Masticatory Performance and Chewing Cycle Kinematics—Are They Related?

Objective:To compare chewing cycle kinematics of subjects with better and poorer masticatory performance.Materials and Methods:A cross-sectional study compared masticatory performance, based on the breakdown of the artificial test food Cuttersil®, in 30 subjects with Class I occlusion. Individuals with median particle sizes greater and lesser than the median value for the entire sample were categorized as poorer (15) and better (15) performers, respectively. While chewing Cuttersil, three-dimensional jaw movements of subjects were tracked with an optoelectric computer system. Multilevel linear modeling was used to evaluate differences in estimated cycle shape, cycle duration, and maximum excursions, as well as within-subject variation between the two groups.Results:Poorer performers had a significantly longer opening duration (0.274 ± 0.225 sec vs 0.325 ± 0.270 sec) than better performers. Poorer and better performers also showed significant differences in cycle shape, including a less horizontal path of closure and more posterior jaw movement in the poorer performers. In addition, poorer performers exhibited significantly more cycle-to-cycle (within-subject) variability in chewing cycle duration, excursive movements, and lateral velocity than did better performers.Conclusions:Poorer performers lacked consistency in their chewing cycles, and their cycle shape differs from that of better performers.     

Sclerotherapy for the treatment of postmastectomy seroma

BACKGROUND: Seroma is a common complication after mastectomy. We review our experience with sclerotherapy for postmastectomy seroma management. METHODS: Patients who underwent outpatient sclerotherapy for postmastectomy seroma were reviewed. Ninety-five percent ethyl alcohol or povidone iodine, which was administered by way of percutaneous catheter, was the initial sclerosant, and dwell time was 20 to 30 minutes. Povidone iodine solution was instilled 2 to 3 times daily. Catheters were removed when output reached <30 mL/d or when cavity size was <20 ml by sinogram. RESULTS: Sixteen patients (18 seromas) had sclerotherapy initiated at median of 34 days after surgery. Mean number of treatment days was 3 (median duration 16). Seven patients (44%) developed infection during treatment, which was associated with increased duration. Three seromas recurred and were successfully treated with single aspiration. COMMENTS: Sclerotherapy is a feasible treatment for chronic seroma after mastectomy. Longer treatment duration was associated with infection; antibiotic prophylaxis should be considered. Research is necessary to determine optimal regimens and superiority over other approaches.     

The effects of isometric exercise on maximum voluntary bite forces and jaw muscle strength and endurance

The effects of training and exercise on the strength and endurance of limb muscles has been investigated extensively, but the response of the jaw muscles to exercise remains poorly known. The purpose of this study was to determine whether short-term isometric training increases strength and endurance of the superficial masseter and anterior temporalis muscles. Maximum and submaximum voluntary bite forces and corresponding electromyographic (EMG) activity were measured in 28 young adults, randomly divided into exercise and non-exercise (control) groups. Subjects in the exercise group performed isometric clenches against a soft maxillary splint for five 1-min sessions per day over a 6-week period. After exercise, subjects increased their maximum bite forces by 37%, but control subjects' bite forces also increased by 25%. After exercise, EMG levels per unit of bite force generally decreased, but similar decreases were also seen in the non-exercised controls. Masseter muscle activity levels during standardized 10-kg bites decreased after 6 weeks of exercise. Fatigue resistance increased significantly with exercise but did not differ significantly from control values after 6 weeks of exercise. The results of this study indicate that increases in maximum bite force can be easily produced with training, but that actual strengthening of the jaw muscles is more difficult to achieve.     

The relationship between surgical changes in dentofacial morphology and changes in maximum bite force.

PURPOSE: This study determined whether patients with greater surgical changes, and presumably greater normalization of their skeletal morphology, showed greater increases in their maximum voluntary bite forces after orthognathic surgery. PATIENTS AND METHODS: A total of 104 adult patients (32 males and 72 females) treated with 1 of 8 different orthognathic surgical procedures were examined. Patients' presurgical and postsurgical morphologic and biomechanical measurements were taken from lateral cephalograms. Measurements known to be related to maximum bite force were used in the analysis. Patients' presurgical and postsurgical maximum bite forces were measured at 8 tooth positions (ie, right and left incisors, canines, premolars and molars). RESULTS: Presurgical and postsurgical morphology and biomechanics variables were strongly correlated with each other, suggesting that orthognathic surgery produced relatively little change in patients' overall craniofacial form. Maximum voluntary bite forces were primarily correlated with variables relating to jaw size-both before and after surgery. No correlations were noted between the increases in maximum voluntary bite forces and surgically produced changes in skeletal morphology and the biomechanics variables. CONCLUSIONS: Factors other than surgically produced changes in skeletal morphology are responsible for increases in maximum voluntary bite force after orthognathic surgery.     

