Aes,thetie :Reslorative Dentistry­

A Gen_0�al Dentis;t's Persp,ective

Dr Charles Joffe

Student Number: 14001047

Date: June 2003

Contents

Page Number

Introduction ........................................................................................................... 3

Aetiology of Tooth Discolouration ...................................................................... .4

• Table 1.1 Aetiology of Tooth Discolouration ........................................... 5

• Table 1.2 Tooth Discolouration: Causes and Colours .............................. 6

• Mechanism of Dental Staining .................................................................. 7

Case Study ............................................................................................................ 8

Patient History, Extra-oral and Intra-oral Examination ........................................ 8

• Patient History .......................................................................................... 8

• Extra-oral Examination ............................................................................. 9

• The Anatomy of a Smile ......................................................................... 10

• Intra-oral Examination ............................................................................ 11

• Special Tests ........................................................................................... 12

• Shade Assessment and Selection ............................................................ 13

Treatment and Management ............................................................................... 14

• Treatment Plan ........................................................................................ 15

Materials of Choice in the Management of the Discoloured Dentition

and the Restoration of the Teeth and the Properties There-of.. .......................... 17

• Bleaching Materials ................................................................................ 17

• Direct Aesthetic Restorations ................................................................. 21

Conclusion .......................................................................................................... 27

Acknowledgements ............................................................................................. 28

References ........................................................................................................... 28

2

Introduction

A smile can play a major role in one's life. An aesthetically pleasing smile creates a \I

warmth and positivity that can travel a far way. Smile, and the whole world smiles with II

you.

Aesthetic restorative dentistry is a very dynamic and important field of dentistry. We as

dental care providers can play a major role in improving the appearance of our patients as

well as educating our patients to a certain degree as to what is aesthetically pleasing.

Everyone really wants to have an aesthetically pleasing appearance, which includes an

ideal smile. Dentists should know the indications and contra-indications and have the

knowledge to do aesthetic restorative procedures, whether it is restorative, bleaching and

contouring or a combination.

One must bear in mind that aesthetic restorative dentistry can never be taught or learnt by

means of fixed rules, recipes or patterns. There are simply too many variables! All

signs, symptoms and special test information must be considered in the light of basic

science knowledge and then analysed logically where the 'dis-ease' is located.

It is important to understand the treatment and management of patients that require

aesthetic restorative dentistry, as well as having a lucid understanding of the techniques,

mechanisms, methods and materials to be used.

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Aetiology of Tooth Discolouration

Teeth are polychromatic.6 The colour varies among the gingival, incisal and cervical

areas according to the thickness, reflection of different colours and translucency in

enamel and dentine and is modified by:

I. The colour of the enamel covering the crown

2. The translucency of the enamel which varies with different degrees of

calcification

3. The thickness of enamel which is greater at the occlusal/incisal edge of the tooth

and thinner at the cervical third.7

Many researchers classify staining as either extrinsic or intrinsic. 7

•8

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Extrinsic staining is

defined here as staining that can be easily removed by a normal prophylactic cleaning.7

Intrinsic staining is defined here as endogenous staining that has been incorporated into

the tooth matrix and thus cannot be removed by prophylaxis.

Some discolouration is a combination of both types of staining and may be multifactorial.

In our case study, the patient presents with intrinsic staining, but nevertheless Table 1.1

gives an overview of the aetiology of tooth discolouration, including intrinsic and

extrinsic staining. Table 1.2 gives an overview the colour presentation of the causes of

tooth discolouration.

4

Table 1.1 Aetiology of tooth disclouration5

Extrinsic Stains

Plaque, chromogenenic bacteria, surface protein denaturation Mouthwashes, e.g. chlorhexidine Beverages (tea, coffe, red wine, cola) Foods ( curry, cooking oils and fried foods, foods with colourings, berries, beetroot) Dietry precipitate Illness Antibiotics ( erythromycin, amoxicillins) Iron supplements

Intrinsic Stains

Pre-eruptive

Disease:

• Haematological diseases

• Liver diseases

• Diseases of enamel and dentine

Medication:

• Tetracycline stains

• Other antibiotic use

• Fluorosis stains

Post-eruptive

Trauma Primary and secondary caries Dental restorative materials Ageing Smoking Chemicals Some food stuffs (long term use causes deeper intrinsic staining) Minocycline Functional and parafunctional changes

5

Table 1.2 Tooth discolouration: causes and colours10

Cause

Extrinsic discolouration

Cigarettes, pipes, cigars, chewing tobacco Marijuana Coffee, tea, foods Poor oral hygiene

