Three-dimensional assessment of facial asymmetry in class III subjects, part 2: evaluating asymmetry index and asymmetry scores.

OBJECTIVES: To evaluate the outcomes of corrective surgical treatment for craniofacial asymmetry using four different methods with the aim of developing the best technique for craniofacial asymmetry assessment. MATERIALS AND METHODS: CBCT images of twenty-one class III subjects with surgically corrected craniofacial asymmetry and twenty-one matched controls were analyzed. Twenty-seven hard tissue landmarks were used to quantify asymmetry using the following methodologies: the asymmetry index (AI), asymmetry scores based on the clinically derived midline (CM), Procrustes analysis (PA), and modified Procrustes analysis (MPA). RESULTS: Modified Procrustes analysis successfully identified pre-operative asymmetry and revealed severe asymmetry at the mandibular regions compared to controls, which was comparable to the asymmetry index and clinically derived midline methods, while Procrustes analysis masked the asymmetric characteristics. Likewise, when comparing the post-surgical outcomes, modified Procrustes analysis not only efficiently determined the changes evidencing decrease in facial asymmetry but also revealed significant residual asymmetry in the mandible, which was congruent with the asymmetry index and clinically derived midline methods but contradictory to the results shown by Procrustes analysis. CONCLUSIONS: In terms of quantifying cranio-facial asymmetry, modified Procrustes analysis has evidenced to produce promising results that were comparable to the asymmetry index and the clinically derived midline, making it a more viable option for craniofacial asymmetry assessment. CLINICAL RELEVANCE: Modified Procrustes analysis is proficient in evaluating cranio-facial asymmetry with more valid clinical representation and has potential applications in assessing asymmetry in a wide spectrum of patients, including syndromic patients.

The reliability of analytical reference lines for determining esthetically pleasing lip position: An assessment of consistency, sensitivity, and specificity.

INTRODUCTION: This study aimed to identify a simple yet reliable soft-tissue parameter for the clinical determination of esthetic lip position by investigating the most consistent reference lines and assessing their sensitivity and specificity. METHODS: A total of 5745 records from Chinese patients aged >18 years were screened. In part I of the study, lateral view photographs of 96 subjects (33 males, 63 females) with esthetic facial profiles were selected. The profile esthetics of each photograph was first scored by 52 dental students, followed by 97 laypeople on a 5-point attractiveness scale. For the top 25% of photographs with the highest score for each sex (8 males, 16 females), the consistency of 6 commonly used reference lines were assessed to determine the esthetic lip position. In part II of the study, lip positions relative to Steiner's (S) and Ricketts' (E) lines in the profile photographs of 86 patients (43 males, 43 females) deemed to have an esthetically unpleasing profile were compared with those in 86 Chinese movie star idols (43 males, 43 females). RESULTS: In part I of the study, the S, E, and Burstone's (B) lines exhibited the lowest standard deviations for the upper and lower lips. B line was excluded from further analysis because of its higher mean absolute values, and S and E lines were used for the subjective assessment in part II of the study. In part II, the S line showed a sensitivity of 86.0% and 86.0% and a specificity of 81.4% and 83.7% for males and females, respectively. In contrast, the E line presented a sensitivity of 88.4% and 93.0% and a specificity of 79.1% and 74.4% for males and females, respectively. CONCLUSIONS: S, E, and B lines were the most consistent soft-tissue parameters among both sexes; however, because of the smaller absolute values, the S line would be more convenient among the 3 for a quick clinical assessment of lip position. Moreover, the performance of both S and E lines was similar among both sexes, which supports using these lines in assessing the esthetic lip position.

Three-dimensional assessment of facial asymmetry in Class III subjects. Part 1: a retrospective study evaluating postsurgical outcomes.

