Human alveolar osteoblast response to date-expired dental implants renewed by hydrogen peroxide gas plasma sterilization
Al-Hashemi, Jacob Yousef Kadhum
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Dental implants, otherwise uncompromised, are occasionally found to be date-expired within intact or opened packages, denying their clinical use unless they can be reliably re-sterilized and made equivalent in reaction to new implants within receiving bone sites. This investigation identified an FDA-approved low-temperature gas plasma sterilization approach—in residual hydrogen peroxide (H2O2) vapor at low pressure—capable of quickly (within an hour) restoring even grossly contaminated dental implants to sterility and renewing their surface qualities to those of as-manufactured implants with regard to their support for attachment and growth of human alveolar osteoblasts. Pilot studies with flat commercially pure titanium (cpTi) discs used the methods of contact angle measurement, ellipsometry, scanning electron microscopy (SEM), energy-dispersive x-ray analysis (EDS), scanning Auger microscopy, and x-ray photoelectron spectroscopy (XPS) to demonstrate that cpTi surface properties could be optimized for bioadhesion using the H2O2 gas plasma sterilization approach. The main studies then monitored actual date-expired dental implants of three different types, as packaged as well as after deliberate contamination with Candida albicans or adventitious atmospheric organisms, through microbiological broth-based and agar-based assays to prove sterility and through tissue culture assays with human alveolar osteoblasts to prove renewed cellular attachment and growth characteristics. Osteoblast growth and viability was confirmed by statistically equivalent outcomes for as-manufactured implants and clean/re-sterilized (by H2O2 gas plasma) implants, judged by cellular mitochondrial activity assays (MTT), differential interference contrast (DIC) light microscopy, and SEM. These results demonstrated that date-expired dental implants can be safely and effectively restored to conditions generally associated with the good clinical performance of osseointegated cpTi devices.