The influence of sample dimensions on hydroxyl ion release from calcium hydroxide products

The purpose of this study was to compare the rate of hydroxyl ion release from commercially available setting and non-setting calcium hydroxide products. The rate of hydroxyl ion release is important, as this has been suggested to be the main factor in the therapeutic activity of these products. In total, hydroxyl ion release was measured from 1104 samples of Dycal, Life, Calasept and Hypocal in solution using in vitro titration. The rate of hydroxyl ion release was measured for up to 14 days, using two sizes of sample surface area. The dimensions of the exposed sample surface area was found to be an important physical constraint to the hydroxyl ion release from non-setting calcium hydroxide products, whereas this was not found to be the case with setting products. The range in hydroxide activity between products was found to be 298%. In rank order of hydroxide ion release, from the most to the least active was: Hypocal, Calasept, Life and Dycal. The differences in the rate of hydroxyl ion release from these products may have some implications for their clinical applications. It is suggested that in cases where the oral healing responses have been poorer than expected, the size and seal of prepared cavities could have negatively influenced the therapeutic release of hydroxyl ions from non-setting calcium hydroxide products.     

In vitro release of calcium and hydroxyl ions from two types of calcium hydroxide preparation

Non-setting and setting pastes are the most common forms of calcium hydroxide, used in endodontics. The aim of this study was to investigate the differences in the availability of calcium and hydroxyl ions from some commercial preparations of both types. In vitro released calcium and hydroxyl ions were determined by a potentiometric method, after diffusion through sintered glass. The non-setting pastes evaluated were Calcipulpe, Calxyl Red, Calxyl Blue and Cinacal; while setting base materials were represented by Dycal, Nu-Cap and Reolit. The data obtained showed significantly higher availability of calcium and hydroxyl ions from non-setting pastes, compared with‘alkaline cements’(P>0.05). Great variations in the amount of released ions were also found among samples of the same material.     

Calcium hydroxide pastes: classification and clinical indications

REVIEW ARTICLE: Calcium hydroxide has been used in endodontology for many years. The aim of this paper is to review the various formulations of calcium hydroxide that have been described, with specific reference to the vehicle used to carry the compound. The requirements for a vehicle are described, and ex vivo and in vivo studies reviewed. Vehicles can be classified into aqueous, viscous and oily, the clinical properties of calcium hydroxide changing depending on the vehicle. The review also describes the use of various active components that have been added to calcium hydroxide, including antimicrobial and anti-inflammatory agents. This review will help clinicians to make informed judgements about which formulations of calcium hydroxide should be used for specific endodontic procedures.     

A laboratory study evaluating the release of hydroxyl ions from various calcium hydroxide products in narrow root canal-like tubes

AIM: The aim of the present study was to describe pH changes in a variety of buffering solutions within a narrow test tube containing either a gutta-percha point with incorporate calcium hydroxide, a commercial calcium hydroxide paste (Calcicur) or a freshly mixed paste of calcium hydroxide in distilled water. METHODOLOGY: The test material was placed centrally in a test tube of 2 mm inner diameter. Saline (1%) was placed at one end, whilst the buffering solutions were introduced at the other. The pH of the buffering solutions was monitored using electrodes placed at each end of the test tube. RESULTS: It was found that the pH 4.01 buffer strongly resisted pH changes at levels below 6.0, whilst saliva and bovine serum was buffered less and more evenly in the whole range up to pH 11.5. The calcium hydroxide containing gutta-percha points caused the pH to increase quickly in the sodium chloride solution to levels above 11.5. However, in bovine serum, in saliva and in the pH 4.01 buffer the pH remained below 8.5, 8.0 and 6.0, respectively, 1 mm from the point. In contrast, the release of hydroxyl ions from the two calcium hydroxide pastes brought pH above pH 11.5 irrespective of the buffering of the solutions 5 mm from the paste. CONCLUSION: It is concluded that Calcicur and the calcium hydroxide-water mixture contained substantially more available calcium hydroxide than did the calcium hydroxide containing gutta-percha points, with the result that the release of hydroxyl ions from the points was limited in comparison to that from the pastes.     

A comparison of hydroxyl ion diffusion through root dentine from various calcium hydroxide preparations

Different calcium hydroxide [Ca(OH)₂] formulations are available. The aim was to assess differences in hydroxyl ion release with different formulations. Sixty-six teeth were divided one control (n = 6) and four experimental (n = 15) groups: (i) Pulpdent Paste; (ii): DT Temporary Dressing; (iii): Ca(OH)₂ powder/saline; (iv): Ca(OH)₂ points; (v): no medicament. pH was measured in inner dentine and outer dentine cavities over 12 weeks. Inner dentine pH rose rapidly for all groups except the points and controls. Peak pH was reached by day 2 before dropping and stabilising (8.0–9.2). Outer dentine pH rose steadily until day 21 for aqueous solutions and then stabilised (8.0–8.5). The points had minimal pH increase for the entire period. There were no significant differences in hydroxyl ion release between the aqueous solutions. Type of paste base did not affect release and diffusion of hydroxyl ions which continued for 84 days.     

