Contents Introduction

Ways in which restorations fail

Failure rates of common restorations

Causes of failures

Evaluation system for restorations

Failures common to all restorations & causes

Failures of specific restorations

(A) Failures of amalgam restorations

(B) Failures of pin-retained restorations

(C) Failures of glass ionomer restorations

(D) Failures of composite restorations

(E) Failures of inlays

Conclusion

References

1

INTRODUCTION

Failure may be defined as the inability to meet the desired outcome. On

specifications that have been established by national bureau of standards and other

institutions of standardization and specifications, little chances exist of

manufacturers selling inferior quality restorative materials.

Majority of restorative failures in dentistry can be attributed to the

hindrances of the operator himself.

Everything done from the time of cavity preparation, until the restoration is

polished has a definite affect on the success and failure of a restoration.

Being critical about your work is good but being too critical about them aint

so good either.

It is salutary to replace a restoration that has been condemned as , only to

produce a new restoration with just as many, if not ‘more’ faults, When the

manikin turns into a real life person with fears, aspirations, and a small wet

wriggling mouth, the difficulties become compounded.

Combined efforts of meticulously done work, and maintenance by the

patient is bound to yield fruitful results.

Ways in which restorations fail (Acc. to wilson & fuzzi)

Failure

New Disease Technical Failure

Caries & Tooth wear Fractured restoration

Periodontal disease Marginal breakdown

Pulpal problems Tooth fracture

Trauma Defective contours

Failure of retention2

(ACC TO JENDERASON & RONING )

Failures of restorations can be characterized as.

Secondary caries

Marginal deterioration

Tooth fractures

Loss of anatomy

Loss of aesthetics

Restoration fractures

(Acc to mount et al)Failure of tooth structure Failure of restorative material

Failure of enamel margin failure of margins

Failure of dentin margin # or collapse of material

Bulk loss of tooth structure Total loss of restoration

Split root

Loss of vitality

Failure rate of common restorations

(Wilson, roulet, Fuzzi)

Annual Failure % Restoration Type All

Studies Studies 73 yr

Longitudinal studies

Cross-sect studies

Amalgam Restoration Direct post composites GIC restorations Cast gold inlays & onlays composite inlays onlays Ceramic inlays & onlays Anterior Restoration (III & IV) Cervical restorations (Class V)

0-70.7-90-14.40-5.90-100-7.10-11.60-26

0-70.7-90-14.30-5.91.5-9.80-4.30.5-11.60.3-7.2

0-70.7-5.90-14.40-2.60-100-7.10-11.60-26

1-6.33.3-9--0.5-5.9---0.8-41-31.6-5.9

3

Principle problems of individual restoration

Amalgam - Secondary caries, High incidence of bulk &

tooth

Cervical overhang,

Marginal deterioration

Composites - Wear Of restoration,

Discoloration, Marginal Deterioration,

Secondary caries

GIC Bulk fracture Due to low Mechanical strength,

(Ironically) Secondary caries.

Inlays :- Cast Gold :- Tooth fracture Marginal defects,

Retention

ceramic Marginal & Bulk fracture,

Marginal discoloration & degradation

Failures in General occur due to :-

Material used Operator

A) Faulty production (Inferior Products) A) Improper diagnosis & wrong

treatment modality suggested

B) Improper storing & handling, B) lack of knowledge about use

packaging of restorative material

C) Impurities incorporated C) Lack of skill

D) Technique sensitivity of material D) casual attitude & manipulative

techniques

E) Inhibitions of the material itself

patient

4

A) Not following post-operative instructions & maintenance

B) Improper Oral hygiene protocol c)deleterious habit

Any shortcomings occurring during following stages cause adverse effects to

restoration

Operative stage

Handling storage & dispensing of material

Manipulation stage

Insertion stage

Finishing & polishing

Post-Insertion & maintenance stage

Patient maintenance

Common Phenomenon Leading to Failure Microleakage

Def :- ‘The clinically indetectable passage of bacteria and bacterial

products, fluids, molecules or ions from oral environment along various gaps

present in cavity restoration interface’.

Three Possible routes :-

1) Within or VIA smear layer

2) B/W smear layer & cavity varnish/cement

3) B/W varnish/cement & restoration

A minimum of 10 um space definitely exists between a restoration and

tooth surface which is not clinically perceivable but large enough to allow

ingress of bacteria and their products.

Properties of restorative materials promoting microleakage

Major contributors :-

1) Coefficient of thermal expansion (CTE) change in length per unit

length of material per degree change in temperature

More deviation of CTE

5

Of material from Higher rate of

CTE of tooth microleakage

Material CTE (x 10-6 %)

Tooth

Crown enamel

Dentin

Amalgam

Composite

GIC

Pure Gold

Aluminous Porcelain Inlay wax

11.4

8.3

25.0

20.0-25.0

11.0

14.0

6.6

400.0

2) Polymerization shrinkage :-

Seen with resin restorations , occurs when monomer chains are

polymerised to form polymer chains

This shrinkage pulls material away from walls of cavity

Type Value

Conventional Comp

Organic Comp

Microfilmed

Hybrid

1.5-2.0%

2.5-3.5%

1.3-1.5%

2.2-2.5%

3) Property of adhesion

Adhesion is attraction of molecules of two different substances to each

other when brought in close contact.

Influenced by :

Wetting capability

Surface energy6

Presence of water & smear layer

Surface roughness etc.

