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Self-setting acrylic as an immobilizing agent in mandibular fractures
Self-setting acrylic as an immobilizing agent in mandibular fractures A histologic
study
P. Yaman, D.D.S., and R. Diaz-Pe’rez, UNIVERSITY ADMINISTRATION
IV. A. Caste%, D.D.S., M.S., C. E. Nasjleti, M.D., Ann Arbor and Detroit, Mich.
OF MICHIGAN,
DEPARTMENT
HOSPITAL,
ANN
ARBOR;
OF ANATOMY AND
D.D.S.,
; VETERANS
ANNAPOLIS
HOSPITAL,
DETROIT
T
he literature contains few reports on the use of plastic polymers as an intraosseous immobilizing agent in fractured and in diseased bones.lV3 Polyurethane polymer and cyanoacrylate monomer have been used in experimental mandibular fractures as a bonding and immobilizing material, with no encouraging results. The main complications attached to these experiments were a significant number of nonunion fractures and secondary infections at the surgical sites.4p 5 In a general study, CoroneY tested heat-cured polymethyl methacrylate resin in tissue culture and found it to be harmless to polymorphonuclear cells, macrophages, and fibroblasts. He also reported no evidence of negative bone reaction when the resin was tested in vivo. Another group of investigators have tried self-setting acrylic as an intratissular restorative device and found it to be harmless to living tissues.7p 8 Encouraged by these previous results, we decided to test self-setting methyl methacrylate resin in experimental mandibular fractures as a substitute for the traditional techniques of immobilization, namely, interdental, intersegmental wiring, or other intraoral devices. The prospect of packing acrylic into the mandibular bone invariably raises the question of how this material will affect the viability of the bone and how the bone will react immediately or in the immediate future. Considered to be of prime importance was the making of a histologic analysis of probable changes in cellular activities and bone dynamics in areas of the mandible adjacent to the acrylic resin. Hence, the objectives of this study will be focused on the following points: This study was supported by a Dental of Michigan, School of Dentistry.
Student
Research
Fellowship
from
The
University
MATERIALS
AND
METHODS
This study was carried out on eight young adult mongrel dogs with permanent dentition ant1 with an average weight of approximately 19 kilograms. The surgical procctl~wcs were performed with the animals under intravenous pcntoharhital sodium anesthesia. The cxtraoral approach was used during the surgichal interventions. In each of the eight dogs, the vcstibular surface of the mandibular body was exposed at the molar area. With a surgical hur mounted in a dental handpircc, a vertical defect was made at the vestibular cortex of the mandibular bod,v and cxtendetl to the basilar border of the bone. The lingual plat,e was fractured with a blunt instrument by inserting it in the restibular defect and twisting laterally. When a dental root was in the fracture line, the tooth was immediately extracted. In four animals the mandibular fractures were immobilized with acrylic, and in four, with a cross-wiring technique. In the fractures immobilizect with acrylic, in order to increase the retentional capacity of the resin, two cavities were additionally cut in the bone perpendicular to the fracture tlefcct. Self-cured acrylic Sevriton” was prepared and packed into the fracture tract and retentive defects. Excess Serriton was trimmed off 1 to 1.5 mm. below the vestibular,surface of the mandibular body. In the fractures immobilized with wire, four perforations were drilled at the fracture segments to crisscross the wire. Stainless steel wires (Wgauge) were used. The wounds were closed in anatomic layers with 3-O plain catgut sutures. Postoperatively, all eight dogs were kept on a soft diet and given a daily intramuscular injection of Combiotict (penicillin-streptomycin) for 5 days in order to prevent secondary infection of the surgical arcas. Mandibular x-ray films were taken of all dogs at regular timed intervals in order to check the progress of the healing process and evidence of boric formation. The dogs, one from each group, were killed at 1, 3, 5, and 10 weeks after operation. Intraarterial perfusions of 50 per cent aqueous solution of India ink, via the external carotid artery, were also made. The healing bony segments were carefull) removed, fixed in neutral 10 per cent formalin, serially sectioned, and stained with hematoxylin and eosin, Brown and Bree, Mallory, and periodic acid-Schiff (PAS) stains. RESULTS Acrylic
immobilization
The examination of the specimen taken 1 week postoperatively revealed a complete regrowth of the stratified squamous epithelium of the oral lining. The *Amalgamated tpfizer,
Inc.,
Dental Trade D&t., New York, N.Y.