Extrinsic and intrinsic discolouration

Fluorosis Ageing

Intrinsic disclorouration

Genetic conditions e.g. amelogenesis imperfectaSystemic conditionse.g. jaundice

porphyria Medications during tooth development e.g. tetracycline, fluorideBody by-productse.g. bilirubin

haemoglobin Pulp changes e.g. pulp canal obliteration

pulp necrosis

• with haemorrhage

• without haemorrhageIatrogenic causes e.g. trauma during pulp extirpation

tissue remnants in pulp chamber restorative dental materials endodontic materials

Colour

Yellow-brown to black Dark brown to black rings Brown to black Yellow or brown shades

White, yellow, brown, grey, or black Yellow

Brown, black

Blue-green or brown Purple-brown

Blue-green, brown Grey, black

Yellow

Grey, black Yell ow, grey-brown

Grey, black Brown, grey, black Brown, grey, black Grey, black

6

It is also very important to understand the causes of discolouration of non-vital teeth.

The following list shows us some of these causes5:

• Tissue degradation during the necrotic process.

• Trauma causing rupture of blood vessels. This results in haemolysis of red blood

cells, which release haemoglobin and haematin derivatives. Iron in red blood

cells may be aspirated into dentinal tubules. This may also occur if there is

uncontrolled haemorrhage during endodontic treatment.

• Intracanal medications such as phenolics and iodoform-based medications can

cause gradual discolouration. The dentine is penetrated cusing oxidation.

• Silver points may corrode inside the root canal.

• Coronally placed leaking restorative materials.

• Endodontic cement.

• Inadequate coronal access leaves pulp remnants and necrotic tissue in the pulp

chamber.

• Contamination of the pulp cavity during endodontics.

• Insufficient irrigation and debridment

Mechanism of Dental Staining

The deposition of extrinsic stain depends on the attraction of materials to the tooth

surface.'' The attraction forces include long-range interactive forces such as electrostatic

and van der Waals forces and short-range interactions such as hydration forces,

hydrophobic interactions, dipole-dipole forces and hydrogen bonds.12 These chemical

attractive forces allow the chromogen ( coloured material) and prechromogen ( colourless

material) to approach the tooth surface and determine if adhesion will occur. The

chromogens penetrate into the material. 5

Either the staining can be direct dental staining, where the chromogen binds to the tooth

surface to cause tooth discolouration, or indirect dental staining, where the prechromogen

binds to the tooth and undergoes a chemical reaction to cause a stain. It should also be

noted that the chromogen can also change colour after binding to the tooth.5

7

Case Study

Let us look at a case study. A patient presents with intrinsic discoloured teeth in your

dental practice. The maxillary anterior teeth have several old discoloured composite

restorations on the mesial and distal surfaces. The 11 is non-vital and slightly more

discoloured than the rest of the maxillary anterior teeth. The endodontic treatment of the

11 is acceptable. The 12 is vital and has a porcelain fused to metal crown and the colour

of the crown is in harmony with the rest of the discoloured teeth. There are no financial

constraints.

Patient History, Extra-oral and Intra-oral Examination

Patient History

Before any treatment has been done or any treatment options have been discussed, taking

a history is imperative. The patient's medical history should be carefully assessed.

Allergies to plastic, peroxide or any other ingredients of the bleach should be noted.

Patients' smoking habits need to be assessed. Patients' current medications need to be

recorded for example, patients taking hormones sometimes have an exaggerated gingival

response. Patients who are pregnant or breastfeeding should be excluded from bleaching

procedures, because there is a lack of information concerning possible effects on the

developing foetus. 13 The medical history should be followed by a dental history. The

aetiology of the discolouration needs to be assessed because different causes necessitate

different treatments. It is important to evaluate the patient's attitude to dentistry, the

patient's previous experiences such as when was the crown, the fillings and the root

treatment done, who was the previous dentist? (it is important to speak to the previous

dentist if possible and obtain records and x-rays if necessary). It is also important to

evaluate patient's expectations and the patient's compliance.

8

One should bear in mind that communication with the patient is most valuable. Steven

Morrow, DDS, Oakland, California, reminds us to maintain complete records. In a court

of law, there is no substitute for accurate records.

After listening to the patient and having recorded down all the relevant information, I

then proceed to an extra-oral and intra-oral examination, keeping in mind that there is a

patient behind the teeth.

Extra-Oral Examination

Patients are very sensitive to oral stimulation, so one should use a gentle touch. Placing a

hand on their shoulder, for example, works wonders. A gentle touch says "I have to do

this to help you, but I care about you".

After one has donned his gloves, he can no longer place a kind hand on the patient's non­

sterile shoulder. Face masks, eye protection, gowns and gloves tend to depersonalise the

dentist/patient relationship, so one should take a moment to establish the "I care" feeling

before donning one's infection baniers.

Firstly a thorough extra-oral examination should take place. One should look for

symmetry of the face and the ability to open and close the mouth. Feel for swollen

glands and lymph nodes and temperomandibular joint dysfunction. Reference points

such as the interpupillary line, the upper lip line, lower lip line and vertical facial line

should be noted.

