Discussion - References.
In the present study, only two specimens, both in the positive control group, demonstrated epithelial proliferation and pocket formation. Many previous studies had revealed severe pocket formation, often extending to the root apex (Seltzer et al. 1970, ElDeeb et al. 1982, Jew et al. 1982, Balla et al. 1991). However, as in the present investigation, Beavers et al. showed a high rate of repair and suggested that this occurred because the perforations were sealed immediately under rubber dam isolation and were allowed to heal in the absence of bacterial contamination. Particular efforts were made to ensure an adequate coronal seal, which has been demonstrated to be an important factor in success of root-canal therapy (Madison &Wilcox1988). In all specimens in which a perforation was made, severe acute inflammation of the furcal bone was observed at1 week. This can be attributed to the trauma of the mechanical perforation. In the amalgam group this severe reaction continued throughout the experimental period owing to the extrusion of the material into the underlying bone. In both matrix groups, the inflammatory response diminished with time such that at 7 months two thirds of the samples were judged to be free of inflammation. Inthe1-month specimens the evidence of fibrous encapsulation around the matrix materials was observed.
The early capsules were partial and poorly defined. With time these capsules became more complete and organized and the fibres were clearly seen to run parallel to the material. Multinucleated giant cells were seen in association with the capsules in two thirds of cases. No differences were observed in the responses to HAPSET or hydroxyapatite. These findings were similar to those of Jew et al. (1982), who characterized the response as scar tissue formation.
Healing occurs by either repair or regeneration. If the damaged tissue is replaced by dense fibrous connective tissue, this is considered repair. Whilst this is preferable to either continued inflammation or periodontal pocket formation, as demonstrated in the amalgam and unsealed groups, it is not the most favorable response. Healing by regeneration, in which the tissue returns to its original state, is the most desirable reaction. In both matrix groups, a regenerative response was observed in approximately 50% of specimens. New bone formation was evident and bone deposition in direct contact with the matrix materials was observed. However, fibrous encapsulation, which is indicative of a reparative response, was also observed in these groups. It was not possible to determine whether those areas that demonstrated new bone deposition had previously been encapsulated by fibrous tissue or whether the bone was deposited without an intermediate step. It was common to see both reactions occurring side by side in the same specimen. The amount of new bone formation increased with time and one might speculate that had the experiment continued over a longer time period, greater bone deposition would have occurred.
Whilst all groups showed a similar response at1 week, differences were evident at later time periods. In the unsealed group the trend was towards periodontal pocket formation. In the amalgam group a continued severe inflammatory response was observed, with attempts at fibrous encapsulation. In both matrix groups there was a trend toward healing by either scar tissue or new bone formation. Therefore, under the conditions of this study, the histological responses were more favourable in the presence of an internal matrix.
A number of matrix materials, including calcium hydroxide, calcium phosphate or Guided Tissue Regeneration membranes (Salman et al. 1999) have been recommended. It was suggested that HAPSET might prove to be a better material than hydroxyapatite because of its superior handling properties and its hard set (Terry et al.1989). In fact, both materials were difficult to handle due mainly to their granular consistency. One would expect manipulation of these matrix materials to be facilitated by use of the operating microscope and this has proved to be the case in the clinical experience of the authors. The fast set was found to be a disadvantage rather than an advantage as the material tended to set before the procedures were completed. Whilst migration of hydroxyapatite particles may be problematic in periodontal procedures, this was not a concern in the well-defined and enclosed defect that results following perforation of the pulpal floor.
Further studies should increase the experimental period in order to observe whether there is continued bone deposition or persistence of connective tissue encapsulation of the matrix material. In the age of Mineral Trioxide Aggregate (MTA) it is suggested that an internal matrix is not required when this material is used to seal furcation perforations (Lee et al. 1993, Torabinejad et al. 1995, Sluyk et al.1998). It is proposed that extrusion of MTA into the alveolar bone does not pose a problem because new cementum will form in contact with the material, with regeneration of the entire periodontal apparatus. As this is the ultimate aim of repair of furcation perforations, these claims must be further evaluated in future studies.
Alhadainy H, Himel V (1993) Comparative study of the sealing ability of light-cured versus chemically cured materials placed into furcation perforations. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontics 76, 338-42.
Auslander W, Weinberg G (1969) Anatomic repair of internal perforations with indium foil and silver amalgam: outline of a method. New York Dental Journal 39, 454-7.
Balla R, Lomonaco CJ, Skribner J, Lin LM (1991) Histological study of furcation perforations treated with tricalcium phosphate, hydroxyapatite, amalgam and Life. Journal of Endodontics17, 234-8.
Beavers RA, Bergenholtz G, Cox F (1986) Periodontal wound healing following intentional root perforations in permanent teeth of Macaca mulatta. International Endodontic Journal 19, 36-44.
