concepts of occlusion

Information about concepts of occlusion

Published on February 8, 2010

Author: sansritinarain

Source: authorstream.com

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STRUCTURE AND FUNCTION OF ALL ANATOMIC COMPONENTS OF OCCLUSION AND THE MECHANICS OF ARTICULATION. : STRUCTURE AND FUNCTION OF ALL ANATOMIC COMPONENTS OF OCCLUSION AND THE MECHANICS OF ARTICULATION. Presented by: Dr. Sansriti Narain Slide 2: Definition (Jablonski, 1982) The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication and psychological status. Objectives and Goals : Objectives and Goals The subject of occlusion serves as a natural interface between certain of the biologic and behavioural sciences and the clinical sciences. The subject of occlusion is, in the view of many, the medium that brings all branches of dentistry together (Ricketts, 1969) The occlusion of the teeth can be considered under two headings: : The occlusion of the teeth can be considered under two headings: Static occlusion: refers to any position in which the upper & the lower teeth come together in contact. Functional occlusion: refers to the functional movement of the mandible and thus the lower dentition in contact with the upper dentition. The Masticatory System : The Masticatory System A dynamic biomechanical musculoskeletal system Components of the Mastication : Components of the Mastication Dentitions Periodontal supporting tissues Maxilla and Mandible Temporomandibular Joint Mandibular musculature Muscles of lips, cheeks, and tongue Involving soft tissue Supplying innervation and vasculation Primary Dentition : Primary Dentition Maxillary teeth Mandibular teeth Months Permanent Dentition : Permanent Dentition Maxillary teeth Mandibular teeth Years Loss of Teeth Causes Occlusal Disharmony : Loss of Teeth Causes Occlusal Disharmony Early loss of deciduous teeth without space retaining appliances Little adverse effect on function. Localized over-eruption of the teeth. Variable psychological effects on child and parent. Movement of the teeth into extraction spaces. Unilateral extraction of the teeth in a crowded arch leading to asymmetry of arch. Loss of Teeth Causes Occlusal Disharmony : Loss of Teeth Causes Occlusal Disharmony Conditions in which early loss of primary molars will give varying results: Ample space for the successional teeth. Little space loss Just ample space for the successional teeth. Slight space loss will result in crowding . Slight crowding potential. Space loss will aggravate crowding condition, but not beyond the scope of corrective treatment. Severe crowding potential. Further space loss undesirable. The role of permanent dentition in occlusion : The role of permanent dentition in occlusion Loss of mandibular first molar Lingual and mesial tipping of mandibular 2nd and 3rd molar Loss vertical dimension Changing in masticatory habit and muscle tonicity IDEAL OCCLUSION : IDEAL OCCLUSION Andrews (1972) outlined six keys to normal occlusion: : Andrews (1972) outlined six keys to normal occlusion: Correct relationship of the first permanent molars in the sagittal plane. Correct crown angulation of the incisor teeth in the transverse plane. Correct crown inclination of the incisor teeth in the sagittal plane. An absence of rotation of individual teeth. Correct contacts of individual teeth within each dental arch, with no spacing or crowding. A flat or only slightly curved occlusal plane Roth’s concepts (1976) : Roth’s concepts (1976) In the position of maximum intercuspation (centric occlusion) the mandibular condyles should be in their most superior and most retruded position in the condylar fossae. On the closure into centric occlusion, the stress on the posterior teeth should be directed along the long axes of the teeth. The posterior teeth should contact equally and evenly, with no contact on the anterior teeth, in centric occlusion. Roth’s concepts (1976) : Roth’s concepts (1976) There should be minimal incisal overjet and overbite, but sufficient to cause separation of the posterior teeth on any excursion of the mandible out of centric occlusion. There should be minimal interference from the teeth to a full range of mandibular movement as limited by the temporomandibular joints MALOCCLUSION OF THE TEETH : MALOCCLUSION OF THE TEETH When there is a need for the subject to take up an adaptive postural position of the mandible. When there is a translocated closure of the mandible from the rest position or from an adaptive postural position to the intercuspal position. When the tooth positions are such that