Browsing by Subject "Tooth Abrasion"

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    Effect of dentifrice slurry abrasivity and erosive challenge on simulated non-carious cervical lesions development in vitro
    (J-STAGE, 2021-04) Nassar, Hani M.; Hara, Anderson T.; Cariology, Operative Dentistry and Dental Public Health, School of Dentistry
    PURPOSE: To investigate the effect of slurry abrasive levels and acidic challenges on the development of non-carious cervical lesions. METHODS: Ninety-six extracted upper premolars were affixed in pairs to acrylic blocks and had their root surfaces covered by acrylic resin except for 2 mm from the cemento-enamel junction. The specimens were distributed into six groups (n = 8 pairs) based on two experimental factors: (1) slurry abrasivity level [low/medium/high] and (2) citric acid challenge [yes/no]. Specimens were brushed for 5,000, 15,000, 35,000, and 65,000 strokes. Volume loss (VL) was determined based on optical profilometry scans of specimens impressions at the baseline and at subsequent brushing levels. Data were analyzed using repeated measures analysis of variance and Bonferroni pairwise comparison (α = 0.05). RESULTS: Higher VL values were associated with high-abrasivity slurries relative to low- and medium-abrasivity slurries (P < 0.001). Increasing the slurry abrasivity level increased the VL regardless of the acidic challenge, which did not have a significant effect (P = 0.184). After 65,000 strokes, significant VL was recorded in all groups relative to preceding brushing levels (P < 0.001). CONCLUSION: Higher values of time-dependent surface loss were associated with increased dentifrice slurry abrasivity, regardless of the citric acid challenge.
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    Effect of fluoride and abrasives on artificial enamel caries lesions
    (2012) Nassar, Hani M., 1979-; Hara, Anderson T.; González-Cabezas, Carlos, 1966-; Lippert, Frank; Fontana, Margherita Ruth, 1966-; Chu, Tien-Min Gabriel
    Hypothesis: The interaction between the abrasive level and fluoride concentration of dentifrice slurries modulates the surface loss (SL) and remineralization of incipient enamel caries (IEC). Methods: Three types of IEC were created and six experimental slurries with different combinations of fluoride content and abrasive level were tested. In experiment 1, the three IEC were subjected to brushing (with experimental slurries) and remineralization cycles for 5 days. Fluoride concentrations (0 and 275 ppm as NaF) and abrasive levels (Low and High) were tested. SL was determined by optical profilometry at baseline and after 1, 3, and 5 days. In experiment 2, changes in IEC mineral content (Δ(ΔZ)C) and depth (ΔLC) were investigated at baseline and after the 5-day cycling with transverse microradiography. In experiments 3 and 4, SL of MeC and CMC lesions were further studied, respectively; testing not only fluoride concentration (275 and 1250 ppm as NaF) and abrasivity (low and high) of the slurry, but also the brushing frequency (1x, 2x, and 3x/day). Brushing-remineralization cycles were performed for 7 days. Statistical analyses were performed at 5% significance level. Results: Experiment 1: overall, brushing with the high-abrasive slurry caused more SL than with the low-abrasive. For CMC and MeC lesions, 0 ppm F had more SL than 275 ppm F only after day 3. Fluoride had no effect on the SL of HEC lesions. Experiment 2: fluoride and abrasives did not have a significant effect on IEC. HEC had significantly lower Δ(ΔZ)C than CMC and MeC, with CMC and MeC not differing from each other. Lesion type had no effect on ΔLC. Experiment 3: brushing CMC lesions 3x/day with 1250 ppm F increased SL compared to 1x/day, after 5 and 7 days. Study 4: brushing MeC lesions with high abrasive slurry containing 1250 ppm F increased SL after 5 and 7 days. Conclusions: The IEC tested showed different SL and remineralization behaviors. The fluoride content and abrasive level of the toothpaste showed to be relevant modulating the SL of enamel caries lesions as well as their remineralization behavior.
