Cholesterol 7 alpha-hydroxylase activity in hypothyroidism and hyperthyroidism in humans

The effects of three root-end filling materials on healing following endodontic surgery were assessed radiologically and correlated with histological findings reported elsewhere. The materials compared were a light-cured glass ionomer cement (Vitrebond), a reinforced zinc oxide-eugenol cement (Kalzinol) and amalgam. The root canals of 27 two-rooted mandibular premolar teeth of six beagle dogs were inoculated with endodontic pathogenic bacteria to induce periradicular lesions. The roots were apicected and root-end cavities filled with the tested filling materials. The teeth and surrounding jaw were removed after 4 weeks (30 roots) or 8 weeks (24 roots). Radiographs were taken of each jaw section and subjected to image analysis. Healing was evaluated based on measurements of the size of the periradicular radiolucent areas. ANOVA disclosed no statistically significant differences in the size of the periradicular areas either between time periods or between materials. These results did not correlate with the tissue responses in the same material as assessed histologically and previously reported. The use of radiographs alone to assess healing after endodontic surgery in the dog mandible is unsatisfactory, and should not be regarded as a substitute for histological examination for the determination of healing.     

Short-term tissue response to potential root-end filling materials in infected root canals

The short-term tissue responses to two potential root-end filling materials, a light-cured glass ionomer cement (Vitrebond) and a reinforced zinc oxide-eugenol cement (Kalzinol), were compared with that to amalgam using a previously devised experimental model. In 24 premolar teeth of beagle dogs (47 roots), a collection of endodontic pathogenic bacteria was first inoculated into the root canals to induce periradicular lesions. On each root, an apicoectomy was performed and root-end cavities prepared to receive fillings of each material. The teeth and surrounding jaw were removed after 2 weeks (23 roots) and 1 week (24 roots); they were then prepared for histological examination. The tissue response to amalgam fillings after 2 weeks and 1 week was marked by moderate or severe inflammation on all roots, and extended to < or = 0.5 mm or > 0.5 mm in 15 out of 16 roots. In contrast, after 2 weeks, the majority of roots filled with Kalzinol showed little or moderate inflammation, while the tissue response to Vitrebond was the best of the three materials, and was also the least extensive. After 1 week, the overall best tissue response was with Vitrebond, followed by Kalzinol. The differences between materials for both time periods with either none or few inflammatory cells when compared with that with either moderate or severe inflammation were not statistically significant (P < 0.02). However, the differences between materials for both time periods with no inflammation or inflammation extending < 0.2 mm when compared with that with inflammation extending > 0.2 mm (< or = 0.5 mm or > 0.5 mm) were statistically significant (P < 0.01). Apart from amalgam, in which healing was marked by the persistence of a localized focus of inflammation adjacent to the root-end filling, even though there were intersample variations, there was little overall difference in the temporal and qualitative healing response to Vitrebond and Kalzinol. Both Vitrebond and Kalzinol have potential as root-end filling materials, as the tissue response was considerably more favourable than that to amalgam even in the short-term.     

The experience of a clinical trial of bioceramic-based materials in dentistry

Bioceramics-based materials manufactured in Russia were experimentally and clinically tried with the aim of optimizing repair osteogenesis of the jaws. Powder, granules, and porous blocks of hydroxyapatite alone and mixed with tricalcium phosphate may be effectively used for plastic repair of osseous pouches and post-operative defects of the jaws in surgical treatment of periodontitis, periradicular cysts of the jaws, and for filling the wells after removal of teeth.     

Periradicular curettage

Periradicular curettage is a part of the treatment procedure of periradicular surgery. Its main purpose is to remove pathological periradicular tissues for visibility and accessibility to facilitate the treatment of the apical root canal system, or sometimes for the removal of harmful foreign materials present in the periradicular area. Inflammatory periradicular lesions (granuloma and cysts) are the responses of the periradicular tissues to irritants from the root canal and not from the periradicular area unless medicaments and/or filling materials have been forced through the apical foramina or perforations into the periodontium. Histologically, the inflammatory periradicular lesion is similar to healing granulation tissue, which is composed of cells which have natural and specific immunological defence capability and cooperate by means of cytokines to amplify the protective mechanisms of the host. Accordingly, it is not necessary to completely curette out all the inflamed periradicular tissues during surgery, since this granulation-like tissue will be incorporated into the new granulation tissue as part of the healing process. To control the source of irritants in the root canal is far more important than to remove all periradicular tissues affected by the irritants. The successful removal of all irritants from the root canal system results in resolution of pulpally induced periradicular lesions. In the case where the periradicular lesion is caused by endodontic instruments or cytotoxic filling materials placed in the periradicular tissues, removal of these foreign objects is required for resolution of the lesion.     

