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Pre-endodontic Build-up: Methods and Applications


May 2, 2012
by Bojidar Kafelov, DDS

Contemporary nonsurgical endodontic treatment includes several stages that have to be done lege artis in order to be successful:

• A good access cavity that reveals all of the canal orifices, facilitates instrument introduction, and serves as a reservoir for the irrigant;

• Mechanical instrumentation of the root canal system, which provides debridement of soft tissues and root canal filling remnants and prepares the root canal to a specific form in order to be obturated predictably;

• Irrigation with various liquids to remove all the infected tissues, open the dentinal tubules so they can be sealed properly, and disinfect the root canal system;

• Obturation of the canal system to seal the root canal from the orifice to the portals of exit;

• Final coronal seal, which according to the literature, is as important as the endodontic treatment itself.

The access cavity is the first critical step for well performed endodontic treatment, and it has to meet several requirements:

• Facilitate the removal of all pulp chamber contents;

• Permit the direct vision of the root canal anatomy openings;

• Facilitate the straight line introduction of endodontic instruments to the canal orifices and apical thirds;

• Provide a retention for the temporary filling material.

The question here is, “Are these requirements always fulfilled?” If one or several of these conditions are not met when the treatment begins, a pre-endodontic build-up is advised. A tooth that needs a root canal treatment rarely has an intact crown — nearly all of the cases have severe loss of tooth structure, making it difficult to place a rubber dam, maintain a dry field, and perform state-of-the-art endodontic treatment.

The scope of this article is the pre-endodontic build-up and the way I do it in clinical conditions.

When preparing a tooth for endodontic treatment, one faces several obstacles:

• The canal should be easily found when the RCT is initiated;

• The build-up should mimic the natural anatomic structures so they can be used as a guide for the access cavity;

• The build-up should be performed with all the adhesive procedures followed so it will last during the root canal treatment and provide support for temporization.

With the following cases, I want to show several different clinical situations which need a pre-endodontic build-up in order to restore the aesthetic and functional integrity of the treated tooth.

CASE 1
Severe loss of tooth structure in a molar (functional pre-endodontic build-up)
The patient, a 31-year-old female, came to our practice for dental treatment and prosthetic restoration of teeth 2.6 (#14), 2.7 (#15) and 2.8 (#16).The radiograph revealed that a very large amount of tooth structure was lost and an overhanging amalgam filling that irritates the gingiva on tooth 3.7 (Fig. 1). The patient was motivated to save the tooth, and after explanation of the treatment choices we decided to perform endodontic treatment and place a PFM crown. After cleaning the decay and the old amalgam filling (Fig. 2), it was clear that a pre-endodontic build-up was necessary due to functional reasons — the patient would experience discomfort during mastication, there is no way to temporize such a damaged tooth predictably, and the palatal gingiva would grow over the defect. A retraction cord (Ultrapak, Ultradent Products, Inc., USA) soaked with 20% ferric sulphate (Viscostat, Ultradent Products, Inc.) was placed in the sulcus to retract the soft tissues in order to be able to do the bonding procedures (Fig. 3). After a copious rinsing with water spray, a total-etch procedure was performed using 37% etching gel and a two-step bonding system with One Coat Self-etching bond (Coltene/Whaledent, Switzerland). The technique used to do the build-up was a version of the “Doughnut technique” that was modified for this case. Increments of flowable composite were placed and light cured for 20 sec. The remaining parts of the walls were built with Gradia AO3 (GC, Japan) (Figs. 4 & 5). After building the walls, they were finished using a sharp diamond bur and polishers. The final endodontic cavity was made and the endodontic treatment was initiated (Fig. 6). The cleaning and shaping was performed using ProTaper rotary files (Dentsply Maillefer, Switzerland) and the apical finishing was done with NiTi hand files (Fig. 7). After cleaning and shaping the root canal system, the canals were obturated using the squirting technique with the Beta device from B&L (Figs. 8 & 9). Then, a fiber post was placed and the final build-up was made using Gradia XBW so that the color of the pre-endodontic build-up will differ from the color of the final restoration (Figs. 10 & 11).

The final restorations were made by Dr. Svetoslav Velichkov (Figs. 12-17).

CASE 2
Severe loss of tooth structure in a molar (functional pre-endodontic build-up)
The patient, a 25 year-old female, is a sister of a friend and a colleague. She was referred to our office for endodontic retreatment of tooth 1.6 (#3) (Fig. 18). The initial situation was a fractured palatal wall deep under the gingival level. The bone level was not reached, and after assessing the tooth structures and the lack of vertical fracture, I, along with the patient and my colleague, decided that we would try to save the tooth. In order to have a predictable prosthetic rehabilitation, a crown lengthening procedure should be made. But before the crown lengthening, the soft tissues should be prepared and not inflamed. In this particular case, this objective can be obtained with the pre-endodontic build-up. The provisional build-up will make an artificial matrix that will help in contouring the soft tissues and reduce the inflammation. The overhanging soft tissues were removed with a diamond bur and the preparation margin was finished using a red finishing diamond bur. Very good haemostasis was mandatory and it was obtained again with a Viscostat soaked retraction cord (Ultrapak, Ultradent) and the soft tissues were prepared with the haemostatic gel as well (Figs. 19 & 20). A sectional matrix was placed to contour the build-up and was secured with a drop of flowable composite on the distal (Fig. 21). The walls were built with flowable composite G-aenial Flo and Gradia X-AO2 (GC, Japan). The walls were finished with soft polishing disks and polishers (Figs. 22 & 23). The endodontic treatment was started, and after the retrieval of the fractured lentulo in the DB root canal, the tooth was temporized with Ca(OH)2 paste for two weeks. When the endodontic treatment and post-endodontic build-up were completed, a crown lengthening procedure was advised.

