Evaluation of functional dynamics during osseointegration and regeneration associated with oral implants

Analysis of Gingival Fibroblasts Behaviour in the Presence of 3D-Printed versus Milled Methacrylate-Based Dental Resins-Do We Have a Winner?

Computer-aided design and computer-aided manufacturing (CAD/CAM) techniques are based on either subtractive (milling prefabricated blocks) or additive (3D printing) methods, and both are used for obtaining dentistry materials. Our in vitro study aimed to investigate the behavior of human gingival fibroblasts exposed to methacrylate (MA)-based CAD/CAM milled samples in comparison with that of MA-based 3D-printed samples to better elucidate the mechanisms of cell adaptability and survival. The proliferation of human gingival fibroblasts was measured after 2 and 24 h of incubation in the presence of these samples using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and the membrane integrity was assessed through the lactate dehydrogenase release. The level of reactive oxygen species, expression of autophagy-related protein LC3B-I, and detection of GSH and caspase 3/7 were evaluated by fluorescence staining. The MMP-2 levels were measured using a Milliplex MAP kit. The incubation with MA-based 3D-printed samples significantly reduced the viability, by 16% and 28% from control after 2 and 24 h, respectively. There was a 25% and 55% decrease in the GSH level from control after 24 h of incubation with the CAD/CAM milled and 3D-printed samples, respectively. In addition, higher levels of LC3B-I and MMP-2 were obtained after 24 h of incubation with the MA-based 3D samples compared to the CAD/CAM milled ones. Therefore, our results outline that the MA-CAD/CAM milled samples displayed good biocompatibility during 24-h exposure, while MA-3D resins are proper for short-term utilization (less than 24 h).

The Suitability of Trabecular Patterns in the Assessment of Dental Implant Osseointegration Process through 2D Digital and 3D CBCT Radiographs

OBJECTIVE

 The research aims to determine the suitability of the trabecular pattern in the assessment of the dental implant osseointegration process through two-dimensional (2D) digital and three-dimensional (3D) cone-beam computed tomography (CBCT) radiographs.

MATERIALS AND METHODS

 This is a correlation description that explains the relationship between variables. The population consisted of 24 data points on 3D CBCT and 2D digital radiographs from the procedure after dental implants were inserted into the tibia of a New Zealand white rabbit (Oryctolagus cuniculus) on days 3, 14, and 28. The radiograph was selected based on the region of interest (ROI), which covers the peri-implant area with a width of 1 mm and length following the height of the implant. The ROI was analyzed for trabecular thickness (Tb.Th), separation (Tb.Sp), number (Tb.N), and fractal dimension.

STATISTICAL ANALYSIS

 The intraclass correlation coefficient (ICC) was used to statistically test the data to assess the consistency of intraobserver measurements and the r value (Pearson's correlation coefficient). This determines the correlation between trabecular patterns in both radiographic modalities and the Bland-Altman plot to observe the limits of acceptable discrepancies.

RESULTS

 The ICC test showed high intraobserver consistency in trabecular pattern measurements on 2D digital radiographs and 3D CBCT. The trabecular space pattern and number showed an r value of 0.88 with radiographic modalities of 0.72 mm and 0.018, respectively. Additionally, the trabecular thickness and fractal dimension had an insignificant correlation, with an r value of 0.22, and the mean of the 2D radiograph was lower than that of CBCT.

CONCLUSION

 The 2D radiograph and 3D CBCT showed correlations in the trabecular number and space results but had no correlation in the trabecular thickness and fractal dimension results. Based on intraclass correlation analysis, 3D CBCT appeared to be more reliable for measuring trabecular patterns (Tb.Th, Tb.Sp, Tb.N, and fractal dimension) than 2D radiograph.

A Comprehensive Mechanical Characterization of Subject-Specific 3D Printed Scaffolds Mimicking Trabecular Bone Architecture Biomechanics

This study presents a polymeric scaffold designed and manufactured to mimic the structure and mechanical compressive characteristics of trabecular bone. The morphological parameters and mechanical behavior of the scaffold were studied and compared with trabecular bone from bovine iliac crest. Its mechanical properties, such as modulus of elasticity and yield strength, were studied under a three-step monotonic compressive test. Results showed that the elastic modulus of the scaffold was 329 MPa, and the one for trabecular bone reached 336 MPa. A stepwise dynamic compressive test was used to assess the behavior of samples under various loading regimes. With microcomputed tomography (µCT), a three-dimensional reconstruction of the samples was obtained, and their porosity was estimated as 80% for the polymeric scaffold and 88% for trabecular bone. The full-field strain distribution of the samples was measured using in situ µCT mechanics and digital volume correlation (DVC). This provided information on the local microdeformation mechanism of the scaffolds when compared to that of the tissue. The comprehensive results illustrate the potential of the fabricated scaffolds as biomechanical templates for in vitro studies. Furthermore, there is potential for extending this structure and fabrication methodology to incorporate suitable biocompatible materials for both in vitro and in vivo clinical applications.

The Action of Angiocrine Molecules Sourced from Mechanotransduction-Related Endothelial Cell Partially Explain the Successful of Titanium in Osseointegration

Since Branemark's findings, titanium-based alloys have been widely used in implantology. However, their success in dental implants is not known when considering the heterogenicity of housing cells surrounding the peri-implant microenvironment. Additionally, they are expected to recapitulate the physiological coupling between endothelial cells and osteoblasts during appositional bone growth during osseointegration. To investigate whether this crosstalk was happening in this context, we considered the mechanotransduction-related endothelial cell signaling underlying laminar shear stress (up to 3 days), and this angiocrine factor-enriched medium was harvested further to use exposing pre-osteoblasts (pOb) for up to 7 days in vitro. Two titanium surfaces were considered, as follows: double acid etching treatment (w_DAE) and machined surfaces (wo_DAE). These surfaces were used to conditionate the cell culture medium as recommended by ISO10993-5:2016, and this titanium-enriched medium was later used to expose ECs. First, our data showed that there is a difference between the surfaces in releasing Ti molecules to the medium, providing very dynamic surfaces, where the w_DAE was around 25% higher (4 ng/mL) in comparison to the wo_DAE (3 ng/mL). Importantly, the ECs took up some of this titanium content for up to 3 days in culture. However, when this conditioned medium was used to expose pOb for up to 7 days, considering the angiocrine factors released from ECs, the concentration of Ti was lesser than previously reported, reaching around 1 ng/mL and 2 ng/mL, respectively. Thereafter, pOb exposed to this angiocrine factor-enriched medium presented a significant difference when considering the mechanosignaling subjected to the ECs. Shear-stressed ECs showed adequate crosstalk with osteoblasts, stimulating the higher expression of the Runx2 gene and driving higher expressions of Alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin. Mechanotransduction-related endothelial cell signaling as a source of angiocrine molecules also stimulated the higher expression of the Col3A1 gene in osteoblasts, which suggests it is a relevant protagonist during trabecular bone growth. In fact, we investigated ECM remodeling by first evaluating the expression of genes related to it, and our data showed a higher expression of matrix metalloproteinase (MMP) 2 and MMP9 in response to mechanosignaling-based angiocrine molecules, independent of considering w_DAE or the wo_DAE, and this profile reflected on the MMP2 and MMP9 activities evaluated via gelatin-based zymography. Complimentarily, the ECM remodeling seemed to be a very regulated mechanism in mature osteoblasts during the mineralization process once both TIMP metallopeptidase inhibitor 1 and 2 (TIMP1 and TIMP2, respectively) genes were significantly higher in response to mechanotransduction-related endothelial cell signaling as a source of angiocrine molecules. Altogether, our data show the relevance of mechanosignaling in favoring ECs' release of bioactive factors peri-implant, which is responsible for creating an osteogenic microenvironment able to drive osteoblast differentiation and modulate ECM remodeling. Taking this into account, it seems that mechanotransduction-based angiocrine molecules explain the successful use of titanium during osseointegration.

