10.59987/ads/2013.3-4.250-258
Background. Even today, use of Glass Ionomer Cements (GIC) as restorative material is indicated for uncooperative patients.
Aim. The study aimed at estimating the surface roughness of different GICs using or not their proprietary surface coatings and at observing the interfaces between cement and coating through SEM.
Materials and methods. Forty specimens have been obtained and divided into 4 groups: Fuji IX (IX), Fuji IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finishing Gloss (VFG). Samples were obtained using silicone moulds to simulate class I restorations. All specimens were processed for profilometric evaluation. The statistical differences of surface roughness between groups were assessed using One-Way Analysis of Variance (One-Way ANOVA) (p&lt;0.05). The Two-Way Analysis of Variance (Two-Way ANOVA) was used to evaluate the influence of two factors: restoration material and presence of coating. Coated restoration specimens (IXC and VFG) were sectioned perpendicular to the restoration surface and processed for SEM evaluation.
Results. No statistical differences in roughness could be noticed between groups or factors. Following microscopic observation, interfaces between restoration material and coating were better for group IXC than for group VFG.
Conclusions. When specimens are obtained simulating normal clinical procedures, the presence of surface protection does not significantly improve the surface roughness of GICs.
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Annali di stomatologia
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Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment
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Original Article
2022-08-16
2022-08-16
2013-12-01
2023-12-04
250-258
Ann Stomatol (Roma)
A. Polimeni
2013
10.59987/ads/2013.3-4.250-258
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Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment
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                                                                                                                     Original article



                   Surface roughness of glass ionomer cements
                   indicated for uncooperative patients according
                   to surface protection treatment




                                                                                                                                        li
                                                                                  na
                   Edoardo Pacifici, PhD1                                    VFG) were sectioned perpendicular to the restora-
                   Maurizio Bossù, DDS, PhD1                                 tion surface and processed for SEM evaluation.




                                                                                io
                   Agostino Giovannetti, DDS, PhD2                           Results. No statistical differences in roughness
                   Giuseppe La Torre, MD3                                    could be noticed between groups or factors. Fol-
                   Fabrizio Guerra, MD, DDS4                                 lowing microscopic observation, interfaces be-
                   Antonella Polimeni, MD, DDS1                              tween restoration material and coating were better




                                                                             az
                                                                             for group IXC than for group VFG.
                                                                             Conclusions. When specimens are obtained simu-
                   1 Department of Oral and Maxillo-facial Sciences, Pedi-   lating normal clinical procedures, the presence of
                     atric Dentistry Unit, “Sapienza” University of Rome,    surface protection does not significantly improve




                                                                          rn
                     Italy                                                   the surface roughness of GICs.
                   2 Department of Oral and Maxillo-facial Sciences,

                     Prosthodontics Unit, “Sapienza” University of Rome,     Key words: GIC, roughness, coating.
                     Italy




                                                                       te
                   3 Department of Public Health and Infectious Diseases,

                     “Sapienza” University of Rome, Italy                    Introduction
                   4 Department of Oral and Maxillo-facial Sciences, Oral
                                                                    In
                     Diagnosis Unit, “Sapienza” University of Rome, Italy    Glass ionomer cements (GIC) were introduced by Wil-
                                                                             son and Kent in 1972 (1). These materials are used in
                                                                             restorative dentistry for a variety of qualities such as
                   Corresponding author:                                     adhesion to enamel and dentin in humid conditions,
                   Edoardo Pacifici                                          less volumetric contraction (2), preservation of the pulp,
                                                           ni
                   Department of Oral and Maxillo-facial Sciences            coefficient of thermal expansion similar to dentin, low
                   Pediatric Dentistry Unit                                  solubility in the oral environment and release of fluo-
                   “Sapienza” University of Rome                             ride, that can aid the affected dentin remineralization
                   Via Caserta, 6                                            process (3). Nevertheless, their sensitivity to moisture,
                                           o

                   00185 Rome, Italy                                         low mechanical strength and low wear resistance make
                   Phone: +39 06 49976612                                    glass ionomer restorations usually less durable (4).
                                       izi


