Third molar agenesis in individuals with supernumerary teeth.

OBJECTIVES: To explore the association between third molar agenesis and supernumerary tooth formation in a white-European population. MATERIALS AND METHODS: A record review in various orthodontic clinics identified 380 eligible white-European individuals, half of whom had non-syndromic permanent supernumerary teeth (122 males and 68 females, totalling 244 supernumerary teeth; median age: 13.1, iqr: 1.5 years), and the other half were age- and sex-matched controls with full dentition, excluding the third molars. Tooth sequences were identified in panoramic radiographs. RESULTS: In the supernumerary group, approximately 80% of the individuals had a single supernumerary tooth, followed by those having two additional teeth. In both groups, there was no sexual dimorphism in third molar agenesis severity. The prevalence of third molar agenesis in the supernumerary group was similar to that of the control group (28/190 = 14.7% in both groups; p = 1.0). In total, 53 third molars were missing in the supernumerary group (n = 190) compared to 67 in the control group (n = 190; p = .862). The ratio of bilateral to unilateral third molar agenesis was significantly lower in the supernumerary group than in the control group (1.0 vs. 3.7, respectively; p = .026). CONCLUSION: The presence of supernumerary teeth did not significantly alter the likelihood of third molar agenesis or its severity. Bilateral third molar agenesis was considerably less prevalent in individuals with supernumerary teeth compared to controls. The present novel findings have important clinical and developmental implications.

Characteristics of Orthodontic Treatment in Cancer Survivors: A Systematic Review.

Background: Survival rates of cancer patients have increased globally and across age groups. Challenges arising from craniofacial growth-development disturbances and dental abnormalities might warrant modifications to standard orthodontic pathways of care. Objective: The aim of this study was to systematically summarize and critically assess the available literature regarding the characteristics of orthodontic treatment in cancer survivors. Materials and Methods: A systematic search was conducted in seven databases for studies on malignant tumor survivors having undergone orthodontic intervention with fixed appliances following cancer treatment up to August 2023. The outcomes of interest included quantitative data regarding various characteristics of orthodontic treatment and the post-treatment period. The risk of bias was assessed individually with the Newcastle-Ottawa scale. Results: Out of 347 records, 4 cohort studies were eventually included in the qualitative synthesis. Leukemia was the most common malignancy type, with treatment involving mainly chemotherapy and/or radiotherapy. The duration of orthodontic treatment in cancer survivors varied. Occlusal results, quality of life, and satisfaction were comparable to healthy peers. However, in some survivors' groups, treatment was shorter and the final results were compromised. Root resorption and oral mucositis were reported among the treated cancer survivors. Reduced occlusal outcome stability during the retention period was also reported. Conclusions: Overall, the duration of orthodontic treatment varied among cancer survivors. The occlusal results achieved were similar to those of their healthy peers, though potentially less stable. Patient-reported outcomes did not differ significantly between cancer survivors and healthy individuals treated orthodontically.

Evidence-based potential of generative artificial intelligence large language models in orthodontics: a comparative study of ChatGPT, Google Bard, and Microsoft Bing.

