Poly(dl-lactide) Polymer Blended with Mineral Phases for Extrusion 3D Printing-Studies on Degradation and Biocompatibility.

A promising therapeutic option for the treatment of critical-size mandibular defects is the implantation of biodegradable, porous structures that are produced patient-specifically by using additive manufacturing techniques. In this work, degradable poly(DL-lactide) polymer (PDLLA) was blended with different mineral phases with the aim of buffering its acidic degradation products, which can cause inflammation and stimulate bone regeneration. Microparticles of CaCO3, SrCO3, tricalcium phosphates (α-TCP, ß-TCP), or strontium-modified hydroxyapatite (SrHAp) were mixed with the polymer powder following processing the blends into scaffolds with the Arburg Plastic Freeforming 3D-printing method. An in vitro degradation study over 24 weeks revealed a buffer effect for all mineral phases, with the buffering capacity of CaCO3 and SrCO3 being the highest. Analysis of conductivity, swelling, microstructure, viscosity, and glass transition temperature evidenced that the mineral phases influence the degradation behavior of the scaffolds. Cytocompatibility of all polymer blends was proven in cell experiments with SaOS-2 cells. Patient-specific implants consisting of PDLLA + CaCO3, which were tested in a pilot in vivo study in a segmental mandibular defect in minipigs, exhibited strong swelling. Based on these results, an in vitro swelling prediction model was developed that simulates the conditions of anisotropic swelling after implantation.

A cross-sectional study of the anatomy of the jaws of a central-European caucasian population using cone beam computer tomography as a prerequisite for designing pre-formed calcium phosphate cement scaffolds.

PURPOSE: This study aims to measure the cortical and cancellous bone thickness in the upper and lower jaws, serving as a data template for developing pre-defined calcium phosphate cement primary implant forms. These measurements are crucial for creating a biphasic scaffold. METHODS: Forty complete jaws were assessed for cortical bone shape and thickness using statistical analysis and specific software tools. Sex and age were considered, and four groups were created. RESULTS: The cumulative thickness of the cortical layer varied from region to region. In both the upper and lower jaws, the cortical layer in the molar region was significantly thicker than in the frontal region. Within the alveolar process, cortical thickness increases with distance from the alveolar crest on both sides. The oral side of the lower jaw is significantly thicker than the vestibular side. For the upper jaw, no significant differences between the oral and vestibular sides were found in this study. Additionally, it is noteworthy that men have a significantly thicker cortical layer than women. Regarding age, no significant overall differences were found. CONCLUSION: Mathematical analysis of anatomical forms using polynomial functions improves understanding of jaw anatomy. This approach facilitates the design of patient-specific scaffold structures, minimizing the need for costly and time-consuming planning and enabling more efficient implementation of optimal therapy.

A single-centre retrospective 10-year experience of the rhombic 3D condylar fracture plate for open reduction and internal fixation of condylar neck and base fractures.

Fractures of the mandibular condyle account for a significant proportion of mandibular fractures. The specific functional loads require particular specifications for the implant design used for open reduction and internal fixation of such fractures. The clinical and radiographic outcomes in patients treated using a single rhombic 3D condylar fracture plate for open reduction and internal fixation at a single institution, and who fulfilled the inclusion and exclusion criteria, are presented. The primary outcome variables were: occlusion, maximum interincisal distance and mandibular excursion at 1, 3, and 6 months postoperatively, and radiographic measurements for mandibular height and gonion angle. In total, 263 patients were included, of whom 173 (65.8%) were male and 90 (34.2%) female. The mean age was 40.4 ± 18.9 years. There was satisfactory occlusion in 98.9% of patients at the 6-month follow-up, and a significant improvement in all parameters for mandibular excursion (p < 0.001), with a reduced ramus height and an increase in the gonion angle on the fractured side. Excellent clinical and radiographic results were achieved using the rhombic-shaped implant, deeming it appropriate for the osteosynthesis of mandibular condyle fractures.

Development of a test bench for biomechanical simulation-a preliminary study of mandibular forces.

