PEDIATRIC DENTISTRY V 34 I NO 2 MAR i APR 12

cientiñc Article

Assessment of Diffusion of Hydroxyl and Calcium Ions of Root Canal Filling Materials inPrimary TeethMarcos Ximenes, DDS, MD' • Mariane Cardoso, DDS, MD, PhD'̂

Abstract: Purpose: The purpose of this study was to evaluate the diffusion of hydroxyl (0H-) and calcium (Ca+2) of 2 intracanal calcium hydroxide-based

medications through the root dentin and cementum of primary teeth. Methods: Forty roots were selected and a single operator instrumented the

canals. The irrigation was performed with a 1% sodium hypochlorite soiution, and a finai irrigation used 17% ethyienediaminetetraacetic acid soiution.

The teeth were divided into 3 groups: (1) Group 1 (N=15)— thickened calcium hydroxide paste blended with propyiene glycol paste; (2) Group 2 (N=15)—Calen;

and (3) Group 3 (N=10)—no medication. Diffusion of the OH- ions was determined using a digital pH meter, and diffusion of Ca+2 ions was determined

through atomic absorption spectrometry at baseline, 24 hours, 7 days, 15 days, and 30 days later. Results: Two-way analysis of variance and Tuke/s test

revealed that Group 1 achieved significantiy higher pH values (P<.01), followed by Groups 2 and 3. There was a statistically significant difference between

groups (PK.01) in the amount of Ca+2 ions released; Group 1 had the highest diffusion values, followed by Group 2, both with peak diffusion at 7 days.

Conclusions: Thickened calcium hydroxide paste biended with propyiene glycol paste achieved the greatest diffusion of hydroxyl and calcium through the

dentin and cementum of primary teeth. (Pediatr Dent 2OI2;34:122-6) Received July 19, 2010 i Last Revision September 26,2010 / Accepted October 10,2010

KEYWORDS: PRIMARY TEETH, TRAUMA, CALCIUM HYDROXIDE, FILLING MATERIALS

There is a high prevalence of dental trauma in primary teeth.Epidemiological studies report as much as a 39% frequencyamong preschoolers.' While there are no differences in genderor affected side, the most affected teeth are the maxillary centralincisors.'''

Consequences of trauma upon the primary tooth are similarto those on the permanent tooth, involving the same structuresin one same tissue environment. Thus, therapeutic maneuverssimilar to those used for permanenr teeth can be applied to pri-mary ones. The remporary nature of the primary tooth does notjustify conducting precarious treatments where biologic prin-ciples are overlooked or neglected.^

Calcium hydroxide (Ca(OH)^) has been suggested as anintracanal medication because of its ability to dissociate intohydroxyl (OH ) and calcium ions (Ca*^), resulting in a higher pHin rhe adjacent medium and inducing mineralized tissue.^' Ithas been demonstrated in vitro that the action of Ca(OH)" onpathologic root résorptions occurs through the inhibition of themacrophage s adherence capacity, which is the first stage of aphagocytosis process. Thus, Ca(OH)" applied to the intracanalor direcrly on pulpal tissue reduces the infiammatory reactionof periapical and pulpal tissues.^

Studies conducted on permanent teeth proved that Ca(OH)'has the capacity to release OH , which is diffused through ex-posed dentin tubules and raises the pH of the root's surface.*'The rise in pH through the release of OH' has a beneficial effectof inhibiting the action of clastic cells on the root surface and

'Dr. Ximenes is a PhD student in pédiatrie dentistry and ^Dr. Cardoso is a professor

of pédiatrie dentistry. Department of Dentistry. Federal University of Santa Catarina.

Florianópolis. Santa Catarina, Brazil.

Correspond with Dr. Ximenes at marcosximenes@hotmail.com

creating a medium that favors the repair of hard tissue.'" Whenabundant, Ca'' participates in the activation of calcium-dependentadenosine triphosphatase. By binding with carbonic gas in thetissue, Ca*̂ forms calcium carbonate crystals, which serve as thecalcification nucleus, thereby favoring remineralizarion."'^

The purpose of the present study was to evaluate thediffusion of hydroxyl and calcium of 2 intracanal calciumhydroxide-based medications through the root dentin and ce-mentum of primary teeth.

