Diabetes mellitus negatively affects peri-implant bone formation in the diabetic domestic pig

Sustained Release of Salicylic Acid for Halting Peri-Implantitis Progression in Healthy and Hyperglycemic Systemic Conditions: A Gottingen Minipig Model

To develop a peri-implantitis model in a Gottingen minipig and evaluate the effect of local application of salicylic acid poly(anhydride-ester) (SAPAE) on peri-implantitis progression in healthy, metabolic syndrome (MS), and type-2 diabetes mellitus (T2DM) subjects. Eighteen animals were allocated to three groups: (i) control, (ii) MS (diet for obesity induction), and (iii) T2DM (diet plus streptozotocin for T2DM induction). Maxillary and mandible premolars and first molar were extracted. After 3 months of healing, four implants per side were placed in both jaws of each animal. After 2 months, peri-implantitis was induced by plaque formation using silk ligatures. SAPAE polymer was mixed with mineral oil (3.75 mg/μL) and topically applied biweekly for up to 60 days to halt peri-implantitis progression. Periodontal probing was used to assess pocket depth over time, followed by histomorphologic analysis of harvested samples. The adopted protocol resulted in the onset of peri-implantitis, with healthy minipigs taking twice as long to reach the same level of probing depth relative to MS and T2DM subjects (∼3.0 mm), irrespective of jaw. In a qualitative analysis, SAPAE therapy revealed decreased levels of inflammation in the normoglycemic, MS, and T2DM groups. SAPAE application around implants significantly reduced the progression of peri-implantitis after ∼15 days of therapy, with ∼30% lower probing depth for all systemic conditions and similar rates of probing depth increase per week between the control and SAPAE groups. MS and T2DM conditions presented a faster progression of the peri-implant pocket depth. SAPAE treatment reduced peri-implantitis progression in healthy, MS, and T2DM groups.

Dental implants in large animal models with experimental systemic diseases: A systematic review

This systematic review aims to identify and discuss the most used methodologies in pre-clinical studies for the evaluation of the implementation of dental implants in systemically compromised pigs and sheep. This study provides support and guidance for future research, as well as for the prevention of unnecessary animal wastage and sacrifice. Preferred Reporting for Systematic Reviews and Meta-Analyses (PRISMA) was used as a guideline; electronic searches were performed in PubMed, Scopus, Scielo, Web of Science, Embase, Science Direct, Brazilian Bibliography of Dentistry, Latin American and Caribbean Literature in Health Sciences, Directory of Open Access Journals, Database of Abstracts of Reviews of Effects, and gray literature until January 2022 (PROSPERO/CRD42021270119). Sixty-eight articles were chosen from the 2439 results. Most studies were conducted in pigs, mainly the Göttinger and Domesticus breeds. Healthy animals with implants installed in the jaws were predominant among the pig studies. Of the studies evaluating the effect of systemic diseases on osseointegration, 42% were performed in osteoporotic sheep, 32% in diabetic sheep, and 26% in diabetic pigs. Osteoporosis was primarily induced by bilateral ovariectomy and mainly assessed by X-ray densitometry. Diabetes was induced predominantly by intravenous streptozotocin and was confirmed by blood glucose analysis. Histological and histomorphometric analyses were the most frequently employed in the evaluation of osseointegration. The animal models presented unique methodologies for each species in the studies that evaluated dental implants in the context of systemic diseases. Understanding the most commonly used techniques will help methodological choices and the performance of future studies in implantology.

Bone reconstruction of extensive maxillomandibular defects in adults

Reconstruction of significant maxillomandibular defects is a challenge that has been much discussed over the last few decades. Fundamental principles were developed decades ago (bone bed viability, graft immobilization). Clinical decision-making criteria are highly relevant, including local/systemic factors and incision designs, the choice of material, grafting technique, and donor site morbidity. Stabilizing particulated grafts for defined defects-that is, via meshes or shells-might allow significant horizontal and vertical augmentation; the alternatives are onlay and inlay techniques. More significant defects might require extra orally harvested autologous bone blocks. The anterior iliac crest is often used for nonvascularized augmentation, whereas more extensive defects often require microvascular reconstruction. In those cases, the free fibula flap has become the standard of care. The development of alternatives is still ongoing (i.e., alloplastic reconstruction, zygomatic implants, obturators, distraction osteogenesis). Especially for these complex procedures, three-dimensional planning tools enable facilitated planning and a surgical workflow.

Bone regeneration in implant dentistry: Which are the factors affecting the clinical outcome?

The key factors that are needed for bone regeneration to take place include cells (osteoprogenitor and immune-inflammatory cells), a scaffold (blood clot) that facilitates the deposition of the bone matrix, signaling molecules, blood supply, and mechanical stability. However, even when these principles are met, the overall amount of regenerated bone, its stability over time and the incidence of complications may significantly vary. This manuscript provides a critical review on the main local and systemic factors that may have an impact on bone regeneration, trying to focus, whenever possible, on bone regeneration simultaneous to implant placement to treat bone dehiscence/fenestration defects or for bone contouring. In the future, it is likely that bone tissue engineering will change our approach to bone regeneration in implant dentistry by replacing the current biomaterials with osteoinductive scaffolds combined with cells and mechanical/soluble factors and by employing immunomodulatory materials that can both modulate the immune response and control other bone regeneration processes such as osteogenesis, osteoclastogenesis, or inflammation. However, there are currently important knowledge gaps on the biology of osseous formation and on the factors that can influence it that require further investigation. It is recommended that future studies should combine traditional clinical and radiographic assessments with non-invasive imaging and with patient-reported outcome measures. We also envisage that the integration of multi-omics approaches will help uncover the mechanisms responsible for the variability in regenerative outcomes observed in clinical practice.

