Influence of different palatal morphologies on the accuracy of intraoral scanning of the edentulous maxilla: A three-dimensional analysis.

PURPOSE: This study investigated the influence of different palatal morphologies on the accuracy of intraoral scanning (TRIOS 4) of edentulous maxillae. METHODS: Six typodonts were fabricated for different palatal morphologies with flat (F), medium (M), and deep (D) palates, with palatal wrinkles (W), or smooth palates (S), resulting in six groups: WF, WM, WD and SF, SM, SD. Ten scans were performed for each group; standard tessellation language files obtained were imported into a software to measure trueness and precision in micrometer. Trueness was calculated as the mean of the standard deviation values obtained by superimposing each scan onto the reference scan. Precision was achieved by overlapping each scan with that with the best trueness in the group. Descriptive and post-hoc analyses were conducted. RESULTS: The mean values for trueness were as follows: WM=48.7±4.7, WD=161.7±18.4, WF=85.9±16, SM=48.1±2.4, SD=349.9±8.8, and SF=349.1±25.5. The precision values were as follows: WM=46.7±7.3, WD=46.9±9, WF=48.9±6.7, SM=46±2.7, SD=105.9±17.4, SF=72.6±10.8. Significant differences were observed for trueness between SM and SD (P < 0.001), SM and SF (P < 0.001), and WF and SF (P = 0.003); whereas for precision, significant differences were reported between WD and SD (P = 0.015). Regarding trueness and precision, no difference was found between WM and SM (P = 1.0). CONCLUSIONS: Medium palatal depth showed the best accuracy. The mean accuracy values were within the clinical acceptability thresholds for all palatal morphologies. The presence of rugae improved the precision of deeper palates and the trueness of flat palates. No differences were observed in the medium palates with or without rugae.

Optical behaviors, surface treatment, adhesion, and clinical indications of zirconia-reinforced lithium silicate (ZLS): A narrative review.

OBJECTIVES: The present narrative review was focused on the optical properties, surface treatment, adhesion, and clinical indications of zirconia-reinforced lithium silicate ceramics (ZLS) for Computer-aided design / Computer-aided manufacturing (CAD/CAM) technologies. DATA/SOURCES: A literature search was performed by 3 calibrated independent researchers on PubMed, Scopus, Embase, Google Scholar, Dynamed, and Open Grey. The criteria for inclusion were: 1) papers addressing at least one of the following variables about ZLS: optical properties, surface treatment, adhesion, and clinical indications; 2) in vitro, in silico, or in vivo studies; 3) case reports; 4) systematic reviews. The exclusion criteria were: 1) animal studies; 2) non-dental studies; 3) studies only focusing on ZLS used in the heat-pressed process. STUDY SELECTION: 98 records among in vitro studies and case reports were included. CONCLUSIONS: Despite the promising microstructure characteristics of ZLS, increased translucency compared to lithium disilicate ceramics (LS2) was not proven, but acceptable color changes and stability were reported. Mechanical polishing was the most effective method to reduce surface roughness. Moreover, machinability and handling of ZLS resulted harder than LS2. Conventional acid etching procedures seemed effective in conditioning ZLS surface, but no protocol has been established yet. Besides, silane-coupling and dual-curing resin cements were recommended. CLINICAL SIGNIFICANCE: ZLSs can be used for anterior and posterior fixed single-unit CAD/CAM restorations onto both natural teeth and implants, but do not seem to represent a viable treatment option for endocrowns onto posterior teeth or fixed dental prostheses.

Fourteen-year evaluation of posterior zirconia-based three-unit fixed dental prostheses: A Prospective clinical study of all ceramic prosthesis.

OBJECTIVES: the purpose of the present prospective trial was to evaluate the clinical performance of posterior 3-unit zirconia-based fixed dental prostheses (FDPs) after 14 years of clinical function. METHODS: thirty-seven patients needing to replace either premolars or molars were involved and 48 FDPs were fabricated (Procera Zirconia, Nobel Biocare AB). Frameworks with a9 mm2 cross section of the connectors and 0.6 mm minimum thickness of the retainers were made by means of Procera Forte CAD-CAM System (Nobel Biocare AB). The patients were recalled after 6 and 12 months and then yearly up to a total follow-up of 14 years. Two independent survival curves for patients wearing 1 or 2 FDPs were calculated by means of Kaplan-Meier analysis and a log-rank test was performed in order to compare these curves. The United States Public Health Service criteria were used to examine technical and esthetic outcomes. The biological examination was performed evaluating plaque control, pocket depth, attachment level, bleeding on probing at both abutments and contralateral teeth and evaluated by means of the Wilcoxon test (p < 0.05) between the baseline and the 14-year follow-up. RESULTS: descriptive statistics resulted in 91 % and 99 % cumulative survival rates for patients wearing 1 and 2 FDPs, respectively. There were no significant differences in periodontal parameters between control and test teeth. Both function and esthetic results were successful for FDPs over a 14-year follow-up period. CONCLUSIONS: the results of this prospective clinical study confirmed the effectiveness of zirconia as a clinical option to fabricate short-span posterior FDPs. CLINICAL SIGNIFICANCE: within the limitations of the present prospective clinical study, zirconia-based three-unit fixed dental prostheses perform satisfactorily on long term, in posterior areas and in patients with standard biomechanical conditions.

