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, Ruofang Zhang , Zhuoying Zhang, Chao Geng, Yanpeng ZhangAbstract : Objective: To investigate changes in the immature teeth of Sprague–Dawley rats during orthodontic treatment and to explore the changes in the peri-radicular alveolar bone through micro-computed tomography (CT). Methods: Twenty-five 26-day-old male Sprague–Dawley rats were included. The maxillary left first molar was moved mesially under a continuous force of 30 cN, and the right first molar served as the control. After orthodontic treatment for 7, 14, 21, 28, and 42 days, the root length, tooth volume, and alveolar bone mineral density (BMD) around the mesial root were measured through micro-CT. Results: The immature teeth continued to elongate after application of orthodontic force. The root length on the force side was significantly smaller than that on the control side, whereas the differences in the volume change between both sides were not statistically significant. Alveolar bone in the coronal part of the compression and tension sides showed no difference in BMD between the experimental and control groups. The BMD of the experimental group decreased from day 14 to day 42 in the apical part of the compression side and increased from day 7 to day 42 in the apical part of the tension side. The BMD of the experimental group decreased in the root apex part on day 7. Conclusions: The root length and volume of immature teeth showed continued development under orthodontic forces. Alveolar bone resorption was observed on the compression side, and bone formation was observed on the tension side.
, Ji-Yeon Lee Abstract : Objective: This study aimed to retrospectively analyze the prevalence of orthodontic problems and the proportion of patients who underwent orthodontic diagnosis among children aged 6 (n = 300), 7 (n = 400), and 8 (n = 400) years who had undergone panoramic radiography. Methods: Children were divided into five groups according to their chief complaint and consultation: conservative dentistry, oral and maxillofacial surgery, orthodontics, periodontics, and prosthodontics). Chief complaints investigated included first molar eruption, lack of space for incisor eruption, frequency of eruption problems, lack of space, impaction, supernumerary teeth (SNT), missing teeth, and ectropion eruption. The number of patients whose chief complaint was not related to orthodontics but had dental problems requiring orthodontic treatment was counted. The proportion of patients with orthodontic problems who received an orthodontic diagnosis was also examined. Results: Dental trauma and SNT were the most frequent chief complaints among the children. The proportion of patients with orthodontic problems increased with age. However, the orthodontic diagnosis rates based on panoramic radiographs among children aged 6, 7, 8 years were only 1.5% (6 years) and 23% (7 and 8 years). Conclusions: Accurate information should be provided to patient caregivers to correct misconceptions regarding the appropriateness of delaying orthodontic examination until permanent dentition is established.
, Kelly Chiqueto , Franciele Alberton , Katherine Jaramillo Cevallos , Juliana Faria , Bianca Heck , Leonardo Machado , Pedro Noritomi Abstract : Objective: To evaluate tooth displacement and periodontal stress generated by the dual action vertical intra-arch technique (DAVIT) for open-bite correction using three-dimensional finite element analysis. Methods: A three-dimensional model of the maxilla was created by modeling the cortical bone, cancellous bone, periodontal ligament, and teeth from the second molar to the central incisor of a hemiarch. All orthodontic devices were designed using specific software to reproduce their morpho-dimensional characteristics, and their physical properties were determined using Young’s modulus and Poisson’s coefficient of each material. A linear static simulation was performed to analyze the tooth displacements (mm) and maximum stresses (Mpa) induced in the periodontal ligament by the posterior intrusion and anterior extrusion forces generated by the DAVIT. Results: The first and second molars showed the greatest intrusion, whereas the canines and lateral incisors showed the greatest extrusion displacement. A neutral zone of displacement corresponding to the fulcrum of occlusal plane rotation was observed in the premolar region. Buccal tipping of the molars and lingual tipping of the anterior teeth occurred with intrusion and extrusion, respectively. Posterior intrusion generated compressive stress at the apex of the buccal roots and furcation of the molars, while anterior extrusion generated tensile stress at the apex and apical third of the palatal root surface of the incisors and canines. Conclusions: DAVIT mechanics produced a set of beneficial effects for open-bite correction, including molar intrusion, extrusion and palatal tipping of the anterior teeth, and occlusal plane rotation with posterior teeth uprighting.
