Conquering a Difficult Case, Part 2: Lithium Disilicate as a Restorative Solution for Amelogenesis Imperfecta

This is part 2 of a series of articles defining ways to simplify treatment of complicated cases. Dr. Auster, president of the New York affiliate of the American Academy of Cosmetic Dentistry, discusses a systematic way to create beautiful cases built to last.

INTRODUCTION
Dentistry presents us with challenges every day. Our professional comfort zone defines how well we deal with these challenges. The more we learn and grow as clinicians, the more comfortable we get at attempting difficult tasks and the more fulfillment we feel in our dental and personal lives. Occasionally, a patient touches our heartstrings. When that happens, we so want to help them and give them a stunning smile. The case of a female patient with amelogenesis imperfecta (AI) can present both issues…a need to find that comfort zone in fixing the problem and a goal-directed systematic approach to create a beautiful smile to make the patient (and the dentist) happy.
This article will demonstrate the manner in which a complex case can be compartmentalized into a predictable series of steps that lead to a beautiful outcome. A clinical team, led by the restorative dentist as the “quarterback,” can make these cases simple and infinitely more rewarding. The ultimate goal is to have a patient who is thrilled by the result, as altering teeth can truly alter a life!

A Brief Review of Amelogenesis Imperfecta
Amelogenesis imperfecta is not a systemic disorder, but a group of genetic abnormalities causing defects in dental enamel without systemic manifestations. The condition is extremely variable and affects all or some of the teeth in the primary and/or secondary dentition, and defects can range from enamel formation oddities to mineral and protein related changes. Sometimes the condition is barely noticeable, while in others, it is severely disfiguring and can lead to early demise of the teeth, as well as major cosmetic issues for the patient.
Amelogenesis imperfecta has been observed in one in 718 to one in 14,000 people, depending on the population studied.¹ Problems resulting from AI include obvious aesthetic abnormalities, vertical dimension issues, and dental/gingival sensitivity. Other effects include higher instance of decay, anterior open bite, delayed eruption, tooth impaction, and food impingement.² The AI trait can be transmitted from autosomal dominant and autosomal recessive varitations.³ Incomplete formation of the enamel, teeth with deep coloration (eg, yellow, brown, or gray), or simply, abnormal dental aesthetics are possible.⁴
Fully explaining the genetic causation of AI is beyond the scope of this article. However, it presents an approach for developing a strategy to treat its ensuing problems. Patients with AI have obvious dental issues, but psychological implications of discolored, deformed teeth must also be considered. Dentists can truly reshape self-esteem and confidence by redesigning the teeth and smile.

Complex Case Planning
Restoration of a complicated case requires a systematic approach in which patient priorities, smile design, occlusion, function, and long-term treatment results are considered. Relevant specialists and knowledgeable laboratory technicians must be consulted, and it is essential to recognize the desired restoration outcome for the case prior to undertaking any procedures.
`The author advocates the following treatment planning steps. Although the order may change slightly, this system of care results in the best predictability for long-term success for complex dental treatments.

1. An in-depth interview with the patient (and the patient’s parents if under age 18 years), which is essential to learn the patient’s hopes and goals of treatment.
2. A comprehensive examination that includes necessary x-rays and analysis of the teeth, periodontium, muscles, and joint.
3. A set of photographs. The American Academy of Cosmetic Dentistry (AACD) provides the optimal photographic series necessary to communicate with collaborating dentists and laboratory technicians.
4. A cone beam scan, if necessary, to analyze potential implant placement and/or joint discrepancies.
5. An occlusal analysis with the case mounted in centric relation. A strong background in occlusal theory is essential. Courses at the Dawson Academy and Spear Institute instruct dentists in techniques beyond what they learned in dental school in order to instill confidence when deciding “where to go from here.” The AACD emphasizes “responsible aesthetics” and minimally invasive dentistry for creating long-term, beautiful restorations. This is an essential starting point for the journey toward excellent, comprehensive care.
6. After reviewing the information gathered from steps Nos. one to 5, a consultation with dental specialists who will be involved in treatment.
7. A discussion with a knowledgeable laboratory technician about restoration design and material preferences and limitations.
8. Treatment of acute issues (eg, initial removal of gross decay and immediate periodontal and surgical needs).
9. Discussion with the patient and possibly family members about potential treatment options, as determined by the dentist and his collaborative team.
10. Formation of diagnostic wax-ups on which treatment will be based. This is essential for treatment success.
11. Phased treatment as determined by the restorative team. This may involve tooth preparation, temporization, or specialized care first (ie, orthodontics, periodontal or surgical care, and/or implant placement).
12. Following temporization, analysis of the results of this treatment phase (eg, cosmetically and functionally, with an emphasis on symmetry, function, muscle and joint harmony, and patient comfort and approval of cosmetics).
13. Impressions of preparations and approved temporaries, as well as a stick bite and shade decision, including stump shade. Photographs of shade tabs next to the patient’s teeth are essential.
14. Try-in and approval of final restorations by the patient prior to insertion.