Purpose: The aim of this study is to develop a test bench, which integrates different complexity levels and enables in that way a flexible and dynamic testing for mid and long term intervals as well as testing of maximum loads till implant failure of different osteosynthesis systems on the mandible. Material and Methods: For this purpose, an analysis of the state of the art regarding existing test benches was combined with interviews of clinical experts to acquire a list of requirements. Based on these requirements a design for a modular test bench was developed. During the implementation of the test stand, functional tests were continuously carried out and improvements made. Depending on the level of complexity, the test bench can be used either as an incorporated variant or as a standalone solution. In order to verify the performance and the degree of fulfilment of the requirements of these two variants of the test bench, preliminary studies were carried out for all levels of complexity. In these preliminary studies, commercially available osteosynthesis and reconstruction plates were investigated for their biomechanical behaviour and compared with data from the literature. Results: In total, fourteen test runs were performed for the different levels of complexity. Firstly, five test runs were executed to test the simplified load scenario in the incorporated variant of the test bench. High forces could be transmitted without failure of the miniplates. Secondly a quasi-static test scenario was examined using the incorporated variant with simplified load insertion. Five experiments with a number of cycles between 40,896 and 100,000 cycles were carried out. In one case the quasi-static testing resulted in a fracture of the tested reconstruction plate with a failure mode similar to the clinical observations of failure. The last four test runs were carried out using the standalone variant of the test bench simulating complex load patterns via the insertion of forces through imitated muscles. During the test runs joint forces were measured and the amplitude and vector of the resulting joint forces were calculated for both temporomandibular joints. Differences in the force transmission depending on the implant system in comparison to the zero sample could be observed. Conclusion: The presented modular test bench showed to be applicable for examination of the biomechanical behavior of the mandible. It is characterized by the adjustability of the complexity regarding the load patterns and enables the subsequent integration of further sensor technologies. Follow-up studies are necessary to further qualify and optimize the test bench.

Alloplastic reconstruction of the mandible after subtotal mandibulectomy for medication-related osteonecrosis of the jaw: An update of the method.

BACKGROUND: Reconstruction of continuity defects following osteonecrosis in multimorbid patients is challenging. In all cases of the predescribed palliative treatment method for alloplastic mandible reconstruction, plate fractures were detected in follow-up. We hypothesized that a modification could avoid these fractures, leading to stable long-term results. METHODS: This retrospective study compares the original method with a modification using single, laser-sintered CAD-CAM plates instead of manually bent miniplates. The predescribed shuttering technique was used to reconstruct the mandible in its original shape with bone cement. RESULTS: Uneventful wound healing was observed in 86% of the cases after modification of the method. No implant or plate fracture occurred. CONCLUSIONS: The presented method should be considered as a treatment option for mandible reconstruction in elderly, multimorbid patients in palliative situations. The results of this study suggest that the modification of the method leads to significantly improved long-term stability. Donor site morbidity is avoided with this method of palliative surgery.

Probing real-world Central European population midfacial skeleton symmetry for maxillofacial surgery.

OBJECTIVES: Symmetry is essential for computer-aided surgical (CAS) procedures in oral and maxillofacial surgery (OMFS). A critical step for successful CAS is mirroring the unaffected side to create a template for the virtual reconstruction of the injured anatomical structure. The aim was to identify specific anatomical landmarks of the midfacial skeleton, to evaluate the symmetry in a group of the real-world Central European population, and to use these landmarks to assess midfacial symmetry in CT scans. MATERIAL AND METHODS: The retrospective cross-sectional study defined landmarks of the midface's bony contour using viscerocranial CT data. The distances of the skeletal landmarks (e.g., the frontozygomatic suture and temporozygomatic suture) of the left and right sides from the midline were measured and statistically compared. Midfacial symmetry for reference points was defined as a difference within 0 mm and their mean difference plus one standard deviation. RESULTS: We examined a total of 101 CT scans. 75% of our population shows symmetrical proportions of the midface. The means of the differences for the left and right sides ranged from 0.8 to 1.3 mm, averaging 1.1 ± 0.2 mm for all skeletal landmarks. The standard deviations ranged from 0.6 to 1.4 mm, with a computed mean of 0.9 ± 0.3 mm. CONCLUSION: We established a methodology to assess the symmetry of the bony midface. If the determined differences were equal to or lower than 2.5 mm in the mentioned midfacial skeletal landmarks, then the symmetry of the bony midface was considered present, and symmetry-based methods for CAS procedures are applicable. CLINICAL RELEVANCE: Many CAS procedures require facial symmetry. We provide an easy-to-apply method to probe for symmetry of the midface. The method may be used for population-based research, to check for proper reduction of fractures after reposition or to screen for symmetry prior to CAS planning.

