Stress Analysis of Periodontal Tissue in en Masse Retraction With Integration of Maxillary Anterior Teeth: A Three-Dimensional Finite Element Method Study.

OBJECTIVE: To simulate the en masse traction technique with the integration (EMTI) of six maxillary anterior teeth using a finite element model (FEM) and explore various protocols for maxillary protrusion. The study aimed to investigate root displacement and stress distribution in the periodontal ligament (PDL) by varying the retraction position and direction of EMTI applied to the maxillary anterior teeth. No actual participants were involved. MATERIALS AND METHODS: The FEM model included six teeth (central and lateral incisors and canines) with a PDL thickness of 0.3 mm. The model encompassing the alveolar bone (ALB) and EMTI had 180,528 elements and 47,836 nodes. The EMTI integrated six anterior teeth via a 0.9-mm-diameter stainless steel lingual wire, equipped with three moment arms extending toward the root apex: one midline (central arm) and two distal to the canines (lateral arms). The position and direction of the traction force applied to the three moment arms of the EMTI were varied to assess crown and apex displacement, as well as PDL stress. RESULTS: Lingual tipping was consistent across all protocols, emphasizing controlled incisor tipping. The application of horizontal traction at 10 mm and traction at 7 mm from the central and lateral arms of the EMTI, respectively, demonstrated the most uniform stress distribution across the PDL of all six anterior teeth. CONCLUSIONS AND CLINICAL SIGNIFICANCE: The FEM analysis results suggest that the new EMTI method, which retracts the maxillary anterior teeth as a unit, is effective for tooth movement and PDL stress distribution. The EMTI technique, with its specific traction protocols and emphasis on controlled tipping, appears to be a promising approach for addressing maxillary protrusions.

The effects of orthodontic anchor screw inserted into the femur of growth-phase or mature rats -Osteoid formation, bone mineral density, collagen fiber bundles, biological apatite crystal orientation.

The purpose of this study is to investigate the effect of orthodontic anchor screws (OASs) inserted into the femur of growth-phase or mature rats using histological observation and bone structure analysis. The experimental animals are growth-phase (6-week-old) or mature (25-week-old) male Wistar rats. OAS was placed into the point one-third of the femoral length from the proximal end of the femur, and the response of the surrounding bone was observed and measured. The results showed at the OAS bone interface, in growth-phase rats, bone mineral density (BMD) was reduced and the running angle of collagen fiber bundles varied significantly. In mature rats, more osteoid was observed and biological apatite (BAp) crystals showed a different orientation. It was suggested that after the insertion of OASs, bone volume and quality are decreased, but after a sufficient healing period, a new bone micro/nano structure, different from the original structure, are reconstructed.

Fixation of an orthodontic anchor screw using beta-tricalcium phosphate in a screw-loosening model in rats.

OBJECTIVES: To create an orthodontic anchor screw (OAS)-loosening model and to investigate whether filling the bone hole with beta-tricalcium phosphate (ß-TCP) can fix the OAS against orthodontic force. MATERIALS AND METHODS: Bone holes with different diameters (1.6, 2.1, or 2.5 mm) were drilled in the tibias of 11-week-old male Wistar rats, and an OAS (3.0 mm in length and 1.2 mm in diameter) was inserted. After a healing period of 2 or 4 weeks, orthodontic force was applied, and the diameter of the bone hole appropriate for the loosening model was determined. Subsequently, under the loosening model, the bone hole was filled with ß-TCP, orthodontic force was applied, and movement of the OAS and surrounding tissue changes were evaluated by micro-computed tomography images and histological specimen analysis. RESULTS: The bone hole of 1.6 mm in diameter was employed as the OAS-loosening model. When ß-TCP was inserted into the bone hole, the linear distance and mesial tipping angle of the OAS movement decreased markedly. Furthermore, the values of bone morphometry significantly increased with ß-TCP filling. CONCLUSIONS: An OAS-loosening model was established in rats and demonstrated that the loosening OAS was stabilized by ß-TCP filling through bone formation. ß-TCP may be useful for fixation of a loosening OAS.

