Applications of Sustainable Polymer-Based Phase Change Materials in Mortars Composed by Different Binders

Eco-sustainable, low toxic and low flammable poly-ethylene glycol (PEG) was forced into flakes of the porous Lecce stone (LS), collected as stone cutting wastes, employing a very simple cheap method, to produce a “form-stable” phase change material (PCM). The experimental PCM was included in mortars based on different binders (hydraulic lime, gypsum and cement) in two compositions. The main thermal and mechanical characteristics of the produced mortars were evaluated in order to assess the effects due to the incorporation of the PEG-based PCM. The mortars containing the PEG-based PCM were found to be suitable as thermal energy storage systems, still displaying the characteristics melting and crystallization peaks of PEG polymer, even if the related enthalpies measured on the mortars were appreciably reduced respect to pure PEG. The general reduction in mechanical properties (in flexural and compressive mode) measured on all the mortars, brought about by the presence of PEG-based PCM, was overcome by producing mortars possessing a greater amount of binder. The proposed LS/PEG composite can be considered, therefore, as a promising PCM system for the different mortars analyzed, provided that an optimal composition is identified for each binder.

The Effect of Surface Treatments on the Shear Bond Strength of Indirect Esthetic Restorative Materials to Dentin

AIM: The purpose of this research was to evaluate the influence of air abrasion, hydrofluoric acid, and combination of air abrasion and hydrofluoric acid on the shear bond strength between dentin and CEREC, VITA VM7, and E-max. MATERIAL AND METHODS: Ninety extracted human lower molars were used. The teeth were divided into three groups (n = 30) according to the surface treatment (air abrasion, hydrofluoric acid, and air abrasion + hydrofluoric acid). Each group was then subdivided into three subgroups (n = 10) according to the ceramic material (CEREC, E-max, and VITA VM7). Shear bond strength was determined by the compressive mode of force applied at the ceramic-tooth interface. The collected data were analysed using two-way analysis of variance (ANOVA), and Tukey’s post-hoc test statistical significance was set at P < 0.05. RESULTS: The highest mean shear bond strength value was recorded with the CEREC group treated by hydrofluoric acid (8.01MPa). While the least mean shear bond strength was recorded with the Cerec group but when treated by air abrasion alone, it was 4.33MPa. CONCLUSION: Hydrofluoric acid etching for various types of ceramic restoration improved the bond strength to dentin.

Observations of Thoracic Neuromuscular Oscillation Subsequent to Thoracic Pathology

In this paper we propose that a tremor occurring over a thoracic myotomal region as representative of a motor manifestation of thoracic radicular injury. We term this process thoracic neuromuscular oscillation. It is characterized by synchronous firing of the unilateral oblique muscles at one or more adjacent thoracic myotomal distributions at a frequency of 8 to 10 Hz. Six cases of observed regular continuous abdominal wall muscular tremor occurring after traumatic thoracic spine pathology are presented. These cases were drawn retrospectively from patient files obtained over 20 years. We refer to this tremor, measured to be 8–10 Hz, as thoracic neuromuscular oscillation. The neuromuscular oscillation was influenced by mechanical forces, specifically spine loading in either a bending or compressive mode. In some cases, cervical position modulated the tremor. Other examples of thoracic spine pathology that occurred comorbid to thoracic neuromuscular oscillation are noted.