Influence of implant macro-designs on primary and secondary implant stability / Influencia de los macrodiseños de implantes en la estabilidad primaria y secundaria del implante

Introduction: Tapered implants have shown that thanks to their macro design they are capable of expanding the surgical bed performed by the surgeon, which in clinical practice gives a feeling of greater stability, however it is highly subjective and dependent on the operator. Aim: To analyze the influence of the implant macro design in the primary and secondary stability by means of analysis of resonance frequency and force of insertion. Methods: 38 Screw Type and Tapered Type implants were placed in 18 patients in the Bucomaxillofacial Implantology program of the University of Chile during 2006 and 2007 in type II or III bone jaws according to Leckholm and Zarb. Implant stability, implant stability coefficient (ISQ), was measured through Ostell® mentor at the time of installation (ISQ1) and then at connection (ISQ2) and the Insertion Torque through the Osseoset® machine: 17 Screw Type implants with an approximate average contact area of 237 mm2 (3.75/15 mm; 3.75/13 mm) and 17 Tapered Type implants with an approximate average contact area of 226 mm2 (4.3/13 mm; 4.3/16 mm). Results: The averages of ISQ1 and ISQ2 and Insertion Torque respectively for implants with an approximate contact area of 237 mm2 were 71.3 ISQ1, 66.6 ISQ2 and 44.52 Ncm; for 226 mm2 implants it was 75 ISQ1, 72.5 ISQ2 and 48.82 Ncm. Conclusion: Implants with an average contact area of approximately 226 mm2 (Tapered Type) present significantly higher primary and secondary stability than those with an average contact area of approximately 237 mm2 (Screw Type). (Average ISQ1: p = 0.0473; Insertion Torque: p = 0.0031 and Average ISQ2: p = 0.0039)(AU)

Introducción: Los implantes Cónicos han demostrado que gracias a su macro diseño son capaces de expandir el lecho quirúrgico realizado por el cirujano, lo que en la práctica clínica da una sensación de mayor estabilidad, sin embargo, ella es altamente subjetiva y dependiente del operador. Objetivo: Analizar la influencia del diseño del implante en la estabilidad primaria y secundaria mediante análisis de frecuencia de resonancia y Torque de Inserción. Métodos: 38 implantes Tipo Tornillo y Tipo Cónico fueron colocados en 18 pacientes en el programa de Implantología Bucomáxilofacial de la Universidad de Chile durante el año 2006 y 2007 en maxilares de hueso tipo II o III según Leckholm y Zarb. Se midió la estabilidad implantaria, coeficiente de estabilidad del implante (ISQ), a través de Ostell® mentor al momento de la instalación (ISQ1) y luego en la conexión (ISQ2) y el Torque de Inserción a través de el motor Osseoset®: 17 implantes Tipo Tornillo de área de contacto promedio aproximada de 237 mm2 (3.75/15 mm; 3.75/13 mm) y 17 implantes Tipo Cónico de área de contacto promedio aproximada de 226 mm2 (4.3/13 mm; 4.3/16 mm). Resultados: Los promedios de ISQ1 e ISQ2 y Torque de Inserción respectivamente para implantes de área contacto aproximada de 237 mm2 fue de 71,3 ISQ1, 66,6 ISQ2 y 44,52 Ncm; para implantes de 226 mm2 fue de 75 ISQ1, 72,5 ISQ2 y 48,82 Ncm. Conclusión: Los implantes de área contacto promedio aproximada de 226 mm2 (Tipo Cónicos) presentan estabilidad primaria y secundaria significativamente mayor a los de área contacto promedio aproximada de 237 mm2 (Tipo Tornillo). (Promedio ISQ1: p = 0.0473; Torque de Inserción: p = 0.0031 y Promedio ISQ2: p = 0.0039)(AU)

Variability of slot size in orthodontic brackets.

