Comparing the effect of a desensitizing material and a self-etch adhesive on dentin sensitivity after periodontal surgery: a randomized clinical trial

Cervical dentin sensitivity (CDS) is one of the most common painful conditions affecting oral comfort and function and can be defined as a painful symptom of the exposed dentin in response to chemical, thermal, tactile or osmotic stimuli which cannot be explained by any other dental defect or pathology [1, 2]. The occurrence of CDS ranges from 3 up to 98%. This vast range can be explained by the differences in the selection criteria for the study sample and also the variety in diagnostic approaches or time frames. Women are slightly more affected than men with an age peak of 30 to 40 years [3]. Exposure of root surface by loss of the overlying cementum and periodontal tissues is one of the most common etiological factors related to CDS [4].

The most widely accepted explanation for tooth sensitivity is Brännström and Åström's hydrodynamic theory [5]. According to this theory, the exogenous stimuli applied to the exposed dentinal tubules result in the flow of dentinal tubular fluid, activate the intratubular nerve endings, and create pain. The number, size, and diameter of the open dentinal tubules are important factors that determine the degree of hypersensitivity in the subjects [6]. Recently, two strategies are used for the treatment of CDS. One is occluding the dentine tubules and the other is interfering with the sensitivity of the mechanoreceptors [7]. A variety of products have been developed with the aim of alleviating the discomfort arising from the CDS [8].

Some researchers believe that self-etch adhesives can reduce dentin sensitivity by decreasing dentin permeability [9, 10] due to production of an acid-resistant hybrid layer [11]. This acid-base resistance zone may result in longer lasting clinical effectiveness. Yu et al. [12] showed that the one-bottle self-etching adhesives and dentin desensitizers could significantly relieve CDS (which was not due to periodontal surgery) immediately and over the course of a month after treatment.

The aim of the current clinical study was to compare the clinical effectiveness of a dentin desensitizer, a one-bottle self-etching adhesive, and a placebo for CDS treatment after periodontal surgery and the null hypotheses of the present study was that all three methods have the same clinical effectiveness at different interval times.

According to the study of Yu et al. [12], 14 patients who were planned to undergo surgical periodontal treatment in at least three posterior sextants were recruited into this randomized, double-blinded, placebo-controlled, split-mouth study.

These patients were referred to the Department of Restorative and Cosmetic Dentistry of Mashhad University of Medical Sciences for desensitizing treatment if they had complained about CDS after removing the periodontal pack of the first sextant. Participants were given a brief explanation about the investigation and all consented to participate and signed a consent form approved by the Committee on Ethics in Research, Mashhad University of Medical Sciences. This trial was registered at: http://www.IRCT.ir and its identification number is IRCT201408176267N2.

The inclusion and exclusion criteria are stated in Figure 1.

Figure 1
Inclusion and exclusion criteria.

ICDAS, International Caries Detection and Assessment System.

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All the patients had moderate to severe chronic periodontitis. This means that all of them had more than 4 mm attachment loss and more than 5 mm periodontal pockets, so all of them needed periodontal surgery which was contained flap debridement, scaling and root planning and respective osseous surgery as needed, suturing, and covering the area with dressing. Generally, patients with periodontal diseases suffer from some degrees of dental hypersensitivity which usually increases after scaling and root planning or periodontal surgery. Because the periodontal pack was removed between 1 to 2 weeks after the surgery, the first treatment session was scheduled 10–20 days after the surgery of the first sextant.

A total of 96 teeth with CDS after periodontal surgery were considered suitable for the study and the rate of sensitivity to the cold air stimulation was recorded at baseline (T0) for each tooth according to visual analog scale (VAS). To produce the stimuli, 2-second air blast (45 psi, 19°C–24°C) was applied using an air syringe held 2 mm away, and perpendicular to the tooth surface whilst shielding adjacent teeth with the operator's fingers. In this step only teeth with VAS score of 4 and more (teeth with moderate to severe sensitivity) were selected for study. In order to avoid bias, each sextant was randomly allocated to one of 3 treatment groups by choosing an envelope containing the order of treatment options which were placebo (distilled water), Gluma Desensitizer (Heraeus Kulzer, Hanau, Germany), and Clearfil S³ Bond (Kuraray Dental, Okayama, Japan). The teeth of the different sextants received different treatment and the adjacent teeth received the same material. By using a split mouth study design, three study groups, had the advantages of similar pain perception, oral hygiene habits, dietary habits, and psychosomatic factors in the same patient. Allocating the samples in each group is showed in Figure 2.

Figure 2
Flowchart of allocating the samples in each group.

VAS, visual analog scale.

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At the beginning of the survey, 6 males and 8 females between the ages of 20 and 65 years recruited in the study but one of the patients excluded, because all his teeth in the last sextant undergone surgery showed VAS scores less than 4, so we had not 3 sensitive sextants to treat. Therefore, a total of 52 premolars and 38 molars remained in the three study groups.

First, the normality of the data was confirmed with Kolmogorov-Smirnov test. There was no significant difference between all groups in base line sensitivity (p = 0.83).

Repeated measurement analysis considering follow-up time and treatment group showed the interaction of this 2 variables. So, Hotelling's Trace test showed a significant difference between all assessment times in all 3 groups. Therefore, paired comparison of groups according to the assessment times was done. The results have been shown in Table 1.

