Orthodontic treatment outcome: the relationship between anterior dental relations and anterior inter-arch tooth size discrepancy.

OBJECTIVE: This study investigated the pre- (T1) and post-treatment (T2) relationship between anterior (canine to canine inclusive) inter-arch tooth size ratio and various dental and skeletal variables. DESIGN: Retrospective longitudinal clinical study. SETTING: Swedish Health Board Clinic 2000. SUBJECTS: Random selection of T1 and T2 orthodontic records of 137 Swedish patients (56 male and 81 female). The sample included non-extraction (77), and four premolar extraction (60) cases across a range of dental and skeletal malrelationships. MAIN OUTCOME MEASURES: Dental cast and lateral cephalogram measurements were recorded. Exploratory modelling investigated whether a significant relationship existed between the anterior inter-arch tooth size ratio and these measurements. RESULTS: Data was normally distributed with no statistically significant differences between males and females (P = 0.88) and extraction and non-extraction (P = 0.52) treatment modalities with respect to the anterior ratio. T1 bivariate regression analysis failed to show a relationship (p < 0.05) between variables. T2 bivariate analysis showed a statistically significant relation between three variables and anterior tooth size ratio. Multiple regression analysis led to a final model where maxillary inter-canine width (P = 0.002) and upper arch crowding (0.001) were statistically significantly related to the anterior inter-arch ratio. The coefficient of determination was however uniformly low (R(2) < 0.2) for all variables. CONCLUSION: The anterior inter-arch tooth size ratio was not associated with any common pre- or post-treatment variables in the population studied, therefore measurement of an anterior tooth size ratio pre-treatment was not clinically beneficial for determining anterior dental relations post-treatment.

Outcome of a scheme for specialist orthodontic care.

With the purpose of examining the outcome of specialist orthodontic care on a population level (Halland, Sweden), a random sample of previously treated 19-year-olds (n=118) was clinically examined and interviewed. Thirty-three per cent of the cohort (n=1554) had received treatment, and mean treatment time was 19 months requiring 20 visits. Changes in occlusion were assessed using the PAR Index applied to dental study casts representing the pre- and post-treatment and follow-up (19 years) condition. The subjects' responses to questions addressing their past and present attitudes to dental appearance and orthodontic treatment were combined to represent "orthodontic concern", at the pre-treatment stage and at 19 years of age. A mean reduction in weighted PAR scores of 83% was observed from pre-treatment to post-treatment, whereas at follow-up, the net improvement was 69%. A significant shift in attitudes was observed, as 72% of the individuals expressed orthodontic concern pre-treatment compared to less than 10% at 19 years. The improvement obtained was similar to other studies on outcome of orthodontic treatment provided by specialist orthodontists. Compared to most PAR-studies providing information about orthodontic services, the present scheme appeared to be efficient on the assumption that duration of treatment and number of visits are expressions of costs.

Outcome of a scheme for orthodontic care: a comparison of untreated and treated 19-year-olds.

The organization of the orthodontic service within the Public Dental Health Service in the southern part of the county of Halland, Sweden is described, and data for the provision of treatment are presented. The aim of this study was to examine the outcome of this service by studying the prevalence of malocclusion and residual need, as well as attitudes to treatment in previously treated and untreated individuals. Three samples of 19-year-olds were established: patients treated by specialists (n=132), patients treated by general practitioners (GP) (n=132), and untreated individuals (n=492). All samples were examined clinically, and radiographs, photographs, and study casts were obtained from the two treated groups. Attitudes to own teeth and orthodontic treatment were recorded by use of questionnaires. Deviant occlusal traits were recorded, and all the individuals were categorised according to a treatment need index. Generally, good occlusal conditions were observed in all samples. More deviant traits were observed in individuals that had been treated by GPs, and significant differences were observed for overjet, overbite, and crowding compared to the other samples. The majority of individuals belonged to the little/no treatment need index categories. Of those treated by GPs, one third belonged to the moderate (22%) or urgent (11%) need categories. About 10% reported dissatisfaction with their dental appearance, but only 2% expressed a desire for (further) orthodontic treatment.

An ex-vivo investigation into the effect of bracket displacement on the resistance to sliding.