, Tony Weir , Elissa Freer , Brett Kerr Abstract : Objective: This retrospective cohort study aimed to assess and compare the accuracy of 3 different Invisalign® treatment regimens in terms of variations of aligner change frequency and type of aligner material in achieving maxillary dental buccal expansion. Methods: Altogether, 120 adult patients whose treatment involved maxillary dental expansion with Invisalign® were included. The patients were divided into 3 groups, with each group comprising 40 patients as follows: SmartTrack® 1-week changes (ST1), SmartTrack® 2-week changes (ST2), and EX30® 2-week changes (EX2). The groups were assessed by comparing actual changes achieved with those prescribed by ClinCheck®. The rates of clinically significant inaccuracies (CSI) observed for buccal expansion (≥ 0.5 mm) and buccolingual inclination (≥ 2°) during expansion were then determined. Results: In terms of expansion, the ST1 group demonstrated the highest CSI rate at all tooth levels, whereas the ST2 group had the lowest rate of CSI and the lowest mean inaccuracy for each tooth level. In terms of buccolingual inclination, the ST1 group had the highest CSI rate across all tooth levels, whereas the EX2 group had the lowest CSI rate at all tooth levels except for the canine level where the ST2 group had the lowest CSI rate. A tendency toward overexpression of buccal crown inclination, and underexpression of buccal expansion was observed at all tooth levels. Conclusions: Two-week aligner change regimens offer improved accuracy compared with 1-week aligner changes. SmartTrack® 2-week changes were the most accurate for buccal expansion, whereas EX30® 2-week changes were the most accurate for buccolingual inclination.
, Hana Pervez, Sidra Maqsood, Wajeeh Syed ZeeshanAbstract : Objective: Pain following the insertion of separators and archwires varies with age, sex, race, ethnicity, threshold, and health status. This study aimed to evaluate the characteristics of pain in orthodontic patients after the insertion of elastomeric separators, its effects on daily life, and its association with age and sex in a population not previously studied in this regard. Methods: A cross-sectional study of 130 patients undergoing orthodontic treatment included collecting data on demographics, pain experienced following the placement of separators, time of onset, duration, characteristics, change in dietary pattern or chewing side, intake of analgesics, and severity of pain on the Wong Baker’s scale. The results are reported as counts and percentages. Associations between sex and age were evaluated using Pearson’s chi-square test. Results: Among the 130 patients, 56.2% were 9–20 years old, 63.8% experienced pain following the insertion of separators, 22.9% had their first episode of pain at 4 hours, 56.6% experienced intermittent pain, and 37.3% experienced discomfort; 18.1% males and 81.9% females experienced pain following the insertion of separators. Pearson’s chi-square test showed a significant association between pain and sex (P = 0.04). Most patients (37.3%) reported “hurts little more” for pain intensity on Wong Baker’s scale and 21.7% reported all four quadrants as sites of pain. Conclusions: The pain experienced after separator insertion was associated with sex and age. Females experienced more pain than males and patients between the age range of 21 and 36 years suffered more pain during mastication than between 9 and 20 years old.
, Jung-Jin Park , Seong-Hun Kim Abstract : Objective: Lingual fixed retainers, made from 0.0175-inch 3-strand twisted stainless steel wire (TW) and 0.016 × 0.022-inch straight rectangular wire (RW), are generally used in clinical practice. This study aimed to calculate their accuracy by comparing the discrepancy between computer-aided customized retainers made from these two types of wires. Methods: Eleven orthodontic patients were selected, resulting in 22 maxillary and mandibular three-dimensional printing dental models. Two types of lingual fixed retainers were bonded from canine to canine. To determine the accuracy, five points were chosen for each model, resulting in 110 selected points. The absolute values of the distances on the x-, y-, and z-axes were measured to compare the accuracy of the two types of computer-aided retainers. Results: The accuracy of the two types of retainers did not differ significantly in the x- and z-axes, but only in the y-axis (P < 0.01), where RW-fixed retainers exhibited a slightly but significantly increased distance compared to the TW. Conclusions: Both types of retainers showed high accuracy; however, RW had a slight but statistically significant difference along the y-axis compared with TW. This type of computer-aided design/computer-aided manufacturing bending machine is limited to two dimensions, and the dental arch is curved. Therefore, RW may require slight manual adjustment by the practitioner after manufacturing.
