Solvability and regularity for the electrostatic Born-Infeld equation with general charges

In electrostatic Born-Infeld theory, the electric potential u ρ generated by a charge distribution ρ in R m (typically, a Radon measure) minimizes the action ∫ R m ( 1 − √ 1 − ∣ D ψ ∣ 2 ) d x − ⟨ ρ , ψ ⟩ among functions which decay at infinity and satisfy ∣ D ψ ∣≤ 1 . Formally, its Euler-Lagrange equation prescribes ρ as being the Lorentzian mean curvature of the graph of u ρ in Minkowski spacetime L m + 1 . However, because of the lack of regularity of the functional when ∣ D ψ ∣= 1 , whether or not u ρ solves the Euler-Lagrange equation and how regular is u ρ are subtle issues that were investigated only for few classes of ρ . In this paper, we study both problems for general sources ρ , in a bounded domain with a Dirichlet boundary condition and in the entire R m . In particular, we give sufficient conditions to guarantee that u ρ solves Ethe uler-Lagrange equation and enjoys improved W 2 , 2 loc estimates, and we construct examples helping to identify sharp thresholds for the regularity of ρ to ensure the validity of the Euler-Lagrange equation. One of the main difficulties is the possible presence of light segments in the graph of u ρ , which will be discussed in detail

Lithium disilicate posterior overlays: clinical and biomechanical features

The aim of this study was to evaluate the survival rate of lithium disilicate overlays in increasing occlusal vertical dimension (OVD) in the setting of minimally invasive techniques and the restoration thicknesses at different tooth sites. This is an observational study evaluating 43 lithium disilicate overlays (Lithium IPS e.max Press, Ivoclar Vivadent) on 8 patients, prepared with minimally invasive criteria over a follow-up period between 19 to 45 months (mean follow-up of 32 months). Occlusal vertical dimension's increase was planned using occlusal treatment plan and diagnostic wax-up. Prior to adhesive cementation, restoration thicknesses were measured with a caliber. The survival rate was calculated by Kaplan-Meier analysis. Restoration survival rates at 32 months were 97.7%. One infiltration was observed, no cases of fracture occurred. The greatest thickness in monolithic restorations was detected in the cusp sides of teeth, whereas the thinnest was highlighted in the central fossa. The average amount of dental tissue removed during preparation was 0.98 mm in non-functional cusps, 0.88 mm in functional cusps, and 0.57 mm in the central fossa. Lithium disilicate posterior overlays show an excellent complication-free survival rate, and the material allows for conservative restorations with minimum thickness. Monolithic lithium disilicate overlays feature a satisfying 32-month survival rate. The technique allows to perform restorations with a minimal removal of dental tissue, while limiting fractures over time. Its esthetical performance is excellent

Clinical and Esthetical Evaluation of 79 Lithium Disilicate Multilayered Anterior Veneers with a Medium Follow-Up of 3 Years

Objectives Primary aim of this study was to evaluate survival rate of lithium disilicate veneers in upper and lower anterior teeth. Secondary aims were to evaluate changing in proportions of teeth before and after restorations and to assess mean thickness of the veneers. Materials and Methods Seventy-nine upper and lower lithium disilicate veneers were made in 13 patients with worn teeth. Mean follow-up was 3 years. To perform anterior definitive rehabilitations, malocclusions and loss of vertical dimension were treated by full mouth rehabilitations to obtain proper occlusal conditions. Veneers were made of lithium disilicate core and fluorapatite-based ceramic stratification. Survival rate was calculated by Kaplan-Meier analysis. Changing in teeth proportion before and after restorations was analyzed by a paired t -test. Descriptive statistics of thickness values were also performed. Results One case of detachment was observed with a 98.7% survival rate. Teeth's proportions were preserved although the first upper right incisor and canine changed in dimension. Conclusions Lithium disilicate veneers in esthetical rehabilitations of worn teeth proved to be an effective way of treatment in a medium follow-up of 3 years. Proportions seemed to be maintained with a minimum dental removal