At this point it is imperative to evaluate the aesthetic zone i.e. to do a smile analysis. One

should go into detail and this should be recorded in the patients file.

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The Anatomy of a Smile

The perfect smile requires an optimal relationship between the lip, gingival scaffold and

the teeth. When disharmony exists between any of these three components, the result is a

smile that is likely to be perceived as unaesthetic. 2

Ideal anterior aesthetics reqmre a healthy periodontal envirorunent with sufficient

relevant tissue volume to fill the interproximal spaces. Left and right side symmetry

should exist so that there is no disparity between contralateral tooth types. 3 Each tooth

type exhibits a distinct incisogingival length and mesiodistal width, which in harmony

builds a maxillary anterior unit that is visually pleasing. 2

Generally, aesthetic dentistry

pertains to the smile line, which is normally related to the maxilla and is usually from

teeth 16-26. One should be aware that each case is different and at times lower teeth are

implicated in the patient's smile and one should treat appropriately.

When a person is smiling, generally the cusps of the upper maxillary teeth should touch

and follow the lower lip, and the necks of the upper teeth should follow the upper lip.

About O - ± 1mm of gingiva can be showing between the upper lip and the necks of the

upper maxillary teeth.

One should, however, take into consideration our diverse ethnic population in South

Africa and understand that what may be pleasing to some, may not be pleasing to others.

It should be noted that one should be aware of the golden proportion, which is a

mathematical formula regarding the relationship between harmony and beauty, which

was attributed to Pythagoras. Basically, the golden proportion is a ratio of 1: 1.618. 14 For

example the width of a lateral incisor is ± two thirds of the width of the central incisor.

This should be kept in mind during the operative stage of treatment.

10

Intra-Oral Examination

The existing condition of the teeth and periodontium needs to be examined prior to both

bleaching of teeth and direct aesthetic restorative procedures. In the mouth, examine the

soft tissue, the palate and the teeth. A thorough oral hygiene evaluation and a full

occlusal analysis should be done; ideally one wants a stable occlusion. All existing

restorations should be checked to see if they are sound or not. A closer detailed

examination can be done on the discoloured teeth to determine if possible, the exact

aetiology, so that the discolouration can be treated effectively.

When examining intra-orally, it is imperative for the dental care provider to have a lucid

understanding of the biologic, anatomical and aesthetic principles in order to realise the

full potential of dental aesthetics.

One must bear in mind that the purpose of operative and restorative dentistry is to restore

and maintain health and functional comfort of the natural dentition combined with a

satisfactory aesthetic appearance. Thus, all dental restorations should comply with

established requirements for the periodontal physiology and health with regard to both

surface and functional characteristics. 1

Probably one of the most important principles in maintaining periodontal health around a

restoration is the biological width, which is a measurement from the gingival margin to

the crest of osseous bone. One should use caution when using a periodontal probe as a

tool to measure the biological width since the pressure used by different practitioners can

vary. The distance can vary from 2 - 5mm.

The biological width is viewed as a critical sub-gingival physiologic dimension and

encroachment of a restorative margin results in the initiation of gingival inflammation

and bleeding, and alternately leads to gingival recession, apical migration of the

junctional epithelium and alveolar bone loss. The biological width cannot be ignored

when any restorations are taken into account. 4

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It must be noted that future relationships between the margin of the restorations and the

gingival tissues cannot be assessed with certainty in areas of gingival inflammation and

periodontal pockets until about 1 month after prophylaxis and instruction of good home

care.

Where violation of biologic width becomes evident, conservative periodontal measures

may help keep this inflammation under reasonable control. At other times, however,

surgical treatment may be necessary to re-establish proper biologic width.

In health, the facial aspect of the biological width has a ±3mm depth, and the

interproximal surfaces have depths ranging from 3 - 4,5mm. The interproximal variation

depends on the amount of the scallop of the interproximal alveolar bone. The gingival

scallop is always equal to or greater than the underlying scallop. The osseous scallop

parallels the cemento-enamel junction circumfrentially. For purposes of cosmetic

restoration or periodontal plastic surgery, maintaining or recreating the biologic width

remains one of the most important principles in maintaining periodontal health.

During the intra-oral examination, the incisal and occlusal plane, the midline and

inclination of the teeth should be noted as well as the shape and position of teeth and the

sex of the patient. Principle of line can be applied in deciding whether one needs a wider

or longer appearance of the upper anterior teeth.

Special Tests

Impressions for study models can be taken, preferably two sets of study models. If

necessary, a diagnostic wax-up can be done to show how the teeth will appear after

completion of treatment. Vitality testing of all teeth should be undertaken. This can be

done by using heat, cold or electric pulp testing. Routine radiographs should be taken,

including periapical radiographs to confirm that no periapical pathology is present and

that all the teeth are sound.

