The Relationship of Facial Anatomic Landmarks with Midlines of the Face

August 2009 95

The relationship of facial anatomic Clinical Implications landmarks with midlines of the face and The midline of the oral commissures, natural dental midline, and tip mouth of the philtrum, in this order, can be chosen as preferential landmarks in the determination of the midline of the face and mouth in smile. Avinash S. Bidra, BDS, MDentSc,a Flavio Uribe, DDS, MDentSc,b Thomas D. Taylor, DDS, MSD,c John R. Agar, DDS, Symmetry, normalcy, sexual di- able guidelines, and must determine to objectivity and repeatability for morphism, and youthfulness have the midline based on unverified land- research purposes. The Glossary of d e MA, Patchnee Rungruanganunt, DDS, MSD, and William P. been considered the classical ele- marks. Prosthodontic Terms,17 American As- Neace, PhDf ments of facial beauty.1,2 By definition, In dental esthetics, it is more im- sociation of Orthodontists (AAO) symmetry is the “correspondence in portant that the maxillary dental mid- Glossary,18 and the Glossary of Terms University of Texas Health Science Center at San Antonio, San size, shape, and relative position of line and the facial midline coincide, for the American Academy of Facial Antonio, Texas; University of Connecticut School of Dental parts on opposite sides of a dividing than the mandibular and facial mid- Plastic and Reconstructive Surgery19 line or median plane or about a cen- lines. This is due to the dominant visi- currently do not have any definitions Medicine, Farmington, Conn; University of Hartford, Hartford, ter or axis.”3 This dividing line, which bility of the maxillary anterior teeth in for facial and dental midlines. To the Conn is used to attain symmetry, is known smile and function. The coincidence authors’ knowledge, there is no litera- as the midline. It is the fundamental of facial, maxillary, and mandibular ture describing the relationship of the reference for all esthetic deviations. midlines is desirable, but not man- midline of the mouth to the midline Statement of problem. The importance of the midline is well known to dentists. Currently, there are no verifiable Therefore, knowledge of the midline dated. The maxillary dental and facial of the face. guidelines that direct the choice of specific anatomic landmarks to determine the midline of the face or midline of the will invariably result in a better under- midlines have an important role in Miller et al15 was the first to study mouth. standing of facial and dental esthet- esthetics and occlusion in many disci- the clinical relationship of the dental Purpose. The purpose of this study was to determine the hierarchy of facial anatomic landmarks closest to the midline ics. Historically, a diverse number of plines, including removable and fixed midline and the facial median line, of the face as well as midline of the mouth. facial anatomic landmarks located on prosthodontics, implant prosthodon- in a study involving a sample of 500 the middle third of the face, such as tics, orthodontics, and facial plastic human subjects. No objective meth- Material and methods. Three commonly used anatomic landmarks, nasion, tip of the nose, and tip of the philtrum, the bisector of the pupils, nasion, tip surgery. Not being able to match the ods were used in this study. The au- were marked clinically on 249 subjects (age range: 21-45 years). Frontal full-face digital images of the subjects in smile of the nose, tip of the philtrum, and dental midline coincident to the mid- thors demonstrated that 70.4% of the were then made under standardized conditions. A total of 107 subjects met the inclusion criteria. Upon applying ex- chin, have been used to determine the line of the face or mouth is a common sample showed a coincidence of the clusion criteria, images of 87 subjects were used for midline analysis using a novel concept called the Esthetic Frame. facial and dental midlines.4,5 Some cause of frustration for dentists. This dental midline and facial median line. Deviations from the midlines of the face and mouth were measured for the 3 clinical landmarks; the existing dental advocate the use of intraoral land- generally results in elaborative proce- Owens et al20 conducted a multicenter midline was considered as the fourth landmark. The entire process of midline analysis was done by a single observer marks, such as the incisive papilla, for dures for correction, causing loss of study involving 5 centers around the and repeated twice. Reliability analysis and 1-sample t tests were conducted at alpha values of .001 and .05, respec- determination of the maxillary dental clinical time. world to compare facial appearance tively. midline.6,7 It has been argued in the Most of the literature available across 6 racial groups. Two hundred Results. The results indicated that each of the 4 landmarks deviated uniquely and significantly (P<.001) from the mid- literature whether the dental midline with regard to this topic is restricted fifty-three subjects from the 5 cen- lines of the face as well as the mouth. should be made coincident with the to monographs written by various ters were chosen. Coincidence of the midline of the face or the midline of authors. Clinical studies have been dental midline with the line bisecting Conclusions. Within the limitations of the study, the hierarchy of anatomic landmarks closest to the midline of the the oral commissures.8 Some believe limited to the amount of tolerance the interpupillary line was one of the face in smile was as follows: the midline of the oral commissures, natural dental midline, tip of philtrum, nasion, and that making the dental midline co- of deviated dental midlines from the analyzed variables. The results of the tip of the nose. The hierarchy of anatomic landmarks closest to the midline of the oral commissures was: natural incident with the midline of the oral facial midline, a span of approxi- study showed that 70% of all subjects dental midline, tip of philtrum, tip of the nose, and nasion. These relationships were the same for both genders and all commissures is adequate, as patients mately 2 to 3 mm.5,11-14 Textbooks had their dental midline coincident ethnicities classified. (J Prosthet Dent 2009;102:94-103) tend to relate their dental midline to and monographs written by various with the line perpendicular to the in- proximal structures rather than ana- authors reveal a division of thought terpupillary line. Latta7 studied the tomic structures which are farther with respect to whether or not the relationship between facial midline from the mouth.9,10 However, the dental midline should be placed ex- and intraoral landmarks in 100 pa- literature is not clear regarding veri- actly coincident to the facial mid- tients requiring maxillary dentures. Presented as a table clinic at the American Academy of Fixed Prosthodontics meeting, February 2009. fiable guidelines for the determina- line.15 Lombardi suggests placing the The philtrum was used to represent Supported by the Tylman Grant award, American Academy of Fixed Prosthodontics. tion of midlines of the face or mouth. dental midline in the location on the the facial midline and its marking was Third place winner of the Academy of Prosthodontics