Effect of bone to implant contact percentage on bone remodelling surrounding a dental implant

The Biocompatibility and the Effect of Titanium and PEKK on the Osseointegration of Customized Facial Implants

The purpose of this study was to investigate the optimization of computer-aided design/computer-aided manufacturing (CAD/CAM) patient-specific implants for mandibular facial bone defects and compare the biocompatibility and osseointegration of machined titanium (Ma), Sandblasted/Large-grit/Acid-etched (SLA) titanium, and polyetherketoneketone (PEKK) facial implants. We hypothesized that the facial implants made of SLA titanium had superior osseointegration when applied to the gonial angle defect and prevented the senile atrophy of the bone. Histologic findings of the soft-tissue reaction, hard-tissue reaction, and bone-implant contact (BIC (%) of 24 Ma, SLA, and PEKK facial implants at 8 and 12 weeks were investigated. There was no statistical difference in the soft tissue reaction. Bone was formed below the periosteum in all facial implants at 12 weeks and the BIC values were significantly different at both 8 and 12 weeks (p < 0.05). Ma, SLA, and PEKK facial implants are biocompatible with osseointegration properties. SLA can enhance osseointegration and provoke minimal soft tissue reactions, making them the most suitable choice. They provide an excellent environment for bone regeneration and, over the long term, may prevent atrophy caused by an aging mandible. The bone formation between the lateral surface of the facial implant and periosteum may assist in osseointegration and stabilization.

Improved Biocompatibility and Osseointegration of Nanostructured Calcium-Incorporated Titanium Implant Surface Treatment (XPEED®)

Surface treatment of implants facilitates osseointegration, with nanostructured surfaces exhibiting accelerated peri-implant bone regeneration. This study compared bone-to-implant contact (BIC) in implants with hydroxyapatite (HA), sand-blasted and acid-etched (SLA), and SLA with calcium (Ca)-coated (XPEED®) surfaces. Seventy-five disk-shaped grade 4 Ti specimens divided into three groups were prepared, with 16 implants per group tested in New Zealand white rabbits. Surface characterization was performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), digital microscopy, and a contact angle analyzer. Cell viability, proliferation, and adhesion were assessed using MC3T3-E1 cells. Apatite formation was evaluated using modified simulated body fluid (m-SBF) incubation. After 4 weeks of healing, the outcomes reviewed were BIC, bone area (BA), removal torque tests, and histomorphometric evaluation. A microstructure analysis revealed irregular pores across all groups, with the XPEED group exhibiting a nanostructured Ca-coated surface. Surface characterization showed a crystalline CaTiO3 layer on XPEED surfaces, with evenly distributed Ca penetrating the implants. All surfaces provided excellent environments for cell growth. The XPEED and SLA groups showed significantly higher cell density and viability with superior osseointegration than HA (p < 0.05); XPEED exhibited the highest absorbance values. Thus, XPEED surface treatment improved implant performance, biocompatibility, stability, and osseointegration.

Single missing molar with wide mesiodistal length restored using a single or double implant-supported crown: A self-controlled case report and 3D finite element analysis

PURPOSE

Based on a self-controlled case, this study evaluated the finite element analysis (FEA) results of a single missing molar with wide mesiodistal length (MDL) restored by a single or double implant-supported crown.

METHODS

A case of a missing bilateral mandibular first molar with wide MDL was restored using a single or double implant-supported crown. The implant survival and peri-implant bone were compared. FEA was conducted in coordination with the case using eight models with different MDLs (12, 13, 14, and 15 mm). Von Mises stress was calculated in the FEA to evaluate the biomechanical responses of the implants under increasing vertical and lateral loading, including the stress values of the implant, abutment, screw, crown, and cortical bone.

RESULTS

The restorations on the left and right sides supported by double implants have been used for 6 and 12 years, respectively, and so far have shown excellent osseointegration radiographically.The von Mises stress calculated in the FEA showed that when the MDL was >14 mm, both the bone and prosthetic components bore more stress in the single implant-supported strategy. The strength was 188.62-201.37 MPa and 201.85-215.9 MPa when the MDL was 14 mm and 15 mm, respectively, which significantly exceeded the allowable yield stress (180 MPa).

CONCLUSIONS

Compared with the single implant-supported crown, the double implant-supported crown reduced peri-implant bone stress and produced a more appropriate stress transfer model at the implant-bone interface when the MDL of the single missing molar was ≥14 mm.

Comparative analysis of the in vivo kinetic properties of various bone substitutes filled into a peri-implant canine defect model

PURPOSE

Deproteinized bovine bone or synthetic hydroxyapatite are 2 prevalent bone grafting materials used in the clinical treatment of peri-implant bone defects. However, the differences in bone formation among these materials remain unclear. This study evaluated osteogenesis kinetics in peri-implant defects using 2 types of deproteinized bovine bone (Bio-Oss® and Bio-Oss/Collagen®) and 2 types of synthetic hydroxyapatite (Apaceram-AX® and Refit®). We considered factors including newly generated bone volume; bone, osteoid, and material occupancy; and bone-to-implant contact.

METHODS

A beagle model with a mandibular defect was created by extracting the bilateral mandibular third and fourth premolars. Simultaneously, an implant was inserted into the defect, and the space between the implant and the surrounding bone walls was filled with Bio-Oss, Bio-Oss/Collagen, Apaceram-AX, Refit, or autologous bone. Micro-computed tomography and histological analyses were conducted at 3 and 6 months postoperatively (Refit and autologous bone were not included at the 6-month time point due to their rapid absorption).

RESULTS

All materials demonstrated excellent biocompatibility and osteoconductivity. At 3 months, Bio-Oss and Apaceram-AX exhibited significantly greater volumes of formation than the other materials, with Bio-Oss having a marginally higher amount. However, this outcome was reversed at 6 months, with no significant difference between the 2 materials at either time point. Apaceram-AX displayed notably slower bioresorption and the largest quantity of residual material at both time points. In contrast, Refit had significantly greater bioresorption, with complete resorption and rapid maturation involving cortical bone formation at the crest at 3 months, Refit demonstrated the highest mineralized tissue and osteoid occupancy after 3 months, albeit without statistical significance.