Ltd.,
London,
W.1.
England.
Volume Numher
36 3
Fig. 1. One week alveolar canal (IAC). predominant reaction
Self-setting
acry&
as irnswbilizi?~g
agent
461
postoperatively. Bottom of fracture defect (BD) is adjacent to inferior The increased vascularity of the tissue in this area (VA) is the at this stage of the healing process.
epithelium was very thin, and the rete ridges appeared to be shorter than in the traumatized area. The organizing hematoma was represented by an irregular layer of fibrin which included small bits of dead bone. No evidence of inflammatory reaction was noticed. An irregular layer of necrosed bone was observed adjacent to the acryIic material. About the endosteal and periosteal sides of the fracture there were a proliferation and differentiation of cells (most likely of mesenchymal origin) into fibrous connective tissue, which filled almost all the defect produced by the surgical bur. There was no evidence of bone formation in the defect, although some digitations of bony tissue appeared to be insinuated into it. An increased rascularity was present at the side of the inferior alveolar canal adjacent to the acrylic material, with vascular connective tissue proliferating quite rapidly (Fig. 1). The specimen obtained at the third week after operation showed almost a complete closure of the fracture defect by young bony tissue with the same amount of PAS material as in the mature bone. The site where the acrylic was placed appeared to be empty and was surrounded by an irreguIar pseudocapsule formed by loose, highly vascular connective tissue. A process of bone remodeling was taking place in areas of the bone adjacent to the acrylic material (Fig. 2). The Brown and Bree stain revealed no colonies of bacteria in this tissue. Occasional, scattered cocci organisms mere present in some fields, but the number was considered to be within the expected normal limits. Five weeks postoperatively, a better and advanced organization of the pseudocapsule was developed, with an increase in fibrous density. The surface adjacent to the acrylic had a well-vaseularized layer of fibrin admixed in a myxomatoid type of tissue. The surface of the capsule adjacent to the bone was also richly vascularized and exhibited cIusters of red Hood corpuscles. The active part of the pseudocapsule, however, was dominated by young connective
Yaman et al.
462
Fig. highly
8. Three weeks postoperatively. vascular connective tissue (PZ)
Oral surg. September,
1973
An irregular pseudocapsule (PC) formed by a loose, is isolating the acrylic material (AC) from the bone.
tissue which was invading the nearby marrow spaces (Fig. 3). In the area of the external callus, the collagenous bundles were arranged in a disorderly manner, &th a minimal amount of ground substance between them. This arrangement was indicative of scar and regenerative process. Cartilaginous tissue had developed about the borders of the fracture and, in areas in which vascular channels were available, t,his tissue was progressively transforming into lamellar bone. Ten weeks postoperatively, the pseudocapsule had increased in thickness and exhibited no evidence of inflammatory changes (Fig. 4). A rich vascularity was present in the surfaces of the capsule adjacent to both acrylic and bone, while projections of connective tissue from the pseudocapsule were obliterating nearby marrow spaces, Wiring
immobilization
The healing process in the series of fractures immobilized by using a crosswiring technique showed the typical histologic findings already described elsewhere. A brief description of these findings follows: In the specimen 3 weeks postoperatively, generous endosteal and periosteal calluses had been formed, with an active induction of bone formation advancing centripetally from the fracture borders. Five weeks postoperatively, there was a complete closure of the fracture defect by regenerated bone, and the tract left by the wire was
Self-setting
Fig. 3. an increase Fibrin layer Fig. 4. evidence of
acrylic
as immobilizing
agent
443
Five weeks postoperatively. The pseudocapsule is better organized and exhibits in fibrous density (FD). Blood vessels in pseudocapsule are adjacent to bone (BT). (FL). Ten u;eeks postoperatively. The well-organized pseudoeapsule (PC) exhibits no inflammatory changes. Acrylic (AC). Magnification, x100.
