Search

The water thermal accumulators for heat and cold storage are an important part of various engineering installations. This article examines a tank with volume of 1000 [l] in a consumption mode with a constant debit and a fixed temperature. The output volumes of hot water in two regimes – weak stratification and strong stratification are calculated analytically and are compared with the results from an analogical simulation in ANSYS. The ANSYS simulations are unconditionally more accurate, but require specialized knowledge and software. The solutions without simulation procedures are suggested. The output volume of hot water with fixed temperature - as a function of initial and final temperatures in accumulator, flow debit, tank construction and external conditions - can be calculated fast and accurate enough for the engineering practice. Relative differences between analytic and simulations results for all regimes are below 10.5%.

The world population is continuously getting older in developed and undeveloped countries. According to WHO over 20% of the population in Europe is over 65 years old. Geriatric population in North Macedonia is presented with 16% and with high prevalence of anodontia over 45, 1%, poor oral hygiene and urgent demand of prosthodontics treatment. Aging is a process with different and specific changes of all systems and organs, including the orophacial system. In this population, the number of remaining teeth is evidently reduced, their condition has changed, and soft and hard oral tissues are affected. It is very important to discover all the factors that lead to the development of leukoplakia and other precancerous lesions as early as possible. Precancerous lesions and oral carcinoma are more common in the elderly compared to the younger population. Almost 90% of oral cancers occur in patients older than 50 years. Early detection of oral mucosa diseases in elderly and potentially malignant disorders requires careful examination because of high malignant transformation frequency. The aim of the study was to determine the condition of oral soft tissues in geriatric prosthodontics patients, their general health and the impact of oral health on their quality of life. The value of the VELscope instrument as an adjunct to oral examination in geriatric prosthodontics patients was also evaluated. The study was performed in the University Dental Clinic Ss’ Panteleimon in Skopje, NM. Clinical protocol for 300 patients over 60 years old was questionnaire with risk factors, clinical intra and extraoral observation and VELscope mucosal tissue examination. Tissue changes were classified as inflammatory, traumatic, dysplastic and other. Abnormal tissue was associated with auto fluorescence loss and dark appearance in contrast to the surrounding healthy tissue. In 21% of patients abnormal premalignant lesions were detected. Leukoplakia was the most common premalignant disorder 42 (12, 6%), 16 (4, 8%) had lichen planus, 6 (1, 8%) cheilitis actinica and 5 patients (1, 5%) were diagnosed with squamous cell carcinoma. We found 118 inflammatory lesions (35, 4%) where 58 (17, 4%) were denture stomatitis, 18 (5, 4%) angular cheilitis, traumatic lesions were found in 38 patients (11, 4%) and 4 (1, 2%) were diagnosed with epulis fissuratum. In 54 patients (16, 2%) we diagnosed infectious changes from which aphtous ulcerations and candidiasis were most common. The VELscope fluorescence instrument can be used as a part of diagnostic process to detect abnormal tissue and oral lesions that might have been overlooked. A validation of the study was carried out and it was approved by the ethics committee of the Faculty for dentistry Ss Cyril and Methodius University Skopje on 18.12.2018. No. 02-38363.

Background: Gingivectomy is a procedure often performed in everyday clinical practice using numerous instruments. Aim: To evaluate and compare the gingival cut surface after gingivectomy with 6 different surgical instruments – a surgical scalpel, an Er:YAG laser, a CO2 laser, a ceramic bur, an electrocautery device, and a diode laser. Materials and methods: Gingivectomy using the above listed instruments was performed in 18 patients. The histological samples excised with a surgical scalpel were assigned as a control group and the other five types – as test groups. The following histological parameters were measured: coagulation layer thickness (in μm); presence or absence of a microscopic rupture and presence or absence of hemostasis in-depth. Results: The best instrument of the above listed ones which demonstrated excellent results is the CO2 laser. The Er:YAG laser has a thin coagulation layer and lack of hemostasis in-depth. The diode laser has the widest coagulation layer which is an advantage from a clinical point of view. Electrocautery proved to be as effective as the diode laser, but it should not be used around metal restorations. The ceramic bur has less pronounced hemostasis in-depth. Conclusions: Modern dentistry uses a wide variety of methods that are designed to be applied in everyday practice. Good knowledge of the ways to use them, their advantages and disadvantages is essential to obtaining the optimal result depending on the clinical case.

