The International Journal of Prosthodontics, 01/2005

Purpose: Dentists may be the first health care professionals to recognize unusual and abnormal oral movements collectively termed oral dyskinesias. The aims of this clinical overview are to raise the dental community's awareness about this important and complex topic and describe the clinical features and management of the main entities. Materials and Methods: A MEDLINE search of the different entities reported in the English and French literature was conducted. The main findings of a field study on oral dyskinesia were also reviewed. Results: Involuntary movement disorders are often drug related. In other cases, excessive oral movements may occur at any age in relation to various neuropsychiatric conditions. Orofacial dystonia apparently triggered by dental procedures has also been reported. Edentulousness has been associated with oral stereotypes. In a survey of 352 edentulous elderly individuals attending daycare centers, only 7% displayed visible oral sterotypes, and ill-fitting dentures were suggested as a possible triggering factor for the majority. Conclusion: A multidisciplinary evaluation is desirable in the care of individuals with oral dyskinesia and in the selection of those who may benefit from a prosthodontic approach. A good knowledge of potentially offending drugs may allow avoidance of unnecessary procedures.

Purpose: Edentulous patients with denture problems benefit from implant treatment with overdenture prostheses. The aim of this prospective study was to investigate a method of analyzing cost effectiveness in dentistry. As an example, overdenture treatment with two or four implants was compared to the conventional complete denture (CD). Materials and Methods: In a self-selected trial, 20 patients each were treated with implant-retained overdentures (two implants, IRET), implant-supported overdentures (four implants, ISUP), or CDs (control group) in the edentulous mandible. A cost-effectiveness analysis was performed from the patient's perspective, with a time horizon of 6 months. Direct health-care costs were calculated in Swiss Francs (in 2000), and effects were defined as improvements in perceived chewing ability compared with the baseline value before treatment (measured on a VAS). Point estimates for mean incremental cost-effectiveness ratios were complemented with cost-effectiveness acceptability curves to account for uncertainties associated with costs and effects. Results: Mean incremental costs were CHF 4,329 (IRET-CD), CHF 13,360 (ISUP-CD), and CHF 9,031 (ISUP-IRET); these cost differences were all statistically significant. The mean incremental effects at 6 months were 19% (IRET-CD), 23% (ISUP-CD), and 4% (ISUP-IRET). Incremental cost-effectiveness ratios were CHF 228 (IRET-CD), CHF 581 (ISUP-CD), and CHF 2,258 (IRET-ISUP) per percentage increase in chewing ability. Conclusion: From an economic point of view, IRETs were more attractive than ISUPs. The latter were associated with a statistically significant improvement in perceived chewing ability compared to CDs, but at substantially higher costs.

Purpose: The effect of water sorption on the flexural strength and flexural modulus of three fiber-reinforced composites was studied. Materials and Methods: Bar-shaped specimens of each material were prepared according to the manufacturers' instructions. The flexural strength and modulus of each specimen were tested after the specimens were immersed in distilled water for 1, 7, 60, and 180 days. SEMs were taken to examine the mode of failure. The volume percentage of fiber content of each fiber-reinforced composite was experimentally estimated. Results: The ascending order of flexural strength and modulus among the materials was generally: FibreKor Stick Vectris. The flexural strengths of Stick and FibreKor specimens at 1 and 180 days were not significantly different. Although the 180-day Vectris specimens possessed significantly lower flexural strength than the 1-day specimens, the flexural strengths of Vectris specimens at 1, 7, 60, and 180 days remained significantly higher than those of Stick and FibreKor. The difference in flexural modulus for each fiber-reinforced composite related to the duration of water immersion was not significant. Conclusion: Water immersion affected the flexural strengths of the three composites to a different degree but did not affect their flexural moduli significantly. For each duration of water immersion, the flexural property of the fiber-reinforced composite, in ascending order of significant difference, was: FibreKor Stick Vectris.

