Three-dimensional orthodontic anchorage management of impacted maxillary canines: A systematic review

Objectives:

Our work aims to provide scientific evidence by conducting a serious systematic review of the efficacy of three-dimensional (3D) anchorage devices for orthodontic traction of impacted maxillary canines.

Material and Methods:

An electronic search extending from 2012 to 2022, targeting mainly clinical trials was performed on the following databases PUBMED (MEDLINE), The Cochrane Library, SCIENCE DIRECT, EBSCO HOST DATABASES, and GOOGLE SCHOLAR. The search was established on a well-defined research question following the PICO principle: population, intervention, comparator, and outcome. Search evaluation and the assessment of the risk of bias (RoB) were undertaken in each study following its type and design.

Results:

Thirteen studies were included for qualitative analysis, with a low to moderate RoB. Ten studies used only heavy conventional palatal anchorage such as a fixed trans palatal arch (TPA), while one study used skeletal anchorage to manage the orthodontic traction of impacted maxillary canines. Two studies compared trans palatal arch and mini-screws efficiency to treat impacted maxillary canines.

Conclusion:

Studies proved that the trans palatal arch (TPA) presents a particular anchorage unpredictability in the sagittal, transversal, and vertical dimensions. Whereas, anchorage management using mini-screws proved to be very beneficial clinically; however, further studies must be implemented to evaluate the 3D efficacy of skeletal anchorage to place an impacted maxillary canine to its rightful position into the arch.

[Impact of incisor repositioning on the cephalometric position of points A and B]

Introduction

points A and B are bony landmarks used in cephalometric studies to assess sagittal ratio between maxilla and mandible. The purpose of this study is to assess the reliability of points A and B as bony landmarks, by investigating the role of incisor repositioning on their cephalometric position.

Method

superposition of cephalometric tracings at beginning and end of treatment of 30 patients without bone growth disorders, presenting with biproalveolia and having undergone orthodontic treatment with extraction of four first premolars was carried out to estimate changes in points A and B position. The significance threshold was set at 0.05.

Results

our study showed that the influence of orthodontic treatment on point A position was not statistically significant, while its influence on point B position was statistically significant (p= 0,01). Indeed, for every 1mm of incremental repositioning, point B moved back by 0.17mm.

Conclusion

incisor repositioning in the mandibular arch induces a change in the position of point B backwards.

Additive manufacturing in fighting against novel coronavirus COVID-19

Nowadays, COVID-19 also known as novel coronavirus has become a global pandemic by causing severe respiratory tract infections in humans without any definite treatment or vaccine. Therefore, disease control measures include slowing down or averting the transfer of this viral infection from person to person. Continuous efforts are carried out to avoid the transmission of this disease to frontline healthcare personnel using single-use personal protective equipment (PPE). However, a critical shortage in this equipment around the world is becoming an alarming concern. Therefore, it is vital to present a possible alternative to overcome the acute shortage of protective gear such as face masks against this infectious disease which can have universal accessibility and is easily available. Additive manufacturing (AM), also known as 3D printing, is a possible solution to overcome the shortage of protective gear and can play a vital role in supporting their conventional production supplies during this global pandemic situation. In this context, this paper provides a brief background study of COVID-19, its conventional preventive measure, and a detailed overview regarding the latest AM efforts including designers' providers and makers in the 3D printing community. Moreover, numerous inquiries and questions such as technical factors, testing recommendations and characterization methods and biological concerns such as biocompatibility and sterilization for the AM manufactured medical devices are addressed in this paper. In the end, two examples of AM medical devices, i.e., face mask and Ambu bag ventilator, are presented and studied through numerical simulations.

