Restoration of Endodontically Treated Teeth PDF

Restoration of Endodontically Treated Teeth By Assoc. Prof. Marwa Beleidy Assessment of endodontically treated teeth Quality of The Endodontic Treatment Amount of Remaining Tooth Struct...

Restoration of Endodontically Treated Teeth By Assoc. Prof. Marwa Beleidy Assessment of endodontically treated teeth Quality of The Endodontic Treatment Amount of Remaining Tooth Structure Periodontal Health Occlusal Forces Esthetic Requirements  Quality of the endodontic treatment ❖ Good Apical seal ❖ No coronal leakage ❖ No pain with percussion or biting ❖ No missed canal ❖ No periapical pathosis or widening of PMS ❖ No exudate, sinus tract or perforation ❖ No over or under filling  Amount of remaining tooth structure The strength of ETT is directly proportional to the amount of remaining tooth structure. The remaining coronal tooth structure should be properly evaluated after caries and old defective restoration removal. To consider a wall in the tooth should be 3 mm length and 1.5 thickness minimum. A tooth to be restorable should have at least ferrule effect.  Periodontal Health Crown/Root ratio: Optimum ratio 1:2, normal 2:3 and minimum 1:1. It is affected by horizontal & vertical bone resorption.  Biological width: It starts from base of the sulcus to the crest of the alveolar bone. Epithelial attachment + Connective tissue attachment Mobility: Grade 2 mobility affect the longevity of the restoration.  Occlusal and parafunctional stresses Type of occlusion Parafunctional habits If the tooth will serve as abutment Position of tooth in the arch  Esthetic requirements Discoloration of endodontically treated tooth may be caused by: Remnants of degenerated pulp Or endodontic fillings. Treatment Planning  The line of treatment starts from core only, endocrown, extra-coronal restoration (with or without post) Depending on: 1- Remaining amount of tooth structure 2- Amount of stresses received  Anterior + Premolar teeth 1- If there is favorable loading, no parafunctional habits & not acting as bridge retainer. Access Access cavity Access + only + Two axial One axial walls wall Bonded Bonded Core (Composite) (Composite) + restoration restoration Crown  2- If it’s subjected to high stresses, para-functional habits or act as a bridge retainer. Access Access + + three axial Four axial walls walls post Post + + core core + + crown crown  Molar Teeth Access Access Access Access + Access + cavity + one axial + Four axial only Three axial wall Two axial walls walls walls Bonded Core Post (Composite) Core Post + + + restoration crown + core crown core + + crown crown Post crown system  Post crown system It is a full coverage restoration gaining it’s retention by a post that accurately fitted inside the prepared root canal. Components 1 Post (Dowel) A rigid part that provide retention for core material. 2 Core The part that fits inside the prepared pulp chamber to rebuild the lost coronal portion in the form of prepared tooth. 3 Extra coronal part The artificial restoration that restore function & esthetic.  Requirement of ideal post 1 Provide good retention to the core 2 Transfer minimal stress to the tooth/root 3Accept bonding to dentin & have physical properties similar to dentin 4- High Strength 5 Accurate passive fit inside root 6Allow conservation of tooth structure 7- Easily removed to allow retreatment 8- High esthetic properties & be biologically compatible 9- Less time consuming & simple procedures Indications 1 As individual restoration for badly mutilated endodontically treated tooth 2 Retainer for short span bridge 3 When the tooth can not be restored by any other type of restoration 4 When having GOOD root (s) of endo. treated tooth Contra-indications: 1 Improper root canal filling 2 Presence of any periapical pathosis 3Tooth with short, thin, curved or weak roots 4- Inadequate bone or periodontal support 5- Abnormal occlusion & bad habits Advantages 1 Excellent retention 2 Excellent aesthetics 3Restoring any tooth even with complete loss of the coronal portion 4- Easily correction of mal-aligned tooth 5- Provides strengthening of badly mutilated ETT Disadvantages 1 Limited to the non-vital teeth 2 Weakening of the root due to improper widening of the root canal 3 Root fracture due to improper canal preparation or improper post selection  Classification of post crown system I -According to the II- According to the material retention 1 All metallic 1 By post only 2All non metallic 2By post & pin (s) 3- Combination 3- By post and collar  III-According to attachment IV- According to method of construction 1-Attached post crown 1- Ready made 2-Detached post crown 2- Custom made a) Two pieces b) Three pieces  Attached post crown (one piece post crown) is NOT used now 1Extra-coronal restoration can be replaced without disturbing the post core system. 