Deep learning-based prediction of osseointegration for dental implant using plain radiography

BACKGROUND

In this study, we investigated whether deep learning-based prediction of osseointegration of dental implants using plain radiography is possible.

METHODS

Panoramic and periapical radiographs of 580 patients (1,206 dental implants) were used to train and test a deep learning model. Group 1 (338 patients, 591 dental implants) included implants that were radiographed immediately after implant placement, that is, when osseointegration had not yet occurred. Group 2 (242 patients, 615 dental implants) included implants radiographed after confirming successful osseointegration. A dataset was extracted using random sampling and was composed of training, validation, and test sets. For osseointegration prediction, we employed seven different deep learning models. Each deep-learning model was built by performing the experiment 10 times. For each experiment, the dataset was randomly separated in a 60:20:20 ratio. For model evaluation, the specificity, sensitivity, accuracy, and AUROC (Area under the receiver operating characteristic curve) of the models was calculated.

RESULTS

The mean specificity, sensitivity, and accuracy of the deep learning models were 0.780-0.857, 0.811-0.833, and 0.799-0.836, respectively. Furthermore, the mean AUROC values ranged from to 0.890-0.922. The best model yields an accuracy of 0.896, and the worst model yields an accuracy of 0.702.

CONCLUSION

This study found that osseointegration of dental implants can be predicted to some extent through deep learning using plain radiography. This is expected to complement the evaluation methods of dental implant osseointegration that are currently widely used.

Analysis of Bone Density and Bone Morphometry by Periapical Radiographs in Dental Implant Osseointegration Process

Objective. This research aimed to analyze the differences in bone density and bone morphometry by periapical implant radiography in the dental implant osseointegration stages. Methods. This experimental research uses 12 periapical radiographs of tibial bones from a New Zealand white rabbit (Oryctolagus cuniculus). The analysis was performed on day 3, 14, and 28 of the osseointegration stages with density, trabecular thickness (Tb.Th.), trabecular separation (Tb.Sp.), and trabecular number (Tb.N.) as parameters. The implant used is a titanium alloy and coated by SA (sunblasted with alumina acid) of 4 mm in diameter and 7 mm in length. The radiographic assessment of the osseointegration process is obtained with the region of interest (ROI) segmentation results. Additionally, each ROI was analyzed for bone density and morphometry using the open-source ImageJ software with the BoneJ plugin. The significant difference was evaluated by analysis of variance (F-test) with $p<0.05$ and nonparametric Kruskal–Wallis test with $p<0.05$ . Results. Analysis of the osseointegration images of dental implants at day 3, 14, and 28 with the periapical X-ray modality shows significant differences ( $p<0.05$ ) in the parameters measuring density and trabecular thickness (Tb.Th.). In the variables of trabecular separation (Tb.Sp.) and number (Tb.N.) ( $p>0.05$ ), there is no significant difference. Conclusion. Based on the results, density and trabecular thickness (Tb.Th.) showed a significant difference between healing times. However, trabecular separation (Tb.Sp.) and trabecular number (Tb.N.) showed no difference in healing time.

Effectiveness of biomolecule-based bioactive surfaces, on os-seointegration of titanium dental implants: A systematic review and meta-analysis of in vivo studies

Titanium and alloy osseointegrated implants are used to replace missing teeth; however, some fail and are removed. Modifications of the implant surface with biologically active substances have been proposed. MEDLINE [via Pubmed], Embase and Web of Science were searched with the terms “titanium dental implants”, “surface properties”, “bioactive surface modifications”, “biomolecules”, “BMP”, “antibacterial agent”, “peptide”, “collagen”, “grown factor”, “osseointegration”, “bone apposition”, “osteogenic”, “osteogenesis”, “new bone formation”, “bone to implant contact”, “bone regeneration” and “in vivo studies”, until May 2022. A total of 10,697 references were iden-tified and 26 were included to analyze 1,109 implants, with follow-ups from 2 to 84 weeks. The ARRIVE guidelines and the SYRCLE tool were used to evaluate the methodology and scientific evidence. A meta-analysis was performed (RevMan 2020 software, Cochane Collaboration) with random effects that evaluated BIC at 4 weeks, with subgroups for the different coatings. The heterogeneity of the pooled studies was very high (95% CI, I2 = 99%). The subgroup of BMPs was the most favorable to coating. Surface modification of Ti implants by organic bioactive molecules seems to favor osseointegration in the early stages of healing, but long-term studies are necessary to corroborate the results of the experimental studies.

Use of Eggshells as Bone Grafts around Commercially Pure Titanium Implant Screws Coated with Nano Calcium Sulfate

Background. Implant insertion in regions with poor bone quantity, such as the posterior maxilla, is potentially associated with an increased rate of implant failure. Calcium sulfate can be used as the coating material for commercially pure titanium (CpTi) and as the bone graft material around implants when bound to eggshell powder to enhance the bone quality and quantity of bone defect regions. This study performed a torque removal test to evaluate the effectiveness of eggshell powder as a bone substitute for filling bone defects around CpTi-coated implants coated with nanocrystalline calcium sulfate. Materials and Methods. Eighty screw implant designs were used in the tibiae of 20 white New Zealand rabbits. A total of uncoated 20 screws constituted the control group, and the remaining 60 screws coated with nano calcium sulfate nanoparticles were used as the experimental groups as follows: 20 screws coated with nano calcium sulfate were used alone in the tibiae without gaps around them, 20 screws coated with nano calcium sulfate were used with the gaps made around them and filled with eggshell powder as the bone graft material, and 20 screws coated with nano calcium sulfate were used with the gaps made around them left unfilled. Results. After 2 to 6 weeks of healing, a significant improvement in bone regeneration and an increase in torque removal values were observed when the bone defect around the CpTi implant coated with nano calcium sulfate was filled with eggshell powder as the bone substitute. Conclusions. Nano calcium sulfate particles applied through the dip-coating method can successfully work as the coating material of CpTi implants. These particles work in synergy with eggshell powder to act as the bone graft around the implants.

Improvement of Osseointegration by Ultraviolet and/or Simvastatin Treatment on Titanium Implants with or without Bone Graft Materials

We evaluated and compared ultraviolet (UV) treatment and simvastatin (SIM) immersion effects on the osseointegration of sandblasted, large-grit, acid-etched (SLA) titanium dental implants at two different time points in rabbit tibias, with or without xenogenic bone graft materials. The surface alteration on simvastatin treatment titanium discs was analyzed using an infrared spectrometer. Implants were categorized into four groups according to the surface treatment type. Twelve rabbits received two implants per tibia. A tibial defect model was created using a trephine bur, with implants in contact with the bone surface and bovine bone graft materials for gap filling. The rabbits were sacrificed after 2 or 4 weeks. UV treatment or SIM immersion increased the bone-to-implant contact (BIC) on nongrafted sides, and both increased the BIC and bone area (BA) on grafted sides. The application of both treatments did not result in higher BIC or BA than a single treatment. At two different time points, BIC in the nongrafted sides did not differ significantly among the UV and/or SIM treated groups, whereas BA differed significantly. UV or SIM treatment of SLA titanium implants accelerates osseointegration in tibias with or without xenogenic bone graft materials. The combination of both treatments did not show synergy.

Influence of bisphosphonates on oral implantology: Sodium alendronate and zoledronic acid enhance the synthesis and activity of matrix metalloproteinases by gingival fibroblasts seeded on titanium

OBJECTIVE

This study aimed to assess the influence of the bisphosphonates zoledronic acid and sodium alendronate on MMP-2 and MMP-9 synthesis and activity by gingival fibroblasts seeded onto titanium substrate.

