Establishment of the mid-sagittal reference plane for three-dimensional assessment of facial asymmetry: a systematic review : Establishment of the mid-sagittal reference plane: a systematic review.

OBJECTIVE: To systematically review the literature for mid-sagittal plane establishment approaches to identify the most effective method for constructing the mid-sagittal plane for the evaluation of facial asymmetry. MATERIALS AND METHODS: Six electronic databases (PubMed, Medline (via Ovid), EMBASE (via Ovid), Cochrane Library, Web of Science, and Scopus) and grey literature were searched for the studies that computed the mid-sagittal reference plane three-dimensionally, using a combination of MeSH terms and keywords. The methodological quality and the level of evidence for the included studies were analyzed using QUADAS-2 and GRADE, respectively. RESULTS: The preliminary search yielded 6746 records, of which 42 articles that met the predefined inclusion criteria were included in the final analysis. All the included articles reported the construction of the mid-sagittal reference plane (MSP) using varied methods. The risk of bias and concerns regarding the applicability of the included studies were judged to be 'low'. The level of evidence was determined to be 'low' for the effectiveness of the technique and 'moderate' for the ease of clinical applicability. CONCLUSION: Despite methodological heterogeneity, this review substantiates the comparable efficacy of cephalometric and morphometric MSP construction methods. A fully automated morphometric MSP holds promise as a viable option for routine clinical use. Nevertheless, future prospective studies with an emphasis on the impact, accuracy, and clinical applicability of MSP construction techniques in cases of facial asymmetry are required. CLINICAL RELEVANCE: The present review will assist clinicians in selecting the most suitable method for MSP construction, leading to improved treatment planning and ultimately more favorable treatment outcomes.

Frontiers in Three-Dimensional Surface Imaging Systems for 3D Face Acquisition in Craniofacial Research and Practice: An Updated Literature Review.

Digitalizing all aspects of dental care is a contemporary approach to ensuring the best possible clinical outcomes. Ongoing advancements in 3D face acquisition have been driven by continuous research on craniofacial structures and treatment effects. An array of 3D surface-imaging systems are currently available for generating photorealistic 3D facial images. However, choosing a purpose-specific system is challenging for clinicians due to variations in accuracy, reliability, resolution, and portability. Therefore, this review aims to provide clinicians and researchers with an overview of currently used or potential 3D surface imaging technologies and systems for 3D face acquisition in craniofacial research and daily practice. Through a comprehensive literature search, 71 articles meeting the inclusion criteria were included in the qualitative analysis, investigating the hardware, software, and operational aspects of these systems. The review offers updated information on 3D surface imaging technologies and systems to guide clinicians in selecting an optimal 3D face acquisition system. While some of these systems have already been implemented in clinical settings, others hold promise. Furthermore, driven by technological advances, novel devices will become cost-effective and portable, and will also enable accurate quantitative assessments, rapid treatment simulations, and improved outcomes.

Can smartphones be used for routine dental clinical application? A validation study for using smartphone-generated 3D facial images.

OBJECTIVES: To compare the accuracy of smartphone-generated three-dimensional (3D) facial images to that of direct anthropometry (DA) and 3dMD with the aim of assessing the validity and reliability of smartphone-generated 3D facial images for routine clinical applications. MATERIALS AND METHODS: Twenty-five anthropometric soft-tissue facial landmarks were labelled manually on 22 orthognathic surgery patients (11 males and 11 females; mean age 26.2 ± 5.3 years). For each labelled face, two imaging operations were performed using two different surface imaging systems: 3dMDface and Bellus3D FaceApp. Next, 42 inter-landmark facial measurements amongst the identified facial landmarks were measured directly on each labelled face and also digitally on 3D facial images. The measurements obtained from smartphone-generated 3D facial images (SGI) were statistically compared with those from DA and 3dMD. RESULTS: SGI had slightly higher measurement values than DA and 3dMD, but there was no statistically significant difference between the mean values of inter-landmark measures across the three methods. Clinically acceptable differences (≤3 mm or ≤5°) were observed for 67 % and 74 % of measurements with good agreement between DA and SGI, and 3dMD and SGI, respectively. An overall small systematic bias of ± 0.2 mm was observed between the three methods. Furthermore, the mean absolute difference between DA and SGI methods was highest for linear (1.41 ± 0.33 mm) as well as angular measurements (3.07 ± 0.73°). CONCLUSIONS: SGI demonstrated fair trueness compared to DA and 3dMD. The central region and flat areas of the face in SGI are more accurate. Despite this, SGI have limited clinical application, and the panfacial accuracy of the SGI would be more desirable from a clinical application standpoint. CLINICAL SIGNIFICANCE: The usage of SGI in clinical practice for region-specific macro-proportional facial assessment involving central and flat regions of the face or for patient education purposes, which does not require accuracy within 3 mm and 5° can be considered.

