Incisors Research Articles

A 3D finite element analysis of biomechanical effects on teeth and bone during true intrusion of anteriors using miniscrews

The primary objective of this study was to investigate the biomechanical effects and stresses on bone, periodontal ligament (PDL), cementum and displacement along X-, Y- and Z-axis during true intrusion of incisors using mini-implants with Finite Element Analysis; the secondary objective of the study was to find out the best method for anterior intrusion in clinical practice to treat anterior deep bite malocclusions. A 3D finite element method was used to simulate true anterior intrusion with sliding mechanics using mini-implants. Two groups were modelled with mini-implants placed distal to lateral incisors for Model1, and below the anteriornasalspine (ANS) for Model2, to achieve intrusion. von Mises stress, principal stress on PDL and alveolar bone, displacements in all 3 planes were determined. Amongst the modalities compared in the present study, the stresses on bone and PDL were showing best behavior for mini-implants placed distal to lateral incisors (Model1). The teeth showed controlled tooth movement in Model1. Maximum stress was found in the cortical bone and in the PDL. Nature of the stress changed from compressive to tensile from cervical area to root apex, concentrating mainly at the apical area. Amongst the modalities compared, the best controlled tooth movements for anterior intrusion to treat anterior deep bite malocclusions, was for mini-implants placed distal to lateral incisors (Model1).

Three-dimensional analysis of force distribution on maxillary dentition while distalization of first and second molars simultaneously with clear aligners

Objective: To explore the force distribution on the maxillary dentition when the first and second molars distalized simultaneously with different step sizes using clear aligners in vitro in order to provide a theoretical basis for the rational design of molar distalization. Methods: Clear aligners were designed to simultaneously distalize the maxillary first and second molars bilaterally, with rectangular attachments placed on the buccal surfaces of the first and second premolars, as well as the second molars. Based on different step sizes, the aligners were divided into three groups: Group A (0.15 mm per step), Group B (0.20 mm per step), and Group C (0.25 mm per step). Ten aligners were fabricated for each group using 0.76 mm thick polyethylene terephthalate glycol (PET-G) sheets. A three-dimensional force measurement system was used to measure the forces exerted on each tooth by the aligners, the first and second molars served as the target teeth and the remaining teeth as anchorage teeth. The three-dimensional force data were compared among the three groups. Results: In the mesiodistal direction, the forces on the central and lateral incisors were relatively small among all three groups, with no statistically significant differences (P>0.05). However, significant differences were observed in the forces on the canines, first premolars, second premolars, first molars, and second molars (P<0.05). The distal forces on the second molars in Groups B and C were (6.13±1.45) N and (6.83±1.58) N, respectively, significantly higher than that in Group A [(3.51±1.01) N] (P<0.05). The distal force on the first molars in Group C [(6.62±0.89) N] was significantly higher than that in Groups A and B (P<0.05). The mesial reactive forces on the first and second premolars in Groups B and C were significantly higher than those in Group A (P<0.05). The mesial reactive force on the canines in Group C [(-2.98±1.33) N] was significantly higher than that in Group A [(-1.69±0.68) N] (P<0.05), while there were no significant differences between Groups B and C in the forces on the canines, first premolars, and second premolars (P>0.05). In the buccolingual direction, there were no statistically significant differences in the forces on the central and lateral incisors among three groups (P>0.05), but significant differences were observed in the forces on the canines, second premolars, and second molars (P<0.05). The buccolingual forces on the canines, second premolars, and second molars in Group B were (-0.56±0.54), (-2.07±0.95), (1.13±0.55) N, respectively, significantly higher than those in Group A (P<0.05), but there were no significant differences compared to Group C (P>0.05). Compared to the mesiodistal and buccolingual forces, the vertical forces on the target and anchorage teeth were relatively small in all three groups. Conclusions: When using 0.76 mm thick PET-G sheets to fabricate clear aligners for simultaneous molar distalization, a step size of 0.20 mm per step is recommended. To prevent buccal tipping of the molars during distalization, it is advisable to design lingual displacement for the molars and buccal displacement for the adjacent anchorage teeth to counteract the unfavorable forces, with attachments placed on the primary anchorage teeth.

