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Biomedical subjects

H C Karkazis

Publications and source records attributed to H C Karkazis.

15 recordsLinked to original sources
PubMed1995

Random variation in the masseteric silent period after chin taps.

Although the silent period duration has often been evaluated as a potential indicator of stomatognathic system dysfunction, there is still some uncertainty as to its normal biologic variation. This study investigated the subject variation in the silent period in a group of 22 young and healthy subjects under standardized conditions. Electromyographic recordings were obtained from the masseter muscle at 40% clenching after chin taps. Four different patterns of the silent period were recorded: one simple and three combined. Although the latencies of the early and late phases of depression were generally consistent, the results for duration were more variable and depended on the pattern of the silent period.

Adult↗
PubMed1994

The influence of gender on the masseter electromyographic jaw-jerk reflex in young human subjects.

The purpose of this study was to investigate the effect of gender on the masseteric jaw-jerk reflex, evoked in a sample of nine male and nine female young subjects. Electromyographic jaw-jerk recordings elicited by chin-taps in the relaxed masseter muscle of the preferred chewing side, were obtained using a computerized recording and analysis system. In both groups, a jaw-jerk reflex was recorded in 95.56% out of the total number of chin-taps. The mean latency was significantly shorter in the females (5.75 ms) than in the males (6.14 ms, P = 0.0045), while the amplitude of the reflex was significantly higher in the females (P = 0.0005). No significant differences were found in the mean duration between males (6.86 ms) and females (6.73 ms). It was concluded that sex variation should be taken into consideration in the interpretation of the jaw-jerk reflex.

Adult↗
PubMed1994

EMG study on the effect of ageing on the human masseteric jaw-jerk reflex.

The effect of age on the masseteric jaw-jerk reflex was investigated in 22 young (11 males and 11 females with mean age 23.2 years) and 22 older dentate subjects (11 males and 11 females with mean age 61.3 years). Electromyographic (EMG) recordings were obtained, after chin taps, from the relaxed masseter muscle of the preferred chewing side, by use of a computerised recording and analysis system. With increasing age the occurrence of the reflex was reduced, the latency was increased, while the amplitude was decreased. Those findings are probably related to the general age related changes in the muscular tissue, the sense organs, the peripheral nerves and especially the central nervous system. Increased biological variance was also observed in the older subjects, as in most aspects of performance in the latent years. Furthermore, the effects of ageing were generally similar in men and women. The age-related decrement in the monosynaptic reflex response is indicative of a generalised decline in the motor performance of the stomatognathic system and the decreased ability of the older dental patient to easily adapt to any dramatic changes in the sensory input.

Adult↗
PubMed1994

Changes in mandibular alveolar bone and anterior face height after four years of complete denture wearing.

A 4-year cephalometric study was conducted on 14 wearers of complete dentures to quantify the anterior alveolar bone loss and to study any associated changes in the maxillomandibular relationships. Both the occlusal and the rest-face heights underwent a significant decrease while a parallel tendency for anterior rotation was recorded. The continuous bone loss in the anterior mandible had a significant relationship to the reduction of the anterior face height.

Alveolar Bone Loss↗
PubMed1992

Changes in the mandibular rest position after removal of remaining teeth and insertion of complete dentures.

A 24-month study was conducted to determine changes in the mandibular rest position after removal of the remaining teeth and insertion of complete dentures. A total of 24 patients with at least 10 teeth acting as occlusal stops were included in this study. Serial lateral cephalometric radiographs were made for each patient on four occasions (1) before extraction (2) 7 to 10 days after the initial denture insertion (3) 12 months later, and (4) 24 months later. Two angular measurements and one linear measurement were made for each radiograph and compared. A statistically significant increase in the face rest height with a tendency for posterior mandibular rotation was recorded between stages 1 and 2. This initial posterior rotation was followed by a gradual forward and upward movement, which finally brought the mandibular rest position even below the preextraction levels. The findings confirm the concept of the variability of posture and suggest that the mandibular rest position is an unreliable means of reestablishing the vertical dimension of occlusion that existed before extraction of the natural teeth.

