Time-lasting ceramic stains and glaze: A toothbrush simulation study.

OBJECTIVE: To evaluate and compare color stability and gloss retention of ceramic stains and glaze under simulated toothbrushing using dentifrices with different relative dentin abrasion (RDA). MATERIALS AND METHODS: Feldspathic porcelain, lithium disilicate, 3 mol% yttria partially stabilized zirconia, and 5 mol% yttria partially stabilized zirconia were evaluated. Ceramics were externally stained, glazed and mounted in the toothbrush simulator. A toothbrush with 300 g force was applied. Regular toothpaste (72 RDA) and charcoal toothpaste (RDA <200) were used. Linear brushing motion with cycle intervals: 5 k, 10 k, 30 k, and 50 k was achieved. Change in color (CIEΔE2000) and gloss measurements were collected using a reflection spectrophotometer (Ci 7600, X-rite) at baseline and cycle intervals. Repeated measures analysis of variance within specimen factors (ceramic type, toothpaste and cycles) was performed. RESULTS: ΔE00 was significantly different at 50 k cycles and with zirconia ceramics (P < .0001). Charcoal toothpaste was significantly different in ΔE00 compared to regular toothpaste (P > .0001). Loss of gloss was observed at 5 k and 30 k (charcoal and regular toothpaste respectively) regardless type of ceramic (P > .0001). CONCLUSION: Glass-phase ceramics retain stains longer than zirconia ceramics. Charcoal toothpaste affect color and gloss stability. Ceramic glaze maybe lost within the first 6 months in patients' mouth. CLINICAL SIGNIFICANCE: Long-term color and gloss stability of externally stained and glazed ceramics maybe a clinical concern. Charcoal toothpastes enhance loss of color and gloss of ceramic restorations.

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.

Potential erosive effect of mouthrinses on enamel and dentin.

This in vitro study measured the pH values, titratable acidity (TA), and erosive potential of commercially available mouthrinses. A pH analysis of 6 mouthrinses (Listerine Total Care, Listerine Ultraclean, Listerine Original, Crest Pro-Health, Scope Classic, and ACT Total Care) was performed using a calibrated pH meter, and the neutralizable acidity was measured by titrating the mouthwashes against 0.1 M of sodium hydroxide. A gravimetric analysis was performed by submerging human enamel and dentin specimens in 5 mL of each mouthrinse for a total of 2 weeks. Specimens were weighed on a calibrated analytical balance at baseline, 24 hours, 48 hours, 96 hours, 1 week, and 2 weeks, and finally the loss of mass was calculated. The differences in erosive potential among the 6 mouthrinses were verified using nonparametric tests (Kruskal-Wallis and Mann- Whitney). The level of significance was set at 0.05. The mouthrinses were found to have the following mean pH/ TA values: Crest Pro-Health, 7.05/0.00; ACT Total Care, 6.31/5.44; Scope Classic, 5.18/0.42; Listerine Original, 3.98/9.26; Listerine Total Care, 3.43/5.88; and Listerine Ultraclean, 3.87/10.36. A significant correlation between pH and TA was observed for this dataset (P > 0.0001). No statistically significant difference in enamel loss among the groups was observed (P = 0.0631). However, a significant difference in dentin loss was observed among the 6 mouthrinses (P = 0.0011). Within the limitations of this in vitro study, it can be concluded that some mouthrinses have a pH lower than the critical pH of enamel and dentin. There is a significant association between acidic pH values and higher TA. Some of the tested mouthrinses presented an erosive potential on dentin.

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.

Effect of Finishing Techniques on the Marginal Integrity of Resin-Based Composite and Resin-Modified Glass Ionomer Restoration.

UNLABELLED: The purpose of this study was to evaluate the marginal integrity of resin-based composite (RBC and resin-modified glass ionomer cement (RMGIC) restorations as a function of finishing technique and location of the tooth. Forty extracted third molars were assigned to four groups (N = 10) according to finishing instruments (aluminum oxide discs, fluted carbides, fine diamonds, and coarse diamond). Each specimen received standardized Class V preparations on the facial and lingual surfaces with occlusal margins on enamel and gingival margins on dentin. Each preparation was randomly assigned to be restored with either RBC or RMGIC. Specimens were finished with standardized pressure at approximately 0.16 N and evaluated at a magnification of 600× using an environmental scanning electron microscope. Occlusal and gingival margins were analyzed using an imaging software, and means for all measured gaps were calculated. Data were analyzed with a factorial analysis of variance. All possible two-way interactions were included, and the level of significance was set at 0.05. There were no statistically significant differences among the four types of finishing instruments used in the study. RBC-restored specimens exhibited significantly smaller mean marginal gaps (1.70-7.56 µm) than RMGI-restored specimens (5.24-14.24 µm) in enamel and dentin margins, respectively. There was a statistically significant difference between enamel and dentin with regard to marginal gap formation. Under the conditions of this study, marginal gap formation was not affected by finishing technique. RBC margins exhibited significantly less marginal gap than RMGI margins, whereas enamel margins resulted in significantly less marginal gap than did dentin margins. CLINICAL SIGNIFICANCE: Multiple factors can affect the marginal integrity and the longevity of direct restorations. From these, the finishing and polishing techniques are critical steps that are under the clinician's control, and proper finishing and polishing techniques should be applied for avoiding introduction of stress to the margin of the restoration. It seems that instrumentation do not play a significant role, as much as the restorative material and the substrate to bond.

Survival rate of lithium disilicate restorations at 4 years: A retrospective study.