                   E-mail: edoardo.pacifici@uniroma1.it                      Because of the abovementioned qualities this cement
                                                                             finds a broader application in pediatric dentistry. In par-
                                                                             ticular, it can become the material of excellence in all
                   Summary                                                   cases where it is not possible either to isolate properly
                          Ed




                                                                             the operative field from saliva (with a rubber dam) or to
                   Background. Even today, use of Glass Ionomer Ce-          perform all the steps of adhesion and stratification re-
                   ments (GIC) as restorative material is indicated for      quired by the composites. In young patients with a low
                   uncooperative patients.                                   level of cooperation the possibility of using a high quali-
                   Aim. The study aimed at estimating the surface            ty material that can be quickly applied in non-optimal
                   roughness of different GICs using or not their pro-       conditions is extremely important.
               C




                   prietary surface coatings and at observing the in-        In the past decade several studies were conducted to
                   terfaces between cement and coating through SEM.          improve the characteristics of GICs.
    CI




                   Materials and methods. Forty specimens have been          Resin-modified glass ionomer cements (RMGIC) and
                   obtained and divided into 4 groups: Fuji IX (IX), Fuji    highly-viscous glass ionomer cements (HVGIC) were
                   IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finish-      developed to overcome the poor mechanical strength
                   ing Gloss (VFG). Samples were obtained using sili-        associated to conventional GICs, thus maintaining their
                   cone moulds to simulate class I restorations. All         clinical advantages (4).
                   specimens were processed for profilometric evalu-         RMGICs, introduced by Mitra in 1991, are made with
©




                   ation. The statistical differences of surface rough-      the addition of light-cured resin hydrophilic (4). HV-
                   ness between groups were assessed using One-              GICs were designed as an alternative to amalgam for
                   Way Analysis of Variance (One-Way ANOVA)                  posterior preventive restoration (4), where access/isola-
                   (p<0.05). The Two-Way Analysis of Variance (Two-          tion are compromised and aesthetics is of secondary
                   Way ANOVA) was used to evaluate the influence of          importance, particularly for the Atraumatic Restorative
                   two factors: restoration material and presence of         Technique (ART) introduced by the World Health Orga-
                   coating. Coated restoration specimens (IXC and            nization for use in developing countries (2).

                   250                                                                       Annali di Stomatologia 2013; IV (3-4): 250-258
5_Pacifici_Riv Annali 3-4 2013 13/02/14 10:54 Pagina 251




                   Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection
                   treatment

                   Hardening of RMGICs occurs both through the tradi-             water, the result will be a loss of calcium and aluminum
                   tional acid-base reaction of GICs and through light-cur-       ions, surface erosion and loss of the translucency (12).
                   ing polymerization (4). However, acid-base reaction is         Surface protection for GICs was assessed by some
                   still the dominant one, while photo polymerization can         studies (13). Protecting RMGICs with resin coating
                   be considered as an auxiliary one (4). Photo-polymer-          helps HEMA (highly hydrophilic) not to absorb water,




                                                                                                                                              li
                   ization only acts on the resin component. The acid-            and consequently increases the quality of the cement,
                   base reaction used to harden and reinforce the matrix          in particular reducing dimensional variations (11). A




                                                                                     na
                   is relatively immature, just after using the lamp. This re-    clinical study has shown that GIC protection can im-
                   action is delayed in RMGICs because of the presence            prove esthetics, counteracting the color change due to
                   of water inside the mixture of powder and liquid (5),          contamination during acid-base reaction (14).
                   which is partially replaced with a water-soluble               Therefore, the aim of this study was to assess the inter-




                                                                                   io
                   monomer (4). The structure of the resin reduces water          action and the influence on topography as well as the
                   spreading within the material (4). GICs come to com-           changes in average roughness provided for by different
                   plete polymerization after 1 week, even though the ma-         GICs and surface coatings in dental restorations when




                                                                                az
                   trix reaches a sufficient level of acid-base reaction (4)      finishing/polishing procedures cannot be implemented.
                   after only five minutes.                                       Surface roughness will be assessed with profilometric
                   In restoration procedures, a surface character, such as        measurements and the interface between materials will
                   roughness, can determine the quality and the clinical          be examined with SEM analysis.




