Finite element study of controlling factors of anterior intrusion and torque during Temporary Skeletal Anchorage Device (TSAD) dependent en masse retraction without posterior appliances: Biocreative hybrid retractor (CH-retractor).

OBJECTIVES: To evaluate, using the finite element method (FEM), the factors that allow control of the anterior teeth during en masse retraction with the Biocreative hybrid retractor (CH-retractor) using different sizes of nickel-titanium (NiTi) archwires and various gable bends on the stainless-steel (SS) archwires. MATERIALS AND METHODS: Using FEM, the anterior archwire section, engaged on the anterior dentition, was modeled in NiTi, and another assembly, the posterior guiding archwire, was modeled in SS. Two dimensions (0.016 × 0.022- and 0.017 × 0.025-inch NiTi) of the anterior archwires and different degrees (0°, 15°, 30°, 45°, and 60°) of the gable bends on the guiding wire were applied to the CH-retractor on the anterior segment to evaluate torque and intrusion with 100-g retraction force to TSADs. Finite element analysis permitted sophisticated analysis of anterior tooth displacement. RESULTS: With a 0° gable bend all anterior teeth experienced extrusion. The canines showed a larger amount of extrusion than did the central and lateral incisors. With a gable bend of >15°, all anterior teeth exhibited intrusion. Bodily movement of the central incisor required a 30°âˆ¼45° gable bend when using anterior segments of 0.016 × 0.022-inch NiTi and 15°âˆ¼30° gable bend with the 0.017 × 0.025-inch NiTi. CONCLUSIONS: With the CH-retractor, varying the size of the NiTi archwire and/or varying the amount of gable bend on the SS archwire affects control of the anterior teeth during en masse retraction without a posterior appliance.

Effect of archwire stiffness and friction on maxillary posterior segment displacement during anterior segment retraction: A three-dimensional finite element analysis.

OBJECTIVE: Sliding mechanics using orthodontic miniscrews is widely used to stabilize the anchorage during extraction space closure. However, previous studies have reported that both posterior segment displacement and anterior segment displacement are possible, depending on the mechanical properties of the archwire. The present study aimed to investigate the effect of archwire stiffness and friction change on the displacement pattern of the maxillary posterior segment during anterior segment retraction with orthodontic miniscrews in sliding mechanics. METHODS: A three-dimensional finite element model was constructed. The retraction point was set at the archwire level between the lateral incisor and canine, and the orthodontic miniscrew was located at a height of 8 mm from the archwire between the second premolar and first molar. Archwire stiffness was simulated with rectangular stainless steel wires and a rigid body was used as a control. Various friction levels were set for the surface contact model. Displacement patterns for the posterior and anterior segments were compared between the conditions. RESULTS: Both the anterior and posterior segments exhibited backward rotation, regardless of archwire stiffness or friction. Among the conditions tested in this study, the least undesirable rotation was found with low archwire stiffness and low friction. CONCLUSIONS: Posterior segment displacement may be unavoidable but reducing the stiffness and friction of the main archwire may minimize unwanted rotations during extraction space closure.

The 3-dimensional zone of the center of resistance of the mandibular posterior teeth segment.

INTRODUCTION: We sought the 3-dimensional (3D) zone of the center of resistance (ZCR) of mandibular posterior teeth groups (group 1: first molar; group 2: both molars; group 3: both molars and second premolar; group 4: both molars and both premolars) with the use of 3D finite element analysis. METHODS: 3D finite element models comprised the mandibular posterior teeth, periodontal ligament, and alveolar bone. In the symmetric bilateral model, a 100-g midline force was applied on a median sagittal plane at 0.1-mm intervals to determine the anteroposterior and vertical positions of the ZCR (where the applied force induced translation). The most reliable buccolingual position of the ZCR was then determined in the unilateral model. The combination of the anteroposterior, vertical, and buccolingual positions was defined as the ZCR. RESULTS: The ZCRs of groups 1-4 were, respectively, 0.48, 0.46, 0.50, and 0.53 of the mandibular first molar root length from the alveolar crest level and located slightly distobuccally at anteroposterior ratios of 2:3.0, 2:2.3, 2:2.4, and 2:2.5 to each sectional arch length and at buccolingual ratios of 2:1.5, 2:1.1, 2:1.6, and 2:2.4 to the first molar's buccolingual width. CONCLUSIONS: The ZCR can be a useful reference for 3D movement planning of mandibular posterior teeth or segments.

