Post and core buildup

post and core buildup had been of utmost importance in maintaining a tooth that has lost a major portion of its coronal tooth structure in the dental arch and also ultimately helps preserve bone around it.

1. POST AND CORE BUILDUP Dr. Shannon Fernandes Dept. of P rosthodontics

2. INTRODUCTION Post and core buildup connects a tooth that has been root canal treated to a crown. Hence it is generally performed on a tooth after a root canal treatment and prior to placing a crown on the tooth . It is Performed on a tooth that has no crown structure left for support or with the most minimal tooth structure remaining. The quantity and quality of the bone, the soft tissue architecture in the area and the condition of the remaining dentition need to be addressed first. Pic . Courtesy google

3. Crown lengthening or orthodontic extrusion may create an esthetic problem, as the diameter of the exposed tooth is less and an unfavorable crown-to-root ratio might occur Few studied have shown the cast post and core to last as long as 10-14 years. Oral fluids and bacteria have to be prevented from gaining access to the periradicular areas by placement of adequate coronal restorations .

4. GUIDELINES The post should be more than the incisocervical or occlusocervical dimension of the crown. The post should be longer than the crown. The post should be 1 1/3 the length of the crown. The post should end halfway between the crestal bone and the root Pic . Courtesy google

5. The longer the post, the superior the retention. A guideline of one half to three quarters of the root length is often followed but may not necessarily be reasonable for extremely long, short, narrow, or curved roots Pic . Courtesy google

6. The diameter of the post is dictated by root canal anatomy. A minimal dentin thickness of 1 mm around the post should be provided Posts can be serrated, smooth, roughened or threaded. Parallel , serrated posts are cemented into the canal passively. They are very retentive and produce less stress in the root dentine than threaded systems

7. TYPES OF POSTS METALLIC NON-METALLIC Stainless Steel composite Titanium ceramic Titanium Alloy carbon fiber Gold-Plated brass glass fiber reinforced

8. Types Types of Posts Prefabricated posts Custom made posts made by: Direct technique Indirect technique

9. Prefabricated Parallel - Sided Smooth Post have number of advantages : Excellent clinical retention Minimal stress production within root Ease of placement Superior rating They also do have few Disadvantages : Precious material post expensive Corrosion of stainless-steel Less conservative of tooth Prefabricated Threaded Posts have advantages like: High retention Disadvantages seen are : Stresses generated in canal may lead to fracture. Does not conserve coronal and radicular tooth structure. Such posts are only recommended when: Only when maximum retention is essential

10. Carbon Fiber Post show Advantages like: Dentin bonding and Easy removal Disadvantages faced with such posts are: Its Low strength (compared to metal) Lack of radiopacity Carbon color presents an esthetic problem Hence the recommended use is in posteriors with moderate loss of coronal Fiber Reinforced Post has its own advantages: Esthetic being the primary . Disadvantages: Low strength High failure rate Recommended Use: Should not be used where remaining tooth structure is less than ideal or where high occlusal forces are present.

11. Zirconia Ceramic Post Advantages: Esthetics High stiffness High modulus of elasticity Disadvantages: Expensive Uncertain clinical performances Recommended Use: High esthetic demands

12. Among several techniques, cast post and core has been traditionally used due to its high mechanical strength and desirable fit in the root canal. However, teeth that have been restored by such systems may show more frequent oblique/horizontal fractures in the middle third of the root or vertical root fractures caused by both increased stress concentration in the apical region of the post and a difference in the Young's modulus between dentin and metal.

13. An ideal core and post improves the biomechanical stability of an abutment tooth preventing debonding and root fracture or fracture of the abutment. Therefore, over the last decades, prefabricated glass fiber posts have been used as an alternative for custom metallic posts. Ideally, the post diameter should be less than one third the diameter of the root at the cemento -enamel junction and 1 mm or more of dentin should remain around the post

14. Post removal, internal resorption , or current coronal flaring done to gain access to the apical portion may result in reduced dentin thickness at the coronal portion of tooth. R educed thickness of the coronal walls may diminish the effect of the ferrule. The restorative procedures essential for endodontically treated teeth are dependent upon the amount of coronal dentin remaining.

15. Fiber post Peroz et al described a classification of the amount of tooth structure remaining, that depends on the amount of axial walls .   This classification is useful in determining the need for a post Class I has all four axial walls remaining and only the access preparation involves removal of tooth structure. Class II has one cavity wall removed, which can consist of a mesio-occlusal or a disto-occlusal cavity. Class III, a MOD cavity and two remaining cavity walls are present. Class IV has only one cavity wall remaining (either the buccal or lingual wall). Class V, no cavity wall remains.

