Stainability of different ceramic materials against mouth rinses and effect of polishing after staining.

STATEMENT OF PROBLEM: Mouth rinses are known to stain tooth surfaces. However, their staining effect on different ceramics after prolonged use and the effect of polishing after staining are still unclear. PURPOSE: The purpose of this in vitro study was to evaluate the stainability of different ceramic materials against different mouth rinses and the effect of polishing on staining. MATERIAL AND METHODS: Forty disk-shaped specimens were prepared from each material (total of 160 specimens): lithium disilicate (IPS e.max CAD), zirconia-reinforced lithium disilicate (VITA SUPRINITY PC), leucite-reinforced feldspar (GC Initial LRF), and resin matrix ceramic (CERASMART). Baseline color measurements (T0) were recorded with a clinical spectrophotometer (VITA Easyshade V). The specimens were immersed in chlorhexidine gluconate (CHX) 0.2% mouth rinse (Klorhex), (KLO) chlorhexidine gluconate 0.1% mouth rinse (Eludril) (ELU), a daily mouth rinse (LISTERINE Cool Mint) (LIS), artificial saliva (CON) continuously for 7 days (T1), 14 days (T2), and 28 days (T3). Discoloration values (ΔE) between the immersion time points (T0,T1,T2,T3) were calculated by using the following formula: ΔE= ([ΔL∗]2 + [Δa∗]2 + [Δb∗]2)1/2. After the immersion process, specimens were polished and ΔE values remeasured. The Kruskal-Wallis and Mann-Whitney U tests were performed (α=.05) and were adjusted by postanalysis Bonferroni testing. RESULTS: KLO caused the highest ΔE values in all groups. IPS e.max CAD had the lowest ΔE values, and CERASMART showed the highest ΔE values against all of the solutions (P<.05). However, polishing caused a decrease in the ΔE values in all groups. CONCLUSIONS: Prolonged use of mouth rinses may cause color change in different ceramic materials. Polishing affected the color change and resulted in a decrease in ΔE values. Mouth rinses containing CHX should be recommended with caution for daily use.

Comparing the precision of reproducibility of computer-aided occlusal design to conventional methods.

PURPOSE: Reconstruction of patients' dental occlusion should be performed to fulfill esthetic and functional demands. These applied restorations should be in harmony with the existing occlusion and should not have any negative effects on intraoral dynamics. The aim of this clinical study is to compare the accuracy of the occlusal design shaped by conventional Wax Up methods and computer-aided design (CAD) regarding their similarity to the natural tooth morphology. METHODS: Impressions of 10 caries-free jaws were taken, and the resulting gypsum casts were scanned with a laboratory scanner. Preparations for all-ceramic full crowns were performed on second premolars and second molars. Occlusal design of 40, 3-member fixed partial dentures (FPD) were obtained with two different methods 10 FPD was designed with conventional wax up technique (Wax Up), 30 design was performed with CAD Dental wings open system (DWOS) software using three different anatomy libraries (Dental Wings (DW), Merz, Vita). The data of the bridges in the STereo-Lithography Interface Format (STL) was compared with the pre-cut data, which was regarded as a reference in terms of accuracy in the Atos so high end 3D digitizer. RESULTS: According to the results of Kruskal-Wallis test, there was no statistical difference between the Wax Up, Vita, Merz and Dental Wings groups (p>0.05) when compared to the natural teeth. The main difference between all four groups and natural surface was 550±130µm. CONCLUSIONS: Occlusal design produced by conventional techniques and CAM DWOS system compared to natural tooth morphology showed no statistically significant difference.

The effect of light sources and CAD/CAM monolithic blocks on degree of conversion of cement.

PURPOSE: To assess the degree of conversion (DC) and light irradiance delivered to light-cured and dual-cured cements by application of different light sources through various types of monolithic computer-aided design and computer-aided manufacturing (CAD/CAM) materials. MATERIALS AND METHODS: RelyX Ultimate Clicker light-cured and dual-cured resin cement specimens with 1.5-mm thicknesses (n=300, 10/group), were placed under four types of crystalline core structure (Vita Enamic, Vita Suprinity, GC Ceresmart, Degudent Prettau Anterior). The specimens were irradiated for 40 seconds with an LED Soft-Start or pulse-delay unit or 20 seconds with a QTH unit. DC ratios were determined by using Fourier transform infrared spectroscopy (FTIR) after curing the specimen at 1 day and 1 month. The data were analyzed using the Mann-Whitney U test (for paired comparison) and the Kruskal-Wallis H test (for multiple comparison), with a significance level of P<.05. RESULTS: DC values were the highest for RelyX Ultimate Clicker light-cure specimens polymerized with the LED Soft-Start unit. The combination of the Vita Suprinity disc and RelyX Ultimate Clicker dual-cure resin cement yielded significantly higher values at both timepoints with all light units (all, P<.05). CONCLUSION: Within the limitations of this study, we conclude that the DC of RelyX Ultimate Clicker dual-cure resin cement was improved significantly by the use of Vita Suprinity and the LED Soft-Start light unit. We strongly recommend the combined use of an LED light unit and dual-cure luting cement for monolithic ceramic restorations.

