Occlusion and restorative dentistry: Part 1

Dentists are responsible for the health of the masticatory system--the musculature, temporomandibular joints, and the dentition. The influence of occlusion in restorative dentistry would appear to be directly proportional to the complexity of the treatment. The criteria of a mutually protected and optimum occlusion provide sets of sound guidelines for analysis of the occlusion and for subsequent procedures. In occlusal analysis, it is important to record the several characteristics of mandibular movements made during "empty mouth" movements, and later treat when necessary, because these movements can be more damaging to the masticatory system than mastication of food.     

Treatment evaluation in otitis media research

Contrary to popular assumptions that temporomandibular disorders may become more prevalent with increasing age, a review of the literature shows that this is clearly not the case. Instead, it seems that most objective "signs" of temporomandibular disorders, namely clicking, tender joints and muscles, crooked opening, limited movement, and so forth, are found either less often in the elderly or at approximately the same rate in all adult age groups. Subjective complaints, however, decrease as populations get older, and the demand for treatment declines accordingly.     

Pathology of temporomandibular joint internal derangement and osteoarthrosis

Temporomandibular joint (TMJ) osteoarthrosis and disk displacement seem to be strongly related, but they may also represent mutually independent temporomandibular disorders. This paper presents relevant aspects of normal physiology and degeneration of synovial joints, aspects of normal temporomandibular articular disk physiology and of displacement of the disk, the relationship between TMJ osteoarthrosis and disk displacement, and a general classification of temporomandibular disorders.     

The health of our children continues to improve--but... (a litany of change--Part III)

Interarch occlusal relationships are defined by temporomandibular joint (TMJ) position. Determination of the most physiologic joint position is a logical prerequisite for occlusal analysis. Existing classification systems for occlusion do not consider TMJ position or condition when relating the mandibular arch to the maxillary arch or the range of adaptive changes that can affect the position of the condyles or influence long-term occlusal stability. If the relationship between occlusion and TMJ position is as important as many clinicians believe, condylar position must be defined precisely as an essential control in any clinical study that purports to evaluate the relationship between occlusion and any masticatory system disorder to include temporomandibular disorders. This article presents a new classification system that defines the relationship between maximal intercuspation and the position and condition of the TMJs. The classification uses guidelines that are specific enough to be consistent and verifiably reproducible. A recently introduced term, "adapted centric posture," is used in this classification to distinguish deformed TMJs that have remodeled or adapted to a conformation that can comfortably accept maximal loading. This classification is necessary because deformed but adapted joints may within certain conditions function with the same degree of comfort as intact, properly aligned condyle disk assemblies in centric relation.     

Induction of metallothionein synthesis by bismuth in cultured vascular endothelial cells

The accuracy and reliability of the TMJ Scale were originally determined in cross-validation studies on large, research-based patient samples. It had been assumed that the demographic characteristics and test responses of these research-based samples would be representative of the clinical population in which the TMJ Scale would ultimately find use. The present study on more than 10,000 patients that were evaluated for temporomandibular disorders in clinical practice demonstrates that the test scores, demographic variables, and the patterns of symptom severity that characterize the original TMJ Scale research sample accurately represent the general temporomandibular disorder patient population in which the TMJ Scale is now being used. The results suggest a high degree of confidence in the clinical efficacy of this assessment tool. The overall symptom severity of temporomandibular disorders was found to be normally distributed in the patient population. Women with temporomandibular disorders report a higher level of severity of all physical and psychological symptoms than men. This may explain the high female-to-male ratio in patients seeking treatment. However, a higher percentage of male temporomandibular disorder patients has clinically significant psychological and stress-related problems than do women. The severity and prevalence of symptoms associated with joint dysfunction and range of motion limitation are lower in older age groups, and the overall symptom severity of temporomandibular disorders is not higher in older age groups. However, the severity and prevalence of symptoms associated with joint dysfunction are greater in groups in which temporomandibular disorders have existed for longer durations, although pain levels do not follow this trend. There is also an association between time duration of the temporomandibular disorder and the severity of psychological problems and chronicity. Patients with chronic problems are symptomatically more impaired than those with acute problems.     

