Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
ENDODONTIC POST SYSTEM
Document Type and Number:
WIPO Patent Application WO/2014/201543
Kind Code:
A1
Abstract:
An endodontic post system for placing a post into a prepared canal space following a root canal procedure comprises a biocompatible, non-corrosive filling material and a biocompatible, non-corrosive rigid or semi-rigid post having a length and a longitudinal taper, at least a portion of the length of the post being substantially coungruent along at least a portion of its length with at least a portion of the canal space. In some preferred embodiments the post comprises a lumen.

Inventors:
YARED GHASSAN (CA)
DE-DEUS GUSTAVO (BR)
Application Number:
PCT/CA2014/000502
Publication Date:
December 24, 2014
Filing Date:
June 16, 2014
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
YARED GHASSAN (CA)
DE-DEUS GUSTAVO (BR)
International Classes:
A61C5/40; A61C5/50
Foreign References:
US20030148247A12003-08-07
US6183253B12001-02-06
Attorney, Agent or Firm:
EISEN, Mark B. (The Toronto-Dominion Centre77 King Street West,Suite 201, P.O. Box 301 Toronto Ontario M5K 1K2, CA)
Download PDF:
Claims:
CLAIMS:

1. For use with an endodontic post system comprising a non-corrosive, biocompatible filling material for insertion into a root canal space created during a root canal procedure, a non-degradable rigid or semi-rigid post having a length and a longitudinal taper, the post being substantially congruent, along at least a portion of its length for insertion into the root canal space, with a portion of the canal space.

2. The post of claim 1 wherein post is substantially congruent along its entire length with a portion of the canal space.

3. The post of claim 2 wherein the filling material comprises an obturating cone having a length and a longitudinal taper and the post is substantially congruent, along at least a portion of its length for insertion into the root canal space, with at least a portion of the filling element.

4. The post of claim 3 wherein the post is substantially congruent with the obturating cone along an entire length of the obturating cone.

5. The post of claim 1 comprising a lumen extending at least partially through the post.

6. The post of claim 5 wherein the lumen extends fully through the post.

7. An endodontic post system, comprising a non-corrosive, biocompatible filling material for insertion into a root canal space created during a root canal procedure, and a non-degradable rigid or semi-rigid post having a length and a longitudinal taper, the post being substantially congruent, along at least a portion of its length for insertion into the root canal space, with a portion of the canal space.

8. The post system of claim 7 wherein the post is substantially congruent with the canal space along the entire length of the post.

9. The post system of claim 7 wherein the filling material comprises an obturating cone having a length and a longitudinal taper and the post is substantially congruentj along at least a portion of its length for insertion into the root canal space, with at least a portion of the filling element.

10. The post system of claim 9 wherein the post is substantially congruent with the obturating cone along an entire length of the obturating cone.

11. The post system of claim 7 comprising a lumen extending at least partially through the post.

12. The system of claim 11 wherein the lumen extends fully through the post.

13. A method of sizing a post in an endodontic post system comprising a non- corrosive, biocompatible filling material and a non-corrosive rigid or semi-rigid post having a length and a longitudinal taper, for insertion into a root canal space created during a root canal procedure on a tooth having a root and a crown, , the method comprising the steps of: a. following preparation of the canals determining a size of the canal space, b. selecting a post which most closely matches the size of the canal space, for insertion into the canal space, c. measuring a space remaining in the canal after insertion of the filling material, and d. in any order, i. trimming a tip of the selected post to fit in the canal space abutting the filling material, and ft. trirrrmmg a head of the post to leave a space in the crown.

14. The method of claim 13 wherein the filling material comprises an obturating cone having a length and a longitudinal taper, the size of the canal space being determined in step a. by the size of the obturating cone and the post being selected in step b. to be substantially congruent with the obturating cone along at least a portion of its length.

