Does curve of Spee affect the precision of 3D-printed curvature-adaptive splints?

OBJECTIVES: This study aimed to propose a standardized protocol for the fabrication of three-dimensionally (3D)-printed curvature-adaptive splints (CASs) and assess the precision of CASs on dentitions with different depths of the curve of Spee (COS). METHODS: 76 lower dental resin models, each exhibiting one of the four types of COS (0-, 2-, 4-, and 6-mm deep), were selected and digitally scanned. CASs were designed, 3D printed, and grouped into C0, C2, C4, and C6, corresponding to the four types of COS depths. To assess precision, the CASs occluded with the resin model were scanned as a whole and compared with the originally designed ones. RESULTS: In terms of translational deviations observed in the CASs, the mean value of absolute sagittal deviation (0.136 mm) was significantly higher than those of vertical (0.091 mm) and transversal deviations (0.045 mm) (P < 0.01). Regarding rotational deviations of the CASs, the mean deviation in pitch (0.323°) was significantly higher than those in yaw (0.083°) and roll (0.110°) (P < 0.01). However, when comparing the accuracy of CASs across C0, C2, C4, and C6 groups, no statistically significant difference was found. Additionally, the translational deviations, rotational deviations, and RMSE of all groups were significantly lower than the clinically acceptable limits of 0.5 mm, 1°, and 0.25 mm, respectively (P < 0.01). CONCLUSIONS: The depth of the COS has no significant impact on the precision of CASs, as evidenced by the absence of statistically significant differences in translational, rotational deviations, and RMSE among all groups (C0, C2, C4, and C6). Moreover, despite relatively high deviations in the sagittal dimension and pitch, all dimensional deviations and RMSE remained statistically significantly lower than the corresponding clinically acceptable limits (CALs) in all groups. CLINICAL SIGNIFICANCE: This standardized protocol incorporating "curvature-adaptation" represents an optimized approach to fabricating diverse 3D-printed splints tailored to dentitions with different anatomical features in contemporary digital dentistry.

Correlation between Depth of the Curve of Spee and Some Specific Malocclusion Characteristics in a Population from Sibiu County, Romania-A Cross-Sectional Study.

Background: This study aimed to investigate the relationship between the Curve of Spee (COS) depth and malocclusion characteristics in a population from Sibiu County, Romania. The research sought to understand how the COS's anatomical dimensions correlate with different classes of malocclusion and the position of the frontal teeth. Methods: A total of 265 participants from the Dentistry Ambulatory of the Military Hospital of Sibiu were included in this study. It employed digital intraoral scanning technology to measure the COS, overjet, and overbite, with malocclusion classification. Statistical analyses, including correlation and regression, were conducted to examine the relationships between COS depth, frontal teeth position, and malocclusion characteristics. Results: The average COS depth measured was 1.0564 mm, presenting variability when compared to existing literature. Most of the study participants had Class I malocclusion. A significant positive correlation between COS depth and overjet was identified, with no notable gender-based differences in these occlusal parameters. Conclusions: The findings affirm the integral role of COS in occlusal dynamics and malocclusion diagnosis. The COS measurement of a mean of 1.0564 mm, when compared to other results emphasizes the differences in occlusal curvature among various populations. The results contribute to a refined understanding of occlusal relationships, supporting the need for personalized orthodontic and prosthetic treatments based on precise anatomical measurements.

Influence of the Curve of Spee on Tooth Displacement Patterns: A Finite Element Analysis at Varying Implant Heights.

