Effects of different tooth movement patterns and aligner thicknesses on maxillary arch expansion with clear aligners: a three-dimensional finite element study.

Objectives: The objective of this study was to investigate the biomechanical effects of different tooth movement patterns and aligner thicknesses on teeth and periodontal tissues during maxillary arch expansion with clear aligners, to facilitate more precise and efficient clinical orthodontic treatments. Methods: Three-dimensional models including teeth, maxilla, periodontal ligament, and aligner were constructed and subjected to finite element analysis. Tooth displacement trends and periodontal ligament stresses were measured for seven tooth displacement patterns (divided into three categories including overall movement of premolars and molars with gradually increasing molar expansion in each step; distributed movement of premolars and molars; and alternating movement between premolars and molars at intervals) and two aligner thicknesses (0.5 mm and 0.75 mm) during maxillary arch expansion with clear aligners. Results: When expanding the maxillary arch with clear aligners, the effective expansion of the target teeth mainly showed a tilting movement trend. Increasing the amount of molar expansion increased the buccal displacement of the first molar but decreased the buccal displacement of the premolars. The mean buccal displacement of the target teeth was greater in the posterior teeth interval alternating movement group (0.026 mm) than in the premolar/molar distributed movement group (0.016 mm) and the overall movement group (0.015 mm). Increasing aligner thickness resulted in greater buccal displacement of the crowns and increased stress on the periodontal ligaments. Conclusion: Increasing the amount of molar expansion reduces the efficiency of premolar expansion. Alternating movement of premolars and molars at intervals achieves a higher arch expansion efficiency, but attention should be paid to the anchorage of adjacent teeth. Increasing the thickness of the aligner increases the expansion efficiency but may also increase the burden on the periodontal tissues.

The predictability of arch expansion with the Invisalign First system in children with mixed dentition: a retrospective study.

This study aimed to quantify the predictability of arch expansion in children with early mixed dentition treated with the Invisalign First® system and evaluate the clinical factors for the predictability of arch expansion. Pretreatment, predicted and posttreatment digital models from Invisalign's ClinCheck® software were obtained for 90 children with mean (standard deviation) age of 8.42 (0.93) who planned arch expansion. Arch width measurements were collected using Invisalign's arch width table. The predictability of expansion was calculated by comparing the amount of expansion achieved with the predicted expansion. Linear regression analysis was used to evaluate clinical factors associated with predictability of expansion. The predictability of the expansion of the maxillary teeth was as follows: 71.1% primary canines (n = 55), 67.5% first primary molars (n = 46), 65.2% second primary molars (n = 79), and 53.4% first permanent molars (n = 90); the predictability of the expansion of the mandibular teeth was 81.1% primary canines (n = 31), 81.2% first primary molars (n = 51), 77.8% second primary molars (n = 80), and 69.4% first permanent molars (n = 90). The predictability of arch expansion was significantly higher in the mandibular arch compared to the maxillary arch and significantly lower in the permanent first molar than in the other primary teeth. Predictability decreased significantly as the amount of predicted expansion per aligner increased in the upper and lower permanent first molars, primary second molars, and upper primary canines. Predictability significantly increased when buccal or palatal attachments were placed on the bilateral side compared to cases without attachment at the upper permanent first and primary second molars. The predictability of arch expansion using the Invisalign First® system varies according to arch and tooth type. The amount of predicted expansion per aligner and the number of attachments to the maxillary teeth are potential clinical factors that can affect the predictability of expansion.

Effects of upper arch expansion using clear aligners on different stride and torque: a three-dimensional finite element analysis.

