Post-treatment Panoramic Radiographs Research Articles

Exploring etiologic contributions to the occurrence of external apical root resorption

External apical root resorption (EARR) is often an undesirable sequela of orthodontic treatment. Prior studies have suggested a substantial link between EARR and certain genetic components. Single nucleotide polymorphisms (SNPs) may play a role as predisposing factors. This study aimed to investigate the potential association between EARR and various SNPs. The study included 218 orthodontic participants of all malocclusions who had available pretreatment and posttreatment panoramic radiographs. The most severely affected maxillary incisor on the radiograph was assessed for EARR using a 0-4 categorical scale. DNA was taken from the saliva samples of the participants, and the SNPs were analyzed using polymerase chain reaction and TaqMan chemistry. Statistical testing was performed to verify any associations with EARR (P<0.05). From all genes tested, the rs678397 SNP of ACT3N (P= 0.003) and the rs1051771 SNP of TSC2 (P= 0.03) were significantly associated with EARR. No association could be established between other polymorphisms and EARR. In addition, patients with Class III malocclusion and extended treatment times were at increased risk of developing EARR. Our results support the concept of gene polymorphisms as risk factors in EARR. In particular, a significant association was found between ACT3N and TSC2 and EARR. Clinically, predisposing risk factors for EARR should be assessed for each patient.

Third molar angulation and retromolar space after functional orthodontic treatment : Evaluation of panoramic radiographs after monoblock or Herbst appliance.

The aim of this respectively cohort study was to evaluate the lower second and third molars and canine angulations, retromolar space and occlusal relationships after functional orthodontic treatments with the monoblock or Herbst appliance using panoramic radiographs. Pre- and posttreatment cephalometric and panoramic radiographs of 133 patients (mean age 13.89 ± 1.14years) treated non-extraction with monoblock (n: 44), Herbst (n: 45) and fixed orthodontic appliances (control group; n: 44) were included to the study. Dental and skeletal measurements were performed on cephalometric radiographs. The angle between the third and second molars, and canines with the lower border of the mandible and the occlusal plane, gonial angle, the angle between the third and second molars and the retromolar space width were assessed on pre- and posttreatment panoramic radiographs. Paired and independent ttests were used for the statistical analysis of the data for intragroup and intergroup comparisons. Functional treatment with both the monoblock and the Herbst appliances resulted in improvement of skeletal classII relationships. Retromolar space significantly increased in the functional appliance groups compared to the control group (p ≤ 0.001), but improvement of the angulations of posterior teeth was significant only in the monoblock group (p ≤ 0.001). While both the Herbst and monoblock appliances led to an increase in retromolar space, monoblock treatment resulted in more favorable angulation of the third molars compared to the Herbst treatment.

Timing for extraction of permanent first molars in school aged children: a pilot study.

Extraction of permanent first molars (P1Ms) could create gaps, tipping and/or rotating of neighboring teeth, which depend on the extraction timing. This study evaluated the outcomes of P1Ms extraction in children who were classified based on their permanent second molar's (P2Ms) dental calcification at the time of extraction. In this retrospective study, the evaluations were made for 406 panoramic radiographs (PRs) of children aged 7-14 years who had single P1M extracted. Twenty-nine children having pre- and post-treatment PRs were selected based on the inclusion criteria. First, 2 groups were formed based on the extraction time by using the pre-treatment PRs; Early extraction group (EE) (n = 15) including Nolla Grades 5-6-7, and late extraction group (LE) (n = 14) including Nolla Grades 8-9-10 for P2Ms. Then, the inclination degrees of neighbouring teeth on extraction side and contralateral quadrant (non-extraction) side were measured by using the post-extraction PRs. Mann-Whitney U test was employed, and the statistical significance was set at p < 0.05. The mesial tipping tendency of P2M was significant towards the extraction side both at EE or LE calcification grades of P2Ms (p > 0.05). The mesial inclination degrees of maxillary P2Ms showed no statistically significant difference between the two sides of LE group. The ideal extraction time should be determined according to the dental age to plan an appropriate occlusal maintenance.