氢氧化钙类根管充填材料的研究进展

根管充填材料与根管治疗效果密切相关。大量的实验室和临床实验表明：氢氧化钙类根管充填材料的短期疗效较理想，它们均具有抑制根管内细菌生长、促进根尖形成及根尖周缺损组织重建等优点。本文就近年来国内外对氢氧化钙类根管充填材料的研究作一简要综述。     

Influence on pH of vehicle containing glycerin used with calcium hydroxide

Abstract  – The pH values of the external aqueous medium, relative to the roots of 41 human premolar teeth filled with Ca(OH)₂ in to several vehicles, were evaluated in the present study. After root canal biomechanical preparation and smear-layer removal, the teeth were stored individually, immersed in flasks containing 800 ml of ultra-pure deionized water for a period of 118 days. A pH meter was used to analyse the pH values as a function of time. The measurements were divided into phase 1: dissolution, in which all canals remained empty and open in the absence of medicament for 48 days, and phase 2: diffusion, in which the specimens were divided into 10 groups which consisted of three control groups: group 1, water control; group 2, sealing control; and group 3, opened canal dissolution control, and seven experimental groups, with five teeth each, whose canals were filled with Ca(OH)₂ paste associated with the following vehicles: group 4, saline solution; group 5, polyethylene glycol (Calen); group 6, glycerin and parachlorophenol (PMCC); group 7, PMCC; group 8, glycerin; group 9, glycerin and formo cresol (FC); and group 10, anesthetic solution. This phase lasted for 70 days. A total of 1058 measurements of the pH values were made. Regression analysis was used for statistical evaluation. The results show that all groups containing polyol in the composition of the paste had a trend to acidification in the interval between filling and 14 days later (therapeutic period) and, at the end of the experiment (1687 h to 70 days after canal filling), the pH was slightly alkaline. We conclude that polyhydroxy alcohol (glycerin and polyethylene glycol, Calen) diffusion enhances acidification of the aqueous medium.     

Release and diffusion of hydroxyl ion from calcium hydroxide-based medicaments

The release and diffusion of hydroxyl ions (OH(-)) of calcium hydroxide (Ca(OH)(2))-based intracanal medications may be affected by the association with other substances. The aim of this study was to evaluate the diffusion of OH- ions through root dentin by the medications: G1, Ca(OH)(2)/saline; G2, Calen; G3, Calen/camphorated p-monochlorophenol (CMCP); and G4, Calen/0.4% chlorhexidine (CHX). Root canals from bovine teeth were prepared in a standardized manner. A cavity until dentin was prepared in the middle third of the root surface of each specimen. The external surface of the root was made impermeable using a layer of adhesive, except the prepared cavity. The root canals were filled with different medications, and teeth were individually stored in flasks containing 10 ml distilled water at 37°C. The water pH was measured at 1, 3, 7, 14, 21, 30, and 60 days. Data obtained were subjected to anova and Tukey's tests. Increase in pH was observed at 3 days for Calen/CHX and from 7 to 14 days for the other mixtures. Calen paste promoted pH increase up to 21 days. Calen/CMCP had the highest pH up to 21 days, and all groups had similar results at 30 days. At 60 days, the greatest pH values were observed for Calen/CMCP and Calen alone. All different formulations of Ca(OH)(2)-based medications tested release hydroxyl ion that can diffuse through the dentin.     

