Elken Gomes Rivaldo

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

STATEMENT OF PROBLEM Prosthetic crown fit to the walls of the tooth preparation may vary depending on the material used for crown fabrication. PURPOSE The purpose of this study was to compare the marginal and internal fit of crown copings fabricated from 3 different materials. MATERIAL AND METHODS The 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. RESULTS The 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. CONCLUSIONS The marginal and internal fit parameters of the 3 tested materials were within clinically acceptable range.

Functional evaluation of oral rehabilitation with removable partial dentures after five years

Most removable partial denture (RPD) wearers are satisfied with their prostheses, but the factors that influence satisfaction and acceptance are still not determined. Objective: This study explored technical, biological, and satisfaction variables for the functioning of RPDs after five years, and compared the evaluation by the patient and by the clinician. Materials and Methods: Fifty adults (39 females, 11 males) were reexamined after five years of RPD service. Data were collected through clinical examination and a structured questionnaire to record the conditions of supporting soft tissues, prosthesis acceptance and technical characteristics, mastication, esthetics, comfort, hygiene, and need for professional intervention. Data were analyzed by descriptive statistics and Spearman correlation. Results: More than 50% of patients classified their RPDs as excellent regarding retention, mastication, esthetics, comfort, and hygiene. In the professional evaluation, retention and stability were considered excellent in more than 66% of cases, and hygiene of teeth and prostheses was considered good in 52% and 46%, respectively. The metallic framework and acrylic base were considered adapted in 92% of cases. Prosthesis acceptance was associated with retention, mastication, esthetics, hygiene, and comfort evaluated by the patient, and with retention, stability, and condition of the framework evaluated by the clinician. Retention and mastication/comfort evaluated by the patient had moderate positive correlation with retention and stability measured by the clinician. There was no association of hygiene evaluation by the patient and by the clinician. Conclusions: After five years, the oral rehabilitation with RPDs was satisfactory for most cases. There was correspondence between retention/retention and mastication-comfort/stability variables evaluated by the patient and by the clinician. Oral and prosthesis hygiene were not related.

Three-dimensional FEA of effects of two dowel-and-core approaches and effects of canal flaring on stress distribution in endodontically treated teeth.

PURPOSE The aim of this 3D finite element analysis (FEA) was to assess stress distribution and levels in endodontically treated teeth restored with two dowel-and-core systems with differing root canal configurations. MATERIALS AND METHODS Four 3D finite element models of a laser-digitalized maxillary central incisor embedded in alveolar bone were created. Internal morphology data and mechanical properties of the materials were obtained from the literature. Models included a (1) sound tooth (control) versus an endodontically treated maxillary central incisor with a crown ferrule preparation with two restorative approaches of a ceramic crown over a (2) gold alloy dowel-and-core or (3) glass-fiber dowels with composite cores (4) the latter with a flared root canal. A 100 N static load was applied in the center of the palatal surface at a 45° angle, and the stress distribution pattern was analyzed using ANSYS(®) software. RESULTS In Model 1 (control), maximum stresses occurred at the coronal third of the buccal (2.32 × 10(7) Pa) and palatal aspects of dentin. The stress peak value of the model (2.45 × 10(7) Pa) occurred on the palatal aspect of the enamel at the level of the cementoenamel junction. With the insertion of dowels with thin cement layers (Models 2 and 3), stress concentrations in radicular dentin decreased, while they increased in the dowel/cement/dentin interface. These models exhibited the greatest stress peak values in the incisal margin of the gold alloy core (18.9 × 10(7) Pa) and in the cement layer (4.7 × 10(7) Pa). In Model 4, stress peak value was observed in the porcelain crown (4.62 × 10(7) Pa), and there was no stress concentration inside the cement layer. CONCLUSIONS Within the limits of this study, the results suggest that the use of dowels and cements with mechanical properties similar to those of dentin, and an increased cement layer thickness, results in mechanical behavior similar to the physiological behavior of a sound tooth.