BACKGROUND: During maxillary arch expansion with a clear aligner (CA), buccal tipping of the posterior teeth often occurs, resulting in an unsatisfactory arch expansion effect. The aim of this study was to analyze the appropriate maxillary arch expansion stride length and torque compensation angle for maxillary dentition to achieve an ideal moving state when a CA was used for upper arch expansion. METHODS: This study established a three-dimensional (3D) finite element model including a CA, maxilla, periodontal ligament (PDL), and maxillary dentition. The stress distribution, stress situation, expansion efficiency, and movement trends of the maxillary dentition during upper arch expansion of different stride (0.1 mm, 0.2 mm, and 0.3 mm) and torque compensation (0°, 0.5°, 1°, and 1.5°) were measured. RESULTS: Maxillary arch expansion lead to buccal tilt of the posterior teeth, lingual tilt of the anterior teeth, and extrusion of the incisors. As the angle of compensation increased, the degree of buccal tilt on the posterior teeth decreased, with this reducing the efficiency of upper arch expansion. When the stride length was 0.1 mm, the torque compensation was 1.2°, and when stride length was 0.2 mm and the torque compensation was approximately 2°, there was a tendency for the posterior teeth to move bodily. However, when the stride length was 0.3 mm, the increase in torque compensation could not significantly improve the buccal tilt phenomenon. In addition, the equivalent von-Mises stress values of the maxillary root, PDL, and alveolar bone were in the same order of magnitude. CONCLUSIONS: This study indicated that the posterior teeth cause a degree of buccal tilt when maxillary arch expansion is ensured. The specific torque compensation angle should be determined based on the patient's situation and the desired effect.

Treatment effects after maxillary expansion using invisalign first system vs. acrylic splint expander in mixed dentition: a prospective cohort study.

BACKGROUND: Invisalign First System (First) is a new type of orthodontic appliance for maxillary arch expansion in mixed dentition children. Till now, few studies have evaluated the expansion effects of First versus other appliances. What's more, most studies of arch expansion did not include a natural group to rule out growth effects. This prospective cohort study aimed to evaluate the dental and dentoalveolar effects using First or acrylic splint rapid maxillary expander (RME) in adolescents excluding growth factors. MATERIALS AND METHODS: After screening by strict inclusion criteria and propensity score matching (PSM), fifty-one patients were included: First group (n = 17), RME group (n = 17), and natural growth (NG) group (n = 17). Nine indicators including dental arch width, dentoalveolar arch width, and inclination of the molars were measured on digital dental casts at baseline (T0) and six-month follow-up (T1). Paired t-tests were used for intra-group results, and two-sample independent t-tests were used for inter-group comparisons. RESULTS: There was no significant increase in all indicators within six months in the NG group (p > 0.05). In the First group and RME group, all width indicators were significantly increased after treatment (p < 0.05). The RME group exhibited greater expansion than the First group in intercanine width, first interpremolar width, second interdeciduous molar width, first intermolar width, arch perimeter, intercanine dentoalveolar width, intermolar dentoalveolar width, and inclination of the molars (p < 0.05). Whereas, there was no significant difference in arch depth between the two treated groups. CONCLUSIONS: Both First and RME can expand the maxillary arch in mixed dentition. In case of mild to moderate maxillary transverse deficiency (MTD), Invisalign First System could be a reasonable option. RME shows significant better efficiency of dental arch expansion than First, recommended for patients with severe MTD. TRIAL REGISTRATION: This prospective study was registered on ClinicalTrials.gov (01/02/2022, registration number: ChiCTR2200056220). The trial was approved by the Ethical Committee of the Hunan Xiangya Stomatological Hospital Central South University (20,200,088), and informed consent was obtained from all subjects and their legal guardian(s).

Improvements of tooth movement efficiency and torque control in expanding the arch with clear aligners: a finite element analysis.

Objectives: The purpose of this study was to analyze the effect of different movement strategies, embossment structures, and torque compensation of the aligner on tooth movement during arch expansion using clear aligners by finite element analysis. Methods: Models comprising the maxilla, dentition, periodontal ligament, and aligners were created and imported into a finite element analysis software. The tests were performed using the following: three orders of tooth movement (including alternating movement with the first premolar and first molar, whole movement with second premolar and first molar or premolars and first molar), four different shapes of embossment structures (ball, double ball, cuboid, cylinder, with 0.05, 0.1, 0.15-mm interference) and torque compensation (0°, 1°, 2°, 3°, 4°, and 5°). Results: The expansion of clear aligners caused the target tooth to move obliquely. Alternating movement resulted in higher movement efficiency with lower anchorage loss as compared with whole movement. Embossment increased the efficiency of crown movement but did not contribute positively to torque control. As the angle of compensation increased, the tendency of oblique tooth movement was gradually controlled; however, the movement efficiency decreased concurrently, and stress distribution on the periodontal ligament became more even. For each 1° increase in compensation, the torque per millimeter of the first premolar would decrease by 0.26°/mm, and the crown movement efficiency eliminate decreased by 4.32%. Conclusion: Alternating movement increases the efficiency of the arch expansion by the aligner and reduces anchorage loss. Torque compensation should be designed to enhance torque control in arch expansion using an aligner.