Foundation award. Based upon convention and dogma, face where it appears most “stable.”8 transferred to a cast manually using aAssistant Professor, Department of Prosthodontics, University of Texas Health Science Center at San Antonio; Former Resident, most clinicians choose one specific Farkas16 described the facial midline an occlusal rim. The results showed Graduate Prosthodontics, University of Connecticut School of Dental Medicine. anatomic landmark and an imaginary in anthropometric interest, as a line that the incisive papilla was the clos- b Assistant Professor and Program Director, Division of Orthodontics, University of Connecticut School of Dental Medicine. line passing through it. Others use defined by 3 anatomic points: na- est landmark, followed by the maxil- cProfessor and Chair, Department of Reconstructive Sciences, University of Connecticut School of Dental Medicine. dental floss and hold it in front of the sion, subnasale, and the gnathion lary frenum and the midpalatal su- dProfessor and Program Director, Division of Prosthodontics, University of Connecticut School of Dental Medicine. eAssistant Professor, Department of Reconstructive Sciences, University of Connecticut School of Dental Medicine. face from glabella to menton. Thus, or menton. However, this definition ture. All of the previously mentioned fAssistant Professor, Department of Psychology, University of Hartford. the clinician is left with no predict- is not clear and does not lend itself studies have lacked objectivity in the The Journal of Prosthetic Dentistry Bidra et al Bidra et al 96 Volume 102 Issue 2 August 2009 97 evaluation criteria for facial midlines. NY) with a 105-mm lens and a point Photoshop CS2; Adobe Systems, Inc, of the head along the sagittal axis. Thus, the gaps in knowledge in flash, as well as an additional flash San Jose, Calif ) was used to digitally Table I. Application of exclusion criteria to sample for midline analysis Subjects with ophthalmic asymmetry this field are the lack of a repeatable with a wireless speedlight (Nikon analyze the photographs. Number of were excluded for analysis using this and verifiable definition for facial and SB-R200 Wireless Speedlight; Nikon Upon initial screening of 249 sub- Exclusion Criteria Subjects Rejected frame due to this reason. The 2 lateral dental midlines and lack of scientific USA), was used in the 12 o’clock po- jects, 142 of them did not meet the borders of the frame were then drawn information on relationships of spe- sition. The camera had an aperture inclusion criteria, which were as fol- Rotation of head along vertical axis 8 as perpendicular lines from the exo- cific anatomic landmarks with the setting of F4.5 and was mounted on lows: age range of 21-45 years, no canthion of each eye and were parallel Ophthalmic asymmetry 5 facial midline. Furthermore, there is a tripod (Canon Deluxe 200 Tripod; history of any congenital conditions to each other. The inferior border of Inaccurate markings 5 a lack of information about the rela- Canon USA, Lake Success, NY) with a or trauma affecting facial form and the frame was parallel to the superior tionship of the 2 standard midlines: standardized focus and at a standard- appearance, no history of orthodon- Unreadable images 2 line drawn at the most inferior border midline of the face and the midline of ized distance of 5 feet (1.5 m) from tic treatment, no missing maxillary Total 20 of the lower lip. This completed the 4 the mouth. All of these provided the the subject. The lighting conditions anterior teeth, no prosthetic maxillary sides of the frame (Fig. 2). It was as- rationale for this study. remained the same for all the pho- anterior teeth, no interdental spacing Table II. Distribution of sample based on ethnicity and gender sumed that it was more imperative The objectives of the study were tographs. This procedure was similar in the maxillary teeth, ability to under- to obtain the midline of that portion to define: (1) the hierarchy of facial to the protocol described by Owens stand written informed consent docu- Category Distribution of the face included in this Esthetic anatomic landmarks closest to the et al.20 Full-face digital images of sub- ments and the verbal explanation. Frame, rather than the “true” midline midline of the face; (2) the hierarchy jects in smile were made, with the The inclusion criteria were applied Asians 9 using the “entire” face. It was also as- of facial anatomic landmarks closest subject in a seated position. The head based on the above data recorded on Blacks 9 sumed that the tissues excluded from to the midline of the oral commis- position was guided by the observer a separate sheet for each subject. The Whites 50 the Esthetic Frame, such as the chin, sures (mouth); and (3) the relation- to assist the subjects in assuming their predetermined exclusion criteria were Other ethnicities 19 buccal soft tissues, and forehead, ship between the midline of the oral natural head position, an approach applied to the images of the 107 in- Men 49 have little to do with the perception commissures and the midline of the which has been well documented in cluded subjects. The exclusion criteria of the facial midline. This is simply Women 38 face. The facial anatomic landmarks the literature.21-24 The height of the were as follows: images with rotations because of the dynamic nature of analyzed were those traditionally used lens of the camera was adjusted on of head around the vertical axis, ob- Total 87 the mandible, the irregular hypertro- in clinical practice such as: nasion, tip the tripod to match the eye level of vious ophthalmic asymmetry, inac- phies of the buccinators and masseter of the nose (pronasale), tip of phil- the subject when seated upright with curate clinical markings, and images tion opposite to the side of rotation; Philtrum was defined as the vertical muscles, and the variable size of the trum (labiale superioris), and dental shoulders and head held straight and without a good resolution. Upon ap- hence, these subjects were excluded. groove on the median line of the up- forehead, all of which could poten- midline. The null hypothesis was that facing forward (Fig. 1). As the subject plying the exclusion criteria, the total The study excluded subjects who had per lip.3 Commissure was defined as tially serve as confounding variables there would be no difference between looked straight ahead at the lens of number of subjects used for midline obvious ophthalmic asymmetry (eyes a point or line of junction between in midline perception (Fig. 3). the chosen facial anatomic landmarks the camera on a tripod, the natural analysis was 87 (Tables I and II). All located at different levels) when they 2 anatomic parts (the lips).3,17 Chei- For this study, the facial midline and the midlines of the face and oral head position was standardized along images were made with the subject’s were positioned in their natural head lion was defined as the point located was defined as the midline of the es- commissures. both horizontal and vertical axes. As head in a natural head position. Prior position. Subjects who were excluded at each labial commissure.16 Tip of thetic frame of the face. The dental long as the eyes of a subject were not to