1 Private Dental Practice in Wrocław
2 Polish Endodontic Association Research Unit, head of unit Dr. Wojciech Wilkoński MD, PhD
The purpose of this article is to describe two cases of root canal treatment. The first concerns primary treatment of a first lower molar, and the retreatment of a first upper molar and its subsequent build-up with adhesive prosthetic restoration. The article discusses the treatment of molar teeth and the importance of ensuring hermetically-sealed restoration following treatment.
Endodontic treatment is a common procedure performed by many dentists. The success of such treatment, i.e. the absence of pain and pathologies in the periapical region in X-ray images, is determined by many factors. Alongside proper chemical and mechanical preparation and effective irrigation and obturation of the root canal system, another essential factor is ensuring a permanent and hermetically-sealed restoration following endodontic treatment. Within the framework of the aforementioned procedure the restoration is very often performed by means of an indirect technique. As a result of advances in composite materials and adhesive systems, restorations in the form of onlays or adhesively cemented composite endocrowns are becoming increasingly popular.
Case report 1
The patient sought treatment for idiopathic pain located on the right side of the mandible. A clinical examination revealed extensive hard tissue loss on the distal aspect of tooth 46. A periapical photograph taken (Fig. 1) revealed a carious defect penetrating into the pulp chamber. Under regional anaesthesia, the defect was first prepared, disinfected with sodium hypochlorite and then medication (Dexadent – Chema Elektromet, Rzeszów, Poland) was placed in the chamber. Owing to the great difficulty of restoring the distal wall of the tooth it was secured with a temporary restoration and the patient was referred to an endodontist working with a microscope (Fig. 2).
During the visit, the endodontist performed block anaesthesia and prepared the defect using a Zeiss OpmiPico surgical microscope (Carl Zeiss Meditec, Jena, Germany), and restored the distal wall with Herculite Ultra Flow (Kerr, Orange, USA) and an OptiBond XTR adhesive system (Kerr ) (Fig. 3).
Then, the endodontist began to prepare the root canals. A rubber dam (Kerr) was applied for this purpose. After ensuring proper endodontic access using a conical diamond coated bur on the high-speed handpiece as well as round burs on a low-speed handpiece, the chamber was initially disinfected with sodium hypochlorite at a concentration of 5.25%. Then the patency of three visible canals – mesiolingual, mesiobuccal and distal – was checked with a size ISO10C-pilot hand file (VDW, Munich, Germany). The tool reached approximately half the working length in the mesial canals and around ¾ of the length in the distal canal. This was checked on the basis of a preliminary calculation of the working length on the periapical photograph as well as by means of an Element Diagnostic Unit apex locator (SybronEndo, Orange, USA), which did not indicate reaching of the apical constriction.
Then the canal entries were prepared with rotary instruments which is known as “preflaring”. With this aim in mind, an Elements Motor (Sybron Endo) endodontic motor was used together with size 25/12 K3 nickel-titanium instruments and a size 25/08 Twisted File (Kerr). This procedure made it possible to establish the working length with a size IS010 C-pilot (VDW) hand file and an Element Diagnostic Unit (SybronEndo) apex locator. Next, the glide path procedure was performed using ISO 10,12 and 15 C-pilot (VDW) files combined with an oscillation tip for M4 Safety hand tools (SybronEndo). Each tool was inserted when the chamber was filled with 5.25% sodium hypochlorite, and when the procedure passed onto the next file size the hypochlorite was replaced with a fresh solution. The canals were then prepared with Twisted File nickel-titanium instruments (Kerr Company), an Elements Motor (Kerr Company) and Adaptive Motion technology. Adaptive Motion technology is a combination of rotary and reciprocating movements programmed by the Elements Motor. The following sequence of filed was employed: 25/08 and 35/06.
