Osteocyte morphology and orientation in relation to strain in the jaw bone.

Bone mass is important for dental implant success and is regulated by mechanoresponsive osteocytes. We aimed to investigate the relationship between the levels and orientation of tensile strain and morphology and orientation of osteocytes at different dental implant positions in the maxillary bone. Bone biopsies were retrieved from eight patients who underwent maxillary sinus-floor elevation with β-tricalcium phosphate prior to implant placement.

Comparison of gamma- and DVH-based in vivo dosimetric plan evaluation for pelvic VMAT treatments.

Background And Purpose: To compare DVH-based quality assurance to a multi-parametric γ-based methodology for in vivo EPID dosimetry for VMAT to the pelvis.

Materials And Methods: For 47 rectum, 37 prostate, and 44 bladder VMAT treatments we reconstructed the 3D dose distributions of 387 fractions from in vivo EPID dosimetry. The difference between planned and measured dose was evaluated using γ analysis (3%/3mm) in the 50% isodose volume (IDV) and DVH differences (ΔD2, ΔD50 and ΔD98) of targets and organs at risk.

Virtual patient 3D dose reconstruction using in air EPID measurements and a back-projection algorithm for IMRT and VMAT treatments.

Purpose: At our institute, a transit back-projection algorithm is used clinically to reconstruct in vivo patient and in phantom 3D dose distributions using EPID measurements behind a patient or a polystyrene slab phantom, respectively. In this study, an extension to this algorithm is presented whereby in air EPID measurements are used in combination with CT data to reconstruct 'virtual' 3D dose distributions. By combining virtual and in vivo patient verification data for the same treatment, patient-related errors can be separated from machine, planning and model errors.

Abutment-to-fixture load transfer and peri-implant bone stress.

Purpose: To uncover design principles for the abutment-fixture complex that reduce the stress concentration on the bone.

Methods: A 3-dimensional finite element model was used to vary shape, elasticity, and connectivity of the abutment-fixture complex. We compared peri-implant bone stress of these designs.

Osteocyte shape and mechanical loading.

There is considerable variation in the shape of osteocyte lacunae, which is likely to influence the function of osteocytes as the professional mechanosensors of bone. In this review, we first discussed how mechanical loading could affect the shape of osteocyte lacunae. Recent studies show that osteocyte lacunae are aligned to collagen.

Bone cell mechanosensitivity, estrogen deficiency, and osteoporosis.

Adaptation of bone to mechanical stresses normally produces a bone architecture that combines a proper resistance against failure with a minimal use of material. This adaptive process is governed by mechanosensitive osteocytes that transduce the mechanical signals into chemical responses, i.e.

Mechanical cell-matrix feedback explains pairwise and collective endothelial cell behavior in vitro.

In vitro cultures of endothelial cells are a widely used model system of the collective behavior of endothelial cells during vasculogenesis and angiogenesis. When seeded in an extracellular matrix, endothelial cells can form blood vessel-like structures, including vascular networks and sprouts. Endothelial morphogenesis depends on a large number of chemical and mechanical factors, including the compliancy of the extracellular matrix, the available growth factors, the adhesion of cells to the extracellular matrix, cell-cell signaling, etc.

Osteocyte-viability-based simulations of trabecular bone loss and recovery in disuse and reloading.

Osteocyte apoptosis is known to trigger targeted bone resorption. In the present study, we developed an osteocyte-viability-based trabecular bone remodeling (OVBR) model. This novel remodeling model, combined with recent advanced simulation methods and analysis techniques, such as the element-by-element 3D finite element method and the ITS technique, was used to quantitatively study the dynamic evolution of bone mass and trabecular microstructure in response to various loading and unloading conditions.

Simulations of trabecular remodeling and fatigue: is remodeling helpful or harmful?

Microdamage-targeted resorption is paradoxal, because it entails the removal of bone from a region that was already overloaded. Under continued intense loading, resorption spaces could potentially cause more damage than they remove. To investigate this problem, we incorporated damage algorithms in a computer-simulation model for trabecular remodeling.

A sclerostin-based theory for strain-induced bone formation.

Bone formation responds to mechanical loading, which is believed to be mediated by osteocytes. Previous theories assumed that loading stimulates osteocytes to secrete signals that stimulate bone formation. In computer simulations this 'stimulatory' theory successfully produced load-aligned trabecular structures.

Relating osteon diameter to strain.

Osteon diameter is generally smaller in bone regions that experience larger strains. A mechanism relating osteon diameter to strain is as yet unknown. We propose that strain-induced osteocyte signals inhibit osteoclastic bone resorption.

A unified theory for osteonal and hemi-osteonal remodeling.

The process of bone remodeling is carried out by 'basic multicellular units' of osteoclasts and osteoblasts. Osteoclasts excavate a resorption space that is subsequently filled with new bone by osteoblasts. In cortical bone osteoclasts dig tunnels through solid bone, in cancellous bone they dig trenches across the trabecular surface.