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DENTAL ARTICULATION, FACE-BOW AND ARTICULATORS

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Title: DENTAL ARTICULATION, FACE-BOW AND ARTICULATORS


1
DENTAL ARTICULATION, FACE-BOW AND ARTICULATORS
  • Dr. Waseem Bahjat Mushtaha
  • Specialized in prosthodontics

2
1- dental articulation
  • Dental articulation
  • It means the contact relationships of maxillary
    and
  • mandibular teeth as they move against each other.
    This is a dynamic process.
  • Articulator
  • It is a mechanical instrument that represents the
    tempomandibular joints and jaw members, to which
    maxillary and mandibular cast may be attached to
    simulate some or all-mandibular movements.
  • Occlusion
  • It is the static relation ship (process of
    closure) between the incising or masticating
    (occluding) surfaces of the maxillary and
    mandibular teeth when they are in contact.

3
  • Centric occlusion
  • It is the relation of opposing occlusal surfaces
    which provides the maximum planned contact and\or
    intercuspation.
  • Centric relation
  • It is the relation of the mandible to the maxilla
    when the condyles are in uppermost and rearmost
    position in the glenoid fossa at a given degree
    of vertical dimension (jaw separation). This
    position may not be recorded in the presence of
    dysfunction of the masticatory system.
  • Centric occluding relation
  • It is a term sometimes used to describe the
    condition in which the jaws are in centric
    relation and the teeth or occlusal surfaces in
    centric occlusion.

4
  • Anatomical articulation
  • It is an occlusal arrangement where the posterior
    artificial teeth have masticatory surfaces (can
    make normal masticatory movements with comfort
    and efficiency) that closely resemble those of
    the natural healthy dentition and articulate with
    similar natural or artificial surfaces.
  • Balanced occlusion
  • It means that the artificial teeth are set up so
    that as many teeth as possible are in occlusion
    in any occlusal relationship.
  • Balanced articulation
  • It is bilateral, simultaneous, anterior, and
    posterior occlusal contact of teeth in centric
    and eccentric positions. It means an arrangement
    of the teeth so that in any occlusal relationship
    as many teeth as possible are in occlusion, and
    when changing from one relationship to another
    they move with a smooth, sliding motion , free
    from cuspal interference and maintaining even
    contact

5
  • Curve of Spee (anteroposterior curve)
  • It is the anatomic curve established by the
    occlusal alignment of the teeth, as projected
    onto the median plan, beginning with the cusp tip
    of the mandibular canine and following the buccal
    cusp tips of premolar and molar teeth, continuing
    through the anterior border of the mandibular
    ramus, ending with the anterior most portion of
    the mandibular condyle
  • Curve of Menson
  • It is the curve of occlusion in which each cusp
    and incisal edge touches or conforms to a segment
    of the surface of a sphere 8 inches in diameter
    with its center in the region of the glabella

6
  • Curve of Wilson (mediolateral curve)
  • It means in mandibular arch, that curve , as
    viewed in frontal plane, which is concave
    inferiorly and contacts the buccal and lingual
    cusps of the mandibular molars. In the maxillary
    arch, that curve, as viewed in frontal plane,
    which is convex superiorly and contacts the
    lingual and buccal cusps of the maxillary molars.
    The curved is formed by the facial and lingual
    cusp tips on both sides of dental arch
  • Compensating curve
  • It is anteroposterior curvature (in the median
    plane) and the mediolateral curvature (in the
    frontal plane) in the alignment of occluding
    surfaces and incisal edges of artificial teeth
    that are used to develop balance articulation.
    These curves introduced in the construction of
    complete dentures to compensate for the opening
    influences produced by the condylar and incisal
    guidance during lateral and protrusive mandibular
    excursive movements, these curves are artificial
    counterparts of the curve of Spee and monsoon,
    which are found in the natural dentition.

7
  • The working side
  • It is the side on which the chewing is being done
    at the movement it is the side to which the
    mandible has moved.
  • The balancing side
  • It is the side opposite to the working side. It
    is the side on which, although there is greater
    separation of the teeth, there is at least one
    point of contact between the upper and lower
    teeth. It is also the side on which the grater
    condylar movement has occurred

8
II-FACE-BOW
  • Def the face-bow is a caliper-like device that
    is used to record the relationship of the jaws to
    the temporomandibular joints or the opening axis
    of the jaws and to orient the casts in this same
    relationship to the opening axis of the
    articulator.

9
Types of face-bow
  • 1-the arbitrary (maxillary) face-bow
  • 2-the kinematic (mandibular, hinge axis locator)
    face-bow

10
1-the arbitrary (maxillary) face-bow
  • A-The maxillary face-bow is one generally used in
    construction of complete denture
  • B-it is used to record the position of the upper
    jaw in relation to the hinge axis and
    transferring the relation to an articulator.
    The maxillary face-bow is simple to use and
    relatively accurate, and is based on
    average computations of an axis
    opening of the jaw.

