CENTRIC RELATION RECORD TECHNIQUE
This record should be taken at a position where the teeth are slightly separated (0.5-1.0). This is a position as close to initial contact as possible without actually permitting the teeth to contact. If the teeth are allowed to contact, a proprioceptive response would be initiated which would alter the correct positioning of the condyles in the centric relation position and result in an inaccurate registration. The closer the teeth are to the vertical dimension of occlusion, the less opportunity for error is introduced when the articulator approximates the mounted casts along the arc of closure on the articulator.
There are many different methods of obtaining a record of the centric relation position. The record may be registered in various media: wax, elastic impression pastes, zinc oxide and euginol (ZOE) pastes, acrylic materials, compound, and fast set plaster. The material that sets the fastest within the operatorŐs control is the material that should be utilized.
The material can not be perforated with the cusp tips as this would permit the potential for proprioceptive distortion of the correct mandibular position. The recording media should be placed over the posterior teeth only. When anterior teeth are given the opportunity to contact the record, the patient may have a tendency to bite into the record and possibly distort the correct position of the mandible. The record should not be an impression of the occlusal surfaces of the posterior teeth. Only a small imprint of the cusp tips is necessary to place the dental casts accurately into the registration. The proper placement and stabilization of the mandible, with the correct separation of the posterior teeth, can be greatly facilitated by custom fabricated acrylic positioner known as an anterior programmer or Lucia Jig.
PROTRUSIVE ECCENTRIC RECORD
The protrusive record is necessary for programming the condylar inclination of a semi-adjustable articulator. The condylar tracts are adjusted and set in accordance with the condylar path inclination (the angle of the condylar eminentia) of the patient in the sagittal plane.
The protrusive record should be obtained when the mandible is protruded 5-6 mm from the centric relation position. If the registration is made at a lesser or greater distance the condylar inclination determination will be inaccurate. Because the true anatomical form of the eminentia is "S" shaped and the condylar path of the semi-adjustable articulator is directed by a straight guidance track, the protrusive registration must be obtained at a position that record the flattest position of the patientŐs eminentia. This straight path is not truly representative of the curve presented by the articulator eminence so these instruments present a a comprise between the mechanical simulating capability of the condylar element of the articulator and the anatomical form of the condylar path.
LATERAL ECCENTRIC RECORD
The lateral eccentric record is a registration of the spatial position of the mandible in relationship to the maxilla at a point along an infinite number of points that describe the eccentric lateral path of mandibular movement. This path of movement is directed by the temporomandibular joint mechanism and is considered reproducible. These records should be made no further than 5 mm lateral from the centric relation position or when the buccal cusps of the maxillary and mandibular teeth and/or the canine cusp tips are aligned over one another.
Semi-adjustable articulators are capable of simulating certain factors of occlusal morphology and mandibular movement within a given limit of their design and adjustability. Functionally correct dental restorations are enhanced by the similarity in function of these articulators to the actual mandibular movements. Two of the factors of occlusal morphology, the angle of the eminentia and the influence of laterotrusion (Bennett Movement or side shift) can be described and transferred to the articulator by utilizing lateral eccentric records.
MOUNTING CASTS ON THE ARTICULATOR
The maxillary cast is mounted to the articulator utilizing a face bow transfer from the patient. This will orient the maxillary cast on the articulator in the correct spatial relationship to the patientŐs horizontal condylar axis.
The mandibular cast can be mounted to the articulator and, subsequently, in correct relationship to the maxillary arch, in one of three ways Remember, the facebow has absolutely, positively, nothing to do with the mounting of the mandibular cast to the articulator.
1.Maximum intercuspation through hand articultion--a.k.a centric occlusion (CO) or intercuspal position (ICP). This can be accomplished by hand articulation, if enough teeth are present to provide a stable mounting position for the casts
2. Maximum intercuspation through recording medium (wax, etc.) if the remaining teeth do not provide adequate cast positioning and stability. This position is dictated by the patientŐs habitual closure pattern (muscular engrams) as a consequence of the alignment of the teeth.
3. Centric relation (CR) - - That is, when the condyles are in their most superior anterior position with the articulator discs properly interposed between the heads of the condyles and the articulator fossae. This position is manipulated by the Dentist with all patient musculature deprogrammed.
