Lingual Appliance Research Articles

Oral Impacts of Aligners versus Fixed Self-Ligating Lingual Orthodontic Appliances

The aim of this prospective study was to compare a fixed lingual orthodontic appliance with a commonly used aligner system, focusing on oral impacts and speech disturbances, during the first 3 months of orthodontic treatment. Two groups of adults were evaluated: 21 treated with Invisalign® and 26 with In-Ovation L® lingual brackets. Health-related quality of life questionnaires were used to assess the oral impacts, and speech samples were collected for speech evaluation by professionals. The levels of pain and painkiller intake were similar, increasing on the first day, and decreasing at 3 months. Subtle injuries on the lip and cheeks were initially reported in the aligner group. Lingual patients experienced more discomfort in swallowing and opening the mouth, tongue injuries and food residues, even at 3 months. The consonants “s” and “z” were mainly affected in both groups immediately after appliance insertion, but more often in the aligner group. These speech disturbances recovered in the following 3 months. In conclusion, both groups reported disturbances in quality-of-life measures; however, patients wearing lingual appliances experienced more disturbances, which persisted after three months. Speech disturbances were slightly more pronounced in the aligner group and recovered after three months.

Application of corticotomy associated with customized lingual orthodontics in treatment of severe bimaxillary protrusion in adults

Bimaxillary protrusion is a clinical condition with high prevalence rate, which damages facial esthetics and affects the mental health of patients. Its clinical manifestations include protrusion of lips, overexposure of teeth, vertical and sagittal overdevelopment of alveolar bone in the anterior areas of upper and lower anterior jaws, and so on. The common protocols for the treatment of severe bimaxillary protrusion is orthodontic treatment with exaction of premolars or combined orthognathic-orthodontic treatment. However, either method is of great difficulty. By systematic mechanical design, the author used the treatment system of customized lingual appliances associated with corticotomy to realize the vertical and torque control of the anterior teeth, and obtain the orthodontic treatment effect of both esthetics and health. The clinical strategies for the treatment of severe bimaxillary protrusion were provided.

Comparative analysis of growth factors and chemokine secretions between conventional lingual and labial fixed orthodontic appliances

Orthodontic appliances elicit the secretions of some cytokines, chemokines, and growth factors which further have some significances in the remodeling of periodontium tissues. The significant differential forces applied on the periodontium by different types of orthodontic appliances. The secretion of these factors is indirectly responsible for the proper resorption of bones of the periodontal region through molecular signaling, which further supports to facilitate organized movement of the teeth. Objective: In the present study, we carried out the assessment and comparative analysis of the growth factors and chemokines present in the saliva samples of the human subjects of orthodontic treatment with two different treatment modalities: conventional lingual and labial fixed orthodontic appliances. Total 40 saliva samples were collected of which 20 subjects were treated with the conventional lingual appliances and 20 subjects with the labial fixed appliances. All the salivary samples were acquired from the subjects after 21 days treatment. Cytometric bead array was performed to assess the growth factors and chemokines in the saliva on the flow cytometer. No significant differences were seen in the growth factor secretion in the saliva of both types of subjects. The same trend was observed for the chemokine secretion in the saliva except CXCL8, CCL11, CCL2, CCL5, and CXCL9. The similarity in chemokine and growth factor profile between labial and lingual fixed orthodontic appliances indicates that their molecular mechanisms and overall effect on the periodontium are analogous.

Vertical and Orovestibular Forces Generated by Beta-Titanium and Stainless-Steel Rectangular Wires in Labial and Fully Customized Lingual Bracket Systems.

