Wilson maxillary curve analyzed by CBCT. A study on normocclusion and malocclusion individuals

Digital analysis of the relationship between maximum bite force and 3-dimensional arrangement of mandibular first molars

Background

Bite force is one of the important factors that determine the chewing efficiency of molars. This study aimed to investigate the relationship of the maximum bite force (MBF) to the 3-dimensional (3D) arrangement of the first mandibular molars in Angle's class I healthy adults using a digital protocol.

Material and Methods

Subjects were 33 adults (16 males and 17 females) aged 18-25, with Angle's class I occlusions and healthy dentitions. MBF was recorded by a digital occlusal force gauge (BFM 4th generation, Vietnam). 3D models were scanned using TRIOS 3 intra-oral scanner (3Shape, Denmark), and analyzed using Geomagic Design X software (Artec, Luxembourg). The digital measurement included two steps: reorientation and measuring. First, all the virtual upper models were reoriented into the same Oxyz coordinates using 3 landmarks: one at the incisive papilla and two at the intersection of the palatal sulci of the first permanent molars with the gingival margin. Next, 3D position of the first mandibular molars was measured using crown angulation (CA), crown inclination (CI), and depth of curve of Spee (DCOS). t-tests were conducted to compare the mean values between sides and gender. Pearson's correlation coefficient was performed to evaluate the statistical relationships.

Results

Mean MBF was 619.66±36.25 N; mean DCOS was 1.73±0.30 mm; mean CA and CI were 2.21±1.70° and -29.65±6.93°, respectively. Male adults showed greater MBF than females significantly. Correlation coefficient between MBF and CA was -0.60, and between MBF and CI was -0.43 significantly. MBF and DCOS were not related.

Conclusions

MBF was influenced by gender and the first mandibular molar CA and CI. Hence, it should be considered carefully when the treatment plan includes restoration or any change in the position of the first mandibular molars. Key words:Bite force, curve of Spee, crown angulation, crown inclination, digital dentistry.

Comparative evaluation and co-relation in variation of curve of Spee and curve of Wilson in Class II div. 1, Class II div. 2, and Class III as against Class I malocclusion in central India population- an in vitro study

Introduction

Getting acceptable cosmetic results in the soft tissues of the face serves as the foundation for orthodontic treatment planning. Also, in order to achieve healthy static and dynamic occlusal interactions, the teeth must be positioned within the basal bone at the correct position, angle, and inclination. To avoid periodontal issues, provide stability, and achieve a functional occlusion, it is essential to ascertain the individual's dental arch form before starting of treatment and thus to utilise the mechanics that follow throughout the treatment.

Objectives

To evaluate and compare variation in Curve of Spee and Curve of Wilson in Class II Div.-1, Class II-Div-2 and Class-III as against Class I malocclusion in central India population.

Methodology

Irreversible hydrocolloid impression will be taken with perforated metal stock trays and stone cast will be poured. This will be scanned using CAD CAM machine and curve of Spee and Wilson will be measured using reverse engineering.

Expected Result

It will assist us in treatment planning for preventing periodontal issues, assuring stability, and achieving functional occlusion by evaluating and comparing the Spee and Wilson curves in Class II Divison-1, Class II Divison-2, and Class-III malocclusion with Class-I malocclusion.

Conclusion

Every single patient receiving orthodontic treatment has the COS, which is crucial to achieving a stable occlusion. Almost every patient who receives orthodontic treatment eventually experiences the Spee Curve. Since there aren't many studies examining the relationship between the Curves of Spee and Wilson, their impact on dentoskeletal morphology, and their role in occlusal stability.

Invisible treatment with lingual appliance for the correction of an adult class II subdivision with asymmetrical Wilson and Spee curves: A case report

This article describes a class II subdivision malocclusion successfully treated by an invisible lingual appliance. The combination of en-masse distalization by interradicular palatal mini-screws and inner unilateral class II auxiliaries, first by intermaxillary elastic, later by a class II coil spring, resulted in a dento-alveolar correction, allowing one to maintain the appliance completely invisible. At the same time, the inclination of buccal sectors was normalized by a correct torque expression with set-up overcorrections, resulting in a significant improvement of the buccal corridors. This case report demonstrates the possibility of successfully solving class II division 2 subdivision malocclusion in adult patients without surgery by means of a completely invisible appliance. It also demonstrates that correct levelling and torque expression, for the correction of asymmetrical Spee and Wilson curves, are achievable with an accurate set-up planning. On the other hand, it underlines the necessity of mini-screws, auxiliaries and set-up overcorrections in order to obtain the best results.

