Packing acrylic resin into the denture flasks

# After packing acrylic resin into the denture flasks, one should wait to cure the resin to:

A. Assure full flow of acrylic into the denture mold

B. Allow the monomer to reach all acrylic polymer

C. Allow for pressure to be equalized between the acrylic and flask

D. Make sure temperature equilibrium exists between the flask and acrylic 

The correct answer is D. Make sure temperature equilibrium exists between the flask and acrylic

Allowing the dental flask packed with acrylic to remain under the bench press until equilibrium in temperature is achieved will give enough time for the acrylic to achieve better monomer-polymer interaction and create stronger chemical bond.

The curing of resin should be uniformly completed to lessen any chances of distortion before and during the time the flask is immersed in a water bath.

 

Packing the acrylic during the rubbery stage

# When fabricating dentures, what would be the most likely outcome if the lab compressed/packed the acrylic during the rubbery stage?

A. Higher porosity than normal

B. A lot of extra resin being attached to the denture that will take a long time to trim

C. Incomplete picking up of anatomical details

D. The denture would have an increased VDO 

The correct answer is C. Incomplete picking up of anatomical details

Packing and compressing acrylic during denture fabrication should be done in its doughy stage.

The doughy stage is the ideal for packing acrylic resin because it is the moment when acrylic is most packable and workable.

The rubbery stage of acrylic denotes the start of the setting when heat is released from the setting acrylic.

Rubbery acrylic also has a tendency to revert back to its original position regardless of the forces applied to it during packing, resulting in incomplete packing.

VDO (Vertical Dimension of Occlusion) is synonymous with OVD (Occlusal Vertical Dimension) and is the relationship of the maxilla and mandible when the teeth are in maximum intercuspation. 

 

Excess height of the posterior palatal seal

 # Excess height of the posterior palatal seal of a complete maxillary denture will usually result in which of the following?

A. Gagging

B. Increased retention

C. A tingling or tickling sensation

D. Unseating of the denture

The correct answer is D. Unseating of the denture.

Over contouring or excessive beading of the posterior palatal seal causes too much pressure to be exerted on the palatal tissues resulting in the unseating of upper dentures.

The posterior palatal seal is typically placed approximately on the vibrating line between the hard and soft palate and provides a physiologically acceptable tissue pressure within the compressible portion of the soft palate to attain retention and peripheral seal.

Over extending the coverage of seal will cause gaggling and painful swallowing for the part of the patient. 

Flabby maxillary anterior ridge

# Which of the following is associated with a flabby maxillary anterior ridge under a complete denture?

A. Retained mandibular anterior teeth

B. A "V" shaped ridge

C. A "U" shaped ridge

D. A patient with Class Il occlusion

E. Osteoporosis 

The correct answer is A. Retained mandibular anterior teeth.

Combination syndrome is a condition that usually occurs when retained mandibular

anterior teeth opposes a maxillary complete denture.

In combination syndrome, the anterior aspect of upper maxillary ridge becomes highly resorbed and flabby due to the biting force against its natural tooth antagonist.

Since the occlusal force of a natural tooth is stronger than the force of a denture supported by an alveolar ridge, the area under pressure will exhibit higher resorption pattern than the rest of the denture.

Pterygomandibular raphe is a tendon between

# Pterygomandibular raphe is a tendon between which of the following muscles?

A. Masseter and medial pterygoid

B. Anterior belly of the digastric and Buccinator

C. Buccinator and Superior constrictor

D. Buccinator and Masseter

The correct answer is C. Buccinator and Superior constrictor.

Pterygomandibular raphe acts as a tendon between the buccinator and superior Constrictor muscle. It is a landmark used often for the identification of the pterygomandibular space for the administration of an inferior alveolar nerve block.

The injecting needle pierces the buccinator muscle to inject the local anesthetic solution in the pterygomandibular space.

 

Number of lobes in a tooth

 # The minimum number of lobes from which any tooth may develop is:

A. Two

B. Three

C. Four

D. Five

The correct answer is: C. Four.

Tooth development begins with increased cell activity in growth centers in the tooth germ. A growth center (lobe) is an area of the tooth germ where the cells are particularly active. These lobes are primary centers of calcification and are primary sections of formation in the development of the crown of a tooth. They are represented by a cusp on posterior teeth and mamelons and cingula on anterior teeth. They are always separated by developmental grooves, which are very prominent in the posterior teeth and form specific patterns. With anterior teeth, their presence is much less noticeable and these lobes are separated by what are known as developmental depressions.

Summary of number of lobes:

•All anterior teeth: three labial and one lingual (cingulum)

• Premolars: three buccal and one lingual.

Exception: The mandibular second premolar has three buccal and two lingual lobes.

• First molars (maxillary and mandibular): five lobes, represented by five cusps - one lobe for each cusp

•Second molars (maxillary and mandibular): four lobes, one for each cusp

• Third molars: at least four lobes. one for each cusp ***variations arc seen

Lethal dose of Fluoride

# The lethal dose of fluoride for a typical three-year-old child is approximately :

A. 100 mg

B. 200 mg

C. 350 mg

D. 500 mg

 

The correct answer is D. 500 mg.

The studies and surveys link fluorosis to three factors:

• Fluorosis is more common in geographic areas where the endemic levels of fluoride in the drinking water is higher than three parts per million

• Fluorosis is associated with fluoride supplementation at inappropriately high levels

• The use of fluoridated toothpaste has been implicated in fluorosis

In acute fluoride toxicity, the goal is to minimize the amount of fluoride absorbed. Therefore, syrup of ipecac is administered to induce vomiting. Calcium-binding products, such as milk or milk of magnesia, decrease the acidity of the stomach, forming insoluble complexes with the fluoride and thereby decrease its absorption. Note: Emergency Medical Service should be activated.

In acute fluoride toxicity, symptoms may appear within 30 minutes of ingestion and persist for up to 24 hours. Patients may experience some nausea, vomiting, diarrhea, and abdominal cramping. This may be due to the fact that 90-95% of ingested fluoride is absorbed through the stomach and small intestines. Fluorides are primarily eliminated from the body by way of the kidneys. However, the fluoride that does remain in the body is found mostly in skeletal tissue. In acute fluoride poisoning (which is rare), the most common causes of death are cardiac failure and respiratory paralysis. Fluoride toxicity shows up in the bones as osteosclerosis.

Important: The lethal dose of fluoride for a typical 3-year-old child is approximately 500 mg and would be proportionately less for a younger child and smaller child. To avoid the possibility of ingestion of large amounts of fluoride it is recommended that no more than 120 mg of supplemental fluoride be prescribed at any one time.

Note: If a six-year old child were receiving fluoridated water in the amount of 3 ppm, the result would most likely be fluorosis but not systemic toxicity. On the other hand, if a child in the same age range (6-7) were receiving 8 ppm of fluoridated water, there would be a good chance of systemic toxicity and moderate to severe fluorosis occurring.