Publications by authors named "Čedomir Oblak"

7 Publications

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One-Year Results Assessing the Performance of Prosthetic Rehabilitations in the Posterior Maxilla Supported by 4-mm Extrashort Implants Splinted to 10-mm Implants: A Prospective Case Series.

Int J Oral Maxillofac Implants 2021 Mar-Apr;36(2):371-378

Purpose: The aim of this study was to evaluate the survival and success rates of oral rehabilitations in a shortened maxillary dental arch and expanded maxillary sinus with 4-mm extrashort implants splinted to longer ones.

Materials And Methods: One 10-mm and one/two extrashort 4-mm titanium-zirconium SLActive tissue-level dental implants were inserted into 11 patients with limited vertical bone availability due to an expanded maxillary sinus antrum. Immediately and 6 months after insertion, implant stability resonance frequency analysis (RFA) values were assessed with an Osstell device. Splinted crowns combining 4- and 10-mm implants were supplied to all 11 cases.

Results: In 10 cases, the bone quality was type III, and in one case, type IV. Among 17 4-mm and 11 10-mm implants, the median RFA values were 61 (interquartile ranges [IQR]: 59 to 64) and 66 (IQR: 64 to 72). One 4-mm implant failed to osseointegrate and was removed. After 6 months of healing, secondary-stability measurements of 16 of the remaining 4-mm implants increased to 68 (IQR: 62 to 72) and of 10-mm implants to 78 (IQR: 77 to 80). After 1 year, all (11/11) oral rehabilitations supported by 10-mm (11/11) and 4-mm (16/16) implants were functional. The medians and IQRs of the probing depths (median: 2.8 mm, IQR: 2.3 to 3.1 mm vs median: 2.9 mm, IQR: 2.4 to 3.1 mm) and the crestal bone loss (median: 0.75 mm, IQR: 0 to 0.9 mm vs median: 0.22 mm, IQR: 0 to 0.4 mm) for the 10-mm and 4-mm implants, respectively, were similar.

Conclusion: Rehabilitations with splinted crowns combining 4- and 10-mm implants demonstrated a favorable 1-year performance in a shortened maxillary dental arch.
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http://dx.doi.org/10.11607/jomi.8645DOI Listing
April 2021

Clinical evaluation of monolithic zirconia multiunit posterior fixed dental prostheses.

J Prosthet Dent 2021 Apr 23. Epub 2021 Apr 23.

Assistant Professor, Department of Prosthodontics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.

Statement Of Problem: Monolithic zirconia restorations have been evaluated with in vitro studies, but limited clinical evidence of their longevity and reliability is available.

Purpose: The purpose of this clinical study was to evaluate the clinical performance of posterior multiunit glazed monolithic zirconia fixed dental prostheses.

Material And Methods: A total of 20 participants received 33 monolithic posterior zirconia fixed dental prostheses (Zolid white; Amann Girrbach AG) with minimally invasive preparations. Bilaterally supported fixed dental prostheses with a connector area of at least 9 mm were luted with resin-modified glass ionomer cement. The clinical evaluations were performed after 1 week, 6 months, and then annually after completion of the treatment. The biologic outcomes were evaluated by assessing the pocket depth, attachment level, plaque control, bleeding on probing, caries, and tooth vitality. Esthetics and the functional performance of the prostheses (color match, cavosurface marginal discoloration, anatomic form, marginal adaptation) were evaluated as per the rating scales of Cvar and Ryge. An analysis of survival was made by using the Kaplan-Meier method.

Results: After 39.8 ±16.7 months of observation, the overall survival rate of the monolithic zirconia multiunit posterior prostheses was 93.9%. No caries were found on the abutment teeth, signs of gingivitis were noted in 1 participant after 24 months, and increased probing depths of the abutment teeth were detected in 5 prostheses (15.1%). No loss of retention was detected. Two prostheses had to be replaced: 1 because of a biologic complication and 1 because of a technical complication. The remaining 31 prostheses received Alfa scores for marginal adaptation, cavosurface marginal discoloration, and caries. Twenty-seven (87.1%) prostheses were rated as Alfa and 4 (12.9%) as Bravo for anatomic form. The color match was noted as Alfa in 15 (48.3%) prostheses, and 16 (51.6%) were rated as Bravo.