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.

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.

Morphometric characteristics of the sphenoid sinus and potential influencing factors: a retrospective assessment using cone beam computed tomography (CBCT).

The present study aimed to evaluate the morphological characteristics of the sphenoid sinus (SS), and the impact of potential influencing factors on the morphometric features using CBCT imaging. CBCT scans of 148 patients, aged between 15 and 85 (32.88 ± 15.33) years were retrospectively evaluated. DICOM files from the CBCT scans were imported into semi-automatic software and the SS of each patient was assessed for the morphological characteristics including configuration, symmetry, extension, shape, septation, volume, and maximum diameter. Furthermore, potential influencing factors such as age, gender, side, and sinus condition were analysed. A significant association was observed between sinus extension and age. Septation was also found to be significantly associated with age, gender and sinus condition. Besides, sinus volume was significantly associated with gender and sinus condition. No significant influence of shape and side on the morphometric features was noticed. The average volume and diameter of the SS were 6576.92 ± 3748.12 mm3 and 30.48 ± 9.28 mm, respectively. In conclusion, the present findings indicate that age, gender and sinus condition have a significant impact on the morphometric characteristics of the SS. Mature sinuses exhibit a post-sellar extension pattern until middle age. In addition, males, and sinuses with healthy sinus condition have larger volumes compared to females and pathological sinuses.

Three-dimensional evaluation of soft-tissue response to osseous movement after orthognathic surgery in patients with facial asymmetry: A systematic review.

To systematically assess the current literature on soft-tissue response associated with osseous movement following orthognathic surgery in patients with facial asymmetry. Six electronic databases (PubMed, EMBASE (via Ovid), Medline (via Ovid), Cochrane Library, Scopus, and Web of Science) and gray literature were searched for studies evaluating hard- and soft-tissue responses three-dimensionally after orthognathic surgery, using MeSH terms and keywords. The methodological quality and level of evidence of the included studies were analyzed using EPHPP and GRADE, respectively. The primary search yielded 125 articles, and 10 articles that satisfied the predefined inclusion criteria were finally included. All the included articles evaluated soft-tissue response, with six of them additionally investigating the magnitude of this response. Soft tissues move with hard tissues horizontally and anteroposteriorly; however, soft-tissue movement is less than hard tissue movement. In addition, soft tissue movement is more pronounced in the lower central facial region. Six articles were judged as having 'strong' methodological quality, while the evidence was found to be of 'low' quality for the soft-tissue response and the magnitude of this response. Despite a low level of evidence, the review substantiates a favorable three-dimensional soft-tissue response following osseous surgery. The soft-tissue response is more pronounced horizontally, anteroposteriorly, and in the lower central facial region. Nevertheless, well-designed prospective studies with a higher level of evidence are needed.

Evaluation of the relationship between malar projection and lower facial convexity in terms of perceived attractiveness in 3-dimensional reconstructed images.

BACKGROUND: This study aimed to investigate dental student's perception of facial attractiveness with regard to different combinations of anteroposterior malar-jaw positions using 3-dimensional (3-D) reconstructed images of subjects. METHODS: Two Chinese young adults (1 male and 1 female) with straight profiles and average malar projections were selected for the study. 3-D facial images and cone-beam computed tomography images of these two subjects were superimposed using 3-D imaging software. Lateral and oblique views of nine different images were created by moving the maxillomandibular complex and/or zygomatic bone by 4 mm either forward or backward along the sagittal plane. One hundred three undergraduate dental students (n = 24, 33, and 46 students from the Year 3, 4, and 5, respectively) then scored lateral and 45° oblique view images of the newly reconstructed faces. RESULTS: In the present study, images with a neutral malar and retruded jaws were found to be the most attractive in both male and female subjects. In addition, the Protruded malar (PM) group (p < 0.001), and the Retruded Jaws (RJ) group were rated more attractive (p < 0.001). Furthermore, the Relatively Prominent malar (RP) group was rated more attractive (p < 0.001) when malar-jaw relative positions were compared. CONCLUSION: This study shows that a neutral or a protruded malar favours facial attractiveness in both Chinese male and female subjects. Therefore, an appropriate relationship between malar projection and lower facial convexity should be taken into consideration while designing the orthodontic/orthognathic treatment plans for enhanced aesthetic outcomes.

Analysis of dentoalveolar structures with novel corticotomy-facilitated mandibular expansion: A 3-dimensional finite element study.

