Angelika Wildburger

Color stability of different composite resin materials

STATEMENT OF PROBLEM Data are needed to better predict the color stability of current composite resin materials. PURPOSE The purpose of this study was to evaluate the impact of different storage solutions on the color stability of different composite resin materials. MATERIAL AND METHODS Different restorative and adhesive composite resin specimens (dual-polymerizing self-adhesive resin cement, autopolymerizing resin-based composite resin, dual-polymerizing resin-based composite resin, nanohybrid composite resin, and microhybrid composite resin) were fabricated and stored in red wine, black tea, chlorhexidine, sodium fluoride, tea tree oil, or distilled water for 4 weeks at 37°C. Color parameters were measured with a colorimeter before and after storage. Total color differences and specific coordinate differences were expressed as ΔE, ΔL, Δa, and Δb. A 2-way and 1-way analysis of variance (ANOVA) with Bonferroni adjustment for multiple comparisons were applied for statistical calculations (α=.05). RESULTS Red wine caused the most severe discoloration (ΔE >10), followed by black tea with perceptible (ΔE >2.6) to clinically unacceptable discoloration (ΔE >5.5). Colored mouth rinses discolored the materials to a lesser extent with clinically acceptable values. Dual-polymerizing resin adhesives showed a higher amount of discoloration. CONCLUSIONS Current restorative and adhesive composite resin materials discolor over time under the influence of different storage solutions. The composition related to the polymerizing mode seemed to be a causative factor.

Impact of autogenous concentrated bone marrow aspirate on bone regeneration after sinus floor augmentation with a bovine bone substitute--a split-mouth pilot study.

PURPOSE Mesenchymal stem cells (MSC) with biomaterials have osteoinductive potential. The aim of this study was to evaluate early bone formation in xenogenic sinus grafts in a direct comparison with and without MSCs after 3 and 6 months. Literature on bone formation in pure xenogenic graft materials after 3 months in a human model is still lacking. MATERIALS AND METHODS In a split-mouth design, seven patients with a bilateral highly atrophic posterior maxilla were included. The test side was grafted with MSCs from concentrated bone marrow aspirate admixed to the bone graft material. On the control side, pure bovine bone material was applied. Biopsies were taken navigated after 3 and 6 months. RESULTS After 3 months, new bone formation in the control group was 11.8% (SD 6.2%) and in the test group 7.4% (SD 4.1%). After 6 months, the control group showed 13.9% (SD 8.5%) of new bone and the test group 13.5% NB (SD 5.4%). The fraction of bovine bone material after 3 months was 42.6% (SD 3.5%) in the test group and 34.9% (SD 11.8%) in the control group. After 6 months, the biomaterial content was comparable at both sides (test 36.2%, SD 7.8%; control 39.5%, SD 9.3%). CONCLUSIONS There was no significant difference in new bone formation between the test and control group with n = 7. The results may be dominated by the high mineral content of the biomaterial but could nevertheless be valuable for meta-analysis in the future.

Influence of different conditioning methods on immediate and delayed dentin sealing

STATEMENT OF PROBLEM Data are needed to evaluate the effect of various conditioning methods on immediate and delayed dentin sealing. PURPOSE The purpose of this study was to test bond strength and surface configuration of immediate and delayed dentin sealing surfaces after applying different surface conditioning methods. MATERIAL AND METHODS A total of 96 premolars were allocated to the immediate and delayed groups. The groups differed in the timing of dentin sealing. The immediate-group specimens were sealed with a self-etching adhesive immediately after preparation. The delayed-group specimens were sealed before the final ceramic restoration bonding. Provisional restorations were cemented on immediate-group and delayed-group specimens for 1 week. Four conditioning methods were used: polishing with fluoride-free pumice paste, airborne-particle abrasion with silicoated aluminum oxide, glycin, or calcium carbonate. After 24-hour storage, the shear bond strength was tested. The fractured specimens were optically inspected with a stereomicroscope. An optical 3-dimensional surface analysis was performed for quantitative and qualitative evaluation. A 2-way ANOVA with post hoc Tukey honestly significant difference tests for significant effects was performed to investigate effects of the 2 factors, sealing and conditioning, and their interaction (α=.05). RESULTS Two-way ANOVA found significant differences between the sealing and conditioning groups. The immediate group had significantly lower bond strengths than the delayed group. In all groups, surface polishing produced the highest bond strengths, and airborne-particle abrasion with calcium carbonate produced the lowest. Fracture analysis found more failures in the adhesive layers in the immediate groups and a prevalence of mixed failures in the delayed groups. The surface analysis found significant abrasion and roughness when airborne-particle abrasion with silicoated aluminum oxide was used for immediate and delayed dentin sealing surfaces. CONCLUSIONS Polishing and airborne-particle abrasion with silicoated aluminum oxide or glycin are efficient methods in conditioning immediate and delayed dentin sealing surfaces. Airborne-particle abrasion with silicoated aluminum oxide leaves significant surface alterations on both types of surfaces.