composed of loose connective tissue with focal areas of condensation (Fig. 5). Ten weeks postoperatively, the healing process was almost complete and a good consolidation of the fracture had been attained by way of heavy bony bridging between fracture segments. DlSCUSSION A difference in histologic reactions was noticed in the healing process of fractures immobilized with wire and those immobilized with acrylic. In fractures in which wire was used, the healing process was uneventful and fast. There was an organization of the blood clot into bone trabeculae, and a good consolidation of the fracture followed. In cases in which acrylic was used, a
Oral September,
Fig. 5. Wiring completely closed
immobilization. by regenerated
Five xeekx postoperativeiy. bone (XB). M:lgnification,
Fracture
tract
(FT)
Surg. 1973
has been
x10.
rigid immobilization of the fracture fragments was obtained immediately after operation. Later, hecause of a concomitant process of boric remodeling and formation of the pseudocapsule around the acrylic, the tight contact at the acrylic-bone interface was lost. This event indirectly provoked metaplastic changes of the newly formed bone trabeeulae, at the periosteal callus, into a fibrocartilaginous tissue. The prcscnce and c*onsolidation of cartilage in areas in which a fracture is healing might be a determinant factor in the formation of a pseudojoint. Since acrylic is a solid and insoluble substance, its “reactivity” when exposed to an internal biological medium should be nil. In this instance, the medium might exhibit a simple foreign-body reaction, consisting in the encapsulation of the substance.!’ In a way, this is what happened in the mandible in those areas in which the acrylic was packed. The resin was thoroughly encapsulated by a young fibr0~1s vonneetivc tissue, but there was no evidence in the tissue of multinuclcatetl giant cells or of inflammatory cells which are typically present in a foreign-body reaction. The marked vascularization and ncocapillarization of the pseudocapsule, which appeared to bc more prominent in the first stages of the healing process, were c~onsitlerctl to be the normal pattern of vascularity usually present in any repair and healing process. Close examination of the capsule in all specimens studied demonstrated also the absence of a granulomatous type of reaction, and no elements of the rcticulorndothelial system were identified. The absence of granulation tissue appears to have resulted from the fact that thcrc was 110 se.condary infections in the animals operated on, and that the tight packing of the acrylic resin against the walls of the retentive cavity left no space or gap to be tilled in with reparative tissue. Although our histologic study did not revcal any healing abnormality in areas of the tissue adjacent to the acrylic, other than the formation of the pseudocapsule, previous reports have demonstrated an irritating effect of self-
Self-setting
acrylic
as immobilizing agent 465
cured acrylic when used in a biological medium. This effect is probably due to the release of monomer from the surface of the solid because of an incomplete polymerization of the resinlo There appears to be an agreement among a group of investigators to accept the fact that the inclusion of acrylic in oral tissues induced the formation of fibrous connective tissue and the loss of bonc.l17’” Oppenheimer and associates*” and Hueper18 and Stinson17 have warned of the cancerogenetic potential of acrylic resin, since they were able to induce the formation of fibrosarcomas after a relatively short period of time when the resin was implanted subcutaneously in small laboratory animals. In any event, the divergent opinions of various authors7, 8, 11-16, 16-18 in regard to the suitability of acrylic to become incorporated into living tissues is a good indication that the acrylic-internal biological medium relationship needs further study and consideration. In a previous report we emphasized, following the concept of Freyberg,l$ that there must be certain factors or variations in the composition of the connective tissue in different individuals or animals which make some react with significant inflammatory infiltrates or cellular proliferations while others, subjected to the same stimulus or exposure, have only slight changes or none at all. SUMMARY