MethodsThis study was approved by the Committee for Ethics in Re-search in Humans of the Federal University of Santa Catarina,Florianópolis, Santa Catarina, Brazil (process no. 051/09).

The sample was made up of 40 primary molar roots inwith one-third of the root was intact. The specimens were ob-tained through transverse sectioning of the root 2.0 mm coronalto the cementoenamel junction using a double-face no. 7016diamond disk (KG Sorensen, Sao Paulo, Brazil). The roots wereindividually analyzed macroscopically using a stereoscopic mag-nifying glass (20x). Only intact roots with no perforating ré-sorption were included in the sample.

The preparation of the entrance of the canal was performedwith an Endo-Z bur (21 mm, Dentsply-Maillefer, Sao Paulo)using a high-speed drill (Silent MS 350 PB, Dabi Atlante,Ribeiráo Preto, Brazil). All the roots were in the initial processof physiological résorption, thus presenting apexes with dif-ferent degrees of résorption. Therefore, to standardize rootlengths, the apices were cut at 7 mm using a double-face no.7016 diamond disk (KG Sorensen). The apices were then sealedwith Super Bonder Gel (Flex Gel, Lacatite Ltda, Sao Paulo).After the material cured, each canal was individually shapedwith first-series no. 20 to 35 files (Dentsply-Maillefer) at a

122 D I F F U S I O N OF O H A N D C A ' I N PRIMARY TFETH

PEDIATRIC DENTISTRY V 34 I NO 2 MAR : APR 12

length of 7 mm using a new set of files for each group. Irriga-tion was performed with a 1% sodium hypochlorite solution(Miyako, Guarulhos, Brazil), with an average of 2.5 mL of so-lution in each canal. The canals received a final irrigation of1 mL of a 17% ethylenediaminetetraacetic acid (EDTA) so-lution (Biodinâmica, Ibiporá, Brazil) for 3 minutes and weredried with absorbent paper points (Tannari, Sao Paulo).

The specimens were randomly divided into 3 groups, with15 roots in each experimental group (Groups 1 and 2) and 10 inthe control group (Group 3): (1) Grotip 1—thickened calciumhydroxide paste blended with propylene glycol paste (CaPE);(2) Group 2—Calen paste (SS White, Rio de Janeiro, Brazil);and (3) Group 3—no medication. The roots were cleaned usingultrasound (Ultrasonic Cleaner 1440D, Odonto Bras, RibeirâoPreto, Sao Paulo, Brazil) with distilled water in 3 5-minutecycles. The roots were further sealed with Super Bonder gel(Flex Gel, Lacatite Ltda), with 1 drop applied to the existinglayer in the apex of each root. A layer of nail polish was thenapplied over rhe Super Bonder gel for greater impermeability.

The CaPE paste was blended with 400 mg of Ca(OH)-powder and 0.2 mL of propylene glycol (Officinale, Floria-nópolis, Brazil), thereby obtaining a thick blend. The paste wasinserted with the aid of a lentulo spiral (Dentsply-Maillefer,Sao Paulo, Sâo Paulo, Brazil) previously cut at 16 mm and cali-brated to 1 mm short of the root's length.

The Calen paste, composed of 2.5g calcium hydroxide, 0.5gzinc oxide, 0.05 g colophony, and 2mL polyethylene glycol 400(vehicle)(SS White), was used according to the manufacturer'sinstructions and inserted into the canal using a carpule syringewith a disposable 27 guage needle calibrated to 1 mm short ofthe root's length. The needle was introduced into the canal, andthe paste was injected using up-and-down movements.

Before and after the insertion of the medication into Groups1 and 2, the roots were individually weighed on a high preci-sion balance (Electronic Balance FA 2104N, Bioprecisa, Riode Janeiro), thus providing the weight of the medication insidethe canal. The average amount of material inserted was 0.037 g.