Three-dimensional radiographic assessment of immediate implant placement in the posterior mandible: A novel parameter-based classification

OBJECTIVES

To assess the implant position (IP), the interradicular septum width (ISW) and radiographic bone to implant contact (BIC), when simulating an immediate implant placement in first and second mandibular molars.

STUDY DESIGN

75 patients (150 sites) were studied using cone beam computed tomography scans (CBCT) and computer aided design software. Implants were placed in a prosthetically driven position; subsequently, IP and BIC were digitally calculated. Linear ISW was also analyzed at 2, 4 and 6mm apically to the highest septal bony peak. Multiple linear regressions were performed to assess relationships between BIC and the different predictive variables. Additionally, the receiver operating characteristics (ROC) curve was used to create a model for BIC based on the ISW at 2mm.

RESULTS

BIC in implants replacing first molars was the highest at the septal (S) position when compared to those in septal-mesial (S-M) position (p-value 0.001). As for the second molar, the highest percentage of BIC was recorded at the septal (S) position, followed by those in S-M and mesial (M) positions (p<0.001).

CONCLUSION

According to the proposed classification, clinician must consider the ISW and IP when placing immediate implant in the first and second mandibular molar sites. When tackling first molars, S position is predominant, while S-M position is the most common in the second molars. ISW at 2mm should be at least respectively 2mm and 2.5mm at the first and second molar sites to achieve 50% of BIC.

The predictability of the mandibular curve of Wilson, buccolingual crown inclination, and transverse expansion expression with Invisalign treatment

INTRODUCTION

This study aimed to provide an initial investigation into the mandibular curve of Wilson (COW) handling using the Invisalign appliance (Align Technology, Santa Clara, Calif). Individual buccolingual crown inclinations and transverse expansions were also investigated to detect any regions of ineffectiveness in the dental arch.

METHODS

A retrospective sample of patients treated by an experienced Invisalign provider in private practice was used. All adult patients with Class I or II Angle malocclusions and mild to moderate crowding treated using a minimum of 14 Invisalign aligners without intermaxillary elastics, bite ramps, or auxiliaries and a nonextraction mandibular arch from 2013-2019 were selected. Dental models at the initial scan, the ClinCheck prediction, and the outcome after the initial series of aligners were analyzed with Geomagic Control X software (version 2017.0.3; 3D systems, Rock Hill, SC). The COW, buccolingual crown inclination relative to the occlusal plane and cusp tip expansion were compared between ClinCheck changes and achieved changes.

RESULTS

Forty-two subjects met the selection criteria. 74% of subjects experienced a flatter COW than ClinCheck predictions, and the mean difference was 0.76 mm (P = 0.0149). The first molars encountered 0.52 mm (P <0.001) more buccal crown inclination than ClinCheck predictions. No other teeth experienced statistically significant buccolingual inclination differences to ClinCheck. The second molars were the only teeth to experience significantly more arch expansion than ClinCheck at 0.68 mm (P = 0.0046).

CONCLUSIONS

The Invisalign appliance tended to over-flatten the mandibular COW compared with ClinCheck because of the lack of buccal root torque in the mandibular first molars during expansion. The mandibular second molars were the only teeth to experience more expansion than ClinCheck.

Buccolingual Inclination of Second Molars in Untreated Adolescents and Adults with Near Normal Occlusion: A CBCT Study

The mandibular second molars are lingually positioned relative to the alveolar ridge and have a limited amount of lingual alveolar bony support. As the maxillary second molars are articulated with the mandibular second molars, maintaining the normal buccolingual inclination of both maxillary and mandibular second molars would potentially help to not only optimize the masticatory function, but also avoid dehiscence and fenestration. The current study evaluated the buccolingual inclination of second molars in untreated adolescents and adults. One hundred and two Caucasian subjects with skeletal class I and minimum dental arch crowding/spacing were selected and divided into two groups: (1) adolescent group: age 12-18 years, N = 51 (21 females, 30 males); (2) adult group: age 19-65 years, N = 51 (40 females, 11 males). For each subject, the inclination for each second molar was measured as the angle between the long axis of each tooth and a vertical line on cone beam computed tomography images. The Mann-Whitney U test was used for intergroup comparisons. Maxillary second molars exhibited a buccal inclination of 15.30° in the adolescent group and 15.70° in the adult group. Mandibular second molars exhibited a lingual inclination of 17.05° in the adolescent group and 15.20° in the adult group. No statistically significant differences were detected between the age groups. In addition, a statistically significant difference was only found between genders in the adolescent group for the maxillary second molar inclination. In summary, maxillary second molars exhibited buccal inclination and mandibular second molars exhibited lingual inclination. The amount of buccolingual inclination of the second molars was similar in the adolescent and adult groups.

