Effect of different palatal expanders with miniscrews in surgically assisted rapid palatal expansion: A non-linear finite element analysis.

INTRODUCTION: Surgically assisted rapid palatal expansion (SARPE) has been the treatment of choice in subjects presenting skeletally mature sutures. OBJECTIVE: The purpose of this study was to analyze stress distribution and displacement of the craniofacial and dentoalveolar structures resulting from three types of palatal expanders with surgical assistance using a non-linear finite element analysis. MATERIAL AND METHODS: Three different palatal expanders were designed: Model-I (tooth-bone-borne type containing four miniscrews), Model-II (tooth-bone-borne type containing two miniscrews), and Model-III (bone-borne type containing four miniscrews). A Le Fort I osteotomy was performed, and a total of 5.0 mm palatal expansion was simulated. Nonlinear analysis (three theory) method (geometric nonlinear theory, nonlinear contact theory, and nonlinear material methods) was used to evaluate stress and displacement of several craniofacial and dentoalveolar structures. RESULTS: Regardless of the maxillary expander device type, surgically assisted rapid palatal expansion produces greater anterior maxillary expansion than posterior (ANS ranged from 2.675 mm to 3.444 mm, and PNS ranged from 0.522 mm to 1.721 mm); Model-I showed more parallel midpalatal suture opening pattern - PNS/ANS equal to 54%. In regards to ANS, Model-II (1.159 mm) and Model-III (1.000 mm) presented larger downward displacement than Model-I (0.343 mm). PNS displaced anteriorly more than ANS for all devices; Model-III presented the largest amount of forward displacement for PNS (1.147 mm) and ANS (1.064 mm). All three type of expanders showed similar dental displacement, and minimal craniofacial sutures separation. As expected, different maxillary expander designs produce different primary areas and levels of stresses (the bone-borne expander presented minimal stress at the teeth and the tooth-bone-borne expander with two miniscrews presented the highest). CONCLUSIONS: Based on this finite element method/finite element analysis, the results showed that different maxillary expander designs produce different primary areas and levels of stresses, minimal displacement of the craniofacial sutures, and different skeletal V-shape expansion.

Effect of different palatal expanders with miniscrews in surgically assisted rapid palatal expansion: A non-linear finite element analysis

ABSTRACT Introduction: Surgically assisted rapid palatal expansion (SARPE) has been the treatment of choice in subjects presenting skeletally mature sutures. Objective: The purpose of this study was to analyze stress distribution and displacement of the craniofacial and dentoalveolar structures resulting from three types of palatal expanders with surgical assistance using a non-linear finite element analysis. Material and Methods: Three different palatal expanders were designed: Model-I (tooth-bone-borne type containing four miniscrews), Model-II (tooth-bone-borne type containing two miniscrews), and Model-III (bone-borne type containing four miniscrews). A Le Fort I osteotomy was performed, and a total of 5.0 mm palatal expansion was simulated. Nonlinear analysis (three theory) method (geometric nonlinear theory, nonlinear contact theory, and nonlinear material methods) was used to evaluate stress and displacement of several craniofacial and dentoalveolar structures. Results: Regardless of the maxillary expander device type, surgically assisted rapid palatal expansion produces greater anterior maxillary expansion than posterior (ANS ranged from 2.675 mm to 3.444 mm, and PNS ranged from 0.522 mm to 1.721 mm); Model-I showed more parallel midpalatal suture opening pattern - PNS/ANS equal to 54%. In regards to ANS, Model-II (1.159 mm) and Model-III (1.000 mm) presented larger downward displacement than Model-I (0.343 mm). PNS displaced anteriorly more than ANS for all devices; Model-III presented the largest amount of forward displacement for PNS (1.147 mm) and ANS (1.064 mm). All three type of expanders showed similar dental displacement, and minimal craniofacial sutures separation. As expected, different maxillary expander designs produce different primary areas and levels of stresses (the bone-borne expander presented minimal stress at the teeth and the tooth-bone-borne expander with two miniscrews presented the highest). Conclusions: Based on this finite element method/finite element analysis, the results showed that different maxillary expander designs produce different primary areas and levels of stresses, minimal displacement of the craniofacial sutures, and different skeletal V-shape expansion.

