Adult skeletal Class II high-angle case treated with a fully customized lingual bracket appliance

Non-surgical correction of an adult Class II high-angle with occlusal plane cant by four compromised permanent first molars extraction, preadjusted lingual appliance and miniscrews: A case report

This case report describes a complex full-step asymmetrical Class II division 1 high-angle in an adult patient treated by extraction of compromised first molars with a preadjusted lingual appliance. Since the patient presented severe sagittal and vertical discrepancies combined with an Izard orthofrontal profile with upper lip protrusion, an extraction camouflage was performed with the twofold aim of obtaining ideal occlusal relationship and profile improvement, correcting occlusal plane cant by selective intrusion with interradicular miniscrews. Appropriate biomechanical strategies, including extraction choice and anchorage control during space closure, were needed to achieve the planned results. This case report demonstrates the possibility of solving successfully severe sagittal and vertical discrepancies with significant asymmetric component in adult patient without surgical treatment by means of a completely invisible technique, with the extraction of the most compromised teeth in both arches. This report also underlines the need for careful planning during both diagnostic and treatment phases, with appropriate skeletal anchorage management, in order to obtain the best results.

Predicting changes of incisor and facial profile following orthodontic treatment: a machine learning approach

BACKGROUND

Facial aesthetics is one of major motivations for seeking orthodontic treatment. However, even for experienced professionals, the impact and extent of incisor and soft tissue changes remain largely empirical. With the application of interdisciplinary approach, we aim to predict the changes of incisor and profile, while identifying significant predictors.

METHODS

A three-layer back-propagation artificial neural network model (BP-ANN) was constructed to predict incisor and profile changes of 346 patients, they were randomly divided into training, validation and testing cohort in the ratio of 7:1.5:1.5. The input data comprised of 28 predictors (model measurements, cephalometric analysis and other relevant information). Changes of U1-SN, LI-MP, Z angle and facial convex angle were set as continuous outcomes, mean square error (MSE), mean absolute error (MAE) and coefficient of determination (R²) were used as evaluation index. Change trends of Z angle and facial convex angle were set as categorical outcomes, accuracy, precision, recall, and F1 score were used as evaluation index. Furthermore, we utilized SHapley Additive exPlanations (SHAP) method to identify significant predictors in each model.

RESULTS

MSE/MAE/R2 values for U1-SN were 0.0042/0.055/0.84, U1-SN, MP-SN and ANB were identified as the top three influential predictors. MSE/MAE/R2 values for L1-MP were 0.0062/0.063/0.84, L1-MP, ANB and extraction pattern were identified as the top three influential predictors. MSE/MAE/R2 values for Z angle were 0.0027/0.043/0.80, Z angle, MP-SN and LL to E-plane were considered as the top three influential indicators. MSE/MAE/R2 values for facial convex angle were 0.0042/0.050/0.73, LL to E-plane, UL to E-plane and Z angle were considered as the top three influential indicators. Accuracy/precision/recall/F1 Score of the change trend of Z angle were 0.89/1.0/0.80/0.89, Z angle, Lip incompetence and LL to E-plane made the largest contributions. Accuracy/precision/recall/F1 Score of the change trend of facial convex angel were 0.93/0.87/0.93/0.86, key contributors were LL to E-plane, UL to E-plane and Z angle.

CONCLUSION

BP-ANN could be a promising method for objectively predicting incisor and profile changes prior to orthodontic treatment. Such model combined with key influential predictors could provide valuable reference for decision-making process and personalized aesthetic predictions.

Effect of torque customization with composite resin bases on the shear bond strength and adhesive remnant patterns of lingual brackets : An in vitro evaluation

PURPOSE

This study evaluated the effect of torque customization of lingual brackets with resin-modified bases on their shear bond strength (SBS), adhesive remnant index (ARI), and bond failure patterns (BFP).

