To investigate the behaviour of early loaded palatal implants when observed with resonance frequency analysis (RFA). Twenty patients (seven males and 13 females, mean age 26.4 years) received one palatal implant each (length: 4 mm, diameter: 3.3 mm; Orthosystem) for maximum orthodontic anchorage. The implants' stability was observed by RFA. Measurements were carried out at the time of surgery, after first orthodontic loading and subsequently once a week over a period of 12 weeks. Two palatal implants were lost. The other 18 remained stable. The average period from insertion to first loading was 6.7+/-0.8 days. The mean orthodontic force applied was 272.2+/-73.2 cN. The implant stability quotient (ISQ) value at the time of surgery averaged 69.4+/-3.9. The mean ISQ value 6.7 days after insertion was 69.8+/-3.6. Twelve weeks post-surgery the mean ISQ value was 69.8+/-3.5. A statistically significant decrease in stability was observed after 2 and 3 weeks post-surgery (P=0.005 and 0.04). The behaviour of early loaded palatal implants showed an initial decrease of the ISQ values. From 6 weeks post-surgery onward the ISQ values increased. Within the limitations of this study, the results suggest that the healing time of palatal implants reported in the literature (12 weeks) should be discussed. An orthodontic loading of palatal implants 6 weeks post-surgery with a force up to 400 cN seems to be justified. Yet further investigations are necessary to evaluate the behaviour of early loaded palatal implants considering observation periods of over 12 weeks.

Ankylosed teeth are considered in orthodontic treatment planning; however, diagnostic tools to quantify the rigidity of the tooth-to-bone connection are rare. Resonance frequency analysis (RFA) can quantify the rigidity of the dental implant-to-bone connection and thus may serve as a potential diagnostic tool to identify ankylosed teeth. To test this assumption, we examined 15 and 30 primary mandibular molars, with and without clinical signs of ankylosis, using the Osstell Mentor system. A cut-off implant stability quotient (ISQ) of 43 provided a specificity of 100% and a sensitivity of 53.3% when measured in the mesio-distal direction or a sensitivity of 20% when measured in the bucco-lingual direction. Based on a receiver-operating characteristic (ROC), the area under the curve (AUC) of 0.807 showed the mesio-distal direction of measurement to be a test of moderate discriminatory power. Given its non-invasiveness, RFA may serve as a quantitative diagnostic supplement to the clinical examination of potentially ankylosed primary molars.