Infrazygomatic Crest Research Articles

Assessing bone thickness in the infrazygomatic crest area aiming the orthodontic miniplates positioning: a tomographic study.

ABSTRACTIntroduction: Due to the increasing use of miniplates for anchorage purposes in orthodontics, it is very important to know more about infrazigomatic crest anatomy (thickness), in adult patients. Objectives: Evaluate the infrazygomatic crest region thickness, in adult (male and female) patients. Methods: Cone-beam computerized tomography (CBCT) images from 40 patients were used to assess cross-sectional measurements of the infrazygomatic crest region. Measurement 1 considered thickness 2 mm above the distobuccal root of the permanent maxillary first molar, while measurement 2 was taken 2 mm above the first measurement. Results: The mean thickness of the infrazygomatic crest in males was 3.55 mm for measurement 1 and 2.84 mm for measurement 2, while in females these were 2.37 mm and 2.24 mm, respectively. Conclusion: The authors concluded that the overall mean thickness of the infrazygomatic crest was 2.49 mm with respect to measurement 1, and 2.29 mm for measurement 2, with no statistically significant differences between gender.

Safe zones for miniscrews in maxillary dentition distalization assessed with cone-beam computed tomography.

The purpose of this study was to assess the anatomic structure of the buccal alveolar bone in the infrazygomatic crest region with cone-beam computed tomography to locate safe zones for miniscrews in maxillary dentition distalization. The buccal alveolar bone was analyzed in 3 regions of 60 patients: between the maxillary second premolar and first molar (U5-U6), between the mesiodistal roots of the first molar (U6), and between the maxillary first and secondmolars (U6-U7). Alveolar bone thickness at the buccal side of the roots and the interradicular space at the buccal side of the roots were measured at the planes of 5, 7, 9, and 11mm apically from the alveolar crest to the maxillary sinus floor. The buccal bone height was measured from the alveolar crest edge to the sinus floor. The buccal alveolar bone was thicker in the U6-U7 region than in the U6 and U5-U6 regions. The buccal alveolar bone thickness tended to get thicker from the alveolar crest to the sinus floor. The thickest buccal alveolar bone of 4.07mm was observed at the plane of 11mm of the U6-U7 region. The percentages for the height of bone from the crest edge to the sinus floor were smaller than 10mm at the regions of U5-U6, U6, and U6-U7: 38%, 52%, and 43%, respectively. The interradicular space was smallest in the U6 region and largest in the U5-U6 region. The results of this study suggest that the U6-U7 region is the most ideal safe zone for placing miniscrews in the buccal alveolar bone in the infrazygomatic crest region for maxillary dentition distalization.

Computed tomography and anatomical measurements of critical sites for endosseous implants in the pterygomaxillary region: a cadaveric study

The aim of this study was to obtain computed tomography (CT) and physical measurements of the pterygomaxillary region to determine the anatomical and radiographic landmarks that clinicians need for pterygoid implant placement. Seventy-eight hemi-heads with an atrophic posterior maxilla from 46 cadaveric samples were measured using CT. Twenty-one hemi-heads were selected randomly for physical measurements. CT measurements showed that the mean and minimum distance between the maxillary tuberosity point (MT) and the most lateral lowest point of the pterygomaxillary fissure (PF) were 18.7mm and 10.0mm, respectively. The mean and minimum distance between the alveolar crest point passing the extended line of the infrazygomatic crest and the PF were 22.7mm and 14.7mm, respectively. The mean and minimum distance between the PF and the greater palatine canal were 2.9mm and 0.2mm, respectively. Physical measurements showed that the mean and minimum distances between the MT and the descending palatine artery (DPA) were 19.4mm and 12.7mm, respectively, and those between the PF and the DPA were 3.7mm and 0.0mm, respectively. The results confirmed considerable variation in the values of the pterygomaxillary region measured at the specific sites. Therefore, careful and sufficient consideration is required in each case of pterygoid implant placement.

