Patients' perception of orthodontic retainers: a systematic review.

BACKGROUND: Orthodontic retainers are widely used to prevent relapses after orthodontic treatment; however, evidence about patients' perceptions of retainers is lacking. OBJECTIVE: To assess patients' perception of orthodontic retainers. SEARCH METHODS: PubMed, Web of Science, Scopus, LILACS, LIVIVO, Cochrane Library, and gray literature (Google Scholar) were searched without date or language restrictions. A manual search of the reference lists of the included articles was also performed. SELECTION CRITERIA: Studies comparing patients' perceptions of wearing orthodontic retainers were included. DATA COLLECTION AND ANALYSIS: According to the study design, the risk of bias (RoB) assessment was performed using RoB 2.0 or ROBINS-I. The level of evidence was assessed through the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) tool. RESULTS: Seventeen studies met the eligibility criteria. After the RoB assessment, 12 randomized controlled trials presented a high RoB, and 4 non-randomized controlled trials presented a moderate RoB. The certainty of evidence was classified as very low for the four assessed outcomes. The studies generally reported an initial temporary negative impact of orthodontic retainers. Different esthetic, functional, and ease-of-use advantages are reported using removable and fixed retainers. A quantitative analysis was not performed due to the considerable clinical and methodological heterogeneity among the studies. CONCLUSION: The current evidence, although very limited, suggests that orthodontic retainers have an initial negative impact related to discomfort and functional limitations, but they seem to regress over time. There is a preference for thermoplastic over Hawley-type retainers. However, thermoplastic retainers cause different functional difficulties, and bonded retainers present the advantage of affecting speech function less than orthodontic removable retainers, although they can facilitate oral hygiene problems. REGISTRATION: PROSPERO (CRD42022306665).

Self-correction of the ectopic eruption of the maxillary first permanent molar and its predictive factors: A systematic review.

BACKGROUND: Ectopic eruption of the maxillary first permanent molar is a local disturbance that affects the development of the occlusion. AIM: To evaluate the occurrence of self-correction of maxillary first permanent molar's ectopic eruption and its predictive factors. DESIGN: Five electronic databases and part of the gray literature were investigated. The risk of bias was assessed using the Newcastle-Ottawa scale and the certainty of evidence using the GRADE tool. RESULTS: Four studies were selected: Three had a low risk of bias, and one, moderate. Evidence with a moderate level of certainty was generated, indicating a possibility of 47%-78% of spontaneous correction up to 7 years of age. Supporting the prognosis, whether reversible or irreversible, there was a positive correlation between the severity of the atypical distal resorption of the second primary molar, a higher magnitude of impaction, a larger eruption angle, and a bilateral occurrence with the irreversibility of the cases. CONCLUSION: Spontaneous correction of the ectopic eruption of the maxillary first permanent molar is feasible and dependent on the severity of predictive factors. Early intervention is mandatory in irreversible cases.

Self-correction of posterior crossbite in childhood: a systematic review of long-term follow-up studies.

BACKGROUND: The concept that posterior crossbite is not self-correcting has been controversial in the literature. OBJECTIVE: To evaluate the incidence of self-correction of crossbite in different stages of dentition in childhood. SEARCH METHODS AND SELECTION CRITERIA: A bibliographic search using the acronym PECOS was performed in five databases and in partial grey literature. Studies evaluating children with posterior crossbite in the deciduous or mixed dentition at initial examination and followed for at least 3 years were included. DATA COLLECTION AND ANALYSIS: The data extraction of the studies included presents information on authorship, clinical characteristics, main results, and conclusions. The risk of bias in the studies was evaluated through the Joanna Briggs Institute tool. The certainty of the evidence was assessed using the GRADE tool. RESULTS: Among the 3045 references identified, seven cohort studies met the eligibility criteria. The studies evaluated patients in transition from deciduous to mixed, mixed to permanent, and deciduous to mixed dentition. Two studies had a low risk of bias, three had a moderate risk, and two had a high risk of bias. The results showed posterior crossbite self-correction frequencies ranging from 12.2 to 77.1% during the transition from primary to mixed dentition, approximately 16% from mixed to permanent dentition, and a range from 20 to 82.8% from deciduous to permanent dentition. The level of certainty of the evidence generated ranged from very low to moderate. LIMITATIONS: The observational design of the studies, without adequate control for confounding factors, and non-classification of the samples considering the types or the severity of the posterior crossbite. CONCLUSION: The self-correction of posterior crossbite in childhood is possible. However, the results of this research do not allow to affirm how often the self-correction of posterior crossbite can occur. New studies that assess factors associated with the occurrence of self-correction of this malocclusion, including oral habits, may increase the certainty of the evidence. REGISTRATION: PROSPERO CRD42022311935.