Background Monocortical mini-screw-type temporary anchorage devices (TADs), or mini-screws, have significantly impacted orthodontic treatment strategies, especially in severe crowding and protrusion cases. These devices offer flexibility in placement sites, but the chosen location can considerably influence tooth displacement patterns. Key factors include the 'line of force' and the biomechanical properties of orthodontic tools. By analyzing tension distribution and three-dimensional displacements, the finite element method (FEM) provides a thorough means to comprehend these patterns. The Curve of Spee (COS) is a crucial factor potentially affecting displacement. Objective This study aimed to leverage finite element analysis (FEA) to understand the impact of varying mini-implant heights (10 mm, 13 mm, and 16 mm) on the displacements of different tooth types under a consistent force of 150 gm and compare these displacements both in the presence and absence of the COS. Materials and methods A CAD model of the jaw and teeth was developed using CT scan data and a Rexcan III 3D White Light Scanner. This model was meshed in Altair HyperMesh using tetrahedral elements, resulting in a Finite Element Model. The model incorporated various components, including teeth, the periodontal ligament (PDL), alveolar bone, brackets, a titanium mini-screw, and an archwire measuring 0.019 x 0.025 inches. Unique material properties were assigned to the PDL, and the assembly accurately replicated the clinical alignment of the archwire and brackets. Subsequently, stress and strain analyses were conducted on the model using the FEM. Results The displacement patterns of various teeth at implant heights of 10 mm, 13 mm, and 16 mm under a 150-gm force were analyzed in relation to the COS. Notably, for the central incisor, the COS significantly affected displacements in the Y and Z directions. Similarly, the Lateral Incisor and Canine exhibited marked changes in the Z direction with the presence of the COS. The Second Premolar's apex displacement showed significant variation due to the COS, while the First Molar displayed notable changes in the X direction. Generally, the presence of the COS either maintained or slightly increased Z-directional displacements across teeth, particularly at the apices. Conclusion The presence of COS significantly influences tooth displacement patterns when using mini-screws at different implant heights. Central incisors, lateral incisors, and canines are particularly sensitive to changes in the Z direction with the COS. The biomechanical analysis emphasizes the importance of considering COS in treatment planning for optimal results with mini-implants in orthodontics.

Effects of different patterns of movement for correcting a deep curve of Spee with clear aligners on the anterior teeth: a finite element analysis.

OBJECTIVE: To analyse the anterior teeth effects of clear aligners on five different patterns of mandibular molar movement and to define the most effective configuration to be implemented with clear aligners through finite element analysis. METHODS: A three-dimensional mandibular model with a deep overbite in the mandible was constructed using cone beam computerized tomography (CBCT) data. The model included the mandibular dentition, mandibular periodontal ligaments, attachments, and aligners. Five models were created: (1) configuration A: second molar distalization (0.25 mm); (2) configuration B: second molar distalization (0.25 mm), first molar extrusion (0.15 mm); (3) configuration C: second molar distalization (0.25 mmm), first and second premolar extrusion(0.15 mm); (4) configuration D: second molar distalization (0.25 mm), first molar and first/second premolar extrusion(0.15 mm); and (5) configuration E: second molar distalization (0.25 mm), first molar and first/second premolar extrusion (0.15 mm), first molar and first/second premolar expansion (0.15 mm). RESULTS: In all configurations, the anterior teeth exhibited labial tipping and the mandibular central incisor of configuration E showed the highest labial tipping. Configuration E demonstrated a relatively minor impact on mandibular molars distalization compared with configuration A. Configuration A showed the highest distal displacement value, and configuration E produced the lowest displacement value. Configuration E caused the highest periodontal ligament (PDL) pressure of the central and lateral incisors. The differences in the canines between configurations C and D,were not significant, and the stress distribution differed among the five groups. CONCLUSIONS: All patterns utilizing clear aligners facilitated mandibular molar distalization. Extruding the premolars and second molar distalization at the same time had little impact on second molar distalization; When expansion and extrusion were simultaneously performed during the distalization of mandibular molars, our prime consideration was the alveolar bone on the labial side of the anterior teeth to prevent the occurrence of gingival recession, dehiscence, and fenestration. Due to the lack of consideration for periodontal tissues in this study, clinical protocols should be designed based on the periodontal status of the mandibular anterior teeth.

Long-term stability of curve of Spee depth among orthodontically treated patients: A retrospective longitudinal study.