METHODS

The sample comprised 200 lingual lower incisor brackets (DTC® ORG, DTC Medical Apparatus, Hangzhou, China); 40 brackets were tested as-received and 4 groups with 40 brackets each were customized for -10, -20, +10 and +20° torque respectively with light-cured composite resin (Transbond XT™, 3M Unitek, Monrovia, CA, USA) bases. All brackets were bonded to bovine mandibular incisors. Their SBS were estimated in a universal testing machine (INSTRON®, Norwood, MA, USA) with a gingivally directed force applied at the incisal bracket-adhesive interface with 1 mm/min crosshead speed. Their ARI and BFP were evaluated under 20× magnification.

RESULTS

The SBS was 19.9 ± 7.6 MPa for noncustomized brackets, 20.1 ± 9.0 and 18.7 ± 8.2 MPa for brackets with 10 and 20° of negative torque, and 16.6 ± 5.68 and 19.45 ± 5.84 MPa for brackets with 10 and 20° of positive torque, respectively. The differences were not statistically significant (p = 0.097). Teeth with the -20° brackets exhibited higher median ARI scores than noncustomized brackets (1.5 vs 2, p = 0.018). Adhesive-cohesive bond failure with nearly axial split was more frequent in noncustomized brackets than customized ones, the reverse being true for adhesive-cohesive failure with nearly vertical split (p < 0.05). Truly cohesive bond failures were seen only in brackets with positive torque.

CONCLUSIONS

Torque customization with a resin base is an acceptable strategy for metal orthodontic brackets as it does not affect their SBS. However, their BFP differed from noncustomized brackets, depending on the type of torque introduced.

Numerical Simulation of Maxillary Anterior Teeth Retraction Utilizing Power Arms in Lingual Orthodontic Technique

AIMS

It was the scope of this study to explore the biomechanical implications of retraction force application point modifications in lingual orthodontics, aiming to mitigate the bowing effect and enhance anchorage stability in the anterior teeth.

METHODS

Using the FE method on an idealized maxillary model, en masse retraction was simulated using a modified lingual fixed appliance including edgewise lingual brackets, a 0.017″ × 0.025″ mushroom-shaped archwire, and power arms between lateral incisors and canines, with a transpalatal arch (TPA) connecting the first molars. Applying bilateral retraction forces of 1.5 N at twelve positions, initial tooth displacements during space closure were evaluated.

RESULTS

Shifting power arms gingivally did not effectively counteract palatal tipping of incisors but reduced posterior and palatal tipping of canines with a power arm length of 11.3 mm preventing posterior tipping. Apically displacing the TPA retraction force increased mesiobuccal rotation while preventing mesial molar tipping for retraction forces applied 12.6 mm from the archwire.

CONCLUSIONS

Apically shifting retraction forces can mitigate vertical bowing effects in lingual orthodontics, yet it also highlights the challenges in maintaining torque in the anterior teeth. Further research and clinical validation are essential in order to confirm these results, emphasizing the complexity and need for advanced biomechanical strategies in personalized lingual orthodontic treatments.

Digital lingual appliance combined with micro-screws for the treatment of a skeletal bimaxillary protrusion and ‘gummy’ smile

This case report describes the lingual orthodontic treatment of a 28-year-old female patient who presented with a bimaxillary protrusion malocclusion, a hyperdivergent facial pattern, mentalis strain, and a ‘gummy’ smile. To achieve favourable occlusal and facial results, the four first premolars were extracted, and micro-screws utilised to provide maximum anchorage. With the widespread application of three-dimensional technology, a digital goal-oriented treatment plan was applied for its predictability and precision. A fully customised lingual appliance system with preset torque in the anterior teeth combined with ribbon-wise arch wires was placed to prevent excessive lingual inclination of the incisors during retraction. As a result, an attractive facial profile and a well-aligned dentition with ideal intercuspation was obtained.