Temporomandibular disorders: a critical review of the nature of pain and its assessment

Temporomandibular disorders is a common form of chronic pain affecting the head, face, and jaw. The distinguishing symptoms of this disorder include pain and impairment of the masticatory function, and frequent display of symptoms, ranging from aches in the head, neck, ears, and eyes, to atypical toothaches, throat symptoms, and occlusal changes. It is recognized that pain is a complex, multifactorial experience including not only sensory dimensions, but also affective and cognitive factors. Recent recommendations regard temporomandibular disorders as a dual-axis disorder with physical and psychologic dimensions, but little research has incorporated measures of multidimensional pain characteristics in the assessment of temporomandibular disorders. This article is a review of the literature on the psychophysiologic factors contributing to temporomandibular disorders and its limitations. Recommendations for future research are also given.     

Aspects of masticatory form and function in common tree shrews, Tupaia glis

Tree shrews have relatively primitive tribosphenic molars that are apparently similar to those of basal eutherians; thus, these animals have been used as a model to describe mastication in early mammals. In this study the gross morphology of the bony skull, joints, dentition, and muscles of mastication are related to potential jaw movements and cuspal relationships. Potential for complex mandibular movements is indicated by a mobile mandibular symphysis, shallow mandibular fossa that is large compared to its resident condyle, and relatively loose temporomandibular joint ligaments. Abrasive tooth wear is noticeable, and is most marked at the first molars and buccal aspects of the upper cheek teeth distal to P2. Muscle morphology is basically similar to that previously described for Tupaia minor and Ptilocercus lowii. However, in T. glis, an intraorbital part of deep temporalis has the potential for inducing lingual translation of its dentary, and the large medial pterygoid has extended its origin anteriorly to the floor of the orbit, which would enhance protrusion. The importance of the tongue and hyoid muscles during mastication is suggested by broadly expanded anterior bellies of digastrics, which may assist mylohyoids in tensing the floor of the mouth during forceful tongue actions, and by preliminary electromyography, which suggests that masticatory muscles alone cannot fully account for jaw movements in this species.     

Women's oral health issues: an exploration of the literature

As interest in women's health issues grows, there is increasing concern that today's practice of medicine may not meet the health needs of women. A primary reason is the gender bias that has been inherent in medical education, research and clinical practice. The prevailing medical viewpoint has often been that the male body is considered to be the norm and that the female body exactly the same except for the reproductive function. This attitude has led to a lack of interest in researching gender differences and a consequent lack of knowledge of women's health issues. Fortunately, there is a movement for change. The Women's Health Interschool Curriculum Committee was formed in January 1992 to develop curricula concerning women's health and examine bias that may exist in existing curricula. The Canadian Women's Health Network has been growing across the country and there have been calls to create a new specialty in women's health. According to Angell, this proposal for a new specialty was provocatively debated in the Journal of Women's Health, which started publication in 1992. There is also a growing concern on how to conduct better research to address women's health needs. As more attention is paid to women's health issues, what will happen in the area of oral health? In health care, it would seem that the mouth has become completely separated from the rest of the body. Health conferences rarely have any oral health content at all. To correct this problem, there must be an increase in general awareness of the importance of oral health as it relates to the overall health of both women and men. Good oral health is more than just decay-free teeth. Oral health encompasses the teeth, the supporting periodontal structures, soft tissues of the mouth and oral pharynx area, temporomandibular joints and muscles of mastication. The mouth is a gateway to the body and will also reflect many systemic health problems, such as diabetes, leukemia and lupus. The second step would be the recognition that women may have different oral health needs and issues than men. The common view may be that teeth are gender free, but how can this be when teeth exist in a body, and that body is male or female? For many years, the primary acknowledged difference between men and women's oral health was pregnancy gingivitis. Like medicine, dentistry must re-examine the viewpoint that women's oral health differs from men's only as it is influenced by reproductive processes. There are many areas where women's oral health may differ from that of men. This paper will explore the literature for potential women's oral health issues in the areas of oral hygiene behaviours, esthetics, eating disorders, temporomandibular disorders, and hormonal influences on periodontal health.     

