Effect of Mandibular Third Molars on Anterior Crowding Assessed by CBCT

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Objective: The aim of this cross-sectional randomized study was to investigate the prevalence and angulation of third molar impaction in patients between 19‒26 years old who were living in the Middle Black Sea region of Turkey. Patients and Methods: Total 1006 patients between 19 and 26 years of age who were referred to the Ordu University Faculty of Dentistry Department of Oral Maxillofacial Surgery between 2010 and 2015 were included in the study. Of these 1,006 patients, 410 were male and 596 were female. The prevalence and positions of the impacted third molar teeth from the 4th quadrant on the panoramic radiographs were documented according to the classifications of Pell and Gregory as well as that of Winter. In the Pell and Gregory classification, the teeth in class C were evaluated as impacted teeth. Results: There was a total of 1,518 impacted molars. Of the included patients, 48.3% had impacted third molars. The most common angulation of impacted third molars was the vertical position in both mandible (28.4%) and maxilla (28.8%). The prevalence of impacted mandibular third molars (57.3%) was significantly higher than that of the impacted maxillary third molars (42.7%) (P<0.05). The prevalence and angulation of impacted third molars between genders was not significant (P>0.05). Conclusion: The pattern of third molar impaction in the Middle Black Sea region was characterized by a high prevalence of level C impaction with a vertical position that was greater in the mandibles and had no sex predilection.

Background the position and angulation of mandibular third molars have both been found to influence the angle and condylar fractures. Objective: To identify whether there is an association between the depth and angulation of third molar impaction and the relative risk of fracture of the mandibular angle and condyle. Method Four-hundred and eighty-two panoramic dental radiographs were assessed for the period from January 2012 to June 2020. The study variables included the presence of mandibular third molars, position and angulation. The outcome variables were angle and condylar fractures. Results the mean age was 28.5 years (range 15-89) and 93.2% (n = 499) were male. Angle fractures were significantly more frequent with an impacted wisdom tooth (M3) ( p = 0.023) whereas condylar fractures were more commonly associated with a fully erupted M3. The highest incidence of angle fractures was observed with wisdom teeth classified as class II ( p = 0.026) and position B ( p = 0.05). In contrast, class I wisdom molars were more frequently associated with condylar fractures. With regards to the angulation of wisdom teeth, angles between 80 o – 100 o were highly correlated with angle fractures ( p = 0.020) whereas M3 angulations of 60 o – 80 o were related to condylar injuries (p = 0.025). Conclusions fractures of the mandibular angle were significantly associated with Class II and position B wisdom teeth whereas class I third molars were associated with fracture of the condyles. The likelihood of angle and condylar fractures almost doubled when M3 angulations were (80-100) and (60-80) respectively.

The influence of the third molars on mandibular incisor crowding has been extensively studied but remains controversial. The purpose of this study was to ascertain whether, in Mongolian subjects, the lower third molar can affect anterior crowding and/or the inclination of teeth in the lower lateral segments. Panoramic radiographs, 45° oblique cephalograms, and dental casts were taken from Mongolian subjects (age range 18.3-24.1years, mean 21.0years) exhibiting impaction of all four third molars and an Angle Class I molar relationship. The Ganss ratio was calculated using panoramic radiographs, whereas the gonial angle and angulation of lower canines, premolars and molars were measured using 45° oblique cephalograms. Little's index of irregularity was calculated using dental casts. Significant relationships between the angulation of the third and second molars and between the first molars and second premolars were found. Conversely, there was no significant correlation between the angulation of third molars, first premolars and canines. The Ganss ratio calculations showed that the lower first and second molars and the second premolars inclined mesially if there was insufficient space for the lower third molars. However, there was no significant correlation between Little's index of irregularity and third molar angulation. Furthermore, although the third molar influences the lateral segments, no obvious relationship between the third molar and anterior crowding was observed. Therefore, the angulation of the third molar appears not to cause anterior crowding.

