J . BIOMED. MATER. RES. SYMPOSIUM
NO. 6 , pp. 257-262 (1975)
Alumina and Zirconia Coated Vitallium Oral Endosteal Implants in Beagles A. NORMAN CRANIN, PAUL A. SCHNITMAN, MICHAEL RABKIN, and T H O M A S D E N N I S O N , The Brookdale Hospital Medical Center, Brooklyn, New York, and E. J. ONESTO, IIT Research Institute, Chicago, Illinois
Summary The purpose of this study was to assess the addition of a ceramic coating upon a Vitallium implant to increase the implant’s biologic acceptability in the oral environment. The mandibular premolar teeth in 9 adult beagle dogs were removed bilaterally and these areas allowed to heal for 6 weeks. Ceramic coating with either AI,O, or ZrO, was carried out by flame spray deposition upon Vitallium anchor implants (9 of each), and the implants placed into the 18 healed premolar areas. Clinical and radiographic evaluation was conducted by 2 independent investigators over a 32 week period. Implants which exhibited mobility greater than I 1 on a scale of 0 to 111, at intervals of one-half, were judged unsatisfactory. After 19 weeks, all 9 AI,O, coated implants and 5 ZrO, coated implants were rated unsatisfactory. After 32 weeks, 4 ZrO, coated implants were in situ with 0 or I mobility. Radiographically the width of the peri-implant space increased in direct proportion to both time and mobility. Histologic sections demonstrated encapsulating dense fibrous connective tissue which was oriented parallel to both ZrO, and AI,O, implants. Results suggest the zirconia used is a superior ceramic coating to the alumina. Neither seemed to increase biologic acceptability over uncoated Vitallium implants.
I NTRO D U CTIO N The purpose of this study was to determine whether ceramic coating improved the biologic acceptability of Vitallium endosteal dental implants. Vitallium dental implants in beagle dogs, in a previous study by the authors, were shown to evoke chronic inflammation, no epithelial attachment and thick fibrous encapsulation with accompanying mobility [ I ] . Researchers have indicated that the ceramics, alumina and zirconia, have considerable potential as implant materials [ 2 ] , [3], [4]. These materials by themselves, however, have limited strength, especially in the thin designs required for many dental applications. MATERIALS AND METHODS Cast Vitallium devices in the shape of an anchor, that would be accommodated by the prepared site, were reduced in all aspects by grinding, 251
0 1975 by John Wiley & Sons, Inc.
258
C R A N I N ET A L .
to accept a 500 jim to 800 p m plasma-sprayed, granular-surfaced ceramic coating of Z r 0, or Al, 0,. The mandibular premolar teeth of nine 10-month old beagle dogs were removed bilaterally and these areas allowed to heal. Six weeks postextraction, the healed bone was exposed from the mesial of the first molar t o the canine. Using a #700 surgical bur in a high-speed air turbine, a 2.5 cm groove (1 mm in width) was prepared along the crest of the ridge to a depth of 8 mm. The implants were placed into the prepared groove with hand pressure and gently tapped into place (Fig. 1). With reapposition of the gingiva, 4 mm of the post protruded. These implants were not placed into function. Nine implants of each coating were placed into the 18 healed premolar areas. Three dogs received alumina coated implants in one side of the mandible and zirconia on the opposite side. Two dogs received alumina coated implants bilaterally. Two dogs received zirconia coated implants bilaterally. One dog received a zirconia implant in the left mandible, and 4 weeks later received the other zirconia implant in the right mandible. One dog received an alumina implant in the left mandible, and 4 weeks later received the other alumina implant in the right mandible. Each animal was examined by two examiners biweekly and mutual agreement arrived at by consultation. Evaluation was carried out using the following criteria: Mobility. Grade 0-no observable mobility. Grade 1-slight mobility; buccolingual movement 1 mm or less. Grade 2-moderate mobility; buccolingual movement 1 to 2 mm. Grade 3-marked mobility; buccolingual
Fig. I. Ceramic coated Vitallium implant being placed into mandibular site mesial to first molar of beagle.
C E R A M I C COATED V l T A L L l U M I M P L A N T S
259
movement greater than 2 mm and/or depressible. Observable mobility greater than Grade 2 was considered unsatisfactory. Gingival Color. The color of tissue approximating the implant was compared to the uniform color of attached gingival tissue surrounding the natural teeth for the animal being evaluated. It was recorded as normal or deviated. Gingival Condition. Recorded as normal; minimal, or marked hyperplasia. Hemorrhage. Recorded as present or absent. Radiographs. were made pre- and postoperatively and just prior to sacrifice. Animals were sacrificed when both implants were rated unsatisfactory on the basis of mobility. Representative sections were studied by decalcifying the specimen, splitting it lengthwise and lifting the implant from its bed. Six p m buccolingual sections were stained in H & E. Other representative specimens were embedded in epon and sectioned with the implants in place. These 1 mm sections were stained with Paragon 1301 and viewed with reflected and transmitted light.
