Experiment and simulation of resistance of nanoporous dentin biomaterial to CO₂ laser irradiation

The resistance of nanoporous dentin biomaterial to CO₂ laser irradiation was investigated by experiment and simulation for potential tooth hypersensitivity treatment. The controlled parameters including laser power of 0.03-0.150 W, scanning speeds of 11.4-34.2 mm/s and focus/defocus modes were used for studying interaction between laser energy and dentin of human tooth. Most of the dentin specimens were etched after CO₂ laser irradiation with the power larger than 0.12 W at a scanning speed of 11.4 mm/s. Compared with the simulation results of temperature distribution, the maximum temperature at laser powers from 0.12 to 0.15 W is increased from 1961 to 2245°C, which exceeded the melting point (1570°C) of dentin's main content hydroxyapatite (HA). Increasing scanning speed can reduce the linear density of laser output energy for just locally melting porous microstructure of dentin surface without etching. Varying focus mode can also improve the damage of nanoporous dentin microstructure. At parameters of 0.150 W power and 34.2 mm/s scanning speed under defocus operation, laser treatment was successfully performed on the nano-HA coated dentin with well-molten sealing on tubules of porous microstructure at a simulate surface temperature of about 574°C, which was the potential for dentin hypersensitivity cure application.

Effect of various surface protections on the margin microleakage of resin-modified glass ionomer cements

STATEMENT OF PROBLEM

Because conventional glass ionomer cements are moisture sensitive, a surface coating is recommended during the initial setting stage. It is unknown whether resin-modified glass ionomer cements also need surface protection.

PURPOSE

This study investigated the effect of various surface protections on microleakage with Class V resin-modified glass ionomer restorations.

MATERIAL AND METHODS

Forty extracted molars with buccal and lingual Class V cavity preparations were restored with a resin-modified glass ionomer (Fuji II LC). The occlusal margin of each restoration was on enamel and the cervical margin on dentin. After immediate finishing and polishing, the teeth were divided into 4 groups according to the following surface protection treatments: group I, unprotected; group II, Fuji varnish; group III, resin adhesive; and group IV, acid etching and resin adhesive. After these procedures, all teeth were stored in isotonic saline for 24 hours, thermocycled 1500 times at 5 degrees C to 60 degrees C, and soaked in dye solution for 24 hours. The teeth then were longitudinally sectioned and observed under a stereomicroscope. The degree of dye penetration was recorded and analyzed with the Kruskal-Wallis and Mann-Whitney tests (P<.05)

RESULTS

None of the 4 groups demonstrated complete margin sealing at either the occlusal or cervical margins. Groups II and III displayed the least microleakage at cervical margins; a significant difference existed between groups I and III (P=.034). Compared with the other 3 groups, group IV showed significantly greater microleakage at the cervical margins.

CONCLUSION

Although resin-modified glass ionomers can be finished immediately, they remain moisture sensitive. Within the limitations of this study, the results suggest that resin adhesive should be used as a surface protection to reduce margin microleakage of resin-modified glass ionomer restorations.

Effects of flowable composite lining and operator experience on microleakage and internal voids in class II composite restorations

STATEMENT OF PROBLEM

When inexperienced clinicians perform class II composite restorations, improper placement techniques can lead to problems, including marginal adaptation and void formation.

PURPOSE

The aim of this study was to determine the influence of flowable composite linings on marginal microleakage and internal voids in class II composite restorations performed by practitioners with different levels of experience.

MATERIAL AND METHODS

Eighty extracted molars were prepared with mesial and distal class II cavity preparations and divided into 4 groups. Each group was restored separately with the following materials: Prodigy/Revolution lining (group I), Prodigy (group II), Tetric Ceram/Tetric Flow lining (group III), and Tetric Ceram (group IV). Each group was equally divided and restored by 2 practitioners, one experienced and another untrained in composite restorations. After restoration, all teeth were stored for 24 hours, thermocycled (at 5 degrees C to 60 degrees C) 1500 times, and soaked in 2% basic Fuchsin dye for 24 hours. After soaking, the teeth were sectioned, and gingival marginal microleakage and internal voids (at the gingival wall interface and in the cervical and the occlusal parts) were recorded. Data were analyzed with the Kruskal-Wallis test.

