Medication with Calcium Hydroxide Improved Marginal Adaptation of Mineral Trioxide Aggregate Apical Barrier

Medication with Calcium Hydroxide Improved Marginal Adaptation of Mineral Trioxide Aggregate Apical Barrier

Basic Research—Technology Medication with Calcium Hydroxide Improved Marginal Adaptation of Mineral Trioxide Aggregate Apical Barrier Maryam Bidar, D...

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Basic Research—Technology

Medication with Calcium Hydroxide Improved Marginal Adaptation of Mineral Trioxide Aggregate Apical Barrier Maryam Bidar, DDS, MSc,* Reza Disfani, DDS, MSc,* Salman Gharagozloo, DDS, MSc,† Shirin Khoynezhad, DDS,‡ and Armita Rouhani, DDS, MSc* Abstract Introduction: The purpose of this study was to evaluate the effect of calcium hydroxide premedication on the marginal adaptation of the mineral trioxide aggregate (MTA) apical barrier. Methods: Forty single-rooted teeth were prepared and apically resorbed using sulfuric acid for 4 days. Teeth were allocated into two groups according to whether calcium hydroxide was placed in the canals for 1 week (medicated group) or not (nonmedicated group) before placing a 4-mm MTA apical plug in the canals. The roots were mounted on aluminum stubs, the root apex was viewed from the top under scanning electron microscopy, and the maximum distance between MTA and the surrounding dentin was measured. Results: The mean gap widths in the medicated and nonmedicated groups were 70.2 mm and 130.0 mm, respectively (p < 0.05). Conclusions: Calcium hydroxide treatment improves marginal adaptation of the MTA apical plug. (J Endod 2010; 36:1679–1682)

Key Words Apical barrier, calcium hydroxide, marginal adaptation, mineral trioxide aggregate, scanning electron microscopy

From the *Dental Research Center of Mashhad University of Medical Sciences, Mashhad, Iran; †Faculty of Dentistry, Zahedan University of Medical Sciences, Zahedan, Iran; and ‡Private Practice, Mashhad, Iran. Supported by the Dental Research Center of Mashhad University of Medical Sciences. Address requests for reprints to Dr Armita Rouhani, Department of Endodontics, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran. E-mail address: [email protected] 0099-2399/$0 - see front matter Copyright ª 2010 American Association of Endodontists. doi:10.1016/j.joen.2010.06.010

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oot canal treatment of immature teeth has many potential complications including endodontic and reparative problems. Without apical stop or constriction, it is difficult to achieve complete debridement and to limit the filling process to the tooth. The thin root walls are very susceptible to fracture during mastication. Furthermore, rootend resorption and iatrogenic overfiling in immature teeth can distract the apical constriction. Long-term calcium hydroxide apexification has historically been used to establish apical closure and avoid surgery (1). Apexification induces a calcified barrier in the root with an open apex or the continued apical development of an incomplete root in teeth with necrotic pulp (2). However, there are several disadvantages to apexification. The treatment requires multiple appointments over an extended period, which results in challenging patient-compliance issues. Additionally, the extended treatment period is associated with susceptibility to fracture, esthetic concerns, and coronal microleakage (3). Artificial apical barriers with a variety of materials have been considered as an alternative to traditional calcium hydroxide apexification (4–7). Mineral trioxide aggregate (MTA) has become the material of choice in artificial apical barrier procedures (8). MTA can be placed in one visit, thereby eliminating the long waiting time required for calcium hydroxide apexification (9–11). Furthermore, MTA is biocompatible, nonmutagenic, and nonneurotoxic (12–15); can induce hard tissue formation (16, 17); and has good sealing properties (15, 18, 19). To disinfect the root canal, one or two treatments with calcium hydroxide are typically performed before MTA application (8). However, complete calcium hydroxide removal from the dentinal walls is reportedly impossible (20, 21). In the present study, we examine the effects of residual calcium hydroxide on the marginal adaptation of the MTA apical barrier.

