A New Concept of Posterior Mini-invasive Restorations: Clinical Procedures and Requirements—Case Report
Corresponding Author: Imen Kalghoum, Department of Fixed Prosthodontics, Faculty of Dental Medicine of Monastir, University of Monastir, Monastir, Tunisia, Phone: +21655882694, e-mail: email@example.com
Received on: 25 May 2023; Accepted on: 21 June 2023; Published on: 29 September 2023
Aim: To highlight the principle of tooth preservation in the case of endodontically treated teeth and show the particularities of its preparation and material choice according to the clinical case.
Background: Endodontically treated tooth with moderately to large cavities often requires full coverage restoration that provides optimum replacement of anatomy and function. However, posterior indirect adhesive restorations are becoming very common nowadays in clinical practice, as they offer superior marginal adaptation with maximum tissue preservation; different approaches are in practice to provide better survival and advantages.
Case description: A clinical case about a 25-year-old female patient with the complaint of repetitive fracture of her coronal restoration, diagnosed with localized periodontitis of the maxillary molar tooth (26) and treated with a hybrid ceramic endocrown.
Clinical significance: The indication of minimally invasive restorations should be carefully raised, taking into consideration various factors such as remaining tissue of the tooth preparation design, type of material, and bonding procedure. The balance is between the tissue preservation of endodontically treated molars and sufficient thickness of material.
How to cite this article: Kalghoum I, Riahi Z, Mejri O, et al. A New Concept of Posterior Mini-invasive Restorations: Clinical Procedures and Requirements—Case Report. CODS J Dent 2022;14(2):61-66.
Source of support: Nil
Conflict of interest: None
Patient consent statement: The author(s) have obtained written informed consent from the patient for publication of the case report details and related images.
Keywords: Case report, Ceramic, Endocrown, Minimal invasive restoration, Molars, Onlay, Preparation, Tissue preservation.
Posterior minimal invasive restorations are nowadays a very common treatment option in clinical practice; it’s considered a suitable solution for cases of cavities with extended coronal destruction.1,2 This type of restoration offers new approaches with the use of new materials. Moreover, the use of adhesion for restorations has changed some fundamental principles of classic dentistry and has led to some advantages3 tissue conservation, function, sealing, and esthetics;4 nevertheless, for a good prognosis, a specific clinical protocol should be followed: the right and careful indication, the right evaluation of preparation design, the good choice of material, adequate impression and bonding protocol4 as well as the isolated procedures that should be carefully used to get predictable result.5
The use of full glass-ceramic crown restorations in endodontically treated molars remains problematic for many practitioners. Minimally invasive alternatives to the full post- and core-supported prostheses endocrowns as a treatment modality were brought in 1999 by Bindl and Mörmann.5
In 2008, Magne and Knezevic developed the correct choice of restorative materials considering ceramics and composites in intracoronal molar restorations.6,7 Using this concept for maxillary premolars and maxillary incisors was an idea given by many authors throughout their studies, but they require more evidence to support it.
The endocrown is a monolithic ceramic bonded structure having a butt joint with increased enamel for better adhesion. The endocrown enters the pulp cavity but not the root canal. A new generation of ceramics and assembly materials may make this treatment option an alternative to conventional restorations.
The revolutionary concept is based on a specific preparation that can be used in order to adapt the restoration to the remaining tissue, not the opposite.6
The purpose of this article is to illustrate a clinical case of a maxillary molar treated with a ceramic endocrown, emphasizing the details of its preparation and principles of tissue preservation.
A 25-year-old healthy female patient visited the Department of Prosthodontics, the academic hospital center of dentistry of Monastir, Tunisia. She reported the repetitive fracture of her coronal restoration with interproximal bleeding between the maxillary molar tooth number (26) and the tooth number (27) (Fig. 1). The patient requested good esthetics.
The intraoral examination showed good hygiene. A defective ionomer glass cement restoration in the tooth number (26) was evident, with a residual caries of 2 mm depth under the filling related to the leakage between the restoration and residual tooth structure. Food impaction and contact area loss (Fig. 1), expect a localized periodontitis. This diagnosis was confirmed by probing that led to bleeding and a pocket of 5 mm depth.
