Endodontic therapy provides opportunities to maintain teeth in function and improve the health of the dentition.
Reinfection may result due to coronal leakage through temporary fillings to the apex within 30 days and may be a significant contributing factor to endodontic failure. Khayat1 found that significant coronal dye and bacterial leakage following exposure of sealed root canals to artificial and natural saliva occurred within 30 days through to the apex.
Root fracture, another reason for endodontic failure may result from forceful obturation techniques such as lateral or vertical condensation of gutta percha.2-4 Lateral and vertical condensation with zinc oxide and eugenol (ZOE) or epoxy sealers, which has been the standard obturation method have demonstrated high fracture rates. Meister’s study5 suggested that excessive force during lateral condensation of gutta percha resulted in 84.38% of the fractures noted in a study of 32 cases of vertical fracture. Whereas, obturation with a single cone of gutta percha and a passive fit with a strong resin sealer resulted in more favorable results.6
This paper will address a fiber-reinforced obturator combined with an adhesive and sealer, called Fiberfill (Pentron, Wallingford, CT) which is biocompatible, bacteriostatic, strengthens the root structure, decreases apical and coronal leakage and provides anchorage for a restorative core.
APICAL AND CORONAL LEAKAGE
The long-term prognosis for endodontically treated teeth is greatly influenced by how well the coronal and apical seal are achieved. Two factors that influence the seal of the canal are the obturation method and the sealer.
Single cone techniques were significantly more effective than lateral condensation techniques regarding length of dye penetration.7 The single cone procedure provided an adequate apical seal against dye penetration, sealing the apical portion passively. Leakage was greatest in the laterally condensed samples with leakage most significant in the first 3 mm from the apex.8
Carrier delivered gutta percha was found to be superior to lateral condensation technique in terms of both core/sealer ratio and dye leakage.9 Condensation techniques (lateral and vertical) may remove sealer from the canal walls during the procedure so forceful obturation may not only increase vertical fracture potential but decrease the sealability of the obturation.10 It was also seen that cold lateral condensation has a higher proportion of specimens with leakage in canals with curvature greater than 20 degrees than in canals with curvatures less than 20 degrees. Therefore, gutta percha delivered to the apex in curved canals had lower leakage.11 Hence the carrier delivered gutta percha will allow better placement in the canal and improve sealability. The drawback is that the carrier or a portion needs to be removed in order to restore the tooth, possibly disrupting the apical seal in the process.
Although warm lateral condensation resulted in a poor obturation, it was the only thermoplasticized technique analyzed that did not produce significant volumetric changes between 0 min and 30 min. All the other thermoplasticized filling techniques showed important shrinkage during cooling.12
Thermoplastisizing and inecting the gutta-percha into the root canal was a fast and a relatively easy technique, but the resultant filling was no more denser, and was shorter apically than the laterally condensed gutta-percha.13 Lateral condensation specimens showed voids at the 1.5 mm section; no voids were detected in specimens filled by Ultrafil or Thermafil at any level.14 Thermoplastized carrier method gutta percha although having fewer voids, extruded out the apical foramen more than in the lateral condensation group owing to the greater difficulty in controlling the obturation material.15 The gutta-percha coated rigid carrier technique and the cold lateral condensation technique were equally effective in filling lateral canals. In filling the main canal, however, the coated rigid carrier technique was more effective.16
Filling of the canal, with warm gutta percha may show a lower dimensional stability over time then cold gutta percha. Comparison of dimensional stability of warm and cold gutta percha found a much higher permanent deformation (10x) in warm gutta percha, as well as having a variance in dimensional stability (+5.50 to +7.20).17,18
Endodontic sealers can be divided into different groups based on the main component of the sealer; calcium hydroxide (CaOH), zinc oxide and eugenol (ZOE) and epoxy resins.
Significantly less leakage has been reported with calcium hydroxide-containing sealers than with the traditional zinc oxide-eugenol sealers.19 Comparison of calcium hydroxide sealer with zinc oxide and eugenol sealer found CaOH has a sealing ability comparable to ZOE and can withstand long-term exposure to tissue fluids without significant leakage.20 Both laterally condensed gutta-percha and CaOH as the sealer or with a single master cone and the CaOH paste sealer demonstrated sealing ability.21
The greatest dimensional changes with regard to sealers take place within the first 4 weeks. Zinc-oxide-eugenol based sealers generally showed shrinkage ranging from 0.3 to 1%. The epoxy-based materials, AH 26 and AH 26 silver-free, exhibited a large, initial expansion of 4-5%. AH Plus expanded from 0.4% to 0.9% (after 4 weeks). Calcium hydroxide based materials show only minor variation round a baseline value of -0.14 to +0.19%. Bacterial penetration may be a real threat from sealers shrinking as little as 1%.22
Endodontic failure has been associated with leakage within the canal system following obturation. No matter what our intentions are following obturation of the canal system in the tooth, patients may delay restoration of the tooth that has been treated. Financial and time constraints often influence when the final restoration is completed.
