ental learning - continuing education for the dental … skramstad updated.pdf · 2016-01-04 ·...

The Clinical Application of

CAD/CAM Technology and Materials

Knowledge for Clinical Practice

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DENTAL LEARNING

Michael Skramstad, DDS

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August 2015

The Clinical Application of CAD/CAM Technology and Materials

EDUCATIONAL OBJECTIVES

The overall goal of this article is to provide the reader with informa-tion about the use of CAD/CAM technology and materials for the fabrication of defi nitive restorations. After reading this article, the reader will be able to:1. Delineate the main differences between digital impressions and

traditional techniques;2. List and describe the various CAD/CAM materials and their uses;3. Review the treatment of restorative surfaces and luting agent

options; and4. Describe the chairside steps required to deliver an indirect, resin

nano-ceramic, same-day restoration.

Restoring indirect restorations using digital impres-sions and CAD/CAM technology is a topic that has created a tremendous amount of interest in both the dental offi ce and the dental laboratory. CAD/CAM technology has evolved into several systems that can be used for the fabrication of indirect restorations, together with the development of several restorative materials. The properties of these restorative materi-als and their indications and appropriate use must be understood in order to enable the achievement of predictable and esthetic results for patients.

ABOUT THE AUTHOR

Michael Skramstad, DDS, graduated from the University of Minnesota School of Dentistry in 2000. He currently is on the faculty in the CAD/CAM Department at the Scottsdale Center for Dentistry and a national website for continuing education in CEREC Dentistry. He is a basic and advanced trainer for Patterson Dental and has lectured internationally on digital dentistry. Dr. Skramstad is an Alpha/Beta tester for Sirona Dental Systems and a product consultant for multiple dental companies. Dr. Skramstad maintains a private practice in Orono, MN focusing on esthetic and CAD/CAM computerized dentistry. Dr. Skramstad can be reached at [email protected].

ABSTRACT

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SPONSOR/PROVIDER: This is a Dental Learning, LLC continuing education activity. COMMERCIAL SUPPORTER: This course has been made possible through an unrestricted educational grant from 3M ESPE. DESIGNATION STATEMENTS: Dental Learning, LLC is an ADA CERP recognized provider. ADA CERP is a service of the American Dental Association to assist dental professionals in identifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry. Dental Learning, LLC designates this activity for 2 CE credits. Dental Learning, LLC is also designated as an Approved PACE Program Provider by the Academy of General Dentistry. The formal continuing education programs of this program provider are accepted by AGD for Fellowship, Mastership, and membership maintenance credit. Approval does not imply acceptance by a state or provincial board of dentistry or AGD endorsement. The current term of approval extends from 2/1/2012 - 1/31/2020. Provider ID: # 346890. Dental Learning, LLC is a Dental Board of California CE provider. The California Provider number is RP5062. This course meets the Dental Board of California’s requirements for 2 units of continuing education. EDUCATIONAL METHODS: This course is a self-instructional journal and web activity. Information shared in this course is based on current information and evidence. REGISTRATION: The cost of this CE course is $29.00 for 2 CE credits. ORIGINAL RELEASE DATE: September, 2012. REVIEW DATE: August, 2015. EXPIRATION DATE: July, 2018. REQUIREMENTS FOR SUCCESSFUL COMPLETION: To obtain 2 CE credits for this educational activity, participants must pay the required fee, review the material, complete the course evaluation and obtain a score of at least 70%. AUTHENTICITY STATEMENT: The images in this course have not been altered. SCIENTIFIC INTEGRITY STATEMENT: Information shared in this continuing education activity is developed from clinical research and represents the most current information available from evidenced-based dentistry. KNOWN BENEFITS AND LIMITATIONS: Information in this continuing education activity is derived from data and information obtained from the reference section. EDUCATIONAL DISCLAIMER: Completing a single continuing education course does not provide enough information to result in the participant being an expert in the fi eld related to the course topic. It is a combination of many educational courses and clinical experience that allows the participant to develop skills and expertise. PROVIDER DISCLOSURE: Dental Learning does not have a leadership position or a commercial interest in any products that are mentioned in this article. No manufacturer or third party has had any input into the development of course content. CE PLANNER DISCLOSURE: The planner of this course, Casey Warner, does not have a leadership or commercial interest in any products or services discussed in this educational activity. She can be reached at [email protected]. TARGET AUDIENCE: This course was written for dentists, dental hygienists, and assistants, from novice to skilled. CANCELLATION/REFUND POLICY: Any participant who is not 100% satisfi ed with this course can request a full refund by contacting Dental Learning, LLC, in writing. Please direct all questions pertaining to Dental Learning, LLC or the administration of this course to [email protected]. Go Green, Go Online to www.dentallearning.net take your course. © 2015

