Occlusion 3 Flashcards
Define what an articulator is, including its requirements and main purposes in dental practice.
An articulator is a device to which casts are attached to allow simulation of jaw position and movement. It requires accurate casts and mounting to function properly.
Its main uses are:
1) Occlusal examination,
2) Planning treatment through trial occlusal adjustment and diagnostic waxing
3) Making restorations that will require minimal adjustment in the mouth.
Compare and contrast the different types of articulators, including their specific angular settings when applicable.
1) Simple Hinge
2) Arcon
3) Average Value with Bennett Angle set at 15° and Condylar Guidance Angle set at 30°
4) Semi-Adjustable (allows setting of Bennett and Condylar Guidance Angles)
5) Fully Adjustable (not common practice).
Explain how to mark the anterior reference point, including its specific anatomical location and measurement.
The anterior reference point is marked on the patient’s right side using the Reference Plane Locator and marker. It is located 43mm apical to the incisal edge of the anterior teeth (ideally tooth 12) and approximates the position of the infraorbital foramen.
Describe the complete process of bite registration using the bite fork, including material options and critical positioning considerations.
Apply bite registration paste (or rigid wax) to the bite fork with the fork arm to the right and locating notch facing up.
Firmly seat to record cusp tips of maxillary teeth without engaging undercuts.
Ensure it is parallel with the patient’s coronal and horizontal planes.
Align the dental midline with the locating notch and verify that indentations of maxillary teeth are clearly visible for accurate repositioning and mounting of the maxillary cast.
Detail the step-by-step process of assembling and positioning the earbow and transfer jig on a patient, including all alignment requirements.
1) Position earbow with numbers 1 and 2 facing towards you and reference pointer to patient’s right
2) Attach vertical shaft to measuring bow with clamp #2 on patient’s right and tighten finger screw on earbow
3) Ensure finger screws 1 and 2 are loose and loosen center wheel to allow earbow to open/close
4) Assemble by sliding bitefork arm through clamp #2
5) Fit earpieces tightly into patient’s ear canals and tighten center wheel
6) Adjust bow height so pointer aligns precisely with anterior reference point, then tighten clamps #1 and #2 without altering position
7) Verify bow is parallel to interpupillary line/floor
8) Loosen finger screw on measuring bow, slide open, remove from patient, detach measuring bow from transfer jig, and disinfect.
Explain the two approaches for mounting the lower cast using interocclusal registration.
An interocclusal registration is used to mount the mandibular cast in relation to the already-mounted maxillary cast.
Two options exist:
1) Intercuspal Position (ICP) - used for the Conformative Approach
2) Retruded Contact Position (RCP) - used for the Reorganized Approach.
Compare the different materials and situations for ICP registration.
1) NO MATERIAL - Used when plenty of tooth contacts make ICP obvious to technician
2) WAX - Used when ICP is not obvious to technician
3) REGISTRATION PASTE - Used when ICP is not obvious to technician
4) RECORD BLOCK - Used with free end saddles when casts cannot be hand articulated.
Distinguish between the different registration position options and their associated approaches.
Registration options include:
1) ICP registration WITHOUT OVD increase (Conformative Approach - Simple)
2) RCP registration WITH or WITHOUT OVD increase (Reorganized Approach - Not simple)
3) ICP registration WITH OVD increase (Reorganized Approach - Not simple)
4) Unorganized Approach (should be avoided).
What characterizes the unorganized approach to occlusion and why is it problematic?
The unorganized approach is characterized by: not assessing occlusion before starting restorations; changing occlusion with restorations without planning; not planning where ICP will be and its related jaw relationship; and providing an occlusion that doesn’t conform to the previously well-tolerated one. This approach should be avoided.
Define the conformative approach and explain when it is appropriate.
The conformative approach is defined as “the provision of restorations in harmony with the existing jaw relationships.” This means the occlusion of the new restoration is provided in a way that the occlusal contacts of the other teeth remain unaltered. It’s a simple approach appropriate when using ICP registration WITHOUT OVD increase.
Identify clinical scenarios where the conformative approach should not be used.
1) An increase in vertical height is needed to make space for restorations
2) Tooth/teeth are significantly out of position (overerupted, tilted, or rotated)
3) A significant change in appearance is wanted
4) There is a history of occlusally related failure or fracture of existing restorations.
Outline the process of reorganizing occlusion and identify the three key elements needed in an occlusal plan.
1) Examining the existing occlusion
2) Planning and designing the new occlusion
3) Performing pre-definitive restoration treatment to verify the plan works
4) Providing definitive restorations.
The plan requires:
a) A reproducible jaw position
b) An appropriate vertical dimension
c) An appropriate occlusal scheme
Explain the rationale and conditions for using RCP registration in the reorganized approach.
1) ICP is non-existent or unusable
2) Space is needed to place restorations
3) RCP is a reproducible position of the mandible independent of the teeth. The retruded arc of closure (CR) provides a reference point with RCP occurring on specific teeth (e.g., tooth 23).
Describe techniques for recording RCP and their proper execution.
1) Bimanual Manipulation
2) Chin Point guidance
3) Chin point guidance with anterior jig.
The RCP record is taken at a slightly increased OVD just prior to initial tooth contact, with the mandible rotating about its terminal hinge axis.
Compare materials for RCP registration and their appropriate use.
1) WAX - Used with registration medium;
2) PASTE - Used with registration medium; may use an anterior jig
3) RECORD BLOCK - Used for free end saddles where casts cannot be hand articulated.
When recording RCP, take the registration just before teeth contact in RCP.
Explain the retruded arc of closure concept and its relationship to RCP and initial tooth contact.
The retruded arc of closure represents the path of mandibular movement around the terminal hinge axis (R). Initial tooth contact (RCP) can occur at any point on this arc and is sometimes called a centric relation premature contact. From the point of maximum opening (T), the mandible can slide forward on the retruded arc of closure to a more acceptable OVD increase that is still not ICP. This demonstrates how the mandible moves from RCP toward ICP.
Describe the RCP to ICP slide phenomenon, including its prevalence and measurements.
If initial contact occurs on posterior teeth, there is likely a slide from RCP to ICP as the patient attempts to achieve maximum intercuspation. In 90% of patients, RCP and ICP differ (only 10% have coincident RCP/ICP), with RCP usually located 0.5-2mm infero-posterior to ICP. The slide represents the mandible’s movement from initial contact to maximum intercuspation.
Explain the step-by-step process of implementing the reorganized approach from initial mounting to finished restorations.
1) Mount casts on articulator in RCP using registration material (showing initial contact on tooth 14)
2) Determine if there is adequate interocclusal space (noting when OVD is increased too much)
3) Establish a new ICP at a “convenient” vertical dimension on the retruded arc of closure
4) Create a diagnostic wax-up of restorations in the new occlusal scheme;
5) Fabricate finished restorations where ICP=RCP, creating a stable occlusion.
Summarize the key principles for successful occlusal management in restorative dentistry.
1) Where possible, conform to the patient’s existing occlusion (you know it works!)
2) Good impressions and accurate registrations are essential because the lab doesn’t have the patient in front of them
3) A facebow isn’t needed for every crown and bridge case - it’s specifically for reorganizing unfavorable occlusal schemes.
