Does a true knowledge of dental crowding affect orthodontic treatment decisions?

Computer-Guided Evaluation of the Use of Two Different Devices in the Reduction of Inferior Tooth Crowding

OBJECTIVE

Lower tooth crowding is considered one of the most common malocclusions in growing patients and due to the potential complications associated with it, it is recommended to intercept this condition as soon as possible. The purpose of this paper is to examine and compare the effectiveness of two different orthodontic devices (elastodontic device and clear aligners) in the treatment of anterior tooth crowding in the jaws of young patients.

MATERIALS AND METHODS

Seventy patients aged between 10 and 16 years with anterior inferior tooth crowding were recruited into this study and divided into case and control groups. The former group comprised 35 patients (15 males and 20 females, average age 10.2 years) who were treated with elastodontic devices (EQ CP series, Eptamed), while the control group consisted of 35 patients (15 males and 20 females, average age 10.5 years) who received aligners (Invisalign). All patients underwent periodic visits after 6 months from the start of treatment (T1) and after 1 year (T2) in which the progress of therapy was evaluated by measuring the inferior intercanine distance using a digital caliper. A parametric ANOVA test was conducted for statistical analysis.

RESULTS

There is no statistically significant difference between the two groups at either T1 or T2 (p < 0.05), thus making the two treatment modalities comparable.

CONCLUSIONS

Both elastodontic devices and aligners can be considered as effective tools to successfully conduct inferior expansive treatment for the resolution of tooth crowding; however, the elastodontic devices are considered more comfortable to wear and they are required to be worn for less time during the day.

Clinical implications of a mathematical-geometrical model to predict changes in the anterior arch dimension

PURPOSE

Anterior arch length (AL) and the alterations in its dimension following incisor movements were shown to be predictable for an individual patient using a mathematical-geometrical model based on a third-degree parabola. Although the model has been validated previously, it is hard to apply in daily orthodontic routine. Thus, the aim of this study was to modify the model using different approaches to allow its establishment in daily routine.

METHODS

This retrospective study was based on a study collective, which was described previously and consisted of 50 randomly chosen dental casts and lateral cephalograms taken before (T0) and after (T1) orthodontic treatment with fixed appliances. A JAVA computer program (Oracle, Austin, TX, USA) was developed to predict AL changes following therapeutic changes of arch width, depth or incisor inclination/position, taking the type of tooth movement into account. Performing exemplary AL calculations with the computer program, general rules and nomograms were set up, followed by multiple linear regression analyses to establish easy-to-use regression equations.

RESULTS

The JAVA computer program is available for download. Sagittal changes showed more effect on AL than transverse modifications. Protruding incisors increased AL, but also reduced overbite. The extent of alteration in AL depended on the initial depth, width, incisor inclination, tooth movement type and distance between the incisal edge and the centre of rotation.

CONCLUSIONS

The computer program precisely predicts individual changes in AL but is time-consuming. The presented regression equations and nomograms, considering metric variables, are easier to apply clinically and the differences compared to the AL calculated by the computer program are negligible.

Association between crowding estimation and extraction recommendations in orthodontics

INTRODUCTION

Little is known about how precisely orthodontists in the United States (US) assess crowding or at what range of crowding they recommend extraction. This study aimed to assess the relationship between estimated crowding in patients with a Class I relationship and extraction recommendation by orthodontists in the US. The secondary aims were to evaluate the accuracy and precision of clinician estimations and determine if clinician background traits play a role in extraction decision-making.

METHODS

An electronic survey was prepared using 4 patients with a Class I relationship with anterior crowding selected from a University Orthodontics Clinic and was sent to approximately 10,400 subjects through Facebook and the American Association of Orthodontists Partners in Research program.

RESULTS

From the 297 responses received, most clinicians recommended extraction once crowding reached 9-10 mm in either the maxilla or the mandible. The data from 2 patients suggest this decision was more strongly correlated with mandibular crowding. Clinician estimations varied widely but, on average, were precise within approximately 2 mm of objective measurements. There was a tendency to overestimate crowding, especially by Northeastern practitioners. Clinicians who reported routinely measuring crowding or who reported that they recommended extractions to >10% of their patients were 1.2-2.0 and 1.4-1.6 times more likely, respectively, to recommend extraction in the patients.

