Occlusion is different between natural and artificial teeth. Natural teeth have proprioception and move independently, while artificial teeth move as a unit on the denture base. Anatomic teeth can cause trauma in edentulous patients due to horizontal forces from cuspal inclines. Non-anatomic teeth are flat with no cusps, reducing horizontal forces but losing some function. An ideal artificial occlusion balances stability, function, and minimizing trauma.
Occlusion is different between natural and artificial teeth. Natural teeth have proprioception and move independently, while artificial teeth move as a unit on the denture base. Anatomic teeth can cause trauma in edentulous patients due to horizontal forces from cuspal inclines. Non-anatomic teeth are flat with no cusps, reducing horizontal forces but losing some function. An ideal artificial occlusion balances stability, function, and minimizing trauma.
Occlusion is different between natural and artificial teeth. Natural teeth have proprioception and move independently, while artificial teeth move as a unit on the denture base. Anatomic teeth can cause trauma in edentulous patients due to horizontal forces from cuspal inclines. Non-anatomic teeth are flat with no cusps, reducing horizontal forces but losing some function. An ideal artificial occlusion balances stability, function, and minimizing trauma.
Occlusion is different between natural and artificial teeth. Natural teeth have proprioception and move independently, while artificial teeth move as a unit on the denture base. Anatomic teeth can cause trauma in edentulous patients due to horizontal forces from cuspal inclines. Non-anatomic teeth are flat with no cusps, reducing horizontal forces but losing some function. An ideal artificial occlusion balances stability, function, and minimizing trauma.
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OCCLUSION IN EDENTULOUS
PATIENT INTRODUCTION Occlusion is the factor that is common to all branches of the dentistry.
According to G.P.T.-8 , It is defined as-
1. the act or process of closure of being closed or shut off, 2. the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues. ARTICULATION According to G.P.T – 8 , it is defined as the dynamic contact relationship between the occlusal surfaces of the teeth during function. The force that develop during occlusal contacts , may vary in magnitude and direction, it must always be resisted by supporting tissue. Control of this resultant force is a basic and perplexing problem that is controversial, especially in the field of complete dentures. Q. How occlusion in dentulous mouth is different from that in an edentulous mouth ? Natural Occlusion Artificial Occlusion 1. Each tooth individually is 1. All the teeth are supported by periodontal supported by a tissue and has its common denture base proprioceptive feedback that rests upon the slippery tissue i.e. mucosa 2.Each tooth can move 2. All the teeth move independently and can as a unit with the migrate slowly to favorable denture base. occluding positions. Natural Occlusion Artificial Occlusion 3. Incising with the anterior 3. Incising from anterior teeth does not affect the teeth can potentially cause posterior teeth. tipping of the denture from the posterior. 4.Balancing side contact 4. Balancing side contact rarely found, if present (bilateral balancing) considered as balancing side necessary for base stability. interference. 5. Due to proprioceptive 5. Due to lack of mechanism a person can proprioceptive mechanism avoid premature contacts any premature contacts and and interferences. cuspal interference will dislodge the denture. 6. Malocclusion of natural 6. Malocclusion on artificial teeth does not evoke any teeth evokes an immediate immediate response. response and affects all the teeth and base. Natural Occlusion Artificial Occlusion 7. Horizontal thrusts on one 7. The effect is bilateral and side during mastication are is usually traumatic in well tolerated and affect nature. only the side involved.
8. Molars are the power 8. Chewing from II molar
points of masticatory force , region wil shift the denture esp. II molars which are base if it is on inclined important for chewing of foundation . tough food. REQUIREMENTS OF COMPLETE DENTURE OCCLUSION
The difference between the natural and artificial
teeth and the requirements for artificial occlusion make it necessary to consider the dentist created occlusion as an unique problem. As we all know that mandibular dentures are inherently less stable than the maxillary dentures, so the occlusal design and the positions of the lower occlusal units should be given FIRST preference. Acc. To Ortmann (1971) the requirements for complete denture occlusion are – Stability of occlusion in centric relation; Balanced occlusion for eccentric contacts; Unlocking of the cusps mesiodistally to accommodate the inevitable settling of the denture base; Control of horizontal force by buccolingual cusp height reduction according ridge;
Functional balance by favourable tooth to ridge
crest relation; Cutting and shearing efficiency; Anterior clearance of teeth during masticatory function; Minimal occlusal stop areas for reduced pressure during function. REQUIREMENTS OF THE INCISING UNITS
