Osseointegration of a novel injection molded 2-piece ceramic dental implant: a study in minipigs.

OBJECTIVES: This study compared the osseointegrative potential of a novel injection molded zirconia dental implant (Neodent Zi ceramic implant, test) and a commercially available titanium implant (Neodent Alvim implant, control) in terms of histomorphometrically derived bone-to-implant contact (BIC), first bone-to-implant contact (fBIC), and the ratio of bone area to total area (BATA) around the implant. MATERIALS AND METHODS: A total of 36 implants, 18 per individual test device, were implanted in a split-mouth arrangement in either side of the edentulous and fully healed mandible of 6 minipigs. Histomorphometric analysis of BIC, fBIC, and BATA were performed 8 weeks post implantation and subjected to statistical non-inferiority testing. Surface characteristics of both implant types were compared in terms of contact angle, surface topography, and elemental composition. RESULTS: BIC, fBIC, and coronal BATA values of test and control implants were statistically comparable and non-inferior. BIC values of 77.8 ± 6.9% vs. 80.7 ± 6.9% (p = 0.095) were measured for the test and control groups. fBIC lingual values were - 238 ± 328 µm compared with - 414 ± 511 µm (p = 0.121) while buccal values were - 429 ± 648 µm and - 588 ± 550 µm (p = 0.230) for the test and control devices, respectively. BATA in the apical segment was significantly higher in the test group compared with the control group (67.2 ± 11.8% vs. 59.1 ± 11.4%) (p = 0.0103). Surface topographies of both implant types were comparable. Surface chemical analysis indicated the presence of carbonaceous adsorbates which correlated with a comparable and predominantly hydrophobic character of the implants. CONCLUSION: The results demonstrate that the investigated zirconia implants, when compared with a commercially available titanium implant, show equivalent and non-inferior bone integration, bone formation, and alveolar bone level maintenance. This qualifies the investigated zirconia implant as a potential candidate for clinical development. CLINICAL RELEVANCE: This study investigated the osseointegration of a novel zirconia 2-piece dental implant prototype intended for clinical development. With the aim of translating this prototype into clinical development preclinical models, procedures and materials within this study have been selected as close to clinical practice and human physiological conditions as possible.

Peri-implant bone preservation of a novel, self-cutting, and fully tapered implant in the healed crestal ridge of minipigs: submerged vs. transgingival healing.

OBJECTIVES: The aim of this study was to assess the influence of transgingival compared with submerged healing on peri-implant bone maintenance around a novel, fully tapered implant in a healed crestal ridge in minipigs. MATERIALS AND METHODS: In each of 12 minipigs, two implants (Straumann® BLX, Roxolid® SLActive®, Ø 3.75 × 8 mm) were placed. Implants were either left for submerged or for transgingival healing for 12 weeks. Measurements performed were bone-to-implant contact (BIC), first bone-to-implant contact (fBIC), bone area to total area (BATA), perpendicular bone crest to implant shoulder (pCIS), bone height change from placement, and bone overgrowth (for submerged implants). RESULTS: No significant differences were found between transgingival and submerged healing in any of the measured parameters, except for BATA on the buccal aspect in which significantly more bone formation was found for the transgingival healing group. For both groups, there was a gain in crestal bone height during the 12-week healing period. CONCLUSIONS: Loaded compared with unloaded implants displayed comparable levels of osseointegration and equivalent marginal bone levels. This qualifies the implant placement protocol with respect to the osteotomy dimensions and subcrestal placement protocol for immediate loading. CLINICAL RELEVANCE: The here presented results related to osseointegration and crestal bone maintenance after submerged or transgingival healing have demonstrated a high level of consistency in the used in vivo translational model. The obtained results support the translation of the novel implant type in conjunction with the developed surgical workflow and placement protocol into further clinical investigation and use.

Case Report: Canine Strain- and Study Condition-Dependent Formation of Renaut Bodies in Sciatic Nerves of Beagle Dogs.

Two beagle dog strains were used in a 14-day intrathecal infusion study for a small molecule test article. A moderate number of Renaut bodies (RBs) were observed in the sciatic nerves of control and test article-treated adult animals as early as 1 day after test article infusion (ie, 5 days after catheter implantation in the lumbar cistern). In most cases, the sciatic nerve was affected unilaterally, apparently in association with extended lateral recumbency on one side. The lighter beagle strain (Marshall), and especially the females (which weighed less than age-matched Marshall males), developed more RBs. In contrast, neither females nor males of the larger strain (Harlan) developed any nerve lesions. These data support the hypothesis that RBs develop following mechanical stress to sciatic nerves, suggest that this change may develop fairly quickly following an insult, and demonstrate that different dog strains exhibit strain-specific nerve changes.

