Endocrowns Versus Post-core Retained Crowns as a Restoration of Root Canal Treated Molars - A Review Article

Abstract

Normally root canal-treated teeth are covered with crowns to prevent fracture, which becomes challenging in cases where the tooth is extensively damaged. In such instances, various restorative methods such as post-core and endocrowns have been in use. The former methodology in recent times is being discouraged owing to impending tooth weakening. Due to this reason, an uncommon type of reconstruction, endocrowns are preferred. We carried out a comparative review of restorations for endodontically treated molars.

INTRODUCTION

For decades, the classic method of restoring Endodontically Treated Teeth (ETTs) was to use metal or fiber posts, which would weaken the root structure due to preparations to expand the root canal.[1,2] A 1.5 to 2 mm ferrule is required to counteract the wedging force caused by the post and increase the fracture resistance.[3] However, in severely damaged ETT, providing a ferrule usually requires a crown extension, which may damage the tooth structure, delay the final restoration, and even reduce the tooth's resistance to fracture.[4] In addition, postspace preparation can lead to more significant enamel loss, which is essential when using adhesive restoration techniques.[5,6]

It was found that when a tooth undergoes restoration, it enters a “death restoration cycle.”[7] The restoration will have defects at some point, a larger restoration will replace it, and the tooth will ultimately be removed. Recently, minimally invasive restorations have received more attention as these preserve the tooth structure. Moreover, recent studies showed that the post has no substantial role in the success rates after endodontic treatment; however, it deteriorates the remaining tooth structure.[8,9] An alternative restorative treatment is needed that is less invasive, requires minimal preparation, and preserves the structure of the remaining teeth. One of the alternative restoration solutions is to have an internally extending crown in the pulp chamber, called an endocrown.[10]

Pissis (1995) introduced the term “endocrown.”[11] The term “endodontic adhesive crown” was proposed by Bindl and Mörmann in 1999.[12] It is a one-piece cemented prosthesis used to repair ETT without an apical post. This technique uses the pulp cavity for macro-mechanical retention. It is based on an adhesive system.[13] The purpose of crown use is to maintain the biomechanical integrity of the damaged ETT structure and preserve the larger tooth structure for attachment with fewer clinical steps and lower cost.[14,15] Studies have shown that when used for molars, premolars, and even incisors, the endocrown has the same or better fracture resistance than traditional crowns.[4,8,12,15]

Porto et al. in 2016[13] recommended that the endocrown is similar to or better than conventional treatments, such as post-retained crowns, direct composite restorations, inlays, and onlays. Rayyan et al. in 2019[16] reported that severely broken molars were simulated, in which the 2 mm ferrule did not have enough coronal structure. Therefore, the recommended restoration plan is that the crown without a post is retained, the crown is lengthened, followed by a post-core retained crown with a 2-mm ferrule or an endocrown. Govare and Contrepois[17] also suggested that endocrowns can be used as a better alternative to post-retained restorations in molars. In this study, we comparatively reviewed restorations for endodontically treated molars.

Conventional vs. Endocrowns

Indications and contraindications

The preparation of a post space adds a level of danger to restorative treatment. During post-space preparation, strip perforation might occur. This increases the chance of root fracture with the placement of the posts, and treatment failure, especially if an oversized post channel is prepared.[17,18,19,20]

All molars can benefit from endocrowns, especially those with short clinical crown height, calcified root canals, or very slender roots. If adhesion cannot be assured and there is a very little tooth structure remaining, adhesion cannot be assured.[21] Endocrowns are indicated when small intermaxillary spaces are used post and crowns are not possible because of an insufficient thickness of ceramic material and extensive tooth structure loss.[22]

Preparation techniques

The preparation technique of an endocrown is different from conventional crowns.[18] Various studies supported the preparation of an endocrown following the method of Bindl and Mormann.[11] In contrast, a few studies have mentioned a few modifications to the original preparation.