                                                                             rn
                   behavior of the restoration material (6). Consequently,        The tested null hypotheses showed that a statistically
                   great relevance has been given to studies on the               similar surface roughness is achieved using or not us-
                   roughness of filling materials and of glass ionomer ce-        ing coating on GICs surface and that similar interfaces
                   ments in particular.                                           are achieved using different GICs in combination with




                                                                          te
                   Smooth surfaces can influence the wear of material (2),        the proprietary coating.
                   the aesthetic aspect of restorative materials, the onset
                   of spots and can also increase the risk of secondary
                   caries (7). On the other hand, rough surfaces can help         Materials and methods
                                                                       In
                   retention, survival and proliferation of many caries-in-
                                                                                  Forty specimens were obtained and divided into 4
                   ducing microorganisms (Streptococcus mutans and
                                                                                  groups (n=10):
                   Lactobacillus spp.) in the oral cavity and also favor peri-
                                                                                  Group A (IX): Fuji IX GP Fast Capsule (GC Corp.,
                   odontal diseases (Porphyromonas gingivalis and Acti-
                                                                                  Tokyo, Japan);
                   nobacillosis actinomicetemcomitans) (8); they also fa-
                                                             ni
                                                                                  Group B (IXC): Fuji IX GP Fast Capsule (GC Corp.,
                   vor plaque retention causing gingival irritation. Although
                                                                                  Tokyo, Japan)/G-Coat Plus (GC corporation, Tokyo
                   surface free energy can play a role in bacterial adhe-
                                                                                  Japan);
                   sion and retention, surface roughness overrules the in-
                                              o

                                                                                  Group C (V): Vitremer (3M ESPE, Seefeld, Germany);
                   fluence of surface free energy (9).
                                                                                  Group D (VFG): Vitremer (3M ESPE, Seefeld, Ger-
                   In addition, smoother reconstructions are also easier to
                                                                                  many)/Finishing Gloss (3M ESPE, Seefeld, Germany).
                                          izi


                   maintain (9) and therefore more durable (8).
                                                                                  Specimens were obtained following manufacturers’ in-
                   There are many roughness parameters in use, but
                                                                                  structions and at controlled temperature of 23±2°C.
                   arithmetic mean roughness is by far the most common
                                                                                  To create a standardized first-class cavity, silicone
                   one. Each roughness parameter is calculated using a
                                                                                  molds were prepared with putty impression material, to
                           Ed




                   formula to describe the surface. Arithmetic mean rough-        obtain 4 mm wide and 5 mm long samples with a height
                   ness (Ra) is the arithmetic average of all frames of the       of about 2.5 mm (Fig. 1).
                   profile filtered by measuring the length from the line of      In Groups A and B, after vibrating the capsule for 10s
                   the reference profile.                                         with TAC 400/M (4200 rpm; Linea TAC s.r.l. - Monte-
                   The threshold value of Ra below which no plaque forma-
                   tion is observed (supra-and subgingival) is 0.2 μm (9).
               C




                   No further reduction in bacterial accumulation is expect-
                   ed below this threshold value. Any increase in surface
    CI




                   roughness, above 0.2 μm, results in a simultaneous in-
                   crease in plaque accumulation with subsequent increase
                   of the risk of caries and periodontal inflammation (9).
                   GICs are usually hydrolytically unstable during the initial
                   stages of setting (2); in particular, the resin-modified
                   ones, appear susceptible to dehydration (10). RMGICs
©




                   water absorption appeared to be dependent on hy-
                   drophilic resin HEMA (2-hydroxyethyl methacrylate) con-
                   tent (11). Drying of these materials leads to a large loss
                   of water, and consequently to irreversible changes in
                   shape, loss of the interface in few minutes and formation
                   of trines and cracks, caused by the material being ex-
                   posed to air (4). In the event of premature contact with       Figure 1. First-class cavity replacement silicone molds.