1. Should be sharp to cut efficiently.
2. Should be out of contact during mastication. 3. Should have as flat an incisal guidance as is possible. 4. Should have horizontal overlap to allow for setting of the bases. 5. Should engage only during protrusive incising function. REQUIREMENTS OF WORKING OCCLUSAL UNITS 1.Should be efficient in cutting and grinding. 2.Should be narrow buccolingually to decrease work force transfer to denture foundation. 3. Should be over the ridge crest or slightly lingual to it , for lever balance. 4.Should have surface to transmit occlusal force vertically. 5.Should center the work load anteroposteriorly on the denture foundation. 6.Should present a occlusion as nearly parallel to the mean foundation plane as is possible. REQUIREMENTS OF THE BALANCING OCCLUSAL UNITS
1. Should contact in 2nd molar region when the
incising units contact during function. 2. Should contact at the end the masticatory stroke when the working units contact. 3. Should have smooth gliding contact for lateral and protusive sliding extrusions Types of Posterior Teeth 1. Anatomic teeth: Acc. To G.P.T- 8 , this is defined as artificial teeth that have cuspal inclination greater than 0 degree, and which tend to duplicate natural teeth in appearance.
(a) Standard anatomic teeth: Those anatomic teeth
which have cusp inclines of approximately 33o or more and closely resemble natural teeth. (b) Modified or semi anatomic teeth: Those anatomic teeth which have cusp inclines lesser than 33o (I.e. less steep) and they look somewhat like natural teeth.
2. Non-anatomic teeth: Non-anatomic teeth are flat with
no cusp heights to intercuspate with opposing teeth. Their occlusal surface has various designs of flat planes and sulci to enhance their masticatory efficiency. ANATOMIC TEETH The natural teeth in dentulous mouth function in harmony with their opposing member giving efficient and comfortable mastication.
However in edentulous mouth these same teeth can
cause trauma , discomfort, and instability to the bases because of the horizontal components they generate.
The basic problem initially is the coordination of these
cuspal inclines to harmonize with the mandibular movements. Even if this is done , with meticulous records on adjustable articulator, it can not exist for long when transferred to the mouth. PROBLEMS OF UNMODIFIED ANATOMIC TEETH 1. It is mandatory to use an adjustable articulator. 2. Both centric and eccentric records need to be made for articulator adjustments. 3. Mesio – distal locking will not permit settling of the bases without development of horizontal forces . 4. Carefully balanced lateral positions become unbalanced with settling. 5. The bases need prompt and frequent refitting to keep the occlusion harmonious. 6. The presence of cusp generate more horizontal force during mastication. 7. Tooth contacts do not always occur in the same horizontal position (I.e. the centric recorded). Many jaw closures also occur anterior and lateral to this centric position. But due to prominence of the cusps, there is no freedom of tooth contact during such jaw closures, hence deflective forces act on the base during such jaw closures leading to base instability and increased residual ridge resorption. NONANATOMIC TEETH
Acc. To G.P.T – 8 , nonanatomic teeth are defined as
artificial teeth with occluding surfaces that are not anatomically formed. The term nonanatomic as applied to artificial posterior teeth , and especially their occlusal forms , means that such teeth are designed in accordance with the principles rather than from the viewpoint of anatomic teeth with flat occlusal surfaces set to flat occlusal plane. ADVANTAGES OF NON-ANATOMIC TEETH 1. Versatility of use, hence can be used in class II and III jaw relations also. 2. They are used more easily when variation in the width of upper and lower jaws indicate a cross bite setup. 3. Centric occlusion is more of an area and less of a precise point in these teeth hence they allow closure of jaws over a broad contact area. 4. Minimal horizontal pressures are created because of elimination of inclined planes.