Skeletal anchorage in the past, today and tomorrow

Skeletal anchorage was not introduced as an alternative to conventional anchorage modalities. The first skeletal anchorage was a ligature through a hole in the infrazygomatic crest. This was replaced by surgical screws and finally the TADs, which were optimized with respect to the material and morphology, were developed. A bracket-like head allows for the use of the mini-implant as indirect anchorage, but should not be a tool for lost control resulting from badly planned biomechanics or failing compliance. Skeletal anchorage should serve as an adjunct to correct biomechanics, to enable treatments that could not be performed prior to the introduction of skeletal anchorage. The aim of this study was to test the hypothesis that temporary anchorage mini-screws help maintain bone density, height and width of alveolar processes in the extraction sites, and thus prevent the thinning of the alveolar ridge usually observed. In adult patients with degenerated dentitions the application of skeletal anchorage can allow for the displacement of teeth where no anchorage units are present, but also for the redevelopment and maintenance of atrophic alveolar bone. The basis for the optimal use of skeletal anchorage is that the correct line of action for the desired tooth displacement is defined and the necessary force system constructed either with the skeletal anchorage as direct or as indirect anchorage. After a period, during which osseointegrated implants were used as anchorage for tooth movement and bone maintenance, it was accepted that the mini-implants could serve also as anchorage for skeletal displacements avoiding loading of teeth.

Canine-lateral incisor transposition: Controlling root resorption with a bone-anchored T-loop retraction

A 12-year-old girl presented with a Class II Division 1 malocclusion, complicated by a complete transposition of the maxillary left canine into the position normally occupied by the left lateral incisor. Dental and medical histories were noncontributory. Brackets were bonded on all maxillary teeth, from first molar to first molar, except for theleft lateral incisor. Because the lateral incisor was not engaged on the archwire, the tooth was free to physiologically move out of the path of canine root movement. To prepare the site for canine retraction, a coil spring was used to open space between the left central incisor and the first premolar. A 2×12-mm stainless steel miniscrew was placed in the infrazygomatic crest, labial to the mesiodistal cusp of the maxillary left first molar. A 0.019×0.025-in titanium-molybdenum alloy T-loop, anchored by the miniscrew, was used to retract the canine root over the labial surface of the root of the distally positioned lateral incisor. In 24months, this difficult malocclusion, with a Discrepancy Index score of 18, was treated to a Cast-Radiograph Evaluation score of26.

Are temporary anchorage devices truly effective in the treatment of skeletal open bites?

Objective:The aims of this study were to evaluate the effects of temporary anchorage devices (TADs) in the treatment of skeletal open bites and to compare the results with untreated controls.Materials and Methods:A total of forty patients with skeletal anterior open bites were assigned to two groups of twenty each. The mean chronological age for the treatment group (14 female, 6 male) was 16.68 ± 2.80 years old, compared with 16.63 ± 2.83 years old for the control group (11 female, 9 male). Titanium miniplates fixed bilaterally to the infrazygomatic crest area were used as TADs and intrusive forces were applied to the posterior teeth with Ni-Ti coil springs. The treatment and normal growth changes were evaluated using 24 measurements (2 angular, 22 linear).Results:Statistically significant differences were found between the groups in Bx, By, Sn/GoGn, Ax-Bx, U6x, U6y, overjet, overbite, SN/OccP, N-Me, Ans-Me, S-Go/N-Me, interpremolar width, and intermolar width (P < 0.05). In the treatment group, statistically significant upper molar intrusion (mean ± standard deviation [SD], 3.59 ± 1.34; 95% confidence interval [CI], 2.96–4.22), posterior rotation of the occlusal plane (mean ± SD, 3.42 ± 2.17; 95% CI, 2.39–4.43), anterior rotation of the mandible (mean ± SD, 2.25 ± 1.91; 95% CI, 1.36–3.14), and resultant overbite improvement (mean ± SD, 4.82 ± 1.53; 95% CI, 4.10–5.53) were found (P < 0.05).Conclusions:Mild to moderate skeletal anterior open bites could easily be treated with TADs without orthognathic surgery. With the rigid anchorage of miniplates, true molar intrusion of up to 4 mm was achieved. With molar intrusion, anterior rotation of the mandible and a significant reduction in anterior face height were determined.

Maxillary protraction using orthodontic miniplates in correction of Class III malocclusion during growth

IntroductionThis study was carried out to investigate the effect of bone-anchored maxillary protraction in treatment of growing patients with Class III malocclusion. MethodsThe sample of this study consisted of 10 subjects (5 boys and 5 girls; 9–12 years old). Each treated patient had four miniplates (HUBIT, Seoul, Korea) that were inserted between the lower left and right lateral incisor and canine and on the left and right infrazygomatic crest of the maxillary buttress. Class III elastics were applied between the miniplates on each side 24/7. The initial force was 300 g per side increased to 350 after 1 month and increased to 450 g per side 2 months later. Lateral cephalograms of each patient were evaluated at the beginning of treatment (T1), at the end of active treatment (T2). The effect of treatment was compared to the effect of growth changes in a matched untreated control group of the same malocclusion. ResultsIn the anteroposterior plane, the sella nasion point A angle increased 2.80°, and the sella nasion point B angle decreased 0.20°. The A point, nasion, B point angle increased 3.40°, the nasion A-point–pogonion angle increased 4.70°. No significant changes were observed in the vertical parameters measured nasion A-point pogonion while the maxillary incisors proclined significantly. ConclusionsThe bone-anchored maxillary protraction approach induced a significant orthopedic maxillary advancement, and retarded the mandibular growth with improvement of facial profile. Maxillomandibular divergency was increased mainly due a counterclockwise rotation of the maxilla.