Better adhesion – lesser gap – lesser Microleakage

e.g Leaving margins of inlay unfurnished exposes cement more to leakage

Improper isolation of composites

Surface contaminants More Leakage

Inadequate bond

Minor contributors :

Creep

Elasticity

Resistance to fatigue

Solubility

Role of smear layer :-

Generally 1-2 mm thick consists of :

Blood saliva, bacteria’s enamel & dentin particles smear layer may be

pushed to 1-5 um in tubules forming ‘Smear plugs’

2 Schools of thought for smear plugs

1) Prevent permeability of dentin by blockage

2) Smear itself source of bacteria’s

Best way :- Fixing smear layer by 25% tannic acid, polyacrylic acid 10%

Partial removal of layer

Leaves smear plug intact

Makes sterile, inert, non-toxic synthetic smear layer.

Secondary cariesThese are caries around a restoration, also known as ‘Recurrent caries’

Etiological Factors 7

Marginal leakage – around restoration

When width of marginal defect is than 50 um risk is lower

Ditching of restoration

Marginal fractures

Rough restoration surface

Poor hygiene maintenance

Improper cavity preparation

Microbiology :-

Resemble pit & tissue caries type

S. Mutans & lactobacilli

Found in increased number in secondary caries

(Fonta na t al 1996, 12)

Fitzgerald et al (1994)

stated role of 3 major organisms

S. Mutans – 35 %

S. Sanguis – 24 %

S- Salivarius – 14% in samples

Other isolates,

S. gordonii

S. milleri

S. oralis

S. mitis

Actinomyces found in 46% samples though in less numbers.

Studies :-

I) Pimento et al (1995) 47

Study on amalgam restoration (1497 samples)

47.16% - non-ditched surfaces

52.94% - non-ditched surfaces without caries

58.82 – ditched with caries8

41.18 – ditched without caries

II) Espelid and tveit (1991)10

Classified secondary caries.

S1 initial carious lesion characterized by discoloration only

S2 lesions characterized by softness and/or cavitation on root surface

S3 Lesions cavitation on root surface only.

S1 73.3 %, S2- 58.5%, S3 – 89.7%

didn’t specify status of occlusal caries

Major (1998) 44

3.8 % - Secondary caries with class I amalgam

0.4 % class I composite

4.3 % GIC

2.3 % unspecified

Class II restorations

Amalgam

composite GIC

Gingival

90%

75%

60.5 %

Occlusal

5%

8%

10%

Other surf

10%

15%

10%

Histopathology :-

Process :

Penetration of hydrogen ions-key role in demineralization

Penetration occurs along

Microspaces – capillary forces, diffusion difference in electrical potential b/w

tooth & restoration.

Defects in restoration

Fracture lines in tooth or restoration9

Studies show,

Both wall and outer surface lesions 60%

Outer lesion and no wall lesion 20%

Wall lesion and no outer lesion – 11.9%

Diagnosis

Visual and tactile method

Transillumination

Anterior portion of oral cavity

Radiographs

Especially bitewing

Inhibition – incipient lesions

Latest

Tuned Aperture computer topography (Tact)

Offers 3-dimensional images of synthesized image slices, by tuning number of

projections at angular disparity b/w projections

Advantage :- Can be added to digital system without added costs.

Loss of anatomy(Faulty contacts)

I) Too broad a contact c(buccolingually or occlusogingivaly)

Change in anatomy of co1 and tooth increased degree of food impaction due to

improper shunting of food

II) Too narrow a contact

Food impaction vertically, plaque accumulation. Inaccessibility to hygiene

measures

III) Loose contact

Continuity created b/w co1 & embrasure leads to periodontal destruction &

Secondary caries

IV) Contact too occlusally

Flattened marginal ridge leads to fracture of restoration10

V) Contact too gingival

increased Depth of occlusal – embrasure

Impingement of food

VI) Contact placed too buccally or lingually

Flattened restoration on expense of buccal or lingual proximal wall

Decreased Strength prone to fracture

Failures of specific restorationsFailures of amalgam

Introduction

Silver amalgam is indoubtly the most commonly used restorative material.

It correctly used and compared with any other restorative material the advantages

of silver amalgam always surpass the disadvantages.

The average life span of an amalgam restoration is upto 8-10 yrs if

manipulated correctly. Though failures occur. They are mostly due to faulty cavity

preparation or faulty manipulation.

Healy and Philips (1949) evaluated 1521 defected amalgam restorations and

reported

56 % Failures :- Due to improper cavity preparation

42 % Failures :- Due to faulty manipulation

Types of Amalgam Failures

At Visual Level:

Secondary caries

Marginal fractures

Buck fractures

Tooth fractures

Dimensional change

11

At Microstructural Level

Corrosion and tarnish

Stresses associated with masticatory forces

Pain following restoration

Pulpal and periodontal involvement

Amalgam Failures Can Be Attributed To following Causes

Failures due to faulty cavity preparation.

Failures due to poor matrix adaptation.

Due to faulty amalgam manipulation.

Due to improper condensation.

Failures due to contamination.

Improper finishing and polishing procedures.

Post-operative pain.

Microleakage of amalgam.

Tarnish and corrosion

Role of creep

Role of faulty contacts

Effects of bleaching.

Faulty Cavity Preparation :

Improper cavity preparation leading to recurrence of caries and fracture of

restorations is greatest single factor responsible for failures in amalgam.