RESUMO Introdução: A expansão rápida da maxila assistida cirurgicamente (ERMAC) tem sido o tratamento de escolha em indivíduos que apresentam suturas esqueleticamente maduras. Objetivo: O objetivo deste estudo foi avaliar, utilizando uma análise não linear com elementos finitos, a distribuição de tensões e os deslocamentos das estruturas craniofaciais e dentoalveolares gerados por três tipos de expansores palatinos usados na ERMAC. Material e Métodos: Três tipos de expansores palatinos foram projetados: Modelo I (dento-osseossuportado com quatro mini-implantes), Modelo II (dento-osseossuportado com dois mini-implantes) e Modelo III (osseossuportado com quatro mini-implantes). Uma osteotomia Le Fort I foi realizada e foi simulada uma expansão palatina total de 5,0 mm. Um método de análise não linear (três teorias - teoria da não-linearidade geométrica, teoria do contato não linear e métodos para materiais não lineares) foi utilizado para avaliar a tensão e o deslocamento de diversas estruturas craniofaciais e dentoalveolares. Resultados: Independentemente do tipo de aparelho expansor palatino, a ERMAC produziu maior expansão anterior da maxila do que posterior (ENA variou de 2,675 mm a 3,444 mm e ENP variou de 0,522 mm a 1,721 mm); o Modelo I apresentou padrão de abertura mais paralela da sutura palatina mediana, com ENP/ENA igual a 54%. Com relação à ENA, o Modelo II (1,159 mm) e o Modelo III (1,000 mm) apresentaram maior deslocamento para baixo do que o Modelo I (0,343 mm). A ENP deslocou-se mais para anterior do que a ENA com todos os aparelhos; o Modelo III apresentou o maior deslocamento para anterior da ENP (1,147 mm) e da ENA (1,064 mm). Os três tipos de expansores apresentaram deslocamento dentário semelhante e separação mínima das suturas craniofaciais. Como esperado, diferentes designs de expansores palatinos produzem diferentes áreas primárias e níveis de tensões (o expansor osseossuportado apresentou tensão mínima nos dentes, e o expansor dento-osseossuportado com dois mini-implantes apresentou o maior). Conclusões: Com base nesse estudo de elementos finitos, os resultados mostraram que diferentes designs de expansores palatinos produzem diferentes áreas primárias e níveis de tensão, com deslocamento mínimo das suturas craniofaciais e diferentes expansões esqueléticas em forma de V.

Comparisons of soft tissue changes after Herbst appliance treatment in three different growth phases.

BACKGROUND: This study aimed to compare the soft tissue effects of Herbst appliance in Class II malocclusion patients treated in three different craniofacial growth phases: prepubertal (PRE), circumpubertal (CIR), and postpubertal (POS). METHODS: In total, 95 patients with Class II Division 1 malocclusion previously treated with a Herbst appliance were analyzed. Through the cervical vertebral maturation stages method, patients were allocated into three groups depending on the growth craniofacial phase at the beginning of treatment: PRE, CIR, and POS. Seventeen cephalometric measures were evaluated from each lateral radiograph before and after Herbst therapy using the Radiocef 2 software (Radio Memory, Belo Horizonte). Intragroup and intergroup treatment changes were compared statistically using a paired t test and MANOVA test, respectively. RESULTS: Soft tissue thickness changes were related only to mandible; all three mandibular measurements (L1_LL, B_B', and Pog_Pog') showed thickening for the PRE group ranging from 0.92 mm (Pog_Pog') to 2.02 mm (B_B'), and only lower lip thickened overtime for the POS group (L1_LL = 0.99 mm). Soft and hard tissue pogonion displaced anteriorly, but only the soft tissue showed differences among groups; PRE group presented more anterior displacement than POS group (3.61 mm and 1.39 mm, respectively). Hard and soft tissue facial convexity decreased more in the PRE and CIR groups than in the POS group. Mentolabial sulcus depth reduced more in the PRE (1.07 mm) and CIR (1.29 mm) groups than in the POS (0.55 mm) group. Horizontal movement of the skeletal and soft pogonion presented a moderate-high positive correlation (r = 0.783), and hard and soft facial convexity showed a moderate-low positive correlation (r = 0.403). CONCLUSIONS: Herbst appliance therapy produces soft tissue improvements in the three phases of craniofacial growth, being greater in patients in the PRE and CIR phases.

Evaluation of maxillary canine and molar movement during the first phase of extraction space closure: a multilevel analysis.

OBJECTIVE: This study was designed to analyze and compare the cusp and apex movements of the maxillary canines and first molars during canine retraction in the first step of extraction space closure, and to evaluate if these teeth follow a curvilinear (acceleration and/or deceleration) movement rate. MATERIAL AND METHODS: Twenty-five patients (23.3 ± 5.1 years of age) were enrolled. The retraction of the maxillary canines was accomplished using nickel-titanium closed coil springs (100gf) on 0.020-in stainless steel archwire. Oblique cephalograms were traced and superimposed on the anatomic best fit of the maxilla (before the retraction [T0], and after one month [T1], three [T3], five [T5] and seven [T7] months). Statistics was based in a normally distributed data. Multilevel procedures were used to derive polynomials for each of the measurements. Student's t-test and one-way repeated measures ANOVA were conducted. The level of significance of 5% was adopted. RESULTS: Canine cusps and apexes did not follow a quadratic curve regarding horizontal movement (neither accelerate nor decelerate). Canine and molar cusps showed more horizontal movement than apexes (4.80 mm vs. 2.78 mm, and 2.64 mm vs. 2.17 mm, respectively). CONCLUSIONS: Canine did not accelerate or decelerate overtime horizontally; the cusps and apexes of the canines and molars showed more horizontal movement and larger rate at the beginning of canine retraction, followed by significantly smaller and constant movement rate after the first month.

Evaluation of maxillary canine and molar movement during the first phase of extraction space closure: a multilevel analysis

ABSTRACT Objective: This study was designed to analyze and compare the cusp and apex movements of the maxillary canines and first molars during canine retraction in the first step of extraction space closure, and to evaluate if these teeth follow a curvilinear (acceleration and/or deceleration) movement rate. Material and Methods: Twenty-five patients (23.3 ± 5.1 years of age) were enrolled. The retraction of the maxillary canines was accomplished using nickel-titanium closed coil springs (100gf) on 0.020-in stainless steel archwire. Oblique cephalograms were traced and superimposed on the anatomic best fit of the maxilla (before the retraction [T0], and after one month [T1], three [T3], five [T5] and seven [T7] months). Statistics was based in a normally distributed data. Multilevel procedures were used to derive polynomials for each of the measurements. Student's t-test and one-way repeated measures ANOVA were conducted. The level of significance of 5% was adopted. Results: Canine cusps and apexes did not follow a quadratic curve regarding horizontal movement (neither accelerate nor decelerate). Canine and molar cusps showed more horizontal movement than apexes (4.80 mm vs. 2.78 mm, and 2.64 mm vs. 2.17 mm, respectively). Conclusions: Canine did not accelerate or decelerate overtime horizontally; the cusps and apexes of the canines and molars showed more horizontal movement and larger rate at the beginning of canine retraction, followed by significantly smaller and constant movement rate after the first month.

