Natural position of the head: review of two-dimensional and three-dimensional methods of recording

A new method to orient a 3-dimensional facial model to natural head position: A preliminary report on accuracy and reproducibility

OBJECTIVES

To establish and validate a novel method to orient a 3-dimensional (3D) facial model to natural head position (NHP) in a stereophotogrammetric system using a 2-dimensional frontal full-face photograph of NHP.

MATERIAL AND METHODS

Specific technique procedure was reported for our method, and in vitro model experiment was performed for accuracy test. A preliminary volunteer study was then planned for reproducibility test.

RESULTS

The accuracy on a 3D-printed test model was within 0.15°. Within an observational cohort of 22 dental students, the angular deviations of different maxillofacial regions (e.g., central forehead, left and right zygomatic regions, apex of nose and mental region) were no more than 2° between the 3D NHP models acquired with a shorter time-interval (1 h from baseline) or a longer time-interval (7 days from baseline), which were all considered clinically insignificant. In addition, the angular deviations were significantly larger with a 7d-interval than with a 1h-interval, indicting a decline in 3D NHP reproducibility over short time duration.

CONCLUSION

The current method may represent a clinically useful protocol for recording and transferring 3D NHP in stereophotogrammetry.

CLINICAL RELEVANCE

It may provide reliable and meaningful reference information for evaluating craniofacial morphology, and be of clinical use in the diagnosis, treatment and follow-ups of patients with aesthetic or deformed craniofacial problems.

Evaluation of a Fully Digital, In-House Virtual Surgical Planning Workflow for Bimaxillary Orthognathic Surgery

BACKGROUND

The advantages of virtual surgical planning (VSP) for orthognathic surgery are clear. Previous studies have evaluated in-house VSP; however, few fully digital, in-house protocols for orthognathic surgery have been studied.

PURPOSE

The purpose of this study was to evaluate the difference between the virtual surgical plan and actual surgical outcome for orthognathic surgery using a fully digital, in-house VSP workflow.

STUDY DESIGN, SETTING, SAMPLE

This is a prospective cohort study from September 2020 to November 2022 of patients at the Victoria General Hospital in Halifax, NS, Canada who underwent bimaxillary orthognathic surgery. Patients were excluded if they had previously undergone orthognathic surgery or were diagnosed with a craniofacial syndrome.

MAIN OUTCOME VARIABLES

The primary outcome variables were the mean 3-dimensional (3D) (Euclidean) distance error, as well as mean error and mean absolute error in the transverse (x axis), vertical (y axis), and anterior-posterior (z axis) dimensions.

COVARIATES

Covariates included age, sex, and surgical sequence (mandible-first or maxilla-first).

ANALYSES

The primary outcome was tested using Z and t critical value confidence intervals. The P value was set at .05. The 3D distance error for mandible-first and maxilla-first groups was compared using a 2-sample t-test as well as analysis of variance.

RESULTS

The study sample included 52 subjects (24 males and 28 females) with a mean age of 27.7 (± 12.1) years. Forty three subjects underwent mandible-first surgery and 9 maxilla-first surgery. The mean absolute distance error was largest in the anterior-posterior dimension for all landmarks (except posterior nasal spine, left condyle, and gonion) and exceeded the threshold for clinical acceptability (2 mm) in 16 of 23 landmarks. Additionally, mean distance error in the anterior-posterior dimension was negative for all landmarks, indicating deficient movement in that direction. The effect of surgical sequence on 3D distance error was not statistically significant (P = .37).

CONCLUSION AND RELEVANCE

In general, the largest contributor to mean 3D distance error was deficient movement in the anterior-posterior direction. Otherwise, mean absolute distance error in the vertical and transverse dimensions was clinically acceptable (< 2 mm). These findings were felt to be valuable for treatment planning purposes when using a fully digital, in-house VSP workflow.

Digital maxillomandibular relationship and mandibular motion recording by using an optical jaw tracking system to acquire a dynamic virtual patient

A technique for digitally recording the maxillomandibular relationship, including the maximum intercuspation and centric occlusion and the patient's mandibular motion, by using an optical jaw tracking system is described. Advantages of this technique include the digital registration of the maxillomandibular relationship and mandibular motion. This technique incorporates the mandibular motion into the 3-dimensional (3D) virtual patient representation to integrate the 3D dynamic virtual patient visualization.

Using an additively manufactured natural head position reference device to transfer the horizon orientation plane and integrate it with a 3-dimensional virtual patient: A dental technique

A virtual patient is obtained by aligning a patient's digital information, including facial and intraoral digital scans with or without hard tissue information from a cone beam computed tomography scan. However, while computer-aided design programs facilitate virtual patient integration, they do not provide a way to relate the horizon orientation with the patient's horizontal and vertical facial references. The present technique describes a way of relating the horizon orientation plane to the natural head position of the patient. An additively manufactured natural head position reference device was used to transfer the horizon orientation plane to the 3-dimensional virtual patient.

Photography in orthognathic surgery: A standardized protocol and storage legal implications

Medical photography is an essential tool in orthognathic surgery to facilitate diagnosis, preoperative planning, and follow-up. Photographic documentation has clinical, research, teaching and legal applications. An accurate diagnostic approach and surgical planning of dentofacial deformity requires the ability to work with reproducible and measurable photographic images. It must also respect certain legislative rules for its use within a health institution and the dissemination of images in the educational and scientific framework. We propose through this narrative review a standardized protocol to obtain reproducible images in the different planes of space. We also review and discuss fundamental points for setting up a photographic room dedicated to photography in orthognathic surgery.

Pharyngeal airway subdivisions in 3-dimensional analysis: Differences between anterior and posterior anatomic boundaries

INTRODUCTION

This study aimed to evaluate if there were differences between anterior and posterior anatomic boundaries used for the 3-dimensional determination of pharyngeal airway.

METHODS

The sample included 150 cone-beam computed tomography scans from healthy patients divided according to (1) age: 6-11, 12-16, and ≥16 years; (2) sex: female and male; (3) anteroposterior skeletal pattern: Class I, II, and III; (4) vertical pattern: brachyfacial, mesofacial, and dolichofacial; and (5) craniocervical inclination (CCI): natural head posture, head flexion, and head extension. Anatomic regions were created to determine the correspondences between structures anteriorly and posteriorly to the pharyngeal airway.

RESULTS

The location of the epiglottis, vallecula, hyoid, C2, and C3 were statistically different according to the CCI, and the location of vallecula, C3, and C4 were different according to sex. However, no statistically significant differences were observed between the frequencies of anterior and posterior anatomic region locations among age and different anteroposterior and vertical skeletal patterns. Posterior landmarks tend to be located below the anterior ones; consequently, the anatomic subregion they define will also be located below.

CONCLUSIONS

Anterior and posterior structures and vertical and anteroposterior skeletal patterns may determine upper airway limits regardless of age. However, the studies must be paired according to sex, and CCI must be standardized.

