It has been suggested that occlusal interference may increase habitual activity in the jaw muscles and may lead to temporomandibular disorders (TMD). We tested these hypotheses by means of a double-blind randomized crossover experiment carried out on 11 young healthy females. Strips of gold foil were glued either on a selected occlusal contact area (active interference) or on the vestibular surface of the same tooth (dummy interference) and left for 8 days each. Electromyographic masseter activity was recorded in the natural environment by portable recorders under interference-free, dummy-interference, and active-interference conditions. The active occlusal interference caused a significant reduction in the number of activity periods per hour and in their mean amplitude. The EMG activity did not change significantly during the dummy-interference condition. None of the subjects developed signs and/or symptoms of TMD throughout the whole study, and most of them adapted fairly well to the occlusal disturbance.

No abstract

Objective: To compare the surface roughness of different orthodontic archwires. Materials and Methods: Four nickel-titanium wires (SentalloyH, SentalloyH High Aesthetic, Titanium Memory ThermaTi LiteH, and Titanium Memory EstheticH), three b-titanium wires (TMAH, Colored TMAH, and Beta TitaniumH), and one stainless-steel wire (Stainless SteelH) were considered for this study. Three samples for each wire were analyzed by atomic force microscopy (AFM). Three-dimensional images were processed using Gwiddion software, and the roughness average (Ra), the root mean square (Rms), and the maximum height (Mh) values of the scanned surface profile were recorded. Statistical analysis was performed by one-way analysis of variance (ANOVA) followed by Tukey's post hoc test (P , .05). Results: The Ra, Rms, and Mh values were expressed as the mean 6 standard deviation. Among as-received archwires, the Stainless Steel (Ra 5 36.6 6 5.8; Rms 5 48 6 7.7; Mh 5 328.1 6 64) archwire was less rough than the others (ANOVA, P , .05). The Sentalloy High Aesthetic was the roughest (Ra 5 133.5 6 10.8; Rms 5 165.8 6 9.8; Mh 5 949.6 6 192.1) of the archwires. Conclusions: The surface quality of the wires investigated differed significantly. Ion implantation effectively reduced the roughness of TMA. Moreover, TeflonH-coated Titanium Memory Esthetic was less rough than was ion-implanted Sentalloy High Aesthetic. (Angle Orthod. 2012;82:922-928.)

The BJA can effectively correct class II malocclusions by a combination of dentoalveolar and skeletal effects. The long-term stability of the correction needs to be evaluated.

No abstract

Rapid maxillary expansion is not more effective than SME in expanding the maxilla in patients with posterior crossbite.

Gum chewing has been accepted as an adjunct to oral hygiene, as salivary stimulant and vehicle for various agents, as well as for jaw muscle training. The aim of this study was to investigate the effects of prolonged gum chewing on pain, fatigue and pressure tenderness of the masticatory muscles. Fifteen women without temporomandibular disorders (TMD) were requested to perform one of the following chewing tasks in three separate sessions: chewing a very hard gum, chewing a soft gum, and empty-chewing with no bolus. Unilateral chewing of gum or empty chewing was performed for 40 min at a constant rate of 80 cycles/min. In each session, perceived muscle pain and masticatory fatigue were rated on visual analog scales (VAS) before, throughout, and after the chewing task. Pressure pain thresholds (PPTs) of masseter and anterior temporalis muscles were assessed before and immediately after the chewing tasks, and again after 24 h. The VAS scores for pain and fatigue significantly increased only during the hard gum chewing, and after 10 min of recovery VAS scores had decreased again, almost to their baseline values. No significant changes were found for PPTs either after hard or soft gum chewing. The findings indicate that the jaw muscles recover quickly from prolonged chewing activity in subjects without TMD.

The aim of this study was to investigate the relationship between the curve of Spee and skeletal facial morphology. Dental casts and lateral cephalograms were obtained from 59 orthodontic patients. The amount of concavity of the curve of Spee was calculated by a second-order quadratic interpolation of buccal cusp tips obtained from lateral digital photographs of the teeth. The cephalometric analysis aimed to evaluate the sagittal and vertical craniofacial dimensions as well as the position of the mandibular condyle with respect to the occlusal plane. These variables, included in a multiple regression model, could explain 34% of the total variance of the curve of Spee. The amount of the curvature was significantly related to (a) the horizontal position of the condyle with respect to the dentition, (b) the sagittal position of the mandible with respect to the anterior cranial base, and (c) the ratio between the posterior and anterior facial height. No significant relationship was found between the curve of Spec and any of the other cephalometric variables. The curve of Spee was not influenced by age and gender of the subjects investigated.