Conclusions: Monolithic zirconia restorations demonstrated a reliable treatment option after medium-term clinical use for the replacement of missing posterior teeth.
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http://dx.doi.org/10.1016/j.prosdent.2021.02.034DOI Listing
April 2021

The Use of 4-mm Implants Splinted to 10-mm Implants for Replacement of Multiple Missing Teeth in the Posterior Maxilla Region with Expanded Maxillary Sinus. An Observational Cases Series: Patient Characteristics and Preliminary Results.

Int J Periodontics Restorative Dent 2021 Mar-Apr;41(2):261-268

This study aimed to rehabilitate shortened maxillary dental arch with splinted crowns by connecting ultra-short implants with longer ones. In the posterior maxilla of 11 patients, one 10-mm (n = 11) and one or two ultra-short 4-mm (n = 17) dental implants were inserted. The insertion torque was lower than 20 Ncm in 55% of the 10-mm implants and in 94% of the 4-mm implants ( > .05). Median (range) implant stability quotients at the time of insertion and after 6 months were 61 (14 to 72) and 68 (51 to 79), respectively, for 4-mm implants, and 66 (52 to 78) and 78 (60 to 83), respectively, for 10-mm implants ( < .05). One 4-mm implant failed to integrate. All patients were restored with splinted metal-ceramic crowns connecting 4- and 10-mm implants. Median (range) clinical crown/implant ratios of 4-mm and 10-mm implants were 2.79 (1 to 3.66) and 1.06 (0.85 to 1.46), respectively ( < .05). Six months after prosthetic rehabilitation, the median (range) crestal bone loss was 0.3 mm (-0.7 to 1.7 mm) for 4-mm implants and was 0.5 mm (-0.8 to 3.5 mm) for 10-mm implants ( > .05). Splinted crowns combining 4- and 10-mm implants may contribute to a better force distribution in the treatment with ultra-short implant-supported prosthesis in the posterior maxilla.
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http://dx.doi.org/10.11607/prd.4389DOI Listing
April 2021

The Prevalence of Musculoskeletal Pain of Dental Workers Employed in Slovenia.

Workplace Health Saf 2019 Sep 9;67(9):461-469. Epub 2019 Jul 9.

2 University of Ljubljana.

Work-related musculoskeletal (MS) disorders are considered one of the most frequent occupational diseases among dental workers. Dental work consists of static, demanding tasks that involve repeated gripping of small-sized instruments. The purpose of this study was to investigate the prevalence of MS pain, the areas of pain, and the risk factors for MS pain in dental workers. A self-administrated questionnaire was used as a data collection instrument for dental workers who voluntarily responded to the invitation. To determine the prevalence and severity location of MS pain, the Cornell Musculoskeletal Discomfort Questionnaire was administered among 87 dental workers, with a total of 79.8%, who reported at least one MS complaint. MS pain occurred in 82.6% of general dentists, 75.0% of dental specialists, 66.7% of dental assistants, and 33.3% of dental technicians. Pain most frequently occurred in the neck (60.7%), upper back (52.4%), right shoulder (44.0%), lower back (41.7%), hips/buttocks (29.8%), and the right wrist (23.8%). The prevalence of pain among dental workers could be reduced by ergonomic working environment, regular breaks, maintenance of health, and performing specific exercises designed to dental workers.
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http://dx.doi.org/10.1177/2165079919848137DOI Listing
September 2019

Nanoparticle concentrations and composition in a dental office and dental laboratory: A pilot study on the influence of working procedures.

J Occup Environ Hyg 2018 05;15(5):441-447

e Department of Prosthodontics, Faculty of Medicine , University of Ljubljana , Ljubljana , Slovenia.

During material treatment in dentistry particles of different size are released in the air. To examine the degree of particle exposure, air scanning to dental employees was performed by the Scanning Mobility Particle Sizer. The size, shape and chemical composition of particles collected with a low-pressure impactor were determined by scanning electronic microscopy and X-ray dispersive analysis. The average concentrations of nanoparticles during working periods in a clean dental laboratory (45,000-56,000 particles/cm), in an unclean dental laboratory (28,000-74,000 particles/cm), and in a dental office (21,000-50,000 particles/cm), were significantly higher compared to average concentrations during nonworking periods in the clean dental laboratory (11,000-24,000 particles/cm), unclean laboratory (14,000-40,000 particles/cm), and dental office (13,000-26,000 particles/cm). Peak concentration of nanoparticles in work-intensive periods were found significantly higher (up to 773,000 particles/cm), compared to the non-working periods (147,000 particles/cm) and work-less intensive periods (365,000 particles/cm). The highest mass concentration value ranged from 0.055-0.166 mg/m. X-ray dispersive analysis confirmed the presence of carbon, potassium, oxygen, iron, aluminum, zinc, silicon, and phosphorus as integral elements of dental restorative materials in form of nanoparticle clusters, all smaller than 100 nm. We concluded that dental employees are exposed to nanoparticles in their working environment and are therefore potentially at risk for certain respiratory and systematic diseases.
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http://dx.doi.org/10.1080/15459624.2018.1432864DOI Listing
May 2018

