The Hydrostatic Pressure Distribution in the Periodontal Ligament and the Risk of Root Resorption-A Finite Element Method (FEM) Study on the Nonlinear Innovative Model.

Excessive orthodontic force can induce inflammatory tooth root resorption due to sustained high stresses within the periodontal ligament (PDL). This study aimed to analyze the PDL pressures during upper incisor retraction using the en masse method with TISAD. The finite element method (FEM) ensured consistent conditions across cases. The models included bone geometry, adjacent teeth, PDL, and orthodontic hardware, analyzed with LS-Dyna. The pressure ranged from 0.37 to 2.5 kPa across the dental arch, with the central incisors bearing 55% of the load. The pressure distribution remained consistent regardless of the force or hook height. The critical pressure (4.7 kPa) was exceeded at 600-650 g force, with notable pressure (3.88 kPa) on the palatal root wall of the right central incisor. Utilizing 0.017 × 0.025 SS archwires in MBT 0.018 brackets provided good torque control and reduced the root resorption risk when forces of 180-200 g per side were applied, maintaining light to moderate stress. Triple forces may initiate resorption, highlighting the importance of nonlinear finite element analysis (FEA) for accurate oral cavity simulations.

Recovery bone formation on radiographic palatal bone dehiscences after incisor retraction with microimplants.

OBJECTIVES: To investigate the difference in labial and palatal alveolar bone thickness and height during the retention period after incisor retraction treatment with microimplant. MATERIALS AND METHODS: A sample of 21 patients (mean age: 17.80 ± 4.38 years) who underwent incisor retraction treatment using microimplants after premolar extraction was investigated. The cone-beam computed tomography images at pretreatment, posttreatment, and retention were used to measure anterior alveolar bone thickness (labial, palatal, and total; at three vertical levels) and height (labial and palatal) and differences in the incisor position during treatment or retention. Repeated-measures analysis of variance with Bonferroni correction was performed to compare the variables at T0, T1, and T2. RESULTS: The maxillary central incisor moved posteriorly by approximately 8.0 mm along with intrusive movement of 1.8 mm after treatment. The alveolar bone thickness significantly decreased on the palatal side and increased on the labial side after treatment. Thereafter, the palatal bone thickness significantly increased and labial bone thickness decreased during the retention period. The palatal interdental bone depressed by incisor retraction showed substantial bone deposition after retention. CONCLUSIONS: Radiographic palatal bone dehiscences on the incisor root and palatal bone depression between the incisor roots were apparent after treatment. This palatal bone loss around the incisor roots noticeably recovered with newly formed bone during retention.

Alveolar bone remodelling and stability of mandibular incisors in adult patients after orthodontic treatment with premolar extractions: A prospective follow-up study.

OBJECTIVE: To evaluate alveolar bone remodelling and stability of mandibular incisors in adult orthodontic extraction patients. MATERIALS AND METHODS: Cone-beam computed tomography images of 25 adult patients undergoing extraction were collected before orthodontic treatment (T1), after orthodontic treatment (T2), and after at least 1 year of retention (T3). The labial and lingual alveolar bone heights (ABH), thickness (ABT), and tooth movement of the mandibular incisors were measured during the retraction (T2-T1) and retention (T3-T2) periods. According to the tooth movement during the retention period, the mandibular incisors were further divided into stable and unstable groups, and the correlation between L1-BMe and stability was evaluated. RESULTS: The labial and lingual ABHs significantly increased after orthodontic treatment and decreased during the retention period. The lingual ABH was 7.36 ± 2.27 mm at T2 and 5.37 ± 1.98 mm at T3, indicating a great bone remodelling capacity. The labial ABT exhibited a significant increase during orthodontic treatment and a slight decrease during the retention period, while the lingual ABT showed an opposite trend. During the retention period, the root apex moved labially into the alveolar bone housing. L1-BMe significantly increased during orthodontic treatment and decreased during the retention period. Compared to the stable group, lingual ABH and L1-BMe at T2 was significantly higher, and lingual ABT was smaller in the unstable group. CONCLUSION: Post-treatment lingual alveolar bone defects of the mandibular incisors could recover to some extent during the retention period. There was a negative correlation between post-treatment L1-BMe and mandibular incisor stability.

