WWW.DENTALLEARNING.NET DENTAL LEARNING A PEER-REVIEWED PUBLICATION Knowledge for Clinical Practice

The Clinical Application of CAD/CAM Technology and Materials Michael Skramstad, DDS

INSIDE Earn 2 CE Credits

Written for dentists, hygienists and assistants

Dental Learning, LLC is a Dental Board of California CE Provider. The California Provider # is RP5062. All of the information Integrated Media Solutions Inc./DentalLearning.net is an ADA CERP Recognized Provider. contained on this certi cate is truthful and accurate. Completion ADA CERP is a service of the American Dental Association to assist dental professionals in Approved PACE Program Provider FAGD/MAGD of this course does not constitute authorization for the attendee identifying quality providers of continuing dental education. ADA CERP does not approve or Credit Approval does not imply acceptance by to perform any services that he or she is not legally authorized to endorse individual courses or instructors, nor does it imply acceptance of credit hours by a state or provincial board of or AGD perform based on his or her license or permit type. This course boards of dentistry. Concerns or complaints about a CE provider may be directed to the pro- endorsement. (2/1/2016) to (1/31/2020). meets the Dental Board of California’s requirements for 2 units vider or to ADA CERP at www.ada.org/cerp. Integrated Media Solutions Inc./DentalLearning. Provider ID #346890 of continuing education. CA course code is 02-5062-15045. net designates this activity for 2 continuing education credits. The Clinical Application of DENTAL LEARNING CAD/CAM Technology and Materials

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 . 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].

EDUCATIONAL OBJECTIVES ABSTRACT The overall goal of this article is to provide the reader with informa- Restoring indirect restorations using digital impres- tion about the use of CAD/CAM technology and materials for the sions and CAD/CAM technology is a topic that has fabrication of defi nitive restorations. After reading this article, the created a tremendous amount of interest in both the reader will be able to: dental offi ce and the dental laboratory. CAD/CAM 1. Delineate the main differences between digital impressions and technology has evolved into several systems that can traditional techniques; be used for the fabrication of indirect restorations, 2. List and describe the various CAD/CAM materials and their uses; together with the development of several restorative 3. Review the treatment of restorative surfaces and luting agent materials. The properties of these restorative materi- options; and als and their indications and appropriate use must 4. Describe the chairside steps required to deliver an indirect, resin be understood in order to enable the achievement of nano-ceramic, same-day restoration. predictable and esthetic results for patients.

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 contactingDental 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

Copyright 2015 by Dental Learning, LLC. No part of this publication may be repro- duced or transmitted in any form without prewritten permission from the publisher. CE Editor Creative Director FIONA M. COLLINS MICHAEL HUBERT

August 2015 DENTAL LEARNING Managing Editor Art Director BRIAN DONAHUE MICHAEL MOLFETTO 500 Craig Road, First Floor, Manalapan, NJ 07726 DENTAL LEARNING www.dentallearning.net

