Comparison of screw loosening and fracture resistance in different hybrid abutment crown restorations after thermomechanical aging.

PURPOSE: The purpose of the study is to investigate the screw loosening and fracture resistance of different hybrid abutment crown restorations after thermomechanical aging. MATERIALS AND METHODS: Restorations were produced from zirconia, lithium disilicate, and hybrid ceramics with CAD-CAM system (n=10). Restorations and titanium bases (Tibases) were cemented and the abutment screws were torqued to 30 Ncm. They were retorqued after 10 minutes, and removal torque values (RTV) were measured. When 250000 and 500000 cycles of thermomechanical aging were completed, the RTVs were measured again and removal torque loss (RTL) ratios were calculated. The specimens were subjected to fracture resistance test after 750000 cycles of thermomechanical aging. The load at failure was recorded as the fracture resistance (N). The results were statistically analyzed (α=0.05). RESULTS: Aging was effective on the RTVs and RTL ratios (P<0.001). The highest RTV was observed before aging; however, the RTVs significantly decreased and RTL ratios significantly increased after aging (P<0.05). The fracture resistance values significantly differed among the ceramic materials. All lithium disilicate and hybrid ceramic specimens showed restoration fracture, while most of the zirconia specimens were displayed Tibase related failure. CONCLUSION: Hybrid abutment crowns made of zirconia, lithium disilicate, and hybrid ceramics can withstand the average occlusal forces in the molar region; however ceramic type may affect the failure type. Retightening of the abutment screws after 10 minutes after first tightening and annually may be beneficial to prevent the adverse effects of screw loosening on the integrity of implant-abutment connection.

Translucency Parameters and Masking Abilities of Monolithic CAD/CAM Ceramics.

PURPOSE: The purpose of the study was to compare the translucency parameters and masking abilities of different monolithic CAD-CAM ceramics placed on different colored substructures. MATERIALS AND METHODS: Squared-shaped specimens (12x12x1.5 mm) were prepared from feldspathic (C), leucite (Emp), lithium disilicate (e.max), zirconia reinforced lithium silicate (VS), resin nano ceramic (LU), polymer infiltrated ceramic (VE), nanoparticle resin hybrid (GC), monolithic zirconia (TZI), and composite resin (TC) blocks (n=10). After mechanical polishing, the translucency parameter (TP) was calculated. Then, each ceramic specimen was measured on 8 substructures and the color difference between ND2 and each substrate was calculated with CIEDE2000 formula. TP values were analyzed with 1-way ANOVA and Games-Howell tests and the color differences indicating masking ability were analyzed with 2-way ANOVA and Tukey HSD tests. RESULTS: The highest TP was observed in TC, and followed by LU, Emp, C =GC, e.max, VS, VE, and TZI. The ∆E00 color difference values of TZI, VS, and VE on all abutment colors, except for ND9, were below the acceptable threshold value. CONCLUSION: All of the monolithic ceramic materials used in the study masked the ND1 and ND3 substrates. The ND9, representing the severely discolored or devitalized preparations, could not be masked by any of the monolithic CAD-CAM ceramics used in the study.

Effects of ceramic type, connector dimension, and thermomechanical-aging on the fracture resistance and fit of CAD-CAM produced inlay-retained fixed partial dentures.

The purpose of the present study is to evaluate the fracture resistance and the fit of CAD-CAM produced inlay-retained fixed partial dentures. Eighteen experimental groups were generated according to different CAD-CAM ceramic materials (zirconia, lithium disilicate, and zirconia-reinforced lithium silicate), different connector dimensions (12, 14, and 16 mm2), and application of thermomechanical-aging (1,200,000 cycles of cyclic loading with simultaneous thermal cycling). Gap values of thermomechanically-aged groups were measured by using periapical radiographs. Then, the specimens were tested for fracture resistance and failure types were examined. The results were statistically analyzed (α=0.05). Higher gap values were observed after aging. Zirconia showed the highest fracture resistance values among the most of the experimental groups. In non-aged groups, the most frequent failure type was decementation in zirconia group. In the aged groups, the most frequent failure type was molar connector fracture. Thermomechanical-aging increased the gap values and decreased the fracture resistance values.

