Self-ligating brackets in orthodontics: Do they deliver what they claim?

Self-ligating brackets have enjoyed recent popularity in the orthodontic marketplace with various claims made including faster ligation, lower friction, faster treatment, less pain, waking up the tongue, and fewer appointments. Although various designs of self-ligating brackets have been available for many years they have only recently surged in popularity on the back of these claims but what evidence is there to support these claims? This review article examines the current available evidence regarding treatment duration, influence on archform, and the speed of tying and untying self-ligating brackets compared with conventional brackets and methods of ligation.

A clinical comparison of two chemically-cured adhesives used for indirect bonding.

OBJECTIVE: To compare and evaluate the clinical failure rates of the chemically-cured composite bonding resins Sondhi Rapid Set (SD) and Maximum Cure (MC) when used in an indirect bonding technique. SETTING: In vivo study in the private orthodontic practice of a solo practitioner. MATERIALS AND METHODS: Forty consecutive patients meeting the inclusion criteria were assigned to alternating groups in a split-mouth study design. Group 1 had the maxillary right and mandibular left quadrants indirectly bonded using SD adhesive, while the contralateral quadrants were bonded using MC adhesive. Group 2 had the opposite sides bonded to Group 1. One patient was lost from each group. Over a 6-month observation period, all loose brackets were recorded and the data compared with a Wilcoxon sign-rank test. RESULTS: Of the 363 brackets placed in each group, 36 with the SD adhesive came loose (9.9 per cent failure rate) compared with five from the MC group (1.4 per cent failure rate, P = 0.0001). In the maxillary arch, seven brackets from the SD quadrants came loose versus one for the MC (P = 0.109). In the mandibular arch 29 brackets from the SD quadrants came loose during the 6-month observation period compared with four from the MC quadrants (P = 0.001). CONCLUSIONS: Both chemically-cured adhesives (SD and MC) examined in this study were suitable for the indirect bonding of brackets. The SD adhesive had seven times the number of breakages than the MC adhesive in both arches (P = 0.0001).

A comparison of retention rates of brackets with thermally-cured and light-cured custom bases in indirect bonding procedures.

This study compared the retention rates of thermally-cured (TC) and light-cured (LC) custom bases attached to metal mini-diamond brackets and clear Spirit MB brackets, when used in indirect bonding procedures. The custom base comprised either the light-cured or thermally-cured material attached to the bracket base and prepared in the laboratory, the whole unit later being bonded to the natural teeth. Thirty consecutively treated patients had fixed appliances fitted in both arches, with Spirit MB brackets on the maxillary anterior teeth, and metal brackets on the maxillary posterior and all mandibular teeth. All brackets were bonded using either the LC or TC method. All procedures and treatment was by the same operator, using identical techniques. Observation was for six months. All bonding failures were recorded. The results indicated no significant differences in the retention rates of either of the custom-base materials when used with metal brackets. However, the Spirit MB brackets exhibited a significantly higher bonding failure rate when a TC custom base was used. It was therefore concluded that either material could be used in the indirect bonding of metal brackets, and that LC custom bases should be used in the indirect bonding of Spirit MB brackets.

Dentistry's role in obstructive sleep apnoea. Review and case report.

Obstructive sleep apnoea (OSA) has been associated with many life-threatening conditions but has only recently appeared in the dental literature. Dental appliances and orthognathic surgery are two strategies which are currently used in the treatment of sleep apnoea. This article provides a background on OSA and these treatment approaches, and discusses the potential risks and benefits of each. A case is reported to illustrate the use of a dental appliance in the treatment of OSA.

Craniofacial structure and obstructive sleep apnea syndrome--a qualitative analysis and meta-analysis of the literature.

The etiologic relevance of craniofacial structure to obstructive sleep apnea syndrome (OSAS) is controversial yet the premise of a causal association serves to justify many treatments. A qualitative and quantitative analysis of the literature was performed to examine the foundation for any relationship between craniofacial structure and OSAS. A MEDLINE search and investigation of the published and unpublished literature on diagnostic imaging and OSAS was toxonomically arranged. Each sample study was evaluated by using the following criteria: (a) appropriate control group, (b) "blinding" of evaluators, (c) reliability measured, (d) random assignment of treatment, and (e) "success" was defined adequately in efficacy studies. Morphologic variables were combined among studies and compared with controls drawn from either the same patient pool as the OSAS group, or matched for gender, age, and body mass index. Analysis revealed 32 review articles, 16 case reports, and 95 sample studies. Only seven sample studies drew a control group from the same patient pool, whereas five used matched controls. Only one of these studies satisfied all the qualitative criteria. Of the treatment efficacy studies, 10 defined outcome adequately. However, none of these met all the qualitative criteria. The most consistent, strong effect sizes with the highest potential diagnostic accuracies were for mandibular plane to hyoid, mandibular plane angle, and mandibular body length. Only mandibular body length demonstrated a clinically significant association with and diagnostic accuracy for OSAS. However, since this variable's controls were selected from the literature, possible explanations for a positive association include methodologic differences between studies, varying magnification factors, and morphologic differences.

Maxillomandibular advancement surgery in obstructive sleep apnea syndrome patients: long-term surgical stability.

PURPOSE: This study examined the long-term skeletal stability of relatively large maxillomandibular advancement surgery in the treatment of obstructive sleep apnea syndrome (OSAS). MATERIALS AND METHODS: The presurgical, immediate (< 1 month), and long-term (> 12 months) postsurgical cephalometric radiographs of 19 patients undergoing maxillomandibular advancement with simultaneous genioplasty for OSAS were studied. The cephalometric measurements and calculations were performed using a commercial cephalometric software. RESULTS: Maxillary and mandibular advancement seems to be stable in the horizontal and vertical planes over the long term. There was no significant correlation between the amount of surgical advancement and the amount of postsurgical instability, with the exception of gonion in the vertical plane. CONCLUSION: The results from this study indicate that large surgical advancements in OSAS patients result in relatively stable repositioning of the maxilla and mandible over the long term.

