Budi Kusnoto

How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign.

INTRODUCTION The purpose of this prospective clinical study was to evaluate the efficacy of tooth movement with removable polyurethane aligners (Invisalign, Align Technology, Santa Clara, Calif). METHODS The study sample included 37 patients treated with Anterior Invisalign. Four hundred one anterior teeth (198 maxillary and 203 mandibular) were measured on the virtual Treat models. The virtual model of the predicted tooth position was superimposed over the virtual model of the achieved tooth position, created from the posttreatment impression, and the 2 models were superimposed over their stationary posterior teeth by using ToothMeasure, Invisaligns proprietary superimposition software. The amount of tooth movement predicted was compared with the amount achieved after treatment. The types of movements studied were expansion, constriction, intrusion, extrusion, mesiodistal tip, labiolingual tip, and rotation. RESULTS The mean accuracy of tooth movement with Invisalign was 41%. The most accurate movement was lingual constriction (47.1%), and the least accurate movement was extrusion (29.6%)- specifically, extrusion of the maxillary (18.3%) and mandibular (24.5%) central incisors, followed by mesiodistal tipping of the mandibular canines (26.9%). The accuracy of canine rotation was significantly lower than that of all other teeth, with the exception of the maxillary lateral incisors. At rotational movements greater than 15 degrees, the accuracy of rotation for the maxillary canines fell significantly. Lingual crown tip was significantly more accurate than labial crown tip, particularly for the maxillary incisors. There was no statistical difference in accuracy between maxillary and mandibular teeth of the same tooth type for any movements studied. CONCLUSIONS We still have much to learn regarding the biomechanics and efficacy of the Invisalign system. A better understanding of Invisaligns ability to move teeth might help the clinician select suitable patients for treatment, guide the proper sequencing of movement, and reduce the need for case refinement.

Relationship between rapid maxillary expansion and nasal cavity size and airway resistance: Short- and long-term effects

INTRODUCTION The availability of new, reliable, objective, and 3-dimensional techniques to assess the effects of rapid maxillary expansion on the morphology of the maxillary dental arch, nasal cavity dimensions, and nasal airway resistance led to the development of this research. METHODS Thirty-eight subjects participated in this study (mean age, 13 years). Data were collected before expansion, when the expander was stabilized, when the expander was removed, and 9 to 12 months after the expander was removed. Subjective assessment of improvement in nasal respiration was obtained when the expander was stabilized. Three-dimensional imaging and acoustic rhinometry were used to assess the virtual cast and the nasal cavity, respectively. RESULTS AND CONCLUSIONS The statistically significant short-term effects of RME were (1) mean increases in palatal area, volume, and intermolar distance; (2) a mean reduction of nasal airway resistance; and (3) mean increases in total nasal volume and nasal valve area. Our long-term findings were the following: (1) mean palatal area and intermolar distance were reduced, while palatal volume was stable, and (2) nasal airway resistance was stable, whereas mean nasal cavity volume and minimal cross-sectional area increased. Additionally, 61.3% of our subjects reported subjective improvement in nasal respiration. Weak correlations were found between all variables analyzed.

Craniofacial applications of three-dimensional laser surface scanning.

Recent innovations in technology have generated a variety of techniques for medical imaging. One of these initially developed for industry is laser surface scanning. Laser surface scanning is a noninvasive method for acquiring three-dimensional (3D) images. In this article, the technology of 3D laser surface scanning is described, and a few applications are reported as it relates to craniofacial research and clinical practice. Advantages and disadvantages of this imaging modality are discussed. Three-dimensional laser surface scanning holds great promise as it relates to the documentation, analysis, and evaluation of treatment results in craniofacial anomalies.

