Question

part 2: free response: answer each question in the space provided.

1. dental cavities, also known as caries, are primarily caused by bacteria streptococcus mutans and lactobacilli. bacteria thrive in the presence of sugar and produce acid as a by - product, which can lead to demineralization of tooth enamel. if left untreated, this process can result in tooth pain, infection, and eventual tooth loss. teeth are composed of minerals such as calcium and phosphate, making them particularly sensitive to changes in ph. a low ph environment around the teeth, often caused by the acids produced by these bacteria, can lead to the erosion of enamel and the formation of cavities. to evaluate the effectiveness of two new toothpastes, researchers conducted an experiment with three groups of patients. initially, the baseline ph levels of all patients’ upper molars were measured. after exposure to sugar, the ph levels were recorded again. the first group rinsed their mouths with water. the second group was instructed to brush their teeth for two minutes with toothpaste a. the third group was instructed to brush their teeth for two minutes with toothpaste b. the researchers then measured the ph levels on the upper molars of all three groups after the treatments. the summarized data is presented in table 1.

(a)
(i) identify the independent and dependent variables in the experiment. (1 pt)
(ii) state a null hypothesis for the experiment. (1 pt)
(iii) identify the control group(s) for the experiment. (1 pt)
table 1

treatment group	mean ph before sugar	mean ph on upper molars (± 2 sex)	mean ph after sugar	mean ph after treatment
rinsing with water	7.2 ± 0.2	6.6 ± 0.2	6.5 ± 0.2	7.2
brushing with toothpaste a	7.3 ± 0.1	6.3 ± 0.2	6.7 ± 0.2	7.2
brushing with toothpaste b	7.2 ± 0.2	6.5 ± 0.2	6.6 ± 0.2	7.2

(b) using the template in the space provided for your response, construct a bar graph that represents the data shown in table 1. your graph should be appropriately plotted and labeled. (3 pts)
(c) based on the data in table 1, evaluate the effectiveness of the new toothpastes in restoring the ph of the upper molars to their initial (pre - sugar) values. (1 pt)
(d) the new toothpaste being tested works by changing the chemical environment of the mouth. explain how this change might affect the proteins produced by streptococcus mutans and lactobacillus bacterial activity. (1 pt)

Explanation:

(i) The independent variable is the treatment (rinsing with water, brushing with toothpaste A, brushing with toothpaste B). The dependent variable is the mean pH level on the upper molars. This is because the treatment is being manipulated to observe its effect on the pH level.
(ii) A null hypothesis could be: There is no difference in the mean pH levels of the upper molars after treatment with water, toothpaste A, and toothpaste B.
(iii) The control group is the group that rinsed with water. This group serves as a baseline to compare the effects of the toothpastes.
(b) To construct a bar - graph, the x - axis would have the treatment groups (rinsing with water, brushing with toothpaste A, brushing with toothpaste B). The y - axis would have the mean pH levels. Each treatment group would have multiple bars representing the mean pH before sugar, after sugar, and after treatment.
(c) Toothpaste A seems to be more effective in restoring the pH of the upper molars to their initial values as the final mean pH (7.2) is closest to the pre - sugar mean pH (7.3). Toothpaste B also shows some effectiveness but not as much as toothpaste A.
(d) If the toothpaste changes the chemical environment of the mouth, it could potentially denature or inhibit the function of the proteins produced by Streptococcus mutans and Lactobacillus. This could reduce the bacteria's ability to produce acid from sugar, thus preventing or reducing the formation of cavities.

Answer:

(i) Independent variable: Treatment (rinsing with water, brushing with toothpaste A, brushing with toothpaste B). Dependent variable: Mean pH level on upper molars.
(ii) There is no difference in the mean pH levels of the upper molars after treatment with water, toothpaste A, and toothpaste B.
(iii) The group that rinsed with water.
(c) Toothpaste A is more effective in restoring pH to initial values compared to toothpaste B.
(d) It could denature or inhibit the function of bacterial proteins, reducing acid production.