Case Report

The Subject

A 68-year-old woman with postmenopausal osteoporosis determined by DPX-IQ AP in the lumbar spine and femoral neck (Figure 1) was referred for prosthetic evaluation of an implant-supported restoration. The diagnosis of osteoporosis was established based on criteria employed by the World Health Organization (WHO) which is a bone density (or bone mass) at least 2.5 standard deviations below peak bone mass. Standard deviation from the mean peak bone mass is termed the T score. Therefore, a T score of the lumbar spine of at least 2.5 standard deviations below the norm constitutes a condition of osteoporosis.

Figure 1. A. Determination of osteoporosis in the patient by means of DPX-IQ AP in the lumbar spine according to the spine bone density reference shown in B.

The patient was referred for a clinical evaluation of a dental implant-supported fixed partial prosthesis in the area of the mandibular first molar. The patient reported the placement of the machined implant and fixed prosthesis six years previously. The radiographic evaluation revealed a high level of bone loss around the implant (Figure 2). The decision was made to remove the implant due to an inadequate restoration design and presence of the cantilevered prosthesis.

Figure 2. Radiographic aspect of the peri-implant bone loss.

Histologic and Histomorphometric Evaluation

The implant was removed using an internal 4.25 mm wide trephine. The implant together with surrounding bone tissue was immediately stored in 10% buffered formalin and processed to obtain thin ground sections using the Precise 1 Automated System (Assing, Rome, Italy). The specimen was dehydrated in an ascending series of alcohol rinses and embedded in a glycol methacrylate resin (Technovit^® 7200 VLC, Kulzer, Wehrheim, Germany). After polymerization, the specimen was sectioned longitudinally along the major axis of the implant with a high-precision diamond disk at about 150 µm and ground down to approximately 30 µm. Three slides were obtained for this implant.

The slides were stained with basic fuchsin and toluidine blue. Histomorphometry of bone-implant contact percentage was performed using a Laborlux S^® light microscope (Leitz, Wetzlar, Germany) connected to a 3CCD^® high-resolution video camera (JVC KY-F55B, Milan, Italy) and interfaced to a monitor and personal computer (Intel Pentium III 1200 MMX). This optical system was associated with a digitizing pad (Matrix Vision GmbH, Milan, Italy) and Image-Pro Plus^® 4.5 histometry software package with image-capturing capabilities (Media Cybernetics Inc., Immagini & Computer Snc, Milan, Italy).

Histologically, the peri-implant bone appeared healthy (Figure 3). The bone tissue was mostly compact, and several osteocytes were present in their lacunae either in pristine or in the newly formed bone.

Figure 3. Ground section of the retrieved implant with remaining pristine bone along the implant surface. (Acid fuchsin and toluidine blue, original magnification x20).

The peri-implant bone appeared to be in close contact with the implant surface, whereas marrow spaces could be detected in other areas along with prominently stained cement lines. Osteocytes could be detected in newly formed peri-implant bone indicating ongoing bone formation. Minor apposition of new bone at the implant surface could be found inside the implant threads. No foreign body reaction was found at the bone-to-implant contact. The bone-to-implant contact presents a mean of 62.51+1.96 (Figures 4 and 5).

Figure 4. Cement lines suggesting bone remodelation (arrows). (Acid fuchsin and toluidine blue, original magnification x100).	Figure 5. Bone tissue in direct contact with implant surface. (Acid fuchsin and toluidine blue, original magnification x100).