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Rationale of post endodontic restoration   /certified fixed orthodontic courses by Indian dental academy Rationale of post endodontic restoration /certified fixed orthodontic courses by Indian dental academy Presentation Transcript

  • RATIONALE OF POST ENDODONTIC RESTORATION INDIAN DENTAL ACADEMY Leader in Continuing Dental Education www.indiandentalacademy.com www.indiandentalacademy.com
  • Contents Introduction Historical perspective Causes of tooth fracture Treatment planning Post systems Evidence based practice Principles of tooth preparation Core Corono-radicular restoration Restoration of resected root Over dentures www.indiandentalacademy.com Conclusion
  • Why restore endodontically treated teeth? Why ask Why? www.indiandentalacademy.com
  • Historical perspective More than 200 years 1747, Pierre Fauchard: Posts made of gold or silver and held in the root canal space with a heat-softened adhesive called “mastic.” “Pivot crown.” Dubois de Chemant – 1800, used seasoned wood Prothero reported removing two central incisor crowns with wooden pivots that had been successfully used for 18 years. www.indiandentalacademy.com
  • Historical perspective Metal pivot retention similar to Richman’s Crown Dental Physiology and Surgery, written by Sir John Tomes in 1849. Tomes’s post length and diameter conform closely to today’s principles in fabricating posts minimal efforts to clean, shape, and obturate Wooden post associated with swelling &pain. But allowed escape of “morbid humors.” www.indiandentalacademy.com
  • Causes of tooth fracture Altered physical properties of the tooth Weakening due o the loss of tooth structure Prestressed laminates – Tidmarsh 1974 Loss of proprioception www.indiandentalacademy.com
  • Classification of Posts POSTSCustom-made Prefabricated Metallic Non-metallic Stainless steel Zirconia Ni-Cr alloy Ceramic Titanium Fiber www.indiandentalacademy.com
  • Active Passive Threaded, engage dentin Retained by luting agentMore retentive, more stress Retention & stress less Thick but short roots Long slender roots Parallel Tapered More retentive Less retentive Less stress Wedging forces Less removal, slender & delicate More dentin removal roots Success rate high www.indiandentalacademy.com Success rate low
  • Post Designwww.indiandentalacademy.com
  • Metallic Posts Rigid except titanium posts Round hence lack rotational resistance Metallic posts tend to corrode, except Ti posts Ti posts – not strong & easily fracture; retrieval difficult Flexi-post www.indiandentalacademy.com
  • Cast Post & Cores Used for many years Unpopular – 2 appointments, laboratory fee, temporization Advantageous in certain clinical situations:  multiple teeth requiring posts  mal-aligned tooth  slender roots like mandibular incisors Requires proper temporization to prevent inter appointment contamination www.indiandentalacademy.com
  • Ceramic & Zirconia Posts Metal posts & all ceramic crowns White or translucent – esthetic posts Lack rigidity hence require larger post diameter Zirconia posts cannot be etched Retrieval is difficult Ceramic posts can be ground but procedure is dangerous Zirconium posts are impossible to grind www.indiandentalacademy.com
  • Fiber Posts Carbon posts were first of its kind; mod of elasticity similar to dentin When bonded with resin cement, distribute stresses evenly Retrieval easy – boring through the uniaxial fibers Dark – esthetic incompatibility Newer fiber posts – quartz fiber, glass fiber, silicon fiber www.indiandentalacademy.com
  • Treatment Planning Good apical seal No sensitivity to pressure No exudates No sinus No apical sensitivity No active inflammationwww.indiandentalacademy.com
  • Considerations For Anterior Teeth do not always require complete coverage fracture toughness for teeth with and without endodontic treatment- SAME (lab) strengthen the teeth replacing part of the root canal filling with a metal post when the tooth is loaded, the lingual side is under tension and the buccal side under compression www.indiandentalacademy.com
  • Considerations For Anterior Teeth When there is considerable loss of crown structure or when the tooth is to serve as an abutment for FPD or RPD, complete crown becomes mandatory. Retention and support then must be derived from within the root canal because the coronal dentine remaining after tooth preparation will be thin and fragile. Use of powerful organic solvents ZOE sealers and composite resins www.indiandentalacademy.com
