Ales Obrez

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.

Jaw muscle pain and its effect on gothic arch tracings.

Perceived changes in occlusion and decreased range of motion are often expressed by patients with masticatory muscle pain. The adverse loading of craniomandibular tissues that results from an inadequate maxillomandibular relationship in combination with the coexisting dysfunction is widely regarded as the cause of pain. This study was designed to test whether pain can cause significant changes in position of the mandible and therefore form the basis for any perceived changes in the maxillomandibular relationship. A second objective was to determine whether pain can cause changes in the mandibular range of motion. Five subjects who rated pain intensity on a visual analog scale were used in a single-blind, randomized, repeated-measures study design. Tonic muscle pain was induced by infusion of 5% hypertonic saline solution into the central portion of the superficial masseter muscle. Isotonic saline solution was used as a control, with subjects blinded to the type of substance given. The effect of pain on the position of the apex of the gothic arch tracing, the direction of the lateral mandibular border movements, and the mandibular range of motion was studied in a horizontal plane with minimal occlusal separation. Pain significantly affected the position of the apex of the gothic arch tracing in anterior (F = 11.46, p = 0.03) and transverse (F = 35.0, p = 0.004) directions. Similarly, pain affected the orientation of the mandibular lateral border movements (F = 12.44, p = 0.02) and their magnitude (F = 14.97, p = 0.01). All pain-induced effects proved to be reversible. The observed effect of pain can explain the perceived change of bite that is frequently noted by patients with orofacial pain. This study provided evidence of an alternative causal relationship between pain and changes in occlusal relationship and questions occlusal therapy as treatment, directed toward the elimination of the underlying cause in patients with masticatory muscle pain.

New acrylic resin composite with improved thermal diffusivity

STATEMENT OF PROBLEM Studies have shown that physical characteristics of denture base materials may affect patient acceptance of denture prostheses by altering sensory experience of food during mastication. Thermal diffusivity is one material property that has been cited as being important in determining gustatory response, with denture base acrylic resins having low thermal diffusivity compared with denture base metal alloys. PURPOSE This study prepared and characterized experimental acrylic resin composite material with increased thermal diffusivity. MATERIAL AND METHODS Sapphire (Al2O3) whiskers were added to conventional denture base acrylic resin during processing to achieve loadings of 9.35% and 15% by volume. Cylindrical test specimens containing an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 degree to 70 degrees C). RESULTS Thermal diffusivities of the sapphire containing composites were found to be significantly higher than the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the volume percentage of sapphire filler, which suggested that the high aspect ratio ceramic particles formed a pathway for heat conduction through the insulating polymer matrix. CONCLUSION The thermal diffusivity of denture base acrylic resin was increased by the addition of thermally conducting sapphire whiskers.

The effect of musculoskeletal facial pain on registration of maxillomandibular relationships and treatment planning: A synthesis of the literature

STATEMENT OF PROBLEM A significant number of patients exist who are in need of prosthodontic rehabilitation and who at the same time report musculoskeletal pain in the facial area. PURPOSE This article, which is based on an assessment of both the past and the most recent basic science and clinical literature, evaluates the effect of musculoskeletal facial pain on two static (physiologic rest position and centric relation) and two dynamic (protrusive border and lateral border movements) maxillomandibular relationships. MATERIAL AND METHODS To find the relevant studies addressing the association between musculoskeletal facial pain and maxillomandibular relationships, a MEDLINE search was conducted, which was complemented by a hand search in selected journals. RESULTS AND CONCLUSIONS Musculoskeletal facial pain seems to variably affect the aforementioned positions and movements. Hence, the validity of maxillomandibular registrations in patients with existing facial pain is questioned. In those patients with facial pain who simultaneously are in need of a prosthodontic rehabilitation, clinicians should be cautious with regard to the timing of the restorative procedures.

Assessment of occlusion curriculum in predoctoral dental education: report from ACP Task Force on Occlusion Education.

