An animal model for subperiosteal tissue expansion

Tissue Expander Followed by Autogenous Bone Graft Versus Autogenous Bone Graft Alone for Mandibular Reconstruction: Quantitative Assessment

BACKGROUND

The use of a tissue expander in maxillofacial intraoral tissue reconstruction is a developing approach, which provide adequate tissue coverage and aesthetics.

OBJECTIVES

The purpose of this study was to quantitatively compare the use of a soft tissue expander in conjunction with autogenous bone graft with bone graft alone for the repair of the mandible's anterior region.

METHODS

The study comprised 24 patients with bone defects in the anterior mandibular region. Patients were divided into 2 groups at random. In group I, expander with bone graft was used, whereas in group II, bone graft was used alone. Volumetric measures of the grafted area was performed using CBCT, and cephalometric evaluations of the anteroposterior and vertical skeletal relationship, as well as the soft tissue profile were recoded. A comparison was made between the 2 groups 6 and 24 months after surgery with P ≤ 0.05 considered significant.

RESULTS

The mean difference in grafted bone volume between the 2 groups was 1.95 cm 3 , indicating a significant difference between the 2 groups ( P = 0.05) with superior group I results. The soft tissue profile of group I demonstrated a considerable improvement and stability of the lower lip, the labiomental sulcus, and the thickness of the soft tissue Pogonion compared with group II.

CONCLUSION

The use of a tissue expander in conjunction with a bone graft resulted in a better soft tissue profile, making it a favored approach in maxillofacial 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.

Reshapable hydrogel tissue expander for ridge augmentation: Results of a series of successive insertions at the same intraoral site

BACKGROUND

Oral mucosa expansion before ridge augmentation is a procedure to reduce soft tissue exposure and to improve bone graft density and volume after augmentation. This study explored a novel, shapeable hydrogel tissue expander (HTE) in intraoral sites that had undergone previous expansion and surgery.

METHODS

Nine beagle dogs had all premolar teeth extracted and adjacent alveolar bone reduced. After at least 3 months healing hydrogels were placed at 4 sites in each dog: maxilla and mandible, right and left. After 6 weeks of expansion, the hydrogels were removed and measured for volume expansion and physical condition. Punch biopsies were taken of the expanded oral mucosa. After 3 months, a second hydrogel insertion was performed at each of the same sites. After this second expansion cycle, volume and hydrogel condition were recorded. Three dogs received ultrasound imaging of the hydrogels during the second expansion. Necropsy specimens were taken of both expanded and non-expanded oral mucosa.

RESULTS

Within 2 weeks after HTE insertion in both first and second insertions, blood flow returned to the pre-insertion level. The first and second insertions resulted in linear oral mucosa gain of 8.13 mm, and 6.44 mm, respectively. First and second insertion hydrogels erupted from 4% of the first expansion sites, and 3% of the second expansion sites. There was no directional migration of the expanding hydrogel at any site. Histology found little inflammatory reaction to any hydrogel implant.

CONCLUSION

Oral mucosa can be consistently and successfully expanded before bone graft for ridge augmentation even at sites with a history of prior surgeries.

Oral tissue response to soft tissue expanders prior to bone augmentation: in vitro analysis and histological study in dogs

Purpose

To determine whether the swelling and mechanical properties of osmotic self-inflating expanders allow or not the induction of intraoral soft tissue expansion in dogs.

Methods

Three different volumes (0.15, 0.25, and 0.42 mL; referred to respectively as the S, M, and L groups) of soft tissue expanders (STEs) consisting of a hydrogel core coated with a silicone-perforated membrane were investigated in vitro to assess their swelling behavior (volume swelling ratio) and mechanical properties (tensile strength, tensile strain). For in vivo investigations, the STEs were subperiosteally inserted for 4 weeks in dogs (n=5). Soft tissue expansion was clinically monitored. Histological analyses included the examination of alveolar bone underneath the expanders and thickness measurements of the surrounding fibrous capsule.

