Mauro Farella

Oral parafunctions as risk factors for diagnostic TMD subgroups.

The frequency of diurnal clenching and/or grinding and nail-biting habits was assessed in patients affected by temporomandibular disorders (TMDs) and in healthy controls in order to investigate the possible association between these oral parafunctions and different diagnostic subgroups of TMDs. The case group included 557 patients (127 men, mean age +/- SD = 34.5 +/- 15.4 years; 430 women, mean age +/- SD = 32.9 +/- 14.1 years) affected by myofascial pain or disc displacement or arthralgia/arthritis/arthrosis. The control group included 111 healthy subjects (55 men, mean age +/- SD = 37 +/- 15.2 years; 56 women, mean age +/- SD = 38.2 +/- 13.8 years). Multinomial logistic regression analysis was used to assess the association between oral parafunctions and TMDs, after adjusting for age and gender. Daytime clenching/grinding was a significant risk factor for myofascial pain (odds ratio (OR) = 4.9, 95% confidence interval (CI): 3.0-7.8) and for disc displacement (OR = 2.5, 95% CI: 1.4-4.3), nail biting was not associated to any of the subgroups investigated. Female gender was a significant risk factor for myofascial pain (OR = 3.8; 95% CI: 2.4-6.1), whereas the risk factor for developing disc displacement decreased with ageing. No association was found between gender, age and arthralgia/arthritis/arthrosis.

Ultra sonographic assessment of the swelling of the human masseter muscle after static and dynamic activity

Work-related fatigue, pain and disorders in skeletal muscles have been related to prolonged static and dynamic activity. Such contractions have been shown to impair blood flow and increase muscle thickness and fluid. In the present study the effect of static and dynamic activity was evaluated from changes in masseter thickness as a measure of oedema, simultaneously with assessment of perceived pain/discomfort and cardiovascular responses. As static activity, fourteen young healthy women bit at 15% maximal voluntary contraction on bite-force transducers in the molar regions until exhaustion or 20 min at maximum (median endurance time 7.1 min). For dynamic activity, the same individuals chewed gum unilaterally until exhaustion or 40 min at maximum (all endured 40 min) with a cycle time of 725 ms, an average load of 9.3% of maximal electromyographic activity (maxEMG) and a peak mean voltage of 54.3% of maxEMG. Muscle thickness was measured by ultrasonography at the mid-portion of the ipsilateral masseter. Immediately after exercise, muscle thickness was significantly increased, more after static (14.0%) than dynamic (8.6%), and returned to pre-exercise values after 20-min recovery. Visual analogue scales (VAS) revealed the concomitant occurrence of pain (static 11.9 VAS%; dynamic 5.9 VAS%), and discomfort (static 8.1 VAS%; dynamic 5.9 VAS%), and both sensations decreased to pre-exercise values after 20-min recovery. Systolic blood pressure increased significantly, more during static (12.5%) than dynamic activity (4.3%), whereas heart rate rose significantly only during dynamic exercise (13.3%). Hence, activity was associated with muscular swelling and pain, and, despite the relatively small size of the masticatory muscles, also with general cardiovascular responses.

Time-Frequency Analysis of Chewing Activity in the Natural Environment

The aim of this observational study was to investigate the features of the chewing activity and the variability of the human chewing pace, as assessed in the natural environment. It was hypothesized that the chewing pace is relatively constant within individuals across different days but is variable across individuals. Electromyographic surface activity was recorded unilaterally from the masseter in 21 participants for 3 hours over 3 recording days, in the natural environment, by means of portable recorders. The time-frequency properties of chewing activity were assessed with a previously validated algorithm. Repeated-measurements ANOVA was used for statistical analysis. Chewing activity mainly occurred in the range of 0.94 Hz (5th percentile) and 2.17 Hz (95th percentile). Mean and median chewing frequencies were 1.57 Hz and 1.58 Hz, respectively (95% confidence intervals: 1.45-1.68 Hz). The mean duration of chewing episodes was 13.0 sec, the 5th and 95th percentiles being 2.7 sec and 34.9 sec, respectively. Variability of the mean chewing frequency between individuals was much greater than that within individuals (F = 29.8; p < 0.001). The individual chewing paces were stable across different days (intraclass correlation coefficient = 0.88; 95% confidence intervals = 0.79-0.94). Our findings provide evidence that each individual, in the natural environment, chews with a consistent pace across different days. Abbreviations: ANOVA, analysis of variance; CPG, central pattern generator; EMG, electromyography; ICC, Intra-class Correlation coefficient; SD, standard deviation.

