Lower Intermolar Widths Research Articles

Dimensional Accuracy of 3D-Printed, Digital and Conventional Stone Dental Cast of Dentate Patients Using Arch and Teeth Measurements

Aim: This study aimed to compare the conventional, digital, and three-dimensional (3D)-printed casts in terms of their accuracy in quantifying arch and teeth measurements. Materials and Methods: The conventional casts were prepared using polyether dental impressions. Digital impressions of the typodont reference casts were accomplished using an intra-oral scanner. The digital casts were first converted to stereolithography (STL) files which were then edited, and printed using an SLA printer and photo-polymer resin material. The measurements of the first two groups were completed using a digital caliper, while an imaging software was used to measure digital casts. The occlusocervial (OC) height and mesiodistal (MD) width of canines, second premolars (PMs), and molars of each jaw were measured. Additionally, intercanine width (ICW) and intermolar width (IMW) were also measured. Results: Overall, the lowest OC measurement errors were observed for 3D-printed casts for the upper canine, lower canine, and lower molar (0.003±0.01 mm). Similarly, the lowest MD measurement errors were observed for 3D-printed casts for upper canine, upper PM, and lower PM (0.002±0.01 mm). The ICW and IMW measurement errors for the 3D-printed casts were significantly lower (p < 0.01) for the upper ICW (0.011±0.01 mm) and lower IMW (0.017±0.01 mm) than the other two groups. Compared to the conventional and digital casts, the lower ICW (0.013±0.01 mm) and upper IMW (0.017±0.01 mm) measurement errors observed for the 3D-printed casts were also lower, but non-significantly (p > 0.01). Conclusions: 3D-printed casts presented the lowest OC, MD, ICW, and IMW measurement errors, than the conventional and digital casts. The highest measurement errors were associated with the digital casts.

Dental changes induced by a modified Herbst appliance followed by fixed appliances: A digital dental model analysis.

Herbst therapy is an effective treatment for Class II malocclusions. However, the maintenance of the effects after fixed appliances treatment remains questionable. This retrospective study aimed to assess, using digital dental models, the sagittal and transverse dental arch changes in young patients during two Class II Division 1 treatment phases, first with modified Herbst appliance (HA) and then with fixed appliances. The treated group (TG) comprised 32 patients (17 boys, 15 girls; mean age, 12.85 ± 1.16 years) treated with HA and fixed appliances. The control group comprised 28 patients (13 boys, 15 girls; mean age, 12.21 ± 1.35 years) with untreated Class II malocclusions. Digital models were obtained immediately before and after HA therapy and after fixed appliances. Data were statistically analyzed. Compared with the control group, the TG showed an increase in maxillary and mandibular arch perimeters and in intercanine and intermolar arch widths, a decrease in overjet and overbite, and an improvement in canine and molar relationships. In the time after HA therapy until the end of fixed appliances treatment, the TG showed a decrease in maxillary and mandibular arch perimeters, overjet, upper and lower intermolar widths; an increase in molar Class II relationship; and no changes in canine relationship, overbite, and upper and lower intercanine widths. In this sample of patients treated with HA, on average, there was an improvement in the Class II relationship, which seemed to remain after fixed appliances. The transverse dental changes achieved in HA phase relapsed after treatment with fixed appliances.

The Reliability of ClinCheck® Accuracy before and after Invisalign® Treatment—A Multicenter Retrospective Study

The objective was to evaluate the accuracy of ClinCheck® reliability in the sagittal, vertical, transverse, and arch length dimensions before and after Invisalign® (Align Technology, Santa Clara, CA, USA) treatment. This retrospective study was conducted on 206 patients who underwent dual-arch clear aligner therapy exclusively with Invisalign®. Digital models were obtained from iTero® scanners from three different private practices where the treatment plans were performed and executed by multiple orthodontists with varying degrees of experience. The ClinCheck® models of the initial, achieved, and predicted outcome were obtained from Align Technology® and the values were compared using Pearson correlation (p < 0.05) to determine if predicted values were correlated with achieved values. ANOVA was used to compare the different centers. The highest reliabilities were associated with interincisal angle (96.23%), upper intercanine width (97.97%), lower intercanine width (97.67%), upper intermolar width (97.58%), and lower intermolar width (97.72%) (p < 0.001). The lowest reliabilities were associated with arch length parameters in which the upper was 38.79% and the lower at 30.02% (p = 0.03, p < 0.001). However, there were no statistically significant differences between the centers in terms of the accuracy of treatment provided. The mean predicted accuracy of Invisalign® was 76.85% overall; however, Invisalign® providers may need to exaggerate the digital tooth movements to achieve the desired outcome.

