Dental implants with different primary stabilities give rise to distinct stress distributions at the implant-bone interface after placement and exert mechanical force on the cells in the bone tissue. This study aimed to investigate whether the mechanical forces in peri-implant bone participate in the body\'s immune response and influence macrophage polarization. Therefore, an in vivo rat implantation model with different primary implant stabilities was established. The osteoimmune response and macrophage polarization were investigated, and the osseointegration of the implants was evaluated. In an in vitro experiment, an external compressive force was applied to RAW264.7 cells, and the polarization phenotype was observed. MC3T3-E1 cells were cultured in macrophage-conditioned medium to investigate the regulatory effect of the macrophage-secreted cytokines on the osteogenic differentiation of osteoblasts. In vivo experimental results indicated that the primary stability of implants is positively correlated with the mechanical force. The osteoimmune response was significantly amplified by compressive force generated from implants. This compressive force first induced both M1 and M2 macrophage polarization and then accelerated the progression of the transition to M2 macrophages in the bone repair phase. In vitro, compressive force significantly upregulated the M1 and M2 macrophage polarization. In addition, the suppressive effect of macrophages on the osteogenesis of MC3T3 cells was relieved by cytokines secreted by macrophages under compressive force loading, which promoted their osteogenesis. Overall, these results clarify that compressive force from different primary stabilities is an important influencing factor regulating the osteoimmunne response and macrophage polarization in addition to maintaining the implant.

Currently, a new non-subtractive drilling technique, called osseodensification (OD), has been developed. It involves using specially designed drills with large negative cutting angles that rotate counterclockwise, causing expansion through plastic bone deformation, thus compacting the autologous bone to the osteotomy walls, which improves the primary stability of the implant.The present systematic review aimed to determine whether the OD technique can increase the primary stability of dental implants in the posterior maxilla region as compared to the conventional drilling (CD) technique.Five databases were searched up to June 30, 2022. The inclusion criteria embraced observational clinical studies, randomized and non-randomized controlled trials, human studies in vivo, comparing OD and CD, with the measurement of the primary stability of implants in the posterior maxilla region by means of the implant stability quotient (ISQ). The tools used to assess the risk of bias were RoB 2 and the NewcastleOttawa Scale (NOS).Seven articles met the inclusion criteria, with 4 classified as having a low risk of bias and 3 with a moderate risk of bias. The OD technique consistently demonstrated an average ISQ value of 73 KHz across all studies, whereas CD yielded an average value of 58.49 kHz (p < 0.001 for 5 articles).It can be concluded that in comparison with CD, OD improves primary stability at baseline in low-density bone, such as the maxilla.

Background: The objective of our study was to biomechanically evaluate the use of kyphoplasty to stabilize post-traumatic segmental instability in incomplete burst fractures of the vertebrae. Methods: The study was performed on 14 osteoporotic spine postmortem samples (Th11-L3). First, acquisition of the native multisegmental kinematics in our robot-based spine tester with three-dimensional motion analysis was set as a baseline for each sample. Then, an incomplete burst fracture was generated in the vertebral body L1 with renewed kinematic testing. After subsequent kyphoplasty was performed on the fractured vertebral body, primary stability was examined again. Results: Initially, a significant increase in the range of motion after incomplete burst fracture generation in all three directions of motion (extension-flexion, lateral tilt, axial rotation) was detected as proof of post-traumatic instability. There were no significant changes to the native state in the adjacent segments. Radiologically, a significant loss of height in the fractured vertebral body was also shown. Traumatic instability was significantly reduced by kyphoplasty. However, native kinematics were not restored. Conclusions: Although post-traumatic segmental instability was significantly reduced by kyphoplasty in our in vitro model, native kinematics could not be reconstructed, and significant instability remained.

Adequate primary stability is a pre-requisite for the osseointegration and long-term success of dental implants. Primary stability depends essentially on the bone mechanical integrity at the implantation site. Clinically, a qualitative evaluation can be made on medical images, but finite element (FE) simulations can assess the primary stability of a bone-implant construct quantitatively based on high-resolution CT images. However, FE models lack experimental validation on clinically relevant bone anatomy. The aim of this study is to validate such an FE model on human jawbones. Forty-seven bone biopsies were extracted from human cadaveric jawbones. Dental implants of two sizes (Ø3.5 mm and Ø4.0 mm) were inserted and the constructs were subjected to a quasi-static bending-compression loading protocol. Those mechanical tests were replicated with sample-specific non-linear homogenized FE models. Bone was modeled with an elastoplastic constitutive law that included damage. Density-based material properties were mapped based on μCT images of the bone samples. The experimental ultimate load was better predicted by FE (R2 = 0.83) than by peri-implant bone density (R2 = 0.54). Unlike bone density, the simulations were also able to capture the effect of implant diameter. The primary stability of a dental implant in human jawbones can be predicted quantitatively with FE simulations. This method may be used for improving the design and insertion protocols of dental implants.

