Scoring facial attractiveness with deep convolutional neural networks: How training on standardized images reduces the bias of facial expressions.

OBJECTIVE: In many medical disciplines, facial attractiveness is part of the diagnosis, yet its scoring might be confounded by facial expressions. The intent was to apply deep convolutional neural networks (CNN) to identify how facial expressions affect facial attractiveness and to explore whether a dedicated training of the CNN is able to reduce the bias of facial expressions. MATERIALS AND METHODS: Frontal facial images (n = 840) of 40 female participants (mean age 24.5 years) were taken adapting a neutral facial expression and the six universal facial expressions. Facial attractiveness was computed by means of a face detector, deep convolutional neural networks, standard support vector regression for facial beauty, visual regularized collaborative filtering and a regression technique for handling visual queries without rating history. CNN was first trained on random facial photographs from a dating website and then further trained on the Chicago Face Database (CFD) to increase its suitability to medical conditions. Both algorithms scored every image for attractiveness. RESULTS: Facial expressions affect facial attractiveness scores significantly. Scores from CNN additionally trained on CFD had less variability between the expressions (range 54.3-60.9 compared to range: 32.6-49.5) and less variance within the scores (P ≤ .05), but also caused a shift in the ranking of the expressions' facial attractiveness. CONCLUSION: Facial expressions confound attractiveness scores. Training on norming images generated scores less susceptible to distortion, but more difficult to interpret. Scoring facial attractiveness based on CNN seems promising, but AI solutions must be developed on CNN trained to recognize facial expressions as distractors.

Leaching from a 3D-printed aligner resin.

AIM: To quantitatively assess the degree of conversion and the water-leaching targeted compound from 3D-printed aligners. MATERIALS AND METHODS: 3D-printed aligners were made of photopolymerized resin (Tera Harz TC85A). The molecular structure and degree of conversion of the set resin were investigated by ATR-FTIR spectroscopy (n = 5). The aligners (n = 10) were immersed in double distilled water for 1 week at 37°C and the eluents were analysed using liquid chromatography/mass spectrometry methods (LC-ESI-MS/MS for urethane dimethacrylate [UDMA] and LC-APCI-MS/MS for bispenol-A [BPA]). RESULTS: The resin was composed of aliphatic vinyl ester-urethane monomers, with acrylate and/or methacrylate functionalization. The degree of conversion was estimated as to 83%. There was no detection of BPA in any of the assessed samples (0.25 µg/l). Quantifiable amounts of UDMA were detected in all the exposed samples, ranging from 29 to 96 µg/l. CONCLUSIONS: Although efficiently polymerized and BPA free, the great variability in the amount of UDMA monomer leached from the examined samples may raise concerns on potential health hazards after repeated intraoral exposure, which is indicated for this class of materials.

Artificial intelligence in medico-dental diagnostics of the face: a narrative review of opportunities and challenges.

OBJECTIVES: This review aims to share the current developments of artificial intelligence (AI) solutions in the field of medico-dental diagnostics of the face. The primary focus of this review is to present the applicability of artificial neural networks (ANN) to interpret medical images, together with the associated opportunities, obstacles, and ethico-legal concerns. MATERIAL AND METHODS: Narrative literature review. RESULTS: Narrative literature review. CONCLUSION: Curated facial images are widely available and easily accessible and are as such particularly suitable big data for ANN training. New AI solutions have the potential to change contemporary dentistry by optimizing existing processes and enriching dental care with the introduction of new tools for assessment or treatment planning. The analyses of health-related big data may also contribute to revolutionize personalized medicine through the detection of previously unknown associations. In regard to facial images, advances in medico-dental AI-based diagnostics include software solutions for the detection and classification of pathologies, for rating attractiveness and for the prediction of age or gender. In order for an ANN to be suitable for medical diagnostics of the face, the arising challenges regarding computation and management of the software are discussed, with special emphasis on the use of non-medical big data for ANN training. The legal and ethical ramifications of feeding patients' facial images to a neural network for diagnostic purposes are related to patient consent, data privacy, data security, liability, and intellectual property. Current ethico-legal regulation practices seem incapable of addressing all concerns and ensuring accountability. CLINICAL SIGNIFICANCE: While this review confirms the many benefits derived from AI solutions used for the diagnosis of medical images, it highlights the evident lack of regulatory oversight, the urgent need to establish licensing protocols, and the imperative to investigate the moral quality of new norms set with the implementation of AI applications in medico-dental diagnostics.

