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Cervical resorption

Cervical resorption

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  • 1. J Clin Periodontol 2002: 29: 580–585 Copyright C Blackwell Munksgaard 2002Printed in Denmark . All rights reserved 0303-6979Cervical external root resorption L. Bergmans1, J. Van Cleynenbreugel2, E. Verbeken3, M. Wevers4,in vital teeth B. Van Meerbeek1 and P. Lambrechts1 Departments of 1Operative Dentistry andX-ray microfocus-tomographical and Dental Materials, BIOMAT, 2Radiology and Electrical Engineering, ESAT, 3Morphologyhistopathological case study and Medical Imaging, 4Metallurgy and Materials Engineering, MTM, Catholic University of Leuven, BelgiumBergmans L, Van Cleynenbreugel J, Verbeken E, Wevers M, Van Meerbeek B,Lambrechts P. Cervical external root resorption in vital teeth. X-ray microfocus-tomographical and histopathological case study. J Clin Periodontol 2002; 29: 580–585. C Munksgaard, 2002AbstractExternal resorptions associated with inflammation in marginal tissues present adifficult clinical situation. Many times, lesions are misdiagnosed and confusedwith caries and internal resorptions. As a result inappropriate treatment is ofteninitiated. This paper provides three-dimensional representations of cervical externalresorption, based on X-ray microfocus-tomographical scanning of a case, which Key words: cervical resorption; external rootwill aid the dental practitioner in recognizing characteristic features during clin- resorption; peripheral inflammatory rootical inspection. In addition, histopathological examination reveals the cellular resorption; tooth resorption; XMCTmorphology of the adjacent tissues. Accepted for publication 21 May 2001 special type of pathological tooth con- pulp tissues and an infected root canalIntroduction dition that could be classified in the content (Andreasen 1985).External resorption is a process that group of inflammatory resorptions. In Cervical external resorption occursleads to an (ir)reversible loss of ce- recent years, several etiologic factors immediately below the epithelial attach-mentum, dentin and bone. It takes have been advocated and some ment of the tooth. As a result, it mustplace in both vital and pulpless teeth morphological descriptions were made. be noticed that the location is not al-and the identification is mostly made Nevertheless, prediction and prevention ways cervical but related to the level ofduring routine radiographic or clinical are still impossible and an exact diag- the marginal tissues and the pocketexamination as the majority of cases are nosis and treatment is often far from depth. Unless proper treatment is in-asymptomatic. External resorptions easy, depending on the severity and itiated, this type of resorption continuesmay be physiological or pathological. localization of the defect. and a large irreversible loss of toothAndreasen suggested an advanced Clinically, cervical external resorp- structure may appear by time.classification in 1985 (Andreasen 1985). tion is associated with inflammation of As mentioned before, the pulp playsToday, his categories of surface, in- the periodontal tissues and does not no role in cervical external resorptionflammatory and replacement-ankylosis have any pulpal involvement (Frank & and is mostly normal in these situ-resorption are commonly used. How- Torabinejad 1998). The pulp remains ations. However, a number of cases ob-ever, other investigators have intro- protected by a thin layer of predentin served in recent years have suggestedduced subgroups or new categories. until late in the process and it has been that part of this pathology may be as-Consequently, a lack of uniformity in postulated that bacteria in the sulcus sociated with intracoronal bleachingnomenclature is still present, thus con- sustain the inflammatory response in procedures in endodontically treatedfusing the dental practitioner. the periodontium (Tronstad 1988, Hei- teeth (Harrington & Natkin 1979). Al- Cervical external resorption, fre- thersay 1999a). This feature differen- though this relationship has not beenquently called invasive cervical resorp- tiates cervical external resorption from firmly established by scientific study,tion (Heithersay 1999a) or peripheral another type of inflammatory resorp- strong suspicions exist that bleachinginflammatory root resorption (PIRR) tion called external inflammatory re- agents such as 30% H2O2 were able to(Gold & Hasselgren 1992), presents a sorption, which is continued by necrotic penetrate the dentin from the inside
