Evaluation of maxillary canine and molar movement during the first phase of extraction space closure: a multilevel analysis

OBJECTIVE

This study was designed to analyze and compare the cusp and apex movements of the maxillary canines and first molars during canine retraction in the first step of extraction space closure, and to evaluate if these teeth follow a curvilinear (acceleration and/or deceleration) movement rate.

MATERIAL AND METHODS

Twenty-five patients (23.3 ± 5.1 years of age) were enrolled. The retraction of the maxillary canines was accomplished using nickel-titanium closed coil springs (100gf) on 0.020-in stainless steel archwire. Oblique cephalograms were traced and superimposed on the anatomic best fit of the maxilla (before the retraction [T0], and after one month [T1], three [T3], five [T5] and seven [T7] months). Statistics was based in a normally distributed data. Multilevel procedures were used to derive polynomials for each of the measurements. Student's t-test and one-way repeated measures ANOVA were conducted. The level of significance of 5% was adopted.

RESULTS

Canine cusps and apexes did not follow a quadratic curve regarding horizontal movement (neither accelerate nor decelerate). Canine and molar cusps showed more horizontal movement than apexes (4.80 mm vs. 2.78 mm, and 2.64 mm vs. 2.17 mm, respectively).

CONCLUSIONS

Canine did not accelerate or decelerate overtime horizontally; the cusps and apexes of the canines and molars showed more horizontal movement and larger rate at the beginning of canine retraction, followed by significantly smaller and constant movement rate after the first month.

Speech performance in adult patients undergoing Invisalign treatment

OBJECTIVES

To assess speech performance of adult patients undergoing orthodontic treatment with Invisalign.

MATERIALS AND METHODS

Twenty-four adult patients with Invisalign (Invisalign group: 6 men, 18 women; average age; 34.88 years) and 20 adult patients with fixed labial appliances (fixed group: 5 men, 15 women; average age; 38.85 years) were evaluated. Speech was recorded immediately before delivery of the first set of clear aligners or bonding of labial appliances (T0), immediately after delivery or bonding (T1), and 2 months after delivery or bonding (T2). Speech was evaluated via a combination of three auditory analyses: (1) objective acoustic analysis through digital sonography, (2) semiobjective assessment by six speech and language pathologists, and (3) subjective assessment patient questionnaire.

RESULTS

The objective acoustic analysis showed a statistically significant difference over time from T0 to T1, T1 to T2, and T0 to T2 for Invisalign patients. The semiobjective analysis revealed a significant speech alteration from T0 to T1 and T1 to T2 for both groups, and from T0 to T2 in the Invisalign group. The subjective analysis showed a significant difference between means of Invisalign and fixed group patient perception at both T1 and T2.

CONCLUSIONS

Invisalign treatment significantly affected speech, and although patients experience some level of adaptation, speech does not return to normal after 2 months of treatment.

Class II malocclusion correction with Invisalign: Is it possible?

INTRODUCTION

This research aimed to determine whether Class II malocclusion can be treated with clear aligners after completing treatment with the initial set of aligners.

METHODS

A sample of 80 adult patients were divided into Group 1 with Class I molar malocclusions (n = 40 [11 men and 29 women]; 38.70 ± 15.90 years) and Group 2 with Class II molar malocclusions (n = 40 [11 men and 29 women]; 35.25 ± 15.21 years). All patients had finished treatment with the initial set of Invisalign aligners (Align Technology, Santa Jose, Calif) without known centric occlusion-centric relation discrepancies, issues of compliance, or overcorrection. The 7 measurements using the American Board of Orthodontics (ABO) Model Grading System and millimetric measurements for anteroposterior (AP) and vertical dimensions were assessed and compared between the 2 groups at pretreatment, posttreatment ClinCheck (Align Technology) prediction, and posttreatment.

RESULTS

No improvements were observed in the AP correction. The amount of AP correction in patients with Class II malocclusion was 6.8% of the predicted amount. The amount of overbite correction achieved was 28.8% and 38.9% of the predicted amounts in patients with Class I and Class II malocclusion, respectively. Significant improvements in alignment and interproximal contact scores were observed, with only slight improvements in total ABO scores. An increase in mean occlusal contacts score was observed after treatment. No patient with Class II malocclusions would meet the ABO standards after Invisalign treatment.

CONCLUSIONS

The Invisalign system successfully achieves certain tooth movements but fails to achieve other movements predictably. No significant Class II correction or overjet reduction was observed with elastics for an average of 7-month duration in the adult population. Additional refinements may be necessary to address problems created during treatment, as evidenced by a posterior open bite incidence.

