Root canal treatment in primary- teeth: a review - PDF Document

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  1. Root canal treatment in primary- teeth: a review LTC Albert C. Goerig, DDS, MS Joe H. Camp, DDS, MSD Although preventive premature loss of pulpally mains a common problem. The resultant the permanent teeth frequently Retention of the pulpally preserve arch space is preferable if the tooth can be restored free of pathology. Additional reasons to preserve the integrity primary dentition are to (1) aid in mastication, (2) serve a pulpally involved primary tooth in the absence of a succedaneous tooth, (3) prevent aberrant habits, (4) prevent possible speech problems, (5) main- tain esthetics, (6) prevent the psychological effects as- sociated with early tooth loss, and (7) maintain normal eruption time of the succedaneous teeth. Premature loss of the primary tooth may lead to accelerated eruption of the succedaneous development of the permanent tooth. 1 Because of high failure rate, pulp capping is not rec- ommended for carious exposures in primary teeth. 2’3 Other than mechanical exposure in a healthy tooth, all pulp exposures in primary teeth should be treated pulpot0my, pulpectomy, or extraction. In primary teeth, the formocresol pulpotomy is a well documented and accepted procedure with a success rate of over 90%.4’~ However, in order to achieve this success rate, the treatment must be confined to teeth which are judged clinically to have inflammation only in the cor- onal pulp. Contraindications for the formocresol pulpotomy are: (1) teeth with history of spontaneous pain, (2) pain percussion due to periapical tion in the canals, (4) the presence of a parulis or sinus tract, (5) hemorrhage which cannot be controlled in five minutes after extirpation of the coronal pulp, (6) evi- dence of periapical or furcal pathology, and (7) presence of necrotic pulp in the chamber. Pulpally involved pri- mary teeth with any of the above symptoms are candi- dates for root canal therapy or extraction. measures have reduced caries, involved primary teeth re- Root Canal Anatomy and Morphological Changes in the Primary Teeth Before beginning root canal therapy, should understand the morphologic changes that contin- ually occur within primary teeth and be familiar the basic differences between primary and permanent root canal anatomy. The root canals of anterior teeth are relatively simple, have few irregularities, are easily treated endodontically. canal systems found in posterior quently contain many ramifications canals making thorough debridement quite difficult. 6’v Generally, there is only one canal present in each root of the primary molars when the formation of the roots has been completed (Figure la). The primary tooth root will begin to resorb as soon as the root length is com- pleted. This resorption causes the position of the apical foramen to change continually. ary dentin is deposited within the root canal system, v-9 mesial drift of the clinician leads to malocclusion. involved primary tooth to to space maintenance to normal function and is with primary and of the Conversely, the root primary teeth and deltas between fre- tongue or delayed tooth depending upon Simultaneously, second- with (S) (A) (c) Figure 1. Cross section (top) and sagittal section (bottom) the mesial root of the primary mandibular molar, B (buccal), L (lingual), F (furcal), and P (proximal) views. (A) Initial mation of the root with only one canal present. (B) As the tooth develops, there is deposition of secondary dentin (lined areas) within the root canal system and continual resorption of the root apex. Small fins and connecting branches develop between canals (arrows). (C) During late development of the tooth canals are completely divided as the roots continue to resorb. involvement, (3) suppura- PEDIATRIC DENISTRY: Volume 5, Number 1 ,33

  2. This deposition the number and size of the root canals, as well as many small connecting branches or fins between the facial and lingual aspects of the canals (Figure lb). deposition of dentin within the root will divide it into separate canals (Figure lc). In addition, accessory canals, lateral canals, and apical ramifications be found in 10-20% of primary molars. ~’1° The maxillary primary molars may have two to five canals, with the palatal root usually rounder and longer than the two facial roots. In the mesiofacial canals occur in approximately illary first molars and 85-95% of primary maxillary second molars. 