This study aimed to investigate the force values exerted from rectangular wires when combined with conventional labial and fully customized lingual appliances under predefined, idealized activation. Fully customized lingual brackets of two brands Incognito™ (3M Unitek, Monrovia, CA, USA) and WIN (DW Lingual Systems, Bad Essen, Germany) and labial brackets of another brand, discovery® MIM and discovery® smart systems (Dentaurum, Ispringen, Germany), were chosen. Stainless-steel and beta-titanium wires of 0.018” × 0.025” were examined. For IncognitoTM, 0.0182” × 0.025” beta-titanium wires were tested. Intrusion/extrusion and orovestibular movements were performed in a range of 0.2 mm, and the forces were recorded for each 0.1 mm of the movement. Mean values and standard deviations were calculated for all measurements, and ANOVA was performed for statistical analysis. Slight differences were observed between the forces generated from beta-titanium and stainless-steel wires. The same wire generated in some cases 5–53% higher forces with the lingual appliance due to the vertical orientation of the long walls during intrusion/extrusion and increased wire stiffness at the anterior region. Beta-titanium and stainless-steel 0.018” × 0.025” wires can generate similar force values during the final stages of the orthodontic therapy; thus, possibly only one of the two alloys could be used in each orthodontic wire sequence.

Frictional Forces of Three Types of Lingual Appliance with Self-ligating Mechanisms

The present study compared the frictional forces of three types of self-ligating lingual appliances. The lingual appliances (2D, Forestadent; Alias, Ormco; and Clippy L, Tomy International) consisted of a self-ligating bracket (second premolar) and two self-ligating tubes (first and second molars) bonded to a stainless steel jig and attached to a "drawing-friction tester." Full-size and non-full-size stainless steel archwires were tested, and the static and kinetic friction acting on six lingual appliance/wire combinations was estimated (n = 5). Three-dimensional micro-computed tomography (micro-CT) analysis of each premolar bracket was performed. The frictional forces were compared between the bracket/wire combinations using the Kruskal-Wallis and Mann-Whitney U tests. The Alias and Clippy L bracket/wire combinations had greater contact between the wire surfaces and bracket slots compared to the 2D bracket/wire combination. For all lingual appliances, the static and kinetic frictional forces were significantly higher for the full-size than non-full-size archwire. The 2D bracket, which had a wider outer wing, had less frictional force than the other appliances. The Alias, which had a narrower outer wing, had a significantly lower frictional force than the Clippy L. Frictional force was significantly higher for heavier full-size bracket/archwire combinations than for non-full-size archwires. The 2D bracket had lower frictional force due to its archwire-holding mechanism. The outer wing width may influence the frictional resistance. The frictional forces of self-ligating lingual appliances vary, and bracket design and archwire size may influence the frictional performance.

Objective treatment outcome assessment of a completely customized lingual appliance: A retrospective study

ObjectiveTo assess the outcome quality of subjects treated with a completely customized lingual appliance (CCLA) in a postgraduate university program, using the ABO Objective Grading System (OGS), by testing the null-hypothesis of a significant proportion of post-treatment cases exceeding an adjusted ‘exam failure’ threshold value of OGS=24. Materials and MethodsThis retrospective single-arm study included 66 consecutively debonded CCLA cases (m/f 19/47; mean age: 25.1±9 years) treated at Hannover Medical School (MHH, Hannover, Germany). The discrepancy index (DI) was assessed on initial plaster casts. The OGS of the cast-radiograph evaluation was scored for both set-up and post-treatment casts, including the seven components of alignment/rotation, marginal ridges, buccolingual inclination, overjet, occlusal contacts, occlusal relationships and interproximal contacts, to parameterize differences between those. ResultsDI score distribution (≥20, <20) was 25 (37.9%)/41 (62.1%) subjects. Mean initial DI was 17.3±8.5. Mean set-up OGS was 10.4±4.4 (min-max: 3–21), mean final OGS was 17.7±5.9 (min-max: 7–33), and the difference 7.3 (post-treatment - set-up) was statistically significant (p<0.0001; 95% CI [5.8, 8.7]). The null-hypothesis was rejected: A statistically significant proportion of the final casts (n=58; 87.8%) scored below OGS=24 by exact binomial test (P<0.0001; 95% CI [77.5%, 94.6%]). The rate of a final OGS score<24 was not significantly different (P=0.98) between both DI (≥20, <20) groups. ConclusionsThe outcome quality of the CCLA treatment in this postgraduate university setting was high and therefore sufficient for a vast majority of treated cases to pass the ABO-OGS clinical examination.

