Noncontact remineralization of incipient lesions treated with a 5% sodium fluoride varnish in vitro

PURPOSE

Fluoride varnishes are appealing topical fluoride preparations that may provide anticaries benefits. The purpose of this in vitro study was to assess the noncontact remineralization effects of a commercial 5% sodium fluoride varnish on white spot lesions (WSLs).

METHODS

Three-millimeter diameter enamel cores were extracted from bovine teeth, mounted in acrylic rods, ground and polished, and initially demineralized to create WSLs. Specimens were evaluated for surface microhardness and divided (N=6) into two groups (water control or noncontact 5% sodium fluoride white varnish with tricalcium phosphate, where one 0.50 ml unit dose was applied to acrylic rods instead of directly on WSLs). Groups were cycled in a three-day regimen consisting of two rounds of one-hour treatments and one-hour static immersions in demineralization solution. Between these events, WSLs were immersed in artificial saliva. Remineralization was evaluated using surface and cross-sectional microhardness and high-resolution scanning electron microscopy (SEM).

RESULTS

The noncontact varnish treatment produced significantly greater percent surface microhardness recoveries (P<.05) and smaller subsurface lesions compared to the control group (P<.05). SEM revealed comparatively greater WSL porosity reduction for noncontact varnish.

CONCLUSIONS

Noncontact application of a commercial 5% sodium fluoride varnish reduced white spot lesion porosity and produced significant acid-resistant white spot lesion remineralization.

Remineralization of eroded enamel lesions by simulated saliva in vitro

Purpose:

The purpose of this study was to evaluate the effects of two simulated saliva (SS) remineralization solutions comprising different calcium-inorganic phosphate (Ca/P_i) ratios on eroded enamel.

Methods:

3 mm diameter enamel cores were extracted from bovine teeth, mounted in acrylic rods, ground and polished,and initially demineralized with either 0.3% (120 minutes) or 1.0% (30 minutes) citric acid solutions (pH 3.8). Both sets of initially eroded specimens were evaluated for surface microhardness (N=10) and treated with either 0.3 or 1.6 Ca/P_i ratio SS. Groups were first exposed to a seven-day remineralization period and then were cycled in a three-day regimen consisting daily of three rounds of two-hour plus overnight SS treatments and three 10-minute static immersions in demineralization solution. Specimens were assessed using surface microhardness and scanning electron microscopy.

Results:

Initial erosion from 0.3% citric acid led to elliptical-shaped pore openings several microns in length and in depth and contrasted significantly with respect to 1% citric acid. The greatest remineralization was observed from the 0.3 Ca/P_i SS, while the 1.6 Ca/P_i SS produced the least.

Conclusions:

This study demonstrated the nature of remineralization of eroded enamel depends on both initial erosive conditions and the Ca/P_i ratio of simulated saliva.

Effects on dentin treated with eluted multi-mineral varnish in vitro

PURPOSE

The purpose of this pilot study was to assess the non-contact effects of a NaF varnish on the morphology and elemental compositions of sound and demineralized dentin in an in vitro pH cycling model.

METHODS

3 mm diameter dentin cores were extracted from bovine teeth, mounted in acrylic rods, and ground and polished. Sound and demineralized (in 10 mL unstirred 50% citric acid (pH = 1.2) for two minutes) specimens were divided into four groups (N=6) corresponding to treatments with either water (control group) or non-contact Vanish® 5% NaF White Varnish with tri-calcium phosphate (3M ESPE). For the non-contact varnish group, one 0.50 ml unit-dose was applied to acrylic rods and positioned in the same stopper as three dentin specimens. The four groups were then cycled in a regimen consisting of three rounds of one-hour treatments with each round followed by immersion in a three-minute static acid challenge (0.3% citric acid, pH = 3.8). For each one-hour treatment immersion the test groups were immersed in distilled water. The specimens were thoroughly rinsed with distilled water after each treatment and after each acid challenge. After the last challenge, specimens were rinsed with distilled water and immersed in artificial saliva (AS) overnight. All treatments, acid challenges and immersion in AS solution were performed in an incubator set at 37°C. After three days, the specimens were assessed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).

