Evaluation of mineral trioxide aggregate as root canal sealer: A clinical study.

AIM: The aim of this study was to compare the clinical and radiological outcome of mineral trioxide aggregate (MTA) or epoxy resin as a root canal sealer compared with zinc oxide eugenol sealer.
MATERIALS AND METHODS: 45 single rooted teeth with periapical index Score 2 or more were allotted to three groups with 15 teeth in each group. Root canal treatment was performed in two visits and obturated with Gutta-percha as obturating material and zinc oxide eugenol as sealer in Group 1, epoxy resin as sealer in Group 2 and MTA mixed with propylene glycol as sealer in Group 3. Visual analog scale, periapical index and VixWin digital Pro image analysis software were used for evaluation. The quantitative data was analyzed by t-test and analysis of variance. Ordinal data was analyzed by Wilcoxon's signed rank test, Mann-Whitney and Kruskall-Wallis test.
RESULTS: Results suggested that there exists no statistically significant difference in clinical or radiological outcome of root canal therapy with three different types of sealers used in this study.
CONCLUSIONS: MTA could be used as a root canal sealer with equal effectiveness compared with epoxy resin and zinc oxide eugenol sealers. Further long-term studies should be carried out to prove the effectiveness.

INTRODUCTION

Root canal treatment is an effective, less invasive and ideal treatment modality for pulpally involved tooth and salvaging it from extraction. Cleaning, shaping and three dimensional obturation of root canal system are essential steps in root canal treatment.[1] The bacteria impervious seal that is essential for success is provided by the root canal sealer and obturation material.[2] Innumerable root canal sealers are time tested with definitive success rates.[3]

Lee et al. introduced mineral trioxide aggregate (MTA), a tricalcium silicate cement as a perforation repair material.[4] Being biocompatible and bioactive it gained popularity for pulp capping, pulpotomy, apexification and as root end filling material. Recently, it is finding application as a root canal sealer[5] and as obturation material.[6] When used as a root canal sealer, MTA has the ability to regenerate periodontal ligament and form cementum in the root canal space and accessory canals, thus closing the leeway spaces that can result in the treatment failure.[7] More recently, sealers based on MTA have been introduced[5] and found to have good sealing ability and higher push-out bond strengths.[8] In addition, sealers based on MTA demonstrated apatite-like deposits in contact with physiological solutions and a biocompatibility similar to MTA.[8] A sealer of good working consistency could be developed by mixing MTA with adequate quantities of water-soluble polymer.[9]

Epoxy resin sealers like AH Plus was found to bond better to the core obturation material and root dentine.[10] They have the advantages such as less shrinkage, high radio opacity, low solubility, better periapical repair and biocompatibility.[11] Studies have evaluated the success of root canal treatment, the incidence of pain and healing ability and many other aspects of the root canal sealers both in vivo and in vitro. Evaluation of post-operative pain with visual analogue scale (VAS), periapical healing with periapical index (PAI) are widely used methods and morphometric evaluation with VixWin Pro digital image analysis software is a new, reliable and accurate technique. No in vivo human studies are available using MTA as a root canal sealer. Zinc oxide eugenol is an efficient and proven root canal sealer while epoxy resin has equivalent properties to compete with it. This study was done to compare the clinical and radiological outcome of MTA or epoxy resin as a root canal sealers compared to zinc oxide eugenol sealer using Gutta-percha as the obturating material in teeth with periapical radiolucency.

MATERIALS AND METHODS

This study was conducted in patients in an age group of 18-50 years with teeth indicated for root canal treatment. Single rooted tooth with periapical radiolucency and PAI[12] Score 2 or more were included. Teeth with calcified canals, retreatment cases, pregnant patients, systemic diseases and lactating mothers were excluded.

The 45 teeth indicated for root canal treatment were allotted into three groups with 15 teeth in each group. Ethical permission was obtained from the university ethical committee. Informed consent was obtained from all patients after explaining the treatment procedure in detail. The cases were assigned into any one of the following groups:

Group 1: Zinc oxide eugenol (Tubliseal) as root canal sealer (n = 15)

Group 2: Epoxy resin (AH Plus) as root canal sealer (n = 15)

Group 3: MTA (ProRoot MTA) as root canal sealer (n = 15).

Rubberdam was used for isolation of all cases. Caries was excavated and if necessary pre-endodontic management was done with composite resin. Access cavity was prepared with access preparation kit (Dentsply Maillefer, Ballaigues, Switzerland). After irrigation with 2.5% sodium hypochlorite (NaOCl) (Prime dental products, Thane, India), a K-File of appropriate size was introduced in the root canal and working length was verified with Propex II apex locator (Dentsply Maillefer, Ballaigues, Switzerland). This was confirmed by taking a radiograph using parallel cone technique with the help of a film positioning device (Endoray II, Densply Rinn. Elgin, US).

