Scanning Electron Microscopy (SEM) and Optical Microscopy: Effects of Er:YAG and Nd:YAG Lasers on Apical Seals after Apicoectomy and Retrofill

Evaluation of surface roughness after root resection: An optical profilometer study

The aim of this study was to evaluate the roughness of the apical surface after apical resection performed by six different methods with an optical profilometer. Sixty human single root premolar teeth were used in this in vitro study. After root canal preparation, root canals were filled with gutta-percha and AH Plus root canal sealers by lateral condensation technique. The teeth were randomly divided into six groups according to the apical resection method: steel fissure bur, tungsten carbide fissure bur, Lindeman bur, diamond fissure bur, laser, and ultrasonic surgical piezo with a diamond tip. The root ends were resected 3 mm away from the root apex and at a 90° angle. The time required for apicectomy was recorded for each group. After apical resection, the root surfaces were analyzed by an optical profilometer. The Kruskal-Wallis method was used to analyze the differences between groups. The significance level was set at 5%. The roughest surfaces were obtained by laser (25.54 ± 9.01 μm) and Lindeman bur (17.35 ± 6.03 μm), respectively. The longest mean resection times were recorded in piezosurgery and laser surgery (57 ± 14.39 s and 50.9 ± 16.86 s), respectively. Although the diamond-tipped piezo surgical cutting time is long, it has the best results in terms of surface roughness (5.50 ± 1.73 μm). The optical profilometer is a more convenient tool for evaluating the surface after apical surgery, as it provides an opportunity to evaluate objectively with both visual and numerical data.

A comparison of Er, Cr: YSGG laser with ultrasonic preparation on the seal of retrograde cavities

BACKGROUND AND AIM

The aim of this in vitro study was to compare Er, Cr: YSGG laser with ultrasonic preparation on the seal of retrograde cavities.

MATERIALS AND METHODS

Twenty-eight maxillary anterior teeth were used in this study. After removing the crowns, the canals were prepared with the step-back technique and filled with guttapercha. Three millimeters below the apex; each root was cut with a fissure diamond bur. The root surfaces were then covered with nail polish and three millimeters deep retrograde class I cavities were prepared, using Er, Cr: YSGG laser (group L=12 roots) or ultrasonic retro-tip (group U=12 roots). Four roots were arranged for negative and positive control groups. Retrograde cavities were then filled with mineral trioxide aggregate (MTA) and teeth were placed in 2% methylene blue dye for 72 hours. The amount of dye penetration in sagittal sections of each tooth was measured with a stereomicroscope. An independent sample t-test was used for statistical analysis.

RESULTS

Cavities prepared with the Er, Cr: YSGG laser (1.61 + 0.81) showed significantly less micro-leakage than those prepared with the ultrasound (2.55+ 1.84) (P value =0.02).

CONCLUSIONS

Under the conditions of this research, the use of Er, Cr: YSGG laser for retrograde cavity preparation causes significantly less apical leakage and may increase the success rate of endodontic surgeries.

Effect of Nd: YAG laser on the apical seal after root-end resection and MTA retrofill: a bacterial leakage study

Laser irradiation has been investigated in terms of preventing leakage in retrofilled root canals. The aim of the present study was to evaluate the effect of neodymium-doped yttrium aluminum garnet (Nd: YAG) laser on the bacterial leakage of mineral trioxide aggregate (MTA)-retrofilled roots. In this ex vivo experimental study, 90 single-rooted incisor teeth were filled with gutta-percha and AH26 sealer. The apical 3 mm of all the roots were resected and 3-mm retrocavities were prepared by an ultrasonic device. The specimens were randomly divided into two experimental (n = 25), one positive control (n = 10), and two negative control (n = 10) groups. In the laser + MTA group, the cavity walls were irradiated by Nd: YAG laser prior to MTA placement. In the MTA group, MTA was placed without laser irradiation. The root surfaces were covered with two layers of nail varnish except for the apical 2 mm. The specimens were then embedded in a bacterial leakage test system and examined daily for 90 days. Contamination periods were recorded. Data were analyzed by Kaplan-Meier and Mann-Whitney U tests (α = 0.05). Five teeth with and five teeth without laser irradiation underwent scanning electron microscopic evaluation. The specimens in the laser + MTA group were contaminated earlier than those in the MTA group (p < 0.05). Comparison of survival times between the two groups showed significant differences (p < 0.05). Nd: YAG laser irradiation can decrease the sealing capacity of MTA in comparison to the apical seal achieved by MTA without laser irradiation. Further studies are recommended to provide a better seal for the MTA-retrofilled teeth after laser irradiation.

Effects of dentin surface modifications treated with Er:YAG and Nd:YAG laser irradiation on fibroblast cell adhesion

OBJECTIVE

The purpose of this in vitro study was to evaluate the effect of surface modifications induced by erbium (Er):YAG and neodymium (Nd):YAG laser irradiation on cell adhesion by comparing it to that of conventional methods for surface preparation after root-end resection.

BACKGROUND DATA

Many studies have been seeking a favorable method to produce a resected root end with optimal conditions for cell response. However, little improvement has been achieved. This study evaluated the biocompatibilities of resected root surfaces after Er:YAG or Nd:YAG laser irradiation on initial cell adhesion.

