Mesiodistal Angulation Research Articles

Three-Dimensional Evaluation of Impacted Mandibular Third Molar Angulation and its Impact on Lingual Cortical Bone Thickness: A Retrospective Cone-Beam Computed Tomography Study

Background: The removal of impacted lower third molars surgically can cause complications, and the lingual cortical bone thickness in this region becomes a determining factor in the risk of perforation and injury to the lingual nerve (LN). This study was conducted to assess the relationship between different angulations of impacted lower third molars based on Winter’s classification and the thickness of the lingual cortical bone. Variations in lingual cortical bone thickness among the genders were evaluated as well. Methods: Cone-beam computed tomography (CBCT) scans of 50 impacted lower third molar teeth of 50 patients (26 men and 24 women) were evaluated in this study. The lingual bone thickness surrounding impacted lower mandibular teeth was measured at three key points, namely, the cemento-enamel junction of the second mandibular molar, the mid-root of the impacted third molar, and the root apex of the impacted third molar. Mesiodistal angulation and buccolingual angulations of the impacted mandibular third molars underwent investigation. Statistical analysis was conducted using SPSS 23. Data were analyzed using the independent sample t test, one-way ANOVA, multiple linear regression analysis, and Fisher’s exact test. Results: There was a statistically significant relationship between the means of lingual cortical bone thickness surrounding the third molars based on Winter’s classification of third molars impacted at mesiodistal angulation (P=0.00). Regarding gender, buccolingual angulation demonstrated a statistically significant relationship among the means of lingual bone thickness around the third molars (P=0.022). Conclusion: In our study, the thickness of the lingual cortical bone was notably affected in the middle and apical areas of the impacted third molar region. The variable position of the LN near the mandible third molar region was significant in dental procedures due to its proximity. Three-dimensional (3D) imaging CBCT provides preoperative risk assessment that reduces preventable complications that cannot be answered by 2D imaging.

Effectiveness of different intrusion modes of maxillary anterior teeth with mini-implants in clear aligner treatment: a three-dimensional finite element analysis

BackgroundThe intrusion of maxillary anterior teeth is often required and there are various intrusion modes with mini-implants in clear aligner treatment. The objective of this study was to evaluate the effectiveness of maxillary anterior teeth intrusion with different intrusion modes, aiming to provide references for precise and safe intrusion movements in clinical practice.MethodsCone-beam computed tomography and intraoral optical scanning data of a patient were collected. Finite element models of the maxilla, maxillary dentition, periodontal ligaments (PDLs), clear aligner (CA), attachments, and mini-implants were established. Different intrusion modes of the maxillary anterior teeth were simulated by changing the mini-implant site (between central incisors, between central and lateral incisor, between lateral incisor and canine), loading site (between central incisors, on central incisor, between central and lateral incisor, between lateral incisor and canine), and loading mode (labial loading and labiolingual loading). Ten conditions were generated and intrusive forces of 100 g were applied totally. Then displacement tendency of the maxillary anterior teeth and CA, and stress of the PDLs were analyzed.ResultsFor the central incisor under condition L14 and for the canine under conditions L11, L13, L23, and L33, the intrusion amount was negative. Under other conditions, the intrusion amount was positive. The labiolingual angulation of maxillary anterior teeth exhibited positive changes under all conditions, with greater changes under linguoincisal loading. The mesiodistal angulation of canine exhibited positive changes under labial loading, while negative changes under linguoincisal loading except for condition L14.ConclusionsThe intrusion amount, labiolingual and mesiodistal angulations of the maxillary anterior teeth were affected by the mini-implant site, loading site, and loading mode. Labial and linguoincisal loading may have opposite effects on the intrusion amount of maxillary anterior teeth and the mesiodistal angulation of canine. The labiolingual angulation of the maxillary incisors would increase under all intrusion modes, with greater increases under linguoincisal loading.

Evaluation of Mesiodistal Angulation of Maxillary Anterior Teeth in Incisal View Using Manual and Digital Methods: An In Vivo Study.