Introduction single-unit crowns using traditional techniques. First, the AD/CAM technology and materials are currently preparation must be made in accordance with the restor- used in a number of clinical applications, includ- ative material being used, and the adjacent soft tissue ing the fabrication of indirect restorations, occlusal managed to prevent bleeding or fluid encroaching on the C 1,2 splints, and implant-related components. More recently, preparation and to expose any subgingival margins. For CAD/CAM has become available for the treatment plan- this purpose, one or more of the following may be used: ning and execution of orthodontic treatment, and it is also retraction cord, lasers, hemostatic agents, electrosurgery, possible for clinicians to measure and track the morphol- or one of the more recently introduced silicone polymer ogy of gingival tissues during treatment associated with retraction materials. Gingival retraction cord was reported different clinical disciplines.3,4 Indirect single-unit restora- in one survey to be the most frequently-use method.7 Clini- tions are one of the most common procedures currently cal preference, ease-of-use, the specific clinical case and fa- performed in the dental office. For many years, porcelain- miliarity play a role in the selected method. The next step fused-to-metal (PFM) and gold crowns were the materials is to take an impression of the preparation as well as the of choice for the fabrication of indirect restorations for adjacent and opposing teeth so that the die and models can teeth with inadequate tooth structure remaining for direct be poured for laboratory fabrication of the crown. During restorations. In addition, porcelain-only single-unit restora- this period, the patient is provided with a provisional res- tions were fabricated in selected non-stress-bearing situa- toration for function and/or esthetics, as well as to protect tions due to their esthetic qualities relative to PFM crowns. the preparation and gingival margins, prevent sensitivity In the last several years, a number of different material in a vital tooth, and maintain periodontal health and the options have been introduced as alternatives to these more position of the prepared tooth relative to the adjacent and traditional materials, including some that have the ability opposing teeth.8-10 This traditional procedure is still the to be milled in the office for indirect same-day restorations. most prevalent method of restoring teeth with indirect Digital scanning and CAD/CAM fabrication of indirect restorations – it is what clinicians have been most familiar single- and multi-unit restorations is a procedure performed with and how they were taught in dental school. As such, with increasing frequency. Furthermore, more advanced there is no new learning curve for the clinician. adhesive luting cement systems have become available that While generally reliable, this traditional approach enable reliable placement and retention of these restora- involves some limitations, including the period of time it tions. This paradigm shift, involving both CAD/CAM takes to fabricate the restorations (typically one to two technology and new materials, has changed the way both weeks), the need for a provisional restoration, and the dentists and dental laboratories think about restoring teeth, need for the patient to return for a second visit. Physical and the use of CAD/CAM technology has increased.5 Many models are necessary to create the restoration and must be of these restorations not only make the dentistry more poured from the impression. However, the impression itself predictable, but offer great convenience to patients. Patients is a potential source of error, despite the availability of also are increasingly demanding all-ceramic restorations.6 highly accurate and dimensionally stable impression mate- rials; some common errors include the inclusion of voids, Fabrication of Indirect Single-Unit Restorations marginal discrepancies, and minor tears. High-precision Using Traditional Techniques impression materials must be handled according to the Traditional materials used for restoring a tooth indi- manufacturers’ instructions, and the soft tissue at the clini- rectly include the use of cast metal crowns, metal-ceramic cal site appropriately managed, to help avoid such errors. crowns with or without porcelain margins, and ceramic Other factors that can result in inadequate impressions crowns. All these materials are used for the fabrication of include how soon the model was poured, and the man-

2 The Clinical Application of CAD/CAM Technology and Materials

ner in which the impression was stored and transported to traditional methods.13 As with the traditional approach, before pouring. This is especially important for alginate, the preparation design must consider multiple factors, which is typically the material of choice for the opposing including the material that will be used to fabricate the (preparation-free) arch due to its ease-of-use and low cost. indirect restoration and the required dimensions, as well as If left out to dry or transported without being wrapped in the amount of retention that will be achieved as a result of damp gauze or a damp towel, these impressions will shrink the preparation form. CAD/CAM technology has evolved which causes dimensional errors in the model.11 into several versions using different devices and combi- Similarly, models may also include voids and other nations of techniques: 1) taking the CAD/CAM scans dimensional errors. These errors are related to the mixing, chairside and transmitting these through a secure Internet pouring and handling of the stone (or plaster) models. Mar- portal to a standard laboratory or to a central location for ginal discrepancies may not be evident until after the models fabrication of the indirect restoration in a milling machine; have been poured or until the time of try-in of the restora- 2) taking the CAD/CAM scans chairside and sending these tion, resulting in additional time and costs. Digital photog- through a secure Internet portal to a central location for raphy and modern shade selection options and techniques digital creation of the models, after which they are sent to have increased the ability of the clinician and the laboratory a standard laboratory for traditional fabrication of the res- to communicate, and therefore to deliver a case with the toration; and 3) taking the scan chairside and milling the desired esthetics. Nonetheless, this setup may still not be indirect restoration chairside using CAD/CAM technology ideal for a given case. Well-executed indirect restorations at the same visit (Figure 1). fabricated using the traditional approach offer excellent fit, When the clinician uses any of these devices and tech- functionality, and esthetics. niques, it is not necessary to take a traditional impression or to pour dies and models. This removes the risk of associ- CAD/CAM Technology ated errors and increases patient comfort. Both chairside CAD/CAM technology has been around long enough milling and laboratory milling of restorations removes the that is not “new”; earlier versions of the technology have possibility of abrading or damaging dies and models dur- been available in dentistry for almost 30 years.12 It is now ing their use for restoration fabrication – abraded models accepted as a viable, predictable, and efficient alternative would result in restorations that were either too tight and

