Eleonore Behrens

Prospective observation of 41 perforations of the Schneiderian membrane during sinus floor elevation

OBJECTIVES The aim of this study was to follow 41 intraoperative perforations of the Schneiderian membrane during sinus floor elevation and to identify potential differences from patients without perforations. MATERIAL AND METHODS Two hundred and one sinus floor elevations were performed at the department of oral and maxillofacial surgery of the University Hospital of Schleswig-Holstein in the years 2005 and 2006. Forty-one intraoperative perforations (20.4%) were documented and treated according to the following scheme: defects smaller than 5 mm were covered with a collagen membrane. Larger defects were additionally sutured. Particulated jawbone mixed 50 : 50 with bone substitute (25 cases) and a 50 : 50 mix of particulated iliac crest bone and BioOss (six cases) mainly served as graft material in the perforation group. In 12 cases, implants were installed at the time of sinus grafting, and in 27 cases, a second operation was performed. RESULTS Four sinus lift procedures had to be discontinued intraoperatively. Over a mean control interval of 162 days, one implant of the 93 inserted had to be replaced in the perforation group. After 1 year, the implant survival rate was 14 out of 14 in the perforation group vs. 81/92 in the control group. CONCLUSIONS With appropriate treatment, intraoperative sinus membrane perforations did not represent an elevated risk for implant loss, infectious complications or displacement of graft material in the investigated population.

A comparison of biocompatibility and osseointegration of ceramic and titanium implants: an in vivo and in vitro study

This study compared the biocompatibility in vitro and the osseointegration in vivo of zirconium and titanium implants regarding implant surfaces and the bone-implant contacts. The different implant surfaces and the biocompatibility of zirconium versus titanium implants were determined by vitality and cytotoxic tests in vitro. The contact of the osteoblasts to the implant surface was determined by scanning electron microscopy (SEM). The in vivo study for osseointegration was performed in domestic pigs over 4 and 12 weeks. In each animal, 4 zirconium and 4 titanium implants (WhiteSky, BlueSky, Bredent, Germany) were inserted in the os frontale and analysed by histomorphometry. Cytotoxicity and SEM showed good biocompatibility in relation to the investigated implant materials. Histological results showed direct bone-implant contact of the implant surfaces. The zirconium implants showed a slight delay in osseointegration in terms of bone-implant contact as measured by histomorphometry (after 4 weeks, zirconium (59.3 ± 4.6%) versus titanium (64.1 ± 3.9%); after 12 weeks, zirconium (67.1 ± 2.3%) versus titanium (73.6 ± 3.2%). A statistically significant difference between the two groups was not observed. The results indicated similar biocompatibility and osseointegration for zirconium compared to titanium implants.

Regenerative Treatment of Peri‐Implantitis Bone Defects with a Combination of Autologous Bone and a Demineralized Xenogenic Bone Graft: A Series of 36 Defects

AIM As the treatment of peri-implantitis-induced bone loss is still a problem, we studied the regenerative treatment of these defects with a mix of autologous bone and a new type of bone graft substitute (demineralized xenogenic bone graft) including growth factors. MATERIAL AND METHODS In a prospective manner, 36 cases of peri-implantitis-induced bone loss (depth >4 mm) in 22 patients were followed for 1 year. After resolving the acute infection by local rinsing, granulation tissue was removed. The implants were decontaminated with etching gel and the defects were filled with autologous bone mixed 1:1 with a xenogenic bone graft. The prosthetic reconstructions did not have to be removed. Values of probing depths as well as bone defects were analyzed. RESULTS The radiologic evaluation of the bone defects after regenerative treatment revealed a mean reduction of 3.5 mm comparing the values from 5.1 mm prior to surgery to 1.6 mm 1 year after treatment. Average reduction of the probing depth was 4 mm. The remaining bone defects were larger than 3 mm in 4 out of 36 implants 1 year after treatment. Probing depths of more than 4 mm were present in seven implants. CONCLUSION Within the limits of the study, we conclude that for bone defects larger than 4 mm in case of peri-implantitis, this single surgical intervention provided a reliable method to reduce bone defects.

Morbidity after iliac crest bone graft harvesting over an anterior versus posterior approach.

PURPOSE For larger augmentations before implant insertions, as well as spinal arthrodesis surgery, the iliac crest is the standard source of bone grafting. This study assesses iliac morbidity after bone graft harvesting from the anterior and posterior ilium. MATERIALS AND METHODS A total of 97 patients who underwent corticocancellous iliac crest bone harvesting for augmentations of the jaws from 2004 to 2007 at the Department of Oral and Maxillofacial Surgery, University Hospital Kiel, Kiel, Germany, were included. Their morbidity was assessed with specially designed questionnaires. RESULTS Pain levels were rated nearly equally on a visual analog scale (1, no pain; 10, strongest pain) by the anterior and posterior groups. At 1 week after bone harvesting, pain was rated 4.9 for the anterior approach and 4.8 for posterior (P = .89). The corresponding values after 6 months were 1.4 and 1.6, respectively (P = .64). Subjective evaluation of the scars showed scores of 2.7 and 3.0, respectively (P = .76). Of the patients, 81% and 88%, respectively, would opt to undergo the operation again. CONCLUSIONS Patients reported a noticeable reduction in quality of life after elective bone graft harvesting. Nevertheless, nearly all patients would undergo the same procedure again. Both approaches were rated similarly, so for smaller amounts of bone graft needed, the anterior and posterior approaches can be recommended, whereas the posterior approach is suitable for larger amounts.

