From Volume 49, Issue 10, November 2022 | Pages 848-851
Forward migration of the upper incisors can be very distressing for patients and difficult for the dentist to manage and treat. We summarize the aetiology of this condition in older patients and discuss how this can be managed with a combined orthodontic and restorative approach.
The upper incisor teeth have several forces acting on them that serve to maintain their position in the adult patient. In a stable dentition, the forces from the lips and tongue are in balance and tooth movement is prevented. Periodontal disease and occlusal forces can combine to initiate tooth movement. When migration of the maxillary teeth is progressing, the lower lip becomes trapped underneath the palatal surfaces and no longer serves to restrain further tooth movement. This accelerates the forward proclination and splaying of the maxillary teeth.
Periodontitis has been described as a primary aetiological factor in tooth drifting,1,2 and this seems logical because good bone support for the teeth is important in its prevention. Inflammation of the periodontium will predispose to tooth movement. More important in the case report described here is that the length of the crowns relative to the periodontal support was increased. This increases the leverage on the teeth so that any force has a greater effect in tilting the teeth.
The severe wear of the lower anterior teeth is evidence of a bruxist habit over many years. With gradual tooth wear, restorative treatment can be further complicated by compensatory over-eruption of the opposing teeth, which can reduce the space for the replacement restorations.
The aetiology of the migration of teeth is often multifactorial, but the main aetiological factor has to be diagnosed before a treatment plan can be initiated. Medical conditions such as hiatus hernia, eating disorders, alcoholism and pregnancy may cause gastric reflux and tooth erosion. In addition, the frequent consumption of acidulated beverages or other acidic drinks may cause erosion. Treatment is often multidisciplinary and involves occlusal, periodontal, orthodontic and other restorative therapies.
A lack of posterior occlusion can be instrumental in concentrating occlusal load on the anterior teeth. Even the extraction of a single posterior tooth can cause movement of teeth and a posterior occlusal interference can result. Craddock3 analysed 100 dentitions with at least one unopposed posterior tooth and 100 control patients. Following this study it was suggested that premature contacts in the retruded contact position were associated with the supra-eruption of the unopposed teeth. These contacts can cause forward translation of the mandible onto the anterior teeth during closure, resulting in anterior tooth migration. The strong association of unopposed teeth with retruded contact position contacts is important when planning posterior restorations.4
Diagnosis requires positioning of the maxillary casts using a facebow mounting and accurate recording of the retruded contact position. Once the models have been mounted, the accuracy of the mounting should be verified in the patient's mouth. Trial adjustment of the duplicated mounted casts can be considered to determine the feasibility of removing the premature contacts prior to attempting this in the patient's mouth.
Bruxism is also a cause of anterior tooth migration. The patient described in this case report had severe lower incisor and canine toothwear, but she said there was no history of bruxism. The most likely explanation is that the enamel of the lower dentition was worn by the rough, unglazed palatal surface of the maxillary crowns.
One of the critical factors in determining the prognosis of periodontal treatment is the severity of the disease and the patient's susceptibility. This must be assessed first before embarking on extensive and complex treatment. A particular elderly patient may be classed as having lower susceptibility to periodontal disease than a younger person, but the level of bone destruction in each could be similar. Therefore, the prognosis for treatment is better for the older patient. When considering the severity of the disease, most patients with pathological anterior tooth migration will have at least mild disease (bone loss of up to one-third of the root length). There are many additional risk factors that will influence the treatment prognosis, but a good response to initial therapy and excellent oral hygiene indicate a better prognosis. The modifiable risk factors, such as smoking, poor diet, diabetes and stress will affect the probability of the development of disease and its progression. A detailed analysis of all the risk factors will determine the treatment provided and its likely prognosis. A level of plaque that is inconsistent with the amount of attachment loss would indicate a diagnosis of aggressive periodontitis.