Chairside Scanning

Delivery to the Digital creation of models centrally and laboratory or central Chairside milling of traditional laboratory the restoration location for milling of fabrication of the the restoration restoration

Figure 1. Chairside scanning and delivery

August 2015 3 DENTAL LEARNING www.dentallearning.net

left insufficient space for the luting agent, or simply would Provisionalization for Laboratory-Milled or not seat on the preparation. Of course, to avoid incurring Fabricated Indirect Restorations errors when using CAD/CAM technology, the clinician Provisionalization materials include acrylic resins, pre- must accurately take scans and follow procedures accord- fabricated composite resin temporary crowns, and metal- ing to the instructions of the given manufacturer. All avail- based prefabricated temporary crowns. The use of acrylic able CAD/CAM devices involve the use of a handheld scan- resins allows the provisional restoration to be customized ner, although each uses different technology to capture the chairside. Desirable features of a provisional material are images. Options for capturing images include continuous a setting reaction that does not produce heat (or produces video streaming of the teeth, the acquisition of multiple still minimal heat) and that avoids shrinkage of the material images that are then melded together with software, and during setting, as well as being sufficiently durable to last the use of a laser that captures images by reflecting off the until the definitive indirect restoration is ready for place- surface of the tooth or preparation. “Bite registration” and ment. Bis-acryl results in less heat production during the the determination of centric relation also differ by system. setting reaction than other acrylics, has low polymerization For CAD/CAM restorations milled in a laboratory or shrinkage and offers adequate durability for provisional central location, a provisional restoration is required as restorations, although it is a more costly acrylic compared with the traditional impression technique (Table 1). 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 Table 1. Trad itional and CAD/CAM procedures required. On the other hand, they are only available in a number of shapes and sizes, require marginal adjustments, Traditional CAD/CAM Chairside and may not be suitable for a given case. Recently, fillers Approach Laboratory Milling Fabricated have been added to bis-acryl to increase surface smooth- ness and gloss for provisional restorations. Scanning and Soft tissue chairside same-visit milling of the restoration is the only Yes Yes Yes management option that removes the need for a provisional restoration Impression or for a second patient visit for try-in and placement of the Yes No No taking restoration.

Scanning No Yes Yes Preparation and CAD/CAM Scanning Die and model For all systems, as with the traditional technique, the Yes No No pouring preparation must be isolated and the soft tissue man- aged at the margins. The same techniques are used for Model milling No Yes/No No soft tissue management as with the traditional approach. Depending on the system, a light and rapid dusting of an Restoration No Yes/No Yes milling opaquing powder agent may be required prior to capturing the digital scans of the preparation arch, opposing arch, Provisional Yes Yes No and buccal bite registration. Digital scanning and rapid restoration transmission of the scans to the laboratory, and/or chair- Second patient side viewing of the scans, allows for immediate or almost visit Yes Yes No immediate feedback on margins and clearance. If correc- tions are needed, it takes just minutes with the patient still