OBJECTIVE: The present study aimed to determine the site and severity of maxillomandibular asymmetry before and after orthognathic surgery in asymmetric patients. MATERIALS AND METHODS: Presurgery and postsurgery cone beam computed tomography (CBCT) data of 21 facial asymmetry patients (7 males and 14 females, mean age: 23.0 ± 3.36 years) with soft tissue chin deviation ≥ 3 mm who had undergone bimaxillary surgery were evaluated. Seven midline and twenty bilateral hard tissue landmarks were identified for the evaluation of facial asymmetry and outcomes were assessed against age- and gender-matched control subjects. RESULTS: In the asymmetry group, bilateral landmarks exhibited significant deviation in the mandible and midface regions. Before surgery, asymmetry was more severe at the mandibular midline and sites close to it, in the asymmetry group. Bimaxillary surgery proved to be highly effective, with a significant correction of the menton to a clinically normal value (2.90 mm, p < 0.001). After surgery, significant residual asymmetry was observed at the mental foramen (p = 0.001) in the R-L direction. Moreover, significant asymmetry persisted at the sigmoid notch (p = 0.001) in the S-I direction. CONCLUSIONS: Mandibular midline landmarks and chin peripheral regions contribute significantly to overall facial asymmetry characteristics. Despite significant correction after bimaxillary surgery, asymmetry persisted at several sites, thereby requiring secondary correction. Comprehensive 3D presurgical planning is central for asymmetry correction in a single surgery. CLINICAL RELEVANCE: The present study specifies the location of residual asymmetry sites and advocates the correction of those sites during initial surgery.

A comparative assessment of information recall and comprehension between conventional leaflets and an animated video in adolescent patients undergoing fixed orthodontic treatment: A single-center, randomized controlled trial.

INTRODUCTION: The objective of this 2-arm parallel trial was to investigate the recall and comprehension of the information of orthodontic patients undergoing fixed orthodontic treatment using either the verbal explanation supported with the British Orthodontic Society (BOS) leaflet or 3-dimensional (3D) animated content. METHODS: Patients aged 12-18 years, with no relevant medical history or learning and reading difficulties, who were to undergo orthodontic treatment, were randomized to receive information about fixed orthodontic treatment, using either verbal explanation supported with the BOS leaflet or 3D animated content on the basis of the BOS leaflet. Randomization was performed by block randomization; block size of 4 was used, from which 6 blocks with 6 different sequences (AABB, ABBA, ABAB, BBAA, BAAB, BABA). The blinded author asked patients a series of open-ended questions. The primary outcome measure was the total score of the questions. An independent 2 sample t test was conducted to determine if there was a statistical difference in total questions score between the conventional method (verbal and leaflet) and the 3D animation at the time of consent taking (T0) and again 1 year later (T1). The secondary outcome measure was the time spent by the clinician delivering the information to the patient. RESULTS: Thirty-two patients were randomized into each group. After 1 year, 1 patient was lost in each group. At the time of consent, the conventional group scored 79.1 ± 18.4 compared with 76.4 ± 12.8 for the 3D animation group with no statistically significant difference (95% confidence interval, -11.0 to 5.3), (P = 0.492). One year later, again, there was no statistically significant difference (P = 0.639) between the conventional group (75.6 ± 12.3) and the 3D animation group (74.4 ± 9.0) (95% confidence interval, -7.0 to 4.4). The average exposure time to the educational intervention in the conventional group was 8.5 minutes more than the 3D animation group. CONCLUSIONS: The use of 3D animation or verbal and leaflet information is relatively equivalent in transferring knowledge to the orthodontic patient. The use of a 3D animated video reduces the clinician time needed in the clinic to deliver information to the patients and also allows multiple views and better suits the younger generation. Patients undergoing short- or long-term orthodontic treatment do not recall root damage as a risk of orthodontic treatment, which requires special attention from the orthodontist to reinforce this information. REGISTRATION: This trial was not registered. PROTOCOL: The protocol was not published before trial commencement.

A study of smile aesthetic perception among dental professionals, patients and parents towards impacted maxillary canine treatment options.

OBJECTIVE: To evaluate the smile aesthetics of the different treatment options for impacted maxillary canines as perceived by orthodontists, dentists, patients and parents. DESIGN: Cross-sectional survey. SETTING: Four rater groups were selected to complete the questionnaire consisting of an orthodontist group, a general dental practitioner group, a patient group consisting of patients aged 11-18 years who were considered to be 'Gillick competent' and a parent group consisting of parents/guardians who accompanied the patients to their orthodontic appointments. METHOD: Four digitally manipulated images were created to imitate different treatment options available for the treatment of ectopic maxillary canines including: alignment of the impacted maxillary canine; substituted premolars; retained deciduous canines; or gaps present. The images were embedded into piloted questionnaires. Each participant completing the questionnaire was asked to mark the visual analogue scale (VAS) beneath each image according to their perception of attractiveness of each image. Quantitative scoring of the perceived attractiveness of the smile was assessed by one calibrated assessor measuring the distance from the start of the scale to the marked cross placed on the VAS. A two-way ANOVA (mixed between-within subject's ANOVA) was used to compare perception of differences in smile aesthetics. RESULTS: There were significant differences found in the VAS between the groups (P = 0.002) and between the treatment options (P < 0.001) There was no statistically significant difference found between the aligned canines and substituted premolars images by the patient (P = 0.2) or parent group (P = 0.5). All groups most disliked the treatment option where gaps were present at the end of treatment. CONCLUSION: The patient and parent groups showed similar perception in smile aesthetics for aligned canines and substituted premolars and all groups showed a strong dislike to the presence of gaps. The orthodontist group showed the most critical aesthetic perceptions.