Background: The erosive-atrophic form of oral lichen planus (OLP) is associated with severe pain and burning sensation and is often unresponsive to treatment. Topical corticosteroids are considered as a medication of first choice but they can produce adverse effects. Therefore, new therapeutic approaches are required. Aim: The aim of this study was to investigate the effectiveness of biomodulation with diode laser in patients presenting with long-standing erosive-atrophic OLP. Materials and methods: Twelve patients, clinically and histologically diagnosed with OLP, participated in this study. The level of pain and the clinical scores of total 59 lesions were recorded before treatment using visual analog scale and Thongprasom sign scoring system respectively. All patients received low level laser therapy (LLLT) with diode laser (810 nm) with parameters (0.5 W, 30 s, 1.2 J/cm2) three times weekly for a month. The response rate was assessed according to the decrease in pain and sign scores. Treatment efficacy index was calculated. Results: There was a significant reduction in pain after LLLT (p Conclusion: The present results indicate that LLLT is an effective and harmless modality for management of erosive-atrophic OLP.

Purpose: With the advance of the modern technologies, the identification of dysplastic changes in the oral mucosa on a molecular level seems to have transferred into the dental office. With the new methods, however, new responsibilities and problems arise. The current review is an attempt to present the advantages and disadvantages of the clinical technologies used for early diagnostics of the oral precancerous lesions. Materials and Methods: This study is based on an extensive literature review and personal clinical experience with these contemporary evaluating methods of oral precancerous lesions. Results: The results from the pathohistological evaluation reveal stratified squamous epithelium with pronounced parabasal hyperplasia, disturbed maturation and loss of polarity of the basal cells. The latter demonstrates hyperchromatic polymorphic nuclei and single mitotic figures in half of the epithelial thickness. The morphological data points to a moderate epithelial dysplasia. Conclusion: The loss of autofluorescence seems to be the most promising non-invasive method for identification of epithelial dysplasia in the oral cavity. The presence of some non-dysplastic lesions, which can also be non-fluorescent, i.e. produce “false negative” results, is one of the disadvantages of this method. Despite that most modern technologies are practical and convinient, they should be approached with a critical eye and should not be used as single and independent diagnostic means but only as an adjunct to the established classical methods of diagnostics.

This study aimed to retrospectively evaluate the efficacy and safety of laser treatment of oral vascular lesions using the multiple spot irradiation technique with a single-pulsed wave.In laser therapy for vascular lesions, heat accumulation induced by excessive irradiation can cause adverse events postoperatively, including ulcer formation, resultant scarring, and severe pain. To prevent heat accumulation and side effects, we have applied a multiple pulsed spot irradiation technique, the so-called "leopard technique" (LT) to oral vascular lesions. This approach was originally proposed for laser treatment of nevi. It can avoid thermal concentration at the same spot and spare the epithelium, which promotes smooth healing. The goal of the study was to evaluate this procedure and treatment outcomes.The subjects were 46 patients with 47 oral vascular lesions treated with the LT using a Nd:YAG laser (1064 nm), including 24 thick lesions treated using a combination of the LT and intralesional photocoagulation.All treatment outcomes were satisfactory without serious complications such as deep ulcer formation, scarring, bleeding, or severe swelling.Laser therapy with the LT is a promising less-invasive treatment for oral vascular lesions.

Summary Oral/perioral piercing may provide an ideal environment for adhesion and colonization of microorganisms. The aim of this study is to perform an “in vitro” research on the capabilities of adhesion of Candida albicans on oral piercings made of plastic and metal. Acrylic and metal piercings were incubated with Candida albicans and then were observed using scanning electron microscopy under different magnifications. A lot of irregularities and roughness were observed on the surface of the plastic piercing unlike the surface of the metal one, which is not so rough. Nevertheless, the number of Candida albicans colonies was considerably larger on the scanned metal surface in comparison to the plastic surface. In vitro the metal surface of the piercing creates better environment for the adhesion and colonization of microorganisms than the acrylic. This could be attributed to the electrostatic forces that most likely attract Candida albicans to the metal piercing in the early stages of biofilm formation.

