Characteristics of the leg extensors in male volleyball players with jumper's knee.

The aim of the present study was to characterize the performance ability of the leg extensor apparatus in a group of athletes with jumper's knee and to compare the results with those of a matched control group without knee symptoms. Patient and control groups (12 players in each) were selected from a population of 141 well-trained male Norwegian volleyball players, of which 55 (39%) satisfied the diagnostic criteria for jumper's knee. The testing program consisted of a standing jump, a countermovement jump, a 15-second rebound jump test, a standing jump with a 20-kg load, and a standing jump with a load corresponding to one-half of the subject's body weight. Jump height and power were measured using a contact mat connected to an electronic timer. The test results of the patient group were significantly higher than those of the control group for the countermovement jump (15% increase), power during rebound jump (41%), work done in standing jump (12%) and countermovement jump (22%), and the difference between countermovement jump and standing jump (effect of adding eccentric component). Athletes with jumper's knee demonstrated better performance in jump tests than uninjured athletes, particularly in ballistic jumps involving eccentric force generation.

Incidence and mechanisms of acute ankle inversion injuries in volleyball. A retrospective cohort study.

In a retrospective cohort study of ankle inversion injuries performed after the 1991-1992 season in the top two divisions of the Norwegian Volleyball Federation, 63 injuries were found among 318 players during 60,612 hours of training and 928 matches. The study was limited to acute ankle inversion injuries that caused an absence of 1 or more days from training or match play. The total injury rate was 0.9 +/- 0.12 per 1000 player hours: 0.7 +/- 0.11 during training and 2.6 +/- 0.56 during match play. The relative risk of injury during match play versus training was 3.9 (P < 0.001). Women had an injury rate of 1.1 +/- 0.18, whereas that of men was 0.7 +/- 0.15 (relative risk = 1.47; not significant). Most of the players (78%) had suffered at least one previous injury of the affected ankle. Most injuries were mild to moderate. The majority of the injuries (86%) occurred at the net, mainly when landing after blocking (63%) or attacking (29%). We suggest that simple measures such as rule changes, technical training, and prophylactic taping or bracing may lead to a significant reduction in the incidence and severity of such injuries.

In vivo fluoride uptake in enamel and dentin from fluoride-containing materials.

The ability of fluoride-containing materials to deposit fluoride into the cavity walls could be a measure of their anticariogenic properties. Great penetration depths of fluoride were found in all groups in this study, with deeper penetration in dentin compared to enamel.

Microleakage in fissures sealed with resin or glass ionomer cement.

The purpose of this study was to investigate if microleakage occurs in fissures after being sealed with a glass ionomer cement (Fuji III). Ten pairs of contralateral maxillary premolars, to be extracted for orthodontic reasons, were sealed in vivo. Glass ionomer cement was randomly used on one tooth and diluted composite on the contralateral. An air-polishing instrument was used for cleaning the fissures before sealing them. After 14 days the sealant status was recorded clinically and the teeth were extracted. They were placed in a 0.5% solution of methyl blue, subjected to a thermal cycling procedure, and finally sectioned. The sections were photographed in a stereomicroscope, and two observers recorded the microleakage according to a scoring system. Three glass ionomer sealings were clinically recorded as missing, one partly missing, and six intact, while all the resin sealings were present. Extensive leakage was seen in all glass ionomer specimens with dye penetration throughout the material as well as at the interface between cement and enamel. No leakage was seen in the composite specimens. Remnants of glass ionomer cement were observed in most of the sections from teeth which clinically seemed to have lost the sealing. This study indicates that Fuji III is poorly retained in the fissures, and that the material permits leakage even when it is fully retained. The material may, however, prevent caries by release of fluorides, and the fact that remnants of cement were found in fissures which clinically seemed to have lost it, indicates that this may even occur in cases with loss of retention.