making images, careful attention due to obvious ophthalmic asymme- the nose (pronasale) was defined as midline was defined as the vertical MATERIAL AND METHODS naturally located at different levels was given to ensure that the subjects try were reanalyzed. The magnitude the most protruded point of the apex line through the tip of the incisal em- in the natural head position, any mi- did not rotate their heads, especially of asymmetry was quantified, result- of the nose.16 These definitions were brasure between the 2 maxillary cen- Institutional Review Board ap- nor rotations of the head along the along the vertical axis. In addition, ing in exclusion of subjects with more used for all clinical markings as well tral incisors and parallel to the verti- proval (#07-117-2) was obtained for sagittal axis were nullified when the the analysis of subjects with heads ro- than 1 degree of discrepancy between as to digitally construct an “Esthetic cal lines of the esthetic frame of the convenience sampling of 249 medi- intercanthal line was digitally made tated along the vertical axis resulted the true horizontal line and the in- Frame.” face. The midline of the oral commis- cal and dental students/employees parallel to the true horizontal before in the midline being obviously dis- tercanthal line. Finally, images which The Esthetic Frame is novel and sures was defined as a line bisecting with an age range of 21-45 years at analysis. Imaging software (Adobe placed, by a large amount, in a direc- showed that the clinical markings did unique to this study. As it is almost the distance between the cheilions of the University of Connecticut Health not conform to the standard anatom- impossible to define the midline of the the subject in smiling posture. Rela- Center. Each subject had 3 small ic definitions at a magnification of at face in both static and dynamic move- tive facial midline value (RFV) and marks placed by a single observer least 200% were considered inaccu- ments, the Esthetic Frame comprising relative commissural midline value using a fine-tipped erasable marker, rate, and they were excluded from the of a rectangular enclosure was used (RCV) were 2 operational tools used with a tip approximately 0.5 mm in study. to define the facial midline objec- to quantify the relationships of the diameter (Expo; Sanford Ink Co, Oak Standard definitions for anatomic tively. It was defined as an area on the anatomic landmarks to the respec- Brook, Ill) on the nasion, tip of the landmarks were used for all purposes human face, within which items of es- tive midlines. The Esthetic Frame was nose, and tip of the philtrum, to sim- of the study. Lateral canthus was de- thetic interest such as midlines, cants, first constructed on a subject’s im- ulate a clinical situation. Standardiza- fined as the lateral angle formed by and smile parameters are sensitively age digitally. The facial midline was tion was given to application of all the meeting of the upper and lower perceptible and objectively verifiable. established by bisecting the distance anatomic marks in terms of the stan- eyelids.3 Exocanthion was defined as Its superior border was defined by a between the 2 lateral borders on the dard anatomic and anthropologic the point at the outer commissure of line originating at the exocanthion of frame. Three vertical lines were then definitions described below. A digital the eye fissure.16 Nasion was defined 1 eye and meeting the exocanthion of drawn along each of the anatomic camera (Nikon D70s digital camera, 1 Schematic illustration showing methodology of obtaining as the point in the midline of both the the other eye. This line helped to ne- points, which had been marked clini- 6.1 Megapixel; Nikon USA, Melville, standard digital images of subject in natural head position. nasal root and nasofrontal suture.3,16 gate the effect of any minor rotations cally. The fourth line was drawn along The Journal of Prosthetic Dentistry Bidra et al Bidra et al 96 Volume 102 Issue 2 August 2009 97 evaluation criteria for facial midlines. NY) with a 105-mm lens and a point Photoshop CS2; Adobe Systems, Inc, of the head along the sagittal axis. Thus, the gaps in knowledge in flash, as well as an additional flash San Jose, Calif ) was used to digitally Table I. Application of exclusion criteria to sample for midline analysis Subjects with ophthalmic asymmetry this field are the lack of a repeatable with a wireless speedlight (Nikon analyze the photographs. Number of were excluded for analysis using this and verifiable definition for facial and SB-R200 Wireless Speedlight; Nikon Upon initial screening of 249 sub- Exclusion Criteria Subjects Rejected frame due to this reason. The 2 lateral dental midlines and lack of scientific USA), was used in the 12 o’clock po- jects, 142 of them did not meet the borders of the frame were then drawn information on relationships of spe- sition. The camera had an aperture inclusion criteria, which were as fol- Rotation of head along vertical axis 8 as perpendicular lines from the exo- cific anatomic landmarks with the setting of F4.5 and was mounted on lows: age range of 21-45 years, no canthion of each eye and were parallel Ophthalmic asymmetry 5 facial midline. Furthermore, there is a tripod (Canon Deluxe 200 Tripod; history of any congenital conditions to each other. The inferior border of Inaccurate markings 5 a lack of information about the rela- Canon USA, Lake Success, NY) with a or trauma affecting facial form and the frame was parallel to the superior tionship of the 2 standard midlines: standardized focus and at a standard- appearance, no history of orthodon- Unreadable images 2 line drawn at the most inferior border midline of the face and the midline of ized distance of 5 feet (1.5 m) from tic treatment, no missing maxillary Total 20 of the lower lip. This completed the 4 the mouth. All of these provided the the subject. The lighting conditions anterior teeth, no prosthetic maxillary sides of the frame (Fig. 2). It was as- rationale for this study. remained the same for all the pho- anterior teeth, no interdental spacing Table II. Distribution of sample based on ethnicity and gender sumed that it was more imperative The objectives of the study were tographs. This procedure was similar in the maxillary teeth, ability to under- to obtain the midline of that portion to define: (1) the hierarchy of facial to the protocol described by Owens stand written informed consent docu- Category Distribution of the face included in this Esthetic anatomic landmarks closest to the et al.20 Full-face digital images of sub- ments and the verbal explanation. Frame, rather than the “true” midline midline of the face; (2) the hierarchy jects in smile were made, with the The inclusion criteria were applied Asians 9 using the “entire” face. It was also as- of facial anatomic landmarks closest subject in a seated position. The head based on the above data recorded on Blacks 9 sumed that the tissues excluded from to the midline of the oral commis- position was guided by the observer a separate sheet for each subject. The Whites 50 the Esthetic Frame, such as the chin, sures (mouth); and (3) the relation- to assist the subjects in assuming their predetermined exclusion criteria were