Effect of coffee thermocycling on the surface roughness and stainability of nanographene-reinforced polymethyl methacrylate used for fixed definitive prostheses

Bond strength of recently introduced computer-aided design and computer-aided manufacturing resin-based crown materials to polyetheretherketone and titanium

STATEMENT OF PROBLEM

Several additively and subtractively manufactured resin-based materials indicated for interim and definitive fixed dental prostheses have been launched. However, knowledge of the bond strength of these materials to different implant abutment materials is limited.

PURPOSE

The purpose of this in vitro study was to evaluate the shear bond strength (SBS) of additively and subtractively manufactured resin-based materials to different implant abutment materials.

MATERIAL AND METHODS

One hundred and ten disk-shaped specimens (Ø3×3 mm) were fabricated either additively from 2 resins indicated for definitive use (Crowntec; AM_CT and VarseoSmile Crown Plus; AM_VS) and 1 resin indicated for interim use (FREEPRINT temp; AM_FP) or subtractively from a nanographene-reinforced polymethyl methacrylate (G-CAM; SM_GC) and a high-impact polymer composite (breCAM.HIPC; SM_BC). After allocating 2 specimens from each group for scanning electron microscope evaluation, the specimens were divided according to the abutment material (CopraPeek; polyetheretherketone, PEEK and Dentium Superline Pre-Milled Abutment; titanium, Ti) (n=10). All specimens were airborne-particle abraded with 50-µm aluminum oxide. After applying a resin primer (Visio.link) to PEEK and an adhesive primer (Clearfil Ceramic Primer Plus) to Ti specimens, a self-adhesive resin cement (PANAVIA SA Cement Universal) was used for cementation. All specimens were stored in distilled water (24 hours, 37 °C), and a universal testing device was used for the SBS test. SBS data were analyzed with 2-way analysis of variance and Tukey honestly significant difference tests, while the chi-squared test was used to evaluate the difference among the abutment-resin pairs in terms of failure modes (α=.05).

RESULTS

The interaction between the material type and the abutment type and the main factor of material type affected the SBS (P<.001). SM_BC-PEEK and SM_GC had the lowest SBS followed by SM_BC-Ti, whereas AM_VS-PEEK had the highest SBS (P≤.001). AM_CT-Ti had higher SBS than AM_FP-PEEK (P=.026). SM_GC had the lowest and AM_VS had the highest SBS, while AM_CT and AM_FP had higher SBS than SM_BC (P≤.004). The distribution of failure modes was significantly different among tested material-abutment pairs, and only for AM_CT among tested materials (P≤.025). Most of the material-abutment pairs had a minimum of 80% adhesive failures.

CONCLUSIONS

Regardless of the abutment material, additively manufactured specimens had higher bond strength and one of the subtractively manufactured materials (SM_GC) mostly had lower bond strength. The abutment material had a small effect on the bond strength. Adhesive failures were observed most frequently.

Evaluation of the Colour Stability and Surface Roughness of Polymethylmethacrylate and Indirect Composites With and Without Ageing: An In-Vitro Study

BACKGROUND

Indirect restorations are a staple restorative option in dentistry due to their versatility, exceptional aesthetics, and desirable strength and longevity. Metal ceramics and all ceramics are the material of choice for permanent restorations but come with certain disadvantages, such as chipping, fracture, and wear of the antagonist tooth or restoration. Polymethylmethacrylate (PMMA) and indirect composite resins are commonly used materials due to their favourable properties for temporary restorations, but lately, they have been chosen as the restorative material of choice for implant-supported full-mouth rehabilitations. This study aimed to evaluate and compare the colour stability and surface roughness of PMMA and indirect composite resins under both ageing and non-ageing conditions. This would greatly help a clinician in choosing materials depending on the clinical scenarios.

AIM

This study aims to evaluate the colour stability and surface roughness of PMMA and indirect composite resins with and without ageing.

METHODS

Specimens of PMMA and indirect composite resins were fabricated and subjected to an ageing process involving thermocycling in the TW-C4.4 (Tae-Won Tech, Incheon, Korea) and immersion in a staining solution. Colour stability was assessed using a spectrophotometer (SpectraMagic NX, RM2002QC, Konica Minolta Corp., Ramsey, Japan), and surface roughness was measured using a stylus profilometer (Mituyoto, Mituyoto Corporation, Kawasaki, Japan). Statistical analysis was performed using IBM SPSS Statistics for Windows, Version 24 (Released 2016; IBM Corp., Armonk, New York) to determine significant differences between materials and ageing effects.