Bone healing around implants placed in subjects with metabolically compromised systemic conditions

The aim of this study was to evaluate the bone healing of tight-fit implants placed in the maxilla and mandible of subjects compromised with metabolic syndrome (MS) and type-2 Diabetes Mellitus (T2DM). Eighteen Göttingen minipigs were randomly distributed into three groups: (i) control (normal diet), (ii) MS (cafeteria diet for obesity induction), (iii) T2DM (cafeteria diet for obesity induction + Streptozotocin for T2DM induction). Maxillary and mandibular premolars and molar were extracted. After 8 weeks of healing, implants with progressive small buttress threads were placed, and allowed to integrate for 6 weeks after which the implant/bone blocks were retrieved for histological processing. Qualitative and quantitative histomorphometric analyses (percentage of bone-to-implant contact, %BIC, and bone area fraction occupancy within implant threads, %BAFO) were performed. The bone healing process around the implant occurred predominantly through interfacial remodeling with subsequent bone apposition. Data as a function of systemic condition yielded significantly higher %BIC and %BAFO values for healthy and MS relative to T2DM. Data as a function of maxilla and mandible did not yield significant differences for either %BIC and %BAFO. When considering both factors, healthy and MS subjects had %BIC and %BAFO trend towards higher values in the mandible relative to maxilla, whereas T2DM yielded higher %BIC and %BAFO in the maxilla relative to mandible. All systemic conditions presented comparable levels of %BIC and %BAFO in the maxilla; healthy and MS presented significantly higher %BIC and %BAFO relative to T2DM in the mandible. T2DM presented lower amounts of bone formation around implants relative to MS and healthy. Implants placed in the maxilla and in the mandible showed comparable amounts of bone in proximity to implants.

Adipogenesis-Related Metabolic Condition Affects Shear-Stressed Endothelial Cells Activity Responding to Titanium

PURPOSE

Obesity has increased around the world. Obese individuals need to be better assisted, with special attention given to dental and medical specialties. Among obesity-related complications, the osseointegration of dental implants has raised concerns. This mechanism depends on healthy angiogenesis surrounding the implanted devices. As an experimental analysis able to mimic this issue is currently lacking, we address this issue by proposing an in vitro high-adipogenesis model using differentiated adipocytes to further investigate their endocrine and synergic effect in endothelial cells responding to titanium.

MATERIALS AND METHODS

Firstly, adipocytes (3T3-L1 cell line) were differentiated under two experimental conditions: Ctrl (normal glucose concentration) and High-Glucose Medium (50 mM of glucose), which was validated using Oil Red O Staining and inflammatory markers gene expression by qPCR. Further, the adipocyte-conditioned medium was enriched by two types of titanium-related surfaces: Dual Acid-Etching (DAE) and Nano-Hydroxyapatite blasted surfaces (nHA) for up to 24 h. Finally, the endothelial cells (ECs) were exposed in those conditioned media under shear stress mimicking blood flow. Important genes related to angiogenesis were then evaluated by using RT-qPCR and Western blot.

RESULTS

Firstly, the high-adipogenicity model using 3T3-L1 adipocytes was validated presenting an increase in the oxidative stress markers, concomitantly with an increase in intracellular fat droplets, pro-inflammatory-related gene expressions, and also the ECM remodeling, as well as modulating mitogen-activated protein kinases (MAPKs). Additionally, Src was evaluated by Western blot, and its modulation can be related to EC survival signaling.

CONCLUSION

Our study provides an experimental model of high adipogenesis in vitro by establishing a pro-inflammatory environment and intracellular fat droplets. Additionally, the efficacy of this model to evaluate the EC response to titanium-enriched mediums under adipogenicity-related metabolic conditions was analyzed, revealing significant interference with EC performance. Altogether, these data gather valuable findings on understanding the reasons for the higher percentage of implant failures in obese individuals.

Gene-activated titanium implants for gene delivery to enhance osseointegration

Osseointegration is the direct and intimate contact between mineralized tissue and titanium implant at the bone-implant interface. Early establishment and stable maintenance of osseointegration is the key to long-term implant success. However, in patients with compromised conditions such as osteoporosis and patients beginning early load-bearing activities such as walking, lower osseointegration around titanium implants is often observed, which might result in implant early failure. Gene-activated implants show an exciting prospect of combining gene delivery and biomedical implants to solve the problems of poor osseointegration formation, overcoming the shortcomings of protein therapy, including rapid degradation and overdose adverse effects. The conception of gene-activated titanium implants is based on "gene-activated matrix" (GAM), which means scaffolds using non-viral vectors for in situ gene delivery to achieve a long-term and efficient transfection of target cells. Current preclinical studies in animal models have shown that plasmid DNA (pDNA), microRNA (miRNA), and small interference RNA (siRNA) functionalized titanium implants can enhance osseointegration with safety and efficiency, leading to the expectation of applying this technique in dental and orthopedic clinical scenarios. This review aims to comprehensively summarize fabrication strategies, current applications, and futural outlooks of gene-activated implants, emphasizing nucleic acid targets, non-viral vectors, implant surface modification techniques, nucleic acid/vector complexes loading strategies.

