- Email: [email protected]
Instruments for retreatment of root canals
posterior region were identified with the touch-probe scanner. Both scanners had repeatability within 10 µm. Relative accuracy was within ±6 µm for both digitization devices. Qualitatively, the optical digitizer produced an even distribution of the deviations. With the mechanical digitizer, the dominating part of the surfaces showed no deviations. Discussion.—The use of the laser scanner produced a point cloud with fewer points and a less-dense distribution than use of the touch-probe scanner. The touch-probe scanner is currently used in clinical settings and produces satisfactory clinical fit. The laser scanner could provide input in a manufacturing system for fixed dental prostheses. Both digitizing devices showed repeatability within the range of 10 µm.
Clinical Significance.—Two very different scanner technologies are available for CAD/CAM coping production. In this study, both mechanical and optical digitalizing devices produced acceptable results.
Persson A, Andersson M, Oden A, et al: A three-dimensional evaluation of a laser scanner and a touch-probe scanner. J Prosthet Dent 95:194-200, 2006 Reprints available from A Persson, Karolinska Institutet, Inst of Odontology, PO Box 4064, Alfred Nobels Allé 8, Huddinge SE-14104, Sweden; fax: 46-8-746-7915; e-mail: [email protected]
Endodontics Instruments for retreatment of root canals Background.—Nonsurgical retreatment is preferred for failing endodontic cases. In this approach, the original root canal filling material must be removed, further cleaning done, and the canal refilled. Removing all obturation material does not ensure the success of endodontic treatment, but removing as much as possible should help reveal necrotic tissues or bacteria that can cause periapical inflammation and failure of the restoration. Rotary instruments can reduce the clinical time needed to accomplish gutta-percha removal. FlexMaster instruments have been used to prepare curved canals quickly and with minimal straightening when compared with hand instruments. ProTaper instruments combine different tapers in one. The RaCe file system is a reamer with alternating cutting edges and is supposed to prevent threading or blocking and operate at an extremely low torque with improved efficiency. The ability of these 3 rotary instruments to handle guttapercha removal for curved root canal retreatment was investigated.
350 Dental Abstracts
Methods.—Four groups of 15 specimens each were used to assess the cleanliness of root canal walls after retreatment with the 3 systems or Hedström files. The specimens consisted of curved mandibular premolars with angles between 20° and 36° of curvature. All were enlarged and obturated with the use of the lateral condensation technique, then reprepared with the test instruments. Measurement of the area of any remaining obturation material was determined from 2 directions. Results.—Residual gutta-percha/sealer was present in the apical half of the root beyond the curvature in all the root canals that did not involve fractured files or other procedural errors. The groups did not differ significantly in the amount of residual gutta-percha/sealer present when assessed from the buccolingual direction, but imaging from the mesiodistal direction revealed significantly larger areas of obturation left in the Hedström file and FlexMaster groups than in the RaCe group. Adding the 2
results together, canals retreated with RaCe files had fewer areas of remaining obturation material than those retreated with FlexMaster files. When all root canals were considered, RaCe-treated canals had less remaining guttapercha/sealer than all the other canals when viewed from the mesiodistal direction. Thus, the high percentage of broken ProTaper and FlexMaster instruments affected the results. Neither the Hedström files nor the RaCe files fractured. Gutta-percha removal was significantly quicker with the use of Hedström files than with ProTaper and FlexMaster files. The use of RaCe instruments required significantly more time than the use of any of the other instruments. No significant differences were noted in the ability to remove obturation material extruded from the apical foramen. Discussion.—The RaCe rotary system was both safe and efficient in removing gutta-percha in curved root canals, but required considerably more time than the other instruments. ProTaper and FlexMaster instruments tended to fracture more often than RaCe and Hedström files, reducing their effectiveness for gutta-percha removal. With
respect to apical extrusion, all the groups were able to reduce apically extruded debris to similar degrees.
Clinical Significance.—Removal of old canal filling material and residual bacterial contaminants is an essential first step in salvaging a failing root canal-treated tooth. Of the systems tested here, 1 rotary, the RaCe from Switzerland, while not the fastest, proved effective and safe.
Schirrmeister JF, Wrbas K-T, Schneider RH, et al: Effectiveness of a hand-file and three nickel-titanium rotary instruments for removing gutta-percha in curved root canals during retreatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 101:542-547, 2006 Reprints available from JF Schirrmeister, Dept of Operative Dentistry and Periodontology, Albert-Ludwigs-Univ of Freiburg, Hugstetterstr 55, 79106, Freiburg, Germany; e-mail: [email protected]
Photo-activated disinfection Background.—A 94% success rate has been reported for endodontic treatment when negative cultures are obtained from the root canal. This rate falls to 68% when cultures are positive. A novel method of disinfection involves the use of photo-activated disinfection (PAD), in which photosensitizer molecules attach to the bacterial membrane. Singlet oxygen is produced with exposure to irradiation with light at a specific wavelength matched to the peak absorption of the photosensitizer. The oxygen kills the bacteria by rupturing the bacterial cell wall. The 2 components of the system have no effect on bacteria separately, but when the light and photosensitizer are combined, bacteria are eliminated. The bacterial load within the root canal walls was determined after initial access, immediately after conventional preparation, and after treating the canal with the PAD method.
