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By removing a part of the structure, the tooth preparation provides restorative space, bonding surface, and finish line for various restorations on abutment. Preparation technique plays critical role in achieving the optimal result of tooth preparation. With successful application of microscope in endodontics for >30 years, there is a full expectation of microscopic dentistry. However, as relatively little progress has been made in the application of microscopic dentistry in prosthodontics, the following assumptions have been proposed: Is it suitable to choose the tooth preparation technique under the naked eye in the microscopic vision? Is there a more accurate preparation technology intended for the microscope? To obtain long-term stable therapeutic effects, is it much easier to achieve maximum tooth preservation and retinal protection and maintain periodontal tissue and oral function health under microscopic vision? Whether the microscopic prosthodontics is a gimmick or a breakthrough in obtaining an ideal tooth preparation should be resolved in microscopic tooth preparation. This article attempts to illustrate the concept, core elements, and indications of microscopic minimally invasive tooth preparation, physiological basis of dental pulp, periodontium and functions involved in tool preparation, position ergonomics and visual basis for dentists, comparison of tooth preparation by naked eyes and a microscope, and comparison of different designs of microscopic minimally invasive tooth preparation techniques. Furthermore, a clinical protocol for microscopic minimally invasive tooth preparation based on target restorative space guide plate has been put forward and new insights on the quantity and shape of microscopic minimally invasive tooth preparation has been provided.
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Objective To compare the effects of different composite resins as core material on the degree of microleakage in post-core repairation.Methods A total of 46 recently extracted single-rooted mandibular premolars were distributed into different groups according to different core material including ParaCore,AP-X and Ceramage.Then we used direct or indirect forming method to make post-core restorations.All of the specimens were submerged in dyes.Then,they were demineralized,dehydrated and processed to be transparent.The extent of the dye leakage was examined under a stereomicroscope.Results The microleakage value was significantly higher in Group of direct-mold-cement with ParaCore (4.94± 1.71)mm than in Group of indirect-mold-secondary-cement with ParaCore (0.91 ± 0.33) mm,Group of indirect-mold-secondary-cement with AP-X (0.87 ± 0.27) mm,and Group of indirect-mold-secondary-cement with Ceramage (1.02 ± 0.34)mm.Conclusion Different methods of building and cementing FRC post-core restorations,but not different composite resins as core material,have significant effects on the extent of microleakage in post-core repair.
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To compare the microleakage of fiber post and resin-core system fabricated by different methods.The roots of 36 recently extracted single-rooted mandibular premolars were undergone endodontic treatment.Fiber posts and Paracore flowable resin composite were used for fabricating post-core restorations.Microleakage was examined by dye penetration method.The microleakage value was significantly higher in Direct-Mold-Cement-Method group(4.94 ± 1.71) mm compared to Direct-Mold-Secondary-Cement-Method group(0.91 ±0.33) mm and Indirect-Mold-Secondary-Cement-Method group (0.87 ± 0.27) mm (P ＜ 0.05).
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Objective To evaluate whether S-100β protein could be a serum marker for traumatic spinal cord injury (SCI). Methods From June, 2013 to October, 2014, 24 patients with complete SCI were measured the serum S-100β protein concentrations with en-zyme-linked immunosorbent assay, one week, three and six months after SCI. Serum from ten healthy persons was as normal control. Re-sults The serum S-100βprotein concentrations increased one week and 3 months after SCI (Z>4.273, P<0.001). Conclusion The increase of serum S-100βprotein may help assessing early impairment after complete SCI.
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80 extracted human mandible premolars were divided into 10 groups(n =8)based on the post with different tilted angles(0°, buccal 15°and 30°,ligual 15°and 30°).The samples in experiment group were restored with fiber post while in the control group with cast post.Then all the teeth were restored with cast crown and bonded by glass ionomer.Compressive load with the speed of 1.0 mm/min was ap-plied to the restored teeth with a universal material testing machine until failure and the fracture modes were observed.The fracture load of fi-ber post and cast post restoration with the same tilted angles was similar(P >0.05).The main fracture mode of the teeth in all groups was unfavorable tooth fracture.No significant interaction was observed(P =0.217)between the 2 kinds of post and angulation of tilted teeth.
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Various functional proteins are differently expressed in each pathologic stage after spinal cord injury, representing injury and the pathological change of repair. Ideal biomarker is helpful to evaluate complicated biological reactions of spinal cord injury and predict prognosis. As specific serum markers of central nerve injury, neuron-specific enolase (NSE) and astrocyte primary calcium binding protein S-100βhad been studied preliminarily, but the specificity and sensitivity need more research. Future efforts still need to develop ideal bio-markers to predict functional outcome.
