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PubMed1997

The effect of timing of archwire placement on in vivo bond failure.

At the commencement of fixed appliance therapy the operator has the choice of either placing bands, brackets, and archwires at one visit, and hence loading the brackets within an hour of initial placement, or placing the brackets and separators at one visit, and the bands and archwires at a subsequent visit. In the case of the latter, the brackets will only be loaded intermittently during the intervening period, for example during mastication. The present study investigated the effect of loading bonded brackets for 2 weeks prior to measuring shear debonding force in vitro, and compared the results with in vivo bond failure rates for two groups of patients whose brackets were loaded by the archwire either immediately after bonding, or not less than 1 week later. Shear testing and survival analysis indicated in vitro loading prior to testing had no significant effect on the shear debonding force. When the in vivo data were studied there was no significant difference in the rate of bond failure between those patients whose archwires were placed at the time of fitting the appliance, and those whose archwires were placed no less then 1 week after bracket placement.

Acid Etching, Dental↗

PubMed1989

Muscle function as a determinant of mandibular growth in normal and hypocalcaemic rat.

The aim of the present investigation was to study the influence of low muscle function on the form, growth and structure of the mandible in rats with a metabolic bone disturbance due to hypocalcaemia. Growing rats were randomly divided into four groups where two factors were combined: hard or soft diet consistency to normal or calcium deficient diet. The experimental period was 30 days. At day 0 and day 15 the animals were injected with oxytetracycline. At the end of the experiment X-rays were taken from the mandibles for cephalometric analysis and the bone remodelling pattern was studied under a fluorescence microscope and with help of microradiograms. The cephalometric analysis showed that calcium deficiency was an unfavourable factor for the growth of the mandible as a whole, while muscle function was a significant factor affecting the angular and the condylar processes. General decreased bone apposition and increased endosteal resorption were found in the two calcium deficient diet groups. The cortical bone in these groups was thinner and the trabecular system sparser than in the two normal diet groups. The hard diet groups had higher bone apposition rate and better organized trabecular system than the respective soft diet groups. It was concluded that changes in the mechanical strain environment of the mandible, caused by reducing the vigorous mastication, is a powerful determinant of remodelling behaviour at certain sites, even in situations when a metabolic bone disturbance exists.

Animals↗

PubMed1997

Chewing-induced visual impairment from a dumbbell dermoid cyst.

A 29-year-old woman presented with a 1-year history of blurred vision in her left eye while chewing. Examination revealed a rubbery mass with ill-defined borders in the superotemporal brow region. Imaging studies demonstrated a cystic lesion extending from the temporal fossa into the orbit through a bony defect in the lateral orbital wall, assuming a dumbbell configuration. Histopathology of the excised specimen confirmed the clinical diagnosis of a dermoid cyst of cutaneous origin. We believe that the patient's visual disturbance was caused by transient displacement of orbital contents by the dermoid cyst as it was compressed into the orbit during mastication. Dermoid cysts are frequently associated with bony defects, which may require preoperative imaging and may produce unexpected symptoms.

Adult↗

PubMed1994

Gustatory rhinorrhea--a complication of septoplasty.

A previously unreported complication of septoplasty, which is the profuse flow of thin clear nasal drainage on mastication, is described. Of a combined group of 1332 patients with septoplasty and septorhinoplasty, 6 females and 1 male presented with gustatory rhinorrhea after surgery. The average age of the patients who experienced this complication was 44.43 years. Three patients tested the efficacy of antihistamines, which proved helpful in reducing the severity of this condition. The cause of gustatory rhinorrhea is postulated as inadvertent injury to the nasopalatine nerve within the septal layers after removal of the deviated portion of the vomer and the perpendicular plate of the ethmoid bone during septoplasty. It is the authors' supposition that regenerating nerve sprouts are inappropriately directed toward nasal, rather than palatal, target receptors. Consequently, rhinorrhea results while eating. The pathophysiology of this new finding is not dissimilar to gustatory sweating after parotidectomy. Although this complication is not life-threatening, it is socially disturbing to patients. The authors believe that awareness of this sequela will lead to the discovery of a larger patient population and a potential treatment or prevention.

