Parafunctional habit
Encyclopedia
A para-functional habit or parafunctional habit is the habitual exercise of a body part in a way that is other than the most common use of that body part. The term is most commonly used by dentist
s, orthodontists, or maxillofacial specialists to refer to parafunctional uses of the mouth
, tongue
and jaw
. Oral para-functional habits may include bruxism
(tooth-clenching or grinding), tongue
tension, mouth-breathing, and any other habitual use of the mouth unrelated to eating, drinking, or speaking.
Contrary to common belief, functional habits such as chewing are not the main cause of the wearing of teeth. Parafunctional habits are the most destructive forces for several reasons. Whereas teeth rarely come into contact during normal chewing, grinding of teeth may occur 1–4 hours in a 24 hour period, most often during sleep. The amount of pressure
placed on teeth during functional habits is 20–80 psi (0.14–0.55 MPa), but the pressure can range from 300 to 3000 psi (2.07 to 20.7 MPa) during parafunctional habits. The direction of forces during functional habits are placed vertically along the long axis of teeth, which is the least harmful because of the anatomical structure of the attachment
of teeth to the bone. On the other hand, parafunctional habits direct their forces horizontally. Normally, the temporomandibular joint
(TMJ) acts as a class III lever
, which helps to restrict the amount of force generated. Class I or class II levers may be created during bruxism, which generates more force from the same amount of muscle activity and subsequently delivers more force to the teeth.
The extreme force over teeth can occur during some situations, as a reflex of protection. For example, when a person feels a risk of an imminent car crash, normally the teeth arches are firmly occluded. It is a protective reflex, although it is considered parafunctional: over clenching. The maxilo-mandibular complex is bonded by muscles and interposed teeth and much less vulnerable to harm and dislocation. When this kind of reflex acts it is very important to have a good memory of one's "best bite" position in order to avoid fractures. It is one hypothesis why military jet pilots crack more teeth than auxiliary crew.
Dentist
A dentist, also known as a 'dental surgeon', is a doctor that specializes in the diagnosis, prevention, and treatment of diseases and conditions of the oral cavity. The dentist's supporting team aides in providing oral health services...
s, orthodontists, or maxillofacial specialists to refer to parafunctional uses of the mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
, tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
and jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...
. Oral para-functional habits may include bruxism
Bruxism
Bruxism is characterized by the grinding of the teeth and typically includes the clenching of the jaw. It is an oral parafunctional activity that occurs in most humans at some time in their lives. In most people, bruxism is mild enough not to be a health problem...
(tooth-clenching or grinding), tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
tension, mouth-breathing, and any other habitual use of the mouth unrelated to eating, drinking, or speaking.
Contrary to common belief, functional habits such as chewing are not the main cause of the wearing of teeth. Parafunctional habits are the most destructive forces for several reasons. Whereas teeth rarely come into contact during normal chewing, grinding of teeth may occur 1–4 hours in a 24 hour period, most often during sleep. The amount of pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
placed on teeth during functional habits is 20–80 psi (0.14–0.55 MPa), but the pressure can range from 300 to 3000 psi (2.07 to 20.7 MPa) during parafunctional habits. The direction of forces during functional habits are placed vertically along the long axis of teeth, which is the least harmful because of the anatomical structure of the attachment
Periodontium
Periodontium refers to the specialized tissues that both surround and support the teeth, maintaining them in the maxillary and mandibular bones. The word comes from the Greek terms peri-, meaning "around" and -odons, meaning "tooth." Literally taken, it means that which is "around the tooth"...
of teeth to the bone. On the other hand, parafunctional habits direct their forces horizontally. Normally, the temporomandibular joint
Temporomandibular joint
The temporomandibular joint is the joint of the jaw and is frequently referred to as TMJ. There are two TMJs, one on either side, working in unison. The name is derived from the two bones which form the joint: the upper temporal bone which is part of the cranium , and the lower jaw bone called the...
(TMJ) acts as a class III lever
Lever
In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to either multiply the mechanical force that can be applied to another object or resistance force , or multiply the distance and speed at which the opposite end of the rigid object travels.This leverage...
, which helps to restrict the amount of force generated. Class I or class II levers may be created during bruxism, which generates more force from the same amount of muscle activity and subsequently delivers more force to the teeth.
The extreme force over teeth can occur during some situations, as a reflex of protection. For example, when a person feels a risk of an imminent car crash, normally the teeth arches are firmly occluded. It is a protective reflex, although it is considered parafunctional: over clenching. The maxilo-mandibular complex is bonded by muscles and interposed teeth and much less vulnerable to harm and dislocation. When this kind of reflex acts it is very important to have a good memory of one's "best bite" position in order to avoid fractures. It is one hypothesis why military jet pilots crack more teeth than auxiliary crew.