Reproduction toxicity study with the synthetic amorphous silica SYLOID® AL-1 FP, HDK® N20, LUDOX® P T-40 F and SYLOID® MX 107 in the earthworm species Eisenia fetida.

Ecotoxicology studies were performed in the earthworm Eisenia fetida with four different synthetic amorphous silica (SAS) (SYLOID® AL-1 FP, SYLOID® MX 107, LUDOX® P T-40 F, and HDK® N20) mixed into artificial soil to determine a NOEC/LOEC for effects on reproduction (56 days after application), mortality and biomass development (28 days after application) using a standardized artificial soil with 10% peat. The LC50 for test-item effects on adult mortality, and an EC10 and EC50 for reproduction were also determined. Furthermore, earthworms underwent histopathology evaluation, and the amount of silica in different organs from these organisms was evaluated using EDX (Energy Dispersive X-ray Spectroscopy). Histopathology revealed no findings in any organ of the earthworms, except for desiccated dissepiments in evaluated decedents at extremely high SAS doses. To measure SAS uptake into the organs, a fully quantitative method for silica was established and validated using standards containing known concentrations of silica to ensure the accuracy of the analyses undertaken. Results from EDX analysis demonstrated the negligible presence of silicon within the brain ganglia and gonads of adult earthworms comparable to controls. Therefore, any deposition of the test items within these two organs was excluded. In contrast, traces of silicon higher than in controls were found in the intestinal lumina of the earthworms due to ingestion of SAS with soil and feed, but not in other organs.

Eosinophilic globules (syn. hyaline inclusions) and protein crystalloids in the nasal mucosa of rats treated with synthetic amorphous silica, an unspecific chitinase-like-protein-positive background lesion.

In a 13-week inhalation toxicity study with three recovery periods (3, 6, and 12 months), Crl: WI rats were allocated to nine groups, each containing 25 animals per sex. Eight groups were treated daily by inhalation with the test items at concentrations of 0.5, 1.0, 2.5, or 5.0 mg/m3 (SAS 1 groups 2, 3, 4, or 5, respectively; SAS 2 groups 6, 7, 8, or 9, respectively). Controls (group 1) were treated with air only. In nasal cavities, the major lesions consisted of increased eosinophilic globules and chitinase-3-like-protein-positive crystalloids* in the nasal mucosa, mainly in nasal cavity levels 2-4 up to week 26 of recovery without any further injury in olfactory mucosa, mainly in SAS 1-treated animals. Eosinophilic globules in the rodent nasal cavity are common and increase with age; they represent a particular finding of the rodent nasal mucosa. The relevance of chitinase-3-like protein (Ym1 + Ym2) expression in the rodent nasal mucosa is unknown but is normal in control animals. Both findings developed without any indicator for inflammatory processes. The increase of these unspecific background findings is considered an indicator of minor irritative effects. Due to the clear lack of nasal tissue injury or concurrent changes (degeneration, necrosis, inflammatory infiltrate, dysplasia, and/or neoplasia) following repeated inhalation exposure to SAS, it is deemed that the eosinophilic globules (hyaline inclusions) combined with the formation of eosinophilic protein crystalloids in this study represent an adaptive response.

Onset and progression of postmortem histological changes in the central nervous system of RccHan™: WIST rats.