A comparative analysis of 3D printed scaffolds consisting of poly(lactic-co-glycolic) acid and different bioactive mineral fillers: aspects of degradation and cytocompatibility.

Their excellent mechanical properties, degradability and suitability for processing by 3D printing technologies make the thermoplastic polylactic acid and its derivatives favourable candidates for biomaterial-based bone regeneration therapies. In this study, we investigated whether bioactive mineral fillers, which are known to promote bone healing based on their dissolution products, can be integrated into a poly(L-lactic-co-glycolic) acid (PLLA-PGA) matrix and how key characteristics of degradation and cytocompatibility are influenced. The polymer powder was mixed with particles of CaCO3, SrCO3, strontium-modified hydroxyapatite (SrHAp) or tricalcium phosphates (α-TCP, ß-TCP) in a mass ratio of 90 : 10; the resulting composite materials have been successfully processed into scaffolds by the additive manufacturing method Arburg Plastic Freeforming (APF). Degradation of the composite scaffolds was investigated in terms of dimensional change, bioactivity, ion (calcium, phosphate, strontium) release/uptake and pH development during long-term (70 days) incubation. The mineral fillers influenced the degradation behavior of the scaffolds to varying degrees, with the calcium phosphate phases showing a clear buffer effect and an acceptable dimensional increase. The amount of 10 wt% SrCO3 or SrHAp particles did not appear to be appropriate to release a sufficient amount of strontium ions to exert a biological effect in vitro. Cell culture experiments with the human osteosarcoma cell line SAOS-2 and human dental pulp stem cells (hDPSC) indicated the high cytocompatibility of the composites: For all material groups cell spreading and complete colonization of the scaffolds over the culture period of 14 days as well as an increase of the specific alkaline phosphatase activity, typical for osteogenic differentiation, were observed.

Dental Pulp Stem Cells for Salivary Gland Regeneration-Where Are We Today?

Xerostomia is the phenomenon of dry mouth and is mostly caused by hypofunction of the salivary glands. This hypofunction can be caused by tumors, head and neck irradiation, hormonal changes, inflammation or autoimmune disease such as Sjögren's syndrome. It is associated with a tremendous decrease in health-related quality of life due to impairment of articulation, ingestion and oral immune defenses. Current treatment concepts mainly consist of saliva substitutes and parasympathomimetic drugs, but the outcome of these therapies is deficient. Regenerative medicine is a promising approach for the treatment of compromised tissue. For this purpose, stem cells can be utilized due to their ability to differentiate into various cell types. Dental pulp stem cells are adult stem cells that can be easily harvested from extracted teeth. They can form tissues of all three germ layers and are therefore becoming more and more popular for tissue engineering. Another potential benefit of these cells is their immunomodulatory effect. They suppress proinflammatory pathways of lymphocytes and could therefore probably be used for the treatment of chronic inflammation and autoimmune disease. These attributes make dental pulp stem cells an interesting tool for the regeneration of salivary glands and the treatment of xerostomia. Nevertheless, clinical studies are still missing. This review will highlight the current strategies for using dental pulp stem cells in the regeneration of salivary gland tissue.

Three-Dimensional Plotted Calcium Phosphate Scaffolds for Bone Defect Augmentation-A New Method for Regeneration.