, Xi Wen , Jing Geng , Yan Gu Abstract : Objective: This study aimed to determine the maxillary and mandibular basal bone regions and explore the three-dimensional positional relationship between the dentition and basal bone regions in patients with skeletal Class I and Class II malocclusions with mandibular retrusion. Methods: Eighty patients (40 each with Class I and Class II malocclusion) were enrolled. Maxillary and mandibular basal bone regions were determined using cone-beam computed tomography images. To measure the relationship between the dentition and basal bone region, the root position and root inclination were calculated using the coordinates of specific fixed points by a computer program written in Python. Results: In the Class II group, the mandibular anterior teeth inclined more labially (P < 0.05), with their apices positioned closer to the external boundary. The apex of the maxillary anterior root was positioned closer to the external boundary in both groups. Considering the molar region, the maxillary first molars tended to be more lingually inclined in females (P = 0.037), whereas the mandibular first molars were significantly more labially inclined in the Class II group (P < 0.05). Conclusions: Mandibular anterior teeth in Class II malocclusion exhibit a compensatory labial inclination trend with the crown and apex relative to the basal bone region when mandibular retrusion occurs. Moreover, as the root apices of the maxillary anterior teeth are much closer to the labial side in Class I and Class II malocclusion, the range of movement at the root apex should be limited to avoid extensive labial movement.
, Youn-Kyung Choi , Yonghun Cho , Yunju Baek , Sung-Hun Kim , Seong-Sik Kim , Soo-Byung Park , Ki Beom Kim , Yong-Il Kim Abstract : Objective: This study aimed to investigate the effect of three-dimensional (3D) printed clear aligners (CA) with different designs on the extrusion of mandibular premolars using a force/moment measurement system and digital image correlation (DIC). Methods: The forces and moments applied to the mandibular canines, first and second premolars were measured using a multi-axis force/moment transducer when an extrusion of 0.5 mm was planned, assuming the mandibular first premolars were intruded by 1 mm. In addition, displacement and strain changes in the CA were analyzed using the DIC method. CA designs were categorized based on the presence of first premolar attachment and subdivided into equigingival margins, 1-mm extended margins, equi-margins with 1-mm thickness and height, and equi-margins with 1-mm reduced buccolingual width. The CA was printed directly at a thickness of 0.5 mm, and the experiments were conducted at 37°C. Results: The results showed that attachment played an important role in the extrusion of first premolars in both the force/moment measurement system and the DIC method. Intrusion was observed without attachment, even though extrusion was planned. CA designs apply greater force to the cervical region by extending the margin or reducing the buccolingual width, thereby improving extrusion efficiency. Conclusions: Force and moment changes in direct 3D printed CA are complex and difficult to predict; however, modifying aligner designs, such as extending the margin or reducing buccolingual width, and using appropriate attachments could minimize unwanted tooth movement, optimize planned treatment, and increase treatment predictability.
, Fatemeh Safari , Allahyar Geramy , Tabassom Hooshmand , Mohammad Javad Kharazifard , Sepideh Arab Abstract : Objective: This study aimed to assess the effects of commonly consumed hot drinks on the force decay of orthodontic elastomeric chains. Methods: This in vitro experimental study evaluated 375 pieces of elastomeric chains with six rings placed on a jig. Four rings were stretched by 23.5 mm corresponding to the approximate distance between the canine and the second premolar. Fifteen pieces served as reference samples at time zero, and 360 pieces were randomized into four groups: control, hot water, hot tea, and hot coffee. Each group was further divided into six subgroups (n = 15) according to the different exposure periods. The specimens in the experimental groups were exposed to the respective solutions at 65.5°C four times per day for 90 seconds at 5-second intervals. The control group was exposed to artificial saliva at 37°C. The force decay of the samples was measured at 1, 2, 7, 14, 21, and 28 days using a universal testing machine. Data were analyzed using repeated-measures analysis of variance. Results: Maximum force decay occurred on day 1 in all groups. The minimum force was recorded in the control group, followed by the tea, coffee, and hot water groups on day 1. At the other time points, the minimum force was observed in the tea group, followed by the control, coffee, and hot water groups. Conclusions: Patients can consume hot drinks without concern about any adverse effect on force decay of the orthodontic elastomeric chains.
2.6
2023 IF
