Deep Characterization and Comparison of Different Retrovirus-like Particles Preloaded with CRISPR/Cas9 RNPs

The CRISPR/Cas system has a broad range of possible medical applications, but its clinical translation has been hampered, particularly by the lack of safe and efficient vector systems mediating the short-term expression of its components. Recently, different virus-like particles (VLPs) have been introduced as promising vectors for the delivery of CRISPR/Cas genome editing components. Here, we characterized and directly compared three different types of retrovirus-based (R) VLPs, two derived from the γ-retrovirus murine leukemia virus (gRVLPs and "enhanced" egRVLPs) and one from the lentivirus human immunodeficiency virus, HIV (LVLPs). First, we unified and optimized the production of the different RVLPs. To ensure maximal comparability of the produced RVLPs, we adapted several assays, including nanoparticle tracking analysis (NTA), multi-parametric imaging flow cytometry (IFC), and Cas9-ELISA, to analyze their morphology, surface composition, size, and concentration. Next, we comparatively tested the three RVLPs targeting different genes in 293T model cells. Using identical gRNAs, we found egRVLPs to mediate the most efficient editing. Functional analyses indicated better cargo (i.e., Cas9) transfer and/or release as the underlying reason for their superior performance. Finally, we compared on- and off-target activities of the three RVLPs in human-induced pluripotent stem cells (hiPSC) exploiting the clinically relevant C-C motif chemokine receptor 5 (CCR5) as the target. Again, egRVLPs facilitated the highest, almost 100% knockout rates, importantly with minimal off-target activity. In conclusion, in direct comparison, egRVLPs were the most efficient RVLPs. Moreover, we established methods for in-depth characterization of VLPs, facilitating their validation and thus more predictable and safe application.

Acute myeloid leukemia derived from lympho-myeloid clonal hematopoiesis

We studied acute myeloid leukemia (AML) patients with lympho-myeloid clonal hematopoiesis (LM-CH), defined by the presence of DNA methyltransferase 3A (DNMT3A) mutations in both the myeloid and lymphoid T-cell compartment. Diagnostic, complete remission (CR) and relapse samples were sequenced for 34 leukemia-related genes in 171 DNMT3A mutated adult AML patients. AML with LM-CH was found in 40 patients (23%) and was associated with clonal hematopoiesis of indeterminate potential years before AML, older age, secondary AML and more frequent MDS-type co-mutations (TET2, RUNX1 and EZH2). In 82% of AML patients with LM-CH, the preleukemic clone was refractory to chemotherapy and was the founding clone for relapse. Both LM-CH and non-LM-CH MRD-positive AML patients who achieved CR had a high risk of relapse after 10 years (75% and 75%, respectively) compared with patients without clonal hematopoiesis in CR with negative MRD (27% relapse rate). Long-term survival of patients with LM-CH was only seen after allogeneic hematopoietic stem cell transplantation (HSCT). We define AML patients with LM-CH as a distinct high-risk group of AML patients that can be identified at diagnosis through mutation analysis in T cells and should be considered for HSCT.

Three-dimensional cone beam computed tomography analysis of maxillary sinus and alveolar bone anatomy in the restorative axis of dental implants using radiopaque drill guides

The objectives were to assess the sinus anatomy and alveolar ridge dimensions and to identify clinical factors and morphological relationships that may predict the characteristics of the sinus anatomy. A total 336 edentulous molar and 168 edentulous premolar regions were analyzed. The mediolateral maxillary sinus (5mm and 10mm above alveolar bone), lateral maxillary sinus wall, ostium height, and alveolar ridges were measured. Measurement regions were defined by radiopaque simulation of the restoration goal. Mean molar mediolateral dimensions were >10mm: first molar, 11.8mm (range 3.8-21.1mm); second molar, 12.2mm (range 7.9-20.1mm). The extent of the sinus differed significantly between premolars and molars (P<0.001). The first molar region had the highest mean value for the lateral sinus wall (2.4mm, range 0.2-7.9mm) and the greatest distance between the alveolar crest and simulated restorative goal (8.1mm, range 1.1-16.3mm). Septum prevalence was 46% in the molar region and 27% in the premolar region. A lower alveolar ridge height was associated with a wider transverse extent of maxillary sinus and consequently longer distances between the crest and restorative goal. Systematic three-dimensional analysis of the maxillary sinus yields precise preoperative information about sinus configurations. There were significant variations and relationships among characteristics of the maxillary sinus, ridge, and the restorative goal.

