Trismus Research Articles

Assessment of pain, swelling and trismus following impacted third molar surgery using injection dexamethasone submucosally: A prospective, randomized, crossover clinical study

Background: Corticosteroids are known to reduce inflammation, fluid transudation, and edema. Secreted from the adrenal glands, these compounds have a significant role in maintaining metabolism. One of the essential roles played by steroids is their anti-inflammatory role. Aims and Objectives: This prospective, randomized, crossover, clinical study was conducted with the following aims and objectives: (a) to assess pain, swelling and trismus in patients undergoing surgical removal of impacted third molars, (b) to compare the pain, swelling and mouth opening with injection of submucosal dexamethasone 4 mg administered preoperatively, and (c) to compare the results with similar studies conducted elsewhere. Materials and Methods: The study sample involves 20 patients (40 impacted teeth-split arch) with the following inclusion criteria: Patient's reporting for surgical removal of symptomatic impacted mandibular third molars aged between 18 and 45, impacted mandibular third molar with similar anatomical position, and similar surgical difficulty (Pell-Gregory classification was followed), no allergies to medicines prescribed in the postoperative period, patients who are nonsmokers, nonalcoholics and without any systemic diseases, and not systemically compromised or not under long-term steroid therapy. Syndromic patients, patients with periapical pathologies were excluded from the study. Results: The results of the present study suggest that there is a significant reduction of pain, swelling and improvement in mouth opening following submucosal injection of dexamethasone at the end of the 1st postoperative day and the results are statistically significant. Conclusion: (a) Corticosteroids decrease pain, edema and swelling by exerting their anti-inflammatory role, (b) there is statistically significant difference in reduction of pain, swelling and improvement of mouth opening at the end of 1st postoperative day, (c) submucosal injection of dexamethasone is less traumatic, less painful and is effective in limiting postoperative discomfort to the patient, and (d) a similar prospective study is suggested comparing the efficacy of intravenous dexamethasone versus submucosal administration of dexamethasone.

Functional differentiation of teeth in the wolf (Canis lupus, Canidae, Carnivora)

Vector analysis has been used to investigate the functions of incisors, canine teeth, premolars, and molars in a sample of 411 wolf skulls and to elucidate the morphological features that confer resistance to mechanical loading (pressure from the prey tissues upon jaw clenching and fracture under pressure directed along the jaw) to the teeth. Differentiation of the teeth was due to functional differences and showed only partial conformity to the anatomical nomenclature. Canine teeth and i3 serve for the infliction of wounds upon an attack. These teeth, together with I1-2/1-3, are used to tear off parts of the prey. The premolars p1-3/2-4 are used to hold, tear off, and carry parts of the prey. The carnassials р4 and m1 are used to break bones and cut the soft tissues. The rear part (talonid) of m1 and m1-2/2 serve for further disintegration of food. The anterior premolars p1/1 and m3 are undergoing a rudimentation process, as evident from higher frequency of developmental defects compared to that in other teeth. Breakage and chipping of the teeth is rare, except for cases of extreme loading, since mechanical strength of the teeth is sufficiently high.

Sleep Bruxism-Tooth Grinding Prevalence, Characteristics and Familial Aggregation: A Large Cross-Sectional Survey and Polysomnographic Validation.

Sleep bruxism (SB) is characterized by tooth grinding and jaw clenching during sleep. Familial factors may contribute to the occurrence of SB. This study aims are: (1) revisit the prevalence and characteristics of SB in a large cross-sectional survey and assess familial aggregation of SB, (2) assess comorbidity such as insomnia and pain, (3) compare survey data in a subset of subjects diagnosed using polysomnography research criteria. A sample of 6,357 individuals from the general population in Quebec, Canada, undertook an online survey to assess the prevalence of SB, comorbidities, and familial aggregation. Data on familial aggregation were compared to 111 SB subjects diagnosed using polysomnography. Regularly occurring SB was reported by 8.6% of the general population, decreases with age, without any gender difference. SB awareness is concomitant with complaints of difficulties maintaining sleep in 47.6% of the cases. A third of SB positive probands reported pain. A 2.5 risk ratio of having a first-degree family member with SB was found in SB positive probands. The risk of reporting SB in first-degree family ranges from 1.4 to 2.9 with increasing severity of reported SB. Polysomnographic data shows that 37% of SB subjects had at least one first-degree relative with reported SB with a relative risk ratio of 4.625. Our results support the heritability of SB-tooth grinding and that sleep quality and pain are concomitant in a significant number of SB subjects.