Craniofacial growth and SITAR growth curve analysis.

BACKGROUND: SITAR (SuperImposition by Translation And Rotation) is a shape invariant growth curve model that effectively summarizes somatic growth in puberty. AIM: To apply the SITAR model to longitudinal mandibular growth data to clarify its suitability to facial growth analysis. SUBJECTS AND METHODS: 2D-cephalometric data on two mandibular measurements (AP: articulare-pogonion; CP: condylion-pogonion) were selected from the Denver Growth Study, consisting of longitudinal records (age range: 7.9-19.0 years) of females (sample size N: 21; number of radiographs n: 154) and males (N: 18; n: 137). The SITAR mixed effects model estimated, for each measurement and gender separately, a mean growth curve versus chronological age, along with mean age at peak velocity (APV) and peak velocity (PV), plus subject-specific random effects for PV and mean size. The models were also fitted versus Greulich-Pyle bone age. RESULTS: In males, mean APV occurred at 14.6 years (AP) and 14.4 years (CP), with mean PV 3.1 mm/year (AP) and 3.3 mm/year (CP). In females, APV occurred at 11.6 years (AP and CP), with mean PV 2.3 mm/year (AP) and 2.4 mm/year (CP). The models explained 95-96 per cent of the cross-sectional variance for males and 92-93 per cent for females. The random effects demonstrated standard deviations (SDs) in size of 5.6 mm for males and 3.9 mm for females, and SDs for PV between 0.3 and 0.5 mm/year. The bone age results were similar. CONCLUSION: The SITAR model is a useful tool to analyse epidemiological craniofacial growth based on cephalometric data and provides an array of information on pubertal mandibular growth and its variance in a concise manner.

Using artificial intelligence to determine the influence of dental aesthetics on facial attractiveness in comparison to other facial modifications.

BACKGROUND: Facial aesthetics is a major motivating factor for undergoing orthodontic treatment. OBJECTIVES: To ascertain-by means of artificial intelligence (AI)-the influence of dental alignment on facial attractiveness and perceived age, compared to other modifications such as wearing glasses, earrings, or lipstick. MATERIAL AND METHODS: Forty volunteering females (mean age: 24.5) with near perfectly aligned upper front teeth [Aesthetic Component scale of the Index of Orthodontic Treatment Need (AC-IOTN) = 1 and Peer Assessment Rating Index (PAR Index) = 0 or 1] were photographed with a standardized pose while smiling, in the following settings (number of photographs = 960): without modifications, wearing eyeglasses, earrings, or lipstick. These pictures were taken with natural aligned dentition and with an individually manufactured crooked teeth mock-up (AC-IOTN = 8) to create the illusion of misaligned teeth. Images were assessed for attractiveness and perceived age, using AI, consisting of a face detector and deep convolutional neural networks trained on dedicated datasets for attractiveness and age prediction. Each image received an attractiveness score from 0 to 100 and one value for an age prediction. The scores were descriptively reviewed for each setting, and the facial modifications were tested statistically whether they affected the attractiveness score. The relationship between predicted age and attractiveness scores was examined with linear regression models. RESULTS: All modifications showed a significant effect (for all: P < 0.001) on facial attractiveness. In faces with misaligned teeth, wearing eyeglasses (-17.8%) and earrings (-3.2%) had an adverse effect on facial aesthetics. Tooth alignment (+6.9%) and wearing lipstick (+7.9%) increased attractiveness. There was no relevant effect of any assessed modifications or tooth alignment on perceived age (all: <1.5 years). Mean attractiveness score declined with predicted age, except when wearing glasses, in which case attractiveness was rated higher with increasing predicted age. CONCLUSIONS: Alignment of teeth improves facial attractiveness to a similar extent than wearing lipstick, but has no discernable effect on perceived age. Wearing glasses reduces attractiveness considerably, but this effect vanishes with age.

Improving headgear wear: why force level and direction of traction matter.

