|Year : 2017 | Volume
| Issue : 1 | Page : 75-82
Comparative evaluation of secondary caries formation around light-cured fluoride-releasing restorative materials
N Sathyajith Naik1, VV Subba Reddy2, ND Shashikiran3
1 Department of Pedodontics and Preventive Dentistry, Institute of Dental Sciences, Bareilly, Uttar Pradesh, India
2 Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere, Karnataka, India
3 Department of Pedodontics and Preventive Dentistry, School of Dental Sciences, Krishna Institute of Medical Sciences, Karad, Maharashtra, India
|Date of Web Publication||31-Jan-2017|
N Sathyajith Naik
Department of Pedodontics and Preventive Dentistry, Institute of Dental Sciences, Bareilly - 243 006, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: The aim of this study was to compare and evaluate secondary caries formation around light-cured fluoride-releasing restorative materials. Methodology: Standard Class V cavities were prepared on the buccal and lingual surfaces of forty extracted healthy premolars. The teeth were randomly divided into four groups of ten teeth each and labeled as Group I, II, III, and IV and restored with one of the following materials, namely, Fuji II LC (Group I), Vitremer (Group II), F-2000 (Group III), and Z-100 (Group IV; Control). The teeth were thermocycled and immersed in jars containing an acid gel for caries-like lesion formation. After 15 weeks, the samples were removed, washed, and sectioned buccolingually through the restoration. The sections were then grounded to a thickness of 80–100 µm. After imbibition in water, the sections were mounted on slides and lesions were examined, measured, and photographed with Leica DMRB Research Microscope. The observation recorded was subjected to (a) analysis of variance, (b) Studentized range test (Newman–Keuls), (c) Snedecor's F-test. Results: The depth of the outer lesion in teeth restored with Z-100 (Group IV; Control) was significantly higher than the teeth restored with F-2000 (Group III), Vitremer (Group II), and Fuji II LC (Group I) (P < 0.01). The depth of the outer lesion in teeth restored with F-2000 (Group III) was also significantly higher than the teeth restored with Vitremer (Group II) and Fuji II LC (Group I) (P < 0.01). However, there was no significant difference in depth of the outer lesions among the teeth restored with Vitremer (Group II) and Fuji II LC (Group I). No wall lesion (WL) was evident in teeth restored with Vitremer (Group II) and Fuji II LC (Group I). The WL length and body depth in teeth restored with Z-100 (Group IV; Control) were significantly higher than the teeth restored with F-2000 (Group III) (P < 0.01). Conclusion: It was concluded that Fuji II LC and Vitremer had a inhibitory effect on the development of WL and OL depth. Even though F- 2000 was not fully effective in preventing the development of WL, there was significant reduction in WL and depth when compared to Z-100.
Keywords: Artificial caries, fluoride-releasing restoratives, secondary caries, thermocycling
|How to cite this article:|
Naik N S, Subba Reddy V V, Shashikiran N D. Comparative evaluation of secondary caries formation around light-cured fluoride-releasing restorative materials. J Indian Soc Pedod Prev Dent 2017;35:75-82
|How to cite this URL:|
Naik N S, Subba Reddy V V, Shashikiran N D. Comparative evaluation of secondary caries formation around light-cured fluoride-releasing restorative materials. J Indian Soc Pedod Prev Dent [serial online] 2017 [cited 2017 Apr 26];35:75-82. Available from: http://www.jisppd.com/text.asp?2017/35/1/75/199235
| Introduction|| |
Amalgam has been the traditional material for filling cavities in posterior teeth for the last 150 years due to its effectiveness and cost. Resin composite has become an esthetic alternative to amalgam restoration. However, secondary caries formation around existing restoration represents the primary reason for replacement of amalgam and composite resin restorations. Lack of marginal integrity  and contraction of the restoration away from the cavity walls to form a micro-gap followed by leakage are considered to be the important factors leading to the eventual development of “secondary caries” at the restoration/tissue interface.
The ability of a restorative material to resist a secondary caries attack and microleakage at its margins will largely determine whether a restoration will succeed or fail. Development of an ideal restorative material, which provides a permanent seal with tooth structure, has been thwarted by complicating factors present in the oral environment, i.e., changes in intraoral temperature (thermal expansion), solubility of the certain restorative material in saliva, and changes in pH. Consequently, increased emphasis has been placed on the development of a restorative material with anticariogenic properties.