The aim of the present research was to assess the mesiodistal angulation of the maxillary anterior teeth utilizing Image J computer software, a Profile projector, and a Custom-made jig. A total of 34 subjects (17 males and 17 females) were chosen from a group of 18-30 years old with bilateral Angle Class I molars and canine relationships. One manual approach (Custom-made jig) and two digital methods (J computer software, a Profile projector) were used to record the mesiodistal angulation in incisal view. The individuals had alginate impressions made, and a facebow was used to capture the maxilla's spatial relationship with the cranium. The articulated cast with the help of mounting ring moved to the specially customized jig, then the angulations was measured in the incisal view after the casts were placed in a semi-adjustable articulator. Data were recorded and statistically analyzed. The mesiodistal angulation in the incisal view via three methods between the 17 males and 17 females has statistically significant different. Although the mesiodistal angulation for maxillary lateral incisor and canine did not show any statistically significant difference, the maximum and minimum values obtained were always greater in males in comparison with the females. This indicates that the positions of six maxillary anterior teeth in the males resulted in the creation of upward sweep of incisal edges of central and lateral incisors which was also referred to as "smiling line" producing masculine surface anatomy more squared and vigorous while feminine surface anatomy being more rounded, soft, and pleasant. There was no statistically significant difference between the right and left sides, indicating bilateral arch symmetry and the symmetrical place of the right teeth compared with the left side's corresponding teeth. On conclusion, according to the current study's findings, all three approaches can measure the mesiodistal angulations of maxillary anterior teeth in incisal view with clinically acceptable accuracy. The digital methods, which included using the Image J computer software and the profile projector, achieved more accurate results than the manual method. The outcomes of this study's mesiodistal angulations can be used as a reference for placing teeth in both fully and partially edentulous conditions. This study contributes to a better understanding of the importance of achieving the ideal occlusion in the Indian population by placing the maxillary anterior teeth at the proper mesiodistal angulation. How to cite this article: Shadaksharappa SH, Lahiri B, Kamath AG, et al. Evaluation of Mesiodistal Angulation of Maxillary Anterior Teeth in Incisal View Using Manual and Digital Methods: An In Vivo Study. J Contemp Dent Pract 2024;25(4):320-325.

Investigation of the Mesiodistal Angulations of Maxillary Canines and Central Incisors for Missing Bilateral Maxillary Lateral Incisor.

(1) Background: A missing bilateral maxillary lateral incisor (MBMLI) causes aesthetic and functional problems and a multidisciplinary approach is required for treatment. This study aimed to compare the changes in the mesiodistal axial angulations of the maxillary canines and central incisors with orthodontic treatment of MBMLI. (2) Methods: A total of 56 patients with MBMLI were included in the study, and three groups were formed: the control group (Group 1, n = 20) with untreated ideal occlusion and the space opening (Group 2, n = 20) and space closure (Group 3, n = 16) groups as treated study groups. The mesiodistal angulations between the long axes of the maxillary right canine (tooth no 13), right central incisor (tooth no 11), left central incisor (tooth no 21) and maxillary left canine (tooth no 23), and the bicondylar plane, were measured on the panoramic radiographs taken pre (T0) and post treatment (T1). p < 0.05 was accepted for statistical significance. (3) Results: At T0, while there was no significant difference between the mesiodistal angulations of the right-left maxillary canines and central incisors in all groups (p > 0.05), the mesiodistal angulations of the canines in the Group 1 were significantly higher than the study groups (p < 0.05). With treatment, while the mesiodistal angulation of the canines increased in Group 2, it decreased in Group 3 (p < 0.05). On the other hand, the mesiodistal angulation of the central incisors decreased in Group 2 and did not change in Group 3 (p > 0.05). At T1, the mesiodistal angulation of the canines was found to be lower in Group 3 than in Groups 1 and 2, while the angulation of the central incisors was found to be lower in Group 2 compared to Group 1 (p < 0.05). (4) Conclusions: In the orthodontic treatment of MBMLIs, changes in the mesiodistal angulations of the maxillary canine and central incisors should be taken into account for satisfactory outcomes. It was concluded that there should be a tendency to select the space closure method in which normal mesiodistal angulations are obtained in maxillary central incisors for aesthetics and planned incisor position, and also at a low cost.

Comparative Evaluation of Accuracy of Adjacent Parallel Implant Placements Between Dynamic Navigation and Static Guide: A Prospective Study.