Peri-Implant Repair Using a Modified Implant Macrogeometry in Diabetic Rats: Biomechanical and Molecular Analyses of Bone-Related Markers

DM has a high prevalence worldwide and exerts a negative influence on bone repair around dental implants. Modifications of the microgeometry of implants have been related to positive results in bone repair. This study assessed, for the first time, the influence of an implant with modified macrodesign based on the presence of a healing chamber in the pattern of peri-implant repair under diabetic conditions. Thirty Wistar rats were assigned to receive one titanium implant in each tibia (Control Implant (conventional macrogeometry) or Test Implant (modified macrogeometry)) according to the following groups: Non-DM + Control Implant; Non-DM + Test Implant; DM + Control Implant; DM + Test Implant. One month from the surgeries, the implants were removed for counter-torque, and the bone tissue surrounding the implants was stored for the mRNA quantification of bone-related markers. Implants located on DM animals presented lower counter-torque values in comparison with Non-DM ones, independently of macrodesign (p < 0.05). Besides, higher biomechanical retention levels were observed in implants with modified macrogeometry than in the controls in both Non-DM and DM groups (p < 0.05). Moreover, the modified macrogeometry upregulated OPN mRNA in comparison with the control group in Non-DM and DM rats (p < 0.05). Peri-implant bone repair may profit from the use of implants with modified macrogeometry in the presence of diabetes mellitus, as they offer higher biomechanical retention and positive modulation of important bone markers in peri-implant bone tissue.

Strontium-incorporated titanium implant surfaces treated by hydrothermal treatment enhance rapid osseointegration in diabetes: A preclinical vivo experimental study

OBJECTIVES

The aim of the current study was to explore effects of strontium-incorporated titanium implant surfaces by hydrothermal treatment on osseointegration in diabetic rats.

MATERIALS AND METHODS

The surface characteristics of SLA and SLA-Sr surfaces were detected by related instruments. Thirty-six male Sprague-Dawley rats were induced into diabetes, and thirty-six rats were normal. SLA and SLA-Sr implants were, respectively, inserted into bilateral tibial metaphysis of each rat. Percentage of bone-to-implant contact (BIC%) and percentage of bone area (BA%) were analyzed at 4 and 8 weeks after implantation. Immunohistochemistry of osteoprotegerin (OPG) and Wnt5a were conducted at 1 and 4 weeks. Gene expression levels of inflammatory cytokines and related signaling molecules in peri-implant bone tissue were detected at 3 and 7 days.

RESULTS

Strontium was uniformly distributed on SLA-Sr surfaces, and it was released in an effective concentration range. SLA-Sr surfaces showed significantly higher BIC% in diabetic rats at 4 (p < .05) and 8 weeks (p < .05). Besides, it displayed higher BIC% at 4 weeks (p < .05) in normal rats. Also, SLA-Sr surfaces upregulated expression of OPG at 4 weeks (p < .05) in diabetic rats. What's more, SLA-Sr surfaces downregulated inflammation (TNF-α, IL-1β, and IL-6; p < .01) in diabetic rats at 3 days. In addition, expression of Wnt5a and ROR2 was upregulated (p < .05) at 7 days after implantation under diabetes.

CONCLUSION

It is suggested that strontium-incorporated titanium implant surfaces by hydrothermal treatment could enhance implant osseointegration as compared with SLA implant surfaces in diabetic rats.

Histomorphometric analysis of implant osseointegration using hydrophilic implants in diabetic rats

OBJECTIVES

To evaluate peri-implant bone formation of titanium implants using an in vivo rat model with and without uncontrolled diabetes mellitus (DM) to evaluate osseointegration of hydrophobic (Neoporos®) and hydrophilic (Acqua®) surfaces.

MATERIALS AND METHODS

54 rats were divided into two groups: DM group (DMG) (streptozotocin-induced diabetes) and a control group (CG). Implants with hydrophobic (Neoporos®) and hydrophilic surfaces (Acqua®) were placed in the left or right tibia of animals. Animals were further divided into three groups (n = 9) euthanized after 7, 14, or 28 days. Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were assessed in total, cortical, and medullary areas.

RESULTS

The DMG group, after a 7-day healing period, yielded with the Acqua implants presented significantly higher total BIC (+37.9%; p=0.03) and trabecular BIC (%) (+46.3%; p=0.02) values in comparison to the Neoporos implants. After 28 days of healing, the CG yielded that the cortical BAFO of Acqua implants to be significantly, 14%, higher (p=0.04) than Neoporos implants.

CONCLUSION

The positive effects of the Acqua surface were able to counteract the adverse impact of uncontrolled DM at early osseointegration periods. After 28 days in vivo, the metabolic systemic impairment caused by DM overcame the surface treatment effect, leading to impaired osseointegration in both hydrophilic and hydrophobic implants.

CLINICAL RELEVANCE

The adverse effects of diabetes mellitus with respect to bone healing may be minimized by deploying implants with strategically modified surfaces. This study evaluated the effects of implants with Acqua® and Neoporos® surfaces in both diabetic and healthy animals. During the initial healing period in diabetic animals, the hydrophilic surface was demonstrated to have beneficial effect on osseointegration in comparison to the hydrophobic surface. The results provide an insight into early healing, but the authors suggest that a future short-term and long-term clinical study is needed to assess the possible benefit of the Acqua® implant as well as in increasing the predictability of implant osseointegration.

Zoledronate Causes a Systemic Shift of Macrophage Polarization towards M1 In Vivo

BACKGROUND

Immunomodulatory properties of bisphosphonates (BP) are suggested to contribute to the development of medication-associated osteonecrosis of the jaw (MRONJ). Furthermore, bisphosphonate-derived immune modulation might contribute to the anti-metastatic effect observed in breast cancer patients. Macrophages are potential candidates for the mediation of immunomodulatory effects of bisphosphonates. The study aimed to investigate the influence of bisphosphonates alone and in combination with surgical trauma on systemic macrophage polarization (M1 vs. M2) using an in vivo rat model.

METHODS

A total of 120 animals were divided into four groups. Groups 2 and 4 were treated with 8 × 40 μg/kg body weight of the BP Zoledronate i.p. (week 0-7). Groups 3 and 4 were exposed to surgical trauma (week 8, tooth extraction + tibia fracture), whereas in Group 1 neither medication nor surgical trauma was applied. After 8, 10, 12 and 16 weeks, skin, lung and spleen were immunohistochemically examined for macrophage polarization via expression analysis of CD68, CD163 and iNOS using a tissue microarray (TMA).

