Occlusion Review.pdf

 What happens when you restore a tooth “too high”? Tooth sensitivity? Other teeth are not hitting? Patient isn’t happy? What happens when you restore a tooth that causes the jaw to shift? Jaw or joint pain? Patient’s bite feels off? Patients isn’t happy? Ne...

 What happens when you restore a tooth “too high”? Tooth sensitivity? Other teeth are not hitting? Patient isn’t happy? What happens when you restore a tooth that causes the jaw to shift? Jaw or joint pain? Patient’s bite feels off? Patients isn’t happy? Need to Know the Interarch Relationship Where do the lingual and buccal cusps of the maxillary teeth contact the lower teeth? What is the relationship? Is there an opposing tooth? Need to Know the Interarch Relationship Is there malocclusion? Anything other than a molar class I change your restorative plan? Knowing these answers will save you time in restoration placement and adjustment… If you drew an imaginary line along the lingual cusp tips (the functional cusps) of maxillary posterior teeth, this line would coincide with an imaginary line along the central grooves and marginal ridges of mandibular teeth. Likewise, if you drew an imaginary line along the buccal cusps (functional cusps) of mandibular posterior teeth, that line would coincide with the central grooves and marginal ridges of maxillary teeth. Functional Cusps Cusps that contact opposing teeth in their corresponding faciolingual center of a marginal ridge or fossa. 5 features: 1. Contact opposing teeth in maximal intercuspation (MI) 2. Support vertical dimension 3. Nearer faciolingual center of tooth than nonsupporting (aka nonfunctional) cusps 4. Outer incline has potential for contact 5. More rounded than nonfunctional cusps Nonfunctional Cusps Cusps that OVERLAP the opposing tooth without contacting the teeth Normally located: 1. Opposing embrasure 2. Opposing developmental grooves  Functional Cusps Nonfunctional Cusps More rounded and robust which Maxillary molars and premolars help to makes them better suited for keep the cheek out of the occlusal table, cutting, crushing, grinding food avoiding soft tissue trauma. Prevent drifting or passive Maxillary premolars play a role in eruption = supporting vertical esthetics dimension Mandibular lingual cusps are sharp and Think of this cusp to central fossa help to shear food as it passes to the relationship as a mortar and functional cusps for chewing. pestle. Mandibular lingual cusps also serve to keep the tongue away from the occlusal table to avoid trauma. Centric Stops: Areas of occlusal contact that a functional (supporting) cusp makes with the opposing teeth in centric occlusion.  Centric Contacts Up Close A. Relationship of functional cusps to marginal ridges. B. Relationship of functional cusps to fossae. Why does all this matter? Connecting the Dots…. The central developmental grooves of the posterior teeth are normally aligned continuously with each other in each quadrant. In any dental restorative procedure, the occlusal anatomy should be reproduced to preexisting or near preexisting form, including relative depth and height. How will the shape of your restoration be affected by contacts on the marginal ridge? How will the anatomy look in the pit and central groove areas? What is the Relationship of the Occlusion to the TMJ? Curve of Spee The curvature which begins at the tip of the canines and follows the buccal cusps of the posterior teeth, when viewed from the facial. It continues as an arc up through the condyle. Curve of Monson The three-dimensional curvature of the occlusal plane, which is a combination of the Curve of Spee and Curve of Wilson. The Condyles Working side: the side toward which the mandible moves. When the mandible moves laterally, the condyle on the working side stays in its fossa, rotates and moves laterally. That condyle is known as the working condyle. The inclination of the condylar path during protrusive movement can vary from steep to shallow in different patients. It forms an average angle of about 30° with the horizontal reference plane. If the protrusive inclination is steep, the cusp height may be obviously longer. Similarly, if the inclination is shallow, the cusp will be shorter. This factor is the most important aspect of condylar guidance that affects the selection of posterior teeth with appropriate cusp height. Anterior guidance (vertical and horizontal overlap of anterior teeth) also affects the surface morphology of posterior teeth. The greater the overlap, the longer the cusp height. Important: Anterior guidance must be preserved, especially when restorative procedures change the surfaces of anterior or posterior teeth that guide the mandible in excursive (lateral, protrusive) movements. Important: A protrusive movement requires the condyles to move in a downward and forward direction. In lateral movements, the working condyle moves down, forward, and laterally. In lateral movements, the non-working condyle moves down, forward, and medially.  