Magnetic retention of dental prostheses in a child with ectodermal dysplasia
Roy A. Rockman, DDS,
K. Brad Hall, DMD and
Mark Fiebiger
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ABSTRACT
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Background. Ectodermal dysplasia (ED) is a group of heterogeneous disorders that result in hypodontia. In pediatric patients with ED, using prostheses to restore form and function can be a challenge.
Case Description. The authors present a case report that demonstrates a technique using magnets to enhance the retention of maxillary and mandibular prostheses in a 9-year-old boy.
Clinical Implication. The case report introduces an alternative prosthetic design for children who have ED.
Key Words: Dental prosthesis; ectodermal dysplasia; pediatric dentistry; prosthetics; dental restorationAbbreviations: ED: Ectodermal dysplasia • PVS: Polyvinyl siloxane
Ectodermal dysplasia (ED) is a large group of heterogeneous inherited disorders that share a common feature: defects in two or more tissues derived from embryonic ectoderm. The tissues affected by this abnormal morphogenesis include hair nails, teeth, eccrine glands and other secretory glands such as salivary and lacrimal. The condition is hereditary and nonprogressive. More than 192 distinct disorders have been described.1 The most common form of ED is the X-linked recessive hypohydrotic variant called Christ-Siemens-Touraine syndrome. In the United States, the frequency of this syndrome is estimated to be one case per 100,000 births. The majority of the morbidity and mortality are related to the dysfunction of the eccrine glands, resulting in intermittent hyperpyrexia due to decreased sweating. Resultant high fevers may lead to seizures and other neurological sequelae. Pharyngitis, rhinitis, cheilitis and dysphagia may result from the decreased number of mucous glands in the respiratory and gastrointestinal tracts. Growth delay, dermatitis and alopecia also are common findings.
The typical facial features of X-linked hypohydrotic ED include frontal bossing, sunken cheeks, saddle nose deformity, thickened everted lips, hyperpigmentation of the periorbital skin and large low-set ears. The dental manifestations include conical or pegged teeth, hypodontia or complete anodontia, and delayed eruption of the permanent teeth. Most patients with this form of the disorder have sparse, lusterless, fair hair with minimum pigmentation. Onychodystrophy and eczematous dermatitis are common. Intelligence is normal.1
Treating children who have ED with prostheses can have a profound impact. The children are given the opportunity to develop normal forms of speech, chewing and swallowing, and they can benefit from normal facial support, improved tempromandibular joint function and improved self-esteem.2 Removable prosthetics are the most frequently reported treatment modalities for the dental management of ED. The choice of the prosthesis depends on the status of the patient’s condition. If children have complete anodontia, clinicians can use complete dentures. The underdevelopment of the alveolar ridges, however, can compromise denture retention and stability. In children with hypodontia, clinicians can use removable prosthetic dentures. Often, clinicians can correct the contours on malformed teeth with direct composite restorations.3 Bryant4 reported early implant placement in patients up to 6 years of age; however, in a growing child, early implant placement can be problematic since implants act like ankylosed teeth. This situation can result in the reduced vertical development of the jaws and a distorted occlusal relationship.5,6 In this article, we present a case report that introduces a technique that uses magnetic retention of the prostheses that is cost-effective and noninvasive.
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THE USE OF MAGNETS IN DENTISTRY
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Magnets have been used in dentistry for many years. Initially, dentists used magnets in prosthetic dentistry to aid in the retention of dentures. Orthodontists also have used magnets in tooth movement and dentofacial orthopedics. Magnets used earlier were either aluminum-nickel-cobalt or platinum-cobalt alloys. Their use was limited, owing to the size of the magnet required to obtain the desired magnetic force. Also, the magnets corroded when they were exposed to oral fluids, and the corrosion caused a decrease in magnetic force.7 The introduction of rare earth magnets, which are smaller and have greater magnetic force than the magnets used earlier, revived interest in magnets in the 1970s and 1980s.
Investigators have raised questions about the potentially harmful biological effects of magnets. There are several studies in the literature that report no microscopic, radiologic or clinical evidence of deleterious effects of magnets on osseous or soft tissues.7 Evidence available from biological safety tests suggests that the risks magnets hold for biological systems are negligible. Animal studies have not detected harmful effects from magnets on blood cells, dental pulpal tissue, periodontal tissues, buccal mucosa or alveolar bone.8–16
The major issue confronting the use of magnets in prosthetic dentistry is their longevity. Keeping the magnet encapsulated is critical in maintaining the magnet’s strength. Once the encapsulation is breached, oral fluids can corrode the magnets, which decreases their strength.17 In pediatric patients, unlike adult patients, pros-theses may have to be replaced more frequently to accommodate the children’s growth and development. The design of the prostheses we describe in the case report below allows the clinician to replace the magnets in the denture to increase its retention. This, along with relining the denture, can add to its longevity.
Magnetic systems used in dentistry consist of two components: a magnet and a keeper. The keeper is made of alloys that can be magnetized, such as stainless steel or high-palladium alloy. When a denture is seated, the keeper becomes an induced magnet because of its contact with the magnet in the denture. When the denture is removed, the keeper reverts to its unmagnetized state, and the magnetic field around the keeper disappears.18
Another key factor in the design of the pros-theses is the retention of keepers on natural tooth structure. Cements are available that yield high bond strengths, allowing the keepers to be retained adequately on natural tooth structure.16
The following case report describes how we used magnets to retain dental prostheses for a child with ED.
