Morphology Qns- Need answers

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cutesmileDDS

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Can someone give me the correct answer and a possible explanation for these questions. I very much appreciate your help.:)


The two types of dentin are sclerotic and non-sclerotic. Clinically they can be differentiated because dentin appears heavily stained while non-sclerotic dentin appears milky white or opaque
1. True
2. False


which of the following statements is true concerning the fabrication of a wax pattern?
1. Acute duplication of the original tooths occlusal morphology is essential
2. Occlusal morphology should be in harmony with the patients function
3. Occlusal contacts should be in maximum intercuspal position
4. The pattern should be invested immediately after margination
5. The external surface should be free of roughness or irregularities

A) 1,2,4,5 B)2,3,4,5 C) 2,3,4 D)1,2,3,5 E) 2,3,5



Which statement concerning ovate pontic forms is true?
1. The ovate pontic form is bulky and therefore its use should be limited to posterior edentulous areas
2. The ovate pontic form can only be cleaned with the use of a proxy brush between surface of the residual ridge and gingival side of the pontic.
3. The ovate pontic form cannot be cleaned at all between the surface of the residual ridge and the gingival side of the pontic
4. The ovate pontic form is esthetic but the residual ridge surface and pontic contact cannot be effectively cleaned with the aid of dental floss
5. None of the above



The disadvantage of the saddle type full ridge lap pontic is :
1. Esthetics
2. Food entrapment
3. Uncomfortable for patient
4. Requires surgical preparation
5. Not amenable for oral hygiene


To create the illusion of a narrow tooth or restoration:
1. Open the facial embrasures
2. Moving the transitional angles closer together
3. Move the transitional angles farther apart
4. 1&2
5. 1&3

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Can someone give me the correct answer and a possible explanation for these questions. I very much appreciate your help.:)


The two types of dentin are sclerotic and non-sclerotic. Clinically they can be differentiated because dentin appears heavily stained while non-sclerotic dentin appears milky white or opaque
1. True
2. False


which of the following statements is true concerning the fabrication of a wax pattern?
1. Acute duplication of the original tooths occlusal morphology is essential
2. Occlusal morphology should be in harmony with the patients function
3. Occlusal contacts should be in maximum intercuspal position
4. The pattern should be invested immediately after margination
5. The external surface should be free of roughness or irregularities

A) 1,2,4,5 B)2,3,4,5 C) 2,3,4 D)1,2,3,5 E) 2,3,5



Which statement concerning ovate pontic forms is true?
1. The ovate pontic form is bulky and therefore its use should be limited to posterior edentulous areas
2. The ovate pontic form can only be cleaned with the use of a proxy brush between surface of the residual ridge and gingival side of the pontic.
3. The ovate pontic form cannot be cleaned at all between the surface of the residual ridge and the gingival side of the pontic
4. The ovate pontic form is esthetic but the residual ridge surface and pontic contact cannot be effectively cleaned with the aid of dental floss
5. None of the above



The disadvantage of the saddle type full ridge lap pontic is :
1. Esthetics
2. Food entrapment
3. Uncomfortable for patient
4. Requires surgical preparation
5. Not amenable for oral hygiene


To create the illusion of a narrow tooth or restoration:
1. Open the facial embrasures
2. Moving the transitional angles closer together
3. Move the transitional angles farther apart
4. 1&2
5. 1&3
1.) True
However, this is a poorly worded questions. I am assuming that by non-slerotic they are referring to primary dentin which is the white/yellow-ish in color dentin you see after total caries removal or in a caries free tooth and sclerotic dentin refers to secondary/tertiary dentin form due to pulpal insult (i.e. caries) which is laid quickly can include cellular inclusions causing a darker appearence.

2.) B
Statement 1 is grossly wrong. If you make an exact copy of what you are replacing, you may be disposing the patient to the same etiology as what caused the problem in the first place. For example, cusp fracture due to non-working interference, edge to edge relationships, etc.
Statement 2 is correct for the same reasons statement 1 is wrong.
Statement 3 is mostly correct (because we must accept it due to the answer choices if 1 is wrong) but could be challanged if you are talking about a full mouth rehab case where CR would be preferrable or even a long centric (occusal morphology allows for slide between MI and CR). Since the question says "a" wax pattern, I assume single crown where MI is preferred.
Statement 4 is correct, margination is where you re-wax you margins again after your pattern is done. You should invest immediately after margination to minimize possible distortions due to cooling/wax memory.
Statement 5 is true, better polish at wax pattern stage = less work and less waste polishing after casting.

3.) 5
Ovate pontic is most esthetic and is cleansible by floss due to convexity of pontic gingval surface which allows complete adaptation of floss to FPD pontic surface.

4.) 5
Due to pontinc gingival suface concavity over alveolar ridge, it cannot be effectively cleaned with floss (or anything for that matter). Full ridge lap pontic is exact opposite of ovate pontic above.

5.) 4
An old prosth trick, deepen (open) your facial embrasures and narrow your line angles (same as transitional angles in this question) for a narrower tooth. By doing this you reduce and narrow the labial surface area making the tooth more rectangular and taller. Closing the facial embrasures and widening the line angles will give you the classic "picket fence" look with a larger labial surface area and will lend to a more flat and square looking tooth.
 
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