Dental Science for Dental Assisting Exam Study Guide (page 5)
Practice problems for this study guide can be found at:
Tooth numbering systems, tooth surfaces, cavity classifications, anatomic features of the teeth, and angles and divisions of the teeth are the framework for understanding most dental procedures. Oral embryology and histology, along with head and neck anatomy, are also important subjects of interest for the dental assistant.
Concepts and Skills
Dental Science is broken down into 11 main areas:
- Dentition Overview
- Tooth Morphology
- Oral Embryology and Histology
- Head and Neck Anatomy
- Dental Caries Process
- Periodontal Disease Process
- Preventive Dentistry
- Oral Pathology
- General Anatomy
- General Physiology
The outline below chronicles the most current information available regarding each area of Dental Science, but remember to study your textbook as well.
A dentition is a complete set of teeth. Humans have two dentitions, or sets of teeth, in their lifetimes. These are the primary and the permanent dentitions.
Primary Dentition – 20 teeth
The primary dentition, commonly referred to as “baby teeth,” occurs between six months and six years of age. Other names for this dentition include the deciduous dentition and the succedaneous dentition. These teeth are exfoliated, or “lost,” beginning at approximately age six.
Mixed Dentition – varied numbers
This dentition occurs on a child between the ages of approximately seven to 12 years of age. In a mixed dentition, there are both primary and permanent teeth present in the mouth at the same time.
Permanent Dentition – 32 teeth
The permanent dentition, also known as “adult teeth,” begins erupting at about age six. The teeth will continuously erupt until approximately age 12. There will be a pause in eruption until ages 17 to 21, when the wisdom teeth, or third molars, begin the eruption process. These are the last teeth to erupt.
The upper arch in the mouth is referred to as the maxillary arch. This is named for the bone of the upper arch, which is called the maxilla. The maxillary arch holds 16 of the 32 permanent teeth and 10 of the 20 primary teeth.
The lower arch in the mouth is referred to as the mandibular arch. This is named for the bone of the lower arch, which is called the mandible. The mandible is the only movable bone in the skull. The mandibular arch holds the lower 16 of the 32 permanent teeth, and the lower 10 of the 20 primary teeth. The curvature formed by the maxillary and mandibular arches is known as the curve of Spee.
The mouth can be divided into smaller areas to make charting and communication easier. One such division is called a quadrant. The mouth is divided into four quadrants: Upper Right, Upper Left, Lower Left, and Lower Right. Each quadrant holds eight teeth.
These teeth are located at the front of the mouth. They consist of the central and lateral incisors and the cuspids (canines). Anterior teeth are designed for cutting and tearing of food. These teeth have incisal edges. There are six anterior teeth in each arch in both the primary and permanent dentitions.
These teeth are located at the back of the mouth. They consist of premolars (bicuspids) and molars. Posterior teeth are designed for chewing and grinding of food just prior to swallowing. These teeth have biting surfaces that have grooves, pits, and fissures to aid in chewing, which are known as the occlusal surfaces. There are ten posterior teeth in each arch in the permanent dentition and only four posterior teeth per arch in the primary dentition.
Names of the Teeth
These teeth are located at the midline of the face, at the anterior of the mouth. They are the teeth that are most visible when smiling. These teeth are used for cutting and tearing of food.
These teeth are located next to the centrals, at the anterior of the mouth, and are smaller in size than the centrals. These teeth are also used for cutting and tearing of food.
These teeth are located at the corners of both arches and are the longest rooted teeth in the mouth. Cuspids are sometimes referred to as canines or “eye-teeth” because of their pointy shape. They are anterior teeth and are considered to be the cornerstone of the arches.
Premolars or Bicuspids
These teeth are located in the posterior of the mouth and used for chewing and grinding of food. They are smaller than the molars and can be single or double rooted, depending on the individual. There are two premolars in each quadrant: a first premolar and a second premolar.
