Inclination Of Molars Research Articles

Evaluation of mesiodistal inclination of permanent maxillary and mandibular first molars in different Angle's molar relation: A cephalometric study

Introduction: Angle's molar relationship is the most widely used classification in spite of the introduction of various other classifications. At the end of the treatment, the molars are finished in a Class I, II, or III molar relation. Thus, it is important to know the ideal inclinations of upper and lower 1st molars, thereby assisting in achieving a stable relationship. Aims and Objectives: The aim and objective of this study was to evaluate the mesiodistal inclination of permanent maxillary and mandibular first molars in Angle's Class I, II, and III molar relationships in relation to the occlusal plane. Methodology: Lateral cephalograms of 16–30-year-old individuals with Class I, II, and III molar relations were selected and traced in Dolphin imaging software, and the angle between the first molar and occlusal plane was calculated. Results: There was a statistically significant difference in the inclination of maxillary 1st molar in between Class I and Class III. No significant difference was noted in the inclination of maxillary first molar in case of Class I and Class II. In case of mandibular molars, there was a statistically significant difference in case of Class I and Class II and between Class I and Class III. Conclusion: When the end molar relationship of a case is planned to be Class I, the upper molar should be at an angle of 84.12° to the occlusal plane. When the end molar relationship of a case is planned to be Class II, the upper molar should be 84.15° to the occlusal plane. When the end molar relationship of a case is planned to be Class III, the upper molar should be inclined at an angle of 87.07° to the occlusal plane.

Evaluation of buccolingual molar inclinations among different vertical facial types.

ObjectiveThe aim of this study was to compare the buccolingual inclination of maxillary and mandibular molars in adults with different vertical facial types.MethodsCone-beam computed tomography images of 135 adult patients (age, 20–45 years) with skeletal Class I maxillomandibular relationships were assigned to normodivergent (n = 46), hypodivergent (n = 49), and hyperdivergent groups (n = 40) according to linear and angular sella-nasion/gonion-menton measurements. The normodivergent group consisted of 24 females and 22 males, hypodivergent group of 26 females and 23 males, and hyperdivergent group of 24 females and 16 males. Buccolingual inclination of the maxillary and mandibular first and second molars was measured relative to the occlusal plane. One-way analysis of variance was used for intergroup comparison. Gender differences were evaluated using independent t-tests.ResultsBuccolingual molar inclinations did not differ significantly between females and males (p > 0.05). There were no statistically significant differences among the buccolingual inclinations of the first and second maxillary and mandibular molars of the groups (p > 0.05).ConclusionsBuccolingual inclinations of maxillary and mandibular molars are similar in normodivergent, hyperdivergent, and hypodivergent adults with Class I sagittal relationships.

Cone-beam computed tomography analysis of transverse dental compensation in patients with skeletal Class III malocclusion and facial asymmetry.

ObjectiveThe purpose of this study was to analyze the transverse dental compensation in reference to the maxillary and mandibular basal bones using cone-beam computed tomography (CBCT) and evaluate the correlations between transverse dental compensation and skeletal asymmetry variables in patients with skeletal Class III malocclusion and facial asymmetry.MethodsThirty patients with skeletal Class I (control group; 15 men, 15 women) and 30 patients with skeletal Class III with menton deviation (asymmetry group; 16 men, 14 women) were included. Skeletal and dental measurements were acquired from reconstructed CBCT images using OnDemand3D 1.0 software. All measurements were compared between groups and between the deviated and nondeviated sides of the asymmetry group. Correlation coefficients for the association between skeletal and dental measurements were calculated.ResultsDifferences in the ramus inclination (p < 0.001), maxillary canine and first molar inclinations (p < 0.001), and distances from the canine and first molar cusp tips to the midmaxillary or midmandibular planes (p < 0.01) between the right and left sides were significantly greater in the asymmetry group than in the control group. In the asymmetry group, the ramus inclination difference (p < 0.05) and mandibular canting (p < 0.05) were correlated with the amount of menton deviation. In addition, dental measurements were positively correlated with the amount of menton deviation (p < 0.05).ConclusionsTransverse dental compensation was correlated with the maxillary and mandibular asymmetry patterns. These results would be helpful in understanding the pattern of transverse dental compensation and planning surgical procedure for patients with skeletal Class III malocclusion and facial asymmetry.