Survival-rate analysis of surface treated dental zirconia (Y-TZP) ceramics.

J Mater Sci Mater Med 2014 Oct 29;25(10):2255-64. Epub 2014 Apr 29.

Department of Prosthodontics, Medical Faculty, University of Ljubljana, Ljubljana, Slovenia.

The role of surface preparation, hydrothermal ageing exposure and subsequent cyclic fatigue testing on the biaxial strength of a dental Y-TZP material are investigated. The initial strength and survival rate of a dental Y-TZP ceramic material to fatigue testing was found to be highly dependent upon surface preparation more so than exposure to various hydrothermal exposure conditions. The results suggest that the monoclinic phase generated by either surface damage (especially sandblasting) and to a lesser extent hydrothermal exposure does appear to mitigate strength and fatigue degradation. The results are discussed in terms of the size of defects generated following various surface treatments and the role of cyclic fatigue induced crack growth. A critical ratio is established between the monotonic strength and fatigue stress survival. From the specimens that failed and exhibited reduced strength after cycling a plot of averaged crack growth rate versus max cyclic stress intensity factor was established which closely matched existing results for Y-TZP ceramics.
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http://dx.doi.org/10.1007/s10856-014-5217-1DOI Listing
October 2014

Fracture resistance and reliability of new zirconia posts.

J Prosthet Dent 2004 Apr;91(4):342-8

Faculty of Medicine, Unversity of Ljubljana and Jozef Stefan Institute, Ljubljana, Slovenia.

Statement Of Problem: The radicular portion of zirconia endodontic posts often need to be reshaped to achieve a definitive form and may be airborne-particle abraded to improve adhesion during luting. Therefore, the surface of the tetragonal zirconia ceramics may be transformed and damaged, influencing the mechanical properties of the material.

Purpose: This study compared the fracture resistance of prefabricated zirconia posts with a new retentive post-head after different surface treatments.

Material And Methods: Experimental zirconia posts of 2 different diameters, 1.3 mm and 1.5 mm, were produced from commercially available zirconia powder. A cylindro-conical outline form was used for the root portion of the system and a post-head with 3 retentive rings was designed. Sixty posts of each diameter were divided into 3 groups (n=20). Group 1 was ground with a coarse grit diamond bur; Group 2 was airborne-particle abraded with 110-microm fused alumina particles, and Group 3 was left as-received (controls). Posts were luted into the root-shaped artificial canals with the Clearfil adhesive system and Panavia 21 adhesive resin luting agent. The posts were loaded in a universal testing machine at an inclination of 45 degrees with the constant cross-head speed of 1 mm/min. The fracture load (N) necessary to cause post fracture was recorded, and the statistical significance of differences among groups was analyzed with 1-way ANOVA followed by the Fischer LSD test (alpha=.05). The variability was analyzed using Weibull statistics.

Results: Load to fracture values of all zirconia posts depended primarily on post diameter. Mean fracture loads (SD) in Newtons were 518.4 (+/-101.3), 993.6 (+/-224.1), and 622.7 (+/-110.3) for Groups 1 through 3, respectively, for thicker posts, and 385.9 (+/-110.3), 627.0 (+/-115.1), and 451.2 (+/-81.4) for Groups 1 through 3, respectively, for thinner posts. Airborne-particle-abraded posts exhibited significantly higher resistance to fracture (P<.05) than those in the other 2 groups for diameters 1.3 mm and 1.5 mm. Grinding reduced Weibull modulus compared with controls, and the values were 4.1 and 6.5 for thicker and thinner posts, respectively.

Conclusion: Within the limitations of this study, the results suggest that grinding leads to a significant drop in load to fracture of zirconia posts, whereas airborne-particle abrasion increased the fracture load.
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http://dx.doi.org/10.1016/j.prosdent.2004.01.009DOI Listing
April 2004