BACKGROUND: The increasing utilization of large language models (LLMs) in Generative Artificial Intelligence across various medical and dental fields, and specifically orthodontics, raises questions about their accuracy. OBJECTIVE: This study aimed to assess and compare the answers offered by four LLMs: Google's Bard, OpenAI's ChatGPT-3.5, and ChatGPT-4, and Microsoft's Bing, in response to clinically relevant questions within the field of orthodontics. MATERIALS AND METHODS: Ten open-type clinical orthodontics-related questions were posed to the LLMs. The responses provided by the LLMs were assessed on a scale ranging from 0 (minimum) to 10 (maximum) points, benchmarked against robust scientific evidence, including consensus statements and systematic reviews, using a predefined rubric. After a 4-week interval from the initial evaluation, the answers were reevaluated to gauge intra-evaluator reliability. Statistical comparisons were conducted on the scores using Friedman's and Wilcoxon's tests to identify the model providing the answers with the most comprehensiveness, scientific accuracy, clarity, and relevance. RESULTS: Overall, no statistically significant differences between the scores given by the two evaluators, on both scoring occasions, were detected, so an average score for every LLM was computed. The LLM answers scoring the highest, were those of Microsoft Bing Chat (average score = 7.1), followed by ChatGPT 4 (average score = 4.7), Google Bard (average score = 4.6), and finally ChatGPT 3.5 (average score 3.8). While Microsoft Bing Chat statistically outperformed ChatGPT-3.5 (P-value = 0.017) and Google Bard (P-value = 0.029), as well, and Chat GPT-4 outperformed Chat GPT-3.5 (P-value = 0.011), all models occasionally produced answers with a lack of comprehensiveness, scientific accuracy, clarity, and relevance. LIMITATIONS: The questions asked were indicative and did not cover the entire field of orthodontics. CONCLUSIONS: Language models (LLMs) show great potential in supporting evidence-based orthodontics. However, their current limitations pose a potential risk of making incorrect healthcare decisions if utilized without careful consideration. Consequently, these tools cannot serve as a substitute for the orthodontist's essential critical thinking and comprehensive subject knowledge. For effective integration into practice, further research, clinical validation, and enhancements to the models are essential. Clinicians must be mindful of the limitations of LLMs, as their imprudent utilization could have adverse effects on patient care.

The Prevalence of Congenitally Missing Permanent Teeth in a Sample of Orthodontic and Non-Orthodontic Caucasian Patients.

BACKGROUND: Hypodontia represents a notable clinical and public health concern. OBJECTIVE: To assess the prevalence of congenitally missing permanent teeth in a sample of orthodontic/dental patients of Caucasian origin originating from the Greek island of Lesvos. MATERIALS AND METHODS: Panoramic X-rays from 621 children and adolescents, aged 9 to 16 years (average age 12.5 years), 521 seeking orthodontic care (orthodontic group) and 100 seeking dental care (non-orthodontic group) were examined to identify congenitally missing permanent teeth. RESULTS: The orthodontic group exhibited a 5.5% prevalence of congenitally missing permanent teeth (2.8% females; 2.7% males), while the non-orthodontic group showed a prevalence of 4% (3% females; 1% males). The descending order of prevalence for missing tooth types was as follows: lower second premolars, upper laterals, lower central incisors, lower canines, upper second premolars, and lower second molars. Among orthodontic patients with missing teeth, 62% presented with an Angle's Class II malocclusion. Hypodontia was most frequently observed in the mandible. No statistically significant differences were observed between the orthodontic and non-orthodontic groups in terms of the percentage of children and types of congenitally missing teeth. CONCLUSIONS: Congenitally missing teeth were observed in about 4-5% of the studied population with a female predilection. The lower second premolar was the most commonly absent tooth, followed by the maxillary lateral incisors. An Angle's Class II malocclusion was present in the majority of orthodontic patients with hypodontia, mostly in the mandible.

Supernumerary Tooth Patterns in Non-Syndromic White European Subjects.

Supernumerary teeth form at an incidence of about 3% in the population, with differences among races and various clinical consequences. Information on detailed patterns, and especially on white subjects, is scarce in the literature. Therefore, we aimed to investigate the patterns of non-syndromic permanent supernumerary teeth in a white European population. A record review was performed in different orthodontic clinics and identified 207 eligible individuals with 258 supernumerary teeth. Approximately 80% of the subjects had one supernumerary tooth, while 15% had two. Supernumerary tooth formation was more often evident in males (male/female: 1.65). However, there was no sexual dimorphism in its severity. The following pattern sequences, with decreasing prevalence order, were observed in the maxilla: 21 > 11 > 12 > 18 > 28 and in the mandible: 34 > 44 > 35 > 45 > 42. Supernumerary teeth were most often unilaterally present, without sexual dimorphism. In the maxilla, they were more often anteriorly present, whereas in the mandible, an opposite tendency was observed. Supernumerary teeth were consistently more often observed in the maxilla than in the mandible; 74% were impacted, 80% had normal orientation (13% horizontal, 7% inverted), and 53% had normal size. The present thorough supernumerary tooth pattern assessment enables a better understanding of this condition with clinical, developmental, and evolutionary implications.

