Lecture 08 - Occlusal Schemes and Try-in PDF

Denture Occlusal Schemes and Try in Appointment Preclinical Prosthodontics 1-4/12/2024 First Semester 2024 Dr Ibrahim Khatib DDS, MPros Week 8  Outline This lecture will cover two important topics o Complete denture occlusal schemes...

Denture Occlusal Schemes and Try in Appointment Preclinical Prosthodontics 1-4/12/2024 First Semester 2024 Dr Ibrahim Khatib DDS, MPros Week 8  Outline This lecture will cover two important topics o Complete denture occlusal schemes o Natural Occlusion o Complete denture occlusion o Balanced occlusion o Unbalanced occlusion o The wax try in appointment 2  Importance of Complete Denture Occlusion Provides functional denture stability while minimizing complications Prevents denture dislodgment during function Important for denture longevity and patient comfort 3  Important Terms Maximum Intercuspation Centric relation Occlusion vs Articulation Protrusion Laterotrusion Working side vs non working side 4  Maximum Intercuspation The complete intercuspation of opposing teeth, independent of condylar position. It is the position where the teeth fit together in their most stable and tightest contact, often referred to as the "habitual bite" or "centric occlusion." 5  Centric relation A maxillomandibular relationship in which the condyles are positioned in their most superior, anterior position within the glenoid fossa, resting against the thinnest, avascular portion of the articular disc, regardless of tooth contact. It is a joint position, not dependent on teeth. It is repeatable and considered the most stable position of the temporomandibular joints (TMJs). Used as a reference for denture fabrication and occlusal rehabilitation. 6  Occlusion Vs Articulation Occlusion: The static relationship between the maxillary and mandibular teeth when they are in contact. Articulation: The dynamic relationship between the maxillary and mandibular teeth during mandibular movements, such as lateral or protrusive movements. Example: Tooth contacts during chewing or speaking. 7  Protrusion: A mandibular movement in which the lower jaw moves forward from centric relation or maximum intercuspation. Laterotrusion: A lateral movement of the mandible toward one side (working side) during mandibular function, such as chewing. 8  Working Side: The side of the mandible that moves away from the midline during lateral movements. Teeth on this side are typically in contact during laterotrusion. Example: If the jaw moves to the right, the right side is the working side. 9  Non-Working Side (Balancing Side): The side of the mandible that moves toward the midline during lateral movements. Teeth on this side typically do not contact, or contacts are minimized to avoid interferences. Example: If the jaw moves to the right, the left side is the non-working side 10  Occlusal Schemes in Natural Teeth Mutually Protected Occlusion (canine guidance) Unilateral balanced Occlusion (group function) Bilateral Balanced Occlusion 11  Mutually protected occlusion An occlusal scheme in which the anterior teeth protect the posterior teeth during excursive movements (lateral and protrusive), and the posterior teeth protect the anterior teeth during centric occlusion. This arrangement distributes forces efficiently and reduces the risk of damage to teeth, restorations, and surrounding structures. Sometimes referred to as 'canine guidance' 12 13  Unilateral Balanced Occlusion (Group function) Group function is an occlusal scheme where multiple teeth on the working side (canines, premolars, and sometimes molars) share the occlusal load during lateral (side-to-side) mandibular movements. The non-working side (balancing side) has no tooth contacts to avoid interferences. Disadvantages include non-axial loads on posterior teeth 14 15  Bilateral Balanced Occlusion An occlusal scheme in which simultaneous and evenly distributed contacts occur between the upper and lower teeth on both the working side and the non-working side during centric occlusion, protrusion, and lateral movements (teeth remain in contact at all times!). This scheme is rarely found in natural occlusion and primarily used in complete dentures to enhance stability and prevent tipping or dislodgment. 16 Complete Denture Occlusal Schemes 17  Maximizes denture stability Improves chewing efficiency Distributes forces evenly helps preserve residual ridges Enhances patient comfort Facilitates speech Maintains good esthetics 18  Complete Denture Occlusal Schemes Balanced (limits tipping during functional movements) o Bilateral Balanced Occlusion o Lingualized Occlusion o Monoplane occlusion with ramps Unbalanced o Monoplane occlusion without ramps 19  Bilateral Balanced Occlusion Most commonly used occlusal scheme in complete dentures Other schemes include Lingualized Occlusion and Monoplane Occlusion Different occlusal schemes require different prosthetic tooth molds. With balanced occlusion, anatomic teeth are utilized (20° or 33°) Non anatomic molds are used with monoplane Lingualized can be created with a combination of anatomic and non- anatomic molds. 