adverse avoiding mechanisms are set up during masticatory function of the mandible. MALOCCLUSION OF THE TEETH : MALOCCLUSION OF THE TEETH When the teeth are causing damage to the oral soft tissues. When there is crowding or irregularity of the teeth which may predispose to periodontal and dental disease. When there is adverse personal appearance caused by tooth position. When the position of the teeth interferes with normal speech. Incisal overbite : Incisal overbite Incisal overjet : Incisal overjet Class 1 Molar Relationship(Edward Angle (1899) : Class 1 Molar Relationship(Edward Angle (1899) Class 2 Molar RelationshipDivision 1 : Class 2 Molar RelationshipDivision 1 Class 2 Molar Relationship Division 2 : Class 2 Molar Relationship Division 2 Class 3 Molar Relationship : Class 3 Molar Relationship Periodontal Supporting Tissues : Periodontal Supporting Tissues Cementum Periodontal ligament Supporting bone Usually, periodontium is protected against injury by neuromuscular reflexes Problems to Periodontium : Problems to Periodontium Periodontal trauma Pattern of mastication Loss of teeth Loss of periodontal support Faulty restoration Abnormal occlusal force; bruxism, clenching Temporomandibular Joint (TMJ) : Temporomandibular Joint (TMJ) A complex ginglymoarthrodial (hinge and glide) articulation with limited capability of diarthrosis (free movement) Histology of TMJ Area : Histology of TMJ Area Temporomandibular Joint (TMJ) : Temporomandibular Joint (TMJ) Composed of Condyle Mandibular fossa Articular capsule Synovial tissue Articular disc Ligaments Mandibular Condyle : Mandibular Condyle Modified barrel shape approx. 20 x 10 mm (ML x AP) Perpendicular to the ascending ramus of mandible. From the inferior view of the cranium, the condyles seem to be rotated. Composed of the cancellous bone covered by a thin layer of compact bone Mandibular Fossa : Mandibular Fossa Formed by the dense cortical bony surface of temporal bone It is present posterior to articular eminence Posterior non articular fossa is formed by tympanic plate Thin at the roof of the fossa and tympanic plate Articular Capsule and Disk : Articular Capsule and Disk Articular Capsule : Articular Capsule Ligamentous capsule surrounds the joint It is attached to the neck of the condyle and around the border of the articular surface of the temporal bone Anterolateral aspect of the capsule may thicken to form the Temporomandibular ligament function as stabilising structure Articular Capsule : Articular Capsule Consists of : internal synovial layer outer fibrous layer containing veins, nerves, and collagen fibres. Innervation of capsule & disk arises from CN V; auriculotemporal and masseteric nerves Venous plexus is present at the posterior aspect. Synovial tissue : Synovial tissue Lubrication of the joints surfaces during all joint movements. Two mechanisms: 1)Boundary lubrication 2)Weeping lubrication Provides essential nutrients for the chondrocytes within the cartilage matrix. Aids in the phagocytosis and elimination of particulate and dissolved substances within the closed joint cavities. Transport and diffusion of substances into and out of the joint cavities and joint tissues. Articular Disk (Meniscus) : Articular Disk (Meniscus) Biconcave oval structure interposed between the condyle and the temporal bone 1 mm in the middle and 2-3 mm at periphery Composed of dense collagenous connective tissue Central area is a vascular, hyaline and devoid of nerve Articular Disk (Meniscus) : Articular Disk (Meniscus) Fuses to a strong ligament at lateral side and connects to the neck of the condyle The other borders are attached to capsule ligaments or synovial membranes separately between two joint spaces. TMJ Ligaments : TMJ Ligaments Ligaments : Ligaments Temporomandibular ligament Extends from base of zygomatic process of the temporal bone downward and oblique to the neck of the condyle The ligament reinforces and strengthens the lateral part of the capsular ligament Ligaments : Ligaments Stylomandibular ligament From styloid process and runs downward and forward to attach broadly on the inner aspect of the angle of mandible Separates the parotid and submandibular salivary gland. Ligaments : Ligaments Sphenomandibular ligament Arises from the angular spine of sphenoid bone and petro-tympanic fissure, ending at lingula of mandible Remnant of the dorsal part of the Meckel’s cartilage. Functions of Ligaments : Functions of Ligaments Accessory ligaments may limit border movements of the mandible Fibrous capsule and TM ligament may limit of extreme lateral