Current trend of restoration of endodontically treated teeth with extensive subgingival caries: A case series.

Endodontically treated teeth (ETT) are structurally and esthetically compromised. Conventionally, after endodontic therapy, the tooth is restored with full-coverage crowns to improve their fracture resistance and ensure their long-term success rate. However, the tooth preparation required for these restorations can result in the significant loss of enamel and dentin. The periodontal health will be affected if the margin of prosthesis is extended subgingival. Restoring ETT using minimally invasive methods is an effective way to preserve the remaining tooth structure. This case series show cases restoration of four endodontically treated mandibular first molars with extensive subgingival caries restored with short fiber-reinforced composite resin (everX Posterior, GC Europe N.V. Interleuvenlaan, Leuven), with 2-year follow-up. Copyright:

INTRODUCTION

Successful outcome of endodontically treated teeth (ETT) depends on fluid-tight seal of the root canal system followed by appropriate postendodontic restoration. There is a variety of treatment options for restoring an endodontically treated tooth which presents a challenging task for clinicians. ETT is structurally and esthetically compromised due to the loss of tooth structure, cusps, ridges, and the roof of the pulp chamber.[1] As there is an extensive loss of tissue at root and crown levels, there will be significant biomechanical changes accounting to high incidence of fractures.[23]

Conventionally, after endodontic therapy, the coronal aspect of the teeth is restored with full-coverage crowns to improve their fracture resistance and ensure their long-term success rate.[4] However, the tooth preparation required for these restorations can result in significant loss of enamel and dentin.[24] The restoration margin directly influences the periodontal health. Despite the fact that the supragingival is the optimal restorative margin, many restorations do have margins that are within the gingival crevice, which can result in irreversible tissue damage.[56] This may result in increased gingival inflammation and probing depth.

Restoring ETT using minimally invasive methods is an effective way to preserve the remaining tooth structure. This is made possible by advancements in adhesive systems and composite resin material. Composite resins were reinforced with nanofillers, bioactive glass, prepolymerized resin, ceramic whiskers, and fibers such as polyethylene, glass fibers, carbon fibers, Kevlar fibers, and Vectran fibers to improve the marginal integrity and fracture strength of composite resins.[78] Fiber-reinforced composites have been used clinically for various applications in dentistry such as interim and permanent fixed partial denture, post and core, onlay, and crown. Eapen et al. stated that short fiber-reinforced composite (SFC) can effectively resist high occlusal forces.[2] The same authors reported that the fractures occurring in ETT restored with SFC were mostly in enamel and hence were repairable.[2]

Tanner clinically evaluated composite restorations modified with SFC using modified USPHS criteria. The study results showed good clinical performance of such restorations. SFC bio mimics dentin by architecturally replicating its behavior under strain.[9] Since the ETT have less proprioception, the long-term survival depends upon the dentin thickness and the postendodontic restoration. This case series showcases restoration of endodontically treated mandibular first molars with extensive subgingival caries restored with minimally invasive SFC resin (everX Posterior, GC Europe N.V. Interleuvenlaan, Leuven), with 2-year follow-up.

CASE SERIES

From our clinical records, we present postendodontic management of four mandibular molars with more than half of tooth structure loss and proximal caries lesions extending subgingivally that were restored effectively and their follow-up up to 2 years [Figure 1]. Informed consent was obtained from the patients whose records were analyzed. All the cases were treated in a similar manner as follows. The occlusion and the integrity of remaining tooth structure were assessed. Under rubber dam isolation, the temporary restoration and the remaining subgingival caries were removed, sectional matrix (Palodent V3, Dentsply Caulk, Milford, USA) was placed on the proximal surface, and proper contouring of the inner surface of the matrix was done with a burnisher.

Figure 1

Subgingival cavity in – 1A: 46 (MO), 2A: 46 (DO), 3A: 46 (DO), 4A: 46 (MO), 1B to 4B: The access cavity after removal of the temporary restoration, 1C to 4C: Radiographic images post endodontic restoration done using short fiber-reinforced composite, 1D to 4D: Clinical photographs of post endodontic restoration done using short fiber-reinforced composite, 1E to 4E: 2-year follow-up radiographic images, F to 4F: 2-year follow-up clinical photographs

The enamel along the access cavity margins was etched using 37% phosphoric acid (N-Etch, Ivoclar Vivadent AG, Liechtenstein) for 15s, rinsed, and dried. Dentin bonding agent (Solare Universal Bond, GC, Japan) was then applied using a micro applicator tip and cured for 10s. The cavity floor was lined with flowable nanohybrid composite resin (Tetric N-Flow, Ivoclar Vivadent AG, Liechtenstein) and cured. The proximal cavity wall was built with nanohybrid composite resin (Tetric N-Ceram, Ivoclar Vivadent AG, Liechtenstein).