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Objective To evaluate DTI for early diagnosis and prognosis of diffuse axonal injury (DAI)in the moderate and sever traumatic brain injury (sTBI).Methods 30 patients with sTBI and 30 healthy controls were studied with T1 WI and DTI.The frac-tional anisotropy(FA)and ADC were quantified from different regions of interest(ROI)including the genu of corpus callosum(gCC), the trunk of CC,the splenium of CC(sCC)and the integrity CC.The FA and ADC of the same R0I was compared between TBI group and control group,and FA and ADC of the different parts of CC were compared in TBI group.Correlations between the FA or ADC and coma duration of the TBI patients were analyzed by Pearson linear correlation.Results Compared with control group,the FA value decreased significantly in each ROI,while ADC was reversed.The FA or ADC of the different ROI were correlated with co-ma duration in TBI group.Conclusion DTI is sensitive to detect the white matter injury of TBI.FA value detected in the CC can help diagnose DAI earlier and evaluate the degree of injury.
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@#Various functional proteins are differently expressed in each pathologic stage after spinal cord injury, representing injury and the pathological change of repair. Ideal biomarker is helpful to evaluate complicated biological reactions of spinal cord injury and predict prognosis. As specific serum markers of central nerve injury, neuron-specific enolase (NSE) and astrocyte primary calcium binding protein S-100β had been studied preliminarily, but the specificity and sensitivity need more research. Future efforts still need to develop ideal biomarkers to predict functional outcome.
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<p><b>OBJECTIVE</b>This study aims to compare the fracture resistance of teeth restored with different post and core systems by cyclic loading test and to predict long-term effects.</p><p><b>METHODS</b>A total of 15 recently extracted mandibular premolars without crowns were endodontically treated. The teeth were randomly divided into three groups with five teeth in each group. Group A, teeth restored with cast metal post and core. Group B, teeth with fiber post and resin core. Group C, teeth with resin filling. All of the teeth were restored with full-cast metal crowns. The specimens were exposed to 300,000 cyclic loadings in a cyclic loading machine and 1,000 thermal cycles between 5 and 55 °C. All of the samples were loaded in AG-IS mechanical testing machine with a compressive load until fracture occurred. The fracture load and the fracture mode of each tooth were recorded.</p><p><b>RESULTS</b>The fracture resistance in group B and C were higher than that of the cast metal post and core restoration (P < 0.05). Repairable fractures were observed in group B and C, whereas unrestorable and catastrophic fractures were found in group A.</p><p><b>CONCLUSION</b>Fiber post and resin filling is a good choice to restore endodontically treated teeth.</p>
Subject(s)
Humans , Bicuspid , Dental Stress Analysis , Post and Core Technique , Tooth Fractures , Tooth, NonvitalABSTRACT
The objective of the research is to investigate the elements of routine sandblast technique on the evolution of bending strength of dental infiltrated Al2O3 ceramics and the underlying erosion mechanism. The plane specimens of an infiltrated ceramic were manufactured, polished and then tested under the modified pen-like sandblasting apparatus (90 degrees erosive angle and 10 mm sandblasting distance), with different grit sizes, working pressure and disposing time. Half of samples were selected randomly and sintered subsequently with Vitadur alpha veneering porcelain. Before and after sintering, the three-point-bending strengths was measured, and the surfaces of dental porcelain were observed with SEM and LCSM. The bending strength of ceramics decreased significantly after sandblast as compared with that of empty control group. After the procedure of sintering the veneering porcelain, the descending evolution of bending strength slowed down. Under the present manufacturing conditions, grit size effect is prominent among those correlative elements of sand grit size, working pressure and disposing time. And fatigue cracking characterizes the mechanism of erosion of dental infiltrated Al2O3 ceramics.
