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

The purpose of this study was to evaluate the in vitro effect of orthodontic bracket base shape on shear bond strength (SBS) to human enamel and assess the nature of debonding fractures using the Adhesive Remnant Index (ARI). Orthodontic brackets with different-shaped bases (flower, heart, rectangle) were bonded to 120 extracted human third molars. Shear bond strength was measured using a Servohydraulic Test System at 24 h and 2 months after bonding. Adhesive Remnant Index scores were evaluated under 10x magnification to assess the amount of resin left on the tooth. The control bracket (rectangular base shape) had the highest mean SBS (26.8 ± 8.2 megapascals [MPa]), and significantly differed from the flower (17.2 ± 4.4 MPa) and heart (18.9 ± 3.5 MPa) base shapes (p < 0.001). The mean SBS between debonding times at 24 h (21.5 ± 7.4 MPa) and 2 months (20.4 ± 6.7 MPa) were not statistically significant (p > 0.05). Analysis of ARI scores showed a significant difference between flower-24 h versus heart-2 months (p = 0.039), flower-24 h versus heart-24 h (p = 0.004), and control-2 months versus heart-24 h (p = 0.015). Bracket base shape influenced SBS, with the rectangular base shape having a higher mean SBS compared to flower and heart base shapes. Variations in ARI scores occurred based on bracket shape and were of a mixed adhesive-cohesive nature. All bracket shapes had bond strengths above the clinically acceptable range of 6-8 MPa, and may thus provide adequate SBS in a clinical situation.

Cephalometric effects of Twin-block and van Beek Headgear-Activator in the correction of Class II malocclusion.

INTRODUCTION: The Twin-block (TB) and the van Beek Headgear-Activator (vBHGA) are indicated for patients with Class II malocclusion with a retrognathic mandible. Although the former is commonly prescribed for horizontally growing patients, the latter is often recommended for those growing vertically. This study aimed to compare the skeletal, dentoalveolar, and soft-tissue short-term effects of TB and vBHGA, taking growth patterns into account. METHODS: Immediate prefunctional (T1) and postfunctional appliance (T2) lateral cephalometric radiographs were retrospectively obtained for vBHGA (n = 46), TB (n = 45), and untreated control (n = 45) groups. The interaction of several variables at T1, T2, and T2 - T1, as well as the resultant treatment effect, were analyzed using the analysis of covariance regression models at the 5% significance level. RESULTS: Except for a greater reduction in Wits measurement (3.0 mm; P <0.0001) in the TB group, no anteroposterior (AP) skeletal difference was observed between the 2 appliances (ANB, 0.530; P = 0.07) (Harvold, 0.13 mm; P = 0.81). Both improved the AP skeletal relationship (ANB and Harvold) compared with the control (P <0.05). Although this mostly occurred because of the forward positioning of the mandible with the TB (SNB, 0.960; P = 0.01), the maxillary restriction was the main mechanism with the vBHGA (SNA, 1.590; P <0.01). Dentoalveolar compensations were more pronounced with the TB (IMPA, 1.92; P = 0.02), leading to greater overbite and overjet correction. Only the inclination of the maxillary incisors showed interaction with the growth pattern, with the TB horizontal growers experiencing more retroclination (U1-NA°. 3.620; P = 0.0067). CONCLUSIONS: Both appliances produced similar modest AP skeletal changes that, together with dentoalveolar compensations, were able to correct the Class II malocclusion regardless of growth pattern.

Current status of undergraduate orthodontic education in Canada.

