MDS PREP
If PMBAW% is 44 in Howe"s analysis, it indicates
1) Extraction case
2) Expansion case
3) Borderline case
4) None of the above
Orthodontics
Answer: 3
The primary purpose of Howe's Analysis is to assess the width of the
dental arches and to identify any discrepancies between the maxillary
(upper) and mandibular (lower) arches. This is particularly important in
cases of malocclusion, where the alignment of the teeth and the relationship
between the jaws may be compromised.
The analysis involves measuring specific distances on the dental casts,
including:
Intercanine Width: The distance between the cusp
tips of the canines.
Interpremolar Width: The distance between the cusp
tips of the first premolars.
Intermolar Width: The distance between the cusp
tips of the first molars.
These measurements are used to calculate the Percentage of
Maxillary Buccal Arch Width (PMBAW%), which is a key indicator in
the analysis.
The results of Howe's Analysis can indicate different treatment needs:
Normal Case: A PMBAW% within a certain range
(typically around 50-60%).
Narrow Case: A PMBAW% below the normal range,
indicating a need for arch expansion.
Wide Case: A PMBAW% above the normal range, which
may suggest the need for extraction or other interventions.
Borderline Case: A PMBAW% around 44, indicating
that the arch width is at a threshold where careful consideration is
needed for treatment options.
In Angle’s class III malocclusion, mandibular anterior teeth will be
1) Proclined
2) Retroclined
3) Inclined
4) Any of the above
Orthodontics Answer: 2
SOLUTION
The reason is found in the concept of "dental compensation for skeletal discrepancy. This can occur naturally as well as being created by orthodontic camouflage treatment.
In mandibular prognathism, for instance, as the individual grows the upper incisors tend to protrude while the lower incisors incline lingually.
By the time growth is completed, the dental discrepancy usually is smaller than the jaw discrepancy.
Tooth position has compensated at least partially for the jaw discrepancy.
If the tooth has not erupted to the line of occlusion it is called
1) Supraversion
2) Torsiversion
3) Rotated
4) Infraversion
Orthodontics Answer: 4
Terms used to describe the position of teeth.
Mesioversion - A tooth in the arch located more mesial than normal
Distoversion - A tooth in the arch located more distal than normal
Labioversion - An incisor or canine outside of arch towards the lips
Buccoversion - A posterior tooth outside the arch toward the cheek
Linguoversion - A tooth inside the arch form toward the tongue
Infraversion - A tooth that has not erupted to the occlusal plane
Supraversion - A tooth the has over-erupted
Torsiversion - A tooth rotated on its axis
Transversion (Transposition) - Teeth that are in the wrong sequential order.
Which of the following is a noninvasive method of gaining the space
1) Slenderisation and extraction
2) Expansion and extraction
3) Expansion and distalization
4) All of the above
Orthodontics
Answer: 3
Expansion and distalization are considered noninvasive methods for
gaining space in orthodontic treatment.
Facial profile of a typical mouth breather is
1) Long and wide
2) Short and wide
3) Long and narrow
4) Short and narrow
Orthodontics Answer: 3
SOLUTION
Altered respiratory pattern, such as breathing through the mouth rather than the nose, could change the posture of the
head, jaw, and tongue. This in turn could alter the equilibrium of pressures on the jaws and teeth and affect both jaw growth and tooth position.
In order to breathe through the mouth, it is necessary to lower the mandible and tongue, and extend (tip back) the head.
If these postural changes were maintained, face height would increase, and posterior teeth would super-erupt;
unless there was unusual vertical growth of the ramus, the mandible would rotate down and back, opening the bite
anteriorly and increasing overjet; and increased pressure from the stretched cheeks might cause a narrower maxillary dental arch.
Orthodontic tooth movement is inhibited by which of the following drugs
1) NSAIDS, such as Brufen
2) OPIOIDS, such as CORTISONE
3) Antibiotics such as tetracycline
4) Vasoconstrictors such as adrenaline
Orthodontics Answer: 1
SOLUTION
NSAIDS, i.e. Brufen, etc. inhibit tooth movement as they interfere with production of prostaglandins.
• Nimesulide does not interfere with PG production and so can be safely given during tooth movements.
In mixed dentition, which of the following may be considered as a self correcting problem with age?
1) Unilateral loss of primary canine
2) Lack of interdental spaces
3) A distal step
4) Open bite
Orthodontics Answer: 2
SOLUTION
The possibility that a distal step would become class II is very real, and this not self correcting problem. When the central incisors erupt, these teeth use up essentially all of the excess space in the normal primary dentition. With the eruption of the lateral incisors, space becomes tight in both arches.
Normal child will go through a transitory stage of mandibular incisor crowding at age 8 to 9 even if there will eventually be enough room to accommodate all the permanent teeth in good alignment. In other words, a period when the mandibular incisors are slightly crowded is a normal developmental stage.
Continued development of the arches improves the spacing situation, and by the time the canine teeth erupt, space is once again adequate.
The first ossification center of the mandible in six weeks old human embryo is found in which of the following locations
1) Future coronoid process
2) Future condylar process
3) Future mental foramen
4) Future mandibular foramen
Orthodontics Answer: 3
SOLUTION
The mandible is ossified in the fibrous membrane covering the outer surfaces of Meckel’s cartilages.
These cartilages form the cartilaginous bar of the mandibular arch, and are two in number, a right and a left.
Ossification takes place in the membrane covering the outer surface of the ventral end of Meckel’s cartilage , and each half of the bone is formed from a single center which appears, near the mental foramen, about the sixth week of fetal life.
By the tenth week the portion of Meckel’s cartilage which lies below and behind the incisor teeth is surrounded and invaded by the membrane bone