CONCLUSIONS

Overall, the materials demonstrated varying post-implantation behaviors in vivo. Thus, in a clinical setting, both the properties of these materials and the specific conditions of the defects needing reinforcement should be considered to identify the most suitable material.

Human umbilical cord mesenchymal stem cells accelerate and increase implant osseointegration in diabetic rats

OBJECTIVE

This study was conducted to assess the effect of hUCMSCs injection on the osseointegration of dental implant in diabetic rats via Runt-related Transcription Factor 2 (Runx2), Osterix (Osx), osteoblasts, and Bone Implant Contact (BIC).

METHODOLOGY

The research design was a true experimental design using Rattus norvegicus Wistar strain. Rattus norvegicus were injected with streptozotocin to induce experimental diabetes mellitus. The right femur was drilled and loaded with titanium implant. Approximately 1 mm from proximal and distal implant site were injected with hUCMSCs. The control group was given only gelatin solvent injection. After 2 and 4 weeks of observation, the rats were sacrificed for further examination around implant site using immunohistochemistry staining (RUNX2 and Osterix expression), hematoxylin eosin staining, and bone implant contact area. Data analysis was done using ANOVA test.

RESULTS

Data indicated a significant difference in Runx2 expression (p<0.001), osteoblasts (p<0.009), BIC value (p<0.000), and Osterix expression (p<0.002). In vivo injection of hUCMSCs successfully increased Runx2, osteoblasts, and BIC value significantly, while decreased Osterix expression, indicating an acceleration of the bone maturation process.

CONCLUSION

The results proved hUCMSCs to accelerate and enhance implant osseointegration in diabetic rat models.

Submodelling approach to screw-to-bone interaction in additively manufactured subperiosteal implant structures

Thanks to new digital technologies, complex cases of severe maxillary atrophy may now be treated with additively manufactured subperiosteal implant structures (AMSISs). However, there are few studies addressing this topic and most of them focus on the mechanical behaviour of the AMSIS itself without considering its interaction with the maxilla bone. The aim of this study is to provide a methodology based on finite element analysis (FEA) to evaluate the effect of interaction between the maxilla bone and the screws fixing the AMSIS. The mechanical performance of an AMSIS was examined via a FEA based on submodelling. Significant differences were encountered in displacements and reaction forces when bone-screw interaction was considered. Stress in the cortical layer was found to be close to the maximum strength while the trabecular layer seems to have no effect on the results; stresses in the AMSIS are lower than the fatigue stress limit. Finally, the comparison of stresses between models with and without osseointegration shows how stresses drop once osseointegration is complete. The proposed submodelling approach considerably reduces the computational effort and enables both a detailed model of the interaction between the thread of the screws and the bone and an accurate evaluation of displacement and stress fields on the interface. The results have shown that stresses in the cortical bone are highly affected by the initial geometry of the thread inside the bone, which demonstrates the importance of modelling the effect of the thread.

Nanostructured Calcium-Incorporated Surface Compared to Machined and SLA Dental Implants-A Split-Mouth Randomized Case/Double-Control Histological Human Study

Background: Implant surface topography is a key element in achieving osseointegration. Nanostructured surfaces have shown promising results in accelerating and improving bone healing around dental implants. The main objective of the present clinical and histological study is to compare, at 4 and 6 weeks, (w) bone-to-implant contact in implants having either machined surface (MAC), sandblasted, large grit, acid-etched implant surface (SLA) medium roughness surface or a nanostructured calcium-incorporated surface (XPEED®). Methods: 35 mini-implants of 3.5 × 8.5 mm with three different surface treatments (XPEED® (n = 16)—SLA (n = 13)—MAC (n = 6), were placed in the posterior maxilla of 11 patients (6 females and 5 males) then, retrieved at either 4 or 6w in a randomized split-mouth study design. Results: The BIC rates measured at 4w and 6w respectively, were: 16.8% (±5.0) and 29.0% (±3.1) for MAC surface; 18.5% (±2.3) and 33.7% (±3.3) for SLA surface; 22.4% (±1.3) and 38.6% (±3.2) for XPEED® surface. In all types of investigated surfaces, the time factor appeared to significantly increase the bone to implant contact (BIC) rate (p < 0.05). XPEED® surface showed significantly higher BIC values when compared to both SLA and MAC values at 4w (p < 0.05). Also, at 6w, both roughened surfaces (SLA and XPEED®) showed significantly higher values (p < 0.05) than turned surface (MAC). Conclusions: Nanostructured Calcium titanate coating is able to enhance bone deposition around implants at early healing stages.

Biomechanical application of finite elements in the orthopedics of stiff clubfoot

BACKGROUND

The purpose of this study was to evaluate the effect of varying the different correction angles of hindfoot osteotomy orthosis on the biomechanical changes of the adjacent joints after triple arthrodesis in adult patients with stiff clubfoot to determine the optimal hindfoot correction angle and provide a biomechanical basis for the correction of hindfoot deformity in patients with stiff clubfoot.

METHODS

A 26-year-old male patient with a stiff left clubfoot was selected for the study, and his ankle and foot were scanned using dual-source computed tomography. A three-dimensional finite element model of the ankle was established, and after the validity of the model was verified by plantar pressure experiments, triple arthrodesis was simulated to analyze the biomechanical changes of the adjacent joints under the same load with "3°" of posterior varus, "0°" of a neutral position and "3°, 6°, 9°" of valgus as the correction angles.

RESULTS

The peak plantar pressure calculated by the finite element model of the clubfoot was in good agreement with the actual plantar pressure measurements, with an error of less than 1%. In triple arthrodesis, the peak von Mises stress in the adjacent articular cartilage was significantly different and less than the preoperative stress when the corrected angle of the hindfoot was valgus "6°". In comparison, the peak von Mises stress in the adjacent articular cartilage was not significantly different in varus "3°", neutral "0°", valgus "3°" and valgus "9°" compared with the preoperative stress.

