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Table of Contents
ORIGINAL ARTICLE
Year : 2013  |  Volume : 3  |  Issue : 2  |  Page : 86-90

Profilometric study to compare the effectiveness of various finishing and polishing techniques on different restorative glass ionomer cements


1 Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, Karnataka, India
2 Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Manipal, Karnataka, India
3 Department of Dental Materials, Manipal College of Dental Sciences, Manipal, Karnataka, India

Date of Web Publication11-Feb-2014

Correspondence Address:
Puttur Laxmish Mallya
Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2229-5194.126867

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   Abstract 

Objective: The aim of the present study was to evaluate the effect of various finishing and polishing techniques on the surface roughness of different types of glass ionomer (GI) restorative cements. Materials and Methods: Surface roughness of conventional, resin modified and nano-ionomer cements was evaluated after different polishing regimens. Totally 20 specimens of 12 mm thick and 10 mm diameter were prepared using Teflon mold. Prepared specimens were subjected to polishing (n = 5) by Sof-Lex discs, diamond finishing points and 30-fluted carbide burs. Control specimens did not receive any polishing treatment, but mylar trip was used as matrix. Average surface roughness (Ra) in micrometers was measured using Surtronic 3 + profilometer. Results were analyzed using Kruskal-Wallis and Mann-Whitney test. Results: Control specimens (mylar strip) showed least Ra values followed by Sof-Lex disc, carbide finishing burs and diamond finishing points with all types of glass ionomer cements used in the study. Among the GIs tested, Nano-ionomer showed least Ra followed by resin-modified GI and conventional GI. Conclusion: Mylar strip produced the smoothest surface on all the GIs tested. Nano-Ionomer showed the best polish ability with least Ra values.
Clinical Relevance to Interdisciplinary Dentistry

  • Glass ionomer cements (GIC) is one of the most commonly used direct restorative material used in non-stress bearing areas especially to restore cervical lesion at tooth gingival interface
  • Polished GIC surface reduces plaque accumulation and thus decreases the incidence of gingival inflammation and thereby prevents periodontal problems
  • Finishing and polishing of the GIC enhances the longevity and color stability of the restoration.

Keywords: Conventional glass ionomer, nano-ionomer, polishing, resin ionomer, surface roughness


How to cite this article:
Mallya PL, Acharya S, Ballal V, Ginjupalli K, Kundabala M, Thomas M. Profilometric study to compare the effectiveness of various finishing and polishing techniques on different restorative glass ionomer cements. J Interdiscip Dentistry 2013;3:86-90

How to cite this URL:
Mallya PL, Acharya S, Ballal V, Ginjupalli K, Kundabala M, Thomas M. Profilometric study to compare the effectiveness of various finishing and polishing techniques on different restorative glass ionomer cements. J Interdiscip Dentistry [serial online] 2013 [cited 2019 Aug 25];3:86-90. Available from: http://www.jidonline.com/text.asp?2013/3/2/86/126867


   Introduction Top


The surface roughness greatly influences the esthetics and longevity of the clinical restorations. A rough surface facilitates plaque accumulation, surface discoloration and gingival inflammation. It decreases the esthetic qualities of the restoration as the light reflection from the surface of the restoration decreases. A rough surface provides a suitable condition for the colonization of microbial agents, which could possibly lead to oral disease conditions. [1] More importantly, a smooth surface on the restoration decreases the surface area and surface energy of the material thereby decreasing the chances of accumulation of food debris on the surface. [2] Polishing of the surface generally removes the surface flaws and greatly improves the strength characteristics of the materials. Use of Mylar strip is the most common practice to attain a smooth surface on the direct esthetic restorative materials. [3] However, several systems such as abrasive impregnated discs, carbide burs and diamond points are often used clinically to produce a smooth surface on the restorative material. Ability of these systems in producing smooth surface finish on various esthetic restorative materials has been well documented. [2],[4],[5]

Since the introduction of glass ionomer cements (GIC) to the dental profession in early 1970s, they have become the material of choice for direct esthetic restoration of non-load bearing areas. [6] Research in improving the properties of this material produced metal modified and resin modified GIC. [6] Recently Ketac N 100, a paste/paste, resin-modified glass ionomer (GI) material based on the bonded nanofiller technology cement, has been introduced which contains bonded nanofillers and nanoclusters along with fluoroaluminosilicate glass to provide better esthetics. [7]

Several studies have reported the efficacy of various polishing techniques on the surface roughness of GIC. [8],[9] Polishing of GIC surface with diamond burs produced greater roughness compared to Sof-Lex or Mylar strip. [10] In another study, it was observed that all the polishing procedures on the surface of GIC resulted in rough surface compared with unpolished surface. [11] It was also observed that there is no significant difference in the surface roughness of GIC when polished in sequence using Mylar strip, diamond burs and carbide burs. [12]

Hence the purpose of the present study was to evaluate the surface roughness of three different types of GIC, which were polished using different polishing and finishing regimens.


