Hardness and surface roughness of differently processed denture base acrylic resins after immersion in simulated gastric acid.

STATEMENT OF PROBLEM: The effect of gastric acid on the surface properties of denture base acrylic resin is unknown. PURPOSE: The purpose of this in vitro study was to evaluate changes in the surface roughness and hardness of denture base acrylic resins after immersion in simulated gastric acid. MATERIAL AND METHODS: Acrylic resin specimens (n=10) were prepared with 3 different processing techniques (compression-molded, injection-molded, and computer-aided design and computer-aided manufacturing [CAD-CAM] milled) and exposed to either gastric acid or artificial saliva (control). Surface roughness and hardness were measured at baseline (T0) and after 24-hour (T24) and 96-hour (T96) immersion in the solutions. The surface roughness and hardness data were analyzed by 3-way ANOVA and the Tukey HSD test (α=.05). RESULTS: At T24, the greatest change in surface hardness was observed for compression-molded specimens in gastric acid (P<.05). At T96, changes in hardness values were higher in compression-molded specimens than those in milled specimens (P<.05). Regarding surface roughness, at T24, compression-molded and injection-molded specimens showed higher values than milled specimens in gastric acid (P<.05). Concerning specimens in artificial saliva, compression-molded specimens showed significantly higher changes in roughness than those of the others (P<.05). At T96, injection-molded specimens had the greatest roughness values (P<.05). Among specimens immersed in artificial saliva, milled specimens showed lower roughness values than the injection-molded or compression-molded specimens (P<.05). CONCLUSIONS: Gastric acid exposure adversely affected the roughness and hardness of all the acrylic resins evaluated. CAD-CAM milled specimens showed better resistance to acid exposure after 24 and 96 hours in terms of roughness and hardness.

Effect of home and over the contour bleaching on stainability of CAD/CAM esthetic restorative materials.

OBJECTIVE: To determine the effect of home and over the counter bleaching on the stainability of CAD/CAM restorative materials, and to correlate the surface roughness with discoloration. MATERIAL AND METHODS: Specimens were fabricated from feldspathic ceramic, an hybrid ceramic, a resin nano-ceramic, and lithium disilicate-reinforced glass ceramic. After baseline surface roughness (Ra1) and color measurement, each material was randomly divided into three groups according to bleaching regimen as Opalescence PF and; Opalescence Go; control. Then, the second color and surface roughness (Ra2) measurements were made. Thereafter, all specimens were immersed in a coffee solution for 12 days and the third color measurement was made. Color and whiteness change (CIELAB- ΔEab , CIEDE2000-ΔE00 , whiteness index-ΔWID ) were calculated after bleaching (ΔE1;ΔE00 1;ΔWID 1) and immersion in the coffee solution (ΔE2;ΔE00 2;ΔWID 2). RESULTS: According to both CIELAB, CIEDE 2000 and WID formulas, the highest mean ΔE1, ΔE2, ΔWID 1, ΔWID 2 values were observed for LAVA Ultimate groups while the lowest values were measured for e.max CAD groups. The findings also showed that there was a positively significant relationship between Ra2, and ΔE2 and ΔWID 2. CONCLUSIONS: Type of restorative materials and bleaching agents had an impact on color change after bleaching and immersion in coffee. CLINICAL SIGNIFICANCE: Home and over-the-counter bleaching agents may cause an increase in susceptibility of restorative materials to staining.

Influence of type of cement on the color and translucency of monolithic zirconia.

STATEMENT OF PROBLEM: With the development of translucent zirconia, questions regarding the influence of cements on the final color of monolithic zirconia restorations have arisen. PURPOSE: The purpose of this in vitro study was to evaluate color changes in terms of the perceptibility and acceptability of monolithic zirconia-and-cement combinations with 2 monolithic zirconia thicknesses and 3 types of cement. The translucency parameters of these combinations were also compared. MATERIAL AND METHODS: Sixty monolithic zirconia ceramic disks were milled with 2 different thicknesses (0.6 mm and 1 mm). A conventional glass ionomer cement, a resin-modified glass ionomer cement, and a resin cement from the same manufacturer were applied to the ceramic surfaces of both thickness disks (n=10). Translucencies and color changes of the monolithic zirconia specimens after cement application were examined by using a spectrophotometer, and translucency parameters (TPs) and color changes (ΔEs) were calculated and statistically analyzed. RESULTS: Colors and TPs of the zirconia disks changed significantly after being cemented to 0.6- and 1-mm-thick disks (P<.05). The lowest ΔE values (3.53 for the 0.6-mm and 2.23 for the 1-mm thick disks) were observed for the zirconia-resin modified glass ionomer combination, whereas the highest ΔE values (5.64 for the 0.6-mm and 5.06 for the 1-mm thick disks) were observed for the zirconia-resin cement combination. The glass ionomer cement most strongly affected the TP values of both of the thicknesses. CONCLUSIONS: Cement types and zirconia thickness affected the colors and translucencies of the monolithic zirconia specimens.

A review on biodentine, a contemporary dentine replacement and repair material.