Other ethnicities 19 buccal soft tissues, and forehead, ship between the midline of the oral natural head position, an approach applied to the images of the 107 in- Men 49 have little to do with the perception commissures and the midline of the which has been well documented in cluded subjects. The exclusion criteria of the facial midline. This is simply Women 38 face. The facial anatomic landmarks the literature.21-24 The height of the were as follows: images with rotations because of the dynamic nature of analyzed were those traditionally used lens of the camera was adjusted on of head around the vertical axis, ob- Total 87 the mandible, the irregular hypertro- in clinical practice such as: nasion, tip the tripod to match the eye level of vious ophthalmic asymmetry, inac- phies of the buccinators and masseter of the nose (pronasale), tip of phil- the subject when seated upright with curate clinical markings, and images tion opposite to the side of rotation; Philtrum was defined as the vertical muscles, and the variable size of the trum (labiale superioris), and dental shoulders and head held straight and without a good resolution. Upon ap- hence, these subjects were excluded. groove on the median line of the up- forehead, all of which could poten- midline. The null hypothesis was that facing forward (Fig. 1). As the subject plying the exclusion criteria, the total The study excluded subjects who had per lip.3 Commissure was defined as tially serve as confounding variables there would be no difference between looked straight ahead at the lens of number of subjects used for midline obvious ophthalmic asymmetry (eyes a point or line of junction between in midline perception (Fig. 3). the chosen facial anatomic landmarks the camera on a tripod, the natural analysis was 87 (Tables I and II). All located at different levels) when they 2 anatomic parts (the lips).3,17 Chei- For this study, the facial midline and the midlines of the face and oral head position was standardized along images were made with the subject’s were positioned in their natural head lion was defined as the point located was defined as the midline of the es- commissures. both horizontal and vertical axes. As head in a natural head position. Prior position. Subjects who were excluded at each labial commissure.16 Tip of thetic frame of the face. The dental long as the eyes of a subject were not to making images, careful attention due to obvious ophthalmic asymme- the nose (pronasale) was defined as midline was defined as the vertical MATERIAL AND METHODS naturally located at different levels was given to ensure that the subjects try were reanalyzed. The magnitude the most protruded point of the apex line through the tip of the incisal em- in the natural head position, any mi- did not rotate their heads, especially of asymmetry was quantified, result- of the nose.16 These definitions were brasure between the 2 maxillary cen- Institutional Review Board ap- nor rotations of the head along the along the vertical axis. In addition, ing in exclusion of subjects with more used for all clinical markings as well tral incisors and parallel to the verti- proval (#07-117-2) was obtained for sagittal axis were nullified when the the analysis of subjects with heads ro- than 1 degree of discrepancy between as to digitally construct an “Esthetic cal lines of the esthetic frame of the convenience sampling of 249 medi- intercanthal line was digitally made tated along the vertical axis resulted the true horizontal line and the in- Frame.” face. The midline of the oral commis- cal and dental students/employees parallel to the true horizontal before in the midline being obviously dis- tercanthal line. Finally, images which The Esthetic Frame is novel and sures was defined as a line bisecting with an age range of 21-45 years at analysis. Imaging software (Adobe placed, by a large amount, in a direc- showed that the clinical markings did unique to this study. As it is almost the distance between the cheilions of the University of Connecticut Health not conform to the standard anatom- impossible to define the midline of the the subject in smiling posture. Rela- Center. Each subject had 3 small ic definitions at a magnification of at face in both static and dynamic move- tive facial midline value (RFV) and marks placed by a single observer least 200% were considered inaccu- ments, the Esthetic Frame comprising relative commissural midline value using a fine-tipped erasable marker, rate, and they were excluded from the of a rectangular enclosure was used (RCV) were 2 operational tools used with a tip approximately 0.5 mm in study. to define the facial midline objec- to quantify the relationships of the diameter (Expo; Sanford Ink Co, Oak Standard definitions for anatomic tively. It was defined as an area on the anatomic landmarks to the respec- Brook, Ill) on the nasion, tip of the landmarks were used for all purposes human face, within which items of es- tive midlines. The Esthetic Frame was nose, and tip of the philtrum, to sim- of the study. Lateral canthus was de- thetic interest such as midlines, cants, first constructed on a subject’s im- ulate a clinical situation. Standardiza- fined as the lateral angle formed by and smile parameters are sensitively age digitally. The facial midline was tion was given to application of all the meeting of the upper and lower perceptible and objectively verifiable. established by bisecting the distance anatomic marks in terms of the stan- eyelids.3 Exocanthion was defined as Its superior border was defined by a between the 2 lateral borders on the dard anatomic and anthropologic the point at the outer commissure of line originating at the exocanthion of frame. Three vertical lines were then definitions described below. A digital the eye fissure.16 Nasion was defined 1 eye and meeting the exocanthion of drawn along each of the anatomic camera (Nikon D70s digital camera, 1 Schematic illustration showing methodology of obtaining as the point in the midline of both the the other eye. This line helped to ne- points, which had been marked clini- 6.1 Megapixel; Nikon USA, Melville, standard digital images of subject in natural head position. nasal root and nasofrontal suture.3,16 gate the effect of any minor rotations cally. The fourth line was drawn along The Journal of Prosthetic Dentistry Bidra et al Bidra et al 98 Volume 102 Issue 2 August 2009 99

