralization and hence win the battle. For this to occur,

4

two main issues are to be focussed upon; first is the elimination of

microorganisms to suppress demineralization and second is the saturation

of saliva with fluorides, calcium and phosphates to drive them inside the

tooth, thus enhancing remineralization.

These changes in concepts thus require that the knowledge, experience

and skill of the operator should be synchronized to outline the treatment

strategy to be followed.

2. The tools used Microdentistry replaced macrodentistry to allow microscopic removal of

diseased tissue. Therefore, maintenance of as much healthy tissue and

structural integrity of the tooth as possible while still allowing feasible

visualization and access is becoming a main requirement.

To practice minimal invasive and microdentistry, it was found essential

for this ultraconservative approach to utilize magnification, precise

diagnostic equipment and non-invasive cutting tools.

Magnification: Using the naked eye to perform a restorative procedure sometimes limits its

accuracy. This triggered the profession to magnify the field of operation

using loupes or microscopes. Visual acuity helped accuracy of incipient

caries diagnosis and minimization of healthy tooth destruction cutting.

Loupes They are similar in appearance to eyeglasses and allow a

magnification in the range of 2X- 5X.

The lenses are built into the line of sight of the eyewear

and should be customized to the user.

They are sometimes associated with lighting by single

spot halogen or fiberoptic lamps but this adds to

them more weight.

Microscopes They allow a magnification in the range of 10X-

25X.

The majority of procedures are undergone in the

range of 10X-12X while localization and

identification requires 16X-25X.

Microscopes are either fixed (wall-mounted or

ceiling-mounted) or mobile to serve in several.

Advanced diagnostic tools to detect incipient

lesions:

Up to date, no diagnostic tool could make caries detection full proof.

5

The use of sharp explorer and the analysis of high quality bitewing

radiographs have been the mainstays of the dentist up to the present day.

Probing may disrupt the tooth surface and predispose to cavitation or

may erroneously result in misdiagnosis because stickiness may be due to

fissure morphology or probe pressure.

This raises the question “Is there a single tool to use to detect smooth surface or occlusal carious lesions? This led to the development of

several techniques that help the operator to reach an accurate diagnosis.

Amongst which is the use of intraoral camera, digital radiography, the

laser-based device (DIAGNOdent), the fiberoptic transillumination and

the electric caries monitor.

The intraoral camera: It’s a camera placed inside the oral cavity to allow display

of intraoral images of exceptional quality on a computer.

It serves to communicate and demonstrate to patients the

need for treatment.

It also allows to increase the quality of care dentists

provide because they offer improved visual access to the

dental cavity, improved lighting, and magnification.

Digital radiography Digital images offer tremendous advantages in

terms of potential for lower exposure of

radiation for patients, absence of darkroom and

convenience of image enhancement,

magnification, density assessment and color

coding if required.

It was found to diagnose initial approximal

caries lesions adequately while it possesses

minimal diagnostic value for detection of occlusal enamel caries and

superficial dentinal caries

The main disadvantage lies in that radiography underestimates the size of

the lesion considerably and provides high false positive results when used

for occlusal caries detection. Laser-based device (DIAGNOdent) This tool has been introduced to the restorative dentistry field in February

2000. It utilizes laser fluorescence that satisfies both sensitivity and

specificity requirements regarding occlusal caries diagnosis.

The device works on the fluorescing nature of bacterial (mutans

streptococci) metabolic by-products.

6

This fluorescence is detected into a meaningful numerical figure that can

be used in the diagnostic protocol. It thus allows measuring the level of

cariogenic bacterial activity.

In other words, it detects caries–induced changes in the tooth that cause

an increase in the fluorescence at specific excitation wavelengths.

A major advantage that adds to it, is that the quantitative nature of its

readings gives a basic guideline that could be followed up longitudinally

to monitor the decay extent.

The high-resolution transilluminator: Digital Imaging Fiber Optic

Transillumination tool (DIFOTI) Its technology is based on the fact that carious

enamel has a lower index of light transmission than

sound enamel. The diagnostic tool allows the

capture and view of real-time digital images on a

computer monitor. Its mouthpieces enable dentist to

view decay on occlusal surfaces, around

restorations, in addition to both facial and lingual

surfaces. It detects incipient caries as well as fractures.