A comparative study of shade-matching performance using intraoral scanner, spectrophotometer, and visual assessment

This study aimed to explore the clinical applicability of the shade-matching function in intraoral scanners. This study measured the tooth colors of maxillary anterior dentitions of 83 adults using visual matching, a spectrophotometer, and a scanner according to two color systems: VITA Classical (VC) and VITA 3D-Master (V3D). Agreement between each method was assessed by weighted Cohen’s kappa coefficient (KW, α = 0.05). For V3D, the overall agreement between the scanner and spectrophotometer (KW = 0.498) was higher than that between the scanner and visual matching (KW = 0.473). Similarly, the agreement between the scanner and spectrophotometer (KW = 0.283) was higher than that between a scanner and visual matching (KW = 0.140) for VC. Regarding tooth position, the highest agreement between the scanner and spectrophotometer was observed on the right central incisor (KW = 0.542) for V3D. Tooth color measurement with a scanner was comparable to that with a spectrophotometer, especially on the central incisors when using the VITA 3D-Master system. A scanner could serve as an alternative to a spectrophotometer for shade selection. However, color matching should still be visually verified.

Математическое моделирование бипланетарного механизма для привода смесительных машин

A study on the development of a kinematic scheme of a planetary mechanism with an opening kinematic circuit for driving the working body of mixing machines is presented. The main purpose of the study is to create two kinematic cycles in the planetary mechanism, in which, during one revolution, the satellite drivers consistently perform movements of the epicyclic trajectory of hypocyclic motion. To achieve this goal, braking devices for damping the kinematic energy of satellites and synchronizer devices were used in the transition zones between two segments of different names, for smooth entry of the satellite gear into the gear engagement of these gears. The oscillatory process of the synchronizer at the entrance of the tooth of the satellite gear with the front teeth of the synchronizer is considered. Practical significance includes ensuring the possibility of assembling a planetary mechanism, taking into account the choice of the angle of rotation of the synchronizer around the axis of the support. The discussion makes recommendations for further improvement of the developed biplanetary mechanism for driving mixing machines.

In Vitro Investigation Using a New Biomechanical Force-Torque Analysis System: Comparison of Conventional and CAD/CAM-Fixed Orthodontic Retainers.

(1) Background: After more than a decade since their first description, Inadvertent Tooth Movements (ITMs) remain an adverse effect of orthodontic retainers without a clear etiology. To further investigate the link between ITMs and the mechanical properties of different retainers, the response upon vertical loading was compared in three retainer types (two stainless steel and one nickel-titanium). The influence of different reference teeth was also considered. (2) Methods: Three retainers (R1, R2, R3) were tested in a newly developed biomechanical analysis system (FRANS). They were bonded to 3D-printed models of the lower anterior jaw and vertically displaced up to 0.3 mm. Developing forces and moments were recorded at the center of force. (3) Results: The vertical displacement caused vertical forces (Fz) and labiolingual moments (My) to arise. These were highest in the lateral incisors (up to 2.35 ± 0.59 N and 9.27 ± 5.86 Nmm for R1; 1.69 ± 1.06 N and 7.42 ± 2.65 Nmm for R2; 3.28 ± 1.73 N and 15.91 ± 9.71 Nmm for R3) for all analyzed retainers and with the R3 retainer for all analyzed reference teeth, while the lowest Fz and My values were recorded with the R1 retainer. (4) Conclusions: Displacements of 0.2 mm and larger provided forces and moments which could be sufficient to cause unwanted torque movements, such as ITMs, in all analyzed retainers. Clinicians must be mindful of these risks and perform post-treatment checkups on patients with retainers of all materials.

Three-dimensional assessment of root canal morphology of primary dentition using cone beam computed tomography.

