Chairside Assisting for Dental Assisting Exam Study Guide (page 3)

Updated on Jun 23, 2011

Local Anesthetics and Analgesics

All dental assistants must be knowledgeable about anesthetics and analgesics.

Topical Anesthetic

The topical anesthetic numbs the gum and nerves to allow the dentist to administer the local anesthetic to the patient with the least irritation or pain. The most common form of topical anesthetic is gel.

The mandibular block injection is placed in the retromolar pad area in order to anesthetize the fifth cranial trigeminal nerve. Because the maxilla is more porous than the bone of the mandible, infiltration anesthesia is used. The operator injects the anesthetic around the area of the root above the target tooth/teeth. A vasoconstrictor is found in some anesthetics in varying ratios (1:20,000; 1:50,000; 1:100,000; and 1:200,000). This chemical gives a deeper anesthesia and lasts longer than plain anesthetics. Caution should be used for medically compromised patients (cardiac or hypertensive patients) with the use of vasoconstrictors. Parasthesia is the prolonged effect of the anesthetic and may be caused by expired anesthetic solution, anesthetic apparatus prepared in advance (metal ions from the needle leach into the solution), or if the nerve is damaged or nicked during the anesthetic process. Parasthesia may be permanent or subside after several days, weeks, or months.

Assembly of Syringe

Dental assistants cannot administer local anesthetics, but they must be knowledgeable about them and be able to prepare the syringe for the dentist. This preparation involves aspirating the syringe, inserting the carpule, engaging the harpoon, selecting the proper size needle, and transfering the syringe to the dentist.

Needle Lengths and Usage

Needles come in two lengths: short or long. Long needles are used for mandibular injections, while short needles are used for maxillary injections.


Carpule labels have a wealth of information: name of the anesthetic, the concentration, expiration date, manufacturer’s name, and so on. The assistant should always double-check the expiration date and color code, and inspect the carpule for signs of damage.

Disassembly of Syringe

To disassemble the syringe, remove the needle, place it in a sharps container, disengage the harpoon, remove the carpule, and dispose of it properly. Remember to sterilize the syringe after use.

Proper Disposal of Sharps

Dispose of all used needles in a sharps container.

Nitrous-Oxide Sedation

Nitrous-oxide sedation is a gas mixture of oxygen and nitrous oxide administered through an inhalation technique. This is generally the responsibility of the dentist. However, in some states, assistants with expanded function credentials may also perform this function. Following the procedure, the patient should be flushed with 100% pure oxygen ten minutes prior to the end of the procedure. The patient should never be left alone while on nitrous oxide. The patient should be awake and responsive. Prior to leaving the office, the patient should be as alert as he or she was on entering the office. Note that the nitrous-oxide and oxygen tanks and gas lines are color coded. Nitrous oxide is blue and oxygen is green. There are hazards associated with exposure to nitrous oxide and it should never be administered to pregnant women or patients with breathing difficulty. A scavenger system is mandatory to protect dental personnel from ambient gases released by the patient upon exhaling.

Dental Support Aides

Rubber Dam

The rubber dam is utilized for retraction, moisture control, isolation, and patient management. The entire dam system includes the frame, punch, rubber dam material, template, napkins, lubricant, forceps, and clamps.

The dental dam frame holds the material taut and secures it extraorally. The dental dam clamp comes in varying sizes and may be winged or wingless. The clamp secures the dental dam material around the tooth. The dental dam punch makes the holes in the dental dam material that isolate the tooth/teeth. The #1 hole (smallest) is used for mandibular anteriors, #2 for maxillary anteriors, #3 for premolars, #4 for molars, and #5 for bridges or as the anchor tooth. The material between the holes is called the septum. This is cut using crown and bridge scissors when removing the dental dam material after the procedure. The various-sized holes correlate to the different teeth in the arch. One hole is used for endodontic treatment, while 6–8 teeth are recommended for multiple-tooth isolation. The dental dam forcep is used to open and release the clamp in order to place and remove the clamp from the tooth.

Other Moisture-Control Aides

These include dry angles (or dry aids) and cotton rolls.

Tofflemire Retainer with Matrix Band

The main parts of this retainer include the outer nut, inner nut, spindle, diagonal slot vise, and guide channels. It is used to build a temporary wall or matrix to replace lost tooth structure while the filling material is being placed. There are two types of matrix bands: universal and MOD. Other types of matrix systems include automatrix, omni matrix, and palodents.

Other Duties of Dental Assistants

Before dental procedures even begin, the dental assistant must welcome the patient into the operatory and make him or her comfortable. It is customary for the dental assistant to take the patient’s pulse and blood pressure. Normal resting pulse rate is between 60 and 100 beats per minute. Blood pressure consist of two numbers, the higher one being the systolic and the lower the diastolic. Normal blood pressure is considered to be 120 over 80.

