Assessment of the Efficacy of Different Desensitizing Agents on Dentinal Tubules Occlusion- An In vitro Study.

Aim: The aim of the current research was to evaluate the effectiveness of three desensitizing agents on the occlusion of dentinal tubules. Materials and
Methods: Eighty human maxillary and mandibular permanent premolar teeth that were subjected to extraction in the course of orthodontic treatment were utilized in this study. The teeth were subjected to sectioning by employing a double-sided diamond disk. A block was procured from every even cervical dentinal surface with dimensions of 4 mm × 4 mm × 3 mm (L × B × H) by sectioning the tooth transversely. Further, 35% phosphoric acid was utilized for 30 s to cause dentinal etching, thereby exposing the dentinal tubules. The blocks of dentin were assigned at random to one of the following four groups (n = 20): group I: control, group II: bioactive glass containing desensitizing agent, group III: 1% nano-hydroxyapatite containing desensitizing agent, group IV: tri-calcium phosphate-containing desensitizing agent. The exterior of the specimens was scanned and evaluated using a scanning electron microscope.
Results: 1% nano-hydroxyapatite-containing desensitizing agent (2.04 ± 0.08) exhibited higher mean dentinal tubular blockage, followed by the bioactive class-containing desensitizing substance (2.26 ± 0.19), tri-calcium phosphate desensitizing agent (2.84 ± 0.10), and the control group (4.18 ± 0.12) in that order. Amid the experimental groups employing the various desensitizing substances, there were significant differences statistically with P < 0.001.
Conclusion: The current research concluded that each of the three desensitizing agents was efficient in dentinal tubular occlusion regardless of their different chemical constitution. However, it was noted that 1% nano-hydroxyapatite-containing desensitizing agent was marginally superior to the bioactive glass- and tri-calcium phosphate-containing desensitizing agents. Copyright:

INTRODUCTION

In routine dentistry, dentinal hypersensitivity (DH) is among the most frequent reasons for pain. Owing to dentin-tubular ramification at the dentino-enamel junction (DEJ) of the bucco-cervical area, higher DH is noted in this region, with the greatest prevalence in the second to fourth decade of life. By definition, DH is a short, severe pain of acute onset that cannot be ascribed to some other dental pathology. Cold stimuli evoke DH, and the pain is subject to aggravation by mechanical strain, as in tooth brushing.[1]

Ions/salts, iontophoresis with fluoride, dentin sealants, lasers, and periodontal soft tissue grafts are among the varied techniques utilized to clinically treat dentin that is highly sensitive.[2] Currently, nerve conduction blockade and occluding the dentinal tubules are the chief dual therapeutic and preventive approaches of dentinal hypersensitivity. The former utilizes ionic potassium, which causes depolarization of the neuronal fibers, thereby interfering with nerve conduction. The latter management strategy uses mechanical blockage of the dentin-tubules with a physical/chemical substance that avoids pulpal fluid current plus causes a decrease in dentinal.[3]

Off late, bioactive glass consequential to the original 45S5 bioglass constitution has been integrated with dentifrices to serve as remineralizing agents in the treatment of dentinal hypersensitivity. Dentinal tubular blockade is brought about by the precipitation of hydroxycarbonate apatite (HCA) on the surface of the tooth.[4]

The toothpaste, Aclaim, is employed for the management of dentinal hypersensitivity as it contains hydroxyapatite nanocrystals. Nanocrystals act as fillers as nanoparticles effortlessly infiltrate through uncovered dentinal tubules and powerfully adsorb dentine apatite, consequently occluding the uncovered dentinal tubules.[5]

Calcium in Clinpro enhances the probability of formation of globular calcium fluoride on the tooth. The existence of calcium fluoride leads to the occlusion of dentinal tubules, thereby reducing dentinal hypersensitivity.[6] Thus, this in vitro research was performed to appraise the effectiveness of three desensitizing agents in the occlusion of dentinal tubules by employing scanning electron microscopy.