Soft-tissue lasers in orthodontics: An overview

Soft-tissue lasers have numerous applications in orthodontics, including gingivectomy, frenectomy, operculectomy, papilla flattening, uncovering temporary anchorage devices, ablation of aphthous ulcerations, exposure of impacted teeth, and even tooth whitening. As an adjunctive procedure, laser surgery has helped many orthodontists to enhance the design of a patients smile and improve treatment efficacy. Before incorporating soft-tissue lasers into clinical practice, the clinician must fully understand the basic science, safety protocol, and risks associated with them. The purpose of this article is to provide an overview regarding safe and proper use of soft-tissue lasers in orthodontics.

ASSESSMENT OF 3-DIMENSIONAL COMPUTER-GENERATED CEPHALOMETRIC MEASUREMENTS

The purpose of this study was to assess the reliability of 3-dimensional computer-generated linear and angular measurements produced by different computer algorithms and various combinations of cephalogram projections compared with direct and CT measurements. A computer program was written to provide 4 computer algorithms and 4 combinations of cephalogram projections generating 22 linear and 10 angular 3-dimensional measurements from 20 landmarks. A new technique to produce biplanar cephalograms from a single x-ray source using a special facebow was developed, and its reliability was assessed. Sets of lateral, frontal, and basilar cephalograms of a human dried skull were taken both with 20 radiopaque landmark markers and without markers. Paired t tests based on marker position demonstrated reliability of the facebow; there were no statistically significant differences in repositioning the skull over time using the facebow at P <.05. In the ideal situation, with minimal head rotation and landmark identification error (with the facebow and radiopaque markers), the average error of linear measurements was 1. 5 mm and 3.5(o) for the angular measurements. Subsequent trials evaluated the errors in head position (within 5(o) of head rotation) and in landmark identification (by removing all markers); two-way ANOVA with Scheffé groupings concluded that the vector intercept with manual adjustment algorithm using the lateral-frontal biplanar projection provides not only greater accuracy but also clinical practicality for both linear (mean of 2.2 mm error) and angular (mean of 4.0(o) error) measurements compared with direct or CT measurements (P <.05). The effect of landmark identification error was found to be slightly greater than the head rotation error in the accuracy of 3-dimensional linear and angular measurements (mean, 2.85 mm error for linear and 4.4(o) error for angular measurements). Lastly, this study concluded that linear measurements in the transverse direction were found to have a slightly larger error than vertical measurements. Anteroposterior measurements have the least error.

Influence of Attachments and Interproximal Reduction on the Accuracy of Canine Rotation with Invisalign

OBJECTIVE To evaluate the influence of attachments and interproximal reduction on canines undergoing rotational movement with Invisalign. MATERIALS AND METHODS In this prospective clinical study, 53 canines (33 maxillary and 20 mandibular) were measured from the virtual TREAT models of 31 participants treated with anterior Invisalign. The pretreatment virtual model of the predicted final tooth position was superimposed on the posttreatment virtual model using ToothMeasure, Invisaligns proprietary measurement software. A one-way analysis of variance (ANOVA) (P < .05) compared three treatment modalities: attachments only (AO), interproximal reduction only (IO), and neither attachments nor interproximal reduction (N). Students t-tests (P < .05) compared the mean accuracy of canine rotation between arches. RESULTS The mean accuracy of canine rotation with Invisalign was 35.8% (SD = 26.3). Statistical analyses indicated that there was no significant difference in accuracy between groups AO, IO, and N (P = .343). There was no statistically significant difference (P = .888) in rotational accuracy for maxillary and mandibular canines for any of the treatment groups. The most commonly prescribed attachment shape was the vertical-ellipsoid (70.5%). CONCLUSIONS Vertical-ellipsoid attachments and interproximal reduction do not significantly improve the accuracy of canine rotation with the Invisalign system.

Intrusion of overerupted upper first molar using two orthodontic miniscrews. A case report.

