Keywords fluoride - NovaMin - vickers surface microhardness - scanning electron microscope
- white spot lesions - hydroxycarbonate apatite
Introduction
Initial carious lesions are represented clinically as white spot lesions (WSLs), which
are softer than intact enamel and whiter when dried.[1 ] Treating WSLs of primary teeth by traditional methods is considered a challenge,
especially for uncooperative patients with early childhood caries (ECC).[2 ] Applying remineralization agents to WSLs may prevent cavity formation and therefore
preserve enamel integrity.[3 ]
In the remineralization of tooth structure, fluoride is considered the gold standard.
Fluoride inhibits demineralization by forming fluorapatite crystals (FAP). These crystals
are more resistant to acid attack compared with hydroxyapatite crystals.[4 ] Furthermore, fluoride enhances the growth of new FAP, and it inhibits the activity
of acid production by carious bacteria.[5 ] High concentrations of fluoride are toxic, and levels even slightly above therapeutic
levels can lead to fluorosis and therefore can limit its use.[6 ] Recently, researchers are trying to find an alternative material that can provide
beneficial remineralization effects without the potential dangers associated with
fluoride.
NovaMin (calcium sodium phosphosilicate) is a synthetic and highly biocompatible material
developed as bone regenerative and sensitivity reducing material.[7 ] Recently, NovaMin has been introduced as a remineralization agent in toothpaste
and prophy pastes. When exposed to the aqueous environment of the oral cavity, the
sodium ions from NovaMin particles rapidly exchange with hydrogen in the tooth structure
to release calcium and phosphate ions. This ion release causes a rapid increase in
pH and the subsequent creation of a hydroxycarbonate apatite layer (HCA) on the tooth
structure. HCA is chemically and structurally similar to natural biological apatite,[8 ] which makes the use of NovaMin a potential substitute for fluoride in toothpaste.
To the best of our knowledge, this is the first study to compare the remineralization
effect of NovaMin and fluoride application to primary teeth using Vickers surface
microhardness testing and scanning electron microscope (SEM). The null hypothesis
is that there is no significant difference between fluoride and NovaMin.
Materials and Methods
Twenty deidentified primary canines were selected, in accordance with the ethical
treatment of human tissue ethical committee IRB approval 1818, from freshly extracted
for orthodontic reasons without any visible caries, WSLs, cracks, or fractures under
a stereoscopic microscope (Meiji, Japan) at ×2 magnification. All teeth were then
examined with laser fluorescence DIAGNOdent (Kavo, Germany) “wavelength 655 nm.” Samples
with DIAGNOdent values between 0 and 13, which referred to intact enamel, were selected
for this study according to the manufacturer’s instructions.
Specimens’ Preparation
The teeth were cleaned from residual soft tissue using a hand scaler (ck-6 [Zeffiro,
Italy]) and then stored in 0.5% chloramine T in a plastic container for 1 week for
disinfection.
The apical third of the teeth were removed, and the teeth then sectioned mesiodistally
with a diamond disk. A 4 × 4 mm square was created in the middle third of the labial
and lingual surfaces using nail varnish and then fixed firmly into an acrylic block
for secure handling. The baseline Vickers surface microhardness was measured for all
specimens after numbering them from 1 to 40.
Baseline Vickers Surface Microhardness Testing
A Vickers microhardness tester machine (Galilio, Italy) was used to determine the
hardness values for each specimen before de/remineralization cycling.
A load of 100 g at an angle of 136 degrees was applied on the teeth surface ([Fig. 1 ]) for 10 seconds at a distance of 100 microns, creating a prism above the surface
([Fig. 2 ]). Therefore, SMH was measured according to the equation:
P (power): the applying load.
D (diameter): the diameter of the prism.
Fig. 1 The applying load on the tooth surface.
Fig. 2 The forming prism above the tooth surface.
