Composite resins may exhibit variation in color within different brands and lots
Considerable variation exists between dental composite resin lots of the same shade designation, as well as between brands of similar shade designations, according to research published online September 13 in Journal of Esthetic and Restorative Dentistry.
A pair of researchers at the College of Dentistry at The Ohio State University, Columbus, OH, wanted to measure differences of 2 appearance characteristics among lots of dental composite resin of the same shade and brand. They also wanted to compare differences among similar shade designations of a different brand.
The authors noted that optimal color matching depended on several factors, including shade selection method, accurate representation of tooth colors on a shade guide, and consistency of shade designations within and among brands of material. They observed that layering was the most common technique used to create a natural looking restoration.
Researchers measured spectral optical scattering and absorption using the Kubelka-Munk reflectance theory, a mathematical model generally accepted as a reliable way to describe the optical behavior of reflectance when layering is used. They compared 3 different lots of shades A1, B2, D3 made by 1 company, with 1 lot of shade EA1 made by another company.
They also measured thickness. Shades were chosen to follow an equal distribution across the lightness scale using a Vita scale guide. Since the main thicknesses used were below 1 millimeter, enamel shades were chosen. Disk-shaped samples of Lot 1 for shades A1, B2, and D3 were fabricated using circular polyvinyl chloride (PVC) templates of 20 mm in diameter and 0.25-mm, 0.6-mm, and 3.9-mm thick, respectively. Samples for shade EA1 were made with circular PVC templates with thicknesses of 0.25 mm and 0.6 mm. One thickness was used to make samples for Lots 2 and 3.
Using a universal testing machine, researchers pressed all samples with a force of about 800 newtons to achieve uniformity. After light curing for about 30 seconds on each side using overlapping irradiation zones, they sanded with 600-grit sandpaper and 1,000-grit sandpaper to remove the surface layer and achieve the desired thickness.
Each sample was placed in a 0-degree observation and a 45-degree optical configuration for radiance measurement. The spectral radiance was measured at its central point in optical contact with white, gray, and black backings. Measurements in the visible spectrum were converted to a reflectance standard using a certified reflectance standard.
Researchers found a wide variation in color and translucency among the lots studied. For instance, they noted the L value of shade A1, Lot 2 was closer to the L value for B2, Lot 1 than it was to other lots of A1. The B value for A1, Lot 2 was closer to the B value of B2, Lot 3 than it was to other A1 lots as well. Researchers also found significant variations of translucency between lots of the same shade.
“These variations,” they concluded, “can introduce error at multiple points in the shade selection process and can present error for color matching in restorative and esthetic dentistry.”
Read the article original article.
Consulting Editor: Luiz Meirelles DDS, MS, PhD
Director, Professional Products and Standards
ADA Science Institute
At-home versus in-office bleaching: a systematic review and meta-analysis
Neither the risk or intensity of tooth sensitivity nor the effectiveness of the bleaching treatment was influenced by the choice of bleaching technique, according to a systematic review appearing in the July/August issue of Operative Dentistry.
A team of researchers conducted a systematic review and meta-analysis to evaluate the risk and intensity of tooth sensitivity during in-office and at-home bleaching in adult patients. They also evaluated the efficacy of dental bleaching.
Among the 12 studies chosen, 7 used a parallel-study design and 5 used a split-mouth design. Six of the 12 studies used a 0 through 10 visual scale for pain evaluation, and 3 used a 0 through 4 rating scale. Two studies did not evaluate tooth sensitivity, and 1 evaluated only the risk of tooth sensitivity.
A total of 10 studies used a shade guide to evaluate color, while 6 added an objective instrument such as a spectrophotometer or colorimeter. Color slide photography was used in 1 study, and photography was used for 2 others.
For at-home bleaching, 9 studies used 10% carbamide peroxide. Carbamide peroxide with different concentrations—15%, 16%, 20%, and 32%—were also used. For in-office bleaching, 7 studies used 35% hydrogen peroxide, 3 used 38% hydrogen peroxide and 2 used 25% hydrogen peroxide.