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Shade Assessment and Selectio1t

It is essential to warn those patients with existing matching anterior composite

restorations, that after bleaching, the actual composite restorations do not change colour.

It should also be noted that white spots or opacities do not disappear during bleaching

and in the early stages of bleaching may become more visible, so to with tetracycline

staining, the banded appearance is retained in the teeth after bleaching. Thus, one must

take these factors into consideration when selecting the correct shade of the teeth prior to

bleaching and direct restorative work. At this point, the patient should be aware and

informed of the potential colour that realistically can be achieved. Initial colour of the

patient's teeth should always be recorded before treatment commences. The study of

colour and shade taking is a vast subject in itself and selecting the appropriate shade has

always been difficult, as it is dependant on so many factors. Factors that determine shade

value are:

• The amount of natural light ii:t the area where the shade is taken.

• The hue of the tooth colour (yellow or blue range)

• The value of the colour, i.e. the lightness and brightness

• Chroma: the strength or weakness of the colour

There are three dimensions of colour: hue, chroma and value.15 Hue is the pigment or

most commonly called the 'colour". Chroma denotes the strength or concentration of the

hue and may also be referred to as the colour saturation. Value is the relative whiteness

or blackness of a colour and is a qualitative assessment of the grey component. Value is

independent of hue or chroma and, in dental shade matching, it is the most important of

the three dimensions of colour. Value should be selected first. Rearrangement of the

colour guide from the lightest to the darkest shade is recommended to avoid distractions.

Hue selection should be undertaken next. The basic hue can be best seen in the middle

and cervical thirds. Chroma variations can be perceived within the same tooth. The

cervical third usually presents higher than the middle third. The incisal third often

presents a lower value when compared with the middle and cervical thirds.5

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Never forget that it is important to still be communicating with your patient and

discussing the patient's perception of aesthetics. If possible, extra-oral cameras and

computer imaging can be useful in illustrating to the patients so they can better

understand what we as dental care providers are trying to achieve.

For optimal treatment a multidisciplinary app�oach involving an orthodontist, a

periodontist, an orthognathic surgeon a prosthodontist and a restorative dentist should be

kept in mind.

Once all relevant information has been recorded, the dental care provider can, with the

patient's understanding and compliance, form a diagnosis and treatment plan.

Treatment and Management

The composition of a beautiful smile, the form, balance, symmetry and relationship of the

elements make it attractive or unattractive. An expanse of soft tissue should not be

considered to be unaesthetic per se, but the way this soft tissue is arranged, relative to the

teeth and lips, is of aesthetic concern. Thus a high lip line or gummy smile may not be

unaesthetic, but due to today's mass media influence, many people consider even the

slightest excessive display of gingival tissue unattractive. 3

It is important to note that the definitive diagnosis of the gummy smile is crucial and

determines the treatment. The gummy smile may be due to either altered passive

eruption or vertical maxillary excess.3 After a proper diagnosis, one should know that the

vertical maxillary excess gummy smile should be referred for orthognathic correction,

whereas the altered passive eruption can be corrected by gingival surgery. 3 The example

of a "gummy smile" is to illustrate the importance of a correct diagnosis.

Once you are happy that no pathology exists, whether it be dental caries or periodontal

disease, a treatment plan for our case study can be formulated. It is important to have

14

signed consent by the patient for the treatment plan, making sure the patient has an in­depth understanding of all that is required in achieving the desired result.

The following is a brief description of the proposed treatment to be done. Please note that in the "materials of choice section" a more in-depth explanation of some of the treatments will be highlighted.

Treatment Plan

Please note, most, if not all the following procedures should be performed under rubber dam to ensure safety to the gingival tissues and other oral tissues as well as allowing restorative dentistry to be effective, since bonding is very technique sensitive. The following is a brief description of the proposed treatment to be done.

1. Bleaching:

• Vital bleaching: Upper arch and if necessary lower arch (but not at the same time due to sensitivity and that the patient might not realise the bleaching achieved if both arches were done at the same time) - an initial power bleach in office can be 30 minutes to 2 hours ( If a heat source is to be used, one should not give local so patient can say whether the heat treatment is too high or not). Thereafter a home bleach can be done.

• Non-vital bleaching of tooth 11: In office and walking bleach - need good barrier to seal dentinal tubules. May use glass ionomer or composite to seal the dentinal tubules.

2. Wait at least two weeks before composite restorations can be done, since bonding is

reduced just after bleaching. 3. Redo composite@n;]\on mesial and distal surfaces of the teeth. 13

•21

•22

•23 When cutting

cavity preparations use long bevel. Ideally one must redo these discoloured composite fillings with direct aesthetic restorations, however, depending on the available tooth stru cture porcelain veneers or full porcelain in-ceram or VMK crowns can be done.