Evolution of the local calcium content around irradiated beta-tricalcium phosphate ceramic implants: in vivo study in the rabbit

To evaluate whether dissolved calcium from tricalcium phosphate implants contributes to osseous wound healing in bone defects, the authors used nuclear radioactivated materials. Six months after irradiation, the calcium was still radioactive. Samples of the material were prepared and placed in rabbit condyles for 1, 3 and 9 months. Over time the condyles were retrieved and treated for histology or radiocounting. Measurements of the radioactivity of the slices and histomorphometry of the implants and surrounding tissues were performed. The authors observed that the radioactivity decreased regularly. Connective tissue had penetrated the pores and totally invaded the implants, first at the periphery of the implants, then inside the pores. Comparison of the results of radioactivity and histomorphometry suggest that part of the calcium from the implants was re-used specifically in the new osseous tissue.     

Longitudinal sealing ability of mineral trioxide aggregate as a root-end filling material

This study evaluated the ability of mineral trioxide aggregate (MTA) to seal the root end effectively. Seventy-six single-rooted, extracted human teeth were cleaned and shaped using a step-back technique. After root-end resection and ultrasonic preparation, 72 root sections were randomly allocated to three groups and filled with dental amalgam and cavity liner, Super-EBA, or MTA. Microleakage was assessed at 24 h, 72 h, 2 wk, 4 wk, 8 wk, and 12 wk, using a fluid filtration measurement system. MTA demonstrated excellent sealing ability throughout 12 wk of fluid immersion, comparable with that observed for Super-EBA. Microleakage in the MTA group, as well as the Super-EBA group, was significantly less (p < 0.05) than in the amalgam group at 24 h, 72 h, and 2 wk. At the subsequent periods, there were no significant differences among the three materials. In this study, MTA was determined to be superior to amalgam, and comparable with Super-EBA in preventing microleakage when used as a root-end filling.     

Laparoscopic versus open Nissen fundoplication: outcome of surgery in monozygotic twins

Many clinicians use ultrasonics for root-end preparations. The purpose of this study was to evaluate resected root-end surfaces of bilaterally matched human teeth for cracks before and after ultrasonic root-end preparation. Twenty matched pairs of extracted single rooted teeth were divided into two experimental groups. In group 1, root-end resection was performed on uninstrumented teeth. In group 2, root-end resection was performed after the canals were instrumented and filled with gutta-percha. All teeth in both groups received root-end preparations using ultrasonic instrumentation at low power. Two examiners evaluated the root-ends after root-end resection and again after root-end preparation using zoom magnification of 20x to 63x. The number, types, and location of cracks were mapped. There were no significant differences when gutta-percha filled roots were compared to uninstrumented roots with regard to the number or type of cracks after root-end resection or root-end preparation. In addition, there were no significant differences in the number or type of cracks following root resection and ultrasonic root-end preparation when compared to teeth with root resection alone.     

TGF-beta1 influences early gingival wound healing in rats: an immunohistochemical evaluation of stromal remodelling by extracellular matrix molecules and PCNA

The effect of topically applied transforming growth factor beta1 (TGF-beta1) on the rat gingival wound healing process after flap surgery was evaluated by immunohistochemistry for extracellular matrix molecules (ECM), such as tenascin, heparan sulfate proteoglycan (HSPG) and type IV collagen, and for proliferating cell nuclear antigen (PCNA) in fibroblasts. TGF-beta1 solution was applied to the surgical wound experimental sites. Two microg/microl were applied at the time of the operation, and 1 microg/microl at days 1 and 2 after surgery, with contralateral control sites receiving the vehicle alone. Periodontal tissues were histologically examined at 3 and 7 days post-surgery. Tenascin was found to be more strongly stained in the granulation tissue from experimental sites at 3 days post-surgery. At 7 days postsurgery, HSPG-positive areas in granulation tissue had become smaller and there was a prominent proliferation of PCNA-positive fibroblast-like cells and type IV collagen-positive blood vessels. These results suggest that TGF-beta1 applied to surgical wounds influences early proliferation of gingival fibroblast-like cells, the formation of blood vessels, and ECM remodelling. In conclusion, TGF-beta1 application appears to promote granulation tissue formation in periodontal wound healing.     