RESULTS

There was no significant reduction in microleakage for either practitioner. There were fewer interface voids within pairs with or without flowable composite linings made by the experienced practitioner (P<.05).

CONCLUSION

When flowable composite lining was placed at the gingival floor of a class II composite restoration by an experienced practitioner, voids in the restored interface were reduced. Gingival marginal sealing was not improved by the same technique.

Applicability of BSID-II in diagnosing developmental delay at Kaohsiung area

The purpose of this study was to investigate the applicability of BSID-II in diagnosing children with developmental delay in Kaohsuing area. Five hundred and forty-four children, all who were patients of Developmental Delay Clinic of Kaohsuing Medical University, participated in this study. The instrument of this study was the Bayley Scales of Infant Development--second edition (BSID-II), the primary value of which was in diagnosing developmental delay and planning intervention strategies. The standardization and statistical properties of BSID-II made it one of the best measures of infant development available. The findings as follows: (1) the alpha coefficients were between .95 and .99, which were higher than data on manual of BSID-II; (2) the reproducibilities, which were different with each examiner, were between .9503 and .9633, that were good enough to be a developmental scale; (3) Standard Errors of Measurement were between 2.8589 and 3.8206. It was a restricted sample so that these also were lower than the data on manual of BSID-II. This evidence shows BSID-II is a highly reliable instrument of developmental assessment at Kaohsuing area. A special norm for developmentally delayed children and quality control of examiners are suggested.

[Evaluation of factors affecting nutritional assessment based on anthropometric data of Chinese undergoing health screening in Taiwan]

This study is aimed at the establishment of anthropometric data in normal Chinese undergoing health screening in Taiwan, in order to provide reference values for nutritional assessment and to compare them with those standard values of the Western population. Seven hundred and thirty-two Chinese who underwent health screening in Chang Gung Memorial Hospital at Linkou (1981-1984) and at Kaohsiung (1986-1988) were enrolled in the study. These included 394 male Chinese and 338 female Chinese whom were considered normal in nutritional status and who did not have diabetes mellitus, tuberculosis, malignancy, liver and renal disorders, as well as those with hypoalbuminemia of unknown etiology. The following parameters were examined: body height (BH), body weight (BW), triceps skin fold (TSF), midarm circumference (MAC), midarm muscle circumference (MAMC), serum albumin and total lymphocyte count (TLC). The results revealed that: (1.) Besides a lower BH and BW, the 50th percentile for TSF in female Chinese fell between 50th-25th percentile of the Western women. As for the males, the Chinese fell below 50th percentile for TSF of the Western population of the same age and sex groups; (2.) The 50th percentile for MAMC in Chinese of both sexes fell below the 25th percentile of the Western population of the same age and sex groups; (3.) Aside from normal ranges, the serum albumin level decreased significantly with increasing age. Such a change was not found in TLC. This study stressed the difference in anthropometric data in terms of race and age and the importance of assessing patients' nutritional status by making reference to the standard value of their pertinent population and age group.

The interaction between locomotion, striatal dopamine and paramedian reticular nucleus in rats

Either intact rats, sham-operated rats, or rats with lesions of the paramedian reticular nucleus (PRN) were exposed to cold (2 degrees C) or heat (36 degrees C) stress and their locomotor activity responses and striatal dopamine (DA) release were compared. At room temperature (22 degrees C), results analyzed revealed significant effects in the PRN-lesioned rats: increases in locomotion (including both horizontal and vertical motion), direction of turnings (including both clockwise and anticlockwise) or striatal DA release. In both the intact rats and the sham-operated rats, either cold or heat stress increased the locomotion, the direction of turnings and the striatal DA release. The increases in both vertical motion and striatal DA release following cold or heat stress were attenuated by PRN lesions. The data suggest that a PRN-striatal DA link existing in rat's brain which affects both the spontaneous and the thermal stress induced locomotor activities.

