Lesson 2: Carious Lesions

Dr. Lee to Sara: "Now I am going to examine each of your teeth. Please open wide. Let me know if your mouth gets sore or tired."

To review the surfaces of each tooth, we will start from the midline. A good point to keep in mind is that each tooth has five surfaces. To start, the mesial surface of any tooth is the surface that is closest to the midline. The distal surface is furthest away from the midline. So, keep in mind that each tooth has both a mesial surface and a distal surface. Facial is a general term that refers to the surface of the tooth on the outside, or nearest the lips and cheeks. There are also a couple of specific terms to describe the outside surfaces of the posterior and anterior teeth. For example, buccal describes the outer surfaces of posterior teeth (molars and premolars) closest to the cheek. The other term for outside surfaces is labial, which describes the outside surface of the anterior teeth nearest the lips. Know that you can use the term facial for ease when referring to any outside surface of any tooth. However, when speaking with a dental professional, using the terms buccal and labial refer to more specific areas in the mouth.

Image: The five surfaces of teeth.
Image: Interproximal and proximal surfaces of teeth.

Now that we've covered three of the five surfaces – mesial, distal, and facial – let us go to our fourth surface which is closest to the tongue. All surfaces, of all teeth, that are closest to the tongue are called the lingual surface. Lastly, let us learn the two different names for the tops of the teeth, which are the fifth surface. To start, incisal is the name of the biting edge of the anterior teeth. For the posterior teeth, the top surface is called the occlusal surface. The occlusal surface typically makes first contact with food and the other teeth.

Now that we have covered the five distinct surfaces of the teeth, let us discuss what we call the areas where the teeth come together. Proximal surfaces are those that are close together. Interproximal is the area between two proximal surfaces. The small area where the proximal surfaces of two adjacent teeth touch each other is called the contact point.

Dr. Lee to Sara: "I heard that you like to eat candy. Even though candy tastes good, it can hurt your teeth, and I am going to explain how."

Sugary foods, like candy, or fermentable carbohydrates (sucrose and fructose) form acid that combines with certain bacteria to buildup on teeth.

Dr. Lee to Sara: "I want to show you why it’s so important to clean your teeth thoroughly every day. We’ve asked you to chew a colored tablet that contains a dye that binds to plaque. Take a look in this mirror. The colored areas of your teeth are those with plaque build-up."

Image: Child smiling after chewing a colored tablet that contains a dye that binds to plaque.

Because plaque is a sticky substance composed of millions of bacteria, it collects around and between the teeth. Plaque is a major cause of tooth decay and gum disease.

Dr. Lee to Sara’s Parents: "Disclosing tablets are useful at home to help improve Sara’s brushing and flossing by highlighting missed areas."

Image: Types of cavities.

Dr. Lee to Sara: "These pictures contain types of cavities. Do you see the white spot on that molar in the middle frame? That is the first sign of trouble."

Plaque bacteria form acid that erodes the white enamel on teeth in a process known as demineralization.

At this stage, the decay process is reversible. Using various forms of fluoride–such as fluoridation of public water supplies and in toothpastes. There are dental rinses that contain Sodium monofluorophosphate, neutral sodium fluoride (stannous fluoride), in addition to regular plaque removal-can help the tooth repair itself.

Fluoride promotes remineralization because the incorporated fluoride makes enamel more resistant to demineralization and, thus, more resistant to decay.

Dr. Lee to Sara: "Do you see the dark spots in the teeth in this picture? They are cavities, which are holes in the teeth. Cavities can be very painful."

Once the enamel has decayed, a carious lesion, which is also known as caries or a cavity, leaves the enamel unable to repair itself. The decay can spread further into the dentin, further weakening the enamel. This process is not reversible, and requires intervention by a dentist, usually in the form of cleaning and filling.

Image: Cavity.

Untreated, the dentin decay can spread to the tooth’s pulp, and the nerve can become exposed, painful, or infected. This pain can be worsened by hot, cold, or sweet food.

Once enamel and dentin have decayed, the tooth is drilled out and filled with either metal amalgam or composite resin. Dental fillings preserve the structural integrity of the tooth, prevent further damage from decay, and potentially save the tooth from extraction.