Preaugmentation Soft Tissue Expansion: A Report of Four Pilot Cases

Soft tissue expansion using self-inflating osmotic hydrogel expanders prior to bone augmentation: healing and complications. Evidence-based review

AIM

This review aims to assess complication rates, soft tissue gain, and bone gain associated with the use of self-inflating osmotic hydrogel tissue expanders (SOHTEs) for soft tissue expansion (STE).

METHODS

A comprehensive search on Pubmed and Google Scholar databases was conducted to identify human studies using SOHTEs for STE; last searched in March 2023. Expansion phase details and expander variables were documented. Complication rates, soft tissue gain, and bone gain reported in each study were also recorded. The inclusion criteria encompassed human studies ranging from evidence levels II-IV (Oxford Centre for Evidence-Based Medicine Levels of Evidence), without specific date limits. For assessing bias in randomized controlled trials (RCTs), a Risk of Bias tool was employed. The synthesised results were presented through tables, sunburst plots, and bar charts.

RESULTS

A total of 13 studies were identified, comprising 4 RCTs, 1 cohort study, and 8 case-series. Employment of SOHTEs yielded an overall complication rate of 17% (24/140 sites), with expander perforation accounting for 9.3% (13/140) of the sites. Specific complication rates included dehiscence (1.4%, 2/140 sites), paraesthesia (1.4%, 2/140 sites), and infection (1.4%, 2/140 sites). All randomized controlled trials (RCTs) were categorised at Level II. The remaining investigations primarily consisted of Level IV case-series lacking controls. All studies demonstrated some concerns towards bias.

CONCLUSION

STE studies using SOHTEs exhibit a reduction in complications associated with bone augmentation in scenarios of inadequate soft tissue coverage. Preliminary evidence suggests potential benefits even in cases with sufficient soft tissue. Adherence to procedural precautions may reduce the risk of expander perforations, further diminishing complications. Subsequent studies should incorporate individual patient and expander variables in their reports to explore the impact of expansion phases on complication rates, as well as bone and soft tissue augmentation.

Self-swelling tissue expander for soft tissue reconstruction in the craniofacial region: An in vitro and in vivo evaluation

BACKGROUND

Craniofacial soft-tissue defects mostly have an impact on the treatment of various oral diseases. Tissue expander is an important technique for tissue reconstruction, especially for soft tissues in reconstructive surgery.

OBJECTIVE

This research aimed to develop a new self-swelling tissue expander, namely hydrogel, for soft tissue reconstruction in craniofacial region.

METHODS

In vitro, the chemical and physical characteristics of hydrogel were evaluated by SEM, swelling rate, mechanical testing, EDS, and FT-IR. In vivo, the craniofacial implant model of SD rats were divided into group A as control, group B with hydrogels for 1 week expansion, group C for 2 weeks and group D for 4 weeks (n = 5), and the effects were analyzed by HE staining, histological and radiographic evaluation.

RESULTS

The in vitro results suggested that dry hydrogel possessed a uniform surface with micropores, the surface of post-swelling hydrogel formed three-dimensional meshwork. Within 24 hours, hydrogels expanded markedly, then slowed down. The mechanical property of hydrogels with longer expansion was better, whose main elements were carbon and oxygen. FT-IR also verified its molecular structure. In vivo, the wounds of rats recovered well, hydrogels could be removed as one whole piece with original shape and examined by radiographic evaluation, besides, the expanded skin and developed fibrous capsule formed surrounding hydrogels.

CONCLUSION

The new expander was designed successfully with good chemical and physical characteristics, and could be applied in an animal model to help tissue reconstruction.

Tissue Expansion Improves the Outcome and Predictability for Alveolar Bone Augmentation: Prospective, Multicenter, Randomized Controlled Trial

Objectives: The purpose of this study was to evaluate the effectiveness of the intraoral use of subperiosteally placed self-inflating tissue expanders for subsequent bone augmentation and implant integrity. Material and methods: A prospective, multicenter, randomized controlled trial was performed on patients requiring alveolar bone graft for dental implant insertion. Patients were assigned to three groups: tissue expansion and tunneling graft (TET group), tissue expansion and conventional bone graft (TEG), and control group without tissue expansion. Dimensional changes of soft tissue and radiographic vertical bone gain, retention, and peri-implant marginal bone changes were evaluated and secondary outcomes; clinical complications and thickness changes of expanded overlying tissue were assessed. Results: Among 75 patients screened, a total of 57 patients were included in the final analysis. Most patients showed uneventful soft tissue expansion without any inflammatory sign or symptoms. Ultrasonographic measurements of overlying gingiva revealed no thinning after tissue expansion (p > 0.05). Mean soft vertical and horizontal tissue measurements at the end of its expansion were 5.62 and 6.03 mm, respectively. Significantly higher vertical bone gain was shown in the TEG (5.71 ± 1.99 mm) compared with that in the control patients (4.32 ± 0.97 mm; p < 0.05). Hard tissue retention— measured by bone resorption after 6 months—showed that control group showed higher amount of vertical (2.06 ± 1.00 mm) and horizontal bone resorption (1.69 ± 0.81 mm) compared to that of the TEG group (p < 0.05). Conclusion: The self-inflating tissue expander effectively augmented soft tissue volume and both conventional bone graft and tunneling techniques confirmed their effectiveness in bone augmentation. With greater amount of bone gain and better 6 month hard tissue integrity, the TEG group compared to the control group—without tissue expansion—showed that the combined modality of tissue expander use and guided bone regeneration (GBR) technique may improve the outcome and predictability of hard tissue augmentation.