15. The method of claim 13 wherein wherein the filling element comprises a fluid filling material and the size of the canal space is determined in step a. by the size of the largest engine-driven instrument used to prepare the canal space and the post is selected in step b. by selecting a post which most closely matches the size of the largest engine-driven instrument used to prepare the canal space.

16. The method of claim 13 wherein the filling element comprises an obturator comprising a carrier coated with the filling material, the size of the canal space is determined determined in step a. by inserting different sizes of size verifiers and selecting the size verifier with the closest fit, and the post is selected in step b. by selecting a post which most closely matches the size of the selected size verifier.

17. The method of claim 13 wherein the post comprises a lumen extending at least partially through the post.

18. The method of claim 17 wherein the lumen extends fully through the post.

Description:
ENDODONTIC POST SYSTEM FIELD OF THE INVENTION

[0001] This invention relates to endodontic equipment. In particular, this invention relates to an endodontic post system for augmenting support for a crown after a root canal procedure.

BACKGROUND OF THE INVENTION

[0002] An important endodontic procedure, known as a "root canal" procedure, involves removing organic material from the root canals of an infected tooth and filling the canal with an inert obturating material such as gutta-percha gum.

[00031 An effective root canal procedure avoids extraction of the infected tooth. In this procedure, a dentist or endodontist utilizes a series of endodontic instruments, for example files, for the debridement, cleaning and sterilization of the root canal. These files are rotated within the canal to clean the canal surfaces, removing debridement (organic) material in the process, facilitating improved irrigation, and in some cases shaping the canal for easier filling with the obturating material.

[0004] Once the root canal treatment has been completed, the restoration of the tooth should be performed as soon as possible to restore teeth for functionality and comfort, and also to re-establish aesthetics. However, frequently root canal-treated teeth have decayed to the point of significant loss of tooth structure, making the restoration of the tooth with a filling or a crown (cap) challenging due to the lack of adequate and sound tooth structure to support these restoration structures.

[0005] In such situations, a peg or "post" may be positioned within one of the roots to support the subsequent filling or cap. Such posts can be made from different materials, and are characterized by their rigidity, being able to resist strong masticatory functional loads, and resistance to corrosion or decomposition.

[0006| According to conventional techniques, an additional enlargement of the filled root canal space is required to accommodate the post. This additional enlargement, conventionally created by a drill bit, extends through the coronal- and middle-thirds of the root canal space and usually does not involve the apical part of the root. However, the additional enlargement of the root canal space will weaken the tooth strength and subject the root to additional physical stresses, which can cause the formation of cracks, dentin defects and root fractures, ultimately leading to tooth loss. Accordingly, even though this procedure is standard, it is contrary to the standard of care principles of tooth structure preservation and conservative treatment, which are essential for the longevity of root canal-treated teeth. Also, root perforation leading to tooth loss may occur during the additional canal enlargement.

[0007] Under optimal clinical conditions, access to the root canals through the crown and the canal enlargement must be effected in such a way as to preserve dentin tissue as much as possible. Dentists are becoming more aware a) that the mechanical enlargement of the root canal space should attempt to preserve dentin tissue, especially in the critical coronal part root, and b) the failure to respect dentin preservation, mainly in that area, following the creation of a post space and the placement of the post will likely lead to loss of the tooth. Whenever possible coronal and radicular tooth structure should be conserved. Decreasing the thickness of root dentin, especially in the ovoid and fluted root canals, mainly in lower molars, predisposes the root to fracture (Clark D, Khademi. Modern molar endodontic access and directed dentin conservation. Dent Clin North Am. 2010 Apr; 54 (2): 249-73). Directed dentin and enamel conservation is the only proven method for buttressing an endodontically treated molar. No man-made material or technique can compensate for tooth structure lost in key areas of the pericervical dentin.

[0008] Ideally, preparation of a post space should not require any removal of additional radicular dentin beyond the requirements for root-canal treatment.

