Effect of simulated gastric acid on aesthetical restorative CAD-CAM materials' microhardness and flexural strength.

Background: Gastric acid, which is among erosive substances, gradually rises to the mouth in individuals with reflux and bulimia nervosa disorders, and this causes various effects on dental restorations. Aim: The objective of this study is in vitro investigation of gastric acid's effect on flexural strength and hardness on aesthetic restorative computer-aided design and computer-aided manufacturing (CAD-CAM) materials. Materials and Methods: For this study, four materials have been used, namely Enamic (Vita), Superfect Zir (Aidite) Zirconia, IPS e.max CAD (Ivoclar Vivadent), and Mark II (Vita). From these four different materials, 24 samples with 14 × 4 × 1 dimensions in rectangular prism form are used, which makes a total of 96 samples. One group was separated as the control group, while the rest was allowed to wait at 37°C, 5 ml gastric acid for 96 hours. Hardness value and flexural strengths were measured as pre-exposure and post-exposure to gastric acid. Results: There is a statistically significant difference between the groups in terms of the amount of decrease in the mean hardness after exposure to gastric acid compared to pre-exposure values (p: 0,000; P < 0,05). There was no statistically significant difference between the groups in terms of the amount of decrease in the post-exposure average flexural strength compared to the pre-exposure value (p: 0.063; P > 0.05). There is a statistically significant difference between the groups in terms of the average flexural strength after exposure to the acid. Conclusions: According to the data obtained, it was concluded that exposure to gastric acid affects the hardness and flexural strength properties of dental restorative ceramic materials.

Evaluation of the effect of anodization-colored titanium abutments and zirconia substructure thickness on zirconia substructure color: An In vitro study.

Background and Aim: The aim of this study is to evaluate the effect of anodized titanium abutments and zirconia substructure thickness on the color of zirconia substructure. Materials and Methods: In this study, an electrochemical anodization setup was prepared for titanium coloring. Commercial titanium, anodization-colored yellow and pink titanium, and zirconia were used as different abutment specimens. Thirty zirconia discs in 0.7, 0.9, and 1.1 mm thickness were prepared from zirconia blocks as zirconia substructure specimens (n = 10). Zirconia substructure specimens of different thicknesses were placed on abutment specimens of different colors and L*, a*, b* values were measured with a spectrophotometer device. Color difference (ΔE) was calculated according to the CIELab formula by comparing the L*, a*, and b* values obtained on the zirconia abutment with the L*, a*, and b* values obtained on the other abutments. Statistical analyzes were performed with two-way analysis of variance and Tukey Honestly Significant Difference (HSD)test (p < 0.05). Results: The increase in the thickness of the substructure resulted in a statistically significant difference on ΔE, L*, a*, and b* values (p < 0.001). The effect of abutment color had no significant effect on ΔE values. The highest ΔE value was 18.10 at zirconia substructure with 0.7 mm thickness when paired with pink-anodized titanium abutment specimens. Conclusion: The thickness of zirconia substructure and the color of titanium abutments affect zirconia substructure color.

Implant-Supported Extra-Orally Cemented Monolithic Zirconia Crowns: A Prospective Controlled Clinical Study up to 18 Months in Function.

This study evaluated the clinical performance of implant supported, extra-orally cemented, monolithic zirconia crowns after a follow-up to 18 months. Thirty-one patients with 50 posterior dental implants were consecutively selected for this study. A total of 50 crowns were cemented onto titanium abutments extra-orally and then screwed to the implants with the required torque intra-orally. The patients were followed at 12 months and 18 months after placement of restorations. During the follow-up period, all restorations were evaluated according to following technical parameters: implant failure, crown fracture, screw loosening, loss of retention due to decementation, fracture of antagonist tooth or restoration. Data were analyzed using Kaplan Meier method. One implant and its corresponding crown was lost during the follow-up period, yielding a 18 months survival rate of 98%. During the study, 2 complication events were observed, including one screw loosening and one veneering porcelain chipping in an antagonist bilayered zirconia restoration. The overall success rate of the observed prosthesis was 96%. According to the results of this study, the extra-orally cemented, monolithic zirconia crowns resulted in a favorable short-term outcome for posterior implant supported restorations within this short observation time.

Assessment of hygiene habits and attitudes among removable partial denture wearers in a university hospital.

AIMS: The aim of this study was conducting a survey of hygiene habits and use of removable partial dentures (RPDs) and correlate them with the social conditions of the interviewees. METHODS: A total of 145 RPD wearers were interviewed by experienced clinical staff using a structured questionnaire. A Chi-squared test was performed to evaluate statistical significance between the variables, and the level of significance was P<0.05. RESULTS: A total of 72 (49%) patients reported that they had not been well informed by the dentists. Brushing was the most frequent cleaning method (57.6%). 77 (53.1%) patients did not take off their dentures at night. The frequency of cleaning dentures and using cleansing tablet was significantly higher in females than in males (P<0.05). The frequency of denture cleaning, cleaned parts of denture, use of cleansing tablet, removal of dentures at night, frequency of tooth brushing, does not show any significant difference according to age, educational status or duration of denture usage (P>0.05). RPD wearers did not clean their dentures and natural teeth satisfactorily and had limited knowledge of denture cleansing and oral hygiene maintenance. CONCLUSIONS: Hygiene habits and attitudes may be affected by gender, but education level and hygiene attitudes may not always present positive correlation. Dentists should thoroughly inform patients about the harmful effects of overnight wearing and motivate to clean metal parts of RPD's and cleansing tablet use in order to minimize the abrasive effect of widely preferred cleaning method of brushing with toothpaste.

Effect of screw access channel filling materials on uniaxial retentive force of cement-retained implant restorations.

BACKGROUND: This study aimed to investigate the effect of various abutment screw access channel filling materials on the uniaxial retention of castings cemented onto the abutment using temporary cement. METHODS: Ten straight, regular platform Esthetic Abutments were used. Fifty castings were divided into five groups and the abutment screw access channels were filled with composite resin (Filtek Z 250), light-cured temporary filling (Clip), temporary filling (Coltosol), polyvinyl siloxane impression material (Elite H-D), or polytetrafluoroethylene (PTFE) tape. Castings were cemented and thermal cycled. A uniaxial tensile force with a cross-head speed of 5 mm/min, was applied to the castings until cement failure occurred. One-way analysis of variance was used to perform intergroup comparisons of the mean uniaxial retentive force (URF) values and Tukey's HSD test was used to determine the group causing the difference. RESULTS: There were statistically significant differences between the mean URF values for the groups (p < 0.01). The mean URF value for the composite resin group was statistically higher than those for the other filling material groups respectively (p < 0.05). CONCLUSIONS: The retention of castings cemented to straight implant abutments using non-eugenol temporary cement may be influenced by the screw access channel filling material.