Impacted Lower Third Molar Research Articles

Clinical and orthopantomographic evaluation of mandibular third molar

Objective:To evaluate sensitivity of orthopentograph (OPG) in assessing the number and morphology of roots of the mandibular third molar.Materials and Methods:The study population consisted of 100 ILTMs (impacted lower third molars) ranging from 18 to 42 years with equal sex distribution. All the teeth were subsequently extracted, collected and compared with OPG features for position, number, morphology, and relation to mandibular canal.Conclusion:In conclusion, a large sample study is suggested with techniques like Clark's and right angle technique which determines the three-dimensional orientation of the impacted teeth.

Prevalence of commonly found pathoses associated with mandibular impacted third molars based on panoramic radiographs in Turkish population

The objective was to determine the association between commonly found pathologic conditions and angulations and impaction depths of lower third molar teeth. In this retrospective study 1,914 panoramic radiographs with 3,050 impacted lower third molars (ILTMs) were examined. The problems and the prevalence evaluated were caries on mandibular second molar (12.6%), caries on ILTM (5.3%), bone loss at the distal aspect of ILTM (9.7%), and periodontal tissue damage on adjacent tooth (8.9%). A total of 26.5% of all the cases were affected by any one of the 4 pathologic changes. It was determined that horizontal and mesioangular ILTMs had high risk of caries development on second or third molar; in contrast, vertical and distoangular ILTMs had low risk. Distoangular and vertical ILTMs had high risk of development of bone loss at the distal aspect. Mesioangular and horizontal ILTMs had a high risk for periodontal tissue damage on an adjacent tooth. When evaluating impaction depth of the ILTM, class A had a higher risk of pathology than class B or C. Horizontal and mesioangular impactions were found with more pathologic situations; especially in class A impaction depth. Angulation and impaction depth of the ILTM should be taken into consideration when making a decision whether to extract an ILTM or not.

Incidence of cystic changes in radiographically normal impacted lower third molar follicles

The objective of this study was to investigate the cystic changes in radiographically normal follicles associated with impacted lower third molars (ILTM). The relation between the cystic changes and both the angular position and the contact of ILTM with the adjacent tooth was also evaluated. Follicular spaces of patients who were referred to our clinic for removal of ILTM for a variety of reasons were measured from panoramic radiographs by each author independently. Pericoronal tissues of radiographically normal impacted third molars were examined histopathologically. Then the data were analyzed for associations with age, sex, angular position, and contact of the ILTM with the second molar. There were 30 male and 64 female patients, ages ranging from 14 to 45 years (mean = 21.11). Forty-seven (50%) of the 94 specimens showed cystic changes as the only pathological condition other than inflammation. Most of the cystic changes occurred in the 20-25 year age range. The relation between cystic changes and angular position was statistically significant (chi 2 = 7.46, P < .05). The higher probability of cystic changes was found in the vertically positioned ILTM. The relation between the cystic changes and communication of ILTM with the second molar was not statistically significant (chi 2 = 2.068, P > .05). Cystic changes may be encountered in the histopathologic examination of asymptomatic third molars, especially in patients older than 20 years. Vertically positioned ILTM especially may be suspected for the higher possibility of cystic changes.

A device to predict lower third molar eruption

This study was designed to create a transparent device to be superimposed on a panoramic tomogram taken of a patient at age 20 years to make predictions of future eruption or impaction of lower third molars. The device was developed from data on 40 lower third molars initially retained at age 20 years; one half of these remained impacted, and the other half of them erupted by age 26 years. Tracings were made from panoramic tomograms taken at age 20 years. The critical point for prediction in the overlay was the intersection of a horizontal reference line and the anterior border of the ascending ramus. To estimate this critical separation line, Bayes' Decision Theory was used. The sum of false negatives and false positives was least at a distance of 14.5 mm from the distal surface of the second molar. Mesial from this point, the probability of impaction was 76%; distal from this point, the probability of eruption was 72%. Tested against 35 initially unerupted lower third molars, the predictions made by the device and the actual clinical findings were in conformity in relation to 97% of the test teeth. It could thus be concluded that the method was simple to use and may prove a good addition for predicting lower third molar development.