                   Annali di Stomatologia 2013; IV (3-4): 250-258                                                                            251
5_Pacifici_Riv Annali 3-4 2013 13/02/14 10:54 Pagina 252




                   E. Pacifici et al.


                   grosso d’Asti, AT, Italy), the material was dispensed             For each specimen, images of the surface were ac-
                   through the capsule tip to bulk fill the mould.                   quired at 350 magnifications and were then recon-
                   In Groups C and D cement was manually mixed using                 structed with 3D geometry. Scan area measured ap-
                   a cement spatula and following the manufacturer’s in-             proximately 886×670 μm. For each specimen, acquisi-
                   structions, in a ratio of two scoops of powder for two            tions ranged from one to five.




                                                                                                                                                li
                   drops of liquid. Afterwards, the cement was placed into           An excel file containing the coordinates of points in
                   the silicone mould.                                               space was obtained from the 3D geometry of the surface




                                                                                          na
                   In all groups, restoration surface was modeled with a             profile of the sample. RA values, profile analysis and its
                   Heidemann spatula to obtain a surface as flat as possi-           regression line were obtained for each acquisition. Ra
                   ble, however, simulating clinical procedures.                     field parameter and formula are shown in Table 2.
                   In Groups C and D, GIC was light cured for 30s with a             The excel file obtained from the acquisition that de-




                                                                                        io
                   conventional quartz-tungsten-halogen light (Polylight 3           scribes the cloud of points on the 3D surface is a matrix
                   Steril; Castellini, Castel Maggiore, BO, Italy; power con-        of 1200 rows by 1600 columns. Each column appeared
                   sumption 52 W, wavelength (range) 400-515 nm).                    to contain from 10 to 200 data due to spurious values.
                   Group B surfaces were covered with coating G-Coat




                                                                                     az
                                                                                     The values described above were filtered removing
                   Plus using a disposable brush followed by light cure for          those data showing three orders of magnitude higher
                   30 seconds.                                                       than the average. The elimination of erroneous data
                   Group D surfaces were varnished with Finishing Gloss,             makes surface roughness more evident.
                   included in the manufacturer packaging, using a dis-




                                                                                  rn
                                                                                     Data always show a gradient, either due to imperfect
                   posable brush and light cure for 30 seconds. All proce-           flatness of the surface or to imperfect positioning of the
                   dures were carried out by a single researcher.                    sample under the microscope. This affects the determi-
                   Glass Ionomer Cements used in the study, their manu-              nation of the reference line. To overcome this problem




                                                                               te
                   facturers, batch numbers and compositions are report-             the regression line was calculated and roughness mea-
                   ed in Table 1. Coating and their relevant information             surements were made with respect to this.
                   are also reported in Table 1.                                     For each acquisition excel cannot filter more than 1200
                   Before final testing, all specimens were stored for 1             values per column, (1200x1600 = 1920000 values);
                   week at 37°C to complete the self-curing reaction.
                                                                            In       due to this amount of data, for each sample, data were
                                                                                     collected from 9 different points of the surface. Of
                                                                                     these, the surface profile has been viewed. For the
                   Profilometric analysis                                            samples with fewer irregularities the regression line and
                                                                                     the values of roughness were assessed.
                                                            ni
                   Profilometric analysis was carried out according to ISO           For each sample, in addition to numerical data, two 3D
                   4287: 1997 (and 4288: 1996). As to the roughness                  scans of the area type were carried out and were defined
                   analysis, a HIROX 3D digital microscope (distributed in           reticulated axonometric and continues axonometric.
                   Italy by Simitecno Srl for Hirox - USA Inc., River Edge           A simulation picture, that is a two-dimensional recon-
                                               o

                   (NJ) USA) was used.                                               struction of the surface, was also made.
                                           izi



                   Table 1. Composition, batch numbers and the application modes of the materials used in the study.
                           Ed




                   Table 1                                            The Glass Ionomer Cements Investigated
                   Material             Classification   Manufacturer       Components                        Batch           Average particle
                                                                                                                              size (μm)
                   Fuji IX GP Fast      Highly viscous   GC Corporation,    Powder:                           # 0603204       7
               C




                                        Glass Ionomer    Tokyo, Japan       Alumino silicate
                                        Cement                              glass, pigments
                                                                            Liquid:
    CI