However, this is not possible with currently available post systems. Moreover, the additional enlargement of the root canal space to allow the placement of a post, frequently performed by rotary engine-driven drills following the completion of the root canal treatment, can lead to iatrogenic complications such as a root perforation and subsequent tooth loss.

100091 In practice the guidelines, principles and procedures for the creation of a post space and the placement of a post in a root canal are complicated and challenging, considering the large variation in the dimensions of treated root canals and the thickness of the roots, and in the posts' dimensions amongst the different commercial brands.

[0010] Following a root canal treatment and the restoration of the tooth, a root canal infection can develop. The root canal treatment may have to be re-done in order to eliminate the infection. This procedure is known as a root canal retreatment. The first step in the retreatment procedure consists of removing any restorations such as fillings, caps and posts, in order to gain access to the canals and remove the infection. For this reason, it is important that an implanted post can be easily and safely retrieved from the root canal space if a root canal retreatment becomes necessary.

[0011| Regardless of the type of post used, the procedure for removing a post can be technically very difficult and time consuming, requiring additional systems (typically known as 'post removal systems') and the use of ultrasonic devices. Consequently, post removal procedures are usually reserved to specialists such as endodontists. Overall, general dentists are not trained in post removal procedures, and frequently do not possess the additional equipment or skills required for such procedures. Post removal can also be associated with complications such as root fracture and root perforation which may lead to tooth loss. Some types of posts, such as ceramic and zirconium posts, are very difficult and sometimes almost impossible to retrieve from the root canal space. Therefore, retrievability should be considered when planning the placement of posts, in anticipation of the possibility of subsequent complications, as this can be a major obstacle in root canal retreatment procedures.

[0012] At least one study has shown that post-space preparation and the removal of a fiber-reinforced post may damage the root and result in dentine defects: Dentinal Damage After Removal of Fiber-Reinforced Posts, H. Shemesh et al., Journal of Endodontics 2012, Vol. 38, No. 3 (March), p. el 4. In some cases, the head of the post is inadvertently cut off during the removal of the restoration, which renders the post removal procedure even more challenging and time-consuming because it becomes more difficult to use available post removal systems and to apply ultrasonic energy to the post. Also, some available fibre posts may be hard to see due to their colour, which can be very close to that of the composite restorative materials; consequently, the likelihood of cutting the head of the post is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In drawings which illustrate by way of example only a preferred

embodiment of the invention,

[0014] Figure 1 is a side elevational cross-section of a tooth requiring a root canal procedure, prior to canal preparation.

10015] Figure 2 is a side elevational cross-section of the tooth of Figure 1 showing the canal following preparation for filling.

|0016| Figure 3 a side elevational view of an obturating cone used to fill the canal space in one type of post placement procedure.

[0017] Figure 4A is a side elevational cross-section of a post according to the invention for augmenting support of a filling or cap.

[0018] Figure 4B is an end elevation of the post of Figure 4A.

|0019| Figure 5 is a side elevational cross-section of the tooth of Figure 2 with the obturating filling material implanted in the root canal space.

|0020] Figure 6 is a side elevational cross-section of the tooth of Figure 2 showing the obturating filling material condensed in the root canal space.

[0021] Figure 7 is a side elevational cross-section of the tooth of Figure 2 showing post positioned over the obturating filling material.

DETAILED DESCRIPTION OF THE INVENTION

10022] The present invention is directed to a post system for the restoration of a root canal-treated tooth. The system of the invention utilizes posts 20 designed to match the dimensions (taper and various diameters at the different levels, and preferably the length) of the canal space, which may for example be filled with an obturating material composed of gutta-percha gum or an inert synthetic polymer such as Resilon (Trademark). The obturating material may be in the form of an obturating cone 10 which is selected to fit snugly within the prepared root canal. The post placement procedure in each case may be performed without further enlargement of the canal space as is required by conventional posts.