CONCLUSION

The results of this study showed that different angles of hindfoot correction in triple arthrodesis did not increase the peak von Mises stress in the adjacent joints, which may not lead to the development of arthritis in the adjacent joint, and a hindfoot correction angle of "6°" of valgus significantly reduced the peak von Mises stress in the adjacent joints after triple arthrodesis.

Wound healing after ridge preservation: A randomized controlled trial on short-term (4 months) versus long-term (12 months) histologic outcomes

BACKGROUND

The amount of time it takes for bone allograft particles to be replaced with new vital bone during ridge preservation is unclear. The purpose of this article was to compare the wound healing and vital bone formation following ridge preservation using a combination allograft of 70% mineralized and 30% demineralized freeze-dried bone allograft at 4 months (short-term, ST) versus 12 months (long-term, LT).

METHODS

Fifty-seven patients were enrolled in the study who required extraction of a single tooth (excluding second and third molars) and were planned for replacement with a dental implant. After tooth extraction, all sites were grafted with a combination allograft procured from a single donor, and patients were randomized into the ST or LT healing groups. Patients returned for implant placement and an 8-mm bone core biopsy was harvested using a trephine drill during initial implant osteotomy preparation. The cores were then analyzed histologically to determine the percentages of vital bone formation, residual graft particles, and connective tissue/other.

RESULTS

There was significantly greater vital bone formation in the LT group (51.38%) compared with the ST group (31.39%) (p = 0.0025) and significantly fewer residual graft particles in the LT group (18.04%) compared with the ST group (40.38%).

CONCLUSIONS

A longer healing time following ridge preservation results in more vital bone formation and less residual graft particles at the time of implant placement. However, residual allograft material still remains at 12 months after ridge preservation.

Understanding the Stress Distribution on Anatomic Customized Root-Analog Dental Implant at Bone-Implant Interface for Different Bone Densities

The aim of this study is to assess the stress distribution on the bone tissue and bone-implant interface of a customized anatomic root-analog dental implant (RAI) by means of finite element analysis (FEA) for different types of bone density. A mandibular right second premolar was selected from the CBCT database. A DICOM file was converted to an STL file to create a CAD model in FEA software. The bone boundary model was created, while bone density types I-IV were determined. Von Mises stress was measured at bone tissues and bone-implant interfaces. To validate the models, the RAI was 3D printed through a laser powder-bed fusion (L-PBF) approach. The results revealed that all RAI designs could not cause plastic deformation or fracture resulting in lower stress than the ultimate tensile stress of natural bone and implant. Compared to a conventional screw-type implant, RAIs possess a more favorable stress distribution pattern around the bone tissue and the bone-implant interface. The presence of a porous structure was found to reduce the stress at cancellous bone in type IV bone density.

Effect of implant placement depth on bone remodeling on implant-supported single zirconia abutment crown: A 3D finite element study

PURPOSE

This study aimed to evaluate the influence of subcrestal implant placement depth on bone remodeling using time-dependent finite element analysis (FEA) with a bone-remodeling algorithm over 12 months.

METHODS

Seven models of different subcrestal implant placement depths (0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm) were analyzed using FEA to evaluate the biomechanical responses in the bone and implant, including von Mises equivalent stress, strain energy density (SED), and overloading elements. SED was used as a mechanical stimulus to simulate cortical and cancellous bone remodeling over the first 12 months after final prosthesis delivery.

RESULTS

The highest increase in cortical bone density was observed at Depth 1.5, whereas the lowest increase was observed at Depth 3.0. In contrast, the highest increase in bone density was observed at Depth 3.0 in the cancellous bone, whereas the lowest increase was observed at Depth 0. The highest peak von Mises stress in the cortical bone occurred at Depth 2.5 (107.24 MPa), while that in the cancellous bone was at Depth 2.5 (34.55 MPa). Notably, the maximum von Mises stress values in the cancellous bone exceeded the natural limit of the bony material, as indicated by the overloading elements observed at the depths of 2.0, 2.5, and 3.0 mm.

CONCLUSION

Greater bone density apposition is observed with deeper implant placement. An implant depth of more than 1.5 mm exhibited a higher maximum von Mises stress and greater overloading elements.

Crystalline Biomimetic Calcium Phosphate Coating on Mini-Pin Implants to Accelerate Osseointegration and Extend Drug Release Duration for an Orthodontic Application

Miniscrew implants (MSIs) have been widely used as temporary anchorage devices in orthodontic clinics. However, one of their major limitations is the relatively high failure rate. We hypothesize that a biomimetic calcium phosphate (BioCaP) coating layer on mini-pin implants might be able to accelerate the osseointegration, and can be a carrier for biological agents. A novel mini-pin implant to mimic the MSIs was used. BioCaP (amorphous or crystalline) coatings with or without the presence of bovine serum albumin (BSA) were applied on such implants and inserted in the metaphyseal tibia in rats. The percentage of bone to implant contact (BIC) in histomorphometric analysis was used to evaluate the osteoconductivity of such implants from six different groups (n=6 rats per group): (1) no coating no BSA group, (2) no coating BSA adsorption group, (3) amorphous BioCaP coating group, (4) amorphous BioCaP coating-incorporated BSA group, (5) crystalline BioCaP coating group, and (6) crystalline BioCaP coating-incorporated BSA group. Samples were retrieved 3 days, 1 week, 2 weeks, and 4 weeks post-surgery. The results showed that the crystalline BioCaP coating served as a drug carrier with a sustained release profile. Furthermore, the significant increase in BIC occurred at week 1 in the crystalline coating group, but at week 2 or week 4 in other groups. These findings indicate that the crystalline BioCaP coating can be a promising surface modification to facilitate early osseointegration and increase the success rate of miniscrew implants in orthodontic clinics.