The histological features of teeth with hypocalcified amelogenesis imperfecta (AI) have been poorly studied, which calls into question the effectiveness of modern adhesive techniques used in the treatment of these noncarious defects. Aim: The aim of this study was to investigate the morphological features of the enamel and dentin of teeth with AI using scanning electron microscopy (SEM), and compare these features with those of healthy teeth. Materials and methods: We examined four primary teeth extracted on indication from a 10-year-old girl with hypocalcified amelogenesis imperfecta. The same number of primary teeth extracted from healthy subjects was used as controls. The morphological characteristics of the enamel and dentin are described after investigating the teeth and photographing the specimens with scanning electron microscope. Results: The SEM photos of the enamel of AI teeth show presence of external defects, incorrectly oriented enamel prisms and enlarged interprism spaces. Thickening of the peritubular dentin and partially obliterated dentinal tubules characterize the dentin of these teeth. Conclusion: The enamel and dentin of teeth affected by hypocalcified AI diff er considerably from normal hard dental structures in their morphological characteristics.

Introduction: Vital pulp therapy involves biologically based therapeutic activities aimed at restoring health and preserving the vitality of cariously or traumatically damaged pulp. Adaptation of pulp-capping materials to the prepared tooth surface may be the key to the success of biological tooth treatment. Aim: To investigate the area of adaptation of synthetic tricalcium silicate cement, calcium hydroxide cement and mineral trioxide-aggregate to the dentin surface, prepared with the help of Er:YAG dental laser. Material and methods: Four extracted human tooth cavities were prepared with the help of Er:YAG dental laser (LiteTouch, Syneron, Israel), establishing microcommunication with the pulp chamber less than 1 mm in diameter. As pulp-capping materials in the cavities we used tricalcium silicate cement (Biodentine, Septodont, France), calcium hydroxide cement (Dycal) and mineral-trioxide aggregate (ProRoot MTA), stirred and administered according to manufacturers’ instructions. The first material fills the whole cavity and the other two are spread in a thin layer and sealed with glass ionomer cement. Thus prepared, the samples were left for three days at 37°C in humidified environment. The samples were prepared for scanning electron microscopy (SEM) by standard methodology. The border area surfaces of the materials and the dentin were scanned using electron microscopy. Results: The morphological changes occurring to the Er:YAG laser prepared dentin and the structural characteristics of the studied pulp-capping materials are demonstrated using scanograms. The border areas where good contact of materials and dentinal tubules is established are thoroughly studied. Good adaptation is seen in three-calcium silicate cement, followed by mineral trioxide aggregate and calcium hydroxide cement. Conclusion: The dentin surface, prepared with Er:YAG laser demonstrates a very good adaptation of the three tested pulp-capping materials.

Tooth anatomic factors like ectopic enamel pearls are often associated with localized periodontal inflammation and bone loss. There are no existing paleopathological data for such structural anomalies in ancient populations associated with periodontal pathology in the literature. A rare case of enamel pearl on the maxillary right first molar of women associated with localized periodontitis is presented and discussed.

Introduction: A venous lake (VL) is a vascular lesion with common occurrence in many patients, manifested as a dark blue-to-violet compressible papule, caused by dilation of venules. The main reasons for the treatment of VL are aesthetic. The haemorrhaging episodes or impairment of oral normal functions are also under considerations. Treatment of lip VL includes surgical excision, selective photocoagulation, cryotherapy, sclerotherapy and electrodessication. The high-intensity diode laser is an option. The 980 nm diode laser is selectively absorbed by haemoglobin and selectively destroys blood vessels, minimising injury to the surrounding healthy skin.Aim: The purpose of this study was to evaluate the effectiveness of diode laser in the treatment of VL lesions with the accent on the postoperative defects and aesthetic results.Methods: 35 patients aged 37 to 71 were included in this study. A 980 nm diode laser was used in noncontact mode, under local anaesthesia in continuous wave (2-3W, for 20-60s). All patients received only one procedure.Results: Healing process was completed within 2 to 4 weeks after treatment with no scarring. None of the typical adverse effects were observed in the process of healing.Conclusions: Selective photocoagulation is an effective method for treatment of VL. Lower morbidity, minimal patient discomfort and satisfactory functional and aesthetic results are favourable for patients. To optimise the results and to reduce the adverse effects, basic knowledge on lasers and laser-tissue interactions is requisite.

