Alvin G. Wee

The combination of a nylon and traditional partial removable dental prosthesis for improved esthetics: A clinical report

A benefit of a nylon partial removable dental prosthesis (PRDP) is the absence of a metal framework, providing improved esthetics. Unfortunately, the lack of a traditional framework reduces rigidity and the support of occlusal rests. This clinical report describes a combination of a nylon PRDP (polyamide denture base resin) and a traditional PRDP (framework/resin) for a Kennedy Class II, Modification 1, partially edentulous mandible.

Proposed shade guide for attached gingiva--a pilot study.

PURPOSEnThe purpose of this study was to evaluate the effect of race, age, and gender on Commision Internationale de lEclairage Lab color space (CIELAB) values of attached gingival colors. The color coordinates of an optimal proposed attached gingival shade guide were also determined.nnnMATERIAL AND METHODSnParticipants (n = 120) were recruited to fulfill the following stratification of five age groups: 18-29, 30-39, 40-49, 50-59, and 60-85, with four racial categories (white, black, Asian, and others) and balanced for gender. Reflectance measurements of participants attached gingiva were made using a spectroradiometer and Xenon arc lamp with a 45/0 optical configuration. A stepwise discriminant analysis was carried out to identify gingival color contribution from race, age, and gender. A hierarchical clustering analysis was used to identify color groups that clustered together. The coverage error of the proposed shade guide was calculated to the original gingival color.nnnRESULTSnThe stepwise discriminant analysis showed a statistically significant difference in gingival color contribution from the factors evaluated. Significant influence was found for the race/gender factors (p < 0.05), but not for age. The cluster analysis results revealed three cluster centroids with mean L*a*b* as follows: (1 = 51.0 ± 4.2, 27.7 ± 4.7, 18.3 ± 3.2), (2 = 61.4 ± 4.5, 24.3 ± 4.3, 17.6 ± 2.3), and (3 = 36.1 ± 4.1, 21 ± 4.9, 16 ± 5.2). The coverage errors to the following racial categories were: Asian (ΔE = 6.0 ± 4.8), black (ΔE = 6.7 ± 3.9), others (ΔE = 5.8 ± 2.9), and white (ΔE = 4.6 ± 2.7).nnnCONCLUSIONSnThe study showed that L*a*b* was significantly affected by race and gender. Clustering analysis was able to identify clusters in 120 participants for three gingival tones.

Proposed shade guide for human facial skin and lip: A pilot study

STATEMENT OF PROBLEMnCurrently, no commercially available facial shade guide exists in the United States for the fabrication of facial prostheses.nnnPURPOSEnThe purpose of this study was to measure facial skin and lip color in a human population sample stratified by age, gender, and race. Clustering analysis was used to determine optimal color coordinates for a proposed facial shade guide.nnnMATERIAL AND METHODSnParticipants (n=119) were recruited from 4 racial/ethnic groups, 5 age groups, and both genders. Reflectance measurements of participants noses and lower lips were made by using a spectroradiometer and xenon arc lamp with a 45/0 optical configuration. Repeated measures ANOVA (α=.05), to identify skin and lip color differences, resulting from race, age, gender, and location, and a hierarchical clustering analysis, to identify clusters of skin colors) were used.nnnRESULTSnSignificant contributors to L*a*b* facial color were race and facial location (P<.01). b* affected all factors (P<.05). Age affected only b* (P<.001), while gender affected only L* (P<.05) and b* (P<.05). Analyses identified 5 clusters of skin color.nnnCONCLUSIONSnThe study showed that skin color caused by age and gender primarily occurred within the yellow-blue axis. A significant lightness difference between gender groups was also found. Clustering analysis identified 5 distinct skin shade tabs.

Lighting conditions used during visual shade matching in private dental offices.