MATERIALS AND METHODS

The current in vitro research was performed in the department of periodontics, Kalinga Institute of Dental Sciences, Bhubaneswar, India. Eighty human maxillary and mandibular permanent premolar teeth that were subjected to extraction in course of orthodontic treatment were utilized in this study. Exclusion criteria were teeth presenting with evident/clinically noticeable cracks, stains, dental caries, wear facets, erosive/abrasive regions, attrition, restorations, white spot lesions, or hypoplastic areas.

Preparation of dentine block

The premolar teeth were subjected to scaling with an ultrasonic scaler and meticulously cleansed using normal saline, followed by storage in 10% formalin at room temperature for not more than 2 months before being used. Teeth were subjected to mesiodistal sectioning by employing a two-sided diamond disk. A block was procured from every even cervical dentinal surface with dimensions of 4 mm × 4 mm × 3 mm (L × B × H) by sectioning the tooth transversely. The samples were subjected to ultrasonication by using distilled water for a duration of 10 min to eradicate the leftover smear layer, thereby opening the dentinal tubules. Next, 35% phosphoric acid was utilized for 30 s to cause dentinal etching, thereby exposing the dentinal tubules. The samples were subjected to rinsing with distilled water, followed by sonication for 5 min to eradicate the remaining etchant. The samples were immersed in phosphate-buffered solution (PBS) till future utilization.

Application of desensitizing agents

The blocks of dentin were assigned at random to one of the following four groups (n = 20).

Group I: Control (artificial saliva)

Group II: Bioactive glass-containing desensitizing agent

Group III: 1% nano-hydroxyapatite-containing desensitizing agent

Group IV: Tri-calcium phosphate-containing desensitizing agent

Scanning electron microscopic evaluation of occlusion of dentinal tubules

Following the therapy, the samples were subjected to drying and organized for examination by SEM. Following drying, the individual blocks were placed on stubs of aluminum and then covered with a slim layer of gold/palladium in a sputter coater. The exterior of the specimens was scanned and evaluated with SEM at 1000× magnification, operating at 20 kV. The tubule occlusion was scored in each image of every sample by means of tubule occlusion classification scoring scheme as follows:[7]

Score 1- Occluded (Closure of 100% of dentinal tubules)

Score 2- Mostly occluded (50%–<100% of dentinal tubular closure)

Score 3- Partially occluded (25%–<50% of dentinal tubular closure)

Score 4- Mostly unoccluded (<25% of dentinal tubular closure)

Score 5- Unoccluded (0%, absent dentinal tubular closure)

Statistical analysis

SPSS version 20.0 was employed for data analysis. The mean and standard deviation was calculated. The appraisal of the effectiveness of different desensitizing agents on dentinal tubules blockage was performed with the one-way analysis of variance (ANOVA) and the post hoc Tukey test. P < 0.05 indicated statistical significance.

RESULTS

Table 1 depicts the evaluation of the mean dentinal tubular exposure prior to applying the desensitizing agent to the samples in the respective experimental groups. Marginally higher (4.96 ± 0.12) dentinal tubular exposure was exhibited by the desensitizing agent containing bioactive glass, followed by the control group (4.88 ± 0.09), the 1% nano-hydroxyapatite-containing desensitizing agent (4.82 ± 0.11), and the desensitizing agent group using tri-calcium phosphate (4.79 ± 0.07) in that order. Amid the experimental groups, there was no significant difference statistically.

Table 1

Assessment of the mean exposure of the dentinal tubules before application of desensitizing agents among investigation groups

Desensitizing agents groups	n	Mean±SD (μ)	F	P
Group I: Control	20	4.88±0.09	18.104	0.828
Group II: Bioactive glass-containing desensitizing agent	20	4.96±0.12
Group III: 1% Nano-hydroxyapatite-containing desensitizing agent	20	4.82±0.11
Group IV: Tri-calcium phosphate-containing desensitizing agent	20	4.79±0.07

Table 2 delineates the appraisal of the mean dentinal tubular blockage following the application of the respective desensitizing agents in the experimental groups. 1% nano-hydroxyapatite-containing desensitizing agent (2.04 ± 0.08) exhibited higher mean dentinal tubular blockage, followed by the bioactive class-containing desensitizing substance (2.26 ± 0.19), tri-calcium phosphate desensitizing agent (2.84 ± 0.10), and the control group (4.18 ± 0.12) in that order. Amid the experimental groups employing the various desensitizing substances, there were significant differences statistically with P < 0.001.