Orthodontic Mini-Implants have a high success rate, but it is crucial to assess the load that they bear in order to maintain their primary stability. Increasing the diameter can improve this stability, but there are limitations due to the proximity of the tooth roots. To avoid damage, smaller diameters are used, which can decrease resistance and cause permanent deformations.
OBJECTIVE: The objective of this study is to evaluate the influence of the diameter of Mini-Implants through bending force tests, taking into account primary stability after one and two insertions.
METHODS: Here, 40 Ti6AI4V alloy Mini-Implants of two different brands and diameters were divided into eight groups, half of which received one insertion in the artificial bone, and the rest received two. All were subjected to a constant bending force using an INSTRON-Electropuls E10000LT (Norwood, MA, USA) until fracture.
RESULTS: The smaller-diameter Mini-Implants were less resistant to fracture, but both were able to withstand the necessary loads produced by orthodontic movements. As for the inserts, there were no statistically significant differences.
CONCLUSIONS: There is an advantage to using 1.6 mm Mini-Implants over 2.0 mm ones, as a smaller diameter does not lead to fracture due to the forces used in orthodontic treatment. Having one or two inserts did not have a statistically significant effect.

OBJECTIVE: To determine the correlation between the primary implant stability quotient and the implant percussion sound frequency.
METHODS: A total of 14 pigs\' ribs were scanned using a dental cone beam computed tomography (CBCT) scanner to classify the bone specimens into three distinct bone density Hounsfield units (HU) value categories: D1 bone: >1250 HU; D2: 850-1250 HU; D3: <850 HU. Then, 96 implants were inserted: 32 implants in D1 bone, 32 implants in D2 bone, and 32 implants in D3 bone. The primary implant stability quotient (ISQ) was analyzed, and percussion sound was recorded using a wireless microphone connected and analyzed with frequency analysis software.
RESULTS: Statistically significant positive correlations were found between the primary ISQ and the bone density HU value (r = 0.719; p < 0.001), and statistically significant positive correlations between the primary ISQ and the percussion sound frequency (r = 0.606; p < 0.001). Furthermore, significant differences in primary ISQ values and percussion sound frequency were found between D1 and D2 bone, as well as between D1 and D3 bone. However, no significant differences were found in primary ISQ values and percussion sound frequency between D2 and D3 bone.
CONCLUSIONS: The primary ISQ value and the percussion sound frequency are positively correlated.

UNASSIGNED: Recent years have seen a rise in the usage of dental implants to restore lost teeth. The stability of a dental implant is the main factor in determining its success. Implant stability is influenced by various factors. Several approaches have been employed clinically to evaluate stability at different time intervals. One non-invasive way to assess implant stability is by resonance frequency analysis. Utilizing the resonance frequency analysis method, this study seeks to understand how implant length and diameter affect primary and secondary stability.
UNASSIGNED: The current prospective study was conducted in the Prosthodontics Department of Institute of Dentistry, CMH Lahore Medical College. The duration of the study was six months. A total of 90 implants of sizes 4.5 x 8.5 mm and 4 x 10mm were placed. Resonance frequency measurements were recorded using Osstell™ AB device for primary stability at implant insertion and at 12 weeks for secondary stability. All the measurements were carried out by only one of the researchers to minimize inter-observer bias.
UNASSIGNED: The average primary stability was 70.33±6.60, and the average secondary stability was 71.43±5.44. The data was stratified for age, gender, and implant site, and the mean primary and secondary stability of both sizes didn\'t show any statistically significant differences.
UNASSIGNED: Without forfeiting implant stability, both implant sizes (4 x 10mm and 4.5 x 8.5mm) can be used interchangeably, depending on available space and anatomical constraints.