INTRODUCTION: Surgically assisted mandibular arch expansion is an effective treatment modality for alleviating constriction and crowding. However, only mandibular symphyseal osteotomy is recommended for mandibular arch expansion. No relevant studies have compared the biomechanical responses of different corticotomy designs on mandibular expansion. Therefore, the aim of this study was to evaluate the effect of different corticotomy approaches and modes of loading on the expansion of adult mandibles using biomechanics. METHODS: Nine finite element models including 2 novel corticotomy designs were simulated. Stress, strain, and displacement of crown, root, and bone were calculated and compared under different corticotomy approaches and loading conditions. RESULTS: The biomechanical response seen in the finite element models in terms of displacement on the x-axis was consistent from anterior to posterior teeth with parasymphyseal step corticotomy and tooth-borne force application. In addition, the amount of displacement predicted by parasymphyseal step corticotomy in the tooth-borne mode was greater compared with other models. CONCLUSIONS: These results suggest that parasymphyseal step corticotomy with tooth-borne force application is a viable treatment option for true bony expansion in an adult mandible.

Analysis of potential dynamic concealed factors in the difficulty of lower third molar extraction

BACKGROUND: The purpose of this study was to identify potential concealed variables associated with the difficulty of lower third molar (M3) extractions. MATERIAL AND METHODS: To address the research purpose, we implemented a prospective study and enrolled a sample of subjects presenting for M3 removal. Predictor variables were categorized into Group-I and Group-II, based on predetermined criteria. The primary outcome variable was the difficulty of extraction, measured as extraction time. Appropriate univariate and multivariate statistics were computed using ordinal logistic regression. RESULTS: The sample comprised of 1235 subjects with a mean age of 29.49 +/- 8.92 years in Group-I and 26.20 +/- 11.55 years in Group-II subjects. The mean operating time per M3 extraction was 21.24 +/- 12.80 and 20.24 +/- 12.50 minutes for Group-I and Group-II subjects respectively. Three linear parameters including B-M2 height (distance between imaginary point B on the inferior border of mandibular body, and M2), lingual cortical thickness, bone density and one angular parameter including Rc-Cs angle (angle between ramus curvature and curve of spee), in addition to patient's age, profile type, facial type, cant of occlusal plane, and decreased overbite, were found to be statistically associated ( p < or = 0.05) with extraction difficulty under regression models. CONCLUSIONS: In conclusion, our study indicates that the difficulty of lower M3 extractions is possibly governed by morphological and biomechanical factors with substantial influence of myofunctional factors. Practical Implications: Preoperative evaluation of dynamic concealed factors may not only help in envisaging the difficulty and planning of surgical approach but might also help in better time management in clinical practice

Association of Common Variants in MMPs with Periodontitis Risk.

Background. Matrix metalloproteinases (MMPs) are considered to play an important role during tissue remodeling and extracellular matrix degradation. And functional polymorphisms in MMPs genes have been reported to be associated with the increased risk of periodontitis. Recently, many studies have investigated the association between MMPs polymorphisms and periodontitis risk. However, the results remain inconclusive. In order to quantify the influence of MMPs polymorphisms on the susceptibility to periodontitis, we performed a meta-analysis and systematic review. Results. Overall, this comprehensive meta-analysis included a total of 17 related studies, including 2399 cases and 2002 healthy control subjects. Our results revealed that although studies of the association between MMP-8 -799 C/T variant and the susceptibility to periodontitis have not yielded consistent results, MMP-1 (-1607 1G/2G, -519 A/G, and -422 A/T), MMP-2 (-1575 G/A, -1306 C/T, -790 T/G, and -735 C/T), MMP-3 (-1171 5A/6A), MMP-8 (-381 A/G and +17 C/G), MMP-9 (-1562 C/T and +279 R/Q), and MMP-12 (-357 Asn/Ser), as well as MMP-13 (-77 A/G, 11A/12A) SNPs are not related to periodontitis risk. Conclusions. No association of these common MMPs variants with the susceptibility to periodontitis was found; however, further larger-scale and multiethnic genetic studies on this topic are expected to be conducted to validate our results.

Biomechanical Effects of Novel Osteotomy Approaches on Mandibular Expansion: A Three-Dimensional Finite Element Analysis.

