Relationship between jaw movement and food breakdown in human mastication.

Different quantities and sizes of peanuts were offered to six human subjects for mastication at two or three experimental sessions during which jaw movements and chewing cycle duration were measured. The amplitude of vertical movement and cycle duration depended on the position of a chew in a sequence of chews (masticatory sequence). Cycle duration also depended on the position of a given masticatory sequence during the first experimental session, the earlier sequences tending to be longer. Lateral jaw movements fluctuated about a reasonably constant value during a sequence and were unaffected by different food inputs. The amplitude of vertical movements increased markedly with an increase in food weight but was unaffected by change in the initial food particle size. These results were analyzed in the light of previous reports on the comminution of peanuts. It is hypothesized that observed jaw movements were unrelated to food particle size but that the amplitude of each vertical movement depended on the volume of food that was broken by the teeth during the next closing stroke. This food volume was provided and selected by bulk movements of the tongue during the preceding jaw opening.

Analysis of incidence and associated factors with fractured implants: a retrospective study.

Osseointegrated threaded titanium screw-type implants rarely lose integration after the first year of clinical function. Implant failure can occur for other reasons, with implant fracture being one of the major reasons for late failure. The purpose of the present study was to determine the incidence of implant fracture in completely edentulous and partially edentulous arches and to determine what factors may predispose an implant to a higher fracture risk. A retrospective evaluation of 4,937 implants was performed to determine the incidence of and factors common to fractured implants from a sample of implants placed and restored in one institutional setting. Based on the results of this study, the following observations were made: implants fracture at similar rates in the maxilla as in the mandible (0.6%), implant fractures occur more frequently in partially edentulous restorations (1.5%) than in restorations of completely edentulous arches (0.2%), all observed fractures occurred with commercially pure 3.75-mm-diameter threaded implants, and prosthetic or abutment screw loosening preceded implant fracture for the majority of the implants. More studies would be helpful to further explore the relationship and progression of factors associated with implant fracture.

Responses and evaluation of patients with temporomandibular disorders in relation to conservative treatment.

The main purpose of the study was to evaluate the pattern of response of an identified subgroup of patients having clinically diagnosed myofascial pain dysfunction of the stomatognathic system to conservative methods of treatment. 10 affected female adults fulfilling the criterion for selection, were allowed to undergo a closely-monitored treatment regime and evaluated on two occasions, employing accepted clinical indices for gauging the severity of the condition. The patients had clinical features of dysfunction graded as moderately severe to very severe. Evaluation showed that severe symptoms were ameliorated for 4 subjects thus affected. Moderate to marked improvement in condition was observed in 6 cases out of the 10 subjects investigated over the 5 to 8 weeks of therapy. The patients showed an encouraging interim response to treatment and their prognosis in general appeared fairly good.

A keloidal scar of the floor of the mouth and its associations. Case report.

A case of extensive scarring of the floor of the mouth mucosa is reported. Its unusual position and possible association with keloid formation of the skin is discussed.

Eyelid grafting as a preprosthetic measure for restoring facial defects.

Prosthetic restoration of a facial defect involving the loss of an eye and associated orbital tissues may be restricted by incorrect orientation of the prosthesis if the reconstructed tissue bed is uniform and without distinctive orbital landmarks. A surgically grafted eyelid is useful in this situation. The lower eyelid graft serves to provide an anatomical guide with which to position the ocular component of the orbital prosthesis in relation to its established visual axis. This assists the subsequent orientation of the adjoining tissue portion of the orbital prosthesis, contributing to a well-positioned and cosmetically pleasing result.

Biting forces in patients with craniomandibular disorders.

Treatment for 10 female patients having craniomandibular disorders of neuromuscular origin showed a reduction in dysfunctional symptoms and improvement in their condition. In response to treatment, a standardized recording method was used to measure alterations to bite force values. In about 60 percent of categories representing various positions in the dental arch from which maximal and submaximal biting forces were measured, there was significant variation between replicate registrations. This persisted after treatment, indicating some loss of sensory acuity for fine bite-force adjustments in these patients. Discriminatory ability for large force adjustments was not, however, observed to be affected. Bite force values showed considerable fluctuation both before and after treatment. The lack of substantial increase in force values after a reduction in muscular dysfunction with treatment appears to suggest that an inhibitory mechanism controlling jaw-closing activity and pressure persists as a protective reflex for these patients.

Colourfast pigments in silicone hand and maxillofacial prostheses.

