Early loading of nonsubmerged titanium implants with a chemically modified sand-blasted and acid-etched surface: 6-month results of a prospective case series study in the posterior mandible focusing on peri-implant crestal bone changes and implant stability quotient (ISQ) values

PURPOSE: The aim of this prospective case series study was to evaluate the short-term success rates of titanium screw-type implants with a chemically modified sand-blasted and acid-etched (mod SLA) surface after 3 weeks of healing. MATERIAL AND METHODS: A total of 56 implants were inserted in the posterior mandible of 40 partially edentulous patients exhibiting bone densities of class I to III. After a healing period of 3 weeks, all implants were functionally loaded with a screw-retained crown or fixed dental prosthesis. The patients were recalled at weeks 4, 7, 12, and 26 for monitoring and assessment of clinical and radiological parameters, including implant stability quotient (ISQ) measurements. RESULTS: None of the implants failed to integrate. However, two implants were considered "spinners" at day 21 and left unloaded for an extended period. Therefore, 96.4% of the inserted implants were loaded according to the protocol tested. All 56 implants including the "spinners" showed favorable clinical and radiographic findings at the 6-month follow-up examination. The ISQ values increased steadily throughout the follow-up period. At the time of implant placement, the range of ISQ values exhibited a mean of 74.33, and by week 26, a mean value of 83.82 was recorded. Based on strict criteria, all 56 implants were considered successfully integrated, resulting in a 6-month survival and success rate of 100.0%. CONCLUSION: This prospective study using an early-loading protocol after 3 weeks of healing demonstrated that titanium implants with the modified SLA surface can achieve and maintain successful tissue integration over a period of at least 6 months. The ISQ method seems feasible to monitor implant stability during the initial wound-healing period.

Focal adhesion kinase is a load-dependent governor of the slow contractile and oxidative muscle phenotype

Striated muscle exhibits a pronounced structural-functional plasticity in response to chronic alterations in loading. We assessed the implication of focal adhesion kinase (FAK) signalling in mechano-regulated differentiation of slow-oxidative muscle. Load-dependent consequences of FAK signal modulation were identified using a multi-level approach after electrotransfer of rat soleus muscle with FAK-expression plasmid vs. empty plasmid-transfected contralateral controls. Muscle fibre-targeted over-expression of FAK in anti-gravitational muscle for 9 days up-regulated transcript levels of gene ontologies underpinning mitochondrial metabolism and contraction in the transfected belly portion. Concomitantly, mRNA expression of the major fast-type myosin heavy chain (MHC) isoform, MHC2A, was reduced. The promotion of the slow-oxidative expression programme by FAK was abolished after co-expression of the FAK inhibitor FAK-related non-kinase (FRNK). Elevated protein content of MHC1 (+9%) and proteins of mitochondrial respiration (+165-610%) with FAK overexpression demonstrated the translation of transcript differentiation in targeted muscle fibres towards a slow-oxidative muscle phenotype. Coincidentally MHC2A protein was reduced by 50% due to protection of muscle from de-differentiation with electrotransfer. Fibre cross section in FAK-transfected muscle was elevated by 6%. The FAK-modulated muscle transcriptome was load-dependent and regulated in correspondence to tyrosine 397 phosphorylation of FAK. In the context of overload, the FAK-induced gene expression became manifest at the level of contraction by a slow transformation and the re-establishment of normal muscle force from the lowered levels with transfection. These results highlight the analytic power of a systematic somatic transgene approach by mapping a role of FAK in the dominant mechano-regulation of muscular motor performance via control of gene expression.

Implant loading protocols for partially edentulous maxillary posterior sites

PURPOSE: To evaluate early and immediate loading of implants in the posterior maxilla and to investigate whether there is a difference in success rates, survival rates, and peri-implant parameters, including marginal bone level changes. MATERIALS AND METHODS: A comprehensive systematic review of the literature was conducted. The selection of publications reporting on human clinical studies was based on predetermined inclusion criteria and was agreed upon by two reviewers. RESULTS: Twelve papers were identified on early loading (two randomized controlled clinical trials [RCTs] and 10 prospective case series studies). Six papers were found on immediate loading (one RCT, four prospective case series, and one retrospective study). CONCLUSIONS: Under certain circumstances it is possible to successfully load dental implants in the posterior maxilla early or immediately after their placement in selected patients. The success rate appears to be technique sensitive, although no study has directly assessed this. A high degree of primary implant stability (high value of insertion torque) and implant surface characteristics play an important role. It is not possible to draw evidence-based conclusions concerning contraindications, threshold values for implant stability, bone quality and quantity needed, or impact of occlusal loading forces. As for the impact of the surgical technique on implant outcome in different bone densities, no studies prove significant superior results with one technique over another. Well-designed RCTs with a large number of patients are necessary to make early/immediate loading protocols in posterior maxilla evidence based, but ethical and practical considerations may limit the real possibility of such studies in the near future.