Assessment of Surgical Accuracy in Maxillomandibular Advancement Surgery for Obstructive Sleep Apnea: A Preliminary Analysis

This retrospective study aimed to: (1) investigate the surgical accuracy of maxillomandibular advancement (MMA) in obstructive sleep apnea (OSA) patients, with a specific focus on maxillary and mandibular advancement and counter-clockwise rotation and (2) investigate the correlation between the amount of achieved advancement and the reduction in the relative apnea hypopnea index (AHI). Sixteen patients, for whom a three-dimensional virtual surgical plan was generated preoperatively and a computed tomography scan (CT) or cone-beam computer tomography (CBCT) was acquired postoperatively, were included. The postoperative CT or CBCT was compared to the virtual surgical plan, and differences in the mandibular and maxillary advancement and counter-clockwise rotation were assessed. Maxillary and mandibular advancement (median 3.1 mm, p = 0.002 and 2.3 mm, p = 0.03, respectively) and counter-clockwise rotation (median 3.7°, p = 0.006 and 4.7°, p = 0.001, respectively) were notably less than intended. A significant correlation was found between the planned maxillary advancement and the difference between the planned and actual maxillary advancement (p = 0.048; adjusted R2 = 0.1979) and also between the planned counter-clockwise rotation and the difference between the planned and actual counter-clockwise rotation for the mandible (p = 0.012; adjusted R2 = 0.3261). Neither the maxilla-first nor the mandible-first surgical sequence proved to be superior in terms of the ability to achieve the intended movements (p > 0.45). Despite a significant reduction (p = 0.001) in the apnea hypopnea index (AHI) from a median of 62.6 events/h to 19.4 events/h following MMA, no relationship was found between the extent of maxillary or mandibular advancement and AHI improvement in this small cohort (p = 0.389 and p = 0.387, respectively). This study underlines the necessity for surgeons and future research projects to be aware of surgical inaccuracies in MMA procedures for OSA patients. Additionally, further research is required to investigate if sufficient advancement is an important factor associated with MMA treatment outcome.

Evaluation of optimal anterior-posterior position of upper incisors through ANS point: a retrospective study on a Chinese sample

OBJECTIVES

This study was designed to determine the optimal anterior-posterior (AP) position of upper incisors through Anterior Nasal Spine (ANS) point.

MATERIALS AND METHODS

Lateral cephalometric radiographic images of 690 patients were collected and divided into a derivation group and a validation group, and the former were subdivided into a proper AP position (PAP) group and an improper AP position (iPAP) group. The distance from facia-axis (FA) point of upper incisors to the line perpendicular to Frankfort horizontal (FH) plane through ANS (FA-ANS) was measured, and the relationship between FA-ANS and several cephalometric indices were studied through Pearson correlation analysis. Receiver operating characteristic (ROC) curves for different clinical indices were analyzed to evaluate the diagnostic efficiency of optimal AP position of upper incisors.

RESULTS

The average value of FA-ANS in PAP group was 0.57±1.99, which was significantly different from FA-ANS in iPAP group. Cephalometric indices such as U1-NA, U1-SN, AB-NPo, UL-TVL, Wits, and ANB were found to be correlated with FA-ANS. The receiver operating characteristic (ROC) curves represented a greater diagnostic efficiency of FA-ANS compared with other clinical indices.

CONCLUSIONS

ANS point, as a stable skeletal landmark, could be used to access an optimal AP position of upper incisors, providing aids to clinical diagnosis and treatment goal determination for clinical practice.

CLINICAL RELEVANCE

A new index FA-ANS, together with other traditional indices, could help determine the optimal position of upper incisors and provide a personalized therapeutic plan.

Slim the face or not: 3D change of facial soft and hard tissues after third molars extraction: a pilot study

BACKGROUND

Whether slim the face or not after removed third molars is the concern of some orthodontic treatment candidates. The aim of this article is to explore the volume changes of facial soft and hard tissues after third molars extraction, as well as develop a reproducible clinical protocol to precisely assess facial soft tissue volume change.

METHODS

A non-randomized, non-blind, self-controlled pilot study was conducted. 24 adults aged 18-30 had ipsilateral third molars extracted. The body weight change was controlled within 2 kg. Structured light scans were taken under a standardized procedure pre-extraction (T0), three (T1), and six (T2) months post-extraction; CBCTs were taken at T0 and T2. The projection method was proposed to measure the soft tissue volume (STV) and the soft tissue volume change (STVC) by the Geomagic software. The hard tissue volume change (HTVC) was measured in the Dragonfly software.

RESULTS

The final sample size is 23, including 5 males (age 26.6 ± 2.5 years) and 18 females (age 27.3 ± 2.5 years). The HTVC was - 2.33 ± 0.46ml on the extraction side. On the extraction side, the STV decreased by 1.396 (95% CI: 0.323-2.470) ml (P < 0.05) at T1, and increased by 1.753 (95% CI: -0.01-3.507) ml (P = 0.05) at T2. T2 and T0 had no difference (P > 0.05). The inter and intra-raters ICC of the projection method was 0.959 and 0.974. There was no correlation between the STVC and HTVC (P > 0.05).

CONCLUSIONS

After ipsilateral wisdom teeth extraction, the volume of hard tissue on the extraction side reduces, and the volume of facial soft tissue does not change evidently. However, further research with large sample size is still needed. The STV measurement has excellent repeatability. It can be extended to other interested areas, including forehead, nose, paranasal, upper lip, lower lip and chin, which is meaningful in the field of orthodontics and orthopedics.

TRIAL REGISTRATION

ChiCTR, ChiCTR1800018305 (11/09/2018), http://www.chictr.org.cn/showproj.aspx?proj=28868 .

Definition of New Three-Dimensional Cephalometric Analysis of Maxillomandibular Sagittal Relationship for Orthodontics and Orthognathic Surgery: Normative Data Based on 700 CBCT Scans

The objective of the study was to define the norm of new 3-dimensional cephalometric analysis of maxillomandibular sagittal relationship with the patient in Natural Head Position. A cross-sectional study was performed using 700 consecutives cone beam computed tomography datasets of pre-orthodontic patients received for three-dimensional craniofacial analysis. To stablish the clinical norm of the new sagittal reference (linear distance A-B), the correlation with the gold standard (ANB angle) was estimated with the Pearson's correlation coefficient. Subsequently, the prognostic values of the linear distance A-B was calculated to define the clinical norm. The sample was composed by 463 women (66.1%) and 237 men (33.9%). The mean age was 30 ± 14,5 years old (range 6-71 y old). According to the skeletal class classification (ANB), 46.1% (323) were class I, 42% (294) class II, and 11.9% (83) class III. The regression model found that each additional grade of the ANB angle imply a mean increase of 1.24 mm of the distance A-B ( P <0.001). The normative value of the linear distance A-B was obtained through the prognostic values of the distance for the limits of the ANB norm 0 to 4. These values were on the range of 0.52 to 5.48 mm. Therefore, the clinical norm for cephalometric maxillomandibular sagittal relationship using linear distance from point A-B is: 3±2.48 mm. With this new approach, we can define the skeletal sagittal relationship of the patient in natural head position overcoming the limitations of using intracranial or occlusal plane references improving the diagnosis and orthognathic surgical planning process.

