OCCLUSION IN JOINT PROSTHESIS
1) Introduction
- The success of a joint prosthetic restoration depends on maintaining the harmony of occlusal relationships. It is essential that the practitioner be occluso-aware. Competence requires that he be able to diagnose and treat simple occlusal disorders, as well as to produce constructions that do not cause iatrogenic disharmonies.
2) Fundamental notions in occlusodontics
21) occlusal concepts in joint prosthesis
Definition of occlusion:
- Dental occlusion is the study of how teeth fit together when they are in contact.
- Dental occlusion follows very precise rules that have been established for many years.
- Strict application of the rules of dental occlusion is the very basis of dentistry because it ensures comfort for the patient, it keeps the mandible in balance so as to avoid the appearance of a DAM
Definition of the concept:
This is the school philosophy that governs the development of an occlusal diagram with the aim of establishing an ideal dento-dental relationship.
Definition of an occlusal scheme:
- It is the set of factors which characterize the different reports or inter-arch relationships within the framework of an occlusal concept, any occlusal scheme is governed by:
- Static cusp relationships;
- Dynamic cusp relationships;
- Relationship between cusp ratios and mandibular position;
- Need or not to search for an insertion axis depending on the chosen concept.
22) criteria for optimal occlusion:
It is the one that requires the least effort of neuro-musculo-articular adaptation to satisfy this requirement certain criteria must be respected and met, namely:
- Tripodal dento-dental contacts.
- Centric relation corresponds to the position of maximum intercuspation
- A perfect and functional anterior guide.
- A canine disengagement.
- Dento-dental contacts cusps fossae.
- Canine or group protection.
- Occlusal forces directed along the long axis of the teeth
- Stability of teeth which should not move after prosthetic treatment
- Harmony of the stomatognathic system: no dysfunctional disorders should exist.
- Stable occlusal relationships both in RC and in the field from RC to occlusion in PIM and laterality.
- Immediate disocclusion of the posterior teeth on the non-working side.
- The DV must allow a resting position with a space free of physiological exclusion
- Initial contact should be made by a multitude of small points rather than by a large tooth surface.
- Absence of interference and prematurity.
- Anterior guide harmonized with the movement envelope.
OCCLUSION IN JOINT PROSTHESIS
23) the different occlusal concepts :
In joint prosthesis 03 occlusal concepts govern the occlusion:
231) concept of canine contact : Mac Collum’s gnatologist school
Indicated whenever the periodontal support of the canine is resistant, it is characterized by:
Cusp/fossa ratio
ICM is only in RC ( centric occlusion – centric point)
In propulsion: extended anterior contact and posterior disocclusion
In diduction: canine function on the working side, no contact on the non-working side
– In OIM, antagonistic cusp-pit relationships (1 tooth/1 tooth).
- Very precise punctiform contacts.
-At rest, no dental contact.
- In propulsion, anterior guidance ensures the absence of any posterior contact.
-In diduction, an exclusive canine function on the working side ensures the absence of contact
non-working side.
– Laterality is exclusively supported by the canine
-the separation of the cuspid groups is established by a slow progression at the start of the movement, then more abruptly at the end of the stroke.
232) concept of group contact : Functionalist school of Pankey Mann Schuyller
it is indicated when: the incisal coverage is weak, the canine support is weakened and the periodontal context requires a good distribution of occlusal forces
This concept is characterized by:
– cusp-marginal crest ratio.
– ICM does not coincide with the CR but is anterior to it by 0.3 to 1.3 mm and tolerates displacement without increasing the DV ( Ramfyord freedom in centric )
– In propulsion: extended anterior contact 6 to 8 teeth posterior disocclusion (anterior guidance ensures the absence of posterior contact.)
– In laterality or diduction group function on the working side, ensures the absence of contact on the non-working side and a group function on the working side This group protection corresponds to a working slide of the opposing molar, premolar, canine and sometimes incisor teeth.
– The OIM is reconstructed, the mandible being stabilized in RC.
– At rest, no dental contact.
- In OIM, cusp-marginal crest ratios (1 tooth/2 teeth) to ensure stability
from the mandibular position.
- Less punctiform contacts.
- Slight lateral and frontal movements are tolerated at the DVO from the position
IOM: tolerance area (long, wide centric).
233) concept of mutually protected or organic occlusion
It joins the concept of canine occlusion it was born from the work of the members of the gnatological society it is characterized by:
The anterior teeth protect the cuspid teeth during all mandibular excursions
In ICM the posterior teeth protect the anterior teeth
The anterior teeth are in very slight occlusion of 25u
- In OIM, all cusps make contact.
- Efforts are directed along their major axis.
- The anterior teeth are very slightly inoccluded.
- They are thus spared, the majority of the occlusal load being absorbed by the cuspid teeth.
During mandibular movements, the anterior teeth bear all the load.
The forelegs protect the hindlegs during movements.
cusped groups do not make contact during movements, whether on the W side or the non-W side.
OCCLUSION IN JOINT PROSTHESIS
24) determinants of occlusion
241) anatomical determinants
A) ATMs
B) The anterior guide: defined by
The incisor-canine palatal concavity
The overjet
The overbite
The shape of the arches
Its role:
Limits mandibular movements in ICM
Protects the cuspid teeth during propulsion
C) the occlusal plane D) the curve of Spee E ) condylar trajectory F) the curve of Wilson G ) the curve of MONSON or the free edges of the incisors and canines (smile line)
242) neuromuscular factors
neuromotor and sensory-sensory mechanism
25) The remarkable positions of occlusion
251) The centric relation (CR) : It allows the different mandibular excursions. It is referential because it is a position from which all lateral movements are still possible. It is an easily reproducible position and therefore referential.
