Site News  |   Monitor Keywords  |   Monitor Archive  |   Organizer  |   Account Info  |

Methods for chair-side coating of endodontic cones

Methods for chair-side coating of endodontic cones description/claims

This application is a division of U.S. application Ser. No. 11/691,052, filed Mar. 26, 2007, the disclosure of which is incorporated herein in its entirety.

1. The Field of the Invention

The present invention relates to the field of dentistry, more particularly to endodontic cones, such as those made of gutta percha, used in filling root canal chambers.

2. The Relevant Technology

When a dental practitioner performs a root canal, pulp and other material in the root canal chamber is removed. Once a dentist has removed diseased and soft tissue from a tooth's root canal, the chamber must be filled. The purpose of filling the root canal is to seal the area, and to eliminate the possibility of bacterial attraction and infection in the chamber. Filling and sealing the chamber is necessary to prohibit material from draining into the canal, which could attract bacterial contamination of the root canal chamber. In addition, filling the chamber provides a base that may be drilled out later for placement of one or more posts to which may be mounted a crown or other restorative appliance.

The current method of filling the root canal is by inserting shaped cones of gutta percha into the prepared root canal. Gutta percha typically includes a matrix of trans-isoprene, zinc oxide filler, a radiopacifier such as bismuth, barium or strontium, wax or resin, color pigment, plasticizers and other additives. One difficulty with using gutta percha has been that it does not readily bond to and seal against the tooth tissue. Tooth tissue is quite hydrophilic, while gutta percha itself is extremely hydrophobic. Typical endodontic pastes, used to bond and seal the gutta percha to the tooth tissue, comprise zinc oxide and eugenol. This mixture is also hydrophobic, and while it bonds quite well to the gutta percha, its bond with hydrophilic tooth tissue is often poor. In addition, eugenol is believed to act as a polymerization inhibitor, which can also result in poor bonding and sealing in the event polymericable resins are used.

Recently, hydrophilic resins have been developed which bond much better to tooth tissue, but they may still bond poorly to gutta percha because of its extremely hydrophobic nature. The result may be a root canal chamber that is not completely sealed, which increases the chance of irritation of the affected area or bacterial contamination, leading to infection and possible failure of the root canal. The level of discomfort and pain associated with an irritated, inflamed, and/or infected root canal area can be great, followed by loss of the tooth.

As one solution to this problem, U.S. Pat. No. 6,986,662 proposes providing an endodontic cone to which a particular adhesive coating has been attached during manufacture so as to render the cone more chemically compatible with a hydrophilic sealing resin. The adhesive includes a hydrophobic portion that is chemically compatible with the gutta percha substrate and a hydrophilic portion that is chemically compatible with a hydrophilic resin. The adhesive may be applied by dipping or brushing during manufacture. While such a manufactured endodontic cone appears to solve the problem of poor bonding between the tooth tissue, the sealing resin, and the gutta percha, the present inventors have found the manufacturing process including coating of the adhesive to be extremely messy and difficult to perform. For example, the adhesive can easily clog and gum up manufacturing equipment, requiring frequent shut downs, cleaning, and maintenance, which makes it difficult and relatively expensive to produce coated endodontic cones on a mass economic scale.

It would be an improvement in the art to provide kits and methods that would solve the poor bonding issues, while also minimizing or eliminating the difficulties and messiness associated with current manufacturing methods.

The present invention provides kits and methods that advantageously allow a practitioner to apply an adhesive coating to an endodontic cone chair-side just prior to inserting the coated cone into the root canal. The kit includes one or more endodontic cones formed of a hydrophobic elastomer substrate (e.g., gutta percha), each cone being sized and shaped so as to be at least partially insertable into an exposed root canal of a tooth. The kit also includes a micro-dose container containing an adhesive composition into which the endodontic cone is inserted so as to coat at least a portion of the cone with the adhesive composition and facilitate successful bonding between the hydrophobic substrate and a hydrophilic sealing resin used within the root canal. The micro-dose container advantageously has a length, diameter, and volume configured to accept the endodontic cone so as to allow the cone to be coated with the adhesive composition. For example, an exemplary micro-dose container may be sized so as to advantageously hold sufficient material to fill a single root canal. Such an exemplary micro-dose container may have a volume between about 20 and about 55 micro-liters, more preferably between about 25 and about 50 micro-liters, and most preferably between about 30 and about 40 micro-liters. The inside diameter of the distal portion of the chamber is preferably between about 0.04 inch and about 0.09 inch, more preferably between about 0.045 inch and about 0.07 inch, and most preferably between about 0.05 inch and about 0.065 inch. Wall thickness of the chamber is typically between about 0.02 inch and about 0.04 inch (e.g., about 0.025 inch). The overall length of the micro-dose container is preferably between about 0.75 inch and about 1.5 inches, more preferably between about 1 inch and about 1.25 inch.

The adhesive composition includes an adhesive resin compound comprising at least one hydrophobic region and at least one hydrophilic region. The hydrophobic region is compatible with the hydrophobic elastomer of the endodontic cone so as to chemically and/or physically adhere to the hydrophobic elastomer. The hydrophilic region is chemically compatible with a hydrophilic endodontic resin. The adhesive facilitates the formation of a good seal between the hydrophilic tooth tissue of the canal chamber and the endodontic cone, while the inventive kit and method facilitate coating of the endodontic cone(s) while overcoming the difficulties associated with coating during mass manufacture.

The endodontic cones may be dipped into the adhesive composition contained within the micro-dose container so as to coat at least a portion of the surface of the endodontic cone substrate. Advantageously, performing the coating chair-side by simply dipping the cone into the composition within the micro-dose container results in little or no mess. In addition no curing or powder coating is required to prevent adhesion between cones during shipment and storage. Because the hydrophobic region is compatible with the hydrophobic material comprising the endodontic cone, the hydrophobic region of the adhesive component will tend to orient itself toward the endodontic cone while the hydrophilic region will tend to orient itself away from the endodontic cone, thereby creating a hydrophilic surface on the endodontic cone.

Advantageously, it will often be unnecessary to cure the adhesive composition prior to insertion of the coated cone into the root canal, as the curable adhesive composition can be cured by components within the sealing composition used to seal around the endodontic cone within the root canal. Although not required, the practitioner may wish to partially or fully cure the adhesive composition and/or apply a powder coating so as to reduce adhesion between multiple coated endodontic cones. For example, this may be helpful if several cones are to be prepared, placed on a tray or other holding device chair-side, and then inserted into the prepared root canal.

In practice, the root canal chamber is prepared by removing diseased and surrounding tissue. The endodontic cone may be coated before or after preparing the root canal chamber. Once both of these steps have been completed, the coated endodontic cone is inserted into the chamber. One or more cones may be used as necessary so as to fill the chamber. An endodontic sealing composition is introduced into the prepared canal, which can then be cured to provide a good seal of the root canal chamber. When using a dipped endodontic cone that has not been cured prior to insertion, the presence of initiators within the sealing composition will advantageously initiate curing of the adhesive component within the adhesive coating, resulting in strong bonds between the hydrophobic elastomer substrate of the endodontic cone, the adhesive composition, the sealing composition, and the hydrophilic tooth tissue. A hydrophilic sealing composition, such as Endo-REZ, available from Ultradent Products, Inc., may be used, and will bond well to the tooth tissue because of its hydrophilic nature and its ability to penetrate into dentinal tubules. Once the root canal chamber has been filled, the hub of the cone may be removed.

These and other advantages and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

• Provisional Patent
• Utility Patent

• What Is a Patent?
• What Is a Trademark or Servicemark?
• What Is a Copyright?
• Patent Laws