Influence of root fragility and irrigation on external root temperature variation during preparation for fiberglass posts.

Background: This paper analyses the effects of root canal fragility and irrigation on external temperature change (ΔT) of different sections of roots during post-space preparation. Material and Methods: Forty endodontic treated human premolars were evaluated. Roots were divided into four groups based on their root wall thickness (fragile or non-fragile), and whether they received irrigation (yes or no) during post-space preparation. Initial root canal temperature was kept at 37°C. ∆T was evaluated with thermistors attached to the cervical and apical thirds of the roots during two preparation steps: 1) removal of gutta-percha with Largo drills, and 2) using the specific drill for post-space preparation for cementation of fiber-reinforced posts. In the irrigated groups, we used a 2% chlorhexidine solution during the exchange of drills. ∆T data was analyzed using four-way ANOVA with repeated measures and Tukey's test (α = 0.05). Results: Significant differences in ∆T based on root fragility (p = 0.017), root canal third (p = 0.013), and preparation step (p = 0.006). We found that non-fragile roots tended to have higher ∆T than fragile roots, particularly in the apical third, during the use of the second drill. Irrigation did not have a significant effect on temperature variation, regardless of root wall thickness or the third evaluated (p> 0.05). Conclusions: Findings suggest that root wall thickness and the third evaluated influence temperature changes during post-space preparation for cementation of posts. Non-fragile roots showed greater temperature variation than fragile roots, while irrigation did not significantly impact temperature changes. Key words:Temperature, post and core technique, tooth preparation.

Prolonged use of alendronate alters the biology of cranial repair in estrogen-deficient rats' associated simultaneous immunohistochemical expression of TGF-ß1+, α-ER+, and BMPR1B.

OBJECTIVES: TGF-ß1 is a cytokine that may induce both osteoneogenesis through Runx-2 or fibrosis via the transcription of α-smooth muscle actin (α-SMA). Because it has been previously known that alendronate increases the level of TGF-ß1 and that under the usual condition of bone metabolism the estrogen may prevent the fibrotic effect of TGF-ß1, the aim of this study was to evaluate if alendronate alters the cellular differentiation process post calvarial surgery in estrogen-deficient specimens. MATERIALS AND METHODS: A transosseous defect that was 5 mm in diameter was created on the calvarium of each of 32 female rats with previous ovarian-salpingo-oophorectomy. All defects were treated with autografts, and 16 rats received the administration of 1 mg/kg of alendronate three times a week until euthanasia on the 15th and 60th day post surgery. Histomorphometric and immunohistochemical analyses of the expression of TGF-ß1, estrogen receptor alpha nuclear (α-ER), α-SMA, BMPR1B, and Runx-2 were performed, and ELISA was used to measure the level of estrogen. RESULTS: All animals demonstrated low levels of estrogen post ovarian-salpingo-oophorectomy. The histological results demonstrated larger bone matrix deposition in specimens treated with alendronate on the 15th day post surgery. The result was associated with a higher co-expression of TGF-ß1, BMPR1B, and Runx-2 when compared with the control group. In addition, on the 60th day post surgery, the increase of bone matrix deposition from 15th to 60th day was discrete in specimens treated with alendronate compared with the control group. This result coincided with the intense simultaneous expression of TGF-ß1, α-ER, and α-SMA, whereas the expression of BMPR1B and Runx-2 decreased. CONCLUSION: The prolonged administration of alendronate altered the cranial repair in ovarian-salpingo-oophorectomized specimens due to the simultaneous occurrence of low estrogen and the presence of TGF-ß1+/α-ER+ inducing the presence of α-SMA+, whereas BMPR1B and Runx-2 were suppressed. CLINICAL RELEVANCE: The prolonged administration of alendronate alters osteoneogenesis and induces an unusual microenvironment in the bone that seems to imitate the physiological tissue damage that culminates in the loss of the functional layer of endometrium.

Would Be Prophylactic Administrations of Low Concentration of Alendronate an Alternative for Improving the Craniofacial Bone Repair? A Preliminary Study Focused in the Period of Cellular Differentiation and Tissue Organization.