  • 2. Cervical external root resorption 581(Rotstein 1991), alter the root surface several etiologic factors and many the- root caries. Caries lesions are ratherstructure and irritate the periodontal ories have been presented. Other than soft because the organic component ofligament and surrounding tissues systemic and idiopathic forms, this type the dentin has been disintegrated not by(Friedman et al. 1988, Dahlstrom et al. of external resorption in vital teeth can the bacterial acid production but by1997). In particular, teeth with ce- occur late after orthodontic tooth proteolytic enzymatic degradation. Ifmentum deficiencies related to previous movement, orthognathic and other the lesion is more apically or proximallytrauma (Cvek & Lindvall 1985) or a ce- dentoalveolar surgery, periodontal root situated, it may be detectable by deepmento-enamel disjunction (10%) due to scaling or planing, trauma, bruxism, probing. When the local ‘pocket’ ishistological variation (Schroeder & fracturing, developmental defects or a probed, copious bleeding and a spongyScherle 1988) seemed to be at high risk. combination of these predisposing fac- feeling are commonly observed as theThis type of cervical resorption, which tors (Cvek 1981, Tronstad 1988, granulation tissue of the resorptive de-is occasionally found after bleaching of Trope & Chivan 1994, Heithersay fect is disturbed. Radiographs may re-a non-vital tooth, is often excessive, as 1999b). It remains to be seen whether veal the lesions once a certain criticalit can rapidly progress through the root even vital bleaching in some teeth will dimension has been reached. In a studywithout being hindered by pulp and result in cervical root resorption at a from Andreasen et al. (1987) conditionspredentin. later date. favoring radiographic visibility of cervi- This article will review the clinical As with most external resorptions, cal resorptive defects were a lesion di-and therapeutic concepts associated the cervical root resorptions are usually ameter of greater than 1.2 mm and thewith cervical external resorption in vital painless and go unnoticed by the pa- use of high contrast X-ray technique.teeth. The purpose of the joined case tient unless pulpal or periodontal infec- Cavities located on the proximal surfacereport is to describe a clinical case of tion supervenes. In addition, a deep re- are more easily detected than thosea central incisor with massive external sorptive cavity can result in sensitivity located on the buccal surface. In ad-resorption of cervical crown and root to changes in temperature because of dition, if the site of entry is visible onstructure that had to be extracted. It proximity to the pulp. In most cases, the radiograph, the accompanying bonegave us the opportunity to observe the cervical resorptions are detected during resorption may be noticed. In most in-resorptive defect in vivo by standard routine radiographic or clinical exami- stances, the appearance of the crestaland digital radiology and clinical ex- nation. If the lesion is located margin- bone remains unchanged. A compari-amination, and also in vitro by means ally, there may be no external signs, or a son with previously taken radiographsof histological sections and X-ray pink coronal discoloration of the tooth can increase the rate of detection. Fur-microfocus computed tomography crown may be noticed (Fig. 1). The lat- thermore, the use of varying X-ray(XMCT). The outcome of this exami- ter is caused by the translucent appear- angles has been suggested to distinguishnation will be discussed. ance of granulation tissue, which has a internal resorption from external re- deep red color under the overlaying en- sorption and to locate the site of entry amel structure. It bleeds freely on prob- (Seward 1963). Because the pulp in thePathogenesis, clinical features and ing. By investigating the resorption cav- root canal is not involved in cervical ex-treatment