2 Computer-generated human face 3 Tissues excluded from Esthetic 4 Computer-generated human face 5 Method of determination of RFV values for 6 Method of determination of RFV5 and RCV (FaceGen Modeller; Singular Inver- Frame have little to do with percep- seen in Figure 1 was digitally altered each anatomic landmark. F: midline of face/mid- values for each anatomic landmark. F: midline sions, Toronto, Ont) to schematically tion of facial midline. to produce deviated anatomic land- line of esthetic frame; n: distance between nasion of face/midline of esthetic frame; C: midline of illustrate concept of Esthetic Frame marks. Figure illustrates methodology and lateral border of esthetic frame; t: distance oral commissures; Cx: distance between midline used to obtain objectivity and reli- of lines drawn along each deviated between tip of nose and lateral border of es- of commissures and lateral border of esthetic ability. anatomic landmark and determina- thetic frame; p: distance between tip of philtrum frame; nx: distance between nasion and oral tion of facial midline. and lateral border of esthetic frame; d: distance commissures; tx: distance between tip of nose between dental midline and lateral border of and oral commissures; px: distance between tip the subject’s existing dental midline right/left cheilion was considered a nasion to midline of the face and esthetic frame. of philtrum and oral commissures; dx: distance as defined above (Fig. 4). constant termed C. The measured commissures; RFV2 and RCV2: rela- between dental midline and oral commissures. Relative facial midline value (RFV) distances (variables) were: from the tivity of tip of the nose to midline of was defined as the relative closeness nasion, nx, from the tip of the nose, the face and commissures; RFV3 and was coincident with the facial or the RESULTS from 1.00 (whether they all lined up of an anatomic landmark to the facial tx, from the tip of philtrum, px, and RCV3: relativity of tip of the philtrum commissural midline, then it was as- with the facial midline). The analysis midline. The measured distance from from the dental midline, dx. The RCV to midline of the face and commis- signed an RFV or RCV value of 1. Intraclass correlation coefficients indicated that the difference between the lateral border of the frame to the was then obtained by dividing nx/C, sures; RFV4 and RCV4: relativity of A total of 9 values were recorded (ICCs) for reliability analysis of RFV the mean ratio of each anatomic defined facial midline was considered tx/C, px/C, and dx/C. The measured dental midline to midline of the face per subject, along with gender and and RCV measures made 2 times re- landmark and the midline of the face a constant called “F.” The measured distance from the lateral border of the and commissures; and RFV5: relativ- ethnicity. The entire process of data vealed that the reliabilities were all ac- was statistically significant (P<.001). distance from the lateral border of Esthetic Frame to the midpoint of the ity of the midline of the commissures analysis was repeated twice to ensure ceptable, ranging from 0.85 to 0.96, The midline of the commissures was the frame to the nasion was consid- commissures was described as a vari- with the midline of the face. Thus, in reliability and validity. A reliability indicating a high consistency between the closest, followed by the dental ered a variable termed “n.” The RFV able called Cx. Thus, the relationship perfect symmetry, all 5 of the RFVs analysis test was performed between measurements made the first and the midline, tip of philtrum, nasion, and was then obtained by dividing n by F. between the midline of the commis- and all 4 of the RCVs would be equal the first and second set of data us- second time by the same rater. Items the tip of the nose (Table IV) (Fig. 7). Similarly, RFVs were obtained for the sures and the midline of the face was to each other and to the numeral 1. ing intraclass correlation coefficients measured at analysis 1 are paired A second set of 4 t tests was con- other 3 anatomic landmarks: tip of obtained by dividing Cx/F (Fig. 6). The right or left lateral border of the (ICCs). To determine whether the with same items measured at analy- ducted to test the null hypothesis that the nose (t), tip of philtrum (p), and The primary reason to use RFV esthetic frame or the commissures selected landmarks significantly dif- sis 2 (for example, RFV11 = “RFV1” the mean ratios of the 4 specified an- dental midline (d), by dividing them and RCV was to develop a propor- was chosen, based on the direction of fered from the midline of the face and measured the first time, and RFV12 atomic measures did not differ from by the constant F. Numerical values tional relationship between an ana- deviation of the anatomic landmark. mouth, a series of 1-sample t tests = “RFV1” measured the second time). 1.00 (whether they all lined up with for n/F, t/F, p/F, and d/F were thus tomic landmark and the midline in Therefore, the shorter distance to the were conducted with an alpha value All ICCs were statistically significant the intercommissural midline). In line obtained (Fig. 5). question. This ensured a standard lateral border of the frame was always of .05. Finally, a Pearson correlation beyond the alpha value of .001 (Table with the previous analysis, the results Relative commissural midline common denominator for all ana- chosen. Thus, an RFV and an RCV analysis was performed to determine III). indicated that the difference between value (RCV) was defined as the rela- tomic landmarks within the esthetic could never be a number greater than whether there was a significant cor- Two sets of 1-sample t tests were the mean ratio of each anatomic tive closeness of an anatomic land- frame and negated the need for size the numeral 1. If a line drawn along relation between RCV1 (nasion) and conducted. One set of 5 t tests was landmark and the midline of the com- mark to the midline of the oral com- matching the images with the sub- one anatomic landmark coincided RCV2 (tip of the nose), as nasion and conducted to test the null hypothesis missures was statistically significant missures (center of the mouth). The ject’s face. The assignments for rela- with any of the other landmarks, the tip of the nose showed reversal in hi- that the mean ratios of the 5 speci- (P<.001). The natural dental midline measured distance from the midpoint tivity of landmarks for both midlines same RFV or RCV value was recorded erarchy in relationship to the midline fied anatomic measures did not differ was the closest, followed by the tip of of the intercommissural line to the were: RFV1 and RCV1: relativity of for both. If an anatomic landmark of the commissures. philtrum, tip of the nose, and nasion The Journal of Prosthetic Dentistry Bidra et al Bidra et al 98 Volume 102 Issue 2 August 2009 99

Table III. Reliability analysis table Table V. One-sample t test for hierarchy of landmarks for midline of commissures Item Pair Reliability Landmark Mean Standard Deviation P

Dental midline (RCV4) 0.9751 0.023 <.001 RFV11 (nasion) RFV12 0.85 RFV21 (tip of nose) RFV22 0.92 Tip of philtrum (RCV3) 0.9748 0.024 <.001 RFV31 (tip of philtrum) RFV32 0.87 Tip of nose (RCV2) 0.9512 0.034 <.001 RFV41 (dental midline) RFV42 0.85 Nasion (RCV1) 0.9477 0.032 <.001 RFV51 (midline of commissures) RFV52 0.86

RCV: Relative commissural midline value RCV11 (nasion) RCV12 0.93 RCV21 (tip of nose) RCV22 0.96

RCV31 (tip of philtrum) RCV32 0.90 Midline of RCV41 (dental midline) RCV42 0.94 mouth Dental RFV: Relative facial midline value midline RCV: Relative commissural midline value Tip of philtrum Table IV. One-sample t test for hierarchy of landmarks for midline of face Tip of nose Landmark Mean Standard Deviation P Nasion Midline of commissures (RFV5) 0.979 0.017 <.001 0.94 0.95 0.96 0.97 0.98 0.99 1.00 Dental midline (RFV4) 0.977 0.018 <.001 8 Hierarchical relationship of anatomic landmarks with midline of mouth. Tip of philtrum (RFV3) 0.974 0.021 <.001

