To assess the hardness differences, the examiner placed each test specimen on the tongue with chopsticks, and then the participants chewed on all sides and swallowed. They were asked to remember the hardness of the first specimen, which always had medium hardness and served as a control, and then to determine the level of hardness (hard, medium, or soft) of four consecutive and randomly administered specimens by comparing them with the first one. This test was conducted in a double-blind manner to eliminate examiner bias.

The number of correct answers of hardness was used as a measure of hardness recognition. The subjects were allowed to expectorate any specimen that could not be chewed well enough to be swallowed and could change their answers until the last specimen was chewed.

Occlusal contact area, maximum bite force measurements, masticatory efficiency, and discriminating hardness assessments were performed on four occasions: (1) before implant surgery with the complete denture in situ, (2) 3 h after surgery, (3) 1–2 weeks, and (4) 3 months after insertion of the provisional screw-retained restoration.

Considering the small sample size in the present psychophysical experiments, the option was taken to report mainly the descriptive statistics, in terms of average (SD, range) values for bite force, occlusal contact area, glucose concentration, and number of correct answers regarding hardness. Some nonparametric analyses were added in the difference between baseline prior to surgery and the follow-up data (Wilcoxon test, SPSS for Macintosh ver.21, SPSS, Chicago, USA). A p value <0.05 was considered to be statistically significant.