Antagonistic effects of stimulation of the paramedian reticular nucleus in the rat medulla oblongata and of amphetamine on locomotor activity and striatal release of dopamine-like material

The effects of stimulation of the paramedian reticular nucleus (PRN) in the rat medulla oblongata on both amphetamine-induced locomotor activity and striatal release of dopamine-like material were assessed. PRN stimulation (by intra-PRN injection of the excitatory amino acid, kainic acid) decreased vertical motion and total distance travelled, and increased postural freezing, in freely moving rats. On the other hand, a small dose (e.g. 1.25 mg/kg, i.p.) of amphetamine increased locomotor activity (including horizontal motion, vertical motion, total distance travelled and lines crossed counts), increased the number of turnings (both clockwise and anti-clockwise), induced locomotor stereotypy (including both gamma value and number of trip types), and inhibited postural freezing. The changes in activity induced by amphetamine administration were suppressed following PRN stimulation. In vivo voltammetric data revealed that electrical stimulation of the PRN decreased the release of dopamine-like material in the corpus striatum. This effect could be mimicked by intra-PRN injection of kainic acid in anesthetized rats. In contrast, i.p. administration of amphetamine increased the release of dopamine-like material in the corpus striatum. Furthermore, the enhanced release of dopamine-like material induced by amphetamine was attenuated by simultaneous stimulation of the PRN. The results reported here indicate that PRN stimulation decreases the striatal dopamine release and results in attenuation of the amphetamine-induced locomotor activity responses in rats.

[Primary treatment of contaminated syringes and needles in a ward]

Body fluid transmitted viruses become the major enemies of human health. These viruses have been reported as occupational hazards for health care personnel, and they may become environmental hazards as well. We conducted this study to examine the primary treatment of used syringes and needles in a ward, and to evaluate the effects of re-education. For questions such as "The used syringes with bloody contamination should isolated from those without" and "The cover of used needles should not be put back on", we recorded error rates during the 1st one-week observation. A lecture about the standard treatment methods of discarding instruments was given to all nurses in this ward after the 1st observation. The 2nd and 3rd one-week observations were repeated one day and one month after the lecture, respectively. The misclassification rates of discarded syringes were 4.4% (33/758), 1.4% (9/661) and 3.9% (18/616). There was a significant decrease between the 1st and 2nd observations (p less than 0.05), but no significant difference between the 1st and 3rd observations (p greater than 0.05). The rates of covered discarded needles were 50.4% (287/569), 44.3% (198/447) and 38.5% (269/699), respectively. These rates showed a trend to decrease (p less than 0.05). The misclassification rates of discarded syringes were low. Although re-education achieved only temporary effects, self-protective education on not re-covering used needles was effective. However, about 40% of all discarded syringes were still being covered after use. Based on our finding, some improvements have been made in this ward.

Implication of a distant septic focus in parenteral nutrition catheter colonization

During a 4-year period, 244 surgical patients receiving total parenteral nutrition (TPN) were studied with emphasis on the relationship between TPN catheter colonization and a preexisting distant septic focus (DSF). A colonized catheter was defined as a catheter with a positive semiquantitative culture of the catheter tip (greater than or equal to 15 colonies on the plate). Catheter-related sepsis (CRS) was defined as a catheter with either the same organisms cultured from the catheter tip and from blood or with defervescence following catheter removal. Two hundred sixty-nine catheters were inserted for TPN for a total of 4433 patient days, with a mean length of stay of 16.5 days. Forty-two of the 269 catheters (15.6%) were colonized and more than half (57.1%) of the organisms cultured were Gram-negative bacilli or enterococci. Nineteen of the 42 colonized catheters were associated with CRS with a CRS rate of 7.1% among the 269 catheters. A DSF was present in 165 of the 244 patients or in 188 of the 269 catheters (69.9%). The colonization rate of 19.1% (36/188) in those catheters with DSF was significantly higher than that of 7.4% (6/81) in those without DSF (p less than 0.05). Those patients with DSF or with a colonized catheter were associated with a high mortality (p less than 0.001). Sepsis was responsible for 33 of the 48 patients (68.8%) who died. The data stress the important contribution of DSF to the colonization of TPN catheters and to the mortality of these critically ill surgical patients.