Glass-ionomer cement has replaced silicate cement, and clinical experience indicated that fluoride release from glass ionomer provides a reduction on secondary caries. Conventional glass-ionomer materials have shown to inhibit secondary caries formation on the tooth surface and along the tooth/restorative interface. However, the conventional glass-ionomer cement suffers from certain disadvantages. These disadvantages are short working time, long setting time, and susceptibility to early moisture contamination, desiccation after setting and brittleness.
In recent years, to overcome these disadvantages, hybrid glass-ionomer materials have been introduced that combine resin composite and glass ionomer cement technologies. The ability of these new materials to impart resistance to the development of secondary caries, however, is unproven and would be dependent on the physiochemical properties of the materials itself, enabling sufficient fluoride release in its resin-based formulations and on its ability to seal the tooth/restoration interface.
Since, there is a paucity of information available on the use of newer light-cured fluoride-releasing restorative materials with improved properties, especially in relation to the prevention of secondary caries around such materials; this in vitro study was designed to compare and evaluate secondary caries formation around the following light-cured fluoride-releasing restorative materials, namely,
- Fuji II LC
- F-2000 Compomer
- Z-100 Composite (Control).
| Methodology|| |
Selection and distribution of samples
Forty healthy premolars extracted due to orthodontic reasons were collected, cleaned of debris and tissue tags, and stored in 10% formalin solution until were used further. The samples were divided into four groups, comprising ten teeth each and labeled as Group I, II, III, and IV and kept in separate containers.
- Group I: Restored with Fuji II LC
- Group II: Restored with Vitremer
- Group III: Restored with F-2000 Compomer
- Group IV: Restored with Z-100 Composite (Control).
Preparation of samples
For each tooth, two standardized Class V cavity were prepared, one each in buccal and lingual surface measuring 3.0 mm mesiodistally, 1.5 mm occluso-gingivally, and 1.5 mm in depth. The cavity was prepared using No. 557 straight fissure diamond bur mounted in a high-speed handpiece with bur being oriented at right angle to the tooth surface to produce a cavosurface angle close to 90°. The prepared cavity was rinsed with distilled water and dried with compressed air. The samples in each group were restored with the respective materials assigned to the group as mentioned above. The procedure was carried out as per the manufacturer's instructions.
Group I: Restored with Fuji II LC
After conditioning the tooth surface for 10 s, the cavity was rinsed with water and air-dried. Powder and liquid mixture was placed in the cavity and light cured for 40 s. The overfilled material was reduced to the correct contour.
Group II: Restored with Vitremer
The primer was applied to the prepared cavity for 30 s and air-dried and light cured for 20 s. Powder and liquid mixture was placed in the cavity and light cured for 40 s. The overfilled material was reduced to correct contour. The gloss was applied, and light cured for 20 s.
Group III: Restored with F-2000 Compomer
F-2000 Compomer primer/adhesive was applied to the prepared cavity. After 30 s, it was gently air-dried for 5–10 s and light cured for 10 s. The material was then carried to the prepared cavity using a plastic filling instrument and light cured for 40 s. The overfilled material was reduced to correct contour.
Group IV: Restored with Z-100 composite
The prepared cavity was etched using Scotchbond Etchant for 15 s, then rinsed and dried. Then, the adhesive was applied and light cured for 10 s. The materials were carried to the prepared cavity using a plastic filling instrument and light cured for 40 s. The overfilled material was reduced to correct contour.
The samples were then subjected to thermocycling for 800 cycles between 5°C and 55°C with a dwell time of 30 s. Subsequently, the samples were coated with an acid-resistant varnish except 1 mm around the cavosurface margin. The teeth were then immersed in jars containing an acid gel for caries-like lesion formation for 15 weeks. The gel consisted of 10% methylcellulose and 0.1M lactic acid, with pH adjusted to 4.5 using potassium hydroxide. After 15 weeks, the samples were removed, rinsed thoroughly with water, and sectioned buccolingually through the restoration using a diamond sectioning saw. The sections were then ground to a thickness of approximately 80–100 µm. After 24 h of imbibition in water, the sections were mounted on slides, and the lesions were examined, measured, and photographed with Leica DMRB Research Microscope.
The lesions formed consists of two parts, outer surface lesion (OL) and cavity WL. Measurements of both buccal and lingual lesions were made using a calibrated eyepiece reticule.