Purpose: This study tested whether: (1) the survival rate of cast post-and-core restorations is better than the survival of direct post-and-core restorations and post-free all-composite cores; and (2) the survival of these buildup restorations is influenced by the remaining dentin height after preparation. Materials and Methods: In a clinical trial, 18 operators made 319 core restorations in 249 patients. The restorations involved were: (1) cast post-and-core restorations; (2) direct post and composite core restorations; and (3) post-free all-composite cores. All restorations were made under single porcelain-fused-to-metal crowns. Treatments were allocated after dentin height assessment using balanced drawing. Failures were registered during a 5-year period. Results: Fifteen restorations failed during the follow-up period. Five failures occurred during the first month; they were considered to be independent from clinical aging and excluded from further survival assessments. The overall survival was 96% ± 2%. No difference was found between the survivals of the different types of restorations. The factor "remaining dentin height" appeared to have a significant effect on the survival of post-and-core restorations (98% ± 2% survival for "substantial dentin height" vs 93% ± 3% for "minimal dentin height"). Conclusion: The type of post and core was not relevant with respect to survival. The amount of remaining dentin height after preparation influenced the longevity of a post-and-core restoration.

Traditionally, structurally compromised and endodontically treated teeth are restored with post-and-core restorations and covered with conventional crowns. The purpose of this study was to explore whether direct composite buildup restorations, with or without a post and not protected by a covering cast crown, can show acceptable durability over a 5-year observation period. Materials and Methods: The present study was one part of a series of multipractice clinical trials in which the clinical behavior of various types of buildup restorations was the central theme. All patients and teeth included in the present trial were selected as previously described and were chosen because they were either unwilling to have or could not afford a cast crown to cover the buildup restoration. They were treated with a direct composite crown. This trial compared 99 of these restorations either with (n = 53) or without (n = 46) a prefabricated post (Radix or RS; Maillefer) in 87 patients (43 men, 44 women). Application of a post was assigned by balanced drawing. Cores were made from Clearfil Core resin composite (Kuraray), and the restoration was finally covered and finished with Clearfil Ray Posterior (Kuraray). The restorations were made in 27 molars, 54 premolars, and 18 anterior teeth (Fig 1). Operators (17 general practitioners and 1 university clinician) were instructed to strictly observe protocols, and the operative procedures were calibrated. Before entering the study, patients were informed about the protocol, and those who agreed signed an informed consent form. The patients were reviewed at regular 6-month recalls. Life tables were constructed, and log-rank and Wilcoxon tests were used to test the variable "post" for its influence on restoration longevity, with a cutoff value of P = .05. Results: None of the post-free restorations failed (100% survival). Two restorations with posts failed after almost 5 years (survival 96% ± 2%). Both failures were in the maxillary left second premolar and comprised dislodgment of the restorations, with tooth fracture above the cementoenamel junction. Survival difference was not statistically significant. Discussion: The restoration of structurally compromised and endodontically treated teeth with complete composite buildup restorations has been previously described (Fokkinga et al; Roeters; and Smidt and Venezia). However, the reports are in vitro and from short-term study periods. While direct comparison is inappropriate (no intertrial randomization between the present study and the parallel trial), it is worth mentioning that the restorations in the present study showed a similar survival rate to the crowned buildup restorations in the parallel trial. It therefore appears that the technique of direct teeth restorations with resin composite is both promising and feasible, particularly when transitional solutions are required for teeth that need longer evaluation periods. The need for posts in buildup restorations for cast crowns has been questioned in the dental literature. The present study does not support the need for posts for structurally compromised and endodontically treated teeth restored with composite buildups and not covered by cast crowns.

