Influence of different methods of cleaning custom bases on the shear bond strength of indirectly bonded brackets.

OBJECTIVE: To determine the influence on shear bond strength and bond failure location of four cleaning methods for orthodontic bracket custom bases. DESIGN: In vitro laboratory study. MATERIAL AND METHODS: Eighty bovine teeth were divided at random into four groups. The bracket custom bases were cleaned with different methods: group 1 with methyl methacrylate monomer, group 2 with acetone, group 3 with 50 µm aluminium oxide particles and group 4 with detergent. The brackets were indirectly bonded onto the teeth with the Sondhi Rapid-Set self-curing adhesive. The maximum required shear bond strength to debond the brackets was recorded. The bond failure location was evaluated using the Adhesive Remnant Index (ARI). One-way analysis of variance (ANOVA) analysis (P<0·05) was used to detect significant differences in the bond strength. Kaplan-Meier survival plots and log-rank test were done to compare the survival distribution between the groups. The Kruskal-Wallis test (P<0·05) was used to evaluate the differences in the ARI scores. RESULTS: The mean bond strengths in groups 1, 2, 3 and 4 were 23·7±5·0, 25·3±5·1, 25·6±3·7 and 25·7±4·2 MPa, respectively. There were no significant statistically differences in either the bond strength or the ARI score between the groups. CONCLUSION: The four custom base-cleaning methods presented the same efficiencies on indirect bond of the brackets; thus, practitioners can choose the method that works best for them.

Photobiomodulation increases uprighting tooth movement and modulates IL-1ß expression during orthodontically bone remodeling.

This study investigated the effects of photobiomodulation (PBM) in acceleration of orthodontic movement of inferior molar uprighting movement. Thirty-four individuals, with indication of molar uprighting movement for oral rehabilitation, were randomly divided in two groups: verticalization + PBM (808 nm, 100 mW, 1 J per point, 10 points and 25 J/cm2 ) or verticalization + PBM simulation. Elastomeric chain ligatures were changed every 30 days for 3 months. FBM was performed immediately, 24 h, 72 h, 1 and 2 months after activation. The primary outcome was the amount of uprighting movement. Secondary outcomes were pain, amount of medication, OHIP-14 questionnaire, and cytokine IL-1ß. PBM group increase uprighting movement when compared to control after 3 months and modulate IL-1ß expression. For pain control, the amount of medication and OHIP-14 no difference were found. This study suggests that PBM accelerates tooth movement during molar uprighting, due to modulation of IL-1ß during bone remodeling.

Evaluation of the effects of photobiomodulation on orthodontic movement of molar verticalization with mini-implant: A randomized double-blind protocol study.

