|DENTAL SCIENCE - REVIEW ARTICLE
|Year : 2015 | Volume
| Issue : 5 | Page : 213-215
A Paradigm shift in the concept for making dental impressions
Sanjna Nayar, R Mahadevan
Department of Prsothodontics, Sree Balaji Dental College and Hospital, Chennai, Tamil Nadu, India
|Date of Submission||31-Oct-2014|
|Date of Decision||31-Oct-2014|
|Date of Acceptance||09-Nov-2014|
|Date of Web Publication||30-Apr-2015|
Dr. Sanjna Nayar
Department of Prsothodontics, Sree Balaji Dental College and Hospital, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Digital dental impression is a revolutionary technological advancement that so surpasses the accuracy and efficiency of former techniques for obtaining replicas of prepared teeth for the purpose of fabricating restorations that its adoption by dentists is rapidly eclipsing the use of elastomeric impression materials. The ultimate goals of dentists dedicated to quality restorative dentistry are to make their treatment of patients as accurate, stressless, and efficient as possible. By elimination of the everyday problems described above, there is no question that the significant advantages of digital impressions will make intraoral digital scanning standard procedure in most dental offices within the next several years. Furthermore, digital impressions have proven to reduce remakes and returns, as well as increase overall efficiency. The patient also benefits by being provided a far more positive experience. Finally, through the use of digital impression making, it has been determined that laboratory products become more consistent and require less chair time at insertion.
Keywords: Digital impressions, impression, optical impressions
|How to cite this article:|
Nayar S, Mahadevan R. A Paradigm shift in the concept for making dental impressions. J Pharm Bioall Sci 2015;7, Suppl S1:213-5
Ever since the introduction of the first digital scanner for making dental impressions in the 1980s, development engineers at a number of companies have enhanced the technologies and created in-office scanners that are increasingly user-friendly and produce precisely fitting dental restorations. These systems are capable of capturing three-dimensional virtual images of tooth preparations from which restorations may be directly fabricated or can be used to create accurate master models for the restorations in a dental laboratory. The use of these products presents a paradigm shift in the way dental impressions are made. Several of the leading three-dimensional dental digital scanning systems are presented and discussed in this article.
The acquisition of an accurate negative copy of the prepared tooth or teeth and of the adjacent and opposing teeth, are the ultimate goals of the impression process in restorative dentistry.
Many dentists are reluctant to become involved with newer technologies in impression making. The computer-aided design/computer-aided manufacture dental systems that are currently available are able to feed data obtained from accurate digital scans of teeth directly into milling systems capable of carving restorations out of ceramic or composite resin blocks without the need for a physical replica of the prepared, adjacent, and opposing teeth. 
This article outlines the features of two dedicated three-dimensional impression digital scanners that have been gaining in popularity in this emergent field of technology.
| Dedicated Impression Scanners|| |
Dedicated three-dimensional digital dental impression scanners eliminate several time-consuming steps in the dental office, including tray selection, dispensing and setting of materials, disinfection, and shipment of impressions to the laboratory. In addition, the laboratory saves time by not having to pour base and pin models, cut and trim dies, or articulate casts. 
With these systems, the final restorations are produced in the laboratory, but they are fabricated on models created from the data in the digital scans, as opposed to gypsum models made from physical impressions. Patient comfort, treatment acceptance, and education are added benefits. Digital scans can be stored on computer hard drives indefinitely, whereas conventional models, which may chip or break, must be stored physically, which often requires extra space in the dental office. 
| iTero|| |
In early 2007, the Cadent iTero (Cadent, Carlstadt, NJ, USA) digital impression system came into the market. The iTero system uses parallel confocal imaging to quickly capture the digital impression. Parallel confocal imaging uses laser and optical scanning to digitally capture the surface and contours of the tooth and gum structure. The Cadent iTero scanner (Cadent, Carlstadt, NJ) captures 100,000 points of red laser light and has perfect focus images of more than 300 focal depths of the tooth structure. All of these focal depth images are spaced approximately 50 μm apart.
Parallel confocal scanning with the iTero system captures all structures and materials found in the mouth without the need for scanning powders that coat the teeth.
While the ability of the iTero camera to scan without the need for powdering may be advantageous, it necessitates the inclusion of a color wheel into the acquisition unit itself, resulting in a camera with a larger scanner head than the other systems being discussed in this article.
The electronic laboratory script is complete with patient information, delivery date, restoration type, material choice, shade requirements, and any other information particular to the case. The laboratory script initiates the scan process and the visual as well as audible prompts that guide the clinician throughout the digital impression.
Once the teeth have been prepared, capturing the digital impression follows a consistent series of steps for every impression. Soft tissue management, retraction, moisture control, and hemostasis are essential in capturing digital data. Once tissue management has been confirmed, the operator is guided through a consistent series of scanning steps. This will include five scans of the prepared area: Occlusal, lingual, buccal, and interproximal contacts of the adjacent teeth. Once these scans are obtained, buccal and lingual 45°-angle views of the remaining teeth in the quadrant or arch and opposing arch are obtained.