Graphene nanofillers as a player to improve the dynamic compressive response and failure behavior of carbon/epoxy composite

Vast research has been going on to improve the mechanical performance of carbon fiber reinforced polymers composite (CFRP) when subjected to quasi-static loading but investigation and modification of their dynamic behavior are still underdeveloped. This paper presents an experimental investigation on the effect of randomly dispersed graphene nanoplatelets (GNPs) on the mechanical properties of CFRP composites under dynamic loading. Four different mass fractions of GNPs, 0%, 0.5%, 1%, and 2%, were considered in the experiments. Specimens were tested experimentally using the split Hopkinson pressure bar device (SHPB) to examine their dynamic response and damage behavior at high strain rates. During the dynamic compression tests, a high-speed camera was used to monitor and record the damage kinetics. The experimental characterization showed that the integration of GNPs has greatly influenced the dynamic response and damage mechanism of the CFRP. Composite doped with 1% GNPs demonstrates the optimum enhancement of the mechanical properties of the composite specimens and shows an increase of the dynamic characteristics and fracture resistance.

Enamel protection after stripping procedures: An in vivo study

INTRODUCTION

Interproximal enamel reduction (IPR) is a clinical procedure that has been in use since the advent of non-extraction orthodontic techniques. However, such a procedure affects the surface condition of the enamel and may predispose patients to cavities and hypersensitivity. The use of a remineralizing agent is recommended to prevent these side effects. The objective of our study was to evaluate the evolution of stripped proximal dental surfaces after exposure to the oral environment for 4 months with and without fluoride protection.

MATERIALS AND METHODS

Our sample consisted of 14 premolars (PM) from 6 patients of the Dentofacial Orthopaedics Department of the Consultation and Dental Treatment Centre of Rabat (CDTC) who required orthodontic treatment with PM extraction and had given their informed consent. The teeth were divided into 5 groups: group 1: intact enamel; group 2: intact enamel+fluoride varnish+4-month oral exposure; group 3: IPR (manual and mechanized)+extraction; group 4: IPR (manual and mechanized) without varnish+4-month oral exposure; group 5: IPR (manual and mechanized)+fluoride varnish+4-month oral exposure. Proximal surfaces were subjected to qualitative analysis by scanning electron microscopy and quantitative analysis by Dispersive Energy Spectroscopy (DES) to quantify the percentage of mineral elements.

RESULTS

Exposure of stripped dental surfaces to the oral environment for 4 months with or without fluoride protection showed the persistence of surface irregularities caused by stripping. We noted an improvement in the percentage of mineral elements for both groups with and without fluoride protection. However, the percentages of calcium (Ca) and phosphorus (P) were close to that of intact enamel in the fluoride varnish group.

CONCLUSION

Protecting stripped surfaces with fluoride varnish could help preserve the integrity of the enamel surface by restoring some of the mineral elements lost during stripping.

In vivo enamel stripping: A macroscopic and microscopic analytical study

INTRODUCTION

Interdental stripping is often used in orthodontics to correct discrepancies of tooth shape or size. However, this procedure involves significant risks for the enamel. The roughness of the enamel surface might depend on the instruments used; it can lead to the accumulation of cariogenic plaque and periodontal problems. The main objective of our study was to evaluate the enamel surface condition after interproximal stripping in the mouth, by comparing different manual and mechanized enamel reduction protocols; on the other hand, the topography of the stripped area was observed to specify its location on the stripped proximal surfaces.

MATERIALS AND METHODS

An in vivo study was carried out: interdental stripping was performed in the mouths of patients undergoing orthodontic treatment and on healthy teeth intended for extraction for orthodontic or periodontal reasons. The sample was divided into four groups: in group 1, the distal faces were stripped with conventional single-sided diamond abrasive strips and non-stripped mesial faces (control faces); in group 2: the distal faces were stripped with the manual ContacEZ IRP Kit (single-sided abrasive files of different grain sizes) and non-stripped mesial faces (control faces); in group 3: the faces were stripped with ContacEZ IRP diamond discs attached to a handpiece and the mesial faces were not stripped (control faces); in group 4: the distal faces were stripped with the Intensiv Ortho-Strips mechanized system and the mesial faces were not stripped (control faces).

