Enamel remineralization potential of bioactive glass air abrasion studied via elemental and surface morphology analysis.

Background: This study evaluates the remineralization potential of enamel after bioactive glass (BAG) air abrasion, using Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy Analysis (SEM-EDS), Electron Probe Microanalysis (EPMA), and Atomic Force Microscopy (AFM). Material and Methods: Forty extracted human third molars were divided into four groups with ten samples each. Three groups were subjected to a demineralizing solution of 2.2 mM calcium chloride, 2.2 mM monopotassium phosphate, and 0.05 mM acetic acid, adjusted to a pH of 4.4 using 1 M potassium hydroxide at an intraoral temperature of 37°C for 96 hours. Of the three groups, two were subjected to air abrasion with BAG. One of the air abrasion groups was then further remineralized in 1.5 mM calcium chloride, 0.9 mM sodium phosphate, and 0.15 M potassium chloride, adjusted to a pH of 7.0 at 37°C. The teeth were then evaluated via SEM-EDS and EPMA to measure the calcium-to-phosphorous (Ca:P) ratios, and the surface morphology was investigated using AFM. Results: A measurable decrease in the Ca:P ratio was found after demineralization, which subsequently increased after remineralization. A thin layer of demineralized enamel was removed by the BAG air abrasion. AFM image analysis showed the presence of pits on the surface, which decreased in depth after demineralization, and further after BAG abrasion. Remineralized samples, in contrast, showed a slight increase in pit depth. While the observation of remineralization was statistically significant throughout our study, we could not find any evidence for BAG retention on the surface of the enamel. Conclusions: It is demonstrated that BAG, when delivered via air abrasion, indeed contributes to remineralization of the enamel; however, it does not seem to be a direct result of the presence of retained glass beads on the enamel surface. Given the increase of the Ca:P ratio after remineralization, a possible therapeutic benefit was observed, potentially reducing the probability of fractures in weakened enamel. Key words:Enamel, Demineralization, Remineralization, White Spot Lesions, Bioactive Glass, Air Abrasion, Energy Dispersive X-ray Spectroscopy, Electron Probe Microanalysis, Atomic Force Microscopy, Ca:P ratio, surface morphology.

Does pre-operative clindamycin administration during dental implant surgery reduce implant failure or post-surgical complications?

Study design Prospective randomised placebo-controlled clinical trial.Cohort selection and data analysis Sixty-two healthy adults who underwent single dental implant placement without previous infection of the surgical bed or the need for bone grafting were included in this clinical trial. They were randomly divided into two groups (test and control). The test group was given a single dose of oral clindamycin (600 mg) one hour before surgery and the control group with a placebo. The surgical procedures were carried out by one oral surgeon and all the patients were observed post-operatively on days 1, 7, 14, 28, and 56 by a single observer for clinical, radiological, surgical variables, adverse events, and complications. Statistical analysis was performed with STATA 15 software and the number required to treat or harm (NNT/NNH) was also evaluated.Results In the test group, the authors observed two implant failures and one patient experienced gastrointestinal disturbances and diarrhoea. They also observed post-operative infections in three patients (two in the control group and one in the test group which eventually failed).Conclusions The authors concluded that pre-operative clindamycin administration during dental implant surgery in healthy adults may not reduce implant failure or post-surgical complications.

An overview of orthodontic malpractice liability based on a survey and case assessment review.