A minimum of 2 mm occlusal height reduction should be achieved. In areas where esthetic is not critical, the margins should be supragingival. The margin should be wide, uniform, and parallel to the occlusal surface resistance to stress forces along the long axis of the tooth.[23]

A traditional treatment choice is a custom-made casting post-and-core covered by metal or porcelain fused to a metal crown with enough ferrule. Surgical crown lengthening, to make a ferrule, revealed a seriously lower fixed failure weight because of the reduction in the preparation of the cross-section, which comes together with a changed/damaged crown-to-root ratio. Designing enough ferrule might lead to loss of tooth structure and might result in compromised bonding strength.[24]

Endocrown lets minimal tooth reduction, supporting the tooth by protecting the sound dental tissue and root canal construction.[25] Endocrown restorations seemed to clear the need for posts and buildups. Many factors like the variance in arrangement/planning, density, elastic moduli, low cost, time saving, and more functional endocrowns have been compared to that of conventional systems.[26]

Mechanical properties

Endocrown is a form of treatment in endodontically treated teeth, endocrowns show a success rate ranging from 94% to 100%; endocrowns are a great conservative option when used for endodontically treated teeth, showing a success rate of an estimate of 5 years (77.7%) in comparison to conventional crowns that showed a success rate of 94%.[1,24] As for survival rates with regard to endocrowns in an estimate of 5 years, a success rate of 91.4% was observed in comparison to 98.3% for conventional crowns.[1]

The stiffness mismatch between the restorative system, cement, and dentin may affect many factors. For instance, conventional restorations are usually prepared with different elastic moduli, which can influence the stress distribution and may increase the risk of root fracture. Also, monolithic endocrowns can support more stress loading than the multi-facial of conventional restoration.[11]

Biacchi et al.[20] showed that lithium disilicate reinforced ceramic endocrowns have a higher fracture resistance than glass fiber post-supported conventional crowns. They suggested that the material of endocrowns should be made with reinforced ceramics. A systematic review was conducted to evaluate the fracture strength of endocrown restoration compared to conventional intra-radicular posts treatment. Although the conventional intra-radicular posts treatment has been commonly referred to restore endodontically treated teeth and may help in the retention of the restoration, the sub-analysis showed that the conventional intra-radicular metal posts could lead to root fracture and catastrophic failure. In contrast, the fiber posts can result in debonding at the interface of post/restoration.[23,24,25]

According to the previous situation, the greater rigidity of metal posts compared to dentin can lead to stress concentration and, eventually, root fracture.[23] The endocrowns performed comparably similar to conventional built-up restoration with an intra-radicular post. Forberger et al.'s[27] study showed that endocrowns have fracture strength similar to that of groups restored by various materials of posts such as ceramic (zirconia), glass fiber, or gold.

Moreover, Biacchi and Basting[20] and Chang et al.[4] reported that endocrowns have a higher fracture strength than the group restored by glass fiber post.[20] Therefore, the thickness of the occlusal portion of restoration is considered a significant factor that may affect the fracture resistance of the restoration. Because the occlusal thickness of endocrowns is 3–7 mm and the occlusal thickness of the conventional crowns is 1.5–2 mm, endocrowns have a higher fracture resistance compared to conventional crowns.[28,29]

According to Chia-Yu et al.'s[4] study, there was no notable difference in the fracture mode with glass fiber or endocrowns. However, fractures were unfavorable in both groups. Biacchi and Basting have also shown that endocrowns and glass fiber have a similar type of fracture.[20] However, Sebastia et al.[29] reported that the long glass fiber post (10 mm) showed a higher number of irreparable fractures than other groups restored with an endocrown or short glass fiber post (5 mm) that mainly cause favorable fractures. Also, they concluded that it was feasible to restore teeth without using a post. Furthermore, Sherfudhin et al.[30] show that restoring a tooth with post reduces the chance of unfavorable failures. Therefore, one of the reasons for endocrown failure was due to secondary caries. Also, no fracture or loss of retention was reported with endocrowns.

CONCLUSION

In summary, endocrowns performed better when compared to conventional treatment of severely compromised molars. To be successful, endocrowns need a systematic approach that includes good design and technique.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.