OBJECTIVE: The curve of Spee is deemed important characteristic of the dentition for a balanced occlusion and distribution of masticatory forces, while orthodontic levelling of an accentuated curve of Spee is generally included as a treatment goal for deepbite correction. However, relapse is often seen and can be problematic. METHODS: A retrospective longitudinal study of predominantly young patients with a deep curve of Spee, who had been treated orthodontically with 0.018"-slot Edgewise fixed appliances, was performed. The depth of the curve of Spee was digitally measured before treatment (T1), at debond (T2), and an average of 7 years post-debond (T3) and analysed statistically at 5%. RESULTS: A total of 157 patients were included (56.7% female; 11.6-year-old at T1), 16.6% of which were treated with premolars extractions. Non-extraction treatment reduced the curve of Spee at the first premolar from 1.87 mm (T1) to 0.22 mm (T2), which relapsed 0.12 mm (T3; P = .04). The respective depths for the second premolar were 2.0 mm (T1), reduced to 0.80 mm (T2). No significant relapse was seen for the second premolar (0.08 mm; P > .05) or the first permanent molar (0.06 mm; P > .05). No overall significant differences in absolute relapse were seen between extraction and non-extraction patients, but premolar extractions were associated with less clinically relevant relapse at the first molar (odds ratio 0.27; 95%-confidence interval 0.08-0.88; P = .003). CONCLUSION: Steep curves of Spee can be satisfactorily levelled orthodontically with satisfactory stability in the long term, while premolar extractions might be associated with less relapse.

Curve of Spee modification in different vertical skeletal patterns after clear aligner therapy: a 3D set-up retrospective study.

OBJECTIVE: The purpose of the present study was to evaluate: (1) changes in the curve of Spee (COS) after clear aligner therapy and (2) whether such changes correlated with the patient's skeletal patterns. MATERIALS AND METHODS: Three-dimensional mandibular models of 106 patients (47 males and 59 females; mean age 22.3 SD ± 3.4 years) treated with clear aligners were retrospectively analysed. The perpendicular distance between the occlusal reference plane and the buccal cusp tip of each lateral tooth was measured. Five angular cephalometric measurements (PP-MP, PP-OP, OP-MP, AFH, and PFH) were performed and correlated with the T1-T0 difference in linear distances. The patients were divided into three groups according to facial divergence. Variance analysis with Tukey post hoc correction was performed to evaluate the differences among groups. RESULTS: The one-way ANOVA test showed a statistically significant difference for all analysed variables, except for the change in the distance of the second molar from the occlusal reference plane. Tukey's HSD test showed the following differences: In normodivergents, the T1-T0 difference in the distance of the first molar from the occlusal plane was 1 mm greater than that observed in the hyperdivergent group (p < 0.05); in the normodivergent group, the T1-T0 difference in the distance of the second premolar from the occlusal plane was 1.23 mm greater than that observed in the hyperdivergent group (p < 0.05), while in the hypodivergent group, it was 1.08 mm greater than in the hyperdivergent group (p < 0.05); finally, in normodivergents, the T1-T0 difference in the distance of the first premolar from the occlusal plane was 0.97 mm greater than that observed in the hyperdivergent group (p < 0.05). CONCLUSION: Treatment with aligners did not lead to a clinically significant change in COS depth. However, when dividing the sample into groups based on craniofacial divergence, COS depth change differed significantly between the three groups.

The Effect of Accentuation of Curve of Spee on Masticatory Efficiency-A Systematic Review and Meta-Analysis.

BACKGROUND: The appropriate alignment of the lower teeth is indicated by the Curve of Spee (COS), which can be observed in the sagittal profile view of human skulls. Graf Von Spee made the initial observation on this occlusal curvature. Through this systematic review and meta-analysis, we evaluated studies that looked at how COS affected masticatory activities. METHODS: The databases PubMed-MEDLINE, Web of Science, Cochrane, and Scopus were all searched. A total of 12 documents were ultimately picked because they met the necessary inclusion and exclusion requirements. The data was then loaded into the RevMan 5 programme for meta-analysis after being chosen for information on the sample size, variables analyzed, and various aspects of the research. RESULTS: The Curve of Spee was found to have a noticeable impact on both the masticatory efficiency as well as dentofacial alignment in the 12 studies that we selected for the review and meta-analysis. In addition, other occlusal curvatures such as the Curve of Monson and the Curve of Wilson were found to be of vital importance on a similar level to the COS. The meta-analysis further revealed that seven of the included clinical trials had mentioned the noticeable impact on masticatory efficiency. CONCLUSIONS: This study focused on the significance of the COS on force distribution in the oral cavity as well as the necessity of COS corrections after receiving full orthodontic care. Following orthodontic treatment, the COS, along with other occlusal curves such as the Curve of Wilson and the Curve of Monson, is essential in removing strains from the condyle, as well as the maxilla and mandible, which enhances masticatory effectiveness and lessens the overall strain on a patient's oral cavity.