CONCLUSIONS

Crowding estimation was highly subjective and varied widely among clinicians. Most clinicians recommended extraction once maxillary or mandibular crowding approximated 9-10 mm. Some clinician demographics were correlated with the precision and accuracy of estimations and the likelihood of extraction in the patients.

Improvement of the Impacted Level of Lower Third Molars After Orthodontic Treatment

OBJECTIVES

The early or delayed surgical removal of an asymptomatic lower third molar (M3) in orthodontic patients remains controversial. This study aimed to determine the changes in the impacted level of M3 such as angulation, vertical position, and eruption space, after orthodontic treatment in 3 groups, namely non-extraction (NE), first premolar (P1) extraction, and second premolar (P2) extraction.

METHODS

Relevant angles and distances related to 334 M3s from 180 orthodontic patients were assessed pre- and posttreatment. Angle between lower second molar (M2) and M3 (M3-M2) was used for evaluating M3 angulation. For M3 vertical position, distances from occlusal plane to the highest cuspid (Cus-OP) and fissure (Fis-OP) of M3 were used. Distances from the distal surface of M2 to anterior border (J-DM2) and centre (Xi-DM2) of the ramus were used for assessing M3 eruption space. Pre- and posttreatment values of the angle and distance in each group were compared using a paired-sample t test. Measurements of the 3 groups were compared using analysis of variance. Hence, multiple linear regression (MLR) analysis was used to determine significant factors that impacted changes in M3s' related measurements. Independent factors used for MLR analysis included sex, treatment starting age, pretreatment respective angle/distance, and premolar extraction (NE/P1/P2).

RESULTS

M3 angulation, vertical position, and eruption space at posttreatment were significantly different from those at pretreatment in all 3 groups. MLR analysis showed that P2 extraction significantly improved M3 vertical position (P < .05) and eruption space (P < .001). P1 extraction significantly decreased Cus-OP (P = .014) and eruption space (P < .001). Treatment starting age was significant factor that affected Cus-OP (P = .001) and M3 eruption space (P < .001).

CONCLUSIONS

After orthodontic treatment, M3 angulation, vertical position, and eruption space changed in favour of the impacted level. These changes in the 3 groups were clearer in order: NE, P1, and P2, respectively.

Accuracy and eligibility of Bonwill⁃Hawley arch form established by CBCT image for dental crowding measurement: a comparative study with the conventional brass wire and caliper methods

OBJECTIVES

The purpose of this study was to develop a novel Bonwill⁃Hawley method (Bonwill⁃Hawley arch form based on CBCT image) for the assessment of dental crowding, and to investigate and compare the accuracy and eligibility with the conventional brass wire and caliper methods under different crowding conditions.

MATERIAL AND METHODS

Sixty patients with the pair of plaster casts and CBCT data were collected. All the casts were marked and transformed into digital models using iTero scanner, and imported into OrthoCAD software to measure the required space. Using the conventional brass wire (M1) and caliper methods (M2), the available space and dental crowding were measured and calculated basing on digital models, respectively. Correspondingly, the axial planes in the level of dental arches were oriented and captured from the CBCT images to draw the Bonwill⁃Hawley arch forms (M3), which were used to measure and calculate the available space and dental crowding. For each method, intra and inter-examiner reliabilities were evaluated with intra-class correlation coefficients (ICCs). Wilcoxon test and Kruskal-Wallis test were performed for statistically analyzing the discrepancy among different groups.

RESULTS

Both intra- and inter-examiner reliability were generally excellent for all parameters obtained by the three methods, except for the dental crowding measured using M1(ICC: 0.473/0.261). The dental crowding measured using M2 were significantly increased in mild, moderate and severe-crowding groups compared with M1. However, no significant difference was detected between M1 and M3 in severe-crowding group (maxilla, p = 0.108 > 0.05; mandible, p = 0.074 > 0.05). With the deterioration of crowding condition, the discrepancy of dental crowding between M1 and M2, or M1 and M3 were significantly decreased (maxilla, M2-M1, mild VS serve, p = 0.003 < 0.05; maxilla, M3-M1, mild VS serve, p = 0.003 < 0.05; mandible, M2-M1, mild VS serve, p = 0.000 < 0.001; mandible, M3-M1, mild VS serve, p = 0.043 < 0.05).