A case of skeletal maxillary protrusion with high angle and gummy smile treated with anchor screws.

This report discusses a case of a 20 year and 7-month-old female patient with a skeletal maxillary protrusion with gummy smile, crowding, and high angle due to horizontal protrusion of the maxillary anterior teeth. The gummy smile in this case was improved by an upward movement of the occlusal plane associated with maxillary molar intrusion and sufficient lingual movement while performing maxillary anterior teeth intrusion. Following treatment, it was stable even after 8 years of retention. Thus, it is important to ascertain the cause of gummy smile, and establish whether it is due to the vertical maxillary excess in the maxillary anterior teeth, or the horizontal protrusion of the maxillary anterior teeth.

Paravertebral foramen screw fixation for posterior cervical spine surgery: clinical case series.

OBJECTIVE: The goal of this study was to clarify the clinical utility of paravertebral foramen screws (PVFSs) and to determine intraoperative indicators for appropriate screw placement during posterior cervical fusion surgery to improve its safety. METHODS: The authors included data from 46 patients (29 men and 17 women, mean age 61.7 years) who underwent posterior cervical spine surgery with 94 PVFSs. Of the 94 PVFSs, 77 were used in C6, 9 in C3, 5 in C4, and 3 in C5. According to the cervical lateral radiographic view, the authors divided the 94 PVFSs into 3 groups as follows: a longer group, in which the tip of PVFS was located anteriorly from the line of the posterior wall of the vertebral body (> +0 mm); an intermediate group, in which the screw tip was located up to 2 mm posteriorly to the posterior wall of the vertebral body (-2 to 0 mm); and a shorter group, in which the screw tip was located more than 2 mm posteriorly (< -2 mm). The accuracy of screw placement was assessed using CT imaging in the axial plane, and the proportion of screws penetrating a vertebral foramen or a transverse foramen was compared between the 3 groups. Screw loosening was defined as a lucent zone around the screw evaluated on cervical radiography at 1 year after surgery. Complications related to PVFS insertion and revision surgery related to PVFS were evaluated. RESULTS: The authors classified 25 PVFSs into the longer group, 43 into the intermediate group, and 26 into the shorter group. The proportion of screws penetrating a vertebral foramen was largest in the shorter group, and the proportion penetrating a transverse foramen was largest in the longer group. Screw loosening was confirmed for 3 of 94 PVFSs. One PVFS inserted in C6 unilaterally within a long construct from C2 to C7 showed loosening, but it did not cause clinical symptoms. Revision surgery was required for 2 PVFSs inserted in C3 bilaterally as the lower instrumented vertebra in occiput-cervical fusion because they pulled out. There was no neurovascular complication related to PVFS insertion. CONCLUSIONS: PVFSs are useful for posterior cervical fusion surgery as alternative anchor screws, and the line of the posterior wall of the cervical body on lateral fluoroscopic images is a potential intraoperative reference to indicate an appropriate trajectory for PVFSs.

Influence of pre-drilling diameter on the stability of orthodontic anchoring screws in the mid-palatal area.

PURPOSE: The aim of this study was to investigate the stability of orthodontic anchor screws (OASs) in the mid-palatal area according to pre-drilling diameter. METHODS: The success rate of 161 OASs (83 patients, φ2.0 mm, 6.0 mm in length) placed in a corresponding area to the mesial and distal borders of the first molar (mesial zone and distal zone) was assessed according to placement location and pre-drilling diameter (1.2 and 1.5 mm). Placement torque values from 73 OASs with a pre-drilling diameter of 1.2 mm were compared between success and failure groups. RESULTS: The success rates of OASs pre-drilled with φ1.2 and 1.5 mm were 94.5% and 83.0%, respectively (P < 0.05); corresponding rates in the mesial zone were 100.0% and 77.3% (P < 0.005), and those in the distal zone were 89.2% and 88.6%, respectively. Placement torques of OASs predrilled with φ1.2 mm in the success and failure groups were 25.9 and 19.2 N·cm, respectively (P < 0.05). CONCLUSION: A smaller pre-drilling diameter was associated with a higher success rate of OASs in the mid-palatal area, especially in the mesial zone. When pre-drilling diameter of 1.2 mm was used for φ2.0 mm OAS, greater placement torque was indicative of greater OAS stability.

