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

Nanosecond infrared laser (NIRL) for cutting roots of human teeth: thermal effects and quality of cutting edges

A nanosecond infrared laser (NIRL) was investigated in cutting dental roots. The focus of the investigation was defining the preparation accuracy and registration of thermal effects during laser application. Ten teeth were processed in the root area using a NIRL in several horizontal, parallel incisions to achieve tooth root ablation as in an apicoectomy. Temperature change was monitored during ablation and the quality of the cutting edges in the roots were studied by means of micro-CT, optical coherence tomography, and histology of decalcified and undecalcified specimens. NIRL produced clearly defined cut surfaces in dental hard tissues. The automated guidance of the laser beam created regular, narrow dentin defects that tapered in a V-shape towards the ablation plane. A biologically significant increase in the temperature of the object and its surroundings did not occur during the laser application. Thermal dentin damage was not detected in histological preparations of treated teeth. Defined areas of the tooth root may be ablated using a NIRL. For clinical translation of NIRL in apicoectomy, it would be necessary to increase energy delivered to hard tissue and develop beam application facilitating beam steering for oral treatment.

Effectiveness of Sectioning Method and Filling Materials on Roughness and Cell Attachments in Root Resection Procedure

OBJECTIVES

 The purpose of the present study was to investigate the created roughness and cell attachment of intact teeth (C), obturated teeth with bioceramic (BR), or epoxy resin (AH) after root resection using piezoelectric ultrasonic and carbide bur.

MATERIALS AND METHODS

 Three groups of first mandibular premolars were used in the present study: control group (without any preparation or obturation) (C); second group was obturated with an epoxy resin sealer (AH, AH Plus Jet); and finally, the third one was obturated with a bioceramic sealer (BR, BioRoot RCS). All teeth were incubated for 4 months at 37°C. After that, the samples were sectioned using tungsten carbide bur or piezoelectric ultrasonic. Roughness and then cell attachment of periodontal ligament cells on the sectioned surfaces were investigated by profilometer and confocal microscope, respectively.

STATISTICAL ANALYSIS

 Data were statistically analyzed using one-way analysis of variance.

RESULTS

 After root resection, no significant difference was found between the roughness among the three groups sectioned using the piezoelectric technique (p > 0.05). In contrast, concerning the sectioned samples by burs, C demonstrated a rougher surface compared with BR (p < 0.05). There was a significant higher cell attachment in BR compared with AH in the piezoelectric groups (p = 0.047), while no statistically significant difference was found between the groups sectioned with bur (p > 0.05).

CONCLUSION

 Dentists are now focused on the use of calcium silicate-based sealers due to their bioactivity. The present study advises dentists to use bioceramic sealer which could improve the dentin characteristics which ameliorate the cell attachment.

Three-Dimensional Sag Tracking in Falling Liquid Films

Coating defects often arise during application in the flash stage, which constitutes the ∼10 min interval immediately following film application when the solvent evaporates. Understanding the transient rheology and kinematics of a coating system is necessary to avoid defects such as sag, which results in undesirable appearance. A new technique named variable angle inspection microscopy (VAIM) aimed at measuring these phenomena was developed and is summarized herein. The essence of this new, non-invasive, rheological technique is the measurement of a flow field in response to a known gravitational stress. VAIM was used to measure the flow profile through a volume of a liquid thin film at an arbitrary orientation. Flow kinematics of the falling thin film was inferred from particle tracking measurements. Initial benchmarking measurements in the absence of drying tracked the velocity of silica probe particles in ∼140 μm thick films of known viscosity, much greater than water, at incline angles of 5° and 10°. Probe particles were tracked through the entire thickness of the film and at speeds as high as ∼100 μm/s. The sag flow field was well resolved in ∼10 μm thick cross sections, and in general the VAIM measurements were highly reproducible. Complementary profilometer measurements of film thinning were utilized to predict sag velocities with a known model. The model predictions showed good agreement with measurements, which validated the effectiveness of this new method in relating material properties and flow kinematics.