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ORIGINAL ARTICLE
Year : 2012  |  Volume : 6  |  Issue : 2  |  Page : 51-56

A comparative analysis between Nd:YAG and CO2 lasers for their sealing ability of dentinal tubules with and without fluoride varnish: An in vitro study


Department of Conservative Dentistry and Endodontics, Rajah Muthiah Dental College, Annamalai University, Tamil Nadu, India

Date of Web Publication31-Jan-2013

Correspondence Address:
Deepa V Kumar
Department of Conservative Dentistry and Endodontics, Rajah Muthiah Dental College, Annamalai University, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0976-2868.106653

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  Abstract 

Background: Application of laser energy onto exposed dentinal tubules provides instantaneous relief from dentin hypersensitivity. The aim of the present study was to compare between CO 2 and Nd:YAG laser irradiation for their sealing ability on human dentinal tubules when treated with and without fluoride varnish, using Scanning Electron Microscopy. Materials and Methods: Twenty extracted human intact third molar teeth were selected. A total of six samples were obtained from each tooth. One hundred and twenty dentin samples from 20 teeth were then divided into six groups with 20 samples in each group. These slabs were treated with 17% ethylenediaminetetraacetic acid (EDTA) for 5 min and with 5% NaOCl for the next 2 min for removal of the smear layer. Each of the samples from a single tooth was then subjected to six different treatment protocols according to the groups given below.
Group 1 (n = 20) : CO 2 laser
Group 2 (n = 20) : Nd:YAG laser
Group 3 (n = 20) : Varnished with fluoride and lased with CO 2 laser
Group 4 (n = 20) : Varnished with fluoride and lased with Nd:YAG laser
Group 5 (n = 20) : Varnished with fluoride
Group 6 (n = 20) (control) : Not subjected to lasing and fluoride application
All samples were examined under scanning electron microscope. Results were subjected to statistical analysis using one-way analysis of variance (ANOVA) and the multiple comparisons among groups were carried out by Student's t-test. Results: Compared to conventional fluoridation or laser irradiation, in the treatment of dentin hypersensitivity, CO 2 lasers in combination with fluoride varnish appear to show better efficacy than either treatment modality alone.

Keywords: CO 2 , dentin hypersensitivity, fluoride, Nd:YAG


How to cite this article:
Ahamed S, Gurucharan N, Meyappan R, Kulandaivelu A, Kumar DV, Sreenadh B. A comparative analysis between Nd:YAG and CO2 lasers for their sealing ability of dentinal tubules with and without fluoride varnish: An in vitro study. J Dent Lasers 2012;6:51-6

How to cite this URL:
Ahamed S, Gurucharan N, Meyappan R, Kulandaivelu A, Kumar DV, Sreenadh B. A comparative analysis between Nd:YAG and CO2 lasers for their sealing ability of dentinal tubules with and without fluoride varnish: An in vitro study. J Dent Lasers [serial online] 2012 [cited 2017 Mar 29];6:51-6. Available from: http://www.jdentlasers.org/text.asp?2012/6/2/51/106653


  Introduction Top


Dentinal hypersensitivity is characterized by short, sharp pain arising from exposed dentin, in response to stimuli, typically thermal, evaporative, tactile, osmotic, or chemical, and which cannot be ascribed to any other form of dental defect or pathology. [1] It is estimated that one in seven patients suffer from some degree of dentinal hypersensitivity. [2] Erosion, abrasion, attrition, gingival recession, periodontal treatment, and anatomic defects have been suggested as possible risk factors for dentinal hypersensitivity. [3] Dentinal pain is elicited by cold stimuli in up to 90% of dental patients, although mechanical and chemical stimuli are also effective. [4]

According to the hydrodynamic theory proposed by Brannstrom, rapid dentinal fluid flow serves as the final stimulus in activating intradental nociceptors for many different types of stimuli. [3] The management of dentinal hypersensitivity involves the application of therapies that reduce the flow of dentinal fluid or lower the activity of dentinal neurons. These include application of resins, [5],[6] oxalate salts, isobutyl cyanoacrylate, [7] and fluoride-releasing resins or varnishes [8] to exposed dentinal tubules and the use of devices that burnish exposed dentin. [9] It was reported that potassium nitrate-containing dentifrices, [10] fluoride-containing medicaments, [11] and agents containing 10% strontium chloride were partially effective in reducing dentinal hypersensitivity. [3]