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Introduction

CAD/CAM technology and materials are currently used in a number of clinical applications, includ-ing the fabrication of indirect restorations, occlusal

splints, and implant-related components.1,2 More recently, CAD/CAM has become available for the treatment plan-ning and execution of orthodontic treatment, and it is also possible for clinicians to measure and track the morphol-ogy of gingival tissues during treatment associated with different clinical disciplines.3,4 Indirect single-unit restora-tions are one of the most common procedures currently performed in the dental office. For many years, porcelain-fused-to-metal (PFM) and gold crowns were the materials of choice for the fabrication of indirect restorations for teeth with inadequate tooth structure remaining for direct restorations. In addition, porcelain-only single-unit restora-tions were fabricated in selected non-stress-bearing situa-tions due to their esthetic qualities relative to PFM crowns. In the last several years, a number of different material options have been introduced as alternatives to these more traditional materials, including some that have the ability to be milled in the office for indirect same-day restorations. Digital scanning and CAD/CAM fabrication of indirect single- and multi-unit restorations is a procedure performed with increasing frequency. Furthermore, more advanced adhesive luting cement systems have become available that enable reliable placement and retention of these restora-tions. This paradigm shift, involving both CAD/CAM technology and new materials, has changed the way both dentists and dental laboratories think about restoring teeth, and the use of CAD/CAM technology has increased.5 Many of these restorations not only make the dentistry more predictable, but offer great convenience to patients. Patients also are increasingly demanding all-ceramic restorations.6

Fabrication of Indirect Single-Unit Restorations Using Traditional Techniques

Traditional materials used for restoring a tooth indi-rectly include the use of cast metal crowns, metal-ceramic crowns with or without porcelain margins, and ceramic crowns. All these materials are used for the fabrication of

single-unit crowns using traditional techniques. First, the preparation must be made in accordance with the restor-ative material being used, and the adjacent soft tissue managed to prevent bleeding or fluid encroaching on the preparation and to expose any subgingival margins. For this purpose, one or more of the following may be used: retraction cord, lasers, hemostatic agents, electrosurgery, or one of the more recently introduced silicone polymer retraction materials. Gingival retraction cord was reported in one survey to be the most frequently-use method.7 Clini-cal preference, ease-of-use, the specific clinical case and fa-miliarity play a role in the selected method. The next step is to take an impression of the preparation as well as the adjacent and opposing teeth so that the die and models can be poured for laboratory fabrication of the crown. During this period, the patient is provided with a provisional res-toration for function and/or esthetics, as well as to protect the preparation and gingival margins, prevent sensitivity in a vital tooth, and maintain periodontal health and the position of the prepared tooth relative to the adjacent and opposing teeth.8-10 This traditional procedure is still the most prevalent method of restoring teeth with indirect restorations – it is what clinicians have been most familiar with and how they were taught in dental school. As such, there is no new learning curve for the clinician.

While generally reliable, this traditional approach involves some limitations, including the period of time it takes to fabricate the restorations (typically one to two weeks), the need for a provisional restoration, and the need for the patient to return for a second visit. Physical models are necessary to create the restoration and must be poured from the impression. However, the impression itself is a potential source of error, despite the availability of highly accurate and dimensionally stable impression mate-rials; some common errors include the inclusion of voids, marginal discrepancies, and minor tears. High-precision impression materials must be handled according to the manufacturers’ instructions, and the soft tissue at the clini-cal site appropriately managed, to help avoid such errors. Other factors that can result in inadequate impressions include how soon the model was poured, and the man-


3August 2015

ner in which the impression was stored and transported before pouring. This is especially important for alginate, which is typically the material of choice for the opposing (preparation-free) arch due to its ease-of-use and low cost. If left out to dry or transported without being wrapped in damp gauze or a damp towel, these impressions will shrink which causes dimensional errors in the model.11

Similarly, models may also include voids and other dimensional errors. These errors are related to the mixing, pouring and handling of the stone (or plaster) models. Mar-ginal discrepancies may not be evident until after the models have been poured or until the time of try-in of the restora-tion, resulting in additional time and costs. Digital photog-raphy and modern shade selection options and techniques have increased the ability of the clinician and the laboratory to communicate, and therefore to deliver a case with the desired esthetics. Nonetheless, this setup may still not be ideal for a given case. Well-executed indirect restorations fabricated using the traditional approach offer excellent fit, functionality, and esthetics.

CAD/CAM TechnologyCAD/CAM technology has been around long enough

that is not “new”; earlier versions of the technology have been available in dentistry for almost 30 years.12 It is now accepted as a viable, predictable, and efficient alternative

to traditional methods.13 As with the traditional approach, the preparation design must consider multiple factors, including the material that will be used to fabricate the indirect restoration and the required dimensions, as well as the amount of retention that will be achieved as a result of the preparation form. CAD/CAM technology has evolved into several versions using different devices and combi-nations of techniques: 1) taking the CAD/CAM scans chairside and transmitting these through a secure Internet portal to a standard laboratory or to a central location for fabrication of the indirect restoration in a milling machine; 2) taking the CAD/CAM scans chairside and sending these through a secure Internet portal to a central location for digital creation of the models, after which they are sent to a standard laboratory for traditional fabrication of the res-toration; and 3) taking the scan chairside and milling the indirect restoration chairside using CAD/CAM technology at the same visit (Figure 1).

When the clinician uses any of these devices and tech-niques, it is not necessary to take a traditional impression or to pour dies and models. This removes the risk of associ-ated errors and increases patient comfort. Both chairside milling and laboratory milling of restorations removes the possibility of abrading or damaging dies and models dur-ing their use for restoration fabrication – abraded models would result in restorations that were either too tight and

Figure 1. Chairside scanning and delivery

Chairside Scanning

Digital creation of models centrally and traditional laboratory

fabrication of the restoration

Chairside milling of the restoration

Delivery to the laboratory or central location for milling of

the restoration

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left insufficient space for the luting agent, or simply would not seat on the preparation. Of course, to avoid incurring errors when using CAD/CAM technology, the clinician must accurately take scans and follow procedures accord-ing to the instructions of the given manufacturer. All avail-able CAD/CAM devices involve the use of a handheld scan-ner, although each uses different technology to capture the images. Options for capturing images include continuous video streaming of the teeth, the acquisition of multiple still images that are then melded together with software, and the use of a laser that captures images by reflecting off the surface of the tooth or preparation. “Bite registration” and the determination of centric relation also differ by system.