Effects of oral appliances on serum cytokines in adults with obstructive sleep apnea: a systematic review.

PURPOSE: This review aimed to evaluate the effects of oral appliance (OA) therapy on serum inflammatory cytokines in adults diagnosed with obstructive sleep apnea (OSA). METHODS: Seven electronic databases and partial gray literature were searched without restrictions through March 2021. Articles evaluating the levels of serum inflammatory cytokines in patients with OSA after OA treatment were included. The risk of bias (RoB) was assessed using the before-and-after tool or RoB 2.0. The level of certainty was assessed using the GRADE tool. RESULTS: Five studies met the eligibility criteria. One was a randomized clinical trial (RCT), while four were non-randomized clinical trials (NRCTs). Among the studies, C-reactive protein (CRP), IL-6, IL-10, IL-1ß, and tumor necrosis factor α (TNF-α) were investigated. The RCT reported no significant differences in marker levels after 2 months of OA therapy, while the NRCTs showed improvement on CRP, TNF-α, and IL-1ß levels after longer follow-up periods. The RoB was evaluated as showing some concern in the RCT. Three NRCTs presented good RoB, and one showed a fair RoB. The level of certainty was graded as moderate quality for inflammatory marker levels assessed in the RCT The levels of certainty evaluated in NRCTs were classified as very low. CONCLUSIONS: Although limited, existing scientific evidence showed that OA therapy may improve serum cytokine levels in adults with OSA. However, short treatment periods are not effective in reducing markers of systemic inflammation which may require extended time and a decrease of in apneic events to improve.

Mandibular advancement analysis among orthodontists, lay people and patients in class II malocclusion subjects. A three-dimensional imaging study.

OBJECTIVE: To evaluate the acceptance of orthodontists, laypeople and the patient when progressive mandibular advancements are performed in class II subjects with mandibular retrognathism. SETTING AND SAMPLE: 3D images were obtained by an optical surface scanning of fifteen individuals (12 males and three females, mean age of 23 years and 8 months) with mandibular retrognathism in three mandibular positions: maximum intercuspation (MIC) and progressive mandibular advancement of 2 and 4 mm. METHODS: The images (n = 45) were evaluated through a scale by two groups of panellist, 20 orthodontists, 20 laypeople and by the patients themselves (n = 15). The participants evaluated and rated each video and give scores between 0 and 10, according to their perception of facial harmony. MANOVA for repeated measures was used for intra- and intergroup differences and to evaluate the patients' self-perception. RESULTS: Laypeople reported better face acceptance than orthodontists in MIC and progressive mandibular advancement of 2 and 4 mm (P < .0001). 80% of the patients evaluated their own face as pleasant in MIC. Around half of them did not note significant difference following mandibular advancement of 2 mm as compared with MIC and even two-third attributed lower scores when the mandible was advanced 4 mm. CONCLUSION: A high variability was observed among all groups of raters. Patient´s opinion should be taken into account when mandibular advancement of 4 mm or more is planned. This study suggests that a thorough discussion of facial changes resulting from mandibular advancement should be carried out among professionals, parents and patients.

Is catastrophising associated with pain perception in early phase of orthodontic treatment? A cohort study.