Leveling the curve of Spee using different sized archwires: a randomized clinical trial of blood flow changes.

OBJECTIVES: To compare blood flow (BF) changes of teeth subjected to orthodontic forces during curve of Spee (COS) leveling using different archwires (AW). MATERIAL AND METHODS: Thirty subjects with COS > 5 mm were randomly assigned (1:1:1) into three groups based on the AW used: group 1: 0.017 × 0.025-inch stainless-steel (SS)AW, group 2: 0.019 × 0.025-inch SSAW, and group 3: 0.021 × 0.025-inch ß-titanium (TMA)AW. In the 3 groups, a 5 mm-depth reverse COS was placed in the AWs. A laser Doppler flowmeter was used to measure BF at different time intervals (T0-T4). RESULTS: In the 3 AWs group, BF of all measured teeth was reduced 20 min after force application. Afterwards, the BF values started to increase until the baseline values were almost restored within 1 week. Differences in BF changes between the extrusion and intrusion subgroups were observed within groups 1 and 3 during the first 20 min of force application (P < 0.05). Similar BF changes were recorded using the 3 different AWs. BF changes were associated with tooth type and the amount of COS depth change. CONCLUSIONS: During CoS leveling, similar BF changes were recorded using the 3 different AWs. Tooth type and the amount of COS depth change were associated with BF changes within the first 20 min of force application. Greater BF reduction was found in premolars compared to incisors during the first 20 min of AW placement. CLINICAL RELEVANCE: It is important to select a type of applied forces that minimally affect the BF. Intrusive forces appeared to have lower negative effects on the BF of teeth during COS leveling. TRIAL REGISTRATION: ClinicalTrial.gov (# NCT04549948).

Investigation of the change in the degree of Frankfort mandibular plane angle after levelling the curve of spee in different malocclusion groups.

BACKGROUND AND OBJECTIVES: The curve of Spee is a naturally occurring phenomenon in the human dentition. Leveling the curve of Spee can affect the Frankfort-mandibular plane (FMP) Angle and thus the lower anterior facial height. This study examined the degree of change in FMP angle after leveling the curve of Spee in different malocclusion groups. METHODS: In this study, 75 patients who were aged >14 years and had undergone fixed appliance therapy using a 0.022-slot MBT bracket system were included. The pre- and post-treatment casts and lateral cephalograms of the patients were divided into three groups, namely Class I, II, and III malocclusions, with 25 patients in each group. The curve of Spee and FMP angle were measured before and after orthodontic treatment, and their correlation was evaluated. RESULTS: After leveling the curve of Spee, the FMP angle decreased in Class I and II groups and increased in Class III group. These results were statistically significant except in Class I malocclusion group. A mild positive correlation was observed between the curve of Spee and FMP angle in Class I and III malocclusion groups and a negative correlation in Class II malocclusion group. CONCLUSION: The change in FMP angle, following the leveling of the curve of Spee, in Class II and III malocclusion group, is attributed to alterations in lower anterior facial height. The study observed a mild positive correlation between the curve of Spee and FMP angle in Class I and III malocclusion groups and a negative correlation in Class II malocclusion group.

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.

The Effect of Leveling the Curve of Spee on the Inclination of Mandibular Incisors: A Retrospective Cephalometric Study.

