1. SIB Labs, University of Eastern Finland, Kuopio, Finland;
2. Department of Applied Physics, University of Eastern Finland, Kuopio, Finland;
3. Institute of Dentistry, University of Eastern Finland, Kuopio, Finland;
4. Research Unit of Oral Health Sciences, University of Oulu, Oulu, Finland;
5. Educational Dental Clinic, Kuopio University Hospital, Kuopio, Finland