The Effects of a Self-Adapted, Jaw Repositioning Mouthpiece and Jaw Clenching on Muscle Activity during Vertical Jump and Isometric Clean Pull Performance

Purpose: The purpose of this study was to investigate the effects of a self-adapted, jaw repositioning mouthpiece and jaw clenching on muscle activity during the countermovement vertical jump (CMVJ) and isometric mid-thigh clean pull (MTCP). Methods: Thirty-six healthy, recreationally trained males (n=36; age, 23 ± 2.8 years; height, 178.54 ± 9.0 cm; body mass, 83.09 ± 7.8 kg) completed maximal CMVJ and MTCP assessments under six experimental conditions: jaw repositioning mouthpiece plus clenching (MP+C), jaw repositioning mouthpiece with jaw relaxed (MP), traditional mouthguard plus clenching (MG+C), traditional mouthguard with jaw relaxed (MG), no mouthpiece plus clenching (NoMP+C) and no mouthpiece with jaw relaxed (NoMP) while muscle activity of the dominant leg medial gastrocnemius (G), medial hamstring (H), vastus medialis (VMO), and erector spinae (ES) was recorded. Results: Repeated measures ANOVA revealed no changes in MTCP muscle activation for any mouthpiece or clench condition. Jaw clenching, regardless of mouthpiece condition, significantly improved prime mover muscle activation during CMVJ ( p < .001). Prime mover muscle activation was significantly greater during CMVJ assessment for jaw repositioning mouthpiece and no mouthpiece conditions over the use of a traditional mouthguard ( p < .001), but the repositioning mouthpiece did not lead to improved muscle activation compared to no mouthpiece ( p > .05). Conclusion: These findings support jaw clenching as a viable technique to elicit concurrent activation potentiation (CAP) of prime mover muscle activity during dynamic but not isometric physical activity. Keywords: jaw repositioning mouthpiece, jaw clenching, concurrent activation potentiation, muscle activation

Sympathomimetic effects of chronic methamphetamine abuse on oral health: a cross-sectional study.

BackgroundMethamphetamine, a highly addictive sympathomimetic stimulant, is currently widely abused worldwide and has been associated with devastating effects on oral health, resulting in the term “meth mouth”. However, “meth mouth” pathology is primarily based on case reports with a lack of systematic clinical evaluation. Therefore, we have conducted a systematic study to investigate (1) the pharmacological impact of methamphetamine on oral health with regard to saliva function, including the parameters saliva flow rate and total saliva production (ml/5 min) and the buffering capacity of saliva; (2) the contribution of the symptoms of bruxism and muscle trismus to potential oral health damage.MethodsWe assessed the data of 100 chronic methamphetamine abusers and 100 matched-pair comparison participants. Primarily, we conducted an anamnesis with all methamphetamine abusers with regard to saliva dysfunctions, jaw clenching and pain in the temporomandibular joint. Subsequently, in the first part of the clinical enquiry, we tested the saliva flow rate and the total saliva production (ml/5 min) by using the sialometry method and the buffer capacity of saliva by determining the pH-value. In the second part of the clinical enquiry, we evaluated bruxism symptoms with respect to generalized tooth attrition, dentine exposure and visible enamel cracks and examined a potential muscle trismus by measuring the maximal opening of the mouth.ResultsThe majority of methamphetamine abusers reported a dry mouth (72 %) and jaw clenching (68 %). Almost half of all methamphetamine abusers experienced pain in the temporomandibular joint (47 %). With regard to the clinical findings, methamphetamine abusers showed significantly lower total saliva production (ml/5 min) (p < 0.001), lower pH-values of their saliva (p < 0.001) and more bruxism symptoms (p < 0.001). However, we found no relevant trismus symptoms on comparing the two groups (p > 0.05).ConclusionsThe sympathomimetic effects of chronic methamphetamine abuse may lead to dry mouth and extensive bruxism and therefore can increase the risk for caries decay, periodontal lesions and tooth wear. Furthermore, a significant decline of saliva buffer capacity in methamphetamine abusers may trigger the risk for dental erosions. Methamphetamine abusers and practitioners should be aware of these symptoms.