Different causes that can occur at various steps while preparing cavities are:-

Inadequate occlusal extension:-Inadequate extensions into pits and fissures increases the chances of

recurrent caries particularly in patients with high caries index. Thus all

12

susceptible pits and fissures should be included while terminating margins in

areas that can be finished.

Inadequate extension of proximal box:-Embrasures if not involved adequately are not amneable to brushing and

cleaning. These result in secondary caries affecting the life of the restoration.

However radical extension of the proximal box will weaken the tooth structure

leading to fracture of restoration.

Special attention in this category should be given to lower bicuspid and

distal embrasures of maxillary and mandibular 1st molars where frail walls can

be formed easily.

Over extensions of cavity prepared walls:-

One fourth of inter-cuspal distance facio-lingually is the ideal requirement

for amalgam restoration to possess adequate strength for functioning.

Caries Involvement Suggested protocol

1. 1/4th of Facio-lingual distance

2. ½ of facio-lingual distance

3. 2/3rd of facio-lingual distance

Simple preperation

Considering cuspal capping

Cuspal capping mandatory

This is because amalgam acts as a wedge between the opposite cusps and

tries to split them apart thickness of amalgam required for capping :

Functional cusps-2 mm

Non-Functional cusps-1.5mm

If thickness required is not provided fractures result inadverently.

It has been calculated that 1.5mm of minimal amalgam bulk is necessary to

resist fractures

13

It pulpal floor is not smooth or is curved the restoration causes a wedging

effect and increases chances of tractor of tooth.

Butt joints especially where occlusal stresses are to be encountered are

essential. Thus the cavo-surface angle has been suggested to be 90o or

preferably 110o.

Cavosurface angle

More acute :- Fractures of tooth margins

More obtuse :- Marginal amalgam fracture

under occlusal tresses.

Cavity margins are to be finished so as to remove unsupported enamel rods

susceptible to fractures and resulting secondary caries failure to round off axio-

pulpal line angle as well as internal line-angles and point angles results in

concentration of forces at these places resulting in fractures of the material or

worse the tooth itself.

By rounding axio-pulpal line angle increase bulk of amalgam for strength is

also obtained. Very narrow isthmus related to rest of the cavity preparation and

co-positioning of the isthmus and axio-pulpal line angle results in fracture of

proximo-occlusal restoration due vulnerability of these areas to be the weakest

points of cavity preparation.

Such phenomenon can also occur due to inadequate proximal retention

form. Undermining of mesial and distal walls of preparations can result in fracture

of mescal or distal marginal ridge due to these areas being unsupported. Thus it is

always advised to keep mesial and distal walls straighter.

The retentive element of the cavity should be in dentine without undermining

enamel so as to give proper support to the restoration or it lead to fractures.

Incomplete caries removal:-

Incomplete caries removal:-14

Incomplete caries removal can lead to failures either by:-

1. FURTHER INVOLVEMENT AND PULPAL INSULT.

2. FRACTURE OF RESTORATION DUE TO UNSUPPORTED

MATERIAL.

If pulpal floor is not flat there will be inability of the restoration to resist forces

directed along long axis of tooth.

This leads to stress concentration and as a result fracture of restoration.

Poor Matrix Adaptation :-

Proper matrix selection is mandatory for a proximal restoration to be

successful. A Minimal thickness of 0.03-0.05mm is required for a matrix to be

burnishable and allow condensation of amalgam without deformation.

Also an extension of 0.5-1mm beyond cavo-gingival line angle of cavity

and similarly above level of marginal ridge is required for proper condensation of

amalgam.

The band should also be stable after application because if not so it can lead

to distorted restoration, gross marginal excess, uncondensed mass of amalgam,

leading to failure. The use of a wedge is justified and mandatory. Also, if band

width is too large it will lead to creations of an open contact or a contact too

occlusally.

If Band width is less it will allow amalgam to escape and form an overhang

resulting in tissue irritation & destruction or incorporation of amalgam in tissues.

Faulty Amalgam Manipulation:-

Mercury – Alloy Ratio :-

Serious loss of structure was reported when residual mercury is in an excess

of 55% in a restoration.

Higher mercury content used during mixing results in higher residual

mercury which cannot be effectively removed by squeezing or condensation.

This high mercury results in :-15

Decrease in crushing strength.

increase in flow and increased susceptibility to tarnish and corrosion .

One should prefer minimal mercury technique which gives proper mixes with

use of dispensers for correct proportioning or amalgamation.

Mulling with bare hands causes incorporation of contaminants esp moisture

into the mix which is deleterious.

esp in zinc containing alloys.

Hardened set amalgam if not removed from the mortars will act as points of

weakness in the matrix of the mix, rendering the restoration prone to failure as

stress concentration occurs at these points.

Undertriturated and over triturated mixes and their effects:-

Undertriturated - Soft-Powdery, Non-coherent mass

Overtriturated Mix - May break already forming matrix

Effective removal of residual mercury is possible only within 4 mins of triturating.

Replastiasing mix by adding mercury seriously decreases strength and

rendering the restoration weak.

Improper Condensation :-

Condensation is a very important step in amalgam restorative procedures as

it reduces the residual mercury contents, and ensures amalgam reaches to all parts

of preparation to obtain a homogenous mix.

Due to improper condensation if voids occur these serve as areas of least strength

in the restoration very susceptible to fracture.