RESUMO Objetivo: O objetivo deste estudo foi analisar a movimentação das cúspides e dos ápices de caninos e primeiros molares superiores durante a retração de caninos na primeira fase do fechamento do espaço pós-extração, e avaliar se esses dentes apresentam mudança na taxa de movimentação (aceleração e/ou desaceleração). Material e Métodos: Vinte e cinco pacientes (idade = 23,3 ± 5,1 anos) foram incluídos. A retração dos caninos superiores foi realizada com molas helicoidais fechadas de níquel-titânio (100gf) em arco 0,020" de aço inoxidável. Foram feitos traçados cefalométricos de telerradiografias oblíquas e sobrepostos ao melhor ajuste anatômico da maxila (antes da retração [T0]; após um mês [T1], três meses [T3], cinco meses [T5] e sete meses [T7]). A estatística foi baseada em dados com distribuição normal. Procedimentos multiníveis foram usados para derivar polinômios para cada uma das medidas. Teste t de Student e ANOVA de uma via para medidas repetidas foram realizados, adotando-se um nível de significância de 5%. Resultados: As cúspides e os ápices dos caninos não seguiram uma curva quadrática em relação ao movimento horizontal (sem aceleração ou desaceleração). As cúspides dos caninos e molares apresentaram mais movimento horizontal do que os ápices (4,80 mm vs. 2,78 mm e 2,64 mm vs. 2,17mm, respectivamente). Conclusões: A movimentação horizontal dos caninos não acelerou ou desacelerou ao longo do tempo; as cúspides e os ápices dos caninos e molares apresentaram maior movimento horizontal e maior taxa de movimentação no início da retração dos caninos, seguida por uma taxa de movimentação significativamente menor e constante após o primeiro mês.

Midsagittal Plane First: Building a Strong Facial Reference Frame for Computer-Aided Surgical Simulation.

PURPOSE: A facial reference frame is a 3-dimensional Cartesian coordinate system that includes 3 perpendicular planes: midsagittal, axial, and coronal. The order in which one defines the planes matters. The purposes of this study are to determine the following: 1) what sequence (axial-midsagittal-coronal vs midsagittal-axial-coronal) produced more appropriate reference frames and 2) whether orbital or auricular dystopia influenced the outcomes. METHODS: This study is an ambispective cross-sectional study. Fifty-four subjects with facial asymmetry were included. The facial reference frames of each subject (outcome variable) were constructed using 2 methods (independent variable): axial plane first and midsagittal plane first. Two board-certified orthodontists together blindly evaluated the results using a 3-point categorical scale based on their careful inspection and expert intuition. The covariant for stratification was the existence of orbital or auricular dystopia. Finally, Wilcoxon signed rank tests were performed. RESULTS: The facial reference frames defined by the midsagittal plane first method was statistically significantly different from ones defined by the axial plane first method (P = .001). Using the midsagittal plane first method, the reference frames were more appropriately defined in 22 (40.7%) subjects, equivalent in 26 (48.1%) and less appropriately defined in 6 (11.1%). After stratified by orbital or auricular dystopia, the results also showed that the reference frame computed using midsagittal plane first method was statistically significantly more appropriate in both subject groups regardless of the existence of orbital or auricular dystopia (27 with orbital or auricular dystopia and 27 without, both P < .05). CONCLUSIONS: The midsagittal plane first sequence improves the facial reference frames compared with the traditional axial plane first approach. However, regardless of the sequence used, clinicians need to judge the correctness of the reference frame before diagnosis or surgical planning.

Effects of stress relaxation in beta-titanium cantilevers used in orthodontic mechanics.

OBJECTIVE: This study evaluated the force decay and design shape changes caused by stress relaxation in two different orthodontic cantilever configurations. METHODS: Eighty cantilevers made of 0.017 x 0.025-in beta-titanium wires were standardized in a passive position, using real scale templates, and randomly divided into two groups (n = 40): Type 1 and Type 2. Each group received a different design (Type 1 with three bends, and Type 2 with two bends), and both were divided in four subgroups (n = 10) according to the evaluation periods: G1 = 24h, G2 = 1 week, G3 = 4 weeks, and G4 = 8 weeks. Mechanical tests were performed immediately after preactivation and at the end of each period, to evaluate force decay. The cantilevers were also scanned and the angles of the bends were measured to assess shape changes. RESULTS: Cantilever forces decayed over time. Type 1 - G1 showed less force decay than Type 2 (10.83 cN vs 17.87 cN). Type 1 cantilevers showed significant force decay only when G4 was compared to G1 (9.05 cN), G2 (11.73 cN), and G3 (9.78 cN). Type 2 cantilevers presented differences when G1 was compared to G2 (9.57 cN) and G3 (7.89 cN). Regarding to the cantilever angle closest to the bracket insertion, Type 1 cantilevers showed significant decrease for G2 (1.58°) and G4 (1.52°). CONCLUSIONS: Cantilevers' design and proximity of the bends influenced force decay pattern overtime. Type 1 cantilevers presented more stable design at the first weeks than Type 2.

