Standard Brackets Research Articles

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

BackgroundNanosilver 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.MethodsNanosilver 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.ResultsNo 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.ConclusionsNanosilver-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.

Nanosilver coated orthodontic brackets: in vivo antibacterial properties and ion release.

Silver nanoparticles are currently utilized in the fields of dentistry. The aim of this study was to evaluate the antibacterial properties and ion release of nanosilver coated orthodontic brackets compared to conventional brackets. Nanosilver coating process was applied to standard orthodontic brackets placed on the mandibular incisors of Wistar Albino rats in the study group and conventional brackets in the control group. Dental plaque, mucosal vestibular smears, saliva, and blood samples were collected from rats at various days. The amounts of nanosilver ions in blood and saliva were measured and microbiological evaluation was made for Streptococcus mutans. For testing cariogenicity, all rats were sacrificed at the end of 75 days under anaesthesia. Teeth were stained using a caries indicator, then the caries ratio was assessed. Nanosilver coated orthodontic bracket favoured the inhibition of S.mutans on Day 30 and reduction of caries on the smooth surfaces. The nanosilver amounts in the saliva and serum samples were significantly higher in the study group on Day 7. It is suggested that nanosilver coated orthodontic brackets, as an antibacterial agent without patient compliance, could be helpful for the prevention of white spot lesions during fixed orthodontic treatment.

Comparative evaluation of efficacy of self-ligating interactive bracket with conventional preadjusted bracket: A clinical study.

Aims and Objectives:This clinical study was conducted to compare the interactive self-ligating twin brackets and the standard double width brackets for their efficiency in Rate of Retraction.Materials and Methods:A total of 20 patients with Angle's class I or class II or class III dento-alveolar malocclusions between the age group of 18-25 years were selected. 10 patients in each group both males and females were randomly selected for the study. Ten patients were bonded using conventional brackets (Group I) the other ten patients were bonded using Interactive self-ligating brackets (Group II). The Rate of retraction was quantified using the scanned models. Pretreatment and post treatment models were taken and scanned to measure the amount of Incisor movement and Anchor loss.Results:(1) Interactive Self-ligating brackets showed significant Rate of retraction when compared with conventional brackets on right and left quadrant. (Group I 0.545 ± .205: Group II 0.827 ± .208 P = .013*) (Group I 0.598 ± .160: Group II 0.804 ± .268 P = .071) (2) Interactive self-ligating brackets when compared with conventional brackets had significant amount of incisor movement on right and left quadrant. (Group I 3.51 ± .548: Group II 4.38 ± .1.06 P = .047*) and (Group I 3.66 ± .899: Group II 4.67 ± 1.02 P = .047*) (3) Conventional brackets showed significant Amount of Anchor loss when compared with that of Interactive self-ligating brackets on right and left quadrant. (Group I .948 ± .392: Group II 0.501 ± .229 P = .013*). In the left side (Group I 0.861 ± .464: Group II 0.498 ± .227 P = .060).Conclusion:The interactive self-ligating brackets show more efficiency in Rate of Retraction, Amount of Incisor movement and Amount of Anchor loss when compared with the conventional brackets.

Comparison of the Load-Deflection Characteristics of Aesthetic and Conventional Super Elastic Ni-Ti Orthodontic Arch Wires in Conventional and Metal-Insert Ceramic Brackets.

Coated arch wires and ceramic brackets have been introduced to improve aesthetics during orthodontic treatment. The aim of this study was to determine the effects of coating on the physical properties of aesthetic orthodontic wires. Five round wires (0.016 inch) were obtained from each of three brands: conventional uncoated super elastic Nickel Titanium (Ni-Ti) (Rematitian Lite; Dentaurum, Ispringen, Germany), HUBIT (Teflon Coated, Korea), G&H (Epoxy Coated, Greenwood, Indiana, USA) which belonged to maxillary arch. Two types of standard ceramic brackets (conventional and metal-insert type, Ortho Technology, Tampa, Florida, USA) with the slot size of 0.022×0.028 inches were used. A simulation device was fabricated to resemble a model of human dental arch and each of the specimen was tested in three-point bending test. The test was conducted in the buccolingual plane with crosshead speed of 1mm/minute pressure from metal pole. Each sample was loaded until a deflection of 3.0 mm was produced. The mean values of maximum loading force, unloading force and clinical plateau length were recorded. One-way ANOVA and Tukey tests were used at p<0.05. Uncoated Ni-Ti arch wire showed higher mean values of maximum loading and unloading force than that of coated aesthetic wires similar to ceramic brackets while G&H wire and metal-insert ceramic brackets presented the lowest values. The longest clinical plateau length was observed in G&H wires and metal-insert ceramic bracket. The coating processes for HUBIT (Teflon Coated, Korea), G&H (Epoxy Coated, Greenwood, Indiana, USA) wires might influence bending behaviour which can cause decrease in loading and unloading force.