  • Considerations For Posterior Teeth Closer to the transverse horizontal axis & cuspal morphology Exceptions to cuspal coverage are mandibular premolars and first molars - intact marginal ridges, conservative access preparations, less load. Complete coverage is required on teeth with a high risk of fracture. This is especially true in maxillary premolars. www.indiandentalacademy.com
  • Minimal loss of tooth structure GP should be cleared off the access cavity with hot instruments or GG drills. All traces of sealer must be removed to prevent discoloration of the crown Effective use of alcohol Posterior teeth can be restored with amalgam or composite resin The core must extend 2-3 mm into the canal entrances. www.indiandentalacademy.com
  • Moderate loss of tooth structure Anterior teeth - minimal loss of tooth structure. Treatment options may be simple core restoration or post and core Posterior teeth, loss of one or both marginal ridges additional to tooth lost in access preparation. Amalgam or composite cores emanating 2-3 mm from canals, post and core with compulsory cuspal coverage. Extra coronal restoration must extend 1-2 mm onto sound tooth structure Interim restoration for cuspal coverage – bonded amalgam or composite resin. www.indiandentalacademy.com
  • Extensive loss of tooth structure Little or no coronal tooth structure is remaining Crown lengthening, forced eruption followed by cast post & diaphragm with a ferrule. Or pre- fabricated posts with crown. Metal collar must extend 2-3mm onto sound tooth structure Immature tooth, relined with dentine bonding composites followed by fiber posts. www.indiandentalacademy.com
  • Evidence Based Practice The conscientious, explicit andjudicious use of current BESTEVIDENCE in making decisionsabout the care of individual patients Sackett DL, et al BMJ 1996;312:71-2 www.indiandentalacademy.com
  • SHOULD CROWNS BE PLACED ON ENDODONTICALLY TREATED TEETH? www.indiandentalacademy.com
  • • 1,273 teeth endodontically treated 1 to 25 years. Coronal coverage crowns did not significantly improve the success of endodontically treated anterior teeth• Structurally weakened or they require significant form/color changes that cannot be effected by bleaching, resin bonding, or porcelain laminate veneers• A significant increase in the clinical success was noted when cuspal coverage crowns were placed on maxillary and mandibular molars and premolars. Scurria et al. www.indiandentalacademy.com
  • • Multiple clinical studies of fixed partial dentures, many with long spans and cantilevers, have determined that endodontically treated abutments failed more often than abutment teeth with vital pulps owing to tooth fracture• It has been shown that endodontic procedures reduce tooth stiffness by 5%, attributed primarily to the access opening. Also, with aging, greater amounts of peritubular dentin are formed, which decreases the amount of organic materials that may contain moisture.• Dentin from endodontically treated teeth has been shown to exhibit significantly lower shear strength and www.indiandentalacademy.com toughness than vital dentin. (Tidmarsh )
  • • Rivera et al. stated that the effort required to fracture dentin may be less when teeth are endodontically treated because of potentially weaker collagen intermolecular cross-links.Conclusions:• Restorations that encompass the cusps of endodontically treated posterior teeth have been found to increase the clinical longevity of these teeth.• Limited use in anterior teeth www.indiandentalacademy.com
  • WITH PULPLESS TEETH, DO POSTS IMPROVE LONG-TERM CLINICAL PROGNOSIS OR ENHANCE STRENGTH? www.indiandentalacademy.com
  • Laboratory Data Lovdahl and Nicholls - endodontically treated maxillary central incisors were stronger when the natural crown was intact, except for the access opening, than when they were restored with cast posts and cores or pin- retained amalgams Lu found that posts placed in intact endodontically treated central incisors did not lead to an increase in the force required to fracture the tooth or in the position and angulation of the fracture line Trope et al. determined that preparing a post space weakened endodontically treated teeth compared with ones in which only an access opening was made but no post space. www.indiandentalacademy.com
