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Implants in children and inherited disorders.

INTRODUCTION

Hedegard's report from the 1965 European Orthodontic Society Congress recommends that "every effort should be taken to avoid prosthetic treatment as the final stage", and this recommendation has been an overall goal in dental therapy treatment planning for young individuals with missing teeth [1].

In an effort to minimise the number of missing teeth that need replacement, different methods can be used, and since the methods are age dependent, an early diagnosis of which teeth are missing is crucial. Growth-adapted measures--such as early extraction of primary teeth to allow eruption of existing permanent teeth into more favourable positions--and orthodontic treatment are the most widely used strategies4 [2,3,4,5] Auto transplantation of permanent teeth into positions where teeth are missing can be done with highly predictable results and good long-term outcomes [6,7,8].

One of few reports on treatment outcomes in young individuals with many missing teeth is a Danish study on [15] consecutive patients with oligodontia [9]. Their patients were missing 10 teeth on average, and 10 patients had ED. Ninety-seven per cent had had some kind of orthodontic treatment and 90% of the 51 patients whose treatment was finalised had dental implants.

Bergendal et al. [10] made a compilation of 61 Swedish patients with oligodontia whose treatment had been planned in a multidisciplinary team and was finalised. The compilation revealed that some type of prosthetic restoration replaced only 42% of teeth absent due to agenesis, the remaining missing teeth had not been replaced. Forty patients (66%) had 174 dental implants -the most frequent form of restoration [10].

Multi-disciplinary treatment planning in teams of dental specialists has many advantages in cases with many missing teeth, but little is known about patients' attitudes toward and expectations of treatment. A British study of complaints at a hypodontia clinic revealed that 40% of 451 referred young individuals had "no complaints", while only 14.6% considered "appearance" to be their most important problem [2]. A study in Hong Kong on oral healthrelated quality of life (OHRQoL) targeted individuals with severe hypodontia [12]. Twenty-five children aged 11-15 years lacked a mean of 8.9 teeth (range 4-20) and reported considerable OHRQoL impact. A majority (88%) reported functional limitations and impacts on emotional well-being. Locker et al. [13] studied OHRQoL in 36 Canadian children with hypodontia [13]. The children were missing a mean of 6.8 teeth (range 1-14), and 75% reported functional and psychosocial impacts "Often" or" Every day/almost every day".

Dental implant treatment in young individuals:

After dental implants were introduced in adults as a highly predictable method for replacing teeth lost to dental disease sequelae, new indications in young individuals were explored. An early attempt to replace an upper central incisor lost due to trauma in a young individual revealed that the implant behaves like an anchylosed tooth and prevents further growth of alveolar bone in the region [14]. Experimental studies in growing pigs [15,16] and a long-term follow-up in a child where implants were placed early (Rossi & Andreasen, 2003) confirm this principle. A Swedish consensus conference on the use of dental implants in young individuals was held in 1995. According to conference statements, although implants should not as a rule be placed in healthy young individuals until growth is completed, implants may be placed in individuals with anodontia or severe oligodontia before the pubertal growth spurt [16], a recommendation which is still valid [19].

In several cases of dental implant placement in young boys with x-linked hypohidrotic ED--treated from 1.5 to 6 years of age--treatment outcome has been reported to be successful [20,23,21]. A prospective study on six patients who were followed from age 5 years for an average of 7.8 years reported favourable outcomes with the loss of only one implant [22]. At present, the Guckes et al. study is the only prospective study done on a large group of individuals with ED [23]. Fifty-one patients aged 8-68 years had 243 implants placed in the anterior mandible and 21 in the anterior maxilla. The survival rates were 91% in the mandible and 76% in the maxilla. Fourteen individuals had lost an implant, and all but two of these were lost before loading.

A retrospective evaluation from Australia reported treatment outcomes in 14 young patients with ED [24]. Of the 61 implants placed, 88.5% integrated successfully, while 3 of 15 in the anterior maxilla and 4 of 46 in the anterior mandible were lost. Five patients (36%) had lost at least one implant before abutment connection. A review of 12 articles on dental implant treatment in patients with ED reported implant survival rates to vary between 88.5% and 97.6% [25]. These results are comparable to those of a meta- analysis on implant supported fixed dental prostheses (FDPs). The meta-analysis reported a 5-year survival of 95.2%, and a 10-year survival of 86.7% [26]. However, both removable and fixed prostheses were used in the ED studies.

