Clinical Value of Endodontic Patients Treated with Calcium Hydroxide Preparations

Objective: To investigate the clinical value of endodontics patients treated with calcium hydroxide preparation. Methods: The study cases were selected from the endodontics patients who visited our hospital during the period from January 2022 to December 2023, and 97 cases were randomly selected according to the numerical table method and divided into two groups. There were 49 cases in the control group and 48 cases in the experimental group. The control group received conventional therapy, while the experimental group received treatment with calcium hydroxide preparation, and the clinical value of the two different treatment modalities was observed and analyzed. Results: In the experimental group, 45 out of 48 patients (93.75%) showed effectiveness, compared to 39 out of 49 patients (79.59%) in the control group. The effectiveness rate was significantly higher in the experimental group (P < 0.05). Initially, the VAS scores between the two groups were similar (P > 0.05), but after 1 and 3 months of treatment, the scores decreased in both groups. However, the experimental group had a greater decrease, indicating lower pain levels (P < 0.05). The experimental group had fewer complications (8.33%) compared to the control group (24.49%), with a significant difference (P < 0.05). Satisfaction with treatment was higher in the experimental group (95.83%) compared to the control group (95.83%), resulting in an overall higher satisfaction rate in the experimental group (83.67%;P < 0.05). Conclusion: The treatment effect of endodontics with calcium hydroxide preparation is remarkable, which not only can effectively help patients to relieve their pain and reduce the incidence of complications but also plays an important role in improving patients’ satisfaction with treatment, which is worthwhile to be vigorously promoted in the clinic and learn from it.

Calcium Hydroxide in Endodontics: An Overview

Background: Calcium hydroxide has been used in dentistry since several decades. It has been used in a number of applications in the field of endodontics such as root resorption, intracanal medicament, and root canal sealers. Although this material exhibits several advantages, it also has some limitations. Objectives: To review the role of calcium hydroxide in the field of endodontics, focusing on its mechanism of action, antimicrobial effects, different applications, cytotoxicity or biocompatibility, and its removal from the root canals. Materials and Methods: An electronic search was done using different databases. Out of 2,664 articles, only 33 articles have been selected to be included in this review because they are directly related to the topic and matched the inclusion criteria of this review: “Language: English” and “Year: 2000-2016”. Results: The antimicrobial effect of calcium hydroxide is controversial. Although some studies supported the effectiveness of calcium hydroxide against some bacteria others reported its limitation against fungal infection. Calcium hydroxide can be used effectively as intracanal medicament, root canal sealer, in weeping canals, for perforation management and root resorption. Conclusions: Despite the limitation of antimicrobial activity of calcium hydroxide, it is used effectively in a number of treatment modalities in endodontics. Due to its biological and therapeutical properties, calcium hydroxide is the material of choice for all pulp therapy. However, when using calcium hydroxide as a dressing material in root canal treatment caution should be taken to prevent the overextension of the paste beyond the tooth apex and avoid the harmful side effects.

An in vitro study on the efficacy of removing calcium hydroxide from curved root canal systems in root canal therapy

To compare the efficacy of various irrigants(citric acid, ethylenediaminetetraacetic acid(EDTA) and Na OCl) and techniques in removing Ca(OH)2in two types of curved root canal systems, simulated root canals with specific curvatures were used to investigate the effects of different irrigants and instruments on Ca(OH)2removal. The optimal methods were verified on extracted human teeth. Simulated root canals were assigned to one of two groups based on the irrigation solution: 10% citric acid or2.5% Na OCl. Each group was divided into four subgroups according to the technique used to remove Ca(OH)2. The percentage of Ca(OH)2removal in different sections of root canals was calculated. On the basis of the results obtained for the simulated canals, 10% citric acid and 17% EDTA were applied to remove Ca(OH)2from the extracted human teeth with curved root canal systems. The teeth were scanned by micro computed tomography to calculate the percentage of Ca(OH)2removal in the canals.In simulated root canals, we found that 10% citric acid removed more Ca(OH)2than 2.5% NaOCl in the 0–1 mm group from the apex level(Po0.05). Ultrasonic and Endo Activator activation significantly removed more Ca(OH)2than a size 30 K file in the apical third(Po0.05). However, there were no significant differences in any sections of the canals for 10% citric acid or 17%EDTA in removing Ca(OH)2in extracted human teeth. We concluded that it was effective to remove residual Ca(OH)2using the decalcifying solution with Endo Activator or Passive Ultrasonic Irrigation in a curved root canal system. A protocol for Ca(OH)2removal was provided based on the conclusions of this study and the methods recommended in previous studies.