Root canal therapy in primary teeth is exceedingly complex due to the unique internal geometry of the pulp cavity. The purpose of this study was to evaluate variations in primary teeth root canal morphology and applicability of the Ahmed etal. (Int Endod J, 50, 2017, 761) alphanumeric system for classifying them. A retrospective analysis of 2024 primary teeth from an existing CBCT database was performed for assessing variations in root canal morphology. Descriptive statistics and the chi-squared test were used for data analysis. The maxillary canines exhibited splitting levels of 5.9% (right) and 6.6% (left), and merging levels of 1% (both sides); maxillary lateral incisors showed splitting levels of 2.6% (right) and 0.8% (left), with no merging observed; mandibular second molars had splitting levels of 1.5% (right) and 0.8% (left), with no merging observed; and mandibular lateral incisors exhibited a merging level of 0.9% (right), with no splitting observed. This study provides new insights into the variations in root canal morphology of primary teeth, particularly highlighting the variations found in primary canines. The Ahmed etal. (Int Endod J, 50, 2017, 761) classification system was found to be a useful tool for categorizing these variations.

Biomechanical effects of anew crimpable gate spring combined with conventional rectangular archwires for torque adjustment of individual anterior teeth : Acomparative finite element study.

Precise root torque adjustment of anterior teeth is indispensable for optimizing dental esthetics and occlusal stability in orthodontics. The efficiency of traditional rectangular archwire manipulation within bracket slots seems to be limited. The crimpable gate spring, anovel device, has emerged as apromising alternative. Yet, there is apaucity of guidelines for its optimal clinical application. This study used finite element analysis (FEA) to investigate the biomechanical impact of the gate spring on torque adjustment of individual anterior teeth and to elucidate the most effective application strategy. AFEA model was constructed by amaxillary central incisor affixed with an edgewise bracket featuring a0.022 × 0.028 inch (in) slot. Arange of stainless steel rectangular archwires, in conjunction with agate spring, were modeled and simulated within the bracket slots. Acontrol group utilized aconventional rectangular wire devoid of agate spring. Palatal root moments were standardized to 9, 18, and 36 Nmm for both experimental and control groups. The gate spring significantly amplified palatal root movement, notably with the 0.019 × 0.025 in archwire. However, this was accompanied by an increase in stress on the tooth and periodontal ligament, particularly in the cervical regions. The synergistic use of a0.019 × 0.025 in rectangular archwire with agate spring in a0.022 × 0.028 in bracket slot was identified as most efficacious for torque control of individual anterior teeth. The gate spring is aviable auxiliary device for enhancing torque adjustment on individual teeth. However, caution is advised as excessive initial stress may concentrate in the cervical and apical regions of the periodontal ligament and tooth.

Effects of mini-implant anchorage on mandibular rotation and esthetic outcomes in hyperdivergent skeletal Class II malocclusion treatment

Objectives: This research aimed to investigate the effects of mini-implants (MIs) on mandibular position and changes in lower face height, as well as their relationship with the position of the maxillary molars and incisors in the camouflage treatment of patients with hyperdivergent skeletal Class II malocclusion. Material and Methods: This retrospective study included 27 patients aged 15–38 years. The hyperdivergent patients were diagnosed with skeletal Class II malocclusion and treated with tooth compensation, tooth extraction, posterior repositioning of the maxillary incisors, and anchoring with MIs. Cephalometric analyses of these patients were performed before (T1) and after (T2) treatment. Measurements were taken at each treatment stage and analyzed. Results: Significant correlations were observed in the mandibular position and lower face height (P &lt; 0.05). The GoGnSN angle decreased (−1.05 ± 1.61°), the ANS-Me distance reduced (−1.98 ± 4.76 mm), and the NBaPtGn angle increased (1.67 ± 4.08°). In addition, the vertical height position of the maxillary first molar significantly decreased (6M-FH, −1.61 ± 3.74 mm), while the vertical height position of the maxillary incisor increased (U1-FH, 1.48 ± 2.11 mm). Conclusion: During the camouflaging treatment of patients with hyperdivergent skeletal Class II malocclusion using MIs anchorage, MIs helped intrude the maxillary first molar and extrude the maxillary incisor, leading to a difference in a mandibular counterclockwise rotation. Controlling the rotation of the lower jawbone helps create an improved esthetic for the patient after treatment.