7’1° Fusion of the palatal and distofacial approximately one-third of the primary maxillary molars and occasionally in the primary maxillary second molars. The primary mandibular first ally have three canals which generally correspond to the external root canal anatomy. Two to five canals occa- sionally may be found. Approximately 75% of the mesial roots in primary first molars contain two canals; whereas in primary second molars, contain two canals. Only 25% of the distal roots in either tooth contain more than one canal, v’l° produces variations and alterations in Continued of the pulp may Figure 2. A #4 round bur has been used to gain access to the pulp chamber and remove the dentin ledges over the canal or- ifices. Note minimum length of bur needed to penetrate to the pulpal floor. root, two 75% of the primary max-. roots occurs in first and second molars usu- prevent possible just beneath the primary tooth. If signs of resorption are visible radiographically at the apex, it is advisable to establish the working length of the endodontic instru- ments 2-3 mm short of the radiographic imum accuracy when measuring canal length, long-cone paralleling radiographic Root canal filling materials used to obturate primary root canals must be absorbable so as not to interfere with the eruption of the permanent tooth. Gutta percha is contraindicated as primary root canal filler, where there is no succedaneous tooth. damage to the permanent tooth bud, 85% of the mesial roots apex. For max- use the technique. Differences and Obturation in Primary and Permanent Teeth Between Root Canal Instrumentation except Primary teeth are smaller in all dimensions than the corresponding permanent teeth. and dentin coronal to the pulp chamber is also thinner in a primary tooth. The distance from the occlusal sur- face to the floor of the pulp chamber is much shorter than in the permanent tooth. Because of this, be taken when making an access opening into the pulp chamber to prevent perforation the furcation area (Figure 2). Primary molar roots are widely divergent and curved to allow for the development of the succedaneous tooth. During instrumentation these curves increase the chance of perforation of the apical portion of the root or the coronal one-third of the canal into the furcation. curving all instruments is recommended to reduce the possibility of perforation. In addition, flaring of the canal should be kept to a minimum because of the thin dentin walls of the roots. Intracanal is contraindicated for the same reason. The variation of the root canal system in primary molars makes it difficult to remove completely necrotic tissue by instrumentation. Profuse irrigation sodium hypochlorite (NaOC1) is recommended strongly over a two-appointment period to help dissolve necrotic tissue left behind by routine instrumentation, n-13 Placement of root canal instruments and filling rials beyond the radiographic The thickness of enamel Pulpectomy and Instrumentation The following are contraindications apy for primary teeth: (1) a nonrestorable tooth with a mechanical or carious perforation floor of the pulp chamber, (3) pathologic root resorption involving more than one-third of the root, (4) pathologic loss of bone support resulting periodontal attachment, (5) the presence of a dentigerous or follicular cyst, and (6) radiographically visible internal root resorption. If the internal radiographically, it probably has perforated dentin adjacent to the furcation. cause of the short distance from the furcation to the oral cavity. That enables the inflammatory process inside the tooth to communicate with the oral cavity resulting loss of the periodontal attachment and, ultimately, ther resorption and loss of the tooth. to root canal ther- tooth, (2) care must of the through the floor into in loss of the normal resorption can be seen the thin Pre- This is important be- use of rotary instruments in fur- Anterior Teeth Access and instrumentation root canals is relatively cated canal systems. The tooth is anesthetized, dam placed and the canals are cleaned and shaped in the same manner as the corresponding with 5.25°7o of the primary anterior simple because of the uncompli- rubber mate- apex must be avoided to permanent teeth. ROOT CANAL TREATMENT IN PRIMARY TEETH: Goerig and Camp 34

  3. Figure 4. Hedstrom files are used in a rasping motion to flair the coronal one-half of the canal. Figure 5. The canal is instru- mented to a minimum final file size of 30-35, developing a pos- itive apical stop 2-3 mm from the radiographic apex. Figure 3. A small diameter file is curved and placed into the canal, 1-2 mm from the radio- graphic apex. Primary Molars After administering dam, an access opening to the pulp chamber is made in the same manner as in the permanent teeth. be taken not to perforate the pulpal floor. bur is used to gain access to the pulp chamber and remove the dentin ledges hindering direct line access to the canal orifices (Figure 2). A double-ended endodontic explorer is used to identify each of the canals. Before instrumentation the pulp chamber should be copiously irrigated with sodium hypochlorite. A trial length is obtained by measuring the tooth on the preoperative radiograph and subtracting small diameter file is placed into the canal to the trial length and another exposure taken from which the work- ing length is determined (Figure 3). Whenever possible, all radiographs should be taken utilizing technique in order to minimize distortions. length should be 1-2 mm short of the radiographic ideally. If obvious signs of root resorption are present, it may be necessary to further