Diagnosing and planning an implant-retained provisional bridge using a fully digital workflow — a case study

Dr. Anthony Mak illustrates how digital dentistry helps him simplify clinical protocols, increase accuracy over conventional analog techniques, and improve his patient’s comfort

Introduction

Advances in digital technologies are providing today’s clinicians with the tools to eliminate challenges associated with conventional analog techniques in the diagnosis, treatment planning, placement, and restoration of dental implants.

In the case that follows, Dr. Anthony Mak uses the 3Shape TRIOS^® intraoral scanner, BioHorizons^® Digital Library, 3Shape Implant Studio™ software, and a CBCT scan from Instrumentarium Maxio OP.

His clinical case with 3Shape demonstrates the digital workflow he uses for the provision of implant-retained restorations. The case highlights the many benefits of digital workflows. Dr. Mak provides commentary and tips throughout the case.

Digital workflow

Dr. Mak’s case illustrates key advantages of fully digital workflows:

1. A reduction in the number of patient visits for the procedure
2. A simplified and predictable workflow in implant treatment planning and guided surgery
3. Better angulation and accuracy of placement of single and multiple implants
4. A simpler and easier prosthetic design process

Digital workflows enable professionals to combine both surface and CBCT scan data in software to virtually plan implant positions as well as design and fabricate surgical implant guides. When compared with free-hand surgery, computer-generated surgical guides significantly reduce the chances for positional errors at the time of implant placement.¹

Because the implant procedure in this case is first planned in software (3Shape Implant Studio) using combined intraoral and CBCT scan data, Dr. Mak can accurately assess bone volume, bone density, and the restorative space. This, in turn, enables him to plan implant placement and identify and avoid critical anatomical landmarks, such as nerves, sinuses, and adjacent teeth, by setting up safety zones in the software.

Digital workflows also eliminate the potential for distortion of conventional impression material and inaccuracies of subsequent steps in the manufacturing process, and the potential of damage to the dental cast and treatment delay, due to logistics of sending lab work between the dental practice and the laboratory — a digital impression is simply cloud-sent, shortening the time needed to manufacture the wax-ups and prosthesis. Digitally designed and fabricated provisional restorations can be manufactured before or immediately post-surgical procedure for immediate temporization.

The patient’s comfort is enhanced. A digital workflow can mean less time in the chair and the elimination of patient discomfort commonly associated with the conventional impression procedure.

Case information

A patient in his early 80s presented with the chief complaint of recurrent pain, discomfort, and swelling from his lower dentition. An examination revealed moderate-to-advanced bone loss of his remaining mandibular teeth. Periapical radiolucencies associated with chronic apical periodontitis were also diagnosed on the lower anterior segment. His lower dentition at the time of presentation was restored with a fixed crown and bridge prosthesis with implant fixtures on the 37 and 47 site, placed 20 years prior. The implant fixtures were abutments for fixed bridges that were linked to natural teeth abutments.

The patient requested for his lower dentition to be rehabilitated with the use of dental implants due his good perception of longevity stemming from his past treatment experience. It was the patient’s brief and request that the procedure be simple and not time-consuming due to several factors. These factors included:

1. His struggle to keep his mouth open for long periods of time
2. Difficulty in tolerating conventional impression techniques
3. His perceived age and health status

Treatment description

Appointment 1 — consultation and treatment planning

The patient’s failing lower dentition was heavily restored with metal ceramic crowns on the anterior segment and implant-to-teeth bridge on the posterior segment.

The teeth were virtually extracted using 3Shape Implant Studio software, leaving behind the 47 and 37 implant prosthesis. These crowns will act as reference points — stability anchors for the implant surgical guide. By maintaining the distal abutment implant prosthesis, we will also maintain the occlusion and vertical dimension of occlusion (VDO).

Then a 3D-printed surgical guide was designed using 3Shape Implant Studio. We used the distal abutment teeth and a guide pin in the anterior mandible to create trapezoidal stability of the surgical guide in the mouth during surgery. Stability of the guide is extremely important in immediate extraction of full-arch cases.

Placing the guide pin/osteotomy in immediate extraction cases can sometimes be less accurate as the guide can rock on the soft tissue area where the extractions just took place. To avoid this, a simple 3D-guide was designed to place the guide pin/osteotomy when the teeth were still present. Hence, once the teeth were extracted, the implant surgical guide was easily referenced and fitted without any loss of accuracy, using the distal implant prosthesis and the anterior guide pin/osteotomy that was already placed with the first guide-pin 3D guide. This is easily achieved with 3Shape Implant Studio.

The problem with immediate extractions and guided surgery is that there are no reference points for the surgical guide to sit after the extractions. Using soft tissue and opposing occlusions is less than ideal and not as accurate as it should be. The beauty of having a guide-pin surgical guide is that we were able to place the guide pin/osteotomy prior to extraction of the teeth. Hence, this guide was using the hard tissue of the existing teeth prior to extractions occurring. Having the guide holes, we were able to accurately locate our second implant surgical guide once all the extractions and full clearance had occurred.

Appointment 2 — surgical appointment

Immediately after surgery, BioHorizons^® snap-on digital markers were placed. A 3Shape IOS scan was also performed immediately after surgery and soft tissue closure had taken place. I find this option more accurate than planning the prosthesis at the same time as implant planning. There are tolerances that may affect passive fit in multiple implant cases.

The laboratory component — Bradley Grobler Oral Dynamics

Superimposing the preoperative scan for fabrication of the temporary bridge allows an exact copy of what the patient had prior to extractions. With the ability of the previous picture where we were able to scan the occlusion, the digital workflow allows for an effortless prosthetic portion of the whole treatment process.

Bradley Grobler Oral Dynamics was directed to design and mill an immediate temporary bridge on non-engaging temporary cylinders. PMMA (Kulzer) framework was designed with pink composite and stains.

Virtual articulation in 3Shape Dental Design software ensures that there are no lateral or excursive interferences.

The wonders of digital implant dentistry! With good planning and use of technology, we were able to achieve a direct-to-fixture prosthesis. No multi-unit abutments were required to achieve perfect prosthetic screw-access channels.

Appointment 3 — fitting the temporary prosthesis

Guided surgery allows for a much more minimally invasive approach leading to much better healing and better morbidity for the patient.

Final result

Start-to-finish the case took three appointments.