Relationship between fractures of the mandibular angle and the presence and state of eruption of the lower third molar

This study attempted to relate the incidence of fractures at the mandibular angle with the presence and state of eruption of lower third molars. The records and radiographs of 200 patients with mandibular fractures were examined. The presence and degree of impaction of lower third molars were assessed for each patient and related to the occurrence of fractures of the mandibular angle. Data were analyzed by chi-square statistic and the Student's t test. The incidence of angle fractures was found to be significantly greater when unerupted lower third molars were present (p < 0.001). Bilateral unerupted third molar teeth predisposed to a fracture at the angle significantly more than unilateral unerupted third molars (p < 0.01). Furthermore, the amount of bony space occupied by an unerupted third molar tooth directly related to the weakness of that area of bone (p < 0.001). This study provides clinical evidence to suggest that unerupted third molar teeth weaken the mandibular angle both quantitatively and qualitatively.

Predictive model for impaction of lower third molars

The study was carried out to create and test a model for predicting impaction of lower third molars on the basis of radiographic findings at age 20 years. Fifty-six initially unerupted lower third molars were followed up for 6 years. Five radiographic findings in panoramic tomograms at age 20 were taken as variables. Clinical status at age 26 was taken as response. The radiographic features studied were angulation of tooth, development of root, state of impaction, depth in bone, and relation of the tooth to the ramus of the mandible and the second molar. With the use of logistic regression, univariate and bivariate analyses, and clustering techniques, a decision tree was constructed that indicated accuracies of prediction on the basis of single variables or pairs of variables. The most important predictor was the type of impaction. The model predictions and test teeth findings were in agreement in 94% of instances. It was concluded that the model is suitable for predicting lower third molar impaction at age 20.

Oral midazolam sedation in third molar surgery

A double-blind randomised study was designed to assess the value of oral midazolam in patients undergoing minor oral surgery. 30 young healthy Hong Kong Chinese with bilateral symmetrical impaction of lower third molars to be surgically removed in 2 visits, were included in the study. Randomly selected, a powdered midazolam tablet or placebo was given on the 1st visit and the alternative on the 2nd visit. 45 min were given for the drug to act. Surgical removal of the teeth was carried out by a single operator, randomly, one side being done at one visit. The majority who had midazolam were relaxed during the operation. Nearly 75% had partial to complete amnesia. Midazolam sedation lasted about 45 min, produced good operating conditions and stable vital signs with adequate verbal response. The main adverse effects were drowsiness and dizziness on the same day. The majority had never heard of oral sedation being available to supplement local anaesthesia. The majority preferred midazolam to placebo and preferred to have local anaesthesia supplemented with oral sedation for minor oral surgery in the future.

Reliability and validity of lower third molar space-assessment techniques

Present techniques for predicting eruption or impaction of lower third molars are based on measurements of the space between the second molar and the ramus. This study was designed to investigate the reliability and validity of radiographic techniques often used for assessing this space. Rotational tomograms (O.P.G.s) yielded the best estimates of the Space Width Ratio (found by dividing the space available by the mesiodistal width of the lower third molar) as measured directly on dried skulls. Estimates for lateral cephalograms were unreliable. The use of Xi point to lower second molar for assessing the space for lower third molars is not supported.

The Eruption of Lower Third Molars following the Loss of Lower Second Molars: A Longitudinal Cephalometric Study

In the orthodontic assessment of mild malocclusion of the lower arch, the impaction of lower third molars is often ignored. In such cases lower arch alignment is frequently, later, compromised by the continued presence of the impacted third molars. The authors have produced a simple geometric procedure, to be applied to rotated cephalograms, which will enable clinicians to forecast accurately those lower third molars which will reach occlusion, after the extraction of lower second molars. In addition, such extractions will correct mild buccal arch crowding without the use of appliances. Results of the eruptive progress of 50 lower third molars, over a 7 year period, are presented to support the theory.

Back from the cuspid.

Denture reduction in formal orthodontic treatment does not appear to prevent the impaction of lower third molars. The extraction of premolar teeth is best carried out as close as possible to the eruption time of the cuspids. The posterior part of the mandibular arch should be evaluated by the study of lateral oblique roentgenograms and one of several options regarding treatment should then be adopted.