Quantitative Comparison of Calcium Hydroxide Removal by EndoActivator, Ultrasonic and ProTaper File Agitation Techniques: An in vitro Study

Calcium hydroxide （CH） dressing residues can compromise endodontic sealing. This study aimed to evaluate the amount of remaining CH in root canals after mechanical removal by four groups of irrigation techniques including needle irrigation only, ProTaper file, EndoActivator, and ultrasonic file. Fifteen extracted single-rooted teeth were collected and used for all four groups. The samples were firstly prepared by ProTaper rotary instruments, and then sectioned longitudinally through the long axis of the root canals, followed by final reassembling by wires. CH was kept in the canals for 7 days setting. The removal procedure began with 5 mL of 2.5% sodium hypochlorite （NaOC1） followed by 1 mL of 17% ethylenediaminetetraacetic acid and a final irrigation with 5 mL of 2.5% NaOC1 solution for all groups. No additional agitation of the irrigant was performed in group 1, while agitation for 20 s be- tween irrigants was done with F2 ProTaper rotary file in group 2, EndoActivator with tip size 25/.04 in group 3 and by an ultrasonic file 25/.02 in group 4. The total activation time was 60 s. The roots were then disassembled and captured by digital camera. The ratio of CH coated surface area to the surface area of the whole canal as well as each third of the canal was calculated. The data were statistically ana- lyzed by one-way ANOVA using post hoc Tukey test. Results showed that none of the four techniques could remove all CH. No significant difference was found between EndoActivator and ultrasonic tech- niques. However, they both removed significantly more CH than ProTaper and needle irrigation （P=0.0001）. In conclusion, the sonic and ultrasonic agitation techniques were more effective in removing intracanal medicaments than the ProTaper rotary file and needle irrigation in all thirds of the canal.

Application of Hydrosoluble Polymers to Preparation of Nanoscale Calcium Hydroxide

Calcium hydroxide with uniform diameters about 50—100 nm was firstly prepared under moderate condition by adding different kinds of hydrosoluble polymers. From the results of TEM and IR, the polymers were proved not only to improve the agglomeration of the nanoparticles but also to be used as a template to control the formation of the special structure and the needed size of Ca(OH) 2 by changing the concentration of the polymers. The experimental results of TG-DTA indicate that the Ca(OH) 2 can absorb most of the acid gases released during the decomposition of polymers. So this kind of nano- Ca(OH) 2 can be used as a useful additive of environmental friendly plastics.

Recovery of magnetite from FeSO_4·7H_2O waste slag by co-precipitation method with calcium hydroxide as precipitant

Proper utilization of the FeSO4·7H2O waste slag generated from TiO2 industry is an urgent need, and Fe3O4 particles are currently being widely used in the wastewater flocculation field. In this work, magnetite was recovered from ferrous sulphate by a novel co-precipitation method with calcium hydroxide as the precipitant. Under optimum conditions, the obtained spherical magnetite particles are well crystallized with a Fe304 purity of 88.78%, but apt to aggregate with a median particle size of 1.83 μm. Magnetic measurement reveals the obtained Fe304 particles are soft magnetic with a saturation magnetization of 81.73 A-m2/kg. In addition, a highly crystallized gypsum co-product is obtained in blocky or irregular shape. Predictably, this study would provide additional opportunities for future application of low-cost Fe3O4 particles in water treatment field.