Aim The study aims to compare the accuracy of dynamic navigation (DN) and static guides (SGs) for simultaneous adjacent parallel placement of implants, the time taken for the surgery, and the ease of handling the instruments. Materials and methods This prospective trial was carried out at the Department of Implantology of Saveetha Dental College from October 2022 to February 2023. A total of 20 patients who needed simultaneous adjacent dental implants were allocated randomly into two groups: Group 1SG surgeryand Group 2DN surgery. Forty implants were placed, 20 under DN and 20 under SG. Bucco-lingual displacement, apico-coronal displacement, mesiodistal displacement, and mesiodistal angulation were compared between the two groups. The patients' data in both groups were evaluated by operating surgeons along with the surgical time taken and the ease of handling of instruments. Results The 20 patients who underwent implant placement in the DN and SG groups all had adjacent missing teeth in posterior sites, including lower posteriors (70%)and upper posteriors (30%). There was improved precision in relation to the mesiodistal displacement and angulation of the anterior implant of the adjacent parallel implants. The mesiodistal displacement in Group 1 (SG) was 5.61 + 3.1 mm, which was higher than Group 2 (DN), which was 0.55 + 0.56 mm. The mesiodistal angulation was 3.1 + 2.9 degrees in Group 2 and 0.42 + 0.5 degrees in Group 1. The second implant had a significant difference (p < 0.005) in mesiodistal displacement, mesiodistal angulation, and bucco-lingual displacement. The difference between the intergroup surgical time (mean + SD) in Group 1 was 30 + 4.5 mins and in Group 2 was 60.7 + 10.1 mins, with p < 0.05 statistically significant. The comfort of the operator was better in the SG group. Conclusion Any digitally aided implant placement technique can improve placement accuracy but each has itsdownfalls. Achieving the highest levels of precision and long-lasting prosthetic results hinges on both the suitability of the chosen case and the expertise of the surgeon performing the implant placement.

Evaluation of the effect of extraction in comparison to distalization on the maxillary third molars in class II malocclusion: a retrospective study

ObjectiveTo compare the effects of first premolar extraction versus distalization on the vertical position and mesiodistal angulation of maxillary third molars (MxM3) in adolescent class II patients.MethodsThe panoramic x-rays (OPGs) of 200 adolescent class II patients with developing MxM3s were screened. The chosen sample consisted of 2 groups: Group 1 (Distalization) comprising 48 MxM3s, and Group 2 (Extraction) comprising 50 MxM3s. The pre- and post-treatment OPGs were traced to detect the mesiodistal angulation changes of the second molars (MxM2) and MxM3s.ResultsThe angulation and vertical position of the MxM3s at T0 & T1 were also evaluated using Archer’s classification. The distalization group presented a non-significant decrease in the mean angulation of MxM2 and MxM3 (-2.4o & -4.5o uprighting respectively). In the extraction group, both MxM2 and MxM3 presented a highly significant decrease in the mean angulation (-10.5o & -11o uprighting respectively). The angulation and vertical position change of MxM3 significantly improved in the extraction group when compared to the distalization group (P < .001).ConclusionSignificant uprighting and occlusal positioning of the maxillary third molars occurred in the premolar extraction treatment group when compared to the distalization treatment group. The results of the current study highlight the importance of recognizing maxillary third molars during orthodontic treatment planning of Class II malocclusion cases.

Third Molar Comparison in Class I and II Extraction and Non-extraction Orthodontic Treatment: A Retrospective Longitudinal Study.

This study compared third molar angulation and eruption status in Class I and II malocclusions after orthodontic treatment with and without first premolar extractions. The sample comprised 93 patients divided into four groups: Group 1, Class I malocclusion treated with first premolar extractions; Group 2, Class I malocclusion treated without extractions; Group 3, Class II malocclusion treated with first premolar extractions; and Group 4, Class II malocclusion treated without extractions. Panoramic radiographs were used to evaluate the third molar mesiodistal angulations at T1 (pretreatment), T2 (posttreatment), and T3 (long-term posttreatment). Third molar eruption status was assessed in dental casts. Intergroup angulations and eruption status comparisons were performed using one-way analysis of variance (ANOVA), followed by Tukey's test and Kruskal-Wallis test, respectively. Significantly greater mesial angulation and percentage of erupted right maxillary third molars were observed in the Class I extraction group. Significantly greater eruption status of the right mandibular third molars was observed in the Class I and Class II malocclusion extraction groups. Class I and II malocclusion extraction treatment exhibited more favorable angulations and a greater number of erupted third molars than non-extraction treatment. The non-extraction groups exhibited a greater percentage of unerupted third molars.