For sinus grafting, different methods and materials are available. One possible shortcoming of particulate bone grafts is either overfilling or augmenting the planned implant area insufficiently. To overcome this risk and to determine the implant position prior augmentation, we present an approach using three-dimensional printed scaffolds. A patient with a remaining anterior dentition and bilateral severely atrophied posterior maxilla was seeking oral rehabilitation. The cone beam computed tomography (CBCT) showed residual bone heights between one and two millimeters. Following the three-dimensional reconstruction of the CBCT data, the positions of the implants were determined in areas 16 and 26. Three-dimensional scaffolds adapted to the topography of the sinus were virtually designed and printed using a calcium phosphate cement paste. Bilateral sinus floor augmentation applying the printed scaffolds with an interconnecting porosity followed. After nine months, a satisfying integration of the scaffolds was obvious. At the re-entry, vital bone with sufficient blood supply was found. One implant could be placed in positions 16 and 26, respectively. After five months, the implants could be uncovered and were provided with a temporary denture. The application of three-dimensionally printed scaffolds from calcium phosphate cement paste seems to be a promising technique to graft the severely atrophied posterior maxilla for the placement of dental implants.

[Cleft lip and palate : One of the most frequent congenital malformations]. / Lippen-Kiefer-Gaumen-Spalte : Eine der häufigsten angeborenen Fehlbildungen.

With a frequency of 1 per 500 live births, a cleft lip and palate is one of the most frequent congenital malformations. Untreated, it leads to disturbances in feeding, speech, hearing, tooth position and esthetics. A multifactorial genesis is assumed. The fusion of the different facial processes takes place in the first 3 months of pregnancy and a cleft can develop during this time. Surgical treatment includes the early anatomical and functional restoration of the affected structures within the first year of life in order to enable normal intake of food, articulation, nasal breathing and middle ear ventilation. Breastfeeding is possible in children with a cleft formation but alternative feeding methods, such as finger feeding, often have to be used. In addition to the surgery for primary closure of the cleft, otorhinolaryngological (ENT) interventions, speech therapy, orthodontic treatment as well as other surgical interventions are part of the interdisciplinary treatment concept.

Accuracy of full-guided vs. pilot-guided implant insertion - A prospective laboratory study in fifth-year dental students.

BACKGROUND: Education of undergraduates in implant dentistry has been extended. In order to assess the correct implant position, the accuracy of implant insertion using templates for pilot-drill guided and full-guided implant insertion was examined in a laboratory set-up in a cohort of undergraduates. METHODS: After three-dimensional planning of the implant position in partially edentulous mandibular models, individual templates for the pilot-drill guided or full-guided implant insertion in the region of the first premolar were produced. A total of 108 dental implants were inserted. The results of the radiographic evaluation of the three-dimensional accuracy were statistically analyzed. Furthermore, the participants completed a questionnaire. RESULTS: The deviation of the three-dimensional angle of the implants inserted fully guided was 2.74 ± 1.49 degrees compared to 4.59 ± 2.70 degrees for pilot-drill guided. The difference was statistically significant (p < 0.01). The returned questionnaires revealed a high interest in oral implantology and a positive evaluation of the hands-on course. CONCLUSIONS: In this study, the undergraduates benefited from applying full-guided implant insertion considering the accuracy in this laboratory examination. However, the clinical effects are not clear as the differences are within a small range. Based on the returned questionnaires, the implementation of practical courses in the undergraduate curriculum should be encouraged.

Cost minimization analysis of indication-specific osteosynthesis material in oral and maxillofacial surgery.

