OSTEOGENIC REPLACEMENT PHOSPHATE CERAMIC IMPLANTS
OF TRICALCIUM IN THE DOG PALATE
W. A. MORS and E. J. KAMINSKI Cleft Palate. Orthodontic and Pathology Departments, Dental and Medical Schools, Northwestern University, Chicago, Illinois 60611 U.S.A. effects of tricalcium phosphate implants in surgically created cleft palates in Beagle dogs were studied. Radiographic studies indicated evidence of resorption of the ceramic and no alteration of normal growth patterns. Histologic studies showed definite implant replacement by normal appearing bone tissue. Summary-The
INTRODUCTION Various
methods
and materials
have been used in
attempting surgical correction of cleft palates with varying degrees of success. Timing of surgical closure is also somewhat controversial, but current philosophies generally subscribe to closure of hard tissue defects after most or all of growth of the maxilla is complete. Development of a material biologically compatible with human tissues that would not restrict growth would permit early surgical correction of the hard tissue defects found with cleft palates and other bone defects with a universal non-human implant material. In this study we present preliminary results of experiments for correction of artificially created cleft palate defects using bioresorbable materials which are biocompatible and do not appear to restrict normal growth. MATERIALS AND METHODS
Nine true-bred Beagle dogs (obtained from Ridgland Research Farms, Inc., 301 West Main Street, Mt. Horeb. Wisconsin 53572), five males and four females, 1-6 weeks of age, were divided into three groups: Group I consisted of three control animals, two animals with no surgery or implants, and one animal with surgical removal of bone only. Group II consisted of three animals having surgical removal of bone followed by immediate implant placement. Group III consisted of three animals having surgical removal of bone followed 3 months later with implant placement. Initial and final alginate impressions were made of the maxilla of each animal while anaesthetized I.M. with Inovar Vet and stone models were poured with orthodontic plaster. Initial, immediate post-implant or post-surgery. 3-month and final occlusal radiographs were taken of each maxilla using Kodak occlusal film. Initial and final blood samples were drawn from each animal for biochemical tests which included standard SMA12 parameters: total protein, albumin, total calcium. total lipids, total cholesterol, uric acid, creatine, total bilirubin, alkaline phosphatase, creatine phosphokinase, lactic dehydrogenase and serum transaminase. At the time of surgery each dog was anaesthetized intravenously with Diabutal and local anaesthetic, Xylocaine HCl 2 per cent with epinephrine 1: 100,000 was injected into the palate. Four stainless steel im-
plant markers, two in the anterior and two in the posterior part of the hard palate were placed with the Bjiirk implant instrument according to Bjijrk (1955). The mucoperiosteum was reflected unilaterally from the left side of the palate. The palatal bone was cut with a surgical bur as shown in Fig. 1 to allow removal of a continuous section of bone 25 x 7 mm from the left side of the palatal midline which continued along the premaxill~maxillary suture. Care was taken not to rupture or damage the mucoepithelial tissues on the nasal side. Sections of resorbable tricalcium phosphate (resorbable porous ceramic made from a high purity, specially prepared and processed form of tricalcium phosphate by M.I.T.E.R. Inc., 633 High Street, Washington, Ohio 43095) were cut and shaped with a diamond disc to the specific dimensions of the defect and placed without any means of fixation. The mucoperiosteum was reapproximated and sutured with 3-O silk. The same surgical procedure of bone removal was followed in Group III without immediate implant placement. After 3 months from initial bone removal animals of this group again had the same procedure performed and implants placed in the same manner as before described. All animals were maintained throughout the test period on Science Diet, (manufactured by Riviana Foods, Ind., Hill’s Division. Topeka, Kansas 66601) which together with water was supplied in crushed form to avoid discomfort to the animals during eating and pr5vent traumatic dislodgment of the implants. One week prior to death, all animals were given tetracycline for bone labelling purposes according to Boyne (1962) and Bevelander (1964).
