Written by Robert A. Lowe, DDS Wednesday, 23 April 2014 12:51
Today, restorative materials are being developed to be more compatible biologically to the tissues that they replace. Bioactive, bioidentical, and biomimetic are all terms used to describe these types of dental materials that more closely match, and therefore, “behave” like the naturally occurring tissues that they replace. Because of the acidic microenvironment that exists in the oral cavity due to bacterial metabolism, natural tooth tissues (enamel and dentin) and the restorative materials that are used to replace them face an ongoing challenge to resist breakdown and ultimate failure. It therefore stands to reason that dental materials that either positively change that microenvironment or are less affected by it will better stand the test of time. All dental restorative margins that exist are “open margins” that are filled with the luting agent (or bonding resin) used to place the restoration. Thirty microns is considered to be a clinically closed margin; however, bacteria are much smaller in size (one µm in diameter). Therefore, any margin where a restorative material meets natural tooth, by nature of any imprecision in our work, may then serve as an area that is more susceptible to plaque accumulation, resultant acid attack, and breakdown at the margins.
This article will discuss the use of both a restorative material and luting cement that have unique properties to help the clinician achieve better long-term results for crown and bridge cases, particularly for those in which the oral environment is less than ideal. Together, these 2 materials can help solve certain clinical problems, including recurrent decay around restorative margins and chronic inflammation of the periodontium surrounding those margins.
A Unique, Oxide-Free PFM: The Perio Crown
During the time when all-ceramic crowns are considered the overall material of choice for lab-fabricated restorations, it is important not to exclude the use of PFM as a viable alternative restorative option. Captek (Argen), using a coping consisting of a composite metal restorative material (internally reinforced gold), has been used successfully for many years and has been shown to be both aesthetic and biocompatible.
According to the manufacturer, this restorative system has several clinical advantages over conventional PFM and all-ceramic materials.
This article will focus on 2 of this material’s advantages:
1. Excellent retention of luting cement to the internal surface of Captek restorations. The micromechanically retentive internal surface of the Captek coping gives the clinician the capability to bond or conventionally cement the restoration, thus making the system useful in clinical situations with aesthetic margins (at the gingival crest or slightly below), or in situations with deeper margins where isolation for use of resin cements is not possible.
2. Studies have shown less bacterial accumulation around Captek margins that extend to the restorative margin edge. Seventy-five percent less bacterial accumulation was found around Captek composite gold margins when compared to adjacent natural enamel surfaces.1-3 When aesthetic and restorative needs require equigingival or subgingival margin placement, a material that is both aesthetic and “bioprotective” is highly desirable.
An Extraordinary Dental Cement
Ceramir Crown and Bridge (Doxa) is a biomimetic dental cement that integrates and becomes part of the apatite of the surrounding tooth, forming an impenetrable biologic seal that repels acid challenge as well.4 At this time, there is no other luting agent in dentistry that can make that claim. According to the manufacturer, some of the key benefits of Ceramir Crown and Bridge are as follows:
1. Nanostuctural integration with restorative substrate and tooth structure. Being structurally similar to hydroxyapatite, which is the building block of tooth structure, this unique cement bonds to the tooth using the same process as remineralization. The nanocrystals that form integrate with and become part of the structure of the tooth itself by creating apatite when in contact with phosphates. On the restorative interface, these same nanocrystals micromechanically “lock” into and around microscopic surface irregularities of the restorative substrate to create a strong bond that, in many cases, is equal to or stronger than resin luting agents.5-6
2. Ceramir Crown and Bridge is a hydrophilic system with an alkaline pH. With a pH of approximately 8.5, Ceramir Crown and Bridge resists attack from both acid and acid-producing bacteria.7
3. Ceramir Crown and Bridge is dimensionally stable after setting, and its thermal properties are similar to those of natural tooth structure. Ceramir is moisture tolerant (hydrophilic) during placement with no expansion after setting. It forms a stable, sealed interface on the molecular level between the restorative material and the tooth.