Objective: The accuracy of the information incorporated into brackets is a determining factor for the efficacy of torque applied to teeth. The aim of this study was to compare the dimensions of a bracket's slots with the nominal values announced by the manufacturer. Materials and methods: A total of 730 maxillary right central brackets manufactured by seven companies (Dentsply Gac, American Orthodontics, Rocky Mountain Orthodontics, GC Orthodontics, 3M Unitek, and Dentaurum) were studied. The sample included 0.018 × 0.025 and 0.022 × 0.028 in., metal and ceramic, conventional and self-ligating brackets. Images were obtained with an Olympus BX51 optical microscope. Slot dimensions were measured at the base and at the face on both mesial and distal sides using ImageJ software. Data were analyzed using Wilcoxon, sign tests, two- and three-way ANOVA, and Tukey's tests. Intraclass correlation coefficient was employed to assess the intraobserver and interobserver variability. The threshold for statistical significance was p ≤ .05. Results: Statistical analysis showed that the slot dimensions of 90% to 97% of studied brackets were significantly different from nominal values. In general, slot size was oversized, with a face size larger than the base size. Comparison between mesial and distal sides showed that up to 45% of the brackets were significantly asymmetrical. The manufacturer had a significant effect for base and face widths (p = .0001) and for length (p = .003). Conclusion: This study shows that a large proportion of measured brackets displays dimensional inaccuracies when compared with stated values. Clinically, the slot oversize and the divergence of slot walls cause an increase of wire-slot play, inducing a loss of torque control. Practitioners cannot fully trust the precision of used appliances and should be aware that adjustments could be needed in the finishing stages of the treatment.

Multidisciplinary treatment with a customized lingual appliance for an adult patient with severe Class III malocclusion and multiple missing teeth.

A 24-year-old man presented with a severe skeletal class III malocclusion, associated with an anterior and posterior crossbite in the left side, upper and lower lip eversion, skeletal asymmetry, midline discrepancy, diastemas in the maxillary and mandibular dental arches, and agenesis of maxillary lateral incisors and canines with retained deciduous teeth. Treatment was performed with the use of the Win Lingual System. When the 0.016 × 0.022-inch NiTi archiwire was applied, the deciduous teeth were extracted and replaced with temporary crowns connected to the appliance. After the aligning, leveling, and diastema closure phases, a modified Le Fort II osteotomy, a mandibular setback with a bilateral sagittal split osteotomy and a genioplasty were performed. Implants were placed in the canine site through a flapless guided surgery, and cantilevered temporary bridges were delivered. Final prosthetic rehabilitation included veneers for the central incisors and zirconia-ceramic cantilevered bridges for the canine and lateral incisors. After 36 months of active treatment, the patient showed an Angle Class I molar and canine relationship and an ideal overbite and overjet. His profile had improved, lips were competent, and gingival levels were acceptable. The lateral radiograph and cephalometric analysis showed a good balance of the skeletal pattern, a good profile of the soft tissue, and proper inclinations of the maxillary and mandibular incisors in relation to maxilla and mandible. After 2 years of follow-up, the patient had a pleasant smile and no relapse, or joint or muscular pain.

Effects of size and insertion angle of orthodontic mini-implants on skeletal anchorage.

INTRODUCTION: The primary aim of this in vitro study was to compare the insertion torque (IT) and anchorage force (AF) values of 4 different sizes of orthodontic mini-implants with 2 different angles. The second aim was to evaluate the relationship between IT and AF values under different diameter, length, and insertion angle variables. METHODS: A total of 160 mini-implants, including 20 implants in each group, with 4 different sizes (1.6 × 8 mm, 1.6 × 10 mm, 2.0 × 8 mm, and 2.0 × 10 mm) at 2 different angles (70° and 90°), were inserted into bovine iliac bone segments. The IT and AF values leading to 1.5 mm deflection were compared. The correlations between IT and AF values under different variables were also analyzed. RESULTS: The mini-implants with greater diameter and length showed greater IT and AF values (P <0.05). The IT and AF values of mini-implants inserted at 70° angle were significantly greater than those of mini-implants inserted at 90° angle (P <0.001). Significant correlations were found between IT and AF values in all variables. CONCLUSIONS: The diameter, length, and insertion angle of orthodontic mini-implants have significant effects on IT and AF values. Insertion angle and diameter of mini-implants are more effective than implant length on skeletal anchorage. Significant correlations are present between IT and AF values of mini-implants regardless of their diameters, lengths, and insertion angles.

