Publication No. 12790
Student Laboratory Kit
Materials Included In Kit
Alizarin red solution, 50 mL
Zirconyl chloride solution, 50 mL
Cotton swabs, 75
Microscope slides, plastic, 72
pH test paper, 6.0–8.0, 1 roll
Pipets, Beral-type, 90
Test tubes, 10 x 75 mm, 60
Additional Materials Required
Beakers, 250-mL, 5 per group
Graduated cylinder, 100-mL, 1 per group
Microscope, 1 per group
Stirring rod, 1 per group
Test tube rack, 1 per group
Toothpaste samples (5 different types)
Toothpaste is considered a non-hazardous material; however, any material that has been in the lab should not be put in the mouth. Zirconyl chloride solution contains hydrochloric acid which is toxic by ingestion or inhalation and corrosive to body tissue. Alizarin red solution is a body tissue irritant. Use these chemicals in a fume hood and avoid all contact with eyes, skin and clothing. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All solutions may be flushed down the drain with water according to Flinn Suggested Disposal Method #26b.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering PracticesAnalyzing and interpreting data
Engaging in argument from evidence
Developing and using models
Disciplinary Core IdeasMS-PS1.A: Structure and Properties of Matter
MS-ETS1.B: Developing Possible Solutions
HS-ETS1.A: Defining and Delimiting Engineering Problems
HS-ETS1.B: Developing Possible Solutions
HS-ETS1.C: Optimizing the Design Solution
Crosscutting ConceptsSystems and system models
Structure and function
MS-ETS1-2: Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.
Answers to Questions
Consumer Reports, September 1992; pp 602–606.
Whitens teeth! Freshens breath! Fights cavities! Removes plaque! Toothpaste ads make all sorts of promises, but are these claims true? Is one toothpaste really superior to another? Does it make sense to buy the more expensive brand? These questions will be answered as you learn about the tooth and tooth decay as well as about the role of toothpaste in maintaining healthy teeth.
In order to appreciate the function of toothpaste, an understanding of the parts of the tooth, how tooth decay occurs, and how it can be prevented is important.
The crown is covered by a glossy, white, hard coating called enamel. Enamel is composed primarily of calcium salts and is the hardest substance in the body. Enamel, in spite of its toughness, can be damaged or worn down by abrasive action, injury or acids.
The main mass of a tooth is located beneath the protective enamel. This bone-like calcified tissue is called dentin. Dentin is not as hard as the enamel, which makes it more susceptible to tooth decay. In a healthy tooth, this is not a cause for worry because there is only a shallow crevice between the enamel and the firm, pink gum, exposing little or no dentin. However, in a tooth with receding gums, a pocket forms around the tooth where the gum has pulled away from the tooth. Thus, dentin is exposed and is much more likely to decay (see Figure 2).
The dentin surrounds the tooth’s soft central cavity called the pulp cavity. This cavity contains blood vessels, nerves and connective tissue (pulp). The blood vessels and nerves reach this cavity through tubular root canals which extend upward into the root.
So why does tooth decay occur? Less than one minute after the teeth receive a thorough cleaning, a thin, transparent film called the pellicle begins to coat the teeth, tongue and gums. This film, derived from proteins in saliva, anchors bacteria and collects stains from food, drink and tobacco. The pellicle is swarming with bacteria which reproduce and then live in the sticky, gel-like substance known as plaque. The bacteria in the plaque ferment the sugars in foods to produce acids, which attack the tooth enamel. When enough erosion of the enamel has occurred, microorganisms can pass through the weakened barrier to begin the decay process on the interior dentin. The result is dental caries, better known as tooth decay or cavities.
Over time, plaque deposits bond with minerals in saliva to form tartar, also called calculus, a calcified or hardened deposit that only professional cleaning can remove. Calcification can start within 2 to 14 days of plaque formation. Plaque can also seep below the gumline and cause gingivitis, a mild gum disease causing gum inflammation. With more extreme gum recession and prolonged neglect, plaque can form in the periodontal pockets and can attack the deeper tissue and bone causing periodontitis, a severe gum disease.
So what is the key to keeping the teeth free of cavities and disease? The key lies in the frequent removal of the accumulated plaque. This feat depends mainly on grinding it away with a good dental abrasive. With daily removal of plaque, the minerals normally present in saliva replace those on the teeth that may have been removed by mouth acids. To be effective as a dental abrasive, the grinding agent must be harsh enough to remove food residue, pellicle, accumulated plaque and tartar, yet not so harsh as to grind away at the enamel itself. Typical abrasives include salts of calcium, magnesium, aluminum or titanium (see Table 1).
The Food and Drug Administration considers the abrasive to be the active ingredient in toothpaste and it is usually present at ~27%. Toothpaste also has other ingredients in specific proportions, each with its own important function (see Table 2). Water, which is a solvent and filler, is the most abundant ingredient at 37%. The second most abundant ingredient at ~32% is a humectant which helps maintain the consistency and moisture content of the paste. Glycerin is a common humectant. A common standard for toothpaste states that when it is heated to 45 °C and kept there for 28 days, toothpaste should not form a gas, separate, or ferment. It must not run out of the tube if the cap is left off and the tube is on its side, nor should it sink into the bristles of the toothbrush as soon as it is applied. On the other hand, it should not be so firm as to roll off the brush under normal use.
A small amount of detergent, or surfactant, is added to most toothpaste formulations as a foaming agent. While this detergent is not a principal protection against tooth decay, it aids in the removal of plaque and loose debris from the mouth and also gives the sense of cleanliness.
Fluoride is included at about 0.1 percent concentration in most brands to fight decay by helping to maintain the strength of the enamel. The fluoride seems to act in two ways. First it speeds the replacement of some of the mineral on the enamel, converting it to a harder mineral more resistant to corrosion by acids. Second, it suppresses the bacteria’s ability to generate acids.
Other toothpaste additives include preservatives, thickeners, colors, flavors and sweeteners.
In this laboratory activity, abrasive power, pH, fluoride ion content and foaming ability will be measured. After gathering data from various toothpaste samples, results will be analyzed and judgments will be made about the different toothpastes.
(for each student group)
Alizarin red solution, 2–3 mL
Zirconyl chloride solution, 2–3 mL
Beakers, 250-mL, 5
Cotton swabs, 5
Graduated cylinder, 100-mL
Microscope slides, plastic, 5
pH test paper, 6.0–8.0
Pipets, Beral-type, 7
Test tubes, 10 x 75 mm, 5
Test tube rack
Toothpaste samples, 5
Toothpaste is considered a non-hazardous material; however, any material that has been in the lab is now considered a chemical and should not be consumed. Zirconyl chloride solution contains hydrochloric acid which is toxic by ingestion or inhalation and corrosive to body tissue. Alizarin red solution is a body tissue irritant. Use these chemicals in a fume hood and avoid all contact with eyes, skin and clothing. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory.
Test 1. Appearance
The pH of pure distilled water cannot accurately be measured using pH test paper due to the low ion count and the rapid absorption of carbon dioxide. For the purposes of this lab, assume the water has a neutral pH of 7.
Student Worksheet PDF