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CASE REPORT
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We first saw a boy at the Medical College of Georgia Pediatric Dental Clinic, Augusta, in February 2003 when he was 6 years old. The clinicians (R.A.R., K.B.H.) confirmed the diagnosis of ED. The child’s family history revealed that his mother and maternal grandmother also had ED. A clinician from a private pediatric dental office where the child had been receiving regular routine preventive dental care referred the child and provided a panoramic radiograph (Figure 1
).
The panoramic radiograph confirmed that multiple primary and permanent teeth were missing. When we conducted a clinical examination, we found that the intact primary dentition included all primary second molars, the primary maxillary canines, the primary mandibular right canine and the primary maxillary left central incisor. When we conducted intraoral and radiographic examinations, we found permanent maxillary and mandibular first and second molars, a permanent maxillary right second premolar, permanent mandibular right and left second premolars and permanent mandibular central incisors. The primary second molars had short crowns and the primary canines were conical in shape. The alveolar ridges in the region of absent teeth were flat and atrophied.
When we reviewed the child’s medical history, we found a mild hypohydrotic component to his condition. The boy’s hair was sparse and had little pigmentation. Our review of the panoramic radiograph revealed the extent of the child’s hypodontia (Figure 1
). A review of his medical systems revealed that they were within a normal range. Since the boy’s mother and grandmother also had ED, they understood the impact of the condition, they wanted the best possible treatment for him, and they complied with all instructions and home care suggestions. He was progressing at an above-average pace in school, and his behavior in the dental office was age-appropriate.
In March 2003, we fabricated maxillary and mandibular conventional pediatric partial dentures. The child wore these dentures for approximately one year. The mother reported that retention of the dentures in the child’s mouth was problematic, and, as a result, he did not wear them full-time. As the child became older, having teeth like his peers became more important to him and his family. In March 2006, when the boy was 9 years old, we and his family decided to try to fabricate new prostheses using magnets to increase their retention and comfort.
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TREATMENT
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We used pediatric stock metal trays to take alginate impressions for diagnostic models. We fabricated custom trays and made a final impression using a polyvinyl siloxane (PVS) material. We obtained records of the boy’s jaw and completed an initial diagnostic set-up using the smallest permanent tooth size, which was necessary owing to the limited amount of space in his dental arch.
Because previous wax try-ins and esthetic evaluations had proven problematic owing to space limitations, we fabricated a matrix (Essix C+ Plastic, Raintree Essix, Metarie, La.) and used it as a carrier for the esthetic evaluation. The clear plastic vacuum-formed matrix allowed us to evaluate the small prosthetic teeth esthetically when they were in position touching the edentulous ridge.
We selected a magnetic attachment set (Magnedisc 800, Attachments International, San Mateo, Calif.) as the retentive attachment because of its minimum vertical space requirements. This set includes a magnet that is incorporated into the prostheses and a keeper that is bonded to the teeth. According to the manufacturer, these magnets are made of a neodymium/boron alloy that is fully encapsulated and laser-welded, and they provide 800 grams of retention.19
We waxed the copings (the metal castings cemented to the teeth to house the keepers) for the primary right canine, the primary maxillary left second molar and the primary mandibular second molars. We cast them in Rexillium III alloy (Pentron Alloys, San Diego) (Figure 2). We used a resin-based adhesive system (Panavia 21, Kuraray Dental, Osaka, Japan) to cement the copings to the boy’s primary second molars and primary canines, and then we attached the keepers to the copings.
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Figure 2. Models illustrating the dental cast with the maxillary (A) and mandibular (B) keepers. Maxillary (C) and mandibular (D) keepers cemented intraorally.
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We took maxillary and mandibular PVS impressions and poured new casts in stone. We then waxed and cast maxillary and mandibular partial denture frameworks (Figure 3). We transferred the prosthetic teeth from the matrix to the frameworks and scheduled the patient for a try-in. To evaluate the esthetics of the denture, we employed a set-up using only the anterior teeth. Because of the vertical space limitations, we carved occlusal anatomy into the posterior maxillary wax rim. We left the posterior mandibular wax rim monoplane to create a lingualized nonbalanced occlusal scheme. Decreased vertical stress, denture stability during parafunctional movements, decreased lateral forces, ease of adjustments and centralization of forces are advantages of lingualized nonbalanced occlusion.20
We processed the dentures (Figure 4A–B) and then cold-cured the magnetic attachment system into the dentures with repair resin. This allowed for the magnets to be replaced if necessary. We delivered the final prostheses to the patient and provided wear and care instructions to both him and his family (Figure 4C–F).
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Figure 4. Processed maxillary (A and B) dentures. The dentures in the patient’s mouth (C, D and E). A full-face photo of the patient wearing the dentures (F).
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CONCLUSION
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The esthetics, function and comfort of these dentures that used magnetic retention surpassed that of conventional prosthetic appliances. The child adapted to the dentures quickly and within a few days was able to eat and speak while wearing the appliances. The magnets provided adequate retention. The psychological effect of looking and functioning like his peers was immeasurable. We informed the child and his family about the importance of oral hygiene and regular recall visits. We anticipate that the prostheses will have to be replaced every three to five years until the child reaches an age at which fixed prostheses can be fabricated using dental implants.
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FOOTNOTES
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Dr. Rockman is an assistant professor, Department of Pediatric Dentistry, School of Dentistry, Medical College of Georgia, 1120 15th St., Augusta, Ga. 30912, e-mail "rrockman{at}mail.mcg.edu". Address reprint requests to Dr. Rockman.
Dr. Hall is a clinical instructor, Department of Pediatric Dentistry, School of Dentistry, Medical College of Georgia, Augusta.
Mr. Fiebiger is a prosthetic laboratory technician, Prosthetic Laboratory, Medical College of Georgia, Augusta.
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REFERENCES
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ABSTRACT
THE USE OF MAGNETS...
