Browsing by Author "Locs, Janis"
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Item Bone Loss around Dental Implants 5 Years after Implantation of Biphasic Calcium Phosphate (HAp/βTCP) Granules(2018) Klimecs, Vadims; Grishulonoks, Alexanders; Salma, Ilze; Neimane, Laura; Locs, Janis; Šauriņa, Eva; Skagers, Andrejs; Department of Doctoral Studies; Department of Oral and Maxillofacial Surgery and Oral Medicine; Rīga Stradiņš University; Statistics UnitBiphasic calcium phosphate ceramic granules (0.5-1.0 mm) with a hydroxyapatite and β-tricalcium phosphate ratio of 90/10 were used. Biphasic calcium phosphate ceramic granules produced in the Riga Technical University, Riga Rudolph Cimdins Biomaterials Innovation and Development Centre, were used for filling the bone loss on 18 patients with peri-implantitis. After 5 years at the minimum, clinical and 3D cone-beam computed tomography control was done. Clinical situation confirmed good stability of implants without any signs of inflammation around. Radiodensity of the previous gap and alveolar bone horizontally from middle point of dental implants showed similar radiodensity as in normal alveolar bone.Item Chemically Pretreated Densification of Juniper Wood for Potential Use in Osteosynthesis Bone Implants(2024-10) Andze, Laura; Ņefjodovs, Vadims; Andzs, Martins; Skute, Marite; Zoldners, Juris; Kapickis, Martins; Dubnika, Arita; Locs, Janis; Vētra, Jānis; Department of Morphology; Institute of Anatomy and AnthropologyThe aim of the study was to perform treatment of juniper wood to obtain wood material with a density and mechanical properties comparable to bone, thus producing a potential material for use in osteosynthesis bone implants. In the first step, partial delignification of wood sample was obtained by Kraft cooking. The second step was extraction with ethanol, ethanol–water mixture, saline, and water to prevent the release of soluble compounds and increase biocompatibility. In the last step, the thermal densification at 100 °C for 24 h was implemented. The results obtained in the dry state are equivalent to the properties of bone. The swelling of chemically pre-treated densified wood was reduced compared to chemically untreated densified wood. Samples showed no cytotoxicity by in vitro cell assays. The results of the study showed that it is possible to obtain noncytotoxic wood samples with mechanical properties equivalent to bones by partial delignification, extraction, and densification. However, further research is needed to ensure the material’s shape stability, water resistance, and reduced swelling.Item Development of local strontium ranelate delivery systems and long term in vitro drug release studies in osteogenic medium(2018-12-01) Loca, Dagnija; Smirnova, Anastasija; Locs, Janis; Dubnika, Arita; Vecstaudza, Jana; Stipniece, Liga; Makarova, Elina; Dambrova, Maija; Faculty of PharmacyIt has been recognized that the operative stabilization of osteoporotic fractures should be followed up with an appropriate osteoporosis treatment in order to decrease the risk of repeated fractures. Despite the good clinical results of strontium ranelate (SrRan) towards the osteoporosis treatment, high drug doses and long treatment period cause an increased risk of serious side effects. Novel local SrRan/poly(lactic acid) (SrRan/PLA) delivery systems containing from 3.57 ± 0.28 wt% to 24.39 ± 0.91 wt% of active substance were developed. In order to resemble the naturally occurring processes, osteogenic media (OM) was used as a release medium for long term (121 days) in vitro drug release studies and UV/VIS method for the determination of SrRan content in OM was developed and validated. Biomimetic calcium phosphate precipitates were found on the surface and in the pores of prepared delivery system after microcapsule exposure to OM for 121 days as well as SrRan particles, indicating that the release of the drug have not been completed within 121 days. In vitro cell viability evaluation approved no cytotoxic effects of microcapsule suspensions and extracts.Item Development of local strontium ranelate delivery systems and long term in vitro drug release studies in osteogenic medium(2018-12-01) Loca, Dagnija; Smirnova, Anastasija; Locs, Janis; Dubnika, Arita; Vecstaudza, Jana; Stipniece, Liga; Makarova, Elina; Dambrova, Maija; Faculty of PharmacyIt has been recognized that the operative stabilization of osteoporotic fractures should be followed up with an appropriate osteoporosis treatment in order to decrease the risk of repeated fractures. Despite the good clinical results of strontium ranelate (SrRan) towards the osteoporosis treatment, high drug doses and long treatment period cause an increased risk of serious side effects. Novel local SrRan/poly(lactic acid) (SrRan/PLA) delivery systems containing from 3.57 ± 0.28 wt% to 24.39 ± 0.91 wt% of active substance were developed. In order to resemble the naturally occurring processes, osteogenic media (OM) was used as a release medium for long term (121 days) in vitro drug release studies and UV/VIS method for the determination of SrRan content in OM was developed and validated. Biomimetic calcium phosphate precipitates were found on the surface and in the pores of prepared delivery system after microcapsule exposure to OM for 121 days as well as SrRan particles, indicating that the release of the drug have not been completed within 121 days. In vitro cell viability evaluation approved no cytotoxic effects of microcapsule suspensions and extracts.Item Effect of Temporary Cement, Surface Pretreatment and Tooth Area on the Bond Strength of Adhesively Cemented Ceramic Overlays—An In Vitro Study(2023-01) Grīnberga, Sanita; Papia, Evaggelia; Aleksejuniene, Jolanta; Zalite, Vita; Locs, Janis; Soboļeva, Una; Department of Prosthetic DentistrySeveral viewpoints have been reported regarding the effect of temporary cements, different