Bone quality analysis of jaw bones in individuals with type 2 diabetes mellitus-post mortem anatomical and microstructural evaluation

Five-year change of panoramic radiomorphometric indices and fractal dimension values in type 2 diabetes patients

OBJECTIVES

Diabetes mellitus is a chronic disease characterized by dysregulation of glucose metabolism, with characteristic long-term complications accompanied by changes in bone quality. The purpose of this study is to compare the results with a control group by performing radiomorphometric analyses on panoramic radiographs obtained 5 years apart to examine changes in the mandibular bone cortex and microstructures of type 2 diabetes mellitus (T2DM) patients.

METHODS

Two panoramic radiographs that were taken 5 years (mean 5.26 ± 0.134) apart from 52 patients with T2DM (n:26) and a control group (n:26) were used. A total of 104 images were evaluated. Analyses were done from the condyle (FD1), angulus (FD2), distal second premolar apex (FD3), and anterior to the mental foramen (FD4) for fractal dimension (FD) in the mandible. Symphysis index (SI), anterior index (AI), molar index (MI), posterior index (PI), and panoramic mandibular index (PMI) measurements were taken for cortical analysis. Three-way ANOVA, three-way robust ANOVA, two-way ANOVA, and two-way robust ANOVA tests were used for statistical analysis (p < 0.05).

RESULTS

After a 5-year period, there was a significant decrease in all FD measures of the mandible in both T2DM and control groups (p < 0.05). This resulted in a statistical difference in the main effect of time. After a 5-year period, no significant difference in mandibular cortical measures was identified between the T2DM and control groups (p > 0.05).

CONCLUSION

According to panoramic radiography, the mandibular trabecular structure deteriorated after 5 years, whereas cortical values remained the same. It concluded that T2DM had no effect on these results.

Micropetrosis: Osteocyte Lacunar Mineralization in Aging and Disease

PURPOSE OF REVIEW

As the importance of osteocytes for bone mineral homeostasis is increasingly recognized, there is growing interest in osteocyte cell death as a relevant indicator in various physiological and pathological conditions. Micropetrosis is an established term used to describe osteocyte lacunae that are filled with minerals following osteocyte death. While the early reports of micropetrosis were purely descriptive, there is now an increasing body of literature showing quantitative data on micropetrosis in various conditions such as aging, osteoporosis, immobilization, and diabetes, and in osteoporosis treatment (denosumab and bisphosphonates). This review summarizes quantitative findings on micropetrosis, with a particular emphasis on the recent advances in the field.

RECENT FINDINGS

There is growing evidence that micropetrosis is more common in older, osteoporotic, and immobilized individuals, as well as in individuals with type 1 or type 2 diabetes. Denosumab and bisphosphonates seem to affect lacunar mineralization differently, where specifically bisphosphonates have been shown to prolong osteocyte viability and reduce micropetrosis. Despite continuous proceedings in the field of osteocyte-lacunar-network characteristics, more studies are necessary to further clarify the mechanisms of lacunar mineralization, the inter-site variability of micropetrosis accumulation, the relevance of micropetrosis in various diseases and conditions, and whether micropetrosis could be an indicator of bone fragility or a target for treatment.

Bone intrinsic material and compositional properties in postmenopausal women diagnosed with long-term Type-1 diabetes

The incidence of diabetes mellitus and the associated complications are growing worldwide, affecting the patients' quality of life and exerting a considerable burden on health systems. Yet, the increase in fracture risk in type 1 diabetes (T1D) patients is not fully captured by bone mineral density (BMD), leading to the hypothesis that alterations in bone quality are responsible for the increased risk. Material/compositional properties are important aspects of bone quality, yet information on human bone material/compositional properties in T1D is rather sparse. The purpose of the present study is to measure both the intrinsic material behaviour by nanoindentation, and material compositional properties by Raman spectroscopy as a function of tissue age and microanatomical location (cement lines) in bone tissue from iliac crest biopsies from postmenopausal women diagnosed with long-term T1D (N = 8), and appropriate sex-, age-, BMD- and clinically-matched controls (postmenopausal women; N = 5). The results suggest elevation of advanced glycation endproducts (AGE) content in the T1D and show significant differences in mineral maturity / crystallinity (MMC) and glycosaminoglycan (GAG) content between the T1D and control groups. Furthermore, both hardness and modulus by nanoindentation are greater in T1D. These data suggest a significant deterioration of material strength properties (toughness) and compositional properties in T1D compared with controls.