STATEMENT OF PROBLEMnTo our knowledge, no data are available on the actual lighting that is used for visual shade matching in private dental offices.nnnPURPOSEnThe purpose of this study was to determine the shade matching practices and interest in continuing education in dental practices and to determine the quantity and quality of the ambient lighting used during visual shade matching in a sample cohort of dentists in private practices.nnnMATERIAL AND METHODSnThirty-two private practices were enrolled, and each completed a 1-page survey on the clinics shade matching practices. A spectrophotometer was used to measure the ambient lighting in each practice, collecting data on color temperature (Kelvin), color rendering index (CRI), and light intensity (foot candles/fc). A 2-sided nonparametric sign test was used to compare the true median color temperature with the standard (5500°K). A 1-sided t test was used to compare the CRI with the standard (CRI >90) (α=.05 for all statistical analyses).nnnRESULTSnAll dental practitioners surveyed used mainly visual shade matching in their practices. Of those, 87.5% showed interest in attending continuing education on this topic, with 56.3% preferring a clinical demonstration course. The mean color temperature was 4152.9°K and was significantly different from the standard 5500°K (P<.001). The 1-sided t test indicated that the mean CRI was less than 90 (P=1). The 95% confidence interval for the intensity was 80.7 to 111.6 fc.nnnCONCLUSIONSnThe ambient light in the majority of the 32 dental private practices measured was not ideal for visual shade matching.

Evaluating a Web-Based Educational Module on Oral Cancer Examination Based on a Behavioral Framework

Patients at risk of developing oral and/or oropharyngeal cancer (OPC) are more likely to see primary care providers (PCPs) than a dentist. Many PCPs do not regularly perform oral cancer examination (OCE). The purpose of this study was to design a web-based educational program based on a behavioral framework to encourage PCPs to conduct OCE. PCPs were solicited to provide feedback on the program and to evaluate their short-term knowledge. The integrated behavioral model was used to design the program. Fifteen PCPs (five in each group: physicians, physician assistants, and nurse practitioners) reviewed the program and took a posttest: (1) index of knowledge of risk factors for oral cancer (RiskOC) and (2) index of knowledge of diagnostic procedures for oral cancer (DiagOC). Findings from the process evaluation were mainly positive, with comments on the length of the program comprising the ten negative comments. No significant difference among groups of PCPs (physicians, physician assistants, and nurse practitioners) was detected for DiagOC (pu2009=u20090.43) or RiskOC (pu2009=u20090.201). A program on OPC for PCPs should be less than 40xa0min. Postviewing knowledge outcomes were similar for all PCPs. The web-based program on OPC based on a behavioral framework could have similar short-term knowledge outcomes for all PCPs and may increase the number of PCPs performing OCEs.

Long-term clinical evaluation of the color stability and stainability of acrylic resin denture teeth

STATEMENT OF PROBLEMnThe color stability and staining of acrylic resin denture teeth remains an esthetic problem for complete denture wearers.nnnPURPOSEnThe purpose of this study was to evaluate the long-term clinical color stability and stainability of acrylic resin denture teeth in complete denture wearers over a period of 5 years.nnnMATERIAL AND METHODSnFifty participants rehabilitated with complete dentures from February 2008 to December 2013 were selected. The demographic data and the clinical characteristics of participants were recorded. Color change (ΔE) in 3 regions of the denture teeth (incisal, middle, and cervical) was evaluated by spectrophotometry in the CIE L*a*b* system. Participants were asked whether they had noticed any changes in the coloring of the teeth in their dentures. Hierarchical clustering analysis was used to identify groups formed from variables related to demographic questions and color analysis. Two-way ANOVA among the color cluster groups was performed and the Tukey-Kramer test was used as a post hoc test (α=.05). A chi-square test and Fisher exact test were used to identify the association between the study variables and color changes in the participants responses (α=.05).nnnRESULTSnFour cluster groups from 50 participants were identified in the clustering analysis. The ΔE was statistically significant for the interaction between the dental third and cluster groups (P<.001). Cluster groups 1 and 4 exhibited statistically higher ΔE values than cluster groups 2 and 3 (P<.05). Greater chromatic alterations were noted in the incisal third of the teeth than in the cervical and medium thirds in the cluster groups 1 (ΔE=11.03 ±1.22) and 3 (ΔE=4.14 ±1.14) (P<.05). No relationship was found with the participants personal opinions about color change (P>.05).nnnCONCLUSIONnAlthough the acrylic resin denture teeth exhibited color instability and staining in vivo, the participants were unable to identify the color change. The cluster groups with higher color change values consumed more staining solutions.