Demineralization Cycle
Teeth were immersed for 1 hour in numbered plastic vials containing 20 mL of demineralization
solution (2 mM CaCl2 , 2 mM NaH2 Po4 , 50 mM CH3 COOH, with the addition of 0.1M NaOH to pH 4.55). Specimens were then rinsed with
10 mL deionized water and immersed for 22 hours in 20 mL of remineralization solution
(2 mM CaCl2 , 2 mM NaH2 Po4 , with the addition of 0.1M NaOH to pH 6.8) at room temperature.[9 ] The teeth were then subjected to the de/remineralization solutions three times to
create artificial carious lesions.[9 ] Then SMH was measured to all specimens under the same conditions. Samples were then
stored in deionized water, which was replaced daily until remineralization agents
were applied.
Specimens were then randomly divided into two groups as follows:
Group 1: Novamin containing paste NUPRO (Prophylaxis Paste with NovaMin; Dentsply
International, United States; [Table 1 ]).
Table 1
The ingredients of the prophylaxis paste used in this study
Ingredients
(Prophylaxis paste, DEFEND, Mydent International, United States)
1.23% fluoride ion, glycerin, sodium silicate, titanium dioxide, methyl salicylate,
water, sodium carboxymethylcellulose, sodium saccharin, flavor
NUPRO (prophylaxis paste with NovaMin; Dentsply International, United States).
Calcium sodium phosphosilicate (NovaMin), glycerin, sodium silicate, titanium dioxide,
methyl salicylate, water, sodium carboxymethylcellulose, sodium saccharin, flavor
Group 2: Fluoride 1.23% (DEFEND Prophylaxis Paste; Mydent International, United States;
[Table 1 ]).
Remineralization Cycle
Group 1: 0.5 g of NUPRO paste was applied with a rubber cup to each tooth for 2 minutes
in a clockwise direction. Then the teeth were immersed in deionized water for 2 minutes
and then gently rinsed with deionized water.
Group 2: The fluoride-containing DEFEND paste (1.23%) was applied in the same manner
as in group 1.
The remineralization cycle was repeated twice daily for 10 days.[9 ] All teeth were then soaked in deionized water until SMH was measured to determine
the acquired microhardness.
Statistical Analysis
Kolmogorov–Simonov was used to determine if the data were normally distributed. Mann–Whitney
U test was used to identify statistically significant differences in enamel microhardness
between intact and demineralized specimens, and between demineralized and remineralized
samples treated with NUPRO paste and DEFEND paste; and the difference between NUPRO
paste and DEFEND fluoride paste as a remineralization agent.
Data were analyzed using SPSS version 23 (IBM Corp.; Armonk, New York, United States),
where the p -value was set at 0.05, and the level of confidence was set at 95%.
Results
Descriptive results of testing—minimum, maximum, mean, standard deviation of microhardness
including intact, demineralized, and remineralized enamel with NUPRO paste (Group
1) and DEFEND Fluoride paste (Group 2)—are shown in ([Table 2 ]).
Table 2
The descriptive results of the microhardness of study specimens (g/mm2 )
Study specimens
n
Minimum
Maximum
Mean ± SD
Abbreviation: SD, standard deviation.
Intact enamel
40
215.40
393.00
319.4 ± 53.7
Demineralized enamel
40
112.20
277.00
142.7 ± 46.3
NUPRO paste (Group 1)
20
245.90
450.40
368.8 ± 69.03
Fluoride paste (Group 2)
20
254.60
596.30
365.7 ± 104.7
The Mann–Whitney U test showed (1) a statistically significant difference in the microhardness
of intact enamel specimen when compared with demineralized enamel specimen (p = 0.000); (2) a statistically significant difference in microhardness between demineralized
enamel and both remineralized enamel with either Group 1 or Group 2 (p = 0.000 and p = 0.000, respectively); and (3) no statistically significant difference in microhardness
values of remineralization observed with NUPRO paste (Group 1) and fluoride paste
(Group 2) ([Table 3 ]).