Taurodontism is a morphological abnormality of the tooth shape with the following characteristic features: vertically enlarged pulp chamber, apical displacement of the bifurcation and trifurcation, shortened roots and no constriction at the level of the cementoenamel junction. This anomaly is still neglected by orthodontists when it comes to making treatment plans in spite of the reports in the literature of a close association of this condition with hypodontia and oligodontia. Aim: The article discusses the orthodontic problems arising in treating patients with hypodontia and taurodontism and suggests approaches to reducing the risk of complications during orthodontic tooth movement. Discussion: Failure to identify taurodont teeth in hypodontic patients can cause serious complications in their orthodontic management because of the greater susceptibility of these types of teeth to root resorption in orthodontic tooth movement. Besides, these types of teeth are less anchorage. Conclusion: The high incidence of taurodontism in hypodontic patients presents a clinical challenge for general dental practitioners and orthodonists alike. Furthermore, successful management of hypodontia rests on the orthodontist’s ability to identify taurodont teeth and correctly include them in treatment plan.

Introduction. Taurodontism is an aberration of teeth that lacks the constriction at the level of the CEJ and characterized by elongated pulp chambers and apical displacement of bifurcation or trifurcation of the roots, giving it a rectangular shape. Aim. To summarize the available literature on taurodontism phenomenon in the contexts of paleodontology, evolutionary biology and clinic. Materials and methods. In order to clarify the prevalence of taurodontism in modern dentitions and the critical need for its true diagnosis and management, this review addresses the aetiology, clinical and radiographic features of taurodontism, its association with various syndromes and anomalies, as well as important considerations in various areas of expertise dental treatments of such teeth. Results. Although permanent molar teeth are most commonly affected, this aberation can also be seen in both the permanent and deciduous dentition, unilaterally or bilaterally, and in any combination of teeth or quadrants. Whilst it appears most frequently as an isolated anomaly, its association with several syndromes and abnormalities has also been reported. Discussion. It is apparent that taurodont teeth are presumed characteristic of neanderthal man and are still present as a morphological entity in modern man. The occurrences seem to have a biased racial expression in different populations. It can be seen that taurodontism has until now received insufficient attention from clinicians. No long-term follow-up studies have been published regarding treatment of taurodont teeth. Despite the clinical challenges, taurodontism has received little attention from clinicians.

Background: The cosmetic oral mucosa tattoos occur infrequently but the social stigma that may be associated generally with tattoos is motivating factor for its removal. The development of infrared lasers has revolutionized the ability to remove cosmetic oral tattoo effectively. The wave-length of choice is 1,064 nm but there is no relevant histological data regarding effects of Nd:YAG laser on oral tissues after tattoo removal. The aim of this study is to provide histological evidences and to clarify the healing processes in oral mucosa after tattoo removal with 1,064 nm wavelength laser. Methods: Five patients with professional black tattoo of inner lip were included in this study. The clinical procedures were performed using 1,064 nm wavelength. Two equal specimens were taken from the treated and non-treated sites for further histological evaluation. Results: The specimens after the treatment revealed fragmentation of black ink particles up to 1.5 mm below the surface. Mild fibrosis was observed in the superficial submucosal area where collagen fibers replaced the pigment-containing cells altered by the laser. Clinically, the treatment results showed excellent recovery of the oral mucosa. One year later, the laser treated areas were healthy and without esthetical and functional disturbances. Conclusions: Both histological and clinical results advocated Nd:YAG laser treatment as safe and very effective means of removing cosmetic tattoos on the oral mucosa.