Comparison of the Treatment Effectiveness between Labial and Lingual Fixed Mechanotherapy and Patients’ Response toward Lingual Fixed Mechanotherapy: A Prospective Clinical Study

Objective: The present study was conducted to evaluate the effectiveness of treatment outcome using American Board of Orthodontics (ABO) scoring and total treatment time between labial and lingual appliance and also to assess patients’ perception of the lingual appliance system. Materials and Methods: Twenty patients requiring first premolar extraction were selected; 10 patients were treated with a lingual and 10 with a labial appliance. The treatment duration and ABO scores were recorded from the posttreatment dental casts and orthopantomogram (OPG). A questionnaire was used to evaluate the perception of patients on lingual treatment using a visual analogue scale (VAS). Results: The total ABO scores of the 2 groups were not statistically significant. The lingual- and labial-appliance treatments were completed in 19.30 ± 7.50 and 22.40 ± 6.35 months, respectively. The VAS showed that lingual-appliance patients experienced a moderate amount of pain and discomfort to the tongue and soft tissues. Patients did not have considerable difficulty with speech and in maintaining oral hygiene. Conclusion: Lingual appliance cases finished with a comparable quality of orthodontic treatment precision well within the normal treatment time frame. These patients had moderate difficulties with speech, tongue irritation, and pain. They did not have difficulty in maintaining their oral hygiene and were satisfied with their smile and treatment outcome.

Class II correction by maxillary en masse distalization using a completely customized lingual appliance and a novel mini-screw anchorage concept \u2013 preliminary results

BackgroundThe aim of the study was to evaluate the efficacy of a novel en masse distalization method in the maxillary arch in combination with a completely customized lingual appliance (CCLA; WIN, DW Lingual Systems, Germany). Therefore, we tested the null-hypothesis of a significant deviation from an Angle-Class I canine relationship and a normal overjet defined by an individual target set-up after dentoalveolar compensation in Angle Class II subjects.Methods This retrospective study included 23 patients, (m/f 3/20, mean age 29.6 years (min/max, 13.6/50.9 years)), with inclusion criteria of an Angle Class II occlusion of more than half a cusp prior to en masse distalization and treatment completed consecutively with a CCLA in combination with a mini-screw (MS) anchorage for uni- or bilateral maxillary distalization (12 bilateral situations, totalling 35). Plaster casts taken prior to (T0) and following CCLA treatment (T3) were compared with the treatment plan / set-up (TxP, with a Class I canine relationship and a normal overjet as the treatment objective). MSs were placed following levelling and aligning (T1) and removed at the end of en masse distalization at T2. Statistical analysis was carried out using Schuirmann’s TOST [two one-sided tests] equivalence test, based on a one-sample t-test with α = 0.025 on each side (total α = 0.05).ResultsNinety-seven percent of planned correction of the canine relationship was achieved (mean 3.6 of 3.7 mm) and also 97 % of the planned overjet correction (mean 3.1 of 3.2 mm), with a statistically significant equivalence (p < 0.0001) for canine relationship and overjet between the individual treatment plan (set-up) and the final outcome. Adverse effects were limited to the loss of n = 2 of 35 mini-screws. However, in each instance, the treatment was completed, as scheduled, without replacing them. Accordingly, the null-hypothesis was rejected.ConclusionsThe technique presented allows for a predictable correction of an Angle-Class II malocclusion via dentoalveolar compensation with maxillary en masse distalization.

How efficient is customized lingual orthodontics? An assessment of treatment outcome.