Cleaning and shaping was done with K-files (Sybron endo, orange, CA) and Protaper rotary system (Dentsply Maillefer, Ballaigues, Switzerland) for all the teeth. 2.5% NaOCl, ethylenediaminetetraacetic acid (Anabond Stedman, Kanchipuram, India) and normal saline (Baxter, Alathur, India) were used as irrigants. After cleaning and shaping, the canals were dried and medicated with calcium hydroxide (Endo cal, M Dent, BKK, Thailand) mixed with normal saline. After 1 week, patients were recalled and the intracanal medicament was removed and evaluated. Once the patient was free of pain, discomfort and canals were dry, the teeth were obturated according to their groups.

For Group 1: Zinc oxide eugenol (Tubliseal, Kerr/Sybron, Romulus, MI) was used as root canal sealer. The apical extent of the master cone was confirmed with radiograph and the canals were dried. Manufacturer's instructions were followed for mixing the sealer. The root canal was coated with the sealer using lentulospirals (Densply Canada, Woodbridge, Canada) in a slow speed handpiece (NSK, Tochigi, Japan). Obturation was performed with Gutta-percha cones and sealer by lateral compaction technique.

For Group 2: Epoxy resin (AH Plus, Dentsply DeTrey, Konstanz, Germany) was used as a sealer. Manufacturer's instructions were followed for mixing the sealer. The same steps were followed for obturation as in Group 1.

MTA (ProRoot MTA, Densply Tulsa, Johnson City) was used as root canal sealer in Group 3. To improve the handling properties of MTA and to get a sealer like consistency, the powder was mixed with propylene glycol[913] in a mixing pad. MTA sealer was coated in canal walls using lentulo spirals in a slow speed handpiece and obturated as in Groups 1 and 2. All treated teeth if required, were reduced to relieve occlusal load. Permanent restorations were done with composite resin (Filtek Z 350, 3M ESPE) and full coverage restoration if necessary after obturation. Follow-up evaluations were done after an interval of 1 week and after 6 months.

Pain evaluation — VAS

Before commencing the evaluation for pain, every patient was explained about the usage of VAS[13] using the following criteria:

Immediately after obturation and placement of coronal seal every patient was asked to mark the pain intensity using a 10 cm VAS. All subjects were recalled after 1 week of post-obturation for evaluation of pain and clinically examined. After 6 months, pain was evaluated using the same criteria.

Periapical status — PAI

Immediate post-obturation radiograph (base line data) was evaluated for PAI score and recorded in the evaluation sheet using the criteria described by Orstavik.[1214] At the 6 month follow-up visit, again a radiograph was taken using parallel cone technique and the PAI score was assessed [Figure 1].

Figure 1

Sample radiographs: (a) Pre-operative, (b) immediate post-operative and (c) after 6 months for the groups respectively

Area measurement — VixWin Pro digital image analysis software

Immediately after obturation, a digital radiograph was taken (base line data) with Gendex RVG unit for morphometric analysis (Gendex Dental Systems, Hatfiled, PA, USA). The image was then subjected to morphometric area measurement with the area measurement tool in the VixWin Pro digital image analysis software (Version 1.3, Gendex Dental Systems, Hatfiled, PA, USA) by outlining the radiolucency.[15] Calibration was done automatically by the software. The area measured was recorded in the evaluation sheet. At the 6 month, again the same procedure was repeated and the area was measured using the same criteria as mentioned before [Figure 2].

Figure 2

Area measurement by outlining the radiolucency using VixWin Pro digital image analysis software

Statistical analysis

Wilcoxon's signed rank test was used for comparison of pain and PAI score within the groups at different intervals. Kruskall-Wallis analysis of variance test followed by Mann-Whitney U test was used for comparison of pain and PAI scores between groups at different intervals. Wilcoxon's signed rank test was used for the comparison of area among the three groups at base line and at 6 months.

RESULTS

VAS score (evaluation for pain)

Pain comparison was performed intergroup and intragroup at three specific time periods. The standard deviation (SD) of VAS score immediately after obturation for the groups are 8.46 (11.26), 10.46 (14.86) and 7.63 (8.46) respectively. Group 2 was found to have more VAS score (P = 0.19) than other two groups but was statistically not significant (P = 0.19). When the pain was compared within the group at 1 week and at 6 months, there was no difference. VAS score after 6 months were 1.63, 1.06 and 0.33 respectively and there was no statistically significant difference [Tables 1 and 2].

Table 1

Comparison of pain between groups measured by VAS at baseline, 1 week and at 6 months

Table 2

Comparison of pain within group measured by VAS at baseline, 1 week and at 6 months

PAI score (periapical status)

There was a highly significant (HS) difference in the PAI score was found on comparing the base line and at 6 months. However, no difference among the groups was found at any interval [Table 3].

Table 3

Comparison of periapical index score within groups at baseline and at 6 months

Area measurement (regression of periapical radiolucency)

The SD of area measured immediately after obturation for the groups were 8.14 (8.40), 9.57 (9.20) and 4.32 (5.20) respectively and area after 6 months were 5.4 (5.7), 6.80 (8.11) and 4.14 (3.93) respectively. There was a HS difference in the area measurement comparing the base line and at 6 months, but no difference among the groups at any interval [Table 4].

