Journal of Prosthetic Dentistry
Friday, July 29, 2016
Thursday, July 28, 2016
Journal of Prosthetic Dentistry
Statement of problemMonolithic zirconia crowns fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) have recently become a common practice for the restoration of posterior teeth. The marginal fit of monolithic zirconia crowns may be affected by different cement space parameters set in the CAD software. Information is scarce regarding the effect of cement space on the marginal fit of monolithic zirconia crowns fabricated with CAD-CAM technology.
PurposeThe purpose of this in vitro study was to evaluate the effect of cement space on the marginal fit of CAD-CAM-fabricated monolithic zirconia crowns before cementation.
Material and methodsFifteen right maxillary first molar typodont teeth with standardized anatomic preparations for complete-coverage ceramic crowns were scanned with a 3-dimensional laboratory scanner. Crowns were designed 3-dimensionally using software and then milled from presintered monolithic zirconia blocks in a computer numerical control dental milling machine. The cement space was set at 25 μm around the margins for all groups, and additional cement space starting 1 mm above the finish lines of the teeth was set at 30 μm for group 25-30, 40 μm for group 25-40, and 50 μm for group 25-50 in the CAD software. A total of 120 images (3 groups, 5 crowns per group, 8 sites per crown) were measured for vertical marginal discrepancy under a stereoscopic zoom microscope and the data were statistically analyzed with 1-way analysis of variance, followed by the Tukey honestly significant difference test (α=.05).
ResultsThe results showed that different cement space values had statistically significant effect on the mean vertical marginal discrepancy value of tested crowns (P<.001). The mean marginal discrepancy was 85 μm for group 25-30, 68 μm for group 25-40, and 53 μm for group 25-50.
ConclusionsWithin the limitations of this in vitro study, it was concluded that the cement space had a significant effect on the marginal fit of CAD-CAM-fabricated monolithic zirconia crowns. The marginal fit improved as the cement space decreased.
Wednesday, July 27, 2016
Randomized controlled within-subject evaluation of digital and conventional workflows for the fabrication of lithium disilicate single crowns. Part I: digital versus conventional unilateral impressions
Journal of Prosthetic Dentistry
Statement of problemTrials comparing the overall performance of fully digital and conventional workflows in reconstructive dentistry are needed.
PurposeThe purpose of the first part of this randomized controlled clinical trial was to determine whether optical impressions produce different results from conventional impressions with respect to time efficiency and patient and operator perceptions of the clinical workflow.
Material and methodsThree digital impressions and 1 conventional impression were made in each of 10 participants according to a randomly generated sequence. The digital systems were Lava COS, iTero, and Cerec Bluecam. The conventional impression was made with the closed-mouth technique and polyvinyl siloxane material. The time needed for powdering, impressions, and interocclusal record was recorded. Patient and clinician perceptions of the procedures were rated by means of visual analog scales. The paired t test with Bonferroni correction was applied to detect differences (α=.05/6=.0083).
ResultsThe mean total working time ±standard deviation amounted to 260 ±66 seconds for the conventional impression, 493 ±193 seconds for Lava, 372 ±126 seconds for iTero, and 357 ±55 seconds for Cerec. The total working time for the conventional impression was significantly lower than that for Lava and Cerec. With regard to the working time without powdering, the differences between the methods were not statistically significant. The patient rating (very uncomfortable=0; comfortable=100) measured 61 ±34 for conventional impression, 71 ±18 for Lava, 66 ±20 for iTero, and 48 ±18 for Cerec. The differences were not statistically significant. The clinician rating (simple=0; very difficult=100) was 13 ±13 for the conventional impression, 54 ±27 for Lava, 22 ±11 for iTero, and 36 ±23 for Cerec. The differences between the conventional impression and Lava and between iTero and Lava were statistically significant.
ConclusionsThe conventional impression was more time-effective than the digital impressions. In terms of patient comfort, no differences were found between the conventional and the digital techniques. With respect to the clinician perception of difficulty, the conventional impression and the digital impression with iTero revealed more favorable outcomes than the digital impression with Lava.
Tuesday, July 26, 2016
Clinical Oral Investigations
We investigated the effect of different dietary substances on deciduous and permanent enamel.
Materials and methods
Enamel specimens were prepared from human teeth (n = 108 deciduous molars and n = 108 permanent premolars). We measured the chemical parameters (pH, titratable acidity, viscosity, calcium, phosphate, fluoride concentration and degree of saturation) of nine dietary substances. The teeth were immersed in the respective substance (2 × 2 min; 30 °C; shaking), and we measured the baseline surface hardness (SH) in Vickers hardness numbers (VHN), and the changes in SH after 2 min (ΔSH2–0) and the 4 min (ΔSH4–0) immersion. We analysed the differences between deciduous and permanent teeth using the Wilcoxon test and correlated ΔSH to the different chemical parameters.
