Luis Carlos da Fontoura Frasca

Evaluation of marginal and internal fit of ceramic and metallic crown copings using x-ray microtomography (micro-CT) technology

STATEMENT OF PROBLEMnProsthetic crown fit to the walls of the tooth preparation may vary depending on the material used for crown fabrication.nnnPURPOSEnThe purpose of this study was to compare the marginal and internal fit of crown copings fabricated from 3 different materials.nnnMATERIAL AND METHODSnThe selected materials were zirconia (ZirkonZahn system, group Y-TZP), lithium disilicate (IPS e.max Press system, group LSZ), and nickel-chromium alloy (lost-wax casting, group NiCr). Five specimens of each material were seated on standard dies. An x-ray microtomography (micro-CT) device was used to obtain volumetric reconstructions of each specimen. Points for fit measurement were located in Adobe Photoshop, and measurements were obtained in the CTAn SkyScan software environment. Marginal fit was measured at 4 points and internal fit at 9 points in each coping. Mean measurements from the 3 groups were compared by analysis of variance (ANOVA) at the 5% significance level, and between-group differences were assessed with the Tukey range test.nnnRESULTSnThe nickel-chromium alloy exhibited the best marginal fit overall, comparable with zirconia and significantly different from lithium disilicate. Lithium disilicate exhibited the lowest mean values for internal fit, similar to zirconia and significantly different from the nickel-chrome alloy.nnnCONCLUSIONSnThe marginal and internal fit parameters of the 3 tested materials were within clinically acceptable range.

Wear Potential of Dental Ceramics and its Relationship with Microhardness and Coefficient of Friction.

PURPOSEnTo evaluate, by means of pin-on-disk testing, the wear potential of different dental ceramic systems as it relates to friction parameters, surface finish, and microhardness.nnnMATERIALS AND METHODSnThree groups of different ceramic systems (Noritake EX3, Eris, Empress II) with 20 disks each (10 glazed, 10 polished) were used. Vickers microhardness (Hv) was determined with a 200-g load for 30 seconds. Friction coefficients (μ) were determined by pin-on-disk testing (5 N load, 600 seconds, and 120 rpm). Wear patterns were assessed by scanning electron microscopy (SEM). The results were analyzed using one-way ANOVA and Tukeys test, with the significance level set at α = 0.05.nnnRESULTSnThe coefficients of friction were as follows: Noritake EX3 0.28 ± 0.12 (polished), 0.33 ± 0.08 (glazed); Empress II 0.38 ± 0.08 (polished), 0.45 ± 0.05 (glazed); Eris 0.49 ± 0.05 (polished), 0.49 ± 0.06 (glazed). Microhardness measurements were as follows: Noritake EX3 530.7 ± 8.7 (polished), 525.9 ± 6.2 (glazed); Empress II 534.1 ± 8 (polished), 534.7 ± 4.5 (glazed); Eris, 511.7 ± 6.5 (polished), 519.5 ± 4.1 (glazed). The polished and glazed Noritake EX3 and polished and glazed Eris specimens showed statistically different friction coefficients. SEM image analysis revealed more surface changes, such as small cracks and grains peeling off, in glazed ceramics.nnnCONCLUSIONSnWear potential may be related to the coefficient of friction in Noritake ceramics, which had a lower coefficient than Eris ceramics. Within-group analysis showed no differences in polished or glazed specimens. The differences observed were not associated with microhardness.

Direct method for construction of prosthetic bite opening and positioning stents for head and neck tumor radiotherapy

INTRODUCTION: Radiotherapy for head and neck tumors causes a series of adverse effects. Some effects are temporary, such as oral mucositis and taste disorders, and others are permanent, such as xerostomia and increased risk for dental caries and osteoradionecrosis. One way to diminish radiotherapy’s adverse effects is to decrease the radiation dose on healthy tissues outside the tumor area through more precise radiotherapy techniques, such as intensity-modulated radiation therapy (IMRT), which depends on positioners and stabilizers to the anatomic structures. CASE REPORT: This paper presents direct construction technique examples of mouth openers and positioning stents for tongue and mandible, which allow distance from the radiation field for healthy organs as well the precise stabilization required for the IMRT technique. CONCLUSION: The clinical cases shown in the present paper also illustrate that the intra-oral devices for stabilization of the dental arches and tongue are effective in reducing unnecessary radiation on healthy organs.

Impact of Cleft Lip and Palate on Oral Health-Related Quality of Life (OHRQOL) in Brazilian Patients

Objective: To evaluate self-esteem, satisfaction with facial aesthetics and the impact of oral health on the quality of life of patients with cleft lip and palate aged from 12 years treated at the Hospital for Rehabilitation of Craniofacial Anomalies (HRAC), Brazil. Material and Methods: A cross-sectional study was conducted with patients (n=94) with cleft lip and palate, aged 12 years and older, treated at the Hospital for Rehabilitation of Craniofacial Anomalies, University of Sao Paulo, Brazil. The instruments used in this study were: Rosenberg’s Self-Esteem Scale, the Oral Health Impact Profile-14 (OHIP), and a visual analogue scale of self-perceived facial aesthetics were applied, and socioeconomic and contextual data were collected from all patients. The statistical analysis included Poisson regression with robust variance (RR – rate ratio) and it was performed to evaluate the association between predictors and the outcome oral health related-quality of life. Results: Worse OHRQoL was reported by female patients (RR 1.21; 95%CI: 1.09-1.35) and older individuals (RR 1.25; 95%CI:1.13-1.39). Conclusion: The presence of cleft lip and palate has a negative impact on OHRQoL. Females and older individuals reported worse qualify of life.

Inside Marginal Adaptation of Crowns by X-ray MicroComputed Tomography

Prosthetics treatments with total or partial reconstruction are highly recommended in order to investigate caries, fractures and for better aesthetic. The purpose of this study was to evaluated marginal and internal fit of infrastructures (ceramic and metal) by using a high resolution X-ray micro-computed tomography. Each framework was placed on the original model and scanned. Image processing analysis and statistical approaches were combined together to evaluated directly in 3D the gap between the crown and the dental, which makes it possible to have a realistic dental arcade model.