WHEN TO USE THE MANDIBULAR MOUNTING TECHNIQUE
1. When enough teeth are present to allow the casts to be related to one another in stable MI position
2. As a routine diagnostic procedure in conjunction with a face bow transfer in the prosthodontic clinics.
3. Most routine fixed prosthodontic restorative and removable partial denture procedures one at MUSC, CDM.
MAXIMUM INTERCUSPATION RECORDS
1. When not enough teeth are present to allow for stable hand articulation for diagnostic procedures in the prosthodontic clinics.
2. When teeth have been prepared for the construction of posterior fixed partial dentures or multiple single crowns when those teeth previously provided the most distal occlusal contacts with the opposing teeth.
3. During the fabrication of removable partial dentures that donŐt have stable natural tooth contact.
CENTRIC RELATION RECORDS
The mounting of the mandibular cast in a relationship reflecting the position of the maxillary and mandibular arches when the condyles are in a CR position is, by in large, a diagnostic procedure. This is always accomplished in the patientŐs mouth without any teeth contacting (i.e., at an increased vertical dimension).
1. When extensive restorative procedures (fixed or fixed/removable combinations) are anticipated.
2. When occlusal equilibration procedures are anticipated.
3. When occlusal splint therapy is anticipated.
4. When treating temporomandibular disorders (TMD).
5. When orthodontic and/or orthognathic surgery procedures are anticipated.
6. Virtually all complete removable prosthodontic procedures. This is the only situation where you will routinely be making CR records at MUSC, CDM.
An interocclusal record is a registration of the spatial relationship between the mandible, the movable component of the maxillomandibular system, and the maxilla, the fixed component.
This registration can be a record of the centric relation position or eccentric mandibular position. When working casts for the fabrication of certain restorations are mounted in maximum intercuspation, occasionally a record over the preparation teeth only is used. The record of the lateral positions can be a description of a point spatial relationship along the path of eccentric movement of the mandible in relationship to the maxilla; this is termed a "lateral checkbite". Lateral checkbites record one point along the limitations of the lateral border pathways of mandibular movement, which are anatomically directed in a reproducible manner by the temporomandibular joint mechanism. Registrations of the eccentric, protrusive pathway of the mandible are termed "protrusive checkbites". The protrusive pathway is not a reproducible mandibular movement, because it is directed anatomically by the musculature.
A registration of the entire eccentric pathway from the centric relation position is termed a pantogram. This record is obtained through the utilization of a pantograph. A pantograph will record the eccentric border pathways and the protrusive pathway in three dimensions. It is necessary to the programing procedures used with a fully adjustable articulator.
A record of the relationship of the mandible and its potential spatial positions relative to the maxilla is necessary for an accurate evaluation and determination of the functional and parafunctional relationship of the dentral arches for a particular patient. This registration permits a transfer of these relationships to the articulator that will simulate these tooth positions relative to the anatomic controls. The data obtained from these registrations must be precisely and accurately acquired in order that they may be of value in the transfer and orientation of this information to an articulator.
CENTRIC RELATION POSITION RECORD
The registration of the spatial relationship of the mandible to the maxilla at a reproducible position is the single most important procedure in restorative and diagnostic dental procedures. It is also a very difficult procedure, requiring precise accuracy. Without an accurate positioning of the mandibular cast in relationship to the maxillary cast within the articulator, all additional programming procedures and simulating capabilities of the articulator are useless.
MAXIMUM INTERCUSPATION RECORD
A maximum intercuspation record requires no registration techniques nor material if the casts are adequately stable when hand articulated. When a cast is mounted in maximum intercuspation, the mandibular cast is positioned into its most stable position which duplicates the clinical situation, the casts luted together, and mounted on the articulator. This technique is limited to single unit restorations, multiple unit replacement fixed restorations that are not the distal abutment in the arch and certain quadrant restorative procedures. If a replacement fixed restoration is the distal abutment of the arch, and the casts are to be mounted in maximum intercuspation, the prepared teeth alone are supported by a registration obtained intraorally in that position. No recording media should separate or increase the occlusal vertical dimension.