[Dental complications during orthodontic preparation and orthognathic surgery]

INTRODUCTION

Orthodontic-surgical treatment can present risks to the dental organ and the periodontium. Despite the low incidence of such cases, these complications can compromise a treatment plan. Practitioners should be aware of these potential complications, take them into account during treatment in order to reduce their negative impact and, if necessary, manage them by orthodontic-surgical collaboration.

MATERIALS AND METHODS

In this article, the authors present several potential complications that can occur during treatment.

CONCLUSION

The information given to the patient about the risks inherent in the implementation of an orthodontic-surgical protocol must necessarily include the risks of lesion to the dental organ and the periodontium.

[Orthognathic surgery: the incisor decompensation and its effect on articulation]

INTRODUCTION

The surgical protocols are based on arches preparation before or immediately after the surgical phase. Incisor guides normalization is achieved by incisor decompensation in three dimensions. Place and extend of surgical movements depend on the incisor position obtained at the end of orthodontic preparation. Extraction versus non extraction depends on incisor position planning. Orthognathic surgery induces muscular and temporo-mandibular joint stress which can cause temporo mandibular dysfunction (TMD).

OBJECTIVES

This article studies relations between incisor decompensation amplitude, orthognathic surgical procedures and risk to create or to increase TMD.

CONCLUSIONS

Sagittal, vertical and transversal incisor decompensation impact to place and amplitude of surgical movements. Incisor decompensation does not seem to induce TMD during orthodontic preparation even if occlusal guide controls are lost. Temporo mandibular dysfunction degrees define surgical movements area, moderate specially mandibular surgical movements and incisor decompensation objectives.

[Aesthetic success in genioplasties procedures criteria]

Maxillomandibular dysmorphia may be associated with structural chin pathologies. Three-dimensional jaws displacements have limits. Specific genioplasty is an additional surgical mean for soft tissues profile normalization. Osteotomy line is examined according an incline angle and a possible lateral extension, as chin wing technique, improves facial shape. Cephalometric set-up with R line analyzes surgical chin movements and impact of lower incisors labial inclination on lower lip and mentolabial fold after advancement genioplasty. Micro-implant anchorage is a precious help to find lower incisors good position and optimum lower occlusal plane frontal shift in asymmetric facial pattern. Orthodontics criteria are essential factors to access an aesthetic success in genioplasties procedures.

[Innovations in diagnosis and treatment about a case of primary failure eruption linked to a PTHR1 gene mutation]

Primary failure of eruption is a rare condition marked by non-eruption of the posterior teeth due to mutation of a gene responsible for tooth eruption. Today, this anomaly can be detected early using innovative 3D-imaging techniques. Genetic and histologic testing will confirm the diagnosis and unfavorable prognosis. Alveolar growth must be followed in other areas too in order to avoid structural and functional asymmetry. An analysis of the diagnostic and therapeutic options using bone-borne anchorage is presented via the long-term monitoring of a female patient presenting primary failure of eruption linked to mutation of the PTHR1 gene.

[Skeletal discrepancies: could we avoid surgical procedures?]

Orthodontic-surgical protocols are nowadays considered as the state-of-the-art in cases of skeletal dentomaxillary dysmorphosis. However, for some reasons, it may happen that unquestionable indications for orthodontic-surgical procedures are not respected, patients being treated by orthodontics alone. This kind of mistake in the treatment planning lay the patient open to various potential complications such as: abnormal duration of the orthodontic treatment, dental root resorptions, questionable tooth extraction, unfavorable facial aesthetics, treatment instability... The authors discuss these points illustrated by clinical cases. Although orthognathic surgery protocols became considerably simplified these last two decades, orthodontic-surgical protocols are still relevantly considered as heavy both by patients and practitioners. As a consequence, their indication must be carefully weighed by a multidisciplinary team, keeping in mind that these protocols represent the ultimate functional and aesthetic treatment for dento-skeletal dysmorphoses.

[Does dental class II division 2 predispose to temporomandibular disorders?]

Because of its anatomical/physiological characteristics, the Class II division 2 (class II, div. 2) is one of the malocclusions considered as a possible risk factor for Temporomandibular disorders (TMD). A literature review was conducted from the electronic databases of Medline and Elsevier Masson, through the year 2010, in order to clarify the relationships that may exist between Class II division 2 and TMD. This research helped identify 50 articles: 7 articles specifically concerned the Class II div. 2, 37 articles concerned some of the characteristics of the Class II div. 2, considered individually (Class II, deep bite, retroclined maxillary incisors, mandibular retrognathism) and 6 articles orthodontic treatment. From the conclusions of these studies, the Class II, div. 2 does not appear to represent a significant risk factor for TMD. The clearest association would involve mandibular retrognathism and the risk of articular disk displacement. However, given the low number of articles published on this topic, the methodological variability and the contradictory results, it is difficult to identify reliable conclusions and, consequently, the therapeutic indications for the treatment of Class II div. 2 patients with TMD.

