Articulators: Definition, Uses, and Classification PDF

Definition Components Uses Advantages Requirements By Classifications Dr. Mohammed A. El-Sawy BDS, MSc, PhD (Mansoura University) Selection Lecturer of Prosthetic Dental Science Faculty of Dentistry...

Definition Components Uses Advantages Requirements By Classifications Dr. Mohammed A. El-Sawy BDS, MSc, PhD (Mansoura University) Selection Lecturer of Prosthetic Dental Science Faculty of Dentistry Limitations Menoufia University A mechanical device that represents the temporomandibular joint and jaw members to which maxillary and mandibular casts may be attached to simulate jaw movement. ⦿ Upper member : represent maxilla ⦿ Lower member : represent mandible ⦿ Condylar track: where condylar element(ball) fitted within it ,make its movement ⦿ Condylar element and condylar ball is called condylar guidance, in some articulator adjusted according to angles of patients). ⦿ Vertical Rod (incisal post) maintain vertical dimension distance between upper and lower cast to be fixed during all steps with articulator. ⦿ Incisal guide table where incisal post fitted to it in some articulator incisal table is movable and adjusted according to incisal path ⦿ The primary function of an articulator is to act as a patient in absence of a patient: 1Diagnosis and treatment planning. 2Arrangement of artificial teeth. 3-Fabrication of occlusal surfaces for dental restorations. 4-Correct and modify completed restoration. 5-Study occlusion and mandibular movement. 1-Better visualize the patient occlusion, especially from the lingual view. 2-patient co operation is not a factor. 3-Difficulty in refinement of complete denture occlusion because shifting of denture base from Patient saliva, tongue and check and resiliency of oral mucosa that covers the ridge. 4-More chair time and the patient appointment is required when utilizing the patient mouth as an articulator.  Revision (Remember). 1 Orientation relation. 2 vertical relation. 3 Horizontal relations. ⦿ Therelationship between the maxilla and the condyles or the cranium is recorded by the face bow and transferred unchanged to the articulator. ⦿ The amount of separation between the maxilla and the mandible. ⦿ 1- Centric relation: The maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective discs with the complex in the anterior superior position against the slopes of the articular eminences. This position is independent of tooth contact. This position is clinically discernible when the mandible is directed superior and anteriorly. It is restricted to a purely rotary movement about the transverse horizontal axis”  ⦿2- Eccentric relations: any relationship of the mandible to the maxilla other than centric relation. 1-Protrusive relation: a jaw relation that results from protrusion of the mandible. Posteriorly ◼The condyle moves with the disk forward and downward. The path of the condyle during this movement is termed the horizontal (sagittal) condylar path. ◼ It make an angle with horizontal called horizontal condylar path angle. ◼When this angle is recorded by protrusive record and transferred to the articulator it is called horizontal (sagittal) condylar guidance angle. Anteriorly  2-Lateral relation: the relationship of the mandible to the maxilla in a position to the left or to the right. Left lateral Right lateral ◼The side to which the mandible moves is called working side. The condyle do rotation with slight translation (Bennett movement). ◼The other side is called non working (balancing side); the condyle moves downward forward and medially (Bennett angel). ◼ The lateral condylar path is the path along which the balancing condyle head moves medially during lateral movement. ◼ The lateral condylar path angle it is the angle between the lateral condylar path and the sagittal plane. ◼ When this angle is recorded and transferred to the articulator it is called lateral condylar guidance angle. ◼ Anteriorly canine make an angle with the sagittal plane called canine guidance angle. Lateral movement of the mandible. 1, the lateral condylar path angle in the balancing side. 2, is the Bennett movement in the working side.  