Nasion (RFV1) 0.967 0.019 <.001 Table VI. Pearson correlation coefficient between RCV1 and RCV2 to demonstrate reversal of hierarchy Tip of nose (RFV2) 0.965 0.025 <.001 RCV1 RCV2 RFV: Relative facial midline value Nasion (RCV1) Pearson correlation 1 0.229 Significance (2-tailed) 0.033 Midline of n 87 87 face

Table III. Reliability analysis table Table V. One-sample t test for hierarchy of landmarks for midline of commissures Item Pair Reliability Landmark Mean Standard Deviation P

RCV: Relative commissural midline value RCV11 (nasion) RCV12 0.93 RCV21 (tip of nose) RCV22 0.96

Midline of Tip of nose (RCV2) Pearson correlation 0.229 1 mouth Significance (2-tailed) 0.033 Dental midline n 87 87 Tip of RCV: Relative commissural midline value philtrum (Table V) (Fig. 8). These hierarchical RCV2 are significantly correlated at a missures. There is no standard defini- Nasion relationships remained the same for .05 level (2-tailed), indicating these tion for facial midline in the literature. Tip of both genders and all ethnicities con- 2 values were similar to each other; Therefore, the authors defined the fa- nose sidered. hence, the hierarchy is negligible. cial midline using the Esthetic Frame. A Pearson correlation analysis was Many authors have shown the validity 0.94 0.95 0.96 0.97 0.98 0.99 1.00 done to determine any significant DISCUSSION of the natural head position and its 7 Hierarchical relationship of anatomic landmarks association between the 2 samples, long-term reproducibility over a pe- with midline of face. RCV1 (nasion) and RCV2 (tip of the The results support rejection of riod of up to 15 years.21-24 In the pres- nose), as nasion and tip of the nose the null hypothesis that there would ent study, the natural head position showed reversal in hierarchy in rela- be no difference between the chosen was guided to the true horizontal by a tionship to the midline of the commis- facial anatomic landmarks and the single investigator, and care was taken sures. Table VI shows that RCV1 and midlines of the face and oral com- to ensure that the subjects did not ro- The Journal of Prosthetic Dentistry Bidra et al Bidra et al 102 Volume 102 Issue 2 August 2009 103 tate their heads along the vertical axis. ing the dental midline with respect this could be a limitation in the study, 3. The hierarchy of anatomic land- 9. Tjan AH, Miller GD, The JG. Some es- 20.Owens EG, Goodacre CJ, Loh PL, Hanke However, human error in detection of to the face and commissures. Thus, as ratios by nature cannot differenti- marks closest to the midline of the thetic factors in a smile. J Prosthet Dent G, Okamura M, Jo KH, et al. A multicenter 1984:51;24-8. interracial study of facial appearance. Part this rotation cannot be ruled out. The it can be inferred that the incisive pa- ate whether the observed difference commissures is: (1) dental midline, 10.Arnett GW, McLaughlin RP. Facial and 1: A comparison of extraoral parameters. smiling image of the subject was cho- pilla, usually found in between the 2 is due to the numerator or denomi- (2) tip of philtrum, (3) tip of the nose, dental planning for orthodontists and Int J Prosthodont 2002;15:273-82. oral surgeons. St. Louis: Elsevier; 2004. p. 21.Peng L, Cooke MS. Fifteen-year reproduc- sen for all purposes of analysis, as it is maxillary central incisors, may be an nator term. However, from a clinical and (4) nasion. 52-70. ibility of natural head posture: A longitudi- a standard for esthetic analysis, and acceptable landmark for the deter- standpoint, the authors believe that 11.Kokich VO Jr, Kiyak HA, Shapiro PA. Com- nal study. Am J Orthod Dentofacial Orthop it revealed the dental midline as well. mination of midlines, as reported by it is more important for a clinician to REFERENCES paring the perception of dentists and lay 1999;116:82-5. people to altered dental esthetics. J Esthet 22.Cooke MS. Five-year reproducibility of No subject in this study had a grossly authors in the past.6,7 Future studies know the hierarchy or the best choice 1. Rhodes G. The evolutionary psychol- Dent 1999;11:311-24. natural head posture: a longitudinal asymmetric smile or a smile which did are needed to verify this. The philtrum of anatomic landmarks that could be ogy of facial beauty. Annu Rev Psychol 12.Johnston CD, Burden DJ, Stevenson MR. study. Am J Orthod Dentofacial Orthop not reveal the maxillary central inci- or tip of the vermillion border has used in the determination of midline 2006;57:199-226. The influence of dental to facial midline dis- 1990;97:489-94. crepancies on dental attractiveness ratings. 23.Cooke MS, Wei SH. The reproducibility of sors. All exclusion criteria reported in been assumed by several studies in for a particular patient, rather than to 2. Bashour M. History and current concepts in the analysis of facial attractiveness. Plast Eur J Orthod 1999;21:517-22. natural head posture: a methodological this study was stringently applied to the past to represent the facial mid- know mean linear deviations of ana- Reconstr Surg 2006;118:741-56. 13.Rosenstiel SF, Rashid RG. Public prefer- study. Am J Orthod Dentofacial Orthop minimize the number of confounding line.5,7,10-12,14,15 The present study tomic landmarks of a certain popula- 3. Merriam-Webster’s medical dictionary. ences for anterior tooth variations: a 1988;93:280-8. web-based study. J Esthet Restor Dent 24.Lundström F, Lundström A. Natural head factors. showed that the tip of the philtrum tion. Furthermore, the applied meth- Springfield: Merriam-Webster; 2006. Avail- able at: http://www.nlm.nih.gov/medlin- 2002;14:97-106. position as a basis for cephalometric This study was designed to be ranked third in the hierarchy, super- odology would not have permitted eplus/mplusdictionary.html. Accessed on 14.Cardash HS, Ormanier Z, Laufer BZ. analysis. Am J Orthod Dentofacial Orthop as clinically applicable as possible; seded only by the midline of the com- sufficient accuracy to analyze linear May 1, 2008. Observable deviation of the facial and 1992;101:244-7. 4. Arnett GW, Bergman RT. Facial keys to anterior tooth midlines. J Prosthet Dent therefore, the markings for each ana- missures and the dental midline. This deviations, as the image dimensions orthodontic diagnosis and treatment 2003;89:282-5. Corresponding author: tomic landmark were made clinically reinforces the credibility of the tip of did not correspond to the exact di- planning--Part II. Am J Orthod Dentofacial 15.Miller EL, Bodden WR Jr, Jamison HC. Dr Avinash S. Bidra and not on the digital image. The the philtrum as a reliable landmark in mensions of the subject’s face. The Orthop 1993;103:299-312. A study of the relationship of the dental University of Texas Health Science Center at 5. Beyer JW, Lindauer SJ. Evaluation of midline to the facial median line. J Prosthet San Antonio lines on the image were drawn along the determination of the midlines of authors did not report the direction dental midline position. Semin Orthod Dent 1979;41:657-60. 7703 Floyd Curl Drive, MSC 7912 these markings. Although meticulous the face and mouth. of deviation of each anatomic land- 1998;4:146-52. 16.Farkas LG. Anthropometry of the head and San Antonio, Texas 78229-3900 face in medicine. 