Effect of Occlusal Interference on Habitual Activity of Human Masseter

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.

Mandibular rest position and electrical activity of the masticatory muscles.

STATEMENT OF PROBLEM The determination of a correct vertical dimension of occlusion is a critical procedure in clinical dentistry. PURPOSE The objectives of this study were to analyze the relation between mandibular rest position and electrical activity of masticatory muscles and to compare clinical and electromyographic rest position in subjects with different vertical facial morphologic features. MATERIAL AND METHODS Clinical rest position and electromyographic rest position were investigated in 40 subjects. Electromyographic rest position ranged from 0.4 to 12.7 mm (average 7.7 +/- 2.7 mm). Clinical rest position ranged from 0.1 to 4.4 mm (average 1.4 +/- 1.1 mm). The average difference between electromyographic rest position and clinical rest position was 6.3 +/- 2.5 mm (range 0.3 to 10.3 mm). Sixteen subjects were selected according to the Frankfort mandibular plane angle and separated in two groups having a mandibular plane angle > or = 28 degrees. RESULTS Rest position was significantly greater (p < 0.05) in the low-angle group (2 +/- 1.3 mm) than in the high angle group (0.8 +/- 0.8 mm). Electromyographic rest position did not differ between subjects with different facial morphologic features (8.1 +/- 1.7 mm low-angle group; 7.6 +/- 4.1 mm high angle group). By varying the vertical dimension millimeter by millimeter, masseter and anterior temporal electromyographic activity demonstrated a considerable decrease over an interocclusal distance of 3 to 4 mm. Further mandibular opening up to 18 mm corresponded to small changes in postural activity. CONCLUSION This study suggests that a jaw posture with a few millimeters of interocclusal distance involves a great reduction of masticatory muscle activity.

Long-term remineralizing effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on early caries lesions in vivo: A systematic review

OBJECTIVE To assess the long-term (>3 months) remineralizing effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on early caries lesions in vivo. DATA SOURCES PubMed, Web of Science, Embase, Cochrane-Central, Science Direct, CBM, and CNKI were searched up to April 2013. Only articles in English and Chinese were included. Grey literature was also searched. Randomized or quasi-randomized clinical trials in which CPP-ACP was delivered by any method were considered. All relevant studies underwent two independent reviews. STUDY SELECTION Of the 738 studies screened, 83 studies were reviewed and eight selected for inclusion in the final sample. The follow-up period of the studies included varied from 3 to 24 months. The long-term remineralizing effect of CPP-ACP in vivo was demonstrated in comparison with placebo in randomized controlled trial. However, there is conflicting evidence regarding the clinical efficacy of CPP-ACP when used in conjunction with fluoride toothpastes. No specific side effect related to CPP-ACP usage was found. CONCLUSIONS CPP-ACP has a long-term remineralizing effect on early caries lesions in comparison with placebo, although this does not appear to be significantly different from that of fluorides. The advantage of using CPP-ACP as a supplement to fluoride-containing products is still unclear. High-quality, well-designed clinical studies in this area are still required before definitive recommendations can be made. CLINICAL SIGNIFICANCE CPP-ACP is a promising remineralizing agent with a significant remineralizing effect that has been demonstrated in both in vivo and in vitro studies. The evidence to support its synergistic effect with fluoride is insufficient based on the current existing long-term human randomized controlled trials.

Postural stability and unilateral posterior crossbite : Is there a relationship?

