1,358,728 research outputs found
Early bond strength to low pressure sandblasted zirconia : evaluation of a self-adhesive cement
No full textThe debonding of a densely sintered zirconia prosthesis is a clinically reported, and undesirable event. A standardized, affordable adhesive cementation protocol for zirconia-based restorations is not yet available. The aim of this investigation was to assess the influence of several surface treatments on the initial shear bond strength of self-adhesive resin cement to densely sintered zirconia ceramic. Thirty densely sintered zirconia cylinders were divided into three groups (n = 10). Each of them received a different surface treatment: control (No_T), with the zirconia surface unconditioned; low pressure air abrasion (Sand_S) (50 μm, 1 bar); and standardized air abrasion (Sand_H) (50 μm, 2.8 bar). Three more surface-treated only specimens were addressed to scanning electron microscope (SEM) for qualitative observations. After specimen fabrication, self-adhesive cementceramic interface was analyzed using SBS (shear bond strength) test. Mean shear bond strengths (MPa) obtained for Sand_H and Sand_S were 16.24 ± 2.95 and 16.01 ± 2.68, respectively; no statistically significant difference (P = 0.8580) was found between sandblasted groups. Low-pressure air abrasion positively affected the initial self-adhesive cement adhesion to zirconia with respect to the No_T control group; however it did not prevent scratches and the formation of microcracks on the ceramic surface
Comparison of marginal fit of Lava CAD/CAM crown-copings with two finish lines
No full textPURPOSE: Marginal fit is valued as one of the most important criteria for the clinical quality and success of all-ceramic crowns. The aim of this in vitro study was to investigate the marginal fit of Lava Zirconia crown-copings on chamfer and shoulder preparations.
METHODS: Two acrylic model teeth were selected to simulate the clinical preparations: one molar was prepared with a chamfer finish line (C) and one premolar was prepared with a rounded shoulder finish line (RS). Each resin model was duplicated 10 times using silicon-based impression material and poured in type IV dental stone for the fabrication of working dies. A total of 20 copings were divided into two groups (n = 10 for each finish line). Fifty measuring locations were chosen randomly along the margin on the dies and the gap width - vertical marginal discrepancy - was measured under a light microscope with a magnification of x100. Measurements were made without cementation. The mean marginal gap widths and standard deviations were calculated and a one-way analysis of variance (ANOVA) was performed for different types of preparations in order to detect differences (α = 0.05).
RESULTS: The mean marginal gap was 30 ± 3 μm for the C group and 28 ± 4 μm for the RS group. The one-way ANOVA showed no statistical significant difference between the two groups (P = 0.23).
CONCLUSIONS: Within the limitations of this study, the marginal discrepancies were all within the clinical acceptable standard set at 120 μm. Chamfer and shoulder preparations did not show differences regarding the gap dimension.
CLINICAL SIGNIFICANCE: Bur design is an easily selected parameter before natural tooth preparation. Both tested finish lines are able to help clinicians in obtaining acceptable marginal fit values for the investigated zirconia copings
Biomimetic Orthodontic treatments: preferences of adult patients and analysis of the willingness-to-pay index
No full textOBJECTIVES: Minimal knowledge is available concerning adult patient preferences and evaluations in terms of biomimetic orthodontic treatments. The first objective of this study was to evaluate the degree of acceptance of an orthodontic treatment accomplished with three different highly aesthetic orthodontic appliances: 1) clear removable aligners, group CA; 2) fixed vestibular appliances with aesthetic ceramic brackets, group FV; 3) fixed lingual appliances with customized brackets, group FL. The second objective was to analyse the strength of preference in a Western population of adult patients, expressed according to the Willingness-To-Pay (WTP) method, against an orthodontic treatment delivered with these appliances. MATERIALS AND METHODS: WTP values were recorded in 83 subjects on the basis of a starting bid of 3,000 £ (one year of therapy) modifiable through increases or decreases (100 £). Data were collected through an individually delivered online questionnaire. Specific information and details regarding the appliances were provided by means of an interactive web-area of the survey. Population characteristics and choices, median and WTP values and associations with socio-demographic parameters (Mann-Whitney and Kruskal-Wallis tests), correlations between variables (Chi-square test in contingency tables) and significant parameters for predicting WTP values obtained in a multiple linear regression model were revealed. RESULTS: The visualization of details about "limitations and complications" associated with the use of the three appliances was most frequent (31% of requests); the other two major areas of interest were "duration of therapy" (21%) and "discomfort" (13%). The appliances preferred by patients for treatment were, in decreasing order, CA (51.2%), FL (28.8%) and FV (20%); the recorded WTP median values were 3,500, 3,000 and 2,000 £ for FV, CA and FL respectively; no significant difference was found by comparing medians in the three groups (Wilcoxon test: p = 0.2254). An annual income higher than 30,000 £ and regular dental check-ups (once/year) were positive predictors (p = 0.0167 and p = 0.0020, respectively) of the WTP values (regression analysis). CONCLUSIONS: Over half the investigated population (51.2%) indicated the removable clear aligner as the preferential choice for a biomimetic treatment. Despite the high aesthetic value of CA and FL, patients didn't show a greater willingness to put efforts and money for a treatment specifically accomplished with one of those appliances