Validation of Andrews Analysis in the Virtual Environment

BACKGROUND

Andrews analysis is a tool to establish the aesthetic anteroposterior position of the maxilla. Andrews analysis has not been evaluated through computer-aided surgical simulation (CASS).

PURPOSE

The purpose of this study was to evaluate the accuracy of Andrews profile analysis when performed in the virtual environment.

STUDY DESIGN, SETTING, SAMPLE

A retrospective cohort study was implemented with consecutive patients undergoing orthognathic surgery between February 2020 and February 2022 at the University of Alabama, Birmingham. Traditional Andrews analysis with lateral smiling photographs were taken during the presurgical appointment in adjusted natural head position (aNHP). The standard cone-beam CT obtained for CASS and archived on the KLS Martin (Jacksonville, Florida) database was accessed for retrospective measurement. Lateral facial photographs in aNHP were imported into the virtual environment and the three dimensional (3D) composite model was then oriented into aNHP. The software engineer, blinded to the traditional measurements, then performed the Andrews analysis in the virtual environment by placing a vertical glabella line on the 3D composite model in aNHP. The linear horizontal distance of the maxillary central incisor perpendicular to the vertical glabella line was recorded.

PREDICTOR/EXPOSURE/INDEPENDENT VARIABLE

Method of Andrews analysis measurement (traditional photographic evaluation vs CASS) MAIN OUTCOME VARIABLE: Linear Andrews analysis measurement.

COVARIATES

Additional covariates evaluated were sex, age at surgery, and dentofacial deformity diagnosis.

ANALYSES

Descriptive statistics were computed to compare photographic analysis versus CASS analysis. A P value of <.05 was considered statistically significant.

RESULTS

The average age was 25.7 years old and 54% of patients were female. For the photographic analysis, the mean incisor-goal anterior limit line distance was -0.44 ± 7.12 mm (95% CI, -1.13 to 0.37 mm; P = .46). For the virtual analysis, the mean incisor-goal anterior limit line distance was 0.13 ± 7.21 (95% CI, -0.004 to 0.30; P = .89). The Pearson correlation coefficients between the photograph and 3D analysis were very strong (0.93). The root mean square deviation between the photographic and 3D analysis cohorts was 2.7 mm.

CONCLUSION AND RELEVANCE

Given the high correlation coefficients between all demographics, CASS can be utilized for Andrews analysis to determine ideal anteroposterior maxillary position to streamline data collection and the planning process.

Impact of facial profile on young adults' oral health-related quality-of-life item levels: A hierarchical analysis

Objective:

To assess the impact of facial profile on young adults’ oral health-related quality of life (OHRQoL) item levels.

Methods:

A cross-sectional study was carried out with a population-based sample of 205 young adults, with a mean age of 23.1 years. The individuals answered questions about OHRQoL (OHIP-14) and self-esteem (Global Negative Self-Evaluation). The Dental Health Component (DHC) of the Index of Orthodontic Treatment Need (IOTN) was used to evaluate normative orthodontic treatment needs and define dental malocclusion clinically. Facial profile was analyzed using photographs and dichotomized into two levels: normal (straight) and altered facial profile (convex or concave). A calibrated researcher performed the clinical examination. Association between the independent variables and the outcome (OHRQoL) was established by hierarchical multiple linear regression analysis for each item level. Considering the variable of interest (facial profile), the psychological incapacity domain was the most affected item.

Results:

Individuals with changed facial profile had 2.47 (1.04-5.85) times higher chances of reporting impacts on psychological incapacity than those with a normal profile (p> 0.05). The association was modulated by dental malocclusion and self-esteem.

Conclusions:

The convex and concave facial profile showed a negative impact on the psychological aspects of young adults’ quality of life.

Morphologic reproducibility in 6 regions of the 3-dimensional facial models acquired by a standardized procedure: An in vivo study

INTRODUCTION

A standardized procedure was proposed to control involuntary motion and other factors during the capture of structural light scanning that could influence the morphology of 3-dimensional facial models; interoperator reproducibility was evaluated.

METHODS

Twenty subjects volunteered for facial scanning. Three researchers scanned each volunteer 3 times on the same day using the FaceScan structural light scanning system (Isravision, Darmstadt, Germany) and after the proposed procedure. Captures were done at 5-minute intervals. The 3 facial scans acquired by the same researcher were compared by reverse engineering software (Geomagic; 3D Systems, Rock Hill, SC). Six facial regions, including forehead, nose, paranasal, upper lip, lower lip and chin, and cheek, were divided. With the first scan as a reference, the other 2 scans were registered, and surface-to-surface distance maps were acquired to calculate the mean, standard deviation, and root mean squares (RMS) between 2 surfaces. The reproducibility between 3 researchers was then evaluated by a 1-way analysis of variance.

RESULTS

The mean of 6 facial regions was close to 0. The RMS of lip regions were largest (0.48-0.53 mm), the forehead was smallest (0.21 mm), and the others ranged 0.37 mm to 0.42 mm. The standard deviation was slightly smaller than RMS and had the same trend of change. There was no significant difference in RMS among the 3 researchers (P >0.05).

CONCLUSIONS

With the constraint of the standardized procedure, the morphologic reproducibility of facial models in 6 regions was satisfying.

Evaluation of head posture using an inertial measurement unit

An inertial measurement unit (IMU) is an electronic device that measures and track the orientation of a body. We conducted this study in accordance with the STARD guidelines to evaluate the accuracy of IMU (index test) for measuring head posture compared to the current gold standard using a cervical range of motion (CROM) device. The reproducibility of the hunter and mirror-guided head posture was also evaluated. In vitro and in vivo tests were carried out to assess the validity of the IMU. To assess reproducibility, thirty healthy young adults were asked to look at four different locations in two different sessions while the head posture was recorded. Excellent correlation (r = 0.99; p < 0.001) was found between the IMU and CROM device with an absolute mean difference of 0.45° ± 0.58° (p = 0.85) for the in vitro test and 0.88° ± 1.20° (p = 0.99) for the in vivo test. For the reproducibility test, moderate to good correlation coefficients were found (r = 0.55 to 0.89; all p < 0.05) between the two sessions. The intraclass correlation coefficient ranged from moderate to excellent reliability (ICC from 0.74 to 0.96). These results suggest that the IMU sensors, when calibrated correctly, can be adequate to analyze head posture.