Unplanned tooth movement in deepbite correction with Invisalign: A retrospective study

This study aimed to investigate unplanned tooth movements in deepbite correction with Invisalign. The sample consisted of 34 adult patients with deepbite malocclusion treated with Invisalign. Pretreatment and predicted digital models were exported from ClinCheck software, while the post-treatment model was obtained from an intraoral scan taken at the end of the first set of aligners. Digital models' superimposition was done using the eModel "Compare" software. Frequency and percentage of occurrence of unplanned linear and angular movements, their magnitude, and direction were then determined. In addition, comparison of unplanned movements was performed between anterior and posterior teeth as well as between linear and angular measurements. The percentage of unplanned movements ranged from 1.68% to 25.63% in the maxilla and 3.36% to 23.95% in the mandible, being most evident in the first and second molars. Unplanned movements were statistically significantly more frequent in posterior teeth compared with the anterior teeth (P > 0.05). In addition, the frequency of angular movements was statistically significantly higher for each tooth than linear movement (P < 0.05) with a higher mean value. Unplanned mesiodistal movements were the least frequent. Unplanned linear as well as angular movements were evident in almost all teeth. Unplanned faciolingual inclination and mesiodistal angulation movements were the most frequently observed. Unplanned vertical movements can affect the predictability of deepbite correction and thus merit particular attention in those cases.

A comparison of the upper anterior teeth movements with optimized and conventional attachment.

Invisalign® attachments are divided into two main groups: the conventional group and the optimized group, which is also known as the SmartForce™. The aim of this study is to compare the movements produced by an optimized crescent-shaped attachment in superior incisor teeth with the movements produced by a conventional rectangular attachment (vertical and horizontal) in the same teeth. This retrospective study examined the movement table of the initial ClinCheck® and the first refinement of 95 patients (mean age 44.18 ± 4.125, 40 males and 55 females). It represented 147 upper incisors divided into two groups: 87 with rectangular attachment and 60 with optimized attachment. Applying Kravitz's accuracy formula for each movement and each tooth of interest (with attachments of interest), we underlined the effectiveness of each attachment. Mann-Whitney U test, Kruskal-Wallis test, and Pearson and Spearman correlation coefficients were used for statistical analysis. The accuracies of rotation, mesio-distal angulation and vestibulo-lingual inclination are highly significantly related to the type of attachment used on the upper lateral incisor. The optimized attachment presented greater accuracy in the rotation of the lateral incisors than the conventional attachment. However, conventional vertical attachment showed a higher accuracy (p<.01) in the mesio-distal angulation and horizontal attachments showed a higher accuracy (p<.01) in the vestibulo-lingual inclination in the same group of teeth. Optimized attachments rotate better lateral incisors; conventional vertical attachments are more efficient to improve mesio-distal angulation; and horizontal attachments serve best for torque movements. Key words:Orthodontics, clear aligners, orthodontic tooth movements, attachments.

Comparison of mesiodistal angulations of premolars and molars in anterior open bite subjects with different sagittal malocclusions: A retrospective study

Mesiodistal angulation of premolars and molars can be altered by forces of open bite malocclusion. The aim of this study was to compare the mesiodistal angulations of the posterior teeth in class I, II, and III individuals with anterior open bite (AOB) versus individuals with harmonious occlusion. This comparative cross-sectional study used 299 lateral head radiographs of individuals with permanent dentition. There were 4groups (harmonious occlusion [n=89], Class I open bite [OB] [n=75], Class II OB [n=66], and Class III OB [n=69]). Premolar (1UPM, 2UPM) and molar (1UM, 2UM) angulations were measured relative to the occlusal plane and the palatal or mandibular plane by a trained and calibrated evaluator. ANOVA and Scheffe tests were used for statistical analyses (P<0.05). The mesial angulation of the upper premolars showed greater angulation of between approximately 2° and 5° in the OB groups compared to the harmonious occlusion group (P<0.05). Only in the Class II OB group did the first and second upper molars show distal angulation in relation to the palatal plane (1UM 81.85°±5.42°; 2UM 75.32±7.4°) (P<0.05). The Class III OB group presented the greatest distal angulations of the lower premolars and molars (between 3° to 5° of difference, P<0.05) in relation to those of the harmonious occlusion group. The upper first premolars in all the AOB groups and the lower second premolars in the Class II OB group had greater mesioangulation. Additionally, the upper molars of the Class II OB group and the lower molars of the Class III OB group showed distoangulation compared with the molars in the group with harmonious occlusion.