5. Zero degree teeth permit the use of a simplified
and less time consuming technique and offer greater comfort and efficiency for longer duration. 6. The accommodate better to the inevitable negative changes in the ridge that occur with aging. According to the Jones ,the use of zero degree teeth should not only be limited to the patients with unfavorable prognosis, and their uses should be extended to include those patients with favorable prognosis, because those mouths which are favorable today will get unfavorable a decade or two later. We must not forget the De Van's famous lines that we be as concerned with preserving what is left as with the restoration of what is missing. DISADVANTAGES OF NON- ANATOMIC TEETH 1.Since these teeth are flat hence occlusion occurs only in 2 dimensions , but the mandible, due to the incline of condylar path, moves in three dimensional arcuate path.
Fig 13.25 , 238, winklr
2. Due to flatness of occlusion, bilateral and protrusive balance is not possible. But it can be made to develop in monoplane occlusion with the help of balancing ramps, tripodization with tilting the 2nd molars, and by the incorporation of compensating curve.
3. They appear dull and unnatural to some patients
and may create a psychological problem concerning function and esthetics. 4. The vertical component present in mastication and nonfunctional movements is not provided for , so that this form loses shearing efficiency. 5. They cannot be corrected much by occlusal grinding without impairing their efficiency. 6. They don't function efficiently unless the occlusion surface provides cutting ridges and generous spillways (sluiceways). 7. If for phonetic and esthetic demands, a deep vertical overlap is required and overjet cannot be increased beyond a limit, then the monoplane occlusion has potential for anterior interference during, due to absence of cusp lift. BALANCE AS RELATED TO COMPLETE DENTURE
When forces act on a body in such a way that no
motion results, then there is balance or equilibrium. This should be the primary aim of the dentist I.e. to achieve a stable base. In order to do so the following axioms have to be followed: by Sears 1. The wider and larger the ridge and closer the teeth are to the ridge, the greater the balance. 2. Conversely, the smaller and narrower the ridge and farther the teeth from the ridge, the poorer the balance. 4. The wider the ridge and narrower the teeth buccolingually, the greater the balance. 5. Conversely, the narrower the ridge and wider the teeth, the poorer the balance. 6. The more lingual ( with in limits provided by the tongue) the teeth are placed in relation to alveolar ridge crest, the greater the balance. 7. The more buccal the teeth are positioned, the poorer the balance. TYPES OF BALANCE Balance may be lever or occlusal and unilateral, bilateral, or protrusive.
1. UNILATERAL LEVER BALANCE
This is present when there is balance of the base on its supporting structures when bolus food is interposed between the teeth on one side and a space exits between the teeth on the opposite side. Following points encourages the lever balance- a) Teeth placement should be such that to direct the resultant force on the functioning side over the ridge or slightly lingual to it. b) Having the denture base cover as wide an area on the ridge as possible. c) Placing the teeth as close to the ridge as other factors will permit. d) Using as narrow a buccolingual width occlusal food table as practical.
2. UNILATERAL OCCLUSAL BALANCE
This is present when the occlusal surfaces of
teeth on one side articulate simultaneously as a group , with a smooth uninterrupted glide. 3. BILATERAL OCCLUSAL BALANCE
This is present when there is equilibrium on
both sides of the denture due simultaneous contact of the teeth in centric and eccentric occlusion. It requires a minimum of three contacts to establish a plane of equilibrium. This balance is dependent on the interaction of the incisal guidance, plane of occlusion, angulations of teeth, compensating curve, and condylar guidance. 4. PROTRUSIVE OCCLUSAL BALANCE
This is present when the mandible moves essentially
forward and the occlusal contacts are smooth and simultaneous in the posterior both on right and left sides and on the anteriors.
It is slightly different from bilateral balance in that i
requires a minimum of three contacts, one on eac side posteriorly and one anteriorly, and is dependent on interaction of the same factors as bilateral occlusal balance. This entire concept of balanced occlusion must be considered in terms of the following: 1) The tooth size and position in relation to the ridge size and shape. 2) The extent of denture base coverage. 3) Occlusal balance with stable contacts at the retruded border position and in an area (long centric) anterior to it. 4) Right and left eccentric occlusal balance by simultaneous contacts at the limit of functional and parafunctional activity. 5) Intermediate occlusal balance for all positions between centric occlusion and all other functional or parafunctional excursions to the right, left and protrusive. this balance is probably the most important , as it allows for smooth uninterrupted tooth contacts in the dynamics of daily mandibular movements. ADVANTAGES OF BILATERALLY BALANCED OCCLUSION Prime gave the concept of “ ENTER BOLUS EXIT BALANCE” which implies that introduction of food on one side will prevent the teeth of opposite side from contacting and hence occlusal balance is impossible during mastication.
