Evaluation of masticatory muscle response to clear aligner therapy using ambulatory electromyographic recording.

INTRODUCTION: Patients undergoing clear aligner therapy (CAT) report muscle tenderness and produce wear facets on their aligner trays. However, little is known about the masticatory muscle response to clear aligners. Here, we measured the activity of the masseter during CAT using ambulatory electromyography. We also explored whether psychological traits modulate the masticatory muscle response to CAT. METHODS: Using portable data loggers, we recorded the electromyographic (EMG) activity in the right masseter muscle of 17 healthy adults without temporomandibular disorder (16 females, 1 male; mean age ± standard deviation, 35.3 ± 17.6 years) commencing treatment with CAT over 4 weeks, under the following conditions: week 1 without aligners (baseline), week 2 with a passive aligner (dummy), week 3 with their first active aligner (active1), and week 4 with their second active aligner (active2). We used a mixed-effect model to test differences in EMG activity over the 4-weeks and a general linear model to test the effect of psychological traits on EMG activity. RESULTS: The EMG activity of the masseter increased significantly with aligners compared with baseline. The largest relative increase in EMG activity was seen during the dummy (152%; P <0.001) and active1 (155%; P <0.001) stages. During active2, the activity of the masseter decreased significantly toward baseline levels. Participants' trait anxiety was positively associated with increases in EMG activity (P = 0.027). CONCLUSIONS: CAT is associated with a transient increase in masticatory muscle activity, possibly because of an increase in wake-time parafunctional tooth clenching. Temporomandibular disorder-free patients adapt well to CAT as the masticatory muscle activity decreases toward baseline levels after 2 weeks.

Surgical uprighting of mandibular second molars: A single-group retrospective cohort study.

INTRODUCTION: The management of impacted, unerupted, or malpositioned mandibular second molars with orthodontic therapy requires special attention in order to achieve normal anatomic positioning within the dental arch. We present a surgical approach to managing these teeth combining exposure and surgically-assisted forced eruption. METHODS: This retrospective single-group cohort study followed 260 impacted mandibular second molars. The molars were exposed and surgically uprighted. An orthodontic bracket was bonded to aid in orthodontic traction, and the wound was packed to prevent soft tissue growth over the crown of the exposed molar. Patients were followed for a minimum of 6 months after uprighting, during which the following outcomes were measured: the degree of success of the eruption one the basis of the clinical occlusal relationship to the opposing dentition, radiographic evidence of bone fill, the periodontal status of the teeth involved, and tooth vitality. RESULTS: A total of 260 mandibular second molars were uprighted in 177 patients (83 female, 94 male) with an average age of 14.8 years. Outcomes showed that 255 molars (98.1%; 95% confidence interval, 96.3-99.8) were successfully uprighted. Complications included infection/abscess in 3 molars and fractured root requiring extraction in 2 molars. All remaining 255 teeth tested vital, 17 teeth had periodontal pocketing of more than 5 mm, and 235 of the teeth had occlusal contact after healing. CONCLUSIONS: Surgically-assisted forced eruption with or without orthodontic forced eruption is a safe, successful, and viable approach to managing unerupted or malpositioned mandibular second molars in the adolescent population.

Impact of clear aligner therapy on tooth pain and masticatory muscle soreness.

BACKGROUND: Clinical findings suggest that orthodontic treatment with clear aligners (clear aligner therapy/CAT) may cause masticatory muscle soreness in some patients. OBJECTIVE: This multi-site prospective study investigated tooth pain and masticatory muscle soreness and tenderness in patients undergoing CAT and explored whether psychological traits affected these outcomes. METHODS: Twenty-seven adults (22F, 5M; mean age ± SD=35.3 ± 17.6 years) about to start CAT were recruited at three clinics. During CAT, they reported on 100-mm visual analogue scales their tooth pain, masticatory muscle soreness and stress three times per day over 4 weeks (week 1 = baseline; week 2 = dummy aligner; week 3 = first active aligner; week 4 = second active aligner). Pressure pain thresholds (PPTs) were measured at the masseter and temporalis at baseline and after week 4. Mixed models were used to evaluate the outcome measures over time. RESULTS: Clear aligner therapy caused mild tooth pain, which was greater with the passive than the first and second active aligners (both P < .001). Mild and clinically not relevant masticatory muscle soreness was produced by all aligners (all P < .05), with the first active aligner producing less soreness than the dummy aligner (P < .001). PPTs did not change significantly after 4 weeks. Both tooth pain and masticatory muscle soreness were affected by stress and trait anxiety, whilst muscle soreness was affected also by oral behaviours. CONCLUSIONS: In the short term, CAT produces tooth pain and masticatory muscle soreness of limited significance. Frequent oral behaviours are related to increased masticatory muscle soreness during CAT. The medium- and long-term effects of CAT should be further explored.

Clear Aligner Orthognathic Splints.

Orthodontic treatment has been transformed by the introduction and overwhelming adoption of clear aligner therapy (CAT). Many patients are demanding esthetic and metal-free treatment alternatives, including those requiring orthognathic surgery (OGS), to correct their dentofacial deformities. The adoption of performing OGS for CAT has been cautious and challenging for many reasons. Intermaxillary fixation, postoperative occlusal control, preoperative decompensation management, and long-term stability need to be tested and assessed. This report presents an accurate 3-dimensional (3D) printed hard acrylic splint specifically for patients without any orthodontic attachment to be used in the positioning and fixation of osteotomized jaws. It is simple to manufacture and its use intraoperatively is efficient, straightforward, and accurate. This report introduces the Clear Aligner Orthognathic Splint for surgery and the steps required for 3D planning with recommendations for perioperative orthodontic support.

Bending rigid molecular rods: formation of oligoproline macrocycles.

Bent but not broken: cyclic oligoprolines are accessed in a reaction that effectively bends rigid oligoproline peptides (see scheme; TBDMS=tert-butyldimethylsilyl). The stitching is accomplished during macrocyclization enabled by aziridine aldehydes and isocyanides. Molecular modeling studies suggest that electrostatic attraction between the termini of the linear peptide is pivotal for macrocyclization. The macrocycles were studied by circular dichroism with a polyproline II structure being observed in larger macrocycles.

Carbon-based leaving group in substitution reactions: functionalization of sp3-hybridized quaternary and tertiary benzylic carbon centers.

Lewis acid promoted substitution reactions employing Meldrum's acid and 5-methyl Meldrum's acid as carbon-based leaving groups are described which transform unstrained quaternary and tertiary benzylic C(sp(3))-C(sp(3)) bonds into C(sp(3))-X bonds (X = C, H, N). Importantly, this reaction has a broad scope in terms of both suitable substrates and nucleophiles with good to excellent yields obtained (typically >90%).