A different treatment modality for reducing dentinal hypersensitivity involves the use of laser technology. The first laser use for the treatment of dentin hypersensitivity was reported by Matsumoto et al. (1985) using Nd:YAG laser. [12] Among the different lasers used, desensitizing mechanism is distinct for each emitted wavelength; success rates reported differ according to laser device, irradiation parameters (adequate wavelength, power density, wave mode, frequency of pulses, and number of irradiation repetitions), and investigation methods used to assess dentinal pain. [13] The lasers used for the treatment of dentinal hypersensitivity may be divided into two groups: Low-output power lasers [helium-neon and gallium/aluminum/arsenide (diode)] and middle-output power lasers [Nd:YAG and carbon dioxide [12] (CO 2 )]. The effects of middle-output lasers have been variously described by different authors. Scanning electron microcopy (SEM) after irradiation has been performed as an attempt to detect in vitro the mechanism of high-level lasers in desensitization. [1] Occlusion of dentinal tubules has been observed in several studies, thus suggesting this may be the possible mechanism involved in pain relief. [2],[13],[14] Additional benefits in occluding tubules may be obtained when laser irradiation is combined with conventional desensitization therapies. [13]

When examining SEM photographs of dentin irradiated by lasers such as CO 2 and Nd:YAG, melting and resolidification of dentin is usually observed. A solid, uninterrupted, melted, and resolidified area would likely be less permeable and could effectively block external stimuli associated with dentinal hypersensitivity and the penetration of microorganisms into the dentinal tubules. The purpose of this in vitro study was to compare between CO 2 and Nd:YAG lasers using SEM for their sealing ability on dentinal tubules when treated with and without fluoride varnish.


  Materials and Methods Top


Selection of teeth sample

A total of 20 extracted intact third molar teeth were used in this study. Teeth which had caries, enamel-dentin defects, restorations, or fractures were excluded. Before preparation, soft tissue and debris were removed using a scaler.

Sample preparation

Three transverse cuts were made to prepare two dentin slabs from each tooth using a diamond disk, that is one cut was made at cemento-enamel junction and the other two cuts were made 4 mm apically and 4 mm coronally to the first cut. A total of 40 dentin slabs were obtained, that is, 20 samples from the coronal part and 20 from the apical part. To expose the dentinal tubules, cementum and enamel surrounding each sample was removed with a high-speed bur. Each slab was then sectioned into three equal parts using diamond disk, that is, a total of six samples, three apical and three coronal, were obtained from a single tooth. Six samples obtained from every tooth were distributed as one sample per group. One hundred and twenty dentin samples were then divided into six groups with 20 samples in each group. These slabs were treated with 17% ethylenediaminetetraacetic acid (EDTA) for 5 min and with 5% NaOCl for the next 2 min. After removal of smear layer; samples were washed with distilled water and dried. Each of the samples from a single tooth was then subjected to six different treatment protocols according to the groups 1-6. So, a total of 20 samples were studied in each group.



Lasing application was light contact on the exposed dentin area with a method of painting parallel to each contact line.

Lasing parameters were:

CO 2 laser - 0.5 W, CW for 5 s, 6× Nd:YAG laser - 2 W, 20 Hz for 0.5-60 s

All of these specimens were then mounted on aluminum slabs and sputter coated with a layer of gold and examined using an SEM at magnification of 2500× and photographed.