However Sheppard (1964) later gave the concept of
ENTER BOLUS ENTER BALANCE according to which even while chewing, the teeth cut through the bolus and come in contact with each other, for few fractions of a second. Hence the stability of the denture is maintained during various movements of mandible during chewing. Moreover, the bilateral balanced occlusion is even more important during functional and the parafunctional activities like swallowing of the saliva, closing to seat the denture and bruxing of the teeth during times stress,etc.
Patient with balanced occlusal design do not upset
the normal static , stable , and retentive position of their denture
Balanced occlusion thus will make such episode less
damaging to the supporting structures during the times of stress. FACTORS AFFECTING BALANCED OCCLUSION As described by the Rudolph L.Hanau there are five factors involved in balanced occlusion of CD. These factors are: 1. Condylar guidance 2. Incisal guidance 3. Plane of occlusion 4. Compensating curve 5. Inclination of the cusps. Vincent r. Trapozanno (1963) criticized Hanau `s Five factors of occlusion , and concluded that only three factors out of five are important, viz, Condylar guidance, incisal guidance, and cusp angulation. CONDYLAR GUIDANCE As defined by G.P.T-8, it is mandibular guidance generated by the condyle and articular disc traversing the contour of glenoid fossae. There is controversy that whether condylar path is precise or not. However some studies says some thing different. Kurth (1954) claims that condylar path is not same for varying incisal guidance. Payne (1951) has shown that mandible can move to follow steep cusps, modified cusps and zero degree teeth when there is posterior harmony and no anterior interference is present. Weinberg (1976) has demonstrated that the condylar path may vary with the variable pressure of occlusion. As stated by Hanau ( and agreed by Trapozzanno) the condylar guidance is the factor edentulous patient presents and can no way be modified by the operator. Factors which determine the registration of condylar guidance are – a) Shape of the bony contour of glenoid fossae; b) Muscles attaching to the mandible ; c) Limitation of the movement by attached ligaments. d) The registration method used. i.e. If registration method require bases to rest on tissue of mandible and maxilla, the REALEFF can modify the recordings. INCISAL GUIDANCE As defined by G.P.T- 8 it is the influence of the contacting surfaces of the mandibular and maxillary anterior teeth on mandibular movements. And incisal guide angle is defined as the angle formed by the intersection of the plane of occlusion and a line within the sagittal plane determined by the incisal edges of the maxillary and mandibular central incisors when the teeth are in maximum intercuspation. As it is more near to masticating teeth surfaces ( as compared to condylar guidance) it has a dominant influence on contacting surfaces of the teeth posterior to it. In C.D construction it is largely under the control of the dentist , the limitations governing it are- a) Ridge relation, b) Arch shape, c) Ridge fullness d) Interridge space e) Phonetics and esthetic requirements of the patients. Originally Hanau described 2 incisal guidance viz sagittal protrusive I.G and lateral I.G.
Coming to lateral I.G, is determined by
considering the relationship of all incisors and cuspids , both maxillary and mandibular ( in pure right and left lateral movements ) . Trapozanno( 1963) defined it as the steepest angle formed with the horizontal plane by drawing a line between the incisal edges of the maxillary and mandibular incisors and cuspids of both right and left segments when the teeth are in centric occlusion
For C.D construction Incisal guidance should be
as flat as esthetics and phonetics will permit. PLANE OF OCCLUSION Acc. To G.P.T -8 it is defined as the average plane established by the incisal and occluding surfaces of the teeth . Generally , it is not a plane but represents planer mean of the curvature of these surfaces.