For CAD/CAM restorations milled in a laboratory or central location, a provisional restoration is required as with the traditional impression technique (Table 1).

Provisionalization for Laboratory-Milled or Fabricated Indirect Restorations

Provisionalization materials include acrylic resins, pre-fabricated composite resin temporary crowns, and metal-based prefabricated temporary crowns. The use of acrylic resins allows the provisional restoration to be customized chairside. Desirable features of a provisional material are a setting reaction that does not produce heat (or produces minimal heat) and that avoids shrinkage of the material during setting, as well as being sufficiently durable to last until the definitive indirect restoration is ready for place-ment. Bis-acryl results in less heat production during the setting reaction than other acrylics, has low polymerization shrinkage and offers adequate durability for provisional restorations, although it is a more costly acrylic compared to polyethyl or polymethyl methacrylate.14 Prefabricated temporary crowns may be quicker to place, and still offer a smooth surface provided only minimal adjustments are required. On the other hand, they are only available in a number of shapes and sizes, require marginal adjustments, and may not be suitable for a given case. Recently, fillers have been added to bis-acryl to increase surface smooth-ness and gloss for provisional restorations. Scanning and chairside same-visit milling of the restoration is the only option that removes the need for a provisional restoration or for a second patient visit for try-in and placement of the restoration.

Preparation and CAD/CAM ScanningFor all systems, as with the traditional technique, the

preparation must be isolated and the soft tissue man-aged at the margins. The same techniques are used for soft tissue management as with the traditional approach. Depending on the system, a light and rapid dusting of an opaquing powder agent may be required prior to capturing the digital scans of the preparation arch, opposing arch, and buccal bite registration. Digital scanning and rapid transmission of the scans to the laboratory, and/or chair-side viewing of the scans, allows for immediate or almost immediate feedback on margins and clearance. If correc-tions are needed, it takes just minutes with the patient still

Table 1. Traditional and CAD/CAM procedures

Traditional Approach

CAD/CAM Laboratory Fabricated

Chairside Milling

Soft tissue management

Yes Yes Yes

Impression taking

Yes No No

Scanning No Yes Yes

Die and model pouring

Yes No No

Model milling No Yes/No No

Restoration milling

No Yes/No Yes

Provisional restoration

Yes Yes No

Second patient visit Yes Yes No


5August 2015

in the chair and anesthetized. This avoids having to bring the patient back for a second visit involving adjustments to the preparation or/and a second impression, or not discovering the error until the patient’s seat appointment when the restoration has already been fabricated and then causing additional laboratory costs to be incurred as well as causing patient disappointment.

Clinical ResultsSeveral studies have evaluated CAD/CAM restorations

and found that they have a marginal fit as good as or supe-rior to that of traditional impressions.15-16 A further benefit found with CAD/CAM restorations has been the reduced incidence of secondary caries (the leading cause of direct restoration failure with both amalgam and composite materials), attributed to the high accuracy of the approxi-mal fit and the ability to ascertain that this is accurate prior to completion of the restoration and cementation. In fact, the longevity of CAD/CAM restorations was reported by Mjör et al to be close to that of gold restorations.17 A recent review assessed the survival rates of single-tooth indirect restorations fabricated with CAD/CAM and found the long-term survival rate to be similar to indirect restora-tions fabricated using the traditional approach.18

CAD/CAM scanning and fabrication of indirect resto-rations has been proven in numerous studies and is now accepted as a viable, predictable alternative to traditional methods.19-20

As with all treatments, proper procedures and tech-niques must be followed to achieve clinically acceptable results. CAD/CAM technology also requires the use of specific materials that can be milled to fabricate durable and esthetic restorations.

CAD/CAM Restorative MaterialsThe movement toward CAD/CAM fabrication of

restorations has been directly responsible for a number of material innovations over the past few years. For quite some time, both leucite and feldspathic glass ceram-ics have been used for laboratory-based fabrication of ceramic restorations. These materials result in beautifully

esthetic restorations regardless of which method is used for their fabrication, particularly in the anterior region. However, their relatively low flexural and compressive strengths have limited their use in posterior stress-bearing areas. High-strength leucite also has been used as a block for CAD/CAM milled restorations. These materials must be adhesively resin-bonded to the preparation and can-not be placed using traditional luting cements. In recent years, we have seen the evolution of high-strength ceram-ics – lithium disilicate, alumina, and zirconia – that have allowed CAD/CAM dentistry to move into new territory. The advantages of these materials are twofold: they pos-sess very high compressive and flexural strength, and can be bonded or cemented. This has resulted in a very strong, predictable, and esthetic option for posterior ceramic dentistry. In a recent study, both alumina and zirconia crown copings fabricated using CAD/CAM were found to have clinically acceptable marginal adaptations.21 A sepa-rate study recently conducted on milled lithium disilicate crowns found these to be free of fractures, chipping, or other defects two years post-placement.22 For CAD/CAM restorations milled with these materials, in addition to the CAD/CAM device a porcelain furnace is required for crystallization of lithium disilicate, and a sintering oven for full-contour zirconia. In the case of lithium disilicate, this can add 15 to 30 minutes to the fabrication time, and with zirconia up to an additional 8 hours may be re-quired. It should be noted that high-speed sintering ovens for zirconia are now sintering these restorations in about 90 minutes and other options include semi-sintered zir-conia and fully-sintered zirconia. The advantage of using zirconia for milling and then sintering it is the increased strength following sintering and the relative ease of mill-ing prior to sintering.

