Ceramic-coated subperiosteal implants. Part II. Clinical and histologic evaluations

Implant dentures

Ceramic-coated

subperiosteal

Part II. Clinical

and

implants.

histologic

evaluations

David Benson, D.D.S., KS.,* M. H. Reisbick, D.M.D., M.S.,** Lawrence 1. Furstman, D.D.S., M.S., Ph.D.*** School of Dentistry, University of California, Los Angeles, Calif.

and

lh e purpose of this study was to compare the clinical and histologic responses of adult stump-tail monkeys to chrome-cobalt and alumina-coated subperiosteal implants. MATERIALS

AND

METHOD

Two adult stump-tail monkeys, who had been rendered partially edentulous by surgery eight weeks previously, received bilateral subperiosteal implants to replace the missing mandibular molars. A standard chrome-cobalt? implant was inserted on the left side of each animal. A similar chrome-cobalt implant coated with aluminat was inserted on the right side of each animal. The method and materials for preparing and inserting the implants have been previously rep0rted.l The implants in animal No. 1 were removed at three months because of mobility associated with traumatic occlusion from the extrusion of the opposing maxillary molars. A second series of implants were reinserted in animal No. 1 following a six-week rest and healing period. The second series of implants in animal No. 1 and the original implants in animal No. 2 were allowed to remain in place for an additional six months, at which time the animals were sacrificed. EVALUATIONS Clinical evaluation. Each animal was evaluated clinically at two-week intervals. Photographs were made of each implant site, and the implants were checked for mobility. A periodontal probe was used to determine the depth of the gingival sulcus adjacent to each implant post. *Assistant

Professor,

Removable

Prosthodontics

**Associate

Professor

and Chairman,

***Adjunct

Professor,

Orthodontics

+Surgical

Vitallium,

$Pl&ma

Technology,

Biomaterials

Section.

Section.

Buttress Laboratories, Torrance,

Section.

Los Angeles, Calif.

Calif.

323

324

Benson, Reisbick,

Fig. 1. Alumina-coated

J. Prosthet. Dent. March, 1974

and Furstman

implant:

Fig. 2. Chrome-cobalt

implant:

Fig. 3. Alumina-coated

implant

Fig. 4. Chrome-cobalt

implant.

B, site of biopsy. A-A, the plane of sectioning. with attached Note

fibers.

the dehiscence

of the mesial-lingual

strut.

Histologic evaluation. Prior to the sacrifice of the animals, biopsies were made of the tissue adjacent to each implant post at two-month intervals (Fig. 1). Standard paraffin sections stained with hematoxylin and eosin were prepared from the biopsy specimens for histologic examination. Following sacrifice, a block section containing the implants and adjacent tissue was removed from both sides of each mandible. Each implant and adjacent tissue was sectioned in plane A-A shown in Fig. 2. The sections anterior to A-A were decalcified and the implants carefully removed. The tissue was embedded in celloidin and cut into 20 p sections parallel to plane A-A. The sections were stained with hematoxylin and triosin for general observation and study and with Mallory’s stain to identify connective tissue. The undecalcified section posterior to A-A was embedded in methyl methacrylate. Ground sections were cut at 80 to 100 p parallel to plane A-A and stained with hematoxylin and eosin.

RESULTS Clinical results. At three months in vivo, the first series of implants in animal No. 1 became mobile. The tissue surrounding the implants was acutely inflamed and edematous. The tissue over the implant was incised, and the implants were removed. The chrome-cobalt implant was readily retrieved with no tissue adherence. However, the alumina-coated implant had a strong fibrous attachment which tenaciously adhered to most of the implant surface (Fig. 3).

Volume 31 Number 3

Ceramic-coated subperiosteal implants

Fig. 5. Biopsy of gingival tissue adjacent (Original magnification X70.)

to the alumina-coated

implant:

I, implant

space.

tissue adjacent to the alumina-coated (Original magnification x70.)

implant:

I, implant

space;

Fig. 6. Biopsy

P, alumina;

of gingival

E, epithelium.

Fig. 7. A ground section of an alumina-coated implant: I, implant space; P, alumina; connective tissue; X, area for higher magnification. (Original magnification x24.) Fig. 8. Higher magnification of section X of alumina-coated implant plant space; P, alumina; CT, connective tissue. (Original magnification

325

CT,

shown in Fig. 7: I, imx150.)

The chrome-cobalt and alumina-coated implants in both animals (No. 1 and No. 2) caused a moderate inflammatory response around each post. There was no significant swelling or visual suppuration. The remaining tissue surrounding the implants was healthy (Figs. 1 and 2). The tissue immediately adjacent to the posts hemorrhaged readily when probed. The depth of the gingival sulcus ranged from 1 to 2 mm. Only in animal No. 1 was there equal bilateral dehiscence of the tissue covering the mesial-lingual strut of the implant. The tissue at the junction of the dehiscence was mildly inflamed, and yet the tissue was tightly adapted to the implant (Fig. 4) . There was no mobility of the implants in either animal. Histologic results. The typical response of the gingival tissue adjacent to the alumina implant post is shown in Fig. 5. In this biopsy section, there is a severe-tomoderate inflammatory cell infiltrate composed primarily of lymphocytes next to the implant. Subjacent to this area, there is a band of dense fibrous connective tissue