                                                                            Polyacrylic acid,
                                                                            distilled water
                   Vitremer             Resin Modified   3M, St Paul, MN,   Powder:                           # N186025       6.25
                                        Glass Ionomer    USA                Aluminum fluoride                 Powder and
                                        Cement                              silicate glass                    # N190949
©




                                                                            Liquid:                           Liquid
                                                                            Polymethacrylic acid,
                                                                            hydroxyethylmethacrylate
                   GC Coat Plus         Surface coating GC Corporation,                                       #0708031
                                                        Tokyo, Japan
                   Finishing Gloss                       3M, St Paul, MN,   Bis-GMA,                          # N190764
                                                         USA                Triethyleneglycoldimethacrylate


                   252                                                                               Annali di Stomatologia 2013; IV (3-4): 250-258
5_Pacifici_Riv Annali 3-4 2013 13/02/14 10:54 Pagina 253




                   Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection
                   treatment

                   Table 2. Ra surface roughness parameter informations.           phosphate buffer (pH 7.4) for 24 h and then washed
                                                                                   under running water for 30 min.
                   Parameter       Field Parameter         Formula                 Later they were post-fixed in osmium tetroxide (OsO4)
                   Ra              Amplitude                                       for 2 h, at air temperature.
                                                                                   Afterwards, they were washed in a phosphate buffer for




                                                                                                                                               li
                                                                                   30 min with 3 changes. The samples were dehydrated
                                                                                   with ethyl alcohol at increasing concentrations for a to-




                                                                                     na
                                                                                   tal of 2 h at air temperature.
                                                                                   For maximum drying, specimens were subjected to
                   Statistical analysis                                            “critical point drying” through carbon dioxide (CO2) fluid.
                                                                                   The samples were mounted on stubs with silver adhe-




                                                                                   io
                   Data obtained following the above mentioned proce-              sive conductor (“Silver dag”) and metallized with gold
                   dures were tabulated and statistically analyzed using           by sputter coat S150 (Edwards, London, UK).
                   SigmaPlot for Windows 11,0. Mean (standard devia-               The samples were examined and observed under field




                                                                                az
                   tion) and median values of rugosity were calculated for         emission SEM Hitachi S 4000 (Hitachi Ltd. Tokyo,
                   each group. For each variable, boxplots and whiskers            Japan) operating at magnifications ranging from x40 to
                   were plotted for all groups.                                    2000 and at an accelerating voltage of 8-10 kV.
                   Group’s roughness data distribution was evaluated




                                                                             rn
                   with the Kolmogorov-Smirnov test. As their distribu-
                   tion was abnormal, the use of One-Way Analysis of               Results
                   Variance (One-Way ANOVA) for groups was preclud-
                   ed. Data were tested resorting to Kruskal-Wallis                Profilometric analysis




                                                                          te
                   Analysis of Variance (ANOVA) that was applied to as-
                   sess the statistical significance of between-group dif-         No significant differences were detected between
                   ferences.                                                       groups for profilometric value (p>0.05). Results and
                   Roughness data were also assessed with Two-Way                  statistics regarding Ra values for each tested group are
                   Analysis of Variance (Two-Way ANOVA). The two fac-
                                                                       In          shown in Table 3.
                   tors taken into account were restoration material (Fuji         Neither material nor surface coating turned out to be
                   IX and Vitremer) and presence of surface coating.               a significant factor for profilometric analysis to GICs
                   For all the analyses the level of significance was set at       (p>0.05). In addition there was not a statistically sig-
                   α = 0,05.                                                       nificant interaction between material and type
                                                             ni
                                                                                   (p>0.05). Table 4 and 5 show the results and statis-
                                                                                   tics regarding the comparison between coated and
                   SEM analysis                                                    not-coated GICs.
                                               o

                                                                                   The digital microscope also reported three types of digi-
                   Group B and D specimens, after profilometer testing,            tal images: continues axonometric (Fig. 2); reticulated
                   were sectioned perpendicular to the restoration sur-            axonometrics (Fig. 3); 2D reconstructions also called
                                           izi


                   face, with sections parallel to long axis of the surface,       simulation picture (Fig. 4).
                   up to 0.5 mm from the interface between GIC and var-
                   nish. This procedure was performed using a low-speed
                   diamond blade (Isomet 1000, Buehler, Lake Bluff, IL,            SEM analysis
                             Ed