Effects on Facial Growth Following Masseter Muscle Resection in Growing Rats-A Systematic Review.

An individual's facial appearance is heavily influenced by facial symmetry. In the asymmetric mandible, periosteal apposition and endochondral ossification in one of the condyles may stimulate asymmetric growth of the body. Our aim was to review the impact on the growth following masseter resection. Relevant studies up to October 2022 were retrieved from PubMed, Scopus, and Web of Science. The PICOS method was utilized to determine eligibility, and the SYRCLE risk of bias tool was utilized to provide an estimate of potential bias. A predetermined algorithm was used to search the databases. The results of our systematic review of seven studies indicate that the masseter muscle strongly impacts craniofacial growth and development. Resection of the masseter muscle significantly reduces the sagittal and vertical development of the jaw in rats. In addition, the masseter muscle excision influences the mandibular morphology, including the condylar area, angle, and development direction of the jaw.

Are asthma and allergy associated with increased root resorption following orthodontic treatment? A meta-analysis.

OBJECTIVE: The aim of this study is to systematically investigate the available evidence from human studies regarding the association of asthma and/or allergy with EARR. MATERIALS AND METHODS: Unrestricted searches in 6 databases and manual searching were performed up to May 2022. We looked for data on EARR after orthodontic treatment in patients with/without asthma or allergy. Relevant data were extracted, and the risk of bias was assessed. An exploratory synthesis was carried out using the random effects model, and the overall quality of the evidence was assessed with the Grades of Recommendation, Assessment, Development, and Evaluation. RESULTS: From the initially retrieved records, nine studies met the inclusion criteria (three cohort and six case-control). Overall, increased EARR was observed in the individuals with allergies in their medical history (Standardised Mean Difference [SMD]: 0.42, 95% Confidence Interval [CI]: 0.19 to 0.64). No difference in EARR development was observed among individuals with or without a medical history of asthma (SMD: 0.20, 95% CI: -0.06 to 0.46). The quality of available evidence, excluding studies at high risk, was rated as moderate for the exposure to allergy, and low for the exposure to asthma. CONCLUSION: Increased EARR was noted in individuals with allergies compared to the control group, while no difference was observed for individuals with asthma. Until more data become available, good practice would suggest that it is important to identify patients with asthma or allergy and consider the possible implications.

Do the various interceptive treatment modalities improve the position of palatally displaced permanent canines? A meta-analysis.

BACKGROUND: Removal of maxillary primary canines and other interceptive treatment modalities in the mixed dentition have been suggested as methods used to increase the rate of normal eruption of palatally displaced permanent canines (PDCs). However, the information on the overall effect on PDCs' position has been inconclusive. OBJECTIVE: To assess whether this practice improves the position of PDCs and to investigate the quality of the evidence. SEARCH METHODS: Unrestricted searches in 7 databases and manual searching of the reference lists in relevant studies were performed up to June 2022 (Medline via PubMed, CENTRAL, Cochrane Database of Systematic Reviews, Scopus, Web of Science, ClinicalTrials.gov, ProQuest Dissertations, and Theses Global). SELECTION CRITERIA: We looked for data on the positional changes of PDCs (mesial inclination, vertical position, canine crown cusp tip to midline) from randomized controlled trials assessing the various interceptive treatment modalities. DATA COLLECTION AND ANALYSIS: Following study retrieval and selection, relevant data were extracted, and the risk of bias was assessed using the Cochrane Risk of Bias 2 Tool. Exploratory synthesis and meta-regression were conducted using the random effects model and the overall quality of the available evidence was assessed with the Grades of Recommendation, Assessment, Development, and Evaluation approach. RESULTS: Five studies (3 at low risk of bias) were identified, involving 238 individuals, followed for up to 18 months post-intervention with OPG (orthopantomogram) or CBCT (cone-beam computed tomography). Exploratory data synthesis showed that PDCs' position improved more in the extraction sites compared to non-extraction. Analysis of the studies at low risk confirmed the above observations (6- and 12-month). Improvements were observed in patients using headgear after extraction of primary canines compared to extraction alone, but not in patients with double extraction of primary canines and first molars. The quality of available evidence was rated at best as moderate. CONCLUSIONS: Interceptive treatment modalities in the mixed dentition may improve the position of PDCs. However, more studies are necessary in order to determine the clinical significance of the changes. REGISTRATION: PROSPERO (CRD42015029130).