PURPOSE: This study evaluated teaching hours and mode of instruction of undergraduate orthodontic education dental students in Canada receive, changes implemented by each educational dental institution (EDI) in response to the COVID-19 pandemic, and plans for mode of orthodontic education delivery post-COVID-19. METHODS: An electronic survey was administered to the program directors of undergraduate orthodontics at each EDI to reveal details regarding the (i) time and details of didactic, preclinical, and clinical experience provided to students and (ii) perceptions of undergraduate program directors about the adequacy of the current curricula. RESULTS: All 10 Canadian EDIs participated in the survey during the year 2021. Most EDIs deliver their orthodontic curricula beginning in the second year of the program (7, 70.0%), continuing through third (7, 70.0%) and fourth (6, 60.0%) years. The number of hours of didactic, preclinical, and clinical instruction varied by as much as 50 h per academic year across different EDIs. In response to the COVID-19 pandemic, almost all EDIs (9, 90.0%) maintained the same amount of didactic lecture time yet most switched to synchronous (5, 50.0%) or asynchronous (3, 30.0%) online delivery format. Most EDIs (8, 80.0%) indicated the quality of education was maintained during the pandemic. CONCLUSIONS: There exists significant variation in undergraduate orthodontic time allotment among Canadian EDIs. During the COVID-19 pandemic, most Canadian EDIs maintained a consistent amount of teaching hours while transitioning to some form of online course delivery. Most program directors indicated they believed students received the same quality of education after the change in mode of course delivery. The future of undergraduate orthodontic education will likely continue the accelerated trend toward online education.

Adult patient preference for an orthodontic care provider in Canada.

INTRODUCTION: This study evaluated the factors influencing potential orthodontic patients' choice between an orthodontist, general dentist (GD), and direct-to-consumer (DTC) aligners for their treatment and their choice of orthodontic appliance type and explored their motivating factors for seeking orthodontic treatment and preference for appliance type. METHODS: An electronic survey was administered to 330 Canadian adults to determine demographic background, choice of the orthodontic treatment provider, the preferred mode of treatment, orthodontic issues they wished to address, and motivation for treatment. RESULTS: When participants were asked their preference in provider type, 49.4% of participants selected an orthodontist, 19.2% would follow the recommendation of their GD, 18.9% selected a GD, and 12.5% selected DTC aligners. Younger adult participants (P = 0.037) and those living in metropolitan areas (P = 0.0005) were significantly more likely to select an orthodontist than GD or DTC aligners. When asked about their preference in the mode of orthodontic treatment, 45.4% selected clear braces, 34.1% selected clear aligners, 14.3% selected metal braces, and 6.1% indicated they currently have no interest in orthodontic treatment. Older participants (P = 0.0005) and those in moderate-sized population centers (P = 0.001) were significantly more likely to select clear braces or aligners. CONCLUSIONS: Adults in Canada have a high preference for orthodontic treatment performed by orthodontists, especially among younger participants and those in metropolitan areas. Although all ages preferred clear braces, younger adult participants tended to be more open to metal braces, whereas older participants' preference for clear braces was the strongest. Preference for clear aligners is positively correlated to increased community size.

Orthodontists' perceptions of and adaptations to nonspecialist and direct-to-consumer orthodontic service providers.

OBJECTIVES: To evaluate orthodontists' perceived impacts on their practices as a result of general practitioners (GPs) and direct-to-consumer (DTC) orthodontic care providers and the adaptational changes implemented in the past 10 years. MATERIALS AND METHODS: An electronic survey was administered to 270 orthodontists in Canada and the United States to determine demographic background, perception of perceived impact, and specific changes implemented to improve practice competitiveness. RESULTS: More experienced orthodontists (P = .0001) and males (P = .027) were more likely to indicate a perceived impact from GP orthodontics. American orthodontists were significantly more likely than Canadian orthodontists to perceive an impact from DTC providers (P = .017). There was a positive association with orthodontists' years of experience and having implemented adaptational changes to their practice for a period greater than 10 years across multiple categories. Female orthodontists were more likely to have implemented adaptational changes for a period of less than 10 years across multiple categories. CONCLUSIONS: The perceived impact of GPs providing orthodontic care was greater than that of DTC providers. American orthodontists were significantly more likely to perceive an impact from DTC providers. Orthodontists have experienced a reduction in referrals from GPs and an increase in referred case difficulty. Less experienced and female orthodontists have made the most adaptive changes to their practices in the past 10 years.

Quality of life in an adolescent orthodontic population.