Background: The purpose of this survey study and case review was to identify 1) the common causes related to filing a malpractice claim against an orthodontist and, 2) the factors mitigating against a potential malpractice claim in the United States (U.S). The objectives of the case review were to examine the current state of orthodontic malpractice litigation from a cause and mitigating point of view. Material and Methods: Data for this research was collected and reviewed using the following two methods: 1) A survey questionnaire on aspects of malpractice liability was electronically distributed to 2,241 active U.S. members of the American Association of Orthodontists (AAO). 2) Legal cases were reviewed on the online legal research database Lexis Advance Research, and 35 cases were analyzed. Results: Survey questionnaire results and legal case review results are as follows: 1) 77 orthodontists completed the survey. 9.1% of the respondents reported a malpractice claim having been filed against them with periodontal issues accounting for most of the claims. Survey participants reported good doctor-patient communication as being the most relevant contributory factor and most relevant mitigating factor in malpractice claims. 2) Negligence is the main reason patients sue a doctor for clinically related litigation, and failure to obtain a proper informed consent from the patient is the main cause of action for non-clinically related litigation. Conclusions: Most respondents reported doctor-patient communication, periodontal issues, and a lack of informed consent as the main triggering elements of a lawsuit, which is similar to other studies and case review analysis. Good doctor-patient rapport was ranked as being most helpful in mitigating a potential claim, which is also similar to other studies. Another aspect of the survey questionnaire that was evaluated was whether a non-orthodontist can provide expert testimony against an orthodontist, with most respondents reporting that this is not possible. It has been ruled, though, that a general dentist can be an expert witness and provide expert testimony against an orthodontist in a lawsuit depending on the circumstances. Negligence was the most common cause of clinically related orthodontic litigation, and a failure of the practitioner to obtain a proper informed consent from the patient was the most common cause of non-clinically related orthodontic litigation. Key words:Orthodontist, malpractice, legal, lawsuit, liability, medicolegal.

Public Perceptions and Understanding of Risks Associated with Do-It-Yourself Orthodontics: A Survey Study.

Background: The purpose of this study was to evaluate general public's perception, knowledge and preferences on orthodontic treatment rendered by an orthodontist versus the "Do-It-Yourself" orthodontics (DIYO) concept without professional supervision. The secondary objective was to assess laypeople's awareness on the risks and limitations of DIYO. Material and Methods: A 24-question online survey questionnaire was administered to 526 laypeople who had no professional experience or background in dentistry and orthodontics. All data was collected over 3 days (July 20-23, 2020) by Qualtrics server and forwarded to the principal investigator. Statistical analysis was done with statistical software SPSS® version 26. Results: The most important reason for laypeople to opt for DIYO is financial reason. People who have undergone orthodontic treatment know the difference between a general dentist and an orthodontist, whereas people who have not had orthodontic treatment are less likely to know the difference. Of the 285 people who did not receive orthodontic treatment before by a dental professional, 43 have considered DIYO. 122 of the 526 people considered DIYO, and 79 of the 122 had orthodontic treatment before. 26 of the 122 did not consider the clinical exam and diagnostic records important and would be comfortable without in-person supervision. 83 of the 122 would be comfortable not having in-person supervision, and still considered this treatment modality "Doctor-Directed". Conclusions: The main reason laypeople utilize DIYO is the low cost. Some DIYO users do not consider risks involved and a small percentage consider their own dentist to be responsible if any issues arise with DIYO. One third of survey respondents will consider DIYO in the future. Key words:Do-It-Yourself (DIY), Direct-To-Consumer (DTC), Adult, Orthodontics, Dentistry, Surveys and Questionnaires.

Is computer-guided implant placement with a flapless approach more accurate than with a flapped surgical approach?

Study design Retrospective cohort study.Cohort selection and data analysis In total, 89 implants were placed in 34 patients (19 men and 15 women; average 62.1 years of age) using computer-guided implant surgery with cone beam computed tomography (CBCT). All patients included in this study were adults and the computed-guided implant surgery was planned according to a digital guide protocol based on CBCT. Group 1 patients received the implants with the guide and flapped surgical approach, Group 2 with the guide and flapless approach. Group 3 was the drop-out group which included other patients in who the implant could not be placed according to the guide. CBCT data from before and after the surgeries were superimposed to evaluate the accuracy of implant positioning among all the groups. The differences in distance of the entry point (deviation distance) and in the degree of the insertion angle (deviation angle) were measured on the superimposed CBCT. Statistical analysis was performed with SPSS software and an independent sample t-test was done to analyse the difference of measurements among the groups.Results The authors observed greater accuracy in Group 2 in terms of deviation distance and angulation when compared to Group 1. The deviated position of the implant fixtures was greater in the drop-out group when compared to the guided groups in terms of the displacement of entrance point and the degree of insertion.Conclusions The authors concluded that flapless guided implant surgery is more accurate than flap guided implant surgery. The results of this study can be useful to clinicians in making decisions between flapless surgical approach and flapped approach when using a guide for implant placement.

Screening for obstructive sleep apnea by orthodontists in the United States - A survey study.