External apical root resorption in African American orthodontic patients.

External apical root resorption (EARR) is a side effect of orthodontic treatment that results in root shortening. However, this condition has yet to be evaluated in African Americans. The aim of this study was to determine the EARR prevalence within this ethnicity and investigate how patient and treatment-related factors contribute to root resorption. The records of 336 African Americans treated at the University of Alabama at Birmingham School of Dentistry Department of Orthodontics were retrospectively analyzed with Dolphin Imaging software. Pre-treatment and post-treatment panoramic radiographs were used to measure EARR. Resorption was recorded when final roots were at least 2 mm shorter after orthodontic treatment. Additionally, moderate and severe EARR was reported when 20% and 50% or more of the root structure was lost for any of the four maxillary incisors, respectively. The Pearson chi-square test was used to evaluate the associations of individual patient and treatment-related factors with EARR. The prevalence of root resorption with 2 mm or greater of root structure loss was 51.8%. The prevalence of ≥ 20% EARR was 29.8%. Only one patient displayed severe resorption (0.3%). The associations between the patient-specific and treatment-specific variables and EARR were not statistically significant (P > .05). More than half of the African American patients exhibit at least 2 mm of root resorption with orthodontic treatment. However, in this ethnicity, patient-related factors such as age, gender, dental malocclusion, and skeletal classifications, as well as treatment-related factors do not indicate a significant correlation with the risk of developing EARR.

Factors that may increase the risk of external apical root resorption during orthodontic treatment : Retrospective clinical investigation.

To determine the correlation between external apical root resorption and malocclusion-related variables in patients treated with fixed orthodontic appliances. In all, 103patients aged 12-15years and treated with edge-wise appliances either without extractions or with four premolar extractions were included in this retrospective cohort study. External apical root resorption was assessed in the pre- and posttreatment panoramic radiographs of these patients for incisors, canines, premolars, and first molars. Atotal of 2332 teeth were evaluated in 206 panoramic radiographs obtained from 103patients. The gender of the patients, duration of orthodontic treatments, presence of premolar extractions, Angle classification, overbite, overjet and amount of crowding were assessed. Wilcoxon signed-rank test, Mann-WhitneyUtest, and Kruskal-Wallis test were used for statistical analysis of the data. Statistically significant (p < 0.001) root resorption occurred in all examined teeth during orthodontic treatment. The degree of root resorption observed in the premolars was significantly greater in premolar extraction cases than in nonextraction cases. Statistically significant negative correlations were found between the degree of root resorption of the maxillary lateral teeth and between the maxillary first premolar teeth and the amount of maxillary crowding. The orthodontic treatment protocols and the amount of tooth movements achieved were shown to be dependent on the severity of dental malocclusions and they have an influence on the amount of external apical root resorption that occurs during the course of orthodontic treatment.

Relationship between the amount of mesial movement of the mandibular first molar and angular changes of the mandibular third molar: A retrospective comparative study in growing patients with and without first premolar extraction

The main objective of this study was to assess the relationship of the amount of mesial movement of mandibular first molar (MFM) and angular changes of the mandibular third molar (MTM) in orthodontic patients. The secondary objective of this study was to compare the obtained values in extraction and non-extraction orthodontic patients. In this cross-sectional retrospective study were enrolled all the eligible patients (12-16 years) with and without first premolar extraction that met the inclusion criteria. The angle between the longitudinal axis of MTM and horizontal reference plane (HRP) (to calculate the angular change of MTM), and the distance between the cementoenamel junction of the mesial surface of MFM and the bisector of the anterior nasal spine and nasal septum (to determine the amount of mesial movement of MFM) were measured on pre- and post-treatment panoramic radiographs. The correlation between the two variables was analysed and compared between extraction and non-extraction patients using STATA v. 14.2 software. A total of 100 fixed orthodontic patients with and without first premolar extraction (n=50) whose treatment had been accomplished were included in the study. In the non-extraction group, the mean amount of mesial movement of MFM was 1.45mm and the mean angular change of MTM was 4.28 degrees; this correlation was significant (P<0.05). These values were 2.98mm and 7.17 degrees in the first premolar extraction group, respectively, with a significant correlation (P<0.05). However, the difference in this respect was not significant between the two groups (P>0.05). According to the regression model, 1mm mesial movement of MFM would averagely cause 2.2-degree angular change in MTM, adjusting for the effect of extraction/non-extraction treatment plan. The mesial movement of MFM was significantly correlated with the angular changes of MTM in extraction and non-extraction orthodontic patients, with no significant difference between them.