RESULTS

A significant shift of macrophage polarization towards M1 was observed in skin, spleen and lung tissue of animals, with and without surgical trauma, treated with BP when compared to those without BP application. Surgical trauma did not cause a significant increase towards M1 polarization.

CONCLUSIONS

BP application leads to a systemic pro-inflammatory situation in vivo, independent of surgical trauma, as evidenced by the shift in macrophage polarization towards M1 in various somatic tissues. This provides a possible explanation for the clinically observed anti-tumor effect of bisphosphonates and might also contribute to pathogenesis of MRONJ.

Inhibition of GDF11 could promote bone healing in the tooth extraction socket and facilitate mesenchymal stem cell osteogenic differentiation in T2DM pigs

BACKGROUND

Growth differentiation factor 11 (GDF11) might be a key factor responsible for the weakening of mesenchymal stem cell (MSC) osteogenic differentiation in tooth extraction sockets in patients with type 2 diabetes mellitus (T2DM). This study aimed to confirm that inhibition of GDF11 could promote bone healing in tooth extraction sockets and facilitate MSC osteogenic differentiation under T2DM conditions.

METHODS

Three streptozotocin-induced T2DM pig models and two control pig models were established. The T2DM pigs were treated with an intrasocket injection of GDF11 inhibitor in the left mandible, whereas the right side was maintained for natural healing. The postextraction socket healing of the T2DM pigs was compared with that of nondiabetic controls. Healing was quantitatively verified by microcomputed tomography, and the GDF11 expression level was detected. MSCs from T2DM pig sockets were cultured and treated with a GDF11 inhibitor. The osteogenic differentiation ability of MSCs was also compared among groups.

RESULTS

The expression of GDF11 in the tooth extraction sockets from T2DM pigs increased significantly post extraction. Bone healing was promoted by periodic injection of the GDF11 inhibitor into the extraction sockets of T2DM pigs. Furthermore, the osteogenic differentiation ability of T2DM-MSCs was improved in pigs treated with the GDF11 inhibitor.

CONCLUSIONS

GDF11 inhibition could promote bone healing in the tooth extraction socket and facilitate MSC osteogenic differentiation under T2DM conditions. GDF11 could be a potential therapeutic target for undesirable alveolar bone healing in T2DM patients.

Evaluation of biologic implant success parameters in type 2 diabetic glycemic control patients versus health patients: A meta-analysis

AIM

The aim of the present systematic literature review was to evaluate bleeding on probing (BOP), pocket depth (PD), and marginal bone loss (MBL) in type 2 diabetes mellitus (T2DM) control patients.

METHODS

An electronic literature search was conducted through PubMed, Web of Science, Cochrane, Embase, and ScienceDirect. The search included prospective human clinical studies that analyzed the success of dental implants in T2DM control patients. For inclusion, studies should have had a minimum of 1-year follow up and should have assessed the following parameters: MBL, BOP and PD. Prior to meta-analysis, all of the studies were assessed for quality, bias, and heterogeneity.

RESULTS

Risk of bias analysis indicated that all studies were of moderate quality. After a full-text evaluation, only seven studies met the inclusion criteria for this meta-analysis, with a combined total of 443 patients and 530 dental implants. The meta-analysis indicated a statistically significant difference between parameters of implants placed in the glycemic-controlled group and healthy group in MBL (P < .001), BOP (P < .04), and PD (P < .001).

CONCLUSION

The results of the present study indicated that, despite being glycemic controlled, patients with T2DM were associated with a higher risk of peri-implant disease.

Effect of Obesity or Metabolic Syndrome and Diabetes on Osseointegration of Dental Implants in a Miniature Swine Model: A Pilot Study

PURPOSE

The increasing prevalence of obesity or metabolic syndrome (O/MS) and type 2 diabetes mellitus (DM) remains a global health concern. Clinically relevant and practical translational models mimicking human characteristics of these conditions are lacking. This study aimed to demonstrate proof of concept of the induction of stable O/MS and type 2 DM in a Göttingen minipig model and validate both of these disease-adjusted Göttingen minipig models as impaired healing models for the testing of dental implants.

MATERIALS AND METHODS

Nine minipigs were split into 3 groups-control (normal diet), obese (cafeteria diet), and diabetic (cafeteria diet plus low-dosage streptozotocin)-followed by placement of dental implants. Inflammatory markers including tumor necrosis factor α, C-reactive protein, and cortisol were recorded for each study group. Removal torque was measured, and histomorphometric analysis (bone-to-implant contact and bone area fraction occupancy) was performed.

RESULTS

O/MS pigs showed, on average, a 2-fold increase in plasma C-reactive protein (P < .05) and cortisol (P < .09) concentrations compared with controls; DM pigs showed, on average approximately, a 40-fold increase in plasma tumor necrosis factor α levels (P < .05) and a 2-fold increase in cortisol concentrations (P < .05) compared with controls. The impact of O/MS and DM on implants was determined. The torque to interface failure was highest in the control group (200 N-cm) and significantly lower in the O/MS (90 N-cm) and DM (60 N-cm) groups (P < .01). Bone formation around implants was significantly greater in the control group than in the O/MS and DM groups (P < .02).

CONCLUSIONS

Both O/MS and DM minipigs express a human-like disease phenotype, and both presented bone-healing impairment around dental implants. Our finding of no significant difference between type 2 DM and O/MS in bone formation around implants provides evidence that further investigation of the impact of O/MS is warranted.