The material in Groups 1 and 2 was compressed with acotton ball until there was a 2-mm space—1 mm for the gutta-percha (Dentsply-Maillefer) and 1 mm for the first layer of aphotopolymerizable compound resin (Opallis, FGM—ProdutosOdontológicos, Joinville, Brazil). Thereafter, a second layer ofcomposite resin was placed to complete the restoration. In Group3, the same sealing procedure was performed, but with thecanal empty.

Using another layer of photopolymerizable compound resin(Opallis), the roots were individually attached to a metal rodfashioned from orthodontic wire (0.7-mm thick and 5-cm long)in the plastic top of the acrylic recipient containing 20 mL ofsaline solution. The roots were kept at a constant temperature of37° C and 100% relative humidity throughout the test period.

The pH of the medium (saline solution) was determinedtising a digital pH meter (ML 1010, Hanna Instruments, SaoPaulo). Readings were performed after 2 minutes of immersionof the electrode in each flask. Measurements were taken at re-gular intervals in all groups (baseline, 24 hours, 7 days, 15 days,and 30 days), with the temperature and pH of each samplerecorded for each reading. After the pH reading, the specimenswere then transferred to a new medium containing saline solu-tion, and the previously used solution was stored in a refriger-ator at 4° C until submitted to analysis.

Atomic absorption spectrometry was employed for thedetermination of Ca*- concentrations in the medium (ContraA700, Analytic Jena, Jena, Germany). Prior to the analysis, areading was performed of the saline solution used in the studyto determine whether it contained Ga*-, thereby establishingthe baseline for the equipment.

The amount of Ga*- and pH were determined for subse-quent analysis. The results were obtained with the aid of thestatistical program SPSS 10.0 software (SPSS Inc, Chicago, 111).Two-way analysis of variance (ANOVA) was used to analyze thechange in pH and difîiision of Ca' ' in each group throughoutthe test period. Tukey's test for groups of unequal sizes wasemployed for each of the criteria and its interactions.

ResultsFigure 1 displays the distribution of mean pH values in the 3groups over the 4 periods studied. Two-way ANOVA revealedstrong statistical significance in the variation in pH among thematerials, periods, and their interactions iP<.0\). Tukey's test(unequal HSD-honestly significant difference) revealed statisti-cally significant differences between groups (P<.0\), with thehighest mean pH values in Group 1, followed respectively byGroups 2 and 3. The analysis of periods revealed the lowest pHvalues at 24 hours, regardless of the material used. A statisti-cally significant difference {P<.0\) was found between the 24-hour period and other periods (7, 15, and 30 days). No signi-ficant differences were found, however, between the 7-, 15-,and 30-day periods, indicating that these periods are equivalentin terms of mean pH. The interactions between materials and

-G l -CaPE

I-G II-Calen"

Figure 1. Di.stributioii of mean pH values according to group andperiod analyzed.

Figure 2. Mean quantity of calcium ions released (mg/l.) in all groups andperiods analyzed.

DIFFUSION OF OH AND CA' ' IN PRIMARY TEETH 123

PEDIATRIC DENTISTRY V 34 ( NO 2 MAR I APR 12

periods demonstrate that all values were equivalent in Group1. In Group 2, the 24-hour period had poorer results than theother periods analyzed. Thus, compared to the Calen paste, theCaPE paste was able to produce higher pH values, even in theinitial 24-hour period.

The data from the atomic absorption spectrometry analysisof the solutions are expressed as mg/L. Figure 2 displays themean diffusion of Ca*- in the periods analyzed. Two-wayANOVA revealed strong statistical significance regarding theamount of Ca*̂ for the materials and periods, but not in theirinteractions, indicating that Ca*- was not influenced by any in-teraction between the materials and periods. Tukey's test(unequal HSD) revealed statistically significant differences be-tween groups (P<.OV), with the greatest diffusion of Ca*̂ inGroup 1, followed respectively by Groups 2 and 3. The lowestvalues occurred at 24 hours and 30 days, regardless of the typeof material employed. The diffusion of Ca'- was equivalentbetween 7 and 15 days as well as between 15 and 30 days, al-though with an obsetved decrease.