Early intervention of unerupted maxillary central incisor: A case series

Early intervention of an impacted maxillary central incisor is crucial to avoid space loss with tipping of the adjacent teeth and allows normal root development. This case series demonstrates the clinical considerations of a surgical-orthodontic approach in managing this eruption anomaly and its challenges. All three cases involved young patients aged 7–9 years with an impacted upper left central incisor and a positive history of dental trauma. An upper sectional fixed appliance was bonded to facilitate the closed eruption of the impacted central incisor. The treatment duration increases when more space is required for the impacted tooth. There was a marginal gingival discrepancy of all the treated central incisors with vertical relapse seen upon review, indicating the need for a careful surgical approach with good hygiene maintenance and a bonded retainer as retention. Early referral for the management of an impacted maxillary central incisor through a surgical-orthodontic approach is often successful, but treatment risks, duration, and retention regimen should be discussed with the parents for informed consent.

Vertical root fracture detection with cone-beam computed tomography in Biodentine™ filled teeth

PurposeThis study aimed to evaluate the accuracy of detecting vertical root fractures in Biodentine™-filled teeth using the Promax 3Dmax cone-beam computed tomography (CBCT) unit compared to periapical radiographs. It tested hypotheses regarding CBCT’s diagnostic superiority in non-root-filled and Biodentine™-root-filled maxillary central incisors and assessed the impact of smaller field of view and lower intensity settings on detection accuracy.Materials and methodsExtracted maxillary incisors were divided into groups based on fracture status and root filling material, then placed in a Thiel-embalmed skull to simulate clinical conditions. The teeth were imaged using periapical radiographs and the CBCT unit under different settings. Fracture thickness was measured with microcomputed tomography for accuracy benchmarking. Multiple observers assessed the images, and statistical analyses were conducted to evaluate diagnostic performance.ResultsIntra-rater reliabilities of consensus scores ranged from good to very good. Specificities were generally higher than sensitivities across all imaging modalities, but sensitivities remained constantly low. None of the Area Under the Curve scores exceeded 0.6, indicating poor overall accuracy for all imaging modalities. Paired comparisons of the area differences under Receiver Operator Characteristic curves revealed no significant differences between the CBCT and periapical radiograph techniques for detecting vertical root fractures in either Biodentine™-filled or non-root-filled teeth.ConclusionsThere was no significant accuracy improvement of the current CBCT device (Promax 3Dmax, Planmeca, Finland) over periapical radiographs in detecting small vertical root fractures in both non-root-filled and Biodentine™-root-filled maxillary central incisors. A smaller field of view with lower intensity did not enhance detection accuracy. These results highlight the challenges in accurately detecting small VRFs, emphasizing the need for further research and technological advancements in this domain.

Seating Accuracy of Prefabricated Interim Crowns on Immediate and Delayed Implants: A Laboratory Study.

Evaluation of seating accuracy of interim crowns for the immediate restoration of immediate implants (I-Imp) and delayed implants (D-Imp) placed via static computer-assisted implant surgery (sCAIS). A maxillary training model was modified by removing the central incisors and simulating fresh extraction socket in one site and healed ridge on the other site. An I-Imp was planned in the extraction socket and D-Imp was planned in the healed site. The planned implants were used to design sCAIS surgical template and interim crowns for immediate restoration of the implants. Fourteen surgical models received sCAIS implants after which the interim crowns were inserted. Subsequently, the models with the seated crowns were scanned by a laboratory scanner. The planning virtual model was superimposed against every surgical model to measure vertical, horizontal and proximal contact errors of each crown. All the crowns were positioned more incisally than the planned crowns. This was significantly more noticeable for the D-Imp crowns (0.81 mm) than the I-Imp crowns (0.55 mm). The 2 crown groups had similar horizontal errors (I-Imp &#61;0.35 mm, D-Imp &#61; 0.36 mm). The D-Imp crowns had minimal proximal contact error (0.14 mm), but the I-Imp crowns had significantly greater proximal contact error (0.74 mm) in the form of open distal contacts. This pattern of error appears related to the relationship between the socket morphology and the planned implant position. Prefabricated interim I-Imp crowns suffered from greater errors that affected the proximal contact quality than DImp crowns. The observed deviation of the I-Imp crowns can be attributed to the socket morphology and its relation to the planned implant position. The deviations of the I-Imp crowns are clinically significant and will require clinical adjustments. Thus, caution is needed before routine use of prefabricated interim crowns on I-Imp.