Adult↗

PubMed2001

Pain and dental implantology: sensory quantification and affective aspects. Part I: At the private dental office.

After an extensive review of the dental literature, few articles were found related to pain and implantology. Management of orofacial pain has traditionally been a difficult challenge for the dental-medical profession. Patients may be afraid of dental pain, particularly in cases of dental implantology. Therefore, a study to obtain more conclusive data was developed. Taking into account that the perception of pain and the threshold of pain vary among individuals, a 2-year clinical study was established in private practice utilizing a verbal method (double-blind). The study was used to quantify sensory and affective aspects of pain associated with dental implantology on 75 patients in a private dental office. All of the implants were placed by the same clinician. Data were recorded following a Pain Data Sheet designed for this particular study. The aim of this study was to obtain different aspects of data as follows: 1) Fear of the dentist and fear of dental implant procedures utilizing a descriptive scale of 1 to 10, with 1 indicative of no fear. 2) Dental areas and ridges: Dental pain, pain in edentulous areas, and pain in the implanted area utilizing a scale of 0 to 8, with 0 indicative of no pain. 3) Function and pain: during mastication, swallowing, speech, yawning, opening, closing, and lateral excursions and indication of cervical pain or back pain, each calibrated by the presence or absence of pain. 4) Palpation and pain of the temporomandibular joint, the temporal muscle, the area of the pterygoid muscles, masseter muscle, and sternocleidomastoid muscle, all calibrated on the indication of presence or absence of pain. 5) Others: ear pain, neuralgia, headaches, edema, and hematoma, calibrated on the basis of presence or absence. The aforementioned factors were evaluated immediately before surgery and after surgery, at 24 hours, and during a follow up for a period of 2 years at intervals of 1 week; 1, 2, 3, 4, and 6 months; and 1 and 2 years after surgery. Also recorded were the uses of presurgical and postsurgical medication at the first and second surgical phases, age, sex, buccal opening, number and position of implants, previous dental experiences, and the psychological preparation for dental implant treatment. The results of the statistical analysis indicate no correlation between pain and dental implantology procedures, in a private dental practice, at the level of significance of P > .001.

Adolescent↗

PubMed2005

The effect of rate of distraction osteogenesis on structure and function of anterior digastric muscle fibers.

The authors hypothesized that distraction at a rate of 3 mm/day, compared with mandibular distraction at a rate of 1 mm/day, would produce a maladaptive response in adjacent muscles of mastication. The authors further hypothesized that the maladaptive response would manifest at the single fiber level by means of increased sarcomeric heterogeneity, decreased maximum force output, and increased susceptibility to stretch-induced injury. In an ovine model, distraction osteogenesis of the right hemimandible was performed at either 1 mm/day for 21 days (n = 2) or 3 mm/day for 7 days (n = 2) to achieve a total distraction distance of 21 mm. The left hemimandibles served as controls. After a consolidation period of 2 days, the anterior digastric muscles were harvested; in six randomly selected single fibers from each muscle, maximum calcium-activated force (Po) was measured at optimal sarcomere length. The amount of damage to the sarcomeres in each fiber was assessed microscopically. To test susceptibility to contraction-induced injury, each fiber was given an activated stretch of 20 percent. Compared with control fibers and fibers distracted at 1 mm/day, maximum tetanic force (Po) was significantly lower in fibers distracted at 3 mm/day. Compared with control fibers, specific Po (Po/cross-sectional area) was lower in fibers distracted at 3 mm/day. The number of sarcomeres appearing damaged in fibers distracted at 3 mm/day was significantly higher than in control fibers or in fibers distracted at 1 mm/day. A greater deficit in Po was observed after a single activated stretch in fibers distracted at 3 mm/day than in control fibers or in fibers distracted at 1 mm/day. The authors conclude that distraction of the anterior digastric muscle in sheep at 3 mm/day produces a maladaptive response in the muscle fibers but a rate of 1 mm/day is tolerated by the muscle fibers. These data are consistent with the hypothesis that distraction of skeletal muscle at high rates results in increased heterogeneity of sarcomere lengths and that this increase in heterogeneity is the most likely potential mechanism resulting in whole muscle force deficits and in increased susceptibility to stretch-induced injury in distracted muscles.