DESIGN

Titanium discs were placed in 24-well cell culture plates and gingival fibroblasts were seeded (1 × 10⁵ cells/discs) on them using Dulbecco's Modified Eagle's Medium (DMEM) + 10 % fetal bovine serum (FBS) for 24 h. After this period, a fresh serum-free DMEM containing zoledronic acid or sodium alendronate at 0.5 μM, 1 μM or 5 μM was applied on the cells for an additional of 24 h. Serum-free DMEM and tumor necrosis factor alpha (TNF-α) were used as negative and positive controls, respectively. MMP-2 and MMP-9 synthesis and activity were determined by ELISA (Enzyme-Linked Immunosorbent Assay) and conventional/in situ zymography. Quantitative data were analyzed by one-way ANOVA and Tukey's tests (α = 0.05). The in situ zymography data were qualitatively described.

RESULTS

Despite both bisphosphonates increased the MMPs synthesis, this effect was significant higher in zoledronic acid groups. MMPs activity resembled by gelatinolytic activity was also enhanced by sodium alendronate and zoledronic acid in a similar pattern.

CONCLUSIONS

Zoledronic acid and sodium alendronate increased in a dose-dependent manner MMP-2 and MMP-9 synthesis by gingival fibroblasts seeded on titanium. MMP-2 activity was up-regulated by zoledronic acid treatment.

Photobiomodulation using LLLT and LED of cells involved in osseointegration and peri-implant soft tissue healing

This study evaluated the influence of photobiomodulation (PBM) using low-level laser therapy (PBM/LLLT) or light-emitting diode (PBM/LED) therapy on peri-implant tissue healing. A laboratory model was used to assess the adhesion and metabolism of osteoblasts (SaOs-2), human gingival fibroblasts (HGF), and normal oral keratinocytes (NOK) seeded on a titanium (Ti) surface. After seeding the cells on disks of Ti placed in wells of 24-well plates, three irradiations were performed every 24 h at energy density of 3 J/cm². For PBM/LLLT, a LaserTABLE device was used with a wavelength of 780 nm and 25 mW, while for PBM/LED irradiation, a LEDTABLE device was used at 810 nm, 20 mW, at a density of 3 J/cm². After irradiations, the number of cells (NC) attached and spread on the Ti surface, cell viability (CV), total protein (TP), and collagen (Col) synthesis were assessed. Alkaline phosphate activity (ALP) was evaluated only for SaOs-2. Data were submitted to ANOVA complemented by Turkey statistical tests at a 5% significance level. PBM significantly increased adherence of NOK to the Ti surface, while no significant effect was observed for SaOs-2 and HGF. PBM positively affected CV, as well as Col and TP synthesis, in distinct patterns according to the cell line. Increased ALP activity was observed only in those cells exposed to PBM/LLLT. Considering cell specificity, this investigation reports that photobiomodulation with low-power laser and LED at determined parameters enhances cellular functions related to peri-implant tissue healing in a laboratory model.

Effects of low-dose aspirin on the osseointegration process in rats

BACKGROUND

Several drugs are capable of promoting changes in bone metabolism. The aim of this study was to evaluate the effect of long-term low-dose aspirin (LDA) therapy on implant osseointegration.

METHODS

Male Wistar rats were divided into 4 groups (n = 8/group) according to oral gavage solution received prior (42 days) to the implant surgery on the tibia. The control group was treated with saline solution for 7 (CG-7) and 28 (CG-28) days. The use of low-dose aspirin was performed in AG groups (6.75 mg/kg of aspirin) for 7 (AG-7) and 28 (AG-28) days. After experimental periods, histomorphometric evaluation of bone-to-implant contact (BIC) and the bone area between threads (BABT) was performed.

RESULTS

Reduced BIC values were detected in AG-7 (62.8% ± 17.1) group compared to AG-28 (91.9% ± 5.4), CG-7 (82.7% ± 15.2), and CG-28 (89.9% ± 9.7). BABT evaluation revealed lower values in AG-7 (70.9% ± 15.2) compared to AG-28 (95.4% ± 3.7) and CG-28 (87.1% ± 10.2) groups.

CONCLUSIONS

The treatment with low doses of aspirin promoted a discrete inhibitory effect in the early stages (7 days) of repair after implant placement, specifically in the bone deposition. However, these effects were not detected in the late stages (28 days), considering BIC and BABT parameters.

Reliability of the Resonance Frequency Analysis Values in New Prototype Transepithelial Abutments: A Prospective Clinical Study

Resonance frequency analysis (RFA) requires abutment disconnection to monitor implant stability. To overcome this limitation, an experimental transepithelial abutment was designed to allow a SmartPeg to be screwed onto it, in order to determine the prototype abutments repeatability and reproducibility using Osstell ISQ and to assess whether implant length and diameter have an influence on the reliability of these measurements. RFA was conducted with a SmartPeg screwed directly into the implant and onto experimental abutments of different heights of 2, 3.5 and 5 mm. A total of 32 patients (116 implants) were tested. RFA measurements were taken twice for each group from mesial, distal, buccal and palatal/lingual surfaces. Mean values and SD were calculated and Intraclass Correlation Coefficients (ICC) (p < 0.05, IC 95%). The implant stability quotient (ISQ) mean values were 72.581 measured directly to implant and 72.899 (2 mm), 72.391 (3.5 mm) and 71.458 (5 mm) measured from the prototypes. ICC between measurements made directly to implant and through 2-, 3.5- and 5-mm abutments were 0.908, 0.919 and 0.939, respectively. RFA values registered through the experimental transepithelial abutments achieved a high reliability. Neither the implant length nor the diameter had any influence on the measurements' reliability.

Influence of Bisphosphonates on the Behavior of Osteoblasts Seeded Onto Titanium Discs

Abstract Among other factors, types of bisphosphonates and treatment regimens seem to be strongly associated with the success or failure of installation of osseointegrated implants. This study investigated the influence of two bisphosphonates, sodium alendronate (SA) and zoledronic acid (ZA), on the metabolism of osteoblasts. Human osteoblasts (Saos-2) were seeded onto machined or acid-treated titanium discs previously placed on 24-well plates in complete culture medium. After 24 h, cells were exposed to bisphosphonates at 0.5, 1 or 5 µM for 24 h, 48 h or 7 days. The effects of SA and ZA on osteoblasts were assessed based on the adhesion of these cells to the titanium surfaces by direct fluorescence, cell viability, total protein and collagen synthesis. Alkaline phosphatase activity and mineral nodule deposition by these cells were also evaluated. Data were evaluated by ANOVA and Tukey tests (α=0.05). Decreased adhesion of cells to the titanium discs was observed when exposed to both bisphosphonates; however, this lack of cell adhesion was more evident for ZA-treated cells. In addition, the exposure of osteoblasts to ZA decreased the viability, ALP activity and mineral nodule deposition, which may be related to poor osseointegration after implant installation.

Comparative Evaluation of Bone Repair with Four Different Bone Substitutes in Critical Size Defects

This study evaluated the osteoconductive potential of four biomaterials used to fill bone defects. For this, 24 male Albino rabbits were submitted to the creation of a bilateral 8 mm calvarial bone defect. The animals were divided into four groups-bovine hydroxyapatite, Bio-Oss® (BIO); Lumina-Bone Porous® (LBP); Bonefill® (BFL); and an alloplastic material, Clonos® (CLN)-and were euthanized at 14 and 40 days. The samples were subjected to histological and histometric analysis for newly formed bone area. Immunohistochemical analysis for Runt-related transcription factor 2 (Runx2), vascular endothelial growth factor (VEGF), and osteocalcin (OC) was performed. After statistical analysis, the CLN group showed greater new bone formation (NB) in both periods analyzed (p < 0.05). At 14 days, the NB showed greater values in BIO in relation to LBP and BFL groups; however, after 40 days, the LBP group surpassed the results of BIO (p < 0.001). The immunostaining showed a decrease in Runx2 intensity in BIO after 40 days, while it increased for LBP (p < 0.05). The CLN showed increased OC compared to the other groups in both periods analyzed (p < 0.05). Therefore, CLN showed the best osteoconductive behavior in critical defects in rabbit calvaria, and BFL showed the lowest osteoconductive property.

