RECORDING OF OCCLUSION IN PPA
Introduction :
When determining intermaxillary relationships, the desired mandibular position is defined by three parameters:
-A vertical parameter: which is the DVO.
-Two horizontals:
*anteroposterior position of the mandible: RC
*its lateral wedging.
“Prosthetic occlusion plane”
1)-Prosthetic occlusion plan:
The ideal plan according to which the two artificial arches must meet so that simultaneously the following are ensured: respect for the integrity of the support surfaces, restoration of aesthetics, restoration of phonation and all other functions.
1-1 sagittal orientation is done according to aesthetic criteria.
-It must ensure correct support of the upper lip by restoring the nasolabial angle.
-A lip that is too full appears short.
-A lip that is not supported appears long.
1-2 Frontal orientation Is determined by the height of the anterior bead.
-It is evaluated according to aesthetic and phonetic criteria.
-The incisive discovery should not be estimated in a stereotypical way, it varies depending on the age, sex and personality of the patient.
-With age, the maxillary incisors become less and less apparent, this reduction is more pronounced in men than in women.
-Generally, in older women, there is a slight overflow of the upper incisors (about 1 mm) whereas in men of the same age, the upper lip covers all of the maxillary central incisors.
-The anterior vertical height is controlled through phonetics.
-The height is adjusted so as to obtain a light contact of the upper incisal edge on the lower lip at the junction of the dry part and the wet part “Vermilion line” when pronouncing the phonemes “F” and “V”.
1-3 Horizontal orientation:
-Thanks to Fox’s plate.
-Look for parallelism with the bipupillary and bicommissural line at the anterior level.
-At the posterior level, it is necessary to look for parallelism with the Camper plane which connects the subnasal point to the lower part of the tragus.
2)-Determination of the DV
- Height of the lower floor of the face
- Distance between subnasal point and gnathion
Vertical occlusal dimension: Height of the lower level of the face when the teeth are in ICM.
Resting vertical dimension: Height of the lower level of the face when all facial muscles are at rest.
Freeway space = Thompson = freeway space: This is the space that can be objectified between the teeth when the subject is in a resting posture.
DONDERS space: This is the space between the dorsal surface of the tongue and the palate.
3)-Determination of the DVR:
Two cases may arise:
-The occlusion is not altered, it is essential to preserve it (convenience occlusion);
-The occlusion is altered: therefore determine the DVR
3-1)-The restoration of aesthetics: harmony between all facial features will be sought while respecting the sex, age, and constitutional type of our patient (the aesthetic appearance of the face).
3-2)-Willis technique: this author reports the frequency of equality between the distance separating the lip cleft from the external angle of the eye and that separating the subnasal point from the gnathion.
3-3-)-Tactile sense of comfort: the sensation of comfort felt at the moment when the muscular tenacity of the depressor and elevator muscles are balanced constitutes an ideal means of determining the DVR
3-4)-Electro-myographic technique: the DVR as being the position characterized by the minimum of muscular contractions.
3-5)-Functional tests:
*swallowing: during swallowing, the Donders space is cancelled and the mandible then passes through the DVR. For Smith, a patient keeping a mouthful of water in his mouth is in DVR, when he swallows it, he is in DVO
*yawning: after a prolonged yawn, a tonic balance is established between all the muscles and the mandible passes through the DVR
*laughter, daydreaming: they result in the relaxation of the muscles.
3-6)-Phonetic technique: for some authors the position of the mandible is the same at rest as during the pronunciation of phonemes:
“me”, “ma” of Emma, the explosive bilabials “pe, be”
the emission of the palato-linguals “mississippi, saucisson, tissimsilet”.
4)-Determination of the DVO
4-1)-Direct techniques:
4-1-1)-Boos technique: using a dynamometer => the DVO is obtained when the maximum pressure is recorded.
4-1-2)-Maximum mouth opening technique: the two occlusion models placed in the mouth must allow the passage of three of the patient’s fingers.
4-2)-Indirect technique:
It consists of subtracting the ELI from the DVR;
DVO = DVR – ELI
ELI = 2 mm
5)-Determination of the centered relation
It is a constant mandibulo-cranial relationship independent of the teeth which places the mandibular condyles in their most superior position in their glenoid cavity.
• This is the unforced position which can only be obtained if no nociceptive (forced) defense reflex develops and if the musculature is in a state of normal balanced muscle tone.
5-1)-Fatigue of the external pterygoids: extreme chin propulsion, maintained for 45 to 60 seconds, fatigues the external pterygoid muscles and causes them to relax with a return to CR
5-2)-Linguo-mandibular homotropy: a retracted position of the tongue corresponds to a retracted position of the mandible
5-3)-Swallowing:
5-4)-Practitioner’s assistance: by guidance from the practitioner
5-5)-Molar occlusion reflex: caused by placing the pulp of the two index fingers at the level of the molars.
5-6)-Forced hyper extension of the head: the head is thrown back, the gaze fixed on the ceiling = the elimination of the play of the external pterygoids and the use of gravity act in the desired direction.
Conclusion :
-In the presence of a small or medium extent of edentulism, the occlusion is materialized by the remaining teeth.
-In the presence of a large extent of edentulism, it is constant to have recourse to the techniques used in total prosthesis.
RECORDING OF OCCLUSION IN PPA
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