Treating the Amelogenesis Imperfecta Patient

INTRODUCTION
Amelogenesis imperfecta (AI) represents a group of inherited conditions that affect the structure and appearance of the enamel of all or nearly all the teeth, with a prevalence in the United States of approximately one in 14,000 people.^1,2 The variable range of AI enamel defects involve abnormalities that are classified as hypoplastic (defect in quantity of enamel), hypomaturation (defect in final growth and development of enamel crystallites), and hypocalcified (defect in initial crystallite formation followed by impaired growth), with diagnosis traditionally determined by clinical presentation.^2,3 Four main types of AI classifications exist and are based on the type of enamel defect; 14 unique subtypes exist and are based on clinical appearance and mode of inheritance.^3,4

CASE REPORT
Diagnosis and Treatment Plan
Our 14-year-old patient presented with 2 major dental problems (Figure 1), AI as well as generalized severe wear.

This patient’s hypoplastic enamel contributed to the discolored appearance of her teeth and approximately 50% of tooth height had been lost due to the wear and defective enamel (Figures 2 and 3). Although there was no sensitivity with the wear, there was an obvious aesthetic deficit. The preoperative photos demonstrate how porous and stained the enamel was due to the AI. Our patient was self-conscious about the appearance of her teeth and desired a more attractive smile.

Figure 1. Frontal view at initial pre-op visit.

Figure 3. Smiling view showing the classic look of enamel pitting due to AI.

Defective enamel was a functional, aesthetic, and psychological concern to address. The severe wear and subsequent passive eruption caused the entire maxillary ridge to supraerupt. A maxillary incisal edge discrepancy with the lower lip-line existed due to the outline of the flat maxillary incisal edges being horizontal and not having a rounded gull-wing shape and harmony with the lower lip-line.

Knowing that we needed to postpone final restoration until this patient had reached her growth potential, we decided to first begin by increasing restorative space. An initial gingivectomy followed by placing composite veneers (Renamel Microfill [Cosmedent]) on teeth Nos. 6 to 11 provided our patient with an immediate aesthetic improvement until definitive restorations could be placed to enhance her smile. After reaching her growth potential, we would proceed with crown lengthening, followed by preparation for 24 single-unit Captek (Argen Corporation) restorations.

Clinical Protocol: Definitive Restorative Treatment
She returned 6 years later, at age 20 years, ready for the definitive restorations (Figure 4). The composite restorations held up well during the previous 6 years, and now the time to restore her teeth had arrived.

Figure 4. The patient returned 6 years later at age 20, ready to have her teeth repaired.

Figure 5. Occlusal view of the maxillary arch demonstrates the effects of AI.	Figure 6. Crown lengthening was done in the maxillary arch.
Figure 7. The 3-bite technique of capturing vertical dimension of occlusion and centric relation was utilized. This photo shows the third bite (O-BITE [DMG America]) taken with both posterior quadrants prepped.	Figure 8. Maxillary and mandibular provisional restorations (Luxatemp [DMG America]) in place.
Figure 9. Twelve Captek (Argen Corporation) mandibular restorations on master model.	Figure 10. Twelve Captek maxillary restorations on master model.

Figure 11. Lingual view of restorations mounted on the SAM 3 Articulator (Great Lakes Orthodontics).

In order to address the 50% loss in tooth height, crown lengthening was necessary. This allowed us to maintain her existing vertical dimension of occlusion (VDO) while achieving a more appropriate and aesthetic width-to-height ratio of the dentition, as captured with our initial diagnostic wax-up. Ideal width-to-height ratios of aesthetically perceived maxillary anterior teeth range from 75% to 80%.⁵ This ratio was considered in her smile design; however, the patient’s unique facial dimensions and characteristics and upper and lower lip positions ultimately dictated the width-to-height proportions.

As the teeth wear down and get shorter, due to an increased rate of attrition caused by AI, the passive eruption process brings the alveolar bone and gingival tissue in an incisal direction, as seen in Figure 4. Elongation of the dento-alveolar process matched the lost VDO of the abraded teeth.⁶ The dimension from a fixed bony landmark to the occlusal surface remains constant with severe wear, but the measurement from a fixed bony landmark to the cemento-enamel junction increases.⁷ The occlusal view demonstrates the effects of AI on the integrity of the enamel and the incisal and occlusal surface wear (Figure 5).

To obtain the desired gingival architecture, crown lengthening was done on the maxillary teeth Nos. 2 to 15 and tooth No. 23 (Figure 6). Due to the linguoversion of No. 23, the restorative margin required an apical placement that would have impeded biologic width if crown lengthening was not performed. The periodontist was provided with a translucent surgical stent fabricated from the diagnostic wax-up to locate the gingival zeniths.