20 21 22  Monoplane Occlusion An occlusal scheme characterized by flat, non-anatomic teeth with no cusp inclines. It is designed to eliminate horizontal forces and minimize lateral interferences during function, promoting denture stability The occlusal plane is flat and there are no balancing contacts. This eliminates non axial forces on the denture however may result in denture tipping during lateral excursions. Elimination of non axial forces provides stability in severely resorbed ridges or patients with poor neuromuscular control The lack of cusps reduces mastication efficiency and compromises esthetics 23 24 25 Adding a ramp makes this a BALANCED MONOPLANE OCCLUSION 26 27  Lingualized Occlusion This form of denture occlusion articulates the maxillary lingual cusps with the mandibular occlusal surfaces in centric occlusion, working and nonworking mandibular positions. (GPT 9) As the residual ridges resorb to the point that there is little or no ridge, a discrepancy may develop between the size of the narrowing and receding upper ridge compared with the widening and receding lower jaw. Lingualized occlusion is a set-up technique developed to enhance denture stability in such patients. Tooth set up is easier than BBO but maintains better esthetics and function than monoplane occlusion 28  In conventional denture set-ups, both the buccal and lingual cusps of the upper and lower denture come into contact on the working side during lateral jaw movement. This achieves balance and distributes the bite force over the widest area of the jaw. In a lingualized occlusion scheme, buccal cusp contacts are eliminated to alleviate lateral stresses or lateral dislodging forces. In lingualized occlusion, the lingual cusps of the upper posteriors make contact in the central fossae of the lower posteriors in centric relation and are in simultaneous contact with the mandibular teeth in working and balancing movements, thus creating stability. 29 30 31  Christensen's Phenomena Christensen’s phenomenon refers to the separation of the posterior teeth in both the maxilla and mandible when the mandible moves into a forward (protrusive) position. This occurs because of the downward and forward movement of the mandibular condyles along the articular eminences, which creates a gap between the posterior teeth. This is only present in natural dentition and its presence in complete dentures compromises stability! 32 33  How do we achieve bilateral balanced occlusion? 34 Denture Try in Appointment 35 36 37  The try-in appointment is a significant one for successful edentulous patient care. It will be the first time that dentist and patient can see what has been created. The decision will then be one of acceptance, modification, or change. The purpose of the try in appointment is verification of the fit, function, esthetics, and phonetics before finally processing as it is an IRREVERSIBLE process. This reduces post insertion adjustments and ensures patient satisfaction. 38  At the try-in, you will want to find out the following information in the following order of priority: 39  Are the teeth acceptable in color and mold? If not, reorder and reappoint for another try-in. Is the articulator mounting of the models an accurate record of the patient’s jaw position? If not, make new records in order to remount the models. Then reset teeth for another try-in. If both the teeth and mounting are acceptable, are the teeth in the best position? If not, change the midline, vertical dimension, occlusal plane, and/or arch form to be more appropriate. Are there any small improvements that will make the try-in fully acceptable to your patient and you (e.g., moving teeth to create a subtle rotation or diastema)? Should the wax contour be changed to improve tongue space or lip support? 40 The try-in appointment will have one of three conclusions: Your patient and you are completely satisfied You and your patient identify a significant change that is needed For a very few and memorable people in your practice, you may not be able to make a wax-up that is satisfactory, even after two or three appointments. 41  Before the try in appointment Find out who decides Encourage patient to get a second opinion from a trusted spouse or friend Support from a significant other can make adaptation to new dentures easier Assess the wax set up, make sure it ‘looks good’, is neat, and tidy 42  At the try in Start with explaining the following: This is NOT the actual denture They are only for looking, NOT CHEWING Retention may not be ideal The gingival color is pink tinted wax We want to check everything 43  If the patient has a previous set of dentures, compare the wax up to the denture and point out similarities e.g. teeth shade/mold/size or differences (new denture will likely be bigger than previous denture) 44  Intra-oral try in Check denture base comfort and retention. Retention may be compromised but should be sufficient so the patient can focus on the teeth! Use denture adhesive if necessary Are the teeth the right color and size? Is the bite similar to the articulated bite? Are the teeth in the correct position? Are the lips sufficiently supported? Are any changes necessary? 