Porcelain-titanium bonding with a newly introduced, commercially available system.

STATEMENT OF PROBLEM: Titanium is widely used in implant dentistry because of its high strength, toughness, biocompatibility, and low cost. The fabrication of complex substructures is now possible with a number of automated systems. One major obstacle to broad clinical acceptance of porcelain-titanium prostheses is the poor ceramic-metal bonding. PURPOSE: The purpose of this study was to compare titanium bonding with a traditional bonder and a newly introduced titanium bonding system. Bonding was characterized by the delamination crack initiation stress per ISO 9693:2009. MATERIAL AND METHODS: Grade 4 titanium strips were laser machined to meet ISO 9693:2009 standards. Bonding and firing of opaque porcelain was accomplished by using a traditional titanium ceramic system and a newly introduced bonding system. Variables tested besides the bonding system included the length of the porcelain block (7 mm, 8 mm, 9 mm); the thickness of the block (1.0 mm, 1.6 mm); testing the specimens 1 mm off-center; and reusing the strips. Crack initiation stresses were calculated and compared by ANOVA and the Duncan test (α=.05). RESULTS: The newly introduced commercially available system gave the strongest bond (41.82 ±5.7 MPa), followed by the 9 mm specimens (32.2 ±3.9 MPa), then a statistically similar group of the 8 mm, 7 mm, and 1.6 mm thick specimens with new Ti (approximately 23 MPa), and last a similar group with 7 mm, 8 mm, and 1 mm offset loading on reused Ti (approximately 16 MPa). The lower limit under ISO 9693:2009 was 23 MPa. CONCLUSIONS: The newly introduced commercially available system achieved much higher bond strengths than traditional titanium systems, even better than those for many high-gold alloys.

Plasma catecholamines and blood volume in native Andeans during hypoxia and normoxia.

Plasma catechols and blood volume were measured in 20 male, native high-altitude residents of Cerro de Pasco, Peru (4338 m), while hypoxic and subsequently while normoxic at sea level. Ten subjects were healthy controls,with hematocrits lower than 61%, and ten had chronic mountain sickness (CMS), a syndrome of maladaptation to altitude, characterized by polycythemia (hematocrit > 61%), profound hypoxemia, and neurologic symptoms. The main aim of the study was to evaluate the chronic effects of hypoxia on plasma catechols and on blood volume, by studying these parameters during hypoxia at high altitude (HA) and shortly after exposure to normoxia at sea level (SL). Subjects were first studied at HA in their habitual hypoxic environment, and measurements were repeated within 4 hours of arrival at SL (Lima, Peru, 150 m). All subjects had higher plasma norepinephrine (NE), dopamine (DA), and dihydroxyphenylglycol (DHPG) levels in HA (NE in controls and CMS: 414+/-47 and 514+/-35 pg/mL; DA: 9+/-1 and 13+/-1 pg/mL, DHPG: 817+/-48 and 972+/-77 pg/mL) than at SL (NE: 164+/-9 and 243+/-28 pg/mL; DA: 4+/-0.5 and 5+/-1 pg/mL DHPG: 502+/-23 and 649+/-39 pg/mL). Group differences were statistically significant only for NE in the CMS group. Plasma volume was higher in HA in both groups (p<0.05); red cell volume was higher in HA only in the CMS group. The results indicate sympathetic nervous stimulation by chronic ambient hypoxia at altitude in Andean natives, independent of maladaptation to their native environment.