Treatment of Dento-alveolar Traumatic Injuries in a Child with Autism Spectrum Disorder (ASD)

This case report details the multidisciplinary management and follow-up of a 9-year-old boy diagnosed with autism spectrum disorder (ASD). He presented with severe intrusion injuries after a fall to his permanent maxillary central and lateral incisor teeth. The patient was initially seen in the emergency department by the maxillofacial team. Owing to the complexity of the dento-alveolar injury, it was felt that a multidisciplinary approach would improve patient outcomes. In theatre, both maxillofacial and paediatric dental teams managed the acute trauma. The paediatric dental team continued to review and follow-up with the child. A multidisciplinary team is ideal for managing paediatric patients with severe dental trauma and complex behavioural needs. This approach ensures the best care for patients and favourable outcomes. CPD/Clinical Relevance: Multidisciplinary management is important in paediatric dento-alveolar trauma.

Electrosurgical Adjunct for Soft Tissue Management of the Paediatric Dental Trauma Patient

The interface between dental restorations and the neighbouring soft tissue is of key significance for restorative success and longevity. Trauma-related enamel–dentine fractures are frequently present with the restorative challenge of subgingival margins and little remaining tooth structure. This report looks at two paediatric dental trauma patients with extensive crown fractures resulting in subgingival margins, which posed a poor long-term tooth survival. Electrosurgery was used before definitive composite restorations to allow for supragingival margins and access. Each patient attended the Child Dental Health Department at the University of Manchester Dental Hospital for assessment and treatment provision. CPD/Clinical Relevance: This article identifies electrosurgery as an increasingly useful adjunct to restorative management of traumatized permanent incisor teeth in paediatric patients.

Evaluating the reproducibility and validity of maximal mouth opening measurement techniques

ObjectivesA limitation of the maximal mouth opening (MMO) is a frequent complication of oral (cancer) surgery. The measurement between the right central incisors is considered the golden standard for assessing MMO, although it has been noted to overestimate MMO in edentulous patients. This study aims to evaluate the reproducibility and validity of four MMO techniques and to determine the extent to which they are dependent on the remaining dentition. Materials and MethodsFour methods for capturing the MMO were recorded in consecutive patients with mixed dentition. The degree of agreement between the different measurement methods was compared using Bland-Altman plots. To investigate the reproducibility of each method, intersession, interobserver and intraobserver reliability were calculated for measurements performed by two clinicians across two sessions. Two subgroups were created based on dentition: (A) cases missing at least one right central incisor, and (B) patients with both right central incisors present. ResultsAll but one intraclass correlation coefficient (ICC) demonstrated excellent reproducibility (ICC > 0.9). The highest ICC values were found for the intraoral MMO(iMMO) and corrected intraoral MMO(ciMMO) method. A significant relationship between the MMO in both subgroups was identified only for the intraoral Range of Motion (iROM) method (p=.010*). ConclusionThe findings suggest that the current golden standard for measuring MMO does not adequately account for the absence of the right central incisor(s). Two of the proposed methods, which include corrections for missing incisors, should be incorporated into future clinical trials on MMO.

Comparative evaluation of alveolar bone remodeling and root length changes in fixed appliances versus clear aligners: A retrospective cohort study on skeletal Class III malocclusion treatment