Results

The volume swelling ratio of all STEs did not exceed 5.2. In tensile mode, the highest mean strain was registered for the L group (98.03±0.3 g/cm), whereas the lowest mean value was obtained in the S group (81.3±0.1 g/cm), which was a statistically significant difference (P<0.05). In addition, the S and L groups were significantly different in terms of tensile strength (1.5±0.1 g/cm for the S group and 2.2±0.1 g/cm for the L group, P<0.05). Clinical monitoring showed successful dilatation of the soft tissues without signs of inflammation up to 28 days. The STEs remained volumetrically stable, with a mean diameter in vivo of 6.98 mm, close to the in vitro post-expansion findings (6.69 mm). Significant histological effects included highly vascularized collagen-rich fibrous encapsulation of the STEs, with a mean thickness of 0.67±0.12 mm. The bone reaction consisted of resorption underneath the STEs, while apposition was observed at their edges.

Conclusions

The swelling and mechanical properties of the STEs enabled clinically successful soft tissue expansion. A tissue reaction consisting of fibrous capsule formation and bone loss were the main histological events.

Mucosal Perfusion Preservation by a Novel Shapeable Tissue Expander for Oral Reconstruction

Background:

There are few methods for expanding oral mucosa, and these often cause complications such as tissue necrosis and expander eruption. This study examines mucosal blood perfusion following insertion of a novel shapeable hydrogel tissue expander (HTE). The canine model used subgingival insertion of HTE following tooth extraction and alveolar bone reduction. The primary goal of this study was to gain understanding of epithelial perfusion and reparative responses of gingival mucosa during HTE expansion.

Methods:

Nine Beagle dogs underwent bilateral premolar maxillary and mandibular tooth extraction. Three to four months later, HTE-contoured inserts were implanted submucosally under the buccal surface of the alveolar ridge. After removal and following a 6- to 7-month period of healing, new HTE implants were inserted at the same sites. The area was assessed weekly for tissue perfusion and volume of expansion. Biopsies for histological analysis were performed at the time of expander removal.

Results:

Within 2 weeks following the second insertion, blood flow returned to baseline (defined as the values of perfusion measurements at the presurgery assessment) and remained normal until hydrogel full expansion and removal. Volume expansion analysis revealed that the hydrogel doubled in volume. Histological assessment showed no macrophage or inflammatory infiltration of the mucosa. No superficial fibrosis, decreased vascularity, or mucosal change was seen.

Conclusion:

Maintenance of adequate tissue perfusion is a clinically important aspect of tissue expander performance to reduce risk of device loss or injury to the patient, particularly for areas with a history of previous surgeries.

Pre-augmentation soft tissue expansion improves scaffold-based vertical bone regeneration - a randomized study in dogs

OBJECTIVE

Soft tissue (ST) dehiscence with graft exposure is a frequent complication of vertical augmentation. Flap dehiscence is caused by failure to achieve tension-free primary wound closure and by the impairment of flap microcirculation due to surgical trauma. Soft tissue expansion (STE) increases ST quality and quantity prior to reconstructive surgery. We hypothesized that flap preconditioning using STE would reduce the incidence of ST complications after bone augmentation and that optimized ST healing would improve the outcome of bone regeneration.

MATERIALS AND METHODS

Self-filling tissue expanders were implanted in mandibular bone defects in ten beagle dogs. After expansion, alloplastic scaffolds were placed for vertical bone augmentation in STE sites and in control sites without STE pre-treatment. ST flap microcirculation was analysed using laser Doppler flowmetry. The incidence of graft exposures was evaluated after 2 weeks. Bone formation was assessed after 2 months, using histomorphometry and immunohistochemistry.

RESULTS

Test sites showed significantly less impairment of perfusion and faster recovery of microcirculation after bone augmentation. Furthermore, no flap dehiscences occurred in STE sites. Bone regeneration was found in both groups; however, significantly greater formation of new bone was detected in test sites with preceding STE.

