Introduction
Pressurized-air polishing system ejecting simultaneously water and
abrasive powder is a less traumatic alternative method for removing
supragingival extrinsic stains and bacterial deposits from teeth or
restorative material surfaces when compared to rubber-cup polishing or
to other invasive methods [1,2].
However, even air polishing may produce roughness on both tooth
and restoration surfaces [3,4]. Surface damage of enamel, cement and
restorative materials may accelerate biofilm accumulation and can cause
aesthetic and gingival problems, depending on the abrasive powder
employed, spraying time, working distance and angulation from the
surface to be cleaned [5-8]. Although sodium bicarbonate powder has
been largely used to perform air polishing procedure [9], concerns about
gingival erosion have led to the recent development of a glycine-based
powder. Considered as a highly water-soluble amino acid and presenting
Morse hardness lower than that of NaHCO3, glycine powder is considered
clinically effective and it has a low abrasive effect on dental and restorative
material surfaces [3,10-12].
Since air polishing method is becoming more popular, it is relevant
to clarify the effect produced by different polishing powders on the most
commonly used materials that may be exposed to this procedure, such as composite resins and ceramics, and also clarify if the effect they produce is the same for all kinds of restorative materials.
Scientific evidence regarding to the effect of bicarbonate and glycine
powder on direct and indirect restorative materials surfaces is still quite
scant, and no study has evaluated the impact of these powders on ceramic
and composite resin surfaces simultaneously. So, the aim of this in vitro
study was to examine the roughness and morphological effect produced
by glycine and sodium bicarbonate based powder on two composite resins
with different filler particle size and one glass-ceramic surfaces after an air
polishing process.
Two null hypothesis were set in the present study. The first null
hypothesis was that there will be no differences on the effect produced by
both polishing powders on restorative materials’ surface roughness. The
second hypothesis set was that there will be no differenceson the behavior
of restorative materials tested after both polishing treatments.
Materials and Methods
Two commercial composite resins (Filtek Supreme Ultra
(nanocomposite)/ 3M/ESPE, St. Paul, MN; and IPS Empress direct
(nanohybrid composite)/IvoclarVivadent, Schaan, Lichtenstein) and a
feldspathic ceramic (Vitabloc Mark II/Vita, Bad Säckingen, Germany) were used (Table 1). Each commercial composite resin was dispensed into
Teflon molds (6.5 ± 0.1 mm in diameter and 0.5 ± 0.05 mm in thickness)
and immediately light-cured (Optilight Max, Gnatus, Brazil; light output:
600 mW/cm2) for 20 seconds, following manufacturers’ instructions.
Material |
Lot./Color |
Composition* |
Manufacturer |
Filtek Supreme Ultra |
N220206
Enamel A2 |
Bis-GMA, UDMA, TEGDMA, bis-EMA, fillers (non- aglomerated/ non-agregated 20 nm silica and 4-11 nm zirconia filler, aggregated zirconia/silica cluster filler. |
3M ESPE St. Paul, MN, USA |
IPS Empress Direct |
R67351
Enamel A2 |
Dimethacrylates (UDMA, Bis-GMA, tricyclodocanedimethanoldimethacrylate), fillers 40-3000 nm (barium glass, ytterbium trifluoride, mixed oxide, silicon dioxide, and copolymer), additives, catalysts, stabilizers and pigments. |
Ivoclar Vivadent, Schaan, Liechtenstein |
Vitablock Mark II |
|
SiO2 , Al2O3 , Na2 O, K2O, CaO, TiO2
|
Vita, Bad Säckingen, Germany |
Table 1: Restorative materials used in this study *Bis-GMA: Bisphenol A diglycidyl ether dimethacrilate; UDMA: Urethane dimethacrylate; Bis-EMA: Ethoxylated bisphenol-A dimethacrylate; TEGDMA: Triethylene glycol dimethacrylate.
