Surface roughness and Streptococcus mutans adhesion on surface sealant agent coupled interim crown materials after dynamic loading

Background

With the application of surface sealant agents, smooth surfaces can be achieved in a shorter time when compared with conventional polishing. However, studies on the performance of these agents against chewing forces are not many. The purpose of this study was to evaluate the surface roughness and Streptococcus mutans adhesion on surface sealent coupled interim prosthetic materials after chewing simulation.

Methods

One hundred and twelve specimens were fabricated from two poly(methyl methacrylate) (Tab 2000, Dentalon Plus) and two bis-acryl (Tempofit, Protemp 4) interim crown materials and divided into 4 groups (n = 7) according to applied surface treatment: conventional polishing (control) and 3 surface sealant (Palaseal, Optiglaze, Biscover) coupling methods. The surface roughness values (R_a) were measured with a profilometer before (Ra0) and after aging through dynamic loading in a multifunctional chewing simulator for 10,000 cycles at 50 N load combined with integral thermocycling (between 5 and 55 °C) (Ra1). Specimens were incubated with Streptococcus mutans suspension and the total number of adherent bacteria was calculated by multiplying the counted bacterial colonies with the dilution coefficient.

Results

Surface sealant agent application significantly decreased the surface roughness compared with conventionally polished specimens, except for Optiglaze or BisCover LV applied Protemp 4 and Palaseal or Biscover LV applied Tempofit. Surface roughness after dynamic loading showed a statistically significant increase in all groups, except for the control groups of Tab 2000 and Protemp 4. A positive correlation was found between surface roughness values of interim prosthodontic materials and the quantitiy of Streptococcus Mutans.

Conclusions

Even though surface sealant agent application significantly decreased the surface roughness compared with conventionally polished specimens, dynamic loading significantly increased the surface roughness of all surface sealant coupled materials. The R_a values of all test groups were higher than the plaque accumulation threshold (0.20 µm). Streptococcus mutans adhered more on rougher surfaces.

Comparison of surface roughness and color stainability of 3-dimensionally printed interim prosthodontic material with conventionally fabricated and CAD-CAM milled materials

STATEMENT OF PROBLEM

Studies on the surface roughness and color stainability of interim prostheses produced with 3-dimensional-printing technology are lacking.

PURPOSE

The purpose of this in vitro study was to investigate the effect of different surface treatments on the surface roughness and stainability of 3-dimensionally printed, computer-aided design and computer-aided manufacturing (CAD-CAM) milled and conventional interim materials.

MATERIAL AND METHODS

A total of 320 specimens were fabricated from autopolymerizing polymethyl methacrylate, bis-acryl composite resin, CAD-CAM polymethyl methacrylate resin (milled), and 3-dimensionally printed composite resin (printed) (n=80). A group of each material was divided into 2 groups (n=40) as per the applied surface treatment procedure: conventional polishing (C) or coated with a surface sealant (B). Surface roughness values were measured with a profilometer. Each group of specimens was then divided into 4 subgroups (n=10) and stored for 1 day, 7 days, and 30 days at 37 °C in different solutions: distilled water, cola, coffee, and red wine. Color parameters were measured with a spectrophotometer before and after each storage period, and color differences (CIEDE2000 [ΔE₀₀]) were calculated. Data were statistically analyzed with the Shapiro-Wilk test, Kruskal-Wallis test, and Mann-Whitney U test followed by the Friedman test (α=.05).

RESULTS

The highest surface roughness values were determined for the polymethyl methacrylate -C, and the lowest were observed in the printed-B. After 30 days, the highest mean ΔE₀₀ values were observed in polymethyl methacrylate-C for all staining solutions (P=.001). The highest ΔE₀₀ for all materials was observed in the red wine group. Color change increased significantly with storage duration (P=.001).

CONCLUSIONS

All tested materials had a surface roughness higher than the plaque accumulation threshold (0.2 μm). The surface roughness values of coated materials were significantly lower than those of their conventionally polished groups, except for the printed groups. The application of a surface sealant agent significantly decreased the staining of the materials.

Polishing Methods' Influence on Color Stability and Roughness of 2 Provisional Prosthodontic Materials

PURPOSE

To evaluate the roughness and color change of a conventional acrylic resin and a bis-acryl resin, submitted to different types of polishing and exposed to a staining solution.

MATERIALS AND METHODS

One hundred specimens were manufactured from an autopolymerizing conventional acrylic resin (Duralay, shade 66) (n = 50) and a bis-acryl resin (Protemp 4, shade A3) (n = 50) according to the manufacturers' instructions. Specimens were subdivided into 10 groups (n = 10), according to the type of resin and polishing method, including no-polishing (control groups for acrylic resin [tungsten bur finishing] and bis-acryl resin [cotton and alcohol]), Enhance System, Edenta kit, Labordental kit, and sandpaper. The specimens were immersed in a staining solution (coffee at 60°C) for 7 days. Surface roughness was evaluated before the first immersion (baseline - Ra1) and after 7 days (Ra2). The color change (∆E) was determined after 24 hours (∆E1) and 7 days (∆E2), by CIE L^* a^* b^* scale. Data were statistically analyzed with 3-way ANOVA for repeated measures test and Tukey test (α = 0.05).