Displacement of mandibular dentition during total arch distalization according to locations and types of TSADs: 3D Finite element analysis.

OBJECTIVE: The aim of this study was to evaluate the biomechanical effects of temporary skeletal anchorage devices (TSADs) on the mandibular dentition and mandible during total arch distalization according to locations and types of the TSADs using finite element (FE) analysis. SETTING AND SAMPLE POPULATION: A model of the mandible and teeth was used to build an FE analysis model. MATERIALS AND METHODS: Four FE models were constructed: Ramal plate (Type A), Sugawara plate (Type B), buccal shelf miniscrew (Type C) and interradicular miniscrew (Type D). A retraction force of 300 g per side was applied to the mandibular archwire. RESULTS: In the sagittal plane, the plates Type A and B showed more distal displacement than the miniscrew Types C and D, especially in the posterior teeth. Type A presented the greatest amount of distal displacement, followed by Types B, C and D. Type A was closest to the line of occlusion, which showed the lowest degree of buccolingual angulations of the molar crowns. Vertically, Type A showed a greater amount of extrusive displacement of the posterior teeth than the other types of TSADs, while Type B showed intrusive displacement of the molars. CONCLUSIONS: The ramal plate showed a greater amount of distal and extrusive displacement of the posterior teeth than the miniscrews. Therefore, clinicians should consider the displacement of mandibular dentition during total arch distalization according to types of the TSADs.

Heritability of Facial Skeletal and Dental Characteristics of Monozygotic and Dizygotic Twins Using Cephalometric Analysis and Falconer's Method.

The purpose of this study was to investigate the heritability of facial skeletal and dental characteristics of the monozygotic (MZ) and dizygotic (DZ) twins. The samples consisted of Korean MZ and DZ twins (n = 13 pairs/each twin; 7 pairs of males and 6 pairs of females; mean age, 39 years, respectively). The linear, angular, and ratio variables, which could describe the size and shape of the facial horizontal and vertical, dental, mandible and cranial base structure, were measured. The Falconer's method was used to calculate the heritability (h; close to or below 0, low heritability; close to or above 1, high heritability). In the facial horizontal and vertical aspects, the highest h values were shown at SNA (degree, 1.53), SNB (degree, 2.12), SN-Pog (degree, 2.19), SN-palatal plane angle (degree, 1.29), SN-mandibular plane angle (degree, 1.59), N-ANS/ANS-Me (1.66), and ANS-Me/N-Me (1.62). In the dental aspects, although L1-occlusal plane angle (degree, 1.38) and SN-occlusal plane angle (degree, 2.09) showed high h values, most of the dental variables showed low h values. In the mandible and cranial base, lower gonial angle, mandibular body length, and cranial base angle showed high h values (N-Go-Gn [degree], 1.07; Go-Pog [mm], 0.92; N-S-Ba [degree], 1.51). The descending order of the overall mean h values was the facial horizontal (1.10), facial vertical (0.71), mandible (0.59), cranial base (0.37), and dental characteristics (-0.11). The shape of facial skeletal structure and location of the occlusal plane within skeletal framework was more influenced by genetic factors than environmental factors.

Finite-element analysis of the center of resistance of the mandibular dentition.