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    The Impact of Mouthrinses on the Efficacy of Fluoride Dentifrices in Preventing Enamel and Dentin Erosion/ Abrasion
    (2018) Albeshir, Ebtehal; Lippert, Frank; Cook, Norman B.; Hara, Anderson
    Objective: Toothbrushing with fluoride toothpaste followed by rinsing with mouthwash is a routine procedure to maintain good oral hygiene. It is unknown to what extent these rinses can modulate the effect of fluoride in its ability to prevent erosion/abrasion.The aim of this in-vitro study was to investigate and compare the impact of chlorhexidine (CHX), essential oils (EO) and cetylpyridinium chloride (CPC) mouthrinses on erosive tooth wear protection afforded by conventional fluoride toothpastes. Materials and Methods: The following experimental factors were considered: five rinses: CHX, EO, CPC, a fluoride rinse, and deionized water, two fluoride toothpastes: stannous fluoride (SnF2) or sodium fluoride (NaF) and two models: (erosion/ erosion+abrasion). Slabs of bovine enamel and dentin were prepared and embedded in resin blocks and generated 10 enamel and dentin testing groups (n = 8). UPVC tapes were placed on the sides of each slab leaving 1mm area exposed in the center. The blocks were subjected to a five-day cycling model. Then, the blocks were placed in a brushing machine and exposed to fluoride toothpaste slurry (one side was brushed and the other wasn’t). The blocks were then exposed to rinse treatments. Artificial saliva was used to remineralize the specimens after erosions and treatment challenges, and as storage media. After the fifth day of cycling, surface loss (in micrometers) was determined by profilometer. Data were analyzed using ANOVA (α = 0.05). Results: There was no interaction among the three factors (type of toothpaste, mouthrinse and abrasion or not (dentin p = 0.0520, enamel p = 0.4720). There were no significant two-way interactions as SL was only affected by toothpaste and mouthrinse. NaF caused less SL than SnF2 (4.60 vs. 5.83 μm; p < 0.0001) in dentin, whereas the opposite was found in enamel (5.20 vs. 3.56 μm; p < 0.0001). Toothbrushing abrasion caused comparatively more SL in enamel (6.53 vs. 2.23 μm; p < 0.0001) than in dentin (6.06 vs. 4.38 μm; p < 0.0001). None of the tested mouthrinses affected SL. Conclusion: Commonly used mouthrinses containing antimicrobial agents or additional fluoride, do not impair the erosion/abrasion protection afforded by fluoride toothpastes. Tested SnF2 dentifrice offered greater protection against enamel surface loss and NaF dentifrices showed more protection for the dentin surface. Clinical relevance: The understanding of the interaction between commonly used rinses and fluoride dentifrices will help dentists provide better recommendations to patients with erosive lesions.
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    Influence of dentrifice abrasivity and toothbrush stiffness on the development of non-carious cervical lesions
    (2016) Binsaleh, Fahad; Hara, Anderson T.; Lippert, Frank; Bottino, Marco; Cook, Norman Blaine; Diefenderfer, Kim Edward
    Background: Non-carious cervical lesions (NCCLs) can be defined as the loss of dental hard tissue near the cemento-enamel junction without bacterial involvement. Abrasion, erosion and abfraction have been mentioned as common etiological factors of NCCLs. Abrasion is the loss of tooth structure due to friction by materials such as toothbrushes or abrasives in toothpaste. In contrast, dental erosion is the loss of tooth structure driven by acids. Abfraction, on the other hand, starts due to the weakening of the tooth structure in areas of concentrated stress as a result of cuspal flexure from heavy and repeated occlusal loading, which progresses to dental hard-tissue loss. Purpose: The present study focused on the abrasion aspect of NCCLs. Specifically, it aimed to investigate the influence of dentifrice abrasivity and toothbrush stiffness on the development of NCCLs in vitro Hypothesis: NCCL development is affected by both the abrasive level of the dentifrice and the stiffness of the toothbrush, as well as their interaction. Materials and Methods: A total of 288 extracted human upper first premolars, free of any dental caries and root defects, were selected. The teeth were be cleaned with a hand periodontal scaler and randomly assigned into twelve groups (total of 24 teeth/group). Specimens were brushed in an automated toothbrushing machine, using simulated toothpaste slurries of varying abrasivity and toothbrushes of varying stiffness. This study examined three experimental factors: 1. Toothpaste abrasivity, at four levels: high, medium, low, and non-abrasive slurry (as negative control); 2. Toothbrush stiffness, at three levels: soft, medium, and hard; 3. Toothbrushing cycles at three levels: baseline, 35k, and 65k strokes. Specimens were analyzed by optical profilometry at baseline and after each brushing level. The response variable was the dentin volumetric loss, in mm3. All toothbrushes caused significantly higher tooth wear when associated to the high abrasive slurry, compared to medium- and low-abrasive slurries. Medium- caused more tooth wear than low-abrasive slurry, which in turn led to more tooth wear than the control. Hard and medium toothbrushes were not significantly different, but both caused significantly higher volumetric loss than Soft toothbrushes. There were no differences among toothbrushes, when used with the non-abrasive (control) and low- abrasive slurries. Overall, 35k strokes resulted in significantly less tooth volumetric loss than 65k.