Three-dimensional assessment of periodontal support of lower incisors for skeletal Class II malocclusion undergoing presurgical orthodontic treatment with different vertical skeletal patterns.

BACKGROUND: The aim of the present study was to compare periodontal support changes during retraction of mandibular anterior teeth for skeletal Class II malocclusion with different facial divergence and to analyze relevant factors influencing bone remodeling by applying three-dimensional (3D) cone-beam computed tomography (CBCT) reconstruction technology. METHODS: Forty-eight patients with Class II malocclusion requiring surgical orthodontic treatment enrolled in the study were divided into the hyperdivergent group (n = 16), normodivergent group (n = 16) and hypodivergent group (n = 16) according to their vertical skeletal patterns. Cone-beam computed tomography (CBCT) scans were obtained before treatment (T1) and after presurgical orthodontic treatment (T2). The two-dimensional (2D) alveolar bone morphology, movement of mandibular central incisors and volume of the alveolar bone around incisors were measured on the labial and lingual sides by 3D CBCT reconstruction technology. Statistical analyses were performed with one-way ANOVA, paired t tests and multiple linear regression. RESULTS: During presurgical orthodontic treatment, the alveolar bone height on the labial side of the hyperdivergent group decreased significantly (P ≤ 0.05), but was maintained in the normodivergent and hypodivergent groups (P > 0.05). However, the alveolar bone volume, alveolar bone thickness at each level and alveolar bone height on the lingual side decreased significantly for all the groups. Apart from the initial morphometric measurements at T1, the morphology of lingual alveolar bone at T2 was significantly influenced by the direction and amount of tooth movement. Horizontal retraction and vertical protrusion of the root apex were negatively related to the alveolar bone on the lingual side after presurgical orthodontic treatment. CONCLUSION: For Class II malocclusion patients undergoing presurgical orthodontic treatment, the changes in the periodontal support of the lower central incisors varied in different vertical skeletal patterns. There exists a great periodontal risk of alveolar bone resorption on the lingual side for various vertical types. To avoid alveolar bone deterioration, it is essential to investigate the bone remodeling of patients with different alveolar bone conditions and cautiously plan tooth movement prior to orthodontic treatment. Moreover, 3D measurements based on CBCT construction can provide complementary information to traditional 2D measurements.

Three-dimensional morphologic analysis of the maxillary alveolar bone after anterior tooth retraction with temporary anchorage devices.

OBJECTIVES: To investigate three-dimensional (3D) morphologic changes in the alveolar bone around the maxillary central incisors of patients who underwent premolar extraction and subsequent anterior tooth retraction using temporary anchorage devices (TADs). MATERIALS AND METHODS: The subjects consisted of 16 patients with bimaxillary protrusion. The maxillary anterior teeth were retracted using sliding or loop mechanics and TADs for anchorage reinforcement. Cephalograms and computed tomography scans taken pretreatment and posttreatment were registered with respect to the palatal structures. The movement of the maxillary central incisors and morphologic changes in the anterior alveolar bone were evaluated quantitatively. RESULTS: Displacement in the palatal direction was observed in the alveolar bone around the incisors and the interdental septum. The displacement and bone remodeling/tooth movement ratio were larger on the labial side than the palatal side, and decreased progressively from the crest to apex level. The bone thickness was significantly increased on the labial side and decreased on the palatal side. CONCLUSIONS: Regional differences exist in morphologic changes of the alveolar bone during anterior tooth retraction using TADs. Attention should be paid to the crest region of the palatal alveolar bone because of its small original thickness and low remodeling activity.

Changes in condylar position during orthodontic treatment depending on the amount of incisor retraction: a cone-beam computed tomography study.