EB 2017 Article: Changes in advanced glycation end products, beta-defensin-3, and interleukin-17 during diabetic periodontitis development in rhesus monkeys

The bidirectional relationship between diabetes mellitus (DM) and periodontal disease has drawn great attention; however, the mechanisms underlying their association remain unclear. In this study, we aimed to develop a rhesus monkey model of diabetic periodontitis and explore the potential mechanisms by which DM affects the progression of periodontal disease. Three healthy rhesus monkeys were selected as the control group. Five streptozotocin-induced diabetic rhesus monkeys were chosen as the experimental group. Ligature placement was used to induce periodontitis. The changes in the levels of advanced glycation end products (AGEs), beta-defensin-3 (BD-3), and interleukin-17 (IL-17) were measured using enzyme-linked immunosorbent assays (ELISA) and real-time reverse transcription polymerase chain reaction (RT-PCR) at different stages during disease progression. Periodontitis was confirmed by clinical assessment, radiographic images, and histological examination. Significant changes in the levels of AGEs and BD-3 in serum were observed at the periodontitis stage in diabetic rhesus monkeys ( P < 0.05). The expression of BD-3 mRNA in the gingiva of diabetic group at baseline was significantly high ( P < 0.05). Diabetic monkeys exhibited significantly enhanced IL-17 mRNA expression at the periodontitis stage ( P < 0.05). Our findings indicated that the rhesus monkey can serve as an ideal model for exploring the pathogenesis of diabetic periodontitis, and the hyperglycemic environment may accelerate inflammatory response and weaken the defense system in periodontal tissues. Impact statement The mechanism underlying the association between diabetes mellitus (DM) and periodontal disease is not yet fully understood. Hence, there is a need to establish animal models to reveal the effect of DM on the pathogenesis of periodontitis. In this study, we explored the appropriate methods for inducing periodontitis and shortening the modeling time in rhesus monkeys, to investigate the pathogenesis of diabetic periodontitis and develop innovative therapies. Our results suggest that a hyperglycemic environment might lead to the destruction of periodontal tissues by accelerating inflammatory response and weakening the defense system in periodontal tissues. Therefore, this study has significant treatment implications regarding the regulation of the immune response against periodontal diseases in patients with DM.

The Effects of Hierarchical Micro/Nano-Structured Titanium Surface on Osteoblast Proliferation and Differentiation Under Diabetic Conditions

PURPOSE

The aim of the present study was to mimic the hierarchical structure of bone tissues by simple sandblasting/acid-etching and anodization to investigate the effects of such surface characteristics on proliferation and differentiation of osteoblasts in high glucose concentrations. By the way, the effects of high glucose levels on osteoblast functions were tested.

METHODS

MC3T3-E1 cells cultured on sand-blasted and acid-etched (SLA) surface and nano-modified SLA (NMSLA) surface were subjected to normal serum (NS) and diabetic serum (DS), respectively. The surface characteristics were evaluated by scanning electron microscopy. Cell proliferation was assessed using MTT assay. The levels of alkaline phosphatase (ALP) activity and mineralization were measured and compared. Real-time polymerase chain reaction was applied to detect the expression levels of osteogenic genes.

RESULTS

NMSLA significantly increased cell proliferation at time points ranging from 3 to 7 days under both serums. Cells cultured on NMSLA surfaces displayed significantly higher ALP activities and mineralization. The expression levels of Runx2 (indicates runt-related protein 2), collagen I (COL1), and osteocalcin (OCN) were notably increased on NMSLA surface compared with SLA surface. Moreover, we found that high glucose increased osteoblast proliferation but decreased differentiation of osteoblast slightly.

CONCLUSION

The hierarchical micro/nano-structured titanium surface has a favorable biocompatibility on simultaneously improving osteoblast proliferation and differentiation in diabetic serum.

Does Oxidative Stress Play a Role in Altered Characteristics of Diabetic Bone? A Systematic Review

Diabetes mellitus (DM) has been associated with increased bone fracture rates, impaired bone regeneration, delayed bone healing, and depressed osteogenesis. However, the plausible pathogenic mechanisms remain incompletely understood. The aim of the present systematic review was to investigate whether oxidative stress (OS) plays a role in altered characteristics of diabetic bone under in vivo conditions. An electronic search of the MEDLINE (via PubMed) and Embase databases was performed. In vivo animal studies involving DM and providing information regarding assessment of OS markers combined with analyses of bone histology/histomorphometry parameters were selected. A descriptive analysis of selected articles was performed. Ten studies were included in the present review. Both bone formation and bone resorption parameters were significantly decreased in the diabetic groups of animals compared to the healthy groups. This finding was consistent regardless of different animal/bone models employed or different evaluation periods. A statistically significant increase in systemic and/or local OS status was also emphasised in the diabetic groups in comparison to the healthy ones. Markers of OS were associated with histological and/or histomorphometric parameters, including decreased trabecular bone and osteoid volumes, suppressed bone formation, defective bone mineralisation, and reduced osteoclastic activity, in diabetic animals. Additionally, insulin and antioxidative treatment proved to be efficient in reversing the deleterious effects of high glucose and associated OS. The present findings support the hypotheses that OS in the diabetic condition contributes at least partially to defective bone features, and that antioxidative supplementation can be a valuable adjunctive strategy in treating diabetic bone disease, accelerating bone healing, and improving osteointegration.

The influence of direct laser metal sintering implants on the early stages of osseointegration in diabetic mini-pigs

Background

High failure rates of oral implants have been reported in diabetic patients due to the disruption of osseointegration. The aim of this study was to investigate whether direct laser metal sintering (DLMS) could improve osseointegration in diabetic animal models.

Methods

Surface characterizations were carried out on two types of implants. Cell morphology and the osteogenic-related gene expression of MG63 cells were observed under conditions of DLMS and microarc oxidation (MAO). A diabetes model in mini-pigs was established by intravenous injection of streptozotocin (150 mg/kg), and a total of 36 implants were inserted into the mandibular region. Micro-computed tomography (micro-CT) and histologic evaluations were performed 3 and 6 months after implantation.