Different Modalities to Record and Transfer Natural Head Position to Virtual Planning in Orthognathic Surgery: Case Reports of Asymmetric Patients

Aim

To describe different modalities to record and transfer natural head position (NHP) to 3D facial imaging by using the virtual surgical planning software in three facial asymmetry patients.

Case Reports

Three patients with facial asymmetries (A, B, and C) were evaluated by means of dental and facial analysis, photographs, cone-beam computed tomography (CBCT) and digitized dental arches. Before starting the VSP workflow with Dolphin Imaging, NHP was recorded by three modalities and transferred to three-dimensional (3D) facial images as follows: (a) facial photographs taken with digital camera and the estimated NHP was transferred to 3D images by comparing lines and planes from both images; (b) cross-line level laser was used to place radiopaque markers on the face skin for recording the estimated NHP, which was transferred to 3D images by alignment of planes and markers in the software; and (c) photographs of the face were processed to generate facial surface mesh by using the Agisoft PhotoScan software, which maintained the same position of the estimated NHP in 3D for aligning the images of the soft tissue with the facial surface mesh by using superimposition. All the three patients underwent bi-maxillary orthognathic surgery.

Conclusion

There are different modalities using simple and available technologies in the clinical routine, but whose reproducibility, reliability and validation could not be assessed nor compared to each other. There was no trend for better predictability, feasibility and efficiency because the postoperative outcomes were adequate regarding the patients' satisfaction and facial symmetry.

Measuring the difference in natural head position between the standing and sitting positions using an inertial measurement unit

Aims

The purpose of this study was to compare the natural head position (NHP) in the sitting position to the NHP in a standing position using inertial measurement unit (IMU) and lateral photographs.

Matierials & Methods

Twenty healthy young adult volunteers were asked to look at a mirror located at 1 metre in front of their eyes while being recorded with the IMU system. Lateral photographs were also taken. This procedure was undertaken for the standing and sitting positions, on two separate occasions within a one‐week interval.

Results

A strong correlation was found between the IMU system and the lateral photographs (r > .99) with regard to the pitch axis, the absolute mean difference was 0.4 ± 0.5 (p = .99) for both standing and sitting positions. We found that in the sitting position the head was elevated by 2.5 ± 2.4 (p < .05) more than in the standing position, but no significant differences were observed for the other two axes (roll and yaw).

Conclusion

The IMU system is comparable to lateral photographs for pitch assessment. Except for a slight elevation of the head in the sitting position, no clinical differences were observed for the NHP when comparing the standing and sitting positions.

Are the Reasons Why Patients Are Referred for an Orthodontic Visit Correct?

Who does refer patients for an orthodontic consultation? Which are the main reasons for the referral? Does the visit of the orthodontic specialist confirm these reasons or reveal undiagnosed problems? Is there the risk that only evident dental problems are addressed, while craniofacial malformations remain underdiagnosed? This cross-sectional epidemiologic study aims to answer these questions, analysing the clinical data collected during the orthodontic visits of 500 Caucasian young patients referred to a public health structure of northern Italy. All patients were visited by the same expert specialist in orthodontics. Clinical data were collected, analysing both dental and skeletal features. The reasons for the referral of the visit were analysed and compared with the specialistic diagnoses. In our sample, dentists, relatives/friends and paediatricians were the major source of the referrals, followed by family doctors and other facial specialists. In most cases, the reasons for the referral were dental irregularities, but approximately 80% of dental irregularities were associated with undiagnosed facial dysmorphism. Skeletal facial anomalies need an early diagnosis to prevent the development of severe facial malformations that would require invasive and expensive treatments. These findings reveal poor diagnostic skills regarding skeletal anomalies in dentists and paediatricians and the need for better specific training.

Does Head Orientation Influence 3D Facial Imaging? A Study on Accuracy and Precision of Stereophotogrammetric Acquisition

This study investigates the reliability and precision of anthropometric measurements collected from 3D images and acquired under different conditions of head rotation. Various sources of error were examined, and the equivalence between craniofacial data generated from alternative head positions was assessed. 3D captures of a mannequin head were obtained with a stereophotogrammetric system (Face Shape 3D MaxiLine). Image acquisition was performed with no rotations and with various pitch, roll, and yaw angulations. On 3D images, 14 linear distances were measured. Various indices were used to quantify error magnitude, among them the acquisition error, the mean and the maximum intra- and inter-operator measurement error, repeatability and reproducibility error, the standard deviation, and the standard error of errors. Two one-sided tests (TOST) were performed to assess the equivalence between measurements recorded in different head angulations. The maximum intra-operator error was very low (0.336 mm), closely followed by the acquisition error (0.496 mm). The maximum inter-operator error was 0.532 mm, and the highest degree of error was found in reproducibility (0.890 mm). Anthropometric measurements from alternative acquisition conditions resulted in significantly equivalent TOST, with the exception of Zygion (l)–Tragion (l) and Cheek (l)–Tragion (l) distances measured with pitch angulation compared to no rotation position. Face Shape 3D Maxiline has sufficient accuracy for orthodontic and surgical use. Precision was not altered by head orientation, making the acquisition simpler and not constrained to a critical precision as in 2D photographs.

Variation between natural head orientation and Frankfort horizontal planes in orthognathic surgery patients: 187 consecutive cases

The purpose of this study was to assess the relationship between the Frankfort horizontal (FH) and natural head orientation (NHO), their correlation between patients' malocclusion, and the impact of counterclockwise rotation (CCW) on the FH-NHO angle variation after orthognathic surgery. An evaluation of 187 consecutive patients was performed at the Maxillofacial Institute (Teknon Medical Center, Barcelona). FH-NHO° was measured pre- and postoperatively at 1 and 12 months, after three-dimensional (3D) superimposition using a software (Dolphin®). Patients were classified as follows: 3.2%, 48.7% and 48.1%, class I, II and III, respectively. Baseline FH-NHO° was significantly positive for patients with dentofacial deformities (2.73°±4.19 (2.12-3.33°, P<0.001). The impact of orthognathic surgery in FH-NHO° was greater in class II when compared with class III patients, with a variation of 2.04°±4.79 (P<0.001) and -1.20°±3.03 (P<0.001), respectively. FH-NHO° increased when CCW rotational movements were performed (P=0.006). The results of this study suggest that pre- and postoperative NHO differs from FH in orthognathic patients. The angle between FH and NHO is significantly larger in class III than in class II patients at baseline, which converges after orthognathic surgery when CCW rotation is performed. Therefore, NHO should be used as the real horizontal plane when planning for orthognathic surgery.

A comparative study of the accuracy between two computer-aided surgical simulation methods in virtual surgical planning

OBJECTIVE

The aim of this retrospective and observational study was to compare the accuracy of two different virtual surgical planning (VSP) protocols, namely, the CASS method and the modified CASS method.