These teeth are located in the posterior of the mouth and are used for chewing and grinding of food. There are three molars in each quadrant: first molar, second molar, and third molar (wisdom teeth). These teeth are multirooted and can have as many as four roots.
This is the surface of the tooth closest to the midline. It is located interproximally, or in between the teeth.
This is the surface of the tooth that is the furthest distance away from the midline. It is located interproximally, or in between the teeth.
This is the surface of the tooth closest to the tongue.
This is the surface of the tooth closest to the face or cheek. Facial is the term used for the anterior teeth. Buccal is the term used for the posterior teeth. The two names designate the same area of the tooth but are site-specific to the area of the mouth.
This is the surface of the tooth used for chewing or cutting of food. Occlusal is the term used for the chewing surface of posterior teeth, and incisal is the term used for the cutting edge of the anterior teeth. The two names designate the same area of the tooth but are site-specific to the area of the mouth.
Tooth Numbering Systems
Numbering systems are utilized as a means of communication and identification among dental team members. Documentation and insurance companies require a consistent format of charting procedures. There are three numbering systems that are utilized in dentistry.
Universal Numbering System
The Universal Numbering System is the most common in the United States and is approved by the American Dental Association (ADA). Teeth are numbered from 1 to 16 on the upper arch, beginning with the patient’s upperright quadrant. Teeth are numbered from 17 to 32 on the lower arch, beginning with the patient’s lower-left quadrant. The primary dentition is charted using letters instead of numbers. The primary teeth are lettered A–T.
ISO Numbering System
The International Standards Organization (ISO) numbering system is accepted by the World Health Organization (WHO) and used internationally. This numbering system assigns each quadrant a number—for example, UR quadrant = 1. Next, each quadrant numbers the teeth 1–8. The charting would look like this: 1, 8. This would be read as: upper-right third molar. This is true for both primary and permanent charting.
Palmer Notation System
This numbering system assigns a number and bracket to each tooth. For the primary dentition, a letter and a bracket are assigned to each tooth. The bracket designates the quadrant in which the tooth is located, depending upon its position. This system is common for charting in orthodontics.
Anatomic Features of the Teeth
Teeth should have contours, contacts, and embrasures. Contours of the teeth refer to the curving of the tooth. This can be either concave (curved inward) or convex (curved outward). Contacts are the areas where two surfaces of the teeth touch, which is also referred to as interproximal. Embrasures are the V-shaped space just below or just above the contact points of two teeth.
Tooth morphology is the study of the shape of teeth.
Anterior Permanent Dentition
The anterior teeth have a distinct shape. They are generally smaller than the posterior teeth, have a straight flat edge, and have concave lingual surfaces. These teeth are designed and shaped in this manner to aid in the process of chewing and swallowing food. Anterior teeth also provide the patient with an esthetically pleasing smile.
Posterior Permanent Dentition
The posterior teeth are the powerhouse teeth in the mouth. They are generally larger in size than the anterior teeth; have wide chewing surfaces with pits, fissures, and grooves; and are multi-rooted. These teeth are designed and shaped in this manner to prepare food for being swallowed and digested.
The primary dentition consists of 20 “baby” teeth. These teeth are the incisors, the cuspids, and the molars. Children do not have premolars or bicuspids. These teeth erupt when the primary, or baby, first molar is lost. These teeth are usually not very large and are similarly shaped to those in the permanent dentition.
Oral Embryology and Histology
Oral embryology is the study of the prenatal development of the oral cavity. Histology is the study of the function and structure of tissues.
Oral embryology is the study of prenatal oral development, from zygote to embryo to fetus.
Preimplantation: This stage occurs the week following fertilization. The ovum implants itself, and the cells begin to multiply to begin forming body systems. The teeth are one of the first structures to begin formation.
Embryonic: This stage occurs from week two to week eight of the pregnancy. At about six weeks, the teeth begin to form at a more consistent rate. The zygote is now called an embryo.
Fetal: This stage occurs from week nine to birth, at approximately 40 weeks. The teeth continue to develop and form through gestation.