Determining whether periodontal disease affects just the migrated teeth or is more general should be considered. Generalized disease affects more than 30% of sites.5 Reassessment in those who have had initial therapy is carried out after about 6–12 weeks to assess healing. Detailed six-point probing depths are needed in this assessment, and not the Basic Periodontal Examination (BPE). Some spontaneous improvement in tooth position following periodontal therapy has been described,6,7, but it is rare. Practitioners should consider referral of cases where periodontal disease is severe, and treatment is difficult and complex.
For successful orthodontic treatment of migrated teeth, both occlusal and periodontal considerations must have been addressed. In the presence of archwires, there is an increased risk of plaque accumulation and periodontitis, which if combined with untreated occlusal trauma, can cause more rapid progression of periodontal disease. Orthodontic movement of teeth should not be commenced until their periodontal status is satisfactory. This can be assessed using the BPE system and either a full (recommended) or a simplified BPE measurement may be undertaken to assess the periodontal health at orthodontic assessment. The evidence would suggest that reduced bone support or increased pocket depth are not necessarily contraindications for orthodontic treatment, on the condition that good oral hygiene is being maintained.8 There is no evidence that orthodontic treatment in the presence of good oral hygiene and absence of gingival inflammation contributes to any further attachment loss in a well-motivated patient. With good plaque control, and in the absence of any active periodontal disease, orthodontic treatment should not be contraindicated. However patients need to be regularly reviewed regarding their periodontal status and good oral hygiene emphasized.
Orthodontic movement of teeth does not reduce any pre-existing vertical periodontal defects, rather, the opposite will occur. These can be treated successfully using regenerative periodontal therapies such as guided-tissue regeneration with membranes or using enamel matrix proteins.9
With anterior tooth migration, the teeth must be retracted and ideally intruded as a simple retraction may produce a deep overbite. This can be achieved with light forces as demonstrated in the case report.
There is a risk of the composite restorations fracturing, especially if the patient has any active bruxism. The patient in our case report was made fully aware of this risk and gave informed consent. The orthodontic retainer, worn at night, reduced any potential damaging forces to the restorations. The dental technician needs to construct the wax-up so that the composite restoration bonds in the mouth to the maximum amount of available enamel for optimum restoration retention and aesthetics.
The wax-up allows the occlusal relationship of the composite restorations to be planned. Reducing the incisal overjet by protruding the restorations on the lower teeth results in shorter lower incisors so a satisfactory compromise must be found. The width of unworn lower incisors varies between 5 and 6 mm. 10 In the majority of mandibular tooth wear patients, the width of the teeth is maintained and the difficulty centres around determining the height of the clinical crown. Using the golden ratio (width to height of 0.62) results in an unsatisfactory squat tooth appearance.11 A normal width to height ratio of lower incisors is 0.8, meaning that the optimum height of these teeth is about 7 mm.12
A 72-year-old female patient requested orthodontic treatment to correct the alignment of her upper teeth and restoration of the normal height of her lower teeth (Figures 1 and 2).
The restorative requirements were to reduce the overbite to allow vertical space for satisfactory placement of a lower denture and addition of composite restorations to the lower incisors. The patient presented with severe tooth wear affecting the lower incisors. There was no evidence of an erosive diet, but the lower teeth occluded against the worn palatal porcelain surfaces of the maxillary crowns. In this regard, if the palatal surface of a porcelain crown is adjusted during fitting to achieve an even occlusion, the unglazed porcelain becomes abrasive if it is not re-glazed or polished.
The orthodontic aims were to:
A full clinical and radiographic assessment was undertaken that indicated bone loss affecting the upper anterior teeth. There was no history of smoking. The bone loss ranged from 10% to 30% across the upper labial segment, as seen from the panoramic radiograph taken at the orthodontic assessment (Figure 3). However, the patient demonstrated good oral hygiene, and a BPE assessment indicated little or no bleeding, suggesting the absence of active gingivitis. It was therefore deemed appropriate to undertake orthodontic treatment to facilitate the restorative intervention.
