when it comes to placing the teeth on the middle of the ridge, this processes makes a great difference in the stability of the denture when the patience bites or masticates. if the teeth are not placed in the middle of the ridge, it will cause the denture to dislodge as there is no form of anchorage on the ridges; this can occur when a patient bites as well as when a patient masticates.
the opposing denture (the maxillary denture) is affected because of the movements that occur when biting or chewing, therefore if the mandibular denture gets displaced when masticating, the maxillary denture will dislodge as the teeth are set in relation to one another and therefore operate with each other. the entire denture will dislodge which could lead to the denture breaking or cracking under the stresses it undergoes.
i agree... the mandibular denture relies more on setting the teeth on the ridge for stability. furthermore the occlusal forces are directed through the acrylic teeth onto the ridge, if it was directed of the ridge the denture will be unstable and tilt. positioning the teeth hear causes maximum stability. placing the teeth too far lingual will cause displacement of the denture by the tongue.
-stability of the lower denture: so that vertical forces are directed down the centre of the alveolar bone. -the closer the teeth are to the ridge; the greater the balance. -conversely, the further the teeth from the ridge, the less balance there is of the denture. consequences for not placing teeth on crest of ridge: dentures will see -saw or tip, therefore dislodging of dentures. also the dentures will slide on the supporting tissues when the forces are not directed down the centre of ridge.
if a see-saw can used to illustrate the scenario... if one side is loaded more than the other it will cause the balance to be out and cause the see-saw to move or tilt in the direction of the greater mass. the exact same can be described in the case of a mandibular denture. if the teeth are not placed on the "crest" of the alveolar ridge (the centre) it will cause a tilting action during mastication. therefore, the placing of the teeth is vital as both dentures loose there function during rocking or tilting of dentures. cross-bites are the result in such cases. the teeth are rather set up in a cross bite relation rather than cusp-to-fossa relation in specific cases to avoid the mandibular teeth from being placed too far lingually or buccally. therefore, the applied force is transmitted to the centre of the alveolar ridge.
In the ideal complete denture case, the teeth for both arches is set exactly on the ridge as this contributes to denture stability by directing occlusal forces onto the ridge (support). In reality however, the technician often has to choose to place either the mandibular OR maxillary teeth exactly on the ridge. In such cases, one should always coose to place the mandibular teeth on the ridge as this arch has less aspects contributing to the retention of a denture (the maxillary denture is provided enough retention by the posterior palatal seal and large fitting surface). it is also indiicated that the mandibular ridge resorb four times faster than the maxillary ridge (Rahn, et al., 2009:42).
Rahn, O.A., Ivanhoe, J.R., and Plummer, K.D. 2009. Textbook of complete dentures, sixth edition. People's Medical Publishing House: Shelton
when it comes to placing the teeth on the middle of the ridge, this processes makes a great difference in the stability of the denture when the patience bites or masticates. if the teeth are not placed in the middle of the ridge, it will cause the denture to dislodge as there is no form of anchorage on the ridges; this can occur when a patient bites as well as when a patient masticates.
ReplyDeletethe opposing denture (the maxillary denture) is affected because of the movements that occur when biting or chewing, therefore if the mandibular denture gets displaced when masticating, the maxillary denture will dislodge as the teeth are set in relation to one another and therefore operate with each other. the entire denture will dislodge which could lead to the denture breaking or cracking under the stresses it undergoes.
i agree... the mandibular denture relies more on setting the teeth on the ridge for stability. furthermore the occlusal forces are directed through the acrylic teeth onto the ridge, if it was directed of the ridge the denture will be unstable and tilt. positioning the teeth hear causes maximum stability. placing the teeth too far lingual will cause displacement of the denture by the tongue.
ReplyDelete-stability of the lower denture: so that vertical forces are directed down the centre of the alveolar bone.
ReplyDelete-the closer the teeth are to the ridge; the greater the balance.
-conversely, the further the teeth from the ridge, the less balance there is of the denture.
consequences for not placing teeth on crest of ridge: dentures will see -saw or tip, therefore dislodging of dentures. also the dentures will slide on the supporting tissues when the forces are not directed down the centre of ridge.
if a see-saw can used to illustrate the scenario... if one side is loaded more than the other it will cause the balance to be out and cause the see-saw to move or tilt in the direction of the greater mass. the exact same can be described in the case of a mandibular denture. if the teeth are not placed on the "crest" of the alveolar ridge (the centre) it will cause a tilting action during mastication. therefore, the placing of the teeth is vital as both dentures loose there function during rocking or tilting of dentures. cross-bites are the result in such cases. the teeth are rather set up in a cross bite relation rather than cusp-to-fossa relation in specific cases to avoid the mandibular teeth from being placed too far lingually or buccally. therefore, the applied force is transmitted to the centre of the alveolar ridge.
ReplyDeleteIn the ideal complete denture case, the teeth for both arches is set exactly on the ridge as this contributes to denture stability by directing occlusal forces onto the ridge (support). In reality however, the technician often has to choose to place either the mandibular OR maxillary teeth exactly on the ridge. In such cases, one should always coose to place the mandibular teeth on the ridge as this arch has less aspects contributing to the retention of a denture (the maxillary denture is provided enough retention by the posterior palatal seal and large fitting surface). it is also indiicated that the mandibular ridge resorb four times faster than the maxillary ridge (Rahn, et al., 2009:42).
ReplyDeleteRahn, O.A., Ivanhoe, J.R., and Plummer, K.D. 2009. Textbook of complete dentures, sixth edition. People's Medical Publishing House: Shelton