Dental Material Selection
The multitude of new dental materials available makes this process a bit more confusing, but has allowed greater success when a material chosen as best suited for a given case is used. In the author’s opinion, lithium disilicate restorations (such as IPS e.max [Ivoclar Vivadent]) provide a conservative, strong option for many difficult cases. These restorations are highly aesthetic, can be placed without overly reducing tooth structure, and may be seated using either conventional cementation or adhesive bonding techniques.^5,6 The material can be pressed as thin as 0.3 mm, so minimal tooth preparation can be achieved while still ensuring strength of 400 MPa.^6,7
In the author’s view, lithium disilicate restorations have shown excellent adaptation to tooth structure and the surrounding gingiva. The material can be used to fabricate a combination of restorations for the same case, so aesthetic issues that can occur from attempting to match dissimilar materials and/or natural tooth structure are eliminated.⁸ Lithium disilicate safely interacts with its surroundings without causing adverse biological reactions.⁹
Inlays, onlays, thin veneers, veneers, partial crowns, anterior and posterior crowns, 3-unit anterior bridges, 3-unit premolar bridges, telescope primary crowns, and implant superstructures can be fabricated from the pressable lithium disilicate (IPS e.max Press).^6,10-13 Machineable lithium disilicate is indicated for inlays, onlays, veneers, partial crowns, anterior and posterior crowns, telescope primary crowns, and implant superstructures.^6,10-13

CASE REPORT
Diagnosis and Treatment Planning
A 17-year-old female, accompanied by her parents, presented with a desire to improve her smile and address functional issues. She had recently completed 3 years of orthodontic care, but the patient and her parents were still unhappy with the appearance of her teeth. She also complained of tiredness and occasional pain “in front of her ears.”
A visual examination revealed severe enamel issues, consistent with AI. Her teeth had bands of very dark yellow, with areas of lighter yellow and brown (Figure 1). All of them showed severe pitting and an irregular surface. Many of her posterior teeth showed wear patterns, and several teeth were missing or unerupted. She showed evidence of an anterior open bite, and she was biting on previously prepared tooth No. 19, which was only 1.0 mm above the gingival margin. Some teeth were in an edge-to-edge occlusion, with others in a Class 1 arrangement (Figure 2).

Figure 1. Pre-op photograph showing severe mottling and dark orange and gray varied patterns. Also note the anterior wear and small size of the incisors.	Figure 2. Pre-op photograph in occlusion, after 3 years of orthodontic treatment. Note the uneven occlusion, with some teeth edge-to-edge and others out of occlusion with anterior open bite tendencies.
Figure 3. The author strongly advocates using a face-bow to deliver jaw relationship information to the mounted models and, hence, to the laboratory for creating wax-ups and the final case. The Combi Slidematic (Whip Mix) face-bow uses a simple, rapid approach to creating records.	Figure 4. The initial provisionals were created from a template made from laboratory wax-ups. The change in her smile was obvious immediately. Smile and bite changes were tolerated well, and the patient was thrilled with the changes.