Loss of the mandibular first molar often leads to the overeruption of the opposing maxillary first molar, resulting in occlusal interference, loss of periodontal bony support, and inadequate room to restore the mandibular edentulous space. Without orthodontic molar intrusion or segmental surgical impaction, restoring the posterior occlusion often entails the need for significant reduction of maxillary molar crown height, with the potential need for costly iatrogenic root canal therapy and restoration. The literature has cited successful maxillary molar intrusion with minor prosthodontic reduction using palatal orthodontic miniscrews and buccal zygomatic miniplates. In this report, the authors present successful maxillary molar intrusion with two orthodontic miniscrews in a patient with extreme dental anxiety and significant dental erosion due to gastric reflux. Using two orthodontic miniscrews for skeletal anchorage to intrude the maxillary molar simplified the orthodontic treatment by eliminating the need for extensive surgery, headgear, and intraoral multiunit anchorage and preserved indispensable tooth enamel. The clinical results showed significant intrusion through the maxillary sinus cortical floor while maintaining periodontal health, tooth vitality, and root length.

Factors affecting stresses in cortical bone around miniscrew implants A three-dimensional finite element study

OBJECTIVE To evaluate various types of stress in cortical bone around miniscrew implants using finite element analysis. MATERIALS AND METHODS Twenty-six three-dimensional assemblies of miniscrew models placed in alveolar bone blocks were constructed using Abaqus (Dassault Systèmes Simulia Corp, Providence, RI), a commercial finite element analysis software package. The model variables included implant design factors and bone-related factors. All miniscrew implants were loaded in the mesial direction with a linear force equal to 2 N. Peak von Mises and principal stress values in cortical bone were compared between the different models for each factor. RESULTS The results demonstrated that some factors affected the stresses in bone (implant diameter, implant head length, thread size, and elastic modulus of cancellous bone), while other factors did not (thread shape, thread pitch, and cortical bone thickness). CONCLUSIONS Miniscrew implant diameter, head length, and thread size as well as the elastic modulus of cancellous bone affect the stresses in cortical bone layer surrounding the miniscrew implant and may therefore affect its stability.

THE EFFECT OF MAXILLARY FIRST MOLAR DEROTATION ON ARCH LENGTH

In the correction of Class II malocclusions, derotation of the maxillary first molars is required to obtain an idealized Class I relation. Because of its trapezoidal shape, the maxillary first molar is believed to provide an arch length gain attendant to its derotation, which may subsequently be used to resolve deficiencies mesial to it. Two commonly used mechanisms for maxillary first molar derotation and its associated centers of rotation were studied. A transpalatal arch, when accompanied by distal force equivalent at the level of the maxillary first molar center of resistance, can provide a center of rotation approximating the lingual attachment. This produces an arch length gain of 2.1 mm anterior to the molar, while simultaneously impinging on the maxillary second molar space 1.2 mm (per side). In reality, this may be a transference of a problem in one area of the dental arch to another. The 2 x 4 and 2 x 6 arch wires provide for various centers of rotation along an axis from the molar center of resistance--as projected to the occlusal surface--to the region of the maxillary first molar distal marginal ridge. These centers of rotation do not provide any meaningful alteration in arch length. These arch wires are useful, however, for maxillary first molar derotation necessary to achieve an idealized Class I molar occlusion. It is evident that the arch length gain related to derotation of the maxillary first molars, irrespective of the center of rotation, is insufficient to achieve Class I premolar intercuspation. Additional factors as growth, surgical intervention, or extractions are needed to achieve Class I premolar articulation.

A new accurate approach to the anterior ratio with clinical applications: Part 1: A computer program

The arcs of the six anterior maxillary and mandibular teeth have recently been described mathematically by the hyperbolic cosine function with a maxillary correlation coefficient (r ) of 0.885 and a mandibular correlation coefficient (r ) of 0.951. Because the geometric relationships of the anterior dental arcs are known when the occlusion is Class I, a computer program has been developed for use in clinical practice. Rapid forecasting of the interrelationships between the maxillary and mandibular arc depths (related to overjet) with variations in the mesiodistal sums of the six maxillary and mandibular anterior teeth for various intercanine widths is now possible with ease and accuracy (+/- 0.1 mm). Clinical applications are illustrated.