Preclinical in vitro study of streptococcus mutans accumulation in three fixed retainer designs: Microbiological assay

The use of fixed retainers in the lower arch is frequent; however, its presence increases the accumulation of biofilm and dental calculus. The objective of this research was to evaluate, in vitro, the accumulation of Streptococcus mutans (S. mutans) in 3 designs of fixed retainers. Nine models were reproduced in heat-cured acrylic resin and divided into groups: straight retainer (SR), retainer with vertical strap (RVS), retainer with horizontal strap (RHS). The accumulation of S. mutans was assessed using the MTT assay (3-4,5-dimethyl-thiazol-2-yl-2,5-diphenyltetrazolium bromide) and then measured using an automated reader. The RHS group showed less biofilm accumulation compared to the other groups (p<0.05). The distance between the tooth surface and the retainer showed a strong negative correlation with biofilm accumulation (rs=-0.79, p=0.00037). The RHS showed significantly less accumulation of S. mutans due to the distance between the retainer and the tooth surface. This research provides relevant data for a future randomized clinical trial.

Which one closes extraction spaces faster: en masse retraction or two-step retraction? A randomized prospective clinical trial

OBJECTIVES

To compare the time to close extraction spaces between en masse (ER) and two-step retraction (TSR).

MATERIALS AND METHODS

Forty-eight patients with bimaxillary protrusion underwent treatment with extraction of four first premolars. All patients were randomly allocated to one of two groups: ER (n = 24) or TSR (n = 24). The main outcome was the time required to close spaces between ER and TSR; the closing time of spaces between females and males was a secondary outcome. The size of premolars was measured on the models and data were collected on clinical records at the following times: retraction start date (T1) and space closure completion date (T2). The total time to close the extraction spaces was calculated for each extracted premolar (T1 to T2). The Kaplan Meier method and the Log-Rank test were used to compare the groups.

RESULTS

The time to close extraction spaces showed significant differences between the ER and TSR groups. While ER took between 12.1 and 13.8 months, TSR took between 24.7 and 26.8 months. The TSR group showed a significant difference between sexes; male patients took 5.5 months longer than female patients for the extraction spaces to close.

CONCLUSIONS

TSR takes between 1.8 and 2.2 times longer than ER to close the extraction spaces and it took longer in males than females.

Scientific use of the finite element method in Orthodontics

INTRODUCTION:

The finite element method (FEM) is an engineering resource applied to calculate the stress and deformation of complex structures, and has been widely used in orthodontic research. With the advantage of being a non-invasive and accurate method that provides quantitative and detailed data on the physiological reactions possible to occur in tissues, applying the FEM can anticipate the visualization of these tissue responses through the observation of areas of stress created from applied orthodontic mechanics.

OBJECTIVE:

This article aims at reviewing and discussing the stages of the finite element method application and its applicability in Orthodontics.

RESULTS:

FEM is able to evaluate the stress distribution at the interface between periodontal ligament and alveolar bone, and the shifting trend in various types of tooth movement when using different types of orthodontic devices. Therefore, it is necessary to know specific software for this purpose.

CONCLUSIONS:

FEM is an important experimental method to answer questions about tooth movement, overcoming the disadvantages of other experimental methods.

Impaction of Maxillary Central Incisors: Surgical and Orthodontic Treatment--Case Report

The aim of this paper is to report two clinical cases, which was performed with surgical exposure and orthodontic traction of a maxillary central incisors. Light forces were used during the orthodontic treatment applied on rigid wires as anchorage. It was noted that teeth presented adequate clinical crown height and gingival contours.

Orthodontic Treatment in Adult Patient with Reduced Periodontium: A Case Report

Patients presenting reduced periodontium represent a major concern for orthodontists. The purpose of this article is to present the clinical case of an adult patient who presented sequel of periodontal disease (diastemas) compromising her dental aesthetics. She was subjected to an orthodontic treatment with the application of light forces distant from the teeth with reduced periodontium. A periodontal support therapy was successfully implemented. The final stage of the treatment indicated satisfactory occlusal and periodontal characteristics.

Influence of maxillary incisor edge asymmetries on the perception of smile esthetics among orthodontists and laypersons

INTRODUCTION

Our objective was to determine the perception of smile esthetics among orthodontists and laypeople with respect to asymmetries on the maxillary incisor edges in a frontal smile analysis.

