Saudi Endodontic Journal

REVIEW ARTICLE
Year
: 2020  |  Volume : 10  |  Issue : 3  |  Page : 181--186

Decision making and restorative planning for adhesively restoring endodontically treated teeth: An update


Vidhi Kiran Bhalla1, Sherin Jose Chockattu2, Shyambhavi Srivastava1, Sathya Prasad3,  
1 Department of Conservative Dentistry and Endodontics, ITS Centre for Dental Studies and Research, Ghaziabad, Uttar Pradesh, India
2 Department of Conservative and Endodontics, Bapuji Dental College and Hospital, Davangere, Karnataka, India
3 Private Practitioner, Davangere, Karnataka, India

Correspondence Address:
Dr. Vidhi Kiran Bhalla
Department of Conservative Dentistry and Endodontics, ITS Centre for Dental Studies and Research, Ghaziabad, Uttar Pradesh
India

Abstract

Restoration of pulpless teeth presents a clinical challenge and a controversial topic of debate even today. The preservation of coronal tooth structure is crucial for clinical success and for maintaining biomechanical, adhesive, functional, and esthetic balance. The advent of adhesive dentistry and advancement in dental materials have resulted in mechanical properties close to the dental tissues, thereby offering a conservative treatment option to restore, reinforce, and protect endodontically treated teeth (ETT). Directly bonded restorations are indicated for teeth with the minimal loss of coronal tooth structure and can be considered effective for short-term success of root canal treated teeth. However, indirect restorations could be considered for the strengthening of the tooth with moderate loss of tooth structure, following the adequate adhesive protocols. The present review assesses literature on direct versus indirect adhesive restorations such as endocrowns, adhesive onlays, and overlays for restoring ETT. Furthermore, the article attempts to present clinical guidelines and decision-making for restoring endodontically treated anterior and posterior teeth.



How to cite this article:
Bhalla VK, Chockattu SJ, Srivastava S, Prasad S. Decision making and restorative planning for adhesively restoring endodontically treated teeth: An update.Saudi Endod J 2020;10:181-186


How to cite this URL:
Bhalla VK, Chockattu SJ, Srivastava S, Prasad S. Decision making and restorative planning for adhesively restoring endodontically treated teeth: An update. Saudi Endod J [serial online] 2020 [cited 2020 Nov 29 ];10:181-186
Available from: https://www.saudiendodj.com/text.asp?2020/10/3/181/293571


Full Text



 Introduction



Endodontically treated posterior teeth are more susceptible to biomechanical failure because of coronal destruction from dental caries, fractures, previous restorations, and endodontic access cavity and root canal chemo-mechanical preparation The loss of mechanoreceptors after endodontic therapy increases the threshold of the pressure receptors in the periodontium, leading to a functional overload, thus making the tooth highly susceptible to fracture.[1],[2] In addition, the irrigating solutions and medicaments used during the chemo-mechanical preparation reduces the mechanical properties of root dentin and increases the risk of fracture. These factors can affect the prognosis of endodontically treated teeth (ETT). The successful outcome in ETT depends not only on an adequate root canal treatment but also to a far greater extent on an adequate coronal restoration. The classic study by Ray and Trope has confirmed this evidence.[3] A recent survey demonstrated high knowledge and clinical judgment skills among the graduates in Saudi Arabia in selecting the appropriate methods for restoring ETT and maximum respondents opted for full coverage restorations than other partial coverage restorations.[4]

The best way to restore ETT has been extensively discussed and is still a matter of debate. The conventional approach to restoration involves the fabrication of a full-coverage crown, as this was believed to provide better protection and reinforcement of the tooth structure.[5],[6]

However, the advances in adhesive techniques, composite resin materials, fiber post, and indirect ceramic material have brought on a revolution in the restoration of root canal treated teeth. Adhesively bonded ceramic inlays, onlays, and endocrowns offer a minimally invasive solution and have been suggested in various studies.[7],[8] While some studies emphasize on complete coverage crowns to restore ETT, others are of the opinion that complete coverage crowns require extensive tooth preparation which further compromises the strength of the remaining tooth structure. These minimally invasive bonding techniques are advantageous in the preservation of the health of the dental tissues as well as restoring the integrity of the periodontium without compromising the esthetic and functional requirements.[9],[10] The present review emphasizes the recent adhesive therapeutic options for post endodontic restorations, the factors governing the decision-making process and the fundamental principles along with the adhesive techniques for long-term clinical success.