Seventy extracted single-rooted mandibular premolars were studied to determine the length of time needed for bacteria present in natural human saliva to penetrate through three commonly used temporary restorative materials and through the entire root canal system obturated with the lateral condensation technique.23 The average time for broth contamination of access cavities closed with gutta percha (7.85 days), IRM (12.95 days) and Cavit-G (9.80 days) indicating that even in short periods of time normally seen between visits complete leakage may result. IRM long a common temporary material was shown to leak to a significantly higher degree then glass inomers.24 Glass-ionomer cement due to its adhesive nature may prevent bacterial penetration to the periapex of root-filled teeth over a 1-month period as compared to IRM or Cavit temporary restorations.25 Another important consideration with regard to the temporary restorations ability to prevent coronal leakage is how the material behaves under mechanical load and thermocycling. Non-adhesive temporaries show an increased percentage of marginal breakdown and increased microleakage after thermocycling and loading. There was no significant improvement with increased thickness of the temporary material.26-28
Studies confirm that a sound coronal seal is of paramount importance to the overall success of root canal treatment.29,30 Regardless of the obturation method the best rule is: a properly cleaned, shaped, and obturated tooth should be permanently restored as soon as possible.31 But, between visits an adhesive material will prevent leakage and contamination of the canal.
Coronal sealing ability is not the only factor to influence the seal of the canal and prevent apical leakage. How well the sealer adheres to the canal walls is also important. Smear layer can play a factor which may prevent sealer penetration into the dentinal tubules. The frequency of bacterial penetration through teeth obturated with intact smear layer (70%) was-significantly greater than that of teeth from which the smear layer had been removed (30%). Removal of the smear layer enhanced sealability as evidenced by increased resist
ance to bacterial penetration.32 The incidence of apical leakage was reduced in the absence of the smear and the adaptation of gutta-percha was improved no matter what obturation method was used layer.33,34,35 However, regardless of the obturation technique (Thermoplastized, lateral or vertical condensation or single cone) when a non-adhesive sealer was used leakage increased after 30 days.36
A significantly better seal (in both the apical and coronal directions) can be achieved when using the dentine bonding agent and resin obturation material.37 The better the adaption and penetration of the dentinal walls, the less leakage is to be expected along the entire root length.
BIOCOMPATIBILITY
The systemic affects of components of the sealer used may have distant affects in the body. As root canal sealers constantly dissolve when exposed to an aqueous environment for extended periods, moderate or severe cytotoxic reactions may result. Calcium hydroxide-based materials as a root canal sealer initially may result in a more favorable response to periradicular tissues.38
Eugenol, a key component of ZOE sealers, demonstrates an inflammatory reaction in polymorphonuclear cells.39 Mittal found that ZOE was severely toxic by 48 hours and gradually decreased over time.40 The cytotoxicity of six different zinc oxide-eugenol root canal sealers as tested by Briseno, determined the incorporation of [L-14C] leucine in human gingival fibroblasts that had been in contact with root canal sealers after setting for 24 and 48 h. showed a toxic potential increase.41 Apical leakage may not be the only source of leeching, small quantities of eugenol diffuse through the dentin to the pulp, which can be another source of toxic potential.42 Numerous authors have reported that zinc-oxide-eugenol sealers possess a marked cytotoxic and tissue-irritating potency, leading one to question its continued use.43
Epoxy resin sealers like AH26, contain small quantities of two mutagenic substances that may leech systemically, bisphenol A diglycidyl ether and formaldehyde.44 Resin-based sealers were found to cause a dose-dependent increase in genotoxicity, but no such effect was seen with the calcium hydroxide-based sealer (Sealapex). The highest level of DNA damage was induced by the resin-based sealers.45 Both AH26 and AH26 plus have shown toxicity to rat hepatocytes. Although, AH26 had a higher toxicity than AH26 Plus.46,47 As with eugenol containing sealers, epoxy resin sealers results can cause cytotoxicity in hepatocytes and can also cause oxidative stress in hepatocytes.
