Tip, torque and rotation of maxillary molars during distalization using Invisalign: a CBCT study.

BACKGROUND: Desirable molar distalization by bodily movement is challenging and can be difficult to achieve. This study investigated changes in molar angulation (mesiodistal tipping), molar inclination (buccolingual torque) and rotation during distalization using clear aligner therapy (CAT). MATERIALS AND METHODS: This retrospective study included 38 cone beam computed tomographic images (CBCTs) taken for patients treated with molar distalization using CAT. The study evaluated pre- (T0) and post-treatment (T1) CBCTs of 19 adult patients (36.68 ± 13.50 years) who underwent maxillary molar distalization using Invisalign® aligners (Align Technology, Inc., San José, CA, USA) with a minimum of 2 mm distalization. Changes in maxillary molar tip, torque and rotation were measured for 61 molars (183 roots). Paired t-test was used to evaluate the differences between pre- and post-treatment readings. The level of significance was set at p ≤ 0.05. The reproducibility of measurements was assessed by the intraclass correlation coefficient (ICC). RESULTS: Molar angulation did not show significant change after distalization (p = 0.158) however, there was significant increase in buccal molar inclination (p = 0.034) and mesiobuccal molar rotation (p < 0.001). CONCLUSION: Molar distalization of 2 mm did not cause significant molar tipping. Maxillary molars showed significant buccal inclination (increased torque) and mesiobuccal rotation after distalization.

Evaluation of Mandibular Projection in Class II Division 2 Subjects Following Orthodontic Treatment Using Clear Aligners.

AIM: The purpose of this study was to evaluate the mandibular growth and/or projection following maxillary incisor proclination, overbite correction, and maxillary dentoalveolar expansion without the use of any class II mechanics, in growing class II division 2 patients treated with clear aligners. MATERIALS AND METHODS: Before and after treatment cone-beam computed tomographic (CBCT) generated lateral and posteroanterior cephalograms of thirty-two patients with skeletal class II division 2, 16 in the treatment group and 16 in the untreated group, were reviewed to evaluate treatment-related changes. Upper incisors were proclined and protruded, as well as upper arch expansion and overbite correction were performed as part of their regular treatment. Cephalometric analysis was performed to evaluate skeletal and dental changes. Unpaired statistical t-tests were performed to determine if significant skeletal class II correction was achieved in the treatment group. RESULTS: In the treatment group, after treatment, the upper incisors became more proclined and protruded, and the inter-molar width increased while the overbite was reduced compared to the control group. An increase in skeletal mandibular growth and forward projection was also observed, thus contributing to an improvement of the sagittal skeletal relationship as evidenced by ANB and Wits values compared to the control group. CONCLUSION: A combination of upper incisor proclination, correction of deep overbite, and maxillary dentoalveolar expansion using clear aligners appears to contribute to an improvement of the skeletal class II relationship in growing patients with class II division 2. CLINICAL SIGNIFICANCE: This study shows that unlocking the mandible by correcting a deep overbite, proclining upper incisors, and expanding the upper arch in growing class II division 2 patients can improve skeletal class II using clear aligners. How to cite this article: Mirzasoleiman P, El-Bialy T, Wiltshire WA, et al. Evaluation of Mandibular Projection in Class II Division 2 Subjects Following Orthodontic Treatment Using Clear Aligners. J Contemp Dent Pract 2024;25(4):295-302.

Positional, morphologic, and volumetric differences in TMJ in unilateral posterior crossbites and controls: A retrospective CBCT study.

