Comparison of the light transmission of new generation monolithic zirconia materials and lithium disilicate.

PURPOSE: To compare the effects of different thicknesses of ceramic veneering on the light transmission of various monolithic zirconia and lithium disilicate materials used in esthetic restorations. METHODS: Zirconia (i.e., Katana UT, Katana HT, Prozir Diamond, Prozir HT, and Zenostar MO) and lithium disilicate specimens (i.e., Emax HT and Emax MO) were prepared at thicknesses of 0.5 mm, 0.8 mm, and 1.2 mm. Additionally, 0.8 mm-thick specimens and 0.3 mm-thick ceramic veneer were prepared for veneering groups. The total transmittance of light values were measured using a spectrophotometer. The light transmission values were analyzed using the Kruskal-Wallis and the post-hoc Dunnett tests (α= 0.05). RESULTS: The Emax HT group defined significant differences from all groups (P< 0.05) at all thicknesses. The mean total transmittance of light ranged from 5.53% to 19.55%. There was no significant difference between the Katana UT and Prozir Diamond groups at the 0.5 mm, 0.8 mm, and 1.2 mm thicknesses (P> 0.05). CLINICAL SIGNIFICANCE: The results of this study showed no significant effects of veneering ceramic on the light transmittance of the specimens at a thickness of 0.8 mm. Novel monolithic zirconia materials may be preferred over porcelain veneering in 0.8 mm-thick restorations, as the esthetic appearance of the restorations would not change.

Evaluation of quality of life and oral hygiene attitudes of individuals using dental prostheses during the COVID-19 pandemic.

STATEMENT OF PROBLEM: The COVID-19 pandemic impacted every area of our lives, including delaying urgent dental care. However, studies evaluating how patients using dental prostheses have been affected by the pandemic are lacking. PURPOSE: The purpose of this study was to investigate how patients using different types of dental prostheses were being affected by the COVID-19 pandemic. MATERIAL AND METHODS: A total of 129 randomly selected individuals from among those who had been examined in the same clinic before the COVID-19 outbreak were included in the study. The study participants were divided into 4 groups according to their type of prosthesis: complete dentures, implant-retained removable dentures, tooth-supported fixed partial dentures, and implant-supported fixed partial dentures. The Oral Health Impact Profile (OHIP-14) questionnaire was implemented by telephone interviews with the study participants, who were also asked about their concerns and steps made regarding prosthetic hygiene during the COVID-19 pandemic. Data were evaluated by the Kruskal-Wallis and post hoc Dunn tests, and multivariate logistic regression analysis with forward selection was carried out to identify predictors of the oral health-related quality of life (OHRQoL) status (α=.05). RESULTS: OHIP-14 total scores did not vary significantly among the groups (P>.05). When the domain scores of OHIP-14 were considered separately, the analysis revealed that the implant-retained removable denture group had significantly poorer functional limitations when compared with the tooth-supported fixed partial denture (P=.005) and implant-supported fixed partial denture (P=.031) groups. The results of the multivariate logistic regression analysis indicated a statistically significant association between OHRQoL during the COVID-19 pandemic and the frequency of tooth or denture cleaning (1 time a day versus less than 1 time a day: P=.011; 2-3 times a day versus less than 1 time a day: P=.032). CONCLUSIONS: All prosthesis users exhibited increased interest in dental hygiene and an increase in the frequency of prosthesis cleaning during the pandemic. Furthermore, the study determined that the frequency of tooth or denture cleaning was associated with significantly improved OHRQoL during the time of the COVID-19 pandemic. Among the denture groups, those treated with implant-retained removable dentures had the poorest functional limitation in terms of OHRQoL, which can be linked to postponement of routine maintenance appointments. Therefore, providing all patients with scientifically sound information on prosthetic care during a pandemic would be highly beneficial.

Influence of anodized titanium abutment backgrounds on the color parameters of different zirconia materials.

PURPOSE: To characterize the color outcome on different zirconia types of various colored titanium backgrounds produced with a newly developed anodized technique. METHODS: Blue, green, pink and gold-colored titanium backgrounds were produced via different anodization voltage values. Non-anodized grey colored titanium was used as a control. A total of 40 disc-shaped zirconia specimens were prepared from four different zirconia types (Cercon HT, Noritake Alliance, Prettau, and Ice Zirkon). The zirconia specimens were placed on different titanium backgrounds to evaluate color differences (ΔE) by recording the L, a and b values. ΔE, ΔL, Δa and Δb values were compared for different titanium backgrounds and zirconia types. To analyze the results, repeated measures ANOVA and Bonferroni adjustments for pairwise comparison were used (α= 0.05). RESULTS: The Cercon HT group had the highest ΔE value, while the Noritake group showed the lowest ΔE value (P< 0.05). ΔL, Δa and Δb values showed significant color changes depending on the color of the titanium background, the sintering procedure of zirconia and the zirconia ingredients (P< 0.05). CLINICAL SIGNIFICANCE: Anodized titanium abutments may improve color in esthetic regions when a ceramic abutment cannot be used. The study showed that the gold-colored titanium produced via anodization was better than other colors at producing a tooth-like color for implant-supported zirconia restorations. Also, by adjusting the color of zirconia restorations, the effect of the background could be altered using the zirconia sintering protocol.