2nd Ed. New York: Raven Fax: 210-567-6376 care and clinical judgment were exer- The nasion has been considered to mark with regard to the midlines, as 6. Zarb GA, Carlsson GE, Bolender CL, edi- tors. Boucher’s prosthodontic treatment Press Limited; 1994. p. 20-5. E-mail: [email protected] cised during the marking procedure, be a good location along the middle it has little clinical applicability. The for edentulous patients. 11th ed. St. Louis: 17.The glossary of prosthodontic terms. J inherent human errors in marking fifth of the face, but its relation to the numerical values of the mean ratios Mosby;1997. p. 309-10. Prosthet Dent 2005;94:10-92. Acknowledgements 18.American Association of Orthodontists The authors thank Patricia Montgomery for the anatomic landmarks clinically facial and commissural midline has were different for the same landmark 7. Latta GH Jr. The midline and its relation to the anatomic landmarks in the edentulous (AAO) Glossary 2008. Available at http:// her support with the images and all partici- cannot be eliminated. Of the various not been studied previously. Based depending upon the midline in ques- patient. J Prosthet Dent 1988;59:681-3. www.braces.org/knowmore/glossary/ pants who volunteered for the study. clinical landmarks, marking the soft on the current study, soft tissue na- tion; however, the hierarchy of land- 8. Lombardi RE. The principles of visual upload/2008-AAO-Glossary.pdf. Accessed on May 1, 2008. Copyright © 2009 by the Editorial Council for tissue nasion and the tip of the nose sion may not be an adequate clinical marks was not affected. Finally, the perception and their clinical application to denture esthetics. J Prosthet Dent 19.The American Academy of Facial Plastic The Journal of Prosthetic Dentistry. was most difficult due to the inherent landmark to determine either of the study was done by a single observer 1973;29:358-82. and Reconstructive Surgery. Glossary of anatomy of the nose.16 Hence, the re- midlines. Furthermore, its distant lo- and the population chosen in this terms. Available at http://www.aafprs.org/ patient/procedures/glossary.html. Accessed sults related to these anatomic land- cation from the dental midline may study was based on convenience sam- on May 1, 2008. marks should be carefully considered, not result in easy determination and pling, with the sample distribution and future studies are needed to verify analysis. The tip of the nose was the being approximately normal. This these results. The use of cephalomet- most deviated landmark with regard study provides baseline information rics was considered, but not used, as to the facial midline. However, it about the hierarchical relationships it would not simulate a clinical situa- ranked higher than the nasion with of various facial anatomic landmarks tion for recording the midline. regard to midline of the commissures. to the midlines of the face and mouth. The midline of the oral commis- Pearson correlations used to examine Similar studies on different samples sures was considered as a determined the relationships of these 2 anatomic are needed to confirm the results. anatomic landmark while analyzing landmarks showed that these 2 values the hierarchical order for facial mid- were similar; therefore, the reversal of CONCLUSIONS lines. It ranked the closest to the facial hierarchy could be due to a sampling midline, in comparison to all of the error and is not significant. Further- Based on the limitations of this landmarks analyzed. This may reveal more, both of these landmarks ranked study, the following conclusions were that nature centers the mouth quite lowest in their proximity to the mid- drawn: symmetrically in relationship to the lines of the face and mouth; for most 1. There was a significant differ- eyes. The dental midline in this popu- clinical situations, the ranking of the ence between the mean ratios of the lation with no history of orthodontics first 3 anatomic landmarks, namely, chosen anatomic landmarks and the was ranked second for midline of the the midline of the commissures, tip midlines of the face and mouth. face and midline of the commissures. of philtrum, and dental midline, ap- 2. The hierarchy of anatomic land- The study protocol, however, did not pears to be more relevant. marks closest to the midline of the address the axial angulations of the The study used RFV and RCV (ra- face is: (1) midline of the commis- dental midline in its analysis. The re- tios) as tools to examine the relation- sures, (2) dental midline, (3) tip of sults indicate that a symmetrical pat- ship of the anatomic landmarks and philtrum, (4) nasion, and (5) tip of tern might exist in nature in arrang- develop the hierarchy. Theoretically, the nose. The Journal of Prosthetic Dentistry Bidra et al Bidra et al 102 Volume 102 Issue 2 August 2009 103 tate their heads along the vertical axis. ing the dental midline with respect this could be a limitation in the study, 3. The hierarchy of anatomic land- 9. Tjan AH, Miller GD, The JG. Some es- 20.Owens EG, Goodacre CJ, Loh PL, Hanke However, human error in detection of to the face and commissures. Thus, as ratios by nature cannot differenti- marks closest to the midline of the thetic factors in a smile. J Prosthet Dent G, Okamura M, Jo KH, et al. A multicenter 1984:51;24-8. interracial study of facial appearance. Part this rotation cannot be ruled out. The it can be inferred that the incisive pa- ate whether the observed difference commissures is: (1) dental midline, 10.Arnett GW, McLaughlin RP. Facial and 1: A comparison of extraoral parameters. smiling image of the subject was cho- pilla, usually found in between the 2 is due to the numerator or denomi- (2) tip of philtrum, (3) tip of the nose, dental planning for orthodontists and Int J Prosthodont 2002;15:273-82. oral surgeons. St. Louis: Elsevier; 2004. p. 21.Peng L, Cooke MS. Fifteen-year reproduc- sen for all purposes of analysis, as it is maxillary central incisors, may be an nator term. However, from a clinical and (4) nasion. 52-70. ibility of natural head posture: A longitudi- a standard for esthetic analysis, and acceptable landmark for the deter- standpoint, the authors believe that 11.Kokich VO Jr, Kiyak HA, Shapiro PA. Com- nal study. Am J Orthod Dentofacial Orthop it revealed the dental midline as well. mination of midlines, as reported by it is more important for a clinician to REFERENCES paring the perception of dentists and lay 1999;116:82-5. people to altered dental esthetics. J Esthet 22.Cooke MS. Five-year reproducibility of No subject in this study had a grossly authors in the past.6,7 Future studies know the hierarchy or the best choice 1. Rhodes G. The evolutionary psychol- Dent 1999;11:311-24. natural head posture: a longitudinal asymmetric smile or a smile which did are needed to verify this. The philtrum of anatomic landmarks that could be ogy of facial beauty. Annu Rev Psychol 12.Johnston CD, Burden DJ, Stevenson MR. study. Am J Orthod Dentofacial Orthop not reveal the maxillary central inci- or tip of the vermillion border has used in the determination of midline 2006;57:199-226. The influence of dental to facial midline dis- 1990;97:489-94. crepancies on dental attractiveness ratings. 