INTRODUCTION: Loss of a dental element can generate several repercussions in the stomatognathic system. According to the latest survey by the Ministry of Health, in 2010, Brazilian adults had, on average, 7 missing teeth. This loss may lead to movement of the adjacent teeth and the antagonist, which would make prosthetic rehabilitation harder to do. Anchoring systems, such as mini-implants, have been increasingly used as a treatment option because they act with heavy but controlled forces and without side effects. Recent studies have shown that photobiomodulation (PBM) can accelerate orthodontic movement in molar intrusion. The objective of this study will be to evaluate the effect of PBM on the acceleration of the orthodontic movement of molar verticalization and its effect on pain and inflammation of the periodontal tissues. PATIENT CONCERNS:: the concerns assessments will be done over the study using anamnesis interviews and specific questionnaire. DIAGNOSIS: verticalization will be evaluated by clinical and radiographic analysis. INTERVENTIONS: Thirty four healthy patients aged 30 to 60 years, who need to recover the prosthetic space for oral rehabilitation after loss of the posterior inferior dental elements and inclination of the adjacent element, will be randomly divided into 2 groups: G1 (control group) - verticalization by mini-implant + PBM simulation (placebo); G2 (experimental group) - verticalization by mini-implant + PBM. The movements will occur with the aid of mini-implants and elastomeric chains ligatures. The PBM will occur with diode laser application, 808 nm, 100 mW, receiving 1J per point, 10 seconds, 10 points (5 per buccal and 5 per lingual) and radiant exposure of 25 J/cm. The orthodontic forces of verticalization (corresponding to any exchange of elastomeric ligation) will be applied every 30 days and the PBM will be applied immediately, 3 and 7 days of each month, for a period of 3 months. The crevicular gingival fluid (CGF) will be collected on the 1st, 3rd, and 7th days after the first activation, and then on the 3rd day of the following 2 months. OUTCOMES: Interleukins IL1ß, IL-6, IL-8, IL-10, and TNF-α will be analyzed by ELISA. Panoramic radiography will be performed at baseline and 90 afterwards to ascertain the amount (in degrees) of verticalization. To evaluate the pain, the Visual Analog Scale (VAS) will be used in all the consultations, and to evaluate the quality of life, the Oral Health Impact Profile (OHIP-14) questionnaire will be applied. Analgesics will be given and the quantity of drugs will be counted. If the data are normal, they will be submitted to Student t test. The data will be presented as means ± SD and the value of p will be defined as <0.05. DISCUSSION: This protocol will determine the effectiveness of photobiomoduation regarding the orthodontic movement of molar verticalization. ETHICS AND DISSEMINATION: This protocol received approval from the Human Research Ethics Committee of Universidade Nove de Julho (certificate number: 3 533 219). The data will be published in a peer-reviewed periodical.

Efficacy of photodynamic therapy and periodontal treatment in patients with gingivitis and fixed orthodontic appliances: Protocol of randomized, controlled, double-blind study.

It is known that the presence of orthodontic brackets predisposes for a change in the biofilm, facilitating the development of gingivits. The sites are difficult to access with a toothbrush and periodontal curette, worsening inflammation, in addition, a gingival hyperplasia is associated with poor hygiene. The objective of this study is to evaluate the impact of photodinamyc therapy (PDT) as an adjuvant treatment, considering clinical immunoregulatory and microbiological parameters. This randomized, controlled, double-blind clinical study will include 34 patients, both genders, having used fixed appliance for more than 12 months, with gingivitis. Participants will be divided into two groups: G1 (n = 17)- Scaling and Root Planing + PDT placebo and G2 (n = 17)- Scaling and Root Planing + PDT. In G2 the following dosimetric parameters will be used: methylene blue 0.005%, λ= 660 nanometers (nm), 9 Joules (J) per site, irradiance= 3.5Watts (W)/ centimeters (cm), radiant exposure= 318J/cm. All participants will receive oral hygiene guidance prior the curetes scaling. The clinical periodontal data to be analyzed are plaque index, gingival index and probing depth. Crevicular fluid, from 4 pre-determined sites and saliva, will be collected and analysed for IL-6, IL-1ß, IL-8, TNF-α and IL-10 cytokines using ELISA (Enzyme immunoabsorption assay) method. Total Bacteria count will also be performed, by qPCR and Universal16SrRNA gene. All analysis will be realized using in the baseline (T0), 7 (T1) and 21 (T2) days after treatment. Oral health-related quality of life will be assessed using the OHIP-14 questionnaire at times T0 and T2. If sample distribution is normal, the Student T-test will be applied if it is not normal, the Mann-Whitney test will be used. The data will be presented in terms of ±â€ŠPD and The significance level will be set at p < 0.05. Our results may improve quality of life and add data to establish a therapeutic alternative for gingivitis during the orthodontic treatment. Registration: clinicaltrials.gov NCT04037709. https://clinicaltrials.gov/ct2/show/NCT04037709 - Registered in July 2019.

Microflora associated with successful and failed orthodontic mini-implants.