The complexity of the case was discussed with the patient and her parents. A comprehensive examination, occlusal analysis, and photographs were suggested. There were time constraints involved in her treatment, since she would be leaving the country for a year the following September.
It was determined that the orthodontic bands should be removed due to blunted roots of teeth Nos. 7, 9, and 10. After the bands were removed, a full-mouth series was taken. Surprisingly, no decay was noted, other than on prepared tooth No. 19. The patient experienced occasional pain in this tooth following root canal therapy earlier that year. The patient was referred back to the endodontist who had completed the treatment.
A load test was positive. The patient wore a Lucia jig (Great Lakes Orthodontics) in the office for 20 minutes. Her muscles felt more relaxed after this test, and she was comfortable using a leaf gauge to establish a centric bite. Upper and lower impressions and a facebow (Combi Slidematic Facebow [Whip Mix]) were taken, and the models were then mounted on a Combi Articulator (Whip Mix) (Figure 3).
The records were sent to the dental laboratory team. Our technicians are “Dawson Academy trained” and they demonstrated a great understanding of the systematic approach to treating complex bite cases.

Preliminary Phase
Laboratory wax-ups were necessary to help plan the patient’s treatment. An accurate centric bite was essential, especially when treating a patient with temporomandibular joint disorder (TMJ) symptoms at such a young age. The preoperative models were used to create a deprogrammer appliance. The patient was instructed to wear it for 24 hours a day for 3 days, and to remove it only during meals and to clean it. Following 3 days of wearing the device, a negative load test still could not be accomplished, even though the patient said her pain was diminishing. Following 2 more days of compliance, a negative load test was achieved. However, the patient still experienced discomfort when the appliance was not being worn, so she was referred to a TMJ specialist for an opinion prior to fabricating the wax-ups. The specialist determined that her TMJ issues were minimal and manageable if her bite was opened; prosthetic reconstruction would help treat the TMJ issues. He also suggested fixed bridges to replace missing mandibular teeth, since all teeth required restoration and the pontic areas were extremely narrow.
At this time, the models were returned to our laboratory team to create the wax-ups. The patient’s bite needed to be opened 1.0 to 2.0 mm and all teeth required crowns. Due to the very small tooth size resulting from the AI, minimal preparation of each tooth was needed to realize the desired result.
Once the wax-ups were delivered to us, the patient and her parents returned for an office visit. Her parents declined gingival crown lengthening because the patient’s gingival margins did not display when smiling. They were very happy with the wax-ups.
Sequencing treatment and the benefits and drawbacks of various restorative materials were then discussed. Lithium disilicate (IPS e.max Press [Ivoclar Vivadent]) was selected for the crowns based on its strength and aesthetics; this material would mask the very dark internal shade without requiring aggressive tooth preparation of the young dentition. Bilayered zirconia would be used for the 2 fixed bridges. Additional orthodontics also was discussed but not advised due the blunted roots on the anterior teeth. Shorter appointments were advised, given the patient’s TMJ issues.
Overall, the potential complications of treatment or no treatment were presented to her parents. These included potential future root canal issues and exacerbation of TMJ symptoms. After all was explained, the patient, with the support of the parents, was anxious to begin treatment.