Composite resin blocks are also available for CAD/CAM restorations. Another option is the use of a new resin nano-ceramic block that consists of ceramic clusters within a highly cross-linked resin matrix. The resulting block is homogenous, and the restoration can be CAD/CAM-milled chairside or in the laboratory. The wear resistance of this material is reported to be comparable to that of felspathic

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glass ceramic and lithium disilicate, and it has a compres-sive strength similar to high-strength ceramics. Unlike lithium disilicate and zirconia, no porcelain furnace or sin-tering oven is required, saving fabrication time. In fact, a recent study found that composite blocks (and experimen-tal composite blocks) were more resistant to fracture than reinforced ceramics when used for ultra-thin veneers.23 The use of nano-fillers and resin technology has improved the strength and esthetics of composite blocks. A 2006 study comparing resin nano-ceramic and zirconia used for CAD/CAM four-unit bridges found that the margins were most accurate and marginal gaps least using the resin nano-ceramic material.24

Placement and Retention of CAD/CAM Restorations

As noted above, some CAD/CAM restorative materi-als can be cemented with either traditional luting cements such as zinc phosphate, polycarboxylate cement, glass ionomers, or resin-modified glass ionomers. Materials that can be luted with these include zirconia, lithium disili-

cate, alumina, and resin nano-ceramics. The caveat for non-bonded materials is that the preparation form was sufficiently retentive in the first place. Resin-based bond-ing can be used for all CAD/CAM restorative materials, including those mentioned above (Table 2). Resin-based luting cements bond to the ceramic restorations, not only the tooth structure, and are now regarded by some clini-cians as the preferred luting agent for ceramic and other non-metal restorations. They offer excellent esthetics and retention of the restoration to the preparation.25 These luting cements utilize etching and bonding technology, and they bond by micromechanical locking of the cement to both the tooth and the restorative material. The resin-based luting cement itself may be dual-cured, self-cured, or light-cured – the latter is only suitable if the restoration is thin enough to enable the transmission of light for curing. A further requirement is roughening of the intaglio surface to increase the area available for bonding,26 with either hydrofluoric acid or sandblasting/air abrasion depending on the restorative material used. The intaglio surface of lithium disilicate restorations is treated with 5% hydroflu-oric acid for 20 seconds to etch and roughen that surface.27 The intaglio surfaces of feld spathic porcelain and leucite-contain ing restorations are also treated with hydrofluoric acid, with the time of etching depending on the material. Options for other materials are the use of sandblasting or treatment with a silica coating, with the method depending on the material – the restoration material manufacturer’s instructions must be followed and the correct treatment used. Irrespective of the luting agent and technique, the primary objectives are retention and sealing of the restora-tion-tooth interface.

CASE STUDIESWhen considering milling and delivering same-day

restorations, there are many options available. The two case studies below will concentrate on the use

of resin nano-ceramic blocks for the chairside fabrication of an inlay and a veneer. Case Study #2 involves the com-plication of an aligner with attachments that were on the fractured tooth to be veneered.

Table 2. Luting agents for indirect restoratives

Traditional Luting Cements

Alumina

Zirconia

Lithium disilicate

Composite

Resin-nano-ceramic

Adhesive Resin-Based Luting Cements

Alumina

Zirconia

Lithium disilicate

Composite

Resin-nano-ceramic

Feldspathic porcelain

High-strength leucite


7August 2015

Case Study #1A 17-year-old male presented for examination with no

chief complaint. Upon routine full-mouth examination and after bitewing radiographs were taken, carious lesions were found on the distal of tooth #12, the mesial and dis-tal of tooth #13, and the mesial and occlusal of tooth #14 (Figure 2).

A traditional way to restore these lesions would be to prepare class II preparations on tooth #12 and tooth #14 and mesial and distal one-surface restorations on tooth #13. It is always the goal to restore teeth in a minimally invasive fashion. When carious lesions are limited in size, it is ideal to restore conservatively with direct composite restorations. However, when carious lesions are more ex-tensive, this method can be complicated with large-cavity preparations28 by a number of factors that include opera-tory time, polymerization shrinkage, layering in proper thicknesses, and especially contours and contacts. There are many different band, matrix, and wedge combinations on the market that all promise to deliver ideal contours and contact; in this author’s experience, however, these methods rarely provide the predictability of indirect CAD/CAM restorations. After discussing the options with the patient, it was decided to restore these teeth indirectly with resin nano-ceramic CAD/CAM restorations. Prior to pre-paring the teeth, these teeth were isolated with a non-latex rubber dam and preoperative scans were taken (Figure 3). When these preoperative scans are taken, the software allows use of a design method called “biogeneric copy” (since the carious lesions did not compromise the natural shape and contour of the virgin teeth). It is quite advanta-geous for the fi nal restorations to be exact duplicates of what nature created, provided the contacts and contours are functionally ideal and esthetically pleasing.

