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Table of Contents   
ORIGINAL ARTICLE  
Year : 2015  |  Volume : 18  |  Issue : 6  |  Page : 427-430
Enamel surface changes caused by hydrogen sulfide


1 Department of Endodontology, Tsurumi University School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-8501, Japan
2 Department of Operative Dentistry, Tsurumi University School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-8501, Japan
3 Department of Oral Anatomy, Tsurumi University School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-8501, Japan

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Date of Submission01-Jul-2015
Date of Decision02-Sep-2015
Date of Acceptance08-Oct-2015
Date of Web Publication2-Nov-2015
 

   Abstract 

Background: Volatile sulfur compounds (VSCs) produced inside the mouth are a well-known cause of halitosis. Recent studies have suggested that VSCs modify the pathology of periodontitis by encouraging the migration of bacterial toxins associated with increased permeability of gingival epithelia, and enhancing the production of matrix metalloproteinases in gingival connective tissue. Nonetheless, the effects on the enamel of direct exposure to VSCs within the oral cavity remain unclear.
In the present study, we observed the effects of VSCs in the form of hydrogen sulfide (H 2 S) on enamel surfaces and determined their effects on restorations.
Materials and Methods: Extracted human tooth and bovine tooth samples were divided into the H 2 S experimental side and the control side. We observed the effects of H 2 S on enamel surfaces using electron microscopy and conducted a shear test.
Results: We found that exposure to H 2 S obscured the enamel surface's crystal structure. The surface also exhibited coarseness and reticular changes. Shear testing did not reveal any differences in bond strength.
Conclusions: Our findings suggested that H 2 S occurring inside the mouth causes changes to the crystal structure of the enamel surface that can lead to tooth wear, but that it does not diminish the effects of dental bonding in adhesive restorations.

Keywords: Hydrogen sulfide; tooth enamel; tooth wear; volatile sulfur compounds

How to cite this article:
Yamaguchi T, Hanabusa M, Hosoya N, Chiba T, Yoshida T, Morito A. Enamel surface changes caused by hydrogen sulfide. J Conserv Dent 2015;18:427-30

How to cite this URL:
Yamaguchi T, Hanabusa M, Hosoya N, Chiba T, Yoshida T, Morito A. Enamel surface changes caused by hydrogen sulfide. J Conserv Dent [serial online] 2015 [cited 2023 Feb 1];18:427-30. Available from: https://www.jcd.org.in/text.asp?2015/18/6/427/168794

   Introduction Top


Hydrogen sulfide (H 2 S), methyl mercaptan (CH 3 SH), and dimethyl sulfide are volatile sulfur compounds (VSCs) known to cause halitosis. [1],[2] In mouth, VSCs are produced by the metabolism of bacteria in the tongue coating and bacteria associated with periodontitis. [3] Various foods, particularly, vegetables, contain large amounts of sulfates that are converted into VSCs after cooking or biological modification. [4] Trace amounts of H 2 S in vivo reportedly modify anti-inflammation, radical scavengers, signal transduction, proteins, ion channel regulation, and transition metal complexes, and are essential in maintaining homeostasis. [4] Approximately, 90% of VSCs produced in the mouth consist of H 2 S and CH 3 SH [1],[5] and, in addition to halitosis, can cause discoloration of crown restorations, prostheses, and dentures. [6] They can also increase the epithelial permeability and bacterial toxins in the soft gingival tissue, [7],[8] enhance the production of collagenase and prostaglandin, [9] and induce apoptosis in gingival connective tissue, [4],[10] and are involved in the pathological modification and progression of periodontitis. [4] Hard tissue in the form of enamel functions inside the mouth in an exposed state, and thus is affected by direct exposure to VSCs. This in turn triggers the deterioration and loss of dentin, which is believed to be involved in the onset and modification of tooth wear. However, the role of VSCs in enamel changes and tooth wear remains unclear due to a lack of published literature. When tooth wear causes wedge-shaped defects and removal of crown restorations, the dentist may choose to perform a restorative procedure using adhesive composite resins. However, the enamel surface where the crown will be attached is exposed and therefore vulnerable to the effects of VSCs, which may affect how well the composite resin bonds to the enamel.

We investigated whether VSCs in the oral cavity in the form of H 2 S are involved in tooth wear by observing its effect on enamel using an electron microscope (transmission electron microscope [TEM] and scanning electron microscopy [SEM]). We also conducted a shear test to determine whether the effect of H 2 S on the enamel surface translated to an effect on the adhesive properties of composite resin restorations.