Role and influence of growth factors on early osseointegration in animal jaw bone: A meta-analysis

Aim:

Growth factors (GFs) are polypeptides, which are intricately involved in the regulation of bone formation, preservation, and regeneration through gene expression. However, the role of these bioactive agents in osseointegration of dental implants has not been substantially proven. The objective of this systematic review (SR) and meta-analysis was to explore the effect of GFs on early osseointegration of dental implants in animal jaws. An attempt to decipher an adjunctive role of GFs in modulating predictable bone growth in peri-implant areas was done.

Materials and Methods:

An electronic and manual search of different databases was performed. Only randomized controlled trials (RCTs) were included and reviewed. The risk of bias (ROB) of the selected studies was assessed using the SR Centre for Laboratory Animal Experimentation (Cochrane) tool. A meta-analysis was also performed to evaluate the different study characteristics quantitatively.

Statistical Analysis used:

The total Weighted mean difference was evaluated using the Rev-Manv5.3 algorithm. Chi-square test and I² test were done to assess the heterogeneity between the studies.

Results:

Seven RCTs were included in the study. These were associated with a high ROB. The total weighted mean difference (WMD) of the percentage of bone–implant contact was 3.25% (95% confidence interval [CI] = 1.49%–6.03%; P = 0.001; I² = 91%) between groups with and without exogenous application of GFs. The total WMD of the percentage of newly formed bone area was 4.48% (95% CI = 2.31%–5.90%; P < 0.00001, I² = 84%). A high level of heterogeneity (P < 0.001 for Chi-square test; I²>50 %) among comparable studies was observed.

Conclusion:

The ancillary application of external GFs exhibited evidence of early osseointegration, resulting in more predictable and faster results. However, a careful discernment of conclusions drawn from this SR is a must before conducting any human trials.

The role of concentrated growth factor on implant stability: A preliminary study

PURPOSE

The purpose of this preliminary study was to evaluate the effect of concentrated growth factor (CGF) on dental implant stability in type 2 bone using the resonance frequency analysis (RFA) device Smartpeg®.

METHODS

The researchers carried out a prospective cohort study on a sample group composed of 12 patients (mean age=67) who required dental implants. Implant socket preparation (with and without CGF) was the primary predictor variable. In each patient, two dental implants were inserted in the anterior mandible. For the test group, one dental implant socket was covered with CGF membrane, while the other socket was prepared conventionally for the control group. Implant stability, as measured by RFA, was the outcome variable. Measurements were taken using the Ostell device at the time of implant placement and at the 1st, 2nd and 4th weeks.

RESULTS

Mean implant stability quotients (ISQs) were 67.00±4.573 for the study group and 64.75±5.065 for the control group. The difference between the two groups was not statistically significant.

CONCLUSION

It was found that CGF did not provide beneficial effect on dental implant stability in the early healing period in type 2 bone.

Antiseptic sealant and a nanocoated implant-abutment interface improve the results of dental implantation

BACKGROUND

Clinical measures and implant design innovation to improve primary osseointegration and reduce the bacterial contamination of the peri-implant area are intended to reduce the incidence of late inflammatory complications in dental implantation.

PURPOSE

To study the effect of nanostructured coating and antiseptic sealant on the outcomes of dental implantation.

MATERIALS AND METHODS

Ninety-six individuals were clinically supervised. In the first group (Screw Ti + sealant), a special antiseptic sealant matrix was used; the same sealant was used with nanocoated implants in the second group (Nanocoat + sealant), and the conventional treatment protocol was used in the control group (Screw Ti). Patients were evaluated longitudinally during treatment and rehabilitation phases with clinical examinations, radiography, periodontal pathogen detection, and patient experience surveys.

RESULTS

For patients who received a nanocoated implant and an antiseptic sealant (Nanocoat + sealant), relatively better hygienic indices were observed; there was less contamination with periodontal pathogens, bone density remained at the required level, and the overall results of treatment were better.

CONCLUSIONS

Using a matrix for sealing the dental implant-abutment interface with a nanostructured surface provides reliable results regarding stable osseointegration and clinical and patient-reported outcomes of treatment success.

A review on the latest advancements in the non-invasive evaluation/monitoring of dental and trans-femoral implants

Dental implants and transcutaneous prostheses (trans-femoral implants) improve the quality of life of millions of people because they represent the optimal treatments to edentulism and amputation, respectively. The clinical procedures adopted by surgeons to insert these implants are well established. However, there is uncertainty on the outcomes of the post-operation recovery because of the uncertainty associated with the osseointegration process, which is defined as the direct, structural and functional contact between the living bone and the fixture. To guarantee the long-term survivability of dental or trans-femoral implants doctors sometimes implement non-invasive techniques to monitor and evaluate the progress of osseointegration. This may be done by measuring the stability of the fixture or by assessing the quality of the bone-fixture interface. In addition, care providers may need to quantify the structural integrity of the bone-implant system at various moments during the patients recovery. The accuracy of such non-invasive methods reduce recovery and rehabilitation time, and may increase the survival rate of the therapies with undisputable benefits for the patients. This paper provides a comprehensive review of clinically-approved and emerging non-invasive methods to evaluate/monitor the osseointegration of dental and orthopedic implants. A discussion about advantages and limitations of each method is provided based on the outcomes of the cases presented. The review on the emerging technologies covers the developments of the last decade, while the discussion about the clinically approved systems focuses mostly on the latest (2017-2018) findings. At last, the review also provides some suggestions for future researches and developments in the area of implant monitoring.

Systematic review of clinical and patient-reported outcomes following oral rehabilitation on dental implants with a tapered compared to a non-tapered implant design

BACKGROUND

Dental implants are available in different shapes.

AIMS

This systematic review aims to address whether tapered compared to non-tapered implants demonstrate similar clinical and patient-reported outcomes. The review follows the preferred reporting items for systematic reviews and meta-analyses (PRISMA) format.

MATERIALS & METHODS

We searched electronic databases including MEDLINE through PubMed and the Cochrane Central Register of Controlled Trials for randomized clinical trials (RCT) that compare tapered versus non-tapered implants with at least 10 treated participants and a minimum mean follow-up time of 3 years. There were no restrictions to a particular treatment indication or outcome measures. Two authors independently conducted screening, risk of bias assessment, and data extraction of eligible trials in duplicate. We applied the Cochrane risk of bias assessment tool to consider risk of bias.

RESULTS

We identified 18 different RCTs, of which three reported outcomes at 3 years or greater. The three trials described the results of 245 participants with 388 implants at 3 years, from the initially 306 participants with 494 implants at baseline. The three trials compared, respectively, two, two, and three different commercially available implant brands and reported only clinically insignificant differences. We judged all three trials to be at moderate risk of bias. The low number and heterogeneity of RCTs did not allow for meta-analyses.

DISCUSSION AND CONCLUSION

Appropriate professional judgment in clinical decision making must include a comprehensive diagnosis of the patient's jawbone quality and quantity and consideration of osteotomy protocol in accordance with the patient's treatment preferences, where the shape of the dental implant is only one contributory factor.