CONCLUSIONS

Preconditioning using STE improved ST healing and bone formation after vertical augmentation. The combination of STE and the subsequent placement of alloplastic scaffolds may facilitate the reconstruction of severe bone defects.

Hydrogel tissue expanders for stomatology. Part I. Methacrylate-based polymers

In order to create a soft tissue surplus, implantable volume expanders are often utilized in dental surgery. Implanted tissue expanders should gradually increase their volume, exerting a constant pressure on the surrounding tissue for weeks. Current tissue expanders are based predominantly on externally inflatable balloons or on osmotically active tissue expanders that use soft hydrogels wrapped in perforated plastic coatings, which limit fluid entry and swelling. We have designed and examined tissue expanders based on the controlled rate expansive hydrogels synthesized from copolymers of selected methacrylates and N-vinylpyrrolidone, cross-linked with a combination of non-degradable (glycol dimethacrylates) and hydrolytically degradable (N,O-dimethacryloylhydroxylamine) cross-linkers. These copolymers have close-to-linear volume expansion rates (up to 6-9 times their original volume) and exert an increasing swelling pressure in vitro. The anesthetic benzocaine has been incorporated into the hydrogels, and kinetic release experiments have shown that most of the drug (90%) was released within 48 h. Our proposed hydrogel expanders are homogeneous and have suitable mechanical properties, thus simplifying the surgical manipulations required. Further studies will be needed to completely evaluate their biocompatibility and tissue response to the implants.

Pre-augmentation soft tissue expansion: an overview

OBJECTIVES

The aim of this study was to explore the development of soft tissue expanders, their different types and their potential applications prior to bone augmentation and implant placement.

MATERIAL AND METHODS

A review of pertinent literature was performed using PubMed to comprehend the dynamics of soft tissue expanders and determine the current position of their pre-augmentation applications.

RESULTS

There is promising, albeit preliminary information regarding the benefits of pre-augmentation soft tissue expansion. Findings cannot be generalised due to relatively small sample size.

CONCLUSIONS

Further clinical trials with larger sample sizes and long-term follow-up are needed before soft tissue expanders can be confidently applied in everyday clinical practice.

Soft tissue expansion before vertical ridge augmentation: Inflatable silicone balloons or self-filling osmotic tissue expanders?

Recent advances in periodontal plastic surgical procedures allow the clinician to reconstruct deficient alveolar ridges in more predictable ways than previously possible. Placement of implant/s in resorbed ridges poses numerous challenges to the clinician for successful esthetic and functional rehabilitation. The reconstruction frequently utilizes one or combination of periodontal plastic surgical procedures in conjunction with autogenous bone grafting, allogenic bone block grafting, ridge split techniques, distraction osteogenesis, or guided bone regeneration (GBR) for most predictable outcomes. Current surgical modalities used in reconstruction of alveolar ridge (horizontal and/or vertical component) often involve the need of flap transfer. Moreover, there is compromise in tissue integrity and color match owing to different surgical site and the tissue utilized is insufficient in quantity leading to post surgical graft exposition and/or loss of grafted bone. Soft tissue expansion (STE) by implantation of inflatable silicone balloon or self filling osmotic tissue expanders before reconstructive surgery can overcome these disadvantages and certainly holds a promise for effective method for generation of soft tissue thereby achieving predictable augmentation of deficient alveolar ridges for the implant success. This article focuses and compares these distinct tissue expanders for their clinical efficacy of achieving excess tissue that predominantly seems to be prerequisite for ridge augmentation which can be reasonably followed by successful placement of endosseous fixtures.

Periosteal expansion before local bone reconstruction using a new technique for measuring soft tissue profile stability: a clinical study

PURPOSE

To evaluate the outcome of intraoral soft tissue expansion by measuring the profile change using objective 3D metering equipment and to evaluate localized bone grafting after soft tissue expansion with regard to gain of bone and complications.