   Materials and Methods Top


The materials tested in the present study were as follows; a high strength conventional GIC (Ketac Molar [3M ESPE, St. Paul, USA]), a light cured GIC (VitreBond [3M ESPE, St. Paul, USA]) and a nanofilled light cured GIC (Ketac N100 [3M ESPE, St. Paul, USA]). The finishing and polishing were performed with Sof-Lex Disks (3M ESPE, St. Paul, USA), diamond finishing points (Mani, Dia Burs, Japan), tungsten carbide finishing bur (SS White burs Inc., USA) and Mylar Strip (Samit Products, Delhi, India).

Preparation of test specimen

Different types of GIC were mixed according to the manufacturer's instructions and placed into disposable, cylindrical Teflon molds with a diameter of 10 mm and height of 2 mm and then sandwiched between Mylar strip covered glass slides on both sides of the mold. The resin-containing materials were light cured on both sides of the mold for 40 s using a light-emitting diode curing unit (Star light Pro, Mectron Medical Technology, Italy). Using the above procedure 20 specimens of each material were prepared then retrieved and stored at 37˚C and 100% relative humidity for 24 h.

Polishing regimen

Specimens of each material were randomly divided into four groups (n = 5). Group I served as control did not receive any polishing treatment except for the use of Mylar strip during preparation of the specimen, whereas Group II, III and IV were subjected to polishing using Sof-Lex discs, Fine Diamond finishing points and 30-Fluted Carbide finishing bur respectively. Polishing procedure was carried according to the manufacturer's instructions. During the polishing process, light pressure was applied in multiple directions to obtain a visually smooth surface on the specimen. Single investigator polished all the samples in order to control variability. Carbide and diamond finishing burs were used in sequence with a micro motor contra angled handpiece (NSK, Japan) with water spray. After the polishing, all the specimens were stored at 37˚C and 100% relative humidity till further study.

Evaluation of surface roughness

Surface roughness of the specimens was evaluated using Surtronic 3 + profilometer (Taylor Hobson limited, England) utilizing Talyprofile software. Results obtained in the study were statistically analyzed using Kruskal-Wallis and Mann-Whitney tests for comparison and the P < 0.01 was considered to be significant.


   Results Top


[Table 1] summarizes the average surface roughness values (Ra). Comparative surface roughness values of the different types of GIC with various polishing techniques are presented in [Figure 1]. From the results, it was observed that there is a significant difference in the surface roughness values of the different materials tested (P < 0.01) after polishing. Among the materials tested, Nano-ionomer showed the least surface roughness values compared with other types of GIC. A resin modified GIC, responded better to the polishing techniques with less roughness compared with conventional GIC (P < 0.01). Conventional GIC, showed the maximum Ra values indicating that the surface roughness is greater with these materials. This observation was consistent with all the polishing techniques employed in the present study. On comparison between the different polishing techniques, Mylar produced the smoothest surface on all types of GIC tested and it was statistically significant when compared with other polishing techniques (P < 0.01) employed. Use of diamond finishing points and carbide finishing bur produced significantly greater surface roughness on different types of GIC tested (P < 0.01). However, the types of GIC used in the present study did not exhibit greater differences in average surface roughness values when polished with Sof-Lex system (P > 0.01).
Figure 1: Surface roughness (Ra) of glass ionomer cements with different finishing and polishing techniques

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Table 1: Average surface roughness values of the materials tested


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   Discussion Top


GIC have a great demand in clinical dentistry due to their favorable properties such as biocompatibility with the pulpal tissues, chemical bonding to the tooth structure and similar coefficient of thermal expansion to that of tooth structure and fluoride release. However, lack of mechanical strength, moisture sensitivity during the initial stages of setting and poor wear resistance limits their use in load bearing areas. [13] Improvements have addressed the drawbacks of these materials by incorporating new technologies. Development of resin modified GIC is a significant advancement in the GI technology. Incorporation of resin component to the GIC not only addressed the moisture sensitivity but also improved the working characteristics of these materials. [14] Similarly, conventional GIC was reinforced with the addition of nanofillers and nanoclusters. In the present study Ketac N100 by 3M ESPE has been used and the manufacturer claims superior esthetic qualities because of the presence of smaller filler particle size. Further, this material also contains resin component in the composition which helps in improving the surface characteristics of the material. [7] A smooth polished surface has a favorable effect on the esthetic quality and longevity of a dental restoration, as well as on its biocompatibility with the oral tissues. Hence polish ability of a restorative material is an important quality for the longevity of the restoration.

