Protease-active extracellular protein preparations from Porphyromonas gingivalis W83 induce N-cadherin proteolysis, loss of cell adhesion, and apoptosis in human epithelial cells

BACKGROUND: The protease-induced cytotoxicity of P. gingivalis may partly result from alteration of the extracellular matrix and/or surface receptors that mediate interaction between the host cells and their matrix. While P. gingivalis-induced degradation of E-cadherin has been documented, there is no information on the effects of P. gingivalis proteases on other members of this family of cell adhesion proteins. METHODS: Human epithelial KB cells were exposed to protease-active extracellular protein preparations from isogenic mutants of P. gingivalis. Quantification of apoptosis was performed by visualization of nuclei stained with 4,6'-diamidino-2-phenylindole. Alteration of cell adhesion proteins was examined by immunoblotting of cell lysates using monoclonal antibodies to those proteins. RESULTS: Treated cells exhibited loss of cell adhesion properties with apoptotic cell death subsequently observed. These effects correlated with the different levels of cysteine-dependent proteolytic activities of the isogenic mutants tested. Cleavage of N-cadherin was observed in immunoblots of lysates from detached cells. There was a direct correlation between the kinetics of N-cadherin cleavage and loss of cell adhesion properties. Loss of cell adhesion, as well as N-cadherin cleavage, could be inhibited by preincubation of P. gingivalis protease active extracellular protein preparations with the cysteine protease inhibitor TLCK. In control experiments, the cleavage of N-cadherin was detected after treatment of KB cells with trypsin but not after cell dissociation by a non-enzymatic method. CONCLUSIONS: These results suggest that extracellular proteases from P. gingivalis can induce degradation of N-cadherin, which could have implications for the pathogenicity of this bacterium.     

Human periodontal ligament cell responses to recombinant human bone morphogenetic protein-2 with and without bone allografts

BACKGROUND: Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been found to promote the osteoblastic differentiation of human periodontal ligament cells. Its effect depends on the delivery system used. In this study we examined the effect of rhBMP-2 on the proliferation and osteoblastic differentiation of human periodontal ligament cells cultured alone or with 3 different bone allografts. METHODS: The rhBMP-2 effect on cell proliferation and osteoblastic differentiation was examined by measuring [3H] thymidine incorporation and ALPase activity, respectively, on human periodontal ligament (hPDL) cells. Two human demineralized freeze-dried allografts of cortical (DFDBAco) and cancellous (DFBDAca) bone origin and 1 non-demineralized freeze-dried allograft (FDBA) of cancellous bone origin, derived from different tissue banks, were used to evaluate the rhBMP-2 effect on cell osteoblastic differentiation. The measurements were taken on various days. RESULTS: rhBMP-2 decreased hPDL cell proliferation. rhBMP-2 acted on the third day of the process of cell differentiation, had a specific time of action, achieved its peak effect on the fourth and fifth days, and then did not provoke any further effects. The 3 bone allografts were efficiently combined with rhBMP-2. The combination of rhBMP-2 and DFDBAco showed the effect with the longest duration. rhBMP-2, on day 4, made the inactive bone allograft more active while, on the other days, its effect was dependent on the allograft alone. CONCLUSIONS: rhBMP-2 promotes the osteoblastic differentiation of human periodontal ligament cells and decreases cell proliferation. In this study rhBMP-2 in the presence of the bone allografts tested resulted in hPDL cell differentiation.     

Immunocytochemical examination of immune cells in periapical granulomata and odontogenic cysts

Monoclonal antibodies (mAbs) were used to determine the presence and distribution of immune cells including lymphocytes, macrophages and Langerhans cells, in normal periodontal ligament, periapical granulomata, periapical cysts and dental developmental cysts. Isolated T-lymphocytes, but not B-lymphocytes, were detected in specimens of non-inflamed periodontal ligament. Increased numbers of T and B lymphocytes were found in all of the lesions examined. Monocytes/macrophages were associated with most periapical granulomata, dental developmental cysts and all periapical cysts. Langerhans cells, intraepithelial lymphocytes, and monocytes/macrophages were not detected in the rests of Malassez but were found in some epithelia within periapical granulomata and in most epithelial linings of odontogenic cysts. Increased numbers of immune cells were seen around proliferative epithelia and adjacent to the epithelial linings of cysts. Epithelium, particularly that of odontogenic cysts, showed positive reactions for HLA-Dr, lysozyme and for α-1 antitrypsin. The presence of immune cells in periapical granulomata and odontogenic cysts, suggests that cell-mediated and humoral immunoreactions occur in these lesions and may be associated with the epithelial proliferation within the periapical lesions.     

The removal torque of titanium implant inserted in rabbit femur coated with biomimetic deposited Ca-P coating

A number of experimental data on biomimetic deposition CaP (BDCaP) coating implants have reported promising outcomes by histological evaluation. But little is investigated on the role of the BDCaP coating and osseointegration mechanism by interface shear strength. To make a direct biomechanical comparison between the BDCaP coating implants and the uncoated rough titanium implants (control), a well-established animal model for implants removal torque testing was employed in rabbits, using a self-matching experimental design. All implants had an identical cylindrical screw shape without any macroscopic retentive structure. After 2, 4, 6, 8 and 12 weeks of bone healing, removal torque testing was performed to evaluate the interfacial shear strength of each implant type. The torqued implants were sputter-coated with gold for morphology observation and observed with a field-emission electron microscopy. Results showed that the interfacial shear strength of the BDCaP coating implants was similar to that of the uncoated rough implants at 2 and 4 weeks of healing. The mean removal torque values of the BDCaP coating implants were lower than those of control implants (P < 0.05) after 6 weeks of healing. The removal torque values for both types of implants revealed similar mean values after 8 and 12 weeks of healing; there were no significant difference between the two types of implants (P > 0.05). It can be concluded that the BDCaP coating implants had no beneficial effect on the interfacial shear strength at early bone healing stage.     

