Search

The use of odontological or orthopedic metal implants requires the availability of techniques to estimate tissue response to the corrosion processes. In previous experimental studies we showed the deposition of corrosion products not only locally (Olmedo et al., Implant Dent 2003; 12: 75-80) but also systemically (Olmedo et al., J Mater Sci: Mater in Medic 2002; 13: 793-796) in organs such as liver, spleen and lung. The aim of the present study was to propose a method to quantitatively assess the tissue deposits of the corrosion products of the materials used to manufacture implants. The samples (liver and lung) were embedded in paraffin, and the histological sections were submitted to thickness standardization. The quantitative evaluation of the deposits was performed in an MPM-800 (Carl Zeiss)* microscope. The light microscopy images were digitalized and then analyzed employing the DNA-IBAS-Kontron software that allows for the identification and evaluation of cells loaded with corrosion products (objective 20x). The following end-points were assessed: total field area, number of deposits of corrosion products, partial and total area of the deposits, and the ratio between volume of the deposits and tissue volume. The method proposed serves to quantitatively evaluate, at light microscopy level, the deposition of corrosion products in tissues.

Among the local and systemic factors affecting bone repair, great interest is focused on age and gender. The aim of this work was to perform a histomorphometric evaluation of peri-implant bone healing response in male and female rats aged 1 and 3 months. Forty Wistar rats were i.p. anesthetized with xylazine and ketamine. A c.p. Ti implant (Implant Vel, Buenos Aires-Argentina) was placed in the right tibia following the method described by Cabrini et al. (Implant Dent 1993; 2:264-267). Group I: (GI, n = 10) female rats aged 1 month; Group II: (GII, n = 10) female rats aged 3 months; Group III: (GIII, n = 10) male rats aged 1 month; Group IV: (GIV, n = 10) male rats aged 3 months. All the animals were killed by ether overdose 30 days post-implantation. The tibiae were resected, radiographed and embedded in methyl-methacrylate. Ground sections perpendicular to the longer axis of the tibia were obtained and stained with toluidine blue. Percentage of osseointegration and peri-implant bone tissue volume were evaluated. No differences in peri-implant bone tissue histology were observed among groups. No statistically significant differences in peri-implant bone volume and percentage of osseointegration were observed between GII (adult females) and GIV (adult males). Peri-implant bone volume and percentage of osseointegration were markedly greater in GIV (adult males) than in GIII (young males) (14 +/- 1 mm2 and 8 +/- 2 mm2) p < 0.01 and (49 +/- 6% and 24 +/- 9%) p < 0.01 respectively. Using this experimental model, differences in peri-implant osteogenesis (bone volume and percentage of osseointegration) associated to gender were only observed in the young rats, and differences associated to age were found between the groups of males.

Corrosion phenomena would appear to play a decisive role in metallic implant long term behaviour. This study presents a method to correlate results obtained in "in vivo" and "in vitro" studies on materials used for metallic implants. Samples of titanium and copper immersed in saline solution (pH 7.4 and 5.2) were used for the "in vitro" study. Implants of these same materials were placed in rat tibiae following the method previously described by Cabrini et al. The animals were killed 14 days post-implantation, the tibiae were resected, radiographed and embedded in acrylic resin. Polarization curves revealed high corrosion in copper implants and low corrosion in titanium implants. It is important to point out that the titanium samples suffered slightly higher corrosion when immersed in a lower pH medium (pH 5.2), as in chronic inflammatory processes. A passive film was found on titanium samples as opposed to the strong corrosion observed in the copper implants. Microscopy revealed osseointegration around titanium implants and a severe inflammatory reaction with abscesses surrounding the copper implants. The method presented herein would allow to correlate "in vivo" and "in vitro" studies on corrosion in different implant materials and establish their relation with cell response.