Wedge Shaped vs Round Implants: Bone Strain During the Insertion Process.

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. Statistical analysis was based on Welch's 2-sample tests (α = 0.05). In general, greater strain development was found on the buccal aspect of bone compared to the occlusal aspect with an overall range between -724 µm/m and 9132 µm/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 = .0137) while, on the occlusal aspect, significantly lower strain development was seen for wedge implants (P = .0012). Primary stability of wedge implants was significantly lower compared to round implants (P = .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.

Students at Saarland University dental school-A survey on their background and curriculum perception.

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.

Observational study on primary and secondary stability of two current bone level implant designs.

Objective: Achieving high levels of primary implant stability is considered to be desirable, despite some studies warning of the risk of bone damage. It was the goal of this observational clinical study to compare two current bone level implant systems with respect to primary and secondary stability. Method and materials: Data on bone quality, insertion torque, implant stability at insertion and after healing, as well as number of implants lost during healing were obtained from two centers either placing BLT (Bone Level Tapered, Straumann) or Nobel Parallel CC (Nobel Biocare) implants. Statistical analysis was based on Spearman rank correlation tests, analysis of variance, and t tests with the level of significance set at α = .05. Results: A total of 312 BLT and 92 Nobel Parallel CC implants were placed. Ten BLT and two Nobel Parallel CC implants failed resulting in survival rates of 96.79% and 97.83%, respectively. Mean insertion torque recorded in the different bone classes showed large standard deviations, and only torque values for BLT implants recorded in type 3 bone differed significantly from type 2 bone and type 1 bone (P = .024). For BLT implants, bone quality and insertion torque correlated (Spearman rho = -.3326; P = .0023) as did ISQ at insertion (Spearman rho = -.2241; P = .0429). Implant diameter significantly affected primary (P = .0013) and secondary (P = .0050) stability of Nobel Parallel CC implants while for BLT implants a significant effect was only seen for secondary stability (P = .0000). Bone quality had a significant effect on implant insertion torque for BLT implants (P = .0059). Bone quality had no general effect on ISQ changes during healing but 3.3-mm BLT implants showed significantly (P = .0005) lower stability after healing. Conclusion: Huge variation with respect to primary and secondary stability seems to exist among similar looking implant systems clinically used for identical indications.

Comparison of extraction sites versus artificial defects with xenogenic bone substitute in minipigs.

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.

Insertion and Loading Characteristics of Three Different Bone-Level Implants.

PURPOSE: While primary stability still constitutes an important factor for implant success, high levels of insertion torque resulting from bone compression are controversial and may constitute a co-factor in peri-implant bone loss. MATERIALS AND METHODS: Adhering to the manufacturers' protocols for medium-quality bone, implant surgery was performed in polyurethane foam blocks equipped with strain gauges attached to the buccal aspect. Following insertion and attachment of provisional abutments, oblique loading was performed. The following parameters were recorded for three different implant types (Straumann Bone Level Tapered [BLT], MIS V3 [V3], Dentsply Sirona ASTRA TX [ASTRA]): maximum insertion and removal torque, maximum strain during insertion and loading, and implant stability before and after loading (resonance frequency analysis [RFA]). Statistical analysis was based on analysis of variance (ANOVA), Tukey honest significant difference test, and Pearson's product moment correlation (α = .05). RESULTS: Maximum insertion torque (59.9 ± 4.94 Ncm) was recorded for BLT followed by V3 and ASTRA (P < .01 for all comparisons). Maximum removal torque (43.7 ± 9.69 Ncm) was also recorded for BLT, but the pairwise comparisons reached significance only for BLT vs ASTRA (P < .01) and V3 vs BLT (P = .03). Implant stability differed among groups only after loading, where the pairwise comparison between BLT and ASTRA reached significance (P = .02). Maximum strain during insertion was caused by BLT reaching 19,482.62

Insertion torque/time integral as a measure of primary implant stability.