Effect of Titanium Implants Coated with Radiation-Crosslinked Collagen on Stability and Osseointegration in Rat Tibia

This study aimed to evaluate the titanium (Ti) implants coated with collagen type Ⅰ crosslinked using gamma-irrigation or glutaraldehyde (GA). The in vitro surface observations, quantification assay, and cell studies using human mesenchymal stem cells (hMSCs) were conducted. For in vivo experiments, the implants were divided into three groups and inserted into the rat tibias: control group (non-treated Ti implant), GA group (Ti implants coated with GA-crosslinked collagen) and 25 kGy group (Ti implants coated with gamma-radiation-crosslinked collagen at dose of 25 kGy). The animals were sacrificed at 4 weeks after implantation and the tissue sections were obtained. New bone volume (mm³) and bone-to-implant contact (BIC, %) within the region of interest (ROI) was measured. The in vitro results showed the highest osteogenic differentiation and levels of osteogenesis-related gene expressions in the 25 kGy group without cytotoxicity. The new bone volume of GA group was significantly higher than the control (p < 0.05). In the result of the BIC, the 25 kGy group was significantly higher than the control (p < 0.05). However, there was no significant difference between the experimental groups. Within the limitations of this study, Ti implant coated with gamma-radiation-crosslinked collagen has potential utility without side effects from chemical agents.

Development of a quantitative preclinical screening model for implant osseointegration in rat tail vertebra

Objectives

Functional tooth replacement and bone regeneration are parts of the daily practice in modern dentistry, but well-reproducible and relatively inexpensive experimental models are still missing. We aimed to develop a new small animal model to monitor osseointegration utilizing the combination of multiple evaluation protocols.

Material and methods

After cutting the tail between the C4 and C5 vertebrae in Wistar rats, costume made, parallel walled, non-threaded implants were placed into the center of the tail parallel with its longitudinal axis using a surgical guide. Osseointegration of the titanium implants was followed between 4 and 16 weeks after surgery applying axial extraction force, and resonance frequency analysis as functional tests, and histomorphometry and micro-CT as structural evaluations.

Results

In functional tests, we observed that both methods are suitable for the detection of the time-dependent increase in osseointegration, but the sensitivity of the pull-out technique (an approximately five times increase with rather low standard error) was much higher than that of the resonance frequency analysis. In structural evaluations, changes in the detected bone implant contact values measured by histomorphometry (yielding 1.5 times increase, with low variations of data) were more reliable than micro-CT based evaluations to screen the developments of contact between bone and implant.

Conclusion

Our results provide evidence that the caudal vertebrae osseointegration model is useful for the preclinical evaluation of implant integration into the bone.

Clinical relevance

The combination of the biomechanical and structural tests offers a well-reproducible small animal system that can be suitable for studying the integration of various implant materials and surface treatments.

Sclerostin-Neutralizing Antibody Enhances Bone Regeneration Around Oral Implants

BACKGROUND

Dental implants are an important option for replacement of missing teeth. A major clinical challenge is how best to accelerate bone regeneration and reduce the healing time for functional restoration after implant placement. A sclerostin-neutralizing antibody (Scl-Ab) has been shown to enhance alveolar bone formation and fracture repair. The aim of this study was to investigate the effects of systemic administration of Scl-Ab on dental implant osseointegration and bone regeneration in an experimental alveolar ridge tooth extraction model.

MATERIALS AND METHODS

To investigate the effects of Scl-Ab on bone regeneration and dental implant osseointegration, an experimental alveolar bone osteotomy rat model was adopted. One month after extraction of maxillary right first molars, osteotomy defects were created at the coronal aspect of each of the extraction sites, and 1 × 2-mm custom titanium implants were installed into the osteotomies. Coincident with implant placement, Scl-Ab was administered subcutaneously at a dose of 25 mg/kg twice weekly for 10-28 days and compared with a vehicle control. Animals were sacrificed 10, 14, and 28 days after surgery, and maxillae were harvested and analyzed by microcomputed tomography (microCT), histology, and histomorphometry.

RESULTS

microCT analysis demonstrated that the maxillary bone volume fraction was approximately 2- to 2.5-fold greater in Scl-Ab-treated animals compared with vehicle alone at days 14 and 28. Consistent with those findings, two-dimensional bone fill percentages within the coronal osteotomy sites were highest in Scl-Ab treatment groups at 28 days. In addition, bone-implant contact at 28 days was approximately twofold greater in the Scl-Ab group compared with the vehicle control.

CONCLUSIONS

These results indicate that systemic Scl-Ab administration enhances osseointegration and bone regeneration around dental implants. This approach offers potential as a treatment modality for patients with low bone mass or bone defects to achieve more predictable bone regeneration at alveolar bone defects and to enhance dental implant osseointegration.

Clinical Assessment of Dental Implant Stability During Follow-Up: What Is Actually Measured, and Perspectives

The optimization of loading protocols following dental implant insertion requires setting up patient-specific protocols, customized according to the actual implant osseointegration, measured through quantitative, objective methods. Various devices for the assessment of implant stability as an indirect measure of implant osseointegration have been developed. They are analyzed here, introducing the respective physical models, outlining major advantages and critical aspects, and reporting their clinical performance. A careful discussion of underlying hypotheses is finally reported, as is a suggestion for further development of instrumentation and signal analysis.

Two Variants of Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) with Additional Protein Domains: Synthesis in an Escherichia coli Heterologous Expression System

Two variants of recombinant human bone morphogenetic protein-2 (rhBMP-2) with additional N-terminal protein domains were obtained by expression in E. coli. The N-terminal domains were s-tag (15-a.a. oligopeptide from bovine pancreatic ribonuclease A) and lz (leucine zipper dimerization domain from yeast transcription factor GCN4). The s-tag-BMP-2 and lz-BMP-2 were purified by a procedure that excluded a long refolding stage. The resulting dimeric proteins displayed higher solubility compared to rhBMP-2 without additional protein domains. Biological activity of both proteins was demonstrated in vitro by induction of alkaline phosphatase in C2C12 cells, and the activity of s-tag-BMP-2 in vivo was shown in various experimental animal models.

Effect of microthreads on coronal bone healing of narrow-diameter implants with reverse-tapered design in beagle dogs

OBJECTIVES

The objective of this study was to investigate the effect of microthreads on the coronal bone healing of narrow-diameter implants with reverse-tapered design.

MATERIAL AND METHODS

A total of 52 implants were classified into two groups according to presence or absence of coronal microthreads, the reverse-tapered narrow-diameter implant (RTN) group, and the reverse-tapered narrow-diameter implant with microthreads (RTNM) group. The implants were installed in split-mouth design in the edentulous mandible of six dogs. Three animals were sacrificed at 4 weeks and three at 8 weeks. Resonance frequency analysis, bone measurement using microcomputed tomography (micro-CT), removal torque test, and histometric analysis were performed.

RESULTS

No significant differences in implant stability quotient value were observed between the groups at baseline, 4 weeks, or 8 weeks. Bone measurement using micro-CT showed that bone-implant contact volume (BICV) and bone-implant contact volume ratio (BICVR) in the coronal part of RTNM were statistically higher than those in RTN at 4 and 8 weeks. Histometric analysis showed statistically higher bone-implant contact length (BICL) in the coronal part of RTNM than in RTN at 4 weeks; however, bone-implant contact ratio (BICR) was not significantly different between the groups. At 8 weeks, the BICL and BICR did not differ significantly between the groups. Removal torque test showed no significant differences between the groups at 4 and 8 weeks.

CONCLUSIONS

The microthreads might facilitate more coronal bone-implant contact due to increased surface areas at an early healing phase; however, they did not significantly affect coronal bone healing at 8 weeks.

The influence of three different apical implant designs at stability and osseointegration process: experimental study in rabbits

OBJECTIVES

The aim of this study was to perform a histomorphometric and biomechanical comparison of three implants with different designs of the apical area to promote a better bone initial stability and its correlation with the osseointegration.

MATERIAL AND METHODS

Fifty-four tapered implants with same length, diameter and surface properties but with three different apical configurations (Group I: MK4: Group II: C1 and Group III: MK7) were inserted in the tibia of rabbits. Implant stability and bone formation were evaluated by resonance frequency analysis measured at 0, 6, 8 and 12 weeks and by histomorphometric analysis performed at 6, 8 and 12 weeks.

