Improved Wear-Resistant Performance of Epoxy Resin Composites Using Ceramic Particles

This work investigated the effects of using a new fabrication technique to prepare polymer composite on the wear-resistant performance of epoxy resin composites under dry friction conditions. Polymer composite samples with different weight contents of silicon carbide (SiC) particles were manufactured. This paper addresses the wear behavior of the obtained samples. With the suggested technique, the samples were prepared from epoxy/silicon carbide particles using a layer of thin kraft paper to prevent the sedimentation of the ceramic particles and to control the weight content of ceramic in the polymer. Kraft paper was used as a layer in the polymer composite. The hardness, wear resistance, and water absorption capacity of the produced epoxy composite samples prepared using the kraft paper technique were evaluated. The morphology of epoxy composite samples showed a significant improvement in the ceramic distribution and enhancement of interface bonding between ceramic and the polymer. The hardness values of the developed polymer composites were enhanced by up to 42.8%, which was obtained at 18 wt.% SiC particles. Increasing the ceramic content in the epoxy also led to the enhancement of wear resistance compared with pure epoxy. The results of the microstructure study also showed that the kraft paper layers helped in maintaining the distribution of the ceramic particles according to the previously specified content in each layer in the sample. Wear tests showed that the wear rate of the polymer composite decreased with the increase in the ceramic content. This study provides a new recycling method for using old kraft paper in polymer composite manufacturing to improve the distribution of ceramic particles in the polymer matrix.

Long-Term Follow-Up of Restorations of Equine Cheek Teeth Infundibula (2006–2017)

Background:Caries of the infundibula of equine cheek teeth can lead to significant dental disease including increased attritional wear, pulpar and apical disease, secondary sinusitis, and dental fracture. Restorations of cavities of equine cheek teeth infundibula have been performed since 1889. Recent advances in dental materials, instrumentation, and techniques have facilitated the use of dental restoration techniques by equine veterinary practitioners. No studies to date have demonstrated the safety or efficacy of restorations of equine cheek teeth infundibula.Objectives:To assess the long-term results of restorations of equine cheek teeth affected by infundibular caries, to report on the safety of the procedure, and to give guidelines for future restorative therapies.Study Design:Retrospective analysis of results of clinical and oroscopic examination of horses that underwent infundibular restoration procedures between 2006 and 2017.Methods:A total of 223 infundibula in 185 maxillary cheek teeth in 92 horses were restored using a variety of dental materials including glass ionomer cement, flowable and compactible resin composites. The time between restoration and re-examination was recorded along with findings of clinical signs in the interim, restorative material loss, and any further pathological changes of the teeth including caries progression, fracture, or apical disease. Follow-up examinations were performed over two study periods 2006–2012 and in 2017.Results:Over the full study period, 99% of treated horses available for follow-up examinations had no adverse clinical signs or developed any abnormalities of restored teeth observable on oroscopic examination. Of horses re-examined, 83% of restorations were shown to have minimal or no loss of the restoration material, with occlusal surface wear visibly comparable to other adjacent maxillary teeth. Statistical analysis showed success of the procedure was related to the restorative material used, the restoration technique, and the caries grade present at the time of restoration (grade 2 is more successful than grade 3).Main Limitations:There are no case controls in this study and therefore it is not clear if restoration of equine infundibula is a consistently beneficial procedure, or at which grade of caries progression restorations should be performed for optimum benefit. The procedures were not re-examined at consistent regular times creating some difficulties in standardizing results. Re-examinations of treated horses did not consistently include radiography or computed tomography and therefore some apical changes may have occurred in treated teeth without visual oroscopic or external clinical signs.Conclusion:Restoration of equine infundibula using materials developed for human dentistry including flowable resin composites is a safe and long-lasting procedure and appears to prevent the development of further pathological changes including apical infection and dental fracture.

The Effect of Mouthrinses on Surface Roughness of Two Nanohybrid Resin Composites

Objective: The aim of this study was to evaluate the effect of four different mouthrinses on the surface roughness of two nanohybrid resin composites. Material and Methods: Fifty samples were prepared for each of the resin composites (2x8 mm) and a profilometer was used to determine the initial surface roughness (Ra) of each sample. Then, they were divided into 5 subgroups (n= 10), and exposed to the following mouthrinses (12h, 37 ºC): containing alcohol and essential oils; alcohol and chlorhexidine; alcohol-free and essential oils; alcohol free and cetil prydinium chlorite; or distilled water (control). The surface roughness of each sample was measured again. Statistical analyses of the data were performed via two-way ANOVA and Bonferroni tests. Results: Overall, statistically significant differences were not found between the resin composites (p> 0.05), but significant differences were found among the mouthrinses (p< 0.05). Interactions between the mouthrinses and the resin composites was statistically significant (p< 0.05). Both of the resin composites had the highest surface roughness after exposure to mouthrinse with alcohol and essential oils (p< 0.05), followed by mouthrinse with alcohol and chlorhexidine. Both alcohol-free mouthrinses caused surface roughness either similar to distilled water (p> 0.05) or lower than distilled water (p< 0.05) on the nanohybrid resin composites used. Conclusion: The mouthrinses affected the surface roughness of the resin composites in different ways. This was dependent on mouthrinse contents and the chemical structure of the resin composites. Alcohol-containing mouthrinses caused the most changes in the surface roughness of both resin composites. Keywords Alcohol; Chlorhexidine; Composite resin; Essential oil; Roughness.