There was a large amount of Ca*"* released after 24 hours,with a peak at 7 days with both materials and a decrease invalues thereafter. The interactions occasionally demonstratedstatistical significance in individual comparisons, but the equi-valence in the ANOVA demonstrated that these results wereexplained by the strength of the variables, and no combinationof material and period was sufficient to alter the expected be-havior regarding the release of Ca*'.

DiscussionThe results of the present investigation, as well as those of pre-vious studies in permanent teeth''^ and primary teeth,'^ de-monstrate that there is diffusion of OH and Ca*̂ through dentintubules. This is explained by the fact that the crown and apicalportion of the root were sealed, with the only possible passageof ions through the root dentin and cementum. Other studiesreport different results, however, and demonstrate that Ca(OH)^may be inactivated by the buffering capacity of the dentin. ""'

The removal of the smear layer from the interior of theroot canal facilitates the diffusion of ions through the dentintubules, thereby enhancing the action of the medication.'^"Thus, prior to using an intracanal Ca(OH)^-based medication,irrigation should be performed with 17% EDTA for 3 minutesto allow greater action of the medication and a better prognosisof the treatment.'"'^''

Another factor that may affect permeability is the presenceof cementum.'"''̂ '-^ A number of in vitro studies on ion diffu-sion opted for removing the cementum,"'•^' whereas othersmaintained it.'̂ '"* In the present investigation and in previousstudies,'''" the presence of cementum did not impede ion dif-fusion. Removing the cementum simulates roots that havealready begun the process of pathological résorption. In clinicalsituations, a single tooth always has some areas of the rootscovered with cementum and others without cementum.̂ ^ Theaim of endodontic treatment with the use of Ca(OH)^ as theintracanal medication is not only to act on areas with root ré-sorption (absence of cementum), but also to prevent résorptionin areas with cementum.

For the assessment of OH" and Ca*- diffusion, the rootsremained immersed in saline solution for the time periods estab-lished (24 hours, 7 days, 15 days, and 30 days).*'-'Unlike inprevious studies,'"•'•''''•^' the saline solution in which the roots

were immersed was replaced on every measurement day toobtain the maximum diffusion of ions without saturating themedium. A similar method was used in 2009 by Duarte et al. '̂

The minimal amount of OH' capable of making a mediumunviable for bacterial proliferation by neutralizing the acid envi-ronment remains unknown. Ideally, one should use a materialthat releases the greatest possible number of these ions in orderto alkalinize the medium.''' A more acidic medium leads togreater ion diffusion, as there is a tendency toward neutraliza-tion. Thus, it may be suggested that the release of these ions inprimary teeth would be greater in vivo due to the presence of anacid environment caused by infiammatory processes. Otherauthors''* also suggest that diffusion is greater in vivo due to thepresence of the apical foramen as well as both physiological andpathological root résorption.

The diffusion of ions through the root dentin may be alteredby the interaction of the dentin and ions, permeability of thetubules, and characteristics of the vehicle in which the Ca(OH)^is contained.^'' In the present study, both medications testedwere associated with viscous water-soluble vehicles: propyleneglycol in the CaPE paste and polyethylene glycol 400 in theCalen paste. The use of propylene glycol as a vehicle forCa(OH)- has been widely investigated and has proven to befavorable to inducing the dissociation of OH and Ca*- andsatisfactory diffusion through dentin tubules." Polyethyleneglycol 400 is used as a vehicle for endodontic medications dueto the fact that it provides a viscous consistency for the formu-lation, thereby allowing greater permanence and action of themedication in the root canal.̂ ''•^

Studies on OH" diffusion measured through the determi-nation of pH values report greater diffusion with the use ofpastes that associate Ca(OH)^ powder with propylene glycolwhen compared to nonviscous mediums, such as distilled water,saline solution, and an anesthetic solution.''''*'^'' Likewise, theassociation of Ca(OH)- powder with polyethylene glycol is alsoreported to be more effective at ion diffusion than nonviscousmedia.'"'" In the present study, both groups exhibited constantdiffusion of OH% with the CaPE paste achieving higher meanpH values than the Calen paste at all evaluation times. Thismay be attributed to the manual blending of the paste, whichallowed a greater powder-liquid proportion and directly in-fluenced the diffusion, as reported by other authors.'--'

