Hydrogel Expanders Research Articles

Ocular prosthetics in children-Possibilities and challenges

One of the greatest challenges for ocularists is prosthetic fitting in children, especially in children with congenital anomalies such as clinical anophthalmia or functionless (blind) microphthalmia. The most frequent reason for prosthetic fitting in children is acondition following enucleation for retinoblastoma, followed by trauma and congenital pathologies. The standard treatment after enucleation or evisceration begins intraoperatively with the selection of an suitable implant and the use of aconformer at the end of the operation to shape the prosthetic cavity. An initial prosthesis can be fitted 4weeks postoperatively, with afinal fitting taking place 3months later. If iatrogenic scarring or scarring due to an infection of the prosthetic cavity occurs, the approach of the ocularist must be appropriately adapted with the use of modified prosthesis shapes and shorter treatment intervals. Surgical options include scar excision and oral mucosa or amniotic membrane transplantation. Congenital anomalies require the shortest treatment intervals and even more so for anophthalmia than for microphthalmia. The strategy is characterized by simultaneous stimulation of the soft tissue of the ocular adnexa as well as the bony orbit. As self-inflating hydrogel expanders are no longer available, conservative prosthetic treatment is the only option. Close cooperation between child/parent, ocularist and ophthalmic plastic surgeon is the best prerequisite for agood long-term treatment outcome.

Intraorbital self-inflating hydrogel expander implantation with a modified technique in congenital microphthalmia

PurposeTo investigate the long-term outcomes of intraorbital self-inflating hydrogel expander implantation with optic nerve transection in children with congenital microphthalmia. MethodsThe medical records of unilaterally blind microphthalmic pediatric patients undergoing intraconal hydrogel expander implantation with optic nerve transection were reviewed retrospectively. For each patient, the microphthalmic eye was preserved. The orbital volume and globe volume were measured and analyzed based on computed tomography scans taken preoperatively and 36 months postoperatively. The palpebral length was measured between the medial and lateral canthus at every follow-up. Surgical complications were also recorded. ResultsTwelve patients were included (median age, 44.25 ± 17.5 months). At 36 months postoperatively, the microphthalmic and contralateral orbital volumes increased by 3.07 ± 0.77 ml and 2.03 ± 0.67 ml, respectively. The mean microphthalmic/contralateral ratio (MCR) of the orbital volume increased significantly from 76.60% ± 5.46% to 83.81% ± 5.41% (P < 0.001). The microphthalmic palpebral length increased by 6.17 ± 1.85 mm, whereas the contralateral palpebral length increased by 2.67 ± 1.44 mm. Significant changes were observed in the palpebral length MCR (68.00% ± 4.83% vs 85.07% ± 3.87%; P < 0.001). There was no significant change in the microphthalmic globe volume at 36 months postoperatively (P = 0.215). For the fellow eye, the globe volume increased significantly by 0.53 ± 0.34 ml (P < 0.001). During the follow-up period, 2 patients developed a sunken prosthesis. One patient had difficulty opening the eye after wearing the conformer. There were no cases of expander rejection or extrusion. ConclusionsIn this small cohort of patients with congenital microphthalmia, intraorbital self-expanding hydrogel expander implantation with optic nerve transection led to excellent osseous and eyelid growth throughout the 36-month follow-up period.

Outcomes of the use of orbital hydrogel expanders in the management of congenital anophthalmia: CT-based orbital parameter analysis