PURPOSE: To assess mandibular incisor inclination after leveling the curve of Spee (CoS) in patients treated with fixed appliances. MATERIALS AND METHODS: This was a retrospective study, which included 80 consecutive patients with a mild CoS treated without extraction but with various biomechanical approaches. The depth of CoS was digitally measured on scanned plaster casts and mandibular incisor inclination was assessed with lateral cephalograms pre- and posttreatment. Patients were treated with 0.018"-slot edgewise fixed appliances and cinched back wires. Data were analyzed using linear regression modeling at 5%. RESULTS: A total of 80 patients (40% female; mean age 13.8 years) were included with mean ANB = 4.4 ± 1.9°, mean SN/ML = 31.7 ± 4.7°, mean L1/ML = 95.0 ± 7.7°, and a mean depth of CoS = 1.1 ± 0.4 mm. The depth of CoS was leveled by -0.85 ± 0.39 mm to a post-treatment median of 0.18 mm (interquartile range = 0.09 to 0.35 mm). A small mandibular incisor proclination was observed through treatment (2.49 ± 9.1°), but this was not associated with the reduction in the depth of CoS (p > 0.05) and no statistically significant modifying effect from the different treatment mechanics was observed. CONCLUSION: Under the limitations of this study, leveling a mild CoS was not associated with mandibular incisor proclination during fixed-appliance treatment.

Association of Craniofacial Patterns with the Curve of Spee and the Time Required for Orthodontic Levelling.

The curve of Spee (CoS) is an important parameter for an individualized treatment plan. The available information regarding a potential association of the depth of the curve of Spee with various skeletal craniofacial characteristics is conflicting and it is also unknown whether certain craniofacial parameters affect the duration of the levelling phase of orthodontic treatment. A prospective sample of 32 patients with mild to moderate crowding that underwent orthodontic treatment with full fixed appliances was used to study these topics. The craniofacial characteristics were captured on pre-treatment lateral cephalometric radiographs and measurements of the CoS were performed on the initial 3D digital dental models using the Viewbox 4 software. Non-parametric statistics and Spearman's correlations were applied. Weak negative correlations were detected between the CoS depth and the SNA and SNB angles. There was no other association between the CoS and craniofacial parameters, including various anteroposterior measurements. Furthermore, there was no significant association of any craniofacial parameter with the duration of the levelling. Contrary to certain clinical beliefs, it can be argued that the craniofacial characteristics are not associated with the CoS and the time required for its levelling in subjects with moderate pre-treatment CoS depth.

Efficacy of lower arch leveling, lower incisors' root resorption, and pain associated with the correction of curve of Spee using different orthodontic archwires: a randomized clinical trial.

OBJECTIVES: To compare between 3 archwires (AWs) for leveling curve of Spee (COS) in terms of efficacy of reduction, external apical root resorption (EARR), pain experienced, and the lower arch dimensional changes during COS leveling. TRIAL DESIGN: Randomized clinical trial. SETTING: Jordan University of Science and Technology Postgraduate dental clinics. MATERIAL AND METHODS: Fifty-three subjects with COS > 5 mm were included in this study. The subjects were randomly divided into three groups based on the AW used: group 1, 0.017 × 0.025-inch stainless-steel (SS) AW; group 2, 0.019 × 0.025-inch SS AW; and group 3, 0.021 × 0.025-inch ß-titanium (TMA) AW. The intervention was randomly allocated using the permuted random block size of 3 with a 1:1:1 allocation ratio. In the three groups, a 5-mm depth reverse COS was placed in the AWs. The following time points were defined for COS assessment: T1, before interventional leveling AW placement; and T2-T7, 1-6 months after interventional leveling AW placement. Records consisted of dental study models and periapical (PA) radiographs. Pain scores were recorded using visual analogue scale. Patients were followed up on a monthly basis until COS < 1.5 mm. MAIN OUTCOME MEASURES: COS depth reduction, lower incisors' EARR, pain scores, and arch dimensional changes. RESULTS: An overall reduction of 3.82 mm, 4.47 mm, and 3.85 mm of the depth of COS was achieved in groups 1, 2, and 3, respectively. The mean differences of 0.65 mm between groups 1 and 2 and 0.62 mm between groups 2 and 3 were significant at P < 0.05. Lower incisors' EARR during leveling COS ranged from 0.68 to 0.72 mm, from 0.63 to 0.82 mm, and from 0.53 to 0.88 mm in groups 1, 2, and 3, respectively (P > 0.05). Higher pain scores were reported by group 2 subjects during the first 24 h. Arch length and width increased significantly in groups 2 and 3 (P < 0.05). In all groups, COS leveling was achieved by lower incisor intrusion and proclination and lower molar extrusion. CONCLUSIONS: All investigated AWs were effective in leveling COS with minimal lower incisors' EARR (< 1 mm). COS was leveled by lower incisors' intrusion and proclination and lower molar extrusion. Pain scores were the highest in group 2 during the first 24 h. CLINICAL RELEVANCE: The 3 investigated leveling AWs were effective for the leveling COS and at the same time safe on the roots of the lower anterior teeth.