BACKGROUND AND OBJECTIVES: This study aimed to investigate the association between pain perception and catastrophising at the beginning of orthodontic treatment; and the association between pain during orthodontic treatment and demographic, clinical and other psychological factors. METHODS: A cohort study with 44 patients (28.9 ± 15.05 years old; 25 females and 19 males) under orthodontic treatment with fixed appliances had their pain perception evaluated through a visual analogue scale at baseline (before activation), 6 h, 24 h, 2nd day, 3rd day, 5th day and 7th day after activation. The scores at each evaluation period after the first (T1), second (T2) and third (T3) appointments were compared by analysis of variance. A multivariate Poisson regression analysis verified the association between pain perception and Pain Catastrophising Scale (PCS); and demographic (age, gender), clinical (tooth crowding, tooth loss, analgesic intake and archwire characteristics) and other psychological (dental anxiety and previous negative dental experiences) independent variables (p < .05). RESULTS: Catastrophising (RR = 1.03, 95%CI 1.01-1.05, p = .0001) showed a weak risk of pain perception at T1. The peak of pain occurred 24 h after activation at T1, T2 and T3. Significant higher scores were observed at T1 in comparison to T2 (FT1,T2  = 11.82, p = .005) and T3 (FT1,T3  = 5.09, p = .03). Wire diameter, tooth crowding and single-arch treatment were found as risk factors for pain. Patients without tooth loss had half of the risk of pain perception, while analgesics intake and older patients were also found with a weak protective association. Dental anxiety and negative dental experience were not associated with pain perception. CONCLUSION: Catastrophising has a mild influence on pain perception and only after the first orthodontic activation. Patients with tooth losses, tooth crowding and using thicker archwires are more likely to report pain after orthodontic activations.

Orthodontic Retainers and the Stability of the Maxillary Arch in Unilateral Cleft lip and Palate Patients: A Systematic Review.

OBJECTIVE: The aim of this systematic review was to elucidate the role of orthodontic retainers on the stability of compensatory orthodontic treatment in patients with unilateral cleft lip and palate. METHODS: Five electronic databases (PubMed, Scopus, Web of Science, LILACS, and LIVIVO) and the grey literature (OpenGrey and Google Scholar) were investigated, according to the population, exposure, comparator, outcomes and Study design eligibility criterion. The risk of bias assessment was determined based on the Risk of Bias In Nonrandomized Studies of Exposure (ROBINS-E) and the level of evidence with the GRADE tool. RESULTS: Three studies were included: two presented moderate risk of bias and one high. A moderate level of evidence revealed a mean value of 0.6 mm of intercanine relapse distance, and great variability between the data, regardless of the use or type of retention or rehabilitation. Relapse in the posterior region showed clinical significance, from -1 to -1.7 mm, especially in individuals who did not use retention, except in patients with symmetrical arches with Hawley retainer, where this value varies from -0.2 ± 0.63 mm. CONCLUSIONS: Orthodontic retainers do not seem essential to prevent relapse at anterior maxillary dimensions after compensatory orthodontic treatment in patients with unilateral cleft lip and palate. Relapse in the posterior region can achieve greater clinical significance, which highlights the need for prolonged use of Hawley retainers and periodic evaluation of the stability of treatment results. Prospective studies with a longer follow-up can improve the certainty of the evidence.

Treatment stability with bonded versus vacuum-formed retainers: a systematic review of randomized clinical trials.