Ten specimens of each nanocomposite and nanohybrid composite
were isothermally conditioned at 35°C for 1 hour immediately after
polimerization process. Cured specimens were retrieved, and stored for
24 hours at 100% relative humidity. Also, ten disc-shaped specimens (6.5
± 0.1 mm in diameter and 0.5 ± 0.05 mm in thickness) were milled from
feldspathic ceramic CAD/CAM blocks on an E4D Dentist System (D4D
Technologies, LLC, Richardson, TX) using a custom-mill file. Both sides
of each disk (composite resin and glass ceramic) were polished with 1000
grit sandpaper in order to calibrate inicial roughness for all materials.
One specimen for each material was left untreated in order to serve as
morphological control.
Air polishing process
Specimens from each material were divided in two groups of five
specimens to be treated with two different abrasive powders: sodium
bicarbonate (Polidental, Ind. E Com Ltda, SP, Brazil) and glycine-based
powder (Clinpro Prophy Powder, 3M ESPE, Seefeld, Germany). All
specimens were treated using a standard air polishing device (ProfiII
Ceramic – DabiAtlante, RibeirãoPreto, SP, Brazil) at a working distance of
10 mm for 10 seconds and at an angulation of 60°. The working pressure
was kept in 4.0 bar. All specimens were washed with tap water for 1 minute,
ultrasonically cleaned in a water bath for 10 minutes, and air-dried.
Surface roughness measurement and scanning electron microscopy procedures
To measure the surface roughness of all specimens, a profilometer
(Surcorder SE 1700, Kosaca Laboratory ltd, Tokio, Japan) with speed of 0.5
mm/s (0.25-mm cutoff) was used. All specimens were measured before
being submitted to airpolishing procedure to record an initial roughness
point for each one (control). For control and post polishment measuring,
three measurements taken in different positions (left side, right side and
the middle of the disk) were recorded automatically by the equipment,
calculating then a surface roughness average (Ra) for each specimen.
Finally a group average was obtained. Obtained data was analized by twoway
ANOVAand Tukey test at significance level of 5%.
For SEM evaluation, all specimens were mounted on aluminum stubs,
sputter coated with gold/palladium powder(SCD 050; Balzers, Schaan,
Liechtenstein) and examined using a scanning electron microscope (JSM
5600LV;JEOL, Tokyo, Japan) operating at 15 kV.
Results
Both factors (“Restorative Material” (p<0.0001) and” Polishing Powder” (p=0.0055)) and also the interaction between them were statistically significant (p<0.0001). A summary of all surface roughness means is shown in table 2.
Roughness means of groups serving as control to sodium bicarbonate
treatment (taken before polishing treatment), showed no statistical
differences between materials, except for the nanohybrid composite
(IPS Empress Direct) that presented statistically higher values (p<0.05)
than the nanocomposite (Filtek Supreme Ultra). For the glycine groups,
control measures demonstrated no statistical differences within the three
materials (Table 2). Within the groups treated with sodium bicarbonate,
nanohybrid composite roughness mean was statistically higher (p<0.05)
than the nanocomposite and the feldspathic ceramic (Vitablock Mark
II). For glycine treated groups, no statistical differences were detected
(p>0.05).
For the nanohybrid composite just the sodium bicarbonate treatment
rose the surface roughness compared to its control (p<0.05), while glycine
treated group presented no significant difference with its control. On the
other hand, both nanocomposite and feldspathic ceramic showed no
statistical difference between their control and post-treatment groups for
both polishing treatments (p>0.05).
Representative SEM photomicrographs of the control and treated specimens are shown in figures 1-3.
Figure 1a shows the typical morphological surface of nanocomposite
(control), whereas figures 1b and 1c show the surfaces of nanocomposite
after air polishing with glycine powder and sodium bicarbonate,
respectively. Overall, it may be qualitatively observed that control surface
seems to be less rough than that one polished with sodium bicarbonate but
presented similar morphological surface to that one treated with glycine
powder (Figures 1a-1c). Moreover, nanocomposite surface treated with
glycine powder presented a smoother morphological surface than the one
air-polished with bicarbonate powder (Figures 1b and 1c). It could also
be observed that sodium bicarbonate produced small surface defects (a
few filler particles were dislodged from the surface) on the nanocomposite
surface, while glycine powder produced a surface pattern that may be
characterized as a kind of “cleanliness”, with composites´ nanofiller
particles remaining on its surface.
