A Comparison of Biomechanical Properties of Implant-Retained Overdenture Based on Precision Attachment Type.

This paper aims to compare, in vitro, the biomechanical properties of an overdenture retained by two bar-retained implants and an overdenture retained by two bar-retained implants with ball attachments. An edentulous mandible model was prepared for the study based on the FRASACO mold with two implants. In the first system, the "rider" type (PRECI-HORIX, CEKA) retention structure and the complete mandibular denture with the matrix were made. In the second system, the "rider" type retention suprastructure was also used. In the distal part, (CEKA) clips were placed symmetrically, and a complete mandibular denture, together with the matrix on the bar, and the clip patrices were made. A numerical model was developed for each system where all elements were positioned and related to geometric relations, as in reality. The FEA analysis (finite element analysis) was carried out for seven types of loads: with vertical forces of 20, 50, and 100 N and oblique forces of 20 and 50 N acting on individual teeth of the denture, namely central incisor, canine, and first molar. Displacements, stresses, and deformations within the systems were investigated. Maximum denture displacement in the first system was 0.7 mm. Maximum bar stress amounted to 27.528 MPa, and implant stress to 23.16 MPa. Maximum denture displacement in the second system was 0.6 mm. Maximum bar stress amounted to 578.6 MPa, that of clips was 136.99 MPa, and that of implants was 51.418 MPa. Clips cause smaller displacement of the overdenture when it is loaded but generate higher stress within the precision elements and implants compared to a denture retained only by a bar. Regardless of the shape of the precision element, small deformations occur that mainly affect the mucosa and the matrix.

Effects of a hydroxyapatite coating on the stability of endosseous implants in rabbit tibiae.

BACKGROUND: A dental implant surface which would promote rapid and strong osseointegration is a key factor of success in modern implantology. To achieve this goal, different implant surface modifications are developed. A hydroxyapatite (HA) coating changing a bioinert titanium surface into bioactive is one of them. OBJECTIVES: The objective of the study was to investigate the effects on bone osseointegration in rabbits resulting from the application of a HA coating deposited on titanium endosseous implants using a modified electrochemical method. MATERIAL AND METHODS: Titanium implants with HA coatings and controls with Al2O3 grit-blasted surfaces were embedded into rabbit tibiae. The chemical composition, roughness and morphology of the implants were determined. Implant stability tests were performed, and the Periotest® value (PTV) and the implant stability quotient (ISQ) value for Osstell Mentor were recorded in order to evaluate the osseointegration. RESULTS: The surface characterization of the implants revealed a microstructure with an arithmetical mean height (Sa) in the range of 0.71-1.04 µm. The HA coating was free of contamination, whereas the controls were enriched with corundum. After healing, a statistically significant increase in the mean ISQ and a decrease in the mean PTV for the HA-coated implants was observed. In the case of the control implants, only PTV decreased significantly with time. CONCLUSIONS: The present study found that implant surface properties affected implant stability as determined by Osstell and Periotest measurements. The HA coating reported herein was found to have chemical and physical properties which appear to improve osseointegration compared to grit-blasted implants.

Hydroxyapatite coating on titanium endosseous implants for improved osseointegration: Physical and chemical considerations.

BACKGROUND: For many years, hydroxyapatite (HA) has been used as a bioactive endosseous dental implant coating to improve osseointegration. As such, the coating needs to be of high purity, adequate thickness, crystalline, and of a certain roughness in order to stimulate rapid fixation and form a strong bond between the host bone and the implant. There are a number of ways of preparing the HA coating, resulting in various coating properties. Herein, we report the preparation of the HA coating using a direct electrochemical method without the need for subsequent heat treatment. OBJECTIVES: The aim of this study was to investigate the physicochemical properties of the HP coating, deposited on titanium implants by a modified electrochemical method. MATERIAL AND METHODS: The coating was characterized in terms of surface chemical composition, structure, morphology, coating thickness and roughness. RESULTS: The coating was found to be composed of homogenous HA with Ca/P and Ca/O ratios of 1.62 and 0.35, respectively. No other forms of calcium phosphate were detected. The degree of crystallinity of HA was 92.4%. The surface roughness was moderate (Sa = 1.04 µm) with the coating thickness of 2-3 µm. The scanning electron microscopy (SEM) analysis revealed a uniform, integrated layer of rod-like HA crystals with the longitudinal axes parallel to the implant surface. CONCLUSIONS: The coating reported herein was found to have potentially favorable chemical and physical characteristics fostering osseointegration.

Temporomandibular disorders in adolescents with headache.