Effect of plasma treatment on the peel bond strength between maxillofacial silicones and resins.

The study aimed to investigate the effects of surface treatments, including plasma, on the peel bond strength between two maxillofacial silicones and two resins with and without thermocycling. Forty-eight experimental groups (n=10) were generated incorporating the two different resins (auto-polymerizing acrylic resin and light-curing urethane dimethacrylate resin [AR and LR, respectively]), two different silicones (M511 and Z004), aging (thermocycled/no thermocycling), and six different surface treatments, including polishing, grinding, polishing+argon plasma, polishing+oxygen plasma, grinding+argon plasma, and grinding+oxygen plasma. Surface topography of a specimen from each surface treatment group was examined by atomic force microscopy. After surface treatments, silicones were polymerized. The peel bond strength values of the control and thermocycled groups were determined. Atomic force microscopy showed that surface topographies of the ground specimens were irregular. Polished specimens showed higher peel bond strength than ground specimens. Plasma application appeared to have improved the bond strength between the resins and silicones.

Oral health behavior differences between dental students in graduate and doctoral programs.

PURPOSE: This study aimed to compare oral health behavior between dental students in graduate programs and those in doctoral programs (PhD students) and determine the effects of parental education and occupation on these behaviors. MATERIALS AND METHODS: A questionnaire on oral health behaviors was distributed in a faculty of dentistry in Ankara, Turkey. A total of 629 questionnaires were distributed, and 528 dental graduate and 101 PhD students responded. Parental education and occupation were also recorded, and data were statistically analyzed. RESULTS: Statistically significant differences were found between the two groups with respect to the frequency of replacing toothbrush (p=0.001), use of electric toothbrush (p<0.001), frequency of brushing (p<0.001), amount of water used to rinse mouth (p<0.001), toothpaste selection criteria (p<0.001), use of dental floss (p<0.001), amount of toothpaste used for brushing (p=0.018), frequency of professional care (p<0.001), and sugar consumption (p<0.001). The PhD group showed more favorable outcomes for these behaviors except for toothpaste selection. Parental education and occupation were correlated with higher frequencies of flossing and mouth rinsing. CONCLUSION: The outcomes of this study show that the self-reported quality of overall oral health behavior is more pronounced in PhD students than in graduate students, with the exceptions of behaviors regarding the duration of brushing, toothpaste selection criteria, and use of mouth rinse. The current dental curriculum in the universities should be revisited with respect to oral health attitudes. This study also implies that educational and occupational status of parents had little effect on oral health behavior of the students, including the use of dental floss and mouth rinse.

Clinical Guidelines and Implementation into Daily Dental Practice.

INTRODUCTION: The purpose of this study is to assess the extent of the familiarity, attitude and perceptions of dental professionals regarding clinical dental guidelines and their implementation into daily dental practice. MATERIAL AND METHODS: For this purpose, a questionnaire which was developed by the members of the World Dental Federation, European Regional Organization Working Group - 'Relation Between Dental Practitioner and Universities', was implemented by the National Dental Associations of six European Regional Organization-zone countries (Georgian Stomatological Association - Georgia, Associazione Nazionale Dentisti Italiani - Italy, Portuguese Dental Association - Portugal, Russian Dental Association - Russia, Swiss Dental Association - Switzerland, and Turkish Dental Association - Turkey. The questionnaire was filled by a total of 910 dental professionals who are members of one of these national dental associations and who voluntarily wanted to participate to this survey. RESULTS: Most of the survey participants were familiar with clinical dental guidelines (68%), claimed that they implemented them into daily practice (61.7%), and generally acknowledged their benefits (81.8%). Many participants believed that clinical dental guidelines could help to improve the clinical treatment plan (50.6 %) and the accuracy of diagnosis (39.4%); which increased with age and years of practice (p < 0.05). The most frequently perceived barrier to the effective implementation of clinical dental guidelines was expressed as 'lack of awareness', while participants suggested a role for national dental associations in spreading clinical dental guidelines. DISCUSSION: A better understanding of the perceptions and attitudes of dentists towards clinical dental guidelines and the potential impact of factors affecting such perceptions and attitudes may be of particular importance for attempts aiming at overcoming the barriers for effective implementation of clinical dental guidelines into daily practice. CONCLUSION: Despite a significant familiarity and a common positive attitude, dental professionals are likely to have different perceptions towards clinical dental guidelines, especially regarding their effective implementation into daily practice, benefits and barriers.