4 The Clinical Application of CAD/CAM Technology and Materials

in the chair and anesthetized. This avoids having to bring esthetic restorations regardless of which method is used the patient back for a second visit involving adjustments for their fabrication, particularly in the anterior region. to the preparation or/and a second impression, or not However, their relatively low flexural and compressive discovering the error until the patient’s seat appointment strengths have limited their use in posterior stress-bearing when the restoration has already been fabricated and then areas. High-strength leucite also has been used as a block causing additional laboratory costs to be incurred as well for CAD/CAM milled restorations. These materials must as causing patient disappointment. be adhesively resin-bonded to the preparation and can- not be placed using traditional luting cements. In recent Clinical Results years, we have seen the evolution of high-strength ceram- Several studies have evaluated CAD/CAM restorations ics – lithium disilicate, alumina, and zirconia – that have and found that they have a marginal fit as good as or supe- allowed CAD/CAM dentistry to move into new territory. rior to that of traditional impressions.15-16 A further benefit The advantages of these materials are twofold: they pos- found with CAD/CAM restorations has been the reduced sess very high compressive and flexural strength, and can incidence of secondary caries (the leading cause of direct be bonded or cemented. This has resulted in a very strong, restoration failure with both amalgam and composite predictable, and esthetic option for posterior ceramic materials), attributed to the high accuracy of the approxi- dentistry. In a recent study, both alumina and zirconia mal fit and the ability to ascertain that this is accurate crown copings fabricated using CAD/CAM were found to prior to completion of the restoration and cementation. In have clinically acceptable marginal adaptations.21 A sepa- fact, the longevity of CAD/CAM restorations was reported rate study recently conducted on milled lithium disilicate by Mjör et al to be close to that of gold restorations.17 A crowns found these to be free of fractures, chipping, or recent review assessed the survival rates of single-tooth other defects two years post-placement.22 For CAD/CAM indirect restorations fabricated with CAD/CAM and found restorations milled with these materials, in addition to the long-term survival rate to be similar to indirect restora- the CAD/CAM device a porcelain furnace is required for tions fabricated using the traditional approach.18 crystallization of lithium disilicate, and a sintering oven CAD/CAM scanning and fabrication of indirect resto- for full-contour zirconia. In the case of lithium disilicate, rations has been proven in numerous studies and is now this can add 15 to 30 minutes to the fabrication time, and accepted as a viable, predictable alternative to traditional with zirconia up to an additional 8 hours may be re- methods.19-20 quired. It should be noted that high-speed sintering ovens As with all treatments, proper procedures and tech- for zirconia are now sintering these restorations in about niques must be followed to achieve clinically acceptable 90 minutes and other options include semi-sintered zir- results. CAD/CAM technology also requires the use of conia and fully-sintered zirconia. The advantage of using specific materials that can be milled to fabricate durable zirconia for milling and then sintering it is the increased and esthetic restorations. strength following sintering and the relative ease of mill- ing prior to sintering. CAD/CAM Restorative Materials Composite resin blocks are also available for CAD/ The movement toward CAD/CAM fabrication of CAM restorations. Another option is the use of a new resin restorations has been directly responsible for a number nano-ceramic block that consists of ceramic clusters within of material innovations over the past few years. For quite a highly cross-linked resin matrix. The resulting block is some time, both leucite and feldspathic glass ceram- homogenous, and the restoration can be CAD/CAM-milled ics have been used for laboratory-based fabrication of chairside or in the laboratory. The wear resistance of this ceramic restorations. These materials result in beautifully material is reported to be comparable to that of felspathic

