Tuesday, May 30, 2023

The protrusive condylar guidance should be set on the articulator at.. 30 - 35 degree

The protrusive condylar guidance should be set on the articulator at:

  • A- 30 - 35  degree***
  • B- 50 degree.
  • C- 60 degree.
  • D- 70 degree.

The articulator is defined as "a mechanical device that represents the temporomandibular joints and components of the jaws to which models of the maxilla and mandible can be incorporated to simulate the movement of the latter".

The articulators recreate, although they do not duplicate, all the bordering mandibular movements, so that their primary function is to act as if they were a patient in their absence, reproducing the mandibular dynamics at the condyle level and its relationship with the dental arches and the massive skull. -facial.

Although it has often been said that "the patient's mouth is the best articulator", these mechanical devices offer many advantages over the mouth for the development of occlusion, among others:

  • Well-mounted models allow them to be observed from the lingual surfaces and thus detect possible occlusal interferences that would be difficult to identify in the mouth.
  • Patient cooperation is no longer critical once the records required to program the articulator are obtained.
  • The discomfort caused by the patient's saliva, tongue and cheeks is avoided, which simplifies diagnostic procedures (including wax-ups), planning and occlusal adjustment.
  • In fixed prostheses they allow a correct reconstruction of the occlusal surfaces; In removable partial dentures they are useful for a correct assembly of artificial teeth and in full dentures their use is essential to achieve a balanced bilateral occlusion.

The minimum requirements for an articulator are the following:

  • Must accurately maintain the horizontal and vertical relationship of the patient casts, which entails the need for the articulator to have a centric relation fixation device.
  • The patient casts can also be easily removed and placed on the articulator without losing said correct horizontal and vertical relationship.
  • The articulator shall have a positive torque incisal guide stem that can be adjusted and calibrated. This allows the dentist and laboratory technician to control the vertical dimension of the patient.
  • It will allow its opening-closing axis to coincide with the terminal hinge axis and reproduce the mandibular border movements.
  • You must accept the transfer of a facebow using a previous reference point. This will make it possible to introduce minor changes in the vertical dimension of the patient with little change in the centric position. In addition, the transfer of the anterior reference point facilitates the arrangement of the incisor group with the desired buccolingual inclination.
  • Its construction will be precise, rigid and made of non-corrosive material. Moving parts must resist wear. It will be necessary to be able to make the adjustments freely and fix them definitively.
  • Its design will guarantee an adequate distance between the upper and lower limbs, without hindering the vision of the rear. The articulator must be stable on the work table and not bulky or heavy.
  • The incisal guide table can be an adjustable metal platform in the frontal and sagittal plane (eg Dentatus); or a customizable plastic table with self-curing resin.
  • Finally, the articulator will allow an at least relatively simple adjustment of the inclination of the condylar track and the Bennett angle.

Articulator Classification:

Articulators can be classified according to two criteria:
  • Depending on the position occupied by the condylar elements.
  • Due to the ability to adjust and reproduce the specific condylar movements of the patient.

1- Position occupied by the condylar elements:

Articulators are subdivided into two main groups:

  • Arcon articulators (articulated condyle): Whip-mix, Perfect, Denar, Dentatus ARA, Hanau 130-21, Protar 2…
  • Non-Arcon articulators (non-articulated condyle): Dentatus ARL/ARH, Hanau H2.
  • Those of the arch type present the condylar cavity attached to the upper branch of the articulator and the condylar spheres in the lower part.
  • The arrangement of condylar cavities and spheres in non-arcon is the other way around.
  • In non-arch articulators, the condylar spheres describe a forced path within the condylar cavities, so that, regardless of the type of movement, it is not possible for said spheres to lose contact with the cavities.
  • This does not happen in arcon articulators, in which the cavities are simply supported on the spheres, and since in protrusion and laterality these spheres can lose contact with the condylar cavities with relative ease, non-arcon articulators are the ones of choice when the Rehabilitation requires a balanced bilateral occlusion.
  • On the other hand, there are authors who affirm that the arcon-type articulators allow a more exact adjustment of the condylar trajectory with respect to the non-archon ones, indicating that the difference in adjustment is 8º.

2- Adjustment capacity:

The articulators are also classified according to their degree of adjustability, that is, the possibility of adjusting them according to the individual parameters of the patient.
They are thus divided into non-adjustable and adjustable, subdividing the latter in turn into semi-adjustable and fully adjustable.

2-1- Non-adjustable articulators:

  • They are fixed guide positioners that can carry out movements following predetermined and non-modifiable inclinations, which correspond to average and statistically representative values ​​of the majority of the population; such as the 40º condylar guide and the 15º Bennett angle for the realization of complete prostheses and 25º/10º for fixed prostheses.
  • On the other hand, they do allow the height of the incisal pointer to be adjusted.
  • These articulators admit the transfer of a face bow and their use is limited to the reconstruction of not very extensive fixed prostheses, which must be adequately balanced after placement in the mouth.
  • They can also be used in tooth-supported or tooth-mucosal-supported removable partial dentures, in those cases in which maximum intercuspation is indicated, that this is stable and there is no functional pathology.
  • Within this group of articulators, occluders or hinges could be included, which simply position the models in maximum intercuspation without taking into account the condylar factor and only allow opening-closing movements that do not even accurately reproduce the paths followed by the patient's teeth. , since the distance from the cusps to the condyles is not transferred.
  • They can only reproduce the position of maximum intercuspation without intermediate wax registration.
  • The rest of the positions and movements do not correspond to the real ones of the patient.

2-2- Semi-adjustable articulators:

  • This type of articulators allows individualizing some guide parameters.
  • Using a defined anatomical face bow, it is possible to correlate the spatial orientation of the upper cast with respect to a reference cranial plane, for example, the plane of the orbital axis.
  • Wax records of mandibular protrusion and laterality are used to program the horizontal condylar inclination and the Bennett angle.
  • This system has a limit, since it takes as a reference a starting point that is facilitated by the recording of the most retruded unforced position, usually called "centric wax", and arrival points, represented by the edge-to-edge position of opposing guide teeth, either in protrusion or laterality.
  • In this way, the controls of the articulator are adjusted according to rectilinear trajectories, while in the patient the displacement made by the condyle in the glenoid cavity is curved, taking into account the anatomical structure of the latter.
  • Obviously, it is always possible to program in average values.

Indications for a semi-adjustable articulator are:
  • Diagnosis and occlusal analysis.
  • Selective carving
  • Study wax-ups.
  • Manufacture of complete prosthesis.
  • Manufacture of removable partial denture.
  • Manufacture of fixed prostheses.
  • Manufacture of mixed prosthesis.
  • Manufacture of prostheses on implants.
  • Reassembly and occlusal adjustment.

2-3- Fully adjustable articulators:

  • These articulators offer the possibility of modifying several parameters, such as: the horizontal condylar inclination, the incisor guide, the intercondylar distance and the Bennett angle.
  • In addition, the articulator can be adjusted by exchanging the condylar cavities or using the appropriate curved inserts, to reproduce the functional path much more exactly.
  • For the programming of this type of articulators, kinematic, axiograph and pantograph face bows are used, by means of which we will obtain the position of the hinge axis, and the recording on graph paper of the functional displacements of the condyles.
  • The Denar and Stuart articulators are among the fully adjustable.
  • In general practice, the use of these articulators is not required. They require a long time to use and adjust, and a high level of skill and understanding on the part of both clinician and technician. Its main indication is research on occlusion and prosthetic aspects.