Diagnosis and Treatment Planning
The patient seen in preoperative photos Figures 1 to 3 presented for treatment referred from another dentist for a full-mouth reconstruction. She had implants placed in the sites of teeth Nos. 3, 4, 13, 20, 21, and 31 that were osseointegrated and ready for restoration. Her dental history also included posterior tooth loss with localized alveolar bone recession. As a result, there was an excessive amount of space between the maxillary and mandibular alveolar crests. The patient presented with a Class II, division I with a deep overbite anteriorly. From a periodontal standpoint, she was stable, but for a person aged in her 50s, had experienced a moderate amount of generalized bone loss and gingival recession around her remaining teeth; the large “black triangles” seen between the mandibular anterior teeth in Figure 1 were evidence of this.
|Figure 1. A preoperative retracted full-arch view of a Class II, division I patient with posterior tooth loss secondary to periodontal disease.||Figure 2. A preoperative occlusal/incisal view of the maxillary arch.|
The overall plan for restoration of this patient would include individual crowns on the natural teeth, and free standing fixed restorations on the implants. It is the preference of the author to splint multiple side-by-side fixed implant restorations; if there is a problem later, the restorations are retrievable. Based on the dental history of the patient, Captek was an obvious choice for both posterior conventional and implant crowns because of the plaque-repelling properties of composite gold metal margins that would help prevent peri-implantitis. In addition, splinted Captek frameworks are ideal for fixed implant restorations because they are totally passive in fit. Since the anterior tooth (prep) color was bright, all-ceramic (lithium disilicate) (IPS e.max [Ivoclar Vivadent]) was chosen as the material of choice for the maxillary and mandibular anterior restorations to maximize aesthetics while also providing adequate strength.
At the first appointment, the maxillary teeth were prepared for full-coverage restorations (Figure 4). A preoperative diagnostic wax-up was fabricated, and then duplicated in dental stone, to be used in the construction of the provisional restorations. Once the preparations were completed, implant impression copings (Straumann) were placed on the maxillary fixtures. The gingiva around the teeth was retracted using a 2-cord retraction technique, and the maxillary master impression (Panasil [Kettenbach LP]) was taken (Figure 5). After a face-bow (Denar Slidematic Facebow [Whip Mix]) registration was taken, relating the positions of the maxillary preparations to the cranial base for mounting on a semi-adjustable articulator (Denar Combi II [Whip Mix]), the maxillary provisional restoration was fabricated out of Tuff Temp Plus (Pulpdent), sectioned into one anterior and 2 posterior segments (distal to the lateral incisors) and cemented (Cling2 [CLINICIAN’S CHOICE]) over the prepared teeth.
|Figure 3. A preoperative occlusal/incisal view of the mandibular arch.||Figure 4. A retracted facial view of the maxillary teeth after preparation for full-coverage lab-fabricated restorations.|
|Figure 5. A view of the maxillary full-arch master impression (Panasil Initial Contact Light [Kettenbach LC]).||Figure 6. A full-arch retracted facial view of the maxillary provisional restorations and retraction of the soft tissue (UltraPak [Ultradent Products]) on the mandibular arch.|
|Figure 7. The centric bite registration (Panasil Putty Soft [Kettenbach LC]) was made on the patient’s left side while the provisional restorations on the right side maintain the vertical dimension of occlusion.||Figure 8. The anterior centric bite registration (Affinity Quick Bite [CLINICIAN’S CHOICE]) was made after cementation of the posterior mandibular provisional restorations.|
|Figure 9. A retracted facial view of the first bake try-in. The doctor and the patient evaluated the aesthetics of the anterior teeth at this time, communicating any needed changes to the dental ceramist.||Figure 10. The posterior centric check bites were remade with the anterior bisque baked units in place to verify the correctness of the original mounting of the master models in the laboratory.|
At the second appointment, the mandibular teeth were prepared, gingival tissues retracted, implant impression copings placed (Figure 6), and the mandibular master impression was made. Following the master impression registration, the provisional restoration was fabricated and sectioned into right and left segments. This was done to facilitate taking the centric bite registration. With the maxillary and mandibular provisional restorations maintaining the vertical dimension of occlusion (VDO) on the patient’s right side, a putty registration (Panasil Putty Soft [Kettenbach LP]) was made of the preparations and edentulous areas on the patient’s left side. Vinyl polysiloxane putty was the best choice for this registration because of the excessive distance between the alveolar ridges in the posterior areas. An appropriate amount of base and catalyst were hand mixed and formed into a rectangular shape. The putty was then placed as far posterior as possible and the patient was instructed to close until the provisional restorations on the opposite side were in maximum intercuspation (Figure 7). This procedure was then repeated on the opposite side. Next, the maxillary anterior provisional restorations were removed so that an anterior centric bite registration could be taken (Figure 8). The cemented mandibular posterior restorations maintained the VDO while recording the vertical stop in the registration material. The anterior maxillary and mandibular provisional restorations were then cemented to place. Then, both full-arch master models were mounted at the correct vertical dimension on the semi-adjustable articulator in the dental laboratory using the face-bow transfer and 3 centric occlusion (CO) relation records.