After taking the initial images, all caries was removed and the preparations were fi nalized. Care was taken to avoid encroaching on the interproximal papillae during preparation, by placing small wooden wedges between the teeth. The preparations should be smooth and fl ow-ing, with no undercuts and with clear separation from the adjacent teeth. After removal of the wedges, a light dusting

Figure 2: Pretreatment view of teeth #12, 13, and 14

Figure 3: Pretreatment images of teeth #12, 13, and 14 (biogeneric copy)

Figure 4: Imaged and marginated preparations

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of the CAD/CAM powder (Optispray) was applied, and the preparations were captured by scanning to create the digital impressions (Figure 4). Figure 5 shows the prepara-tions that were scanned. Once the preparations were digi-tized and marginated, the software used the overlay of the preoperative condition (Figure 6) to create proposals that were an exact replicate of the patient’s virgin teeth (Figure 7). Furthermore, all interproximal contacts can be manipu-lated to the desired contact size and strength directly in the software with intuitive three-dimensional tools. This case demonstrates one of the advantages of chairside CAD/CAM fabrication of Class II restorations: by eliminating the need for bands and wedges, predictability for contacts and contours was realized.

After the inlay designs were fi nalized, the restorations were milled from resin nano-ceramic blocks with the mill-ing unit. Milling resin nano-ceramic material results in excellent marginal integrity; SEM images of restorations milled with these blocks show less marginal chipping than with traditional glass ceramics. When the milling of the restorations was complete, the inlays were steam-cleaned (to remove all milling oil) and the sprue was removed with coarse So-Flex discs. Initial extra-oral polishing was performed using coarse, medium, and fi ne rubber wheels. Since the restorations were quite small and therefore dif-fi cult to handle, fi nal polishing was completed intraorally Figure 6: Pretreatment images overlaid on top of prepara-

tions for “biocopy” design

Figure 7: Initial restoration proposal by the software Figure 8: Final resin-bonded resin nano-ceramic inlays

Figure 5: Isolation and preparation of teeth for indirect restorations (note residual powder mesially and distally post-scanning)


9August 2015

post-bonding. It should be noted that because this material does not need to be fired in a porcelain furnace, milling and polishing can be completed quite efficiently intra-orally or extra-orally. The restorations were next tried-in to ensure that their marginal fit and contours were correct.

To prepare for bonding of the inlays, the intaglio surface of the restorations was sandblasted with aluminum oxide at two bars (30psi), to increase the surface area available for bonding,29 and was then cleaned with alcohol. A universal adhesive agent was then applied to the intaglio surface for 20 seconds and air-dried for five seconds. The restorations were placed aside without curing the adhesive. Note also that using a universal adhesive that contains silane primer eliminates the need for a separate silanation step. To prepare the teeth for the restorations, the enamel was selectively etched with phosphoric acid for 15 seconds, rinsed, and dried. The same adhesive agent was agitated on the enamel for 20 seconds with two applications, and then air-dried for five seconds to evaporate the solvents. The resin-based luting cement was then placed into the inlay preparations (with no prior curing of the adhesive), and the restorations were all seated. Initial cleanup was performed with a gingi-val stimulator, and the remaining excess was tack-cured for one second with an LED light prior to being removed with a curved explorer. Removing excess cement when it is only tack-cured, and before it has set, helps retain the bond while the material is still not at full strength.30 The resin-based luting cement in the restorations was then light-cured for 20 seconds per surface. Finally, the resin-bonded nano-ceramic inlays were polished with diamond-impregnated composite cups and polishing paste. No adjustments to the occlusion were necessary, and the final restorations mimicked the contours of the original teeth extremely closely and offered excellent esthetics (Figure 8).

Case Study #2An 18-year-old male presented with a significant

fracture on tooth #8, sustained while playing basketball (Figure 9). An existing composite bonding was present on both the remaining tooth and the fractured fragment; the fracture did not involve the pulp. To significantly compli-

Figure 10: Fractured segment bonded back to tooth

Figure 9: Initial fracture of tooth #8 following trauma

Figure 11: Veneer preparation and isolation

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cate matters, the patient was midway through orthodontic treatment with an aligner, and tooth #8 had two attach-ments present: one still present on the tooth (cervical) and one that had fractured off with the incisal portion of the tooth. Under normal circumstances, restoring an anterior tooth with these aligner attachments is quite a daunting task; it is often necessary to have the orthodontist replace the attachments and review the patient’s orthodontic treatment plan. Using the tools available with CAD/CAM technology, however, it was possible to restore this tooth to its original shape without compromising the orthodon-tic treatment. The success rate for CAD/CAM fabricated veneers is high, with one study finding a high clinically ac-ceptable result up to nine years after placement and a 94% survival rate.31

Since the patient had found the fractured portion of the tooth, it was possible to etch and bond this back into position with a total-etch technique (Figure 10). Under some circumstances, rebonding the fragment is a good short-term solution for this situation. However, since this patient was leaving for college and had an esthetic concern with the tooth, it was decided to fabricate a CAD/CAM veneer. In this situation, temporarily bonding the fragment to the tooth in its natural position allowed positioning of the aligner attachments at the appropriate places. The patient’s current aligner was then tried-in to verify proper fit. Prior to preparing the tooth and after rebonding the fragment to the tooth, a preoperative scan was taken (after applying a light dusting of powder). As with Case Study #1, this scan served as a guide for the final restoration using biogeneric copy. The veneer preparation was then made and the tooth isolated with retraction cord (Figure 11). A digital impression of the preparation was taken, which showed the marginated veneer preparation clearly and accurately (Figure 12). The preoperative scan can also be overlaid on top of the preparation using this CAD/CAM technology, and can be copied on a 1:1 basis to obtain a proposed final restora-tion that exactly duplicates the existing tooth. Note how precisely the camera (scanner) captured the two aligner attachments with the preoperative scan (Figure 12) and