OBJECTIVES: To investigate adolescent orthodontic patient experiences and quality of life with fixed appliances compared to Invisalign. MATERIALS AND METHODS: Adolescent patients in active treatment with Invisalign or fixed appliances for a minimum of 6 months were provided with the Child Oral Health Impact Profile-Short Form 19 questionnaire, along with additional items of interest that were assessed separately. Pearson's χ2 test was used to compare responses (P < .05), and unpaired t-tests (P < .05) were used to test for differences in mean satisfaction, quality of life, and domain scores. RESULTS: In total, 74 patients (37 in each treatment group) participated. Overall, no significant differences were noted in the mean quality of life, satisfaction, or domain scores between the two groups. A significant difference was noted in the time taken to adjust to appliances, with the Invisalign group demonstrating faster adaptation. Additionally, the fixed appliance group was 3.8 times more likely to report missing school because of their appliance (95% confidence interval [CI]: 1.2, 12.5) and 2.7 times more likely to report having difficulty eating certain foods (95% CI: 1.1, 7.1). When the sample of females between the ages of 14 and 18 was analyzed, the Invisalign group reported feeling attractive more often than the fixed appliance group. CONCLUSIONS: Both treatment groups were generally very satisfied with their treatment modality. The overall quality of life of adolescent orthodontic patients undergoing treatment with fixed appliances and Invisalign for a minimum of 6 months was similar.

Effect of Low Intensity Pulsed Ultrasound (LIPUS) on Tooth Movement and Root Resorption: A Prospective Multi-Center Randomized Controlled Trial.

The aim of this study was to evaluate the possible effect of low intensity pulsed ultrasound (LIPUS) on tooth movement and root resorption in orthodontic patients. Twenty-one patients were included in a split-mouth study design (group 1). Ten additional patients were included with no LIPUS device being used and this group was used as the negative control group (group 2). Group 1 patients were given LIPUS devices that were randomly assigned to right or left side on upper or lower arches. LIPUS was applied to the assigned side that was obtained by randomization, using transducers that produce ultrasound with a pulse frequency of 1.5 MHz, a pulse repetition rate of 1 kHz, and average output intensity of 30 mW/cm2. Cone-beam computed tomography (CBCT) images were taken before and after treatment. The extraction space dimensions were measured every four weeks and root lengths of canines were measured before and after treatment. The data were analyzed using paired t-test. The study outcome showed that the mean rate of tooth movement in LIPUS side was 0.266 ± 0.092 mm/week and on the control side was 0.232 ± 0.085 mm/week and the difference was statistically significant. LIPUS increased the rate of tooth movement by an average of 29%. For orthodontic root resorption, the LIPUS side (0.0092 ± 0.022 mm/week) showed a statistically significant decrease as compared to control side (0.0223 ± 0.022 mm/week). The LIPUS application accelerated tooth movement and minimized orthodontically induced tooth root resorption at the same time.

Comparison of AdvanSync and intermaxillary elastics in the correction of Class II malocclusions: A retrospective clinical study.

INTRODUCTION: Our objectives were to compare the skeletal, dentoalveolar, and soft tissue effects of the AdvanSync appliance (Ormco, Glendora, Calif) with intermaxillary elastics in the correction of Class II malocclusions in growing patients. METHODS: A retrospective study was conducted using lateral cephalograms of patients taken before and after comprehensive orthodontic treatment; 41 patients consecutively treated with the AdvanSync were compared with 41 similar patients treated with intermaxillary Class II elastics. All patients had significant growth potential during treatment, as assessed by cervical vertebral maturation. A comparison group was generated from historical data bases and matched to the experimental groups for skeletal age, sex, and craniofacial morphology. Treatment changes were evaluated between the time points using a custom cephalometric analysis generating 31 variables as well as regional superimpositions. Data were analyzed using 1-way analysis of variance and Tukey-Kramer tests. RESULTS: The effects of the AdvanSync and fixed orthodontics included maxillary growth restriction, protrusion, proclination, and intrusion of the mandibular incisors as well as mesialization of the mandibular molars (P <0.01). The effects of Class II elastics and fixed orthodontics were similar to AdvanSync, with the exceptions of less maxillary growth restriction and greater retrusion and retroclination of the maxillary incisors (P <0.01). Significant mandibular growth stimulation, relative to the untreated controls, did not occur with either modality. CONCLUSION: AdvanSync and intermaxillary elastics were effective in normalizing Class II malocclusions during comprehensive fixed orthodontics. AdvanSync produced its effects through maxillary skeletal growth restriction and mandibular dentoalveolar changes. Class II elastics worked primarily through dentoalveolar changes in both the maxilla and the mandible.

An investigation into bisphenol A leaching from materials used intraorally.

