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original Paper SeM eVALUAtION OF tHe MORPHOLOGICAL CHANGeS IN HARD DeNtAL tISSUeS PRePAReD BY eR: YAG LASeR AND ROtARY INStRUMeNtS Georgi Tomov – Bulgaria, Plovdiv, Medical University, Faculty of Dental Medicine, Department of Operative dentistry and endodontic, Assistant Professor, PhD, MD.

удК 616.314-091.8:615.849.19:[615.837.3:621.385.833]-07(497.2)(045)=111 Оригинальная статья оценка морФологичеСкиХ иЗменений твердыХ ЗУБныХ тканей, оБраБотанныХ лаЗером и ротационными инСтрУментами С Помощью УльтраЗвУкового электронного микроСкоПа Георгий Томов – Болгария, Медицинский университет, факультет стоматологической медицины, кафедра оперативной стоматологии и эндодонтии, доцент, доктор философии, доктор медицинских наук.

дата поступления – 20.06.2010 г. дата принятия в печать – 16.09.2010 г.

Tomov Georgi. sem evaluation of the morphological changes in hard dental tissues prepared by er: YaG laser and rotary instruments // saratov Journal of medical scientific Research. 2010. vol. 6, № 3. p. 667–671.

effective ablation of dental hard tissues by means of the erbium:yttrium-aluminum garnet (er: yag) laser has been reported recently, and its application to caries removal and cavity preparation has been expected. however, few studies have investigated the morphological changes in hard dental tissues after er: yag laser caries treatment.

In the present study the morphological changes in hard dental tissues after er: yag laser caries ablation in vitro was compared with that of conventional mechanical treatment.

thirty extracted human teeth with caries were used. ten tooth was treated with the er: yag laser, and the other was treated with a conventional steel and diamond burs. laser treatment was performed by means of a non-contact irradiation modes with cooling water spray, with a new er: yag laser (litetouch). conventional bur treatment was conducted by means of a low-speed micromotor and air turbine with water cooling. Scanning electron microscope (SeM) observations were performed for each treatment.

the er: yag laser ablated carious dentin effectively with minimal thermal damage to the surrounding intact dentin, and removed infected and softened carious dentin to the same degree as the bur treatment. In addition, a lower degree of vibration was noted with the er: yag laser treatment. the SeM examination revealed characteristic micro-irregularities of the lased dentin and enamel surfaces with potential benefits for adhesive restorations.

our results show that the er: yag laser is promising as a new technical modality for caries treatment.

Key words: er: yag laser, SeM, morphological changes.

Томов Георгий. оценка морфологических изменений твердых зубных тканей, обработанных лазером и ротационными инструментами с помощью ультразвукового электронного микроскопа // Саратовский научно-медицинский журнал. 2010. Т. 6, № 3. С. 667–671.

эффективные методы удаления твердых зубных тканей с помощью лазерного иттрий-алюминиевого граната (ИАГ) стали применяться сравнительно недавно с целью подготовки полости зуба и удаления кариеса. Однако ряд исследователей выявили морфологические изменения в твердых зубных тканях после лечения лазерным ИАГ.

целью настоящего научного исследования является сравнительный анализ лазерного лечения и инструментального традиционного лечения.

В качестве материала для исследования были взяты 30 экстрактированных кариозных зубов пациентов, из них 10 подверглись лазерному лечению, остальные 20 – традиционному лечению с помощью стальной и алмазной пластинок. лазерное лечение проводилось на основе неинвазивного распыления охлаждающего спрея на водяной основе с новым лазерным компонентом (ИАГ). Традиционное лечение осуществлялось с помощью низкоскоростного микродвигателя и воздушно-турбинной бормашины с охлаждением воды. Результаты каждого метода лечения оценивались ультразвуковым электронным микроскопом. эффективность лечения лазерным ИАГ доказана при удалении кариозного дентина с минимальным термическим повреждением, окружающего интактного дентина и инфицированного и размягченного дентина в такой же степени, как и эффективность традиционного лечения. Низкая степень вибрации доказана как одно из преимуществ лазерного метода лечения.

данные, полученные при исследовании ультразвуковым электронным микроскопом, выявили микронеровности в дентине, подверженном лазерному излучению, и эмалированном покрытии зуба, требующем дальнейшего адгезивного восстановления.