Oral Health-Related Quality of Life throughout Treatment with Clear Aligners in Comparison to Conventional Metal Fixed Orthodontic Appliances: A Systematic Review.

BACKGROUND: Orthodontic clear aligners constitute an alternative and increasingly used orthodontic treatment modality, offering enhanced esthetics with potential consequences regarding patients' oral health-related quality of life (OHRQoL). OBJECTIVE: Summarize and systematically evaluate existing evidence on the OHRQoL of patients treated with orthodontic clear aligners compared to treatment with conventional metal, fixed appliances. SEARCH METHODS: We searched without limitations six databases and searched manually the reference lists of relevant studies up to the end of October 2022. SELECTION CRITERIA: We looked for data from prospective studies that compared OHRQoL, using instruments that had undergone full psychometric validation, between orthodontic patients with clear aligners and labial, fixed, metal orthodontic appliances. DATA COLLECTION AND ANALYSIS: We extracted the data from the located studies, and we assessed the risk of bias with the Cochrane Collaboration suggested tools. The quality of available evidence was based on the GRADE approach. RESULTS: Three studies were identified. OHRQoL was impacted less by clear aligners compared to treatment with conventional labially placed, fixed, metal appliances. The exploratory meta-regression, with the time point of assessment as predictor, did not reveal any statistically significant effect. The quality of the available evidence ranged from very low to low. CONCLUSIONS: According to the exploratory synthesis of the limited available dataset, treatment with clear aligners could be associated with better OHRQoL ratings compared to treatment with conventional labially placed, metal, fixed appliances. However, the quality of the presented evidence renders further high-quality studies warranted to be able to reach safer conclusions.

May alcoholic and non-alcoholic drinks affect the rate of orthodontic tooth movement? A systematic review of animal studies.

BACKGROUND: Humans may consume various beverages in everyday life. Previous research has shown that the administration of different substances (medicinal or not) may affect bone turnover and, thus, orthodontic tooth movement. It would be anticipated that the substances contained in beverages could have an impact on tooth movement, as well. OBJECTIVE: To investigate in a systematic way and appraise the quality of the available evidence from animal studies regarding the impact of various drinks or the main ingredients included in beverages on the rate of orthodontic tooth movement. SEARCH METHODS: Search without restriction in six databases (including grey literature) and hand searching were performed until March 2022. SELECTION CRITERIA: We looked for controlled animal studies investigating the effect of drinks, or the main ingredients included in beverages, on the rate of orthodontic tooth movement. DATA COLLECTION AND ANALYSIS: After study retrieval and selection, relevant data was extracted, and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. The quality of available evidence was assessed with the Grades of Recommendation, Assessment, Development, and Evaluation. RESULTS: The initially identified records were finally reduced to nine studies conducted on animals. Carbonated soft drinks were shown to decrease the rate of tooth movement, but alcohol consumption did not have an impact. Exploratory meta-analysis showed that caffeine exhibited an acceleratory effect after 3 weeks of force application. Exploratory meta-regression results indicated that high dosages of caffeine reduced the rate of tooth movement. CONCLUSIONS: The located animal experiments reported that caffeine accelerates, carbonated drinks decelerate, while alcohol does not affect the rate of orthodontic tooth movement. However, due to various limitations it remains unclear whether caffeine, alcohol, or carbonated drinks finally influence tooth movement in animal studies. REGISTRATION: Open Science Framework (https://osf.io/jyhbd/).