Long-Term Assessment of Periodontal Tissues after Corticotomy-Assisted Orthodontic Arch Expansion.

OBJECTIVES: The aim of the study was the long-term assessment of the condition of periodontal tissues after corticotomy-assisted orthodontic expansion in patients with transverse maxillary deficiency. MATERIALS AND METHODS: The study included a group of 18 adults (9 women, 9 men) aged between 24 and 40 years who were at least 5 years post treatment. The following parameters were assessed: the full mouth plaque index (FMPI), full mouth bleeding on probing (FMBOP), probing depth (PD), clinical attachment level (CAL), gingival recession height (GR), recession width (RW), papilla height (PH), papilla width (PW), bone sounding (BS), phenotype, and KT. RESULTS: During examination performed at least 5 years after the completion of orthodontic treatment, the values of PD and CAL were found to be considerably decreased compared to the examination one year post treatment (PD: -0.23; 95% Cl: -0.29, -0.16) (CAL: -0.04; 95% Cl: -0.17, 0.10). The other parameters-FMPI, FMBOP, GR, RW, PH, PW, BS, phenotype, and KT-did not change significantly. CONCLUSIONS: Corticotomy-assisted orthodontic arch expansion does not have a negative effect on the periodontium in long-term observations. CLINICAL RELEVANCE: Orthodontic arch expansion can lead to bone dehiscence and gingival recession. Long-term observations revealed that corticotomy-assisted orthodontic expansion of the upper arch is not followed by negative changes in periodontal status.

Displacement and stress distribution of the craniomaxillofacial complex under different surgical conditions: a three-dimensional finite element analysis of fracture mechanics.

OBJECTIVE: To provide a simplified treatment strategy for patients with maxillary transverse deficiency. We investigated and compared the fracture mechanics and stress distribution of a midline palatal suture under dynamic loads during surgically-assisted rapid palatal expansion. METHODS: Based on the cone-beam computed tomography (CBCT) data of a 21-year-old female volunteer, a three-dimensional model of the cranio-maxillofacial complex (including the palatal suture) was constructed. A finite element analysis model was constructed based on meshwork. After the yield strength of the palatal suture was set, an increasing expansion force (0-500 N) was applied within 140 ms to calculate the time-load curve, which mimicked nonsurgical bone expansion (model A). The same method was used to evaluate the fracture process, time and stress distribution of the palatal suture in maxillary lateral osteotomy-assisted (model B) and LeFort osteomy I (LFIO)-assisted expansion of the maxillary arch (model C). RESULTS: Compared with model A, the palatal suture of model B and model C showed a faster stress accumulation rate and shorter fracture time, and the fracture time of model B and model C was almost identical. Compared with model A, we discovered that model B and model C showed greater lateral extension of the maxilla, and the difference was reflected mainly in the lower part of the maxilla, and there was no difference between model B and model C in lateral extension of the maxilla. CONCLUSIONS: Compared with arch expansion using nonsurgical assistance (model A), arch expansion using maxillary lateral wall-osteotomy (model B) or LFIO had a faster rate of stress accumulation, shorter time of fracture of the palatal suture and increased lateral displacement of the maxilla. Compared with arch expansion using LFIO (model C), arch expansion using lateral osteotomy (model B) had a similar duration of palatal suture rupture and lateral maxillary extension. In view of the trauma and serious complications associated with LFIO, maxillary lateral wall-osteotomy could be considered a substitute for LFIO.

Achondroplasia from the viewpoint of orthodontics / Az achondroplasia a fogszabályozás szemszögébol.

