The aim of this clinical report is to describe a maxillary full-arch implant supported restoration with immediate loading performed by means of an entirely digital work flow with photogrammetric system and intraoral scanning. A female patient with an edentulous maxillary arch attended the dental clinic seeking a maxillary fixed restoration. After treatment planning, 6 implants were placed using a surgical splint fabricated digitally by intraoral scanning of her previous removable prosthesis. Multiunit abutments were fitted, and 2 digital impressions were taken, one with a photogrammetric system for determining implant positions and the other with an intraoral scanner for soft tissue registration. The acrylic resin structure of the immediate prosthesis was milled and placed within 8 hours of implant surgery. This provisional structure fitted correctly and provided adequate esthetics and function. Radiographic and clinical follow-up after 24 months observed adequate implant evolution.

Impression taking is one of the most important procedures involved in dental implant–supported restoration. Its level of accuracy will determine the fit between prosthesis and model and thus the passive fit of the final prosthesis on the implants.1  Good passive fit of an implant-supported prosthesis will improve its long-term prognosis.2  Construction of implant-supported fixed prostheses begins by taking impressions of both soft tissues and implants, using impression transfers to indicate the implant positions and create a working model.3 

In recent years, dentistry has undergone important technical advances.4  Computer-aided design/computer-aided manufacturing (CAD/CAM) technology5,6  and shorter osseointegration protocols allow earlier prosthetic loading of the implants.7,8  In addition, this development has increased patient satisfaction in terms of comfort, esthetics, and shorter restorative treatment times.

The introduction of intraoral scanners (IOSs) has provided an alternative to conventional impression-taking techniques. However, they continue to suffer certain limitations, especially for preparing complete implant-supported fixed prostheses.911  Photogrammetry offers another alternative to conventional impression taking, reading the geometric characteristics of objects and their distribution in space. This is done by processing metric data obtained from 2- and 3-dimensional images, which then establish direction vectors and exact distances between points. The most important characteristic of photogrammetry is its precision.12 

As far as the authors are aware, this is the first case report to describe maxillary full arch restoration with immediate loading employing an entirely digital work flow (photogrammetry system and intraoral scanning) from beginning (surgical splint design) to end (final fixed prosthesis).

A 62-year-old woman, without relevant medical antecedents, visited the University Dental Clinic seeking implant-supported fixed restoration of the maxillary arch (Figures 1 and 2). The patient wore a removable partial denture supported by both maxillary second molars and the first quadrant canine.

Figures 1 and 2.

Figure 1. Intraoral front view of patient before treatment.

Figure 2. Occlusal view of maxilla.

Figures 1 and 2.

Figure 1. Intraoral front view of patient before treatment.

Figure 2. Occlusal view of maxilla.

Close modal

After intraoral examination, an orthopantomograph and a cone beam computed tomogram were taken to assess the feasibility of implant placement. It was decided that 6 implants could be inserted to support a fixed implant–supported prosthesis with immediate loading. The patient was given full information about the procedure and gave her consent to undergo treatment in awareness of the possible risks and complications of immediate loading.

Sixteen weeks before implant placement, the canine was extracted for periodontal reasons preserving the alveolus. An acrylic partial prosthesis was fabricated, providing a safe interim prosthesis until immediate implant loading. This prosthesis was also used as a diagnostic tool to plan implant positions and for fabricating a surgical splint.

Step 1. Surgical Splint Design: Intraoral Scanning With and Without the Patient's Previous Removable Prosthesis

To fabricate the surgical splint, the residual alveolar ridge was scanned with a digital IOS (Trios 3Shape, Copenhagen, Denmark) with (Figure 3a) and without (Figure 3b) the acrylic partial prosthesis in place. The 2 digital impressions were superimposed (Figure 3c), and a surgical splint was designed to correspond to the available bone identified in the scans (Figure 3d).

Figure 3.

Digital impressions taken with intraoral scanner. (a) Impression of the alveolar ridge and remaining teeth. (b) Impression with the maxillary acrylic prosthesis. (c) Planning implant positions. (d) Surgical splint.

Figure 3.

Digital impressions taken with intraoral scanner. (a) Impression of the alveolar ridge and remaining teeth. (b) Impression with the maxillary acrylic prosthesis. (c) Planning implant positions. (d) Surgical splint.

Close modal

Step 2. Surgical Phase: Implant Placement

Six implants with internal connections were placed (Coral, Avinent, Barcelona, Spain) at positions #3, #5, #7, #10, #12, and #14 measuring 3.8 × 13 mm, 3.8 × 13 mm, 4.2 × 11.5 mm, 3.3 × 13 mm, 3.3 × 13 mm, and 4.2 × 10 mm, respectively. After surgery, transepithelial abutments were placed on the implants.