OBJECTIVES: Mini-implants are used for orthodontic bone anchorage. The reasons for a potential instability or loss of the mini-implants during treatment are multiple. Among other factors, colonization of implants with pathogenic bacteria is discussed. Therefore, the microflora associated with successful and failed mini-implants has been screened. MATERIAL AND METHODS: A total of 76 mini-implants collected from 25 patients were observed during regular orthodontic treatment. Bacterial samples of eight failed and - exemplarily - four successful (control) cases were subjected to a universal Bacteria-directed real-time quantitative polymerase chain reaction for quantification in combination with a microarray-based identification of 20 selected species. RESULTS: The failure rate in the present investigation was 10.5%. The bacterial analysis did not reveal any major difference in the total amount or species composition between control and failed mini-implants. However, Actinomyces viscosus was found in four (100%) and Campylobacter gracilis in three (75%) stable controls, whereas both species were rarely found (12.5%) in failed implants. CONCLUSIONS: In the present study, the peri-implant sulcus surrounding failed orthodontic mini-implants did not show a specific aggressive bacterial flora.

Low-level laser therapy for pain caused by placement of the first orthodontic archwire: a randomized clinical trial.

INTRODUCTION: The purpose of this study was to clinically evaluate the effect of low-level laser therapy (LLLT) as a method of reducing pain reported by patients after placement of their first orthodontic archwires. METHODS: The sample comprised 60 orthodontic patients (ages, 12-18 years; mean, 15.9 years). All patients had fixed orthodontic appliances placed in 1 dental arch (maxillary or mandibular), received the first archwire, and were then randomly assigned to the experimental (laser), placebo, or control group. This was a double-blind study. LLLT was started in the experimental group immediately after placement of the first archwire. Each tooth received a dose of 2.5 J per square centimeter on each side (buccal and lingual). The placebo group had the laser probe positioned into the mouth at the same areas overlying the dental root and could hear a sound every 10 seconds. The control group had no laser intervention. All patients received a survey to be filled out at home describing their pain during the next 7 days. RESULTS: The patients in the LLLT group had lower mean scores for oral pain and intensity of pain on the most painful day. Also, their pain ended sooner. LLLT did not affect the start of pain perception or alter the most painful day. There was no significant difference in pain symptomatology in the maxillary or mandibular arches in an evaluated parameter. CONCLUSIONS: Based on these findings, we concluded that LLLT efficiently controls pain caused by the first archwire.

Ceramic brackets and low friction : A possible synergy in patients requiring multiple MRI scanning.

AIM: To investigate any advantages of low friction biomechanics in orthodontic patients with fixed appliances without producing metal artifacts during magnetic resonance imaging (MRI). MATERIALS AND METHODS: Frictional resistance generated by bracket-wire-ligature systems was analyzed via an experimental model that reproduced upper canine misalignment. Each sample was tested 10 consecutive times in a dry state; a total of 160 tests were carried out. We documented the frictional forces generated by a 0.012- and 0.014-inch superelastic nickel-titanium wire (SENT) with ceramic self-ligating brackets (SLB) with metal insert and ceramic monocrystalline brackets with nonconventional elastic ligatures (NCEL) in conjunction with various degrees of canine misalignment (1.5, 3.0, 4.5, and 6.0 mm). Comparisons between the frictional forces released by the two different bracket-wire-ligature systems were made by conducting 3-way analysis of variance (ANOVA) with Tukey HSD pairwise test (P < 0.005). RESULTS: We observed no clinically relevant difference between the frictional forces released by ceramic SLB and ceramic brackets in conjunction with a 0.012- and 0.014-inch SENT. Statistically significant differences were apparent with a 0.012-inch SENT at 4.5 and 6.0 mm of canine misalignment, where the SLB revealed higher frictional forces. CONCLUSIONS: Ceramic brackets with NCEL revealed frictional forces similar to those generated in conjunction with ceramic SLB, thereby helping to avoid metal artifacts in case of expected necessary MRI during orthodontic treatment with fixed appliances.

Frictional resistance in monocrystalline ceramic brackets with conventional and nonconventional elastomeric ligatures.