4. Since the colour of crown 12 matched the colour of the other teeth before they were

bleached, one would have to redo crown 12, either porcelain fused to metal or an in-

15

ceram crown. One must be careful in removing the old crown 12 so that one does not

fracture the underlying structure of tooth 12. A temporary acrylic crown would have

to be made while the laboratory technician is constructing the new crown. 5. Here again, depending on the available tooth structure of tooth 11, one can either do:

• Post core crown

• Direct composite restoration

• Stainless steel post/ or pins and a direct composite restoration

Please note that in this assignment I will not go into detail about indirect aesthetic

restoration.

6. Contouring of restorations/ or teeth if necessary. It is important to note that overcontouring of restorations or faulty placement of contour is a much greater hazard to periodontal health than lack of contour, since both

supra-gingival and sub­gingival plaque accumulation may be enhanced by overcontoured crowns because an inadequate amount of facial tooth substance was removed during the preparation. Such an overcontour interferes with the sealing effect of the gingiva against the tooth and the self-cleansing mechanism of

the gingival sulcus:4 Another common error is when the technician makes the crown short of the cemento-enamel junction, which results in an anatomically abnormal relationship among the contour of the patient's tooth, the restoration and the gingiva, leading to increased plaque retention at the dento-gingival junction. Overcontouring of composite restorations and bulging and thick margins on crown restorations may change the anatomy of the interdental space and thus accentuate the normal@between the buccal and lingual papillae in the posterior region of the mouth, enhancing plaque retention there.

7. Post-operative x-rays8. Oral hygiene instruction and post operative patient information9. Maintainance and recall visits

16

Materials of Choice in the Management of the Discoloured Dentition

and the Restoration of the Teeth and the Properties There-of.

Bleaching Materials

Dentists have been perplexed by the problem of tooth discolouration for the last 200

years and have tried numerous chemicals and methods to remove the various types of

discolouration. Many of the early attempts, although highly innovative in their time,

were not successful and bleaching techniques were considered to be experimental and

unpredictable. Colour regression was a problem.5 However the technique of using 35%

hydrogen peroxide to bleach vital teeth has been available for nearly 100 years.

Attempts to bleach teeth started in earnest in the nineteenth century and have continued

until successful bleaching techniques could be found. Numerous techniques have been

tried, including those for bleaching of non-vital teeth.

In this case study, bleaching of the non-vital 11 needs to be done as well as bleaching of

the upper arch and then later the lower arch. Before discussing the properties of the

bleaching agents, one should have the knowledge of the minor or transient effects that

could take place due to the bleaching agents. Examples are21:

• tooth sensitivity (Patient should be told that this is reversible)

• reduced bonding (Residual hydrogen peroxide in the enamel inhibits

polymerisation)

• altered enamel morphology (Not as bad as the altered enamel morphology from

etching)

• problems with restorative dental materials

• gingival tissue irritation (Night guard should be trimmed correctly)

It should be noted that potential major long term or systemic risks have been

documented. As an oxidant, hydrogen peroxide has been adversely associated with

carcinogenesis, genotoxicity, cytotoxicity, ageing and lung injury.21

17

The following are indications for vital bleaching:

• Yellow, orange, light brown in colour

• Brown fluorosis stains

• Single/multiple discoloured anterior teeth

• Extrinsic food stains

The following are contra-indications for vital bleaching:

• Extremely large pulps

• Hypersensitivity

• Severe loss of enamel - in cervical areas

• Extensive restorations - especially glass 1onomer restorations - normally

roughened

• Peroxide allergy

• Latex allergy - rubber dam

• Lack of compliance

• Pregnancy and breast feeding

Vital bleaching can either be in office or home bleach.

In Office (Power Bleach to kick start the bleaching process)

One can use 30-35% hydrogen peroxide. It may be light or laser activated for 30 minutes

to 2 hours to increase the efficacy. Usually this is done in combination with the home

bleaching. One should not give local anaesthetic so one can assess any sensitivity the

patient might have. A gingival barrier such as Opaldam (a resin that is light cured) can

be used. It covers 2-3mrn of the gingiva and also slightly covers the necks of the teeth.

Just to mention here that one can also use Ora seal and rubber dam. Bleaching gel is <....../

placed on the teeth and then light cured. Thereafter, all bleaching gel is removed by

rinsing off with water and using a high suction. The gingival barrier can also be

removed.

18

Another concept is a compressive bleaching technique. They found that when light was

placed on the gel, the free radicals (02 molecules) moved in the direction of the light.