Összefoglaló. Az achondroplasia kialakulásáért az FGFR3-gén mutációja teheto felelossé, mely a porc növekedési lemezében található chondrocyták érésében okoz zavart. Az esetbemutatásban szereplo lánygyermeknél a születést követo elso hónapban a klinikai, laboratóriumi és röntgenvizsgálatok alapján achondroplasia igazolódott. A klinikai tünetek közé tartoznak a rövid végtagok - különösen a proximalis szegmensben -, a macrocephalia, a hypotonia és a horkolás. Szembetuno a középarc hypoplasiája. A középfül diszfunkciója tovább súlyosbítja a kórképet, sok esetben megfigyelheto a hallás nagyfokú csökkenése, illetve kezelés hiányában akár a hallás elvesztése. A közlemény részletesen bemutatja az obstruktív alvási apnoe szindróma diagnózisrendszerét és kezelési alternatíváit, hangsúlyozva az orthodontiai szempontokat. A fül-orr-gégészeti és a fogszabályozó terápiának köszönhetoen, a diagnózistól számított harmadik évre, az alvási apnoe szindróma megszüntetésével a folyamatos pozitív nyomású lélegeztetést el lehetett hagyni. A horkolás és az alvási apnoe szindróma kezelése napjainkban egyre nagyobb hangsúlyt kap, melynek komplex kezelésében a fogszabályozás is jelentos lehet. A harmonikus együttmuködés és teamkezelés betegünknél jelentos életminoség-javulást eredményezett. Orv Hetil. 2021; 162(17): 683-688. Summary. Development of achondroplasia is due to the mutation of FGFR3 gene, which disrupts the maturation of chondrocytes found in the growth plate. The diagnosis of the girl in the present case study was established based on clinical symptoms, laboratory tests and X-ray imaging in the first month following childbirth. Clinical symptoms include shorter limbs especially in the proximal segments, macrocephaly, hypotonia and snoring. Hypoplasia of the midface is apparent. Dysfunction of the middle ear further worsens the condition, in many cases severe hearing loss and, without treatment, even deafness can be observed. The publication describes the diagnostic criteria and therapeutic options of obstructive sleep apnea syndrome in detail, with an emphasis on the orthodontic aspects. A comprehensive combined three-year oto-laryngological and orthodontic treatment finally succeeded in controlling the sleep apnea syndrome and it was possible to discontinue the continuous positive airway pressure therapy by the end of the orthodontic therapy. Nowadays, even more alternative therapeutic approaches are available to treat snoring and sleep apnea syndromes, in which the role of orthodontics must not be neglected. Harmonic collaboration and team work treatment resulted in a significant improvement in the quality of life of our patient. Orv Hetil. 2021; 162(17): 683-688.

The biomechanics of posterior maxillary arch expansion using fixed labial and lingual appliances.

OBJECTIVE: To compare the biomechanics of straight labial, straight lingual, and mushroom lingual archwire systems when used in posterior arch expansion. MATERIALS AND METHODS: An electro-mechanical orthodontic simulator allowing for buccal-lingual and vertical displacements of individual teeth and three-dimensional force/moment measurements was instrumented with anatomically shaped teeth for the maxillary arch. In-Ovation L brackets were bonded to lingual surfaces, and Carriere SLX brackets were bonded to labial surfaces to ensure consistency of slot dimensions. Titanium molybdenum archwires were bent to an ideal arch form, and the teeth on the orthodontic simulator were set to a passive position. Posterior teeth from the canine to second molar were moved lingually to replicate a constricted arch. From the constricted position, the posterior teeth were simultaneously moved until the expansive force decreased below 0.2 N. Initial force/moment systems and the amount of predicted expansion were compared for posterior teeth at a significance level of α = 0.05. RESULTS: Archwire type affected both the expected expansion and initial force/moment systems produced in the constricted position. In general, the lingual systems produced the most expansion. The archwire systems were not able to return the teeth to their ideal position, with the closest system reaching 41% of the intended expansion. CONCLUSIONS: In general, lingual systems were able to produce greater expansion in the posterior regions when compared with labial systems. However, less than half of the intended arch expansion was achieved with all systems tested.

Transverse dentoalveolar response of mandibular arch after rapid maxillary expansion (RME) with tooth-borne and bone-borne appliances.

OBJECTIVES: To assess and compare spontaneous expansion of mandibular posterior teeth between tooth-borne (TB) and bone-borne (BB) rapid maxillary expansion (RME). MATERIALS AND METHODS: This study included 36 adolescents with bilateral maxillary crossbite receiving tooth-borne (average age: 14.4 ± 1.3 years) or bone-borne (average age: 14.7 ± 1.4 years) maxillary expansion. Cone beam computed tomography was acquired before expansion (T1) and after 6 months' retention (T2). Specific linear and angular measurements were performed in the coronal view to assess buccal inclinations and widths of mandibular posterior units. All data were statistically analyzed. RESULTS: In both groups there was a significant increase in buccal-lingual inclination of mandibular posterior teeth ranging from 1.67° to 2.30° in the TB group and from 1.46° to 2.11° in BB group. Mandibular posterior widths showed an increase ranging from 0.80 mm to 1.33 mm in TB group and from 0.64 mm to 0.96 mm in the BB group. No differences between groups were found for linear or angular measurements. CONCLUSIONS: A clinically significant gain of space in the mandibular arch should not be expected after RME.

