Antonio González Cantalapiedra

Influence on early osseointegration of dental implants installed with two different drilling protocols: a histomorphometric study in rabbit.

OBJECTIVEnto evaluate early osseointegration of dental implants installed with two different drilling protocols.nnnMATERIAL AND METHODSnthirty-six cylindrical shape Mozo Grau implants, with a diameter of 3.75 and 11 mm long, were placed into the distal condyle (submerged) of each femur of 18 New Zealand rabbits. In the control group, a 3.3 mm diameter drill was used as the last one prior implant installation (standard protocol). In the test group, the same procedure was carried out but an additional 3.5 mm drill was used as the final one (oversized protocol) Thus, we could obtain different primary stability at day 0 between groups. Sacrifice of the animals was after 2, 4 and 8 weeks. Histomorphometric analysis (bone-to-implant contact ratio [BIC%]) and implant stability quotient (ISQ) values (Ostell ) were registered at each sacrifice time.nnnRESULTSnthe ISQ values were statistically significant different between groups at day 0 (control: 69.65; test: 64.81); and after 2 weeks (control: 77.93; test: 74). However, after 4 and 8 weeks the results were similar. BIC% showed a similar tendency, with 58.69% for the control group and 40.94% for the test group after 2 weeks, this difference being statistically significant. At 4- and 8-week interval, BIC% was similar.nnnCONCLUSIONnat 2-week interval (early healing), osseointegration had been influenced by different primary stability at implant installation, being slower in the oversized protocol (lower primary stability), which could be especially risky in challenging clinical situations, such as soft bone (class 3 and 4) and early/immediate loading. However, from 4 week on, these differences disappeared. Nevertheless, we have to consider that a direct transfer of the results of this animal study (time bone repair mechanisms) into clinic has to be done with caution.

In vivo behaviour of two different biphasic ceramic implanted in mandibular bone of dogs

Alloplastic calcium phosphate bone substitutes such as hydroxyapatite (HA) and tricalcium phosphate (TCP) have been studied extensively due to their composition closely resembling the inorganic phase of bone tissue. On the same way, by manipulating the HA/TCP ratio it may be possible to change the substitution rate and the bioactivity of these materials, an advantage which has brought them to clinical use in oral and orthopaedic surgery. In this work, we evaluated the histological response in bone of two biphasic calcium phosphate ceramics by varying the proportion of their components. All premolars of 6 beagle dogs were removed from both sides of the mandible. Three months later, four cylinders composed of 85% HA and 15% β-TCP (BCP 1) were implanted in the right side of mandible and other four cylinders composed of 15% HA and 85% β-TCP (BCP 2) were implanted in the left side of mandible of dogs for 4, 12 ad 26xa0weeks, respectively. Two dogs were used in each time point. The histological study indicated that both biphasic ceramic were biocompatible. The earlier and more quantity of bone formed in BCP 2 than in BCP 1 suggested that the first one had a higher osteoinductive potential than the second one in mandibular bone. The resorption of the phosphate phase and the subsequent migration of bone into the resorbed portions were detected in both biphasic ceramics although two processes appeared faster in BCP 2 than in BCP 1. These dates conclude that varying the components of our biphasic ceramic we improve its osteoinductive potential.