  • Laboratory Data A potential situation in which a post and core could strengthen a tooth was identified by Hunter et al. using photoelastic stress analysis. They also determined that minimal root canal enlargement for a post does not substantially weaken a tooth, but when excessive root canal enlargement has occurred, a post strengthens the tooth. When loaded vertically along the long axis, a post reduced maximal dentin stress by as much as 20%. However, only a small (3 to 8%) decrease in dentin stress was found when a tooth with a post was subjected to masticatory and traumatic loadings at 45 degrees to the incisal edge. www.indiandentalacademy.com
  • Clinical Data Sorenson and Martinoff clinically evaluated endodontically treated teeth with and without posts and cores. Posts and cores significantly decreased the clinical success rate of teeth with single crowns and improved the clinical success of RPD abutment teeth but had little influence on the clinical success of FPD abutments A 1994 survey (1,066 practitioners and educators) 10% of the dentist respondents felt that each endodontically treated tooth should receive a post. 62% of dentists > 50yrs believed that a post reinforces the tooth, whereas only 41% of the dentists under age 41 believed in that concept. www.indiandentalacademy.com
  • Conclusions Both laboratory and clinical data fail to provide definitive support for the concept that posts strengthen endodontically treated teeth. Therefore, the purpose of a post is to provide retention for a core. www.indiandentalacademy.com
  • WHAT IS THE CLINICALFAILURE RATE OF POSTS AND CORES? www.indiandentalacademy.com
  •  A 9% overall average for absolute failure was calculated by averaging the absolute failure percentages from eight studies (an average study length of 6 years). Range 7 – 14 % Kaplan-Meier survival statistics ranged from a high of 99% after 10 years or more of follow-up to a 78% survival rate after a mean time of 5.2 years. The percent failure per year has also been calculated and ranged from 1.56%/year to 4.3%/year.Conclusions Posts and cores had an average absolute rate of failure of 9% (7 to 14% range) when the data from eight studies were combined (average study length of 6 years). www.indiandentalacademy.com
  • WHAT ARE THE MOST COMMON TYPES OF POST AND CORE FAILURES? www.indiandentalacademy.com
  •  Turner reported on 100 failures of post-retained crowns and indicated that post loosening was the most common type of failure. 59% 42 - apical abscesses 19 - carious lesions 10 - root fractures 6 - post fractures Lewis and Smith presented data regarding 67 post and core failures after 4 years. 47 (70%) - posts loosening 8 - root fractures 7 - caries 4 -bent or fractured posts www.indiandentalacademy.com
  •  Sorenson & Martinoff evaluated 420 post & cores and recorded 36 failures  8 - restorable tooth fractures  12 -non-restorable tooth fractures  13 - loss of retention  3 - root perforations Torbjörner et al. reported on the frequency of 3 technical failures (loss of retention, root fracture, and post fracture) www.indiandentalacademy.com
  • Conclusions Loss of retention and tooth fracture are the two most common causes of post and core failure. www.indiandentalacademy.com
  • WHICH POST DESIGN PRODUCES THE GREATEST RETENTION? www.indiandentalacademy.com
  • Laboratory Data Threaded posts provide the greatest retention, >by cemented > parallel-sided posts. Tapered cemented posts are the least retentive. Cemented, parallel-sided posts with serrations are more retentive than cemented, smooth-sided parallel posts.Clinical Data Torbjörner et al – 7% Sorenson and Martinoff - 4% Bergman et al. and Mentink et al - 6% Weine et al. They found no clinical failures from loss of retention with cast tapered posts. Hatzikyriakos et al. - tapered threaded posts, parallel cemented posts, and tapered cemented posts. www.indiandentalacademy.com
  • Conclusions Tapered posts are the least retentive and threaded posts the most retentive in laboratory studies. Most of the clinical data support the laboratory findings. www.indiandentalacademy.com
  • IS THERE A RELATIONSHIP BETWEEN POST FORM AND THEPOTENTIAL FOR ROOT FRACTURE? www.indiandentalacademy.com
  • Laboratory Data Henry - threaded posts Standlee et al - tapered, threaded posts Deutsch et al - tapered, threaded posts increased root fracture by 20 times that of the parallel threaded posts Thorsteinsson et al- determined that split-threaded posts did not reduce stress concentration during loading Henry - parallel- sided posts distribute stress more evenly to the root parallel posts concentrate stress apically and tapered posts concentrate stress at the post-core junction. Assif et al. - tapered posts -equal stress distribution between the CEJ and the apex compared with parallel www.indiandentalacademy.com posts (apical pressure).
