How do teeth erupt?

The development of normal occlusion requires eruptive migration of teeth from their developmental position in the jaw into a functional position within the oral cavity. This process involves significant and coordinated movement in an axial direction and appropriate eruption through the gingival tissues. The mechanisms regulating these developmental events are poorly understood, and teeth retain eruptive potential throughout their lifespan. In recent years, the use of mouse models has helped to elucidate some of the underlying molecular and biological mechanisms of mammalian tooth eruption. Here, we outline our current understanding of tooth eruption mechanisms and discuss their relevance in terms of known human disorders of tooth eruption.

Cellular mechanisms of reverse epithelial curvature in tissue morphogenesis.

Epithelial bending plays an essential role during the multiple stages of organogenesis and can be classified into two types: invagination and evagination. The early stages of invaginating and evaginating organs are often depicted as simple concave and convex curves respectively, but in fact majority of the epithelial organs develop through a more complex pattern of curvature: concave flanked by convex and vice versa respectively. At the cellular level, this is far from a geometrical truism: locally cells must passively adapt to, or actively create such an epithelial structure that is typically composed of opposite and connected folds that form at least one s-shaped curve that we here, based on its appearance, term as "reverse curves." In recent years, invagination and evagination have been studied in increasing cellular detail. A diversity of mechanisms, including apical/basal constriction, vertical telescoping and extrinsic factors, all orchestrate epithelial bending to give different organs their final shape. However, how cells behave collectively to generate reverse curves remains less well-known. Here we review experimental models that characteristically form reverse curves during organogenesis. These include the circumvallate papillae in the tongue, crypt-villus structure in the intestine, and early tooth germ and describe how, in each case, reverse curves form to connect an invaginated or evaginated placode or opposite epithelial folds. Furthermore, by referring to the multicellular system that occur in the invagination and evagination, we attempt to provide a summary of mechanisms thought to be involved in reverse curvature consisting of apical/basal constriction, and extrinsic factors. Finally, we describe the emerging techniques in the current investigations, such as organoid culture, computational modelling and live imaging technologies that have been utilized to improve our understanding of the cellular mechanisms in early tissue morphogenesis.

Clinical communication in orthodontics: Any questions?

OBJECTIVE: To measure patient-perceived standards of clinician communication and identify elements of deficient performance. Good communication can improve the quality of care, patient satisfaction and compliance with treatment. DESIGN: Cross-sectional questionnaire service evaluation. SETTING: Two university dental hospital orthodontic departments. PARTICIPANTS: Any patients aged 10 years and over attending the orthodontic department for treatment or consultation were eligible for inclusion. Patients who required third-party translation services were excluded. METHODS: Clinicians provided the modified 15-item Communication Assessment Tool (CAT) to up to five patients in a clinical session. A front sheet for clinician characteristics was used and anonymised with a unique identifier. Univariable logistic GEE models examined associations among responses and clinician characteristics. RESULTS: There were 55 clinicians with 204 patient responses. The overall percentage of '5=excellent' ratings was 88% (SD 0.16). The lowest scoring item was 'encouraged me to ask questions' (55.8%). Based on clinician characteristics, there were lower odds of an excellent response for certain CAT items. There were higher odds of an excellent response if English was not the clinician's first language (1.05; 95% confidence interval = 1.00-1.09; P=0.03). CONCLUSION: There is a high standard of patient-clinician communication in the hospital orthodontic setting. Key areas of communication that require attention include encouraging patients to ask questions, talking in terms they can understand, recognising their main concerns and involving them in the decision-making process. The results of this study can be used to inform communication skills training and be replicated in similar dental settings (primary and secondary care) as part of quality improvement.

Radiographic outcome of secondary alveolar bone grafting in patients with alveolar clefts.