Frequency of temporomandibular disorder signs and symptoms among call center employees.

OBJECTIVE: The current study aimed to investigate the frequency of signs and symptoms of temporomandibular disorders (TMD) among call center employees. METHODS: Workers from four call centers (CC) were invited to participate in this study. The examination was based on the Research Diagnostic Criteria for Temporomandibular Disorder (RDC/TMD). The tenderness of the masticator muscles was assessed on both sides by bilateral palpation. The mobility of the mandible was measured with a plastic millimeter ruler on opening, lateral excursions, and protrusion. RESULTS: In total, 124 call center employees with a mean age of 28.61 ± 4.71 (between 22 and 47 years of age) were enrolled in this study. There was no statistically significant relation between the numbers of calls answered in a day and teeth clenching, teeth grinding, earache, tinnitus, or pain on yawning/chewing. Only protrusive movement pain and joint noise were significantly higher among employees who answered more than 140 calls/day (p < 0.01). An evaluation of the TMD signs and symptoms in relation to job stress level revealed that job stress level significantly affected the incidence of headaches among call center employees (p < 0.01). CONCLUSION: The present study demonstrated no statistically significant relation between TMD signs and symptoms and call center employees except protrusive movement pain and joint noise. This relation was seen only in the employees who answered more than 140 calls per day. Headache, teeth clenching, and TMJ noise were the signs and symptoms encountered most often in this study. Multicentered studies in different geographic locations should be conducted to eliminate the limitation of this study.

A comparative study of marginal fit of copings prepared with various techniques on different implant abutments.

This study evaluated fabrication techniques of recently introduced all-ceramic copings' marginal adaptation on two different implant abutments with different finish lines. Five different copings were prepared (Casted chrome-cobalt metal coping, Zirkonzahn, Cercon, In Ceram Alumina and IPS e.max Press) on two cementable implant abutments with two marginal designs. Ten samples for each coping group were prepared (totally 100 samples). Copings were cemented to implant abutments and marginal gap measurements were done from 24 points with stereomicroscope and the datas were analyzed by the Kruskal-Wallis test before cementation. Cercon copings showed the lowest marginal fit scores and metal copings showed the highest scores. After cementation, all marginal gap values have been increased. All marginal gap values obtained from crown copings can be considered in clinically acceptable limits (<120 µm) except metal copings after cementation on abutment with 135 degrees shoulder group (123 µm).

Early results of low-level laser application for masticatory muscle pain: a double-blind randomized clinical study.

BACKGROUND: To evaluate the effect of Low Level Laser (LLL) application at the points of greatest pain in patients with chronic masticatory muscle pain. METHODS: A total number of 30 (21 women, 9 men, with a mean age of 39.2) were selected after the diagnosis of MPDS according to the Research Diagnostic Criteria for Temporomandibular Disorder (RDC/TMD). The patients were randomly divided into three groups; laser group I (n = 10); patients received the LLL at the point of greatest pain, laser group II (n = 10); patients received LLL at pre-established points in the effected muscles and placebo group (n = 10). LLL and placebo were applied three times per week, for a total of 12 sessions. Mandibular mobility was examined, masticator muscles tenderness were assessed and PPT values were obtained. Subjective pain levels were evaluated using VAS. The measurements performed before the treatment and after the completion of the therapy. Descriptive statistics (mean, standard deviation, and frequency) Student's t-test, Mann-Whitney U-test and paired-sample t-tests were used for analysis. RESULTS: In both laser groups, there was a statically significant reduction in PPT values of the muscles, number of muscles without any pain on palpation increased significantly, mandibular movements' ranges were improved. Laser group I demonstrated statistically better results than the Laser group II in all of the measured values. Plasebo group did not show any statistically difference in any of the measured values. CONCLUSIONS: LLLT can be accepted as an alternative treatment modality in the management of masticatory muscle pain and direct irradiation seems to effect better. TRIAL REGISTRATION: Current Controlled Trials ISRCTN31085 , Date of registration 28/08/20145.

Polymerization efficiency of two dual-cure cements through dental ceramics.

PURPOSE: The aim of this study was to evaluate the effect of thickness of zirconia on curing efficiency of resin cements. MATERIALS AND METHODS: Four discs with 4.0 mm in diameter were prepared from non-HIP translucent zirconia blocks using a CAD/CAM system and feldspathic ceramic was layered onto discs. Thus, 4 ceramic disc samples were fabricated: (G) 0.5 mm zirconia- as a control group, (G1) 0.5 mm zirconia and 0.5 mm feldspathic, (G2) 1.0 mm zirconia and 0.5 mm feldspathic and (G3) 2.0 mm zirconia and 0.5 mm feldspathic ceramic layer. 2 different dual cure cements were polymerized using a LED curing unit. Degree of conversion was evaluated using Vickers Hardness Test and depths of cure of samples were measured. Data were analyzed statistically using One-way ANOVA and Tukey's HSD test (p<0.05). RESULTS: Microhardness and depth of cure values were different under same thickness of ceramic discs for two resin cements. As the thickness of the zirconia discs increased, the microhardness values and depth of cure decreased. CONCLUSION: Photocuring time cannot be the same for all clinical conditions, under thicker zirconia restorations (>2.0 mm), an extended period of light curing or a light unit with a high irradiance should be used.

