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The things that you’re liable to read in the Journals: it ain’t necessarily so!

Published: June 2014

Bulletin #34 – June 2014

The things that you’re liable to read in the Journals: it ain’t necessarily so!

We don’t all see things the same way and, sometimes, misdirected investigations seem to slip through the safety net of a usually foolproof peer review and they get published. Once they are in print in a respectable journal, the findings of the study are often accepted without further question. Few researchers and even fewer clinicians look beyond the author’s conclusions. The design of the study, the inclusion criteria, the parameters defined or the interpretation of the findings may be at fault. Assumed “facts” are thus established on the ground, which are subsequently difficult to refute. Once in print, the paper is wrongly quoted in support of untenable positions………. and all Hell breaks loose! The outcome then may develop a life of its own when it goes viral on the internet. If the assumed findings are of a clinical nature, then the judgment of the clinician in daily practice is likely to be slanted, when faced with a case of the type investigated.

I would like to discuss a specific article which, I consider, fits this description. The article was published in 20121 and its aim was to determine the occurrence of root resorption in impacted maxillary central incisors following their successful resolution and to retrospectively search out features in the dentitions of such individuals that could help predict root resorption. The authors considered that, if the quest for predictors were successful, then it would provide the orthodontist with important information to take into consideration before embarking on treatment. Information regarding potential predictors was looked for in the patients’ charts including demographics, existing radiographs, treatment duration, crown angle, crown height, crown depth and root dilacerations. Pre-treatment cephalograms and post-treatment periapical films were evaluated.

The study was conducted on a sample of 80 patients and one of the conditions for inclusion was that none of these patients had suffered trauma to the anterior region of the mouth. Within this sample, 16 (20%) of these patients were described as exhibiting root dilacerations in the impacted teeth. A dilacerate incisor is characterized by an abrupt change in the axial inclination between crown and root at some point along the root length. The pre-treatment radiographs were used to confirm the presence of unilateral incisor impaction and to describe its three-dimensional orientation in space. The post-treatment periapical views were used to compare the lengths of the two central incisors after they had been brought to their final place in the dental arch, by direct measurement on the film.

The authors of the study under discussion found that the greater the distance moved by the impacted teeth from their initial location to their finally aligned destination, the shorter their roots. They interpreted this root shortening as having been due to the ravages of root resorption, although this assumption was made on evidence gleaned from the periapical radiograph alone and not confirmed by more comprehensive examination. They reported that, in their study,”………. cases involving root dilacerations tended to have greater root resorption” and that “…… a high incidence of dysmorphic roots was also found in patients with severe root resorption” and, further “….. no evidence is available to understand why a dilacerated root would resorb more easily”.

Only towards the end of the conclusions section of the article do they finally concede that perhaps “…..dilacerated incisors lack the root length of normally erupting incisors, and this difference results from developmental differences rather than resorptive differences.”

The following observations are in order:-

1. It is well documented that trauma is widely recognized as a dominant factor in the causation of incisor dilaceration2-5 and, as such, the statement that none of the individuals in the sample suffered trauma must be questioned.

2. Within the immediate context of the present discussion, the root length of dilacerate incisor teeth whose development has been compromised is, not surprisingly, shorter than a normally developed tooth. However, even if the eventual root length were to be fully expressed as with a normal tooth, an abrupt change in the axial inclination between crown and root must “shorten” the measured length of the root when viewed on a two-dimensional periapical film.

3. The post-treatment alignment of dilacerate incisors is complicated by the orientation of the apical portion of the root in relation to the labial alveolar plate. When orthodontic treatment of these teeth is undertaken, the aim is to bring the crown to its fully bucco-lingually torqued orientation, parallel to the normally-aligned (in the sagittal plane), adjacent and unaffected central incisor. The authors of the article presently under discussion were at pains to point out that they needed to accept a lesser-than-ideal degree of torque in some cases, so as not to expose the apex in the labial sulcus “…. special care was taken not to expose the root despite an insufficient torque”. Clearly, therefore, the fact that measurement was made on the periapical radiograph with the two incisors at different angles in the sagittal plane must invalidate the comparison.

4. Teeth which develop in a restricted anatomic environment generally grow shortened roots. Impacted third molars present an excellent example of this, since they often have short and curved roots. However, when second permanent molars are extracted early, as is sometimes performed remedially in orthodontic treatment, the wisdom teeth migrate mesially as they erupt and develop much more normal molar root forms and root lengths. Similarly, impacted maxillary incisors which have been displaced high in the alveolus by the presence of an odontoma or supernumerary tooth, may sometimes be seen to develop very close to the floor of the nose. In these cramped circumstances, the root development will often be subject to “premature closure” of the apex – premature insofar as the root length is less, but normal in its timing, when compared to its antimere.

Root resorption is an ogre that haunts all orthodontists and figures widely in our risk-benefit calculations in regard to “collateral damage” that accompanies the treatment that we undertake. It certainly cannot be ignored as a potential unwanted side effect. However, if it is a factor in regard to compromised root length of successfully treated impacted central incisors, it is certainly not the main factor. From the above observations, it should be abundantly clear that not all root shortening is root resorption. Neither is it true that all cases of impacted central incisors will necessarily end up with shortened roots and, ipso facto, have a potentially short life span. The thrust of the article unjustly casts a shadow on the prognosis of the treated results and might well lead an orthodontist to advise the extraction of a tooth that could faithfully serve the patient well for many years, in favor of a considerably inferior artificial substitute.

References

1. Ho KH, Liao YF, Pre-treatment radiographic features predict root resorption of treated impacted maxillary central incisors. Orthodontics and Craniofacial Research 2012,15:198-205.

2. Malcic A, Jukic S, Brzovic V, Miletic I, Pelivan I, Anic I, Prevalence of root dilacerating in adult dental patients in Croatia. Oral Surg Oral Med Oral Path Oral Radiol Endod 2006, 102:104-109,

3. Jafarzadeh H, Abbott PV. Dilaceration: Review of an endodontic challenge. J Endod 2007;33:1025-30, 

4. Regezi JA, Sciubba J, Oral Pathology: Clinical-Pathologic Correlations, 2nd ed. Philadelphia: WB Saunders Company; 1993.  

5. Udoye CI, Jafarzadeh H. Dilaceration among Nigerians: Prevalence, distribution, and its relationship with trauma. Dent Traumatol 2009;25:439-41

Postscript

Dilacerate incisor etiology has been the subject of much debate over several decades and is the subject of the April 2012 Bulletin #10 on this website1.

Upon the request of several members of the audience who attended the lecture that Prof. Stella Chaushu and I presented at the 114th Annual Session of the American Association of Orthodontics in April of this year in New Orleans, I have uploaded a video movie clip that we showed during our presentation. The clip graphically illustrates the hypothesis that I first proposed in 19972 and which appears in each of the three editions of my textbook on impacted teeth, explaining the development of the classic form of dilaceration of the maxillary central incisor. Permission is granted for the use the clip as a teaching model by whomsoever wishes provided that it be accompanied by an appropriate acknowledgement regarding its source.

The following is the YouTube URL  -   http://youtu.be/Se2_qOCgRy0

References

1. Becker A. The “Classic” dilacerate maxillary incisor, Bulletin #10 - April 2012 http://www.dr-adrianbecker.com/page.php?pageId=281&nlid=29

2. Becker A. The Orthodontic Treatment of Impacted Teeth. 1st Ed. London: Martin Dunitz Publishers. Published 1998. ISBN 1 85317 328 2.