Terahertz plastic compound lenses

We present terahertz (THz) lenses made of highly refracting polymeric compounds which provide a better focusing performance and an increased functionality in comparison to conventional THz lenses. Using mixtures consisting of polypropylene (PP) and alumina as well as PP and zinc sulfide allows a significant increase of the refractive index while simultaneously keeping a low extinction and dispersion. With these new material combinations, lenses with an increased focusing capability are realized. This is evaluated by focal plane measurements using a fiber coupled THz time-domain spectrometer.

i.lect, a pre-graduate education model of implantology

OBJECTIVE

In 2008, a consensus meeting of the Association for Dental Education in Europe stated that dental implant treatment represents a popular treatment alternative and, therefore, it should be an integral part of dental student pre-graduate education. In 2009, the Friedrich-Alexander University, Erlangen-Nuremberg implemented a voluntary, structured, education program for pre-graduate dental students, called 'i.lect'. The present study evaluated the effectiveness of the i.lect program.

METHODS

Concurrent to the dental curriculum, the i.lect program provides 200 hours in 3 years of theoretical and practical education on all aspects of modern dental implantology. We recruited dental students in the i.lect program and additionally students from 15 other universities that voluntarily participated in a single, 3-day implantology camp (R = 58). To demonstrate their knowledge on dental implant issues, both student groups completed a written examination that covered 'Basic information and materials of implantology', 'Implant planning' and 'Soft tissue management'.

RESULTS

The students in the i.lect program achieved higher scores than students from the implantology camp on questions concerning 'basic implantology' and 'implant planning'.

CONCLUSION

The results indicated that the structured i.lect undergraduate curriculum enhanced individual knowledge in the specific field of implantology. This program could have pilot character for use in other universities.

Possibilities and limitations of implant placement by virtual planning data and surgical guide templates

The use of computer-aided surgical systems for dental implant bed preparation and implant placement results in an average precision within 1 mm of implant position and within 5 degrees of deviation for implant inclination. The accuracy of axis and implant position is significantly more precise with the three-dimensional surgical guide than with the free-hand method. The three-dimensional assessment of the restorative goal (radiopaque simulation of prosthesis with scanning template) allows virtual planning of implants, which enables optimized positioning of implants with surgical guide templates in oral surgery. If there is a clear indication for three-dimensional diagnostics, it should always be checked whether the data can be used as planning data for a surgical guide template, otherwise the chance for guided surgery remains unused. Since uncertainties still exist despite the use of a drilling template, it is recommended that the minimum safety distance from adjacent structures be maintained. The successful use of surgical guide templates requires comprehensive knowledge of and experience in using three-dimensional information for the virtual planning of implant position.

Evaluation of tooth preparations - a comparative study between faculty members and pre-clinical students

INTRODUCTION

Preparation of teeth is a basic technique for dental treatment and plays an essential role in pre-clinical education. The purpose of this study was to evaluate whether undergraduate students' evaluations of prepared teeth were consistent with faculty assessments and correlated with students' performance in test preparations.

MATERIALS AND METHODS

Thirty four of 52 dental students having attended a pre-clinical course on basic prosthodontic topics including tooth preparation volunteered to participate in this study. The students were given 10 casts each containing one tooth with an intentionally applied preparation fault of a certain type prepared by an experienced clinician. The students were asked to mark on a list the fault type found in every tooth. The association of students' ratings with their performance during the course was analysed by means of a contingency table, and a generalised linear model was used to compare students' and faculty ratings (α = 0.05).

RESULTS

No significant difference between students' and faculty ratings could be found by analysis of deviance (P = 0.953). Significant deviations of fault detection probabilities from their group mean were found for six of ten fault types. No significant association between students' performance in test preparations and students ratings could be found (P = 0.564).

DISCUSSION

It was possible to achieve a level of calibration within the group of students, which was comparable to that in the group of faculty members.