The position of the upper first molar (UFM) is currently considered the “key of occlusion”. The purpose of this study was to evaluate the prevalence of the mesiorotated UFM, and its relationship with anterior dental crowding in mixed and permanent dentition. Intra-oral scans of upper dental arches of 180 subjects with mixed dentition and 169 subjects with permanent dentition were retrospectively analyzed to investigate the presence of UFM mesiopalatal rotation and presence of anterior crowding. The occlusal relationship and the presence of caries were also recorded. In subjects with permanent dentition, there was a statistically significant correlation between anterior crowding and UFM mesiopalatal rotation (Pearson’s chi-square = 9.03; p = 0.06). Among cases with permanent dentition, subjects with UFM mesiopalatal rotation showed an OR = 3.28 (95% CI = 0.99–10.93; p = 0.042) of moderate/severe anterior dental crowding, respect to subjects without UFM rotation. In subjects with mixed dentition, there was a statistically significant correlation between molar occlusal relationship and UFM mesiopalatal rotation (Pearson’s chi-square = 14.98; p = 0.002), and subjects with molar class II showed a OR = 10.2 (95% CI = 2.16–48.22; p = 0.0005) to present UFM mesiopalatal rotation, with respect to subjects with molar class I. UFM mesiopalatal rotation is associated to anterior dental crowding in permanent dentition, and to class II malocclusion in mixed dentition.

The purpose of this study was to three-dimensionally evaluate the relationship between the degree of bilateral impacted mandibular third molar (IM3M) angulation and the mandibular dental arch parameters in normal skeletal and dental malocclusion patients. In this retrospective cross-sectional comparative study, 120 adult subjects' cone-beam computed tomography (CBCT) images were three-dimensionally analyzed. The sample included 120 adults aged 20-30years, with a gender distribution of 51 male and 69 female participants. The sample was divided into 100 adults with bilateral IM3M (study group) and 20 adults with normal bilateral erupted M3M (control group). The study group was sub-divided into three groups according to the degree of IM3M buccolingual angulation (BL°): group A, < 12° on the center of the ridge (N = 30), group B, 12-24° off-center of the ridge (N = 40), group C, > 24° off-center of the ridge (N = 30). The study group was also sub-divided into two groups according to IM3M mesiodistal angulation (MD°): group 1 from 10 to 45° (N = 36), group 2 > 45° (N = 64). Comparison within and between groups was performed using one-way ANOVA followed by Tukey's post hoc test. The correlation between IM3M, BL, and MD angulation and the mandibular arch parameter was calculated using Pearson's correlation coefficient. Statistically significant differences (P < 0.001) were found between the IM3M BL° and anterior teeth inclination, arch length (AL), and inter-second molar width (inter 2nd MW) as well as between the IM3M MD° with anterior crowding and the arch length (P < 0.001). A significant positive correlation was found between IM3M BL° and anterior teeth inclination and between IM3M MD° and anterior teeth crowding and inter 2nd MW. A significant negative correlation was observed between IM3M BL° and inter 1st MW and 2nd MW. The degree of buccolingual and mesiodistal angulation of the impacted mandibular third molars was related with mandibular dentoalveolar changes. Increased buccolingual angulation is generally associated with increased anterior teeth inclination and decreased 1st and 2nd inter-molar width. The increase in mesiodistal angulations was generally related with increased anterior teeth crowding and 2nd inter-molar width. Assessment of the relationship between the impacted mandibular third molars and the degree of arch discrepancy, and the position of mandibular incisors in the three planes of space might help in the decision-making process for the extraction of the impacted third molars in adult patients.

Is the angulation of mandibular third molars associated with the thickness of lingual bone?

BackgroundOur purpose was to investigate the relationship between the angulation of mandibular third molars and the thickness of the lingual bone, which can affect the risk of lingual nerve damage during lower third molars surgical extraction.Material and MethodsThis study consisted of 104 patients (42 males and 62 females), aged between 18-42 years (24.67 ± 6.11 years). Cone Beam Computed Tomography (CBCT) images were taken for preoperative assessment. The teeth were divided into four groups according to their positions: mesioangular, distoangular, vertical and horizontal. Lingual bone thickness around impacted teeth were measured at three points: cementoenamel junction (CEJ) of the mandibular second molar, mid-root of the impacted third molar, and apex of the impacted third molar root. Two predisposing factors of lingual nerve damage were recorded: lingual bone perforated by the impacted tooth and lingual bone thinner than 1 mm. Additionally, buccolingual angulations of the teeth in each group were measured.Impacted mandibular third molars were removed in usual way. One week after surgery, the patients were evaluated regarding lingual nerve paresthesia.ResultsNone of the 104 patients experienced paresthesia, including the ones who had teeth with close proximity with lingual nerve. The mean thickness of bone was 1.21±0.63 mm at CEJ of the second molar; 1.25±1.02 mm at the mid-root; and 1.06±1.31 mm at the apex. Horizontally impacted teeth had thinner lingual bone at mid-root level (p=0.016). Buccolingual angulated teeth were more often associated with perforated lingual bone (p=0.002). Buccolingual and mesial/distal angulation had negative correlation with lingual bone thickness (p<0.05).ConclusionsAs the buccolingual and mesiodistal angulations increase, lingual bone thickness decreases. Horizontally impacted teeth seemed to compromise the integrity of the lingual bone more than impacted teeth in other positions. During the surgery, thin or perforated lingual bone may result in displacement of the impacted tooth lingually. Key words:Lingual bone, impacted third molar, cone beam computed tomography, angulation, paresthesia.

