As orthodontists, we are often unaware of the technical and methodological advances in other dental specialties. However,many of these new experimental developments may ultimately become accepted dental therapy and inpuence the diagnosisand treatment of our orthodontic patients. Therefore, as part of the dentaI community, we must keep abreast of currentinformation in all areas of dentistry. The purpose of this section of The Angle Orthodontist is to provide a brief summaryof what`s new in dentistry.
Mandibular anterior repositioning appliances attempt to diminish temporomandibular joint pain, soft tissue noise, and myofascial discomfort by altering condyle-disc relationships. Secondary stabilization of the occlusion to this arbitrary anterior position through orthodontic tooth movement may significantly alter functional and muscular relationships. A case report is illustrated to show that as the functional environment attempted to reestablish equilibrium through adaptation, relapse occurred as the condyles “seated” posteriorly and superiorly toward their original relationship within the fossa. For all practical purposes, complete relapse of the orthodontic treatment result took place over time.
Establishing a knowledge-based protocol for the treatment of orthodontic patients who report a history of temporomandibular dysfunction can alert the practitioner to potential treatment pitfalls before they happen. While the joints can be extremely adaptive, some individuals are subject to painful and/or limited function. Others have acquired condylar positions that, if not recognized, could lead to serious alterations in the original treatment plan. Combining a thorough diagnostic protocol with a therapeutic regimen that seeks to establish a stable condylar and occlusal position-prior to initiating treatment- is essential.
Soft tissue dynamics may contribute to maxillomandibular allometry (size-related changes in shape) associated with the development of Class III malocclusions. Lateral cephalographs of 124 prepubertal European American children were traced and 12 soft tissue landmarks were digitized. Resultant geometries were normalized, and Procrustes analysis established the statistical difference (p<0.001) between mean Class III and Class I configurations. Comparing the Class III configurations with normals for size-change, color-coded finite element analysis revealed a superoinferior gradient of positive allometry of the Class III facial nodal mesh. A conspicuous area of negative allometry (≈40%) was localized near soft subspinale, with a ≈70% increase in size in the mental region. For shape-change, the Class III facial mesh was isotropic, except in the anisotropic circumoral regions. Conventional cephalometry revealed that about 50% of linear and 75% of angular parameters differed statistically (p<0.001). Soft tissue dynamics during early postnatal development may contribute to the development of Class III malocclusions.
Cephalometric superimposition on cranial base is the accepted method for evaluating mandibular displacement during orthodontic treatment and /or growth. However, assessing mandibular position relative to the maxillary base may yield different information. The aim of this study was to evaluate the effects of regional superpositions (cranial versus maxillary) on interpreting mandibular displacement. Both methods were applied to pre- and posttreatment cephalograms of 22 growing children (12 female, 10 male) treated for Class II Division 1 malocclusion. Differences in linear and angular measurements of three mandibular landmarks (pogonion, gnathion, menton) between cranial and maxillary superpositions were statistically significant (p=0.0001). Vertical displacement of these landmarks contributed significantly to the differences (p=0.0001). The contribution of horizontal displacement was not statistically significant. The results support the proposition that, in growing children, posttreatment displacement of mandibular skeletal and dental components should be assessed by both maxillary and cranial base superimpositions. The maxilla is subject to rotational and translational changes during growth that may affect the position of the mandible relative to the maxilla in a way inconsistent with the mandibular displacement perceived upon cranial superposition. Since occlusion is directly associated with the positions of the maxillary and mandibular basal bones, the positions of these bones relative to each other is critical in assessing occlusal changes in individual patients.
The objectives of this study were to examine the esthetic preferences of lip position in males and females, and to compare them with each other and with a common orthodontic standard using a custom computer animation program. The sample consisted of 53 young adult subjects, 25 males and 28 females. The sample was divided into orthodontically treated and untreated subjects. ANOVA and Scheffé tests were carried out to determine differences between the responses of the various groups. Also, t-tests were used to compare subjects' responses to a commonly used orthodontic standard (Ricketts' E-line). The results indicated a sex-effect, with females preferring fuller lips than males. Significant differences were also found between orthodontically treated subjects and untreated subjects, with untreated subjects preferring fuller lips. Differences were significant at p < 0.05. Furthermore, both males and females preferred lip fullness greater than the Ricketts' values.