Camouflage Treatment for Skeletal Maxillary Protrusion and Lateral Deviation with Classic-Type Ehlers-Danlos Syndrome.

We herein report the case of a 19-year-old female with a transverse discrepancy, skeletal Class II malocclusion, severe crowding with concerns of classic-type Ehlers-Danlos syndrome (EDS), aesthetics problems and functional problems. The main characteristics of classic EDS are loose-jointedness and fragile, easily bruised skin that heals with peculiar "cigarette-paper" scars. The anteroposterior and transverse skeletal discrepancies can generally be resolved by maxilla repositioning and mandibular advancement surgery following pre-surgical orthodontic treatment. However, this patient was treated with orthodontic camouflage but not orthognathic surgery because of the risks of skin bruising, poor healing and a temporomandibular disorder. A satisfactory dental appearance and occlusion were achieved after camouflage treatment with orthodontic anchor screws and the use of Class II elastics, including the preservation of the stomatognathic functions. Acceptable occlusion and dentition were maintained after a two-year retention period. This treatment strategy of orthodontic camouflage using temporary anchorage, such as anchor screws and Class II elastics, may be a viable treatment option for skeletal malocclusion patients with EDS.

Innovative Fixation Technique for Avulsion Fractures of the Calcaneal Tuberosity.

Avulsion fractures of the calcaneal tuberosity, although relatively uncommon, occur more frequently in patients with osteoporosis and in the elderly. The results of closed manipulation are poor in these fractures, usually requiring open reduction and internal fixation. However, it is difficult to fix the bone fragment rigidly, because the avulsed bone fragment is small and thin, and the bone quality of the calcaneal body in the elderly is poor. Hence, it is necessary to limit prolonged weight-bearing after the operation. We performed an innovative surgical procedure of suture fixation to the anchor screw in four cases, following which earlier postoperative rehabilitation with full weight-bearing walking and range of motion exercises was possible, and bony union was achieved without repeated displacement of the fragment in all patients. We believe this technique would prove useful in surgical management of calcaneal tuberosity avulsion fractures.

Palatal en-masse retraction of segmented maxillary anterior teeth: A finite element study.

OBJECTIVE: The aim of this finite element study was to clarify the mechanics of tooth movement in palatal en-masse retraction of segmented maxillary anterior teeth by using anchor screws and lever arms. METHODS: A three-dimensional finite element method was used to simulate overall orthodontic tooth movements. The line of action of the force was varied by changing both the lever arm height and anchor screw position. RESULTS: When the line of action of the force passed through the center of resistance (CR), the anterior teeth showed translation. However, when the line of action was not perpendicular to the long axis of the anterior teeth, the anterior teeth moved bodily with an unexpected intrusion even though the force was transmitted horizontally. To move the anterior teeth bodily without intrusion and extrusion, a downward force passing through the CR was necessary. When the line of action of the force passed apical to the CR, the anterior teeth tipped counterclockwise during retraction, and when the line of action of the force passed coronal to the CR, the anterior teeth tipped clockwise during retraction. CONCLUSIONS: The movement pattern of the anterior teeth changed depending on the combination of lever arm height and anchor screw position. However, this pattern may be unpredictable in clinical settings because the movement direction is not always equal to the force direction.

Esthetic Improvement through Orthodontic Treatment Involving Extraction: Use of Orthodontic Anchor Screws.