BACKGROUND: In orthodontics, the retention phase can be considered challenging and unpredictable. Therefore, evidence obtained from different retention protocols is important to facilitate clinical decision-making. OBJECTIVES: This systematic review aimed to compare the clinical effectiveness of bonded versus vacuum-formed retainers (VFRs) regarding their capacity to maintain treatment stability, periodontal effects, and failure rates. SEARCH METHODS AND ELIGIBILITY CRITERIA: Ten databases comprising published and unpublished literature were systematically searched up to August 2021. Randomized clinical trials (RCTs) comparing both retainers were included. DATA COLLECTION AND ANALYSIS: The risk of bias (RoB) evaluation was performed with the Cochrane Collaboration RoB Tool 2.0. All steps of the screening phase and RoB assessment were performed independently by two reviewers. The Grade of Recommendations, Assessment, Development, and Evaluation (GRADE) was used to evaluate the certainty of the evidence. RESULTS: Initial database search yielded 923 studies. After duplicates removal and full-text assessment, five RCTs remained. Overall, the studies presented Low RoB, except one study judged with 'Some concerns'. Based on the included studies, on a short-term (3-6 months) and long-term (4 years) basis, bonded retainers (BRs) were more effective to maintain treatment stability than VFRs in the lower arch. However, from 12 to 24 months both retainers presented the same efficacy. In the upper arch, the retainers were equally effective. BRs were associated with greater plaque and calculus accumulation than VFRs after 12 months. The retainers' failure rates were similar in the upper arch on the first year of retention; however, after 2 years VFRs showed significantly greater failure rates. Contrarily, BRs presented greater failure rates in the lower arch than VFRs. LIMITATIONS: The findings of the included studies may be influenced by different factors related to the unpredictability of relapse. CONCLUSIONS: Most of the evidence generated in this systematic review derived from a moderate level of certainty. In the lower arch, BRs are more effective than VFRs to maintain treatment stability in the initial 6 months of retention and in the long term. In the upper arch, both retention protocols are equally effective. REGISTRATION: Regist0ration number: PROSPERO CRD42020199392. FUNDING: Coordination for the Improvement of Higher Educational Personnel (CAPES, Process code-001).

The effect of extraction of lower primary canines on the morphology of dental arch: A systematic review and meta-analysis.

BACKGROUND: The beneficial effect of the extraction of primary canines in the resolution of incisor irregularity and its side effects are controversial. AIM: To systematically review the effects of the extraction of primary canines in incisor irregularity and dental arch morphology. DESIGN: Controlled non-randomized (non-RCT) and randomized clinical trials (RCT) evaluating children treated with extraction of primary canines compared with those without intervention. RESULTS: A total of 984 articles were found, of which two RCTs and one non-RCT met the inclusion criteria. Both had a low RoB. A high level of evidence was observed through GRADE. A meta-analysis showed the extraction of primary canines produced a significant decrease in incisor irregularity (95% CI: -3.56, -2.09 mm). This decrease, however, was associated with a reduction of arch length (95% CI: -1.58, -0.94 mm), intermolar width (95% CI: -0.61, -0.22 mm), and overjet (95% CI: -075, -018). A mild overbite increase was found (95% CI: 0.10, 0.76 mm). CONCLUSION: A high level of evidence showed that the extraction of primary canines improved incisor irregularity in the mixed dentition. Side effects included reduced arch length and intermolar width. A slight reduction in overjet and a mild increase in overbite were also observed. When they are not part of the treatment goal, these occlusal changes can be prevented by installing a lingual arch.

Is the extraction of third molars a risk factor for the temporomandibular disorders? A systematic review.

BACKGROUND: The aim of this study was to evaluate through a systematic review the extraction of third molars as a risk factor for temporomandibular disorders (TMDs). TYPES OF STUDIES REVIEWED: Randomized and nonrandomized controlled clinical trials where patients underwent third molar extraction and with qualitative evaluation of TMDs before and after extraction were included. RESULTS: After applying the inclusion criteria, seven nonrandomized clinical studies were included. QUIPS tool showed that four articles presented a moderate and three a high risk of bias (RoB). Six studies reported that TMDs presented higher level after removal of third molars ranging from OR, 1.81 to 2.15/RR, 2.1. However, one study showed no significant association. GRADE showed heterogeneity in relation to general results, which means that confidence in the estimated effects varied from low to moderate GRADE. The quality of clinical recommendations decreased especially due to the risk of bias in some of the included studies evaluated with the QUIPS tool. CONCLUSIONS AND PRACTICAL IMPLICATIONS: Third molar extraction can be associated with the development of TMD signs and symptoms. Furthermore, TMD can be aggravated according to the third molar location, the degree of impaction and surgical difficulty, age, and gender. This systematic review highlights the need to perform randomized clinical trials with diagnostic criteria and standardized surgical procedures.

