Jörg Neugebauer

Growth and Proliferation of Human Osteoblasts on Different Bone Graft Substitutes An In Vitro Study

The purpose of this study was to investigate the effect of different bone graft substitutes onto the growth and proliferation pattern of bone cells derived from human iliac cancellous bone. Five different bone graft materials were used to investigate the effect on the proliferation of osteoblasts in vitro: phytogene hydroxyapatite (Algipore®), &agr;-Tricalcium phosphate (Bio-Base®), bovine hydroxyapatite (low temperature) (Bio-Oss®), bovine hydroxyapatite (high temperature) (Osteograf®), and bovine hydroxyapatite (high temperature) enhanced with p-15, synthetic peptide (PepGen p-15®). The osteoblasts were derived from human iliac cancellous bone and seeded with the different bone substitutes. The cell proliferation and viability (WST-1), alkaline phosphatase as an early marker of osteoblast proliferation, was evaluated after 6 and 9 days. The cultures were examined for cell growth pattern and morphology by normal light and scanning electron microscopy. The human osteoblasts showed a different proliferation pattern according to the type of applied bone graft substitute. PepGen P-15 showed the highest proliferation and differentiation rate followed by Osteograf, Algipore, and Bio-base. Bio-Oss showed the lowest. These results were confirmed by electron microscopy and light microscopy evaluation in which similar growth pattern were observed. Distinct bone graft materials have different impact onto the proliferation pattern of human osteoblasts in vitro.

Accuracy of a newly developed integrated system for dental implant planning

OBJECTIVES To evaluate the accuracy of the first integrated system for cone-beam CT (CBCT) imaging, dental implant planning and surgical template-aided implant placement. MATERIALS AND METHODS On the basis of CBCT scans, a total of 54 implant positions were planned for 10 partially edentulous anatomical patient-equivalent models. Surgical guides were ordered from the manufacturer (SICAT). Two different types of guidance were assessed: for assessment of the SICAT system inherent accuracy vendors titanium sleeves of 2 mm internal diameter and 5 mm length were utilized for pilot drills. The guide sleeves of the NobelGuide system were implemented for fully guided surgery and implant insertion. Deviations perpendicular to the implant axes at the crestal and apical end, as well as the angle deviations between the virtual planning data and the surgical results, were measured utilizing a follow-up CBCT investigation and referential marker-based registration. RESULTS The SICAT system inherent mean deviation rates for the drilled pilot osteotomies were determined to be smaller than 500 mum even at the apical end. Mean angle deviations of 1.18 degrees were determined. Utilizing the NobelGuide sleeve-in-sleeve system for fully guided implant insertion in combination with the investigated template technology enabled to insert dental implants with the same accuracy. Crestal deviations, in general, were significantly lower than the apical deviations. CONCLUSION Although hardly comparable due to different study designs and measurement strategies, the investigated SICAT systems inherent accuracy corresponds to the most favourable results for computer-aided surgery systems published so far. In combination with the NobelGuide surgical set for fully guided insertion, the same accuracy level could be maintained for implant positioning.

Concise Review: Induced Pluripotent Stem Cells and Lineage Reprogramming: Prospects for Bone Regeneration†‡§

Bone tissue for transplantation therapies is in high demand in clinics. Osteodegenerative diseases, in particular, osteoporosis and osteoarthritis, represent serious public health issues affecting a respectable proportion of the elderly population. Furthermore, congenital indispositions from the spectrum of craniofacial malformations such as cleft palates and systemic disorders including osteogenesis imperfecta are further increasing the need for bone tissue. Additionally, the reconstruction of fractured bone elements after accidents and the consumption of bone parts during surgical tumor excisions represent frequent clinical situations with deficient availability of healthy bone tissue for therapeutic transplantations. Epigenetic reprogramming represents a powerful technology for the generation of healthy patient‐specific cells to replace or repair diseased or damaged tissue. The recent generation of induced pluripotent stem cells (iPSCs) is probably the most promising among these approaches dominating the literature of current stem cell research. It allows the generation of pluripotent stem cells from adult human skin cells from which potentially all cell types of the human body could be obtained. Another technique to produce clinically interesting cell types is direct lineage reprogramming (LR) with the additional advantage that it can be applied directly in vivo to reconstitute a damaged organ. Here, we want to present the two technologies of iPSCs and LR, to outline the current states of research, and to discuss possible strategies for their implementation in bone regeneration. STEM CELLS 2011;29:555–563