OBJECTIVES: Orthodontic treatment may be associated with temporomandibular disorders through changes in the condylar position. This study aimed to evaluate changes in the condylar position among different amounts of maxillary incisor retraction during orthodontic treatment using cone-beam computed tomography images. MATERIALS AND METHODS: Fifty-four participants were enrolled and divided into minimal (n = 14), moderate (n = 20), and maximal (n = 20) retraction groups based on the amount of incisor retraction (< 1, 1-6, and > 6 mm, respectively). Changes in condylar position before (T0) and after (T1) orthodontic treatment were assessed for the superior, anterior, posterior, and medial joint spaces (SJS, AJS, PJS, and MJS, respectively). Changes in joint spaces were compared between T0 and T1 in each group using paired t-tests and among the three groups using analysis of variance. RESULTS: Anterior movement of the condyle was observed in the maximal retraction group with a 0.2 mm decrease in ΔAJS and a 0.2 mm increase in ΔPJS, significantly greater than those in the minimal retraction group. The AJS and PJS showed statistically significant differences between T0 and T1 (P < 0.05) in the maximal retraction group. CONCLUSIONS: The condyle may show a statistically significant but clinically insignificant forward movement in the maximal incisor retraction group, whereas it was relatively stable in the minimal and moderate incisor retraction groups. CLINICAL RELEVANCE: More attention should be paid to the signs and symptoms of the condyle in patients with excessive incisor retraction during orthodontic treatment.

Cone-beam computed tomography assessment of maxillary anterior alveolar bone remodelling in extraction and non-extraction orthodontic cases using stable extra-alveolar reference.

OBJECTIVE: To explore alveolar cortical positional change in response to tooth movement in extraction and non-extraction orthodontic cases, using cone-beam computed tomography (CBCT) and stable extra-alveolar references. MATERIALS AND METHODS: The pre-treatment (T1) and post-treatment (T2) CBCT scans of 25 extraction (EXT) and matched 25 non-extraction (Non-EXT) orthodontic cases were imported into Dolphin Imaging 3D, and oriented uniformly. Sagittal and axial CBCT cross-sections were traced using customized software-generated guides. The displacement of teeth and alveolar bone cortices were automatically measured using the palatal plane (PP) and the line perpendicular to PP and passing Sella as reference. Intra- and inter-group differences between T1 and T2 were analysed. Subjects were also superimposed three-dimensionally using Geomagic Control X for qualitative analysis of cortical remodelling. RESULTS: The EXT group showed incisor retraction, while the Non-EXT group exhibited statistically significant incisor anterior tipping (P < .05). In EXT, both the labial and palatal cortices are resorbed. Non-EXT showed labial cortex anterior modelling, and statistically significant palatal cortex resorption (P < .05). In both groups, statistically significant decrease in total and palatal alveolar widths, increase in labial widths, and palatal dehiscence were observed. Comparatively, EXT showed significantly more incisal total and palatal width decrease and palatal vertical bone loss. CONCLUSION: Labial cortical remodelling was shown to follow anterior tooth movement, but the palatal cortical response to incisor retraction and labial cortical remodelling in general remained inconclusive. Narrowing of the alveolar housing and palatal dehiscence were observed regardless of extraction following orthodontic treatment.

Factors that affect lip changes following incisor retraction in Vietnamese adults with a convex facial profile.

OBJECTIVE: This study aimed to evaluate the factors that influence lip change through the results of tooth anterior retraction by fixed orthodontic treatment in Vietnamese adult patients with a convex facial profile. MATERIALS AND METHODS: This prospective study included 32 Vietnamese adults who have convex facial profiles. Digital software measurements according to Arnett's analysis and the superimposition method were performed to evaluate the changes in dentoskeletal structures, and soft tissue variables included lip change. A multiple logistic regression model was applied with various explanatory variables to analyze the correlation. RESULTS: The study revealed a strong correlation of lip change at the site of the cervical point and incisal edge of the upper incisors, and the cervical position demonstrated a stronger correlation. The ratio between lip change and incisor retraction in patients is approximately 1:2.3 at the incisal edge and 1:1.3 at the cervical point. CONCLUSION: Lip change was associated with incisor retraction at the cervical and incisal edge, but it did not correlate with the rotation axis of the upper incisors.

Augmented Corticotomy on the Lingual Side in Mandibular Anterior Region Assisting Orthodontics in Protrusive Malocclusion: A Case Report.