Effect of print orientation on the dimensional accuracy of orthodontic aligners printed 3-dimensionally.

INTRODUCTION: Fabrication of orthodontic aligners directly via 3-dimensional (3D) printing presents the potential to increase the efficiency of aligner production relative to traditional workflows; however tunable aspects of the 3D-printing process might affect the dimensional fidelity of the fabricated appliances. This study aimed to investigate the effect of print orientation on the dimensional accuracy of orthodontic aligners printed directly with a 3D printer. METHODS: A digitally designed aligner of 500 µm thickness was printed in 3D in Grey V4 (Formlabs, Somerville, Mass) resin at 8 angulations at 45° intervals (n = 10 per angulation) using a stereolithography 3D printer. Each aligner was scanned with an optical scanner, and all but the intaglio surface of each scan was digitally removed. Each resultant scan file was superimposed onto the isolated intaglio of the designed master aligner file. The dimensional deviation was quantified with Geomagic Control software (3D Systems, Rock Hill, SC), and data were analyzed using R statistical software (version 2018; R Core Team, Vienna, Austria) (P <0.05). RESULTS: Print angle showed a statistically significant effect on standard deviation, average positive deviation, absolute average negative deviation, and percentage of points out of bounds (tolerance bounds defined as ±250 µm) (P <0.05). Qualitative analysis of the 3D surface deviation maps indicated that the 0° and 90° groups showed less deviation and appeared to be the most accurate in the anterior regions. Overall, the majority of the print angle groups studied were not printed within clinically acceptable tolerance ranges, with the major exception being the 90° group, which printed nominally within clinically acceptable tolerance ranges. CONCLUSIONS: With the workflow applied, print orientation significantly affects the dimensional accuracy of directly 3D-printed orthodontic aligners. Within the limitations of this study, printing at the 90° angulation would be advised as it is the group with the most accurate prints relative to the 7 other orientations investigated, although not all differences were statistically significant.

Cephalometric evaluation of changes in vertical dimension and molar position in adult non-extraction treatment with clear aligners and traditional fixed appliances.

INTRODUCTION: Orthodontists have been using clear aligners to treat malocclusions, and one potential effect of treatment with orthodontic aligners is the intrusion and/or resists extrusion of the posterior teeth. This "bite-block effect" is primarily anecdotal due to the frequent occurrence of posterior open bites in patients after clear aligner therapy. OBJECTIVE: The purpose of this study was to compare changes promoted by clear aligners and traditional fixed appliances in cephalometric measurements of the vertical dimension and molar position in adult patients with Class I malocclusion treated with non-extraction. METHODS: Pre- and post-treatment lateral cephalometric radiographs of adult patients treated with either clear aligners (n=44) or traditional fixed appliances (n=22) were selected for retrospective analysis. Eight interval measurements and one nominal measurement were evaluated: anterior overbite (OB), mandibular plane angle related to cranial base (SN_MP) and related to Frankfort (FMA), lower molar height (L6H) and upper molar height (U6H), palatal plane to mandibular plane angle (PP_MP), lower facial height (LFH), total facial height (TFH), and posterior open bite (Posterior_OB). A single evaluator traced all cephalographs, and changes in select measures of the vertical dimension were compared within and between groups. RESULTS: OB decreased (1.15 mm) and L6H increased (0.63 mm) in the traditional fixed appliance group. Mandibular plane angles (related to cranial base and to Frankfort) increased (0.43° and 0.53°, respectively) in the clear aligner group, but just FMA showed significant difference between groups (difference of 0.53°). LFH and TFH increased (ranging from 0.52 mm to 0.80 mm) in both groups, with no differences between treatment modality. Presence of visible posterior open bite significantly increased over the course of treatment. OB, FMA and L6H exhibited an interaction between treatment stage (pre- and post-treatment) and modality (clear aligner therapy and traditional fixed appliances), but no interaction among these three variables was found. CONCLUSIONS: The evidence does not support the theory that clear aligner therapy produces better vertical dimension control than traditional fixed appliances. Traditional fixed appliance therapy slightly extruded the lower molar, and clear aligner therapy produced a slightly mandibular backward rotation.

Functional characterization of ATF1, GREM2 AND WNT10B variants associated with tooth agenesis.

OBJECTIVE: To determine the functional effects of ATF1, WNT10B and GREM2 gene variants identified in individuals with tooth agenesis (TA). SETTINGS AND SAMPLE POPULATION: Stem cells from human exfoliated deciduous teeth (SHED) were used as an in vitro model system to test the effect of TA-associated variants. MATERIALS AND METHODS: Plasmid constructs containing reference and mutant alleles for ATF1 rs11169552, WNT10B rs833843 and GREM2 rs1414655 variants were transfected into SHED for functional characterization of variants. Allele-specific changes in gene transcription activity, protein expression, cell migration and proliferation, and expression of additional tooth development genes (MSX1, PAX9 and AXIN2) were evaluated. Data analyses were performed using Student's t-test. P-values ≤ .05 were considered statistically significant. RESULTS: Mutant variants resulted in significantly decreased transcriptional activity of respective genes (P < 0.05), although no changes in protein localization were noted. Expression of MSX1 was significantly decreased in ATF1- and GREM2-mutant cells, whereas PAX9 or AXIN2 mRNA expression was not significantly altered. Mutant WNT10B had no significant effect on the expression of additional TA genes. ATF1- and GREM2-mutant cells presented increased cell migration. Cell proliferation was also affected with all three mutant alleles. CONCLUSIONS: Our results demonstrate that ATF1, WNT10B and GREM2 mutant alleles have modulatory effects on gene/protein function that may contribute to TA.