In mandibular fractures immobilized with acrylic, the response of the bone tissue adjacent to the resin was a simple process of repair and scarring, with formation of a pseudocapsule composed of fibrous connective tissue, which isolated the acrylic material from the adjacent bone. There was also a delay in the consolidation of the endosteal and periosteal calluses due to the presence of fibrocartilaginous tissue. These conditions might pave the way for a nonunion fracture or formation of a pseudojoint. There was a marked vascularization and neocapillarization of the pseudocapsule, which appeared to be more predominant in the first phase of the healing process. There was no evidence of a granulomatous type of reaction or atypical cellular response and no elements of the reticuloendothelial system to be identified. In fractures immobilized with wire, the healing process was uneventful and fast. Cellular activity was oriented toward the production of periosteal and endosteal calluses, containing centripetally progressing bony trabeculae which readily obturated the fracture defect and line. REFERENCES
1. Mandarino, M. P.., and Salvatore, J. E.: Polyurethane Polymer; Its Use in Osseous Lesions: An Experimental Study, Ann. Surg. 149: 107-109, 1959. 2. Mandarino. M. P.: A Pol.vurethane Polymer (Ostamer) : Its Use in Fractured and Diseased Bones, Arch. Surg.-80: 623-627, 1960. 3. Struthers, A. M., Grindley, J. H., and Figi, F. A.: An Experimental Study of Polyvinyl Sponges as a Substitute for Bone, Plast. Reconstr. Surg. 15: 274-289, 1955. 4. Lighterman, I., and Farrell, J. J.: Mandibular Fractures, Treated With Plastic Polymers, Arch. Surp. 87: 868.878. 1963. 5. Yrastorza, J. A., and Kruger, G. 0.: Polyurethane Polymer in the Healing of Experimentally Fractured Mandibles. ORAL SURG. 16: 978-984. 1963. 6. Coronell S.: Les R&sines Acryliques en Prothese et en’Biologie, Thesis, Paris, 1947. 7. Hodosh, M., Povar, M., and Shklar, G.: Periodontal Fiber Attachment to the Plastic Tooth Implant, J. Periodontal. 39: 5-7, 1968.
Oral surg. Septembrr,
Polymer Implant Concept J. Prosthet. M., Povar, WI., and Shklar, G.: The Dental Dent. 22: 371-380, 1969. in Sodcman, \V. A., editor: Pathologic Dinman, B. D.: Chemical Agents and Disease, 1967, W. B. Saunders Co., pp. 253-274. Physiology-Mechanism of Disease, Philadelphia, Brown, D. E.: Tissue Reaction to Plastic and Metal Implants, Awh. Otolaryngol. 88: “83.28?, 1968. Castelli,, W. A., Nasjleti, C. E., Huelke, D. E’., and Diaz-PCrez, R.: Revnscularixation of the Prrlodontium After Tooth Grafting in Monkeys, J. Dent. lies. 50: 414-421, 1971. of Acrylic on Periodontium Nasjleti, C. E., Castelli, W. A., and Keller, B. E.: Effects of Monkeys, J. Dent. Res. 51: 13X2-1387, 1971. II.: Implantation of Acrylic Roots in Tooth Sockets, OK.I\I, Wnerhaug, J., and Zander, fhRG. 9: 46-54, 1956. Tobin-White, A.: Implantation of Acrylic Teeth in the Jaws, ht. Dent. J. 8: 15, 1958. Narang, R., and Wells, H.: Decalcified Allogenic Bone Enhances the Successful Maintenance of Implanted Acrylic Teeth, Int. Assoc. Dent. Res. Program and Abstracts of Papers, No. 259, 1971. E. T., Stout, A. P. Willhite, M., and Danishefsky, I.: Oppenheimer, B. S., Oppenheimer, The Latent Period in Carcinogenesis by Plastics in Rats and Its Relation to the I’resarcomatous Stage, Cancer 11: 204-213, 1958. Rtinsoy, N. E.: The Tissue Raeaction Induced in Rats and Guinea Pigs by Polymathacrylate (Acryhc) and Stainless Steel, Br. J. Exp. Pathol. 45: 21-29, 1966. Hueper, W. C.: Carcinogenetic Studies on Water Soluble and Insoluble Macromolecules, Arch. Pathol. 67: 587-617, 1959. Freyberg, R. H.: The Joints, in Sodeman, W. A., editor: Pathologic PhysiologyMechanism of Disease, Philadelphia, 1967, W. B. Saunders Co., pp. 935.957.