length by an additional 1-2 mm in order to avoid over- extension of the instruments into the periapical Once the working length has been established, are thoroughly cleaned. If hemorrhage is encountered after the pulp tissue has been removed, this is an indi- cation that root resorption working length should be shortened radiographic apex. One should not attempt to instrument to the apex as this would force contaminants and toxic by-products into the periapical possible injury to the underlying permanent tooth bud. To aid in access to the canals, Hedstrom files used to flair the canal orifices (Figure 4). Because Hed- anesthesia and placing the rubber strom files pulp tissue tation with Hedstrom files is always directed toward the areas of the greatest bulk and away from the furcation area (Figure 4 arrows) to prevent stripping and perfora- tion of the furcal position of the thin root canal system. Instrumentation with standard much the same manner as is done to prepare a canal to receive gutta percha, creating from the apex. The canals should be enlarged several sizes beyond the size of the first file that fits snugly into the canal to a minimum final size of 30-35 (Figure 5). During instrumentation the canals should be irrigated frequently with sodium hypochlorite mentJ2 After the canals have been debrided thoroughly and instrumentation is complete, the canals again are irrigated copiously with sodium hypochlorite with sterile paper points. A sterile cotton pellet is placed into the chamber and the tooth is sealed temporarily, if an intracanal medicament is used, it is placed on a cotton pellet and blotted dry before application 6). Either single or double temporary seals can be used. While it may be necessary to anesthetize in order to place the rubber dam, the use of anesthesia rarely is indicated during the obturation The patient’s response can help determine filling material approaches the apical foramen. The fill- ing material in primary teeth must be absorbable so that it will resorb with the roots and not interfere eruption of the permanent tooth. The filling choice is Zinc oxide eugenol (ZOE) without a catalyst insure adequate working time during obturation. ZOE is mixed to a very stiff quickly open the canal orifice they must be used with caution. and eliminate Instrumen- Care must A ~ round files is performed in an apical stop 2-3 mm 1-2 mm. A to aid in debride- the paralleling The working and dried apex or shorten the working (Figure tissues. the canals the gingiva appointment. when the likely has occurred and the 2-3 mm from the with the material of tissues, thereby causing may be The consistency and carried to PEDIATRIC DENISTRY: Volume 5, Number 1 35

  4. Figure 8. If needed, an end- odontic plugger is used to in- sure placement of the filling material to the apical end of the canal. Figure 6. Sterile cotton is placed and intra-appointment double temporary placed. Figure 7. A cotton pellet is used as a plunger to force the ZOE down the canals. Figure 9. Final endodontic fill with stainless steel crown res- toration. seal is vals (i.e., six months to one year). This recall is important to check for success of the treatment and to intercept any problems associated with a failing root canal. A primary tooth in which endodontic treatment has been successful will be asymptomatic, firm in the alveo- lus, and free of pathosis. The primary tooth should resorb normally and in no way interfere with the for- mation or eruption of the permanent tooth. During recall if there is any evidence of swelling, ankylosis, periapical or furcal pathosis, or the presence of a sinus tract, extraction is recommended. The success rate of pulpectomies in primary teeth is extremely high, particularly if the selection criteria men- tioned above are followed. Studies have reported success rates of 95 and 99%.16'17 Many of the arguments advanced against root canal treatment of primary teeth are falla- cious. The claim that endodontic treatment is more the canal with a plastic instrument. After ZOE is placed in the chamber, a cotton pellet is used as a plunger within the pulp chamber to force the filling material down the canals (Figure 7). The cotton is removed and a #5-7 endodontic plugger or lentula can be used to push the ZOE to the apex (Figure 8). The addition of zinc oxide powder to the pulp chamber will aid in condensation of the ZOE paste. Adequacy of the filling procedure is determined by radiographs. The endodontic pressure syringe also has been found to be effective in placing ZOE into root canals or primary teeth.14'15 Small amounts of ZOE which may have been forced inadvertently into the periapical tissues are left alone since they are absorbable. The main problem with all paste filling materials is the inability of the clinician to control adequately the flow of the paste, thereby increasing the chance of forcing the material into the periapical tissues. Certain points should be remembered to minimize the extrusion of ZOE past the apex: (1) an apical stop should be developed 2-3 mm from the radiographic