OBJECTIVES: The objective of this study was to evaluate if there are any morphologic, positional, and volumetric differences in the temporomandibular joint (TMJ) of patients with unilateral posterior crossbite (UPC) compared to controls. Another objective was to analyse the discrepancy in the TMJ between the crossbite versus non-crossbite side in UPC versus right and left sides in controls. Additionally, this study aimed to evaluate the differences in the bone density at the masseteric insertion site at the angle of mandible in the UPC group and control group. MATERIAL AND METHODS: One hundred and thirty-two CBCTs were analysed with 66 patients in UPC group and 66 patients in control group (non-crossbite). Temporomandibular joint spaces - Anterior joint space (AJS), Superior joint space (SJS), Posterior joint space (PJS), Medial joint space (MJS), Middle joint space (MiJS), and Lateral joint space (LJS) were measured. Additionally, bone density at angle of mandible and volume of mandibular condyle were evaluated. The measurements were compared between the groups as well as between the crossbite and non-crossbite sides within the UPC group and between right and left sides within the control group. Furthermore, the associations between UPC and changes in TMJ regarding joint space availability, bone density, condylar head volume, and the effects of sex and age were evaluated using regression analysis. RESULTS: It was observed that UPC group showed a greater condylar volume, than the control group. Additionally, a larger mean discrepancy was observed between the crossbite side and non-crossbite side within the UPC group concerning condylar volume than controls. Concerning age, condylar volume was observed to be larger in adults than children. Adults showed significantly greater bone density and condylar volume than adolescents. Concerning sex, it was observed that males showed a larger SJS (right), MiJS, LJS, and bone density at the mandibular angle than females. CONCLUSION: There is a difference in the TMJ parameters particularly condylar volume in patients with UPC compared to controls.

The Effect of Low-Intensity Pulsed Ultrasound on Temporomandibular Joint Arthritis in Juvenile Rats.

Juvenile idiopathic arthritis is an inflammatory disease that can affect the temporomandibular joint (TMJ) and lower jaw growth. Better treatment options are needed, so this study investigated the effect of low-intensity pulsed ultrasound (LIPUS) on TMJ arthritis. Seventy-two 3-week-old male Wistar rats were in vivo microcomputed tomography (micro-CT) scanned and divided into eight groups (n = 9). These groups were Group 1-TMJ arthritis and immediate LIPUS treatment (20 min/day, 4 weeks); Group 2-immediate LIPUS treatment and no TMJ arthritis; Group 3-TMJ arthritis and no LIPUS; Group 4-no TMJ arthritis and no LIPUS; Group 5-TMJ arthritis and LIPUS treatment with a delayed start by 4 weeks; Group 6-Delayed LIPUS and no TMJ arthritis; Group 7-TMJ arthritis and no (delayed) LIPUS; and Group 8-no TMJ arthritis and no (delayed) LIPUS. Ex vivo micro-CT scanning was completed, and samples were prepared for tissue analysis. Synovitis was observed in the TMJ arthritis (collagen-induced arthritis [CIA]) groups, but the severity appeared greater in the groups without LIPUS treatment. Fibrocartilage and hypertrophic cell layer thicknesses in the CIA group without LIPUS treatment were significantly greater (p < 0.05). Proteoglycan staining appeared greater in the LIPUS groups. Immediate LIPUS treatment increased the expression of type II collagen, type X collagen, and transforming growth factor-beta 1 (TGF-ß1) immunostaining, and CIA (no LIPUS) increased MMP-13, vascular endothelial growth factor, and interleukin-1 beta (IL-1ß) immunostaining. LIPUS treatment prevented growth disturbances observed in the CIA groups (no LIPUS) (p < 0.005). Our results have contributed to the understanding of the uses and limitations of the CIA juvenile rat model and have demonstrated the effects of LIPUS on the TMJ and mandibular growth. This information will help in designing future studies for investigating LIPUS and TMJ arthritis, leading to the development of new treatment options for children with juvenile arthritis in their TMJs.

An evaluation of root resorption associated with the use of photobiomodulation during orthodontic treatment with clear aligners: a retrospective cohort pilot study.

OBJECTIVES: To evaluate the change in tooth root volume using cone-beam computed tomography (CBCT) in a group of patients treated concurrently with clear aligners and an adjunctive photobiomodulation (PBM) device. MATERIALS AND METHODS: This retrospective cohort pilot study included the records of 32 consecutively treated clear aligner patients (23 female, 9 male) from the private practice of one orthodontist. The PBM group (n = 16) used the device once per day for 5 minutes per arch and was compared with a matched control group (n = 16). A semiautomated segmentation technique was used to obtain tooth volume of anterior teeth from CBCT imaging prior to (T0) and during or immediately following (T1) orthodontic treatment with clear aligners. The change in root volume between time points was assessed. RESULTS: There was no statistically significant difference between the pre- and posttreatment root volumes of maxillary and mandibular anterior teeth, regardless of which intervention group the patient belonged to (P > .05). There was also no difference in the mean percentage change in root volume between clear aligner patients in this study who were treated with the PBM device compared with a matched control group (P > .05). CONCLUSIONS: Clear aligner patients in this study who changed their aligners every 3 to 5 days and used adjunctive photobiomodulation therapy did not experience clinically relevant orthodontically induced external root resorption. Due to the small sample size and measurement error in the root segmentation process, the results should be interpreted with caution.