Transverse Analysis of Maxilla and Mandible in Adults with Normal Occlusion: A Cone Beam Computed Tomography Study

Objectives: To study the transverse widths of maxilla and mandible and their relationship with the inclination of first molars. Materials and Methods: Fifty-six untreated adults (12 males, 44 females) with normal occlusion were included. On each Cone Beam Computed Tomography (CBCT) image of the subject, inter-buccal and inter-lingual bone widths were measured at the levels of hard palate, alveolar crest and furcation of the first molars, and maxillomandibular width differentials were calculated. In addition, the buccolingual inclination of each first molar was measured and its correlation with the maxillomandibular width differential was tested. Results: At the furcation level of the first molar, the maxillary inter-buccal bone width was more than the mandibular inter-buccal bone width by 1.1 ± 4.5 mm for males and 1.6 ± 2.9 mm for females; the mandibular inter-lingual bone width was more than the maxillary inter-lingual bone width by 1.3 ± 3.6 mm for males and 0.3 ± 3.2 mm for females. For females, there was a negative correlation between the maxillomandibular inter-lingual bone differential and maxillary first molar buccal inclination (p < 0.05), and a positive correlation between the maxillomandibular inter-lingual bone differential and mandibular first molar lingual inclination (p < 0.05). Conclusions: This is a randomized clinical study on transverse analysis of maxilla and mandible in adults with normal occlusion using CBCTs. On average: (1) At the furcation level of the first molars, the maxillary inter-buccal bone width was slightly wider than mandibular inter-buccal bone width; whereas the mandibular inter-lingual bone width was slightly wider than maxillary inter-lingual bone width; (2) A statistically significant correlation existed between the maxillomandibular transverse skeletal differentials and molar inclinations.

Standard orthodontic treatment after condylectomy for patients with active unilateral condylar hyperplasia

INTRODUCTION

Unilateral condylar hyperplasia (UCH) is a progressive, nonneoplastic overgrowth of the condyle of the temporomandibular joint. For treating active UCH, a popular method combines orthognathic surgery with high condylectomy and orthodontic treatment. The goal of this study was to introduce a new method to correct asymmetry for active UCH.

METHODS

Retrospectively, 47 patients with active UCH were divided into horizontal-type, vertical-type, and combined-type. All patients were treated with condylectomy plus postsurgery standard orthodontics (CPSO) with applied miniscrews implanted in infrazygomatic crest and hard palate to intrude affected side of maxillary molars and apply intermaxillary traction for contralateral molars. Cone-beam computed tomography was taken at presurgery, postsurgery, and the end of orthodontics (T3).

RESULTS

In the vertical (n = 10) and combined (n = 28) types, deviation of the chin and the canting of the mandible and maxillary occlusal plane were significantly reduced at T3. A difference in the torque of bilateral maxillary first molar (U6) and bilateral mandibular first molar (L6) was significantly reduced at T3. The anterior, superior, and posterior joint spaces in the vertical-type and combined-type were significantly decreased at T3 compared with postsurgery. In contrast, in the horizontal-type group (n = 9), the deviation of the chin was corrected; however, the canting of the mandible and maxillary occlusal plane was significantly increased at T3 compared with presurgery.

CONCLUSIONS

CPSO restored facial and occlusal symmetry for vertical-type and combined-type active UCH and returned affected-side condyle to the glenoid fossa. However, CPSO was not suitable for treating the horizontal-type UCH.

Effect of treatment of transverse maxillary deficiency using rapid palatal expansion on oral health-related quality of life in children: A randomized controlled trial

INTRODUCTION

This trial aimed to longitudinally evaluate the effect of the treatment of transverse maxillary deficiency using rapid palatal expansion (RPE) on self-perceived oral health-related quality of life (OHRQOL) in children.

METHODS

Eighty participants aged 8-10 years with transverse maxillary deficiency and bilateral posterior crossbite were randomly assigned to 2 groups (n = 40 each): a group treated with RPE using hyrax-type appliances and a nontreated control group. OHRQOL was assessed by using the Child Perceptions Questionnaire for 8-10-year-olds at 4 times: before RPE, during RPE (T₁), at the end of RPE (T₂), and 1 month after the appliance removal (T₃). Generalized mixed models were used for data analysis (α = 0.05).