PURPOSE: Following the introduction of the Regulation (EU) 2017/745 by the European Parliament, any bioactive substance or surgical implant introduced into the human body must be documented. The regulation requires any implant to be traced back to the manufacturer. Lot numbers need to be available for every single medical implant. Also, the manufacturer is required by law to provide implants individually packaged and sterilized. Previously, model tray systems (MOS tray) were used for osteosynthesis in oral and maxillofacial surgery, in which the individual implants could not be registered separately. The new regulation made it impossible to use such processes during surgery anymore and a need for a change in the medical practice surged. We examined a possible solution for the new legislation. The aim of this prospective cohort study is to analyze the MOS tray systems to osteosynthesis materials prepackaged in sets. We record and evaluate parameters such as surgical time and documentation time. We perform a short cost analysis of our clinic. The primary aim is to determine how much time is gained or lost by the mandatory increased patient safety. The secondary aim is to describe change in costs. METHODS: Patients that underwent standard surgical procedures in the clinic of oral and maxillofacial surgery of the faculty hospital Carl Gustav Carus in Dresden were included. We chose open reduction and internal fixation (ORIF) of anterior mandibular corpus fractures as well as mandibular advancement by means of bilateral sagittal split osteotomies (BSSO) as standardized procedures. Both of these procedures require two osteosynthesis plates and at least four screws for each plate. MOS trays were compared to prepackaged sterilized sets. The sets include a drill bit, two plates, and eight 5-mm screws. A total number of 40 patients were examined. We allocated 20 patients to the ORIF group and the other 20 patients to the BSSO group. Each group was evenly subdivided into a MOS tray group and a prepackaged group. Parameters such as the incision-suture time (IST) as well as the documentation time (DT) by the operating room (OR) staff to complete documentation for the implants are the main focus of investigation. RESULTS: For open reduction, the incision-suture time was significantly different in favor of the MOS tray (p < 0.05). There was no difference in the BSSO groups. However, we observed a significantly different (p < 0.01) documentation time advantage for the prepackaged sets in both the ORIF and BSSO groups. On top of that, we find that by using the prepackaged kits, we are able to reduce sterilization costs by €11.53 per size-reduced container. Also, there is also a total cut of costs of €38.90 and €43.70, respectively, per standardized procedure for implant material. CONCLUSIONS: By law, a change in the method of approaching surgery is necessary. For standardized procedures, the right choice of implants can lead to a reduction of documentation time and costs for implant material, sterilization, as well as utilizing less instruments. This in turn leads to lower costs for perioperative processing as well as provision of state-of-the-art implant quality implementing higher patient security.

Socioeconomic disparities between oral cavity cancer patients in Germany.

Objective: In many countries the access to high quality medical service depends on socioeconomic factors. Therefore, these factors are associated with the treatment and prognosis of many diseases. In Germany health care is claimed to be independent from such factors due to obligatory health insurance and a well-developed medical infrastructure. Thus, socioeconomically caused health disparities should be absent. The aim of this study was to analyze the association between socioeconomic factors and the survival of oral cavity cancer in Germany. Patients and methods: In this descriptive cohort study socioeconomic status related factors as well as demographic, tumor-specific, and comorbidity factors of 500 patients treated for oral cavity cancer were obtained in the university hospital of Dresden. Pearson correlation was used to describe associations between continuous variables. Associations between categorical variables were assessed using the chi-square test. Overall and recurrence-free survival were studied using the Kaplan-Meier method. Log-rank test was carried out to test between-group differences. Cox proportional hazard models were used to estimate the risk of death and the risk of recurrence. Results: Significant differences in overall survival were found between the different educational levels and sex. Seventy-nine percent of the patients did not have a university degree or master craftsman/craftswoman. Less discrepancy was observed according to the marital status (49.4% married/engaged vs. 47.8% single, divorced, or widowed). In the multivariable analysis only sex, age at diagnosis, the Charlson score, the number of positive lymph nodes, and the nodal status were identified as independent predictors for overall survival whereas sex and the age at diagnosis were identified as independent predictors for recurrence-free survival. Conclusion: Despite the equitable health system in Germany, significant associations between overall survival of oral cavity cancer and different socioeconomic factors could be found. For elimination of these disparities, health education programs should be established in socially deprived areas. Furthermore, clinicians should keep these factors in mind when determining recall periods for dental check-ups.

Enhancing Anticoagulation Monitoring and Therapy in Patients Undergoing Microvascular Reconstruction in Maxillofacial Surgery: A Prospective Observational Trial.

BACKGROUND: In reconstructive surgery, loss of a microvascular free flap due to perfusion disorders, especially thrombosis, is a serious complication. In recent years, viscoelastic testing (VET) has become increasingly important in point-of-care (POC) anticoagulation monitoring. This paper describes a protocol for enhanced anticoagulation monitoring during maxillofacial flap surgery. OBJECTIVE: The aim of the study will be to evaluate, in a controlled setting, the predictive value of POC devices for the type of flap perfusion disorders due to thrombosis or bleeding. VET, Platelet monitoring (PM) and standard laboratory tests (SLT) are comparatively examined. METHODS/DESIGN: This study is an investigator-initiated prospective trial in 100 patients undergoing maxillofacial surgery. Patients who undergo reconstructive surgery using microvascular-free flaps will be consecutively enrolled in the study. All patients provide blood samples for VET, PM and SLT at defined time points. The primary outcome is defined as free flap loss during the hospital stay. Statistical analyses will be performed using t-tests, including the Bonferroni adjustment for multiple comparisons. DISCUSSION: This study will help clarify whether VET can improve individualized patient care in reconstruction surgery. A better understanding of coagulation in relation to flap perfusion disorders may allow real-time adaption of antithrombotic strategies and potentially prevent flap complications.