A Three-Dimensional Clinical Evaluation of The Effect of Tandem Appliance in The Treatment of Class III Malocclusion

Purpose: This study was conducted to evaluate the skeletal and dental effects of the Tandem appliance in three dimensions for the correction of skeletal Class III malocclusion. Materials and methods: Twenty-two female girls with skeletal Class III malocclusion due to maxillary retrognathia were selected for this study with age of 7 to 10 years. All patients received The Tandem appliance for treatment of class III malocclusion. CBCT images and digital study models were made at two stages; before and after treatment with The Tandem appliance. CBCT images and digital study models were analyzed and data were statistically analyzed. Results: The use of Tandem appliance significantly enhanced the forward growth of the maxilla without any noticeable effects on the mandible. The anterior and posterior facial height were significantly increased. There was a significant increase in the proclination of the upper incisors and retroclination of the lower incisors. In addition, there was a significant increase in the upper and lower inter-molar widths and also, in the upper inter-canine width. Conclusion: The Tandem appliance showed effective results in the treatment of skeletal Class III malocclusions with maxillary retrognathia. It had a combination of skeletal and dental effects

Safety and Effects of the Rapid Maxillary Expander on Temporomandibular Joint in Subjects Affected by Juvenile Idiopathic Arthritis: A Retrospective Study.

Background: In Juvenile Idiopathic Arthritis (JIA) temporo-mandibular joints are often affected causing skeletal and dental malocclusions. The most frequent condition is mandibular hypoplasia, that may be associated with maxillary hypoplasia. The aim of this retrospective case control study is to investigate the effects and the safety of rapid maxillary expansion (RME) in growing patients affected by JIA. It was evaluated whether RME could be performed without complications on TMJs of JIA patients using DC/TMD protocol, and naso-maxillary transversal parameters were compared with the ones obtained on healthy patients. Methods: Twenty-five patients affected by JIA that ceased to manifest TMJ (Temporo-Mandibular Joint) symptoms in the previous year were treated with RME to solve the maxillary transverse hypoplasia. Postero-anterior cephalometric tracings were collected before and after treatment; linear measurements were obtained to study maxillary and nasal cavity modifications. Data were compared to those of a similar group of twenty-five healthy patients. Paired t-test and Independent t-test were used to evaluate changes before and after treatment in each group and to perform a comparison between the groups. Results: All patients demonstrated a statistically significant increase in nasal cavity width, maxillary width and upper and lower intermolar width. No patients presented a worsening of their TMJs condition. Intragroup comparisons revealed significant changes of cephalometric measurements, but no difference was found when comparing JIA and healthy patients. Conclusions: Growing patients with JIA that ceased to show signs of active TMJ involvement for at least one year could be safely treated with RME, expecting similar benefits to those of healthy patients. Dentists and rheumatologists should be informed of safety and potential benefits of palatal expansion in JIA patients in order to improve the outcome of orthodontic treatment and reduce the indication for more invasive procedures (i.e., Surgical Assisted Rapid Maxillary Expansion).

The dental arch dimensions in Vietnamese children at 7 years of age, and their variation by gender and ethnicity

PurposeDental arch dimensions are important not only in dentistry (e.g. orthodontists and prosthodontists, and forensic odontology), but also other medical fields, biology, biometrics, painting or sculpture. This study aimed to determine these dimensions in Vietnamese children and compare these measurements across four ethnic groups and genders. MethodsA cross-sectional study was conducted on 3204 Vietnamese children at 7 years of age from four major ethnic groups in Vietnam (Kinh, Tay, Thai and Muong). ResultsThe means variables in study subjects were 33.72 ± 2.16 mm for upper inter-canine width (UCW); 52.74 ± 2.55 mm for upper inter-molar width (UMW); 8.69 ± 1.79 mm for upper anterior length (UAL); 29.59 ± 1.97 mm for upper posterior length (UPL); 26.94 ± 2.49 mm for lower inter-canine width (LCW); 45.89 ± 2.59 mm for lower inter-molar width (LMW); 5.04 ± 1.53 mm for lower anterior length (LAL); and 26.22 ± 2.07 mm for lower posterior length (LPL). The UCM, UMW, and LMW of Muong were significantly wider in males, but narrower in females compared with other ethnic groups. The Kinh, Tay and Thai groups had no significant differences between genders in all dimensions, but these sizes were significantly larger in males than females of Muong group. ConclusionsThis study presents the means of dental arch dimensions in 7 year-old Vietnamese children, and there is no statistical differences in these dimensions between genders of almost studied groups, except Muong group. Ethnic differences are observed only in UCW, UMW and LMW of Muong vs other groups. Furthermore, Vietnamese children have dental arch width similar to the African and Caucasian.

No difference in effectiveness of Hawley and vacuum-formed retainers at 12 months

Randomised trial. Patients were randomised to either a Hawley or vacuum-formed retainer following completion of straight wire fixed appliance therapy. Study models were fabricated for each patient on day of debond and 2 months, 6 months, and 12 months after debond. Models were assessed at each time point for upper and lower intermolar widths, intercanine widths, arch length and a modified Little's index of irregularity. Method error was determined by repeating the measurements on 10 sets of models. There were no statistically significant differences between each of the two retainers for any of the variables under test at any time period. There is no statistical or clinically significant difference in the measured arch width, arch length or modified Little's index over a 12-month period between Hawley and vacuum-formed retainers when worn full-time. Therefore, other factors may be more important when deciding on the more appropriate form of retainer.