Biodentine is a calcium-silicate based material that has drawn attention in recent years and has been advocated to be used in various clinical applications, such as root perforations, apexification, resorptions, retrograde fillings, pulp capping procedures, and dentine replacement. There has been considerable research performed on this material since its launching; however, there is scarce number of review articles that collates information and data obtained from these studies. Therefore, this review article was prepared to provide the reader with a general picture regarding the findings about various characteristics of the material. The results of a PubMed search were classified and presented along with some critical comments where necessary. The review initially focuses on various physical properties of the material with subheadings and continues with biocompatibility. Another section includes the review of studies on Biodentine as a vital pulp treatment material and the article is finalized with the summary of some case reports where the material has been used.

The effect of prophylactic polishing pastes on surface roughness of indirect restorative materials.

The purpose of this study was to evaluate the influence of prophylactic polishing pastes (PPP; Detartrine (DT), Topex (TP)) on surface roughness (R(a)) of indirect composites (IRC; Tescera (TES), Gradia (GRD), and Estenia C&B (EST)), a glass ceramic (Empress 2 layering (E2)), and a leucite reinforced glass ceramic (Empress Esthetic (EE)) with two different (glazed (G); polished (P)) surface preparations. A total of 90 IRC and 120 ceramic discs, 8 mm in diameter and 2 mm thick, were prepared. E2 and EE specimens were randomly divided into two groups (n = 30). One group was glazed (GE2; GEE), while the other group was polished (PE2; PEE) the same as the IRCs. The specimens in each group were subsequently divided into three subgroups: control (C), DT, and TP. R(a) (µm) was evaluated with a profilometer. Data were analyzed by Kruskal Wallis, followed by the Dunn's multiple comparison tests (P < 0.05). DT and TP resulted in significant surface roughening for TES, GRD, and EST, while no significant differences were detected between DT and TP (P > 0.05). PE2 and PEE were not affected by DT or TP (P > 0.05), while GE2 and GEE exhibited significant roughening after TP (P < 0.05). Surface roughness of IRCs and glazed ceramics can be affected by PPP applications.

Comparison of the fracture resistance of simulated immature permanent teeth using various canal filling materials and fiber posts.

BACKGROUND: The purpose of this study was to compare the fracture resistances of immature teeth treated with MTA along with root canal obturation methods using AH Plus, MetaSEAL, MTA Fillapex sealers + lateral compaction technique, and Unicore quartz fiber posts. MATERIALS AND METHODS: Fifty single-rooted maxillary anterior teeth were divided into five groups. The crowns were dissected and root canals were enlarged. #6 Peeso reamers were allowed to protrude 1 mm. beyond the apex to simulate immature teeth. The apical 4-5 mm of each tooth was filled using Angelus white MTA. The remaining portions of canals were obturated as follows: Group 1: No backfilling (control), Group 2: AH Plus + gutta-percha, lateral compaction, Group 3: MetaSEAL + gutta-percha, lateral compaction, Group 4: MTA Fillapex + gutta-percha, lateral compaction, Group 5: UniCore Fiber posts luted using PermaFlo DC. The specimens were embedded into self-curing acrylic poured into identical cylinders which were mounted on a jig providing a 45° angle. A compressive load increasing at 1 mm min(-1) was applied and the maximum load at which fracture occurred was recorded. Statistical analysis was performed using Kruskal-Wallis and Dunn's multiple tests. RESULTS: The highest fracture resistance was obtained with Group 5 (Fiber posts) whereas Group 4 (MTA Fillapex) yielded the lowest values. The mean fracture resistance value of Group 2 (AH Plus) was significantly higher than Group 4 (MTA Fillapex) (P = 0.001). The mean fracture value of Group 5 (Fiber posts) was significantly higher than Group 2 (AH Plus), Group 3 (MetaSEAL), and Group 4 (MTA Fillapex) (P = 0.02, 0.004, and 0.0001, respectively). CONCLUSION: Within the limitations of this study, UniCore quartz fiber posts provided the highest resistance. This methodology may specifically be advantageous for teeth with arrest of development at early stages, as these teeth are more susceptible to fracture owing to their excessively weak dentinal walls.

Effect of bleaching on microhardness of esthetic restorative materials.

This study evaluated the effect of a high-concentration carbamide peroxide­containing home bleaching system (Opalescence PF) and a hydrogen peroxide­containing over-the-counter bleaching system (Treswhite Supreme) on the microhardness of two nanocomposites (Filtek Supreme XT and Premise) and leucite-reinforced glass ceramic (Empress Esthetic), glass ceramic (Empress 2 layering), and feldspathic porcelain (Matchmaker MC). A total of 100 specimens, 20 of each kind of the restorative materials, 2 mm in thickness and 10 mm in diameter, were fabricated. Then the specimens were polished with SiC paper and 1 µm alumina polishing paste. After polishing, porcelain specimens were glazed in accordance with the manufacturer's instructions. Each type of restorative material was then randomly divided into two groups (n=10), and the specimens were treated with either Opalescence PF or Treswhite Supreme. The microhardness of the specimens before bleaching (baseline) and after bleaching was determined using a digital microhardness tester. Data were analyzed using the Mann-Whitney U-test and the Wilcoxon test. Opalescence PF significantly influenced the hardness of all the restorative materials. Statistically significant decreases with respect to before bleaching were found for Premise (p=0.005), Empress Esthetic (p=0.003), Empress 2 layering (p=0.005), and Matchmaker-MC (p=0.003), whereas a statistically significant increase was observed in Filtek Supreme XT (p=0.028). The difference in the microhardness values between before and after bleaching using Treswhite Supreme was statistically significant only for Premise (p=0.022). High-concentration carbamide peroxide­containing home bleaching may affect the microhardness of restorative materials.

