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Endodontics

Authors: Dr. Kajal Agarwal, Dr. Shashit B. Shetty, Dr. Rohit Paul


INTRODUCTION

Dental practitioners are often faced with the task of restoring endodontically treated teeth. Root canal treatment is usually the consequence of caries followed by pulpal infection or traumatic damage to a tooth. Trauma and caries are mostly associated with an extensive loss of tooth structure.Fracture of the anterior teeth by trauma ,is the most frequent type of injury in permanent dentition, especially among children and adolescents, affecting up to 25% of this patient population.

It may be a result of sports injuries, automobile accidents, and the like, although falls are the most frequent cause. The most commonly involved teeth are the maxillary central incisors, because of their exposed position in the dental arch.1 The injury is defined as a complicated crown fracture or Class III fracture (Ellis and Davey classification), if the fracture also exposes the dental pulp. Anterior crown fractures lead to discomfort and serious psychological, aesthetic, functional, and phonetic problems that can affect social relationships and it poses a challenge for the child, the parents, and the dentist to save these teeth.2

Several factors influence the management of coronal tooth fractures, including, extent of the fracture, pattern of the fracture, and the restorability of the tooth, as also the presence or absence of the fractured tooth fragment, occlusion, and aesthetics. In cases where the teeth are severely fractured, endodontic treatment and placement of intracanal posts or retainers become necessary, before crown restoration. The pulpless tooth has already lost substantial coronal tooth structure from the access preparation for the endodontic treatment which necessitates restoration of the tooth with a complete crown for esthetic and functional rehabilitation. When a large portion of the clinical crown has been lost to damage, it is often impossible to achieve optimum retention of a restoration in the remaining dentin. Therefore the type of restoration of endodontically treated teeth is closely related to the amount of the tooth structure that remains after endodontic therapy. 3

The factors to be considered when restoring endodontically treated teeth are the role of moisture loss, the nature of dentin, alteration in strength caused by architectural changes in morphology of teeth, concepts of biomechanical behavior of tooth structure under stress, and changes in the collagen alignment. 4,5,6,7,8 Traditionally complicated crown fractures have been restored with conventional post-core and crown techniques after endodontic treatment. If the remaining tooth structure is inadequate for permanent retention of a direct core build-up material, a root post must be used for retaining the core. For this purpose, a prefabricated root post or an indirect, custom-fabricated post and core can be used.

BRIEF HISTORICAL BACKGROUND

For more than 250 years, clinicians have written about the placement of posts in the roots of teeth to retain restorations.9 As early as 1728, Pierre Fauchard described the use of “tenons,” which were metal posts screwed into the roots of teeth to retain bridges. In the mid-1800s, wood replaced metal as the post material, and the “pivot crown,” a wooden post fitted to an artificial crown and to the canal of the root, was popular among dentists.9 Often, these wooden posts would absorb fluids and expand, frequently causing root fractures.10 In the late 19th century, the “Richmond crown,” a single-piece post-retained crown with a porcelain facing, was engineered to function as a bridge retainer. During the 1930s, the custom cast post-and-core was developed to replace the one-piece post crowns. This procedure required casting a post-and-core as a separate component from the crown.10 This 2-step technique improved marginal adaptation and allowed for a variation in the path of insertion of the crown.9

Custom-fabricated, cast post and cores are still regarded as the established technique or gold standard for restoring extensively damaged teeth. In the basic evaluation of the therapeutic value of post and core treatment, survival time is an important parameter. For many years, custom cast metal posts were considered the standard. There are several long-term clinical studies that report high success rates with cast gold posts. From the endodontist’s perspective, they are easily removed for retreatment. Many investigators have reported that the design and the material of the post and core affect the resistance to fracture of endodontically treated teeth restored with post and core systems. The cast gold alloy dowel and core has been regarded as the gold standard for foundation restorations. Because of its very good properties such as high biocompatibility, high corrosion resistance, and high rigidity, it has been used extensively in the past, but currently its use has diminished due to the high cost of gold.12,13 Cast post and core, when compared with prefabricated post and core, are suggested to be used in non-radicular root canals because of their accurate adaptation to the remainder tooth structure. Cast post is capable of resisting rotational forces, has superior success rate, and can be easily removed to permit endodontic retreatment.