Death initiates a cascade of physiological and biochemical alterations in organs and tissues, resulting in microscopic changes that challenge the histopathological evaluation. Moreover, the brain is particularly susceptible to artifacts owing to its unique composition and its location within the cranial vault. The aim of this study was to compile and illustrate the microscopic changes in the central nervous system (CNS) of rats subjected to delayed postmortem fixation. It also scrutinizes the influence of exsanguination and cooling methods on the initiation and progression of these alterations. Twenty-four Wistar Han outbred rats (RccHan™: WIST) were sacrificed and stored either at room temperature (18-22°C) or under refrigeration (2-4°C). Necropsies were conducted at different time points postmortem (i.e., 0.5 h, 1 h, 4 h, 8 h, 12 h, 24 h, 36 h, 48 h, 7 days and 14 days). Brain sections underwent simultaneous digital evaluation by 14 pathologists until a consensus was reached on terminology, key findings, and intensity levels. Microscopic observations varied among cell types. Glial cells were similarly affected throughout the CNS and showed pericellular halo, chromatin condensation and nuclear shrinkage. Neurons showed two types of postmortem changes as most of them showed progressive shrinkage, cytoplasmic dissolution and karyorrhexis whereas others acquired a dark-neuron-like appearance. Neuronal changes showed marked differences among neuroanatomical locations. Additional postmortem changes encompassed: granulation and microcavitation in neuropil and white matter; retraction spaces; detachment of ependyma, choroid plexus, and leptomeninges. Severity of findings after 48 h at room temperature was higher than after seven days under refrigeration and similar to or slightly lower than after 14 days under refrigeration. No clear differences were observed related to the sex or weight of the animals or their exsanguination status. This work elucidates the onset and progression of autolytic changes in the brains of Wistar Han rats, offering insights to accurately identify and enhance the histopathological evaluation.

Enhanced study design for acute inhalation studies with hydrophobic surface-treated particles to determine toxicological effects including suffocation.

High concentrations of low-density particles may cause effects in acute inhalation toxicity studies which can be easily underestimated or misinterpreted following strictly the OECD TG 436, i.e., limited parameters as mortality and gross lesions will be evaluated only. Seven particle types (synthetic amorphous silica (SAS) HMDZ-SAS, silica gel, pyrogenic SAS, and precipitated SAS, calcium carbonate, aluminum oxide pyrogenic alumina, organic red pigment) were chosen at the highest technically feasible concentration of approximately 500 mg/m3 for acute inhalation studies with an expanded endpoint setup. Therefore additional parameters and a thorough histopathological evaluation of an extensive set of organs, including the respiratory tract emphasizing the nasal cavities were added. Six Crl:WI rats per study were exposed for four hours from which three animals were sacrificed after 24 hours and three animals after 14 days. HMDZ-SAS caused early death in all animals due to blockage of the nasal passages caused by its hydrophobicity. For all other Si-containing compounds, histology revealed minor inflammatory and reactive lesions in lungs after 24 hours that were still present after 14 days, except in silica gel-treated animals. After 14 days, for pyrogenic SAS, precipitated SAS, and pyrogenic alumina, granulomas formed in the BALT and lung-associated lymph nodes. In contrast, the calcium carbonate induced almost no findings, and the red pigment (also tested for the additional dose of 1000 mg/m3) stuck partially to the nasal mucosa without causing pathological damage and partly entered the lungs without showing any adverse effects. The results of the present study highlight the advantage of improving the rather simple study design of acute inhalation studies by implementing an extended study design.

Investigation on the skin penetration of synthetic amorphous silica (SAS) used in cosmetic products.

Synthetic amorphous silica (SAS) is used as additive in a variety of industrial applications for many decades and has been approved to be used in food, food contact materials, pharmaceuticals, and cosmetics. Due its internal structure, SAS is considered as a nanomaterial, thus it is affected by a general safety discussion. Based on the production process, SAS for cosmetic application is a nanomaterial by the EU Recommendation, although it was not considered as such, because the solely size-dependent definitions of the term "nanomaterial" emerged in recent times first in Recommendation 2011/696/EU. Therefore, former physicochemical and toxicological evaluations of SAS were already performed on nanomaterials, however, without being addressed as such. Safety concerns can only emerge if two criteria, (toxicological) hazard and exposure towards the substance is fulfilled at the same time. In case of SAS, the Scientific Committee on Consumer Safety (SCCS) challenged provided data to be insufficient to draw a conclusion regarding the safety of SAS and thus, requested further investigations, in particular by exploring skin penetration of particulate SAS.Investigation of specific particulate substances in skin penetration tests is an analytical challenge. The number of available analytical techniques that are capable to detect nanomaterials in complex matrices, like receptor fluids from skin penetration testing, are limited and still emerging. In the new studies, a comprehensive set of analytical techniques were used to investigate the skin penetration potential of SAS. Particle-sensitive, element and particle-specific combinations of techniques and different sample preparation procedures, that respected the particulate nature of SAS, were used to detect SAS in receptor fluids directly. In addition, electron microscopic techniques were used to examine different layers of skin to detect adsorbed SAS.The combination of Asymmetric Flow Field-Flow Fractionation (AF4) in combination with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for examination of receptor fluids and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM/EDX) for examination of skin itself, were identified as suitable techniques for the detection of SAS in skin penetration tests. Data from literature was used to compare the results of the studies with the outcome of other test systems (other particles, other techniques). Both, the test results, and literature evaluation led to the conclusion, that SAS does not penetrate skin. Based on this outcome and local and systemic dermal toxicity review of SAS, it can be concluded that dermal application of SAS in cosmetic formulations is negligible.

