Prospective radiographic evaluation of peri-implant bone maintenance on osseointegrated implants with frictional morse taper connection and platform switching: Cases report Avaliação radiográfica prospectiva da manutenção óssea peri-implantar nos implantes osseointegráveis com conexão cone morse friccional e plataforma switching: Relato de casos Evaluación radiográfica prospectiva del mantenimiento óseo peri-implantario en implantes osteointegrados con conexión de cono morse por fricción y plataforma de switching: Informes de casos

Objective: The aim of the present study was to evaluate radiographically the remodeling of the peri-implant bone crest in prosthetic friction morse cone implants, with platform switching, after 12 months of application of prosthetic load. Materials and Methods: 16 implants were installed, in 10 patients, rehabilitated with partial, single and multiple metalceramic prostheses, submitted to prosthetic function in the period of 12 months. Periapical radiographs to measure the Research, Society and Development, v. 10, n. 2, e23010212467, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i2.12467 2 distance between the mesial and distal marginal bone crest and the platform of each implant, were performed at the time of installing the prostheses and 12 months later. The images obtained at different intervals were digitized and analyzed using Image J software . Results: At the time of installing the prostheses, the averages of measurements on the distal and mesial surfaces were 0.57 mm (standard deviation 0.45) and 0.55 mm (standard deviation 0.41) respectively. After 12 months in function, the averages obtained were 0.59 mm (standard deviation 0.48) on the distal surface and 0.57 mm on the mesial surface, (standard deviation 0.34). Conclusion: In this radiographic evaluation, it was possible to observe that the implants with prosthetic connection of the frictional Cone Morse type with platform switching presented an average of 0.2mm of cervical bone remodeling, after 12 months in function, seeming to be a good alternative for periodic bone maintenance deploy.

distance between the mesial and distal marginal bone crest and the platform of each implant, were performed at the time of installing the prostheses and 12 months later. The images obtained at different intervals were digitized and analyzed using Image J software TD . Results: At the time of installing the prostheses, the averages of measurements on the distal and mesial surfaces were 0.57 mm (standard deviation 0.45) and 0.55 mm (standard deviation 0.41) respectively. After 12 months in function, the averages obtained were 0.59 mm (standard deviation 0.48) on the distal surface and 0.57 mm on the mesial surface, (standard deviation 0.34). Conclusion: In this radiographic evaluation, it was possible to observe that the implants with prosthetic connection of the frictional Cone Morse type with platform switching presented an average of 0.2mm of cervical bone remodeling, after 12 months in function, seeming to be a good alternative for periodic bone maintenance deploy. Keywords: Dentistry; Dental implants; Osseointegration.

Introduction
Osseointegrated implants are now an indispensable tool in the oral rehabilitation of patients who have partially or totally lost their dental arch. Nowadays, it is well established that dental implants contribute to the masticatory and aesthetic rebitration after tooth loss (Schropp et al., 2003;Paolantonio et al., 2001;Covani et al., 2003). In addition, studies show the healing time of the socket after a dental extraction for implant installation, which was 6 months in the protocol advocated by Branemark in 1985, can be abbreviated, as full medical use is not required. The implant socket can be installed at the time of dental extraction without the same surgical procedure or after early healing of the socket 8 weeks after dental extraction (Covani et al., 2003;Juodzbalys, 2003;Schropp et al., 2005). The morse cone system has advantages in terms of interface sealing, which results in less micro-infiltrations by micro-organisms that cause peri-implantation and has superior mechanics when compared to the external hexagon (Silva et al., 2020).
In the posterior mandible region, osseointegrated implants are subjected to great chewing forces, such that their micro and macrogeometry and prosthetic connection are important characteristics in order to adequately support these forces. The geometrical characteristics and surface treatments of the implant are factors that influence the success of the immediate or early installation, increasing the primary stability and the bone-implant contact and associated with the type of prosthetic connection, are factors that will preserve the peripheral biological tissues. implant, such as alveolar bone and soft tissue (Schropp et al., 2005).
Increased preservation of these structures avoids or decreases the occurrence of biological complications such as periimplant bone loss, infectious / inflammatory diseases such as peri-implantitis and soft tissue recession. These complications lead to aesthetic sequelae and diminish long-term implant success.

Methodology
The study followed the regulatory norms of research in human beings and was approved by the Research Ethics Committee of the Metropolitan University of Santos -UNIMES, having been given a favorable opinion (Opinion Number: 2.399.592). The patients were informed of the clinical and surgical procedures to which they were submitted and signed the informed consent form previously approved by the Research Ethics Committee.

Sample Calculation
The sample effect size (x / sd) is considered large at 1.07 (Figure 1). With this effect, the power analysis of the test shows that to reach a power of 80% would require at least 15 cases per group, and the study was performed with a total of 16 implants. Source: Authors. Research, Society and Development, v. 10, n. 2, e23010212467, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i2.12467

Inclusion criteria
Individuals who lacked the premolars or lower or upper premolars who needed prosthetic rehabilitation with osseointegrated implants were selected for the study. Patients should be in good general and dental health.