BACKGROUND: In this study, the authors quantitatively determined the bisphenol A (BPA) leached from intraoral materials during simulated intraoral exposure. METHODS: The authors subjected samples of intraoral materials to simulated abrasion, immersion in artificial saliva, thermal shock via temperature cycling, and simulated intraoral exposure. The authors collected sample aliquots for up to 2 weeks after artificial saliva immersion, derivatized, and then analyzed the aliquots for BPA by gas chromatography and mass spectroscopy. RESULTS: Quantifiable amounts of leached BPA were observed from only 1 of 13 intraoral materials tested: a silicone baby bottle nipple (20 micrograms). BPA leaching was only observed after 3 days of artificial saliva immersion, with no additional leaching thereafter. CONCLUSIONS: Under the test conditions, BPA was observed to leach from a silicone baby bottle nipple. PRACTICAL IMPLICATIONS: Although the quantities of leached BPA were below the reference dose for daily intake, investigators have shown a possible association between low levels of BPA and many medical disorders. BPA exposure, and thus the use of the leaching material identified in this study, should be reduced or eliminated.

Changes in mandibular incisor position and arch form resulting from Invisalign correction of the crowded dentition treated nonextraction.

OBJECTIVE: To investigate changes in mandibular incisor position resulting from Invisalign correction of the crowded dentition without extraction. MATERIALS AND METHODS: A retrospective chart review was completed on 61 adult White patients. Patients were categorized into three groups based on the value of pretreatment crowding of the lower dentition: 20 mild (2.0-3.9 mm), 22 moderate (4.0-5.9 mm), and 19 severe (>6.0 mm). Cephalometric radiographs were measured to determine lower incisor changes. Interproximal reduction and changes in arch width were also measured. Statistical evaluation of T0 and T1 values using paired t-tests and analysis of covariance were applied to evaluate mean value changes. RESULTS: Lower incisor position and angulation changes were statistically significant in the severe crowding group. There were no statistically significant differences in lower incisor position between the mild and moderate crowding groups. There was a statistically significant increase in buccal expansion in each of the three groups. CONCLUSIONS: Invisalign(®) treatment can successfully resolve mandibular arch crowding using a combination of buccal arch expansion, interproximal reduction, and lower incisor proclination. When there is <6 mm of crowding, lower incisor position remained relatively stable. The lower incisors proclined and protruded in the more severely crowded dentitions (>6 mm).

Differences in the gingival crevicular fluid composition between adults and adolescents undergoing orthodontic treatment.

OBJECTIVES: To investigate differences in the gingival crevicular fluid (GCF) composition between adolescent and adult patients undergoing orthodontic treatment with fixed appliances. MATERIALS AND METHODS: Ten adolescents (14.4 ± 1.43) and 10 adults (28.5 ± 7.83) with Class I malocclusions and minor upper incisor crowding were allocated to two different age groups. Brackets were bonded only in the upper arch over the 20-week period of the experiment. Samples of GCF were collected from the labial sides of the upper incisors (experimental sites) and lower incisors (control sites) of each subject at five time points. Aliquots from diluted GCF were screened for the presence of receptor activator of nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG), interleukin-1 (IL-1), interleukin-1 receptor antagonist (IL-1RA), and metalloproteinase-9 (MMP-9) using a microarray technique. The values were statistically analyzed. RESULTS: In adults, the ratio of IL-1 to IL-1RA decreased significantly (P  =  .033) in experimental sites 3 weeks after appliance placement and first archwire activation. In adolescents, the ratio of RANKL to OPG peaked 6 weeks after the insertion of the first rectangular archwire. This ratio peak found in adolescents was a consequence of a decrease in the mean concentration of OPG. No significant changes over time were observed in the concentration of MMP-9. CONCLUSION: This study demonstrates age trends in the GCF levels of IL-1, IL-1RA, RANKL, and OPG that may be used to track differences in tissue response between adults and adolescents undergoing orthodontic treatment.

An investigation into bisphenol-A leaching from orthodontic materials.