Bergendal et al. recently compiled 57 reports of dental implant treatment in individuals with rare disorders. These reports contained 31 (54%) publications that described 110 individuals with ED. Thus, publications on individuals with ED constituted over half of the reports, and the 110 individuals constituted nearly three-quarter of the treated patients. Individuals with ED seem to be predominant among the individuals with rare disorders who undergo oral habilitation with dental implants.

Krieger et al. assessed failures and complications of prosthetic treatment in patients with birth defects, including hypodontia/oligodontia126. After more than 8 years, over 60% of single crowns and 64% of FDPs on implants were free of complications. But when complications with implant- and tooth supported restorations did occur, they occurred earlier with the implant-supported restorations. Still, the authors recommended implant-supported restorations as the treatment of choice, due to the benefits of avoiding the need for tooth preparation. However, the trend for earlier and more frequent complications must be weighed in, since many years in function can be expected in young individuals. An evaluation of cumulative prosthetic treatment costs for young adult patients with birth defects included 22 individuals with hypodontia/ oligodontia. About half of the patients with implant-supported reconstructions experienced no failures or complications over a median observation period of 8 years. Cumulative long-term costs were similar for implant-supported and tooth-supported restorations [27].

Rare disorders:

According to the Rare Diseases Act of 2002, and the National Institutes of Health Office of Rare Diseases Research, a rare disease is generally considered to have a prevalence of fewer than 200,000 affected individuals in the US, equivalent to around 1 in 1,500 citizens. The European Organisation for Rare Diseases (EURORDIS), defines a disorder or disease as rare in Europe when it affects less than 1 in 2,000 citizens. In her thesis, Storhaug (1989) emphasised that individuals with rare disorders and their families need special attention concerning information and accessibility to medical and dental care--to prevent unfavourable development and dental disease 132. Trulsson and Klingberg (2003) used qualitative methods to explore the perspectives of parents of children with rare disorders and found that respect, involvement, continuity, knowledge, and availability were aspects of professional attitude which were considered desirable 133.

The concept of evidence-based medicine (EBM) was originally established to identify the most efficient cures for common diseases and public health problems [31]. Different levels of scientific evidence were defined, the highest level being "strong evidence from at least one published systematic review of multiple well-designed randomised controlled trials", and the lowest level "opinions of respected authorities based on clinical evidence and descriptive studies or reports of expert consensus committees". EBM has also had an enormous impact in dentistry on study designs and research funding, besides being indispensable in developing the best methods for preventing and curing major dental diseases and evaluating outcomes of common therapies. But many clinical problems and types of treatment do not fit into that scheme [32].

Reports on treatment of individuals with rare disorders often reach only the lowest levels of evidence. Editors and clinicians alike often reluctantly refer to case reports as anecdotal and of negligible importance for the advancement of clinical know-how. However, long-term follow-ups of treatment in small groups of individuals can have enormous news value, despite low group size. Clinical knowledge requires an understanding of the patient and the disease, and many important aspects of clinical encounters cannot be studied using the traditional quantitative research paradigm [33]. Ideally, prospective monitoring of larger cohorts will contribute substantially to clinical knowledge. But in the case of rare disorders and many treatment modalities that cannot be tested in a randomized manner, research designs with lower levels of evidence, as well as the use of qualitative methods, will provide the best possible evidence. Our general aim was to advance knowledge on signs and symptoms, genetics, and outcomes of dental implant treatment in individuals with ectodermal dysplasia.

Ectodermal Dysplasia:

Severe hypodontia or even adontia in children are very rare conditions, most often associated with congenital syndromes such as Down syndrome (trisomy 21) [46] or ectodermal dysplasia [53]. There exist more than 170 clinically distinct hereditary syndromes in which ED is present [44]. They are caused by an impaired development of epidermal appendages and are characterized by a primary defect at least in one of the following tissues: nails, hair, teeth or sweat glands [50]. EDs are rare diseases with an estimated incidence of seven in 100,000 births for all Eds. The pattern of inheritance is different, including Mendelian modes and sporadic cases. Several classifications of EDs have been proposed from a clinical point of view [49], with molecular genetic attributes (Priolo et al. 2000) and based on identified causative genes that most often are involved in processes of intercellular communication and signalling [45].