 Direct Restorations for Endodontically Treated Teeth



Direct restoration with composite resins is mainly indicated for teeth with minimal to moderate loss of tooth structure. The amount of remaining tooth structure is crucial for success.[11] A recent systematic review has concluded that the survival rates against the fracture of endodontically treated posterior teeth with minimal-to-moderate loss of tooth structure restored with crowns or restorations had no significant differences. Therefore, preparing a sound tooth structure to receive a full crown may not be suitable in the current era of adhesive dentistry.[12]

Resin-based composite (RBC) restoration allows for adhesive bonding to the tooth substrate. However, the long-term durability of the bond is a concern due to the effect of polymerization shrinkage inherent in resin composites.[13] A recent retrospective study concluded that ETT with 1 or 2 tooth surface losses and 2 proximal contacts which were restored with resin composite showed a high survival rate that was comparable to ETT restored with crowns.[14]

A 13 years retrospective study concluded that there is a significant difference in the success rate of RBC in vital teeth (98.97%) and ETT (76.8%). The authors have further concluded that the presence of occlusal stress decreases the survival of RBCs in ETT.[15] Another study recommended the preparation of conservative access and placement of glass ionomer cement base to reduce tooth strain and microleakage, when restoring ETT with direct resin composites.[16]

Considering the available data, the use of composite resins may be limited to teeth with conservative access cavities and teeth with minimal loss of tooth structure. In cases with bruxism, tooth wear and heavy occlusal forces, use of composite resins is not indicated. The long-term prognosis is significantly affected by the type of composite resin (filler content) and adequate isolation using rubber dam application.[17]

 Adhesive Indirect Partial Restorations



Bonded indirect ceramic crowns, in the form of “Onlays,” “Overlays,” “Endo-Crowns” have been documented in the literature as minimally invasive treatment options for restoring larger defects, that cannot be managed successfully with a direct approach.[9] Partial restorations are advantageous in preserving the sound tooth structure as well as providing cuspal coverage to protect the weakened cusps. However, the success of these adhesive restorations depends on a proper preparation design, the choice of ceramic material and the high technique sensitive adhesive luting protocol.[10] A literature review assessed the best approach to restore ETT which includes the minimal sacrifice of sound tooth structure and ensuring an adequate ferrule, using adhesive procedures at both coronal and radicular levels to strengthen and reinforce sound tooth structure and the use of post and core materials having physical properties close to natural dentin.[11]

 Post and Core Restorations for Endodontically Treated Teeth



ETT with moderate-to-extensive loss of tooth structure often require post and core restorations for retention of the crown. The amount of remaining coronal tooth structure is an important factor in postselection. Various in vitro[18],[19] andin vivo studies[20] suggest that fiber post are indicated when sufficient coronal dentin remains while cast posts are indicated for moderate-to-severe tooth structure loss.

A structured review of laboratory and clinical studies[21] demonstrated that endodontically treated posterior teeth with limited tissue loss can be restored without posts, particularly when total coverage is planned. A recent systematic review has concluded that there is insufficient evidence to support or reject the use of posts even for cavities with no remaining walls having circumferential ferrule 2 mm in height and 1 mm thick. The authors further concluded that the clinical decision-making should be based on factors such as remaining tooth structure, tooth type and position, occlusal and functional requirements, type of final restoration.[22]

Regarding the type of postselection, a recent systematic review and meta-analysis have concluded that fiber posts demonstrated higher survival rates than metal posts in restoring ETT with not more than two walls remaining.[23] Fiber posts, with similar elastic moduli (20 GPa) to dentin lead to a better stress distribution pattern compared to metal posts (200 GPa) which concentrate higher stresses at the apical region of the root, leading to catastrophic root fractures.[23],[24]

 Endocrowns



The use of intraarticular posts to rehabilitate ETT is associated with additional removal of sound tooth structure for postplacement with increased risk of catastrophic failure of the tooth.[24] This occurs due to altered biomechanics of post and core treated teeth which concentrates stresses at the cervical third (for fiber posts) and at the apical thirds (for metal posts). A post less alternative to restore teeth is an “Endocrown.”[25] Endocrowns are ceramic monoblock, which are adhesively luted to the internal portion of the pulp chamber and to the cavity margins of an endodontically treated tooth. This allows for a macromechanical retention provided by the walls of the pulp chamber as well as micromechanical retention provided by the cavity margins which are in enamel.[26],[27]

A recent systematic review and meta-analysis concluded that endocrowns may perform similarly or better than the conventional treatments using intraradicular posts, direct composite resin or inlay or onlay restorations.[28] The superiority of endocrown restorations when compared to conventional crowns could be attributed to the presence of sound enamel around the margins of the cavity, which is lost when the tooth is prepared for a full-coverage restoration. Furthermore, the occlusal portion of the endocrowns varies from 3 to 7 mm vertical thickness, while for conventional crowns, it is in the range of 1.5–2 mm.[7],[29] Furthermore, the monoblock nature of endocrowns would support increased stresses, compared to conventional multi-interfacial restorations.[30]

Regarding endocrown preparation, a butt joint margin called as “cervical side walk” is prepared [Figure 1]a and [Figure 1]b. This prepared peripheral band of enamel optimizes bonding and resists compressive stresses. The walls of the access cavity are made divergent with a depth of at least 3 mm to ensure retention and stability.[31]{Figure 1}

