Laboratory Procedures Prior To Try In Short Question and Answers

Laboratory Procedures Prior To Try In Short Answers

Question 1. Pre-extraction guides in selection of teeth.
Answer:

• The diagnostic cast prepared before extraction of teeth
  • It provides 3 dimensional view.
• Photographs – Showing frontal & lateral view
  • Limitation: Anterior teeth should be seen in the photograph.
• Radiographs Accurate measurements are not obtained
  • They provide only 2-dimensional view
• Close relatives- If other methods fail
• Extracted teeth- Best method
  • But all the extracted teeth are not preserved.

Question 2. Compensatory curves.
Answer:

The anteroposterior & lateral curvatures in the alignment of the occluding surfaces & incisal edges of artificial teeth which are used to develop balanced occlusion

• Steep compensatory curves for steep condylar path
• Shallow curves for loss of balancing molar contacts

• Thus balance must be present between all the five factors
• The effect of incisal & condylar guidance must counteract by the effect of other three factors
• If the balance is lost, balanced occlusion cannot be achieved

Question 3. Color selection of teeth.
Answer:

Color For Anterior Teeth:

Age:

• Young people-lighter teeth
• Old people Dark teeth
• More shiny
• Brownish tinge
• Habits smokers porcelain teeth
• Complexion teeth selected in harmony with

Question 4. Factors in denture design affecting speech.
Answer:

• Denture wearers have shallow pronunciation In dentulous patient, rugae enhance speech
  • In a denture wearer speech is affected due to absence of rugae
  • The use of metal denture improves speech
  • Injury to the external laryngeal nerve
  • Presence of tongue tie

Read And Learn More: Prosthodontics Question And Answers

• • Production of various sounds:
    1. Bilabial-b, p, m
    2. Labiodental-f, v
    3. Linguodental- th
    4. Linguoalveolar-t, d, s, z, v, 1
    5. ‘s’ sound is controlled by the anterior part of the palatal plate of the denture base

Question 5. Neutral zone.
Answer:

• It is the potential space between the lips & cheeks on one side & the tongue on other side
• An area or position where the forces between the tongue & cheek or lips are equal
• If the teeth are placed buccally, it leads to cheek biting

If the teeth are placed lingually, it leads to encroachment into tongue space

Question 6. Shortcomings of plane line articulator.
Answer:

• It is single hinge joint
• No lateral or sliding movement is possible
• No guide for mounting the cast
• Single-use
• Difficult for prosthetic work as metallic frame must be hold together with the cast
• Removal of cast is by breaking which leads to loss of integrity of cast & loss of strength of articulator

Question 7. Incisal guidance.
Answer:

The influence of the contacting surfaces of the mandibular & maxillary anterior teeth on mandibular movements

• Second factor of occlusion
• Customized
• If overjet increases, it decreases If overbite increases, it increases
• If incisal guidance is steep, steep cusps, steep occlusal plane & steep compensatory curves are required
• It must be as flat as possible

Question 8. Condylar guidance.
Answer:

• It is the first factor of occlusion to be considered
• Measured using protrusive registration
• Increased in condylar guidance increases jaw separation
• It cannot be modified

Question 9. Hinge axis
Answer:

• It is also known as the transverse axis
• Hinge axis is the axis that runs horizontally from the right side of the mandible to the left
• Rotation around it is seen during protrusive movement It varies during different phases of protrusive movements
  • During the initial mouth opening, the hinge axis passes through the head of the condyle
  • During later stages, the axis passes through the mandibular foramen

Question 10. Posterior teeth form.
Answer:

Factors Effecting Posterior Teeth Form:

• Condylar inclination
• Height of the residual ridge
• Patient’s age
• Ridge relationship
• Hanau’s quint

1. Cusp teeth:

• They have cusps and fossae-like natural teeth
  • Anatomic teeth
    1. Resemble normal newly-erupted teeth
    2. Have the best esthetics
    3. Have 30-degree cuspal angulation
  • Semi-anatomic teeth
    1. Have 20 or 10-degree cuspal angulation
    2. They are more flexible than anatomic teeth

2. Cuspless teeth:

• Have no cuspal angulation
• Very flexible to set

Question 11. Anatomic teeth.
Answer:

Teeth that have prominent pointed or rounded cusps on the masticatory surfaces & which are designed to occlude with the teeth of the opposing denture or natural dentition

Advantages of Anatomic teeth.:

• Efficient cutting
• Balanced occlusion is obtained
• Guide the mandible in centric occlusion
• Aesthetic
• More resemble to natural dentition

The disadvantage of Anatomic teeth.:

Difficulty In Teeth Arrangement

• (a) Incisoe
• (b) Canine
• (c) Premolar
• (d) Molar

Question 12. Advantages of an adjustable articulator.
Answer:

• Capable of adjustability in all directions
• Have numerous adjustable readings
• Customized for each patient
• Have receptacles in which acrylic dough is contoured to form customized condylar & incisal guidance

Question 13. Buccolingual width of posterior teeth in the complete denture.
Answer:

• The buccolingual width of posterior teeth should be decreased to provide a proper path of escapement of food
• It should be such that the forces from the tongue neutralizes the forces from cheek
• If the buccolingual width increases the rate of ridge resorption also increases
• Teeth with broader dimensions interfere with the tongue leading to instability of the denture
• Of the teeth are broader buccally, it may lead to cheek biting.

Question 14. Bilabial sounds.
Answer:

• Bilabial sounds are b, p, and m
• These are controlled by the lip support
• These become defective in the absence of lip support or with alteration in the vertical dimension at occlusion

Question 15. Hanau articulator.
Answer:

• It is an semi-adjustable articulator
• It accepts face bow transfer
• It is capable of the hinge and lateral movements

Parts:

1. Upper member:
   • It is T shaped
   • The vertical arm runs anteroposteriorly and the horizontal arm runs transversely
2. Lower member:
   • It is L shaped structure
   • The horizontal arm is a rectangular strip
   • It has a dowel for attachment of the mounting ring
   • The incisal guide table is located at the anterior end of the horizontal arm
   • The vertical arm is sloping
   • It contains roll pin
3. Condylar guidance:
   • It is attached to the upper member of the articulator
   • It represents the glenoid fossa of the TMJ
4.  Incisal guide table:
   • It is customized
5.  Incisal pin:
   • It is double sided pin’
   • One end is sharp but chisel-like with a flat edge
   • The other end tapers to a pointed tip

Question 16. Beyron’s point.
Answer:

• The first step in placing a face bow is to locate hinge axis on the skin on each side of the face
• One frequently recommended method is to position condylar rods on a line extending from the outer canthus of the eye to the tragus approximately 13 mm in front of the eternal auditory meatus
• This is called Beyron’s point
• The placement generally locates the rods within 5 mm of the true of center of the opening axis of the jaw
• The imaginary line joining two Beyron’s points is approx. hinge axis
• The posterior reference point is 10 mm in front of the external auditory meatus.
• 7 mm below Frankfort horizontal plane
• The anterior reference point is
• 7 mm from orbitale
• 25 mm from nasion
• 18 mm from inner canthus of eye
• 43 mm superior from tip of central incisors