Figure 12a: Marginated veneer preparation and overlaying of pretreatment image

Figure 12b: Marginated veneer preparation and overlaying of pretreatment image

Figure 12c: Marginated veneer preparation and overlaying of pretreatment image


11August 2015

how the software reproduced them in the final initial proposal (Figure 13).

As discussed earlier, when choosing the appropriate material, one has to consider many factors. In this par-ticular situation a low-translucency resin nano-ceramic CAD/CAM block was selected because of the patient’s age, the flexibility of the material, its excellent polish-ability, the precise marginal edge quality, and the low translucency (which would prevent shine-through, help-ing to ensure an esthetic result). But the most important factor, considering that the patient would be using an aligner for the next year, was the material’s reparability.

After the restoration was milled, the initial polish was achieved using medium and fine diamond-impregnated rubber wheels. Care was taken to avoid over-polishing the surface of the restoration, which would affect the surface texture and aligner attachments. In order to facilitate natural shade transitions and provide an excel-lent match with the contralateral central incisor, the restoration was characterized with light-cured resin in several shades. To accomplish this, the external (non-bonding side) of the restoration was sandblasted with aluminum oxide at 30psi, cleaned with alcohol, and dried. As with Case Study #1, universal adhesive was

Figure 14: Final bonded restoration

Figure 15: Maxillary aligner seated into position perfectly

Figure 13a: Initial restoration proposal by the software, including aligner attachments

Figure 13b: Initial restoration proposal by the software, including aligner attachments

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applied to the surface, thinned appropriately, and light-cured. Several shades of resin were then applied to the surface of the restoration and light-cured to character-ize the restoration and match it as closely as possible to tooth #9. Final polishing of the restoration was achieved using a fine polishing paste on a #9 soft brush at low rpms (< 10,000 rpm), and a final buff was performed with a muslin rag wheel. Finally, the restoration was bonded using universal adhesive and a resin-based lut-ing cement. The final restoration exhibited contours almost identical to the original, pre-fracture contours, and the patient’s esthetic concerns were satisfied (Figure 14). Furthermore, the aligners snapped into place with no adjustments at all (Figure 15).

SummaryCAD/CAM technology has transformed the ways in

which clinicians can provide patients with functional, esthetic, and durable indirect restorations. CAD/CAM technology removes the risk of some errors and of-fers the opportunity to review restoration designs (and adjust them, if necessary) before they are completed. As the demand for CAD/CAM indirect restorations grow, more advanced materials have become available that can be resin-bonded to preparations with excellent results. The material of choice depends on the clinical situation, with consideration given to strength, esthetics, and ease of use.

References1. Lauren M, McIntyre F. Digital occlusal splints. Dent Today. 2008 Feb;27(2):150, 152,

154-5.2. Beuer F, Schweiger J, Edelhoff D. Digital dentistry: an overview of recent develop-

ments for CAD/CAM generated restorations. Br Dent J. 2008 May 10;204(9):505-11.3. Fukawa R. Lingual orthodontics in the new era treatment according to criteria for oc-

clusion and aesthetics. Int Orthod. 2009 Dec;7(4):370-402. 4. Ronay V, Sahrmann P, Bindl A, Attin T, Schmidlin PR. Current status and perspec-

tives of mucogingival soft tissue measurement methods. J Esthet Restor Dent. 2011 Jun;23(3):146-56.

5. Davidowitz G, Kotick PG. The use of CAD/CAM in dentistry. Dent Clin North Am. 2011 Jul;55(3):559-70.

6. Miyazaki T, Hotta Y. CAD/CAM systems available for the fabrication of crown and bridge restorations. Aust Dent J. 2011 Jun;56 Suppl 1:97-106.

7. Hansen PA, Tira DE, Barlow J. Current methods of finish-line exposure by practicing prosthodontists. J Prosthodont. 1999 Sep;8(3):163-70.

8. Burke FJ, Murray MC, Shortall AC. Trends in indirect dentistry: provisional restora-tions, more than just a temporary. Dent Update. 2005;32(8):443-52.

9. Wassell RW, St. George G, Ingledew RP, Steele JG. Crowns and other extracoronal restorations: provisional restorations. Brit Dent J. 2002;192(11):619-30.

10. Bral M. Periodontal considerations for provisional restorations. Dent Clin North Am. 1989;457-65.

11. Nassar U, Hussein B, Oko A, Carey JP, Flores-Mir C. Dimensional accuracy of 2 ir-reversible hydrocolloid alternative impression materials with immediate and delayed pouring. J Can Dent Assoc. 2012 Jan;78:c2.

12. Calamia JR. Advances in computer-aided design and computer-aided manufacture technology. Curr Opin Cosmet Dent. 1994:67-73.

13. Fasbinder DJ. Digital dentistry: innovation for restorative treatment. Compend Contin Educ Dent. 2010;31 Spec No 4:2-11.

