PROSTHODONTICS VIVA QUESTIONS

COMMON VIVA QUESTIONS

Q51. What are the permanent record base fabricating materials?

Ans. The basic materials that are used for permanent record bases are:

1. Processed heat cure acrylic resin
2. Gold alloys
3. Chromium-cobalt alloy

Q52. What are the temporary record base materials? 

Ans. The basic materials that are frequently used are:

1. Shellac base plate wax
2. Cold cure acylic resin
3. Light curing acylic resin

Q53. What is an occlusal rim?

Ans. The occlusal surfaces fabricated on a record base for the purpose of making maxillomandibular relationship records and/or arranging teeth.

Q54. What is an articulator?

Ans. A mechanical instrument that represents the temporomandibular joints and jaws, to which maxillary and mandibular casts may be attached to simulate same or all mandibular movements.

Q55. What are the functions of an articulator?

Ans. The primary functions of an articulator are:

1. The articulator should be capable of producing some degree of movements
2. Mounting of dental casts for diagnosis, treatment planning and patient presentation
3. Fabrication of occlusal surfaces for dental restorations
4. Arrangement of artificial teeth for complete and removable partial dentures

Q55. What are the requirements of articulator?

Ans. Minimal requirements:

1. The articulator must accurately maintain the correct horizontal and vertical relationship of the patient’s cast.
2. The patient’s cast must be easily removable and attachable to the articulator without losing their correct horizontal and vertical relationship.
3. The articulator should have an incisal guide pin with a positive stop that is adjustable and calibrated.
4. The articulator should be able to open and close in a hinge-like fashion.
5. The articulator should accept a face-bow transfer utilizing an anterior reference point.
6. The articulator should be accurate, rigid, made of a noncorrosive material. The moving parts should resist wear.
7. There should be adequate distance between the upper and lower members. It should be stable and not bulky.

Additional requirements:

1. The condylar guides should allow right lateral, left lateral and protrusive movements.
2. The condylar guides should be adjustable horizontally.
3. The articulator should have provisions for adjustment of Bennett movement.
4. The incisal guide table should be a mechanical table that can be adjusted in the sagittal and frontal planes.

Q56. What are the theories of articulator?

Ans. The three theories of articulation are:

1. Bonwill’s theory
2. Monson’s spherical theory
3. Conical theory

Q57. What is Bonwill’s theory?

Ans. Described by Bonwill in 1858, a 4 inch equilateral triangle bounded by lines connecting the contact points of the mandibular central incisor’s incisal edge (or the mid-line of the mandibular residual ridge) to each condyle (usually its midpoint) and from one condyle to the other.

Q58. What is Monson’s spherical theory?

Ans. An arrangement of teeth that places their occlusal surfaces on surface of an imaginary sphere (usually 8 inches in diameter) with its centre above the level of the teeth.

Q59. What is Angle classification of malocclusion?

Ans. It is a classification system of occlusion based on interdigitation of first molar teeth originally described by angle as four major groups depending on the anteroposterior jaw relationship.

1. Class I molar relation
2. Class II molar relation
3. Class III molar relation

Q60. What is horizontal overlap or overjet?

Ans. The horizontal relationship of the incisal egdes of the maxillar incisors to th mandibular incisors when the teeth are in maximum intercuspation.

Q61. What is vertical overlap or overbite?

Ans. The vertical relationship of the incisal edges of the maxillary incisors to the mandibular incisors when the teeth are in maximum intercuspation.

Q62. What is the curve of occlusion?

Ans. The average curve established by the incisal edges and occlusal surfaces of the anterior and posterior teeth in ither arch.

Q63. What is curve of Monson?

Ans. It is a proposed ideal 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 centre in the region of glabella.

Q64. What is curve of Pleasure?

Ans. It is a helicoids of occlusion that when viewed in frontal plane, conforms to a curve that is convex from superior view except for the last molars which reverse that pattern.

Q65. What is Anti-Monson curve or reverse curve?

Ans. In excessive wear of the teeth, the obliteration of the cusps and formation of either flat or cupped-cut occlusal surfaces, associated with reversal of the occlusal plane of the premolar, first and second molar teeth (the third molars being generally unaffected), whereby the occlusal surfaces of the mandibular teeth slope facially instead of lingually and those of the maxillary teeth incline lingually.

Q66. What is Curve of Spee?

Ans. Curve of Spee is an anteroposterior curve.The anatomic curve established by the occlusal alignment of the teeth, as projected onto the median plane ,beginning with the cusp tip of the mandibular canine and following the buccal cusp tips of the premolar and molar teeth , continuing through the anterior border of the mandibular ramus, ending with the anterior most portion of the mandibular condyle.It was first described by Ferdinand Graf Spee, German anatomist, in 1890.

Q67. What is curve of Wilson?

Ans. Eponym for the mediolateral curve. In the theory that occlision should be spherical, curvature of the cusps as projected on the frontal plane expressed in both arches, the curve in the lower arch being concave and the one in the upper arch being convex. The curvature in the lower arch is affected by an equal lingual inclination of the right and left molars so that the tip points of the corresponding cross-aligned cusps can be placed into the circumferences of a circle.The transverse cuspal curvature of the upper teeth is affected by the equal buccal inclination of their long axes.

Q68. What is compensating curve?

Ans. The anteroposterior curving (in the median plane) and the mediolateral curving (in the frontal plane) within the alignment of the occluding surfaces and incisal edges of artificial teeth that is used to develop balanced occlusion. The arc introduced in the construction of complete removable dental prosthesis to compensate for the opening influences produced by th condylar and incisal guidance’s during laterl and protrusive mandibular excursive movements which is also called Compensating Curve.

Q69. What is Christensen’s phenomenon?

Ans. It is a space that occurs between the opposing occlusal surfaces of the upper and lower teeth during mandibular protrusion.This phenomenon occurs only in natural dentition.

Q70. Define centric occlusion?

Ans. The occlusion of opposing teeth when the mandible is in centric relation.This may or may not coincide with the maximal intercuspal position.

Q71. Define centric relation?

Ans. This maxillomandibular relationshipin which the condyles articulate with the thinnest avascular portion of their respective discs with the complex in the anterosuperior position against the shapes of the articular eminences.This position is independent of tooth contact.This position is clinically discernible when the mandible is directed superiorly and anteriorly.It is restricted to a purely rotary movement about the transverse horizontal axis.

Q72. What is a transitional denture?

Ans. A removable dental prosthesis serving as an interim prosthesis to which artificial teeth will be added as natural teeth are lost and that will be replaced after postextraction tissue changes have occurred.A transitional denture may become an interim complete dental prosthesis when all of the natural teeth have been removed from the dental arch-called also complete denture.

Q73. What is a treatment denture?

Ans. A dental prosthesis used for the purpose of treating or conditioning the tissues.

Q74. Define retention?

Ans. The quality inherent in the dental prosthesis acting to resist the forces of dislodgement along the path of placement.

Q75. Define stability?

Ans. Stability is the ability of the prosthesis to be firm, steady and constant and resists the forces of dislodgement along the horizontal direction.