The control group, although it contained no intracanalmedication, showed a slight increase in the pH and Ca*-. Thisincrease differs from the results found by others authors -̂'̂ ;̂ inthe control group, for example, there was no increase in pHor Ca*̂ . The explanation of the different results may be due tothe different methodologies used. This study used the roots ofhuman primary teeth, where there is a release of OH" and Ca*'from the dental tissue and dentine plays an important buffereffect.'^'"" The studies conducted by Zmena et al.,'^ andTanomaru et al.,'^ used glass tubes instead of roots, which pre-vents any diffusion of OH" and Ca*'.

The low pH values in Group 2 in the first 24 hours demon-strate that the material diffuses few ions in this period. This maybe attributed to the paste's viscosity, which reduces solubilityand provides a slower dissociation. In 2004, Ferreira et al.'°describe a similar finding. Regarding other periods, the 2 groupsexhibited the same hydroxyl ion diffusion behavior. This find-ing disagrees with that described by Chamberlain et al.' whoreported a drop in mean pH values after a period of 21 days in

124 DIFFUSION OF OH AND CA' ' IN PRIMARY TEETH

PEDIATRIC DENTISTRY V 34 i NO 2 MAR ) APR 12

a study assessing the change in pH on the surface of the rootsof permanent teeth filled with Ca(OH)'.

Peak OH' and Ca*'' diffusion occutred at 7 days in Groups1 and 2. This finding differs from that teported in studies in-volving permanent teeth,'"' which state that a minimum of14 days is needed for OH' and Ca*̂ to penetrate dentin tubulesand reach the toot's external surface.

The diffusion of Ca*' may be explained by the presenceof the viscous vehicle, which provides better contact with thedentin ttibules and, consequently, a greatet release of ions. Thediffusion of Ca*̂ was greater in roots treated with the CaPEpaste, which corroborates the findings of previous studies carriedout on primary'^ and permanent teeth.'"-' Although Group 2released a smaller amount of Ca*^ the values were much higherthan those in Group 3. Moreover, this paste offers easy insertiondue to the fact that it is pteviously blended by the manufac-turer and is injected using a syringe.

In this study, all materials tested showed a prolonged effecton the alkaline environment showing high pH values through-out the days analyzed. The diffusion of Ca*'' was also signifi-cant. Within the limitations of this experimental design andin vitro study, no definitive conclusions can be drawn.

When evaluating the diffusion of Ca*̂ and OH' in vivo, onemust consider other factors that can have an influence, such as:the ptesence of the open apex (which was closed in this study);the presence of physiologic and pathologic root résorption(present in most endodontic treatment cases); and the presenceof an inflammatoty ptocess (which reduces the extetnal pHatotmd the root, providing greater diffusion of ions).

The present study's results help establish the best materialand length of use of Ca(OH)^ as an intracanal medication.When treating the roots of a traumatized primary tooth, the useof CaPE (Ca(OH)^ powder + propylene glycol) is recom-mended. The action of this medication (diffusion of hydroxyland calcium ions together) occuts in 7 to 15 days. The mainte-nance of the material in the canal offers no further benefit inthe control of résorption. Thus, after the 7- to 15-day period,the tooth may be filled ot the treatment may be repeated incases in which thete is a need for greater Ca(OH)- action.

ConclusionsBased on this study's results, the following conclusions can bemade:

1. Hydroxyl and calcium ions in a calcium hydroxide-basedmedication are diffused through the dentin and cemen-tum of the toots of primary teeth.

2. The CaPE paste achieved better diffusion of these ions,with peak diffusion occutring at 7 days.

AcknowledgmentThe authors wish to thank Setgio Freitas, DDS, MD, PhD(Professor of Biometrics, Department of Dentistty, Fedetal Uni-versity of Santa Catatina, Florianópolis, Santa Catarina, Brazil)for conducting this study's statistical analysis. There are no po-tential conflicts of interest relevant to this article.

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