|Year : 2015 | Volume
| Issue : 1 | Page : 23-26
Application of Dahl's principle in severe hypodontia patient: A clinical report
Tong Wah Lim
Faculty of Dentistry, Centre for Restorative Dentistry Studies, Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia
|Date of Web Publication||12-Aug-2015|
Tong Wah Lim
Faculty of Dentistry, Centre for Restorative Dentistry Studies, Universiti Teknologi MARA, Shah Alam, Selangor
Source of Support: None, Conflict of Interest: None
| Abstract|| |
One of the biggest challenges in management of severe hypodontia cases is the inadequate space for restorations. Increasing the occlusal vertical dimension (OVD) using conventional prosthodontics can be aggressive, technically challenging and accompanied with high maintenance. Application of Dahl's principle to create space is well-documented and is commonly applied in tooth wear patients. To date, there is no evidence to use Dahl's principle in severe hypodontia patients. However, with the signs of dentoalveolar compensation, Dahl's concept should be considered at an earlier stage to increase OVD due to its conservative nature. This article illustrates and provides a detailed description regarding this technique to create the restorative space for implant supported restorations.
Clinical Relevance to Interdisciplinary Dentistry
- Severe hypodontia is rare and ideally should be managed since young
- This full mouth rehabilitation case was carefully planned using conservative prosthodontics approach to achieve optimum outcome
- Interdisciplinary management is always needed involving different specialties to contribute their own expertise and working together to achieve an ideal outcome for the patient.
Keywords: Dahl′s concept, restorative space, severe hypodontia
|How to cite this article:|
Lim TW. Application of Dahl's principle in severe hypodontia patient: A clinical report. J Interdiscip Dentistry 2015;5:23-6
| Introduction|| |
Hypodontia can be defined as developmentally missing teeth. Generally severe hypodontia is referred to six or more teeth missing excluding third molars. However, it is extremely rare and the reported prevalence of severe hypodontia is 0.3% of the population. 
In general, severe hypodontia patients always complain about compromised aesthetics and function which have been significantly affect their quality of life. The commonly associated dental implications including microdontia, malformed shape of teeth, hypoplastic enamel, retained deciduous teeth, disordered occlusal plane, lack of bone development and insufficient restorative space may further complicate the treatment planning. 
One of the biggest challenges in management of severe hypodontia cases is the inadequate space for restorations. However, increasing occlusal vertical dimension (OVD) using full mouth reconstruction can be technically challenging and requiring long term high maintenance. Management of these cases should, therefore, be carefully planned and carried out using a minimal invasive approach. One of the commonly used techniques to create localized interocclusal space of tooth wear is Dahl's concept. , Dahl's concept can be defined as the minor relative tooth axial movement when localized restorations are placed to cause an increased OVD. The rest of the dentition will then re-establish occlusal contacts after a period of time.  No evidence exists to justify the feasibility of application of Dahl's principle in hypodontia patients. However with the signs of dentoalveolar compensation, Dahl's concept could be considered at an earlier stage to increase the OVD due to the conservative nature of this approach. 
| Case report|| |
A 26-year-old male patient was referred to the Implant Unit at Guy's Hospital for management of severe hypodontia. His presenting complaints were essentially being unhappy with his smile and would like to have a definitive management of his problem which had severely affected his quality of life. There was no relevant medical, dental, social and family history.
He presented with medium smile line and no abnormality detected on extra-oral examination. Intra-orally, he had 13 missing permanent teeth (excluding third molar) and 8 retained deciduous teeth. Due to worn deciduous teeth and compensatory erupted opposing permanent teeth, there were inadequate spaces for restorations. With regards to bone quantity, there were firm, good ridge form with good height and width on missing permanent teeth region. Preoperative photographs demonstrated all the clinical appearance of this patient [Figure 1].
|Figure 1: Preoperative labial view, showing the clinical appearance of severe hypodontia|
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From the clinical and radiographic assessment [Figure 2], the following diagnoses were made: Severe hypodontia, retained deciduous teeth and tooth wear. The aim of treatment for this patient was to improve aesthetics and function by means of implant supported restorations to replace some developmentally missing teeth.