BACKGROUND: Acute total hip arthroplasty has gained increasing popularity in the treatment of complex acetabular fractures in elderly patients, but the biomechanical evidence is lacking. Therefore, we measured the primary stability to evaluate whether acute total hip arthroplasty using a multi-hole acetabular cup and posterior column plating through a single K-L approach can safely be used for treating complexed acetabular fractures in the elderly.
METHODS: In 18 composite osteoporotic hemipelves, T-type acetabular fractures were treated in three ways: CSP (Cup with acetabular screws augmentation combined with posterior plate) group, CP (Cup without acetabular screw combined with posterior plate) group and CSPA (Cup with acetabular screws combined with posterior plate and anterior plate) group. Each specimen was dynamically loaded (300 to 1700 N, 1 Hz). Primary stability of the acetabular cup and fracture gap was evaluated by 3-dimensional (3D) micromotions.
RESULTS: No significant differences in the 3D-micromotions were observed among the CSP, CP and CSPA groups except the test point on the anterior column of the acetabulum in the CP scenario (CSP 49.33 ± 21.08 μm vs. CP 224.83 ± 52.29 μm, p < 0.001; CSPA 45.50 ± 12.16 μm vs. CP 224.83 ± 52.29 μm, p < 0.001). No significant differences in the fracture gap displacement on the posterior column of acetabulum were observed among the CSP, CP and CSPA groups.
CONCLUSIONS: Our results show, that acute total hip arthroplasty using a multi-hole cup with acetabular screws and posterior column plating through single a K-L approach offers good primary stability to allow good osseous integration for treating complex acetabular fractures in the elderly. Furthermore, it also provides good fracture gap displacement on the posterior column.

BACKGROUND: Stemless implants were introduced to prevent some of the stem-related complications associated with the total shoulder arthroplasty. Although general requirements for receiving these implants include good bone quality conditions, little knowledge exists about how bone quality affects implant performance. The goal of this study was to evaluate the influence of age-induced changes in bone density, as a metric of bone quality, in the primary stability of five anatomic stemless shoulder implants using three-dimensional finite element (FE) models.
METHODS: The implant designs considered were based on the Global Icon, Sidus, Simpliciti, SMR, and Inhance stemless implants. Shoulder arthroplasties were virtually simulated in Solidworks. The density distributions of 20 subjects from two age groups, 20-40 and 60-80 years old, were retrieved from medical image data and integrated into three-dimensional FE models of a single humerus geometry, developed in Abaqus, to avoid confounding factors associated with geometric characteristics. For the designs which do not have a solid collar covering the entire bone surface, ie, the Sidus, Simpliciti, SMR, and Inhance implants, contact and noncontact conditions between the humeral head component and bone were considered. Primary stability was evaluated through the assessment of micromotions at the bone-implant interface considering eight load cases related to rehabilitation activities and demanding tasks. Three research variables, considering 20 μm, 50 μm, and 150 μm as thresholds for osseointegration, were used for a statistical analysis of the results.
RESULTS: The decreased bone density registered for the 60-80 age group led to larger micromotions at the bone-implant interface when compared to the 20-40 age group. The Global Icon-based and Inhance-based designs were the least sensitive to bone density, whereas the Sidus-based design was the most sensitive to bone density. The establishment of contact between the humeral head component and bone for the implants that do not have a solid collar led to decreased micromotions.
CONCLUSIONS: Although the age-induced decline in bone density led to increased micromotions in the FE models, some stemless shoulder implants presented good overall performance regardless of the osseointegration threshold considered, suggesting that age alone may not be a contraindication to anatomic total shoulder arthroplasty. If only primary stability is considered, the results suggested superior performance for the Global Icon-based and Inhance-based designs. Moreover, the humeral head component should contact the resected bone surface when feasible. Further investigation is necessary to combine these results with the long-term performance of the implants and allow more precise recommendations.

BACKGROUND: Aseptic loosening and periprosthetic fractures are main reasons for revision after THA. Quite different from most other stem systems, Corail cementless hip stems show better survival rates than their cemented counterpart, which can possibly be explained by the use of a collar. The study aimed to investigate primary stability with standard and undersized hip stems both collared and collarless.
METHODS: Primary stability of cementless, collared and collarless, femoral stems was measured in artificial bones using both undersized and standard size. After preconditioning, 3D micromotion was measured under cyclic loading at the bone-implant interface.
RESULTS: The use of a collar resulted in higher micromotion within the same stem size but showed no statistically significant difference for both standard and undersized hip stems. The collared and collarless undersized stems showed no significant differences in 3D micromotion at the upper measuring positions compared to the standard stem size. Micromotion was significantly higher in the distal measuring positions, with and without collar, for the undersized stems (vs. standard collarless stem size).
CONCLUSIONS: The key finding is that the collarless and collared Corail hip stems, within one stem size, showed no significant differences in primary stability. Undersized stems showed significantly higher micromotion in the distal area both with and without collar.