| Background As a kind of biomedical inorganic materials shouldhave good biocompatibility, low content of impurity elements, non-toxic,no cancer, no genetic toxicity, insoluble in tissue fluid, stable structure,convenient operation, etc. So, as excellent oral material shall have toprevent bacteria invasion again and good sealing ability and antimicrobialproperties, radiopacity, pressure and abrasion resistance, the shorter settingtime and so on. Most biomedical inorganic materials are synthesizedthrough a chemical reaction then made of sintered, when choosingchemical raw materials will inevitably contain a amount of impurityelements, some impurity elements harmful to human body, such as heavymetals, when the content of heavy metals exceeds a certain threshold valuewill cause human poisoning.MTA widely applied in the dental disease and periapical disease,because of long time for solidification, making tooth discoloration, not easyto remove, expensive its application is limited. Because PC’s compositionis similar to the MTA, foreign scholars have done a lot of research on their physical and chemical properties which find similarity both of them,besides the PC is cheap. In direct pulp capping, pulpotomy, bottom wearpatches, root barrier, root end filling technology needs X-ray resistance andgood sealing ability. Portland cement of our country production process isin strict compliance with the provisions of GB/T2015-2005. and foreignuses EN197standard. The results can not completely replace foreigncountry. PC divids into WPC and GPC from the color, So this part of theresearch on the basis of the previous studies, to join the developer in theWPC and to explore the clinical feasibility of WPC.Objectives Scholars from abroad research methods explore theaverage particle size and particle size distribution of the WPC, some heavymetals content, and sealing ability as a root canal filling material. Thisresearch is mainly about:(1) detecting particle size of WPC GPC andMTA with S3500series laser particle size analyzer, indirect evaluation theseal of the WPC, pressure and abrasion resistance and setting time.(2)Using ICP-AES to analyze the levels of7heavy metals (bismuth, lead,arsenic, nickel, manganese, cadmium and chromium) in WPC,WPC+20%BO, and MTA.(3)Use the dye penetrant and transparentspecimen to evaluate the sealing ability of WPC, WPC+20%BO, WPC+20%ZO, MTA and GPC as root end filling.Materials and Methods1. Using S3500series laser particle sizeanalyzer analyze the particle size and paticle size distribution of WPC, GPC and MTA.0.05gram of each sample, to the nearest of0.0001g, wasweighed and transferred to the beaker (50mL) added90%alcohol. Fullymixing with a glass rod. At last put the beaker in the ultrasonic oscillatorsfor5min, with frequency of24KHZ. Using90%alcohol flush analyzercyclically, and detect whether the container contains impurities, if theimpurities particle size does not affect the result of the experiment range,After mixing with a glass rod will shock solution into the container. Gasbottle contains90%alcohol solution, The particle size of each group willmeasure10times. If particle size of the WPC and the MTA are similar,they can indirectly proof the WPC and the MTA which may be similar insealing ability, compressive strength, and wear resistance, setting time andso on2. The levels of7heavy metals (bismuth, lead, arsenic, nickel,manganese, cadmium,chromium.) in WPC alone, WPC+BO, and MTAwere analyzed by ICP-AES. One gram of each sample, to the nearest of0.0001g, was weighed and transferred to the beaker (50mL). A mixture of7.0mL of nitric acid (HNO3;60%by weight) and21.0mL of hydrochloricacid (HCl;35%by weight) was added to the reaction beaker and left tostand for2hours. After the beaker was slightly capped, it was transferred tothe hood containing an exhaust vent and heated to80°C by placing on theheating block and allowed to equilibrate at80°C for150minutes. Thetemperature of the mixture was raised slowly to eliminate losses of traces by abrupt boiling. After reaction of the sample and the mixture acids, thereaction vessel was cooled to room temperature. Then, this mixture wasfiltered through Whatman No.42filtration paper. A blank test was carriedout in parallel by the same procedure, using the same quantities of allreagents but omitting the test sample. A total of1000mg/L of stockstandard solutions of7heavy metal species (bismuth, lead, arsenic, nickel,manganese, cadmium and chromium) were purchased and diluted into5different concentrations using deionized water. ICP-AES measure thecontent of seven heavy metals.3. Objective One hundred and four premolars with single root canalwere instrumented and set as retrograde filling modle. The teeth wererandomly divided into five test groups (WPC, WPC+BO, WPC+ZO, MTAand GPC; n=20) and two control groups (positive and negative controlgroups; n=2). The teeth were exposed to Indian ink. And the extent of dyepenetration was measured with stereomicroscope. The deeper thepenetration depth, sealing ability worse, and vice versa, the better.Results1. The mean particle size of WPC is similar toMTA(P>0.05). The mean particle size of GPC is greater than WPC andMTA(P<0.01). When the particle size is in (0.289-1.944)μm and (2.312-5.500)μm, WPC’s distribution of particle size is lower than MTA;When the particle size is in (6.540-13.080)μm and (15.550-31.110)μm,WPC’s distribution of particle size is higher than MTA, which maintain that the large particles of WPC is more than MTA. When the particle size is(0.289-31.110)μm, WPC’s distribution of particle size is similar to theMTA (P>0.05).2. WPC in arsenic, nickel, manganese, chromium content is higherthan that of the MTA, MTA respectively2.0times,1.8times,1.7times,1.8times; Bismuth, lead and cadmium content is lower than that of the MTA,MTA respectively0.07%,38%,68%. WPC+20%bismuth in BO, lead,arsenic, nickel, manganese, chromium content is higher than that of theMTA, MTA respectively1.4times,1.5times,1.8times,1.5times,1.4times,2times; Cadmium content is lower than the MTA,68%of the MTA.WPC+20%bismuth in BO, lead, chromium content is higher than that ofWPC, WPC respectively1762.0times,4.0times,1.1times; Arsenic, nickel,manganese content is significantly lower than that of WPC, for WPC of88%,82%,81%, and the cadmium content is the same as the WPC.3. The negative controls showed no dye penetration while dyepenetration was seen in the entire root canal of positive controls. However,WPC, WPC+BO, WPC+ZO and MTA groups showed slight dyepenetration, and there was no statistically significant difference(P>0.05) intheir extent of dye penetration; There was more dye penetration in groupGPC and there was statistically significant difference between GPCgroup and the other four experimental groups (P＜0.01).Conclusions1. Size of the test results can not be assessed the difference of WPC and MTA at the setting time、compression wear、sealing ability and other properties, But it can prompt that the GPC maybe poor on these properties.2. In accordance with ISO inorganic materials for the medicalrequirements of impurity elements, The levels of arsenic, cadmium andlead are not exceeded in WPC; Because the manganese content of WPCis higher than in MTA, it is possible to make tooth discoloration; Becausebismuth content in WPC+BO is higher than the MTA group, thepercentage of the developer to join also need to study; After joining BOchanged the content of heavy metals in WPC, so when added to thedeveloper, and its purity is also need to consider.3. Sealing ability of WPC, WPC+BO,WPC+ZO are the same as thatof MTA when used as root filling materials. All of them are better thanGPC. ZO and BO might be good alternatives as radiopacifying agents. |
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