Introdução: Este estudo tem como objetivo avaliar a abrangência da familiaridade, das atitudes e das perceções dos profissionais da área da saúde oral em relação às normas clínicas dentárias e a sua implementação na prática da Medicina Dentária diária. Material e Métodos: Com esta finalidade, desenvolveu-se um questionário pelos membros da Federação Dentária Mundial, pelo Grupo de Trabalho da Organização Regional Europeia - "Relação entre Médicos Dentistas e as Universidades" e, foi implementado pelas Associações de Medicina Dentária/Estomatologia Nacionais de seis países da Organização Regional Europeia (Associação Estomatológica da Geórgia - Geórgia, Associação Nazionale Dentisti Italiani - Itália, Ordem dos Médicos Dentistas - , Associação Dentária Russa - Rússia, Associação Dentária Suíça - Suíça e Associação Dentária Turca - Turquia. O questionário foi preenchido por um total de 910 profissionais da área da saúde oral, membros de uma dessas associações de medicina dentária/estomatologia Nacionais e que, voluntariamente quiseram participar neste inquérito. Resultados: A maioria dos entrevistados estava familiarizada com os normas clínicas dentárias (68%) e implementam-nas na clínica diária (61,7%) reconhecendo os seus benefícios (81,8%). Muitos participantes acreditavam que as normas clínicas dentárias poderiam ajudar a melhorar o plano de tratamento clínico (50,6%) e a precisão do diagnóstico (39,4%); que aumentou com a idade e os anos de prática (p < 0,05). A barreira mais frequentemente percecionada para a implementação efetiva dos normas clínicas dentárias foi expressa como 'falta de conscientização'. Os participantes sugeriram o papel das associações de medicina dentária/estomatologia nacionais na disseminação das normas clínicas dentárias. Discussão: Uma melhor compreensão das atitudes e perceções dos médicos dentistas em relação às normas clínicas dentárias, e do impacto potencial dos fatores que afetam tais atitudes e perceções, pode ser particularmente importante tendo em vista a necessidade de superar as barreiras existentes quando da implementação efetiva das normas clínicas dentárias na clínica diária. Conclusão: Apesar da familiaridade significativa e de uma atitude positiva comum, os profissionais de saúde oral têm perceções diferentes em relação às normas clínicas dentárias, especialmente em relação à sua implementação efetiva na prática diária, benefícios e barreiras.

Effect of surface treatments on shear bond strength of resin composite bonded to CAD/CAM resin-ceramic hybrid materials.

PURPOSE: The purpose of this study was to assess the effect of surface treatments on shear bond strength of resin composite bonded to thermocycled and non-thermocycled CAD/CAM resin-ceramic hybrid materials. MATERIALS AND METHODS: 120 specimens (10×10×2 mm) from each material were divided into 12 groups according to different surface treatments in combination with thermal aging procedures. Surface treatment methods were airborne-particle abrasion (abraded with 50 micron alumina particles), dry grinding (grinded with 125 µm grain size bur), and hydrofluoric acid (9%) and silane application. According to the thermocycling procedure, the groups were assigned as non-thermocycled, thermocycled after packing composites, and thermocycled before packing composites. The average surface roughness of the non-thermocycled specimens were measured after surface treatments. After packing composites and thermocycling procedures, shear bond strength (SBS) of the specimens were tested. The results of surface roughness were statistically analyzed by 2-way Analysis of Variance (ANOVA), and SBS results were statistically analyzed by 3-way ANOVA. RESULTS: Surface roughness of GC were significantly lower than that of LU and VE (P<.05). The highest surface roughness was observed for dry grinding group, followed by airborne particle abraded group (P<.05). Comparing the materials within the same surface treatment method revealed that untreated surfaces generally showed lower SBS values. The values of untreated LU specimens showed significantly different SBS values compared to those of other surface treatment groups (P<.05). CONCLUSION: SBS was affected by surface treatments. Thermocycling did not have any effect on the SBS of the materials except acid and silane applied GC specimens, which were subjected to thermocycling before packing of the composite resin.