RESULTS

Our study showed that regardless of the type of stripping material used, the enamel surface showed some roughness with the presence of striations and grooves of different widths and depths. Our observations objectivised more regular and less roughened enamel surface conditions when using the Intensiv oscillating files. Manual instruments (abrasive strips and files) have shown rougher and more irregular surface conditions that may constitute a real risk of carious and periodontal disease. The macroscopic evaluation of the topography of the stripped area showed that there is great variability in the situation and extent of the stripped area in relation to several parameters.

CONCLUSION

The current mechanized instruments (oscillating files) provide enamel stripping with more comfort for the patient and the practitioner, and seem to produce a more regular and less harmful surface condition for the tooth and periodontium.

Cephalometric norms of a Burkina Faso population

INTRODUCTION

After a clinical examination, in order to implement an appropriate treatment planning, additional examinations such as lateral cephalograms, were performed. They were submitted to a cephalometric analysis such as the Tweed-Merrifield analysis. These cephalometric analyses based on a synthesis of aesthetic criteria established for a Caucasian European-American white people population could not serve as the reference for an African population. The aim of our study was to help establish the cephalometric norms of the Tweed-Merrifield's craniofacial and aesthetic analysis for a consulting population in the city of Ouagadougou.

MATERIALS AND METHODS

This is a retrospective cross-sectional descriptive study conducted on a sample of lateral cephalograms selected among the files of patients consulting in the department of dental surgery at the Yalgado Ouédraogo university hospital centre of Ouagadougou. The patients were selected upon their balanced facial aesthetics. The same operator using acetate paper traced cephalogram on radiographs and collected the angular and linear values for the analysis.

RESULTS

A total of 84 cephalograms, 42 male lateral cephalograms and the same number of females, were included. Their age ranged from 11 to 21 years old, with a mean age of 14.34 years. The mean SNA angle was 84.94°±2.59, the ANB angle was 4.88°. The vertical dimension was within the mean values, which was not the case for the mandibular incisor axis, very tipped buccally with an IMPA angle of 95.97°. The profile of the African subject was characterized by a closed Z angle.

CONCLUSION

The profile of the African subject was rather prognathic, the maxilla and the mandible were prominent in relation to the cranial base. The maxillary-mandibular relationship is Ballard's class II. The typical alveolar biprotrusion must be considered as an ethnical data, which our treatment plans must consider.

A predictive model of advancement genioplasty in Class III bimaxillary surgical cases

INTRODUCTION

The aim of our study was to try to standardize the surgeon's clinical sense in order to avoid revision surgery.

MATERIALS AND METHODS

Twenty-nine patients with skeletal Class III treated by bimaxillary surgery were selected according to inclusion and exclusion criteria. These patients were divided into two groups according to the type of surgery: Group 1 (G1): bimaxillary surgery alone, and Group 2 (G2): bimaxillary surgery with genioplasty. The study was conducted based on the presurgical (t₀) and postchirurgical (t₁) lateral cephalograms. The different changes were compared between the two groups using the Mann-Whitney Test. One way and multiple linear regression analyses were used to determine the variables influencing the amount of displacement of the chin fragment during the genioplasty procedure. The significance level was fixed at 0.05.

RESULTS

The labiomental profile was significantly more improved in group G2 (bimaxillary surgery with genioplasty), the aesthetic changes included the thickness increase of the lower labial sulcus and soft tissue pogonion, and also the reduction of the labiomental angle (P<0.05). Only the presurgical value of the labiomental angle would influence the amount of chin displacement. Starting from the regression analysis, we suggested a predictive equation allowing to predict this amount of displacement, based on the presurgical value of the labiomental angle.

CONCLUSION

The analysis of changes (specifically the aesthetic ones) between the two groups of patients, allowed the proposal of a model predicting the amount of chin displacement performed in genioplasty group, based on the presurgical parameters. This model could contribute to determine an indicative value for bimaxillary surgery with additional genioplasty.