Currently, the material of choice for custom-made cast-metal dowel-core system is Ni-Cr alloy. Due to high rigidity of Ni-Cr posts, less reduction of tooth structure is needed so that the maximum retention and fracture resistance of the post will be provided. In the study conducted by Hayashi et al.11the teeth restored with Ni-Cr cast posts had significantly higher fracture resistance than other groups and had the lowest risk of vertical root fracture. Also, Ni-Cr alloys create a layer of chromium oxide that resists tarnish. These alloys have also some disadvantages, for example, most of them have a breaking point over half of the root length due to the high post stiffness. If these teeth become fractured, they are repairable. The other disadvantages are difficulty in finishing and polishing processes, doubt in biocompatibility due to presence of nickel and subsequent allergic reactions, and absence of physical characteristics similar to dentin. However, in spite of these disadvantages, it still has the highest usage in fabricating post-cores.12

This Case Report Presents The Use Of Cast Metal Post And Core For The Restoration Of Traumatically Fractured Left Permanent Maxillary Central Incisor In A 22-year-old Male Patient. CASE REPORT

A 22-year-old male patient , Pramod reported to the department of conservative dentistry and endodontics at K.D.Dental college, mathura , with a chief complaint of pain and broken upper left front teeth. The trauma, which was caused by falling from the roof, had occurred one day back. The patient gave a history of sensitivity to hot and cold and pain , which was subsided after taking medication and aggravates on touching. His medical history was irrelevant.

On intra oral examination there was an exposure of pulp irt 21 and fracture involving enamel and dentin irt 22 . Percussion test showed tenderness irt 21. Vitality test was not performed on the affected teeth as patient reported 1 day following trauma. No mobility and swelling was seen.

On radiographic examination fracture involving enamel , dentin and pulp irt 21 with widening of lamina dura and fracture involving enamel , dentin irt 22.

Diagnosis: Elli’s clas III fracture in relation to 21
Elli’s class II fracture irt 22.
Treatment Plan: Root canal therapy with cast metal post followed with all
ceramic crown irt 21 and composite build up irt 22.
PROCEDURE

Initially, local anesthesia was administered.

After rubber dam application, Access cavity was performed with endo acess bur and the working length was established radiographically with #20 k-file. Pulp extirpation was done and the canal was gently instrumented till 80 k-file and irrigated with 3% sodium hypochlorite solution and saline. Composite build up was done irt 22. Patient was recalled after three days. After 3 days, Patient had pain irt 21 on percussion so calcium hydroxide dressing was given for 2 weeks. After 2 weeks patient was asymptomatic, the canal was irrigated with sodium hypochlorite, saline and 2 % chlorhexidine and then dried with paper points and were obturated with lateral condensation of gutta percha and AH plus sealer. Cavity was sealed with temporary restoration and patient was recalled after 3 days for post space preparation. The length of the post was determined from the X-ray taken and a 5 mm portion of the gutta percha was left to maintain the apical seal and rest was removed with peeso reamers to prepare the post pace till peeso size no 3. The remaining tooth structure was prepared with chamfer finish line on labial side and the palatal side and core ferrule was given. Canal impression was obtained and Once post pattern was made, the core was fabricated with same material. Casting was performed and patient was recalled after a day.The fit of the cast post and core was first assessed and then it was luted with glass ionomer cement. After the application of gingival retraction cord , impression was taken with putty material and then poured with die stone.

DISCUSSION

Practitioners performing endodontic treatment should follow these principles when planning and performing the restoration of endodontically treated teeth:

