Impact of simultaneous placement of implant and block bone graft substitute: an in vivo peri-implant defect model

Abstract

Background: Insufficient bone volume around an implant is a common obstacle when dental implant treatment is considered. Limited vertical or horizontal bone dimensions may lead to exposed implant threads following placement or a gap between the bone and implant. This is often addressed by bone augmentation procedures prior to or at the time of implant placement. This study evaluated bone healing when a synthetic TiO2 block scaffold was placed in circumferential peri-implant defects with buccal fenestrations.

Methods: The mandibular premolars were extracted and the alveolar bone left to heal for 4 weeks prior to implant placement in six minipigs. Two cylindrical defects were created in each hemi-mandible and were subsequent to implant placement allocated to treatment with either TiO2 scaffold or sham in a split mouth design. After 12 weeks of healing time, the samples were harvested. Microcomputed tomography (MicroCT) was used to investigate defect fill and integrity of the block scaffold. Distances from implant to bone in vertical and horizontal directions, percentage of bone to implant contact and defect fill were analysed by histology.

Results: MicroCT analysis demonstrated no differences between the groups for defect fill. Three of twelve scaffolds were partly fractured. At the buccal sites, histomorphometric analysis demonstrated higher bone fraction, higher percentage bone to implant contact and shorter distance from implant top to bone 0.5 mm lateral to implant surface in sham group as compared to the TiO2 group.

Conclusions: This study demonstrated less bone formation with the use of TiO2 scaffold block in combination with implant placement in cylindrical defects with buccal bone fenestrations, as compared to sham sites.

Keywords: Animal experimentation; Bone ring technique; Bone substitute.

Conflict of interest statement

Haugen, Ellingsen, Tiainen and Lyngstadaas are inventors of the technology behind the production of TiO2 scaffold (WO2014044672, WO2008078164). The commercial rights for the TiO2 scaffold belongs to Corticalis AS. Haugen, Ellingsen, Lyngstadaas, Rønold and Wohlfahrt are shareholder of Corticalis AS.

© 2021. The Author(s).

Figures

Fig. 1

Clinical photos depicting the experimental model. Circumferential defects were created before implant placement with a block scaffold (TiO2 group) and implant only (sham)

Fig. 2

3D reconstructions of the microCT scan (a) Illustration of circumferential area evaluated for defect fill in blue. (b) Cross section of the same sample in bucco-lingual direction (buccal left)

Fig. 3

Histological samples (a) Illustration of defect analysis. Blue box depicting regions of interest in the buccal and lingual sides, yellow = bone, grey = TiO2 scaffold. b Vertical linear measurements from the implant top (green line) to the first bone contact at the implant surface (blue line) and 0.5 mm lateral to the implant (yellow line). c Horizontal linear measurements from implant surface to the first bone contact. Measured from implant top and five consecutive millimetres apically. Lingual side left and buccal side right for all figures

Fig. 4

Soft tissue measurements in histological samples. Lingual side left and buccal side right for both figures. a Shortest distance from implant shoulder to oral cavity marked in yellow. b Area of soft tissue above the implant measured within the dotted blue lines

Fig. 5

Histological samples of best (a-b) and worst (c-d) samples from sham (a) and (c) and TiO2 (b) and (d). New bone stained deep purple and irregular in shape. Lingual side left and buccal side right for all figures. a Complete healing of the defect. b Extensive bone growth within the porous scaffold. c Resorption of the lingual bone wall and epithelium in contact with the implant. d Missing scaffold at the buccal side and no bone contact between bone and scaffold lingually. Arrows: mucosal perforations also visible on both sides

Fig. 6

Defect fill measured by (a) histomorphometry and (b) microCT. *** p < 0.001

Fig. 7

Bone to implant contact by histomorphometry. a Percentage of bone to implant contact. b First bone to implant contact by vertical measurements at implant surface and 500 μm laterally. c First bone to implant contact by horizontal measurements at the upper most 6 mm increments. * p < 0.05

Fig. 8

Soft tissue measurements. a Shortest soft tissue distance to oral cavity from implant shoulder. b Area of soft tissue above the implant