Effect of time on tooth dehydration and rehydration.

OBJECTIVE: To estimate the time required for teeth to dehydrate and rehydrate and its relation to the accuracy of tooth shade selection. MATERIALS AND METHODS: Thirty-two participants were recruited, and color measurements were conducted using a spectrophotometer placed with a custom jig. After isolation, baseline measurements were made at 1, 2, 3, 5, 7, 10, and 15 min intervals to determine dehydration time. After mouth rinsing, measurements were made to determine rehydration time. CIEDE2000 values were obtained for color change between the baseline recordings and all intervals and compared to the 50:50% perceptibility and acceptability thresholds. Analysis of variance (anova) and Tukey test was used for multiple comparisons. RESULT: The tooth color changes were beyond the ΔE00 perceptibility threshold (0.8) within the first minute of dehydration (P > 0.0001). After the first minute, 87% of the teeth were beyond the ΔE00 perceptibility threshold (0.8), and 72% of the teeth were beyond the ΔE00 acceptability threshold (1.8). After 15 min of rehydration, 90% of the teeth were beyond the perceptibility threshold, and 65% were beyond the acceptability threshold. CONCLUSIONS: Shade selection procedures should be carried out within the first minute and before teeth dehydrate by means of isolation. Teeth do not rehydrate within 15 min after rehydration. CLINICAL SIGNIFICANCE: Teeth dehydration has a negative impact on shade selection, which can affect the final esthetic outcome. Shade selection should be performed at the beginning of any restorative procedure.

Effect of composite type and placement technique on cuspal strain.

OBJECTIVE: To compare the cuspal strain in Class II restorations made with bulk-fill and conventional composite resins. MATERIALS AND METHODS: Fifty extracted maxillary premolars were mounted into phenolic rings and divided into five groups (n = 10). Specimens received standardized MOD preparations. A two-step self-etch adhesive was applied and the preparations were restored using a custom matrix as follows: Filtek Supreme Ultra in eight 2-mm increments (FSUI); Filtek Supreme Ultra in bulk (FSUB); SonicFill in bulk (SF); SureFil SDR flow in bulk, covered with a 2-mm occlusal layer of Filtek Supreme Ultra (SDR/FSU); Tetric EvoCeram Bulk Fill in bulk (TEBF). Strain gages bonded to the buccal and lingual cusps recorded cuspal strain during restorations. End strain values were determined and data were subjected to Kruskal-Wallis testing, followed by one-way ANOVA and Tukey´s post hoc test. RESULTS: Combined strain values and standard deviations (in µÉ›) were: FSUI: 723 ± 102.8, FSUB: 929.2 ± 571.9, SF: 519.1 ± 80.2, SDR-FSU: 497.4 ± 67.6 and TEBF: 604.5 ± 127.1. A significant difference was found between group FSUI and groups SF, SDR-FSU, and TEBF. Group FSUB showed significantly higher mean strain and greater standard deviation than all other groups due to cuspal fractures, and was thus excluded from the statistical analysis. CONCLUSIONS: The tested bulk-fill composite resins exerted less strain onto tooth structure than the incrementally placed conventional composite resin, although the magnitude of generated strain was product-dependent. Bulk-filling with conventional composite resins is contraindicated. CLINICAL SIGNIFICANCE: Bulk-fill composite resins exerted less strain onto adjacent tooth structure than a traditional composite, even when that composite is was placed incrementally. Bulk-filling with traditional composite resins is unpredictable and contraindicated.

Acidic oral moisturizers with pH below 6.7 may be harmful to teeth depending on formulation: a short report.

Xerostomia affects 30% of the population and manifests as a side effect of medications, systemic diseases, or cancer therapy. Oral moisturizers are prescribed to overcome the ailments of dry mouth and its symptoms. It is imperative that these products help to restore hyposalivation and that they do not present any secondary effect that can harm oral health. It has been shown in the literature that some oral moisturizers may have an erosive potential due to their acidic pH, which is below the critical pH of dentin and enamel. The purpose of this paper was to make clinicians aware of the erosive potential of these products and make recommendations to manufactures for future formulations avoiding acidic pH. For this reason, care should be taken to formulate these products with safe pH values for both enamel and root dentin which, based on specific formulation should be around 6.7 or higher.

