The International Journal of Prosthodontics, 01/2000

Purpose: The objective of this study was to evaluate the clinical quality of 191 porcelain laminate veneers and to explore the gingival response in a long-term survey. Materials and Methods: The clinical examination was made by two calibrated examiners following modified California Dental Association/Ryge criteria. In addition, margin index, papillary bleeding index, sulcus probing depth, and increase in gingival recession were recorded. Two age groups were formed to evaluate the influence of wearing time upon the clinical results. The results were statistically evaluated using the Kaplan-Meier survival estimation method, Chi-squared test, and Kruskal-Wallis test. Results: A failure rate of 4% was found. Six of the total of seven failures were seen when veneers were partially bonded to dentin. Marginal integrity was acceptable in 99% and was rated as excellent in 63%. Superficial marginal discoloration was present in 17%. Slight marginal recession was detected in 31%, and bleeding on probing was found in 25%. Conclusion: Porcelain laminate veneers offer a predictable and successful treatment modality that preserves a maximum of sound tooth structure. An increased risk of failure is present only when veneers are partially bonded to dentin. The estimated survival probability over a period of 10 years is 91%.

Purpose: The aim of this study was to calculate the effect of a soft liner on stress distribution within a mandibular complete denture. Although patients have welcomed softlined complete dentures, early fracture is one of the main reasons for failure. To minimize and prevent prosthesis fracture, the understanding of the stress distribution within a prosthesis is important. Materials and Methods: A 3-dimensional finite element model of a mandibular complete denture for a severely reduced residual alveolar ridge was constructed. The stress was calculated with linear static finite element analysis. The stress distribution in the soft-lined acrylic resin mandibular complete denture was compared with that of a conventional acrylic resin denture. The resulting stresses were displayed in terms of von Mises equivalent stress and the major principal stresses according to 5 different loading conditions: vertical loads in premolar, molar, and incisor regions; and oblique loads in premolar and molar regions. Results: Oblique loads produced higher levels of stress in the labial notch regions than vertical loads, where tension was the primary mode of stress. Significantly reduced levels of von Mises stress were calculated in soft-liner layers under all loading conditions. Acrylic resin denture base portions, however, exhibited higher levels of von Mises stress in soft-lined complete dentures. Conclusion: Three-dimensional finite element analysis gave a realistic explanation of denture fractures and patient response to mandibular complete dentures with and without soft linings. Control of excess lateral occlusal contact might be helpful to reduce the probability of a fracture in soft-lined mandibular complete dentures.

Purpose: The aim of this study was to retrospectively evaluate the clinical retention and abutment movement of 2-unit cantilevered resin-bonded fixed partial dentures (FPD) that were inserted at Prince Philip Dental Hospital in Hong Kong. Materials and Methods: Of 45 patients who were identified from a hospital computer search after receiving a 2-unit cantilevered resin-bonded FPD, 31 were clinically examined (33 FPDs). For each patient the following data were recorded: gender, age, cementation date, endodontic treatment if performed, bone support, tooth mobility, and FPD tipping or drifting. Data about any debonds with subsequent treatment and patient satisfaction on a 10-point scale were also recorded. Results: The mean service life for the 33 prostheses was 30 ± 18 months, with a range of 72 days to 67 months. One prosthesis debonded, resulting in a clinical retention rate of 97%. No rotation, drifting, or tipping was observed for any of the prostheses during the short period of this study. Conclusion: Two-unit cantilevered resin-bonded FPDs are successful in the short term, but further research is required to determine if they offer a viable alternative to fixed-fixed resin-bonded FPD designs.

Purpose: The effect of the aging process on color stability of light-cure, dual-cure, and selfcure resin cements used for luting laminate veneers was investigated in this study. Materials and Methods: Dyract Cem (self cure), Twinlook (dual cure), and En Force (light cure) cements, 0.30 mm thick, were polymerized on laminate veneers that were 13 mm in diameter and 0.50 mm thick in an A2 shade. Five specimens were made for each material. The specimens were subjected to an accelerated aging process in a Weather-Ometer for 900 hours. Spectrophotometric analyses were made after 300, 600, and 900 hours of accelerated aging time. Overall color difference (DE*ab) was determined using the CIE-LAB system for measuring small color differences. Chroma changes (DC*ab) and hue differences (DH*ab) were also determined. DE*ab, DC*ab, and DH*ab were analyzed by one-way analysis of variance, t test for dependent samples, and Tukey honestly significant difference (HSD) tests. Results: DE*ab values determined for the materials in this study varied in the acceptable range of 1.9 to 2.7. Different aging times caused no significant differences in DE*ab, DC*ab, or DH*ab values for any of the materials. There were no significant differences in the amount of overall color change among the 3 resin cements at the same aging period. Twinlook material showed the greatest chroma change at each aging time. The greatest hue change was determined for Dyract Cem material. Conclusion: The light-cure resin cement tested can be proposed as a suitable material for luting laminate veneers, but long-term clinical studies are necessary to verify these experimental findings.