BACKGROUND: Headache is a common complaint in all age groups and is a frequent cause of medical consultations and hospitalization. OBJECTIVES: The aim of this study was to evaluate the prevalence of bite and non-bite parafunctions as well as the signs and symptoms of temporomandibular disorder (TMD) in adolescents presenting with primary headaches. MATERIAL AND METHODS: Parents of adolescents presented with headaches to the Department of Developmental Neurology within a 12-month period were asked to complete a questionnaire developed by the authors of this study. Of the 1000 patients evaluated, 19 females and 21 males, aged 13 to 17 years, met the inclusion criterion - a confirmed clinical diagnosis of migraine or a tension headache according to the International Classification of Headache Disorders, 2nd edition. The diagnostic algorithm of the study group consisted of a full medical history, an assessment of the occurrence of bite habits and a physical examination based on the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). RESULTS: Bite and non-bite parafunctions were found in 36 of the study group patients. A significant difference (p = 0.0003) between the number of bite parafunctions and non-bite parafunctions was found in females but not in males. However, bite parafunctions were more frequent in boys compared to girls (p = 0.01). CONCLUSIONS: Our findings suggest that it may be useful for pediatricians and neurologists to include TMD dysfunctions as a part of a standard examination of adolescents presenting with persistent headaches.

Relations between the results of complex clinical and neurophysiological examinations in patients with temporomandibular disorders symptoms.

OBJECTIVE: Reinvestigation of clinical importance of surface electromyography recordings (sEMG) from the masticatory, neck and shoulder girdle muscles in patients with various clinically detected temporomandibular disorders (TMDs). METHODS: Fifty women with myalgia diagnosis of Axis I DC/TMD and the same number of healthy female volunteers were studied clinically and neurophysiologically by means of sEMG. RESULTS: Unilateral more than bilateral complex symptoms of TMDs were related to the non-neurogenic masticatory rather than neck and shoulder girdle muscles dysfunctions at rest. A strong negative correlation between masticatory muscles activity at rest and during maximal contraction was found (rs = -0.778), mainly in the masseter muscle. CONCLUSION: sEMG is a suitable tool for prosthodontists because it provides objective results on the stomatognathic system muscles function. Pain and other temporomandibular symptoms detected mostly unilaterally significantly increase muscle tension of the masticatory muscles and diminish muscle motor units recruitment during maximal contraction. Effects may spread to the neck and shoulder girdle muscles.

The electrical properties and glass transition of some dental materials after temperature exposure.

The physicochemical properties of dental materials will remain stable only when these materials in question are resistant to the changes in the oral cavity. The oral environment is subject to large temperature variations. The aim of the study was the assessment of electrical properties and glass transition of some dental materials after temperature exposure. Composite materials, compomers, materials for temporary prosthetic replacement and resin-based pit and fissure sealants were used in the study. The method used was electric conductivity of materials under changing temperature. The order of materials presenting the best characteristics for insulators was as follows: materials for temporary prosthetic replacement, resin-based pit and fissure sealants, composites, and compomers. Thanks to comparisons made between graphs during I and II heating run, the method could be used to observe changes in the heated material and determine whether the changes observed are reversible or permanent. The graphs also provided temperature values which contain information on glass transition during heating. In the oral cavity the effect of the constant temperature stimulus influences maturity of dental materials and improves their properties. But high temperatures over glass transition temperature can cause irreversible deformation and changes of the materials properties, even in a short time.

Photofunctionalization of dental zirconia oxide: Surface modification to improve bio-integration preserving crystal stability.

The use of zirconium oxide in dental implantology is rapidly increasing as it is regarded as being more aesthetical and biologically friendly than titanium oxide. The interaction of titanium oxide with cells and proteins has proven to be significantly affected by the inevitable atmospheric hydrocarbon contamination, defined as biological ageing. The latter has proven to be effectively reversed by UVC irradiation. Crystal structures of both Zr and Ti oxides are very similar, thus also ZrO2 is prone to contamination by hydrocarbons. In the present study we have characterized the chemical-physical changes occurring to ZrO2 after UVC irradiation. Firstly a reduction by 3-fold of carbon present on its surface. XRD analysis has indicated that UVC irradiation treatment does not affect the crystalline structure of ZrO2, suggesting that it is possible to improve cell attachment on the surface without sacrificing the mechanical strength of the material. In addition a chemical model of interaction of cell surface proteins with the almost carbon free ZrO2 surface obtainable after UVC irradiation is proposed, pointing to the important role likely played by integrins and RGD sequences originating in soluble proteins adsorbed at the cell/ZrO2 interface. Hence in clinical practice UVC photofunctionalization could improve the soft tissue seal around dental implants functioning as a valid barrier between implant and peri-implant bone, thereby improving the long-term success of implants.