Multiple deprivation and geographic distance to community physical activity events - achieving equitable access to parkrun in England

Objectives

To evaluate geographic access to free weekly outdoor physical activity events (‘parkrun’) in England, with a particular focus on deprived communities, and to identify optimal locations for future events to further maximise access.

Study design

This study is a cross-sectional ecological analysis of the socio-economic disparities in geographic access to parkrun events in England in late 2018.

Methods

We combined geolocation data on all English Lower Layer Super Output Areas and parkrun events to calculate geodesic distances to the nearest event for more than 32,000 communities in England. We use this measure of geographic access to summarise the relationship between access and socio-economic deprivation, measured using the index of multiple deprivation. We then used geographic coordinates of public green spaces in England to conduct a simple location-allocation analysis to identify 200 locations for future event locations that would maximise access.

Results

In England, 69% of the population live within 5 km of one of the 465 parkrun events. There is a small negative correlation between distance and deprivation, indicating that access is slightly better in more socio-economically deprived areas. Setting up an additional 200 events in optimal locations would improve access: the average distance to the nearest parkrun event would improve by 1.22 km, from 4.65 km to 3.43 km, and approximately 82% of the English population would live within 5 km of a parkrun event.

Conclusion

Over two-thirds of the English population live within 5 km of a parkrun event, and contrary to our expectation, we find that geographic access is slightly better for those living in more deprived communities. Creating additional events may improve geographic access, but effective strategies will still be needed to increase engagement in new and existing events by those living in socio-economically deprived areas.

•

Parkrun in a grass-roots movement that organises free weekly 5 km running and walking events.

•

In England, the median distance to the nearest parkrun event was 3.4 km; 69% of the population lived within 5 km of an event.

•

Access showed no negative socio-economic gradient. In fact, people in deprived communities had better geographic access.

•

Sport England provided funding to set up 200 new events. We identified optimal locations, to further maximise public access.

Esthetic perception of clear aligner therapy attachments using eye-tracking technology

INTRODUCTION

The purpose of this research was to assess and compare esthetic perceptions of clear aligner therapy with attachments and esthetic brackets by measuring differences in eye fixations using eye-tracking technology.

METHODS

The sample involved 250 adult subjects. The subjects gave verbal consent, then viewed photographs showing 4 variations of orthodontic appliances: clear aligner control with minimal attachments, clear aligner with anterior and posterior attachments, esthetic brackets, and clear aligner with posterior attachments. Images were displayed for 6 seconds each on a computer monitor. Location and time to first fixation, total fixation duration, and total visit count and duration for each type of appliance were measured. Subjects were then asked to complete an online survey.

RESULTS

Participants spent the least amount of time looking at the photograph of the control, followed by those of the ceramic brackets, posterior attachments, and anterior and/or posterior attachments. The anterior and/or posterior image had the least number of visits but garnered the longest visit duration (1.32 visits averaging 0.74 seconds per visit). This was followed by the images of the posterior attachments (1.40 visits, 0.70 seconds per visit), ceramic brackets (1.43 visits, 0.65 seconds per visit), and minimal attachments control (1.45 visits, 0.61 seconds per visit). The hierarchy of most preferred appliances across all 250 respondents was as follows: minimal attachments control, ceramic brackets, posterior attachments, and anterior and/or posterior attachments. Overall, 88.4% of subjects would compromise appliance esthetics during treatment for a better outcome (n = 221).

CONCLUSIONS

Eye-tracking data show that time to the first fixation was negatively correlated with its survey ranking and that an increase in attachments led to an increase in total fixation duration. There is a general desire for clear aligners without attachments and ceramic brackets over clear aligners with multiple attachments. Survey data suggest that although respondents viewed appliance esthetics as highly important, nearly all would compromise appliance esthetics during treatment if it resulted in a better outcome.

Who has access and who participates in parkrun? - implications for selecting future event locations

Background

parkrun is an international organisation which hosts free, weekly volunteer-led, running events. More than 300,000 people participate across 21 countries each week. The present study investigates how access to, and participation in, parkrun events varies across England. We go on to make policy recommendations for new parkrun event locations, in order to maximise geographical access and participation whilst taking account of the impact on inequalities.

Methods

We combined location data of census areas, parkrun events and public parks in England. For the census areas, access was defined as the distance of the area’s centroid to the nearest parkrun event, and parkrun UK provided information on 2018 participation rates per area. Linear regression was used to investigate the effect of deprivation on access, and the effect of deprivation and access on utilisation. We propose a flexible algorithm for identifying optimal new parkrun event locations and provide two sample sets of recommendations.

Results

The median distance to the nearest parkrun event was 3.4 km, but the distribution was heavily skewed: for approximately 10% of the population, the nearest event was more than 10 km away.