RESULTS

Both groups exhibited similar demographic characteristics and OHRQOL scores at baseline. All participants completed the study. RPE had a time-dependent effect on OHRQOL. At T₁ and T₂, this therapy is expected to increase the overall OHRQOL scores by 1.17 times (ie, ∼17% increase; T₁ 95% confidence interval [CI], 1.08-1.26; T₂ 95% CI, 1.09-1.27; P = 0.001). In contrast, the overall OHRQOL scores at T₃ are expected to be 0.28 times the baseline scores (ie, ∼72% reduction; T₃ 95% CI, 0.26-0.31; P = 0.001). All individual domains of the OHRQOL evidenced a positive impact of treatment at T₃ (P = 0.001). Only the oral symptoms and social well-being domains showed a significantly negative impact of the treatment at T₁ and T₂.

CONCLUSIONS

Correction of the transverse maxillary deficiency by RPE in children aged 8-10 years improves OHRQOL. There is a temporary worsening of OHRQOL during the treatment of this condition using RPE.

REGISTRATION

This trial was not registered.

PROTOCOL

The protocol was not published before trial commencement.

FUNDING

This study was financed by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brazil, Financing Code 001.

Genetic influence on the curves of occlusion in children seeking orthodontic treatment

OBJECTIVE

To examine the proportion of variability in the Curve of Wilson (COW) and the Curve of Spee (COS) that is explained by genetic factors in siblings seeking orthodontic treatment.

MATERIALS AND METHODS

Pre-treatment cone-beam computed tomography (CBCT) of 148 sibling patients were selected. The sample consisted of 79 females and 69 males with a mean age of 12 years 7 months. The COS was measured by creating a tangent line from the distobuccal cusp of the mandibular first molars and the highest incisal tip of the mandibular incisors. Measurements were taken from that tangent line to the deepest point on the premolars and canines. The COW was measured using the molar axis line to the perpendicular to WALA (Will Andrews Lawrence Andrews) points' axis line.

RESULTS

The results indicate that these occlusal curves are generally moderate to highly heritable. Heritability of COW-maxilla was 78.3%, heritability of COW-mandible was 43.2% and heritability of COS was 100% (P-value<0.05).

CONCLUSIONS

Most of the developmental variability in the curves of occlusion comes from genetic differences, with very little contribution from environmental factors. Therefore, siblings tend to show similar occlusal curves.

In situ observations on the dentition and oral cavity of the Neanderthal skeleton from Altamura (Italy)

The Neanderthal specimen from Lamalunga Cave, near Altamura (Apulia, Italy), was discovered during a speleological survey in 1993. The specimen is one of the most complete fossil hominins in Europe and its state of preservation is exceptional, although it is stuck in calcareous concretions and the bones are mostly covered by calcite depositions. Nevertheless, it is possible to carry out some observations on craniodental features that have not previously been described. In this work, we present an account of the oral cavity, made possible by the use of a videoscope, which allowed us to reach some hidden parts of the mandible and palate. This is the first detailed overview of the teeth and maxillary bones of the Neanderthal skeleton from Altamura. The dentition is almost complete. However, two teeth (upper right P3 and upper left M1) were lost ante mortem and four teeth (lower right I1 and P3 and lower left I1 and I2) were lost most probably post mortem. Dental wear is marked. The erupted M3s and the inversion of the compensating curve of Wilson in the M1s and M2s but not in the M3s suggest that the individual is fully adult, but not old. Although most of the teeth have their roots exposed for several millimeters, the periodontal bone appears to be in good condition overall, except in correspondence of the two ante-mortem tooth losses. X-rays of the anterior teeth show a periapical lesion, probably linked to the advanced dental wear. We also observed a weak expression of taurodontism in the posterior dentition and the presence of a retromolar space, features consistent with an attribution to the Neanderthal hypodigm; this attribution is also supported by aspects of the cranial morphology, the morphometric analysis of the scapula and preliminary mtDNA data. There is also a well-developed palatine torus, to the best of our knowledge a feature not previously described in Neanderthals.

Can palatal depth influence the buccolingual inclination of molars? A cone beam computed tomography-based retrospective evaluation

Objective:

To interpret a correlation between buccolingual inclination of molars and palatal depth in hyperdivergent patients and to identify importance of determining inclination of molars in assessing transverse discrepancies (as skeletal or dental)

Design:

This was a retrospective cone beam computed tomography (CBCT) study.

