Near-IR transillumination and reflectance imaging at 1,300 nm and 1,500-1,700 nm for in vivo caries detection.

INTRODUCTION: Several studies suggest that near-IR imaging methods at wavelengths longer than 1,300 nm have great potential for caries detection. In this study, the diagnostic performance of both near-IR transillumination and near-IR reflectance was assessed on teeth scheduled for extraction due to orthodontic treatment (n = 109 teeth on 40 test subjects). METHODS: Three intra-oral near-IR imaging probes were fabricated for the acquisition of in vivo images using a high definition InGaAs camera and near-IR broadband light sources. Two transillumination probes provided occlusal and approximal images using 1,300 nm light which manifests the highest transparency in enamel. A third reflectance probe utilized cross-polarization and operated at wavelengths greater than 1,500 nm where water absorption is higher which reduces the reflectivity of sound tissues, significantly increasing lesion contrast. Teeth were collected after extraction and sectioned and examined with polarized light microscopy and microradiography which served as the gold standard. In addition, radiographs were taken of the teeth and the diagnostic performance of near-IR imaging was compared with radiography. RESULTS: Near-IR imaging was significantly more sensitive (P < 0.05) than radiography for the detection of lesions on both occlusal and proximal surfaces. CONCLUSION: Near-IR imaging methods are ideally suited for screening all tooth surfaces for carious lesions. Lasers Surg. Med. 48:828-836, 2016. © 2016 Wiley Periodicals, Inc.

Effects of pamidronate on human alveolar osteoblasts in vitro.

PURPOSE: Administration of bisphosphonates has recently been associated with the development of osteonecrotic lesions of the jaw (ONJ). To elucidate the potential contributions of osteogenic cells to the development and regeneration of ONJ, we have isolated primary cells from human alveolar and long/iliac bones, and examined the effects of pamidronate on cell viability, proliferation, osteogenesis, and wound healing. MATERIALS AND METHODS: Primary human osteoblasts and bone marrow stromal cells were isolated from alveolar and iliac/long bone and marrow tissue. Cellular proliferation, alkaline phosphatase activity, apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling, caspase-3, and 4,6-diamidino-2-phenylindole dihydrochloride assays) and wound healing in an in vitro scratch assay were assessed after exposure to pamidronate at a range of clinically relevant doses. RESULTS: Primary alveolar osteoblasts proliferated at significantly higher rates than long/iliac bone osteoblasts in vitro. Upon exposure of alveolar osteoblasts and long/iliac bone marrow stromal cells to pamidronate for more than 72 hours, we have observed significantly decreased cell viability, proliferation, osteogenesis, and in vitro wound healing at ≥6 × 10(-5) mol/L pamidronate, with the induction of apoptosis in approximately 20% of cell population. CONCLUSIONS: The remodeling activity of alveolar bone, indicated by higher proliferation of alveolar osteoblasts, could be negatively affected by exposure to high concentrations of pamidronate over extended periods. The absence of anabolic effects of pamidronate on alveolar osteoblasts and the induction of apoptosis in osteogenic cells could negatively affect bone balance at this site and contribute to osteonecrosis of the jaw.

Novel therapy to reverse the cellular effects of bisphosphonates on primary human oral fibroblasts.

PURPOSE: Osteonecrosis of the jaws (ONJ) is a clinical condition that is characterized by a nonhealing breach in the oral mucosa resulting in exposure of bone and has been increasingly reported in patients receiving bisphosphonate (BP) therapy. Although the pathogenesis and natural history of ONJ remain ill-defined, it appears that the oral soft tissues play a critical role in the development of this condition. We examined the effects of the nitrogen-containing BPs pamidronate and zoledronate on primary human gingival fibroblasts. MATERIALS AND METHODS: Primary gingival fibroblasts were exposed to clinically relevant doses of pamidronate and zoledronate. Cellular proliferation was measured with an MTS/PMS reagent-based kit (Promega, Madison, WI), scratch wound assays were performed to measure cellular migration, and apoptosis was measured by use of terminal deoxynucleotidyl transferase-mediated dUTP-FITC end labeling and caspase assays. The BP-exposed cells were treated with 10-ng/mL recombinant human platelet-derived growth factor BB (rhPDGF-BB) and 50-µmol/L geranylgeraniol (GGOH). RESULTS: Gingival fibroblasts are significantly more sensitive to inhibition of proliferation by zoledronate compared with pamidronate. Exposure of these cells to pamidronate but not zoledronate resulted in an increase in cellular apoptosis. Furthermore, exposure of gingival fibroblasts to pamidronate or zoledronate resulted in a decrease in cellular migration. We show that these defects are due to a loss of cell-substratum adhesion and a reduction of F-actin bundles. Finally, we show that the addition of rhPDGF-BB and GGOH in vitro is able to partially rescue the cell proliferation, migration, and adhesion defects. CONCLUSION: The cytotoxic effects of BPs on oral fibroblasts and their significant reversal by the addition of GGOH and rhPDGF-BB provide both the potential mechanism and treatment options for ONJ.

