Estrogen Deficiency Affects Bone Healing Around Titanium Implants: A Histometric Study in Rats

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Estrogen Deficiency Affects Bone Healing Around Titanium Implants: A Histometric Study in Rats
December 2003
Mendes Duarte, Poliana DDS, MS; Neto, Jo?£o Batista C?©sar DDS, MS; Gon??alves, Patricia Furtado DD, MSǃ?; Sallum, Enilson Antonio DDS, MS, PhD; Nociti, Francisco Humberto Jr., DDS, MS, PhD
Implant Dentistry: Volume 12(4) December 2003 pp 340-346
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Abstract
The purpose of this study was to evaluate the influence of an estrogen-deficient state on bone around titanium implants placed in rats. Thirty female Wistar rats were divided into 2 groups: test (n = 15), ovariectomized rats (OVX); and control (n = 15), sham-operated rats. Screw-type titanium implants were placed bilaterally in rats 21 days after ovariectomy or sham surgery. After 60 days, the animals were killed and undecalcified sections obtained. Blood samples were collected to obtain serum levels of alkaline phosphatase at the time of killing. Bone-to-implant contact (BIC), bone area (BA) around the implants, and bone density (BD) in a 500 ¨µm-wide zone lateral to the implant were obtained and arranged separately for the cortical (zone A) and cancellous (zone B) regions. In zone A, there was no significant difference between test and control groups regarding BIC and BD (P >0.05). A lower BA was observed in the estrogen-deficient animals (P <0.05). In zone B, data analysis showed that estrogen deficiency could result in a lower percentage of BIC, BA, and BD (P <0.05). In addition, a higher concentration of alkaline phosphatase was observed for the test group. An estrogen-deficient state could affect bone healing and bone density around titanium implants placed in rats, especially in the cancellous bone area.
The use of titanium endosseous dental implants in the treatment of edentulous or partially edentulous patients has become an alternative to restore function and esthetics. 1-3 The contact between bone tissue and implant surface is known as osseointegration and involves numerous complex factors. 4 These include not only implant-related factors such as material, shape, and surface chemistry, but mechanical loading, surgical technique, and patient variables such as bone quantity and quality. 4 There are various risk factors that might affect bone quality, quantity, and healing around titanium implants. 5 The influence of bone quality and quantity on the outcome of dental implants has been discussed in several studies in which a high failure rate has been observed in patients presenting poor bone quality and an inadequate bone volume. 5-7
Osteoporosis has been defined as a systemic skeletal disease characterized by gradual loss and microarchitectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. 8 Pathologic conditions causing bone loss such as hyperparathyroidism, hyperthyroidism, Cushing's disease, and glucocorticoid treatment can induce osteoporosis. 9 However, the most common cause of osteoporosis is the decrease of estrogen during menopause or after ovariectomy. 8,9
Estrogen plays an important role in the regulation of bone turnover in adult bone. Thus, estrogen deficiency is associated with inhibition of osteoclast differentiation and reduction of their action, inducing cancellous as well as cortical bone loss. 10,11 In addition, interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor-a (TNF-a), and other cytokines have been reported to have either direct or indirect effects on the pathogenesis of postmenopause osteoporosis. The production of all of these cytokines is suppressed or regulated by the estrogen level. 12,13
Significant relationships have been reported between oral bone and skeletal bone mass in postmenopausal women with osteoporosis. 14,15 Osteoporosis could, therefore, be considered a risk factor in treatment planning and in determining the prognosis for patients considering dental implants. 16 However, clinical reports have been contradictory in correlating postmenopausal osteoporosis as a risk factor for dental implants. Although it has been suggested that estrogen deficiency could constitute a risk factor for implant placement in the maxilla, 17 a literature review did not find evidence to expect osteoporosis to be a risk factor for osseointegrated dental implants. 18 On the other hand, a few animal studies, using ovariectomized animal models, have demonstrated that estrogen deficiency could induce histologic changes around hydroxyapatite-coated and titanium screw dental implants. 19-21
The aim of this study was to evaluate, by histometric analysis, whether estrogen deficiency, before implant placement, influences bone healing and bone density around titanium implants placed in rats.
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