A 3D Finite Element Analysis of biomechanical effects on teeth and bone during true intrusion of posteriors using miniscrews.

OBJECTIVE: The primary objective of this study was to investigate the biomechanical effects and stresses on bone, PDL, cementum and displacement along X-,Y- and Z-axis during true intrusion of molars using mini-implants with finite element analysis; the secondary objective of the study was to find out the best method for posterior intrusion in clinical practice. MATERIAL AND METHODS: A 3D finite element method was used to simulate true molar intrusion using sliding mechanics. Two groups were made, with mini-implants placed on buccal side and palatal side with a cap splint for MODEL1, and a single mini-implant placed buccally with transpalatal arch (TPA) for MODEL2. The material characteristics which include the Young's modulus and Poison's ratio were assigned. von Mises stress, principal stress on PDL and alveolar bone, displacements in all the 3 planes were determined. RESULTS: Bone stress patterns showed compressive stresses on the buccal aspect and tensile stresses on the palatal aspect for both MODELS. Stresses in the PDL and cementum were mainly concentrated in the apex region, with a more uniform distribution of stresses for MODEL 1. Tooth displacement showed true intrusion for both MODELS, i.e. the Z axis, and a more controlled buccal tipping for MODEL 1. CONCLUSION: Of the modalities compared, the best controlled tooth movements for posterior intrusion in the treatment of open bite were obtained with mini-implants placed with a cap splint (MODEL 1).

Does leukocyte-platelet-rich fibrin (L-PRF) cause long term acceleration in the rate of canine retraction? A split-mouth, two-arm parallel group, randomized control trial.

OBJECTIVE: The present study was conducted to investigate the effects of leukocyte-platelet-rich fibrin (L-PRF) on the rate of maxillary canine retraction for a period of 5 months. METHODS: A split-mouth study was conducted on 16 subjects (9 males and 7 females; age range 17-25 years; mean age, 21.85±2.45 years) who required therapeutic extraction of bilateral maxillary first premolars. After the initial leveling and alignment, L-PRF plugs were placed in a randomly selected extraction socket (Experimental Group), and the other side served as a control (Control Group). Canine retraction was carried out by the activation of nickel-titanium (NiTi) closed-coil springs delivering 150 g of force. The rates of canine movement, canine rotation, tipping, root resorption, and molar movement were assessed at monthly intervals for five months (T0-T5). Pain, swelling and discomfort accompanying the procedure were assessed using a Likert scale. RESULTS: The study revealed a significant increase in the rate of canine movement on the experimental side in the first two months, and significant molar anchorage loss was observed only in the first month for control side. There were no statistically significant differences between the groups regarding canine rotation, tipping, probing depth, root resorption, and pain perception. CONCLUSIONS: The use of L-PRF plugs in extraction sockets considerably enhanced the rate of canine movement only in the first two months, and long-term efficacy was not observed in this study.

Does leukocyte-platelet-rich fibrin (L-PRF) cause long term acceleration in the rate of canine retraction? A split-mouth, two-arm parallel group, randomized control trial

ABSTRACT Objective: The present study was conducted to investigate the effects of leukocyte-platelet-rich fibrin (L-PRF) on the rate of maxillary canine retraction for a period of 5 months. Methods: A split-mouth study was conducted on 16 subjects (9 males and 7 females; age range 17-25 years; mean age, 21.85±2.45 years) who required therapeutic extraction of bilateral maxillary first premolars. After the initial leveling and alignment, L-PRF plugs were placed in a randomly selected extraction socket (Experimental Group), and the other side served as a control (Control Group). Canine retraction was carried out by the activation of nickel-titanium (NiTi) closed-coil springs delivering 150 g of force. The rates of canine movement, canine rotation, tipping, root resorption, and molar movement were assessed at monthly intervals for five months (T0-T5). Pain, swelling and discomfort accompanying the procedure were assessed using a Likert scale. Results: The study revealed a significant increase in the rate of canine movement on the experimental side in the first two months, and significant molar anchorage loss was observed only in the first month for control side. There were no statistically significant differences between the groups regarding canine rotation, tipping, probing depth, root resorption, and pain perception. Conclusions: The use of L-PRF plugs in extraction sockets considerably enhanced the rate of canine movement only in the first two months, and long-term efficacy was not observed in this study.

RESUMO Objetivo: O presente estudo foi realizado para investigar os efeitos da fibrina rica em leucócitos e plaquetas (L-PRF) na taxa de retração do canino superior, durante um período de cinco meses. Métodos: Um estudo de boca dividida foi realizado em 16 indivíduos (9 homens e 7 mulheres; faixa etária de 17 a 25 anos; idade média de 21,85 ± 2,45 anos) que precisavam de extração terapêutica dos primeiros pré-molares superiores de ambos os lados. Após o nivelamento e o alinhamento iniciais, os plugs de L-PRF foram colocados em um alvéolo pós-extração, selecionado aleatoriamente (Grupo Experimental), e o outro lado serviu como controle (Grupo Controle). A retração do canino foi realizada pela ativação de molas fechadas de níquel-titânio (NiTi) com 150 g de força. As taxas de movimentação do canino, rotação, inclinação e reabsorção radicular do canino e movimentação do molar foram avaliadas em intervalos mensais durante cinco meses (T0-T5). A dor, o inchaço e o desconforto após o procedimento foram avaliados por meio de uma escala de Likert. Resultados: O estudo revelou um aumento significativo na taxa de movimentação do canino no lado experimental nos dois primeiros meses, e uma perda significativa de ancoragem do molar foi observada apenas no primeiro mês no lado controle. Não houve diferenças estatisticamente significativas entre os grupos, com relação à percepção da dor e rotação, inclinação, profundidade de sondagem e reabsorção radicular do canino. Conclusões: O uso de plugs de L-PRF em alvéolos pós-extração aumentou consideravelmente a taxa de movimentação do canino apenas nos dois primeiros meses, não sendo observada uma eficácia em longo prazo.