Fig. 1. Diagrammatic dog palate showing are of bone resection for implant. 365
366
W. A. Mors and E. J. Kaminski
The animals were killed with an overdose of Diabutal i.v. The entire maxilla of each animal was placed in 10 per cent buffered formalin fixative for histologic examination. Complete autopsy was performed and tissue fragments of all vital organs were also taken for histologic examination. The entire palate of each dog was serially sectioned into blocks of 2 mm thickness, and alternate blocks were decalcified in Perenyi solution and EDTA solution and then embedded in paraffin. The remaining blocks were prepared for fluorescent microscopy. RESULTS
Gross observation of the palates of the animals in Group III at the time of re-intervention after 3 months from initial bone removal revealed areas of incomplete repair where bone had been removed. The surgical control animal in Group I showed similar if not more extensive lack of repair of the osseous defect. Gross analysis of growth patterns was done through observation of the initial and final study models and revealed no alteration or restriction of growth due to the surgical procedure or implant placement (Fig. 3). Closer examination of growth by measurements of the metallic implants visualized from occlusal radiographs also showed there were no alterations in growth causing asymmetries (Fig. 2). The measurements also showed that the palatal width remained relatively unchanged while the antero-posterior dimension increased approximately 1Omm in each animal of each group. Microscopic examination of decalcified, haematoxylin and eosin stained serial sections throughout the entire implant areas of Group III, the 3-month delayed implants, demonstrated partial resorption of the implant material and immediate replacement of the resorbed ceramic by normal appearing mature bone tissue throughout. the implant area (Fig. 4). No callus bone formation was seen. There was conspicuous absence of fibrous tissue proliferation, encapsulation or inflammation and no evidence of foreign body reaction. There appeared to be more new bone formation on the palatal side of the implant area relative to the nasal side as also seen in Fig. 4. Sections from Group II, &month implants, showed greater resorption of the ceramic implant, formation of mature blood vessels and increased osteoblastic activity followed by calcification of the osteoid tissue than seen at three months in the Group III animals (Fig. 5). Decalcified sections stained by Heidenhein’s Azan method for connective tissues confirmed the absence of excessive and mature fibrous tissue. Silver-stained sections using Bodian’s method showed normal nerve fibre processes throughout the area of new bone formation, which were histologically comparable with control sections. Undecalcified ground sections prepared from Group III when viewed with U.V. light showed highly fluorescent areas indicative of active bone growth. Other sections viewed in this manner also showed active calcification occurring at the implant-bone interphase. Histologic sections prepared from the tissue ftag-
ments of major organs obtained at autopsy showed no abnormalities. Initial and final values for SMA12 analyses for all dogs also were within normal limits. DISCUSSION
Experimental use of various porous and nonporous ceramics in skeletal bone repair or replacement has received favourable response from investigators in the last decade because of the biocompatibility of this artificial material with living tissues. Bioresorbable ceramics have been tested for biocompatibility in skeletal bones in various physical forms (Bhaskar et al., 1971; Getter rt ul., 1972; Driskell et al., 1973; Biggs ct al., 1974; Mors et al.. 1974) and were found to be biocompatible and were reported to induce osseous repair (Biggs et al.. 1974; Mors
OF TRICALCIUM IN THE DOG PALATE
W. A. MORS and E. J. KAMINSKI Cleft Palate. Orthodontic and Pathology Departments, Dental and Medical Schools, Northwestern University, Chicago, Illinois 60611 U.S.A. effects of tricalcium phosphate implants in surgically created cleft palates in Beagle dogs were studied. Radiographic studies indicated evidence of resorption of the ceramic and no alteration of normal growth patterns. Histologic studies showed definite implant replacement by normal appearing bone tissue. Summary-The
INTRODUCTION Various
methods
and materials
have been used in
attempting surgical correction of cleft palates with varying degrees of success. Timing of surgical closure is also somewhat controversial, but current philosophies generally subscribe to closure of hard tissue defects after most or all of growth of the maxilla is complete. Development of a material biologically compatible with human tissues that would not restrict growth would permit early surgical correction of the hard tissue defects found with cleft palates and other bone defects with a universal non-human implant material. In this study we present preliminary results of experiments for correction of artificially created cleft palate defects using bioresorbable materials which are biocompatible and do not appear to restrict normal growth. MATERIALS AND METHODS
Nine true-bred Beagle dogs (obtained from Ridgland Research Farms, Inc., 301 West Main Street, Mt. Horeb. Wisconsin 53572), five males and four females, 1-6 weeks of age, were divided into three groups: Group I consisted of three control animals, two animals with no surgery or implants, and one animal with surgical removal of bone only. Group II consisted of three animals having surgical removal of bone followed by immediate implant placement. Group III consisted of three animals having surgical removal of bone followed 3 months later with implant placement. Initial and final alginate impressions were made of the maxilla of each animal while anaesthetized I.M. with Inovar Vet and stone models were poured with orthodontic plaster. Initial, immediate post-implant or post-surgery. 3-month and final occlusal radiographs were taken of each maxilla using Kodak occlusal film. Initial and final blood samples were drawn from each animal for biochemical tests which included standard SMA12 parameters: total protein, albumin, total calcium. total lipids, total cholesterol, uric acid, creatine, total bilirubin, alkaline phosphatase, creatine phosphokinase, lactic dehydrogenase and serum transaminase. At the time of surgery each dog was anaesthetized intravenously with Diabutal and local anaesthetic, Xylocaine HCl 2 per cent with epinephrine 1: 100,000 was injected into the palate. Four stainless steel im-