Comparison of Rate of Canine Retraction and Anchorage Potential between Mini-implant and Conventional Molar Anchorage: An In vivo Study.

Aim:The aim of this study was to compare the rate of canine retraction, the anchorage loss, and the change in the inclination of the first molars between molar and mini-implant anchorage.Objective:(1) To compare the rate of canine retraction between conventional molar anchorage and mini-implant anchorage in the maxilla and mandible. (2) To compare the amount of anchor loss between mini-implant-anchored and molar-anchored sides during canine retraction in the maxilla and mandible.Materials and Methods:Ten patients were included in the study. The implants were loaded immediately by applying a force of 100 g. Measurements were made in the pre-retraction and post-retraction lateral cephalograms. A line drawn vertically from the sella-nasion plane through the distal pterygomaxillary point was used as a reference line.Results:The mean rates of canine retraction were 0.95 and 0.82 mm/month in maxilla on the implant and molar sides, respectively, and were 0.81 and 0.76 mm/month in mandible on the implant and molar sides, respectively. The mean anchorage loss was 0.1 mm on the implant side and 1.3 mm on the molar side of the maxilla and 0.06 mm on the implant side and 1.3 mm on the molar side of the mandible. The mean change in molar inclination was 0.3° on implant side and 2.45° on molar side of the maxilla and was 0.19° on implant side and 2.69° on molar side of the mandible.Conclusions:Implant anchorage is an efficient alternative to molar anchorage.

Orthodontic uprighting of severely impacted mandibular permanent second molar with TMA spring

Treating impacted teeth is very challenging for an orthodontist. Although canine impactions are common, second molar impactions are also encountered in orthodontics. The fate of impacted second molar depends on various factors such as the degree of its inclination and position of third molars. A case of molar uprighting using a 0.017″ × 0.025″ titanium molybdenum alloy uprighting spring is discussed in this case report. Treatment included surgical exposure and crown lengthening along with orthodontically assisted eruption.

Construction and assessment of a three-dimensional finite element model of mandibualr second molar mesialization using customized lingual appliance and mini-implant

Objective: To construct a three-dimensional (3D) finite element model and analyze the biomechanical characteristics during mandibular second molar mesialization using customized lingual appliances and mini-implant. Methods: One adult student volunteer from The First Affiliated Hospital of Zhengzhou University with lower left first molar extraction was selected. After CT scanning, Mimics, Geomagic, ANSYS were employed to develop a 3D finite element model including customized lingual brackets, stainless steel lingual arch wire, buccal buckles, lower dentition, periodontal ligaments and alveolar bone. Four different loading methods (1. the force of 1.470 N loaded at the lingual side only; 2, 3, 4. the forces of 0.490, 0.735 and 0.980 N loaded at both buccal and lingual sides, respectively.) were included. The initial displacements of the lower second molar and stress distribution in the periodontal ligaments were analyzed. Results: More uniform stress distributions in the periodontal membrane of mandibular left second molar were found when the mesial force were loaded at both buccal and lingual sides than the force loaded at lingual side only. More inclination of the second molar was observed when force loaded at both sides than at lingual side only. With the values of the force increased, the mesial inclination potential of the second molar, the initial movement of the second molar and the stress distribution in the periodontal membrane increased. Under the force of 0.735 N at both buccal and lingual sides, mesially inclined initial displacements of the mandibuar second molar were observed and the stress values of von Mises was in the suitable area. Conclusions: Less second molar rotation was found when the force loaded at both buccal and lingual sides than loaded at lingual side only. However, force loaded at both sides would increase the measial inclination potential of the second molar.

Three-dimensional evaluation of molar buccolingual inclinations after orthodontic treatment using edgewise mechanics.