A high-intensity light is shone through the tooth and the transilluminated

image of the tooth is captured on a charge – coupled device (CDD) intra-

oral camera, analyzed by computer software and displayed on a computer

screen for diagnosis.

Electrical caries monitor (ECM) It’s based on the electrical conductivity

differences between sound dentinal tissues

and carious dental tissues.

It works effectively for detection of

occlusal caries and measures the electrical

resistance of a site on the tooth during

controlled drying. The resistance should be recorded in the absence of

liquid (saliva).

High measurements indicate well-mineralized tissue while low values

indicate demineralized tissue. It has the ability to detect demineralization

even when the surface remains macroscopically intact.

Minimal or Non-invasive cutting tools

The ideal cutting instrument should fulfill certain requirements as

comfort, ease of use and ability to discriminate and remove diseased tissues

only. Other factors that are essential is that it has to be painless, silent,

requires minimal pressure for optimal use, does not generate heat or

vibration during operation periods, affordable and easy to maintain. All this

led to the appearance of several tools that possess certain of these benefits:

7

Air-abrasion technology Air abrasion equipment has been produced and

used since 1950 but its use was limited at that

time due to the presence of restorative

materials that did not comply with this

technology.

No bonding was adequately achieved to tooth structure and hence large

cavities were required to be cut to provide ample resistance and retention.

These large cavities with definite walls and floors could not be cut with

air-abrasion.

Nowadays, bondodontics have paved the way to the re-emergence of this

technology, as very conservative cavities could be prepared using air-

abrasion and restored using resinous materials.

This technique allows the flow of a stream of compressed air (40-140psi)

that carries aluminum oxide particles (20-50µm), which strike the tooth

surface to effectively cut sound enamel, dentin and defective restorations

that are to be replaced. However, it’s less effective in achieving caries removal.

It has shown its safety concerning tooth vitality and has also proven not

to be hazardous to the patient nor to the operator so long that the

protective measures are taken into consideration during its use. These

essentials are the use of a rubber dam, high velocity suction unit and face

shields or protective facemasks to control the messy procedure.

Chemico-mechanical removal of tooth tissues: New methods of caries dissolution allowed the use of

combination of amino acids and a weak solution of sodium

hypochloride in a gel form.

The recommended procedure for caries removal using this

technique consists of applying the gel over the diseased

tissue for several minutes until it performs its action then

gentle scrapping is done using specially designed

instruments that resemble excavators.

This gel focuses on diseased tissue only. The specially

designed instruments are used then to remove the

unsupported mineral in the softened materials.

It does not affect healthy dentine or soft tissue nor does it

affect enamel. However, it could be used in root caries,

coronal caries with open access and in deep caries

approaching the pulp.

Ultrasonic cutting This modality of cutting was suggested to allow the use of ultrasonic

power that could be highly controlled. Early generations could not preserve

8

tooth structure owing to their large sizes but

later on smaller sizes were incorporated into

the armamentarium and have shown success.

However, the preparations could not be totally

performed using this technique and hence they

cannot be used alone.

Laser cutting There are several types of lasers that depend on different wavelengths.

Lasers range from long wavelengths (infrared) through visible

wavelengths to short wavelengths (ultraviolet).

The most commonly used types are excimers, which are special

ultraviolet lasers. CO2 and Nd: YAG lasers have also shown to be

promising.

The use of the laser beam is focused to deliver a total energy to the

subjected substrate. Care is to be taken to use the correct wavelength for

absorption of the energy and prevention of side effects from heat.

Lasers are used with caution for cavity preparations, as they are

inefficient at removing large amounts of enamel and dentin and result in

generating extensive amounts of heat.

Enzymes This approach is still surrounded with extensive researches. The enzyme

preparation pronase successfully disintegrates decayed dentin. It’s said to perform digestion of carious dentin. Pronase does not attack sound dentin

but solubilizes more than 90% of the nitrogen present in carious dentin. It

has no ability to remove sound or carious enamel.

Ozone treatment An innovative simple, timesaving, effective and

efficient approach also uses ozone as a powerful

biocide. No cutting is performed using this technique.

Ozone was first suggested as a disinfectant for water in

the 19th century because of its ability to inactivate

microorganisms. It rapidly penetrates the bacteria and

kills them in their protected niches. It could alter the

metabolic products of bacteria that inhibit

remineralization and thus allows clinical reversal of the

lesion.