Interface potential of calcium phosphate in simulated body fluid

Calcium phosphate ceramics are used in the substitution of injured or damaged bones. Nevertheless, the behaviour of these materials, and in particular, the mechanisms guiding their interface response in physiological environment is still unknown. This work describes the construction of hydroxyapatite and tricalcium phosphate electrodes used to determine the interface potential behaviour of these materials in a simulated body fluid, in a pH range corresponding to the variation observed in human body injuries, at ambient and physiological temperatures. These measurements are associated with the adsorption/desorption of ions from the materials. The results show that hydroxyapatite and tricalcium phosphate have similar behaviour in that they reach an interface potential equilibrium state faster when the solution pH is decreased and the temperature increased. This behaviour may be attributed to their ability to form a calcium-rich layer and is relevant to their quality as implantable materials.     

Effects of resorbable membrane placement and human osteogenic protein-1 on hard tissue healing after periradicular surgery in cats

Periradicular surgeries were performed on the maxillary cuspid teeth of twelve cats. Before reapproximation of the surgical flaps, eight of the osteotomies were covered with a resorbable membrane and eight were filled with human osteogenic protein-1 (hOP-1) on a collagen carrier. The remaining eight sites received no further treatment and served as controls. The animals were euthanized after 12 wk, and the specimens were examined histomorphometrically for the presence or absence of osseous regeneration, inflammation, and cementum formation on the root ends. The results showed that the sites treated with the membrane exhibited significantly more inflammation adjacent to the resected root ends (p < 0.05), and that the use of the membrane had no statistically significant effect on osseous healing or new cementum formation. The use of hOP-1 was associated with a significant decrease in the thickness of new cementum formed on the resected root ends (p < 0.05), but had no statistically significant effect on osseous healing or degree of inflammation. Based on these results, it seems that neither the use of hOP-1 nor resorbable membranes have a positive effect on periradicular tissue healing in endodontic surgery.     

Stabilization of an inserted tricalcium phosphate spacer enhances the healing of a segmental tibial defect in sheep

The effect of inserting a tricalcium phosphate (TCP) spacer stabilized by a rigid or non-rigid fixation technique on the healing of segmental tibial defects of critical size was established. The osteotomized tibiae, 11 with and 8 without TCP spacers, were fixed by an external circular device in 11 mature sheep and by plates in 8 mature sheep, respectively. Healing was evaluated roentgenographically 16 weeks after the operation. Compared with the defects without TCP spacers, enhanced stability and healing were observed in the defects with TCP spacers under an identical external fixation. Furthermore, a significantly higher incidence of healing was obtained with plate fixation than with external device fixation in the TCP-implanted defects (P < 0.04). An abundant bridging callus was roentgenograpically demonstrated in most of the healed defects, but none in the unhealed defects. The TCP spacer with its mechanical integrity enhances the stability of external fixation, and the stable immobilization provided by rigid fixation is essential for osteoconduction of an inserted TCP spacer in the healing of segmental diaphyseal defects in sheep.     

基于GA?SVM的钢渣基胶凝材料开发及料浆配比优化

针对某露天转地下矿山充填成本高的问题,充分利用矿山周边的工业废弃物开发满足嗣后充填采矿法所要求的充填胶凝材料,并对充填料浆的配比进行了优化。首先,分析了材料的物化特性,采用不同的激发配方进行了室内试验,构建了用于钢渣基胶凝材料配方预测的GA?SVM模型,确定了钢渣基胶凝材料的最佳配方（质量分数）为:钢渣30%、脱硫石膏4%、水泥熟料12%、芒硝1%;其次采用XRD和SEM分析了钢渣基胶凝材料的水化机理;最后基于灰靶多目标决策模型对料浆配比进行优化实验,以强度（7 d和28 d）、工作特性（坍落度、泌水率）、成本为指标优化料浆配比。结果表明,采用新型钢渣基胶凝材料,充填料浆的最佳配比参数为:灰砂比1∶4,固相质量分数为72%。并进行了验证实验,得到相应强度参数和工作特性参数分别为1.74 MPa、3.61 MPa、24.2 cm和5.91%,均满足嗣后充填的要求,此配比条件下的充填成本为每立方米113元,较水泥充填成本降低了38.92%。      