options ity walls with an explorer, a hard, min- ternal resorption, it is usually possibleThe exact etiology of cervical resorp- eralized tissue sensation will be felt, to clearly distinguish the radiopaquetion is still unknown. It appears, accompanied by a sharp, scraping mineralized outline of the canalthough, that for it to occur there must sound. This feature and the appearance through the radiolucency of the exter-be an unprotected, locally destroyed or of knife-edge cavity borders are import- nal resorptive defect (Fig. 1). As the cer-altered root surface which has become ant in the differential diagnosis with vical root resorption is long standing, asusceptible to resorbing clastic cells mottled appearance may be seen due toduring an inflammatory response of the deposition of calcified reparative tissueperiodontal ligament to traumatic (in- within areas of the cavity surfacejury) or bacterial (irritation) stimulus, (Goldman 1954).maintained by infection in the adjacent It has to be emphasized that electricmarginal tissues (Gold & Hasselgren and thermal pulp tests remain positive1992). It has been suggested that the throughout the continuation of theperiodontal ligament, the cementum, pathological process. The resorptionand especially the intermediate ce- starts on the root surface, but when thementum, may serve a resorption-pre- predentin is reached, the resorptionventing function on the root surface proceeds laterally and in an apical and(Lindskog & Hammarström 1980, coronal direction, progressively envel-Lindskog et al. 1985). The resistance to oping the root canal (Figs 2, 3 and 4).resorption of uncalcified, newly formed Fig. 1. (Left) Pinkish discoloration of the left This coronal extension process resultstissue on cemental surfaces (cementoid) central incisor caused by invasion of the cer- ultimately in cavitation of the overlyinghas been observed (Gottlieb 1942). In vical region of the tooth by fibrovascular enamel (Tronstad 1988). Furthermore, tissue derived from the periodontal ligament.addition, it appears that a hard tissue a series of channels containing resorp- (Right) The parallel radiograph shows amatrix is a barrier that has to be broken rather irregular radiolucency (*), involving tive tissue are present, and they usuallyto trigger osteoclastic activity not only the coronal dentin but also ex- have connections further apically with(Chambers 1981). This can be caused tending to the coronal third of the root. The the periodontal ligament (Heithersayby damage to the root surface. characteristic radiopaque line separating the 1999a). Cervical root resorption can have lesion from the root canal can be identified. In severe external resorptions, only a
  • 3. 582 Bergmans et al.thin layer of dentin remains protecting hibitor against resorption (Weden- ostectomy by contouring the alveolarthe pulp (Makkes & Thoden van Velzen berg & Lindskog 1985). crest some 2 mm apical to the defect1975) (Fig. 5). This could be explained Besides extraction, different ap- margins (Meister et al. 1986). The in-by the fact that predentin possesses a proaches have been suggested by several vasive nature of the resorption mayresistance to resorption, as was demon- authors for the treatment of cervical ex- necessitate a considerable reduction ofstrated by Stenvik & Mjör (1970). It has ternal root resorptions of various ori- bone, and the filling of the irregularbeen suggested that the organic phase gins. Arresting the resorption may be cavities, with subsequent difficult clin-of the predentin contains an enzyme in- attempted by means of subgingival ical control. Regarding the restoration curettage, but with a ‘high failure rate of the resorptive defects, glass ionomers due to recurrence, or rather persistence, (Heithersay 1985) or light-cured resin of the resorptive tissue’ (Heithersay composite materials have been recom- 1985). The use of calcium hydroxide to mended, recognizing, however, that any neutralize external resorption has been subgingival restoration may well cause suggested. Webber (1983) has compre- periodontal complications (Heithersay hensively summarized the benefits of 1985, Meister et al. 1986). Performing this approach in some cases. Exposure the periodontal surgery as a