Comorbidity of depression with chronic facial pain and temporomandibular disorders

OBJECTIVE: The objective of this study was to examine the comorbidity of depressive disorders in patients with chronic facial pain presenting to a multidisciplinary facial pain clinic. STUDY DESIGN: Data were collected from 72 consecutive patients with chronic facial pain who had received a maltidisciplinary evaluation including a psychiatric examination for the presence of depressive disorders. RESULTS: Twenty-eight percent of patients met criteria of the latest Diagnostic and Statistical Manual of Mental Disorders for major depression, and 25% met the criteria for minor depression. A further 22% reported subsyndromal depressive symptoms. Temporomandibular disorders were demonstrable in 71% of these patients, but the remaining 29% had no objective physical findings. There was no statistical difference in comorbidity of depressive disorders in patients with temporomandibular disorders compared with patients without temporomandibular disorders. CONCLUSION: Screening for symptoms of depression should be an integral part of the evaluation of all patients with chronic facial pain, even when masticatory muscle or temporomandibular joint disorders are identified.     

Symptoms of temporomandibular joint osteoarthrosis and internal derangement 30 years after non-surgical treatment

To evaluate the long-term condition of temporomandibular joints (TMJs) affected by osteoarthrosis and internal derangement, 99 patients treated non-surgically between 1958 and 1962 were recalled for follow-up. The patients, 16 men and 83 women (mean age 58.2 years) with either reducing or permanent disk displacement, were submitted to a structured interview concerning previous treatment, masticatory function, and the presence of symptoms of osteoarthrosis and internal derangement of the masticatory system, and of complaints of the musculoskeletal system in general. A control group, consisting of eight men and 27 women (mean age 58.9 years) without complaints of the masticatory system, matching the patient group for sex, age and state of dentition, was included in the study to avoid simply documenting age-related joint conditions. Satisfaction with the treatment outcome was high. Chewing ability of the the patients did not differ from that of the controls, although patients more often expected pain and difficulty with opening the mouth wide. The main TMJ symptoms of the patients had decreased significantly; patients reported joint noises more often than controls. It is concluded that, despite some persisting symptoms, the non-surgical treatment approach of TMJ osteoarthrosis and internal derangement provides long-lasting satisfactory subjective results and is well-accepted by the patients.     

Correlation of clinical improvement with pontine lesions in opsoclonus-myoclonus syndrome

A total of 868 patients aged 25 to 68 with various types of occlusion and dentition defects were examined. 212 (24.4%) patients presented with a shortened interalveolar distance (height of occlusion). Abnormal abrasion of hard dental tissues, dentition defects in the lateral sections of dental arches, abnormal occlusion (deep or prognathic), reduced tolerance of periodontal tissues, and dysfunction of the masticatory muscles (bruxism) were found to be the pathogenetic factors leading to the development of this condition. Dysfunction of the masticatory muscles was detected in 41.5% of patients with shortened interalveolar distance and dysfunction of the temporomandibular joint in 9.9%; moreover, in many of them traumatic occlusion and disorders in the regional circulation in the periodontium of teeth exposed to overexercise were observed. Orthodontic treatment of patients with shortened interalveolar distance was carried out in two stages: the first stage consisted in functional and adaptation restructuring of the maxillodental system by repair of the height of occlusion and normalization of the mandibular position on a plastic cup which the patients wore for 3 months, and then the second stage ensued, at which they were fitted with dentures. Good results were attained in 95.7% patients.     

MR of the spine with a fast T1-weighted fluid-attenuated inversion recovery sequence

Much is unclear about the pathophysiological mechanisms underlying painful temporomandibular disorders. In addition to various other theories, masticatory muscle dysfunction and pain have also been attributed to primary central nervous system hyperactivity. We assessed this possibility in a study using recent neurophysiological techniques. From among outpatients whose diagnosis of temporomandibular disorders had been obtained in stomatognathic facilities, we studied 10 patients with bilateral pain and 15 patients with unilateral pain, in whom electromyographic examination of the trigeminal reflexes disclosed normal findings except for absence or amplitude asymmetry of the jaw jerk. Transcranial magnetic stimulation yielded masseter motor evoked potentials of normal latency and amplitude, but five patients had to exert a near-maximum contraction to obtain their responses. The masseter silent periods elicited by the double-shock technique recovered normally. Because these tests measure the excitability of the masticatory system (including motor cortex, corticobulbar and corticoreticular connections, reticular interneurones and lower motoneurones), the lack of facilitation in these patients' responses excluded central hyperactivity as the primary cause of their masticatory dysfunction and pain.     