They found that in walking bleach of non-vital teeth, because it was closed, the bleaching

molecules moved towards the dentine. So with vital bleach they placed the bleaching gel

into the night/mouth guard and then sealed it with resin barriers and then placed the light

onto it.5

The in office bleaching can be followed by home bleaching. The bleaching agent of

choice at my dental practice is Opalescence® tooth whitening systems by Ultradent of 10,

15 or 20% Carbomide peroxide. For vital bleaching a good impression is needed and

laboratory fabricated trays (night guard) can be made and this is what the patient would

wear at home. One should always try and do the first treatment for the patient in the

chair thus making sure that the night guard fits well and that there is no blanching of the

gingival and that the patient can see and understand what is required for him/her to do at

home. I prefer the patient to wear the bleaching tray at night for 8-10 hours, as salivary

flow decreases during sleep. It is preferable to examine the patient every 3-5 days to

monitor progress, dispensing only what is necessary to reach the next evaluation

appointment. The patient should be informed to cease treatment if any sensitivity is felt.

The patient should also be told to store the bleaching agent in a cool place out of direct

sunlight. It is best to store the bleaching agent in the refiigerator. It should be noted that

patients with heavy occlusion or bruxes may require a thicker tray.

In general, the constituents of the bleaching gels are5:

• Carbomide peroxide

• Hydrogen peroxide and sodium hydroxide

• Non-hydrogen peroxide containing materials e.g. Sodium perborate

• Thickening agent - Carbopol or polyx

• Urea

• Vehicle - glycerine, dentifrice, glycol

• Surfactant and pigment dispersants

• Preservatives

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• Flavourings

• Flouride (in some recent products to reduce sensitivity)

Carbomide peroxide breaks down to a solution of hydrogen peroxide and solution of

urea. The hydrogen peroxide breaks down into water and oxygen. It is the oxygen

molecules that penetrate the tooth and liberate the pigment molecule causing the tooth to

whiten. The urea is used to stabilise the hydrogen peroxide, elevate the pH of the

solution and enhance anticariogenic effects, saliva stimulation and wound healing

properties. The glycerine enhances the viscosity of the preparation and ease of

manipulation. The surfactant functions as a wetting agent, which allows the hydrogen

peroxide to diffuse across the gel/tooth boundary. A pigment dispersant keeps pigments

in suspension. The preservatives give the bleaching gels greater durability and stability.

Flavourings are used in the bleaching material to help improve patient acceptability of the

product. Opalescence contains carbopol, which enhances the viscosity of the bleaching

material, helps release oxygen slowly, and the increased viscosity of carbopol prevents

the saliva from breaking down hydrogen peroxide.

To bleach the non-vital tooth 11, the walking bleach technique should be attempted first,

requiring intra-coronal bleaching. The tooth is isolated by rubber dam. All materials are

removed to below the level of the labial gingival margin. A seal of either composite or

glass ionomer is applied at least 2mm on top of the endodontic obturation, the barrier

should slope buccally towards the cemento-enamel junction. The purpose of this is to

seal the dentinal tubules and prevent external root resorption. The walking bleach paste

can be prepared by mixing sodium perborate and an inert liquid such as water, saline or

anaesthetic solution to a thick consistency of wet sand. Place this bleaching agent into

the coronal chamber and compress it. Thereafter, place a temporary filling to ensure a

good seal. Recall the patient 2 weeks later and repeat if necessary. Just to mention in

any bleaching case, whether vital or non-vital, over bleaching can cause destruction of

the enamel matrix and therefore the extent of the bleach should be monitored all the time.

One could also implement a home bleach tray for the non-vital tooth. Here the patient

would apply in this case Opalescence bleaching gel in the access cavity that was left open

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by the dentist. The patient would wear a similar tray to that used for vital bleaching, but

in this case, only tooth 11 would be bleached, one should not forget to give a syringe to

the patient so that he/she could rinse out with water after bleaching and to place a cotton

pellet in the access cavity. It should also be noted that in office power non-vital

bleaching can be done in a similar way to that of in office power bleaching for vital teeth.

In all bleaching cases, special care must be taken by both the dentist and patient so that

no damage to the surrounding soft tissue. If sensitivity arises, one should halt the

bleaching process, apply fluoride and ifthere is exposed dentine, one can apply a bonding

agent. Patient instruction is probably the most valuable tool in home bleaching

techniques.

Direct Aesthetic Restorations

In this case study the following materials and instruments could be used for the aesthetic

restorative procedures:

Etching agents (37% phosphoric acid). Enamel should be etched longer than dentine.

Excessive etching of the dentine can produce poor bonding when collagen fibres at the

base of the demineralised dentine are not completely impregnated with resin.

Furthermore, there is a risk of collagen collapse after etching. Moisture control has been

shown to be critical under such clinical conditions. One approach to prevent the risk of

defective dentine hybridisation is the use of self etching adhesive systems. 23

Bonding agents

Bonding systems are the foundations of adhesive and aesthetic dentistry. Bonding

systems have evolved over the past 50 years and today we are in our sixth generation of

bonding systems.