Functional treatment of skeletal Class II malocclusion using bone-anchored devices and intermaxillary elastics

Introduction: Dentofacial functional appliances used for the treatment of skeletal Class II malocclusion are divided into two groups: Removable appliances and fixed (bonded) appliances, each with certain advantages and disadvantages. Considering the problems related to functional appliances such as high volume in the oral cavity, patient noncompliance, esthetics, tissue irritation or ulceration, speech or breathing difficulties, etc., there is considerable demand to develop a new appliance that can overcome these issues. Thus, the aim of the current study is to present a hypothesis regarding a new functional treatment technique. The hypothesis: We hypothesize that by fixing mini-plates or -implants in the posterior region of the mandible and the anterior part of the infrazygomatic crest region of the maxilla using intermaxillary elastics, we can expect a forward growth of the mandible in a growing child. Using this technique, the force vector will be in the oblique (forward-upward) direction. By installing mini-plates with a long connecting bar in the infrazygomatic crest region (with the orthodontic attachment head approximating the level of the occlusal plane), and mini-plates or -implants in the most posterior and superior regions of the mandible, such as the retromolar region, the force vector can be placed in the most horizontal direction possible. Evaluation of the hypothesis: In the literature, significant growth modification results were reported in skeletal Class III patients using intermaxillary elastics and bone-anchored devices fixed in both jaws, when compared with those in the nontreatment group. Therefore, in practice, intermaxillary elastics can produce enough traction to stimulate the bone to change and grow. Thus, we presume that inverting the direction of the force vector (i.e., posterior-anterior force) may have similar growth effects on the mandibles of growing children.

Non-Osteotomy Treatment of Class III Skeletal Malocclusion Using Bollard Plates

A total of 14 patients were enrolled in the study at cervical vertebral maturation stage CVM2. Bilateral FDA approved miniplates (Bollard plates) were surgically inserted in the infrazygomatic crests of the maxilla and between the canine and the lateral incisor in the anterior mandible. The patients were treated by intermaxillary elastics for an average of 16 months. Cephalometric analysis was done before, during and at the end of the treatment. Intraoral and extraoral photographs were taken for comparisons. In this study, we analyze the effect of maxillary advancement in patients with class III skeletal malocclusions using a nonosteotomy technique that produces combined maxillary advancement and mandibular retraction using bone anchored Bollard plates (Tita-Link, Brussels, Belgium). We evaluate the change in WITS appraisal and ANB values for each patient before and after treatment. OMaxillary hypoplasia is frequently found in Class III Malocclusion patients O Traditional Treatment options include use of protraction face mask anchored to dentition or a more invasive Le Fort osteotomy OBone Anchored Maxillary Protraction devices provide skeletal anchorage O Requires active sutures in growth phase, skeletal anchorage buttress and remodeling of adjacent bone OLess invasive than osteomies

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

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. 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. 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. Type A showed asymmetric results; however, it was not of clinical significance. 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.

Temporary anchorage device usage: a survey among Swiss orthodontists.

BackgroundThe aim of the survey was to obtain information on the treatment plan preferences, mechanics and characteristics of temporary anchorage device (TAD) application using a single case presented to orthodontists in Switzerland.MethodsA structured questionnaire to be completed by all study participants with case-specific (treatment plan including mechanics and TAD usage) and general questions (general fixed appliance and TAD usage as well as professional, educational and demographic questions) together with an orthodontic borderline case was utilised. The case was a female adult with dental Class II/2, deep bite and maxillary anterior crowing, who had been treated in childhood with extraction of four premolars and fixed appliance followed by wisdom tooth extraction.ResultsThe response rate was 24.4% (108 out of 443). The majority (96.3%, 104) proposed comprehensive treatment, while 3.7% (4) planned only alignment of maxillary teeth. 8.3% (9) included a surgical approach in their treatment plan. An additional 0.9% (1) combined the surgical approach with Class II mechanics. 75.1% (81) decided on distalization on the maxilla using TADs, 7.4% (8) planned various types of Class II appliances and 3.7% (4) combined distalization using TADs or headgear with Class II appliances and surgery. Palatal implants were the most popular choice (70.6%, 60), followed by mini-screws (22.4%, 19) and mini-plates on the infrazygomatic crests (7.0%, 6). The preferred site of TAD insertion showed more variation in sagittal than in transversal dimension, and the median size of mini-screws used was 10.0-mm long (interquartile range (IQR) 2.3 mm) and 2.0-mm wide (IQR 0.3 mm).ConclusionsDistalization against palatal implants and then distalization against mini-screws were the most popular treatment plans. Preferred site for TAD insertion varied depending on type and size but varied more widely in the sagittal than in the transversal dimension.