Setting:

The study was conducted in the Department of Orthodontics, Saveetha Dental College and Hospital, Tamil Nadu, India.

Methods:

This was a retrospective CBCT study of 79 patients who underwent diagnostic CBCT for treatment purposes. The CBCT scans were evaluated systematically and the required parameters were accessed with suitable reference planes. Student’s t-test (95% confidence interval) was performed to determine buccolingual inclination of first molars between the right and left sides. Only patients with a vertical growth pattern and skeletal class I relation were included and they were classified into three groups based on their palate depth.

Results:

In patients with palatal depth > 22 mm, the mean inclination of molars was 7.4°; with palatal depth in the range of 19–22 mm, the mean inclination of molars was 5.23°; and with palatal depth < 19 mm, the mean inclination of molars was 2.9°. Results showed that there was a significant correlation between the buccolingual inclination of molars and the palate depth in vertical growers ( P < 0.05).

Conclusion:

The buccolingual inclination of first molars is increased in patients with greater palatal depth. This parameter is helpful in classifying crossbites as skeletal or dental. The amount of compensation required to correct the cross bite can be adjusted using Korkhaus Index.

Buccolingual Inclination of Canine and First and Second Molar Teeth and the Curve of Wilson in Different Sagittal Skeletal Patterns of Adults Using Cone-Beam Computed Tomography

Objectives

This study aimed to assess the buccolingual inclination of canine and first and second molar teeth and the curve of Wilson in different sagittal skeletal patterns in untreated adults using cone-beam computed tomography (CBCT).

Materials and Methods

Sixty-six CBCT scans of adults (mean age: 28.74 ± 5.25 years) were evaluated in this cross-sectional study. The images were standardized using the Frankfurt horizontal plane and the interorbital line. The sagittal skeletal pattern was determined using the ANB angle and Wits appraisal. Inclination angles were measured by NNT Viewer and Mimics software. The curve of Wilson was measured by connecting the tips of mesiobuccal and mesiolingual cusps of maxillary first and second molars along the buccal groove and measuring the formed angle. Data were analyzed using ANOVA.

Results

The intraobserver agreement was 0.969. The mean inclination of maxillary first and second molars in class I and III patients was significantly higher than that in class II patients (P < 0.05). The mean inclination of mandibular first and second molars in class II patients was significantly higher than that in class I and III patients (P < 0.05). The difference in inclination of maxillary and mandibular canine teeth was not significant (P > 0.05). The mean curve of Wilson in second molars of class II patients was significantly higher than that in class I patients (P < 0.05).

Conclusion

In different sagittal skeletal patterns, a compensatory relationship exists between the opposing teeth, which, along with the standards of crowns, can be used to determine the appropriate position of teeth in dental arch.

Quad-helix compression to decompensate molar inclination prior to skeletal expansion

OBJECTIVES

To demonstrate that patients without posterior crossbite (PCB) but with maxillary transverse deficiency, not previously observed due to an increased curve of Wilson, can benefit from the same palatal expansion as patients with PCB, after correction of the buccal inclination.

MATERIALS AND METHODS

A total of 41 patients presenting a maxillary skeletal transverse deficiency were treated: 26 without PCB and 15 with PCB. In the non-PCB group, quad-helix compression was followed by a Hyrax expander (QH+HY), whereas the PCB group only underwent Hyrax expander treatment (HY). The maxillary intercanine, interpremolar, intermolar widths (cusp tips and gingival level) and molar inclination were measured at baseline and at the end of treatment in both groups.

RESULTS

No significant differences were found between groups at the end of treatment, and no PCBs remained. The same maxillary expansion was achieved in the QH+HY and HY groups in the region of the canines, at both the gingival (3.4 ± 2.0 vs. 3.4 ± 2.7 mm; P = 0.999) and cusp tip levels (4.5 ± 3.1 vs. 3.8 ± 2.2 mm; P = 0.981). The molar inclination in the QH+HY group decreased, while there was a slight increase in the HY group (-6.50° ± 5.34° vs. 2.3° ± 4.1°; P < 0.001).

CONCLUSIONS

Some patients with maxillary transverse deficiency do not present with PCB, due to an increased curve of Wilson. However, these patients require skeletal expansion similar to that of patients with a bilateral PCB. The curve of Wilson should be flattened prior to expansion in order to increase the amount of maxillary skeletal expansion.

Buccolingual inclination of molars in untreated children and adults: A cone beam computed tomography study

OBJECTIVES

To evaluate and compare the buccolingual inclinations of maxillary and mandibular first molars in untreated children and adults.