The quality of fixed prosthodontic impressions: An assessment of crown and bridge impressions received at commercial laboratories.

BACKGROUND: The authors evaluated and quantified clinically detectable errors commonly seen in impressions sent to commercial laboratories and determined possible relationships between finish line errors and other factors involved. METHODS: The authors visited 3 large and 1 small commercial dental laboratories over a 12-month period. Three calibrated examiners evaluated the impressions. The examiners evaluated all impressions for errors by using ×2.5 magnification loupes under ambient room lighting without the aid of additional illumination. RESULTS: The authors evaluated 1,157 impressions; 86% of the examined impressions had at least 1 detectable error, and 55% of the noted errors were critical errors pertaining to the finish line. The largest single error categories evaluated were tissue over the finish line (49.09%), lack of unprepared stops in dual-arch impressions (25.63%), pressure of the tray on the soft tissue (25.06%), and void at the finish line (24.38%). The factors blood on the impression (odds ratio, 2.31; P < .001) and tray type (odds ratio, 1.68; P < .001) were associated significantly with finish line errors. CONCLUSIONS: Marginal discrepancies made up the largest category of error noted in impressions evaluated. The authors noted an increase in errors at the finish line with dual-arch impression techniques and in the presence of blood. PRACTICAL IMPLICATIONS: Dentists have ethical, moral, and legal obligations bestowed on them by the profession and need to evaluate critically the work they send to laboratories. The authors strongly recommend an improvement in technique and reviewing of all impressions and working casts.

pH and Erosive Potential of Commonly Used Oral Moisturizers.

PURPOSE: To measure the pH values of commonly used oral moisturizers and to evaluate their erosive potential using a gravimetric analysis. MATERIALS AND METHODS: A pH analysis was performed for seven commercially available oral moisturizers using a calibrated pH meter. The pH recording was repeated three times, from three different bottles each of the same product. The gravimetric analysis was performed by submerging human dentin blocks in 5 ml of each of the moisturizers for a total of 2 weeks, with gravimetric measurements made at baseline, 24 hours, 48 hours, 96 hours, 1 week, and 15 days. Tap water was used as positive control and citric acid as the negative control. The erosive potential was descriptively analyzed, and a Spearman correlation coefficient was used to assess the relationship between the erosive potential and the pH values. RESULTS: The average pH values are as follows: Oasis, 6.3, Bioténe Moisturizing Mouth Spray, 6.1, CTx2 Spray, 9.1, Mouth Kote, 3.0, Thayer's, 6.3, Bioténe Oral Balance, 6.6, Rain, 7.1, tap water 6.99, and citric acid 1.33. The results (% of tooth structure lost) of the gravimetric analysis were as follows: Mouth Kote, 9.6%, Bioténe Moisturizing Mouth Spray, 4.6%, Oasis, 3.2%, Thayer's, 2.0%, Bioténe Oral Balance, 0.0%, Rain, 0.0%, CTx2 Spray, 0.0%, tap water 0.0%, and citric acid 18.8%. There was a significant negative correlation between the pH values and the erosive potential (r(s) = -0.73; P ≤ 0.0001). CONCLUSIONS: There is large variation in the composition and pH values of commonly used oral moisturizers, and there is a strong correlation between pH values and erosive potential of commonly used oral moisturizers. CLINICAL SIGNIFICANCE: Patients with dry mouth are at increased risk for erosion and root caries. Oral moisturizing agents are often prescribed for patients with hyposalivation to be used as needed for symptomatic relief. This study shows that there is large variation in the pH values and erosive potential of commonly used oral moisturizing agents.