Numerical investigation of the mechanical loading of supporting soft tissue for partial dentures

The aim of this research was to study the impact of loading on partial dentures within the supporting soft tissue with respect to different attachment techniques. A finite element model was developed to calculate the stress and strain distribution in this tissue. The model consisted of the left half of a mandible with three remaining teeth that had suffered an atrophy in the anterior region, and a partial denture over the toothless area that was connected at the left mandibular canine using an attachment system. Resulting stress/strain distributions are presented for different load cases using a commercially available prefabricated attachment system.

Effect of oral calcium loading on intact PTH and calcitriol in idiopathic renal calcium stone formers and healthy controls

The calciuric response after an oral calcium load (1000 mg elemental calcium together with a standard breakfast) was studied in 13 healthy male controls and 21 recurrent idiopathic renal calcium stone formers, 12 with hypercalciuria (UCa x V > 7.50 mmol/24 h) and nine with normocalciuria. In controls, serum 1,25(OH)2 vitamin D3 (calcitriol) remained unchanged 6 h after oral calcium load (50.6 +/- 5.1 versus 50.9 +/- 5.0 pg/ml), whereas it tended to increase in hypercalciuric (from 53.6 +/- 3.2 to 60.6 +/- 5.4 pg/ml, P = 0.182) and fell in normocalciuric stone formers (from 45.9 +/- 2.6 to 38.1 +/- 3.3 pg/ml, P = 0.011). The total amount of urinary calcium excreted after OCL was 2.50 +/- 0.20 mmol in controls, 2.27 +/- 0.27 mmol in normocalciuric and 3.62 +/- 0.32 mmol in hypercalciuric stone formers (P = 0.005 versus controls and normocalciuric stone formers respectively); it positively correlated with serum calcitriol 6 h after calcium load (r = 0.392, P = 0.024). Maximum increase in urinary calcium excretion rate, delta Ca-Emax, was inversely related to intact PTH levels in the first 4 h after calcium load, i.e. more pronounced PTH suppression predicted a steeper increase in urinary calcium excretion rate. Twenty-four-hour urine calcium excretion rate was inversely related to the ratio of delta calcitriol/deltaPTHmax after calcium load (r = -0.653, P = 0.0001), indicating that an abnormally up-regulated synthesis of calcitriol and consecutive relative PTH suppression induce hypercalciuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical evaluation of the stabilizing function of the atlantoaxial ligaments under shear loading: A canine cadaveric study

OBJECTIVES To evaluate the stabilizing function of atlanto-axial ligaments in dogs. STUDY DESIGN Cadaveric biomechanical study. ANIMALS Beagle dog cadavers (n = 10). METHODS The craniocervical region was collected from 10 Beagle cadavers, and the occipito-atlanto-axial region was prepared and freed from the surrounding muscles. Care was taken to preserve integrity of the atlantoaxial ligaments and atlantoaxial joint capsule. The atlanto-occipital joints were blocked with 2 diverging transarticular 1.8 mm positive threaded K-wires. Specimen extremities were embedded in polymethylmethacrylate (PMMA) and mounted on a simulator testing shear load at the atlantoaxial joint. Range of motion (ROM) and neutral zone (NZ) were determined with all ligaments intact, after cutting the apical ligament, both alar ligaments, the transverse ligaments and finally after cutting the dorsal atlantoaxial ligament. RESULTS ROM increased similarly and stepwise during testing. The most significant increase was observed after transection of the alar ligaments. CONCLUSION The alar ligaments seem to be the most important ligamentous structures for stabilization of the atlantoaxial joint under shear load.

Flow-R, a model for susceptibility mapping of debris flows and other gravitational hazards at a regional scale