2Superior marginal adaptation & fit because the crown is constructed separately. 3 Dowel choice is not restricted to cast posts only. 4In case of FPD, it is necessary to prepare root canal parallel to the CPI in case of one piece post crown system, which is difficult. Principles of post preparation Preparation of Endodontically Treated Tooth to Receive A Post Crown System Principles of tooth preparation: A- Conservation of tooth structure 1 Root canal preparation 2 Coronal portion preparation B- Retention form 1- Root canal geometry 2- Post design 3 Post length 4 Post diameter C- Resistance form 1 Stress distribution 2 Rotation resistance  Preservation of tooth structure Preparation of post space Only minimal tooth structure should be removed from the canal as remaining dentin thickness is the prime variable in fracture resistance of the root. Excessive enlargement can perforate or weaken the root. Preparation of Coronal Tissue Reduction is needed internally to remove undercuts from the chamber and internal walls to accommodate the post and core restoration and externally to accommodate a complete crown.  The ferrule effect Functions of a ferrule: 1- Binds tooth structure together → ↑ resistance to lateral & occlusal forces. 2- ↓ stress concentration at the post/core junction. 3- Maintains integrity of the cement seal & enhances resistance to dislodgement. Factores Affecting on Ferrule Functionality a) Ferrule height Achieved by having 1.5-2 mm vertical tooth structure. b) Ferrule width A thickness of at least 1 mm should remain c) Number of walls Various studies have demonstrated the superiority of a uniform all around ferrule over a ferrule. The literature suggests that a non-uniform ferrule is still superior to no ferrule at all. d) Type of tooth, the extent of lateral load and ferrule location Most of the forces in the posterior segment of the mouth are OG and BL in nature. Thus adequate ferrule should be present on the functional cusp. In anterior teeth, where the load is generally BL. Palatal ferrule on maxillary teeth and labial ferrule on mandibular teeth should be present. e) Type of post & f) Core materials  How to gain ferrule? If not present, we do one of the following: 1. Surgical crown lengthening 2. Orthodontic extrusion  Retention Form Resistance of restoration to displacement along the path of insertion. Factors affecting retention form: 1. Post Length 2. Post Surface Texture 2. Post diameter 4. Luting Agent 5. Preparation Geometry  1) Post Length As post length increases, retention increases.  Guidelines for post length: 1. The post should equal the OG dimension of the crown. 2. The post should be longer than the crown. 3. The post should be one and one third of the crown length. 4. The post should be a certain fraction of the length of the root such as one half, two thirds, or four fifths. 5. The post should end halfway between the crestal bone and the root apex. 6. The post should be as long as possible without disturbing the apical seal. Other important factors to be considered in the selection of the post length include: At least 3-5 mm of the apical gutta-percha should be retained. To decrease the dentinal stress, post should extend at least 4 mm apical to the the bone crest. Molar posts should not extend more than 7 mm apical to the canal orifice so as to avoid the risk of perforation of the root canal. 2) Post Surface Texture Threaded or serrated post is more retentive than a smooth one, and controlled grooving or roughening of the post and root canal also increase the retention. 3) Post diameter Different theories/philosophies regarding the post diameter in literature. I. Minimal canal preparation II. Post should be surrounded by a minimum of 1mm of sound dentin III. Post width should not be greater than one third of the root width at its narrowest dimension. 4) Luting agent Has little effect on the post retentions. Proper cement choice is only important if the post fits poorly. Adhesive resins ???? may be indicated post is dislodged. 