Effectiveness and efficiency of a CAD/CAM orthodontic bracket system

The first straight-wire appliance was introduced over 40 years ago to increase the consistency and efficiency of orthodontic treatment. More recently, computer-aided design and computer-aided manufacturing (CAD/CAM) technology has been used to create individualized orthodontic appliances. The purpose of this study was to investigate the clinical effectiveness and efficiency of CAD/CAM customized orthodontic appliances compared with direct and indirect bonded stock orthodontic brackets. This retrospective study included 3 treatment groups: group 1 patients were direct bonded with self-ligating appliances, group 2 patients were indirect bonded with self-ligating appliances, and group 3 patients were indirect bonded with CAD/CAM self-ligating appliances. Complete pretreatment and posttreatment records were obtained for all patients. The American Board of Orthodontics (ABO) Discrepancy Index was used to evaluate the pretreatment records, and the posttreatment outcomes were analyzed using the ABO Cast-Radiograph Evaluation. All data collection and analysis were completed by 1 evaluator. There were no statistically significant differences in the ABO Discrepancy Index or the ABO Cast-Radiograph Evaluation among the groups. Treatment times for the 3 groups were significantly different; the CAD/CAM group was the shortest at 13.8 ± 3.4 months, compared with 21.9 ± 5.0 and 16.9 ± 4.1 months for the direct bonded and indirect bonded groups, respectively. The number of treatment appointments for the CAD/CAM group was significantly fewer than for the direct bonded group. The CAD/CAM orthodontic bracket system evaluated in this study was as effective in treatment outcome measures as were standard brackets bonded both directly and indirectly. The CAD/CAM appliance was more efficient in regard to treatment duration, although the decrease in total archwire appointments was minimal. Further investigation is needed to better quantify the clinical benefits of CAD/CAM orthodontic appliances.

Force to Debond Brackets from High-fusing and Low-fusing Porcelain Systems

The purpose of this study was to test the hypothesis that porcelain surface finishing, ie, low- and high-fusing porcelain, has an effect on the amount of force required to debond orthodontic brackets. A total of 20 high-fusing and 20 low-fusing porcelain specimens were prepared, polished, and bonded with standard edgewise brackets using a suggested porcelain bonding protocol. The brackets were debonded with a universal testing machine at shear mode. Resin removal was performed using two methods: a multifluted carbide bur with and without the use of Sof-Lex polishing discs. Representative specimens were studied under a scanning electron microscope before and after debonding to assess the surface morphology and potential surface damage. Statistical analysis with a t-test revealed that there was no difference between the two porcelain treatments on the force to debond values and no qualitative differences were observed on the porcelain surface between the two resin clean-up methods. From a clinical perspective, the practitioner can bond ceramic restorations without previous knowledge of the porcelain type used.

Comparación in vitro de la fuerza de adhesión sobre esmalte de brackets Clarity estándar (Transbond XT 3M) con los brackets Clarity APC Plus (3M), mediante una prueba de cizallamiento.

En un intento de ahorrar tiempo durante la adhesión de brackets, las casas comerciales han fabricado brackets metálicos y de cerámica con un recubrimiento previo de material adhesivo. El sistema adhesivo utilizado en los brackets con recubrimientos previo (APC) es similar en composición al sistem a adhesivo utilizado en los brackets convencionales sin recubrimiento. La diferencia es esencialmente en los porcentajes de los diversos ingredientes incorporados en el material adhesivo. El objetivo de este estudio es determinar si los brackets Clarity APC Plus (3M), tendrán mayor fuerza adhesiva que los brackets Clarity estándar (Transbond XT) frente a una fuerza de cizallamiento. Cuarenta y cinco primeros premolares inferiores humanos, recién extraídos, fueron montados en bases de acrílico y utilizados para adherir los dos tipos de brackets de acuerdo a las instrucciones del fabricante. La fuerza de cizallamiento fue realizada en la máquina de fuerzas universales MTS. Los resultados encontrados fueron: (1) los brackets Clarity APC Plus no generaron una mayor fuerza adhesiva que los brackets Clarity estándar frente a la fuerza de cizallamiento. (2) Los brackets Clarity APC Plus y Clarity estándar no tuvieron una diferencia estadísticamente significativa en cuanto a su adhesión frente a una fuerza de cizallamiento. (3)Todas las muestras de brackets-adhesivo, sometidas a una prueba de cizallamiento, generan una fuerza adhesiva clínicamente aceptable.