Adequate alveolar bone volume is a prerequisite condition for successful orthodontic tooth movement and posttreatment stability. Mandibular anterior teeth are more likely to exhibit dehiscence and fenestration in adult patients, which make orthodontic treatment in adults challenging, especially when the amount of retraction of the anterior teeth is large. Herein, we report the treatment of augmented corticotomy only on the lingual side in the mandibular anterior region to increase the volume of soft and hard tissue assisting orthodontics in a Class I bialveolar protrusive malocclusion and propose management strategies of mandibular incisor retractions. A 22-year-old female with a chief complaint of protrusive mouth presented to the Department of Orthodontics for orthodontic treatment, diagnosed with Class I bialveolar protrusive. The orthodontic treatment plan involved the extraction of four premolars and extensive retraction of the anterior teeth using microimplant anchorage. In consideration of the fenestration and dehiscence in the mandibular anterior alveolar bone and the pattern of tooth movement, augmented corticotomy was performed on the lingual side combined with bone grafting. Clinical and radiographic evaluation after treatment revealed significant improvements in the facial profile and in periodontal phenotype. Augmented corticotomy assisting orthodontic treatment could be a promising treatment strategy for adult patients with alveolar protrusion to maintain periodontal health.

Alveolar bone thickness and height changes following incisor retraction treatment with microimplants.

OBJECTIVES: To evaluate alveolar bone remodeling following incisor retraction treatment with microimplants and to examine the relationship between crown/root distal movement and thickness/height changes of the alveolus. MATERIALS AND METHODS: A total of 24 patients (mean age, 19.29 ± 4.64 years) with bialveolar protrusion treated by incisor retraction with microimplants were included. The distances of the crown and root tip movements as well as the thickness (alveolar bone thickness [ABT]; labial, lingual, and total) and vertical level (vertical bone level [VBL]; labial and lingual) of the alveolar bone were assessed using cone-beam computed tomography images obtained before treatment (T1) and after treatment (T2). All T1 and T2 variables were compared, and further comparisons of alveolar bone changes were conducted between the two groups based on the distance of the crown (low-crown-movement and high-crown-movement groups) and root movements (low-root-movement and high-root-movement groups). To determine the correlation of the crown or root movement with the variables of alveolar bone changes, Pearson correlation coefficients were calculated. RESULTS: Significant differences were found in all VBL and ABT variables after treatment in both jaws but not in total ABT. Based on the crown and root movements, alveolar bone change significantly differed between the root-movement groups, whereas there was no significant difference between the crown-movement groups. In addition, root movement showed significant correlations with the variables. CONCLUSIONS: Remarkable changes in the height and thickness of alveolar bone were found after microimplant-aided incisor retraction treatment in all groups except for total ABT. Root movement was significantly correlated with the alveolar bone changes.

Morphological changes of the anterior alveolar bone due to retraction of anterior teeth: a retrospective study.

BACKGROUD: To analyze the morphological changes of the anterior alveolar bone after the retraction of incisors in premolar extraction cases and the relationship between incisor retraction and remodeling of the alveolar base represented by points A and B displacements. METHODS: Pre- (T0) and post-treatment (T1) lateral cephalograms of 308 subjects in the maxilla and 154 subjects in the mandible who underwent the orthodontic treatment with extraction of 2 premolars in upper or lower arches were included. Alveolar bone width and height in both the maxillary and mandible incisor area were measured at T0 and T1 respectively. By superimposing the T0 and T1 cephalometric tracings, changes of points A and B, and the movement of the incisors were also measured. Then the correlation between incisor movement and the displacements of points A and B was analyzed. RESULTS: The alveolar bone width (ABW) showed a significant decrease in both maxilla and mandible (P < 0.001) except the labial side of the mandible (P > 0.05). The alveolar bone height (ABH) showed a significant increase in the labial side of maxilla and a significant decrease in the lingual side of maxilla and mandible. A strong positive correlation was verified between incisor movement and position changes of points A and B in both horizontal and vertical directions. CONCLUSIONS: Anterior alveolar bone width and height generally decreased after orthodontic treatment. Incisor retraction led to significant position changes of points A and B. The decrease of anterior alveolar bone due to significant incisor retraction should be taken into account in treatment planning.

Alveolar cortical plate changes associated with incisor retraction and its influence on the limits of orthodontic tooth movement.