RESULTS After 19 weeks, all 9 alumina coated implants and 5 zirconia coated implants were rated unsatisfactory on the basis of mobility. I n general, gingival inflammation and mobility increased with time. This was especially clear in the two dogs having 2 of the same type implant performed 4 weeks apart. I n all zirconia implants still satisfactory after 32 weeks, gingival color and condition were only minimally deviated from normal. .After 32 weeks, the 4 remaining zirconia coated implants were still in situ with 0 t o 1 mobility. In each of the 3 animals receiving both an alumina and zirconia coated implants the zirconia routinely fared better (Table I). All implants judged unsatisfactory on a basis of mobility showed ginTABLE I Implants Present with Less Than Class I1 Mobility. At Nineteen Weeks A11 Alumina Greater than Class I 1 Mobility.
18 IMPLANTS
I
I
I
I
I I
11-
260
CRANIN ET AL
gival color deviated, gingival condition markedly hyperplastic, hemorrhage present and at least a 1 mm radiographic lucency around the implant [Fig. 2 (a) (b)]. Tissue response to the alumina was in all cases more pronounced than to zirconia. The degree of radiolucency was invariably proportional to the mobility. In decalcified H & E sections tissue adjacent to zirconia and alumina appeared similar. A dense fibrous capsule could be demonstrated around the implants. Fibers were oriented parallel to the implant. Capsular thickness was proportional to mobility. Bone healing over the implant was a consistent finding. I n these specimens with marked gingival hyperplasia, color change and bleeding, inflammatory infiltrate of the chronic
(b) Fig. 2. Coated implants. (a) 3-month zirconia implants and (b) 3-month alumina implants. Note: radiolucency at arrows.
CERAMIC COATED VITALLIUM IMPLANTS
Fig. 3.
I
=
implant crypt; C
=
fibrous capsule, B
=
26 1
bone.
type could be demonstrated extending along the neck deep into the implant crypt. Relatively little epithelial downgrowth was in evidence (Fig. 3). Undecalcified ground sections with the implants in place, under transmitted and reflected light, revealed the fibers of the capsule to be in close apposition to the granular surface of the ceramic coating (Fig. 4). Cellular detail was unresolvable in these sections."
Fig. 4. C
=
fibrous capsule; A
=
alumina coating; V
=
Vitallium substrate
* Histology: Dr. Sam J . Piliero, Professor of Histology, Brookdale Dental Center of New York University.
262
C R A N I N ET AL
DISCUSSION Several investigators have published optimistic reports concerning A1,0, and ZrO, as implantable materials [ 2 ] , [3], [4]. The results of our studies, however, show that the coating of Vitallium with these ceramics not only failed to improve biologic acceptability of these dental implants, but in fact reduced their effectiveness. Possibly, the reason for this concerns the method of ceramic coating employed. No intermediate coat was used, which may account for the noted friability of the ceramic coating. The marked gingival inflammatory reaction was undoubtedly related to the fact that the coating covered the whole neck and therefore presented a very rough granular surface to the epithelial and subepithelial tissues at the permucosal area. This promoted the easy collection of debris as well as serving as a local irritant. When the coated implants were withdrawn from the decalcified sections, they seemed to be more tenacious than the uncoated Vitallium implants in a previous study. This might indicate that the fibers of the capsule did in fact produce a mechanical inlocking effect due to the granular surfaces of the ceramic. CONCLUSIONS 1. Zirconia is superior to alumina as a endosteal implant coating. 2. Neither zirconia nor alumina significantly increase endosteal implant acceptability. Supported in part by a grant from Howmedica Corporation, Chicago, Illinois. The authors also wish to thank Dr. S. Bortz, I.I.T. Research Institute, Chicago, Illinois for his advice and support.
References [ I ] S. J. Piliero, P. Schnitman, L. Pentel, A. N . Cranin, and T. A . Dennison, J . Dent. Res., 52, ( 5 ) . 1 I17 (1973). [2] R . L. Hentrich, G. A . Graves, H . G. Stein, J . Biomed. Muter. Res. 5 , 25 (1971). [3] S. F. Hulbert, E. A. Young, R . S. Mathews, J. J. Klawitter, C . D. Talbert, and F. H. Stelling, J . Biomed. Muter. Res., 4 , 433 (1970). [4] T. D. Driskell, H. D. Spangenberg Jr., V. J . Tennery, and L. R. McCoy, I.A.D.R. Abstr., N o . 260, 1973.