Background: Obstructive Sleep Apnea (OSA), a sleep-related breathing disorder that can affect both children and adults with systemic co-morbidities beyond disrupted sleep yet remains underdiagnosed in a substantial portion of the pediatric and adult orthodontic patient populations. The objective of this study was to assess the prevalance of orthodontists screening patients for OSA, their confidence level in screening, and to identify the various screening methods most commonly used in practice. Material and Methods: A survey on screening for OSA was emailed to 6,675 members of the American Association of Orthodontists (AAO) in the United States. Frequency distribution of different responses and their association with various demographic factors was assessed. Results: Out of 234 orthodontists completing the survey, 62% reported screening all of their patients for OSA, while 38% reported doing no OSA screening at all. More hours of continuing education (CE) and younger ages were observed to be statistically significantly associated with practice of screening for OSA (p<0.001 and 0.034, respectively, on regression analysis). Role of longer practice duration observed to be significant on univariate analysis, lost its statistical significance on regression analysis. Conclusions: CE hours on OSA seemed to be the most important factor that motivated the orthodontist to screen for OSA. A majority of orthodontists in the 35-54 year old age-group were screening their patients for OSA. Key words:Orthodontics, obstructive sleep apnea, screening, survey study.

Novel 3-chloro-6-nitro-1H-indazole derivatives as promising antileishmanial candidates: synthesis, biological activity, and molecular modelling studies.

An efficient pathway was disclosed for the synthesis of 3-chloro-6-nitro-1H-indazole derivatives by 1,3-dipolar cycloaddition on dipolarophile compounds 2 and 3. Faced the problem of separation of two regioisomers, a click chemistry method has allowed us to obtain regioisomers of triazole-1,4 with good yields from 82 to 90% were employed. Also, the antileishmanial biological potency of the compounds was achieved using an MTT assay that reported compound 13 as a promising growth inhibitor of Leishmania major. Molecular docking demonstrated highly stable binding with the Leishmania trypanothione reductase enzyme and produced a network of hydrophobic and hydrophilic interactions. Molecular dynamics simulations were performed for TryR-13 complex to understand its structural and intermolecular affinity stability in a biological environment. The studied complex remained in good equilibrium with a structure deviation of ∼1-3 Å. MM/GBSA binding free energies illustrated the high stability of TryR-13 complex. The studied compounds are promising leads for structural optimisation to enhance the antileishmanial activity.

Are ceramic implant-supported single crowns clinically better than metal-ceramic implant-supported single crowns?

Data sources Data was collected from six databases (Medline, Embase, Web of Science, The Cochrane Central Register of Controlled Trials [CENTRAL], China National Knowledge Infrastructure [CNKI] and Chinese Biomedical Literature Database). Studies published in English and Chinese languages comparing ceramic and metal-ceramic implant-supported fixed dental prostheses (FDPs) were searched. The literature search was performed on studies published until 2018. Manual search of the reference lists of the identified articles was also performed to find related review articles and studies.Study selection Randomised controlled trials (RCTs), prospective and retrospective cohort studies involving the comparison of ceramic and metal-ceramic implant-supported FDPs were selected using the PICOS model for the meta-analysis. For ceramic and metal-ceramic single crowns, the survival rate, marginal adaptation, marginal bone loss, pocket probing depth, crown colour match and mucosal discolouration were assessed. The authors also included studies on survival rate of implant-supported fixed partial dental prostheses (FPDPs) in this meta-analysis.Data extraction and synthesis Two investigators independently screened the articles from the literature search and extracted and analysed data from the included studies. The quality of the included RCTs were assessed using the Cochrane collaboration tool for assessment of risk of bias. For the selected non-randomised studies, the quality and risk of bias were assessed using the Newcastle-Ottawa scale. Twenty studies were included in data synthesis.Results Of the selected 20 studies, ten were RCTs and ten were prospective or retrospective cohort studies.Conclusions The results of this study can be useful to clinicians in making decisions between ceramic and metal-ceramic implant-supported single crowns. This study concluded that the ceramic implant-supported single crown has better crown colour match over a metal-ceramic single crown, but poorer marginal adaptation, and there was no difference observed in other parameters studied (survival rate, marginal bone loss, pocket probing depth and mucosal discolouration). The conclusions on survival rate of implant-supported FPDPs needs to be further evaluated with RCTs with larger samples.