PURPOSE: Surgically assisted mandibular arch expansion has proved to be an effective treatment modality in alleviating constriction and crowding issues. However, only mandibular symphyseal distraction osteogenesis has been in favor for the purpose of mandibular arch expansion. In addition, no relevant study has compared the biomechanical response of different osteotomy designs on mandibular expansion. The present study evaluated the effect of different osteotomy approaches and modes of loading on the expansion of the adult mandible using biomechanics. MATERIALS AND METHODS: To address the research purpose, 9 finite element (FE) models, including 2 novel osteotomy designs, were simulated. Stress, strain, and displacement of crown, root, and bone were calculated and compared under different osteotomy approaches and loading conditions. RESULTS: The biomechanical response envisaged by the FE models in terms of displacement on the X axis was consistent from the anterior to posterior teeth with parasymphyseal step osteotomy and a hybrid mode of force application. In addition, the amount of displacement predicted by parasymphyseal step osteotomy with the hybrid mode was greater compared with that of the other models. CONCLUSIONS: The results of our study suggest parasymphyseal step osteotomy with the hybrid mode is a viable treatment option for true bony expansion in the adult mandible.

A meta-analysis of MMP-9 promoter -1562 C/T polymorphism on susceptibility of chronic periodontitis.

BACKGROUND: Although many studies have focused on the association of the MMP-9 promoter -1562 C/T polymorphism with the susceptibility and/or severity of chronic periodontitis (CP), results have been inconsistent. Therefore, a meta-analysis of all eligible studies was performed to derive a more precise estimation of the association between this polymorphism and CP risk. METHODS: All relevant studies were identified through a database search in PubMed, Medline, and Web of Science. All the full-text studies with appropriate analytical design, published in English, which evaluated the association of MMP-9 promoter -1562C/T polymorphism with CP risk using validated genotyping methods, and with non-duplicated data were selected for this study. A fixed-effect model was used to calculate pooled ORs in the absence of heterogeneity across included trials (P > 0.1 and I(2) < 50 %), otherwise the random-effect model was applied. RESULTS: In an overall meta-analysis, pooled ORs revealed that T variant in the MMP-9 promoter -1562 C/T polymorphism was associated with a significantly decreased risk for CP under all comparison models. In subgroup analyses by ethnicity, pooled ORs showed that a significant association of the MMP-9 promoter -1562 C/T polymorphism with CP risk was only detected in Caucasians and Asians but not in mixed population. In the subgroup analysis by severity of CP, pooled ORs indicated that T allele of the MMP-9 promoter -1562 C/T polymorphism was associated with decreased susceptibility to severe CP while there was no significant association between this polymorphism and moderate CP. CONCLUSIONS: Our meta-analysis showed that T allele in the MMP-9 promoter -1562 C/T polymorphism might be a protective factor for CP, especially in Caucasians and Asians. Moreover, there was a significant association of the MMP-9 promoter -1562 C/T polymorphism with decreased susceptibility to severe CP, while the allelic and/or genotype distributions of this polymorphism were not associated with moderate CP.

Simulated bone remodeling around tilted dental implants in the anterior maxilla.

Dental implants have to be placed with the long axis in different angulations due to the change in bone morphology. The objective of this study was to investigate the different bone remodeling response induced by the tilted dental implants and to assess whether it could lead to bone loss and implant failure. In this study, bone remodeling due to palato-labially inclined dental implants placed in the anterior maxillary incisor region was simulated. CT-based finite element models of a maxillary bone with dental implants were created herein. Five dental implants were placed at [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], respectively. The remodeling progression was recorded and compared. Model [Formula: see text] (palatal side) shows the highest bone density values, but the inclined implant at [Formula: see text] (labial side) leads to significant bone loss. From a biomechanical perspective, it is speculated that a palatally inclined implant is more likely to enhance the bone density in the maxillary anterior region, but labial inclination of implant could jeopardize its stability.

P Elevator: An Innovatively Designed Elevator for Extraction of Third Molars.

OBJECTIVE: To modify the conventional straight elevator with a unique and innovative design in respect to approach and accessibility during extraction for patients with abrasions around corners of the mouth and with thick buccal mucosa, without causing overstretching of angles of the mouth. METHODS: The shank of the straight elevator in the shape of a 'U' was modified, giving it a shape similar to 'P' in the English alphabet hence it is named the P Elevator. The P elevator utilises a 'U' shaped bend in the shank of the conventional straight elevator making space for the buccal soft tissues and the angle of the mouth, to accommodate properly in the 'U' shank. The application of this elevator in the successful removal of third molars is described. RESULTS: Two hundred patients underwent extraction of third molars with the P elevator including 166 patients with disimpaction of all third molars, 23 patients with abrasion around the angle of the mouth, and 11 patients with thick buccal mucosa. Satisfactory results were obtained in all the cases with no postoperative complications. CONCLUSION: The P elevator permits prudent, meticulous, innovative and proficient extraction of third molars in patients with thick buccal mucosa and abrasions around the angle of the mouth, without overstretching the corners of the mouth. We introduce novel applications of the P elevator in third molar extraction that provide substantial advantages over a conventional straight elevator.