Complete denture occlusion may be: ⦿ 1- Non balanced occlusion: Simultaneous even bilateral and posterior contact in centric relation. Or: ⦿ 2- Balanced occlusion: The simultaneous contacting of the maxillary and mandibular teeth on the right and left side and in the posterior and anterior occlusal areas in centric and eccentric positions, developed to lessen or limit tipping or rotating of the denture bases in relation to the supporting structures”- 1- Minimal requirements (denture fabricated in non blalanced occlusion): 1- Articulator must accurately maintain the horizontal and vertical relationship of the casts. ⦿ Have incisal pin to maintain vertical dimension. ⦿ It should be rigid and resist wear. ⦿ Cast must be easily removed and attached to the articulator without losing of their horizontal and vertical relationship. ⦿ Able to open and close in hinge like movement. ⦿ Have adequate distance between upper and lower member. ⦿ 2- Additional articulator requirement (Denture fabricated in balanced occlusion): ⦿ Articulator should accept face-bow transfer. ⦿ Articulator should have adjustable condylar guidance. ⦿ Articulator have adjustable Bennett movement. ⦿ Articulator have adjustable incisal guidance. 1- According to instrument capability, record acceptance and intent into: ⦿ Class I: articulator (non adjustable) simple holding instrument. Include plaster slab relators and simple hinge articulator. ⦿ Class II: articulator (average value). ⦿ Class III: articulator (Semi adjustable). ⦿ Class IV: articulator (fully adjustable). ⦿ Class I: articulator (non adjustable) simple holding instrument. ✓ Vertical motion may or may not be possible. ✓ These are simple capable of accepting a single registration. 1- Plaster slab relators: 2- Simple hinge articulators: Design: ⦿ Two bows by hinge. ⦿ Screw adjustment that raise and lower the distance between the bows. Possible movements: This type of articulators gives only opening and closing movements. Record: ⦿ Static centric relation record non balanced occlusion or Plaster and pumice (dynamic)record balanced occlusion.  ⦿ Class II: articulator (average value). ✓ These articulator permits horizontal and vertical movements, but they do not orient the movement to TMJ by a face-bow. ✓ The condylar path is fixed and can not be adjusted. Also, it has a fixed incisal guidance. ✓ Fixed intercondylar distance. ✓ They can not accept eccentric records that are used to adjust the condylar guidance of the articulator. These are capable of accepting only a single registration. Type A Type B Type C ⦿ Class II type A Eccentric motion is based on average values which is the average value of population. Design Possible movements ⦿ Opening and closing. ⦿ Protrusive movement at a fixed horizontal condylar guidance angle. Record: ✓ These are capable of accepting a single registration. Ex. Mean-Value articulator ⦿ Class II type B: ⦿Instruments in this class permit eccentric motion based on arbitrary theory of motion; Ex. 1- Monson’s articulator: based on spherical theory of occlusion. (lower teeth move against upper teeth in part of sphere its center at glabella (between orbits) its radius is 8 inch) 2- Bonwill theory articulator: theory of equilateral triangle. 3- Hall articulator: based on conical theory of occlusion. (lower teeth move against upper teeth in part of cone ‫خمروط‬ The angle between occlusal plane and center of the cone is 45°) Monson’s articulator Bonwill articulator Hall articulator Bonwill mentioned that the distance between the condyles and the distance from each condyle to the contact point of the lower central incisors, is 4 inches ( nearly 10 cm.). Bonwill, thus, formulated the theory of the equilateral triangle and designed an articulator to this theory. 2-Mean value, average or fixed condylar path articulators BONWILL 1854 4” 4” Class II type C :- Instruments in this class permit eccentric motion based on engraved records obtained from the patient and will not accept a face-bow transfer Ex.:- House’s articulator ⦿ Class III (Semi adjustable): ⦿ They permit horizontal and vertical motion. ⦿ They differ from class II in that: The condylar guidance is not fixed but can be adjusted. However they are limited to providing only a straight pathway. So that the articulator movements will simulate or nearly duplicate the jaw movements of the patient. They have adjustable incisal guidace. Also, they accept face-bow transfer. They can accept some eccentric records that are used to adjust the condylar guidance of the articulator. These are capable of accepting static centric record, static protrusive record, and some lateral records (positional records). ⦿ They are called semi adjustable because they do not / Cannot allow total customization of condylar pathways. They simulate condylar pathways by using average or mechanical