Despite statistical significance, the relationship between deprivation and access was very weak. However, access and deprivation had a considerable effect on participation: less deprived areas, and areas with good access had higher participation rates. The best locations for new events are contingent on what parkrun aims to maximise. We demonstrate that optimal locations for maximising equitable geographic access differ from locations for maximising participation.

Conclusions

Access to parkrun is generally good and is similar across socioeconomic groups, but participation is markedly higher in less deprived areas. Our algorithm can be used by parkrun to further improve access for deprived communities. However, better access alone is unlikely to reduce inequities in participation.

Key messages

In England, access to parkrun is generally good, and our algorithm can be used to further optimise it. However, better access alone is unlikely significantly increase participation from deprived areas.

Which one closes extraction spaces faster: en masse retraction or two-step retraction? A randomized prospective clinical trial

OBJECTIVES

To compare the time to close extraction spaces between en masse (ER) and two-step retraction (TSR).

MATERIALS AND METHODS

Forty-eight patients with bimaxillary protrusion underwent treatment with extraction of four first premolars. All patients were randomly allocated to one of two groups: ER (n = 24) or TSR (n = 24). The main outcome was the time required to close spaces between ER and TSR; the closing time of spaces between females and males was a secondary outcome. The size of premolars was measured on the models and data were collected on clinical records at the following times: retraction start date (T1) and space closure completion date (T2). The total time to close the extraction spaces was calculated for each extracted premolar (T1 to T2). The Kaplan Meier method and the Log-Rank test were used to compare the groups.

RESULTS

The time to close extraction spaces showed significant differences between the ER and TSR groups. While ER took between 12.1 and 13.8 months, TSR took between 24.7 and 26.8 months. The TSR group showed a significant difference between sexes; male patients took 5.5 months longer than female patients for the extraction spaces to close.

CONCLUSIONS

TSR takes between 1.8 and 2.2 times longer than ER to close the extraction spaces and it took longer in males than females.

Comparison of anterior retraction and anchorage control between en masse retraction and two-step retraction: A randomized prospective clinical trial

OBJECTIVES

The purpose of this two-arm parallel trial was to compare en masse (ER) and two-step retraction (TSR) during space closure.

MATERIALS AND METHODS

Forty-eight adult patients with bimaxillary protrusion who were planned for treatment with extraction of four first premolars were enrolled. All patients were randomly allocated in a 1:1 ratio to either the ER (n = 24) group or the TSR (n = 24) group. The main outcome was the amount of posterior anchorage loss in the molars and the retraction of the incisors between ER and TSR; the difference in incisor and molar inclination was a secondary outcome. Lateral cephalometric radiographs and oblique cephalometric radiographs at 45° were taken before retraction (T1) and after space closure (T2). Cephalograms were digitized and superimposed on the anatomic best fit of the maxilla and mandible by one operator who was blinded to the treatment group.

RESULTS

Neither incisor nor molar crown movements showed any significant differences between the ER and TSR. There were no significant differences in the tipping of incisors and molars between the two groups.

CONCLUSIONS

No significant differences existed in the amount of retraction of incisors and anchorage loss of molars between ER and TSR. Changes in incisor and molar tipping were similar, with the crowns showing more movement than the apex.

Beam transport and space charge compensation strategies (invited)

The transport of intense ion beams is affected by the collective behavior of this kind of multi-particle and multi-species system. The space charge expressed by the generalized perveance dominates the dynamical process of thermalisation, which leads to emittance growth. To prevent changes of intrinsic beam properties and to reduce the intensity dependent focusing forces, space charge compensation seems to be an adequate solution. In the case of positively charged ion beams, electrons produced by residual gas ionization and secondary electrons provide the space charge compensation. The influence of the compensation particles on the beam transport and the local degree of space charge compensation is given by different beam properties as well as the ion beam optics. Especially for highly charged ion beams, space charge compensation in combination with poor vacuum conditions leads to recombination processes and therefore increased beam losses. Strategies for providing a compensation-electron reservoir at very low residual gas pressures will be discussed.

An unusual case of adenoid cystic carcinoma with hard palate perforation

Adenoid cystic carcinoma is a malignant tumor which occurs frequently in hard palate associated with minor salivary glands. The lesion generally presents as a painful slow growing mass and it is characterized by recurrences and distant metastasis resulting in a poor prognosis for the patient. This paper reports an atypical adenoid cystic carcinoma with palatal perforation which occurred in a young woman. Initial diagnostic hypothesis were necrotizing sialometaplasia and lues. Although adenoid cystic carcinoma is common in hard palate, cases with palatal perforation are uncommon and may lead to delay in diagnosis and therapy.