Clinical and Periodontal Charting

It is important for the dental team to keep good records, and charting is an essential part of that. Traditional records were kept on paper charts, but today, more and more dental offices are computerizing charts.

Black’s Cavity Classifications

Black’s Cavity Classifications describes the location of the decay on the tooth. It includes six classes according to the location of the cavity. The system also suggests the best way of restoring the tooth. For example, in perio charting, Class II indicates moderate mobility. In orthodontics, patients are screened by their occlusion. Once established, the orthodontist will classify the type of malocclusion according to Angle’s classification. Class I is normal, Class II is distocclusion where the maxillary teeth stick out beyond the mandible in an abnormal degree, giving the appearance of buck teeth. Class III is known as mesiocclusion and the mandible juts out anterior to the maxilla. For example, an occlusion with tongue thrusting is a Class II.

Tooth Preparation

During a composite procedure, the steps of tooth preparation basically mirror that of an amalgam restoration. Once the tooth is prepared with orthophosphoric acid (etchant) and the bonding agent is placed, a clear plastic mylar strip (or celluloid strip) is placed to act as a matrix. The clear matrix allows for operator visibility, as well as for the curing light to polymerize the composite material. The composite will not stick to or become discolored from the mylar material.

Tooth Staining

Staining of the teeth can come from several sources. Stains are categorized according to their location and source. Extrinsic stains occur on the outside of the tooth structure, while intrinsic stains are integrated into the tooth itself. Exogenous stains occur from sources outside of the tooth (smoking, drinking coffee and colas, etc.). Extrinsic stains are removed during the coronal polishing portion of a dental prophylaxis, or by using bleaching techniques.

Dental Specialties

Each specialty uses highly specialized instrumentation and procedure setups. There are nine dental specialties, as listed below:

  • endodontics—treatment and diseases of the dental pulp
  • periodontics—treatment of the diseases of the supporting structures, gingiva, and alveolar bone of the oral cavity
  • pediatric dentistry—treatment of children from birth through adolescence
  • orthodontics and dentofacial orthopedics—treatment and correction of all forms of malocclusion
  • prosthodontics—restoration of oral function by restoring natural teeth or replacing missing teeth with a prosthesis (denture, partial, bridge, or implant)
  • oral and maxillofacial surgery—diagnosis and surgical treatment of diseases, injuries, and defects of the oral and maxillofacial regions
  • oral and maxillofacial pathology—diagnosis and treatment of abnormalities of the soft tissues and surrounding oral region
  • oral and maxillofacial radiology—production and interpretation of X-ray images
  • dental public health—promotes dental health in the community; prevents and controls dental diseases via educational means

Oral and maxillofacial surgeons extract teeth, biopsy lesions (abnormalities), correct anatomical defects, and place dental implants, to name a few procedures. For instance, rongeurs are used to contour the alveolar bone to eliminate sharp edges prior to the fabrication of a complete or partial denture. After an extraction, some patients experience alveolitis, also commonly known as a “dry socket.” This occurs due to the loss or lack of development of a healthy blood clot in the alveolar socket. A surgical dressing is placed in the alveolus until adequate healing has occurred.

Pediatric dentists treat children from newborn through adolescence. Older patients with special needs may continue to be treated by the pediatric dentist. Patients with physical or mental disorders can be treated in a hospital under the care of a pediatric dentist with hospital privileges. All others are seen in the pediatric dental office. Aside from the regular dental procedures, pediatric dentists also treat many emergencies seen in children. For instance, traumatic intrusion occurs when a tooth has been forced inward by a fall or sports injury. Avulsion occurs when the tooth is completely knocked out of the alveolar socket.

In the specialty of endodontics, the dentist treats diseases of the pulp and surrounding tissues. Pulpal irritation can be classified as reversible pulpitis or irreversible pulpitis. In reversible pulpitis, the dentist places a sedative medicament over the pulpal floor in order to give the pulp time to heal and calm down. If this works, further treatment is not necessary at this time. Irreversible pulpitis occurs when the pulp becomes infected or dies due to trauma or decay. Root canal therapy is then performed by the dentist unless the patient chooses an extraction.

During the course of a root canal, the dentist cleans out and enlarges the canal(s) of the tooth. This is done using small instruments such as broaches, reamers, and files. Once the chamber is uniform in size and enlarged enough to accept the final filling material, the doctor will irrigate the canal(s) with a mixture of sodium hypochlorite and water. This step will “sterilize” the canal by removing any tissue particles or debris from the small chamber of the canal. The canal is thoroughly dried with paper points prior to the placement of the gutta percha filling material. The gutta percha is cemented into the canal with a sealer cement.

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