Evaluation of self-etching primer and erbium-doped yttrium aluminum garnet laser on bracket bond strength: An in-vitro study

Introduction: The purpose of this study was to evaluate and compare the shear bond strength, the adhesive remnant scores and surface characteristics of the teeth prepared for bonding with erbium-doped yttrium aluminum garnet (Er:YAG) hard tissue laser, self-etching primer (SEP) and phosphoric acid etching. Materials and Methods: Seventy-eight human premolars, extracted for orthodontic purposes were randomly divided into three groups, enamel was irradiated with 37% phosphoric acid in Group-1, with SEP in Group-2 and with Er:YAG laser at 1.5-W in Group-3. After surface preparation standard edgewise stainless steel premolar brackets were bonded; one tooth in each group was not bonded and was examined under a scanning electron microscopic. The brackets were debonded 24 h later; shear bond strengths were measured, and adhesive remnant index scores were recorded. Results: Statistically significant differences were found between phosphoric acid etching, SEP, 1.5-W laser irradiation. Adhesive remnant scores were compared with the Chi-square test, and statistically significant differences were found between all groups. Conclusions: The mean shear bond strength obtained with 37% phosphoric acid etching, SEP and Er-YAG laser etching were clinically acceptable. SEP produces a more conservative etch pattern and more shear bond strength than phosphoric acid. More adhesive was left on the SEP treated enamel as compared to enamel treated with acid and laser etching.

Photoelastic analysis of stress generated by wires when conventional and self-ligating brackets are used: a pilot study.

OBJECTIVE: By means of a photoelastic model, this study analyzed the stress caused on conventional and self-ligating brackets with expanded arch wires. METHOD: Standard brackets were adhered to artificial teeth and a photoelastic model was prepared using the Interlandi 19/12 diagram as base. Successive activations were made with 0.014-in and 0.018-in rounded cross section Nickel-Titanium wires (NiTi) and 0.019 x 0.025-in rectangular stainless steel wires all of which made on 22/14 Interlandi diagram. The model was observed on a plane polariscope - in a dark field microscope configuration - and photographed at each exchange of wire. Then, they were replaced by self-ligating brackets and the process was repeated. Analysis was qualitative and observed stress location and pattern on both models analyzed. CONCLUSIONS: Results identified greater stress on the region of the apex of premolars in both analyzed models. Upon comparing the stress between models, a greater amount of stress was found in the model with conventional brackets in all of its wires. Therefore, the present pilot study revealed that alignment of wires in self-ligating brackets produced lower stress in periodontal tissues in expansive mechanics.

GALVANIC CORROSION AMONG DIFFERENT COMBINATION OF ORTHODONTIC ARCHWIRES AND STAINLESS STEEL BRACKETS

Introduction: The aim of this study was to assess the galvanic behavior of different bracket and archwire combinations that are commonly used in orthodontic treatments. Methods: Three types of orthodontic archwires with a diameter of 0.016×0.022 inch and 80 standard edgewise maxillary central incisor brackets were selected. Three groups consisted of different wire-bracket couples and one group was just brackets as a control group. Each group had five samples. Four brackets were then connected to each wire by elastic bands made from electrochemically neutral material. The samples were immersed into capped containers of Fusayama-Meyer artificial saliva. After six weeks, the released nickel ions were quantified via ion absorption technique. The mean and the standard deviation of all four groups were calculated and the data were compared together with Kruskal-Wallis non-parametric statistical test. Results: The highest concentration of released nickel ions was for bracket+ steel archwire and the least for the bracket without archwire. Conclusion: There were not significant differences among experimental groups, so it could be concluded that galvanic corrosion would not be a serious consideration through orthodontic treatment.