RESULTS

Statistical test to compare the stability through the implant stability quotient in the four times showed few differences between the groups and time periods proposed, with significance set at P < 0.05. In the bone-implant contact, by comparing the groups in the three times proposed, it was possible concluded that there is a similar behavior among the three implant design (P < 0.05).

CONCLUSION

With the limitations of this animal study, it can be concluded that the design of the apical area influences the implant stability and the bone-to-implant contact.

Stress Distribution on Short Implants at Maxillary Posterior Alveolar Bone Model With Different Bone-to-Implant Contact Ratio: Finite Element Analysis

The aim of this study was to evaluate the stress distribution of the short dental implants and bone-to-implant contact ratios in the posterior maxilla using 3-dimensional (3D) finite element models. Two different 3D maxillary posterior bone segments were modeled. Group 1 was composed of a bone segment consisting of cortical bone and type IV cancellous bone with 100% bone-to-implant contact. Group 2 was composed of a bone segment consisting of cortical bone and type IV cancellous bone including spherical bone design and homogenous tubular hollow spaced structures with 30% spherical porosities and 70% bone-to-implant contact ratio. Four-millimeter-diameter and 5-mm-height dental implants were assumed to be osseointegrated and placed at the center of the segments. Lateral occlusal bite force (300 N) was applied at a 25° inclination to the implants long axis. The maximum von Mises stresses in cortical and cancellous bones and implant-abutment complex were calculated. The von Mises stress values on the implants and the cancellous bone around the implants of the 70% bone-to-implant contact group were almost 3 times higher compared with the values of the 100% bone-to-implant contact group. For clinical reality, use of the 70% model for finite element analysis simulation of the posterior maxilla region better represents real alveolar bone and the increased stress and strain distributions evaluated on the cortical and cancellous bone around the dental implants.

Comparing the influence of crestal cortical bone and sinus floor cortical bone in posterior maxilla bi-cortical dental implantation: a three-dimensional finite element analysis

OBJECTIVE

This study aimed to compare the influence of alveolar ridge cortical bone and sinus floor cortical bone in sinus areabi-cortical dental implantation by means of 3D finite element analysis.

MATERIALS AND METHODS

Three-dimensional finite element (FE) models in a posterior maxillary region with sinus membrane and the same height of alveolar ridge of 10 mm were generated according to the anatomical data of the sinus area. They were either with fixed thickness of crestal cortical bone and variable thickness of sinus floor cortical bone or vice versa. Ten models were assumed to be under immediate loading or conventional loading. The standard implant model based on the Nobel Biocare implant system was created via computer-aided design software. All materials were assumed to be isotropic and linearly elastic. An inclined force of 129 N was applied.

RESULTS

Von Mises stress mainly concentrated on the surface of crestal cortical bone around the implant neck. For all the models, both the axial and buccolingual resonance frequencies of conventional loading were higher than those of immediate loading; however, the difference is less than 5%.

CONCLUSION

The results showed that bi-cortical implant in sinus area increased the stability of the implant, especially for immediately loading implantation. The thickness of both crestal cortical bone and sinus floor cortical bone influenced implant micromotion and stress distribution; however, crestal cortical bone may be more important than sinus floor cortical bone.

Inflammatory cytokine release is affected by surface morphology and chemistry of titanium implants

To investigate in vitro cellular cytokine expression in relation to commercially pure titanium discs, comparing a native surface to a fluorinated oxide nanotube surface. Control samples pure titanium discs with a homogenous wave of the margins and grooves and an often smeared-out surface structure. Test samples pure titanium discs with a fluorinated titanium oxide chemistry and surface morphology with nanopore/tube geometry characterized by ordered structures of nanotubes with a diameter of ≈ 120 nm, a spacing of ≈ 30 nm, and a wall thickness of ≈ 10 nm. Cross-section view showed vertically aligned nanotubes with similar lengths of ≈ 700 nm. Peripheral blood mononuclear leucocytes were cultured for 1, 3, and 6 days according to standard procedures. BioPlex Pro™ assays were used for analysis and detection of cytokines. Selected inflammatory cytokines are reported. A pronounced difference in production of the inflammatogenic cytokines was observed. Leucocytes exposed to control coins produced significantly more TNF-α, IL-1ß, and IL-6 than the test nanotube coins. The effect on the TH2 cytokine IL-4 was less pronounced at day 6 compared to days 1 and 3, and slightly higher expressed on the control coins. The morphology and surface chemistry of the titanium surface have a profound impact on basic cytokine production in vitro. Within the limitations of the present study, it seems that the fluorinated oxide nanotube surface results in a lower inflammatory response compared to a rather flat surface that seems to favour inflammation.

Association between implant apex and sinus floor in posterior maxilla dental implantation: A three-dimensional finite element analysis

The aim of the present study was to evaluate the effect of the association between the implant apex and the sinus floor in posterior maxilla dental implantation by means of three-dimensional (3D) finite element (FE) analysis. Ten 3D FE models of a posterior maxillary region with a sinus membrane and different heights of alveolar ridge with different thicknesses of sinus floor cortical bone were constructed according to anatomical data of the sinus area. Six models were constructed with the same thickness of crestal cortical bone and a 1-mm thick sinus floor cortical bone, but differing heights of alveolar ridge (between 10 and 14 mm). The four models of the second group were similar (11-mm-high alveolar ridge and 1-mm-thick crestal cortical bone) but with a changing thickness of sinus floor cortical bone (between 0.5 and 2.0 mm). The standard implant model based on the Nobel Biocare^® implant system was created by computer-aided design (CAD) software and assembled into the models. The materials were assumed to be isotropic and linearly elastic. An inclined force of 129 N was applied. The maximum von Mises stress, stress distribution, implant displacement and resonance frequencies were calculated using CAD software. The von Mises stress was concentrated on the surface of the crestal cortical bone around the implant neck with the exception of that for the bicortical implantation. For immediate loading, when the implant apex broke into or through the sinus cortical bone, the maximum displacements of the implant, particularly at the implant apex, were smaller than those in the other groups. With increasing depth of the implant apex in the sinus floor cortical bone, the maximum displacements decreased and the implant axial resonance frequencies presented a linear upward tendency, but buccolingual resonance frequencies were hardly affected. This FE study on the association between implant apex and sinus floor showed that having the implant apex in contact with, piercing or breaking through the sinus floor cortical bone benefited the implant stability, particularly for immediate loading.

High-frequency loading positively impacts titanium implant osseointegration in impaired bone

High-frequency loading via whole body vibration promotes bone formation and increases bone strength. Whether this translates to positive titanium implant osseointegration in osteoporotic bone was explored in this animal study. An anabolic effect of not only bisphosphonate treatment but also high-frequency loading on implant osseointegration in osteoporotic bone was observed.

INTRODUCTION

The present study investigated the impact of high-frequency (HF) loading, applied via whole body vibration (WBV), on titanium implant osseointegration in healthy versus ovariectomy-induced compromised versus pharmacologically treated compromised bone.

METHODS

A custom-made Ti implant was inserted into the metaphyseal tibia of 59 rats and left to heal for either 4 or 14 days. Rats were divided into six groups according to their hormonal and mechanical status. WBV, consisting of 10 consecutive frequency steps at an acceleration of 0.3 g, was applied daily for either 4 or 14 days. Tissue samples were processed for quantitative histology at the tibial cortical and medullar level. Data were analyzed by three-way ANOVA and by post hoc pairwise comparisons.

RESULTS

The bone healing response at the interface and surrounding titanium implants was negatively influenced by osteoporotic bone conditions, mainly at the trabecular bone level. Furthermore, the administration of bisphosphonates for preventing the ovariectomy-induced impaired peri-implant response was successful. Finally, the effect of HF WBV loading on the peri-implant bone healing was dependent on the bone condition and was anabolic solely in untreated osteoporotic trabecular bone when applied for an extended period of time.