Marginal Bone Loss around Implant-Retaining Overdentures versus Implant-Supported Fixed Prostheses 12-Month Follow-Up: A Retrospective Study

Few studies have compared marginal bone loss (MBL) around implant-retaining overdentures (IODs) vs. implant-supported fixed prostheses (FPs). This study evaluated the mean MBL and radiographic bone-implant interface contact (r-BIIC) around IODs and implant-supported FPs. We also investigated osseointegration and MBL around non-submerged dental implants. We measured the changes between the MBL in the mesial and distal sites immediately after prosthetic delivery and after one year. The mean MBL and its changes in the IOD group were significantly higher. The mean percentage of r-BIIC was significantly higher in the FP group. MBL and its changes in males were significantly higher in the IOD group. The percentage of r-BIIC was significantly higher in the FP group. MBL in the lower site in the IOD group was significantly higher. Regarding MBL, the location of the implant was the only significant factor in the IOD group, while gender was the only significant predictor in the FP group. Regarding the r-BIIC percentage, gender was a significant factor in the FP group. We concluded that non-submerged dental implants restored with FPs and IODs maintained stable bone remodeling one year after prosthetic delivery.

Nanocomposite fibrous scaffold mediated mandible reconstruction and dental rehabilitation: An experimental study in pig model

Mandible reconstruction and dental rehabilitation after trauma or tumor resection represent a serious challenge for maxillofacial surgeons. This study aimed to investigate the bone formation potential of nanocomposite fibrous scaffold (silica-nanohydroxyapatite-gelatin reinforced with poly L-lactic acid yarns - CSF) for delayed Titanium (Ti) implantation, which was compared to autograft (AG) taken from the iliac crest. The grafts were placed in critical-sized mandibular defects in an adult pig model for 6 months followed by dental implant placement for another 3 months. There was complete union and vascularised lamellar bone formation within 6 months. Moreover, the biological processes associated with angiogenesis, bone maturation and remodelling were seen in CSF, which was comparable to AG. Later, when Ti dental implant was placed on newly formed bone, CSF group demonstrated better osseointegration. In short, nanocomposite fibrous scaffold promoted quality bone formation in mandible defect that leads to successful osseointegration, suggesting as a potential candidate for implant-based rehabilitation in clinics in future.

Effects of irradiation in the mandibular bone loaded with dental implants. An experimental study with a canine model

Radiation therapy may compromise the quality of bone around dental implants, and its ability to regenerate, remodel, and revascularize. This study aimed to describe the irradiation effect on the bone microstructure of the mandible using dental implants in a canine model. Five beagle dogs were exposed to 40 Gy fractionated radiation. In total, 20 dental implants were inserted, two in the irradiated and two in the non-irradiated side. The mandible bone blocks were subjected to 3D micro-computed tomography (µCT) imaging, later evaluated histomorphometrically by light microscopy and scanning electron microscopy. Alterations in irradiated bone were observed under µCT imaging showing an increased anisotropy, porosity, and pore volume. Bone surface-to-bone volume decreased. The bone to implant contact index was significantly reduced in the irradiated bone (75.6% ± 5.8%) as compared to the non-irradiated bone (85.1% ± 6.8%). In the irradiated mandible, osteocytes with their filopodial processes, the bone beneath the periosteum, and subperiosteal veins showed structural differences but were not significant, whereas the diameter of Haversian canals were smaller statistical significant as compared to the control side. The study highlights that radiation dosage of fractioned 40 Gy causes alterations in the alveolar bone microstructure with compatible osseointegration and clinically stable dental implants.

Integration of mechanics and biology in computer simulation of bone remodeling

Bone remodeling is a complex physiological process that spans across multiple spatial and temporal scales and is regulated by both mechanical and hormonal cues. An imbalance between bone resorption and bone formation in the process of bone remodeling may lead to various bone pathologies. One powerful and non-invasive approach to gain new insights into mechano-adaptive bone remodeling is computer modeling and simulation. Recent findings in bone physiology and advances in computer modeling have provided a unique opportunity to study the integration of mechanics and biology in bone remodeling. Our objective in this review is to critically appraise recent advances and developments and discuss future research opportunities in computational bone remodeling approaches that enable integration of mechanics and cellular and molecular pathways. Based on the critical appraisal of the relevant recent published literature, we conclude that multiscale in silico integration of personalized bone mechanics and mechanobiology combined with data science and analytics techniques offer the potential to deepen our knowledge of bone remodeling and provide ample opportunities for future research.

Local tissue effects and peri-implant bone healing induced by implant surface treatment: an in vivo study in the sheep

OBJECTIVE

The aim of this study was to assess, through biological analysis, the local effects and osseointegration of dental implants incorporating surface micro/nanofeatures compared with implants of identical design without surface treatment.

BACKGROUND

Known to impact bone cell behavior, surface chemical and topography modifications target improved osseointegration and long-term success of dental implants. Very few studies assess the performance of implants presenting both micro- and nanofeatures in vivo on the animal models used in preclinical studies for medical device certification.

METHODS

Implant surfaces were characterized in terms of topography and surface chemical composition. After 4 weeks and 13 weeks of implantation in sheep femoral condyles, forty implants were evaluated through micro-computed tomography, histopathologic, and histomorphometric analyses.

RESULTS

No local adverse effects were observed around implants. Histomorphometric analyses showed significantly higher bone-to-implant contact in the coronal region of the surface-treated implant at week 4 and week 13, respectively, was 79.3 ± 11.2% and 86.4 ± 6.7%, compared with the untreated implants (68.3 ± 8.8% and 74.8 ± 13%). Micro-computed tomography analyses revealed that healing patterns differed between coronal and apical regions, with higher coronal bone-to-implant contact at week 13. Histopathologic results showed, at week 13, bone healing around the surface-treated implant with undistinguishable defect margins, while the untreated implant still presented bone condensation and traces of the initial drill defect.

CONCLUSION

Our results suggest that the surface-treated implant not only shows no deleterious effects on local tissues but also promotes faster bone healing around the implant.