Curing efficiency of dual-cure resin cement under zirconia with two different light curing units.

PURPOSE: Adequate polymerization is a crucial factor in obtaining optimal physical properties and a satisfying clinical performance from composite resin materials. The aim of this study was to evaluate the polymerization efficiency of dual-cure resin cement cured with two different light curing units under zirconia structures having differing thicknesses. MATERIALS AND METHODS: 4 zirconia discs framework in 4 mm diameter and in 0.5 mm, 1 mm and 1.5 mm thickness were prepared using computer-aided design system. One of the 0.5 mm-thick substructures was left as mono-layered whereas others were layered with feldspathic porcelain of same thickness and ceramic samples with 4 different thicknesses (0.5, 1, 1.5 and 2.0 mm) were prepared. For each group (n=12) resin cement was light cured in polytetrafluoroethylene molds using Light Emitting Diode (LED) or Quartz-Tungsten Halogen (QHT) light curing units under each of 4 zirconia based discs (n=96). The values of depth of cure (in mm) and the Vickers Hardness Number values (VHN) were evaluated for each specimen. RESULTS: The use of LED curing unit produced a greater depth of cure compared to QTH under ceramic discs with 0.5 and 1 mm thickness (p<0.05).At 100µm and 300 µm depth, the LED unit produced significantly greater VHN values compared to the QTH unit (p<0.05). At 500 µm depth, the difference between the VHN values of LED and QTH groups were not statistically significant. CONCLUSION: Light curing may not result in adequate resin cement polymerization under thick zirconia structures. LED light sources should be preferred over QTH for curing dual-cure resin cements, especially for those under thicker zirconia restorations.

Comparative evaluation of the effects of implant position, impression material, and tray type on implant impression accuracy.

PURPOSE: To evaluate the effect of implant position, impression, and tray material on the accuracy of implant impressions of edentulous arches with multiple implants. MATERIALS AND METHODS: Four experimental groups were produced; medium-viscosity polyvinyl siloxane (PVS) was used in 3 groups and polyether was used in 1 group. In PVS groups, different tray types were used; metal stock trays, custom acrylic tray, and full-arch perforated plastic trays. In polyether group, custom acrylic trays were used. The discrepancies in 3 dimensions were measured. RESULTS: The casts obtained exhibited small deviations (7.50-9.71 µm) from the master cast. There was no statistically significant difference between the polyether and PVS groups. Similarly, different tray materials did not produce any statistically significant discrepancies within the PVS groups. There was no significant difference among the groups when the accuracy of anterior implants were compared, but within-the-group comparisons showed that except group 1 (GR1), the posterior implants demonstrated more accuracy than anterior ones. CONCLUSIONS: Polyether and PVS can safely be used for the impressions of the edentulous arches with multiple implants and different tray types produce similar accuracy results.

Visual and instrumental evaluation of color match ability of 2 shade guides on a ceramic system.

STATEMENT OF PROBLEM: There is limited information on the visual and instrumental evaluation of color match between a natural tooth and a ceramic crown. PURPOSE: The purpose of this study was to evaluate the influence of 2 shade guides on color match, and to evaluate the relationship between color difference (ΔE) values and examiners' assessments of the color match in ceramic crowns. MATERIAL AND METHODS: Thirty-three subjects were selected for a ceramic crown restoration of the maxillary central incisor. Two crowns were fabricated with selected shades from Vitapan Classical and Vita Toothguide 3D-Master shade guides for each subject. The color values of maxillary central incisors, selected shade tabs, and corresponding crowns were measured with a spectrophotometer. The ΔE values between the natural teeth and the crowns and between the selected shade tabs and the corresponding crowns were calculated for each subject and compared with the Student's t test (α=.05). In addition, 3 examiners visually evaluated the clinical acceptability of each crown on a scale from 1 to 6. The agreement among the examiners was assessed with the Kappa test. The scores of examiners for both shade guides were analyzed with the Wilcoxon signed rank test (α=.05). RESULTS: The results revealed that the color difference values between the teeth and the crowns fabricated with the selected shades from the Vita Toothguide 3D-Master shade guide were significantly smaller than those of the Vitapan Classical guide (P=.003). Similarly, the color difference values between the selected shade tabs from the Vita Toothguide 3D-Master guide and the corresponding crowns were significantly smaller than those of the Vitapan Classical guide (P=.001). However, the ΔE values obtained for both shade guides were within the clinically acceptable range (ΔE<3.7). The kappa values implied moderate agreement among the 3 examiners. The median value of the examiners' scores was 2, which denoted an acceptable color match. In addition, the recorded scores of the 3 examiners showed that there was no significant difference in terms of the color match between the crowns fabricated with either of the 2 shade guides. CONCLUSIONS: The ceramic crowns fabricated with the Vita Toothguide 3D-Master shade guide resulted in a closer color match to the natural teeth than those of the Vitapan Classical guide. However, the ΔE values and the examiners' scores were within the clinically acceptable range for both shade guides.