The digital revolution is changing the world of dentistry [
In the prosthetic field, the digital revolution has a strong impact because the dentist can capture optical impressions with IOS [
Although IOSs are becoming widespread and have become a very useful tool for capturing impressions in partially edentulous patients [
However, data emerging from these revisions stem from the analysis of previous clinical trials, in which first-generation IOSs were used [
Recently, in fact, some clinical studies have shown that using the latest-generation IOS, it is possible to design and fabricate clinically precise CAD/CAM implant-supported bars [
The aim of the present prospective clinical study is to present a digital method that combines intraoral and face scanning for the CAD/CAM fabrication of implant-supported bars for maxillary overdentures.
Over a 2-year period (2017–2018), all patients presenting to a private dental clinic, and seeking prosthetic rehabilitation with implants, were considered for inclusion in this prospective clinical study. Inclusion criteria for enrollment in the study were (1) fully edentulous maxilla; (2) functional problems with the complete removable denture (e.g., lack of stability, discomfort due to the size of the prosthesis); (3) presence of opposing natural or artificial dentition in the antagonist arch; (4) sufficient bone volume to be able to insert four implants of standard diameter and length (at least
The surgery took place under local anesthesia, as previously described [
Extraoral scan of the preexisting complete removable denture, suitably relined with CS 3600® (Carestream Dental, Atlanta, GE, USA). (a) Anterior perspective view; (b) vision of the inner part in contact with the mucosal tissues; (c) posterior perspective view; (d) right side view; (e) front view; (f) left side view.
The copy of the preexisting complete removable denture, relined and extraorally scanned, is printed with a stereolithographic 3D printer (3500PD®, DWS, Thiene, Vicenza, Italy) and subsequently discarded and opened in the area of scanbodies. (a) Complete copy of the preexisting denture, internal view; (b) full copy of the preexisting denture, anterior view; (c) full copy of the preexisting denture, perspective view; (d) the copy of the preexisting denture discarded and opened in the anterior area, in correspondence with the emergencies of the scanbodies, internal view; (e) the copy of the preexisting denture in the anterior area, in correspondence with the emergencies of the scanbodies, frontal view.
Intraoral scanning clinical images. (a) The implants before the removal of healing abutments; (b) scanbodies (BTSafe® scan abutments, BTK, Dueville, Vicenza, Italy) in position, occlusal view; (c) scanbodies in position, frontal view.
Intraoral scanning with CS 3600® (Carestream Dental, Atlanta, GE, USA), .STL files. The intraoral scan is performed with the patient wearing the copy of the preexisting denture, printed in 3D, properly discarded and opened in the scanbody area. The presence of this copy is essential to give the correct references for the vertical dimension of occlusion. (a) Master model with mucosal collars, antagonist, and copy of the preexisting denture opened in the anterior area; (b) master model with mucosal collars, antagonist, copy of the preexisting denture opened in the anterior area, and scanbodies; (c) copy of the preexisting denture and antagonist arch; (d) master model with mucosal collars and antagonist in the correct spatial relationship; (e) master model with mucous collars and scanbodies; (f) master model with mucosal collars, scanbodies, and antagonist in the correct spatial relationship.
Designing and 3D printing of the individual reference tray (IRT), useful for the superimposition between intraoral scans and face scans. (a) IRT in Meshmixer® and its spatial relationship with the antagonist model; (b) detail of the IRT with known geometry; (c) printing of the tray and the model of the antagonist assembled together; (d) detail of the individual reference tray (IRT).
Once the IRT was ready, it was possible to recall the patient for the third appointment, in order to take the face scans of the patient, using the aforementioned face scanner (OBI®). The first face scan was captured with the smiling patient, without the IRT (Figure
Face scan with OBI® (Fifthingenium, Milan, Italy), performed with the patient wearing a preexisting denture. (a) Face scan without an individual reference tray (IRT); (b) the individual reference tray is ready to be used; (c) extraoral detail of the individual reference tray (IRT) worn by the patient; (d) face scan with OBI® and individual reference tray (IRT).
Import of all files from intraoral scan and face scan into the CAD software (Exocad®), in order to design the bar. (a) Import of face scan with individual reference tray (IRT); (b) superimposition by points and by surfaces of the face scan with individual reference tray (IRT) on the intraoral scan files, using the original CAD drawing of the tray; (c) import of the face scan without individual reference tray (IRT) and its superposition, by points and by surfaces, on the previous face scan, using facial landmarks; (d) when the superimposition is completed, it is now possible to design the bar having the morphology of the patient’s face in the correct spatial position, without individual reference tray (IRT).
Design of the bar with the face references. (a) Detail of the modeled bar and scanbodies; (b) the bar modeled with precision attachments; (c) all the files are perfectly aligned within the CAD; (d) files of the final modeling of the bar.