Comparison of the Mesiodistal Angulations of Canine and Molar Teeth in Different Types of Orthodontic Malocclusions: A Retrospective Study

(i) Objective: Changes in the mesiodistal axial angulations of teeth with orthodontic treatment have been a topic of interest in orthodontics for many years, although it has not been clarified enough yet. Therefore, this present study aimed to compare mesiodistal axial angulations of canine and first molar teeth by measuring from pre- and post-treatment panoramic radiographs in different types of orthodontic malocclusions. (ii) Materials and Methods: In the study, the mesiodistal axial angulation angles of the lower-upper canines (teeth numbered 13, 23, 33, and 43) and first molars (teeth numbered 16, 26, 36, and 46) were compared on panoramic radiographs taken pre- (T0) and post- (T1) orthodontic treatment of 353 patients: 237 female (mean age 14.74 ± 2.96) and 116 male (mean age 14.44 ± 2.50), who had not received any prior orthodontic treatment. The groups were formed according to pre-/post-treatment, gender, angle classification, skeletal classification, bilaterally first premolar extraction/non-extraction, and the use/non-use of miniscrews in the extraction cases. The mesiodistal angulations between the long axes of both the lower and upper canines and first molars and the interorbital plane were measured separately and recorded. The reliability analysis between the repeated measurements was evaluated using the intraclass correlation coefficient (ICC). For statistical analysis, a paired sample t-test and Wilcoxon test were used for the normally and non-normally distributed data, respectively. For the between-groups comparison, independent sample t-test and one-way ANOVA were used for normally distributed data, while the Mann-Whitney U and Kruskal-Wallis tests were used for non-normally distributed data. A value of p < 0.05 was considered statistically significant. (iii) Results: ICCs showed excellent reliability, ranging from 0.804 to 0.913 in other teeth, yet were good in tooth 43 (ICC = 0.712). Regardless of the groups, statistically significant differences were found between the T0 and T1 angulations for all teeth, except teeth 13 and 16. In all groups, the increase in the angulations of teeth 33 and 43 and the decrease in the angulations of teeth 36 and 46 (except skeletal class 3) were found to be statistically significant. The T0 and T1 angulation changes in the miniscrews in the used and non-used groups in extraction cases were similar to the differences found in all teeth, regardless of the groups. There was no significant difference between gender, skeletal classes, and angle classes in the amounts of change in the mesiodistal angulations. (iv) Conclusion: It was concluded that orthodontic treatment caused significant changes in the mesiodistal axial angulation of the canine and the first molar teeth. Furthermore, the fact that the angulations tended to increase in the lower canine teeth and decrease in the lower first molar teeth revealed the importance of tooth movement control, especially in orthodontic mechanics in the mandibula.

Eruption Pattern of Third Molars in Orthodontic Patients Treated with First Permanent Molar Extraction: A Longitudinal Retrospective Evaluation.

The aim of this study was to evaluate angular and positional changes in the second (M2) and third molars (M3) of orthodontically treated patients undergoing a first molar (M1) extraction. A retrospective longitudinal study with a sample of 152 pre- and post-treatment panoramic radiographs was conducted. Thirty-nine patients (51.3%) were orthodontically treated with M1 extraction and thirty-seven (48.7%) were treated without extraction. Angulations of M2 and M3 relative to the infraorbital (IOP) and the palatal planes (PP) were measured and compared between the groups before orthodontic treatment (T1) and after the completion of orthodontic space closure (T2). The prognosis of M3 eruptions was evaluated by assessing their horizontal and vertical position (inclination) using different classification systems. The angular (p < 0.001) and inclination improvement (p < 0.01) of the maxillary M3 was significant for the M1 extraction group. The mandibular M3 inclination significantly improved (p < 0.01), whereas the groups' angulation and vertical position were not significantly different. These findings suggest that extraction therapy has a favorable effect on the maxillary M2 and M3 angulation, but not on the mandibular. M1 extraction showed a signi- ficant effect on the horizontal position of M3 and thus may improve the eruption space and prognosis.