August 2015 5 DENTAL LEARNING www.dentallearning.net

glass ceramic and lithium disilicate, and it has a compres- cate, alumina, and resin nano-ceramics. The caveat for sive strength similar to high-strength ceramics. Unlike non-bonded materials is that the preparation form was lithium disilicate and zirconia, no porcelain furnace or sin- sufficiently retentive in the first place. Resin-based bond- tering oven is required, saving fabrication time. In fact, a ing can be used for all CAD/CAM restorative materials, recent study found that composite blocks (and experimen- including those mentioned above (Table 2). Resin-based tal composite blocks) were more resistant to fracture than luting cements bond to the ceramic restorations, not only reinforced ceramics when used for ultra-thin veneers.23 The the tooth structure, and are now regarded by some clini- use of nano-fillers and resin technology has improved the cians as the preferred luting agent for ceramic and other strength and esthetics of composite blocks. A 2006 study non-metal restorations. They offer excellent esthetics and comparing resin nano-ceramic and zirconia used for CAD/ retention of the restoration to the preparation.25 These CAM four-unit bridges found that the margins were most luting cements utilize etching and bonding technology, accurate and marginal gaps least using the resin nano- and they bond by micromechanical locking of the cement ceramic material.24 to both the tooth and the restorative material. The resin- based luting cement itself may be dual-cured, self-cured, or Placement and Retention of CAD/CAM light-cured – the latter is only suitable if the restoration is Restorations thin enough to enable the transmission of light for curing. As noted above, some CAD/CAM restorative materi- A further requirement is roughening of the intaglio surface als can be cemented with either traditional luting cements to increase the area available for bonding,26 with either such as zinc phosphate, polycarboxylate cement, glass hydrofluoric acid or sandblasting/air abrasion depending ionomers, or resin-modified glass ionomers. Materials that on the restorative material used. The intaglio surface of can be luted with these include zirconia, lithium disili- lithium disilicate restorations is treated with 5% hydroflu- oric acid for 20 seconds to etch and roughen that surface.27 Table 2. Luting agents for indirect restoratives The intaglio surfaces of feld­spathic porcelain and leucite- Traditional Luting Cements contain­ing restorations are also treated with hydrofluoric Alumina acid, with the time of etching depending on the material. Options for other materials are the use of sandblasting or Zirconia treatment with a silica coating, with the method depending Lithium disilicate on the material – the restoration material manufacturer’s Composite instructions must be followed and the correct treatment used. Irrespective of the luting agent and technique, the Resin-nano-ceramic primary objectives are retention and sealing of the restora- Adhesive Resin-Based Luting Cements tion-tooth interface. Alumina Zirconia CASE STUDIES When considering milling and delivering same-day Lithium disilicate restorations, there are many options available. Composite The two case studies below will concentrate on the use Resin-nano-ceramic of resin nano-ceramic blocks for the chairside fabrication of an inlay and a . Case Study #2 involves the com- Feldspathic porcelain plication of an aligner with attachments that were on the High-strength leucite fractured tooth to be veneered.

6 The Clinical Application of CAD/CAM Technology and Materials

Case Study #1 A 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 Figure 2: Pretreatment view of teeth #12, 13, and 14 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 Figure 3: Pretreatment images of teeth #12, 13, and 14 rubber dam and preoperative scans were taken (Figure (biogeneric copy) 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- Figure 4: Imaged and marginated preparations ing, with no undercuts and with clear separation from the adjacent teeth. After removal of the wedges, a light dusting

August 2015 7 DENTAL LEARNING www.dentallearning.net

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 Figure 5: Isolation and preparation of teeth for indirect the need for bands and wedges, predictability for contacts restorations (note residual powder mesially and distally post-scanning) 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- Figure 6: Pretreatment images overlaid on top of prepara- fi cult to handle, fi nal polishing was completed intraorally tions for “biocopy” design

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

8 The Clinical Application of CAD/CAM Technology and Materials

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 Figure 9: Initial fracture of tooth #8 following trauma 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 Figure 10: Fractured segment bonded back to tooth 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 #2 An 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 Figure 11: Veneer preparation and isolation both the remaining tooth and the fractured fragment; the fracture did not involve the pulp. To significantly compli-