This prospective Herbst study analyzed the sagittal dental and skeletal changes contributing to Class II correction in young adults. Additionally, the alteration in skeletal and soft tissue convexity occurring during treatment was assessed. Early adolescent subjects in the permanent dentition who had been treated with the Herbst appliance were used for comparison. Lateral headfilms from before and after an average treatment period of 8.5 months for the young adults and 7.1 months for the adolescents were evaluated. All adult and adolescent subjects were treated to either Class I or overcorrected Class I occlusal relationships. In both groups the improvement in sagittal incisor and molar relationships was achieved more by dental changes than by skeletal ones. The amount of skeletal change contributing to overjet and molar correction was smaller in the young adult group (22% and 25%, respectively) than in the early adolescent group (39% and 41%, respectively). Skeletal and soft tissue facial profile convexity was reduced in adults and adolescents. Facial profile improvement did not differ between the two groups. The results of this study revealed that the Herbst appliance is most effective in the treatment of Class II malocclusion in young adults. It is suggested that this treatment method could be an alternative to orthognathic surgery in borderline Class II cases.
The first report of lateral maxillary expansion by separation of the maxilla, written by Angell and published in 1860, was discredited. Applying our present-day knowledge of the technique to the original documents indicates that the case history agrees in general with current observations. The arguments mounted against Angell, especially by McQuillen, may be dismissed as irrelevant and Angell's thesis is upheld. In addition, good reason exists to accept three further “firsts” in this unprecedented work: (1) The significance of the first permanent molars in occlusal development, (2) the use of a double-action jackscrew, and (3) the use of a retention plate.
The aim of this prospective study was to evaluate changes in the transverse plane following use of an acrylic bonded rapid maxillary expansion (RME) appliance in growing individuals during the active phase of treatment. The sample comprised 14 consecutively treated orthodontic patients (11 girls, 3 boys) who required the use of an RME device on the basis of their individual treatment plans. The mean patient age at the start of treatment was 12.8 years, and the mean overall treatment time was 3.08 years. Seven posteroanterior cephalometric and two dental cast measurements were assessed. Repeated measure analysis of variance and Duncan's multiple range test were used to assess treatment changes. Lower nasal and maxillary base widths and angles, and upper intermolar width increased significantly during RME treatment. Upper intermolar and intercanine widths measured from the dental casts also increased significantly. Except for upper intercanine width, all measurements remained constant at the end of orthodontic treatment. The results of this study suggest that dentoskeletal changes in the transverse dimension following the use of an acrylic bonded RME are maintained satisfactorily at the end of fixed appliance therapy.
An evaluation of 96 treated orthodontic patients with maxillary median diastema ranging from 0.50 mm to 5.62 mm (mean 1.22, SD 0.85) was performed 4.0 to 9.0 years after completion of active treatment. Pre- and posttreatment data were gathered from available records. Follow-up data were gathered from records and interviews of 37 patients, and from phone interviews of 59 patients. The incidence of diastema relapse was 49% when scored as either presence of a measurable space at follow-up, a history of orthodontic or prosthetic retreatment to close a reopened space, or continued use of a retainer to control relapse tendency. Logistic regression analysis revealed that pretreatment diastema size and presence of a family member with a similar condition were the only significant risk factors for relapse (p<0.05), while pretreatment spacing in the maxillary anterior dentition approached significance (p=0.10). No association was found between relapse and presence of an abnormal frenum or an osseous intermaxillary cleft, although patients with an abnormal frenum had a wider pretreatment diastema than those with a normal frenum (p<0.05). Fremitus of the maxillary incisors was the only parameter at follow-up associated with space reopening (p<0.01).
