All that glitters is not gold: X-ray fluorescence analysis of a fixed dental prosthesis from Colecção de Esqueletos Identificados Século XXI, Portugal (CEI/XXI).

Access to better health care anticipates that more medical devices can be found alongside skeletal remains. Those employed in oral rehabilitation, with available brands or batch/series, can prove useful in the identification process. A previous study in the Colecção de Esqueletos Identificados Século XXI described macroscopically the dental prostheses. An unusual case of a dental device with chromatic alterations demonstrated to require a more detailed analysis. The individual, a 53-year-old male, exhibited, at both arches, a fixed tooth-supported rehabilitation, with gold colouring classified initially as a gold-palladium alloy. Simultaneously, a green pigmentation deposit was observable in bone and prosthesis. This investigation aimed to verify the elemental composition of the dental prosthesis alloy. Elemental analysis was performed by X-ray fluorescence in two regions (labial surface of the prosthetic crown and the root surface of the lower right lateral incisor). Both the spectra and the qualitative results found higher levels of copper and aluminium, followed by nickel, iron, zinc, and manganese. No gold or palladium was detected. The most probable assumption is that a copper-aluminium alloy was used, as its elemental concentration corresponds to those measured in similar devices. Dental prostheses of copper-aluminium alloys have been made popular since the 1980s, particularly in the USA, Japan, and Eastern Europe. Apart from the biographical information, it was also known that the individual's place of birth was an Eastern European country, which highlighted the usefulness of this type of information when dealing with missing people cases.

The dental prosthesis (removable and fixed) from the Colecção de Esqueletos Identificados Século XXI (CEI/XXI).

For identification of the unknown, the analysis of individualizing characteristics is a paramount procedure, which allows the reconciliation of antemortem with postmortem data. Worldwide, populations are commonly affected by tooth loss, leading to procedures of oral rehabilitation, such as dental prostheses. Although the potential of these devices for human identification is well known, the lack of marks or serial numbers as well as scarce systematic register on databases may difficult its use. The objective of this paper is to present and describe the cases with dentures and bridges of an identified osteological collection, the Colecção de Esqueletos Identificados Século XXI. All the individuals were macroscopically observed, and the cases presenting dental prostheses were registered. A total of thirty-one individuals (20 females; 11 males), ages 38 to 91 years, presented 49 dental prosthesis (removable or fixed), of various materials. The removable acrylic dentures (n = 42) were the most frequent. No identifying marks or production labels were found. This research reinforces two focal points: the value of studying and recognizing medical devices and their application for identification, and the relevance of identified skeletal collections for the advance of forensic science in the current multidisciplinary approach.

In Vitro Biocompatibility Assessment of Nano-Hydroxyapatite.

Hydroxyapatite (HA) is an important component of the bone mineral phase. It has been used in several applications, such as bone regenerative medicine, tooth implants, drug delivery and oral care cosmetics. In the present study, three different batches of a commercial nanohydroxyapatite (nHA) material were physicochemically-characterized and biologically-evaluated by means of cytotoxicity and genotoxicity using appropriate cell lines based on well-established guidelines (ISO10993-5 and OECD 487). The nHAs were characterized for their size and morphology by dynamic light scattering (DLS) and transmission electron microscopy (TEM) and were found to have a rod-like shape with an average length of approximately 20 to 40 nm. The nanoparticles were cytocompatible according to ISO 10993-5, and the in vitro micronucleus assay showed no genotoxicity to cells. Internalization by MC3T3-E1 cells was observed by TEM images, with nHA identified only in the cytoplasm and extracellular space. This result also validates the genotoxicity since nHA was not observed in the nucleus. The internalization of nHA by the cells did not seem to affect normal cell behavior, since the results showed good biocompatibility of these nHA nanoparticles. Therefore, this work is a relevant contribution for the safety assessment of this nHA material.

Combining local antibiotic delivery with heparinized nanohydroxyapatite/collagen bone substitute: A novel strategy for osteomyelitis treatment.

Osteomyelitis is a major challenge in bone surgery and conventional treatment is frequently ineffective to control the infection, with an alternative approach being required. In the present work, a heparinized nanohydroxyapatite/collagen biocomposite was produced in granular form, and loaded with vancomycin, to work as a local drug delivery system for osteomyelitis and as a bone substitute. This strategy involves the local delivery of high concentrations of vancomycin, to eradicate the infection. Additionally, these granules work as a scaffold with regenerative properties, to induce bone regeneration after antibiotic release. The heparinized nanohydroxyapatite/collagen granular bone substitute was produced using two different sintering temperatures to study their effect on granules properties and on vancomycin release profile. Morphological, topographic, chemical and mechanical characterization were carried out for granules sintered at both temperatures and some relevant differences were found. The mechanical strength was increased by several orders of magnitude with increasing sintering temperature, being able to maintain their porous macrostructure and withstand important processes for their commercialization such as packaging, shipping and surgical manipulation. The nanohydroxyapatite/collagen granules were able to release high concentrations of vancomycin, always above MIC, for 19 days. The released antibiotic was able to eradicate both planktonic and sessile methicillin-resistant Staphylococcus aureus. The cytotoxicity was assessed according to ISO 10993-5:2009 and the granules sintered at higher temperature showed no cytotoxic effect. Considering these results nanohydroxyapatite/collagen biocomposite loaded with vancomycin is a promising solution for osteomyelitis treatment.