A systematic review of orthodontic retention systems: The verdict

INTRODUCTION

Retention during both the active and passive phases of treatment has given rise to numerous publications concerning its efficacy, the range of systems available and its variability over time. There are currently many different retention protocols regularly used by orthodontists; however, their efficacy and duration are still subject to debate. There is as yet no consensus as to which retention protocol is the most effective or for how long the retention device needs to be worn. The aim of this research was to perform a systematic review of the scientific literature in order to evaluate the efficacy of the different retention systems and clinical protocols among those most widely used, so as to make recommendations beneficial to both patient and practitioner.

MATERIALS AND METHODS

A search of the literature was performed in the following databases: PubMed (MEDLINE), ScienceDirect and Cochrane Library. The search was limited to publications in English and French during the period 2006-2016.

RESULTS

Out of 1952 references initially identified, 17 articles corresponded to our inclusion criteria. The results show that: fixed retention is more effective than removable retainers for the maintenance of incisor alignment during the first six months of retention; there is no significant difference in efficacy between the different fixed retention systems; there is no significant difference in efficacy between the vacuum-formed systems and the Hawley retainer; part-time use of removable retainers (between 8-10h/day) is sufficient; the most widely used retention protocol combines a vacuum-formed splint or Hawley retainer in the upper arch with mandibular fixed retention.

CONCLUSION

Despite the large number of studies devoted to orthodontic retention only a few articles corresponded to the methodological criteria of bio statistical analysis. Also, on account of the variations in experimental protocols, the levels of proof relating to the efficacy of different systems are very weak. Research into this topic should first seek to normalize methods of analysis and then perform randomized controlled long-term trials to shed light on this problem.

Relationship between the curve of Spee and craniofacial variables: A regression analysis

INTRODUCTION

The aim of this regression analysis was to identify the determining factors, which impact the curve of Spee during its genesis, its therapeutic reconstruction, and its stability, within a continuously evolving craniofacial morphology throughout life.

MATERIAL AND METHODS

We selected a total of 107 patients, according to the inclusion criteria. A morphological and functional clinical examination was performed for each patient: plaster models, tracing of the curve of Spee, crowding, Angle's classification, overjet and overbite were thus recorded. Then, we made a cephalometric analysis based on the standardized lateral cephalograms. In the sagittal dimension, we measured the values of angles ANB, SNA, SNB, SND, I/i; and the following distances: AoBo, I/NA, i/NB, SE and SL. In the vertical dimension, we measured the values of angles FMA, GoGn/SN, the occlusal plane, and the following distances: SAr, ArD, Ar/Con, Con/Gn, GoPo, HFP, HFA and IF. The statistical analysis was performed using the SPSS software with a significance level of 0.05.

RESULTS

Our sample including 107 subjects was composed of 77 female patients (71.3%) and 30 male patients (27.8%) 7 hypodivergent patients (6.5%), 56 hyperdivergent patients (52.3%) and 44 normodivergent patients (41.1%). Patients' mean age was 19.35±5.95 years. The hypodivergent patients presented more pronounced curves of Spee compared to the normodivergent and the hyperdivergent populations; patients in skeletal Class I presented less pronounced curves of Spee compared to patients in skeletal Class II and Class III. These differences were non significant (P>0.05). The curve of Spee was positively and moderately correlated with Angle's classification, overjet, overbite, sellion-articulare distance, and breathing type (P<0.05). We found no correlation between age, gender and the other parameters included in the study with the curve of Spee (P>0.05). Seventy five percent (75%) of the hyperdivergent patients with an oral breathing presented an overbite of 3mm, which is quite excessive given the characteristics often admitted for this typology; this parameter could explain the overbite observed in the hyperdivergent population included in this study. For the multivariate analysis, the overbite and the sellion-articulare distance remained independently related to the curve of Spee according to the breathing type, Angle's classification, and overjet. This regression model explains 21.4% of the changes in the curve of Spee.

Topographic and chemical surface modifications to metal brackets after a period in the mouth

INTRODUCTION

In the current state of our knowledge, the effects of corrosion on the performance of orthodontic appliances and on patient health are far from clear. Awareness of these problems has led to a growing demand for nickel-free products. Titanium brackets were recently launched on the market as an alternative to stainless-steel brackets. However, the use of fluorides for caries prevention creates a risk of corrosion of these titanium appliances. The aim of this study is to examine the corrosion of stainless-steel and titanium brackets in clinical orthodontic use, focusing on the impact of fluorine.