RESULTS

According to 3-way ANOVA test, material, polishing techniques, and polishing*material factors exhibited statistically significant influence (p < 0.0001) on the roughness, and, for color change, material, polishing techniques, time, polishing*material, and material*time factors were statistically significant (p < 0.0001). The polishing techniques successfully reduced the surface roughness of acrylic resin groups, when compared to control (p < 0.001), but for bis-acryl resin, results were not different from the control group (Enhance: p = 0.954, Edenta: p = 0.866, sandpaper: p = 0.366, Labordental: p = 0.945). Surface roughness was not affected by the immersion in staining solution for 7 days. Color change of acrylic resin groups after 24 hours and 7 days of immersion exhibited a clinically acceptable value (ΔE < 3.7) with the exception of the Enhance group, and all bis-acryl resin groups exhibited a clinically unacceptable color change value (ΔE > 3.7) independent of polishing technique and time interval (∆E1 and ∆E2).

CONCLUSIONS

Roughness of both materials was similar when the polishing techniques studied were performed, although Ra values were superior to the clinically acceptable values (0.20 µm), and were not affected by the immersion protocol studied; however, when esthetics are critical, the selection of material type is more important than the surface treatment technique used, and bis-acryl resin was more susceptible to clinically unacceptable color change after immersion in a staining solution.

Effect of different surface treatment methods on the surface roughness and color stability of interim prosthodontic materials

STATEMENT OF PROBLEM

The effects of surface sealant agents on the surface roughness and color stability of interim crown materials are unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of different polishing methods on the surface roughness and color stability of 4 interim crown materials.

MATERIAL AND METHODS

A total of 160 specimens were fabricated from 2 poly(methyl methacrylate) (PMMA; Tab 2000, Dentalon Plus) and 2 bis-acryl (Tempofit, Protemp 4) interim crown materials and divided into 4 groups (n=10) according to applied surface treatment procedures: conventional polishing (control) and 3 surface sealant (Palaseal, Optiglaze, Biscover) coupling methods. Surface roughness (Ra) values were measured with a profilometer. Color parameters were measured with a spectrophotometer before and after staining in coffee. Color differences (CIEDE 2000 [ΔE00]) were calculated. Data were statistically analyzed with 2-way ANOVA and the Tukey honest significant differences test (α=.05).

RESULTS

The Ra values of Tempofit with Biscover were significantly lower than their control group, Tab 2000 and Dentalon Plus control groups (P<.05). The highest ΔE00 was calculated for Tempofit control (P<.05). The Dentalon Plus control group had significantly higher ΔE00 values than the other groups, except for the Tempofit and Tab 2000 control groups.The Tab 2000 control ΔE00 was significantly higher than the other groups, except for Dentalon Plus with Palaseal and Dentalon Plus with Optiglaze.

CONCLUSIONS

All specimens had a surface roughness higher than the plaque accumulation threshold (0.20 μm). Smoother surfaces were observed for Tempofit with Biscover when compared with theTempofit control. The color change observed with the Dentalon Plus, Tab 2000, and Tempofit control groups was clinically unacceptable. Nonperceivable color changes were seen with Protemp 4 with Optiglaze, Tempofit with Optiglaze, and Tempofit with Biscover. Perceivable but clinically acceptable color changes were observed when sealants were used for all other test groups and Protemp 4 control.

Analysis of stress relaxation in temporization materials in dentistry

OBJECTIVE

Although temporization is intended as an interim step, complexity of individual treatment situations may demand medium to longer term use of temporary appliances in clinical practice. The durability and integrity of these restorations for continued use to meet the treatment demands is therefore an important clinical problem. The goal of this study was to evaluate the short to medium term stability of these materials under controlled loading to study their stress relaxation behavior.

METHODS

Acrylic resins (poly(methyl) and poly(ethyl) methacrylate) and bis-acryl composite resins were tested in vitro in this study. The stress decay data with time (under an applied constant strain) due to internal strain caused by molecular relaxation were systematically analyzed using important parameters derived from stress changes with time.

RESULTS AND SIGNIFICANCE

The results showed significant differences in the stress relaxation behavior between different materials which may have significant bearing on their durability in medium to longer term interim clinical applications. Poly(ethyl) methacrylate (PEMA) resins subjected to applied constant strain over a period of time showed large time dependent decay of applied stress, indicating very high internal molecular relaxation effects, relative to those of poly(methyl) methacrylate (PMMA) and bis-acryl composites. The results showed that PMMA and composite resins were superior in their ability to maintain constant strain without excessive dissipation of applied stress than PEMA resin. This suggests that internal strain caused by molecular relaxation events may lead to excessive dimensional instability in PEMA.

A novel technique for the direct fabrication of fixed interim restorations

This article describes an alternative technique for the fabrication of interim restorations. A thermoplastic, vacuum-formed template and translucent vinyl polysiloxane material are combined in the waxed diagnostic cast to fabricate a matrix in which the interim material can be placed. With this matrix, a variety of materials, such as dual-polymerized or light-polymerized resins, can be used in a predictable way. The major advantage of this technique is that it allows for the fabrication of accurate restorations with excellent reproduction of surface anatomy and for alterations of the tooth shape with light-polymerized materials.