First premolar extraction effects on upper airway dimension in bimaxillary proclination patients

To determine how orthodontic treatment with first premolar teeth extracted and the associated arch dimensional changes in bimaxillary proclination patients affect the upper airway dimensions. Pre- and postorthodontic treatment cephalograms and dental casts of 40 bimaxillary proclination patients (ages ranged between 18 and 23 years) were used for this study. Patients were all treated with extraction of the four first premolars. Cephalometric radiographs were used to measure airway dimensions, and dental casts were used to measure the changes in the arch dimensions. A paired t-test was used to detect differences at P < .05. The results showed statistically significant reductions in tongue length (P < .05), posterior adenoids thickness (AD2-H) (P < .05), upper and lower incisor inclination, and lower incisor to A-Pog line (P < .001). Considering the dental cast results, statistically significant reductions in upper arch length, lower arch length, and lower intermolar width were also found (P < .001). The only statistically significant increase was recorded for the upper intercanine width (P < .001). Extraction of the first premolars for the treatment of bimaxillary proclination does not affect upper airway dimensions despite the significant reduction in tongue length and arch dimensions.

A retrospective randomized double-blind comparison study of the effectiveness of Hawley vs vacuum-formed retainers

To compare Hawley with vacuum-formed retainers. Eighty-two patients who had received treatment with upper and lower fixed appliances were randomly assigned either a Hawley or a vacuum-formed retainer. Study models were fabricated for each patient on day of debond and 2 months, 6 months, and 12 months after debond. Using a specially constructed pantograph, four variables were measured for each set of models at each of these time periods. These were upper and lower intermolar widths, intercanine widths, arch length, and a modified Little's index of irregularity. Method error was determined by repeating the measurements on 10 sets of models. For each of the variables under test and at each of the four time periods, there were no statistically significant differences (α = .05) between each of the two retainers, vacuum-formed and Hawley. The degree of relapse that is likely to occur following a course of fixed appliance therapy is unlikely to be affected by the choice of retainer, vacuum-formed or Hawley. Therefore, when deciding on the type of retainer to be fitted following fixed appliance therapy, other factors such as cost may play a more significant role.

Variations in tooth size and arch dimensions in Malay schoolchildren

Abstract Aims To compare the mesio-distal tooth sizes and dental arch dimensions in Malay boys and girls with Class I, Class II and Class III malocclusions. Methods The dental casts of 150 subjects (78 boys, 72 girls), between 12 and 16 years of age, with Class I, Class II and Class III malocclusions were used. Each group consisted of 50 subjects. An electronic digital caliper was used to measure the mesio-distal tooth sizes of the upper and lower permanent teeth (first molar to first molar), the intercanine and intermolar widths. The arch lengths and arch perimeters were measured with AutoCAD software (Autodesk Inc., San Rafael, CA, USA). Results The mesio-distal dimensions of the upper lateral incisors and canines in the Class I malocclusion group were significantly smaller than the corresponding teeth in the Class III and Class II groups, respectively. The lower canines and first molars were significantly smaller in the Class I group than the corresponding teeth in the Class II group. The lower intercanine width was significantly smaller in the Class II group as compared with the Class I group, and the upper intermolar width was significantly larger in Class III group as compared with the Class II group. There were no significant differences in the arch perimeters or arch lengths. The boys had significantly wider teeth than the girls, except for the left lower second premolar. The boys also had larger upper and lower intermolar widths and lower intercanine width than the girls. Conclusion Small, but statistically significant, differences in tooth sizes are not necessarily accompanied by significant arch width, arch length or arch perimeter differences. Generally, boys have wider teeth, larger lower intercanine width and upper and lower intermolar widths than girls.

Long-term stability of rapid palatal expander treatment and edgewise mechanotherapy

Previous studies on long-term stability of orthodontic treatment primarily have focused on the stability of the lower arch treated with edgewise appliances. The aim of this study was to evaluate the long-term stability of the upper and the lower dental arches of patients treated with a rapid palatal expander. The sample comprised of 165 dental casts randomly selected from patients who had been out of retention for 8 to 10 years at a mean age of 30 years. Measurements were made directly on dental casts obtained at the three time intervals: before treatment, after treatment, and after retention. Differences over time between the upper and the lower dental arches and between intervals were analyzed by a two-way multivariate analysis of variance (MANOVA) and post hoc Bonferroni t tests. Differences between after treatment and after retention were statistically significant ( P < 0.006) for all except lower intermolar width. However, only for lower and upper arch lengths and perimeters were the differences greater than 2.0 mm. Treatment with the rapid palatal expander presented good stability for upper intercanine width, upper and lower intermolar widths and incisor irregularity. Lower intercanine, arch length, and perimeter presented poor stability. (A M J O RTHOD D ENTOFAC O RTHOP 1995;108:478-88.)