Impact of clear aligner therapy on speech: does clear aligner therapy cause any speech difficulty?

DATA SOURCES: Electronic search was conducted up to September 2021 in three electronic databases including Scopus, Web of Science, and EMBASE. Only studies in English language were selected. STUDY SELECTION: Prospective and retrospective studies including cohort, cross-sectional, randomized control trials, and qualitative studies were included. Both the inclusion and exclusion criteria were reported. The search in the databases and the selection of the studies were performed independently by two reviewers. The included studies assessed the effects of clear aligner therapy on the speech difficulty. DATA EXTRACTION AND SYNTHESIS: Data extraction was performed independently by two reviewers. The data from the relevant studies were extracted into a customized Template. The systematic review was carried out and reported based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines. Details regarding the authors, year of publication, sample size, included participants, age, groups, outcome assessment, results, and inferences were extracted from the selected studies. The quality of the selected studies was assessed based on the relevant guidelines from Cochrane Handbook for Systematic Reviews. The criteria examined sequence generation, allocation concealment, blinding, outcome data, selective reporting, and other sources of bias. Non-randomized studies were assessed using the ROBINS-I tool (Risk of Bias in Non-randomized studies). The strength of evidence was assessed by the evidence grading system developed by the GRADE collaboration as described in the Cochrane Handbook for Systematic Reviews of Interventions. RESULTS: The search identified 283 results. 269 articles were excluded based on their title and abstract after evaluation against the inclusion criteria. 14 articles were assessed in full text. Finally, 7 papers were included in the qualitative analysis. The included studies were 5 cohort studies and 2 randomized clinical studies. 332 patients were examined in the included studies. There were 195 females and 137 males. 191 patients were treated using clear aligner therapy (CAT) while 122 patients were treated using labial fixed appliances and 19 patients were treated using lingual orthodontic treatment. Out of the 191 patients who were treated using CAT, 179 patients were treated using Invisalign (Santa Clara, CA, USA) while 12 patients were treated using Smile Align (Mumbai, India). All seven selected studies examined speech dysfunction. The speech difficulty was assessed through two tools - semiobjective assessment by speech pathologists and professionals and subjective evaluations by the patients themselves through a patient questionnaire that assess the effects of aligners on speech. The risk of bias assessment revealed that two studies had moderate risk of bias while five articles had serious risk of bias. Meta-analysis was not performed due to the high heterogeneity of the included studies. The level of evidence was assessed as low due to the methodological insufficiencies and risk of bias in the included studies. The results showed that both CAT and fixed appliances (FA) resulted in speech difficulties in terms of clarity and delivery of speech that include speech alteration, slurring of words, lisping, and nasality. Some patients who were treated using CAT reported impairment in the lingual space that affected their speech. Lingual FA resulted in more speech difficulty when compared to labial FA and CAT. Aligners caused errors in the articulation of /s/,/z/,/zh/,/sh/,/th/,/ch/. Acoustic analysis revealed /s/ sound appeared most affected. Aligners had an effect on speech while reading, with patients slowing down to their speed to better articulate. The above-mentioned speech difficulties were transient. The included patients normalized their speech within 7-14 days from start of treatment while few patients took 30-60 days to recover. CONCLUSIONS: Although the likelihood of speech difficulties would be high with CAT, the current evidence states that speech difficulties shown with CAT are similar to those found with FA. However, the patients who were treated using CAT adapt quickly and speech recovers within a few weeks. Time to recovery varied greatly, ranging from a week to two months in certain cases.

Does short-term treatment with clear aligner therapy induce changes in muscular activity?