prelimi- of the resorption defects for the pur- nary stage has also been recommended, pose of restoration has been recom- restoring the resorption defects only mended by means of orthodontic ex- after the periodontal tissues have healed trusion (Latcham 1986), intentional re- (Heithersay 1985, Meister et al. 1986). plantation (Heithersay 1985) or It is important that most external cervi- cal resorptive lesions not be treated as endodontic problems. In many cases, this resorptive condition may be treated without sacrificing the pulpal vitality. Histological findings The histological presentation of cervi- cal peripheral inflammatory root re- sorption (PIRR) is identical to that of other inflammatory root resorption.Fig. 2. The reconstructed image (XMCT) was Early investigators observed a simi-longitudinally sectioned and partially cleared larity between tooth resorption and os-by means of software to visualize the thinlayer of dentin that remained, protecting the teoclastic bone resorption, including re-pulp in this case from severe cervical external sorption bays or Howship lacunae andresorption. Fig. 4. Reconstructed images (XMCT) of the resorbing cells (Coyler 1910, Black extracted tooth were partially cleared by soft- 1920, for review see Shafer et al. 1974). ware to three-dimensionally investigate the There are differing reports in the litera- extent and characteristics of the resorption ture regarding the morphology of these process. resorbing cells for dentin. The presence of large cells with multiple nuclei, simi- lar to osteoclasts, in contact with dentin has been described (Dragoo & Sullivan 1973). In general, all hard tissue-re- sorbing cells appear to be remarkably similar and therefore they are referred to as osteoclasts. Osteoclasts are multi- nucleated giant cells with cytoplasmic vacuoles that originate from blood- borne leukocytes from the bone mar- row. They have two kinds of mem- branes: one that attaches the cell to the hard tissue surface and another that is conceivably involved in the resorption process (Hammarström & Lindskog 1985).Fig. 3. Upper part of the crown (bottom The presence of fibrovascular tissueview) visualized through a horizontal sec-tioning and partial clearing of the recon- Fig. 5. (Left) Tooth immediately after careful adjacent to an unprotected root surfacestructed image (XMCT) by software. When extraction. (Right) Same tooth after exca- has been postulated as the conditionthe predentin is reached, the resorption pro- vation of the granulation tissue. Notice the necessary for root resorption (Gold &ceeds laterally to gradually envelop the root layer of dentin and predentin that separated Hasselgren 1992). The cellular compo-canal, preserving the pulpal vitality. the resorbing tissue from the dental pulp. nents of this soft tissue portion of the
  • 4. Cervical external root resorption 583Fig. 6. The fibrovascular tissue connected Fig. 9. Multinucleated clastic cells (arrows) Fig. 10. The occlusal radiograph denotes awith the periodontal tissues is infiltrated by present in the mass of fibrous tissue adjacent small invasive resorptive lesion (*) near themononuclear cells, mainly lymphocytes and to the dentin surface. (Hematoxylin-eosin cervical area with a shallow penetration intoplasma cells, and entirely re-epithelialized. stain, ¿ 400). the dentin.(Hematoxylin-eosin stain, ¿ 200). 1954). This calcified, poorly organized noted (Fig. 1), together with palato-inci- bone-like tissue indicates replacement sal wear of the front teeth (Fig. 2). The or healing of the resorbed tooth struc- patient said that he had consulted a ture. dentist about 3 years previously because of a tingling sensation in the same re- gion. There was no history of trauma. X-ray microfocus computed Apparently, at that time a small swell- tomography ing buccal of the left central incisor was Optical microscopes and standard present without color change of the radiographic equipment used to investi- crown. The tooth responded to cold but gate the condition of cervical external on percussion no pain could be evoked.Fig. 7 Higher magnification of Fig. 8 shows resorption cannot provide accurate An occlusal radiograph (Fig. 10) waschronically inflamed vascular connective three-dimensional