Factors associated with the stability of compensatory orthodontic treatment of Class III malocclusion in the permanent dentition.

INTRODUCTION: This study aimed to assess the stability of compensatory treatment of Class III malocclusion in permanent dentition. METHODS: Thirty-six patients (21 women and 15 men; mean age, 20 years) with Class III malocclusion were subjected to the compensatory treatment of permanent dentition and followed up for at least 3 years after orthodontic treatment (T3). Multivariate Poisson regression was performed to assess the influence of clinical, cephalometric, and dental cast variables at the beginning (T1) and the end of treatment on the stability of Class III malocclusion. RESULTS: Overjet changed from -0.25 mm (-3 to 0.5 mm) at T1 to 1.4 mm (1-2.5 mm) at the end of treatment and 0.8 mm (0-1.5 mm) at T3. Clinical relapse (overjet <1 mm and/or canine Class III relations) was observed in 11 patients (30.6%). Patients treated with extraction of mandibular premolars (risk ratio [RR] = 2.13 × 10-07, P <0.001), with better orthodontic end outcomes (RR = 1.16, P = 0.009) and which had lower maxillary incisor inclination at T1 (RR = 1.08, P = 0.035) showed a lower risk of relapse. Demographic (sex, age), clinical (length of treatment and posttreatment, number of treatment phases, time of Class III elastics), cephalometric (SNA, SNB, ANB, Wits appraisal, SNGoGn, IMPA), and dental cast (peer assessment rating index and arch dimensions) variables were not significantly associated with clinical relapse at T3. CONCLUSIONS: The stability of compensatory treatment of Class III malocclusion in permanent dentition is multifactorial, with few predictive variables. Patients treated with extraction and better orthodontic finishing had a lower risk of relapse, whereas larger maxillary incisor inclination at baseline increased the risk of relapse.

Dentofacial biometry as a discriminant factor in the identification of remote Amazon indigenous populations.

INTRODUCTION: This study aimed to examine the role of dentofacial morphology in discriminating semi-isolated indigenous groups. These populations present a similar pattern of dietary habits. Studies in human genetics have reported a large intertribal genetic distance and low intratribal variation. METHODS: This study was conducted following the Strengthening the Reporting of Observational Studies in Epidemiology guidelines. Face dimensions were measured through facial photogrammetry, and dental arches and tooth size were evaluated using plaster models. A total of 98 subjects in the permanent dentition and belonging to 4 indigenous groups were analyzed: Arara-Iriri (n = 20), Arara-Laranjal (n = 33), Assurini (n = 25), and Xicrin-Kayapó (n = 20). The random and systematic errors were verified using the Dahlberg formula and the intraclass correlation coefficient (ICC), respectively. In order to evaluate the discrimination of the variables to identify the indigenous groups, a discriminant analysis was performed (P <0.05). RESULTS: A small causal error (Dahlberg, 0.13-1.81) and excellent replicability (ICC, 0.75-0.99) for face dimensions as well as for models (Dahlberg, 0.10-0.68; ICC, 0.94-0.99) were observed. The discriminant analysis allowed the identification of 4 populations by facial and dental arch dimensions and tooth size. Dentofacial biometry revealed an accuracy of 98% for females and 100% for males, which confirms a high intragroup homogeneity and considerable intergroup heterogeneity for dentofacial features. CONCLUSIONS: Biometric measurements of the human face added with tooth size and dental arch dimensions are very useful to identify remote indigenous populations with high accuracy. Supported by previous studies in human genetics, these findings reinforce the role of genetic variation in the determination of dentofacial features.

Mandibular propulsion appliance for adults with Class II malocclusion: a systematic review and meta-analysis.