ABSTRACT Purpose To evaluate the outcomes of orbital hydrogel expanders in the management of congenital anophthalmia. Methods In this retrospective one-armed cohort study, a chart review was performed of eight children with congenital anophthalmia who underwent orbital expansion using orbital hydrogel tissue expander from January 2006 to July 2018. Computed tomography (CT) of orbital parameters was evaluated before and after surgery. Changes in the orbital parameters were correlated with clinical factors. Results The study sample comprised 11 anophthalmic orbits of eight children (seven males, one female; median age = 12 months), with a median postoperative follow-up of 3.8 years. The anophthalmic orbital parameters after hydrogel expander implantation improved significantly compared to preoperative assessment as follows: mean orbital height improved from 21.7 mm to 25.4 mm (P < .001); width from 19.2 mm to 23.8 mm (P < .001); depth from 27.5 mm to 32.6 mm (P = .008); and volume from 3.7 cm3 to 5.3 cm3 (P = .001). Despite enlargement in all dimensions, the anophthalmic orbits with hydrogel expander had a significantly lower development than the normal orbits, mainly in height and volume. At the last postoperative visit, four (36.4%) cases had fornices deep enough to maintain the conformer. Migration and extrusion occurred in two (18.2%) cases. Conclusions Orbital hydrogel expander can improve the orbital development in congenital anophthalmia. However, the enlargement is not as extensive as that observed in the normal orbit. Orbital expanders associated with external conformers were not sufficient to induce normal growth of lids and fornix.

Expanding intestinal segment using osmotic hydrogel: An in vivo study.

Intestinal circumferential expansion is essential for bowel lengthening in patients with Short Bowel Syndrome. We hypothesized use of an endoluminal osmotic hydrogel expander (EOHE) as a novel approach for intestinal expansion. An EOHE was introduced into an isolated intestinal segment of New Zealand rabbits, with a similar segment created as a control. After 4weeks, the segments were retrieved for analysis. Weight, inflammatory markers and fluoroscopy data was recorded weekly. EOHE allowed successful expansion of intestinal segments from 4.68 ± 0.35 to 9.79 ± 0.35 cm (p = 0.01). Increase in intestinal length was 167.8 ± 35.21% in segments with EOHE vs. 23.03 ± 4.2% in the control group (p < 0.01). A significant intestinal dilatation (214.4 ± 1.58 vs. 34.59 ± 1.23%, p < 0.01) was demonstrated. Hematoxylin and eosin stain revealed conservation of intestinal architecture with muscle hypertrophy and flattening of the epithelium possibly due to compression. No reduction of rabbit weight, inflammatory markers or liver damage was described. EOHE appears to produce safe intestinal expansion, achieving increased length and dilatation suitable for lengthening procedure. This approach may allow development of similar techniques to expand bowel in short bowel patients. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1304-1309, 2019.

Reshapable polymeric hydrogel for controlled soft-tissue expansion: In vitro and in vivo evaluation

Tissue expansion is the process by which extra skin is generated using a device that applies pressure from underneath the skin. Over the course of weeks to months, stretching by this pressure creates a flap of extra tissue that can be used to cover a defect area or enclose a permanent implant. Conventional tissue expanders require a silicone shell inflated either by external injections of saline solution or air, or by internal osmotic pressure generated by a hydrophilic polymer. In this study, a shell-free tissue expander comprised only of a chemically cross-linked biocompatible polymeric hydrogel is developed. The cross-linked network of hydrophilic polymer provides for intrinsically controlled swelling in the absence of an external membrane. The new type of hydrogel expanders were characterized in vitro as well as in vivo using a rat-skin animal model. It was found that increasing the hydrophobic polyester content in the hydrogel reduced the swelling velocity to a rate and volume that eliminate the danger of premature swelling rupturing the sutured area. Additionally, increasing the crosslinking density resulted in enough mechanical strength of the hydrogel to allow for complete post-swelling removal, without the hydrogel cracking or crumbling. No systemic toxicity was noted with the expanders and histology showed the material to be highly biocompatible. These expanders have an advantage of tissue expansion without requiring an external silicone membrane, and thus, they can be cut or reshaped at the time of implantation for applications in small or physically constrained regions of the body.

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.

Successful conjunctival socket expansion in anophthalmic patients until the age of 2 years: an outpatient procedure.