METHODS

Two frontal close-up smile photos of 2 women, 1 white and 1 Afro-Brazilian, were selected for this study. Both smiles displayed healthy maxillary anterior dentitions. The images were digitally altered to create tooth wear on the maxillary left central and lateral incisors in 0.5-mm increments. The final images were randomly assembled into a photo album that was given to 120 judges, 60 orthodontists and 60 laypersons. Each rater was asked to evaluate the attractiveness of the images with visual analog scales. The data collected were statistically analyzed with 1-way analysis of variance with the Tukey post-hoc test and the unpaired Student t test.

RESULTS

The most attractive smiles in both types of smiles were those without asymmetries and the 0.5-mm wear in the lateral incisor. In general, tooth wear was considered unattractive by both groups of raters following a pattern: the more tooth wear, the more unattractive the smile; tooth wear in the central incisor was considered more unattractive than in the lateral incisor. For both group of raters, 0.5 mm of wear in the central incisor was considered unattractive, whereas the thresholds for lateral incisor discrepancies were 0.5 mm for orthodontists and 1.0 mm for laypersons.

CONCLUSIONS

The result of this study corroborates the clinical assumption that symmetry between the maxillary central incisors is a paramount goal for esthetic treatments.

Controlling mechanical undesirable side effects with a tooth indicated for extraction: free anchorage

This manuscript describes the use of a tooth indicated for extraction due to orthodontic reasons as an anchorage aid to receive undesirable side effects caused by orthodontic uprighting of a contralateral molar tooth. The mandibular right second molar was mesially tipped as a result of loss of the adjacent first molar. Since the treatment plan involved extraction of the mandibular left first premolar, undesirable side effects associated with the molar uprighting movement were transferred to this tooth. Once the second molar was vertical, the premolar was extracted and the treatment continued. The results suggest that treatment time can be reduced if undesirable orthodontic mechanical side effects can be directed to a tooth whose extraction is indicated.

Photographic assessment of cephalometric measurements

OBJECTIVE

To investigate the relationship between craniofacial measurements obtained from cephalometric radiographs and analogous measurements from profile photographs.

MATERIALS AND METHODS

Lateral cephalograms and standardized facial profile photographs were obtained from a sample of 123 subjects (65 girls, 58 boys; age 7-12 years). Intraclass correlation coefficients (ICCs) were calculated from repeated photographic measurements to evaluate method reliability. Analogous cephalometric and photographic measurements were compared to assess Pearson correlation coefficients. Linear regression analyses were conducted between the measurements that achieved correlation coefficients greater than r  =  0.7.

RESULTS

The reliability of the photographic technique was satisfactory. Most measurements showed ICCs above 0.80 and highly significant correlations (P ≤ .001) with cephalometric variables. Among all measurements used, the A'N'B' angle was the most effective in explaining the variability of its analogous cephalometric, mainly for female subjects (r(2)  =  0.80). The FMA' angle showed the best results for vertical assessment (r(2)  =  0.65).

CONCLUSIONS

The photographic method has proven to be a repeatable and reproducible tool provided that a standardized protocol is followed. Therefore, it may be considered a feasible and practical diagnostic alternative, particularly if there is a need for a low-cost and noninvasive method.

Rapid palatal expansion: a comparison of two appliances

This study analyzed occlusal radiographs to compare the transverse changes produced in patients treated with rapid maxillary expansion using two types of appliances. The sample consisted of 31 children aged 7 to 10.6 years, of both genders, with posterior cross-bite. Fifteen children were treated with a tooth-borne expander and 16 were treated with a tooth-tissue-borne expander. Occlusal radiographs obtained at treatment onset and at the end of the retention period were digitized. The following variables were measured: intermolar distance (IMD), interapical distance (IApD), interbase distance (IBaD) and interarm distance (IArD). The results revealed increases in all measurements in both groups after rapid maxillary expansion. Comparison between groups revealed that the increases were greater in patients treated with the tooth-borne expander, except for the IArD measurement, which presented the same increase in both groups. Even though the IMD measurements differed between expanders, they were proportional to the activation of the appliances (IBaD). The increase in the IApD measurement was proportionally greater in the group treated with the tooth-borne expander (0.7:1.0) than in that treated with the tooth-tissue-borne expander (0.4:1.0). It was concluded that both appliances had similar effects, although the tooth-tissue-borne expander produced a lesser opening at the apical region of the incisors.

The role of orthodontics as an auxiliary tool to lip augmentation

In recent years, facial esthetics excellence has become a major focus in health professional offices and for the public worldwide. Among the main concerns of the patients is lip augmentation, since it has been associated with beauty and youth. This procedure has been increasingly performed and studied by dermatologists and plastic surgeons. Although good outcomes for lip augmentation have been achieved with different techniques, literature shows several complications and collateral effects. This paper demonstrates, through two clinical cases, how Orthodontics may be an excellent tool to assist in lip augmentation, highlighting the need for an interdisciplinary approach to enhance a more effective strategy to achieve facial esthetics goals.