[Cervical vertebrae: Mandibular growth dynamism indicators?]

A study of mandibular growth maturation was performed on a population of 103 patients during orthodontic treatment (69 girls and 34 boys) from 11 to 16 years, having initially a Class II skeletal discrepancy. The relationship between wrist maturation indices and the cervical vertebrae maturation was studied by Lamparski classification. Significant correlations were found between Björk stages, MP3=, MP3 cap and MP3 U and respectively Lamparski stages as CVS 2, CVS 3-4 and CVS 5-6. This retrospective longitudinal study identified three mandibular variables at three different maturation stages according to Björk classification and to the six stages of Lamparski classification. The relationships between these different maturation stages and a quantitative mandibular response permit to estimate optimal time for our orthodontic therapy. The results indicate a significant increase in mandibular length between CVS 4 and CVS 5, suggesting the persistence of a condylar response to a stimulation therapy after CVS3 or CVS 4 stages (MP3 cap). Mandibular growth seems to continue after MP3 U stage or CVS 5 stage.

Le facteur ethnique est-il un indicateur thérapeutique?

Face au diktat de la beauté imposée par la société à travers des stéréotypes, il est devenu légitime de s’interroger sur le concept universel du “ beau ”. Est-ce que les normes esthétiques en orthodontie, établies à partir d’échantillons de Nord-Américains, peuvent être applicables à d’autres populations? Les différentes analyses céphalométriques menées chez des sujets afro-américains, africains et asiatiques en occlusion normale non traitée mettent en évidence des critères esthétiques éloignés des critères nord-américains. Leurs conclusions relatent comme principal caractère ethnique la biprotrusion alvéolo-dentaire en relation avec un angle naso-labial réduit. Pour le sujet africain, on note très fréquemment une antéro-position du maxillaire avec une position mandibulaire inchangée ou rétruse. Pour le sujet asiatique, une similitude des profils cutanés est rapportée avec une divergence quant aux profils squelettiques : les Japonais présentent une rétrognathie maxillaire plus prononcée; les Chinois montrent souvent une promaxilie et une rétromandibulie. Les Coréens se rapprocheraient des Japonais. Il semble donc nécessaire de constituer des données spécifiques à l’origine ethnique afin d’optimiser le diagnostic esthétique et les objectifs du traitement orthodontique.

[Orthognathic surgery is a team work!]

Orthodontic-surgical treatment of dentofacial anomalies involves a multidisciplinary approach that demands to be finely coordinated in order to get a good result. Historically, orthognathic surgery stemmed from the close collaboration between the orthodontist and the maxillo-facial surgeon; however thanks to the collaboration of many other specialists along the diagnostic and therapeutic process, orthognathic surgery nowadays reached an unprecedented level of quality, reliability, and safety. We discuss herein the role of the various specialists that may be involved in the treatment of a patient requiring an orthodontic-surgical coordinated approach, as we see it in the Department of MaxilloFacial Surgery of Centre Hospitalier Lyon-Sud.

[Cephalometric deciding factors in the early treatment of Class III malocclusion]

Many authors recommend early treatment for patients with Class III malocclusions in order to make their appearance more acceptable and also to re-channel the growth of basal bone into a normal pattern. However, the long-term effects and the stability of the results of this type of treatment have not been studied extensively. In the best interests of our patients, it would behoove us to know when early intervention is indicated and in what circumstances a strategy of watchful waiting and postponement of definitive treatment until the end of the growth period would be preferable. This retrospective study of a population of 30 patients from six to nine years old with skeletal and dental Class III malocclusions offers information on results obtained in early interceptive treatment, the potential for relapse, and the cephalometric criteria upon which a determination of the probable success or failure of treatment at this precocious stage can be made. A one-year treatment period began with rapid palatal expansion and was completed with alignment of the upper arch with a full-bonded appliance on the upper arch that was followed by orthopedic force delivered through an antero-posterior Delaire type facemask. In an evaluation eight years after the close of this early treatment, patients were separated into two groups, one of orthopedic success and the other of orthopedic failure. The inclination of the upper incisors proved to have descriptive value: the cases determined to be failures showed more inclination, a sign of early compensation. This meant that labio-version of upper incisors could be considered a predictive sign of relapse of an early treatment result. By means of a multiple regression analysis, we were able to discern three cephalometric components whose positive or negative readings would help to predict the probable prognosis for the success or failure of early treatment.

