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Improving Accuracy, Efficiency and Cost-Effectiveness with Digital Implant Impressions

Siamak Abai, DDS, MMedSc
Timothy F. Kosinski, DDS, MAGD
Paresh B. Patel, DDS

by Siamak Abai, DDS, MMedSc;

Timothy F. Kosinski, DDS, MAGD;

and Paresh B. Patel, DDS

Practitioners have much to gain from using an intraoral scanner to capture the final impression for implant restorations. Intraoral scanners are highly accurate and eliminate the need to send physical impressions to the lab, providing the patient with a better-fitting crown in less time. Besides saving costs on shipping, it isn’t necessary to purchase impression materials, trays and adhesives. There is no potential for “pulling” of the impression material, and voids, tears and other distortions are avoided. Further, at Glidewell Laboratories, restorations produced from digital impressions are offered at significantly reduced fees. And because the digital impression is submitted electronically with the push of a button, the design of the restoration can begin immediately, decreasing the in-lab working time.

Digital impressions represent cutting-edge technology that allows dentists to create a virtual, computer-generated replica of the hard and soft tissues. In addition to being more efficient than traditional impressions, the restorative workflow initiated by an intraoral scanner leaves less room for error because, already in a digital format, the case proceeds directly to CAD/CAM design and fabrication, without the intermediary steps and time required to pour and scan stone models. This results in a more accurate fit for the CAD/CAM-produced restoration.1-3 The high degree of precision minimizes the need for chairside adjustments and can thus reduce the time it takes to deliver the final restoration.

The digital technology captures clear, highly detailed impression data in minutes, without the need for traditional elastomeric materials, which some patients — especially those with a sensitive gag reflex — find inconvenient and messy. In addition to the increased comfort, patients are often pleased to see that their dentist is working with the latest, most efficient technology.

To create a digital impression, a scanning abutment, which is the digital version of a traditional transfer coping, is connected to the implant. The practitioner then performs a series of intraoral scans, including the area of treatment, opposing dentition and bite. The intraoral scanner records the topographical characteristics of the patient’s oral anatomy, including the contours of the edentulous space, adjacent and opposing dentition, and surrounding soft tissue. After completing the scans, the clinician need only verify the digital impression, enter the patient’s information, and fill out the online Rx, indicating the implant system, size and desired restoration.

The lab receives the impression as a virtual model upon which the restoration can be digitally designed, avoiding the inaccuracies that can occur as the dental stone used to fabricate traditional casts expands. Because the digital impression produces a direct representation of the mouth, without the potential for distortion, the lab is able to create custom abutments and implant-retained restorations with ideal contours, interproximal contacts and occlusion.

The following three cases will demonstrate how, whatever the practitioner’s preferred intraoral scanner, digital impressions offer an efficient, highly accurate and cost-effective means of providing patients with CAD/CAM-produced implant restorations.

Case 1: TRIOS®

Clinical Dentistry by Siamak Abai, DDS, MMedSc

A male patient in generally good dental health presented with an edentulous space in the area of tooth #30. A treatment plan for a single-implant restoration was accepted by the patient, and at the next appointment, a 5.0 mm x 11.5 mm Hahn™ Tapered Implant was placed. Three months later, the patient returned for evaluation, and favorable soft-tissue health and implant integration were observed. The final impression was taken with a TRIOS® intraoral scanner (3Shape North America; Warren, N.J.), which created a highly accurate rendition of the implant site, surrounding dentition and gingival contours.

After verifying the digital impression generated by the scans, a digital Rx was completed and the case was submitted to the lab. Because the implant angulation was favorable, a screw-retained crown was selected for the final restoration. The final monolithic restoration was designed directly on the virtual model generated by the intraoral scanner, resulting in a faster turnaround time.

At the final delivery appointment, the BruxZir® Full-Strength Solid Zirconia crown was seated without the need for any adjustments. The prosthetic screw was tightened and the access channel was sealed with composite, completing a predictable, esthetic restoration for the patient, who was pleased with the efficiency and convenience of the digital restoration process.