METHODS

After approval by the ethics committee and the informed consent of the patients, 30 candidates for multi-bracket treatment were selected on the basis of certain exclusion criteria. The patients were divided into 4 groups: group 1: titanium brackets and fluorine protection; group 2: titanium brackets without fluorine protection; group 3: stainless-steel brackets and fluorine protection; group 4: stainless-steel brackets without fluorine protection.

RESULTS

Analysis of the brackets removed after 4months in the mouth, using scanning electron microscopy (SEM) with phase contrast, revealed a difference in the surface topography of the metal brackets and the presence of chromium coating on the surface of the titanium appliances.

Therapeutic efficacy of self-ligating brackets: A systematic review

INTRODUCTION

Over the last few years, the use of self-ligating brackets in orthodontics has progressed considerably. These systems have been the subject of numerous studies with good levels of evidence making it possible to evaluate their efficacy and efficiency compared to conventional brackets. The aim of this study was to evaluate the therapeutic efficacy of self-ligating brackets by means of a systematic review of the scientific literature.

MATERIALS AND METHODS

A systematic study was undertaken in the form of a recent search of the electronic Pubmed database, oriented by the use of several keywords combined by Boolean operators relating to the therapeutic efficacy of self-ligating brackets through the study of tooth alignment, space closure, expansion, treatment duration and degree of discomfort. The search was limited to randomized controlled studies, and two independent readers identified studies corresponding to the selection criteria.

RESULTS AND DISCUSSION

The chosen articles comprised 20 randomized controlled trials. The studies analyzed revealed the absence of significant differences between the two types of system on the basis of the clinical criteria adopted, thereby refuting the hypothesis of the superiority of self-ligating brackets over conventional systems.

[How to treat hypoplasia of the lateral upper incisors by canine substitution : a clinical case]

INTRODUCTION

Facing a patient with a morphological or numerical disorder of the lateral upper incisors (mainly pegged or missing incisor), the orthodontist has to choose between two treatment options : either spatial planning for a prosthetic restoration, or space closure with substitution of the lateral incisors by canines; the choice depends on the clinical context we are faced with. Each treatment option has its advantages and disadvantages and it is hard to tip the balance in one direction or another.

MATERIAL AND METHOD

This article illustrates the rationale for therapeutic management of space closure, in a patient with skeletal class III, with hypoplastic and peg-shaped upper lateral incisors.

A systematic study of the release of bisphenol A by orthodontic materials and its biological effects

INTRODUCTION

Bisphenol A (BPA) is a synthetic chemical substance used as a starting ingredient in the manufacturing process of a number or orthodontic materials. It is a well-known endocrine disruptor with low estrogenic properties. The aim of this investigation is to present a systematic review regarding the issue of bisphenol A release by orthodontic materials and its impact in orthodontics.

MATERIALS AND METHODS

A systematic analysis was performed by electronic search (between 1936 and 2015) on several data bases. The search was limited by using several specific key-words in two languages, English and French. Two investigators selected the responses, which met the selection criteria.

RESULTS AND DISCUSSION

Of the 376 studies found, only 21 met our selection criteria: 11 of these dealt with the release of bisphenol by orthodontic materials and 10 in vitro studies described the effects of BPA leaching from orthodontic materials on human and murine cells. The rate of BPA release was well below the daily tolerable intake (DTI) (50mg/kg/day in 2006, then 50μg/kg/day in 2015) according to the European Food Safety Authority (EFSA). Theoretical exposure to BPA was 11,000 times lower than recommendations. However, other studies have shown the presence of BPA and of monomers released in large quantities at very low doses. The effects of observed BPA varied significantly (toxic and carcinogenic potential) while some studies found no effects at all. The relatively small number of studies dealing with the release of Bisphenol A by orthodontic materials, apart from orthodontic materials and their significant biological effects, has led to the absence of standard protocols and has hindered precise determination of released BPA. Moreover, the lack of coherence between the various methodological approaches and variations in the experimental protocols have resulted in a low level of proof regarding the impact of BPA by orthodontic materials.