Inhibition of oral mucosal cell wound healing by bisphosphonates.

PURPOSE: Bisphosphonates (BPs) are a widely used class of drugs that are effective in the treatment and prevention of osteoporosis, hypercalcemia of malignancy, and bone metastases associated with multiple myeloma, breast cancer, and other solid tumors. In the past several years there have been numerous reports describing the occurrence of osteonecrosis of the jaws (ONJ) associated with these drugs. Whether the ONJ lesion initiates in the oral mucosa or derives from the underlying bone is not well understood. In this report we describe the effect of pamidronate, a second-generation BP, on oral mucosal cells. MATERIALS AND METHODS: Murine oral keratinocytes were isolated and exposed to pamidronate at a range of clinically relevant doses. Cellular proliferation was measured using a MTS/PMS reagent-based kit and wound healing was examined with a scratch assay. To determine whether oral keratinocytes undergo apoptosis following exposure to pamidronate, TUNEL, caspase-3, and DAPI apoptosis assays were performed. RESULTS: We show that BP pretreatment of oral mucosal cells inhibits proliferation and wound healing at clinically relevant doses, and that this inhibition is not due to cellular apoptosis. CONCLUSIONS: To our knowledge this is the first report investigating the effect of nitrogen-containing BPs on oral mucosal cells. This study suggests that BPs inhibit oral keratinocyte wound healing which may play a significant role in the initiation of ONJ.

Potential pathophysiological mechanisms in osteonecrosis of the jaw.

Bisphosphonates are used in the treatment of hypercalcemia of malignancy, skeletal complications associated with metastastic bone disease, Paget's disease, and osteoporosis. Osteonecrosis of the jaw (ONJ) is a recently described clinical condition that has been associated with the use of nitrogen-containing bisphosphonates. Reports describing this entity first appeared in the literature in 2003. While there have been significant numbers of case reports and a limited number of retrospective and prospective studies examining risk factors associated with ONJ, the pathophysiology of this condition remains elusive. In this review, we explore proposed mechanisms underlying ONJ development and identify potential areas for future investigation.

The expression of the receptor for glycation endproducts (RAGE) in oral squamous cell carcinomas.

Advanced glycation endproducts (AGEs) and their receptors, receptor for advanced glycation endproducts (RAGE), are novel groups of molecules with roles in inflammation, cytokine activation, and promotion of cell growth. Recently, RAGE has been implicated in the progression and metastasis of several epithelial tumors. The expression of RAGE was examined in 38 oral squamous cell carcinoma (OSCC) cases by immunohistochemistry. In the OSCCs, RAGE positivity, interpreted as more than 25% positive cells, was detected in 10 of 10 well-differentiated, 3 of 4 well-to-moderately differentiated, 3 of 9 moderately differentiated, 1 of 7 moderate-to-poorly differentiated, and 0 of 8 poorly differentiated tumors. The staining percentage was significantly higher in well-differentiated tumors compared to moderately (P < .05) and poorly differentiated (P < .05) tumors. All normal mucosa samples were RAGE-positive. Western blot analysis for RAGE was performed on 2 OSCCs and 2 normal oral mucosa samples. Higher expression was observed in the normal tissues compared to the OSCCs. Our results show that RAGE immunoreactivity correlates with histologic differentiation in OSCC.

Controlled delivery of platelet-rich plasma-derived growth factors for bone formation.

Platelet-rich plasma (PRP) represents an autologous source of growth factors essential for bone regeneration. The clinical efficacy of PRP is, however, unpredictable, and this is likely due to the inefficient and inconsistent delivery of PRP-derived growth factors. Previous investigations have shown that current methods of PRP preparation result in a premature release of the relevant bone stimulatory factors. As successful bone regeneration requires multiple factors presented in a physiologic temporal and spatial cascade, the objective of this study is to control the bioavailability of PRP-derived growth factors using a hydrogel carrier system. Specifically, the release of platelet-derived growth factor, transforming growth factor beta-1, and insulin-like growth factor from two types of alginate carriers was compared over time. The effects of the released factors on the growth and alkaline phosphatase (ALP) activity of human osteoblast-like cells were also evaluated. It was found that factor release profiles varied as function of carrier type, and binding of growth factors to the alginate matrix also modulated their release. The bioactivity of released factors was maintained in vitro and they promoted cell proliferation and ALP activity. These results demonstrate the potential of this autologous multifactor delivery system for controlling the bioavailability of PRP-derived factors. Future studies will focus on optimizing this system to increase the clinical efficacy of PRP by matching the distribution and temporal sequencing of PRP-derived factors to the bone healing cascade.