Obstructive sleep apnoea in a patient with chronic lymphocytic leukaemia.

A 69-year-old Caucasian woman presented with chronic lymphocytic leukaemia (CLL; stage 1-Rai System), significant oropharyngeal lymphoid enlargement, snoring and fatigue. Overnight polysomnography revealed moderately severe obstructive sleep apnoea (OSA), which was managed successfully with oral appliance therapy with resolution of snoring and daytime fatigue. Structural abnormalities of the upper airways are known to cause OSA. Airway narrowing can result from bony structural abnormalities, nasopharyngeal growth, soft tissue redundancy, macroglossia, malignant and benign growth of the upper aero-digestive tract, and adenotonsilar enlargement. Clinicians should be encouraged to consider a diagnosis of OSA in patients with CLL when they present with symptoms of worsening fatigue.

CAD-CAM-fabricated mini-implant insertion guides for the delivery of a distalization appliance in a single appointment.

This article reports on the technical aspects of using a computer-aided design-computer-aided manufacturing (CAD-CAM) insertion guide for the placement of orthodontic mini-implants used for the purpose of providing anchorage support for maxillary molar distalization. A 10-year-old girl presented with a bilateral full-step Angle Class II molar relationship in the permanent dentition, with anterior arch-length insufficiency and blocked out maxillary canine teeth. The primary treatment objective was to provide an esthetic and functional occlusal outcome, and secondarily to avoid the removal of multiple premolar teeth. The patient was initially treated with an implant-supported distalization device, and the occlusion was subsequently detailed with preadjusted fixed orthodontic appliances. The CAD-CAM procedure facilitates the safe and precise insertion of mini-implants in the anterior palate, potentially broadening the scope of use of palatal mini-implants for less experienced clinicians. The illustrated protocol allows for the insertion of mini-implants and fitting of a prefabricated appliance in a single office appointment.

Treatment of class II malocclussion: A comparative study of the effects of twin-block and fatigue resistant device.

AIM: This is a retrospective cephalometric study aimed to compare the treatment effects of Twin-Block (TB) appliance with The Forsus Fatigue Resistant Device (FRD) appliance in class II division I patients in a composite of peak and post peak growth of period time. MATERIALS AND METHODS: The experimental sample consisted of the lateral cephalograms of 40 patients who were treated with either TB appliance (n = 15), FRD (n = 15) or the untreated control ones. In treatment groups lateral cephalograms taken before therapy as initial records (T1) and at the completion of functional therapy (T2) were used. The control group comprised 10 children with untreated skeletal Class II malocclusions. The normality of distribution of continuous variables was tested by Shaphiro wilk test. Oneway ANOVA and LSD test in parametric; Kruskall Wallis and all pairwaise multible comparison tests in non-parametric samples were used for comparing differences among 3 groups. RESULTS: Cephalometric analysis revealed that both TB and FRD appliances stimulated mandibular growth (P < 0.05) and no restriction was seen in maxilla in both groups (P > 0.05). The unwanted mandibular proclination was seen more in FRD group (P ≤ 0.001). Soft tissue didn't imitate the hard tissue (P > 0.05). CONCLUSION: FRD group produced skeletal effects as much as TB group in peak and post peak period of growth with still more mandibular incisor proclination.

[Possibilities and limitations of treatment with clear aligners. An orientation]. / Mogelijkheden en beperkingen van orthodontische behandeling met clear aligners. Een verkenning.

The aim of this research was to evaluate the efficiency and effectiveness of an orthodontic treatment with clear-aligner systems, specifically with Invisalign®. In addition to a review of the literature, 4 orthodontists and 9 patients treated with fixed orthodontic therapy and Invisalign® were interviewed. The literature showed that it is difficult to correct an extrusion, rotation or overjet with clear aligners. Often 'refinement' (additional intervention during treatment) is necessary to achieve the best possible end result. The patients interviewed experienced few limitations in their daily lives caused by the clear aligners and hardly any pain. Treatment duration was comparable to that with fixed appliances; it depended on the experience of the orthodontist, the complexity of the case and cooperation of the patient. The cost of an Invisalign® treatment is higher than that of fixed-appliance therapy. Additionally, making a plan for clear-aligner treatment often takes more time for the orthodontist than planning treatment for fixed-appliance therapy.