August 2015 9 DENTAL LEARNING www.dentallearning.net

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 Figure 12a: Marginated veneer preparation and overlaying of veneers is high, with one study finding a high clinically ac- pretreatment image 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 Figure 12b: Marginated veneer preparation and overlaying places. The patient’s current aligner was then tried-in to of pretreatment image 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- Figure 12c: Marginated veneer preparation and overlaying of tion that exactly duplicates the existing tooth. Note how pretreatment image precisely the camera (scanner) captured the two aligner attachments with the preoperative scan (Figure 12) and

10 The Clinical Application of CAD/CAM Technology and Materials

how the software reproduced them in the final initial After the restoration was milled, the initial polish was proposal (Figure 13). achieved using medium and fine diamond-impregnated As discussed earlier, when choosing the appropriate rubber wheels. Care was taken to avoid over-polishing material, one has to consider many factors. In this par- the surface of the restoration, which would affect the ticular situation a low-translucency resin nano-ceramic surface texture and aligner attachments. In order to CAD/CAM block was selected because of the patient’s facilitate natural shade transitions and provide an excel- age, the flexibility of the material, its excellent polish- lent match with the contralateral central incisor, the ability, the precise marginal edge quality, and the low restoration was characterized with light-cured resin in translucency (which would prevent shine-through, help- several shades. To accomplish this, the external (non- ing to ensure an esthetic result). But the most important bonding side) of the restoration was sandblasted with factor, considering that the patient would be using an aluminum oxide at 30psi, cleaned with alcohol, and aligner for the next year, was the material’s reparability. dried. As with Case Study #1, universal adhesive was

Figure 13a: Initial restoration proposal by the software, Figure 14: Final bonded restoration including aligner attachments

Figure 13b: Initial restoration proposal by the software, Figure 15: Maxillary aligner seated into position perfectly including aligner attachments