PurposeTo report the results of a simple outpatient method for soft tissue socket expansion in young children with congenital anophthalmos.MethodsSeventeen congenital anophthalmic sockets of 15 infants of a mean age of 4.2±4.4 months were fitted with specially designed serial solid acrylic shapes or hydrogel expanders using cyanoacrylate for eyelids closure when using the latter.ResultsAt the age of 2 years, the mean horizontal eyelid length increased from a mean of 11.6±4.5 to 19.4±4.6 mm and the volume of the last expander from a mean of 0.6±0.2 to 2.0±0.3 cm2. The specially designed acrylic shapes could be a substitute to the custom-made molds, which require general anesthesia.ConclusionSuccessful increase in the horizontal eyelid length as well as the conjunctival socket volume could be achieved by a simple outpatient procedure without the need for repeated hospitalization and general anesthesia in these infants.

Digital evaluation of orbital development after self-inflating hydrogel expansion in Chinese children with congenital microphthalmia

Assessment of the growth of bony orbit in children with blind microphthalmia is essential to its management. In this study, variables were measured to evaluate the development of the bony microphthalmic orbits after treatment with self-inflating hydrogel expanders. This is a retrospective study with an interventional case series. Thirteen pediatric patients with congenital unilateral blind microphthalmia who had undergone tissue expansion with hydrogel expanders and computed tomography (CT) scanning before and after operation were included in the study. The orbital volume, depth, width, and height and retardation of the orbital rims before and after treatment were measured and analyzed using the iPlan Cranial Software. The mean age at the time of first implantation was 44 months (range, 3-113 months). Of the 13 patients, eleven received orbital expansion, while two received socket expansion. In the orbital expansion group, the mean microphthalmic/contralateral ratio (MCR) of orbital volume was 79.3% before surgery, which increased to 89.8% 3 years post operation (P<0.001). The mean MCR of orbital width also increased from 88.8% to 91.8% (P=0.003). The development of inferior and lateral rims showed the greatest retardation before treatment; the retardation of these two rims decreased significantly at the final measurement (P=0.004). It is also noted that the development of the microphthalmic orbits was limited in the two patients who only underwent socket expansion. The affected orbit enlarged in children with congenital blind microphthalmia following treatment with hydrogel expanders; this suggested that microphthalmia-associated orbital asymmetry can be treated with self-inflating hydrogel expanders.

Second Generation Self-Inflating Tissue Expanders: A Two-Year Experience

Background. Tissue expansion is a well-established surgical technique that produces an additional amount of normal skin to cover a defect. This technique is appealing because the skin quality and color are from the patient's own. The widely used injectable expanders are of great reliability but carry the disadvantage of being painful during injection and most of the time require multiple clinic visits. So the idea of self-inflation became attractive and hydrogel expanders were developed and became widely known for being painless during clinic visit and decrease number of visits. The first generation expanders were modified by adding an enclosing plastic shell to decrease the unopposed expansion that occurred in the first generation expanders, which lead to pressure necrosis of the skin flaps. This made it an attractive option for tissue expansion in children and some adult patients. Patients, Materials, and Methods. Charts of 17 patients were retrospectively reviewed, all of them had second generation self-inflating expanders implanted over a 2-year period for one of two purposes, the treatment of giant nevi or burn scars. Results. Fifteen patients were females and 2 were males. The indication was large burn scar in 14 cases (14/17), in which 47/55 expanders were implanted, and giant nevus in 3/17 cases in which 8/55 expanders were implanted. Extrusion of the expander occurred in 8/55 expanders (14.5%), which occurred in 6/14 patients. The highest percentage of extrusion occurred in the neck in which two out of three expanders extruded; otherwise this complication does not seem to be related to the indication, gender, nor age of the patients. It seems to be that it is technical in nature. The patients did not have to get any injections to fill the tissue expanders, which made the expansion process less painful and more convenient. Conclusion. This seems to be currently the largest published review in which second generation expanders were used. Those expanders seem to offer a desirable advantage of being painless for children, also they do not require repeated visits to the surgeon's clinic, which is of great value for patients living in the periphery.