Material and Methods Preparation of Teeth Forty extracted human maxillary single-root teeth were selected. The teeth were placed in a sterile saline solution after extraction, incubated with 5.25% sodium hypochlorite (NaOCl) for 5 hours, rinsed, and stored in saline solution. The teeth were radiographed and examined for fracture and for internal and external resorption. Clinical crowns were sliced from the cement-enamel junction with a high-speed diamond bur (D & Z, Lemgo, Germany) under excess water to create a standardized length of 14 mm. A 25-mm #15 K-file (Dentsply Maillefer, Tulsa, OK) was placed into each canal so that its tip was seen at the foramen. Canals were instrumented using K-files up to master apical file #45 in a step-back manner with Gates-Glidden drills #1 through 4 (Dentsply Maillefer). Sodium hypochlorite (1 mL of 0.5% solution) was used between each instrument size to irrigate canals. The access opening was sealed with Coltozol (Coltene, Altstatten, Switzerland). Apical Resorption To produce apical resorption, the method of Ghoddusi et al (22) was used. Briefly, the roots were drowned in melted rose wax (Cavex Holland, Haarlem, The Netherlands) up to 3 mm from the apex. Waxed teeth were macerated in 20% sulfuric acid for 4 days and then rinsed with a saline solution; the wax was removed with a scalpel (Supa, Tehran, Iran). The temporary filling was also removed from the access opening.

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Ca(OH)2 Improved Marginal Adaptation of MTA Apical Barrier

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Basic Research—Technology

Figure 1. SEM micrographs (57). A gap between the MTA plug and dentinal wall at the root end can be observed in the (A) medicated group (with prior calcium hydroxide dressing and the (B) nonmedicated group (without prior calcium hydroxide dressing).

itate manipulation under scanning electron microscopy (SEM). Each root segment was mounted on an aluminum stub, gold sputter coated, and viewed from the top (root apex) under SEM (S360; Oxford Co, Cambridge, UK) at 100 magnification. To assess the marginal adaptation between MTA and surrounding dentin at the root apices only, measurement was performed at four points. To determine the maximum distance between the MTA and surrounding dentin, the width of largest gap in each specimen were scored and recorded (Figures 1 and 2).

Calcium Hydroxide and MTA Treatment The teeth were randomly divided into medicated (n = 20) and nonmedicated (n = 20) groups. In the medicated group, pure calcium hydroxide mixed with distilled water (Cina Bartar, Tehran, Iran) was applied into the root canals using a Lentulo spiral (Moyco Union Brach, York, PA). Radiographs were taken to ensure complete coverage of the canal. After 1 week, the medication was removed with stainless steel hand files (Dentsply Maillefer) and 0.5% NaOCl irrigation. In the nonmedicated group, the canals were untreated before MTA use, and MTA was immediately placed in the canals after preparing the specimens. In both experimental groups, a 4-mm apical barrier of MTA (ProRoot MTA; Dentsply, Tulsa, OK) was applied into the canals. The MTA was mixed according to manufacturer’s directions, and a messing gun was used to place the material as close to the apex as possible. A hand condenser was used to condense the material to the apex. Radiographs were taken to ensure the proper placement and thickness of the MTA plug. Dankish paper points were placed in the canals. All specimens were stored at 37 C and 100% humidity for 7 days. The MTA was then tested to ensure that it had adequately set.

SEM of the root ends revealed gaps between MTA and the dentinal walls in all 40 cases. The average gap width of the medicated group (70.2  34.8 mm) was markedly less than that of the nonmedicated group (130.0  67.1 mm).

Marginal Adaptation Using a high-speed diamond saw (D & Z Germany), 5 mm of the root apex was resected perpendicular to the long axis of the root to facil-

In this study, sulfuric acid was used to produce open apex teeth (22). Other studies have used different methods, such as overfiling

Statistical Analyses Preliminary analysis with the Kolmogorov-Smirnov test was used to confirm the normal distribution of the data. The results were analyzed by t test, with the significance level defined as a = 0.05.