Comparison of two different absorbable membranes for the coverage of lateral osteotomy sites in maxillary sinus augmentation: A preliminary study

INTRODUCTION Barrier membranes, both absorbable and non-absorbable, have been used in sinus augmentation for many years. Some years ago, a new autologous blood substrate called Platelet-Rich-Fibrin (PRF) was introduced, and to date, the supporting effect on bone regeneration has been controversial. This study aimed to evaluate the effect of PRF on bone regeneration when used as a barrier membrane at the lateral osteotomy site in sinus augmentation. MATERIAL AND METHODS Twelve sinuses from six patients requiring bilateral sinus floor augmentation were treated with a two-stage surgical technique using sinus augmentation and implant placement after 5 months. The sinuses were grafted with autologous bone and bone-substitute material (Bio-Oss(®)) mixed in a 1:1 ratio and were covered in a randomized split-mouth design with a PRF or a conventional collagen membrane (Bio-Gide(®)), respectively. Five months later threaded titanium dental implants were inserted and bone specimens harvested with a trephine burr were evaluated histomorphometrically. RESULTS Bone quality seemed to be equal at both sites of the grafted sinuses. Mean vital bone formation after 5 months was 17.0% and 17.2%, for the PRF and collagen sites, respectively. The mean of residual bone-substitute was 15.9% and 17.3% for PRF and collagen, respectively. No local complications, such as dehiscences or membrane exposures, were detected at either site in any of the treated patients. After 12 months all implants reached primary stability in the augmented maxillary sinus floor without any peri-implant tissue inflammation. CONCLUSIONS Within the limits of the study the coverage of the lateral sinus window with two different absorbable membranes has been shown to result in a similar amount of vital bone formation and residual bone-substitute.

Long-term Survival of Straumann Dental Implants with TPS Surfaces: A Retrospective Study with a Follow-up of 12 to 23 Years.

PURPOSE The aim of this study was to evaluate the long-term dental implant survival rates of Straumann dental implants in a university hospital environment over 12 to 23 years. MATERIALS AND METHODS A total of 388 Straumann dental implants with titanium-sprayed surfaces (TPS) were inserted in 92 patients between 1988 and 1999 in the Department of Oral and Maxillofacial Surgery of the University Hospital Schleswig-Holstein in Kiel, and they were reevaluated with standardized clinical and radiological exams. Kaplan-Meier analyses were performed for individual factors. Cox proportional hazard regression analysis was used to detect the factors influencing long-term implant failure. RESULTS The long-term implant survival rate was 88.03% after an observation time of 12.2 to 23.5 years. Cox regression revealed statistically significant influences of the International Team for Implantology (ITI) implantation type (p = .00354) and tobacco smoking (p = .01264) on implant failure. A proportion 82.8% of the patients with implant losses had a medical history of periodontitis. Peri-implantitis was diagnosed in 9.7% of the remaining implants in the long-term survey. CONCLUSIONS This study emphasized the long-term rehabilitation capabilities of Straumann dental implants in complex cases. The survival rates after several years constitute important information for patients, as well as for clinicians, in deciding about different concepts of tooth replacement. Patient-related and technical factors - determined before implant placement - could help to predict the risk of implant loss.

Platform switch versus platform match in the posterior mandible – 1-year results of a multicentre randomized clinical trial.

Objective The purpose of this ongoing randomized study was to assess differences in bone level changes and success rates using implants supporting single crowns in the posterior mandible either with platform matched or platform switched abutments. Material and Methods Patients aged 18 and above, missing at least two teeth in the posterior mandible and with a natural tooth mesial to the most proximal implant site were enrolled. Randomization followed implant placement. Definitive restorations were placed after a minimum transgingival healing period of 8 weeks. Changes in crestal bone level from surgery and loading (baseline) to 12-month post-loading were radiographically measured. Implant survival and success were determined. Results Sixty-eight patients received 74 implants in the platform switching group and 72 in the other one. The difference of mean marginal bone level change from surgery to 12 months was significant between groups (p < 0.004). Radiographical mean bone gain or no bone loss from loading was noted for 67.1% of the platform switching and 49.2% of the platform matching implants. Implant success rates were 97.3% and 100%, respectively. Conclusions Within the same implant system the platform switching concept showed a positive effect on marginal bone levels when compared with restorations with platform matching.

Mechanical properties of collagen membranes: Are they sufficient for orbital floor reconstructions?