Purpose: The purpose of this retrospective study was to compare the functional outcomes of patients who had mandibular resection and reconstruction with and without prosthetic intervention, and to identify predictive factors that may have an impact on functional outcomes. Materials and Methods: Two hundred twenty head and neck cancer patients who had undergone mandibular resection and reconstruction with at least 6 months of postoperative convalescence formed the basis of this retrospective review. Patients who did not receive prosthetic intervention formed group I (n = 142); those who received prosthetic intervention formed group II (n = 78). Functional outcomes were measured using four individual assessments (nutritional status, swallowing, masticatory performance, and speech) and one that combined the information from these assessments, the global measure of functional outcome (GMFO). Statistical analyses were used to compare the baseline characteristics and functional outcome between groups I and II and to analyze independent predictors for GMFO. Results: Of the 220 patients reviewed, 78 (35%) had prosthetic intervention; group II patients had better individual functional outcome measures and GMFO. Use of a prosthesis remained associated with GMFO after controlling for other significant predictors; other independent predictors were xerostomia, number of remaining mandibular teeth, number of tooth-to-tooth contacts, type of reconstruction, flap interference, and tongue defect. Patients who had fewer mandibular teeth and received a smaller prosthesis had better overall outcome than patients who received a larger prosthesis. Conclusion: Patients who had prosthetic intervention after mandibular reconstruction had significantly better functional outcomes than patients who did not receive prosthetic intervention, even after adjusting for confounding variables.

Purpose: Candida albicans is a component of the normal oral microflora, but local and systemic factors can transform this commensal C albicans to a pathogen. The most frequent cause of Candida opportunistic infections (candidiasis) is dentures, especially if poorly fitting or poorly cleaned. Management of oral candidiasis depends on an accurate diagnosis, identification and elimination of predisposing factors, and, often, use of antifungal agents. The aim of this study was to examine fingernail varnish, currently used for onychomycosis therapy, to reduce the fungal colonization in prosthetic biofilms. Materials and Methods: A varnish containing 5% amorolfine was applied once or twice a week for 6 months in six patients affected by nystatin-resistant denture-related stomatitis. In all six patients, the prostheses had previously been removed at night, and daily antimycotic topical therapy with nystatin had failed to resolve the stomatitis; after 30 days, these patients all showed persistence of candidal stomatitis. Results: After 1 month, five of the six patients were negative for Candida ; this situation was unchanged in the following monthly controls. Only in the patient with suspected Sjögren syndrome was oral Candida found 15 days after the last varnish application. None of the patients had any complaints about the medication. Conclusion: This varnish containing 5% amorolfine, applied once or twice a week for 6 months, was able to suppress the nystatin-resistant denture-related stomatitis.

Purpose: This study tested the hypothesis that the tribochemical silica coating on ceramic surfaces increases the bond strength of resin cement to a glass-infiltrated zirconium-based ceramic. Materials and Methods: Fifteen blocks of In-Ceram Zirconia from CEREC InLab (5 per group) and 15 composite blocks (Z-250) 5 mm × 5 mm × 4 mm were made. The ceramic surfaces were polished, and the blocks were divided into three groups: (1) airborne abrasion with 110-µm aluminum oxide particles; (2) Rocatec system, tribochemical silica coating; and (3) CoJet system, tribochemical silica coating. The ceramic blocks were cemented to the composite blocks using Panavia F according to the manufacturer's specifications. All samples were stored in 37°C distilled water for 7 days and later sectioned in two axes using a diamond disk under cooling to obtain specimens with a cross-sectional area of approximately 1 mm² (n = 45). Each specimen was then attached with cyanoacrylate glue to an adapted device for the microtensile test, which was carried out on a universal testing machine. Results: The results were subjected to ANOVA and Tukey's test. Group 2 (23.0 ± 6.7 MPa) and group 3 (26.8 ± 7.4 MPa) showed greater bond strength than group 1 (15.1 ± 5.3 MPa). There was no significant difference between groups 2 and 3. All failures were in the adhesive zone. Conclusion: The hypothesis was confirmed-the tribochemical systems increased the bond strength between Panavia F and In-Ceram Zirconia.