August 2015 11 DENTAL LEARNING www.dentallearning.net

10. Bral M. Periodontal considerations for provisional restorations. Dent Clin North Am. applied to the surface, thinned appropriately, and light- 1989;457-65. cured. Several shades of resin were then applied to the 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 surface of the restoration and light-cured to character- pouring. J Can Dent Assoc. 2012 Jan;78:c2. 12. Calamia JR. Advances in computer-aided design and computer-aided manufacture ize the restoration and match it as closely as possible to technology. Curr Opin Cosmet Dent. 1994:67-73. 13. Fasbinder DJ. Digital dentistry: innovation for restorative treatment. Compend tooth #9. Final polishing of the restoration was achieved Contin Educ Dent. 2010;31 Spec No 4:2-11. using a fine polishing paste on a #9 soft brush at low 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. rpms (< 10,000 rpm), and a final buff was performed 2010;38(12):964-73. 15. Sorensen JA, Sorensen PN, Mizuro K. Marginal fidelity of crowns made with optical with a muslin rag wheel. Finally, the restoration was versus conventional impressions. IADR Abstract #1599. April 2009. 16. Hirayama H, Chang YC. Fit of zirconia copings generated from a digital impres- bonded using universal adhesive and a resin-based lut- sion technique and a conventional impression technique. Tufts University of Dental Medicine master’s thesis. ing cement. The final restoration exhibited contours 17. Mjör IA, Davis ME, Abu-Hanna A. CAD/CAM restorations and secondary caries: a almost identical to the original, pre-fracture contours, 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- and the patient’s esthetic concerns were satisfied (Figure 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 14). Furthermore, the aligners snapped into place with 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 no adjustments at all (Figure 15). 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 Summary 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 CAD/CAM technology has transformed the ways in lithium disilicate CAD/CAM crowns:A two-year report J Am Dent Assoc 2010;141(6 suppl):10S-14S. which clinicians can provide patients with functional, 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 esthetic, and durable indirect restorations. CAD/CAM erosion. J Prosthet Dent. 2011 Apr;105(4):217-26. technology removes the risk of some errors and of- 24. Piwowarczyk HC, Lauer C. Determining the marginal fit of CAD/CAM bridge frame- works. Pan Eur Fed Conf. 2006; Abstract #0254. fers the opportunity to review restoration designs (and 25. Haddad MF, Rocha EP, Assunção WG. Cementation of prosthetic restorations: from conventional cementation to dental bonding concept. J Craniofac Surg. 2011 adjust them, if necessary) before they are completed. May;22(3):952-8. 26. Tsuo Y, Yoshida K, Atsuda M. Effects of aluminablasting and adhesive prim- As the demand for CAD/CAM indirect restorations ers on bonding between resin luting agent and zirconia ceramics. Dent Mater. 2006;25(4):669-674. grow, more advanced materials have become available 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 that can be resin-bonded to preparations with excellent Prosthet Dent. 2006;96;412–7. results. The material of choice depends on the clinical 28. Puri S. Predictable preparation, staining, and cementation procedures for chairside CAD/CAM dentistry. Pract Proced Aesthet Dent. 2008 May;20(4):209-14. situation, with consideration given to strength, esthetics, 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. and ease of use. 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 References veneers: a nine-year report. Int J Comput Dent. 2005;8:233-46. 1. 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- Webliography ments for CAD/CAM generated restorations. Br Dent J. 2008 May 10;204(9):505-11. Fasbinder DJ. Clinical performance of chairside CAD/CAM restorations. JADA 3. Fukawa R. Lingual in the new era treatment according to criteria for oc- 2006;137(9 supplement):22S–31S. Available at: http://jada.ada.org/content/137/ clusion and aesthetics. Int Orthod. 2009 Dec;7(4):370-402. suppl_1/22S.abstract?ijkey=24969cbaa0bb04f7453ddfdf45afb2725a09b127&keytype2= 4. Ronay V, Sahrmann P, Bindl A, Attin T, Schmidlin PR. Current status and perspec- tf_ipsecsha tives of mucogingival soft tissue measurement methods. J Esthet Restor Dent. 2011 Giordano R. Materials for chairside CAD/CAM–produced restorations. JADA 2006;137(9 Jun;23(3):146-56. supplement):14S–21S. Available at: http://jada.ada.org/content/137/suppl_1/14S.full. 5. Davidowitz G, Kotick PG. The use of CAD/CAM in dentistry. Dent Clin North Am. pdf+html 2011 Jul;55(3):559-70. Hickel R, Manhart J. Longevity of restorations in posterior teeth and reasons for failure. J 6. Miyazaki T, Hotta Y. CAD/CAM systems available for the fabrication of crown and Adhes Dent. 2001 Spring;3(1):45-64. Abstract available at: http://www.ncbi.nlm.nih.gov/ bridge restorations. Aust Dent J. 2011 Jun;56 Suppl 1:97-106. pubmed/11317384 7. Hansen PA, Tira DE, Barlow J. Current methods of finish-line exposure by practicing Trost L, Stines S, Burt L. Informed decisions about incorporating CEREC into a practice. prosthodontists. J Prosthodont. 1999 Sep;8(3):163-70. JADA 2006;137(9 supplement):32S–36S. Available at: http://jada.ada.org/content/137/ 8. Burke FJ, Murray MC, Shortall AC. Trends in indirect dentistry: provisional restora- suppl_1/32S.full.pdf+html tions, more than just a temporary. Dent Update. 2005;32(8):443-52. Wittneben JG, Wright RF, Weber HP, Gallucci GO. A systematic review of the clinical 9. Wassell RW, St. George G, Ingledew RP, Steele JG. Crowns and other extracoronal performance of CAD/CAM single-tooth restorations. Int J Prosthodont. 2009 Sep- restorations: provisional restorations. Brit Dent J. 2002;192(11):619-30. Oct;22(5):466-71. Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/20095195

12