In vivo arrhythmogenicity of the marine biotoxin azaspiracid-2 in rats

Azaspiracids (AZAs) are marine biotoxins produced by the dinoflagellate Azadinium spinosum that accumulate in several shellfish species. Azaspiracid poisoning episodes have been described in humans due to ingestion of AZA-contaminated seafood. Therefore, the contents of AZA-1, AZA-2 and AZA-3, the best-known analogs of the group, in shellfish destined to human consumption have been regulated by food safety authorities of many countries to protect human health. In vivo and in vitro toxicological studies have described effects of AZAs at different cellular levels and on several organs, however, AZA target remains unknown. Very recently, AZAs have been demonstrated to block the hERG cardiac potassium channel. In this study, we explored the potential cardiotoxicity of AZA-2 in vivo. The effects of AZA-2 on rat electrocardiogram (ECG) and cardiac biomarkers were evaluated for cardiotoxicity signs besides corroborating the hERG-blocking activity of AZA-2. Our results demonstrated that AZA-2 does not induce QT interval prolongation on rat ECGs in vivo, in spite of being an in vitro blocker of the hERG cardiac potassium channel. However, AZA-2 alters the heart electrical activity causing prolongation of PR intervals and the appearance of arrhythmias. More studies will be needed to clarify the mechanism by which AZA-2 causes these ECG alterations; however, the potential cardiotoxicity of AZAs demonstrated in this in vivo study should be taken into consideration when evaluating the possible threat that these toxins pose to human health, mainly for individuals with pre-existing cardiovascular disease when regulated toxin limits are exceeded.

Anaesthetic potency of isoflurane in cattle: determination of the minimum alveolar concentration

OBJECTIVEnTo determine the minimum alveolar concentration (MAC) of isoflurane in cattle.nnnSTUDY DESIGNnProspective study.nnnANIMALSnSixteen healthy adult female Holstein-Friesian cattle weighing 612 ± 17 kg (× ± SEM) and aged 5.7 ± 0.9 years old.nnnMETHODSnThe unsedated cattle were restrained in right lateral recumbency using a rope harness technique. Anaesthesia was induced with isoflurane (ISO) in oxygen via a face mask connected to a large-animal, semiclosed anaesthetic circle system. Each cow was intubated with a cuffed orotracheal tube (25 mm ID). Inspired and end-tidal ISO were monitored using a calibrated infra red analyser with a methane filter. The MAC of ISO that prevented gross purposeful movement in response to a tail and dewclaw clamp was determined. The time from the start of ISO administration to intubation, the time interval between discontinuance of ISO and the time the animal regained sternal recumbency, were recorded. Time to standing and quality of recovery were also recorded.nnnRESULTSnThe time from the start of ISO administration to tracheal intubation was 18.68 ± 2.77 minutes. The MAC of ISO in these cattle was 1.27 ± 0.03% (1.14 ± 0.01% corrected to sea level). Time to sternal recumbency after 90 ± 16 minutes of anaesthesia from intubation was 4.60 ± 0.58 minutes and time to standing was 6.70 ± 1.02 minutes. All cattle were extubated when they regained sternal recumbency.nnnCONCLUSIONnThe MAC of isoflurane in these cattle was 1.27 ± 0.03% (1.14 ± 0.01% corrected to sea level). ISO provided a smooth induction to, and rapid recovery from, anaesthesia.nnnCLINICAL RELEVANCEnKnowledge of the MAC of ISO in cattle will facilitate its appropriate clinical use.

Acute Cardiotoxicity Evaluation of the Marine Biotoxins OA, DTX-1 and YTX

Phycotoxins are marine toxins produced by phytoplankton that can get accumulated in filter feeding shellfish. Human intoxication episodes occur due to contaminated seafood consumption. Okadaic acid (OA) and dynophysistoxins (DTXs) are phycotoxins responsible for a severe gastrointestinal syndrome called diarrheic shellfish poisoning (DSP). Yessotoxins (YTXs) are marine toxins initially included in the DSP class but currently classified as a separated group. Food safety authorities from several countries have regulated the content of DSPs and YTXs in shellfish to protect human health. In mice, OA and YTX have been associated with ultrastructural heart damage in vivo. Therefore, this study explored the potential of OA, DTX-1 and YTX to cause acute heart toxicity. Cardiotoxicity was evaluated in vitro by measuring hERG (human èter-a-go-go gene) channel activity and in vivo using electrocardiogram (ECG) recordings and cardiac damage biomarkers. The results demonstrated that these toxins do not exert acute effects on hERG channel activity. Additionally, in vivo experiments showed that these compounds do not alter cardiac biomarkers and ECG in rats acutely. Despite the ultrastructural damage to the heart reported for these toxins, no acute alterations of heart function have been detected in vivo, suggesting a functional compensation in the short term.