  •  Sorenson and Engelman determined that tapered posts > fractures than parallel-sided posts, but the load required to create fracture was significantly higher with tapered posts In analyzing the stress distribution of posts, tapered posts generate the least cementation stress: thin root walls, are nearly perforated, or have perforation repairs. www.indiandentalacademy.com
  • Clinical Data threaded posts - mean fracture rate of 7% (5 studies) parallel-sided cemented posts - 1% (4 studies) tapered posts - 3% ( 7 studies) Creugers et al. - 91% tooth survival rate for cemented cast posts and cores & 81% survival rate for threaded posts with resin cores In comparing fracture rates - parallel and tapered posts Hatzikyriakos et al, Ross & 2 other studies – no difference in fracture rates bet parallel & tapered posts www.indiandentalacademy.com
  • Conclusions Threaded posts ↑ root fracture – lab & clinical Stress analysis & fracture rates - Tapered and parallel cemented posts Further research to study designs of posts www.indiandentalacademy.com
  • WHAT IS THE PROPER LENGTH FOR A POST? www.indiandentalacademy.com
  • Various recommendations…… equal the incisocervical or occlusocervical dimension of the crown longer than the crown one and one-third the crown length half the root length two-thirds the root length four-fifths the root length terminated halfway between the crestal bone and root apex as long as possible without disturbing the apical seal. www.indiandentalacademy.com
  •  Radiographic study of 217 posts - only 5% of the posts were 2/3 to ¾ the root length Sorensen and Martinoff - clinical success was markedly improved when the post was equal to or greater than the crown length Ideal root length – 2/3rds post length, but hampered apical seal in short roots. Abou-Rass et al. 150 molar teeth. They determined that molar posts should not be extended more than 7 mm apical to the root canal orifice ( risk of root perforation) diminished bone support, ↑ stresses are concentrated in the dentin near the post apex. To ↓ stress in the dentin & in the post, the post should extend > 4 mm apical www.indiandentalacademy.com to the bone
  • ConclusionsReasonable clinical guidelines for length include the following:(1) three-quarters - long-rooted teeth(2) When average root length - retain 5 mm of apical gutta-percha(3) Whenever possible, posts should extend at least 4 mm apical to the bone crest to decrease dentin stress(4) Molar posts should not be extended more than 7 mm into the root canal apical to the base of the pulp chamber www.indiandentalacademy.com
  • HOW MUCH GUTTA-PERCHA SHOULD BE RETAINED TOPRESERVE THE APICAL SEAL? www.indiandentalacademy.com
  • Apical seal…. 4 mm of GP - only 1 of 89 specimens showed leakage Mattison et al. 3, 5, and 7 mm Nixon et al. 3, 4, 5, 6, and 7 mm Kvist et al. radiographic examination of 424 posts. Teeth with 3mm seal leaked the mostConclusions Greater leakage - 2 to 3 mm 4 to 5 mm should be retained apically to ensure an adequate seal. www.indiandentalacademy.com
  • DOES POST DIAMETER AFFECT RETENTION AND THE POTENTIAL FOR TOOTH FRACTURE? www.indiandentalacademy.com
  •  Krupp et al - retention - post diameter was a secondary factor Mattison - stress - increased diameter Deutsch et al - six fold increase in the potential for root fracture with every millimeter the tooth’s diameter was decreased.Conclusions Laboratory studies on retention - mixed results, definitive relationship between root fracture and large-diameter posts. www.indiandentalacademy.com
  • Large diameter causing root fracture and failure www.indiandentalacademy.com
  • WHAT IS THE RELATIONSHIPBETWEEN POST DIAMETER AND THE POTENTIAL FOR ROOT PERFORATIONS? www.indiandentalacademy.com
  • Lloyd and Palik – 3 distinct philosophies of post space prep. the conservationists the proportionists the preservationistsTilk et al 1,500 roots based on the proportionist 0.6 to 0.7 mm – small teeth Large-diameter roots - 1.0 mm Remaining teeth - 0.8 to 0.9 mm. www.indiandentalacademy.com
  • Shillingburg et al- 700 root dimensions - minimize the risk of perforation mandibular incisors- 0.7 mm maxillary central incisors or other large roots, 1.7 mm (max) post tip diameter, at least 1.5 mm less than root diameter at that point post diameter at the middle of the root length, 2.0 mm less than the root diameter. www.indiandentalacademy.com
  •  mesial roots of mandibular molars & buccal roots of maxillary molars For the principal roots not more than 7 mm into the root canal Instrument size - No. 2 Peeso instrument safe. but perforations are more likely when the larger No. 3 and 4 Peeso instruments were used. Raiden et al. 0.7 mm or less for maxillary I pre-molars with single canals (mesial and distal developmental root depressions). Dual canals, as large as 1.1 mm because the canals are located buccally and lingually into thicker areas of the roots. www.indiandentalacademy.com