Calcium Hydroxide Removal in Curved Root Canals with Apical Transportation In Vitro

Calcium hydroxide（CH） is applied to improve disinfection of root canals in most root canal retreatment. This study aimed to analyze the CH removal efficacy using 7 different root preparing files（K file, pre-curved K file, EndoActivator, Ultrasonic file, pre-curved ultrasonic file, F file and needle irrigation alone） with apical transportation. Standardized models of curved canal with such apical transportation or not were set up before applying CH to root canal for 7 days. Seven techniques described above were used for its removal. Then the roots were disassembled and digital photos were taken. The ratio of residual CH in the overall canal surface was calculated using the image analyzer image pro plus 6.0. The data were analyzed using one-way ANOVA with post hoc Tukey test. Results revealed that CH was effectively removed（P〈0.05） by using all 6 mechanical methods except irrigation alone. In curved root canals with apical transportation, EndoActivator, pre-curved ultrasonic file and F file were found to be more effective in removing CH than the other four file（P〈0.001）, while there was no significant difference among EndoActivator, pre-curved ultrasonic file and F file groups（P〉0.05）. The percentage of residual CH in the canal with apical transportation was higher than that in the canal without apical transportation（P〈0.05）. In conclusion, CH can be hardly removed completely. Canal with apical transportation will result in insufficient CH removal. EndoActivator, pre-curved ultrasonic file and F file are more effective in the curved root canal with apical transportation.

Antibacterial activity of calcium hydroxide combined with chitosan solutions and the outcomes on the bond strength of RealSeal sealer to radicular dentin

The purpose of this study was to investigate the antibacterial activity of calcium hydroxide [Ca（OH）2] combined with chitosan solutions against Enterococcus faecalis-infected root canal dentin and the effect of this new intraca- nal medicament on the bond strength of RealSeal sealer to radicular dentin. An experimental intracanal medicament was prepared by mixing different concentrations of chitosan solution （25%, 50%, and 100%, W/V） to Ca（OH）2 powder. Antibacterial activity was evaluated and the total numbers of colony forming units were determined. Bonding ability of RealSeal sealer to radicular dentin was evaluated using push-out bond strength test. Data were analyzed using one-way analysis of variance （ANOVA） and Tukey＇s multiple comparison tests. We found that Ca（OH）2 combined with different concentrations of chitosan solutions showed better antibacterial activity than Ca（OH）2 mixed with saline, without significantly affecting the bond strength of RealSeal sealer to radicular dentin （P 〉 0.05）. The findings suggest that Ca（OH）2 combined with chitosan is a promising intracanal medicament and may be effective in endodontic therapy.

Influence of Compaction Pressure on the Accelerated Carbonation of Calcium Hydroxide

Mineral carbonation using waste cement is a promising method to solve the problems caused by CO_2 emission and waste cement. Compaction pressure is an important parameter for mineral carbonation of calcium hydroxide, one of the most dominant composite of waste cement that can be carbonated. The carbonation degree, morphology of products and compressive strength of carbonated compacts are influenced by compaction pressure significantly. Results show that the carbonation degree of calcium hydroxide increases at first（0-8 MPa） and then decreases in the higher compaction pressure range（10-14 MPa）. At the meantime, results also indicate that lower compaction pressure accelerates the early carbonation but hinder carbonation in the later stages. For the morphologies of carbonation products, calcium carbonate tends to form typical crystal morphology of calcite（rhombohedral） under lower compaction pressure, while it will become ellipsoidlike when compaction pressure reaches 8 MPa. TGA and water content results show that there is an optimal water content for the carbonation. In addition, lower water content is adverse to the carbonation at later stage and the CO_2 is difficult to penetrate into the inside of compacts when water content is high, which will hinder the carbonation. XRD and TGA results show that the carbonation products are calcite and small amount of amorphous calcium carbonate.

Lignin-containing Microfibrillated Cellulose Prepared from Corncob Residue via Calcium Hydroxide Co-grinding and Its Application in Paper Reinforcement

In this study,lignin-containing microfibrillated cellulose(MFC)was prepared from corncob residue after xylose extraction via co-grinding with calcium hydroxide.The product was then compared with the MFC obtained by direct grinding and applied to strengthen paper.The chemical composition and morphological structure analysis results showed that the corncob residue can be used to prepare lignin-containing MFC and does not require further purification.Moreover,the co-grinding with calcium hydroxide is easier to fibrillate corncob residue.The MFC obtained by cogrinding with calcium hydroxide had a higher aspect ratio,and its surface was coated with calcium carbonate nanoparticles.MFCs obtained by both the methods mentioned above had an obvious strengthening effect on paper.Compared with the paper without MFC,the tensile index,elongation,burst index,and folding strength of the paper with MFC obtained by co-grinding with calcium hydroxide significantly increased by 17.5%,22.1%,19.5%,and 157.1%,respectively.This study provides a novel idea for the utilization of corncob residue,which may enhance the value and promote the comprehensive utilization of corn by-products.