RECOMMENDATIONS

Through this study, the authors encourage clinicians to observe the following recommendations designed to reduce the amount of BPA released by materials used in orthodontics: keep the tip of the light-curing lamp as close as possible to the composite and perform indirect rather than direct light-curing; Pumice-polish the composite after bonding so as to reduce the potential amount of BPA released; reduce exposure by brushing or rinsing with a mouthwash during the first hour after bonding; follow a standardized, reproducible and expert-validated research protocol aimed at better understanding of BPA release.

[Original conception of polymerized diagnostic wax-up in an occlusal rehabilitation of distal unilateral edentulous by combined prosthesis]

Rehabilitation by combined prosthesis is a therapy that requires a methodical approach especially in the case of large unilateral edentulous when all occlusal parameters are to be restored. The recording of the maxilla-mandibular position is requested at various stages of the treatment. In this context, the use of polymerized diagnostic wax up, is an evident tool for accurately recording and transfer of all occlusal data previously validated, yet concerning the global rehabilitation of unilateral distal edentulous, its stability and exact re-positioning at various prosthetic sequences remain uncertain. The aim of this study was to develop an original conception of the polymerized diagnostic wax up that will allow us to benefit from all its advantages in complex rehabilitation of edentulous unilateral of large extent.

Resorption of maxillary incisors after orthodontic treatment--clinical study of risk factors

INTRODUCTION

External apical root resorption (EARR) is one of the major problems associated with orthodontic treatment. Such lesions represent an iatrogenic risk that must be detected as early as possible, with regular radiological follow-up and appropriate therapeutic precautions. The causes and mechanisms leading to susceptibility to root resorption following the application of an orthodontic force are often not clear and are generally said to be of multifactorial origin. The aim of this clinical study was to analyze the factors linked to the occurrence of moderate to severe resorption (MSR) of upper incisors during orthodontic treatment in a group of Moroccan patients treated in the Dento-Facial Orthopedic Department of the Dental Consultation and Treatment Center (Centre de consultation et de traitements dentaires [CCTD]) in Rabat.

MATERIAL AND METHODS

A total of 82 patients (28% males, 72% females) aged between 12 and 27, with various malocclusions, who had been treated with fixed appliances for at least 1 year and for whom panoramic X-rays at the start, during and at the end of treatment were available, were selected randomly. The reduction in maxillary incisor root length was evaluated using resorption scores. The factors studied in relation to the risk of occurrence of MSR were: age, sex, treatment duration, extraction or non-extraction, type of malocclusion (Class I arch-length discrepancy, Class II, Class III), the vertical diagnosis (normal, supraocclusion, open bite), presence of dysfunction, impacted canines and root morphology. Statistical analysis was performed using SPSS software, version 18.0. Statistical tests used were: Kaplan-Meier analysis and the univariate and multivariate Cox models for the study of factors associated with MSR. The threshold of significance adopted was 0.05.

RESULTS

The factors that were significantly associated with the occurrence of MSR at the level of the upper incisors were: tooth type, with a greater risk for the lateral incisor (HR=3.2 95% CI [2.3-4.5] P<0.001), treatments with extraction (HR=1.64 95% CI [1.16-2.33] P<0.05), the presence of supraocclusion (HR=2.17 95% CI [1.33-3.53] P<0.05) or open bite (HR=3.12 95% CI [1.66-5.86] P<0.001) and root malformation (HR=1.5 95% CI [1.09-2.07] P<0.05). Age, sex, type of malocclusion, dysfunction and impaction of canines were not associated at a statistically significant level with the risk of occurrence of MSR of the upper incisors.

