Rómulo Luis Cabrini

An experimental study of the dissemination of Titanium and Zirconium in the body.

Metallic implants can generate and release titanium oxide (TiO2) and zirconium oxide (ZrO2) to the tissues. These products can accumulate locally or disseminate systemically. The aim of the present study was to assess the distribution of TiO2 and ZrO2 administered intraperitoneally to rats. We used male Wistar rats of approximately 100 g body weight throughout the study. An intraperitoneal injection of a suspension of TiO2 or ZrO2 (16, 1600 and 16×103 mg/kg body weight) was administered. The animals were killed at 5–10 months post-administration by ether overdose. Samples of peritoneum, liver, kidney, lung and spleen were taken, fixed in formalin and routine processed for embedding in paraffin. One set of sections was stained with hematoxylin and eosin and another set was prepared unstained. The presence of titanium in the tissues was detected by X-ray diffraction crystallography. The histological analysis revealed the presence of abundant intracellular aggregates of metallic particles of Ti and Zr in peritoneum, liver, lung and spleen. The crystallographic study revealed the presence of anatasa. The dissemination of metallic particles from orthopedic or odontological implants would not be restricted to a local phenomenon. The particles also target vital organs. The distribution of these deposits over lengthy periods deserves meticulous attention given the clinical relevance of this phenomenon.

Biocompatibility of Two Calcium Hydroxide-based Endodontic Sealers: A Quantitative Study in the Subcutaneous Connective Tissue of the Rat

In this study, the biocompatibility of two calcium hydroxide-based endodontic sealers was investigated. Silicone tubes containing freshly mixed Sealapex or CRCS were implanted in the dorsal subcutaneous connective tissue of the rat. Equal size solid silicone rods were also implanted and used as controls. The tissue reaction to test and control materials was histometrically and quantitatively analyzed under light microscopy. After 7, 30, and 90 days of implantation, different grades of tissue reaction to the tested materials were recorded at the end of the tubes. A granulomatous tissue containing foreign body giant cells and macrophages with engulfed material in their cytoplasm as well as many fibroblasts and vessels was initially observed in contact with Sealapex. This reaction increased progressively at the 30- and 90-day observation period. An acute inflammation was detected in tissues in contact with CRCS. However, the severity of this reaction decreased with time and it seemed to be resolved at the 90-day observation period. Taking into account the limitations of the experimental model used in this study, we consider that more extensive experiences will be necessary prior to extrapolating these findings to the actual clinical situation.

Uranium inhibits bone formation in physiologic alveolar bone modeling and remodeling

The toxic effect of uranium (U) on bone modeling and remodeling was studied by performing histomorphometric measurements in the periodontal cortical bone of rats. Two different single intraperitoneal doses of uranyl nitrate (238U) were administered to two sets of rats respectively (2 and 0.8 mg/kg body wt). Rats treated with the first dose were killed 14 days postinjection (PI) and those treated with the second were killed 14, 30, and 60 days PI. The results revealed a decrease in bone formation in rats treated with uranium. On the remodeling side the decrease in bone formation was coupled to an increase in bone resorption on the 14th day PI. On the modeling side no bone resorption was observed and the decrease in bone formation was linked to an increase in resting bone zones. Bone formation depression as a key event in U intoxication is stressed.

Oral Mucosa Tissue Response to Titanium Cover Screws

BACKGROUND Titanium is the most widely used metal in dental implantology. The release of particles from metal structures into the biologic milieu may be the result of electrochemical processes (corrosion) and/or mechanical disruption during insertion, abutment connection, or removal of failing implants. The aim of the present study is to evaluate tissue response of human oral mucosa adjacent to titanium cover screws. METHODS One hundred fifty-three biopsies of the supra-implant oral mucosa adjacent to the cover screw of submerged dental implants were analyzed. Histologic studies were performed to analyze epithelial and connective tissue as well as the presence of metal particles, which were identified using microchemical analysis. Langerhans cells, macrophages, and T lymphocytes were studied using immunohistochemical techniques. The surface of the cover screws was evaluated by scanning electron microscopy (SEM). RESULTS Forty-one percent of mucosa biopsies exhibited metal particles in different layers of the section thickness. Particle number and size varied greatly among specimens. Immunohistochemical study confirmed the presence of macrophages and T lymphocytes associated with the metal particles. Microchemical analysis revealed the presence of titanium in the particles. On SEM analysis, the surface of the screws exhibited depressions and irregularities. CONCLUSIONS The biologic effects seen in the mucosa in contact with the cover screws might be associated with the presence of titanium or other elements, such as aluminum or vanadium. The potential long-term biologic effects of particles on soft tissues adjacent to metallic devices should be further investigated because these effects might affect the clinical outcome of the implant.