Antimicrobial activity of calcium hydroxide and chlorhexidine on intratubular Candida albicans

This study investigated the efficacy of calcium hydroxide and chlorhexidine gel for the elimination of intratubular Candida albicans (C.albicans).Human single-rooted teeth contaminated with C.albicans were treated with calcium hydroxide,2%chlorhexidine gel, calcium hydroxide plus 2%chlorhexidine gel,or saline(0.9%sodium chloride) as a positive control.The samples obtained at depths of 0-100 and 100-200μm from the root canal system were analyzed for C.albicans load by counting the number of colony forming units and for the percentage of viable C.albicans using fluorescence microscopy.First,the antimicrobial activity of calcium hydroxide and the 2%chlorhexidine gel was evaluated by counting the number of colony forming units.After 14 days of intracanal medication,there was a significant decrease in the number of C.albicans colony forming units at a depth of 0-100μm with chlorhexidine treatment either with or without calcium hydroxide compared with the calcium hydroxide only treatment.However,there were no differences in the number of colony forming units at the 100-200μm depth for any of the medications investigated.C.albicans viability was also evaluated by vital staining techniques and fluorescence microscopy analysis.Antifungal activity against C.albicans significantly increased at both depths in the chlorhexidine groups with and without calcium hydroxide compared with the groups treated with calcium hydroxide only.Treatments with only chlorhexidine or chlorhexidine in combination with calcium hydroxide were effective for elimination of C.albicans.

Effects of Sustained-Release Calcium Hydroxide and Sustained-Release Hydrochloric Acid on Nutrient Di-gestion and Absorption of Rabbits

Rabbits with the body weight of （2.0 ± 0.5 ） kg were chosen, to study the effects of sustained-release calcium hydroxide and sustained-release hydro- chloric acid on nutrient digestion and absorption of rabbits. The results showed that sustained-release calcium hydroxide promoted digestion and absorption of nutri- ents, especially calcium and crude protein. The digestibility of calcium and crude protein was increased from 89.8% and 93.8% to 41.0% and 65.2%, respec- tively. Sustained-release hydrochloric acid was adverse to digestion and absorption of nutrients, especially calcium and crude protein. The digestibility of calcium and crude protein were decreased from 55.5% and 84.9% to 28.4% and 68.7%, respectively. The promotion effects of sustained-release hydrochloride on diges- tion lasted for 3 -4 d. Therefore, sustained-release calcium hydroxide promoted digestion and absorption of calcium and protein, while digestion and absorption of fat remained at a high level no matter what the condition was. Consequently, increasing the intake of fat would cause over nutrition. However, taking sustained-re- lease hydrochloric acid would reduce nutrient digestion and absorption.

Mechanism of calcium hydroxide inhibiting methicillin resistant Staphylococcus aureus

Objective:To investigate the inhibitory effect of calcium hydroxide on methicillin-resistant Staphylococcus aureus and the related inhibition mechanism.Methods:To determine the minimum inhibitory concentration of calcium hydroxide using microplate dilution method;to compare the effects of calcium hydroxide at 8MIC,MIC,1/4MIC and 0 concentrations on MRSA using growth curve method;to determine the effects of calcium hydroxide on the cell membrane of methicillin-resistant Staphylococcus aureus using calcium xanthophyll and propidium iodide fluorescence staining The effect of calcium hydroxide on the morphology of methicillin-resistant Staphylococcus aureus was observed by scanning electron microscopy;the inhibition mechanism of calcium hydroxide on MRSA was investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis of protein bands.Results:The MIC of calcium hydroxide on MRSA was 3.125 mg/mL;the fluorescence intensity showed significant changes after co-culture of calcium hydroxide with bacteria;MRSA appeared to be significantly crumpled and broken in the presence of calcium hydroxide;the SDS-PAGE experimental bands indicated that the protein inside the bacteria decreased accordingly with the increase of calcium hydroxide concentration.Conclusion:Calcium hydroxide has a significant inhibitory effect on the growth of MRSA,and its bactericidal mechanism may be related to the destruction of bacterial body structure.

