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Biomedical subjects

J G Burch

Publications and source records attributed to J G Burch.

At least 19 recordsLinked to original sources
PubMed2001

Evaluation of biomechanical properties of Expanded-Polytetrafluoroethylene Soft Tissue Patch after dorsal implantation in the rat to mimic TMJ lateral reconstruction.

Clinically, Gore-Tex Expanded-Polytetrafluoroethylene (E-PTFE) has been used to reconstruct the lateral temporomandibular joint (TMJ) ligament. The purpose of this study was to assess changes in the biomechanical properties of implanted E-PTFE over time with respect to tissue infiltration. Ninety-six specimens of implants were divided into four groups. Group A was the experimental group. Thirty-six autoclave-sterilized specimens were subcutaneously implanted into the backs of 36 rats. The rats were randomly sacrificed at 2 (n = 12), 7 (n = 12) and 12 (n = 12) weeks. The implants were tested for mechanical properties including maximal stress, strain and Young's modulus of elasticity (E) using the servo-hydraulic material testing system (MTS). Group B was the in vitro control group. Thirty-six specimens were placed in tissue culture media at 37 degrees C for a time period equivalent to the experimental group to simulate the effect of a moist, warm environment on biomechanical properties. Group C was the temperature and pressure control group. Twelve specimens were autoclave-sterilized to determine the changes of tensile strength under high temperature and pressure. Control group D (no treatment) was tested to determine the initial tensile strength. The results showed significantly larger maximal stress as well as an increase in E and smaller maximal strain in experimental group A than in control groups B, C and D. There was no significant difference among control groups B, C and D. Histological examination of implants at 12 weeks demonstrated that 0.2-0.3 mm of 1-mm thick implants were occupied by connective tissue from each side. It may be concluded that E-PTFE implants become stronger and less flexible after implantation in vivo.

Analysis of Variance↗
PubMed1998

Lateral cephalometric analysis of asymptomatic volunteers and symptomatic patients with and without bilateral temporomandibular joint disk displacement.

Few studies of dentofacial and orthodontic structural relationships relative to temporomandibular joint (TMJ) dysfunction have been reported. We undertook this investigation to determine any correlation of orthodontic and dentofacial characteristics with TMJ bilateral disc displacement. The population of patients was selected from a TMJ clinic where a control group of asymptomatic volunteers had been previously established and standardized. Differences in skeletal structural features were determined among three study groups: (1) asymptomatic volunteers with no TMJ disk displacement, (2) symptomatic patients with no TMJ disc displacement, and (3) symptomatic patients with bilateral TMJ disk displacement. Thirty-two asymptomatic volunteers without disk displacement (25 female, 7 male) were compared with the same number each of symptomatic patients without TMJ disk displacement and symptomatic patients with bilateral TMJ disk displacement. All subjects had undergone a standardized clinical examination, bilateral TMJ magnetic resonance imaging, and lateral cephalometric radiographic analysis. The groups were matched according to sex, TMJ status, age, and Angle classification of malocclusion. Seventeen lateral cephalometric radiographic cranial base, maxillomandibular, and vertical dimension variables were evaluated and compared among the study groups. The mean angle of SNB, or the intersection of the sella-nasion plane and the nasion-point B line (indicating mandibular retrognathism relative to cranial base), of the symptomatic patients-with-displacement group was significantly smaller than that in the asymptomatic volunteers and symptomatic patients without bilateral disk displacement (p < 0.05). Female subjects showed smaller linear measurements of mandibular length, lower facial height, and total anterior facial height than male subjects in all three groups (p < 0.05). The mean angle of ANB, or the intersection of the nasion-point A and nasion-point B planes (indicating retrognathism of mandible relative to maxilla), was significantly greater in female than in male subjects, in all groups (p < 0.05). Symptomatic patients with bilateral disk displacement had a retropositioned mandible, indicated by a smaller mean SNB angle compared with that in asymptomatic volunteers and symptomatic patients with no disk displacement on either side. Lateral cephalometric radiographic assessment may improve predictability of TMJ disk displacement in orthodontic patients but is not diagnostic; nor does the assessment explain any cause-and-effect relationship.

Adult↗
PubMed1998

Evaluation of shear stress of the human temporomandibular joint disc.