Long-term efficacy and adverse effects of intensity-modulated radiotherapy for nasopharyngeal carcinoma

Objective To investigate the long-term efficacy and adverse effects of intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods A total of 869 patients with biopsy-proven NPC without distant metastasis who underwent the whole course of IMRT from 2009 to 2010 were enrolled. Of all the patients, 84.8% received cisplatin-based chemotherapy. The prescribed dose to the primary lesion in the nasopharynx was 66-70 Gy in 30-32 fractions, and the dose to the positive lymph nodes in the neck was 66 Gy in 30-32 fractions. The Kaplan-Meier method was used to calculate survival rates, the log-rank test was used for difference analysis and univariate prognostic analysis, and the Cox proportional hazards model was used for multivariate prognostic analysis. Results The 5-year overall survival (OS), local recurrence-free survival, regional recurrence-free survival, distant metastasis-free survival, and disease-free survival (DFS) were 84.0%, 89.7%, 94.5%, 85.6%, and 76.3%, respectively. In the patients with locally advanced NPC, concurrent chemotherapy tended to reduce distant metastasis (83.6% vs. 75.7%, P=0.050) and improve OS (82.6% vs. 77.0%, P=0.082). Induction chemotherapy tended to improve OS (80.7% vs. 71.4%, P=0.057), and the induction chemotherapy containing docetaxel or gemcitabine tended to improve OS (83.3% vs. 72.2%, P=0.058). The patients who received a boost after the initial radiotherapy had a significantly lower DFS rate than those who did not (52.2% vs. 71.1%, P=0.004). The concurrent chemotherapy increased the incidence rates of long-term xerostomia and trismus, while a high dose of cisplatin increased the incidence rates of xerostomia and hearing impairment. Conclusions IMRT for NPC provides satisfactory long-term efficacy. Concurrent chemotherapy combined with IMRT tends to reduce the incidence of distant metastasis, and other values need further investigation. The boost therapy after radiotherapy may be associated with poor prognosis. Chemotherapy increases the incidence of long-term toxicities. Key words: Nasopharyngeal neoplasms/intensity-modulated radiation therapy; Concurrent chemotherapy; Radiation boost; Late toxicity

Bruxism in Movement Disorders: A Comprehensive Review.

Bruxism is an abnormal repetitive movement disorder characterized by jaw clenching and tooth gnashing or grinding. It is classified into two overlapping types: awake bruxism (AB) and sleep bruxism (SB). Theories on factors causing bruxism are a matter of controversy, but a line of evidence suggests that it may to some extent be linked to basal ganglia dysfunction although so far, this topic has received little attention. The purpose of this article was to review cases of bruxism reported in various movement disorders. The biomedical literature was searched for publications reporting the association of bruxism with various types of movement disorders. As a whole, very few series were found, and most papers corresponded to clinical reports. In Parkinsonian syndromes, AB was rarely reported, but seems to be exacerbated by medical treatment, whereas SB is mainly observed during non-REM sleep, as in restless leg syndrome. AB is occasionally reported in Huntington's disease, primary dystonia, and secondary dystonia; however, its highest incidence and severity is reported in syndromes combining stereotypies and cognitive impairment, such as Rett's syndrome (97%), Down syndrome (42%), and autistic spectrum disorders (32%). Taken as a whole, AB seems to be more frequent in hyperkinetic movement disorders, notably those with stereotypies, and is influenced by anxiety, suggesting an involvement of the limbic part of the basal ganglia in its pathophysiology.

Effect of Jaw Clenching on Balance Recovery: Dynamic Stability and Lower Extremity Joint Kinematics after Forward Loss of Balance.