Step 3. Implant Impression Taking (PIC-Camera) and Soft Tissue Intraoral Scanning

After checking that implant primary stability was adequate for immediate loading, impressions were taken for fabricating a provisional fixed prosthesis. Implant stability was measured by resonance frequency analysis (Osstell, Gothenburg, Sweden) obtaining implant stability quotients (ISQ) that varied between 60 and 65 ISQ for all implants.

A fully digital work flow was followed to fabricate the prosthesis by means of a standard tessellation language (STL) file. A computer equipped with CAD software (PIC Pro, Position Implants Correctly, PIC Dental) transforms digital impressions taken from the patient into an STL file used to design the prosthetic structure. Two impressions are taken to obtain the STL file: one of the soft tissues with multiunit abutments screwed onto the implants using the IOS (3Shape TRIOS) and another of the implant positions, with a digital stereo camera (PIC camera, PIC Dental, Miami, Fla). To capture implant positions, flag-shaped abutments (PIC abutments) are screwed onto the multiunit abutments, placed so that the “flag” surfaces face the extraoral camera (Figure 4). The stereo camera is placed in front of the patient's mouth and captures these surfaces automatically, taking 350 images in under 2 minutes. With a margin of error of less than 10 μm between 2 flags, the system uses the data captured to identify the spatial position of each implant and its inclination without making physical contact. A file (PIC file) is generated that contains precise information about the position of each implant platform.

Figure 4.

Flag-shaped markers (PIC abutments) screwed onto implants for impression taking.

Figure 4.

Flag-shaped markers (PIC abutments) screwed onto implants for impression taking.

Close modal

Step 4. STL Best-Fit Alignment and Immediate Fixed Prosthesis Design and Fabrication

When the 2 impressions have been taken, they are aligned automatically (best-fit alignment) to create a high-precision model used to fabricate a provisional prosthesis with optimal passive fit (Figure 5a through d). The intraoral scans of the previous removable prosthesis are used to design this immediate prosthesis: its vertical dimensions, tooth positions, tooth sizes, and so on. The provisional prosthesis is milled within 6 hours (Figure 6). In the present case, the prosthesis was made from acrylic resin, polyoxymethylene (POM), which offers favorable mechanical and esthetic properties. The milled interim prosthesis was fitted and screwed in place within 8 hours of implant surgery with adequate esthetic and functional outcomes (Figures 7 through 9).

Figure 5.

Alignment by means of best-fit method of photogrammetric impression and intraoral digital impression. (a) Impression of alveolar ridge. (b) Spatial simulation of implant positions. (c) Designing the prosthesis. (d) Occlusal view of prosthesis and implant emergence.

Figure 5.

Alignment by means of best-fit method of photogrammetric impression and intraoral digital impression. (a) Impression of alveolar ridge. (b) Spatial simulation of implant positions. (c) Designing the prosthesis. (d) Occlusal view of prosthesis and implant emergence.

Close modal
Figure 6.

Milling the polyoxymethylene (POM) structure.

Figure 6.

Milling the polyoxymethylene (POM) structure.

Close modal
Figures 7–9.

Figure 7. Intraoral frontal view of immediately loaded fixed interim prosthesis.

Figure 8. Occlusal view of immediately loaded interim prosthesis.

Figure 9. Extraoral image with immediate loading.

Figures 7–9.

Figure 7. Intraoral frontal view of immediately loaded fixed interim prosthesis.

Figure 8. Occlusal view of immediately loaded interim prosthesis.

Figure 9. Extraoral image with immediate loading.

Close modal

Step 5. Final Prosthesis Design: Intraoral Scanning of Soft Tissues and Provisional Prosthesis

After the 4-month osseointegration period, final impressions of the implants were taken. As the implant positions had already been recorded by the digital stereo camera, it was necessary to take impressions of the soft tissues using only the IOS. As the patient was satisfied with the position and size of the teeth in the immediate provisional prosthesis, this was also scanned to reproduce its design in the final prosthesis.

Steps 6 and 7. Plastic Test Model and Final Prosthesis Fabrication and Delivery

All the data obtained (soft tissue scan, provisional prosthesis scan, and PIC file) were sent to the laboratory, where best-fit alignment of the 3 files was used to fabricate the definitive prosthesis. Before milling the final prosthesis, a plastic test model was delivered to check fit, esthetics, vertical dimensions, and occlusion. At this stage, if any modifications are needed, these can be made by rescanning the plastic test model in position in the mouth. When the plastic test model had been checked and approved, the laboratory fabricated the final metal-ceramic prosthesis. The entire digital work flow is detailed in Figure 10.

Figure 10.

Diagram illustrating the entire work flow, step-by-step.

Figure 10.

Diagram illustrating the entire work flow, step-by-step.

Close modal

Step 8. Recalls and Follow-Up

The patient was recalled every 6 months after delivery of the definitive restoration for clinical and radiographic examination, and during the 24-month follow-up, no mechanical or biological complications occurred (Figures 11 through 13).