Human tibial cortical bone with high porosity in type 2 diabetes mellitus is accompanied by distinctive bone material properties

Diabetes mellitus is a metabolic disease affecting bone tissue at different length-scales. Higher fracture risk in diabetic patients is difficult to detect with common clinical fracture risk assessment due to normal or high bone mineral density in diabetic patients. The observed higher fracture risk despite normal to high areal bone mineral density in diabetic patients points towards impaired bone material quality. Here, we analyze tibial bone from individuals with type 2 diabetes mellitus using a multiscale-approach, which includes clinical and laboratory-based bone quality measures. Tibial cortical bone tissue from individuals with type 2 diabetes mellitus (T2DM) and age-matched healthy controls (n = 15 each) was analyzed with in situ impact indentation, dual energy X-ray absorptiometry (DXA), high resolution peripheral microcomputed tomography (HR-pQCT), micro-computed tomography (microCT), cyclic indentation, quantitative backscattered electron microscopy (qBEI), vibrational spectroscopy (Raman), nanoindentation, and fluorescence spectroscopy. With this approach, a high cortical porosity subgroup of individuals with T2DM was discriminated from two study groups: individuals with T2DM and individuals without T2DM, while both groups were associated with similar cortical porosity quantified by means of microCT. The high porosity T2DM group, but not the T2DM group, showed compromised bone quality expressed by altered cyclic indentation properties (transversal direction) in combination with a higher carbonate-to-amide I ratio in endocortical bone. In addition, in the T2DM group with high cortical porosity group, greater cortical pore diameter was identified with HR-pQCT and lower tissue mineral density using microCT, both compared to T2DM group. Micromechanical analyses of cross-sectioned osteons (longitudinal direction) with cyclic indentation, qBEI, and nanoindentation showed no differences between the three groups. High tibial cortical porosity in T2DM can be linked to locally altered bone material composition. As the tibia is an accessible skeletal site for fracture risk assessment in the clinics (CT, indentation), our findings may contribute to further understanding the site-specific structural and compositional factors forming the basis of bone quality in diabetes mellitus. Refined diagnostic strategies are needed for a comprehensive fracture risk assessment in diabetic bone disease.

Pulsed electromagnetic fields inhibit mandibular bone deterioration depending on the Wnt3a/β-catenin signaling activation in type 2 diabetic db/db mice

Type 2 diabetes mellitus (T2DM) patients have compromised mandibular bone architecture/quality, which markedly increase the risks of tooth loosening, tooth loss, and failure of dental implantation. However, it remains lacks effective and safe countermeasures against T2DM-related mandibular bone deterioration. Herein, we studied the effects of pulsed electromagnetic fields (PEMF) on mandibular bone microstructure/quality and relevant regulatory mechanisms in T2DM db/db mice. PEMF exposure (20 Gs, 15 Hz) for 12 weeks preserved trabecular bone architecture, increased cortical bone thickness, improved material properties and stimulated bone anabolism in mandibles of db/db mice. PEMF also upregulated the expression of canonical Wnt3a ligand (but not Wnt1 or Wnt5a) and its downstream β-catenin. PEMF improved the viability and differentiation of primary osteoblasts isolated from the db/db mouse mandible, and stimulated the specific activation of Wnt3a/β-catenin signaling. These positive effects of PEMF on mandibular osteoblasts of db/db mice were almost totally abolished after Wnt3a silencing in vitro, which were equivalent to the effects following blockade of canonical Wnt signaling using the broad-spectrum antagonist DKK1. Injection with Wnt3a siRNA abrogated the therapeutic effects of PEMF on mandibular bone quantity/quality and bone anabolism in db/db mice. Our study indicates that PEMF might become a non-invasive and safe treatment alternative resisting mandibular bone deterioration in T2DM patients, which is helpful for protecting teeth from loosening/loss and securing the dental implant stability.

Glimepiride Loaded Poly(D,L-lactide-co-glycolide) Microspheres Improve Osseointegration of Dental Implants in Type 2 Diabetic Rats

The patients with type 2 diabetes mellitus (T2DM) have high dental implant failure frequency. This study explores the function of glimepiride local delivery on dental implant osseointegration in diabetes animal. Glimepiride loaded PLGA microspheres were loaded on the surface of the dental implant, and transplanted into ten Goto-Kakizaki (GK) rats. Blood sugar level and Implant Stability Quotient (ISQ) were measured every week after surgery. Histological, osseointegration rate and bone-implant contact (BIC) rate analysis were performed to evaluate dental osseointegration. The results showed that Glimepiride loaded Poly-lactide-co-glycolide (PLGA) microspheres have sustained-release curve. The glimepiride group exhibited greater ISQ than the control group. The BIC rate of the control and glimepiride group was 44.60%±1.95% and 59.80%±1.79%, respectively. This study demonstrated that the glimepiride group has a significantly greater osseointegration rate than that of the control group. Thus, Glimepiride could provide an alternative drug release microspheres for enhance the dental implant osseointegration in diabetes patients.