Effect of Different Denture Base Cleansers on Surface Roughness of Heat Polymerised Acrylic Materials with Different Curing Process / Efecto de diferentes limpiadores para dentaduras en la rugosidad de la superficie de acrílicos polimerizados por calor con diferentes procesos de curado

Abstract Avoiding biofilm formation on dentures is associated with maintaining the surface properties of acrylic-based dentures. The aim of the study is to investigate the effects of two different cleaning agents (Corega and Klorhex 0.2% chlorhexidine gluconate) on surface roughness of the denture regarding efficacy of curing procedures. A total of sixty disc-shaped specimens were prepared with two different methods as long and short curing processes. The specimens were divided into subgroups according to the immersion solutions (distilled water, Corega tablet group and Klorhex 0.2% chlorhexidine gluconate group) (n=10). The samples were kept in a solution for 8 hours per day during a month. The average Ra1 (before exposure to the cleanser agent) and Ra2 (after exposure to the cleanser agent) of each sample was measured. A two- way ANOVA and post hoc Tukey test was used for statistical analysis. The solutions significantly increased the Ra values in both acrylic groups (p0.05). The long-term curing time is highly effective in decreasing the surface roughness of the acrylic base material.

Resumen Evitar la formación de biopelículas en las prótesis dentales se asocia con el mantenimiento de las propiedades de la superficie de las prótesis de base acrílica. El objetivo del estudio es investigar los efectos de dos agentes de limpieza diferentes (Corega y Klorhex 0,2% gluconato de clorhexidina) en la rugosidad de la superficie de la dentadura postiza en cuanto a la eficacia de los procedimientos de curado. Se prepararon un total de sesenta muestras en forma de disco con dos métodos diferentes como procesos de curado largos y cortos. Las muestras se dividieron en subgrupos según las soluciones de inmersión (agua destilada, grupo de pastillas Corega y grupo de gluconato de clorhexidina al 0,2%) (n=10). Las muestras se mantuvieron en una solución durante 8 horas al día durante un mes. Se midió el promedio de Ra1 (antes de la exposición al agente de limpieza) y Ra2 (después de la exposición al agente de limpieza) de cada muestra. Para el análisis estadístico se utilizó un ANOVA de dos vías y una prueba post hoc de Tukey. Las soluciones aumentaron significativamente los valores de Ra en ambos grupos acrílicos (p 0,05). El tiempo de curado a largo plazo es muy eficaz para disminuir la rugosidad de la superficie del material de base acrílica.

Effect of different surface treatments on the shear bond strength of luting cements used with implant-supported prosthesis: An in vitro study.

PURPOSE: The aim of this study was to investigate the shear bond strength of luting cements used with implant retained restorations on to titanium specimens after different surface treatments. MATERIALS AND METHODS: One hundred twenty disc shaped specimens were used. They were divided into three groups considering the surface treatments (no treatment, sandblasting, and oxygen plasma treatment). Water contact angle of specimens were determined. The specimens were further divided into four subgroups (n=10) according to applied cement types: polycarboxylate cement (Adhesor Carbofine-AC), temporary zinc oxide free cement (Temporary Cement-ZOC), non eugenol provisional cement for implant retained prosthesis (Premier Implant Cement-PI), and non eugenol acrylic-urethane polymer based provisional cement for implant luting (Cem Implant Cement-CI). Shear bond strength values were evaluated. Two-way ANOVA test and Regression analysis were used to statistical analyze the results. RESULTS: Overall shear bond strength values of luting cements defined in sandblasting groups were considerably higher than other surfaces (P<.05). The cements can be ranked as AC > CI > PI > ZOC according to shear bond strength values for all surface treatment groups (P<.05). Water contact angles of surface treatments (control, sandblasting, and plasma treatment group) were 76.17° ± 3.99, 110.45° ± 1.41, and 73.80° ± 4.79, respectively. Regression analysis revealed that correlation between the contact angle of different surfaces and shear bond strength was not strong (P>.05). CONCLUSION: The retentive strength findings of all luting cements were higher in sandblasting and oxygen plasma groups than in control groups. Oxygen plasma treatment can improve the adhesion ability of titanium surfaces without any mechanical damage to titanium structure.

Evaluation of reliability of zirconia materials to be used in implant-retained restoration on the atrophic bone of the posterior maxilla: A finite element study.

PURPOSE: Zirconia materials have been used for implant-retained restorations, but the stress distribution of zirconia is not entirely clear. The aim of this study is to evaluate the stress distribution and risky areas caused by the different design of zirconia restorations on the atrophic bone of the posterior maxilla. MATERIALS AND METHODS: An edentulous D4-type bone model was prepared from radiography of an atrophic posterior maxilla. Monolithic zirconia and zirconia-fused porcelain implant-retained restorations were designed as splinted or non-splinted. 300-N occlusal forces were applied obliquely. Stress analyses were performed using a 3D FEA program. RESULTS: According to stress analysis, the bone between the 1) molar implant and the 2) premolar in the non-splinted monolithic zirconia restoration model was stated as the riskiest area. Similarly, the maximum von Mises stress value was detected on the bone of the non-splinted monolithic zirconia models. CONCLUSION: Splinting of implant-retained restorations can be more critical for monolithic zirconia than zirconia fused to porcelain for the longevity of the bone.