The reliability of upper airway landmark identification.

Research involving the upper airway has assessed linear measurements of certain structures on the assumption that the landmarks involved can be reliably identified. This study was conducted to determine the reliability of landmark identification for those structures most commonly reported in the obstructive sleep apnoea literature. Three judges were asked to identify specific landmarks on 20 randomly selected radiographs and 10 superior quality radiographs. This was repeated one week later. The results of the analysis of variance (ANOVA) indicated that the majority of the landmarks could be reliably identified, irrespective of the quality of the radiograph. However, the quality of the radiograph did affect identification of the horizontal position of the hyoid bone and the linear measure of posterior airway space although these were not clinically significant. The vertical position of the tip of the soft palate was highly unreliable, irrespective of the quality of the radiograph. This resulted in errors in the measurement of soft palate length. Future airway-related research should consider the potential inaccuracies when attempting to identify these dynamic three-dimensional structures on static two-dimensional images.

Reliability of computer-generated cephalometrics.

The use of computer-generated cephalometric analyses has gained popularity in both research and clinical applications. This study was conducted to determine the reliability of the computerized cephalometric methodology. A customized cephalometric analysis of 40 cephalometric radiographs was performed using 22 cephalometric landmarks to evaluate 40 measurements. Reproducibility studies were performed for each step of the computerized cephalometry used. The computer-generated measurements were also compared with those obtained through the conventional hand-measured method. The measurements obtained through the computerized methodology were reproducible for most parameters studied, although point B was found to be unreliable in the vertical plane. The combined errors from video imaging, digitization of the image, and the software were not methodologically significant. No statistically significant errors were found for the repeated measurements of the retrieved digital images. However, the absolute values of all parameters related to the horizontal plane from the computerized method were 0.7 to 1.0 mm greater than those from the conventional hand-measured method, indicating that some horizontal magnification occurred. This information is useful for the interpretation of data obtained from computerized cephalometry.

Maxillomandibular advancement surgery in patients with obstructive sleep apnea: mandibular morphology and stability.

Causal associations between various craniofacial morphologic variables and obstructive sleep apnea have been inferred and serve to justify many treatments. The purposes of this study were to examine the presurgical and postsurgical mandibular morphology of patients with obstructive sleep apnea who were undergoing maxillomandibular advancement and to assess the stability of the observed changes. Various mandibular morphologic variables of 32 male subjects were measured on presurgical, immediately postsurgical, and short-term and long-term postsurgical radiographs. The results demonstrated that presurgical mandibular morphology was not significantly different from that of control samples derived from the literature. The presurgical mandibular plane-hyoid measurement was an average of 11.4 mm greater than that in matched controls. On average, surgery resulted in a significantly longer mandible, a greater gonial angle, and a reduced mandibular plane-hyoid distance, although the response of the hyoid was quite variable. The surgical changes in mandibular length were relatively stable over the long-term. Obstructive sleep apnea did not appear to be related to abnormal presurgical mandibular morphology in this sample.

The validity of maxillary expansion indices.

Numerous indices have been proposed to help the clinician decide how much maxillary expansion will be required to alleviate crowding. The purpose of this investigation was to examine the validity of Pont's index, Schwarz's analysis and McNamara's rule of thumb. Records of 40 patients (20 females and 20 males) were selected from 155 consecutive pretreatment records. The discrepancy between actual intermolar/interpremolar widths and the index-generated widths were correlated against measures of crowding, and linear regressions were computed. Statistical analysis revealed that (1) males had more significant correlations between arch width and crowing than females, (2) interpremolar widths were more strongly correlated than intermolar widths, (3) Pont's index and McNamara's rule of thumb overestimated required arch width by 2.5 mm to 4.7 mm and 2.7 mm to 3.7 mm respectively, and (4) Schwarz's analysis overestimated interpremolar width by 2.5 mm to 4.3 mm but was reasonably accurate for intermolar width in males. The results suggest that these indices potentially overestimate the arch expansion required to alleviate crowding.

The effect of carbamide peroxide bleach on the tensile bond strength of ceramic brackets: an in vitro study.

Recent advances in cosmetic dentistry have led to the development of a variety of new products and techniques including vital bleaching and ceramic brackets. Therefore this study was conducted to see whether the use of an at-home carbamide peroxide bleaching agent before bonding affected the tensile bond strength of a precoated ceramic orthodontic bracket. Sixty extracted human premolar teeth were randomly separated into three groups of 20. Group 1 was a control group that was etched and bonded in the usual manner. Group 2 was immersed in a carbamide peroxide home bleaching agent for 72 hours before pumicing and bonding. Group 3 was also bleached for 72 hours but was immersed in distilled water for 1 week before bonding. The results indicated that recently bleached teeth have significantly reduced bond strength values when compared with both groups 1 and 3. We suggest that if a patient is using a tooth whitening product, that they discontinue its use at least 1 week before the bonding of orthodontic attachments.

Facial palsy in the dental surgery. Case report and review.

Facial palsy is a relatively uncommon condition with a variety of causes including dental intervention. A brief history of two cases of facial palsy with dental implications is presented. The aetiology of facial palsy is reviewed and the management of such cases is discussed. The option of immediate treatment of Bell's palsy with prednisone is stressed.

New technique of sample preparation for respirometry of filamentous fungi.

Various difficulties in the respirometry of filamentous fungi were avoided by using samples of moist mycelium layered thinly on tantalum grids. A variety of measurements is feasible with such preparations and are illustrated with samples of Schizophyllum commune from liquid and solid cultures.