14. Seelbach P, Finger WJ, Ferger P, Balkenhol M. Temperature rise on dentin caused by temporary crown and fixed partial denture materials: influencing factors. J Dent. 2010;38(12):964-73.

15. Sorensen JA, Sorensen PN, Mizuro K. Marginal fidelity of crowns made with optical versus conventional impressions. IADR Abstract #1599. April 2009.

16. Hirayama H, Chang YC. Fit of zirconia copings generated from a digital impres-sion technique and a conventional impression technique. Tufts University of Dental Medicine master’s thesis.

17. Mjör IA, Davis ME, Abu-Hanna A. CAD/CAM restorations and secondary caries: a literature review with illustrations. Dent Update. 2008 Mar;35(2):118-20.

18. Wittneben JG, Wright RF, Weber HP, Gallucci GO. A systematic review of the clinical per-formance of CAD/CAM single-tooth restorations. Int J Prosthodont. 2009;22:466-471.

19. Otto T, Schneider D. Long-term clinical results of chairside CEREC CAD/CAM inlays and onlays: a case series. Int J Prosthodont. 2008 Jan-Feb;21(1):53-9.

20. Estefan D, Dussetschleger F, Agosta C, Reich S. Scanning electron microscope evaluation of CEREC II and CEREC III inlays. Gen Dent. 2003:51(5):450-4.

21. Alghazzawi TF, Liu PR, Essig ME. The effect of different fabrication steps on the mar-ginal adaptation of two types of glass-infiltrated ceramic crown copings fabricated by CAD/CAM technology. J Prosthodont. 2012 Apr;21(3):167-72.

22. Fasbinder DJ, Dennison JB, Heys D, Neiva G. A clinical evaluation of chairside lithium disilicate CAD/CAM crowns:A two-year report J Am Dent Assoc 2010;141(6 suppl):10S-14S.

23. Schlichting LH, Maia HP, Baratieri LN, Magne P. Novel-design ultra-thin CAD/CAM composite resin and ceramic occlusal veneers for the treatment of severe dental erosion. J Prosthet Dent. 2011 Apr;105(4):217-26.

24. Piwowarczyk HC, Lauer C. Determining the marginal fit of CAD/CAM bridge frame-works. Pan Eur Fed Conf. 2006; Abstract #0254.

25. Haddad MF, Rocha EP, Assunção WG. Cementation of prosthetic restorations: from conventional cementation to dental bonding concept. J Craniofac Surg. 2011 May;22(3):952-8.

26. Tsuo Y, Yoshida K, Atsuda M. Effects of aluminablasting and adhesive prim-ers on bonding between resin luting agent and zirconia ceramics. Dent Mater. 2006;25(4):669-674.

27 Pisani-Proenca J, Erhardt MC, Valandro LF, et al. Influence of ceramic surface conditioning and resin cements on microtensile bond strength to a glass ceramic. J Prosthet Dent. 2006;96;412–7.

28. Puri S. Predictable preparation, staining, and cementation procedures for chairside CAD/CAM dentistry. Pract Proced Aesthet Dent. 2008 May;20(4):209-14.

29. Tsuo Y, Yoshida K, Atsuda M. Effects of aluminablasting and adhesive prim-ers on bonding between resin luting agent and zirconia ceramics. Dent Mater. 2006;25(4):669-674.

30. Kendzoir GM, Leinfelder KF. Characteristics of zinc phosphate cements mixed at sub-zero temperatures. J Dent Res. 1976;55(Special Issue B):B95, Abstract #134.

31. Wiedhahn K, Kerschbaum T, Fasbinder DF. Clinical long-term results with 617 CEREC veneers: a nine-year report. Int J Comput Dent. 2005;8:233-46.

WebliographyFasbinder DJ. Clinical performance of chairside CAD/CAM restorations. JADA 2006;137(9 supplement):22S–31S. Available at: http://jada.ada.org/content/137/suppl_1/22S.abstract?ijkey=24969cbaa0bb04f7453ddfdf45afb2725a09b127&keytype2=tf_ipsecshaGiordano R. Materials for chairside CAD/CAM–produced restorations. JADA 2006;137(9 supplement):14S–21S. Available at: http://jada.ada.org/content/137/suppl_1/14S.full.pdf+htmlHickel R, Manhart J. Longevity of restorations in posterior teeth and reasons for failure. J Adhes Dent. 2001 Spring;3(1):45-64. Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/11317384Trost L, Stines S, Burt L. Informed decisions about incorporating CEREC into a practice. JADA 2006;137(9 supplement):32S–36S. Available at: http://jada.ada.org/content/137/suppl_1/32S.full.pdf+htmlWittneben JG, Wright RF, Weber HP, Gallucci GO. A systematic review of the clinical performance of CAD/CAM single-tooth restorations. Int J Prosthodont. 2009 Sep-Oct;22(5):466-71. Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/20095195


13August 2015

1. CAD/CAM technology and materials have been used for __________. a. occlusal splintsb. the fabrication of indirect restorationsc. implant-related componentsd. all of the above

2. For many years, __________ were the materials of choice for the fabrication of indirect restorations. a. porcelain and gold crowns b. porcelain-fused-to-metal and gold crownsc. porcelain-fused-to-metal and titanium crownsd. resin and porcelain crowns