Результаты проведенного исследования подтверждают необходимость признания лазерного лечения ИАГ новейшим, модернизированным и эффективным методом лечения кариозных зубов.

ключевые слова: лазерный иттрий-алюминиевый гранат, ультразвуковой электронный микроскоп, морфологические изменения.

introduction. the main categories of techniques mechanical cleaning with carisolv gel, air abrasion and for microinvasive preparation (MIP) include chemo- dental lasers [1, 2]. the trends for the replacement of the conventional method of preparation led to focus the ataddress for correspondence:

tention of researchers on the impact of alternative techassist. Prof. Dr. georgi tomov.

niques for MIP on hard dental tissues and underlying faculty of Dental Medicine Department of operative dentistry and endodontic.

dental pulp. MIP techniques claim for controlled removal 3 hristo botev str.

of infected and softened dentin while preserve healthy 4000 Plovdiv, bulgaria.

hard dental tissues and do it with minimal discomfort e-mail: stomatolog79@abv.bg Saratov Journal of Medical Scientific Research. 2010. Vol. 6, № 3.

668 СтоматологиЯ for the patient. however, currently available data provide contradictory the impact of alternative techniques of MIP on hard dental tissues compared to conventional preparation. Possible reasons for this are the variety of experimental studies and difficulties to standardize the results of clinical researches. It is striking that researchers who give the most positive evaluation of alternative methods of preparation are using mainly clinical criteria for evaluation (perception and tolerance of the patient, noise, atraumatic work, color and texture of the dentine when probing etc) which are some subjective. oposite, the SeM and histologic evaluations are not unanimous for its benefits and advantages. on the dental market new improved versions of alternative systems for preparation are available claiming for clinical efficiency, but а scientific data are still scarce (these are generally the multi-frequency high-energy lasers and air abrasion devices). for that reason periodic updates of researches in this rapidly developing and promising field of dentistry are needed.the purpose of this in vitro study was to evaluate by SeM the ultrastructural changes in the hard dental tissues treated with er: yag laser (litetouch) and conventional preparation with diamond burs/air turbine and steel burs/micromotor.

methods. experimental design: the study used human teeth freshly extracted due to advanced periodontal disease. the preparation involved natural carious lesions on tooth surface.

according to the preparation technique the teeth were divided into 3 groups of 10 teeth (n=10):

group 1. laser preparation by er: yag laser (liteб touch, Syneron, Israel) (fig. 1 a, b, c);

group 2. Mechanical rotary preparation by diamond burs/air turbine);

group 3. Mechanical rotary preparation by steel burs/micromotor.

Preparations are made strictly according to manufacturer’s instructions for service.

the removal of caries is proved by clinical methods – observation and probing. after preparation the teeth are immersed for 1 hour in 4% buffered fixative solution of glutaraldehyde (0.075 M, ph 7.3). then rinsed with distilled water and placed for 90 min in cold buffer solution of sodium kakodilate (0.02M, ph 7.2, 660 mosm) for fixation of organic matter. Subsequent dehydration is carried out in ethanol in ascending series of 30, 50, 70, 80, 95 and 100% in one hour in each series, such as drying of the teeth is based on cPD (critical Point Drier) method in a dessicator. Dried specimens are fixed on metal stand and covered with gold layer (200-250nm) by cathode atomization under vacuum. Scanning microscopy is performed with the electron microscope of Philips (holland) 515 model SeM with accelerating voltage of 25 kV in secondary emission mode. on each specimen were made respectively five pictures with the same magnification (x 2000) of randomly chosen areas and different numbers of photos with other magnification.

on SeM photos are rated, described and compared morphological findings and differences in enamel and dentin tissues after treating with alternative methods for caries removal and cavity preparation.

Results. cavity forms prepared with er: yag laser (group 1) are characterized by a lack of definite and precise geometric configuration and outlined cavity ele- с ments. there is rough and irregular surface without presence of smear layer (fig. 2 a). Dentinal tubules orifices fig. 1. a, b, c. laser preparation with er: yag laser litetouch are clearly exposed. Intertubul dentin is ablated more (Syneron, Israel) than peritubular dentin and that made dentinal tubules «hard tissue mode» (400mJ/20hz; 8.00w) appearance more prominent (fig. 3 b). In enamel the Саратовский научно-медицинский журнал. 2010. Том 6, № 3.