Torque efficiency of a customized lingual appliance : Performance of wires with three different ligature systems

PURPOSE

Torque control in lingual orthodontics is key to obtain optimal esthetic results. The aim of this in vitro experimental study was to verify the efficiency of the ligature-archwire-slot system in torque control using a customized lingual appliance.

METHODS

An idealized cast with eight extracted human teeth was created and a set of customized lingual brackets was obtained. Tests were performed with the following wires: 0.016″ × 0.022″ nickel-titanium (NiTi), 0.016″ × 0.024″ stainless steel (SS), 0.017″ × 0.025″ βIII titanium (βIIITi), 0.0182″ × 0.0182″ βIIITi, 0.018″ × 0.025″ SS, 0.018″ × 0.025″ NiTi, 0.018″ × 0.025″ βIIITi, and three types of ligatures were tested using a universal testing machine to calculate the efficiency in torque control. A blind statistical analysis was performed.

RESULTS

Based on post hoc multiple comparisons, differences were found for two of the three ligatures when using the 0.016″ × 0.022″ NiTi wires (p < 0.001 for both ligatures). When considering all ligatures, 0.018″ × 0.025″ SS and 0.018″ × 0.025″ βIIITi were significantly different from all other wires (p < 0.001 in all cases). With a moment of 5 Nmm, the 0.016″ × 0.022″ NiTi wire developed median angles of 26.7, 29.8, and 38.7° with the three ligatures, respectively, while the 0.018″ × 0.025″ SS developed median angles of 12.9, 10.7, and 12.7°, respectively.

CONCLUSIONS

The ligature type and geometry did not affect the efficiency of torque control, except for the 0.016″ × 0.022″ NiTi wire. The wires generating the greatest moments were the 0.018″ × 0.025″ SS and 0.018″ × 0.025″ βIIITi.

Ribbon-wise customized lingual appliance and orthodontic anchor screw for the treatment of skeletal high-angle maxillary protrusion without bowing effect

This case report demonstrates the treatment of a skeletal Class II high-angle adult patient with bimaxillary protrusion, angle Class I occlusion, and crowded anterior teeth. A ribbon-wise arch wire and a customized lingual appliance with anterior vertical slots were used to achieve proper torque control of the maxillary anterior teeth. An orthodontic anchor screw and a palatal bar were used for vertical control to avoid increasing the Frankfort-mandibular plane angle (FMA) by maxillary molar extrusion. Through the combined use of the ribbon-wise customized lingual appliance, palatal bar, and orthodontic anchor screw, vertical control and an excellent treatment result were achieved without the vertical and horizontal bowing effects peculiar to conventional lingual treatment.

Dentoskeletal and soft tissue changes associated with miniscrew anchorage in customized lingual orthodontics

Objectives

The goal of this study was to analyze skeletal, dental, and soft tissue changes of patients treated with customized lingual systems and to evaluate the clinical effectiveness of miniscrew anchorage.

Methods

Nine upper first premolar extraction patients who were treated with customized lingual appliances were included in this study. Miniscrews were used for reinforcement of molar anchorage. Cephalometric films and study models were obtained before treatment (T1), after alignment (T2), and after treatment (T3). Treatment effects were analyzed by cephalometric radiographs and study models.

Results

The upper anterior teeth were retracted significantly at T2 and T3 (4.41 ± 4.14 mm and 5.51 ± 2.48 mm, respectively). During space closure, the upper first molars showed slight mesial movement (1.50 ± 1.97 mm). The intercanine width of the upper arch increased at T2 (1.59 ± 1.81 mm), but decreased at T3 (0.11 ± 1.00 mm). The sella-nasion-A, A-nasion-B, and mandibular plane angles were not significantly changed at T3. The upper lip showed continuous retraction at both T2 and T3 (1.40 ± 1.46 mm and 2.32 ± 2.48 mm, respectively).

Conclusions

By using miniscrew anchorage for lingual orthodontics, patients’ dental and soft tissue changes considerably improved and molar anchorage was reinforced.