Enamel bonding is predictable after etching with 37% of phosphoric acid. The etch

creates irregularities in the enamel into which the resin can flow and thus leads to micro

mechanical interlocking after polymerisation. Dentine bonding on the other hand is

21

unpredictable. Dentine being hydrophilic, sclerotic dentine, the fact that dentine is highly

permeable, the smear layer, open tubules of dentine and the fact that the pulp is nearby

makes bonding to dentine difficult.

I usually use Prime & Bond® NT™ 2: 1 by Dentsply as an adhesive. This is a self­priming dentine/enamel bonding agent. Light cure and dual cure with one system. Use a

curing light for one-bottle performance. No multiple brushes, mixes and wells are

necessary. Acetone based effectiveness for minimal moisture uptake, low film thickness

and quick evaporation for a strong dentine structure. There is complete dentine seal. The

Prime & Bond® NT™ by Dentsply is a fifth generation bond. It has a thinner hybridlayer ( exposed collagen of superficial dentine + adhesive = hybrid layer). It is an

improvement on the third generation. The smear layer is either modified or dissolved.

There is good demineralisation of the collagen fibres so that resin can infiltrate, but the

depth of the demineralisation is a lot less than the depth of the demineralisation of the

fourth generation, thus causing a lot less sensitivity. It should be noted that we are into

our sixth generation of bonding systems. These bonding systems are characterised by the

possibility to achieve a proper bond to enamel and dentine using only one solution.

Bonding can determine the outcome of the composite resin restoration. Thus, the ideal

bonding system should be biocompatible, bond indifferently to enamel and dentine, have

sufficient strength to resist failure as a result of masticatory forces, have mechanical

properties close to those of tooth structures, be resistant to degredation in the oral

environment and easy to use for the clinician.22 One must bear in mind, in the light of the

well documented internal dentine wetness, which is directly related to the permeability of

dentine and the positive pulpal fluid pressure in the dentinal tubules, hydrophyllic wetting

agents are known to be essential for effective clinical performance of modern adhesive

systems.

In the South African Dental Journal (May 2003), there an advert from dentsply

advertising the new one step self etching dental adhesive called Xeno III, which I would

like to try in the near future.

22

Composite materials

Although many materials are available on the market, most dentists limit their choice to a

few brands. The factors influencing the selection of materials are complex, but cost, ease of manipulation combined with effective marketing by distributors appear to be important factors in the ultimate choice. In this case study, I would use either Dyract (a compomer) or a hybrid or a microfill composite, depending on the severity of the occlusal stress. It seems that there are however very interesting products out there that I have seen demonstrated but I have not yet used. An example is Esthet#, where one could build up a tooth in layers of different colours to match as closely as possible the tissues that have

to be restored.

The composition of resin based composites consist of: I. Organic phase - which is the matrix and consists of the monomer (Bis GMA),

initiator, polymerisation inhibitors and pigments for different shades.2. Dispersed phase - which is the filler and consists of quartz, alumina silicate,

borosilicate glass for strength/reinforcement and barium strontium, zirconium andzinc for radiopacity.

3. Interfacial phase - which consists of coupling agents which connects the resinmatrix to the inorganic filler

A compomer is a water free single component, light cured composite consisting of

polyacid modified dimethacrylate monomers reinforced with strontium or barium aluminosalicate glass particles. Compomers are very popular because of its unique

combination of ease of use, fluoride release, aesthetics and physical properties and the fact that it was marketed as a hybrid of composite and glass ionomer cement. The initial setting reaction occurs through light activation of the resin matrix as in a composite. An acid-base reaction between the strontium and the carboxylic groups occurs in the presence of water within the oral cavity, which leads to further cross-linking of the polymer and the release of fluoride.

23

The following are the advantages and disadvantages of compomers24:

Advantages:

• Ease of placement

• No mixing

• Easy to polish

• Good aesthetics

• Excellent handling

• I:,ess susceptible to dehydration

• Radiopaque

Disadvantages:

• Limited clinical experience and few long term clinical trials

• Require bonding agent like composites

• More marginal staining and chipping

• Wears more than composites

• Enormous variation of products makes longevity difficult to predict

• Weaker physical properties than composites that decrease over time

• Clinical significance of fluoride release undetermined

Composites are often subdivided into two categories: Hybrids and microfills. The

successful restoration of a patient's condition often requires the use of both these

materials. Hybrid composites consist of several types of filler particles - a glass in the

lµm to 3µm range that contains radiopaque oxides (e.g. strontium, barium, or zirconium)

and silica, which generally have a size of a 0.04µm. Though noted for their strength and

polishability, the initial luster attained on these composites diminishes over extended

function. Hybrids provide ease of use, natural refractive indices (that allow light to blend

into the tooth), and enhanced physical properties.16 The hybrid composite resins exhibit

superior tensile strength and improved abrasion resistance as well as reduced

polymerisation shrinkage, coefficient of thermal expansion, and water sorption; 17 they

also exhibit greater fracture resistance as a result of the inclusion of heavy inorganic

24

filters.18 Consequently, these materials are clinically indicated for Class I, Class II,

substructure and incisal regions of Class IV restorations, diastema closures and direct

veneers.