Calcium release and pH-characteristics of calcium hydroxide plus points

AIM: To evaluate calcium ion release and pH-characteristics of calcium hydroxide plus points (CHPP), conventional calcium hydroxide points (CHP, both Coltène/Whaledent, Langenau, Germany) and aqueous calcium hydroxide suspension (CHS) (Calxyl, OCO, Dirmstein, Germany). METHODOLOGY: Ten CHPP or CHP of size 50 were immersed into 5 mL isotonic sodium chloride solution. Conventional Ca(OH)2-free gutta-percha points served as negative control. Calcium release was measured up to 44 days by means of complexometric titration. Time dependent pH behaviour of all points in comparison with CHS was determined immersing 30 points of size 50 into 2.3 mL 0.9% wt NaCl-solution at time intervals of 0.5-72 h by a microelectrode measuring chain and a pH-meter. The surface morphologies of new and used gutta-percha points were evaluated qualitatively under a scanning electron microscope. Statistical evaluation was carried out using Kolmogorov-Smirnov-tests, Mann-Whitney-tests and multifactorial anova. RESULTS: For CHPP, a threefold greater calcium release was measured compared with CHP. Both types of points as well as CHS showed a maximum pH of approximately 12. Differences between groups were statistically significant for calcium release and pH (multifactorial anova; P < 0.001). Both types of points showed porous surfaces after usage, with a rougher surface for CHPP. CONCLUSIONS: CHPP and CHP increased the pH of isotonic sodium chloride >11 within 3 min. CHPP had a greater release of Ca2+ compared with CHP.     

The alkalizing properties of calcium hydroxide compounds

Abstract Calcium hydroxide compounds are available in various forms, such as in aqueous suspensions or as cements, liners, pastes or filled resins. When such compounds are exposed to water, the calcium hydroxide dissociates and the pH value shifts to the basic. In this study the compounds Pulpdent®, Dycal®, Hydroxyline®, Gangraena Merz® and Prisma VLC-Dycal® were subjected to analysis, including quantitative measurement of the amount and the chronological course of ion release following exposure to water, qualitative analysis of the alkalizing effects at the dentin surface and examination of antimicrobial properties. The results showed that calcium hydroxide compounds differed greatly. The strongest degree of ion release, combined with definite antimicrobial properties, was found for the aqueous calcium hydroxide suspension (Pulpdent). The cement (Dycal) demonstrated significantly weaker activity. The liner and the paste (Hydroxyline and Gangraena Merz), as well as the calcium hydroxide filled resin (Prisma VLC-Dycal), were largely lacking in both ion release and antimicrobial properties under the experimental conditions.     

树脂基体对光固化氢氧化钙Ca2+释放的影响

目的：评价树脂基体的组成对光固化氢氧化钙[VLC Ca(OH)2]Ca^2 释放的影响，为筛选 树脂基体提供依据。方法：配制氢氧化钙含量相同、树脂基体不同的7种光固化氢氧化钙，每种材料制备3个圆片试样（d 6mm，h3mm），分别浸泡于37℃5mL去离子水中。于浸泡后1d、2d、1周、2周测定浸泡液的Ca^2 浓度。结果：不同材料的Ca^2 浓度在浸泡初期差异特别显著，随着浸泡时间的延长，差异逐渐缩小。以聚乙二醇（600）二甲基丙烯酸酯为交联剂的材料具有最大的Ca^2 释放量，以甲基丙烯酸乙二醇酯为交联剂的材料Ca^2 释放量最小。结论：光固化氢氧化钙的树脂基质对材料的Ca^2 释放速度有明显影响，含有较多极性基团的树脂基质的Ca^2 释放速度较快。     

In vitro diffusion of hydroxyl ions through root dentine from various calcium hydroxide medicaments

The purpose of this study was to determine diffusion of hydroxyl ions through dentine from different calcium hydroxide [Ca(OH)2] medicaments. Forty-five single-rooted teeth were instrumented and cavities (3 mm in diameter and 1 mm in depth) were prepared on the facial surface of each root. After smear layer was removed with 17% EDTA all surfaces of roots, except cavities, were coated with nail polish. Teeth were randomly divided into four experimental groups (each 10 samples) and a control group (five samples). They were filled with: group 1, Ca(OH)2 and distilled water mixture; group 2, TempCanal; group 3, Calasept; and group 4, Ca(OH)2 plus point. Control group, in which nothing was applied to the canals. All samples were immersed in distilled water maintained at 37 degrees C. pH values were measured at 1 h, 2 h, 3 h, 24 h, 48 h, 72 h, 4 days, 5 days, 6 days, 7 days and 14 days. Ca(OH)2-distilled water mixture and TempCanal showed highest pH values at 24 h. Calasept, Ca(OH)2 plus point and control showed highest pH values at 3 h. Time intervals after 24 h, Ca(OH)2-distilled water mixture, TempCanal and Calasept showed higher pH values than Ca(OH)2 plus point, with a statistically significant difference (P<0.05). The pH value of Ca(OH)2 plus point was lower than the values of other materials after 3 h. This study indicates that non-setting Ca(OH)2 based materials have an effective release of hydroxyl ions compared with Ca(OH)2 plus point.     