Finite element analysis of slot wall deformation in stainless steel and titanium orthodontic brackets during simulated palatal root torque.

INTRODUCTION: Torque applied on anterior teeth is vital for root positioning and stability. The aim of this study was to evaluate the detailed slot wall deformation in stainless steel (SS) and titanium (Ti) edgewise brackets during palatal root torque using finite element analysis. METHODS: A finite element model was developed from a maxillary central incisor SS bracket (0.022 in). The generated torque values from an SS rectangular archwire (0.019 × 0.025 in) while twisting from 5° to 40° were obtained experimentally by a spine tester, and the calculated torque force was applied in the bracket slot. The deformations of the slot walls in both SS and Ti brackets were measured at various locations. RESULTS: There were gradual increases in the deformations of both bracket slot walls from the bottom to top locations. In the SS bracket slot for the 40° twist, the deformations were 9.28, 36.8, and 44.8 µm in the bottom, middle, and top slot wall locations, respectively. Similarly, in the Ti bracket slot for the 40° twist, the deformations were 39.2, 62.4, and 76.2 µm in the bottom, middle, and top slot wall locations, respectively. The elastic limits were reached at 28° for SS and at 37° for Ti. CONCLUSIONS: Both SS and Ti bracket slots underwent deformation during torque application. There are variations in the deformations at different locations in the slot walls and between the materials.

Expanding torque possibilities: A skeletally anchored torqued cantilever for uprighting "kissing molars".

Several uprighting mechanics and devices have been used for repositioning tipped molars. "Kissing molars" (KMs) are an uncommon tooth impaction involving 2 severely tipped mandibular molars with their occlusal surfaces positioned crown to crown, with the roots pointing in opposite directions. Orthodontic uprighting of KMs has not been a usual treatment protocol, and it can be a challenging task due to the severe tipping and double impaction, requiring efficient and well-controlled uprighting mechanics. An innovative skeletally anchored cantilever, which uses the torque principle for uprighting tipped molars, is suggested. This torqued cantilever is easy to manufacture, install, and activate; it is a well-known torque that is effective for producing root movement. A successful treatment of symptomatic KMs, involving the first and second molars, was achieved with this cantilever. Thus, clinicians should consider the suggested uprighting mechanics and orthodontic device as a more conservative alternative to extraction of KMs, depending on the patient's age, involved teeth in KMs, tipping severity, and impaction positions.

A new elastic slot system and V-wire mechanics.

OBJECTIVE: To biomechanically test a new elastic slot system and V-wire mechanics. MATERIALS AND METHODS: Conventional twin and self-ligating brackets and the new elastodynamic bracket were biomechanically tested. The conventional brackets had a rectangular 0.022'' slot and the new elastodynamic bracket had a V-slot, a new slot geometry. Torque measurements were performed with 0.018'' × 0.025'' and 0.019'' × 0.025'' stainless steel (ss) archwires. A nickel-titanium V wire was used for the biomechanical measurements on the elastodynamic bracket. The measurements were done with the aid of a six-component measuring sensor. RESULTS: The results of the biomechanical testing revealed play in the brackets with rectangular slot geometry. The V slot in the elastodynamic bracket assured that the wire fit perfectly in the slot. Dynamic moments of 5 to 10 Nmm were transmitted without any play. No permanent deformation of the slot occurred in the new elastodynamic bracket because of the elastic slot. CONCLUSION: Control of torque for three-dimensional positioning of the teeth in the dental arch with rectangular slot geometry as used in straight-wire therapy is difficult. If torque is bent into the wire, because of the play there is a high risk that either too much, too little, or no moment is transmitted to the teeth. The V-slot archwire/bracket geometry in conjunction with nickel titanium composition has no play and allows a reduction of forces and moments with direct and continuous transmission of torque in the bracket. Because of the elasticity of the bracket, there is an upper limit to the moment possible.