   Materials and Methods Top


Changes in enamel crystals

Extracted human teeth were sectioned at the cervical portion, and the crown portion was sealed with wax before coating half of these sections with nail polish. Samples were then prepared from these sections using the uncoated portion as the experimental side and the coated portion as the control side. Next, a saturated H 2 S solution was prepared by bubbling H 2 S in 50 ml physiological saline for 30 min. Samples were immersed in saturated H 2 S solution in a sealed container, which was placed in an incubator for 14 days at 37°C before observation under a TEM.

Effect on enamel surfaces

The H 2 S source was prepared by dissolving 50 g sodium hydrosulfide hydrate (Sigma-Aldrich, St. Louis, MO, USA) in distilled pure water (Invitrogen Corporation, Carlsbad, CA, USA) up to a volume of 100 ml. The H 2 S gas released from the aqueous solution of sodium hydrosulfide inside the sealed container was collected and dissolved in distilled water for the application to tooth samples.

Extracted tooth samples were divided into the experimental side and the control side. Experimental side samples were placed in individual  Petri dish More Detailses with the aqueous solution of sodium hydrosulfide from inside the sealed container, and the control side samples were placed in individual Petri dishes with sterilized distilled water. The aqueous solution of saturated hydrosulfide was replaced, and distilled water was added every 2 days, and samples were stored in a sealed container for 1 week. Enamel surfaces were then observed by SEM.

Effects on enamel in dental bonding

Twenty bovine tooth root samples were sectioned, the pulp was removed, and the cervical portion was sealed with glass ionomer cement. Teeth were then placed in a mold and embedded in self-curing resin before exposing the enamel using #100 waterproof sandpaper and polishing from the cervical side to the crown side using #600 waterproof sandpaper. These teeth were used as samples.

Teeth were then divided evenly into 10 H 2 S experimental group samples and 10 control samples. Experimental group samples were immersed in distilled water and placed in individual Petri dishes with an aqueous solution of sodium hydrosulfide from inside the sealed container, and the control group samples were immersed in distilled water and placed in individual Petri dishes with sterilized distilled water. The aqueous solution of saturated hydrosulfide was replaced, and distilled water was added every 2 days, and samples were stored for 1 week. After 1 week, the polished surface of the tooth samples was treated with self-etching bonding system (CLEARFIL SE BOND, Kuraray Noritake Dental, Tokyo, Japan), packed with resin composite (Clearfil AP-X A3, Kuraray Noritake Dental), and immersed in water for 24 h before undergoing a shear test with a cross-head speed of 1.0 mm/min (Model 444, Instron, Darmstadt, Germany).


   Results Top


TEM observation revealed distinctly hexagonal pillar-shaped hydroxyapatite crystals on the control side, but the crystals on the experimental H 2 S side were reduced in size, and their structure was not be clearly defined [Figure 1]. SEM observation at low magnification indicated the greater surface coarseness on the H 2 S side than on the control side. Observation of the control side at high magnification revealed concavo-convex patterns believed to be the ends of small enamel pillars. On the H 2 S side, however, the surface structure had collapsed, and the reticular pattern had changed [Figure 2]. Bond strength between enamel and composite resin bonding applied with a self-etching system was 14.4 ± 5.3 MPa in the experimental group samples (n = 10) and 13.1 ± 5.2 MPa in the H 2 S side samples (n = 10), but t-test did not reveal any significant differences [Table 1].
Figure 1: (a) Control side transmission electron microscope, (b) Experimental side transmission electron microscope, distinct hexagonal crystal structure can be seen on the control side (a), but crystals are diminished and crystal structure cannot be clearly seen on the experimental side (b)


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Figure 2: (a and b) Control side scanning electron microscopy;© and (d) Experimental side scanning electron microscopy on control side, the surface is generally consistent (a) and recesses believed to be the ends of small enamel pillars (b) can be seen. On experimental side, the surface appears coarse (c) and exhibits reticular changes (d)


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Table 1: Mean values of bond strength of enamel to composite resin in H 2 S and control groups


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   Discussion Top


H 2 S occurs in trace amounts in living organisms and is believed to be involved in gene expression via intracellular signal transduction and enzyme activation to maintain homeostasis. [4] However, H 2 S occurring inside the mouth [1],[5],[11] can cause localized halitosis, [11],[12] periodontal tissue disorders, [4] and discoloration and corrosion of metal restorations. [6]

