Immediate versus early loading of immediately placed bone-level tapered dental implants with hydrophilic surface in full arch maxillary rehabilitation: A pilot randomized clinical trial with 2-year follow-up.

This study aimed to compare implant stabilities between the immediate and early loaded, immediately placed bone-level tapered dental implants in the maxilla and to evaluate marginal bone loss (MBL), oral health-related quality of life (OHRQoL), and patient satisfaction at a 2-year follow-up. A pilot, prospective, randomized, controlled clinical trial was conducted on 24 maxillary failing dentition patients. The bone-level tapered implants of 12 patients were immediately loaded with temporary restorations, while the other 12 patients did not receive any kind of temporization. Implant-supported screw-retained complete porcelain-fused-to-metal prostheses were delivered to all patients in the seventh postoperative week. The insertion torque values of implants assigned to the immediate and early loading groups were 33.0 ± 4.87 and 29.26 ± 8.31 Ncm, respectively. The dynamics of implant stability changes from implant placement up to a 2-year follow-up were similar for both groups (Penguin®, p = 0.268; Ostell®, p = 0.552), while the MBL was at submillimeter level. The cumulative implant survival rate was 91.80% for immediately loaded implants and 97.22% for early loaded implants, without significant difference (p = 0.162). The total score on the Oral Health Impact Profile questionnaire significantly decreased over time in both groups, indicating improvement in OHRQoL (p < 0.001), and the high level of patient satisfaction remained after 2 years of function regardless of a loading protocol. Both loading protocols, immediate and early, of six immediately placed bone-level tapered dental implants are an adequate treatment choice for fixed rehabilitation of the maxillary failing dentition.

Influence of implant location on titanium-zirconium alloy narrow-diameter implants: A 1-year prospective study in smoking and nonsmoking populations.

STATEMENT OF PROBLEM: Titanium-zirconium (Ti-Zr) alloy (Roxolid) narrow-diameter implants (NDIs) have been widely used for implant-supported prostheses in anterior and posterior regions in the jaws. However, the relationship between implant location and clinical outcome remains unclear. PURPOSE: The purpose of this clinical study was to evaluate and compare the clinical and radiographic outcomes of NDIs placed in different regions of the jaws in both smokers and nonsmokers. MATERIAL AND METHODS: Eighty-four participants scheduled to receive NDIs for tooth rehabilitation were included, and the inserted NDIs were divided into 3 groups depending on their locations: implants used to restore anterior teeth, implants used to restore premolars, and implants used to restore molars. Crestal bone loss (CBL), implant survival and success rates, bleeding on probing (BOP), and pocket probing depth (PPD) were evaluated 6 and 12 months after implant loading (α=.017 for implant survival and success rates after Bonferroni correction, α=.05 for other parameters). RESULTS: Statistical analysis of 6- and 12-month CBL of all participants presented no statistically significant difference among the 3 groups. For smokers, the molar group presented significantly more CBL than the premolar group (0.90 ±0.94 versus 0.16 ±0.27 mm, P=.027) at the 6-month examination. The implant survival rates were 95.65%, 100%, and 100% for anterior, premolar, and molar regions, respectively (P=.283). No statistically significant difference was observed regarding periodontal parameters (P>.05). CONCLUSIONS: Implant location has no influence on the clinical and radiographic parameters of Ti-Zr NDIs placed in a nonsmoking population. However, the combination of posterior location and smoking may induce higher risk of crestal bone loss. Caution should be taken when restoring molars for smokers with NDIs.

Immediate Vs Early Loading of Bone Level Tapered Dental Implants With Hydrophilic Surface in Rehabilitation of Fully Edentulous Maxilla: Clinical and Patient Centered Outcomes.