The purpose of this study was to measure changes in buccolingual inclination and in thickness of maxillary and mandibular buccal and lingual bone of maxillary and mandibular molars following orthodontic treatment using edgewise mechanics. Cone-beam computed tomography scans of 48 patients taken before and after completion of comprehensive orthodontic treatment were collected for this retrospective study. Buccolingual molar inclinations were reported as angular measurements using the long axis of the teeth and inferior border of the nasal floor and inferior border of the mandible, respectively. Distances between the buccal and lingual cusps of maxillary and mandibular molars, respectively, were measured to the occlusal plane to assess the change in buccolingual inclination after orthodontic treatment. The amount of buccal and lingual bone at the level of the root apex of each molar was also evaluated before and after orthodontic treatment. Orthodontic edgewise mechanics caused significant increases in mandibular first molars' inclination angle, lingual bone, and mandibular second molars' buccal bone and inclination angle. Significant decreases were noted in mandibular first molars' buccal bone, inclination distance and mandibular second molars' lingual bone and inclination distance. Maxillary teeth had fewer significant changes than the mandibular teeth. Significant decreases were found for maxillary first molars' buccal bone, inclination distance, and maxillary second molar buccal bone.

Correction of Transverse Discrepancy with Slowly Maxillary Expansion by Hyrax type expander in Adult Patient

Approximately 30% of adult patients who want orthodontic treatment have transverse discrepancy with insufficient width of the maxilla. Particularly, in Class III patients requiring orthognathic surgery, the frequency of insufficient width of the maxillary arch related to respiratory problems is high. We report a case of non-surgical maxillary expansion using a Hyrax type expander with an orthognathic surgery, based on the reports that the ratio of non-fused midpalatal suture is not high in adults. A 30 years and 2 months old woman with a long face showed an Angle Class III with a vertical growth pattern. Class III molar and canine relation, anterior edge bite, and mandibular incisor compensatory lingual inclination were observed. The posterior buccal overjet seemed to be appropriate, but I diagnosed that there was a transverse discrepancy, for the following reasons. The inter-canine and inter-molar widths were sufficient but excessive lingual inclination of the mandibular molars was observed when assessing the bucco-lingual inclination based on the center of resistance of the maxillary and mandibular first molar. For this reason, it was expected that intercuspal interference would occur during orthodontic decompensation. Therefore, slow maxillary expansion using Hyrax type expander was performed and 2-jaw rotation surgery was performed to improve aesthetic and occlusion. Adults can also improve width discrepancy by non-surgical methods, which can avoid SARPE requiring additional surgery or segmental surgery lacking stability and predictability.

Relationship between molar occlusion and masticatory movement in lateral deviation of the mandible.

The relationship between molar occlusion and chewing patterns was examined in subjects with laterally deviated mandibles. Twenty-three patients with mandibular deviation from the midline (4mm or more) and skeletal Class I (0°≤ANB≤4°) were divided into 2 groups: normal bite and crossbite. The chewing pattern was classified as normal, reversed, or crossover. The normal bite group had a normal chewing pattern on the affected side 100% of the time and a reversed chewing pattern on the affected and unaffected sides 0% and 7.2% of the time, respectively. Additionally, the normal bite group showed no evidence of a crossover chewing pattern and also had significantly less axial inclination of the mandibular teeth on the affected side compared with the crossbite group; lingual inclination was also evident. The crossbite group had a normal chewing pattern on the affected and unaffected sides 0% and 55.6% of the time, respectively, and reversed and crossover chewing patterns on the affected side 55.6% and 44.4% of the time, respectively. A normal chewing pattern tends to result in lingual axial inclination of the mandibular molars on the affected side, as well as a more consistent chewing pattern.

Changes in the buccolingual inclination of first molars with growth in untreated subjects: A longitudinal study

To assess longitudinal changes in the buccolingual inclination of the maxillary and mandibular first molars in untreated male and female subjects. Forty-seven male and 48 female subjects whose longitudinal dental casts were available at ages 6-16 years, with normal maxillary and mandibular arch forms were included. The original casts at ages 6, 7, 8, 9, 10, 12, 14, and 16 years were digitized and standardized. Measurements were recorded as the differences in cusp heights in the vertical dimension for the mandibular and maxillary first molars using OrthoInsight software. On average, for boys from age 6 to 16 years, both maxillary and mandibular first molars uprighted with age. Maxillary molars uprighted 0.403 mm on the left and 0.418 mm on the right; mandibular molars uprighted 0.441 mm on the left and 0.589 mm on the right. Similarly, for girls from age 6 to 16, both maxillary and mandibular molars uprighted with age. Maxillary molars uprighted 0.67 mm on the left and 0.574 mm on the right; mandibular molars uprighted 0.358 mm on the left and 0.329 mm on the right. Maxillary molars erupted with buccal crown inclination at age 6 in both boys and girls and uprighted lingually with growth. At age 16, maxillary molars were not completely upright but rather maintained some buccal crown inclination. Mandibular molars erupted with lingual crown inclination at age 6 and uprighted buccally with age. At age 16, mandibular molars were not completely upright but rather maintained some lingual inclination.