RESULTS

PMMA exhibited significantly higher colour changes and increased surface roughness post-ageing compared to indirect composite resins. The findings underscored PMMA's susceptibility to discolouration and surface degradation under thermal stress conditions.

CONCLUSION

PMMA demonstrates inferior colour stability and increased surface roughness following thermocycling compared to indirect composite materials, suggesting careful consideration in material selection for provisional restorations. Further research should explore additional ageing processes and materials to enhance understanding and improve clinical outcomes.

Stainability and translucency of potassium aluminum sulfate applied computer-aided design and computer-aided manufacturing materials after coffee thermocycling

OBJECTIVE

The purpose of this in vitro study was to evaluate the effect of potassium aluminum sulfate (alum) application on the stainability and translucency of computer-aided design and computer-aided manufacturing (CAD-CAM) materials after coffee thermocycling (CTC).

MATERIALS AND METHODS

Disk-shaped specimens (Ø10 × 1 mm; N = 200) were fabricated by using additively (Crowntec [CT] and Varseo Smile Crown Plus [VS]) and subtractively manufactured (Brilliant Crios [RCR], CEREC Block [FC], and Vita Enamic [VE]) CAD-CAM materials and polished. All specimens were randomly divided into two groups as alum applied and control (n = 10). All specimens were then subjected to CTC (10,000 cycles at 5-55°C) and color coordinates were measured at each time interval. Color differences (ΔE00 ) and relative translucency parameters (RTPs) were calculated and the data were statistically analyzed (a = 0.05).

RESULTS

Among tested time intervals, alum applied specimens had their lowest ΔE00 after alum application (p ≤ 0.006), except for FC (p = 0.177). In addition, alum applied RCR had lower ΔE00 values than its control specimens (p = 0.029). Alum applied specimens had their lowest RTP after CTC (p < 0.001) and alum application decreased the RTP of CT (p = 0.010). CTC reduced the RTP of all materials in control groups (p < 0.001). Alum applied CT had higher RTP than its control specimens (p = 0.049).

CONCLUSIONS

Alum application's effect on color change varied depending on the material and alum mostly resulted in clinically acceptable changes in translucency. CTC led to unacceptable color and translucency changes based on previously reported threshold values.

CLINICAL SIGNIFICANCE

Optical properties of CAD-CAM materials and the sustainability of these properties over time is critical for longevity. Alum may improve the color stability of reinforced composite resin when subjected to long-term coffee consumption.

Effect of coffee thermocycling on the surface roughness and stainability of denture base materials with different chemical compositions manufactured with additive and subtractive technologies

OBJECTIVE

To evaluate the effect of coffee thermocycling (CTC) on the surface roughness (Ra ) and stainability of denture base materials with different chemical compositions fabricated by using additive and subtractive manufacturing.

MATERIALS AND METHODS

Disk-shaped specimens were additively (FREEPRINT denture, AM) or subtractively (G-CAM, GSM and M-PM, SM) fabricated from three pink denture base materials in different chemical compositions (n = 10). Ra was measured before and after polishing, while color coordinates were measured after polishing. Specimens were subjected to CTC (5000 cycles) and measurements were repeated. Color differences (ΔE00 ) after CTC were calculated. Ra among different time intervals within materials was evaluated by using repeated measures analysis of variance (ANOVA), while 1-way ANOVA was used to evaluate the Ra of different materials within each time interval and the ΔE00 values. Color coordinates within each material were compared by using paired samples t-tests (α = 0.05).

RESULTS

Ra before polishing was the highest for all materials (p < 0.001), while SM had its lowest Ra after CTC and AM had its lowest Ra after polishing (p ≤ 0.008). Before polishing, AM had the highest Ra among the materials (p < 0.001). After polishing, SM had higher Ra than AM (p < 0.001). After CTC, GSM had the lowest Ra (p ≤ 0.048). SM had the lowest (p ≤ 0.031) and AM had the highest (p < 0.001) ΔE00 . CTC decreased the a* and b* values of SM and AM (p ≤ 0.017), and increased the L* values of AM (p < 0.001).