OBJECTIVE: The aim of this study was to investigate the three-dimensional (3D) position of the center of resistance of 4 mandibular anterior teeth, 6 mandibular anterior teeth, and the complete mandibular dentition by using 3D finite-element analysis. METHODS: Finite-element models included the complete mandibular dentition, periodontal ligament, and alveolar bone. The crowns of teeth in each group were fixed with buccal and lingual arch wires and lingual splint wires to minimize individual tooth movement and to evenly disperse the forces onto the teeth. Each group of teeth was subdivided into 0.5-mm intervals horizontally and vertically, and a force of 200 g was applied on each group. The center of resistance was defined as the point where the applied force induced parallel movement. RESULTS: The center of resistance of the 4 mandibular anterior teeth group was 13.0 mm apical and 6.0 mm posterior, that of the 6 mandibular anterior teeth group was 13.5 mm apical and 8.5 mm posterior, and that of the complete mandibular dentition group was 13.5 mm apical and 25.0 mm posterior to the incisal edge of the mandibular central incisors. CONCLUSIONS: Finite-element analysis was useful in determining the 3D position of the center of resistance of the 4 mandibular anterior teeth group, 6 mandibular anterior teeth group, and complete mandibular dentition group.

A three-dimensional finite element analysis of molar distalization with a palatal plate, pendulum, and headgear according to molar eruption stage.

OBJECTIVE: This study aimed to (1) evaluate the effects of maxillary second and third molar eruption status on the distalization of first molars with a modified palatal anchorage plate (MPAP), and (2) compare the results to the outcomes of the use of a pendulum and that of a headgear using three-dimensional finite element analysis. METHODS: Three eruption stages were established: an erupting second molar at the cervical one-third of the first molar root (Stage 1), a fully erupted second molar (Stage 2), and an erupting third molar at the cervical one-third of the second molar root (Stage 3). Retraction forces were applied via three anchorage appliance models: an MPAP with bracket and archwire, a bone-anchored pendulum appliance, and cervical-pull headgear. RESULTS: An MPAP showed greater root movement of the first molar than crown movement, and this was more noticeable in Stages 2 and 3. With the other devices, the first molar showed distal tipping. Transversely, the first molar had mesial-out rotation with headgear and mesial-in rotation with the other devices. Vertically, the first molar was intruded with an MPAP, and extruded with the other appliances. CONCLUSIONS: The second molar eruption stage had an effect on molar distalization, but the third molar follicle had no effect. The application of an MPAP may be an effective treatment option for maxillary molar distalization.

Finite element analysis of maxillary incisor displacement during en-masse retraction according to orthodontic mini-implant position.

OBJECTIVE: Orthodontic mini-implants (OMI) generate various horizontal and vertical force vectors and moments according to their insertion positions. This study aimed to help select ideal biomechanics during maxillary incisor retraction by varying the length in the anterior retraction hook (ARH) and OMI position. METHODS: Two extraction models were constructed to analyze the three-dimentional finite element: a first premolar extraction model (Model 1, M1) and a residual 1-mm space post-extraction model (Model 2, M2). The OMI position was set at a height of 8 mm from the arch wire between the second maxillary premolar and the first molar (low OMI traction) or at a 12-mm height in the mesial second maxillary premolar (high OMI traction). Retraction force vectors of 200 g from the ARH (-1, +1, +3, and +6 mm) at low or high OMI traction were resolved into X-, Y-, and Z-axis components. RESULTS: In M1 (low and high OMI traction) and M2 (low OMI traction), the maxillary incisor tip was extruded, but the apex was intruded, and the occlusal plane was rotated clockwise. Significant intrusion and counter-clockwise rotation in the occlusal plane were observed under high OMI traction and -1 mm ARH in M2. CONCLUSIONS: This study observed orthodontic tooth movement according to the OMI position and ARH height, and M2 under high OMI traction with short ARH showed retraction with maxillary incisor intrusion.

Displacement and stress distribution of the maxillofacial complex during maxillary protraction with buccal versus palatal plates: finite element analysis.