Practice of lingual orthodontics and practitioners' opinion and experience with lingual braces in the United States.

BACKGROUND: A survey was done on practicing Orthodontists in the United States on their experience with lingual orthodontics. The objectives of this survey study were to assess 1) the satisfaction level with cases treated with lingual orthodontics, 2) factors that influence clinicians' decision to utilize or not utilize lingual braces in their current practices, and 3) intention of using lingual braces in their future practices, if not used currently, in the U.S. MATERIAL AND METHODS: A survey questionnaire was electronically distributed to 2,200 active U.S. members of the American Association of Orthodontists (AAO). RESULTS: 85 orthodontists completed the survey. About 25% of respondents practiced lingual orthodontics. Direct mentorship was the most common approach used by orthodontists to learn lingual technique. The most used lingual system among the clinicians that use lingual braces was INBRACE® (34.6%). All respondents were either satisfied or very satisfied with their treatment outcome of cases treated with lingual braces. Improved esthetics and practice differentiation were perceived to be the biggest advantages of practicing lingual orthodontics. Biggest challenges with lingual orthodontics were found to be patient discomfort, cost, longer chair time and technical difficulties. Most common reason for not using lingual braces was technical difficulty, followed by availability of alternative appliances, lack of demand and patient discomfort. Approximately, 70% of those that did not use lingual orthodontics in their current practices responded that they were very likely to incorporate lingual orthodontics in their future practices. CONCLUSIONS: Overall outcome satisfaction level with cases treated with lingual braces was high among the orthodontists that practiced lingual orthodontics. There seemed to be a strong interest in incorporating lingual orthodontics in future practices by clinicians that did not use lingual braces in their current practices. Some of the factors that influenced clinicians' decision to practice lingual orthodontics were improved esthetics, practice differentiation and increased case acceptance. Technical difficulties, availability of alternative appliances, lack of demand and patient discomfort were some of the factors that were identified to have influenced practitioners' decision to not offer lingual orthodontics in their current practices. Key words:Orthodontic brackets, Lingual braces, Lingual orthodontics.

Orthodontists' preference on type of rigid fixed functional appliance for skeletal Class II correction: A survey study.

BACKGROUND: Rigid fixed functional appliances are most commonly used to correct skeletal Class II malocclusions. The objective of this study was to assess orthodontists' preference of different rigid fixed functional appliances used in the U.S.A for correction of skeletal Class II malocclusions. MATERIAL AND METHODS: A survey on use and preference of rigid fixed functional appliances for skeletal Class II correction was emailed to 2,227 members of the American Association of Orthodontists (AAO) in the U.S.A. Frequency distribution of different responses and their association with demographic factors was assessed. RESULTS: Out of 140 orthodontists completing the survey, 110 responded as using rigid fixed functional appliances. Eight incomplete responses were eliminated from data analysis. 51.5% (68/132) orthodontists used rigid fixed functional appliances. The most preferred rigid fixed functional appliance was the Herbst appliance with 72% response followed by Mandibular Anterior Repositioning Appliance (24%) and AdvanSync (4%). There was no statistically significant difference in use of rigid fixed functional appliances between different age groups (p=0.284). However, the 40-54 age group used the most rigid fixed functional appliances in practice, followed by the 25-39 year age group and the 55-69 age group using these appliances the least. There was statistical significance between the type of practice setting one works in and the use of rigid fixed functional appliances in practice (p=0.022). CONCLUSIONS: About 52% of orthodontists use rigid fixed functional appliances to correct skeletal Class II malocclusions. The Herbst appliance is the most commonly used and most preferred amongst all rigid fixed functional appliances with a 72% preferred rate. Key words:Orthodontic, Rigid fixed functional appliance, Skeletal Class II, Class II Malocclusion, Mandibular retrognathism, Herbst, Mandibular Anterior Repositioning Appliance (MARA), AdvanSync, Molar to molar, M2M.

Reductive domino reaction to access chromeno[2,3-c]isoquinoline-5-amines with antiproliferative activities against human tumor cells.