Life Cycle of a Tooth
Every tooth passes through stages of growth. The bud, cap, and bell stages are the growth periods of a tooth. Teeth grow very similarly to the way a baby grows. They are contained in a sac and continue to move through the growth periods prior to eruption.
Oral histology is the study of the function and structure of the teeth as well as the tissues surrounding them. Each tooth consists of a crown and root. The surrounding tissues are called the periodontium and support the tooth in its socket.
Layers of the Tooth
Teeth have three layers. The first layer is the enamel. This is a protective layer that is stronger than bone. Enamel is the hardest structure in the body. The second layer is the dentin. Dentin is softer than enamel and will decay very rapidly. Dentin is the only layer of the tooth that can regenerate, or rebuild, itself, known as secondary dentin. The third layer of the tooth is the pulp. The pulp is the “heart” of the tooth. It supplies oxygen, blood, nutrients, and vitamins to the tooth. If the pulp becomes damaged or injured, it is possible that it will die or begin the process of dying. The tooth will need a root canal if this occurs.
Head and Neck Anatomy
A dental assistant should be knowledgeable in the anatomy of the head and neck. Bones, muscles, glands, nerves, and sinuses all play a role in dental health.
Bones of the Skull
The human skull is divided into the cranium and the face. The cranium consists of eight bones that protect the brain. The face has 14 bones.
Features of the Face and Neck
The face muscles are responsible for our facial expressions and play important roles in chewing, digestion, and speaking. Facial landmarks include the nostrils, known as anterior nares.
Saliva lubricates, cleans the mouth, and begins the digestion process. There are three major salivary glands and numerous minor salivary glands. The three major glands are the parotid salivary, the submandibular, and the sublingual.
Parotid Salivary Gland
- It is located in the cheeks, just below the ears.
- It is the largest of the three major salivary glands.
- It secretes approximately 25% of the saliva in the mouth.
- The Stensen’s duct delivers the saliva to the mouth from the gland.
- The Stensen’s duct opens on the buccal surface of the maxillary first molars.
Submandibular Salivary Gland
- It is the size of a walnut, located in the deep floor of the mouth.
- It secretes approximately 60% of the saliva in the mouth.
- The Wharton’s duct delivers saliva to the oral cavity.
Sublingual Salivary Gland
- It is located in the floor of the mouth just under the tongue.
- It is the smallest of the three major salivary glands.
- It provides approximately 10% of the saliva in the mouth.
- The Bartholin’s duct delivers saliva to the oral cavity.
Blood and Nerve Supply
Arteries and veins carry blood to the neck and face. The internal carotid artery carries blood to the brain, and the exterior carotid artery carries blood to the face and mouth. There are 12 pairs of cranial nerves.
Sinuses are air-filled cavities in the face and skull that produce mucus. There are several sinus cavities: ethmoid sinuses, sphenoid sinuses, maxillary sinuses, and frontal sinuses. The sinuses can become blocked, which can cause discomfort for the patient similar to a toothache.
Dental Caries Process
Dental caries are known as tooth decay and are often called “cavities” by patients. This is an infectious process. Caries is caused by a bacterial infection and is contagious. The bacteria are found in dental plaque. The bacteria can be transmitted from person to person. The condition of the mouth must have the following present for caries to form: Lactobacillus (LB) bacteria, Mutanstreptococci (MS) bacteria, a diet high in fermentable carbohydrates (sugars), and a susceptible tooth.
The caries process takes approximately two years, but it can be halted or disrupted.
Stages of Carious Lesions
- Incipient: This is the very start of tooth decay. The decay has not yet reached the dentinal layer.
- Overt: The decay has reached the dentinal layer, and there is a visible hole in the tooth.
- Rampant: There are overt carious lesions present in many teeth in the mouth at the same time. This is common in patients with poor oral hygiene.
Diagnosis of Caries
A dentist will check for dental caries at each exam appointment. There are two main ways in which a dentist can detect caries: radiographs and dental explorers.