RESULTS

SEM and EDS results demonstrated the non-contact varnish group can provide mineralization benefits relative to the control group for both sound and demineralized dentin substrates. Depositions from mineral eluting from the varnish developed on the intertubular and intratubular regions alike, with the most prominent depositions appearing on initially demineralized dentin.

CONCLUSIONS

In this observational study, acid-resistant mineral depositions were produced on the sound and dentin surfaces without direct application from a multi-mineral varnish containing fluoride, calcium and phosphate.

SEM evaluation of demineralized dentin treated with professional-strength NaF topical pastes

PURPOSE

To qualitatively explore the effects of prescription-strength topical NaF pastes on patent tubules in a pH cycling model comprising remineralization and demineralization phases.

METHODS

3 mm diameter dentin cores were extracted from bovine teeth, mounted in acrylic rods, ground and polished, and initially demineralized in 10 mL unstirred 50% citric acid (pH = 1.2) for 2 minutes to remove the smear layer and expose the dentin tubules. 72 acceptable specimens were then divided into six groups (12 per group) and subjected to a two-phase pH cycling study. The six pastes evaluated were as follows: fluoride-free Silly Strawberry, Clinpro 5000 and Clinpro Tooth Crème, MI Paste Plus, Sensodyne NUPRO 5000 and Topex Renew. First, the specimens were subjected to a remineralization regimen (Phase A), with each day comprising inverted immersion of specimens in three paste treatments (10 g paste: 20 mL distilled water) performed for 1 minute apiece with the immersion in artificial saliva (pH = 7.0) for 2 hours in between each treatment as well as overnight. After 7 days, the specimens were imaged using field emission scanning electron microscopy (FESEM). The remaining six specimens from each group were then cycled through a demineralization regimen (Phase B), with each day comprising inverted immersion of specimens in three rounds of a 1-minute treatment (10 g paste: 20 ml distilled water) followed immediately by a 3-minute static acid challenge (0.3% citric acid, pH = 3.8) with 2 hours in artificial saliva in between each round as well as overnight. After 3 days, the specimens were again imaged using FESEM.

RESULTS

After the Phase A regimen (i.e. remineralization phase), treatment with Silly Strawberry (fluoride-free), Sensodyne NUPRO 5000 and Topex Renew yielded qualitatively similar tubule pore appearance, whereby deposits appeared to have formed around the tubule openings. Clinpro 5000, MI Paste Plus and Clinpro Tooth Crème appeared to occlude dentin tubules as shown by the relatively smaller diameter tubule openings. Relative comparisons among these pastes revealed Clinpro 5000 appeared especially effective in narrowing and incorporating mineral within the tubule, while the MI Paste Plus and Clinpro Tooth Crème appear to produce comparable tubule occlusion. After the Phase B regimen (i.e. resistance to demineralization), qualitative comparisons revealed the fluoride-free, MI Paste Plus, NUPRO and Renew pastes did not appear to occlude dentin tubules as well as Clinpro 5000 and Clinpro Tooth Crème.

Elemental compositions of comet 81P/Wild 2 samples collected by Stardust

We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed ( approximately 180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.

Impact Features on Stardust: Implications for Comet 81P/Wild 2 Dust

Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on the collector surfaces that were returned to Earth. The morphologies of these surprisingly diverse features were created by particles varying from dense mineral grains to loosely bound, polymineralic aggregates ranging from tens of nanometers to hundreds of micrometers in size. The cumulative size distribution of Wild 2 dust is shallower than that of comet Halley, yet steeper than that of comet Grigg-Skjellerup.

Comet 81P/Wild 2 Under a Microscope

The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.

Locking compression plate fixation of radial and tibial fractures in a young dog

A six-month-old, male Bernese Mountain Dog in which radius-ulna and tibia-fibula concomitant fractures were treated each with a 3.5 mm Locking Compression Plate (LCP) is presented. Both fractures were approached and plated medially. The tibial fracture had to be revised with a 4.5 mm intramedullary nail and a new 3.5 mm LCP at the second post-operative day because of fixation breakdown. The follow-up radiographs taken at days 14 and 53 revealed uneventful healing of both fractures. Implants were removed 53 days after surgery.