Effects of Orthodontic Treatment on Pulp Stone Formation: A Retrospective Study.

This retrospective study was aimed at determining the incidence of dental pulp stone formation during fixed orthodontic treatment. A total of 100 patients who received fixed orthodontic treatment were included in this study. Pre- and posttreatment panoramic radiographs of the patients were examined to identify pulp stones. The data were analyzed using McNemar's and Pearson's chi-square tests to investigate the correlations between having a dental pulp stone and gender, age, treatment type, and duration. Dental pulp stones were detected in 17% of patients on pretreatment panoramic radiographs and 35% of patients on posttreatment panoramic radiographs. The incidence of pulp stones sharply increased in the pre- and posttreatment radiographs (38%) (P < 0.001). In addition, there were associations between age, treatment duration, and the incidence of pulp stones (P < 0.05). Nevertheless, no associations were found between treatment type, gender, and the presence of pulp stones. Dental pulp stones were most frequently observed in first molars (62%), followed by second molars (36%). Fixed orthodontic treatment may trigger pulp irritation and calcification, resulting in the formation of pulp stones. Although pulp stones have no serious consequences, an orthodontist must consider the probability of pulp stone formation because it can cause difficulties in endodontic treatment.

The effects of a corticotomy on space closure by molar protraction using TSADs in patients with missing mandibular first molars.

The purpose of this study was to evaluate the effects of a triangular-shaped corticotomy on the protraction of second and third molars in patients with missing mandibular first molars. The corticotomy and non-corticotomy groups consisted of sixteen first molars in fifteen patients (28.6±9.4years) and nineteen first molars in fifteen patients (26.6±8.4years), respectively. A triangular-shaped corticotomy was performed between the second premolar and molar. Temporary skeletal anchorage devices (TSADs) were placed between the first and second premolars in both groups. Mandibular dentition variables were measured on the pre and post-treatment panoramic radiographs and lateral cephalograms. Analysis of covariance was performed. The corticotomy group exhibited 2.8mm more inter-radicular correction between the second molar to second premolar roots (P<.001) and 1.6mm more inter-radicular distance correction between the third molar to second premolar roots compared to the non-corticotomy group (P<.01). The corticotomy group required 5.5months less treatment time for space closure (P<.05), but the total treatment time was the same for both groups. The inter-radicular distance between the mandibular second premolar and molar and treatment times for space closure was significantly reduced in the corticotomy group.

Factors associated with alveolar bone depth mesial to the mandibular third molars after orthodontic protraction

The objective of this research was to study the factors associated with the alveolar bone depth mesial to the mandibular third molars (M8) after the mandibular second (M7) and third molars were protracted into the space of the mandibular first molars (M6), which were newly extracted for orthodontic treatment or extracted more than 1year before treatment. This retrospective study included 57 adult patients (mean age 23.40±4.40years) in whom M6 were newly extracted for orthodontic treatment or extracted more than 1year before treatment. The alveolar bone depth mesial to M8 was measured on posttreatment panoramic radiographs. The vertical, horizontal, and angular changes of M8 were measured on both pre- and posttreatment panoramic radiographs. Linear correlation and regression analyses were conducted to explore the factors associated with the alveolar bone depth mesial to M8. The alveolar bone conditions of M6 (R= -0.391, P<0.001) and the vertical movement directions of M8 (R= -0.433, P<0.001) were significant factors associated with the alveolar bone depth mesial to M8 after orthodontic protraction. Without considering the pretreatment periodontal status of M8, patients with M6 extracted exceeding 1year before treatment and with M8 extruded after orthodontic protraction may exhibit deeper alveolar bone depth mesial to M8.