[Severe Class III malocclusion: long-term stability. Retrospective analysis of 12 cases]

PURPOSE

Long-term stability of severe class III is rarely evaluated in the literature. We present our findings with 12 patients who underwent surgery from June 1995 to December 1997 and analyze cephalometric superpositions.

MATERIALS AND METHODS

Twelve operated patients were reviewed to analyze long-term results (follow-up 3 years 8 months). The sex ratio was well balanced. Mean age was 23 years. All patients were given pre- and postoperative orthodontic care and underwent bimaxillary surgery with Lefort 1 osteotomy and sagittal osteotomy of the rami. Delaire cephalometry on preoperative and early and late postoperative films was used to analyze outcome. Skeletal instability was defined as displacement greater than 4 mm. Recurrence was defined as secondary loss of the functional and esthetic result.

RESULTS

Four patients (33%) developed skeletal instability. All patients achieved long-term stability.

DISCUSSION

To detail the cause of skeletal instability, study of the principal factors of instability is presented together with a discussion of data in the literature.

[Orthognathic surgery and facial asymmetry: successes and disappointments]

Used alone, Lefort I procedures and surgical mandibular reduction and de-rotation do not always restore facial symmetry; but by first correcting mesiodistal disharmonies, the orthodontist makes it possible for the surgeon to achieve the best results. Sometimes, long term stability of these improvements is jeopardized when the occlusal plane gradually begins to tilt again and asymmetry reappears in the mandible. By using electromyographic analysis in a series of patients with severe transverse facial disharmony she has treated, the author shows the important role played by the muscles of mastication in such relapses.

[Orthodontic implications in the correction of the transverse dimension in orthognathic surgery]

Transverse skeletal discrepancies are treated in skeletally mature patients with an association of orthodontics and surgical procedures. The orthodontics procedures used depend on the type of surgical maxillary expansion performed. Orthodontics procedures performed before surgery are designed around the analysis of frontal asymmetry. Indications and proper treatment strategy for surgically-assisted maxillary expansion, or for Lefort I osteotomy depend on the magnitude of the transverse deficiency. The orthodontics implications of facial asymmetry remains one of the specific points requiring special care before and after surgery. Long length orthodontics stabilization is required after surgically-assisted rapid maxillary expansion to limit transversal relapse by use of a rigid fixation or another auxiliary stabilizing arch wire.

[Muscular equilibrium and orthognathic surgery. A preliminary electromyographic study]

Few studies have been written about the effects of orthodontic preparation and of the consequences of surgical movements on mandibular motricity. The aim of this preliminary report is to evaluate the modifications of muscular activity between the pre-surgical phase and its evolution during the year after surgery, together with the skeletal modifications found. The muscular activity of six patients with serious vertical discrepancies requiring rehabilitation of the lower facial height has been studied using electromyographical recordings. A longitudinal study of the EMG data has been established in order to discover a muscular adaptation method towards physiological equilibrium following the realization of a new facial diagram. The reduction of the lower facial height obtained through a surgical procedure including a maxillary impaction, appears to indicate that, at rest, the masseter muscles activity tends to normalize, whereas that of the temporal muscles may sometimes increase. During maximal contraction, facial hyper-divergence reduction would lead to a sharp decrease in temporal and masseter muscular activity which would subsequently return to normal. The increase in vertical dimension would also cause significant changes in muscular tonus depending on the sagittal direction of the associated mandibular osteotomy. It would take longer to achieve muscular activity stability. These few results show: The existence of significant modifications following orthognathic surgery, possible reduction of high rest muscular activities, often revealing a cranio mandibular dysfunction, after vertical typology rehabilitation. The electromyographic recordings during treatment then enable to perfect the therapeutic re-evaluation of these major vertical discrepancies.

Dimensions and form of dental arches in subjects with normal occlusions

To determine the main mandibular dental arch forms, 278 dental casts of untreated French adults with normal occlusions were examined. Six measurements of the mandibular dental arches were performed, and five independent ratios were determined. By following the k-means clustering method on the basis of these ratios and the use of polynomial functions of the sixth degree, five mandibular dental arch forms were defined, and an arch guide was developed. The proposed forms are relatively narrow in comparison with previous studies. No significant differences in their distributions were seen between male and female subjects. However, the dental arches of the women have smaller dimensions.