Histomorphometry of initial bone healing around zirconium implants in rats.

Histometric evaluations as a function of time were performed with zirconium implants during the healing period in 10 Wistar rats. The implants (7 mm × 1 mm × 0.1 mm) were placed in the right tibia of the animals. Five rats were killed after 14 days and the remainder were sacrificed 30 days after implantation. The tibiae were resected, radiographed, and embedded in poly(methyl methacrylate). Three cross-sections were obtained transverse to the major axis of each tibia. Osseointegrated tissue thickness, percentage of direct bone-to-implant contact, and osseointegrated tissue volume were evaluated for each specimen. Bone formation was observed on the surface of the implanted strip that was in contact with tibia marrow. This method is proposed for the evaluation of the first stage of healing of bone in contact with different implant materials subjected to various surface treatments. (Implant Dent 1993;2:264–267)

Exfoliative Cytology and Titanium Dental Implants: A Pilot Study

BACKGROUND Oral exfoliative cytology is a diagnostic method that involves the study of cells exfoliated from the oral mucosa. Ions/particles released from metallic implants can remain in the peri-implant milieu. The aim of the present study is to assess the presence of metal particles in cells exfoliated from peri-implant oral mucosa around titanium dental implants. METHODS The study comprised 30 patients carrying titanium dental implants, who had neither a metallic prosthesis nor metal restorations in neighboring teeth. Individuals undergoing orthodontic therapy and those who had oral piercing were also excluded from the study. The study sample included patients with and without peri-implantitis. Cytologic samples of the peri-implant area were collected. Samples of the marginal gingiva on the contralateral side of the implant were taken from the same individuals to serve as control. Cytologic analysis was performed using light microscopy. Titanium concentration was determined using inductively coupled plasma-mass spectrophotometry. RESULTS Metal-like particles were observed inside and outside epithelial cells and macrophages in cytologic smears of peri-implant mucosa of both patients with and without peri-implantitis. No particles were found in the control cytologic samples. The concentration of titanium was higher in the peri-implantitis group compared with the group without peri-implantitis; no traces of titanium were observed in controls. CONCLUSIONS Regardless of an inflammatory response, ions/particles are released from the surface of the implant into the biologic milieu. Exfoliative cytology is a simple technique that may be used to detect metal particles in cells exfoliated from the peri-implant mucosa.

Orally administered ethane-1-hydroxy-1,1-biphosphonate reduces the lethal effect of oral uranium poisoning.

Abstract—Intoxication with uranium compounds is both an occupational risk for the workers engaged in the different processes of the elaboration of nuclear fuel and a risk for the population at large in terms of contaminated water and food. The toxic effects of uranium can be reduced by the administration of a biphosphonate, ethane-1-hydroxy-1,1-biphosphonate (EHBP), subcutaneously or intraperitoneally. The aim of the present work was to examine whether orally administered EHBP reduces the lethal effect of a single orally administered toxic dose of uranyl nitrate. Nine groups of 20 male Balb-c mice were used. Five groups received 350 mg kg−1 of uranyl nitrate orally administered by gavage, four were co-treated 20 min later with EHBP either by gavage (350, 500, or 700 mg kg−1) or by subcutaneous injection (50 mg kg−1), and one group was not treated. Four groups of animals received only EHBP in doses and routes the same as those used in the intoxicated animals. Survival was assessed for 14 d. On day 14 the surviving animals of all groups were killed. An additional group of uranium intoxicated animals was killed on day 2 after the start of the experiment. Kidneys were examined histologically. On day 3 all the animals treated with uranyl nitrate alone and 20% of the animals treated with 700 mg kg−1 of EHBP alone were dead. Survival at day 14 of the groups of mice intoxicated with uranyl nitrate and treated with EHBP (50 mg kg−1 orally or 50 mg kg−1 subcutaneously) was 45.0 and 49.6%, respectively. Tubule necrosis lesions were present in kidneys of mice intoxicated with uranyl nitrate, whereas lesions were less severe in mice treated with EHBP. Oral administration of EHBP is effective for reducing the lethal effect of uranium, and it is at least as useful as subcutaneous administration for prompt therapy of oral uranium exposure, achieving a survival rate of almost 50%.