Subject(s)
Humans , Aluminum Oxide , Chemistry , Dental Materials , Chemistry , Dental Stress Analysis , Materials Testing , Metal Ceramic Alloys , Chemistry , Shear Strength , Stress, MechanicalABSTRACT
<p><b>OBJECTIVE</b>The purpose of this study was to introduce cryotreat technique into prosthetic dentistry by investigating the wear resistance changes of SDA-II medium melting-point castable alloy before and after cryotreat.</p><p><b>METHODS</b>15 samples were divided into three groups, i.e. control group, cryotreat group, cryotreated plus post-cryogenic treat group. Weight loss measurement was used to examine the wear resistance.</p><p><b>RESULTS</b>For SDA-II medium melting-point castable alloy, cryotreat effectively improved its wearing resistance; so far as the wear resistance was concerned, the post-cryogenic treatment was unnecessary.</p><p><b>CONCLUSION</b>The results obtained above suggest that cryotreat was an effective method in enhancing the wear resistance of SDA-II medium melting-point castable alloy.</p>
Subject(s)
Humans , Cold Temperature , Dental Alloys , Dental Stress Analysis , Hardness , Materials Testing , Stress, Mechanical , Surface PropertiesABSTRACT
<p><b>OBJECTIVE</b>Today metal-ceramic restorations are widely accepted in dental practice because of their good aesthetic and biocompatible properties, but there are still several problems to be resolved, among which the influences of their margins on gingival health is noticeable. The purpose of this study was to investigate the influences of metal-ceramic restoration margin on gingival health.</p><p><b>METHODS</b>129 abutments of metal-ceramic restorations, including their margins' fitness, location and smoothness were examined and their influences on gingival health were analyzed.</p><p><b>RESULTS</b>There was a close relation between the metal-ceramic restorations' margins and the gingival health.</p><p><b>CONCLUSION</b>In order to maintain the gingival health, the margins should be smooth, closely fitted, no overhanging and in a moderate location (i.e. not below the gingival more than 1 mm).</p>
Subject(s)
Female , Humans , Male , Gingival Diseases , Gingivitis , Hemorrhage , Metal Ceramic AlloysABSTRACT
<p><b>OBJECTIVE</b>The purpose of this study was to investigate effects of cryotreat on the corrosion resistance of SDA-II medium melting-point castable alloy.</p><p><b>METHODS</b>12 samples were divided into three groups, including the control group, the cryotreated group and the cryotreated & post-cryogenic treated group. The cryotreating process was firstly dropping the temperature from room temperature to -170 degrees C with dropping rate 3 degrees C/min, maintaining -170 degrees C for 2 hrs, and then returning to ambient temperature with an increasing rate of 1 degree C/min. The post-cryogenic process was maintaining the samples in 300 degrees C for 1 hr. Finally, all samples were subjected to the electrochemical potentiodynamic polarization after immersed in the artificial saliva (ISO/TR 10271: 1993 (E), pH 6.8) for 24 hrs at ambient temperature. The exposing area of each sample was 10 mm x 10 mm. The electrochemical tests were carried out in the artificial saliva under 37 degrees C, with the scanning rate of 20 mV/min, starting potential -200 mV below OCP and stopping current 10(-3) A. The corrosion currents (Icorr), the pitting corrosion potentials (Eb) and the potentiodynamic polarization curves were observed using the 283 electrochemical corrosion measuring system automatically.</p><p><b>RESULTS</b>For SDA-II medium melting-point castable alloy, cryotreat reduced corrosion rate of the alloy, but had no effect on the pitting corrosion potential. As far as the post-cryogenic treatment, it didn't affect the corrosion resistance.</p><p><b>CONCLUSION</b>The results suggested that cryotreat was an effective procedure in enhancing the corrosion resistance of SDA-II medium melting-point castable alloy, and it may be applicable in prosthetic dentistry.</p>
Subject(s)
Humans , Cold Temperature , Corrosion , Dental Alloys , Dental Casting Technique , Hardness , Materials Testing , Mechanics , Saliva, Artificial , TemperatureABSTRACT
Objective:To investigate the feasibility of improving the corrosion resistance of nickel-chromium alloys by the means of cryogenic treatment. Methods:16 disk samples were divided into 4 groups, including control group(C), cryotreat group(E1),tempering after cryotreat group(E2) and simulative porcelain sintering after cryotreat group(E3). All samples were subjected to electrochemical potentiodynamic polarization after immersed in the artificial saliva ISO/TR 10271:1993(E) pH 6.8 for 24 h at ambient temperature. The metallography of all groups were observed by SEM. Results:①Cryogenic treatment elevated the pitting corrosion potential and dropped the corrosion current of Ni-Cr alloys. Following simulative porcelain sintering,as well as tempering after cryotreat, decreased the corrosion current. But the corrosion potential of Ni-Cr alloys fell after cryotreat and following simulative porcelain sintering. Tempering after cryotreat did not affect the pitting corrosion potential. ②Much small secondary substance separated out and evenly distributed along the crystals of Ni-Cr alloys after cryotreat. Conclusion:Cryogenic treatment effectively improves the electrochemical corrosion resistance of Ni-Cr alloys, and tempering following cryotreat is unnecessary. It is not recommended to sintering porcelain after cryogenic treatment.
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To study the effects of high salt intake together with cold stress on rat cardiac renin angiotensin aldosterone system (RAAS) in rats. Male Wistar rats were randomly divided into four groups: control, high salt (8%NaCl), cold stress (5 2℃) and compound group (8%NaCl+cold stress). Blood pressure and body weight were measured once a week. The experiment ran for 8 weeks. Renin activity (RA), angiotensinⅡ (AngⅡ), and aldosterone (Aldo) in plasma and left ventricle were determined with radioimmunoassay. Angiotensin II receptor mRNA was determined with RT PCR. The results showed that ①Rats in compound group had higher blood pressure than rats in the other three groups ( P