This plane is established in anterior region by
the height of lower cuspid which coincides with the commissure of the mouth and in the posterior region by the center ( Winkler) or junction of posterior and middle third of the retromolar pad ( Boucher). These landmarks also provide a physiologically and functionally acceptable anteroposterior inclination of the occlusal plane that is nearly parallel to the lower mean foundation plane. These landmarks also creates an occlusal plane essentially parallel to the ala-tragus line( Camper`s plane). Okane (1979) showed that when occlusal plane is parallel is to the ala – tragus line, the closing force during maximum clenching was greater than when it was altered by +/- 5 degree. • Its position can be altered only slightly without creating serious functional problem. • Its role is not as important as are the other determinants. COMPENSATING CURVE
Acc. To G.P.T -8 , it is defined as (1) the anterio-
posterior curving (in median plane) and the medio-lateral curving ( in frontal plane) within the alignment of occluding surfaces and incisal surfaces of artificial teeth used to develop balanced occlusion. (2) the arc introduced in the construction of complete denture to compensate for the opening influence produced by the condylar and insical guidance's during lateral and protrusive mandibular excursive movements. Fig 6 , 131 ortman article Or 1328 245 wink
It is determined by the inclination of the posterior
teeth and their vertical relationship to the occlusal plane so that the occlusal surface results in a curve that is in harmony with the movement of the mandible as guided by the condylar path posteriorly and incisal guidance anteriorly. A steeper condylar path requires a steeper compensating curve .A lesser compensating curve for steeper condylar guidance would result in steeper incisal guidance acting as anterior interference, causing loss of molar balancing contacts.
The primary function thus of compensating
curve is to provide balancing contacts for protrusive mandibular movements.Without this curve it would be necessary to incline the entire occlusal plane at an angle. With compensating curve it is possible to produce eccentric balance in monoplane occlusal scheme, which is otherwise said to be deficient in this. The compensating curve incorporated in a properly oriented plane of occlusion starts with the first molar by raising it at distal and continuing this initiated curve with further rise in the 2nd molar. The radius of the curve is the result of the guiding influence of the angle of the incisal and condylar guidance. Acc. to Boucher (1963) the value of compensating cusp is that it permits an alteration of the cusp height without changing the form of the manufactured teeth .It is means for making cusps longer or shorter to produce steeper or flatter cusps, simply by inclining the long axis of the teeth to conform to the end guidances. INCLINATION OF THE CUSPS
It is also a determinant, as it modifies the effect of
the plane of occlusion and the compensating curve. The angulation of the cusp is more important than te height of the cusps per se. The mesiodistal cusp heights that interdigitate lock the occlusion so that reposition of the teeth due to setting of the base cannot take place.To prevent this problem, it is advocated that all mesiodistal cusp heights be eliminated in anatomic type teeth.With the teeth so modified, only the buccolingual inclines need be considered as determinants of balanced occlusion. Out of the five factors , only four can be controlled by the dentist. The incisal guidance and plane of occlusion can be altered but only slightly because of esthetic and phonetic limitations. The main factors which can be used and changed effectively are compensating curve and inclinations of the cusps of the teeth . TYPES OF OCCLUSION SCHEMES
Now let us discuss the three main occlusal
schemes i.e Monoplane occlusion, Classical bilaterally balanced occlusion , and Lingulized occlusion . It is of interest to note that none of the occlusal scheme has been proved to be superior to other (for all presenting conditions of edentulous mouths), although one type of scheme may offer some advantages over other. MONOPLANE OCCLUSION Acc. To G.P.T -8 ,it is defined as an occlusal arrangement wherein the posterior teeth have masticatory surfaces that lack cuspal height . Hall (1929) is credited for the introduction of Zero degree teeth calling them inverted cusp tooth, but these teeth have the problem of clogging of food in the depressions onto the occlusal surfaces. Myerson later designed a cusp less teeth with series of transverse buccolingual ridges and sluiceways between them. ADVANTAGES OF MONOPLANE OCCLUSION / ZERO DEGREE TEETH 1. Versatility of use, hence can be used in class II and III jaw relations also. 2. This is used more easily when variation in the width of upper and lower jaws indicate a cross bite setup. 3. Centric occlusion is more of an area and less of a precise point in these teeth hence they allow closure of jaws over a broad contact area. 4. Minimal horizontal pressures are created because of elimination of incline plane. 5. Zero degree teeth permit the use of a simplified and less time consuming technique and offer greater comfort and efficiency for longer duration. 6. They accommodate better to the inevitable negative changes in the ridge that occur with aging. As far as balanced occlusion is concerned in monoplane occlusion two important concepts prevail- A) Non Balanced occlusion (in centric relation only) E.g Neutrocentric concept.