Results

Discussion

Figure 2. The gap size was measured at 300 magnification.

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Basic Research—Technology with large files (23) or the retrograde application of NiTi rotary files (1). However, these methods produce a round apical foramen that may not be similar to the clinical situation. Sulfuric acid resorbs the root surface in a disordered manner that may be more like natural resorption. Mechanical instrumentation of very immature teeth may weaken the root or result in perforation in thin roots. The application of Ca(OH)2 in the root canal is highly effective at killing root canal flora and dissolving necrotic pulp tissue (24, 25). In this study, instrumentation and 0.5% NaOCl were used to remove calcium hydroxide from the root walls. High concentrations of NaOCl in open apex teeth may be pushed to the periapical tissue, leading to a hypochlorite accident in the clinical situation. The manner of MTA placement in the root canal (ie, orthograde or retrograde) can affect the marginal adaptation and gap size. In retrograde placement, MTA can be packed against a barrier like guttapercha. When MTA is orthogradely placed in open apex teeth, there is limited barrier for complete compaction. Several studies have evaluated the marginal adaptation of MTA as a root-end filling material. Torabinejad et al (26) compared MTA, amalgam, Super EBA, and IRM (Harry J. Bosworth Co., Skokie, IL) and found that MTA has the best adaptation. Gondim et al (27) found that MTA, with or without finishing, has a good marginal adaptation. Shipper et al (28) found that gaps were significantly smaller in root ends filled with MTA compared with those filled with amalgam. In this study, MTA was placed in root canals orthogradely, and the root-end and marginal adaptation were assessed. The mean gap size in premedicated and nonpremedicated root canals was 70.2 mm and 130.0 mm, respectively. These sizes are greater than those observed by Torabinejad et al (26) (2.68 mm), Bidar et al (29) (14.8 mm), and Xavier et al (30) (1.051and 0.812 mm). This difference can be attributed to several factors. First, in the previous studies, MTA was placed retrogradely in the root canals (as a root end filling material). Second, there are differences in how the gaps were evaluated. Torabinejad et al and Bidar et al longitudinally resected the teeth and measured gap widths between MTA and the root canal walls. Xavier et al used transverse 1-mm and 2-mm root-end sections to evaluate the marginal adaptation of MTA as a root-end filling material. Here, the gaps between MTA and the root canal walls at the root apices was evaluated, without performing sectioning at the MTA and dentinal wall interface. Finally, the large gap size observed in this study may be because of the use of sulfuric acid to produce open apex teeth. Sulfuric acid resorbs the root apex in a disordered manner, producing irregularities at the root end that may hinder adaptation of MTA to the dentinal walls and thereby increase the gap size. The present research showed that medication with calcium hydroxide improved marginal adaptation of the MTA plug. Hachmeister et al (1) also found that calcium hydroxide therapy for 1 week did not affect the sealing ability of MTA for 70 days and concluded that residual calcium hydroxide on the root walls in an open apex does not affect the MTA properties. Porkaew et al (31) found decreased dye leakage in canals obturated with gutta-percha after premedication with calcium hydroxide. They concluded that the calcium hydroxide reacts and forms calcium carbonate, providing an initial decrease in permeability. The observed improvement of the marginal adaptation of the MTA plug may have been caused by the conversion of calcium hydroxide to calcium carbonate at the root end or the reaction of MTA with residual calcium hydroxide. Finally, it should be emphasized that this article presents an in vitro procedure. To obtain clinically relevant results, in vivo studies are recommended.

Conclusion Calcium hydroxide medication improved the marginal adaptation of the MTA apical plug. Because the MTA apical plug technique elimi-

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nates the lengthy apexification procedure, future studies focused on the success rate of MTA plug formation in vivo are warranted.

Acknowledgments This study was supported by the Dental Research Center of Mashhad University of Medical Sciences. We would also like to thank Dr. Hamid Jafarzadeh for his kind help and Dr. Habibollah Esmaili for his advice as a statistician in this study.

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