Apps for oral hygiene in children 4 to 7 years : fun and effectiveness

Nowadays apps in preschool age are largely used in learning improvement. The aim of this work was to test effectiveness of apps in improving oral hygiene in children patients aged from 4 to 7 years and evaluating correlation between parents educational attainment and children oral hygiene. 100 patients aged from 4 to 7 years were randomly assigned by an external office in the study group (SG: 32 females, 18 males) and in the control group (CG: 28 females and 22 males). Plaque index (PI) and carious lesions localisation were detected. At baseline all patients and one of the parents were instructed at chair-side about the proper oral hygiene techniques. SG patients were also given app as an aid in oral hygiene practice. Follow-up was 12 months. Measurements were made every three months at chair-side visits. Information about children compliance in oral hygiene and educational level of parents were obtained by questionnaires at t0 and after 12 months. SG patients showed stronger oral hygiene and PI lower than those in CG. Questionnaire showed higher compliance of SG patients and parents educational level seemed to affect children oral hygiene. Apps in children allowed achieving encouraging results with improvement of oral hygiene and health

The 'Alternating Osteotome Technique': a surgical approach for combined ridge expansion and sinus floor elevation. A multicentre prospective study with a three-year follow-up

The aim of this multicentre prospective study was to evaluate the efficacy and safety of a surgical approach based on a novel osteotome technique, in order to obtain both alveolar ridge expansion and sinus floor elevation. Partially edentulous patients requiring an implant-prosthetic rehabilitation with a fixed prosthesis in the posterior maxilla were included in this study according to pre-established inclusion and exclusion criteria. All implants were placed after site preparation with the 'Alternating Osteotome Technique', which consists of the use of alternating concave and convex osteotomes. After a 4 to 6-month healing period, all implants were restored with a definitive fixed prosthesis. Clinical and radiographic examinations were scheduled over a 36-month follow-up of functional loading according to a well-established protocol. Statistical analysis was used to detect any significant differences or correlations (P = 0.05). Seventy-six patients were consecutively treated with a total of 120 implants in three different centres. The mean ridge expansion and sinus floor elevation were 1.8 ± 0.3 and 2.5 ± 0.7, respectively. After three years of functioning, the implant success rate was 99.1% since one implant had failed and the mean marginal bone loss was 0.6 ± 0.3 mm. No complications occurred during the intraoperative and postoperative periods. All parameters analysed were stable and steady throughout the three-year follow-up. The 'Alternating Osteotome Technique' enables the dental surgeon to achieve an adequate implant osteotomy with limited ridge expansion and sinus floor elevation, increasing modestly the vertical and horizontal dimensions of the alveolar crest but reducing significantly the risk of surgical complications

Traditional, 2D and 3D Workflows: What Is Better for Aesthetic Rehabilitation of Superior Anterior Teeth?

This study aimed to compare conventional, digital 2D and digital 3D workflows as possible aesthetic rehabilitation processes for the maxillary anterior area using “open-source” software. For the conventional workflow, a diagnostic wax-up was produced by a dental technician. For the 2D digital workflow, Keynote software (version 11.1) was used to perform digital aesthetic analysis and smile planning. Measurements were taken and used by the technician to obtain a dental wax-up. For the 3D session, a plaster model was scanned and used to perform 3D analysis and the guide for the mock-up was digitally printed. Symmetry and aesthetic parameters were assessed for each mock-up, and the opinion of dental professionals and laypeople about the aesthetic outcome of three mockups was assessed by an anonymous questionnaire. The 2D mock-up received the highest score, and this mock-up was found to be the most symmetrical, even though it had the longest operating times. There was a statistically significant difference (p = 0.000) between the scores given to this picture: experts in the dental field gave lower scores compared with non-professionals. Digital planning of aesthetic rehabilitation represents a technologically innovative procedure in dental practice, making it possible to achieve excellent aesthetic results, even when using open-source software