Animals↗

PubMed1991

An artificial oral environment for testing dental materials.

Two servo-hydraulic actuators were combined to produce the force movement cycle of human mastication. A closed-loop method of control was used which functions in a manner similar to the human neuromuscular system. The horizontal closed-loop uses a linearly variable differential amplifier (LVDT) to monitor the position. The vertical closed-loop uses both an LVDT to monitor position and a load cell to monitor force with a "mode switch" being made between the two mechanisms of control. A function generator is used to produce a sine wave which is modified to produce the movement and force programs for the two servo-hydraulic actuators. An acrylic chamber was constructed which contains the test samples and maintains an environment similar to that which occurs in the mouth. Natural or artificial saliva maintained at 37 degrees C is continuously circulated through the chamber. The time to complete a single chewing cycle was decreased by eliminating that part of the cycle where no force is produced. This enables the chewing rate to be increased to four cycles per second. The wear produced in the artificial mouth was found to have a high correlation with clinical wear if 250,000 cycles in the artificial mouth are assumed to be equivalent to one year in the human mouth.

Dental Materials↗

PubMed2003

Effects of masticatory muscle function on craniofacial morphology in growing ferrets (Mustela putorius furo).

Studying the effects of masticatory muscle function on craniofacial morphology in animal models with different masticatory systems is important for further understanding of related issues in humans. Forty 5-wk-old male ferrets were equally divided into two groups. One group was fed a diet of hard pellets (HDG) and the other group was fed the same diet but softened with water (SDG). Lateral and dorsoventral cephalograms were taken on each group after 6 months. Cephalometric measurements were performed by digital procedures. For SDG ferrets, the hard palate plane was more distant from the cranial base plane, and canines were more proclined compared with HDG ferrets. The SDG ferrets were also found to have smaller interfrontal and interparietal widths, and a slenderer zygomatic arch than the HDG ferrets. In the mandible, the coronoid process was generally shorter and narrower for the SDG ferrets. The effects of the altered masticatory muscle function on craniofacial morphology in growing ferrets seemed to differ from those previously reported in other animal models studied under similar experimental conditions. Such differences in the effects are presumably related to the differences in the mode of mastication, craniofacial anatomy and growth pattern in different animal models.

Animal Feed↗

PubMed1975

Masticatory function--a review of the literature. 1. The form of the masticatory cycle.

Recently, the authors realized that an evaluation of the literature on mastication had never been undertaken, and it is hoped that this review presented in three parts, will be of value, not only to the dental clinician, but to other scientists working in associated fields. The first paper discusses the form of the masticatory cycle in the natural and artificial dentitions, including the controversial question of whether tooth contact occurs during function. The second paper reviews the literature concerning the speed of movement of the mandible, rate of chewing and the forces developed in chewing. The final paper describes masticatory efficiency and performance, the effect of food on masticatory function, and incorporates a summary of all these three papers.

Cineradiography↗

PubMed1976

Masticatory function - a review of the literature. III. Masticatory performance and efficiency.

A review and evaluation of the literature on mastication has been undertaken. Part I discusses the form of the masticatory cycle in the natural and artificial dentitions, including the controversial question of whether tooth contact occurs during function. Part II reviews the literature concerning the speed of movement of the mandible, rate of chewing, and the forces developed in chewing. Part III describes masticatory efficiency and performance, the effect of food on masticatory function, and incorporates a summary of all these three papers.