Experimental studies on the effect of lidocaine on wound healing

Local anesthetics have several effects on wound healing. In experimental studies, procaine at high concentrations has been proved to retard healing in surgical wounds by diminishing the synthesis of mucopolysaccharides and hence probably collagen. Other studies have shown that lidocaine and bupivacaine inhibit collagen synthesis in fibroblast tissue cultures in rats. This study was designed to evaluate the effect of lidocaine on wound healing. An experimental, prospective, comparative, crossover and double-blind study was designed. Forty male guinea pigs, weighing 300 to 600 g, were randomly assigned to two groups. In control group A (20 animals), skin and subcutaneous tissue in a clean wound were incised and infiltrated with regular saline solution; in group B 20 animals were infiltrated with 1% lidocaine. All animals were sacrificed on day 8 and evaluated for breaking strength, number of collagen fibers by morphometry, and histologic examination of collagenization, edema, vascularity, and presence of acute and chronic inflammatory cells. The histopathologic appearance of tissues infiltrated with lidocaine did not vary consistently in relation to collagenization, edema, or acute and chronic inflammatory processes. The mean breaking strength between both groups was not statistically significant (p = 0.120). Important statistical differences were observed in vascularity (p < 0.003) and morphometric results (p < 0.001), where collagen was found in small amounts in the lidocaine group. The results of this study suggest that local infiltration of lidocaine produces significant histopathologic changes, but it does not substantially alter wound healing as there were no differences in the breaking strength of the wounds.     

The clinical, angiographic and procedural predictors of thrombosis and restenosis in Micro stent II (AVE) coronary stents]

In the present study, the potential of a diphenylphosphorylazide-crosslinked type I bovine collagen membrane was evaluated in the healing of mandibular bone defects applying the biological concept of guided bone regeneration. The experiment was carried out on 25 Wistar rats. After exposing the mandibular ramus bilaterally, 5 mm diameter full-thickness circular bone defects were surgically created. While the defect on one side was covered by the membrane (experimental), the defect on the other side was left uncovered (control) before closure of the overlying soft tissues. The rats were sacrificed in groups of 5 after 7, 15, 30, 90, and 180 days of healing. Although at early stages of healing similar amounts of bone formation were observed in the experimental and control defects, after 1 month of healing, most of the experimental defects were completely closed with new bone, while in the control defects, only limited amounts of new bone were observed at the rims and in the lingual aspect of the lesions. In the 90- and 180-day animals, all experimental defects were completely closed, while in the control defects, no statistically significant increase in bone regeneration was observed. The increase in percentage of bone regeneration in the experimental defects was statistically significant between the 15-day specimens as compared with the 7-day specimens (P < 0.01) and likewise between 30-day and 15-day specimens (P < 0.001). It can be concluded that a DPPA-crosslinked collagen membrane yields biocompatibility, ad hoc mechanical hindrance, and handling characteristics suitable for guided bone regeneration applications in this experimental model.     

Results of surgical treatment of oesophageal cancer

The objective of this laboratory study was to compare root-end cavities prepared with sonic Retro-prep tips in a MM1500 Sonic Air handpiece with those created by burs in a conventional handpiece. A total of 80 single-rooted extracted human teeth with mature apices and straight canals were included in the study. Four groups of 20 extracted teeth were prepared as follows: I, a 3-4 mm root-end resection perpendicular to the long axis of the root, with a size 40 sonic Retro-prep tip creating an apical cavity 3 mm into root canal system; II, a 45 degrees bevel of the root-face removing a 3-4 mm root segment and root-end preparation as per group I; III, root-end resection as per group I, with an apical cavity prepared using a size 010 inverted cone bur 3 mm down the long axis of the root; IV, resection as per group II, followed by an apical cavity preparation with a size 010 inverted cone bur 3 mm into the root canal system. The apical root portion and root-end cavities were replicated and prepared for SEM analysis at x 20 and x 80 magnification. The degree of chipping associated with the margin of the root-end cavities, as evaluated with a standard grading system, and the incidence of root-face cracks were noted. Marginal chipping of root-end cavities prepared using sonic instrumentation was significantly worse than that produced by burs (P < 0.001). Perpendicular root-end resections showed significantly better scores than bevelled root-end resections (P < 0.005). The incidence of root-face cracking was low with no significant difference between the experimental groups.     

Use of the operating microscope in dentistry

Microsurgery is a discipline of multiple surgical procedures performed with optical magnification and illumination. The operating microscope has recently been introduced in dentistry. Magnification improves the performance of fixed prosthodontic laboratory and clinical procedures. The operating microscope has dramatically improved endodontic nonsurgical perforation repair and periradicular surgery. The use of the operating microscope and microsurgical instrumentation has resulted in more-precise periodontal surgical procedures with less operative trauma and improved healing. Use of the operating microscope and microsurgical instrumentation is described.     