information. As a re- taken and sensitivity tests were per-tissue bordered by normal squamous epithel- sult, another technique called X-ray formed, but no final diagnosis wasium of the gingiva. (Hematoxylin-eosin stain, microfocus computed tomography has made and the patient was advised to¿ 400). been used. wait and see if any changes occurred. In medical and dental imaging, when Three years later, with ongoing dis- the use of a reliable method for the comfort, a pink discoloration of the localization and size determination of crown appeared and the patient was re- the internal body features is required, ferred for suspected resorption path- X-ray computed tomography (XCT) ology. has proved to be a necessary tool (Tach- The patient was a healthy young man ibana & Matsumoto 1990). Its mini- without significant medical antecedents aturized form, X-ray microfocus com- and was not taking any medication. puted tomography (XMCT), can be There was some minor gingivitis, but used non-destructively on bioptic speci- the patient had fairly good control of mens such as an extracted tooth (Niel- his dental plaque. No caries or restora- sen et al. 1995, Bjørndal et al. 1999). By tions were present in the left central in- combining X-ray microfocus trans- cisor. Vitality tests disclosed a vitalFig. 8. Young, highly vascularized (left) and mission technique with tomographical tooth. There was slight gingival swellingolder (right) parts of granulation tissue pres- reconstruction, high-resolution (up to and the sulcus was intact at the site ofent in the resorption cavity and surroundingspace. (Hematoxylin-eosin stain, ¿ 25). 10 mm) and magnified three-dimen- the resorption, which could be probed sional pictures based on 30-mm-spaced (sulcular depth of 4 mm). There was no tomographic sections can be produced. sinus tract and the tooth was a little ten- der to percussion, indicating advancedresorptive complex include most of the involvement of the periodontal liga- Case illustrationinflammatory cells commonly described ment. As the cervical root resorptionin inflammatory periodontal disease: On May 2, 2000, a 36-year-old man was was long standing, granulomatouslymphocytes, plasma cells, histiocytes seen at the Department of Operative tissue could be seen undermining theor macrophages, and fibroblasts, in ad- Dentistry, University Hospital of the enamel of the crown of the tooth, givingdition to the already mentioned multi- Catholic University of Leuven, with a it the pinkish appearance. This shouldnuclear clast cells (Figs 6–9). In ad- chief complaint of ‘tenderness by pal- not be confused with the pathogno-vanced lesions, ectopic calcifications pation on the skin under the left nose monic clinical picture of internal rootcan also be observed both within the in- entrance’ combined with ‘a pink resorption (Fig. 1).vading fibrous tissue and deposited on colored appearance of the left front Radiographs are presented in Figs 1,the resorbed dentin surface (Goldman tooth’ (Fig. 1). A central diastema was 10 and 11. Reexamination of the oc-
  • 5. 584 Bergmans et al. mation infiltrate were mainly lympho- internal macromorphology in 3D-recon- cytes and plasma cells. A few multi- structed maxillary molars using computer- nucleated resorbing cells were seen, in- ized X-ray microtomography. International dicating an active resorptive process. Endodontic Journal 32, 3–9. Black, G. V. (1920) A work on special dental Lacunae were not histologically exam- pathology. pp. 32–42. Chicago: Medico- ined because the tooth itself was used Dental Publishing Co. for XMCT examination (SkyScan 1072, Chambers, T. J. (1981) Phagocytic recog- SkyScan N.V., Belgium). nition of bone by macrophages. Journal of Pathology 135, 1–7. Coyler, J. F. (1910) Dental surgery and pathol- Zusammenfassung ogy, pp. 558–564. New York: Longmans,Fig. 11. Digital radiography (Sens-a-Ray) Zervikale externe Wurzelresorptionen bei vi- Green.allows distance measuring and can be used talen Zähnen – Ein Fallbericht mit Röntgen- Cvek, M. (1981) Endodontic treatment ofto provide views from different angles with a Mikrofokus-Tomographie und histopathologi- traumatized teeth. In: Andreasen, J.O.reduced dose of radiation. scher Untersuchung (ed.): Traumatic injuries of the