Comparison of Mandibular Arch Expansion by the Schwartz Appliance Using Two Activation Protocols: A Preliminary Retrospective Clinical Study.

BACKGROUND AND OBJECTIVES: Dental crowding is more pronounced in the mandible than in the maxilla. When exceeding a significant amount, the creation of new space is required. The mandibular expansion devices prove to be useful even if the increase in the lower arch perimeter seems to be just ascribed to the vestibular inclination of teeth. The aim of the study was to compare two activation protocols of the Schwartz appliance in terms of effectiveness, particularly with regard to how quickly crowding is solved and how smaller is the increasing of vestibular inclination of the mandibular molars. MATERIALS AND METHODS: We compared two groups of patients treated with different activation's protocols of the lower Schwartz appliance (Group 1 protocol consisted in turning the expansion screw half a turn twice every two weeks and replacing the device every four months; Group 2 was treated by using the classic activation protocol-1/4 turn every week, never replacing the device). The measurements of parameters such as intercanine distance (IC), interpremolar distance (IPM), intermolar distance (IM), arch perimeter(AP), curve of Wilson (COW), and crowding (CR) were made on dental casts at the beginning and at the end of the treatment. RESULTS: A significant difference between protocol groups was observed in the variation of COWL between time 0 and time 1 with protocol 1 with protocol 1 subjects showing a smaller increase in the parameter than protocol 2 subjects. The same trend was observed also for COWR, but the difference between protocol groups was slightly smaller and the interaction protocol-by-time did not reach the statistical significance. Finally, treatment duration in protocol 1 was significantly lower than in protocol 2. CONCLUSION: The results of our study suggest that the new activation protocol would seem more effective as it allows to achieve the objective of the therapy more quickly, and likely leading to greater bodily expansion.

Comparison of effectiveness of quad helix appliance with other slow maxillary expanders in children with posterior crossbite: A systematic review.

OBJECTIVE: The present review was conducted to compare the effectiveness of Quad Helix (QH) appliance with other slow maxillary expanders in children with posterior crossbite. MATERIALS AND METHODS: Randomized controlled clinical trials and retrospective studies published between January 1, 1995, and December 31, 2016, were identified from MEDLINE, the Cochrane Central Register of Controlled Trials, the National Institutes of Health Trials, Clinical Trials Registry India, Google Scholar and major journals. After a comprehensive search, the articles were independently screened for eligibility by two reviewers. All cross-reference lists of the selected studies were screened for any additional papers. RESULTS: The preliminary screening consisted of 608 articles, of which 33 articles were selected. A final total of only 9 articles were included as they met the inclusion and exclusion criteria. Of the nine papers, four articles clearly state that QH appliance was a more effective appliance, while the remaining five studies suggest that the maxillary expansion caused by QH is comparable to other slow maxillary expansion appliances. Of the nine included articles, four articles also describe the complications of QH in comparison to other slow maxillary expansion devices. CONCLUSION: The QH appliance is a viable alternative for the correction of posterior crossbite. The QH appliance is comparable to or even better than other slow maxillary expanders in terms of maxillary expansion while being cost-effective with very few complications.

Adjustable selective maxillary expansion combined with one-stage maxillomandibular surgery: A prospective study of osseous widening in fifty-five consecutive patients.

