Effect of beverage solutions and toothbrushing on the surface roughness, microhardness, and color stainability of a vitreous CAD-CAM lithium disilicate ceramic.

STATEMENT OF PROBLEM: Computer-aided design and computer-aided manufacturing (CAD-CAM) has enhanced the physicomechanical stability of ceramics. However, various factors in the oral cavity may impair the longevity of restorations by negatively affecting their properties. Appropriate surface treatments such as glaze application or mechanical polishing are necessary to diminish these effects. PURPOSE: The purpose of this in vitro study was to evaluate the influence of common beverages and toothbrushing on the surface roughness, microhardness, and color stainability of a vitreous CAD-CAM lithium disilicate ceramic with a glazed or mechanically polished surface. MATERIAL AND METHODS: Specimens (N=160) were divided into 2 groups according to the surface treatment method: polishing with abrasive disks or glaze application. Each group was subdivided (n=8) according to the immersion solution and toothbrushing: distilled water and distilled water plus brushing; coffee and coffee plus brushing; black tea and black tea plus brushing; red wine and red wine plus brushing; and cola and cola plus brushing. Before and after simulating a 5-year period of immersion and toothbrushing, a contact profilometer and a Vickers microhardness tester were used to measure the surface roughness and microhardness. CIELab parameters were assessed by using a portable spectrophotometer, and color differences were calculated by using the CIEDE2000 formula (ΔE00). Data were compared by using 3-way ANOVA/Bonferroni test for post hoc analysis (α=.05). RESULTS: Surface roughness increased irrespective of solution (P=.763), being influenced by surface treatment (P<.001), with the glazed groups presenting higher values. Microhardness decrease was influenced by solutions (P<.038) and surface treatment (P<.001), and glazing was associated with lower values. Irrespective of the surface treatment, color stainability was influenced by solutions (P<.001), with ΔE00 values for red wine being above the perceptibility threshold (ΔE00>1.30). No influence of toothbrushing was found for any parameter (P>.05). CONCLUSIONS: Despite its excellent mechanical properties, CAD-CAM lithium disilicate ceramic degraded after exposure to commonly consumed beverages. Irrespective of surface treatment, beverages decreased microhardness and caused color changes. Surface roughness increased, showing higher variation for glazed groups. Toothbrushing was unable to potentiate or diminish the observed effects. In general, the results showed that proper mechanical polishing can produce a surface with desirable properties.

Single-stage osseointegrated implants for nasal prosthodontic rehabilitation: A clinical report.

Malignant tumors in the nasal region may be treated by means of invasive surgical procedures, with large facial losses. Nasal prostheses, retained by osseointegrated facial implants, instead of plastic surgery, will, in most patients, offer good biomechanical and cosmetic results. This clinical report describes the prosthetic rehabilitation of a patient with nasal cancer who had the entire nasal vestibule removed in a single-stage surgical procedure in order to shorten the rehabilitation time. The nasal prosthesis was built on a 3-magnet bar and was made of platinum silicone with intrinsic pigmentation, thereby restoring the patient's appearance and self-esteem. The authors concluded that single-stage implants may reduce the rehabilitation time to as little as 1 month, and the correct use of materials and techniques may significantly improve the nasal prosthesis.

Is a two-step impression mandatory for complete denture fabrication on the severely resorbed mandible? A randomized trial on mastication, patient satisfaction and adjustments.

OBJECTIVES: To compare one- vs two-step impression procedures for the provision of conventional complete dentures (CCDs) for edentulous individuals with severe mandibular resorption, in terms of (1) masticatory performance and ability; (2) satisfaction with mandibular CCDs; and (3) post-delivery adjustments. METHODS: Fifty-two patients requiring maxillary + mandibular CCDs were randomly divided into two parallel arms according to the impression method of the mandibular ridge: (SI) single impression with stock trays (irreversible hydrocolloid); (TI) two-step impression in custom trays, with border molding (impression compound) followed by the impression itself (polyether). Mastication performance was evaluated by a colorimetric test, whereas patients answered questions on masticatory ability and satisfaction with mandibular CCDs (100-mm visual analogue scale). The number of post-delivery sessions for adjustments were also quantified. Outcomes were assessed at 3 and 6 months after delivery. RESULTS: The masticatory performance was similar for both groups, regardless of time (3 months, P = 0.62; 6 months, P = 0.61). No significant difference was found for patient-reported (P > 0.05), i.e. masticatory ability (general ease of chewing and quality of grinding food; ability to chew specific foods), general satisfaction with the mandibular CCD (general satisfaction, comfort, aesthetics, ability to speak and to perform correct cleaning, retention and stability). Both methods resulted in a similar number of post-delivery adjustment sessions [SI: 3.8 (1.7); TI: 3.2 (1.4); P = 0.09]. CONCLUSIONS: Compared to a traditional approach, CCDs obtained from a single impression achieve similar masticatory performance/ability and patient satisfaction, even in patients with severely reabsorbed mandibular ridge. Both methods demand the same amount of post-delivery adjustment. CLINICAL SIGNIFICANCE: A simplified impression technique which eliminates the secondary impression can provide CCDs of good clinical quality, which influences the OHRQoL, and satisfaction in the same extent they would by a two-step procedure, even for patients with severely reabsorbed mandibular ridges (ClinicalTrials.gov: NCT02339194).

Effect of flask closure method and post-pressing time on the displacement of maxillary denture teeth.

The purpose of this study was to verify the influence of flask closure methods and post-pressing times on tooth displacement in maxillary dentures. Twenty similar maxillary dentures were made using a heat-polymerized acrylic resin, and randomly assigned to 4 experimental groups (n=5) according to the protocol: 1-conventional flask closure and immediate polymerization; 2- conventional flask closure and polymerization after 6-hour post-pressing time; 3- RS flask closure system and immediate polymerization; and 4- RS flask closure system and polymerization after 6-hour post-pressing time. Three transverse and 2 anteroposterior linear distances between teeth were measured before and after the denture processing with an optical microscope with accuracy of 0.0005mm. Analysis of variance (ANOVA) and Tukey's test were performed to compare the results. The 6-hour post-pressing time (conventional = 0.44mm and RS = 0.33mm) showed no statistically significant difference in tooth movement, in relation to the flask closure methods, when compared to the immediate time (conventional = 0.40mm and RS = 0.28mm). The RS system standardized the tooth displacement, independently of the post-pressing times. Dimensional changes were more uniform when the dentures were submitted to the 6-hour post-pressing time and RS flask closure method, suggesting that these factors may reduce the magnitude of tooth movement.