RESUMO
The material of the enamel is similar to the polycrystalline dense microporous hydroxyapatite crystals. Its biocompatibility has been tested before in experimental animals. In this study we tested up the enamel biofunctionality in human middle ear [ME]. Thirty-six patients [14 males and 22 females] with history of conductive deafness due to chronic suppurative otitis media were selected. From those patients, twenty patients were randomly selected to reconstruct their ossicular chain by the enamel homografts. While in the other 16 patients [control group], cortical bone grafts were used. Each study group was subdivided into 4 subgroups according to the type of the ossicular defect and the shape of the homograft. Those groups are: incus graft assembly [IGA], incus/stapes graft assembly [ISGA], and partial ossicular graft assembly [POGA] and total ossicular graft assembly [TOGA]. Thirty-six patients were followed up prospectively for nearly one and half years. Audiological assessment was done preoperatively as well as every three months postoperatively. The hearing improvement was evaluated through measuring the postoperative hearing gain. A gain equal or more than 20 dB was considered good result. All data were collected and subjected to statistical analysis. No case of extrusion has been recorded over the follow up period in both groups. The total success rate was 70% [14/20] in the enamel group and 43.8% [7/16] in the control group. IGA patients showed 87.5% [7/8] success rate in the enamel group and 50% [3/6] in the corresponding control subgroup. ISGA patients showed a success rate of 80% [4/5] in enamel group and 50% [2/4] in the corresponding control subgroup. POGA patients showed a success rate of 50% [2/4] in enamel group and 33.3% [1/3] in the corresponding control subgroup. TOGA patients showed 33.3% [1/3] in each group. In general, The results were considered unsatisfactory in the POGA and TOGA patients in both groups of the study. Statistically, there was a significant difference between the results of the enamel group and the control group as regard the IGA, ISGA [Z test p<0.05] However, there was no significant difference in the success rate in the POGA and TOGA subgroups. However, the postoperative hearing gain achieved by the enamel homografts was significantly better than that achieved by cortical bone grafts in all the study subgroups [T-test p<0.05]. Moreover, there were no limitations in fashioning and grinding of the enamel homografts into the desired shape during the operation. The smooth surface of the enamel allows one to place the graft with slight tension against the reconstructed DM without interposing cartilage. Our results are similar or, more or less, better than the previously published results of hydroxyapatite. Enamel homografts have proved to fulfill most of the criteria of suitable compatible middle ear implants. Till now, the postoperative hearing was stable in the enamel group meaning that the enamel is not liable to bony fixation, non-degradable. The similarity of the enamel to hydroxyapatite and its availability, stability, biocompatibility and minimal cost of preparation may give it the chance to be superior over the other biological and non-biological materials