Cephalometry↗
PubMed1991

Cephalometrically predicted occlusal plane: implications in removable prosthodontics.

Although the determination of the occlusal plane is crucial in clinical removable prosthodontics, none of the existing methods gives sufficient guidelines for that purpose. The aim of this investigation was to check the hypothesis that the angulation of the occlusal plane is generally related to the skeletal base of the maxillae. Statistical analysis revealed (1) no strong linear correlation (p greater than 0.05) between the following variables: (a) the length of Cook's plane to Cook's occlusal plane angle, (b) the length of the maxillary plane to the maxillary occlusal plane angle, and (c) the Po Na ANS angle to the occlusal Frankfort plane angle; (2) no parallelism between the occlusal and HIP plane with a mean angle of 4.57 degrees, SD 2.57 degrees, and range of 0 to 9.5 degrees; and (3) no correlation between the predicted and clinically determined occlusal planes (r0.267, t1.797, p greater than 0.05).

Adult↗
PubMed1987

Dimensional stability of dentures processed in boilable acrylic resins: a comparative study.

An investigation was conducted to evaluate and compare the dimensional stability of three fast boilable denture resins with a conventional and a high-impact denture resin processed with a long-curing cycle. Although the boilable denture resins have been introduced to the dental profession and offer merits such as faster processing, saving time for the dentist, patient, and technician, reduction of energy costs, and dramatic increase in denture laboratory production without adding personnel or purchasing new equipment, the relevant dental literature is sparse. The results of this investigation indicate that all five denture resins produced dentures that shrink. Also measurements between certain teeth showed shrinkages. Linear shrinkages of denture bases and teeth distances were less than 1%. Flange-to-flange and molar-to-molar changes were less than 0.5 mm and 0.2 mm respectively. Maxillary complete dentures processed in boilable resins presented less distortion in the midpalatal area across the posterior section than dentures processed in the conventional heat-cured resin. Although linear changes reported in this investigation were thought to be clinically insignificant, clinical studies should be conducted to establish correlation with laboratory findings.

Acrylic Resins↗
PubMed1987

A study of the occlusal plane orientation in complete denture construction.

A cephalometric study was conducted on eighteen dentulous subjects and fifty-six complete denture wearers to determine the location of the natural and artificial occlusal planes as related to Camper's plane. The results indicated that both the natural and artificial occlusal planes were not parallel to Camper's plane. However, the final anteroposterior inclination of the artificial occlusal plane in complete dentures was almost the same as the inclination of the natural occlusal plane.

Cephalometry↗
PubMedDate not supplied

[A simplified technique for the clinical measurement of the Frankfort-mandibular plane angle].

The FMA is an angle formed by the intersection of the Frankfort horizontal plane and the mandibular plane. The significance of the FMA to prosthodontic diagnosis, treatment planning and prognosis has been well documented. The objective of this study was to determine the reliability of an instrument designed for the clinical measurement of the FMA. 10 dried skulls (dentate dentulous or partially edentulous) were used in this preliminary study. To ensure the firm position of the mandibles during measurements all mandibles were firmly attached to the upper members of the skulls by a combination of compound and adhesive tape. The FMA was measured on both sides (right-left) of each skull a total of two times by two examiners. The average of the four readings was taken as the final clinical measurement. Lateral cephalometric roentgenograms were obtained for all skulls using standard Radiological techniques. Tracings were made on acetate from all the radiographs and the deviation between the two planes (Frankfort-Mandibular) was measured. The data were statistically analyzed using the student's paired t-test. The results of this preliminary study indicate that the instrument is reliable. Further clinical application however and research is needed to confirm our results and make the instrument a valuable tool to the hands of the clinician.

Cephalometry↗