Microfills are composed of submicroscopic silica particles that average approximately

0.04µm in size. The production of a homogenous, nonadherent composite paste requires

increased volume of filler particles in the composite. This agglomeration occurs through

the wetting of the fillers with resins, which are then polymerised together. As a result of

the difficulty in wetting these small particles, the filler concentration is strictly limited

(35% by weight). 17 Consequently, inhomogenous materials that allow a higher

proportion of filler to be incorporated (45% - 80% by weight) have been developed; this

type of microfill composite is often used as a restorative material. This resin-rich

environment results in excellent polishability and allows the restoration to retain a surface

smoothness over function.19 The limitations of microfilled composites include high water

sorption, lack of radiopacity, the tendency to have lower compressive strengths, fracture

resistance, fatigue strength, and hardness. Accordingly, these materials are generally

contraindicated for high stress-bearing restorations ( e.g. Class IV, large Class I and Class

II restorations in occlusal contact with opposing cusps). These composites are indicated

for direct veneers and the replacement of enamel in Class III, IV, and V restorations.

Particle size thus represents crucial information in the determination of how best to utilise

composite materials.20 The composites of choice for Hybrid composites are TPH

Spectrum from Dentsply and Restorative 2100 from 3M. The composite of choice for

microfill composites is 3M Al 10/Silux Plus from 3M. It should be noted that when

restoring these teeth in this case study, the composites should be cured in increments,

bearing in mind that flow composites in combination with the hybrid and microfill

composites can be used.

The following instruments can be used for aesthetic correction25:

• Number 12 scalpel blade for interproximal separation pnor to light curing,

trimming overhangs and performing minor shape corrections after light curing.

25

• Transparent matrix strips and light cunng provisional material for creating

proximal moulds.

• Small double-ended flat plastic instrument for the application and contouring of

composite, for separating teeth to create light proximal contacts and to gain access

to the interproximal surfaces for contouring and finishing.

• Flame shaped fine particle diamond-coated finishing burs, reciprocating files for

contouring after light curing and finishing discs and strips.

• Medium and fine particle abrasive rubber points for polishing, together with

silicone-carbomide-containing brushes for final polishing.

• Airborne particle abrasion unit for creating a retentive surface for composite

repair.

Composites and adhesive techniques have improved tremendously over the years. As a

consequence, it is possible to perform aesthetic corrections by placing direct restorations

that previously would have required indirect restorations.25

26

Conclusion

Mankind has always been plagued by the problem of restoring parts of the body lost as a

result of accident or disease.26 Practitioners of dentistry have been confronted with this

problem since the beginning of dental practice, and the means of replacing missing tooth

structure by artificial materials continues to account for a large part of dental science.

As we grow in years, and looking back at dental school days, one can see the rapid

advancements in dentistry. It is imperative to keep up and maintain the knowledge that is

being developed, as this is constantly changing and growing especially in the world of

anterior aesthetic dentistry.

Anterior aesthetic dentistry, whether restorative or bleaching, is very diverse, especially

with all the current dental products available out there. Thus it is no use becoming a

jack-of-all-trades and a master of none. One should select certain dental materials that

one is happy with in order to perfect his/her skills and thus optimally provide one's

patients with treatment that ultimately can be perfected technically, bearing in mind that

there should be an in depth knowledge and understanding of the mechanisms and

techniques involved in anterior aesthetic dentistry. Hopefully this will lead to satisfaction

both from the dentist's and patient's perspective.

27

Acknowledgements

Courtesy to Stellenbosch University for th�ir collection of journal articles and sattelite

lectures.

To my wonderful wife Mandi for helping me type this assignment.

References

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Lea & Febiger - 1988

2. Galler C., DDS, MSD, The Periodontal Infrastructure, Esthetic Dentistry, 42:4,

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3. Garber D.A., Salama M.A., The Aesthetic Smile: Diagnosis and Treatment,

Periodontology 2000, 11: 18-28 - 1996

4. Kois J.C., The Restorative-Periodontal Interface: Biological Parameters,

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6. Louka A.N., Esthetic Treatment of Anterior Teeth, Journal of the Canadian Dental

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28

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58(1 ):21-28

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Stellenbosch University, Page 71

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-1989

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