Thus proper condensation is a “Stepping” motion to drive away anyvoids is

advice.

Contamination:-

By Moisture :-16

Bare hand mulling leads to decreased strength esp in Zinc containing alloys

Moisture contamination in oral cavity by saliva and blood:-

Leads to delayed expansion, resulting in marginal flaws, tarnish, pitting

corrosion and pain.

By Materials :-

Any impurities incorporated during the procedure.

e.g. Bare hand manipulation of material to add impurities

Using mix kept on unclean apparatus leads to incorporation of flaws into the

matrix rendering the mix weak and susceptible to degradation.

Improper carving, finishing & polishing

Caries may recur in stagnation areas formed marginal gaps, excess of

amalgam, or in crevices resulting from fracture of excess amalgam.

The main carving should be delayed until the surface offers resistance to

instrumentation.

The correct time is indicated by a particular “Squeaking” sound deviated

from surface “Cry of tin”. The instruments used should be sharp and proper

otherwise defects can be produced in the carvings occasionally excess amalgam at

margins is dressed down to thin flakes or “SPUR” like overhangs which get #ed

away from restoration resulting in areas susceptible to secondary caries.

A rough pitted and corroded surface leads to increased susceptibility for furnish

and corrosion and increased failure rate.

Overcarving :-

Leads to decreased thickness of restoration with increased chances of

fracture.

Undercarving :-

Leads to production of high points causing increased forces on tooth

resulting in post operative pain and potential source for fractures. When carving 17

marginal ridges the instrument should be directed into bulk of restoration,

otherwise the ridge amalgam remains relatively unsupported & may fracture.

Polishing :-

Should not be initiated less than 24 hrs after condensation and carving and

should be done adequately and sufficiently.

If rough surfaces exist they act as sources of plaque adhesion and

subsequent caries progression. These spots also promote corrosion of the material.

If polishing temperature increases more than 65% mercury is released from

amalgam leading to failure by rendering the matrix weak.

Inadvertently this heat may also irritate the pulp and cause deleterious

effects.

Marginal degradation (Ditching)

The “Ditching” around amalgam restorations misthought to be due to

amalgam contraction is mainly due to stress/corrosion dependent defect occuring

in areas subjected to occlusal loading. Magnitude of extent of ditching is directly

related to creep properties so

Increased Creep Increased Ditching

Role of Creep :-

Creep is a critical factor leading to fracture of restoration or teeth. e.g. The

mere fact that incidence of fracture of lingual cusps in mandibular teeth and

buccal cusps in maxilla explains the phenomenon of creep High copper alloys

have low creep rates and are thus more stable.

Material type % CU % Creep Comp Str at 24 HRS(Mpa)

Amalcap Lathecut 6 2.5 410

Dispersalloy Admixed 12 0.25 44018

Sybralloy Spherical 30 0.05 500

Other Factors Responsible for Marginal Deterioration :-

1. Improper Marginal preparation

Poorly supported enamel rods may fracture resulting in crevice

formation.

2. Improper Carving and finishing

“Flashes” around margins may fracture.

3. Excess Mercury

Excess mercury induces weak gamma – 2 phase resulting in weaker

amalgam.

4. Low copper amalgams

Low copper alloys have hi8gh corrosion rates, making margins

porous and # prone.

5. Amalgam Expansion

Material expands – Protrudes- Margins unsupported.

Post – operative pain

Caused due to :-

Hyperocclusion due to undrcarving

Cracks in teeth

Galvanism

Delayed expansion

- Zinc containing alloys on contamination with water.

Microleakage in amalgam :-

Amalgam when freshly condensed does not adapt closely to walls of

prepared cavity.19

Generally a gap of 10-15 mm exists around a restoration and is justified.

Though amalgam later becomes a self-sealing material by virtue of products

of corrosion.

e.g. – Different oxides and chlorides, but if spherical particles of alloy are used or

faulty manipulation done chances of increased Microleakage.

Amalgam “Blues” and “Tattoo” :-

Penetration of amalgam products into dentinal tubules leads to very

anaesthetic condition called “Amalgam Blues” needing re-restoration as desired

by the patient caused by not adhering to proper lining systems. Penetration of

amalgam residuals during restoration in marginal gingiva and when not removed

results in “Tattooing” of gingiva which discolors the mucosa and irritates the

attachment apparatus.

Effects of bleaching :-

These can also have deleterious effects on amalgam

6 % H2O2 Gels – Do not alter surface texture

10-16% carbamide Peroxide - On non-polished surfaces causes corrosion and

increases corrosion susceptibility on polished amalgams too.

Caused due to active oxidation.

Bleaching also Greens the tooth – amalgam interface.

Failures of Pin Retained Restoration Failures may occur in 5 areas :-

1. Within Restoration

2. At Interface B/W Pin & Restorative Material

3. Within pin (Pin Fracture)

4. At interface B/W pin & dentin (Pin-dentin separation)

5. Within dentin (Dentin Fracture)

Within Restoration -

20

Due to :-

1. Improperly retained matrix

2. Movement of matrix

3. Improper condensation

4. Premature removal of matrix

5. High points in restoration

Solution :- Repair or Re-restoration

2) At Pin –Restoration Interface

Due to :- Corrosion products at interface resulting in # of restoration

Solution :- Use of titanium pins or Re-restoration

3) Within Pin (Pin #)

Due to :- Wrongs placement, leading to inadvertent force concentration on body

of pin

Solution :- Removal of restoration & pin drilling another hole 1.5-2 mm away

from original site

Re-Restoration

4) At pin –Dentin Interface

Due to :- Loose pins that do not properly engage dentin, as hole size too large.