  • Preserve coronal and radicular dentin.
  • Avoid contamination of the root canal system.
  • Restore the tooth immediately after root canal treatment, if possible.
  • Use posts only when necessary to retain a core buildup.
  • Restore teeth in a way that allows for future retreatment of the root canal system.
  • In most cases, the particular post system used is not as important as following the principles of adequate length, adequate resistance form, adequate strength to allow preservation of dentin, and an adequate ferrule. If these principles are followed, most post systems will perform well. The custom–cast post has a long history of clinical success. They provide excellent service for endodontically treated teeth with moderate to severe damage. A 6-year retrospective study of 96 endodontically treated teeth with extensive loss of tooth structure and restored with cast post and cores indicated a 90.6% success rate (Bergman B et al; 1989), and are best applied to single rooted teeth, especially incisors and canines. Custom cast post and core is usually preferred for the change in mesiodistal and labiopalatal angulation of the proclined or rotated teeth as compared with the prefabricated post. It is a single assembly in which core can be shaped until satisfactory aesthetic is achieved although the core might not be in the same axis as the post or the root. But in prefabricated post–core system, the core is build around the post after post cementation in the prepared canal. According to Massoud YA et al,14 an opaque layer is necessary over a metal structure, such as a cast core, to reduce light absorption and increase the reflectance of the metal. The desired effect is to raise the value of the core in order to approach the optic qualities of dentin.However, the problem of reflectance is fully eliminated by the use of an opaque layer of ceramic.The translucence of a ceramic crown may not be limited by the use of opaque material under the crown. This procedure requires the placement of an opaque layer of ceramic on the core, thereby moving such a layer 0.3 to 0.5 mm more deeply from the surface of the restoration.This allows more depth and translucence to the crown, as light penetrates further into the crown.
POST AND CORES --- PAST TO PRESENT
  • Currently, an increased demand for clinically convenient post-andcore systems to replace lost tooth structure has provided the clinician with a plethora of simplified “one-visit” post-and-core restorative options.However, in view of the previous considerations, it is understandable that clinicians have uncertainties about selection of restorative materials and techniques to achieve optimal results for post-and-core build-up procedures.9
  • According to studies by the CR Foundation (formerly known as Clinical Research Associates), the fiber-reinforced systems are superior to metal prefabricated posts. In the last few years, there has been a major shift away from metal custom cast post-and-cores toward resin-based composite cores. Prefabricated composite post systems are replacing metal post systems because an adhesive procedure with the fiber reinforced composite post system adds strength to the tooth restorative interface after bonding. Therefore, the fiber-reinforced post has an advantage after assembly. The fiber-reinforced composite post system has a similar modulus of elasticity to the dentin after bonding, whereas the metal post assembly has an appreciably higher modulus of elasticity.10
  • CONCLUSION

    Although the quest for the ideal material to restore lost tooth structure continues to be a focus of modern dental research, there are many post-and-core materials and techniques that are available to the clinician for a variety of clinical procedures and thus each clinical situation should be evaluated on an individual basis.

    References:
    1. Cortes MI, Marcenes W, Sheiham A. Prevalence and correlates, of traumatic injuries to the permanent teeth of school-children aged 9–14 years in Belo Horizonte, Brazil. Dent Traumatol. 2001;17:22–6.
    2. Gutmann JL, Gutmann MS. Cause, incidence and prevention of trauma to teeth. Dent Clin North Am.1995;39:1–13
    3. Sirimai S, Riis DN, Morgano SM. An in vitro study of the fracture resistance and the incidence ofvertical root fracture of pulpless teeth restored with six post-and-coresystems. J Prosthet Dent. 1999; 81: 262–269.
    4. Bolhuis P, de Gee A, Feilzer A. Influence of fatigue loading on four post-and-core systems in maxillary premolars. Quintessence Int. 2004; 35: 657–667.
    5. Huang TJ, Schilder H, Nathanson D. Effects of moisture content and endodontic treatment on some mechanical properties of human dentin. J Endod. 1992; 18: 209–215.
    6. Schwartz RS, Robbins JW. Post placement and restoration of endodontically treated teeth: a literature review. J Endod. 2004; 30: 289–301.
    7. Trope M, Ray HL Jr. Resistance to fracture of endodontically treated roots. Oral Surg Oral Med Oral Pathol. 1992; 73: 99–102.
    8. Heydecke G, Butz F, Hussein A, Strub JR. Fracture strength after dynamic loading of endodontically treated teeth restored with different post-and-core systems. J Prosthet Dent. 2002; 87: 438–445.
    9. Smith CT, Schuman NJ, Wasson W. Biomechanical criteria for evaluating prefabricated post-and-core systems: a guide for the restorative dentist. Quintessence Int. 1998;29:305-312.
    10. Smith CT, Schuman N. Prefabricated post-and-core systems: an overview. Compend Contin Educ Dent. 1998;19:1013-1020.