326

Benson, Reisbick, and Furstman

J. Prosthet. Dent Ma&. 191’

Fig. 9. A decalcified section of tissue around a chrome-cobalt implant: I, implant space; CT, connective tissue; E, epithelium; 9, bone. (Original magnification x24.) Fig. 10. A decalcified section of tissue around a chrome-cobalt implant: I, implant space; E, epithelium; K, keratin; CT, connective tissue. (Originai magnification x24.) composed of cellular elements and collagen. The inflammatory response of the tissue adjacent to the coated posts was generally more intense than the response to the chrome-cobalt implants. In the biopsy and ground sections, the tissue in contact with the coated implant was strongly adherent to the alumina. A biopsy specimen of the gingival tissue adjacent to the coated implant is shown in Fig. 6. The specimen is composed of chronic granulation tissue containing proliferating endothelial buds, young plump fibroblasts, numerous large vascular spaces, and a moderate-to-severe inflammatory cell infiltrate. Subjacent to the implant (I), there is a thin margin of stratified squamous epithelium. In intimate apposition with the epithelium is a thin layer of alumina. The ground section of the alumina-coated implant is shown in Fig. 7. The chrome-cobalt inner core fractured from the specimen during preparation of this section. However, the entire alumina coating remained, adhering to the connective tissue surrounding the implant. A higher magnification of this same section (Fig. 8) demonstrates the close apposition of the connective tissue to the alumina coating. This is suggestive of fibrous ingrowth into the alumina pores. A decalcified section of tissue from animal No. 1 that surrounds the chromecobalt implant is shown in Fig. 9. Subjacent to the area of the implant, epithelium with a moderate tendency toward keratin production is observed. The connective tissue that formerly encapsulated the implant is acellular and composed almost entirely of dense bundles of collagen. The bone (B) shows evidence of former osteoclastic activity secondary to resorption lacunae. No osteoclasts are seen. It appears that osteoclastic activity was arrested at a previous date. In animal No. 2, a decalcified section from the chrome-cobalt implant area clearly demonstrates the presence of epithelium (E, Fig. 10) that encapsulated the implant. This is a well-developed stratified squamous epithelium with a tendency toward keratin formation (K) . Numerous cells within the stratified squamous epithelium also show individual cell keratinization. There were no sections from the alumina-coated implant in either animal that showed evidence of epithelial ingrowth.

Volume 31 Numbm 3

Ceramic-coated

Fig. 11. Ground artificial

section space. (Original

of chrome-cobalt implant: magnification X150.)

I,

subperiosteal

implant;

CT,

implants

connective

327

tissue;

S,

The ground sections of the chrome-cobalt implants did not show close apposition of the tissue to the implant (Fig. 11) _ The fibrous connective tissue did not adhere to the Vitallium. There is an artifactual space (S) between the tissue and the implant. This suggests there was no ingrowth or bonding of the fibrous connective tissue to the implant.

DISCUSSION There was no clinical difference in tissue responses to the implant materials. The lingual dehiscence that was observed bilaterally in one animal was related to implant design. Normally, the lingual strut is eliminated in this type of design, but for this study, the authors intended to test the implant materials under the most adverse clinical conditions, The degree of dehiscence observed did not appear to have any effect on the results of this study. The inflammatory reaction of the gingival tissue observed histologically can be attributed in part to poor oral hygiene observed in the animals. The rough surface of the alumina-coated implant tended to accumulate more plaque and debris than did the smoother chrome-cobalt surface. This explains the more severe tissue reaction seen microscopically around the posts of the coated implants. The optimum design for either implant material should have included a highly polished surface at the point of oral penetration that would tend to deter plaque formation. The gross evidence of tissue adhering to the alumina-coated implant removed from animal No. 1 (Fig. 3)) in conjunction with the later histologic evaluation, strongly indicates that a bond forms at the junction of the tissue and the porous alumina. This bonding or fibrous ingrowth is consistent with the finding of other investigators as reported previous1y.l A particular advantage of a direct fibrous attachment to the implant is the prevention of downward growth of the oral epithelium. In both animals, there was histologic evidence of oral epithelium below the surface of the chrome-cobalt implant. Since no epithelium was observed beneath the alumina-coated implant, the findings of this study support the concept that a fibrous attachment may deter epithelial downgrowth.

328

Benson, Reisbick,

SUMMARY

AND

J. Prosthet. Dent. Match. 1974

and Furstman

CONCLUSIONS

Two stump-tail monkeys received bilateral subperiosteal implants to replace missing mandibular molars. A standard chrome-cobalt implant was inserted on the left side and an alumina-coated implant was inserted on the right side of each animal, and the implants remained in place for a period of six months. There was no clinical difference in the tissue responses to the implant materials. Histologically and clinically, the alumina-coated implant appeared to form an adherent bond to the adjacent tissue. Additional long-term studies using a larger sample size are needed to further evaluate these implant materials. Reference 1. Reisbick, M. H., and Benson, D.: Ceramic-Coated Study, J. PROSTHET. DENT. 31: 204-210, 1974. OF DENTISTRY, UNIVERSITY OF CALIFORNIA

SCHOOL

Los ANGELES,

CALIF.

90024

AT Los ANGELES

Subperiosteal

Implants.

Part I. A Pilot