Evaluation of Retention Forces and Resistance to Fatigue of Attachment Systems for Overdentures: Plastic and Metal Components

Purpose:To compare retention forces of 3 overdenture attachment systems with metal and plastic components. Materials and Methods:Four samples of each system evaluated (Ball-Attachment [metal]; O-Ring, and ERA [plastic]) were prepared and underwent fatigue and retention force in a universal testing machine. Maximum retention force (N) was measured at 6 time points (from 0 to 36 months—0.5 mm/min). Two-way analysis of variance and the Tukey test were used (&agr; = 0.05). Results:The Ball-Attachment group showed the highest retention values, statistically greater than the other systems, without differences during the trial (42.75–44.75). The ERA group had intermediate values and a statistically significant decrease during the trial (20.75–14). The lowest retention forces were found for the O-Ring group (13.75–11.75), with no statistical differences during the trial. Conclusion:Retention forces are significantly affected by abutment type because the metal retainer was more retentive than plastics, possibly providing better fixation of the prosthesis in position, and more difficult to remove. After 6 months of simulation, retentiveness of both plastic components was similar. There was no fracture of any component.

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

PURPOSE To 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. MATERIALS AND METHODS Three 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. RESULTS The 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. CONCLUSIONS Wear 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.

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.

Evaluation of 1211 Third Molars Positions According to the Classification of Winter, Pell & Gregory

Panoramic radiographs are important for the evaluation and classification of the third molars position, allowing the diagnosis and planning of extraction. The objective of this study is to evaluate upper and lower third molars positions in panoramic radiographs with the classification methods proposed by Pell and Gregory (1933) and Winter (1926) and the subsequent comparison of results with other authors. Panoramic radiographs of 310 patients were analyzed, 197 female and 113 male, totaling 1,211 third molars. In relation to the upper third molars, the most prevalent positions were: angle compared to the long axis of the second molar of Distoangular form (53.23 %) and the depth of impaction as Class C (48.25 %). In the lower third molars, the most prevalent positions were: angle to the long axis of the second molar in Mesioangular classification (52.96 %), the depth of impaction was B (46.54 %) and the tooth relationship with the mandibular ramus was identified as class I (55.26 %). These results provide information that can be utilized in predicting third molar development in terms of impaction or eruption, assisting dental surgeons in making decisions regarding surgical planning and treatment.

Surgical Treatment of Condylar Hyperplasia Associated with Dentofacial Deformity: Low Condylectomy, Articular Disc Repositioning, and Orthognathic Surgery

Debido a la complejidad del tratamiento de la hiperplasia condilar asociada con deformidades dentofaciales y sus complicaciones, si no se trata, el cirujano debe estar alerta ante estos factores en el momento de la planificacion quirurgica para adaptar la terapia optima para cada paciente. Este caso describe un paciente con hiperplasia condilar derecha asociada con la deformidad dentofacial que fue tratado quirurgicamente con condilectomia baja, reposicionamiento y anclaje del disco articular, y la cirugia ortognatica, concomitantemente, con resultados estables, oclusion satisfactoria y armonia facial.

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.

Food intake selection influenced by opposing functional natural teeth or removable denture: observational study

AIM: The purpose of this study was to investigate the relationship between types of dentition in occlusion and the perceived ability to eat a range of common foods in elderly. MATERIAL AND METHODS: We included 363 individuals (117 men, 246 women; mean age = 73.4 ± 5.8 years) Self-reported information on questionnaires were linked to oral examination to establish types of dentition in occlusion assessing their influence on the needs to alter the food selection and on the difficulty to chew key foods. RESULTS: The individuals were classified as having their occlusion performed by completed removable prostheses (D/D) (51.2%), mixed dentition (D/N-N/D) (32.8%) or with natural teeth (N/N) (16%). Individuals with natural teeth N/N or mixed dentition (N/D-D/N) had less necessity to change their food intake, relative to individuals with their occlusion performed by complete removal denture (D/D) (p<0.05). Most of the individuals that had to modify their food intake avoided hard-to-chew food (p<0.05). CONCLUSION: The reduced masticatory ability may lead to changes in dietary selection with risk of an impaired nutritional status especially in elderly complete denture wearers.