Aging changes in maxillary anterior teeth in untreated individuals: an observational longitudinal study

ObjectiveThe aging of the occlusion and tooth wears influence the smile design This study aimed at evaluating the aging changes of maxillary anterior teeth in nontreated subjects.MethodsThe sample comprised dental models of 23 subjects (13 male, 10 female) with normal occlusions, taken at 13 (T1), 17 (T2) and 61 (T3) years of age. The following variables were measured in the maxillary anterior teeth using digital dental models: crown width/height proportion, anterior view width, crown angulation, gingival and incisal steps between central/lateral incisors and central incisors/canines. Interphase comparisons were evaluated using repeated measures analysis of variance followed by Tukey tests or Friedman tests. Sexual differences were evaluated using t tests (P < 0.05).ResultsFrom 13 to 61 years of age, a decrease of crown width/height proportion (P = 0.008 and P = < 0.001, for the lateral incisor and canines, respectively) and mesiodistal angulation (P = < 0.001, P = 0.001 and P = 0.025 for the central incisor, lateral incisor and canines, respectively) of the maxillary anterior teeth were observed. The steps of the gingival margin and the incisal steps decreased with aging.ConclusionsFrom adolescence to late adulthood, untreated individuals with normal occlusions demonstrated changes in the maxillary anterior teeth that may impair the smile esthetics and attractiveness.

Mesiodistal angulation and developmental stages of unerupted mandibular second premolars in nonsyndromic oligodontia

Oligodontia is a serious developmental dental anomaly that requires long-term multidisciplinary treatment, but its clinical characteristics are not well understood because it is rare. This study evaluated the mesiodistal angulation and developmental stages of unerupted mandibular second premolars (MnP2s) in orthodontic patients with nonsyndromic oligodontia. Thirty-seven patients with oligodontia with at least 1 unerupted MnP2 in Demirjian's developmental stages between D and G were selected. Age- and sex-matched patients without tooth agenesis, excluding third molars, were selected as the control group. Mesiodistal angulation between the long axis of the available MnP2 and the mandibular plane was measured on panoramic radiographs. The MnP2 was significantly more distally angulated in the oligodontia group than in the control group. The developmental stage of the MnP2 in the oligodontia group was significantly delayed (1.04 ± 0.26 years; 95% confidence interval, 0.53-1.55 years). No correlation between the mesiodistal angulation and the developmental stage of the MnP2 was found in both groups. Significant distal angulation and delayed developmental stages of MnP2s were found in patients with nonsyndromic oligodontia compared with age- and sex-matched patients without agenesis of permanent teeth, excluding third molars. However, no significant correlation was found between them. Regardless of the severity of the distal angulation of MnP2, observing delayed dental development in each patient is important.

Effect of different implant angulations on the biomechanical performance of prosthetic screws in two implant-supported, screw-retained prostheses: A numerical and experimental study

Statement of problemA mesiodistal angle frequently forms between 2 splinted implant-supported, screw-retained fixed dental prostheses (TIS-FDPs). Mechanical complications commonly occur in prosthetic screws. Studies regarding the effect of the degree of implant angulation on the biomechanical performance of prosthetic screws in TIS-FDPs are sparse. PurposeThe purpose of this numerical and experimental study was to investigate the effects of different implant angulations on the biomechanical performance, including stress distribution, stability of the screw joint, and surface morphology change of the prosthetic screws in TIS-FDPs. Material and methodsTIS-FDPs were classified into 4 groups: 0, 10, 20, and 30 degrees based on the degree of mesiodistal angle between the long axes of the 2 implants. In the finite element analysis (FEA), 4 series of 3D models were constructed and loaded with simulated occlusal forces. The von Mises stresses and rotational angles of the prosthetic screws were then calculated. In the mechanical test, each group of 5 TIS-FDPs with 10 prosthetic screws was tested under 1 million loading cycles by using a universal testing machine. The removal torque values (RTVs) and the surface roughness of the prosthetic screws were measured after cyclic loading. The normality of the outcome variables was assessed by the Shapiro-Wilk test. Analysis of variance and the Kruskal-Wallis test were used for further analysis (α=.05). ResultsThe FEA results showed that the von Mises stresses of the prosthetic screws were concentrated in the first screw thread crest engaged with the abutment, and the maximum values of the threads and the rotation angles of the prosthetic screws increased in the 2-implant mesiodistal angulation from 0 to 30 degrees. The mechanical tests showed that the RTVs of the prosthetic screws in each group were not significantly different after 1 million loading cycles (P=.107). The surface roughness of the crest of the first 2 threads of the prosthetic screws in the 30-degree group changed significantly compared with those in the other groups. ConclusionsWhen TIS-FDPs were delivered, larger angulations of the 2 splinted implants seemed to increase the stress concentrated on the crest of the first engaged thread and the rotation angles of the prosthetic screws. After 1 million loading cycles, significant surface adhesive wear was identified on the crest of the first 2 threads of the prosthetic screws in the 30-degree group compared with groups with a smaller angulation.