Histological analysis of loaded zirconia and titanium dental implants: an experimental study in the dog mandible

OBJECTIVEnTo assess whether or not peri-implant soft tissue dimensions and hard tissue integration of loaded zirconia implants are similar to those of a titanium implant.nnnMATERIALS AND METHODSnIn six dogs, two one-piece zirconia implants (VC, ZD), a two-piece zirconia implant (BPI) and a control one-piece titanium implant (STM) were randomly placed. CAD/CAM crowns were cemented at 6xa0months. Six months later, animals were killed and histomorphometric analyses were performed, including: the level of the mucosal margin, the extent of the peri-implant mucosa, the marginal bone loss and the bone-to-implant contact (BIC). Means of outcomes variables were calculated together with their corresponding 95% confidence intervals.nnnRESULTSnIn general, the mucosal margin was located coronally to the implant shoulder. The buccal peri-implant mucosa ranged between 2.64xa0±xa00.70xa0mm (VC) and 3.03xa0±xa01.71xa0mm (ZD) (for all median comparisons pxa0>xa00.05). The relative marginal bone loss ranged between 0.65xa0±xa00.61xa0mm (BPI) and 1.73xa0±xa01.68xa0mm (ZD) (buccal side), and between 0.55xa0±xa00.37xa0mm (VC) and 1.69xa0±xa01.56xa0mm (ZD) (lingual side) (pxa0>xa00.05). The mean BIC ranged between 78.6%xa0±xa017.3% (ZD) and 87.9%xa0±xa013.6% (STM) without statistically significant differences between the groups (pxa0>xa00.05).nnnCONCLUSIONSnOne- and two-piece zirconia rendered similar peri-implant soft tissue dimensions and osseointegration compared to titanium implants that were placed at 6xa0months of loading. Zirconia implants, however, exhibited a relatively high fracture rate.

Subacute Cardiovascular Toxicity of the Marine Phycotoxin Azaspiracid-1 in Rats

Azaspiracids (AZAs) are marine toxins produced by Azadinium spinosum that get accumulated in filter feeding shellfish through the food-web. The first intoxication was described in The Netherlands in 1990, and since then several episodes have been reported worldwide. Azaspiracid-1, AZA-2, and AZA-3 presence in shellfish is regulated by food safety authorities of several countries to protect human health. Azaspiracids have been related to widespread organ damage, tumorogenic properties and acute heart rhythm alterations in vivo but the mechanism of action remains unknown. Azaspiracid toxicity kinetics in vivo and in vitro suggests accumulative effects. We studied subacute cardiotoxicity in vivo after repeated exposure to AZA-1 by evaluation of the ECG, arterial blood pressure, plasmatic heart damage biomarkers, and myocardium structure and ultrastructure. Our results showed that four administrations of AZA-1 along 15 days caused functional signs of heart failure and structural heart alterations in rats at doses ranging from 1 to 55 µg/kg. Azaspiracid-1 altered arterial blood pressure, tissue inhibitors of metalloproteinase-1 plasma levels, heart collagen deposition, and ultrastructure of the myocardium. Overall, these data indicate that repeated exposure to low amounts of AZA-1 causes cardiotoxicity, at doses that do not induce signs of other organic system toxicity. Remarkably, human exposure to AZAs considering current regulatory limits of these toxins may be dangerously close to clearly cardiotoxic doses in rats. These findings should be considered when human risk is estimated particularly in high cardiovascular risk subpopulations.

