ABSTRACT
Severe impaction of lower second molars often leads to their extraction to avoid potential damage to the first molar root. We present a case in which we used the clinical application of simple biomechanical principles to allow us to upright bilaterally impacted lower second molars into the desired location in a fairly short time.
Subject(s)
Molar , Orthodontic Appliances , Tooth Movement Techniques , Tooth, Impacted/therapy , Bicuspid/surgery , Child , Female , Humans , Malocclusion/therapy , Malocclusion, Angle Class II/therapy , Orthodontic Appliance Design , Orthodontic Retainers , Serial Extraction , Stainless Steel , Tooth Movement Techniques/instrumentation , Tooth Movement Techniques/methodsABSTRACT
The purpose of this study was to compare the properties of muscle fatigue in the masseter and temporalis muscles of normal individuals and those with myofascial pain-dysfunction syndrome (MPD). The MPD muscle is presumed to have different characteristics of fatigue than its healthy counterpart; these characteristics can be quantitated using standard electromyogram (EMG) signal-processing techniques. A total of 18 patients diagnosed as having MPD comprised the experimental group and 15 adults with no history or present symptoms of temporomandibular joint pain and dysfunction served as controls. Surface EMG recordings were made for both the masseter and anterior temporalis muscles while the subject held an incisal bite force level of 10 N for as long as possible. The EMG data were transferred to a microcomputer where the power-density spectrum of the signals were calculated for 2-s samples at 10-s intervals. The mean power frequency (MPF) and power (root mean square, r.m.s.) of the signals were calculated from the power-density spectra. Results showed: (1) the endurance times were significantly shorter for the MPD patients; (2) the masseter was not active in three of 17 MPD patients; (3) decreases in MPF over time were significantly greater for the MPD patients than normal subjects; (4) increases in r.m.s. power were significantly greater over time for the MPD patients; (5) bandwidths of the power-density spectra were similar for the two groups. The implication of these results is the MPD muscle is not in a state of constant fatigue, as is currently believed, but rather demonstrates accelerated fatigue.
Subject(s)
Masseter Muscle/physiopathology , Muscle Fatigue/physiology , Temporal Muscle/physiopathology , Temporomandibular Joint Dysfunction Syndrome/physiopathology , Adolescent , Adult , Bite Force , Case-Control Studies , Electromyography , Female , Humans , Muscle Contraction , Myofascial Pain Syndromes/physiopathology , Regression Analysis , Signal Processing, Computer-Assisted , Time FactorsABSTRACT
Rapid palatal expansion (RPE) is recognized as a very successful orthopedic therapy to correct maxillary transverse deficiencies in growing patients. However, the transverse forces delivered during RPE have been shown to create undesirable orthodontic and orthopedic side effects in patients exhibiting skeletal open bite tendency, large interlabial gap, or severe Class II skeletal patterns, with long lower facial height and increased facial convexity. The application of extraoral forces during RPE therapy by the concomitant use of a high-pull chincap is described and clinically illustrated as a method to control the vertical dimension.