The aim of this study was to determine the shear stress of the human postmortem temporomandibular joint (TMJ) disc. Correlation of shear stress with age or with the region of the disc was determined. Nine discs were removed unilaterally from postmortem humans, ages 36 to 76 years. Discs were sectioned into lateral (eight), central (eight), and medial (eight) specimens. Each specimen was attached by cyanoacrylate adhesive to a servohydraulic test system apparatus within 48 hours of retrieval. Shear properties were measured under quasistatic conditions with a linear increase of displacement until the specimen failed to maintain maximum resistance to the applied force. The shear moduli were analyzed by means of the Wilcoxon's signed ranks test. The results showed that values of shear moduli on peripheral portions (lateral and medial) were significantly higher than on central portions (P = 0.0013). The correlation between the shear moduli of TMJ discs and age showed a regression slope for shear moduli of -0.326 + 0.031 x age (r = 0.769; P < 0.01). Peripheral portions (lateral and medial) have a higher shear moduli and are stiffer than the central portions of discs and shear moduli or stiffness of TMJ discs increase with age.

Adult↗
PubMed1994

Incidence and size of pretreatment overlap and posttreatment gingival embrasure space between maxillary central incisors.

Five hundred sets of orthodontic diagnostic records of patients (age 15 years +/- 3) (228 males, 272 females) whose six maxillary anterior teeth had erupted were studied. Incidence of overlapped and crowded maxillary central incisors and magnitude of that crowding were determined, also the incidence of postorthodontic open gingival embrasures (black triangles) and width of those triangular spaces between maxillary central incisors were determined. Of the 500 patients 185 (37%) had preorthodontic crowding of maxillary central incisors. Magnitude of crowding was 1.08 mm +/- 0.94, n = 185. One hundred twenty-nine of these patients were treated. Their postorthodontic records were studied. Of the 129 cases 54 (41.9%) had a black triangular gingival embrasure space between the two maxillary central incisors postorthodontically. Width of the triangular space was 0.43 mm +/- 0.32, n = 54. One third of a similar population of orthodontic patients can be expected to have crowded central incisors. Two-fifths of those can be expected to have a postorthodontic black triangle when treated similarly.

Adolescent↗
PubMed1994

A two-month study of the effects of oral irrigation and automatic toothbrush use in an adult orthodontic population with fixed appliances.

Forty-seven adult orthodontic patients with fixed orthodontic appliances were divided into three study groups: (1) oral irrigation with automatic toothbrush, (n = 16); (2) oral irrigation with manual toothbrushing, (n = 16); (3) control group with continued normal toothbrushing only, (n = 15). Gingival and plaque indices, bleeding after probing, and gingival sulcus depths were assessed at baseline, 1-month, and 2-month periods. Marked and significant gingival and plaque improvements from baseline were measured in all three study groups. After 1 to 2 months use of the automatic toothbrush and/or the oral irrigation device, there was a significant reduction in plaque when compared with the control group who used only the manual toothbrush (p = 0.026). Also, there was a significant reduction in gingival inflammation (p = 0.045) and evidence for reducing bleeding after probing (p = 0.037). No significant differences were found in probe depths among the three study groups, however, use of both devices reduced the pocket depth significantly from baseline by 0.5 mm (p < 0.0002). For this population of orthodontic patients, significant reductions in plaque, gingival inflammation, and a tendency for reduced bleeding after probing occurred in both groups with the power device. These improvements were most attributable to the effect of the oral irrigation device.

Adult↗
PubMed1992

Periodontal changes in furcations resulting from orthodontic uprighting of mandibular molars.

Periodontal examinations were carried out preorthodontically and again 2 to 28 months after orthodontic uprighting of 20 molars (40 furcation areas) in 16 patients. Preorthodontically, patients presented with generalized periodontitis. Postorthodontically, nine of 20 buccal furcations had become more severe, one had improved, and ten remained unchanged. Lingually, nine worsened, and 11 had no change. Furcation area pocket depths increased in 35.0% of furcations, but did not change in 57.5%. Furcation root form was not associated with the degree of change. Possible mesial root extrusion was found in 60.0% of the uprighted molars. The molars showing root extrusion had furcations that increased in severity. Heavy uprighting forces contributed to extrusion, and some effect may have been due to periodontal inflammation and bone loss. Mandibular molars can be uprighted in patients with moderate periodontitis, but light intrusive forces in an inflammation-free environment are recommended.

Alveolar Bone Loss↗
PubMed1991

Grafted and ungrafted labial gingival recession in pediatric orthodontic patients: effects of retraction and inflammation.

The purpose of this retrospective study was to determine changes in recession and other periodontal factors after orthodontic treatment of malocclusions. Twenty patients with preorthodontic labial recession on one or more mandibular central incisors were studied. Ten patients had received autogenous gingival grafts in the area of recession prior to orthodontics, while ten received no graft. The teeth presenting recession had been retruded from a preorthodontically prominent arch position. Moderate inflammation of marginal tissues and fair-to-poor oral hygiene were maintained by the patients. Statistically significantly less gingival recession was found in both groups after orthodontic treatment than was found pretreatment. The results of this study indicated that labial recession tends to decrease with retrusion of mandibular incisors even when moderate inflammation and fair-to-poor oral hygiene persist. Preorthodontic gingival grafting did not further decrease the postorthodontic gingival recession.