The goal of this in vitro study was to determine the insertion torque/time integral for three implant systems. Bone level implants (n = 10; BLT - Straumann Bone Level Tapered 4.1 mm × 12 mm, V3 - MIS V3 3.9 mm × 11.5 mm, ASTRA - Dentsply-Sirona ASTRA TX 4.0 mm × 13 mm) were placed in polyurethane foam material consisting of a trabecular and a cortical layer applying protocols for medium quality bone. Besides measuring maximum insertion torque and primary implant stability using resonance frequency analysis (RFA), torque time curves recorded during insertion were used for calculating insertion torque/time integrals. Statistical analysis was based on ANOVA, Tukey's honest differences test and Pearson product moment correlation (α = 0.05). Significantly greater mean maximum insertion torque (59.9 ± 4.94 Ncm) and mean maximum insertion torque/time integral (961.64 ± 54.07 Ncm∗s) were recorded for BLT implants (p < 0.01). V3 showed significantly higher mean maximum insertion torque as compared to ASTRA (p < 0.01), but significantly lower insertion torque/time integral (p < 0.01). Primary implant stability did not differ significantly among groups. Only a single weak (r = 0.61) but significant correlation could be established between maximum insertion torque and insertion torque/time integral (p < 0.01) when all data from all three implant groups were pooled. Implant design (length, thread pitch) seems to affect insertion torque/time integral more than maximum insertion torque.

Mechanical stress during implant surgery and its effects on marginal bone: a literature review.

OBJECTIVE: High levels of primary implant stability have been advocated particularly for immediate loading protocols. Current implant systems and drill protocols are intended not to cause excessive stress on bone during implant insertion as resorptive processes might compromise esthetics and function. The goal of this narrative review was to summarize current data on the effect of mechanical stress on alveolar bone. METHOD AND MATERIALS: PubMed was searched (final search conducted on 30 September 2019) applying the user query "(dental implant insertion) AND (mechanical stress) AND (bone)." The papers identified were grouped according to the research methodology applied (in vitro studies and finite element analysis, animal studies, and clinical trials). RESULTS: In total, 176 articles were identified, of which 58 were included. A clear tendency towards increased stress in bone resulting from the use of undersized osteotomies was shown. Depending on the degree of undersizing, the inner parts of implant threads create healing chambers in which bone formation seems to progress very well, while areas of direct contact between implant body and alveolar bone experience resorption during healing. More resorption seems to occur when implants have been placed with higher insertion torque, although these implants maintain greater total bone-to-implant contact during initial healing. Clinically, mobile implants seem to have a compromised prognosis and high insertion torques seem not to guarantee successful osseointegration. Marginal bone level changes obviously have a tendency of being greater in implants inserted with high levels of torque. CONCLUSION: Clinicians should be cautious during implant surgery not to overstress bone. Future implant systems should focus on optimized drill protocols and apply macrodesigns that also derive stability from trabecular bone as well, instead of merely compressing the cortical layer.

Evaluation of Insertion Energy as Novel Parameter for Dental Implant Stability.

Insertion energy has been advocated as a novel measure for primary implant stability, but the effect of implant length, diameter, or surgical protocol remains unclear. Twenty implants from one specific bone level implant system were placed in layered polyurethane foam measuring maximum insertion torque, torque-time curves, and primary stability using resonance frequency analysis (RFA). Insertion energy was calculated as area under torque-time curve applying the trapezoidal formula. Statistical analysis was based on analysis of variance, Tukey honest differences tests and Pearson's product moment correlation tests (α = 0.05). Implant stability (p = 0.01) and insertion energy (p < 0.01) differed significantly among groups, while maximum insertion torque did not (p = 0.17). Short implants showed a significant decrease in implant stability (p = 0.01), while reducing implant diameter did not cause any significant effect. Applying the drilling protocol for dense bone resulted in significantly increased insertion energy (p = 0.02) but a significant decrease in implant stability (p = 0.04). Insertion energy was not found to be a more reliable parameter for evaluating primary implant stability when compared to maximum insertion torque and resonance frequency analysis.