Table 1
Mean visual analog scale (VAS) scores for each treatment group within each assessment time

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ANOVA test was used to assess each treatment group in different investigation times (baseline, 1 day, 1 week, and 1 month after treatment). The results of this test showed a significant difference only in the last follow-up time (T3, p = 0.029). Accordingly, Tukey test was used for paired comparison of treatment groups in the last follow-up time and showed a significant difference between G2 and G3 (p < 0.05).

The current clinical study tried to compare the clinical effectiveness of Gluma Desensitizer, Clearfil S³ Bond (one-bottle self-etching adhesive), and placebo (distilled water) for CDS treatment after periodontal surgery in different evaluation times by using VAS. Several studies noted that the patient may encounter abrupt and severe dentin sensitivity after periodontal therapies [13, 14]. Also, the occurrence and severity of CDS directly depend on the type of periodontal treatment and are greater after surgical procedures [15]. The main reason for sensitivity is exposing dentinal tubules to the oral environment [16]. Thus, the basis of most desensitizing treatments is to block these tubules.

To date, only few studies have evaluated the effect of dentin bonding agents in reducing CDS [17, 18, 19, 20, 21]. Even these studies rarely assessed all-in-one adhesives and CDS following periodontal surgery [12, 22]. The results of this study showed that in the group treated with Clearfil S³ Bond, CDS values reduced 1 day after treatment and the reduction continued for 1 week after treatment. This may be due to the concurrent effect of natural tubule blocking factors over time and blocking effect of adhesive material. According to microscopic findings, topical application of these adhesives on the sensitive dentinal areas resulted in occlusion of the patent tubules and produced an acid-base resistant hybrid layer on the dentin surface [23]. This acid-base resistant zone is a combination of dentin and the adjacent hybrid layer. Since this layer is mechanically, chemically, and biologically more resistant than normal dentin, it is also called ‘Super Dentin’ [23]. One of the functional monomers with the ability to create Super Dentin is 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) [24]. Clearfil S³ Bond contains 10-MDP.

On the other hand, Yu et al. [12] showed that some occluded dentinal tubules partly reopened 1 month after treatment and so some sensitivity returned after 1 month. The reason might be the fact that all-in-one adhesives contain mixtures of more hydrophilic monomers, and thus, are permeable to water after application to the dentinal surface [9]. However, our study showed reduction of CDS over time after applying Clearfil S³ Bond. It seems that time factor could add some positive effect during 1 month.

According to this study, as there were significant difference between T1 and T2 with T3, Gluma can reduce CDS 1 day after treatment. Moreover, gradual reduction of CDS happened in this treatment group over the investigation period. These results are consistent with the results of other studies, which have shown the same reduction [12, 22, 25, 26]. It has been noted that the effect of Gluma (5% glutaraldehyde and 35% hydroxyethyl methacrylate [HEMA] marketed as Gluma Desitizer) as a desensitizer to block dentinal tubules occurs through 2 mechanisms: first, through denaturation of dentinal fluid proteins by glutaraldehyde and second, through polymerization of HEMA. Both of them result in decrease in dentin permeability [27].

The present study showed that placebo can significantly reduce CDS one day after treatment. Patient's supposition of receiving a treatment can be effective on decreasing CDS, because pain is a subjective phenomenon. This mechanism is undeniable and is shown by many investigations. Therefore, the efficacy of placebo in one day after treatment can be explained by its psychological effects [12, 18, 22]. Additionally, the mean of VAS in placebo group decreased gradually over time. This is not in line with the results of the study by Yu et al. [12], which showed that some of the CDS will return during one month. This difference may be explained by the various conditions of studies. The present study was implemented on CDS following periodontal surgery, but in the study by Yu et al. [12], it was performed on sensitive teeth which did not passed any surgical procedure. Therefore, in this study, cervical dentin had been suddenly exposed to oral environment and the natural factors such as saliva protein precipitation, smear layer formation, and remineralization, did not have enough time to block tubules and decrease CDS. While, in the study by Yu et al. [12], cervical dentin have been exposed to oral environment for long a time and those natural processes would not meet any additional effect even if they had more time. Studies have shown that some natural factors, can decrease dentin permeability and therefore decrease CDS over time [28, 29, 30].

This study noted that Gluma was the most effective and placebo the least effective treatment of CDS among three groups in the last follow up time. The effectiveness of Gluma may be due to its dual effect of HEMA and glutaraldehyde. Since Gluma has low viscosity and does not need light curing, it is more user-friendly and less technique sensitive than Clearfil S³ Bond, especially in interproximal areas. Also, our investigation showed that the effectiveness of Clearfil S³ Bond is the same as Gluma and placebo in 1 day and 1 week follow-up times and have significant difference with Gluma after 1 month. Since this adhesive affects CDS reduction only by polymerization into the dentinal tubules, it seems that it can merely meet just one of the action mechanisms of Gluma Desensitizer. The problem of not being sure of the successful light curing of resin in more difficult accessible areas might also reduce its effectiveness in CDS treatment. Although, the all-in-one adhesive tested in the current study did not perform better than the dentin desensitizer, but it could reduce the CDS to some degree.

According to the limitations of this study, it was shown that also dentin sensitivity following periodontal surgery will decrease spontaneously over time, but treating the sensitive teeth with Gluma Desensitizer and Clearfil S³ Bond can have some benefits.