OBJECTIVE: To quantitatively determine the bisphenol-A (BPA) leached from orthodontic materials during simulated intraoral exposure. MATERIALS AND METHODS: Samples of orthodontic materials were subjected to simulated abrasion, immersion in artificial saliva, thermal shock via temperature cycling, and simulated intraoral exposure. Sample aliquots were collected for up to 2 weeks after artificial saliva immersion, derivatized, then analyzed for BPA by gas chromatography/mass spectroscopy. RESULTS: Quantifiable amounts of leached BPA were observed from a thermoformed orthodontic retainer material (7.63 µg/g of material) and an orthodontic adhesive (2.75 µg/g of material). BPA leaching was only observed within the first 3 days of artificial saliva immersion. CONCLUSIONS: Under the test conditions, BPA was observed to leach from two orthodontic materials. While the quantities of leached BPA were below the reference dose for daily intake, existing data of low-dose effects and medical disorders associated with elevated urinary BPA levels suggest that BPA exposure, and thus the use of the leaching materials identified in this study, should be reduced or eliminated.

Use of cone-beam computed tomography in the diagnosis of sensory nerve paresthesia secondary to orthodontic tooth movement: a clinical report.

In this article, we report an incident of transient neuropathy secondary to tooth movement involving the inferior alveolar nerve. This clinical report reflects the need to thoroughly examine potentially high-risk patients for neuropathy using advanced diagnostic tools such as cone-beam computed tomography when diagnosing and planning treatment.

Digital analysis of staining properties of clear aesthetic brackets.

OBJECTIVE: To analyse the staining properties of clear orthodontic brackets using a digital analysis. DESIGN: In vitro, laboratory study MATERIAL AND METHODS: A total of 500 tooth-coloured brackets from 10 brands (five ceramic and five plastic) were investigated. The cumulative discolouring effect of staining agents (tea, coffee, curry and red wine) were analysed at two consumption levels: light and heavy, based on a 6-month period of exposure. Study group brackets were immersed in the agents consecutively at 37°C. The control group was only exposed to artificial saliva. Samples were analysed digitally to obtain L*, a* and b* (lightness, red-green and yellow-blue) colour readings. Using these values, total colour change (ΔE*) at each level was also calculated. Three-way analysis of variance (ANOVA) test was used for statistical comparisons. RESULTS: L* and b* colour parameters showed significant differences (P<0·001) between different bracket groups, consumption levels and the type of exposure. However, the a* value only differed between bracket groups (P<0·001). According to the ΔE* values, ceramic brackets had less colour change than plastic brackets at the end of phase 1 for both the study and control groups. However, as consumption time increased, the rate of colour change decreased for the plastic brackets. In general, ceramic brackets demonstrated much more resistance to staining agents than plastic brackets. CONCLUSIONS: Both plastic and ceramic brackets showed changes in colour when exposed to heavy consumption of staining agents, with plastic brackets being the most affected.

Relapse of orthodontically corrected deepbites in accordance with growth pattern.

INTRODUCTION: A common orthodontic problem is a deep overbite malocclusion. Because of its high relapse tendency, it is also one of the most challenging problems to treat. To minimize relapse, the morphologic characteristics of patients need to be considered. The aim of this study was to compare deepbite relapse in 3 groups of patients categorized by vertical growth type. METHODS: The total sample included 60 patients treated at the University of Washington in Seattle, all with initial overbites greater than 50%. Data were collected from casts and cephalometric radiographs at 3 time points: pretreatment, posttreatment, and 10 years postretention. A mixed-effects model (analysis of variance) and post-hoc t tests were used for the statistical evaluations. RESULTS: The high-angle subjects showed the least deepbite relapse (0.1 ± 1.1 mm), whereas the low-angle (1.2 ± 0.9 mm) and the normal-angle (1.4 ± 1.3 mm) subjects had statistically significant relapses P <0.001. This overbite relapse might be partially due to changes in the mandibular and interincisal angles, which were also observed in these 2 groups. CONCLUSIONS: High-angle subjects tend to relapse less in overbite than do low-angle and normal-angle subjects in the long term.

Motivations of orthodontic residents in Canada and the United States to treat patients with craniofacial anomalies, cleft lip/palate, and special needs.