plant markers, two in the anterior and two in the posterior part of the hard palate were placed with the Bjiirk implant instrument according to Bjijrk (1955). The mucoperiosteum was reflected unilaterally from the left side of the palate. The palatal bone was cut with a surgical bur as shown in Fig. 1 to allow removal of a continuous section of bone 25 x 7 mm from the left side of the palatal midline which continued along the premaxill~maxillary suture. Care was taken not to rupture or damage the mucoepithelial tissues on the nasal side. Sections of resorbable tricalcium phosphate (resorbable porous ceramic made from a high purity, specially prepared and processed form of tricalcium phosphate by M.I.T.E.R. Inc., 633 High Street, Washington, Ohio 43095) were cut and shaped with a diamond disc to the specific dimensions of the defect and placed without any means of fixation. The mucoperiosteum was reapproximated and sutured with 3-O silk. The same surgical procedure of bone removal was followed in Group III without immediate implant placement. After 3 months from initial bone removal animals of this group again had the same procedure performed and implants placed in the same manner as before described. All animals were maintained throughout the test period on Science Diet, (manufactured by Riviana Foods, Ind., Hill’s Division. Topeka, Kansas 66601) which together with water was supplied in crushed form to avoid discomfort to the animals during eating and pr5vent traumatic dislodgment of the implants. One week prior to death, all animals were given tetracycline for bone labelling purposes according to Boyne (1962) and Bevelander (1964).
Fig. 1. Diagrammatic dog palate showing are of bone resection for implant. 365
366
W. A. Mors and E. J. Kaminski
The animals were killed with an overdose of Diabutal i.v. The entire maxilla of each animal was placed in 10 per cent buffered formalin fixative for histologic examination. Complete autopsy was performed and tissue fragments of all vital organs were also taken for histologic examination. The entire palate of each dog was serially sectioned into blocks of 2 mm thickness, and alternate blocks were decalcified in Perenyi solution and EDTA solution and then embedded in paraffin. The remaining blocks were prepared for fluorescent microscopy. RESULTS
Gross observation of the palates of the animals in Group III at the time of re-intervention after 3 months from initial bone removal revealed areas of incomplete repair where bone had been removed. The surgical control animal in Group I showed similar if not more extensive lack of repair of the osseous defect. Gross analysis of growth patterns was done through observation of the initial and final study models and revealed no alteration or restriction of growth due to the surgical procedure or implant placement (Fig. 3). Closer examination of growth by measurements of the metallic implants visualized from occlusal radiographs also showed there were no alterations in growth causing asymmetries (Fig. 2). The measurements also showed that the palatal width remained relatively unchanged while the antero-posterior dimension increased approximately 1Omm in each animal of each group. Microscopic examination of decalcified, haematoxylin and eosin stained serial sections throughout the entire implant areas of Group III, the 3-month delayed implants, demonstrated partial resorption of the implant material and immediate replacement of the resorbed ceramic by normal appearing mature bone tissue throughout. the implant area (Fig. 4). No callus bone formation was seen. There was conspicuous absence of fibrous tissue proliferation, encapsulation or inflammation and no evidence of foreign body reaction. There appeared to be more new bone formation on the palatal side of the implant area relative to the nasal side as also seen in Fig. 4. Sections from Group II, &month implants, showed greater resorption of the ceramic implant, formation of mature blood vessels and increased osteoblastic activity followed by calcification of the osteoid tissue than seen at three months in the Group III animals (Fig. 5). Decalcified sections stained by Heidenhein’s Azan method for connective tissues confirmed the absence of excessive and mature fibrous tissue. Silver-stained sections using Bodian’s method showed normal nerve fibre processes throughout the area of new bone formation, which were histologically comparable with control sections. Undecalcified ground sections prepared from Group III when viewed with U.V. light showed highly fluorescent areas indicative of active bone growth. Other sections viewed in this manner also showed active calcification occurring at the implant-bone interphase. Histologic sections prepared from the tissue ftag-
ments of major organs obtained at autopsy showed no abnormalities. Initial and final values for SMA12 analyses for all dogs also were within normal limits. DISCUSSION
Experimental use of various porous and nonporous ceramics in skeletal bone repair or replacement has received favourable response from investigators in the last decade because of the biocompatibility of this artificial material with living tissues. Bioresorbable ceramics have been tested for biocompatibility in skeletal bones in various physical forms (Bhaskar et al., 1971; Getter rt ul., 1972; Driskell et al., 1973; Biggs ct al., 1974; Mors et al.. 1974) and were found to be biocompatible and were reported to induce osseous repair (Biggs et al.. 1974; Mors