CONCLUSION

EARR is difficult to avoid; the orthodontist's role remains crucial in identifying risk factors so as to adopt a treatment strategy taking these factors into account. In our population, the risk of MSR in the upper incisors appeared to increase in treatments with extraction, situations of supraocclusion or open bite, and in the presence of root abnormalities. Finally, clinical recommendations for the prevention of the occurrence of MSR of the maxillary incisors are proposed, taking into account all the risk factors identified.

[Orthodontic correction of a Brodie syndrome case related to oral habits]

Unilateral Brodie bite, called also Scissor bite, is a form of transversal malocclusion that often leads to minor facial asymmetry. The prevalence of this form of malocclusion is rare, especially met in mixed denture. We report a case of 11-year-old girl who presents unilateral scissor bite related to oral habits, with a skeletal class II. Modified activation by contraction of a bi-helix appliance was used to treat the unilateral scissor bite occlusion, before approaching the correction of the sagittal relationship.

[Contribution of the cervical vertebral maturation (CVM) method to dentofacial orthopedics: update]

The successful orthopedic treatment of skeletal Class II malocclusions is closely related to the reasoned determination of the optimal time to initiate the treatment. This is why various methods have been proposed to assess skeletal maturation, such as a hand-wrist radiograph or the cervical vertebral maturation (CVM) method. The hand-wrist radiograph was up to now the most frequently used method to assess skeletal maturation. However, the clinical and biological limitations of this technique, as well as the need to perform an additional radiograph, were reasons to develop another method to explore the maturation stages of visible cervical vertebrae on a simple lateral cephalometric radiograph. The authors compare the 2 methods and prove the greater contribution of the CVM method compared to the hand-wrist radiograph.

A systematic review of force decay in orthodontic elastomeric power chains

INTRODUCTION

Elastomeric chains are one of several devices used to provide force for orthodontic tooth movement, but the force they exert diminishes over time and can thus be difficult to control. The objective of this investigation was to provide a systematic review of publications pertinent to force decay in orthodontic elastomeric chains.

MATERIALS AND METHODS

A systematic review was performed via electronic querying of multiple databases for the period 1970-2011. Queries were limited to a set of specific keywords in two languages (English and French). Five main reviews were consulted manually to identify relevant publications. Two investigators sorted out those studies that complied with selection criteria.

RESULTS AND DISCUSSION

A total of 53 studies were found to be relevant to force decay in elastomeric chains, including 22 on force decay over time, seven on the force consequences of pre-stretching, 12 on the impact of the environment on the force delivered, and 11 on clinical efficacy.

CONCLUSION

The force delivered by elastomeric chains decays rapidly over time, affecting their mechanical properties and clinical efficacy when studied in either human saliva or laboratory test media.

Effects of sterilization and disinfection procedures on the corrosion of orthodontic ligature cutters

OBJECTIVE

The objective of our study was to investigate the corrosion resistance of orthodontic ligature cutters subjected separately to two different sterilization procedures, namely, autoclaving and chemical disinfection with main focus on the cutting section of each instrument.

MATERIALS AND METHODS

Twenty-four ligature cutters were obtained from three different manufacturers: Hu-Friedy, ETM, and Nadir & Co. The study included a control group (G0) and four experimental groups (G1-4). G1 was subjected to 50 autoclave sterilization cycles. G2, G3, and G4 were subjected to 50 chemical disinfection cycles using, respectively, Peridiol E, Hexanios G+R, and Steranios 2%. Manufacturer recommendations were followed. The instruments' blades were studied via SEM and X-ray microanalysis (EDX spectrum).

RESULTS

These cutters have inserts made from various resistant alloys. SEM micrographs revealed different forms of corrosion depending on whether autoclaving or chemical disinfectant sterilization procedures were used, and depending on the alloys present. Chemical disinfection is more aggressive than autoclave sterilization, and is responsible for localized corrosion in the form of pitting. This is more detrimental to the lifespan of orthodontic cutters.

CONCLUSION

Sterilization/disinfection procedures should be adapted to the chemical profile of the metal alloys present. Recommendations for use published by instrument manufacturers must be followed.