Ultrasonic preparation and obturation of root-end cavities

This study evaluated the preparation of root-end cavities using an ultrasonically activated file, and the obturation of such cavities. In the first part, the root canals of 40 extracted teeth were prepared to size 40 and irrigated with NaOCl and EDTA. The root ends were resected and the teeth inoculated with Enterococcus faecalis, incubated for 10 days and divided into four groups: control; saline; irrigation; hand instrumentation performed via a retrograde approach up to size 50 using saline irrigant; ultrasonic instrumentation with prebent size 40 K-flex file inserted into a Piezon Master using saline irrigant. The teeth were fixed, sectioned longitudinally and viewed under scanning electron microscopy. Bacterial and smear layer scores were obtained at 1, 3, and 5 mm from the resected end. The bacterial scores for control and saline groups were similar; the scores for each instrumentation group were significantly lower than the control group (P<0.001). In addition, there were significantly fewer bacteria in the ultrasonic group compared with the hand instrument group (P<0.001). The smear layer scores for control and saline groups were similar, and significantly lower than in either instrumentation group (P<0.001). In the second part, root-end cavities were ultrasonically prepared in 20 extracted teeth. Ten cavities were filled with amalgam, and 10 with thermoplasticized gutta-percha and Grossman's sealer. After 24-h storage, the root ends were immersed in dye for 48 h. Cross-sectional slices of the obturated part of the root were evaluated using both light and confocal microscopy for dye leakage along the interface of filling material and dentine. There were no statistical differences between the leakage of amalgam and gutta-percha root-end fillings, nor between the two methods of microscopy.     

Prevention of arachnoiditis and postoperative tethering of the spinal cord with Gore-Tex surgical membrane: an experimental study with rats

OBJECTIVE: Arachnoidal adhesions and inflammation were evaluated in 72 rats after spinal dural repair with one of three materials, i.e., Gore-Tex surgical membrane, collagen-coated Vicryl mesh, or lyophilized spinal dural allograft. METHODS: Laminectomy at L1 was performed, and then a 3- x 4-mm segment of spinal dura mater and arachnoid membrane was excised. After implantation of the dural substitute, the animals were divided into normal and injured groups. In the injured group, a spinal cord injury was produced at the midpoint of the duraplasty site by the clip compression technique, with 25-g force for 1 minute. Neurological performance was assessed by the inclined plane technique, and groups of rats were killed at 8 to 24 weeks after surgery. The spinal column was removed en bloc and processed for histological examination. RESULTS: There were no differences in neurological function among the three dural substitutes in either injured or noninjured rats. However, there were major differences among the groups in the incidence and severity of arachnoid adhesions and tethering. The neural tissue was bound to a thick neomembrane surrounding the lyophilized dural allograft and the collagen-coated Vicryl mesh. In contrast, the Gore-Tex surgical membrane induced only a thin membranous adhesion, which was loose and flexible. The inflammatory and foreign body response was most pronounced in rats treated with collagen-coated Vicryl mesh, at 8 and 24 weeks. CONCLUSION: In the present study, Gore-Tex surgical membrane was a very good material for the surgical repair of spinal dural defects. Additional experimental studies are required to compare Gore-Tex membrane with autologous tissues.     

A photoelastimetric analysis of stress induced by root-end resection

The aim of this study was to place into perspective some factors that played an important role in the healing of periapical lesions after surgical endodontic procedures. Root-ends were sectioned at different angulations on models and analyzed by photoelastimetry. Results showed that a section of the root-end through a plane perpendicular to the long axis of the tooth offers a better distribution of the stresses exerted on the apical region that the use of an inclined plane. The biological implications of these results have led the authors to propose a plan of resection that is perpendicular to the long axis of the tooth instead of the inclined plane commonly used.     

Hypothalamic-pituitary-adrenal axis suppression and inhaled corticosteroid therapy. 2. Review of the literature

In order to overcome the need for secondary intervention to remove metallic osteosynthesis devices after fracture healing, endeavours have been directed towards developing resorbable osteosynthesis materials during the last decade. The resorbable material must fulfil a number of basic demands. For example, an adequate holding strength of these materials is essential for undisturbed fracture union, complete resorption after bone healing, good histocompatibility without any damage to the surrounding tissues and without detrimental distant effects within the organism. Suggested materials are primarily high-polymerlactic acid or glycolic acid compounds. In particular, research was concentrated on the enhancement of the mechanical properties and biodegradation of polylactides. Debris high in crystallin was found to be responsible for late soft tissue reactions. To achieve disintegration products with lower crystallin content stereocopolymeres of lactic acids are preferred nowadays. Based on our experimental work, another osteosynthesis system manufactured from autoclaved allogenic bone tissue was developed as an alternative. This has osteoconductive properties and converts by creeping substitution into bone. In contrast to metallic plates and screws, the modulus of elasticity is quite similar to vital bone tissue. The initial strength enables its use in the field of maxillofacial surgery.