In the present study, we placed tooth samples exposed to H 2 S in distilled water and observed its effect on enamel surfaces using TEM and SEM. At least 96% of mature enamel consists of inorganic components. The major component is hydroxyapatite crystals with a hexagonal pillar configuration having a width of 40-50 nm, thickness of 25-60 nm, and height of 120-160 nm. [4],[13] In our study, the tooth samples exposed to H 2 S had a smaller, obscured crystal configuration when compared with control samples. The findings also showed what appeared to be disintegration of the reticular structure on the surface of the H 2 S samples. In other words, the sustained action of H 2 S on the enamel surface had caused the hydroxyapatite crystals to decay, triggering a reduction and loss of crystal structure, which in turn led to the progressive breakdown of dentin on the crown surface, ultimately resulting in deterioration of the enamel's physical properties and loss of dentin. Tooth surface loss that cannot be attributed to tooth decay is known as tooth wear, which is a multifactorial disease that includes attrition due to occlusal contact; wear caused by nonocclusal mechanical contact, acid-induced tooth decay, and abfraction. Our study findings of H 2 S-induced decay of enamel surfaces suggest that H 2 S occurring inside the mouth is a cause of dentin surface loss.

In clinical dentistry, one treatment for tooth wear is restoration with adhesive composite resin. Our findings revealed changes to the crystal morphology and surface structure of the enamel to which these restorations are applied. Although we initially suspected that these changes would affect the adhesive restoration, the results did not reveal any differences between the H 2 S-exposed samples and control samples in terms of the bond strength between the enamel and composite resin applied using a self-etching system. We attributed this finding to the effect of etching using a self-etching primer, whereby enamel exposed to H 2 S dissolved to reveal new enamel.


   Conclusion Top


Although our findings suggest that H 2 S can cause tooth wear by triggering changes to enamel's surface structure and crystal morphology, dental bonding by decalcification using a self-etching system does not impact the bond strength of enamel and composite resin when applying an adhesive restoration to enamel that has been affected by H 2 S.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

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2.
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Tocmo R, Liang D, Lin Y, Huang D. Chemical and biochemical mechanisms underlying the cardioprotective roles of dietary organopolysulfides. Front Nutr 2015;2:1.  Back to cited text no. 3
    
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Yaegaki K, Sanada K. Volatile sulfur compounds in mouth air from clinically healthy subjects and patients with periodontal disease. J Periodontal Res 1992;27 (4 Pt 1):233-8.  Back to cited text no. 4
    
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Fujii K. Inhibitory effects of volatile sulfur compound adsorbents on the discoloration of gold-silver-palladium alloy. Jpn J Conserv Dent 2014;57:229-38.  Back to cited text no. 5
    
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Rizzo AA. Histologic and immunologic evaluation of antigen penetration into oral tissues after topical application. J Periodontol 1970;41:210-3.  Back to cited text no. 6
    
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Ng W, Tonzetich J. Effect of hydrogen sulfide and methyl mercaptan on the permeability of oral mucosa. J Dent Res 1984;63:994-7.  Back to cited text no. 7
    
8.
Ratkay LG, Waterfield JD, Tonzetich J. Stimulation of enzyme and cytokine production by methyl mercaptan in human gingival fibroblast and monocyte cell cultures. Arch Oral Biol 1995;40:337-44.  Back to cited text no. 8
    
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Yaegaki K, Qian W, Murata T, Imai T, Sato T, Tanaka T, et al. Oral malodorous compound causes apoptosis and genomic DNA damage in human gingival fibroblasts. J Periodontal Res 2008;43:391-9.  Back to cited text no. 9
    
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Calenic B, Yaegaki K, Murata T, Imai T, Aoyama I, Sato T, Ii H. Oral malodorous compound triggers mitochondrial-dependent apoptosis and causes genomic DNA damage in human gingival epithelial cells. J Periodontal Res 2010;45:31-7.  Back to cited text no. 10
    
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Oho T, Yoshida Y, Shimazaki Y, Yamashita Y, Koga T. Characteristics of patients complaining of halitosis and the usefulness of gas chromatography for diagnosing halitosis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;91:531-4.  Back to cited text no. 11
    
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L.M. Silverstone, J.S. Wefel. The effect of remineralization on artificial caries-like lesions and their crystal content. J Crystal Growth 1981;53:148-59.  Back to cited text no. 12
    
13.
Miake Y, Saeki Y, Takahashi M, Yanagisawa T. Remineralization effects of xylitol on demineralized enamel. J Electron Microsc (Tokyo) 2003;52:471-6.  Back to cited text no. 13
    

Top
Correspondence Address:
Prof. Noriyasu Hosoya
Department of Endodontology, Tsurumi University School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-8501
Japan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-0707.168794

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