Solution :- Preparing pin hole for next pin size or drilling hole at another site.

5) Within Dentin

Due to :- Preparation kept rough on floor uneven direction of forces

stress concentration

dentin fracture

Solution :- Reduce to Hat surface & redrill pin hole

Pulpal damage or exposure, biologic space invasion

1) Heat generation while drilling

Solution :- Pulp capping with calcium hydroxide, redrilling hole 1.5-2 mm away.

21

As most of teeth receiving such restoration have/had extensive restorations /caries

health of pulp already compromised so ideal treatment is ENDODONTIC

THERAPY.

Failures of glass ionomer cements.

Introduction :-

Glass ionomers are one of the most versatile of the acid-base cement and

have many application, used as Restoratives, liners, bases and luting cement.

Outside profession used as bone cement, model material etc. With so, many uses

and implications, criticisms are bound to be associated with the material. Though

failures are to be encountered but most of them still remain within confines of the

operator only.

Disadvantages of the material :-

* Sensitivity to moisture at placement leads to expansion

* Technique sensitive esp in powder : liquid

* Susceptible to dehydration over time

* Less colour stable

* Poor abrasion resistance * Poor acid resistance

* Average esthetics

* Less strength thus contraindicated in stress bearing areas.

* Less tensile strength than composite

Failures of Gic can be visualized as :-

1) Fractures

2) Dislodgment of restoration (By swelling D.T. hydration)

3) Microleakage

4) Gic Sensitivity

5) Porosities

22

6) Colour instability

Failures can be attributed to following reasons. :-

Altering powder liquid ratio :-

Altering powder : liquid – alteration of physical properties

It more than Required powder is incorporated physical properties are altered by

1. Increase in no. of voids & faults

decrease in translucency

2. Marked decrease in strength

Improper Dispensing :-

Bottle of powder it not shaken and fluffed up properly before dispensing

improper mix with weak matrix. occurs

It liquid left to lie on slab or pad takes up moisture and renders restoration weak.

So liquid should be dispensed immediately before mixing.

Altering mixing time, working time :-

Working time of 2 mins from completion of mixing can be achieved with a

mixing time of 7-10 secs.

Decreased Mixing Time :- Leaves unreacted liquid visible in cement

Increased Mixing Time :-Increased Viscosity, decreased Working Time

By 25 secs (30 secs Max) Mixing should be complete any continuation of mixing

will begin to break up newly formed polyacrylate chains & weaken material.

Improper Storage :-

As Gic is a water based material the lids should always be replaced at earliest as

there is increase in viscosity and deleterious effects on physical properties.

Contamination :-

Use of metal instruments for manipulation-corrosion of metal surface –

Incorporation into mix

Colour instability23

Decreases Strength by weakening matrix

Contamination by saliva, blood, pellicle, plaque decrease in strength of GIC

tooth interface bond , leads to adhesive fracture of restoration

Improper or non-removal of smear layer :-

Essential for formation of bond with tooth surface.

Failure to remove smear layer Adhesive # of restoration

10 % Polyacrylic acid conditioning for 10-15 secs (Aboesh & Jenkins 1987)

To dissolve smear layer. It left for more than 20 secs – Demineralization of

dentin. Another alternative, Fixing smear layer by mineralizing solution of 25%

tannic acid or ferric chloride. Unites smear layer to dentin and seals tubules.

Improper tooth support :-

GIC is a tooth supported material at least 2-3 mm of tooth structure required. If

placed at stress bearing areas like cups tips or marginal Ridges

- Restoration likely to #

- Due to Poor Tensile Strength

Porosity :-

Some degree of Porosity is inevitable as two part material mixing.done

Main hazard with Porosity

Compressive strength

Tensile strength

Promotion of crack propagation

Porosity Increased by

Improper dispensing

Improper mixing

Porosity Decreased by

Mixing at low atmospheric pressure 38 % increase in strength achieved (Ngo et

al, 1997a)

Using capsulated materials machine mixed. 24

Dehydration :-

GIC Prone to dehydration, even varnishes seen not to provide significant results.

Leads to Crack propagation

Leads to Bulk fractures

Resin – modified (Light – activated) least prone to dehydration.

Hydration :-

Prone to water uptake during placement and first 24 hrs.

Swelling of restoration - Displacement

Requiring :- Repolishing or replacement

GIC sensitivity :-Caused by dessication

Attributed to washout and open margins from early saliva contamination.

Removal of smear layer by conditioning followed by early cement loss

Permits access to bacteria to open tubules.

Sol :- A hydration period of 2-10 mins prior to restoration es post – op sensitivity.

Improper Finishing :- Dry finishing has deleterious effects.

Marginal Leakage :- Esp in cervical third of tooth prone to leakage more.

Though less critical than other materials.

If occurs leads to

Secondary caries

Pulpal irritation

Failures of direct filling gold :-Due to material

Impurities in material added during production- even small amounts of

impurities in material have pronounced effects on mechanical properties e.g. 0.2%

lead makes gold brittle and thus creation of a non-uniform restoration.