Introduction: Er:YAG lasers generate wave length of 2940 nm which coincides with the absorptions spectrum of water. For these reasons it is possible to work with Er:YAG lasers both on soft and hard tissues with minimal thermal effects. Lasers due to their wide-spectrum of biological action and high therapeutic effectiveness are used long ago in certain specialties like oral surgery and cariesology. In orthodontic lasers are poorly known and are not routine tool despite their beneficial application abilities.Aim: The presented case report discusses alternative surgical approach for laser-assisted uncovering of ectopically impacted canines for orthodontic reasons.Conclusions: Er:YAG laser is a revolutionary technology providing alternatives for orthodontists in solving different problems in their everyday practice. It is effective and comfortable tool to reduce treatment time and to promote excellent clinical results.To patients is offered method of choice with comfort guarantee, less pain sensations and accelerated healing process.

Aim This in vitro investigation aimed to study by means of scanning electron microscope the morphological changes in hard dental tissues after using several different methods for caries removal and cavity preparation. Materials and methods Twenty freshly extracted human teeth with carious lesions were used in the study. They were assigned to four groups depending on the method used for preparation: Group 1--Cavity preparation using Er: YAG laser (LiteTouch, Syneron, Israel). Group 2--Chemomechanical preparation using colourless Carisolv gel (MediTeam AB, Savedalen, Sweden). Group 3--Mechanical rotary preparation using diamond burs and air turbine. Group 4--Mechanical rotary preparation using by steel burs and micromotor. The preparations were performed strictly according to the manufacturer's instructions for proper use of instruments. The teeth samples were prepared for histological study and investigated by a scanning electron microscope at different magnification; the morphological changes in the tissues were registered and compared. Results There were considerable differences in the surface characteristics of the dental tissues when we analysed the photomicrographs of the specimens obtained using scanning electron microscopy (SEM). The surface after laser treatment remained highly retentive with no residual smear layer; the second best results in this respect were registered when teeth were chemomechanically excavated with Carisolv gel. The mechanical methods of cavity preparation resulted in surfaces with a smear layer of dentin without any microretentions. Conclusion The scanning electron microscopy of hard dental tissues prepared using steel and diamond burs showed surfaces covered with a thick smear layer that may be relevant to the subsequent bonding of adhesive restorative materials to the prepared cavity. In preparing the surface using a turbine with diamond burs the smear layer was thinner and part of the dentinal tubules orifices were open in the area of water turbulence. SEM analysis of hard dental tissues prepared with the help of colourless Carisolv gel showed a rough, retentive surface, some of the dentinal tubule lumens obstructed by denaturated collagen and surface contaminants. The teeth surfaces prepared with Er:YAG laser Lite Touch (Syneron) remained without smear layer and clearly exposed dentinal tubules orifices. The surfaces were highly retentive.

Background - In oral pathology, laser devices can provide important advantages, especially in the treatment of certain lesions. However, there is controversy about the use of some wavelengths in the analysis of suspected dysplastic or neoplastic lesions, raising doubt about the laser's suitability for use in biopsy procedures. The present pilot study evaluates the pathomorphological characteristics and suitability of Er:YAG and diode lasers for performing excisional biopsies in the oral mucosa with special emphasis on the extent of the thermal damage zone created. Material and Methods - 10 patients were randomly assigned to one diode or one Er:YAG laser groups. The Er:YAG laser(2940nm) was used in a pulsed wave mode 200mJ/35Hz with a power of 7 W. Power settings for the diode laser(810 nm) were 3 W in a pulsed mode. The thermal damage zone of the two lasers and intraoperative and postoperative complications were assessed and compared.All biopsy specimens were evaluated by optical microscopy by threeblinded pathologists. After establishing the pathomorphological diagnosis of the lesion assessed, the pathologists measured the maximal width of the peripheral thermal damage zone in the specimen in μm and classified it using appropriate index. Results - The peripheral thermal damage zone on the borders of the excisional biopsies was significantly smaller with the Er:YAG laser compared to the diode laser regarding values in μm or pathomorphological index scores. No postoperative complications occurred in any of the two groups. Conclusions - The Er:YAG laser seems to be appropriate for excisional biopsies of benign oral mucosal lesions. The Er:YAG laser offers clear advantages in terms of smaller thermal damage zones over the diode laser. Although in some samples thermal damage was minimally visible, in all samples histological evaluation was clearly possible. The study demonstrated that the Er:YAG laser can be safely used in oral biopsy investigations while ensuring a successful histological evaluation, which is fundamental to correct clinical management.