?Surgery First? and Low Level Laser Therapy to Reduce Treatment Time in Ortho-Surgical procedures

Aim: To show how the integration of two highly efficient developed techniques used to reduced orthodontic treatment time in a case that required orthognathic surgery to correct a class III Dento-Maxillo-Facial anomaly. Methods: A 21 years old class-III male patient, with prognathism, macrognathism and mandibular levognathism treated with the following treatment plan: surgical- orthodontic treatment with no extractions, using fixed standard prescription brackets with slot 0.022 × 0.028 inches, Surgery first for mandibular set-back and para-nasal grafts. Low Level Laser extra oral irradiation after surgery and intra oral up to the end of the orthodontic active phase. Retention with Esssix superior and inferior splints. Results: The class-III anomaly was treated in ten months using the “Surgery First” approach and low intensity laser therapy to potentiate the effect in the overall treatment. Conclusion: A class-III Dento-Maxillo-facial anomaly was corrected in a patient during a full treatment time of 10 months, combining the “Surgery First” approached with low level laser therapy to potentiate the effect that both techniques provide to accelerate the rate of tooth movement.

Distortion of Brackets by Conventional Debonding Technique

Introduction: Various debonding techniques have been suggested by several investigators which claim to remove brackets from the tooth with minimum distortion. The present study has been done to compare three conventional debonding techniques using debonding pliers. Objective: To know the best method of debonding the brackets from the tooth surface with minimal distortion. Materials and methods: The present study is done in vitro on extracted teeth. Thirty standard edgewise brackets with 0.022 × 0.028 were bonded on to the teeth. Three groups were made to compare three different techniques. Occlusal side 'A' and gingival side 'B' of the wings were marked. Optical profile projector with accuracy to 0.001 mm was used to measure the slot width and interwing distance accurately. An indigenous bracket debonding plier was used in three different ways for comparison. Results: Slot width: The minimum mean decrease in slot width was 0.027 in group 3. Interwing distance on ‘A’ side: Group 1 showed significantly higher difference in interwing distance on ‘A’ side (0.061) as compared to groups 2 and 3 (0.019). Interwing distance on ‘B’ side: The minimum mean decrease in interwing distance on ‘B’ side was 0.012 with group 3. Discussion: A number of studies have been done to describe the effects of conventional debonding techniques on the tooth surface. In most of the studies, different techniques were used with different bonding materials and different bracket system. This study has been evaluated in three ways: (i) Change in slot width: The slot width got affected minimally when the brackets were deboned by holding them gingivoocclusally with archwire into the slot and rotate it gingivoocclusally; (ii) change in interwing distance on occlusal side: Bracket debonded by holding it gingivoocclusally and rotating it gingivoocclusally with or without holding archwire did not show any difference; (iii) change in interwing distance on gingival side: Brackets debonded by holding it gingivoocclusally and rotating it gingivoocclusally with or without holding archwire did not show much difference. Conclusion: The brackets can be reused after recycling (provided they do not get distorted significantly). Among conventional debonding techniques (with bracket removing plier), the best method found was to debond bracket by holding it occlusogingivally with the archwire into the slot.

The effects of composite resin types and debonding pliers on the amount of adhesive remnants and enamel damages: a stereomicroscopic evaluation.

Background and aims. This in vitro study was designed to evaluate the effect of composite resin types and orthodontic debonding pliers on the amount of adhesive remnants and enamel damages using a novel method of measurement. Materials and methods. 120 extracted human premolars were randomly divided into four groups (n = 30). The standard edgewise metallic brackets were bonded to the teeth with light-cured composite resin “Transbond XT” in the first and second groups, and No-mix composite resin “Unite” in the third and fourth groups. Bracket debonding was carried out with Lift Off Debonding Instrument “LODI” (3M Unitek) in the first and third groups, and with Bracket Removing Pliers (Dentaurum) in the second and forth groups. yStereomicroscopic evaluation was performed by unbiased sterelogy. All teeth were evaluated for the amount of adhesive remnants and the number and length of enamel cracks. The obtained data on each step was analyzed by two-way ANOVA, chi-square, Wilcoxon, and Kruskal-Wallis. Results. Teeth in group 4 had the lowest adhesive remnants on the enamel surface (p < 0.01); and the highest increase in the number of enamel cracks (p < 0.01) among the groups. In addition, groups bonded with Unite showed the highest increase in the length of enamel cracks. Conclusion. Dentaurum debonding pliers with sheer–peel force, when used with the Unite adhesive (group 4), decreased the amount of adhesive remnants on the enamel surface while it increased enamel damages.