The aim was to: (1) compare changes among primary and secondary implant stability between immediate and early loaded implants in edentulous maxilla, (2) evaluate oral health-related quality of life (OHRQoL), and (3) determine patient satisfaction with 6 implant supported fixed full-arch dentures. A prospective, randomized controlled clinical trial was conducted on 24 edentulous maxilla patients. The BLT SLActive implants in 12 patients were immediately loaded with temporary restorations while 12 patients did not receive temporary restorations. Definitive (final) dentures were delivered to all patients after 6 weeks. Stability of the implants were assessed by insertion torque (IT) and resonance frequency analysis (RFA). Oral Health Impact Profile-19 (OHIP-19) questionnaire was used to evaluate OHRQoL and a visual analogue scale (VAS) was used for patient satisfaction. The IT value of implants assigned for immediate and early loading group was 27.17 ± 9.55 Ncm and 25.01 ± 11.06 Ncm, respectively. Changes in implant stability from baseline to week 6 were similar in both groups when measured by Penguin (P = .881) and Ostell (P = .828). Patients in the immediate loading group reported significantly lower OHIP physical pain scores (P = .016) and OHIP psychological disability score (P = .046), and the patients reported significantly higher VAS function score (P = .009) and VAS esthetics score (P = .009). Implant loading protocols do not have a significant effect on the change in implant stability 6 weeks after implantation; however, immediate loading significantly improves OHRQoL as well as satisfaction of patients with maxillary edentulism treated by fixed full-arch dentures. Future trials will determine the role of immediate loading protocol in clinical scenarios with various amounts of available jaw bone using different numbers of implants to retain a fixed prosthetic restoration in the edentulous maxilla.

Osteogenic effects of microRNA-335-5p/lipidoid nanoparticles coated on titanium surface.

OBJECTIVE: In this study, we aimed to investigate the therapeutic potential of miR-335-5p lipidoid nanocomplexes coated on Titanium (Ti) SLActive surface by lyophilization. DESIGN: In our model, we coated miR-335-5p/Lipidoid nanoparticles on titanium implant, seeded GFP-labelled mouse bone marrow stromal cells (BMSCs) onto the functionalized Ti implant surface, and analyzed the transfection efficiency, cell adhesion, proliferation, and osteogenic activity of the bone-implant interface. RESULTS: The Ti SLActive surface displayed a suitable hydrophilicity ability and provided a large surface area for miRNA loading, enabling spatial retention of the miRNAs within the nanopores until cellular delivery. We demonstrated a high transfection efficiency of miR-335-5p lipidoid nanoparticles in BMSCs seeded onto the Ti SLActive surface, even after 14 days. Alkaline phosphatase (ALP) activity and cell vitality were significantly increased in BMSCs transfected with miR-335-5p at 7 and 14 days as opposed to cells transfected with negative controls. When miR-335-5p transfected BMSCs were induced to undergo osteogenic differentiation, we detected increased mRNA expression of osteogenic markers including Alkaline phosphatase (ALP), collagen I (COL1), osteocalcin (OCN) and bone sialoprotein (BSP) at 7 and 14 days as compared with negative controls. CONCLUSION: MiR-335-5p lipidoid nanoparticles could be used as a new cost-effective methodology to increase the osteogenic capacity of biomedical Ti implants.

Full versus partial thickness flap to determine differentiation and over keratinization of non-keratinized mucosa. A 3-year split mouth randomized pilot study.