At the third patient visit, an anterior bisque bake try-in of the maxillary/mandibular units and a custom abutment try-in for the implant restorations were done (Figure 9). After verification of marginal and interproximal fit, the 4 maxillary and mandibular incisors were placed on the preparations and posterior bite registrations in putty were made to verify the accuracy of the original laboratory mounting (Figure 10). With the incisor point of contact established in the bisque baked units without any posterior contacts present, the condyles were fully seated in their respective glenoid fossae. Retaking the centric registrations at this time verified that the laboratory mounting on the semi-adjustable articulator was in centric relation (CR) (Figure 11).
|Figure 11. The second set of posterior check bites was used to verify the position of the master models on the semi-adjustable articulator.||Figure 12. A lateral view of the mounted master models with the custom implant abutments in place. It was critical to have correct anterior-posterior positioning of the model since the copings for the implant restorations needed to be designed to compensate for the large interocclusal space and properly support the porcelain.|
|Figure 13. A full-arch retracted view of the implant abutment coping try-in. Compare to the lateral view in Figure 12 to see how the copings compensated for a great deal of interocclusal space, leaving the proper 1.5 to 2.0 mm of space on both maxillary and mandibular copings for ceramic material.|
At the fourth appointment, a try-in of all individual ceramic and Captek units was done, as well as a try-in of the implant custom abutments and Captek implant copings (Figures 11 and 12). Figure 13 shows the try-in with the patient in occlusion on the anterior teeth. Note that this was also a check for posterior occlusal clearance of the metal frameworks. This was important because the ceramist needed adequate space (3.0 to 4.0 mm between maxillary and mandibular coping in CO) for the porcelain to be structurally strong and for replication of the intricacies of posterior tooth anatomy. Again, posterior bite registrations were taken to verify the laboratory-articulated position with the frameworks in place (Figure 14). Also, a pick-up impression with light- and heavy-bodied impression materials was taken to provide the laboratory team with an accurate soft-tissue model to refine emergence profiles and proximal contours of the all-ceramic restorations. To aid in the stability of the restorations during this pick-up impression, a small amount of temporary cement was placed in each restoration prior to seating them to place (Figure 15).
Delivery of the Reconstruction
Great care had been taken with each clinical step to ensure precision of fit. It should be noted that Captek restorations exhibit excellent fit (to 17 µm).8 In terms of final cementation of the definitive restorations, the nanocrystals of Ceramir Crown and Bridge, while integrating with the natural apatite of the tooth, also integrate with the microretentive internal surface of Captek or ceramic, creating retention to the crown substructure that is as good as or better than other cements. Also, Ceramir having the ability to repel acid attack at the restorative margin, as well as in the presence of saliva, forming apatite over the surface of the cement, completes the biomimetic interface between tooth and restorative material. Therefore, the combination of these 2 systems may provide the clinician with an optimal choice for restoring cases in which the bacterial attack on the tooth-restorative interface due to depth of the marginal position in the gingival sulcus, the lack of effective plaque removal, or both, may compromise the long-term stability of the case (Figure 16). After placement of the custom implant abutments and tightening with a torque wrench per the manufacturer’s instructions, the definitive restorations were tried in, minor adjustments in proximal contact were made as needed, and the case was prepared for cementation. The units were all cleaned with Ivoclean (Ivoclar Vivadent) to remove salivary contaminants that are present from the try-in. Next, Ceramir cement was triturated per the manufacturer’s instructions and dispensed into each crown (or splinted unit) as they were placed (Figures 17 and 18), one at a time, on the implant abutments. Figure 19 shows the posterior units in place after cement cleanup was easily accomplished. In this case, no occlusal adjustment was required. It is the author’s opinion that this is due to the repeated CO/CR records-taking during each try-in phase that ensured the accuracy of the articulator mounting. Figure 20 shows the case after cementation of the maxillary anterior teeth. These lithium disilicate all-ceramic units were etched internally with hydrofluoric acid for 30 seconds and thoroughly rinsed after try-in. It is important to mention that Ceramir Crown and Bridge can be used on lithium disilicate (such as e.max) restorations as well as restorations with zirconia and metallic inner surfaces. However, in aesthetic areas of the mouth, when using more translucent high-strength materials (such as lithium disilicate crowns), it is recommended that the ceramic thickness be greater than 1.0 mm due to the white, opaque color of the cement. Remember, do not use silane on etched glassy ceramics (porcelain) when cementing with Ceramir Crown and Bridge. Silane will decrease the bond strength of this unique cement! A self-etching dual-cured resin cement (GC LinkAce [GC America]) was chosen to place the mandibular anterior e.max units because of their limited thickness. GC LinkAce was placed into the etched and silanated restoration prior to cementation (Figure 21). The excess cement was removed using a Keystone No. 2 flat sable brush (Figure 22). The restorations were held in place to allow flossing of interproximal contacts prior to light curing. After light curing the mandibular anterior restorations, the case was complete (Figures 23 to 25).