BACKGROUND: The objective of this study was to compare the frictional forces generated by three types of monocrystalline ceramic brackets coupled with conventional elastomeric ligatures (CEL) and nonconventional elastomeric ligatures (NCEL) during the alignment of apically displaced teeth at the maxillary arch. METHODS: All tests (a total of 480 tests) were carried out in a dry state on a universal testing machine with a testing model consisting of three 0.022-in. monocrystalline ceramic preadjusted brackets (from the maxillary right second premolar through the right central incisor). The canine bracket was bonded to a sliding bar that allowed for different vertical positions. The frictional forces generated by a 0.012- and 0.014-in. superelastic nickel titanium wire (SENT) with conventional and nonconventional ligatures at various amounts of canine misalignment (1.5, 3.0, 4.5, and 6.0 mm) were recorded. Comparisons between the different types of bracket-wire-ligature systems were carried out by means of analysis of variance on ranks with Tukey's post hoc test (P<0.05). RESULTS: No significant differences were assessed among the three types of monocrystalline brackets with NCEL when coupled with 0.012-in. SENT. Radiance brackets with NCEL coupled with 0.014-in. SENT showed significantly greater frictional force than Inspire Ice brackets and Pure brackets with NCEL. A significantly greater amount of frictional force was generated with CEL when compared with NCEL for all the tested variables, with the exception of the Pure brackets with 0.012-in. SENT at 1.5 and 3.0 mm of canine misalignment where similar frictional forces were found. CONCLUSIONS: Nonconventional elastomeric ligatures are able to reduce friction in monocrystalline ceramic brackets.

A comparative clinical study of the failure rate of orthodontic brackets bonded with two adhesive systems: conventional and self-etching primer (SEP).

OBJECTIVE: This study compared the clinical performance of orthodontic brackets bonded with Transbond adhesive paste after two primer systems: a two-stage conventional system (acid etching + Transbond XT adhesive primer) and a single-stage self-etching primer (SEP) (Transbond Plus). METHODS: The sample comprised 480 metal brackets bonded to the teeth of 24 consecutive patients treated for 36 to 48 months. A split-mouth design was used for bonding, and both systems were used in each patient. Bracket failure rates for each system were analyzed; and failure causes as reported by the patients and the quadrant of teeth for which brackets failed were recorded. RESULTS: The conventional system group had a failure rate of 5.41%, whereas the rate for SEP was 4.58%. In this group, there were 5 failures (38.4%) in the right maxillary quadrant, 2 (15.4%) in the left maxillary quadrant, 4 (30.8%) in the right mandibular quadrant, and 2 (15.4%) in the left mandibular quadrant. In the SEP group, there were 4 (36.4%) failures in the right maxillary quadrant, 1 (9%) in the left maxillary quadrant, 3 (27.3%) in the right mandibular quadrant, and 3 (27.3%) in the left mandibular quadrant. Results of descriptive statistical analysis and odds ratio did not show any significant differences between rates (p = 0.67). CONCLUSIONS: The clinical efficiency of SEP was similar to that of the conventional system.

Applicability of Moyers analysis in mixed dentition: A systematic review.

INTRODUCTION: Moyers analysis is widely used for analyzing mixed dentition, however, the accuracy of its theoretical probability tables has been recently questioned. Taking into consideration the fact the mixed dentition analysis is of paramount importance to precisely determine the space needed for alignment of canines and premolars, this research aimed at objectively assessing in the literature such an important step for orthodontic diagnosis. METHODS: A computerized search involving articles published on PubMed and Lilacs between 1990 and September, 2011 was conducted in accordance with the method described in the Cochrane 5.1.0 handbook. RESULTS: The research resulted in a sample composed of 629 articles. The inclusion criteria were: Articles using the Moyers analysis with a sample greater or equal to 40 patients. Conversely, the exclusion criteria were: Dental casts of patients with syndromes or oral cleft, researches conducted with a literature review, only, or clinical case reports and researches conducted before 1990. For this systematic review, 19 articles were selected. CONCLUSIONS: Based on the literature available, we can conclude that Moyers mixed dentition analysis must be carefully used, since the majority of the articles analyzed showed that the probability of 75% was not as accurate as expected, leading to the need of adapting the probability levels depending on the study population.

