Many procedures are used to recover denture foundation, but the majority is considered sophisticated techniques [51–53]. Observations tried to notify bone modifications with different types of implant-assisted restoration [23, 40, 54]. The clinical and radiographic investigations, detection of the altered mineral levels, or bone density within the bone may give a valuable data for the bony state around loaded implants [55–57]. In a prospective study, Adell et al. [19] noticed a reduction of probing depth around implants, resembling approximately that surround natural dentition which indicates active positive bone repair. A further sign of bone preserving is the radiopacity close to the fixture due to increasing in density [58]. Such radiopacity affirmed to increased bone volume and/or increased mineral content. Maxillary implants reflected more bone density rather than mandibular and distal cantilevered implants due to the stresses which may produce more unfavorable bone restoring condition. After 10 years of implant placement, a significant increase in peri-implant bone density was noted in a clinical study for 18 patients [59]. In two separate clinical reports, Taylor [21] reported patient’s complain with cantilevered part after 32 months of loading. He elaborated that with mandibular growing for about 3 mm. In the other case report by Oikarinen and Silrila [60], they mentioned new boney layer formation. Naert et al. [61] agreed with the role of the implant in residual ridge preservation even if there is no bone formation recorded.

Occlusal load and different forces induced on the implant overdenture restoration, with the diminished supportive area, might be the main predisposing factor for bone resorption [62]. According to finite element analysis study, the available bearing area in case of complete denture is 4608.7 mm² comparing to 2833.4 mm² for the implant overdenture posteriorly which leads to an even pressure at the usage of complete denture comparing to higher load concentration on the posterior area available with overdenture [63]. This agreed with other study comparing hydrostatic pressure under the conventional versus implant overdenture which conceded the evenness of load distribution over the wide area of residual ridge, approximately 1926 mm², and the volume average hydrostatic pressure at 10.670.8 kPa, in case of complete denture. While the tissue-bearing area reduced to 71% with two implants and to 60.5% for four implant-assisted overdenture, the corresponding hydrostatic pressure was 14.370.9 and 13.370.9 kPa, respectively. The peak of posterior stresses was recorded with the two implant-assisted overdentures [64]. In a clinical retrospective study for 10 years, there was a significant difference in posterior ridge resorption with overdenture assisted with two and/or four implants. This was interpreted as the improved oral function and increased bite force may lead to more force concentration which does not exist in floated conventional denture [65]. Due to the anchorage of the denture anteriorly in the symphyseal area, the axial direction of force and the free movement posteriorly may exert more resorption in comparing to preserved bone close to implant anteriorly [66, 67]. On the other hand, the best selection for supra-structure attachment with implant overdenture and the pre-intervention planning may reduce implant/ridge load by distributing forces in an even manner to act as the norm of implant-supported fixed dentures [68, 69]. Additional investigation elected the symphyseal implant overdenture as a good treatment modality without overestimation for posterior bone loss [70].