[Migration of a retained premolar into the processus muscularis of the mandible]. / Migration eines retinierten Prämolaren in den Processus muscularis des Unterkiefers.

Migration of an impacted mandibular premolar is a rare finding, whereas dystopia of lower jaw cuspids is described much more often in the literature. We present a patient in whom radiographic studies show the migration of a mandibular premolar to the muscular process over a period of 14 years. Most of the tooth migration along the vertical portion of the mandibula into the processus muscularis took place after the root development had ended. Neither radiological nor clinical examination revealed the stimulus which changed the path and the direction of the impacted tooth.

Effects of various hygiene procedures on the surface characteristics of titanium abutments.

The use of cleaning instruments on titanium implants may cause undesired surface alterations. In a qualitative and quantitative assessment of these alterations, 5 titanium implant abutments were treated with a steel curet, a prototype pure titanium curet, an air abrasive polishing system, and an ultrasonic system. Custom-made polymer templates, used to secure the curet to a vertical guide bar and a spring scale to maintain a constant instrument pressure, guaranteed a standardized procedure and reproducible results. The ultrasonic and the air abrasive polishing method were also standardized. Evaluation by scanning electron microscopy (SEM) revealed surface alterations for all instruments and systems except the plastic curet, which did not roughen the surface at all. The confocal laser-scanning microscope allows a 3-dimensional reproduction of these surface alterations and their direct measurement. The profilometric tracing was not sensitive enough to register the minor effects caused by the titanium curet and the air abrasive polishing system. Dimensions of the resulting surface microstructure could be determined with the laser-scanning microscope. Since the influence of such surface defects on the peri-implant tissue reaction is unpredictable, the titanium curet and the air abrasive system can only be recommended with restrictions. The steel curet and the ultrasonic system proved to be totally unsuitable for cleaning titanium implants.