The measurement includes:
- The body depth of the outer lesion (OL) was measured as the largest distance between the enamel surface and the inner border of the lesion
- The body depth of the wall lesion (WL) was measured as the largest distance between the restoration and the inner border of the lesion
- The WL length was measured from the enamel surface to the innermost extended portion of the WL toward the axial wall of the cavity.
All relative measurements from both buccal and lingual lesions were averaged, and the data from each group were recorded and subjected to the standard statistical analysis, namely:
- Analysis of variance
- Studentized range test (Newman–Keuls)
- Snedecor's F-test.
| Results|| |
[Table 1] shows the observations of the outer lesions depth, WL length, and WL body depth.
|Table 1: Measurement in μm of the lesion developed in relation to restorative materials|
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Outer lesion depth
It was observed that the outer lesion depth for Group I ranged from 115.50 to 225.75 µm with a mean of 161.7 ± 38.20 µm, Group II ranged from 78.75 to 162.75 µm with a mean of 121.30 ± 28.60 µm, Group III ranged from 157.50 to 325.50 µm with a mean of 231.80 ± 58.60 µm, and Group IV ranged from 294.00 to 425.25 µm with a mean of 364.7 ± 44.4 µm [Table 2] and [Figure 1], [Figure 2], [Figure 3], [Figure 4]. The depth of the lesion in teeth restored with Z-100 (Group IV) was significantly higher than the teeth restored with F-2000 (Group III), Vitremer (Group II), and Fuji II LC (Group I) (P < 0.01). However, there was no significant difference in the depth of lesion among the teeth restored with Vitremer (Group II) and Fuji II LC (Group I).
|Table 2: Mean (±sd) in μm of the outer lesions developed in relation to the restorative materials|
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|Figure 1: View of the section showing a typical caries-like lesion formed around a light-cured glass-ionomer (Fuji II LC) restoration that has been lost from cavity preparation during sectioning. An outer surface lesion present but no cavity wall lesion exists|
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|Figure 2: View of the section showing a typical caries-like lesion formed around a light-cured glass-ionomer (Vitremer) restoration that has been lost from the cavity preparation during sectioning. An outer surface lesion present but no cavity wall lesion exists|
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|Figure 3: View of the section showing a typical caries-like lesion formed around compomer (F-2000) restoration that has been lost from the cavity preparation during sectioning. It consists of an outer surface lesion and cavity wall lesion|
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|Figure 4: View of the section showing a typical caries-like lesion formed around composite resin (Z-100) restoration that has been lost from the cavity preparation during sectioning. It consists of an outer lesion (OL) and cavity wall lesion (WL)|
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Wall lesion (wall lesion length and wall lesion body depth)
Regarding the WL, no microscopic evidence of demineralization was found along cavity wall adjacent to Vitremer (Group II) and Fuji II LC (Group I) restorations. On the other hand, WL was found in teeth restored with F-2000 (GROUP III) and Z-100 (Group IV). It was observed that the WL length for Group III ranged from 220.50 to 384.50 µm with a mean of 300.70 ± 51.80 µm [Table 3] and the WL body depth ranged from 10.50 to 47.25 µm with a mean of 26.80 ± 12.00 µm [Table 4].
|Table 3: Mean (± sd) in μm of the wall lesion length developed in relation to the restorative materials|
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|Table 4: Mean (± sd) in microns of the wall lesion body depth developed in relation to the restorative materials|
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The WL length for Group IV ranged from 314.50 to 556.50 µm with a mean of 471.60 ± 84.30 µm [Table 3] and the WLs body depth for Group IV ranged from 52.50 to 136.50 µm with a mean of 85.00 ± 27.80 µm [Table 4].
The WL length and body depth in teeth restored with Z-100 were significantly higher than in the teeth restored with F-2000 (P < 0.01) [Figure 5].
|Figure 5: Schematic representation of various parts of caries like lesions formed around a restoration. The carious lesion consists of a primary surface lesion (OL) and a secondary cavity wall lesion(WL). The measurements made on each lesion are: (1) The body of depth of the outer surface lesion is measured as the largest distance between the enamel surface and the inner border of the lesion; (2) the body depth of the WL is measured as the largest distance between the restoration and the inner border of the lesion; (3) the WL length is measured from the enamel surface to the innermost extended portion of the WL toward the axial wall of the cavity|
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| Discussion|| |
Clinical evaluation of the caries preventing capability of all the new material being produced would be both an expensive and lengthy process. Yet, there is a need to determine the relative efficacies of different materials so that clinicians can make rational decisions on what material to use. Keeping this in mind, the present in vitro study was carried out.