The clinical diagnosis of hypohidrotic EDs in the neonatal period and in early infancy is sometimes difficult because sparse hair and absent teeth are often normal findings at this stage. Dysmorphic facial features such as prominent suporaorbital ridges, frontal bossing and a depressed nasal bridge might be interpreted as normal variants. However, as seen in the presented case, the diagnosis becomes easier during childhood based on the medical history and clinical examination. Sparse hair growth and deficient teeth become increasingly recognized, probably associated with hypoplastic mucous membranes and a decreased mucous production in the aerodigestive tract due to absent mucous glands. This can lead to chronic upper respiratory tract infections, otitis, dysphagia, hoarseness, bronchitis and sometimes hemoptysis [52]. Facial symptoms become increasingly manifest and include maxillary hypoplasia, 'saddle' nose formation, prominent lips and linear wrinkles around the eyes. The hair is fine, dry, brittle and sparse, and the skin is thin and dry with hypohidrosis. Absent or decreased sweating in patients with anhidrotic, respectively, hypohydrotic ED is caused by absence of sweat glands. Affected children have difficulty controlling fevers and already mild illness may produce extremely high fevers because of absent temperature regulation by sweating. Affected adults are unable to tolerate a warm environment and require special measures to maintain a normal body temperature [49]. The diagnosis of hypohydrotic ED is usually performed by a biopsy of the skin that shows absent or hypoplastic sweat glands. Additionally, for some subtypes of EDs genetic testing is available [55]. Currently, there is no causative treatment available.

The insertion of dental implants in children or adolescents before completion of craniofacial growth is related to several problems. Experimentally, it was shown that endosseous implants placed in young pigs have imitated the effects of ankylosed teeth [51]. Placed in alignment with adjacent teeth, the implants did not participate in growth processes, resulting in an infraocclusion and multidimensional dislocation when compared with the developing teeth [51]. Additionally, adjacent tooth germs exhibited morphologic changes and disorders of eruption [54]. In the nearly anodontic child, however, these problems can be neglected.

The finding of the ideal time of implant treatment in children seems quite difficult because many different aspects have to be considered while finding the best individual treatment strategy. It seems clear that the placement of implants in children with ED must be a team effort consisting of a surgeon, prosthodontist, orthodontist and periodontist. In younger ages, additionally, a pediatric dentist might also be required. First, the medical diagnosis of ED must be confirmed to avoid mistreatment. Profound dental clinical and radiographic examination to determine the extent of hypodontia is fundamental for further planning. The role of the dental team includes the preservation of the existing dentition, especially in patients with xerostomia, and maintenance of an adequate oral hygiene. If some teeth are present, their prognosis might be estimated.

There are reports that implant treatment should be ended before puberty for optimum functional and psychosocial development [38]. Nevertheless, reports in the literature describe placement of implants as early as 3 years [23] or 5 years of age. From the orthodontic view the safest time to place implants seems to be during the lower portion of the declining adolescent growth curve at or near adulthood that can be determined by cephalographic radiographs, serial measure of stature or handwrist radiographs. Other relevant aspects to consider include the individual status of the existing dentition, the functional status of mastication and phonetics, esthetic aspects and emotional/ psychological well-being [43]. Finally, both the parents and the child have to be compliant to implant treatment and implant hygiene [22].

Study design:

Of the 164 individuals, two had radiation therapy in early childhood and were excluded. The remaining 162 individuals were invited to participate in a clinical examination, and 123 (75.9%) consented--71 females (57.7%) and 52 males (42.3%). The study group comprised 26 patients, 18 girls and 8 boys, reported to be treated with dental implants before 16 years of age. Patients were divided into three subgroups according to treatment reason: tooth agenesis, trauma, or hypohidrotic ED. Table 1 describes the study groups in (I)--(II).

