Results
The endodontic retreatment and endocrown restoration of a badly damaged molar were carried out in a single clinical session. Postoperative clinical photographs and radiographs verified the results of the treatment: the molar recovered its anatomical forms and thus its function.
The endocrown restoration and the build-up material occupied the enlarged pulp chamber completely; the access to the root canals was thus closed hermetically. The margins of the endocrown also showed an adequate seal. The tight seal of the restoration will play a crucial role in the long-term results of the endodontic treatment.
Regarding the endodontic retreatment, the preparation and seal of the root canals were appropriate, a suitable 3D seal was achieved and the working length was corrected. Also, the previously untreated root canal in the distal root was properly prepared and sealed (Fig. 23).
Discussion
The radiographically diagnosed hypercementosis of tooth #46 was a factor with no therapeutic consequences. This hyperplastic formation of radicular cementum could have arisen from irritation of infected root canals and/or by the hyperactivity or hypoactivity of the tooth root due to dysfunctional occlusal forces associated with the defective anatomy of the old restoration.
In one clinical session, the badly damaged tooth #46 was endodontically retreated and restored with an endocrown fabricated chairside by means of CAD/CAM technology. This combination is both time- and money-saving.
The microscope-assisted cleaning of the gutta-percha and endodontic sealer are expected to enhance the adhesion over the floor of the cavity.1 The quality of the coronal restoration is at least as important for periapical health as the quality of the endodontic treatment itself.9
In the case of endodontically treated teeth, several advantages result from carrying out the definitive coronal restoration in the same session as the post-endodontic treatment of the root canals.10 It ensures a better coronal seal and increases the success of the endodontic treatment. Moreover, the time between the root canal filling and the coronal restoration should be as short as possible to avoid root canal recontamination.11 Better mechanical protection is provided to residual tissue from the very beginning of the process if a definitive restoration is inserted in the same session. In fact, the probability of dislodgement of the definitive restoration is much lower compared with that of a provisional one. The final function of the tooth is restored from the very beginning of the process, subsequently offering greater comfort to the patient. Patients normally appreciate having the process finished in just one clinical appointment although it is a longer session.
The material of choice for this endocrown was an industrially polymerised highly filled nano-ceramic hybrid material. Together with lithium disilicate-reinforced glass-ceramics, feldspathic ceramics and polymer-infiltrated feldspathic ceramics (hybrid ceramics), highly filled nano-hybrid composites are considered among the most suitable for the fabrication of endocrowns. Case reports and clinical studies have shown additional advantages of the fabrication of endocrowns with nano-ceramic hybrid materials like the one used for this case: the greater elasticity results in higher absorption of mechanical stress and thus higher protection of weakened tooth tissue.8, 12, 13
Compared with a conventional provisional indirect restoration made of regular composite inserted and polymerised over a plaster model, an industrially polymerised highly filled nano-ceramic hybrid material such as Grandio blocs used in this case shows better physical and mechanical properties13 and features a higher degree of polymerisation. The higher degree of polymerisation reduces water absorption and degradation in the oral environment. A restoration made from Grandio blocs is expected to have a higher fracture resistance, no chipping fractures and no deformation (because it is prepolymerised). Compared with analogue procedures, the CAD/CAM approach adds precision to the final restoration.12
The cavity preparation is also a sensitive aspect when working with endocrowns. Butt joint occlusal margins are preferred, and axial reduction is not recommended.4, 2 Some recent investigations have suggested that butt joints implemented with 20° bevels are more effective than flat butt joints.14 In this case, no axial reduction was performed.
Subgingival preparation margins must be accessible, and this can be achieved, among other methods, by placing retraction cord before taking conventional or digital impressions. No contact should be present between the cavity and the adjacent tooth. The occlusal space should be adequate as well and have been carefully checked previously.12
According to various studies, the adhesion protocol when cementing the restoration is also crucial. The dentine of an endodontically treated tooth and especially the dentine of the root canal and of the floor of the pulp chamber might represent an altered substrate, offering lower adhesive power.15 Clinically, tooth #46 had become brown and translucent because several years had passed since the tooth had lost its vitality. Research indicates that dentine in this condition might have modified collagen (lower density collagen with short and cut fibres). This could negatively affect the adhesive technique when depending exclusively on the collagen fibre–adhesive–hybrid layer. Dentinal tubules should be open in order to generate resin tags and compensate for the loss of adhesion due to the poor quality of the collagen.16
In this clinical situation, by the time the restoration process had started, the dentinal tubules were open, endodontic treatment having just been completed and before the adhesive post-endodontic treatment. Here, it was important not to use rotary instrumentation for removing the excess gutta-percha, as this would have generated a secondary smear layer. This is more difficult to dissolve, the usual smear layer being associated with plasticised gutta-percha and endodontic sealer.17 Thus, for such cases, the use of ultrasonic tips and hand instrumentation is preferable for removing excess gutta-percha. Excess endodontic sealer should also be carefully removed with alcohol or a detergent substance using micro-brushes or sponges (e.g. Pele Tim, VOCO). Carrying out total-etch conditioning using a 35%–40% phosphoric acid gel after removing gutta-percha and sealer excess will also help keep the dentine clean and its tubules open.
Conclusion
Performing the restoration immediately after endodontic treatment ensures a better and immediate coronal seal, ensures immediate protection of the sound tissue, saves time, and offers comfort and confidence to the patient and the clinician. Endocrowns made of the highly filled nano-ceramic hybrid material Grandio blocs represent a new alternative for treating badly damaged teeth, especially molars, while freeing the dentist from the use of root posts. In vitro and clinical studies as well as clinical experience with this material are promising. These endocrowns represent a less invasive and better mechanical option compared with posts and crowns.
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