CONCLUSIONS

Polishing significantly reduced the surface roughness of all materials. CTC did not increase the surface roughness of materials above the clinically acceptable threshold. Only AM had perceptible color change when previously reported threshold values for denture base materials were considered.

CLINICAL SIGNIFICANCE

Tested denture base materials may have similar surface stability after coffee thermocycling. However, subtractively manufactured denture base materials may have improved color stability when subjected to long-term coffee consumption.

Effect of polishing and denture cleansers on the surface roughness of new-generation denture base materials and their color change after cleansing

PURPOSE

To evaluate the effect of polishing and denture cleansers on the surface roughness (Ra ) of new-generation denture base materials that are additively, subtractively, and conventionally fabricated, while also assessing their color change after cleansing.

MATERIAL AND METHODS

One hundred and fifty disk-shaped specimens (Ø10 × 2 mm) were prepared from five denture base materials (one subtractively manufactured nanographene-reinforced prepolymerized polymethylmethacrylate (PMMA) (SM-GC), one subtractively manufactured prepolymerized PMMA (SM-PM), two additively manufactured denture base resins (AM-DT and AM-ND), and one heat-polymerized PMMA (CV) (n = 30). The Ra of the specimens was measured before and after conventional laboratory polishing, while color coordinates were measured after polishing. Specimens were then divided into three subgroups based on the denture cleanser: distilled water, 1% sodium hypochlorite (NaOCl), and effervescent tablet (n = 10). The Ra and color coordinates were remeasured after nine cleansing cycles over a period of 20 days. The CIEDE2000 formula was used to calculate the color differences (ΔE00 ). Two-way analysis of variance (ANOVA) was used to analyze the Ra values before (n = 30) and after (n = 10) cleansing, while repeated measures ANOVA was used to analyze the Ra of material-time point pairs within each denture cleanser (n = 10). ΔE00 data after denture cleansing was also analyzed by using two-way ANOVA (n = 10) (α = 0.05).

RESULTS

Before polishing, Ra varied significantly among the materials. SM-GC and SM-PM had the lowest and AM-ND the highest Ra values (P < 0.001). Polishing significantly reduced Ra of all materials (P < 0.001), and after polishing, Ra differences among materials were nonsignificant (P ≥ 0.072). Regardless of the denture cleanser, the Ra of AM-DT, AM-ND, and CV was the highest before polishing when different time points were considered (P < 0.001). After cleansing, AM-ND had the highest Ra of all the materials, regardless of the cleanser (P ≤ 0.017). AM-DT had higher Ra than SM-PM when distilled water (P = 0.040) and higher Ra than SM-GC, SM-PM, and CV when NaOCl was used (P < 0.001). The type of cleanser significantly influenced the Ra of AM-DT, AM-ND, and CV. For AM-DT, NaOCl led to the highest Ra and the tablet led to the lowest Ra (P ≤ 0.042), while for AM-ND, distilled water led to the lowest Ra (P ≤ 0.024). For CV, the tablet led to lower Ra than distilled water (P = 0.009). Color change varied among the materials. When distilled water was used, SM-GC had higher ΔE00 than SM-PM and AM-DT (P ≤ 0.034). When NaOCl was used, AM-ND had higher ΔE00 than SM-GC, SM-PM, and AM-DT, while CV and SM-GC had higher ΔE00 than SM-PM and AM-DT (P ≤ 0.039). Finally, when the tablet was used, AM-ND and CV had the highest ΔE00 , while AM-DT had lower ΔE00 than SM-GC (P ≤ 0.015).

CONCLUSIONS

The tested materials had unacceptable surface roughness (>0.2 μm) before polishing. Roughness decreased significantly after polishing (<0.2 μm). Denture cleansers did not significantly affect the surface roughness of the materials, and roughness remained clinically acceptable after cleansing (<0.2 μm). Considering previously reported color thresholds, AM-ND and CV had unacceptable color change regardless of the denture cleanser, and the effervescent tablet led to perceptible, but acceptable color change for SM-GC, SM-PM, and AM-DT.