MATERIALS AND METHODS

The patients underwent bimaxillary orthognathic surgery, planned using either the CASS method or the modified CASS method. Linear and angular discrepancies between the VSP outcome and postoperative outcome for both groups were compared for maxilla, mandible, and chin segments. Aside from the comparison between both groups, additional criteria were used to determine the accuracy of the protocol based on a linear and angular difference between planned and actual outcomes of less than 2 mm and 4°, respectively. The intergroup comparisons were performed by one-way ANOVA, with the level of significance set at 5%.

RESULTS

A total of 21 patients, of both genders, were assigned into group I (n = 11), planned with the CASS method, and group II (n = 10), planned with the modified CASS method. Both the CASS and modified CASS methods presented similar accuracy with regard to linear differences for the maxilla, mandible, and chin segments, except for ΔX for the mandibular segment, where the modified CASS method showed slightly better accuracy. However, there was a statistically significant difference with regard to angular differences in the chin segment, with the CASS method shown to be the more accurate. Aside from Δpitch for the chin segment, no linear or angular differences exceeded 2 mm or 4°.

CONCLUSION

Although statistically significant differences were found with regard to angular measurements in the chin segment, the accuracy of the modified CASS method for virtual planning can be considered as clinically equivalent, with a performance comparable to that of the CASS method.

Occlusal Plane and Skeletal Changes After Cervical Headgear Treatment With and Without Lower Utility Arch in Class II Growing Patients

The purpose of this study was to investigate skeletal and dental changes affecting occlusal plane inclination after cervical headgear treatment with and without lower utility arch. In order to distinguish the orthodontic changes from natural growth a control group was employed.The sample of this study consisted by 20 Class II subjects (10 males, 10 females; mean age 8.54) treated by using cervical headgear, 19 class II children (19 males, 9 females; mean age 8.64) treated with cervical headgear and utility arch, and 21 Class II patients (11 males, 10 females; mean age 8.41) who had no therapy.Lateral head films were studied for all the patients before treatment (T1) and after therapy (T2) for all the treated groups and at the beginning and at the end of observational period for the control group; cephalometric analysis was carried out in order to seek for the modifications between time points and between groups.Means and standard deviation have been analyzed for all the groups. In order to compare the modification between the time points within the same group the ANOVA test was applied. The ANOVA test was used to compare the mean differences (T2-T1) of 3 groups.The study revealed that there were significant changes in occlusal plane inclination after the different treatment modalities employed instead control group. The treatment with cervical headgear and utility arch is more effective than cervical headgear alone in lowering occlusal plane posteriorly when it is compared with controls.

Associations Among Temporomandibular Joint Osteoarthritis, Airway Dimensions, and Head and Neck Posture

PURPOSE

This study sought to investigate associations among progressive temporomandibular joint osteoarthritis (TMJ OA), airway dimensions, and head and neck posture.

MATERIALS AND METHODS

In total, 114 temporomandibular disorders (TMDs) patients were enrolled. Among 114 patients, 28 had no pathologic bony changes in the TMJ condyles (TMDnoOA), 45 had progressive TMJ OA (TMJOApro), and 41 demonstrated TMJ OA which had not progressed for 12 months (TMJOAnopro). TMJ OA was diagnosed based on the Diagnostic Criteria for TMD axis I. Computed tomography (CT) images and lateral cephalograms were obtained at baseline (T0) and 12 months after treatment (T1). The head and neck posture and airway area in upright position were analyzed using lateral cephalograms whereas airway volume in supine position was determined by 3D reconstructed CT images.

RESULTS

The volume change of the oropharynx in supine position was more prominent in the TMJOApro than in the TMDnoOA but no significant differences in changes in the pharyngeal airway while in upright position were detected. The retrognathic facial profile became more remarkable at T1 in the TMJOApro and TMJOAnopro compared to those at T0. The forward head posture seemed to be progressed in the TMJOApro than in either the TMJOAnopro or TMDnoOA.

CONCLUSION

Progressive TMJ OA may have associations with retrognathia and decreased oropharyngeal airway volume in the supine position but not in the upright position. Progressive TMJ OA may be related with altered head posture in the upright position to compensate for reduced airway dimensions.

Accuracy of 3D virtual surgical planning for maxillary positioning and orientation in orthognathic surgery

OBJECTIVE

This retrospective and observational study evaluated the accuracy of a 3D virtual surgical planning (VSP) for the maxillary positioning and orientation in patients undergoing bimaxillary orthognathic surgery, comparing the planned and postoperative outcomes.

SETTING AND SAMPLE POPULATION

Seventy consecutive patients of both sexes, who were submitted to bimaxillary orthognathic surgery between 2015 and 2019 were included in our study.

MATERIAL AND METHODS

The patients were evaluated by fusing preoperative planning and postoperative outcome using cone-beam computed tomography scan evaluation. Three-dimensional VSP and postoperative outcomes were compared by using three linear and three angular measurements. The main outcome interest was the difference between the VSP movement, and the surgical movement obtained. The success criterion adopted was a mean linear difference of <2 mm and a mean angular difference of <4°.

RESULTS

Results were analysed using a linear mixed model with fixed and random effects, at α = .05. No significant statistical differences were found for linear and angular measurements between the planned and postsurgical outcomes (P > .05). All overlapping points presented values within the range considered clinically irrelevant (<2 mm; <1°).

CONCLUSIONS

Three-dimensional VSP was executed with a high degree of accuracy. When comparing the planned and postsurgical outcomes, all overlapping points presented values within the range considered clinically irrelevant.

Splintless orthognathic surgery in edentulous patients-a pilot study

The aim of this pilot study was to evaluate the accuracy and predictability of a splintless treatment protocol for edentulous patients undergoing orthognathic surgery in four consecutive cases. All operations were virtually planned, followed by computer-aided design of individual osteotomy guides and patient-specific fixation implants, which were three-dimensionally printed in titanium. In order to evaluate the discrepancy between the planned and the achieved postoperative result, the postoperative outcome was compared to the virtual treatment plan. Rotational and translational movement and discrepancies with the planned movements were quantified for the maxilla; the advancement was quantified for the mandible. For the maxilla, there was a mean translation discrepancy of 0.6mm. With regard to rotation, there was a mean discrepancy of 1.9°, 0.1°, and 0.4° for pitch, yaw, and roll, respectively. The mean discrepancy in translation of the mandible was 0.4mm. The results of this pilot study indicate that the splintless treatment protocol for orthognathic surgery in edentulous patients presented here is accurate and predictable.

Internal and external sagittal craniovertebral alignment: A comparison between radiological and photogrammetric approaches in asymptomatic participants

BACKGROUND

Photogrammetric measures are a commonly applied, highly reliable tool for appraising craniovertebral postures during clinical assessments, rehabilitation, and research interventions.