Agar diffusion tests to determine cytoxicity with fibroblast cells found AH26 and AH26 plus did not meet the requirement and were cytoxic.48 The affects on human fibroblast has shown cytotoxicity and may prevent resolution of periapical lesions when epoxy resin sealers are utilized.49 This leads one to conclude that sealers with formaldehyde-releasing materials should no longer be applied in practice because safer alternatives are available. Ca(OH)2-based sealers are rated as possessing good or excellent cytocompatibility.50,51
Calcium hydroxide based sealers when in contact with tissue had enhanced healing when compared to the other sealers.52 Cytotoxicity as compared to other type sealers, CaOH was lower than both ZOE and epoxy resin materials.53
ANTIMICROBIAL AFFECT
Siqueira indicated that endodontic sealers containing calcium hydroxide presented satisfactory physicochemical properties when compared with a zinc oxide-eugenol sealer commonly used in endodontics. Calcium hydroxide based sealers alkalinized the surrounding medium, which will create an environment that does not favor bacterial growth making these materials bacteriostatic.54 CaOH sealers demonstrate pH greater then 7.0 making a higher alkaline level then resin based sealers which had a pH level less then 7.0.55 With regard to antibacterial activity, although ZOE based sealers are more potent, CaOH containing sealers are less cytotoxic.56,57
ROOT REINFORCEMENT
Endodontically treated teeth are under increased possibility of vertical fracture. Most fracture lines occurring in a buccolingual direction. Instrumentation of the root canals significantly weakened the roots.58 Lertchirakarn found that teeth which had the canal filled with an adhesive material (glass ionomer) resisted vertical fractures. Force that fracture of roots obturated with glass ionomer was significantly higher than those obturated with epoxy resin or ZOE sealer. The results suggested that adhesive sealers strengthen endodontically treated roots and may be used for weak roots, which are likely to be susceptible to vertical root fracture.59 Significant strengthening of the root structure could be demonstrated by use of adhesive sealers. This was supported by Trope, who found that bonded resin techniques significantly strengthened teeth against fracture.60
THE FIBERFILL SYSTEM
The Fiberfill system consists of an adhesive bonding agent, a light-curable CaOH based resin sealer and a fiber post with an apical terminus of gutta percha (Fig. 1).
A primer included in the system is a self etching two bottle liquid that allows the sealer to chemically bond to the canal dentin. The primer is a self curing adhesive.
The Fiberfill root canal sealer (RCS) is a radiopaque dual cure resin sealer, which contains; UDMA, PEGDMA, HDDMA, and BISGMA resins with silane treated bariumborosilcate glasses, barium sulfate, calcium hydroxide with initiators. The material comes in a two barrel automix syringe. Once mixed it provides a working time of 10-12 minutes and a self cure setting time of approximately 25 minutes. It provides a depth of light cure of 1.7mm with a final Barcol hardness of 80.
Pameijer, evaluated Fiberfill RCS with regard to cytotoxicity using L929 cell cultures in an agar medium, according to ISO 10993-5 (1992) and ISO 7405 (1997). Based on zones of decolonizations and cell lysis after 24 and 48 hours were consistent and no decolonization and cell lysis were observed. It was determined that Fiberfill RCS was non-cytotoxic.61 He further evaluated its potential to induce histidine reversion and tryptophan reversion in the genomes of Salmonella typhimurium and Eschericia coli, a test to determine genotoxicity. Fiberfill was determined to be non-mutagenic.62 Oral irritation and sensitization of buccal tissues (golden hamsters) was tested by acute exposure comparing injection of 0.9% USP sodium chloride, cottonseed oil and extracts of Fiberfill RCS. Exposure was set at 5 minutes every 4 hours. No erythema or edema was demonstrated and histological evaluation found Fiberfill RCS to be non-irritating to the tissue. Contact allergenicity was also tested in guinea pigs. While the tests can be extrapolated to humans, the test does not establish actual risk of sensitization Fiberfill RCS elicited no reaction to the challenge and showed 0% sensitization.63
The Fiberfill obturator is a resin and glass fiber post with a terminal gutta percha tip. The gutta percha is available either in 5 or 8mm lengths (Fig. 2). The diameter of the post is available in sizes 30, 40, 50, 60, 70 and 80.
The canal is instrumented using hand instruments, rotary niti files or a combination and cleaned using standard irrigation methods. An obturator is selected that matches the final diameter of the canal. The yellow Peeso reamer (included in the kit) is introduced into the canal set either to 5 or 8mm from the working length. Next, the blue Peeso reamer (also in the kit) is taken to the same depth as the previous reamer. The canal is irrigated, disinfected and dried. A drop of primer A and B are mixed in a dish and applied in the canal with the kits spiral brush. The brush tip is introduced to the depth made by the Peeso reamers. An automix tip is placed on the Fiberfill RCS syringe and the sealer is introduced into the canal with a lentulo or other sealer applicator. The obturator is gently seated to working length allowing excess sealer to be expressed coronally. The dual cure Fiberfill RCS is light cured to stabilizer the coronal portion. Additional
primer is applied on the protruding portion of the obturator post and over any dentin and enamel that will be in contact with the core buildup material. A resin core buildup material in then injected around the post filling the coronal portion of the tooth. The material is light cured and ready for either crown preparation or dismissal of the patient. The result is a durable restoration with a resin/fiber reinforced root that is optimally sealed apically and coronally (Fig. 3).
