Objective: the aim of the current study was to evaluate clinically and radiographically the split crest of the ridge and immediate Implant placement in maxilla and mandible.Study design: the present study was conducted to compare clinically and radiographically between ridge expansion in maxilla and mandible, The included patients will be randomly divided into two groups ,group I: (Six Implants) in maxilla, group II: (Six Implants) in mandible.Results: At the mesial surface, mandible showed statistically significantly higher mean bone density than maxilla. At the distal surface, mandible showed statistically significantly higher mean bone density than maxilla. At the buccal surface, mandible showed statistically significantly higher mean bone density than maxilla. At the palatal and lingual surface, there was no statistically significant difference between mandibular and maxillary bone density. Maxilla showed statistically significantly higher mean amount of expansion than mandible. There was a statistically significant negative (inverse) correlation between diagonal expansion, mid mesial density, mid distal density and bone loss. An increase in diagonal expansion is associated with a decrease in these variables and vice versa. There was a statistically significant positive (direct) correlation between diagonal expansion and mid buccal density. An increase in diagonal expansion is associated with an increase in mid buccal density and vice versa. Conclusion: The use of threaded bone expanders results in an atraumatic, cheap, successful technique for placements of implant in cases suffering from horizontal alveolar ridge deficiency with the following advantages, increased bone-to-implant contact ratio, decreasing bone drilling with the possibility of overheating and decrease the amount of removed bone, decrease the need to graft ridges which decreases thenumber of surgeries and the cost of the operation, eliminating the need for malleting and reducing its drawbacks, decrease the used instruments that decreases the cost of the operation, decrease the need for highly skilled operator due to easier technique, it is a versatile, cheap, quick and immediate placing dental implants with sufficient width in horizontally deficient ridges, ridge expansion technique give better results in the maxilla than mandible.