Functionally Generated Pathways Question And Answers

Functionally Generated Pathways Question And Answers

Functionally generated pathways (Meyer)

The functionally generated pathway is a technique in which tracing is made in the mouth to capture the pathways traveled by the opposing cusps in mandibular function.

Functionally generated pathways Advantages

• Teeth are modified to accept every possible eccentric jaw movement
• Eliminates the need to use extraoral tracking devices
• Accurate
• Occlusion thus established will have complete harmony with the opposing natural or artificial teeth
• An articulator is not required.

Read And Learn More: Fixed Partial Denture Short Essay Question And Answers

Functionally generated pathways Disadvantages

• Opposing teeth need to be cleaned as wax particles accumulate on it
• The patient needs to understand the mandibular movements
• The procedure takes a long as wax needs to be added to deficient areas as patients start the mandibular movements
• Need to correct occlusal plane irregularities before this technique is done
• Registration of occlusal pathways requires a completely intact opposing arch
• Takes more appointments to complete the procedures.

The final result of the registration

• After 24 hours, the occlusal surface of the wax rim should be glossy
• After a second 24–48 hour period of wear, the registration should be complete.

A technique using functionally generated pathway (by Pankey and Mann)

• Based on the spherical theory of occlusion the mandibular teeth are reduced
• To bring the occlusal surfaces into harmony with the surface of the theoretical sphere
• Buccal and lingual preparation guides plane are used as a guide to reduce the mandibular tooth
• The reduced tooth is restored to an ideal plane and a functionally generated recording of the mandibular cusp paths is made against which the maxillary tooth is restored.

Fabrication of functional core:

• The occlusal reduction is done and functional tracing is made before the axial reduction. Apply lubricating agent to the opposing quadrant
• A wax adherent like Copalite is applied to the adjacent tooth before a layer of tacky wax is placed on the occlusal prepared tooth
• Ensure the stability of tacky wax and ask the patient to do all mandibular movements
• Paint the wax with a die lubricant to ensure a smooth complete functional core.

Pouring the functional core

• Dental stone is brushed and poured onto the wax record in the mouth to produce a functional core
• The functional index tray poured in stone should record the adjacent tooth to the prepared tooth
• This stone replica of the movements of the cusp tips is called the functional core/functional index, or the counter die.

Continuing preparation of the tooth
After recording the functional core the rest of the tooth preparation is continued.

Impression making

• An impression is made of the quadrant containing the prepared tooth, using a custom acrylic tray made previously
• A bite registration at the intercuspal position using bite registration paste is done in a bite registration frame using zinc oxide and eugenol paste.

Making of die

• Die is prepared using the Di-Lok tray technique
• After the die is retrieved, a wax pattern is fabricated against the functional core of an articulator.

Question 42. Interocclusal records.

Type of relationships in partial denture

• Centric registrations (interocclusal records)
  • Centric occlusion records
  • Centric relation records.
• Eccentric registrations (interocclusal records)
  • Lateral excursive records (lateral “check-bites”)
  • Protrusive records (protrusive “check-bite”).

Centric Occlusion

• It is the simultaneous bilateral contact of several pairs of opposing posterior teeth
• At least two posterior and one anterior point contact should be present.

Direct intercuspation is indicated when:

• The indicated fixed restorations do not interfere with the stable periodization
• When the vertical dimension is normal and when the patient’s centric relation is coincident with the centric occlusion.

Methods

• Hand articulation of the patient casts
• When the distal tooth is prepared interocclusal relationship is made in maximum inter-cuspation with an interocclusal record or occlusal stop.

Interocclusal stop technique:

• An interocclusal record (polyether silicone or acrylic resin) is placed over the prepared tooth.
• The patient is asked to close to the normal interocclusal position.
• After the recording material is set, the record is trimmed and articulation is done.

Centric Relation

This is a contact relationship in which the mandible is located 1–1.5 mm distal to the inter-cuspal position.

Techniques for guiding mandible

Active technique
Interocclusal registration is directed by the patient’s neuromuscular effort.

Passive technique
In which the dentist guides the mandible into a centric relation.

Techniques for record-making

Bite wafer technique

• A thermoplastic bite wafer made from baseplate wax (such as a warm wax wafer) is used to support the registration medium.
• After evaluation of the record the indentations in the wax are brushed with zinc oxide eugenol/elastomer and the recording is repeated.
• The resulting interocclusal record represents a stable laminate consisting of the thermoplastic wafer and a wash of paste or elastomer.

Anterior stop technique

• This technique utilizes an anterior deprogramming appliance (anterior acrylic jig).
• This jig deprograms the influence of the posterior dentition by the contact of the incisal edge of the mandibular central incisor on a platform.
• This contract provides posterior space for the interocclusal material and the carrier.