Preparation, Impressions, and Provisional Phase
Decay was removed from tooth No. 19, and a titanium post (Flexi-Post [Essential Dental Systems]) and core (Clearfill Photocore [Kuraray America]) were placed. Then, the patient returned to begin preparation of teeth Nos. 2 to 14 for lithium disilicate crowns. A modified shoulder design was created using preparation guides fabricated by our dental laboratory.
A template of the wax-ups also was made for creating the provisional crowns. Splinted temporaries (Luxatemp Ultra [DMG America]) were provisionally cemented with (Tempbond NE [Kerr]) with Vaseline in shade Vita B1 (Vident) (Figure 4). The patient was very happy with her new smile. During a follow-up phone call that night, the patient said her TMJ issues had not been a problem.
The patient returned 6 days later to prepare the lower dentition and establish her new bite. She was doing very well with the new upper alignment and had no significant symptoms in her teeth, muscles, or joint. Modified shoulder preparations were completed, with care not to overprepare due the proximity of pulp horns in her young teeth. Teeth Nos. 22 to 27 and No. 31 were prepared for pressed lithium disilicate (IPS e.max Press) crowns, and teeth Nos. 28 to 30 and Nos. 19 to 21 were prepared for bilayered zirconia bridges. The preparation guides established the minimum reduction necessary, especially in the lower anterior teeth.
The provisionals were cemented as previously described. Impressions were not taken, since it was necessary to ensure that the patient would tolerate the increased vertical dimension and larger tooth size. The patient was instructed to return in 2 weeks with her parents to evaluate the provisionals and to discuss the next treatment steps.
Upon return, the patient was very happy with the size and shape of the provisionals. Her parents, however, were uncertain if they liked the size, since they were accustomed to seeing her with very small teeth throughout her childhood. After a few days, they consented to slightly shorter crowns and decided they loved her new look. Together, we reviewed her new smile and determined a final color (Vita B1).
The following day, the maxillary provisionals were removed, final touchups completed on the prepared teeth, and a full-arch impression of the maxillary preparations was taken (Flexitime [Heraeus Kulzer]). A double cord technique was used (Ultrapak Cord; sizes 00 and 0 [Ultradent Products]). Note: The author always takes a minimum of 2 full-arch impressions for a large case to provide the laboratory team with more options and to ensure against pour-up/breakage issues. A stick-bite impression was taken to prevent any improper canting in the final restorations. Bite records were taken (ACU-flow [Great Lakes Orthodontics]), along with impressions of the lower provisionals as a counter model. New upper provisionals were created and adjusted in centric relation and excursions. They were cemented as previously described.
Two days later, the patient appeared for impressions of the new approved provisional restorations after slight touchups, as well as photographs of the provisionals in place. The bite was adjusted slightly, and the temporaries shortened slightly as per the patient and her parents.

Delivery of Restorations
The patient returned with her parents several weeks later to insert the upper crowns. They were tried in with clear and white try-in pastes (NX3 [Kerr]). They were very happy with the color and size of the lithium disilicate crowns and requested cementation that day. This was accomplished using white cement (NX3), porcelain primer (Silane Primer [Kerr]), and Optibond XTR (Kerr) with a selective-etch technique.

Figure 5. The initial try-in of the permanent crowns showed an obvious cant to the left. It became necessary to recontour tooth No. 9 to create improved symmetry. Teeth Nos. 8 through 10 were returned to the laboratory team, and the other anterior restorations were adjusted.	Figure 6. Note the fine attention to detail in the crowns on the lower master model.

Figure 7. A computerized occlusal analysis (T-Scan III [Tekscan]) is an excellent tool to help achieve long-term results when perfecting a new bite.

However, prior to cementation, a slight cant (distal to tooth No. 9) was observed (Figure 5). Therefore, the restorations for teeth Nos. 2 to 7, and Nos. 11 to 14, were permanently cemented. A pickup of teeth Nos. 8 to 10 with face-bow was taken and sent to the laboratory team to correct these teeth. New provisionals for teeth Nos. 8 to 10 were made and cemented, and the lower provisionals were adjusted to create anterior guidance and disclussion of the posteriors in excursions.
Five days later, the patient stated that she was comfortable and happy with the new crowns. The temporary crowns for teeth Nos. 8 to 10 were re-moved, and she was very happy with the slightly altered definitive crowns. Following cementation of these crowns (as previously described), the lower provisionals were removed and the preparations refined. Impressions with new facebow of the uppers and bite were taken (Flexitime) using the same technique as the upper teeth. Several impressions were taken, and new provisionals were created and adjusted in centric relation and excursions. The provisionals were then cemented (as previously described).
The definitive lower crowns and bridges were tried-in 2 weeks later. All fit beautifully, except the lower left bridge (Figure 6). There was a slight cant observed, so all restorations were returned to the laboratory team for adjustment. A new Lucia jig bite and impression were taken.
The patient returned 2 weeks later, and all crowns and bridges were definitively cemented with the patient’s and parents’ consent. The bridges were cemented with FujiCEM (GC America), and the crowns were cemented with Nx3 and Optibond XTR.
A computerized occlusal analysis (T-Scan III [Tekscan]) was used to assist in equilibrating all the new restorations (Figure 7). During a follow-up call that night, our patient said that she (and everyone) was very happy with her new smile. An additional bite adjustment (again using the T-Scan) was performed a week later and a nightguard appliance (Dawson B [Great Lakes Orthodontics]) was inserted. Two weeks later, the patient left for her year abroad, very comfortable and loving her new smile (Figures 8 to 11).