[0023] A post 20 according to the invention can be removed utilizing the same tools (e.g. endodontic files and instruments) that were used to prepare the canal for the retreatment procedure. Accordingly, no additional equipment or devices (such as special post removal systems or ultrasonic devices) are required for removal of the post 20. Further, the time required for the procedure and the associated cost of the procedure to the patient is significantly reduced. The cost to the practitioner is also reduced, because no specialized equipment is required for the procedure. Possible complications such as root fracture, additional root structure loss and damage to the surrounding tissues by heat generated during the use of ultrasonic energy are eliminated.

|0024] Also, a post removal procedure utilizing the post 20 of the invention will have a very short learning curve, because the same endodontic files and instruments that the practitioner (including for example a general dentist) is already using for canal enlargement during a root canal procedure can be used in the same manner to remove the post of the present invention. This will have a significant impact on dental curriculums and teaching, because utilizing the post of the invention, the post removal procedure will become an easy technique to teach and learn in dental schools.

|0025] The invention thus provides, for use with an endodontic post system comprising a non-corrosive, biocompatible filling material for insertion into a root canal space created during a root canal procedure, a non-degradable rigid or semirigid post having a length and a longitudinal taper, the post being substantially congruent, along at least a portion of its length for insertion into the root canal space, with a portion of the canal space.

[0026] The present invention further provides an endodontic post system comprising a non-corrosive, biocompatible filling material for insertion into a root canal space created during a root canal procedure, and a non-degradable rigid or semirigid post having a length and a longitudinal taper, the post being substantially congruent, along at least a portion of its length for insertion into the root canal space, with a portion of the canal space.

10027) In further embodiments the post is substantially congruent along its entire length with a portion of the canal space; the filling material comprises an obturating cone having a length and a longitudinal taper and the post is substantially congruent, along at least a portion of its length for insertion into the root canal space, with at least a portion of the filling element; the post is substantially congruent with the obturating cone along an entire length of the obturating cone; and/or a lumen extends partially or fully through the post.

[0028| The present invention further provides a method of sizing a post in an endodontic post system comprising a non-corrosive, biocompatible filling material and a non-corrosive rigid or semi-rigid post having a length and a longitudinal taper, for insertion into a root canal space created during a root canal procedure on a tooth having a root and a crown, the method comprising the steps of: a. following preparation of the canal, determining a size of the canal space, b. selecting a post which most closely matches the size of the canal space, for insertion into the canal space, c. measuring a space remaining in the canal after insertion of the filling material, and d. in any order, i. trimming a tip of the selected post to fit in the canal space abutting the filling material, and ii. trimming a head of the post to leave a space in the crown.

[0029] In further embodiments of the method, the filling material comprises an obturating cone having a length and a longitudinal taper, the size of the canal space being determined by the size of the obturating cone and the post being selected to be substantially congruent with the obturating cone along at least a portion of its length; the filling element comprises a fluid filling material and the size of the canal space is determined by the size of the largest engine-driven instrument used to prepare the canal space; the filling element comprises an obturator comprising a carrier coated with the filling material, the size of the canal space is determined determined by inserting different sizes of size verifiers and selecting the size verifier with the closest fit, and the post is selected by selecting a post which most closely matches the size of the selected size verifier; and/or the post comprises a lumen partially or fully through the post.

[0030] Figure 1 illustrates a tooth 2 requiring a root canal procedure. The tooth 2 comprises a crown 3 above the gum line and at least one root 4 below the gum line. The root 4 comprises a canal 6 which, during a root canal procedure, is cleared of organic matter and sterilized in preparation for an obturating filling material, as is well known, resulting in the cleared and debrided canal space 8 shown in Figure 2. The canal space is limited by the desirability of leaving as much pericervical (coronal) root dentin tissue as possible, and since the root 4 is tapered the canal space 8 is invariably also tapered if this principle is properly followed.

|00311 A typical filling material is gutta-percha gum or a synthetic obturating material such as Resilon (Trademark), which is inert and highly resistant to decomposition. The obturating material also provides the advantage of being very malleable when heated to temperatures that are not harmful to the tooth or its surrounding tissue, which allows the obturating cone 10 to be condensed and compressed into the canal space for a snug fit.