Can the Position of the Impacted Third Molars Be an Early Risk Indicator of Pathological Conditions? A Retrospective Cone-Beam Computed Tomography Study.

The aim of this retrospective study was to evaluate the prevalence of pathologies associated with impacted third molars in relation to tooth position on cone-beam computed tomography images. In 348 cone-beam computed tomography images, the position of 640 impacted third molars (mesiodistal angulation, buccolingual inclination, impaction depth, and contact point localization) and the presence of pathologies (distal caries, external root resorption, marginal bone loss, and pathological follicular space) were evaluated. The data were analysed statistically with a significance level set at P < 0.05. Distal caries was mostly detected in relation to Class A (20.4%) and contact point at (12.5%) and above (10.5%) the cementoenamel junction (CEJ) (P = 0.000; P < 0.05). External root resorption and marginal bone loss were more common in mesioangular angulation (52.3% and 80.1%, respectively), Class C (53% and 73.8%, respectively), and contact point below the CEJ (53.2% and 73.3%, respectively) (P = 0.000; P < 0.05). Lingual inclination was identified as a new risk factor for associated pathologies (P < 0.05). Pathological follicular space was significantly more likely to occur in those with inverted angulation (100%) and absence of contact (31.5%) (P = 0.000 and P = 0.010, respectively; P < 0.05). Pathologies arising in second molars in relation to impacted third molars are significantly associated with the three-dimensional position of impacted third molars, and watchful monitoring or prophylactic removal of impacted third molars should be considered, taking into account the relevant risk parameters for the related pathologies.

Three-dimensional relationship between the degree of bilateral impacted mandibular third molars angulation and the mandibular dental arch parameters: a cross-sectional comparative study.

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.

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.

Effect of orthodontic extraction of mandibular premolars on third molar angulation after treatment with fixed appliances : Across-sectional study.

Orthodontic treatment involving premolar extractions might improve the angulation of lower third molars, which are the teeth most often impacted. This study analyzes the impact of first/second lower premolar extraction during orthodontic therapy on the angulation of mandibular third molars. A total of 120patients treated non-extraction (n = 40), with extraction of first (n = 40), or second lower premolars (n = 40) were included. The mesiodistal angulation of lower third molars relative to the adjacent tooth and their developmental stage were evaluated from posttreatment orthopantomograms. Between-group differences were statistically evaluated at asignificance level of 0.05. The orthopantomograms of 120patients (51% female) with amedian age of 15.2years at the time of debonding were evaluated after amean treatment duration time of 2.9years. No difference (P > 0.05) was seen between the average angulation of the lower third molars of the right (mean = 24.4°, standard deviation [SD] 13.6°) and the left side (mean = 23.6°, SD 14.1°). No differences in the angulation of the lower third molar were found between the non-extraction and extraction groups for the right (P = 0.44) or the left side (P = 0.22). Likewise, no differences were found when comparing the first and second premolars for the right (P = 0.26) or the left side (P = 0.10). Premolar extraction was associated with an advanced root development stage of the right third molar (odds ratio 7.1; 95% confidence interval 1.1-48.1; P = 0.04), with no differences between extraction of the first or second premolar (P = 0.10). Orthodontic treatment involving premolars extractions might be associated with asmall acceleration in root development, but not with the angulation, of lower third molars.

Relative anchorage loss under reciprocal anchorage in mandibular premolar extraction cases treated with clear aligners.