Periodontal Soft Tissue Expanders - A Review

Insufficient regeneration of missing bone and soft-tissue may present aesthetic or functional problems in patients indicative for dental implant surgery by using several techniques like bone augumentation ,bone substitutes and guided tissue regeneration.Soft tissue expansion is a technique used by plastic and restorative surgeons to cause the body to grow additional skin ,bone or the other tissues.Extensive bone augumentation procedures are frequently carried out prior to implant surgery.Preaugmentation of soft tissue expansion with expanders leads to higher functional microvessel density in the tissue above the augmentation material and thus to more rapid osseointegration and inceases the probability of success in peri-implant bone augmentation.(1)Also Extensive soft tissue mobilization is required to achieve a tension -free wound closure at the grafted site and thus avoid wound dehiscence and loss of bone graft.(2) Keywords: Complications of expansion,Osmotic hydrogel expanders,Tissue expansion,Tissue expanders.

Use of Cyanoacrylate Glue for Temporary Tarsorrhaphy in Children

Congenital anophthalmia and postenucleation socket contracture are difficult conditions that require serial socket expansion with the use of hydrogel expanders and custom-made conformers along with temporary tarsorrhaphy. The authors undertook a part prospective case review of all children undergoing temporary tarsorrhaphy using cyanoacrylate glue over a 3-year period at a tertiary specialist children's hospital. They report a series of 7 children undergoing temporary tarsorrhaphy with cyanoacrylate glue instead of the conventional suturing technique. Indications were socket expansion (n = 4), fornix deepening (n = 2), prosthesis reposition, and prolapsed conjunctiva following enucleation (n = 1).The age range was 3 weeks to 14 years (mean, 2.7 years). The glue tarsorrhaphy lasted between 0.5 and 13 weeks (mean, 4.5 weeks). There were no adverse outcomes, and the glue tarsorrhaphy was tolerated well in all cases, with relative ease of reapplication of glue in clinic. Their study demonstrates that this technique allows quick and efficient temporary tarsorrhaphy with relative ease of reapplication in a clinic setting, avoiding the need for multiple general anesthetics.

The Use of Self-Inflating Soft Tissue Expanders Prior to Bone Augmentation of Atrophied Alveolar Ridges

Extensive bone augmentation procedures are frequently performed prior to implant surgery. To achieve tension-free wound closure at the grafted site and thus avoid dehiscence and exposure or total loss of the bone graft, extensive soft tissue mobilization is required. In vitro studies have shown the potential of self-filling osmotic tissue expanders to optimize the amount of resulting soft tissue and vascularization of the recipient site. The purpose of this prospective clinical study was to evaluate the application and complication rate of osmotic hydrogel expanders inserted subperiosteally prior to bone grafting. In this prospective observational study, eight patients were implanted with 11 intraoral osmotic hydrogel expanders prior to bone augmentation procedures. All expanders were placed in subperiosteal positions using the tunnel technique. The occurrence of soft tissue-related complications such as necrosis, perforation, infection, or wound dehiscence leading to expander loss was defined as the primary parameter for analysis and evaluation. Further clinical parameters were soft tissue quality and quantity as well as expansion duration. The expansion time depended upon defect size and expander dimensions. Complications, that is, perforation of the expanders through the oral mucosa, occurred in two patients (3 expanders) who suffered from extreme preoperative scarring in the treated areas owing to prior trauma in one patient and cleft surgery in the other. Patients were grafted with autologous (n = 7) or synthetic (n = 1) block grafts. The expanders were removed during bone grafting surgery. No further dehiscence occurred during the observation period, and all patients were treated successfully with dental implants and subsequent prosthetic reconstruction. Within the limits of this observational clinical study, hydrogel expanders may help to generate additional soft tissue, and they might contribute to the overall improvement of the bone augmentation process by reducing the risk of complications related to the lack of soft tissue. Further randomized controlled studies are necessary.