To assess the efficacy of lingual orthodontics by comparing setups and post-treatment casts. Thirty-two consecutive patients treated with a customized lingual orthodontic appliance were included in this retrospective study. Initial casts, post-treatment casts and setups were scanned, and the digital models produced were analysed in terms of overjet; overbite; molar and canine relationships; intercanine, interpremolar and intermolar distances; upper and lower arch lengths; midline deviation; bucco-lingual angulation of all teeth and mesio-distal angulation of anterior teeth. Comparisons between setups and post-treatment casts were performed via paired t tests. Relationships between the planned and actual correction were studied using regression analysis. Statistically significant differences in bucco-lingual torque between setups and post-treatment casts were found for all upper teeth, except for central incisors. In the lower jaw, statistically significant differences in bucco-lingual torque were found between setups and post-treatment casts for the lower incisors and molars. No statistically significant differences in mesio-distal angulation of anterior teeth were found between setups and post-treatment casts. Upper and lower arch widths did not vary significantly between setups and final casts, except upper inter-second premolar and intermolar distances. Customized lingual appliances offer efficient control of mesio-distal angulation of all anterior teeth. Significant differences in torque between setups and post-treatment casts were observed for upper lateral incisors, canines, premolars and molars, as well as lower incisors and molars. However, the torque difference was clinically significant (over three degrees) for upper second premolars and molars only.

Comparative study of effect of different lever arm positions and lengths on transverse and vertical bowing in lingual orthodontics – An FEM study

To assess the influence of changing the size and position of lever arm on transverse and vertical bowing effects during retraction in lingual biomechanics. A three dimensional 3D finite element method was used to simulate en masse anterior teeth retraction using lingual appliance with sliding mechanics. Two groups were made, 1st group had lever arm mesial to canine while 2nd group had distal to canine. Each group had 4 subgroups with lever arm height varying from 0mm to 12mm. Displacements of the maxillary anterior teeth were noted in each group. As the Lever Arm Height (LAH) increased in group I, the vertical bowing effect reduced while the transverse bowing increased with respect to canines. In group II, both vertical and transverse bowing effects increased but transverse bowing was less as compared to group I. Strategic location of the lever arm is required in different clinical situations during en-mass retraction, keeping in mind the location of Centre of Resistance (CRes) as well as the vertical and the transverse bowing effects.

Area and Volume of Remaining Cement and Enamel after Removal and Polishing of Buccal or Lingual Multibracket Appliances

The aim of the present study was to compare the area and volume of remaining cement after lingual and buccal multibracket appliance debonding. Further, the area and volume of cement remaining and the area and volume of enamel were also analyzed using a morphometric digital measurement technique. Ten buccal and 10 lingual multibracket appliances were cemented in 20 extracted teeth embedded into an epoxy resin model simulating a dental arch. The models were scanned before bonding the lingual and buccal multibracket appliances, after debonding the lingual and buccal multibracket appliances, and after polishing the remaining cement. Afterwards, the standard tessellation language (STL) digital files were aligned, segmented, and realigned by using engineer morphometry software. A comparative analysis was performed using Student’s t test statistical analysis. Lingual appliances showed statistically significantly (p &lt; 0.001) less area (7.07 ± 4.85 mm2) and volume (0.87 ± 1.34 mm3) of remaining cement than the area (21.99 ± 4.18 mm2) and volume (p = 0.002) (3.48 ± 0.96 mm3) of buccal appliances. Moreover, lingual appliances showed statistically significantly (p = 0.001) less area (4.48 ± 3.08 mm2) and volume (0.13 ± 0.15 mm3) of remaining cement after polishing than the area (12.22 ± 5.98 mm2) and volume (p = 0.004) (0.70 ± 0.56 mm3) of buccal appliances. Lingual multibracket appliance therapy leads to less area and volume of cement remaining after multibracket appliance debonding and less area and volume of cement remaining after cement polishing than buccal multibracket appliance therapy; however, the area and volume of enamel removed after cement polishing were similar between both lingual and buccal multibracket appliance therapies.