Clinical and radiographic evaluation of new dental implant system: Results of a 3-year prospective study.

BACKGROUND/PURPOSE: The aim of this study was to evaluate implant survival, crestal bone level changes, and clinical parameters of IDcam dental implants over a mean follow-up period of 3 years. MATERIALS AND METHODS: Seventy-two patients, 32 females and 40 males, received 255 implants. Implant-supported metal-ceramic fixed restorations were inserted. Following completion of restorations, each patient was re-examined at 6-month intervals. Radiographic crestal bone level changes were calculated, as well as soft tissue parameters including pocket probing depth, bleeding on probing, plaque index, and gingival index. Examination results were recorded from 18 months to 42 months. Implant survival was estimated using the Kaplan-Meier method. Associations between implant survival and recorded variables were estimated using Cox proportional regression analysis. RESULTS: The Kaplan-Meier survival analysis demonstrated a cumulative survival rate of 97.6%. Three implants in three patients failed to osseointegrate at stage 2 surgery, and three implants in three patients were lost after loading. The mean marginal bone losses were 0.35 ± 0.14 mm, 0.47 ± 0.15 mm, and 0.58 ± 0.16 mm, as determined 6 months, 12 months, and 24 months after prosthetic loading, respectively. Cox proportional regression analysis revealed that the variables such as age, sex, type of the restoration, and implant region had no significant influence on implant failure (P > 0.05). Coefficients of correlation between implant survival and crestal bone loss, pocket probing depth, bleeding on probing, plaque index, and gingival index were found to be nonsignificant (P > 0.05). CONCLUSION: Survival and radiographic and clinical assessments of implants after 2 years of function demonstrated promising results for an IDcam dental implant system.

Implementation of evidence-based dentistry into practice: analysis of awareness, perceptions and attitudes of dentists in the World Dental Federation-European Regional Organization zone.

Based on evidence-based dentistry (EBD) being a relatively new concept in dentistry, the attitudes, perceptions and level of awareness of dentists regarding EBD, and perceived barriers to its implementation into daily practice, were comparatively analysed in six countries of the FDI (World Dental Federation-Federation Dentaire Internationale)-European Regional Organization (ERO) zone (France, Georgia, Poland, Portugal, Slovakia and Turkey). For this purpose, a questionnaire, 'The Relationship Between Dental Practitioners and Universities', was developed by the FDI-ERO Working Group and applied by National Dental Associations (NDAs). A total of 850 valid responses were received, and cumulative data, comparisons between countries and potential impact of demographic variables were analysed. Regarding EBD, similar percentages of respondents reported that they 'know what it is' (32.8%) and 'they practice' (32.1%). Most respondents believed that 'EBD is beneficial' (89.1%); however, they had different thoughts regarding 'who actually benefited from EBD'. Of the participants, 60% believed that 'dentists experience difficulties in implementing EBD'. Although lack of time, lack of education and limited availability of evidence-based clinical guidelines were among the major barriers, there were differences among countries (P<0.05). Significant differences were also observed between countries regarding certain questions such as 'where EBD needed to be taught' (P<0.05), as both undergraduate and continuing education were suggested to be suitable. Age, practice mode and years of practice significantly affected many of the responses (P<0.05). There was a general, positive attitude toward EBD; however, there was also a clear demand for more information and support to enhance dentists' knowledge and use of EBD in everyday practice and a specific role for the NDAs.