Young implant-treated individuals:

A questionnaire was sent to Swedish specialist clinics in oral and maxillofacial surgery and prosthetic dentistry, asking them to report children and adolescents up to the age of 16 who had been treated with dental implants from 1985 to 2005. The questions comprised initials, birth year, syndrome diagnosis, reason for implant treatment, number of placed implants, and complications; each patient was reported on a one-sheet form. The study was made in cooperation with the National Board of Health and Welfare and the Swedish ED society

The responding specialists who had treated the patients in the ED group were contacted and asked, after informed consent of the parents, to send copies of documentation from the patient records, including radiographs and clinical photographs, for review. Results were discussed with the two oral surgeons who had performed surgery in the two most recently treated patients.

All data were processed with the Statistical Package for the Social Sciences (SPSS; versions 10.0-15.0; Chicago, IL, USA). Descriptive statistics were reported as means, frequencies, and ranges. The chi-square test was used for statistical testing of proportions of categorical variables, and the one-way ANOVA for testing group differences in missing teeth.

The total NOT-S score in the ED group was 3.5 (range 0-8) compared to 0.4 (range 0-2) in the healthy reference sample (p < 0.001). Dysfunctions were most frequently recorded in the Chewing and swallowing (82.6%), Dryness of the mouth (45.7%), and Speech (43.5%) domains. The added evaluations of hoarseness and lisping were recorded in 32.6% and 47.8%, respectively.

The ED group was divided into one group with hypohidrotic ED, comprising 32 individuals, 26 males and 6 females, and another group with other EDs comprising 14 individuals, 4 males and 10 females. The total NOT-S score for the hypohidrotic ED group was 3.0 (range 0-6), and for the other ED group 4.6 (range 1-8), but the difference was not statistically significant (p > 0.05). Figure 2 presents the dysfunction profiles of the ED groups and the reference sample.

Dysfunction profiles based on NOT-S domain score frequencies in individuals with EDs and a healthy reference sample.

Forty-two clinics representing 30 specialist centers from north to south Sweden responded to the inquiry. Over a period of 20 years, six centers (20%) treated a total of 26 patients under age 16 years: 18 females and 8 males. Age at implant placement was 12-15 years in the agenesis and trauma groups, and 5-12 years in the ED group.

Of the 47 implants placed in the three groups, 25 implants (53.2%) were placed in 14 patients for tooth agenesis, and two implants failed. The trauma group comprised 7 patients with 8 implants (17.0%), no implant lost. Thus, in individuals with tooth agenesis or trauma 6.1% of the implants were lost. The hypohidrotic ED group comprised 5 children with 14 implants (29.8%) in the anodontic mandible. Four of them lost 9 implants (64.3%) shortly after placement and in all cases before abutment connection.

The first patient was treated in 1985 and the last in 2005. The five patients with ED underwent implant surgery under general anesthesia. The same implant system was used, but with different type, diameter and length of the implants (Table 1, II). The oral surgeons who had operated on the two most recently treated patients reported that the bone volume was limited and that the bone appeared to be extremely hard, which caused difficulties in implant insertion. The four children with ED whose implants failed were successfully reoperated, two of the children when they were in their teens and two directly after primary healing of the mucosa.

Discussion:

Children with few or no permanent teeth present one of the ultimate challenges in dentistry. Despite much attention in the literature concerning the extensive need for dental care compared with other rare syndromes, individuals with ED rarely figure in high-quality studies; most are subjects of case reports with low levels of scientific evidence. Dental treatment of individuals with oligodontia, ED, or both is also a heavy burden on health delivery, in terms of workload (time) and cost.

In recent years, Schalk van der Weide and Nordgarden reported observing other ectodermal symptoms in many individuals with oligodontia [34,35], implying an under-diagnosis of EDs. These studies, however, assessed patient cohorts referred to specialist clinics and a resource center for rare disorders. Because children with oligodontia often need extensive dental treatment, dentists are ideally placed to help improve diagnostics of ectodermal symptoms in this group of patients.

Dentists are ideally placed to identify female carriers for x-linked hypohidrotic ED. As a group they have dental aberrations that differ with statistical significance from unaffected individuals. But there is a covariance between aberrant tooth form and smaller tooth size in hypodontia in general, and the chances of identifying female carriers among individuals with hypodontia seem limited.