Results

The Ra (the average of the absolute height of all points) of MAO surface was 2.3±0.3 µm while the DLMS surface showed the Ra of 27.4±1.1 µm. The cells on DLMS implants spread out more podia than those on MAO implants through cell morphology analysis. Osteogenic-related gene expression was also dramatically increased in the DLMS group. Obvious improvement was observed in the micro-CT and Van Gieson staining analyses of DLMS implants compared with MAO at 3 months, although this difference disappeared by 6 months. DLMS implants showed a higher bone–implant contact percentage (33.2%±11.2%) at 3 months compared with MAO group (18.9%±7.3%) while similar results were showed at 6 months between DLMS group (42.8%±10.1%) and MAO group (38.3%±10.8%).

Conclusion

The three-dimensional environment of implant surfaces with highly porous and fully interconnected channel and pore architectures can improve cell spreading and accelerate the progress of osseointegration in diabetic mini-pigs.

Effects of glucose concentration on osteogenic differentiation of type II diabetes mellitus rat bone marrow-derived mesenchymal stromal cells on a nano-scale modified titanium

BACKGROUND AND OBJECTIVE

Diabetes mellitus (DM) is a common disease worldwide. Patients with DM have an increased risk of losing their teeth compared with other individuals. Dental implants are a standard of care for treating partial or full edentulism, and various implant surface treatments have recently been developed to increase dental implant stability. However, some studies have reported that DM reduces osseointegration and the success rate of dental implants. The purpose of this study was to determine the effects of high glucose levels for hard tissue formation on a nano-scale modified titanium surface.

MATERIAL AND METHODS

Titanium disks were heated at 600°C for 1 h after treatment with or without 10 m NaOH solution. All disks were incubated with type II DM rat bone marrow-derived mesenchymal stromal cells before exposure to one of four concentrations of glucose (5.5, 8.0, 12.0 or 24.0 mm). The effect of different glucose concentrations on bone marrow-derived mesenchymal stromal cell osteogenesis and inflammatory cytokines on the nano-scale modified titanium surface was evaluated.

RESULTS

Alkaline phosphatase activity decreased with increasing glucose concentration. In contrast, osteocalcin production and calcium deposition were significantly decreased at 8.0 mm glucose, but increased with glucose concentrations over 8.0 mm. Differences in calcium/phosphate ratio associated with the various glucose concentrations were similar to osteocalcin production and calcium deposition. Inflammatory cytokines were expressed at high glucose concentrations, but the nano-scale modified titanium surface inhibited the effect of high glucose concentrations.

CONCLUSION

High glucose concentration increased hard tissue formation, but the quality of the mineralized tissue decreased. Furthermore, the nano-scale modified titanium surface increased mineralized tissue formation and anti-inflammation, but the quality of hard tissue was dependent on glucose concentration.

Animal models for peri-implant mucositis and peri-implantitis

The treatment of infectious diseases affecting osseointegrated implants in function has become a demanding issue in implant dentistry. Since the early 1990s, preclinical data from animal studies have provided important insights into the etiology, pathogenesis and therapy of peri-implant diseases. Established lesions in animals have shown many features in common with those found in human biopsy material. The current review focuses on animal studies, employing different models to induce peri-implant mucositis and peri-implantitis.

Peri-implant defect regeneration in the diabetic pig: A preclinical study

OBJECTIVES

The study aims to establish a peri-implant dehiscence-type bone defect in a diabetic animal model of human bone repair and to quantify the influence of diabetes on peri-implant bone regeneration.

MATERIAL AND METHODS

Experimental diabetes was induced in three domestic pigs by streptozotocin. Three animals served as healthy controls. After 12 months four standardized peri-implant dehiscence bone defects were surgically created in the ramus mandibulae. The animals were sacrificed after 90 days. Samples were histologically analyzed to quantify new bone height (NBH), bone-to-implant-contact (BIC), area of newly formed bone (NFB), bone-density (BD), and bone mineralization (BM) in the prepared defect (-D) and in a local control region (-L).

RESULTS

After 90 days, diabetic animals revealed a significantly lower BIC (p = 0.037) and BD (p = 0.041) in the defect area (-D). NBH and BM-D differences within the groups were not significant (p > 0.05). Significant more NFB was measured in the healthy control group (p = 0.046). In the region of local bone BIC-L was significant less in the diabetic group (p = 0.028). In the local control region BD-L and BM-L was lower in the diabetic group compared to the healthy control animals (p > 0.05).

CONCLUSION

Histological evidence indicates impaired peri-implant defect regeneration in a diabetic animal model.

Comparison of clinical and radiographic status of platform-switched implants placed in patients with and without type 2 diabetes mellitus: a 24-month follow-up longitudinal study

OBJECTIVE

The purpose of the present 24-month follow-up longitudinal study was to compare the clinical and radiographic status of platform-switched implants placed in patients with and without type 2 diabetes mellitus (T2DM).

MATERIAL AND METHODS

In total, 45 male non-smokers were included. In Group-1, there were 23 patients with T2DM, and patients in Group-2 comprised of 22 self-reported non-diabetic controls. Under local anesthesia, platform-switched implants were placed in the mandible. Peri-implant bleeding on probing (BOP), probing depth (PD), marginal bone loss (MBL) and hemoglobin A1c (HbA1c) levels were measured at 12 and 24 months of follow-up. Participants were also enrolled in a biannual oral hygiene maintenance program.