Associations between alveolar heights and vertical skeletal pattern in Moroccan adults: a cephalometric study of 127 clinical cases

The aim of our study was to investigate vertical dentoalveolar compensation in untreated patients, in search of an association between vertical facial pattern and alveolar heights. This study involved the participation of 127 untreated Moroccan adults from the patient population of the ODF (Dentofacial Orthopedics) Department at the Center for Dental Treatment and Consultation (CCTD) in Rabat. Full adult dentition was the only criterion for inclusion. Patients with major syndromes and patients with facial clefts were excluded from the study. For the purposes of this analysis, we used profile teleradiography to measure vertical and sagittal skeletal variables as well as vertical dentoalveolar variables in the anterior and posterior maxillary and mandibular regions. We also measured the incisor axes. Analyses and statistical tests were performed with SPSS(®) statistics software (version 9.5 for Windows). Results indicate that: (i) upper posterior alveolar height (UPAH) does not correlate with skeletal variables of facial divergence, but correlates strongly with anterior facial height (AFH) and moderately with posterior facial height (PFH); (ii) lower anterior alveolar height (LAAH) correlates negatively with facial height index (FHI), positively with the FMA and AFH, but does not correlate with PFH; (iii) lower posterior alveolar height (LPAH) does not correlate with skeletal variables of facial divergence; (iv) upper anterior alveolar height (UAAH) changes inversely with FHI, correlates positively with the FMA and does not correlate with PFH.

Behavior of NiTi in the presence of oral bacteria: corrosion by Streptococcus mutans

The aim of this study was to investigate the electrochemical behavior of nickel titanium (NiTi) orthodontic wires in a solution containing Streptococcus mutans oral bacteria. In this article, we explain our choice of bacterial species before describing the culture process in artificial saliva and the precautions needed to prevent contamination by other bacteria. The electrochemical behavior of the alloy (NiTi) was analyzed electrochemically in Ringer sterile artificial saliva and in artificial saliva enriched with a sterile broth and modified by addition of bacteria. The electrochemical procedures chosen for this study were: free corrosion potential, potentiodynamic curves and impedance spectroscopy. In this way, we were able to show that the free corrosion potential of the NiTi in the Ringer solution increases with time and then stabilizes, thus passivating the alloy. We also demonstrated that colonization of the metal surface by bacteria triggered a drop in the free corrosion potential. The electrochemical impedance findings revealed no significant difference in NiTi behavior between the two media. Finally, we observed a slight difference between the two corrosion currents in favor of the bacteria-enriched solution, in which the NiTi underwent greater corrosion. These findings demonstrate the impact of acidogenic bacteria on corrosion behavior of the NiTi wires investigated. However, further research is required, notably incorporating longer immersion times in the two media.

[Loss of molar anchorage: quantitative evaluation with a method of structural superposition]

The goal of this study is to analyze using structural cephalometric superimpositions the quantity of mesial molar drift in the maximum anchorage cases, with mainly extractions of the first four premolars. Molar anchorage is appreciated in cases treated with or without use of directional forces. The influence of various parameters: age, facial divergence, discrepancy and incisor repositioning, on the loss of anchorage is also evaluated. The statistical study called upon the test of Student for independent groups. A value of the risk of first species p<0.05 was considered as significant. The loss of anchorage seems less important with the use of the directional forces. On the other hand it is raised in teenagers and the cases of important incisor repositioning.

[Refinement and study of the performance of a "Mycoplasma UG" kit for the research on urogenital Mycoplasmas]

The pathogenic role of genital Mycoplasmas is no more disputably. The diagnosis is based on the culture which may present some technical difficulties. The present study consist in a perfecting of a miniaturised system called "Mycoplasma UG" for the research, identification and titration of genital Mycoplasmas. The performance of the kit is studied with an important number of different types samples by comparison with the commercial kit "Mycoplasma Duo" and the classic reference method. The results obtained are satisfactory and constitute an important element in favour of a more advanced validation before the kit's trading.