DESIGN: Prospective cohort study. COHORT SELECTION: The inclusion criteria comprised patients older than 18 years who attended the orthodontic department at the University of L'Aquila (L'Aquila, Italy) and requested treatment with clear orthodontic appliance. Only patients with Class I malocclusion with mild (0-3 mm) or moderate (4-6 mm) crowding were included. The exclusion criteria comprised patients who had medical condition that preclude the use of surface EMG (sEMG), patients who had anterior or posterior open bite, patients who had cross bite that include more than one tooth, patients who had edentulous ridges and patients with temporomandibular disorder. DATA ANALYSIS: Included patients were assessed at three points in time: at the start of treatment (T0), after 3 months (T1), and after 6 months (T2). The patients were instructed during the study to wear each set of aligners (Nuvola; Gruppo Europeo di Ortodonzia S.r.l., Rome, Italy) for 2 weeks and 22 h/d and to remove them while eating and drinking (except for still water). The following two assessments were done for each patient at T0, T1, and T2: surface electromyography (sEMG) evaluation and a T-Scan digital occlusal analysis evaluation. Both evaluations were performed in centric occlusion and with aligners worn. The assessments were done by the same operator. The sEMG evaluation aimed to assess the muscular symmetry and balance. The sEMG evaluation was performed using an instrument that recorded analogical sEMG signal (BTS TMJOINT, Teethan S.p.a., Garbagnate Milanese, Milano, Italy). The patients were instructed to clench as much as possible and to maintain the same level of contraction during the test. The software automatically selected the 3 s with the most stable sEMG signal. The following outcomes were assessed using the sEMG: 1. Masseter percentage overlapping coefficient (POC), temporalis POC, and mean POC: which is an index of the symmetrical distribution of sEMG potentials within homologous muscular couples. 2. Torque coefficient (TC): compares the activity of the temporalis muscle to that of the contralateral masseter muscle. 3. Activity index (Ac): compares the activity of the temporalis muscle to that of the homolateral masseter muscle 4. Asymmetry index (Asym): compares the activity of the temporalis and masseter muscles of the right side to those of the left side. The digital occlusal analysis was performed using a 100µ thin, flexible horseshoe-shaped Mylar sensor (Novus HD sensor, Tekscan, Inc. S. Boston, MA, USA) that is used to analyze the dynamic and real-time distribution and timing of occlusal contacts and can reproduce 256 levels of varying occlusal force. A first recording was made without aligners, then a second with the aligners worn on the dental arches. The following outcomes were assessed using the digital occlusal analysis: 1. Position of the center of occlusal force (COF). 2. The maximal intercuspation time (MIC) (i.e., the time interval expressed in seconds between the first dental contact and the maximal intercuspation). The null hypothesis was that no difference exists for the sEMG indexes between the 3-time points and the two occlusal conditions. RESULTS: Twenty-six female adult patients (mean age, 33.67 ± 13.33 years) were enrolled in this study. Statistically significant differences were observed in terms of POC for the temporalis and masseter muscles, as well as the mean POC across the three time points and between occlusal conditions (with or without aligner). Hence, null hypothesis was rejected. On the other hand, TC, Ac, Asym, and MIC variables did not exhibit any statistically significant differences. This confirms that the stable positioning of COF on the transverse plane was accompanied by the absence of torquing muscular couples or imbalances in muscular activation. Symmetry in muscular couples' activation (indicated by POC value) remained consistent over the 6-month follow-up period for the occlusion with aligners, and in fact, demonstrated some improvements. In contrast, there was a decline in POC over time during centric occlusion. Statistically significant variation in COF position was observed in the sagittal plane, but not in the transverse plane. This shift in COF position coincided with changes in muscular balance as assessed by surface electromyography. Regarding the anteroposterior position of the COF, an overall slight posterior shift was observed when aligners were worn. After 3 months of full-time aligner usage, an anterior COF position was detectable in centric occlusion, which exhibited statistical significance when compared with the occlusion involving aligners at T0 and T1. CONCLUSIONS: The use of clear aligners led to an anterior displacement of the COF during biting in centric occlusion, along with a posterior shift while the aligners were worn in healthy female subjects over a 6-month monitoring period. No significant asymmetries in the COF position on the transverse plane were observed. The alterations in occlusal contact were subsequently followed by a short-term improvement in muscular balance when aligners were used, but a worsening muscular balance over time in centric occlusion condition.

Does maxillary sinus proximity affect molar root resorption during distalization using Invisalign? a CBCT study.