Crimpable double tubes for segmental retraction

When a T-loop is used in segmental mechanics, it is generally attached posteriorly to an auxiliary tube in the first molars and anteriorly to a crimpable cross tube or a Burstone canine bracket. This article illustrates the use of a crimpable tube with a 90-degree bend on the base wire to secure a T-loop in segmental retraction. Both of these approaches allow a T-loop to be reactivated in a simple manner without undesirable changes in the system of forces, which could happen if the T-loop is skewed posteriorly.

Changes over time in canine retraction: an implant study

INTRODUCTION

The objective of this study was to analyze rates of canine movement over the first 2 months of continuous retraction, when rate changes are expected.

METHODS

Ten patients with bone markers placed in the maxilla and the mandible had their canines retracted over a 2-month period. Retraction was accomplished with beta-titanium alloy T-loop springs. Standardized 45 degrees oblique cephalograms where taken initially and every 28 days thereafter. The radiographs were scanned and digitized twice (the average was used for the analyses). The radiographs were superimposed by using the bone markers and oriented on the functional occlusal plane. Paired t tests were used to compare side and jaw effects.

RESULTS

There were no significant differences between sides. The maxillary cusp was retracted 3.2 mm, with less movement during the first (1.1 mm) than during the second 4 weeks (2.1 mm). The maxillary apices did not move horizontally. There were no significant vertical movements in the cusps and apices of the maxillary canines. The mandibular cusp was retracted 3.8 mm-1.1 mm during the first and 2.7 mm during the second 4 weeks. The mandibular apices were protracted 1.1 mm. The cusps and apices were intruded 0.6 and 0.7 mm, respectively. The only difference between jaws was the greater protraction of the mandibular apices during the second 4 weeks and in overall movement.

CONCLUSIONS

The rate of canine cusp retraction was greater during the second than the first 4 weeks. The mandibular canines were retracted by uncontrolled tipping whereas the maxillary canines were retracted by controlled tipping.

In vivo and in vitro study of the shear bond strength of brackets bonded to enamel using halogen or LED light

AIM

To evaluate the shear bond strength in vivo and in vitro of metallic brackets bonded to human teeth with light-curing bonding material, using two types of light-curing units.

METHODS

Sixty human premolars were divided into six groups. In the GI and GII groups, the brackets were directly bonded to volunteers' maxillary and mandibular second premolars on the right and left sides, respectively, of their mouths. In the other groups, the brackets were bonded to extracted first premolars. The polymerization was performed in GI, GIII, and GV with an LED (light-emitting diode) device, while in GII, GIV, and GVI, a halogen light was used. In GI and GII, shear strength tests were conducted using a portable digital dynamometer placed directly in the patients' mouths. The teeth from GIII, GIV, GV, and GVI were stored in distilled water at 37 degrees C for 24 hours. Afterward, they were thermocycled between 5 degrees and 55 degrees C. Then, in GIII and GIV, a Universal Testing Machine was used; in GV and GVI, mechanical tests were performed with a digital dynamometer. The bracket/adhesive failure modes were evaluated with the Adhesive Remnant Index (ARI).

RESULTS

The average values of the shear strengths in MPa were: GI = 3.65; GII = 4.39; GIII = 6.45; GIV = 7.11; GV = 4.67; and GVI = 4.21.

CONCLUSIONS

The type of light-curing unit did not interfere with the results of the mechanical tests in vivo or in vitro. The tests performed with a portable digital device obtained average values that were significantly lower than those performed with the Universal Testing Machine.

Esthetic influence of negative space in the buccal corridor during smiling

The purpose of this study was to measure and verify the esthetic influence of the bilateral spaces between maxillary teeth and lip corners, called negative space (NS), during smile. The sample was comprised of 60 smile photographs obtained from 60 individuals (30 men and 30 women) aged 18 to 25 years old. Two orthodontists and two lay people evaluated these pictures regarding esthetics by a visual analogue scale. In each picture, the right and left NS were measured in millimeters and in proportion to the smile width (SW). Data were analyzed for statistical significance (P = .05). The mean NS of the sample was 6.68 +/- 1.99 mm, and the NS proportion in relation to the SW was 9.6 +/- 2.56%, for both sides of the arch. No significant asymmetries were observed between the right and left sides. The NS was significantly larger in men than in women when measured in millimeters (P = .028) (7.08 +/- 2.24 mm in men vs 6.28 +/- 1.62 mm in women), but the NS proportion to the SW was similar (9.94 +/- 2.24% in men vs 9.26 +/- 1.61% in women). When the 12 individuals with the smallest NS in proportion to SW were compared with the 12 individuals with the largest NS in proportion to SW, there was no statistical difference regarding the esthetic evaluation (P = .11). It was concluded that the NS did not influence the esthetic evaluation of smile photographs in the sample in this study, for both orthodontists and lay people.