Sex differences in mandibular movements during opening and closing.

This study evaluated the sex differences in maximum 3-dimensional opening and closing movements. The sample included 29 men (ages, 23-39 years) and 27 women (ages, 23-35 years), who were selected for normal Class I occlusion, temporomandibular function, and skeletal patterns. Condylar (hinge axis) translation and mandibular incisor movements, were recorded with an optoelectric jaw-tracking system; each participant performed 4 maximum opening/closing cycles. The results showed significant (P <.05) sex differences for incisor opening and closing movements, with most of the differences in the vertical component. Male incisor straight-line distances and curvilinear pathways averaged 52.1 mm and 54.8 mm, respectively. Female straight-line distances and curvilinear pathways averaged 46.0 mm and 48.1 mm, respectively. There were significant (P <.05) sex differences for condylar translation, with most of the differences in the anteroposterior component. Male condyles translated 15.4 to 17.6 mm (straight-line distances) and 20.5 to 20.7 mm (curvilinear pathways); female condyles translated 12.4 to 12.7 mm (straight-line distances) and 16.2 to 17.9 mm (curvilinear pathways). Mandibular length accounted for some of the sex difference in interincisal opening and for most of the sex differences in condylar translation. Closing movements showed the same pattern of sex differences as opening movements. Mandibular opening rotation was approximately 4 degrees larger in men than in women. The shapes of the condylar opening and closing pathways also differed significantly between men and women. For both sexes, condylar translation did not correlate with incisor opening or closing movements. It was concluded that (1) significant sex differences exist in incisor opening movements that are independent of mandibular size, (2) sex differences in condylar translation are dependent on mandibular size, (3) incisor opening movements should not be used as an indicator of condylar translation, and (4) sex differences in the shapes of the condylar pathways indicate sex differences in articular eminence morphologic features.     

Surgical bacterial infections and antimicrobial susceptibility patterns at Lilongwe Central Hospital

A cross sectional study was done between October 1999 and February 2000 to determine antimicrobial susceptibility patterns of consecutive bacterial isolates of 102 clinical samples among surgical in-patients at Lilongwe Central Hospital (LCH), Malawi. Antimicrobial susceptibility was determined using comparative disc diffusion techniques. 83 (81.4%) samples were culture positive for bacterial growth while 19 (18.6%) grew nothing. Of the 93 culture positive specimens, Staphylococcus aureus was the predominant organism 43(51.8%) followed by Proteus species 8(9.6%) and E. coli 7(8.4%). Overall, 98.6% of all isolates tested against ciprofloxacin were susceptible, and against gentamicin and flucloxacin were 84.8% and 66.7% respectively. 59.3% of isolates tested against chloramphenicol were resistant. We recommend a review on the use of chloramphenicol as first-line antimicrobial therapy among surgical in-patients at Lilongwe Central Hospital. We also recommend restricted use of antimicrobials so as to minimise development of drug resistance. Periodic susceptibility studies are necessary to guide judicious use of antibiotics.     

The effects of GM-CSF and G-CSF in promoting growth of clonogenic cells in acute myeloblastic leukemia

A small subset of leukemic cells from most patients with acute myeloblastic leukemia (AML) have properties of stem cells and can be assayed by colony formation in agar or methylcellulose. Colony formation generally requires the addition of exogenous growth factors, but the exact factors required are incompletely defined. The AML colony- promoting activities of two recombinant human colony-stimulating factors (GM-CSF and G-CSF) were investigated by using blasts from 48 patients with AML. In nine cases, no colonies formed with either CSF. In seven cases colonies formed only in response to G-CSF and in 11 cases only in response to GM-CSF. In 21 cases colonies formed in response to either GM-CSF or G-CSF, and in 12 of these cases there was an additive effect between the two CSFs in determining maximum colony size. For cases responding to both GM- and G-CSF, the total number of colonies formed in response to the combination of both CSFs was almost always less than additive compared with the number of colonies formed in response to the individual CSFs. Further, the AML-CFU responding to either GM-CSF or G-CSF could not be distinguished by surface markers or by the cytochemical staining pattern of the colonies. These results suggest that there is considerable overlap between the GM-CSF- and G- CSF-responsive AML-CFU subpopulations in most cases. For five of seven cases, the combination of GM-CSF and G-CSF could replace a leukocyte feeder layer in providing maximum growth stimulation. These results indicate that GM-CSF and G-CSF are active growth factors for AML cells and are frequently additive in promoting maximum colony size.