Complete Dentures – Occlusal Schemes – Monoplane – Neutrocentric Concept
Several clinicians have employed monoplane posterior teeth with all the anterior and posterior teeth on the same flat plane. There is no vertical overlap of the anterior teeth with this occlusal scheme although the lateral incisors may be elevated to enhance the esthetic display. This program describes and illustrates this philosophy of complete denture occlusion.
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Complete Dentures – Occlusal Schemes Monoplane-Neutrocentric Concept — Course Transcript
- 1. 20. Occlusal Schemes – Monoplane Neutrocentric Concept John Beumer III, DDS, MS and Michael Hamada DDS Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry UCLA School of Dentistry This program of instruction is protected by copyright ©. No portion of this program of instruction may be reproduced, recorded or transferred by any means electronic, digital, photographic, mechanical etc., or by any information storage or retrieval system, without prior permission.
- 2. This concept of occlusion assumes that the anterior-posterior plane of occlusion should be parallel to the denture foundation area and not dictated by condylar inclination. The plane of occlusion is completely flat and level. There is no curve of Wilson or Curve of Spee (compensating curve) incorporated into the set up. There is no vertical overlap of the anterior teeth. When using this concept of occlusion the patient is instructed not to incise the bolus. With this tooth arrangement DeVan noted that “the patient will become a chopper, not a chewer or a grinder.” When setting these teeth the horizontal and lateral condylar guidances should be set at zero. Monoplane Occlusion – Neutrocentric Concept Background
- 3. Monoplane Occlusion – Neutrocentric Concept Begin by positioning a zero degree protrusive insert, and check to ensure that the incisal guide pin is set at zero and in contact with the incisal guide table. Protrusive inserts Protrusive insert Zero setting
- 4. Mark the casts indicating midline, crest of the ridge, and the retromolar pad . These landmarks will be used to check your denture setup. Maxilla Midline Anterior land Mandible Ridge Retromolar pad Cast Landmarks
- 5. Anterior land Cast Landmarks – Maxilla Midline Incisive papilla
- 6. Lines indicating the crest of the ridge Cast Landmarks -Mandible Midpoint of retromolar pad Land Mark on land indicating the midpoint of the retromolar pad
- 7. As previously mentioned (13c, 1a), the wax rim is ideally contoured on the patient and used to mount the upper cast with a facebow transfer record. When the lower cast is mounted on the articulator with a centric relation record, the plane of occlusion is readily seen. The three landmarks used to identify the plane of occlusion are: The midpoint of the retromolar pads bilaterally as previously marked on the mandibular cast. The incisal edge of the maxillary central incisors Setting the Maxillary Anterior Teeth Midpoint of retromolar pad Midpoint of retromolar pad
- 8. To set the remaining maxillary anterior teeth a clear glass or plastic slab is positioned on the mandibular record base to represent the plane of occlusion. Setting the Maxillary Anterior Teeth Mark indicating midpoint of the retromolar pad
- 9. Setting the Maxillary Anterior Teeth Soften some baseplate wax and attach some to the ridge lap portion of the other maxillary central incisor and attach it to the record base as shown. Set the lateral incisors and cuspids as shown previously (Section 13c, 1a Lingualized occlusion).
- 10. Setting the Maxillary Anterior Teeth Note the angulations of the anterior teeth in relation to the occlusal plane when viewed in profile. Occlusal plane
- 11. Setting the Maxillary Anterior Teeth “ Toed-in” Position Note how the cervical and incisal edges of the cuspid are aligned vertically (yellow line). The facial surface of the cuspid however, is canted inward and appears “toed in” (red line) due to the prominence of the cervical area of the tooth (yellow arrow). The centrals and laterals are inclined slightly towards the distal.
- 12. Setting Mandibular Anterior Teeth Amount of vertical overlap When using a neutrocentric concept of occlusion is no vertical overlap should be incorporated into the set up.
- 13. Magnitude of horizontal overlap ? In Class II patients the mandible tends to travel farther anteriorly in function than the typical Class I patient and consequently more horizontal overlap is necessary to allow for this functional movement. Setting Mandibular Anterior Teeth In contrast Class III patients often demonstrate little or no anterior movement of the mandible during function. Consequently, little or no horizontal overlap is developed in the set up. Class I Class II Class III
- 14. Setting the Mandibular Anterior Teeth The horizontal overlap should be consistent throughout the anterior region. In this setup it is about 1.5 mm.
- 15. Setting the Mandibular Anterior Teeth Positions of the anterior teeth. The lateral incisors should be placed similar in angulation and position to the central incisors. Note that the cuspids are towed out at the cervical.
- 16. Background – Setting the posterior teeth When setting these teeth the horizontal and lateral condylar guidances should be set at zero. The number and combination of the denture teeth utilized varies depending on the arch length of the patient. The mandibular occlusal table should end prior to the ascending ramus. The distal surface of most posterior maxillary denture tooth should extend one half 1-2mm distal to the most posterior mandibular denture teeth. Monoplane Occlusion – Neutrocentric Concept
- 17. Monoplane Occlusion – Neutrocentric Concept Position the posterior mandibular posterior teeth over the crest of the ridge. Check to ensure they are set to a flat plane and on the plane of occlusion. Make corrections as necessary Occlusal Plane Since there is no vertical overlap of the anterior teeth all of the mandibular teeth are on the plane of occlusion.
- 18. Monoplane Occlusion – Neutrocentric Concept Since there is no vertical overlap of the anterior teeth both the anterior teeth and the posterior teeth are on the plane of occlusion. Make corrections as necessary.
- 19. Monoplane Concept – Neutrocentric Concept Position the maxillary posterior teeth.
- 20. Monoplane Occlusion – Neutrocentric Concept Check the horizontal overlap of the posterior teeth. The overlap should be at least one third of the width of the occlusal surface and be sufficient to prevent biting of the cheek and corner of the mouth. Horizontal overlap
- 21. Monoplane Occlusion – Neutrocentric Concept Note that the premolar in the of the Ivoclar Orthoplane tooth form is of sufficient length to harmonize with the cuspid. In addition the the marginal ridges of the premolars have been lowered. This change provides the esthetics usually associated with anatomic teeth.
- 22. Monoplane Occlusion – Neutrocentric Concept The flatness of the maxillary premolars is provided by the flat buccal and lingual cusps. Note that in this set up both lingual and buccal cusps contact the plane of occlusion.
- 23. Monoplane Occlusion –Neutrocentric Concept With this occlusal scheme the plane of occlusion should be parallel to the denture foundation area.
- 24. Monoplane Occlusion –Neutrocentric Concept Verify again that all the maxillary teeth, with the exception of the lateral incisors and perhaps the cuspids, are on the plane of occlusion. Make corrections by manipulating the maxillary teeth. When you have completed this step, thoroughly cool the wax before proceeding to the next step.
- 25. Monoplane Occlusion – Neutrocentric Concept Reestablish centric contacts as necessary by manipulating the mandibular posterior teeth. Make sure that the incisal guide pin maintains contact with the incisal guide table when you have completed this step. While performing this step make sure you do not alter the horizontal overlap of the posterior teeth.
- 26. Monoplane Occlusion- Neutrocentric Concept Note Christiansen’s phenomenon, or the separation between the posterior teeth in the protrusive position. If the patient presents with steep condylar inclination the posterior discrepancy in excursion may become significant. 20 degrees 30 degrees
- 27. Monoplane Occlusion- Neutrocentric Concept The steeper the condylar inclination the greater the posterior discrepancy in excursion and the greater the need for balancing ramps, and so in this patient, balancing ramps were added to improve the stability of the lower denture.