Buccolingual angulation and intermolar width changes in the maxillary first molars of untreated growing children.

Buccolingual inclinations of the maxillary permanent molars and intermolar widths increase with growth for Class I subjects. Changes for untreated Class II subjects have not yet been assessed. The aim of this study was to test the hypothesis that changes in palatal inclination of the maxillary molars and intermolar width throughout growth vary between Class I and Class II molar occlusions. Patients were selected from the Forsyth/Moorrees Twin Study. Dental models taken for 6 consecutive years of 55 untreated subjects (28 with Angle Class I and 27 with Angle Class II occlusion) were scanned. The images were superimposed on the palatal rugae, and the angle between a reference plane and the buccolingual inclination plane was used to calculate the buccolingual molar inclination at each time point. The distance between lingual groove points was used to calculate the intermolar width. All molars showed increasing palatal inclinations over the 6years. The change for each time interval was statistically significant. Class I subjects demonstrated significantly greater palatal inclination at each time point. The molar inclination changed by means of 4.99° for Class I subjects and 6.25° for Class II subjects. Intermolar width increased continuously (P<0.001) and was significantly greater (P<0.05) for Class I patients. These results suggest that palatal inclination of the maxillary permanent first molars occurs continuously between ages 9 and 14years, with Class II subjects showing greater changes. The intermolar width increases steadily during this time, with Class II subjects having a narrower intermolar width and less change over time.

Buccolingual inclination of the mandibular second molars with different anteroposterior skeletal patterns in cone-beam computed tomography

PurposeThe purpose of this study was to evaluate the buccolingual inclination of second mandibular molars between groups with varying sagittal skeletal relationship of maxilla and mandible using cone-beam computed tomography (CBCT). Materials and methodsThe sample consisted of 90 adult non-orthodontic treatment patients' CBCT images. They were divided into 3 groups according to sagittal skeletal pattern using Wits appraisal, which were skeletal Class I (13 men and 17 women), skeletal Class II (17 men and 13 women) and skeletal Class III (13 men and 17 women) with an average age of 37.6 years. All subjects had a normal vertical skeletal pattern and had mandibular deviation less than 3mm. Buccolingual inclination was measured in a radiographic software as the angle between the long axis of lower second molars and a reference line tangent to the lower border of the mandibular body. ResultsThere was a statistically significant difference of second mandibular molar buccolingual inclination between the three groups (p=0.000), with a decreasing trend of the inclination angle from skeletal Class II to skeletal Class III. Wits appraisal had a moderate positive correlation with mandibular second molar buccolingual inclination (R=0.648). ConclusionPretreatment patients with different sagittal skeletal patterns have different buccolingual inclination of mandibular molars. These results might affect the preparation of orthodontic appliances or treatment technique.

Buccolingual inclination of first molars in untreated adults: A CBCT study.

To evaluate the buccolingual inclinations of maxillary and mandibular first molars in untreated adults. Fifty-nine subjects (14 males and 45 females; mean age, 41.2 years) with no missing teeth, no crossbite, and minimal crowding were included. For each subject, a CBCT was taken. The long axis of each first molar was determined, and the inclination of each molar was measured using the long axis and the floor. One hundred seventeen out of 118 mandibular first molars measured had a lingual inclination, with a mean of 12.59° ± 5.47°. For the maxillary first molars, 107 out of 118 had a buccal inclination, with a mean of 4.85° ± 4.22°. There is a curvature to the inclinations of first molars in untreated adults, where the maxillary molars have a slight buccal inclination and mandibular molars have a slight lingual inclination.

