Coffee stains no match for some restorative materials

2017 03 06 17 36 47 535 Coffee 400

The average American drinks a lot of coffee -- 3.1 cups per day to be exact. And while a cup (or three) of joe may have some dental health benefits, regular coffee consumption poses a challenge to dentists who want to create natural-looking restorations.

Fortunately for coffee-loving patients, newer restorative materials may prevent coffee stains better than traditional composite resins, according to a new study published in Restorative Dentistry & Endodontics. Researchers from Thailand and Japan found that CAD/CAM composite resin blocks were less discolored than traditional composite resins after being immersed in coffee for one month.

"The novel CAD/CAM composite resin blocks are industrially polymerized under standardized parameters at high temperature and pressure to achieve optimum properties at microstructure level and high degree of conversion," wrote the authors, led by Sasipin Lauvahutanon (Restor Dent Endod, February 2017, Vol. 42:1, pp. 9-18). "As a result, material characteristics were improved compared to direct restorative composite resin."

Lauvahutanon is from the prosthodontic department at the Chulalongkorn University dental school in Thailand.

How coffee stains affect restorative materials

Ideally, restorations should be aesthetically pleasing as well as functional. Traditional composite resin restorations may match the color of surrounding teeth when first placed, but they tend to become discolored over time, particularly when they are regularly exposed to coffee. The researchers wanted to know if newer CAD/CAM materials were as likely to get darker after coffee exposure as traditional resin materials.

To find out, the researchers measured the change in color of 12 different restorative materials: eight CAD/CAM blocks and four conventional composite resins.

Materials used in study
Material type Brand name
Composite resin block Block HC (Shofu Dental)
Cerasmart (GC)
Gradia (GC)
KZR-CAD (Yamamoto)
Lava Ultimate (3M)
Hybrid ceramic block Vita Enamic (Vita)
Polymethyl methacrylate (PMMA) block Telio CAD (Ivoclar Vivadent)
Feldspar ceramic block Vitablocs Mark II (Vita)
Conventional restorative composite resin Clearfil AP-X (Kurarey Dental)
Durafill VS (Heraeus Kulzer)
Estelite Sigma Quick (Tokuyama Dental)
Filtek Supreme Ulta (3M)

The researchers created 10-mm disks from each of the restorative materials and then calculated the disks' initial color measurements, taking into account brightness and color. After noting the initial color measurements, they placed the disks in an instant coffee solution, which they changed daily.

The researchers measured the color of each disk after one day, one week, and one month and created a formula to calculate the color change. The higher the outputted number from the formula, the more discolored a disk got over time.

The found the coffee solution significantly discolored nearly all disks over time, but the CAD/CAM materials were generally less affected than the conventional resin materials. Only one material, Durafill VS, was not significantly more discolored after one month than after one day.

The effect of coffee immersion on restorative materials
Material type Change in color after 1 day Change in color after 1 week Change in color after 1 month
Composite resin blocks 1.1 1.86 2.9
Hybrid ceramic block 0.5 0.8 1.4
PMMA block 0.9 1.6 2.0
Feldspar ceramic block 0.4 1.1 1.8
Conventional restorative composite resins 1.5 2.9 4.8

Fortunately for coffee drinkers, the researchers also tested whether the coffee stains came off the disks. Nearly all disks had their color significantly restored after being polished with prophylaxis paste for 20 seconds. Gradia was the only material whose color was not significantly lighter after the polish, and only Durafill and Filtek Supreme Ulta were still noticeably discolored.

"The [color change] of CAD/CAM blocks after immersion in coffee varied among products and were comparable to those of restorative composite resins," the authors wrote. "The discoloration of CAD/CAM composite resin blocks could be effectively removed with prophylaxis paste polishing, while that of some restorative composites could not be removed."

More research is needed

The study authors acknowledged one drawback of the study was that it was done in vitro with disks, so it did not mimic the typical environment of the materials. For instance, it is unknown how other factors, including regular toothbrushing, might affect the long-term coloration of the materials when used in patients.

The authors also noted that previous studies have suggested immersing materials in coffee for one week is the equivalent of seven months of coffee drinking, so one month of immersion may have exaggerated the results beyond what would be seen in the real world.

"Future investigations are recommended to evaluate the effect of additional contributing factors on the long-term discoloration resistance of CAD/CAM block materials," the authors concluded. "Within the limitations of this study, the [color change] values ... after immersion in coffee significantly increased with immersion time."

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