OBJECTIVE: The extent to which the modelling behaviour of the anterior alveolus limits tooth movement remains unclear. Will the labial and lingual cortical plates model as incisors retract, or will they remain unchanged, therefore limiting the extent of possible tooth movement? SETTING AND SAMPLE POPULATION: Pre- and post-treatment lateral cephalometric radiographs of 29 bimaxillary protrusive patients of South Korean descent were examined. Treatment consisted of two premolar extractions in one or both arches with en masse retraction of the incisors using miniscrew anchorage. MATERIALS AND METHODS: Pre- and post-treatment measurements of both tooth and cortical plate position were made at various increments along the length of the root and then compared using paired t tests. RESULTS: Despite the use of miniscrew anchorage, the incisors were retracted by controlled tipping. The labial cortical plates in both arches modelled to follow tooth movement. Following retraction of the incisors in the maxilla, the incisor root approached the lingual cortical plate, which remained unchanged. In the mandible, the lingual cortical plate position was unchanged except at the level closest to the cementoenamel junction. CONCLUSIONS: The maxillary and mandibular lingual cortical plates did not model to follow the incisor movement while the labial cortical plates did. These findings suggest that lingual cortical plates may act as limitations to planned orthodontic tooth movement.

The effect of platelet-rich fibrin (PRF) on maxillary incisor retraction rate.

OBJECTIVE: To investigate the efficiency of platelet-rich fibrin (PRF) injection on maxillary incisor retraction rate. MATERIALS AND METHODS: The study included 40 patients (23 women and 17 men; mean age; 20.7 ± 1.45) with Class II Division 1 malocclusion. The treatment plan for all patients was extraction of the maxillary first premolars and canine distalization, followed by retraction of the maxillary incisors. Patients were randomly divided into two groups. The study group received injectable platelet-rich fibrin (i-PRF) two times with an interval of 2 weeks; the control group did not receive i-PRF. In both groups, the measurements were bilaterally assessed as the distances between the lateral and canine teeth on the plaster models at five time points. The rate of incisor movement was evaluated by Student's t-test, analysis of variance, and Tukey honestly significant difference tests. Statistical significance was set as P < .05. RESULTS: The average movements of incisors were significantly higher in the study group than the control group at all time points (P < .05). According to the within-group comparison, none of the measurements showed any significant differences between the right and left sides in both groups at all time points (P > .05). While the movement of incisors was significantly higher in the study group in the week following the PRF injection compared to the other weeks (P < .05), there were no significant differences in the control group at all-time points (P > .05). CONCLUSIONS: Applying i-PRF significantly increased the rate of maxillary incisor retraction at all time intervals. Platelet-rich fibrin injection can be an effective method for shortening treatment duration.

Alveolar bone response to maxillary incisor retraction using stable skeletal structures as a reference.

OBJECTIVES: To evaluate alveolar bone change in relation to root position change after maxillary incisor retraction via cone-beam computed tomography (CBCT) using stable skeletal structures as a reference. MATERIALS AND METHODS: A total of 17 subjects (age 24.7 ± 4.4 years) who required retraction of the maxillary incisors were included. Labial and palatal alveolar bone changes and root change were assessed from preretraction and 3 months postretraction CBCT images. The reference planes were based on stable skeletal structures. The Kruskal-Wallis test and Wilcoxon signed-rank test were used to compare changes within and between groups, as appropriate. Spearman rank correlations were used to identify the parameters that correlated with alveolar bone change. The significance level was set at .05. RESULTS: The labial alveolar bone change after maxillary incisor retraction was statistically significant (P < .05), and the bone remodeling/tooth movement (B/T) ratio was 1:1. However, the palatal bone remained unchanged (P > .05). The change in inclination was significantly related to labial alveolar bone change. CONCLUSIONS: Using stable skeletal structures as a reference, the change in labial alveolar bone followed tooth movement in an almost 1:1 B/T ratio. Palatal alveolar bone did not remodel following maxillary incisor retraction. The change in inclination was associated with alveolar bone change.

Dental and soft tissue changes following extraction of second premolars in females with bimaxillary protrusion: A retrospective study.