This study addresses the clinical problem of long-term discolouration of silicone hand and maxillofacial prostheses. Seven (7) pigment hues, considered essential for achieving a suitable tissue colour-matched prosthesis, were compared for their colourfast property, across three selected proprietary formulations. In all, a series of 21 pigments, were tested for colourfastness. The pigments, presenting as suspensions (PS), pastes (PP) and dry pigments (PD), were exposed, over nine months, to ultraviolet light, elevated temperatures and varying concentrations of salinity. Colour change of the pigments was measured and expressed as Commission International de l'Eclairage (CIE) (L*, a*, b*) units. Pigment discoloration was significantly attributed to ultraviolet light. Pigmented and clear silicone samples showed a "yellowing" (+delta b*) effect. Lighter pigments became darker (-delta L*) in shade. Pigment samples at the elevated temperature of 50 degrees C showed significant but small colour change (delta E, 0.77 to 3.63). Only the master blue pigment (PS-4) recorded a higher delta E, 6.26 at 50 degrees C. At a moderate temperature of 35 degrees C, both pigmented and clear silicone test samples remained relatively colourfast. Comparison was made to control samples, stored in darkness, at 26 degrees C. The pigments were generally colourfast (deltaE<6 units) to saline solutions of 0.15 M and 5.0 M concentrations. Only the monastral red (PD-3) pigment recorded a delta E of 9.33, in 0.15 M normal saline, simulating the vulnerability of this pigment to the salinity of human sweat. Pigment hues were systematically ranked according to colourfastness. Pigment suspensions were more colourfast than pigment pastes.

[Maxillofacial prosthesis]. / Prothèses maxillo-faciales.

The purpose of constructing prosthesis to restore post-surgical deformities of the jaws and the face is to enable such patients to cope better with the difficult process of rehabilitation. Patients with post-surgical maxillofacial defects are presented in this article to illustrate how prosthodontic restoration could improve their functional or cosmetic disability.

Retrieval of the resilient element in an osseointegrated implant system.

A fractured apical fragment of the resilient intramobile element within the IMZ dental implant cylinder is difficult to remove. The continued usefulness of the implant will be compromised if the fractured intramobile element is not removed. Two methods of retrieving the apical fragment without causing damage to the internal threads of the implant cylinder are described.

Ocular prosthetics: use of a tissue conditioner material to modify a stock ocular prosthesis.

The custom-made ocular prosthesis contributes to enhanced tissue health of the anophthalmic socket. For this purpose, an acrylic resin ocular prosthesis may be modified, by using an appropriate dental impression material and being adapted closely to the anophthalmic socket. The modeling impression material is subsequently replaced by acrylic resin. This article describes the application of a viscoelastic tissue conditioner material, as an impression medium for prosthetic modification of an ocular prosthesis. The tissue conditioner material exhibits favorable tissue compatibility, adhesion to acrylic resin, and detailed surface registration. These advantages facilitate the clinical procedure and evaluation of modifications made to the ocular prosthesis.

Perceived masticatory function among elderly people.

This study investigated the status and associations of perceived chewing ability of a group of 891 elderly people, aged 55-91 years (average age 66 years). The majority of subjects (69%) considered that they could chew well. Only 9% reported poor chewing ability. This judgement was not associated with age. More men (11%) than women (6%) had reported poor chewing ability. Subjects with better perceived general and craniomandibular health reported better chewing ability. However, although related to permanent tooth loss, the perception of chewing ability was not seemingly associated with prosthetic rehabilitation. All elderly subjects with complete dental arches had no complaints of perceived chewing difficulty. Freedom from symptoms of craniomandibular pain when chewing, bilateral chewing activity and a wide choice of food range or textures were associated with favourably perceived chewing ability. This study identifies several suitable criteria for judging masticatory function and suggests that these may be used to complement chewing ability as an alternative measure of masticatory performance. These criteria are applicable to the elderly person, in particular, and warrant adequate clinical application.

Orientation of the plane of occlusion.

A study was made of 28 dentulous Chinese Singaporean adults, using lateral skull radiographs. Various craniofacial reference lines and their relations to the maxillary occlusal line were analyzed. The orientation of the natural occlusal line in Chinese adults differed significantly from Swedish white adults. The Frankfort horizontal line in particular was considered disadvantageous as a clinical reference plane largely because of the acknowledged variation of its inclination between Chinese Singaporean and Swedish white adults. The shallow anatomic cant of the maxillary occlusal line in the Chinese patient could be misrepresented by a steep mechanical inclination on the articulator.

Relationship of masticatory mandibular movements to masticatory performance of dentate adults: a method study.

This study evaluated a sieve method for measuring masticatory performance and determined the associations between masticatory performance and masticatory mandibular movements. Ten dentate adults and three complete denture-wearing subjects participated in the study. The masticatory performance indices for these subjects were determined after a 10 s masticatory sequence and another sequence that ended at the swallowing threshold. Almond was used as the test food and almond fragments were sized using a standard 0.65 mm square size brass wire sieve. Masticatory mandibular movements were simultaneously recorded by an optoelectronic device. The reproducibility of the masticatory performance tests was good (r = 0.98 and 0.82 for the 10 s and swallowing threshold test indices, respectively). The masticatory performance indices were markedly different between dentate and denture-wearing subjects. The 10 s masticatory performance index in the dentate subjects, showed moderate to rather strong correlation with all parameters of mandibular velocity (r = 0.6-0.7). The 10 s index also showed a strong negative correlation to the duration of the occlusal level phase and the total duration of the chewing cycle (r = -0.7 to -0.8) in the dentate subjects. This study confirms that masticatory performance levels are relatively stable and associated with the efficacy of specific masticatory mandibular movement parameters.

