Six to seven per cent of the Norwegian population are missing one or more permanent teeth. This means that the permanent teeth do not emerge, as they do not exist. This phenomenon is called hypodontia. In severe hypodontia, six or more teeth are missing and this is the condition Christina Hvaring, a researcher at the University of Oslo, has studied.
Hypodontia is usually diagnosed in children when they are 8 to10 years old. The reasons for this dental development failure are complex. Many genes are involved and the details of why some are afflicted by the condition are not all known.
"Children who have severe hypodontia must expect to be under some form of dental treatment for the rest of their lives. It is therefore very important to gain more knowledge about how people experience this condition and, not least, which treatment options work best under different circumstances", says Hvaring.
The most complicated hypodontia cases are referred to an interdisciplinary team at the Faculty of Dentistry, University of Oslo. This team consists of specialists in various fields and is located at the Department of Orthodontics. Since 1998, the team has collected a large amount of patient data consisting of assessments and treatment plans for patients with this condition. Some of the patients have also been treated at the different specialist clinics at the University of Oslo. Hvaring has used data from 212 referred patients to study which treatments worked best for the patient Group.
"I studied patient records, and recalled all patients above the age of 18 missing six or more teeth for a clinical and radiological consultation and assessment," explains the researcher.
Retaining primary teeth
One treatment option that proved to be a good solution was to try to preserve as many primary teeth as possible. People with hypodontia often keep their primary teeth longer than others, as there are no permanent teeth to replace them.
"Of the 30 patients who were recommended to retain their primary teeth from the outset, 28 still had one functional primary tooth after an average 12 year follow-up period", Hvaring notes. "The most important factor limiting the lifespan of primary teeth is infraocclusion, meaning that the tooth is in a fixed position in the jawbone, as it fuses to the bone. As the child grows and the tooth does not move as the jawbone grows, the primary tooth will eventually lie lower than the other teeth. This may lead to a reduced bone level in the area, and to the neighbouring teeth tilting over the fixed primary tooth. Furthermore, the tooth may be so low that it cannot be used for biting and no longer has a function", explains the researcher.
Different treatment options
Even though having one's own teeth in the mouth is always best, retaining the primary teeth is not always an possible, and the dissertation has analysed several different treatment options.
"I have studied three different treatment alternatives for replacing missing teeth in the frontal segment in the upper and lower jaw", says Hvaring. The alternatives were dental implants, fixed prosthodontics and orthodontic space closure.
Implants are tooth replacements screwed into the jaw bone. Fixed prosthodontics are replacement teeth that are cemented directly onto an existing tooth substance, and space closure involves moving existing teeth around in the jaw using braces. Hvaring used four criteria to assess these treatment options: the form and colour of the replacement, the gums on either side of the replacement and the gum around the replacement.
The patients were generally very satisfied with the treatment outcome, regardless of which treatment option that was carried out. Hvaring believes that the level of satisfaction may be explained by the fact that patients in this group have found it very stressful to spend their childhood and youth with teeth missing, and that they are greatly relieved when they finally receive teeth replacements and have completed this round of treatment.
Contrasts
However, the patients’ satisfaction with the outcome of treatment contrasts with an important finding in the study: that implants, especially in the frontal segment of the lower jaw, turn out to be an unsatisfactory treatment solution. The researcher discovered that nearly all patients who had implants either developed a grey discolouration of the gum or had visible metal around the implant. This can be explained by bone loss around the implant fixture. As patients with severe hypodontia have fewer teeth than normal, they also have a lesser amount of bone in their mouth from the outset, and the implants do not retain bone as a regular tooth would have done.
Orthodontic space closure (braces), where teeth are moved in the jaws replacing missing teeth, resulted in the best bone condition and prettier gums between the teeth. Fixed prosthetics provided a better form for the tooth replacement at the front of the mouth in the lower jaw than orthodontic space closure.
Emotionally stressful
The satisfaction with the treatment outcome must also be viewed in the context of another important finding in the dissertation: that patients with untreated hypodontia have a reduced quality of life.
Along with a patient group with a malocculsion of similar treatment need, the patients with severe hypodontia were asked to fill in a questionnaire. They were asked whether their condition made it difficult to eat, talk, brush their teeth, sleep, smile, be emotionally stable, socialise with others and perform daily tasks.
Both groups reported that their condition had a negative influence on their daily life in these areas. "However, the interesting thing was that patients with hypodontia had greater difficulties with emotional stability than the other group, and reported that the missing teeth were the direct cause of their reduced quality of life", says Hvaring.
Important knowledge
It is very important to focus on research that optimizes the treatment outcome for this group of young "eternal patients", as the solutions must function for the rest of their life, in many cases for up to 80 years.
"Retaining one's own teeth, especially in the frontal segment, and rather use dental implants in the posterior segments of the jaw turned out to be a better solution than having implants in the frontal segments of the jaws", explains Hvaring. "It is also essential to understand the significant emotional struggle this patient group has, and I hope my research has shed new light on this", concludes Hvaring.