BACKGROUND: The effects of mandibular propulsion appliances in adults have some controversial results. While some authors claim that its use in non-growing patients could produce some dentoskeletal effects, other studies indicate that Class II correction occurs only through significant dental effects. OBJECTIVE: To evaluate the effects in non-growing Class II patients with mandibular retrusion, promoted by the treatment with mandibular propulsion appliances and determine if they produce mandibular changes. METHODS: The research was carried out in nine electronic databases and additional manual searches up to July 2019. Selection criteria were no restriction was placed on date and publication language. Randomized or non-randomized clinical trials with/without control were included. They must evaluated non-growing patients with Class II malocclusion, treated with mandibular propulsion appliances; outcomes were assessed before and after treatment. DATA COLLECTION AND ANALYSIS: Data were extracted by two independent examiners in duplicate. The ROBINS-I tool was used to assess the methodological quality of the included studies. RESULTS: Of the 2824 articles identified, 11 non-randomized clinical articles were selected for qualitative analysis and 8 for quantitative analysis. SNB (0.87°, CI 95% 0.08, 1.66), ANB (-0.82°, CI 95% -1.24 to 0.40) and Pg/OLp [2.3 to 1.2 mm (P < 0.001)] presented smallest but significant mandibular changes with some differences regarding the used appliance. The Herbst appliance showed the largest mandibular changes followed by the SUS appliance when evaluated through Ar-Pg. SNA showed non-significant changes. Overbite (-2.85. CI 95% -3.06, -2.64), Overjet (-5.00.CI 95% -5.45, -4.55) showed significant changes in all devices. Class II correction occurs through a significant labial movement of the mandibular incisors, some lingual inclination of the maxillary incisors and minor skeletal changes. CONCLUSIONS: All mandibular propulsion appliances examined, showed efficiency in normalizing the Class II malocclusion in adult patients; however, changes were acquired mainly through dentoalveolar changes. Some minor mandibular forward changes was noted, mainly in patients treated with the Herbst appliance. Randomized clinical trials are needed to improve scientific evidence. REGISTRATION: PROSPERO (code CRD42017067384).

Comparisons of tooth sizes, dental arch dimensions, tooth wear, and dental crowding in Amazonian indigenous people.

INRODUCTION: Our objective was to assess tooth wear, arch dimensions, tooth sizes, and dental crowding in 4 remote indigenous villages on the Xingu River in Brazil. These populations have similar patterns of dietary habits and practice exclusive breast-feeding, whereas studies in human genetics show large intertribal genetic distances and low intratribal variations. METHODS: Dental casts of 107 subjects in the permanent dentition were evaluated. Tooth wear, arch dimensions, mesiodistal tooth widths, and the irregularity index of the incisors were obtained and compared using analysis of variance or the Kruskal-Wallis test (P <0.05). RESULTS: Tooth wear and tooth size in the mandible were similar among villages. Three groups were discriminated. The first group included the Xicrin-Kayapó and Arara-Laranjal villages, since no significant difference was found between them. Larger tooth sizes and arch dimensions (P <0.001) were found in both jaws in the Assurini village compared with the Xicrin-Kayapó and Arara-Laranjal villages; this resulted in similar dental crowding index values in these groups. The Arara-Iriri village, where a high coefficient of inbreeding had been reported, showed intermediate arch dimensions, with the mesiodistal tooth widths similar to those in the Xicrin-Kayapó and Arara-Laranjal villages. This scenario resulted in a group with the lowest irregularity index, close to 0. CONCLUSIONS: These Amazonian indigenous villagers, who have been genetically studied previously, showed large intergroup genetic variations and similar patterns of tooth wear. Thus, we suggest from the findings in this study that the etiology of dental crowding among the inhabitants of the Xingu River area is predominantly associated with variations in the dimensions of dental arches, related to genetic influences.

Validity and reliability of intraoral scanners compared to conventional gypsum models measurements: a systematic review.

