LEC 6,7-1.pdf

Occlusion in Complete Denture Lec. 6,7 ‫ غسق هشام‬.‫ د‬.‫م‬.‫ا‬ OCCLUSION : the static relationship between the incising and masticating surfaces of the maxillary or mandibular teeth or tooth analogues. ARTICULATION : It is contact r...

Occlusion in Complete Denture Lec. 6,7 ‫ غسق هشام‬.‫ د‬.‫م‬.‫ا‬ OCCLUSION : the static relationship between the incising and masticating surfaces of the maxillary or mandibular teeth or tooth analogues. ARTICULATION : It is contact relationship of maxillary and mandibular teeth as they move against each other. centric relation CR; a maxilla mandibular relationship, independent of tooth contact, in which the condyles articulate in the anterior-superior position against the posterior slopes of the articular eminences.it is a clinically useful, repeatable reference position.(bone to bone) centric occlusion : the occlusion of opposing teeth when the mandible is in centric relation; this may or may not coincide with the maximal intercuspal position. (tooth to tooth) occlusal balance : a condition in which there are simultaneous contacts of opposing teeth or tooth analogues on both sides of the opposing dental arches during eccentric movements within the functional range occlusal harmony : a condition in maximal intercuspal position and eccentric jaw relation in which there are no interceptive or deflective contacts of occluding surfaces occlusal interference 1. Any tooth contact that inhibits the remaining occluding surfaces from achieving stable and harmonious contacts; 2. Any undesirable occlusal contact Maximal intercuspal position the complete intercuspation of the opposing teeth,independent to condylar position ✓ Mandibular movement can be: opening closing, protrusive, and lateral in lateral it may be Working side is the side that the mandible move toward it in lateral excursion. Nonworking side is the side that the mandible move away from during lateral excursion. Requirements of ideal complete denture occlusion: 1. Stability of denture in both centric and eccentric relation. 2. Balanced occlusal contact bilateral. 3. Cusp height reduced to control horizontal force. 4. Cutting, penetrating and shearing efficiency of occlusal surface. 5. Incisal clearance during posterior function like chewing. 6. Unlocking (removing interference) of cusps mesiodistally. Objectives of occlusion in complete denture Preservation of the remaining tissues Proper masticatory efficiency Enhancement of denture stability, retention and support Enhancement of phonetics and esthetics TYPES OF OCCLUSION o Balance occlusion o Lingualized occlusion o Monoplane occlusion Balance occlusion Balance occlusion in complete dentures can be defined as stable simultaneous contact of the opposing upper and lower teeth in centric relation position and a continuous smooth bilateral gliding from this position to any eccentric position within the normal range of mandibular function. In lateral excursion: (working side) Anterior teeth- the maxillary & mandibular anterior teeth contact on the working side. Posterior teeth- the buccal & lingual cusps of the maxillary & mandibular posterior teeth are in contact. If lingualized occlusion, the maxillary lingual cusp will be in contact with the mandibular lingual cusp. In lateral excursion: balancing side Anterior teeth- the maxillary & mandibular anterior teeth may contact on the balancing side. Posterior teeth- the lingual cusps of the maxillary teeth will be in contact with the buccal cusps of the mandibular teeth. With monoplane balanced occlusion, usually only the second molars are in contact or the balancing ramp. Advantages of Balance occlusion 1. Distribution of load 2. Stability 3. Reduced trauma 4. Functional movement 5. Efficiency 6. Comfort Factors affecting the balanced occlusion (Laws of Articulation Hanau quint) 1. Condylar guidance 2. Incisal guidance 3. The occlusal plane 4. The compensatory curves 5. Cusp angulation Inter relation between these factors may be described by Theilman̕ s formula. condylar inclination X Incisal guidance s Balanced occlusion = ----------------------------------------------------------- Occlusal plane X compensatory curve X cusps angulation 1.Condylar guidance The angle formed by an imaginary horizontal line at the superior head of the condyle and the path that the condyle will pass through during function. It varies from individual to individual because of anatomical differences. About 33⁰ Definitions 1.condylar guidance: mandibular guidance generated by the condyle and articular disc traversing the contour of the articular eminence GPT9 2.condylar guidance : the mechanical form located in the posterior region of an articulator that controls movement of its mobile memberGPT9 The first factor of occlusion is the condylar guidance, this factor recorded from the patient.so it is fixed factor cannot be modified by the dentist. 2. Incisal guidance: 1. Incisal guidance: - the influence of the contacting surfaces of the mandibular and maxillary anterior teeth on mandibular movements. It is usually expressed in degrees of angulation from the horizontal by a line drawn in the sagittal plane between the incisal edges of the upper and lower incisor teeth when closed in centric occlusion. 