External apical root resorption after orthodontic treatment: Incidence, severity and risk factors.

Background. This study aimed to evaluate the incidence and severity of orthodontically induced inflammatory external apical root resorption (OIIEARR) and the relationship between OIIEARR and possible risk factors such as orthodontic treatment type, treatment duration, gender, and age of the patients. A further aim was to determine the prevalence of OIIEARR in different tooth groups. Methods. The study sample consisted of 1356 orthodontically treated patients (857 females and 498 males; mean age: 14.4±2.8 years). OIIEARR was evaluated using pre- and post-treatment panoramic radiographs for all the tooth groups. Teeth with severe resorption were also assessed. Patient- and treatment-related risk factors for OIIEARR were assessed statistically using Pearson’s chi-squared test, independent-samples t test, and one-way ANOVA. Results. The incidence of severe root resorption following orthodontic treatment was 14.8%. Males exhibited a higher incidence of root resorption compared to females. Orthodontic treatment duration and treatment with extractions were positively correlated with OIIEARR (P < 0.05). OIIEARR was observed most frequently in maxillary incisors, followed by mandibular incisors. Conclusion. Orthodontic treatment with extraction, prolonged treatment duration, and large movements of the incisors should especially be taken into consideration for OIIEARR risk. Routine radiographic follow-up during orthodontic treatment is recommended.

Factors affecting the stability of maxillary extraction site closure.

ABSTRACTIntroduction: A side effect observed in cases treated with extractions is the instability of orthodontic space closure. Objective: The aim of this study was to investigate the influence of gingival invagination, presence of third molars and facial pattern, on the stability of orthodontic space-closure in the maxillary arch. Methods: Ninety-nine subjects (41 male and 58 female) with Class I malocclusion treated with four premolars extraction were evaluated. Extraction sites reopening and gingival invaginations were evaluated in scanned dental models in the posttreatment and 1-year posttreatment stages (mean age 16.1 years). Third molars presence was evaluated at 1-year posttreatment panoramic radiographs, and the facial pattern (SN.GoGn) was evaluated in the initial lateral headfilms. Multiple logistic regression analysis was used to estimate the influence of the aforementioned independent variables on the frequency of extraction space reopening. Results: Space reopening was observed in 20.20% of the subjects 1-year post-debonding. Gingival invaginations were present in 25.73% of quadrants after debonding and in 22.80% 1-year posttreatment. The mean pre-treatment SN.GoGn was 35.64 degrees (SD=5.26). No significant influence was observed of the three independent variables on the instability of extraction site closure. Conclusions: The presence of gingival invaginations, third molars and facial growth pattern do not seem to influence maxillary extraction sites reopening.

Stainless steel and NiTi torque archwires and apical root resorption.

ObjectiveThe amount of apical root resorption when using the torque-segmented archwire (TSA) was investigated as well as the extent and direction of the therapeutically indicated apical movement and the treatment duration.Materials and methodsThe degree of apical root resorption in 18 randomly chosen Class II and Class I patients treated with the TSA, as well as in 18 conventionally treated patients were evaluated using pre- and posttreatment panoramic radiographs. The sagittal and vertical apical movements and inclination changes were determined based on pre- and posttreatment lateral cephalograms. Nonparametric tests were applied to test between treatment groups and steps. The Mann–Whitney U test, Kruskal–Wallis, Pearson correlation and Wilcoxon signed-rank test were applied for statistical analysis (p < 0.05).ResultsThe incidence of root resorptions was 89–94.4% in low or moderate level. The relative root–crown ratio (rRCR) was not statistically different between the TSA and control groups except tooth 12. The axis of the incisors in the TSA group was significantly improved. The main direction of movement of the apices of the central incisors was retrusion and extrusion. No interdependence between the amount of resorption and the parameters of treatment duration, extent and direction of apical movement were found.ConclusionThe results of the study showed that the amount of apical root resorption with the TSA is slight to moderate and can be compared to conventional orthodontic treatment. The TSA is hence a suitable method for applying targeted torques to the incisors.