CONCLUSIONS

Calibration of both students and examiners remains to be an issue with the teaching concepts applied in this study.

Student attitudes towards computer-aided testing

INTRODUCTION

  Computer-aided learning (CAL) is a viable alternative to traditional teaching methods. While CAL is used for teaching only, computer-aided testing (CAT) can be applied as a computer-based examination method. The aim of the present study was to evaluate students' attitude towards CAT as compared to written multiple choice tests.

MATERIALS AND METHODS

  Forty-one undergraduate dental students underwent a mock examination consisting of 15 written multiple choice questions and 15 questions delivered using the interactive MobiTed® system. A questionnaire based on an eight-item seven-point Likert scale was used to evaluate the students' attitude towards CAT. The students' performance in both tests was analysed using paired t-tests. Correlations between test performance and questionnaire were expressed by Pearson correlation coefficients.

RESULTS

  Despite study-design-related differences, students' test performance between written multiple choice and MobiTed® was comparable. No correlations between test results and questionnaire could be set up. Students rated MobiTed® to be equivalent to written multiple choice and had no difficulties with the CAT set up. The pre-defined sequence of questions with each question being shown only once was considered to be a major disadvantage of the CAT system. Complex questions should be displayed longer compared to short questions.

DISCUSSION

  Computer-aided testing appeared to be equivalent to written multiple choice tests not only in terms of student performance but also to their perception. This is consistent with previous studies.

CONCLUSIONS

  Interactive multiple choice tests may provide an alternative to written tests, but should allow examinees to have control over the sequence, as well as the length of time the questions are displayed.

Dental anxiety--an epidemiological study on its clinical correlation and effects on oral health

Pronounced dental anxiety could lead to avoidance strategies to evade dental visits. The aim of the present epidemiological study was to investigate the prevalence and related oral disease patterns of dental anxiety in young adult male soldiers. Therefore, the intensity and frequency of dental anxiety are presented and the correlation with oral clinical findings are evaluated. Three hundred seventy-four soldiers who underwent a compulsory dental check-up were randomly assigned to this study. Psychological parameters were collected based on a protocol integrating the Dental Anxiety Scale (DAS) and the Gatchell Fear Scale (GaFS). Patient-based measures included D3,4MF-scores for dental status and the Community Periodontal Index of Treatment Need (CPITN) for periodontal status. Thirty-two individuals (8.6%) showed DAS-scores of 13 or 14 (anxious), while 4.6% had a DAS-score > or = 15 (highly anxious/phobic). Highest DAS-values were measured among patients' aged 19-29 (n = 262). DMFS-values of anxious and less anxious patients showed only minor differences. However, anxious patients had significantly more carious lesions (P < 0.001). CPITN periodontal values showed no significant differences between both groups. 89.2% of less anxious individuals and 79.6% of anxious patients went for regular dental check-ups. Thus, every tenth patient was considered to have high dental anxiety. Anxiety results in avoidance behaviour, which can only be discovered upon compulsory examinations and which is associated with higher caries morbidity and need for oral rehabilitation. As anxiety has a direct influence on oral health, it should be detected and accounted for in a treatment concept integrating dental and cognitive-behavioural therapeutic approaches.

Comparison between computer-aided testing and traditional multiple choice: an equivalence study

AIMS

Computer-aided learning (CAL) is a viable alternative to traditional teaching methods. While CAL is used for teaching only, computer-aided testing (CAT) can be applied as a computer-based examination method. The aim of the present study was to compare the performance of undergraduate students in computer-interactive tests and traditional multiple choice tests and to evaluate the influence of question length and language skills on test results.

MATERIALS AND METHODS

Fifty-two native German-speaking students and five non-native speaking students were randomly assigned to two groups. They were required to answer 20 conventional multiple choice questions and 20 questions using the interactive MobiTed system. An analysis of variance and t-tests (alpha = 0.05) were used to compare scores.

RESULTS

Non-native speakers scored significantly lower on the interactive test compared with the native speaking students (P = 0.048 for long questions and P = 0.003 for short questions). There were no significant group differences on the conventional multiple choice test (P = 0.052 for long questions and P = 0.089 for short questions). Based on the results of the native speaking students neither test method nor question length had an influence on overall performance.