Table 3
The results of Mann–Whitney U test regarding the microhardness between intact and
demineralized specimens; demineralized enamel and remineralizing agent (NUPRO or fluoride);
and remineralizing agent pastes (NUPRO and fluoride, g/mm2 )
Pairwise comparison
n
Mean rank
p -Value
Intact enamel
40
59.70
0.000
Demineralized enamel
40
21.30
Demineralized enamel
20
10.70
0.000
Remineralization with NUPRO (Group 1)
20
30.30
Demineralized enamel
20
10.90
0.000
Remineralization with fluoride (Group 2)
20
30.10
Remineralization with NUPRO (Group 1)
20
22.10
0.368
Remineralization with fluoride (Group 2)
20
18.90
Scanning Electron Microscope Images
The samples were analyzed under SEM (VEGA II; TESCAN, Czech Republic) at ×70 magnification:
SEM evaluation of the intact enamel before demineralization showed regular deposition
of enamel rods and prisms ([Fig. 3 ]).
The enamel surface after demineralization presented a honeycomb-like appearance, created
by collapsing enamel rods, prism irregularity, and the disorientation of hydroxyapatite
crystals ([Fig. 4 ]).
The enamel treated with the NUPRO NovaMin containing paste lead to deposition of the
material over enamel as a dark, smooth, and uniform thickness area ([Fig. 5 ]).
Enamel treatment with DEFEND fluoride formed an irregular layer of FAP ([Fig. 6 ]).
Fig. 3 Intact enamel surface.
Fig. 4 Demineralized enamel surface.
Fig. 5 Enamel surface after fluoride application.
Fig. 6 Enamel surface after NovaMin treatment.
Discussion
Re/demineralization is a dynamic process that occurs in the oral cavity over time.[10 ] When the delicate balance between them breaks down, a lesion will be formed on tooth
surfaces as a WSL. Supplying these WSLs with calcium and phosphate ions will help
reverse cavity formation.[11 ]
[12 ] Thus, this study aimed to determine the effect of calcium sodium phosphosilicate
(NovaMin) in the remineralization of tooth structure.
The organic content of the primary tooth enamel is higher than that of permanent tooth
enamel so that it may be more susceptible to caries. There are no studies that have
evaluated NovaMin versus fluoride efficacy in primary teeth; therefore, we selected
the anterior primary teeth in this experimental study.[13 ]
Vickers surface microhardness testing was used to evaluate the remineralization effect.
It is a nondestructive, reliable, rapid, and economical method of testing.[14 ]
The results of this study showed that the SMH values after demineralization were less
than initial SMH, which is a statistically significant difference. Therefore, the
demineralization cycle created WSLs, which is similar to Haghgoo et al and Creanor
et al results.[8 ]
[15 ] Moreover, the SMH values after remineralization increased compared with SMH values
after demineralization. This result is a statistically significant difference and
demonstrates that fluoride and NovaMin both trigger the remineralization process,
as illustrated in the individual testing of these agents in prior studies with both
permeant and primary teeth.[9 ]
[16 ]
[17 ]
[18 ]
[19 ]
NovaMin is an inorganic and synthetic compound, which releases sodium, calcium, phosphate,
and silica when it exposed to an aqueous media, increases pH and forms Hydroxycarbonateapatite
crystals, and thus initiates the remineralization process.[20 ]
[21 ]
[22 ]
The pairwise comparisons showed of this study illustrate that there are no statistically
significant differences between NovaMin and fluoride in SMH values. Although NovaMin
did not offer further remineralization effect than did fluoride, this study shows
it equally beneficial. The elimination of potential fluoride toxicity, and fluorosis
of young children’s teeth from overingestion of fluoride toothpaste during daily tooth
brushing, could be one of the benefits in use NovaMin containing paste instead of
fluoride.
Conclusion
The use of NovaMin containing paste in remineralization of incipient enamel lesions
is a promising treatment due to its safety, but further studies on primary teeth should
be taken to confirm its efficacy.
