Journal of Aligner Orthodontics, 04/2020

The dismissal of the causal role of occlusal interference may be the result of the erroneous conception of occlusal interference and functional disorders, including temporomandibular disorders. The majority of researchers measure or assess variation in occlusion in a way that does not correspond to the concept of interference that is applied by many clinicians. Interferences are practically universally acquired risk factors, the result of a soft diet and minimal functional tooth wear. The lack of interference-free subpopulations needs to be taken into account in the design of studies of occlusion. Studies that fail to show the association between occlusion and temporomandibular disorder suffer from methodological bias concerning not only occlusal variation but probably also the nature of temporomandibular disorder. The basic assumption has been that temporomandibular disorder is a self-limiting pain disorder. The Research Diagnostic Criteria for temporomandibular disorders exclude several signs and symptoms associated with pathofunction. In clinical opinion, they often foreshadow painful conditions. Painless patients at risk of becoming pain patients are classified as ‘healthy’ according to these criteria. Randomised clinical trials testing the causal role of occlusion on the assumption that occlusal interferences are universal risk factors have so far clearly failed to exclude occlusion from the causal complex of functional disorders. Elimination of the risk from occlusion remains a valid form of therapy when the cost–benefit assessment is favourable. Keywords: functional disorders, occlusal interference, paradigms

Objective: The aim of this study was to identify laypeople’s preferred facial profile aesthetics in order to obtain standard cephalometric measures that correlate with lay judgements of facial aesthetics. Materials and methods: The study participants were adult Italian laypeople (aged ≥ 18 years) with no prior knowledge of dentistry, recruited in a shopping centre in Italy. A silhouette was created for each cephalometric value (SNGoGn angle, SNA angle, SNB angle, Ls-E, Li-E and G’Sn-SnPg’ angle), then the initial values were increased and decreased by one and one and half times the standard deviation to obtain four other silhouettes for each group, creating six groups of five silhouettes. The primary outcome measure of the present study was the examiners’ personal preference out of the 30 silhouettes, rated on a visual analogue scale ranging from 0 to 100. Results: The highest-rated silhouettes from each group were Silhouette C (GoGn, 32 degrees) for the GoGn group with a mean visual analogue scale score of 71.5 ± 16.4 mm; H (SNA, 82 degrees) for the SNA group with 64.3 ± 20.1 mm; M (SNB, 80 degrees) for the SNB group with 71.4 ± 17.4 mm; R (Ls-E, −4 mm) for the Ls:E group with 66.2 ± 18 mm; W (Li-E, −2 mm) for the Li:E group with 65.9 ± 19.8 mm; and BB (G’Sn-SnPg’, 12 degrees) for the G’Sn-SnPg’ group with 72.6 ± 16.7 mm. Conclusions: The profiles with average values were rated as the most attractive. The age of the observers had a significant impact on the evaluation of profile features, influencing the scores for all parameters. Vertical characteristics seemed to influence profile perception more than anteroposterior features. Keywords: aesthetics, dental, face

Objective: To analyse the effects of clear aligner therapy (CAT) on patients affected by sleep bruxism, recording the effects of CAT on masseter contractions and the overall sleep bruxism index during sleep. Materials and methods: 40 subjects requiring orthodontic treatment and affected by sleep bruxism (17 men, 23 women, 26 ± 5 years) were enrolled and randomly assigned to either the CAT group, with 20 subjects undergoing orthodontic treatment with aligners (8 men, 12 women, 20 ± 6 years), or placebo group (9 men, 11 women, 25 ± 3 years), with 20 subjects wearing a Begg appliance without occlusal coverage. After dropouts were removed, the study was conducted on a total of 34 subjects (13 men, 21 women, 21 ± 6 years), with 17 in the CAT group (6 men, 11 women, 19 ± 4 years) and 17 (7 men, 10 women, 24 ± 3 years) in the placebo group, followed for 1 year. Sleep bruxism index and electromyographic signals were recorded using a portable electromyographic-electrocardiographic device (Bruxoff, Bioelettronica, Turin, Italy) at baseline (T0), after 1 month (T1), 3 months (T2), 6 months (T3) and 12 months (T4). Results: CAT produced no significant changes in the sleep bruxism index. A reduction in masseter contractions, more specifically general phasic contractions not related to sleep bruxism, was observed after 1 year of treatment in patients wearing clear aligners (P < 0.05). Conclusion: The use of CAT in orthodontic patients does not influence the sleep bruxism index, but can affect some specific electromyographic background signals. Keywords: clear aligners, electromyography, orthodontics, sleep bruxism

The aim of this article is to show the effectiveness of Vivera retainers (Align Technology, San Jose, CA, USA) after orthodontic treatment to favour long-term stability. Vivera retainers are produced as a final retainer option following nearly invisible orthodontic treatment (Invisalign, Align Technology). The use of removable plastic appliances is currently gaining popularity among orthodontists thanks to their ability to encapsulate and retain both posterior and anterior teeth. However, traditional thermoformed appliances display some limitations regarding wear resistance and fitting. This article describes the technical features of Vivera retainers and presents a clinical case with a 10-year follow-up to emphasise the effectiveness of Vivera retainers. Keywords: biomaterials, Invisalign, long-term stability, maintenance, thermoplastic, thermoformed retainers, Vivera

Adult orthodontic therapy often requires the treatment of cases with scarce cancellous bone and/or roots too close to the cortical plate. In an attempt to recover maxillary and mandibular shape and to improve smile aesthetics, some orthodontic procedures create expansions which place teeth in extreme locations outside the cancellous bone and even in the cortical bone plate. This leads to tooth instability, supporting tissue damage, fenestrations and bone defects. When a diagnosis is achieved using CBCT, it is possible to assess the amount and quality of bone and the location of teeth in the alveolar ridge. Use of aligners permits the movement of individual teeth with minimal reactive movement of the adjacent teeth. With a careful diagnosis and by applying detailed biomechanics, it is possible to place each tooth in a correct and stable location within the alveolar bone. Keywords: aligners, bone loss, CBCT

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