Other Contaminants :- Bismuth

Mercury

25

Impurities incorporated during procedures :-

1. Contaminated gases like SO2 , Ammonia and water vapours during annealing.

2. If flame used is not of Methanol or Ethanol without additives contaminants

are bound to be incorporated.

3. Overheating done during annealing leads to carbon contamination by flame,

tray or instrument making physical properties inferior.

Due to faulty procedures :-

A) Improper caries removal

B) Large cavities :- Inability to take masticatory stress, role of creep and thus

leading to # of tooth though malleable and ductile.

C) Contamination :- A totally dry cavity is mandatory for cohesive condensation,

contamination by blood, saliva etc lead to lack of strength of restoration.

D) Improper Annealing :-

Improper removal of surface contaminants cohesive form.

Overheating makes gold stiller, difficult to condense and ductility.

Contaminants may get incorporated by over heating, use of faulty flame

etc.

Temp below 315O (600f) were inadequate to attain optimum hardness of gold

during annealing.

Improper condensation :-

It restoration not condensed in a proper “Stepping” motion VOIDS can be

incorporated - decreasing cohesive form when in the bulk .

When on surface called “Pits”

These lead to Corrosion, marginal leakage, secondary caries d.t.

Plaque accumulation

High force concentration by hand can damage tooth and insult pulp.

Also high thermal conductivity of gold causes thermal insult to pulp,

Galvanism.26

Failures of composite restorationsComposites have become one of the most preferred esthetic restorations in

modern times. But as they say ............ “All that looks gold is not gold, even these

restorations have their own hindrances,

failures that can be seen in a composite restoration are as follows :-

Discolorations esp at margins

Marginal fractures

Recurrent Caries

Gross fractures of restorations

Lack of contact maintenance

Post-operative sensitivity

Pulpal irritation or damage

Microleakage around composites

Failures caused by the following factors :-

Limitations of operator and process:-

Improper caries removal

Faulty preparation

Faulty handling, manipulation of material

Improper isolation

Contamination

Improper Etching and bonding

Inadequate curing

Bulk placements

Improper finishing & polishing

Limitations of material composite:-27

Polymerization shrinkage

Weak bond strength when cavosurface margin in dentin

Water sorption

Penetration in tissues to irritate pulp

Inadequate polymerization in deep inter proximal areas

Incomplete caries excavation :-

If incomplete caries excavation is done, the left over caries hinders the

bonding mechanism. As studies suggest that the weakest bonding of composite is

to carious tooth structure and early failures are to be expected.

Also if Zinc Oxide Eugenol is not removed fully in any case it hinders the

methacrylate group of resins making the bonding weaker .

Incomplete etching or failure to remove residual acid from enamel tags:-

Proper concentration of etchant and etching time has to be adhered to -

total etching time should not be more than 60 secs (30-60 Secs range). Though

15 Secs etching sufficient for enamel, washing 20-30 Secs (Gels) 10-15 Secs

(Liquids)

Avoid 3-way syringe for drying – Contamination by machine oils etc.

Role of exit angles :-

90 degree - Conservative - Doesn’t expose ends of rods

45 degree - Most common - Superior seal –decreased Microleakage

exposes rods

Concave exit - Most retentive - Least conservative (used in cl IV cases)

Joining convex exit -

Least practical clinically but illustrated rounded ends provide excellent exits used

for stiff composites provide excellent exits

used for stiff composites only

Sem studies – 90 exit – Poorest seal

28

Improper bonding :-Bonding agent is to be applied gently and uniformly all around cavity

walls. Double Coats are to be avoided as these lead to marginal leakage non-

uniform bonding hinders the bond strength to bonding agent.

Also if one has to shift from microfilled resin to a layer of macrofilled, an

unfilled bonding agent if not place weakens the bond and causes fracture at that

point.

Role of evaporation

Lack of isolation

Isolation is mandatory in a composite restoration ideally rubber dam

should be used, otherwise cotton rolls should be kept ready and changed evenly.

Any contact with gingival fluid, saliva or blood

Potential source of contamination

reduces resin to resin bond strength.

Sol – Etching and bonding to be repeated.

Other contaminants :-

Touching the material with hands or fingers

Picking material from tongue etc and placing back

Using unclean instruments

These add impurities to the material rendering it weak and less

colour stable, changing shade characteristics. Always teflon coated instruments to

be used.

Bulk placements

29

Material is to be cured in increaments and each increament should

be as small as possible as gaps may occur after shrinkage of material at tooth

restoration interface.

These lead to post-operative sensitivity, marginal leakage & secondary caries.

Also due to gaps and voids, material is rendered weak and stress

points – source of #

Improper curing

Curing if not done from all sides and for a stipulated period results

in a restoration with marked decreased strength and prone to marginal leakage.

If first curing is not done gingivally the material due to its property

to shrink towards source of light creates a gap between pulpal floor and bulk of

material in occlusal cavities and also leads to gap formation in gingival seat area

in proximal restorations which are prone to leakage’s and fractures.

Improper angle &Path of light :-

As angle deviates from perpendicular, the penetration and intensity

of light is afflicted & reduced.

e.g. Marginal ridge of adjacent tooth blocks light placed at an angle.

Thickness of resin :-

Optimum polymerization occurs at depth of just 0.5-1mm owing to

air inhibition at surface and difficulty of light penetration.