Deciduous teeth were significantly softer (549.53 ± 59.41 VHN) than permanent teeth (590.15 ± 55.31 VHN; p < 0.001) at baseline, but they were not more vulnerable to erosive demineralization. Only orange juice, which presented milder erosive potential, caused significantly more demineralisation in deciduous teeth at ΔSH4–0. Practically all chemical parameters significantly correlated with ΔSH (p < 0.05). Substances with lower pH, higher titratable acidity, lower Ca, higher Pi and lower F concentrations, higher viscosity and more undersaturated solutions presented more erosive demineralisation.
Different parameters in dietary substances affect erosive demineralisation in deciduous and permanent teeth, but we generally observed no differences in susceptibility to erosion between both types of teeth; only orange juice (less severe acid conditions) caused perceptible differences.
We observe that permanent teeth are harder than deciduous teeth, but most substances cause no perceptible difference in erosive demineralisation in both types of teeth.
Sunday, July 24, 2016
Int J Esthet Dent. 2016 Autumn;11(3):430-41.
OBJECTIVE:The aim of this study was to assess the dental bleaching efficacy of 37.5% hydrogen peroxide (HP), with and without light activation, in HP-exposed and unexposed areas.
METHOD:28 bovine teeth were selected and divided into two groups (n = 14). Crowns were detached and stained with tea. The gingival half was covered with a gingival barrier. In the incisal half, 37.5% HP (Pola Office+, SDI) was applied three times, with a 1-week interval between applications. In HP-A group, the bleaching agent was activated for 3 min with a LED lamp. No light activation was applied in HP-N group. Dental color variation was determined through a spectrophotometer in both halves. Statistical analysis between groups was performed with an ANOVA test, and intragroup differences were evaluated, with an ANOVA test for paired data, with a significance level of P < 0.05.
RESULTS:An increase in lightness and a decrease in chroma were found in both groups and halves. No significant differences in ΔE between groups (P > 0.5) were detected in the incisal half. After treatment, a significantly higher ΔE was found in the gingival half for HP-A group (P < 0.05). For the same group, a significantly higher bleaching effect was found in the gingival half, compared with the incisal half (P < 0.05).
CONCLUSIONS:LED activation did not have a significant effect in terms of bleaching in the incisal half, but increased clearance in the gingival half.
CLINICAL RELEVANCE:HP light activation does not significantly increase the whitening effect, but it can improve the bleaching diffusion to areas where it has not been directly applied.
Friday, July 22, 2016
RESEARCHERS PRESENT KEY FINDINGS ON DETECTION OF CARIES AROUND THE MARGINS OF AMALGAM RESTORATIONS USING FOUR TECHNOLOGIES
Quantum Dental Technologies presented findings of a study last week at the 63rd Congress of the European Organisation for Caries Research (ORCA) in Athens Greece. This study found that The Canary System® can detect caries under the intact margins of amalgam restorations more accurately than Spectra, DIAGNOdent and visual examination.
Finding caries beneath intact amalgam margins is a challenging clinical problem because of the nature of the material. Amalgam is dense, radiopaque and reflects light from its surface. The study found that visual examination could not detect caries. The glow or fluorescence from the amalgam prevented Spectra from detecting any marginal caries. DIAGNOdent was unable to consistently differentiate sound from carious tissue at various distances from the amalgam margins. It was able to detect between 45% - 74% of the lesions beneath the amalgam depending upon the distance from the margin. The Canary System was able to detect 95% of the lesions around the amalgam margins. This study demonstrated that The Canary system is a valuable diagnostic tool for detecting caries that develop around and beneath the margins of amalgam restorations.
“The Canary System provides dentists with the ability to detect and monitor tooth decay beneath the edges of fillings, crowns and bridges; one of the most common clinical conditions that would lead to the failure of these restorations. X-Rays can only aid clinicians to diagnose decay on the sides or interproximal areas of teeth. When an amalgam is placed, x-rays can only detect tooth decay in certain limited areas and not along its visible margins”, said Dr. Stephen Abrams, co-founder of Quantum Dental Technologies. “Early detection of tooth decay, before it is seen on an x-ray or detected with visual inspection means that dentists can treat problems before the decay has destroyed large amounts of vital tooth structure.”
The Canary System, with its unique crystal structure diagnostics, allows oral health professionals to detect, image, track and monitor tooth decay on all tooth surfaces, beneath opaque sealants, around the margins of restorations and detect cracks in teeth. The accompanying Canary Cloud (www.thecanarycloud.com) enables dentists to view and manage this data in an online environment, track Canary usage in the office, and keep up-to-date on Canary products and clinical news. With The Canary System, caries detection is not simply shining a light on a tooth surface but it’s about gathering accurate information on the status of the tooth’s crystal structure and then storing it to allow ongoing analysis and monitoring.
Thursday, July 21, 2016
Dental implant positioning by using the root way. A predictable technique for post extractive surgery.
Minerva Stomatol. 2016 Jun 30. [Epub ahead of print]