teeth, 2nd Externe Resorptionen, die mit der Entzün- edn, pp. 362–363. Copenhagen: Munks- dung der marginalen Gewebe verbunden gaard. sind, stellen eine schwierige klinische Situati- Cvek, M. & Lindvall, A. M. (1985) Externalclusal radiograph from 1997 (Fig. 10) on dar. Häufig werden diese Läsionen fehl- root resorption following bleaching ofdisclosed a small radiolucent spot that diagnostiziert und mit Karies oder internen pulpless teeth with oxygen peroxide. Endo-had initially been overlooked and which Resorptionen verwechselt. Als Ergebnis da- dontics and Dental Traumatology 1, 56–60.corresponded to the ongoing resorp- von wird oft eine ungeeignete Therapie einge- Dahlstrom, S. W., Bridges, T. E. & Heither-tion. Examination of the resorption de- leitet. Diese Veröffentlichung eines Falles lie- say, G. S. (1997) Hydroxyl radical activityfect on the newly taken radiagraphs fert, durch Verwendung der Röntgen-Mikro- in thermocatalytically bleached root-filled(Fig. 11) revealed an intact circumfer- fokus-Tomographie, eine Dreidimensionale teeth. Endodontics and Dental Traumatolo- Darstellung der zervikalen externen Resorp- gy 13, 119–125.ential outline of the alveolar crest with- tion. Dies wird dem praktisch tätigen Zahn- Dragoo, M. & Sullivan, H. C. (1973) A clin-out resorption. The lamina dura was in- arzt dabei helfen, die charakteristischen ical and histological evaluation oftact, the width of the adjacent peri- Merkmale während der klinischen Inspekti- autogenous IIIac bone grafts in humans.odontal ligament space was normal on zu erkennen. Zusätzlich zeigt die histopa- Part II. External root resorption. Journalmesially but widened distally. Measure- thologische Untersuchung die zelluläre Mor- of Periodontology 44, 614–625.ments made by digital radiography phologie der benachbarten Gewebe. Frank, A. L. & Torabinejad, M. (1998) Diag-(Sens-a-Ray) (Fig. 11) revealed maxi- nosis and treatment of extracanal invasivemum distances of 7.4 and 8.1 mm (co- resorption. Journal of Endodontics 7, 500– ´ ´ Resume 504.ronal-apical direction) and 6.7 mm (me-siodistal direction). There seemed to be Resorption radiculaire cervicale externe sur ´ Friedman, S., Rotstein, I., Libfeld, H., Stab-more loss of tooth structure on the dis- les dents vivantes – Etude de cas histopatholo- holz, A. & Heling, I. (1988) Incidence of gique et microfocal tomographique external root resorption and esthetic re-tal side. There was no evidence of re- Les resorptions externes associees avec l’in- ´ ´ sults in 58 bleached pulpless teeth. Endo-sorption elsewhere on the root. dontics and Dental Traumatology 4, 23–26. flammation des tissus marginaux represente ´ Because the restorability of the tooth une situation clinique difficile. La plupart du Gold, S. I. & Hasselgren, S. (1992) Peripheralwas severely compromised, extraction temps, les lesions sont mal diagnostiquees et ´ ´ inflammatory root resorption. A review ofwas performed. Getting sound crown confondues avec des caries et des resorptions the literature with case reports. Journal ofmargins would have been difficult be- internes. Il s’en suit des traitements inap- Clinical Periodontology 19, 523–534.cause the resorptive defect was below proppries. Cet article montre des representa- ´ ´ Goldman, H. M. (1954) Spontaneous inter-the bony crest. Furthermore, peri- tions en trois dimensions d’une resorption ´ mittent resorption of the teeth. Journal ofodontal surgery as an alternative op- externe cervicale basee sur une technique de ´ the American Dental Association 49, 522–tion, consisting of an apically reposi- scanner par tomographie microfocale d’un 532. cas , ce qui aidera le praticien a en reconnaı- ` ˆ Gottlieb, B. (1942) Biology of the cementum.tioned flap on the labial and a gingivec- tre les caracteristiques lors de l’examen clini- ´ Journal of Periodontology 13, 13–17.tomy on the palatal surfaces, would be que. De plus, l’examen histopathologique re- ´ Hammarström, L. E. & Lindskog, S. (1985)associated with extensive gingival re- vele la morphologie cellulaire des tissus adja- ` General morphological aspects of resorp-cession and unaesthetic exposure of the cents. tion of teeth and alveolar bone. Interna-cervical root surfaces. tional Endodontic Journal 18, 93–108. The