The effect of the KTP laser on smear layer and temperature change: an in vitro study

Emissivity evaluation of human enamel and dentin

Background: Human enamel and dentin temperatures have been assessed with non-contact infrared imaging devices for safety and diagnostic capacity and require an emissivity parameter to enable absolute temperature measurements. Emissivity is a ratio of thermal energy emitted from an object of interest, compared to a perfect emitter at a given temperature and wavelength, being dependent on tissue composition, structure, and surface texture. Evaluating the emissivity of human enamel and dentin is varied in the literature and warrants review. The primary aim of this study was to evaluate the emissivity of the external and internal surface of human enamel and dentin, free from acquired or developmental defects, against a known reference point. The secondary aim was to assess the emissivity value of natural caries in enamel and dentin.

Method: Fourteen whole human molar teeth were paired within a thermally stable chamber at 30°C. Two additional teeth (one sound and one with natural occlusal caries–ICDAS caries score 4 and radiographic score RB4) were sliced and prepared as 1-mm-thick slices and placed on a hot plate at 30°C within the chamber. A 3M Scotch Super 33 + Black Vinyl Electrical Tape was used for the known emissivity reference-point of 0.96. All samples were allowed to reach thermal equilibrium, and a FLIR SC305 infrared camera recorded the warming sequence. Emissivity values were calculated using the Tape reference point and thermal camera software.

Results: The external enamel surface mean emissivity value was 0.96 (SD 0.01, 95% CI 0.96–0.97), whereas the internal enamel surface value was 0.97 (SD 0.01, 95% CI 0.96–0.98). The internal crown-dentin mean emissivity value was 0.94 (SD 0.02, 95% CI 0.92–0.95), whereas the internal root-dentin value was 0.93 (SD 0.02, 95% CI 0.91–0.94) and the surface root-dentin had a value of 0.84 (SD 0.04, 95% CI 0.77–0.91). The mean emissivity value of the internal enamel surface with caries was 0.82 (SD 0.05, 95% CI 0.38–1.25), and the value of the internal crown-dentin with caries was 0.73 (SD 0.08, 95% CI 0.54–0.92).

Conclusion: The emissivity values of sound enamel, both internal and external, were similar and higher than those of all sound dentin types in this study. Sound dentin emissivity values diminished from the crown to the root and root surface. The lowest emissivity values were recorded in caries lesions of both tissues. This methodology can improve emissivity acquisition for comparison of absolute temperatures between studies which evaluate thermal safety concerns during dental procedures and may offer a caries diagnostic aid.

Bactericidal effect of Er,Cr:YSGG laser irradiation on endodontic biofilm: An ex vivo study

AIM

This ex vivo study aimed to evaluate the of Er,Cr:YSGG laser effectiveness in the decontamination of an endodontic biofilm.

MATERIALS AND METHODS

Seventy-three single rooted human teeth, freshly were chosen. Each tooth was exposed to four associated species in an endodontic biofilm (Enterococcus faecalis, Streptococcus salivarius, Porphyromonas gingivalis, and Prevotella intermedia) and randomly allocated to one of the seven experimental groups. The group 1 (7 teeth) was used to finalize the reliable biofilm-forming technique. The groups 2 and 3 (15 teeth each group) were irradiated with two different Er;Cr:YSGG laser settings (0,75 W - 40 Hz and 4 W - 40 Hz, respectively). The groups 4 and 5 (15 teeth each group) were irrigated with two different solutions and laser irradiated with the same settings (1,5 W - 15 Hz). The group 6 (6 teeth) was the control group treated only with 4 ml 2,5% NaOCl irrigation during 60 s.

RESULTS

The observations of group 2 and 3 specimens showed the ripeness of the biofilm with the presence of Enterococcus faecalis and Streptococcus salivarius in chains but in group 3 thermal edge effects produced by the optic fiber in the canal walls were present. The group 4 specimens observation showed an average cleaning of the root canal walls while on the canal walls of group 5 samples the apical third presented several debris and smear layer and in the centre cracks and melting dentin of the radicular wall were observed.

CONCLUSION

In those experimental conditions, this study, demonstrated that Er,Cr:YSGG laser has a canals decontamination ability when associated to NaOCl irrigation.

Temperature and time variations during apical resection

OBJECTIVE

The aim of this study was to investigate temperature and time variations during root-end resection.

MATERIAL AND METHODS

Sixty human premolars were selected. The root canals were enlarged up to ProTaper X3 rotary instrument. A thermocouple was placed into the root canal 1 mm behind the resection line. The teeth were randomly divided into six groups according to the apical resection method: steel bur, tungsten carbide bur, Lindeman bur, diamond bur, laser and ultrasonic surgical piezo with a diamond tip. The root ends were resected 3 mm away from the root apex. The temperature of the root dentine during resection was recorded as maximum temperature, mean temperature and temperature change. The time required for apicectomy was recorded for each group. The Kruskal-Wallis method was used to analyse the differences between temperature changes during apical resections. The significance level was set at 5%.

RESULTS

There was no significant difference between bur groups in terms of temperature increase. The maximum temperature in piezo surgery was significantly higher than the Lindeman, tungsten and steel burs (p < .001). In addition, the maximum temperature in laser surgery was higher than the Lindeman bur (p < .05). An increase in the temperature was mostly seen in piezo surgery and the least temperature change occurred in the Lindeman bur. Mean time stayed under 1 min in each group.

CONCLUSIONS

Although piezo caused the highest temperature increase, the measured temperature increase was within physiological limits in all tested techniques.