Changes in Mandibular Third Molar Angulation in High-anchorage Extraction vs Non-extraction Orthodontic Treatment: A Prospective Study

The study aimed to compare the prospective changes in mandibular third molar angulation in high anchorage cases treated with first premolar extractions vs non-extraction orthodontic treatment. The sample consisted of 56 nongrowing patients: Group I had 26 patients with a high anchorage requirement who underwent first premolar extractions and group II had 30 patients who underwent non-extraction treatment. Pretreatment, mid-treatment, and posttreatment panoramic radiographs were obtained for group I and pretreatment and posttreatment for group II. Angle between M2 (second molar)-horizontal reference plane (HRP), M3 (third molar)-HRP, and M2-M3 were measured bilaterally. Data were analyzed using Student t test and ANOVA test (p value < 0.05). Statistically significant increase was found between the pretreatment, mid-treatment, and posttreatment values of M2-M3 in group I (p value = 0.02 R and p value = 0.049 L) and between pretreatment to posttreatment values of M2-HRP in group II bilaterally (p value = 0.001). Significant increase was found in the M2-M3 angulations in group II on the right side (p value = 0.036). M3-HRP decreased in group I without reaching statistical significance. No statistically significant intergroup differences were found between the two groups in relation to M2-HRP, M3-HRP, and M2-M3 angulations. M2-M3 angulations increased significantly bilaterally in group I and on the right side in group II, indicating worsening of third molar angulation. M3-HRP worsened in group I without reaching statistical significance. Extraction therapy in high anchorage cases does not lead to an improvement in third molar angulation. The extraction of first premolars in high anchorage cases does not lead to an improvement in the angulation of mandibular third molars; moreover, the angulation worsened with extraction therapy. Prospective orthodontic patients need to be cautioned against any improvement in mesioangular impaction of mandibular third molars in high anchorage premolar extraction cases.

Orthodontic Treatment and Pulp Stone Formation: Is There a Relationship?

Objective: The aim of this retrospective study was to evaluate the effect of orthodontic treatment on pulp stone formation.Methods: The sample population comprised 504 patients (182 males, 312 females) with a mean age of 17.7 ± 2.9 years that underwent orthodontic treatment. The pre-treatment and post-treatment panoramic radiographs of the patients were evaluated to detect pulp stones before and after orthodontic treatment. The data were analyzed using Mc Nemar, Chi-square and Fisher Exact tests.Results: The statistical analysis showed that pulp stone numbers increased significantly after treatment (p˂0.05) and there was no statistically significant difference between the sexes in terms of pulp stone enhancement. The increment of pulp stone numbers after treatment was found to be significantly higher in molars than other teeth (p˂0.05). In canine teeth, the increase in pulp stones was statistically higher in females than in males (p˂0.05).Conclusion: The results of this study showed that pulp stone numbers increased at different percentages after orthodontic treatment in all tooth groups. It may be concluded that orthodontic treatment can affect calcification metabolism of the pulp and orthodontic forces may increase pulp stone formation.

External apical root resorption in orthodontically treated Class II malocclusions with 2-phase protocol (A 10-year Experience)

Background and objectives: External apical root resorption is one of the proposed sequels of fixed orthodontic appliances used for the treatment of different types of malocclusions specially class II. Many factors may be involved in the etiology and severity of such resorption. This study is conducted to explore the prevalence of root resorption and specify the most possible causative factors during orthodontic treatment. Method: Records of 103 patients (case sheet, panoramic and cephalometric radiograph) with class II malocclusion were retrieved from private clinics and dentistry college clinics. Patients with planned premolar extractions and 2-phase protocol for space closure were involved in the study. The pre- and post-treatment panoramic radiographs were evaluated for external apical root resorption using a scoring method proposed by Levander and Malmgren The effect of variables like age, gender and duration of the treatment on external root resorption were studied. Results: Statistical analysis showed that age and gender has insignificant relation with root resorption. A highly significant relation found between the severe external apical root resorption and the duration of treatment. Conclusion: External apical root resorption is highly associated with long-term duration treatment protocols.