BACKGROUND: Empiric data on headgear wear are scarce. The aim was to examine a possible discrepancy between the duration of wearing and force application, and whether such a difference is influenced by force level or direction of traction. MATERIALS AND METHODS: In this retrospective analysis, 122 consecutive patients were included. All were treated with headgear (three subgroups: high-pull headgear [n = 60], cervical-pull headgear [n = 32], and high-pull headgear in combination with an activator [n = 30]) and were monitored for three successive months using an electronic module. The device recorded chronographically the measured force magnitude and temperature, allowing to differentiate between the duration of headgear wear (recorded body temperature) and actual force application (recorded force). RESULTS: For all subgroups, the average recorded force application was lower than wear time (mean inactivity during wear: 15.9 ± 22.8 minutes/night). The direction of traction significantly influenced the extent and length of wear time without force application (P < 0.001): patients with cervical-pull headgear were more prone to inactive wear time (27.7 minutes/night) than patients with high-pull headgear (13.7 minutes/night) or with headgear-activator (7.8 minutes/night). The observed inter-individual variability of inactive wear time was considerable (0-134 minutes/night). The mean applied force was highly significantly associated with inactive wear time (correlation coefficient: -0.575; P < 0.001), and force levels below 250 g seem particularly related to episodes of inactivity. CONCLUSIONS: There is a clear incongruity between the duration of headgear wear and the duration of force application. Inactive wear time is influenced by the direction of traction and force level applied. Clinicians should be aware of the likelihood of periods of inactive wear time and researchers should search for options to reduce or even eliminate these periods.

Post-orthodontic retention: how much do people deciding on a future orthodontic treatment know and what do they expect? A questionnaire-based survey.

OBJECTIVE: This cross-sectional study aimed to explore the level of knowledge and expectations people deciding on a future orthodontic treatment have about post-orthodontic retention and to investigate the influence of sociocultural characteristics. MATERIAL AND METHODS: A total of 227 consecutive people involved as legal decision maker (as patient, parent, or legal guardian) for a prospective orthodontic treatment (mean age 37.1 years; 37.3 per cent male) received before their first appointment a questionnaire to assess their knowledge and expectations about post-orthodontic retention. Data were analysed descriptively, whereas predictors were identified with logistic regressions at P value of less than or equal to 0.05. RESULTS: Among the 220 responders, 46.3 per cent (n = 99) knew that retention appliances are used after orthodontic treatment and 52.8 per cent (n = 113) believed perfect results can guarantee stability, whereas at the same time, 77.8 per cent (n = 168) knew that teeth can move on their own without any orthodontic appliances. The majority considered stability of the orthodontic result important or extremely important (94.5 per cent; n = 206), preferred bonded over removable retainers (67.2 per cent; n = 133), believed the orthodontist to be primarily responsible for a stable result (73.2 per cent; n = 158), and found it appropriate to charge for recall visits (72.9 per cent; n = 153). Participants' gender, age, education, nationality, and past orthodontic experiences within the close family significantly influenced answers. LIMITATIONS: The setting of a single-centred survey conducted in one university moderates the generalizability of the portrayed results. CONCLUSIONS: Although stability of orthodontic treatment results is very important to people deciding about a prospective orthodontic treatment, knowledge regarding the need for post-orthodontic retention varies and may at times be contradictious. Sociocultural factors seem to influence the level of knowledge and the expectations on post-orthodontic retention.

Roughness and wettability of aligner materials.

