Summary Egyptian desert soils are generally of coarser texture than Nile alluvium with only slight depositional changes within the same profile. Total N is lower in desert soils than in alluvial soils under similar climatic conditions. On the basis of clay mineral analysis the soils fall into four groups, having (1) kaolinite (Ganah and Kharga), (2) montmorillonite (Beris, Boulaq, Nile alluvium), (3) hydrous mica (Kharga), (4) attapulgite (desert road), as the dominant mineral. The very slight difference in clay mineral composition between the soil and subsoil or parent material indicates that clay minerals in these soils are derived mainly from a pre‐existing sediment. The mechanical analysis and mineralogical study of the heavy mineral fraction showed that the soils of Kharga oasis are either water‐laid sediments (Boulaq and Beris) or wind‐modified (Ganah and Kharga). Whether or not the qualitative similarity of the clay minerals of the soils from mid and southern Kharga with those of the Nile alluvium indicates a genetical relationship cannot be definitely ascertained from this study.

INTRODUCTION:Socket preservation is a procedure after tooth extraction to limit the post-extraction reduction of the ridge volume. Noncontact laser photocoagulation is a simple and atraumatic method used for socket sealing. Objectives: Compare the effect of diode laser photocoagulation to non-resorbable dense polytetraflouoroethylene (d-PTFE) membrane on bone dimensional changes. MATERIALS AND METHODS: Thirty-six patients (n =18 for each group) with non-restorable maxillary anterior or premolar teeth were included in this study. After extraction, sites were grafted with deproteinized bovine bone xenograft and sealed either with laser photocoagulation or a non-resorbable d-PTFE membrane. Measurements of the alveolar bone width were performed on cone beam computed tomographs, taken at baseline before and four months after extraction. RESULTS: Both groups showed a reduction in bone width. At the crest, the mean amount of reduction was 0.69 (0.33) mm and 0.78 (0.15) mm for laser and membrane groups, respectively. As for the middle third, less reduction was observed with a mean of 0.56 (0.36) mm and 0.58 (0.18) mm for laser and membrane groups, respectively. The least amount of reduction was in the apical third with a mean of 0.26 (0.36) mm and 0.41 (0.17) mm for laser and membrane groups, respectively. However, this reduction in bone dimensions was insignificant between both groups. CONCLUSION: Laser photocoagulation is as effective as the d-PTFE membranes in sealing sockets after grafting.

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