Balkwill's angle, occlusal plane, mandibular shape, and curve of Spee.

OBJECTIVE: This study proposes a cephalometric method to determine an individual radius of the curve of Spee in cases of occlusal prosthetic rehabilitation. METHODS: A retrospective study was conducted on 469 lateral cephalograms. Statistical analysis was performed. Correlations were computed using simple regression, Z tests, paired t-tests, and one-way repeated measures ANOVA. RESULTS: Regression calculations supported a link between the radius of the curve of Spee and occlusal plane inclination, Balkwill's angle, mandibular parameters (MP), with MP = corpus - ramus + Bonwill height. Based on MP, data that are accessible even in the absence of teeth, a regression formula can be proposed to provide an individualized estimation of the radius of the Spee curve (RCS): RCS = 0.624 * MP + 26.583. CONCLUSION: This study proposes an individualized estimation of the RCS from only skeletal mandibular parameters: the length of the ramus, length of the corpus, and the Bonwill height.

The curve of Spee and its levelling in different vertical skeletal patterns: A 3D set-up study.

OBJECTIVES: Primary: to compare intra-arch measurements [Curve Of Spee (COS) depth, space required to level the COS (δ), uprighting angles of 1st and 2nd lower molars (αM1 & αM2), respectively] between different vertical skeletal patterns. Secondary: to explore the relationship between those measurements in each vertical skeletal pattern. METHODS: 90 Plaster models were scanned and transformed into digital models using 3Shape Ortho System™ intra oral scanner. COS depth, (δ), αM1 & αM2 were measured on digital models using 3Shape Ortho Analyser™ software. The latter was used to achieve the virtual set-up. The sample was dividied into 3 groups according to the vertical skeletal pattern which was identified by measuring the FMA˚ angle (Frankfort mandibular plane) on a lateral cephalogram using Dolphin imaging software. RESULTS: The deepest COS was present in the hypodivergent group (P-value=0.001). No difference for the additional arch space required to level the COS (δ) between different vertical skeletal patterns (P-value=0.063). αM2 is the same in all 3 groups, whereas αM1 is greater in normodivergents compared to hyperdivergents (P-value=0.012). A positive correlation exists between the deepest point of the COS and the uprighting angles, αM1 and αM2. No correlation between (δ) and the different parameters evaluated (deepest point of the COS, αM1 and αM2). CONCLUSIONS: Additional arch space required to level the COS presented no correlation with the vertical skeletal pattern. Levelling the lower arch was carried out by extrusion of the premolars and uprighting of the posterior teeth; confirming that well-planned orthodontic mechanics can minimize side effects (flaring of the lower incisors) encountered during treatment.

Cone-beam Computed Tomography Analysis of the Relationship between the Curve of Spee and the Collum Angle of Mandibular Anterior Teeth.

AIMS AND OBJECTIVES: To evaluate the correlation between the curve of Spee (COS) of a patient and the Collum angle of mandibular anterior dentition using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: This cross-sectional study was based on the analysis of 100 CBCTs of patients divided sagittally into two separate subjects. The Collum angles of the mandibular central incisor, mandibular lateral incisor, and the mandibular canine were measured along with the COS of that quadrant using Dolphin Imaging. A multivariate linear regression and Pearson correlation coefficients were conducted to measure the correlation between the COS and the Collum angle of mandibular anterior dentition. RESULTS: The total number of participants in the cohort was 200 samples out of 100 patients as this was a split mouth study. The mean COS was 2.09 ± 1.239 mm. The mean Collum angle of the mandibular central incisor (L1) was found to be 6.50 ± 3.002 degrees. The mean Collum angle of the mandibular lateral incisor (L2) was 7.19 ± 2.554 degrees and the mean Collum angle of the mandibular canine (L3) was 7.03 ± 2.907 degrees. There was a statistically significant moderate correlation between L1, L2, and L3 and the COS with the Collum angle of the mandibular central incisor most highly correlated to the COS (0.42), followed by the mandibular lateral incisor (0.35) and then the mandibular canine (0.30). CONCLUSIONS: There is a statistically significant low to moderate correlation between the COS and the Collum angles of the mandibular anterior dentition.