RESULTS

The mean age of participants in groups 1 and 2 were 42.4 years (40-46 years) and 41.8 years (39-44 years), respectively. In Group-1, the mean duration of T2DM was 14.5 ± 0.7 months. At 12 and 24 months of follow-up, there was no significant difference in the mean HbA1c levels among patients in groups 1 and 2. At 12 and 24 months of follow-up, there was no significant difference in peri-implant BOP, PD and MBL in both groups.

CONCLUSIONS

Platform-switched implants can remain clinically and radiographically stable in patients with T2DM in a manner similar to non-diabetic individuals. However, it is emphasized that bone loss around implants is influenced by several factors (such as oral hygiene status, glycemic control and tobacco smoking) and not merely platform switching.

Bisphosphonate Induces Osteonecrosis of the Jaw in Diabetic Mice via NLRP3/Caspase-1-Dependent IL-1β Mechanism

Diabetes mellitus is an established risk factor associated with bisphosphonate-related osteonecrosis of the jaw (BRONJ). Sustained activation of Nod-like receptor (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome contributes to the persistent inflammation and impaired cutaneous wound healing in diabetic mice and human. We have recently demonstrated a compelling linkage between M1 macrophages and BRONJ conditions in both murine and human diseases. The aim of this study was to determine whether NLRP3 inflammasome activation is involved in BRONJ development in diabetic mice. We showed an increased incidence of delayed oral wound healing and bone necrosis of extraction sockets in db/db mice compared with those in nondiabetic db/+ controls, which correlated with an elevated expression of NLRP3, caspase-1, and IL-1β in macrophages residing at local wounds. Constitutively, bone marrow-derived macrophages from db/db mice (db/db BMDMs) secrete a relatively higher level of IL-1β than those from db/+ mice (db/+ BMDMs). Upon stimulation by NLRP3 activators, the secretion of IL-1β by db/db BMDMs was 1.77-fold higher than that by db/+ BMDMs (p < 0.001). Systemic treatment of mice with zoledronate (Zol), a nitrogen-containing bisphosphonate, resulted in a 1.86- and 1.63-fold increase in NLRP3/caspase-1-dependent IL-1β secretion by db/+ and db/db BMDMs, respectively, compared with BMDMs derived from nontreated mice (p < 0.001). Importantly, systemic administration of pharmacological inhibitors of NLRP3 activation improved oral wound healing and suppressed BRONJ formation in db/db mice. Mechanistically, we showed that supplementation with intermediate metabolites of the mevalonate pathway, inhibitors of caspase-1 and NLRP3 activation, an antagonist for P2X7 R, or a scavenger of reactive oxygen species (ROS), robustly abolished Zol-enhanced IL-1β release from macrophages in response to NLRP3 activation (p < 0.001). Our findings suggest that diabetes-associated chronic inflammatory response may have contributed to impaired socket wound healing and rendered oral wound susceptible to the development of BRONJ via NLRP3 activation in macrophages.

Establishment of a new pull-out strength testing method to quantify early osseointegration-An experimental pilot study

OBJECTIVES

The animal study aims to evaluate a new experimental model for measuring sole the influence of the surface characteristics independent from implant macro-design on the level of osseointegration by registering the pull-out strength needed for removal of experimental devices with different surfaces from artificial defects.

MATERIAL AND METHODS

Seventy-two test bodies (36 with the FRIADENT(®) plus surface, 36 with the P15/HAp biofunctionalized surface) were inserted in six adult domestic pigs with artificial calvarial defects. The experimental devices were designed to fit in the defects leaving a gap between the test body and the local bone. After 21 days of healing, the animals were sacrificed and the test bodies were pulled out with a standardised reproducible pull-out device measuring the pull-out strength. The pull-out strength for both groups was compared.

RESULTS

Twenty-one days after insertion a mean force of 412 ± 142 N for the P15/HAp group and 183 ± 105 N for the FRIADENT(®) plus group was measured for the removal of the specimens from the calvarial bone. The difference between the groups was statistically significant (p < 0.0001).

CONCLUSION

The experimental set-up seems to be a suitable method when measuring the impact of implant surfaces on the early stage of osseointegration.

Influence of Glycemic Control on Peri-Implant Bone Healing: 12-Month Outcomes of Local Release of Bone-Related Factors and Implant Stabilization in Type 2 Diabetics

BACKGROUND

The poor glycemic status seems to be an important factor affecting implant complication rates, including peri-implant bone loss.

PURPOSE

This trial evaluated the influence of glycemic control of type 2 diabetes mellitus (T2DM) patients on implant stabilization and on the levels of bone markers in peri-implant fluid during the healing.

MATERIALS AND METHODS

Systemically healthy patients (SH,n = 19), better-controlled T2DM (BCDM,n = 16), and poorly controlled T2DM (PCDM,n = 16) indicated for implant therapy were recruited. The implant stability quotient (ISQ) was determined at implant placement, 3, 6, and 12 months. Levels of transforming growth factor- β (TGF-β), fibroblast growth factor (FGF), osteopontin (OPN), osteocalcin (OC), and osteoprotegerin (OPG) in the peri-implant fluid were quantified at 15 days, and 3, 6, and 12 months, using the Luminex assay.

RESULTS

OPG and OPN levels were higher in SH at 12 months than at15 days (p < .05), whereas OC and TGF-β were lower in PCDM at 12 months compared with the 15-day and 3-month follow-ups, respectively (p < .05). Inter-group analyses showed lower OPN levels in PCDM compared with SH at 12 months (p < .05). The ISQ was higher at 12 months when compared with baseline and 3 months in SH (p < .05), whereas no differences were observed during follow-up in diabetics, regardless of glycemic control (p > .05). No difference in ISQ was observed among groups over time (p > .05).

CONCLUSION

Poor glycemic control negatively modulated the bone factors during healing, although T2DM, regardless of glycemic status, had no effect on implant stabilization.