movements in wide opening of mandible Masticatory Muscles : Masticatory Muscles Masseter muscle Temporalis muscle Medial pterygoid muscle Lateral pterygoid muscle Masseter muscle : Masseter muscle Superficial layer O : lower border of malar bone, Zygomatic arch & zygomatic process of maxilla R : Downward and Backward I : Angle of mandible and inferior half of the lateral side of mandible Masseter muscle : Masseter muscle Deep layer O : Internal surface of zygomatic arch R : Downward (vertical) I : Ramus of mandible and base of coronoid process Masseter muscle : Masseter muscle N: Masseteric nerve, a branch of the anterior division of the mandibular nerve. A: The muscle elevates the mandible to close the mouth; and clenches the teeth. Temporalis muscle : Temporalis muscle 3 bundles Anterior bundle (vertical fibre) Action: Mandible elevator (Close jaws), crushing and chewing at C.O. Inaction: Mandible depression (Opening and Opening against resistance) Temporalis muscle : Temporalis muscle Posterior bundle (Horizontal bundle) Action: Mandibular retraction and positioner Inaction: Mandibular depression and protrusion Intermediate bundle Action: Protrusive movement Nerve supply Ant. and Post. deep temporal nerve Med. Pterygoid muscle : Med. Pterygoid muscle O : Pterygoid fossa and medial surf. of the lateral pterygoid plate I : Inf. + Post. border of ramus and angle of mand. R : Downward and Backward N : Medial Pterygoid nerve Rectangular shape at medial surface of ramus, synergistic with Masseter muscle Lat. Pterygoid muscle : Lat. Pterygoid muscle Superior head O: Wing of sphenoid and infratemporal crest R: Downward and Backward Inferior head O: Lateral surf. of lateral pterygoid plate R: Upward and backward Lat. Pterygoid muscle : Lat. Pterygoid muscle Insertion of superior and inferior heads Ant. portion of the condylar neck (pterygoid fovea) Ant. surface of the articular capsule Ant. Border of the disk Function Opens the jaws, protrudes and lateral movement while moving the disk forward Lat. Pterygoid muscle : Lat. Pterygoid muscle Superior head Synergistic with elevator group of muscle for closing and clenching Inferior head Synergistic with supra-hyoid group of muscle for opening jaw Nerve supply Lateral pterygoid nerve Non Masticatory Muscle : Non Masticatory Muscle Digastric muscle Mylohyoid muscle Geniohyoid muscle Orbicularis Oris Mandibular movements : Mandibular movements The important movements are those taking the mandible from the rest position, or from an adaptive postural position, to occlusion, as occurs during swallowing, and those that occur with teeth in contact. Mandibular closure: : Normal closure: Upwards and Forwards Rotational movement Horizontal axis of rotation Frontal (vertical) axis of rotation Sagittal axis of rotation Closure from adaptive postural position: Upwards and backwards Mandibular closure: Rotational Movement : Rotational Movement Around the horizontal axis (hinge axis) Rotational Movement : Rotational Movement Around the frontal (vertical) axis Rotational Movement : Rotational Movement Around the sagittal axis Translocated closure : Translocated closure Mandibular movements in occlusal contact (functional movements) : Mandibular movements in occlusal contact (functional movements) Sagittal Plane Border Movement : Sagittal Plane Border Movement Sagittal Plane Border Movement : Sagittal Plane Border Movement Posterior open border Anterior open border Superior contact border Functional movements Horizontal Plane Border Movement : Horizontal Plane Border Movement 1.Left lateral border 2.Continued left lateral border with protrusion 3.Right lateral border 4.Continued right lateral border with protrusion 5.Functional movements Horizontal Plane Border Movement : Horizontal Plane Border Movement Continued right lateral border with protrusion Horizontal Plane Border Movement : Horizontal Plane Border Movement Functional movements Frontal (Vertical) Border and Functional Movement : Frontal (Vertical) Border and Functional Movement Frontal (Vertical) Border and Functional Movement : Frontal (Vertical) Border and Functional Movement Left lateral superior border Frontal (Vertical) Border and Functional Movement : Frontal (Vertical) Border and Functional Movement Right lateral opening border Frontal (Vertical) Border and Functional Movement : Frontal (Vertical) Border and Functional Movement Functional movements TEMPORO-MANDIBULAR JOINT SOUNDS : TEMPORO-MANDIBULAR JOINT SOUNDS TMJ sounds : TMJ sounds Healthy TMJs with normal function and without degenerative or arthritic changes are