Use of shape correspondence analysis to quantify skeletal changes associated with bone-anchored Class III correction

To evaluate the three-dimensional (3D) skeletal changes in the mandibles of Class III patients treated with bone-anchored maxillary protraction using shape correspondence analysis. Twenty-five consecutive patients with skeletal Class III who were between the ages of 9 and 13 years (mean age, 11.10 ± 1.1 years) were treated using Class III intermaxillary elastics and bilateral miniplates (two in the infrazygomatic crests of the maxilla and two in the anterior mandible). Cone-beam computed tomography (CBCT) was performed for each patient before initial loading (T1) and at 1 year out (T2). From the CBCT scans, 3D models were generated, registered on the anterior cranial base, and analyzed using 3D linear distances and vectors between corresponding point-based surfaces. Bone-anchored traction produced anteroposterior and vertical skeletal changes in the mandible. The novel application of Shape correspondence analysis showed vectors of mean (± standard deviation) distal displacement of the posterior ramus of 3.6 ± 1.4 mm, while the chin displaced backward by 0.5 ± 3.92 mm. The lower border of the mandible at the menton region was displaced downward by 2.6 ± 1.2 mm, and the lower border at the gonial region moved downward by 3.6 ± 1.4 mm. There was a downward and backward displacement around the gonial region with a mean closure of the gonial angle by 2.1°. The condyles were displaced distally by a mean of 2.6 ± 1.5 mm, and there were three distinct patterns for displacement: 44% backward, 40% backward and downward, and 16% backward and upward. This treatment approach induces favorable control of the mandibular growth pattern and can be used to treat patients with components of mandibular prognathism.

Assessment of Positional Variation of Maxillary Permanent First Molar with respect to the Infrazygomatic Crest (Key Ridge) in Skeletal Class I, II and III Cases

ABSTRACT Introduction To assess the positional variations of maxillary first permanent molar in horizontal and vertical plane with respect to infrazygomatic crest (key ridge) in skeletal class I, II and III cases. Materials and methods A total of 103 lateral cephalograms comprising of 40 skeletal class I (control group), 35 class II and 28 class III cases were selected and analyzed. Six parameters were chosen to compare the vertical and the horizontal variations of first permanent molars. Results The angulation of maxillary first molar with respect to key ridge in class II and III was 2.42° and 6.97° as compared to class I which was 5.35°. The mesiobuccal cusp tip of maxillary first molar from key ridge in class II and III was 2.11 and 5.46 mm respectively as compared to class I (1.62 mm). The mesiobuccal root tip of maxillary first molar from key ridge in class II and III was 2.14 and 2.82 mm as compared to class I (1.27 mm). Conclusion The maxillary first molar was not directly under the infrazygomatic crest and was ahead of the key ridge in all the groups. The maxillary first permanent molar was placed more mesially in class II and III cases as compared to the class I cases but, in class III, it was more upright as compared to class I and II. How to cite this article Kamble R, Hazarey A, Hazarey P, Singh J. Assessment of Positional Variation of Maxillary Permanent First Molar with respect to the Infrazygomatic Crest (Key Ridge) in Skeletal Class I, II and III Cases. World J Dent 2013;4(4):228-234.

