International Poster Journal of Dentistry and Oral Medicine, 04/2008

Purpose: The purpose of this study was to evaluate the influence of miniscrew implant diameter and length on the stress distribution in bone and implant using finite element analysis. Materials and Methods: Sixteen finite element models featuring miniscrew implants of various sizes (1.2, 1.4, 1.6 and 1.8 mm in diameter and 6, 8, 10 and 12 mm in length) and surrounding bone were created and loaded with 50 cN force perpendicular to the long axis of the implant in order to investigate resultant stress distribution. Results: Patterns of stress distribution were identical in all models. Stresses were concentrated mainly around the cervical portion of the body of miniscrews. The increase in the miniscrew's diameter resulted in a linear decrease of the stresses values in both the screw and bone, whereas the increase in length of miniscrew showed not significant changes in the stress values. Conclusions: The results of this study suggest that the wider diameter miniscrew implants might ensure a better biomechanical environment for miniscrews. The length of miniscrews did not alter the biomechanical properties of miniscrews inserted in the bone. Keywords: miniscrew implants, orthodontics, anchorage, stress distribution, FEM

The aim of the present study was to evaluate the influence different bleaching agents and concentrations on microtensile bond strength of different dentin adhesives in class V cavities. 135 freshly extracted third molars were included in this study. In all teeth cervical class V dentinal cavities were prepared allowing the simulation of dentin perfusion. The specimens were randomly assigned to nine experimental groups of fifteen each: S0: Syntac/ control; S17: Syntac/ Perfect Bleach 17%; S38: Syntac/ Opalescene Xtra Boost 38%; X0: XP Bond/ control; X17: XP Bond/ Perfect Bleach 17%; X38: XP Bond/ Opalescene Xtra Boost 38%; A0: AdheSE One/ control; A17: AdheSE One/ Perfect Bleach 17%; A38: AdheSE One/ Opalescene Xtra Boost 38%. Bleaching was performed 8 hours at 36°C for 7 days. Between the ranges all samples were stored in physiological saline for 16 hours. The dentin adhesives used as recommended by manufactures instruction were applied on a standardized dentin surface. Microtensile bond strengths of the above mentioned bonding agents was measured using a universal testing machine. For the nine test series following tensile bond strengths were evaluated (mean values and standard deviations in MPa): GroupS0S17S38X0X17X38A0A17A38 Microtensile bond strength25,8921,4417,0822,1518,9914,6124,3318,9717,29 ±2,972,051,943,532,962,246,942,795,78 Keywords: Dentinadhesive, Mikrozugfestigkeit, Bleichtherapie, dentin adhesive, microtensile bond strength, Tooth bleaching

Objective: To detect chodroitin-6-sulfate (C-6-S) in peri-miniscrew implant crevicular fluid (PMICF) under orthodontic forces. Materials and Methods: Two experiments were carried out. The first experiment period was five weeks. Five male patients, aged 22.0 ± 2.9 years and with four premolars extracted, comprised the first experiment. Ten miniscrew implants were placed buccally, bilaterally, in the alveolar bone between the roots of maxillary posterior teeth. Sentalloy closed-coil springs (50 g) were used to load the miniscrew implant and to move the maxillary canines distally. During the unloaded period, PMICF samples were collected on days 1, 3, 5 and 7 after miniscrew implant placement; and on days 14, 21, 28 and 35 during the loaded period. The second experiment period was ten weeks. Three female and two male patients, aged 20.0 ± 1.9 years and with four premolars extracted, comprised the second experiment. Ten miniscrew implants were used as anchorage. During the loaded period, the PMICF samples were collected on days 14, 21, 28, 35, 42, 49, 56, 63, and 70. Clinical mobility assessments of the miniscrew implants were recorded at every visit. The competitive ELISA with WF6 monoclonal antibody was used to detect C-6-S levels in the PMICF samples. Results: In the first experiment, the C-6-S levels during the unloaded period ranged from 0.00 to 58.53 ng/ml, and those during the loaded period ranged from 0.00 to 679.89 ng/ml. Median values of C-6-S levels during the loaded period were significantly higher than those during the unloaded period (P = 0.008). In the second experiment, the C-6-S levels during the unloaded period ranged from 0.00 to 758.03 ng/ml, and those during the loaded period ranged from 0.00 to 6,348.90 ng/ml. Median values of C-6-S levels between the unloaded and loaded periods were not significantly different. We noticed that one miniscrew implant failed at day 70. Interestingly, the C-6-S level in PMICF around that particular miniscrew implant was dramatically elevated 14 days earlier. Conclusions: The C-6-S levels could be precisely detected in PMICF. To draw a reasonable conclusion for using the C-6-S level as a biomarker for assessing alveolar bone remodeling around miniscrew implants, further investigation with an increased sample size is needed. Keywords: miniscrew implants, peri-miniscrew implant crevicular fluid, chondroitin-6-sulfate