Daily time use for at-home bleaching varied from 3 through 10 minutes. The number of days ranged from 6 to 28. For in-office bleaching, most studies noted the application time ranged from 20 through 45 minutes, although the authors found variations in this protocol that included application times of 15 or 60 minutes in each session. In one-half of the studies, clinicians or patients performed 2 to 3 bleaching sessions, while some performed only 1 in-office session.
Researchers based their meta-analysis on 5 factors: risk of tooth sensitivity, intensity of tooth sensitivity, color change in ΔSGU, color change in ΔE*, and sensitivity analysis for imputations. In each instance, the researchers found no statistical differences.
“The high heterogeneity observed in this study is probably due to the different in-office and at-home bleaching protocols, varied number of clinical sessions and different concentrations of bleaching gels among the randomized clinical trials,” the authors wrote. Their review of studies showed similar overall satisfaction in terms of comfort and whitening, demonstrating that at-home and in-office bleaching techniques could yield “satisfactory bleaching efficacy.”
Still, researchers cautioned that the low number of studies identified in the systematic review and meta-analysis prevented them from evaluating the impact of variants such as protocols, bleaching agent concentrations, and product brand and composition.
Read the original article.
Predictable and long-lasting posterior restorations
Today’s practices are different than those of five years ago. Dentists don’t have as much time to place multiple layers of composite with a 10- to 20-second cure in between each layer. Find out how Tetric EvoFlow Bulk Fill and Tetric EvoCeram Bulk Fill ensure efficiency, esthetics, and predictable longevity using one great system.
What lies beneath: abutment material influence on crown color
The color results of an implant-supported lithium disilicate ceramic restoration may be clinically unacceptable if placed on a titanium abutment, and zirconia may be a more suitable abutment material for implant-supported ceramic restorations.
Those 2 findings are from research published online July 9 in The Journal of Prosthetic Dentistry. Researchers designed the study to evaluate the effect of 3 types of implant abutment materials on the color of different ceramic material systems.
Researchers prepared 4 specimen groups from 3 different ceramic material systems. A total of 10 disk-shaped samples were made for each system according to the manufacturers’ instructions. One side of each sample was ground with 600-, 800-, 1,000-, and 1,200-grit abrasive disks on a sanding machine at 100 rotations per minute for 15 seconds under water cooling. Thicknesses were controlled and adjusted with a digital micrometer.
Samples were then placed in a disk-shaped mold. An A2 shade veneering was layered onto the unground surfaces. Firing and layering procedures were repeated until the final thickness was achieved. The disks were then autoglazed according to the manufacturers’ recommendations.
Two types of metallic (titanium, gold-palladium) and 1 type of ceramic (zirconia) backgrounds were made to simulate commonly used implant abutment materials. An A2-shade, disk-shaped nanohybrid composite resin background sample was made from a silicone mold to represent the dentin color.
Researchers found that the type of abutment material and ceramic system significantly affected the final color of tested ceramics. They noted that ceramic crowns placed on a titanium or gold-palladium abutment raised absorption and lowered the transmission of incident light, leaving an unnatural appearance. The zirconia allowed some light transmission and did not absorb light.
“The results of the present study showed that implant abutment materials might influence the final color of translucent ceramic systems more than opaque ones,” researchers concluded. Clinically acceptable results were recorded for zirconia and gold-palladium abutments; clinically unacceptable results were recorded for titanium abutments. Zirconia was the most suitable abutment material for implant-supported ceramic restorations, researchers reported.
The study was limited to samples of 1 thickness and shade of ceramic or luting cement. Unlike previous research, the researchers in this study made color measurements on similar implant abutments, luting cement, and ceramic samples to minimize variability. They also applied a refractive index fluid among the layers to eliminate light scattering through the background cement-ceramic layers.
Read the original article.
There’s more to a perfect smile than meets the eye
Dentists who want to improve esthetics can learn more about how their patients smile. The maxillary anterior teeth should not touch but should follow the curvature of the lower lip, and the second premolars should be considered part of the esthetic zone.
Those 2 findings are from a study published in the September/October 2014 issue of The International Journal of Periodontics and Restorative Dentistry.