Potentialities and limitations of computer-aided design and manufacturing technology in the nonextraction treatment of Class I malocclusion.

INTRODUCTION: Computer-aided design and manufacturing (CAD-CAM) systems have assisted orthodontists to position brackets virtually. The purpose of this study was to evaluate if a CAD-CAM system could predict the orthodontic treatment outcome of patients with Angle Class I malocclusion with mild crowding or spacing and with no need for orthodontic extraction. METHODS: Using the American Board of Orthodontics Cast-Radiograph Evaluation (ABO-CRE) and color map superimposition, the treated occlusion was compared with the virtual final occlusion of 24 young adults with Class I occlusion. Using eXceed software (eXceed, Witten, Germany), we created the final occlusion prediction for each patient (virtual set up group). A digital model of the final occlusion of each patient was created (treated occlusion group). ABO-CRE score was used to compare groups. In addition, a color map was created for all subjects to access the mean and range values between the virtual set up model and treated occlusion model of each patient. Random and systematic errors were calculated. In addition, chi-square and t test were used. RESULTS: Comparisons between virtual set up occlusion and treated occlusion showed statistically significant differences in 3 out of 7 measurements: interproximal contact score was larger for treated than virtual occlusion (0.45 mm and 0.04 mm, respectively), and the treated occlusion showed larger values than the virtual occlusion for occlusal contacts (14.13 mm and 7.62 mm, respectively) and overjet (7.37 mm and 0.66 mm, respectively). Although the treated occlusion showed a larger score than the virtual occlusion (50.41 mm and 34.58 mm, respectively), there is no significant difference between both. Root angulation decreased (from 1.95 ± 1.29 to 0.65 ± 0.71) because of the treatment. CONCLUSIONS: ABO-CRE overall score presents no difference between groups. In addition, CAD-CAM setup occlusion closely predicts the final teeth alignment and leveling with interarch relationships showing less ABO-CRE score deduction.

Cephalometric evaluation of changes in vertical dimension and molar position in adult non-extraction treatment with clear aligners and traditional fixed appliances

ABSTRACT Introduction: Orthodontists have been using clear aligners to treat malocclusions, and one potential effect of treatment with orthodontic aligners is the intrusion and/or resists extrusion of the posterior teeth. This "bite-block effect" is primarily anecdotal due to the frequent occurrence of posterior open bites in patients after clear aligner therapy. Objective: The purpose of this study was to compare changes promoted by clear aligners and traditional fixed appliances in cephalometric measurements of the vertical dimension and molar position in adult patients with Class I malocclusion treated with non-extraction. Methods: Pre- and post-treatment lateral cephalometric radiographs of adult patients treated with either clear aligners (n=44) or traditional fixed appliances (n=22) were selected for retrospective analysis. Eight interval measurements and one nominal measurement were evaluated: anterior overbite (OB), mandibular plane angle related to cranial base (SN_MP) and related to Frankfort (FMA), lower molar height (L6H) and upper molar height (U6H), palatal plane to mandibular plane angle (PP_MP), lower facial height (LFH), total facial height (TFH), and posterior open bite (Posterior_OB). A single evaluator traced all cephalographs, and changes in select measures of the vertical dimension were compared within and between groups. Results: OB decreased (1.15 mm) and L6H increased (0.63 mm) in the traditional fixed appliance group. Mandibular plane angles (related to cranial base and to Frankfort) increased (0.43° and 0.53°, respectively) in the clear aligner group, but just FMA showed significant difference between groups (difference of 0.53°). LFH and TFH increased (ranging from 0.52 mm to 0.80 mm) in both groups, with no differences between treatment modality. Presence of visible posterior open bite significantly increased over the course of treatment. OB, FMA and L6H exhibited an interaction between treatment stage (pre- and post-treatment) and modality (clear aligner therapy and traditional fixed appliances), but no interaction among these three variables was found. Conclusions: The evidence does not support the theory that clear aligner therapy produces better vertical dimension control than traditional fixed appliances. Traditional fixed appliance therapy slightly extruded the lower molar, and clear aligner therapy produced a slightly mandibular backward rotation.