The use of self-inflating hydrogel expanders in pediatric patients with congenital microphthalmia in China

To report the results of enlarging orbital volume in consecutive cases of severe congenital microphthalmia by means of solid hydrophilic tissue expanders. The medical records of consecutive patients with congenital microphthalmia who underwent the placement of a hydrogel expander were retrospectively reviewed. Main outcome measures were orbital tissue expansion, prosthetic retention, and patient family satisfaction. A total of 17 patients were included in the study. All patients were able to retain an ocular prosthesis. The horizontal palpebral length increased from 71.3% of the contralateral unaffected eye to 85.4% of the contralateral unaffected eye. The expansion of orbital volume was assessed in seven patients. The volume of the microphthalmic orbits was expanded from 74.7% of the contralateral unaffected orbits to 83.5% of the contralateral unaffected orbits. Aesthetic results were satisfactory to both physicians and patient families. The following complications were noted in two patients: inferior migration of a spherical expander occurred in one case; a hemispheric expander was removed by the patient in another case. Hydrogel implants can successfully expand the dimensions of the conjunctival sac and the orbit in cases of severe congenital microphthalmia.

Hydrogelexpander als Medikamentenabgabe-System für Antibiotika

The suitability of a high-hydrophilic osmotic self-inflating hydrogel expander consisting of a co-polymer of N-vinylpyrolidone and methyl methacrylate as a drug delivery system for antibiotics to prevent a postoperative infection was investigated in a laboratory setting. The dry expanders were incubated in a 0.3% solution of Ofloxacin or Tobramycin for 24hours. The completely swollen expander had increased in volume from 0.3mL to almost 3mL(adsorbing 2.7 mL of the 0.3% solution, i.e.,8.1mg of Ofloxacin or Tobramycin, respectively). Addressing the elimination of both antibiotics, the concentrations in 15mL elution medium (simulating the volume of the orbit in a newborn baby) were measured after 0.25, 1, 2, 6, 24, 48 and 72 hours of elution. 0.9% sodium chloride (B. Braun Melsungen, Germany) was used as elution medium. To imitate fluid exchange due to blood perfusion in the surrounding tissue the medium was renewed after every sampling. For each substance 10 expanders were tested. Concentrations of antibiotic were determined by HPLC/UV for Ofloxacin and by using a specific fluorescence-polarisation immunoassay (Abbott TDx) for Tobramycin. Mean concentrations of Ofloxacin at 0.25, 1, 2, 6, 24, 48 and 72 hours after beginning of the elution were 50.2, 46.8, 41.2, 75.4, 88.2, 46.2 and 19.1µg/mL, respectively. The cumulative amount of Ofloxacin eluted after 72 hours reached 68% of the loading dose. The corresponding mean concentrations of Tobramycin were 38.8, 48.5, 40.5, 69.8, 88.7, 119.3 and 71.6µg/mL. The cumulative eluted amount was 88%. The investigated hydrogel expanders soaked in 0.3% antibiotic solution can store and later on release sufficient amounts of Ofloxacin or Tobramycin to produce antimicrobial effective concentrations in vitro in the surrounding environment. This principle, when used in a clinical setting, might help to eliminate post-implantation infection which is one of the major complications in clinical use.

Efficacy of reconstruction for congenital microphthalmos

To investigate the therapeutic procedures and their efficiencies for the treatment of congenital microphthalmos during or after the developing period. It was a retrospective case series study. Eighteen cases with congenital microphthalmos, aged less than 12 years, underwent self inflating osmotic hydrogel expanders. Among them, 11 cases were treated by implantation with sphere self-inflating hydrogel expanders into the retrobulbar space and 5 cases had implantations into the conjunctival socket. The remaining 2 cases were treated with implantation of injectable self-inflating hydrogel pellet expanders. Twenty eight cases with congenital microphthalmos, aged more than 12 years, accompanied with other deformities, were treated with proper reconstruction surgery. Fourteen cases were treated with medial canthoplasty, 12 cases were treated with medial and lateral canthoplasty, 3 cases were treated with ptosis correction and medial or lateral canthoplasty and 2 cases with socket reconstruction. T-test was used for the comparison between groups. Sixteen cases obtained satisfactory results without any complications. In one case, the hydrogel expanders migrated inferiorly in the orbit and underwent adjustment. In another case, although the hydrogel expander prolapsed from the socket, the socket was still expanded. In the developing period, the length of palpebral fissure was (15.83 ± 1.87) mm before the operation, and that made much wider after the operation (18.67 ± 1.74) mm. There were statistically significant differences between them (t = -4.029, P = 0.01). The height of palpebral fissure was (1.33 ± 0.67) mm and (6.00 ± 0.58) mm before and after the operation, respectively, which were statistically significant (t = -5.813, P = 0.00). Patients who aged more than 12 years and underwent eyelids and eye socket reconstruction, also obtained satisfactory appearance. Patients with congenital microphthalmos could obtain the development of orbit and satisfactory appearance by reconstruction treatment according to different period of development.