OBJECTIVES: It was shown, that Connective Tissue Grafts (CTG) retrieved from the tuberosity tends to determine hyperplastic responses and may induce a beneficial over-keratinization of non-keratinized mucosa. Clinically evaluate and compare CTG from tuberosity ability to increase soft tissue thickness and the keratinization potential after recipient area is either prepared using split or full thickness flap in edentulous mandible. MATERIALS AND METHODS: Fourty implants were placed in 10 edentulous patients with atrophied mandible (Class IV of Misch) presenting less than 1.0 mm of keratinized tissue using a flapless approach and immediately restored with acrylic temporary bridge on multi-unit abutments. The surgical sites were split-mouth randomized and prepared as CTG recipients by a tunneling procedure. Twenty benefited of a partial thickness approach and 20 of a full thickness one. The CTG was placed buccally using partial thickness or full thickness flap according to the randomization schedule. The width of keratinized tissue (KT), the horizontal soft tissue thickness (STT), the marginal hard and soft tissue levels as well as the implant success parameters were collected and analyzed. RESULTS: After a 3 year follow-up period the increase of KT was statistically significantly (p < 0.001) larger in the partial thickness group from 0.6(0.6) to 5.1(0.72) mm, while full thickness group showed very little improvement from 0.5(0.51) to 1(0.57) mm (p < 0.001). STT was significantly increased in both groups over time: from 2.4(0.88) to 5.4(0.68) mm in full thickness group and from 2.5(0.51) to 5.8(0.41) mm in partial thickness group without any significant difference between the groups. CONCLUSION: The increase of soft tissue thickness by using CTG from tuberosity was found in both groups, while keratinization of non-keratinized mucosa appeared more in the partial thickness group.

Exercise-induced irisin in bone and systemic irisin administration reveal new regulatory mechanisms of bone metabolism.

Irisin is a polypeptide hormone derived from the proteolytic cleavage of fibronectin-type III domain-containing 5 (FNDC5) protein. Once released to circulation upon exercise or cold exposure, irisin stimulates browning of white adipose tissue (WAT) and uncoupling protein 1 (UCP1) expression, leading to an increase in total body energy expenditure by augmented UCP1-mediated thermogenesis. It is currently unknown whether irisin is secreted by bone upon exercise or whether it regulates bone metabolism in vivo. In this study, we found that 2 weeks of voluntary wheel-running exercise induced high levels of FNDC5 messenger RNA as well as FNDC5/irisin protein expression in murine bone tissues. Increased immunoreactivity due to exercise-induced FNDC5/irisin expression was detected in different regions of exercised femoral bones, including growth plate, trabecular bone, cortical bone, articular cartilage, and bone-tendon interface. Exercise also increased expression of osteogenic markers in bone and that of UCP1 in WAT, and led to bodyweight loss. Irisin intraperitoneal (IP) administration resulted in increased trabecular and cortical bone thickness and osteoblasts numbers, and concurrently induced UCP1 expression in subcutaneous WAT. Lentiviral FNDC5 IP administration increased cortical bone thickness. In vitro studies in bone cells revealed irisin increases osteoblastogenesis and mineralization, and inhibits receptor activator of nuclear factor-kB ligand (RANKL)-induced osteoclastogenesis. Taken together, our findings show that voluntary exercise increases irisin production in bone, and that an increase in circulating irisin levels enhances osteogenesis in mice.

Overexpression of MiR-335-5p Promotes Bone Formation and Regeneration in Mice.

MicroRNAs (miRNAs) and the Wnt signaling pathway play critical roles in regulating bone development and homeostasis. Our previous study revealed high expression of miR-335-5p in osteoblasts and hypertrophic chondrocytes in mouse embryos and the ability of miR-335-5p to promote osteogenic differentiation by downregulating Wnt antagonist Dickkopf-1 (DKK1). The purpose of this study was to investigate the effects of miR-335-5p constitutive overexpression on bone formation and regeneration in vivo. To that end, we generated a transgenic mouse line specifically overexpressing miR-335-5p in osteoblasts lineage by the osterix promoter and characterized its bone phenotype. Bone histomorphometry and µCT analysis revealed higher bone mass and increased parameters of bone formation in transgenic mice than in wild-type littermates. Increased bone mass in transgenic mice bones also correlated with enhanced expression of osteogenic differentiation markers. Upon osteogenic induction, bone marrow stromal cells (BMSCs) isolated from transgenic mice displayed higher mRNA expression of osteogenic markers than wild-type mice BMSCs cultures. Protein expression of Runx2 and Osx was also upregulated in BMSC cultures of transgenic mice upon osteogenic induction, whereas that of DKK1 was downregulated. Most important, BMSCs from transgenic mice were able to repair craniofacial bone defects as shown by µCT analysis, H&E staining, and osteocalcin (OCN) immunohistochemistry of newly formed bone in defects treated with BMSCs. Taken together, our results demonstrate constitutive overexpression of miR-335-5p driven by an osterix promoter in the osteoblast lineage induces osteogenic differentiation and bone formation in mice and support the potential application of miR-335-5p-modified BMSCs in craniofacial bone regeneration. © 2017 American Society for Bone and Mineral Research.

