Restoring an Endodontically Treated Tooth with Limited Interocclusal Space

Restoring endodontically treated teeth with extensive coronal destruction and limited interocclusal space presents a significant clinical challenge, as conventional approaches such as crown lengthening and post-retained full-coverage restorations may compromise remaining tooth structure and periodontal support. This article describes the management of a 52-year-old female with a structurally compromised mandibular right second molar following root canal therapy, for which an adhesive partial-coverage endocrown (endocrown-onlay or “endo-crownlay”) was selected to avoid surgical intervention and preserve tooth structure. The tooth was conservatively prepared and restored with a chairside CAD/CAM-fabricated monolithic lithium disilicate endocrown using meticulous adhesive protocols, resulting in excellent fit, esthetics, and occlusal integration. This case highlights endocrowns as a conservative, predictable, and efficient alternative for restoring endodontically treated molars with anatomic limitations, supported by literature demonstrating favorable survival rates and reduced catastrophic failures when proper case selection and bonding principles are applied.

Introduction

This case report addresses a common issue: How do you restore an endodontically treated tooth with limited interocclusal space and a large amount of missing tooth structure? The conventional treatment approach would normally involve a crown lengthening procedure to expose more tooth structure to obtain adequate ferrule. An intracoronal post and core followed by a full coverage restoration can then be placed. However, because this scenario often leads to removal of more tooth structure and therefore decreased fracture resistance, the prognosis of these endodontically treated teeth may become severely compromised.^1,2 Studies have shown that posts used to retain a core can weaken the tooth, creating a scenario where it is more susceptible to fracture.² In addition, post placement can lead to complications like perforations and can make endodontic retreatment more challenging.² It may also not be possible to place a post in narrow or calcified canals.³  

An endocrown is a monolithic, conservative restoration that is an alternative to the conventional restorative approach.¹  These restorations were first described by Pissis in 1995, and Bindl and Mormann introduced the term endocrown in 1999.⁴ They utilize the pulp chamber without the need to extend into the canals. Due to the advances in modern adhesive techniques, this less invasive restoration can be used to conserve healthy tooth structure.^1,5 These restorations rely on micromechanical retention by adaptation to the internal portion of the pulp chamber as well as micromechanical retention using adhesive cementation protocols.²  

Endocrowns offer a more straightforward and efficient way to restore endodontically treated teeth when compared to conventional approaches. With the additional aid of CAD/CAM technology, they significantly reduce the time and cost of the procedure.^1,2,5 Additional studies have also shown that adhesive techniques result in less marginal leakage, lower incidence of catastrophic failures, and improved fracture resistance.^2,6 Literature on the clinical performance of endocrowns has been favorable, with reported survival rates ranging from 81.1% to 98.66% over 2 to 7 years.⁵ Ceramic monolithic blocks, especially lithium disilicate reinforced ceramics, are the preferred materials for endocrown restorations due to their high durability, biocompatibility, and esthetics.^5,7

Patient History

A 52-year-old female presented to the University of Maryland School of Dentistry clinic seeking comprehensive care. She reported a chief complaint at her initial visit of history of pain and swelling in the area of tooth No. 31 associated with a large cavitation. She had taken a course of antibiotics that had resolved the pain and swelling. Endodontic testing revealed a diagnosis of asymptomatic irreversible pulpitis with normal periapical tissues (Figure 1). Root canal therapy was completed (Figure 2). Subsequently at the patient’s comprehensive examination, the tooth was treatment planned for crown lengthening, due to the position of the mesial margin, and a full coverage crown.

The patient presented for the core buildup, and at this time the remaining tooth structure was reassessed. It was decided after careful discussion of the treatment options that the best option to restore the tooth was with a partial coverage restoration that utilized the pulp chamber. This would avoid the need for crown lengthening and conserve the remaining healthy tooth structure. The patient consented to the procedure.

Treatment Methods

Tooth No. 31 was prepared for an MOL onlay to remove thin, unsupported areas of enamel on the lingual cusp, as well as the mesial-occlusal area of original decay. Preparation included porcelain butt margins for ideal fracture resistance. The buccal surface had a thick remaining wall of enamel and dentin, so it was preserved in order to be as conservative as possible. The internal walls of the pulp chamber were also refined so that all internal line angles were slightly rounded and all internal components had a slight divergence for ideal path of insertion. The preparation was then scanned using the CEREC Primescan (Dentsply Sirona) (Figure 3 and Figure 4).

The endocrown was digitally designed and subsequently milled using an IPS e.max (Ivoclar) porcelain block via CEREC Primemill (Dentsply Sirona). The patient decided on shade A3 that matched the implant crown on tooth No. 30, even though it was lighter than her natural tooth structure. The milled endocrown was then glazed and fired in the CEREC Speedfire (Dentsply Sirona) to achieve final sintering (Figure 5 and Figure 6).

An OptraGate (Ivoclar) was placed for proper retraction and isolation during the procedure. A rubber dam was not possible because of the lack of interocclusal space, the fact that this was the most distal molar, and that the clinical crown did not have adequate retention for clamp placement. The restoration was then tried in the patient’s mouth. Full seating of margins was confirmed clinically. Patient was pleased with the appearance and confirmed that we could proceed with bonding. The restoration was cleaned with Ivoclean (Ivoclar) following try-in.

The intaglio surface of the restoration was etched using Monobond Etch & Prime (Ivoclar) for 40 seconds with a microbrush and rinsed and dried thoroughly. Adhese Universal (Ivoclar) was applied to the preparation surfaces for 20 seconds, air thinned and light cured for 10 seconds. Variolink Esthetic (Ivoclar) dual-curing resin was placed inside the preparation, and the restoration was seated with firm pressure. Excess cement was removed with a bend a brush, followed by a three-second tack cure. Floss was used to ensure contact was able to be passed through, and remaining excess cement was removed with a scaler before a final light cure of 20 seconds on the lingual followed by the occlusal surface. A bitewing radiograph was taken to confirm final seating of the endocrown. Occlusal contacts and interproximal contact were checked again to confirm no adjustments were necessary, and remaining interproximal cement noted in the final bitewing was removed (Figure 7 and Figure 8). 