CONCLUSION

Interactive multiple choice tests may provide an alternative to written tests, especially when considering time expenditure. Language skills and question length should be taken into account when setting time limits for examination.

Changes in neurophysiologic parameters in a patient with dental anxiety by hypnosis during surgical treatment

It was hypothesized that dental anxiety, which leads to neurophysiologic alterations in heart rate, respiratory rate and blood pressure prior, during and subsequent to dental treatment, can be influenced by medical hypnosis. We report the positive impact from non-invasive hypno-sedation during dental implant surgery on a 54-year-old female patient who experienced neurophysiologic reactions as a result of the psychosomatic process of dental anxiety (dental anxiety scale value = 13). The neurophysiologic changes during dental surgery performed with and without hypnosis were compared after the patient underwent the same surgical treatment protocol. This case report was part of a study designed to evaluate hypnosis as a non-invasive therapy for dental-anxious patients over six sessions using subjective experience and objective parameters, which included electroencephalogram, electrocardiogram, heart rate, blood pressure, oxygen saturation of the blood, respiration rate, salivary cortisol concentration and body temperature.

Expression of interleukin 1-beta, transforming growth factor beta-1, and vascular endothelial growth factor in soft tissue over the implant before uncovering

BACKGROUND

Overexpression of inflammatory cytokines interleukin 1-beta (IL-1beta), transforming growth factor beta-1 (TGF-beta1), and vascular endothelial growth factor (VEGF) may cause healing impairment following implant insertion, jeopardizing success especially in patients previously irradiated. Limited data is available regarding expression pattern of inflammatory cytokines in peri-implant soft tissue caused by the surgical intervention itself.

STUDY DESIGN

This study examined 21 patients receiving dental implants. Biopsies of peri-implant tissue were harvested at re-entry 4 months after initial surgery. Eight patients underwent probing of untreated mucosa. Three groups were created (group 1: regular peri-implant mucosa; group 2: patients with irradiated peri-implant mucosa, radiation treatment due to oral squamous cell cancer; group 3: control). Immunohistochemical staining was performed for TGFss1, IL-1ss, and VEGF.

RESULTS

Following the placement of dental implants (group 1 vs group 3) a significant increase (P > .05) in TGF-beta1, IL-1beta, and VEGF expression in the peri-implant mucosa was demonstrated. No alteration of this distinct pattern was found for previously irradiated tissue (group 1 vs. group 2).

CONCLUSIONS

The study highlights the fundamental involvement of TGF-beta1, IL-1beta, and VEGF during the regeneration of peri-implant soft tissue structures. The use of extended interim solutions may be one clinical implication of these prolonged tissue remodeling processes.

The aesthetics of all-ceramic veneered and monolithic CAD/CAM crowns

The aim of this study was to examine whether crowns fabricated from machinable blocks would achieve acceptable aesthetics and whether these could compete with the aesthetics of restorations obtained by individual layering technique. Fourteen patients, who were to receive single anterior crown restorations, participated in this study. For each person two kinds of crowns were provided: one crown was made with the Cergogold system. The second one was produced in a Cerec machine and was additionally stained. Three independent examiners assessed the aesthetic appearance of crowns fabricated to match each subject's anterior shade. A scale of 1-6 was used to assess the aesthetic adaptation of each crown, with 1 representing excellent characteristics and 3.5 marking the threshold for clinical acceptability. The examiners' scores were averaged, and the mean values were analysed with the Wilcoxon signed rank test (P<or=0.05). Regardless of the fabrication method the crowns were aesthetically acceptable in all 14 patients. The mean values for the layering technique and for the machined restorations did not differ significantly. Within the limits of this study it was documented, that machinable blocks could attain aesthetically satisfying results.

[Assessment of the tetanus immune status in plasma donors of the Blood Donor Service of the Bavarian Red Cross]

BACKGROUND AND OBJECTIVE

Tetanus is nowadays largely under control, as a result of the preventive immunization programme. This prophylactic measure is important also because there is no specific treatment. In Germany tetanus occurs almost exclusively in elderly, not adequately immunized persons. This study determined the existing immune status of plasma donors in the region of Ingolstadt, Bavaria.