Physical Obstruction of Nasal Cavities With Subsequent Asphyxia, Causes Lethality of Rats in an Acute Inhalation Study With Hydrophobic HMDZ Surface-Treated Synthetic Amorphous Silica (SAS).

The aim of the present study was to understand the mechanism of lethality associated with high dose inhalation of a low-density hydrophobic surface-treated SAS observed in some acute inhalation studies. It was demonstrated that physical obstruction of the upper respiratory tract (nasal cavities) caused the effects observed. Hydrophobic surface-treated SAS was inhaled (flow-past, nose-only) by six Wistar rats (three males and three females) in an acute toxicity study at a concentration of ~500 mg/m3 for an intended 4-hr exposure. Under the conditions of the test set-up, the concentration applied was found to be the highest that can be delivered to the test animal port without significant alteration of the aerosol size distribution over time. None of the test- material-exposed animals survived the planned observation time of 4 h; three animals died between 2 34 h after starting exposure and cessation of exposure at 3 14 h, two died after transfer to their cages and the remaining animal was sacrificed due to its poor condition and welfare considerations. Histology accomplished by energy dispersive X-ray (EDX) analysis demonstrated that test material particles agglomerated and formed a gel-like substrate that ultimately blocked the upper respiratory airways, which proved fatal for the rat as an obligatory nose breather. This observation is in line with the findings reported by Hofmann et al. showing a correlation between lethality and hydrophobicity determined by contact angle measurement. The aerosol characterizations associated with this study are provided in detail by Wessely et al.

First Evaluation of Temporal and Spatial Fractionation in Proton Minibeam Radiation Therapy of Glioma-Bearing Rats.

(1) Background: Proton minibeam radiation therapy (pMBRT) is a new radiotherapy technique using spatially modulated narrow proton beams. pMBRT results in a significantly reduced local tissue toxicity while maintaining or even increasing the tumor control efficacy as compared to conventional radiotherapy in small animal experiments. In all the experiments performed up to date in tumor bearing animals, the dose was delivered in one single fraction. This is the first assessment on the impact of a temporal fractionation scheme on the response of glioma-bearing animals to pMBRT. (2) Methods: glioma-bearing rats were irradiated with pMBRT using a crossfire geometry. The response of the irradiated animals in one and two fractions was compared. An additional group of animals was also treated with conventional broad beam irradiations. (3) Results: pMBRT delivered in two fractions at the biological equivalent dose corresponding to one fraction resulted in the highest median survival time, with 80% long-term survivors free of tumors. No increase in local toxicity was noted in this group with respect to the other pMBRT irradiated groups. Conventional broad beam irradiations resulted in the most severe local toxicity. (4) Conclusion: Temporal fractionation increases the therapeutic index in pMBRT and could ease the path towards clinical trials.

A Potential Renewed Use of Very Heavy Ions for Therapy: Neon Minibeam Radiation Therapy.

(1) Background: among all types of radiation, very heavy ions, such as Neon (Ne) or Argon (Ar), are the optimum candidates for hypoxic tumor treatments due to their reduced oxygen enhancement effect. However, their pioneering clinical use in the 1970s was halted due to severe side effects. The aim of this work was to provide a first proof that the combination of very heavy ions with minibeam radiation therapy leads to a minimization of toxicities and, thus, opening the door for a renewed use of heavy ions for therapy; (2) Methods: mouse legs were irradiated with either Ne MBRT or Ne broad beams at the same average dose. Skin toxicity was scored for a period of four weeks. Histopathology evaluations were carried out at the end of the study; (3) Results: a significant difference in toxicity was observed between the two irradiated groups. While severe da-mage, including necrosis, was observed in the broad beam group, only light to mild erythema was present in the MBRT group; (4) Conclusion: Ne MBRT is significantly better tolerated than conventional broad beam irradiations.