BACKGROUND: The development of 3D technology and the trend of increasing the use of intraoral scanners in dental office routine lead to the need for comparisons with conventional techniques. OBJECTIVE: To determine if intra- and inter-arch measurements from digital dental models acquired by an intraoral scanner are as reliable and valid as the similar measurements achieved from dental models obtained through conventional intraoral impressions. SEARCH METHODS: An unrestricted electronic search of seven databases until February 2015. SELECTION CRITERIA: Studies that focused on the accuracy and reliability of images obtained from intraoral scanners compared to images obtained from conventional impressions. DATA COLLECTION AND ANALYSIS: After study selection the QUADAS risk of bias assessment tool for diagnostic studies was used to assess the risk of bias (RoB) among the included studies. RESULTS: Four articles were included in the qualitative synthesis. The scanners evaluated were OrthoProof, Lava, iOC intraoral, Lava COS, iTero and D250. These studies evaluated the reliability of tooth widths, Bolton ratio measurements, and image superimposition. Two studies were classified as having low RoB; one had moderate RoB and the remaining one had high RoB. Only one study evaluated the time required to complete clinical procedures and patient's opinion about the procedure. Patients reported feeling more comfortable with the conventional dental impression method. LIMITATIONS: Associated costs were not considered in any of the included study. CONCLUSIONS AND IMPLICATIONS: Inter- and intra-arch measurements from digital models produced from intraoral scans appeared to be reliable and accurate in comparison to those from conventional impressions. This assessment only applies to the intraoral scanners models considered in the finally included studies. Digital models produced by intraoral scan eliminate the need of impressions materials; however, currently, longer time is needed to take the digital images. REGISTRATION: PROSPERO (CRD42014009702). FUNDING: None.

Impact on perceived root resorption based on the amount of incisal inclination as determined from conventional panoramic radiography.

INTRODUCTION: Our objective was to measure the impact on perceived root resorption based on the amount of anteroposterior incisal inclination as determined in vitro from conventional panoramic radiography. METHODS: A rapid prototyping model was created to mimic different maxillary and mandibular incisal anteroposterior inclinations. Two titanium beads were placed on the incisors at the apical and incisal edges. Panoramic radiographs were obtained, with the incisors changing relative inclination by 10° increments. The length was measured from the midpoint of the bead on the incisal edge to the midpoint of the bead on the apical edge. By using a length of wire of known size, this value was compared in all images to correct for image magnification. RESULTS: Changes to mandibular incisor anteroposterior inclinations, as either a theoretical proclination or retroclination, resulted in an increase of "apparent" root resorption on a panoramic radiograph. When the maxillary incisors were significantly and severely retroclined, they appeared larger than expected. When the maxillary incisors were mildly retroclined, the length was roughly similar to the theoretical model. When the maxillary incisors were mildly proclined, they appeared shorter than expected. CONCLUSIONS: The foreshortening or forelengthening of incisor root lengths because of incisor inclination vs root resorption cannot be reliably evaluated from panoramic images. The proposed theoretical model helps to understand the direction of the changes produced by the magnification factor. More severe scenarios where either the maxillary or the mandibular teeth are outside the focal trough have not been fully evaluated. The clinical impact of these changes is likely to be questionable.

Short-term treatment effects produced by the Twin-block appliance: a systematic review and meta-analysis.

OBJECTIVE: To evaluate dental, skeletal, and soft tissue effects during Twin-block treatment. METHODS: A systematic search of several electronic databases (Medline, PubMed, Embase, all EBM reviews, and Web of Science) was conducted until July 2013, as well as a limited grey-literature search (Google Scholar). Human cephalometric studies that used a Twin-block appliance in a non-extraction and non-surgical approach were selected. A comparable control group of untreated subjects was required. Two authors independently reviewed and extracted data from the selected studies. Risk of bias was assessed. The type of meta-analysis was selected based on heterogeneity. RESULTS: Ultimately 10 articles were included. Proclination of lower incisors, retroclination of upper incisors, distal movement of upper molars and/or mesial movement of lower molars, increase in mandibular length, and/or forward movement of the mandible were consistently reported. Clinically significant restraint of maxillary growth was not found. Although the mandibular body length is increased, the facial impact of it is reduced by the simultaneous increment of the face height. Changes of lower face height and occlusal plane inclination varied, suggesting that vertical dimension can be manipulated in patients who would benefit from lower molar extrusion. As for lip position, there is not enough evidence to suggest clear lip position changes. CONCLUSIONS: Changes associated with a Class II correction were identified. Most of the changes individually were of limited clinical significance, but when combined reached clinical importance. No long-term changes were available.