This ex-vivo study investigated the effect that repeated bracket displacement has on sliding friction and the magnitude of bracket displacement, and hence tooth movement, required to release bracket/archwire binding. The design consisted of an ex-vivo laboratory study. A jig was designed that allowed repeated displacement of a bracket to occur, while the resistance to sliding (friction) was measured using an Instron universal testing machine. One type of stainless steel bracket was used in conjunction with four archwire types (0.016-inch stainless steel, 0.019 x 0.025-inch stainless steel, 0.021 x 0.025-inch stainless steel, 0.019 x 0.025-inch beta-titanium) and four magnitudes of displacement. Repeated bracket displacement has a significant effect on the sliding resistance at the bracket/archwire interface (P < 0.001). The reduction in sliding resistance noted with displacement depended on the archwire. Over the range of displacements tested, there was an 85 and 80 per cent reduction associated with 0.021 x 0.025-inch and 0.019 x 0.025-inch stainless steel, respectively. For 0.019 x 0.025-inch beta-titanium and 0.016-inch stainless steel, these reductions were 27 and 19 per cent, respectively. The importance of true friction, given the likelihood of bracket and/or archwire displacements in vivo, may be lessened.

An investigation into the behavioural characteristics of orthodontic elastomeric modules.

The object of the study was to investigate the behavioural characteristics of orthodontic elastomeric modules with regard to their effect on frictional resistance and their failure load forces, and involved the use of an experimental laboratory-based study. Six cohorts were assembled employing five types of module and two bracket types. Straight lengths of 0.018 x 0.025-inch stainless steel were pulled through the ligated brackets and frictional resistance was measured using an Instron universal testing machine. Recordings were repeated over a 4-week period, during which time the cohorts were placed in a simulated oral environment. Failure load forces of new and used modules were also recorded, and frictional resistance and failure load forces. Analysis of variance revealed that the Minitwin cohort exhibited significantly higher frictional resistance and that the clear modules demonstrated the lowest levels of friction. Time soaked in a simulated oral environment had a variable effect on frictional resistance. A wide range of failure load forces was seen for the five types of module and all types showed a reduction in failure load force following their soaking in the simulated oral environment. There was variation in performance of the different modules both in friction testing and failure load testing.

Signs and symptoms of temporomandibular disorders in 19-year-old individuals who have undergone orthodontic treatment.

Fifty-five per cent of the 1554 19-year old subjects in Halmstad, Sweden, born in 1975, have received orthodontic treatment. Among these, 520 have been treated by specialists (specialist group) and 340 by general practitioners after consultation with specialists (consultation group). The aims were to study the prevalence of signs and symptoms of temporomandibular disorders (TMD) in these two groups on a long-term basis, to identify any possible difference between the groups, and to compare the results with those from a previously presented epidemiological study (control group). From the population of orthodontically treated subjects, a sample was randomly selected to represent the two groups, and 260 subjects agreed to attend for investigation, the participation rate being 77%. The investigation consisted of a questionnaire and clinical examination focusing on function and dysfunction of the masticatory system. Severe signs and symptoms of TMD were rare, the prevalence did not differ significantly between the two orthodontic groups, and the results were similar in the control group. The prevalence of several signs and symptoms was more common in females than in males. No significant correlation between TMD signs and symptoms and occlusal contact recordings was found. It was concluded that the vast majority of the 19-year old individuals who had undergone orthodontic treatment had well-functioning masticatory systems, and severe signs and symptoms of TMD were rare.

Electrothermal debonding of ceramic brackets: an ex vivo study.

The shear forces necessary to remove ceramic brackets from human premolar teeth using mechanical and electrothermal debonding techniques were compared and the post-debond enamel characteristics were evaluated. The temperature rise in the pulp cavity during electrothermal debonding was recorded. The samples were tested sequentially on a shear jig attached to an Instron Universal Testing Machine. The results indicate that removal of ceramic brackets with an electrothermal debonder requires less force than with a mechanical debonding technique. Furthermore, the associated pulp temperature rise appears to be within currently established biologically acceptable limits. However, the indices that are commonly used to define the condition of the enamel surface following debond may not be applicable to electrothermal debonding.

[Individual response to treatments using Teuscher activator]. / Individuel respons på behandling med Teuscher-aktivatoren.