Using three-dimensional average facial meshes to determine nasolabial soft tissue deformity in adult UCLP patients.

BACKGROUND AND PURPOSE: There is limited literature discussing the residual nasolabial deformity of adult patients prior to undergoing orthognathic surgery. The purpose of this study is to determine the site and severity of the residual nasolabial soft tissue deformity between adult unilateral cleft lip and palate (UCLP) patients and a non-cleft reference group, prior to orthognathic surgery. MATERIAL AND METHODS: Sixteen adult male UCLP patients, who all received primary lip and palate surgery according to a standardised Hong Kong protocol were recruited for this study. Facial images of each individual were captured using three-dimensional (3D) stereophotogrammetry and compared to a previous published Hong Kong non-cleft reference group of 48 male adults. Using two-sample t-tests differences in linear and angular measurements and asymmetry scores were evaluated between the two groups. In addition a "conformed" average UCLP facial template was superimposed and compared to conformed average non-cleft reference group facial template. Reproducibility of the measurements were assessed using Students paired t-tests and coefficients of reliability. MAIN FINDINGS: Significant differences in linear and angular measurements and asymmetry scores were observed between the two groups (p < 0.05). Adult UCLP patients showed significantly narrower nostril floor widths, longer columella length on the unaffected side, a wider nose, shorter cutaneous lip height, shorter upper lip length and shorter philtrum length. Prior to orthognathic surgery adult UCLP patients showed significantly more facial asymmetry. Superimposition of the average facial meshes clearly showed the site and severity of the deficiency in the x, y and z-directions. CONCLUSIONS: Many of the nasolabial characteristics reported to be present in children following primary UCLP repair continue into adulthood. The detrimental soft tissue effects of orthognathic surgery for UCLP patients may be different to non-cleft individuals; and as such the site and severity of the residual deformity should be assessed prior to surgery.

Can the current hypodontia care pathway promote shared decision-making?

OBJECTIVE: To determine the extent to which the current care pathway in hypodontia promotes shared decision-making (SDM). DESIGN: Exploratory cross-sectional study using qualitative methods. SETTING: Orthodontic department of two NHS teaching hospitals in Yorkshire. PARTICIPANTS: Young people aged 12-16 years with hypodontia of any severity and at any stage of treatment, and their parents and guardians. METHODS: (1) Observation and audio-recording of interdisciplinary consultation in hypodontia clinics (n = 5) without any researcher interference; (2) short, structured interviews with young people with hypodontia (n = 8) and their parent (n = 8) using a topic guide to explore themes around decision-making. Audio-recordings were transcribed and analysed using a thematic framework. RESULTS: Consultations were used as an opportunity for interdisciplinary discussion, information provision and treatment planning. Evidence of good communication was observed but patient engagement was low. The decision to be made was usually stated and treatment options discussed, but time constraints limited the scope for adequate information exchange and assessment of understanding. No methods were used to establish patient and family preferences or values. Interviews suggested parents expect the dental team to make decisions and young people rely on parental advocacy. Despite little evidence of SDM, participants reported satisfaction with their treatment. CONCLUSIONS: The current care pathway for hypodontia does not support clinicians in the steps of SDM. Recommendations for improving SDM processes include support to identify preference-based decisions, greater access to comprehensive and accessible patient information to enable preparation for consultation, alternative methods for effective communication of complex information and use of preference elicitation tools to aid value-driven decision-making.

A Comparative Analysis of Tooth Size Discrepancy between Male and Female Subjects Presenting with a Class I Malocclusion.