An interaction of homophthalonitrile with salicylaldehydes proceeds as a novel domino reaction and results in the formation of nineteen 12H-chromeno[2,3-c]isoquinoline-5-amine derivatives. Four new bonds and two cycles are forged in a single synthetic operation, employing cheap and eco-friendly ammonium formate, acting both as a catalyst and a reducing agent. The in vitro cytotoxicity tests revealed antiproliferative activities against five human tumor cell lines, including the cisplatin-resistant ovarian carcinoma one (A2780cp8), with inhibitory potency data (IC50) in the low micromolar range in most cases. Molecular docking calculations and fluorescence quenching studies revealed possible binding properties with DNA of the active compounds.

Microwave-Assisted Synthesis of Fluorescent Pyrido[2,3-b]indolizines from Alkylpyridinium Salts and Enaminones.

Pyridinium ylides are well recognized as dipoles for cycloaddition reactions. In its turn, the microwave-assisted interaction of N-(cyanomethyl)-2-alkylpyridinium salts with enaminones unexpectedly proceeds as a domino sequence of cycloisomerization and cyclocondensation reactions, instead of a 1,3-dipolar cycloaddition. The reaction takes place in the presence of sodium acetate as base and employs benign solvents. The optical properties of the resulting pyrido[2,3-b]indolizines were studied, showing green light emission with high fluorescence quantum yields.

Survey on awareness and preference of ceramic bracket debonding techniques among orthodontists.

BACKGROUND: The objectives of this study was to evaluate the awareness of different ceramic bracket debonding techniques among orthodontists in the USA and the most commonly used debonding technique for ceramic bracket removal. MATERIAL AND METHODS: A survey on preference for debonding and awareness of debonding techniques was emailed to 2,227 members of the American Association of Orthodontists (AAO). RESULTS: 119 orthodontists completed the survey. 111 responses were included in the study analysis of ceramic bracket users. The most common technique used was mechanical debonding. 86.5% used a specially designed bracket removing plier from the manufacturer. Overall, there were 59.5% of surveyed orthodontists who were aware of electrothermal debonding, 73% were unaware of ultrasonic debonding and 83.8% were unaware of laser debonding. There were more orthodontists with an affiliation with an academic institution aware of electrothermal debonding (p=0.002). There also was a trend of orthodontists having no affiliation with an institution who were unaware of laser debonding (p=0.015). CONCLUSIONS: This survey showed that the majority of orthodontists who responded to the questionnaire were unaware of alternative debonding techniques of ceramic brackets. All orthodontists who use ceramic brackets utilized mechanical debonding technique. Key words:Orthodontic ceramic brackets, mechanical, electrothermal, ultrasonic, laser debonding.

Aza-Henry and aza-Knoevenagel reactions of nitriles for the synthesis of pyrido[1,2-a]indoles.

N-(Propargyl)indole-2-carbonitriles undergo DBU-catalyzed addition of CH-acids to nitriles, followed by cyclization to give 9-aminopyrido[1,2-a]indoles. The reaction proceeds through the initial formation of a push-pull enamine, alkyne-allene rearrangement and intramolecular nucleophilic cyclization. Nitromethane and malonate esters can be employed as the CH-acids. The resulting compounds were found to exhibit fluorescence properties.

Enhanced Emission of Zinc Nitride Colloidal Nanoparticles with Organic Dyes for Optical Sensors and Imaging Application.

Herein, we have reported on the efficiency of inorganic Zn3N2 nanoparticles for labeling plant cells and animal cells toward imaging applications with negligible toxicity. We have synthesized zinc nitride (Zn3N2) colloidal nanoparticles with an average size of 25 nm at room temperature. The optical band gap of the prepared Zn3N2 nanoparticles is 2.8 eV and gives a visible range emission at 415 nm. With the addition of Zn3N2 colloids to organic dyes such as protoporphyrin, flavin adenine dinucleotide, fluorescein, and neutral red, the emission intensity of the organic dyes enhanced from 3 to 20 times. The molecular simulation and lifetime studies evidence the possibility of energy transfer from zinc nitride to organic dyes. The enhancement of dye intensity in the presence of Zn3N2 enhanced the vicinity of the cellular environment during confocal imaging of plant cells and animal cells. The detailed results suggested Zn3N2 for bioimaging and biosensor applications.