Adaptation, Physiological↗

PubMed1978

Credibility of morphologic and psychologic theories of TMJ pain-dysfunction aetiology.

An evaluation of the morphologic and psychologic theories of the aetiology of TMJ pain-dysfunction can be revealing if made without resorting too much to scientific experimental results, because the interpretation of results as well as the questions asked are largely dependent on a prior commitment to one of the theories. Accepting that the TMJ pain-dysfunction became a common disease after the industrial revolution gives reason to look for a causative factor connected with it. Both an increase of psychologic stress and a change of dental morphology and function appear as possible factors, but only the latter has factual evidence. The lack of functional wear disturbs the unconscious swallow reflex but apparently not mastication. This suggests that retrusive interferences are a necessary but not always sufficient condition for the initiation of the TMJ pain-dysfunction. Psychologic factors are contributory, they can cause tooth clenching and perhaps grinding, but there seems to be no reason other than interferences from occlusion for that taking place eccentrically. Thus psychogenic tooth clenching and grinding do not seem to be pathogenic without the morphologic factor.

Bruxism↗

PubMed1979

A comparison of two methods of quantifying masticatory pressures developed under dentures with variable occlusal widths.

Pressures developed during mastication with removable dental prostheses have been quantified by two methods. This pilot study (1) compares the peak pressure method of pressure quantification with the integrated curve method of quantification and (2) continues the exploration of the effect of the width of the occlusal table on pressures developed under dentures. A set of specially designed experimental dentures was constructed for one individual. The mandibular experimental denture contained a series of pressure transducers by which masticatory pressures were recorded. These pressures were monitored between the denture base and the residual ridge tissues. Several interchangeable posterior occlusal segments, varying only in the width of the occlusal table, were fabricated for the opposing maxillary denture. Masticatory pressure and total ridge pressure were quantified by the integrated curve method and the peak pressure method. Both methods indicated a direct relationship between masticatory pressures produced and the width of the occlusal table. A similar direct relationship between total ridge pressure and occlusal width was suggested statistically by the integrated curve method, and graphically by both methods.

Alveolar Process↗

PubMed1979

Cusps or no cusps--that is not the question.

Current views of the significance of cusps to oral health range from an emphasis on meticulous recusping of the restored teeth to a recommendation of gradual prophylactic elimination of natural cusps by grinding. Cusps, their morphology and mutual arrangement are associated with masticatory function. The adaptive value of efficient mastication has diminished along with advancing cultural evolution. Industrialization marks a turning point as seen from the almost total disappearance of functional tooth wear. Restoring cusps to achieve maximum structural efficiency thus lacks a rational basis. But the occlusal morphology is also associated with the swallow reflex: retrusive occlusal interferences tend to disturb it. These interferences can be avoided by establishing the freedom in centric or by restoring the occlusion to the retruded position. The prophylactic grinding of teeth also lacks a rational basis. The consequences of artificial wear are not likely to be the same as those of functional wear because the function has changed, the oral environment is different. It seems advisable, therefore, to try to eliminate only unquestionably harmful factors, and to leave the rest of the morphology as unchanged as possible.

Dental Occlusion↗

PubMed1981

The role in masseter muscle activities of functionally elicited periodontal afferents from abutment teeth under overdentures.

Five overdenture wearers with a small number of remaining natural teeth were selected to evaluate the effect of the afferent input from periodontal mechanoreceptors on masseter activity in man. As a control, a full denture wearer was included. The subjects were instructed to chew a piece of gum, and/or tap their teeth. Surface EmG from the bilateral masseter muscles were recorded and analysed. When functional pressure was applied, during chewing, to the abutment teeth as well as to mucosa through the denture base, masseter activities were encouraged. Following application of anaesthesia to the periodontal membrane of the abutments, masseter activities were reduced. The duration of the silent period (SP) appearing in the EMG burst following tooth tapping was significantly increased with root support compared to mucosal support only. With topical anaesthesia of the periodontal tissues, SP duration decreased significantly. In conclusion, it has become apparent that the pressure sensibility of abutment teeth bearing functional pressure under an overdenture base is capable of facilitating masseter activity, as one of the sources of oral sensory input during mastication.