SUBJECTS AND METHODS

Tetanus IgG antibody concentrations were measured with the ELISA test in serum of 1742 plasma donors (891 women, 851 men, age range 18-64 years).

RESULTS

An adequately protective immunity against tetanus was found in 98.7% of men and 94.1% of women, while 5 women and 3 men had no protection. Demographic data indicated that the immunization protected males longer than females, regardless of age, especially in those over 50 years of age (85% of females, 99% of males).

CONCLUSION

Adequate tetanus protection was achieved in the overwhelming majority of test subjects. This demonstrates that the prevalence of protection is lower in females than in males, a difference most marked in those over 50 years of age. It is important that this age group in particular should, as part of health care, be informed by their medical practitioner of the dangers of tetanus and the advantages of immunization.

Zinc gluconate in the treatment of dysgeusia--a randomized clinical trial

In the treatment of dysgeusia, the use of zinc has been frequently tried, with equivocal results. The aim of the present randomized clinical trial, which involved a sufficiently large sample, was therefore to determine the efficacy of zinc treatment. Fifty patients with idiopathic dysgeusia were carefully selected. Zinc gluconate (140 mg/day; n=26) or placebo (lactose; n=24) was randomly assigned to the patients. The patients on zinc improved in terms of gustatory function (p <0.001) and rated the dysgeusia as being less severe (p <0.05). Similarly, signs of depression in the zinc group were less severe (Beck Depression Inventory, p <0.05; mood scale, p <0.05). With the exception of the salivary calcium level, which was higher in the zinc patients (p <0.05), no other significant group differences were found. In conclusion, zinc appears to improve general gustatory function and, consequently, general mood scores in dysgeusia patients.

The self-adjusting crown (SAC)

When previously using Cerec 3D, the occlusal surface could be designed according to morphologically functional aspects with the aid of a bite registration (static and/or dynamic). In addition, different tooth databases could be used for the design of crowns. However, the relevant design suggestion had then to be manually aligned onto the functional registration by the user. The new Cerec 3D software version R 2005 now promises the automatic adjustment of crown proposals in alignment with the corresponding functional registration. In this case, the crown design selected from the tooth databases is adjusted to the morphology of the functional registration and is therefore modified until light contact points are still present. The procedure of the "self-adjusting crown" is demonstrated by reference to a clinical case. As the name "self-adjusting crown" indicates, this automatic tool is possible only in restorations which have a single-segment preparation margin (crowns).

Generation of functional Cerec 3D occlusal surfaces: a comparison of two production methods relevant in practice

The introduction of the Cerec 3D software (R 1500) promised the generation of functional occlusion points and proximal contacts on the basis of a 3-dimensional virtual model on the screen. The objective of this in vitro study was to check this claim in the simulated chairside production of a single tooth restoration. Furthermore, the differences both in conventional finishing and in ceramic glazing were to be determined. For the operator, the latter should simplify or shorten the intraoral finishing and polishing of the occlusal surface, or make it superfluous. To check the suitability of the two methods, these were compared with regard to their quality and the time required to perform them. Ten cavities on articulated models, representing real clinical cases, were each provided with two restorations. One was produced with the glazing method (group A), the other conventionally (group B). The Cerec 3D software, version R 1500, was used for designing the restoration. The restorations made from Vita Mark II ceramic blocks were finished with fine diamond instruments and polished with Sof-Lex disks when using the conventional method. In the alternative method, finishing was practically replaced by glazing the surface. The restorations were evaluated in the articulator, considering both the vertical relation at the incisal pin as well as the accurate position of the contact points. The study showed that functional rehabilitation was possible and no significant qualitative differences occurred in the methods. In this in vitro study, it was found that the glazing method reduced the time required by the operator by around 20% and indicates an improvement in quality. The results of this study promise simplification when the glazing method is used clinically.