Figure 1: Typical SEM morphological surface images from: (a) Untreated nanocomposite surface (control); (b) Nanocomposite surface after treated with glycine powder; and, (c) Nanocomposite surface after treated with sodium bicarbonate. Note some filler-particles dislodged on the surface treated
with sodium bicarbonate (arrows).
Figure 2a exhibits the untreated nanohybrid composite surface
(control), whereas figures 2b and 2c show nanohybrid composite
surfaces after treated with glycine powder and sodium bicarbonate,
respectively. It may be observed an irregular morphological surface of
the control specimen with some visible scratches produced by the grit
paper (Figure 2a). Nevertheless, the control surface was smoother than
sodium bicarbonate treated surface (Figures 2a and 2c). However, the
morphological aspect of the control surface revealed more irregularities
than the one treated with glycine powder (Figures 2a and 2b). So, the
surface of nanohybrid composite treated with glycine powder presented
a smoother morphological surface than the one polished with sodium
bicarbonate (Figures 2b and 2c). Also, it can be observed that the
nanohybrid/sodium bicarbonate-treated surface, shows large surface
depressions (a considerable quantitiy of filler particles were dislodged
from the surface), while the glycine one, a smoother surface.
Figure 2: SEM morphological surface images from: (a) Untreated nanohybrid composite surface (control);(b) Nanohybrid composite surface after treated with glycine powder; and, (c) Nanohybrid composite after treated with sodium bicarbonate. Note the large surface defects produced on the
surface treated with sodium bicarbonate (circles).
On figure 3a, the typical morphological surface of feldspathic ceramic
(control) can be seen, whereas figures 3b and 3c show the surfaces of
feldspathic ceramic after air polishing with glycine powder and sodium
bicarbonate, respectively. It could also be observed that control surface
was smoother than the ones treated with both air polishing materials. The
sodium bicarbonate and glycine powder airpolished surfaces presented
similar morphological configuration and theyseem to have a “clean” or
more regular aspect.
Figure 3: Typical SEM morphological surface image from:.(a) Untreated feldspathic ceramic surface (control); (b) Feldspathic ceramic surface after treated with glycine powder; and, (c) Feldspathic ceramic surface after treated with sodium bicarbonate.
Discussion
The analyzed data in the present study indicated that both factors were
statistically significant and also an interaction between them was detected.
Pointing that differences were found between the effects produced by
the two polishing powders and the behavior of the materials after both
treatments, so both hypothesis must be rejected.
Air polishing procedure has been much utilized in the past years
due to its effectiveness as a non-invasive prophylaxis method for
periodontal treatment [7,11,13,14]. However, concern about its effect
on dental structures and commonly used dental materials have grown,
as all dental tissues and materials may suffer material loss after the
application of this treatment [3]. Therefore, a certain amount of
surface damage was expected when performing airpolishing procedure
regardless of the polishing powder used, in accordance with previous
works [8,10,12,14,15].
The obtained results suggested that the two air polishing powders
produced different surface roughness values within the restorative
materials, a fact confirmed by morphological observations where different
surface patterns could be noted within the restorative materials tested
(Figures 1-3).
Regarding surface roughness values, it could be noted that the
nanohybrid composite resin (IPS Empress Direct) obtained significantly
higher values than the nanocomposite resin (Filtek Supreme Ultra)
and the feldspathic ceramic (these last two not different between them)
when treated with sodium bicarbonate (p<0.05) (Table 2). Also, surface
roughness mean obtained by nanohybrid composite resin was higher
when treated with sodium bicarbonate than when glycine powder was
employed (p<0.05). Thus, the highest roughness mean among all groups
was obtained when nanohybrid composite resin was treated with sodium
bicarbonate (p<
0.05). This is in accordance with SEM images, where it
could be observed profuse irregularities produced by sodium bicarbonate
treatment (Figure 2c). A different morphological pattern could be noted
on nanohybrid composite resin surface when treated with sodium
bicarbonate and glycine. Glycine powder produced a more regular surface
pattern than that produced by sodium bicarbonate (Figures 2b and 2c) and
also smoother than the control group in which sanding marks appeared
clearly (Figure 2a), but it can be said that this morphological difference
between the control and glycine treated groups was not obtained on
roughness values, as no statistical difference was detected between them.
