Vasileios Chronopoulos

The aim of the present study was to review the available evidence on the response of the peri-implant bone when subjected to excessive occlusal forces. The search strategy included papers published in English in the Medline database and the Wiley Online Library from January 1991 to December 2011. Experimental or review papers reporting the conditions of the peri-implant bone of dental implants submitted to excessive occlusal loading in the presence of a controlled oral hygiene regime were eligible for inclusion. The knowledge regarding the response of the peri-implant bone when the dental implant is excessively loaded is limited, and the level of evidence is poor. With animal experimental studies showing conflicting results, it is unclear whether occlusal overload might cause marginal bone loss or total loss of osseointegration to already osseointegrated dental implants when the applied load exceeds the biologically-acceptable limit. This biological limit is also unknown. Furthermore, higher remodeling activity of the peri-implant bone is found around implants subjected to high loading forces.

BACKGROUND: The aim of this study was to investigate the micromorphological differences among three commercially available titanium abutments on Straumann implants. Furthermore, the possible impact of functional loading on the micromorphology and potential complications was investigated with the use of in vitro testing. MATERIAL AND METHODS: Three groups of Titanium abutments (A: Straumann Variobase n = 5, B: EBI best Duo n = 5, and C: Implant Direct n = 5) were torqued on Straumann RN implants, as according to each of the manufacturer's instructions. The implant-abutment units were scanned with Micro-CT. Three units of each group were directly sliced in the microtome and photographed under different magnifications (10×-500×) through a Scanning Electron Microscope. Six units (two from each group) were restored with cement-retained crowns, subjected to 2000,000 load cycles with loads between 30 and 300 N at 2 Hz, examined through Micro-CT and finally sliced and photographed as described above. The micromorphology of each unit was studied, and the total length of tight contact (<3 μm) was calculated between the implant, abutment and screw contact areas. RESULTS: Major morphological differences were identified between the three units, as well as differences in the extent of tight contact in all areas examined. Despite the morphological differences, the 2M cycles of loading via in vitro test did not result in any noticeable complications although some changes in the micromorphology were observed. CONCLUSION: The examined implant-abutment units presented with major morphological differences. Two million cycles of in vitro loading did not appear to affect the stability of the units despite the micromorphological changes. These results need to be interpreted however under the limitations of the small sample size and the specific set-up of the in vitro testing.

BACKGROUND: The objective of this pilot study was to evaluate the effect of local application of low-magnitude high-frequency vibration (LMHFV) on the bone healing of rabbit calvarial defects that were augmented with different grafting materials and membranes. METHODS: Four calvarial defects were created in each of two New Zealand rabbits and filled with the following materials: biphasic calcium phosphate (BCP), deproteinized bovine bone mineral covered with a non-cross-linked collagen membrane (BO/BG), biphasic calcium phosphate covered with a strontium hydroxyapatite-containing collagen membrane (BCP/SR), and non-cross-linked collagen membrane (BG). Four defects in one rabbit served as a control, while the other was additionally subjected to the local LMHFV protocol of 40 Hz, 16 min per day. The rabbits were sacrificed 1 week after surgery. Histomorphometric analysis was performed to determine the percentages of different tissue compartments. RESULTS: Compared to the control defects, the higher percentage of osteoid tissue was found in LMHFV BG defects (35.3 vs. 19.3%), followed by BCP/SR (17.3 vs. 2.0%) and BO/BG (9.3 vs. 1.0%). The fraction occupied by the residual grafting material varied from 40.3% in BO/BG to 22.3% in BCP/SR LMHFV defects. Two-way models revealed that material type was only significant for the osteoid (P= 0.045) and grafting material (P = 0.001) percentages, while the vibration did not provide any statistical significance for all histomorphometric outcomes (P > 0.05). CONCLUSION: Local application of LMHFV did not appear to offer additional benefit in the initial healing phase of rabbit calvarial defects. Histomorphometric measurements after 1 week of healing demonstrated more pronounced signs of early bone formation in both rabbits that were related with material type and independent of LMHFV.

The rehabilitation of the edentulous maxilla with fixed implant-supported restorations is a challenging task for the clinician but very frequently demanded by patients. Prosthetically driven implant placement simplifies the design of the restoration, but severe bone resorption may prohibit the ideal positioning of implants. Bone grafting is often required to improve the bone substrate and to allow proper implant placement. The posterior maxilla can be treated by sinus floor elevation, while alveolar ridge atrophy in the anterior jaw may be improved by horizontal augmentation. The restoration must replace the missing soft and hard tissue, so the use of gingiva-coloured polymer material is often required. The objective of this article is to describe the clinical and laboratory stages of the rehabilitation of a completely edentulous patient with a fixed implant-supported prosthesis. A bilateral sinus lift and horizontal augmentation of the maxilla with bone graft from the iliac crest was performed. The prosthetic rehabilitation is also described in detail, consisting of a combination of screw-retained frameworks and cemented fixed restorations.