Maxillary Sinus Floor Augmentation with Autogenous Bone Graft Alone Compared with Alternate Grafting Materials: a Systematic Review and Meta-Analysis Focusing on Histomorphometric Outcome

Objectives

The objective of present systematic review was to test the hypothesis of no difference in histomorphometric outcome after maxillary sinus floor augmentation with autogenous bone graft alone compared with alternate grafting materials applying the lateral window technique.

Material and Methods

MEDLINE (PubMed), Embase and Cochrane library search in combination with hand-search of relevant journals were conducted. Human studies published in English until the 25^th of March, 2020 were included. Histomorphometric outcomes were evaluated by descriptive statistics and meta-analysis including 95% confidence interval (CI).

Results

Electronic search and hand-searching resulted in 1902 entries. Sixteen randomized controlled trials with unclear risk of bias fulfilled the inclusion criteria. Descriptive statistics showed comparable or improved histomorphometric outcomes with autogenous bone graft. Meta-analysis revealed a mean difference of -7.1% (CI = -11.0 to -3.2) indicating a significant higher amount of bone after maxillary sinus floor augmentation with autogenous bone graft compared with alternate grafting materials. Subgroup analysis demonstrated a non-significantly differences of -3.7% (CI = -10.9 to 3.4), -11.5% (CI = -25.9 to 2.8), 2.2% (CI = -16.9 to 21.3), and -4.6% (CI = -14.4 to 5.2), when autogenous bone graft was compared with allogeneic bone graft, xenograft, composite grafting materials involving xenograft or synthetic biomaterial mixed with autogenous bone graft, respectively.

Conclusions

Maxillary sinus floor augmentation with autogenous bone graft seems to facilitate improved histomorphometric outcomes compared with alternate grafting materials. However, the included studies were characterised by an unclear risk of bias and various methodological confounding factors. Hence, the conclusions drawn from the results of present study should be interpreted with caution.

Biomechanical Evaluation of Stress Distribution in Subcrestal Placed Platform-switched Short Dental Implants in D4 Bone: In Vitro Finiteelement Model Study

The present study was carried out to assess stress distribution in the maxillary posterior bone region (D4 bone) with the help of a short platform switched subcrestal dental implants using the FEM model. Missing teeth surfaces related to the maxillary posterior region were stimulated. The bone model had a cancellous core of (0.5 mm) which represents D4 bone. A 7.5x4.6 mm screw type implant system with 3.5 platform switch abutment was selected. ANSYS WORKBENCH was used to model all the finite element structures. Force of 100 N was tested and adapted at an angle of 0º, 15º, 30º on the tooth model. Overall results from the current study showed that a high amount of stress was seen in cortical than in relation to cancellous bone. Stress values reduced from equicrestal to subcrestal (2 mm) placement of dental implants irrespective of angulation of load from 0o to 30o in both types of bone. However higher stress values were seen when force was applied in an oblique direction (30o) in comparison to a vertical load (0o). Least amount of stress was noticed when platform switched implants were placed 0.5 mm subcrestatlly irrespective of angulations of a load. Platform switched short subcrestal implants reduced the stress in the D4 cortical bone than in contrary equicrestal implant placement. This results in the preservation of marginal bone leading to implant success.

Socket preservation with demineralized freeze-dried bone allograft and platelet-rich fibrin for implant site development: A randomized controlled trial

Aim:

This in vivo study compared clinical, histological, and radiological differences in bone formation in human extraction sockets grafted with demineralized freeze-dried bone allograft (DFDBA) and platelet-rich fibrin (PRF), with nongrafted sockets and bone–implant contact (BIC) at 3 and 6 months after implant placement.

Settings and Design:

Randomised controlled trial.

Materials and Methods:

The study comprised thirty posterior teeth sockets in either arch in patients ranging from 25 to 60 years. The patients were divided into two equal groups – Group I: control group wherein no graft was placed and the extraction socket was left to heal normally and Group II: test group in which DFDBA and PRF were placed after extraction. 12–16 weeks after extraction, a trephine biopsy was done just prior to implant placement, followed by implant placement. Cone-beam computed tomography (CBCT) at 3 and 6 months after implant placement was done to assess BIC.

Statistical Analysis Used:

Descriptive and Inferential statistical analysis was done. Parametric test: Independent t-test was used for intergroup analysis and dependent t-test for intra-group analysis.

Results:

Lower buccal bone levels were seen in the control group versus test group at all intervals though moderately significant. Lingual bone levels significantly reduced at all the three intervals for the control group as compared to the test group. Ridge width in both groups reduced in a time span of 6–7 months without any significant difference. Better bone conversion was noted in the preserved sockets. The preserved sockets also showed better BIC 3 months after implant placement and loading.

Conclusion:

Indigenously developed DFDBA material shows promising results as an osteoinductive material.

A Hybrid Model for Predicting Bone Healing around Dental Implants

BACKGROUND

The effect of the short-term bone healing process is typically neglected in numerical models of bone remodeling for dental implants. In this study, a hybrid two-step algorithm was proposed to enable a more accurate prediction for the performance of dental implants.

METHODS

A mechano-regulation algorithm was firstly used to simulate the tissue differentiation around a dental implant during the short-term bone healing. Then, the result was used as the initial state of the bone remodeling model to simulate the long-term healing of the bones. The algorithm was implemented by a 3D finite element model.

RESULTS

The current hybrid model reproduced several features which were discovered in the experiments, such as stress shielding effect, high strength bone connective tissue bands, and marginal bone loss. A reasonable location of bone resorptions and the stability of the dental implant is predicted, compared with those predicted by the conventional bone remodeling model.

CONCLUSIONS

The hybrid model developed here predicted bone healing processes around dental implants more accurately. It can be used to study bone healing before implantation surgery and assist in the customization of dental implants.

