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A novel implant system resembling the shape of a wedge and employing piezosurgery for implant bed preparation has been introduced with the aim of solving the problem of horizontal bone deficiency. This in vitro study compared emerging bone strain during insertion of a conventionally round implant vs. the wedge implant . Adhering to the manufacturers’ protocols, implant surgery was performed in polyurethane foam blocks equipped with strain gauges attached to the buccal and occlusal surfaces. Five implants per group were placed while strain development during insertion was recorded. Primary implant stability was determined using resonance frequency analysis (RFA). Statistical analysis was based on Welch two sample tests (α=0.05). In general, greater strain development was found on the buccal aspect of bone as compared to the occlusal aspect with an overall range between -724µm/m and 9,132µm/m. A stepwise increase in strain development was seen in the wedge implants while in the round implants a continuous increase in strain development was recorded. Absolute strain development on the buccal aspect of bone was significantly greater in wedge implants (p=0.0137) while on the occlusal aspect significantly lower strain development was seen for wedge implants (p=0.0012). Primary stability of wedge implants was significantly lower as compared to round implants (p=0.0005). Wedge implants differ from round implants with respect to the insertion process characterized by a stepwise increase in bone deformation. High strain development in buccal bone may constitute a risk factor for bone resorption and should be avoided by reducing the degree of underpreparation of the implant site.

Objectives: The preclinical evaluation of bone substitutes is frequently performed in artificially created defects. However, such defects do not reflect the predominant clinical application of bone substitutes for socket preservation. Hence, the goal of this animal study was to compare the performance of a xenogenic bone substitute in extraction sites versus artificial defects.Material and Methods: Four study sites each were created in the mandibles of four minipigs in the region of the third premolars and first molars, respectively. On one side, fresh extraction sockets were established while contralaterally trephine defects were created in healed alveolar bone. All sites were augmented using a particulate xenogenic bone substitute, covered by resorbable membranes and allowed to heal for 12 weeks. The amounts of new bone, non-bone tissue and remaining bone substitute granules were quantified through histological and micro-CT analysis. Comparative statistics were based on t-tests for two samples and ANOVA with the level of significance set at α = 0.05.Results: Histomorphometric data from only two animals could be quantitatively analyzed due to difficulty with identifying the surgical sites. The percentage of newly formed bone ranged between 53.2% ± 5.6% for artificial defects and 54.9% ± 12.4% for extraction sites. With the exception of ANOVA indicating a greater amount of non-bone tissue in extraction sites as compared to artificial sites (p = 0.047), no statistically significant differences were observed. Micro-CT scans showed patterns similar to the ones observed in histomorphometry. As extraction sites could be identified only in two micro-CT reconstructions, quantitative assessment was not undertaken.Conclusions: Despite the comparable performance of bone substitute material in artificial defects and extraction sites found here, the data gathered with this experiment was insufficient for showing equivalence of both approaches.

Purpose: Excessive micromotion at the implant-bone interface may result in fibrous encapsulation instead of osseointegration of dental implants. This study quantified micromotion of implants placed in polyurethane foam and sheep tibia and tried to establish correlations with histologic parameters. Method: Dental implants (n=5) were placed in the tibiae of two sheep and allowed to heal for five and twenty weeks respectively (totalof 10 implants). Identical implants were placed in polyurethane foam with densities of 10 pcf and 20 pcf and a 3 mm thick cortical layer with a density of 40 pcf (n=5 per bone type; total of 10 implants). For determining micromotion at the implant bone interface, specimens were loaded in a universal testing machine and extensometers were used for recording implant displacement during loading. Implant stability, bone mineral density (BMD) and bone to implant contact (BIC) were determined additionally. Statistical analysis was based on Wilcoxon rank sum tests and Spearman rank correlation tests with the level of significance set at p<=0.05. Results: An increase in trabecular bone density and healing time caused a basic trend towards greater implant stability (p<0.05 for polyurethane foam; p>0.05 for sheep) and less implant displacement as a consequence of loading. The histologic parameters BIC and BMD also increased with healing time, however, this effect was only significant for BMD in the cervical (p=0.02) and apical (p=0.05) part. No difference in micromotion was found between implants placed in sheep and those placed in polyurethane foam with trabecular density of 10 pcf. Only few and inconsistent correlations were found between the parameters evaluated. Conclusions: Bone quality seems to affect implant micromotion although the exact determinants remain unclear. Implants placed in cellular polyurethane foam with density 10 pcf combined with a 3 mm layer of solid foam with density 40 pcf showed biomechanical behavior comparable to implants placed in sheep tibia.

Introduction With the aim of optimising dental education without overburdening students, new legislation restructuring the undergraduate dental curriculum in German is under way. The goal of this study was to survey the current situation of dental students at one specific university with respect to their socio‐economic background, admission to dental school, curriculum perception and work‐life balance. Materials and methods An online questionnaire was presented to all undergraduate students enrolled at Saarland University who had at least completed the first preclinical practical course in dentistry. Results A response rate of 85% was reached with two‐thirds of the student body being females. The profession of 40% of students' parents either was physicians or dentist. Students reported a slight reduction in time spent for leisure activities during their studies, however, with sports activities hardly being affected. With respect to a proper work‐life balance, almost 50% of respondents considered their clinical workload as being too high. Students did not express a clear opinion regarding curriculum structure, whilst the content mostly satisfied their expectations (59%). The majority (71%) of students considered their preclinical training as being demanding whilst less than 3% fully agreed that preclinical training provided an optimal background for patient treatment. The learning modules in the first clinical semester were considered as being adequate by 56% of students. Examinations during courses were seen as properly reflecting the students' knowledge by 79% of students. Discussion The status quo of German dental students is characterised by a high workload affecting the students' work‐life balance and by a transition between preclinical and clinical education which only about half the student body perceives as being adequate. Patient‐based examinations obviously are not considered as being problematic.