OBJECTIVES: To evaluate the tooth size discrepancy and Bolton's ratios between male and female subjects with a Class I malocclusion. MATERIALS AND METHODS: The digital e-models of 100 male and 100 female 12-year-old southern Chinese children with a Class I malocclusion were selected. The mesiodistal widths from permanent first molar to the contralateral side first molar of the upper and lower dentitions were measured. Differences between the tooth size discrepancy, together with the anterior and overall Bolton's ratios between male and female subjects, were assessed using a two-sample t-test. A paired t-test was used to determine differences between antimetric pairs of teeth within the same arch. RESULTS: Females had statistically significant smaller teeth than males (P < 0.05) except the upper left and lower left lateral incisor and lower left and right central incisors. The mean values of anterior Bolton's ratios for males and females were 77.04 and 77.03, respectively (P > 0.05), while the mean values of overall Bolton's ratios of male and female are 90.48 and 90.65, respectively (P < 0.05). The clinical significant differences (Cohen's d > 0.2) for contralateral tooth size were shown on the maxillary canines, lateral incisors, and central incisors of males; and mandibular canines and lateral incisors of females. CONCLUSIONS: Southern Chinese females presenting with Class I malocclusions have smaller mesiodistal tooth dimensions compared to males. Both males and females presented several tooth size asymmetries. There are no statistical differences in anterior and overall Bolton's ratios between the genders.

Dental Arch Relationships and Reverse Headgear Effects in Southern Chinese Patients with Unilateral Cleft Lip and Palate: A Retrospective Study.

OBJECTIVE: To evaluate the severity of the dental arch relationships and the treatment outcomes of reverse headgear (RHG) in southern Chinese patients with unilateral cleft lip and palate (UCLP). DESIGN: A retrospective study. SETTING: Faculty of Dentistry, The University of Hong Kong. PATIENTS: Thirty-eight UCLP patients with complete records. Among them, 14 were later treated with RHG (RHG group) and 24 were under review (non-RHG group) before definitive orthodontic or in conjunction with orthognathic surgery. INTERVENTIONS: Study models at T1 (aged 9.4 ± 0.4 years old), prebone grafting and before any orthodontic treatment started; T2 (aged 11.3 ± 0.6 years old), after bone grafting, and RHG treatment (RHG group) or under review (non-RHG group); and T3 (aged 15.3 ± 3.2 years old), pretreatment of definitive orthodontic or in conjunction with orthognathic surgery. MAIN OUTCOME MEASURES: With satisfactory intra- and interexaminer agreement proven by the kappa value, the dental arch relationships of the study models at T1, T2, and T3 were assessed by a solo calibrated examiner using the GOSLON Yardstick. RESULTS: The median GOSLON score for southern Chinese patients with UCLP at T1 was 4.0. Sixty percent of the patients were categorized as "poor" at T1. RHG significantly improved dental arch relationships from T1 to T2, and the improvement was maintained until T3 assessed by the GOSLON Yardstick. CONCLUSIONS: The dental arch relationships in southern Chinese UCLP patients at 8 to 10 years old are unfavorable. RHG treatment shows positive effects in improving the dental arch relationships in UCLP patients, as assessed by the GOSLON Yardstick.

Identification and appraisal of outcome measures used to evaluate hypodontia care: A systematic review.

INTRODUCTION: Identification and appraisal of the outcome measures that have been used to evaluate hypodontia treatment and deliver services are essential for improving care. A lack of alignment between outcomes and patient values can limit the scope for patient-centered care. Our objectives were to identify and appraise the outcomes selected to evaluate hypodontia care. METHODS: Data sources included 10 electronic databases and grey literature, searched using terms for hypodontia and its treatment methods. Study eligibility included mixed study designs to ensure comprehensive identification of outcomes, excluding case reports and case series with fewer than 10 participants and nonsystematic reviews. Participants and interventions involved people with hypodontia receiving any dental treatment to manage their hypodontia. Simulated treatment, purely laboratory-based interventions, and future treatments still in development were excluded. Research outcomes were identified and synthesised into 4 categories: clinical indicators, and patient-reported, clinician-reported, and lay-reported outcomes. No synthesis of efficacy data was planned, and consequently no methodologic quality appraisal of the studies was undertaken. RESULTS: The search identified 497 abstracts, from which 106 eligible articles were retrieved in full. Fifty-six studies and 8 quality-improvement reports were included. Clinical indicators were reported in 49 studies (88%) including appearance, function, dental health, treatment longevity, treatment success and service delivery. Patient-reported outcomes were given in 22 studies (39%) including oral health-related quality of life, appearance, function, symptoms of temporomandibular dysfunction, and patient experience. Clinician-reported outcomes were limited to appearance. Variability was seen in the tools used for measuring outcomes. CONCLUSIONS: There is a lack of rationale and consistency in the selection of outcome measures used to evaluate hypodontia care. Outcomes are largely clinician and researcher-driven with little evidence of their relevance to patients. There was a paucity of outcomes measuring access to care, quality of care, and cost. Evidence from hypodontia research is clinician-focused and likely to have limited value to support patients during decision making. Attempts to synthesise the evidence base for translation into practice will be challenging. There is a need for a core outcomes set with a patient-centric approach to drive improvements in health services.