Sericin protects against diabetes-induced injuries in sciatic nerve and related nerve cells

Sericin from discarded silkworm cocoons of silk reeling has been used in different fields, such as cosmetology, skin care, nutrition, and oncology. The present study established a rat model of type 2 diabetes by consecutive intraperitoneal injections of low-dose (25 mg/kg) streptozotocin. After intragastrical perfusion of sericin for 35 days, blood glucose levels significantly declined, and the expression of neurofilament protein in the sciatic nerve and nerve growth factor in L4-6 spinal ganglion and anterior horn cells significantly increased. However, the expression of neuropeptide Y in spinal ganglion and anterior horn cells significantly decreased in model rats. These findings indicate that sericin protected the sciatic nerve and related nerve cells against injury in a rat type 2 diabetic model by upregulating the expression of neurofilament protein in the sciatic nerve and nerve growth factor in spinal ganglion and anterior horn cells, and downregulating the expression of neuropeptide Y in spinal ganglion and anterior horn cells.

Bone formation in peri-implant defects grafted with microparticles: a pilot animal experimental study

AIM

This study aimed to evaluate the healing of peri-implant defects grafted with microparticles (MPs).

MATERIAL AND METHODS

Six domestic pigs received nine standardized defects at the calvaria, and an implant was inserted in the middle of each defect. The space between the implant and lateral bone portion was filled with MP pellets (n = 18) or MP supernatant (n = 18) or left unfilled (n = 18). After 14 and 28 days, three animals were sacrificed and specimens removed for further processing. Samples were microradiographically and histologically analysed. In addition, we immunohistochemically stained for anti-vWF as a marker of angiogenesis.

RESULTS

In the case of bone regeneration and vessel formation, the null hypothesis can be partially rejected. After 14 and 28 days, no significant difference was observed within groups regarding de novo bone formation, bone density and osseointegration. However, superior vessel formation was found at both time points.

CONCLUSION

Microparticles represent a promising treatment option to accelerate peri-implant vessel formation. Further studies are needed to investigate the regenerative properties of MPs more precisely.

Implants in bone: part II. Research on implant osseointegration: material testing, mechanical testing, imaging and histoanalytical methods

PURPOSE

In order to determine whether a newly developed implant material conforms to the requirements of biocompatibility, it must undergo rigorous testing. To correctly interpret the results of studies on implant material osseointegration, it is necessary to have a sound understanding of all the testing methods. The aim of this overview is to elucidate the methods that are used for the experimental evaluation of the osseointegration of implant materials.

DISCUSSION

In recent decades, there has been a constant proliferation of new materials and surface modifications in the field of dental implants. This continuous development of innovative biomaterials requires a precise and detailed evaluation in terms of biocompatibility and implant healing before clinical use. The current gold standard is in vivo animal testing on well validated animal models. However, long-term outcome studies on patients have to follow to finally validate and show patient benefit.

CONCLUSION

No experimental set-up can provide answers for all possible research questions. However, a certain transferability of the results to humans might be possible if the experimental set-up is carefully chosen for the aspects and questions being investigated. To enhance the implant survival rate in the rising number of patients with chronic diseases which compromise wound healing and osseointegration, dental implant research on compromised animal models will further gain importance in future.

Effect of reactive oxygen species overproduction on osteogenesis of porous titanium implant in the present of diabetes mellitus

Clinical evidence indicates diabetes as a majorrisk factor for titaniumimplant treatment with high failure rates and poor osteointegration, but the underlying mechanism involved remains elusive.We hypothesize that reactive oxygen species (ROS) overproduction may contribute to the impaired osteogenesis of porous titanium implants (pTi) under diabetic conditions. To test this hypothesis, we culturedprimary rabbit osteoblasts onto pTi and studied the cellular performance when subjected to normal serum (NS), diabetic serum (DS), DS + NAC (a potent ROS inhibitor) and NS + H(2)O(2)(an oxidant).In-vivo performance of pTi was investigated by transplanting them intofemoral condyledefects of diabetic rabbits, which received vehicle or NAC treatment respectively.Results showed that diabetic conditions induced significant cellular apoptosis, depressedosteoblast function evidenced by impairedcell attachment and morphology, decreased cell proliferation anddifferentiation, andcompromised in-vivo osteogenesis ofpTi, while cellular ROSgeneration was increased derived from mitochondrial dysfunction. Scavenging ROS with NAC markedly attenuated cell apoptosis and osteoblast dysfunction, and improved bone ingrowth within pTi. Furthermore, treatment withH(2)O(2) exerted similar adverse effect on cellular behavior as diabetes. This study furthers our knowledge on the potential role of ROS overproduction in the diabetes-induced impaired osteogenesis of titanium implants, and indicates anti-oxidative treatment as a promising strategy to promote the treatment efficacy of pTi in diabetic patients.

Animal models of diabetes mellitus for islet transplantation

Due to current improvements in techniques for islet isolation and transplantation and protocols for immunosuppressants, islet transplantation has become an effective treatment for severe diabetes patients. Many diabetic animal models have contributed to such improvements. In this paper, we focus on 3 types of models with different mechanisms for inducing diabetes mellitus (DM): models induced by drugs including streptozotocin (STZ), pancreatomized models, and spontaneous models due to autoimmunity. STZ-induced diabetes is one of the most commonly used experimental diabetic models and is employed using many specimens including rodents, pigs or monkeys. The management of STZ models is well established for islet studies. Pancreatomized models reveal different aspects compared to STZ-induced models in terms of loss of function in the increase and decrease of blood glucose and therefore are useful for evaluating the condition in total pancreatomized patients. Spontaneous models are useful for preclinical studies including the assessment of immunosuppressants because such models involve the same mechanisms as type 1 DM in the clinical setting. In conclusion, islet researchers should select suitable diabetic animal models according to the aim of the study.