PURPOSE The purposes of this report were to (1) assess the current occlusion curriculum in the predoctoral prosthodontic education of US dental institutions and (2) to examine the opinions of faculty, course directors, and program directors on the contents of occlusion curriculum. MATERIALS AND METHODS The Task Force on Occlusion Education from the American College of Prosthodontists (ACP) conducted two surveys using a web-based survey engine: one to assess the current status of occlusion education in predoctoral dental education and another to examine the opinions of faculty and course directors on the content of occlusion curriculum. The sections in the surveys included demographic information, general curriculum information, occlusion curriculum for dentate patients, occlusion curriculum for removable prosthodontics, occlusion curriculum for implant prosthodontics, temporomandibular disorder (TMD) curriculum, teaching philosophy, concepts taught, and methods of assessment. The results from the surveys were compiled and analyzed using descriptive statistics. The results from the two surveys on general concepts taught in occlusion curriculum were sorted and compared for discrepancies. RESULTS According to the predoctoral occlusion curriculum surveys, canine guidance was preferred for dentate patients, fixed prosthodontics, and fixed implant prosthodontics. Bilateral balanced occlusion was preferred for removable prosthodontics and removable implant prosthodontics. There were minor differences between the two surveys regarding the occlusion concepts being taught and the opinions of faculty members teaching occlusion. CONCLUSION Two surveys were conducted regarding the current concepts being taught in occlusion curriculum and the opinions of educators on what should be taught in occlusion curriculum. An updated and clearly defined curriculum guideline addressing occlusion in fixed prosthodontics, removable prosthodontics, implant prosthodontics, and TMD is needed.

Effects of unilateral premolar extraction treatment on the dental arch forms of Class II subdivision malocclusions

Introduction A retrospective study evaluating posttreatment symmetry in dental arch form and midlines was carried out in Class II subdivision patients treated with unilateral and bilateral maxillary premolar extractions. Methods Using Geomagic (version 14; Geomagic, Research Triangle Park, NC) and MATLAB (version 8.4; MathWorks, Natick, Mass) software, best‐fit curves expressed as quartic polynomials were generated for 13 Class II subdivisions treated with unilateral extractions and 20 treated with bilateral maxillary premolar extractions. Transverse and sagittal measurements were recorded to assess symmetry. Dental models were superimposed on constructed reference planes to generate average posttreatment arches. Statistical comparisons were performed with the significance level set at P ≤0.05. Results The unilateral extraction group showed significant differences in transverse arch forms between the right and left sides in the anterior, anterior‐middle, and middle segments of the arch, and all regions other than the posterior segment in the sagittal dimension. Significant differences were found between groups in the anterior and anterior‐middle segments of the arch transversely, the middle and middle‐posterior segments sagittally, and the midline deviation relative to the midsagittal plane. Superimposed average arches showed similar results. Conclusions Unilateral maxillary extraction treatment generally results in a narrower and more posteriorly displaced arch form on the extraction side, with a deviated maxillary midline toward the extraction side of the arch. HighlightsMaxillary arches were evaluated at posttreatment in Class II subdivision malocclusions.Unilateral extractions showed asymmetric transverse and sagittal differences in arch form.Unilateral extraction results in a narrow posteriorly displaced arch on the extraction side.In unilateral extraction patients, the maxillary midline deviates toward the extraction side.

Assessment of vertical changes during maxillary expansion using quad helix or bonded rapid maxillary expander

OBJECTIVE To determine if there is a significantly different effect on vertical changes during phase I palatal expansion treatment using a quad helix and a bonded rapid maxillary expander in growing skeletal Class I and Class II patients. MATERIALS AND METHODS This retrospective study looked at 2 treatment groups, a quad helix group and a bonded rapid maxillary expander group, before treatment (T1) and at the completion of phase I treatment (T2). Each treatment group was compared to an untreated predicted growth model. Lateral cephalograms at T1 and T2 were traced and analyzed for changes in vertical dimension. RESULTS No differences were found between the treatment groups at T1, but significant differences at T2 were found for convexity, lower facial height, total facial height, facial axis, and Frankfort Mandibular Plane Angle (FMA) variables. A comparison of treatment groups at T2 to their respective untreated predicted growth models found a significant difference for the lower facial height variable in the quad helix group and for the upper first molar to palatal plane (U6-PP) variable in the bonded expander group. CONCLUSION Overall, both the quad helix expander and the bonded rapid maxillary expander showed minimal vertical changes during palatal expansion treatment. The differences at T2 suggested that the quad helix expander had more control over skeletal vertical measurements. When comparing treatment results to untreated predicted growth values, the quad helix expander appeared to better maintain lower facial height and the bonded rapid maxillary expander appeared to better maintain the maxillary first molar vertical height.

The Temporomandibular Joint

The two temporomandibular joints (TMJs) form the bilateral articulation of the mandible with the cranium. Together with the neuromuscular system, the anatomy of the TMJ contributes to specific mandibular functions. Studying the TMJ exclusively on dry skulls may lead to erroneous conclusions regarding both mandibular function and joint biomechanics. It is for this reason that in addition to the bony components of the TMJ, the cartilage and soft tissues demand close attention.