CASE 3
Three-wall defect on an upper lateral incisor (aesthetic pre-endodontic build-up)
In this case, a 31 year-old female was referred for RCT of the four upper incisors. Fig. 24 is a photo of the initial situation in the condition in which she entered the referring dentist’s office. After the calculus removal and polishing, she came to our clinic for the endodontic treatment. The second right lateral incisor was the second in the treatment plan. Also, the radiograph revealed a huge carious lesion that involved the root canal system (Fig. 25). The first stage was to clean all the decayed hard tissues, but after the cleaning I had to perform a pre-endodontic build-up so that the patient could walk out of our clinic with a functional, and most of all aesthetic, tooth. All of the decayed tissue was removed, which left only half of the buccal wall and a few millimeters from the lingual (Figs. 26 & 27). A gutta-percha point was placed in the root canal to prevent the composite from entering the canal and obstructing the access (Fig. 28). The build-up was done using a flexible plastic matri
x, flowable composite resin G-aenial A2, and composite G-aenial A2 and AE (Figs. 29 & 30). After building the proximal contacts, the gutta-percha point was removed in order to build a smooth palatal surface. The build-up was finished and polished (Figs. 31 & 32), and after cleaning, shaping, and one week medication with Ca(OH)2, the canal was obturated with MTA due to its large apical diameter (Fig. 33).

CASE 4
Two-wall defect on a lower central incisor (aesthetic pre-endodontic build-up)
This patient was complaining from pain on percussion on tooth 31. The clinical examination showed a large decay on the distal side (Fig. 34) and the radiograph revealed that the decay had engaged the root canal system (Fig. 35). After cleaning the decayed tissues, a large disto-buccal defect was present (Fig. 36). A flexible plastic matrix was placed to form the distal contact point and a gutta-percha point was placed in the root canal so that the canal could be easily found during the access preparation (Fig. 37). A Total-etch procedure was performed (Fig. 38) and a single-bottle of self-priming bond was applied (XP Bond, Dentsply DeTrey). The material of choice for the pre-endodontic build-up was G-aenial Flo A2 (GC, Japan). The build-up was then polished and the patient was scheduled for endodontic treatment.

SUMMARY
The pre-endodontic build-up is a technique that is a very useful adjunct to endodontic treatment. The steps needed to do it are relatively easy and the build-up facilitates the rubber dam placement and the temporization of the tooth between visits. To summarize, the key points I adhere to for this treatment are as follows:

The materials of choice for the pre-endodontic build-up are flowable composite, composite resin (preferably bleach white or a shade that has a high contrast compared to the natural tooth), or a glass-ionomer cement.

If the tooth is going to be prepared for a crown, the build-up is ground from the inside. The purpose is to leave 0.5 — 0.7 mm to serve as a matrix for the final build-up. Then, during the crown preparation the build-up leftovers are removed.

The bonding procedure followed is always the Total-etch procedure with selective enamel etching for 30 sec., then applying the bonding agent, which can be a two-bottle system or a self-priming single bottle system.

The orifices of the root canal system should be blocked in order to prevent the composite resin or the bonding agent from penetrating the canal. This can be done using gutta-percha points, LC Block-Out resin (Ultradent Products, Inc.), or even a cotton pellet.

The contact points between adjacent teeth should be respected when possible.

The pre-endodontic build-up on frontal teeth should be made using the appropriate shades for the tooth so that the build-up will be as aesthetic as possible. OH

Dr. Bojidar Kafelov graduated from the Medical University of Sofia Dental School in 2009. He has completed many continuing education courses in the field of endodontics. He has published his first case report in 2011 in Roots Magazine (Roots 1/2011). He has been a practicing endodontist at the Svedent Dental Clinic full time since 2009 and is a member of the Bulgarian Endodontic Society and the Bulgarian Society of Aesthetic Dentistry. He can be reached at: b.kafelov@gmail.com

Oral Health welcomes this original article.

REFERENCES

1. Castellucci, A. (2004), “Endodontics” vol. 1, Edizioni Odontoiatriche Il Tridente, p. 344-347.

2. Heydrich, R. W. (2005). Pre-endodontic treatment restorations. A modification of the “donut” technique. Journal of the American Dental Association 1939, 136(5), 641-642.

3. Cohen S, Hargreaves KM. Pathways of the pulp. 10th ed. St. Louis, Mo.: Elsevier Mosby, 2010, p. 115-120.