The success of any adhesive restoration depends on strict rubber dam isolation and adequate surface treatment of the ceramic and the tooth.[24],[27]

A retrospective clinical study conducted by Belleflamme et al. evaluated 99 endocrowns made of lithium disilicate glass and Polymer infiltrated ceramic material with a success rate of 99.0% and 89.9%, respectively, over a mean period of 44.7 months. The authors further concluded that when the adhesive technique is correctly applied, endocrowns can be considered as a reliable approach for restoration of severely damaged molars and premolars, even in the presence of significant occlusal risk factors, such as bruxism or unfavorable occlusal relationships.[31]

In comparison to the post and core approaches, this minimally invasive strategy offers several advantages such as conservation of tooth structure, reduced risk of irreparable root fractures, and risk of root perforation that may occur during post space preparation, reduction in the number of adhesive interfaces contributing to lower incidence of microleakage and contamination. Further, endocrowns can be used with limited interocclusal space.[24],[25]

Studies have suggested that Immediate Dentin Sealing (IDS) with a bonding agent directly after tooth preparation further increases the success of these indirect adhesive restorations by improving the bond strength, marginal adaptation, and decreasing the bacterial microleakage.[32]

 Onlays



Adhesive onlays are used to partially cover cusps, but not the entire occlusal surface. They are indicated for the restoration of ETT in the presence of at least one marginal ridge with two well-supported axial walls in continuity with the marginal ridge.[33] Anin vitro study by Alshiddi and Aljinbaz concluded that ETT can be successfully restored using composite inlays and onlays; however, the fractures that accompanied inlay restorations were more severe and unreparable.[34] An ex vivo study assessing the fracture resistance of ETT with ceramic onlays with or without fiber postplacement concluded that partial coverage with ceramic onlays resulted in significant improvement in fracture resistance and the insertion of glass or quartz fibers did not increase the fracture resistance significantly.[35] A 4 years observational study has shown promising results with success rates of over 92.5% with IPS Empress 2 ceramic onlays on ETT.[36] The long-term clinical survival data on the success of ceramic onlays for restoring ETT is, however, lacking and requires more investigation.

 Overlays



Overlays are indicated for total cusp coverage for mesio-occlusal distal cavities, with loss of both the marginal ridges. These adhesive restorations require 50% less reduction of tooth structure, compared to complete crown restorations. Partial restorations in the form of overlays allow the preservation of sound tooth structure while providing cuspal coverage to protect the weakened cusps.[37],[38] IDS improved the success of indirect adhesive partial restorations. The preparation principles by Veneziani are based on morphological considerations in terms of geometry (maximum profile lines and cuspal inclination) and structure (enamel convexity and dentin concavity). This anatomic preparation design improves the adhesion quality by optimized cutting of enamel prisms as well as increasing the available enamel surface and allowing maximum hard tissue preservation.[33]

 Partial Indirect Adhesive Restorations: the Paradigm Shift?



The journey from anecdotal evidence to scientifically validated protocols for restoring pulpless teeth continues. The advent of adhesive restorative procedures and techniques allows for a functional and esthetic reconstruction of debilitated teeth when adequate coronal tooth structure remains.[17] Direct or indirect onlays can be used when the residual tooth structure is not undermined and the marginal ridges are intact. Use of overlays and full coverage crowns restrict cuspal displacement and are indicated in teeth with inadequate coronal tooth structure.[39] The long-term success of these adhesive restorations is dependent on the integrity of residual tooth structure and adhering to strict preparation and adhesive protocols.

 Recommendations/clinical Guidelines



The review by Vârlan et al. has concluded that the choice of final restoration depends on the amount and quality of remaining tooth structure, topography and coronal morphology of the tooth and the functional occlusal forces that the restoration-tooth complex has to withstand.[40] The use of partial coverage restorations allows the clinicians to preserve dentin and when this conservation approach is combined to the use of correct adhesive protocols, it can provide long-lasting esthetic restorative management for ETT.[7] The recommendations for the restoration of endodontically treated anterior and posterior teeth are illustrated in [Figure 2] and [Figure 3].{Figure 2}{Figure 3}

 Conclusion



Preservation of tooth structure is paramount for the success of ETT. The advent of adhesive procedures has heralded the need to switch to “Prevention of extension” and allow for a minimally invasive restorative approach to restore pulpless teeth. Preparing sound tooth structure to receive a full coverage restoration may not be suitable anymore in the current era of adhesive dentistry. Use of strict bonding protocol aided by rubber dam isolation and IDS procedures significantly improve the success of indirect bonded ceramic restorations. The use of endocrowns seems promising. Further studies, comparing indirect restorations of full or partial coverage are of great interest.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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