Table 4

Comparison of area at baseline with area at 6 months

DISCUSSION

Invasion of microorganisms into the pulp is responsible for the pathogenesis and necrosis of the vital tissue.[16] Elimination of infection from the root canal system followed by its maintenance was found to induce healing. Root canal sealers along with obturation material will provide a bacteria proof seal of the root canal system, preventing the leeway space and communications between the intracanal and extracanal environments.[3]

The present study was designed to compare the clinical and radiological outcome of three different root canal sealers. No difference in the age, sex, tooth type, tooth distribution, root morphology, PAI score and area measurement at baseline suggest that the groups were equally distributed [Table 5].

Table 5

Baseline values of VAS score, PAI scores and area measurement

Zinc oxide eugenol was used as a positive control in this study. This is because it has a history of long-term clinical usage with definitive success rate. It has good handling properties, sealing ability,[17] minimal tissue toxicity,[18] less water solubility, antimicrobial property[19] periapical repair and good radio opacity. AH Plus is an epoxy resin based sealer that is widely used because of its compatibility with resin based materials used for obturation and post-endodontic restorations. Because of better flow and long setting time, AH Plus sealer can penetrates deeper into the surface micro irregularities[20] as well inside the lateral root canals. These properties lead to greater intertwining of the sealer with dentin structure, which, together with the cohesion among the cement molecules provides greater adhesiveness and resistance to dislodgment.[21] MTA mixed with propylene glycol was used as a root canal sealer in this study. MTA sets hard and its setting time is long enough (165 ± 5 min)[22] to be used as a sealer. Calcium sulfate sealers based on MTA has demonstrated apatite-like deposits in contact with physiological solutions and a biocompatibility similar to MTA.[5]

Pain was evaluated at 3 time periods-immediately after obturation, 1 week after obturation and 6 months after obturation. On comparison of pain between groups, there was no statistically significant difference in pain experienced by the subjects in any of the time intervals evaluated. Clinical difference in pain intensity was observed by patients with epoxy resin sealer experiencing more pain, but was not statistically significant. The results of this study are in accordance with results obtained by Alacam in his study.[23] He found no statistical significant difference between the presence and type of post-operative discomfort and the type of sealer utilized.[23] Comparison with in the group at different interval has provided a HS difference immediately after the procedure and after 1 week or after 6 months. According to a meta-analysis by Nixdorf et al., the incidence of persistent tooth pain after endodontic therapy is 5.3%.[24] The results of this study are in accordance with these results.

The radiological outcome of root canal treatment using three different sealers was evaluated with PAI. When compared with in the group, there is a highly statistically significant difference in the PAI score at baseline and after 6 months. This dictates that healing of the periapical lesions may take longer time period than 6 months. But, according to a study by Jean Camps, there was a noticeable change in the periapical lesion after comparing the radiographs taken immediately after treatment, after 3 months and 6 months of endodontic therapy.[25] However, there was no increase in PAI score in any of the groups. This implies that all the three sealers used were highly efficient in inducing healing of the periapical tissues.

Morphometric area measurement was done using VixWin Pro digital image analyzing software (Gendex dental systems).[26] The periapical lesions were circumscribed by drawing the outline and the software provided the measured area in cm2. There was no difference in the baseline data. When compared at different time periods within the same group, there was a statistically significant difference in the area measured. There was a decrease in the area measured in all the groups after a period of 6 months.

There are no previous clinical studies evaluating area measurement using VixWin Pro digital image analysis software[15] as criteria for success of endodontic therapy. So, comparison of results with previous studies in the literature is not possible, but ideally it can be judged that, PAI records the periapical status of a tooth based on previous reference radiographs, which is more subjective and differs between the examiners. Area measurement makes it more objective, better comparison between pre-operative and follow-up evaluation with less inter examiner bias. In this study, MTA was mixed with propylene glycol to get a sealer consistency.[913] However in the future studies, an ideal powder liquid ratio with the vehicle should be established. Though radiographically detectable difference in periapical lesions can be appreciated in 6 months as used in this study, further longer period evaluation should be carried out in the future. Furthermore, the removal of material from the root canal system, if retreatment is indicated should also be evaluated. Being a biocompatible material and having the property to induce the deposition of cementum and periapical repair, MTA can prove to be a better material than other sealers. The scope of this study was to evaluate the effectiveness of MTA as a root canal sealer considering its radiological and clinical success rate, usage and feasibility. MTA was found to be as good as epoxy resin and zinc oxide eugenol. Further long-term clinical trials with more criteria should be conducted to conclude the superiority of MTA among other root canal sealers.

CONCLUSIONS

Among the three root canal sealers used in this study, no sealer was proven to be superior. MTA has performed equally well when compared with the zinc oxide eugenol and AH Plus. Further long-term clinical trials with more criteria should be conducted to conclude the superiority among these materials.