BACKGROUND: This study aimed to assess the correlation between maxillary sinus proximity to root apices of maxillary molars and root resorption during molar distalization using clear aligner therapy (CAT). MATERIALS AND METHODS: Thirty-eight cone beam computed tomography scans (CBCTs) obtained pre- (T0) and post-treatment (T1) from 19 adult patients (36.68 ± 13.50 years), who underwent maxillary molar distalization using Invisalign® aligners (Align Technology, Inc., San José, CA, USA) with a minimum of 2 mm distalization, were evaluated in this study At least 22 h of aligner wear per day was a main inclusion criterion. Sinus proximity and changes in root lengths were measured for 61 molars (183 roots). Spearman coefficient analysis was used for assessing correlation between sinus proximity and root resorption. The level of significance was set at p ≤ 0.05. The reproducibility of measurements was assessed by intraclass correlation coefficient (ICC). RESULTS: Spearman coefficient revealed no significant correlation between sinus proximity and molar root resorption for mesiobuccal, distobuccal or palatal roots (p = 0.558, p = 0.334, p = 0.931, respectively). CONCLUSION: There was no correlation between maxillary sinus proximity to root apices of maxillary molars and root resorption.

Correction: Santucci et al. Assessment of Posterior Dentoalveolar Expansion with Invisalign in Adult Patients. Int. J. Environ. Res. Public Health 2023, 20, 4318.

There was an error in the original publication [...].

Treatment effects of Herbst appliance in skeletal Class II cases during pre-pubertal and post-pubertal periods: a cone-beam computed tomographic study.

In the present study, Thirty-six Class patients II (A condition in which the upper jaw is larger than the lower jaw) were randomly selected and assigned to one of two groups based on their maturation stage: the pre-pubertal group (18 patients, mean age 9.15 ± 1.5 years) and post-pubertal group (18 patients, mean age 16.3 ± 1.0 years). All patients were treated with a metallic splint-supported Herbst IV appliance (An appliance that acts like artificial joint working between the upper and power jaws that keeps the lower jaw in a forward position, thus improving the Class II condition). Pretreatment (T1) and post-Herbst IV treatment (T2) scans were obtained for both groups. Dental and skeletal measurements were made on the scans and statistically analyzed using paired and independent t-tests. The study hypothesis was that; the dentoskeletal changes in Class II malocclusion treatment using Herbst appliance in the Pre-pubertal is more than the Post-pubertal growth stage due to the remaining growth potential for the pre-pubertal patients. The comparison between the two groups revealed statistically significant differences in horizontal skeletal parameters in the lower jaw only, while other readings were similar.

Cloning, purification and characterization of human dentine matrix protein 1(DMP1).

Introduction: Human teeth are composed mainly of dentin, formed by the odontoblasts. Dentin matrix protein 1 (DMP1) is one of odontoblast differentiation's most important growth factors. Human DMP1 has yet to be completely identified or studied. This study aimed to clone and characterize human DMP1. Materials and methods: The DMP1 gene sequence was prepared and cloned by transfection of human 293 cells. Results: The recombinant DMP1 was purified and characterized. Conclusion: The results suggested its future use in dental tissue regeneration and tissue engineering.

Does motivation via a smartphone application improve oral hygiene in patients undergoing orthodontic treatment?

DESIGN: This is a randomized cohort study. COHORT SELECTION: The inclusion criteria comprised patients aged 14-19 years who started their orthodontic treatment using fixed appliances at the Orthodontic Clinic at Universidade Cruzeiro do Sul, San Paulo, Brazil. Only patients who had smartphones were included in this study. The exclusion criteria comprised patients who had previous orthodontic treatment, presence of any oral pathology, and chronic use of analgesic medication or presence of syndromes. Included patients were randomized to two groups (control and experimental). DATA ANALYSIS: The oral hygiene of the included patients was evaluated clinically at five points in time: before bonding fixed orthodontic appliance (T0), immediately after randomization (T1), at 30 days after the beginning of the intervention (T2), at 60 days after the beginning of the intervention (T3), and at 90 days after the beginning of the intervention (T4). Oral hygiene was assessed using visual plaque index (VPI) and gingival bleeding index (GBI) at six sites of all teeth in every arch excluding third molars. Prior to the intervention, all patients who participated in this study underwent an oral hygiene session aimed to obtain a plaque index equal to zero and were given standardized oral hygiene instructions. Patients included in the control group were not given any structured oral hygiene follow-up in addition to the standard follow-up already established at the orthodontic clinic. Patients in the experimental group were instructed to install an application (A Dentista Cientista) that was designed especially for this study on their smartphones. This application aimed to guide and motivate patients daily in a playful way about performing oral hygiene practices. The application reminded the patients to perform their oral hygiene through an alarm. RESULTS: A total of 11 patients were screened for study eligibility; 3 patients were excluded from the study. Eight patients were included in this study, four patients in each group. Although VPI and GBI values were reduced at T1 and T2 in the experimental group, there were no statistically significant differences for VPI and GBI between the groups at any time evaluated (P > 0.05). The patients who were included in the experimental group reported a good acceptability of the application and they would recommend it to other people. In addition, the patients who were included in the experimental group agreed that oral hygiene is crucial and 75% of them agreed that the application encouraged them to take better care of their oral health. CONCLUSIONS: This study showed that mobile applications might help in improving the oral hygiene of orthodontic adolescent patients.