Influence of biphasic calcium phosphate surfaces coated with Enamel Matrix Derivative on vertical bone growth in an extra-oral rabbit model.

OBJECTIVE: The aim of this study was to investigate the ability of Enamel Matrix Derivative (EMD) on vertical bone regeneration around dental implants placed in an extra-oral rabbit model. MATERIAL AND METHODS: A total of 30 Straumann BL implants were partially embedded in transverse orientation into the posterior mandibles of 15 rabbits. Macro-structuring BiPhasicCaPST (BCPT1), micro-structuring BiPhasicCaPST (BCPT2), and deproteinized bovine bone mineral (DBBM) were placed around the implant and covered with a scaffold stabilizing "umbrella." EMD was incorporated within the scaffold for test sites, but not control sites. Histological analysis was performed on retrieved specimens after 10 weeks of healing to assess new bone formation. RESULTS: All treatment groups displayed new supracrestal bone formation as determined by histomorphometric measurements, with mean values of new bone height ranging between 0.62 and 1.13 mm. Histological analysis revealed a higher mean bone formation (%) around the test sites where EMD (34.7, 95%CI: 27.1-39.4) was released from the scaffold, whereas the control group without EMD release (26.4, 95%CI: 16.3-31.9) (P = 0.069). The mean fBIC (%) in the BCPT2 group increased by the addition of EMD relative to no EMD (67.2, 95%CI: 48.6-84.1) and (54.7, 95%CI: 32.3-68.9), respectively). The BCPT2/EMD and DBBM/EMD interventions showed the greatest mean bone density (BA/TA), respectively, (12.8, 95%CI: 8.9-36.5) and (11.2, 6.3-16.4) in ROI 1. Values in ROI 2 were, similarly, (24.9, 95%CI: 17.2-31.7) and (27.7, 19.2-35.3). BA/TA in ROI 2 differences between the BCPT2 groups with and without EMD was statistically significant (P = 0.026), as well as the DBBM groups with and without EMD (P = 0.038). CONCLUSIONS: A layer of new bone was formed in both test and controls. The release of EMD from BCPT2 and DBBM adjacent to a bone-level implant with an SLActive surface and scaffold retention umbrella consistently regenerated the greater fBIC and bone density along the length of the implant.

Modified Tunnel Technique Combined with Enamel Matrix Derivative: A Minimally Invasive Treatment for Single or Multiple Class I Recession Defects.

PURPOSE: Gingival recession is a significant problem in the esthetic zone. Connective tissue grafts have been considered the gold standard, but they need a donor site that increases morbidity and discomfort for the patient.The purpose of the present study was to evaluate the clinical results of a modified tunnel technique that consists of replacing the connective tissue graft by enamel matrix derivative, in the treatment of Miller Class I recession defects. MATERIALS AND METHODS: Twenty-six teeth in 14 subjects with Miller Class I recessions were treated using the tunnel procedure plus enamel matrix derivative. The gingival recession, probing depth, clinical attachment level, and the width of the keratinized gingival tissue were recorded. RESULTS: There was a statistically significant reduction in gingival recession (88% of root coverage) and a gain in clinical attachment level (3.1 mm) between baseline and 24 months post-operatively, whereas the change in width of keratinized tissue and in probing depth was not statistically significant. All patients were satisfied with the esthetic appearance and would undergo the same surgery again. CONCLUSION: This technique could be successfully used as an alternative to connective tissue grafts, with the advantage of avoiding the discomfort and morbidity of connective tissue harvesting. CLINICAL SIGNIFICANCE: This modified tunnel technique using enamel matrix derivative potentially represents a clinically and esthetically satisfactory treatment of Miller Class I recession defects.