Variations in facial growth and dentoalveolar development were studied in a group of 40 patients treated with the Teuscher appliance, a functional appliance which is a combination of an activator and a high-pull headgear. Patients were selected for this study on the basis of an initial Class II Division 1 malocclusion and on being consecutively treated with this appliance. The results showed that in 80% of the patients the maxilla either remained unchanged in it's relationship to the anterior cranial base (NSL) or became more retrusive during the treatment period. The mandible in 70% of the patients became more prognathic, only in four cases did the mandible become slightly more retrognathic. The analysis further showed that no statistically significant change occurred in the inclination of the mandible during treatment. Correlation analysis of the association between pretreatment mandibular plane angle and the changes during treatment showed no association. The dentoalveolar changes were characterized by retroclination of the maxillary incisors in 90% of the patients which occurred in spite of the torque springs, intended to maintain the inclination of these teeth. In contrast, the mandibular incisors on average showed no statistically significant change during treatment. This may be attributed to the capping of these teeth. Analysis of the association between the pretreatment inclination and the change during treatment of the mandibular incisors showed an inverse relationship. Mandibular incisors, that initially were proclined, tended to become more upright which is in contrast to previous studies indicating that functional appliance treatment generally increases the inclination of these teeth. The results of this study suggest that the correction of the skeletal component of the Class II malocclusion with the Teuscher appliance in most instances takes place by restriction of forward development of the maxilla in combination with downward-forward growth of the mandible, but with wide individual variations. The control of the incisor inclination in the maxilla with this appliance, however, is not adequate and further development in this area is needed. In contrast, the control of the lower incisors by capping helps effectively control these teeth against undesirable proclination during treatment.

Autotransplantation of teeth in cases with agenesis or traumatic loss of maxillary incisors.

The purpose of this study was to investigate the prognosis of 50 consecutively autotransplanted teeth to the maxillary incisor region. Thirty-five were transplanted in cases of traumatic injuries, eleven in cases of agenesis and four in cases with impaction of maxillary canines. The average follow-up time was 7 years and 6 months (range 4-17 years). The transplants were examined clinically in respect of tooth vitality and radiographically in respect of root canal obliteration, periradicular changes, root formation, and root length. The results show a success rate of 82 per cent. It is concluded that the procedure of tooth transplantation has the advantage of maintaining or restoring alveolar bone volume and gives the opportunity to replace a missing tooth without involvement of neighbouring teeth as prosthetic abutments.

Dental and skeletal contributions to occlusal correction in patients treated with the high-pull headgear-activator combination.

The purpose of this study was to examine dental and skeletal changes in patients treated with the high-pull headgear-activator combination. A group of 40 consecutively treated subjects with a Class II molar relationship and a minimum of 5 mm overjet was used for this study. The results showed that Class II correction often was achieved by distal repositioning of the maxillary teeth (mean, 0.07 mm) and mesial repositioning of the mandibular teeth (mean, 3.3 mm) with a wide range of variation. Correlation of maxillary molar repositioning with total interarch occlusal change showed a positive relationship; however, a weak correlation suggested that other variables were contributing factors, in addition to distal upper molar positioning. The change in mandibular molar position compared with the movement of pogonion strongly suggests that forward growth of the mandible is important to the correction of the Class II malocclusion. When total molar repositioning in the upper jaw was correlated with total molar repositioning in the lower jaw, a strong inverse correlation was found, indicating that upper molar movement parallels lower molar movement.

Overbite and overjet correction in a Class II, division 1 sample treated with Edgewise therapy.

The purpose of this study was to compare the effect of overjet and overbite correction in non-extraction and extraction therapy in a sample of Class II malocclusions treated with the Edgewise appliance. The subjects were 20 children treated without extraction and 20 children treated with extraction of the four first premolars. During the post-treatment period a relapse of overjet and overbite occurred in both groups. However, there was a beneficial net effect of overjet and overbite correction in both groups with no significant difference between the two groups. The study showed that mandibular intercanine width, space conditions in the lower jaw and mandibular incisor position were important factors in treatment planning.

Influence of orthodontic treatment on root development of autotransplanted premolars.

The aim of this study was to clarify whether orthodontic movement of autotransplanted premolars will affect the final root length of the transplants. A group of 29 autotransplanted premolars that had been orthodontically treated was compared with a group of 30 autotransplanted premolars that had not been orthodontically treated. Contralateral teeth in both groups served as controls. The root lengths of the transplants as well as the controls were measured on the radiographs immediately after transplantation and also after orthodontic treatment and complete root formation. The results demonstrated that there was no statistically significant difference between the original and final root lengths of the transplants in the two samples or between the contralateral teeth. The autotransplantation of the premolars resulted in an average shortening of 1 to 2 mm compared to the contralateral control teeth. Futhermore, orthodontic movement of the transplants appeared to have a tendency to shorten the final root length.