Quality of life of patients with implant-retained maxillofacial prostheses: a prospective and retrospective study.

STATEMENT OF PROBLEM: Clinical studies on implant-retained maxillofacial prostheses have focused on biological outcomes. An assessment of the effect of prostheses on patients' quality of life (QOL) by using specific questionnaires developed for this patient population provides important information on treatment outcomes from the patients' perspectives. PURPOSE: The purpose of this study was to report patient-based outcomes of implant-retained maxillofacial prostheses and to evaluate the effect of implant-retained maxillofacial prostheses on QOL of participants in a prospective study. MATERIAL AND METHODS: Eighty-two participants were treated with implant-retained maxillofacial prostheses. Participants were divided into 2 groups: a retrospective group (participants treated and under care) and a prospective group (participants willing to be treated). The posttreatment patient satisfaction scores for each question were statistically analyzed by 2-way ANOVA with variables of defect type and retention type. The Student-Newman-Keuls test was used to determine any significant differences among the groups. In the prospective group, mean scores before and after prosthetic treatment were compared with the paired t test (α=.05). RESULTS: The details of 54 retrospective and 28 prospective participants were reviewed. The posttreatment results of 82 patients showed that patient satisfaction with implant-retained maxillofacial prostheses was significantly different for cleaning the prostheses and recommending treatment to other people, depending on the defect and retention type. In the prospective group, participants reported significant increases in satisfaction for all questions. CONCLUSIONS: Implant-retained prostheses were considered highly satisfactory, indicating good QOL for patients with maxillofacial defects. A comparison of pretreatment and posttreatment assessments revealed that implant-retained maxillofacial prostheses increased patient QOL.

Esthetic, functional, and prosthetic outcomes with implant-retained finger prostheses.

BACKGROUND: Traumatic amputation of fingers results in a serious impairment of hand function and affects the psychological status of the patients. The implant-retained finger prostheses are an alternative treatment. The aim of this case report is to represent the use of osseointegrated implants for retention of finger prostheses in a patient with amputated thumb and index finger. CASE DESCRIPTION AND METHODS: Dental implants were placed in the residual bone of the fingers using two-stage surgery. Custom-made attachments were used to provide retention between implants and silicone prostheses. Prosthetic fingernails were made of composite resin material. FINDINGS AND OUTCOMES: After 6 months, implants were clinically successful, and the patient was satisfied with the appearance and the function of the prostheses. The complications of broken prosthetic nail and mild discoloration were observed. CONCLUSION: Reconstruction of amputated fingers with implant-retained prosthesis is a worthwhile treatment providing esthetic, functional, and psychological benefits, although some complications might be experienced. Clinical relevance Implant-retained finger prostheses are an acceptable treatment modality for patients with amputated fingers. Evaluating implant prognosis, functional results and prosthetic results of the patients are necessary to address the benefits and complications of the treatment.

Effect of different localizations of microgap on clinical parameters and inflammatory cytokines in peri-implant crevicular fluid: a prospective comparative study.

The purpose of this study was to evaluate the effect of microgap on clinical and biochemical parameters around dental implants for 1 year. All patients received four implants: group A-Standard Straumann(®) implants, group B-1 mm subcrestal placement of the polished surface of group A implants, group C-esthetic plus Straumann® implants, group D-subcrestal placement of the polished surface of group C implants. Clinical measurements and peri-implant crevicular fluid (PICF) were collected immediately before loading and at 3rd, 6th, and 12th months after loading, and interleukin-1 beta (IL-1ß) and tumor necrosis factor-alpha (TNF-α) have been assessed in the crevicular fluid. No significant differences were found in plaque index, gingival index, and probing between the groups throughout the study. However, the PICF volumes of group D were significantly higher than that in the other groups, and group A were significantly lower than the other groups (P < 0.05). With respect to bleeding on probing values, the percentage of BOP (+) sides in group A implants were fewer than group C and D implants (P < 0.05). With regard to IL-1ß, the levels of IL-1ß in group A were lower than that in the other groups during the study (P < 0.05). In point of TNF-α total amounts, the levels of TNF-α in group A implants were lower than those in group B and D implants (P < 0.05). Moving microgap coronally from alveolar crest could be recommended for the health of periodontal tissues. Most coronal location of microgap can be suggested in order to maintain the peri-implant health status, particularly in implant sites without esthetic priority.