Evaluation of Mandibular Movement Functions Using Instrumental Ultrasound System.

PURPOSE: The article deals with routinely performed instrumental temporomandibular joint (TMJ) examinations and interpretation of findings obtained from the Arcus Digma ultrasound device in individuals with or without clinical symptoms of temporomandibular disorders (TMD). The aim of this study was to analyze mandibular movement functions and the relationship between incisors and condylar movement parameters during jaw opening, which may be helpful for clinical evaluation in these patients. MATERIALS AND METHODS: The study group consisted of 84 young students with no dental problems and other serious acute or chronic diseases in the medical history; the students were examined both clinically and with the Arcus Digma ultrasound device. RESULTS: Helkimo Di = I was the most common score in 49 participants, and Helkimo Di = II in a significantly (p < 0.01, Di = I vs. Di = II) smaller number of participants. Medical history revealed symptoms of unilateral mastication in 15 participants and a statistically significant increased (p < 0.02, participants with symptoms of unilateral mastication vs. asymptomatic) condylar range of motion parameter during retrusion. Also a significant decrease (p < 0.03, participants with symptoms of unilateral mastication vs. asymptomatic) of the incisal and condylar ranges of motion during mouth opening was found. Limitation of mouth opening, defined as a decrease of inter-incisal distance, appeared in 19 participants (22.6%) and in 25 participants (29.8%) measured instrumentally with the Arcus Digma device. A comparison of instrumental result examinations of the right and left TMJs showed positive correlations of the range of mandible opening movement with the Posselt opening movement (r = 0.75) and opening/closing movements with the Posselt closing movements (r = 0.70). A correlation was demonstrated (r = 0.81) between the condylar range of motion studied on the left and on the right TMJ during mandible opening movement. Correlations were also found between opening-closing movements and the condylar range of motion of the left TMJ, and between the opening-closing movement and the condylar range of motion of the right TMJ during the opening movement. CONCLUSIONS: According to the results of this study with instrumental Arcus Digma ultrasound device measurements of mandibular movements, data were provided on irregularities in TMJ function not detected in participants with or without clinical symptoms of TMD.

Photofunctionalization of Titanium: An Alternative Explanation of Its Chemical-Physical Mechanism.

OBJECTIVES: To demonstrate that titanium implant surfaces as little as 4 weeks from production are contaminated by atmospheric hydrocarbons. This phenomenon, also known as biological ageing can be reversed by UVC irradiation technically known as photofunctionalization. To propose a new model from our experimental evidence to explain how the changes in chemical structure of the surface will affect the adsorption of amino acids on the titanium surface enhancing osteointegration. METHODS: In our study XPS and AES were used to analyze the effects of UVC irradiation (photofunctionalization) in reversing biological ageing of titanium. SEM was used to analyze any possible effects on the topography of the surface. RESULTS: UVC irradiation was able to reverse biological ageing of titanium by greatly reducing the amount of carbon contamination present on the implant surface by up to 4 times, while the topography of the surface was not affected. UVC photon energy reduces surface H2O and increases TiOH with many -OH groups being produced. These groups explain the super-hydrophilic effect from photofunctionalization when these groups come into contact with water. SIGNIFICANCE: Photofunctionalization has proven to be a valid method to reduce the amount of hydrocarbon contamination on titanium dental implants and improve biological results. The chemisorption mechanisms of amino acids, in our study, are dictated by the chemical structure and electric state present on the surface, but only in the presence of an also favourable geometrical composition at the atomical level.

Selected applications of Er:YAG and CO2 lasers for treatment of benign neoplasms and tumorous lesions in the mouth.

INTRODUCTION: Benign neoplasms and hyperplastic tumorous lesions are common oral pathologies. These lesions require to be surgically removed by conventional surgery, laser, or electrosurgery. Surgical treatment aims at complete removal of pathological lesions and ensuring proper healing of the tissues to minimize the risk of lesion recurrence. AIM: To present possible applications of Er:YAG and CO2 lasers in removal of benign neoplasms and tumorous lesions developing on oral mucosa as well as to specify indications and limitations of these two methods. MATERIAL AND METHODS: Temperature-induced injuries due to laser light application, possibility of post-operative histopathological evaluation of the removed tissue, efficacy of the cut and coagulation, healing process and completeness of laser surgeries give rise to our special concern. RESULTS: The main asset of the CO2 laser comparing to Er:YAG laser is an effective coagulation while thermal injury to the tissues is its limitation, especially with multiple passage of the beam and too high power applied. Er:YAG laser application does not exclude histopathological examination of the removed lesion tissue which is its advantage over CO2 laser. CONCLUSIONS: Still, insufficient coagulation is a limitation ofits use in the case of richly vascularized lesions.

