Scripta Scientifica Medicinae Dentalis

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Authors: Tihomir Vasilev, Tsanka Dikova, Dzhendo Dzhendov, Elisaveta Ivanova

The aim of the present paper is to evaluate and compare the strength properties and deformation characteristics of cast and Selective Laser Melted (SLM) Co-Cr dental alloys by using CAD/CAE software. The Solid Works Simulation software is used for simulation of chewing load of the virtual 3D model of a four-part dental bridge. Two Co-Cr dental alloys, cast and SLM were used in this study. During the simulation process by means of linear static analysis the displacements, strains, stresses, and reaction forces under the effect of the applied load were calculated. As a result, the equivalent von Mises stresses, Factor of Safety (FOS) and displacements were evaluated in this study. It was established that the highest values of the equivalent von Mises stresses of cast and SLM bridges are situated in the connectors between the teeth, i.e. the zones with the lowest areas of the cross sections. They are in the range 95-162 MPa, which is lower than the stress limits for the both materials. The minimum FOS of both materials is higher than 1. In the cast bridges it is 1.32-2.64 in the zones with the highest load, while in the SLM samples it is 2.61-5.68. As FOS shows the reserve strength of the material for the applied load, it is obvious that the SLM bridge possesses twice as high reserve strength. This allows optimization of the construction, economy of material and possibility for manufacturing of objects with porous structures.

5

Authors: Vassil Svechtarov, Savina Nencheva - Svechtarova

INTRODUCTION: The aim of this study is to evaluate the distribution of the most common comorbid conditions associated with chronic temporomandibular disorders, and the pharmacological agents which play an integral role in the overall management of temporomandibular joint disorders. MATERIALS AND METHODS: A total of 23 articles are included in this comprehensive review of the relevant studies on common comorbid conditions related to temporomandibular disorders. This review provides summarized clinical and online platform based analyses focused on the five most common comorbid conditions and their relevant pharmacological therapy. RESULTS AND CONCLUSION: The majority of the studies show that comorbid conditions may include fibromyalgia, systemic myofascial pain and chronic fatigue syndrome, chronic headaches, migraine, heart arrhythmias, endometriosis, interstitial cystitis, irritable bowel syndrome, lower back pain, sleep disorders - insomnia, autoimmune diseases, sleep apnea, noises and irritation in the ear, vulvodynia and mental disorders. The top comorbid conditions reported from people with TMJ syndrome, regardless of status are: anxiety, depression, insomnia, fatigue and pain.

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Authors: Albena Gencheva, Tihomir Georgiev, Hristina Arnautska, Ivan Gonkov, Petyr Chankov, Kamen Nogalchev

AIM: The aim of this research is to demonstrate the necessity of CBCT – examination for evaluation of the surgical approach of high-risk impacted lower third molars. As “high-risk” we defined lower third molars which have signs of proximity to the mandibular canal seen on standard panoramic radiography. MATERIALS AND METHODS: All patients who had undergone a CT examination between September, 2015 and October, 2016 were reviewed. We included images from cone beam computed tomography made in the Department of Radiologic Diagnostics, University Medical and Dental Centre of the Medical University of Varna. The device used was Planmeca ProMax 3D Max with software for images Planmeca Romexis. We chose 100 images randomly. From these images we selected 39 images with high-risk lower third molars. We examined different signs with which we defined the exact position to the mandibular canal of 60 wisdom teeth and we managed to asses the risk of damaging the IAN during a classical odontectomy of these teeth. In the research we included the panoramic radiographs of 20 patients from these 39 cases. RESULTS: From the examination of the CBCT images we found: 28 lower third molars where the mandibular canal runs apical and has contact; 11 where the mandibular canal runs apical in contact with the tooth and penetration of the apices of the tooth is seen; 10 where the mandibular canal runs buccal with contact; 8 where the mandibular canal runs lingual with contact; 3 where the mandibular canal runs between the roots touching one/both of them. In three of the cases we found severe deviation of the root apices. From the examination of the panoramic radiographs we found: 5 cases with darkening of roots in the apical area; 8 with interruption of the white line (lamina dura) of the mandibular canal; 1 with diversion of the mandibular canal with/without narrowing of the mandibular canal; 6 without any of these three signs. CONCLUSION: The development and rapid commercialization of new technologies like CBCT allows us to have precise images and exact diagnosis of the diseases in the oral and maxillofacial area. Our study confirmed the high diagnostic value of CBCT regarding to precise the position of the lower third molars to the mandibular canal and IAN. This gives the clinician the opportunity to determine which lower third molars are “high-risk” teeth and to choose the best method for surgical treatment.

4

Authors: Radosveta Andreeva, Ani Beltcheva

In spite of all the methods of prevention, there still are untreated or improperly treated caries and it’s followed by complications. This often leads to premature loss of teeth. The premature loss of the deciduous teeth depends on different factors such as oral hygiene, traumas, complicated caries. The aim of this study is to compare the OHI-S between children with premature loss and those without premature loss of deciduous teeth. Subject of the monitoring of the clinical research were 140 children between ages 6 and 9. The clinical group consisted of 90 children with prematurely extracted teeth, divided into three groups. The control group consisted of 50 children with intact denture. The oral hygiene status was examined and registered by the Greene-Vermillion index-simplified. There was a statistically significant difference in the OHI-S between the control group (1.86±0.05) and the clinical groups (1.90±0.08 and 2.01±0.05). The children with premature extraction of the primary teeth had higher OHI-S compared to the control group (children without premature extraction of teeth). The third group of children, with prematurely extracted temporary teeth and severe orthodontic deformation, have the highest OHI-S. These results demonstrate the connection between OHI, the orthodontic deformations and the need for prevention.