Adolescent↗
PubMed1987

A standardized system for evoking masseteric silent periods with decreased variance.

Masseteric silent periods have been evoked in a group of normal subjects under a standardized system and under nonstandardized conditions. In the designed system, head position, electrode placement, bite force, tap force, direction of tap, and surface zone of tap force delivery were controlled. Analysis of data confirmed the hypothesis that standardization of the procedure for eliciting the silent period results in measurements of duration with decreased standard deviations and variances. In the present study, under the standardized system the SPD range of standard deviations was between 1.37 and 3.68 (mean 2.97) and the range of variances was between 1.89 and 13.54 (mean 8.85). The recorded low variability suggests a high degree of reproducibility of the system. High reproducibility and low variability of measurements are necessary if an accurate measure of silent period duration is to be achieved and used in the interpretation of diagnostic findings for craniomandibular disorders.

Adult↗
PubMed1987

Clinical crown contours: contemporary view.

Crown contours represent a group of characteristics critical for the longevity and success of dental restorations. This article presents the theories that have been developed about crown contours, describes each feature in detail, and clarifies potential interrelationships with all components of the mouth. When identified early, crown contours can be incorporated in treatment planning and restorative procedures.

Crowns↗
PubMed1986

Proximal tooth surface quality and periodontal probing depth.

The proximal tooth surface integrity of 826 patients was correlated with periodontal probing depths. Results show relatively increased probing depths adjacent to restored proximal tooth surfaces, with the greatest probing depths adjacent to overhanging restorations and restorations with recurrent caries. The data confirm the significant tendency of the periodontal condition to deteriorate as a function of decreasing surface quality. Probing depth appeared to increase with the patient's age. Surface condition, however, showed a significant relationship with probing depths in all age groups.

Adult↗
PubMed1984

Risk of ischemic heart disease in patients with TIA.

A prospective study was made of the morbidity and mortality from ischemic heart disease in 390 patients with focal TIA caused by atherosclerotic vascular disease. The 5-year cumulative rate of myocardial infarction or sudden death in these patients was 21.0%, a rate only slightly less than that of fatal or nonfatal cerebral infarction (22.7%). Risk factors including diabetes, angina, and ECG abnormalities were associated with an increase in morbidity and mortality from ischemic heart disease. A major factor associated with these cardiac events was the presence of atherosclerotic obstructive or ulcerative lesions in the carotid arteries. These observations indicate that focal TIA caused by carotid atherosclerosis is a predictor not only of cerebral infarction, but also of serious cardiac disease and death.

Adult↗
PubMed1980

The selection of occlusal patterns in periodontal therapy.

Posterior and anterior occlusal anatomy is discussed primarily from the standpoint of occlusal contact relationships. A few general principles of occlusal morphology have been presented. Certain occlusal considerations have been discussed as they relate to selective grinding as well as to restorative dentistry and orthodontics.

Cuspid↗
PubMed1979

Use of a self-administered questionnaire for detection of transient cerebral ischemic attacks: I. Survey of elderly persons living in retirement facilities.

A self-administered questionnaire designed to identify people with transient cerebral ischemia (TIA) in large population groups was distributed to approximately 10,000 elderly persons living in public and private retirement facilities in the United States. The population resided in eight cities, and 74% completed the survey. Transient focal neurological symptoms compatible with a diagnosis of TIA within the previous year were reported by 6.4% of the respondents. Uncertain manifestations of TIA, i.e., dizziness, light-headedness, or loss of balance, were noted by an additional 15.4%; the remaining 78.2% had no manifestations of this disorder. A clinical history for TIA was taken by a neurologist in a sample of 1,712 respondents to determine the validity of the questionnaire responses. Thirty (7.1%) of 423 persons presumed by the questionnaire to have TIA met the standard clinical criteria for the diagnosis. An additional 8 cases of TIA were found by the neurologist among the 1,289 interviewed persons presumed by the questionnaire to have uncertain TIA or no evidence of the disorder. The twelve-month period prevalence of TIA was estimated to be 8.2 per 1,000 in the total respondent population and 5.8 per 1,000 among those without a history of prior completed stroke. Despite the high proportion of false-positive neurological symptoms of TIA elicited by the questionnaire, this survey instrument nevertheless screened out for further study the 6% of the population in whom 55% of the TIAs occurred.

Aged↗