Relationship between mandibular position and the coordination of masseter muscle activity during sleep in humans

Although bruxism has been regarded as having a possibly important role in the aetiology of craniomandibular disorders, the activity of masticatory muscles relative to mandibular position during sleep grinding as recorded by electromyography (EMG) has not yet been clarified. Surface EMGs of the bilateral superficial masseter muscles were recorded simultaneously with mandibular position during sleep from 12 volunteers for three consecutive nights. The incidence of two mandibular positions were recorded with magnetic sensors for both left- and right-sided mandibular grinding. One of the mandibular positions was the canine edge-to-edge position, and the other was the midpoint between the intercuspal position and the canine edge-to-edge position. The mode of the working/ balancing activity ratio ranged from 1/10 to 2/10, showing the marked predominance of balancing side masseter muscle activity during sleep grinding. During sleep grinding, EMG bursts of masseter muscle were observed mainly with mediotrusive mandibular movement from the canine edge-to-edge position. From the results of the present study, it is suggested that muscular dynamics during sleep are unique compared to that during voluntary clenching, and exert a greater mechanical load to the balancing side temporomandibular joint.     

Need and demand for dental treatment. A comparison between an evaluation based on an epidemiologic study of 35-, 50-, and 65-year-olds and performed dental treatment of matched age groups

The aim of this study was to compare the results of the level of treatment need as judged from a sample drawn from the general population aged 35, 50, and 65 years with treatments performed in 1992 and 1993 of patients of matched ages. Both the sample and the patients lived in V?sterbotten in the northern part of Sweden. In all three age groups there was a significantly higher frequency of restorative treatment performed than the professionally assessed need in the epidemiologic sample. In all ages examined, treatment aimed at rehabilitation of temporomandibular disorders was performed statistically significantly (p < 0.001) less frequently than the evaluated need in the population. A similar result was found for dentures among 65-year-olds. The results may reflect dental care paradigms favoring operations on single teeth rather than treatments aimed at functional rehabilitation on a broader sense.     

Binding characteristics of anti-atrazine monoclonal antibodies and their fragments synthesised in bacteria and plants

OBJECTIVES: The objective of this study was to assess the potential effects of motor vehicle accident impact and injury characteristics on post-motor vehicle accident temporomandibular disorders in terms of presenting signs and symptoms, diagnoses, treatment regimens, and outcomes. STUDY DESIGN: A retrospective chart review of 50 patients with post-motor vehicle accident temporomandibular disorders from a private oral medicine practice was undertaken. Various demographic data and data related to temporomandibular disorders and motor vehicle accident impact and injury characteristics were collected. Chi-square and Fisher exact tests and multiple regression analyses were performed. RESULTS: Patients involved in front-end collisions or motor vehicle accidents resulting in severe vehicle damage reported more direct orofacial injury. However, those in rear-end collisions or accidents resulting in minimal vehicle damage required more treatment. Direct head or orofacial injury was therefore not a prognostic indicator. From multiple regression analyses, indicators of a poorer prognosis were minimal vehicle damage, lack of headrest use, driver position, and settlement of insurance claim. CONCLUSIONS: In this patients group several prognostic indicators for patients with post-motor vehicle accident temporomandibular disorders were identified; these indicators may influence the management approach for this patient population.     