  • CAN GUTTA-PERCHA BE REMOVEDIMMEDIATELY AFTER ENDODONTIC TREATMENT AND A POST SPACE PREPARED? www.indiandentalacademy.com
  •  Bourgeois and Lemon- immediate & 1 week later when 4 mm of GP were retained Madison & Zakariasen; Zmener – imme & 48 hrs Harrington - immediate GP removal - warm and rotary instruments. Karapanou et al- immediate and delayed removal of two sealers (ZOE & resin sealer) Portell et al - removal after 2 weeks > leakage than immediate removal when only 3 mm of gutta-percha were retained apically. Fan et al. found more leakage from delayed removal of gutta-percha. www.indiandentalacademy.com
  • Conclusion Adequately condensed gutta-percha can be safely removed immediately after endodontic treatment. www.indiandentalacademy.com
  • WHAT INSTRUMENTS REMOVE GUTTA-PERCHA WITHOUT DISTURBING THE APICAL SEAL? www.indiandentalacademy.com
  •  Suchina & Ludington and Mattison et al. found no difference between hot instrument removal and removal with GG burs Camp & Todd found no difference between Peeso reamers, GG burs, and hot instruments Haddix et al. a heated plugger < a GPX instrument or GG drills www.indiandentalacademy.com
  • Conclusion Both rotary instruments and hot hand instruments can safely be used to remove adequately condensed gutta-percha when 5 mm are retained apically. www.indiandentalacademy.com
  • CAN A PORTION OF A SILVERPOINT BE REMOVED AND STILL MAINTAIN THE APICAL SEAL? www.indiandentalacademy.com
  •  In one study, all of the specimens leaked when 1 mm of a 5mm long silver point was removed using a round bur. Neagley found that removal of the filling material coronal to the silver point with a Peeso reamer caused no leakage. However, when all of the filling material and 1 mm of the silver point were removed, complete dye penetration occurred in 8 of 9 specimens. www.indiandentalacademy.com
  • DOES THE USE OF A CERVICAL FERRULE THAT ENGAGES TOOTHSTRUCTURE HELP PREVENT TOOTH FRACTURE? www.indiandentalacademy.com
  • Studies to investigate…1. Core Vs crown ferrule2. Manner of engaging the tooth ( beveled Vs parallel)3. Amount of tooth engaged Assif et al. found no difference in the tooth fracture patterns with different types of posts when they were covered by a crown that grasped 2 mm of tooth structure Isidor et al. compared no ferrule with 1.25 and 2.55 mm crown ferrules. Ferrule length was more important than post length in increasing a tooth’s resistance to fracture under cyclic loading. www.indiandentalacademy.com
  •  Libman & Nicholas- improved resistance to fatigue failure with crown ferrule extending 1.5mm apical to core margin Loney et al – higher mean stress in core ferrule than crown ferrule www.indiandentalacademy.com
  • Conclusions Crown ferrule > core ferrule Length of ferrule more important than length of post More effective when the crown encompasses relatively parallel prepared tooth structure than when it engages beveled/sloping tooth surfaces. www.indiandentalacademy.com
  • Principles of Tooth PreparationConservation of tooth structurePreparation of the canal Minimal preparation Teeth with posts thicker than 1.8mm fractured more easily than those with thinner posts(1.3mm) Strength of the root = R4 – r4 one or two additional files than the largest size www.indiandentalacademy.com
  • Principles of Tooth PreparationPreparation of coronal tissue Amount of remaining tooth structure is the most important predictor of clinical success Cast post-core will require reduction to accommodate a complete crown and to remove undercuts from the chamber and internal walls Extension of the axial wall of the crown apical to the missing tooth structure is known as the www.indiandentalacademy.com ferrule
  • Principles of Tooth Preparation ferrule may not be possible in short clinical crowns surgical crown lengthening procedure or orthodontic extrusion www.indiandentalacademy.com
  • Ferrulewww.indiandentalacademy.com
  • Principles of Tooth Preparation Retention FormAnterior TeethPreparation geometry Round canal configuration can be prepared with minimal taper to accommodate prefabricated post Elliptical canals – minimal taper(6-8 degrees) Threaded posts improve retention www.indiandentalacademy.com
  • Principles of Tooth PreparationPost length Longer the post better the retention & stress distribution minimum length of root filling -3 to 7mm Root morphology also influences the length Post length • In teeth with loss of periodontal support the post should extend apical to the alveolar bone. The required length of the post must be weighed against the occlusal loading. If loading is minimal; www.indiandentalacademy.com long posts will become unnecessary.