Orthodontic treatment of patient with maxillofacial fibrous dysplasia: A case report.

Fibrous dysplasia is a benign skeletal disorder in which the normal bone and marrow are replaced by fibrous tissue and haphazardly distributed woven bone. The aim of this case report is to discuss the orthodontic treatment of a 13-year-old patient with fibrous dysplasia in the left maxilla. The patient had rotated maxillary second premolars, moderate crowding in both maxillary and mandibular arches with low maxillary frenal attachment. Orthodontic treatment was done with full fixed appliance and extraction of maxillary and mandibular third molars. Maxillary frenectomy and free gingival graft in mandibular anterior region were performed by a periodontist. The oral and maxillofacial surgery team monitored fibrous dysplasia in the left maxilla on a yearly interval. There is very limited information about orthodontic management of patients with craniofacial fibrous dysplasia. This case report discusses the orthodontic treatment and the importance of interdisciplinary approach in the management of patient with maxillofacial fibrous dysplasia. Key words:Orthodontic treatment, fibrous dysplasia, maxillofacial fibrous dysplasia, case report.

Homophtalonitrile for Multicomponent Reactions: Syntheses and Optical Properties of o-Cyanophenyl- or Indol-3-yl-Substituted Chromeno[2,3-c]isoquinolin-5-Amines.

Malononitrile is a useful reagent for multicomponent reactions with hundreds of methods developed. In this paper, we suggest α-(cyano)-o-tolunitrile (homophtalonitrile) to work as a vinylogous malononitrile. Thus, a organocatalytic pseudo-three-component reaction of homopthalonitrile (2 equiv) and o-hydroxybenzaldehyde, leading to the diastereoselective formation of 5-amino-12H-chromeno[2,3-c]isoquinolin-12-yl)(cyano)methyl)benzonitriles, was discovered. The possibility to employ other nucleophiles was demonstrated for indoles, and a sequential three-component reaction of homophtalonitrile, o-hydroxybenzaldehyde, and (aza)indole, giving 12-(1H-Indol-3-yl)-12H-chromeno[2,3-c]isoquinolin-5-amines, was developed. The photophysical properties of the synthesized compounds have been studied, revealing high fluorescence quantum yields (42-70 %) for indol-3-yl substituted 12H-chromeno[2,3-c]isoquinolin-5-amines and reversible fluorescence quenching under acidic conditions.

The effect of orthodontic bracket pad shape on shear bond strength, an in vitro study on human enamel.

BACKGROUND: To evaluate the effect of bracket pad shape on shear bond strength (SBS) of orthodontic brackets bonded to human enamel. MATERIAL AND METHODS: One hundred and five extracted human maxillary permanent molars were divided into 7 groups of 15 specimens per group (n=15). Each group of teeth was bonded with 6 different shaped WildSmiles® brackets (Star, Heart, Soccer ball, Football, Flower, and Diamond) and GAC® rectangle shaped brackets. Shear debonding force was measured with an Instron universal testing machine using a knife-edged chisel 24 hours after initial bonding. Descriptive statistics (mean, standard deviation, and range) for each bracket pad shape was calculated. Analysis of variance (ANOVA) using SPSS software version 24.0 was performed with P-value set at 0.05. Post-Hoc Tukey analysis was used to analyze differences among groups. Differences in Adhesive Remnant Index (ARI) scores among groups were analyzed using Chi-square test. RESULTS: Debonding force values (N ± SD) ranged from 205.51 ± 49.12 (Star) and 275.96 ± 69.05 (Soccer). SBS values (MPa ± SD) ranged from 13.34 ± 3.18 (Star) and 17.77 ± 6.94 (Rectangle). Even though intergroup comparison of SBS in Newtons revealed statistical significance (p = 0.014) between Star-Soccer and Star-Football group, it does not have any clinical significance since ranges of SBS of all groups are clinically acceptable. Analysis of ARI scores showed no significant differences in mode of bond failure among groups (P = 0.82). CONCLUSIONS: Orthodontic bracket pad shape has no effect on SBS and does not affect the mode of fracture pattern. Key words:Shear bond strength, orthodontic bracket, bracket pad shape, orthodontic bracket base shape, adhesive remnant index.