23.Cooke MS, Wei SH. The reproducibility of sors. All exclusion criteria reported in been assumed by several studies in for a particular patient, rather than to 2. Bashour M. History and current concepts in the analysis of facial attractiveness. Plast Eur J Orthod 1999;21:517-22. natural head posture: a methodological this study was stringently applied to the past to represent the facial mid- know mean linear deviations of ana- Reconstr Surg 2006;118:741-56. 13.Rosenstiel SF, Rashid RG. Public prefer- study. Am J Orthod Dentofacial Orthop minimize the number of confounding line.5,7,10-12,14,15 The present study tomic landmarks of a certain popula- 3. Merriam-Webster’s medical dictionary. ences for anterior tooth variations: a 1988;93:280-8. web-based study. J Esthet Restor Dent 24.Lundström F, Lundström A. Natural head factors. showed that the tip of the philtrum tion. Furthermore, the applied meth- Springfield: Merriam-Webster; 2006. Avail- able at: http://www.nlm.nih.gov/medlin- 2002;14:97-106. position as a basis for cephalometric This study was designed to be ranked third in the hierarchy, super- odology would not have permitted eplus/mplusdictionary.html. Accessed on 14.Cardash HS, Ormanier Z, Laufer BZ. analysis. Am J Orthod Dentofacial Orthop as clinically applicable as possible; seded only by the midline of the com- sufficient accuracy to analyze linear May 1, 2008. Observable deviation of the facial and 1992;101:244-7. 4. Arnett GW, Bergman RT. Facial keys to anterior tooth midlines. J Prosthet Dent therefore, the markings for each ana- missures and the dental midline. This deviations, as the image dimensions orthodontic diagnosis and treatment 2003;89:282-5. Corresponding author: tomic landmark were made clinically reinforces the credibility of the tip of did not correspond to the exact di- planning--Part II. Am J Orthod Dentofacial 15.Miller EL, Bodden WR Jr, Jamison HC. Dr Avinash S. Bidra and not on the digital image. The the philtrum as a reliable landmark in mensions of the subject’s face. The Orthop 1993;103:299-312. A study of the relationship of the dental University of Texas Health Science Center at 5. Beyer JW, Lindauer SJ. Evaluation of midline to the facial median line. J Prosthet San Antonio lines on the image were drawn along the determination of the midlines of authors did not report the direction dental midline position. Semin Orthod Dent 1979;41:657-60. 7703 Floyd Curl Drive, MSC 7912 these markings. Although meticulous the face and mouth. of deviation of each anatomic land- 1998;4:146-52. 16.Farkas LG. Anthropometry of the head and San Antonio, Texas 78229-3900 face in medicine. 2nd Ed. New York: Raven Fax: 210-567-6376 care and clinical judgment were exer- The nasion has been considered to mark with regard to the midlines, as 6. Zarb GA, Carlsson GE, Bolender CL, edi- tors. Boucher’s prosthodontic treatment Press Limited; 1994. p. 20-5. E-mail: [email protected] cised during the marking procedure, be a good location along the middle it has little clinical applicability. The for edentulous patients. 11th ed. St. Louis: 17.The glossary of prosthodontic terms. J inherent human errors in marking fifth of the face, but its relation to the numerical values of the mean ratios Mosby;1997. p. 309-10. Prosthet Dent 2005;94:10-92. Acknowledgements 18.American Association of Orthodontists The authors thank Patricia Montgomery for the anatomic landmarks clinically facial and commissural midline has were different for the same landmark 7. Latta GH Jr. The midline and its relation to the anatomic landmarks in the edentulous (AAO) Glossary 2008. Available at http:// her support with the images and all partici- cannot be eliminated. Of the various not been studied previously. Based depending upon the midline in ques- patient. J Prosthet Dent 1988;59:681-3. www.braces.org/knowmore/glossary/ pants who volunteered for the study. clinical landmarks, marking the soft on the current study, soft tissue na- tion; however, the hierarchy of land- 8. Lombardi RE. The principles of visual upload/2008-AAO-Glossary.pdf. Accessed on May 1, 2008. Copyright © 2009 by the Editorial Council for tissue nasion and the tip of the nose sion may not be an adequate clinical marks was not affected. Finally, the perception and their clinical application to denture esthetics. J Prosthet Dent 19.The American Academy of Facial Plastic The Journal of Prosthetic Dentistry. was most difficult due to the inherent landmark to determine either of the study was done by a single observer 1973;29:358-82. and Reconstructive Surgery. Glossary of anatomy of the nose.16 Hence, the re- midlines. Furthermore, its distant lo- and the population chosen in this terms. Available at http://www.aafprs.org/ patient/procedures/glossary.html. Accessed sults related to these anatomic land- cation from the dental midline may study was based on convenience sam- on May 1, 2008. marks should be carefully considered, not result in easy determination and pling, with the sample distribution and future studies are needed to verify analysis. The tip of the nose was the being approximately normal. This these results. The use of cephalomet- most deviated landmark with regard study provides baseline information rics was considered, but not used, as to the facial midline. However, it about the hierarchical relationships it would not simulate a clinical situa- ranked higher than the nasion with of various facial anatomic landmarks tion for recording the midline. regard to midline of the commissures. to the midlines of the face and mouth. The midline of the oral commis- Pearson correlations used to examine Similar studies on different samples sures was considered as a determined the relationships of these 2 anatomic are needed to confirm the results. anatomic landmark while analyzing landmarks showed that these 2 values the hierarchical order for facial mid- were similar; therefore, the reversal of CONCLUSIONS lines. It ranked the closest to the facial hierarchy could be due to a sampling midline, in comparison to all of the error and is not significant. Further- Based on the limitations of this landmarks analyzed. This may reveal more, both of these landmarks ranked study, the following conclusions were that nature centers the mouth quite lowest in their proximity to the mid- drawn: symmetrically in relationship to the lines of the face and mouth; for most 1. There was a significant differ- eyes. The dental midline in this popu- clinical situations, the ranking of the ence between the mean ratios of the lation with no history of orthodontics first 3 anatomic landmarks, namely, chosen anatomic landmarks and the was ranked second for midline of the the midline of the commissures, tip midlines of the face and mouth. face and midline of the commissures. of philtrum, and dental midline, ap- 2. The hierarchy of anatomic land- The study protocol, however, did not pears to be more relevant. marks closest to the midline of the address the axial angulations of the The study used RFV and RCV (ra- face is: (1) midline of the commis- dental midline in its analysis. The re- tios) as tools to examine the relation- sures, (2) dental midline, (3) tip of sults indicate that a symmetrical pat- ship of the anatomic landmarks and philtrum, (4) nasion, and (5) tip of tern might exist in nature in arrang- develop the hierarchy. Theoretically, the nose. The Journal of Prosthetic Dentistry Bidra et al Bidra et al