curettage of the resorption defect Harrington, G. W. & Natkin, E. (1979) Ex-and the removal of the resorptive tissue References ternal resorption associated with theare illustrated in Fig. 5. After cleaning Andreasen, J. O. (1985) External root resorp- bleaching of pulpless teeth. Journal of En-the defect, no perforation from the re- tion: its implications in dental traumatolo- dodontics 5, 344–348.sorptive defect into the cervical pulpal gy, paedodontics, periodontics, orthodont- Heithersay, G. S. (1985) Clinical endodonticarea was found. ics and endodontics. International Journal and surgical management of tooth and as- of Endodontics 8, 109–118. sociated bone resorption. International En- The pathology report (Van Damme Andreasen, F. M., Sewerin, I., Mandel, U. & dodontic Journal 18, 72–92.2000) described the excavated tissue as Heithersay, G. S. (1999a) Clinical, radio- Andreasen, J. O. (1987) Radiographic as-histologically consisting of chronically sessment of simulated root resorption graphic, and histopathological features ofinflamed vascular connective tissue cavities. Endodontics and Dental invasive cervical resorption. Quintessence(Figs 6–9). The fragment was lined by Traumatology 3, 21–27. International 30, 27–37.normal epithelium of the gingiva. The Bjørndal, L., Carlsen, O., Thuesen, G., Darv- Heithersay, G. S. (1999b) Invasive cervical re-cellular components of this inflam- ann, T. & Kreiborg, S. (1999) External and sorption: an analysis of potential predis-
  • 6. Cervical external root resorption 585 posing factors. Quintessence International quantification of 30% hydrogen peroxide tion. In: Pathways of the pulp, 6th edn, pp. 30, 83–95. penetration through dentine and ce- 493–503. St Louis: Mosby.Latcham, N. L. (1986) Postbleaching cervical mentum during bleaching. Oral Surgery, Van Damme, B. (2000) Patient protocol. resorption. Journal of Endodontics 12, Oral Medicine and Oral Pathology 72, Webber, R. T. (1983) Traumatic injuries and 262–264. 602–606. the expanded endodontic role of calciumLindskog, S. & Hammarström, L. (1980) Schroeder, H. E. & Scherle, W. F. (1988) Ce- hydroxide. In: Gerstein, H., ed. Techniques Evidence in favor of anti-invasion factor mento-enamel junction – revised. Journal in clinical endodontics, pp. 210–201. Phila- in cementum or periodontal membrane of of Periodontal Research 23, 53–59. delphia: W.B. Saunders. human teeth. Scandinavian Journal of Den- Seward, G. R. (1963) Periodontal disease and Wedenberg, C. & Lindskog, S. (1985) Experi- tal Research 88, 161–163. resorption of teeth. British Dental Journal mental internal resorption in monkeyLindskog, S., Pierce, A., Blomlöf, L. & Ham- 34, 443–449. teeth. Endodontics and Dental Traumatolo- marström, L. E. (1985) The role of the ne- Shafer, W. G., Hine, M. K. & Levy, B. M. gy 1, 221–227. crotic periodontal membrane in cementum (1974) A textbook of oral pathology, 3rd resorption and ankylosis. Endodontics and edn, pp. 295–299. Philadelphia: W.B. Address: Dental Traumatology 1, 96–101. Saunders Co. Lars BergmansMakkes, P. C. & Thoden van Velzen, S. K. Stenvik, A. & Mjör, I. A. (1970) Pulp and Department of Operative Dentistry and (1975) Cervical external root resorption. dentine reaction to experimental tooth in- Dental Materials Journal of Dentistry 3, 217–222.Meister, F., Haasch, G. C. & Gernstein, H. trusion. American Journal of Orthodontics BIOMAT (1986) Treatment of external resorption by 57, 370–385. Catholic University of Leuven a combined endodontic-periodontic pro- Tachibana, H. & Matsumoto, K. (1990) Ap- U.Z. St.Rafael, ¨ cedure. Journal of Endodontics 12, 542– plicability of X-ray computerized tomo- Kapucijnenvoer7 545. graphy in endodontics. Endodontics and 3000 LeuvenNielsen, R. B., Alyassin, A. M., Peters, D. Dental Traumatology 6, 16–20. Belgium D., Carnes, D. L. & Lancaster, J. (1995) Tronstad, L. (1988) Root resorption. Etiol- Microcomputed tomography: an advanced ogy, terminology and clinical manifes- Tel: π 32 16 33280 system for detailed endodontic research. tations. Endodontics and Dental Fax: π 32 16 332435/332440 Journal of Endodontics 21, 561–568. Traumatology 4, 241–252. e-mail:Rotstein, I. (1991) In vitro determination and Trope, M. & Chivan, N. (1994) Root resorp- Lars.Bergmans/