Phonetic Alterations Caused by Different Lingual Appliances

Objective: To evaluate the differences in phonetic alterations caused by three different lingual appliances, all bonded in sequence on the same patients. Material and Methods: Lingual brackets (STb, Incognito and Harmony) were bonded from 1.3 to 2.3 with a 0.013 CuNiTi archwire. The text was formulated to evaluate the phonetic variations in a controlled context (logatomi) and more casual sentences. The recording of the text was performed at time t0 (before positioning the brackets), t1 (after positioning the brackets) and t2 (60 minutes after positioning the brackets). An ANOVA-type analysis was performed. Results: A significant correlation was confirmed between the effects of all the linguistic methods used compared to the absence of the same. The most influenced acoustic variables were the center of gravity of the acoustic spectrum of the analyzed sounds (CoG) and the number of zero crossings of the instantaneous amplitude curve of the considered signal. Conclusion: The effects deriving from the positioning of the various brackets were relatively contained: in some cases, for some subjects, for some consonants and in specific contexts, some brackets may occasionally be less invasive than others. However, no lingual system was systematically better than others regarding phonetic alterations.

Comparative Analysis of Stiffness of Lingual Appliances: An in Vitro Study

Objective: To analyze and compare the stiffness of different lingual appliances with different archwires . Material and Methods: The three-point bending test was used to analyze the stiffness of the lingual archwires for the different lingual systems: eBrace, Harmony, Incognito, and STb. The deflection load curve of each archwire was obtained to evaluate how the section, the material and the manufacturer affect the elasticity and stiffness characteristics of the wires. The comparison of the stiffness between different systems was carried out through a factor variance analysis with three factors (manufacturer, cross-section, and material), followed by the post-hoc Tuckey test. Results: An increase in the system's rigidity was reported as the wire section increases, regardless of the manufacturer. The stainless steel archwires have ever higher stiffness values than NiTi and TMA. The STb wires of CuNiTi material, by virtue of the characteristics of the thermal wires, have flatter and lower load-deflection curves than the NiTi wires of other manufacturers . Conclusion: Archwires section and material showed a significant influence on the stiffness of the lingual systems. Archwires of the same section and material but different manufacturers show different load-deflection curves of stiffness.

Accuracy of three different customized lingual orthodontic appliance systems in achieving predicted results on maxillary anterior teeth: A Retrospective Cohort Study.

OBJECTIVE:To comparatively evaluate the ability of three different customized lingual appliance systems in achieving predicted results with respect to the mesiodistal crown tip, labiolingual crown inclination, in–out position of Maxillary permanent anterior teeth, and Maxillary arch form.METHODS:Three commercial houses: Incognito, iLingual 3D, and Lingual matrix were analysed in this study. The final sample size consisted of 42 cases. Fourteen digital prediction and posttreatment models of the maxillary arch were provided by three orthodontic offices each using a different system. Discrepancies between the prediction and posttreatment model in mesiodistal tip, labiolingual inclination, in–out position of anterior teeth, and arch form were analyzed.RESULTS:Incognito displayed the highest accuracy in all parameters except for in–out positioning. Lingual Matrix showed greater precision in achieving planned mesiodistal positions than labiolingual inclination while it was just the opposite for iLingual 3D. All three systems proved to be clinically reliable in achieving the predicted in–out positions of permanent Maxillary anterior teeth.CONCLUSION:These systems were considerably accurate in achieving planned treatment goals with minute deviations from the predicted value.

Effects of debonding a conventional &amp; customized lingual appliance on enamel structure- An invitro study

Introduction: To evaluate the surface changes on enamel structure after debonding of customized and conventional lingual brackets bonded using restorative dual cure bonding material and a chemically cured bonding material with and without sandblasting.&#x0D; Materials and Method: The sample consisted of 40 premolar teeth extracted for the purpose of orthodontic treatment. Enamel surface changes, prior to bonding, were studied using a stereomicroscope (Olympus SZX7) and an optical microscope. 20 extracted premolars were arranged in 2 arch forms with 5 teeth in each quadrant, after which impression of the arches with rubber base impression material was made. These impressions were then sent to the laboratory for the fabrication of a customized lingual appliance. The remaining 20 premolars were divided into 2 arches, each arch having 10 extracted premolars divided into 4 sets, 1st to test customized brackets bonded with chemical cure resin without sandblasting, 2nd to test customized brackets with dual cure resin without sandblasting, 3rd to test conventional brackets with chemical sure resin with and without sandblasting and 4th to test conventional brackets bonded with dual cure resin with and without sandblasting. The post debonding photographs were analyzed using a standardized grid and Surface Roughness Index.&#x0D; Result: Thus, enamel defects are likely to be caused post debonding despite of using any combination. However, the surface roughness index has been shown to be highest post debonding in cases where customized brackets have been bonded using dual cure resin along with sandblasting.&#x0D; Conclusion: While a clinician may opt for a material like Rely X U200 to bond lingual appliances in order to have a better clinical management of the appliance, but he would have to keep the possibility of irreversible damage to enamel post debonding.

