Ultrashort pulsed lasers (USPLs) represent a new generation of laser systems in the field of biophotonical applications. In terms of a pilot project, the study was carried out to evaluate the ablation parameters of bone tissue regarding the medical use of such a laser technology in dentistry. Specimens from ribs of freshly slaughtered pigs were assembled and irradiated with an USP Nd:YVO4 laser (pulse duration 8 ps at 1,064 nm with repetition rates between 50 and 500 kHz) using eligible average output powers in the range of 3.5-9 W and fluences between 1 and 2.5 J/cm(2). Square-shaped cavities of 1-mm edge length in the bone compacta were created employing a scanner system. Cavities were analyzed with an optical profilometer to determine the ablated volume. Ablation rate was calculated by the ablated volume and the recorded irradiation time by the scanner software. Additionally, samples were examined histologically to investigate side effects of the surrounding tissue. Formed cavities showed a precise and sharp-edged appearance in bone compacta. Optimized ablation rate of 5.2 mm(3)/min without any accompanying side effects was obtained with an average output power of 9 W, a pulse repetition rate of 500 kHz, and an applied fluence of 2.5 J/cm(2). Provided that the used laser system will be advanced and adjusted for clinical applications, the outcome of this study shows auspicious possibilities for the use of USPL systems in the preparation of bone tissue.

As to the incidence and severity of gingival invaginations, we did not notice any statistically significant differences between the two timeframes. Our data do, however, provide a basis to identify additional confounders and to improve the accuracy of case-load estimations for future trials.

BackgroundGingival invaginations are a common side effect of orthodontic therapy involving tooth extraction and subsequent space closure. Consequences of gingival invaginations are a jeopardized stability of the space closure and hampered oral hygiene. In a retrospective study, the factor time until initiation of orthodontic space closure after tooth extraction has been identified as a potential risk factor for the development of gingival invaginations. The aim of this pilot study is to proof this hypothesis and to enable a caseload calculation for further clinical trials. The referring question is: is it possible to reduce the number of developing gingival invaginations by initiation of orthodontic space closure after tooth extraction at an early point of time?DesignThe intended pilot study is designed as a multicenter randomized controlled clinical trial, comparing the impact of two different time intervals from tooth extraction to initiation of orthodontic space closure on the development of gingival invaginations.Forty participants, men and women in the age range of 11 to 30 years with orthodontically related indication for tooth extraction in the lower jaw, will be randomized 1:1 in one of two treatment groups. In group A the orthodontic tooth movement into the extraction area will be initiated in a time interval 2 to 4 weeks after tooth extraction. In group B the tooth movement will be initiated in a time interval >12 weeks after extraction. A possible effect of these treatment modalities on the development of gingival invaginations will be documented at the moment of space closure or 10 months +/- 14 days after initiation of space closure respectively, by clinical documentation of the primary (reduced number of gingival invagination) and the secondary endpoint (reduction of the severity of gingival invaginations).Trial registrationUniversal Trial Number U1111-1132-6655; German Clinical Trials Register DRKS00004248