In vitro kinetics of delivery of tobramycin and ofloxacin from osmotic hydro gel expanders

High-hydrophilic osmotic self-inflating hydro gel expanders are well-accepted for implantation to achieve tissue expansion in defined parts of the body like skin, breast and orbital soft tissue. To prevent post-implantation infections effective antibiotic prophylaxis might be helpful. The suitability of this hydro gel consisting of a co-polymer of N-vinyl-pyrolidone and methyl-methacrylate as a drug delivery system for antibiotics was investigated in a laboratory setting simulating the orbit in a newborn. In a first setting the dry expanders were incubated in a 0.3% solution (5 ml) of tobramycin and ofloxacin for 24 h (n = 10 for each substance, adsorbing 2.4 ml of the 0.3% solution, i.e. 7,200 μg antibiotic). Addressing the release of both antibiotics, the concentrations in 15 ml elution medium (0.9% sodium chloride, renewed after every sampling) were measured after 0.25, 1, 2, 6, 24, 48 and 72 h of elution. To simulate the clinical use in a second setting the expanders were dried after incubation in a 0.3% and 0.03% solution of tobramycin (n = 5 for each concentration) before measuring the release. The cumulative amount of tobramycin released after 72 h reached 7,157 μg, i.e. 99% of the initially loaded antibiotic. The cumulatively released amount of ofloxacin was 5,505 μg (76% of loading dose). Main fraction of release (about two thirds) was detected for both antibiotics for a elution period 0 - 24 h. In the periods 24 - 48 and 48 - 72 h the released amount of tobramycin was significantly higher than for ofloxacin. The release from expander dried after loading tobramycin was comparable: The cumulatively released amount of 0.3% and 0.03% incubation solution was 99% and 79% of loading dose, respectively. The investigated hydro gel expanders soaked in antibiotic solution can store and further on release sufficient amounts of tobramycin or ofloxacin to produce antimicrobial effective concentrations in vitro in the surrounding environment according to the breakpoints reported by EUCAST [14]. This principle, when used in a clinical setting, might help to eliminate post-implantation infection, which is one of the major complications in clinical use.

Bone augmentation after soft‐tissue expansion using hydrogel expanders: effects on microcirculation and osseointegration

The success of bone augmentation, for example of the alveolar ridge, might be endangered by dehiscence of the soft tissue that covers the augmented bone. Soft-tissue coverage can be achieved without tension through pre-augmentation tissue expansion with hydrogel expanders. We used a periosteal chamber to study the influence of tissue expansion on microcirculation and osseointegration in an in vivo animal model. Sixteen isogeneic Lewis rats were randomised into two groups. Additional eight animals served as donors of isogeneic bone grafts (Group 3, n=8). The bone grafts were harvested and implanted into Group 1 animals (n=8) (without tissue expansion) and Group 2 animals (after tissue expansion). In Group 2 (n=8), hydrogel expanders were inserted subperiosteally at the site to be augmented for 21 days. We used intravital microscopy to monitor microcirculation in vivo for 19 days after implantation. Specimens from both groups were evaluated histologically. During the entire study period, functional microvessel density in the region above the augmentation material was significantly higher after previous tissue expansion (P>0.05). Both groups showed physiological microcirculation around the augmentation material. Histology revealed bone osseointegration of the bone graft in the group with tissue expansion and the presence of connective and granulation tissue in the group without tissue expansion. Pre-augmentation soft-tissue expansion with hydrogel expanders leads to higher functional microvessel density in the tissue above the augmentation material and thus, to more rapid osseointegration. The use of hydrogel expanders appears to increase the probability of success, especially of pre-implant bone augmentation.