The antibacterial and angiogenic effect of magnesium oxide in a hydroxyapatite bone substitute.

Bone graft infections are serious complications in orthopaedics and the growing resistance to antibiotics is increasing the need for antibacterial strategies. The use of magnesium oxide (MgO) is an interesting alternative since it possesses broad-spectrum antibacterial activity. Additionally, magnesium ions also play a role in bone regeneration, which makes MgO more appealing than other metal oxides. Therefore, a bone substitute composed of hydroxyapatite and MgO (HAp/MgO) spherical granules was developed using different sintering heat-treatment cycles to optimize its features. Depending on the sintering temperature, HAp/MgO spherical granules exhibited distinct surface topographies, mechanical strength and degradation profiles, that influenced the in vitro antibacterial activity and cytocompatibility. A proper balance between antibacterial activity and cytocompatibility was achieved with HAp/MgO spherical granules sintered at 1100 ºC. The presence of MgO in these granules was able to significantly reduce bacterial proliferation and simultaneously provide a suitable environment for osteoblasts growth. The angiogenic and inflammation potentials were also assessed using the in vivo chicken embryo chorioallantoic membrane (CAM) model and the spherical granules containing MgO stimulated angiogenesis without increasing inflammation. The outcomes of this study evidence a dual effect of MgO for bone regenerative applications making this material a promising antibacterial bone substitute.

Nano-hydroxyapatite in oral care cosmetics: characterization and cytotoxicity assessment.

Nano-hydroxyapatite has been used as an oral care ingredient, being incorporated in several products for the treatment of dental hypersensitivity and enamel remineralisation. Despite its promising results, regulatory and safety concerns have been discussed and questioned by the European Scientific Committee on Consumer Safety (SCCS) regarding the usage of hydroxyapatite nanoparticles in oral care products. In this work, a commercially available nano-hydroxyapatite was characterized and its cytocompatibility towards human gingival fibroblasts was evaluated, as well as its irritation potential using the in vitro HET-CAM assay. All the conditions chosen in this study tried to simulate the tooth brushing procedure and the hydroxyapatite nanoparticles levels normally incorporated in oral care products. The commercial hydroxyapatite nanoparticles used in this study exhibited a rod-like morphology and the expected chemical and phase composition. The set of in vitro cytotoxicity parameters accessed showed that these nanoparticles are highly cytocompatible towards human gingival fibroblasts. Additionally, these nanoparticles did not possess any irritation potential on HET-CAM assay. This study clarifies the issues raised by SCCS and it concludes that this specific nano-hydroxyapatite is cytocompatible, as these nanoparticles did not alter the normal behaviour of the cells. Therefore, they are safe to be used in oral care products.

Antibacterial bone substitute of hydroxyapatite and magnesium oxide to prevent dental and orthopaedic infections.

Bone substitutes market is growing due to the great demand for bone regenerative therapies. However, most of the actual products available in the market are incapable of inhibiting bacterial colonization, which can lead to tissue infection and possible implant failure. Some bone substitutes are combined with antibiotics to avoid the development of implant-associated infections, but the growing bacterial resistance to antibiotics often makes these products ineffective. Therefore, it is mandatory to develop new and alternative approaches. In the present work, a granular bone substitute of hydroxyapatite was produced, where different percentages of magnesium oxide were introduced. The antibacterial activity and biofilm formation was evaluated towards Staphylococcus aureus and Escherichia coli. The inclusion of magnesium oxide particles reduced bacterial growth and biofilm formation in a concentration-dependent manner, when compared with pure hydroxyapatite materials. Superior antibacterial activity and inhibition of biofilm formation was observed for Staphylococcus aureus with complete eradication when magnesium oxide percentages were equal or above 3 wt%. The materials cytotoxicity was assessed under ISO 10993-5:2009 guidance and through Live/Dead cell marking and none of the produced granules was cytotoxic. In addition, reactive oxygen species production was also evaluated and the results revealed that the exposure to the materials extracts did not induce the formation of reactive oxygen species by cells.