[A new method to orthodontically correct dental occlusal plane canting: wave-shaped arch].

OBJECTIVE: To introduce a technique of second order wave-shaped arch wire to orthodontically treat dental occlusal plane canting (DOPC) with left-right interactive anchorage, and to test its clinical efficacy. METHODS: Among the permanent dentition malocclusion patients who showed no obvious facial asymmetry, we screened for patients who showed anterior occlusal plane canting (AOPC) after routine orthodontic examination, treatment planning, MBT fixed appliance installation and serial arch wires alignment. Each patient had been clinically appraised in frontal view by 2 orthodontists and the patient him/herself; if all 3 agreed that the AOPC was obvious, the patient was included. By this means, we included 37 patients, including 10 males and 27 females; the average age was (21.9±5.2) years. To correct AOPC, opposite direction equal curvature second order rocking-chair curve was bent on each side of 0.46 mm×0.56 mm stainless steel edgewise wire. With reference to normal occlusal plane, a curve toward the occlusal surface was made to extrude under-erupted teeth on one side while a curve toward the gingiva was made to intrude over-erupted teeth on the other side, so that the arch wire was made into a wave shape in vertical dimension. Before and after application of wave-shaped arch wire, frontal facial photographs were taken when the patient's mouth was open slightly with lips retracted to show anterior occlusal plane (AOP) clearly. An AOP was constructed by connecting the center of the slot in the medial edge of canine bracket on each side in the photograph. The angles between the bipupillary plane(BPP) and the constructed AOP were measured in ImageJ1-48v software and the angle differences before and after treatment were compared with paired Wilcoxon test in SPSS 10.0 software. RESULTS: The wave-shaped arch could correct AOPC effectively in 3 to 10 months time with an average of 5.5±1.7 months; the angles between AOP and BBP before treatment ranged from 2.90° to 6.12° with a median of 4.01°; after treatment the angles were from -0.17° to 2.57° with a median of 1.87°, the decrease of the angles between AOP and BBP after treatment ranged from 1.08° to 4.15° with a median of 2.21°. Paired Wilcoxon test P was 0.000. CONCLUSION: The wave-shaped arch can be used independently or in combination with other treatment methods, which can take advantage of left and right interactive anchorage to correct AOPC effectively, so it has certain application value in clinical practice.

Class I Correction Using a Combination of an Upper Lingual and Lower Labial Appliance.

No orthodontic system combines aesthetics and comfort which delivers optimal treatment outcomes. This case report outlines how combining an upper lingual and a lower ceramic appliance can provide the best combination ofaesthetics whilst maintaining patien comfort, when undertaking class II camouflage treatment involving extraction of the upper first premolars.

Objective assessment of compliance with intra- and extraoral removable appliances.

OBJECTIVE: To conduct an objective assessment of the level of compliance in young patients prescribed various types of removable appliances and to determine the influence of device type, treatment duration, and patient age, gender, psychological maturity, and awareness of monitoring on compliance. MATERIALS AND METHODS: A total of 30 patients were fitted with either a class 2 (Frankel or bionator) or a class 3 (face mask) removable appliance, each bearing a compliance indicator chip, and they were instructed to wear them for 13 hours per day. Compliance was monitored by means of the sensor for an average of 8 months. Of the patients, 14 were informed that their appliance was fitted with a monitoring sensor, and 16 were not. The psychological maturity of all patients was assessed on the Nowicki-Strickland Locus of Control Scale, and the effect on compliance of this score as well as the patient- and treatment-related variables considered were determined via statistical analysis Results: The mean compliance recorded by the chips was 8.6 ± 2.9 hours, far lower than the 13 hours prescribed, and younger patients showed significantly greater compliance than adolescents (P < .01). However, no significant differences in compliance were found between intra- and extraoral appliances, and neither gender, psychological scores, treatment duration, nor awareness of being monitored had any significant effect. CONCLUSIONS: Compliance is generally very poor in young patients, regardless of their gender and psychological maturity. Although awareness of monitoring does not appear to boost compliance, such systems may be a valuable means of providing a dentist with objective information regarding their patients' compliance.

