[Surface roughness and staining stability of infiltrant resin for enamel white spot lesion].

OBJECTIVE: To investigate the influence factors on the surface roughness and staining susceptibility of infiltrant resin. METHODS: In the study, 30 human third molars were used, and each sample had three open enamel windows. The samples were randomly divided into three groups according to their different demineralized time. Each sample had at least one intact spot (A), one infiltrant resin spot (B) and one artificial white spot lesion (C). The surface roughness was tested before color staining for all the three spots of each specimen. The specimens were stored in a staining solution (coffee) for a period of 21 days, before and after which the color Commission Internationaled' Eclairage (CIE)L*a*b* was recorded for A, B and C spots. RESULTS: The B spot's surface roughness of each group was(0.15 ± 0.02)µm,(0.31 ± 0.03)µm and(0.40 ± 0.02)µm, respectively. And the C spot's surface roughness each was (1.08 ± 0.10)µm,(2.89 ± 0.13)µm and(3.41 ± 0.14)µm. The surface roughness of B and C of the three groups increased with demineralization time longer, and had significant difference for both B and C (P < 0.01). The ΔE of the three groups between A and B before staining had significant difference (P < 0.01). And the ΔE of group1 was less than 3.7, but the other two groups' more than 3.7. After staining, the ΔE of groups 1 and 2 was less than 3.7 but that of group 3 was more than 3.7. There were significant differences between groups 1 and 3, and also between groups 2 and 3(P < 0.01). CONCLUSION: The degree of the lesion's demineralization has effect on the surface roughness and color susceptibility of infiltrant resin. The increased surface roughness of infiltrant resin has positive effect on masking enamel white spots.

[Evaluation of the color stability of infiltrant resin in comparison to aesthetic composite resins].

OBJECTIVE: To investigate the color stability of infiltrant resin together with three other composites exposed to staining solution. METHODS: Three types of anterior aesthetic composite resins (Filtek Z250, Filtek Z350 XT, and Beautiful Flow Plus F00) and artificial caries with Icon infiltrant resin were used. The samples were randomly divided into two groups (each contained 10 specimens): coffee solution and distilled water immersion for three weeks. Color parameters were deter-mined with the Crystaleye spectrophotometer. RESULTS: Artificial caries lesions infiltrated by Icon showed much higher ΔE than those infiltrated by other aesthetic resins (P<0.05). The discoloration of all the experimental resins and the artificial caries infil-trated with Icon increased with time, but the discoloration on the 1st week was significantly higher than those on the 2nd and 3rd weeks. CONCLUSIONS: Artificial caries infiltrated with Icon was more vulnerable and susceptive to food color than those infiltrated with other aesthetic composite resins.

[Root resection by Er:YAG laser: a scanning electron microscope study].

OBJECTIVE: To compare the difference of the surface of root resection by Er:YAG laser, ultrasonic or high-speed handpiece with scanning electron microscope (SEM), and to evaluate the possibility of using Er:YAG laser on the root resection in clinical application. METHODS: Thirty maxillary central incisors were divided into three groups (Er:YAG laser group, ultrasonic group, high-speed handpiece group), and the root resection were made at root tip 3 mm with Er:YAG laser, ultrasonic instrument or long needle diamond bur according to grouping. The surface of the root resection by SEM in the aspects of debris, smear layer, opened dentinal tubules, cracks and ablation characteristics were compared. RESULTS: The examination revealed that Er:YAG laser group and ultrasonic group had no or little debris and smear layer and with opened dentinal tubules. High-speed handpiece group had great amount of debris and smear layer and without opened dentinal tubules. Cracks were observed in ultrasonic group and high-speed handpiece group, no in Er:YAG laser group. There were ablation characteristics in ultrasonic group and high-speed handpiece group, but no in Er:YAG laser group. CONCLUSION: From the morphological aspect, Er:YAG laser has much more advantage than ultrasonic instrument and diamond bur for the root resection.

[Comparison of clinical effect of different tapered gutta-percha root filling with warm vertical condensation].

OBJECTIVE: To compare the clinical effect of different tapered gutta-percha root filling by warm vertical condensation with immediate postoperative radiographs and one year follow-up. METHODS: 40 maxillary anterior teeth with single, straight canals were divided into two equal groups. The teeth were instrumented with Hero 642 rotary nickel-titanium files to a master file 0.06 taper No. 30. Group 1 was obturated with 0.02 tapered gutta-percha using System B for downpack and Obtura II for backfilling. Group 2 was the same but 0.06 tapered gutta-percha. Every tooth's X-ray radiographs of immediate postoperative and one year follow-up were taken. In order to compare the quality of root canal filling, the rate of filling material extrusion, and the rate of obturation of lateral canals in each group were evaluated by X-ray radiographs. The clinical effect of one year follow-up's radiographs of the two groups was compared too. RESULTS: There was no significant difference in two groups on the quality of the root canal filling, obturation of lateral canals, and filling material extrusion. The success of the therapy was similar. But the 0.06 tapered gutta-percha group showed more quickly healing trend on apical periodontitis. CONCLUSION: When single, straight root canals were obturated using warm vertical condensation, adaptively tapered gutta-percha showed better clinical effect.

[Quality of apical seal of differently tapered gutta-percha cone using warm vertical condensation technique].

OBJECTIVE: The purpose of this study was to compare the quality of apical seal of the canals that obturated with differently tapered gutta-percha cone using continuous wave technique. METHODS: 62 extracted human mandible incisors were prepared with Gates-Glidden drill and Hero642 to a final file of No. 30 and 0.06 taper. The teeth were randomly separated into 0.02 taper group (30 teeth), 0.06 taper group (30 teeth) and positive control group (2 teeth). The teeth of 0.02 taper group and 0.06 taper group were respectively obturated with a 0.02, or 0.06 tapered gutta-percha cone and Cortisomol sealer using warm vertical condensation technique separately. The teeth of positive control group were not obturated. In 0.02 taper group and 0.06 taper group, 10 teeth were placed in India ink for 24 hours, 10 teeth were placed in India ink for 10 days, 10 teeth were placed in India ink for 90 hours after 67 days storage in Hank's balanced salt solution. The teeth of positive control group were placed in India ink for 24 hours. The apical leakage was evaluated by the linear measurement under the stereomicroscope. RESULTS: The dye penetration of positive control group was along the whole canals. The apical leakage of 0.02 taper group increased along with time, while no difference was found among 0.06 taper group. There was a significant difference in the degree of leakage between 0.02 taper group and 0.06 taper group in 67 days (P = 0.041), but not in 24 hours and 10 days groups (P = 0.601, P = 0.471). CONCLUSION: Better apical seal was obtained when using the same tapered gutta-percha cone with root canal.