The influence of body mass index, age, implants, and dental restorations on image quality of cone beam computed tomography

OBJECTIVE The aim was to determine the influence of patient age, gender, body mass index (BMI), amount of dental restorations, and implants on image quality of cone-beam computerized tomography (CBCT). METHODS Fifty CBCT scans of a preretail version of Galileos (Sirona, Germany) were investigated retrospectively by 4 observers regarding image quality of 6 anatomic structures, pathologic findings detection, subjective exposure quality, and artifacts. Patient age, BMI, gender, amount of dental restorations, and implants were recorded and statistically tested for correlations to image quality. RESULTS A negative effect on image quality was found statistically significantly correlated with age and the amount of dental restorations. None of the investigated image features were garbled by any of the investigated influence factors. CONCLUSIONS Age and the amount of dental restorations appear to have a negative impact on CBCT image quality, whereas gender and BMI do not. Image quality of mental foramen, mandibular canal, and nasal floor are affected negatively by age but not by the amount of dental restorations. Further studies are required to elucidate influence factors on CBCT image quality.

Salivary calculus diagnosis with 3-dimensional cone-beam computed tomography

OBJECTIVE The objective of this study was to evaluate cone-beam CT (CBCT) diagnoses of sialoliths in the major salivary glands. STUDY DESIGN Twenty-nine CBCT images containing salivary calculi were retrospectively evaluated for image quality and artifact influence. Additionally, the reproducibility of calculus measurement and the differences between CBCT measurements and ultrasonography (US) and histomorphometry (HM) measurements were determined. Diagnostic sensitivity and specificity calculations were based on the observations of 3 masked clinicians, who reviewed a total of 58 CBCT volumes. RESULTS Salivary calculi were sufficiently visualized in all patients. Metal artifacts were detected in images of 7 patients, and movement artifacts in 2. CBCT calculi measurements were highly reproducible, with mean differences of less than 350 microm. Mean CBCT measurements of calculi diameters differed from mean US measurements by approximately 500 microm and differed from mean HM measurements by approximately 1 mm. For calculus diagnoses, the mean sensitivity and specificity were both 98.85%. CONCLUSION Although poor image qualities and artifacts can reduce diagnostic information, salivary calculi can be evaluated adequately with CBCT. CBCT measurements of calculi are highly reproducible and differ little from measurements made with US and HM. Diagnostic sensitivity and specificity levels with CBCT are as high as or higher than those obtained with other diagnostic methods. Because of its high diagnostic-information-to-radiation-dose ratio, CBCT is the preferable imaging modality for salivary calculus diagnosis.

Computer-aided manufacturing technologies for guided implant placement.

Implant treatment increasingly focuses on the reduction of treatment time and postoperative impairment. The improvement of 3D dental diagnosis by ConeBeam computed tomography allows detailed preparation for the surgical placement of dental implants under prosthetic considerations. While the first generation of implant planning software used high-contrast multislice computed tomography, software that has been specifically designed for ConeBeam computed tomography is now available. Implant placement can be performed using surgical guides or under the control of optical tracking systems. Surgical guides are more commonly used in private office owing to their availability. The accuracy for both techniques is clinically acceptable for achieving implant placement in critical anatomical indications. When using prefabricated superstructures and in flapless surgery, special abutments or an adjusted workflow are still necessary to compensate misfits of between 150 and 600 µm. The proposition to ensure proper implant placement by dentists with limited surgical experience through the use of surgical guides is unlikely to be successful, because there is also a specific learning curve for guided implant placement. Current and future development will continue to decrease the classical laboratory-technician work and will integrate the fabrication of superstructures with virtual treatment planning from the start.

Comparison of cone-beam computerized tomography and intraoral radiographs for determination of the periodontal ligament in a variable phantom

OBJECTIVES This in vitro study assessed the visualization quality of the periodontal ligament space in cone-beam computerized tomography (CBCT) compared with intraoral radiographs (CR). STUDY DESIGN A phantom mimicking variable periodontal ligament spaces (0-0.42 mm) was radiographed using CBCT and CR. Fifteen datasets of each modality were randomly mixed and presented twice to 19 experienced examiners and once to 19 inexperienced examiners. RESULTS Zero-millimeter gaps were recognized in 84.4% of CBCT and in 81.6% of CR images. On CBCT scans, gaps of 0.19 mm were identified with an accuracy of 93%-100% compared with 70.2%-81.7% using CR. Experienced examiners recognized gaps of >or=0.19 mm on CBCT repeatedly with nearly 100% accuracy. CONCLUSION Compared with CR, CBCT provides better visualization of simulated periodontal ligament space in this phantom.

