Dental Products Report, January 1st, 2007
A young patient's right central and left lateral incisors were devitalized and restored with adhesive composite materials whose appearance degraded with time (Figure 1). Furthermore, the teeth themselves were stained and their appearance meant that ceramic crowns were fitted. Reconstruction of the devitalized front teeth involved three problems: Fragility of the teeth with a root tenon, insufficiency of root tenon retention proportional to the developed surface and influence on the shade of a full ceramic crown in the same colour as the reconstituted stump. This article presents the answers to the problems by making choices among the range of possibilities that are currently available.
Background
Due to progress in aesthetic restorations and high patient expectations, pre-prosthetic stump reconstitution using translucent materials has been considered and new designs for devitalized tooth reconstitution have been developed. Visible metal inlay-cores and carbon fiber stumps through full ceramic crowns is one of the problems that scientists and manufacturers are working on today. The future of roots where a metal tenon has been inserted to hold the stump reconstitution or prosthetic crown (Richmond type) is compromised — many fissures, cracks and fractures have been observed after tooth extraction. The rigidity of tenons with very high flexion-resistance, the complete opposite of root dentine flexion, may be responsible for these unsuccessful prostheses in the mid- and long-term.
Transparent material solutions
The aesthetic and functional value of the root-root tenon-stump reconstitution depends on the mechanical performance of each element and, above all, the assembly. Without immediately abandoning poured or non-poured false stump metal tenons where the visibility can be masked with a sufficient layer of ceramic, two transparent material solutions are possible: corono-radicular reconstructions with a fibrous composite tenon or zirconium and poured ceramic reconstructions. The latter is the undisputed choice of perfectionists, but the mechanical properties (including rigidity and hardness) of a zirconium-rich ceramic material present problems: - during tenon removal,
- due to differences in tenon and dentine flexibility,
- because of adhesive reliability.
These disadvantages can be reduced by using a translucent fibrous tenon, a reconstitution complex in an aesthetic composite. Firstly, the fibrous tenon may be removed from its housing by drilling with an adapted rotary instrument. Fibrous tenons and root dentine have proven that similar levels of flexion-resistance and tenon adhesion, with an acrylic resin matrix, is real and lasting. The root dentine-adhesive composite-fibrous tenon assembly is a cohesive unit made of 'auto-reinforcing' components which are not subject to corrosion degraded with time. The teeth themselves were stained and their appearance was an indication for ceramic crowns.
Corono-radicular preparation of 11
Crown preparation was started and the presence of a cervical dentine ring justified the indication of pre-prosthetic reconstitutions in translucent fibrous tenon composites. The opening of the root tenon housing was done using a Largo drill of adequate diameter. Then the pilot drill was used manually at an angle to eliminate the canal filling material. Finally, a drill suited to the root's morphology was used to prepare the tenon housing for a distance determined by X-ray.
The length may be less than what is generally recommended (2/3 of the root's length) since the tenon is glued and not sealed with much greater retention. The housing was prepared using the drill shape corresponding to the tenon determined on the calibration guide manually and then mechanically (Figure 2). The tenon housing was cleaned with EDTA and the operative field inserted. The peripheral preparation was removed.
The tenon diameter, which corresponded to the last drill used (blue ring) was tried (Figure 3). Insertion should be passive and may be controlled by X-ray — its radiopaque image results from the presence of zirconium powder (approximately 2%) in the matrix. The length was determined and it was sectioned to the required length using a diamond disk held perpendicularly to the axis to prevent microfiber laceration (Figure 4).
Preliminary steps and reconstitution of the stump of 11
The tenon housing and dentinal walls mordant was 37% phosphoric acid (Dento Etch) applied for 30 seconds (Figure 5). These areas were then rinsed abundantly and dried. The surfaces to be glued were prepared in two steps. Firstly, a mixture of equal quantities of DentoBond Adhesive and Activator (Figure 6) that makes the adhesive automatically light-curable, was applied to the walls of the canal housing, then silane (DentoBond Porcelain Silane) was deposited on the tenon and left to dry. The same adhesive (automatically light-curable) covered the tenon and was light-cured.
The tenon sealing cement (DentoCem Resin Cement) was injected into the housing with the auto-mixing nozzle, then a lentula. The tenon was inserted (Figure 7) with gentle friction and the cement left to harden.
The stump was reconstituted with an automatically light-curable composite, DentoCore, (Figure 8) placed in a transparent matrix and injected around the tenon (Figure 9). The matrix previously tailored to the cervical surround was replaced. The composite was light-cured in vestibular, lingual and occlusal. The matrix was deposited. Shaping the stump was simple. Fine grain diamond drills (yellow ring) and flexible polishing cups were used. The transparent tenon that transfixed the stump should not create any perceptible unattractive interference through the final ceramic crown. It can be seen that the reconstitution material is perfectly homogeneous since it was compressed under the closed matrix. No continuity solution was observed (Figure 10).
Preliminary steps and reconstitution of the stump of 22
The left lateral incisor was very stained (Figure 11) and the palate access cavity was particularly voluminous. Preparation involved shaping and was finished using the same instruments as before. Preparation of the canal housing was the same although the tenon was intended for a lateral incisor and so was narrower (yellow ring) (Figure 12). The stump was reconstituted (Figure 13) and preparation finished. A significant advantage of freshly prepared reconstitutions is the possibility of making the impression in the same clinical session (Figure 14).
Prosthetic restorations
Two Procera aluminum caps were made and tested (Figure 15). The adhesive seal of the crowns was obtained with sealing cement from the same range (DentoCem Resin Cement). The prosthetic prepared by Laboratoire Créatif Dentaire. The clinical result satisfied the most exacting aesthetic criteria (Figure 16).
