Genetic Polymorphisms in ACTN3 Contribute to the Etiology of Bruxism in Children.

Objective: Bruxism is a condition defined as a masticatory muscle activity with an unexplored genetic background. The aim of this study was to evaluate the association between genetic polymorphisms in ACTN3 and bruxism. Study design: A total of 151 biological-unrelated children, aged 7-12 years were included in a case control ratio of 1:1.5. The data collection was performed during interview and clinical examination. Saliva samples were collected from all children and 3 genetic polymorphisms in the ACTN3 (rs678397, rs1671064 and rs1815739) were selected for genotyping using real time PCR. Pearson chisquare calculation was used to assess Hardy-Weinberg equilibrium and to evaluate the association between genotypes and alleles frequencies for each genetic polymorphism in the co-dominant and recessive models. An alpha of 5% was used. Results: The genetic polymorphisms rs678397, rs1671064 and rs1815739 were associated with bruxism in the co-dominate model and in the recessive model (p<0.05). Allele distribution was also associated with bruxism for the polymorphisms rs678397 and rs1671064 (p<0.05). Conclusion: The genetic polymorphisms rs678397, rs1671064 and rs1815739 in ACTN3 are associated with bruxism and can contribute to the etiology of this condition in children.

Masticatory muscle activity evaluation by electromyography in subjects with zygomatic implants.

BACKGROUND: Zygomatic implants are an alternative treatment in the rehabilitation of atrophic maxilla to promote stability in the stomatognathic system. The aim of this study was to compare the electromyographic (EMG) activity of masseter and temporalis muscles in controls and in individuals with complete implant-supported dentures anchored in the zygomatic bone. MATERIALS AND METHODS: Fifty-four volunteers of both genders (mean age 52.5 years) were selected and distributed into two groups: Individuals with zygomatic implant (ZIG; n=27) and fully dentate patients (CG; n=27). MyoSystem-BR1 was used to assess masseter and temporalis muscles EMG activity in different mandibular movements: protrusion, clenching, maximal voluntary contraction (MVC) with Parafilm M®, right and left laterality and chewing (peanuts and raisins). Data was processed, normalized (MVC) and analyzed using the SPSS 21.0. Student t-test (P ≤ 0.05) was used for group comparison. RESULTS: The results were statistically significant (P ≤ 0.05) for protrusion, clenching, right and left laterality and raisin chewing. For the mandibular posture conditions, the ZIG obtained higher EMG activity patterns when compared to CG. For the masticatory performance during chewing of peanuts and raisins, the ZIG showed higher EMG mean values when compared to CG. CONCLUSIONS: The zygomatic implant promoted an active response of the muscle fibers (hyperactivity) during both mandibular posture and chewing conditions, probably due to the absence of periodontal receptors, which play a significant role for preparing a bolus for swallowing.

Anatomical variations of the mandibular nerve and its branches correlated to clinical situations.

AIM: The mandibular division of the trigeminal nerve is the largest of the three major divisions of the trigeminal nerve (fifth cranial nerve). In this way, many health professionals belonged to different fields are commonly evaluating patients suffering with orofacial pain and stomatognatic dysfunction associated to this structure. But, in the most cases, it is difficult to establish a correct diagnosis due to the anatomical complexity of the head and neck surfaces, especially when the focus is the trigeminal nerve. Thus, the objective of this research was to present the anatomical variations of the mandibular nerve and its branches correlated to more common clinical situations. METHODS: For this purpose, 20 human heads were anatomically dissected, so to study their structures, an external, medial and endocranial view. RESULTS: No significant variations related to ophthalmic and maxillary nerves were observed. Anatomical variations were observed in 20% of the total human heads dissected, all related to mandibular nerve and its branches: masseter, temporal, auriculotemporal and lingual. Variations in three to seven, on the number of the following nerves ramus, masseter and temporal were described. CONCLUSIONS: According to the present data using the described methodology, it was possible to conclude that anatomical variations are present in many subjects and they can explain many clinical situations that involve the stomatognathic structures.

Adhesive bond strength between a ceramic system and composite resin bonded by resinous cement submitted or not to thermocycling process.

AIM: The success of ceramic restorations is influenced by biocompatibility and resistance provided after bonding with an adhesive system. The aim of this in vitro study was to evaluate the adhesive bond strength between ceramic (IPS Classic V, Ivoclar Vivadent) and composite resin (Z-250, 3M), submitted or not to thermocycling treatment. METHODS: Forty ceramic cylinders were obtained with the following dimensions: 2 mm diameter and 3 mm high. The bond surface was polished with polishing paper (#600), conditioned with 10% hydrofluoric acid and silanized, according to manufacturer's recommendations. Later, the ceramic cylinders were bonded, with resinous cement (Rely X, 3M) to composite resin cylinders (Z-250, 3M) with the same dimensions, under 1 kg load. The assemblies were divided into two groups submitted to the following treatments: Group 1 (control): immersed in distilled water at 37 degrees C for 3 days, and Group 2: thermocycled (500 cycles) into two baths (5 degrees C and 55 degrees C), with 1 min of storing time each. In order to evaluate the adhesive resistance, the assemblies were tractioned in a universal testing machine (EMIC MEM 2000) with a crosshead speed of 0.5 mm/min. Obtained data were submitted to statistical analysis (ANOVA and Tukey's test). RESULTS: The means (MPa) and standard deviation obtained for Groups 1 and 2 were, respectively, 29.64+/-9.48 and 17.55+/-4.78. Group 1 presented significantly higher values than Group 2 (P<0.05). CONCLUSION: The results obtained in this study showed that the thermocycling procedure decreased the adhesive resistance between the materials studied.

Electromyographic evaluation of the masseter and temporal muscles activity in volunteers submitted to acupuncture.

AIM: To assess the effect of acupuncture on the temporal and masseter muscles activity employing surface electromyography. METHODS: Thirty volunteers were evaluated according to three groups of acupuncture application: selected local points, selected points at distance and association of local and distant points. Bipolar surface electrodes were positioned bilaterally on the anterior portion of temporal muscle, as well as in the median region of masseter muscle. An electromyograph connected to a computer and a specific software registered the muscular activity before and after acupuncture, in the following experimental conditions: 1- Rest Position (RP); 2- Maximum Intercuspation Clenching (MIC); 3- Bilateral Molar Clenching with Cotton Rolls (BMCCR). The mean values obtained for the activities of the studied muscles were submitted to Analysis of Variance and Tukey complementary test. RESULTS: The electromyographic activity of the studied muscles was lower after the application of the methods of acupuncture in the Rest, and higher after the application of the acupuncture in the Maximum Intercuspation Clenching; the electromyographic activity of the temporal muscle was higher than the masseter muscle in the Rest and lower in the Bilateral molar clenching with cotton rolls; the electromyographic activity showed to be modified after the three used methods of acupuncture in the Maximum Intercuspation Clenching. In this clinical condition, the method of long-distance acupuncture was higher than the application of local needles and the associated method. CONCLUSION: Acupuncture provided alterations in the activity of the studied muscles, favoring conditions of rest and muscular tightness.