BACKGROUND: Alendronate (ALN) is a nitrogen-bisphosphonate that may induce an anabolic effect on craniofacial bone repair when administrated in low doses. Based on this premise, this study analyzed the influence of prophylactic low doses of ALN on bone healing in defects created in rabbit mandible. METHODS: A 5 × 2-mm diameter deep defect was created in the calvaria of 28 rabbits. Fourteen of these rabbits received previously 50 µg/kg of 1% sodium ALN for 4 weeks, while the other rabbits received only 0.9% physiological saline solution (control). Animals were euthanized at 15 and 60 days postsurgery (n = 7), and the data were analyzed using histomorphometry and immunohistochemistry using the anti-CD34, bone morphogenetic protein -2 (BMP-2), and transforming growth factor (TGF)-ß1 antibodies. RESULTS: On the 15th day postsurgery, the specimens that received previous treatment with ALN demonstrated large vascular lumen and intense positivity to CD34 either concentrated in endothelium or cells spread among the reparative tissue. These results coincided with intense positivity for BMP-2+ cells and TGF-ß1 that was concentrated in both cells and perivascular area. In contrast, the control group revealed scarce cells that exhibited CD34, BMP-2+, and the TGF-ß1 was restricted for perivascular area on well-formed granulation tissue. These patterns of immunohistochemical result, especially found on the 15th day of analysis, seem to be responsible for the development of larger quantities of bone matrix in the specimens that receive ALN on the 60th day postsurgery. CONCLUSION: These preliminary results showed that the prophylactic administration of low doses of ALN might be an alternative to craniofacial bone craniofacial bone repair because it increases the immunopositivity for TGF-ß1 and consequently improves the CD34+ and BMP-2+ cells on reparative sites.

Leukocyte-platelet-rich plasma (L-PRP) induces an abnormal histophenotype in craniofacial bone repair associated with changes in the immunopositivity of the hematopoietic clusters of differentiation, osteoproteins, and TGF-ß1.

BACKGROUND: Leukocyte-platelet-rich plasma (L-PRP) is considered an important source of growth factors, especially Transforming growth factor ß 1 (TGF-ß1), which modulates the proliferation and regulation of mesenchymal cells, and also exerts an influence on the hematopoiesis, osteogenesis, and adipogenesis in bone microenvironment. Thus, the aim of this study was to evaluate the effect of L-PRP on the calvarial bone repair and compare its results on the presence of TGF-ß1, CD34, CD45, bone morphogenetic protein 2 (BMP2), BMPR1B, and Runx2 proteins detected by immunohistochemistry. MATERIAL AND METHODS: Four bone defects were created on the calvaria of 23 rabbits. The defects were treated with autograft, L-PRP alone, and L-PRP mixed with autograft. The animals were euthanized at 2, 4, and 6 weeks post-surgery. RESULTS: Unlike autograft and sham groups, the defects treated with L-PRP demonstrated significant positivity to TGF-ß1, while the BMP2 was scarce. These results coincided with the lower bone matrix deposited and larger medullary area, which were composed of fibrosis, when treated with only L-PRP, or intense adiposity on defects filled with L-PRP mixed with autograft. The fibrosis that occurred was associated with a minor percentage of osteoproteins, intense presence of CD34(+) CD45(-) cells, and significant expression of TGF-ß1 in all time periods analyzed. The adiposity occurred from the major presence of osteoprogenitor BMPR1B (+) Runx2(+) cells simultaneously to BMP2(-) TGF-ß1(+) and CD34(+) CD45(+/-) expressions predominantly on the earlier period. CONCLUSION: From this study, it can be concluded that the L-PRP used alone or mixed to autograft hindered the osteoneogenesis due to suppression of immunoexpression of BMP2, while the immunopositivity of TGF-ß1 was intense. When used alone, the L-PRP induced a fibrotic condition associated with TGF-ß1 presence and lack of osteoproteins, but when L-PRP was mixed to autograft, it induced the presence of the osteolineage cells (BMPR1B (+) Runx2(+) ), but also inhibited the terminal osteoblastic maturation associated with the lack of BMP2 and the presence of TGF-ß1(+) , a fact that contributed to cellular transdifferentiation into fat cells.

Platelet-rich plasma diminishes calvarial bone repair associated with alterations in collagen matrix composition and elevated CD34+ cell prevalence.

The interaction between platelets and both type I and III collagens plays an important role in modulating platelet adhesion and aggregation, also contributing to the chemotaxis of CD34+ cells. The interaction with type III collagen can maintain high levels of collagen and alter the biology of bone repair when the PRP is used. The aim of this study was to evaluate the effect of platelet-rich plasma (PRP) and autograft on the presence of type III and type I collagens, the ratio between them, as well as the presence of CD34+ progenitor cells, while comparing these results by means of a histomorphometric analysis of the bone tissue. Four bone defects (8.0mm in diameter and 2.0mm in depth) were produced on the calvarium of 23 rabbits. The surgical defects were treated with either autogenous bone grafts, autogenous bone grafts with PRP and PRP alone. Animals were euthanized at 2, 4 or 6 weeks post-surgery. Histological, histomorphometric and immunohistochemical analyses were performed to assess repair time, as well as the expression of type I and III collagens, and number of progenitor CD34+ cells. Data were analyzed using the ANOVA and Student-Newman-Keuls test (alpha=5%). An enlarged granulation and medullary tissue areas in the PRP groups were observed. The use of PRP in this study hindered bone deposition, also enhanced type III to type I collagen ratio and the chemotaxis of CD34+ progenitor cells, similarly to a thrombogenic effect.