Leakage was tested with extracted single rooted human teeth. The coronal portion was removed with a diamond disk following storage in 10% formalin for up to 2 weeks. The teeth were divided into two groups and group 1 was treated as described above using the Fiberfill technique. Group 2 was treated with a master gutta percha cone fit to working length and sealed with Roth’s sealer. All teeth were then stored at 37C in deionized water for 4 days. The root surface was coated with fingernail polish leaving a 1mm uncoated zone around the apex and coronal margin. Specimens were then immersed in 5% methylene blue for 18 hours. They were then removed, lightly scrubbed and the fingernail polish removed with the aid of a scalpel blade. Teeth were wet ground and examined under a microscope under 25x to measure dye penetration. There was no significant difference in the apical leakage between both groups. But there was significantly less coronal leakage for the Fiberfill specimens then the lateral condensation group64 (Fig. 4).
Based on studies regarding resin root reinforcement65,66 it is expected that the Fiberfill system should demonstrate similar increases in root strength. Further, studies are currently underway with the Fiberfill system.
CASE STUDIES
Case One
A 42-year-old male presented with pain with cold and percussion on tooth 20 (lower left 1st premolar). A large distoocclusal composite filling was present and radiographic examination showed the restoration to be close to the distal pulp horn with a widening of the lateral periodontal ligament space on the mesial of the root. Cold testing produced a lingering pain and the diagnosis was made of irreversible pulpitis. Treatment was to include; endodontic therapy, post and core and full coverage crown (Fig. 5).
Following administration of a local anesthetic the tooth was isolated with a rubber dam. Access was prepared through the occlusal surface and working length (WL) was established with the aid of an electronic apex locator. Working length was established at 23mm. The canal was irrigated with 17% EDTA (ethylenediaminetraactic acid) and the yellow Peeso reamer was measured to 15mm (8mm less the WL) and introduced into the canal. Similarly, the blue Peeso reamer was taken to 15mm. The apical 8mm was then cleaned and shaped with 0.04 taper niti files to a size 60. The canal was rinsed with 5% sodium hypochlorite and an ultrasonic file was introduced to within 2mm of the WL. Thirty seconds of agitation with the ultrasonic file assisted in dispersing the disinfectant and loosen any debris. The canal was then rinsed with 2% chlorhexidene and dried with paper points.
The primer was applied within the canal with the spiral brush and excess material was removed with a paper point. The Fiberfill RCS was introduced into the canal with a lentulo until the canal was filled. Next, the Fiberfill obturator gently seated and light cured. The post was trimmed with a diamond using a high speed and water to the desired length. A core was constructed using Buildit FR (Pentron, Wallingford, CT) (Fig. 6).
Follow-up with the patient at 18 months post treatment revealed absence of pathology where excess sealer had been expressed through a lateral canal.
Case Two
An 85-year-old female patient presented with carious breakdown of the distal, buccal, lingual and occlusal surfaces of the lower left second premolar (tooth 28). Tooth was asymptomatic and the patient indicated that she “had lost an old filling.” Pulpal exposure was noted on clinical examination and radiographically, a periapical area was observed (Fig. 7).
Local anesthetic was administered and isolation was achieved with a rubber dam. Decay was removed and working length established with a number 15 K file and electronic apex locator. Working length was determined to be 22 mm. The canal was instrumented sequentially with size 20 and 25 K files. The canal was then irrigated with 17% EDTA, followed by 5% NaOCL. The canal was shaped and enlarged with K3 files (Kerr Sybron) with a .04 taper sequentially to a size 30. Reirrigation with EDTA and NaOCL to remove any remaining organic matter and smear layer was performed with ultrasonic files. The yellow Peeso reamer was measured to 17mm (5mm less the WL) and introduced into the canal. Similarly, the blue Peeso reamer was taken to 17mm. The canal was then rinsed with 2% chlorhexidene and dried with paper points.