Introduction: Dental alloys structural analyses are important in order to obtain quality prosthetic pieces. The defects appeard in removable partial dentures metallic components are in connection with the casting, processing and welding. Objectives: The aim of study was to offer the casting, processing and welding optimal parameters for some long lasting prosthetic pieces. Material and Method: CoCrMo alloys were used. Alloys, different castings and metallic compounds laser and micropulse weldings were tested. Radiographic, metallographic and microhardness analyses methods were used. Results: Noninvasive analyses methods point out casting alloys structural defects, distinguish the cracks within the base material. Structural analyses present dendritic structure specific for casted alloys, non-metallic inclusions and some temporary particles. Intergranular pellicular precipitations and spherical shape compounds placed inside the crystalline graines appear on some weldings. Welded area alloys chemical composition discreetly differs from the base material. Conclusions: Dental alloys structural analyses are important for structural defects knowledge. The cracks appear mostly on base material, being caused by casting, non-adequat processing and rapid cooling welding. Keywords: CoCrMo metallic alloys, structural analyses, removable partial dentures

Introduction: The study utilizes noninvasive experimental methods to evaluate the removable partial denture framework stress and distortion areas in order to solve some conception and execution deficiencies. Materials and Methods: There were tested 30 "LiWa" (WP Dental, Beven/Hamburg Germany) wax-patterns and 30 removable partial denture metallic frameworks. They were 3D laser scanned with a LPX 1200 (Roland DG Corporation). Scanned wax-patterns were processed using "Pixform Pro" (Roland DG Corporation) program. They are exported as DXF files and imported by a CAD program Mechanical Engineering Software -SolidWork 2007 (SolidWork Corporation West). Results: The 3D models were used for simulation of external force actions on some RPD components. Wax-pattern or metallic framework stress and deformation analysis allow the distinguish of minimal mechanical strength. Conclusions: Removable partial denture testing, at wax-pattern stage is benefit for determination of the states of tensions, minimum resistance areas, distinguish and appreciation the life time of future dentures. Keywords: finite element analysis, LiWa-wax pattern, removable partial denture

Objectives: Assessment of patient-related factors contributing 1) to tooth loss and 2) to the quality of treatment outcome 10 years after initiation of anti-infective therapy. Methods: All patients who had received active periodontal treatment 10 years ago by the same examiner were recruited consecutively until a total of 100 patients was re-examined. Re-examination was performed by a second examiner and included: clinical examination, test for interleukin-1 polymorphism (IL-1), smoking history, review of patients' files (i.e. regularity of supportive periodontal therapy: SPT). Statistical analysis included Poisson and logistic regressions. Results: Fifty-three patients attended SPT regularly, 59 were females, 38 were IL-1 positive. Poisson regressions identified mean plaque index during SPT, irregular attendance of SPT, gender (p = 0.0001), initial diagnosis (p = 0.0005), IL-1 polymorphism (p = 0.0007), smoking (p = 0.0053), and age (p = 0.0487) as factors significantly contributing to tooth loss. Additionally mean plaque index during SPT (p = 0.011) and irregular SPT (p = 0.002) were associated with a worse periodontal status 10 years after initiation of therapy. Conclusion: The following risk factors for tooth loss were identified: ineffective oral hygiene, irregular SPT, IL-1 polymorphism, initial diagnosis, smoking, age, and gender. Keywords: long-term results, periodontal therapy, prognosis