Fabrication of the anterior (included)

• A foil is burnished over the lingual surfaces and incisal edge of the maxillary central on the cast. Acrylic material is manipulated (in the doughy stage); it is placed on the foil and molded into the sloping ramp.
• After the acrylic sets, it is trimmed.
• It is then seated in the patient’s mouth.
• The patient is asked to close in interdigitation and the space obtained between the posterior teeth should be within 1 mm of interocclusal distance.

Wax wafer bite

• A warm wax wafer is pressed to the occlusal of the maxillary teeth with the jig in place. The wax wafer is refined and shaped to the patient’s arch form.
• After reheating the wax wafer outside the patient’s mouth, the patient’s mandible is guided and the patient is asked to close on his or her back teeth until the lower anterior teeth touch the anterior jig.

Wash registration record

• After confirming the record the record is trimmed and a thin layer of ZOE bite registration paste is applied to the lower cusp indentations of the wafer.
• The centric relation record is repeated with the wash registration material.

Eccentric registrations – Lateral relation

Canine-guided occlusion
In lateral movement canine causes separation of all the other teeth.

Group function
In lateral movement, contact is maintained between a group of teeth.

Lateral Check-bites

Adjustment of articulator:

• Before the lateral interocclusal record is made, the patient’s casts are mounted on an arcon articulator with facebook and centric relation record.
• Superior walls of the fossae are arbitrarily set to an angle of 30 degrees and the medial walls to 15 degrees.
• The mandibular member of the articulator is manipulated so that the left mandibular canine is edge-to-edge with the left maxillary canine.
• The incisal pin is opened to create a 2 mm space between the incisal edges of the canines and the corresponding point is marked on the incisal table.

Recording of wax record on articulator:

• A warm wax wafer is placed on the lower cast, and the articulator is adjusted till it coincides with the pencil mark on the incisal guide table.
• Close the articulator until the incisal guide pin touches the surface of the incisal table.

Evaluating the record in the patient’s mouth:

After chilling the wax wafer record, the record is checked in the patient’s mouth with the canine edge to edge in the left lateral excursion until the lower teeth locate the indentations in the wax made by the mandibular cast.

Wash record:

If the record is accurate it is followed by a wax registration record (ZNOE).

Setting the articulator readings to new record

• After the paste sets, trim the lateral check-bite, seat it on the mandibular cast, and place the maxillary cast over it.
• Loosen the horizontal and medial condylar housing walls of the right condylar housing and allow the horizontal and medial walls to just contact the condyle.
• Tighten the walls and remove the record.
• The same procedure is repeated with the right lateral excursion to set the left condylar housings.

Protrusive relation

Incisal edges of the lower anterior teeth move against the palatal aspect of the upper incisors to an edge-to-edge incisal contact known as incisal guidance.

Adjusting the articulator

• The horizontal condylar inclinations are set at 30 degrees.
• The upper cast is brought with the incisors in an end-to-end relation.
• The incisal guide pin is raised and marked on the incisal table till a 2 mm inter-incisal space is made.

Wax record
Warm wax is placed on the cast till coinciding with the incisal table marking in the incisal edge-to-edge position.

Reevaluating records inpatient
The wax record is evaluated in the patient’s mouth with the incisors in an edge-to-edge position until the lower teeth find the indentations.

Wash record
Reline the pre-registered protrusive record with registration paste and refine the record in the mouth.

Articulator setting

• The trimmed protrusive check bite is placed on the mandibular cast and the maxillary cast is placed over it.
• The horizontal condylar inclination screw is loosened and manipulated till the maxillary casts seat into the refined indentations of the check-bite.
• Once seating is complete tighten the condylar inclination locking nuts.

Question 43. Lug seat

• In non-rigid connectors a keyway and key is present
• The key of the non-rigid connector is referred to as “LUG”
• Lug is a tapering piece of metal usually cast, which fits the key way exactly and is made part of the pontic
• The key way is referred to as dovetail/lug seat and is a depression cut in one of the retainers (anterior retainer)
• It is widest at its occlusal opening and gradually tapers gingivally ending in a flat gingival seat.

Lug seat preparation is used in:

• Stress breakers
• Non-precision stress breakers.

Shapes of lug seat

• Dovetail
• Semicircular
• Triangular
• Round
• T-shaped
• Oval.

Design of lug seat

• Usually prepared on anterior retainer with walls that diverge from the gingival to occlusal
• Buccal, lingual, and gingival walls are dove-tailed
• Twice as deep as it is wide buccolingually and at least 1 mm wide at the gingival wall.

Lug seat Modification

• In molar pontic replacement, an occlusal extension is made mesially and terminates in the center of the tooth.
• Proximal sub-occlusal rest: A slightly tapered opening is made in the proximal surface of the anterior retainer below the marginal ridge at the region of the contact point.