To compare mandibular relative anchorage loss (RAL) under reciprocal anchorage between first and second premolar extraction cases in bimaxillary protrusion mild crowding cases treated using clear aligner therapy (CAT). Adult patients who met the following criteria were included: treated using CAT with bilateral mandibular premolar extractions and space closure using intra-arch reciprocal anchorage. RAL was defined as the percent molar mesial movement relative to the sum of molar mesial plus canine distal movement. Movements of the mandibular central incisor (L1), canine (L3), and first molar (L6) were measured based on superimposition of the pre- and post-treatment dentition and jaw models. Among the 60 mandibular extraction quadrants, 38 had lower first premolar (L4) and 22 had lower second premolar (L5) extracted. L6 mesial movement was 2.01 ± 1.11 mm with RAL of 25% in the L4 extraction group vs 3.25 ± 1.19 mm with RAL of 40% in the L5 extraction group (P < .001). Tooth movement efficacy was 43% for L1 occlusogingival movement, 75% for L1 buccolingual inclination, 60% for L3 occlusogingival movement, and 53% for L3 mesiodistal angulation. L1 had unwanted extrusion and lingual crown torquing whereas L3 had unwanted extrusion and distal crown tipping, on which the power ridges or attachments had little preventive effect. The average mandibular reciprocal RAL is 25% or 40% for extraction of L4 or L5, respectively, in CAT cases. A RAL-based treatment planning workflow is proposed for CAT extraction cases.

Unraveling the canine using labial auxiliary spring and unilateral distalisation using infra zygomatic crestal implants

Impacted canines are a matter of concern in the treatment of malocclusion. After the third molars, maxillary canines are considered the most commonly impacted teeth with a frequency of 0.27% among Japanese and 2.4% among Italians. Unilateral impactions are more prevalent than bilateral impactions. The impacted canine can be detected with palpation, and radiographic techniques such as IOPA (Tube shift technique), panoramic radiographs, occlusal radiographs, and CT. The mesiodistal position and angulation of the canine crown on a panoramic radiograph can possibly predict treatment success. Various treatment approaches are considered depending on the mesiodistal angulation and position of the impacted canine. An auxiliary spring in the buccal region of the impacted canine designed by Kornhauser Et al has advantages such as avoidance of usage of palatal arches, and additional lab work such as soldering thereby incurring at least an extra clinical visit. This case report showcases the treatment of a 13-year-old growing male patient with a palatally impacted right maxillary canine using a Labial auxiliary spring and correction of molar relation using an Infra Zygomatic Crestal Implant.

A new method assessing predicted and achieved mandibular tooth movement in adults treated with clear aligners using CBCT and individual crown superimposition

The purpose of this study was to demonstrate a new method for quantifying the difference between predicted and achieved tooth movement with Invisalign using stable three-dimensional (3D) mandibular landmarks and dental superimposition. Cone-beam computed tomography (CBCT) scans before (T1) and after (T2) the first series of aligners, their corresponding digital models (ClinCheck initial of the first series as T1 and ClinCheck initial of the refinement series as T2), and the ClinCheck final model of the first series as the predicted were obtained from 5 patients treated with non-extraction Invisalign therapy. After segmentation of the mandible and its dentition, T1 and T2 CBCTs were superimposed on stable anatomic structures (Pogonion and bilateral mental foramen) along with the pre-registered ClinCheck models. The 3D prediction differences between the predicted and achieved tooth position for 70 teeth with four types (incisor, canine, premolar and molar) were measured using a combination of software. The method employed in this study was tested to be reliable and repeatable with a very high intraclass correlation coefficient (ICC) for both intra- and inter-examiner reliability. Premolar Phi (rotation), Incisor Psi (mesiodistal angulation), and Molar Y (mesiodistal translation) showed a significant prediction difference (P < 0.05), which is also clinically relevant. The method involving CBCT and individual crown superimposition to measure the 3D positional changes in the mandibular dentition is a robust and novel one. While, our finding in terms of the predictability of Invisalign treatment in the mandibular dentition mainly served as a crude, cursory examination, which warrants further and more rigorous investigations. With this novel methodology, it is possible to measure any amount of 3D tooth position difference in the mandibular dentition either between the simulated and the actual or with treatment and/or growth. Deliberate use of overcorrection of which specific type of tooth movement with clear aligner treatment and to what extent, might be possible with future studies.