Novel method to delineate palatal rugae and assess their complexity using fractal analysis.

Palatal rugae constitute significant morphological landmarks, with wide clinical applications in forensics, insertion of mini-screws, and superimposition. Their morphology has been studied mainly with indices relevant to their qualitative characteristics. The present paper aims at presenting a new quantitative method to evaluate their complexity, by means of box-counting fractal dimension analysis, and to investigate its inter- and intra-rater reliability. Twenty maxillary plaster models were scanned for the needs of this study. A sequence of steps, including cropping of the mesh, ball pivoting, distance mapping and fractal dimension analysis, performed with Viewbox 4 software, was followed. Box-counting fractal dimensions were calculated as a measure of rugae's complexity. Inter- and intra-rater reliability were investigated, using Bland-Altman analysis. Fractal dimensions ranged from 1.274 to 1.491 (average: 1.412). Bland-Altman analysis of inter- and intra-examiner reliability demonstrated that the 95% limits of agreement ranged from - 0.012 to 0.011 and from - 0.004 to 0.004, respectively. The method is reliable and can be applied in research and forensics. It offers comprehensive evaluation of the rugae's complexity and a complete set of information about their outlines and height profiles, with minimum user intervention.

Ingestion of orthodontic appliances: A literature review.

Ingestion is the entry of a substance into the human organism, which occurs by taking it through the mouth into the gastrointestinal tract. One of the adverse events that may happen during the course of an orthodontic treatment is the ingestion of orthodontic appliances. The present review aims to investigate the literature regarding the ingestion of orthodontic appliances. An electronic search was carried out in order to identify case reports of ingestion of foreign objects related to orthodontic treatment in PubMed, Scopus, and Web of Science until July 2019.Nineteen articles were retrieved. In these articles, ingestion had occurred inadvertently, due to patients' or orthodontists' errors. Some of the most commonly ingested appliances were molar bands, segments of wire, and expansion keys. It is likely that patients with a specific medical background are more prone to ingestion of orthodontic appliances. Special precautions need be taken in order to avoid such incidents. These precautions are analyzed in three categories: general, those related to fixed appliances, and those related to removable appliances.

Does interceptive extraction of multiple primary teeth increase the chances of spontaneous eruption of permanent maxillary canines positioned palatally or centrally in the alveolar crest? A Systematic review.

INTRODUCTION: Extraction of primary maxillary canines in the mixed dentition has been suggested to increase the rate of normal eruption of displaced permanent canines (DPCs). In this study we assessed whether extracting multiple primary teeth increases the rate of normal eruption of DPCs positioned palatally or centrally in the alveolar crest. METHODS: Unrestricted searches in 8 databases were performed up to March 2021. We looked for data on the prevalence of physiologic eruption of DPCs and the changes in their position from randomized controlled trials. The risk of bias was assessed using the Cochrane Risk of Bias 2 Tool. Exploratory synthesis was carried out using the random effects model. RESULTS: Three studies (at low risk of bias) were identified, involving 128 individuals, followed for up to 48 months. The double extraction did not result in a benefit regarding successful eruption at 24 months follow-up, nor the change in position after 14.8 months. However, after 48 months the double extraction was beneficial (Risk Ratio: 1.17; 95% Confidence Interval: 1.05 to 1.30, P=0.005). Moreover, after 18 months, the DPCs' position improved more in the double extraction sites. CONCLUSIONS: While the extraction of the deciduous canine and first molar does not increase the chance of normal eruption nor improves the position of DPCs in shorter follow-ups, it might confer a benefit after a longer period of observation. Further studies are warranted in order to clarify the magnitude and clinical significance of any potential benefit and provide guidance to clinical decisions.