OBJECTIVE: The characterisation of surface roughness and energy of contemporary thermoplastic materials used in manufacturing of orthodontic aligners. DESIGN: In vitro, laboratory study. MATERIALS AND METHODS: Four commercially available thermoplastic materials were selected (CA-medium/CAM, Essix-copopyester/COP, Duran/DUR and Erkodur/ERK). Five disks from each, as received, material were tested and subjected to: (1) reflected light microscopy; (2) optical profilometry for the estimation of Sa, Sz, Sq, Sdr, Sc, Sv surface roughness parameters (n = 5); and (3) contact angle measurements with a Zisman series of liquids for the estimation of critical surface tension (γC), total work of adhesion (WA), as well as the work of adhesion due to polar (WP) and dispersion (WD) components employing the Zisman method (n = 5/liquid). Thermoformed disks were prepared against a dental stone model and the roughness parameters were calculated again Statistical analysis was performed by one-way ANOVA/ Tukey multiple comparison test and t-test (a = 0.05). RESULTS: Microscopic and profilometric analyses revealed a smooth surface texture in the as-received materials, but a very rough texture after thermoforming, with insignificant differences within each state. Significant differences in the as-received state were found in the surface energy parameters; CAM showed the lowest γC and the highest WA, WP, WD, whereas ERK with the highest γC demonstrated lower WA. COP and DUR were ranked in an intermediate group regarding γC, with a statistically significant difference in WA between them, mainly attributed to the lower WP of the former. CONCLUSION: Given the differences in surface energy parameters and the lack of roughness differences within the as received or thermoformed groups, it may be concluded that variations in the plaque retaining capacity are anticipated, determined by γC, WA and the WP, WD components.

Emotions experienced during the shedding of the first primary tooth.

AIM: To examine the different emotions expressed by children exfoliating their first primary tooth, evaluate their proportional distribution, and reveal possible influences of child- and parent-related variables on the reported emotions. DESIGN: A cross-sectional questionnaire was directed to parents of children who had recently shed at least one primary tooth. Primary outcome variables were the child's emotions at the time of exfoliation. Child-related determinants were sex, duration of tooth wiggle, previous accident- or caries-related visits at dentist, and having witnessed tooth exfoliation in older siblings. Parent-related determinants included socio-economic variables (education, religion, country of origin). RESULTS: One thousand two hundred and seventy-four of 3617 questionnaires were returned and analysed (35.2%). 82.0% of the parents reported positive, and 22.0% negative emotions in their child. Previous caries-related visits at the dentist diminished the likelihood of positive emotions (OR = 0.65), and accident-related visits increased the odds of positive emotions (OR = 1.57), as did an extended duration of tooth wiggle (OR = 1.98). Higher education of mothers (OR = 2.89) and fathers (OR = 1.96) and an origin from non-Western countries (OR = 2.56 and OR = 1.85, respectively) were also related to positive emotions. CONCLUSIONS: For most children, losing the first primary tooth is associated with positive emotions. Dental visits and parental factors influence these emotions. Parents and dentists should be aware of their impact on children's emotional development.

Facial attractiveness of cleft patients: a direct comparison between artificial-intelligence-based scoring and conventional rater groups.

OBJECTIVES: To evaluate facial attractiveness of treated cleft patients and controls by artificial intelligence (AI) and to compare these results with panel ratings performed by laypeople, orthodontists, and oral surgeons. MATERIALS AND METHODS: Frontal and profile images of 20 treated left-sided cleft patients (10 males, mean age: 20.5 years) and 10 controls (5 males, mean age: 22.1 years) were evaluated for facial attractiveness with dedicated convolutional neural networks trained on >17 million ratings for attractiveness and compared to the assessments of 15 laypeople, 14 orthodontists, and 10 oral surgeons performed on a visual analogue scale (n = 2323 scorings). RESULTS: AI evaluation of cleft patients (mean score: 4.75 ± 1.27) was comparable to human ratings (laypeople: 4.24 ± 0.81, orthodontists: 4.82 ± 0.94, oral surgeons: 4.74 ± 0.83) and was not statistically different (all Ps ≥ 0.19). Facial attractiveness of controls was rated significantly higher by humans than AI (all Ps ≤ 0.02), which yielded lower scores than in cleft subjects. Variance was considerably large in all human rating groups when considering cases separately, and especially accentuated in the assessment of cleft patients (coefficient of variance-laypeople: 38.73 ± 9.64, orthodontists: 32.56 ± 8.21, oral surgeons: 42.19 ± 9.80). CONCLUSIONS: AI-based results were comparable with the average scores of cleft patients seen in all three rating groups (with especially strong agreement to both professional panels) but overall lower for control cases. The variance observed in panel ratings revealed a large imprecision based on a problematic absence of unity. IMPLICATION: Current panel-based evaluations of facial attractiveness suffer from dispersion-related issues and remain practically unavailable for patients. AI could become a helpful tool to describe facial attractiveness, but the present results indicate that important adjustments are needed on AI models, to improve the interpretation of the impact of cleft features on facial attractiveness.