The development of secondary caries around any restorative material is determined by the physiochemical properties of the materials, namely, shrinkage, plasticity, corrosion, solubility, fluoride content and permeability, and its clinical performance, i.e., cavity sealing ability influenced by the adhesion of the materials to tooth substance, microleakage, and cavity preparation. If microleakage of bacteria, fluids, and acidic products takes place along the enamel-restoration interface, secondary caries is likely to develop.
It has been proved that secondary caries formation occurs mainly at the cervical margins of the tooth than when compared with occlusal margins. Hence, in the present study, Class V cavity was prepared on a buccal and lingual aspect of a cervical portion of the crown.
The purpose of thermocycling was to stimulate thermal conditions existing in the oral cavity. If the coefficient of thermal expansion of a restorative material differs significantly from that of the tooth structure, the dimensions of the space around the filling material will change as the tooth is subjected to temperature variations. It will be realistic clinically if the thermocycling regime includes short dwell time and several hundred cycles as done in this study.
The histopathology of the naturally occurring and artificially created lesions associated with secondary caries has been described., The lesion consists of two parts – an outer OL showing the features of primary attack on the enamel surface and the cavity WL formed as a consequence of microleakage of acidic products and hydrogen ions from the dental plaque or acidified gel along the enamel-restoration interface [Figure 1].
Two basic methods exist, i.e., chemical system , and bacterial system,, for an artificial cariogenic challenge to tooth structure. The artificial gel technique is a valuable tool to create artificial caries that appears indistinguishable from the natural lesion when examined by polarized light and microradiography. This technique has the advantage of eliminating the external variables (substrate and microflora) associated with the formation of natural caries. It is efficient in creating a carious lesion within a relatively short period, and the viscosity of the gel simulates a layer of plaque. In the artificial caries system, the surface enamel is subjected to a constant attack of hydrogen ions (i.e., the dissolution of mineral is rate controlled) while the gel acts as a diffusion barrier for dissolved mineral.
Various chemical systems used for the formation of the artificial caries-like lesion are acidified gelatin gel, hydroxyethyl cellulose solution, methane hydroxydiphosphonate, acetic acid-sodium acetate buffer, diphosphate solution, carboxymethyl cellulose gel, and methylcellulose gel. In this study, acidified methyl cellulose gel technique was used because it is efficient in creating a caries-like lesion at rates comparable to those occurring in vivo and utilizes a gel medium with organic and inorganic elements that act as a substitute for the plaque occurring in vivo as observed by Kotsanos et al.
Various authors , have suggested that the thickness of 80–100 µ is most ideal for observations under polarized light microscope. Hence, in this study, histological analysis was done by sectioning the tooth structure to approximately 80–100 µ thickness.
Various media used for imbibition studies are water, quinoline, xylene, benzyl alcohol, methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-heptanol, air, and Thoulet's solution. In this study, water was used as an imbibing medium, because when the samples are imbibed in water (RI - 1.33), the body of the lesion is identified in the subsurface region as an area of observed positive birefringence, and superficial to this, a negative birefringence surface zone is observed. The amount of positive birefringence produced depends on the relative volume of space present in the tissue and on the difference between the refractive indices of the enamel and the medium occupying the space within the enamel. As the difference between these refractive indices increases, the amount of birefringence also increases.
In the present study, on comparative evaluation, it was revealed that Fuji II LC and Vitremer had an inhibitory effect on the development of the experimental WL and decrease in the depth of the outer lesion. Similar observation was reported by Tam et al.
Even though F-2000 was not fully effective in preventing the development of experimental WL, there was a significant reduction in the WL length and body depth and outer lesion depth when compared with Z-100 (Control).
The inhibiting effect on the development of experimental WL and deceased outer lesion in the teeth restored with Fuji II LC and Vitremer and decreased depth of experimental WL and outer lesion in the teeth restored with F-2000 observed in this study may be due to fluoride released from the material, fluoride uptake by the enamel/dentin, and/or less marginal leakage around the filling.