The retrospective study examined changes in the root length and alveolar bone surrounding maxillary incisors in patients with skeletal Class III malocclusion treated by surgical orthodontic treatment with either fixed appliances (FAs) or clear aligners (CAs). A total of 60 subjects were divided based on appliance type used. Cone beam computed tomography scans were taken at three stages: before treatment, after presurgical orthodontic treatment, and post-treatment for both groups. Vertical alveolar bone level and horizontal alveolar bone thickness (ABT) were measured at four heights (3, 6, and 9 mm from the cementoenamel junction, and the root apex), along with root length, at these time points. Both groups showed a decrease in root length, with the CA group experiencing a significantly smaller reduction (0.4 ± 0.79 mm) compared with the FA group (0.64 ± 0.8 mm; P = 0.02). The FA group demonstrated more significant reduction in palatal ABT (P < 0.05) and greater root resorption, whereas the CA group exhibited considerable labial marginal bone resorption (P = 0.007) and a notable decrease in labiolingual inclination (P = 0.042). The findings suggest that FA and CA might lead to decreased ABT and significant root resorption, with FA therapy likely resulting in more pronounced effects. Both modalities led to notable vertical bone loss, particularly, on the labial side of the maxillary incisors in the CA group during postsurgical orthodontic treatment. Preventing iatrogenic deterioration of periodontal support surrounding the incisors is crucial during presurgical and postsurgical phases.

Surgical Endodontic Management Of Maxillary Incisors: A Case Report

In the root canal system, infection of the pulp tissue caused by caries or other pathways is the primary cause of apical periodontitis. The ultimate goal of the endodontic treatment is to create adequate conditions for periradicular tissue healing. Nonsurgical endodontic treatment is a highly predictable treatment option in most cases, but surgery may be indicated for teeth with persistent periradicular pathosis unresponsive to nonsurgical approaches. The aim of this article is to highlight the possibility of the successful outcome of surgical endodontic treatment following failed non-surgical treatment of right maxillary central incisor. With proper case selection and operator skill, periradicular surgery can be considered predictable, cost-effective alternative to tooth extraction and tooth replacement.

3D-Printed One-piece Versus Two-piece Orthodontic Clear Aligner Attachments Bonded with Provisional Crowns: A Proof of Concept

ObjectivesThis study aimed to introduce a novel technique for fabricating provisional crowns integrated as a single unit with aligner attachments. MethodsA total of 60 crowns with attachments were prepared: 20 conventional (Protemp) and 40 3D-printed (20 bonded with attachments; 20 integrated with composite attachments as a single unit) using NextDent resin. Two central incisors were scanned (once without attachments and once with attachments) to create STL files for specimen printing. Half of the specimens (30, n=10 per group) underwent thermal cycling (5000 cycles). Shear bond strengths (MPa) were evaluated using a universal testing machine. The debonded areas and attachment failures were analyzed to determine the fracture type. Data analyses were performed using ANOVA and post hoc Tukey tests (α = .05). ResultsThe 3D-printed specimens showed higher strength values than the bonded attachments per group (P <0.001). The 3D-printed crowns with attachments demonstrated the highest strength (12.39±1.92 MPa). Thermal cycling significantly decreased the bond strength of the attachments (P <0.001), except in the 3D-printed crowns with composite attachments as a single unit, which showed no significant change after thermal cycling (P=0.643). In the bonded attachment groups, the adhesive type was the predominant failure mode, while in the 3D-printed groups, attachment fractures were the primary cause of failure. ConclusionThe 3D-printed provisional crowns with attachments have high strength and is clinically appropriate for orthodontic treatment when temporization of teeth is indicated. Clinical SignificanceThe developed technique for fabricating 3D-printed provisional restorations with orthodontics attachments as a single unit is a promising approach. The technique may be incorporated into the digital orthodontic treatment workflow when temporization is indicated.

Evaluating anchorage and torque control in adolescent patients with Class II Division 1 malocclusion among 3 appliances