Nonsurgical orthodontic treatment for an adult with skeletal open bite, class III malocclusion and posterior crossbite: A case report

Class III malocclusion associated with skeletal anterior open bite pattern in adults can be a challenging orthodontic problem, especially for the nonsurgical treatment. Conventionally, several treatment alternatives are available such as tooth extraction, molar intrusion, and absolute anchorage system or orthognathic surgical correction. Although correction with surgery may be the most effective and stable way, many patients refused surgical treatment plan because of the costs and traumas it may bring. We reported a nonsurgical orthopedic treatment of 22-year-old male with severe skeletal anterior open bite, dental Class III malocclusion, posterior crossbite and a high mandibular plane angle. The patient refused surgery and extraction. So we formulated a treatment plan consisting of using rapid palatal expansion appliance to expand the maxilla, standard edgewise brackets to align the teeth, Class III elastics to correct the canines, premolars, and molars relationship, reverse curve of the nickel-titanium wire combined with anterior vertical elastics to intrude molars and correct open bite. In this case, without suffering of surgery, the posterior crossbite was ideally corrected, and ideal overjet and overbite relationships and functional occlusion were all achieved. The patient obtained satisfactory occlusal as well as functional and stable results.

Laser Etched vs Conventional Etched Enamel: Effect on Shear Bond Strength of Orthodontic Brackets

Aim: The purpose of this study was to assess the shear bond strength of the teeth prepared for bonding with different power outputs of Erbium, Chromium doped: Yttrium-ScandiumGallium-Garnet (Er,Cr:YSGG) laser etching and to compare different power outputs of laser etching with 37% phosphoric acid. Materials and methods: A total of 105 premolars, extracted for orthodontic purposes were randomly divided into five groups. Different methods were used in each group to prepare the tooth enamel for bonding. The methods are as follows: Etching for 15 seconds with 37% phosphoric acid; irradiation with 1.5 W/10 Hz Er,Cr:YSGG laser, 1.5 W/20 Hz, 2 W/10 Hz and 2 W/20 Hz Er,Cr:YSGG laser. After surface preparation standard edgewise stainless steel premolar brackets were bonded and was examined under scanning electron microscope. The brackets were debonded 24 hours later and shear bond strengths were measured. Results: Enamel etching with 37% phosphoric acid for 15 seconds provides a higher shearbond strength for orthodontic bonding but laser etching with 2 W/20 Hz produced a comparable level of shearbond strength to phosphoric acid etched group. While 1.5 W/20 Hz and 2 W/10 Hz produced clinically acceptable shear bond strength for orthodontic bonding and 1.5 W/10 Hz produced the least shearbond strength and not acceptable for orthodontic bonding. Statistical significance was found between the groups (p  0.01). Group 1 is the highest followed by group 5. Conclusion: Irradiation with 1.5 W/20 Hz and 2 W/10 Hz were irregular and superficial, in contrast to phosphoric acid. But etching with laser 2 W/20 Hz produced adequate bond strength and could be a viable alternative to other methods.

Comparison Between Laceback and Tie-back in Sliding Mechanics (An in vitro study)

Aims: The current study aims to investigate the rate of space closure, tipping and rotation of canine during its retraction by laceback and tieback using standard ceramic brackets along 2 types of arch- wires using typodont simulation system (Ormco). Materials and Methods: The standardization crite- ria were all typodont teeth situated in well aligned position, covered and immobilized by the acrylic bite except canine, laceback and tieback were used to slide the canine. Results: The present study showed that when slide the canine on 0.017x 0.025 inch archwire gave rise to significant decrease in the rate of space closure, degree of tipping and rotation as compared when sliding it on 0.020 inch archwire, also sliding the canine using laceback as a method of retraction gave rise to a significant de- crease in the rate of space closure, degree of tipping and rotation as compared with tieback. Conclu- sions: It was concluded that canine retraction using laceback retraction method along 0.017x0.025 inch archwire gave rise to a significant decrease in the rate of space closure, degree of tipping and rota- tion.

IMAGE-BASED 3D RECONSTRUCTION AND ANALYSIS FOR ORTHODONTIA

Abstract. Among the main tasks of orthodontia are analysis of teeth arches and treatment planning for providing correct position for every tooth. The treatment plan is based on measurement of teeth parameters and designing perfect teeth arch curve which teeth are to create after treatment. The most common technique for teeth moving uses standard brackets which put on teeth and a wire of given shape which is clamped by these brackets for producing necessary forces to every tooth for moving it in given direction. The disadvantages of standard bracket technique are low accuracy of tooth dimensions measurements and problems with applying standard approach for wide variety of complex orthodontic cases. The image-based technique for orthodontic planning, treatment and documenting aimed at overcoming these disadvantages is proposed. The proposed approach provides performing accurate measurements of teeth parameters needed for adequate planning, designing correct teeth position and monitoring treatment process. The developed technique applies photogrammetric means for teeth arch 3D model generation, brackets position determination and teeth shifting analysis.