A Holistic Approach for the Identification of Success Factors in Secondary Cleft Osteoplasty.

Cleft lip and palate belong to the most frequent craniofacial anomalies. Secondary osteoplasty is usually performed between 7 and 11 years with the closure of the osseus defect by autologous bone. Due to widespread occurrence of the defect in conjunction with its social significance due to possible esthetic impairments, the outcome of treatment is of substantial interest. The success of the treatment is determined by the precise rebuilding of the dental arch using autologous bone from the iliac crest. A detailed analysis of retrospective data disclosed a lack of essential and structured information to identify success factors for fast regeneration and specify the treatment. Moreover, according to the current status, no comparable process monitoring is possible during osteoplasty due to the lack of sensory systems. Therefore, a holistic approach was developed to determine the parameters for a successful treatment via the incorporation of patient data, the treatment sequences and sensor data gained by an attachable sensor module into a developed Dental Tech Space (DTS). This approach enables heterogeneous data sets to be linked inside of DTS, archiving and analysis, and is also for future considerations of respective patient-specific treatment plans.

Adapting the Pore Size of Individual, 3D-Printed CPC Scaffolds in Maxillofacial Surgery.

Three dimensional (3D) printing allows additive manufacturing of patient specific scaffolds with varying pore size and geometry. Such porous scaffolds, made of 3D-printable bone-like calcium phosphate cement (CPC), are suitable for bone augmentation due to their benefit for osteogenesis. Their pores allow blood-, bone- and stem cells to migrate, colonize and finally integrate into the adjacent tissue. Furthermore, the pore size affects the scaffold's stability. Since scaffolds in maxillofacial surgery have to withstand high forces within the jaw, adequate mechanical properties are of high clinical importance. Although many studies have investigated CPC for bone augmentation, the ideal porosity for specific indications has not been defined yet. We investigated 3D printed CPC cubes with increasing pore sizes and different printing orientations regarding cell migration and mechanical properties in comparison to commercially available bone substitutes. Furthermore, by investigating clinical cases, the scaffolds' designs were adapted to resemble the in vivo conditions as accurately as possible. Our findings suggest that the pore size of CPC scaffolds for bone augmentation in maxillofacial surgery necessarily needs to be adapted to the surgical site. Scaffolds for sites that are not exposed to high forces, such as the sinus floor, should be printed with a pore size of 750 µm to benefit from enhanced cell infiltration. In contrast, for areas exposed to high pressures, such as the lateral mandible, scaffolds should be manufactured with a pore size of 490 µm to guarantee adequate cell migration and in order to withstand the high forces during the chewing process.

Toward Biofabrication of Resorbable Implants Consisting of a Calcium Phosphate Cement and Fibrin-A Characterization In Vitro and In Vivo.

Cleft alveolar bone defects can be treated potentially with tissue engineered bone grafts. Herein, we developed novel biphasic bone constructs consisting of two clinically certified materials, a calcium phosphate cement (CPC) and a fibrin gel that were biofabricated using 3D plotting. The fibrin gel was loaded with mesenchymal stromal cells (MSC) derived from bone marrow. Firstly, the degradation of fibrin as well as the behavior of cells in the biphasic system were evaluated in vitro. Fibrin degraded quickly in presence of MSC. Our results showed that the plotted CPC structure acted slightly stabilizing for the fibrin gel. However, with passing time and fibrin degradation, MSC migrated to the CPC surface. Thus, the fibrin gel could be identified as cell delivery system. A pilot study in vivo was conducted in artificial craniofacial defects in Lewis rats. Ongoing bone formation could be evidenced over 12 weeks but the biphasic constructs were not completely osseous integrated. Nevertheless, our results show that the combination of 3D plotted CPC constructs and fibrin as suitable cell delivery system enables the fabrication of novel regenerative implants for the treatment of alveolar bone defects.