The principle of a suction cup is used to retain an upper full denture. Alveolar resorption results in loss of the vestibular depth and in diminished functional surface to overcome lateral forces. Traditional surgery has the following characteristics in common-need for incisions with steel scalpels, mechanical excision of the muscle attachment from the periosteum, placement of sutures, significant postoperative discomfort, and delayed healing. When the benefits and risks of alternative treatment modalities are taken into account for this mechanical surgical procedure, minimally invasive laser-assisted soft-tissue excision and ablation seems to be very attractive technique. In the presented case report we used an Er:YAG laser (LiteTouch, Syneron, Israel) to deep the oral vestibulum of upper jaw in edentulous patient. Therefore, were indicated, we recommend the laser assisted operation technique for the partial vestibuloplasty to assure the patients a better postoperative outcome.

С развитието на денталната имплантология и непрекъснато нарастващия брой поставени импланти в световен мащаб терапията на усложненията придобива все по-голяма актуалност. Периимплантитът според различни данни се установява при 42% (28 до 56%) от пациентите и 27% (12 до 43%) от имплантите. Това определя необходимостта от търсене на предвидими съвременни методи за лечението на това заболяване. Лазерите, използвани в денталната медицина, са средства, даващи обещаваща ефективност при деконтаминацията на имплантната повърхност и периимплантните тъкани, дебридмен и тъканна аблация. Тези апарати генерират лазерен лъч в различни среди и с различна дължина на вълната, което определя и вариабилност във физичните параметри и въздействие върху структурите в имплантния интерфейс. Детайлното проучване на това въздействие дава възможност за селектирането на лазер с оптимална ефективност и без да уврежда и модифицира имплантното тяло и прилежащите меки и твърди тъкани. От трите типа лазери, които могат да бъдат използвани при консервативното и хирургично лечение на периимплантит с най-добри параметри и биологични ефекти е Er:YAG лазерът според данните, получени чрез лабораторни, експериментални и клинични проучвания, описани в настоящия дисертационен труд., With the development of dental implantology and the ever-increasing number of implants placed worldwide, the therapy of complications is becoming more and more relevant. According to various data, peri-implantitis was found in 42% (28 to 56%) of patients and 27% (12 to 43%) of implants. This determines the need to look for predictable contemporary methods for the treatment of this disease. Lasers used in dental medicine are means that give promising efficiency in the decontamination of the implant surface and periimplant tissues, debridment and tissue ablation. These devices generate a laser beam in different environments and with different wavelengths, which also determines variability in physical parameters and impact on structures in the implant interface. The detailed study of this impact makes it possible to select a laser with optimal efficiency and without damaging and modifying the implant body and adjacent soft and hard tissues. Of the three types of lasers that can be used in the conservative and surgical treatment of peri-implantitis with the best parameters and biological effects is the Er:YAG laser according to the data obtained through laboratory, experimental and clinical studies described in the current dissertation work.

The dissertation offers a method for auto-tuning of PID controllers for multivariable plants. A modified control structure is used for relay experiment, giving the possibility to take into account the interconnections between the loops as an additive uncertainty. The use of two degree of freedom structure for decoupling is proposed for the purpose of easier anti wind-up implementation. A method for improving the performance of the system with the two degree of freedom is proposed by using a correction in the feedback loop. The choice of correction is based on one point of the structured singular value of the closed loop. A necessary software is developed for controlling industrial systems with programmable logic controllers., В дисертацията е предложен метод за автоматична настройка на ПИД регулатори за управление на многомерни обекти. Използва се модифицирана схема за провеждане на експеримент с релейна обратна връзка, чрез който е възможно влиянието между контурите да се отчете на етапа на синтез под формата на адитивна неопределеност. Предложено е използване на схема с две степени на свобода за декуплиране на многомерния обект, с цел по-лесна реализация на механизмите за борба с интегрално насищане. Предложен е метод за подобряване на качеството на системата с две степени на свобода, чрез корекция в обратната връзка. Изборът на коригиращото звено е базирано на една координата от честотната характеристика на структурираното сингулярно число за затворения контур. Разработено е и съответно програмно осигуряване за управление на индустриални обекти с програмируеми логически контролери.