Failures of Dental restorations


Published on

Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.

Published in: Education, Business, Technology
  • I second the first post! It would be a great help if we could download the presentation. Thank you!
    Are you sure you want to  Yes  No
    Your message goes here
  • PLZ let us to download this presentation.
    Are you sure you want to  Yes  No
    Your message goes here
No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Failures of Dental restorations

  1. 1. 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
  2. 2. 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 2
  3. 3.  Trauma  Defective contours  Failure of retention (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 Longitudi nal 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) 0-7 0.7-9 0-14.4 0-5.9 0-10 0-7.1 0-11.6 0-7 0.7-9 0-14.3 0-5.9 1.5-9.8 0-4.3 0.5-11.6 0-7 0.7-5.9 0-14.4 0-2.6 0-10 0-7.1 0-11.6 1-6.3 3.3-9 -- 0.5-5.9 --- 0.8-4 1-3 3
  4. 4. Cervical restorations (Class V) 0-26 0.3-7.2 0-26 1.6-5.9 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 4
  5. 5. D) Technique sensitivity of material D) casual attitude & manipulative techniques E) Inhibitions of the material itself patient 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 5
  6. 6. 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 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. 6
  7. 7. Influenced by :  Wetting capability  Surface energy  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 7
  8. 8. Makes sterile, inert, non-toxic synthetic smear layer. Secondary caries These are caries around a restoration, also known as ‘Recurrent caries’ Etiological Factors  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 :- 8
  9. 9. 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 caries 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 9
  10. 10. Penetration occurs along  Microspaces – capillary forces, diffusion difference in electrical potential b/w tooth & restoration.  Defects in restoration  Fracture lines in tooth or restoration 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 10
  11. 11. 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 restoration 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 restorations Failures 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 11
  12. 12. At Visual Level:  Secondary caries  Marginal fractures  Buck fractures  Tooth fractures  Dimensional change 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. 12
  13. 13. 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 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 13
  14. 14. 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  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 14
  15. 15. 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:- 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. 15
  16. 16. 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 :-  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 :- 16
  17. 17. 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 :- 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 17
  18. 18. 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 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 18
  19. 19. 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 0.25 440 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 19
  20. 20. 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. 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. 20
  21. 21. 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 - 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 21
  22. 22. 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. 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 22
  23. 23. * 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 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 :- 23
  24. 24. 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 instability • 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 24
  25. 25. 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. 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. 25
  26. 26. 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 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. 26
  27. 27.  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. Failures of composite restorations Composites 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 27
  28. 28.  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:-  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 . 28
  29. 29. 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 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 29
  30. 30. 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 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 30
  31. 31. 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 :- 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 31
  32. 32. 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. 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 32
  33. 33.  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 :- 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 33
  34. 34. 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 :-  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 34
  35. 35. 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. Marginal Defects :- 35
  36. 36. 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. 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. 36
  37. 37.  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 Structure of walls :- After inlay seated in mouth, maintenance of retention depends on Strength and integrity of both lingual & buccal walls. 37
  38. 38. 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 Occurs mostly due to removal of smear layer  Fixing of smear layer advised thus,  Through reinforced Zoe has been advised 38
  39. 39. 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 Fractures A 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. 39
  40. 40. 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. 40
  41. 41. 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. 41
  42. 42. 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 42
  44. 44. 44