Current status of clinical orthodontics in European and American countries

Current status of clinical orthodontics in European and American countries was examined by means of a questionnaire survey through internet. In the European and American countries, most popular technique in daily orthodontic practice is preadjusted straight wire edgewise technique. In major developed countries in Europe and America, the treatment fee is considerably high, whereas the fee is relatively low in the countries under development and/or after economic crisis. Rate of non-extraction treatment among all the cases treated with multi-bracket appliances is significantly higher in Europe and America than in Asia except in a few countries. In the European and American countries, treatment system for jaw deformity patients is well developed with higher availability of the social health insurance than in Asia. The maximum CLP prevalence of 0.200 is found in Germany and Austria and the mean is around 0.140 or one to 700 births. In general, CLP treatment is covered by social health insurance in European and American countries. In Europe and America, lingual orthodontic technique has not become popular because patients never want to hide orthodontic appliance. Higher cost of lingual appliance and lack in information and technical skills may be the reasons of less frequent use of lingual appliance. Many interviewees replied that usage of TADs has not become so popular in USA and Canada as compared to that in Asia. In another word, the initial fascination with TADs wore off and are now used in selected patients as needed. This may be due to more harmonious maxillofacial structure with longer and wider dentitions in Caucasians which also results in higher rate of non-extraction treatment with multibracket appliances in European and American countries.

Clinical outcomes of lingual fully customized vs labial straight wire systems : Assessment based on American Board of Orthodontics criteria.

To evaluate orthodontic treatment outcome in patients treated with alingual appliance (Incognito™ Appliance System, 3MUnitek, Monrovia, CA, USA) versus patients treated with alabial appliance (Victory series™, 3MUnitek, Monrovia, CA, USA). Atotal of 72patients were retrospectively analyzed. The complexity of each case was evaluated using the American Board of Orthodontics (ABO) Discrepancy Index (DI), and orthodontic clinical outcomes were evaluated using the ABO Objective Grading System (cast-radiograph evaluation: C‑REval). The mean total ABO C‑REval score was 16 ± 9.1 in the labial appliance group and 12.7 ± 5.4 in lingual appliance group (p = 0.152). The mean total ABO-DI scores were 16.3 ± 7.3 and 15.4 ± 6.6 in the labial and lingual appliance groups, respectively (p = 0.445). A significant correlation was observed between the total DI and total C‑REval scores. In this particular study and in the hands of two experienced orthodontists, no differences in the finishing quality of orthodontic treatments using the lingual technique or the buccal appliance technique were found. However, further prospective studies with larger sample sizes are necessary in order to generalize these results.

The Herbst appliance combined with a completely customized lingual appliance: A retrospective cohort study of clinical outcomes using the American Board of Orthodontics Objective Grading System

