Strontium Carbonate and Strontium-Substituted Calcium Carbonate Nanoparticles Form Protective Deposits on Dentin Surface and Enhance Human Dental Pulp Stem Cells Mineralization.

Strontium acetate is applied for dental hypersensitivity treatment; however, the use of strontium carbonates for this purpose has not been described. The use of Sr-carbonate nanoparticles takes advantage of both the benefits of strontium on dentin mineralization and the abrasive properties of carbonates. Here in, we aimed to synthesize strontium carbonate and strontium-substituted calcium carbonate nanoparticles and test them as potential compounds in active dentifrices for treating dental hypersensitivity. For this, SrCO3, Sr0.5Ca0.5CO3, and CaCO3 nanoparticles were precipitated using Na2CO3, SrCl2, and/or CaCl2 as precursors. Their morphology and crystallinity were evaluated by electron microscopy (SEM) and X-ray diffraction, respectively. The nanoparticles were added to a poly (vinyl alcohol) gel and used to brush dentin surfaces isolated from human third molars. Dentin chemical composition before and after brushing was investigated by infrared spectroscopy (FTIR) and X-ray dispersive energy spectroscopy. Dentin tubule morphology, obliteration, and resistance of the coatings to acid attack were investigated by SEM and EDS. The cytotoxicity and ability of the particles to trigger the mineralization of hDPSCs in vitro were studied. Dentin brushed with the nanoparticles was coated by a mineral layer that was also able to penetrate the tubules, while CaCO3 remained as individual particles on the surface. FTIR bands related to carbonate groups were intensified after brushing with either SrCO3 or Sr0.5Ca0.5CO3. The shift of the phosphate-related FTIR band to a lower wavenumber indicated that strontium replaced calcium on the dentin structure after treatment. The coating promoted by SrCO3 or Sr0.5Ca0.5CO3 resisted the acid attack, while calcium and phosphorus were removed from the top of the dentin surface. The nanoparticles were not toxic to hDPSCs and elicited mineralization of the cells, as revealed by increased mineral nodule formation and enhanced expression of COL1, ALP, and RUNX2. Adding Sr0.5Ca0.5CO3 as an active ingredient in dentifrices formulations may be commercially advantageous since this compound combines the well-known abrasive properties of calcium carbonate with the mineralization ability of strontium, while the final cost remains between the cost of CaCO3 and SrCO3. The novel Sr0.5Ca0.5CO3 nanoparticles might emerge as an alternative for the treatment of dental hypersensitivity.

Influence of adhesives usage in complete dentures during adaptation period varying the degree of resorption of mandibular ridges.

PURPOSE: This study evaluated the effect of the use of a powder-type adhesive on masticatory performance and oral health related quality of life (OHRQoL) in patients with normal and resorbed mandibular ridges during adaptation period with complete dentures. METHODS: Forty-two edentulous subjects (12 men, 30 women) were distributed in four groups: normal mandibular ridges with adhesive, n = 10; normal mandibular ridges without adhesive, n = 10; resorbed mandibular ridges with adhesive, n = 11; resorbed mandibular ridges without adhesive, n = 11. Masticatory performance was evaluated by sieving method and OHRQoL by Oral Health Impact Profile in Edentulous Adults (OHIP-EDENT) inventory at 30, 60 and 90 days after the insertion of new complete dentures. Data were analyzed using 2-way ANOVA test and Generalized Estimating Equations (GEEs), α = 0.05. RESULTS: The use of adhesive resulted in better masticatory performance at 30 (35.76 ± 12.63%) and 60 days (30.06 ± 10.54%) after the insertion of the dentures and did not influence on OHRQoL in participants with normal ridges during the adaptation period. The use of adhesive did not interfere on masticatory performance during adaptation period and had a negative effect on masticatory discomfort/disability subscale OHRQoL at 30-day period [5.2(3.6, 6.8)] for resorbed mandibular ridges with new complete dentures. CONCLUSIONS: The use of adhesive can improve masticatory performance of new complete dentures users with normal mandibular ridges in the initial adaptation period up to 60 days after insertion. For resorbed ridges subjects, the use of adhesive had a negative impact on masticatory discomfort/disability OHRQoL at 30 days after insertion.

Masticatory function in complete denture wearers varying degree of mandibular bone resorption and occlusion concept: canine-guided occlusion versus bilateral balanced occlusion in a cross-over trial.

PURPOSE: The present cross-over study evaluated the masticatory function and maximum occlusal force of edentulous patients with complete dentures with bilateral balanced occlusion (BBO) and canine guidance (CG), with normal (NR) and resorbed mandibular ridges (RR). METHODS: Participants received new complete dentures and both occlusal concepts (BBO and CG) were applied for a period of 30 days each. The masticatory performance was evaluated with the sieving method; masticatory ability with a visual analog scale (VAS) and maximum occlusal force was assessed by means of a gnatodynamometer. Data were analyzed using repeated-measure ANOVA or Generalized Estimating Equations (GEEs), α = 0.05. RESULTS: Thirty women completed the trial. The height of mandibular ridge was significant for the masticatory performance (ANOVA, p < 0.001, NR = 46.35 ± 12.18%, RR = 30.39 ± 9.94%), regardless of the occlusion guidance. A significant effect of the occlusion guidance was observed for the maximum occlusal force (ANOVA, p = 0.021, CG = 31.99 ± 12.74 N, BBO = 28.37 ± 9.83 N). The occlusion guidance was not significant for the masticatory performance (ANOVA, p = 0.156) and the height of the mandibular ridge did not influence on the occlusal force (ANOVA, p = 0.060). The interaction of the factors (guidance × ridge) was not significant for masticatory performance (ANOVA, p = 0.184) and occlusal force (ANOVA, p = 0.236). The VAS scores showed a significant effect of the ridge on chewing of lettuce, resulting in greater ease (GEEs, p = 0.016) and chewing quality (GEE, p = 0.028) of this food for participants with resorbed ridges. Participants with CG reported greater ease of chewing fresh bread and beef, and expressed higher quality of chew raw carrot. Participants with CG and normal ridges exhibited the highest overall chewing ability, in comparison to BBO (Bonferroni, p < 0.05, CG = 91.9, BBO = 72.7). CONCLUSIONS: CG represents a viable alternative to the BBO in complete dentures with satisfactory clinical results related to the self-perception of chewing and occlusal force.