Estudio experimental de la estabilidad de micro implantes e influencia de los metales pesados sobre los sistemas antioxidantes (SOD-1 y glutatión) en portadores de amalgamas dentalesprotocolos con filtros

Abstract

ABSTRACT The aim of this Doctoral Thesis is to study the stability of Microimplants (MIs) under an immediate load by analyzing biomechanical and histological parameters (PIT: Peak Insertion Torque; PRT: Peak Removal Torque; BIC: Bone-to- Implant Contact) in female Beagle dogs. There were 144 MIs placed in dogs&apos; mouths for 16 weeks. The dogs were fed with diets of different consistence (hard/soft) from 5 months of age until the end of the experiment. The dogs fed with the hard diet (HD) showed an increase in the percentage PIT. Conversely, those fed with a soft diet (SD) showed an increase in the percentage of BIC and PRT in comparison to animals fed with hard diet (HD). The histomorphometric analysis reflected statistically significant differences between both experimental groups. Our results suggest that the impactsof mastication not only influence the bone per se but also the stability of the MIs. The advantages associated with the use of MIs are increasing in the orthodontic field and also allow the implementation of multidisciplinary treatments in adult patients. For that reason the alloys used in orthodontics could be combined with prosthesis, implants and/or dental amalgams. In the combination of these alloys and compared with others, dental amalgams stand out for their toxicity and, as they could induce galvanic corrosion, it must be assumed that the patient may suffer some degree of exposure to corrosion products. Therefore, we have evaluated whether levels of a plethora of heavy metals measured in hair samples by mass spectrometry (ICP-MS in µ/g Ba, Sb, As, Be, Bi, Cd, Pb, Pt, Ti, Th, U, Ni; especially those that make dental amalgam: Al, Hg, Ag, Zn, Cu, Sn, Ti) could increase significantly in those who had been carrying amalgam for at least ten years (mean: 15 years, n = 55) compared with healthy controls (without amalgams or implants n = 13). Since mercury can increase levels of free radicals, we have evaluated whether there is a link between release of heavy metals and a possible increase in Glutathione (GSH; reduced form) or upregulation of activity of Superoxide Dismutase-1 (SOD-1), which eliminates the free radical called superoxide anion. In our study, the dental amalgam carriers (average age: 44 years) were classified into those who had four or fewer dental amalgams (<4; n = 27) and those with more than four (> 4, n = 15). All of them had dental amalgams in their mouth for at least 10 years (average: 15 years). The main finding of our study indicates that levels of mercury (Hg), aluminium (Al), silver (Ag) and barium (Ba) were significantly elevated in women who had dental amalgams. Since the glutathione (GSH) levels correlated with aluminium levels and the activity SOD-1 correlated with levels of total mercury, the present study suggests that there are protective endogenous compensatory mechanisms in women who had dental amalgams for a long period of time. According to our results, facing the high prevalence of amalgam changes for cosmetic reasons or as part of multidisciplinary orthodontic treatment, the implementation of biosecurity measures would minimize the release of mercury vapour during removal. Applying the precautionary principle, the use of nasal filters of activated carbon prevent the patient, the clinic staff and the environment from the risk of exposure to heavy metals released in the amalgam removal process.