The orthodontic treatment was planned using light orthodontic forces to minimize any heavy load on the reduced periodontal support. This would prevent any further bone loss and minimize root resorption.
Treatment was undertaken using a semi-invisible pre-adjusted edgewise orthodontic bracket system (3M Unitel Clarity, St Paul, MN, USA) with tooth-coloured archwires. The orthodontic brackets were bonded to the porcelain crown using a well-accepted technique.13 The crown surfaces were micro-etched with hydrofluric acid. A silane coupling agent was applied before conventional bonding with an orthodontic resin on the bracket base.
Treatment progressed with no adverse consequences and the overbite reduced to a level in which the restorative treatment could proceed. The upper incisors were retracted satisfactorily (Figure 4). Prior to removal of the orthodontic appliance, it is good practice to review the position of the teeth with the restorative dentist. This will prevent any desire to change or amend the positions after the debond of the orthodontic braces. Communication between the two specialty teams is paramount for success.
The restorative treatment aims were to:
A wax-up of the intended modifications to the lower teeth was undertaken in the laboratory (Figure 7). This allows the space available for the lower restorations and the resulting occlusion to be planned. The wax-up is an excellent patient educational tool because it allows a comparison with the existing worn dentition and the appearance of the final planned restorations. A plastic shell can be constructed from the wax-up to assist with shape of the final restoration in the clinic.
Retention of the partial denture was improved by creating guide planes on the distal aspects of the mandibular premolar and canine, providing labial composite undercuts for the clasps to engage (Figure 8). The denture base was a cast cobalt–chromium framework with flexible stainless steel clasps on the canine and premolar teeth. The lingual plate provided reciprocation for the clasps and indirect retention. The partial denture was constructed using a new alginate impression of the lower teeth.
The anterior teeth were restored with the nano-hybrid composite, Venus Pearl (Kulzer Ltd, Basingstoke, UK) using the plastic matrix made from the wax-up. This composite was chosen because it has low shrinkage and low viscosity. According to the manufacturers, this composite can be used with all commercially available bonding agents; however, they recommend iBOND Self Etch or iBOND Total Etch (Kulzer Ltd). The composite was cured for 20 seconds on each surface. The teeth were restored alternately, separating the adjacent teeth using PTFE tape. Some freehand modifications were made at the distal and mesial surfaces using transparent mylar strips (Hawe Adapt, Kerr, Bioggio, Switzerland). The restorations were polished with white stones and discs (Sof-Lex, 3M ESPE, St Paul, MN, USA)
Composite resin was added to the lower anterior teeth to increase the occlusal vertical dimension (OVD) by 5 mm inter-incisally. Traditionally, increasing the OVD on natural teeth was thought to lead to discomfort, but recent concepts, such as used with Dahl appliance therapy, have shown that patients adapt well to small increases in OVD. In this patient, the freeway space was reduced to 3 mm) and was well within the comfort zone of the patient. In a study by Ormianer and Palty,14 30 patients had successfully adapted to an increase in the OVD of 3–5 mm after an average followup of 66 months.
After 1 year, the patient had not experienced any relapse of the upper anterior tooth position. However, there is some unpredictability in retaining the retracted upper incisors, so patients should be reviewed at 3-monthly intervals in the early stages to record and monitor the incisor overjet. At these appointments, the periodontal health of the anterior teeth is assessed, and oral hygiene instruction reinforced.
Our report seeks to raise awareness of minimal intervention dentistry as the first consideration in any treatment plan. We have described the use of orthodontics to retract teeth and composite resin to restore the consequences of tooth wear. Other treatment options, for example anterior crowns, could have been considered, but they provide a less cost-effective option and survive less well than posterior crowns.15 When composite was used in an early 2007 clinical trial to increase the anterior occlusal vertical dimension, a high rate of composite restorations failed (6% over 2.5 years).16 However, there have been considerable advances in composite technology during the intervening years. The technique should be adopted widely, and provides an aesthetic solution with minimal biological cost to the pulp or periodontium.
