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Copy of STABILITY AND SUPPORT IN COMPLETE DENTURES
Transcript of Copy of STABILITY AND SUPPORT IN COMPLETE DENTURES
Factors affecting stability
How to check?
Methods for improving stability
CONTENTS SUCCESS OF COMPLETE DENTURE DEFINITION(GPT-8) 1)That quality of maintaining a constant character or position in the presence of forces that threaten to disturb it; the quality of being stable; to stand or endure.
2)The quality of a removable prosthesis to be firm, steady or constant to resist displacement by functional horizontal or rotational stresses.
3) Resistance to horizontal displacement of prosthesis.
FACTORS CONTRIBUTING TO STABILITY Ridge height.
Residual ridge relationships
Form and contour of polished surface
Esthetics RESIDUAL RIDGE ANATOMY Residual ridge height & contour
SHAPE OF PALATAL VAULT A steep or high arched palate enhances the stability by providing greater area of contact and long inclines approaching at right angle to the direction of force
ARCH FORM – square or tapered arches tends to resist rotation of the prosthesis better than the ovoid arches. MANDIBULAR LINGUAL FLANGE Approaches 90 degrees to occlusal plane.
THE RELATIONSHIP OF THE DENTURE BASE TO THE UNDERLYING TISSUES NEUTRAL ZONE MUSCLES INVOLVED DISLOCATING MUSCLES FIXING MUSCLES Vestibular:
Incisive Labii Infer.
INFLUENCE OF OROFACIAL MUSCULATURE The proper contour of the denture flanges permits the horizontally directed forces, that occur during contraction of these muscles, to be transmitted as vertical forces tending to seat prosthesis.
IMPORTANCE OF MODIOLUS Formed by insertion of several muscles of lips & cheek.
None of these muscles contains fibres that have more than one bony attachment, they depend on fixation of the modiolus to allow isometric contraction
In the premolar region the mandibular denture should exhibit both a shortened and narrowed flange to permit the action that draws the vestibule superiorly and the modiolus medially against the dentures
These muscles are:-
Levator anguli oris.
Depressor anguli oris.
Quadratus labii superioris.
Depressor labii inferioris BALANCED OCCLUSION THE RELATIONSHIP OF EXTERNAL SURFACE AND PERIPHERY TO SURROUNDING OROFACIAL MUSCULATURE The bilateral, simultaneous, anterior and posterior occlusal contact of teeth in centric and eccentric positions. (GPT-8)
Absence of occlusal balance will result in leverage of the denture during mandibular movement, compromising stability.
LINGUALIZED OCCLUSION Balancing and working contacts should occur only on the maxillary lingual cusps.
In lingualized occlusion, vertical forces are centralized on the mandibular teeth, it is proposed to aid in stability OCCLUSAL PALNE It should be parallel to & anatomically oriented to the ridges.
Elevated occlusal plane prevents the tongue from reaching over the food table.
If occlusal plane is tipped , loss of stability RIDGE RELATIONSHIP Set the teeth in cross bite when the ridges are in severe cross bite.
In mandibular prognathism – sufficient posterior occlusion must be developed.
POSITION OF TEETH Anterior & posterior teeth should be arranged as close as possible to position once occupied by natural teeth.
The arch curvature should correspond to curvature of alveolar ridge, facial contour and maxillary lip position.
POSITION OF MAXILLARY ANTERIOR TEETH Arranging teeth in square arch form causes canines to be labial to crest than centrals
This results in bicuspids being more buccal to the ridge .
Working side occlusal pressure produces a displacing tendency, the ridge crest acting as a fulcrum.
The labial axial inclination of the natural anterior tooth places the incisal edge labial to the center of rotation of the tooth, if prosthetic tooth is placed exactly in the same position as the natural crown it will be labial to the ridge support.
Incisal pressure causes a displacing torque POSITION OF MANDIBULAR ANTERIOR TEETH It should be in harmony with the maxillary anterior tooth position.
Overbite should be minimum as possible POSITION OF MAXILLARY POSTERIORS The normal residual alveolar ridge resorption pattern leads to increased cross bite relationship.
Tendency to avoid crossbite arrangement results in placing maxillary teeth in buccal position or mandibular teeth in lingual to desired position.
In such cases, the working side occlusal pressure causes a displacing tendency because the line of force is buccal to the fulcrum.
MANDIBULAR POSTERIOR TEETH The buccal cusps and fossae of the posterior mandibular teeth should be directly over the crest of the ridge.
If placed more buccally, working side occlusal pressure causes a displacing tendency because the line of force is buccal to the fulcrum.
If placed more lingually, tongue will displace the denture ESTHETICS Refers to development of buccal & labial borders to support the lips & cheeks.
Avoid thick denture borders HOW 2 CHECK STABILITY????????????? Pressure is applied with the ball of the finger in the premolar-molar regions of each side alternatively.this pressure must be at right angle to the occlusal surface. If pressure on one side causes the denture to tilt and raise on the other side, it indicates that the teeth on the side on which the pressure was applied are outside the ridge.
MAXIMIZING STABILITY Maximum coverage of denture bearing area within physiologic limit.
Giving due respect to muscle actions.
Use of neutral zone.
Establishing correct occlusal plane & teeth position
Non interceptive occlusion.
Patient education regarding tongue position, diet habit etc.
Use of denture adhesives.
Using soft relining materials
Surgeries for ridge correction-
Frenectomies, excision of hyperplastic tissues,correction of bone deformities.