OBJECTIVE

This study aimed to compare and contrast three external measures of postural alignment (EMPA) using photogrammetric and radiological approaches, and to discuss whether the craniovertebral angle (CVA) reflects the shape of the underlying cervical spine.

DESIGN

Cross Sectional Correlation Study.

METHOD

Young adults attended three assessment sessions (S1, S2 and S3). S1 involved a standardised photogrammetric protocol. S2 involved radiographic image acquisition. S3 followed the same protocol in S1 but excluded the self-balancing procedure. Each session's EMPA were compared through either paired or independent samples t-tests. The different radiographic cervical subtypes and their corresponding CVAs were assessed.

RESULTS

There were no significant differences in any EMPA between the two photogrammetric sessions. The CVA was the only EMPA to show a significant difference between photogrammetric (S3) and radiographic approaches. Cervical subtype variability is present throughout the full CVA range.

CONCLUSIONS

Despite the statistically significant difference in the CVA between approaches, the mean difference was small and unlikely to be clinically meaningful. Accordingly, the quantification of EMPA can be undertaken with high levels of precision and reliability using standardised photogrammetric procedures. The CVA, however, does not provide an indication of the shape of the underlying cervical spine. The distinct radiological differences in the inter-segmental orientation of each vertebral motion segment in conjunction with the differences in the overall global cervical alignment, both within and between participants, negate this possibility.

Are orthodontic landmarks and variables in digital cephalometric radiography taken in fixed and natural head positions reliable?

OBJECTIVE

The purpose of the study was to evaluate the reliability of the most common landmarks and variables in digital lateral cephalometric radiographies in fixed and natural head positions.

MATERIALS AND METHODS

Twenty-one patients with anterior or distal displacement of the mandible treated in the Postgraduate Orthodontic Clinic of the Aristotle University of Thessaloniki had a digital lateral cephalometric radiography in fixed and in natural head position. The images where digitized. The main investigator and 6 examiners, digitized 61 landmarks and analysed 34 variables. We examined the intra-observer and inter-observer variability.

RESULTS

There was a significant difference in X-axis in the distribution (hence the mean results) according to the reliability of the landmarks and in only 2 variables in digital lateral cephalograms between fixed and natural head position.

CONCLUSIONS

Cephalometric landmarks and variables showed reliability in digital lateral cephalometric radiography in fixed and natural head position. In lateral cephalograms taken in fixed head position an anterior inclination of the head was noticed compared to those in natural head position.

Thoracic-lumbar-sacral spine sagittal alignment and cranio-mandibular morphology in adolescents

PURPOSE

The relationship between thoracic-lumbar-sacral spine sagittal alignment and craniofacial morphology is still controversial. Evidence-based results are difficult to obtain and scientific studies are inhomogeneous. The aim of this study was to investigate the difference of thoracic-lumbar-sacral spine posture and cephalometric values comparing two groups of subjects with different cranial structure in the sagittal plane.

METHODS

Eighty-one subjects were consecutively selected and divided into two groups, according to the orientation of the condyle-orbital plane (CoOr) with respect to the superior maxilla (SpP): Group1: 49 subjects 11.6 (2.1) years showing posterior-rotation of CoOr: SpP^CoOr ≤ -2°, -4.1°(2.1°); Group2: 32 subjects 12.9 (2.3)years showing anterior-rotation of CoOr: SpP^CoOr ≥ 2°, 3.7°(1.9°). Each patient underwent in blinding, Spinal Mouse recording and cephalometry of the skull.

RESULTS

Group1 showed a significant forward tilting of the spine 4.4°(1.8°) with respect to Group2 2.4°(1.3°) (p < 0.0001) and higher values related to the vertical dimension of the skull: higher maxillary divergency (p < 0.0001), steep occlusal plane (p < 0.0007), higher gonial angle (p < 0.001).

DISCUSSION

The results of this study showed a difference in the thoracic-lumbar-sacral spine inclination between groups with different craniofacial morphology. The achievement of this outcome is important to improve our multidisciplinary evaluation and treatment planning.

An integrated haptic-enabled virtual reality system for orthognathic surgery planning

Conventional Orthognathic surgery (OGS) planning involves cephalometric analyses and dental casts to be mounted on an articulator. Dental segments are subsequently identified, cut and repositioned to allow the fabrication of intraoral wafers that guide the positioning of the osteotomy bone segments. This conventional planning introduces many inaccuracies that affect the post-surgery outcomes. Although computer technologies have advanced computational tools for OGS planning, they have failed in providing a practical solution. Many focuses only on some specific stages of the planning process, and their ability to transfer preoperative planning data to the operating room is limited. This paper proposes a new integrated haptic-enabled virtual reality (VR) system for OGS planning. The system incorporates CAD tools and haptics to facilitate a complete planning process and is able to automatically generate preoperative plans. A clinical pre-diagnosis is also provided automatically by the system based on the patient's digital data. A functional evaluation based on a real patient case study demonstrates that the proposed virtual OGS planning method is feasible and more effective than the traditional approach at increasing the intuitiveness and reducing errors and planning times.

Osteo-regeneration personalized for children by rapid maxillary expansion: an imaging study based on synchrotron radiation microtomography

Background

Personalized maxillary expansion procedure has been proposed to correct maxillary transversal deficiency; different protocols of stem cell activation have been suggested and rapid maxillary expansion (RME) is the most commonly used among clinicians. The present study aimed to quantify in three-dimensions (3D) the osteo-regeneration of the midpalatal suture in children submitted to RME.

Methods

Three patients (mean age 8.3 ± 0.9 years) were enrolled in the study to preform biopsy of midpalatal suture. Two patients (subjects 1 and 2) were subjected to RME before biopsy. The third patient did not need maxillary expansion treatment and was enrolled as control (subject 3). Midpalatal suture samples were harvested 7 days after RME in subject 1, and 30 days after RME in subject 2. The samples were harvested with the clinical aim to remove bone for the supernumerary tooth extraction. When possible, maxillary suture and bone margins were both included in the sample. All the biopsies were evaluated by complementary imaging techniques, namely Synchrotron Radiation-based X-ray microtomography (microCT) and comparative light and electron microscopy.

Results

In agreement with microscopy, it was detected by microCT a relevant amount of newly formed bone both 7 days and 30 days after RME, with bone growth and a progressive mineralization, even if still immature respect to the control, also 30 days after RME. Interestingly, the microCT showed that the new bone was strongly connected and cross-linked, without a preferential orientation perpendicular to the suture’s long axis (previously hypothesized by histology), but with well-organized and rather isotropic 3D trabeculae.

Conclusions

The microCT imaging revealed, for the first time to the authors’ knowledge, the 3D bone regeneration in children submitted to RME.

Electronic supplementary material

The online version of this article (10.1186/s12903-018-0590-7) contains supplementary material, which is available to authorized users.