It was found to halt root caries and treat occlusal

caries in permanent and deciduous teeth.

It’s supplied through a medical device known as HealOzone that produces ozone in the unit by

9

passing air through high voltage. Ozone reaches the lesion via a

handpiece covered by a cup that is placed on the lesion for a period of 10

seconds. This results in deactivation of 99% of bacteria, fungi and

viruses.

This is followed by suction to eliminate any ozone remnants. A time

lapse should be allowed for remineralization of treated tissues which are

rather soft before any restorative procedure.

This takes about 3 months and is done using an at-home care kit

containing dentifrice and mouthrinse. This methodology, if becomes

widespread after its success, would be revolutionary as it means that

tooth tissues even if diseased would not be excised.

3. The restorative materials Bondodontics

The term adhesive dentistry has been familiarized for over four decades.

This is in spite of the fact that true adhesion does not actually occur to the

oral tissues.

Adhesion is different from micromechanical bonding which relies for

retention and sealing on an intermediary joint consisting of a system of

numerous resin microtags and resin tooth hybrid created in the top 2-5

µm layer of substrate tooth.

It seems essential to substitute the term adhesion by bondodontics to be

more precise in description of this science. Bonding thus allows

maximum preservation of tooth structure and hence maximum

conservation.

The cavities to be cut should be complying with the properties of the

different restorative materials .

These properties thus impose certain depth, width, walls’inclinations and finishing of enamel walls.

Thus, selection of materials that would achieve conservatism lead to shift

to direct tooth-colored restoratives rather than metallic and indirect

restoratives.

4. The oral environment conditions Salivary flow and pH

The rate of salivary flow is very important, as it can be a contributing

factor in the occurrence of caries. The resting flow rate has an average that

ranges between 0.3-0.4 ml/min while the stimulated flow rate has an average

rate between 1-2 ml/min. These measurements are considered essential as

they might modify the line of treatment that could be designed for a patient.

Furthermore, the buffering effect of saliva is an important parameter that has

to be considered as caries resistant persons show higher capacity to buffer

01

any lowering in the plaque pH. This could again impose a different strategy

of treatment.

Oral microbes, chemical degradation potentials, masticatory forces and

chewing habits, all these parameters should be evaluated to allow

determination if a conservative approach could be attempted or a shift to a

more radical modality of treatment would be essential.

5. The socioeconomic conditions of the patient. These were also found to alter many plans. This is due to the fact that

privileged, educated, employed patients that would perform regular dental

check-ups are categorized as being low caries risk individuals and hence

would require conservative measures for treatment. On the other hand, the

opposite individuals would require much more radical approach.

To drill or not to drill? or when to prepare a cavity?:

Certain data have to be collected prior to decision making about the

necessity of operative procedure. These are the diet assessment included in

the caries risk evaluation, clinical and radiographic examinations.

1) Diet assessment Estimation of food cariogenicity as well as the frequency of intake of

meals and snacks is rather important to allow determination of the

problem if there is any. Also, motivation of patients for adopting healthy

habits is an essentiality.

A need to adjunct a diet counselor became thus an important issue that is

still neglected by dental professionals.

2) Caries risk assessment Factors that are to be considered in the caries risk assessment are the

amount of plaque, type of bacteria, type of diet, salivary secretion,

salivary buffering capacity, amounts of fluorides ingested,

socioeconomic conditions and general patient’s health. According to this caries risk assessment the patient could be either

classified as:

1. No care advised (NCA) and therefore considered dentally fit if he scores

a low caries risk value.

2. If he is at risk, therefore preventive care advising (PCA) will be the

selected route for treatment. This category of patients could have some

initial lesions that require management. Patients are treated by a non-

surgical model for treatment, which is also termed biological model or

medical model for treatment. Tooth structures would not be cut but rather

treated conservatively.

00

3. When the lesions are not reversible and must be treated by operative

intervention, the patient could be classified as operative care advised

(OCA).

3) Clinical examination: This step allows the identification of the defect and correlation of

previously gathered data with the clinical picture. Upon diagnosis, the

defect should be classified as carious or non-carious as it’s dealt with differently.

Biological or medical model of treatment

This model deals with caries as a disease that should be treated prior

to any restorative procedure. It includes the following:

1. Diet and habits modification if required.

2. Salivary flow and buffering capacity adjustment if required.

3. Mechanical preventive measures (calculus and oral biofilms control) to

fit into a dental office preventive program.