Evaluating factors that affect the shade-matching ability of dentists, dental staff members and laypeople.

BACKGROUND: The authors conducted a study to evaluate the influence of dentists' and nondentists' experience, age, sex, eye color and use of eyeglasses or contact lenses on tooth shade-matching ability. METHODS: The authors included 120 participants in this study conducted in Istanbul (periodontists, oral and maxillofacial surgeons, orthodontists, endodontists, pediatric dentists, prosthodontists, restorative dentists, general dentists in private practice, dental technicians, dental assistants, dental assistant students and laypeople). The authors assigned participants to one of three groups: group 1 was composed of prosthodontists, restorative dentists and dental technicians; group 2 consisted of other dental specialists and general dentists; and group 3 included dental assistants, dental assistant students and laypeople. The authors asked participants to match the shades of three artificial maxillary right central incisors (Vitapan acrylic teeth [shades 2L1.5, 1M2, 2R1.5], Vita Zahnfabrik, Bad Säckingen, Germany) by using a shade guide system (Vita Toothguide 3D-Master, Vita Zahnfabrik). They calculated shade matching for the three color components (value, hue, chroma) and analyzed the results by using a chi(2) test. RESULTS: The rate of success in matching the shade for IM2 was 53.3 percent for participants in group 1, 30 percent for participants in group 2 and 20 percent for participants in group 3 (P = .017). However, there were no significant differences between the three groups for shades 2L1.5 and 2R1.5. Professional experience (P = .003) and age (P = .027) were associated with shade-matching success for tooth shade 2L1.5 only. The results showed no statistically significant differences with respect to sex, eye color or use of eyeglasses or contact lenses. CONCLUSIONS: Dental care professionals who routinely performed restorative procedures matched the shades better than did participants in other groups. Professional experience was associated positively with the outcome, while sex, eye color and use of eyeglasses or contact lenses did not have any effect on shade-matching results. CLINICAL IMPLICATIONS: To improve shade-matching skills, clinicians should participate in hands-on courses, continuing education classes and other training programs.

Effects of different silanes and acid concentrations on bond strength of brackets to porcelain surfaces.

The aim of this study was to determine the optimum silane-coupling agent and the optimum concentration of acid agent when bonding to porcelain surfaces. Eighty deglazed feldspathic porcelain discs with a diameter of 10 mm and a thickness of 2 mm mounted in acrylic resin blocks were randomly divided into four groups. In groups 1 and 2, the porcelain surfaces were etched with 9.6 per cent hydrofluoric (HF) acid and in groups 3 and 4 with 5 per cent HF acid. In groups 1 and 3, the Dynalock maxillary central incisor brackets were bonded with Pulpdent silane and Unite bonding adhesive and in groups 2 and 4 with Reliance silane and Unite. Shear forces were applied to the samples using an Instron universal test machine. The non-parametric Kruskal-Wallis test was used to determine significant differences in bond strengths between the four groups and Dunn's multiple comparison test to compare subgroups. The mean bond strengths and standard deviations of groups 1 to 4 were 5.51 +/- 1.19, 6.54 +/- 0.002, 4.55 +/- 1.93, and 6.39 +/- 0.45 MPa, respectively. Specimens bonded with Reliance showed a statistically significantly higher in vitro bond strength than those bonded with Pulpdent. The concentration of etching gels did not result in any statistically significant difference on the in vitro bond strength when evaluated separately.

Periapical health related to the type of coronal restorations and quality of root canal fillings in a Turkish subpopulation.

OBJECTIVE: The purpose of this study was to evaluate the relationship between the quality of root canal fillings and type of permanent coronal restorations and their association with the periapical status in a Turkish subpopulation. STUDY DESIGN: There were 1268 endodontically treated teeth from 280 panoramic radiographs that were evaluated. Two observers assessed the radiographs using an x-ray viewer with 2 times magnification. Teeth were classified according to the type of restorations. The quality of root canal fillings were evaluated according to the criteria determined by Tronstad et al. Apical status was assessed by the Periapical Index scores (PAI) proposed by Ørstavik et al. Chi-square test was used for statistical analysis. RESULTS: There were 59.5% of endodontically treated teeth that showed healthy periapex. Teeth with good endodontic treatment showed statistically significant high healthy periapex rates regardless of the type of the restoration. In addition, the evaluation of the entire material also showed that the roots with posts had significantly more periapical pathosis than roots without posts (P = .001). CONCLUSIONS: It can be concluded that, although the quality of the root canal filling plays a key role in the outcome of endodontic therapy, the type of restoration can also be a contributing factor in the treatment outcome.