[0032] A conventional obturating cone 10 is illustrated in Figure 3. The obturating cone 10 has a length which preferably (but not necessarily) exceeds the cumulative length of the canal space 8 and the crown, so as to protrude from the tooth 2 when the tip of the cone 10 is fully inserted into the canal space 8, and a longitudinal taper.

|0033] An embodiment of a post 20 according to the invention is illustrated in Figures 4 A and 4B.

10034] The post 20 comprises a body 22 formed from a non-corrosive,

biocompatible rigid or semi-rigid material, for example fibre-reinforced composites or modified fibre-reinforced composites (or any other materials providing suitable physical characteristics for the manufacturing of posts and which can be filed with an endodontic instrument). The post 20 has a length and a longitudinal taper, such that at least a portion of the length of the post is substantially congruent with at least a portion of the length of the gum filling element 10, for reasons which are explained below. [0035] In the preferred embodiment, the post 20 comprises a lumen 24. The lumen 24 is small in diameter so as to maximize the thickness of the post body 22, but large enough to receive the tip of an instrument (not shown) such as an endodontic file for easy removal of the post 20 preceding a root canal retreatment procedure, as described in greater detail below. The lumen 24 extends at least partially though the post 20 longitudinally, preferably through the entire post 20. The lumen 24 may be empty, or may be filled (not shown) with a soft, inert filling material such as gutta-percha or Resilon gum, or any other biocompatible and stable material, which can be easily penetrated and removed with an endodontic instrument.

10036) A post 20 according to the invention can be manufactured in different dimensions, for example matching commercially available obturating cones 10. The length of the post 20 preferably does not exceed the length of the matching cone 10, but can be shorter than the length of the matching cone 10 at the head end 26, for practical reasons. The practitioner will typically trim or cut off the head 26 and tip 28 of the post 20 during the post placement procedure, depending on the desired depth of insertion into the canal space 8 and the desired extent of the post 20 in the crown 3, respectively.

10037) During a post placement procedure, following preparation of the canal 8, there are three methods which can be used for filling the canal: 1 ) an obturating cone 10 formed from gutta-percha gum is coated with a cement sealer (not shown) and placed in the canal space 8, as shown in Figure 5; 2) a fluid filling material such as warm gutta-percha, Resilon (Trademark) or another like material is injected into the canal using an injection device such as Obtura System (Trademark) for example; or 3) gutta-percha is inserted into the canal space 8 with the aid of a carrier such as Thermafil (Trademark) or GuttaCore (Trademark), for example.

[0038] Where an obturating cone is used the obturating cone 10 is dimensioned to match the size of the instrument used to prepare the canal, such that in its initial, uncompressed state it fits snugly within the canal space 8 as shown. The instruments used to prepare the canal for filling may be similarly dimensioned, or smaller, to create a canal space 8 complementary to the shape of the cone 10. Any small gaps between the cone 10 and the wall of the canal space 8 are filled by the cement sealer. [0039| Following insertion into the canal space 8, the obturating cone 10 is softened using a heating instrument and compressed into the canal space 8. At the same time the heating instrument melts away the outer portion of the cone 10 to make room for the post 20, as shown in Figure 6. The practitioner assesses the depth of the compressed portion 10a of the obturating material (in this case from obturating cone 10) and, knowing the length of the canal space 8 and crown 3, thus determines the length available for the post 20 (i.e. from the exposed surface 10b of the remaining obturating cone portion 10a to a desired position recessed within the crown 3 of the tooth 2).