NO. 6 , pp. 257-262 (1975)
Alumina and Zirconia Coated Vitallium Oral Endosteal Implants in Beagles A. NORMAN CRANIN, PAUL A. SCHNITMAN, MICHAEL RABKIN, and T H O M A S D E N N I S O N , The Brookdale Hospital Medical Center, Brooklyn, New York, and E. J. ONESTO, IIT Research Institute, Chicago, Illinois
Summary The purpose of this study was to assess the addition of a ceramic coating upon a Vitallium implant to increase the implant’s biologic acceptability in the oral environment. The mandibular premolar teeth in 9 adult beagle dogs were removed bilaterally and these areas allowed to heal for 6 weeks. Ceramic coating with either AI,O, or ZrO, was carried out by flame spray deposition upon Vitallium anchor implants (9 of each), and the implants placed into the 18 healed premolar areas. Clinical and radiographic evaluation was conducted by 2 independent investigators over a 32 week period. Implants which exhibited mobility greater than I 1 on a scale of 0 to 111, at intervals of one-half, were judged unsatisfactory. After 19 weeks, all 9 AI,O, coated implants and 5 ZrO, coated implants were rated unsatisfactory. After 32 weeks, 4 ZrO, coated implants were in situ with 0 or I mobility. Radiographically the width of the peri-implant space increased in direct proportion to both time and mobility. Histologic sections demonstrated encapsulating dense fibrous connective tissue which was oriented parallel to both ZrO, and AI,O, implants. Results suggest the zirconia used is a superior ceramic coating to the alumina. Neither seemed to increase biologic acceptability over uncoated Vitallium implants.
I NTRO D U CTIO N The purpose of this study was to determine whether ceramic coating improved the biologic acceptability of Vitallium endosteal dental implants. Vitallium dental implants in beagle dogs, in a previous study by the authors, were shown to evoke chronic inflammation, no epithelial attachment and thick fibrous encapsulation with accompanying mobility [ I ] . Researchers have indicated that the ceramics, alumina and zirconia, have considerable potential as implant materials [ 2 ] , [3], [4]. These materials by themselves, however, have limited strength, especially in the thin designs required for many dental applications. MATERIALS AND METHODS Cast Vitallium devices in the shape of an anchor, that would be accommodated by the prepared site, were reduced in all aspects by grinding, 251
0 1975 by John Wiley & Sons, Inc.
258
C R A N I N ET A L .
to accept a 500 jim to 800 p m plasma-sprayed, granular-surfaced ceramic coating of Z r 0, or Al, 0,. The mandibular premolar teeth of nine 10-month old beagle dogs were removed bilaterally and these areas allowed to heal. Six weeks postextraction, the healed bone was exposed from the mesial of the first molar t o the canine. Using a #700 surgical bur in a high-speed air turbine, a 2.5 cm groove (1 mm in width) was prepared along the crest of the ridge to a depth of 8 mm. The implants were placed into the prepared groove with hand pressure and gently tapped into place (Fig. 1). With reapposition of the gingiva, 4 mm of the post protruded. These implants were not placed into function. Nine implants of each coating were placed into the 18 healed premolar areas. Three dogs received alumina coated implants in one side of the mandible and zirconia on the opposite side. Two dogs received alumina coated implants bilaterally. Two dogs received zirconia coated implants bilaterally. One dog received a zirconia implant in the left mandible, and 4 weeks later received the other zirconia implant in the right mandible. One dog received an alumina implant in the left mandible, and 4 weeks later received the other alumina implant in the right mandible. Each animal was examined by two examiners biweekly and mutual agreement arrived at by consultation. Evaluation was carried out using the following criteria: Mobility. Grade 0-no observable mobility. Grade 1-slight mobility; buccolingual movement 1 mm or less. Grade 2-moderate mobility; buccolingual movement 1 to 2 mm. Grade 3-marked mobility; buccolingual
Fig. I. Ceramic coated Vitallium implant being placed into mandibular site mesial to first molar of beagle.
C E R A M I C COATED V l T A L L l U M I M P L A N T S
259
movement greater than 2 mm and/or depressible. Observable mobility greater than Grade 2 was considered unsatisfactory. Gingival Color. The color of tissue approximating the implant was compared to the uniform color of attached gingival tissue surrounding the natural teeth for the animal being evaluated. It was recorded as normal or deviated. Gingival Condition. Recorded as normal; minimal, or marked hyperplasia. Hemorrhage. Recorded as present or absent. Radiographs. were made pre- and postoperatively and just prior to sacrifice. Animals were sacrificed when both implants were rated unsatisfactory on the basis of mobility. Representative sections were studied by decalcifying the specimen, splitting it lengthwise and lifting the implant from its bed. Six p m buccolingual sections were stained in H & E. Other representative specimens were embedded in epon and sectioned with the implants in place. These 1 mm sections were stained with Paragon 1301 and viewed with reflected and transmitted light.
