Impacted 3rd molars

Question 1

etiology of impacted 3rd molars

Answer 1

Systemic Factors
* Primary retention, a hereditary syndrome of cleidocranial dysplasia, can lead to permanent tooth impaction.
* Endocrine deficiencies, febrile diseases, Down syndrome, and irradiation can also influence impaction.

Local factors
1. Prolonged deciduous tooth retention
2. Malposed tooth germs
3. Arch-length deficiency
4. Supernumerary teeth
5. Odontogenic tumors
6. Abnormal eruption path
7. Cleft lip and palate

Question 2

Impacted versus Unerupted Teeth

Answer 2

A tooth is considered
impacted when it has failed to fully erupt into the oral cavity
within its expected developmental time period and can no
longer reasonably be expected to do so

Question 3

Commonly impacted teeth

Answer 3

• Maxillary and mandibular third molars most likely to be impacted.
• Followed by maxillary canines, mandibular premolars, maxillary premolars, and second molars.
• Impaction of first molars or incisors uncommon in both arches.
• True impaction of deciduous teeth is rare.

Question 4

Third Molar Eruption Age Range

Answer 4

Eruption of lower third molars typically completes at 20 years, but can occur as late as 24 years

A tooth impacted at 18 years has a 30% to 50% chance of fully erupting by 25 years

Question 5

Third Molar Development and Eruption Pattern

Answer 5

• The mandibular third molar tooth germ is visible by age 9 years, with cusp mineralization completed about 2 years later.
• At age 11, the tooth is located within the anterior border of the ramus, with its occlusal surface facing almost directly anteriorly.
• Crown formation is usually complete by age 14 years, and roots are approximately 50% formed by age 16.
• The position of the third molar relative to adjacent teeth changes, with the third molar assuming a position at the root level of the adjacent second molar.
• Roots are usually completely formed with an open apex by age 18 years.
• The tooth reaches its final position by age 20 years, with 95% of all third molars erupting by age 24 years.

Question 6

Third Molar Impaction and Its Causes

Answer 6

• Root growth between the mesial and distal roots can cause the tooth to remain mesially inclined or rotate to a vertical position.
• Underdevelopment of the mesial root results in a mesioangular impaction. Overdevelopment of the same root results in overrotation of the third molar into a distoangular impaction.
• Overrotations from mesioangular to horizontal and from mesioangular to distoangular occur during the terminal portion of root development.
• Inadequate bony length leads to a higher proportion of impacted teeth.
• Patients with impacted teeth usually have larger-sized teeth than those without impactions.
• Abnormally positioned lower third molar almost always fails to erupt, possibly influenced by dense bone in the external oblique ridge.
• Retarded maturation, where dental development lags behind skeletal growth and maturation of the jaws, increases the incidence of impaction.

Question 7

Diagnosis of Impacted Permanent Teeth

Answer 7

• Diagnosis involves clinical inspection and radiographic assessment of the tooth’s position.
• Surgeons should evaluate for an underlying systemic cause when multiple or uncommonly impacted teeth are found.
• The SLOB principle, for same-lingual, opposite-buccal, is used in these techniques.
• The tube shift method, the buccal object rule, and the periapical occlusal method are standard radiographic techniques.
• Factors influencing eruption potential of a lower third molar include angulation of the third molar and space available for its emergence.
• By age 18 to 20 years, lower third molars that are horizontal or strongly mesioangular have less eruption potential than those oriented more vertically.
• Unerupted lower third molars that are nearly vertical and have adequate horizontal space are more likely to erupt than to remain impacted.

Question 8

Indications of removal of 3rd molars

Answer 8

1. Pericoronitis
2. Periodontitis
3. Dental caries
4. Orthodontics
   (crowding of mandibular incisors, Obstruction of Orthodontic Treatment, Interference with Orthognathic Surgery, Post-maxillary down-fracture)
5. Preventing Odontogenic Cysts and Tumors (neoplasms are around 3%, 1% and 2% of all third molars extracted are removed due to the presence of odontogenic cysts and tumors, risk of neoplastic change around impacted molars may decrease with age patients under 40)
6. Root Resorption of Adjacent Teeth
7. Teeth under Dental Prostheses
8. Prevention of Jaw Fracture
9. Management of Unexplained Pain

Question 9

Contraindications of 3rd molar extraction

Answer 9

1. Extremes of Age (less than 40)
2. Compromised Medical Status
   Other factors may compromise the health status of younger people, such as congenital coagulopathies, asthma,
   and epilepsy
3. Surgical Damage to Adjacent Structures

Question 10

Classification Systems for Difficulty

Answer 10

• Mesioangular impaction, accounting for 45% of all impacted mandibular third molars, is the least difficult.
• Vertical impaction (40% of all impactions), horizontal impaction (10%), and distalangular impaction (5%) are intermediate in difficulty.

Relationship of the impacted tooth to the Ramus and Second Molar
* Tooth lengths above the ramus border are sufficient to allow tooth eruption.

Deepness of Impaction and Type of Overlying Tissue
* Depth of impaction under hard and soft tissues is a significant factor.
* Soft tissues and partial or complete bony impaction are commonly used to determine difficulty.

Factors Influencing Extraction Process
* Roots can be conical and fused or separate and divergent.
* A large follicular sac around the crown of the tooth provides more room for access.
* Age of the patient is another important determinant of difficulty.

Difficulty of Recovery from Surgery
* Full bony impactions are always more difficult to remove than soft tissue impacts.

• A more challenging and time-consuming surgical procedure results in a more troublesome and prolonged postoperative recovery.

Question 11

Technique for Impressed Third Molar Removal

Answer 11

• The technique requires theoretical learning and repeated practice due to the variety of impacted third molars.
• The surgeon must gain access to the underlying bone and tooth through a well-designed soft tissue flap.
• Bone should be removed in an atraumatic, aseptic, and non-heat-producing manner, minimizing damage.
• The tooth is divided into sections and delivered with elevators, using judicious force to prevent complications.
• The wound should be thoroughly debrided mechanically and by irrigation for a healing environment in the postoperative period.
• The most commonly used flap is the envelope flap, which extends posteriorly to the impacted tooth’s position.
• If greater access is required, a release incision is made on the anterior aspect of the impacted tooth, creating a three-cornered flap.