Chairside Assisting for Dental Assisting Exam Study Guide (page 2)

Updated on Jun 23, 2011

Equipment in the Operatory (Treatment Room)

The operatory, or treatment room, is the heart of the dental operation. It must be designed for efficiency and safety. The equipment in the operatory is divided into ten areas: light, dental chair and controls, portable unit, operator’s equipment, table top, rheostat, assistant’s stool, operator’s stool, operatory sink, and operatory computer.


Each operatory is equipped with an overhead light to aid the dental team with illumination into the oral cavity. Some lights have a dimming switch to use while placing light-sensitive materials. Changing the position of the light is the responsibility of the dental assistant.

Dental Chair and Controls

There are many types of dental chairs from which the dentist can choose. Since sit-down dentistry is most common today, most chairs are built for that purpose. Controls can be located in any area of the chair the dentist chooses. Currently, the most common way to control a dental chair is via foot controls. These controls can be pre-programmed to the positions the dentist prefers. The patient dental chair is contoured for the patient’s comfort. Newer models come with a massager and heat. The chair can be positioned in one of three ways: upright (used for taking impressions, exposing dental radiographs, and seating and dismissing the patient), supine (patients are reclined on their back), and subsupine (used for emergency situations).

Portable Unit

The portable unit consists of the high-volume evacuator (HVE), the saliva ejector, and the air/water syringe (triplex syringe).

High-Volume Evacuator (HVE)

This is a high-speed suction device used by the assistant for removing debris, particles, and large amounts of water very quickly from the oral cavity.

Saliva Ejector

This is a slow-speed suction device used by assistants for removing saliva only.

Air/Water Syringe (Triplex Syringe)

This device is capable of performing three functions. It can blow air, spray water, or “blast” a combination of air and water. The assistant utilizes this device while handling the HVE or saliva ejector.

Operator’s Equipment

The dentist’s equipment includes two types of hand pieces—high-speed and low-speed—as well as the air/water syringe.

High-Speed Hand Piece

This is commonly known as the drill. This piece of equipment is used by the dentist to prepare the tooth to receive a restoration.

Low-Speed Hand Piece

This piece of equipment is used by the dentist, along with the high-speed hand piece, to remove soft decay, polish a restoration, or complete a prophy.

Table Top

This is where the assistant will place the instruments on the tray or in their cassette for the specific procedure. The table top is also known as the “mobile cart.”


This “foot pedal” controls the dental hand pieces.

Assistant’s Stool

This chair is designed specifically for the way an assistant sits at the dental chair. The stool is equipped with wheels and castors, a comfortable cushion, a lever to adjust the height, a foot ring, and often a belly bar for abdominal support.

Operator’s Stool

This chair is designed specifically for the operator and the way she or he is positioned at the dental chair. This stool has a low adjustable backrest, a comfortable cushion, a lever to adjust both the backrest and height, and wheels and castors. There is never a ring on an operator’s stool. The dentist should be able to sit with his or her feet flat on the floor. For maximum visibility, the dental assistant’s stool should be four to six inches above that of the operator.

Operatory Sink

Each treatment room has at least one sink. Typically, there will be a sink on both the operator’s side and the assistant’s side.

Operatory Computer

Today’s operatory is usually equipped with a computer that runs dental office software. It can be utilized for one or all of the following:

  • accessing the patient’s electronic chart
  • digital X-rays
  • intraoral images
  • treatment plan for the patients

Chair Positions

Dental chairs are the centerpiece of the operatory. They are adjustable to accommodate patients of all shapes and sizes. The three main positions are upright, supine, and subsupine.


The patient enters and leaves the dental chair in the upright position.


Dental treatment is performed in this position. The supine position places the patient flat on his or her back, with the head in line with the knees.


Dental treatment can be performed in this position if the dentist desires. The subsupine position places the patient’s head below her or his knees. This position also places the patient’s head directly in the operator’s lap. This is used for emergencies.

Light Positions

The operating light is an essential part of the equipment in the treatment room. It must be placed correctly to illuminate the area to be treated. There are two main light positions: maxillary and mandibular.

Maxillary Position

The light is positioned over the patient’s chest. Once the light is switched on, the beam should be directed toward the maxillary by gently pulling the light forward to the patient’s chin and then tipping it upward.

Mandibular Position

The light is positioned over the patient’s chest. Once the light is switched on, it should be pulled forward until it is directly over the patient’s mouth. The beam should be shining directly onto the mandibular teeth.

Clock Concept of Operating Zones

The dentist and assistant must work in harmony as a coordinated team. Operating zones define what activities take place in which areas. These zones are defined based on the hands of a clock. There are four defined zones: static zone, assistant’s zone, transfer zone, and operator’s zone. These zones differ for right-handed and lefthanded operators.