45  Depending on the answers to the previous questions, a try in may last from 10 minutes to more than an hour! Assess the midline, incisal show, occlusal plane, and tooth appearance Everything from the MMRR and teeth mounting should be checked and confirmed! 46 47 48 49  For the best esthetics in a smile, the curvature of the maxillary anterior teeth should match the curvature of the lower lip and the patient should not show any denture base above the coronal portion of the teeth. 50  Speaking and Phonetic assessment Speaking allows us to assess both the appearance and speech (make sure patient doesn’t have speech impediment) Speech allows us to assess Freeway Space and closest speaking space Fricative sounds: Ask the patient to count from 50 to 55. These labial-dental sounds help us assess the position of the maxillary anterior teeth relative to the lower lip. The teeth should contact the vermilion border of the lip What if ‘F’ sounds like ‘V’? 51  Sibilant sounds: Then ask the patient to count from 60 to 65 This lingual-dental sound will assess the position of the maxillary anterior teeth to the residual ridge, the appropriate height for the upper and lower anterior teeth, and inter occlusal freeway space The sibilant ’s’ should be clear and crisp While producing the ’s’ sound, the maxillary and mandibular teeth should come very close without actually touching. This is referred to as the closest speaking space (1-2mm). This allows us to assess the OVD. 52  Closest speaking space: Teeth contact - OVD is too high, FWS is too little. Strained speech, teeth clicking while talking, difficulty in enunciating sibilants, difficult swallowing, and discomfort. Teeth are more than 2mm apart, OVD is too low, FWS is too much. poor esthetics, poor function, drooling at corner of the mouth, and unclear speech 53  The upper and lower teeth should each be visible with sibilants. However, excessive show of either warrants an adjustment of the occlusal plane. 54  Vertical Dimension of Occlusion With the wax ups in slight occlusion, measure the OVD by marking 2 points similar to the MMRR appointment Remove the mandibular wax rims and measure the Rest Vertical Dimension and calculate the Freeway Space (should be similar to MMRR appointment) A significant change in the FWS may require adjusting the tooth set up, repetition of the set up or remounting the bite. OVD is also assessed using speech 55 56  The occlusion should be identical to the articulated occlusion including the static and dynamic contacts. The patient needs to close (don’t ask the patient to bite!) in CR. If it is then we may proceed to processing the denture If it isn’t then we either: Adjust minor discrepancies intra-orally Retake the MMRR and remount *Make sure the heels are not contacting (heel clash) 57  If the lower denture is not stable, use single base stabilization for the try in assessment 58  If both denture bases are not stable, use double base stabilization 59  If a major discrepancy is present, a clinical remount is needed. If certain teeth are causing an interference then they should be removed before the bite is recorded The bite can be recorded at the same OVD or at an increased OVD 60 61 62  Completing the try in appointment If both the dentist and the patient are satisfied with the results, then the denture can be processed. If the posterior palatal seal was not defined at the definitive impression, it needs to be done now. This is done by scraping a groove 2mm wide and deep into the master model before denture processing. 63  Why do we carve PPS? Compensates for the slight polymerization shrinkage Maintains peripheral seal during slight denture movements Allows denture to blend into the mucosal contour 64 65 66  Denture base shade selection The natural color of the gingiva varies among individuals, ranging from pale pink to darker hues with undertones of brown, blue, or red. Consider the patient’s age, ethnicity, and complexion, as these influence gingival pigmentation The denture base should harmonize with the patient's lips, skin tone, and teeth shade 67  Denture base shade selection Common shade categories include: Light pink Medium pink Dark pink Pigmented shades 68 69 70 71 72  References 1. Prosthodontic Treatment for Edentulous Patients (13th Edition), Chapters 10 and 11: ◦ Zarb, G.A., Hobkirk, J., Eckert, S. and Jacob, R., 2013. Prosthodontic Treatment for Edentulous Patients: Complete Dentures and Implant-Supported Prostheses. 13th ed. St. Louis: Elsevier Mosby, Chapters 10 and 11. 2. Treating the Complete Denture Patient by Driscoll, Chapter 21: ◦ Driscoll, C.F., 2020. Treating the Complete Denture Patient. 1st ed. Hanover Park: Quintessence Publishing, Chapter 21. 3. https://www.slideshare.net/slideshow/15concepts-of-complete-denture- occlusion-10191715/10191715#1 73