OBJECTIVES: The aim of this study was to analyse the displacement and stress distribution in the maxillofacial complex during maxillary protraction with buccal and palatal plates using three-dimensional finite element analysis. MATERIALS AND METHODS: Three anchorage appliance models-palatal plate (Type A), miniplate at the infrazygomatic crest (Type B), and conventional tooth-borne appliance (Type C)-were designed and integrated into a skull model. Protraction force was 500 g per side and force direction was forward and 30 degree downward to the maxillary occlusal plane. The stress distribution around the circum-maxillary sutures and the displacement of the surface landmarks were analysed. RESULTS: All models showed forward and upward displacement at anterior nasal spine, Point A, and prosthion and forward and downward displacement at posterior nasal spine resulting in a counter-clockwise rotation. This anterior displacement was greatest in Type A. At the maxillary process of the zygoma, upward movement was shown only in Type A, whereas downward movement was observed in Types B and C. The greatest stresses in Type A were at the pterygomaxillary and the zygomaticotemporal sutures. Type B showed the greatest stress at the frontomaxillary suture. LIMITATIONS: Type A showed asymmetric results; however, it was not of clinical significance. CONCLUSION: The palatal plate resulted in wider stress distribution and more forward displacement compared to miniplate at the infrazygomatic crest area and conventional tooth-borne appliances. It might be recommended to consider the application of the palatal plate for maxillary protraction in Class III patients.

Stress distribution and displacement by different bone-borne palatal expanders with micro-implants: a three-dimensional finite-element analysis.

The aim of this study was to analyze stress distribution and displacement of the maxilla and teeth according to different designs of bone-borne palatal expanders using micro-implants. A three-dimensional (3D) finite-element (FE) model of the craniofacial bones and maxillary teeth was obtained. Four designs of rapid maxillary expanders: one with micro-implants placed lateral to mid-palatal suture (type 1), the second at the palatal slope (type 2), the third as in type 1 with additional conventional Hyrax arms (type 3), and the fourth surgically assisted tooth-borne expander (type 4) were added to the FE models. Expanders were activated transversely for 0.25mm. Geometric nonlinear theory was applied to evaluate Von-Mises Stress distribution and displacement. All types exhibited downward displacement and demonstrated more horizontal movement in the posterior area. Type 3 showed the most transverse displacement. The rotational movement of dentoalveolar unit was larger in types 1 and 3, whereas it was relatively parallel in types 2 and 4. The stresses were concentrated around the micro-implants in types 1 and 3 only. Type 2 had the least stress concentrations around the anchorage and showed alveolar expansion without buccal inclination. It is recommended to apply temporary anchorage devices to the palatal slopes to support expanders for efficient treatment of maxillary transverse deficiency.

Comparison of tooth displacement between buccal mini-implants and palatal plate anchorage for molar distalization: a finite element study.

The purposes of this study were to mechanically evaluate distalization modalities through the application of skeletal anchorage using finite element analysis. Base models were constructed from commercial teeth models. A finite element model was created and three treatment modalities were modified to make 10 models. Modalities 1 and 2 placed mini-implants in the buccal side, and modality 3 placed a plate on the palatal side. Distalization with the palatal plate in modality 3 showed bodily molar movement and insignificant displacement of the incisors. Placing mini-implants on the buccal side in modalities 1 and 2 caused the first molar to be distally tipped and extruded, while the incisors were labially flared and intruded. Distalization with the palatal plate rather than mini-implants on the buccal side provided bodily molar movement without tipping or extrusion. It is recommended to use our findings as a clinical guide for the application of skeletal anchorage devices for molar distalization.

Torque control during lingual anterior retraction without posterior appliances.