OBJECTIVE: To determine the outcome of secondary alveolar bone grafting (SABG) in a series of consecutive patients with clefts involving the alveolus. DESIGN AND SETTING: Retrospective cohort study of consecutive operations performed between June 2011 and September 2016 by a single surgeon at a single United Kingdom cleft center. PARTICIPANTS: A total of 160 patients with a cleft/s involving the alveolus, inclusive of syndromic patients and those with atypical facial clefts. INTERVENTIONS: A standard protocol involved an oral hygiene program, pre-surgical orthodontics where necessary and autologous bone grafting from the iliac crest. MAIN OUTCOME MEASURE(S): The Kindelan bone-fill index was used to evaluate success using occlusal radiographs. Weighted Cohen's kappa coefficient was used as a measure of intra- and inter-rater agreement. Fisher's exact test was used to examine the effects of type of cleft, pre-surgical orthodontics or age at time of SABG on radiographic outcome. RESULTS: There were 200 SABGs assessed. Mean age at time of SABG was 9.1 years old (SD 1.1) with 99% (n = 198) of grafts deemed successful. There were two failures where re-graft was performed successfully during the study period. A grade 1 outcome was achieved for 92.5% (n = 185) of grafts and this did not appear to be affected by type of cleft (P = .290), pre-surgical orthodontics (P = .380) or age at time of SABG (P = .081). CONCLUSIONS: The high success rate reported in this study supports the favorable outcomes of a high-volume cleft surgeon. These findings can be used for comparative audit with similar units providing cleft care.

Occlusal Outcome of Orthodontic Treatment for Patients With Complete Cleft Lip and Palate.

AIM: To assess occlusal outcomes of orthodontic treatment for patients with complete cleft lip and palate. DESIGN: Retrospective assessment using the Peer Assessment Rating (PAR) index. SETTING: Consecutive patients treated by one consultant orthodontist at a tertiary care cleft center. PARTICIPANTS: One hundred twenty-seven patients with either complete unilateral cleft lip and palate (UCLP) or bilateral cleft lip and palate (BCLP) consecutively treated with fixed appliances. INTERVENTION: Fixed orthodontic appliance treatment and orthognathic surgery when required. OUTCOMES: The PAR index assessment was carried out by a calibrated-independent assessor. Treatment duration, the number of patient visits, and data on dental anomalies were drawn from patient records and radiographs. RESULTS: One hundred two patients' study models were assessed after exclusions. Mean start PAR score for UCLP (n = 71) was 43.9 (95% CI, 41.2-46.6, SD 11.5), with a mean score reduction of 84.3% (95% CI, 81.9-86.7, SD 10.1). The UCLP mean treatment time was 23.7 months with 20.1 appointments. Mean start PAR score for BCLP (n = 31) was 43.4 (95% CI, 39.2-47.6, SD 11.4), with a mean score reduction of 80.9% (95% CI, 76.3-85.5, SD 12.5). The BCLP mean treatment time was 27.8 months with 20.5 appointments. CONCLUSION: These results compare well with other outcome reports, including those for patients without a cleft, and reflect the standard of care provided by an experienced cleft orthodontist. As with high-volume surgeons, orthodontic treatment for this high need group is favorable when provided by a high-volume orthodontist. These findings may be used for comparative audit with similar units providing cleft care.

Prediction intervals reporting in orthodontic meta-analyses.

BACKGROUND: A prediction interval represents a clinical interpretation of heterogeneity. The aim of this study was to determine the prevalence of prediction interval reporting in orthodontic random effect meta-analyses. The corroboration between effect size estimates with 95% confidence intervals (CIs) and prediction intervals were also explored. MATERIALS AND METHODS: Systematic reviews (SRs) published between 1 January 2010 and 31 January 2021 containing at least one random effects meta-analysis (minimum of three trials) were identified electronically. SR and meta-analyses characteristics were extracted and prediction intervals, where possible, were calculated. Descriptive statistics and the percentage of meta-analyses where the prediction interval changed the interpretation based on the 95% CI were calculated. Fisher's exact test was used to examine associations between the study variables and reporting of prediction intervals. RESULTS: One hundred and twenty-one SRs were included. The median number of SR authors was 5 (interquartile range: 4-6). The reporting of prediction intervals was undertaken in only 19.0% (N = 23/121) of meta-analyses. Out of 95 meta-analyses, only in 6 (6.3%, N = 6/95) were the 95% CI corroborated by the prediction interval. In 60 meta-analyses (63.3%, N = 60/95) despite a 95% CI indicating a statistically significant result, this was not corroborated by the corresponding prediction interval. CONCLUSIONS: Within the study timeframe, reporting of prediction intervals is not routinely undertaken in orthodontic meta-analyses possibly due to a lack of awareness. In future orthodontic random effects models containing a minimum of three trials, reporting of prediction intervals is advocated as this gives an indication of the range of the expected effect of treatment interventions.

Assessment of early exaggerated treatment effects in orthodontic interventions using cumulative meta-analysis.