The objective of this study was to compare the differences in anchorage and torque control among the Tweed edgewise, Roth, and physiological anchorage Spee-wire systems (PASS) appliances (Zhejiang Xinya Technology Co, Ltd, Hangzhou, China). A sample of 90 adolescent patients with Angle Class II Division 1 malocclusion (30 Tweed edgewise appliances, 30 Roth appliances, and 30 PASS appliances) with maximum anchorage requirements in the maxilla were collected for this study. The pretreatment baseline levels of the 3 groups were compared initially, and then the differences between the 3 appliances in anchorage and torque control were analyzed after superimposing the pretreatment and posttreatment lateral cephalograms and maxillary 3-dimensional (3D) digital models, respectively. There was no statistical difference in the pretreatment baseline levels of 3 groups, including gender, age, sagittal skeletal types (ANB), vertical skeletal types (SN-GoGn), anchorage requirements, and occlusal plane inclination (SN-OP). After superimposing the pretreatment and posttreatment lateral cephalograms and 3D digital models, respectively, no statistical differences were observed between the measurement results obtained from lateral cephalograms and 3D digital models. Among the measurement variables assessed in this study, statistical differences were observed in the mesial displacement of maxillary first molars, the incisor retraction, and the torque variation of maxillary central incisors among the 3 groups. Specifically, the Tweed group exhibited lower mesial displacement of maxillary first molars compared with the PASS and Roth groups. Furthermore, the Tweed group exhibited the greatest amount of incisor retraction and torque variation of maxillary central incisors, followed by the Roth group and then the PASS group. The remaining measurement variables for the 3 groups showed no statistical differences, including vertical variation of maxillary first molars and central incisors, torque variation of maxillary first molars and canines, mesiodistal inclination variation of maxillary first molars and canines, width variation between maxillary first molars, and width variation between maxillary canines. Compared with contemporary preadjusted straight wire appliances, the Tweed edgewise appliance has superiority in molar anchorage control. In contrast, compared with the Roth appliances, the PASS appliances without any auxiliary anchorage devices could make full use of physiological anchorage to achieve adequate control of molar anchorage. Clinical orthodontists may need to pay extra attention to physiological anchorage. The difference in torque control varies depending on the respective characteristics of bracket designs.

Treatment of Permanent Maxillary Incisor Associated with Supernumerary Tooth

Treatment of Permanent Maxillary Incisor Associated with Supernumerary Tooth

Craniofacial features and incisor position design of esthetics population after orthodontic treatment.

This study aims to provide craniofacial features and incisor position prediction models among esthetics population after orthodontic treatment. A total of 338 patients with esthetic profiles were selected from 1 055 post-orthodontic adults based on inclusion and exclusion criteria and scored by five dental students. Mean values of cephalometric measurement were demonstrated with gender and sagittal skeletal pattern (ANB) differences assessed by generalized estimating equation. Correlations among age, skeletal, and soft tissue variables in different genders were determined. Multivariate analysis was used to assess the influence of skeletal and soft tissue variables on orthodontic incisor position. Within the esthetic cohort after orthodontic treatment, gender differences existed in cranial and mandibular length, mandibular rotation, protrusion of pogonion, inclination of maxillary incisors, upper lip thickness, lower 1/3 face height, and nose protrusion. However, in class Ⅰ malocclusion, the development of the chin showed no significance, whereas the protrusion of the lower lip significantly differed between genders, with less protrusion in males. In males, the protrusion of lip and chin varied among groups, with thinner basic upper lip thickness of class Ⅱ than class Ⅰ and greater lower lip height of class Ⅲ than class Ⅰ. In females, the protrusion and height of the upper lip and chin varied in groups, with thicker basic upper lip thickness of class Ⅲ than class Ⅰ. Upper lip thickness, female basic upper lip thickness, and female lower lip height were correlated with age. The protrusion of the upper lip was mainly correlated with posterior cranial base, mandibular body length, ANB in male and SNA, ANB, sagittal maxillary length, mandibular rotation, and protrusion of pogonion in female. The protrusion of the lower lip in males was mainly correlated with ramus height, mandibular rotation, protrusion of pogonion in male and ANB, mandibular rotation, and protrusion of pogonion in females. After employing skeletal variables to fit dental parameters, optimal results were achieved in male IMPA (adjusted R2=0.712) and female G Vert-U1 (adjusted R2=0.795). After employing skeletal and soft tissue variables simultaneously, optimal results were achieved in male and female G Vert-U1, which was mainly influenced by the protrusion of the chin and nasal base in males (adjusted R2=0.836) and the protrusion of the nasal base as well as ANB in females (adjusted R2=0.842). This study demonstrated the craniofacial features of esthetics population after orthodontic treatment and revealed the correlation of gender, age, skeleton, and soft tissues to provide reliable prediction models for aesthetic orthodontic incisor position.