Surgeries for ridge extension:-
Vestibuloplasty, ridge augmentation procedures.
SURGICAL METHODS VESTIBULOPLASTY RIDGE AUGMENTATION MYLOC SYSTEM SOFT LINERS OVER DENTURES Dentures get more ridge support, this enhances the retention of the denture and ultimately stability gets improved.
Rate of resorption of residual ridge decreases RELATIONSHIP OF OPPOSING OCCLUSLSURFAES STABILITY AND SUPPORT IN COMPLETE DENTURES Maximum coverage without undue displacement of tissue, the development of a good border seal, and close adaptation helps in improving stability.
DENTURE BASE ADAPTATION SUBLINGUAL CRESCENT SPACE The crescent shaped area on the anterior floor of the mouth formed by the lingual wall of the mandible and the adjacent sublingual fold ARCH FORM The potential space between the lips & cheeks on one side & the tongue on the other; that area or position where the forces between the tongue and cheeks or lips are equal.[GPT-8]
FIXNG MUSCLES SUPPORT SUPPORT CONTENTS DEFINITION Support is the resistance to vertical movement of the denture base towards the ridge.
(Jacobson & Krol , JPD 1983)
Maintain established occlusal relations & minimum tissue ward movement of denture Support can be considered by
Dentures should conform to underlying tissues
TYPES OF SUPPORT i) INITIAL DENTURE SUPPORT :
Is achieved by using impression procedures that provide optimal extension and functional loading of the supporting tissues, which vary in their resiliency.
ii) LONG –TERM SUPPORT:
Is obtained by directing the forces of occlusal loading toward those tissue most resistant to remodeling and resorptive changes.
AREAS OF SUPPORT Primary
Slight Primary support Areas of ridge that are at right angles to occlusal forces.
In Maxillary – posterior ridges & flat areas of palate
In Mandibular –posterior ridges, buccal shelf , & pear shaped pad
Secondary support Areas of ridge that are greater than at right angles to occlusal forces
Maxillary - anterior ridge & ridge slopes
Mandibular – anterior ridge & ridge slopes
Slight areas Areas of displaceable tissues i.e., all the vestibular areas provide very little support NATURE OF SUPPORTING TISSUES It mainly includes:
Glickman , Krol -
Biological makeup of individual determines the relative resistance of bone to resorption.
Wolff’s law –
Bone responds to forces by remodelling PRESSURE-TENSION CONCEPT Pressure stimulates resorption where as tension maintains the integrity or actually causes deposition of bone.
Presence of tissues that are relatively resistant to remodeling and resorptive changes.
Cortical bone is more resistant to resorption than cancellous or spongy bone
Soft tissues ORAL MUCOSA – contain 3 layers
Presence of keratinized, firmly bound mucosa permits the tissues to better resist stresses.
Presence of a layer of resilient submucosa permits moderate compressibility without mechanical impingement of the mucosa between the denture base and underlying bone.
Acts as a “ hydraulic cushion”
A keratinized masticatory mucosa firmly bound to underlying cortical bone through a variable zone of connective tissue and submucosa with associated muscle attachments that provides the ideal denture-bearing tissue.
ANATOMIC CONSIDERATIONS OF DENTURE BEARING AREA Denture bearing areas –
Relief areas MANDIBULAR ANATOMIC CONSIDERATIONS Supporting areas Primary
Pear shaped pad Secondary
Ridge slopes Pear shaped pad Pear-shaped pad is the most distal extent of the keratinized masticatory mucosa of the mandibular ridge and is formed by the scarring pattern of the extracted third molar and its retromolar papilla.
Mucosa covering is usually attached gingiva.
Mandibular denture should terminate over the distal edge of pear shaped pad.
Buccal shelf area The surface of the mandible from the residual alveolar ridge or alveolar ridge to the external oblique line in the region of the lower buccal vestibule MAXILLARY ANATOMIC CONSIDERATIONS MAXILLARY ANATOMIC CONSIDERATIONS Support areas PRIMARY
Flat areas of palate
Palatine rugae RELIEF REGIONS Tissues that are susceptible to resorption should not be subjected to functional forces
Regions that have a thin mucosa directly over hard cortical bone
Regions of mucosa overlying neurovascular bundles.
eg.:maxillary and most mandibular ridge crests
eg.:palatal midline raphe, tori & exotoses, lingual surfaces of the mandible, mylohyoid ridges.
eg.:incisive papilla, mental foramen
Factors affecting support Surface area –
Greater the surface area , greater will be the support.
SNOW SHOE PRINCIPLE Maximal extension is that given a constant occlusal force, a broader denture-bearing area decreases the stress per unit area under the denture base, decreases tissue displacement, and reduces denture-base movement Impression procedure
Mucostatic Tissues recorded in passive state.
Unstable during function.
Mucocompressive Records the oral tissues in a compressive state.
Given by carole jones. Selective pressure technique Proposed by boucher.
Place stress upon those areas of maxilla and mandible that are able to resist functional forces of the denture bases.
Use of wax spacer in relieving areas
Escape holes – 1mm in diameter
Methods for improving support Surgical removal of pendulous tissue
Use of tissue conditioning material
Surgical reduction of sharp or spiny ridge
Surgical enlargement of ridge
Implants & over dentures.
They flow for an extended period so that the distorted tissues can rebound and assume their original form
Helps in distribution of occlusal forces evenly. Use of tissue conditioners INTRODUCTION
TYPES OF SUPPORT
METHODS 2 IMPROVE STABILITY