BACKGROUND: Bimaxillary protrusion is a condition wherein esthetic concerns are the main reason behind seeking orthodontic treatment. AIM: The aim of this retrospective cephalometric study was to evaluate the soft tissue profile and dental changes among female Saudi bimaxillary protrusion patients treated with extraction of all second premolars followed by retraction of the anterior teeth. Subjects and Methods: Pre and posttreatment cephalometric radiographs of adult female patients (ages 18-30 years) who underwent orthodontic therapy for Class I bimaxillary protrusion were obtained. Data were analyzed with SPSS® software. A paired t-test and Pearson's correlation coefficients were conducted with the statistical significance set at 95% (P value < 0.05). RESULTS: At posttreatment, there was an overall decrease in the mean values among the majority of the soft tissue and dental cephalometric angles and linear measurements. Among soft tissue variables, there was a marginal increase in the upper lip length by 1.49 mm (P < 0.001), and the nasolabial angle increased markedly by 7.64° (P < 0.001). Similarly, a marked increase in retroclination by 5.95° (P < 0.001) was observed among the dental variables. Conversely, no significant changes were noted in the lower incisors. Pearson's correlation analysis revealed a significant correlation between all the different dental variables. Within the soft tissue variables, there was a significant positive correlation between changes in the upper lip protrusion, lower lip protrusion, upper lip thickness, and the distance from the upper and lower lips to the S-line.

Lingual orthodontics in an adult patient with upper premolar extraction: Case report.

OBJECTIVE: To show with this case report that lingual orthodontics can be a solution in complex adult situation and with interdisciplinary approach. MATERIALS AND METHODS: The patient presented a dental and skeletal high angle class II division 1 with a previous extraction of one mandibular incisor. The strategy of treatment was upper first premolar-extraction to obtain a correction of the incisal-class II relationship with a normal lip function, a class II molar relationship on the right side and a class I on the left side. A lingual appliance and miniscrews were used. RESULTS: The lingual orthodontic treatment with miniscrews responded to the occlusal objectives with a good upper incisors torque and retraction control. DISCUSSION: Limits and advantages of lingual orthodontics were discussed. CONCLUSION: Lingual mechanics can provide good results from both an aesthetic and function point of view in adult complex extractions case. It ensures aesthetics during treatment, incisor control during retraction. Miniscrews were also useful to overcome the periodontal limits and enhance the anchorage.

Airway and cephalometric changes in adult orthodontic patients after premolar extractions.

OBJECTIVE: To examine changes in the airway and cephalometric measurements associated with orthodontic treatment of adults with and without premolar extractions. The study investigated whether extractions had a direct or indirect effect on the airway and examined selected skeletal and dental features. MATERIALS AND METHODS: This retrospective study used pre- (T1) and posttreatment (T2) cone-beam computed tomography scans of 83 adult patients matched for age and sex. A total of 15 airway and 10 skeletal and dental measures were analyzed by means of repeated-measures analysis of variance. RESULTS: There were no results showing that extractions affected airway dimensions that could not be accounted for as reflections of measurement error. There was no evidence that extractions affected the airway indirectly through skeletal and dental changes. There were strong and consistent findings that patients with small airways showed larger ones after treatment and that patients with large airways showed smaller ones later. These effects were independent of whether or not extractions were part of treatment. The measurement phenomena of regression toward the mean and of differential unfolding of natural changes over time could have accounted for the results observed. CONCLUSIONS: There was no evidence that extractions in nongrowing patients have negative consequences on the size of various airway measures in the nasopharynx, retropalatal, or retroglossal regions.

Evaluation of the effectiveness of piezocision-assisted flapless corticotomy in the retraction of four upper incisors: A randomized controlled clinical trial.

BACKGROUND: Comprehensive orthodontic treatment may last for 20-24 months. Reducing the treatment time has become a common demand from both patients and orthodontists. Minimally invasive piezocision is one of the suggested approaches to accelerate the orthodontic tooth movement. OBJECTIVES: The aim of this randomized controlled clinical trial was to assess the effectiveness of the flapless piezocision procedure in accelerating the retraction of upper incisors. MATERIAL AND METHODS: A single-blinded, parallel-group randomized controlled clinical trial was conducted at the Department of Orthodontics at the University of Damascus Dental School, Syria. The study involved 42 patients (11 males, 31 females) at the age of 16-31 years (mean age: 19.15 years). The patients had class II division I malocclusion and were treated with fixed appliances using the two-step retraction technique. With an allocation ratio of 1:1, the participants were randomly assigned to either the experimental group (n = 21) or the control group (n = 21) using a computer-generated list of random numbers. Allocation was concealed due to the use of sequentially numbered, opaque, sealed envelopes. The primary outcomes were the rate of incisor retraction (RIR) and the time required for retraction. The outcome assessor was blinded. RESULTS: The data analysis included 20 patients in each group. The rate of incisor retraction significantly increased in the experimental group by 53%, with a significant shortening of the retraction time in the experimental group by 27% (p < 0.001). The rate of anchorage loss was significantly lesser in the experimental group (p < 0.001). Regarding the cephalometric assessment, incisor tipping was significantly greater in the control group than in the experimental group. Skeletal measurements showed insignificant changes following retraction between the 2 groups. CONCLUSIONS: The piezocision procedure was found to be effective in accelerating the retraction of 4 upper incisors, reducing the retraction time, preserving anchorage and enhancing root torque control during retraction.