equivalents for the whole or part of the condylar motion. ⦿ Have fixed or closely fitted intercondylar distance. Type A Type B ⦿ Class III Type A: ⦿ Design: Have adjustable horizontal condylar guidance, adjustable lateral condylar guidance, adjustable incisal guide table. They don’t accept lateral records. ⦿ Possible movements: ▪ 1-Opening and closing. ▪ 2-Protrusive movement to an angle recorded from the patient. ▪ 3-Lateral movement to an angle calculated from the Hanau’s formula: L=H/8+12. ▪ Where; L = the lateral condylar path ▪ H = the horizontal condylar path angle which is recorded from the patient. ⦿ Records: They can accept the following records: 1. Face bow record to mount the upper cast. 2. Centric relation record to mount the lower cast. 3.Protrusive record, to adjust the articulator's horizontal guidance, that correspond to the patient's horizontal condylar path inclination. Uses equivalents for other types of motions. An example of this type is Hanau model H articulator.  Class III Type B: ⦿ Acceptsome Static Lateral, static protrusive records + facebow transfer + centric relation. ⦿ Use equivalents for other types of motions. But still semi-adjustable articulator because 1-Condylar element move only in straight pathway. 2-Side shift of working condyle not occur well Example is – Whipmix articulator Class IV (Fully adjustable articulators): ⦿ Capable of being adjusted to follow the mandibular movement in all direction. ⦿ They differ from class III in that: They can accept three dimensional dynamic records (in horizontal, sagittal and frontal planes) that are used to adjust the condylar guidance of the articulator. The condylar paths are curved. So, they are capable of accurately reproducing the condylar pathway for each patient. Adjustment of lateral shift of the working condyle. Also, they have adjustable intercondylar distance. Class IV type A: ⦿ It accept custom fossa analogue (Condylar pathways) that is produced from intraoral stereographic tracing. ⦿ Example is TMJ articulator Stereographic record: Generated by studs in auto-polymerizing acrylic resin similar to Needle House technique. This record is then placed on the articulator and used to mold fossa in auto polymerizing acrylic resin.  ⦿ Class IV type B: ⦿ The procedure utilize the pantographic tracing. ⦿ Pantographic record: A graphic record of mandibular movement in three planes as registered by the styli on the recording tables of a pantograph. Tracing of mandibular movements recorded on the sagittal, horizontal and frontal planes. ⦿ Condylar pathway can be selectively angled and customized / modified. ⦿ 2- According to the location of the condyle: ⦿ A- Arcon articulator. The condyle of this articulator are located on the lower member of the articulator. ⦿ B- Non arcon articulator. ⦿ The condyle of this articulator are located on the upper member of the articulator ⦿3- Classification according to the adjustability of the articulator: ❑ Non adjustable. ❑ Mean value ❑ Adjustable: ✓ Semi adjustable. Arcon Non arcon ✓ Fully adjustable. ⦿Incomplete denture construction, articulators are selected according to: 1-The type of occlusion to be developed 2-The type of jaw relation records that can be made to adjust the articulator. ❖ Metal, plastic articulators show errors in tooling, (manufacturer errors). ❖ It doesn’t not exactly simulate the functional movements of the mandible. ❖ Errors in jaw relation procedure are reproduced as errors in the denture occlusion. Articulators do not have any provision to indicate or correct these errors. Summary  Simulation Patient of record mandibular movements Transfer Articulator Selection Occlusion  Types of articulator Point of difference Simple hinge Mean value Semi adjustable Fully adjustable Adjustable ( Horizontal Adjustable - Fixed at (30) dynamic protrusive condylar angle (H) (protrusive record) record) Adjustable Hanau's formula (type A) Adjustable lateral condylar Adjustable by some - Fixed (dynamic lateral angle (L) lateral record record) (type B) Fixed incisal guidance - In some type it can Adjustable Adjustable angle be adjusted. incisal pin - Available Available Available inter condylar - Fixed Fixed Adjustable distance Required (arbitrary Required Not required face-bow transfer Not recorded or kinematic face- (kinematic face- (Bonwill triangle) bow) bow)  Occlusion Non balanced Balanced Non adjustable articulator Non with functional generating adjustable path record or articulator Semi adjustable articulator