Impact of Diet Consistency on the Mandibular Morphology: A Systematic Review of Studies on Rat Models.

Apart from genetics, environmental factors, such as food consistency, may affect craniofacial morphology and development. The present systematic review aims to systematically investigate and appraise the available evidence regarding the effect of diet consistency on the anatomical structures of the basal bone of the rat mandible. The search was performed without restrictions in five databases (PubMed, Scopus, Web of Science, ProQuest Dissertations and Theses Global, including grey literature) and hand searching through January 2022. A total of 14,904 references were initially identified, and 16 articles were finally included in the systematic review. Rats that consumed hard diets were found to exhibit an increase inbigonial width, corpus height, condylar depth, condylar base inclination, condylar process inclination, mandibular plane inclination, height and length of angular process, mandibular body height, depth of antegonial notch, growth rate in the gonial angle, angular process convexity and height of condylar process. It was also noted that mandibular depth, mandibular height, ramus angle and angle between the angular process and mandibular plane were decreased in rats that were fed with a hard diet. On the other hand, there were conflicting results about the growth of mandibular length and width, corpus length, mandibular body length, ramus height, condylar length and width, gonial angle and height of coronoid process. From the abovementioned results, it can be concluded that food consistency may affect the morphology of anatomical structures and the overall growth and development of rat mandibles in various ways.

Intraoral Scanners in Orthodontics: A Critical Review.

BACKGROUND: The use of digital technology has exponentially increased over recent years. Intraoral scanners, especially, have gained traction within orthodontics. The objective of the present review is to investigate the available evidence to create an up-to-date presentation of various clinical aspects of intraoral scanners in orthodontics. METHODS: Search without restrictions in seven databases (Pubmed, CENTRAL, Cochrane Reviews, Scopus, Web of Science, Clinical Trials, Proquest) since inception, and hand searching until October 2020, were conducted. RESULTS: The majority of studies were either cross-over or parallel group studies. The accuracy and reproducibility of intraoral scanners, in comparison to conventional methods, were investigated in several studies, with controversial results. The duration of the procedure did not report any clear outcome in favor of any method. Patients seem to prefer intraoral scanning, even though numerous studies point out the importance of operators' experience and skills. CONCLUSIONS: Despite the innovations that intraoral scanners have brought in orthodontic clinical practice, there are still some challenges and limitations in their use. The majority of existing limitations may be overcome with experience and good clinical skills. More high-quality studies need to be conducted so that clinicians can have a clear image of this new technology.

Patient-reported experiences and preferences with intraoral scanners: a systematic review.

BACKGROUND: Intraoral scanners have become an increasingly popular alternative to conventional impression methods. Although their accuracy and validity have been examined thoroughly, patient-reported information including experiences, preferences, and satisfaction has not yet been investigated in a systematic way. OBJECTIVE: The objective of this systematic review is to investigate the available data and appraise the evidence on patient-reported experiences and preferences following impression taking with intraoral scanners. SEARCH METHODS: Unrestricted search of seven databases (Pubmed, CENTRAL, Cochrane reviews, Scopus, Web of Science, Clinical Trials, and ProQuest) and grey literature were conducted until October 2020. Detailed search strategies were developed for each database. SELECTION CRITERIA: Studies involving individuals of any gender or age, subjected to full arch impression taking with conventional and intraoral scanning methods were eligible for inclusion. DATA COLLECTION AND ANALYSIS: Following the retrieval and selection of the studies, data extraction was performed. Risk of bias assessment was performed using the RoB 2 and ROBINS-I tools. RESULTS: From the initially identified records, nine studies [eight crossover (two of them randomized) and one parallel group] were eventually included in the present systematic review. Randomized studies were shown, overall, to have some concerns regarding bias, whereas the non-randomized studies were found to be at serious risk, mainly because of bias due to confounding. All studies demonstrated some benefit in favour of intraoral scanning compared with conventional techniques. More positive feelings were generally observed with the intraoral scanners regarding smell, taste, sound, vibration, nausea, and queasiness. Overall, comfort assessment mostly favoured digital methods. No differences were found concerning the level of anxiety between the two methods. Among the included studies, time perception was a parameter leading to contradictory results. LIMITATIONS: These emerge due to the nature and characteristics of the information retrieved from the included studies. The validation of the instruments to capture patient-reported outcomes needs to be further elaborated. CONCLUSIONS: Intraoral scanners seem to be a promising new asset in the orthodontic office from the perspective of individuals' experiences and preferences. Nevertheless, to investigate patient-reported outcomes correctly, further high-quality studies are required in the future. REGISTRATION: Open Science Framework (https://osf.io/ayug2/).

