Evaluation of Effectiveness of Mineral Trioxide Aggregate for Root Furcation Repair Using Diode Laser as Adjunct - An In Vitro Study

Introduction

Pathological root perforations may arise due to resorption, caries, or iatrogenic factors during root canal procedures. These injuries to the tooth have the potential to compromise the effectiveness of treatment and may result in additional complications if not addressed properly.¹ A mid-curvature opening in the furcation area of a multi rooted tooth often passes to periodontal ligament space (PDL) leading to poor outcome in root canal therapy.² Furcal perforations occur majorly due to pathological or procedural errors. Therefore, proper management of furcal perforations is essential to prevent damage to the periodontal tissues for long term prognosis.³

Furcal defects are often treated either by surgical or non-surgical methods. Owing to the difficulties associated with surgical procedures such as procedural difficulty, pocket formation, difficulty in isolation, nonsurgical techniques have gained popularity, especially in inaccessible areas.⁴ The success of a furcal perforation repair is determined by the aetiology, location, size, timing of repair, and material selected for the furcal seal. As a result, the furcal perforations should be repaired as soon as possible using a biocompatible material to avoid intrusion of microorganisms and improve prognosis. Ideally, a perforation material should be able to provide adequate seal, should be biocompatible, bacteriostatic, non-toxic, easy to manipulate and place, radiopaque, fast setting and should possess regenerative potential inducing tissue regeneration, osteogenesis and cementogenesis.

A variety of materials have been used to repair furcal perforations.⁵ Super EBA is ZOE cement reinforced with Ethoxy benzoic acid (EBA). It is simple to use and biocompatible to periapical tissues. Besides, it is highly adhesive and adapts well to the dentinal walls.⁶ Super EBA has very low solubility due to the presence of silicone dioxide or alumina with less cytotoxic effect, releasing only 2% eugenol while curing.⁷ It provides better seal, and when encompassed in the furcal defect, does not get resorbed. Thus it is suitable for furcation repair.⁸ However, it lacks few properties like regenerative capacity, has short setting time, is difficult to place, sensitive to temperature and humidity and is moderately radiopaque.

Introduction of Mineral trioxide aggregate (MTA) has revolutionised the endodontic practice due to its improved properties. It is made of tricalcium and dicalcium silicates, tricalcium aluminate, tetra calcium alumina ferrite, calcium sulphate, and bismuth oxide. It has a wide array of clinical implications such as pulpcapping, vital pulp therapy, apexification, root canal filling, apical filling, perforation repair, etc.⁹ It exhibits numerous properties of an ideal repair material due to its tissue bio friendly nature, good sealing ability, peri-radicular tissue regeneration, osteogenesis and cementogenesis.

Prior to the application of dental cements, laser stimulation of dentin surfaces considerably improves bond strength since it causes dentinal surface alterations producing micro irregularities, results in hydrated surface which lead to better penetration of dental cements with tag formations.¹⁰ When irradiated on the root dentin, Diode laser (810 nm) provides maximum reduction in bacterial load by about 63% and reduces the tubule diameter of dentin.11 Very few studies have researched the application of diode laser irradiation for furcation repair. Thus the present study aimed to evaluate the furcal seal with 810 nm diode laser irradiation along with MTA and Super EBA.

Materials and Methods

Institutional clearance was obtained for this in vitro study (Reference No. IEC/2019-20/17) and the procedure was carried out accordingly. About 108 human mandibular molar teeth extracted for periodontal reasons with well developed, non-fused roots and with intact furcation, without cracks or fracture were selected for the study. Ultrasonic scaler (Guilin woodpecker medical instrument Co Ltd, China) was used to remove hard and soft tissue debris, were placed in an ultrasonic bath containing 0.5% sodium hypochlorite (NaOCl) (Vishal Ltd, Maharashtra, India) for 10 mins and then stored in distilled water until use.