Here, we report two cases of dental bimaxillary protrusion in which orthodontic anchor screws were used to improve the esthetics of the mouth and lips and facilitate complete closure of the mouth. Case 1 was a woman with dental maxillary protrusion and constriction of the dental arches, with the main complaint of protrusion of the lips and mandibular crowding. The maxillary and mandibular dental arches were first widened and traction applied to the maxilla via orthodontic anchor screws. The maxillary incisors were retracted 10 mm and the mandibular incisors 3 mm, resulting in upper lip retraction of 3 mm and bottom lip retraction of 5 mm with respect to the E-line. The nasolabial angle increased to 20°, and the inter-vermilion angle, which indicates the thickness of the vermillion, decreased to 20°, improving esthetics by reducing the thickness of the lips. Case 2 was a woman with bimaxillary dental protrusion, with the chief complaint of protruding lips and a gummy smile. Orthodontic anchor screws were used to achieve posterior traction and intrusion in the maxillary incisor region to improve the gummy smile. The maxillary incisors were retracted 9 mm and the mandibular incisors 8 mm. In the soft tissues, this yielded upper lip retraction of 3 mm and bottom lip retraction of 4 mm with respect to the E-line. The nasolabial angle increased to 10° and the inter-vermilion angle decreased to 30°, improving esthetics by reducing the thickness of the lips. The gummy smile was also improved, with 4 mm intrusion of the maxillary incisors. Increased ease in closing of the mouth was also a major factor in patient satisfaction with the results of orthodontic treatment.

Analysis of an in-house technique for temporary mandibulotomy and its impact on postoperative radiotherapy.

The purpose of this study was to describe a newly developed procedure for temporary mandibulotomy and subsequent osteosynthesis. Clinical outcomes were evaluated, including complications and the impact on postoperative treatment, particularly postoperative radiotherapy. Twenty-four patients underwent temporary mandibulotomies for the surgical resection of malignancies located in the posterior oral or oropharyngeal region. All were treated with postoperative radiotherapy. An angulated median mandibulotomy was followed by osteosynthesis with three anchor screws directed towards the inferior aspect of the mandible. Anchor screws are modified conventional lag screws that include an additional biconcave washer. This modification prevents the screw heads from cracking into the cancellous bone during tightening, improving their biomechanical qualities considerably. Insertion of screws at any angle to the bony surface therefore becomes possible, which is a precondition for this technique. Minor complications occurred in two patients in the early postoperative period. However, complications causing bony non-union, leading to postponed postoperative radiotherapy were not noted in this cohort.

Treatment of bimaxillary protrusion with temporary anchorage devices.

For treatment of severe bimaxillary protrusion in adults, a condition known to be among the most difficult to manage, both the maxillary and mandibular anterior teeth must be fully retracted using all the extraction space available. This article reports the treatment of an adult with severe high-angle bimaxillary protrusion. To correct the protrusion of the anterior teeth, orthodontic anchor screws (OASs) were used to provide absolute anchorage during anterior retraction. Acceptable occlusion, facial profile, and balance were achieved. OASs appear to be very useful for treatment of severe bimaxillary protrusion in adults.

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.

Resistance ability analysis of improved anchor screw / 上海交通大学学报（医学版）

Objective: To estimate resistance ability of improved anchor screw. Methods: The experiment consisted of two sections: tensile test and finite element analysis (FEA). In the first part, the traditional anchor screw and the improved anchor screw were implanted into the condylar cortical bone, respectively, tensile force was tested by tension machine. In the second part, the three-dimensional finite element model of mandibular condyle was established after the improved anchor screw was implanted, and the FEA was performed by the force applied from three different directions. Results: The FEA results revealed the minimum force of the traditional and improved anchor screws were 48.2 N and 200.0 N, respectively. The tensile strengths of the traditional and improved anchor screws with a 3-0 suture were significantly different (P=0.033). The difference between the traditional anchor screw (3-0 suture) and the improved anchor screw (2-0 suture) were significantly different (P=0.000). Conclusion: Compared with traditional screw, improved anchor screw has better resistance ability, especially combined with 2-0 suture.