[0040] The practitioner trims off the tip 28 to correspond with the longitudinal position of the exposed surface 10b of the obturating portion 10a within the canal space 8, for example at 28a in Figures 4A and 7, such that the diameter at the tip of the trimmed post 20a is substantially the same as the diameter of the exposed surface of the gutta-percha portion 10a so that when inserted the trimmed tip of the post 20a abuts the filling material 10. This provides substantial continuity of the taper along the cumulative length of the gutta-percha portion 10a and trimmed post 20a.

|0041) If necessary, for example if the remaining portion of the post 20 would protrude from the crown 3, the practitioner also trims the head 26 of the post 20 such that the outer end of the post 20 will terminate at the desired position recessed within the crown 3, for example at 26a in Figures 4A and 7. The trimmed post 20a is coated with cement and depressed into the canal space 8. The remaining open space in the crown 3 after placement of the trimmed post 20a is filled with a filling, such as a conventional composite filling curable by ultraviolet light, and if necessary finished with a cap cemented over the tooth.

|0042) The matching of the shape of the post 20 to the shape of the obturating cone 10 facilitates the custom-fitting of the post 20 to the tooth 2. The available space within the tooth 2 (i.e. length of the canal space 8 plus length of the opening through the crown) can be filled with any desired length of post 20 by selecting the length of the obturating cone 10 accordingly; to accommodate a longer section of post 20, the practitioner will leave a shorter portion of obturating cone 10a. In each case there is no interference with the taper of the canal space 8, which is equally complementary to each of the post 20 and obturating cone 10, so the practitioner is able to completely fill the canal space by trimming the post 20 and obturating cone 10 at the appropriate points, in the manner described above, so as to maintain the same taper along the cumulative length of the post 20 and obturating cone 10.

|0043| If the post needs to be removed for a canal retreatment procedure, the same instrument used to clear and debride the canal 6 can be inserted into the lumen 24. The instrument is used in a manner similar to debriding the canal; the movement imparted to the instrument dislodges the post 20 from the canal space 8, or files the post out of the canal in the direction of the crown 3. To facilitate the canal retreatment procedure the lumen preferably extends fully through the trimmed post 20, so that the endodontic instrument used to remove the post 20 can be inserted past the (trimmed) tip of the post 20. The use of a post 20 with a lumen will also render the post 20 of the invention easier for the practitioner to see when it is embedded in a composite restoration of a similar colour.

[0044] Once the post 20 has been removed the practitioner can remove the obturating portion 10a using the same instruments, and then complete the retreatment procedure. The physical stresses leading to tooth structure degradation and potentially thermal stresses (from ultrasonic devices) which can lead to damage of the tooth structure and the surrounding tissues, which are a hazard of the use of conventional post removal systems and ultrasonic devices, are avoided utilizing the post 20 of the invention due to the presence of the lumen in the post.

[0045] Where a fluid filling material is used, such as Resilon or another obturating material injected into the canal, the dimensions of the post will be selected to be similar to the dimensions of the largest engine-driven endodontic instrument used to prepare the canal. In this case the fluid filling material will be used to form the obturating portion 10a in the apical end of the prepared canal space, which is essentially determined by the dimensions of the largest engine-driven endodontic file used to prepare the canal. In this case the obturating portion 10a is formed by injection and compacting of the injected obturating material while still soft. [0046] In other cases an "obturator" is used, whereby the filling material is inserted into the canal with the aid of a plastic carrier such as Thermafil (Trademark) or GuttaCore (Trademark), for example. Such an "obturator" is formed from a coating of gutta-percha over the carrier the selection of the appropriate post size is typically determined by an instrument similar in shape to an endodontic instrument, known as a "size verifier". At the end of the canal preparation stage, the practitioner will try several differently-dimensioned size verifiers in the prepared canal. The carrier which is selected for the filling of the canal will best match the size verifier with the best fit in the canal; i.e. the largest size verifier that was capable of reaching the apical end of the prepared canal space. In this case, the selected obturator and post will have dimensions similar to the size verifier with the best fit and the obturating portion 10a is formed in the same fashion as in the case where an obturating cone 10 is used.

[0047] Embodiments of the invention having been thus described in detail by way of example only, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the claims.