Study showed:-

7 days after 40 sec curing cycle

1mm deep composite – 68-84% Optimum hardness

At 2 mm same composite – 40-60%

At 3mm – only 34%

Air Inhibition :-30

Oxygen in air competes with polymerization and inhibits setting of

resin.

Extent of surface inhibition is inversely related to filler loading.

Undercured layer can vary from 50-500mm or more, depending on

reactivity of photoinitiator used .

Unfilled resins should be cured, covered with air inhibiting gel

(Oxyguard-Commercial Preparation )

Petroleum jelly glycerin & then recured This reduces air inhibition.

Improper light intensity:-

Optimum curing intensity – 468 + 20nm

Blue light – 400mv/cm2

Causes of decreased intensity :-

Age of bulb

Increased Age – Decreased Intensity

Voltage

- Voltage drops decrease intensity

Sterilization of curing tips reduces light transmission

Filters to increase blue light transmission degrades intensity.

Curing distance :-

Distance of 1 mm from occlusal surface- ideal

increase in distance - Decreased intensity

- Decreased strength

Exposure :-

Minimum exposure of 20-40 secs under continuous light is mandatory.

Any deviations in lesser range results m partially cured, inferior

restorations.

Temperature :-

Light cure composites cure less effectively if they are cold during

application (Freshly taken out of refrigerator )

They cure move rapidly & completely at room temp.31

Also most curing lamps produce heat which speeds curing process.

However excess heat by undue application can result in pulpal irritation and

inflammation.

Improper finishing & polishing :

Meticulous finishing and polishing is to be done, As all rough surfaces act

as a nidus for microorganisms (Plaque accumulation)

Special attention in interproximal area as sharp projections – irritate &

inflame gingiva by impingement

Dry Polishing & Finishing is detrimental as it can open dentin margins at

dentin – restoration interface.

Exception- Microfilled composites

Effect of number of flutes of finishing & polishing bur – more the number of

flutes lesser the damage

Pulp irritation or damage :-

It is difficult to differentiate the effect of components of composite resin

itself, the trauma of cavity preparation, and sequelae such as microleakage at

margins

Cytotoxicity Studies State :-

Cured polymerized resin as far as possible causes minimum irritation. but

incompletely cured resin because of presence of uncured resins or surface active

complexes formed b/w low molecular wt. components of light initiator systems.

One potent component is Hema (Hydroxlethyl Mehacrylate )

an essential component of light cured composites,

Highly Hydrophillic

Allergenic

Studies show that it can transverse in tubules appear in pulp & Cause

deleterious effects.

Composite Discoloration :-32

Composite may undergo extensive surface staining intrinsic colour change

or both.

Extrinsic surface staining

Max. water sorption in first 7-10 days

Strong staining agents (Tea, Coffee, cola) penetrate to

depth of 3.0-5.0 mm (Mount & Hume)

Problems accentuate with wear and incomplete curing .

Intrinsic discoloration

Seen in both chemically activated & light activated

Chemically activated – Substantial yellowing in 1-3 yrs due to oxidation of excess

amine from initiator system

Visible light cured systems :-

Lighten in colour & become more translucent during curing e further in 24-

48 hrs. by decomposition of camphoroquinone.

Degradation in oral environment :-

Unreacted methacrylate groups degrade more rapidly. May be leached from

resins

Hydrolytic degradation of barium & strontium

Glass fillers – Pressure build up at resin –filler

interface – crack formation

Type of composite used -

Microfilled less susceptible to hydrolytic degradation

Chemical attack – Breakdown of silane coating

Weakening of tiller- resin bond

Rapid thermal changes – Breakdown of silane coating

In Microfilled :-

Bond b/w prepolymerised particles & Matrix – potential site for

hydrolytic degradation failures.

Role of water sorption :-33

Limited amount may be beneficial

More sorption – Restoration dimensionally unstable

Aesthetically unpleasant

More Water sorption – More Creep rate

Microfilled Resin – 1.5-2.0 mg/cm2

Hybrid & Macrofilled – 0.61.1 mg/cm2

Water sorption increases when

Filler content less, resin content more

reduced curing time – Increased Water sorption

e.g 25% reduction in curing time

2fold increase in sorption

– 6 fold increase in solubility

Seriously affects – Durability & colour stability.

Microleakage of composites :-

Considerable evidence - Etching itself not a culprit of pulpal inflammation

As acids get buffered in dentin

However etching opens tubules , allowing positive dentinal flow

Should marginal leakage occur & presence of partially or uncured monomers

occurs – Pathway to pulp open.

Adviced – not to etch dentin in vital teeth or a strong GIC base completely

covering all dentine before etching enamel walls.

In vitro study (Haggesmon, Mason – 2001)

Resin Mod GIC Has lesser Microleakage

than (A) Bonding agents

(B) Flow able composites

(C) by dunn’s test.

34

Marginal Defects :-

1. Surface fracture of excess material

2. Crevice formation CD itching, Marginal

3. Porosity or void (incorporation of air b/w restoration & Tooth during

placement)

4. Wear of restoration (Progressive exposure of axially directed cavity wall)

Role of type of composite used :-

Macrofilled – More of wearing type of defects

Hybrides – Tend to chip (Crevice formation) & wearing too

Microfilled – Chipping & Surface fractures

Due to – Fracture toughness, tensile strength elastic modules,

polymerization shrink coeff. of thermal contraction.35

Role of composite fatigue :-

Under certain loading conditions, composites begin to tire, losing strength

over a period of time. Results in cohesive microcracks & external chipping.