Differences between the Cerec-3D software versions 1000 and 1500

The Cerec-3D software was introduced officially at the IDS 2003 with the version 2.00 R1000. The decisive difference compared with the preceding software generations was that the prepared tooth and the restoration were displayed three dimensionally. Thus, the virtual changes which could be made with the aid of editing tools could also be controlled and seen immediately in 3D. The latest officially available version of the Cerec-3D software version 2.10 R1500 differs in some further developments from the first version 2.00 R1000; these are for example: --If the semiautomatic margin detector is switched off while marking the preparation margin, the alternative intensity image appears instead of the 3D display. --Designing has been decisively improved by the extension of the "Drop" tool (function of continuous application and removal of material). --Under morphologically difficult circumstances, the design proposal can be magnified/reduced in size and repositioned in all spatial directions. --The Parameter setting again permits setting an adhesive gap width specific to the dentist and unit. As an example, the version 1500 software is demonstrated on a simple clinical case in which the occlusion points were defined virtually with the aid of a functional bite registration, eliminating the need for occlusal grinding-in.

Pr�operative Nahrungskarenz

In Germany the predominant standard of preoperative care for elective surgery is fasting after midnight, with the aim of reducing the risk of pulmonary aspiration. However, for the past several years the scientific evidence supporting such a practice has been challenged. Experimental and clinical studies prove a reliable gastric emptying within 2 h suggesting that, particularly for limited intake of clear fluids up to 2 h preoperatively, there would be no increased risk for the patient. In addition, the general incidence of pulmonary aspiration during general anaesthesia (before induction, during surgery and during recovery) is extremely low, has a good prognosis and is more a consequence of insufficient airway protection and/or inadequate anaesthetic depth rather than due to the patient's fasting state. Therefore, primarily to decrease perioperative discomfort for patients, several national anaesthesia societies have changed their guidelines for preoperative fasting. They recommend a more liberal policy regarding per os intake of both liquid and solid food, with consideration of certain conditions and contraindications. The following article reviews the literature and gives an overview of the scientific background on which the national guidelines are based. The intention of this review is to propose recommendations for preoperative fasting regarding clear fluids for Germany as well.

[Surgical treatment of pulmonary metastases from renal cancer]

Based on a large single-center follow-up database, we evaluated the long-term results after curative resection of pulmonary metastases from renal cancer. During a 20-year period, 105 patients underwent a total of 150 resections with curative intention. Hospital mortality was 0.95%, 5- and 10-year survival rates were 40% and 33%, respectively. Significant prognostic relevance was shown for complete pulmonary resection, lymph node involvement upon primary resection as well as size of the resected lung metastasis. Our findings of low perioperative morbidity and mortality rates lead us to propose that in patients without additional metastases curative resection of pulmonary lesions should be considered. Moreover, recurrent pulmonary metastases should also be considered for surgical treatment since resection for cure significantly improves survival in these patients.

[Experimental examination concerning the efficacy of silver-coated Dacron prostheses in vascular graft infections following subcutaneous implantation in a standardized infection model]

It was the aim of the study to examine the efficacy of silver coated prostheses in comparison to Rifampin in impregnated prostheses in the prevention of vascular graft infections.

MATERIAL AND METHODS

24 C3H/HcN mice with a bodyweight between 24 and 27 grams were assigned to four different groups. GROUP I: control gel-sealed Dacron graft (Uni-Graft DV) (6), GROUP II: gel-sealed Dacron graft (Uni-Graft DV) contaminated locally with 2 x 10(7) CFU/1.2 ml Staphylococcus aureus ATCC 25923 (6), GROUP III: silver prosthesis (Intergard Silver) contaminated locally with 2 x 10(7) CFU/0.2 ml Staphylococcus aureus ATCC 25923 (6), GROUP IV: Rifampin impregnated prosthesis contaminated locally with 2 x 10(7) CFU/0.2 ml Staphylococcus aureus ATCC 25923 (6). 14 days after primary operation all animals were euthanized and the grafts harvested. Specimens were examined for signs of infections by histology and microbiology.

RESULTS

At termination of the trial on day 14 none of the grafts of group I were contaminated. 6 out of 6 grafts in group II, 6 out of 6 grafts in group III and 1 out of 6 grafts in group IV presented with infected grafts. The use of antimicrobial Rifampin could significantly prevent infection after bacterial challenge in group IV.