Effects of active and passive lacebacks on antero-posterior position of maxillary first molars and central incisors.

The purpose of this study was to compare the effects of active and passive lacebacks on antero-posterior position of maxillary first molars and central incisors during leveling phase. Twenty-three subjects with Class I and Class II malocclusion were treated with first premolars extraction using preadjusted appliances (MBT 0.022-inch brackets). The leveling phase was performed with stainless steel archwires only. The sample was divided into 2 groups: 14 subjects received active lacebacks (Group 1) and 9 subjects received passive lacebacks (Group 2). Lacebacks were made from 0.008-inch ligature wire. Lateral cephalometric radiographs were taken pre- and post-leveling phase. Student's t-test was applied to determine the differences between pre- and post-leveling mean values and to determine the mean differences between groups. In Group I, the first molars showed a significant mesial movement, whereas no change was observed in Group 2. In both groups, maxillary central incisor crowns moved to lingual side. In conclusion, active laceback produced anchorage loss of maxillary first molars whereas passive laceback did not affect the position of these teeth. Active and passive lacebacks were effective in preventing central incisor proclination.

Periodontopathogens around the surface of mini-implants removed from orthodontic patients.

OBJECTIVE: To verify if mini-implant mobility is affected by the presence of periodontopathogens, frequently associated with peri-implantitis. MATERIALS AND METHODS: The surfaces of 31 mini-implants used for skeletal anchorage in orthodontic patients were evaluated. Polymerase chain reaction was used for identification of the presence of DNA from three different periodontopathogens ( P. intermedia [ Pi ], A. actinomycetemcomitans [ Aa ], and P. gingivalis [ Pg ]) in 16 mini-implants without mobility (control group) and 15 mini-implants with mobility (experimental group). RESULTS: The results showed that Pi was present in 100% of the samples, from both groups: Aa was found in 31.3% of the control group and in 13.3% of the experimental group. Pg was detected in 37.4% of the control group and in 33.3% of the experimental group. The Fisher exact test and the odds ratio (OR) values for Aa and Pg (OR  =  0.34; 95% confidence interval [CI]: 0.05-2.10 and OR  =  0.61; 95% CI: 0.13-2.79, respectively) showed no significant association (P > .05) between the periodontopathogens studied and the mobility of the mini-implants. CONCLUSIONS: It can be concluded that the presence of Aa , Pi , and Pg around mini-implants is not associated with mobility.

An in vitro comparison of nickel and chromium release from brackets.

This study aimed at comparing amounts of nickel (Ni) and chromium (Cr) released from brackets from different manufacturers in simulated oral environments. 280 brackets were equally divided into 7 groups according to manufacturer. 6 groups of brackets were stainless steel, and 1 group of brackets was made of a cobalt-chromium alloy with low Ni content (0.5%). International standard ISO 10271/2001 was applied to provide test methods. Each bracket was immersed in 0.5 ml of synthetic saliva (SS) or artificial plaque fluid (PF) over a period of 28 days at 37 degrees Celsius. Solutions were replaced every 7 days, and were analyzed by spectrometry. The Kruskal-Wallis test was applied. Amounts of Ni release in SS (microg L(-1) per week) varied between groups from 'bellow detection limits' to 694, and from 49 to 5,948.5 in PF. The group of brackets made of cobalt-chromium alloy, with the least nickel content, did not release the least amounts of Ni. Amounts of Cr detected in SS and in PF (microg L(-1) per week) were from 1 to 10.4 and from 50.5 to 8,225, respectively. It was therefore concluded that brackets from different manufacturers present different corrosion behavior. Further studies are necessary to determine clinical implications of the findings.