Table 2

Assessment of the mean exposure of the dentinal tubules after application of desensitizing agents among investigation groups

Desensitizing agents groups	n	Mean±SD (μ)	F	P
Group I: Control	20	4.18±0.12	20.382	0.001
Group II: Bioactive glass-containing desensitizing agent	20	2.26±0.19
Group III: 1% Nano-hydroxyapatite-containing desensitizing agent	20	2.04±0.08
Group IV: Tri-calcium phosphate-containing desensitizing agent	20	2.84±0.10

Table 3 shows the pairwise relative estimation of the mean occlusion of the dentinal tubules utilizing the post hoc Tukey test. Statistically significant differences (P < 0.001) were eminent amidst the investigational groups except for group II versus group III and group II versus group IV.

Table 3

Overall assessment of the mean occlusion of the dentinal tubules among investigation groups by using post hoc Tukey test

Study group	Comparison with	Mean Difference	Significance
Group I	Group II	1.92	0.001
	Group III	2.14	0.001
	Group IV	1.34	0.001
Group II	Group I	−1.92	0.001
	Group III	0.22	0.818
	Group IV	−0.58	0.082
Group III	Group I	−2.14	0.001
	Group II	−0.22	0.818
	Group IV	−0.80	0.02
Group IV	Group I	−1.34	0.001
	Group II	0.58	0.082
	Group III	0.80	0.02

DISCUSSION

Dentinal tubules constitute the mineralized and fluid-filled tissue dentin, rendering it porous and penetrable. Receding gingivae, wasting diseases such as attrition/erosion and abfraction lead to lost enamel as well as cementum, exposing the dentinal tubules to the oral milieu and resulting in hypersensitivity.[8] Managing agonizing dental challenges such as DH is extremely tough and has posed a great therapeutic dilemma for several years now.[9] Triumphant management strategies that render quick and enduring tubular blockage while resisting the challenges posed by the oral atmosphere are required. One highly efficient modality presently utilized in managing DH is dentinal tubular blockage.

1% nano-hydroxyapatite-containing desensitizing agent exhibited higher dentinal tubular occluding capacity compared to the bioactive glass and tri-calcium phosphate-containing desensitizing agents. These results are not in harmony with the research by Katakam et al.[6] that delineated greater dentinal tubular blockage in dentin specimens subjected to treatment with Clinpro, although some dentinal tubules remained open. There is a greater chance of calcium fluoride formation on the surface of teeth from the calcium in Clinpro. DH is reduced from globular calcium fluoride that causes occlusion of dentin tubules by being present on the tooth surface.

Nano-hydroxyapatite-containing toothpaste exhibited differences that were statistically significant in causing tubular blockage compared with the other agents, though all three substances could cause dentin tubular blockage. Jena and Shashirekha[10] conducted a study that compared the effectiveness of biomaterials as desensitizing substances. Nano-hydroxyapatite toothpaste was for the most part efficient in attaining tubular occlusion, identical to the study comparing biomaterials. Nevertheless, in a study by Dhillon et al.,[11] calcium sodium phosphosilicate exhibited an appreciably superior proportion of tubular blockage in contrast to hydroxyapatite.

Bioactive glass compared to the tri-calcium phosphate-consisting desensitizing agent in this study showed a higher number of occluded dentin tubules. Moreover, the outcomes depicted that the bioactive glass experimental group also had the uppermost quantity of blocked tubules, chiefly subsequent to the acidic confrontation. This may be credited to the method by which bioactive glass behaves. As per Burwell et al.,[12] the NovaMin component of bioactive glass attaches to the bare dentinal surface and responds to produce a mineralized coating. This coat is mechanically sturdy and resists acidic challenges.

CONCLUSION

The current research concluded that each of the three desensitizing agents was efficient in dentinal tubular occlusion regardless of their different chemical constitutions. However, it was noted that 1% nano-hydroxyapatite-containing desensitizing agent was marginally superior to the bioactive glass-containing and tri-calcium phosphate-containing desensitizing substances.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.