Purpose: Non-Caucasian patients exhibit different characteristics of oral pigmentation and may request that the acrylic resin parts of their dentures look natural, simulating the original mucosal color. Tooth loss, bone resorption, and lack of attached gingiva may, however, make it difficult to determine what the original pigmentation was like. The purpose of this investigation was to study the distribution in oral pigmentation around the natural dentition in non-Caucasians, in a preliminary effort to classify these variations into a chart of oral pigmentation, and to analyze its reproducibility. Materials and Methods: For the study, 106 dentate non-Caucasians were selected from two universities: ACTA (patient group) and UCLA (nonpatient group). A pigmentation scheme was devised on the basis of half of the participants, and the others were divided into categories by four observers independently. Cohen's kappa was then calculated. Results: On the basis of information obtained from the ACTA participants, six categories of mucosal pigmentation were defined. The kappa statistics for the four observers varied from .58 to .79 for intraobserver agreement and from .15 to .55 for interobserver agreement. Conclusion: The Oral Pigmentation Chart is a simple device that makes it possible to simulate oral pigmentation in the acrylic resin parts of removable dentures. The reproducibility appeared to be acceptable when clinician and dental technician were calibrated. Patients can be offered a choice of the kind of pigmentation geography they want in their removable prostheses.

Reinforced core ceramics are commonly used to deliver more esthetic ceramic restorations with weaker, but more translucent, veneering ceramics. The aim of this study was to evaluate the shear bond strengths of four individual veneering ceramics-three feldspathic and one fluorapatite-to their corresponding core ceramics: leucite-reinforced ceramic (Evopress, Wegold); low-leucite-reinforced ceramic (Finesse, Ceramco); glass-infiltrated alumina (In-Ceram Alumina, Vita); and lithium disilicate (Empress 2, Ivoclar Vivadent), respectively. Materials and Methods: Ceramic cores (n = 10/group, total = 40) were fabricated according to manufacturers' instructions (thickness 3 mm, diameter 5 mm) and ultrasonically cleaned for 15 minutes in ethanol and deionized water. The veneering ceramics were condensed in a stainless-steel mold (diameter 5 mm, height 5 mm, core 3 mm, veneer 2 mm) and fired on the core materials. The samples were tried in the mold for minor adjustments, ultrasonically cleaned, and embedded in polymethyl methacrylate. All groups of core-veneering ceramic combinations were randomly divided into two groups (n = 5/group) for dry and thermocycled storing conditions. Dry samples were kept in a dessicator at room temperature for 24 hours prior to testing, and the other groups were subjected to thermocycling (5 cycles; 5 and 55°C; 30-second dwell time). The shear bond strength tests were performed in a universal testing machine (cross-head speed 0.5 mm/min) (Fig 1). The bond strengths (mean, in MPa, ± standard deviation) and modes of failures were recorded. The means of each group were analyzed by one-way analysis of variance, and multiple comparisons were made by repeated measures test (a = .05) (SAS 8.02, SAS Institute). Results: In dry conditions, the shear bond strength of veneering ceramic to core material in the Empress 2 system was significantly higher (41 ± 8 MPa; P , .05) than those of the Finesse (28 ± 4 MPa), In-Ceram Alumina (26 ± 4 MPa), and Evopress (23 ± 3 MPa) systems (Fig 2). Thermocycling significantly decreased the bond strengths in the Empress 2 system (31 ± 4 MPa) when compared with dry conditions, but the decrease was not significant in the Finesse, Evopress, and In-Ceram systems ( P > .05). Although the failure mode was mainly adhesive at the core-veneer interface for In-Ceram Alumina, predominantly cohesive fractures in the core materials were observed in the Empress 2, Finesse, and Evopress systems. Scanning electron microscopic images exhibited cohesive failures, with partially delaminated surfaces revealing no clear crack sites, and the adhesive failures, particularly in glass-infiltrated alumina/feldspathic ceramic, exhibited visible delamination sites at the core-veneer interface. Conclusion: Bilayered ceramic specimens exhibited complex failure modes that could be attributed to differences in the flexural strengths between the two ceramics, as well as to the differences in their thermal expansion coefficients. Although the thickness of the core ceramic was standard for all groups, it was reported that small variations could affect the strength of the restoration. Fluorapatite veneering ceramic demonstrated higher bond strength to lithium disilicate ceramic than the leucite-glass ceramic/feldspathic ceramic or glass-infiltrated alumina/feldspathic core-veneer ceramic combinations did. After thermocycling, core-veneer bond strength was affected the most in lithium disilicate/fluorapatite combinations.