Effect of soft tissue thickness on the morphology of lip in orthodontic treatment / Efecto del grosor del tejido blando en la morfología del labio en el tratamiento de ortodoncia

The aim of this study was to evaluate the effect of soft tissue thickness of upper lip on lip retraction in orthodonticaltreated females and identify the ratio of maxillary incisor retraction to upper lip retraction. Pre- and post-treatment lateral cephalograms of 100 adults were examined to measure the lip thickness in upper lip and establish the classification standard. All subjects were treated with 4 first premolar extractions followed by upper central incisors retraction. Pre- and post-treatment lateral cephalograms of 19 patients were reviewed to determine the changes of the upper lip and incisor positions through landmarks displacement. An independent-samples t test and one-way analysis of variance were performed. The correlations between maxillary incisor retraction and upper lip retraction were explored by the Pearson correlation method. P-values<0.05 were considered statistically significant. The lip thickness of adult male patients was greater than that of adult female patients. The average ratio of maxillary incisor retraction to upper lip repositioning was 1.6:1,1.9:1 and 2.2:1 in the thin lips group, normal lips group and thick lips group, respectively. Gender differences exist in the thickness of upper lip. Horizontal changes of the maxillary incisor showed a significant correlation to horizontal changes of the upper lip (P<0.001).There were negative correlations between the thickness of upper lip and the ratio between change in maxillary incisor protrusion and change in upper lip protrusion.

El objetivo de este estudio fue evaluar el efecto del grosor de los tejidos blandos del labio superior, sobre la retracción del labio en mujeres tratadas con ortodoncia e identificar la proporción de retracción del diente incisivo maxilar con respecto a la retracción del labio superior. Se examinaron cefalogramas laterales, previos y posteriores al tratamiento de 100 adultos, para medir el grosor del labio superior y establecer un estándar de clasificación. Todos los sujetos fueron tratados con 4 extracciones de los primeros premolares seguidas de retracción de los incisivos centrales superiores. Se revisaron los cefalogramas laterales, previos y posteriores al tratamiento de 19 pacientes, para determinar los cambios del labio superior y las posiciones de los incisivos a través del desplazamiento de los puntos de referencia. Se realizó una prueba t de muestras independientes y un análisis de varianza de una vía. Las correlaciones entre la retracción del incisivo maxilar y la retracción del labio superior se exploraron mediante el método de correlación de Pearson. Los valores de p<0,05 fueron considerados estadísticamente significativos. El grosor de los labios de los pacientes adultos masculinos fue mayor que el de las pacientes adultas. La relación promedio de la retracción del incisivo maxilar al reposicionamiento del labio superior fue de 1,6:1,1; 9:1 y 2,2:1 en el grupo de labios delgados, grupo de labios normales y grupo de labios gruesos, respectivamente. Existen diferencias de sexo en el grosor del labio superior. Los cambios horizontales del incisivo maxilar mostraron una correlación significativa con los cambios horizontales del labio superior (P<0,001). Hubo correlaciones negativas entre el grosor del labio superior y la relación entre el cambio en la protuberancia del incisivo maxilar y el cambio en la protrusión del labio superior.

Effect of incisor retraction on facial aesthetics.

Incisor retraction may result in lip retraction, interlabial gap closure and increase of the nasolabial angle but a clear consensus on the effect of incisor retraction on facial aesthetics has not yet been achieved. Despite current evidence being weak, it seems to indicate that in a well-managed orthodontic case, with or without extractions, the soft-tissue and facial aesthetic changes are generally favourable or clinically insignificant.