Bone thickness of the infrazygomatic crest area in skeletal Class III growing patients: A computed tomographic study

PurposeThis study was performed to investigate the bone thickness of the infrazygomatic crest area by computed tomography (CT) for placement of a miniplate as skeletal anchorage for maxillary protraction in skeletal Class III children.Materials and MethodsCT images of skeletal Class III children (7 boys, 9 girls, mean age: 11.4 years) were taken parallel to the Frankfurt horizontal plane. The bone thickness of the infrazygomatic crest area was measured at 35 locations on the right and left sides, perpendicular to the bone surface.ResultsThe bone was thickest (5.0 mm) in the upper zygomatic bone and thinnest (1.1 mm) in the anterior wall of the maxillary sinus. Generally, there was a tendency for the bone to be thicker at the superior and lateral area of the zygomatic process of the maxilla. There was no clinically significant difference in bone thickness between the right and left sides; however, it was thicker in male than in female subjects.ConclusionIn the infrazygomatic crest area, the superior and lateral area of the zygomatic process of the maxilla had the most appropriate thickness for placement of a miniplate in growing skeletal Class III children with a retruded maxilla.

Three-dimensional finite element analysis of occlusal stress distribution in the human skull with premolar extraction

To analyze the effect of orthodontic treatment with premolar extraction on the stress distribution of the occlusal force in the human skull. A three-dimensional finite element (3D FE) model was constructed based on computed tomography scan data, and it served as the pretreatment model. For the extraction model simulating postorthodontic occlusion, the first premolar was removed in the pretreatment model, and the anterior and posterior segments were repositioned. Stress distribution was evaluated by 3D FE analysis in both models under the simulation of 1000 N for occlusal forces and 400 N for masseter muscle force. The occlusal stresses were concentrated at the alveolar bone near the teeth, the infrazygomatic crest, the frontal process, the temporal process of the zygomatic bone, the infraorbital rim, the pyriform aperture region, and the pterygoid plate in both models. The von Mises stress at the pterygoid plate area was lower in the extraction model (3.53 MPa) than in the pretreatment model (5.57 MPa), while the stress at the frontal process of the maxilla was higher in the extraction model (2.32 MPa) than in the pretreatment model (2.16 MPa). The results indicated that the occlusal forces were transferred through the maxillonasal, maxillozygomatic, and maxillopterygoid stress trajectories and that stress distribution moved more "forward" with the orthodontic treatment with premolar extraction.

Three-dimensional assessment of mandibular and glenoid fossa changes after bone-anchored Class III intermaxillary traction

Conventional treatment for young Class III patients involves extraoral devices designed to either protract the maxilla or restrain mandibular growth. The use of skeletal anchorage offers a promising alternative to obtain orthopedic results with fewer dental compensations. Our aim was to evaluate 3-dimensional changes in the mandibles and the glenoid fossae of Class III patients treated with bone-anchored maxillary protraction. Twenty-five consecutive skeletal Class III patients between the ages of 9 and 13 years (mean age, 11.10 ± 1.1 year) were treated with Class III intermaxillary elastics and bilateral miniplates (2 in the infrazygomatic crests of the maxilla and 2 in the anterior mandible). The patients had cone-beam computed tomography images taken before initial loading and at the end of active treatment. Three-dimensional models were generated from these images, registered on the anterior cranial base, and analyzed by using color maps. Posterior displacement of the mandible at the end of treatment was observed in all subjects (posterior ramus: mean, 2.74 ± 1.36 mm; condyles: mean, 2.07 ± 1.16 mm; chin: mean, -0.13 ± 2.89 mm). Remodeling of the glenoid fossa at the anterior eminence (mean, 1.38 ± 1.03 mm) and bone resorption at the posterior wall (mean, -1.34 ± 0.6 mm) were observed in most patients. This new treatment approach offers a promising alternative to restrain mandibular growth for Class III patients with a component of mandibular prognathism or to compensate for maxillary deficiency in patients with hypoplasia of the midface. Future studies with long-term follow-up and comparisons with facemask and chincup therapies are needed to better understand the treatment effects.

Stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall: A 3-dimensional finite element analysis

The purpose of this study was to compare the pattern and amount of stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall. Three-dimensional finite element models for the skull and the curvilinear type of miniplate were constructed. After a protraction force (500 g/side) was applied to the distal end of the miniplate with a forward and 30° downward vector to the maxillary occlusal plane, stress distributions in the circummaxillary sutures and displacements of the surface landmarks were analyzed. There was a difference in the maximum stress distribution area according to the site of the miniplate: infrazygomatic crest and middle part of the maxilla in the infrazygomatic crest and paranasal area adjacent to the pyriform aperture in the lateral nasal wall. Stress values of the frontonasal, frontomaxillary, zygomaticomaxillary, and pterygomaxillary sutures were greater in the infrazygomatic crest than in the lateral nasal wall. The site of the miniplate produced differences in the major displacement areas: infrazygomatic crest, maxillary dentition, anterior maxilla, and upper part of the maxillary tuberosity in the infrazygomatic crest and the lateral nasal wall, maxillary dentition, anterior maxilla, and lower part of the maxillary tuberosity in the lateral nasal wall. The lateral nasal wall exhibited forward, downward, and outward displacements of ANS, Point A, and prosthion. However, the infrazygomatic crest showed forward and upward displacements of ANS, Point A, and prosthion, and outward displacement of the zygomatic process of the maxilla and the maxillary process of the zygomatic bone. The site of miniplate placement should be considered to obtain proper stress and displacement values in different areas with maxillary hypoplasia.