Does the rate of orthodontic tooth movement change during the estrus cycle? A systematic review based on animal studies.

BACKGROUND: As the fluctuation of sex hormone levels in menstruating women results in periodical effects in bone metabolism, understanding the implications for tooth movement could be of benefit to the orthodontist. This type of research presents practical and ethical problems in humans, but animal models could provide useful information. Our objective was to systematically investigate the available evidence on the question whether the rate of orthodontic tooth movement varies between the different stages of the estrus cycle in animals. METHODS: Unrestricted searches in 7 databases and manual searching of the reference lists in relevant studies were performed up to February 2021 (Medline [PubMed], CENTRAL [Cochrane Library; includes records from Embase, CINAHL, ClinicalTrials.gov, WHO's ICTRP, KoreaMed, Cochrane Review Groups' Specialized Registers, and records identified by handsearching], Cochrane Database of Systematic Reviews [Cochrane Library], Scopus, Web of Knowledge [including Web of Science Core Collection, KCI Korean Journal Database, Russian Science Citation Index, SciELO Citation Index and Zoological Record], Arab World Research Source [EBSCO] and ProQuest Dissertation and Theses [ProQuest]). Our search focused on prospective controlled animal studies, whose samples included female subjects of any species that were quantitatively comparing the amount of tooth movement in the different stages of the estrus cycle. Following study retrieval and selection, relevant data was extracted, and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. RESULTS: From the finally assessed records, 3 studies met the inclusion criteria. Two of the studies experimented on Wistar rats, whereas the other on cats. Tooth movement was induced by expansion or coil springs. The rate of orthodontic tooth movement was increased during the stages of the estrus cycle when oestrogen and/or progesterone levels were lower. The risk of bias in the retrieved studies was assessed to be unclear. CONCLUSION: Hormonal changes during the estrus cycle may affect the rate of orthodontic tooth movement. Although these animal experiment results should be approached cautiously regarding their translational potential, it could be useful to consider the possible impact of these physiological changes in the clinical setting until more information becomes available. Registration: PROSPERO (CRD42021158069).

Does exogenous female sex hormone administration affect the rate of tooth movement and root resorption? A systematic review of animal studies.

