Examination of the Bone-Implant Interface in Experimentally Induced Osteoporotic Bone

Examination of the Bone-Implant Interface in Experimentally Induced Osteoporotic Bone
March 2004
Cho, Peter BS*; Schneider, G. B. DDS, PhDÇƒÜ; Krizan, Kenneth BSÇƒ?; Keller, J. C. PhD¨?
Implant Dentistry: Volume 13(1) March 2004 pp 79-87
Lippincott Williams & Wilkins
*Dental Student, Dows Institute for Dental Research, College of Dentistry, The University of Iowa, Iowa City, Iowa.
ÇƒÜAssociate Professor, Dows Institute for Dental Research, Department of Prosthodontics, College of Dentistry, The University of Iowa, Iowa City, Iowa.
Çƒ?Research Assistant Dows Institute for Dental Research, College of Dentistry, The University of Iowa, Iowa City, Iowa.
¨?Professor, Dows Institute for Dental Research, Department of Oral Maxillofacial Surgery, College of Dentistry, The University of Iowa, Iowa City, Iowa.
Reprint requests and correspondence to:
John C. Keller, PhD
Dows Institute for Dental Research
College of Dentistry
The University of Iowa
Iowa City, IA 52242-1010
Phone: (319) 335-7375/2142
Fax: (319) 335-8895
E-mail: john-keller@uiowa.edu
Abstract TOP
The objective of this study was to explore the hypothesis that osteoporotic-like (OP) conditions have a negative effect on osseointegration (OI) of dental implants. Using an ovariectomized (OVX) rat model, the extent of OI using histologic and histomorphometric analysis (HMA) under a variety of OVX conditions was assessed. Five experimental groups (n = 7 rats per group) were used: 1) OP control, 2) OI control, () OI followed by OVX treatment to induce OP (OI?OP), 4) OP induction followed by OI (OP?OI), and 5) OP induction simultaneously with OI (OI = OP). Using undecalcified plastic-embedded cross-sections of the implant site, HMA was performed to determine the percent of bone contact (BC) at the implant-tissue interface and percent of bone area (BA) immediately (1.5-mm diameter) surrounding the implant site. The presence of Bone Sialoprotein (BSP), an important extracellular matrix component of bone, was evaluated using immunohistochemical staining procedures. The implant control resulted in the highest level of OI (BC = 79%; BA = 87%), whereas all groups in which OVX was performed resulted in a significant reduction in BA (70-75%). High levels of BC were observed in established OP conditions (OP?OI; BC = 79%); however, following OI, induction of OP conditions (OI?OP) led to a significant reduction in BC (50%). In each of the OP treatment groups, a diminution of cortical bone, increased trabecularization of the host bone site, and loss of staining of BSP was observed. The results of this work indicate that although OI is possible under a variety of OP-like conditions simulating implant placement, the long-term biomechanical stability of implants under these conditions could be compromised and remains unclear. Further research to understand implant use in the complex bone environment under OP-like conditions is encouraged.
Based on current population trends, by the year 2030, greater than 20% of the U.S. population will be over the age of 65, and the dental profession in the United States will encounter a rise in demands for dental care by the elderly population. 1 Accordingly, the elderly population will encounter compromised health conditions in comparison to the rest of the population as a result of natural aging processes and/or acquired disease(s) such as osteoporosis. This condition is correlated to the postmenopausal effect in women that is localized specifically in trabecular bone, whereas age-related bone loss occurs in both men and women in cortical and trabecular bone. Although osteoporosis is known to affect the vertebral structures and long bones of the body, there is also evidence that osteoporosis and age-related bone loss affects the craniofacial and oral structures, including an increased incidence of tooth loss. 2-4 Osteoporosis is characterized by an imbalance between the formation and resorption of bone, where osteoclastic activity remains relativity normal but osteoblastic activity is diminished. The onset of osteoporosis results in a generalized skeletal fragility, resulting from loss of bone from the cortical and/or trabecular regions. 5 This diminished bone architecture can result in compromised bone strength that is prone to fracture.
Dental implants have been the method of choice among clinicians to restore functional mastication of partially or fully edentulous conditions. Conventional dentures without implant stability are used as an alternative treatment, but dentures alone often provide inadequate bite force and compromised retention and stability. Successful dental implant treatment provides the best restorative treatment by overcoming disadvantages of other restorative measures. For many years, the possible effects of metabolic and age-related bone loss have concerned the dental profession. 6 However, orofacial bone loss becomes a significant variable and potential risk factor for the success of dental implants in patients with a compromised bone condition in the oral cavity. 1,7-11
Some reports suggest that implants are prone to failure as a result of the diminished capacity for bone remodeling, and hence osseointegration and biomechanical maintenance of the implant, within osteoporotic bone, 12,13 whereas other reports have promoted the use of dental implants in the edentulous mandible to minimize physiological and age-related bone loss. 9,14,15 Several studies using either administration of glucocorticoids or ovariectomized animal models have been conducted to address the concerns of implant use under experimentally induced osteoporotic-like conditions. 12,16-19
The aim of this study was to determine the level of implant osseointegration in osteoporotic-like bone using an ovariectomized rat animal model. The amount of osseointegration (bone contact at the interface of the implant) and the bone volume (bone area in 2-dimensional sections) were assessed using histologic and histomorphometric analyses. Immunohistochemical techniques were also used to access the presence of bone sialoprotein (BSP), a key extracellular matrix component of bone.
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