Researchers designed their study to set up esthetic parameters for natural smiles and dentitions. Those guidelines would be used for dentists to analyze, treat, and restore teeth.
Study participants included 106 adults aged 19 through 29 years. Researchers used 3 inclusion criteria: body mass index, age, and race. They also listed 6 exclusion criteria: restorations, aplasia or hypoplasia, caries, gingival recession or hypoplasia, orthodontic treatment, and crowding that hindered an analysis.
Researchers took digital photographs of each participant: right and left profile, frontal full face, and spontaneous smile. Distance, height, and orientation of the camera were standardized, and all photos were taken in 1 room by 1 investigator.
The examiner realigned the photographs to the papillary line using an image editing program and raster graphic. They determined the facial midline by angling the raster graphic to the papillary line and identifying 2 anatomic landmarks: the bisection of the papillary line and the philtrum.
Researchers identified the dental midline as a line through the contact point between the 2 maxillary central incisors perpendicular to the papillary line. They compared this dental midline with the facial midline for each participant.
A total of 85% of participants had dental midlines that coincided with the facial midline. Just 15% showed a midline shift. About one-half showed an average smile line, while 38% had a high smile line, and 10% had a low smile line. A high smile line appeared to be a more female feature, and an average smile line was a more male feature. Three-quarters showed a nontouching relationship between the maxillary anterior teeth and lower lip. About 23% had touching smiles, and 3% had a slightly covering smile.
The number of visible teeth also plays a key role in esthetics, researchers noted.
They found that male and female patients reveal 75% to 100% of the maxillary anterior teeth and a contiguous band of gingiva.
“This is an important factor when treatment planning anterior restorations, especially in terms of a ‘smile makeover,’” they observed. “The width of the smile and number of exposed teeth have to be considered. Esthetic restoration of visible posterior teeth may be necessary to achieve a harmonious outcome.”
Read the original article.
Achieving great impressions
Did you know that up to 25% of impressions sent to the laboratory are inadequate and can dramatically affect the outcome of cases? So, how do you ensure that your first impression is the best impression? Dr. David Rice provides us with 3 key points to taking an accurate impression. It is important to have great preparations, great isolation and retraction, and great materials. See what features Dr. Rice looks for in an impression material to ensure that his laboratory consistently receives adequate impressions.
New edition: ADA whitening brochure
The ADA introduces a new edition of its patient education brochure, “Tooth Whitening for a Brighter Smile.” The brochure can help practitioners can make whitening choices accessible and easy for patients to understand, explaining the merits of whitening toothpastes, at-home whitening, and in-office whitening, as well as possible side effects.
“Tooth Whitening” also includes dramatic before-and-after photos; it touches on the limitations of whitening and states that there is such a thing as too much whitening. The 6-panel brochure is available in packs of 50 from the ADA Catalog. To order, call 1-800-947-4746 or go to adacatalog.org. The title is available personalized as well. Readers who use the code 16406E before Oct. 30 can save 15% on all ADA Catalog products.
IPS e.max patient education kit now available
Today, more dental professionals choose IPS e.max, the world’s leading all-ceramic. With over 100 million IPS e.max restorations placed, it has become the unchallenged leader around the world for dentists who prefer to treat their patients with the very best. Get your free patient education kit now.
Editorial and Advertising Policies
Any statements of opinion or fact are those of the authors and do not necessarily reflect the views of the American Dental Association. Neither the ADA nor any of its subsidiaries have any financial interest in any products mentioned in this publication. Any reference to a product or service, whether in advertisements or otherwise, is not intended as an endorsement or as approval by the ADA or any of its affiliated organizations unless accompanied by an authorized statement that such approval or endorsement has been granted.
All matters pertaining to advertising should be addressed to the advertising sales manager, Sales and Marketing Department, American Dental Association, Publishing Division, 211 E. Chicago Ave., Chicago, IL 60611, 1-312-440-2740, fax 1-312-440-2550. All advertising appearing in ADA publications must comply with official published standards of the American Dental Association, a copy of which is available on request.