MATERIALS AND METHODS

One hundred and thirty-eight subjects were selected and divided into three groups, as follows: (1) age 6-9 years, N = 46; (2) age 10-19 years, N = 56; and (3) age 25-35 years, N = 36. For each subject, existing cone beam computed tomography images were used, and the long axis for each maxillary and mandibular first molar was determined. The converge angles formed by the long axis of left and right maxillary first molars and by the long axis of left and right mandibular first molars were measured.

RESULTS

The maxillary molars exhibited buccal inclination, with the converge angle of 21.1° ± 9.5° in group 1, 17.3° ± 8.6° in group 2, and 9.3° ± 7.3° in group 3. Statistically significant differences were found between groups 1 and 3 and groups 2 and 3, but not between groups 1 and 2. The mandibular molars exhibited lingual inclination, with the converge angle of 34.9° ± 11° for group 1, 26.6° ± 9.2° for group 2, and 26.1° ± 7.7° for group 3. Statistically significant differences were found between groups 1 and 2 and groups 1 and 3, but not between groups 2 and 3.

CONCLUSIONS

Maxillary first molars exhibited buccal inclination. Adults displayed less inclination than did children. Mandibular first molars exhibited lingual inclination. Adults displayed less inclination than did children. Some degree of curve of Wilson should be maintained at the end of orthodontic treatment to fulfill physiologic needs and stability.

Evaluating the Correlation between Anteroposterior and Mediolateral Compensatory Curves and their Influence on Dentoskeletal Morphology-An In vitro CBCT Study

INTRODUCTION

To date, many orthodontist corrects malocclusion based on patients aesthetic concern and fails to correct the compensatory curves. This scenario is due to less insight on understanding relationship of compensatory curves and its correlation in treatment prognosis.

AIM

The purpose of this study was to evaluate the correlation between the curve of Spee, curve of Monson and curve of Wilson, their influence on dentoskeletal morphology and their contribution to occlusal stability.

MATERIALS AND METHODS

This study included 104 non-orthodontic models. The study casts were subdivided into two groups, Group-I consist 52 non- orthodontic models with Class-I molar relationship and Group-II consist of 52 non- orthodontic models with Class-II molar relationship. Curve of Spee was measured with digital vernier caliper, curve of Monson estimated using specially made sphere (7″inch, 8″ inch and 9″inch) and curve of Wilson was evaluated using Cone Beam Computed Technology (CBCT).

RESULTS

Mean value for curve of Spee obtained for Group I and Group II is 1.844 mm and 3.188 mm. For curve of Monson, the mean value obtained for Group I and Group-II is 7.65 inches and 7.40 inches. The mean degree obtained for the curve of Wilson for Group I and Group-II is 12.05 and 16.49. The result showed positive correlation between curve of Spee and curve of Wilson and no correlation between curve of Monson and curve of Wilson and no correlation between curve of Spee and curve of Monson. The Pearson correlation coefficient analysis from the study confirmed these results.

CONCLUSION

The results showed positive correlation between curve of spee and curve of Wilson. The data found in this study can be applied clinically for Class I and Class II malocclusion patients on diagnosis and treatment planning.

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

OBJECTIVE

To evaluate the buccolingual inclinations of maxillary and mandibular first molars in untreated adults.

MATERIALS AND METHODS

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.

RESULTS

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°.

CONCLUSIONS

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.

Evaluation of the Relationship between Curve of Spee, WALA-FA Distance and Curve of Wilson in Normal Occlusion

Objective

To test the hypotheses that (i) there is a significant correlation between the curve of Spee (COS), basal arch (WALA ridge) to dental arch distance (WALA-FA distance) and curve of Wilson (CW) and that (ii) the deepening of the COS is affected by the CW and the WALA-FA distance.

Methods

Mandibular models of 50 patients aged between 20 and 35 years were scanned with TRIOS. The xyz coordinate system was determined, and a reference occlusal plane was generated. The depth of the COS, the CW, and WALA-FA distance were measured using an engineering software.

Results

The greatest difference in the measurement of the depth of the COS between the right and left was found to be 0.41±0.50 mm in the first molar teeth. On the basis of the results of Pearson correlation analysis, there was no strong correlation between the depth of the COS, the CW, and the WALA-FA distance.

Conclusion

It was shown that there was no strong correlation between the depth of COS, CW, and WALA-FA distance. The CW and WALA-FA distance could not be effective in the deepening of the COS.