8. Ilotlosh, 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.
1973
Reprint requests to: Dr. P. Yaman Department of Anatomy University of Michigan School Ann Arbor, Mich. 48104
of Dentistry
study
P. Yaman, D.D.S., and R. Diaz-Pe’rez, UNIVERSITY ADMINISTRATION
IV. A. Caste%, D.D.S., M.S., C. E. Nasjleti, M.D., Ann Arbor and Detroit, Mich.
OF MICHIGAN,
DEPARTMENT
HOSPITAL,
ANN
ARBOR;
OF ANATOMY AND
D.D.S.,
; VETERANS
ANNAPOLIS
HOSPITAL,
DETROIT
T
he literature contains few reports on the use of plastic polymers as an intraosseous immobilizing agent in fractured and in diseased bones.lV3 Polyurethane polymer and cyanoacrylate monomer have been used in experimental mandibular fractures as a bonding and immobilizing material, with no encouraging results. The main complications attached to these experiments were a significant number of nonunion fractures and secondary infections at the surgical sites.4p 5 In a general study, CoroneY tested heat-cured polymethyl methacrylate resin in tissue culture and found it to be harmless to polymorphonuclear cells, macrophages, and fibroblasts. He also reported no evidence of negative bone reaction when the resin was tested in vivo. Another group of investigators have tried self-setting acrylic as an intratissular restorative device and found it to be harmless to living tissues.7p 8 Encouraged by these previous results, we decided to test self-setting methyl methacrylate resin in experimental mandibular fractures as a substitute for the traditional techniques of immobilization, namely, interdental, intersegmental wiring, or other intraoral devices. The prospect of packing acrylic into the mandibular bone invariably raises the question of how this material will affect the viability of the bone and how the bone will react immediately or in the immediate future. Considered to be of prime importance was the making of a histologic analysis of probable changes in cellular activities and bone dynamics in areas of the mandible adjacent to the acrylic resin. Hence, the objectives of this study will be focused on the following points: This study was supported by a Dental of Michigan, School of Dentistry.
Student
Research
Fellowship
from
The
University
MATERIALS
AND
METHODS
This study was carried out on eight young adult mongrel dogs with permanent dentition ant1 with an average weight of approximately 19 kilograms. The surgical procctl~wcs were performed with the animals under intravenous pcntoharhital sodium anesthesia. The cxtraoral approach was used during the surgichal interventions. In each of the eight dogs, the vcstibular surface of the mandibular body was exposed at the molar area. With a surgical hur mounted in a dental handpircc, a vertical defect was made at the vestibular cortex of the mandibular bod,v and cxtendetl to the basilar border of the bone. The lingual plat,e was fractured with a blunt instrument by inserting it in the restibular defect and twisting laterally. When a dental root was in the fracture line, the tooth was immediately extracted. In four animals the mandibular fractures were immobilized with acrylic, and in four, with a cross-wiring technique. In the fractures immobilizect with acrylic, in order to increase the retentional capacity of the resin, two cavities were additionally cut in the bone perpendicular to the fracture tlefcct. Self-cured acrylic Sevriton” was prepared and packed into the fracture tract and retentive defects. Excess Serriton was trimmed off 1 to 1.5 mm. below the vestibular,surface of the mandibular body. In the fractures immobilized with wire, four perforations were drilled at the fracture segments to crisscross the wire. Stainless steel wires (Wgauge) were used. The wounds were closed in anatomic layers with 3-O plain catgut sutures. Postoperatively, all eight dogs were kept on a soft diet and given a daily intramuscular injection of Combiotict (penicillin-streptomycin) for 5 days in order to prevent secondary infection of the surgical arcas. Mandibular x-ray films were taken of all dogs at regular timed intervals in order to check the progress of the healing process and evidence of boric formation. The dogs, one from each group, were killed at 1, 3, 5, and 10 weeks after operation. Intraarterial perfusions of 50 per cent aqueous solution of India ink, via the external carotid artery, were also made. The healing bony segments were carefull) removed, fixed in neutral 10 per cent formalin, serially sectioned, and stained with hematoxylin and eosin, Brown and Bree, Mallory, and periodic acid-Schiff (PAS) stains. RESULTS Acrylic
immobilization
The examination of the specimen taken 1 week postoperatively revealed a complete regrowth of the stratified squamous epithelium of the oral lining. The *Amalgamated tpfizer,
Inc.,
Dental Trade D&t., New York, N.Y.