A prospective randomized split-mouth study on pain experience during chairside archwire manipulation in self-ligating and conventional brackets

To investigate patient discomfort during archwire engagement and disengagement in patients treated with self-ligating and conventional brackets using a split-mouth design. Eighteen consecutive patients (15 female, 3 male; age: 22.2 ± 6.4 years) who requested treatment with fixed orthodontic appliances were randomly assigned for bonding with SmartClip self-ligating brackets on one side of the dentition and conventional standard edgewise brackets on the other. During the course of treatment, patients rated the discomfort experienced during every archwire engagement and disengagement using a numeric rating scale. Results were evaluated for round and rectangular nickel titanium and rectangular stainless steel, titanium molybdenum, and Elgiloy archwires. Patients also rated their overall experience retrospectively for both bracket systems. Regardless of archwire type, disengagement was rated as being significantly more painful on the SmartClip side (P = .027). For rigid, rectangular archwires, engagement and disengagement were rated as being significantly more painful on the SmartClip side (P = .031; P = .004). Retrospective ratings favored conventional brackets beyond ratings recorded during treatment. Engagement and disengagement of rigid rectangular archwires caused more pain with SmartClip self-ligating brackets than with conventional ones. Careful archwire manipulation and patience during full alignment are essential for limiting chairside pain. Low pain levels will help ensure treatment satisfaction and compliance.

Influence of anatomical barriers on maxillary incisor root resorption after orthodontic treatment with premolar extractions

INTRODUCTION: Apical root resorption is a frequent and occasionally critical problem in orthodontic patients undergoing induced tooth movement. One of the factors that might influence prognosis, especially in maxillary incisors, which most frequently present resorptions, are the so-called the anatomical barriers; that is, proximity of the buccal and palatal cortical bones to the maxillary incisor roots. OBJECTIVE: The purpose of this research was to investigate whether patients with excessive vertical growth really present a small distance between the alveolar cortical bones and the maxillary incisor roots, and whether there is a correlation between this distance and the root resorption index in comparison with patients presenting horizontal growth. METHODS: The sample comprised orthodontic records of 18 patients with extraction planning of first maxillary premolars and treatment by the standard and/or preadjusted edgewise brackets. Their initial and final periapical radiographs were evaluated to determine the amount of root resorption that occurred. RESULTS: On the palatal side, patients with excessive vertical growth (Group 2 - SN-GoGn > 43o) showed a narrower alveolar bone than the horizontal growth patients (Group 1 - SN-GoGn < 29o). However, the distance between the buccal cortical bone and the central incisor root apex showed no significant difference between Groups 1 and 2; CONCLUSIONS: It was concluded that there are no correlations between the proximity of buccal cortical bone, maxillary incisor roots and the root resorption index.

Frictional resistance of orthodontic wires tied with 3 types of elastomeric ligatures

The aims of this study were to determine and compare frictional resistance obtained by low-friction and conventional elastomeric ligatures in the presence of artificial saliva, and observe whether this variable changed after 21 days. Super Slick® low-friction elastomeric ligatures and conventional ligatures of the brands TP conventional® and Unitek® were placed on standard edgewise maxillary central incisor metal brackets, slot .022" × .028" tying rectangular orthodontic wires .018" × .025". Three experimental groups were arranged according to the type of ligature and a control group in which no wires were used. The friction values obtained between the bracket/wire/ligature set were measured using a Universal Test Machine at a speed of 20 mm/minute, at two experimental time intervals: T0 - immediately after specimen fabrication; and T1 - 21 days after fabrication and immersion in artificial saliva at 37 ºC. Conventional Unitek ligatures and the low-friction ligature (Super Slick) showed the lowest friction values at T0. After 21 days (T1), however, conventional Unitek ligatures presented the lowest value. All groups assessed from T0 to T1 showed a numerical reduction in friction values, suggesting that time, heat and humidity may cause elastic degradation, however this was not verified statistically (P > 0.05).