Numerical Simulation of Mandible Bone Remodeling under Tooth Loading: A Parametric Study

Bone adapts to the change of mechanical stimulus by bone remodeling activities. A number of numerical algorithms have been developed to model the adaptive bone remodeling under mechanical loads for orthopedic and dental applications. This paper examines the effects of several model parameters on the computed apparent bone density in mandible under normal chewing and biting forces. The density change rate was based on the strain energy density per unit mass. The algorithms used in this study containing an equilibrium zone (lazy zone) and saturated values of density change rate provides certain stability to result in convergence without discontinuous checkerboard patterns. The parametric study shows that when different boundary conditions were applied, the bone density distributions at convergence were very different, except in the vicinity of the applied loads. Compared with the effects of boundary conditions, the models are less sensitive to the choice of initial density values. Several models starting from different initial density values resulted in similar but not exactly the same bone density distribution at convergence. The results also show that higher reference value of mechanical stimulus resulted in lower average bone density at convergence. Moreover, the width of equilibrium zone did not substantially affect the average density at convergence. However, with increasing width, the areas with the highest and the lowest bone density areas were all reduced. The limitations of the models and challenges for future work were discussed for the better agreement between the computed results and the in vivo data.

Improvement of osseointegration by recruiting stem cells to titanium implants fabricated with 3D printing

Slow and incomplete osseointegration and loss of osseointegration are major problems in dental and bone implants. We designed implants with interconnected 3D-tubulous structures and hypothesized that such interconnecting 3D (I3D) structures would serve as a repository for chemoattractants to recruit stem cells to promote osseointegration. A concept Laser Mlab-cusing-R laser-powder-bed-fusion (LPBF) 3D printing system was used to produce titanium implants with designed features. The implants were loaded (coated) with stromal cell-derived factor-1 alpha (SDF-1α), and subjected to stem cell recruitment. Implants were then surgically transplanted into the rabbit skull bone. After 12 weeks, osseointegration was analyzed by reverse-torque test and the implants were examined for calcium deposition by Alizarin Red staining. The I3D implants attracted significantly more stem cells than solid implants when coated (loaded) with SDF-1α. Greater torque force was needed to extract the I3D implants with 200 and 300 µm I3D structures than to extract solid implants from the skull. Generally, more calcium deposition was observed on the I3D implants than on the solid counterparts. LPBF 3D printing can be used to fabricate implants with complex structures. I3D-tubulous structures of implants can retain chemoattractant for recruitment of stem cells to enhance osseointegration.

Load-carrying capacity of short implants in edentulous posterior maxilla: A finite element study

Dental implant dimensions, and bone quality and quantity play a key role in early osseointegration and long-term prognosis in posterior edentulous maxilla. Treatment with short implants, preferably in a bicortical manner, is an accepted modality; however, short implants have limitations leading to increased stress concentrations in alveolar bone, potential overload and implant failure. Implant models of 3.3, 4.1, 4.8 and 5.4 mm diameter and 4.5, 5.5, 6.5, 7.5 and 8.5 mm length were placed in posterior maxilla 3-D models with corresponding residual bone heights. Bone-implant assemblies were analyzed in finite element software ANSYS 15. All materials were assumed to be linearly elastic and isotropic. 118.2 N oblique loading was applied to investigate stress distributions in bone tissues. The concept of ultimate functional load (UFL) was selected as a criterion to compare load-carrying capacity of implants and to evaluate the influence of available bone height and implant dimensions on load-carrying capacity. For all implants, UFL was calculated by limiting von Mises stresses in cortical or cancellous bone with bone strength (100 MPa for cortical and 2 MPa for cancellous bone). Implant load-carrying capacity depends on diameter and available bone height. Wide implants have higher load-carrying capacity than narrow implants. Short implants with proper diameter and length avoid bone overstress, even in Type IV bone.

Implant-supported overdentures with different clinical configurations: Mechanical resistance using a numerical approach

STATEMENT OF PROBLEM

Implant-supported overdentures (IODs) are a treatment option for patients with complete edentulism. However, this treatment increases the possibilities of peri-implant complications, characterized by inflammation or partial loss of surrounding hard and soft tissues.

PURPOSE

The purpose of this finite element analysis study was to evaluate the mechanical performance of different bar-IOD designs under different clinical configurations by comparing the stress and strain distribution on the bone during secondary stabilization.

MATERIAL AND METHODS

A finite element model of the mandible representing a patient with complete edentulism was developed. Different designs of bar-IODs were modeled and compared. The parameters studied were the material properties (cobalt-chromium, zirconium dioxide, titanium grade 5, and titanium grade 4), diameter and bar-IOD cross-sectional shape, tilt of the posterior implants (30 degrees), presence of a distal extension cantilever in the bar-IODs (12 mm), and number of implants (4 or 6). Two different mastication loading conditions were analyzed. One- and 2-way ANOVAs and the Tukey honestly significant differences post hoc test (α=.05) were used to determine the significant von Mises stress and strain values in the bone.

RESULTS

The 4 materials tested in the bar-IOD did not have a significant mechanical effect on the bone (P<.05). A smaller diameter and structure of the bar-IOD led to significantly higher bone stress (P<.001). A distal extension cantilever led to an increased stress concentration (model M1 versus model M3: P<.001), which reached 50% in the event of tilting of the posterior implants (model M2 versus model M4: P<.001). Tilting of the posterior implants alone, without extension, had a nonsignificant effect (model M3 versus model M4: P=.999). Model M5 supported with 6 implants reduces the stress transferred to the bone compared with model M3 supported with 4 implants (P<.05).

CONCLUSIONS

Distal extensions in bar-IODs, the tilt of the posterior implants, and the low amount of material in the cross-sectional area in the bar-IOD were the most influential parameters on the mechanical resistance of dental implants in the mandibular bone.