RESUMO Introdução: Ortodontistas têm usado os alinhadores transparentes para tratar más oclusões, e um potencial efeito desse tratamento é a intrusão e/ou resistência à extrusão dos dentes posteriores. Esse efeito de "bloco de mordida" é principalmente empírico, devido à ocorrência frequente de mordidas abertas posteriores em pacientes após a terapia com alinhadores transparentes. Objetivo: O objetivo do presente estudo foi comparar as mudanças promovidas pelos alinhadores transparentes e aparelho fixo convencional nas medidas cefalométricas de dimensão vertical e posição do molar em pacientes adultos com má oclusão de Classe I tratados sem exodontias. Métodos: Radiografias cefalométricas laterais pré- e pós-tratamento de pacientes adultos tratados com alinhadores transparentes (n=44) ou com aparelho fixo tradicional (n=22) foram selecionadas para uma análise retrospectiva. Oito medidas de intervalo e uma medida nominal foram avaliadas: trespasse vertical anterior (OB), ângulo do plano mandibular em relação à base do crânio (SN_MP) e em relação ao Plano de Frankfurt (FMA), altura do molar inferior (L6H) e altura do molar superior (U6H), ângulo do plano palatal ao plano mandibular (PP_MP), altura facial inferior (LFH), altura facial total (TFH) e mordida aberta posterior (Posterior_OB). Um único avaliador fez todos os traçados cefalométricos, e as mudanças nas medidas da dimensão vertical foram comparadas intra e intergrupos. Resultados: OB reduziu (1,15 mm) e L6H aumentou (0,63 mm) no grupo de aparelho fixo tradicional. Os ângulos do plano mandibular (em relação à base do crânio e ao plano de Frankfurt) aumentaram (0,43° e 0,53°, respectivamente). No grupo dos alinhadores invisíveis, apenas o FMA apresentou diferença significativa entre os grupos (diferença de 0,53º). LFH e TFH aumentaram (variando de 0,52 mm a 0,80 mm) em ambos os grupos, sem diferenças entre as modalidades de tratamento. A presença de uma mordida aberta posterior visível aumentou significativamente durante o curso do tratamento. OB, FMA e L6H exibiram interação entre o estágio do tratamento (pré- e pós-tratamento) e a modalidade (terapia com alinhadores invisíveis ou aparelho fixo tradicional), porém não foi encontrada interação entre essas três variáveis. Conclusões: A evidência não suporta a teoria de que a terapia com alinhadores invisíveis produz melhor controle da dimensão vertical do que o aparelho fixo. O tratamento com aparelhagem fixa extruiu ligeiramente o molar inferior, e o tratamento com alinhadores invisíveis produziu uma ligeira rotação posterior da mandíbula.

Effects of transverse bodily movements of maxillary premolars on the surrounding hard tissue.

INTRODUCTION: This experimental study was designed to (1) produce buccal translation of maxillary premolars and (2) evaluate the effects on the buccal alveolar bone. METHODS: A randomized split-mouth study was designed based on 7 adult male beagle dogs. The experimental side received a custom cantilever appliance fabricated to produce a translatory force through the maxillary second premolar's center of resistance. The contralateral second premolar received no appliance and served as the control. The premolars underwent 6-7 weeks of buccal translation, followed by 3 weeks of fixed retention. Biweekly tooth movements were evaluated using intraoral and radiographic measurements. Pretreatment and posttreatment models were measured to assess tipping. Three-dimensional microscopic tomography was used to quantify the amount and density of buccal bone. Bone formation and turnover were assessed using fluorescent labeling, hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, and bone sialoprotein immunostaining. RESULTS: The applied force (100 g of force) translated (1.4 mm) and minimally tipped (4°) the experimental teeth. Lateral translation produced dehiscences at the mesial and distal roots, with 2.0 mm and 2.2 mm loss of vertical bone height, respectively. Bone thickness decreased significantly (P < 0.05) at the apical (∼0.4 mm), midroot (∼0.4 mm), and coronal (∼0.2 mm) levels. Fluorescent imaging, hematoxylin and eosin staining, and immunostaining for bone sialoprotein all showed new bone formation extending along the entire periosteal surface of the second premolar's buccal plate. Tartrate-resistant acid phosphatase staining demonstrated greater osteoclastic activity on the experimental than that of control sections. CONCLUSIONS: New buccal bone forms on the periosteal surface during and after tooth translation, but the amount of bone that forms is less than the amount of bone loss, resulting in a net decrease in buccal bone thickness and a loss of crestal bone.

Effect of Yd:YAG laser irradiation on the shear bond strength of orthodontic metal brackets.

OBJECTIVE: The purpose of this study was to evaluate the effect of the Yd:YAG laser irradiation on orthodontic bracket base surface. Shear bond strength (SBS) values and sites of the bonding failure interfaces were quantified. METHODS: Brackets were divided into two groups: OP (One Piece - integral sandblast base) and OPL (One Piece - laser irradiation). The brackets were randomly bonded on an intact enamel surface of 40 bovine incisors. The SBS tests were carry out using a universal test machine. A stereomicroscopy was used to evaluate the adhesive remnant index (ARI), and surface characterization was performed by scanning electron microscopy (SEM). Student's t-test was used to compare the SBS between the two groups (p< 0.05). Frequencies and chi-square analysis were applied to evaluate the ARI scores. RESULTS: OPL group showed higher value (p< 0.001) of SBS than OP group (43.95 MPa and 34.81 MPa, respectively). ARI showed significant difference (p< 0.001) between OPL group (ARI 0 = 100%) and OP group (ARI 0 = 15%). SEM showed a higher affinity between the adhesive and the irradiated laser base surface. CONCLUSIONS: Yd:YAG laser irradiation on bracket base increased SBS values, showing that bonding failure occurs at the enamel/adhesive interface. Laser-etched bracket base may be used instead of conventional bases in cases where higher adhesion is required, reducing bracket-bonding failure.

An automatic approach to establish clinically desired final dental occlusion for one-piece maxillary orthognathic surgery.