STATEMENT OF PROBLEM: Ceramic restorations are frequently being placed due to the esthetic demand and the cost of noble metals that has increased considerably. One major disadvantage of ceramic restoration is failure of the material due to fracture by crack propagation. In vitro studies are of little clinical significance and in vivo studies are too short to support clinical success. PURPOSE: The purpose of this retrospective study was to evaluate the failure rate of lithium disilicate restorations (monolithic and layered) at 4 years. MATERIAL AND METHODS: Data were collected over 45 months from 2 commercial laboratories. Restorations were categorized into monolithic restorations and layered restorations. Each category was further classified into complete coverage single crowns, fixed dental prostheses, e.max veneers, and inlay/onlay restorations. Failure rates were compared and analyzed using Chi-square (α=.05). RESULTS: A total of 21,340 restorations were evaluated in this study and included 15,802 monolithic restorations and 5538 layered restorations. The failure rate for single crown monolithic restorations was 0.91% and was 1.83% for single crown layered restorations. For fixed dental prostheses, 4.55% of monolithic restorations failed. For e.max veneers, 1.3% of monolithic veneers fractured and 1.53% of layered veneers fractured. Of the inlay/onlay restorations group, 1.01% of monolithic restorations fractured. CONCLUSION: In the short term (45 months), restorations fabricated with the lithium disilicate material (IPS e.max) had relatively low fracture rates. Layered single crowns fractured at approximately 2 times the rate of monolithic crowns.

Should dentistry be a specialty of medicine? Two viewpoints.

Dentistry and dental education are well-established domains with deep-rooted institutions, educational programs, organizational structures, and advanced specialty fields. Almost 100 years ago, Dr. William Gies, founder of the Columbia University College of Dental Medicine, stated that to best serve the oral health needs of the population, dentistry should be considered a specialty of medicine, and dental students should have the same solid foundation in the basic and clinical sciences as medical students. More recently, the report on "Advancing Dental Education in the 21st Century" recommends an increase in the integration of dental and medical education as a means to address 2 of its key challenges: "shrinking demand for dental services" and "shifting practice environment." However, it has also been argued that making dentistry and dental education a subspecialty of medicine and medical education will create logistical, structural, regulatory, and financial dilemmas. Instead of a drastic change to current dental educational, organizational, and institutional models, some argue a contemporary approach to dental education is required to ensure dentists are well prepared to address the healthcare needs of the population and future healthcare delivery systems and practice models. Recognizing the need for change in dental education to keep pace with changes in patient demographics and healthcare systems, the dental profession has the responsibility and opportunity to develop new models and paradigms that improve educational and clinical outcomes in our educational programs and future practice.

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.

Abfraction lesions: etiology, diagnosis, and treatment options.

Abfraction is a type of noncarious cervical lesion (NCCL) characterized by loss of tooth tissues with different clinical appearances. Evidence supports that abfraction lesions, as any NCCLs, have a multifactorial etiology. Particularly, the cervical wear of abfraction can occur as a result of normal and abnormal tooth function and may also be accompanied by pathological wear, such as abrasion and erosion. The interaction between chemical, biological, and behavioral factors is critical and helps to explain why some individuals exhibit more than one type of cervical wear mechanism than others. In an era of personalized dentistry, patient risk factors for NCCLs must be identified and addressed before any treatment is performed. Marked variations exist in dental practice concerning the diagnosis and management of these lesions. The lack of understanding about the prognosis of these lesions with or without intervention may be a major contributor to variations in dentists' management decisions. This review focuses on the current knowledge and available treatment strategies for abfraction lesions. By recognizing that progressive changes in the cervical area of the tooth are part of a physiologically dynamic process that occurs with aging, premature and unnecessary intervention can be avoided. In cases of asymptomatic teeth, where tooth vitality and function are not compromised, abfraction lesions should be monitored for at least 6 months before any invasive procedure is planned. In cases of abfraction associated with gingival recession, a combined restorative-surgical approach may be performed. Restorative intervention and occlusal adjustment are not indicated as treatment options to prevent further tooth loss or progression of abfraction. The clinical decision to restore abfraction lesions may be based on the need to replace form and function or to relieve hypersensitivity of severely compromised teeth or for esthetic reasons.

Are All Dentiform Teeth with Simulated Caries the Same? A Six-Year Retrospective Study in Preclinical Operative Dentistry.

Dentiform teeth with simulated caries (DTSC), frequently used in preclinical courses, should show no variability in the amount of simulated caries from tooth to tooth. However, the level of caries variability among DTSC is currently unknown. The aim of this study was to assess the variation in simulated caries levels in one group of DTSC and determine whether variation among DTSC impacted the preclinical performance of dental students. In the study, 80 commercially available mandibular first molar DTSC with simulated mesio-occluso-distal caries were sectioned in coronal (n=40) and sagittal (n=40) planes where the caries depth/width was greatest. Section images were analyzed for variation in levels of simulated caries using image-processing software. Three years of practical performance data using DTSC were compared with three years of practical performance data using dentiform teeth without simulated caries, for a total of six years (students' performance on two exams, Practical 1 and Practical 2). The results showed that 70% of the coronally sectioned teeth had manufacturing defects that resulted in caries overextension at the dentino-enamel junctions (DEJs). Overextensions were found at the DEJ in 41.3% of the sagittally sectioned teeth. There was a statistically significant decrease in Practical 1 performance of the students who used DTSC as compared with students who used teeth without simulated caries (p=0.0001); there was no statistically significant difference on Practical 2 performance. Of the DTSC evaluated in this study, 56.6% contained manufacturing defects, and more than 80% were found to have excessive caries variation. Prediction of which DTSC will have caries overextension is not possible. Students preparing DTSC that contain caries overextension are therefore at increased risk of receiving undeserved negative summative assessment on practical examinations.