MATERIALS AND METHODS

Using a prospective study design, we asked patients with an osseous and soft tissue defect on the buccal aspect of the alveolar process to participate in this study. In 10 patients (experimental group) a self-inflatable soft tissue expander was placed under the periosteum. After 2 weeks, the expander was removed and a particulated onlay bone graft was placed in the expanded area, protected by a titanium mesh covered with a collagen membrane. Ten patients (reference group) were treated with a mandibular ramus bone block graft. The soft tissue profile was registered before each surgical procedure. The vertical and lateral dimensions of the bone grafts were noted at the grafting procedure and at the implant installation. P < .05 was considered significant.

RESULTS

The mean soft tissue profile change was 2.9 ± 1.1 mm after soft tissue expansion and 2.3 ± 2.1 mm at implant placement in the experimental group compared with 1.5 ± 1.4 mm at implant placement in the reference group (P = .065). Two patients had minor perforations of the soft tissue expander. In the experimental group, the mean lateral bone augmentation after soft tissue expansion was 4.5 ± 1.3 mm, and after healing, it decreased to 3.9 ± 1.4 mm (P = .063). The mean vertical augmentation was 4.1 ± 1.7 mm and had decreased at implant placement to 3.0 ± 1.4 mm (P = .041). In the reference group, the mean lateral augmentation was 3.8 ± 0.8 mm, and after healing, it reduced to 2.7 ± 0.8 mm (P = .024). The mean vertical augmentation was 2.9 ± 0.9 mm, and after healing of the bone graft at implant placement, it was reduced to 1.6 ± 0.8 mm (P = .01). When smokers were excluded, there was significantly less resorption of the bone grafts in both lateral (P = .049) and vertical (P = .012) dimensions in the experimental group compared with the reference group.

CONCLUSION

Hydrogel expansion of the periosteum is an applicable method to achieve a surplus of soft tissue to cover bone grafts. More refinements to the technique may be required to minimize complications, especially in smoking patients.

Multidisciplinary approach for the rehabilitation of dentoalveolar trauma

Satisfactory dental rehabilitation of dentoalveolar trauma requires intense effort and time. Usually multidisciplinary treatment planning and teamwork are necessary to deal with multitask problems associated with these cases. Dental implants have been successfully used for replacement of missing teeth, but in trauma cases insufficient alveolar bone hinders implantation. In this report we present the multidisciplinary approach for the treatment of a trauma case. Maxillary segmental alveolar osteotomy in conjunction with interpositional and onlay bone grafting was performed to prepare the site for placement of osseointegrated implants. Titanium microplate and screws were used to provide orthodontic anchorage for intrusion of the extruded mandibular incisors. The patient was rehabilitated by implant supported fixed partial denture 6 months after implant placement.

Subperiosteal tissue expansion for mandibular augmentation with hydroxylapatite particles: an experimental study

PURPOSE

The utility of subperiosteal tissue expansion (STE) for mandibular augmentation with hydroxylapatite (HA) particles was evaluated experimentally in two groups of dogs.

MATERIALS AND METHODS

Eight grams of solid HA particles were implanted in previously formed bilateral subperiosteal expanded beds on the mandible. In one group, the HA particles were implanted in the intact subperiosteal expanded bed and in the other the newly formed capsule overlying the bone was removed before implantation of HA.

RESULTS

Despite marked augmentation with a large number of HA particles, there was neither deformity nor infection of the implants, which maintained the original desired contour. The firm fibrous capsule formed by STE allowed consolidation of the HA particles and prevented their migration. In the first group, although histologic evidence of bony union of the implanted particles was not seen even after 2 months, clinical immobilization of the grafts was achieved in 1 to 2 months. After 1 year, substantial bone growth into the implants was observed. In the second group, clinical immobilization was observed even after 2 weeks. Histologic evidence of bony union of the particles located along the surface of the mandible was observed after 1 or 2 months. In these specimens, however, marked bone resorption of the mandibular cortex, was also noted. No evidence of bone or osteoid formation on the expanded periosteal side was noted in either group.

CONCLUSION

These results provide fundamental data regarding mandibular augmentation using STE, and indicate that the subperiosteal expanded bed is an excellent recipient site for onlayed implants.