Healing of cutaneous and mucosal wounds grafted with collagen-glycosaminoglycan/silastic bilayer membranes: a preliminary report

Evaluation of soft tissue coverage over porous polymethylmethacrylate space maintainers within nonhealing alveolar bone defects

Current treatment of traumatic craniofacial injuries often involves early free tissue transfer, even if the recipient site is contaminated or lacks soft tissue coverage. There are no current tissue engineering strategies to definitively regenerate tissues in such an environment at an early time point. For a tissue engineering approach to be employed in the treatment of such injuries, a two-stage approach could potentially be used. The present study describes methods for fabrication, characterization, and processing of porous polymethylmethacrylate (PMMA) space maintainers for temporary retention of space in bony craniofacial defects. Carboxymethylcellulose hydrogels were used as a porogen. Implants with controlled porosity and pore interconnectivity were fabricated by varying the ratio of hydrogel:polymer and the amount of carboxymethylcellulose within the hydrogel. The in vivo tissue response to the implants was observed by implanting solid, low-porosity, and high-porosity implants (n = 6) within a nonhealing rabbit mandibular defect that included an oral mucosal defect to allow open communication between the oral cavity and the mandibular defect. Oral mucosal wound healing was observed after 12 weeks and was complete in 3/6 defects filled with solid PMMA implants and 5/6 defects filled with either a low- or high-porosity PMMA implant. The tissue response around and within the pores of the two formulations of porous implants tested in vivo was characterized, with the low-porosity implants surrounded by a minimal but well-formed fibrous capsule in contrast to the high-porosity implants, which were surrounded and invaded by almost exclusively inflammatory tissue. On the basis of these results, PMMA implants with limited porosity hold promise for temporary implantation and space maintenance within clean/contaminated bone defects.

Surface characteristics of biomaterials used for space maintenance in a mandibular defect: a pilot animal study

PURPOSE

The purpose of the present study was to evaluate the effect of implant porosity on wound healing between solid and porous implants placed within a bony mandibular defect with intraoral exposure.

MATERIALS AND METHODS

Solid poly(methyl methacrylate) (PMMA) implants similar to those used currently in clinical space maintenance applications in maxillofacial surgery were compared with poly(propylene fumarate) implants that contained a porous outer surface surrounding a solid core. A 10-mm diameter nonhealing bicortical defect with open communication into the oral cavity was created in the molar mandibular region of 12 adult male New Zealand white rabbits. Of the 12 rabbits, 6 received the hybrid poly(propylene fumarate) implants and 6 received the solid PMMA implants. At 12 weeks, the rabbit mandibles were harvested and sent for histologic staining and sectioning.

RESULTS

Gross inspection and histologic examination showed all 6 poly(propylene fumarate) implants to be intact within the defect site at the termination of the study period, with 3 of the 6 specimens exhibiting a continuous circumferential soft tissue margin. In contrast, 5 of the 6 PMMA-implanted specimens were exposed intraorally with an incomplete cuff of soft tissue around the implant. One of the PMMA-implanted specimens exhibited complete extrusion and subsequent loss of the implant. Fisher's exact test was used to compare the occurrence of oral cavity wound healing between the 2 groups (P = .09).

CONCLUSIONS

Although statistically significant differences between the 2 groups were not seen, our results have indicated that advantages might exist to using porous implants for space maintenance. Additional study is needed to evaluate these findings.

Clinical evaluation of a new bilayer artificial dermis for repair of oral mucosal defects: report of two cases

Free mucosal grafts or split-thickness skin grafts have been used in patients undergoing repair procedures for oral mucosal defects. Conventional methods require the creation of second surgical wounds for use as donor sites. We applied two bilayers of artificial dermis to repair a buccal mucosal defect in one case and vestibular extension in another case. After removal of the sutures, no infection, pain, or hemorrhage developed in these patients. The results of granulation and epithelialization were good. Satisfactory appearance and function were achieved in both cases. Therefore, bilayer artificial dermis may be recommended for the repair of oral mucosal defects.

Evaluation of speech intelligibility after a secondary dehiscence operation using an artificial graft in patients with speech disorders after partial glossectomy

The purpose of this study was to evaluate speech intelligibility after a dehiscence operation using artificial grafts for patients with speech disorders after partial glossectomy that were caused by scars resulting from the primary operation. The subjects were six men and three women, who had had a partial glossectomy for tongue cancer followed by direct closure without reconstruction. They were operated on a second time operation to mobilise the residual tongue by dividing the cicatrix. An artificial graft was applied to the wound to maintain the dehiscence. Speech intelligibility was evaluated by a standardised Japanese speech intelligibility test before, and 6 and 12 months after the second operation. The intelligibility scores significantly improved during the first 6 months after the second operation, and continued to improve slightly during the following 6 months. This study suggests that the dehiscence operation using an artificial graft could improve speech in patients after partial glossectomy.

Articulatory function in patients who have undergone glossectomy with use of an artificial graft membrane

OBJECTIVE

The purpose of this study was to investigate, by assessing speech intelligibility, the long-term usefulness of an artificial bilayer membrane as a mucosal substitute after glossectomy.

STUDY DESIGN

Artificial membranes were grafted in 8 patients with intraoral defects after glossectomy. Five patients served as a control group and received only standard closure by suture after glossectomy. Speech intelligibility was evaluated by means of a standardized Japanese speech intelligibility test 6 months or more after the operation.

RESULTS

The postoperative courses of all 13 patients were uneventful. Intelligibility scores of those who received grafts were better than those of the control group in the overall score, the glossal sounds score, and the rear portion sounds score.

CONCLUSION

The artificial membrane was useful for the glossectomy as a long-term mucosal substitute, as well as for the short-term.

The use of a new bilayer artificial dermis for vestibular extension

In this study we evaluated the usefulness of a new bilayer artificial dermis (TERUDERMIS; Terumo Corporation, Japan) for vestibular extension. It is composed of a collagen sponge with the silicone layer which is sloughed off as the mucous membrane heals. We have used it for vestibular extension in 50 patients. The material was effective in nearly all patients in promoting haemostasis, relieving pain, inducing granulation, promoting rapid epithelialization, and preventing contracture. There were no side-effects. The greatest problem with such materials in the past has been contracture at the vestibular extension area. However, we found that the degree of contracture was similar to that seen with autogenous mucosa or free skin graft. Our results indicate that the material might be useful for vestibular extension.

A newly developed collagen/silicone bilayer membrane as a mucosal substitute: a preliminary report

A new bilayer membrane proved effective as a mucosal substitute. The membrane is composed of an outer layer of silicone and an inner layer of dehydrothermally cross linked composites of fibrillar and denatured collagen sponge. The membrane was placed on oral mucosal defects of five patients after operations for cancer. Ten to 14 days after application the outer silicone sheet was removed, leaving only the inner collagen sponge layer into which cellular tufts of fibroblasts and capillaries had infiltrated. The infiltrated collagen matrix became a new connective tissue that epithelialised rapidly by migration of peripheral epithelium 4-5 weeks after application. In all cases the postoperative course was unremarkable and the repair was effective.