OBJECTIVE: To evaluate the factors that affect torque control during anterior retraction when utilizing the C-retractor with a palatal miniplate as an exclusive source of anchorage without posterior appliances. METHODS: The C-retractor was modeled using a 3-dimensional beam element (0.9-mm-diameter stainless-steel wire) attached to mesh bonding pads. Various vertical heights and 2 attachment positions for the lingual anterior retraction hooks (LARHs) were evaluated. A force of 200 g was applied from each side hook of the miniplate to the splinted segment of 6 or 8 anterior teeth. RESULTS: During anterior retraction, an increase in the LARH vertical height increased the amount of lingual root torque and intrusion of the incisors. In particular, with increasing vertical height, the tooth displacement pattern changed from controlled tipping to bodily displacement and then to lingual root displacement. The effects were enhanced when the LARH was located between the central and lateral incisors, as compared to when the LARH was located between the lateral incisors and canines. CONCLUSIONS: Three-dimensional lingual anterior retraction of the 6 or 8 anterior teeth can be accomplished using the palatal miniplate as the only anchorage source. Using LARHs at different heights or positions affects the quality of torque and intrusion.

Palatal soft tissue thickness at different ages using an ultrasonic device.

OBJECTIVE: To evaluate the palatal soft tissue thickness among placement sites of temporary anchorage devices (TADs) in late mixed, early permanent and permanent dentition. MATERIALS AND METHOD: The sample consisted of three groups; 42 late mixed dentition (mean age = 11.0 years), 41 early permanent dentition (mean age = 13.8 years), and 38 permanent dentition (mean age = 23.1 years). Soft tissue thickness was measured intraorally with an ultrasonic device using a grid of 27, 4 x 4 mm2 squares to delineate the measurement points. Repeated measures analysis of variance was performed to analyze the data. RESULTS: There was a significant difference in soft tissue thickness among dentition groups with the permanent dentition group showing the highest values (P < 0.001). In each group, the thickness significantly increased from median to lateral and from anterior to posterior sites. Furthermore, the thickness showed a significant difference according to the arch form and gender (P < 0.05). However, there were no significant differences according to irregularity index and Angle classification. CONCLUSIONS: The soft tissue thickness of the palate increases from the late mixed to permanent dentition. These findings may be helpful for clinicians to enhance their successful application of TADs in the palate.

Factors controlling anterior torque during C-implant-dependent en-masse retraction without posterior appliances.

INTRODUCTION: Our objective was to evaluate the factors that affect effective torque control during en-masse incisor and canine retraction when using partially osseointegrated C-implants (Cimplant, Seoul, Korea) as the exclusive source of anchorage without posterior bonded or banded appliances. METHODS: Base models were constructed from a dental study model. No brackets or bands were placed on the maxillary posterior dentition during retraction. The working archwire was modeled by using a 3-dimensional beam element (ANSYS beam 4, Swanson Analysis System, Canonsburg, Pa) with a cross section of 0.016 × 0.022-in stainless steel. Different heights of anterior retraction hooks and different degrees of gable bends were applied to the working utility archwire that was placed into the 0.8-mm diameter hole of the C-implant to generate anterior torque on the anterior segment of the teeth. The amount of tooth displacement after finite element analysis was exaggerated 70 times and compared with tooth-axis graphs of the central and lateral incisors and the canine. RESULTS: The height of the anterior retraction hook and the degree of the gable bend had a combined effect on the labial crown torque applied to the incisors during en-masse retraction. By using 30° gable bends and the longest hook, lingual root movement of the 6 anterior teeth occurred. By using 20° gable bends, the 6 anterior teeth showed a translation tendency during retraction. CONCLUSIONS: Three-dimensional en-masse retraction of the 6 anterior teeth can be accomplished by using partially osseointegrated C-implants as the only source of anchorage, gable bends, and a long retraction hook (biocreative therapy type I technique).

Factors controlling anterior torque with C-implants depend on en-masse retraction without posterior appliances: biocreative therapy type II technique.