Pointing that glycine powder produced a kind of regularization on surface
pattern for this material.
Conversely, SEM images for nanocomposite resin revealed almost no
morphological differences between the control and the surface treated with
glycine powder (Figures 1a and 1b). In the other hand, nanocomposite
resin surface treated with sodium bicarbonate showed some irregularities
and some filler particles dislodged. So, based on morphological analysis
it could be suggested in general, that surface damage was higher for
nanohybrid composite resin than for nanocomposite resin when using
both air polishing powders, being more aggressive sodium bicarbonate
for both nanohybrid and nanocomposite resins. Even though based on
roughness values, it can be seen that just sodium bicarbonate produced
a higher surface roughness for the nanohybrid composite (compared to
nanocomposite) while the glycine produced no statistically different effect
on this task for this two materials. Giacomelli et al. [12] found that sodium
bicarbonate produced greater defects on nanocomposite resin than glycine
powder, and thus being in accordance with the present findings.This fact
can signalize that glycine powder produces less surface erosion than
sodium bicarbonate, probably due to the smaller particle size of glycine,
which is around 4 times smaller than sodium bicarbonate and the low
abrasive characteristics of the crystal-particle present on glycine powder
[15]. That difference in particle size and the lower density of glycine
particles when compared with sodium bicarbonate powder may produce
lower kinetic energy when glycine powder strikes material surface [14,16]
and also it may cause less aggressive effect on gingival [14]. Those issues
are in accordance with previous studies [3,4,12,17-19].
Nevertheless, sodium bicarbonate produced significantly higher
roughness values than glycine powder just for nanohybrid composite
resin. For nanocomposite resin there were no differences between both
polishing powders’ means. This can suggests that this nanocomposite resin
is more resistant to wear effect than nanohybrid composite resin. Previous studies have reported lower properties for some nanohybrid composites compared with nanocomposite resins, maybe due to the incorporation
of pre-polymerized resin fillers and also some bigger particles that could
produce greater surface defects and roughness when submitted to wear
[20,21]. In the case of nanohybrid composite resin (IPS Empress Direct)
the filler particle size is between 40-3000 nm while for nanocomposite
resin (Filtek SupremeUltra) is between 4-20 nm. Another possible factor
that makes nanohybrid composite resin less resistant to wear is that it
has less percentage of filler content than the nanocomposite resin used.
Literature has reported that composites having more filler percentage will
be stronger, stiffer and tougher [22].
To the author´s knowledge, no other study evaluated the effect of
sodium bicarbonate and glycine powder on ceramic material. In the
present work, a feldspathic material was tested along with two composite
resins. When sodium bicarbonate was employed, feldspathic ceramic
presented lower roughness values compared with the nanohybrid
composite resin, but not different from the nanocomposite resin (Table
2). This points that roughness effect produced by sodium bicarbonate on
feldspathic ceramic was similar to the one observed on nanocomposite
resin, and that happened maybe due to their similar high wear resistance
[22]. Also it could be inferred that because ceramic surface is harder than
the two powders particles, no major morphological alteration occurred in
that material (Figure 3).
When ceramic was air polished with glycine, it presented statistically
not different roughness mean when compared with the two composite
resins (Table 2). In fact, glycine produced similar roughness effect within
the three materials. Thus, it can be inferred that glycine powder produced
less roughness regardless of the material employed. Conversely, sodium
bicarbonate produced higher roughness values and more aggressive
morphological alterations on nanohybrid composite resin, when
compared with the other materials used in this study. This can signalize
that sodium bicarbonate roughness effect may be material-dependent.