Orthodontic treatment results evaluated for individual teeth according to the Objective Grading System

BackgroundThe evaluation of orthodontic treatment outcome is usually performed using the Objective Grading System (OGS) developed by the American Board of Orthodontics (ABO). The objective of this study was to evaluate individual tooth contribution to the final OGS score in patients who have finished the orthodontic treatment at the graduate program at Antioquia University. MethodDescriptive, retrospective, cross-sectional study of 40 nonrandomly selected patients. Using the eight OGS criteria, each tooth characteristic was evaluated. ResultsThe total average OGS score was 30.7 ± 8.0. The variable giving the lowest score was for interproximal spaces and the higher was for buccolingual inclination (5.4 ± 2.7). For teeth groups, there are significant differences (P < 0.05). The major contributors to the final score were second molar teeth (9.9 ± 3.7) and per individual tooth was the upper right second molar for buccolingual inclination and marginal ridges (2.73 ± 1.2). There is no correlation between OGS variables except for upper central incisor scores. ConclusionsSecond molar teeth are the main contributors to OGS final score, specifically right second molar inclination. Interproximal spaces are the least relevant aspects to the score. Knowledge of differential tooth and variable contribution is useful to the clinician's care of relevant details.

Correlation Between Transverse Maxillary Discrepancy And The Inclination Of First Permanent Molars. A Pilot Study

Introduction: the development and growth of craniofacial structures allow some dental alterations to be compensated with maxillary reactions. The purpose of this study was to correlate transversal maxillo-mandibular discrepancy with the bucco-lingual inclinations of first permanent maxillary and mandibular molars in a population aged 10 to 16 years, by means of cone beam computed tomography (CBCT). Methods: the sample included 18 CT scans of patients selected by convenience, prior authorization from the radiographic center and with validation of the Bioethics Committee of Universidad Autonoma de Manizales (Agreement No. 51, 2015). The transverse mandibular and maxillary distance was measured, calculating discrepancy and correlating with the bucco-lingual inclination of first permanent molars. Results: average mandibular transverse distance was higher than maxillary transverse distance (p 5 o ) and the inclination of molars (p < 0.05). There was also moderate correlation in patients with negative maxillary discrepancy (< 5 o ). Conclusion: transverse maxillomandibular discrepancy is related to the bucco-lingual inclination of first permanent maxillary and mandibular molars in two different ways according to discrepancy type—positive or negative—. The reaction of the maxillary is a process that requires more studies to understand the timing and extent of the adaptation

Differences and similarities of third molar impaction in the mandible and in the maxilla

Aims: Characteristics of erupted and impacted third molars in the mandible and the maxilla were compared. Materials and Methods: A total of 400 individuals over the age of 20 were included. The eruption status of the third molars in both jaws were examined on orthopantomographs by measuring the distance from the line tangent to the highest points of occlusal cusps of the third molar to that of the adjacent second molar. The presence of available space for the eruption was determined by the ratio of the mesiodistal length of the third molar crown to the length of the alveolar arch distal to second molars. The angle formed between the intersected lines tangential to the highest points of occlusal cusps of the second and third molars were used to measure the degree of third molar inclination. The analysis of variance and Student's t-tests were performed to determine the differences between each class structured according to parameters related to third molars. A Pearson correlation test was performed to determine any correlation between parameters. Results: In the mandible available space for the eruption of third molars was smaller, and the mesiodistal lengths of the third molars were longer as opposed to their maxillary counterparts. In both jaws, vertical position was the most frequent inclination both in the impacted and erupted states. On the other hand, even in the presence of favorable parameters for eruption (teeth having both vertical orientation and sufficient eruption space), 26.7% of mandibular and 59.2% of maxillary third molars had a chance to fully erupt. The presence of favorable parameters does not warrant full eruption of third molars in both jaws. Conclusions: We considered the age of 20 as the stable time point for the eruption and angulation movements of the third molars and therefore included subjects older than 20 years of age in the present study. Likewise, the absence of favorable parameters does not always lead to third molar impaction.

Cone-beam computed tomographic evaluation of the temporomandibular joint and dental characteristics of patients with Class II subdivision malocclusion and asymmetry.