MATERIALS AND METHODS

Dentin disks were divided into three groups. Group A was left untreated, Group B was treated with Er:YAG laser irradiation (60 mJ/pulse, 10 pps, 60 sec), and Group C with Nd:YAG laser irradiation (60 mJ/pulse, 10 pps, 60 sec). After laser irradiation, the dentin disks were incubated with NIH/3T3 fibroblasts cultured in Dulbecco's modified Eagle's medium. A morphological analysis of the dentin surface and cell adhesion was observed under a scanning electron microscope. Surface roughness was measured using a confocal laser scanning microscope. The statistical analysis was undertaken using ANOVA at a level of significance of 5% (p<0.05).

RESULTS

Morphological analysis and roughness measurement showed that dentin surfaces treated with Er:YAG laser irradiation were rougher than those in Groups A and C. Group B (Er:YAG) exhibited the greatest number of attached cells among all groups after 12 and 24 h.

CONCLUSIONS

Morphological alteration induced by Er:YAG laser irradiation showed a favorable effect on the attachment of fibroblasts to dentin surfaces.

Evaluation of apical surface roughness after root resection: a scanning electron microscopic study

OBJECTIVES

The objective of this study was to compare, by scanning electron microscopy, the smoothness of the resected apical root surface after preparation with high-speed #699 bur, #699 bur plus Shofu finishing and Zekrya bur, and with an erbium:YAG laser.

STUDY DESIGN

Thirty-nine extracted human premolars were instrumented and obturated and their root apices were resected. The roots were divided into 4 groups according to the root resection method. The teeth were dried, metallized, and analyzed at x400 by scanning electron microscopy. Scores ranging from 0 to 3 were attributed to surface smoothness. The data were analyzed by the Kruskal-Wallis test for overall comparison, and by Dunn's test for individual comparisons.

RESULTS

Smoother surfaces were observed for the groups treated with the #699 bur and the #699 bur plus Shofu point finishing, while rougher surfaces were obtained with the laser, which differed significantly from the other 2 methods (P < .05).

CONCLUSIONS

Treatment with the #699 bur plus Shofu finishing yielded better results in terms of surface smoothness, whereas the laser treatment produced more irregular and rougher surfaces after root resection.

Computer-assisted evaluation of microleakage after apical resection with laser and conventional techniques

The purpose of this in vitro study was to observe the morphological changes and apical dye penetration at apical dentin surfaces after apicoectomy with conventional techniques and laser beam. Sixty single-rooted extracted teeth were selected for the study. The crowns were resected below the cemento-enamel junction. Then, these teeth were treated endodontically and filled with gutta-percha using AH-26 root canal sealer. The teeth were randomly divided into four groups of 15 teeth in each. The roots were resected perpendicular to its long axis 3 mm from the apex using Er: yttrium-aluminium-garnet (YAG) laser irradiation in groups 1 and 2, and the resected root surfaces were lased with Nd:YAG laser in group 2. The apexes were resected by a high-speed handpiece in groups 3 and 4, and the resected root surfaces were lased with Nd:YAG laser in group 4. Ten teeth in each group were used for leakage studies, and the other five teeth were used for scanning electron microscopic examinations. Seven sections were obtained from each root to assess the microleakage, and the sections were analyzed in a computer-assisted manner. No statistically significant differences were observed between the leakage percentage of groups 1 and 3 and groups 2 and 4 (p>0.05). Morphological differences were observed between apical dentin surfaces resected with conventional techniques and laser beam.

Effects of two types of low-level laser wave lengths (850 and 630 nm) on the orthodontic tooth movements in rabbits

The effects of low-level lasers on bone cellular activity, bone structures, bone healing, fibroblasts activity and inflammation process have already been investigated. Considering orthodontic tooth movement, which is a complicated inflammatory process involving simultaneous bone apposition and resorption, the aim of this controlled study is to investigate the quantitative effects of a pulsed 850 nm laser (Optodan) and a continuous 630 nm laser (KLO3) on the orthodontic tooth movement in rabbits. This experimental study was conducted on 18 male albino rabbits divided into three equal groups of control, Optodan and KLO3. In all the groups, NiTi-closed coil springs were used on the first mandibular molars with 4-oz tension. The control group was not irradiated by laser, but the teeth in the laser groups were irradiated 9 days according to the periodontal therapeutic protocols. After 16 days, samples were sacrificed. The distance between the distal surface of the first molar and the mesial surface of the second molar was measured with 0.05-mm accuracy. The data were subjected to the statistical tests of Kolmogrov Smirnov and variance analysis. The mean orthodontic tooth movements of the first mandibular molars were 1.7 +/- 0.16 mm in control group, 0.69 +/- 0.16 mm in Optodan group and 0.86 +/- 0.13 mm in KLO3 group. There were statistically significant difference between the control and the two other laser-irradiated groups (P < 0.001). The findings of the present study imply that the amounts of orthodontic tooth movement, after low-level laser therapy, are diminished. It could not be concluded that any low-level laser will reduce the speed of teeth movement in orthodontic treatments, and further studies with less or more energies may show different results.