This study shows that irradiation affects microhardness and micro-morphology of enamel and dentin of permanent teeth. The effects of gamma irradiation on dental substrate might contribute to increased risk of radiation tooth decay associated with salivary changes, microbiota shift and high soft and carbohydrate-rich food intake.

Osteoarthrosis is a disorder of synovial joints, resulting from destruction of the cartilage and subchondral bone. The present study is aimed to investigate the molar bite force, thickness and efficiency of the masseter and temporalis muscles of subjects with osteoarthrosis. A total of forty-eight subjects participated in the study. They were distributed into two groups: with osteoarthrosis (n=24) and asymptomatic controls (n=24). Subjects were analyzed on the basis of maximal molar bite force (right and left side), thickness (mandibular rest and dental clenching in maximal voluntary contraction) and electromyographic activity of masticatory cycles through the linear envelope integral in habitual (raisins and peanuts) and non-habitual (Parafilm M) chewing of the masseter and temporalis muscles. All the data were analyzed statistically using t-test with a significance level of p≤0.05. There was no difference between groups in maximal molar bite force, muscle thickness and non-habitual chewing. Differences were found on the raisins (p=0.02) and peanuts (p=0.05) chewing for right temporal muscle, with reduced masticatory muscle efficiency in osteoarthrosis subjects. This study showed that osteoarthrosis induces negative changes in habitual chewing, highlighting the efficiency of the right temporalis muscles. The greater temporal muscle activity in subjects with osteoarthrosis may compromise chewing and consequently the nutritional status of adult subjects.

Children with borderline orthodontic treatment needs show functional disorders of the stomatognathic system.

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Objectives:To compare the molar bite force, electromyographic activity, chewing efficiency and thickness of the masseter and temporalis muscles in individuals with amyotrophic lateral sclerosis (ALS) and healthy individuals.Material and Methods:Thirty individuals enrolled in the study were divided into the study group (with ALS, n=15) and control group (healthy individuals, n=15). Data regarding molar bite force (right and left), electromyographic activity (mandibular rest, right and left laterality, protrusion, and maximum voluntary contraction), chewing efficiency (habitual and non-habitual), and masticatory muscle thickness (rest and maximum voluntary contraction) were tabulated and subjected to statistical analysis (Student’s t-test, p≤0.05).Results:Comparisons between the groups demonstrated a statistically significant increase in the electromyographic activity of the right masseter (p=0.03) and left masseter (p=0.03) muscles during mandibular rest; left masseter (p=0.00), right temporalis (p=0.00), and left temporalis (p=0.03) muscles during protrusion; and right masseter (p=0.00), left masseter (p=0.00), and left temporalis (p=0.00) muscles during left laterality, in individuals with ALS as compared with healthy individuals. A statistically significant decrease was observed in the habitual chewing efficiency of the right masseter (p=0.00) and right temporalis (p=0.04) muscles in individuals with ALS. No statistically significant difference between the groups was found the masticatory muscle thickness and maximal molar bite force.Conclusions:ALS may lead to modifications in the activities of the stomatognathic system, including muscular hyperactivity and reduction in chewing efficiency; however, no change has been observed in the masticatory muscle thickness and molar bite force.

Background Neurodegenerative diseases that affect the cerebellum, especially in elderly individuals, cause impairment of motor coordination and quality of life. The presente study evaluated the electromyographic activity and thickness of the right and left masseter and temporal muscles, and the maximum molar bite force of individuals with spinocerebellar ataxia. Material and Methods Twenty-eight individuals were divided into two groups: those with (n=14) and without (n=14) spinocerebellar ataxia. Data on the masticatory muscles obtained from the electromyographic activity (resting, right and left laterality and protrusion), muscle thickness (maximal voluntary contraction and tensile strength) and maximum bite force (right and left) were tabulated and descriptive analysis using Student’s t-test ( P ≤ 0.05). Results In the comparison between groups, greater electromyographic activity was demonstrated for individuals with spinocerebellar ataxia, with a statistically significant difference in protrusion and laterality for the temporal muscles ( P = 0.05). There was no statistically significant difference between the groups for masticatory muscles thickness in the conditions evaluated. For maximum molar bite force, the group with spinocerebellar ataxia showed lower bite force ( P ≤ 0.05). Conclusions The data obtained suggest that spinocerebellar ataxia promotes functional reduction in the stomatognathic system, mainly affecting the electromyographic activity and bite force, hindering chewing, with a resultant alteration of nutritional intake and a decrease of quality of life. Key words: Spinocerebellar ataxia, electromyography, muscle thickness, bite force, masseter muscle, temporal muscle.

Background Osteoporosis can make bone repair difficult. Low‐level laser therapy ( LLLT ) has been shown to be a promising tool for bone neoformation. This study aimed to analyze the effect of LLLT on calvaria bone defects of ovariectomized rats using stereology. Methods Fifty‐four Wistar rats were subjected to bilateral ovariectomy, and bone defects were created in calvaria after 150 days. The animals were divided into nine groups (n =  6 per group), and 24 hours after the bone defects were created they received 3, 6 or 12 sessions of LLLT at 0, 20 or 30 J/cm 2 , using a 780‐nm low‐intensity GaAlAs laser. One‐way ANOVA followed by Tukey's post hoc test was used for data processing. A difference of P < 0.05 was considered statistically significant. The parameters evaluated were osteocyte density ( Nv ost ), total osteocyte number ( Nto ost ), trabecular surface density ( Sv t ), and trabecular surface area ( Sa t ). Results Data obtained showed that Nto ost , Sv t , and Sa t in group G2 rats were significantly different from G1 (0 J/cm 2 ) ( P < 0.05). Compared to group G4, G5 presented higher values for the parameters Sv t and Sa t , and G6 presented significantly higher values for almost all the analyzed parameters ( Nv ost , Nto ost , Sv t , and Sa t ) ( P < 0.05). Compared to group G7, G8 showed a higher value only for the parameter Sa t , and G9 showed significantly higher values for parameters Nv ost , Nto ost , Sv t , and Sa t . Conclusion We conclude that LLLT stimulated bone neoformation and contributed to an increase in the total number of osteocytes, especially with a laser energy density of 30 J/cm 2 given for 6 and 12 sessions.

Osteoarthrosis on electromyographic activity of masticatory muscles and quality of life e342