  • Principles of Tooth PreparationPost length In any case post length less than that of crown height is least retentive and also increases the chances of root fracture( Fuss et al). The latter occurs because stress is distributed over a small surface area. www.indiandentalacademy.com
  • Principles of Tooth PreparationSurface texture Dramatic effect on retention and stress distribution Retention decreases as one progresses from threaded to serrated to smooth surface configurations Radicular stress is greatest with threaded posts to smooth-tapered post followed by parallel-serrated posts Of the threaded designs, the tapered screw creates greatest wedging effect and highest stress concentration. www.indiandentalacademy.com
  • Principles of Tooth PreparationSurface texture Threaded posts with countersink also generate very high stresses when the countersink is fully engaged. These stresses can be reduced by counter-rotation of the post by half a turn. Placing a split in the shank of tapered threaded posts create stresses comparable to parallel-sided serrated posts www.indiandentalacademy.com
  • Principles of Tooth PreparationLuting agent Adhesive resin luting agents have improved the performance of post and core restorations Resin cements are affected by eugenol containing sealers. This should be removed by irrigation with ethanol or etching with 37% ortho phosphoric acid or alcohol Zinc phosphate and glass ionomer have similar retentive properties. Polycarboxylate and composite resins have slightly less. RMGIC – hydrophilic resins www.indiandentalacademy.com
  • Principles of Tooth PreparationPosterior teeth: Long posts are not indicated in posterior teeth which often have curved roots and elliptical or ribbon shaped root canals. For these teeth retention is better provided by two or more relatively short posts in divergent canals. If more than 3-4 mm of coronal tooth structure remains, use of post is unnecessary. Core build-ups in molars with one or more missing cusps will benefit from cemented posts and amalgam condensed around it. www.indiandentalacademy.com
  • Principles of Tooth PreparationResistance form: laterally directed forces The greatest stress concentrations are found at the shoulder, particularly at the inter-proximal region and the apex. Dentin should be conserved in these areas whenever possible. stresses are reduced as post length increases Parallel sided posts distribute stresses more evenly than tapered posts, which tend to have a wedging effect. However, parallel post concentrate stresses at the apex www.indiandentalacademy.com
  • Principles of Tooth PreparationResistance form: Sharp angles should be avoided Increased stress can be generated during post insertion, especially with smooth- parallel sided posts that have no vent. Threaded posts produce stresses during insertion and loading but distribute stresses evenly if backed off. The cement layer tends to distribute stresses more evenly. www.indiandentalacademy.com
  • Principles of Tooth PreparationRotational resistance circular cross-section In areas where coronal dentin has been completely lost, a small groove is placed in the canal can serve as an anti-rotational element. The groove is place in the bulkiest, usually on the lingual aspect. Alternatively, rotation can be prevented by placing a pin in the root surface. www.indiandentalacademy.com
  • Principles of Tooth PreparationHydrostatic Forces Post cementation – retention, stress distribution, sealing irregularities During cementation – development of hydrostatic pressure This pressure causes problems with seating & also causes root fracture Provision of cement vent Viscosity of cement – Zn PO4 cement Auto-polymerizing resin cement may polymerize prematurely – Dual cure cements www.indiandentalacademy.com
  • CORE It consists of the restorative material placed in the coronal area of the tooth that replaces carious, fractured or otherwise missing tooth structure. Retained by the post Desirable properties of a core include:  High compressive strength  Dimensional stability  Ease of manipulation  Short setting time  An ability to bond to both tooth and dowel www.indiandentalacademy.com
  • Cast core: integral part of the restoration and does not depend on mechanical means of retention. Noble metals are non-corrosive. Ceramic cores can also be fused to zirconia posts in the laboratory.Disadvantages: Cast dowels and cores have shown to have a higher incidence of root fracture. laboratory technique sensitive www.indiandentalacademy.com
  • Amalgam core: High compressive strength and modulus of elasticity. Stable to thermal and functional stress and therefore transmits minimal stress to the residual tooth and to the crown and cement margins. Amalgam cores are highly retentive when used as a corono-radicular core. It requires more force to dislodge than a cast-post metal core. The disadvantage is the potential for corrosion and subsequent discoloration of the gingival. www.indiandentalacademy.com
