The impact of glass ionomer cement and composite resin on microscale pH in cariogenic biofilms and demineralization of dental tissues

OBJECTIVE

Secondary caries is among the most frequent reasons for the failure of dental restorations. Glass ionomer cement (GIC) restorations have been proposed to protect the surrounding dental tissues from demineralization through the release of fluoride and by buffering the acid attack from dental biofilms. In contrast, the lack of buffering by composite resin (CR) restorations has been suggested as a promoting factor for the development of secondary caries.

METHODS

The present study employed transversal microradiography and confocal microscopy based pH ratiometry to quantify mineral loss and map microscale pH gradients inside Streptococcus mutans biofilms grown on compound specimens consisting of enamel, dentin and either GIC or CR.

RESULTS

Mineral loss in dentin was significantly lower next to GIC than next to CR, but no significant differences in local biofilm pH were observed between the two restorative materials.

SIGNIFICANCE

The cariostatic effect of GIC relies predominantly on the provision of fluoride and not on a direct buffering action. The lack of buffering by CR did not affect local biofilm pH and may therefore be of minor importance for secondary caries development.

Investigating Equestrians' Perceptions of Horse Happiness: An Exploratory Study

Happiness is a subjective feeling and associated with positive affective states that can indicate good welfare. It is becoming increasingly agreed that equestrians' ability to recognize indicators of positive emotions has the potential to enhance overall horse wellbeing, but research in this area is limited. Therefore, this study investigated equestrians' perceptions of horse happiness. A survey comprising 25 questions was distributed through equestrian-related social media (internationally) and yielded 332 valid responses. Frequency analysis was conducted within each factor category (e.g., rider type). Pearson chi-squared and Fisher's exact test determined if differences occurred between the tested factor categories (significance level: P < .05). The majority of respondents believed that they were able to recognize when their horses were happy (94%, n = 332; P < .0001) whilst 92.8% (n = 332; P < .0001) believed that their horses could be described as happy. The majority of participants who indicated that they were able to recognize when their horses were happy also believed that their horses were: happy when they interacted with them (98.3%, n = 295; P < .001); when they rode them (83%, n = 270; P < .0001); when they worked them (i.e., unmounted work) (82.7%, n = 312; P < .0001). The largest respondent proportion believed that horses who were very "forward"/energetic every time they were being ridden could be best described as "rather happy" (36.4%, n = 332). Owners more frequently believed that horses were "rather happy" if they did not react to loud noises/scary objects (30.9%, n = 285; P < .013). These results suggest that some equestrians may have overconfidence in interpreting equine affective states. Furthermore, some respondents may have incorrectly perceived behaviors potentially indicating negative emotions as indicators of happiness.

Comparison of the Head and Neck Positions in Ridden Horses Advertised in an Australian Horse Sales Magazine: 2005 Versus 2018

The impact of head and neck position (HNP) on horse welfare has received much attention in the scientific literature within the last two decades. Studies have identified physiological and behavioral signs of distress in horses ridden for prolonged time in an HNP with their noseline behind the vertical (BTV), which may compromise their welfare. The objective of this study was to compare potential differences of HNPs shown in horse sales photographs advertised in an Australian horse sales magazine (Horse Deals) from the years 2005 and 2018. In addition, factors potentially impacting HNPs, such as type of tack presented in (e.g., noseband type), riding discipline, and competition experience of the horse, were investigated. The sample population (n = 570) comprised horses ridden with headgear and bit in walk, trot, or canter/gallop, advertised in an Australian horse sales magazine. Issues from April 2005 and October/November 2018 were selected. Head and neck position was categorized as BTV, on the vertical (OV), slightly in front of the vertical (IFV), or extremely in front of the vertical (EIFV; any HNP >30° IFV). Data were analyzed using the chi-squared test and post hoc testing via a multiple regression approach through SPSS and test of proportions via the Z-score calculator for two independent population proportions. Analysis of combined data from years 2005 and 2018 showed 47.0% (n = 570) of the horse sample population were advertised with HNPs BTV. Behind-the-vertical HNP was observed as the predominant HNP (57.8%; n = 268) in the warmblood/eventers/show/performance (WESP) category (P < .0005). In 2005, 53.4% (n = 303) of the sample population were ridden BTV compared with 39.7% (n = 267) in 2018 (P < .001), 12.9% (n = 303) were OV in 2005 compared with 15.0% (n = 267) in 2018 (P > .05), and 10.9% (n = 303) were IFV in 2005 compared with 27.3% (n = 267) in 2018 (P < .0004). These results suggest a positive development with fewer vendors/riders selecting images where the horse's nose was BTV. However, this may be explained by the larger proportion of horses advertised in the WESP category in 2005 (63.0%; n = 303) versus 2018 (28.5%; n = 267), and the WESP category predominantly comprised of dressage, jumper, and eventing horses. In addition, the reduction of HNPs BTV from 53.4% (n = 303) in 2005 to 39.7% (n = 267) in 2018 could be attributed to the observation that in 2018, a larger proportion of horses were listed in categories that do not require the horses to be worked with a flexed HNP referred to as "on-the-bit" (e.g., western, endurance, Australian sStock horses). The HNP BTV remains preferential by a substantial proportion of the horse-owning public when advertising horses for sale, particularly in disciplines where the horse is worked in a flexed HNP or "on-the-bit."