surface pretreatment protocols before adhesive cementation, and predictive factors. This in vitro study tested if temporary cement, pretreatment of the tooth surface, the size of enamel or dentine influence adhesive cementation to zirconia ceramics. Twenty premolars were prepared for determination of enamel and dentin area, bond strength test and failure analysis. The samples were divided into two groups: untreated prior adhesive cementation (n = 10) and with temporary cementation done, pretreated prior adhesive cementation (n = 10). Zirconia overlays (Katana Zirconia STML) were cemented on the grounded flat teeth surfaces using Panavia V5. An additional six premolars underwent dentine tubule analysis with SEM to detect temporary cement residues after temporary cementation on an untreated tooth surface (n = 3) and on a pretreated surface (n = 3). The independent sample t-test was used to compare the two groups and the means of the total tooth, dentin or enamel areas did not differ significantly between the untreated and pretreated specimens. The mean tensile bond strength was significantly (p = 0.005) higher in the pretreated specimens (337N) than in the untreated ones (204N). The overall multivariable linear regression model with three predictors (surface pre-treatment, enamel area and dentine area) was significant (p = 0.003), among which the size of enamel was the strongest predictor (β = 0.506; p = 0.049), followed by the pretreatment effect (β = 0.478; p = 0.001) and the size of dentin area (β = −0.105; p = 0.022).Item Radiological evaluation of endodontic treatment of chronic apical periodontitis using biphasic calcium phosphate biomaterial(2018) Kurmanalina, Madina A.; Uraz, Raisa M.; Skagers, Andrejs; Locs, Janis; Taganiyazova, Aliya A.; Omargali, Azamat E.The article is dedicated to the study of the efficacy of the periapical therapy of chronic periodontitis with the use of synthetic calcium-phosphate biomaterial. 30 patients aged from 22 to 56 years participated in a clinical study. Radiological evaluation was performed by radiovisiography and radiodensitometry. Follow-up examination was carried out at 3, 6 and 12 months. Densitometry indicators at the destruction site showed an increase in radiodensity from 74.2 ± 9.9 units (58.2%) to 111.9 ± 10.6 units (87.8%) after 12 months. Anterior group of teeth demonstrated statistically significant high rate of lesion compaction compared to posterior teeth.Item Resin Cement Residue Removal Techniques : In Vitro Analysis of Marginal Defects and Discoloration Intensity Using Micro-CT and Stereomicroscopy(2022-04-01) Gaile, Māra; Papia, Evaggelia; Zalite, Vita; Locs, Janis; Soboļeva, Una; Department of Prosthetic DentistryThe objective was to compare marginal defects and evaluate discoloration for adhesively cemented veneers in vitro when using two cement removal techniques. Twenty premolars were prepared with chamfer and borders in enamel. IPS e.max CAD veneers were cemented using Panavia V5 and divided in two groups (n = 10): cement excess removed with a probe after tack-curing for 3–5 s, or cement excess removed with a brush, then completely polymerized. All teeth were stored in alginate gel until micro-CT examination. Scanning was performed twice: directly after cementation and after thermocycling (5000 cycles, between 5 and 55◦ C). To analyze discoloration, teeth were colored using 0.5% basic fuchsine and examined under a stereomicroscope. Depth of dye infiltration was scored 0 (no discoloration) to 5 (discoloration along the entire margin). Statistically significant differences of cement defects before thermocycling were reported, where brushing showed more defects than probing (p = 0.0161). After thermocycling, the defects increased for both groups. Extensive discoloration was the most common (55.56%) when removing excess by probing; by brushing, 90% of the specimens exhibited slight discoloration (p = 0.008). Regression analysis showed no relationship between type of defect and degree of discoloration. Removing cement with a brush causes more marginal defects, however less discoloration after thermocycling.Item The role of Strontium enriched hydroxyapatite and tricalcium phosphate biomaterials in osteoporotic bone regeneration(2019-02-01) Zarins, Janis; Pilmane, Mara; Sidhoma, Elga; Salma, Ilze; Locs, Janis; Institute of Anatomy and Anthropology; Department of Oral and Maxillofacial Surgery and Oral MedicineBackground: Strontium (Sr) enriched biomaterials have been used to improve bone regeneration in vivo. However, most studies provide only two experimental groups. The aim of our study was to compare eleven different bone sample groups from osteoporotic and healthy rabbits' femoral neck, as it is the most frequent osteoporotic fracture in humans. Methods: Osteoporotic bone defects were filled with hydroxyapatite 30% (HA) and tricalcium phosphate 70% (TCP), 5% Sr-enriched HA 30 /TCP 70 , HA 70 /TCP 30 , or Sr-HA 70 /TCP 30 granules and were compared with intact leg, sham surgery and healthy non-operated bone. Expression of osteoprotegerin (OPG), nuclear factor kappa beta 105 (NFkB-105), osteocalcin (OC), bone morphogenetic protein 2/4 (BMP-2/4), collagen I (Col-1α), matrix metalloproteinase 2 (MMP- 2), tissue inhibitor of matrix metalloproteinase 2 (TIMP-2), interleukin 1 (IL-1) and interleukin 10 (IL-10) was analyzed by histomorphometry and immunohistochemistry. Results: Our study showed that Sr-HA 70 /TCP 30 induced higher expression of all above-mentioned factors compared to intact leg and even higher expression of OC, MMP-2 and NFkB-105 compared to Sr-HA 30 /TCP 70 . HA 70 /TCP 30 induced higher level of NFkB-105 and IL-1 compared to HA 30 /TCP 70 . Conclusion: Sr-enriched biomaterials improved bone regeneration at molecular level in severe osteoporosis and induced activity of the factors was higher than after pure ceramic, sham or even healthy rabbits.