Postural control is crucial for most tasks of daily living, delineating postural orientation and balance, with its main goal of fall prevention. Nevertheless, falls are common events, and have been associated with deficits in muscle strength and dynamic postural stability. Recent studies reported on improvements in rate of force development and static postural control evoked by jaw clenching activities, potentially induced by facilitation of human motor system excitability. However, there are no studies describing the effects on dynamic stability. The present study, therefore, aimed to investigate the effects of submaximum jaw clenching on recovery behavior from forward loss of balance. Participants were 12 healthy young adults, who were instructed to recover balance from a simulated forward fall by taking a single step while either biting at a submaximum force or keeping the mandible at rest. Bite forces were measured by means of hydrostatic splints, whereas a 3D motion capture system was used to analyze spatiotemporal parameters and joint angles, respectively. Additionally, dynamic stability was quantified by the extrapolated CoM concept, designed to determine postural stability in dynamic situations. Paired t-tests revealed that submaximum biting did not significantly influence recovery behavior with respect to any variable under investigation. Therefore, reductions in postural sway evoked by submaximum biting are obviously not transferable to balance recovery as it was assessed in the present study. It is suggested that these contradictions are the result of different motor demands associated with the abovementioned tasks. Furthermore, floor effects and the sample size might be discussed as potential reasons for the absence of significances. Notwithstanding this, the present study also revealed that bite forces under both conditions significantly increased from subjects’ release to touchdown of the recovery limb. Clenching the jaw, hence, seems to be part of a common physiological repertoire used to improve motor performance.

Craniomandibular System and Postural Balance after 3-Day Dry Immersion.

The objective of the study was to determine the influence of simulated microgravity by exposure to dry immersion on the craniomandibular system. Twelve healthy male volunteers participated in a 3-day dry immersion study. Before and immediately after exposure we measured maximal bite force using piezoresistive sensors. The mechanical properties of the jaw and cervical muscles were evaluated before, during, and after dry immersion using MyotonPRO. Because recent studies reported the effects of jaw motor activity on the postural stability of humans, stabilometric measurements of center of pressure were performed before and after dry immersion in two mandibular positions: rest position without jaw clenching, and intercuspidal position during voluntary teeth clenching. Results revealed no significant changes of maximal bite force after dry immersion. All postural parameters were significantly altered by dry immersion. There were however no significant differences in stabilometric data according to mandibular position. Moreover the masseter tonicity increased immediately after the end of dry immersion period. Dry immersion could be used as a valid model for studying the effects of microgravity on human subjects. However, 3 days appear insufficient in duration to evaluate the effects of weightlessness on maximal bite force. Our research suggests a link between postural disturbance after dry immersion and masseter tonicity.

Influence of Initial Crank Positions and Jaw Clenching Activity on Cycling Performance

The purpose of this study was to identify the effects of three initial crank positions and jaw clenching activities on seated cycling performance. 10 normal subjects (5 females, 5 males) completed six separate occasions of Wingate Test with three different initial crank positions (0°, 47°, 71°) and two modes of jaw activities (jaw clenching and jaw loose). The findings suggest that, crank angle of 71° has the highest power output compare to other angles. The combination of 71° crank angles and jaw loose the jaw shows the best cycling performance.

Functional and anatomical basis for brain plasticity in facial palsy rehabilitation using the masseteric nerve

Several techniques have been described for smile restoration after facial nerve paralysis. When a nerve other than the contralateral facial nerve is used to restore the smile, some controversy appears because of the nonphysiological mechanism of smile recovering. Different authors have reported natural results with the masseter nerve. The physiological pathways which determine whether this is achieved continue to remain unclear. Using functional magnetic resonance imaging, brain activation pattern measuring blood-oxygen-level-dependent (BOLD) signal during smiling and jaw clenching was recorded in a group of 24 healthy subjects (11 females). Effective connectivity of premotor regions was also compared in both tasks. The brain activation pattern was similar for smile and jaw-clenching tasks. Smile activations showed topographic overlap though more extended for smile than clenching. Gender comparisons during facial movements, according to kinematics and BOLD signal, did not reveal significant differences. Effective connectivity results of psychophysiological interaction (PPI) from the same seeds located in bilateral facial premotor regions showed significant task and gender differences (p<0.001). The hypothesis of brain plasticity between the facial nerve and masseter nerve areas is supported by the broad cortical overlap in the representation of facial and masseter muscles.

Application of polyflaps perforator flaps in surgical treatment of malignant conversion of oral submucous fibrosis

