Predictability of orthodontic tooth movement with aligners: effect of treatment design.

BACKGROUNDS: The present study was designed to define: (1) which are the less predictable OTM with Invisalign aligners when the treatment plan is designed by expert operators, (2) if the presence and shape of attachments influence the predictability of OTM and (3) if patients' demographics influence OTM predictability. The sample comprises 79 prospectively recruited patients (mean age 30.8 years; SD 12.0; 23 M, 56 F), treated by expert operators with an average of 27 aligners (SD 15) in the maxillary arch and 25 aligners (SD 11) in the mandibular arch. Post-treatment digital models and final virtual treatment plan models were exported from ClinCheck® software as STL files and subsequently imported into Geomagic Qualify ®software, to compare final teeth positions. The differences were calculated and tested for statistical significance for each tooth in the mesial-distal, vestibular-lingual and occlusal-gingival directions, as well as for angulation, inclination and rotation. In addition, the statistical significance of categorical variables was tested. RESULTS: The lack of correction was significant for all movements and in all group of teeth (P < 0.01) except for the rotation of maxillary first molar. The prescribed OTM, the group of teeth and movement, the frequency of aligner change and the use of attachment influence the outcome. The greatest discrepancies in predicted and achieved tooth position were found for angular movements and rotation of teeth characterized by round-shaped crowns, for a ratio of approximately 0.4° per 1° prescribed. Optimized attachments for upper canines and lower premolar rotation seem not working properly. Second molar movements are mostly unexpressed. Furthermore, changing the aligner every 14 days will reduce the lack of correction of the 12% with respect to 7 days aligner change. CONCLUSIONS: Predictability of orthodontic movement with aligners still has limitations related to the biomechanics of the system: the shape of some attachments and the characteristics of aligner material need to be redefined. However, the results of this study allow to properly design the virtual treatment plan, revealing how much overcorrection is needed and which attachments are most effective.

Chronic pain and weather conditions in patients suffering from temporomandibular disorders: a pilot study.

OBJECTIVES: Patients with temporomandibular disorders (TMDs) often report increased pain in response to changes in weather conditions. Nevertheless, scientific evidence supporting this relationship is scarce. The aim of this study was to assess a potential relationship between pain intensity and meteorological factors, through a newly developed, portable device, in patients affected by chronic masticatory muscle pain. METHODS: Seven female subjects were diagnosed with myofascial pain of the masticatory muscles, according to RDC/TMD criteria, were recruited, and participated in the study. Each patient was provided with a portable data logger that recorded and stored weather variables (atmospheric pressure, air humidity, temperature) every 15 min. Patients were asked to record the level of perceived pain on an electronic visual analogue scale (VAS) every hour. The relationship between meteorological variables and pain scores was investigated using separate generalized least squares regression models with a correlation structure estimated via autoregressive integrated moving average models. RESULTS: Individual VAS trajectories in the study period were different. The effect of meteorological factors on VAS scores was statistically significant in five subjects, with at least one main effect and/or one two-way interaction between meteorological variables being significant. CONCLUSIONS: The analyses suggest the existence of different interindividual responses to climatic changes. However, the identified putative role of meteorological variables and of their two-way interactions suggests that further investigations on larger samples may be useful to assess the research question under examination.