This purpose of this research was to examine the stability of normal occlusion during the transition from primary to permanent dentition. The sample consisted of 128 children (83 boys and 45 girls) 4.5 to 5.5 years old with normal occlusion in the primary dentition. The subjects were reexamined at 12.5 to 13.5 years. None had received orthodontic treatment. Although all the subjects had normal occlusion in the primary dentition, 72.7% (73.5% boys and 71.1% girls) had developed anomalies following eruption of the permanent teeth. These anomalies included crowding, Class II Division 1 or Class II Division 2 malocclusion, mesial occlusion complex, lateral crossbite, anterior crossbite, premature tooth loss, openbite or other anomalies.
The objectives of this investigation were: (1) to compare the shear bond strengths (SBS) of metal, ceramic, and plastic brackets using different concentrations of maleic and phosphoric acid gels and aqueous solutions, and (2) to determine if a relationship exists between the type of acid etchant and the location of resin after debonding. A sample of 210 bovine incisors was divided among three different bracket groups (Victory series metal, Transcend 6000 ceramic, Spirit MB plastic). Prior to bonding, enamel was acid-etched using 37% phosphoric acid (H3PO4) gel and aqueous solution, 10% maleic acid gel and aqueous solution, 10% H3PO4 gel and aqueous solution, or 2% H3PO4 aqueous solution. SBS testing and the adhesive remnant index (ARI) score provided insight into the effects of the bonding process on enamel. Resin tags associated with each etchant type were inspected under scanning electron microscopy (SEM). Statistical analyses (level of significance, p=0.05) of the data showed significant differences among groups. It was concluded that specific acid-composite-bracket combinations are recommended for use in clinical orthodontic practice in order to achieve efficient bonding.
The purpose of this study was to compare shear bond strength (SBS) of bonded and rebonded orthodontic brackets following a variety of commonly used conditioning treatments and using both light-cured and self-cured composite resin systems. Brackets debonded during the initial determination of SBS were rebonded after the removal of residual resin from enamel surfaces using five different treatments: (1) Remove residual resin using a tungsten carbide bur, re-etch enamel surface, then bond a new bracket; (2) Remove resin from the base mesh with micro-etching then rebond the same bracket, (3) Remove residual resin from the enamel surface using resin-removing pliers, recondition the enamel with an air-powder polisher, then bond a new bracket; (4) Remove residual resin using a rubber cup and pumice, then bond a new bracket; (5) Remove residual resin using pliers alone, then bond a new bracket. The results revealed that the light-cured system produced higher shear bond strength in the initial bond than the self-cured system (p<0.005). Reconditioning the enamel surfaces using a tungsten carbide bur and acid-etching gave the highest SBS (difference 5.8 MPa; p<0.01) and clinically favorable fracture characteristics. The data suggest that the optimal procedure for rebonding dislodged orthodontic brackets is to resurface the enamel using a tungsten carbide bur, acid-etch the enamel, and use a new or re-use an old bracket after microetching.
Enamel decalcification around brackets is sometimes observed during and after orthodontic treatment. Reports in the literature suggest that the preventive advantage of fluoride-releasing adhesive resins may be compromised by an increased incidence of bond failure. The purpose of this study was to determine the effects on shear debonding of incorporating fluoride into the bracket bonding system. Another purpose was to determine the effect of polymerization mode on debonding. Orthodontic brackets were bonded to bovine enamel using one of three types of adhesive resin—no-mix, chemically cured, or light-cured—each formulated with and without fluoride. The teeth were stored in artificial saliva for 24 hours or 30 days and then debonded in shear. Data analysis was performed using ANOVA followed by post-hoc multiple comparison between group pairs. It was found that: (1) fluoride had either no effect or it increased the bond value; (2) the no-mix adhesive demonstrated the lowest bond value; (3) the duration of storage in artificial saliva had no effect on the bond value of the chemically cured and light-cured adhesives but did affect the no-mix adhesive; and (4) the no-mix adhesive released significantly less fluoride than the two other products. Thus, the presence of fluoride in the bonding adhesive does not reduce the force required to debond in shear, and chemically or light-cured adhesives provide consistently higher bond values over extended immersion times than the no-mix product.