Effect of Er,Cr:YSGG on bond strength and microleakage of dentin bonded to resin composite with different distance and irradiation time.

BACKGROUND: To explore the surface modification of dentin using Er,Cr:YSGG phototherapy and bonding system on the shear bond strength and microleakage scores at two different distances and times of laser irradiation. MATERIALS AND METHODS: Ninety disease-free third molars were collected for the experiment. The four laser groups were divided on the basis of non-contact mode distance and time of irradiation: Group-I: Distance of 1 mm with duration of 60 s; Group-II: Distance of 1 mm with duration of 120 s; Group-III: Distance of 2 mm with duration of 60 s and; Group-IV: Distance of 2 mm with duration of 120 s. The surface for control group (Group-EB: Etch & bond group) was treated with etch and rinse bonding regime. Specimens from all the groups were assessed for shear bond strength and microleakage scores. Samples from all groups were immersed in 2% methylene blue for 24 h and assessed under a digital microscope for microleakage. RESULTS: The lowest bond strength and microleakage was observed in the control group EB. The maximum bond strength score was observed in Group-IV with mean scores 23.41 ± 1.83, while the maximum microleakage scores were observed in Group-II and Group-IV with mean scores 1.0 ± 0.36 and 1.0 ± 0.11, respectively. The lowest bond strength and microleakage among laser groups was observed in Group-II and Group-III, respectively. However, specimens in laser groups showed comparable bond strength and microleakge scores (p > 0.05). For bond strength and microleakage values, analysis of variance showed significant difference among the study groups (p < 0.001). Using Tukey post hoc test, bond strength and microleakage of laser groups showed statistically significant values than EB group. CONCLUSION: Use of phototherapy using Er,Cr:YSGG for dentin surface treatment has the potential for clinical application in comparison to conventional conditioning technique. Increasing the distance of laser application and time of irradiation has significant effect on the shear bond strength and microleakage scores of dentin bonded to resin composite. However, further in-vitro analysis should be undertaken in order to prove such findings.

Effects of platelet-derived growth factor, vitamin D and parathyroid hormone on osteoblasts derived from cancer patients on chronic bisphosphonate therapy.

Bisphosphonates consist of a family of pyrophosphate analogues that are currently being used to treat metastatic bone diseases as well as systemic bone diseases such as osteoporosis. There is accumulating evidence suggesting that patients treated with these bisphosphonates can develop, particularly with invasive dental procedures, osteonecrosis of the jaw. This present study investigated the ability of osteoblastic cells obtained from the alveolar bone of patients on long term intravenous bisphosphonate therapy to respond to agents normally involved in bone regulation and repair. The effects of platelet-derived growth factor-BB (PDGF-BB), 1,25-dihydroxycholecalciferol [1,25(OH)2VitaminD3] and parathyroid hormone (PTH) on basic parameters of cell viability, proliferation, and differentiation were studied. Osteoblastic cells from a diagnosed necrotic alveolar bone specimen obtained with consent from a multiple myeloma female patient, and a non-necrotic sample from a breast cancer female patient both on chronic bisphosphonate therapy (zolendronic acid) were successfully cultured. Cells from an alveolar bone specimen obtained from a female donor with no known medical conditions were also studied for comparative responses. The cells were exposed to 1,25(OH)2D3, PDGF, or PTH under various incubation conditions. The osteoblastic cell differentiation marker, alkaline phosphatase activity, was assayed using a biochemical analysis. Cell viability was assessed with an MTT assay which measures mitochondrial activity and cell proliferation with a tritiated thymidine assay. This study on osteoblastic cells grown from a necrotic alveolar bone from a multiple myeloma patient and a non-necrotic sample from a breast cancer patient, both on long term bisphosphonate treatment, suggests that viable cells from the bone are responsive to agents such as PTH, PDGF and 1,25(OH)2D3 with changes in alkaline phosphatase activity, proliferation and viability suggestive of normal osteoblastic cell responses observed in cultures from a donor of the same gender and age, but not on bisphosphonate treatment. This work provides a rationale for clinical studies to further assess whether the osteonecrosis that sometimes develops in patients treated with bisphosphonates, can be controlled or prevented by close attention to the levels of bone/calcium regulatory agents and/or, in some cases, therapeutic intervention with PDGF to restore regenerative processes that may be compromised at the necrotic site.