Objective To investigate the clinical features of malignant conversion of oral submucous fibrosis (OSF) and the application value of polyflaps perforator flaps in its surgical treatment. Methods Ten patients who suffered from malignant conversion of OSF underwent simultaneous multiple defects reconstruction using polyflaps perforator flaps after radical tumor resection from August 2012 to October 2014. The fibrous bands leading to severe trismus near the pterygomandibular ligament as well as other intraoral lesions with malignant tendency were also resected besides from the known carcinoma. Patients with synchronous multiple primary cancers underwent radical resection and neck dissection of all other malignant lesions. The flaps were cut and tailored between adjacent perforators according to the amount and size of defects, forming several independent paddles for each defect reconstruction. Results Twenty-two defects were formed in 10 patients with malignant conversion of OSF. All of them were repaired with polyflaps anterolateral thigh (ALT) perforator flaps, including 8 cases of bipaddled ALT flaps and 2 cases of tripaddled ALT flaps. The total size of the flaps ranges from 3 cm~8 cm×6 cm~24 cm, and the pedicle length ranges from 5~12 (9.7±2.1)cm. Thirty-five perforator vessels were dissected, and each paddle included 1.6 perforators on average. All flaps survived after transplantation, and only 1 patient had infection of the neck incision. Post-operative adjuvant radio-chemotherapy was applied in 2 patients. All patients showed satisfactory accepting-site morphology with good speech function and swallowing recovery, and their trismus was improved during 6 to 30 (11.6±3.7)months. One patient died from lung metastasis 10 months after the surgery while local recurrent or metastasis did not occur in others. The donor sites were closed primarily without skin-grafting, leaving no obvious surgical donor-site complications. Conclusions Polyflaps perforator flaps can reconstruct multiple and sizable complicate defects, increase month opening by one stage operation. They are worth being applied in surgical treatment of malignant conversion of OSF. Key words: Oral submucous fibrosis/SU; Surgical flaps

Temporomandibular pain and jaw dysfunction at different ages covering the lifespan--A population based study.

Temporomandibular pain and jaw dysfunction can have a negative effect on daily life, but these conditions are not well recognized in the health care systems. The general aim was to examine the cross-sectional prevalence of frequent temporomandibular pain and jaw dysfunction in men and women across the lifespan. The analysis was based on data from 137,718 individuals (mean age 35years, SD 22.7) who answered three questions (3Q/TMD) included in the digital health declaration in the Public Dental Health care in the county of Västerbotten, Sweden; Q1: 'Do you have pain in your temple, face, jaw or jaw joint once a week or more?'; Q2: 'Does it hurt once a week or more when you open your mouth or chew?'; and Q3: 'Does your jaw lock or become stuck once a week or more?' The prevalence of frequent temporomandibular pain (Q1) was 5.2% among women and 1.8% among men (p<0.0001). The prevalence of frequent pain on jaw movement (Q2) was 2.5% among women and 0.9% among men (p<0.0001). The prevalence of frequent locking of the jaw (Q3) was 2.7% among women and 1.2% among men (p<0.0001). The study shows that the cross-sectional prevalence of temporomandibular pain and jaw dysfunction varies during the lifespan. For men and women, respectively, symptoms increase during adolescence, peak in middle age and then gradually diminish. The prevalence of these symptoms is significantly higher among women except from the first and last decades of a 100-year lifespan.

Temporomandibular Disorders in a Young Adolescent Brazilian Population: Epidemiologic Characterization and Associated Factors.

To carry out an epidemiologic characterization of the most common subtypes of temporomandibular disorders (TMD) and to identify associated factors in a Brazilian sample of young adolescents. From a population of public schoolchildren (12 to 14 years of age), 3,117 students were randomly invited to participate in this study. TMD was assessed according to the Research Diagnostic Criteria for TMD (RDC/TMD) Axis I, in addition to some questions of the Axis II history questionnaire. The associated factors, ie, difficulty with concentration/attention, anger, sadness, anxiety, headache complaints, oral parafunctions, diurnal jaw clenching, tooth grinding at night, and parents not living together, were assessed based on the responses of the adolescents and their parents to structured questions. For the statistical analyses, descriptive statistics, chi-square tests, odds ratio, and logistic regression models were used, adopting a 95% confidence interval and 5% level of significance. The sample consisted of 1,307 individuals (response rate of 41.9%), 56.8% (n = 742) girls. Overall, 397 (30.4%) adolescents presented with TMD, of whom 330 (25.2%) had painful TMD diagnoses. The majority of these had painful TMD of muscular origin (13.1%) and comprised chronic cases (14.9%). Girls presented higher frequencies of TMD overall, painful TMD, painful combined TMD, and chronic painful TMD diagnoses The final multivariate logistic regression model revealed that headache complaints (odds ratio 2.87; confidence intervals 2.21-3.72), oral parafunctions (2.08; 1.26-3.44), tooth grinding at night (2.05; 1.56-2.70), diurnal jaw clenching (1.96; 1.50-2.55), and parents not living together (1.38; 1.07-1.80) were the factors significantly associated with a TMD (overall) diagnosis. About 25% of the adolescents evaluated presented painful TMD, and the majority of these comprised muscular and chronic cases. Some factors, such as reports of headache complaints, oral parafunctions, tooth grinding at night, and parents not living together, were associated with this condition among young Brazilian adolescents. Special attention should be given to these factors among adolescents with TMD.