Following preparation of teeth Nos. 2 to 15 for full-coverage crowns with a tapered round-ended diamond (No. 112-5161 [Henry Schein]), mandibular preparation began using the same bur. Part of the preparation of the mandibular arch involved a gingivectomy on tooth No. 23 to establish a more balanced gingival zenith. In preparing the mandibular incisors, our first objective was to create a uniform and smooth arch form. The lingual aspect of each incisor was reduced until we created an even curve, then the facial aspect was reduced and the preparations completed. The following 3 aids can be used when preparing teeth: (1) a clear thermoplastic stent (UltraVac [Ultradent Products]), which allows the clinician to see the entire aspect of each prep—sometimes small holes can be made in the stent to allow a periodontal probe to measure the depth of the preparation; (2) an incisal edge putty matrix (Sil-Tech Putty [Ivoclar Vivadent]), which allows the clinician to see how much incisal reduction has been made; while (3) the prep guide fabricated from the same material is used to evaluate facial reduction. We utilized the 3-bite technique of capturing VDO and centric relation. Using this technique, the anterior teeth were prepared first and a closed bite was taken utilizing O-BITE (DMG America) bite registration material. Next, each of the remaining posterior quadrants were prepped, one at a time, and the anterior bite registration material was placed back onto the anterior teeth while obtaining a bite on each side, one side at a time (Figure 7).

A thermoplastic stent (UltraVac) was made to use in fabrication of the provisional restorations based upon the model of the diagnostic wax-up of the mandibular teeth. Figure 8 shows both the maxillary and mandibular provisional restorations (Luxatemp [DMG America]) in place. The Luxatemp provisional material was simply placed into the tray and then inserted over the preps. After the material hardened, the stent and Luxatemp were removed, trimmed, and the bite adjusted.

All 12 mandibular restorations are Captek crowns (Figure 9). These crowns were designed to have facial collars of porcelain for aesthetics and an exposed gold collar on the medial, distal, and lingual surfaces slightly below the gingiva to achieve optimal periodontal health. The high noble gold content of the copings demonstrates a bacteriostatic nature that is beneficial in reducing bacteria and aiding in periodontal health. The posterior restorations were designed similarly to the anterior restorations.

The case was mounted on a SAM 3 articulator (Great Lakes Orthodontics) using 3 separate bites to capture centric relation at her given vertical dimension. The facial view of the finished Captek restorations mounted on the SAM 3 Articulator can be seen in Figures 9 and 10. Figure 11 shows the porcelain butt margins on the lingual of the molars and premolars. We consider this area to be the most overlooked aesthetic zone in the mouth. All too often, a thick gold collar is placed on this lingual area and can easily be seen; however, the lingual gold collars on the anterior teeth are not visible. Figure 11 shows the margin design of the porcelain lingual butt margins on the posterior teeth and lingual gold collar on the anterior teeth. The restorations were bonded into position using the 4th generation bonding system, OptiBond FL (Kerr) and Calibra Esthetic Resin Cement (Dentsply Sirona).

Figure 13. Preoperative photo.	Figure 14. Postoperative photo our very pleased patient.

The treatment outlined was effective in restoring the defective worn dentition, and in creating natural color and shape to her teeth (Figure 12). Although these restorations had only been in place for one month, the gingival tissue looked much improved. The pre-op and post-op photos (Figures 13 and 14) demonstrate how the natural smile can be restored even in the presence of amelogenesis imperfecta, extreme wear, and elongation of the dento-alveolar process.

CLOSING COMMENTS
In this case, all of our efforts were aimed at restoring proper tooth form, function, color, as well as gingiva-osseous contours. After a multidisciplinary treatment plan consisting of numerous appointments during an extended period of time, we were able to accomplish our goals and to exceed our patient’s aesthetic expectations.

References

1. Aldred MJ, Savarirayan R, Crawford PJ. Amelogenesis imperfecta: a classification and catalogue for the 21st century. Oral Dis. 2003;9:19-23.
2. Witkop CJ, Sauk JJ. Heritable defects of enamel. In: Stewart RE, Prescott GH, eds. Oral Facial Genetics. St. Louis, MO: Mosby; 1976:151-226.
3. Witkop CJ Jr. Amelogenesis imperfecta, dentinogenesis imperfecta and dentin dysplasia revisited: problems in classification. J Oral Pathol. 1988;17:547-553.
4. Wright JT. The diagnosis and treatment of dentinogenesis imperfecta and amelogenesis imperfecta. Hellenic Dentistry Journal. 1992;2:17-24.
5. Cooper GE, Tredwin CJ, Cooper NT, et al. The influence of maxillary central incisor height-to-width ratio on perceived smile aesthetics. Br Dent J. 2012;212:589-599.
6. Dawson PE. Functional Occlusion: From TMJ to Smile Design. 3rd ed. London, England: Elsevier Health Sciences; 2007.
7. Crothers A, Sandham A. Vertical height differences in subjects with severe dental wear. Eur J Orthod. 1993;15:519-525.

Dr. William Wynne maintains a private practice in Raleigh, NC, focusing on aesthetic and restorative dentistry. He graduated from the University of North Carolina School of Dentistry in 1971 and has achieved status of Pankey Scholar. He is a Diplomate of the American Society for Dental Aesthetics and a member of the American Society of Dental Practice Administration. Dr. Wynne has published numerous articles on aesthetic dentistry, occlusion, and eating disorders. He can be reached at (919) 851-3716.

Dr. Tyler Wynne received his doctor of dental surgery degree (2014) from the University of North Carolina School of Dentistry. He practices general dentistry in Faison, NC, and is adjunct faculty at the University of North Carolina School of Dentistry. He can be reached at wtwynne@gmail.com.

Disclosure: The authors report no disclosures.

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