5) Preparation Geometry Some canals have a nearly circular cross section. These can be prepared with a twist drill or reamer to provide a cavity with parallel walls or minimal taper. Canals with elliptical cross sections must be prepared with a restricted amount of taper (usually 6 to 8 degrees) to ensure adequate retention while undesired undercuts are eliminated. Parallel-sided root canal → More retentive than tapered canal Parallel posts → More retentive than tapered posts 6) Post design: Threaded posts → Serrated posts → Smooth posts  Resistance form Resistance to displacement during function 1) Stress Distribution 2) Rotational Resistance Stress distribution: ❑Stresses are concentrated at the cervical part of the root & the apex of the post. ❑Post & core → Improves resistance to laterally directed forces by distributing them over a large area of the root ❑If stress conc.→ Root fracture ❑ This is fulfilled by: I- Conservative cervical preparation: ❑Greatest stress conc. → at the shoulder (particularly inter- proximally) & at the apex. So Dentine should be preserved at these areas. II- Use longer post: ❑ Long post ↑ resistance arm in relation to the force arm. III- Parallel-sided post ❑Parallel-sided posts → Distribute stresses better than tapered posts. ❑Parallel-sided posts → Produce high stresses at the apex, so a new parallel post with pointed end is used. IV. Avoid sharp angles V. Avoid pressure during cementation ❑Over pressure during cementation of the post should be reduced to avoid excess cement to escape apically. VI- No threaded post : ❑Threaded posts induce ↑ stresses during insertion and loading that may cause minute cracks leading to root fracture later on. ❑ During insertion of threaded posts, use the quarter turn motion to minimize stresses. ❑ Flexi-post can be used. VII- Ferrule design: ❑Cervical finishing line should be prepared on sound tooth structure 2 mm apical to the junction between the core & the remaining part of the tooth. Rotational Resistance It is to prevent a post with a circular cross section from rotating during function. ❖ When there is sufficient coronal portion, a vertical coronal wall prevent fracture. ❖When coronal dentin has been completely lost, a small groove placed in the canal wall located lingually. Or An auxiliary pin or pins are added beside the post. ❖ Short straight post in multi-rooted canal. Procedures of tooth preparation 1. Designing the post parameter The post length and diameter is determined by using a radiograph (parallel technique). The root length is measured from the radiograph then the post length and diameter are calculated. 2. Removal of the root canal filling Heat an endodontic plugger according to the calculated length. This contraindicated for OLD gutta percha, because it lost its thermo-plasticity. Rotary instrument having a suitable size depending on the size of the tooth (gates and peso reamer in low speed). The more resistant gutta percha an be removed using rotary instrument with chemicals (Chloroform). 3. Preparation of the canal wall Enlarge the canal until the desired size: no more than 1/3 of the diameter of the root and surrounded by a minimum of 1 mm of tooth structure Anti-rotational feature If there is supra-gingival tooth structure, make a counter-bevel around the external peripheral of the preparation 4- Preparation of coronal portion ❖Preservation of sound tooth structure ❖Core construction  Cementation of different types of posts Ideal properties of post cementation: 1 Strong adhesive bond to dentin walls and the metallic post to give retention and minimal microleakage 2High fracture toughness to resist force 3- Removed easily by dentist if required 4- Release fluoride 5 Low film thickness and viscosity 6Adequate working and setting time 7- Biocompatible 8 Resist intra-oral dissolution 9Easy clean excess cement 10- Low cost  The cement is mixed and then smeared onto all sides of the post. The dentist may coat the walls of the post space inside the tooth with cement too. The coated post Is then gently slipped into the tooth to the point where it’s fully seated in the space that’s been created for it. Any excess cement that extrudes out is removed. Post Crown for multi-rooted teeth: One post (casted or ready made) using the full length of the thickest root canal. Parallelism between the prepared canals to have a common pathway of insertion. Interlocking core technique, preparation of each canal without any intention for parallelism, otherwise perforation occurs. The first post and core in one canal “the cast has a dovetail” while the other canal will receive another cast post and core which will interlock with the first canal.