A comparative clinical study of the failure rate of orthodontic brackets bonded with two adhesive systems: conventional and self-etching primer (SEP)

OBJECTIVE: This study compared the clinical performance of orthodontic brackets bonded with Transbond adhesive paste after two priming systems: a two-stage conventional system (acid etching + Transbond XT adhesive primer) and a singlestage self-etching primer (SEP) (Transbond Plus). METHODS: The sample comprised 480 metal brackets bonded to the teeth of 24 consecutive patients treated for 36 to 48 months. A split-mouth design was used for bonding, and both systems were used in each patient. Bracket failure rates for each system were analyzed; and failure causes as reported by the patients and the quadrant of teeth for which brackets failed were recorded. RESULTS: The conventional system group had a failure rate of 5.41%, whereas the rate for SEP was 4.58%. In this group, there were 5 failures (38.4%) in the right maxillary quadrant, 2 (15.4%) in the left maxillary quadrant, 4 (30.8%) in the right mandibular quadrant, and 2 (15.4%) in the left mandibular quadrant. In the SEP group, there were 4 (36.4%) failures in the right maxillary quadrant, 1 (9%) in the left maxillary quadrant, 3 (27.3%) in the right mandibular quadrant, and 3 (27.3%) in the left mandibular quadrant. Results of descriptive statistical analysis and odds ratio did not show any significant differences between rates (p = 0.67). CONCLUSION: The clinical efficiency of SEP was similar to that of the conventional system.

OBJETIVO: o objetivo do presente estudo foi comparar o desempenho clínico da colagem de braquetes ortodônticos com resina Transbond (3M Unitek) associada a dois sistemas adesivos: convencional em duas etapas (ataque ácido + Transbond XT adhesive Primer) e Self-Etching Primer (SEP), em etapa única (Transbond Plus). MÉTODOS: a amostra foi constituída de 480 braquetes metálicos (Victory, 3M Unitek), colados em 24 pacientes, que foram tratados durante um período de 36 a 48 meses. A colagem foi feita por meio do sistema split-mouth, utilizando os dois sistemas de colagem em cada paciente. Foi analisada a taxa de queda dos braquetes para cada sistema de colagem, descrita a causa da queda conforme relato do paciente e a posição dos dentes nas arcadas. RESULTADOS: o sistema adesivo convencional apresentou taxa de queda de 5,41%, enquanto a do SEP foi de 4,58%. O sistema convencional apresentou 5 quedas (38,4%) no quadrante superior direito, 2 (15,4%) no quadrante superior esquerdo, 4 (30,8%) no quadrante inferior direito e 2 (15,4%) no quadrante inferior esquerdo. O SEP apresentou 4 quedas (36,4%) no quadrante superior direito, 1 (9%) no quadrante superior esquerdo, 3 (27,3%) no quadrante inferior direito e 3 (27,3%) no quadrante inferior esquerdo. Por meio da análise estatística descritiva e do teste Odds Ratio, constatou-se que não houve diferença significativa entre essas taxas (p = 0,67). CONCLUSÃO: com base nesses resultados, pode-se concluir que o sistema adesivo SEP apresentou eficácia clínica semelhante à do sistema adesivo convencional.

Applicability of Moyers analysis in mixed dentition: A systematic review

INTRODUCTION: Moyers analysis is widely used for analyzing mixed dentition, however, the accuracy of its theoretical probability tables has been recently questioned. Taking into consideration the fact the mixed dentition analysis is of paramount importance to precisely determine the space needed for alignment of canines and premolars, this research aimed at objectively assessing in the literature such an important step for orthodontic diagnosis. METHODS: A computerized search involving articles published on PubMed and Lilacs between 1990 and September, 2011 was conducted in accordance with the method described in the Cochrane 5.1.0 handbook. RESULTS: The research resulted in a sample composed of 629 articles. The inclusion criteria were: Articles using the Moyers analysis with a sample greater or equal to 40 patients. Conversely, the exclusion criteria were: Dental casts of patients with syndromes or oral cleft, researches conducted with a literature review, only, or clinical case reports and researches conducted before 1990. For this systematic review, 19 articles were selected. CONCLUSION: Based on the literature available, we can conclude that the Moyers mixed dentition analysis must be carefully used, since the majority of the articles analyzed showed that the probability of 75% was not as accurate as expected, leading to the need of adapting the probability levels depending on the study population.