CONCLUSION

Dental crowding measured using the novel Bonwill⁃Hawley method was relatively greater than the caliper method, but not exceeding the brass wire method, which wound gradually come close to the brass wire method with the deterioration of crowding condition.

CLINICAL RELEVANCE

The Bonwill⁃Hawley method basing on CBCT image proved to be a reliable and acceptable choice for orthodontists to analyze the dental crowding.

Estimation of Distances within Real and Virtual Dental Models as a Function of Task Complexity

Orthodontists have seen their practices evolve from estimating distances on plaster models to estimating distances on non-immersive virtual models. However, if the estimation of distance using real models can generate errors (compared to the real distance measured using tools), which remains acceptable from a clinical point of view, is this also the case for distance estimation performed on digital models? To answer this question, 50 orthodontists (31 women and 19 men) with an average age of 36 years (σ = 12.84; min = 23; max = 63) participated in an experiment consisting of estimating 3 types of distances (mandibular crowding, inter-canine distance, and inter-molar distance) on 6 dental models, including 3 real and 3 virtual models. Moreover, these models were of three different levels of complexity (easy, medium, and difficult). The results showed that, overall, the distances were overestimated (compared to the distance measured using an instrument) regardless of the situation (estimates on real or virtual models), but this overestimation was greater for the virtual models than for the real models. In addition, the mental load associated with the estimation tasks was considered by practitioners to be greater for the estimation tasks performed virtually compared to the same tasks performed on plaster models. Finally, when the estimation task was more complex, the number of estimation errors decreased in both the real and virtual situations, which could be related to the greater number of therapeutic issues associated with more complex models.

Does the floor of the maxillary sinus affect tooth movement for premolar extraction space closure?

OBJECTIVE

The study investigated orthodontic tooth movement by comparing various horizontal and angular measures of the teeth having different sinus-root relationship (SRR) of patients undergoing first premolar extraction treatment protocols.

MATERIALS AND METHODS

This retrospective cross-sectional study included 45 Taiwanese adult patients, classified as the control group (n = 15) and the sinus group (n = 30) according to SRR. The control group had type I SRR (sinus floor above the level connecting the buccal and palatal root apices), whereas the sinus group included patients with type V SRR (the buccal and palatal root displayed apical protrusion into the sinus floor). Morphology was identified using pretreatment orthopantomograms. Lateral cephalometric measurements were conducted before treatment (T1) and at debonding (T2).

RESULTS

Post debonding, there were no statistically significant difference in the two groups. However, the incisors in the control group became marginally more upright than those of the sinus group, and the molars demonstrated tipping movement with minimal anchorage loss in the sinus group than in the control group. The total treatment time was not significantly different between the 2 groups.

CONCLUSION

The study revealed that the sinus-root relationship does not affect the orthodontic tooth movement. However, a more extensive 3-D study with larger sample size is strongly recommended before coming to any conclusion.

CLINICAL RELEVANCE

The lining of the floor of the maxillary sinus does not affect the orthodontic tooth movement.

Perception of Smile Aesthetics of Patients with Anterior Malocclusions and Lips Influence: A Comparison of Dental Professionals’, Dental Students,’ and Laypersons’ Opinions

Objectives. The aim of the study was to evaluate the perception of smile aesthetics in patients with varying degrees of anterior crowding and spacing among dental specialists, dentists, dental students, and laypersons and to assess the effect of the lips position. Materials and Methods. Clinical photos of cases of anterior crowding (mild, moderate, and severe) and spacing (mild, moderate, and severe) with and without the associated lips were used. The images were evaluated by 250 persons including dental specialists, dentists, dental students, and laypersons using the rating scale method, (extremely unaesthetic to extremely aesthetic, 1 to 5, respectively). Nonparametric tests were used to analyse the data on SPSS version 24. Results. According to the 250 responses, the aesthetic perception of all severities of anterior crowding and mild and moderate spacing was found to be more aesthetic when displayed with the lips ( $p<0.05$ ). Additionally, the higher the level of dental education, the lower the aesthetic perception with and without the lips ( $p<0.05$ ). Conclusions. The lips play a significant role in improving the aesthetics of crowded anterior teeth and spaced anterior teeth. Dental educational level influences the aesthetic perception of anterior crowding and spacing. This may have an impact on treatment planning and need for orthodontic intervention.