Vitality pulp tests showed a negative response. The periapical radiograph examination showed a satisfactory endodontic treatment of a horizontal overhanging filling material (Fig. 2).
An alginate (Lascod®, Firenze, Italy) impression was performed. A wax-up was made to prefigure the project.
The defective restoration and the residual decay were removed. The temporary restoration was placed in order to identify the topography of the coronal cavity and to relocalize the distal margin (gingival and bone tissue). The margins of the cavity were subgingivally placed (Fig. 3).
A ceramic endocrown was indicated. This treatment option seems to be suitable for this clinical situation as no preparation is required except for slight modification in the tooth cavity, which is more economical for dental tissue.
To optimize the bonding and retention of ceramic posterior restoration, a deep margin elevation (DME) was indicated, as the limit was subgingival. Proper isolation with a rubber dam and curved Tofflemire matrix was the key to proper elevation. In this case, an etch-and-rinse adhesive system (two steps) and a combination of flowable and restorative composites were used. The subgingival composite filling was well tolerated by gingival tissues (Figs 4 to 7).
Bitewing radiographs were taken to assess the fit of the composite resin in the gingival area (no gaps or protrusions, Fig. 8).
An articulating paper was used to mark the patient’s occlusion. The preparation was then made using diamond burs. The thickness of enamel walls should be >2 mm. The cavity depth was made till 1.5 mm axial angles were rounded. Undercuts were avoided with a cervico-axial wall convergence of 12°. The drill was aligned along the long axis of the tooth, and the preparation removed tissue from the walls of the pulp chamber. The cavity depth should be at least 3 mm, and the margins should be finished (Fig. 9).
Once the preparation was validated, gingival retraction with cords was made, then full-arch impression was made using polydimethylsiloxane with high viscosity and washed with low viscosity (Mono Ghenesyl, Lascod®, Firenze, Italy) (Fig. 10). Temporary restoration was performed using an acrylic resin (Texton®) and silicon index, then cemented with a zinc oxide cement devoid of eugenol.
The impression was transported to the lab, where prosthetic pieces were tailored using Exocad Dental 3.00 Galway software (Fraunhofer Society, Germany) (Fig. 11) and milled from etchable hybrid ceramic bulks (Vita Enamic®). After receiving the prosthetic pieces, the fit of the margins was checked. Finally, it required the use of a rubber dam to ensure a secure bond (Figs 12 and 13).
Variolink II (Ivoclar® Vivadent, Schaan, Liechtenstein) was used as the bonding system. In this, polydimethylsiloxane material protects the external surface of prosthetic pieces and is then treated with hydrofluoric acid and silinated, and phosphoric acid 37% was used to etch the cavity for 30 seconds, then rinsed and dried with an air syringe. An adhesive was applied on both the tooth and ceramic surface. The resin luting agent is then placed all over the preparation and the restoration. This was followed by the placement of endocrown along with the luting material, and the excess cement was removed. Gross excess resin can be removed after 2 seconds of spot curing. The interproximal area was cleaned and flossed with due care to avoid the bleeding of the gingiva. The restoration should be held in place carefully while the resin is cured. Followed by a full light curing process of 40 seconds focusing on all sides of the inlay. The procedure should be finalized by covering the sealing joint with a glycerin gel and polymerizing it for 20 seconds. Light curing was done in accordance with the resin manufacturer’s recommendations (DLux®, Diadent Group International) (Figs 11 to 14).
The occlusion was checked carefully after the luting of the endocrown so that the restoration would be prevented from fracture. To evaluate marginal adaptation, color, abrasion, secondary caries, and fracture, the patient was given an appointment for follow-up after 3 and 6 months (Fig. 15).
The endocrown can be considered a reliable option for full crowns restoring endodontically treated teeth. It consists of a circular butt join trim and a central retaining cavity in the pulp chamber without intrapulp fixation. Among available materials, nanofilled composite resin and lithium disilicate glass ceramic were selected. This technique represents a promising and minimally invasive option for the restoration of posterior nonvital teeth that require long-term success and stability.
