Virtual Implant Rehabilitation Of The Severely Atrophic Maxilla: A Radiological Study

Background: Advanced maxillary atrophy is often observed and implant placement could become difficult. Nevertheless, a volumetric evaluation using a proper diagnostic software could facilitate the implant planning. The purpose of the present study is to suggest the potential application of the maxillary retro-canine area as the designated place for virtual tilted implants also in severely atrophic maxillae. Methods: A sample of CBCT images from the Department of Dentistry (IRCCS San Raffaele, Milan) was evaluated. After a 3D anatomical evaluation of the maxilla tilted implants has been virtually positioned in the retro-canine regions. All the implants were inserted with the same procedure at 30° and 45° degrees of tilting. The length, the palatal angulation and the diameter of each implant were identified. Results: 220 tilted implants were placed. An average implant measurement of 13.508 mm of length and 3.42 mm of diameter were calculated. Also, an average buccal-palatal angulation of 6° was identified. After the statistical analysis implant length was found significantly higher at 45° degrees than at 30° degree (<0.0001).Conclusions: A considerable amount of patients show a significant degree of bone atrophy. The implant-supported treatment plan can rely on the three dimensional imaging of the residual bone as a guiding tool to establish the most effective implant position for each specific case. In this study it is founded that an implant could be longer if its mesio-distal angulation is more accentuated. In addition, it is possible to virtually insert tilted implants also in severely atrophic maxilla. This could help clinicians to consider the retro-canine area a viable place to insert longer tilted implant.

Evaluation of Stress in Tilted Implant Concept with Variable Diameters in the Atrophic Mandible: 3D Finite Element Analysis

The beneficial mechanical properties provided by greater diameter or short implants increased their usage in the tilted implant concept. The aim of the present study is to compare the stress distribution of four different treatment models including variable implant numbers and diameters under static loading protocol in the atrophic mandible using 3-dimensional finite element analysis. Three models included two tilted and two vertical positioned implants with different diameters, whereas distally placed two short implants were added to the fourth model. The von Mises stress, maximum and minimum principal stress values were evaluated after applying 200N bilateral oblique loads to the first molar teeth with the inclination of 450 to the longitudinal axis. Tilted implants were associated with higher stress values when compared with vertical implants in all models. The lowest stress values were obtained in the fourth model including short implants. Although all stress values showed slight increases by descending implant diameters, the stress values of the model including implants with 3.3 mm diameter were within physiologic limits. All in all, increasing number or diameter of implants may have a positive effect on implant survival. In addition, when narrow diameter implants need to be inserted in the tilted implant concept, combination with short implants may be recommended for long term success.

Digital versus Traditional Workflow for Posterior Maxillary Rehabilitations Supported by One Straight and One Tilted Implant: A 3-Year Prospective Comparative Study

Objectives. The aim of the study was to evaluate and compare digital and traditional prosthetic workflow for posterior maxillary restorations supported by an upright and a distally tilted implant at 3-year follow-up. Materials and Methods. Twenty-four patients were treated in the posterior maxilla with 24 immediately loaded axial and 24 distally tilted implants supporting 3-unit or 4-unit screw-retained prostheses. Three months after initial loading patients were randomly stratified into two groups: definitive traditional impressions were carried out in the control group, while digital impressions were performed in the test group. The framework-implant connection accuracy was evaluated by means intraoral digital radiographs at 3, 6, 12, and 36 months of follow-up examinations. Outcome considerations comprised implant and prosthetic survival and success rates, marginal bone level changes, and required clinical time to take impressions. Results. A total of 24 patients received immediately loaded screw-retained prostheses supported by an upright and a distally tilted implant (total 48 implants). No implant dropouts occurred, showing an overall survival rate of 100% for both groups. None of the 24 fixed prostheses were lost during the observation period (prosthetic survival rate of 100%). No statistically significant differences in marginal bone loss were found between control and test groups. The digital impression procedure required on average less clinical time than the conventional procedure. Conclusions. Clinical and radiologic results suggest that digital impression is a predictable procedure for posterior maxillary restorations supported by an upright and a distally tilted implant.