The effect of oral motor activity on the athletic performance of professional golfers.

Human motor control is based on complex sensorimotor processes. Recent research has shown that neuromuscular activity of the craniomandibular system (CMS) might affect human motor control. In particular, improvements in postural stability and muscle strength have been observed as a result of voluntary jaw clenching. Potential benefits of jaw aligning appliances on muscle strength and golf performance have also been described. These reports are highly contradictory, however, and the oral motor task performed is often unclear. The purpose of our study was, therefore, to investigate the effect of submaximum biting on golf performance via shot precision and shot length over three different distances. Participants were 14 male professional golfers – seven with sleep bruxism and seven without – randomly performing golf shots over 60m, 160m, or driving distance while either biting on an oral splint or biting on their teeth; habitual jaw position served as the control condition. Statistical analysis revealed that oral motor activity did not systematically affect golf performance in respect of shot precision or shot length for 60m, 160 m, or driving distance. These findings were reinforced by impact variables such as club head speed and ball speed, which were also not indicative of significant effects. The results thus showed that the strength improvements and stabilizing effects described previously are, apparently, not transferable to such coordination-demanding sports as golf. This could be due to the divergent motor demands associated with postural control and muscle strength on the one hand and the complex coordination of a golf swing on the other. Interestingly, subjects without sleep bruxism performed significantly better at the short distance (60 m) than those with bruxism. Because of the multifactorial etiology of parafunctional CMS activity, conclusions about the need for dental treatment to improve sports performance are, however, completely unwarranted.

Evaluation of long-term efficacy of re-irradiation with intensity-modulated radiotherapy for locally recurrent nasopharyngeal carcinoma

Objective To retrospectively analyze the long-term survival, late adverse events, and prognostic factors in patients with locally recurrent nasopharyngeal carcinoma (NPC) after re-irradiation with intensity-modulated radiotherapy (IMRT) . Methods From 2001 to 2010, a total of 335 patients who were diagnosed with locally recurrent NPC and received re-irradiation with IMRT were included in the study. Among all the patients, 69 (20.6%) had radiotherapy complications. There were 268 male patients (80.0%) and the median age was 45.0 years (range:21-75 years). The numbers of patients in disease stages T1, T2, T3, and T4 were 41, 36, 122, and 136, respectively. The median tumor volume was 37.5 cm3, and the median prescribed dose to the target volume was 68 Gy (range:60-70 Gy). The survival rate was determined using the Kaplan-Meier method. Prognostic factors were analyzed by the Cox proportional hazard model. Results The 5-year follow-up sample size was 312 patients. The 5-year overall survival, local-regional failure-free survival, and distant failure-free survival were 34.7%, 64.2%, and 82.2%, respectively. Multivariate analysis indicated that the poor prognostic factors included age> 45 years (P=0.01) , presence of significant radiotherapy complications before IMRT (P=0.00) , tumor stages (T2-T4) (P=0.00) , tumor volume> 38 cm3 (P=0.01) , and the mean dose of gross tumor volume (GTVnx) >68Gy (P=0.01). The incidence rates of nasopharyngeal mucosa necrosis, epistaxis, radiation encephalopathy, cranial nerve injury, and trismus were 28.6%, 16.4%, 22.4%, 15.8%, and 13.7%, respectively. Conclusions Re-irradiation with IMRT is effective in controlling tumor and thus is a reasonable choice for patients with locally recurrent NPC. However, the incidence of severe adverse events is still high. Further investigation on how to maintain the balance between tumor control and normal organ protection is needed. Key words: Nasopharyngeal neoplasms, locally recurrent / intensity - modulated radiotherapy; Untoward effect; Prognosis

Experimental low-level jaw clenching inhibits temporal summation evoked by electrical stimulation in healthy human volunteers