Tooth Fairy guilty of favouritism!

OBJECTIVES: To determine the proportion of children visited by the Tooth Fairy, the child-related factors that influence the likelihood of her visit, and the parent-related variables that affect the amount of money the Tooth Fairy leaves. DESIGN: Cross-sectional questionnaire study. SETTING: Zürich, Switzerland. PARTICIPANTS: 3617 parents of children (mean age of children, 6.8 years; 51.9% girls) who had lost at least one deciduous tooth received a self-developed questionnaire; 1274 questionnaires were returned (35.2%). MAIN OUTCOME MEASURES: Primary outcome variables were the Tooth Fairy's visit after tooth loss and the amount of money given in case of a visit. Child- and parent-related variables were assessed as predictors of the main outcomes. RESULTS: Most parents (71.0%) reported that the Tooth Fairy visited their child. She usually exchanged the lost tooth for money (55.8% of visits) or placed money next to the tooth (40.7%); rarely did she take the tooth without pecuniary substitution. The Tooth Fairy left an average of 7.20 Swiss francs (approximately AU$9.45). The Tooth Fairy favoured visiting for the teeth of older children (odds ratio [OR], per year, 1.87; 95% CI, 1.09-3.21), of boys (OR, 2.65; 95% CI, 1.09-6.42), and of children who believed in her (OR, 4.12; 95% CI, 1.77-9.64). The amount of money was influenced by maternal, but not paternal socio-demographic factors, including level of education (OR, per level, 0.78; 95% CI, 0.66-0.92) and country of origin (OR, Western countries v non-Western countries, 2.35; 95% CI, 1.20-4.62). CONCLUSIONS: The Tooth Fairy does not visit all children after tooth loss, displaying clear preferences in her choice of business partners. The odds of a visit are dramatically increased if she is believed in, and the value of a deciduous tooth is influenced by socio-demographic factors.

Cleaning Efficacy of Manual Toothbrushes Around Brackets - A Pilot Randomised Control Trial.

PURPOSE: To test the cleaning efficacy of different manual toothbrushes in orthodontic patients in a single-blind randomised clinical trial. The brushes tested were selected based on previous in vitro tests. MATERIALS AND METHODS: Thirty-five regular orthodontic patients with a minimum of six bonded brackets on the maxillary anterior teeth were randomly assigned to three experimental groups: staged (2-level) (Candida Parodin, 12 patients) and V-shaped (Oral-B Ortho, 12 patients) toothbrush head designs were compared in a two-phase study to planar control brushes (Paro M 43, 11 patients). First, all participants were advised to brush their teeth twice daily for 2 min for 3 weeks. Prior to the start and at the end of the study, the gingival index was assessed to evaluate the level of oral hygiene. Afterwards, cleaning efficacy was assessed planimetrically by disclosing the respective teeth after two days of not performing any oral hygiene measures. RESULTS: Of the initial 35 participants, two did not attend after 3 weeks and had to be excluded. After 3 weeks, the control (5 out of 180 sites or -2.8% with GI ≥ 2) and staged groups (16 out of 216 sites or 7.5% with GI ≥ 2) showed minor improvement in the oral hygiene level. In contrast, the V-shaped group (29 out of 198 sites or 14.6 % with GI ≥ 2) showed a statistically significant improvement of the oral hygiene level. Planimetric evaluation, however, showed no superior cleaning efficacy of any of the tested head designs. CONCLUSIONS: The use of V-shaped and staged toothbrush head designs might be beneficial in patients with inadequate oral hygiene undergoing orthodontic treatment with a fixed appliance. Further large-scale investigations are, however, necessary to validate the presented results.

The nasopalatine canal, a limiting factor for temporary anchorage devices: a cone beam computed tomography data study.