Micro-Computed Tomography and Histologic Evaluation of the Interface of Hydrogel Expander and Underlying Bone: Influence of Pressure Distributors on Bone Resorption

Tissue expanders lead to changes in the underlying bone and can cause bone resorption. We investigated whether the insertion of mechanical devices that distribute the load on the bone can influence these effects. A total of 28 Lewis rats were assigned to 1 of 4 groups. Hydrogel expanders were placed subcutaneously either directly on the calvaria, on titanium mesh, or on a titanium plate. The fourth group of rats served as the controls. The bone quality and thickness were assessed beneath, and at the periphery of, the expanders using micro-computed tomography and histologic examination. Micro-computed tomography images were obtained before and 21 days after insertion. The images revealed a significant decrease in hydroxyapatite density beneath the expanders in the group with only expanders. This decrease was reduced with the use of titanium mesh and completely prevented with the use of titanium plates. Histologic examination revealed a significant decrease in bone density and marked lacunae beneath the hydrogel expanders in the group with only expanders. In contrast, the titanium mesh decreased the size of the lacunae, and the titanium plates completely prevented both the formation of lacunae and the decrease in bone thickness. The bone resorption caused by hydrogel expanders can be diminished using titanium mesh and completely prevented by the insertion of a titanium plate.

Using a novel self-inflating hydrogel expander for intraoral gingival tissue expansion prior to bone augmentation

The success of bony augmentation is jeopardised by inadequate perfusion and dehiscence of the soft tissue that covers the bone, and the wound should be closed primarily without tension so that vascularisation is not compromised. 1 Cordaro L. Amade D.S. Cordaro M. Clinical results of alveolar ridge augmentation with mandibular block bone grafts in partially edentulous patients prior to implant placement. Clin Oral Implants Res. 2002; 13: 103-111 Crossref PubMed Scopus (310) Google Scholar The increase in bony volume, however, sometimes makes it impossible to achieve tension-free soft-tissue coverage, particularly when a large amount of augmentation material is required, so a mucoperiosteal flap is often raised and mobilised through a periosteal incision. This, however, reduces the perfusion of the mucoperiosteal flap. 2 Esposito M. Grusovin M.G. Maghaireh H. Coulthard P. Worthington H.V. Interventions for replacing missing teeth: management of soft tissues for dental implants. Cochrane Database Syst Rev. 2007; : CD006697 PubMed Google Scholar , 3 Jivraj S. Chee W. Treatment planning of implants in the aesthetic zone. Br Dent J. 2006; 201: 77-89 Crossref PubMed Scopus (49) Google Scholar A possible solution could be soft-tissue expansion. Keeping tissue under constant tension leads to the formation of new cells and growth of tissue. 4 van Rappard J.H. Molenaar J. van Doorn K. Sonneveld G.J. Borghouts J.M. Surface-area increase in tissue expansion. Plast Reconstr Surg. 1988; 82: 833-839 Crossref PubMed Scopus (106) Google Scholar For technical reasons expanders have not yet been used intraorally routinely, but their use is now possible with miniaturised self-inflating hydrogel expanders, which need not be filled from an external source.

Volumenüberschuss durch Hydrogelexpander nach Enophthalmuskorrektur

In the subject of this case report, a self-inflating hydrogel expander was implanted as a treatment for posttraumatic enophthalmos in a fully sighted eye. The intervention caused hypertropia with diplopia, restriction of eye movements, visual field defects, and colour desaturation as a result of excessive swelling of the expander. Once the expander volume was adjusted, clinical signs regressed, and the aesthetic results were excellent. Following the implantation of self-inflating orbit expanders, it is advisable to carry out immediate follow-up during the expander's swelling period, and long-term follow-up is also advised to rule out late sequelae, as a position-dependent secondary glaucoma could occur.