A Comparison of Three Viewing Media for Assessing Dental Arch Relationships in Patients With Unilateral Cleft Lip and Palate.

OBJECTIVE: To determine the repeatability and reproducibility of using three different viewing media to assess the outcomes of the dental arch relationships of patients with unilateral cleft lip and palate (UCLP) using the GOSLON Yardstick. DESIGN: The GOSLON Yardstick was used to rate the dental arch relationships of 29 patients with UCLP. Three experienced calibrated orthodontists rated the plaster study models, digital study models, and stereoscopic projected three-dimensional (3D) study models separately. There was a minimum of a 1-week interval between each rating session. All three rating sessions were repeated 1 month later. A linear weighted kappa statistic was performed to assess intra-rater repeatability and inter-rater reproducibility, as well as the comparison between different viewing media using Kendall's Coefficient of Concordance (Kendall's W) statistic. RESULTS: Intra-rater repeatability was very good for all three viewing media (kappa = 0.83-0.92). Inter-rater reproducibility was good to very good across the three viewing media (kappa = 0.63-0.88). Agreements between plaster study models and digital study models or stereoscopic projected 3D study models were good to very good (kappa = 0.78-0.97 and kappa = 0.72-0.97, respectively), and a Kendall's W ranging from 0.86 to 0.92 (P < .001). CONCLUSIONS: Stereoscopic projected 3D is an alternative method to assess the outcomes of dental arch relationships in patients with cleft lip and palate using the GOSLON Yardstick. It could also be used for viewing patient records, as it recovers the full 3D information captured at the time of the clinical examination.

Evaluation of the Reproducibility of Nonverbal Facial Expressions Using a 3D Motion Capture System.

OBJECTIVE: To evaluate the reproducibility of three nonverbal facial expressions using a three-dimensional motion capture system. DESIGN: Prospective, cross-sectional, controlled study. SETTING: Glasgow Dental Hospital and School, University of Glasgow, United Kingdom. PATIENTS AND PARTICIPANTS: Thirty-two subjects, 16 males and 16 females. METHODS: With a three-dimensional video passive stereophotogrammetry imaging system, maximal smile, cheek puff, and lip purse were captured for each subject. Anatomical facial landmarks were digitized on the first frame and then tracked automatically. The same facial expressions were captured 15 minutes later. MAIN OUTCOME MEASURES: The magnitude of each expression and speed of landmark displacement were calculated. The landmark motion curves were spatially and temporally aligned to calculate the similarity of the dynamic movements of the same landmarks between the captures. RESULTS: There were no significant differences between individuals for magnitude (P = .892) or for speed (P = .456). There were significant differences in landmark movement similarity (P = .011); similarity was more reproducible for maximal smile. There was no significant gender effect on the difference in magnitude. There was a significant gender effect on speed to reach maximal smile (P = .044) and a pursed-lip expression (P = .038). There was a significant gender effect on landmark movement similarities (P = .031) for cheek puff expression. CONCLUSIONS: There were no differences in magnitude and speed for maximal smile, cheek puff, and lip purse between the two captures for all participants. For individual expressions, maximal smile expression had the highest similarity value for individual landmarks.

Do parents of adolescent patients undergoing fixed appliance treatment recall more information using written material or an animated video? A randomized controlled trial.