CONCLUSION

The silver protected prosthesis (Intergard Silver) seems to be not effective in protecting vascular infection in vivo. However, the Rifampin group showed excellent results. In conclusion Rifampin bonded gelatin-sealed Dacron grafts are significantly more resistant to bacteremic infection than are silver/collagen-coated Dacron grafts.

Long-term results of endosteal implants used for restoration of oral function after oncologic surgery

The aim of the present study was to analyse the long-term survival rate of endosteal implants used for restoration of oral function in patients having undergone oncologic surgery. Eighty-three consecutive patients, who had received a total of 409 endosteal implants ad modum Brånemark, subsequent to resections of soft tissue and bone during ablation of oral malignancies, were enrolled into the study. A life-table analysis was used to determine the survival rate of the implants placed during a period of 13 years. Log rank tests and Cox regression analysis were employed to identify relevant effects of surgical parameters on implant survival. A total of 38 implant failures were encountered. Most of the losses (n = 19) occurred during the first year of functional loading. Subsequent failures were evenly distributed across the remaining follow-up period. The cumulative overall survival rate of implants was 56.5%. Previous radiation therapy, insertion into grafted bone or original jaw bone and the technique of grafting did not significantly affect the survival rates. In the Cox regression analysis, the timing of implant placement in the group of patients with bone grafts (primary vs. secondary placement) was significantly related to the survival rate (P = 0.0197), with a lower survival rate of 36.2% for primary insertion of implants and 67.1% for secondary placement.

[Endosseous implants for functional masticatory rehabilitation in the extremely atrophied edentulous maxilla]

PURPOSE

The aim of this retrospective study was to evaluate the long-term survival rate of dental implants in edentulous patients suffering from severe atrophy of the alveolar ridges in the upper jaw.

PATIENTS AND METHODS

In total, 964 implants were inserted in 140 patients. A total of 481 implants were combined with an osteoplastic augmentation of the maxilla, and 483 implants were inserted directly in the atrophic bone. The success rate was determined using survival analysis, log rank tests and a Cox regression analysis.

RESULTS

The overall survival rate for all implants was 42.2% during an observation period of 11 years. Between implants combined with an osteoplasty and implants inserted in local bone tissue there were no significant differences in the survival rate. The survival rate of implants combined with an osteoplasty was significantly reduced in women and in the case of repeated insertion or augmentation. Interestingly, a few of the patients treated with an osteoplasty demonstrated high numbers of individual implant failures. Those patients were postmenopausal women exclusively. Among them there is probably a certain group with a very high risk of implant failures.

CONCLUSION

This study shows that oral rehabilitation with osteointegrated implants in patients with severely atrophic alveolar ridges in the upper jaw is still problematic.

Survival analysis of endosseous implants in bone grafts used for the treatment of severe alveolar ridge atrophy

PURPOSE

The aim of the current study was to evaluate the long-term results of endosseous implants placed into autogenous bone grafts in severely atrophic alveolar ridges.

PATIENTS AND METHODS

A total of 871 implants were placed in 137 patients. The success rate was determined using survival analysis, log rank tests, and a cox regression analysis.

RESULTS

Seventy-four implant failures were encountered in 23 patients. Most implants were lost because of a lack of osseointegration at the time of abutment connection or by asymptomatic loosening during the first months thereafter. The overall 1-year cumulative survival rate (CSR) was 83.4%, with a decrease to 67.8% after 5 years. The only parameter of prognostic relevance in the multivariate analysis of the whole study population was the patients' gender, with a significantly worse prognosis in female patients (5-year CSR, 62.3%). However, when the patients were divided into edentulous and partially edentulous jaws, a change was observed in the overall significance of the parameters introduced into the analysis. In edentulous patients, the maxilla appeared to over-rule all other parameters, with a 5-year cumulative survival rate of 48.8%, whereas the mandible presented a significantly higher rate of implant survival (5-year CSR, 89.3%).

CONCLUSION

This study shows a poorer success rate in females than in males, probably because of differences in the quality of the bone grafts.