应用超声波非破坏性拆除固定修复体

随着人们对口腔美学要求的提高，烤瓷技术的应用越来越广，但烤瓷修复体的损坏，以及修复后基牙出现牙髓炎或根尖周炎的治疗，已成为临床医生颇感棘手的问题。按过去切割等破坏性拆除的方法，往往损坏修复体或使修复体变形，不仅增加病人的就诊次数，也增加了病人经济上的负担。本文利用超声技术对36例固定修复体作非破坏性拆除。取得较满意的效果。报道如下。材料和方法1研究对象选择1995～1996年由口腔修复科转至口腔内科病人共36人，男15人，女21人，年龄24～61岁。其中单冠13例，连冠3例，3个单位固定桥11例，3个位以上的固定桥9例。粘…     

铸造义齿中网状支架的设计

铸造义齿中网状支架的设计李景辉，宋培智，陈官辉，季秋杰，卢玉春，高银凤在可摘局部义齿修复中，网状支架的合理设计既增加了义齿的强度，又具有传递咬力、分散力、保护口腔内软硬组织的功能［１］。常用形态为园孔形、方格形、楼梯的，网状形、三角形、倒锥形、栅栏形...     

Can anti‐erosion dentifrices also provide effective plaque control?

To cite this article:
Int J Dent Hygiene 9 , 2011; 223–228
DOI: 10.1111/j.1601‐5037.2010.00480.x
Bellamy PG, Prendergast M, Strand R, Yu Z, Day TN, Barker ML, Mussett AJ. Can anti‐erosion dentifrices also provide effective plaque control? Abstract: Objective: While gingivitis and caries continue to be prevalent issues, there is growing concern about dental erosion induced by dietary acids. An oral hygiene product that protects against all these conditions would be beneficial. This study investigated the potential of two anti‐erosion dentifrices to inhibit plaque. Methods: This was a randomized, three‐period, two‐treatment, double‐blind, crossover study evaluating a stannous chloride/sodium fluoride dentifrice (SnCl₂/NaF, blend‐a‐med^® Pro Expert) and a popular anti‐erosion dentifrice (NaF, Sensodyne^® ProNamel^?). During Period 3, subjects were randomized to repeat one treatment to evaluate any product carryover effects. Each treatment period was 17 days. Test dentifrices were used with a standard manual toothbrush. Digital plaque image analysis (DPIA) was employed at the end of each period to evaluate plaque levels (i) overnight (am prebrush); (ii) post‐brushing with the test product (am post‐brush); and (iii) mid‐afternoon (pm ). Analysis was conducted via an objective computer algorithm, which calculated total area of visible plaque. Results: Twenty‐seven subjects completed the study. At all time points, subjects had statistically significantly (P ≤ 0.0001) lower plaque levels after using the SnCl₂/NaF dentifrice than the NaF dentifrice. The antiplaque benefit for the SnCl₂/NaF dentifrice versus the NaF dentifrice was: am prebrush = 26.0%; am post‐brushing = 27.9%; pm = 25.7%. Conclusions: The SnCl₂/NaF dentifrice provided significantly greater daytime and overnight plaque inhibition than the NaF toothpaste. When recommending dentifrice to patients susceptible to dental erosion, clinicians can consider one that also inhibits plaque.     

Smart materials in dentistry

Most dental materials are designed to have a relatively 'neutral' existence in the mouth. It is considered that if they are 'passive' and do not react with the oral environment they will be more stable and have a greater durability. At the same time, it is hoped that our materials will be well accepted and will cause neither harm nor injury. This is an entirely negative approach to material tolerance and biocompatibility and hides the possibility that some positive gains can be achieved by using materials which behave in a more dynamic fashion in the environment in which they are placed. An example of materials which have potential for 'dynamic' behaviour exists with structures which are partly water-based or have phases or zones with significant water content and for which the water within the material can react to changes in the ambient conditions. Such materials may even be said to have the potential for 'smart' behaviour, i.e. they can react to changes in the environment to bring about advantageous changes in properties, either within the material itself or in the material-tooth complex. The controlled movement of water or aqueous media through the material may cause changes in dimensions, may be the carrier for various dissolved species, and may influence the potential for the formation of biofilms at the surface. Some of these issues may be closely interrelated. Clearly, materials which do not have the capacity for water transport or storage do not have the potential for this sort of behaviour. Some materials which are normally resistant to the healthy oral environment can undergo controlled degradation at low pH in order to release ions which may prove beneficial or protective. It is doubtful whether such behaviour should be classified as 'smart' because the material cannot readily return to its original condition when the stimulus is removed. Other materials, such as certain alloys, having no means of transporting water through their structure, can display smart behaviour by undergoing predictable changes in structure in response to applied mechanical or thermal stimuli. It has been difficult to harness such behaviour to the benefit of patients but progress in this area is slowly being made.