Purpose: The purpose of this study was to describe how dentists evaluated the importance of various items related to a treatment choice between fixed partial dentures (FPD) and single implants, and to analyze if the differences could be explained by dentistrelated variables such as social and demographic attributes, job situation, and attitudes. Materials and Methods: Questionnaires were sent to a random sample of 2,059 Swedish general dentists, with a response rate of 76%. In the questionnaire, the choice between an FPD and a single-implant restoration in a clinical situation was presented. Fifteen items were constructed and the dentists were asked to mark on visual analogue scales the relative importance he or she gave the different items. The items were analyzed through principal components analysis, where a three-factor solution was obtained; the factors were labeled as "time," "health," and "comfort." The factors were run as dependent variables in multiple regression analyses. Results: The items evaluated as most important were "prognosis for delivered treatment" and "patient's wish." Large individual differences were seen, but the differences between groups of dentists were small. Male dentists considered the "health" and the "comfort" factors to be more important compared to female dentists. The attitudinal variable "patient information" was significantly associated with the "time" factor and, inversely, with the "comfort" factor. Conclusion: Differences between individuals were great, but between groups of dentists the differences were only minor. Multivariately, the attitudinal variable "patient information" showed significant associations with the "time" and the "comfort" factors. Dentist-related variables explained little of the variations. The results further indicated a low personal knowledge concerning implant treatments. Psychologic methods might explain more of the individual differences in prosthodontic decision making, but these are not easily used in a questionnaire study. Int J Prosthodont 2000;13:34-40.

Purpose: The determination of an acceptable occlusal plane is essential for the development of esthetic prosthodontic restorations. However, since most faces are not symmetric, a method was developed for measuring facial angular asymmetry, ie, the divergence from the vertical or horizontal of the line joining the midpoint of the intercanthal line and the philtrum of the lip, the interpupillary line, the intermeatal line, the lip commissure line, and the intercuspid line. Materials and Methods: Standardized frontal images (mouth closed, smiling, and biting on a wooden spatula) of 100 subjects were taken using a digital camera. These images were downloaded into a computer, and the angles between the various facial lines and the horizontal were measured. The subjects were grouped by sex, age, and history of trauma and orthodontic treatment. Results: No statistically significant differences were found between the mean values for each group. Conclusion: Asymmetry of the face can be measured using digital camera imaging and computer analysis. A range of facial asymmetries that can influence the choice of occlusal plane during prosthodontic treatment exists. Thus, the use of an occlusal plane parallel to the ala tragus and interpupillary lines, as often advocated by prosthodontists, may result in less than ideal esthetics in the final restoration.

Purpose: The purpose of this study was to measure the in vitro tensile bond strength of 3 types of adhesive resin cements to stainless steel, titanium, carbon fiber-reinforced resin, and zirconium oxide post materials. Materials and Methods: Disks of post materials were polished to 600 grit, air abraded, and ultrasonically cleaned. Zirconium oxide bonding surfaces were pretreated with hydrofluoric acid and silanated. Bis-Core, C&B Metabond, and Panavia cements were bonded to the post specimens and placed in a humidor for 24 hours. Post specimens were debonded in tension. Means and standard deviations (n = 5) were analyzed by 2-way analysis of variance. Tukey-Kramer intervals at the 0.05 significance level were calculated. Failure modes were observed. Results: Panavia 21 provided the highest bond strengths for all types of post materials, ranging from 22 MPa (zirconium oxide) to 37 MPa (titanium). C&B Metabond bonded significantly more strongly to stainless steel (27 MPa) and titanium (22 MPa) than to zirconium oxide (7 MPa). Bis-Core results were the lowest, ranging from 16 MPa (stainless steel) to 8 MPa (zirconium oxide). In most cases, bonds to carbon fiber post materials were weaker than to stainless steel and titanium, but stronger than to zirconium oxide. In general, higher bond strengths resulted in a higher percentage of cohesive failures within the cement. Conclusion: Panavia 21 provided the highest bond strengths to all post materials, followed by C&B Metabond. In most cases, adhesive resins had higher bond strengths to stainless steel, titanium, and carbon fiber than to zirconium oxide.

Purpose: This article analyzes the influence of different pretreatments on the bond strength between inlays and the resin cement of three different composite inlay systems: Z-100, Targis, and Art Glass. Materials and Methods: Four separate treatments of the composite-bonding agent interface were investigated: (1) untreated surface, (2) grinding, (3) sandblasting, and (4) sandblasting followed by silane treatment. Surface topography, roughness, and shear bond strength were evaluated using digital scanning electron microscopy, confocal laser scanning profilometry, and a Lloyd LRX equipped for shear bond testing, respectively. Results: The bond strength is presented both with respect to composite surface pretreatment and with respect to different composite inlay systems. Independent of the composite inlay system, the sandblasted and silane-treated surface was found to give the highest bond strength values, followed by the sandblasted and ground surfaces. The untreated surface showed the lowest bond strength. For pretreated surfaces, Targis showed the highest (P 0.05) bond strength values, followed by Art Glass and Z-100. This distribution, however, was reversed for the untreated interface, where Z- 100 showed the highest bonding strength (P 0.05). Conclusion: Surface pretreatment and roughness as well as the inlay material have an impact on the bond strength and the retention of composite inlays.

Purpose: The study examined the bond strength between 2 types of denture teeth and 3 denture base resins. The denture teeth were untreated, prepared with diatorics, or treated with dichloromethane, a solvent. Materials and Methods: Conventional denture teeth and cross-linked denture teeth were bonded to either a heat-cured denture base resin, a microwave-cured denture base resin, or a pour-type denture base resin. Compressive load was applied at 45 degrees on the palatal surface of each tooth until fracture. Results: Conventional resin teeth possessed higher bond strength than cross-linked denture teeth. The heat-cured denture base resin significantly surpassed the microwave-cured denture base resin in bond strength. Both materials were better than the pour-type resin. The application of dichloromethane resulted in a significantly better improvement in bond strength compared to the use of diatorics. Conclusion: It is recommended that dichloromethane be applied on the denture teeth ridge-lap area prior to denture base processing.