Initially, study casts were fabricated and mounted on an arcon, semi-adjustable articulator (Denar Mark II system; Water Pik, Inc.) using facebow (Denar Slidematic Facebow; Water Pik, Inc.) transfer and interocclusal record taken in centric relation (CR). Diagnostic wax up was performed and the increased OVD was determined by providing adequate space to restore all teeth back to acceptable tooth length and aesthetic morphology [Figure 3]. Diagnostic try-in of planned restorations with self-cured acrylic resin was carried out during treatment planning stage in order to assess the vertical dimension, aesthetics and give the patient an overview with regards to the outcome of the treatment.
|Figure 3: Diagnostic wax-up at an increased occlusal vertical dimension was done to help the patient visualize the proposed outcome and for fabrication of radiographic and surgical stents|
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Dahl's concept was applied to increase interocclusal space for restorations of the missing permanent teeth region. Palatal gold veneers were cemented using resin cement (Panavia F2.0, Kuraray Noritake Dental Inc.) on maxillary central incisors. Direct composite build-up on the rest of anterior deciduous and permanent teeth was performed under rubber dam isolation. Dahl's principle was applied to achieve posterior tooth contacts by passive eruption of posterior teeth and intrusion on anterior teeth in CR [Figure 4]. New OVD was achieved by posterior teeth re-establishing occlusal contact in 5-6 months' time using Dahl's principle with shimstock holds noted [Figure 5]. Patient compliance was not an issue in this case because the composite resin build-up and palatal gold veneers were cemented and could not remove.
|Figure 4: (a) Dahl's concept was applied in this patient and the yellow arrows pointed the space for posterior teeth to re-establish the occlusal contact. (b) This technique was achieved using palatal gold veneers on 11 and 21, composite build-up on deciduous teeth (blue circle) (c and d) and worn 31 and 41|
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|Figure 5: (a and b) Preoperative lateral view, showing inadequate restorative space on lateral incisors and canines area. (c and d) After 6 months, adequate restorative spaces was created due to Dahl's principle and minimal bone remodeling after deciduous teeth were extracted|
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After achieving desirable interocclusal space, a cone beam computed tomography (CBCT) was taken with radiographic stents in-situ [Figure 6]. Presurgical of treatment planning of implants using CBCT is strongly recommended to assess the bone quantity and quality, location of anatomical structures including maxillary sinus and neurovascular structures to ensure the success of the treatment. Subsequently, a definitive implant therapy was performed. The standard drilling protocol using surgical guides was followed and seven implants (Astra-Tech Implant System, Dentsply Implants) were placed after surgical sites prepared. Placement of provisional implant supported restorations was carried out after 3 months at existing OVD. Provisional restorations were left in-situ for 1-month and canine guidance was prescribed during the provisional stage. The patient reported that he was adapted well to the occlusion, function was satisfactory and he was happy with the appearance. Therefore, screw retained restorations were prescribed for all implant restorations due to the ideal implant angulation and resulting in an optimum aesthetics outcome with a stable occlusal relationship with canine guidance [Figure 7]. Intra-oral long cone periapical radiographs were taken as baseline records after the definitive implant supported restorations were fitted [Figure 8].
|Figure 7: Postoperative labial view, showing aesthetics appearance of implant supported restorations|
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During review visit, the patient was very pleased with the treatment outcome and claimed that his quality of life was significantly improved after treatment. An occlusal splint was fitted and the patient was informed about the maintenance of the implants and restorations.
| Discussion|| |
This case report described the conservative management of a severe hypodontia patient. The planning of this case was started from the prosthodontic point of view and a minimal invasive approach was adopted to fully address this young patient's concern and achieve the optimum treatment outcome.
The difficulty of management in this case was the inadequate interocclusal space for restoration due to dentoalveolar compensation. The conventional prosthodontic approach can be employed which is conforming to the existing maximal intercuspal position and create the required restorative space by occlusal reduction of the opposing teeth. Applying this technique may have severe adverse complications which include tooth preparations on sound teeth for extra-coronal restorations and risk of elective root canal treatment. The second suggested approach was to reorganize the occlusion by increasing the OVD and full mouth reconstruction of the occlusion. Typically, this approach is nonconservative and requires high maintenance on long run. Therefore, relative axial tooth movement (Dahl's concept) was applied in this case to create space anteriorly. , Minor axial tooth movement was closely monitored and posterior onlays will be planned if the outcome was not satisfactory. The principle of this technique is relying on a combination of intrusion of the anterior teeth in contact with the palatal veneers and composite resin build-up in this case and passive eruption of the unopposed posterior teeth. Subsequently the restorative space was created for definitive restorations.  Besides, a few researchers suggested some mandibular repositioning might be involved in this principle. 
As stated by some studies, most of the posterior teeth in tooth wear patients re-established occlusal contacts in 4-9 months' time. ,, The outcome of application of this concept was satisfactory as the posterior tooth contact was re-established in 6 months' time which was considered normal if compared with the studies in tooth wear patients. No complications including wear, pulpal symptoms, loss of vitality, temporomandibular disorder and periodontal disease were reported in this patient during this period of time. Gough and Setchell have reported similar result as the complications in their study were relatively few and outweighed by the benefits. 
| Conclusion|| |
Full mouth rehabilitation of the severe hypodontia patient can be very difficult. Precisely planned on surgical and restorative phases in this case had contributed to achieve optimum and aesthetics final treatment outcome with the least invasive approach.
| Acknowledgement|| |
I would like to acknowledge all my consultants and dental technologists in Guy's Hospital, King's College London.
| References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]