The aim of this study was to test the hypothesis that unilateral posterior crossbite influences postural stability of the whole body. Twenty-six subjects (14 males and 12 females) affected with unilateral posterior crossbite were selected and compared with 52 controls matched for age and gender. Postural stability was assessed using a stabilometric platform. The following stabilometric measurements were assessed: weight distribution on foot area and speed of body sway. Tests were performed under two occlusal conditions: teeth in intercuspal position (ICP) and while keeping two cotton rolls between teeth without clenching. The weight distribution on foot area and the speed of body sway were not significantly influenced from crossbite (with and without lateral mandibular slide), occlusal conditions (ICP, cotton rolls), and gender. Therefore, the treatment of this malocclusion in order to prevent or to treat postural disorders is not justified.

Jaw Muscle Soreness after Tooth-clenching Depends on Force Level

The effects of prolonged tooth-clenching on masticatory muscle pain have not been fully elucidated. We hypothesized that late-onset soreness may develop depending on the clenching force. Ten pain-free females were asked to endure sustained clenching tasks up to exhaustion in randomized sequences of 7.5%, 10%, 15%, 25%, and 40% of maximum clenching force. Perceived pain, fatigue, and pressure-pain thresholds of masseter and temporalis muscles were assessed before, immediately after, and one day after the tasks. Endurance times differed markedly among participants and force levels, ranging from 1.2 to 245.1 min. Masseter pressure-pain threshold decreased immediately after (-13.7%; p = 0.050) and one day after (-22.0%; p = 0.006) the 7.5% task. Temporalis pressure threshold decreased one day after the 7.5 % task (-14.6%; p = 0.003). It was concluded that prolonged low-level tooth-clenching in healthy young women induces a delayed soreness in the jaw elevator muscles.

Prediction of Mechanical Properties of the Cancellous Bone of the Mandibular Condyle

The mechanical properties of cancellous bone depend on the bone structure. The present study examined the extent to which the apparent stiffness of the cancellous bone of the human mandibular condyle can be predicted from its structure. Two models were compared. The first, a structure model, used structural parameters such as bone volume fraction and anisotropy to estimate the apparent stiffness. The second was a finite element model (FEM) of the cancellous bone. The bone structure was characterized by micro-computed tomography. The calculated stiffnesses of 24 bone samples were compared with measured stiffnesses. Both models could predict 89% of the variation in the measured stiffnesses. From the stiffness approximated by FEM in combination with the measured stiffness, the stiffness of the bone tissue was estimated to be 11.1 ± 3.2 GPa. It was concluded that both models could predict the stiffness of cancellous bone with adequate accuracy.

Efficacy of the Sander bite-jumping appliance in growing patients with mandibular retrusion: a randomized controlled trial

OBJECTIVES The efficacy of functional appliances remains highly debated. This randomized controlled trial investigated the skeletal and dentoalveolar effects determined by the Sander bite-jumping appliance (BJA). The null hypothesis to be tested was that the appliance would not induce supplementary mandibular growth compared to untreated controls. SETTING AND SAMPLE POPULATION This study was carried out at the Section of Orthodontics, University of Naples Federico II, Italy. Forty-six patients receiving a clinical diagnosis of skeletal and dental class II due to mandibular retrusion were either allocated to a treatment (23 patients;15 boys, 8 girls; mean age ± SD: 10.9 ± 1.3 years) or to an untreated control group (23 patients;11 boys, 12 girls; mean age ± SD: 10.5 ± 1.2 years), by using a balanced block randomization. METHODS Lateral cephalograms were taken before and after treatment and used for comparisons. Measurements were analyzed by descriptive statistics, univariate and multivariate statistical tests. RESULTS Treated individuals had a significant increase in mandibular length (6.4 ± 2.3 vs. 3.5 ± 2.5 mm; p < 0.001), overjet reduction (-5.0 ± 2.9 vs. 0.3 ± 1.2 mm; p < 0.001) and molar relationship improvement (-5.3 ± 2.4 vs. 0.1 ± 1.1 mm; p < 0.001) compared to controls. The use of the appliance did not significantly affect jaw divergence. Proclination of lower incisors was slightly greater (3.0°, p = 0.023) in treated patients than in controls. The increase in mandibular length was not significantly influenced by cervical stage (p = 0.40). CONCLUSION 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.