  Results Top


The results were statistically analyzed using one-way analysis of variance (ANOVA), and the multiple comparisons among the groups were carried out by the Student's t-test. The level of significance was fixed at P ≤ 0.05. [Table 1] shows the mean dentinal tubule occlusion and standard deviation for each study group. There was a significant difference among the various groups compared. Occluding effect on dentinal tubules was maximum for Group 3 (CO 2 lasing + NaF) followed by Group 4 (Nd:YAG lasing + NaF), Group 5 (NaF alone), Group 1 (CO 2 lasing), and Group 2 (Nd:YAG lasing). Inter-group comparison [Graph 1 [Additional file 1]] showed that there was no statistically significant difference between Group 1 and Group 2 (CO 2 group and Nd:YAG group) and also between Group 3 and Group 5 (CO 2 + fluoride group and fluoride group). All other groups compared had a statistically significant difference [Graph 1].
Table 1: Shows the mean and standard deviation values of the study groups


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  Discussion Top


The problem of dentinal hypersensitivity is an enigma that has interested many clinicians. [15] Cervical dentin hypersensitivity has multi-factorial etiology and generally more than one factor is found to be associated and is active in this painful manifestation. Therefore, more than one treatment method should be associated to desensitize the dentin to satisfactory levels. [16] With the advent of laser technology and its growing utilization in dentistry, an additional therapeutic option is available for the treatment of dentinal pain. The laser, by interacting with the tissue, causes different tissue reactions, according to its active medium, wavelength, and power density, and the optical properties of the target tissue. [16] SEM photographs suggest that lasers have the ability to vaporize, fuse, melt, or seal dentinal tubules probably by means of recrystallization of the mineral component of dentine. Furthermore, it was concluded that the Nd:YAG and CO 2 lasers can be used to reduce pain sensation without detrimental pulpal effects. [17],[18],[19]

In this in vitro SEM study, an attempt was made to evaluate the occluding effect of Nd:YAG and CO 2 laser with or without flouride varnish on human dentinal tubules. According to the hydrodynamic theory, the effectiveness of dentin desensitization agents is directly related to their capacity to promote the sealing of the dentinal tubules. [16] The importance of occluding the dentinal tubules in certain clinical conditions is well established. Reducing the number of open tubules or decreasing their diameter is an aim of therapy for sensitive teeth. For this purpose, substances that occlude dentinal tubules or decrease their size have been applied to the exposed sensitive areas. [2] Topical sealing agents such as fluoride varnish were reported to be effective in reducing the hypersensitivity, but it was stated that their desensitizing effect was transient. Wan-Hong Lan et al. showed that after treatment with fluoride varnish, the dentin surface (including dentinal tubules' orifices) was uniformly occluded by the varnish. This same effect was seen in Group 5 that underwent only fluoride varnishing [Figure 2]. But the former study revealed that in non-lased teeth, the sodium fluoride varnish could be brushed away by electric tooth brush within 30 min, especially the varnish at the central orifices of dentinal tubules. [2]

Fluor Protector is a protective varnish for desensitization and caries prophylaxis, which contains fluoride. One gram Fluor Protector contains bis{4-[2-(difluorhydroxysilyl) ethyl]-2-methoxycyclohexyl}[N, N-(trimethylhexane-1,6-diyl) dicarbamate] (9 mg) (fluorosilane). This corresponds to 1 mg fluoride. Auxillary substances present are ethylacetate, isopentyl propionate, and polyurea forming varnish. The application of fluorides seems to create a barrier by precipitation of the calcium fluoride crystals which are formed especially in the inlet of the dentinal tubules. The precipitate is slowly soluble in saliva, which may explain the transitory action of this barrier. [20],[21]