Effect of mandibular first molar mesialization on alveolar bone height: a split mouth study

ObjectivesTo evaluate the risk of vertical alveolar bone loss (ABL) in mesialized mandibular permanent molars due to space closure in patients with unilateral second premolar agenesis. The contralateral side served as control.Subjects and methodsTwenty-five retrospectively selected subjects (median age 14.9, range 12.0, 31.9 years) were analyzed. Space closure (approximately 10 mm) was performed using skeletal anchorage. ABL was measured at mesial and distal sites of first molars in pre- and post-treatment panoramic radiographs. Measurements were corrected for distortion and magnification of radiographs. Molar angulation according to the occlusal plane was also evaluated. Permutational multivariate analysis of covariance (MANCOVA), followed by pairwise comparisons, was performed.ResultsMANCOVA resulted in no difference in ABL between the distal sites of mesialized molars and the control sites. On the contrary, there was statistically higher ABL, at the mesial sites of mesialized versus non-mesialized molars (p = 0.042; median 0.19 mm; range − 0.82, 1.33); though the difference was not clinically relevant. In the space closure side, mesially, only two patients had ABL higher that 1 mm. No patient had a severe bone level height defect (> 3 mm distance from the cementoenamel junction) at any point.When testing differences in molar angulation between sites and from pre- to post-treatment condition, no significant difference was detected (p > 0.05, median − 1.9°, range − 13.5, 6.2).LimitationsThis is a retrospective study on panoramic radiographs.ConclusionsSpace closure through extensive tooth movement was identified as a risk factor for vertical ABL, at the mesial sites of mandibular first molars. However, the amount of ABL was not clinically relevant, and thus this treatment option is considered safe in terms of ABL.

Comparison of the effect of premolar extraction and non-extraction on the position and developmental changes of the lower third molars

The aim of the present study was to comprehensively assess the posttreatment effect of premolar extraction versus non-extraction on the position and development of the lower third molars. The sample consisted of 227 patient's pre- and posttreatment panoramic radiographs (53 with four premolar extractions, 174 without extractions). The position and developmental stage of the lower third molars were evaluated by using Pell-Gregory's, Winter's, modified Miloro-DaBell's and Demirjian's classifications, respectively. Premolar extraction had a considerably positive influence on the position and development of the lower third molars and therefore could provide better prognosis for their eruption.

Effect of different types of dental anchorage following first premolar extraction on mandibular third molar angulation

The aim of this study was to determine the effect of first premolar extraction with different anchorages as well as non-extraction on mandibular third molar angulation. The pretreatment (T1) and posttreatment (T2) panoramic radiographs of one hundred patients from Hamadan (Iran), who underwent fixed orthodontic treatment were investigated and the angle between long axis of right mandibular third molars and a constructed horizontal plan (HRP) was measured. The sample was equally divided into four groups including first premolar extraction with maximum anchorage, that with moderate anchorage, that with minimum anchorage and non-extraction group. In the first premolar extraction groups with moderate and minimum anchorages, third molar angulation increased (8.12 and 7.48°, respectively) significantly from T1 to T2 (P=0.001 and 0.003, respectively), but in the first premolar extraction group with maximum anchorage and non-extraction group, increase in third molar angulation (2.84 and 0.8°, respectively) was not statistically significant (P=0.082 and 0.943, respectively). Third molar uprighting was significantly different among four groups using one-way ANOVA (P=0.004). Tukey (HSD: honestly significant difference) post hoc test indicated that difference in third molar angulation was statistically significant between first premolar extraction group with moderate anchorage and non-extraction group (P=0.007) and also between the first premolar extraction group with minimum anchorage and non-extraction group (P=0.024). The first premolar extraction groups with moderate and minimum anchorage may lead to more chance of third molar eruption and this can be helpful in borderline cases to consider third molar angulation as one of determining indicators to decide whether to extract or not to extract first premolars.