                   USA) under water-cooling. The cut samples were
                   frozen in liquid nitrogen and fractured with microtome          Microscopic observation has shown differences regard-
                   (Reichert-Jung, Cambridge Instruments GmbH, Nuss-               ing the interfaces between the material and the coating
                   loch, Germany) resulting in 3 slices for every specimen.        in the various groups. G-Coat Plus shows a continuous
                   Slices were partially incorporated into composite resin,        interface with Fuji IX for its entire surface (Fig. 5). No air
                   leaving the interface area free.                                bubbles were found between the two materials even at a
               C




                   For both group B and group D, 30 specimens were ob-             1000x magnification. Vitremer and Finishing Gloss show
                   tained that can be analyzed microscopically.                    a good interdigitation but some bubbles are present
    CI




                   Specimens were first fixed in 2.5% glutaraldehyde               along the interface. Bubbles begin to appear at magnifi-


                   Table 3. Results of Roughness test and statistical significance between Groups.

                                                                                          Ra values
©




                   Group                              N               Mean                sd                 Median                25%-75%
                   Fuji IX                            16              4,69                (6,81)             2.57                  0.22-6.28
                   Fuji IX / G-Coat Plus              13              2,00                (2,94)             0.95                  0.62-1.61
                   Vitremer                           15              1,71                (1,23)             1.38                  0.68-2.54
                   Vitremer / Finishing Gloss         10              0,87                (0,66)             0.64                  0.39-1.29


                   Annali di Stomatologia 2013; IV (3-4): 250-258                                                                           253
5_Pacifici_Riv Annali 3-4 2013 13/02/14 10:54 Pagina 254




                   E. Pacifici et al.


                   Table 4. Results of Roughness test and statistical significance between coated and not-coated restorations.

                                                                                           Ra values
                   Coated/Not-Coated               N                   Mean                sd                 Median                25%-75%




                                                                                                                                                 li
                   Coated                          23                  1,57                (2,38)             0.84                  0.49-1.56
                   Not-Coated                      31                  3,16                (4,98)             1.52                  0.53-3.30




                                                                                      na
                   Table 5. Results of Roughness test and statistical significance between materials.

                                                                                           Ra values




                                                                                    io
                   Material                         N                   Mean               Std Dev            Median                25%-75%
                   Fuji IX                          29                  3,488              5,516              1,18                  0,386-3,41




                                                                                 az
                   Vitremer                         25                  1,439              1,141              0,962                 0,554-2,149



                                                                                                          Figure 2. Continues axonometric: (A)




                                                                              rn
                                                                                                          IX; (B) IXC; (C) V; and (D) VFG.




                                                                           te
                                                                        In
                                            o              ni
                                        izi
                             Ed




                                                                                                          Figure 3. Reticulated axonometric:
                                                                                                          (A) IX; (B) IXC; (C) V; and (D) VFG.
               C
    CI
©




                   254                                                                               Annali di Stomatologia 2013; IV (3-4): 250-258
5_Pacifici_Riv Annali 3-4 2013 13/02/14 10:54 Pagina 255




                   Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection
                   treatment

                                                                                                          Figure 4. 2D reconstructions: (A) IX;
                                                                                                          (B) IXC; (C) V; and (D) VFG.




                                                                                                                                             li
                                                                                      na
                                                                                    io
                                                                                 az
                                                                              rn
                                                                           te
                                                                        In
                                              o              ni
                                          izi
                           Ed
               C




                   Figure 5. Fuji IX - GC Coat Plus interface photomicrographs at different magnification: (A) 40x; (B) 70x; (C) 100x; (D) 400x;
                   (E) 700x; and (F) 1000x.
    CI




                   cations of 400x (Fig. 6). No debris were found between           The two restorative materials commonly used for the
                   GIC and varnish, enabling a more intimate linking.               restoration of primary teeth did not differ in terms of sur-
                                                                                    face roughness. In literature, surface roughness of
                                                                                    GICs was assessed after completion of the polishing
                   Discussion                                                       steps (15, 16) and after the application of the material
©