PURPOSE: One critical step in routine orthognathic surgery is to reestablish a desired final dental occlusion. Traditionally, the final occlusion is established by hand articulating stone dental models. To date, there are still no effective solutions to establish the final occlusion in computer-aided surgical simulation. In this study, we consider the most common one-piece maxillary orthognathic surgery and propose a three-stage approach to digitally and automatically establish the desired final dental occlusion. METHODS: The process includes three stages: (1) extraction of points of interest and teeth landmarks from a pair of upper and lower dental models; (2) establishment of Midline-Canine-Molar (M-C-M) relationship following the clinical criteria on these three regions; and (3) fine alignment of upper and lower teeth with maximum contacts without breaking the established M-C-M relationship. Our method has been quantitatively and qualitatively validated using 18 pairs of dental models. RESULTS: Qualitatively, experienced orthodontists assess the algorithm-articulated and hand-articulated occlusions while being blind to the methods used. They agreed that occlusion results of the two methods are equally good. Quantitatively, we measure and compare the distances between selected landmarks on upper and lower teeth for both algorithm-articulated and hand-articulated occlusions. The results showed that there was no statistically significant difference between the algorithm-articulated and hand-articulated occlusions. CONCLUSION: The proposed three-stage automatic dental articulation method is able to articulate the digital dental model to the clinically desired final occlusion accurately and efficiently. It allows doctors to completely eliminate the use of stone dental models in the future.

Clinical Evaluation of Digital Dental Articulation for One-Piece Maxillary Surgery.

PURPOSE: Methods for digital dental alignment are not readily available to automatically articulate the upper and lower jaw models. The purpose of the present study was to assess the accuracy of our newly developed 3-stage automatic digital articulation approach by comparing it with the reference standard of orthodontist-articulated occlusion. MATERIALS AND METHODS: Thirty pairs of stone dental models from double-jaw orthognathic surgery patients who had undergone 1-piece Le Fort I osteotomy were used. Two experienced orthodontists manually articulated the models to their perceived final occlusion for surgery. Each pair of models was then scanned twice-while in the orthodontist-determined occlusion and again with the upper and lower models separated and positioned randomly. The separately scanned models were automatically articulated to the final occlusion using our 3-stage algorithm, resulting in an algorithm-articulated occlusion (experimental group). The models scanned together represented the manually articulated occlusion (control group). A qualitative evaluation was completed using a 3-point categorical scale by the same orthodontists, who were unaware of the methods used to articulate the models. A quantitative evaluation was also completed to determine whether any differences were present in the midline, canine, and molar relationships between the algorithm-determined and manually articulated occlusions using repeated measures analysis of variance (ANOVA). Finally, the mean ± standard deviation values were computed to determine the differences between the 2 methods. RESULTS: The results of the qualitative evaluation revealed that all the algorithm-articulated occlusions were as good as the manually articulated ones. The results of the repeated measures ANOVA found no statistically significant differences between the 2 methods [F(1,28) = 0.03; P = .87]. The mean differences between the 2 methods were all within 0.2 mm. CONCLUSIONS: The results of our study have demonstrated that dental models can be accurately, reliably, and automatically articulated using our 3-stage algorithm approach, meeting the reference standard of orthodontist-articulated occlusion.

Effect of Yd: YAG laser irradiation on the shear bond strength of orthodontic metal brackets

ABSTRACT Objective: The purpose of this study was to evaluate the effect of the Yd:YAG laser irradiation on orthodontic bracket base surface. Shear bond strength (SBS) values and sites of the bonding failure interfaces were quantified. Methods: Brackets were divided into two groups: OP (One Piece - integral sandblast base) and OPL (One Piece - laser irradiation). The brackets were randomly bonded on an intact enamel surface of 40 bovine incisors. The SBS tests were carry out using a universal test machine. A stereomicroscopy was used to evaluate the adhesive remnant index (ARI), and surface characterization was performed by scanning electron microscopy (SEM). Student's t-test was used to compare the SBS between the two groups (p< 0.05). Frequencies and chi-square analysis were applied to evaluate the ARI scores. Results: OPL group showed higher value (p< 0.001) of SBS than OP group (43.95 MPa and 34.81 MPa, respectively). ARI showed significant difference (p< 0.001) between OPL group (ARI 0 = 100%) and OP group (ARI 0 = 15%). SEM showed a higher affinity between the adhesive and the irradiated laser base surface. Conclusions: Yd:YAG laser irradiation on bracket base increased SBS values, showing that bonding failure occurs at the enamel/adhesive interface. Laser-etched bracket base may be used instead of conventional bases in cases where higher adhesion is required, reducing bracket-bonding failure.