3D Printing of Bone Grafts for Cleft Alveolar Osteoplasty - In vivo Evaluation in a Preclinical Model.

One of the most common hereditary craniofacial anomalies in humans are cleft lip and cleft alveolar bone with or without cleft palate. Current clinical practice, the augmentation of the persisting alveolar bone defect by using autologous bone grafts, has considerable disadvantages motivating to an intensive search for alternatives. We developed a novel therapy concept based on 3D printing of biodegradable calcium phosphate-based materials and integration of osteogenic cells allowing fabrication of patient-specific, tissue-engineered bone grafts. Objective of the present study was the in vivo evaluation of implants in a rat alveolar cleft model. Scaffolds were designed according to the defect's geometry with two different pore designs (60° and 30° rotated layer orientation) and produced by extrusion-based 3D plotting of a pasty calcium phosphate cement. The scaffolds filled into the artificial bone defect in the palate of adult Lewis rats, showing a good support. Half of the scaffolds were colonized with rat mesenchymal stromal cells (rMSC) prior to implantation. After 6 and 12 weeks, remaining defect width and bone formation were quantified histologically and by microCT. The results revealed excellent osteoconductive properties of the scaffolds, a significant influence of the pore geometry (60° > 30°), but no enhanced defect healing by pre-colonization with rMSC.

The Influence of Thrust Force on the Vitality of Bone Chips Harvested for Autologous Augmentation during Dental Implantation.

Bone drill chips that are collected during implant site preparation can be reused as autologous bone-grafting material for alveolar ridge augmentation. This study characterized five market-leading implant drill sets regarding their geometric properties and ability to produce vital bone chips. The drill geometry of each tool of five commercial implant drill sets was characterized while using optical profile projector devices and SEM. Bone chips were collected during the in vitro preparation of porcine jaw bone with the various drill sets. Produced bone chip masses were measured. The bone chips were cultured in vitro and the number of outgrown cells was determined and measurand for vitality. Furthermore, the thrust force and cutting torque were recorded to examine the mechanical loads of the manual drilling process. The tool geometry and set configuration of one out of five implant drill sets appears to be superior regarding chip mass, vitality, and thrust force. It could be proven that there is a correlation between vitality and thrust force. The thrust force is influenced by the cutting behavior of the tool, which in turn depends on the geometry of the tool. The tool geometry has an influence on the vitality of the augmentation material due to this relationship.

Pilot-drill guided vs. full-guided implant insertion in artificial mandibles-a prospective laboratory study in fifth-year dental students.

BACKGROUND: As a growing field in dentistry, the practical education during the undergraduate curriculum in implant dentistry should be extended. Not only the theoretical background but also practical skills are crucial to place implants in patients. In order to determine the exact implant position, several positioning aids are available. In the present laboratory study, the accuracy of implant insertion using two different guiding modes in a group of inexperienced participants was assessed. METHODS: After three-dimensional planning using the data of a cone beam computed tomography of artificial mandibles, surgical templates were manufactured by thermoforming. In region 35, a sleeve for the pilot drill was used, whereas in region 45, a sleeve allowing a full-guided implant insertion was inserted. Subsequently, a total of 104 implants were placed by 52 undergraduates. Radiographical assessment of the three-dimensional accuracy was performed. Furthermore, the time required to insert the implants was recorded. Statistical analysis followed. DISCUSSION: When comparing the three-dimensional accuracy of the virtually planned to the actual inserted implant, a statistically significantly higher accuracy in three-dimensional angulation was achieved for the full-guided (3.388 ± 1.647°) compared to the pilot-drill guided mode (5.792 ± 3.290°). Furthermore, the time required to insert the implant was shorter for the full-guided template (6.23 ± 1.78 min) vs. for the pilot-drill guided (8.84 ± 2.39 min). Both differences reached a statistical significance (p < 0.001). CONCLUSION: Within the limit of this laboratory study, the results suggest that inexperienced surgeons benefit from a full-guided implant insertion. However, the clinical effects have to be discussed as the mismatch was varying in the decimillimeter range.