Figures 11–13.

Figure 11. Intraoral front view of definitive prosthesis 2 y after placement.

Figure 12. Extraoral image of patient with definitive prosthesis.

Figure 13. Panoramic radiograph after 2-y follow-up.

Figures 11–13.

Figure 11. Intraoral front view of definitive prosthesis 2 y after placement.

Figure 12. Extraoral image of patient with definitive prosthesis.

Figure 13. Panoramic radiograph after 2-y follow-up.

Close modal

Immediate loading is defined as prosthesis placement simultaneous to insertion of the supporting implants or within a short interval. This interval can vary between 48 hours and 7 days.13,14  Immediate loading has grown in popularity in recent years, as it shortens the duration of edentulism and so its psychological impact.15,16  Immediate complete implant supported screw-retained restorations achieve a high rate of implant survival.17  Nevertheless, the technique presents certain difficulties and so requires training and correct treatment planning.16,18 

In this context, photogrammetry offers a digital option for implant impression taking as an alternative to conventional techniques. It captures the position and inclinations of multiple implants in 3 dimensions precisely, storing data as a digital file. This eliminates the cumbersome procedures involved in conventional impression taking and in fitting provisional prostheses in the patient's mouth.1921  However, it does not allow the registration of soft tissues and implants simultaneously.22  In the vast majority of previous case reports, preliminary soft tissue impression taking, as well as antagonist arch impression taking, have been performed with irreversible hydrocolloid.2,12,2023  Subsequently, the plaster models were scanned with a laboratory scanner. But in the present case report, these impressions were obtained by intraoral scanning, allowing a fully digital work flow. Another factor that contributed to the completely digital work flow was intraoral scanning of the patient's previous removable prosthesis to design the surgical splint and the immediate provisional prosthesis; this could be done only thanks to the existence of an adequate previous removable prosthesis. All previous case reports have described the use of a wax try-in.20,21 

Accurate impression taking is of paramount importance, especially in full arch restorations with immediate loading, as any error can delay or even prevent delivery of the prosthesis. In this context, the accuracy of IOSs for full-arch implant restoration remains debatable.24,25  But photogrammetry offers the accuracy needed for this type of case and also enjoys some important advantages in situations of recent surgery, where the presence of blood, sutures, and so on make it difficult to perform conventional impression taking or intraoral scanning. Moreover, when it is not possible to screw all the flags at the same time because of space limitations, it is possible to take several different images from different angles.

The photogrammetry technique for impression taking takes only a short time, and, once the flags are screwed in place (also a fast and simple procedure), it is just a matter of taking a few extraoral photos with the PIC camera. Regarding the economic cost, the equipment can be hired, so there is no need to invest in all the technology involved.

Accordingly, a pilot randomized clinical trial published by Peñarrocha-Diago et al23  reported shorter working times and greater patient and dentist satisfaction in the photogrammetry impression group in comparison with the traditional impression group. However, no statistically significant differences in implant success rate, implant survival, marginal bone loss, or prosthetic survival were found.23 

Systematic reviews of the accuracy of IOSs for dental implants have observed adequate results in cases of partial edentulism but have not reached firm conclusion in cases of complete edentulism.2426  Nonetheless, recent in vitro and in vivo studies suggest that IOSs may also be viable in these cases.2730  This reflects the technical improvements to IOSs over the years, as less recent studies found that IOSs were not a valid option,31,32  partly due to an accumulation of error caused by a lack of anatomical references for linking images. Various solutions have been proposed to overcome the lack of intraoral features available for overlapping images in cases of complete edentation: splinting scan bodies,24  adding landmarks to the residual ridge,33  or using scan bodies with elongated extensions.34  However, IOSs need further improvement so that digital impressions may be used with confidence in all cases requiring implant-supported prostheses.

The present case report describes a fully digital protocol for full-arch implant–supported restoration, from immediate loading to the final prosthesis, by means of photogrammetry and intraoral scanning. Within the limitations of this clinical case report, the photogrammetry technique was found to be a successful digital alternative for immediate prosthetic loading. The technique achieved adequate esthetic and functional outcomes and offered several advantages, including shorter working times in both clinic and laboratory. For the final prosthesis, only 1 additional intraoral soft tissue scan and a scan of the immediate provisional's teeth were needed, as the patient was satisfied with the position and size of these teeth. During a 24-month follow-up period, the maxillary full mouth restoration suffered no mechanical or biological complications.

Abbreviations

Abbreviations
CAD/CAM:

computer-aided design/computer-aided manufacturing

IOS:

intraoral scanner

ISQ:

implant stability quotient

PIC:

position implants correctly

POM:

polyoxymethylene

STL:

standard tessellation language

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Note The authors declare no conflicts of interest.