Preparation and characterization of hemihydrate calcium sulfate-calcium hydroxide composite bone repair materials

Objective:To prepare a bone repair material with certain mechanical strength and biological activity,this paper used calcium sulfate hemihydrate(CSH)powder compounded with calcium hydroxide(Ca(OH)2)powder to prepare a bone repair scaffold material for physicochemical property characterization and testing.Methods:The physical and chemical properties and characterization of the dried and cured bone repair materials were determined by Fourier infrared spectroscopy(FT-IR),X-ray diffraction(XRD),and scanning electron microscopy;Universal material testing machine to determine the mechanical and mechanical strength of composite materials.Results:XRD showed that the structure of the composite material phase at 5%concentration was calcium sulfate hemihydrate and calcium hydroxide after hydration.The FT-IR and XRD analyses were consistent.Scanning electron microscopy(SEM)results showed that calcium hydroxide was uniformly dispersed in the hemihydrate calcium sulfate material.0%,1%,5%,and 10%specimen groups had compressive strengths of 3.86±3.1,5.27±1.28,8.22±0.96,and 14.4±3.28 MPa.10%addition of calcium hydroxide significantly improved the mechanical strength of the composites,but also reduced the the porosity of the material.Conclusion:With the addition of calcium hydroxide,the CSH-Ca(OH)2 composite was improved in terms of mechanical material and is expected to be a new type of bone repair material.

Study on the Influence of Alkali Activator Solutions on Strength Improvement of Pozzolan Calcium Hydroxide Binders

Alkali activated binder, commonly known as geopolymer cement, has replaced Portland cement in the production of mortar and concrete globally over the past few years. The density, particle size distribution, and specific surface area (SSA) are important physical parameters affecting strength and durability of alkali activated binders. This study carried out tests for physical and chemical properties of the natural pozzolan and calcium hydroxide and then determines the influence of alkali solution (sodium silicate and sodium hydroxide) on strength development of natural pozzolan calcium hydroxide binders. The particle size distribution (PSD), relative densities (RD), and specific surface areas (SSA) of powder natural pozzolan and calcium hydroxide materials and for the mixture of natural pozzolan and calcium hydroxide were determined by using Blaine air permeability apparatus. The optimum proportion of 75% natural pozzolan and 25% calcium hydroxide was obtained which produces the compressive strength of 7.5 MPa at 28 days cured paste. The mixture of natural pozzolan and calcium hydroxide were further grinded at three different finenesses and the particle size gradation, specific densities, specific surface areas and mean particles sizes for the mixture were determined. The compressive strength of alkali activated binders increased with increasing curing period and fineness. The maximum compressive strength for 28 days cured specimens was 26.1 MPa which was obtained at a solution of 8 moles sodium hydroxide concentration. The test results showed that natural pozzolan materials can be used to make geopolymer binders for mortars and concretes. The geopolymer binders for mortars and concretes reduce green gas emission from cement factory but also it can be used to produce durable mortar and concrete with comparable strengths with mortars and concrete made from conventional Portland cement.

Isoconversional kinetic analysis of decomposition of bastnaesite concentrates with calcium hydroxide

Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energy was calculated,and the results indicate that the overall reaction involves more than one single step.The reaction with a lower content(<15 wt%)of calcium hydroxide can be divided into two steps,while the reaction with a higher content(>15 wt%)involves another step which denotes the decomposition of newly formed calcium carbonate during roasting.The activation energy increases with increasing amount of calcium hydroxide in the lower range(0-15 wt%).This is due to the resistance of calcium hydroxide to heat and mass transport,However,more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy.Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor.The theoretical models were proven to be reliable for kinetic prediction.