Vehicle influence on calcium hydroxide pastes diffusion in human and bovine teeth

Abstract –  The purpose of this study was to compare the pH and calcium ion liberation after use of calcium hydroxide pastes with different paste vehicles in human or bovine teeth. Ninety-two single-rooted human and bovine roots were used. The roots were instrumented and an external cavity preparation was performed. The roots were divided in to human and bovine groups. Each group was subdivided into four subgroups (SB) according to the vehicle:SB1, detergent; SB2, saline; SB3, polyethylenoglycol + camphorated paramonochlorophenol (Calen PMCC) and SB4, polyethylenoglycol + furacyn paramonochlorophenol (FPMC). Specimens were immersed into saline solution at 37°C and after 7 and 14 days pH and calcium ion measurements were made. The results were analyzed by anova and Tukey tests ( P  < 0.05). There was no statistical difference between bovine and human teeth in the pH analysis ( P  < 0.05), but bovine teeth provided larger calcium ion liberation than human teeth. Calen PMCC was statistically more effective for pH increase and calcium ion liberation in all analyses, followed by FPMC and saline. Detergent showed the lowest pH alterations and calcium ion liberation. The period of 14 days showed more calcium ionic liberation than the 7-day period.     

氢氧化钙激动人牙髓细胞内钙释放及其通道的研究

目的：检测Ｃａ（ＯＨ）２激动体外培养的人牙髓细胞内Ｃａ＾２＋的释放和钙释放通道。方法：在ＲＰＭＩ１６４０培养液中分别加入Ｃａ（ＯＨ）２、Ｃａ（ＯＨ）２和肝素、Ｃａ（ＯＨ）２和普鲁卡因,培养第６代人牙髓细胞,用Ｆｌｕｏ－３荧光探针负载后,再次用Ｃａ（ＯＨ）２作用于牙髓细胞,用激光共聚焦显微镜检测胞内Ｃａ＾２＋。结果：含Ｃａ（ＯＨ）２、Ｃａ（ＯＨ）２和普鲁卡因的培养液培养的细胞内Ｃａ＾２＋浓度升高;含     

The effect of calcium hydroxide root filling on dentin fracture strength

Abstract –  This in vitro study measured the effect of calcium hydroxide root filling on the microtensile fracture strength (MTFS) of teeth. A total of 40 extracted human disease-free permanent maxillary incisors were hand and rotary instrumented and vertically compacted with United States Pharmacopeia (USP) calcium hydroxide. The teeth were stored in a moist environment for 7, 28, and 84 days. As a control group, 10 teeth were vertically compacted with gutta percha and sealer. The MTFS of the teeth was measured (Mpa) using an Instron machine. Data were assessed statistically using an unpaired t -test ( P value). The intracanal placement of calcium hydroxide weakened the MTFS of teeth by 13.9 Mpa per 77 days: an average of 0.157 MPa day⁻¹. Between 7 and 84 days, the MTFS of the dentin was reduced by 43.9%. This difference was statistically significant ( P  < 0.05). A statistical difference ( P  < 0.05) was observed between the mean MTFS of the calcium hydroxide-filled dentin between 7 days (45.7 MPa) and 28 days (35.6 MPa) and also between 7 and 84 days (31.8 MPa). There was also a significant difference ( P  < 0.05) between the MTFS of the calcium hydroxide-filled dentin after 84 days (31.8 MPa) and the gutta percha-filled dentin (41.3 MPa) when used as a control root filling material. The weakening of the dentin by 23–43.9% following root canal filling with calcium hydroxide provides compelling evidence to re-evaluate the daily usage of this material in endodontic therapy.     

Calcium ion release from calcium hydroxide stimulated fibronectin gene expression in dental pulp cells and the differentiation of dental pulp cells to mineralized tissue forming cells by fibronectin

Aim The effect of calcium ions on dental pulp cells was examined and the mechanism of dentine bridge formation by calcium hydroxide was investigated. Methodology Human dental pulp cells were treated with high concentration of calcium or magnesium ions for 24 h and fibronectin gene expression was measured by the quantitative PCR method. Human dental pulp cells were then cultured on fibronecin‐coated dishes for 24 h, and osteocalcin and osteopontin gene expression, which are typical phenotypes of mineralized tissue forming cells, were measured by the quantitative PCR method. Results Fibronectin gene expression was stimulated by calcium ions dose‐dependently. On the other hand, magnesium ions did not influence fibronectin gene expression. Furthermore, pulp cells cultured on fibronectin‐coated dishes enhanced the expression of phenotypes of mineralized tissue forming cells. Conclusions Calcium ions released from calcium hydroxide stimulates fibronectin synthesis in dental pulp cells. Fibronectin might induce the differentiation of dental pulp cells to mineralized tissue forming cells that are the main cells to form dentine bridges, via contact with cells.     