Roughness effect on feldspathic ceramic produced by both polishment
powders was similar (Table 2), same case of nanocomposite resin. Bearing
in mind that post treatment roughness values obtained by them were
between 0.14 (± 0.02) and 0.19 (± 0.05) µm (Table 2), it can be inferred
that they had an acceptable performance when submitted to both
powders, as they are in the “safe range” of roughness to avoid high surface
bacterial accumulation, according to one in vitro study that suggested this
safe range to be around 0.20 µm [23]. In the other hand the nanohybrid
composite resin presented post treatment roughness values significantly
higher than 0.20 µm after treated with sodium bicarbonate (Table 2).
Polishing Powder |
Restorative Material |
IPS Empress Direct |
Filtek Supreme Ultra |
Vitablock Mark II |
Control-Sodium Bicarbonate |
0.37 (0.17) Aa |
0.18 (0.03) Ab |
0.25 (0.14) Aab |
Sodium Bicarbonate |
0.62 (0.17) Ba |
0.16 (0.01) Ab |
0.17 (0.05) Ab |
Control-Glycine |
0.28 (0.06) Aa |
0.24 (0.12) Aa |
0.21 (0.05) Aa |
Glycine |
0.22 (0.07) Aa |
0.19 (0.04) Aa |
0.14 (0.02) Aa |
Table 2: Surface roughness means (µm) and standard deviavion (in parenthesis) obtained from each tested restorative material when treated with two air polishing treatments (Sodium bicarbonate and Glycine powder) and their respective control group. Same capital letters (column) and lowercase letters (row) represent no statistical difference by Tukey test (p<0.05).
In general it could be suggested that glycine powder caused less surface
damage than sodium bicarbonate. Various studies referred that glycine
powder is efficient in plaque removal and producing less damage to dental
and gingival structures [8,14-16,18]. Other previous works in the other
hand, found that less surface damage caused by glycine powder may be
associated with limited plaque and staining removal in contrast with
more efficient performance of sodium bicarbonate on this task, leading to a recommendation of incrementing time in procedure employing glycine powder [3]. In the present work, airpolishing was performed for 10s and
plaque removal was not evaluated. Therefore no data regarding plaque
removal effectiveness can be drawn from the present work, so future
investigations evaluating plaque removal and surface damage together,
should be encouraged. Also, knowledge about other aspects associated
with airpolishing using both powders could be also extended such as
dental sensitivity [24], dentin-restorative material bonding affectation
[25] and effect on titanium implant abutments [17] for example.
Within the limitations of this in vitro study, it could be concluded
that glycine powder had better performance than sodium bicarbonate
air polishing on the nanohybrid composite surface. The surface
roughness mean values (Ra) presented by nanocomposite material and
feldspathic ceramic were significantly lower (p<0.05) compared with
nanohybrid composite roughness values when sodium bicarbonate
powder was employed. Also, glycine powder produced no significantly
different roughness values between the three tested materials (p>0.05).
Nanocomposite resin and feldspathic ceramic did not differ significantly
among themselves (p>0.05). Glycine powder produced less aggressive
morphological alterations on both composite resins than sodium
bicarbonate, while in feldspathic ceramic no significant morphological
differences were observed between the two powders employed.
Conclusion
This study showed that glycine powder produced less aggressive
morphological alterations on both composite resins than sodium
bicarbonate, while in feldspathic ceramic no significant morphological
differences were observed between the two powders employed. Sodium
bicarbonateair polishing produced higher roughness values on the
nanohybrid surface, and it also produced more morphological alterations
on the two composite resinsemployed.
Clinical Relevance
Scientific rationale
The effective use of air polishing method for supragingival extrinsic
stains and biofilm removal in comparison with rubber-cup polishing or to
other invasive methods has been established. This study clarifies the effect
produced by air polishing using sodium bicarbonate and glycine powder
on direct (composite resin) and indirect restorative (glass-ceramic)
materials surfaces.
Clinical findings
Glycine-based powder air polishing produces a less aggressive effect
than sodium bicarbonate-based powder on dental materials’ surfaces.
Practical implications
Glycine powder air polishing can be used for clinical prophylaxis
procedure without produce significant surface damage on commercial
composite resin and glass-ceramic
Acknowledgements
The authors want to dedicate this paper to the memory of Dra. Anadelia
Borges Soares and thank her for her invaluable support in the present
investigation.