Subacute cardiotoxicity of yessotoxin: in vitro and in vivo studies

Yessotoxin (YTX) is a marine phycotoxin produced by dinoflagellates and accumulated in filter feeding shellfish. Although no human intoxication episodes have been reported, YTX content in shellfish is regulated by many food safety authorities due to their worldwide distribution. YTXs have been related to ultrastructural heart damage in vivo, but the functional consequences in the long term have not been evaluated. In this study, we explored the accumulative cardiotoxic potential of YTX in vitro and in vivo. Preliminary in vitro evaluation of cardiotoxicity was based on the effect on hERG (human ether-a-go-go related gene) channel trafficking. In vivo experiments were performed in rats that received repeated administrations of YTX followed by recordings of electrocardiograms, arterial blood pressure, plasmatic cardiac biomarkers, and analysis of myocardium structure and ultrastructure. Our results showed that an exposure to 100 nM YTX for 12 or 24 h caused an increase of extracellular surface hERG channels. Furthermore, remarkable bradycardia and hypotension, structural heart alterations, and increased plasma levels of tissue inhibitor of metalloproteinases-1 were observed in rats after four intraperitoneal injections of YTX at doses of 50 or 70 μg/kg that were administered every 4 days along a period of 15 days. Therefore, and for the first time, YTX-induced subacute cardiotoxicity is supported by evidence of cardiovascular function alterations related to its repeated administration. Considering international criteria for marine toxin risk estimation and that the regulatory limit for YTX has been recently raised in many countries, YTX cardiotoxicity might pose a health risk to humans and especially to people with previous cardiovascular risk.

Efficacy of the Komesaroff anaesthetic machine for delivering isoflurane to dogs

The Komesaroff machine is a low-flow, closed-circle circuit with a low resistance vaporiser, of the Goldman type, in circuit. This trial assessed the mechanical consistency of the delivery of isoflurane by the vaporisers, and used six dogs to compare the in vivo cardiorespiratory effects of the anaesthetic agent delivered by the Komesaroff machine with the effects of a circle system with high flows in the semi-closed mode. The delivery of isoflurane was constant for each vaporiser setting and no potentially dangerous concentrations of isoflurane were observed. The mean (sem) percentages of isoflurane were 0.18 (0.019) at setting I, 1.46 (0.055) at setting II, 3.12 (0.066) at setting III and 3.01 (0.047) at setting IV. There were no significant differences between the two types of circuit in vivo, and the measured haemodynamic variables were satisfactory throughout the experiments.

Marginal bone‐level alterations of loaded zirconia and titanium dental implants: an experimental study in the dog mandible

OBJECTIVESnThe aim was to test whether or not the marginal bone-level alterations of loaded zirconia implants are similar to the bone-level alterations of a grade 4 titanium one-piece dental implant.nnnMATERIALS AND METHODSnIn six dogs, all premolars and the first molars were extracted in the mandible. Four months later, three zirconia implants (BPI, VC, ZD) and a control titanium one-piece (STM) implant were randomly placed in each hemimandible and left for transmucosal healing (baseline). Six months later, CAD/CAM crowns were cemented. Sacrifice was scheduled at 6-month postloading. Digital X-rays were taken at implant placement, crowns insertion, and sacrifice. Marginal bone-level alterations were calculated, and intra- and intergroup comparisons performed adjusted by confounding factors.nnnRESULTSnImplants were successfully placed. Until crown insertion, two implants were fractured (one VC, one ZD). At sacrifice, 5 more implants were (partly) fractured (one BPI, four ZD), and one lost osseointegration (VC). No decementation of crowns occurred. All implant systems demonstrated a statistically significant (except VC) loss of marginal bone between baseline and crown insertion ranging from 0.29 mm (VC; P = 0.116) to 0.80 mm (ZD; P = 0.013). The estimated marginal bone loss between baseline and 6 months of loading ranged between 0.19 mm (BPI) and 1.11 mm (VC), being statistically significant for STM and VC only (P < 0.05). The changes in marginal bone levels were statistically significantly different between zirconia implants and control implants (STM vs. BPI P = 0.007; vs. VC P = 0.001; vs. ZD P = 0.011).nnnCONCLUSIONSnZirconia implants were more prone to fracture prior to and after loading with implant-supported crowns compared to titanium implants. Individual differences and variability in the extent of the bone-level changes during the 12-month study period were found between the different implant types and materials.