Ltd.,
London,
W.1.
England.
Volume Numher
36 3
Fig. 1. One week alveolar canal (IAC). predominant reaction
Self-setting
acry&
as irnswbilizi?~g
agent
461
postoperatively. Bottom of fracture defect (BD) is adjacent to inferior The increased vascularity of the tissue in this area (VA) is the at this stage of the healing process.
epithelium was very thin, and the rete ridges appeared to be shorter than in the traumatized area. The organizing hematoma was represented by an irregular layer of fibrin which included small bits of dead bone. No evidence of inflammatory reaction was noticed. An irregular layer of necrosed bone was observed adjacent to the acryIic material. About the endosteal and periosteal sides of the fracture there were a proliferation and differentiation of cells (most likely of mesenchymal origin) into fibrous connective tissue, which filled almost all the defect produced by the surgical bur. There was no evidence of bone formation in the defect, although some digitations of bony tissue appeared to be insinuated into it. An increased rascularity was present at the side of the inferior alveolar canal adjacent to the acrylic material, with vascular connective tissue proliferating quite rapidly (Fig. 1). The specimen obtained at the third week after operation showed almost a complete closure of the fracture defect by young bony tissue with the same amount of PAS material as in the mature bone. The site where the acrylic was placed appeared to be empty and was surrounded by an irreguIar pseudocapsule formed by loose, highly vascular connective tissue. A process of bone remodeling was taking place in areas of the bone adjacent to the acrylic material (Fig. 2). The Brown and Bree stain revealed no colonies of bacteria in this tissue. Occasional, scattered cocci organisms mere present in some fields, but the number was considered to be within the expected normal limits. Five weeks postoperatively, a better and advanced organization of the pseudocapsule was developed, with an increase in fibrous density. The surface adjacent to the acrylic had a well-vaseularized layer of fibrin admixed in a myxomatoid type of tissue. The surface of the capsule adjacent to the bone was also richly vascularized and exhibited cIusters of red Hood corpuscles. The active part of the pseudocapsule, however, was dominated by young connective
Yaman et al.
462
Fig. highly
8. Three weeks postoperatively. vascular connective tissue (PZ)
Oral surg. September,
1973
An irregular pseudocapsule (PC) formed by a loose, is isolating the acrylic material (AC) from the bone.
tissue which was invading the nearby marrow spaces (Fig. 3). In the area of the external callus, the collagenous bundles were arranged in a disorderly manner, &th a minimal amount of ground substance between them. This arrangement was indicative of scar and regenerative process. Cartilaginous tissue had developed about the borders of the fracture and, in areas in which vascular channels were available, t,his tissue was progressively transforming into lamellar bone. Ten weeks postoperatively, the pseudocapsule had increased in thickness and exhibited no evidence of inflammatory changes (Fig. 4). A rich vascularity was present in the surfaces of the capsule adjacent to both acrylic and bone, while projections of connective tissue from the pseudocapsule were obliterating nearby marrow spaces, Wiring
immobilization
The healing process in the series of fractures immobilized by using a crosswiring technique showed the typical histologic findings already described elsewhere. A brief description of these findings follows: In the specimen 3 weeks postoperatively, generous endosteal and periosteal calluses had been formed, with an active induction of bone formation advancing centripetally from the fracture borders. Five weeks postoperatively, there was a complete closure of the fracture defect by regenerated bone, and the tract left by the wire was
Self-setting
Fig. 3. an increase Fibrin layer Fig. 4. evidence of
acrylic
as immobilizing
agent
443
Five weeks postoperatively. The pseudocapsule is better organized and exhibits in fibrous density (FD). Blood vessels in pseudocapsule are adjacent to bone (BT). (FL). Ten u;eeks postoperatively. The well-organized pseudoeapsule (PC) exhibits no inflammatory changes. Acrylic (AC). Magnification, x100.