The development of susceptibility maps for debris flows is of primary importance due to population pressure in hazardous zones. However, hazard assessment by process-based modelling at a regional scale is difficult due to the complex nature of the phenomenon, the variability of local controlling factors, and the uncertainty in modelling parameters. A regional assessment must consider a simplified approach that is not highly parameter dependant and that can provide zonation with minimum data requirements. A distributed empirical model has thus been developed for regional susceptibility assessments using essentially a digital elevation model (DEM). The model is called Flow-R for Flow path assessment of gravitational hazards at a Regional scale (available free of charge under http://www.flow-r.org) and has been successfully applied to different case studies in various countries with variable data quality. It provides a substantial basis for a preliminary susceptibility assessment at a regional scale. The model was also found relevant to assess other natural hazards such as rockfall, snow avalanches and floods. The model allows for automatic source area delineation, given user criteria, and for the assessment of the propagation extent based on various spreading algorithms and simple frictional laws. We developed a new spreading algorithm, an improved version of Holmgren's direction algorithm, that is less sensitive to small variations of the DEM and that is avoiding over-channelization, and so produces more realistic extents. The choices of the datasets and the algorithms are open to the user, which makes it compliant for various applications and dataset availability. Amongst the possible datasets, the DEM is the only one that is really needed for both the source area delineation and the propagation assessment; its quality is of major importance for the results accuracy. We consider a 10 m DEM resolution as a good compromise between processing time and quality of results. However, valuable results have still been obtained on the basis of lower quality DEMs with 25 m resolution.

Region Specific Response of Intervertebral Disc Cells to Complex Dynamic Loading: An Organ Culture Study Using a Dynamic Torsion-Compression Bioreactor

The spine is routinely subjected to repetitive complex loading consisting of axial compression, torsion, flexion and extension. Mechanical loading is one of the important causes of spinal diseases, including disc herniation and disc degeneration. It is known that static and dynamic compression can lead to progressive disc degeneration, but little is known about the mechanobiology of the disc subjected to combined dynamic compression and torsion. Therefore, the purpose of this study was to compare the mechanobiology of the intervertebral disc when subjected to combined dynamic compression and axial torsion or pure dynamic compression or axial torsion using organ culture. We applied four different loading modalities 1. control: no loading (NL), 2. cyclic compression (CC), 3. cyclic torsion (CT), and 4. combined cyclic compression and torsion (CCT) on bovine caudal disc explants using our custom made dynamic loading bioreactor for disc organ culture. Loads were applied for 8 h/day and continued for 14 days, all at a physiological magnitude and frequency. Our results provided strong evidence that complex loading induced a stronger degree of disc degeneration compared to one degree of freedom loading. In the CCT group, less than 10\% nucleus pulposus (NP) cells survived the 14 days of loading, while cell viabilities were maintained above 70\% in the NP of all the other three groups and in the annulus fibrosus (AF) of all the groups. Gene expression analysis revealed a strong up-regulation in matrix genes and matrix remodeling genes in the AF of the CCT group. Cell apoptotic activity and glycosaminoglycan content were also quantified but there were no statistically significant differences found. Cell morphology in the NP of the CCT was changed, as shown by histological evaluation. Our results stress the importance of complex loading on the initiation and progression of disc degeneration.

Impact of loading displacements on SLR-derived parameters and on the consistency between GNSS and SLR results

Displacements of the Earth’s surface caused by tidal and non-tidal loading forces are relevant in high-precision space geodesy. Some of the corrections are recommended by the international scientific community to be applied at the observation level, e.g., ocean tidal loading (OTL) and atmospheric tidal loading (ATL). Non-tidal displacement corrections are in general recommended not to be applied in the products of the International Earth Rotation and Reference Systems Service, in particular atmospheric non-tidal loading (ANTL), oceanic and hydrological non-tidal corrections. We assess and compare the impact of OTL, ATL and ANTL on SLR-derived parameters by reprocessing 12 years of SLR data considering and ignoring individual corrections. We show that loading displacements have an influence not only on station long-term stability, but also on geocenter coordinates, Earth Rotation Parameters, and satellite orbits. Applying the loading corrections reduces the amplitudes of annual signals in the time series of geocenter and station coordinates. The general improvement of the SLR station 3D coordinate repeatability when applying OTL, ATL and ANTL corrections are 19.5 %, 0.2 % and 3.3 % respectively, w.r.t. the solutions without loading corrections. ANTL corrections play a crucial role in the combination of optical (SLR) and microwave (GNSS, VLBI, DORIS) space geodetic observation techniques, because of the so-called Blue-Sky effect: SLR measurements can be carried out only under cloudless sky conditions—typically during high air pressure conditions, when the Earth’s crust is deformed, whereas microwave observations are weather-independent. Thus, applying the loading corrections at the observation level improves SLR-derived products as well as the consistency with microwave-based results. We assess the Blue-Sky effect on SLR stations and the consistency improvement between GNSS and SLR solutions when ANTL corrections are included. The omission of ANTL corrections may lead to inconsistencies between SLR and GNSS solutions of up to 2.5 mm for inland stations. As a result, the estimated GNSS–SLR coordinate differences correspond better to the local ties at the co-located stations when applying ANTL corrections.