Specialist training influences the ability to recognise orthodontic case complexity

General dentists and other dental specialists may be treating orthodontic cases without a proper understanding of the key components of malocclusion. This mini-review aims to identify the discrepancies in recognition of orthodontic case complexity and to give an insight as to why advanced speciality training is a must for the provision of comprehensive orthodontic care.

Intra-observer reliability and agreement of manual and digital orthodontic model analysis

Background and aim

Digital orthodontic model analysis is gaining acceptance in orthodontics, but its reliability is dependent on the digitalisation hardware and software used. We thus investigated intra-observer reliability and agreement / conformity of a particular digital model analysis work-flow in relation to traditional manual plaster model analysis.

Materials and methods

Forty-eight plaster casts of the upper/lower dentition were collected. Virtual models were obtained with orthoX®scan (Dentaurum) and analysed with ivoris®analyze3D (Computer konkret). Manual model analyses were done with a dial caliper (0.1 mm). Common parameters were measured on each plaster cast and its virtual counterpart five times each by an experienced observer. We assessed intra-observer reliability within method (ICC), agreement/conformity between methods (Bland-Altman analyses and Lin's concordance correlation), and changing bias (regression analyses).

Results

Intra-observer reliability was substantial within each method (ICC ≥ 0.7), except for five manual outcomes (12.8 per cent). Bias between methods was statistically significant, but less than 0.5 mm for 87.2 per cent of the outcomes. In general, larger tooth sizes were measured digitally. Total difference maxilla and mandible had wide limits of agreement (-3.25/6.15 and -2.31/4.57 mm), but bias between methods was mostly smaller than intra-observer variation within each method with substantial conformity of manual and digital measurements in general. No changing bias was detected.

Conclusions

Although both work-flows were reliable, the investigated digital work-flow proved to be more reliable and yielded on average larger tooth sizes. Averaged differences between methods were within 0.5 mm for directly measured outcomes but wide ranges are expected for some computed space parameters due to cumulative error.

Reliability and intra-examiner agreement of orthodontic model analysis with a digital caliper on plaster and printed dental models

OBJECTIVE

To investigate if orthodontic model analysis with a digital caliper can be interchangeably performed between plaster and printed dental models.

MATERIALS AND METHODS

Forty-eight plaster models were digitized with orthoX®scan (DENTAURUM) and 48 counterparts were printed with Objet30 Dental Prime (Stratasys). One examiner performed five repeated orthodontic model analyses (41 outcomes) with a digital caliper in each plaster and the corresponding printed model and was externally validated by a second examiner. Inter- and intra-examiner reliability and error were evaluated with intraclass correlation coefficients (ICCs) and Dahlberg's formula, intra-examiner agreement with Bland-Altman analyses and Lin's correlation coefficients (CCCs), and changing bias with regression analyses.

RESULTS

Inter- and intra-examiner ICCs and Dahlberg's error were ≥ 0.75 and ≤ 0.5 mm, respectively, for most outcomes in both plaster and printed models. Intra-examiner agreement (systematic bias) between plaster and printed models ranged from - 0.45 to 0.45 mm. Ranges of limits of agreement were wide for cumulative outcomes, such as crowding maxilla and mandible (2.69 mm and 3.07 mm around zero, respectively). Tooth widths were measured slightly larger in printed models. Lin's CCCs were ≥ 0.87 for all the outcomes between plaster and printed models, while no changing bias was detected.

CONCLUSION

If orthodontic model analyses are consistently performed, plaster casts and their corresponding printed models obtained with orthoX®scan and Objet30 Dental Prime can be interchangeably used for clinical purposes in orthodontics.

CLINICAL RELEVANCE

Orthodontic model analysis is important in treatment planning and printed dental models need to be validated regarding this diagnostic procedure.