Comparative in vitro study of the accuracy of impression techniques for dental implants: Direct technique with an elastomeric impression material versus intraoral scanner.

BACKGROUND: The aim of this study was to compare a conventional technique (elastomeric impression material - EIM) and a digital technique (scanner digital model - SDM) on a six-analog master model (MM) to determine which was the most exact. MATERIAL AND METHODS: Twenty impressions were taken of a master model (EIM) and twenty scanned impressions (SDM) (True Definition). A coordinate measuring machine (CMM) was used to measure the distances between adjacent analogues (1-2, 2-3, 3-4, 4-5, 5-6), intermittently positioned analogues (1-4, 3-6) and the most distal (1-6). Reference values were established from the master model, which were compared with the two impression techniques. The significance level was established as 5% (p<0.05). RESULTS: The precision of each technique was compared with MM. For adjacent analogues (1-2), no significant differences were found between EIM-MM (p=0,146). For intermittently positioned analogues (1-4), SDM did not show significant differences with MM (p=0.255). For the distance between distal analogues (1-6), significant differences were found between both techniques and MM (p=0.001). CONCLUSIONS: In a clinical situation with < three implants, EIM is more exact than SDM, but in cases of four implants SDM is more exact. For rehabilitations (> four implants), neither technique can be considered accurate although error falls within the tolerance limits established in the literature (30-150µm).

A clinical longitudinal study 323 porcelain laminate veneers. Period of study from 3 to 11 years

Objective: The objective of this study was to evaluate the clinical results of 323 porcelain laminate veneers overa period of 3 to 11 years.Material and Methods: This study included 70 patients, aged between 18 and 74 years. Of the 323 total veneers,124 were of a simple design and 199 were of a functional design. The condition of the soft tissues and hygiene, inaddition to the condition of the abutment teeth, the restorations and patient satisfaction were all clinically examined.In carrying out the statistical analysis, a descriptive approach was taken in analyzing the data. The KaplanMeier method was used for statistically analyzing the survival rates of the porcelain laminate veneers.Results: Analysis of the soft tissue revealed marginal recession in 7.7% of the cases, and in 21.6% of the cases,bleeding was detected on probing. Analysis of the condition of the abutment teeth revealed secondary caries andhypersensitivity in 3.1% of the cases, and changes in pulp vitality were observed in 2.8% of the cases. In studyingthe condition of the restorations, marginal integrity was observed to be excellent in 98% of the cases, slight marginalpigmentation was present in 39.3% of the cases, fractures were present in 4% of the cases and decementationin 9% of the cases. The degree of patient satisfaction was considered to be excellent in 97.1% of the cases.Conclusions: Porcelain laminate veneers are a predicable treatment option that offer excellent results (AU)

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A clinical longitudinal study 323 porcelain laminate veneers. Period of study from 3 to 11 years.

OBJECTIVE: The objective of this study was to evaluate the clinical results of 323 porcelain laminate veneers over a period of 3 to 11 years. MATERIAL AND METHOD: This study included 70 patients, aged between 18 and 74 years. Of the 323 total veneers, 124 were of a simple design and 199 were of a functional design. The condition of the soft tissues and hygiene, in addition to the condition of the abutment teeth, the restorations and patient satisfaction were all clinically examined. In carrying out the statistical analysis, a descriptive approach was taken in analyzing the data. The Kaplan Meier method was used for statistically analyzing the survival rates of the porcelain laminate veneers. RESULTS: Analysis of the soft tissue revealed marginal recession in 7.7% of the cases, and in 21.6% of the cases, bleeding was detected on probing. Analysis of the condition of the abutment teeth revealed secondary caries and hypersensitivity in 3.1% of the cases, and changes in pulp vitality were observed in 2.8% of the cases. In studying the condition of the restorations, marginal integrity was observed to be excellent in 98% of the cases, slight marginal pigmentation was present in 39.3% of the cases, fractures were present in 4% of the cases and decementation in 9% of the cases. The degree of patient satisfaction was considered to be excellent in 97.1% of the cases. CONCLUSIONS: Porcelain laminate veneers are a predicable treatment option that offer excellent results.

Response of three types of cast posts and cores to static loading.

OBJECTIVE: An analysis is made of the influence of continuous compression loading on different types of cast posts and cores and its effects on the crowns and teeth. METHOD AND MATERIALS: Thirty extracted maxillary canines were prepared and divided into three groups (n = 10) according to the type of cast posts and cores used for restoration: chrome-nickel alloy, acetalic resin, and IPS-Empress porcelain. Metallic cast crowns were luted onto the cores. The specimens were evaluated with an Instron testing machine at an angulation of 45 degrees and a forward speed of 0.5 mm/min. After testing, the specimens were sectioned along the axis and examined under x40 magnification. RESULTS: Mean load resistance of the restorations until fracture was 2,120 N, 1,491 N, and 2,139 N in the chrome-nickel, IPS-Empress ceramic, and acetalic resin groups, respectively. CONCLUSION: Significant differences in resistance were observed between metal and porcelain and between resin and porcelain. Microscopically, the apical portion was found to be most affected by fracture and compromised the teeth subjected to chrome-nickel restorations. The metal cast posts and cores exhibited different angulations, while the ceramic restorations showed cracks. The acetalic resin cast posts and cores presented no fractures.

Estudio in vitro de las fuerzas de retención de los retenedores directos de resina acetálica frente a los metálicos en prótesis parcial removible / Measurement in vitro of the retention force of the acetalic clasp versus metalic clasp in removable partial prosthesis

Se presenta un estudio experimental in vitro en el que se compara la retención que ofrecen los retenedores circunferenciales tipo Ackers de resina acetálica con los de cromo-cobalto. Se realizan para ello 6 coronas de cromo-níquel, 3 con forma de canino superior y 3 con forma de primer premolar superior y cada una de ellas con un grado diferente de retención (0.25, 0.50 y 0.75 mm). Sobre cada una de ellas se confecciona un retenedor de resina acetálica y uno de cromo-cobalto, siendo testados por una máquina Instron. Los resultados confirman que los retenedores de cromo-cobalto son más retentivos, y que los acetálicos ofrecen una retención suficiente para cumplir su cometido (AU)

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