This case was treated by an endocrown that aims for maximal tissue preservation, on the one hand, it was not necessary to prepare 2 mm of mesial intact cusps in order to respect the butt margin or butt joint. On the other hand, the pulpal chamber was used to assume both stability and retention of the ceramic endocrown. The restoration should be dictated by the amount of remaining coronal substance and not the opposite. No additional preparation was required except for slight modification in the tooth cavity, which is more economical for dental tissue. This approach provided biomechanical integrity, adequate function, and good esthetic outcomes for the compromised tooth.4,6
It also prevents periodontal diseases, thanks to a subgingival position after DME.
In fact, proximal cavities involving margin tissues are challenging for practitioners, starting with cavity preparation, impression, and bonding, which require proper fluid control.
Contamination with saliva or blood during bonding weakens the retention of restoration. Different modalities are used in order to provide better access to paragingival fits. Hence, either flowable or restorative composite can be used for elevation; when a microhybrid resin is indicated, it’s recommended to preheat the material in order to avoid the risk of interlayer gaps and facilitate its placement.
According to the systematic review of Alhumaidan et al.10 the DME is done with direct filling materials like composite resin. Though the follow-up time mentioned in all the studies11-15 was between 1 and 17 years, before the minimal invasive restorations were done during the elevation of the margins using direct fillings, many studies did not report any complications. In terms of mechanical strength, increasing the margin on depulpated teeth had no impact on their mechanical resistance.
A clinical evaluation regarding the prognosis of indirect restorations was performed by Bresser et al. After 12 years, the retention rate was 95.9%. Given this high survival rate, nevertheless, some marginal deterioration had been noted without evidence of a direct effect on restoration survival. Hence, there is a scope for more clinical trials to measure the survival rate and clinical performance of treated teeth restored with marginal elevation procedures.18
On the other hand, surgical crown lengthening (SCL) and orthodontic eruption present excellent alternative modalities to the DME. SCL is the removal of hard and soft tissue supporting teeth surgically in order to avoid a violation of the biological width in case of a short clinical crown, traumatic injury, and deep caries.5,6 However, the survival rate of adjacent teeth may be influenced by this surgery.7 Orthodontic extrusion may be a clever solution in cases of fractured external roots.13,18 When it comes to prosthetic orthodontic treatment, it wouldn’t be possible to indicate an orthodontic extrusion without involving the occlusal relationship between molar and antagonist teeth. Moreover, orthodontic treatment is time-consuming and needs a provisional restoration, which would complicate the treatment.
Impression is considered to be a crucial step, as a high reproduction of details is required to ensure a precise adaptation of the restoration. Additional silicon was used, and a meticulous polishing of the margin as well as the preparation surfaces to ensure a good wettability of the light silicone. A retraction cord was used to allow the penetration of impression material for a better proximal emergence profile.
The ceramic used was a resin-matrix hybrid ceramic. Despite the controversies associated with this material, the manufacturers’ rationale to develop hybrid ceramic materials was to (1) obtain a new material that more closely simulates the modulus of elasticity of dentin when compared to other ceramics and (2) it’s easier to mill and adjust11,12 than glass-matrix ceramics and facilitates modification or repair using composite resin. Resin-matrix ceramic compositions vary considerably, but they are specifically formulated for computer-aided design/computer-aided manufacturing. The survival rate of the short and medium periods was promising, and this new generation was found to be ideal for noninvasive restorations of about 0.5 mm, but more studies were needed to improve outcomes.19-21
The endocrown can be considered a reliable and innovative esthetic solution for endodontically treated molars, which has all the biological and esthetic advantages of ceramic minimal invasive restorations; its indication and contraindication should be observed taking into consideration several factors such as preparation design, type of material and the bonding procedure. The balance is between tissue preservation and sufficient thickness of material.
Imen Kalghoum https://orcid.org/0000-0003-2276-4661
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