The design of the bar is ready for prototyping.
Test of the passive fit of the 3D-printed bar. (a) Healing abutments before removal; (b) the test of the 3D-printed bar in hard and transparent resin; it is essential to obtain a perfect fit on the implants and a passive fit.
Delivery of the bar and the final overdenture. (a) Removal of healing abutments; (b) definitive PEEK bar, occlusal view; (c) definitive PEEK bar, front view; (d) activation of the prosthesis ball attachments directly in the mouth; (e) definitive overdenture, right side; (f) definitive overdenture, frontal view; (g) definitive overdenture, left side.
The outcomes of the study were the adaptation/passive fit of the bar on the implants, the functional/aesthetic integration of the overdenture, the 1-year implant survival, and the success rates of the implant-supported overdenture.
The adaptation and passive fit of the bar were checked clinically, before and after screwing the replica (and the final bar) on the implants. The adaptation and passive fit were defined acceptable, in the absence of any movement of the bar before screwing, and when the bar was seated perfectly on the implants without any noticeable discrepancy. No difficulties were encountered when screwing the bar. In the case of movements of the bar during seating, or given evidence of discrepancies that could render the screwing on the implants difficult, the adaptation and passive fit were defined unacceptable, and so a new digital impression of the position of the implants, with and without scanbodies, had to be captured, in order to investigate the presence of any potential error(s) with the previous scan.
Implant mobility in the absence of clinical signs of infection, nontreatable peri-implant infection (with pain, suppuration, and bone loss), severe progressive marginal bone loss in the absence of infection, and implant body fracture were the conditions for which an implant could be removed and consequently defined as “failed.” A distinction was made between “early” (within 3 months after implant placement) and “late” (at least 3 months after implant placement) failures. The 1-year implant survival rate was therefore calculated as the percentage of implant survival one year after placement. The implant survival rate was calculated at the patient level.
In the absence of any biologic and prosthetic complications throughout the follow-up period, the implant-supported overdenture was considered successful. Biologic complications would include soft tissue inflammation (peri-implant mucositis) and peri-implant infection (peri-implantitis) with fistula formation, pain, and exudation/suppuration. The threshold for peri-implantitis was set by a probing pocket
All data was collected from the records of the patients consecutively enrolled in the study. Descriptive statistics were performed for the patients’ demographics (gender, age at start of the prosthetic treatment) and the diameter/length of the implants. Absolute and relative (%) distributions were calculated for qualitative variables (adaptation and passive fit, survival, and success rates). Finally, means, standard deviations, medians, and 95% confidence interval (95% CI) were estimated for quantitative variables (patient’s age at start of the prosthetic treatment).
The present clinical study was based on a sample of 15 patients (6 males, 9 females, mean age
Distribution of the implants (BTSafe®, BTK, Dueville, Vicenza, Italy) by length and diameter (in mm).
8 mm | 10 mm | 12 mm | 14 mm | Total | |
---|---|---|---|---|---|
3.3 mm | 7 | 8 | 5 | 2 | 22 |
3.75 mm | 4 | 6 | 4 | 3 | 17 |
4.1 mm | 5 | 4 | 6 | 1 | 16 |
4.8 mm | 2 | 2 | 1 | 0 | 5 |
Total | 18 | 20 | 16 | 6 | 60 |
At the time of testing the 3D-printed resin bar, 12 bars out of 15 (12/15: 80%) had a perfect passive adaptation and fit and were consequently considered acceptable; the technician could then proceed to mill the definitive PEEK bars. In contrast, 3 out of 15 resin bars (3/15: 20%) did not present a sufficient passive fit or adaptation, due to the presence of movements before screwing or difficulty in the screwing itself. In all these cases, it was therefore necessary to repeat the scanning, modeling, and production procedure. The repetition of the procedure allowed us to solve the problems and proceed with the manufacture of the final PEEK bars in a completely digital flow. At the time of the test and the delivery of the PEEK bars, on the contrary, no problem occurred. All the PEEK bars fit and screwed perfectly with an ideal passive fit and could therefore be safely delivered to the patient.
No implants were lost, for a 1-year implant survival rate of 100% (60/60 surviving implants) (Figure
Clinical and radiographic control at 1 year from implant placement. (a) Frontal clinical photo; (b) panoramic radiograph.
Conversely, some complications (two fixtures with peri-implantitis, in the same patient; and two repaired overdentures because of tooth fracture, in two different patients) occurred during the follow-up period. This determined a 1-year success rate of 80% (12/15 patients without any complications encountered during the entire follow-up).