OBJECTIVE: SARME is often considered to be the only available treatment for significant or severe maxillary transverse palatal deficiencies (MTD) in skeletally-mature patients. Despite this observation, the aim of our study was to assess a new type of maxilla distraction osteogenesis. Using two innovative tools, we performed selective expansion: the site to be widened and the amount of increase were both pre-selected. Patients were treated in a single maxillomandibular procedure. Our study focuses primarily on the extent of osseous widening. STUDY DESIGN: Post-expansion computed tomography data from 55 non-syndromic patients were included in a prospective study and analyzed in two planes for transverse skeletal widening. Of the 55 patients, 16 underwent isolated posterior distraction for severe posterior endognathia (group I), and 39 were treated in both segments (group II). Diastemas and anterior spaces permitted resolution of crowding and patients with a small, narrow, tapering arch were given a more rounded form. All patients underwent a complete Le Fort I with down fracture. Two novel devices were used: first, an adjustable distractor to achieve an angular opening; and secondly, in group II, new modular plates interlocked for osteosynthesis to provide stability and anterior expansion. RESULTS: In group I, analysis of the width of the gain showed significant posterior values decreasing from back to front, a result never achieved with the SARME procedure. The mean osseous gain at first molars was 7.1 mm. When anterior space was required in group II, it was created as wide as needed (mean 4.2 mm, at canine level) with good preservation of the 1st molar space gain (mean 6.8 mm). CONCLUSION: Total Le Fort I osteotomy associated with two innovative devices provides a new, segmental and adaptable approach for transverse distraction osteogenesis. We demonstrate a good match with the dental enlargement required. All patients were managed in a single orthognathic procedure for all the anomalies to be treated. Long-term results show good stability.

Comparative study on the influence of two kinds of different self-locking brackets on the dental arch shape change in non-extraction patients / 口腔疾病防治

Objective@# By analyzing changes of dental arch width and length during the aligning and leveling period (non-extraction case) with two kinds of self-locking bracket, compare the difference between the active self-locking bracket with the passive bracket.@*Methods@#The data of dental arch perimeter change amount and dental arch width and length change amount (WU/L3, WU/L4, WU/L5, WU/L6, U/LL) were statistically analyzed using the correlation and regression method by comparing active and passive brackets for the correction of dental arch variations. Two different brackets for the correction of the measured values of the dental arch variations was analyzed by t-test. Results There were statistical relationships between the amount of arch perimeter increase and the amount of width and length increase. The regression equation was statistically significant (P < 0.05), It was greater impacted arch width increase to arch perimeter in the self-locking. The t-test results showed WU3, WL3, WL6, LR 4 measured values (P < 0.05) statistically significant in the active self-locking group and passive group. @*Results @#There were statistical relationships between the amount of arch perimeter increase and the amount of width and length increase. The regression equation was statistically significant (P < 0.05), It was greater impacted arch width increase to arch perimeter in the self-locking. The t-test results showed WU3, WL3, WL6, LR 4 measured values (P < 0.05) statistically significant in the active self-locking group and passive group. @*Conclusin @#Active and passive self-locking bracket have good arch expansion effecting. The active self-locking bracket is slightly dominant than the passive bracket in the expansion of the canine width whereas the active self-locking bracket is better than the passive in the expansion of the mandibular first molar and arch perimeter which should be widely applied to the appropriate cases.

The Effects of Quick Self-ligating System on Enlarging Maxillary and Alveolar Arch / 昆明医科大学学报

Objective To analyze the effects of self-ligating bracket on enlarging the maxillary alveolar arch and to investigate the the non-extraction treatment programs.Methods All patients were used heat activated basic and precise theory for the orthodontist in order to make a plan fordeveloping nickel-titanium wire,then assessed by occlusalplane analysis method.The maxillary model andcephalometric radiographs were collected and measured before the treatment.The data of the resultswereanalyzed.Results After the treatment,the increase of the width of the dental arch was related to the /FMA,crowding degree and canines initial position.The increase of arch length was related to the ∠ANB,crowding degree,malocclusion classification,canines initial position andthe second molar eruption.Conclusion The essential factors include the crowding degree of arch,∠FMA,∠ANB,the angle of the anterior teeth,malocclusion classification,canines initial position andthe second molar eruptioncan affect the result of non-extraction quick self-ligating bracket appliance treatment on enlarging the maxillary alveolar.

Changes of maxillary teeth and maxilla following quad helix maxillary expansion observed by Cone-Beam CT (CBCT) / 实用口腔医学杂志