The influence of haemostatic agents on healing of healthy human dental pulp tissue capped with calcium hydroxide

AIM: To investigate the hypothesis that different haemostatic agents could impair the histological response of human pulps capped with calcium hydroxide. METHODOLOGY: Forty-five third molars scheduled for extraction were selected. Class I cavities with pulp exposures were prepared. Three agents were used to control bleeding: 0.9% saline solution (control, n = 14), 5.25% sodium hypochlorite (n = 16) and 2% chlorhexidine digluconate (n = 15). The pulps were dressed with hard-setting calcium hydroxide cement. After 7, 30 or 90 days, teeth were extracted, formalin-fixed and prepared for histochemical techniques. The biological response was categorized using the following criteria: inflammatory response, soft tissue organization, reactionary dentine and reparative dentine. Data were submitted to statistical analysis, using nonparametric Kruskal-Wallis one-way analysis of variance on ranks. Differences amongst groups were detected using Dunn's method. RESULTS: The statistical analysis disclosed that whilst inflammatory response decreased over time, reactionary dentine deposition and reparative dentine formation increased in the latter periods of evaluation (P < 0.05). The three agents had similar performances for all criteria evaluated. The conventional pulp response to calcium hydroxide was observed over time, and complete pulp healing was observed in 88% of the specimens after 90 days. CONCLUSION: The three haemostatic agents did not impair the healing process following pulp exposure and capping with calcium hydroxide at different time intervals investigated.     

医用生物胶加氢氧化钙盖髓的实验研究

目的：观察ＺＴ医用胶加氢氧化钙作为盖髓剂的性能。方法：分别用ＺＴ医用胶加氢氧化钙、ＺＴ医用胶、氢氧化钙和Ｄｙｃａｌ进行狗牙盖髓实验，２只狗共４０个牙，观察４、８周。结果：４、８周时４种材料的牙髓组织学反应基本相似：牙髓组织反应较轻，无坏死层出现，除４周时Ｄｙｃａｌ组有２例出现微小脓肿外无明显炎细胞浸润，８周时ＺＴ医用胶加氢氧化钙组和Ｄｙｃａｌ组均有钙化组织出现。结论：上述结果说明ＺＴ医用胶加氢氧化钙的盖髓性能不亚于Ｄｙｃａｌ。     

The effect of short-term calcium hydroxide treatment on dentin bond strengths to composite resin

Abstract – The purpose of this study was to evaluate the influence of calcium hydroxide (Ca(OH)₂) treatment on the bond strengths to dentin of a resin‐based composite material. Two distinct dental adhesives, Prime & Bond (P&B) NT and Single Bond (SB) were used. One hundred and twenty‐seven bovine incisors were mounted in acrylic, ground flat to expose middle dentin, polished to 600‐grit, and randomly assigned to 10 groups: (i) 0 days, no Ca(OH)₂, P&B NT; (ii) 7 days, no Ca(OH)₂, P&B NT; (iii) 7 days, Ca(OH)₂, P&B NT; (iv) 30 days, no Ca(OH)₂, P&B NT; (v) 30 days, Ca(OH)₂, P&B NT; (vi) 0 days, no Ca(OH)₂, SB; (vii) 7 days, no Ca(OH)₂, SB; (viii) 7 days, Ca(OH)₂, SB; (ix) 30 days, no Ca(OH)₂, SB; (x) 30 days, Ca(OH)₂, SB. All specimens were stored in an incubator at 37°C. Specimens were then retrieved and the dentin surface was rinsed with air/water spray from a triple syringe. Dentin was etched with 37% phosphoric acid (PA) for 15 s, rinsed, blot dried, and coated with adhesive according to manufacturer's instructions. The adhesive was light cured for 10 s, and Filtek Z250 was applied to the surface with a #5 gelatin capsule and light cured for 160 s. Shear bond strengths were measured for each specimen in an Instron unit at a cross‐head speed of 0.5 mm min^?1. The data were subjected to anova and Duncan post‐hoc tests. Mean shear bond strengths for P&B NT ranged from 8.02 to 11.79 MPa. There was no significant difference between P&B NT groups treated with or without Ca(OH)₂ at any time interval. Mean shear bond strengths for SB ranged from 14.70 to 19.54 MPa. No significant difference was found between SB groups treated with or without Ca(OH)₂ at 7 days. At 30 days, SB with Ca(OH)₂ was significantly higher than SB without Ca(OH)₂. Short‐term Ca(OH)₂ treatment had no detrimental effect on dentin bond strengths to the ethanol or acetone‐based adhesive resin systems tested.