                                                                                    against a matrix (9). In this study, we tried to measure
                   The formulated null hypothesis has to be accepted,               GICs surface roughness after teeth restoration clinical
                   since profilometric analysis has shown that coated               procedures in uncooperative patients.
                   GICs are not significantly different compared to not-            Surface roughness was always higher than 0.2 μm,
                   coated GICs in. As to SEM analysis, the articulated null         that is the threshold value of Ra below which there is
                   hypothesis has to be rejected, since HVGIC proved to             no plaque formation (supra- and sub gingival) (9).
                   be different from RMGIC.                                         Most of the papers in literature did not show Ra values

                   Annali di Stomatologia 2013; IV (3-4): 250-258                                                                           255
5_Pacifici_Riv Annali 3-4 2013 13/02/14 10:54 Pagina 256




                   E. Pacifici et al.


                                                                                                          Figure 6. Vitremer - Finishing Gloss
                                                                                                          interface photomicrographs at differ-
                                                                                                          ent magnification: (A) 200x; (B) 500x;
                                                                                                          (C) 1000x; and (D) 2000x.




                                                                                                                                                li
                                                                                        na
                                                                                      io
                                                                                   az
                                                                                rn
                                                                             te
                   lower than 0.2 μm apart from the areas resulting from            these steps were performed after the complete harden-
                   compressing GIC against a matrix, which represent the
                                                                          In
                   surfaces as smooth as possible (9). Other clinically ir-
                                                                                    ing of the matrix (19). The value of roughness obtained,
                                                                                    however, did not reach the limit of 0.2 microns. Per-
                   relevant studies have obtained a surface smoother than           forming finishing and polishing after 7 days also de-
                   0.2 μm but the GIC samples were produced placing a               creased bacterial microleakage (20). This phenomenon
                   glass plate on the surface (2, 9).                               was attributed to moisture contamination and dehydra-
                                                            ni
                   After application of GICs in the cavity, it is often clinical-   tion caused by the procedures of finishing and polishing
                   ly necessary to remove excess material or recontouring           during the initial acid-base reaction (21).
                   the restoration (16), although this was achieved with a          Another cause of material roughness is partly the incor-
                   matrix. After using a matrix and finishing the surface           poration of air bubbles during manual mixing of powder
                                             o

                   with an abrasive strip, a rougher surface (6) can be of-         and liquid. With encapsulated materials, too mechani-
                   ten obtained. Ending the restoration with the matrix ob-         cal vibrations may include air during mixing (9, 18).
                                         izi


                   tained, the result is a polymer-rich and relatively unsta-       Moreover viscosity can add a higher level of porosity to
                   ble GIC (4). For some materials Van Meerbeek B et al.            GICs thus increasing roughness of HVGIC in this study.
                   (17) have found a surface roughness lower than 0.2 μm            The particle size difference of GICs influence physical
                   but only after polishing with 4000 grit silicone carbide         properties such as fracture toughness, compressive
                           Ed




                   paper. However, often times in uncooperative patients            strength, abrasion resistance and surface microhard-
                   polishing and finishing cannot be performed during               ness (22). Also the surface roughness of GICs is depen-
                   teeth restoration; this is particularly true in patients with    dent partly on their particle size range (16). In this study,
                   “special needs” where the pediatric dentist has a short          materials with bigger average particle size (Fuji IX GP
                   period to perform the necessary procedures.                      Fast) have shown a higher surface roughness median
                   In this study, he resulting values were also higher than         value. The mean particle size of Vitremer is 6.25 μm,
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                   0.5 microns (18) that represent the tongue limit of              while that of Fuji IX GP Fast is approximately 7 μm. The
                   roughness distinction. Only RM-GIC used in combina-              mean particle size of regular Fuji IX GP is much larger
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                   tion with its proper coating reached roughness values            (13.5 μm). Vitremer show a more homogeneous distrib-
                   close to this discomfort threshold.                              ution between small and large particles (17).
                   Ra values of 1-1.5 μm were shown in surfaces obtained            According to Gladys and van Meerbeek (17), conven-
                   with various steps of finishing, performed immediately           tional GICs presented larger mean particle sizes. More-
                   after light curing (9, 15, 16). Finishing and polishing          over, these cements are more sensitive to water (7)
                   steps are complicated by the heterogeneity of these ma-          and have longer setting time (17).
©