B) Balanced occlusion in centric relation and
lateral excursions This can be achieved with the use of compensating curve, balancing ramps, Tripodization by tilting the 2nd maxillary and mandibular molars, and using monoplane with zero overbite ( but this will compromise phonetics and esthetics.) NEUTROCENTRIC CONCEPT
This is an important example in first category.
Acc. to DeVan the main objectives of neutrocentric concept are- I – Neutralization of the inclines and, II – Centralization of the occlusal forces acting on the denture foundations.
In order to attain these objectives, it is necessary
to reduce the size and number of teeth and to abandon attempts to secure balancing contacts in eccentric positions beyond the range of masticatory stroke. The neutrocentric concept should not be identified with that of the advocates of nonanatomic teeth, who merely dispense with cuspation. It is dangerous to discard cusps without neutralizing other factors of articulation, that is; 1)Orientation of occlusal plane. 2)Compensating curve. 3)Incisal guidance.
These factors concern inclines of
arrangement of teeth, whereas cusps are related to inclines of form. There is only one factor of articulation which cannot be neutralized, ie., the condylar guidance, but which fortunately can be circumvented by a plan involving neutrocentric concept.
If the patient can be persuaded to avoid incising
with artificial teeth, there is no need to be concerned with the sagittal condylar incline.
When incision is avoided and no projection
exists above and below the occlusal plane, the condylar inclination on the articulator may be set at zero. Stability is a tooth-bone relationship while retention is a tooth-mucosa borne relationship.
Stability is not necessary for function; a denture
to function needs only to be retained.
When a denture is unstable however, the patient
may not be able to maintain the initial chewing performance due to chaffing and irritation of the mucosa.
Furthermore, an unstable denture may prove
traumatic to the ridge bone, in time causing its resorption. According to DeVan, the five factors involved in the relation of the teeth to dental foundation are: (a) POSITION There is probably no single tooth factor as important as position.
Acc. to DeVan posteriors should be positioned in as
central position on the foundation as allowed by the tongue, this way denture will be more stable due to enhanced lever balance, and more of the osseous foundation will be saved by the harmful tensile and shearing forces acting on bone and the overlying mucosa.
Clinical observations support the opinion that balancing
contacts in eccentric positions don't nullify the unstabilizing effect of an off-ridge setup Acc. to DeVan the employment of lateral balance intensifies rather than alleviates the problem of stabilizing the denture.
Eccentric balance does help to maintain
retention; but if the use of inclines is essential for its establishment, then bilateral balance causes a decrease in stability.
Balancing inclines shift the denture farther
toward the side of the mastication, preventing its dislodgement while increasing its side displacement. B) PROPORTION
DeVan recommends reduction in the proportion
of the artificial teeth as compared to size of natural teeth.
Reduction in proportion is necessary to develop
centralization of forces, Reduction of frictional forces developing on occlusal surfaces which will transfer to the underlying mucosa and bone. Reduction by 40% in width is possible without serious diminution of the food table. C) PITCH
Pitch is synonymous with inclinations or tilt .
In neutrocentric concept the plane of
occlusion should be oriented so that it is midway and parallel to mean foundation planes of the maxilla and the mandible.
The compensating curve should be neutralized
so that posteriors are placed on a plane rather than on spherical surface. D) FORM
Artificial posterior teeth should be devoid of
projecting cusps.
Contacting occlusal lines should be on a
single plane.
This arrangement will avoid interference from
TMJ and their inclines. E) NUMBER OF TEETH
DeVan recommends reduction in no. of teeth
from 8 per denture to 6 per denture.
This will aid in stability by freeing the lower
ridge molar incline of occlusion.
Elimination of 2nd molar will result in
establishment of centralization and reduction in occlusal area. The 2nd category in monoplane occlusion involves bilateral balance in centric and eccentric relations.