Treatment with fluorosilicate (SiF) could play an important role in obtaining durable occlusion because some silica composites induce the formation of apatite. The open tubules were completely obliterated with the precipitation of calcium silicophosphate. The precipitate seemed to be a mixture of calcium fluoride and fluoridated apatite. [20],[22] Another positive aspect is that this composite does not present inconvenience of dentin pigmentation by the precipitation of silver ions from silver diamine fluoride. [20],[23] The precipitate formed by substances used in the treatment of dentinal hypersensitivity can disappear by the action of saliva, mechanical factors such as brushing, or chemical factors such as food, acidic beverages, and the acid from dental biofilm. [22] However, the crystals deposited inside the dentinal tubules at a depth of 60-70 μm, such as the ones formed after treatment with fluorosilicates, are difficult to remove. Moreover, demineralization caused by these acids, which exacerbate dentinal sensitivity, can be prevented by the acid resistance of the tooth after treatment with fluorosilicates, which is higher than when acidulated phosphate fluoride and sodium fluoride are used. [20] Whether fluorosilicates will be removed by the chemical or mechanical factors is a matter of debate which has to be addressed in future studies. In this study, the sealing ability of fluoride application followed by CO 2 lasing (Group 3) gave the maximum results [Figure 4]. This was in accordance with the results obtained in various other studies. [12],[24],[25],[26] A study by Pashley et al. explained that CO 2 laser irradiation cannot completely close the dentinal tubules. [18],[27] Similar results were obtained in this study; CO 2 lasing (Group 1) could only cause narrowing of the dentinal tubule orifices [Figure 6]. The combined occluding effect of fluoride varnish and Nd:YAG laser irradiation (Group 4) was second only to Group 3, which was similar to the results of the study conducted by Wan-Hong Lan et al. which revealed that application of Nd:YAG laser to sodium fluoride varnish treated dentin surfaces resulted in 90% of dentinal tubules being occluded [Figure 3] and [Figure 4]. [4] They concluded that fluoride varnish was burned into dentinal tubules by Nd:YAG irradiation and could not be removed by electric tooth brushing. [2] In the present study, Nd:YAG lasing alone (Group 2) could produce only partial occluding of dentinal tubules[Figure 5].

The first use of Nd:YAG laser for the treatment of dentine hypersensitivity was reported by Matsumoto et al. [12] The output power varied and ranged from 0.3 to 10 W, but 1 or 2 W output was the most common. Irradiation methods were dependent on the laser powers and varied. Treatment effectiveness ranged from 5.2% to 100%. According to Lan and Liu and Yonaga et al., the mechanism of Nd:YAG laser effects on dentine hypersensitivity is thought to be the laser-induced occlusion or narrowing of dentinal tubules as well as direct nerve analgesia. [19]

Matsumoto et al. proposed that in hypersensitive dentine, most dentinal tubules appear open when visualized by scanning electron microscopy. [12] There is a significantly high correlation between open dentinal tubule morphology and dentin hypersensitivity. Nd:YAG and CO 2 lasers effectively cause occlusion of dentinal tubules. Laser energy at 1064 nm is transmitted through dentin, producing thermally mediated effects on microcirculation, and pulpal analgesia via its nerve system. [12]

Various theories have been put forward as to how the laser produces its analgesic effect. It has been hypothesized that the laser energy interferes with the sodium pump mechanism, changes the cell membrane permeability, and/or temporarily alters the endings of the sensory axons. Irradiation by semiconductor laser has a suppressive effect by blocking the depolarization of very slowly conducting C-fiber afferents only, but it was reported that the blocking of not only C fibers, but also rapidly conducting Aβ-fibers is performed by Nd:YAG laser irradiation. [12] The sealing depth achieved by Nd:YAG laser irradiation at 30 mJ/pulse and 10 pps on dentinal tubules is usually measured to be less than 4 μm, but it is dependent on the irradiation parameters. [14]

From the statistical data obtained from this SEM study, there is a significant difference among the various groups compared. Occluding effect on dentinal tubules was maximum for Group 3 (CO 2 lasing + NaF) followed by Group 4 (Nd:YAG lasing + NaF), Group 5 (NaF alone), Group 1 (CO 2 lasing), and Group 2 (Nd:YAG lasing). These results suggest that the combination of CO 2 laser and fluoride varnish seems to show an impressive efficacy, when compared to either treatment alone, in treating dentin hypersensitivity with respect to the reduction in number/patency of dentinal tubules [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]. Recurrence of hypersensitivity varied with each laser and treatment protocol and depended on the irradiation methods and time after treatment. The recurrence rate of hypersensitivity after Nd:YAG laser treatment was measured up to 34.0%, and that of the CO 2 laser up to 50.0%. The mechanism of recurrence is unknown. [12] These require clarification to provide safer and effective treatment optimization. Once this knowledge is established, the potential for developing lasers for the treatment of hypersensitivity can be fully explored and realized.
Figure 1: SEM Picture of group 6 showing exposed dentinal tubule orifices (× 2500)