Due to the fact that preparation was greatly facilitated by the aforementioned size, it was decided to use additionally TF size 40/04 to ensure more accurate preparation of the periapical area. Between each use of the rotary tool the canals were rinsed with sodium hypochlorite and the patency of the apex was determined with an ISO10 hand tool. Following chemical and mechanical preparation an irrigation protocol comprising 5.25% sodium hypochlorite and 40% citric acid was followed. Both liquids were applied alternately in appropriate amounts and activated with ultrasonic tips as well as via the hydrodynamic manual method using gutta-percha cones. The canals were then dried with paper points (Kerr). Obturation was achieved through the continuous wave technique using gutta-percha cones with adjusted dimensions (Kerr), ElementsFree (Kerr) instruments and S-condenser (Obtura Spartan, Algonquin, USA) hand condensers. Following obturation a control X-ray was taken (Fig. 4).
Then the chamber was cleaned of the sealer and the rest of the gutta-percha with round burs on a low-speed handpiece, 40% citric acid and microbrushes. In addition, the OptiBond XTR (Kerr) adhesive system was applied. The floor of the pulp chamber was closed, and the undercuts blocked with Herculite Ultra Flow (Kerr) liquid composite. The cavity was temporarily filled with glass-ionomer and the preparation for prosthetic restoration delayed by around 4 weeks due to significant invasiveness of this procedure to gingival papillae around the restoration (Fig. 5).
During the next visit the site was isolated with an OptiDam (Kerr) rubber dam, the temporary material removed, and the preparation surface area cleaned with citric acid, distilled water and a brush on a low-speed handpiece. The fitting of the prosthetic restoration was checked with Take-1 (Kerr) wash silicone material and the contacts points were checked with articulating paper (Bausch GmbH, Cologne, Germany). The prosthetic restoration was then degreased with isopropyl alcohol and silanized and the IDS surface cleaned once more and roughened with a diamond bur. The approximal walls of the teeth adjacent to the cemented restoration were protected with Teflon tape so as to prevent cement residues from sticking (Fig. 6). Then NX-3 dual cure cement (KerrCompany) was placed on the onlay and the onlay itself placed on the stump of the tooth and then pressed in place (Fig. 7). The excess was removed with a microapplicator and dental floss. The site was then initially polymerized with a curing lamp. After waiting five minutes for the completion of the chemical polymerisation the site was polished with HiLusterPLUS Polishing System and the Occlubrush toothbrushes supplied by Kerr. The occlusal fitting of the restoration was checked once more and a control X-ray taken following cementation to ensure no cement remained and the restoration was well adjusted (Figs 8,9). The patient was instructed to make follow-up visits at 6 and 12 months.
A female patient sought treatment for periodically recurring pain of low severity. A CT scan showed that the previously treated root canals had been not filled to the entire length and there was an absence of any preparation in the MB2 canal (Fig. 10).
During the next visit root canal retreatment was performed under local anaesthesia and with an OptiDam (Kerr) rubber dam. For this purpose, following removal of the temporary filling the chamber was disinfected with sodium hypochlorite.
After preparing the coronal third of the canal the second MB mesiobuccal canal was checked to determine if it had connected with the first MB. With this aim in mind a gutta-percha point was placed in canal MB1 while canal MB2 was prepared with a size 10 C-pilot hand file up until the first sign of resistance. After each use of the hand file the gutta-percha cone was extracted from canal MB1 and examined for any traces from the tip of the hand file (Fig. 12). Next, the working length of canal MB2 up to the connection with canal MB1 was determined and the canal was prepared with Twisted File rotary tools, sizes 25/08 and 35/06.
Following chemo-mechanical preparation, it was irrigated with 5.25% sodium hypochlorite and 40% citric acid. Both liquids were applied alternately in appropriate amounts and activated with ultrasonic tips as well as by means of the hydrodynamic manual method using gutta-percha cones. Then the canals were dried with paper pins (Kerr). Obturation was achieved through the continuous wave technique using gutta-percha cones with adjusted dimensions (Kerr), ElementsFree (Kerr) instruments and S-condenser (Obtura Spartan, Algonquin, USA) hand condensers and control X-rays taken at two different angles (Figs 13,14).