4. Use of antimicrobials to fit into a home-care preventive program.

Chlorhexidine mouthwash. It could also be in the form of gel applied in

custom-made trays or applied as a varnish. They reduce substantially and

rapidly mutans streptococci for patients with high counts of bacteria

and/or high caries activity.

5. Remineralization of initial lesions. This is a procedure that could be

referred to as healing of demineralized tissues. It could be performed

using fluorides in the form of solutions or gels, hydroxyapatites, calcium

phosphates and triclosan/ copolymer / sodium fluoride.

6. Fissure sealing for susceptible sites. These sealants are in the form of low

viscosity resinous materials or glass-ionomers and their modifications.

They obliterate pits and fissures that represent good habitats and niches

and allow trapping of microorganisms and food substrate.

7. Close follow up to monitor the healing procedure

8. Perform minimal intervention and preparation for diseased tissues that

cannot be remineralized and restore them conservatively

Surgical model of treatment

In this model, the diseased tissues are beyond healing potentials and

could not be remineralized. Diseased tissues are dealt with by drilling and

cutting away without giving attention to the microorganisms as causative

factor. This gives a chance for the cariogenic organisms to reattack new and

restored surfaces and hence restart the cariogenic process again and again.

Carious defects

A conservative cavity is prepared by minimally removing hard tooth

structure with maximum preservation of its strength and anatomy followed

by its restoration for maximum longevity.

02

Features of a conservative cavity should provide the following:

1. Include all defective enamel and dentin.

2. No extension beyond defective areas.

3. Convenient instrumentation and material placement

4. Freeing of all margins with adjacent surfaces.

5. Necessary resistance and retention forms.

Steps of cavity preparation

There are a number of steps that should be followed during cavity

preparation. A comparison is held to obviate the differences encountered

during each step by adopting Black’s principles or the conservative approach for cutting.

Obtaining the outline form:

According to Black: An extension for prevention concept was performed.

In occlusal surfaces, it allowed the removal of all pits and fissures and

ended into relatively more immune areas. The mesial and distal

extensions were midway between the crest of the marginal ridge and

depth of the triangular fossa. Buccally and lingually the extensions were

midway between cusp tips and depth of fissures.

In proximal surfaces, the facial and lingual margins extended midway

between axial line angles and facial or lingual margin of contact area.

The gingival margin extended below the crest of the healthy gum margin.

According to the conservatism: Caries and convenience dictate the outline.

In occlusal surfaces, extensions include all contiguous fissures only. On

the other hand, shallow fissures penetrating half or less the enamel

thickness (1/3) are removed by enameloplasty. Main fissures should be

included in the dictated outline. However, it’s indicated to seal using a fissure sealant any pit, fissure or groove that sustains a catch with an

explorer but without any signs of caries upon surrounding the margins of

a restoration.

In proximal surfaces, the facial and lingual margins are extended just

beyond the contact to free it with the approximating tooth with a

clearance of 0.5 mm. The gingival margin is extended just to include the

defect.

Obtaining the resistance and retention forms According to Black, the cavity width is governed by margin placement

midway between the cusp tip and depth of the fissure. The cavity depth

was about 0.5mm. pulpal to the DEJ.

Alternatively, the conservative approach allows the cavity width to be

extended just to provide convenience. The cavity depth is located just

03

past the DEJ for amalgam while it could be in dentin or enamel in

modified cavities for composite.

The retention was mainly macromechanical in Black’s cavities, as bondodontics was not yet launched at that time. Nowadays, bonding

offers a micromechanical level of attachment to tooth structure thus

minimizing the need for cutting to create retentive features.

Removal of remaining carious dentin According to Black, all caries must be eliminated completely and if the

pulp becomes exposed it’s to be treated endodontically. He validates his

belief by the inability to ascertain the true condition of the pulp under a

deep carious lesion.

On the other hand, the conservative approach dictates a pulp capping

procedure provided that the pulp does not show any clinical

manifestation of pulpitis or degeneration.

The differentiation between infected dentin (which is loaded with

microorganisms) and affected dentin is facilitated by the use of a caries

detector dye, which is applied over the deeply seated carious lesion. This

is an acid red dye that is painted using a minibrush over the carious tissue

then left for a minute then rinsed adequately. If a red stain remains after

washing this indicates that a further removal of this diseased tissue is

required as it denotes that infected dentin needs to be further removed. If

no stains are left after washing this indicates that remaining tissues could

be considered as affected dentin that could be remineralized if left behind

causing no harm to the pulpal tissues.