OBJECTIVES: To determine the motivation of orthodontic residents in Canada and the United States to treat patients with cleft lip/palate (CLP), craniofacial anomalies (CFA), and special needs (SN). METHODS: In March 2009, an e-mail with a link to a 41-item survey was sent to all orthodontic residents in Canada and the United States (n  =  944). RESULTS: Of 944 residents contacted, 339 viewed and 208 completed the survey (22.03%). Using a seven-point Likert scale, residents recognized the importance of treating patients with CLP/CFA/SN. When asked if they plan to treat patients with CLP/CFA/SN, 54.48% responded yes, 13.46% no, and 36.06% were unsure. A total of 38.05% said they would charge the same fee as a typical multiarch case, while 58.05% would charge more, and 60% of fourth-year residents would charge twice the fee. Of the respondents, 43.00% were aware of the established fellowship programs in CLP/CFA/SN. Canadian residents (67.9%) were more enthusiastic about completing a fellowship than Americans were. Of the respondents, 29.33% would complete a 1-year fellowship, while 70.67% would not. A total of 78.4% of male respondents and 77.4% of American residents indicated they would not pursue a fellowship. CONCLUSIONS: Residents supported the importance of treating patients with CLP/CFA/SN, and more than 54% indicated they plan to treat these patients. Residents who indicated that they would not treat these patients sited limited experience and inadequate expertise as the reasons. Less than 30% indicated a willingness to pursue a fellowship program.

Effect of tooth bleaching on shear bond strength of a fluoride-releasing sealant.

OBJECTIVE: To evaluate the effect of an in-office plus at-home bleaching protocol on shear bond strength of orthodontic buttons when using a fluoride-releasing sealant. MATERIALS AND METHODS: Extracted human molars (160) were randomly divided into bleached (n  =  80) and unbleached groups (n  =  80). The bleached group was treated with 45% carbamide peroxide for 30 minutes, followed by five applications of 20% carbamide peroxide at 24-hour intervals. After 2 weeks, lingual buttons were bonded on the teeth in both groups using either Transbond XT primer or Pro Seal sealant. The teeth were then stored in artificial saliva and subjected to shear testing at 24 hours and 3 months using a Zwick Universal Test Machine. Comparisons of mean shear bond strength values were made with the analysis of variance test. The Fisher's exact test was used to evaluate the adhesive remnant index scores. RESULTS: The analysis of variance of the 24-hour results indicated a significant difference between the four subgroups (P < .0011). Further simple t-tests indicated that the differences were significant only between bleached and unbleached subgroups (P < .0011). The 3-month results showed the mean shear bond strengths of the unbleached group using Pro Seal sealant was significantly lower than that of the other, though still greater than clinically minimal suggested bond strengths. Interestingly, 15% of the bleached teeth exhibited enamel fracture at the 3-month testing. CONCLUSION: Both Pro Seal sealant and Transbond XT primer demonstrated reliable shear bond strength values on both bleached and unbleached teeth over time.

Impact of orthodontic retainers on periodontal health status assessed by biomarkers in gingival crevicular fluid.

OBJECTIVE: To evaluate whether biomarkers of inflammation and periodontal remodeling are differentially expressed in the gingival crevicular fluid (GCF) of patients wearing different types of orthodontic retainers. MATERIALS AND METHODS: Thirty-one adult subjects (17 men and 14 women with an age range of 20 to 35 years) were allocated to three different groups. Group 1 consisted of 10 patients wearing fixed retainers, group 2 included 11 patients using lower removable retainers, and group 3 comprised 10 patients without retainers (control). Periodontal health assessment and GCF collection were carried out at two sites per subject: the lingual side of a central lower incisor and the lingual side of a lower second premolar. Aliquots from diluted GCF were screened for the presence of biomarkers using a microarray technique. RESULTS: Group 1 patients exhibited a higher percentage of sites with visible plaque in the incisor region than the other groups (P = .03); no differences were noted in gingival bleeding and probing depths. The median concentrations (pg/mL) of interferon-gamma and interleukin-10 were significantly higher in the premolar sites of patients in group 2 (P = .01 and P = .04, respectively), whereas the concentration of matrix metalloproteinase-9 was significantly higher at the incisors of patients wearing fixed retainers (P = .02). A significant difference between the two sites was seen only in group 2. CONCLUSIONS: The presence of different orthodontic retainers may promote specific alterations in the GCF composition. With retention periods potentially becoming longer, this finding may be of clinical significance.