Postural assessment in class III patients before and after orthognathic surgery

PURPOSE

This study aimed to assess body posture before and after bimaxillary orthognathic surgery by photogrammetry in skeletal class III patients.

METHODS

Thirty-one patients with skeletal class III dentofacial deformities (14 men, 17 women) who underwent orthodontic preparation for surgery were included in this non-randomized controlled trial. Of these, 15 who did not undergo orthognathic surgery during the period of this study served as controls. Postural assessment was performed by photogrammetry using SAPO® (Postural Assessment Software) based on anterior-, posterior-, and lateral-view images taken 1 month before and 4 months after bimaxillary orthognathic surgery with internal rigid fixation (or 4 months after the initial assessment, for the control group). The study was approved by PUCRS Research Ethics Committee, and written informed consent was obtained from all individual participants prior to their inclusion in the study.

RESULTS

There was no significant difference between groups for age, gender, and GAP. In the intervention group, the right leg/hindfoot angle, which initially indicated a valgus deformity, normalized after intervention (P < 0.048). Posterior displacement of the head (P < 0.005) and trunk (P < 0.004) were observed after intervention.

CONCLUSIONS

These results suggest that correction of class III dentofacial deformities by bimaxillary orthognathic surgery can produce systemic postural adjustments, especially posterior displacement of the head and trunk and knee and ankle valgus.

Impact of pediatric obstructive sleep apnea on the development of Class II hyperdivergent patients receiving orthodontic treatment: A pilot study

OBJECTIVES

To conduct a pilot study to determine if the presence of obstructive sleep apnea (OSA) influences the orthodontic treatment outcome of Class II hyperdivergent patients receiving comprehensive orthodontic treatment.

MATERIALS AND METHODS

Patients between the ages of 12 and 14 who received orthodontic treatment at the Hospital of Stomatology, Wuhan University, China, were included in this study. Patients were divided into two groups: the OSA group and the control group, based on the outcome of pretreatment polysomnography findings and lateral cephalometric radiograph examination. Patients in the control group were matched with the OSA group for age, sex, ethnicity, weight, and height. Cephalometric measurements were used to record the skeletal and dental changes from before to after treatment. Data were analyzed using the t-test.

RESULTS

Twenty three OSA patients and 23 control patients were included. After comprehensive orthodontic treatment, the mandibular plane angle (SN-GoMe), articular angle (SArGo), sum of Jarabak angles (SUM) and the lower gonial angle (NGoMe) were found to increase significantly in the OSA group but remained unchanged or decreased slightly in the control group ( P < .05). In the non-OSA group, the growth pattern became more horizontal. In contrast, in the OSA group the growth pattern became more vertical. Otherwise, similar treatment results were obtained for both groups in terms of sagittal change and occlusion.

CONCLUSIONS

The presence of OSA in pediatric patients has a deleterious effect on the development of hyperdivergent malocclusions. Early diagnosis and management of pediatric OSA can affect the orthodontic treatment outcome of these patients.

Digital Dynamic 3D Monitoring of Lower Incisors Intrusion in Lingual Orthodontics

Objective

The aim of the present study is to propose a 3-dimensional evaluation of lower intrusion obtained with lingual orthodontics considering not only the crowns but also dental roots.

Methods

9 adult patients underwent fixed lingual orthodontic treatment with i-TTя lingual brackets system for the correction of crowding in the lower arch associated with a deep overbite. Initial records, consisting of photos, CBCTs and intraoral scans were collected. Threshold segmentation of the CBCT was performed to generate a three-dimensional virtual model of each the teeth of the lower arch, superimposed with the crown of the same teeth obtained by intraoral scan models to generate a complete set of digital composite lower arch The same procedure was performed to monitor one key step of the i-TT_Я technique consisting in lower incisors intrusion (T2). T1-T2 three-dimensional superimposition and color displacement maps were generated to measure and evaluate the movements obtained at the lower arch.

Results

The root displacement of the incisors during their intrusion in the early stage was totally "bone-safe" in the 88.9% (8 of 9) of the cases observed. No significant extrusion of the premolars used as anchorage unit was measured.

Conclusion

This method has proved to be an accurate and reliable approach to dynamically visualize the 3-dimensional positions of the teeth, including their roots, with no additional radiation for in-progress treatment monitoring. The 3-dimensional evaluation showed that the employed lingual appliance allowed to obtain significant lower incisors intrusion with negligible undesired extrusion of premolars employed as anchorage teeth.

Early Orthopaedic Treatment of Hemifacial Microsomia

The aim of this paper is to report treatment effects of functional therapy in a growing patient affected by hemifacial microsomia (HM). According to Kaban's classification, the patient was classified as grade IIa as she presented all mandibular and temporomandibular joint components and a normal shaped, hypoplastic mandible. The therapeutic approach included the use of an asymmetrical functional activator (AFA) to stimulate the growth of the affected side and consequently to improve symmetry of the mandible and maxillary deficiency. Further effects were the lengthening of the mandibular ramus, restoration of occlusion, and expansion of soft tissues.

Virtual Planning of a Complex Three-Part Bimaxillary Osteotomy

In maxillofacial surgery, every patient presents special problems requiring careful evaluation. Conventional methods to study the deformities are still reliable, but the advent of tridimensional (3D) imaging, especially computed tomography (CT) scan and laser scanning of casts, created the opportunity to better understanding the skeletal support and the soft tissue structures. Nowadays, virtual technologies are increasingly employed in maxillofacial surgery and demonstrated precision and reliability. However, in complex surgical procedures, these new technologies are still controversial. Especially in the less frequent cases of three-part maxillary surgery, the experience is limited, and scientific literature cannot give a clear support. This paper presents the case of a young patient affected by a complex long face dentofacial deformity treated by a bimaxillary surgery with three-part segmentation of the maxilla. The operator performed the surgical study completely with a virtual workflow. Pre- and postoperative CT scan and optical scanning of plaster models were collected and compared. Every postoperatory maxillary piece was superimposed with the presurgical one, and the differences were examined in a color-coded map. Only mild differences were found near the osteotomy lines, when the bony surface and the teeth demonstrated an excellent coincidence.

Digital evaluation of nasal changes induced by rapid maxillary expansion with different anchorage and appliance design

BACKGROUND

Scientific evidence showed that rapid maxillary expansion (RME) affects naso-maxillary complex, increasing nasal width and volume. This study aimed to evaluate nasal changes induced by rapid maxillary expansion with different anchorage and appliance design by using low dose and cone beam computed tomography.