BACKGROUND: The reported initial strong treatment effects reported in early trials that are refuted in subsequent future studies assessing the same interventions have been attributed to novelty bias. The aim of this study was to determine whether there is any evidence of novelty bias in the reported treatment effects of orthodontics interventions. MATERIALS AND METHODS: Relevant orthodontic systematic review (SRs) topics containing at least one meta-analysis on either binary or continuous outcomes with a minimum of three trials considered important areas in the field of orthodontic practice were identified. SR, meta-analysis, and primary study-level characteristics were extracted. Descriptive statistics were calculated at the SRs, meta-analysis, and at the individual study level. All SR and trial-level data were imported into the statistical software and all meta-analyses were replicated using the cumulative random-effects meta-analysis approach. Changes in the size and direction of the estimates between the first trial and the cumulative effect over time were recorded. RESULTS: Forty-seven meta-analyses were included. The total number of primary studies included within these meta-analyses was 408 (N = 408). Overall, the final effect size estimate decreased in 29 (61.7%, N = 29/47) cumulative meta-analyses whilst it increased in the remaining 18 (38.3%, N = 18/47). No association between the level of risk of bias and the cumulative absolute effect size was evident (OR 1.00; 95% CI: 0.98, 1.03; P = 0.717) after adjusting for year of the primary study (P = 0.22). CONCLUSIONS: Clinicians should be wary of the results of trials reporting the effectiveness of new interventions as there is a possibility that the reported effect size will be often exaggerated.

Are treatment effect assumptions in orthodontic studies overoptimistic?

BACKGROUND: At the clinical trial design stage, assumptions regarding the treatment effects to be detected should be appropriate so that the required sample size can be calculated. There is evidence in the medical literature that sample size assumption can be overoptimistic. The aim of this study was to compare the distribution of the assumed effects versus that of the observed effects as a proxy for overoptimistic treatment effect assumptions at the study design stage. MATERIALS AND METHOD: Systematic reviews (SRs) published between 1 January 2010 and 31 December 2019 containing at least one meta-analysis on continuous outcomes were identified electronically. SR and primary study level characteristics were extracted from the SRs and the individual trials. Details on the sample size calculation process and assumptions and the observed treatment effects were extracted. RESULTS: Eighty-five SRs with meta-analysis containing 347 primary trials were included. The median number of SR authors was 5 (interquartile range: 4-7). At the primary study level, the majority were single centre (78.1%), utilized a parallel design (52%), and rated as an unclear/moderate level of risk of bias (34.3%). A sample size was described in only 31.7% (110/347) of studies. From this cohort of 110 studies, in only 37 studies was the assumed clinical difference that the study was designed to detect reported (37/110). The assumed treatment effect was recalculated for the remaining 73 studies (73/110). The one-sided exact signed rank test showed a significant difference between the assumed and observed treatment effects (P < 0.001) suggesting greater values for the assumed effect sizes. CONCLUSIONS: Careful consideration of the assumptions at the design stage of orthodontic studies are necessary in order to reduce the unreliability of clinical study results and research waste.

Clinical evaluation of botulinum toxin A in the management of temporomandibular myofascial pain.

We did a clinical service evaluation of patient-reported outcomes for pain and change in interincisal distance in patients treated with botulinum toxin A (BTX-A) for temporomandibular myofascial pain at nurse-led clinics. We retrospectively reviewed the clinical records of 100 patients and the prescribing patterns of two OMFS consultants. The mean starting pain score of 7.54 out of 10 was reduced by a mean (SD) of 2.48 (2.1) points after the intervention (p<0.001). The most common prescription was for 100 units (n=59 prescriptions). The change in the mean pain scores did not differ significantly whether 100 or 200 units were prescribed (p=0.19). Interincisal distance increased by a mean (SD) of 0.5 (5.24) mm after treatment with BTX-A, which was not significant (p=0.35). In most cases the treatment helped to manage and reduce the symptoms of temporomandibular myofascial pain. Considerable improvement in interincisal distance as a result of this treatment alone, however, is unlikely, but it may have a role in a multifaceted approach, particularly when other conservative methods have failed. The use of a pro forma may allow for more consistent record keeping and the detailed assessment of patient-reported pain scores in the weeks and months after treatment. Development of an electronic patient-reported outcome (ePRO) tool may facilitate this further.