INTRODUCTION: Our objective was to evaluate the factors that affect effective torque control during en-masse anterior retraction by using intrusion overlay archwire and partially osseointegrated C-implants as the exclusive sources of anchorage without posterior bonded or banded attachments. METHODS: Base models were constructed from a dental study model. No brackets or bands were placed on the posterior maxillary dentition during retraction. Different heights of the anterior retraction hooks to the working segment archwire and different intrusion forces with an overlay archwire placed in the 0.8-mm diameter hole of the C-implant were applied to generate torque on the anterior segment of the teeth. The amount of tooth displacement after finite element analysis was exaggerated 70 times and compared with tooth axis graphs of the central and lateral incisors and the canine. RESULTS: The height of the anterior retraction hook and the amount of intrusion force had a combined effect on the labial crown torque applied to the incisors during en-masse retraction. The difference of anterior retraction hook length highly affected the torque control and also induced a tendency for canine extrusion. CONCLUSIONS: Three-dimensional en-masse retraction of the anterior teeth as an independent segment can be accomplished by using partially osseointegrated C-implants as the only source of anchorage, an intrusion overlay archwire, and a retraction hook (biocreative therapy type II technique).

Resistance to immediate orthodontic loading of surface-treated mini-implants.

OBJECTIVE: To test the hypothesis that there is no difference in the stability and resistance to orthodontic forces of immediately loaded sandblasted and acid-etched (SAE) mini-implants and those of machined-surface implants of the same size and shape. MATERIALS AND METHODS: Two types of mini-implants were used in the tibiae of 44 rabbits; some had an SAE surface and some had machined surfaces. Orthodontic loading of 150 g was applied immediately after placement. The success rates and maximum removal torque values (RTVs) of 412 mini-implants were recorded and compared immediately after placement, 3 days after placement, and 1, 6, and 10 weeks after placement. The RTV data were analyzed using multiple regression analysis to evaluate differences with respect to surface treatment, loading, and loading periods (P < .05). Multiple comparisons using the Scheffé method were performed to evaluate the RTVs for the subsequent loading periods. RESULTS: Thirteen mini-implants failed during the experimental period. The SAE group had a higher RTV than the machined group, and there was significant difference in RTVs in accordance with loading periods (P < .001). However, there was no significant RTV difference between loaded and unloaded mini-implants. CONCLUSIONS: The hypothesis was supported. Both SAE mini-implants and machined mini-implants can be loaded immediately and experience similar success rates. RTVs were higher for the SAE mini-implants than for the machined mini-implants. The latter finding suggests that, for immediate loading, SAE mini-implants may provide more stable retention than machined mini-implants.

Class II malocclusion treated by combining a lingual retractor and a palatal plate.

In this article, we describe the treatment of a woman, aged 25 years 8 months, with a Class II malocclusion, severe anterior protrusion, and a high mandibular plane angle. The treatment plan consisted of extracting both maxillary first premolars and mandibular second premolars. En-masse retraction of the 6 maxillary anterior teeth was performed with a lingual approach combining a C-lingual retractor and a C-palatal plate (C-plate). However, the mandibular dentition was treated with conventional labial fixed appliances. After the maxillary anterior retraction, labial fixed appliances were placed on the maxillary dentition only during the finishing stage. Correct overbite and overjet, facial balance, and improved lip protrusion were obtained. The active treatment period was 17 months, and the results were stable for 13 months after debonding. This C-lingual retractor and C-plate combined retraction method can be effective for intrusive retraction of the anterior teeth.

Severe Class II division 1 malocclusion treated by orthodontic miniplate with tube.

A miniplate with tube (C-tube) was placed in the interdental spaces between both left and right upper second premolars and first molars in a 15-year-8 month-old male patient with a Class II malocclusion who with severe anterior protrusion and lower anterior crowding. The treatment plan consisted of extracting both upper first premolars, en masse retraction of the upper six anterior teeth and lower anterior decrowding. C-tubes were used as substitutes for posterior dental anchorage during upper anterior retraction. The particular design of the C-tubes made it possible to retract fully with minimal gingival irritation. The correct overbite and overjet were obtained by intruding and retracting the maxillary incisors to their proper positions and this correction remained stable for at least 27 months after debonding. Also, facial balance was improved. The active treatment period was 14 months. The application of this new appliance, consideration of case selection, and sequence of treatment are presented.