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Figure 2: SEM Picture of group 5 showing smooth surface and almost all of the dentinal tubule orifices were occluded (× 2500)

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Figure 3: SEM Pictures of group 4 showing combined occluding effect of fluoride varnish and Nd:YAG laser irradiation on human dentinal tubules (× 2500)

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Figure 4: SEM Pictures of group 3 showing combined occluding effect of fluoride varnish and CO2 laser irradiation on human dentinal tubules (× 2500)

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Figure 5: SEM Picture of group 2 showing partial occlusion of dentinal tubules (× 2500)

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Figure 6: SEM Picture of group 1 showing melting of dentin and narrowing of exposed dentinal orifices (× 2500)

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  Conclusion Top


SEM pictures revealed that application of Nd:YAG and CO 2 laser at energy output 2 W for 0.5-60 s and 0.5 W for 5 s, respectively, caused melting of dentin and closure of exposed dentinal tubules without dentin surface cracking. Fluoride varnish combined with CO 2 laser irradiation is a suitable tool for the treatment of dentin hypersensitivity.

Further research is therefore required to evaluate the efficacy of CO 2 laser with and without fluoride varnish in the treatment of dentin hypersensitivity in long-term, controlled, clinical trials where the subjective response of the patient may be objectively measured.

 
  References Top

1.Holland GR, Narhi MN, Addy M, Gangarosa L, Orchardson R. Guidelines for the design and conduct of clinical trials on dentine hypersensitivity. J Clin Periodontol 1997;24:808-13.  Back to cited text no. 1
[PUBMED]    
2.Lan WH, Liu HC, Lin CP. The combined occluding effect of sodium fluoride varnish and Nd:YAG laser irradiation on human dentinal tubules. J Endod 1999;25:424-6.  Back to cited text no. 2
[PUBMED]    
3.Stabholz A, Sahar-Helft S, Moshonov J. Lasers in endodontics. Dent Clin North Am 2004;48:809-32.  Back to cited text no. 3
[PUBMED]    
4.Rees JS. The prevalence of dentine hypersensitivity in general dental practice in the UK. J Clin Periodontol 2000;27:860-5.  Back to cited text no. 4
[PUBMED]    
5.Brannstrom M, Johnson G, Nordenvall KJ. Transmission and control of dentinal pain: Resin impregnation for the desensitization of dentin. J Am Dent Assoc 1979;99:612-8.  Back to cited text no. 5
    
6.Nordenvall KJ, Malmgren B, Brännström M. Desensitization of dentin by resin impregnation: A clinical and light-microscopic investigation. ASDC J Dent Child 1984;51:274-6.  Back to cited text no. 6
    
7.Javid B, Barkhordar RA, Bhinda SV. Cyanoacrylate-a new treatment for hypersensitive dentin and cementum. J Am Dent Assoc 1987;114:486-8.  Back to cited text no. 7
[PUBMED]    
8.Tavares M, DePaola PF, Soparkar P. Using a fluoride-releasing resin to reduce cervical sensitivity. J Am Dent Assoc 1994;125:1337-42.  Back to cited text no. 8
[PUBMED]    
9.Pashley DH, Leibach JG, Horner JA. The effects of burnishing NaF/kaolin/glycerin paste on dentin permeability. J Periodontol 1987;58:19-23.  Back to cited text no. 9
[PUBMED]    
10.Nagata T, Shinohara H, Nishikawa S. Clinical evaluation of a potassium nitrate dentifrice for the treatment of dentinal hypersensitivity. J Clin Periodontol 1994;21:217-21.  Back to cited text no. 10
    
11.Plagmann HC, König J, Bernimoulin JP, Rudhart AC, Deschner J. A clinical study comparing two high-fluoride dentifrices for the treatment of dentinal hypersensitivity. Quintessence Int 1997;28:403-8.  Back to cited text no. 11
    
