M. Bossù, A.Dolci, A.Possenti, G.Gambarini
University of Rome "La Sapienza", Dental School

Removal of New Calcium-Hydroxide Points:
a Comparative Study

Abstract
Calcium hydroxide removal before final obturation is routinely accomplished by either sodium hypochlorite (NaOCl) or saline and/or instrumentation. However, studies demonstrated that none of these methods efficiently removed all dressing from the walls when commercial calcium hydroxide preparation were used. A possible solution is to use a new type of calcium hydroxide dressing, like the CaOH-points .The goal of this study was to investigate whether differences in camposition of calcium hydroxide dressings influenced the removal efficiency prior to final canal obturation. Prepared root canals were obturated with two different products. Calcium hydroxide was then removed and teeth were split and observed under magnification.The result of the quantitative measurement showed that a considerable amount of calcium hydroxide paste remained attached to the canal walls when the paste was used. A statistically significant difference was found when the new calcium hydroxide points were used. No or minimal residual were found in the latter case.

Fig.1 The tested material.

Introduction
The elimination of bacteria and their substrates is important for successful endodontic treatment (1,2). This can be done by chemomechanical preparation and the use of intracanal antibacterial dressings. Bystrom and Sundqvist (11) have shown proliferation of residual bacteria in root canal systems following chemo-mechanical preparation. The use of an interappointment calcium hydroxide paste has been suggested as an effective antimicrobial intracanal medication preventing proliferation of residual bacteria (12). Alternating NaOC1 and EDTA irrigation solutions has been shown to remove the smear layer, pulpal remnants, and predentin from canal walls (4, 5). This combination has improved antimicrobial results when compared with NaOCI irrigation alone (6). The removal of the smear layer and use of an interappointment antibacterial dressing have been suggested to be an effective means of cleaning and removing debris and exerting an antibacterial effect on the dentinal walls (11, 13).

Hasselgren et al. (7) and Andersen et al. (8) demonstrated in vitro the ability of calcium hydroxide paste to aid NaOC1 in more rapid dissolution of necrotic porcine muscle tissue and extirpated human pulp tissue. Canal irregularities may be inaccessible harbors for debris and bacteria, thereby making thorough root canal system debridement difficult (9). Metzler and Montgomery (10) found that intracanal calcium hydroxide left for 7 days with subsequent instrumentation using NaOCl irrigation cleaned molar canals and isthmuses, as well as an ultrasonic device. This suggests that calcium hydroxide used in conjunction with NaOC1 may improve the efficacy of debridement, especially in less accessible regions of the root canal system. They advocated intracanal medications in conjunction with combinations of irrigants for more thorough debridement of the root canal system.

Calcium hydroxide removal before final obturation is routinely accomplished by either sodium hypochlorite (NaOCl) or saline and/or instrumentation in a reaming motion with a small endodon- tic instrument, or with the master apical file. However, the effectiveness of these procedures has not been fully documented. Residual calcium hydroxide left intracanally has been shown to interact with zinc oxide-eugenol based sealers substituting the zinc oxide-eugenol chelate formation for calcium eugenolate. Previous studyes demonstrated (3) that none of the methods efficiently removed all dressing from the walls when commercial calcium hydroxide preparation were used. A possible solution is to use a new type of calcium hydroxide dressing, like the CaOH-points (CaOH-plus) recently developped by Roeko (Germany). One of the main advantages of these new products could be the easy placement and removal of the intracanal medicament.

Following this hypothesis,the aim of this study was to investigate whether differences in composition of calcium hydroxide dressings influence the removal efficiency prior to final canal obturation.

Materials and Methods
The calcium hydroxide preparations selected are the two following ones: Endoidrox (Ogna,Milan, Italy) and CaOH-Plus (Roeko, Germany). Both are commercially available products. 22 single-rooted extracted human teeth were used. Access cavities were cut, and the root canals were subjected to chemomechanical preparation with the crown-down technique using ProFiles .04 Ni-Ti rotary files (Maillefer Ballaigues, Switzerland) and 5% NaOC1 as an irrigant. Before the final imgation, a #15 file was passed l mm beyond the apex to remove any dentinal plugs. The teeth were divided randomly in two groups of 10 teeth each. In each group, teeth were assigned to each calcium hydroxide preparation, whereas the remaining two teeth served as controls (positive and negative). The root canals were dried with paper points and then filled with each calcium hydroxide preparation. The negative controls received no calcium hydroxide treatment. Insertion of Endo-idrox calcium hydroxide paste was performed with lentulo paste carriers until the dressing was de- tected through the apex. Calcium hydroxide points were inserted to the working length.. The portion which was above the canal orifice was cut. The access cavities were temporarily sealed with a cotton pellet and Cavit (Espe GmbH, Seefeld, Germany). The teeth were stored at 37 + 1°C and 100% relative humidity for 24 hours. Then the temporary restorations were removed, and the teeth of each group were were treated as follows. Root canals were irrigated with 5 ml of 5% NaOC1, filed with a #25 file, and received a final flush with 5 ml of 5% NaOC1 followed by 5 ml of 17% EDTA. The teeth were sectioned from buccal and lingual directions at the maximum buccolingual diameter up to the root canal walls using a diamond disk and then fractured. The root canal sections were photographed and images were stored in a computer. The percentage ratios of calcium hydroxide-coated surface area to the total canal surface area were calculated by image processing analysis (Corel-Draw). Data were subjected to statistical interpretation by analysis of variance at 95% confidence level (p = 0.05).

Results
Positive control teeth in all groups showed nearly complete coverage of their canal walls with calcium hydroxide as opposed to negative controls. Calcium hydroxide retention was expressed as the percentage ratio of coated area to the total canal area of the section.

Mean values for A group (Endoidrox) were 21.50 (+/- 7.13) SD, while the mean values for B group (CaOH-Plus) were 1.40 (+/- 0.1). Data are shown in fig.2.

The result of the quantitative measurement slowed that a considerable amount of calcium hydroxide paste remained attached to the canal walls when the paste was used. A statistically significant difference was found when the new calcium hydroxide points were used. No or minimal residual were found in the latter case.

Fig.2: Calcium Hydroxide Retention

Blue column = Endoidrox
Red column = CaOH-Plus
White column= Positive Control

Discussion Results showed that when traditional pastes were used the method (irrigation + filing ) was not efficient in removing the entire dressing from the canal walls, leaving approximately. 20% of the surface of the walls covered with the calcium hydroxide dressing. On the contrary, no residual were found when CaOH-Plus points were used. The cones were easily and totally removed by a n.25 hedstroem file.A statistically significant difference regarding removal of the dressing was found between the two groups.

It is known that residual calcium hydroxide influences the setting mechanism of zinc oxide-eugenol type endodontic sealers. The short-term clinical implications were a rapid setting reaction of the sealer that blocked gutta-percha entrance and placement to full working length. It is also known (3) that treatment with EDTA neutralizes calcium hydroxide residues; but, if residues are not removed, they may interfere with the sealing efficiency from a mechanical point of view.

In view of the possible implications of the remnants of calcium hydroxide on the outcome of root canal treatment, the use of the CaOH-Plus points can be adviced. However, more research has to be done on the clinical effectiveness of intracanal dressing with these new points.

Bibliografy

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