Objective:To evaluate dental and skeletal changes following slow maxillary expansion with quad helix using Cone-Beam computer tomography (CBCT).Methods:13 patients(5males and 8 females,mean age 14.38 ±2.22 years)requiring maxillary ex-pansion as a part of their comprehensive orthodontic treatment were included.Each patient had CBCT images taken pre-(T1 )and post-(T2)maxillary expansion with quad helix.Changes of the distances between bilateral canines,first premolars,second premo-lars,first molars,the width of basal bone and palatal suture were measured.paired t-test results were analyzed using SPSS 17.0 soft-ware.Results:The distances between the 4 bilateral teeth increased by (2.47 ±1.05)mm,(2.97 ±1.90)mm,(2.79 ±1.21) mm and (3.15 ±1.15)mm,the apical distances decreased by (1.19 ±0.40)mm,(2.12 ±0.68)mm,(2.02 ±0.65)mm and (1.34 ±0.63)mm,respectively.The inclination of the first molars were decreased by (4.45 ±2.86)°and (4.02 ±1.45)°on the left and right side respectively.The width of basal bone and palatal suture increased by (2.37 ±0.96)mm and (1.21 ±0.50)mm respectively,the differences between T1 and T2 were all statistically different(P <0.001).Conclusion:Quad helix expands maxil-lary arch by greater dental changes than by skeletal changes.

An assessment of conventional and self-ligating brackets in Class I maxillary constriction patients.

OBJECTIVE: To evaluate two different treatment systems with regard to incisor position, transverse dimension changes in maxillary arch, changes in maxillary molar inclinations, clinical periodontal parameters, and pain intensity in patients with a Class I malocclusion. MATERIALS AND METHODS: Seventeen patients (with a mean age of 14.5 years) underwent orthodontic treatment with the Roth prescribed edgewise bracket systems after expanding the maxillary arch with a quad-helix appliance, and 16 patients (with a mean age of 14.8 years) underwent orthodontic treatment with the Damon 3MX bracket system. Each subject's lateral cephalometric and posteroanterior radiographs and dental casts were obtained at the beginning of the treatment and after debonding. In addition to these, the periodontal index and pain scores were taken. RESULTS: Cephalometric data showed that in both treatment systems, overjet value decreased and maxillary and mandibular incisors proclined. Posteroanterior measurements demonstrated a greater increase in the maxillary molar inclination in the Damon group. Significant increase of maxillary intercanine, interpremolar, and intermolar widths was shown in both systems. Periodontal index and pain score changes between different observation periods were the same. CONCLUSIONS: The conventional and Damon systems were found similar with regard to the incisor position, transverse dimension changes in maxillary arch, clinical periodontal parameters, and pain intensity. The only significant difference was that the Damon system inclined the maxillary molars more buccally than the conventional group.

Long-term effect of quad helix expansion of dental arch*☆ / 中国组织工程研究

BACKGROUND: Rapid expansion of the dental arch is an effective way to rapidly expanse the jaw. Compared with rapid expansion, the slow expansion has higher stability and less recurrence, but the reports on the long-term stability of quad helix expansion are rare. OBJECTIVE: To retrospectively analyze the clinical effect of quad helix expansion in orthodontics. METHODS: Twenty-two subjects with dental arch stenosis in mixed dentition and early permanent dentition who experienced an expansion of at least 3 mm with quad helix appliance were selected for this study. Plaster dental casts and posteroanterior radiographs were evaluated at the beginning of the treatment (T1), at the completion of phase I quad helix expansion or ful treatment (T2), and approximately 2 years fol owing the completion of treatment (T3). The distance between two first molars was measured on the model. J point was drawn on the posteroanterior radiograph in order to measure the distance between the bilateral base bones and the molar inclination, as wel as to evaluate the corrective and orthopedic effects of dental arch expansion. RESULTS AND CONCLUSION: Compared with that before expansion, the first permanent molar inclination and the distance between base bones on two sides were significant increased after quad helix expansion; there were no significant differences in the distance between two first permanent molars, first permanent molar inclination and the distance between bilateral base bones on two sides when compared after quad helix expansion and after 2-year fol ow-up (P > 0.05). The results indicate that the long-term effect of quad helix expansion is stable with orthopedic effect.

Correction of Angle Class Ⅱ division 2 malocclusion with upper/lower arch expansion and Class Ⅱ elastics in adults / 实用口腔医学杂志

Objective:To study the effects of treatment of Angle Ⅱ division 2 malocclusion with upper/lower arch expansion and Class Ⅱ elastics in adults. Methods:Expanding upper/lower arch and Class Ⅱ elastic were used to treat Angle Class Ⅱ division 2 malocclusion in 15 adults. Study models and cephalograms were analyzed before and after treatment. Results:Before and after treatment the maxillary variables of cephalograms showed no significant differences, the mandibular variables showed significant differences in sagittal and vertical direction. U1-NA, U1-PP, L1-NB, L1-MP, U1-L1 and L6-Ptm were significantly increased after treatment(P