Strain controlled oxygen vacancy formation and ordering in CaMnO3_3

We use first-principles calculations to investigate the stability of bi-axially strained \textit{Pnma} perovskite CaMnO$_3$ towards the formation of oxygen vacancies. Our motivation is provided by promising indications that novel material properties can be engineered by application of strain through coherent heteroepitaxy in thin films. While it is usually assumed that such epitaxial strain is accommodated primarily by changes in intrinsic lattice constants, point defect formation is also a likely strain relaxation mechanism. This is particularly true at the large strain magnitudes ($>$4%) which first-principles calculations often suggest are required to induce new functionalities. We find a strong dependence of oxygen vacancy defect formation energy on strain, with tensile strain lowering the formation energy consistent with the increasing molar volume with increasing oxygen deficiency. In addition, we find that strain differentiates the formation energy for different lattice sites, suggesting its use as a route to engineering vacancy ordering in epitaxial thin films.Comment: 7 pages, 7 figure

New technologies to improve root canal disinfection

Effective irrigant delivery and agitation are prerequisites to promote root canal disinfection and debris removal and improve successful endodontic treatment. This paper presents an overview of the currently available technologies to improve the cleaning of the endodontic space and their debridement efficacy. A PubMed electronic search was conducted with appropriate key words to identify the relevant literature on this topic. After retrieving the full-text articles, all the articles were reviewed and the most appropriate were included in this review. Several different systems of mechanical activation of irrigants to improve endodontic disinfection were analysed: manual agitation with gutta-percha cones, endodontic instruments or special brushes, vibrating systems activated by low-speed hand-pieces or by sonic or subsonic energy, use of ultrasonic or laser energy to mechanically activate the irrigants and apical negative pressure irrigation systems. Furthermore, this review aims to describe systems designed to improve the intracanal bacterial decontamination by a specific chemical action, such as ozone, direct laser action or light-activated disinfection. The ultrasonic activation of root canal irrigants and of sodium hypochlorite in particular still remains the gold standard to which all other systems of mechanical agitation analyzed in this article were compared. From this overview, it is evident that the use of different irrigation systems can provide several advantages in the clinical endodontic outcome and that integration of new technologies, coupled with enhanced techniques and materials, may help everyday clinical practice

The New Elderly Patient: A Necessary Upgrade

The elderly individual is becoming the most common patient in clinical practice due to the increasing average life span, especially in developed countries. The current elderly patients are different from those of some decades ago. They usually have an active social life, want to be informed, and are actively involved in the current society with consequent high expectations for medical and dental treatment. However, not all the elderly patients are like this. Some of them show limited financial resources, reduced mental and manual skills, and poor motivation. The purpose of this communication is to make a brief characterization of the new elderly population in view of prosthetic and dental management

The impact of endodontic anatomy on clinical practice: a micro-CT study and tribute to Prof. Francesco Riitano

Aim: To evaluate the quality of root canal preparation using two different mechanical NiTi systems. Methodology: 40 maxillary and mandibular molars were selected. Specimens were randomly assigned to two groups and were scanned using a micro-computed tomography scanner before and after root canal preparation that was performed using ProFile instrument sequence and Reciproc single file technique. Each system was used to obtain an optimal apical size for each specimen, following common clinical guidelines. 3D models were reconstructed and evaluated for volume, areas and root canal axis. The total volume of dentine removed and the volume of the coronal, middle and apical thirds of each root canal were calculated, as well as the average deviation of the root canal axis at different levels and the values compared. Student t-test was used to determine the difference between the two experimental groups (P < 0.05). A qualitative evaluation of root canal preparation was also performed. Results: No statistically significant differences were noted between the groups in the volume of dentine removed after root canal preparation, except for the volume of the coronal third (P < 0.05) and the volume of the apical third (P < 0.05) of the disto-buccal canal of maxillary molars and in the mesial canals of mandibular molars, where ProFile instruments produced significantly less enlarged canal volume in the apical third and more enlarged canal volume in the coronal third (P < 0.05). No statistically significant differences were found in the root canal axis deviation. Conclusions: Under the conditions of this study, both the systems analyzed were able to prepare molar teeth with similar amount of dentine removal and a relatively low risk of procedural errors

Implant insertion torque value in immediate loading : a retrospective study

The aim of this study is to verify if the Insertion Torque Value (ITV) of 32 Ncm for immediate loading protocol (ILP), as indicated by literature, is still, with the advance in implant research, a real significant cut-off for long-term implant survival. In this retrospective study, data from 224 patients that during three years of clinical practice, were submitted to the insertion of 322 implants with immediate loading protocol, have been recorded, pooled and analyzed. Data were organized based on Insertion Torque Value (ITV): > 32 Ncm (CG) and 32 Ncm are still characterized by a lower crestal bone resorption, there are no statistically significant differences among the two groups for what concerning the failure rate during the 2 years of follow-up and OR. These results permit us to suppose that the cut-off of ITV >32 Ncm for immediate loading implants, could be reduced to inferior values. However further studies are necessary to indicate precise clinical guidelines

Efficacy of sonic and ultrasonic irrigation devices in the removal of debris from root canal irregularities in artificial root canals

Objective: to evaluate the efficacy of different sonic and ultrasonic devices in the elimination of debris from canal irregularities in artificial root canals. Materials and Methods: a resin model of a transparent radicular canal filled with dentin debris was used. Five groups were tested, namely: Group 1 - ultrasonic insert 15.02; Group 2 - ultrasonic insert 25/25 IRRI K; Group 3 - ultrasonic insert 25/25 IRRI S; Group 4 - sonic insert 20/28 Eddy on a vibrating sonic air-scaler handpiece; Group 5 - 20.02 K-file inserted on a Safety M4 handpiece. Two different irrigants (5% sodium hypochlorite and 17% EDTA) and 3 different times of activation (20, 40, and 60 seconds) were tested. Means and standard deviations were calculated and statistically analyzed with the Kruskal-Wallis and Wilcoxon tests (p0.05). Conclusions: no significant differences were found between 5% sodium hypochlorite and 17% EDTA. When the time of activation rises, the dentin debris removal increases in all groups. Both sonic and ultrasonic activation demonstrate high capacity for dentin debris removal