RESULTS After 19 weeks, all 9 alumina coated implants and 5 zirconia coated implants were rated unsatisfactory on the basis of mobility. I n general, gingival inflammation and mobility increased with time. This was especially clear in the two dogs having 2 of the same type implant performed 4 weeks apart. I n all zirconia implants still satisfactory after 32 weeks, gingival color and condition were only minimally deviated from normal. .After 32 weeks, the 4 remaining zirconia coated implants were still in situ with 0 t o 1 mobility. In each of the 3 animals receiving both an alumina and zirconia coated implants the zirconia routinely fared better (Table I). All implants judged unsatisfactory on a basis of mobility showed ginTABLE I Implants Present with Less Than Class I1 Mobility. At Nineteen Weeks A11 Alumina Greater than Class I 1 Mobility.
18 IMPLANTS
I
I
I
I
I I
11-
260
CRANIN ET AL
gival color deviated, gingival condition markedly hyperplastic, hemorrhage present and at least a 1 mm radiographic lucency around the implant [Fig. 2 (a) (b)]. Tissue response to the alumina was in all cases more pronounced than to zirconia. The degree of radiolucency was invariably proportional to the mobility. In decalcified H & E sections tissue adjacent to zirconia and alumina appeared similar. A dense fibrous capsule could be demonstrated around the implants. Fibers were oriented parallel to the implant. Capsular thickness was proportional to mobility. Bone healing over the implant was a consistent finding. I n these specimens with marked gingival hyperplasia, color change and bleeding, inflammatory infiltrate of the chronic
(b) Fig. 2. Coated implants. (a) 3-month zirconia implants and (b) 3-month alumina implants. Note: radiolucency at arrows.
CERAMIC COATED VITALLIUM IMPLANTS
Fig. 3.
I
=
implant crypt; C
=
fibrous capsule, B
=
26 1
bone.
type could be demonstrated extending along the neck deep into the implant crypt. Relatively little epithelial downgrowth was in evidence (Fig. 3). Undecalcified ground sections with the implants in place, under transmitted and reflected light, revealed the fibers of the capsule to be in close apposition to the granular surface of the ceramic coating (Fig. 4). Cellular detail was unresolvable in these sections."
Fig. 4. C
=
fibrous capsule; A
=
alumina coating; V
=
Vitallium substrate
* Histology: Dr. Sam J . Piliero, Professor of Histology, Brookdale Dental Center of New York University.
262
C R A N I N ET AL
DISCUSSION Several investigators have published optimistic reports concerning A1,0, and ZrO, as implantable materials [ 2 ] , [3], [4]. The results of our studies, however, show that the coating of Vitallium with these ceramics not only failed to improve biologic acceptability of these dental implants, but in fact reduced their effectiveness. Possibly, the reason for this concerns the method of ceramic coating employed. No intermediate coat was used, which may account for the noted friability of the ceramic coating. The marked gingival inflammatory reaction was undoubtedly related to the fact that the coating covered the whole neck and therefore presented a very rough granular surface to the epithelial and subepithelial tissues at the permucosal area. This promoted the easy collection of debris as well as serving as a local irritant. When the coated implants were withdrawn from the decalcified sections, they seemed to be more tenacious than the uncoated Vitallium implants in a previous study. This might indicate that the fibers of the capsule did in fact produce a mechanical inlocking effect due to the granular surfaces of the ceramic. CONCLUSIONS 1. Zirconia is superior to alumina as a endosteal implant coating. 2. Neither zirconia nor alumina significantly increase endosteal implant acceptability. Supported in part by a grant from Howmedica Corporation, Chicago, Illinois. The authors also wish to thank Dr. S. Bortz, I.I.T. Research Institute, Chicago, Illinois for his advice and support.
References [ I ] S. J. Piliero, P. Schnitman, L. Pentel, A. N . Cranin, and T. A . Dennison, J . Dent. Res., 52, ( 5 ) . 1 I17 (1973). [2] R . L. Hentrich, G. A . Graves, H . G. Stein, J . Biomed. Muter. Res. 5 , 25 (1971). [3] S. F. Hulbert, E. A. Young, R . S. Mathews, J. J. Klawitter, C . D. Talbert, and F. H. Stelling, J . Biomed. Muter. Res., 4 , 433 (1970). [4] T. D. Driskell, H. D. Spangenberg Jr., V. J . Tennery, and L. R. McCoy, I.A.D.R. Abstr., N o . 260, 1973.
