Oral health–related quality of life (OHRQOL) of preschool children’s anterior teeth restored with zirconia crowns versus resin-bonded composite strip crowns: a 12-month prospective clinical trial

Objectives To compare oral health–related quality of Life (OHRQOL) of preschool children’s anterior teeth restored with prefabricated zirconia crowns (ZC) versus resin-bonded composite strip crown (RCSC). Materials and methods A prospective clinical trial included 136 children with early childhood caries aged 36–71 months who were assigned into prefabricated ZC and RCSC groups. A total of 344 teeth were restored either with 170 ZCs (49.4%) and 174 RCSCs (50.6%). Wilson and Cleary’s conceptual model was to associate the study predictors to the OHRQOL. Early Childhood Oral Health Impact Scale (ECOHIS) was used to assess the OHRQOL at 6 and 12 months. Mann–Whitney U test was used in comparing OHRQOL mean scores in the two groups and Wilcoxon signed-rank test with the effect size (r) to measure the intragroup OHRQOL change. A Poisson regression model was used to study potential risk factors associated with the overall OHRQOL. Results After 12 months, the USPHS parameters of the ZC were significantly superior compared to the RCSC. Overall ECOHIS mean scores in the ZC group were significantly lower than that of the RCSC group at T1 and T2 (p < 0.001). Remarkable enhancement of the OHRQOL at the follow-ups with a large effect size (r < 0.8) was observed. Restoration type, retention, baseline OHRQOL, and color had a significant impact on the overall OHRQOL at 12 months. Conclusions Preschool children OHRQOL treated with ZC were significantly better than those who received RCSC. Clinical relevance One of the optimum treatment standards in pediatric dentistry is the esthetic demand which has significance on the child’s OHRQOL and subsequently child’s general health quality of life. It is beneficial to the dentist to identify the influence of esthetic restorations on the OHRQOL of preschool children which aids in future decision-making. The longitudinal nature of the study enables the dentist to identify the changes of children’s OHRQOL.

Selected Properties of Cement Bound Spruce and Larch Bark Bio-Aggregates

The aim of this study is to investigate the suitability of spruce and larch bark for the production of cement-bonded composites. At the beginning of this research, the curing behaviour of the admixtures was quantified with temperature profiles when testing spruce, larch, pine and poplar bark, to determine the compatibility between the components of the bio-aggregates, to analyse the cement curing and to establish which bark species should be successfully included in cement bonded composites. Considering the results, it was observed that the average densities of 600–700 kg/m3 of bio-aggregates are 40–55% lower than that of established products on the market, although spruce and larch bark are in a similar range. The situation is different for the compressive strength, as larch bark showed up to 30% higher values than spruce bark. This study revealed also different hardening characteristics of the two cement types used as binders for spruce and larch bark. The results of this study demonstrated that tree bark of Picea abies and Larix decidua Mill. can be successfully utilized for the production of a cement-bonded composite material.

Curing monitoring of bonded composite patch at constant temperature with electromechanical impedance and system parameters evaluation approach

As one of cost-effective maintenance methods, bonded composite patch repair has been receiving more and more attention in the engineering community since past decades. However, realizing real-time monitoring for curing process of bonded repair patch is difficult for most current techniques. In our work, a method based on electromechanical impedance and system parameters evaluation for structural health monitoring issues was developed, which could implement the online monitoring throughout whole curing process. Compared with the dynamic thermomechanical analysis results, the experiment data matches well. It demonstrates that the proposed approach can effectively monitor the curing process of composite repair patch at a constant temperature of 120 °C. Hence, the presented approach in this paper is expected to be a novel, robust, and real-time monitoring method for structural maintenance with the composite patch.

Experimental characterization of Mode II fatigue delamination growth onset in composite Joints

In this article, the structural behavior of co-cured composite joint (CC), co-bonded composite joint (CB), and secondary-bonded composite joint (SB) under Mode II fatigue loading was evaluated. Fatigue performance was evaluated in sub-critical strain energy release rate (SERR) associated with Mode II fatigue induced delamination growth onset. Fatigue tests were carried out using the three-point bending End Notched Flexure test setup for different energy ratios. The experimental results are presented in terms of SERR versus number of cycles, and the SERR threshold for no growth is determined (Gth). Fractographic analyses were performed in order to identify the main failure mechanisms related to each joining technology under Mode II. The results indicated an initial cohesive failure followed by an adhesive failure promoted by crack propagation at the interface between the adhesive and the composite adherend on SB and CB samples, through the coalescence of microcracks that promote the adhesive failure process, leading to fiber pull-out from the matrix and cusps formation in the fracture surface. These results explain the low performance behavior observed on SB and CB bonded techniques. It is worth mentioning that the results and behavior observed in this work are valid only for the laminates, adhesives, surface treatment, and environmental conditions tested herein.