|Figure 14. A check bite (Affinity Quick Bite) was taken with the implant abutments, copings, and anterior units in place.||Figure 15. A view of the internal aspect of the pick-up impression (Honigum [DMG America]) for the maxillary units. The temporary cement was cleaned out of the units using microabrasion (Prep Start [Danville Materials]).|
|Figure 16. This illustrates the microretention of Captek (Argen) copings and an SEM view of Ceramir Crown and Bridge as it integrates on a nano level with the apatite present in dentin and enamel. A “biologic link”?||Figure 17. Ceramir Crown and Bridge and Activator shown with a Captek crown. Note: The internal surface of Captek may be micro abraded (PrepStart [Danville Materials]) as well to further enhance the micro mechanical lock to the cement.|
|Figure 18. Ceramir Crown and Bridge was dispensed into the inner surface of the Captek restorations.||Figure 19. The posterior units after cementation and cleanup of the cement.|
|Figure 20. The maxillary anterior lithium disilicate crowns (IPS e.max [Ivoclar Vivadent]) units, shown here after cleanup of the excess cement.||Figure 21. GC LinkAce (GC America) was placed into one of the mandibular anterior restorations (IPS e.max) after etching and silanation.|
|Figure 22. The excess GC LinkAce was carefully removed using a sable brush prior to light curing.||Figure 23. A maxillary occlusal/incisal view of the completed reconstruction.|
|Figure 24. A mandibular occlusal/incisal view of the completed reconstruction.||Figure 25. A retracted full-arch view of the completed reconstruction. Compare to the preoperative photo in Figure 1. The patient now presented with much-improved aesthetics and proper function that provided immediate disclusion of posterior teeth in all movements from the centric occlusion/relation position.|
Maintenance and home care are a very important part of the success of any complex reconstruction case. The patient was placed on a strict regimen using Sonicare (Philips) and Air Floss (Philips) on a daily basis to expedite plaque removal and maintain the highest quality of gingival health. Air flossing is particularly useful around implant restorations and bridges where the traditional manual flossing may be a challenge for the patient.
As restorative materials and dental cements are designed and manufactured to behave more like the natural tissues that they replace, and be more “neutral” or “invisible” in the challenging environment found in the oral cavity, the better and more long-lasting our restorative efforts will become.
The author would like to acknowledge the ceramic expertise of Kystyna Jasinski of Jasinski Dental Laboratory in Austin, Tex, for the beautiful aesthetic work done on this case.
- Goodson JM, Shoher I, Imber S, et al. Reduced dental plaque accumulation on composite gold alloy margins. J Periodontal Res. 2001;36:252-259.
- Knorr SD, Combe EC, Wolff LF, et al. The surface free energy of dental gold-based materials. Dent Mater. 2005;21:272-277.
- Gottehrer NR. The periodontal crown: creating healthy tissue. Dent Today. 2009;28:121-123.
- Engstrand J, Unosson E, Engqvist H. Hydroxyapatite formation on a novel dental cement in human saliva. ISRN Dent. 2012;2012:624056.
- Pameijer CH, Zmener O, Alvarez Serrano S, et al. Sealing properties of a calcium aluminate luting agent. Am J Dent. 2010;23:121-124.
- Hermansson L, Lööf J, Jarmar T. Integration mechanisms towards hard tissue of Ca-aluminate based biomaterials. Key Engineering Materials. 2009;396-398:183-186.
- Unosson E, Cai Y, Jiang X, et al. Antibacterial properties of dental luting agents: potential to hinder the development of secondary caries. Int J Dent. 2012;2012:529495.
- Shoher I, Whiteman A. Captek: a new capillary casting technology for ceramometal restorations. Quintessence Dent Technol. 1995;18:9-20.
Disclosure: Dr. Lowe reports no disclosures.
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