ObjectiveTo examine the effect of low-level jaw clenching on temporal summation in healthy volunteers. DesignIn 18 healthy volunteers, the pain intensities evoked at the masseter muscle and the hand palm by the first and last stimuli in a train of repeated electrical stimuli (0.3 or 2.0Hz) were rated using 0–100mm visual analogue scales (VAS), in order to evaluate temporal summation before and after three types of jaw-muscle tasks: low-level jaw clenching, repetitive gum chewing and mandibular rest position. A set of concentric surface electrodes with different diameters (small and large) was used for the electrical stimulation. ResultsThe temporal summation evoked by the large diameter electrode with 2.0Hz stimulation decreased significantly both on the masseter and the hand after low-level clenching (P≤0.03), but did not show any significant change after the other tasks (P>0.23). The VAS score of the first stimulation did not show any significant changes after low-level clenching (P>0.57). ConclusionsExperimental low-level jaw clenching can inhibit pain sensitivity, especially temporal summation. Low-level jaw clenching can modify pain sensitivity, most likely through the central nervous system. The findings suggest that potential harmful low-level jaw clenching or tooth contacting could continue despite painful symptoms, e.g., temporomandibular disorders.

Antibiotic prophylaxis for third molar extraction in healthy patients: Current scientific evidence.

Third molar extraction is one of the most frequently performed procedures in the dental clinic, and it is associated with innumerable trans- and postoperative complications, such as pain, trismus, edema, localized alveolar osteitis, and surgical site infection. Some authors advocate the use of local or systemic antibiotics to reduce the incidence of these postoperative complications. However, several studies have revealed an insignificant gain after using antibiotics. Despite the risks of allergic reactions, toxicity, and the development of resistant microorganisms, about 50% of dentists routinely prescribe the use of prophylactic antibiotics for this purpose. The goal of this paper is to evaluate the scientific evidence that justifies antibiotic prescription to healthy patients undergoing third molar extraction.

Effect of three different jaw positions on postural stability during standing

Studies in the literature show that jaw and neck regions are linked anatomically, biomechanically and neurologically. Voluntary clenching has been shown to improve muscle strength and performance of various motor tasks. Information from the neck sensory-motor system is reported to be important for posture. Hence it is reasonable to believe that activation of the jaw sensory-motor system has the potential to modulate posture. In a sample of 116 healthy subjects, we compared center of gravity (COG) velocity during quiet standing on a foam surface during three test positions: i) resting jaw, ii) open jaw, and iii) clenching; these were tested in two conditions: with eyes open and with eyes closed. The COG velocity decreased significantly during clenching in comparison to both open and resting jaw positions (p<0.0001). This suggests that the jaw sensory-motor system can modulate postural mechanisms. We conclude that jaw clenching can enhance postural stability during standing on an unstable surface in both the presence and absence of visual input in healthy adults and suggest that this should be taken into consideration in treatment and rehabilitation planning for patients with postural instability.

Role of Brushing and Occlusal Forces in Non-Carious Cervical Lesions (NCCL)

Objective: To assess the association of occlusal forces and brushing with non-carious cervical lesions (NCCL). Methodology: It was a Cross-sectional study. The study was conducted in Dental clinics, Department of Surgery, The Aga Khan University Hospital Karachi. The study duration was from 1st January 2009 to 28th Feb 2009. Ninety patients visiting dental clinic were examined clinically. Presence of Non- carious cervical lesions, broken restorations, fractured cusps, presence of occlusal facets, brushing habits, Para functional habits were assessed. All the relevant information and clinical examination were collected on a structured Performa and was analyzed using SPSS version 14.0. . Chi square X2 test was applied to assess association among different categorical variables. Result: Twenty three (26%) females and 67 (74%) males were included in the study. Thirty five of them (38.9%) were found to have Non-carious cervical lesions. Presence of NCCL has no association with gender (P value 0.458). A significant association was found between NCCL and teeth sensitivity (P value 0.002).The association between use of hard tooth brush and Non-carious cervical lesions was found significant (P value &lt;0.001). However the association among Non-carious cervical lesions and fractured cups, broken restoration, teeth grinding, jaw clenching, pan chalia chewing and frequency of teeth brushing were insignificant. Conclusion: Hard tooth brushing and teeth sensitivity have significant association with Non-carious cervical lesions. The role of occlusal wear in the formation of NCCL is not significant.