Lug seat Advantage
After the restoration is cemented amount of movement is prevented and also prevents occlusal displacement.

Lug seat Procedure of preparation

The lug seat can be prepared on wax pattern—if consisting of inlay, or on tooth.

Lug seat on wax pattern

• A groove extending occlusogingivally is prepared on the axial surface with No 700 crosscut fissure bur till the depth of diameter of bur
• With an inverted cone bur, the groove is extended in a buccal and lingual direction
• An inverted cone bur is used to create a gingival undercut in the gingival wall
• After completing the preparation, it is invested, cast, and tried in the mouth.

Lug seat on the tooth
A cross-cut fissuring bur can be used to create a groove occlusal and proximally with undercuts in the proximal area. The extended groove on the occlusal surface is rounded and is wider toward the keyway than its mesial side.

Lug seat Other types

Subocclusal spherical keyway (Starr):
In which the peripheral outline is an undercut created with a round bur.

Sullivan type

Combination of dovetail and subocclusal.

Question 44. Soft tissue mask for implant models.

Soft tissue mask for implant models Composition

• Traditionally soft denture lining material has been used for soft tissue casts but the vaporization of the alcohols used in plasticizers deteriorated the material properties rapidly
• Currently, materials specifically marketed for soft tissue casts are now available that are chemically similar to elastomeric impression materials.

Soft tissue mask for implant models Significance

• Soft tissue masks allow increased biological and esthetic harmony of the prosthesis
• The use of soft tissue masks on the casts significantly aids in maintaining the tissue contour and form throughout the laboratory phase of restoration fabrication
• Aids in the selection of abutments that can be clearly visualized because the position of the implant can be observed in relation to soft tissue height and width
• It also enables access to the implant analog without damaging the gypsum cast during removal.

Requirement of soft mask material

• It should have adequate dimensional stability for the period of time necessary to fabricate and finish the prosthesis
• It should not adhere to the matrix impression material
• It should have adequate flow, tensile tear strength, and resilience to allow ease of fabrication and durability during use
• It should be compatible with the matrix impression material.

Question 45. Recall and maintenance.

Recall and maintenance are done to monitor the patient’s dental health, identify any incipient disease, and initiate corrective treatment before irreversible damage occurs.

Appointment scheme

• A week after the cementation of the prosthesis.
• Periodic recall every six months.
• Emergency recall.
• Retreatment.

Evaluations to be made

Review history and general examination

• Oral hygiene and diet.
• Recheck for any residual cement in the gingival sulcus.
• Secondary dental caries: It is better to redo the entire restoration again.
• Root caries.
• Periodontal disease.
• Occlusal dysfunction.
• Pulp and periapical health.

Root caries

Causative factors

• Plaque containing Actinomyces viscosus proliferating on the tongue.
• Xerostomia.
• Radiation treatment.

Treatment
Tongue cleaning can reduce root caries.

Periodontal disease

Causes

• Subgingival placement.
• Overcontouring of restoration.

Evaluate for

• Sulcular hemorrhage.
• Furcation involvement.
• Overcontoured restoration.
• Poor overall oral hygiene.

Care of fixed partial dentures

• Special plaque control measures
• Use of floss around pontics and connectors.

Method of flossing
Floss is looped through embrasure spaces on each side and pulled tightly against the convex pontic tissue surface and floss is gently slided out to remove dental plaque.

Occlusal dysfunction

Evaluate for

• Parafunctional habits.
• Abnormal occlusal wear patterns.
• Abnormal tooth mobility.
• Muscle and joint pain.
• Canine wear can cause excursive interfering contacts on the posterior teeth.

Pulp and periapical health

• Pain in the abutment tooth could have led to loss of vitality of an abutment tooth
• Radiographs need to be taken to evaluate for the presence of periapical pathology.

Emergency Appointment

• Pain.
• Loose abutment retainer.
• Fractured connector.
• Fractured porcelain veneer.

Pain
The location, character, severity, timing, and onset are to be noted.

Causes

• Periapical pathology.
• Root fracture in endodontically treated tooth.

Loose abutment retainer

Symptoms, such as bad taste or smell.

Causes

• Inadequate tooth preparation.
• Poor cementation technique.
• Caries.

Fractured connector
Symptoms, such as pain due to extra force transmitted to the abutment teeth.

Fractured porcelain veneer

Causes

• Faults in framework design.
• Improper laboratory procedures.
• Excessive occlusal function or trauma.

Retreatment

In case the problems are related to inadequate tooth preparation faulty design or lab work, remaking the prosthesis is ideal.

Good plaque removal, patient motivation, and a well-designed and fabricated restoration can give good service for a long time.