Role of bleaching :-

Results in colour instability by changing shade.

10-16% carbamide peroxide, may lead to slight deterioration by statistically

causing Surface roughness & amount of parasites esp in microfilled &

hybrid resins result in increased plaque adhesion & staining

25-35% hydrogen peroxide uniformly showed shear-bond & tensile bond

strength of all composites.

37% carbide peroxide or pastes c 30% H2O2 and Na perorate, lead to

microleakage.

These concentrations after affecting marginal seal may penetrate to pulp and

cause deleterious effects.

Failures of inlays Important failures include :-

Secondary caries

Surface discoloration

Marginal fractures (Esp porcelain inlays)

Restoration dislodgements

Marginal leakage

Tooth fractures

Failures caused due to

(A) Faulty preparation :

Angle of divergence of walls :-

Buccal and lingual walls divergence should be at an angle b/w 5o & 10 0

If Angle < 5o – Remaining structure under undue stresses during cementing

& force loading in function

If Angle > 10o – Compromised retention

36

Structure of walls :-

After inlay seated in mouth, maintenance of retention depends on

Strength and integrity of both lingual & buccal walls.

It is virtually impossible to gain strength and retention from opposite

remaining cusp which is already weak (Extracoronal coverage)

Improper Margins :-

30-40o Marginal metal desirable

angle of 140-150o (Cavosurface angle)

desirable while cutting

Cavosurface angle > 150o – Metal too thin and weak

< 140o – Metal too bulky and difficult to burnish

Gingival bevel of 30o desirable

No mesial tilt of INST – Too steep cutting Metal thin & weak

Not connecting & blending with Sec flares

Distofacial & distolingual

areas exposed for cement dissolution.

Secondary flares :-

If not given results in proximal surfaces in – accessible to surface cleaning

action – leading to plaque accumulation & periodontal problems.

Luting cement dissolution.

Luting cements are prone to dissolution in oral environment

More the gap in restoration- tooth interface

More cement exposed

More dissolution

more marginal leakage

Also in proximal areas any excess cement remaining after cementation,

unchecked-

Becomes an area of continuous periodontal irritation.

Post-insertion sensitivity :-

Seen c both GIC and Zinc phosphate 37

Occurs mostly due to removal of smear layer

Fixing of smear layer advised thus,

Through reinforced Zoe has been advised

But tends to hydrolyze washings around margins

more prone to leakage

Marginal leakage & percolation

Leakage occurs- Teeth subjected to alternative cooling and warming.

Due to – diff in coeff of thermal expansion of tooth and material.

Resulting ingress & egress of fluids – percolation

As a result bacteria’s can gain access & cause deleterious effects

Another cause – increased taper – continuing loads – restoration gives away by

rotating on walls - fractured thin metal margins.

Considerations in porcelain inlays :-

Bevels

If given – Thin sections of porcelain at cavosurface

Highly brittle, prone to fracture

FracturesA strain of only 8-10 mm/cm in dental porcelain is required before it

fractures

Most fractures start from inner surfaces esp- at or near gingival margins

Role of surface flaws :-

Porcelains are brittle materials but not synonymous with weakness.

Because of structure of Si-O2 bonds & absence of grain boundaries, the vitreous

matrices of porcelain have intrinsic strength.

As material perfectly elastic – Measured strength strongly dependent on presence

or absence of surface flaws.

38

Fracture Propagation :-

Caused by stress concentration at tip of surface How. Once initiated , the

extension of crack is ensured by applied stresses & increasing stress

concentration factor of growing crack.

Exposure to water strength of porcelain attributed to stress enhanced B/w

glass & H2O occurs primarily at tips of such cracks water reacts with glass –

destruction of Si-O network –hydroxyl ions attack siloxane bonds.

39

CONCLUSION

As a wise man has said…….

In the wide arena of world failure and success are not accidents as we suppose but

strict justice of nature. If you do your work sincerely you are certain to get

rewarded .

A person who has not seen his or her work fail over the years is myopic,

peripatetic, or simply very young.

It is good to be critical about work but being unfairly critical about work of others

is not done for us we do not know about the circumstances in which the

restoration was done.

40

REFERENCES

A) Studervant – Textbook of operative dentistry

B) Marzovk – Textbook of operative dentistry

C) Vimal sikrj – Textbook of operative dentistry

D) Tooth coloured restorations – albers

E) Mount- Preservation & restoration of tooth strvcture

F) Leinfelders & Lemons – clinical restorative materials & techniques

G) Advanced operative dentistry - Wilson, fuzzi, Voli, vol II

H) Plckards Manual of dentistry

I) Skinners & Philips – dental material science

J) JR. of academy of dental materials

-20 (9) Nov 2004

-20(1) Jan 2004

-20(2) Feb 2004

-20(3) Mar 2004

K) JR of conservative dentistry

-7 (3) Jul – Sep 04

-7 (4) Oct – Dec 04s

-7 (1) Jan –Mar 04

41

SEMINAR

FAILURES OF

RESTORATIONS

: SEMINAR BY :

DR. SHANTUN MALHOTRAP.G. STUDENT

DEPT. OF CONSERVATIVE

DENTISTRY & ENDODONTICS

S.P.D.C. SAWANGI

: GUIDED BY :

DR. W. N. GHONMODE

DR. MANOJ CHANDAK

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