Peri-Implant Bone Organization under Immediate Loading Conditions: Collagen Fiber Orientation and Mineral Density Analyses in the Minipig Model

BACKGROUND Mechanical properties of bones are greatly influenced by percentages of organic and mineral constituents. Nevertheless, information about mineralization level on a microscopic scale and collagen fiber organization in peri-implant bone after immediate loading is scarce. PURPOSE The aim of this work was to analyze and compare the degree of mineralization and collagen fiber orientation in alveolar bone (AB) and peri-implant bone of immediately loaded (IL) and unloaded (NL) implants. MATERIALS AND METHODS A total of 25 dental implants of 3.8 mm in diameter and 11 mm in length were used in the present study. In five minipigs, three premolars and the first molar were removed from the left side of the mandible. Three months later, five implants for each animal were inserted. Four implants were loaded immediately with a fixed restoration, while one implant was left unloaded. After a 4-month healing period, all implants were retrieved. Circularly polarized light and scanning electron microscope with backscattered electron imaging were used to analyze both peri-implant and AB retrieved 5 mm from the implant. RESULTS The bone/implant contact ratio (BIC %) was 77.8 +/- 5.9% for the IL implants and 78.0 +/- 5.8% for the NL implants; the difference was not statistically significant (p = 0.554). In the peri-implant bone, the area related to transverse collagen fibers was 112,453 +/- 4,605 pixels for IL implants and 87,256 +/- 2,428 pixels for NL implants. In the AB, the area related to transverse collagen fibers was 172,340 +/- 3,892 pixels. The difference between groups was statistically significant (p < .001). The degree of mineralization of peri-implant bone was 137 +/- 19 gray level for IL implants and 115 +/- 24 gray level for NL implants, while in the AB, the degree of mineralization was 125 +/- 26 gray level. This difference was statistically significant (p < .001). CONCLUSION In this study, it was found that IL and NL implants showed the same degree of osseointegration. The bone matrix around IL implants had a higher quantity of transverse collagen fibers and presented a higher level of mineralization.

CBCT device dependency on the transfer accuracy from computer‐aided implantology procedures

OBJECTIVES To evaluate the potential influence of different cone-beam computed tomography (CBCT) devices on the transfer accuracy of an open-source system for computer-aided implantology (CAI). MATERIAL AND METHODS A total of 108 implants in 18 partially edentulous patient-equivalent models were planned and fully guided implants were inserted using an open-source CAI system with three different CBCT devices. After follow-up CBCT and fiducial marker-matching procedure, linear horizontal, vertical, and maximal three-dimensional deviations, as well as angle deviations between the virtual planning data and the surgical results were calculated. Variance analysis was carried out to prove whether or not the observed differences between the CBCT devices were statistically significant. RESULTS The observed mean three-dimensional deviation rates between virtually planned and achieved implant positions varied by around 400 μm (45%) at the implants base and around 540 μm (50%) at the implants tip in dependence to the applied CBCT device. Mean vertical deviations varied around 370 μm (76%) at the implants base and 350 μm (69%) at the implants tip, whereas axes deviations varied around 0.81° (40%) between the three investigated CBCT devices. Except for the axes deviations and the horizontal linear deviations at the implants base, observed differences reached significance level between the CBCT devices. CONCLUSIONS Until now, the potential influence from different CBCT devices on the transfer accuracy of CAI systems has not yet been investigated. Data from the present study confirm for the first time the in vitro CBCT device dependency on the transfer accuracy of CAI systems reaching up to axes deviations of 0.6 angle degree and linear deviations around half a millimeter.

A novel method of preparation of surgical template for guided implant placement: a case report.

Currently, the preparation of surgical templates is a multistage process that engages the restorative dentist, dental laboratory, and external computed tomography center. This new method for production of templates and guides, as well as data transfer protocol, significantly simplifies commonly used methods and removes many of the complications inherent in them. A case report of an implantation procedure carried out with the new protocol is presented. Further studies and comparisons with other guided implant surgery methods are needed to establish the advantage of this novel method.