Effects of LiAl-Layered Double Hydroxides on Early Hydration of Calcium Sulphoaluminate Cement Paste

As a 3D micro-nano material, layered double hydroxides have been widely used in many fields, especially for reinforced composite materials. In this paper, Li Al-LDHs was obtained by a hydrothermal method. In order to investigate the effects of Li Al-LDHs on the early hydration of calcium sulphoaluminate（CSA） cement paste, compressive strength, setting time and hydration heat were tested while X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FT-IR）, scaning electron microscopy（SEM） and differential scanning calorimetry（DSC） analysis were employed. The results indicated that Li Al-LDHs could significantly improve the early compressive strength and shorten the setting time of calcium sulphoaluminate cement paste with 3 wt% concentration. Besides, the hydration exothermic rate within 5h was accelerated with increasing Li Al-LDHs content. Moreover, the addition of Li Al-LDHs did not result in the formation of a new phase, but increased the quantity of hydration products providing higher compressive strength, shorter setting time and denser microstructure.

The Characteristics of a Sorption-enhanced Steam-Methane Reaction for the Production of Hydrogen Using CO_2 Sorbent

The objective of the present study is to characterize the production of hydrogen with a sorptionenhanced steam-methane reaction process using Ca(OH)2 as the CO2 adsorbent. Theoretical equilibrium compositions at different operation conditions were calculated using an iterative method. It was found that with Ca(OH)2 as the CO2 sorbent, the concentration of CO2 adsorption was reduced in the product stream, that gave rise to higher methane conversion and higher H2 concentration. An experimental setup was built to test the theoretical calculation. The effects of sorbents and the particle size of Ca(OH)2 on the concentration of CO2 and H2 were investigated in detail. Results showed that the reactor packed with catalyst and Ca(OH)2 particles produced H2 concentration of 94%. It was nearly 96% of the theoretical equilibrium limit, much higher than H2 equilibrium concentration of 67.5% without CO2 sorption under the same conditions of 500℃, 0.2 MPa pressure and a steam-to-methane ratio 6. In addition, the residual mole fraction of CO2 was less than 0.001.

Investigation of the role of Ca(OH)2 in the catalytic Alkaline Thermal Treatment of cellulose to produce H2 with integrated carbon capture

The Alkaline Thermal Treatment(ATT)of biomass is one of the few biomass conversion processes that has a potential for BECCS(bio-energy with carbon capture and storage).Combining in-situ carbon capture withcreates a carbon-neutral process that has the potential to be carbon-negative.This study has shown that the conversion of cellulose tosuppressedcan be achieved through the reforming of gaseous intermediates in a fixed bed of 10%Ni/ZrO2.Reforming occurs at low temperatures≤773 K,which could allow for improved sustainability.

Entire Whitening of Apple Trees to Increase Chill Units in Regions of Warm Temperatures during the Fall-Winter Seasons

Different studies have shown that global warming and climate change have increased the planet’s temperature in different locations. For the apple-growing farmers, this may have a negative impact on the accumulations of chill units when the air temperature during the fall-winter season increases. When the entire trees are covered with a reflective material, the wood temperature may decrease. Therefore, the objective of this study was to evaluate the effect of whitening (with calcium hydroxide) the entire apple trees (Malus domestica Borkh) after defoliation, on the branches and trunks’ internal temperature (under the bark), the accumulation of chill units (CU), its effects on fruit yield and quality and the relation with the use of thidiazuron (TDZ) (inducer of budbreak). The study was conducted during the fall-winter seasons of 2019-2020 and 2020-2021. The results of this study showed that at the hours of the highest incidence of solar radiation, the internal temperature of the whitened trunks and leaves decreases up to 9&deg;C and 6&deg;C respectively. The accumulated CU during the time of the study, of the whitened branches were up to 81% higher than the ones recorded on the branches with no whitening;while the CU was lost at the hours of highest solar radiation (due to a high temperature) were up to 37.2% smaller. Entire tree whitening increased up to 26% of the yield per tree compared to the application of TDZ. No statistical difference in fruit quality was observed between whitened trees and those with no whitening but with the application of thidiazuron.