SFC (everX Posterior, GC Europe N.V. Interleuvenlaan 33B-3001 Leuven) was used to build up the core of the restoration up to 2 mm below the occlusal level, the rest of which was then restored with nanohybrid composite (Tetric N-Ceram, Ivoclar Vivadent AG, Liechtenstein). The rubber dam was removed, and the occlusal surface was finished and polished using diamond polishing burs (Mani Dia burs, Mani Inc, Tochigi, Japan). The postendodontic restoration was clinically evaluated periodically (1 m, 3 m, 6 m, 9 m, 1 year, and 2 years) for marginal adaptation, marginal discoloration, secondary caries, restoration, and tooth fracture using the modified US Public Health Service (USPHS) criteria. The status of all the restorations was found to be clinically and radiologically satisfactory after 2 years of follow-up.

DISCUSSION

The prime objective of a postendodontic restoration is to resist fracture to make the teeth function as an integral part of the masticatory apparatus. Other functions include restoration of the tooth form, function, and esthetics, preserving periodontal tissues as well as preventing coronal microleakage. Conventionally, ETT were reinforced with pins, posts to complete coverage restorations.[2] The preparation done for the majority of these procedures weakens the remaining tooth structure, resulting in crown and/or root fracture.[2]

The remaining coronal tooth structure before the final restoration is directly proportional to its ability to resist occlusal forces.[10] According to Shillingburg, tooth preparation for a metal-ceramic crown requires an occlusal reduction of 1.5 to 2 mm for functional cusp and 1 to 1.5 mm for nonfunctional cusp.[11] Hence, there is a major structural loss during crown preparation of an ETT.

Bader et al. stated that cast restorations do have an influence on local periodontal conditions.[5] Subgingival margins are given in cases of subgingival caries, to increase the retention, for placement of margin in sound tooth structure and for esthetics. Unlike subgingival margin, the supragingival and equigingival margins does not cause adverse tissue reactions to the periodontium. The effects could range from marginal gingivitis to severe periodontitis when there is a violation of the gingival attachment apparatus.[56] A discrepancy in the crown margin tends to be plaque retentive, with open marginal configurations harboring periodontal pathogens.[6] The exposed margin prepared with diamonds is rough.[6] These subgingival rough surfaces are difficult to clean leading to chronic inflammation of the periodontium. Hence, it is important to formulate an appropriate restoration plan, which must aim not only to provide reinforcement of the remaining tooth structure but also prevent microleakage along the subgingival margins. Hence, cases with subgingival margins were included in this case series. The marginal adaptation, marginal discoloration, secondary caries, restoration, and tooth fracture were evaluated for 2 years using the modified USPHS criteria.

Root canal-treated teeth restored with polyethylene and glass fiber-reinforced composite resin showed superior fracture resistance.[12] Composite restorations are not only conservative but also maintains the periodontal health and are economical compared to crowns.[13] In all the cases, the post endorestorations were done using SFRC. It is composed of semi-interpenetrating polymer network, Bis-GMA, TEGDMA, PMMA resin matrix, and fillers such as E-glass fiber and barium borosilicate.[29] These composites have the ability to withstand high stress.

Fibers transfer the stresses from the resin matrix to the fibers under an applied load.[8] The short fiber composite resin controls the polymerization shrinkage stress owing to its fiber orientation.[8] However, the presence of these short fibers results in a rough surface of the SFC resin; hence, it cannot be left exposed to the oral environment.[7] To prevent plaque retention on its rough surface, the SFC layer has to be covered with a 2-mm layer of nanohybrid composite resin. Nanohybrid composite resins are considered to be ideal as a posterior restorative material due to their dense filler loading, excellent optical properties, and improved mechanical properties.[14] The status of the restoration was clinically and radiographically satisfactory after 2 years of follow-up.

CONCLUSION

Based on the outcome of the present case series, it could be concluded that the SFCs along with nanohybrid composite resins can be used effectively as post endodontic restorations in ETT with < 2 wall defects.

Financials support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.