BACKGROUND: The long-term use of contraceptive methods that contain estrogens, progestogens or combinations of the above among women aged 15 to 49 years is extensive. Both estrogens and progestogens affect bone metabolism. OBJECTIVE: To systematically investigate and appraise the quality of the available evidence from animal studies regarding the impact of exogenous administration of female sex hormones on the rate of orthodontic tooth movement and root resorption. SEARCH METHODS: Search without restriction in seven databases (including grey literature) and hand searching were performed until May 2021. SELECTION CRITERIA: We looked for controlled animal studies investigating the effect from exogenous administration of formulations containing female sex hormones on the rate of orthodontic tooth movement and root resorption. DATA COLLECTION AND ANALYSIS: After study retrieval and selection, relevant data was extracted, and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. The quality of available evidence was assessed with the Grades of Recommendation, Assessment, Development, and Evaluation. RESULTS: Three studies were identified, all being at unclear risk of bias. Overall, administration of progesterone and the combinations of estradiol with norgestrel and desogestrel were shown to significantly decrease the rate of orthodontic tooth movement when given for longer periods (>3 weeks). Inconsistent information was detected for shorter periods of consumption. Estradiol, with desogestrel use, resulted in less root resorption. The quality of the available evidence was considered to be low. CONCLUSIONS: Exogenous administration of female sex hormones may decelerate in the long term the rate of tooth movement and decrease orthodontically induced root resorption in animals. Until more information becomes available, an orthodontist should be able to identify a patient consuming such substances and understand the potential clinical implications and adverse effects that may arise. REGISTRATION: PROSPERO: CRD42017078208; https://clinicaltrials.gov/.

Posterior Mandibular Displacement-A Systematic Review Based on Animal Studies.

Treating extreme mandibular growth is challenging. The mandible is pushed backwards to address itsprotrusion. Nevertheless, conclusions after such displacement in animals have been contradictory. The aim of the present review is to present measurable alterations of the mandible and the condyle following retractionin healthy rats or rabbits. PubMed, Scopus and Web of Science were accessed for relevant studies up to October 2020. Eligibility was determined by the PICOS process, while the risk of bias was estimated with SYRCLE's risk of bias tool. Retraction resulted in a more distal molar occlusion and the condyle rested more posteriorly. Mandibular anteroposterior bilateral growth restriction was achieved, the condylar process measured smaller and its angulation increased. The condylar neck thickened, its posterior surface flattened, the coronoid process was measured longer, and enlarged retromolar density was registered. Differences in the ramus height and the intercondylar distance were insignificant. Changes persisted for the period of study and subsequently the mandible resumed its inherited growth pattern. The timing of mandibular shaping and TMJ outcomes might depend on the properties of the applied force. Stability is of concern and well-structured, long-term studies are expected to resolve the issue and further clarify the results of posterior mandibular displacement.

Effect of nicotine exposure on the rate of orthodontic tooth movement: A meta-analysis based on animal studies.

BACKGROUND: Nicotine exposure has been reported to modify bone cell function and the osseous metabolism with potential effects on the rate of orthodontic tooth movement. OBJECTIVES: To systematically investigate and quantitively synthesize the most recent available evidence from animal studies regarding the effect of nicotine exposure on the rate of orthodontic tooth movement. SEARCH METHODS: Unrestricted searches in 7 databases and hand searching were performed until July 2020 (PubMed, Central, Cochrane Database of Systematic Reviews, SCOPUS, Web of Science, Arab World Research Source, ProQuest Dissertations and Theses Global). SELECTION CRITERIA: We searched for controlled studies on healthy animals investigating the effect of nicotine on the rate of orthodontic tooth movement. DATA COLLECTION AND ANALYSIS: Following study retrieval and selection, relevant data was extracted and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. Exploratory synthesis and meta-regression were carried out using the random effects model. RESULTS: From the initially identified records, 5 articles meeting the inclusion criteria were selected and no specific concerns regarding bias were identified. Quantitative data synthesis showed that the rate of orthodontic tooth movement in the nicotine exposed rats was higher than in the control group animals (2 weeks of force application; 0.317 mm more movement in nicotine exposed rats; 95% Confidence Interval: 0.179-0.454; p = 0.000). No effect of the concentration or the duration force application was demonstrated following exploratory meta-regression. CONCLUSION: Rats administered with nicotine showed accelerated rates of orthodontic tooth movement. Although, information from animal studies cannot be fully translated to human clinical scenarios, safe practice would suggest that the orthodontist should be able to identify patients exposed to nicotine and consider the possible implications for everyday clinical practice.