Accuracy of Three Impression Materials on the Totally Edentulous Maxilla: In Vitro/In Silico Comparative Analysis.

BACKGROUND: This study was aimed at comparing the accuracy of impressions of a reference typodont (RT) reproducing a totally edentulous maxilla made with three impression materials: polysulfide, polyether, and polyvinyl-siloxane. METHODS: The RT was scanned using a desktop scanner, obtaining a reference scan. Ten impressions for each of the three tested materials were made using a mechanical device with a standardized and consistent modality. A laboratory scanner performed the digitization of each impression. We produced digital models by processing "in reverse" the scans of the physical impressions using a dedicated software, obtaining three groups (n = 10), respectively. The groups were titled: "polysulfide," "polyvinyl-siloxane," and "polyether." The scans in .stl format were imported into Geomagic Control X and then compared to RT to evaluate the accuracy of each scan by calculating trueness and precision in µm. Recorded data were subjected to descriptive statistics. RESULTS: Trueness (arithmetic proximity) values (95%CI) were: polysulfide = 249.9 (121.3-378.5), polyvinyl-siloxane = 216.8 (123.1-310.6), polyether = 291.1 (219.9-362.3). Precision values (95% CI) were: polysulfide = 261.9 (108.8-415), polyvinyl-siloxane = 209.4 (111.9-306.8), polyether = 283 (227.9-338.1). Statistically significant differences were not detected between the means of the experimental groups, both for trueness and precision. CONCLUSIONS: The accuracy of the scans obtained from polyvinyl-siloxane, polysulfide, and polyether impressions can be considered comparable in a fully edentulous maxilla.

Current status on lithium disilicate and zirconia: a narrative review.

BACKGROUND: The introduction of the new generation of particle-filled and high strength ceramics, hybrid composites and technopolymers in the last decade has offered an extensive palette of dental materials broadening the clinical indications in fixed prosthodontics, in the light of minimally invasive dentistry dictates. Moreover, last years have seen a dramatic increase in the patients' demand for non-metallic materials, sometimes induced by metal-phobia or alleged allergies. Therefore, the attention of scientific research has been progressively focusing on such materials, particularly on lithium disilicate and zirconia, in order to shed light on properties, indications and limitations of the new protagonists of the prosthetic scene. METHODS: This article is aimed at providing a narrative review regarding the state-of-the-art in the field of these popular ceramic materials, as to their physical-chemical, mechanical and optical properties, as well as to the proper dental applications, by means of scientific literature analysis and with reference to the authors' clinical experience. RESULTS: A huge amount of data, sometimes conflicting, is available today. Both in vitro and in vivo studies pointed out the outstanding peculiarities of lithium disilicate and zirconia: unparalleled optical and esthetic properties, together with high biocompatibility, high mechanical resistance, reduced thickness and favorable wear behavior have been increasingly orientating the clinicians' choice toward such ceramics. CONCLUSIONS: The noticeable properties and versatility make lithium disilicate and zirconia materials of choice for modern prosthetic dentistry, requiring high esthetic and mechanical performances combined with a minimal invasive approach, so that the utilization of such metal-free ceramics has become more and more widespread over time.

Complications of endodontically treated teeth restored with fiber posts and single crowns or fixed dental prostheses-a systematic review.

OBJECTIVE: The present systematic review aimed at assessing data from the literature on endodontic and prosthetic complications in endodontically treated teeth restored with fiber posts and single crowns (SCs) or fixed dental prostheses (FDPs). MATERIALS AND METHODS: Available randomized controlled clinical trials evaluating endodontic and prosthetic complications in the teeth treated with fiber posts and restored with different prosthetic restorations were reviewed. PubMed, Evidence-Based Dentistry, BMJ Clinical Evidence, Embase, DynaMed, and gray literature restricted to scientific literature were analyzed; also, manual researches were performed. English language and time filters (from 1990 to 2015) were used. RESULTS: The database search produced 4230 records, many of which were duplicates. The manual research did not produce any other relevant article. After duplications were removed, all the selected databases produced 3670 records. Reading titles and abstracts, two independent reviewers excluded 3664 reports. The full-texts of the remaining six reports were read. Only four studies met the inclusion criteria and were included in this systematic review. CONCLUSIONS: The most frequently reported failures in the available studies were as follows: fiber post debonding, loss of retention of single crowns, and marginal gaps. Less frequently, chippings and fractures were recorded in SCs. No studies about complications related to FDPs were found. CLINICAL RELEVANCE: A correlation between the failure rates of fiber posts and the type of prosthetic restorations just like SCs and FDPs cannot be found to date. Further randomized controlled clinical studies are required to achieve evidence-based conclusions, particularly about the use of fiber posts with FDPs.