OBJECTIVES: There is only little knowledge on topographical predispositions of the nasopalatine canal as a limiting factor for insertion of mid-palatal temporary anchorage devices (TAD). The purpose of the study was to assess the course of the nasopalatine canal, the adjacent vertical bone quantity, and whether it might differ among vertical facial types, using pre-existing cone beam computed tomography (CBCT) scans. MATERIAL AND METHODS: Out of a consecutive sample collected from April 2008 to August 2012, only patient data depicting both upper and lower jaw completely were evaluated retrospectively. The linear measurements were taken on the respective midsagittal view perpendicular to the palate at the level of 1st molar/2nd premolar (5/6), 2nd premolar/1st premolar (4/5), and 1st premolar/canine (3/4). Screen-prints were used to measure the inclination of the nasopalatine canal in relation to the maxillary jaw base. Maxillary and mandibular divergence was assessed on rendered lateral cephalograms. RESULTS: Out of 3869 pre-existing consecutive CBCT scans, data from 398 patients met the inclusion criteria and could be extracted. The mean vertical bone was 4.09 mm at the 5/6 level, 5.22 mm at the 4/5 level, and 3.14 mm at the 3/4 level, respectively. A statistically significant negative correlation exists between jaw divergence and the canal angulation with regard to the maxillary base. A statistically significant negative correlation exists between the canal angulation and vertical bone measurements at the 4/5 and 3/4 levels. CONCLUSIONS: Vertical bone volume is sufficient at 4/5 level for TAD placement, and bares only a small risk for neuro-sensory impairment. Therefore, only in rare cases a CBCT is justified for palatal implant placement. The course of the nasopalatine canal is negatively correlated with the vertical skeletal facial pattern pointing to the fact that in hypodivergent patients a TAD might be placed in a more distal or paramedian region.

Evidence of secular trend in mandibular pubertal growth.

BACKGROUND: During puberty, mandibular growth follows a growth curve comparable to somatic growth. This study aimed to review the relationship between mandibular pubertal peak height velocity (PHV) and skeletal age, and to investigate the possibility of a secular trend. METHODS: Retrospective analysis was performed of two historical craniofacial growth studies (Denver Growth Study; observational time: 1943-1965, and Zurich Growth Study; observational time: 1982-1984) of healthy untreated subjects. Two mandibular growth measures (Articulare-Pogonion [Ar-Pg], Condylion-Pogonion [Co-Pg]) were retrieved from cephalograms (n: 990) and corresponding skeletal age based on hand-wrist radiographs. Mandibular growth velocity was related to skeletal age, PHV was established by use of cubic smoothing splines and variability was calculated by bootstrap resampling for every growth study and gender separately. RESULTS: Sexual dimorphism in mandibular growth was apparent in both cohorts. In subjects of the Denver Growth Study, mandibular PHV occurred at a more advanced skeletal age than in subjects of the Zurich Growth Study. This trend was more pronounced in males, for whom PHV of Co-Pg shifted from 14.4 to 13.8 years and of Ar-Pg from 14.6 to 13.7 years. This tendency was more subtle in females: PHV of Co-Pg shifted from 12.7 to 12.4 years and of Ar-Pg from 12.6 to 11.8 years. CONCLUSIONS: Mandibular growth appears to be subject to a secular trend. When related to skeletal age, this secular trend seems to be more accentuated than the established secular trend for somatic pubertal growth.

Torque differences according to tooth morphology and bracket placement: a finite element study.

INTRODUCTION: Torque of the maxillary incisors is essential in esthetics and proper occlusion, while torque expression is influenced by many factors. The aim of this finite element study was to assess the relative effect of tooth morphology, bracket prescription, and bracket positioning on tooth displacement and developed stresses/strains after torque application. METHODS: A three-dimensional upper right central incisor with its periodontal ligament (PDL) and alveolus was modelled. The tooth varied in the crown-root angle (CRA) between 156°, 170°, and 184°. An 0.018-inch slot discovery® (Dentaurum, Ispringen, Germany) bracket with a rectangular 0.018 × 0.025-inch ß-titanium wire was modelled. Bracket torque prescription varied between 0°, 12°, and 22°, with bracket placement at the centre of the middle, gingival or incisal third of the crown. A total of 27 models were generated and a buccal root torque of 30° was applied. Afterwards, crown and apex displacement, strains in the PDL, and stresses in the bracket were calculated and analysed statistically. RESULTS: The palatal crown displacement was significantly affected by bracket positioning (up to 94 per cent), while the buccal apex displacement was significantly affected by bracket prescription (up to 42 per cent) and bracket positioning (up to 23 per cent). Strains in the PDL were affected mainly by CRA (up to 54 per cent), followed by bracket positioning (up to 45 per cent). Finally, bracket prescription considerably affected the stresses in the bracket (up to 144 per cent). LIMITATIONS: These in silico results need to be validated in vivo before they can be clinically extrapolated. CONCLUSION: Tooth anatomy and the characteristics of the orthodontic appliance should be considered during torque application.