Impact of low intensity pulsed ultrasound on volumetric root resorption of maxillary incisors in patients treated with clear aligner therapy: A retrospective study.

OBJECTIVE: The aim of this study was to evaluate the volumetric root resorption in maxillary incisors following clear aligner therapy (CAT) with low-intensity pulsed ultrasound (LIPUS), and compare the results to CAT alone. MATERIAL AND METHODS: This retrospective study evaluated pretreatment (T0) and post-treatment (T1) cone-beam computed tomography imaging of 42 adult patients. Twenty-one patients (14 females, 7 males, mean age= 38.1±12.96 years) were treated using CAT with LIPUS device, whereas the other twenty-one matching controls patients (15 females, 6 males, mean age= 35.6±11.7 years) were treated using CAT alone. Images were analyzed and a segmentation protocol was applied on the maxillary incisors. Each segmented tooth volume was exported as a surface mesh in the Visualization Toolkit (VTK) file format. The VTK files for all maxillary incisors were coded and corresponding teeth volumes from T0 and T1 were superimposed. Clipping the crown of each tooth was done, then measurements of root volumes and differences between groups were performed. Changes in root volumes were assessed (p<0.05). RESULTS: Root loss was evident in all teeth in both groups, but was significantly increased in all maxillary incisors of the control group (p<0.001) and in upper left central incisor of LIPUS group (p=0.009). When both groups were compared, there was statistically significant minimal volumetric root loss in LIPUS group (3.50-7.32 mm3), when compared to control group (11.48-12.95 mm3) (p<0.05). CONCLUSION: LIPUS group showed less volumetric root resorption compared to control group during the studied treatment time using clear aligners.

Comparison of alveolar bone thickness and height after slow expansion using quad-helix or clear aligners.

Objective: The study was conducted to investigate the thickness and height of the alveolar bone of individual teeth after slow maxillary expansion (SME) with quad helix or clear aligner appliances and hypothesized that there is no difference in buccal alveolar bone thickness or heights in patients treated by either quad helix or clear aligners. Material and Methods: This is a retrospective study; the records of 22 patients treated between December 2019 to April 2020 by dental arch expansion using either clear aligners or quad helix appliances were retrieved and studied. The results obtained through cone beam computed tomography (CBCTs) before and immediately after maxillary expansion (2 + 1 mm per side) were analyzed (11 in the Quad Helix group and 11 in the clear aligner). The data collected was analyzed using linear and angular measurements obtained through On-demand 3D App software. Furthermore, Statistical Package for Social Sciences (SPSS) version 25.0 was used to present the findings by mean and standard deviations, and Scheffe's test was applied for comparing forces. Results: The results showed that the mean age of patients in the clear aligner group and Quad Helix was 16.27 ± 0.56 years and 15.5 ± 1.53 years, respectively. There was no difference in buccal alveolar bone thickness or heights in patients treated by either quad helix or clear aligners. This is due to the findings that suggest that there was a decrease in bone height and bone width when treated with a quad helix as compared to clear alignment. Conclusion: It can be concluded that the quad helix SME treatment affects alveolar bone integrity; therefore, clear aligners might be better for treating patients than the quad helix.

The effect of clear aligners on speech: a systematic review.