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    Interaction between toothpaste abrasivity and toothbrush filament stiffness on the development of erosive-abrasive lesions
    (2015) Arrageg, Mona; Chu, Tien-Mien; Kelton, Stewart; Cook, Norman; Lippert, Frank; Hara, Anderson T.
    Background: Toothpaste abrasivity is considered the major contributor in toothbrushing abrasive wear, while toothbrush stiffness can be considered a secondary factor that may modify the abrasivity of toothpaste. Objectives: To investigate the longitudinal enamel and dentin surface loss caused by the interaction between the abrasives in toothpaste and toothbrush filament stiffness. Study Hypothesis: The amount of enamel and dentin loss depends on the abrasivity of the toothpaste and the filament stiffness of toothbrush. Materials and Methods: The following experimental factors were considered: abrasive suspension, at two levels (L-low: Z113 and H-high: Z103); and toothbrushes at three levels determined by bristle stiffness (soft, medium, and hard) generating 6 testing groups (n = 8). Slabs of bovine enamel and dentin were cut, embedded in acrylic resin, and polished. UPVC tapes were placed on the surface of the specimens, leaving an area of 1 × 4 mm exposed in the center of the each enamel slab. Specimens (n = 8) were subjected to 5 d of erosion/abrasion cycling: erosion (5min, 4×/d, 0.3% citric acid, pH 3.75), abrasion (15 s, 2×/d, 45 strokes each, 150-g load, automated brushing machine), fluoride treatment (15 s with abrasion and 45 s without abrasion; 275 ppm F as NaF in abrasive slurry) with exposure to artificial saliva between erosion and abrasion (1h) and all other times (overnight). Surface loss (SL, in micrometers) was determined by optical profilometry, after the third and fifth days of cycling. Data were analyzed using three-way ANOVA (alpha = 0.05). For enamel, only cycling time was found to affect surface loss with 5 d > 3 d. Overall, there was little SL (mean range: 0.76 µm to 1.85 µm). For dentin (mean SL range: 1.87 µm to 5.91 µm), significantly higher SL was found for 5 d vs. 3 d, with particularly large differences for hard toothbrush high abrasive, and medium toothbrush/low abrasive. Hard toothbrush resulted in significantly higher SL than medium toothbrush for high abrasive after 5 d, with no other significant stiffness differences. High abrasive had significantly higher SL than low abrasive overall with strong effects for all combinations, except medium stiffness after 5 d. In conclusion, the interplay between abrasivity and filament stiffness appears to be more relevant for dentin than enamel.
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    Mechanical properties of a new zinc-reinforced glass ionomer restorative material
    (2012) Al-Angari, Sarah Sultan; Cook, Norman Blaine; Lund, Melvin R., 1922; Cochran, Michael A. (Michael Alan), 1944-; Chu, Tien-Min Gabriel; Platt, Jeffrey A., 1958-; Hara, Anderson T.
    Objective: Zinc-reinforced glass ionomer restorative material (ZRGIC) has been proposed as an improved restorative material. The study compared the mechanical properties of a ZRGIC restorative material (ChemFil Rock, (Dentsply)), with three commercially available glass ionomers (GICs); Fuji IX GP Extra (GC America), Ketac Molar (3M ESPE) and EQUIA Fil (GC America). A resin composite, Premise (Kerr), was included as a control group except for fracture toughness. Methods: Fracture toughness (KIC) testing was done according to ISO 13586, using single edge notched-beam specimens (n=10), loaded until failure in a three-point bending test device. Specimens (n=9) for the hardness, roughness and abrasive wear testing were made by mixing and inserting the restorative materials into individual stainless steel molds followed by flattening and polishing. Knoop microhardness (KHN) was performed (25 g, 30 s),on pre-determined areas of the polished surfaces. For toothbrushing wear resistance and roughness, specimens were brushed in an automated brushing machine (200 g) with a suspension of dentifrice and water (1:1, w/v) for 20,000 strokes. Specimen surfaces were scanned in an optical profilometer before and after brushing to obtain surface roughness (Ra) and mean height (surface) loss using image subtraction and dedicated software. Data were analyzed using Wilcoxon Rank Sum tests (α=0.05). Results: ChemFil Rock had the highest change in surface roughness (Ra)(0.79±0.14; p<0.001) and the lowest microhardness (KHN) values (52.39±2.67; p<0.05) among all GICs. Its wear resistance was comparable to other GICs (p>0.05). ChemFil Rock had lower fracture toughness (0.99±0.07, KIC) compared to Equia Fil (p<0.01) and higher compared to the other GICs (p<0.01). Conclusion: The new ZRGIC restorative material showed intermediate fracture toughness, high change in surface roughness, and low microhardness compared to three other commercial GICs. All materials were supplied by respective manufacturers.