clinically silent. The examiner does not hear any clicking or crepitation at auscultation. Audible TMJ sounds are considered to be cardinal signs of TMJ dysfunction and pathology. TMJ sounds may occur in patients without pain or any other S&S of TMD and are then usually not treated unless disturbing because of being very loud. Reciprocal clicking and disc displacement with reduction (DDR) : Reciprocal clicking and disc displacement with reduction (DDR) Degenerative changes in the disk & Re-modelling of the Condyle : Degenerative changes in the disk & Re-modelling of the Condyle Methods used for TMJ Sound/Vibration Recording : Methods used for TMJ Sound/Vibration Recording Palpation. Auscultation with stethoscope. Patient Report. Electronic recording with microphones. Electronic recording with skin contact transducers. Palpation : Palpation Palpation has a limited value. One may feel low frequency vibrations and the movements of joint components with fingers but that is not hearing. Sounds cannot be palpated with fingers as listening with ears is more appropriate. One cannot store palpation findings in a way that one can make reliable comparisons between sessions and observers. Auscultation : Auscultation The ability to hear differs between examiners. One may hear sounds that are not audible for others. Therefore one cannot compare observations in a reliable way. One cannot store auscultatory findings in a way that you can make reliable comparisons between sessions and observers. Diagnoses based only on auscultation may be directly misleading and lead to false conclusions about type and location of disk dysfunction. People are different : People are different Hearing sound is one thing. Describing what you heard is a totally different story and difficult if not impossible for most people. Classifications such as clicking and crepitations are by necessity very crude and do not make it possible to relate with certainty the sound characteristics to different types of pathology. Even if people could hear sounds the same way they may not be able to describe them in a way that other examiners always understand what they heard. Few people hear sounds the same way. Hearing ability deteriorates with age and may be quickly impaired in those exposed to loud environmental noise. : Few people hear sounds the same way. Hearing ability deteriorates with age and may be quickly impaired in those exposed to loud environmental noise. Players in baseball, tennis, golf can hear the difference between bad and good hits. : Players in baseball, tennis, golf can hear the difference between bad and good hits. TMJ sounds differ too depending on joint conditions but one may need an objective electronic recording to detect and analyze differences. Patient Report : Patient Report In the research it is found that the patient reports are more reliable than recordings with auscultation. One of several reasons could be that the TMJ is very close to the ear canal. Electronic Recording using Earphones : Electronic Recording using Earphones Electronic recording has significant advantages as compared to auscultation and palpation May lead to false conclusions if used without good knowledge about TMJ anatomy, acoustics, and signal analysis. Electronic Recording using Earphones : Electronic Recording using Earphones The Frequency range of TMJ Sounds : The Frequency range of TMJ Sounds The Frequency range of Crepitation : The Frequency range of Crepitation DDR Closing Vibrations are often not audible with stethoscope : DDR Closing Vibrations are often not audible with stethoscope Clinical use of EMG in Jaw Muscle Dysfunction. : Clinical use of EMG in Jaw Muscle Dysfunction. With electromyography (EMG) we can observe and record relevant muscle activity in a way that is not possible with any other method. Measured usually in μV or mV, shows how the potential difference in voltage between two electrodes in or above the muscle changes as a function of time. : Measured usually in μV or mV, shows how the potential difference in voltage between two electrodes in or above the muscle changes as a function of time. Electromyography (EMG) is the study of muscle function through the inquiry of the electrical signal the muscle emanates References : References Text book of orthodontics - T.D. Foster Textbook of orthodontics -Gurkeerat Singh Textbook of Oral Histology -Orbans Burkitt’s Oral Medicine Garden of orthodontics –Cozzani Textbook of Human Anatomy- B.D. Chuarasia Internet sources Thank you : Thank you

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