Aetiology of Malocclusion - Local Factors

Question 1

4 main types of supernumerary teeth in the permanent dentition?

Answer 1

1. Supplemental teeth: extra teeth of normal form occurring at the end of a tooth series (most common 2)
2. Conical teeth: typically occurs in premaxilla, near the midline and often called mesiodens
3. Tuberculate: also occurs in premaxilla, it is a later development than the conical tooth with roots developing later than permanent upper 1.
   Often appears palatal of upper 1s and classically prevents eruption of a permanent tooth
   [4. Odontome: Rare. Both complex and compound forms]

Question 2

What are the effects of supernumerary teeth and what is the management?

Answer 2

1. Failure of eruption
   Management: remove supernumerary and ensure sufficient space to accommodate the unerupted tooth (might have to bond gold chain to unerupted tooth so traction can be applied)
2. Displacement or rotation of erupted tooth (including causing diastema)
   Management: removal of supernumerary and fixed appliances
3. Crowding caused by supplemental tooth
   Management: removal of most poorly formed or displaced tooth
4. No effect (conical chance finding)
   Management: can be left under radiographic examination if inaccessible or removed if signs of enlargement of follicle (cystic formation) and if Ortho tooth movement required

Question 3

What is the management of tooth gemination?

Answer 3

• Usually upper or lower incisors affected
• Tx depends on severity of crowding:
  1. If normal number of incisors and gemination appears to be the merging of two of these teeth no tx may be required
  2. An increase in number of incisor crowns will cause crowding and aesthetic problem. May need to extract and replace prosthetically

Question 4

What are the most common missing teeth?

Answer 4

8s, 
lower 5s (5%), 
upper 2s (2%), 
upper 5s (2%), 
lower 1s (0.5%)

Question 5

Effect of missing U2 and its management?

Answer 5

• Absence on the eruptive path of U3 can cause palatal displacement
• In crowded arch, the canine may erupt into contact with 1 and if not too pointed can be reduced at the tip to achieve good aesthetic result
• In average to large arch, minimal spacing can be accepted, canine can be retracted to make space for bridge
• If not enough space for bridge pontic (distal movement of buccal segment or closure of anterior space by forward movement of buccal segment)

Question 6

Effect of missing L1 and its management?

Answer 6

• Absence can have secondary effect on upper labial segment because of the difficulty of arranging 6 upper teeth around 5 or 4 lower teeth and crowding will appear in the upper labial segment UNLESS increased OJ or upper lateral incisors diminutive
• Uncrowded cases RBB
• Crowded cases space may close spontaneously but fixed appliance may be needed

Question 7

Management of missing U5 and L5?

Answer 7

• L5s should not be assumed missing until 9 yrs
• If arch of ample size and Es are not resorbing, may remain in place until 30-40 yrs UNLESS submerging and are in infra occlusion in which case xla and restorative replacement
• If arch crowded, E xla

Question 8

Name 2 Teeth of abnormal forms?

Answer 8

1. Dens-in-dente (dens invaginatus) - lateral incisors are small and conically produced by coronal invagination. Deep cingulum leads to cavity with deficient enamel where bacteria can access the pulp
2. Dilaceraion - abnormal angulation between the crown and root. Site depends on the timing of the disturbance during tooth development

Question 9

How does ectopic 3 occur and how do you assess an ectopic 3?

Answer 9

• Long path of eruption and tooth commonly deflects palatally and the C is retained
• There is an association between absent/small 2 and ectopic 3s
• Canine is ectopic if crown isn’t detected and can be palpated high in buccal sulcus
• Position confirmed by radiographs and vertical parallax technique (upper anterior occlusal and periapical or DPT and upper anterior occlusal) [SLOB]

Question 10

Treatment options for ectopic canines?

Answer 10

• Remove deciduous tooth and provide space (distalise the buccal segments or xla 4 or space maintain: if not too displaced the 3 will erupt
• In most cases, surgical exposure with or without attachment of gold chain and fixed appliance to align tooth
• Surgical transplantation: splinted for 2-3 weeks to allow normal pdl attachment, if closed apex then RCT needed
• Surgical removal if very ectopic
• Leave but will need radiographic review to see if crypt enlarges with cystic formation

Question 11

Balancing extraction vs compensating extraction?

Answer 11

Balancing extraction is the removal of the contralateral tooth to maintain symmetry
Compensating extraction is the removal of the equivalent opposing tooth to maintain buccal occlusion

Question 12

What is the major effect of early loss of primary tooth

Answer 12

• The localisation of pre-existing crowding although this will not occur in uncrowded cases
• Where there is crowding, the adjacent teeth will drift into the extraction site
• Greater tendency for mesial drift in the maxilla, the younger the pt, and the more crowded dentitions

Question 13

Effect of early loss of A?

Answer 13

Little impact as shed early

if lost by trauma, dilacerations of 1 may occur

Question 14

Effect of early loss of C?

Answer 14

In crowded mouth centreline shift to affected side.

Should be balanced even in mild crowding cases

Question 15

Effect of early loss of D?

Answer 15

E and 6 drift mesially without rotation or tilting and anterior teeth spread around arch
In upper arch 4 erupts first leaving no space for 3 so is displaced
In lower arch 3 erupts first leaving no space for 4

Question 16

Effect of early loss of E?

Answer 16

6 will erupt in more anterior position and total space loss max occur if xla E before 6 erupts
if xla E after 6 erupts the upper 6 tips mesially with some rotation - the upper 5 erupts into the palate and lower 5 erupts lingually

Question 17

Advantages and disadvantages of space maintainers?

Answer 17

• Advantageous where there is acceptable alignment of teeth and where early loss may produce malocclusion (e.g. loss of E causing impaction of 5)
• Disadvantages: need prolonged wear and no guarantee Ortho avoided later on in life, may hinder plaque control. removable SM fail if not worn and permanent need regular inspection

Question 18

How is a lower fraenum attachment indicated?

Answer 18

• When the fraenum is placed under tension there is blanching of the invasive papilla
• Radiographically a notch can be seen at the crest of the interdental bone between upper 1s

Question 19

What is the management of a lower fraenum attachment?

Answer 19

Wait until permanent canines erupt and if the diastema persists then fixed appliance treatment is needed to close the space and fraenectomy

Question 20

Management of median diastema?

Answer 20

• Upper anterior occlusal radiograph to exclude presence of supernumeraries or pathology
• Fixed appliance to close diastema
• Diastema has high tendency to relapse so permanent retention required