composed of loose connective tissue with focal areas of condensation (Fig. 5). Ten weeks postoperatively, the healing process was almost complete and a good consolidation of the fracture had been attained by way of heavy bony bridging between fracture segments. DlSCUSSION A difference in histologic reactions was noticed in the healing process of fractures immobilized with wire and those immobilized with acrylic. In fractures in which wire was used, the healing process was uneventful and fast. There was an organization of the blood clot into bone trabeculae, and a good consolidation of the fracture followed. In cases in which acrylic was used, a
Oral September,
Fig. 5. Wiring completely closed
immobilization. by regenerated
Five xeekx postoperativeiy. bone (XB). M:lgnification,
Fracture
tract
(FT)
Surg. 1973
has been
x10.
rigid immobilization of the fracture fragments was obtained immediately after operation. Later, hecause of a concomitant process of boric remodeling and formation of the pseudocapsule around the acrylic, the tight contact at the acrylic-bone interface was lost. This event indirectly provoked metaplastic changes of the newly formed bone trabeeulae, at the periosteal callus, into a fibrocartilaginous tissue. The prcscnce and c*onsolidation of cartilage in areas in which a fracture is healing might be a determinant factor in the formation of a pseudojoint. Since acrylic is a solid and insoluble substance, its “reactivity” when exposed to an internal biological medium should be nil. In this instance, the medium might exhibit a simple foreign-body reaction, consisting in the encapsulation of the substance.!’ In a way, this is what happened in the mandible in those areas in which the acrylic was packed. The resin was thoroughly encapsulated by a young fibr0~1s vonneetivc tissue, but there was no evidence in the tissue of multinuclcatetl giant cells or of inflammatory cells which are typically present in a foreign-body reaction. The marked vascularization and ncocapillarization of the pseudocapsule, which appeared to bc more prominent in the first stages of the healing process, were c~onsitlerctl to be the normal pattern of vascularity usually present in any repair and healing process. Close examination of the capsule in all specimens studied demonstrated also the absence of a granulomatous type of reaction, and no elements of the rcticulorndothelial system were identified. The absence of granulation tissue appears to have resulted from the fact that thcrc was 110 se.condary infections in the animals operated on, and that the tight packing of the acrylic resin against the walls of the retentive cavity left no space or gap to be tilled in with reparative tissue. Although our histologic study did not revcal any healing abnormality in areas of the tissue adjacent to the acrylic, other than the formation of the pseudocapsule, previous reports have demonstrated an irritating effect of self-
Self-setting
acrylic
as immobilizing agent 465
cured acrylic when used in a biological medium. This effect is probably due to the release of monomer from the surface of the solid because of an incomplete polymerization of the resinlo There appears to be an agreement among a group of investigators to accept the fact that the inclusion of acrylic in oral tissues induced the formation of fibrous connective tissue and the loss of bonc.l17’” Oppenheimer and associates*” and Hueper18 and Stinson17 have warned of the cancerogenetic potential of acrylic resin, since they were able to induce the formation of fibrosarcomas after a relatively short period of time when the resin was implanted subcutaneously in small laboratory animals. In any event, the divergent opinions of various authors7, 8, 11-16, 16-18 in regard to the suitability of acrylic to become incorporated into living tissues is a good indication that the acrylic-internal biological medium relationship needs further study and consideration. In a previous report we emphasized, following the concept of Freyberg,l$ that there must be certain factors or variations in the composition of the connective tissue in different individuals or animals which make some react with significant inflammatory infiltrates or cellular proliferations while others, subjected to the same stimulus or exposure, have only slight changes or none at all. SUMMARY