ObjectiveTreating Class II subdivision malocclusion with asymmetry has been a challenge for orthodontists because of the complicated characteristics of asymmetry. This study aimed to explore the characteristics of dental and skeletal asymmetry in Class II subdivision malocclusion, and to assess the relationship between the condyle-glenoid fossa and first molar.MethodsCone-beam computed tomographic images of 32 patients with Class II subdivision malocclusion were three-dimensionally reconstructed using the Mimics software. Forty-five anatomic landmarks on the reconstructed structures were selected and 27 linear and angular measurements were performed. Paired-samples t-tests were used to compare the average differences between the Class I and Class II sides; Pearson correlation coefficient (r) was used for analyzing the linear association.ResultsThe faciolingual crown angulation of the mandibular first molar (p < 0.05), sagittal position of the maxillary and mandibular first molars (p < 0.01), condylar head height (p < 0.01), condylar process height (p < 0.05), and angle of the posterior wall of the articular tubercle and coronal position of the glenoid fossa (p < 0.01) were significantly different between the two sides. The morphology and position of the condyle-glenoid fossa significantly correlated with the three-dimensional changes in the first molar.ConclusionsAsymmetry in the sagittal position of the maxillary and mandibular first molars between the two sides and significant lingual inclination of the mandibular first molar on the Class II side were the dental characteristics of Class II subdivision malocclusion. Condylar morphology and glenoid fossa position asymmetries were the major components of skeletal asymmetry and were well correlated with the three-dimensional position of the first molar.

Stability of dental, alveolar, and skeletal changes after miniscrew-assisted rapid palatal expansion.

ObjectiveMiniscrew-assisted rapid palatal expansion (MARPE) is a means for expanding the basal bone without surgical intervention in young adults. Here, we assessed the differences in dental, alveolar, and skeletal measurements taken before (T0), immediately after (T1), and 1 year after (T2) MARPE.MethodsTwenty-four patients (mean age, 21.6 years) who had undergone MARPE and cone-beam computed tomography at T0, T1, and T2 were included. Changes in the following parameters were compared using paired t-tests: intercusp, interapex, alveolar, nasal floor, and nasal cavity widths; inclination of the first molar (M1) and its alveolus; and thickness and height of the alveolar bone. A linear mixed-effects model was used to determine variables that affected periodontal changes in the M1.ResultsMARPE produced significant increases in most measurements during T0–T2, despite relapse of some measurements during T1–T2. The alveolar thickness decreased on the buccal side, but increased on the palatal side. The alveolar crest level at the first premolar moved apically. Changes in the thickness and height of the alveolar bone were affected by the corresponding initial values.ConclusionsMARPE can be used as an effective tool for correcting maxillomandibular transverse discrepancy, showing stable outcomes 1 year after expansion.

Modified posterior bite block for scissor bite correction

Scissor bite or complete buccal crossbite can be limited to a single tooth or group of teeth. It is most commonly seen with second molars. Treatment modalities to correct the buccal inclination of maxillary second molar along with lingual inclination of mandibular molar is limited to use of cross-elastics or recently, use of micro-implants. Present case describes a simple method to correct such single tooth scissor bite with minimal side effect of extrusion and no need of any surgical intervention.

How effective is the Invisalign® system in expansion movement with Ex30' aligners?

The aims of this study are to validate a new method for quantifying the predictability of expansion movement with the Invisalign® system and to determine whether there are statistically significant differences between planned expansion with ClinCheck® and actual clinical quantification using upper post-treatment model comparisons. A sample of 116 patients subjected to expansion with Invisalign® was studied. The following variables were measured at T1 and T2 on 3D models and ClinCheck®: canine gingival width, first premolar gingival width, second premolar gingival width, first molar gingival width, canine cuspid width, first premolar cuspid width, second premolar cuspid width, first molar cuspid width, canine depth, arch depth, first molar rotation, first right and left molar rotation, and first molar inclination. Measurement error was tested, showing good precision for all variables. The paired test showed non-significant differences between the 3D model and ClinCheck® at T1 for all variables except first molar cuspid width and arch depth. Statistically significant differences were found for canine gingival width, first premolar gingival width, second premolar gingival width, first molar gingival width, canine cuspid width, first premolar cuspid width, second premolar cuspid width, first molar cuspid width, and canine depth when the 3D model and ClinCheck® were compared at T2. Differences between the 3D model and ClinCheck® at T2 showed that planned expansion at the end of treatment is not predictable. This is the first in vivo human study to quantify the predictability of expansion in patients with Invisalign® Ex30 material.