Cleanliness of dentinal walls following post space preparation using magnification
No full textThe objective of this study was to assess, by means of a scanning electron microscope (SEM), the cleanliness of canal dentine surfaces after post space preparation with the aid of two different magnification devices, either dental loupes or an operating microscope. Materials and methods: Twenty extracted single-rooted human teeth (18 canines and 2 premolars) were selected. Root canals were cleaned, shaped using nickel-titanium instruments and filled with gutta-percha. Samples were divided into two groups (n = 10), according to the device used by the operator: A (microscope) and B (loupes). Gutta-percha/sealer fillings were removed using a sequence of low-speed post drills; root canal walls were also cleaned by means of tips for ultrasound and microbrush. SEM images of post spaces were taken, and the presence of both debris and open dentine tubules was evaluated using a three-step scoring system. Mean scores were calculated at three depth levels of post space. Results: Residual debris was observed in all specimens. Statistically significant differences (P < 0.05) between groups were found at both coronal and apical levels, and better scores for debris and open tubules were obtained by group A. Conclusions: The use of an operating microscope allowed the authors to achieve superior debridement scores at specific levels (coronal and apical levels) of the post space area, compared with the use of dental loupes
Inlay-Retained Fixed Dental Prosthesis: A Clinical Option Using Monolithic Zirconia
No full textDifferent indirect restorations to replace a single missing tooth in the posterior region are available in dentistry: traditional full-coverage fixed dental prostheses (FDPs), implant-supported crowns (ISC), and inlay-retained FDPs (IRFDP). Resin bonded FDPs represent a minimally invasive procedure; preexisting fillings can minimize tooth structure removal and give retention to the IRFDP, transforming it into an ultraconservative option. New high strength zirconia ceramics, with their stiffness and high mechanical properties, could be considered a right choice for an IRFDP rehabilitation. The case report presented describes an IRFDP treatment using a CAD/CAM monolithic zirconia IRFDP; clinical and laboratory steps are illustrated, according to the most recent scientific protocols. Adhesive procedures are focused on the Y-TZP and tooth substrate conditioning methods. Nice esthetic and functional integration of indirect restoration at two-year follow-up confirmed the success of this conservative approach
Spazi del diritto. Città, nazione e ordine giuridico dall’Ottocento a oggi
No full textIn che modo il diritto contribuisce a modellare lo spazio urbano? E come lo spazio, a sua volta, condiziona la trasformazione delle categorie giuridiche, politiche e istituzionali? Spazi del diritto offre una risposta ambiziosa e interdisciplinare a queste domande, intrecciando storia del diritto, diritto pubblico comparato e amministrativo, storia delle istituzioni e urbanistica. Nato all’interno del progetto PRIN PNRR 2022 HiLArI – Histories, Laws & Architectures for Inclusion, il volume esplora le tensioni che, dalla modernità a oggi, attraversano il rapporto tra città, nazione e diritto. Ne emerge una ‘cartografia critica’ che va dall’espulsione giuridica delle città nello ius publicum europaeum alle esperienze post-coloniali e alle sfide contemporanee della marginalità urbana, fino ai nodi attuali della rigenerazione e del diritto all’abitare. I saggi spaziano dalla Los Angeles di Biddy Mason alla Asmara coloniale, dal Brasile schiavista alla Parigi multiculturale, ricostruendo come i dispositivi giuridici abbiano plasmato – e ancora plasmino – territori, identità e poteri. Lo spazio urbano si rivela così non come un fondale neutro, ma come un campo di battaglia dove i diritti si affermano, si negano, si reinventano. Spazi del diritto è una lettura essenziale per chi voglia comprendere come il diritto agisca nello spazio, tra storia e contemporaneità, memoria e progettualità
Optimal resource allocation for seismic reliability upgrading of existing structures and lifeline networks
No full textGli assetti collettivi nell’«opera benedetta» della restaurazione forestale italiana (1914-1952): un problema storico-giuridico
No full textTra gli anni Dieci e Cinquanta del Novecento, l’Italia attraversò un periodo di profonde trasformazioni, segnato da crisi devastanti e tentativi di rinascita. I due conflitti mondiali, veri spartiacque della storia contemporanea, lasciarono un segno indelebile sul territorio e sulle sue comunità, incidendo profondamente anche sul tema delle foreste. L’«opera benedetta» evocata in questo contesto si riferisce ad un ambizioso progetto di restaurazione ambientale, ispirato dalla visione lungimirante di Arrigo Serpieri, economista e agronomo di straordinaria competenza, e sostenuto dalle politiche riformiste del primo ventennio del secolo. Un’opera “magnifica”, tutta volta a rianimare finalmente l’economia sociale italiana partendo da un recupero sostanziale della vita delle comunità montane e rurali, anche e soprattutto grazie a interventi rivoluzionari e incisivi che guardavano ai rimboschimenti, alle ricostruzioni delle aree degradate, alle sistemazioni idraulico-forestali, alla stabilizzazione dei terreni. Era l’opera, corale, di rinascita di un territorio e delle sue comunità che vedeva ora, nei progetti di riorganizzazione legislativa della materia e della ricostituzione forestale in specie, un tentativo complesso ma necessario di recupero sul fronte nazionale
An introduction to compound and coupled buckling and dynamic bifurcations. Part I (G. Augusti , V. Sepe, Cap. I.2, pp.10-14): Effects of imperfections: probabilistic treatment
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