Tooth angulation and dental arch perimeter-the effect of orthodontic bracket prescription.

OBJECTIVE: The aim of this study was to evaluate the effects of upper incisors and canine angulations introduced by different bracket prescriptions on dental arch perimeter. MATERIALS AND METHODS: Cone beam computerized tomography scans collected using I-Cat (Imaging Sciences International, Hatfield, PA, USA) were selected conveniently from a database of routine exams of a clinical radiology center. Crown and radicular measurements of upper incisors and canines were made and exported to the Autocad 2011 software to create a virtual dental model. The virtual teeth were positioned with an angulation of zero; thereafter, a reference value for the perimeter of the arch was measured. Furthermore, teeth angulations were applied according to the standards of the Edgewise bracket system and the Straight-wire systems: MBT, Capelozza, Andrews, and Roth. The largest linear distances for tooth crown (anterior arch perimeter) and root (radicular distance) were obtained for each bracket prescription. RESULTS: The anterior perimeter for well-aligned incisors and canines without angulation was used as reference (crown: 47.34mm; root: 39.13mm). An increase in the arch perimeter was obtained for all bracket prescriptions evaluated, which ranged from 0.28 and 3.19mm in the Edgewise technique, for the crown and root measurements, respectively, to 1.09 and 11.28mm for the Roth prescription. CONCLUSION: Bracket prescriptions with greater angulation led to an increased use of space within the dental arch, mainly in the radicular region. The consequence of this radicular angular displacement will need to be further investigated.

Do statistical heterogeneity methods impact the results of meta- analyses? A meta epidemiological study.

BACKGROUND: Orthodontic systematic reviews (SRs) use different methods to pool the individual studies in a meta-analysis when indicated. However, the number of studies included in orthodontic meta-analyses is relatively small. This study aimed to evaluate the direction of estimate changes of orthodontic meta-analyses (MAs) using different between-study variance methods considering the level of heterogeneity when few trials were pooled. METHODS: Search and study selection: Systematic reviews (SRs) published over the last three years, from the 1st of January 2020 to the 31st of December 2022, in six main orthodontic journals with at least one MA pooling five or lesser primary studies were identified. Data collection and analysis: Data were extracted from each eligible MA, which was replicated in a random effect model using DerSimonian and Laird (DL), Paule-Mandel (PM), Restricted maximum-likelihood (REML), Hartung Knapp and Sidik Jonkman (HKSJ) methods. The results were reported using median and interquartile range (IQR) for continuous data and frequencies for categorical data and analyzed using non-parametric tests. The Boruta algorithm was used to assess the significant predictors for the significant change in the confidence interval between the different methods compared to the DL method, which was only feasible using the HKSJ method. RESULTS: 146 MAs were included, most applying the random effect model (n = 111; 76%) and pooling continuous data using mean difference (n = 121; 83%). The median number of studies was three (range 2, 4), and the overall statistical heterogeneity (I2 ranged from 0 to 99% with a median of 68%). Close to 60% of the significant findings became non-significant when HKSJ was applied compared to the DL method and when the heterogeneity was present I2>0%. On the other hand, 30.43% of the non-significant meta-analyses using the DL method became significant when HKSJ was used when the heterogeneity was absent I2 = 0%. CONCLUSION: Orthodontic MAs with few studies can produce different results based on the between-study variance method and the statistical heterogeneity level. Compared to DL, HKSJ method is overconservative when I2 is greater than 0% and may result in false positive findings when the heterogeneity is absent.