Sample preparation

All the teeth specimens were horizontally cut 3 mm above the cemento-enamel junction (CEJ) and 3 mm below using a diamond disk (Mani, Tochigi, Japan) under water coolant. A standardized access opening was prepared in all the specimens in furcal area using endo access bur (Dentsply Malliefer, Ballaigues, Switzerland) and were sealed with sticky wax (DPI, Mumbai, India).

Except for 18 specimens (negative control), furcal defects of 1 mm width were prepared in all the specimens from the external surface of the tooth with a No. 2 round carbide bur (Dentsply Malliefer, Ballaigues, Switzerland) using a high speed airotor handpiece (NSK, Tokyo, Japan) with water coolant. The specimens were flushed with water, air-dried and were allocated to six groups (n=18) for furcal repair.

Group 1: MTA (Dentsply, Tulsa, USA)

Group 2: Super EBA (Dentsply, Tulsa, USA)

Group 3: Diode laser + MTA Group 4: Diode laser + Super EBA

Group 5: Furcal defect left unrepaired (Positive control)

Group 6: Intact furcation (Negative control)  

In Groups 1 and 2, the materials were manipulated according to the manufacturer’s instructions by mixing power and liquid with a mixing spatula on a mixing pad until a homogenous mix was obtained and placed into the furcal defect of each specimen using amalgam carrier and condensed with hand plugger.

In Groups 3 and 4, the furcal perforation was irradiated using 980 nm diode laser (SIRO laser 2.2; Sirona Dental Systems GmbH, Bensheim, Germany) in pulse mode at power 1.5 W 100 Hz for 10 seconds using a 200 µm fibre optic tip after which the repair materials were placed in the respective groups as mentioned above. In Group 5, the specimens were left unrepaired and in Group 6, the specimens with intact furcation served as negative control. All the specimens were kept at 37o C for seven days.

Microleakage evaluation

The specimens were submerged separately in 2% methylene blue solution in a petri dish for 48 hrs at 37o C and then rinsed with water. The specimens were then split in mesiodistal direction using a diamond disc under water coolant and observed under a stereomicroscope (Labsol Enterprise, Haryana, India) at a magnification of 10X and the extent of microleakage was determined using software Image J (Motic, Barcelona, Spain).

Statistical analysis

Statistical Package for Social sciences (SPSS) version 23.0 (IBM Corporation, New York, USA) was used along with one-way ANOVA and Post hoc Tukey tests at P ≤0.05.

Results

According to one-way ANOVA, Group 3 (MTA+Laser) exhibited the least microleakage, followed by Groups 1 (MTA), 4 (Super EBA with laser), and 2 (Super EBA), whereas among the controls, Group 5 (positive control) showed the highest microleakage, while Group 6 (negative control) did not exhibit any microleakage. 

On further analysis using Tukey’s post hoc test, significant difference between all the groups with P value less than 0.001 was noted, except between Group 1 (MTA) and Group 3 (MTA with laser).

Discussion

The rationale for non-surgical treatment of the perforation is to prevent periradicular inflammation. This can be achieved by immediate sealing of the perforation with a material that can provide a satisfactory seal to prevent microbial penetration. The prognosis is most favourable when the perforation is sealed immediately.¹²

Furcal perforation is repaired using materials such as Glass ionomers, Super EBA and most recent biomimetic materials such as MTA, Biodentine, etc. However, no material can completely prevent microleakage. Considering the beneficial effects of diode laser, this study was undertaken to determine the influence of diode laser on the sealing ability of furcal repair materials, Super EBA and MTA.

