In this study, 51 patients participated with 65 dental implants. The mean age of the patients was 58 ± 11 years (range 38 to 72 years) at the time of surgery, and 28 were females.

The experimental group had 34 Ca²⁺-modified dental implants, and the control group had 31 dental implants (without surface modification with calcium ions).

Tables 1 and 2 show the diameters and lengths of the placed dental implants in the experimental and control groups, respectively. Figure 1 shows the anatomical position of the dental implants in the study groups. The residual alveolar bone was of type II (12 implants), type III (16 implants), and type IV (6 implants) in the experimental group. Table 3 shows the bone type in the control group that had significantly more bone of better quality. Dental implants were placed at a mean insertion torque > 30 N cm in both groups (Table 3). The healing time was 4 months. They were mainly supporting fixed screw-retained prostheses, and delayed implant loading was performed.

No intraoperative complications were recorded. During the follow-up period (13 months), no implant failure was encountered in the experimental group. The control group had two implant failures. However, these differences were not statistically significant (Table 3). The mesial and distal bone loss in the experimental group was 0.3 ± 0.5 and 0.5 ± 7 mm, respectively. The proximal bone loss was significantly lower in the experimental group (Table 3).

The results of this study do not support the acceptance of the null hypothesis. The modification of an acid-etched surface with calcium ions (UnicCa®) has enhanced the marginal bone stability.

Maxillary sinus floor elevation using the transalveolar approach may be a valid and less invasive supplement to the lateral window technique [16, 17]. A prerequisite for using this technique is that primary implant stability could be achieved. Implant’s primary stability is the result of quantity and quality of hosting bone, the design of the implant, and the drilling technique [18]. Implant macro-design is a parameter that significantly influences implant primary stability. Ca²⁺-modified dental implants were placed following the same surgical procedure described by Anitua et al. [15] to place the same dental implant but without Ca²⁺. For that, no statistically significant differences in primary stability were found between the two dental implants.