The success of modern root canal treatment depends in great measure upon decontamination of the endodontic system. The first step essential for achieving this goal is chemo-mechanical preparation. This action is performed with two main objectives in mind. First of all, we mechanically remove live and/or dead pulp, depending on the diagnosis, dentine shavings and biofilm by making a kind of curettage of the root canal walls – shaping the root canal. This procedure creates a place for the irrigants, which, when properly applied, improves the quality of the canal obturation and the treatment outcome. The final stage of root canal treatment is obturation. Ensuring correct, hermetically-sealed, three-dimensional obturation will likewise have an impact on the result of our treatment. According to a study conducted by Ray HA., Trope M., long-term follow-ups show that hermetic build-up and restoration of a tooth is more important than perfectly executed endodontic treatment. While it is thus important not to neglect the endodontic procedure, we should also pay greater attention to the restoration of the tooth following treatment.
When considering whether to use an adhesive prosthetic restoration several factors should be taken into consideration. Above all else the degree of damage to the hard tissue of the tooth should be assessed. At this stage of the assessment three factors are important: the thickness of the available walls, tissue damage in relation to the gingiva and the amount of available enamel. Ideal for restoration would be a tooth with Black class I defect, or possibly class II, but unilaterally. Statistically, in the case of a premolar, Black class II defect in a MOD configuration results in a 63% loss of cusp rigidity. In the case of a molar, a wall considered full-value, i.e. where the cusps require no coverage, should have a thickness of at least 2mm along the entire surface in the case of a wall with balancing cusps and 3mm in the case of walls with working cusps. The author’s own clinical observations show that teeth which require endodontic treatment often possess hard dental tissue defects in a MOD configuration, and wall thicknesses of 2 mm and 3 mm, respectively, are rarely seen. Hence, indirect restorations with cusp coverage are common in clinical practice. Likewise, carious defects in approximal walls often reach subgingival areas. In such cases, following preparation of such a defect taking an accurate impression and ensuring hermetically sealed adhesive cementation of the prosthetic restoration is greatly impeded and sometimes downright impossible, Hence, one idea that has been proposed is that of supragingival elevation, i.e. Deep Margin Elevation. The purpose of this procedure was to ensure smooth passage of the gingival wall and a hermetically sealed restoration by means of a flow-type composite whose border extends into the supragingival region and produces a contact point with the neighbouring tooth. Performing this procedure prior to endodontic treatment additionally ensures four-wall containment of the defect and allows for the placement of a rubber dam.
Following preparation of the tooth, regardless of whether we are planning an endocrown or an onlay, one procedure worth implementing is that of Immediate Dentin Sealing. According to a study conducted by Pascal Magne the strongest bond between adhesive systems and dentin occurs directly after the preparation of the latter. Hence, the concept of IDS provides for the application of the adhesive system immediately following the preparation of the dentin and then applying adhesive system once more during the course of cementing the adhesive restoration. This approach ensures the greatest bonding strength between the prosthetic restoration and the dentin. Prior to taking the impression of the prosthetic area the oxygen inhibited layer should be removed. It is also important not to disturb the polymerisation of the impression material in contact with the IDS covered surface. We can do this, for example, by washing the area with isopropyl alcohol.
Besides ensuring perfect isolation of the treatment area with the help of a rubber dam, one of the key factors at the cementation stage is choosing the right luting cement. A significant factor determining the choice between light-curing cement and dual curing cement is the thickness of the prosthetic restoration. If the thickest part of the restoration does not exceed 2.5 mm we can use light-curing cement. In the case of thicker restorations dual-curing cements are recommended on account of the poorer distribution of light provided by a polymerisation lamp.
Root canal treatment combined with a hermetically sealed restoration offers the best chance of treatment success. Using technologies available in endodontics, such as nickel-titanium instruments, suitable irrigation liquids activated, among other things, by ultrasonics allows for the best possible decontamination of the endodontic system. Hermetic obturation of the root canal system and a permanent restoration safeguard against reinfection and ensure patients a functioning bite for many years.