Another modality of management of deep caries is that using the

chemico-mechanical caries removal approach (Carisolv) to dissolve the

required amount.

Conservative cavity designs.

A design based on the shape and extent of the lesion is advocated.

Overzealous removal of healthy tooth tissue is considered unallowed to

provide neither flat floors nor squaring out the cavity as in Black’s design.

The finished preparation then very much resembles the shape of the

carious lesion it replaces but with refinements to satisfy certain

requirements. The concept of extending approximal walls to be localized

in self-cleansable areas is subject to controversy as Elderton in 1984

denoted that the so-called self-cleansing areas are virtually non-existent.

This was demonstrated readily by disclosing solutions.

He also considered the placement of cervical margin into gingival

crevice other features not recommended as it’s no longer believed to be immune from caries. Upon touching the gingiva it’s very likely that

04

irritation initiates an acidic-medium and thus becomes vulnerable to

future decay.

In approximal caries, a rather rounded design is thought to be suitable

for oral hygiene measures accessibility. The cavity is said to have no

corners.

The different examples of conservative designs could be:

Preventive resin restorations (PRR) It’s a technique that allows the removal of fissure caries, including any

associated dentinal caries and its restoration with a resin composite

material.

No attempt to make special retentive areas or

extension into sound pits or fissures is allowed.

It’s not necessary to prepare beyond the lesion.

When caries is limited to enamel, there’s no need to prepare into dentin. However, small cavities

could be restored with a flowable composite that

may also act as a fissure sealant.

Simple box preparation

Indication

It’s used to restore a small proximal lesion without either occlusal fissures or previously inserted occlusal

restoration. It’s limited to teeth with narrow interproximal contact. The outline could have rounded

margins as in resinous material or could be in the form of

definite walls as in case of amalgam restoration. It’s mainly used whenever there’s a need to avoid cutting into sound occlusal surfaces.

Outline

Buccal and lingual walls of the box should be almost facing each other to

maximize retention. It’s done without an occlusal step. Preparation

To compensate for the lack of occlusal portion that allows retention,

proximal retentive grooves on the expense of facial and lingual walls having

of 0.5mm at the gingival point angles and taper to 0.3mm at the occlusal

surface are done.

Restoration

Using amalgam or resin composite according to the cavity design.

05

Slot preparation

Indication

This type of preparation is used in old patients

who have gingival recession and often experience

cavities on the proximal exposed cementum on

the root surfaces that is gingival to the contact

area. It could also be used whenever wide embrasures are encountered that

allow easy access to the proximal lesion sparing the marginal ridges and the

occlusal surfaces.

Outline

The approach to perform this design is buccally or lingually in the form

of a slot. This non-invasive management offers better esthetic, does not alter

occlusal relationships, may preserve a natural proximal contact and enjoys

greater patient acceptability than traditional approaches

Two retentive grooves could be placed along the occluso-axial and

gingivo-axial line angles if retention is required for non-bonded restoration.

This could be done using amalgam, resin composite or glass-ionomer and its

modifications.

Tunnel preparation According to Black’s model, the approximal lesion

was conveniently approached from the occlusal

aspect.

This extensive destruction is rather rejected with the

advent of microdentistry tools, which allows the

access directly to the lesion via the nearest point

possible that allow preservation of the marginal ridge. The access could

be directly on the lesion by trepanning the occlusal enamel in the fossa

near the marginal ridge keeping it untouched. A diagonal inclination of

the cutting tool is then done to keep the marginal ridge without

undermining it.

Air-abrasion has proven effectiveness lately in performing such a design.

The decayed tissue is then removed with or without involvement of the

approximal enamel. This is referred to, as “partial tunnel” preparation

when this approximal enamel is left undisturbed as it’s neither carious nor cavitated but left supported by sound dentin. The “total tunnel”

preparation is that when the approximal enamel has been perforated by

the carious lesion and removed during the preparation.

highly viscous or packable glass-ionomers were suggested by virtue of

their enhanced physical properties.

The tunnel preparation and restoration are still until now controversy as

no firm data have been given to support its use unrestrictedly.