The effects of rapid maxillary expansion on voice function.

OBJECTIVE: To evaluate the effects of rapid maxillary expansion (RME) on vocal function in patients with bilateral maxillary crossbite. MATERIALS AND METHODS: We designed our research as a prospective, controlled, clinical study. The treatment group and the control group each had 20 subjects for a total of 40 subjects. Acoustic voice samples were recorded from all patients at T1 and T2 by the Multi-Dimensional Voice Program (MDVP Model 5105) for acoustic analysis in Computerized Speech Lab (CSL). RESULTS: No statistically significant differences were found between the treatment and control groups in the means of any parameters. CONCLUSIONS: RME does not change vocal quality or resonance, so it can be safely used with patients.

Effect of Intraoral Aging on Debris Accumulation and Friction of First Molar Tubes.

AIM: The aim of this article was to evaluate the impact of intraoral aging and site specificity on debris accumulation and friction in molar tubes after intraoral use. MATERIALS AND METHODS: A total of 80 intraorally used first molar convertible tubes were provided by 20 orthodontic adolescent patients after 6 months of treatment. The specimens were divided into eight groups (n = 10) according to the mouth quadrant and the type of examination [four groups of ten tubes for scanning electron microscope (SEM) and four groups of ten tubes for friction test]. Scanning electron microscope examination was performed after opening the convertible caps and friction test was executed using a 0.019'' × 0.025'' stainless steel wire, which was inserted in the tubes belonging to each group. The Mann-Whitney test, analysis of variance (ANOVA), and Bonferroni tests were performed for statistical analysis at 0.01 level of significance. RESULTS: There was a significant increase in the amount of debris and frictional force after 6 months of intraoral exposure (p < 0.0001). Debris scores were higher (10% increase) on the upper tubes when compared with the lower ones, with no statistical difference. Mean frictional force ranged from 0.22 to 0.26 N according to the mouth quadrant, but the difference between groups was also not significant. CONCLUSION: After 6 months of intraoral exposure, there was a significant increase in the amount of debris in the first molar tube slots, leading to significantly higher frictional forces during sliding mechanics. The influence of site specificity on the amount of debris and on frictional forces of the first molar tubes could not be demonstrated. CLINICAL SIGNIFICANCE: Molar tubes should be cleaned, before and during sliding mechanics, in order to minimize friction.

Stress and displacement pattern evaluation using two different palatal expanders in unilateral cleft lip and palate: a three-dimensional finite element analysis.

BACKGROUND: In this finite element (FE) study, the stress distribution and displacement pattern was evaluated in the mid-palatal area and around circum-maxillary sutures exerted by bone-borne palatal expander (BBPE) in comparison with conventional HYRAX rapid palatal expander in unilateral cleft lip and palate. METHODS: Computed tomography scan images of a patient with unilateral cleft palate was used to create a FE model of the maxillary bone along with circum-maxillary sutures. A three-dimensional model of the conventional HYRAX (Hygienic Rapid Expander) expander and custom-made BBPE was created by laser scanning and programmed into the FE model. RESULTS: With the BBPE, the maximum stress was observed at the implant insertion site, whereas with the conventional HYRAX expander, it was at the dentition level. Among the circum-maxillary sutures, the zygomaticomaxillary suture experienced maximum stress followed by the zygomaticotemporal and nasomaxillary sutures. Displacement in the X-axis (transverse) was highest on the cleft side, and in the Y-axis (antero-posterior), it was highest in the posterior region in the BBPE. CONCLUSIONS: The total displacement was observed maximum in the mid-palatal cleft area in the BBPE, and it produced true skeletal expansion at the alveolar level without any dental tipping when compared with the conventional HYRAX expander.

Biocompatibility of nanosilver-coated orthodontic brackets: an in vivo study.