Evaluation of Horizontal Distance between WALA-FA Point in Angle's Class I, Class II, and Class III Malocclusion.

INTRODUCTION: The objective of the study was to measure the horizontal distance between the FA-WALA (Facial Axis Point-William Andrews and Larry Andrews) of posterior teeth in Angle's Class I, Class II, and Class III malocclusions and to assess the depth of the Curve of Spee, to find the correlation between intercanine FA and intercanine WALA and its significance. MATERIAL AND METHODS: Sixty pretreatment mandibular casts of patients with an age range of 18-35 years were included. A sample size of 20 was evaluated in Angle's Class I, Class II, and Class III, respectively. The WALA ridge and FA points were marked in the model and calibrated using the digital Vernier caliper. RESULTS: There was an incremental increase in the horizontal distance from the FA-WALA in the posterior teeth. The mandibular intercanine FA-FA and intercanine WALA-WALA distance were greater in Angle's Class III group when compared to Angle's Class II. The Curve of Spee measurement was increased in Angle's Class II group, while Angle's Class III had a flat curve. CONCLUSION: The horizontal distance between FA-WALA increased incrementally in the posterior teeth in Angle's Class I, Class II, and Class III malocclusions. In Angle's Class II malocclusion, the Curve of Spee measurement was increased and had a narrower mandibular arch.

Does the flatting of the curve of spee affect the chewing force distribution in the mandible? (3D finite element study).

OBJECTIVE: To search the effects of Curve of Spee (COS) flatting on the stresses and displacement on the different mandible landmarks and lower teeth during posterior teeth loading using three-dimensional (3D) finite element analysis. MATERIALS AND METHODS: Three-dimensional hemi mandibular model was created from real selected mandible. The lower teeth was aligned originally in a curved form with 2.4 mm depth at the cusp tip of the second premolar. Another replica with flat aligned teeth was formed to confirm the analysis by up righting premolars and molars. A load was applied at mesio-buccal cusp of the lower first molar on both models, and the resultant stresses and displacements on the mandibular landmarks and the lower teeth were tested. RESULTS: Von mises over the mandible was higher in flat than in curve model. The highest stress levels were detected at the Mesio-buccal cusp tip of first molar for flat and curved simulation (5053, 3304) Mpa respectively. Mesio-distally, the teeth displacement was higher in curve model than in flat one. The maximum distal displacement, in flat model, was seen in central and lateral incisors. While, in curve model, the maximum distal displacement was grasped within first and second premolars. CONCLUSIONS: Flatting the COS magnify the stresses over whole mandible and reduce lower teeth displacement mesio-distally. We speculated that the readjustment of the COS after orthodontic treatment could reduce the stress and displacements on the lower anterior teeth and decrease the lower anterior teeth crowding relapse.

Vertical segmental anterior mandibular distraction to aid closure of a severe anterior open bite associated with an accentuated reverse curve of Spee.

BACKGROUND: The correction of severe anterior open bite is technically challenging, often requiring the use of complex orthodontic mechanics and/or orthognathic surgery and has a relatively high risk of relapse. A marked reverse curve of Spee in the lower arch presents additional challenges when correcting a severe anterior open bite. METHODS AND MATERIALS: A 22.2-year-old Caucasian man presented with concerns relating to poor anterior occlusion associated with a 1.3-cm anterior open bite. There was an accentuated reverse curve of Spee to the lower arch, an increased maxillary-mandibular plane angle and increased lower face height. Multidisciplinary treatment involving the use of segmental anterior mandibular distraction to level the curve of Spee before undertaking a Le Fort I posterior maxillary impaction is described in this case report. RESULTS: Long-term post-treatment records showed stable anterior open bite correction. CONCLUSIONS: This case report illustrates the successful use of segmental anterior mandibular vertical distraction followed by conventional Le Fort I posterior impaction surgery to correct a severe anterior open bite associated with an accentuated reverse curve of Spee and high maxillary-mandibular plane angle.