Adult↗

PubMed1981

Recent results concerning physiological tooth movement and anterior guidance.

Physiological tooth movements during mandibular excursions with and without occlusion have been considered. Using electronic and pantographic techniques, anterior guidance and tooth movements during simulated mastication (without a bolus) were investigated. Investigations in the absence of occlusion showed that elastic deformation of the mandible gave rise to tooth movements. During occlusion three-dimensional tooth movements of up to 60 micro m in each direction occurred. Pantographic measurements of anterior guidance showed that each type of occlusion (balanced occlusion, group function and canine protected occlusion) has its own characteristic. Only canine protected occlusion gave values which corresponded to physiological data.

Cuspid↗

PubMed1986

Food breakdown patterns produced by human subjects possessing artificial and natural teeth.

The abilities of thirty-two complete denture wearers and thirty-two dentate subjects to break down raw carrot particles were compared. The particle size distributions produced were broader in those subjects that broke down food rapidly per chew and, conversely, narrower in those that were slower. This did not appear to depend on dental status. An analysis of mastication as composed of two separable processes, one describing the means by which particles come to be broken (selection) and the other, the size distributions of a particle upon fracturing (breakage), indicated that both processes were variable. It is concluded that no qualitative differences in the manner by which the two groups reduce food is apparent. To support this, a small study on dentate subjects suggests the covering of the palatal mucosa with an acrylic plate does not affect masticatory performance.

Adult↗

PubMed1986

Changes in masticatory movement parameters within the chewing period in young dentate persons and patients rehabilitated with bridges supported by implants in the mandible.

Experiments were carried out to study changes in masticatory movements in the chewing sequence of young dentate persons and complete denture wearers rehabilitated with bridges on osseo-integrated implants (OIB) in the lower jaw. Two test foods were used in the dentate group (apple, bread) and bread in the OIB group. A computer-based opto-electronic system (Selspot) was employed to record and analyse all single chewing cycles, regarding parameters reflecting, chewing rhythm, mandibular velocity and displacement. The different parameters were tested both intra- and inter-individually versus the series of the single and overall chewing cycles in the masticatory sequences respectively. The results indicated that different subjects performed different patterns of mastication within the chewing period when chewing the same type of food. Different test foods (texture, size) also seemed to affect the chewing pattern in a different way, e.g. mandibular displacement showed an obvious reduction when chewing apple, probably due to the bigger size of the bolus. The inter- and intra-individual analysis showed in some parameters discrepancies implying problems in analysing the chewing pattern within the chewing sequence without using both methods.

Adult↗

PubMed1988

Pain in the sternocleidomastoid muscle and occlusal interferences.

The EMG of the sternocleidomastoid muscle and the masticatory muscles during function has been observed in relation to opposing occlusal contacts. The purpose was to investigate the possible developmental mechanism of pain which can occur in the muscles. Six subjects with normal function and ten patients were studied. EMG activities of temporal, masseter, sternocleidomastoid (insertion) and sternocleidomastoid (middle) were recorded by surface and needle electrodes. EMG activity was recorded from the insertion of the sternocleidomastoid during activity of the masticatory muscles in tapping, clenching, and mastication. On the other hand little activity was registered from the middle of the sternocleidomastoid. The amplitude of the EMG of SCM-I increased as the occlusal force increased. During chewing the sternocleidomastoid muscle was functioning more actively on the working side than on the non-working side. On the patients, EMG activities of the muscles were of low amplitude and low frequency with no synchronization with the chewing movement, suggesting hyperactivity of the muscle.

Adult↗