StOMAtOLOGY a a b b fig. 2 a, b. laser treated dentin. the surface is clean and free fig. 4. a, b. SeM photomicrographies of tooth surfaces prepared from debris, all dentinal tubules were found open. the surface with steel burs. the surface is covered with a layer of debris, is irregular, rough, which creates strong retentions. at greater dentinal tubules orifices are not visible.

magnification more effective removal of intertubular dentin is (Magnification x 500, 2000) seen, and that makes dentinal tubules orifices to appear convex (Magnification x 500, 2000) when analyzing the SeM photomicrographies of the specimens examined, it is found that the conventional method of cavity preparation with steel burs and micromotor at low speed without water cooling (group 3) leaves contaminated surface covered with smear layer of dentin debris without visible dentinal tubules orifices.

(fig. 4 a, b). thick smear layer covers all treated surfaces. the walls of the cavities are smooth and rounded and the border between enamel and dentin is not perceptible.

discussion. the philosophy of minimally invasive cavity preparation approach is based on several main principles – to remove only irreversibly damaged dental tissues and to avoid macroretention preparation in healthy tissues [1]. additionally these techniques should protect the underlying pulp and to leave the treated surc d face suitable for adhesive bonding [1]. antibacterial effig. 2 c, d. enamel surfaces treated with er: yag laser revealed fects of the alternative preparation techniques must not characteristic architectonics of tufts grouped enamel prisms with be lower than those of standard necrotomy with rotary differ orientation. the surface is very retentive and free from instruments and even to excel them [1].

contaminants and smear layer nowdays the laser devices available for clinical use (Magnification x 500, 2000) are capable for effective and controlled ablation of hard dental tissues [2]. however, not all researchers agree typical architectonics of grouped in bundles enamel with these conclusions. therefore, such studies should prisms is observed. laser ablation changes enamel and be periodically updated due to constant introduction of the surfaces appeared strong retentive (fig. 2 c, d).

new technologies.

In group 2 (preparation with diamond burs, air turbine the experimental results of the presented study reand water cooling) a thin, smooth and in some places vealed significant differences in the surface morphology missing smear layer was observed (fig. 3 a). In the area of the studied samples, which would affect the ability to of water turbulence marked dentinal tubules orifices can be seen, but without having a clear outline of both tu- perform effective adhesive bonding. these morphological differences are highly dependent on the mechanism bules lumens and peri-and intertubular dentin (fig. 3 b).

of action of the used preparation systems.

the boundary between enamel and dentin is unclear laser devices use a variety of physical media as and the cavity forms heve smooth contours.

sources for generating different wavelength that is absorbed and interact with specific molecules in human tissues. the explanation for the hard tissue ablation is the water content that evaporates when exposed on laser radiation creating high internal pressure and subsequent microexplosions. In this interaction of laser radiation with tissue if inadequate water cooling occured, that will lead to undesirable thermal effects [3]. Depending on parameters such as pulse energy and frequency co2 lasers, nd: yag and er: yag lasers cause changes in enamel and dentin as roughing, craters, cracking, slicing, cara b bonification, melting and recrystallisation described in fig. 3. a, b. Smooth and thin smear layer covers tooth surfaces many previous studies [4, 5, 6]. these changes depend prepared with diamond burs and air turbine. In the area of water on the laser type, mode of operation, system for water turbulence partially removed contaminants and single dentinal tubules lumena were observed. (Magnification x 500, 2000) cooling and proper operation [3]. additionally, the opporSaratov Journal of Medical Scientific Research. 2010. Vol. 6, № 3.

670 СтоматологиЯ tunities to ablate carious dentin and enamel strongly vary the results of some contemporary studies showed according to different experimental studies [4 - 6]. for ar- that despite of the differences between individual authors, gon-fluoride laser (aRf) and the excimer laser there are generally the amount of smear layer after treatment with data on their ability to remove dental caries, which is not er: yag laser in all cases is less than that after convenof sufficient efficiency [5]. krypton fluoride excimer laser tional rotating instruments, and surface changes are charemitting in ultraviolet range has been shown to remove acterized by markedly rugged topography [2, 3, 12, 16].

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