Tissue Healing Around Dental Implants With Marginal Bone Defects With and Without Flap Elevation: An Experimental Study in Dogs.

The technique of immediate implant placement after extraction has been conceived for preserving residual bone support and soft tissue morphology. Today, this procedure is still unpredictable and presents inconveniences for both the patient and the dentist. Therefore, the healing process around a dental implant placed into an extraction socket needs to be deeply investigated to increase the predictability of this surgical approach. The aim of the present investigation was to evaluate the healing of bone defects (fresh extraction sockets) after implant installation with flap elevation, and primary closure compared with implant installation without flap elevation. This study use histologic and histomorphometric analyses to evaluate tissue healing around dental implants with marginal bone defects with and without flap elevation 1 week, 4 weeks, and 12 weeks after implantation in the dogs. The main qualitative findings showed that after 1 week of implantation almost no bone repair was observed, and there was no significant difference between the 2 groups in terms of bone-healing performance, inflammatory infiltrates (slight to moderate grade), and bone resorption (moderate to marked grade) limited to the coronal portion of the implanted sites. The 2 groups with or without flap elevation behaved similarly at this point of implantation. Under the experimental conditions of this study, no biological differences were observed between the 2 groups with and without flap elevation in terms of crestal bone repair, inflammation, marginal bone loss, and soft tissue downgrowth. The qualitative differences observed might be imputable to fortuitous events. The histomorphometric measurements confirmed the qualitative trends observed. The limitations of this study, as with all animal studies, are its translational aspects. Investigation of the same topic in a human population by setting up a controlled, randomized, prospective trial including a sufficient amount of patients investigated according to the split-mouth method would be beneficial.

Effect of 3- and 4-mm interimplant distances on the height of interimplant bone crest: a histomorphometric evaluation measured on bone level dental implants in minipig.

PURPOSE: To analyze crestal bone loss changes that may affect the gingival height around an implant and bone loss in interproximal areas. When implants are placed adjacent to one another, interimplant bone loss around 1 implant may combine with the implant bone loss around the adjacent implant to affect the crestal bone loss interproximally. MATERIALS AND METHODS: The primary objective of this study was to evaluate histologically and histomorphometrically the effect that this implant design with a horizontally displaced implant-abutment junction has on the height of the crest of bone, between adjacent implants separated by 2 different distances: 4 mm and 3 mm. A secondary objective was to evaluate the percentage of bone-to-implant contact, interproximal soft tissue height, location of the junctional epithelium, and length of connective tissue contact to abutment and/or implant, for the 2 different distances. RESULTS: Results showed that the interproximal bone loss measured from the edge of the implant platform to the bone crest was not different for interimplant distances of 4 or 3 mm. In addition, the secondary objective parameters also demonstrated similar results between the 2 interimplant distances. CONCLUSION: This study showed that interimplant bone levels can usually be maintained at similar levels for 4- and 3-mm distances during at least 2 months.

Adiponectin ameliorates experimental periodontitis in diet-induced obesity mice.