METHODS

A total of 44 patients (20 males, mean age 8y 8 m ± 1y 2 m; 24 females mean age 8y 2 m ± 1y 4 m) were included in the investigation and divided into three groups according to the appliance: Hyrax-type expander anchored to permanent teeth, modified Hyrax-type expander anchored to deciduous teeth, modified Haas-type expander anchored to deciduous teeth. Maxillary expansion was performed until overcorrection and the expander was passively kept in situ for 7 months at least. All patients had three-dimensional imaging before expansion (T0) and after the retention period (T1). Nasal floor width, nasal wall width, maxillary inter-molar width were measured by means of Mimics software. The paired sample t-test was employed to assess the significance of the differences between the time points; the analysis of variance test (ANOVA) was used to compare differences between groups.

RESULTS

The statistical analysis revealed significant differences between T0 and T1 for each recorded measurement in each group; no significant differences were found by comparing groups.

CONCLUSIONS

Rapid maxillary expansion produces a significant skeletal transverse expansion of nasal region in growing patients. No significant differences in nasal effects are expected when the appliance is anchored onto deciduous teeth, with or without the palatal acrylic coverage.

There is variability in our perception of the standard head orientation

The purposes of this study were to determine: (1) whether an observer's perception of the correct anatomical alignment of the head changes with time, and (2) whether different observers agree on the correct anatomical alignment. To determine whether the perception of the correct anatomical alignment changes with time (intra-observer comparison), a group of 30 observers were asked to orient, into anatomical alignment, the three-dimensional (3D) head photograph of a normal man, on two separate occasions. To determine whether different observers agree on the correct anatomical alignment (inter-observer comparison), the observed orientations were compared. The results of intra-observer comparisons showed substantial variability between the first and second anatomical alignments. Bland-Altman coefficients of repeatability for pitch, yaw, and roll, were 6.9°, 4.4°, and 2.4°, respectively. The results of inter-observer comparisons showed that the agreement for roll was good (sample variance 0.4, standard deviation (SD) 0.7°), the agreement for yaw was moderate (sample variance 2.0, SD 1.4°), and the agreement for pitch was poor (sample variance 15.5, SD 3.9°). In conclusion, the perception of correct anatomical alignment changes considerably with time. Different observers disagree on the correct anatomical alignment. Agreement among multiple observers was bad for pitch, moderate for yaw, and good for roll.

Asymmetric Expansion with a Modified Quad Helix for Treatment of Isolated Crossbite

Unilateral posterior crossbite often involves only one tooth, especially upper first molar; in these cases it is never easy to obtain an asymmetrical movement of a molar and a proper planning of the orthodontic device with its anchorage is necessary to avoid arch overexpansion. Thanks to its simplicity and efficacy, the modified Quad Helix here described represents a valid therapeutic tool in cases of isolated posterior crossbite.

Prediction of Class II improvement after rapid maxillary expansion in early mixed dentition

BACKGROUND

The aim of this study is to identify cephalometric pretreatment parameters for prediction of Class II improvement induced by rapid maxillary expansion.

METHODS

Lateral cephalograms of 30 patients (mean age 8.3 ± 1.6 years old) showing Class II molar relationship and undergone to rapid maxillary expansion on the upper deciduous molars were traced before treatment, and molar relation changes were evaluated on dental casts before and after treatment. Overall treatment time lasted 10.2 ± 2 months. Good responders (18 subjects, 10 females and 8 males) showed improvement of at least 2.50 mm, and bad responders (12 subjects, 7 females and 5 males) showed no improvement, improvement less than 2.50 mm, or worsening of molar relationship after treatment. Student's t test was used to assess significance of differences between groups, and discriminant analysis allowed identification of predictive pretreatment variables.

RESULTS

Articular angle, superior gonial angle, and mandibular dimensions (Co-Gn, S-Ar, Ar-Go, Go-Me) showed significant differences in the comparison between groups. Mandibular length Co-Gn and superior gonial angle were selected as significant predictive variable for discrimination.

CONCLUSIONS

Patients with smaller mandibular length and more acute superior gonial angle are expected to have more chances to improve molar Class II after rapid maxillary expansion.

Pre- and Postsurgical Orthodontics in Patients with Moebius Syndrome

The authors report a combined orthodontic-surgical correction of an adult patient's malocclusion affected by Moebius Syndrome (MS). The treatment was conducted at the Dentistry Unit and the Maxillofacial Surgery Unit of the University Hospital of Parma. Treatment of malocclusion was performed after the correction of facial mimic mobility with smile surgery. The postoperative stability and orthodontic results were good and the correction of the morphological problems related to the syndrome was very satisfactory.

Cellular Midpalatal Suture Changes after Rapid Maxillary Expansion in Growing Subjects: A Case Report

The present case report aimed to investigate immediate histologic changes in midpalatal suture in humans following rapid maxillary expansion compared to control. Three patients (mean age 8.3 ± 0.9 years) were enrolled in the case report and underwent midpalatal suture biopsy. Two patients underwent treatment before biopsy. The third patient did not show transversal maxillary deficiency and was enrolled as a control. Biopsy samples of midpalatal suture at 7 (subject 1) and 30 days (subject 2) after maxillary expansion as well as of one control (subject 3) were collected and processed for histology. In the control (subject 3) inter-digitations at the palatal suture gap were observed. At 7 days (subject 1) mature bone with small marrow spaces and trabecular bone with the peculiar storiform appearance inside the soft tissue and collagen fibers running parallel only in the central part were present. At 30 days (subject 2), a greater number of newly-formed bone trabeculae with a perpendicular orientation to the long axis of the suture could be seen. At 30 days the fibrous component of bone tissue was less represented compared to the sample at 7 days. Data from the preliminary histological results showed that bone formation was observed in the gap after rapid maxillary expansion, although the healing process was still ongoing.

[Inclination of crown and tooth longitudinal axis in cephalometric analysis of normal occlusions]

OBJECTIVE

We measured and analyzed the angle between the longitudinal axis of incisor crown and tooth to provide a reference for orthodontists for selecting orthodontic methods and evaluating treatment results.

METHODS

A total of 120 participants were included according to the criteria of Andrews' six keys, and cephalometric radiograph under the instructions of modified natural head position acquirement method was performed. The angles of maxillary incisor crown longitudinal axis, tooth longitudinal axis, occlusion plane (OP), and true vertical (TV) plane were measured, as well as mandibular incisors.

RESULTS

As for maxillary incisors, the angle between crown longitudinal axis and TV plane, OP, and tooth longitudinal axis were 11.72°±4.71°, 73.29°±5.69°, and 20.04°±3.71°, respectively. For mandibular incisors, the angle between crown longitudinal axis and TV plane, OP, and tooth longitudinal axis were 16.03°±5.40°, 81.76°±4.81°, and 14.82°±4.01°, respectively. For the maxillary incisor, the angles between crown longitudinal axis and tooth longitudinal axis were mainly within 15° to 25°, whereas those for mandibular incisors were within 10° to 20°.

CONCLUSIONS

The longitudinal axis inclinations of the maxillary and mandibular incisor crown and of the incisor tooth need to be considered when cephalometric radiographs are used for treatment planning or for evaluating the treatment result.