The use of IOS for capturing optical impressions on natural teeth and on implants is rapidly spreading in dental offices around the world. The process of taking optical impressions is now comfortable for the patient [
To date, the literature has not yet clarified whether optical impressions are able to capture quality impressions in the completely edentulous patient, both for fixed rehabilitations on implants and for the manufacture of removable implant-supported overdentures [
Despite this, the impressive technological evolution and the improvements in the acquisition software for IOS, with consequent enhancement of accuracy, open up new vistas and make it possible to extend the clinical applications of these instruments today, even to the completely edentulous patient.
In a recent clinical study, Capparè et al. [
This work has the merit of having highlighted how IOS is reliable and accurate in capturing the impression in the completely edentulous maxilla, confirming, in a larger sample of patients, the evidence that emerged in a previous work by the same authors [
Tallarico et al. [
In the present prospective clinical study, 15 patients were enrolled and were rehabilitated with a maxillary bar-retained overdenture. The choice of an overdenture-type restoration (rather than a fixed restoration without fake gingiva) depended in this work on the absence of adequate facial support, as well as on economic (reduced cost) and hygienic reasons (ease of maintaining oral hygiene domiciliary, compared to Toronto fixed and screwed on the implants). The merit of this work was to present a technique for CAD/CAM fabrication of implant-supported bars for overdentures, starting with intraoral scanning. In this study, most of the CAD/CAM bars (80%) had an excellent passive fit and adaptation, with only a limited number of bars (3/15: 20%), which presented problems of fit and adaptation during the resin test. Although this percentage is rather high, representing about one bar out of five, it must be said that the repetition of the intraoral scan and the new design made it possible to overcome the problems and thus to create new test bars, which fitted perfectly on the implants. The passage through a test bar, 3D printed in resin, seems in this sense essential, before being able to pass to the production of the definitive PEEK bar, which obviously presents higher costs. Note that in all three cases of inadequate adaptation, the distal implants were rather tilted and disparallel to each other. These results seem to confirm the evidence emerged from the most recent studies, which show how the evolution of the software of IOS allows us today to capture sufficiently accurate impressions to support the fabrication of full-arch-type fixed prostheses [
This study has limitations: the low number of patients enrolled in the study, the limited follow-up, and the fact that only the bars (and not the prostheses) were manufactured in CAD/CAM. The limited follow-up is a particularly significant limitation of the present study, since we have used a relatively new material (PEEK) for the manufacture of the bars, which are normally made in metal. There are no long-term studies on the performance of PEEK bars and certainly an evaluation of at least 5 years is required, in order to draw adequate conclusions on the reliability of this method. Moreover, in this study, only the bars were CAD/CAM. The next step is undoubtedly represented by the possibility of using intraoral scans for the design and production of the overdenture prostheses themselves (and not just of the bars). This is technically possible today, using the setting and the acquisition protocol used in the present clinical study. The possibility of using the patient’s face scans and working with the files of the prosthetic bases in the correct respective spatial positions, in full compliance with the vertical dimension of occlusion, represents a further merit of this study. The face scan is able to provide information on the patient’s face, in 3D, to the dental technician; this information is very useful for modeling not only the bar with the relative dimensions but also and above all the removable overdenture, in full compliance with the tissue volumes [
In the present clinical study, the integration of intraoral and face scans allowed us to successfully restore 15 fully edentulous maxillae maxillary overdentures supported by 4 implants and a CAD/CAM polyether-ether-ketone (PEEK) bar. In fact, when testing the 3D-printed resin bars (replicas), 12 bars out of 15 (12/15: 80%) had a perfect passive adaptation and fit and were consequently considered acceptable, i.e., the technician could proceed to mill the definitive PEEK bars. In contrast, three out of 15 bars (3/15: 20%) did not present a sufficient passive fit or adaptation, due to the presence of movements before screwing or difficulty in the screwing itself. In all these cases, it was necessary to repeat the scanning, modeling, and production procedure. The repetition of the procedure, however, allowed to solve the problems and proceed with the manufacture of the final PEEK bars in a completely digital flow. A 100% implant survival rate was found in this study; however, some complications (two fixtures with peri-implantitis in the same patient and two repaired overdentures because of tooth fracture in two different patients) occurred during the follow-up period, for a success rate of 80% for the implant-supported overdenture treatment. The digital procedures have the potential to decrease patient discomfort and to reduce the laboratory work associated with the fabrication of implant-supported overdentures. In addition, the use of PEEK can eliminate the need of using metals for the fabrication of the bar. However, this study has limitations, and further investigation is needed to confirm the outcomes emerging from this research.
Data are available from the corresponding author upon reasonable request.
No funding nor materials were received from third parties.
The authors report no conflict of interest related to the preparation of the present study.
This study was self-funded.