In this retrospective study we aimed to evaluate the quality of treatment outcomes using the American Board of Orthodontics (ABO) scoring system with a completely customized lingual appliance used in combination with a Herbst appliance for Class II correction. Patient selection criteria for this study were Class II division 1, II/2 or subdivision treated with a WIN® lingual appliance combined with an L-pin Herbst device. Thirty-two consecutively debonded cases were included in this retrospective case series. Pre- and post- treatment dental casts, dental set-ups, panoramic X-rays, cephalometric analysis, photographs and clinical files were available for data collection. The primary outcome was the ABO score based on the Discrepancy Index (ABO DI) including: overjet, overbite, anterior open bite, lateral open bite, crowding, occlusion (Angle class), lingual posterior crossbite, buccal posterior crossbite, ANB, IMPA and SN-GoGN angles and the Cast-Radiograph Evaluation (ABO CR-Eval) comprising of alignment/rotations, marginal ridges, buccolingual inclination, overjet, occlusal contacts, occlusal relationship (Angle class), interproximal contacts and root angulation. In addition, overjet, overbite and Class II correction were also evaluated on pre- and post-treatment models. The secondary outcome was bracket failure and complications related to the Herbst device. The study cohort included 18 female and 12 male patients with a mean age of 15.8 (range 12, 6- 18, 5). Twenty patients were Class II division 1 and ten were Class II division 2. The mean pre-treatment value of ABO DI was 20.8 (range 10-39); more than two-thirds of the sample were rated as being either of moderate difficulty (ABO DI: 16-24) or severe (ABO DI: over 25). The average post-treatment ABO Cast-Radiograph Evaluation score was 15.0 (SD=4.4), which is considered a passing score. Twenty-six patients had a score equal or lower than 20 (undisputed passing score). The Class II discrepancy was effectively corrected from a score of 16.83 penalty points (SD: 3.65) pre-treatment to a score of 1.57 (SD: 1.70) post-treatment. No association was found between initial and final Class II occlusal relationships (P=0.42), indicating that regardless of the initial discrepancy, no difference in the success of Class II correction was observed. The mean bracket failure rate was 3.8 per patient. Herbst related complications were few: 1.6 per patient, with the majority of complications being of little consequence and with 43% of the patients having no breakages. The completely customized lingual appliance assessed in this study combined with an L-pin Herbst led to effective Class II correction regardless of the initial severity of the sagittal discrepancy. The average ABO CR-Eval score for this sample was well below the undisputed passing score indicating a high quality of treatment outcomes.

Orthodontic Control of Labio-Lingual Inclination of Anterior Teeth Using Multi-Slot Designed Lingual Appliance and Tandem Archwire Technique in Extraction Treatment Case

Orthodontic Control of Labio-Lingual Inclination of Anterior Teeth Using Multi-Slot Designed Lingual Appliance and Tandem Archwire Technique in Extraction Treatment Case

Controlling incisor torque with completely customized lingual appliances.

PurposeTo test the null hypothesis of no significant deviation between the center of rotation (CROT) and the center of resistance (CRES) during space closure in Angle class II division 2 subjects achieved using a completely customized lingual appliance (CCLA) in combination with class II elastics and elastic chains.MethodsThis retrospective study included 29 patients (male/female 11/18; mean age 15.6 [13–27] years) with inclusion criteria of an Angle class II/2 occlusion of least of half of a cusp, maxillary dental arch spacing, completed CCLA treatment (WIN, DW Lingual Systems, Bad Essen, Germany) in one center with a standardized archwire sequence and use of class II elastics and elastic chains only. Maxillary incisor root inclination was assessed by X‑ray superimpositions of the maxilla at the beginning (T1) and the end (T3) of CCLA treatment. Using Keynote software (Apple®, Cupertino, CA, USA), the incisor’s CROT was assessed with the point of intersection of the incisor axes (T1; T3) following vertical correction of overbite changes. CRES was defined at 36% of the incisor’s apex–incisal edge distance.ResultsThe null hypothesis was rejected: the mean CROT − CRES difference was 52.6% (p < 0.001). The mean CROT was located at 88.6% (min–max 51–100%) of the incisor’s apex–incisal edge distance. Although 6.9% of CROT were located between the CRES and the alveolar crest, the vast majority (93.1%) were assessed between the alveolar crest and the incisal edge, or beyond.ConclusionCCLAs can create upper incisor palatal root torque even in cases in which lingually oriented forces applied incisally to the center of resistance of the upper incisors counteract these intended root movements.