Despite the fact that reported color data measurements were made relative to the same illuminant, the measurements vary. This is likely due to the use of different instruments made by different manufacturers. The purpose of this study was to investigate whether there were significant differences among the color data measured by different color instruments. Materials and Methods: A series of 19 specimens of ceramic fused to Ni-Co alloy was made. Each specimen had a 13.5-mm diameter and a 1-mm-thick ceramic layer. The colors of the ceramic specimens were Vita A2 (Vintage Halo, Shofu) mixed with A1 or A3 in different percentages and changed gradually from yellow to dark yellow. Five color-measuring instruments were chosen: PR 650 (Japan Electronic); SP-1000 (Beijing University); ShadeEye NCC (Shofu and Minolta); ColorEye 7000 (Macbeth); and Chroma Meter (CR-321, Minolta). The primary illuminant D65, with a d2° observer setting, was selected for the five instruments to standardize the measurement conditions. The Commission Internationale de l'Eclairage (CIE) color parameters (CIE L*a*b*) were measured three times and averaged for each specimen for each instrument. CIE L*a*b* values were analyzed statistically by two-way analysis of variance (ANOVA), paired t test, and Pearson correlation and regression analysis. Results: ANOVA detected statistical differences among the CIE L*a*b* color coordinates of the same series of samples measured by the five instruments. On the other hand, Pearson correlation and regression analysis showed strong correlation among the color data coming from different instruments. Equations were derived for transforming one set of color values to another to allow researchers to compare color data among different instruments. The maximum error of predicted L* values ranged from 0.5 to 1.6 when the L* value was calculated and transferred from one instrument to another instrument with the derived equation. The maximum error of predicted a* values ranged from 0.07 to 0.23, and the maximum error of predicted b* values ranged from 0.15 to 0.69. There was a linear relationship of the L*a*b* values among the five series of color data (Figs 1 to 3). Discussion: The L*a*b* color coordinates of the same specimens showed high correlation among the five different instruments, and the color data from different instruments were comparable when the same specimens were measured. Although there were statistical differences among the L*a*b* color coordinates from different instruments, derived equations would allow researchers to compare color data from different instruments. The maximum predicted error from transforming calculation was mostly within the range of the color differences that human eyes can hardly detect, meaning that the differences between calculated and actually measured values would not be noticed by most observers. Only ceramic powder of shade A was measured in this experiment. More research should be done to determine if these equations could be applied to other ceramic powders. Conclusion: The color data for the same specimens measured on different instruments were correlated, although there were statistical differences among the data.

Purpose: The concepts of need and demand are central in studies on dental care. In the literature, a normative definition is often used, but it pays little attention to the individual's personal comfort and quality of life. Need and demand for prosthodontic services are difficult to measure, as prosthodontic treatment is highly individual and not closely related to edentulousness. Need, however defined, does not always lead to demand for treatment, depending on a variety of factors. Materials and Methods: The present article is part of a larger study in which the intention is to evaluate need and demand for prosthodontic treatment among the participants in a 1989 and 1999 longitudinal study of a population sample. As the first step, this article reports a conceptual analysis of the need concept from the literature. Results: Need is stated as socially established in the interaction between patient and clinician. It makes demand dependent on available treatment options from the care provider and society. In the prosthetic treatment decision-making process, the emancipatory perspective with the patient-clinician dialogue is of utmost importance to achieve an optimal treatment result. Conclusion: The professional attitude toward need must be that there is no true objective or subjective need. Need is established only in a communicative dialogue with mutual respect between the professional and the patient.