INTRODUÇÃO: a análise de Moyers é amplamente adotada para a análise da dentição mista, porém, recentemente, a acurácia das suas tabelas de probabilidade está sendo questionada. OBJETIVO: sabendo-se da importância da análise da dentição mista, na determinação mais precisa possível do espaço necessário para o alinhamento de caninos e pré-molares, o objetivo dessa pesquisa foi avaliar de forma objetiva na literatura este importante passo do diagnóstico ortodôntico. MÉTODOS: foi realizado um levantamento computadorizado de artigos publicados entre os anos de 1990 a setembro de 2011 nas bases de dados PubMed e LILACS, segundo o método descrito no manual Cochrane 5.1.0. RESULTADOS: a estratégia de busca resultou em 629 artigos. Para ser selecionado, o artigo deveria utilizar a análise de Moyers e ter uma amostra superior ou igual a 40 pacientes. Os critérios de exclusão foram: modelos de gesso de pacientes com algum tipo de síndrome ou fissurados, pesquisas cuja proposta era apenas uma revisão da literatura ou apenas relato de um caso clínico, e pesquisas anteriores ao ano de 1990. Para essa revisão sistemática, 19 artigos foram selecionados. CONCLUSÕES: com base na literatura disponível, pode-se concluir que a utilização da análise de Moyers na análise da dentição mista deve ser utilizada de maneira cautelosa, pois, na maioria dos artigos avaliados, 75% não apresentou a acurácia desejada, necessitando de adaptações nos níveis de probabilidade, dependendo da população em estudo.

An in vitro comparison of the force decay generated by different commercially available elastomeric chains and NiTi closed coil springs.

This in vitro study was designed to compare the forces generated by commercially available elastomeric chains and NiTi closed coil springs, and to determine their force decay pattern. Forty elastomeric chains and forty NiTi closed coil springs were divided into 4 groups according to the following manufacturers: (1) Morelli, (2) Abzil, (3) TP Orthodontics and (4) American Orthodontics. The specimens were extended to twice their original length and stored in artificial saliva at 37 degrees C. Initial force was measured by means of an Instron universal testing machine and then at 1, 4, 7, 14, 21, and 28 days. The results revealed that the elastomeric chains delivered a mean initial force of 347 g for Morelli, 351 g for American Orthodontics, 402 g for Abzil, and 404 g for TP Orthodontics. The NiTi closed coil springs generated a mean initial force of 196 g for American Orthodontics, 208 g for TP Orthodontics, 216 g for Abzil, and 223 g for Morelli. The mean percentage of force decay observed after 28 days for the elastomeric chains was 37.4% for TP Orthodontics(R), 48.1% for American Orthodontics, 65.4% for Morelli, and 71.6% for Abzil. After 28 days, the NiTi closed coil springs presented a mean percentage of force decay of 22.6% for American Orthodontics, 29.8% for Abzil, 30.6% for Morelli, and 45.8% for TP Orthodontics. At the end of the study, significant differences were observed between the elastomeric chains and the NiTi closed coil springs. The results indicated that the studied NiTi closed coil springs are more adequate for dental movement than the elastomeric chains.