  • Composite resin core: Ease of manipulation, very rapid set and strong compressive strength Composite microleakage and retention to tooth structure are dependant on dentin bonding. Hence coronal build up with composite resins requires 2mm of sound tooth structure at the margins www.indiandentalacademy.com
  • Glass ionomer core:Glass ionomer and glass ionomer silver are adhesive materials for small build ups or to fill undercuts. The major benefit is its property of anticariogenecity. Adhesive failure can result from contamination of the tooth structure by saliva, blood, cutting debris or protein. It is not indicated as a core for an abutment tooth.It is indicated in posterior tooth when: a bulk of core material is possible significant crown dentin remains additional retention is available with pins and dentin preparations caries control is indicated www.indiandentalacademy.com
  • Resin-modified glass ionomer core: It exhibits moderate strength and water solubility between GIC and composite resins. Its bond is close to that of composite resins and significantly reduces microleakage. The property of fluoride release is equal to that of GIC. It is indicated in moderate core build ups. www.indiandentalacademy.com
  • Corono-radicular Restoration In this restoration, the core extends 2-4mm into the coronal portions of the canal. Retained by the divergence of the canal, the undercuts in the pulp chamber and adhesion with dentin- bonding agents This type of restoration is indicated for posterior teeth with large pulp chambers and multiple canals for retention It requires a minimum of 50% of tooth structure to be presentwww.indiandentalacademy.com
  • CORONAL COVERAGEIt serves the function of isolating the endodontic filling and dentin from microleakage. They also distribute the stresses and protect the tooth against fracture. This can be achieved with cast metal crowns and high strength ceramic onlays. The crown and crown preparation must achieve the following requirements: A minimum of 2mm dentin axial wall height Parallel axial walls The metal must encircle the tooth Finish line must be on solid tooth structure It must not invade the attachment apparatus www.indiandentalacademy.com
  • Canal Rehabilitation Done in immature and hollowed-out roots Makes use of dentin bonding composites to reinforce the canal Key for success is the remaining tooth structure and length of ferrule. Endodontic Obturator www.indiandentalacademy.com
  • Restoration of tooth with Resected Root Mandibular mesial root resection Mandibular distal root resection Maxillary distobuccal or mesiobuccal root resection Hemisection www.indiandentalacademy.com
  • Over Dentures As long as the root remains, the bone remains Support, stability and retention The abutment selected must have ↓ mobility, ↓ sulcus depth & band of attached gingiva Canines and premolars are ideal abutment candidates Diagonal cross-arch arrangement www.indiandentalacademy.com
  • Crown Cementation Functional forces cause strain against the crown margins, resulting in bond failure. This results in microleakage and secondary caries. RMGIC has shown to expand hygroscopically causing cracking or fracture of low strength all ceramic crowns. Crowns cemented with light cured resin cement are more resistant to fracture than when compared with RMGIC, GIC or zinc phosphate cement. However removal of excess resin cement after setting will be difficult. Dual cure cement can be used. This allows the removal of excess cement, while the internal cement sets chemically. www.indiandentalacademy.com
  • ….. Success can only be achieved when the techniquechoice best meets the needs of the individual clinicaldiagnosis – specifically, the needs of the individualdiseased tooth and the clinical use for which it isindicated. - Weine Now say Why! www.indiandentalacademy.com
  • References Endodontics – Ingle & Bakland; 5th edn Pathways of Pulp – Stephan Cohen; 8th edn Endodontic Therapy – Weine; 5th edn Contemporary Fixed Denture Prosthodontics – Rossensteil; 3rd edn Restoration of endodontically treated teeth – DCNA, 2004, 48; 397-416 Crowns & Extracoronal restoration: Endodontic considerations – BDJ, Mar 2002 192; 6, 315-327 www.indiandentalacademy.com
  • References Post placement & restoration of endodontically treated teeth – JOE, 2004; 30, 5: 289-301 Ferrule design & Fracture resistance of endodontically treated teeth – JDP 1990; 63, 529-36 Clinically significant factors in Dowel Design – JPD; 1984, 52(1), 28-34 JPD – 1990, 63(6), 1984 51(5), 1985 53(5) Color Atlas of endodontics – Christopher Stock www.indiandentalacademy.com