<md-sidenav (mouseover)="toggleHover(true)" (mouseout)="toggleHover(false)" (close)="sidenavToggle(false)" (open)="sidenavToggle(true)" [mode]="(_navigation.mediumScreenAndDown && sidenavStyle !== 'off') ? 'over':sidenavMode" [ngClass]="{'icon-sidenav': ((sidenavStyle === 'icon' || sidenavStyle === 'icon overlay') && _navigation.largeScreen), 'over': (sidenavStyle === 'icon overlay')}">

public get sidenavMode(): string {
      if(this.sidenavStyle === 'icon overlay' && this.isHovering) {
          return 'over';
      } else if(this.sidenavStyle === 'icon' || this.sidenavStyle === 'icon overlay') {
         return 'side';
      } else if(this.sidenavStyle === 'hidden') {
         return 'over';
      } else if(this.sidenavStyle === 'off') {
         return 'over';
      }
      return this.sidenavStyle;
  }

ngOnChanges() {
    this.sidenavMode; //method where I am determining sidenav style
    this.changeDetectorRef.detectChanges();
}