The relationship of upper facial proportions and the plane of occlusion to anatomic reference planes.

A study was made of 28 dentulous Chinese (Singaporean) adults by using lateral skull radiographs. The dimensions of the maxillae and various craniofacial reference lines related to prosthodontic use were analyzed. The craniofacial reference angles that reflect the vertical height and horizontal depth of the maxillae in Chinese adults differed significantly from the norms obtained in a white North American adult population. By comparison, Chinese adults have a vertically high and horizontally receded upper face that could cause planes such as the Frankfort horizontal plane or an arbitrary axis-orbitale plane to assume a steeper anterior inclination, thus modifying the mechanical inclination of the maxillary cast and occlusal plane on the articulator.

Longitudinal peri-implant clinical responses in anterior mandibles of female patients: a preliminary report.

STATEMENT OF PROBLEM: There is a need for specific documentation that successful osseointegration related to Brânemark implants can be maintained, despite an apparent clinically vulnerable peri-implant soft tissue status. PURPOSE: This study monitored longitudinal peri-implant clinical responses in the mandible and sought to question whether a relatively deep mucogingival pocket will give rise to a greater loss of peri-implant bone than a shallow pocket. METHODS AND MATERIAL: Subjects, 8 women patients (mean age 62 years), were treated with Brânemark mandibular osseointegrated implant-supported prostheses. Four of these subjects had limited (average <3.5 mm) and 4 had unlimited (average > or =3.5 mm) peri-implant pocket probing depths and constituted the control and test subgroups, respectively. Longitudinal changes in peri-implant PAL and radiographic bone support were assessed. RESULTS: Overall probing attachment levels (PALs) of the peri-implant mucogingival complex showed little change. The PAL loss was only minimally significant within the control subjects, and not significant for test subjects. The difference in these mucogingival responses between test and control subjects was significant (P = .04). There was no significant overall longitudinal change in peri-implant bone levels. The longitudinal change of peri-implant bone level was not significant within or between the control and test subjects.

Symptoms of craniomandibular disorder among elderly people.

This study investigated the subjective symptoms of craniomandibular disorder and the restriction in maximal mandibular opening of 891 elderly Singaporean citizens. A distribution of 22% of subjects (20% of the women and 26% of the men) reported subjective symptoms of craniomandibular disorders. The most common single symptom reported was occasional to frequent clicking sounds from the temporomandibular joints (in 15% of subjects). The other single symptoms were reported only occasionally in 2-6% of subjects. Nineteen per cent of the subjects had some restriction in maximal interincisal opening (30-39 mm) and about 1% of subjects were severely restricted in maximal opening (less than 30 mm). Subjectively evaluated limitation of wide mandibular opening was recorded for only 2% of the subjects. Background factors included general musculo-skeletal problems (54%), perceived fair to poor general health (29%), headaches (33%), work-related stress (24%), oral parafunctional clenching (4%) and grinding activity (4%). This paper confirms earlier reports that the subjective signs and symptoms of craniomandibular disorder tend to diminish in elderly people.

An international comparative multicenter study of assessment of dental appearance using computer-aided image manipulation.

PURPOSE: The aim of the present investigation was to perform an international multicenter comparison of dental appearance as evaluated by dentists, dental technicians, and nondental subjects. MATERIALS AND METHODS: The participants were drawn from three groups: 203 dentists, 197 dental technicians and 254 nondental subjects. The methods developed in a previous study in Sweden were applied again in seven centers located in six countries. A questionnaire, accompanied by five sets of computer-manipulated images portraying one man and one woman, was used to prompt and record responses to different aspects of dental appearance and function. RESULTS: The questionnaire revealed that both the dental appearance and function of teeth were important to most of the participants, but three quarters of the participants did indicate that good dental function was more important that esthetics. More women (30%) than men (18%), however, placed greater importance on appearance. Age or gender did not influence judgments of the computer-manipulated images, although judgments did vary greatly within the three groups and between the centers. Nonetheless, highly colored teeth were preferred more often by nondental subjects than by dentists or dental technicians. CONCLUSION: Computer-aided image manipulation shows promise as a method for investigating the significance of dental-related beliefs, especially those relating to esthetics, in different population groups. The evaluation of dental appearance and function in this study indicated that dental function is held in greater regard, and that the significance of dental appearance varies widely among dentists, dental technicians, and nondental subjects.