                   terials (15, 16). During these steps, it is easier to abrade     Although high surface roughness values were obtained
                   the soft matrix, leaving the hard glass particles protrud-       by GICs, microbiological tests did not show any
                   ing from the surface (16). Compared to conventional              changes in comparison to healthy teeth. This is due to
                   ones, because of their higher hardness, RMGICs show              the antibacterial activity of the fluoride content in these
                   a lower reduction of surface roughness after polishing.          materials (7). The release of fluoride has a specific bac-
                   Reduced values of roughness were obtained when fin-              tericidal effect on Streptococcus Mutans, but only for a
                   ishing and polishing were made after a week, since               relatively short period of time (23).

                   256                                                                               Annali di Stomatologia 2013; IV (3-4): 250-258
5_Pacifici_Riv Annali 3-4 2013 13/02/14 10:54 Pagina 257




                   Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection
                   treatment

                   The system used to simulate filling procedures could           A bonding failure between GIC and the coating could
                   produce a large spread of values, also among the dif-          create a high-roughness area and a gap. Moreover, all
                   ferent areas of the same restoration. Using filling in-        those benefits given by coating like fluoride release
                   struments only - without any finishing procedure - it is       (28) and microleakage resistance (29) would be lost.
                   impossible to get a homogeneous surface. This lack             Additionally, the bond strength of glass ionomer ce-




                                                                                                                                                   li
                   of homogeneity is also due to the nature of the materi-        ments has not been negatively influenced by early ac-
                   al that changes and hardens during the placement for           cess to water (30), therefore contrary to the instructions




                                                                                      na
                   the self-curing reaction. Surface heterogeneity has            issued by most manufacturers, there is no need for a
                   been highlighted by a statistical analysis that did not        resin coating.
                   show statistical difference. Statistical analysis also in-     The problem of coatings with uncooperative patients
                   dicates that some areas present outlying values. Even          is that two additional steps are required for position-




                                                                                    io
                   if some areas have shown a low degree of roughness,            ing: coating brushing on surface and light curing.
                   it is almost impossible not to find a part of the restora-     These procedures are not always possible with this
                   tion with a high value of roughness. This spread of da-        type of patients, for which glass ionomer cements are




                                                                                 az
                   ta is the main cause of the absence of statistical sig-        more indicated.
                   nificance in this study, even if groups present different      For future developments, our research shall be focused
                   mean values of roughness. Other studies show more              on samples with a wider bearing surface and parallel to
                   homogeneous and smoother surfaces obtained on                  the planar surface that will be evaluated.




                                                                              rn
                   specimens following polishing procedures that cannot           Further studies are necessary in order to clarify the in-
                   always be applicable.                                          fluence of the type of mixing on surface roughness, re-
                   In this study, no statistically significant differences were   sistance of coating under continuous masticatory loads
                   observed among the surfaces regardless of the pres-            and clinical outcomes of GICs protection.




                                                                           te
                   ence of the coating.
                   Data obtained with this study disagree with those ob-
                   tained by Salama et al. (24) that show a statistically sig-    Conclusions
                   nificant difference in the use of coating. However, in
                   this study GIC specimens were prepared pressing the
                                                                        In        Within the limitation of this in vitro study, coated surface
                   material against glass slabs.                                  of glass ionomer cements showed a surface roughness
                   Surface protection was further discussed by many stud-         similar to uncoated ones.
                   ies. Early found that an improvement of the hydration-         Vice versa, better performances were detected for mar-
                   dehydration problem was obtained after the application         ginal sealing ability. However, a better interaction with
                                                             ni
                   of varnish (25). More recent and deeper studies have           proper coating was detected with highly viscous glass
                   strongly recommended protecting the surface of GICs            ionomer cements compared to resin modified glass
                   to preserve water balance in the system (26).                  ionomer cements.
                   Results of study show that the use of coating reduces
                                              o


                   surface roughness of GICs either for HVGICs than for
                   RMGICs, even though this reduction is not statistically        References
                                          izi


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