Renal function in mice poisoned with oral uranium and treated with ethane-1-hydroxy-1,1-bisphosphonate (EHBP)

Abstract— Exposure to uranium is a risk for the workers involved in uranium mining, purification, and manufacture, principally by its ingestion or inhalation. It is also a risk for the population at large in case of intake of contaminated water or food. Uranium induces nephropathy that is characteristic of heavy metals, which can lead to death. The toxic effects of uranium can be prevented by a biphosphonate, ethane-1-hydroxy-1,1-bisphosphonate (bisodic etidronate), administered orally or subcutaneously. Employing bisodic etidronate, our laboratory obtained satisfactory results in terms of survival in adult mice, adult rats, and suckling rats. The aim of the present study was to evaluate the efficacy of bisodic etidronate for preventing renal dysfunction induced by a lethal dose of uranyl nitrate, employing serum levels of urea and creatinine as end-points. Two experiments were performed over different time periods, i.e., Experiment A: 48 h, Experiment B: 14 d. Each experiment was performed with 4 groups of 20 male Balb/c mice each, 25 g average body weight. Three of these groups received 350 mg kg−1 of body weight of uranyl nitrate by gavage (forced oral administration). Two of the three exposed groups were treated with bisodic etidronate either by gavage in a dose of 500 mg kg−1 body weight or with a subcutaneous injection of 50 mg kg−1 body weight. The fourth group served as control. Survivors of the experimental groups were sacrificed at the end of the experiment by overdose of inhalation anesthetic (ether). The kidneys were routinely processed for histological analysis. Blood samples were taken by cardiac puncture to assess urea and creatinine serum levels. Urea and creatinine serum levels were markedly lower at 48 h in exposed animals treated with bisodic etidronate than in untreated exposed animals. On day 14 these values in exposed and treated animals did not differ significantly from control values. The renal function of animals treated with orally or subcutaneous bisodic etidronate that survived uranyl nitrate exposure was markedly improved compared to the controls of untreated exposed animals at 48 h. At 14 days, treatment with bisodic etidronate averted renal damage. At this time, the histologic study of kidneys showed images of tissue recovery. These results suggest that the use of EHBP may be of great value in reducing the renal damage.

Nucleolar Organizer Regions as Markers of Incipient Cellular Alterations in Squamous Epithelium

Transcriptionally active nucleolar organizer regions identified by silver staining (AgNOR) vary in number with cellular activity and/or malignant transformation and have been used as a diagnostic tool. A morphometric study of AgNORs was performed in an experimental model of irradiated squamous epithelium (Wistar rat sole skin) 4, 8, and 14 hours and 1, 2, 5, and 7 days post-irradiation with 50 Gy of x-rays. A statistically significant and progressive rise in AgNOR average volume of up to 238% and reduction in AgNOR number/nucleus of up to 40% were detected as a function of post-irradiation time. A statistically significant 46% increase in AgNOR volume was detected as early as 8 h post-irradiation, when no histological changes were observable in routine preparations. These results suggest that AgNORs may be useful as a quantitative marker of incipient changes in cellular activity and caution against the indiscriminate use of AgNORs in the follow-up of lesions which may have been exposed to radiotherapy. Furthermore, this study suggests the possibility of using AgNORs as a sensitive biological dosimeter in cases of uncontrolled exposure to radiation.

Adhesion of human blood monocytes and lymphocytes to different endodontic cements. A methodological in vitro study

A method of evaluating the adverse effects of different endodontic cements on the behavior of a mixed cell population of human lymphocytes and monocytes is described. Cells were cultured either in direct contact with or near experimental samples of a glass ionomer, AH26, Diaket, Tubli-Seal, and a zinc oxide-eugenol cement (Fynal). The weakest effect was found for the glass ionomer whereas the adverse effects of the other materials increased in the following order: AH26, Diaket, Tubli-Seal, and Fynal. Our results showed that the differences observed between each material and its respective controls as well between the materials themselves were statistically significant (p