RESUMO Objetivo: O objetivo do presente estudo foi avaliar o efeito da aplicação do laser Yd:YAG sobre a superfície metálica da base de braquetes ortodônticos, a resistência da colagem ao cisalhamento (RU) e os locais das falhas nas interfaces adesivas. Métodos: Os braquetes foram divididos em dois grupos, de acordo com o tipo de base: OP (One Piece - monobloco, base jateada) e OPL (One Piece - monobloco, base irradiada a laser). Foram selecionados 40 incisivos bovinos hígidos para a colagem de braquetes na superfície do esmalte. Os testes de RU foram realizados por meio de uma máquina de ensaio universal EMIC DL1000. O Índice de Adesivo Remanescente (ARI) e a caracterização das superfícies foram realizados empregando-se estereomicroscópio e microscópio eletrônico de varredura (MEV). O teste t de Student foi aplicado para comparar a RU entre os dois grupos (p< 0,05). O ARI foi avaliado por meio da análise de Frequência e teste do Qui-quadrado. Resultados: O grupo OPL obteve maiores valores de RU (p<0,001) do que o grupo OP (43,95 MPa e 34,81 MPa, respectivamente), e o ARI obteve diferença significativa (p<0,001) entre os grupos OPL (ARI 0 = 100%) e OP (ARI 0 = 15%). A análise proveniente do MEV mostrou alta interação adesiva entre a resina e a superfície metálica da base irradiada pelo feixe de laser. Conclusões: A irradiação com laser Yd:YAG sobre a superfície da base de braquetes metálicos aumentou os valores da RU, demonstrando que as falhas adesivas ocorreram na interface esmalte/adesivo. O uso de braquetes modificados com irradiação a laser pode ser adotado como alternativa aos braquetes com bases convencionais nos casos em que uma maior retentividade for requerida para reduzir as falhas de adesividade.

A preliminary 3-D comparison of rapid and slow maxillary expansion in children: A randomized clinical trial.

BACKGROUND: This study compared the effects of rapid maxillary expansion (RME) and slow maxillary expansion (SME) using cone-beam computed tomography (CBCT). AIM: To evaluate the skeletal and dentoalveolar effects produced by two different maxillary expansion protocols. DESIGN: Eligibility criteria included maxillary transverse deficiencies in children (mean age, 8.18 years old), randomly assigned to either RME or SME. At the outcome analysis phase, a sample of 29 subjects were analysed (RME group, N = 16 and SME group, N = 13). CBCT scans taken before expansion and 6 months later were evaluated. Five posterior and 6 anterior transverse measurements were made at different vertical levels. Treatment changes were analysed using paired t tests; independent t tests were used to compare the two groups. RESULTS: There were statistically significant (P<.05) increases in maxillary width at the skeletal, alveolar, and dental levels for both groups, with significantly smaller increases at the more superior than inferior levels. The RME group exhibited statistically larger width increases than the SME group for all measures except interorbital width, anterior alveolar process width, and intercanine width. The group differences were greater for anterior than posterior apical base widths. CONCLUSIONS: Rapid maxillary expansion produced greater orthopaedic effects than slow maxillary expansion, with the greatest effects occurring in the anterior apical base.

Há diferença entre as alterações na amplitude da cavidade nasal após expansão maxilar rápida e lenta? / Is there any difference between alterations in the nasal cavity amplitude after slow and rapid maxillary expansion?

Resumo Introdução: O objetivo deste estudo clínico retrospectivo foi verificar os efeitos da Expansão Maxilar Rápida (EMR) e Expansão Maxilar Lenta (EML) na cavidade nasal e seio maxilar em pacientes com dentição mista, por meio de Tomografia Computadorizada de Feixe Cônico (TCFC). Material e Métodos: Trinta e nove crianças entre 7 e 10 anos foram divididas em dois grupos: EMR (n=20) e EML (n=19). Ambos os grupos tiveram a mesma quantidade de expansão maxilar (8mm), mas com diferentes protocolos (EMR=0.4mm/dia, EML=0.4mm/semana). Três diferentes áreas da cavidade nasal foram avaliadas: Anterior (CNA), Intermediária (CNI) e Posterior (CNP), bem como o seio maxilar na região mais anterior (SN). As alterações em cada grupo foram avaliadas através do test t pareado. Teste t student foi utilizado para verificar a diferença entre os grupos. O teste de Scheffé post hoc e ANOVA two-way foram utilizados para comparações múltiplas dentro de cada grupo. Resultados: A expansão maxilar promoveu aumento da largura da cavidade nasal nos dois grupos. Embora não significativa, a cavidade nasal apresentou maiores expansões de anterior para posterior (CNA= 2.23mm, CNI=1.73mm e CNP=1.54mm) no grupo EMR. Nenhum dos dois grupos apresentaram alterações significativas na amplitude do seio maxilar. Conclusões: A expansão maxilar promove aumento na amplitude da cavidade nasal na expansão maxilar rápida e lenta.(AU)

Abstract Introduction: The purpose of this retrospective clinical study was to evaluate the effects in nasal cavity and maxillary sinus of the Rapid Maxillary Expansion (RME) and the Slow Maxillary Expansion (SME) in mixed dentition patients using Cone Beam Computed Tomography (CBCT). Material and Methods: Thirty-nine children between 7-10 years old were allocated into two groups: RME (n=20) and SME (n=19). Both groups received the same amount of expansion (8mm), but with different protocols (RME=0.4mm/day and SME=0.4mm/week). Three different areas of the nasal cavity were evaluated: Anterior (ANC), Intermediate (INC), and Posterior (PNC). Student t-test and paired t-test were applied to comparison between and within group changes. Scheffé post hoc test and two-way ANOVA were used for multiple comparisons within each group. Results:Both Rapid Maxillary Expansion (RME) and Slow Maxillary Expansion (SME) promoted widening of the nasal cavity. Although not significant, RME presented larger widening from anterior to posterior areas of the nasal cavity (ANC=2.23mm, INC=1.73mm, e PNC=1.54mm). None of the groups showed significant alterations in the maxillary sinus amplitude. Conclusions: Maxillary expansion promotes widening in the nasal cavity amplitude in Rapid Maxillary Expansion (RME) and Slow Maxillary Expansion (SME). (AU)