A cross-sectional study of prevalence and etiology of signs and symptoms of temporomandibular disorders in high school and university students

The aim of this study was to evaluate the prevalence and need for treatment of temporomandibular disorders (TMD) in students living in Bauru, Brazil. The role of occlusal and emotional factors was also addressed. The presence and severity of TMD was determined by using a self-reported anamnestic questionnaire composed of 10 questions regarding common TMD symptoms. The symptoms were transposed into a severity classification according to the number and frequency of positive responses. Occlusal evaluation included an analysis of retruded contact position, intercuspal position, anterolateral guidance, and nonworking side contacts during mandibular movements. Palpation of the muscles and temporomandibular joints were performed to detect clinical signs of TMD. A chi square test was used to compare clinical and occlusal data with the presence and severity of TMD. A total of 0.65% of the subjects had severe TMD symptoms, 5.81% had moderate symptoms, and 34.84% had mild symptoms. Those with severe and moderate symptom levels were interpreted to be in need of treatment. Symptoms were found significantly more frequently in females than in males (P < .01). Self-reported emotional tension and parafunctional habits demonstrated strong associations with TMD (P < .01). Occlusion did not seem to influence the presence or severity of TMD. Based on these results, the efficacy of some traditional TMD treatments should be reconsidered, and reversible and conservative procedures should be the first choice for managing TMD patients.     

Reduced performance of male and female athletes at 580 m altitude

Patients with craniocervical mandibular (TMD) disorders can present with tinnitus as a primary or secondary complaint. The embryology and functional anatomy of the middle ear, temporomandibular joint, muscles of mastication and associated tendons, ligaments, blood vessels, nerves and lymphatics was found to be helpful in establishing etiologic concepts which relate tinnitus to these temporomandibular disorders. In addition to etiologic concepts, treatment modalities are described. The authors relate their experiences as well as those of others with different patient populations.     

The role of the lateral pterygoid muscles in TMJ disorders during static conditions

Intramuscular EMG of the lateral pterygoid muscles (LPM), surface EMG of the temporalis and masseter muscles and force measurements of the temporomandibular joint (TMJ) were synchronously used to investigate the biomechanical role of the two heads of the LPM in relation to internal derangement (ID) of the TMJ. EMG and kinetic analysis of five static conditions (resting, protraction, opening, molar and incisor clenching) and three maximum isometric masticatory forces (opening, molar and incisor clenching) were done to compare forces and muscular activity between TMJ ID and control subjects. The analysis of variance results of the integrated linear envelope (LE) EMG showed no significant differences between the two groups for the masseter and temporalis muscles. Therefore, there is no apparent reason to believe that these muscles are hyperactive in TMJ ID. The integrated LE EMG of the SLP was significantly lower in the TMJ group during molar clenching (104 microV + 60.0 over 159 microV + 68.8 for a p = .020). The superior head of the lateral pterygoid muscle (SLP) seemed to have lost its diskal stabilizing function. The integrated LE EMG signals of the ILP were significantly higher in the TMJ ID group during rest, resisted protraction and incisor clenching (p = .029, p = .046, p = .031 respectively). The ILP muscle has probably adapted to control the inner joint instability while continuing its own actions. The ILP muscle seemed to have lost its functional specificity. The results of the isometric forces showed that TMJ ID subjects exhibited significantly lower molar bite forces (297.1N over 419N, p = .042) confirming that they have less muscle strength and tissue tolerance than subjects with healthy masticatory muscle systems. A neuromuscular adaptation could be occurring in the TMJ ID masticatory system affecting muscular actions and forces.     

Tomographic stability of condyle fossa relationships in 40 treated temporomandibular disorder patients

STATEMENT OF PROBLEM: Condylar position and stability after treatment of 40 temporomandibular disorder patients was studied. PURPOSE: This study determined pretreatment position and posttreatment condylar stability. MATERIAL AND METHODS: Forty temporomandibular disorder patients with symptoms of muscles of mastication pain, temporomandibular joint sounds, attrition, interceptive occlusal contacts, and restricted range of motion were used. Axial corrected midcut sagittal tomograms were made of the 80 temporomandibular joints before treatment. Tracings from the tomograms were used to measure and analyze pretreatment position and posttreatment stability. RESULTS: Pretreatment condyle fossa position was not concentric in 26 of 80 patients (32.5%). Posttreatment condylar position showed no change and was statistically stable. CONCLUSION: In this study of 40 temporomandibular disorder patients, no statistical change in condylar position was detected. Variable condylar positions were found in the 80 pretreatment axial corrected midcut sagittal tomograms. All patients were asymptomatic after 1 year.