12.Kimura Y, Wilder-Smith P, Yonaga K, Matsumoto K. Treatment of dentine hypersensitivity by lasers: A review. J Clin Periodontol 2000;27:715-21.  Back to cited text no. 12
[PUBMED]    
13.Raquel A, Batista E, Jacomino E, Pereira JC. Laser therapy for dentin hypersensitivity: A critical appraisal. Oral Laser Appl 2004;4:271-8.  Back to cited text no. 13
    
14.Liu HC, Lin CP, Lan WH. Sealing depth of Nd:YAG laser on human dentinal tubules. J Endod 1997;23:691-3.  Back to cited text no. 14
[PUBMED]    
15.Dilsiz A, Canakci V, Ozdemir A, Kaya Y. Clinical Evaluation of Nd:YAG and 685-nm Diode Laser Therapy for desensitization of teeth with gingival recession. Photomed Laser Surg 2009;27:843-8.  Back to cited text no. 15
[PUBMED]    
16.Christinna T, Gonçalves C, Ladalardo P. Laser therapy in the treatment of dentine hypersensitivity. Braz Dent J 2004;15:144-50.  Back to cited text no. 16
    
17.Kara C, Orbak R. Comparative evaluation of Nd:YAG laser and fluoride varnish for the treatment of dentinal hypersensitivity. J Endod 2009;35:971-4.  Back to cited text no. 17
[PUBMED]    
18.Zhang C, Matsumoto K, Kimura Y, Harashima T. Effects of CO 2 laser in treatment of cervical dentinal hypersensitivity. J Endod 1998;24:595-7.  Back to cited text no. 18
    
19.Israel M, Cobb CM, Rossmann JA, Spencer P. The effects of CO 2 , Nd:YAG and Er:YAG lasers with and without surface coolant on tooth root surfaces. An in vitro study. J Clin Periodontol 1997;24:595-602.  Back to cited text no. 19
[PUBMED]    
20.Porto IC, Andrade AK, Montes MA. Diagnosis and treatment of dentinal hypersensitivity. J Oral Sci 2009;51:323-32.  Back to cited text no. 20
[PUBMED]    
21.Orchardson R, Gillam DG. Managing dentin hypersensitivity. J Am Dent Assoc 2006;137:990-8.  Back to cited text no. 21
[PUBMED]    
22.Suge T, Kawasaki A, Ishikawa K, Matsuo T, Ebisu S. Ammonium hexafluoro-silicate elicits calcium phosphate precipitation and shows continuous dentin tubule occlusion. Dent Mater 2008;24:192-8.  Back to cited text no. 22
[PUBMED]    
23.Suge T, Kawasaki A, Ishikawa K, Matsuo T, Ebisu S. Effects of plaque control on the patency of dentinal tubules: An in vivo study in beagle dogs. J Periodontol 2006;77:454-9.  Back to cited text no. 23
[PUBMED]    
24.Moritz,Gutknecht N, Schoop U, Wernisch J, Lampert F, Sperr W. Effects of CO 2 laser irradiation on treatment of hypersensitive dental necks: Results of an in vitro Study. J Clin Laser Med Surg 1995;13:397-400.  Back to cited text no. 24
    
25.Moritz A, Gutknecht N, Schoop U, Goharkhay K, Ebrahim D, Wernisch J, et al. The advantage of CO 2 -treated dental necks, in comparison with a standard method: Results of an in vivo study. J Clin Laser Med Surg 1996;14:27-32.  Back to cited text no. 25
[PUBMED]    
26.Moritz A, Schoop U, Goharkhay K, Aoid M, Reichenbach P, Lothaller MA, et al. Long-term effects of CO2 laser irradiation on treatment of hypersensitive dental necks: Results of an in vivo study. J Clin Laser Med Surg 1998;16:211-5.  Back to cited text no. 26
[PUBMED]    
27.Pashley EL, Hower JA, Liu M, Pashley DH. Effect of CO 2 laser energy on dentin permeability. J Endod 1992;18:257-62.  Back to cited text no. 27
    


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