Radiographs, or X-rays, are one of the best tools a dentist has to detect caries interproximally. Today, many dentists use digital radiographs that eliminate the need for film.
The explorer is used to check the surfaces of the teeth. The explorer will stick to any suspicious area.
Periodontal Disease Process
Today, 75% of Americans have some form of periodontal disease.
Causes of the disease
The causes of periodontal disease are dental plaque and calculus. Bacteria in dental plaque cause inflammation and destroy tissue. The tissues will pull away from the plaque and bacteria, creating a periodontal pocket. More plaque and bacteria fills the periodontal pocket and hardens. Calculus is hardened plaque, and it is also called tartar. It builds up on the surface of the teeth, irritating the surrounding tissues and perpetuating the disease cycle.
Types of Periodontal Disease
Type I: Gingivitis Gingivitis is the inflammation of the gingiva, which can be caused by lack of oral hygiene, hormonal imbalance, or illness. It is totally reversible at this stage.
Type II: Early Periodontitis There has been a progression from gingivitis into the non-reversible start of periodontal disease. Early periodontitis is the beginning of the periodontal disease process. At this stage, the patient will experience bleeding and maybe some generalized or localized swelling of the gingiva. Pockets may have increased in size.
Type III: Moderate Periodontitis This is the middle stage of the disease process. There has been further progression of the disease. At this point, surgery may be recommended by the dentist or specialist. Bleeding has increased, pockets have grown in size, and the patient may be experiencing bad breath and/or swelling.
Type IV: Advanced Periodontitis The supporting structures of the mouth are being destroyed by the disease. There has been more damage and destruction to the periodontium. The patient is experiencing pain, increased bleeding, tooth mobility, swelling, and extreme bad breath. The patient will lose his or her teeth.
Signs and Symptoms
There are several signs and symptoms of periodontal disease. These include loose teeth, pain when chewing, gums that bleed easily when brushing or flossing, redness, swollen gingiva, bad breath, soreness, and tenderness. In the early stages, periodontal disease is often painless and has minimal symptoms. Early detection through regular examinations is crucial.
Effects on Systemic Health
Periodontal disease has an effect on the entire human body. Whenever there is disease present in the human body, the immune system reacts. Periodontal disease causes the immune system to be on constant alert, thereby making the patient more susceptible to other illnesses by weakening the immune system. Periodontal disease has been scientifically linked with premature childbirth, heart disease and stroke, bacterial pneumonia, and diabetes.
The goal of dentistry is for the patient to keep his or her own teeth for life. This can be achieved through education by working together with the patient as a team regarding a preventative routine.
Patients will be educated regarding the importance of cleanings and examinations every six months, sealants, and oral hygiene at home. The patient will establish an oral hygiene routine and schedule for maintaining dental health with help from the dental team.
A dental prophylaxis should be performed every six months to maintain a proper cleaning schedule. This procedure may be performed by a dentist or dental hygienist.
Fluoride is a naturally occurring mineral found in many of the items that we use daily. Some community drinking water is fluoridated. Many types of toothpaste contain fluoride. Fluoride treatments are applied topically and allowed to contact tooth surfaces for a designated amount of time in the dental setting. Fluoride drops and supplements are prescribed by physicians and dentists to prevent tooth decay in babies and young children.
This preventive measure is a form of flowable composite that is placed into the pits and fissures on the occlusal surfaces of posterior teeth. This technique has been proven to prevent decay on the occlusal surfaces (not interproximal) and is recommended as soon as the permanent teeth have erupted fully into the oral cavity.
Oral Healthcare Instructions
The dentist depends on the dental assistant to provide the patients with accurate, concise oral hygiene instructions. In some offices, the dentist may ask the assistant to present treatment plans as well. Dental assistants are often the dental healthcare provider the patient will look to for clarification of the treatment being recommended by the dentist. It is important for dental assistants to understand the procedures they are assisting in and how to explain each step to the patient in a calm, reassuring, and informative manner.
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