Methods.—Microbiological effectiveness was determined at the times mentioned through samples of the dentin from the canal. The 14 patients all had symptoms of irreversible pulpitis or periradicular periodontitis that required endodontic therapy. The 3 samples from each canal were plated within 30 minutes of being obtained and cultured anaerobically for 5 days. Bacterial load was based on the growth of viable bacteria in each sample. Results.—Of the 32 canals evaluated, 30 had completed microbiological scores. Ten canals had negative cultures, 3 of which were in multirooted teeth that included other canals with high bacterial scores. Three others had inflamed pulpal tissues treated with a corticosteroid and topical polyantibiotic before extirpation. These cases confirmed no cross contamination of the canals occurred with
Volume 51 • Issue 6 • 2006 351
Clinical Significance.—Two very different scanner technologies are available for CAD/CAM coping production. In this study, both mechanical and optical digitalizing devices produced acceptable results.
Persson A, Andersson M, Oden A, et al: A three-dimensional evaluation of a laser scanner and a touch-probe scanner. J Prosthet Dent 95:194-200, 2006 Reprints available from A Persson, Karolinska Institutet, Inst of Odontology, PO Box 4064, Alfred Nobels Allé 8, Huddinge SE-14104, Sweden; fax: 46-8-746-7915; e-mail: [email protected]
Endodontics Instruments for retreatment of root canals Background.—Nonsurgical retreatment is preferred for failing endodontic cases. In this approach, the original root canal filling material must be removed, further cleaning done, and the canal refilled. Removing all obturation material does not ensure the success of endodontic treatment, but removing as much as possible should help reveal necrotic tissues or bacteria that can cause periapical inflammation and failure of the restoration. Rotary instruments can reduce the clinical time needed to accomplish gutta-percha removal. FlexMaster instruments have been used to prepare curved canals quickly and with minimal straightening when compared with hand instruments. ProTaper instruments combine different tapers in one. The RaCe file system is a reamer with alternating cutting edges and is supposed to prevent threading or blocking and operate at an extremely low torque with improved efficiency. The ability of these 3 rotary instruments to handle guttapercha removal for curved root canal retreatment was investigated.
350 Dental Abstracts
Methods.—Four groups of 15 specimens each were used to assess the cleanliness of root canal walls after retreatment with the 3 systems or Hedström files. The specimens consisted of curved mandibular premolars with angles between 20° and 36° of curvature. All were enlarged and obturated with the use of the lateral condensation technique, then reprepared with the test instruments. Measurement of the area of any remaining obturation material was determined from 2 directions. Results.—Residual gutta-percha/sealer was present in the apical half of the root beyond the curvature in all the root canals that did not involve fractured files or other procedural errors. The groups did not differ significantly in the amount of residual gutta-percha/sealer present when assessed from the buccolingual direction, but imaging from the mesiodistal direction revealed significantly larger areas of obturation left in the Hedström file and FlexMaster groups than in the RaCe group. Adding the 2
results together, canals retreated with RaCe files had fewer areas of remaining obturation material than those retreated with FlexMaster files. When all root canals were considered, RaCe-treated canals had less remaining guttapercha/sealer than all the other canals when viewed from the mesiodistal direction. Thus, the high percentage of broken ProTaper and FlexMaster instruments affected the results. Neither the Hedström files nor the RaCe files fractured. Gutta-percha removal was significantly quicker with the use of Hedström files than with ProTaper and FlexMaster files. The use of RaCe instruments required significantly more time than the use of any of the other instruments. No significant differences were noted in the ability to remove obturation material extruded from the apical foramen. Discussion.—The RaCe rotary system was both safe and efficient in removing gutta-percha in curved root canals, but required considerably more time than the other instruments. ProTaper and FlexMaster instruments tended to fracture more often than RaCe and Hedström files, reducing their effectiveness for gutta-percha removal. With
respect to apical extrusion, all the groups were able to reduce apically extruded debris to similar degrees.
Clinical Significance.—Removal of old canal filling material and residual bacterial contaminants is an essential first step in salvaging a failing root canal-treated tooth. Of the systems tested here, 1 rotary, the RaCe from Switzerland, while not the fastest, proved effective and safe.
Schirrmeister JF, Wrbas K-T, Schneider RH, et al: Effectiveness of a hand-file and three nickel-titanium rotary instruments for removing gutta-percha in curved root canals during retreatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 101:542-547, 2006 Reprints available from JF Schirrmeister, Dept of Operative Dentistry and Periodontology, Albert-Ludwigs-Univ of Freiburg, Hugstetterstr 55, 79106, Freiburg, Germany; e-mail: [email protected]
Photo-activated disinfection Background.—A 94% success rate has been reported for endodontic treatment when negative cultures are obtained from the root canal. This rate falls to 68% when cultures are positive. A novel method of disinfection involves the use of photo-activated disinfection (PAD), in which photosensitizer molecules attach to the bacterial membrane. Singlet oxygen is produced with exposure to irradiation with light at a specific wavelength matched to the peak absorption of the photosensitizer. The oxygen kills the bacteria by rupturing the bacterial cell wall. The 2 components of the system have no effect on bacteria separately, but when the light and photosensitizer are combined, bacteria are eliminated. The bacterial load within the root canal walls was determined after initial access, immediately after conventional preparation, and after treating the canal with the PAD method.
Methods.—Microbiological effectiveness was determined at the times mentioned through samples of the dentin from the canal. The 14 patients all had symptoms of irreversible pulpitis or periradicular periodontitis that required endodontic therapy. The 3 samples from each canal were plated within 30 minutes of being obtained and cultured anaerobically for 5 days. Bacterial load was based on the growth of viable bacteria in each sample. Results.—Of the 32 canals evaluated, 30 had completed microbiological scores. Ten canals had negative cultures, 3 of which were in multirooted teeth that included other canals with high bacterial scores. Three others had inflamed pulpal tissues treated with a corticosteroid and topical polyantibiotic before extirpation. These cases confirmed no cross contamination of the canals occurred with
Volume 51 • Issue 6 • 2006 351