A spiral brush was used to apply the primer to the canal walls to the depth achieved by the Peeso burs. A paper point was introduced to remove any excess primer. The Fiberfill RCS was introduced into the canal with a Centrix tip (Centrix) and a lentulo was used to coat the canal walls. A Fiberfill obturator (size 30 with a 5mm gutta percha apical portion) was gently seated to working length and light cured. A core was constructed using Buildit FR and the post was trimmed with a diamond using a high speed and water to the desired length. The core was shaped to restore the tooth morphology (Fig. 8).
Case Three
A 50-year-old patient presented with pain and percussion sensitivity on tooth 8 (upper right central incisor). A porcelain fused to metal crown was present on the tooth and radiographically periapical pathology was noted (Fig. 9). Isolation was achieved with a rubber dam. Access was then performed through the lingual of the crown. Canal patency was performed with a number 15 K file and working length was established with an electronic apex locator at 25mm. A rubber stopper was set on the yellow Peeso bur at 17mm (WL – 8mm) and introduced into the canal. This was followed by the blue Peeso set at 17mm. The canal was irrigated with 17% EDTA followed by 5% NaOCL. The apical 8mm was then instrumented using rotary NiTi K3 files with a .04 taper. A final irrigation was performed with 17% EDTA, 5% NaOCL followed by 2% chlorhexidene.
The canal was dried with paper points. Fiberfill adhesive was introduced into the canal with a spiral brush and excess removed with a paper point. Fiberfill RCS was placed into the canal with a lentulo to ensure coating of the canal walls. A size 60 Fiberfill obturator with a 8mm apical gutta percha segment was gently placed into the canal. Light curing was performed for 60 seconds and the extra length of the obturator was removed with a tapered diamond in a highspeed handpiece with water. The access opening was etched with 35% phosphoric acid gel, allowed to remain for 30 seconds and rinsed with water. The site was air dried and then coated with Bond1 adhesive (Pentron, Wallingford, CT, US). Simile, a light curable hybrid composite (Pentron, Wallingford, CT) was placed to fill the lingual of the crown to a normal contour and light cured (Fig. 10). Excess sealer was noted apically. The patient returned for routine care at 12 months and the tooth was examined radiographically. The excess sealer was noted to have resorbed and the patient indicated the tooth remained sensitivity free (Fig. 11).
CONCLUSION
So how do we define success in endodontics? Clinical absence of pain was found to not be indicative of endodontic success. A better evaluation may be the absence of continued or new periapical pathology.
CaOH based sealers have been shown to be non-cytotoxic, well accepted by the periapical tissue, bacteriostatic and stable dimensionally following placement. Carrier introduced gutta percha can provide a predictable obturation of the canal with minimal force compared to lateral condensation techniques. It has also been documented that resin reinforcement of the root structure can significantly increase the fracture resistance of the tooth.
The Fiberfill
system has incorporated these factors into its design and offering a safe, predictable and simple obturation method. Coronal leakage is eliminated by use of an adhesive sealer that is non-irritating to periapical tissue with a pH in the alkaline range thereby creating a bacteriostatic environment in the canal. The obturator, a fiber post (used to restore hundreds of thousands of teeth over the past 10 years) is adhesively bonded within the tooth during the obturation sealing the coronal portion and providing retention for the core. The gutta percha terminus on the obturator permits retreatment of the canal should it become necessary. In multi-rooted teeth the adhesive and sealer can be used with a single gutta percha cone to obturate the smaller canals.
Abstract
The high failure rate reported in the literature of endodontic procedures to achieve a seal apically may be related to coronal leakage. This is influenced by the material used to obturate the canal, the method of obturation and the restoration placed at the conclusion of the endodontic treatment. Instrumentation of the canal significantly weakens the strength of the root. This can lead to an increase in root fracture. The Fiberfill system addresses these potential problems by providing an adhesive sealer that is a calcium hydroxide based resin that reinforces the root structure. This provides a non-cytotoxic, non-irritating safe predictable method to treated teeth requiring endodontic therapy.
Dr. Kurtzman is in private practice in Silver Spring, Maryland and is an Assistant Clinical Professor at the University of Maryland School of Dentistry, Department of Restorative Dentistry. He has lectured both nationally and internationally on the topics of Restorative dentistry, Endodontics and Dental Implant surgery and prosthetics.
Dr. Lopez maintains a private practice in San Antonio, TX. His clinical emphasis is complex restorative cases, Esthetics and TMJ/TMD disorders. Dr. Lopez has served as the president of the South Texas chapter of the American Academy of Cosmetic Dentistry and president of the San Antonio Pankey study club.
Dr. Jones is a Clinical Associate Professor Department of Endodontics and Director of Undergraduate Endodontics at University of Maryland School of Dentistry, Baltimore, MD.
Disclosure: Dr. Lopez helped to develop the Fibrefill system.
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