Activity 2.1: Identifying Types of Teeth

Aim/Objective: To observe and identify the different types of human teeth and their functions.

Materials Required:

Plane mirror with high clarity.
Antiseptic hand wash.
Latex-free gloves (optional).
10g Piece of apple or 15g Crusty bread.
Dental model or diagram for comparison.

Procedure:

Thoroughly wash your hands with antiseptic soap for 20 seconds.
Use a mirror in a well-lit area to perform an "Intraoral Inspection."
Count the total number of teeth in the maxillary (upper) and mandibular (lower) arches. Record the dental formula.
Use your clean index finger to palpate the "Occlusal Surfaces" (biting surfaces) of different teeth to feel for sharpness or flatness.
Take a bite of an apple and observe which teeth are involved in:
- Initial "Incision" (biting).
- "Tearing" of fibrous tissue.
- "Mastication" (grinding) for 30-40 seconds until the food forms a bolus.

Pro Tip When counting, start from the midline and move backwards to accurately identify each quadrant. A healthy adult typically has 8 teeth per quadrant.

Observation:

Incisors: 4 per jaw, chisel-shaped and sharp for cutting.
Canines: 2 per jaw, dagger-like for piercing.
Premolars & Molars: 10 per jaw, broad and multi-cusped for crushing.

Explanation:

Humans exhibit Heterodonty (different tooth shapes). The physical structure of each tooth is a result of evolutionary adaptation to different mechanical stresses. Incisors use a "Scissor Action," canines provide "Tear Resistance," and molars act as "Biological Grinders" to increase the surface area of food for enzymatic action.

Conclusion:

The human dentition is a specialized mechanical system composed of four distinct tooth types, each fulfilling a specific role in the ingestion and preliminary digestion of food.

Scientific Note Enamel, the outermost layer of the tooth, is the hardest substance in the human body, consisting primarily of Hydroxyapatite (a crystalline calcium phosphate).

Activity 2.2: The Effect of Saliva on Starch

Aim/Objective: To demonstrate that saliva breaks down starch into simpler sugars.

Materials Required:

Two identical Pyrex test tubes (Labeled A and B).
10g Freshly boiled white rice (Starch source).
1% Iodine-Potassium Iodide ( $I_2KI$ ) solution.
10ml Graduated cylinder.
Plastic dropper.
Stopwatch.

Procedure:

Tube A (Control): Add 1 teaspoon (approx. 5g) of boiled rice and 3ml of distilled water.
Tube B (Experimental): Chew 1 teaspoon of boiled rice for exactly 3-5 minutes. Ensure the rice is thoroughly mixed with saliva. Spit the "Salivary-Rice Mixture" into Tube B.
Add 5ml of distilled water to both tubes and shake vigorously for 30 seconds to create a suspension.
Allow both tubes to stand at room temperature (approx. 25-30°C) for 10-15 minutes to facilitate enzymatic reaction.
Add 2-3 drops of Iodine solution to each tube and observe the chromatic transition for 1 minute.

Safety First This activity involves handling biological fluids (saliva). Perform this only with your own saliva. Wash your hands and all apparatus with detergent and disinfectant immediately after the experiment.

Observation:

Tube A: Transitions to an intense Blue-Black colour immediately.
Tube B: Remains Yellow-Brown (the colour of dilute iodine) or shows very faint purple streaks.

Explanation:

Rice contains Amylose (starch). Saliva contains the enzyme Salivary Amylase (Ptyalin), which catalyzes the hydrolysis of alpha-1,4-glycosidic bonds in starch, breaking it down into Maltose (a disaccharide).
Since iodine only reacts with the helical structure of starch, and not with maltose or glucose, the negative result in Tube B proves that chemical digestion has occurred.

Conclusion:

Chemical digestion of carbohydrates is initiated in the oral cavity by the enzymatic action of salivary amylase.

Scientific Note Salivary amylase works optimally at a near-neutral pH (6.7 to 7.0). If the mouth is too acidic (e.g., after drinking soda), the enzyme's efficiency decreases significantly.

Activity 2.1: Identifying Types of Teeth

Aim/Objective: To observe and identify the different types of human teeth and their functions.