Harnessing Nanotopography to Enhance Osseointegration of Clinical Orthopedic Titanium Implants-An in Vitro and in Vivo Analysis

Despite technological advancements, further innovations in the field of orthopedics and bone regeneration are essential to meet the rising demands of an increasing aging population and associated issues of disease, injury and trauma. Nanotopography provides new opportunities for novel implant surface modifications and promises to deliver further improvements in implant performance. However, the technical complexities of nanotopography fabrication and surface analysis have precluded identification of the optimal surface features to trigger osteogenesis. We herein detail the osteoinductive potential of discrete nanodot and nanowire nanotopographies. We have examined the ability of modified titanium and titanium alloy (Ti64) surfaces to induce bone-specific gene activation and extracellular matrix protein expression in human skeletal stem cells (SSCs) in vitro, and de novo osteogenic response within a murine calvarial model in vivo. This study provides evidence of enhanced osteogenic response to nanowires 300 surface modifications, with important implications for clinical orthopedic application.

Biomechanical Effects of Various Bone-Implant Interfaces on the Stability of Orthodontic Miniscrews: A Finite Element Study

INTRODUCTION

Osseointegration is required for prosthetic implant, but the various bone-implant interfaces of orthodontic miniscrews would be a great interest for the orthodontist. There is no clear consensus regarding the minimum amount of bone-implant osseointegration required for a stable miniscrew. The objective of this study was to investigate the influence of different bone-implant interfaces on the miniscrew and its surrounding tissue.

METHODS

Using finite element analysis, an advanced approach representing the bone-implant interface is adopted herein, and different degrees of bone-implant osseointegration were implemented in the FE models. A total of 26 different FE analyses were performed. The stress/strain patterns were calculated and compared, and the displacement of miniscrews was also evaluated.

RESULTS

The stress/strain distributions are changing with the various bone-implant interfaces. In the scenario of 0% osseointegration, a rather homogeneous distribution was predicted. After 15% osseointegration, the stress/strains were gradually concentrated on the cortical bone region. The miniscrew experienced the largest displacement under the no osseointegra condition. The maximum displacement decreases sharply from 0% to 3% and tends to become stable.

CONCLUSION

From a biomechanical perspective, it can be suggested that orthodontic loading could be applied on miniscrews after about 15% osseointegration without any loss of stability.

Remodeling of the Mandibular Bone Induced by Overdentures Supported by Different Numbers of Implants

The objective of this study was to investigate the process of mandibular bone remodeling induced by implant-supported overdentures. computed tomography (CT) images were collected from edentulous patients to reconstruct the geometry of the mandibular bone and overdentures supported by implants. Based on the theory of strain energy density (SED), bone remodeling models were established using the user material subroutine (UMAT) in abaqus. The stress distribution in the mandible and bone density change was investigated to determine the effect of implant number on the remodeling of the mandibular bone. The results indicated that the areas where high Mises stress values were observed were mainly situated around the implants. The stress was concentrated in the distal neck region of the distal-most implants. With an increased number of implants, the biting force applied on the dentures was almost all taken up by implants. The stress and bone density in peri-implant bone increased. When the stress reached the threshold of remodeling, the bone density began to decrease. In the posterior mandible area, the stress was well distributed but increased with decreased implant numbers. Changes in bone density were not observed in this area. The computational results were consistent with the clinical data. The results demonstrate that the risk of bone resorption around the distal-most implants increases with increased numbers of implants and that the occlusal force applied to overdentures should be adjusted to be distributed more in the distal areas of the mandible.

Evaluation of treatment outcomes and clinical indications for antibiotic prophylaxis in patients undergoing implantation procedures

PURPOSE

The use of antibiotic therapy during implantation to reduce the risk of an early implant failure is widely discussed among clinicists. However, half an hour after the procedure a quarter of patients show bacteremia which could decrease the efficacy of the surgery. Implant failure is associated with destruction of bone tissue within the alveolar process and may lead to an alternative but compromised treatment plan. The aim of the study was to evaluate the influence of perioperative antibiotic protection on success of implantation.

MATERIAL AND METHODS

The retrospective study involved 1915 patients (females: 57.3%, males: 42.7%) with no systemic or local diseases, who required antibiotic therapy during surgical procedures. Group 1 comprised 203 patients with diagnosed vertical or horizontal bone atrophy within the alveolar ridge requiring reconstruction procedure before implantation. Group 2 included 1712 patients who did not need any surgical procedures before implantation. All the subjects took three types of antibiotics twice a day for 7 days. The data were statistically analyzed.

RESULTS

A total number of 3309 implants were placed. Implantation efficacy in group 1 amounted to 98.53% and in group 2 it was 99.24%. Complications occurred most commonly after administration of cephalosporin which proved to be statistically significant for the patients who underwent augmentation with a bone block before the implant procedure (p 0.0209).

CONCLUSIONS

Perioperative use of antibiotic therapy beneficially influences tissue healing, provides safety and success of the surgical procedure, as well as translates into high efficacy of implantation (99.52%).

THE MANDIBLE REMODELING INDUCED BY DENTAL IMPLANTS: A MESHLESS APPROACH

This work aims to evaluate the prediction efficiency of a recently developed numerical approach in the mandible bone tissue remodeling process. The remodeling algorithm, seeking the minimization of the strain energy density, includes a phenomenological anisotropic material law capable of predicting the bone tissue mechanical properties based on the bone apparent density. The key factor of the proposed numerical approach is the inclusion of a flexible and efficient meshless method, which is used to obtain the strain energy density field. The inclusion of this advance discretization technique in the process is an asset since meshless methods produce smoother and more accurate strain energy density fields when compared with other numerical approaches. The bone tissue remodeling process of the molar region of the mandible, due to the inclusion of an implant system, is studied. The obtained results are in accordance with other numerical approach results available in the literature.

Implant success remains high despite grafting voids in the maxillary sinus

OBJECTIVES

Given that the nature and presence of voids present within grafted sinuses following maxillary sinus elevation procedures were not known, nor was the contribution of these factors to implant success, the purpose of this study was to investigate these parameters and their relationship to implant success.

