The effect of dowel preparation on the apical seal of three common obturation techniques Larry R. Camp, D.M.D.,* and [email protected]
J. Todd, D.D.S.**
Fort Hood, Tex.
Restoration and reinforcement of pulpless teeth with a dowel core and crown is frequently indicated. Guzy and Nicholls’ demonstrated in an in vitro study that the fracture load of endodontically treated unreinforced crowns was less than that for teeth with cemented posts. The dowel provides retention for the core and at the same time provides support against vertical and horizontal forces. There is little in the literature about the effect of dowel preparation on the apical seal of commonly used obturation techniques. Zeigler,2 in an unpublished study, prepared dowel spaces with Peeso reamers (Union ‘Broach Corp., Long Island City, N.Y.) in 40’ teeth filled with gutta-percha and sealer. Twelve of the 40 teeth displayed apical leakage. Neagley3 investigated the effect of dowel preparation with a tapered fissure bur on root canals filled with gutta-percha, silver cones, and root-end amalgam fillings. His study showed gutta-percha to have a superior sealing ability after dowel preparation. In an in vitro study, Zmener4 showed no effect on the apical seal when dotiel preparation was performed immediately after obturation. He also found that 8 mm of filling material left in the canal provided a good apical seal. The purpose of this investigation was to evaluate, in vitro, the apical seal of three common obturation techniques after dowel space preparation with hot instruments, Peeso drills, and Gates Glidden drills (Union Broach Corp.) (Pig. 1).
MATERIALS AND METHODS Ninety extracted single-rooted maxillary anterior teeth were selected and stored in 0.9% sodium chloride solution at room temperature. The crowns were removed to facilitate access and canal preparation. The root canals of all teeth were instrumented to a size 70
The views expressed herein are those of the authors and not necessarily those of the U.S. Department of Defense or U.S. Army. *Captain (DC), U.S. Army. **Lieutenant (DC), U.S. Army.
Fig. 1.Instruments used for removal of gutta-percha. Left to right: Peeso drills, Gates Glidden drills, and a calibrated plugger used for heat removal. Hedstrom file (Kerr Mfg. Co., Romulus, Mich.). The teeth were divided into three groups, each group consisting of 30 teeth. The teeth in group A were obturated by the Kloraperka technique. A master cone of gutta-percha was coated with Kloraperka sealer (Union Broach Corp.) and the canal was obliterated via the lateral condensation multiple-cone technique. The teeth in group B were obturated with the laterally condensed gutta-percha method with Procosol sealer (Star Dental Co., Inc., Conshocken, Pa). The teeth in group C were obturated with the warm gutta-percha vertically condensed method advocated by Schilder.’ All teeth were radiographed to confirm adequacy of fill and returned to the saline solution. After a week, the teeth from each group were further divided into subgroups of 10 each. In subgroup 1, a dowel space was created by removing the filling material with hot instruments. In subgroup 2, dowel space was created with Peeso drills. In subgroup 3, Gates Glidden drills were used to create the dowel space. In each subgroup, the dowel space extended to a level 5 mm from the apex. A cotton pellet was placed in NOVEMBER 1983
Table I. Amount
of leakage Horizontal
2 mm from apex No. of teeth
Teeth with leakage
No. of teeth
10 10 10
4 4 6 2
10 10 10
Hot instrument Peeso drills Gates Glidden drills Hot instrument
Filling material Kloraperka Kloraperka Kloraperka Gutta-percha condensed) Gutta-percha condensed) Gutta-percha condensed) Cutta-percha condensed) Cutta-percha condensed) Gutta-percha condensed)
Method of removal
the access opening and Cavit (Premier Dental Products, Norristown, Pa.) placed to seal the coronal portion of the canal. The teeth were coated, with the exception of the apex, with Copalite (Cooley and Cooley, Houston, Tex.) and sticky wax to prevent surface penetration of dye. The teeth were placed in a bath of Rhodamine B dye for 60 hours. The teeth were removed, cleaned, and dried; horizontal sections were made at 2 and 4 mm levels from the apex. The sections were mounted on glass slides and coded to allow for double-blind evaluation. The sections were examined by four dentists under x40 magnification with a light microscope. The results are recorded in Table I.