3. __________ have become available that enable reliable placement and retention of indirect restorations. a. Zinc oxide-eugenol cements b. Calcium hydroxide luting systemsc. Advanced adhesive luting cement systemsd. none of the above

4. Patients increasingly are demanding __________ restorations. a. gold b. all-ceramic c. resin-based d. none of the above

5. When preparations are made prior to taking impressions, the adjacent soft tissue must be managed to _________. a. prevent bleeding from encroaching on the preparationb. prevent fluid from encroaching on the preparationc. expose any subgingival margins d. all of the above

6. The most frequently-used method reported in one survey for soft tissue management was the use of __________. a. compound b. gingival retraction cord c. electrosurgeryd. all of the above

7. Well-executed indirect restorations offer excellent __________. a. fit and view b. esthetics and functionalityc. fit, esthetics, and functionality d. functionality and prevention

8. For traditional, laboratory-fabricated indirect restorations, a provisional restoration is provided for __________. a. easeb. esthetics, function, and the protection of the preparation and

gingival marginsc. the protection of the opposing archd. none of the above

9. __________ is a limitation of laboratory fabrication of indirect restorations. a. The need for a provisional restoration b. The need for the patient to return for a second visitc. The capital investment d. a and b

10. __________ is/are a source of errors in impressions. a. Marginal discrepancies b. Minor tearsc. The inclusion of voids d. all of the above

11. If a void is present in an impression, _________. a. the model must be adjustedb. extra impression material can be added in the laboratory c. extra luting agent may be usedd. none of the above

12. CAD/CAM technology requires that the clinician __________. a. accurately take scansb. always provide a provisional c. follow procedures according to the instructions of the

given manufacturerd. a and c

13. CAD/CAM scans can be transmitted __________. a. through a secure Internet portalb. by written instructions c. through thin air d. all of the above

14. A light and rapid dusting of an opaquing powder agent is required prior to capturing the digital scans for __________ CAD/CAM systems. a. allb. somec. nod. wet surfaces for

15. __________ available CAD/CAM devices involve the use of a handheld scanner. a. Allb. Some c. No d. Few

16 __________ is an option for capturing images using CAD/CAM technology. a. The acquisition of a single still image b. Continuous video streaming of the teethc. The use of an ultraviolet light that reflects from the surface

of the tooth d. all of the above

CEQuizTo complete this quiz online and immediately download your CE verifica-tion document, visit www.dentallearning.net/CAD-CAM, then log into your account (or register to create an account). Upon completion and passing of the exam, you can immediately download your CE verification document. We accept Visa, MasterCard, Discover, and American Express.

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17. Scanning and _________ is the only option that removes the need for a provisional restoration. a. transmission to a central location b. transmission to an approved and fast laboratoryc. chairside, same-visit milling of the restorationd. none of the above

18. Feldspathic glass ceramic used for laboratory-based fabrication of ceramic restorations __________. a. has relatively low flexural strengthb. results in esthetic restorationsc. has relatively low compressive strengthd. all of the above

19. __________ possess very high compressive and flexural strength and can be bonded or cemented. a. High-strength leucite and zirconiab. Lithium disilicate, alumina, and zirconiac. Alumina and leucited. none of the above

20. The reduced incidence of secondary caries observed with CAD/CAM restorations was attributed in one publication to the __________. a. high accuracy of the approximal fitb. ability to ascertain, prior to completion of the restoration,

that the marginal fit is accuratec. use of silver nitrate d. a and b

21. CAD/CAM technology has been available in dentistry for almost __________. a. 10 years b. 20 years c. 30 yearsd. 40 years

22. A porcelain furnace is required for __________. a. zirconia b. alumina c. lithium disilicated. resin

23. A sintering oven is required for full-contour __________. a. alumina b. zirconia c. composite d. all of the above

24. Resin nano-ceramic blocks _________. a. consist of ceramic clusters within a highly cross-linked resin matrixb. are homogenous c. can be used for chairside milling or laboratory milling of restorations d. all of the above

25. A 2006 study comparing resin nano-ceramic and zirconia used for CAD/CAM four-unit bridges found that the margins were most accurate and the marginal gaps least accurate using __________. a. either material b. the zirconia c. the resin nano-ceramic d. none of the above

26. __________ is a material that can be cemented with either traditional luting cement or adhesive, resin-based luting cement. a. Zirconiab. Lithium disilicate c. Resin nano-ceramic d. all of the above

27. Resin-based luting cements bond __________. a. to ceramic restorationsb. to tooth structure c. by micromechanical lockingd. all of the above

28. Roughening of the intaglio surface is required with resin-based luting cements to __________. a. decrease the area with peaks and valleysb. thin the restoration’s interior c. increase the area available for bondingd. none of the above

29. Chairside CAD/CAM fabrication of Class II restorations __________. a. eliminates the need for bands and wedgesb. offers predictability for contacts and contoursc. is a viable optiond. all of the above

30. In selecting a material for CAD/CAM fabrication of restorations, consideration must be given to __________. a. the patient’s caries risk b. strength, esthetics, and ease of usec. the capital investment d. periodontopathic bacteria

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EDUCATIONAL OBJECTIVES1. Delineate the main differences between digital impressions and traditional techniques;2. List and describe the various CAD/CAM materials and their uses;3. Review the treatment of restorative surfaces and luting agent options; and4. Describe the chairside steps required to deliver an indirect, resin nano-ceramic,

same-day restoration.

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