INTRODUCTION The most common reconstruction materials for orbital floor fractures are PDS (polydioxanone) foil and titanium meshes. These materials have advantages and disadvantages. Therefore, new materials are needed to improve surgical outcomes. MATERIALS AND METHODS Three resorbable collagen membranes (Smartbrane(®), BioGide(®), Creos(®)) were tested for their mechanical properties (puncture strength) in mint and artificially aged (3, 6, 8 weeks) conditions and were compared to PDS foil, titanium meshes (0.25 mm, 0.5 mm) and human orbital floors (n = 7). RESULTS The following puncture strengths were evaluated: human orbital floor, 0.81 ± 0.49 N/mm(2); 0.25 mm titanium mesh, 5.36 ± 0.25 N/mm(2); 0.5 mm titanium mesh, 16.08 ± 5.17 N/mm(2); Smartbrane, 0.74 ± 0.31 N/mm(2); BioGide, 1.65 ± 0.45 N/mm(2); and Creos, 2.81 ± 0.27 N/mm(2). After artificial aging, the puncture strengths were significantly reduced (p ≤ 0.05) at 3, 6 and 8 weeks as follows: Smartbrane, 0.05 ± 0.03 N/mm(2), 0.03 ± 0.02 N/mm(2), and 0.01 ± 0.01 N/mm(2), respectively; BioGide, 0.42 ± 0.06 N/mm(2), 0.41 ± 0.12 N/mm(2), and 0.32 ± 0.08 N/mm(2), respectively; and Creos, 2.02 ± 0.37 N/mm(2), 1.49 ± 0.42 N/mm(2), and 1.36 ± 0.42 N/mm(2), respectively. CONCLUSION The tested materials showed sufficient puncture strength for orbital floor reconstruction in mint condition. Moreover, after artificial aging, the Creos and BioGide membranes showed sufficient resistance, while Smartbrane showed equivocal data after eight weeks. Therefore, collagen membranes have adequate properties for further in vivo investigations for orbital floor reconstructions.

Effect of platform switching on crestal bone levels around implants in the posterior mandible: 3 years results from a multicentre randomized clinical trial

Abstract Objective Evaluation of differences in the clinical performance and crestal bone levels between implants restored with single crowns with platform‐matched or platform‐switched abutments after 3 years. Material and Methods The study enrolled adult patients missing two or more adjacent teeth in the posterior mandible with natural teeth mesial to the implant site. Randomization followed open‐flap implant insertion and the corresponding matching or switching healing abutments placed at surgery. Conventional loading was made with cemented crowns. Clinical follow‐up took place annually after loading up to 3 years. Bone level changes were measured in standardized radiographs as the variation in crestal bone from one evaluation to the next. Results Sixty‐three patients with a total of 135 implants (66 platform matching, 69 platform switching) were analysed. From surgery to 36 months, mean bone loss was 0.28 ± 0.56 mm for the platform‐switching group and 0.68 ± 0.64 mm for the platform‐matching group. A statistically significant difference was found between groups (p = 0.002) with an estimate of 0.39 mm (0.15–0.64, 95% CI) in favour of platform switching. Conclusions After 3 years, platform‐switching restorations showed a significant effect in the preservation of marginal bone levels compared to platform‐matching restorations.

Highly porous hydroxyapatite with and without local harvested bone in sinus floor augmentation: a histometric study in pigs

OBJECTIVE Sinus floor augmentation with autologous bone is an accepted treatment option in dental implantology. In this study, an entirely synthetic, nano-structured, hydroxyapatite-based bone substitute material (SBSM, NanoBone(®); Artoss, Rostock, Germany) was supplemented with a mixture of locally harvested bone to enhance osteogenesis. METHODS Bilateral sinus augmentation procedures were performed in eight domestic pigs using the lateral window technique. On the right side (control), 2.6 ml of SBSM was used, and on the left side (test), 2.6 ml of SBSM with additional 15% (390 μl) autologous bone was used. At the time of augmentation, a titanium implant (ITI(®)) was inserted from a laterocaudal direction. After 3 months, the sites of augmentation were removed and examined in non-decalcified sections by microradiography and fluorescence microscopy of sequentially labelled specimens and histometry. RESULTS On both sides, a significant amount of newly formed bone was observed. However, a statistically significant difference in the bone-implant contact was observed in the control group (median, 28.9%) compared with the test side with the additional autologous bone (median, 40.6%) (P = 0.01). Different bone density was achieved from the coronal to apical surfaces (medians, 54.6%, 9.6%, and 27.5%) compared with the test side (medians, 55.2%, 40.6%, and 44.2%). The median of augmentation height was 8.6 mm on the control side and 11.5 mm on the test side (P = 0.01). Bone apposition was observed in both groups after 15 days. CONCLUSION The SBSM shows acceptable results in sinus floor augmentation. The additional use of locally harvested autologous bone enhances bone density and osseointegration of the implants.