Three-dimensional finite element analysis to evaluate biomechanical effects of different alveolar decortication approaches on rate of canine retraction.

INTRODUCTION: The aim of this study was to compare different corticotomy approaches and determine their biomechanical effects on rate of canine displacement when compared to conventional orthodontics. METHOD: Three-dimensional Finite Element Models with conventional non-corticotomy approach (model 1) and three corticotomy approaches ensuing buccal and palatal vertical cuts (model 2), interseptal bone reduction (model 3), buccal vertical cuts (model 4) were fabricated. Displacement of the canine and von Mises stresses in the canine and trabecular bone were calculated and compared under a distal retraction force of 1.5N. RESULTS: The maximum displacement of canine with minimum anchorage loss was seen in model 3 followed by model 2, model 4 and model 1. The maximum equivalent (von Mises) stress was concentrated mainly on the distal side of canine in model 3 and had a uniform distribution of stresses on entire root surface. CONCLUSIONS: Corticotomy approaches effectively accelerated maxillary canine retraction, exhibiting twice the rate of canine movement with minimum anchorage loss when compared to non-corticotomy approach. Corticotomy with interseptal bone reduction was most effective in terms of canine displacement and stress distribution.

Comparison of conventional methods of simultaneous intrusion and retraction of maxillary anterior: a finite element analysis.

OBJECTIVE: To study the biomechanical effects of the three-piece intrusion arch and Kalra simultaneous intrusion and retraction arch (K-SIR) on simultaneous intrusion and retraction of maxillary anterior teeth. DESIGN: Three-dimensional analysis of stresses and displacement of the anterior and posterior teeth with the three-piece intrusion arch and K-SIR arch was done using the finite element method (FEM). SETTING: Department of Orthodontics, Surendera Dental College and Research Institute, India. MATERIAL AND METHODS: For this investigation, the geometric model of the maxilla was constructed using a computed tomography scan. 0.022 × 0.028-inch MBT brackets and molar tubes were modelled, with the specified tip and torque values for all maxillary teeth. The wire components for the three-piece intrusion arch and K-SIR arch were modelled initially as a line diagram and then converted to three dimensional models. The material characteristics which include the Young's modulus and Poisson's ratio were assigned. After defining the boundary conditions, force systems were applied as per design. The analysis was carried out using ANSYS Version 12.1 software. The von Mises stress, principal stress on PDL and alveolar bone, change in the inclination of incisors and initial displacement of the teeth in bucco-palatal, mesio- distal and vertical direction were analysed. RESULTS: Stresses in cortical bone were greater than cancellous. Both modalities showed intrusion of the anterior teeth, although this was slightly more in the three- piece intrusion arch. On studying the principal stresses in the PDL, the three-piece intrusion arch displayed uniform stress distribution compared to K-SIR arch. CONCLUSION: The FEM cannot reflect actual biological responses within the human body to orthodontic forces but based on these findings, the three-piece intrusion arch showed better stress distribution and controlled tooth movement than the K-SIR arch.

Comparative evaluation of three mixed dentition analyses and formulation of regression equations for north Indian population: A cross-sectional study.

BACKGROUND: The present study was undertaken to evaluate the accuracy of methods proposed by Tanaka and Johnston, Moyers, and Bernabé and Flores-Mir to forecast the mesiodistal dimensions of permanent canine and premolars in a North Indian population. METHODS: Mesiodistal tooth dimensions were measured from study models representing 68 male and 68 female subjects (aged 12-16 years) of North Indian descent. The mesiodistal dimensions of the teeth were measured using a digital Vernier caliper (providing measurements to 0.01 mm accuracy). The measurements of canine and premolars were summed up and compared with those derived from Tanaka and Johnston equations, Moyers probability tables (75 th percentile), and Bernabé and Flores-Mir equations. RESULTS: All the three methods exhibited overestimation of actual sum of permanent canine and premolars in both the arches and genders in this population. Because of the discrepancy observed, new regression analyses in the form of Y = A + B (X) were formulated similar to those proposed by Tanaka and Johnston originally, but separately for males and females. In males, the correlation coefficient between the sum of mesiodistal widths of mandibular incisors and the sum of widths of canine and premolars was 0.637 and 0.685 for maxilla and mandible, respectively. This value was 0.55 for maxilla and 0.64 for mandible in females. These values were found to be statistically significant. CONCLUSION: All the methods evaluated in the study were found to be inaccurate and they overestimate the mesiodistal widths of permanent canine and premolars in North Indian population. Revised linear regression equations were derived using the data obtained from this population.