Three-dimensional assessment of maxillary changes associated with bone anchored maxillary protraction

Bone-anchored maxillary protraction has been shown to be an effective treatment modality for the correction of Class III malocclusions. The purpose of this study was to evaluate 3-dimensional changes in the maxilla, the surrounding hard and soft tissues, and the circummaxillary sutures after bone-anchored maxillary protraction treatment. Twenty-five consecutive skeletal Class III patients between the ages of 9 and 13 years (mean, 11.10 ± 1.1 years) were treated with Class III intermaxillary elastics and bilateral miniplates (2 in the infrazygomatic crests of the maxilla and 2 in the anterior mandible). Cone-beam computed tomographs were taken before initial loading and 1 year out. Three-dimensional models were generated from the tomographs, registered on the anterior cranial base, superimposed, and analyzed by using color maps. The maxilla showed a mean forward displacement of 3.7 mm, and the zygomas and the maxillary incisors came forward 3.7 and 4.3 mm, respectively. This treatment approach produced significant orthopedic changes in the maxilla and the zygomas in growing Class III patients.

Horizontal Pull-Out Strength of Orthodontic Infrazygomatic Mini-Implant: An In Vitro Study

New modified mini-implants have recently come into use for reinforcing skeletal anchorage in orthodontic application. The aim of this study was to investigate the influence of the design of a mini-implant on its mechanical strength. We measured the insertion torques and horizontal pull-out strengths of 3 brands of infrazygomatic mini-implants (AbsoAnchor, Bioray, and Lomas; 2 mm for all). Five implants of each brand were manually driven 6 mm into the artificial bone. Significant differences in various parameters among the brands were investigated with the Kruskal-Wallis test. There was no significant relationship between insertion torque and horizontal pull-out strength. The Bioray mini-implants had significantly greater horizontal pull-out strength than the AbsoAnchor mini-implants. The design of the mini-implant can influence its insertion torque and horizontal pull-out strength. In our findings, the horizontal pull-out strength of all mini-implants placed in the infrazygomatic crest was significantly greater than the orthodontic force applied.

Cortical bone thickness at common miniscrew implant placement sites

The purpose of this study was to assess age, sex, and regional differences in the cortical bone thickness of commonly used maxillary and mandibular miniscrew implant placement sites. Cone-beam computed tomography images, taken at 0.39-mm voxel size, of 52 patients, including 26 adolescents (13 girls, ages 11-13; 13 boys, ages 14-16) and 26 adults (13 men and 13 women, ages 20-45), were evaluated. The cone-beam computed tomography data were imported into 3-dimensional software (version 10.5, Dolphin Imaging Systems, Chatsworth, Calif); standardized orientations were used to measure cortical bone thickness at 16 sites representing the following regions: 3 paramedian palate sites, 1 infrazygomatic crest site, 4 buccal interradicular sites of the mandible, and 4 buccal and 4 lingual interradicular sites in the maxilla. Multivariate analysis of variance (MANOVA) showed no significant differences in cortical bone thickness between the sexes. There were significant (P<0.05) differences between adolescents and adults, with adult cortices significantly thicker in all areas except the infrazygomatic crest, the mandibular buccal first molar-second molar site, and the posterior palate site. Cortical bone was thicker in the posterior than in the anterior mandibular sites. In the adults, interradicular bone in the maxillary first premolar-second premolar, and second premolar-first molar sites was thicker than bone at the lateral incisor-canine and first molar-second molar sites. Anterior paramedian palatal bone was significantly thicker than bone located more posteriorly. The mandibular buccal and infrazygomatic crest regions had the thickest cortical bone; differences between the maxillary buccal, the maxillary lingual, and the palatal regions were small. Maxillary and mandibular cortical bones at commonly used miniscrew implant placement sites are thicker in adults than in adolescents. There are also differences in cortical bone thickness between and within regions of the jaws that must be considered when placing miniscrew implants.