When these scans (at least 21) are complete, the patient is asked to close into centric occlusion, and a virtual registration is scanned. Overall, complete upper and lower quadrant scans and the virtual bite registration can take < 3 min time, which is less than conventional impressions and bite registration.
Once the digital impression has been completed, the clinician can select from a series of diagnostic tools to evaluate the preparation and complete the impression. The occlusal reduction tool shows in vivid color how much clearance has been created in the preparation for the restoration selected by the clinician. A margin line tool is available to assist in viewing the clearly defined margin. Once the clinician has completely evaluated all aspects of the digital impression, adjustments, if any, are made at that time and a few additional scans will register the changes that were made to the prepared tooth. 
The completed digital impression is sent via a HIPAA-compliant wireless system to the Cadent facility and the dental laboratory. Upon review by the laboratory, the digital file is outputted to a model by Cadent. The model is milled from a proprietary blended resin and is pinned, trimmed, and articulated based on the digital impression created by the clinician. Cadent uses industrial 5-axis milling machines to ensure the precision of the milled models and dies.
Cadent models are unique in that one model is used for both the working model and the soft tissue model. By producing the ditching of the dies virtually, the dies and model are precisely created and eliminate the inaccuracies of hand trimming. The final restoration is then fabricated at the laboratory as specified by the digital prescription. 
| Lava Chairside Oral Scanner|| |
The Lava™ Chairside Oral Scanner (C.O.S.) was created at Brontes Technologies in Lexington, Massachusetts, and was acquired by 3M ESPE (St. Paul, MN, USA) in October 2006. The product was officially launched in February 2008.
The Lava C.O.S. system consists of a mobile cart containing a CPU, a touch screen display, and a scanning wand, which has a 13.2-mm wide tip and weighs 14 ounces. The camera at the tip of the wand contains 192 light emitting diodes (LEDs) and 22 lens systems.
The method used for capturing three-dimensional impressions involves active Wavefront Sampling. The Lava C.O.S. concept of "three-dimensional in motion" incorporates revolutionary optical design, image processing algorithms, and real-time model reconstruction to capture three-dimensional data in a video sequence and model the data in real-time. The scanning wand contains a complex optical system comprised of multiple lenses and blue LED cells. Thus, the Lava C.O.S. is able to capture approximately 20 three-dimensional data sets per second, or close to 2,400 data sets per arch, for an accurate and high-speed scan.
After the preparation of the tooth and gingival retraction, the entire arch is dried and lightly dusted with powder. The Lava C.O.S. only requires enough powdering to allow the scanner to locate reference points, not heavy powdering as with the CEREC. During the scan, a pulsating blue light emanates from the wand head as an on-screen image of the teeth appears instantaneously.
The dentist guides the wand over the occlusal surfaces, rotates the wand so that the buccal surfaces are scanned, then rotates again to capture the lingual surfaces. The "stripe scanning" is completed once the dentist returns to scanning the occlusal of the starting tooth.
After scanning the tooth preparation, the dentist is able to rotate and magnify the view on the screen, and can also switch from the three-dimensional image to a two-dimensional view of the exact images captured by the camera during the scan. The third option allows the dentist to view these images while wearing three-dimensional glasses.
Once the dentist confirms that all of the necessary details were captured on the scan of the preparation, a quick scan of the rest of the arch is obtained. If there are holes in the scan in areas where data is critical, the dentist simply scans that specific area and the software patches the hole.
The patient is then instructed to close into the maximum intercuspal position, the buccal surfaces on one side of the mouth are powdered, and a scan of the occluding teeth is captured. The maxillary and mandibular scans are then digitally articulated on the screen.
When all of the scans have been reviewed for accuracy, the dentist fills out an on-screen laboratory prescription. The data are wirelessly sent to the laboratory technician, who then uses customized software to digitally cut the die and mark the margin. 3M ESPE receives the digital file where it is virtually ditched, and the data is seamlessly articulated with the operative, opposing, and bite scans.
At the model manufacturing facility, a stereolithography (SLA) model is generated and sent to the laboratory. Despite the name of the system, it is not dedicated only to the creation of Lava crowns and bridges, as all types of finish lines may be reproduced on the SLA dies, allowing for any type of crown to be manufactured by the dental laboratory.
| Conclusion|| |
By elimination of the everyday problems described above, there is no question that the significant advantages of digital impressions will make intraoral digital scanning standard procedure in most dental offices within the next several years. Furthermore, digital impressions have proven to reduce remakes and returns, as well as increase overall efficiency. The patient also benefits by being provided a far more positive experience. Finally, through the use of digital impression making, it has been determined that laboratory products become more consistent and require less chair time at insertion.
Since well before the industrial revolution, man has manufactured millions of products through hand crafting analog processes. Over the last 30 years, much of this has been converted to digital because of product consistency and cost. It is no wonder that digital solutions are now being integrated into many dental procedures.
| References|| |
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Cadent debuts "next generation" iTero digital impression system. Implant Tribune, US edition. 2007;1:14.