CONCLUSIONS

The bone healing response to implant installation is compromised in osteoporotic bone conditions, in particular at the trabecular bone compartment. Meanwhile, not only pharmacological treatment but also mechanical loading via HF WBV can exert a positive effect on implant osseointegration in this specific bone micro-environment. The peri-implant cortical bone, however, seems to be less sensitive to HF WBV loading influences.

Microbial Leakage at the Implant-Abutment Connection Due to Implant Insertion Maneuvers: Cross-Sectional Study 5 Years Postloading in Healthy Patients

The aim of this study was to test if stress on the prosthetic connection during insertion maneuvers can induce micro-warping at the implant connection. From September 2011 to July 2013, patients with implants loaded for at least 5 years that were placed with 2 different insertion implant mounters-MP (conventional) and ME (mountless)-were selected from all of those who had received dental implant therapy in the past and were attending routine check-up or spontaneous visits during the study period. Samples were obtained from inside the connection and the abutment surface using absorbent sterile paper tips. Quantitative real-time polymerase chain reaction was performed for total bacterial counts and loads of Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Tannerella forsythensis (Tf), Treponema denticola (Td), Prevotella intermedia (Pi), Peptostreptococcus micros (Pm), Fusobacterium nucleatum (Fn), Campylobacter rectus (Cr), Eikenella corrodens (Ec), and Candida albicans (Ca). The analysis of variance test was used to test for differences. Nine patients (20 implants) were included in the MP group and 5 patients (10 implants) in the ME group. Regarding the red complex, Tf was seen in 80% and 30% of MP and ME implants, respectively (P < .001). Significant differences were also found in microbial load. For Td, proportions were 45% vs 10% (P = .022), with no significant differences at load levels. Regarding the orange complex, higher prevalence values were found in MP implants, although differences were nonsignificant. Microbial load levels for orange complex bacteria were higher for MP than ME, and these differences were statistically significant for Fn (4.94 vs 3.09; P = .001). Finally, Ec was detected only in the MP group, and Ca and Aa were not found in either group. Within its limitation (small sample size, retrospective analysis, indirect measurement method), the present study suggests that a mounter not affecting the prosthetic connection should be used to reduce microbial contamination of implants.

Retrospective clinical outcome of nanopolymorphic crystalline hydroxyapatite-coated and anodic oxidized titanium implants for 10 years

PURPOSE

Nanopolymorphic crystalline Hydroxyapatite (HA)-coated implants were different in surface property from conventional HA-coated implants subjected to previous clinical studies. The purposes of the present study were to retrospectively evaluate 10-years clinical outcome of the HA-coated implants (HA implants) with a comparison to the same system implants with anodic oxidized titanium surface (Ti implants).

METHODS

Cumulative survival rate (CSR) of HA or Ti implants placed in 183 patients (55±12.4 years old) over two decades was calculated with life table analysis. Differences in CSR at each interval year, sex, age, frequency of number of implant placement according to implant location and diameter were compared between both types of implants.

RESULTS

Total 455 HA implants and 255 Ti implants were included. CSR at upper molar site was consistently higher in HA implants than Ti implants until 8 years after placement. The values after 10 years was 89.9% or 77.7% in HA or Ti implants, respectively. There were no significant differences in overall CSR at any interval year. HA implants were more distributed at upper molar site but less at lower molar site than Ti implants. Diameter of HA implants tended to be wider than Ti implants.

CONCLUSIONS

Under limitation of this retrospective study, the nanopolymorphic crystalline HA-coated implants were more survived at upper molar site than anodic oxidized implants until 8 years after placement. This clinical outcome might attribute to differences in topographical and physicochemical characteristics between both types of implants.

Comparative assessment of the interfacial soft and hard tissues investing implants and natural teeth in the macaque mandible

OBJECTIVES

The aim of this study was to conduct a comparative qualitative and quantitative assessment of the interfacial soft and hard tissues investing implants and natural teeth.

MATERIALS AND METHODS

The test sample consisted of six adult healthy male Macaca fascicularis with three-unit splinted crowns, each crown supported by an Ankylos screw-shaped titanium implant. These implants were placed in the mandibular premolar-second molar region, one side by an immediate-loading (IL) and the other by delayed-loading (DL) protocol. The animals were sacrificed after 3 months of functional loading. Another two monkeys with natural dentition served as controls. Nondecalcified sections were prepared for assessment of optical intensities (OI) under a confocal laser scanning microscope.

RESULTS

In both the test (IL and DL) and control, the soft tissue complexes demonstrated a highly fluorescent keratinized layer and diminished cytoplasmic and enhanced membranous fluorescence in the remaining epithelium. Peri-implant mucosa was further characterized by an intense fluorescence at the junctional epithelium-implant interface and in the stromal mononuclear infiltrate. Connective tissue contact and periodontal ligament were weakly fluorescent. In hard tissues, a high fluorescence was observed in peri-implant woven bone and along the implant-bone interface. Mean OI was significantly higher in peri-implant woven bone than around teeth (P < 0.05). In the remaining soft and hard tissue complexes, no significant differences in mean OI between the test and control were observed (P > 0.05).

CONCLUSIONS

Present findings suggest that peri-implant woven bone is highly mineralized, while the peri-implant and gingival mucosa share structural similarities.

CLINICAL RELEVANCE

Optical intensities of interfacial tissues investing implants and teeth are related to their biological properties.

3D finite element modeling and analysis of dynamic force in bone drilling for orthopedic surgery

Three-dimensional finite element modeling and analysis are made to simulate the dynamic process of bone drilling during the orthopedic surgery. This study is proposed to evaluate the performance of various surgical tools and the possible pre-operative biohazard. In the simulation, the strain-stress curve of the bone is divided into linear elastic region and nonlinear plastic region according to the strain range. Rigid-plasticity and elasto-plasticity are used as bone material. The performances of twist drill bit and hollow drill bit are evaluated. The results of finite element analysis give different patterns of stress distribution on the two types of bone models and drill bits. The FE simulations show dynamic drilling process that the drill bit penetrates through the bone model. In vitro drilling experiment on porcine femur is conducted to measure the drilling force for the validation of the FEM.

Evaluation of local cancellous bone amelioration by poly-L-DL-lactide copolymers to improve primary stability of dental implants: a biomechanical study in sheep

OBJECTIVES

The aim of this study was to evaluate the clinical performance of local cancellous bone amelioration by a 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer with two different implant designs on primary stability and after 4 and 12 weeks of healing time.

MATERIAL AND METHODS

In six sheep, n = 36 implants (TH) with a conditioned, sandblasted, thermal acid-etched micro-rough surface and n = 36 implants (NB) with a highly crystalline and phosphate-enriched anodized titanium oxide surface were placed in the pelvic bone. Using an ultrasound-based process named Constant Amelioration Process (CAP), half of peri-implant trabecular bone structures were locally tested with 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer in both implant groups, TH and NB. The CAP technology employs ultrasonic energy to liquefy 70:30 poly-(L-lactide-co-D,L-Lacide) which enters the inter-trabecular space, leading to local reinforcement of the cancellous bone structure after solidification of the copolymer. The CAP test group was compared with reference implants placed with the conventional site preparation according to the manufacturers' description. Primary stability was assessed by the measurement of torque-in values and implant stability quotient (ISQ; n = 18 per group). Secondary stability was analyzed by biomechanical removal torque testing after 4 and 12 weeks (n = 9 per group).