Right-Handed Operator

The four clock zones (based on clock positions) for the right-handed operator are as follows:

  • 12–2 = Static Zone
  • 2–4 = Assistant’s Zone
  • 4–7 = Transfer Zone
  • 7–12 = Operator’s Zone

12–2 = Static Zone

This is the clock zone where very little occurs.

2–4 = Assistant’s Zone

This is the clock zone where the assistant sits while assisting for chairside procedures.

4–7 = Transfer Zone

This is the clock zone where instrument transfer takes place. The assistant hands instruments and medicaments from the instrument tray to the operator through this zone.

7–12 = Operator’s Zone

This is the clock zone where the operator sits and performs all dental procedures.

Left-Handed Operator

A left-handed dentist also has the four operating zones, but they are reversed.

  • 12–5 = Operator’s Zone
  • 5–8 = Transfer Zone
  • 8–10 = Assistant’s Zone
  • 10–12 = Static Zone

The descriptions of these zones are the same as those for the right-handed operator. However, the clock times are switched.

Delivery of Dental Care

Four-handed dentistry involves the operator and one assistant working together at the chair, while six-handed dentistry involves the dentist and two assistants working together at the chair. One assistant is the chairside assistant, and the other is the roving assistant. The chairside assistant is responsible for patient safety and for maintaining a clean, debris-free environment in the oral cavity. The roving assistant is responsible for instrument transfer, mixing of materials, and the pace of the procedure.

Techniques of Four-Handed Dentistry

Four-handed dentistry is also known as team dentistry because the dentist and the assistant work closely together in a coordinated manner.

Instrument Grasps

Various grasps are utilized by the operator depending upon the instrument of choice. These grasps include pen grasp, palm grasp, modified pen grasp, and modified palm grasp. There are two main HVE grasps: thumb-to-nose grasp, and pen grasp. In the thumb-to-nose grasp, the assistant holds the HVE in this grasp for maximum control of the HVE. The hand is wrapped around the HVE, with the thumb pointed toward the patient’s nose. In the pen grasp, the assistant utilizes this grasp primarily for assisting with dental treatment performed in the anterior area of the oral cavity.


Fulcrum is a resting point for the operator’s working hand. A fulcrum allows for stability and control while utilizing an instrument or dental hand piece in the patient’s mouth.

Direct and Indirect Vision

The operator utilizes both direct and indirect vision while performing dental treatment. Direct vision is when the operator has a direct line of sight to the area of the mouth on which she or he is working. Indirect vision is when the operator looks into a mouth mirror to visualize the area of the mouth being worked on. The assistant is responsible for spraying air on the mouth mirror to keep the dentist’s line of vision clear.


Generalized: In a general dental office, one will find a wide variety of dental instrumentation from each specialty. There will be a limited amount of specialized instrumentation, depending on how often the general dentist performs that specialty procedure. Some instrument setups found in a general dental office are basic setup, restorative set-up, crown and bridge setup, and emergency setup.

Specialized: In a specialty office, one will find instruments specific to that specialty. For example, an orthodontic office will have a specific instrument setup for cementation of bands, bonding of brackets, adjustment of arch wire, changing of elastics, and removal of orthodontic appliances.

Hand-Piece Identification and Utilization: High-speed hand pieces are all one unit, spray water, and have a fiber-optic light. They rotate at 450,000 rpm, are used for preparation of teeth for restorations, and are slightly angled. Hand pieces are designed to spray water to wash away debris and to keep the tooth cool and prevent overheating. Slow-speed hand pieces have multiple parts and attachments, with a motor in the base. Attachments include straight, contra-angle, and prophy-angle.

Bur Identification and Utilization: Dental burs are drill bits used in hand pieces. There are two main types of burs—carbide and diamond. The three bur shanks are straight, friction grip, and latch type. The three parts of the bur are the shank, neck, and head. The head of the bur cuts the tooth structure, and comes in many shapes. Burs are inserted into hand pieces to perform dental treatment.

Hand Instruments

Hand instruments are classified according to their use. Hand-cutting instruments are those used by the dentist to cut actual tooth structure (usually dentin). Hand-carving instruments are used to “carve anatomy” into the restorative material (amalgam). Exploratory instruments, also known as exam instruments, are used to perform an intraoral examination. This set includes the mouth mirror, explorer, cotton forceps, and a periodontal probe. The mouth mirror is used to retract the cheeks, lips, and tongue, as well as to reflect light and provide indirect vision.

Another category of hand instruments are accessory in nature. Crown and bridge scissors, articulating paper holders, and dappen dishes are a few examples. Articulating paper holders secure the colored marking paper used to identify high spots on a newly placed restoration (amalgam, composite, crowns, bridges, dentures, or partials).

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