In vitro validation of Digital Image Analysis Sequence (DIAS) for the assessment of the marginal fit of cement-retained implant-supported experimental crowns.

BACKGROUND: The replica technique with its modifications (negative replica) has been used for the assessment of marginal fit (MF). However, identification of the boundaries between prosthesis, cement, and abutment is challenging. The recently developed Digital Image Analysis Sequence (DIAS) addresses this limitation. Although DIAS is applicable, its reliability has not yet been proven. The purpose of this study was to verify the DIAS as an acceptable method for the quantitative assessment of MF at cemented crowns, by conducting statistical tests of agreement between different examiners. METHODS: One hundred fifty-one implant-supported experimental crowns were cemented. Equal negative replicas were produced from the assemblies. Each replica was sectioned in six parts, which were photographed under an optical microscope. From the 906 standardized digital photomicrographs (0.65 µm/pixel), 130 were randomly selected for analysis. DIAS included tracing the profile of the crown and the abutment and marking the margin definition points before cementation. Next, the traced and marked outlines were superimposed on each digital image, highlighting the components' boundaries and enabling MF measurements. One researcher ran the analysis twice and three others once, independently. Five groups of 130 measurements were formed. Intra- and interobserver reliability was evaluated with intraclass correlation coefficient (ICC). Agreement was estimated with the standard error of measurement (SEM), the smallest detectable change at the 95% confidence level (SDC95%), and the Bland and Altman method of limits of agreement (LoA). RESULTS: Measured MF ranged between 22.83 and 286.58 pixels. Both the intra- and interobserver reliability were excellent, ICC = 1 at 95% confidence level. The intra- and interobserver SEM and SDC95% were less than 1 and 3 pixels, respectively. The Bland-Altman analysis presented graphically high level of agreement between the mean measurement of the first observer and each of the three other observers' measurements. Differences between observers were normally distributed. In all three cases, the mean difference was less than 1 pixel and within ± 3 pixels LoA laid at least 95% of differences. T tests of the differences did not reveal any fixed bias (P > .05, not significant). CONCLUSION: The DIAS is an objective and reliable method able to detect and quantify MF at ranges observed in clinical practice.

Full-mouth rehabilitation of a patient with bulimia nervosa. A case report.

Anorexia and bulimia nervosa are eating disorders seen mainly in adolescents or young patients. The dentist should be in the position to recognize early signs of the disorder and alert the patient (and the patient's parents, if necessary) of the possible physical, psychologi cal, and dental consequences. Such dental treatment may help motivate the patient to confront the problem. In this paper the full-mouth rehabilitation, using a combination of galvano- and metal-ceramic restorations, of a young patient suffering from bulimia nervosa is described.

Private practice results of dental implants. Part I: survival and evaluation of risk factors--Part II: surgical and prosthetic complications.

The aim of this study is to present the clinical data from the use of implants that were placed and restored in four independent private dental offices. In part I, the survival rate was calculated and the failure causes were associated with some potential risk factors. In part II, the surgical and prosthetic complications were also recorded and associated both with failures and clinical factors. During 1990-2002 (mean observation 4.6 years), 1692 dental implants were placed and restored in 405 patients in 4 private clinics following the same treatment protocol. The prosthetic restorations included fixed partial dentures, single crowns, and overdentures. The results were statistically analyzed and survival rate probability curves were calculated according to Kaplan-Meier analysis. Part I: Seventy-four implants (4.4%) in a total of 1692 implants failed. The mean of time elapsed before removal of the failed implants was 40 months. The failure rate was higher in the maxilla in patients with metabolic diseases, in D4 bone quality, in smokers, and in patients with insufficient oral hygiene. Part II: Surgical complications happened to 65 implants (3.8%). Prosthetic complications appeared in 152 implants (9%). The overall survival rate (95.6%) in a period of 1 to 12 years is comparable to other studies. The early failures represented a high percentage of failures. Peri-implantitis was the main cause of late failures. The results of this study indicate that the use of implants in private clinics is a safe and predictable method for the treatment of partially or completely edentulous patients, if the proper clinical protocol is followed. The need of a severe recall program must also be emphasized.

Spectrophotometric evaluation of the optical influence of different metal alloys and porcelains in the metal-ceramic complex.

STATEMENT OF THE PROBLEM: Color matching between natural teeth, shade guides, and metal-ceramic restorations is a common clinical problem. Difficulties related to color matching arise from structural differences that exist between metal-ceramic crowns and natural teeth, the limited range of available ceramic shades, inadequate shade guides, different types of metal alloys, and varying compositions of ceramic materials. PURPOSE: The aim of this study was to investigate the influence of various metal alloys and 2 porcelains on the final color of metal-ceramic complex. Material and methods Four commercial alloys for metal-ceramic restorations, a Ni-Cr (Thermobond), a Co-Cr (Wirobond), a Pd-rich noble (Cerapal-2), and a high noble Au-alloy (V-Delta) were combined with 2 porcelains (Vita Omega and Ceramco Silver) in metal-ceramic specimens with a standardized thickness of layers. Five disc-shaped (10 x 1 mm) specimens were prepared for each alloy/porcelain combination. Only opaque and dentin layers were applied (shade A3). The specimens were analyzed with a spectrophotometer, and data were obtained in the CIE Lab color system. The recorded data were analyzed with a 2-way multiple analysis of variance , a pair-wise comparison of group means (Student's t test), and finally, a categorical regression analysis of variance (CATREG) (alpha=.01). RESULTS: The types of alloy substrate and overlying porcelain significantly affected the color (P < .01). Au and Co-Cr alloys were found to be brighter (higher L* values) than the Ni-Cr and the Pd alloys ( P <.01, SE 0.239). Ceramco porcelain was found to be most red (higher a* values) of all tested alloys ( P <.01). Gold and Pd alloys caused a yellow shift to the metal-ceramic color compared to the Ni-Cr and the Co-Cr alloys with both porcelains ( P < .01, SE 0.165). The detected color differences were visually perceptible for some alloy-porcelain combinations. CONCLUSIONS: The final color of metal ceramic specimens was influenced both from the type of alloy substructure and from the type of overlying porcelain.

Selection and modification of prefabricated implant abutments according to the desired restoration contour: a case report.

Implant restorations must fulfill the functional and esthetic demands of the patient. The discrepancy in the diameters of an implant and a natural tooth often leads to compromise. The use of prefabricated abutments that can be individually modified offers certain advantages. Selection and modification of the abutment are simpler when a waxup of the restoration is used as a guideline. This article describes a laboratory technique in which the implant abutment is selected and modified according to the waxup of the restoration.