OBJECTIVE: To assess the effect of clear aligners on the speech of patients undergoing orthodontic therapy through a systematic review of the literature. Search methods and selection criteria: The protocol of this systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) CRD42021278694. An electronic search of the Scopus, Embase, Pubmed, and Web of Science databases was done for papers published between January 2000 till September 2021. Studies that evaluated speech difficulties in patients undergoing orthodontic treatment with clear aligners using objective and subjective analyses were included. The evaluated primary outcome was speech difficulties. Secondary outcomes were time to adaptation and recovery from speech difficulties. Study quality was assessed based on the Cochrane Handbook for Systematic Reviews of Interventions Handbook guidelines and ROBINS-I tool. RESULTS: Two hundred and eighty-three articles were screened to identify seven studies (n = 332 patients) that assessed speech difficulty with aligners, of which two were randomized trials. Meta-analysis was not performed due to the heterogeneity in the study designs. Five studies compared speech difficulty with aligners to fixed appliances. Two studies showed a moderate risk of bias and five studies had a serious risk of bias. Level of evidence was downgraded to low due to the methodological insufficiencies and risk of bias in the studies. All seven studies reported that aligners could influence the clarity and delivery of speech, similar to fixed appliances. Various phonemes were affected including /s/,/z/,/zh/,/sh/,/th/,/ch/ on wearing aligners. Errors in articulation of consonants and sibilants were noted with lisping and speech impairment. These speech difficulties were temporary and most patients recovered in 7-14 days while few patients took 30-60 days to recover. CONCLUSION: The likelihood of speech difficulties appears high with clear aligners. However, patients adapt quickly and speech returns to normal. The results of this review must be interpreted with caution and more well-designed randomized trials examining long-term effects of aligners on speech are indicated. CLINICAL SIGNIFICANCE: Orthodontists should counsel patients opting for clear aligner treatment of the potential transient speech difficulties. REGISTRATION: The protocol for this systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) CRD42021278694.

Comparative assessment of frictional forces between differently designed esthetic brackets during simulated canine retraction.

OBJECTIVES: To evaluate force loss due to friction (FR) with an emphasis on esthetic brackets and their design differences during simulated canine retraction. MATERIALS AND METHODS: The tested brackets were round and sharp-cornered conventional-ligating brackets and round-cornered self-ligating brackets. The tested archwires were stainless steel (0.018â€¯× 0.025″ and 0.019â€¯× 0.025″, and 0.018″) archwires. A total of 90 bracket-archwire combinations in 9 equally-sized groups (n = 10) were analyzed. Canine retraction was experimentally simulated in a biomechanical set-up utilizing the custom-made orthodontic measurement and simulation system (OMSS) using a NiTi coil spring that delivered a constant force of 1 N. The simulated retraction path was up to 4 mm. FR was compared among groups using the Welch t­test. Significance level (α) was set to 0.05. RESULTS: The round-cornered conventional-ligating bracket exhibited the least FR (28.6 ± 5.4%), while there were no significant differences in FR between the round-cornered conventional-ligating bracket and the round-cornered self-ligating bracket with 0.018″ stainless steel wires. However, the round-cornered self-ligating bracket exhibited the least FR (34.9 ± 5.1% and 39.3 ± 4.6%) with 0.018â€¯× 0.025″ and 0.019â€¯× 0.025″ stainless steel archwires, respectively. The sharp-cornered conventional-ligating bracket showed the highest FR of 72.4 ± 3.0% among the bracket systems tested in this study. CONCLUSIONS: The round-cornered conventional-ligating bracket showed less FR when compared to sharp-cornered conventional-ligating bracket. Conversely, the round-cornered conventional-ligating bracket exhibited greater FR when compared to the round-cornered self-ligating bracket, with an exception with respect to the 0.018″ wire. In general, FR increased with increased wire dimension.

Association between nonextraction clear aligner therapy and alveolar bone dehiscences and fenestrations in adults with mild-to-moderate crowding.

INTRODUCTION: This study aimed to assess the association between nonextraction clear aligner therapy (CAT) and the presence of alveolar bone dehiscences (ABDs) and fenestrations (ABFs) in adults with mild-to-moderate crowding. METHODS: Cone-beam computed tomography images from 29 adults were obtained before and immediately after nonextraction CAT. Total root lengths were evaluated in axial and cross-sectional slices. Linear measurement for dehiscence (LM-D) was defined as the distance between the alveolar crest to the cementoenamel junction of each root (critical point set at 2 mm). Linear measurement for fenestration (LM-F) was recorded when the defect involved only the apical one-third of a root (critical point set at 2.2 mm). Counts of ABDs/ABFs and magnitudes of LM-Ds/LM-Fs were recorded before and immediately after nonextraction CAT at buccal and lingual root surfaces. Binary logistic regression analyses and repeated measures analyses of variance were performed. RESULTS: Counts of ABDs/ABFs and magnitudes of LM-Ds/LM-Fs increased at most jaw locations and root surfaces. Nonextraction CAT was associated with an increased presence of ABDs and ABFs. Nonextraction CAT was associated with a higher magnitude of LM-Ds but not LM-Fs. CONCLUSIONS: Immediate posttreatment cone-beam computed tomography scans showed that nonextraction CAT is associated with increased ABDs and ABFs in adults with mild-to-moderate crowding.