The aims of this study were to investigate the association between pericoronitis and the angular position, state of eruption, and the depth of impaction of mandibular third molars as well as to compare these findings with similar studies. A total of 242 patients ranging in age from 18 to 41 years of age suffering from pericoronitis were examined. Subjective and objective observations were recorded on a checklist that included the name, age, gender, type of pericoronitis and state of eruption, position of the affected tooth for each patient as well as any radiographic changes in the mandibular third molars. The peak age for the occurrence of pericoronitis was in the 21-25 year-old age group. The soft tissues adjacent to vertically inclined, partially erupted mandibular third molars at the level of or above the occlusal plane were the most commonly affected. There was a statistically significant association between radiographic changes and the mesioangular position of the tooth (p<0.002) and the age group of the subject (p=0.004), but the association was not statistically significant between the gender of the subject, type of pericoronitis, state of eruption, and depth of impaction. The soft tissues adjacent to vertically inclined, partially erupted mandibular third molars were more frequently affected by pericoronitis than teeth that are soft tissue impacted or erupted. Mesioangular erupted third molars were the teeth most frequently associated with bone loss. The soft tissues at highest risk of developing pericoronitis are those adjacent to mandibular third molars that are partially erupted, in a vertical position, and erupted to the level of or above the occlusal plane.

To evaluate the effects of first premolar extraction on third molar angulation during fixed orthodontic treatment.Panoramic radiographs of 40 patients treated orthodontically by fixed appliances were evaluated for change in third molar angulation. Twenty patients were treated by extraction of first premolars, whereas the other 20 patients were treated nonextraction. The change in upper and lower third molars angulation, relative to the occlusal plane and adjacent second molars, were obtained by subtracting post- treatment from pre- treatment values.Statistically significant change in the angulation of both upper and lower third molars, relative to the occlusal plane and second molars, were found in the extraction group as compared to nonextraction group.The extraction of first premolars during orthodontic treatment significantly improved the angulation of third molars toward uprightening.

BackgroundTooth wear is an important mechanism for reducing dental dimensions and, consequently, dental crowding. The objective of this cohort study was to examine the relation of tooth wear, adjusted for covariates (age, tooth loss, arch perimeter and intercanine width), on tertiary crowding in Amazon Indigenous populations.MethodsA sample of 40 Indigenous people in permanent dentition at T0 (baseline) and after 13 years (T1) were evaluated. The sample included 16 males and 24 females belonging to two villages, Arara (n = 22, mean ages 16.6 and 29.9 years) and Assurini do Xingu (n = 18, mean ages 16.0 and 29.6 years). Clinical, intraoral photograph and dental cast evaluations were performed at both times. The anterior crowding was measured using Little’s Irregularity Index (LI) and modeled through a multilevel linear regression with the predictor variables: village, tooth wear (T1-T0), age (T0), tooth loss (T1-T0), changes in intercanine width (T1-T0) and changes in arch perimeter (T1-T0).ResultsA slight increase was observed (< 1 mm) in anterior dental crowding and a decrease in arch perimeter < 1.5 mm, while tooth wear increased between 0.65 and 0.99 units. The contextual variable (village) had no significant association with LI. In the upper arch, tooth loss was the only variable that showed an inverse association with LI (β=-0.41, p < 0.05). In the lower arch, the increase in dental crowding was inversely associated with tooth wear (β=-1.30, p < 0.05) and changes in arch perimeter (β=-0.31, p < 0.05). The other variables did not show significant associations.ConclusionAfter 13 years, dental crowding and tooth wear increased, while the arch dimensions tended to decrease. The changes in long-term dental crowding seem to have distinct etiological components for each dental arch. In the mandible, the changes in incisor alignment were associated with increased tooth wear and decreased dental arch dimensions. Whereas in the maxilla, only tooth loss caused alterations in tooth alignment. It is suggested that the effect of increased tooth wear on the etiology of tertiary crowding is of small magnitude and restricted to the lower dental arch.