Objectives: This "2-arm parallel" trial investigated the recall of information pertinent to obtaining informed consent of parents of orthodontic patients using; either written material and verbal support or an animation. Materials and methods: Parents of patients, aged 12-18 years, about to undergo fixed applaince treatment, were randomized to either receive information by leaflet or by watching an animation. The parents were asked a series of open-ended questions immediately and one year later. The outcome measure was the total median questionnaire score immediately (T0) and one year later (T1). A Mann Whitney U test was performed to test for differences between T0 and T1. Results: 31 parents were randomized into the leaflet group and 33 in to the animation group. The median leaflet group score was 81 (IQR = 27) at the time of consent (T0) and 87 (IQR = 29) a year later (T1), compared to a median score of 76 (IQR = 23) for the animation group at T0 and 87 (IQR = 32) at T1. Statistically, there was no difference in the questionnaire score at (T0) (p = 0.567) and at (T1) (p = 0.522). The average time spent with the clinician in the leaflet group was an additional 9 min in the animation group. Conclusion: The use of a leaflet and verbal information or an animation are equivalent in providing information to the parents of orthodontic patients. The use of an animation reduces the clinical time needed to deliver the information.

The validity of using profile predictions for class III patients planned for bimaxillary orthognathic surgery.

This study assessed whether preoperative class III patients could recreate their facial difference based on a profile photograph. Twenty class III pre-surgery bimaxillary orthognathic patients used CASSOS (SoftEnable Technology Ltd.) to manipulate a distorted soft tissue image of them until they felt it resembled their current soft tissue profile. Patients were able to move their upper lip and lower chin backward and forwards, as well as the lower chin up and down. Differences in the mean absolute distance between the patient-perceived position of the upper lip (Labrale superious) and chin (Pogonion) and the actual position of their upper lip and chin were measured on two occasions. Intra-patient reproducibility was found to be excellent (ICC 0.93 to 0.98). All differences were statistically significantly greater than 3mm, and would be clinically significant. Patients were better at re-creating their AP chin position rather than their AP upper lip and vertical chin positions. Approximately half of patients undergoing surgical correction of their class III skeletal pattern were unable to correctly identify their pre-surgical facial profile. Given the lack of awareness of their profile, this questions the validity of using profile planning for informed consent.

An overview of three-dimensional imaging in dentistry.

UNLABELLED: This paper reviews the role of three-dimensional digital imaging in dentistry and its related specialties. Current methods of image capture of the dentition are described, along with the current status of CAD/CAM-based restorative treatment. The advantages of cone beam computed tomography (CBCT) in comparison with conventional radiography are outlined in the fields of endodontics, periodontology, oral surgery and orthodontics. The integration of CBCT with state-of-the-art computer planning systems for implantology is described. The application of multi-modal imaging techniques in the management of orthognathic and cleft lip and palate patients is explained and potential future educational benefits are considered. CLINICAL RELEVANCE: With three-dimensional digital imaging and its related technologies advancing rapidly, it is important for both general and specialist dental practitioners to have an awareness of its current and potential future roles in clinical practice.

Development of a Discrete-Choice Experiment (DCE) to Elicit Adolescent and Parent Preferences for Hypodontia Treatment.

OBJECTIVE: Our objective was to develop and test a discrete-choice experiment (DCE) survey to elicit adolescent and parent preferences for dental care for hypodontia (a developmental condition where one or more teeth fail to develop). METHODS: This was a mixed-methods study. Participants were adolescents (aged 12-16 years) with hypodontia and their parents and the dentists providing hypodontia care. Stage one entailed attribute development, as follows. (1) Attribute identification: systematic review of hypodontia literature; interviews with adolescents with hypodontia (n = 8) and parents (n = 8); observation of hypodontia clinical consultations (n = 5); environmental scan of hypodontia patient information resources (n = 30); and systematic analysis of social media posts (n = 176). (2) Attribute selection: stakeholder consultation to develop items for a questionnaire; rating and ranking questionnaire for adolescents with hypodontia and parents (n = 18); further stakeholder consultation. Stage two involved the development of the DCE survey, and stage three included the pre-testing using cognitive interviews with adolescents (n = 12) and parents (n = 8) to assess face and content validity. RESULTS: The attribute long list included 27 attributes focusing on service delivery and treatment outcome, from which seven 'important' attributes were selected for pre-testing. Cognitive interviewing suggested adolescents found the DCE choice tasks challenging to understand; the survey was modified to enhance its acceptability. One attribute was excluded as it showed poor validity with adolescents. Pre-testing suggested DCE choice tasks encouraged thinking and discussion about preferences for treatment. CONCLUSIONS: Including the target respondent group in all stages of DCE development ensured the final DCE survey was valid and acceptable. DCE methods appear to be a useful tool for exploring joint decision making alongside conventional preference elicitation.