Mandibular movements are guided by maxillary teeth from centric occlusion (maximum intercuspation position that lies anterior to centric relation of the mandible). For example, protrusion is guided by maxillary incisors (incisal guidance). In protrusive excursions posterior teeth should be disengaged. Occlusal interference exists if tooth contact occurs where teeth should be disengaged. Lateral movements are guided by maxillary canines (canine-protected occlusion) in unworn dentition. Lateral movements may be guided by incisors and posterior teeth in worn dentition. During the lateral excursive movements in canine-guided occlusion, there is no contact in canines on the nonworking side; all contacts occur between the canines on the working side (the side toward which the mandible moves during lateral excursion). Posterior teeth should disengage on the balancing side in a lateral movement. Five requirements for occlusal stability: 1. Stable stops on all teeth when the condyles are in centric occlusion. 2. Anterior guidance in harmony with the border movement of the envelope of function. 3. Disclusion of all posterior teeth in protrusive movements. 4. Disclusion of all posterior teeth on the nonworking (balancing) side. 5. Noninterference of all posterior teeth on the working side, with either the lateral anterior guidance, or the border movements of the condyle. The working-side posterior teeth may contact in lateral group function if they are in precise harmony with anterior guidance and condylar guidance, or they may be discluded from working-side contacts by the lateral anterior guidance.  Six requirements for the equilibrium of the masticatory system: 1. Stable, comfortable TMJs (even when loaded). 2. Anterior guidance in harmony with functional movements of the mandible. 3. Noninterference of posterior teeth: 4. Equal intensity contacts in centric relation Posterior disclusion when the condyle leaves centric relation 5. All teeth in vertical harmony with the repetitive contracted length of the closing muscles. 6. All teeth in horizontal harmony with the neutral zone. As the Dentist, how do we not disrupt this equilibrium?  Check the Check occlusal contacts on the tooth to be prepared but also the adjacent Occlusal Contacts teeth. Knowing preoperative occlusal contacts help you to preoperatively plan the restoration outline and avoid contacts on cavosurface margins Occlusal contacts on adjacent teeth will provide guidance in knowing when the restoration contacts have been adjusted correctly. Have the patient close and pick a few stable contact points on adjacent teeth or teeth nearby. These areas should contact the same after the restoration is placed and adjusted.  Occlusal Adjustments The basic principles for occlusal adjustment include: Maximum distribution of occlusal stresses in centric relation. Forces of occlusion should be borne as much as possible by the long axis of the teeth (Picture A). When there is surface-to-surface contact of flat cusps, it should be changed to a point-to-surface contact (Picture B). Once centric occlusion is established, never take teeth out of centric occlusion With an articulating paper, the occlusion is checked. The paper will mark where the opposing tooth contacts the restored tooth. To preserve the centric occlusion, you only adjust the markings on your restoration. If the cusp tips teeth on the adjacent teeth do not occlude as they did prior to the procedure, then the contacts over the restorations are occluding prematurely. Lighten the contacts over the restoration to where contacts on the unprepared area and adjacent teeth appear as they did preoperatively. Lateral excursives should be check too. If you know your patient’s occlusion, you will: Know how to create the anatomy in your restoration, functionally and esthetically. Save time in placement and finishing Avoid post-op discomfort from high occlusion (aka traumatic occlusion) – saving time by avoiding adjustment appointments Avoid TMJ issues with your patient due to traumatic occlusion. It is important that functional cusps are not Summary contacting opposing teeth in a manner that results in lateral deflection Some patients are bothered by their “jaw shifting” Can contribute to TMJ issues.