Periodontal diseases are inflammatory disorders that give rise to tissue damage and loss, as a result of complex interactions between pathogenic bacteria and the host's immune response. There is an increasing body of evidence available to implicate reactive oxygen species (ROS) in the pathogenesis of a variety of inflammatory disorders, of which periodontal disease is no exception. Mammalian cells can generate ROS by different biologic mechanisms, such as mitochondrial respiratory chain and polymorphonuclear (PMN) activation in inflammation. It might be expected that ROS-mediated damage to mitochondria may inactivate electron transport complexes or inhibit mtDNA transcription thereby altering normal mitochondrial function. Any cellular insult that leads to disruption of the electron transport chain could lead to an increase in mitochondrial-generated ROS which may lead to the destruction of extracellular matrix components as seen in periodontitis. As there is no comprehensive study on the impact of mtDNA mutations in Periodontotitis, this study was initiated to understand the possible association of mtDNA in causing Periodontitis. Keywords: periodontitis, mitochondrial DNA, mutations

Rheumatic diseases and periodontitis are sharing similar pathophysiological features. It is assumed that periodontopathogens could influence the aetiology of rheumatic diseases. However, the underlying pathomechanisms are still unknown. Therefore, we established a specific and sensitive method based on molecular techniques to detect 5 major periodontopathogens, Actinobacillus actinomycetemcomitans (A.a.), Porphyromonas gingivalis (P.g.), Prevotella intermedia, Treponema denticola, Tannerella forsythensis in synovial fluid. Methods: Nine patients suffering from juvenile idiopathic arthritis or rheumatoid arthritis, respectively, were included in this study. DNA from synovial fluid of affected knee joints was isolated by QiaAmp-kit (Qiagen, Hilden, Germany) using an adapted protocol. PCRs specific for the 16S rRNA genes of these bacteria were developed. For positive control of DNA preparation the samples were spiked with E.coli strain XL2B. Subgingival bacterial colonization was analysed using micro-Ident® test (HAIN-Diagnostik, Nehren, Germany). Results: The PCR was optimized in order to detect up to 10 DNA copies of each periodontopathogen. DNA of 2 periodontophatogens, A.a. and P.g., was detected in synovial fluids of two different patients suffering from both juvenile idiopathic arthritis and periodontitis. In the same patients a subgingival infection with P.g. but not A.a. could be detected. Conclusions: For the first time a highly sensitive molecular based detection system was adapted for the identification of periodontopathogens in synovial fluid. The application of this method allows a better understanding of the interaction of periodontitis and rheumatic diseases. The revealed first results indicate that periodontopathogens may play a role in the pathway of rheumatic diseases. Keywords: periodontitis, rheumatic disease, periodontopathic bacteria

Background: Bone quality plays an important role in the success of orthodontic miniscrew implants. The mechanical properties of bone are highly related to the mineral content, which varies widely according to function and histology. However, in vitro methods for evaluating biomechanical properties of miniscrew implants have not been reported. Purpose: The aim of this study was to assess the biomechanical performance of miniscrew implants using bone samples which were demineralized by timed chemical immersion to alter the mineral content. Materials and Methods: Sections of fresh rib bones from adult pigs were selectively demineralized by timed immersion in 1 % ethylenediamine-tetraacetic (EDTA). Specimens were removed from the solution after 0 (control), 6, 10, 16, 30 and 50 days and embedded in acrylic blocks. Quantification of bone density was performed using radiographic images processed with Photoshop software. Fifty miniscrew implants (8 mm long and 1.6 mm in diameter, BKM, Korea) were inserted. Maximum insertion torque was recorded with a toque gauge. Pullout strength was tested using an Instron Universal testing machine. Statistical analysis was performed using Kruskal-Wallis Test and Spearman correlation coefficients. Results: There was a systematic decrease in bone density that was followed by a significant decrease in the biomechanical properties of the miniscrews. High correlation (r = 0.91) was observed between maximum insertion torque and maximum pullout strength. Conclusions: The biomechanical properties of miniscrew implants can be evaluated in vitro using bones obtained from a single species prepared with the selectively demineralized bone technique. The proposed method can be used to facilitate comparison between different miniscrew implant systems, avoiding the inaccuracy observed in conventional methods. Keywords: miniscrew implants, orthodontics, biomechanics, in vitro