Objective: The present study assessed the association of size, axial angulation, developmental stage and bud position of the mandibular third molar with the second molar impaction in patients with mandibular second molar impaction. Methods: In this descriptive-analytical study (Case-Control Design), dental records of 5,420 patients in the age range of 12-15 years who underwent orthodontic treatment were assessed out of which 20 patients (14 females and 6 males) with lower second molar impaction were studied. Twenty control patients with erupted second molars were selected from the same centers and matched with the case group. Total sample size was 40 (Case and Control) and had normal distribution for the determined measurements. Third molar axial angulation towards the second molar, first molar and mandibular base, mesiodistal width of 3 rd molar /2nd molar ratio, Nolla developmental stage and third molar bud position were measured and calculated in patients with impacted and erupted second molars and analyzed using student t and chi-square tests. Results: The mean degree of third molar angulation towards the second molar, first molar and mandibular base was 30.20, 53.6, and 51.3 degrees in cases and 21.4, 34.65 and 45.15 degrees in controls, respectively. Significant differences were found between the two groups in terms of third molar angulation towards the second molar (30.2 Vs 21.4 degrees p<0.047), and first molar (53.6 Vs 34.65 degrees p<0.0001); while no differences were found between the two groups in terms of third molar angulation towards the mandibular base (51.3 Vs 45.15 degrees). The mean mesiodistal width of third molar/ second molar ratio was 0.99 in cases and 0.95 in controls with no significant difference. Nolla developmental stage and position of the marginal ridge of the third molar bud towards the second molar showed no definite relation with second molar impaction. Conclusion: It seems that angulation of third molar to the second and first molars is a major contributing factor to increase the risk of second molar impaction. Third molars size, developmental stages, and bud positions, do not show a significant relation to the second molar impaction.

The effect of third molars on the stability of orthodontic treatment has been studied extensively. Yet the effect of orthodontic treatment, particularly premolar extractions, on third molars has not been substantially studied. The purpose of this investigation was to compare the changes in third molar angulation in patients treated with and without extractions. Records of 45 Class I, nonextraction and 33 Class I, first premolar extraction patients were examined. The pretreatment and posttreatment pantographs were digitized, and the angles between the third molar long axes and the occlusal plane were measured. Changes in third molar angulation from pretreatment to posttreatment for the two groups were compared for statistical differences using a Student's t-test. Statistical analysis revealed there were no significant differences in the change in third molar angulation in either group. On average, the maxillary and mandibular third molars showed an improvement in angulation relative to the occlusal plane. The results suggest that factors other than first premolar extractions may influence third molar angulation.

Objectives: This retrospective study investigates the prevalence and angulation of impacted mandibular third molars and the most affected sex in a sample of Libyan patients between the ages of (19 and 84) who live in Zliten, Libya. Study Design: Sixty-nine patients between the ages of (19 and 84) referred to the Assalam Dental Centre were included in this retrospective study. Of the 69 patients, 30 females and 39 males were assessed for the prevalence and position of an impacted mandibular third molar on panoramic radiographs. Results: Out of 124 mandibular third molars, seventy-six were found to be impacted on both right and left sides, from which mesioangular impaction was the most common angulation in females. In contrast, vertical impaction was the most common in males. In addition, the prevalence of impacted mandibular third molars were more in females. Conclusion: The prevalence of impacted mandibular third molars is higher in females than males, and mesioangular impaction is the most common in females, while vertical angulation is frequently common in males.

&#x0D; &#x0D; &#x0D; &#x0D; OBJECTIVES:&#x0D; To objectively determine the correlation of lower third molar angulation and posterior space discrepancy with mandibular anterior crowding digitally using intraoral scanner.&#x0D; METHODOLOGY:&#x0D; Cross sectional analytical study conducted at Rehman College of Dentistry (RCD) Peshawar from15th November 2020 till 15th December 2020. Lower third molar angulation and posterior space discrepancy were measured by IC 3.1 measure software, using digital Orthopantomograms (OPG). Digitally scanned models by (CS 3600 intraoral scanner) were analyzed using (CS 3600 3D software). Sample was divided into Control (N=30; perfect alignment), Experimental (N=30; crowding &gt;1mm) groups, based on Little’s Irregularity Index. Both lower third molar angulation and posterior space discrepancy (Ganss Ratio) were correlated with lower anterior crowding using Pearson’s Correlation. To determine any difference between two groups independent t-test was used.&#x0D; RESULTS:&#x0D; Statistically insignificant difference and a weak correlation were found for Ganss ratio and third molar angulation in both control and experimental groups.&#x0D; CONCLUSION:&#x0D; Third molar angulation and the retro molar space has no direct effect on the lower anterior crowding.&#x0D; &#x0D; &#x0D; &#x0D;