Regenerative Dentistry: Animal Model for Regenerative Endodontology.

BACKGROUND: Ectopic tissue has been observed frequently in human root canal specimens when cell homing studies were performed at the dorsum of rodents. In contrast, pulp-like tissue formed when immature teeth were implanted on top of the rat calvaria. It was surmised, yet not tested, that the implantation site might affect tissue ingrowth. METHODS: Four root sections from human immature molars cleaned with 5% sodium hypochlorite (NaOCl) followed by 17% ethylenediaminetetraacetic acid (EDTA) were implanted per rat (n = 5). Two specimens were placed at the dorsum (control), while the other two specimens were implanted at the calvaria. After 6 weeks, the specimens were investigated for histological structure, immunoreactivity to dentine sialoprotein (DSP) and bone sialoprotein (BSP), per-area percentage of tissue ingrowth, and gene expression (DSPP, COL1, NGF and VEGF). Data were statistically compared. RESULTS: Tooth specimens placed at the calvaria generally showed pulp-like tissue and odontoblast-like cells at the dentinal wall where DSP and BSP immunoreactivity were intense. The area of tissue ingrowth was significantly larger in the specimens placed at the calvaria compared to those placed at the dorsum. DSPP was the only gene that was upregulated significantly when specimens were implanted at the calvaria. CONCLUSION: Our findings suggest that the calvarial site is superior to the dorsum to study pulp regeneration in human teeth in the rat.

Retrieval analysis of lingual fixed retainer adhesives.

INTRODUCTION: Our objective was to analyze the surface and bulk properties alterations of clinically aged composites used for fixed retention. METHODS: Twenty-six lingual retainers bonded for different time periods (2.2-17.4 years) were retrieved from postorthodontic patients. Fifteen lingual retainers had been cemented by a chemically cured adhesive (Maximum Cure, Reliance Orthodontic Products, Itasca, Ill), and 11 were treated with a photo-cured adhesive (Flow-Tain, Reliance Orthodontic Products). The first group was in service for 2.8 to 17.4 years and the second for 2.2 to 5.4 years. Five specimens from each material were prepared and used as the control (or reference) group. The debonded surfaces from enamel were studied by attenuated total reflectance Fourier transform infrared spectroscopy (n = 3 per material per group), low-vacuum scanning electron microscopy, and energy dispersive x-ray microanalysis (n = 3 per material per group). All specimens were used for the assessment of Vickers hardness, indentation modulus, and elastic index with the instrumented indentation testing method. The values of Vickers hardness, indentation modulus, and elastic index were compared between the retrieved and the reference groups with 1-way analysis of variance and the Student-Newman-Keuls multiple comparison test (α = 0.05). RESULTS: The attenuated total reflectance Fourier transform infrared spectroscopy analysis showed that both retrieved composites demonstrated reduced unsaturation in comparison with the corresponding reference specimens. Some bonded surfaces showed development of organic integuments. All retrieved specimens showed reduced silicon content. Barium was identified only in the photo-cured group. No significant differences were found between the reference and retrieved groups in Vickers hardness, indentation modulus, and elastic index. CONCLUSIONS: Despite the changes in composition, the mechanical properties of the materials tested remained unaffected by intraoral aging.

Effect of different incisor movements on the soft tissue profile measured in reference to a rough-surfaced palatal implant.