Evaluation of graft cell viability-efficacy of piezoelectric versus manual bone scraper technique.

PURPOSE The aim of the present study was to compare the influence of 2 different bone scrapers with respect to graft quality. MATERIALS AND METHODS The study was conducted as a prospective, controlled experimental study of patients selected from the outpatient unit of the Department of Oral Surgery and Radiology (Dental Clinic, Medical University, Graz, Austria). Bone samples were obtained during routine lower third molar removal. Both a manual bone scraper (MS) and a piezoelectric device (PD) were used in directly adjacent regions in each case. As variables, the chip morphology, cell viability, and osteogenic differentiation were investigated. For statistical analysis, the Student t test and Fishers exact test (P < .05) were applied. RESULTS A total of 20 patients (12 women and 8 men, mean age 28.15 ± 5.8 years) were included in the study. A series of 40 bone samples was obtained during lower third molar removal. MS and PD enabled similar intraoral harvest of bone chips. In vitro outgrowth of adherent cells was found in 90% of the MS and 80% of the PD samples after 7 to 18 days, without statistical significance (P = .67). Similar cell viability of outgrowing cells in both groups was observed (94.7% ± 2.2% in the MS group and 94.1% ± 1.6% in the PD group). Reverse transcriptase-polymerase chain reaction analysis and the staining pattern verified osteopotent cells in both groups. CONCLUSIONS Both manual and piezoelectric techniques are adequate harvesting technologies for limited intraoral augmentations. Our results did not show an advantage for the piezoelectric device.

Tri-lineage potential of intraoral tissue-derived mesenchymal stromal cells

The purpose of this study was to analyse the potential of intraoral tissues as a source of mesenchymal stromal and progenitor cells (MSPCs) for usage in future cell-based therapy models. Cells were isolated from four different tissues harvested during oral surgery intervention: (1) bone explants from the posterior maxilla, (2) bone explants from the oblique line, (3) from the mandibular periosteum, and (4) from the dental pulp. Donor sites and tissues were evaluated in terms of their accessibility, donor-site morbidity and average time period until appearance of MSPC colonies. Cell characterization was performed by flow cytometry and evaluation of in vitro osteogenic, adipogenic and chondrogenic differentiation potential. Adherent cell colonies were isolated from tissues from all sites after 4-8 days. The cells showed characteristics of MSPCs, so they were expanded up to clinical scales and demonstrated multipotency. The lowest donor-site morbidity was observed in the posterior maxilla harvests, while the highest donor-site morbidity was associated with harvests from mandibular sites. All sites seem to be potential sources of mesenchymal stromal and progenitor cells for tissue engineering approaches. Therefore, harvest morbidity and patient acceptance should affect the choice of the appropriate site.

Immediate loading of four interforaminal implants supporting a locator-retained mandibular overdenture in the elderly. Results of a 3-year randomized, controlled, prospective clinical study

BACKGROUND Implant-retained overdentures have become a standard option for the prosthetic treatment of the edentulous mandible in the elderly. PURPOSE This prospective study aimed to compare immediate and conventional loading of four interforaminal implants supporting a Locator-retained mandibular overdenture in elderly patients regarding implant survival, implant stability, and implant-related complications. MATERIAL AND METHODS The study population comprised 20 completely edentulous patients (11 males) aged 60 years and older with severe mandible resorption. Each patient received four interforaminal implants (Neoss Ltd., Harrogate, UK). Following randomization, implants were loaded either immediately after dental implant surgery or 3 months after implant placement with the Locator-abutment system. At follow-up visits 3, 6 12, 24, and 36 months after loading, implant stability was evaluated with Periotest and Ostell. RESULTS Twenty patients received 80 implants. In eight patients, 32 implants were loaded immediately. Two patients had to be switched from the immediate to the conventional loading group due to insufficient primary stability (≤30 Ncm). Implant survival was similar in both groups after 36 months. No implant was lost. Decreasing Periotest, and accordingly, increasing Ostell measurements indicated adequate osseointegration in both groups. The course of treatment was not significantly different in the two groups. There were comparable incidences of postoperative complaints like swelling, hematoma, or wound dehiscence, as well as need for prosthetic treatment due to abutment loosening or occlusal discrepancies. Incidence of pressure marks and number of patient visits were significantly higher in the conventional loading group. CONCLUSION With sufficient primary stability, immediate loading of four interforaminal implants in the edentulous mandible might be the preferential choice in the elderly, reducing total treatment time, and number of patient visits.