Postoperative function after implant insertion in vascularized bone grafts in maxilla and mandible

Between 1988 and 1992, 80 Brånemark-type implants were inserted in 18 patients during reconstruction of the mandible or maxilla with vascularized iliac crest or scapula grafts with or without additional soft tissue pedicles. In these procedures, nine vascularized bone grafts were combined with a primary insertion of 32 implants and a secondary insertion of 48 implants. Twelve patients are currently wearing the implant-borne dentures. From 32 implants inserted primarily, eight could not be used for prosthodontic rehabilitation because three were lost with a graft, three were left as sleepers, and two demonstrated a lack of osseointegration. None of the implants inserted secondarily in grafts were lost. Primary implant insertion should be performed only in close cooperation with the prosthodontist and in selected cases, for example, in free-end reconstruction of the mandible with a straight graft and where a limited number of implants is needed. Although restoration of masticatory function in patients with head and neck cancer can be achieved, compared with a healthy control group, functional impairments remain. Patients subjectively favor the nonreconstructed side of the mandible or maxilla for chewing. These findings can be correlated with a postoperative follow-up investigation using a miniature force transducer and the T-scan system.

A computerized method for evaluating distribution of occlusal load on implant-supported fixed cantilever prostheses

An investigation was conducted to determine whether Dental Prescale, a material that undergoes a graded color-producing chemical reaction when force is applied, could be used to evaluate occlusal load distribution objectively and quantitatively when combined with computer analysis. Ten patients with an implant-supported fixed cantilever prosthesis and a complete conventional maxillary denture were studied. The results indicated that the system can be used to evaluate occlusal load distribution with sufficient reproducibility. However, in its present form, the system is somewhat cumbersome, and its use must now be considered experimental. Further refinement is necessary to allow easier clinical use.

Application of a low-adhesive color-developing chewing gum system to patients with osseointegrated implant-supported prostheses

Few methods have been described that can quantitatively evaluate masticatory function. This study investigated the usefulness of a low-adhesive color-developing chewing gum system for the evaluation of patients with implant-supported prostheses. Fifteen dentate subjects and 22 patients with dental implants participated in this study. The color developed in the gum after chewing reflects masticatory function and is evaluated quantitatively with a color-analyzing system. The results indicate that this system can be used to evaluate occlusal function, and they confirm the importance of stable prostheses for higher masticatory function.

[Studies on the effects of abutment position on the prognosis of endosseous implants]

Although the use of osseointegrated Brånemark implants is associated with a high success rate, late losses of primarily osseointegrated implants have been observed again and again. In this study 50 patients were evaluated to clarify the effects of abutment position on late losses. The results have shown that implant position is less important for the loss of implants than other parameters such as healing disorders or poor oral hygiene.

[Temperature profile in the enamel during cold tests]

The temperatures on the surface of human teeth during pulp vitality tests with frigen and carbon dioxide snow were recorded in an in vitro study. Frigen spray caused particularly rapid changes in temperature. The lowest temperature (-52 degrees C) was measured with CO2-snow (with a pressure of 9.81 N against the tooth surface). To obtain higher temperatures at lower rates of change, the use of a thin latex fingerstall proved to be effective.

[Posttreatment evaluation of root canal fillings performed by dental students]

The present study deals with root canal treatments performed by students in 616 teeth, 322 of which could be reevaluated clinically and radiologically after periods of 3-7 years. 14 (4%) teeth had to be apicectomized. 96% of the teeth had no clinical symptoms.

[Visibility of front and side teeth]

Anterior and posterior tooth visibility was analysed in a population of 220 subjects. Scoring photographic data gave the percentages of anterior and posterior teeth shown in different situations: speaking, laughing, exaggerated smiling. The consequences for planning and manufacturing dentures are shown by examples.

[Measuring the accuracy of various elastomeric impression materials using a CNC coordinate measuring device (Part 1)]

This study compares the accuracy of 23 impression materials. With each material seven impressions of a stainless steel master die were taken under standardized conditions. Characteristical dimensions of the master die and of the stone dies as well were determined by means of a CNC coordinate measuring device. Differences in prepared tooth heights ranged between -36 and +19 microns. The occlusal distances between prepared teeth were 2 to 54 microns greater on the stone dies than on the master die. Diameters differed by -89 to +52 microns. The two phase impressions tended to result in stone dies of reduced size, whereas single phase and double mix impression techniques produced larger stone dies than the master die.