Orofacial function was found to be compromised in individuals with ED (I), and orofacial skills especially speech--may be optimized through treatment and training, and chewing capacity through high quality oral habilitation. However, no background information was obtained about type and severity of symptoms in earlier stages of life, performed treatment and training, or dental status before oral rehabilitation, so no generalized conclusions about treatment needs can be drawn from the results. Many individuals with dryness of the mouth would benefit from information on strategies to enhance swallowing and improve oral comfort. The study was an on-the-spot account, which strongly indicates a need for further analyses of orofacial function in individuals with EDs, outcomes of orofacial skills training, and outcomes of oral habilitation.

Very young individuals with hypohidrotic ED and mandibular anodontia have undergone dental implant treatment. Many case reports have described successful outcomes, but a few studies of larger samples have reported higher failure rates than in unaffected individuals. Stanford et al. [36] surveyed self-reported implant treatment outcome in individuals with EDs and found higher levels of complications and implant loss than in unaffected populations. Of the 109 respondents, 50% reported an implant or a prosthetic complication and 24% reported some form of implant therapy failure. All four children in study (II) with failed implants were successfully re-operated, which supports the idea that implant failures in young Swedish children with hypohidrotic ED may possibly be attributed to surgical difficulties because of the small size of the jaws and preoperative conditions due to "hard bone", indicating altered bone density.

Conclusions:

A goal to improve therapeutic approaches in ED was presented at the 1998 consensus conference on ED. Functional knowledge on specific genes and gene products allows the design of therapeutics, and the first diagnosis where this occurred was x-linked hypohidrotic ED. The EDA gene codes for the protein ectodysplasin, and a possible cure for the symptoms of the disorder was first demonstrated in Tabby mice, the transgenic mouse model for x-linked hypohidrotic ED. Pregnant Tabby mice were injected with recombinant EDA, and the Tabby phenotype was permanently rescued in the offspring. Later, dogs with a similar phenotype were treated postnatally, and their symptoms in teeth as well as sweat glands decreased. These advances in research have raised hope in affected families, and in the US, a human clinical trial is planned for start in 2011. Many steps remain, and until we know how these achievements can be implemented in clinical practice, improving diagnostics to identify female carriers of the disorder remains an important task. Only the future can tell how these new possibilities will be addressed in our society from ethical, cultural, and individual standpoints.

A classic paper first published in 1996 stated that "good care is about integrating individual clinical expertise and the best external evidence" [31]. Translational research, which aims to promote the transfer of findings between basic research and clinical practice, attempts to understand the discrepancies between what is known and what is done. This new field of research also promises quality improvement in the care of individuals with rare disorders. Meanwhile, to improve the way individuals with oligodontia and ED are approached and met in dentistry, development of standards and evaluation of outcomes to establish the best possible treatment remain a challenge.

ARTICLE INFO

Article history:

Received 5 July 2015

Accepted 10 August 2015

Available online 25 August 2015

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(1) Behnaz Poorian, (2) Nima Dehghani, (3) Mehdi Bemanali

(1) Resident of department of oral and maxillo facial surgery, dental school shahid beheshti university of medical science, Tehran, Iran.

(2) Dmd.assistant professor, department of oral and maxillo facial surgery, dental school shahid beheshti university of medical science, Tehran. Iran.

(3) Resident of department of oral and maxillo facial surgery, dental school shahid beheshti university of medical science Tehran, Iran.

Corresponding Author: Behnaz Poorian, Resident of department of oral and maxillo facial surgery, dental school shahid beheshti university of medical science, Tehran, Iran.

Table 1: Inclusion criteria and number of included individuals in
(I)-(II).

       Inclusion criteria   Number of included individuals

                            All     Female      Male

                                  (n)  (%)    (n)  (%)

(1)    ED                   46    16   34.8   30   65.2
       3 years or older

(II)   Dental implant       26    18   69.2   8    30.8
       treatment Younger
       than 16 years
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Author:Poorian, Behnaz; Dehghani, Nima; Bemanali, Mehdi
Publication:Advances in Environmental Biology
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Date:Aug 1, 2015
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