Effect of fatigue on fracture toughness and phase transformation of Y-TZP ceramics by X-ray diffraction and Raman spectroscopy.

The aim of this study was to evaluate the effect of fatigue on fracture toughness and phase transformation of yttria-stabilized zirconia polycrystal materials (Cercon and Lava). The specimens were tested for indentation fracture toughness either with or without being subjected to fatigue (20,000 cycles, 2 Hz, 200 N load). X-ray diffraction (XRD) analysis was used to examine the phase composition of specimens. The indentation images were analyzed using Raman spectroscopy at indentation center (p1), indentation corner (p2), points on crack 100 µm (p3), and 200 µm (p4) away from the corner and a point ∼80 µm away from the crack (p5). Fracture toughness results were statistically analyzed by two-way analysis of variance (ANOVA); XRD and Raman spectroscopy results were analyzed by three-way ANOVA. Fracture toughness of Cercon control (CC) and fatigue (CF) groups were 6.8 and 6.9 MPa√m, respectively, with no significant difference (p > 0.01). Fracture toughness of Lava fatigue (LF; 7.3 MPa√m) was significantly higher than Lava control (LC; p < 0.01). XRD analyses showed CC and LC consisted of tetragonal zirconia, monoclinic zirconia detected after fatigue. After indentation, relative amount of monoclinic phase significantly increased in CC, CF, and LC; decreased in LF. The Raman spectroscopy results indicated that monoclinic fraction was the highest at p2, subsequently at p1 and decreased at p3, p4, and p5 for all groups. Mechanical cycling increased fracture toughness of Cercon and Lava, the second being significant. Phase transformation was also detected after fatigue, which is higher in Lava. Analysis of indentations showed that transformation was highest was at the corner, second at center.

Effect of fatigue on biaxial flexural strength of bilayered porcelain/zirconia (Y-TZP) dental ceramics.

OBJECTIVES: The aim of this study was to evaluate the effect of fatigue on biaxial flexural strength of bilayered disks of two Y-TZP cores. METHODS: Twenty bilayered veneer/zirconia disks were fabricated from each material (Lava veneer+core, 3M/ESPE, and Cercon veneer+core, Densply). Ten specimens from each material were tested for biaxial flexural strength either with or without being subjected to fatigue (20,000 cycles, 2 Hz, 200 N load) in a universal testing machine (1mm/min). Stresses generated at the core and the veneer, at the top and the bottom surfaces, and the interface of bilayered disk were calculated using Huesh's solutions. Data were statistically analyzed using Weibull statistics. The fractured core was also examined via Raman spectroscopy and the monoclinic fraction was calculated at the top, the middle of thickness, and the bottom of the cross-section of fractured core. The results of monoclinic fraction were statistically analyzed by Three-Factor ANOVA with Repeated Measures on One Factor. RESULTS: Weibull modulus (m) of Cercon control (CC), Cercon fatigue (CF), Lava control (LC) and Lava fatigue (LF) were between 11.8 and 14.3, 7.1 and 13.1, 9.4 and 13, and 7.1 and 8.2, respectively. There were no significant differences between characteristic strength (σ(0)) of CC (970.9 MPa) and CF (947.7 MPa) (p>0.05). For Lava, σ(0) of LF (1444.8 MPa) was significantly higher than LC (1240.5 MPa) (p<0.05). At the interfaces, σ(0) values of CC and CF groups were not significantly different while LF showed significantly higher σ(0) than LC. The monoclinic zirconia was significantly lower for CF than CC and significantly higher for LF than LC. SIGNIFICANCE: Fatigue showed different effects on the strength of Cercon and Lava ceramic systems. Decreases in m values were observed at the interfaces of two materials after fatigue.