INTRODUCTION: The aim of this study was to evaluate soft tissue profile changes after a wide range of incisor movements in the anterior and posterior directions in nongrowing patients. Identifying baseline values more prone to substantial soft tissue profile changes was of high interest. METHODS: For this retrospective study, 47 pairs of lateral cephalograms of nongrowing white patients were superimposed. The cephalograms were taken with the same palatal implant in situ before and after treatment. To increase the accuracy of the measurements, the palatal implants were used as stable reference structures in close relation to the incisors. RESULTS: Horizontal changes of the most anterior point of the maxillary incisor showed a significant correlation to horizontal changes of the upper and lower lips (P <0.001). For every millimeter of horizontal change of the most anterior point of the maxillary central incisor, a change of 0.59 mm at labrale superior can be expected. Also, the angulations of the upper and lower lips were significantly correlated to the most anterior point of the maxillary incisor. Lip retraction was less pronounced in patients with initially thicker lips than in those with thinner lips. CONCLUSIONS: The major contributing factors for predicting the soft tissue profile change during orthodontic treatment are the amount of horizontal movement of the most anterior point of the maxillary incisor, the amount of bite opening, and the initial lip thickness. Although there are significant correlations between dental movements and soft tissue changes in larger samples, predictions for individuals may be inconsistent.

New perspectives on the relationship between mandibular and statural growth.

BACKGROUND: Condylar and somatic growth have similar growth curves. The aim of this study was to compare both growth curves in untreated subjects at different ages and investigate if a correlation factor (CF) could be established. MATERIAL AND METHODS: Semi-longitudinal records (cephalograms and body height) of 418 untreated, healthy children (193 girls and 225 boys) from a craniofacial growth study were analyzed. Incremental changes of three mandibular measurements from articulare and three from condylion were compared to statural growth changes separately. Based on the assumption that mandibular and somatic growth both follow a parallel line, a CF was postulated and checked for validity and reliability. RESULTS: Mandibular growth spurt could be observed in all six different mandibular measurements, but distances from condylion were more informative. Gonial measurements were not as indicative as symphyseal distances. Mandibular growth did not coincide with somatic growth precisely, and condylar peak velocity preceded statural peak velocity in boys and was slightly delayed in girls. CF was close to the value of 0.4, and its validity could be ascertained when using the condylion-gnathion distance for all ages in girls and up to the age of 12 in boys. Reliability, however, proved to be poor owing to heterogeneity of the sample. CONCLUSIONS: Although the relationship between mandibular and statural growth increments can be expressed as a CF with some degree of adequacy, the variance rendered CF unreliable. When evaluating growth-related changes, condylion should be preferred as condylar reference, and symphyseal landmarks should be favoured over gonion.

Surface and interfacial analysis of sandblasted and acid-etched enamel for bonding orthodontic adhesives.

INTRODUCTION: The purposes of this study were to characterize enamel surfaces treated with sandblasting, acid etching, or sandblasting followed by acid etching for bonding of orthodontic adhesives and to evaluate the enamel-adhesive interfaces. METHODS: Buccal premolar surfaces were sandblasted, acid etched, sandblasted and subsequently acid etched, or left intact. For 2 treatments (acid etching and sandblasting plus acid etching), orthodontic brackets were bonded for resin infiltration assessment. Surface roughness and enamel loss were evaluated by optical profilometry, and surface morphology and elemental composition were examined by low-vacuum scanning electron microscope/energy dispersive x-ray analysis, whereas interfacial resin infiltration was assessed by high-vacuum scanning electron microscopy. Differences were statistically analyzed by 1-way analysis of variance and Tukey-Kramer multiple comparison tests or t tests (α = 0.05). RESULTS: The sandblasted and sandblasted-plus-acid-etched groups showed higher surface roughness values than the acid-etched group. Sandblasting plus acid etching removed more enamel than did sandblasting or acid etching alone. Sandblasting plus acid etching demonstrated a more uniform type I etching pattern, without alumina particles implanted in the enamel, unlike sandblasting. No difference was found in the extent of resin infiltration between the bonded acid-etched and sandblasted-plus-acid-etched groups, although the latter showed improved infiltration characteristics. CONCLUSIONS: Sandblasting-plus-acid-etching treatment creates a rough enamel surface, typical of type I etching, with the greatest extent of enamel loss, free of alumina interferences, demonstrating the same extent of resin infiltration as acid etching, but exhibiting improved infiltration quality.