11
  • C-it is placed on, the face with condyle rod
    located
  • approximately over the condyles.
  • D- The condyle rods of one particular model are
    positioned on a line extending from the
    outer canthus of the eye to the top of
    the tragus of the ear and approximately 13mm
    in front of the external auditory
    meatus. The rods of another commonly used
    model (ear face bow) are designed
    to fit into the external auditory
    meatuses (as a posterior reference point).
  • E-the fork of maxillary face bow is attached to
    the maxillary occlusion rim so the record is
    a simple measurement from the jaws to the
    approximate axis of the jaws.

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2-the kinematic (mandibular, hinge axis locator)
face-bow
  • A-it is used to locate the true terminal hinge
    axis and transfer this record to the
    articulator when mounting the maxillary
    cast. However, use of it can aid in recording
    centric relation.
  • B-the fork of kinematic face-bow is attached to
    the mandibular occlusal rim.
  • C-since this is used to orient the casts on an
    articulator in the same relation to
    the opening axis of the articulator as the
    jaws are to be the opening axis of jaws

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Functions of a face-bow
  • 1-locate the terminal hinge axis by the use of
    kinematic face bow.
  • 2-relate the maxillary cast to the transfer axis
    of the articulator in the same relationship as
    the maxilla is related to the mandibular hinge
    axis.
  • 3-relate the mandibular cast to the hinge axis by
    means of a centric relation record.

16
  • An arbitrary mounting of the maxillary cast
    without a face-bow transfer can introduce errors
    in the occlusion of the finished denture. A face
    bow transfer is essential when cusp teeth are
    used, allows minor changes in the occlusal
    vertical dimension without having to make new
    maxillo-mandibular records, and is also most
    helpful in supporting the maxillary cast while it
    is being mounted on the articulator.

17
ARTICULATORS
  • DEF is a mechanical device which represents the
    temporo-mandibular joint and jaw members to which
    maxillary and mandibular casts are attached to
    simulate jaw movements. The records made with
    occlusion rims are used to mount the master casts
    and to adjust to articulator. They also help in
    maintaining the desired jaw relationships of the
    casts during setting up of teeth.

18
Articulators are classified according to the
instrument capability and record acceptance into
  • 1-simple hinge articulators.
  • 2-mean value or fixed condylar path articulators
  • 3-adjustable condylar path articulators
  • A-semi-adjustable articulators.
  • B-fully adjustable articulators.

19
1-simple hinge articulators or plain line
articulators
  • 1-They are cold plain line articulators since
    they only permit vertical motion i.e. simple
    opening and closing or hinge-like movement
  • 2-they accept a single interocclusal record,
    which is the centric occluding relation record.
  • 3-Gariot's articulator is a representative for
    this type of articulator. It consist of upper and
    lower members joined by a simple hinge with a set
    of screw against a metal plate posteriorly to
    serve as a vertical stop to increase or decrease
    the distance between the two members of the
    articulator.

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2-mean value or fixed condylar path articulators
  • 1-these articulators accept single interoclusal
    record the centric occluding relation
    record, they permit horizontal as well as
    vertical movements. Eccentric movements
    permitted are based on average value. For
    many patients the condylar path ranges from
    30-40 from the horizontal with an average 32.
    The inclination of the condylar guidance of
    the articulator is fixed to the average value
    and cannot be adjusted in any manner.

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  • 2-Gysi articulator, Mahdy articulator and
    Artek.pro are representive of these types of
    articulators. They consist of upper and
    lower members which are joined by two vertical
    posterior posts "condylar post
    support" fixed to the lower member,
    whereas the upper end of each post has an
    inclined groove representing the condylar
    path, through which the condylar shafts,
    extending from the upper member are
    located and moved in this groove allowing
    horizontal movement of the upper
    member.

24
  • 3-anterior vertical post, "the incisal post"
    which is attached to the upper member of the
    articulator by a screw , while its lower end
    rests on an inclined table, "the incisal guide
    table" which is fixed to the lower member of the
    articulator.Inclination of the incisal guide
    table is fixed at about 30 from the horizontal
    plane.
  • 4-in the incisal post there is a hole, through
    which the incisal pin passes. The tip of this pin
    is designed to touch the midline of the occlusal
    rim labially.

25
  • 5-in Gysi articulator, the upper cast is mounted
    according to Bonwill's triangle which is
    a four inch (10 cm) equilateral triangle
    extending poseriorly from one condyle
    to the other and joining the lower
    incisor's contact point
    anteriorly. While the lower cast is mounted
    according to the recorded centric occluding
    relation record.
  • 6-in Mahdy articulator and Artek pro articulator
    face-bow transfer is used to mount the
    upper cast while the lower cast is mounted on
    this instrument using centric
    occluding relation record.