16. Pic . Courtesy google

17. Fiber posts results in decreased stress concentration under occlusal forces and prevents root fractures as compared to the prefabricated and cast posts. Moreover, the larger cement layer at the post/dentin adhesive interface can absorb the occlusal forces, which decreases the occurrence of root fracture.

18. Most failures related to the fiber posts approach are caused due to debonding between post-cement interfaces, rather than cement-dentin interface, or are associated with a cohesive failure of cement. Minimum ferrule of 2 mm height is needed for the retention of the core buildup n post, failing which can cause excess forces on the buildup when ferrule is minimal or absent.

19. To determine the ferrule height, the teeth should usually be prepared before post selection and cementation in order to facilitate the observation of sound tooth structure.   It is the height of the remaining dentin and not the buccal thickness that affects the failure load. It is also thought that the height and location of the remaining tooth structure will affect the mechanical properties of the restored teeth.

20. The majority of the FRC posts contain a resin matrix with embedded glass or quartz fibers. Quartz fibers possess a higher tensile strength than glass fibers . The pullout resistance of FRC posts decreases when the cement thickness is excessive.

21. If the composite is only cured by light , insufficient light intensity will affect the degree of conversion at the apex and middle third . This reduced degree of conversion will result in the composite being adversely affected by moisture. It is harder to control moisture and placement of adhesive in the apical portion .

22. The smear layer, sealer, and gutta-percha not cleaned off the walls can be found in the canal after acid-etching. They also concluded that the swelling of the composite from water sorption and resulting friction retain the post in the canal despite poor bond strengths. A variety of luting agents and the corresponding adhesives can be used to bond fiber posts into root canals. These adhesives can be of the self-etch or total-etch varieties.

23. PROCEDURE : FIBER POST Root canal dentin is etched with 36% phosphoric acid for 15 seconds. The acid is then removed with water sprayed for 20 seconds and the root walls carefully dried with absorbent paper points prior to bonding procedures. The BOND ( Xp bond) /Self Cure Activator self-cure bonding system is actively applied into the root canal walls for 20 seconds. The adhesive excesses is removed with absorbent paper points and the solvent evaporated by gentle air blowing for 5 seconds.

24. Fiber post cementation and core buildup The Flowable cement ( Core-X flow) is directly applied onto the treated fiber post surface and into the canal and pulp chamber A nd the fiber post is immediately placed into the final position and stabilized. It is light-cured for 40 seconds by a 1200 mW /cm2 curing light output (Radii, SDI, Victoria, Australia). The material excess is removed with diamond bur and a periapical radiograph is taken to confirm the fiber post adaptation and root sealing.

25. PeerlessPost ™ (Sybron Endo, Orange, CA ) features coronal and apical 1-mm adjustable sections and comes in .04 and .06 tapered varieties. Composed of continuous, pre-stressed, high-quality fibers, they are customizable for every canal shape and length. With a low elastic modulus and high tensile and flexural strength, PeerlessPost absorbs and dissipates stress to prevent root fracture. They are bonded, not cemented; their retentive surface prevents rotation and dislodgement. Tooth-colored, radiopaque , and with three sections per post, they are easy to adapt, with minimal dentin removal.

26. REFERENCES Reis, J. M. dos S. N., Oliveira, C. R. de M., Reis, E. G. J., Mascaro , B. A., & Abi‐Rached , F. de O. (2019).  One‐step fiber post cementation and core build‐up in endodontically treated tooth: A clinical case report. Journal of Esthetic and Restorative Dentistry.   doi:10.1111/jerd.12551 Trushkowsky R. Fiber post selection and placement criteria: a review. Inside dentistry. 2008 Apr;4(4):86-94 . Factors affecting retention of post systems: A literature review. J Prosthet Dent 1999;81:380–385. Lloyd PM, Palik JF. The philosophies of dowel diameter preparation: A literature review. J Prosthet Dent 1993;69:32–36. Post Placement and Restoration of Endodontically Treated Teeth: A Literature Review. Richard S. Schwartz, et al. Journal of Endodontics:VOL . 30, NO. 5, MAY 2004 Fundamental of fixed prosthodontics 3 editions Herbert T. shillingburg Page no 345