Discussion

The endocrown option offers a conservative technique that utilizes intracoronal retention and prevents the removal of sound tooth structure in an endodontically treated tooth.⁷ They are ideally recommended when teeth have calcified canals, short clinical crowns, and a loss of coronal tooth structure.⁸ In this particular case, not only did the tooth have a lot of missing tooth structure due to caries and endodontic preparation, but the tooth itself was supererupted with limited interocclusal space. The endocrown option prevented the need to perform crown lengthening surgery to achieve enough retention and ferrule to place a conventional crown. It is widely known today that achieving 1.5 mm to 2 mm of ferrule and 4.5 mm of supra-alveolar tooth structure is essential for long term restorative success.⁹ Without crown lengthening surgery in this case, a conventional crown approach would not be feasible.

In addition, crown lengthening, although a well-established option, could result in an unfavorable prognosis in a tooth with an already compromised root structure due to decreased bony support.^4,9 To further complicate matters in this case, the tooth in question is adjacent to a dental implant, leading to further concerns that crown lengthening may have a negative effect on its bony support. Crown lengthening surgery also requires healing time of at least 6 to 12 weeks in non-esthetic posterior areas, which would significantly lengthen the treatment time and therefore potentially pose a risk to the endodontically treated tooth.¹⁰ In this case, the endocrown is a good alternative to crown lengthening as this would further compromise the tooth, potentially rendering it non-restorable. With the additional use of CAD/CAM technology, the endocrown was able to be completed with a high level of accuracy and efficiently in one visit.

An endocrown to restore an extensively damaged, endodontically treated molar is an excellent treatment solution according to clinical and in vitro studies with good short, medium, and long term success.⁶ Clinical performance is also satisfactory when compared to traditional crown restorations.⁶ It is also noted that endocrowns had fewer catastrophic failures than crowns (with or without a post restoration) and that it was usually limited to the restoration itself and was reparable.^4.6 This can be attributed to the greater occlusal thickness of endocrowns as well as their monolithic nature, which results in greater stress loading.³ 

Consideration for material choice is an important factor in fabrication of an endocrown. There is a wide selection of materials available for CAD/CAM manufacturing. These include lithium disilicate ceramic, polymer infiltrated ceramic, zirconia-reinforced lithium silicate ceramic, and resin nanoceramic.¹¹ Studies comparing these various materials, including IPS e.max CAD used in this case, result in an acceptable marginal gap of less than 120µm.¹¹ As with conventional single unit crowns, lithium disilicate provides a reliable option that is attributed to its superior flexural strength and fracture resistance. It can also be bonded to the underlying tooth structure, which is why it is an optimal material choice for an endocrown restoration when remaining tooth structure is limited. Although monolithic zirconia is an excellent material choice for many restorations due to its optimal strength, it is not recommended in the case of an endocrown, as it would make endodontic retreatment nearly impossible due to the thickness of material in the pulp chamber. It should be noted that any necessary endodontic retreatment should be considered prior to an endocrown restoration, regardless of material choice due to the nature of the restoration. 

It is critical that adhesion protocols be followed closely in order to ensure that the restoration has the greatest chance of success, as this process prevents marginal leakage and reduces the penetration of micro-organisms to the root canal system.⁶ Preparation is also important, as the pulp chamber depth must be maximized to increase the available bonding surface, without prepping into the canals, as this will reduce the internal adaptation.⁶ Ensuring that preparation margins are supragingival and able to be well isolated for bonding also plays an important role on longevity. A rubber dam is recommended whenever possible. 

Conclusion

This case report highlights the clinical value of endocrowns as a conservative and effective restorative option for endodontically treated molars with extensive structural loss and limited interocclusal space. By circumventing crown lengthening and post placement as well as utilizing CAD/CAM technology, healthy tooth structure was preserved, and the procedure was much more efficient. With proper case selection, endocrowns offer a viable alternative to traditional full coverage restorations. 

About the Authors

Lisa D’Affronte, DDS
University of Maryland
School of Dentistry,
Baltimore, Maryland 

Helga Kens
University of Maryland
School of Dentistry,
Baltimore, Maryland 

Ryan Witte
University of Maryland
School of Dentistry,
Baltimore, Maryland 

Howard Strassler, DMD
Professor Emeritus, University of Maryland School of Dentistry,
Baltimore, Maryland

Figures and Images

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Lisa D’Affronte, DDS

Ryan Witte

Helga Kens

Howard Strassler, DMD

Figure 1

Pre root canal therapy radiograph of tooth No. 31.

Figure 2

Post root canal therapy radiograph of tooth No. 31.

Figure 3

Preparation of tooth No. 31 scanned with the CEREC Primescan.

Figure 4

Occlusion of tooth No. 31 scanned with the CEREC Primescan.

Figure 5

Design of endocrown of tooth No. 31.

Figure 6

Milling preview of endocrown of tooth No. 31.

Figure 7

Final bonded endocrown of tooth No. 31.

Figure 8

Final bonded radiograph of tooth No. 31.

Lisa D’Affronte, DDS

University of Maryland School of Dentistry, Baltimore, Maryland

Ryan Witte

University of Maryland School of Dentistry, Baltimore, Maryland

Helga Kens

University of Maryland School of Dentistry, Baltimore, Maryland

Howard Strassler, DMD

Professor Emeritus, University of Maryland School of Dentistry, Baltimore, Maryland