SURGICAL MANAGEMENT OF DEPIGMENTATION IN HYPERPIGMENTATION WITH SCRAPPING METHOD USING SURGICAL SCALPEL

Introduction:The color of healthy gingiva is often influenced by melanin pigmentation as an abnormal deposition of melanocytes located in basal and suprabasal cells. Gingival hyperpigmentation that exceeds normal causes a variety of physiological and pathological conditions. Gingival depigmentation is a periodontal surgical procedure to remove or reduce gingival hyperpigmentation by various techniques to improve aesthetics. The procedures include the use of chemicals such as 90% phenol, diamond drill abrasion, gingivectomy, soft tissue autograft, partial thickness flap, cryosurgery and laser. Case: A 19-year-old male patient came to periodontist office, after an examination he had Smoker's melanosis hyperpigmentation in the upper anterior region. Case Management: The patient was given depigmentation surgery using the scrapping method using a scalpel No. 15c.Discussion: Surgical management of gingival depigmentation with scrapping provides good esthetic results. Conclusion: It is necessary to take a proper history and adequate examination and be wise in determining the various surgical methods of depigmentation.

SEM Evaluation of Tooth Surface after a Composite Filling Removal Using Er:YAG Laser, Drills with and without Curettes, and Optional EDTA or NaOCl Conditioning

(1) Background: This study aimed to evaluate the microporosity of the tooth surface structure adjacent to the cemento-enamel junction (CEJ) after the removal of composite fillings with a drill in comparison with removal by an Er:YAG laser and after cleaning with a periodontal curette, chemical EDTA and NaOCl (sodium hypochlorite) conditioning. (2) Methods: The research material consisted of 30 extracted premolars with cervical composite fillings. The teeth were divided into six groups according to the method of tooth preparation: group G1 (n = 5)—a diamond drill; group G2 (n = 5)—a diamond drill + curette; group G3 (n = 5)—a diamond drill + 24% EDTA (PrefGel, Straumann, Switzerland); group G4 (n = 5)—an Er:YAG laser (LightWalker, Fotona, Ljubljana, Slovenia) set with the following parameters: power: 1.65 W (composite removal, CR), 1.2 (tooth conditioning, TC), energy: 110 mJ (CR), 80 mJ (TC), frequency: 15 Hz, pulse duration: 50 μs, tip diameter: 1 mm, air/fluid cooling: 4, distance 1.5 mm, energy density: 14.01 J/cm2 (CR), 10.19 J/cm2 (TC); group G5 (n = 5)—an Er:YAG laser + 2% sodium hypochlorite (NaOCl); group G6 (n = 5)—an Er:YAG laser + 5.25% NaOCl. In each tooth, three cavities were made and subjected to analysis. The dentin surface was evaluated using a scanning electron microscope (SEM). (3) Results: Groups G1 and G2 exhibited mechanical damage to the tooth surface structure caused by the rotary motion of a diamond drill. The SEM image showed a smear layer that could only be removed chemically using 24% EDTA gel (group G3). The tooth surfaces prepared with the Er:YAG laser (groups G4–G6) revealed a homogeneous structure without damage along with open dentinal tubules (without smear layer) and visible denaturation of collagen fibers. The sodium hypochlorite (NaOCl) conditioning did not increase the visibility of dentinal tubules. (4) Conclusions: Dentin surfaces have open dentinal tubules after removal of the composite filling using the Er:YAG laser and therefore do not require additional NaOCl conditioning.

DEVICE FOR CREATING SLOTS-VOLTAGE CONCENTRATORS IN THE BOUNDARY AREA OF WELLS IN FINE ROCKS

It is shown that in order to expand the field of practical application of directional measuring hydraulic fracturing, it is necessary to create technical means that provide cutting of initiating slots on the walls of boreholes in rock masses of different strength. A new slotter design is proposed, the distinctive feature of which is using carbide cutters that are extended during cutting slots along the normal to the device axis. The device is brought into operation due to its normalized movement tagging the bottom. The slotter dimensions allow using it in diamond drill holes of 76 mm diameter. The device is designed to create stress concentrator slots in adjoining zones of boreholes in hard rocks with a coefficient of 5-8 according to M. M. Protodyakonov’s scale.

Investigation of drilling 2D C_f∕C–SiC composites with brazed diamond core drills

Drilling carbon fiber reinforced silicon carbide composites still forms a big challenge for machining because of their special braided structure and anisotropy. In this study, through the drilling of 2D Cf∕C–SiC composites, two kinds of brazed diamond core drills with different abrasive distributions were compared. The results showed that the drilling force and torque of the two drills decreased with the increase in the spindle speed and increased with the increase in the feed speed. Under the same drilling conditions, the drilling force and torque of the brazed diamond drill with the ordered abrasive distribution were far lower than those of the brazed diamond drill with the random abrasive distribution. Also, the quality of the holes drilled by the drill with the ordered abrasive distribution was better than that of the holes drilled by the drill with the random abrasive distribution, which is attributed to the uniform abrasive spacing provided by the drill with the ordered abrasive distribution.

Tool reliability of sintered diamond drill bit for processing silicon carbide ceramics based on Bayesian theory

Silicon carbide (SiC) ceramics, as a superhard nonmetallic material, would induce severe tool wear during drilling. To ensure the quality of processing, the drill bits must be replaced in advance before failure, which leads to serious waste without effective usage. Aiming at the tool reliability problem determined by the tool wear during drilling of the high hardness nonmetallic materials, this article proposed a reliability analysis method of sintered diamond drill bit for machining SiC ceramics based on the distribution of tool degradation increment and the modeling of gamma process, and a tool reliability model of degradation increment was established based on the Bayesian theory. The drilling experiment of sintered SiC ceramics was carried out by sintering diamond drill bit to obtain the degradation increment data. The accuracy of the model was tested by the reliability model deviation rate, which indicated that the reliability model with considering individual differences was more accurate. This research can provide a theoretical model and analytical method for improving the reliability of the nonmetallic brittle material processing tools.

Obtaining intraoral subepithelial connective tissue graft: Dermabrasion Technique- Case report

Objectives: The present study aims to describe the dermabrasion technique to obtain connective tissue rich in collagen, with satisfactory thickness and anatomy, removing the epithelial layer with diamond drill in high speed handpiece and under refrigeration. Materials and Methods: A 50-year-old patient was selected for immediate dental implant (element 25) and soft tissue augmentation in the periodontal and peri-implant region. An epithelial connective tissue graft was performed in the area comprising elements 23, 24, 25 and mesial of 26. For the preparation of the donor area of the graft, the dermabrasion technique was used through a spherical diamond drill bit (medium or thick granulation) in high speed and under refrigeration, being able to remove the epithelium without losing part of the subepithelial layer. Results: The healing process is by second intention and presented a normal evolution with formation of adequate tissues. Conclusions: The Dermabrasion technique allows to obtain adequate grafts, removing the epithelial layer in a simple way and guarantee the desired thickness.