apex (Figure 5), (2) measurement stops should be placed on all end- odontic instruments and pluggers for effective measure- ment control (Figures 3, 4, 5, and 8), and (3) radiographs should be taken during the fill procedure to verify the depth of filling material. Once the canals have been obturated, the chamber and access opening is filled with a fast-setting temporary cement. The tooth then is restored permanently. In primary anterior teeth, a composite resin is recom- mended to restore the lingual access opening. In primary molars, stainless steel crowns are recommended to pre- vent possible fractures (Figure 9). Although we have described a two-step pulpectomy procedure most pri- mary teeth can be instrumented and obturated during a single appointment. Primary teeth which have received root canal therapy should be evaluated at periodic inter- Figure 10. Clinical photograph of erupted permanent teeth. Although some space had been lost due to caries, adequate space was available for eruption of the permanent premolars. Note that the permanent first premolar is free of any defects. 36 ROOT CANAL TREATMENT IN PRIMARY TEETH: Goerig and Camp

  5. 5. Doyle, W.A., McDonald, R.E., Mitchell, D.F. Formocresol versus calcium hydroxide in pulpotomy. J Dent Child 29:86, 1962. 6. Baker, B.C.W., Parsons, K.C., Mills, P.R., Williams, G.L. Anatomy of root canals. IV deciduous teeth. Aust Dent J 20:101, 1975. 7. Hibbard, E.D., Ireland, R.L Morphology of the root canals of the primary molar teeth. J Dent Child 24:250, 1957. 8. Bevelander, G., Benzer, D. Morphology and incidence in secondary dentin in human teeth. JADA 30:1079, 1943. 9. Ireland, R.L Secondary dentin formation in deciduous teeth. JADA 28:1626, 1941. 10. Zurcher, E. The anatomy of the root canals of the teeth of the deciduous dentition and of the first permanent molars. New York: William Wood & Co., 1925. 11. Grossman, L.I., Meiman, B.W. Solution of pulp tissue by chemical agents. JADA 28:223, 1941. 12. Hand, R.E., Smith, M.L., Harrison, J.W. Analysis of the effect of dilution on the necrotic tissue dissolution property of sodium hypochlorite. J Endod 3:194, 1977. 13. Trepagnier, C.M., Madden, R.M., Lazzari, E.P. Quantitative study of sodium hypochlorite as an in vitro endodontic irrigant. J Endod 3:194, 1977. 14. Berk, H., Krakow, A.A. Endodontic treatment in primary teeth, in Current Therapy of Dentistry, Vol. 5 Goldman, H.M. et al. eds. St. Louis: C.V. Mosby Co., 1974. 15. Greenberg, M. Filling root canals of deciduous teeth by an injection technique. Dent Dig 67:574, 1964. 16. Andrew, P. The treatment of infected pulps in deciduous teeth. Br Dent J 98:122, 1955. 17. Rabinowitch, B.Z. Pulp management in primary teeth. Oral Surg 6.:542, 1953. expensive ated appliance coronal the erupted than space maintainers cannot be substanti- necessary fear of creating clinically 10). when one considers of this defects succedaneous the follow-up Additionally, in an nature. has not been demonstrated tooth (Figure in The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. The authors wish to thank: Dr. Steve Guy for his review and comments of this manuscript; Mr. Vernon Posey for his valuable contribution and expertise as a medical illustrator; assistance in the preparation of this manuscript. and Ms. Marilyn Robson for her Dr. Goerig is commander and chief of endodontics of the 124th Medical Detachment, (Muenchweiler, 09189; and Dr. Camp is in private practice of endodontics in Charlotte, N.C., and is clinical assistant professor at the University of North Carolina School of Dentistry, Chapel Hill, N.C. Requests for reprints should be sent to Dr. Goerig. 1. Fanning, E. Effect of extraction of deciduous molars on the for- mation and eruption of their successors. Angle Orthod 32:44, 1962. 2. Law, D.B., Lewis, T.M., Davis, T. M. Pulp therapy, in An Atlas of Pedodontics, Law, D.B. et al., eds. Philadelphia: W.B. Saunders Co., 1969, pp 187-208. 3. Starkey, P.E. Methods of preserving primary teeth which have exposed pulps. J Dent Child 30:219, 1963. 4. Sweet, C.A, Treatment of vital teeth with pulpal involvement-- therapeutic pulpotomy. J Colo Dent Assoc 33:10, 1955. West Germany) APO N.Y. Quotable Quotes Community water fluoridation prevalence of dental caries in the United States during the past 35 years. There is evidence that the prevalence of caries is declining in communities with unfluoridated water as well as in those with fluoridated be related to an increase of fluoride in the food chain, especially from the use of fluoridated increased use of infant formulas with measurable fluoride dentifrices. This trend should encourage re-evaluation of research optimal fluoride use. and individual use of fluorides have brought about a marked reduction in the water. This phenomenon may water in food processing, ingestion and previously accepted standards for content, and even unintentional priorities of fluoride From: Leverett, D. H. Fluorides and the Changing Prevalence of Dental Caries, Science 217: 26-30, 2 July 1982. PEDIATRIC DENISTRY: Volume 5, Number 1’ 37