BACKGROUND: Nanosilver particles of which antibacterial and antifungal properties have been shown in various in vitro and in vivo studies are used in many medical and dental fields for the prevention of infection. In this study, it is intended to evaluate the biocompatibility of nanosilver-coated brackets. METHODS: Nanosilver coating process was applied to the standard orthodontic brackets by a physical vapor deposition system. Brackets were coated with nanosilver particles of 1 µ thickness. A total of 12 Wistar Albino rats were included in the study (six) and control (six) groups. For the study and control groups, four nanosilver-coated and four standard brackets were aseptically implanted subcutaneously in the dorsal region of each rat. The brackets were removed with the surrounding tissues on days 7, 14, 30, and 60. The specimens were evaluated for inflammatory response. RESULTS: No significant difference was found in terms of tissue reaction between the study and control groups. On day 7, randomly distributed brown-black granules were seen in the granulation tissue adjacent to the bracket in the study group. These foreign particles continued along the bracket cavity in a few samples, but the inflammatory response was insignificant between the groups. Mast cell count was found to be significantly smaller only on day 7 in the study group than in the control group. CONCLUSIONS: Nanosilver-coated orthodontic brackets were found to be similar with the standard type concerning inflammation. Further researches are needed with regard to the assessment of the brown-black granules, especially on the deposition of the vessel walls.

Evaluation of the stiffness characteristics of rapid palatal expander screws.

BACKGROUND: The aim of this study is to evaluate the mechanical properties of the screws used for rapid expansion of the upper jaw. METHODS: Ten types of expansion screw were assessed, seven with four arms: Lancer Philosophy 1, Dentaurum Hyrax Click Medium, Forestadent Anatomic Expander type "S", Forestadent Anatomic Expander type "S" for narrow palates, Forestadent Memory, Leone A 2620-10 with telescopic guide, and Leone A 0630-10 with orthogonal arms; and three with two arms: Dentaurum Variety S.P., Target Baby REP Veltri, and Leone A 362113. A test expander with the mean dimensions taken from measurements on a sample of 100 expanders was constructed for each screw. The test expanders were connected to the supports of an Instron 4467 (Instron Corp., USA) mechanical testing machine equipped with a 500 N load cell, and the compression force exerted after each activation was measured. The mean forces expressed by the two- and four-arm expanders were then compared. RESULTS: After five activations, the forces expressed by the two-arm devices were double than those expressed by the four-arm devices on average (224 ± 59.9 N vs. 103 ± 32.9 N), and such values remained high after subsequent activations. CONCLUSIONS: The expanders tested demonstrated stiffness characteristics compatible with opening of the palatine sutures in pre-adolescent patients. The stiffness of such devices can be further increased during the construction phase.

Maxillary anterior en masse retraction using different antero-posterior position of mini screw: a 3D finite element study.

BACKGROUND: Nowadays, mini screws are used in orthodontic tooth movement to obtain maximum or absolute anchorage. They have gained popularity among orthodontists for en masse retraction of anterior teeth after first premolar extraction in maximum anchorage cases. The purpose of this study was to determine the type of anterior tooth movement during the time when force was applied from different mini screw placements to the anterior power arm with various heights. METHODS: A finite element method was used for modeling maxillary teeth and bone structure. Brackets, wire, and hooks were also designed for modeling. Two appropriate positions for mini screw in the mesial and distal of the second premolar were designed as fixed nodes. Forces were applied from the mini screw to four different levels of anterior hook height: 0, 3, 6, and 9 mm. Initial tooth movement in eight different conditions was analyzed and calculated with ANSYS software. RESULTS: Rotation of anterior dentition was decreased with a longer anterior power arm and the mesial placement of the mini screw. Bodily movements occurred with the 9-mm height of the power arm in both mini screw positions. Intrusion or extrusion of the anterior teeth segment depended on the level of the mini screw and the edge of the power arm on the Z axis. CONCLUSIONS: According to the findings of this study, the best control in the sagittal plane during anterior en masse retraction was achieved by mesial placement of the mini screw and the 9-mm height of the anterior power arm. Where control in the vertical plane was concerned, distal placement of the mini screw with the 6-mm power arm height had minimum adverse effect on anterior dentition.