Candida-associated denture stomatitis in type 2 diabetes mellitus.

OBJECTIVE: To describe the clinical appearance of Candida-associated denture stomatitis (DS) in subjects with type 2 diabetes (T2DM). The relationships between the types of DS, oral complaints and associated conditions were assessed in terms of glycemic control as determined by glycated hemoglobin (HbA1c) measurements. MATERIALS AND METHODS: Demographic and clinical data were obtained from questionnaires and oral examinations of 110 edentulous patients with T2DM and 50 control subjects. RESULTS: Type II DS commonly occurred in diabetics (57.3% vs 30%; p=0.002) together with DS related oral complaints (60.9% vs 24%; p<0.001) compared with controls. Burning sensation of the mouth (BS) was the most common complaint. Dryness of the oral mucosa (DOM) (50.9% vs 6%; p<0.001), angular cheilitis (26.4% vs 8%; p=0.01) and glossitis (27.3% vs 6%; p=0.003) occurred more frequently in diabetics. Oral complaints and associated conditions of DS coincided with elevated HbA1c levels (p<0.001). Diabetics with extensive type of inflammation had higher HbA1c levels than type I/III DS subjects (p<0.001). CONCLUSIONS: Diffuse type of inflammation was associated with T2DM. BS and DOM were the most common oral complaints. Inadequately controlled diabetes with Candida-associated DS was linked to a high incidence of an extensive type of inflammation, oral complaints and associated conditions.

Mechanical strength of an acrylic resin palatal denture base reinforced with a mesh or bundle of glass fibers.

The aim of this pilot study was to evaluate the mechanical strength of an acrylic resin palatal denture base reinforced with a mesh or bundle of glass fibers. Silicon and stone casts of an edentulous maxilla (Frasaco) were used to manufacture palatal denture bases (n = 20) using heat-polymerized acrylic resin (SR Triplex Hot). The denture bases were reinforced with either 1 or 3 layers of glass-fiber mesh (Stick Net) or with a bundle of unidirectional glass fibers (Stick). Denture bases without reinforcement served as the control group. Fracture tests were carried out on a universal testing machine to determine each material's mechanical strength. The highest mean fracture values of 919 N were obtained in samples with 3 layers of Stick Net, with mean values of 677 N in the control samples. The differences between these 2 groups were statistically significant (P < .05). The applied glass-fiber reinforcement increased the mechanical strength of the acrylic resin palatal denture bases.

Specialisation and specialist education in prosthetic dentistry in Europe.

This presentation reports on the results of a meeting of prosthodontists from selected European countries. The aim of the meeting was to analyse and promote specialisation and specialist education in Prosthetic Dentistry in Europe. Representatives for Europe were selected from the European Prosthodontic Association (EPA) board, the Education and Research Committee of International College of Prosthodontists (ICP), countries with a legally recognised speciality, countries without a recognised speciality but organised training programmes and countries with neither of these situations. Data about specialisation and specialist training in Prosthodontics in Europe was scrutinised and discussed. The programmes for countries with specialist training had relatively similar content, mostly of three years duration. There was strong agreement that a recognised speciality raises the level of care within the discipline for both specialists and non-specialists. In several of the countries where a speciality had been introduced it had been initiated by pressure from public health planning authorities. The conclusions are that from a professional viewpoint an advancement of the speciality over Europe would develop the discipline, improve oral health planning and quality of patient care. A working group for harmonisation was recommended.

Comparison of mechanical strength of palatal denture bases made from various plastic materials.

PURPOSE: The aim of the study was to compare the mechanical strength of palatal denture bases made from various plastic materials. MATERIALS AND METHODS: A form and models of an edentulous jaw (Frasaco) were used in the study. The denture bases were made from Zhermacryl H Plus and SR Ivocap Plus (both acrylic resins) and the polyurethane Microbase. Five samples were fabricated for each of the studied polymers. The fracture tests were carried out on a universal testing machine (Hounsfield H5KS). RESULTS: The highest fracture values were assessed on Ivocap specimens. The indicated differences between acrylic resin specimens made of Ivocap and Zhermacryl were not statistically significant. In turn, the differences shown between 2 acrylic resin palatal denture bases and the Microbase were statistically significant (P < .05). CONCLUSION: In this study, samples made from an alternative denture base polymer showed poorer mechanical strength as compared with those made of polymethylmethacrylate.