Coverage error of commercial skin pigments as compared to human facial skin tones

OBJECTIVESnIt is unknown if present-day pigments used for intrinsic colouration of maxillofacial prostheses are representative of human facial skin tones. This studys purpose was to measure L*a*b* values of pigmented elastomers coloured by eleven skin tone pigments and determine coverage error (CE) when the pigments were compared to human facial lip and nose colour data.nnnMETHODSn11 skin tone pigments were combined at 0.1%, 1% and 10% by weight with A-2186 elastomer (n=3). L*a*b* values were measured with a spectrophotometer and group means were used to calculate ΔE* colour differences with each L*a*b* value obtained for human nose and lip. Pigmented elastomer CEs were calculated for nose and lip. Results were compared to CEs for proposed shade guide colours obtained from clustering analyses of facial skin colours.nnnRESULTSnL* values of pigmented elastomers generally were higher than those measured for nose and lip, whereas a* values were lower. CEs for pigmented elastomers were higher than those obtained from the proposed shade guide obtained from clustered skin measurements.nnnCONCLUSIONSnOverall, the current commercial elastomers appeared to be too white and not red enough to adequately match the skin tones of the subject population. Adjustments must be made to the existing pigmenting system in order to adequately match the skin colours of the study population.nnnCLINICAL SIGNIFICANCEnThe creation of a shade guide and a collection of intrinsic pigments representing the realm of human facial skin colours would greatly decrease the time a patient must sit while the clinician is obtaining an acceptable colour match for the silicone to be used for processing the final prosthesis, thereby increasing both patient satisfaction and clinician productivity.

Maxillofacial prosthetics training and practice profiles in the United States

Statement of problem. The motivation of maxillofacial prosthodontists to go into fellowship training and specific procedures in maxillofacial prosthetics practice once they have completed training has not been previously evaluated. Purpose. The purpose of this study was to survey maxillofacial prosthodontists in the United States to investigate their reasons for pursuing maxillofacial prosthetic training and their practice profiles. Material and methods. In June 2015, a survey was sent to all US maxillofacial prosthodontists asking for descriptive demographics, their reasoning as to what prompted entrance into a maxillofacial prosthetic program, and their practice pattern. Frequencies, percentages, means, and standard deviations were calculated and reported. Results. The survey response rate was 60.4%. The main reason for pursuing maxillofacial training was primarily personal satisfaction, prosthodontic residency exposure, and mentorship rather than media exposure and compensation. The time spent in prosthodontic practice varied among practitioners, with the majority of practice time spent accomplishing standard prosthodontic procedures (65.59%) versus maxillofacial (25.53%) or surgical procedures (9.67%). Of 12 clinical maxillofacial procedures inquired about, the most prevalent were obturators, dental oncology, and mandibular resections. Conclusions. This study reveals that personal satisfaction, mentorship, and prosthodontic residency exposure were the reasons most prosthodontists pursued an additional year of maxillofacial prosthetic fellowship. Most were very satisfied with their training and chosen career path and would recommend an additional year of training. The majority of maxillofacial prosthodontists provided maxillofacial prosthetic treatment for approximately one fourth of their practice time. The most common procedures performed were obturators, dental oncology, and mandibular resections.

Flexural strength of small connector designs of zirconia-based partial fixed dental prostheses