Effects of active and passive lacebacks on antero-posterior position of maxillary first molars and central incisors

The purpose of this study was to compare the effects of active and passive lacebacks on antero-posterior position of maxillary first molars and central incisors during leveling phase. Twenty-three subjects with Class I and Class II malocclusion were treated with first premolars extraction using preadjusted appliances (MBT 0.022-inch brackets). The leveling phase was performed with stainless steel archwires only. The sample was divided into 2 groups: 14 subjects received active lacebacks (Group 1) and 9 subjects received passive lacebacks (Group 2). Lacebacks were made from 0.008-inch ligature wire. Lateral cephalometric radiographs were taken pre- and post-leveling phase. Student's t-test was applied to determine the differences between pre- and post-leveling mean values and to determine the mean differences between groups. In Group I, the first molars showed a significant mesial movement, whereas no change was observed in Group 2. In both groups, maxillary central incisor crowns moved to lingual side. In conclusion, active laceback produced anchorage loss of maxillary first molars whereas passive laceback did not affect the position of these teeth. Active and passive lacebacks were effective in preventing central incisor proclination.

O objetivo deste estudo foi comparar os efeitos dos lacebacks ativos e passivos na posição ântero-posterior dos primeiros molares e dos incisivos centrais superiores durante a fase de nivelamento. Vinte e três indivíduos com má oclusão de Classes I e II foram tratados com extrações dos primeiros pré-molares utilizando aparelhos fixos pré-ajustados (bráquetes MBT 0,022"). A fase de nivelamento foi realizada somente com arcos de aço inoxidável. A amostra foi dividida em 2 grupos: 14 pacientes receberam lacebacks ativos (Grupo 1) e 9 pacientes receberam lacebacks passivos (Grupo 2). Os lacebacks foram feitos com fio de ligadura de 0,008" (0,20 mm). Telerradiografias laterais foram realizadas antes e após a fase de nivelamento. O teste t de Student foi aplicado para determinar as diferenças entre as médias de deslocamento entre os períodos pré e pós-nivelamento e para determinar as diferenças entre os grupos. No Grupo 1, o primeiro molar mostrou uma movimentação mesial significativa enquanto nenhuma alteração foi observada no Grupo 2. Em ambos os grupos, os incisivos centrais superiores foram lingualizados. Em conclusão, os lacebacks ativos produziram perda de ancoragem nos primeiros molares superiores enquanto que os lacebacks passivos não afetaram a posição destes dentes. Lacebacks ativos e passivos foram efetivos para prevenir a vestibularização dos incisivos centrais superiores.

Avaliação in vitro da resistência à flexão de um protótipo de mini-implante desenvolvido para ancoragem do aparelho de Herbst / In vitro flexural strength evaluation of a mini-implant prototype designed for Herbst appliance anchorage

OBJETIVO: o propósito do presente estudo é avaliar o limite de resistência à flexão de um protótipo de mini-implante desenvolvido para ancoragem do aparelho de Herbst. MÉTODOS: após a realização de um cálculo do tamanho da amostra, quatro corpos de prova contendo os protótipos de mini-implantes foram submetidos a uma força de flexão por engastamento simples, utilizando-se uma máquina universal de ensaios mecânicos, sendo calculado o limite de resistência à força de flexão. RESULTADOS: após os ensaios mecânicos, os novos mini-implantes apresentaram o limite de resistência à força de flexão de 98,2kgf, que foi o menor valor encontrado. CONCLUSÃO: os protótipos de mini-implantes desenvolvidos para ancoragem do aparelho de Herbst foram capazes de suportar forças de flexão maiores do que as forças de mordida descritas na literatura.

AIM: The purpose of this study was to evaluate the limit of flexural strength of a mini-implant prototype designed for Herbst appliance anchorage. METHODS: After sample size calculation, four specimens with the new mini-implant were submitted to a single cantilever flexure test using a universal testing machine. The limit of flexural force strength was calculated. RESULTS: The mini-implant prototype showed a limit of flexural force strength of 98.2 kgf (982 N), that was the lowest value found. CONCLUSION: The mini-implant prototype designed for Herbst appliance anchorage can withstand flexural forces higher than the maximum human bite forces reported in the literature.