Bhasker SN, Rappaport H(1971) Histologic evaluation of endodontic procedures in dogs. Oral Surgery, Oral Medicine, Oral Pathology 31, 526-35.
Chau JY, Hutter JW, Mork TO, Nicoll BK (1997) An invitro study of furcation perforation repair using calcium phosphate cement. Journal of Endodontics 23, 588-92.
ElDeeb ME, ElDeeb M, Tabibi A, Jensen JR (1982) Evaluation of the use of amalgam, Cavit and calciumhydroxide in the repair of furcation perforations. Journal of Endodontics 8, 459-66.
Evans N, Krajian A (1930) A new method of decalcification. Archives of Pathology10, 447-451.
Himel VT, Brady J, Weir J (1985) Evaluation of repair of mechanical perforations of the pulp chamber floor using biodegradable tricalcium phosphate or calcium hydroxide. Journal of Endodontics 11, 161-5.
Jantarat J, Dashper SG, Messer HH (1999) Effect of matrix placement on furcation perforation repair. Journal of Endodontics 25, 192-6.
Jarcho M, Kay J, Gumaer K, Doremus R, Drobeck H (1977) Tissue, cellular and subcellular events at a bone-ceramic hydroxyapatite interface. Journal of Bioengineering 1, 79-92.
Jew R,Weine F, Keene J, Smulson M (1982) A histologic evaluation of periodontal tissue adjacent to root perforations filled with Cavit. Oral Surgery, Oral Medicine, Oral Pathology 54, 124-35.
Kenney E, Lekovic VSa, Ferreira J, Han T, Dimitrijevic B, Carranza F (1986) Bone formation within porous hydroxyapatite implants in human periodontal defects. Journal of Periodontology 57, 76-83.
Kent J, Quinn J, Zide M, Guerra L, Boyne P (1983) Alveolar ridge augmentation using non-resorbable hydroxyapatite with or without autogenous cancellous bone. Journal of Oral and Maxillofacial Surgery 41, 629-42.
Lantz B, Persson P (1967) Periodontal tissue reactions after root perforation in dog's teeth: a histologic study. Odontologisk Tedskrift 75, 209-37.
Lantz B, Persson P (1970) Periodontal tissue reaction after surgical treatment of root perforations in dog's teeth: a histologic study. Odontologisk Revy 21, 51-62.
Lee SJ, Monsef M, Torabinejad M (1993) Sealing ability of a mineral trioxide aggregate for repair of lateral root perforations. Journal of Endodontics19, 541-4.
Lemon R (1992) Non-surgical repair of perforation defects. Dental Clinics of North America 36, 439-57.
Madison S, Wilcox L (1988) An evaluation of coronal microleakage in endodontically treated teeth. Part III. In vivo study. Journal of Endodontics 14, 455-8.
Moloney L, Feik S, Ellender G (1993) Sealing ability of three materials used to repair lateral root perforations. Journal of Endodontics19, 59-62.
Nicholls E (1962) Treatment of traumatic perforations of the pulp cavity. Oral Surgery, Oral Medicine, Oral Pathology 15, 603-12.
Ricci J, Alexander H, Parsons J, Salsbury R, Weiss A (1986) Partially Resorbable Hydroxylapatite-Based Cement for Repair of Bone Defects. Proceedings of the 12th Annual Meeting of the Society of Biomaterials 28.
Salman MA, Quinn F, Demody J, Hussey D, Claffey N (1999) Histological evaluation of repair using a bioresorbable membrane beneath a resin-modified glass ionomer after mechanical furcation perforation in dogs' teeth. Journal of Endodontics 25, 181-6.
Seltzer S, Sinai I, August D (1970) Periodontal effects of root perforations before and during endodontic procedures. Journal of Dental Reseach 49, 332-9.
Sinai I, Romea D, Glassman G, Morse D, Fantasia J, Furst M (1989) An evaluation of tricalcium phosphate as a treatment for endodontic perforations. Journal of Endodontics 15, 399-403.
Sluyk SR, Moon PC, Hartwell GR (1998) Evaluation of setting properties and retention characteristics of mineral trioxide aggregate when used as a furcation perforation repair material. Journal of Endodontics 24, 768-71.
Terry B, Baker R, Tucher M, Hanker J (1989) Alveolar ridge augmentation with composite implants of hydroxyapatite an plaster for correction of bony defects, deficiencies and related contour abnormalities. Materials Research Society Symposium Procedures 110, 187.
Torabinejad M, Hong CU, Lee SF, Monsef M, Pitt-Ford TR (1995) Investigation of mineral trioxide aggregate for root-end filling in dogs. Journal of Endodontic 21, 603-8.