4

Authors: Tihomir Georgiev, Radosveta Andreeva

The premature extraction of primary teeth of children could be done both under local or under general anesthesia. Тhe method of choice depends on different factors. Dental treatment under GA is an effective way to provide necessary dental care to children with special needs, medically-compromised, cognitively immature, highly anxious. The aim of this study is to compare the average age and the average DMFT index of the children with premature extraction of primary teeth treated under local and under general anesthesia. Subject of monitoring of the research were 60 children. The clinical group consists of 30 children with teeth for premature extraction under general anesthesia and the control group consists of 30 children for premature extraction under local anesthesia. The dental status was examined and registered by the DMFT index. The age of the children was filled out in special registration cards. There was a statistically significant difference in the age and the DMFT index between the first group (4.67±0.26 average age) and second group(4.67±0.26 average age ). The DMFT index for the first (clinical) group is 7.18±0.66 and – 5.17±0.33 for the second (control) group. The results show the connection between the carious activity and the need of prevention in younger children.

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Authors: Elitsa Djongova, Tihomir Georgiev, Karen Dzhabalyan, Radosveta Andreeva, Mariana Dimova-Gabrovska

INTRODUCTION: Bony projections on the inner surface of the maxillary sinus are divided into two main groups: exostoses, which are rounded bone structures, and septa, defined as having a pointed end. Bony septa are common anatomical structures and can lead to complications during sinus augmentation procedures. MATERIALS AND METHODS: The study reports a clinical case of a vertical partial basal bony septum, where upon elevation of the sinus membrane, its perforation was observed (size >5 mm). RESULTS: The present study proposes a method of treatment of perforated sinus membranes.The post-surgical period was uneventful. The bone grafting material remained compact in the sinus augmentation site. CONCLUSIONS: The proposed method for the management of perforated sinus membranes can be applied in surgical procedures for perforations > 5 mm in size.

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Authors: Tsanka Dikova, Dzhendo Dzhendov, Iveta Katreva, Diana Pavlova, Maksim Simov, Svetlana Angelova, Metodi Abadzhiev,Tsvetan Tonchev

The purpose of the present paper is to establish experimentally the possibilities of the 3D printer Rapidshape D30 for the manufacturing of standard cubic samples from different types of monomers and to evaluate their geometrical accuracy and roughness. Standard cubic samples with dimensions 5mm х 5mm х 5mm were printed from all the materials, given by the producer, in two ways of dimensional orientation according to the base – horizontally and inclined at 45о. They were manufactured with 3D printer Rapidshape D30, working on a stereolithography principle with LED light. It was established that: ❖ The samples, made of NextDent Surgical Guide, have the highest dimensional accuracy and the lowest deviation interval in both ways of placement. This polymer is characterized with the highest thickness of the polymerization layer – 0.100 mm, but it is transparent, thus ensuring the entire polymerization throughout the depth of the whole layer. NextDent C+B, intended for manufacturing of temporary crowns and bridges, occupies a middle position in comparison to the other 6 materials. ❖ Nearly in all the materials the surface roughness of the cube with horizontal placement is lower than that of the cube printed inclined (average values of Ra 0.46-2.69µm and Ra 1.74-2.77, respectively). ❖ In 3D printing the surface roughness depends on the thickness of the polymerization layer and the inclination to the printing direction. The thicker the polymerization layer and the larger the slope, the higher the surface roughness.

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Authors: Tihomir Georgiev, Karen Dzhabalyan, Radosveta Andreeva, Krasimira Prodanova

INTRODUCTION: Pneumatization of the maxillary sinus can be triggered throughout a patient‘s life. Prior to any sinus floor augmentation procedure, it is imperative to conduct a linear and volumetric assessment of the maxillary sinus. MATERIALS AND METHODS: The CBCT scans in this randomized retrospective study were selected from 120 patients (50 men and 70 women) to analyze the maxillary sinus dimensions both linearly and volumetrically. RESULTS: The volume of the maxillary sinus was significantly increased in the male patients. Statistically significant differences in the volume of the maxillary sinuses were not observed in dentate or edentulous patients. CONCLUSIONS: CBCT imaging for surgical interventions of the maxillary sinus to assess its volume and size has proven to be an indispensable diagnostic tool.

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Authors: Roussi Minev, Ekaterin Minev

The paper describes the basics of the 3D printing technologies for rapid prototyping (RP). It shows the benefits of their utilization in product design and manufacturing of conventional parts and items with medical and other application. The most mature RP principles are presented and compared. Some trends in developing new 3D printers and corresponding materials for micro/nano and biological applications are described. Some modern budget platforms are suggested for technology users. The paper also provides a summary of the main quality issues in the layering technologies as well as methodologies for studying the process capabilities, accuracy and maturity.