252) The Maximum Intercuspidation Position (MIP)
It is the dental reference position that determines the situation of the mandible when the maxillary and mandibular teeth establish the maximum contacts between them. This IM occlusion position can coexist with RC condyles and in this case we speak of occlusion in centric relation (ORC) (exists in 8% of clinical cases)
253) Closing path
We ask the patient, in a resting position, to clench his teeth; he leaves the posture position (R) to find the IM closure position (PIM). The trajectory described by dentalé (the mandibular inter-incisal point) is called “Closing Path”.
3) Need for the use of an articulator
Due to its anatomical similarity with the facial mass and its design, the articulator facilitates the visualization of the dental arches and their occlusal contacts in all situations and different planes of space. Indeed, there is no tongue, no cheeks, nor any mucous membrane.
It is a tireless mechanism that allows numerous manipulations helping to visualize and understand dento-dental kinematics. In addition, the articulator remains the only mechanical intermediary of dental occlusion between the practitioner and the prosthetist who will build the future joint prosthesis. It can be semi-adaptable or adaptable depending on the extent of the prosthesis.
5) Occlusal criteria in joint prosthesis
A malocclusion is not necessarily followed by an articular problem because the stomotognathic system has the capacity to adapt to new articulated conditions without exceeding the physiological tolerance threshold and we will then speak of a balanced or compensated dysfunctional occlusion of Geoffrion, otherwise we will speak of an unbalanced or pathogenic occlusion of Geoffrion or a decompensated dysfunctional occlusion of Geoffrion.
51) Pre-prosthetic phase
Before undertaking prosthetic treatment with a joint prosthesis, a clinical examination must be carried out which often leads us to a pre-prosthetic treatment, among other things occlusal. We will consider two possibilities:
- The patient has a balanced occlusion without neuro-musculo-articular pathology;
in this case, prosthetic treatment can be started immediately.
OCCLUSION IN JOINT PROSTHESIS
- The patient complains of muscle and joint pain: the presence of disharmony
- occluso-articular (occlusion and articulation disorders) is an important factor in the responsibility of these symptoms, symptomatic treatment is necessary in order to reduce pain and improve mandibular movements followed by a pre-prosthetic occlusal analysis in the clinic and on a semi or fully adaptable articulator, this study allows for a remodeling of the occlusal scheme before undertaking the prosthetic treatment itself.
In this case, an occlusal splint will be used which will distribute the occlusal forces over the entire set of teeth and reduce painful spasms.
511) clinical analysis of occlusion
5111) an examination of the inter-arch relationships directly in the patient’s mouth and then on an adaptable or semi-adaptable articulator, it consists of:
Marking the contacts in the ICM position with articulating paper, assessing their number, location and distribution
Marking with another articulating paper of a different color from the contacts but this time in centric relation.
Three situations can be highlighted:
– the contacts in centric relation are confused with those in ICM and in this case the prosthetic development does not require occlusal treatment
– the contacts in RC are different from those obtained in ICM but distributed on both sides, achieving an occluso-articular balance
– the contacts in RC are isolated, unique or asymmetrically arranged leading to an occluso-articular disharmony that can cause joint disorders
5112) analysis of the occlusal plane: This is the evaluation of the curve of the occlusal plane through the curve of Spee, Wilson and the curve defined by the free edge of the anterior teeth. In the event of alteration of this occlusal curve, it is possible to determine on fully fractionated study models mounted on an articulator the necessary modifications to be made to obtain a correct occlusal plane by remodeling with special wax (wax up).
52) Prosthetic phase:
521) construction of a prosthesis that does not modify the patient’s occlusal pattern:
The production of a prosthesis in the pre-existing occlusal pattern is subject to the following conditions:
a) No pathology of the masticatory apparatus must exist
b) The dental preparations must not affect the key teeth of the anterior guide
c) Presence of posterior dental contact guaranteeing a correct DVO
d) Intercalary edentulism of small extent
e) Correctly oriented occlusal plane
f) Harmonious anterior guide
g) No interference or prematurity
522) construction of a prosthesis with modification of the patient’s occlusal scheme:
This is a situation contrary to the previous one, the occlusal modifications consist of modifications either:
a) by dental movement: calling for orthodontics
b) by subtraction: calling for occlusal equilibration by selective grinding or coronoplasty
c) by addition: calling for conservative dentistry and joint prosthesis.
6) Conclusion:
The success of a single or multiple joint prosthetic reconstruction is based on a solid knowledge of the anatomy and physiology of occlusion, as well as mastery of the use of a semi-adaptable (or adaptable) articulator by both the practitioner and the prosthetist in the laboratory.
OCCLUSION IN JOINT PROSTHESIS
Deep cavities may require root canal treatment.
Interdental brushes effectively clean between teeth.
Misaligned teeth can cause chewing problems.
Untreated dental infections can spread to other parts of the body.
Whitening trays are used for gradual results.
Cracked teeth can be repaired with composite resins.
Proper hydration helps maintain a healthy mouth.