Adiponectin is an adipokine that sensitizes the body to insulin. Low levels of adiponectin have been reported in obesity, diabetes and periodontitis. In this study we established experimental periodontitis in male adiponectin knockout and diet-induced obesity mice, a model of obesity and type 2 diabetes, and aimed at evaluating the therapeutic potential of adiponectin. We found that systemic adiponectin infusion reduced alveolar bone loss, osteoclast activity and infiltration of inflammatory cells in both periodontitis mouse models. Furthermore, adiponectin treatment decreased the levels of pro-inflammatory cytokines in white adipose tissue of diet-induced obesity mice with experimental periodontitis. Our in vitro studies also revealed that forkhead box O1, a key transcriptional regulator of energy metabolism, played an important role in the direct signaling of adiponectin in osteoclasts. Thus, adiponectin increased forkhead box O1 mRNA expression and its nuclear protein level in osteoclast-precursor cells undergoing differentiation. Inhibition of c-Jun N-terminal kinase signaling decreased nuclear protein levels of forkhead box O1. Furthermore, over-expression of forkhead box O1 inhibited osteoclastogenesis and led to decreased nuclear levels of nuclear factor of activated T cells c1. Taken together, this study suggests that systemic adiponectin application may constitute a potential intervention therapy to ameliorate type 2 diabetes-associated periodontitis. It also proposes that adiponectin inhibition of osteoclastogenesis involves forkhead box O1.

The dog as a model for peri-implantitis: A review.

OBJECTIVE: To analyze the current available experimental canine models for peri-implantitis. MATERIAL AND METHODS: Electronic databases of the PubMed, EBSCOhost, and Cochrane Library were searched for dog studies on peri-implantitis induction methodology, until October 31, 2012. The eligibility of the studies for this review was based on the screening of two independent reviewers. RESULTS: After screening, 50 publications were eligible for review. The most used animal model was the Beagle (n = 23). The bilateral mandible four premolar were the most extracted group of teeth (n = 20) and the majority of the studies had the placement of six implants in the jaw with only five (n = 5) of them reporting on interimplant distance. All publications reported peri-implantitis induction using ligature during a variable period of time and with a subsequent heterogeneous loss of peri-implant bone. The ligature placement and maintenance around the implant varied greatly between the publications. The constant use of ligatures, sometimes traumatically forced to the peri-implant sulcus, may influence the degree of bone loss during canine experimental peri-implantitis overlapping the contribution of implant surface to the onset and development of this pathology. CONCLUSIONS: A great heterogeneity exists among the studies reporting on the induction of peri-implantitis in canine. Experimental peri-implantitis model has suffered a change through the last years, from an exclusive ligature-induced to a ligature-induced and nonligature induced progression, thus approaching the natural occurrence of this pathology. The ideal canine peri-implantitis induction model would be a naturally occurring peri-implanititis induction without the action of any ligature.

Predicting bone remodeling around tissue- and bone-level dental implants used in reduced bone width.

The objective of this study was to predict time-dependent bone remodeling around tissue- and bone-level dental implants used in patients with reduced bone width. The remodeling of bone around titanium tissue-level, and titanium and titanium-zirconium alloy bone-level implants was studied under 100 N oblique load for one month by implementing the Stanford theory into three-dimensional finite element models. Maximum principal stress, minimum principal stress, and strain energy density in peri-implant bone and displacement in x- and y- axes of the implant were evaluated. Maximum and minimum principal stresses around tissue-level implant were higher than bone-level implants and both bone-level implants experienced comparable stresses. Total strain energy density in bone around titanium implants slightly decreased during the first two weeks of loading followed by a recovery, and the titanium-zirconium implant showed minor changes in the axial plane. Total strain energy density changes in the loading and contralateral sides were higher in tissue-level implant than other implants in the cortical bone at the horizontal plane. The displacement values of the implants were almost constant over time. Tissue-level implants were associated with higher stresses than bone-level implants. The time-dependent biomechanical outcome of titanium-zirconium alloy bone-level implant was comparable to the titanium implant.

Evaluation of a biodegradable synthetic hydrogel used as a guided bone regeneration membrane: an experimental study in dogs.