Various methods have been employed to assess the microleakage of endodontic materials; however, no test is standardized. Despite criticism, dye leakage tests still remain the method of choice for assessing adaptation and sealing ability.¹³ Dye leak method was used in this study to assess microleakage because it is a simple, inexpensive, fast technique, does not require the use of complex laboratory equipment, is detectable in dilute concentrations and is non-toxic.¹⁴

In this study, group with intact furcation exhibited no microleakage, while unrepaired furcal areas showed highest dye penetration indicating that if the furcation defect is not sealed, it will lead to extreme microleakage. All the other groups repaired with suitable materials demonstrated dye microleakage. Highest microleakage was observed in Super EBA group compared to MTA group, which agrees with the findings of Tsatsas DV et al.,¹⁵ MTA has unique biological properties such as it exerts antibacterial effects, exhibits biocompatibility and low mutagenic effect.¹⁶ The histological sections of root perforations sealed using MTA showed deposition of cementum on its surface. The cementum not only forms in continuance with the existing root cementum but also attaches itself directly to the material extruded into the furcation defects. It provides a better seal compared to amalgam, IRM and Super EBA.¹⁷ In contrast, Weldon JK Jr et al.,⁸ found that Super-EBA had less microleakage than MTA because MTA requires four hours for setting which leads to the initial microleakage, whereas Super EBA sets quickly. Similarly, Karlovic Z et al.,¹⁸ showed that the sealing quality of Super EBA cement in the prepared root-end cavities was better than MTA. Keizer et al.,¹⁹ on the other hand reported that MTA is less toxic to human PDL cells than Super-EBA at all concentrations in both freshly mixed and 24 hour set states. Most of the studies reported good sealing ability of MTA compared to Super EBA. MTA was found to have the highest estimated healing rate, not affected by moisture and exhibits superior biocompatibility and sealing abilities, with regenerating potential and therefore can be an excellent material for furcation repair. However, its disadvantages include poor handling characteristics, slow setting time, and high cost.

Greater microleakage was found in Group 4 (Super EBA with laser) compared to Group 3 (MTA with laser) in this study. This is due to the improved properties of MTA as stated previously and added benefits of laser for better adaptation of repair material to root dentin. Kim M et al.,²⁰ evaluated the effect of Nd:YAG laser irradiation on retrograde adhesion of MTA and Super EBA by micro-computed tomography (CT) and scanning electron microscopy and showed that gap in the MTA group was significantly lower than in the Super EBA. The root-end resection performed with laser results in ablation of the exposed dentinal tubules, which may decrease microleakage and increase resistance to root resorption.

In this study, greater microleakage was found in Group 1 (MTA) compared to Group 3 (MTA with laser). Similar results were observed in a study conducted by Tielemas M et al.,²¹ which reported that the dye penetration with MTA following laser irradiation was lower than that of non-exposed cavities sealed only with MTA and concluded that laser conditioning eliminates the root dentin smear layer and has a less ablative effect on the highly mineralized peritubular dentin. The chemical reaction of MTA with the exposed mineral content of Er:YAG irradiated dentin and the physical effect of open dentin tubules of lased dentin results in micro retention and improves sealing.

In the present study, higher microleakage was found in Super EBA group compared to Super EBA with laser group. According to Gutknecht et al.,²² 980 nm diode laser has good penetration potential, eradicates the microbes in about 500 µm deep from the dentin, whereas chemical solutions can only reach 100 µm. Umana et al., ²³ stated that diode laser ranging from 810 to 980 nm with 0.8 and 1 W power causes the closing and narrowing of dentinal tubules. These surface alterations in dentin after irradiation with laser tends to produce an irregular appearance of the irradiated dentine surface, and the retention of the restorative materials is improved.

Thus from the present study, it can be suggested that laser activation of furcation defect before placement of either MTA or Super EBA enhances the seal of these materials. Among the tested materials, MTA was superior compared to Super EBA due to its inherent improved properties. However, MTA with laser as an adjunct showed superior sealing ability. Hence, results of the present study suggest considering laser irradiation before placement of MTA in furcation repair for superior seal. However, further in vitro, in vivo studies need to be conducted using larger sample size, using different materials in diverse environmental conditions with different models of microleakage tests for confident use of lasers in furcation repair.

Conclusion

MTA with diode laser activation exhibited superior sealing ability in furcal perforation repair.

Conflict of Interest

None