Fourteen of 30 teeth in the Kloraperka group had leakage at the 2 mm level, with one having leakage at the 4 mm level. Eight of 29 teeth with laterally condensed gutta-percha showed leakage at the 2 mm level; one tooth in this group fractured and was eliminated from the study. Ten of the 30 vertically condensed gutta-percha teeth displayed penetration of the dye at the 2 mm level. No teeth showed leakage at 4 mm in the lateral or vertical group. There was no statistical difference among the obturation methods tested (x2 = 2.47, p = .Ol, df = 2).
Dowel preparation comparison Ten of 20 teeth with root canal fillings removed by a hot instrument showed apical leakage at 2 mm. Eleven THE JOURNAL
4 mm from apex
Teeth with leakage
of 30 teeth with fillings removed by Peeso drills had leakage at 2 mm. Eleven of 30 teeth with fillings removed with Gates Glidden drills had leakage at 2 mm, with one having leakage at the 4 mm level. There was no statistical difference among the procedures tested (x2 = 0.03, p = .Ol, df= 2).
DISCUSSION Gutta-percha has been advocated as the material of choice when a treatment plan includes a dowel core restoration.6 This investigation chose three of the most common gutta-percha obturation techniques. Endodontists frequently remove gutta-percha with a hot instrument, whereas prosthodontists generally prepare the teeth by use of rotary instruments such as Peesoand Gates Glidden drills. All three methods of removal have a disruptive effect on the filling material. The filling material’s ability to resist the transmission of this effect throughout the length of the remaining filling determines the quality of the apical seal. This study attempts to evaluate both the amount of this disruptive effect of three different methods of removal and the ability of three different gutta-percha obturation techniques to resist the disruptive forces and maintain the apical seal. In a study of root canal preparation on the quality of apical and coronal obturation, Allison’ found that microleakage generally extended close to the point where the tip of the spreader had penetrated. This fact could account for the incidence of leakage that was observed at the 2 mm level (32 of 89 sections) with only one demonstrating leakage at the 4 mm level. 665
CONCLUSION This investigation has showed no statistical difference among heat removal, Peeso drills, and Gates Glidden drills on the apical seal of three common obturation techniques after dowel space preparation. Laterally condensed gutta-percha, vertically condensed gutta-percha, and Kloraperka showed no statistical difference in apical seal after dowel space preparation. Root canals can be safely prepared for a dowel space to a level 5 mm from the apex.
Research Project, U.S. Naval Hospital, San Diego, Calif., 1965. 3. Neagley, R. L.: The effect of dowel preparation on the apical seal of endodontically treated teeth. Oral Surg 28:739, 1969. 4. Zmener, 0.: Effect of dowel preparation on the apical seal of endodontically treated teeth. J Endodont 6:687, 1980. 5. Schilder, H.: Filling root canals in three dimensions. Dent Clin North Am, 1967, p. 723. 6. Ingle, J. I.: Endodontics, ed 1. Philadelphia, 1965, Lea & Febiger, p 614. 7. Allison, D. A.: The influence of the method of canal preparation on the quality of the apical and coronal obturation. J Endodont 5:298, 1979.
Guzy, G. E., and Nicholls, J. I.: In vitro comparison of intact endodontically treated teeth with and without endo-post reinforcement. J PROSTHETDENT 42:39, 1979. Zeigler, P. E.: The Effects of Instrumentation of a Post Preparation on the Apical Seal of Endodontically Filled Teeth.
Reprint requests to: DR. LARRY R. CAMP U.S. ARMYDENTALACTIVITY DENTALCLINIC No. 6 FORTHWD, TX 76544
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