A study to evaluate the impact of a new mouth gel on dental health Minimising the degradation and loss of enamel is an important aspect of good dental health. A company has recently developed a new gel (S290-Sparkle) that it believes applying in advance of every meal will help to protect teeth from the wear and tear caused by acidic or abrasive materials in food and drink. The company has already recruited a group of volunteers for a study designed to evaluate the effectiveness of S290-Sparkle. The volunteers are all adults who live in the UK and have been screened by an expert nutritionist to confirm that they eat a balanced and broadly similar diet. The company has also assembled a panel of expert dentists who evaluated each volunteer at the point of recruitment to confirm that they all had good dental health, did not have any dental prostheses (e.g. dentures, crowns, veneers, bridges) and followed good oral health practices (e.g. regular tooth brushing). Following the study, the panel will evaluate the participants and produce a 'dental health score' for each person. What are the dependent and independent variables in this study