MATERIALS AND METHODS

This study evaluated data from 25 subjects who had a lateral window maxillary sinus augmentation procedure. Cone-beam computed tomography (CBCT) was performed at baseline and 4 months after surgery. CBCT images were used to evaluate grafted sites prior to implant placement. Using CBCT images, three examiners independently measured bone-grafted areas (BG), void areas (V), and percentage of void areas (V%) from six different sections within grafted sites. The six sections were defined as a cross-sectional (CS) midpoint, CS mesial point, CS distal point, horizontal section (HS) low point, HS midpoint, and HS high point. Implant success was also determined.

RESULTS

The calculated V% (V/BG) for the CS midpoint, CS mesial point, CS distal point, HS low point, HS midpoint, and HS high point were 5.30 ± 6.67%, 5.79 ± 8.51%, 6.67 ± 7.12%, 2.07 ± 2.56%, 5.30 ± 6.62%, and 4.92 ± 5.17% respectively. Implant success after 6 months of follow-up approximated 100%.

CONCLUSIONS

Although voids within grafts varied in terms of distribution and size, the V% within the HS low point were significantly smaller compared to those within the CS midpoint and CS distal point, which had the most intra-subject V%. Thus, more attention should be given to the distal aspect of the sinus when compacting graft materials in the lateral wall sinus augmentation procedure. Implant success was not influenced by the existence of voids as implant success remained high.

Do antibiotics decrease implant failure and postoperative infections? A systematic review and meta-analysis

The purpose of this study was to systematically review and perform a comprehensive meta-analysis of the current literature to answer the following question: among patients receiving dental implants, does the use of antibiotics, when compared with a control group, reduce the frequency of implant failure and postoperative infection? A manual and electronic PubMed search of the literature was made to identify randomized controlled trials (RCTs) on the efficacy of antibiotics compared with a control group (not receiving antibiotics or receiving placebo). Four RCTs were included in the final review. These four RCTs grouped a total of 2063 implants and a total of 1002 patients. Antibiotic use significantly lowered the implant failure rate (P = 0.003), with an odds ratio of 0.331, implying that antibiotic treatment reduced the odds of failure by 66.9%. The number needed to treat (NNT) to prevent one patient from having an implant failure was 48 (95% confidence interval 31-109). In contrast, antibiotic use did not significantly reduce the incidence of postoperative infection (P = 0.754). Based on the results of this meta-analysis, and pending further research in the field, it can be concluded that there is evidence in favour of systematic antibiotic use in patients receiving dental implants, since such treatment significantly reduces implant failure. In contrast, antibiotic use does not exert a significant preventive effect against postoperative infection. Our recommendations for future research focus on the performance of large-scale RCTs to identify the best choice of antibiotic, timing of administration, and dose. Increased effort is also required to reach consensus and define the most effective antibiotic treatment protocol for patients who are allergic to beta-lactams and for those who are not.

The remodeling of alveolar bone supporting the mandibular first molar with different levels of periodontal attachment

The objective of this study was to investigate alveolar bone remodeling of the mandibular first molar with differing levels of periodontal attachment under mastication loading. Three-dimensional finite element models of the mandibular first molar with differing levels of periodontal attachment were established. The stress distributions and bone density changes were analyzed under mastication loading to simulate the remodeling process of mandibular bone based on the theory of strain energy density. The results showed that the alveolar buccal, lingual ridges and root apex areas experienced higher stresses. The stresses and densities of the alveolar bone increased proportionally to increased mastication loading. Decrease in alveolar bone density under extreme loading indicated bone resorption. The remodeling rate was continual with gradual loading. Periodontal ligament support marginally decreased with an increased remodeling rate under extreme loading. Changes in alveolar bone density can reflect the remodeling process of periodontal tissue under mastication loading. The relationship between the change in density and mastication loading during remodeling can provide useful indicators into clinical treatment and diagnosis of the periodontal disease.

Effect of decreased implant healing time on bone (re)modeling adjacent to plateaued implants under functional loading in a dog model

OBJECTIVES

The purpose of this study was to evaluate the effect of early functional loading to plateaued implants on bone formation and implant stability in a dog model.

MATERIALS AND METHODS

Early loading (EL), nonloading control, and delayed loading (DL) groups were compared using six beagle dogs under functional loading. The Periotest® values were measured dynamically for 6 weeks. Peri-implant bone architecture was evaluated qualitatively by microcomputed tomography (μCT) and analyzed quantitatively by mineral apposition rates (MAR), bone-to-implant contact (BIC), and bone volumes (BV/TV) after the euthanasia at 3 and 6 weeks after loading.

RESULTS

The EL implants showed poor stability at 1 week, but greater stability at 2 and 4 weeks after loading compared to DL implants. There was no significant difference between MAR of EL and unloaded implants at both time intervals. The EL implants displayed a significantly higher MAR when compared to DL implants at 3-5 weeks. A significantly higher BIC for the DL group was observed when compared to the EL group at 3 weeks following loading, however at 6 weeks; no significant difference between these groups was observed. The EL group gained a higher BIC than the no-treatment control group at 6 weeks.

CONCLUSIONS

For plateaued implant, the decreased healing time (1 week) displays a positive effect on peri-implant bone (re)modeling under functional loading during the early phase.

CLINICAL RELEVANCE

The early application of functional loading on plateaued implants can be used clinically to shorten the course of treatment and improve esthetics.

Numerical test concerning bone mass apposition under electrical and mechanical stimulus

This article proposes a model of bone remodeling that encompasses mechanical and electrical stimuli. The remodeling formulation proposed by Weinans and collaborators was used as the basis of this research, with a literature review allowing a constitutive model evaluating the permittivity of bone tissue to be developed. This allowed the mass distribution that depends on mechanical and electrical stimuli to be obtained. The remaining constants were established through numerical experimentation. The results demonstrate that mass distribution is altered under electrical stimulation, generally resulting in a greater deposition of mass. In addition, the frequency of application of an electric field can affect the distribution of mass; at a lower frequency there is more mass in the domain. These numerical experiments open up discussion concerning the importance of the electric field in the remodeling process and propose the quantification of their effects.