In vitro evaluation of shear bond strength of orthodontic stainless steel brackets using transillumination.

BACKGROUND: The objective of this study was to compare the effect of transillumination techniques to conventional light curing on shear bond strength (SBS) and adhesive remnant index (ARI) of orthodontic stainless steel brackets. MATERIAL AND METHODS: 240 extracted human maxillary incisors, canines and premolars were randomly separated into four control and four experimental groups, based on tooth type. Labio-lingual thickness was measured. Control groups were light cured from buccal surface and experimental groups from lingual surface (transillumination) from four directions (mesial-distal, incisal-direct, direct, mesial-distal-incisal). SBS was measured using an Instron machine and ARI evaluated by microscopic inspection. RESULTS: Mean SBS on maxillary central incisors was lower when cured from lingual side in comparison with buccal side for three light cure directions, but direct cure direction showed nearly equal SBS. Statistical significance was observed for mesial-distal cure direction only. In contrast to central incisors, lateral incisors showed a higher mean SBS when treated from lingual side, for two cure directions (mesial-distal and incisal-direct) with statistical significance observed only for mesial-distal light cure direction. Mean SBS was lower when cured from lingual direction in comparison with buccal direction for all cure directions for canines and premolars. For canines statistical significance was observed for all directions, except incisal-direct; whereas for premolars statistical significance was observed for direct and mesial-distal-incisal directions only. CONCLUSIONS: Transillumination is an effective and clinically acceptable light curing technique for bonding orthodontic stainless steel brackets to maxillary central and lateral incisors. For the other teeth groups (canines and premolars) tested, the mean SBS values, using transillumination light curing fell below the acceptable clinical SBS values, indicating that transillumination is not beneficial in light curing brackets on these teeth. Key words:Orthodontic stainless steel bracket, transillumination, shear bond strength.

The effect of dental chair light exposure duration on shear bond strength of orthodontic brackets: An in vitro study.

BACKGROUND: The purpose of this study is to determine if the duration of exposure to the halogen overhead dental chair light has an effect on shear bond strength (SBS) of metal orthodontic brackets. MATERIAL AND METHODS: One hundred twenty extracted human lower incisor teeth were divided into six groups (n=20/group). Each group was assigned a predetermined duration of exposure to the halogen dental chair light, set at a fixed distance, before being cured. Light exposure times of 0 minutes (Group 1-Control), 1 minute (Group 2), 2.5 minutes (Group 3), 5 minutes (Group 4), 10 minutes (Group 5), and 15 minutes (Group 6) were tested. Each tooth was subjected to an exclusion criteria examination, scrubbed of all debris, and imbedded in a PVC-stone fixture with the crown of the tooth exposed above the stone surface. All groups had orthodontic brackets bonded with the same materials and process, then light cured for 6 seconds using the Valo LED curing unit after their designated light exposure time. Groups were tested using an Instron E-1000 universal testing machine with a shear load test set at a speed of 1mm/min using a knife-edged chisel. Data was analyzed using a one-way ANOVA test. The Adhesive Remnant Index (ARI) was scored under 10x magnification. The ARI data was analyzed using the Chi-square test (p-value < 0.05). RESULTS: All control and experimental groups for each specific tooth type tested resulted in SBS within or above the clinically acceptable range. Statistically significant differences (p<.05) were found between the control and experimental groups for dental chair light exposure times of 5 minutes, 10 minutes and 15 minutes. A chi-square test determined that there was statistical significance when evaluating the frequency of ARI scores when light exposure duration was greater than 5 minutes. CONCLUSIONS: It can be concluded that dental chair light exposure in the 5 minute, 10 minute and 15 minute groups produced higher shear bond strength than those of the control, 1 minute and 2.5 minute groups. The dental chair light is capable of initiating polymerization and causing higher bond strengths than the clinical acceptability of 5.8-7.9 MPa, thus continued dental chair light exposure over 5 minutes is not recommended. The ARI analysis revealed that as bond strength increased, the fracture pattern shifted from most remaining adhesive attached to the tooth toward that attached to the bracket. Key words:Shear bond strength, orthodontic bracket, adhesive remnant index, dental chair light, light exposure, composite curing.