Influence of Orthodontic Dental Movement on the Healing Process of Teeth With Periapical Lesions

The purpose of this study was to histomorphologically evaluate (in dog's teeth) the influence of tooth movement in the healing of chronic periapical lesions. Thirty roots of incisors and premolars of two dogs (1-year-old) were used in this research. After pulpectomy, the root canals remained exposed to the oral environment for 6 months for achievement of periapical lesions. Twenty root canals were biomechanically prepared and received a calcium hydroxide dressing for 14 days before being filled with gutta-percha points and Sealapex sealer. After root canal treatment, some incisors were submitted to orthodontic movement, whereas the other roots remained without orthodontic movement. The orthodontic appliance was removed at 5 months and 15 days after treatment, the dogs were killed 15 days later and the specimens were prepared for histomorphological analysis. The results showed that the orthodontic movement delayed, but did not hinder, the periapical healing process.

Analysis of the smile photograph

Optimal facial esthetics is one of the objectives in orthodontic treatment and an important issue in modern society. In this context, orthodontic treatment permits individuals with dental malpositions to achieve improved dentofacial esthetics. To reach this result, the orthodontist needs to recognize the characteristics considered normal and pleasant in dental arches and smiles. The objective of this article is to review and discuss criterion adopted by dental literature to technically analyze the smile, such as dental midline, smile line, dental exposure, negative space, dental proportion, and symmetry. This article proposes a way to visualize an ideal smile for each patient.

A new way of analyzing occlusion 3 dimensionally

This article introduces a new method for 3-dimensional dental cast analysis, by using a mechanical 3-dimensional digitizer, MicroScribe 3DX (Immersion, San Jose, Calif), and TIGARO software (not yet released, but available from the author at hayasaki@dent.kyushu-u.ac.jp ). By digitizing points on the model, multiple measurements can be made, including tooth dimensions; arch length, width, and perimeter; curve of Spee; overjet and overbite; and anteroposterior discrepancy. The bias of the system can be evaluated by comparing the distance between 2 points as determined by the new system and as measured with digital calipers. Fifteen pairs of models were measured digitally and manually, and the bias was evaluated by comparing the variances of both methods and checking for the type of error obtained by each method. No systematic errors were found. The results showed that the method is accurate, and it can be applied to both clinical practice and research.

Effects of cervical headgear and edgewise appliances on growing patients

Maxillary basal bone, dentoalveolar, and dental changes in Class II Division 1 patients treated to normal occlusion by using cervical headgear and edgewise appliances were retrospectively evaluated. A sample of 45 treated patients was compared with a group of 30 untreated patients. Subjects were drawn from the Department of Orthodontics, Araraquara School of Dentistry, Brazil, and ranged in age from 7.5 to 13.5 years. The groups were matched based on age, gender, and malocclusion. Roughly 87% of the treated group had a mesocephalic or brachicephalic pattern, and 13% had a dolicocephalic pattern. Cervical headgear was used until a Class I dental relationship was achieved. Our results demonstrated that the malocclusions were probably corrected by maintaining the maxillary first molars in position during maxillary growth. Maxillary basal bone changes (excluding dentoalveolar changes) did not differ significantly between the treated and the untreated groups. Molar extrusion after the use of cervical headgear was not supported by our data, and this must be considered in the treatment plan of patients who present similar facial types.

Maxillary and mandibular width changes studied using metallic implants

The purpose of this implant study was to evaluate the transverse stability of the basal maxillary and mandibular structures. The sample included 25 subjects between 12 and 18 years of age who were followed for approximately 2.6 years. Metallic implants were placed bilaterally into the maxillary and mandibular corpora before treatment. Once implant stability had been confirmed, treatment (4 first premolar extractions followed by fixed appliance therapy) was initiated. Changes in the transverse maxillary and mandibular implants were evaluated cephalometrically and two groups (GROW+ and GROW++; selection based on growth changes in facial height and mandibular length) were compared. The GROW++ group showed significant width increases of the posterior maxillary implants (P <.001) and the mandibular implants (P =.009); there was no significant change for the anterior maxillary implants. The GROW+ group showed no significant width changes between the maxillary and mandibular implants. We conclude that (1) there are significant width increases during late adolescence of the basal mandibular and maxillary skeletal structures and (2) the width changes are related with growth potential.