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3-adjustable condylar path articulators
  • This type of articulators differ from the fixed
    condylar path articulators in that they can
    accept eccentric records which are used to adjust
    the condylar guidance of the articulator, so that
    the movements of its jaw members closely resemble
    that produced by the patient. According to the
    eccentric records accepted by these types of
    articulators they are classified into
  • A-semi adjustable articulators
  • B-fully adjustable articulators

28
A-semi adjustable articulators
  • This type of articulators can accept the
    following records
  • 1-face-bow record to mount the upper cast.
  • 2-centric occluding relation record to mount the
    lower cast.
  • 3-protrusive record, to adjust the articulator's
    horizontal condylar guidance that
    corresponds to the patient's horizontal condylar
    path inclination. Where as the articulator
    lateral condylar guidance is adjusted according
    to the Hanau's formula
  • Hanau's formulaLH\8 12
  • Lthe lateral condylar path inclination.
  • Hthe horizontal condylar path inclination

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B-fully adjustable articulators
  • This type of articulator can accept the following
    records
  • 1-face bow record to mount the upper cast.
  • 2-centric occluding relation record to mount the
    lower cast.
  • 3-protrosive record, to adjust the articulator's
    horizontal condylar guidance which
    corresponds to the patient's horizontal condylar
    bath inclination.
  • 4-right lateral record, to adjust the left
    lateral condylar guidance which
    corresponds to the patient's lateral
    condylar path inclination.
  • 5-left lateral record, to adjust the right
    lateral condylar guidance which
    corresponds to the patient's right
    lateral condylar path inclination.

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Indexing the cast
  • Indexing casts prior to mounting them on an
    articulator permits removal of the cast and
    accurate replacement to the articulator. Indexing
    is also important for remounting procedures made
    for correcting occlusal errors after curing a
    denture. Indexing can be accomplished by placing
    grooves or notches, in the cast or by using
    remounting plates

33
Mounting the master cast on the articulator
  • In the process of mounting master casts on a
    fixed condylar path articulator the following
    steps should be performed
  • 1-the upper and lower casts are prepared for
    laboratory remount by cutting indices on the
    under surface of both casts. These indices
    are protected by tin-foil.

34
  • 2-the upper and lower trial denture bases are
    sealed with wax to their casts, thus the upper
    cast, lower cast and wax rims are all attached
    together. The arms of the articulator to be used
    are lubricated with Vaseline or oil to facilate
    cleaning the articulator from the plaster after
    the case is finished.
  • 3-the incisal guide pin of the articulator is
    adjusted until its top flushes with the top of
    the upper member.
  • 4-a rubber band is placed on the articulator,
    extending from the lower mark of the
    incisal
    guide pin and around each condylar post support.
  • Adjust the rubber band to form a plane that
    divides the space between the upper and lower
    members of the articulator equally "Bonwell
    triangle"

35
  • 5-Three lumps of modeling clay are placed on the
    lower mounting plate to serve as an adjustable
    cast support
  • 6-with the base plate and occlusion rims sealed
    together, place both maxillary and
    mandibular casts in the correct
    relationship on the three clay supports in the
    articulators .then align them until of the
    occlusal plane of occlusion rim is parallel to
    the plane established by the rubber band
  • 7-open the articulator, and paint the base of
    maxillary cast with a separating medium.

36
  • 8-mix, and add plaster to the base of the cast
    and to the upper member of the articulator.
  • 9-close the articulator until the incisal guide
    pin touches the incisal guide table and
    then add more plaster as needed to fill any
    voids.
  • 10-after the stone has set, invert the
    articulator, and open it. Removing the
    modeling clay cast supports, paint
    separating medium on the base of the lower cast
    and attach it to the articulator with plaster.
  • 11-permit the plaster to set, then remove excess
    plaster with a knife.

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Occlusion rims
  • An occlusion rim is a wax form used to establish
  • 1-the proper lip and cheek support (fullness of
    the lips and cheeks)
  • 2-the arch form, which is related to the activity
    of the lips, cheeks and tongue.
  • 3-the level of the occlusal plane.

40
  • 4-accurate maxillo-mandibular jaw relations i.e.
    Help to determine
  • A-vertical dimension and an estimate of the
    interocclusal distance.
  • B-horizontal jaw relations (centric occluding
    relation and condylar path)
  • 5-occlusion rims help to determine the length and
    width of the artificial teeth
  • A-high and low lip lines are used for determining
    the length of the artificial teeth.
  • B-canine line i.e. corners of the mouth the
    distance between the canine lines determines the
    width of the six anterior teeth.
  • C-the distance between the canine line and the
    posterior end of the occlusion rim determines the
    mesiodistal width of the posterior teeth.
  • 6-position of midline of the arch for the correct
    placement of the central incisors.
  • 7-arrangement of the artificial teeth to the
    trial denture (setting up of the teeth).