In mandibular fractures immobilized with acrylic, the response of the bone tissue adjacent to the resin was a simple process of repair and scarring, with formation of a pseudocapsule composed of fibrous connective tissue, which isolated the acrylic material from the adjacent bone. There was also a delay in the consolidation of the endosteal and periosteal calluses due to the presence of fibrocartilaginous tissue. These conditions might pave the way for a nonunion fracture or formation of a pseudojoint. There was a marked vascularization and neocapillarization of the pseudocapsule, which appeared to be more predominant in the first phase of the healing process. There was no evidence of a granulomatous type of reaction or atypical cellular response and no elements of the reticuloendothelial system to be identified. In fractures immobilized with wire, the healing process was uneventful and fast. Cellular activity was oriented toward the production of periosteal and endosteal calluses, containing centripetally progressing bony trabeculae which readily obturated the fracture defect and line. REFERENCES
1. Mandarino, M. P.., and Salvatore, J. E.: Polyurethane Polymer; Its Use in Osseous Lesions: An Experimental Study, Ann. Surg. 149: 107-109, 1959. 2. Mandarino. M. P.: A Pol.vurethane Polymer (Ostamer) : Its Use in Fractured and Diseased Bones, Arch. Surg.-80: 623-627, 1960. 3. Struthers, A. M., Grindley, J. H., and Figi, F. A.: An Experimental Study of Polyvinyl Sponges as a Substitute for Bone, Plast. Reconstr. Surg. 15: 274-289, 1955. 4. Lighterman, I., and Farrell, J. J.: Mandibular Fractures, Treated With Plastic Polymers, Arch. Surp. 87: 868.878. 1963. 5. Yrastorza, J. A., and Kruger, G. 0.: Polyurethane Polymer in the Healing of Experimentally Fractured Mandibles. ORAL SURG. 16: 978-984. 1963. 6. Coronell S.: Les R&sines Acryliques en Prothese et en’Biologie, Thesis, Paris, 1947. 7. Hodosh, M., Povar, M., and Shklar, G.: Periodontal Fiber Attachment to the Plastic Tooth Implant, J. Periodontal. 39: 5-7, 1968.
Oral surg. Septembrr,
Polymer Implant Concept J. Prosthet. M., Povar, WI., and Shklar, G.: The Dental Dent. 22: 371-380, 1969. in Sodcman, \V. A., editor: Pathologic Dinman, B. D.: Chemical Agents and Disease, 1967, W. B. Saunders Co., pp. 253-274. Physiology-Mechanism of Disease, Philadelphia, Brown, D. E.: Tissue Reaction to Plastic and Metal Implants, Awh. Otolaryngol. 88: “83.28?, 1968. Castelli,, W. A., Nasjleti, C. E., Huelke, D. E’., and Diaz-PCrez, R.: Revnscularixation of the Prrlodontium After Tooth Grafting in Monkeys, J. Dent. lies. 50: 414-421, 1971. of Acrylic on Periodontium Nasjleti, C. E., Castelli, W. A., and Keller, B. E.: Effects of Monkeys, J. Dent. Res. 51: 13X2-1387, 1971. II.: Implantation of Acrylic Roots in Tooth Sockets, OK.I\I, Wnerhaug, J., and Zander, fhRG. 9: 46-54, 1956. Tobin-White, A.: Implantation of Acrylic Teeth in the Jaws, ht. Dent. J. 8: 15, 1958. Narang, R., and Wells, H.: Decalcified Allogenic Bone Enhances the Successful Maintenance of Implanted Acrylic Teeth, Int. Assoc. Dent. Res. Program and Abstracts of Papers, No. 259, 1971. E. T., Stout, A. P. Willhite, M., and Danishefsky, I.: Oppenheimer, B. S., Oppenheimer, The Latent Period in Carcinogenesis by Plastics in Rats and Its Relation to the I’resarcomatous Stage, Cancer 11: 204-213, 1958. Rtinsoy, N. E.: The Tissue Raeaction Induced in Rats and Guinea Pigs by Polymathacrylate (Acryhc) and Stainless Steel, Br. J. Exp. Pathol. 45: 21-29, 1966. Hueper, W. C.: Carcinogenetic Studies on Water Soluble and Insoluble Macromolecules, Arch. Pathol. 67: 587-617, 1959. Freyberg, R. H.: The Joints, in Sodeman, W. A., editor: Pathologic PhysiologyMechanism of Disease, Philadelphia, 1967, W. B. Saunders Co., pp. 935.957.
8. Ilotlosh, 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.
1973
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