Materials Required:

Plane mirror with high clarity.
Antiseptic hand wash.
Latex-free gloves (optional).
10g Piece of apple or 15g Crusty bread.
Dental model or diagram for comparison.

Procedure:

Thoroughly wash your hands with antiseptic soap for 20 seconds.
Use a mirror in a well-lit area to perform an "Intraoral Inspection."
Count the total number of teeth in the maxillary (upper) and mandibular (lower) arches. Record the dental formula.
Use your clean index finger to palpate the "Occlusal Surfaces" (biting surfaces) of different teeth to feel for sharpness or flatness.
Take a bite of an apple and observe which teeth are involved in:
- Initial "Incision" (biting).
- "Tearing" of fibrous tissue.
- "Mastication" (grinding) for 30-40 seconds until the food forms a bolus.

Pro Tip When counting, start from the midline and move backwards to accurately identify each quadrant. A healthy adult typically has 8 teeth per quadrant.

Observation:

Incisors: 4 per jaw, chisel-shaped and sharp for cutting.
Canines: 2 per jaw, dagger-like for piercing.
Premolars & Molars: 10 per jaw, broad and multi-cusped for crushing.

Explanation:

Humans exhibit Heterodonty (different tooth shapes). The physical structure of each tooth is a result of evolutionary adaptation to different mechanical stresses. Incisors use a "Scissor Action," canines provide "Tear Resistance," and molars act as "Biological Grinders" to increase the surface area of food for enzymatic action.

Conclusion:

The human dentition is a specialized mechanical system composed of four distinct tooth types, each fulfilling a specific role in the ingestion and preliminary digestion of food.

Scientific Note Enamel, the outermost layer of the tooth, is the hardest substance in the human body, consisting primarily of Hydroxyapatite (a crystalline calcium phosphate).

Activity 2.2: The Effect of Saliva on Starch

Aim/Objective: To demonstrate that saliva breaks down starch into simpler sugars.

Materials Required:

Two identical Pyrex test tubes (Labeled A and B).
10g Freshly boiled white rice (Starch source).
1% Iodine-Potassium Iodide ( $I_2KI$ ) solution.
10ml Graduated cylinder.
Plastic dropper.
Stopwatch.

Procedure:

Tube A (Control): Add 1 teaspoon (approx. 5g) of boiled rice and 3ml of distilled water.
Tube B (Experimental): Chew 1 teaspoon of boiled rice for exactly 3-5 minutes. Ensure the rice is thoroughly mixed with saliva. Spit the "Salivary-Rice Mixture" into Tube B.
Add 5ml of distilled water to both tubes and shake vigorously for 30 seconds to create a suspension.
Allow both tubes to stand at room temperature (approx. 25-30°C) for 10-15 minutes to facilitate enzymatic reaction.
Add 2-3 drops of Iodine solution to each tube and observe the chromatic transition for 1 minute.

Observation:

Tube A: Transitions to an intense Blue-Black colour immediately.
Tube B: Remains Yellow-Brown (the colour of dilute iodine) or shows very faint purple streaks.

Explanation:

Rice contains Amylose (starch). Saliva contains the enzyme Salivary Amylase (Ptyalin), which catalyzes the hydrolysis of alpha-1,4-glycosidic bonds in starch, breaking it down into Maltose (a disaccharide).
Since iodine only reacts with the helical structure of starch, and not with maltose or glucose, the negative result in Tube B proves that chemical digestion has occurred.

Conclusion:

Chemical digestion of carbohydrates is initiated in the oral cavity by the enzymatic action of salivary amylase.

Scientific Note Salivary amylase works optimally at a near-neutral pH (6.7 to 7.0). If the mouth is too acidic (e.g., after drinking soda), the enzyme's efficiency decreases significantly.

Activity 2.1: Identifying Types of Teeth

Activity 2.1: Identifying Types of Teeth

Activity 2.2: The Effect of Saliva on Starch

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Activity 2.1: Identifying Types of Teeth

Activity 2.1: Identifying Types of Teeth

Activity 2.2: The Effect of Saliva on Starch

On this page