Comparison of osseointegration in piezoimplants versus cylindrical implants

BACKGROUND: Dental implants have been successful for the restoration of edentulous areas, but current techniques are inadequate in areas lacking sufficient bone volume. Piezoelectric surgery has shown encouraging effects on both osseous healing. A new wedge-shaped titanium PiezoImplant requires piezoelectric osteotomy. This study compares PiezoImplants to conventional threaded cylindrical shaped implants by microcomputed tomography and histology to assess osseointegration, tissue response, and alveolar ridge changes. METHODS: After 3 months post-extraction, 18 conventional cylindrical implants and 18 wedge-shaped PiezoImplants were placed using a split-mouth design in 3 adult mini pigs. The cylindrical implant sites were prepared for osteotomy with rotary instrumentation while the PiezoImplant sites were prepared with piezoelectric surgical inserts. One animal was sacrificed at 4, 8, and 12 weeks post operation. Quantitative µCT and histological analysis evaluated bone volume, osseointegration, and post-operative cellular events. RESULTS: The results of a multivariable linear regression model demonstrated that the PiezoImplants, arch location, and time were significant factors on higher BV/TV percentage. Bone to implant contact (BIC) analysis by high resolution microscopy and histomorphometry indicated osseointegration though intimate contact between implants and adjacent alveolar bone in both groups. The tissue response displayed no evidence of abnormal healing and the PiezoImplant was classified as a non-irritant. CONCLUSION: The combination of piezoelectric osteotomy and newly designed PiezoImplants had favorable effects on wound healing and osseointegration compared to conventional cylindrical implants. These novel wedge-shaped implants may be beneficial for narrow ridge spaces without additional ridge augmentation. Further research is needed to establish clinical validity

A Bayesian Incentive Compatible Mechanism for Fair Division

We consider the problem of fairly allocating one indivisible object when monetary transfers are possible, and examine the existence of Bayesian incentive compatible mechanisms to solve the problem. We propose a mechanism that satisfies envy-freeness, budget balancedness, and Bayesian incentive compatibility. Further, we establish the uniqueness of the mechanism under an order additivity condition. This result contrasts well with various results on the incompatibility between efficiency and ex post incentive compatibility.

Secure Implementation in Shapley-Scarf Housing Markets

This paper considers the object allocation problem introduced by Shapley and Scarf (1974). We study secure implementation (Saijo, Sjostrom, and Yamato, 2007), that is, double implementation in dominant strategy and Nash equilibria. We prove that (i) an individually rational solution is securely implementable if and only if it is the no-trade solution, (ii) a neutral solution is securely implementable if and only if it is a serial dictatorship, and (iii) an efficient solution is securely implementable if and only if it is a sequential dictatorship. Furthermore, we provide a complete characterization of securely implementable solutions in the two-agent case.

Secure Implementation in Shapley-Scarf Housing Markets

This paper considers the object allocation problem introduced by Shapley and Scarf (1974). We study secure implementation (Saijo, Sjöström, and Yamato, 2007), that is, double implementation in dominant strategy and Nash equilibria. We prove that (i) an individually rational solution is securely implementable if and only if it is the no-trade solution, (ii) a neutral solution is securely implementable if and only if it is a serial dictatorship, and (iii) an efficient solution is securely implementable if and only if it is a sequential dictatorship. Furthermore, we provide a complete characterization of securely implementable solutions in the two-agent case.ISER discussion paperDecember 2008 Revised February 200

A Bayesian incentive compatible mechanism for fair division

We consider the problem of fairly allocating one indivisible object when monetary transfers are possible, and examine the existence of Bayesian incentive compatible mechanisms to solve the problem. We propose a mechanism that satisfies envy-freeness, budget balancedness, and Bayesian incentive compatibility. Further, we establish the uniqueness of the mechanism under an order additivity condition. This result contrasts well with various results on the incompatibility between efficiency and ex post incentive compatibility

Secure implementation in economies with indivisible objects and money

This paper studies the application of the notion of secure implementation (Cason, Saijo, Sjöström, and Yamato, 2006; Saijo, Sjöström, and Yamato, 2007) to the problem of allocating indivisible objects with monetary transfers. We propose a new domain-richness condition, termed as minimal richness. We then establish that on any minimally rich domain, only constant social choice functions are securely implementable

Effects of Propofol on Left Ventricular Mechanoenergetics in the Excised Cross-circulated Canine Heart

Although propofol is commonly used for general anesthesia, its direct effects on left ventricular (LV) contractility and energetics remain unknown. Accordingly, we studied the effects of intracoronary propofol on excised cross-circulated canine hearts using the framework of the Emax (a contractility index)-PVA (systolic pressure-volume area, a measure of total mechanical energy)-Vo2 (myocardial oxygen consumption per beat) relationship. We obtained 1) the Vo2-PVA relationship of isovolumic contractions with varied LV volumes at a constant Emax, 2) the Vo2-PVA relationship with varied LV volumes at a constant intracoronary concentration of propofol, and 3) the Vo2-PVA relationship under increased intracoronary concentrations of either propofol or CaCl2 at a constant LV volume to assess the cardiac mechanoenergetic effects of propofol. We found that propofol decreased Emax dose-dependently. The slope of the linear Vo2-PVA relationship (oxygen cost of PVA) remained unchanged by propofol. The PVA-independent Vo2-Emax relationship (oxygen cost of Emax) was the same for propofol and Ca2＋. In conclusion, propofol showed a direct negative inotropic effect on LV. At its clinical concentrations, decreases in contractility by propofol were relatively small. Propofol shows mechanoenergetic effects on the LV that are similar to those of Ca2＋ blockers or ß-antagonists—i.e., it exerts negative inotropic effects without changing the oxygen costs of Emax and PVA