Bynum and Donly  have proved that light-cured glass-ionomer materials provide a significant protection against caries-like attack at restorative interface. Cao et al., Retief et al., and Yey et al. have proven that the apparent caries resistant of enamel and dentin that forms the cavity walls adjacent to the materials is because of the availability of fluoride, released from the light-cure glass ionomer and compomer.In vitro studies have shown that fluoride release from fluoride-containing restorative materials effectively protected the tooth tissues from demineralization in the region near to restorative materials.,, This ability depends on the amount of fluoride ions released from the material , Mitra  have shown that the fluoride uptake from fluoride-containing materials by enamel/dentin is to a depth of 100 µm, and Robert, Erickson, and Glasspoole  have shown that light-cure glass ionomer had better marginal quality than the resin system.
Short- and long-time fluoride release from the restorative material are related to their matrices, setting reaction, and fluoride content. The release of fluoride from restorative materials occurs by three distinct mechanisms, namely, surface dissolution, diffusion through microchannels, and pores and bulk diffusion. This released fluoride is readily taken up by the cavosurface tooth structure as well as the enamel and root surfaces adjacent to the restoration. Retief et al. have shown that fluoride released from the glass ionomer is not lost over time, but become incorporated into the mineral component of enamel, perhaps as fluoridated hydroxyapatite. It is well known that caries initiation and progression decrease significantly when fluoride is incorporated into the enamel, dentin, and cementum. In addition, fluoride released from glass ionomer restorations may alter the metabolic activity of plaque formed at the margins of the restoration, thereby altering the plaque in the immediate vicinity of the restoration.
The decreased inhibitory effect of F-2000 on the development of the experimental WL s and the outer lesion when compared with Fuji II LC and Vitremer observed in this study may be because F-2000 is more of a composite and less of glass ionomer and have high thermal expansion and decreased fluoride release. In addition, F-2000 is cured by light initiation polymerization whereas Fuji II LC and Vitremer are cured by light initiation polymerization, acid-base reaction, and chemical cure.
It was also observed that there was increased WL and outer lesion depth in teeth restored with Z-100. A similar finding was observed by Flaiz and Hicks. The increase in the WL and the outer lesion depth in teeth restored with Z-100 might be because of the absence of fluoride and increased gap around the restoration. Torstenson and Brannstron, Tjan et al. have shown that in vitro, the initial gap around composite restoration vary between 10 and 30 µm.
The ability of the newer fluoride-releasing light-cure restorative materials to resist caries-like attack at the enamel-restorative interface would appear to be of greater importance in the prevention of secondary caries. In the present study, Fuji II LC and Vitremer provided complete protection against secondary lesion formation in cavity wall enamel, and the extent of outer lesion was also reduced significantly. Even through F-2000 was effective in reducing the WL and outer lesion when compared to Z-100, it was not fully effective in the prevention of experimental lesion such as Fuji II LC and Vitremer.
The chief advantages of resin-modified glass-ionomer cement (Vitremer and Fuji II LC) and polyacid-modified composite resin (F-2000) used in the study are good working time with a degree of command over set and resistant to secondary caries attack. However, in clinical use, the oral environmental has an entirely different effect on the fluoride release, uptake, and resistance to the development of secondary caries. It must be stressed that it is too early to make a final judgment of these interesting materials. At present, the laboratory and clinical information on their performance is limited and yet to be completely developed.
This encouraging in vitro data suggest the need for a well-controlled clinical trial to evaluate the further clinical effectiveness of these restorative materials. The verdict of the cumulative clinical experience must be awaited.
| Conclusions|| |
The following conclusions were drawn from this study:
- Secondary caries (WL and body depth) initiation and progression are totally prevented when Fuji II LC and Vitremer were used
- Secondary caries (WL and body depth) initiation and progression can be reduced significantly (P < 0.01) when F-2000 was used
- Primary caries (outer lesion) initiation and progression can be reduced significantly (P < 0.01) when Fuji II LC, Vitremer, and F-2000 were used when compared to Z-100 (Control)
- No statistical significance was observed between Fuji II LC and Vitremer in preventing secondary caries (WL and body depth) and primary caries (outer lesion) initiation and progression, even though Vitremer was more effective than Fuji II LC
- Statistical significance (P < 0.01) was observed when Fuji II LC and Vitremer were used in preventing primary caries (outer lesion) initiation and progression when compared with F-2000
- The ranked efficacy of the restorative materials examined in the study is Vitremer >Fuji II LC > F-2000 > Z-100.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4]