Analysis of the peri-implant soft tissues in contact with zirconia abutments: an evidence-based literature review

The aim of this study is to evaluate through a literature review, the soft tissue response in contact with zirconia abutments, including case reports comparing prosthetics rehabilitations with zirconia and titanium abutments upto 3 years of follow-up as well as the factors that should be considered on implant's abutment selection. Metallic abutments can provide grayish color when in contact with thin soft tissues which may lead the implant prosthetic treatment to failure. In this context, the abutments of zirconia stand out because there is an excellent linking between esthetics and the health of peri-implant soft tissues. A consult of the published researches was made on the PubMed database from 2000 to September 2012. The including criteria were: literature reviews, clinical studies and case reports in English that focused on the response of the soft tissue in contact with zirconia implant abutments. The studies that were not in English and did not match the tackled issue were excluded. A total of 32 articles were found. According to the search strategy, just 16 articles were selected for this review. Three studies affirmed that zirconia abutments have an excellent soft tissue response; one study showed increased gingival recession with zirconia abutments and nine studies do not stand out any difference on biological behavior between titanium and zirconia abutments. Three studies affirmed that zirconia abutments provide natural gingival appearance, anatomic contour and greater esthetics. The use of zirconia abutments is recommended for anterior regions because of their greater optical properties and esthetic results and more studies should be performed and analyzed longitudinally regarding their biological response. The zirconia abutments have been established to be essential in order to achieve great esthetic results in cases of thin peri-implant soft tissues and in regions where the three-dimensional placement of implants is more superficial.

Zirconia-based dental crown to support a removable partial denture: a three-dimensional finite element analysis using contact elements and micro-CT data

Veneer fracture is the most common complication in zirconia-based restorations. The aim of this study was to evaluate the mechanical behavior of a zirconia-based crown in a lower canine tooth supporting removable partial denture (RPD) prosthesis, varying the bond quality of the veneer/coping interface. Microtomography (μCT) data of an extracted left lower canine were used to build the finite element model (M) varying the core material (gold core - MAu; zirconia core - MZi) and the quality of the veneer/core interface (complete bonded - MZi; incomplete bonded - MZi-NL). The incomplete bonding condition was only applied for zirconia coping by using contact elements (Target/Contact) with 0.3 frictional coefficients. Stress fields were obtained using Ansys Workbench 10.0. The loading condition (L = 1 N) was vertically applied at the base of the RPD prosthesis metallic support towards the dental apex. Maximum principal (σmax) and von Mises equivalent (σvM) stresses were obtained. The σmax (MPa) for the bonded condition was similar between gold and zirconia cores (MAu, 0.42; MZi, 0.40). The incomplete bonded condition (MZi-NL) raised σmax in the veneer up to 800% (3.23 MPa) in contrast to the bonded condition. The peak of σvM increased up to 270% in the MZi-NL. The incomplete bond condition increasing the stress in the veneer/zirconia interface.

Medicinal plants in pregnancy and lactation: perception of the health risk and practical educational group in Araraquara, São Paulo State, Brazil

The use of medicinal plants among pregnant women and lactating is a common practice in diverse countries. However, many medicinal plants are contraindicated during pregnancy and lactating, due to various adverse effects, such as teratogenic, embryotoxic and abortive effects, exposing these women, their fetus and babies to health unknown risks. Thus, the purpose of this commentary, was to analyze the perception about the use of medicinal plants by pregnant women and lactating registered in the "baby on board" NGO, Araraquara, São Paulo state, Brazil, between 2010 at 2013. The group was constituted by 48 women, between the first and last trimester of pregnancy or whilst breastfeeding. Information was collected during group meetings by oral interview, using a questionnaire, as script. The nature of the study was a qualitative analysis. The results were based on reports about the use of medicinal plants by pregnant women during group meetings: use, indication of use, knowledge about risks. All participants received written and oral information about the study and they gave a written informed consent. The use of medicinal plants is a reality among pregnant and lactating women of the "baby on board" NGO. They reported that they feel that "natural" products are not harmful for their health. The primary information sources for the majority of women about medicinal plants during pregnancy are family, neighbors and herbalists. The plants most cited (in popular name in Brazil) were: senna, chamomile, boldo, lemon balm, lemon grass. They were used mainly for: nausea, heartburn, indigestion, flatulence, intestinal and abdominal pain, anxiety, intestinal constipation and low milk production. The pregnant and lactating women lacked knowledge about the health risks of the use of medicinal plants and herbal medicines in pregnancy and lactation. They also reported difficulties in clarifying some questions about the use of medicinal plants with their doctors. The results of the present study showed that educative actions about the rational use of medicinal plants in pregnancy and breastfeeding could be part of the operating protocols to promote the maternal and child health programs in Araraquara. Thus, our results also suggest the importance of creating institutionalized places, to the implementation of continued education programs about rational use of medicinal plants in pregnancy and lactation. These targeted programs are not only for health professionals, but also for community members, pregnant women and breastfeeding. Our results pointed out the importance of guidance of doctors and healthcare professionals on the scientific studies about medicinal plants and herbal medicines and the risk/benefit of using herbs during pregnancy. Finally, it is noted the importance of the health professionals to inform women of childbearing on risks to their health, as well as on possibilities of utilization of herbs during fertile period, giving special attention to the potential risk of self-medication.

Chaos control and sensitivity analysis of a double pendulum arm excited by an RLC circuit based nonlinear shaker

In this paper the dynamical interactions of a double pendulum arm and an electromechanical shaker is investigated. The double pendulum is a three degree of freedom system coupled to an RLC circuit based nonlinear shaker through a magnetic field, and the capacitor voltage is a nonlinear function of the instantaneous electric charge. Numerical simulations show the existence of chaotic behavior for some regions in the parameter space and this behaviour is characterized by power spectral density and Lyapunov exponents. The bifurcation diagram is constructed to explore the qualitative behaviour of the system. This kind of electromechanical system is frequently found in robotic systems, and in order to suppress the chaotic motion, the State-Dependent Riccati Equation (SDRE) control and the Nonlinear Saturation control (NSC) techniques are analyzed. The robustness of these two controllers is tested by a sensitivity analysis to parametric uncertainties.