2. Incisal guidance:-the influences of the contacting surfaces of the guide pin and guide table on articulator movements. Incisal guidance depends on the: 1.Desired over jet. 2.Over bite. This angle varies directly with the vertical overbite and inversely with the horizontal over jet. This angle is set to 10˚ in CD and not exceeding 20˚ This angle determined by esthetic, phonetic, ridge relation, inter-alveolar distance, this means it is under the control of the dentist, 3.plane of occlusion: 1. lt is imaginary surface related anatomically to the cranium and theoretically touches the incisal edge of incisors and the tip of occluding surface of posterior teeth 2. Maxillary occlusal plane should parallel to interpapillary line ,posteriorly usually parallel to the ala-tragus line 3. In the mandible established anteriorly by the cusp height of lower canine near the commissure of the mouth(corner) and posteriorly by the retromolar pad. 4.The compensating curve: the arc introduced in the construction of complete removable dental prostheses to compensate for the opening influences produced by the condylar and incisal guidance’s during lateral and protrusive mandibular eccentric movements GPT9 - The compensating curve incorporated in a properly oriented plane of occlusion - Compensating curve in artificial dentition is anteroposterior curve 5.Cuspal angulations or inclination of cuspless artificial teeth It depends on several factors residual ridge,neuromuscular control, esthetics,etc)however, it’s better to reduce the cuspal inclination to help reduce horizontal forces of occlusion. Interaction of the five factor Of the four that he can control two of them (the incisal guidance and the plane of occlusion) can be altered only a slight amount because of esthetic and physiologic factors. The important working factors for the dentist to manipulate are the compensating curve and the inclinations or cusp on the occlusal surfaces of the teeth. 2- Lingualized occlusion: It involves use of large upper palatal cusp against wide shallow lower central fossa. The buccal cusps of upper and lower teeth do not contact each other. The maxillary palatal cusp tip should contact opposite mandibular central fossa. The cusp incline of mandibular teeth relatively flat result in less lateral force and displacement during function Indication: 1.High esthetic needed. 2.Week muscle of mastication. 3.Displaceable supporting tissue. 4.Sever alveolar bone resorption. 5.Discrepancy in jaws size. Narrow upper arch and wide lower arch 6.implant supported over denture. 7.Previous successful denture with lingualized occlusion. Advantages: 1. Simpler technique. Less precise CR records 2. Esthetics. 3. Better penetration of the food bolus. 4. easer to adjust occlusion 5. it may be used in clII,classIII and cross bite. 6. Centralization of vertical forces. 7. Minimizing tipping force. 8. Potentially of bilateral balance Disadvantages:- 1.Difficulty in obtaining repeatable centric record (incoordination, jaw malrelation) 2.Severe ridge resorption (lateral forces displace the denture) may more easily be handled with a monoplane scheme 3- Monoplane or occlusion (neutrocentric) : o Flat occlusal plane set with non anatomic teeth. o The antero-posterior occlusal plan parallel to the denture foundation area. o There is no vertical overlap of anterior teeth. o Tooth Contact should occur only when mandible in centric relation.. o Opposing artificial teeth should not contact when jaws in eccentric relation. o In protrusion there is disclosure of posterior teeth as a result of arrangement in single plane.the patient is instructed not to incise the bolus o There is no curve of spee or curve of Wilson (compensating curves). Indications 1.Jaw size discrepancies CI II, Cl lll ,malocclusion and cross bite 2.Uncoordinated jaw movement. 3.Mostly for geriatric patients. 4.minimal ridge ,resorbed ridge ,it reduces horizontal forces—implant may help. Advantages: 1.Simple technique and less time consuming. 2.Less precise jaw relation records. 3.Lateral forces are reduced by eliminating Cuspal inclines. 4.Simpler and easier occlusal adjustments. 5.Occlusion is not locked. Disadvantages: 1.Least esthetic. 2.Poor bolus penetration. 3.Cannot be balanced in eccentric excursions Types of Occlusal Scheme: 1.Anatomic teeth. ' Simulate the natural teeth form with inclination approximately 33 degree Advantages: 1.Esthetic. 2.Better food penetration. 3.Vertical stress decrease. 4.Harmony with TMJ and muscle of mastication. 5.Balance occlusion in eccentric position Disadvantages: _ 1.Precise technique requires. 2.More time. 3.Difficult teeth position in CL II &CL III 4.Greater lateral force 2.Semi anatomic teeth Cusp incline less steep than anatomical teeth called modified anatomical teeth (less than33⁰) Advantages: 1.Esthetic. 2.Good chewing efficacy. 3.Less lateral force. 4.Balance occlusion. Disadvantages 1.least esthetic. 2.poor bolus penetration. 3.cannot be balanced in eccentric excursions 3.Non anatomical teeth:-Flat and without cusp height. Advantages 1.Used for patient with poor neuromuscular coordination. 2.Used for patient with malrelation jaws. 3.Used for patient with cross bite or class lll. 4.More comfortable. 5.Less time required in set up. 6. slightly more esthetic than neutrocentric occlusion. Disadvantages: _ Use of compensatory curve may cause the same damaging effects as cuspal inclines. Occlusal adjustment are more difficult to accomplish Balance Occlusion For Non Anatomic Teeth May Be Accomplish By Factors influencing the selection of selection of occlusal scheme 1. Characteristics of occlusal scheme: Tooth form and arrangement Balanced or not 2. Characteristics of the patient: Height and width of the residual ridge Aesthetic demands of the patient Skeletal relations Neuromuscular control Tendency for parafunctional activity