Retention of castings with glass ionomer cement

The retentive abilities of a glass ionomer cement, a zinc phosphate cement, and a zinc silicophosphate cement were compared using 20 cast-gold inlays. The mean retentive strength of the glass ionomer cement was the greatest and that of the zinc phosphate cement the weakest. The differences between the mean retentive strengths of all three cements were statistically significant (p = .001).     

An examination of the surface corrosion state of dental fillings and constructions

A group of 115 patients with orofacial complaints has been examined. A new method for intraoral measurement of electrode potentials on the surface of the amalgam fillings and prosthetic constructions has been developed and applied. The possible connections between the measured electrode potentials and patients' saliva properties and their complaints have been discussed. No correlations between measured electrode potentials of the metallic fillings and constructions and important saliva properties could be found. No connections between the measured electrode potentials and the patients' complaints could be proved.     

Comparison of physical properties of polycarboxylate-based and conventional root canal sealers.

Several physical properties of nine commercial root canal sealers were evaluated in vitro and were compared with those of two experimental endodontic materials based on polycarboxylate formulations. Flow, setting time, compressive strength, radiopacity, adhesion to root dentin, and solubility were evaluated. The zinc oxideeugenol root canal sealers were typically of low strength and high solubility. These sealers and the Diaket polyvinyl resin sealer showed no adhesion to dentin. The epoxy resin AH26 showed superior properties with respect to strength, flow, radiopacity, and adhesion; solubility of this material was high. The polycarboxylate formulation showed significantly higher values over the commercial sealers in properties of strength, adhesion, and reduced solubility. The tensile adhesive bond strength of the polycarboxylate to root dentin was twice that of AH26. A wide variation in properties of the commercial materials tested showed the empirical nature of these "sealers." Further testing of polycarboxylate endodontic sealers is indicated.     

Reflex activity in the masseter muscle of young individuals

The monosynaptic myotatic (jaw jerk) potential (MSP) evoked in the relaxed masseter by a tap on the chin and recorded electromyographically in this muscle (latency 6-3 ms, duration 5-9 ms) was similar in subjects with, or without TMJ clicking. The latency of the myotatic potential was significantly shorter (5.8 ms) when evoked during isometric contraction. The duration was 5-2 ms. A potential with similar characteristics as the MSP was evoked by TMJ clicking, as we believe by excitation of muscle spindles from tissue transmitted vibrations (latency 5-5 ms, duration 5-6 ms). The TMJ click evoked MSP could in the contracting massester be followed by silent periods (SPs) both of the early (latency about 10 ms) and the late type (latency about 50 ms). A tap on the chin during isometric contraction of the jaw elevators, was followed by an SP of the early type (latency 12-2 ms, duration 17-5 ms) and sometimes by an SP of the late type (latency 58 ms, duration 18 ms). The late SP occurred significantly more often in patients with TMJ-dysfunction. The period of lower activity following an MSP can be divided into two phases: a first phase with a complete electrical silence, denoted SP, and a second phase during which the activity is slowly increasing to reach the control level. This latter phase will be called "depressed activity" (DA) and is introduced as a new parameter. The SP with tooth tapping (latency 10-5 ms, duration 9-4 ms) was similar in groups with or without TMJ clicking. The superimposed MSP (SMSP) preceding the SP at tooth tapping is supposed to be a manifestation of the "load-compensation reflex".     

Salivary flow, saliva, pH and buffering capacity in 70-year-old men and women

A representative systematic selection of 30% of all 70-year-olds (1148 persons) in Göteborg were invited to a population study. The participation rate was 85%. Sixteen per cent of the men and 25% of the women reported dryness in the mouth (sex. diff. P<0.01). There was a significant correlation between the number of drugs consumed by the subjects and subjective dryness (in both sexes P<0.001). Intake of drugs from the groups of anticholionergics, antihistamines, sedatives, hypnotics or phenothiazines respectively seemed to have the highest predicative value for dryness in the mouth (men P<0.05 and women P<0.01). There was also a positive correlation between subjective dryness and number of definable diseases in both sexes (P<0.01). In a consecutive sample (fifty-eight men and fifty-three women) a study of salivary flow, direct pH and buffer effect were performed. The mean value of unstimulated salivary secretion was in men 0.25 and in women 0.18ml/min. Corresponding figures for stimulated secretion was 1.65 and 1.04ml/min (sex. diff. P<0.01). A significantly lower unstimulated secretion was noted in women with subjective dryness (P<0.01). A negative significant correlation were found between dental invalidity, according to Eichner's classification, and stimulated secretion when drug treatment had been considered (men P<0.05 and women P<0.01). Only weak relations were noted between salivary secretions and drug treatment. Only intake of drugs with diuretic effect were negatively correlated to stimulated secretion (P<0.01). Diseases of the circulatory system were correlated to subjective dryness (P<0.01).