OBJECTIVES: To test whether or not an experimental polyethylene glycol (PEG) membrane maintains the bone graft volume and contributes to the preservation of the ridge contour in comparison with a commercially available synthetic membrane. MATERIALS AND METHODS: In 18 dogs, all mandibular premolars and the first molars were extracted. Ten weeks later, acute standardized defects were prepared. The defects of four dogs were randomly assigned to three modalities: (1) PEG plus deproteinized bovine bone mineral (DBBM) (PEG), (2) a resorbable glycolide trimethylene carbonate membrane plus DBBM (PGA-TMC), and (3) DBBM alone (DBBM). These dogs were then sacrificed for the baseline measurements. The remaining defects of 14 dogs were randomly assigned to (1) PEG plus DBBM, (2) PGA-TMC plus DBBM, (3) DBBM, and (4) empty defect. The dogs were sacrificed at baseline (n=4), 4 weeks (n=7), or at 16 weeks (n=7). Mixed model regressions and the non-parametric Brunner-Langer method were applied for statistical analysis. RESULTS: At baseline, equal tissue augmentation was observed in all groups. At 4 and 16 weeks, the greatest augmented area fractions were calculated for PEG (103%; 107%, respectively), followed by PGA-TMC (98%; 91%), DBBM (85%; 78%), and empty (46%; 54%), being statistically significant different (P<0.001) between PEG and empty at 4 and 16 weeks, and PEG and DBBM at 16 weeks. The overall decrease (P≤0.01) in the amount of bone graft between baseline and 16 weeks was -14% (PEG), -22% (PGA-TMC), and -23% (DBBM). CONCLUSIONS: The study demonstrates that the combination of the PEG membrane with DBBM maintains the bone graft volume over time better than controls. The PEG membrane with DBBM was also the most effective method to preserve the ridge contour.

Evaluation of a new biodegradable membrane to prevent gingival ingrowth into mandibular bone defects in minipigs.

OBJECTIVE: The aim of this study was to test whether a synthetic, biodegradable membrane made of polyethylene glycol (PEG) can prevent soft-tissue ingrowth into alveolar defects. MATERIAL AND METHODS: In each of 16 minipigs, three mandibular premolars were bilaterally extracted. Three months later, acute standardized defects (diameter 8 mm, depth 8 mm) were prepared. Four treatment modalities were randomly allocated to the defects: (1) PEG membrane plus collagen sponge, (2) polylactide (PLA) membrane plus collagen sponge, (3) collagen sponge alone, and (4) empty defect. Animals were sacrificed at 10 days (n=5), 21 days (n=5), or 2 months (n=6) after treatment. Qualitative and quantitative histological evaluations of soft-tissue ingrowth and bone regeneration were performed on nondecalcified ground sections. For statistical analysis, the Mann-Whitney-Wilcoxon test, the Kruskal-Wallis, and the paired t-test were applied. P-values were adjusted using the Dunnett-Hsu adjustment. RESULTS: At 10 days, the PEG membrane group showed the least soft-tissue ingrowth (mean value -0.75 mm; range -1.35 to -0.10), followed by the PLA membrane group -0.18 mm (-0.80 to 0.44), the collagen group 0.04 mm (-0.65 to 0.73), and the empty defects 0.60 mm (-0.08 to 1.29). Statistically significant differences were observed between the PEG membrane group and the empty defects (P<0.05). At 21 days, the highest percentage of newly formed bone was found in the PEG membrane group (mean 28.4%; range 21.6-35.2) compared with 23.7% (16.9-30.5; PLA membrane), 15.2% (8.2-22.2; collagen group), and 21.6% (14.5-28.8; empty defects). Statistically significant differences were only found between the PEG membrane group and the collagen group (P<0.05). At 2 months, the tested parameters revealed no statistically significant differences between the groups. CONCLUSION: The experimental PEG membrane applied in the present study successfully prevented collapse of the covering soft tissues to a degree similar to the PLA membrane. The combination of a collagen sponge and the PEG membrane showed the least soft-tissue ingrowth at 10 days and promoted more bone formation at 21 days.