The Accuracy of Computer-Assisted Implant Surgery Performed Using Fully Guided Templates versus Pilot-Drill Guided Templates

Purpose. Computer-assisted stereolithographically guided surgery allows an ideal implant placement for prosthetic restoration. Two types of stereolithographic templates are currently available: a fully guided template and a pilot-drill guided template. The purpose of this study was (i) to evaluate the accuracy of implant insertion using these types of surgical templates and (ii) to define parameters influencing accuracy. Materials and Methods. 20 patients were enrolled and divided into 2 study groups: in group A, implants were placed using CAD-CAM templates with fully guided sleeves; in group B, implants were placed with a template with only pilot-drill guided sleeves. Pre- and postoperative computed tomographies were used to measure differences between final positions of implants and virtually planned positions. Three linear discrepancies (coronal, apical, and depth) and two angular ones (buccolingual and mesiodistal) were measured. Correlations between accuracy and jaws of interest, implant length and diameters, and type of edentulism were also analysed. Results. A total of 50 implants were inserted in 15 patients using CAD-CAM templates: 23 implants in group A and 27 in group B. The mean coronal deviations were 1.16 and 1.11 mm (P = 0.35), respectively; the mean apical deviations were 1.65 and 1.71 mm (P = 0.22); the mean depth deviations were 0.95 and −0.68 mm (P = 0.032); the mean buccolingual angular deviations were 4.16° and 6.72° (P = 0.042); and the mean mesiodistal ones were 2.81° and 5.61° (P = 0.029). In addition, the accuracy was statistically influenced only by implant diameter for coronal discrepancy (P = 0.035) and by jaw of interest for mesiodistal angulation (P = 0.045). Conclusion. Fully guided implant surgery was more accurate than pilot-drill guided surgery for different parameters. For both types of surgery, a safety margin of at least 2mm should be preserved during implant planning to prevent damage to nearby anatomical structures

Mechanisms of oxygenation responses to proning and recruitment in COVID-19 pneumonia

Purpose This study aimed at investigating the mechanisms underlying the oxygenation response to proning and recruitment maneuvers in coronavirus disease 2019 (COVID-19) pneumonia. Methods Twenty-five patients with COVID-19 pneumonia, at variable times since admission (from 1 to 3 weeks), underwent computed tomography (CT) lung scans, gas-exchange and lung-mechanics measurement in supine and prone positions at 5 cmH(2)O and during recruiting maneuver (supine, 35 cmH(2)O). Within the non-aerated tissue, we differentiated the atelectatic and consolidated tissue (recruitable and non-recruitable at 35 cmH(2)O of airway pressure). Positive/negative response to proning/recruitment was defined as increase/decrease of PaO2/FiO(2). Apparent perfusion ratio was computed as venous admixture/non aerated tissue fraction. Results The average values of venous admixture and PaO2/FiO(2) ratio were similar in supine-5 and prone-5. However, the PaO2/FiO(2) changes (increasing in 65% of the patients and decreasing in 35%, from supine to prone) correlated with the balance between resolution of dorsal atelectasis and formation of ventral atelectasis (p = 0.002). Dorsal consolidated tissue determined this balance, being inversely related with dorsal recruitment (p = 0.012). From supine-5 to supine-35, the apparent perfusion ratio increased from 1.38 +/- 0.71 to 2.15 +/- 1.15 (p = 0.004) while PaO2/FiO(2) ratio increased in 52% and decreased in 48% of patients. Non-responders had consolidated tissue fraction of 0.27 +/- 0.1 vs. 0.18 +/- 0.1 in the responding cohort (p = 0.04). Consolidated tissue, PaCO2 and respiratory system elastance were higher in patients assessed late (all p < 0.05), suggesting, all together, "fibrotic-like" changes of the lung over time. Conclusion The amount of consolidated tissue was higher in patients assessed during the third week and determined the oxygenation responses following pronation and recruitment maneuvers