Assessment of information resources for people with hypodontia.

AIM: To assess the adequacy of patient information to support understanding and decision-making for people affected by hypodontia. METHODS: 1) Questionnaire to understand the provision of patient information by dentists; 2) Systematic search to identify online open-access patient information; 3) Quality assessment of written patient information. RESULTS: Questionnaire response rate was 49% (319/649); 91% examined and/or treated people with hypodontia. Most general dentists referred patients to specialist services without providing written hypodontia information. The majority of dental specialists provide patient leaflets but less than a third used web-resources. Only 19% of respondents felt current resources were fit-for-purpose. Thirty-one patient resources (18 leaflets and 13 online) were assessed against quality criteria. The aim of the resource was seldom explicit, the content was often incomplete and variation in readability scores indicated high levels of literacy were required. DISCUSSION: Access to, and quality of, patient information for hypodontia is inadequate. Current resources are not sufficiently comprehensive to prepare young patients to engage in shared dental care decisions with their parents and/or dental professionals. CONCLUSION: There is a need for improved access to, and provision of, information about hypodontia if dental professionals want to meet best practice guidance and involve patients in shared decision-making.

Haptic simulation framework for determining virtual dental occlusion.

PURPOSE: The surgical treatment of many dentofacial deformities is often complex due to its three-dimensional nature. To determine the dental occlusion in the most stable position is essential for the success of the treatment. Computer-aided virtual planning on individualized patient-specific 3D model can help formulate the surgical plan and predict the surgical change. However, in current computer-aided planning systems, it is not possible to determine the dental occlusion of the digital models in the intuitive way during virtual surgical planning because of absence of haptic feedback. In this paper, a physically based haptic simulation framework is proposed, which can provide surgeons with the intuitive haptic feedback to determine the dental occlusion of the digital models in their most stable position. METHODS: To provide the physically realistic force feedback when the dental models contact each other during the searching process, the contact model is proposed to describe the dynamic and collision properties of the dental models during the alignment. The simulated impulse/contact-based forces are integrated into the unified simulation framework. RESULTS: A validation study has been conducted on fifteen sets of virtual dental models chosen at random and covering a wide range of the dental relationships found clinically. The dental occlusions obtained by an expert were employed as a benchmark to compare the virtual occlusion results. The mean translational and angular deviations of the virtual occlusion results from the benchmark were small. CONCLUSIONS: The experimental results show the validity of our method. The simulated forces can provide valuable insights to determine the virtual dental occlusion. The findings of this work and the validation of proposed concept lead the way for full virtual surgical planning on patient-specific virtual models allowing fully customized treatment plans for the surgical correction of dentofacial deformities.

A pilot study to assess the feasibility and accuracy of using haptic technology to occlude digital dental models.

OBJECTIVES: The use of haptic technology as an adjunct to clinical teaching is well documented in medicine and dentistry. However its application in clinical patient care is less well documented. The aim of this pilot study was to determine the feasibility and accuracy of using a haptic device to determine the occlusion of virtual dental models. METHODS: The non-occluded digital models of 20 pre-treatment individuals were chosen from the database of Faculty of Dentistry, The University of Hong Kong. Following minimal training with the haptic device (Geomagic(®) Touch™), the upper model was occluded with the lower model until a stable occlusion was achieved. Seven landmarks were placed on each of the corners of the original and haptically aligned upper model bases. The absolute distance between the landmarks was calculated. Intra- and inter-operator errors were assessed. RESULTS: The absolute distance between the 7 landmarks for each original and corresponding haptically aligned model was 0.54 ± 0.40 mm in the x-direction (lateral), 0.73 ± 0.63 mm in the y-direction (anterior-posterior) and 0.55 ± 0.48 mm in the z-direction (inferior-superior). CONCLUSION: Based on initial collision detection to prevent interpenetration of the upper and lower digital model surfaces, and contact form resistance during contact, it is possible to use a haptic device to occlude digital study models. CLINICAL SIGNIFICANCE: The use of 3D digital study models is routine, but new problems arise, such as the lack of "touch" in a virtual environment. Occluding study models requires the sense of touch. For the first time, using haptic technology, it is possible to occlude digital study models in a virtual environment.