Case 2: 3M™ True Definition

Clinical Dentistry by Timothy F. Kosinski, DDS, MAGD

A 64-year-old male presented for restorative treatment six months after having his first and second molars extracted and the socket sites grafted. Radiographic and intraoral evaluation indicated ample vertical bone and a fairly wide edentulous ridge with adequate attached gingiva on the facial aspect. The patient agreed to have the edentulous span in the area of tooth #18 and #19 replaced with dental implants.

At the surgical appointment, two 4.3-mm-diameter Hahn Tapered Implants were placed following the standard protocol. Healing abutments were connected to the implants.

After approximately three months of integration, the healing abutments were removed, exposing healthy tissue cuffs. Scanning abutments were threaded into the conical internal hex prosthetic connection of the Hahn Tapered Implant. A digital impression was easily and accurately made using a 3M™ True Definition intraoral scanner (3M™ ESPE™; St. Paul, Minn.), precisely capturing the oral and dental anatomy surrounding the two edentulous spaces. After confirming accuracy, the scan was approved and the prescription submitted for fabrication of custom abutments and implant-retained crowns.

The custom abutments were designed to align precisely with the gingival margins, support the soft tissue, and establish ideal emergence profiles for the final crowns. After seating the custom abutments without complication, the prosthetic screws were tightened. The final BruxZir Full-Strength crowns were cemented over the abutments, the occlusion was verified, and final radiographs were made. The efficient, highly accurate workflow used in this case resulted in superb function and emergence profile esthetics for the final restorations.

Case 3: iTero®

Clinical Dentistry by Paresh B. Patel, DDS

A female patient in her early 20s presented for initial consultation with a congenitally missing maxillary lateral incisor. The initial patient examination, including measurements of bone volume with ridge calipers, determined that, although the ridge was thin, there was sufficient facial-palatal bone volume and mesial-distal space to accommodate a 3.0 mm Hahn Tapered Implant, which excels at fitting within tight anatomical spaces. This implant would also prove advantageous because it could be restored using a custom zirconia hybrid abutment, which was important considering the restoration’s location in the esthetic zone.

The patient agreed to the treatment plan and returned for the implant placement appointment. After placing the Hahn Tapered Implant to depth, a cover screw was inserted and the implant site sutured.

After healing for 17 weeks, the patient returned for final impressions. An intraoral scanner was used in order to provide the patient with a highly accurate implant crown in as little time as possible. The final digital impression was taken with the iTero® intraoral scanner (Align Technology, Inc.; San Jose, Calif.) and submitted to the lab along with the parameters for the restoration, without the need for physical paperwork or shipping.

An intraoral scanner was used ... to provide the patient with a highly accurate implant crown in as little time as possible.

Using the virtual model generated by the digital impression, an Inclusive® Custom Abutment was designed with CAD software to optimize the emergence profile and esthetics of the BruxZir Anterior restoration. At the final restoration appointment, the custom abutment and implant crown were seated and established the desired form, function and esthetics without the need for any chairside modifications.

Conclusion

Intraoral scanners streamline the restorative process by producing a highly accurate final impression that can be immediately used by the lab to design and fabricate custom abutments and monolithic implant crowns. Note that, in addition to the scanners utilized above, dental CAD software is compatible with any system that can produce impressions in the standardized STL file format, allowing virtually any clinician with an intraoral scanner to take advantage of digital implant restorations. No matter the clinician’s system of choice, digital impressions reduce the cost of the restoration, result in a precise fit, and minimize the time the patient spends without a tooth.

References

  1. Su TS, Sun J. Comparison of marginal and internal fit of 3-unit ceramic fixed dental prostheses made with either a conventional or digital impression. J Prosthet Dent. 2016 Sep;116(3):362-7.
  2. Zarauz C, Valverde A, Martinez-Rus F, Hassan B, Pradies G. Clinical evaluation comparing the fit of all-ceramic crowns obtained from silicone and digital intraoral impressions. Clin Oral Investig. 2016 May;20(4):799-806.
  3. Ahrberg D, Lauer HC, Ahrberg M, Weigl P. Evaluation of fit and efficiency of CAD/CAM fabricated all-ceramic restorations based on direct and indirect digitalization: a double-blinded, randomized clinical trial. Clin Oral Investig. 2016 Mar;20(2):291-300.
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