41
  • Base plate wax is the most commonly used occluasl
    rim material. Compound and a mixture of the
    plaster and pumice are sometimes used for
    constructing occlusal rims. There are four basic
    factors that should be considered in the proper
    fabrication of occlusion rims, to assist the
    dentist and the dental laboratory technician
    throughout the many phases of denture
    construction.

42
  • These factors are
  • 1-relationship of natural teeth to alveolar bone
  • Since the final goal in the treatment of the
    edentulous patient is to provide a functional and
    esthetic prosthesis, the relationship of the
    natural teeth to the alveolar bone must be
    understood. The fabrication of successful
    replacements can be accomplished in most cases
    only if the artificial teeth are placed in the
    same position that was occupied by the natural
    teeth they are replacing.
  • The natural maxillary anterior teeth are inclined
    slightly forward of the alveolar bone. They
    contribute to the support of the upper lip
  • With the canines providing support for the
    corners of the mouth. The mandibular incisors are
    also inclined forward and tend to support the
    lower lip. The maxillary posterior teeth are
    positioned slightly buccal to the alveolar ridge,
    when occluding with the mandibular molars the
    maxillary buccal cusps usually project 2 to 3 mm.
    beyond the buccal cusps of the mandibular teeth.
    The crowns of the lower posterior teeth are
    inclined inward

43
  • 2-relationship of occlusion rims to edentulous
    ridges
  • The location and dimensions of the occlusion rims
    in relation to the edentulous ridge are basically
    the same as those for the crowns of the natural
    teeth that are to be replaced in their relation
    to the alveolar ridge. The occlusion rims simply
    replace the natural teeth both in dimension and
    in their relationship to anatomic structures.
    These relationships should be re-established by
    the occlusion rims even if resorption of the
    residual ridge has occurred following the removal
    of the natural teeth.

44
3-fabrication technique and dimensions of
occlusion rim
  • 1-base plate wax (modeling wax)
  • A sheet of base plat wax is heated over
    approximately one half its length until the wax
    is soft and pliable. The soft wax is rolled to
    point to a point just short of unheated area. The
    wax is again heated and rolled until a soft roll
    has been formed. The soft wax roll is adapted to
    a bead of sticky wax that was previously applied
    to the recording base. The roll is further seated
    to the base. The roll is further seated to the
    base with spatula, with additional molten wax.

45
  • The edges of the roll are extended along the
    lateral surfaces to the border of the recording
    base. Additional wax is added to fill any voids
    in the contour of the rims. A heated broad bladed
    knife or plaster spatula is, used to quickly
    shape the labial surface of occlusion rim. The
    anterior surface should be inclined outward while
    the posterior surface is sloped slightly inward.
  • A hot wax spatula is used to smooth the lingual
    surface and form a rim approximately 5mm wide in
    the anterior area and approximately 8-10mm in the
    posterior area.
  • These basic dimensions are subjected to final
    chair side changes, since the dentist uses the
    rims to determine the proper vertical dimension,
    occlusal plane, facial support, as well as the
    midline of the arch, the length and width of the
    anterior teeth, the buccal eminence, the smiling
    (high) lip line, and the speaking(low) lip line.
  • The occlusal surface of the occlusal rim must be
    smooth and flat. All surfaces of the rim should
    be smooth.

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2-the composition (compound
impression)
  • 1-May be used and softend in warm water, molded
    into a back of the necessary size and placed
    into position.
  • 2-a hot wax knife is used to adapt the edge, the
    surface is best smoothed with a sand
    paper.
  • 3-the use of compound is indicated when it is
    desired to obtain more than one record of
    the occlusion, as with any type of fully
    adjustable articulator, or when gothic
    arch tracing is to be taken.

52
3-plaster and pumice
  • When a functional recording of mandibular
    movements is to be made by the patient chewing on
    bite rims, these should be made of a mixture of
    plaster and pumic. In this technique the patient
    goes through the movement of mastication with the
    bite blocks in occlusion and so produces the
    occlusal plane conforming to those movements. An
    acrylic base is the most satisfactory for this
    technique. The plaster is mixed with pumic equal
    parts of each, to facilate the grinding down in
    the mouth.

53
  • This plaster-pumic combination is mixed with
    water into a thick consistency and a roll of it
    is placed on to the base whilst the initial set
    is taking place. It can be smoothed with
    moistened fingers before setting is completed. A
    preliminary recording of vertical dimension is
    desirable which should be taken 3mm greater than
    finally required to allow for the reduction in
    grinding down in the mouth.
  • These plaster rim should be made less than 24
    hours before they are required , otherwise the
    patient will have difficulty in grinding them
    down owing to the increased hardness of the
    plaster.
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