Different methods used to assess the effectiveness of finishing and polishing instruments include: Visual evaluation (aided, with an optical microscope; unaided, with the naked eye) of the texture of polished surfaces; scanning electron microscopy for a detailed qualitative examination of surface topography and characteristics; profilometric analysis (contact or non-contact stylus tracing) and atomic force microscopy in order to measure quantitatively specific values of the surface roughness of a restorative material after finishing and polishing procedures. [13] In the current study, a contact profilometric analysis was used to determine the polish ability, as it is easy to operate, accurate and versatile.

The smoothest surfaces were produced using Mylar matrix strip on all GIC's tested in the current study. This was consistent with the results of the previous studies. [5],[10] In spite of careful placement of matrices and its contouring, excess material removal will be necessary clinically. Such a procedure generally requires smoothening without removing too much amount of the material from the restoration surface. However, such a procedure is bound to disrupt the smooth surface obtained with Mylar strip. [15] Several polishing systems and methods have been introduced to the dental applications to provide a smooth surface as possible on the restoration. [16]

The critical surface roughness (Ra) for bacterial adhesion is said to be 0.2 μm. Surface roughness higher than 0.2 μm has the potential to plaque accumulation and possibility of periodontal disease or recurrent caries. [17] Ability of polishing technique to produce a smooth surface not only depends on the polishing material used, but also on the material being polished. In the present study, the both nano-ionomers and resin modified GIC in the control group showed Ra less than the critical value of 0.2 μm. A logical approach to maintain the surface finish as obtained with a Mylar strip is with the use of pre-contoured transparent matrix system and removing the excess restorative material cautiously with a fine blade.

It is clear from the results obtained in the study, irrespective of the polishing, the conventional GIC showed higher average surface roughness values, whereas nano-ionomer showed the least surface roughness. High surface roughness on the conventional GIC can be attributed to the large glass particle size compared with nano-ionomers. Nano-ionomer is composed of two types of surface treated nanofillers (approximately 5-25 nanometers) and nanoclusters (approximately 1.0-1.6 microns). Apart from smaller particle size of fillers and glass particles in nano-ionomers, the presence of resin component facilitates the smoothest surface on these materials. The results of the present study are consistent with findings of the previous studies. [18],[19],[20] Previous studies have demonstrated that incorporation of nanofillers imparts wear resistance and polish ability to the materials. [21],[22]

It was also observed that the average surface roughness values of a resin modified GIC, was less compared with conventional GIC. Resin modified GIC has a similar composition as that of conventional GIC with the inclusion of resins like Hydroxylethyl methacrylate. These materials are photocurable and exhibit high fracture toughness, better surface finish and are less brittle when compared with conventional GIC. Again, presence of resin in the composition may help in removal of smaller chips from the surface of the material during polishing thereby producing a smooth surface.

Among the polishing materials used, diamond finishing points produced maximum rough surface compared to the other materials. Similar findings were observed in the previous studies. [23],[24],[25] Surface hardness of diamond point is very high compared to that of GIC thereby facilitating the removal of large amount of material rapidly from the cement surface leaving a rough surface texture. [23],[24],[25] Similar to the previous studies which showed that the use of aluminum discs produces a smoother surface on the GIC, the present study also demonstrated that the polishing of GIC with Sof-Lex which contains aluminum oxide provided a significantly smooth surface when compared to carbide burs and diamond finishing points. [19],[20] The planar motion of these instruments is said to contribute to the smoother surface. [26]


   Conclusions Top


Within the limitations of the present study, it can be concluded that:

  • The use of Mylar strip provides the best surface finish irrespective of the type of GIC
  • Among the types of GIC tested, Nano-ionomer attained smoothest surface when subjected to different polishing techniques used in the study
  • Among the polishing methods employed, Sof-Lex discs produced smooth surface on the GIC.


 
   References Top

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    Figures

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    Tables

  [Table 1]


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