STATEMENT OF PROBLEMnPartial fixed dental prostheses with a small connector size are required for optimal esthetics and limited interarch space; however, final strength is endangered.nnnPURPOSEnThe purpose of this in vitro study was to evaluate the effect of different connector designs on the flexural strength of simulated 3-unit partial fixed dental prostheses made of yttria-stabilized tetragonal zirconia polycrystalline using computer-aided design and computer-aided manufacturing technology.nnnMATERIAL AND METHODSnTo simulate a 3-unit partial fixed dental prosthesis, 20 rectangular bar-shaped specimens were fabricated with dimensions of 4 ± 0.05 mm (H) × 4 ± 0.05 mm (W) × 30 0.5 mm (L). Each bar specimen had 2 constricted parts on both sides, representing the connector and defining a central pontic of 10 ± 0.10 mm in length. The specimens were divided into 4 groups according to the connector diameter and design, as follows: SR: 2 mm (H) × 3 mm (W) round 0.6 mm radius of curvature; SS: 2 mm (H) × 3 mm (W) sharp 0.1 mm radius of curvature; CR: 3 mm (H) × 3 mm (W) round 0.6 mm radius of curvature; and CS: 3 mm (H) × 3 mm (W) sharp 0.1 mm radius of curvature. An additional 5 specimens were fabricated with no constriction and served as the control group. The specimens were subjected to a 3-point flexural strength test in a universal testing machine with a crosshead speed of 0.5 mm/min until failure. Scanning electron microscopic and photomicrograph images were used to examine the fracture surfaces. Two-way ANOVA and the Tukey-Kramer post hoc test were used to analyze the data (α = .05).nnnRESULTSnThe mean flexural strength for SR 2 mm (H) × 3 mm (W) round 0.6 mm radius of curvature (583.6 ± 49.7 MPa) was significantly higher than that of SS, which was 2 mm (H)× 3 mm (W) sharp 0.1 mm radius of curvature (502.8 ± 23.3 MPa). Similarly, the mean flexural strength for CR was 3 mm (H) × 3 mm (W) round 0.6 mm radius of curvature (682.9 ± 36.8), which was significantly higher than that of CC, 3 mm (H) × 3 mm (W) sharp 0.1 mm radius of curvature (486.7 ± 35.6 MPa).nnnCONCLUSIONSnThe flexural strength of the yttria-stabilized tetragonal zirconia polycrystalline-based ceramics was affected by the connector dimension and design. The 2-round connector design was more able to withstand occlusal forces than the sharp design. The 3-connector design with a minimum cross section of 2 × 3 mm is recommended for anterior fixed dental prostheses, provided it has a round curvature.

Color change during the surface preparation stages of metal ceramic alloys.

STATEMENT OF PROBLEMnEven though metal ceramic restorations (MCRs) are widely used by clinicians, the influence of the metal on the color of overlaying porcelain is unknown.nnnPURPOSEnThe purpose of this study was to analyze the color alterations of different types of metal ceramic alloys during several stages of metal surface preparation and to determine the effect of those changes on the resulting color of opaque porcelain (OP).nnnMATERIAL AND METHODSnSeven different types of alloys (3 base metal, 3 noble, and 1 high noble) were used to prepare disk-shaped specimens (1 mm × 10 mm, n=3), followed by OP application (0.1 mm). L*a*b* values of specimens were recorded after different stages of metal surface preparation (ingot, after casting, after oxidation, and after the OP application) in addition to the shade tab of OP B1 (target shade). L*a*b* values of alloys were measured from the ingot structure to the OP application stage and statistically analyzed (Repeated measures ANOVA, and Bonferroni corrected paired t test, α=.05). L*a*b* values of OP applied groups and the OP shade tab (target shade) were analyzed (1-way ANOVA with Dunnetts multiple comparison test, α=.05). The color differences of the target shade both before and after OP application were calculated and statistically analyzed (1-way ANOVA, Ryan-Einot-Gabriel-Welsch Multiple Range Test, α=.05).nnnRESULTSnThe L* values of all alloys changed significantly after each stage except for 2 alloys (V-Deltaloy SF (N-VDSF)) and (Gnathos Plus (HN-GP)) after casting and airborne-particle abrasion (P<.05). The a* value of all alloys increased after casting. Changes in the a* coordinate were significant except for one of the base metal alloys (P<.05). The a* coordinate changes of alloys showed variation in direction after oxidation and OP application (P<.05). The b* coordinate changes of alloys showed variation in direction after each stage (P<.05). The L*a*b* values of some OP applied alloys were significantly different from that of the OP shade tab (P<.05). Color difference values (ΔE (OP applied alloy-target shade)) of 2 OP-applied alloys (Cerapall 2 (N-CP2) and Ceradelta (N-CD)) were significantly different (P<.05) and higher than the other OP-applied alloys.nnnCONCLUSIONSnThe achromatic color behavior of different alloys was all in the same direction at all metal surface preparation stages. The chromatic behavior of the different alloys was primarily towards the same direction after casting and airborne-particle abrasion, whereas it varied after oxidation and OP application. The color difference of OP for all alloys, regardless of their type, was not visually perceivable when compared to the target shade (ΔE<2.6).