PubMed Health⌕ Search

Biomedical subjects

S Erhardson

Publications and source records attributed to S Erhardson.

14 recordsLinked to original sources
PubMed1993

Crown retention and cyclic loading (in vitro).

Cast gold crowns were luted on extracted and prepared human teeth with zinc phosphate cement and subjected to a fatigue test by cyclic loading. The correlation between crown retention and three retention variables was determined by the fatigue test. The results show that the smallest convergence angle tested, 20 degrees, gave better retention than did angles of 40 degrees and 60 degrees, and that surface roughness, surface size, height, and base diameter of the preparations had no influence on crown retention within the parameter sizes tested.

Crowns↗
PubMed1993

Vertical forces developed by the jaw elevator muscles during unilateral maximal clenching and their distribution on teeth and condyles.

The activity of the jaw elevator muscles (EMG) was recorded during maximal clenching in ICP and unilaterally on 2nd and 1st molars, premolars, canines and central incisors in ten subjects with complete dentitions, normal occlusal relationships, and without signs and symptoms of craniomandibular disorders. The EMG activities were converted to relative muscle force. The distribution of this relative muscle force on teeth and condyles was then calculated by means of a three-dimensional mathematical model. The results suggest that the magnitude of the muscle force is strongly associated with the localization of the biting point. Thus the greatest muscle force is produced during clenching in the intercuspal position (100%). At unilateral clenching 75% of this ICP-force is reached during rubber pad clenching on 2nd molars, 85% during rubber pad clenching on 1st molars and 45% during clenching on incisors. The calculations of the mathematical model showed then that highest bite force should be produced on 2nd molars (55% of the muscle force produced in ICP-clenching) and lowest on incisors (20%). Highest condylar load should be found on non-biting side condyles (20% of the muscle force produced in ICP-clenching) and lowest on biting side condyles (0%).

Adult↗
PubMed1983

Pore distribution and fracture localization of flame-soldered joints in dental gold. A metallographic and microfractographic study.

The occurrence of pores and fatigue fractures in flame-soldered joints of dental gold was measured using fractograms and metallographic preparations. All soldered joints contained pores localized mainly in the solder material adjacent to casting/solder and solder/solder interfaces. The porosity portion of these regions was 20-40 volume per cent, consisting chiefly of pores smaller than 0.1 mm. The fatigue fractures were nearly always situated in the same regions or along the casting surfaces themselves.

Dental Casting Investment↗
PubMed1975

Influence of stone mixing agents, impression materials and lubricants on surface hardness and dimension of a dental stone die material.

The influence of different stone mixing agents, impression materials and lubrication methods on the surface hardness of a stone die material has been evaluated. For one impression material the dimensional effect of the mixing agents and lubrication on the dies was also studied. The stone die material was mixed with water or a gypsum hardener and allowed to set on surfaces of glass, agar-agar, polyether, polysulfide and silicone impression materials. The lubrication methods for the stone were mineral oil, water soluble lubricant and mineral oil followed by water soluble lubricant. The surface hardness was measured according to the Brinell test. The Brinell test was chosen after a comparative study of the Brinell, Vickers and Knoop hardness test methods. The results showed that gypsum hardener was preferable to distilled water. The impression materials appear to have influence on the surface hardness of stone. The effect differed on water mixed and hardener mixed stone which emphasizes the importance of the mixing agent. All lubrication decreased the surface hardness of stone. With hardener mixed stone the combination of mineral oil followed by water soluble lubricant seemed preferable. Neither the gypsum hardener nor the lubrication influenced the dimension of the stone die material.

Dental Impression Materials↗