Impact of low intensity pulsed ultrasound on volumetric root resorption of maxillary incisors in patients treated with clear aligner therapy: A retrospective study

ABSTRACT Objective: The aim of this study was to evaluate the volumetric root resorption in maxillary incisors following clear aligner therapy (CAT) with low-intensity pulsed ultrasound (LIPUS), and compare the results to CAT alone. Material and Methods: This retrospective study evaluated pretreatment (T0) and post-treatment (T1) cone-beam computed tomography imaging of 42 adult patients. Twenty-one patients (14 females, 7 males, mean age= 38.1±12.96 years) were treated using CAT with LIPUS device, whereas the other twenty-one matching controls patients (15 females, 6 males, mean age= 35.6±11.7 years) were treated using CAT alone. Images were analyzed and a segmentation protocol was applied on the maxillary incisors. Each segmented tooth volume was exported as a surface mesh in the Visualization Toolkit (VTK) file format. The VTK files for all maxillary incisors were coded and corresponding teeth volumes from T0 and T1 were superimposed. Clipping the crown of each tooth was done, then measurements of root volumes and differences between groups were performed. Changes in root volumes were assessed (p<0.05). Results: Root loss was evident in all teeth in both groups, but was significantly increased in all maxillary incisors of the control group (p<0.001) and in upper left central incisor of LIPUS group (p=0.009). When both groups were compared, there was statistically significant minimal volumetric root loss in LIPUS group (3.50-7.32 mm3), when compared to control group (11.48-12.95 mm3) (p<0.05). Conclusion: LIPUS group showed less volumetric root resorption compared to control group during the studied treatment time using clear aligners.

RESUMO Objetivo: O objetivo deste estudo foi avaliar volumetricamente a reabsorção radicular em incisivos superiores após tratamento com alinhadores transparentes (CAT) com e sem uso adjuvante de ultrassom de baixa intensidade (LIPUS). Material e Métodos: Esse estudo retrospectivo avaliou imagens de tomografia computadorizada de feixe cônico pré-tratamento (T0) e pós-tratamento (T1) de 42 pacientes adultos: 21 pacientes (14 mulheres, 7 homens, idade média= 38,1±12,96 anos) foram tratados com CAT e LIPUS, enquanto os outros 21 pacientes controles correspondentes (15 mulheres, 6 homens, idade média= 35,6±11,7 anos) foram tratados apenas com CAT. As imagens foram analisadas e foi aplicado um protocolo de segmentação dos incisivos superiores. Os volumes de cada dente segmentado foram exportados como malhas de superfície, em arquivos no formato Visualization Toolkit (VTK). Os arquivos VTK de todos os incisivos superiores foram codificados e foram sobrepostos os volumes dos dentes correspondentes a T0 e T1. Foi realizada a clipagem da coroa de cada dente e, em seguida, foram realizadas medições dos volumes radiculares e comparadas as diferenças entre os grupos, avaliando-se as alterações nos volumes de raízes (p<0,05). Resultados: A perda radicular foi evidente em todos os dentes em ambos os grupos, mas foi significativamente maior em todos os incisivos superiores do grupo controle (p<0,001) e no incisivo central superior esquerdo do grupo LIPUS (p=0,009). Quando ambos os grupos foram comparados, houve perda volumétrica mínima estatisticamente significativa no grupo LIPUS (3,50-7,32 mm3), em comparação ao grupo controle (11,48-12,95 mm3) (p<0,05). Conclusão: O grupo LIPUS apresentou menor volume de reabsorção radicular, em comparação ao grupo controle, durante o tempo de tratamento estudado usando alinhadores transparentes.

Corrigendum to "The effect of low intensity pulsed ultrasound on mandibular condylar growth in young adult rats" [Bone Rep. 15 (2021) 101122 (December)].

[This corrects the article DOI: 10.1016/j.bonr.2021.101122.].