CLOSING COMMENTS
The ability to change someone’s life in a positive way is a joy that few professions can achieve. However, dentists and their collaborative teams must be prepared for the challenges ahead. Dentists should listen carefully to the patient’s desires and cater treatments to reach his/her personal goals, as well as theirs.
A systematic approach to addressing a patient’s issues leads to successful outcomes. Whatever resources are needed to address individual challenges should be used, including a competent team of specialists, technicians, and colleagues. Case planning involves understanding the time frame of various treatment phases so the dentist and patient have a firm understanding of what is to be done and when it will be completed. This provides a wonderful opportunity that can make dentistry more rewarding.

Acknowledgement
The author would like to thank Buddy Schaefer, Walt Richardson, and the whole team at Bay View Dental Laboratory (Chesapeake, Va).

References

1. Chaudhary M, Dixit S, Singh A, et al. Amelogenesis imperfecta: report of a case and review of literature. J Oral Maxillofac Pathol. 2009;13:70-77.
2. Doruk C, Ozturk F, Sari F, et al. Restoring function and aesthetics in a Class II Division 1 patient with amelogenesis imperfecta: a clinical report. Eur J Dent. 2011;5:220-228.
3. Santos MC, Line SR. The genetics of amelogenesis imperfecta: a review of the literature. J Appl Oral Sci. 2005;13:212-217.
4. Shetty YB, Shetty A. Oral rehabilitation of a young adult with amelogenesis imperfecta: a clinical report. J Indian Prosthodont Soc. 2010;10:240-245.
5. Fabianelli A, Goracci C, Bertelli E, et al. A clinical trial of Empress II porcelain inlays luted to vital teeth with a dual-curing adhesive system and a self-curing resin cement. J Adhes Dent. 2006;8:427-431.
6. Culp L, McLaren EA. Lithium disilicate: the restorative material of multiple options. Compend Contin Educ Dent. 2010;31:716-725.
7. Reynolds JA, Roberts M. Lithium-disilicate pressed veneers for diastema closure. Inside Dentistry. 2010;6:46-52.
8. Cardoso JA, Almeida PJ, Fernandes S, et al. Co-existence of crowns and veneers in the anterior dentition: case report. Eur J Esthet Dent. 2009;4:12-26.
9. Brackett MG, Lockwood PE, Messer RL, et al. In vitro cytotoxic response to lithium disilicate dental ceramics. Dent Mater. 2008;24:450-456.
10. Wolfart S, Eschbach S, Scherrer S, et al. Clinical outcome of three-unit lithium-disilicate glass-ceramic fixed dental prostheses: up to 8 years results. Dent Mater. 2009;25:e63-e71.
11. Gehrt MA, Rafai N, Reich S, et al. Outcome of lithium-disilicate crowns after 8 years. Presented at: IADR General Session & Exhibition; July 15, 2010; Barcelona, Spain. Abstract 656.
12. Etman MK, Woolford MJ. Three-year clinical evaluation of two ceramic crown systems: a preliminary study. J Prosthet Dent. 2010;103:80-90.
13. IPS e.max 5-year clinical performance. The Dental Advisor. 2012;29(6).

Dr. Auster graduated from the University of Pennsylvania School of Dental Medicine in 1980. A sustaining member of the American Academy of Cosmetic Dentistry (AACD) and a founding alumnus of the Dawson Academy, he also is a member of the AACD board of directors and president of the Empire State Academy of Cosmetic Dentistry, the New York affiliate of the AACD. Dr. Auster maintains an aesthetic and restorative practice with 2 partners in Pomona, NY. He can be reached at (845) 364-0400, or at drpauster@gmail.com.

Disclosure: Dr. Auster reports no disclosures.