A) WITH COMPENSATING CURVE
Acc. to this concept –
a) No. of posterior teeth should be 3, i.e. mandibular 1st premolar should be omitted.
b) Antero-posterior comp. curve begins at the DMR
of the 2nd premolar and continues till 2nd molar. The amount of this curve is dependent on steepness of the condylar guidance, but is rarely more than more than 20 degree from horizontal. This curve is used to provide the needed tooth structure for protrusive balancing contacts c) Mediolateral compensating curve is also needed to achieve lateral balanced contacts. This curve is initiated from first replacement tooth and continued till the second molar. The degree to which the facial cusps are elevated to establish this curve will vary with the condylar and incisal guidances. The curve usually does not exceed 5- 10 degree. B) WITH BALANCING RAMPS Balancing ramps provide a tripodization of the denture base. As the patient moves the mandible from centric relation to protrusive or lateral positions, there is smooth contact anteriorly on the teeth and posteriorly on the ramps. The balancing contacts give improved Nimmo horizontal stability to the art fig 2 dentures. Esthetics and phonetics are greatly enhanced because there is more freedom in placing anterior teeth. The ramps can be developed after the final try-in of the waxed dentures or at the time of clinically remounting the dentures at the insertion appointment The procedure is performed on a properly adjusted articulator. This technique can be applied to existing dentures by clinical remount.
Working contacts Balancing contact
C) WITH TILTING THE SECOND MOLARS Acc to C G Porter, mandibular second molar is inclined to provide contact with maxillary dentures in all excursions. The maxillary molars are also inclined but left out of centric contact. He recommended the use of French modified posterior teeth which have sub- occlusal surfaces of mandibular buccal cusps directing the occlusal force downward and lingually. LINGUALIZED OCCLUSION Acc. to GPT-8, lingualized occlusion is defined as the form of denture occlusion in which the maxillary lingual cusps articulate with the mandibular occlusal surfaces in centric, working and balancing mandibular positions. Although S. H. Payne(1941) has being credited for being the first one to describe, it was Gysi who used this scheme approximately 20 years earlier. The advantages of lingualized occlusion are: 1) Occlusal forces can be directed lingually without placing the teeth lingually 2) It is specially useful where esthetic demands of the patient is high but presenting oral conditions indicate non- anatomic teeth, e.g., severe ridge resorption, class II & III jaw relationships and highly displaceable supporting tissues. 3) The chewing efficiency is comparable to anatomic (semi) and definitely superior to zero degree teeth. 4) As mesiodistal locking is eliminated by grinding the transverse ridges of the cusp teeth, freedom is provided in the occlusion to accommodate for the settling of denture base. 5) The lateral thrust control (during functional and para-functional movements) is provided by grinding the buccolingual inclines, which is based on the shape and prominence of the ridge and its ability to withstand lateral forces. 6) The para-functional habits are usually confined to a zone of activity around centric relation. The lingualized occlusion provides for smooth balancing contacts with excursive movements of 2-3mm around centric relation, owing to creation of common central fossa in mandibular posteriors by selective grinding of transverse ridges in the process of mesiodistal unlocking. CHARACTERISTICS ANATOMIC LINGUALI NEUTRO ZED CENTRI C ESTHETICS + + - EASE OF + + - PENETRATION DENTURE STABILITY + + - (in parafunct movt ) SIMPLER TECHNIQUE - + + DECREASED LATERAL - + + FORCES EASE OF - + + ADJUSTMENT CLASS II & III CASES - + + STABILITY WITH - + + CENTRALIZED & NEUTRALISED FORCE PLEASURE CURVE In 1937, Dr. Max Pleasure described a reverse occlusal scheme in which the posterior teeth are set with buccal tilt providing total lever balance during function.
But with this
scheme, there is no buccal rise on occlusal surface, so a balancing contact is not possible. Later Pleasure himself modified his occlusal scheme by incorporating both a buccal tilt for lever balance, and lingual tilt for occlusal balance. This is called Pleasure curve. Buccal tilt is given at the premolars , no tilt at first molars and a lingual tilt to second molars. This scheme is specially beneficial for patients with class II jaw relation. The lever balance obtained in the premolar area is nearly at the anterio-posterior center of the denture foundation coinciding with the zone where class II patient functions during light to heavy intermediate chewing. The first molar occlusal surface directs the force directly to the ridge . Lingual tilt of the second molar provides a buccal rise to its occlusal surface to provide for a lateral balancing contact.
A compensating curve is developed in the
first and second molar area to provide for protrusive balance.