of impacted incisors. However, based on the differences in the aetiologies of impaction in canines and incisors, it would be reasonable to assume that there could also be differences in the results achieved at the end of treatment.
It was with this in mind that the Jerusalem group [34, 35] undertook a study exclusively relating to maxillary incisors. The findings of the study in the open eruption group showed poor periodontal and aesthetic results, with increased pocket depth and a 10% loss of alveolar bone height. The clinical crowns were elongated and the band of attached gingiva reduced. On the other hand, those treated by the closed surgical procedure showed only minimal changes, with greater bone support, a lesser increase in clinical crown length and better external appearance than in the open surgery group. Crown length and attached gingiva were closely similar to those of the unaffected side, while the bone support level was reduced by between 5% and 6%.
In a later comparative study of open versus closed exposure, similar impacted incisor cases were matched for age, aetiology and location. The overall results favoured the closed surgical exposure method. The open exposure cases showed statistically poorer outcomes, characterized by increased crown length and more significant loss of bone support [9].
A recent split‐mouth investigation of labially impacted maxillary canines was carried out in order to compare the results of a closed eruption surgical exposure of the affected canine with those of the normally erupting antimere. The conclusions were that, at the completion of orthodontic treatment, the previously impacted canines exhibited slight and clinically insignificant periodontal recession, compared with the contralateral normal tooth [33].
It will be clear from the summary of the evidence presented here that a closed surgical exposure approach produces good, predictable, long‐term periodontal and aesthetic results and has advantages over the apically repositioned flap method [34, 35]. It might be appropriate to attribute these advantages to the closer similarity of the full‐flap closed exposure procedure to the natural eruption process.
A Cochrane Collaboration systematic review
The Cochrane Collaboration offers systematic reviews of primary research in human health care and health policy, as well as clinical research in the effects of interventions, for the purposes of prevention, treatment and rehabilitation, in various fields. Existing primary research on a particular topic is collated and, using stringent guidelines, is assessed in order to establish whether or not there is conclusive evidence about a specific treatment. The reviews are updated regularly, ensuring that treatment decisions can be based on the most current and reliable evidence. In this way, these reviews provide us with the ideal framework to objectively adjudicate, without regard to personal subjective preference or bias, the rival claims of those advocating open exposure as opposed to those who advocate closed exposure.
These conflicting opinions were the subject of a Cochrane review that was undertaken in 2008 in the UK [36] and thereafter updated periodically [37–40]. The review only referred to those factors directly related to the surgical aspect and no regard was paid to the age of the patient, the presenting malocclusion or the type of active orthodontic treatment undertaken. The aim was specifically to search the literature for studies involving open and closed surgical exposure of impacted maxillary canines and to compare the outcomes of the two techniques in relation to the claims made by both surgeons and orthodontists. In the 2008 study, however, none of the 191 retrieved studies fulfilled the criteria to be included [36].
An update of the review was undertaken in 2017 [40], in which the researchers found only three studies in the literature that fulfilled their criteria to be included. However, in their assessment the authors stated that they ‘considered the evidence to be of low quality, with two of the three included studies being at high risk of bias’ and that ‘the evidence suggests that neither the open nor closed surgical technique for exposing palatally displaced maxillary canine teeth is superior for any of the outcomes included in this review’. The authors were at pains to point out that their search through the literature had failed to disclose published studies suitable to be included in the review and that therefore evidence of a statistical or clinical difference between the two surgical techniques is lacking, and furthermore that currently the method of exposing a palatally displaced canine may be left to the personal preference and choice of the surgeon and orthodontist.
The UK research group stressed that there are impacted canines whose location and relationship to the roots of the adjacent teeth could render one of these two techniques of exposure impossible, impractical, ill‐advised or potentially harmful. This means that the randomization of patients for the purpose of the study of open versus closed surgical exposure was not valid and the composition of the two sample groups of patients could no longer be considered comparable. It is therefore quite clear that the authenticity of the study is both directly and indirectly compromised. To overcome this unfortunate conclusion, the route taken by the UK group was to eliminate/disqualify difficult cases from the study, in order to achieve the parity needed for proper analysis.
Let us examine whether this corrective step can achieve valid parity of the samples:
In the case of an impacted canine that is associated with severe resorption of the root of the adjacent incisor, ‘open’ surgical exposure is contraindicated, as it would seriously endanger the vitality of the affected incisor and, often, its very existence. Using the ‘closed’ eruption technique would offer the opportunity to salvage both teeth, while maintaining their vitality.
Similarly, consider the case of palatal canines that are severely vertically displaced in the height of the maxilla, above the incisor apices, or those whose roots bucco‐lingually straddle the ridge between the lateral and central incisors. An ‘open’ exposure procedure is highly unsuited to these clinical situations. The necessary broad exposure would place the vitality of the adjacent teeth at risk and, unless the exposure was extremely wide, it would rapidly close over and deny subsequent clinical access.
Accordingly, such cases (i.e. the more difficult cases) cannot be included in the random allocation for a fair comparison of open or closed surgical exposure and would need to be eliminated from the study sample. The very act of excluding these and other more difficult cases creates a heavy bias to the survey and is tantamount to limiting the findings of the study to being valid solely for simple or superficial cases.
Regardless of the method used, it is quite clear that the overall aim of the treatment must include the ability to employ the highest clinical standards of treatment and to produce the ideal outcome (i.e. where it is impossible to recognize which tooth had been impacted). The successfully treated impacted tooth must be identical in its form, its orientation, its colour, its gingival contour and its crown height to its antimere and in harmony with its neighbours. This ideal is achievable in a high proportion of cases when the ‘closed’ eruption technique is used, in combination with properly executed directional orthodontic traction and alignment. It is pertinent here to refer to the pre‐orthodontic open exposure method espoused by Schmidt and Kokich, who, in their study of the method, found that only 19% of the previously impacted canines would escape detection by a panel of experts [41].
It is clear from what has been described here and what will be discussed in later chapters that the quality of the outcome is only partly due to the type of surgical procedure employed. Indeed, there are many other factors that are intimately involved in the final outcome, some of which may be just as influential in dictating the result. A number of these factors may be neutralized in a very large sample, if the randomization has distributed them equally between the two groups. Nevertheless, there are several others that cannot be discounted. It is imperative to recognize four distinct groups of such factors: namely, those related to the patient, those related to the radiologist, those related to the oral surgeon and those related to the orthodontist.
The patient: Patients