Exclusion Criteria
Smokers, pregnant women, diabetics, patients with osteoporosis or any other immunosuppressive disease, or at-risk groups.

Surgical Planning
All patients underwent radiographic examination of the edentulous area and complementary blood tests to assess their health status. If any changes were found, this patient was excluded from the study group.From the imaging exams, the amount of bone available in the region for the installation of osseointegrated implants was determined.

Surgical Procedures
The implant insertion technique followed the following steps: • Local buccal and lingual anesthesia, with vestibular sac fundus infiltrations and lingual / palatal mucosa.
• Mucosal detachment with exposure of underlying bone crest and buccal bone.
• Bed preparation with the sequence of drills corresponding to the implant system (Arcsys TM FGM, Brazil) and installation of 1 to 2 mm infra-bone implants.
• Suture with simple stitches.

Implant reopening and implant prosthesis confection
A period of at least 3 months was expected for reopening of the implants and installation of the healing abutments.
From then on, the implant prosthesis sequence was made. At the time of prosthesis installation over the implants, periapical xray was performed to determine the position of the initial mesial and distal marginal bone crest in relation to the implant platform.
Sixteen implants were installed in 10 patients, rehabilitated as partial, single or multiple metal-ceramic prostheses, submitted to masticatory function during a 12-month period. All installed prostheses were screwed onto the screwed abutment of the Arcsys system. At the time of implant implant prosthesis, pariapical radiographs were performed to initially assess the position of the bone crest.

Radiographic evaluations
At the time of prosthesis installation over the implants, periapical x-ray was performed to determine the position of the mesial and distal marginal bone crest in relation to the platform of each implant.
For the standardization of radiographs, a positioner was used for periapical radiography. A portion of condensation silicon was placed on the surface of the evaluated tooth and its antagonist for the impression of the anatomy of these surfaces and adapted to the positioner. This maneuver allowed the same position of the film at different evaluation periods, as well as the standardization of the same incidence of X-rays, the same vertical and horizontal angulation and distance in all radiographic shots of the same patient.
Radiographic images at different intervals were scanned for analysis and measurement of the distance between the proximal and distal bone ridges and the implant platform. For this, the Image J program was used ( Figure 5). Table 1 shows the distribution of installed implants that received a prosthetic load.

Radiographic Evaluation
Comparison of average results in millimeters over the initial periods (time of prosthesis installation) and final (6 months of functional load) are listed in Table 2. There was no statistically significant difference between initial and final in the measurement, neither mesial nor distal (p> 0.05). Research, Society andDevelopment, v. 10, n. 2, e23010212467, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i2.12467 6 In Figure 2, we can observe the moment of installation of the Arcsys 3.8 x 11.5 mm implants in the region 35 and 4.3 x 8.5 mm in the region 37 and in Figure 3 and 4, respectively, the periapical radiographs when the prosthesis was installed. on the implants and with 12 months in function. The Figure 5 mostra the moment of measurement of the distance from the mesial bone crest to the implant platform, in the Image J software TD .   Source: Authors. Research, Society and Development, v. 10, n. 2, e23010212467, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i2.12467  Albrektsson et al. (1986) defined as successful for implant rehabilitation, an annual bone loss of up to 2 mm in the first year in prosthetic function, and this index is still currently used as a measure of success in implant-supported rehabilitations.

Discussion
In a recent systematic review, Palacios-Garzón et al. (2019) suggested that crestal bone remodeling is always expected when we install osseointegrated implants, varying depending on some factors such as tissue characteristics, vertical implant position, platform switching concept and type of prosthetic connection. Fickl et al. (2010) showed mean values of crestal bone loss at the time of definitive prosthesis insertion of 0.30 ± 0.07 mm for implants with "platform switching" and 12 months after insertion of the definitive prosthesis, the mean loss crestal bone was 0.39 ± 0.07 mm in internal connection implants. Kutan-Misirlioglu et al. (2014) obtained an average of 0.9 mm of crestal bone remodeling in 1mm infra-bone platform switching implants and 0.4 mm of crestal bone remodeling in bone platform platform-switching implants, both with 12 months of prosthetic function.

Conclusion
The present study showed minimal bone loss around implants in the first 12 months of prosthetic load, with no statistically significant difference between the time of prosthesis installation and the first 12 months in prosthetic function, in agreement with other studies that reported less remodeling of the crestal bone around platform switching implants.
In addition, compared to these authors, the present study showed a lower average of crestal bone remodeling, with values obtained of 0.2 mm between the initial measurement at the time of prosthesis installation and the final measurement at 12 months in function.
Based on this radiographic evaluation, it is possible to suggest that Arcsys implants, with platform switching and frictional cone morse prosthetic connection, allow great crestal bone preservation around the implants in the first 12 months of prosthetic function.