RESULTS

Insertion torque value (23.3 N cm ± 13.6) of reference TH implants demonstrated a statistically significant (P = 0.00) difference in comparison with test TH implants (41.9 N cm ± 19.5). Reference NB implants revealed a statistically significant (P = 0.03) lower insertion torque value (23.7 N cm ± 13.5) than test NB implants (39.7 N cm ± 18.6). ISQ values increased for all implants from initial implant placement until sacrifice at 12 weeks. Reference TH implants tended to result in an increase in torque values from 4 weeks (181.9 N cm ± 22.8) to 12 weeks (225.7 N cm ± 47.4). This trend could be also proven for implants of test sites (4 week: 176.8 N cm ± 24.1; 12 week: 201.5 N cm ± 53.4). For reference, NB implants a non-significant increase in removal torque values from 4 weeks (146. 7 N cm ± 18.0) to 12 weeks (170.2 N cm ± 40.4) was observed. Removal torque values of test NB implants did not increase from 4 weeks (153.3 N cm ± 21.5) to 12 weeks (146.1 N cm ± 37.5).

CONCLUSION

Biomechanical data proved significantly enhanced primary stability of dental implants after local amelioration without long-term sequelae and irrespective of implant design. After 4- and 12-week healing time, removal torque of locally test implants was as high as for control implants, and osseointegration was therefore not influenced by the CAP process. No correlation between ISQ values and torque values was found.

Torsional resonance frequency analysis: a novel method for assessment of dental implant stability

OBJECTIVES

To establish and experimentally validate a novel resonance frequency analysis (RFA) method for measurement of dental implant stability by analyzing torsional resonance frequency (TRF).

MATERIAL AND METHODS

A numerical study and in vitro measurements were performed to evaluate the feasibility and reliability of the method of torsional RFA (T-RFA) using a T-shaped bilateral cantilever beam transducer. The sensitivity of this method was assessed by measuring the TRFs of dental implants with 8 sizes of T-shaped transducers during polymerization, which simulated the process of bone healing around an implant. The TRFs of the test implants detected using this new method and the bending resonance frequencies (BRFs) measured by Osstell(®) ISQ were compared. TRFs and BRFs on implant models in polymethyl methacrylate (PMMA) blocks with three exposure heights were also measured to assess the specificity of this method.

RESULTS

Finite element analysis showed two bending modes (5333 and 6008 Hz) following a torsional mode (8992 Hz) in the lower rank frequency. During in vitro measurements, a bending formant (mean 6075 Hz) and a torsional formant (mean 10225 Hz) appeared, which were verified by multipoint measurement with invariable excitation frequency in the laboratory. In the self-curing resin experiments, the average growth rate at all time points of TRFs using the new method with Transducer II was 2.36% and that of BRFs using Osstell(®) ISQ was 1.97%. In the implant exposure height tests, the mean declined rate of TRFs was 2.06% and that of BRFs using Osstell(®) ISQ was 12.34%.

CONCLUSION

A novel method for assessment of implant stability through TRF was established using a T-shape transducer, which showed high reliability and sensibility. The method alleviated the effects of implant exposure height on the measurements compared with Osstell(®) ISQ. The application of T-RFA represents another way in the investigation of dental implant osseointegration.

Sequential platelet-derived growth factor-simvastatin release promotes dentoalveolar regeneration

OBJECTIVES

Timely augmentation of the physiological events of dentoalveolar repair is a prerequisite for the optimization of the outcome of regeneration. This study aimed to develop a treatment strategy to promote dentoalveolar regeneration by the combined delivery of the early mitogenic factor platelet-derived growth factor (PDGF) and the late osteogenic differentiation factor simvastatin.

MATERIALS AND METHODS

By using the coaxial electrohydrodynamic atomization technique, PDGF and simvastatin were encapsulated in a double-walled poly(D,L-lactide) and poly(D,L-lactide-co-glycolide) (PDLLA-PLGA) microspheres in five different modes: microspheres encapsulating bovine serum albumin (BB), PDGF alone (XP), simvastatin alone (SB), PDGF-in-core and simvastatin-in-shell (PS), and simvastatin-in-core and PDGF-in-shell (SP). The microspheres were characterized using scanning electronic microscopy, and the in vitro release profile was evaluated. Microspheres were delivered to fill large osteotomy sites on rat maxillae for 14 and 28 days, and the outcome of regeneration was evaluated by microcomputed tomography and histological assessments.

RESULTS

Uniform 20-μm controlled release microspheres were successfully fabricated. Parallel PDGF-simvastatin release was noted in the PS group, and the fast release of PDGF followed by the slow release of simvastatin was noted in the SP group. The promotion of osteogenesis was observed in XP, PS, and SP groups at day 14, whereas the SP group demonstrated the greatest bone fill, trabecular numbers, and thickest trabeculae. Bone bridging was evident in the PS and SP group, with significantly increased osteoblasts in the SP group, and osteoclastic cell recruitment was promoted in all bioactive molecule-treated groups. At day 28, osteogenesis was promoted in all bioactive molecule-treated groups. Initial corticalization was noted in the XP, PS, and SP groups. Osteoblasts appeared to be decreased in all groups, and significantly, a greater osteoclastic cell recruitment was noted in the SB and SP groups.

CONCLUSIONS

Both PDGF and simvastatin facilitate dentoalveolar regeneration, and sequential PDGF-simvastatin release (SP group) further accelerated the regeneration process through the enhancement of osteoblastogenesis and the promotion of bone maturation.

Heat and radiofrequency plasma glow discharge pretreatment of a titanium alloy promote bone formation and osseointegration

Orthopedic and dental implants manifest increased failure rates when inserted into low density bone. We determined whether chemical pretreatments of a titanium alloy implant material stimulated new bone formation to increase osseointegration in vivo in trabecular bone using a rat model. Titanium alloy rods were untreated or pretreated with heat (600°C) or radiofrequency plasma glow discharge (RFGD). The rods were then coated with the extracellular matrix protein fibronectin (1 nM) or left uncoated and surgically implanted into the rat femoral medullary cavity. Animals were euthanized 3 or 6 weeks later, and femurs were removed for analysis. The number of trabeculae in contact with the implant surface, surface contact between trabeculae and the implant, and the length and area of bone attached to the implant were measured by histomorphometry. Implant shear strength was measured by a pull-out test. Both pretreatments and fibronectin enhanced the number of trabeculae bonding with the implant and trabeculae-to-implant surface contact, with greater effects of fibronectin observed with pretreated compared to untreated implants. RFGD pretreatment modestly increased implant shear strength, which was highly correlated (r(2) = 0.87-0.99) with measures of trabecular bonding for untreated and RFGD-pretreated implants. In contrast, heat pretreatment increased shear strength 3-5-fold for both uncoated and fibronectin-coated implants at 3 and 6 weeks, suggesting a more rapid increase in implant-femur bonding compared to the other groups. In summary, our findings suggest that the heat and RFGD pretreatments can promote the osseointegration of a titanium alloy implant material.

The influence of surface treatment on the implant roughness pattern

An important parameter for the clinical success of dental implants is the formation of direct contact between the implant and surrounding bone, whose quality is directly influenced by the implant surface roughness. A screw-shaped design and a surface with an average roughness of Sa of 1-2 µm showed a better result. The combination of blasting and etching has been a commonly used surface treatment technique. The versatility of this type of treatment allows for a wide variation in the procedures in order to obtain the desired roughness.

Highly Nonlinear Solitary Waves for the Assessment of Dental Implant Mobility

In this paper we present a noninvasive technique based on the propagation of highly nonlinear solitary waves (HNSWs) to monitor the stability of dental implants. HNSWs are nondispersive mechanical waves that can form and travel in highly nonlinear systems, such as one-dimensional chains of spherical particles. The technique is based on the hypothesis that the mobility of a dental implant affects certain characteristics of the HNSWs reflected at the interface between a crystal-based transducer and the implant. To validate the research hypothesis we performed two experiments: first we observed the hydration of commercial plaster to simulate at large the osseointegration process that occurs in the oral connective tissue once a dental-endosteal threaded implant is surgically inserted; then, we monitored the decalcification of treated bovine bones immersed in an acid bath to simulate the inverse of the osseointegration process. In both series, we found a good correlation between certain characteristics of the HNSWs and the stiffness of the material under testing.