An in vivo study to correlate the relationship of the extraoral and intraoral anatomical landmarks with the occlusal plane in dentulous subjects.

Background: The occlusal plane position is considered to be the primary link between esthetic and function. Aim: To evaluate the relationship between extraoral and intraoral soft tissue landmarks with the occlusal plane in dentulous subjects on both sides and to check for any variations. Study and Design: An in vivo study and 100 subjects with all healthy permanent teeth in normal arch and alignment were selected from Modern Dental College and Research Centre, Indore. Materials and Methods: Three custom made instruments (occlusal plane analyzer, buccinator groove relator, and level analyzer) were indigenously designed to check parallelism of the interpupillary line, ala‑tragus line, buccinator groove with the occlusal plane. Relation of retromolar pad with the occlusal plane was checked with the metallic scale. Statistical Analysis: Chi‑square test. Results: In 20.0% subjects, the occlusal plane was parallel to the interpupillary line. The posterior reference point for ala‑tragus line was middle point on right side in 56% and left side in 58% subjects. Intraorally, right side 59% and left side 62% subjects had the occlusal plane at the same level as that of buccinator groove. Right side 48% and left side 45% subjects showed occlusal plane at the middle one‑third of retromolar pad. Conclusion: The occlusal plane is not generally parallel to interpupillary line. The occlusal plane is parallel to the ala‑tragus line with middle point of tragus as posterior reference point on right and left sides. Both sides, the buccinator groove and the middle one‑third retromolar pad are coinciding with occlusal plane level.

Faculty-supervised measurements of the face and of mandibular movements on young adults

PURPOSE: The purpose of this study was to determine the average facial proportions and mandibular movement capacity of 316 first-year dental students who carefully recorded them on each other. MATERIALS AND METHODS: This early exacting clinical experience was closely supervised by the authors in Columbus, Ohio during 1969-70. Five vertical and six horizontal distances were measured on each subject's face. An ala-tragus line and an occlusal line were drawn on the left side of the face to determine if these two lines were parallel. Measurements of mandibular movements involved maximum normal and hinge opening at the incisors and maximum amounts of right, left lateral and protrusive excursions of the mandible. RESULTS: The ala width and distance between the tips of upper right and left canine cusps averaged (35.2 mm and 34.8 mm) but with very large individual variations. The distance between ala to occlusal plane lines was 29.9 mm at the tragus and 31.3 mm near the ala. The angle between orbitale and ala-tragus averaged 13.6 degrees. CONCLUSION: The upper lip length was the most variable and the distance between the pupils was the most stable of the eleven facial measurements. The ala-tragus line and the occlusal plane lines were for all practical purposes parallel. Maximum jaw opening averaged 51.2 mm which was 3.0 times larger than maximal hinge opening of 17.2 mm. The maximum right plus left side jaw excursions (9.2 and 9.4 mm) totaled 18.6 mm, 2.3 times more than the 8.0 mm mean maximum forward protrusion.

Cephalometrically assessing the validity of superior, middle and inferior tragus points on ala-tragus line while establishing the occlusal plane in edentulous patient

PURPOSE: The purpose of this study was to decide the most appropriate point on tragus to be used as a reference point at time of marking ala tragus line while establishing occlusal plane. MATERIALS AND METHODS: The data was collected in two groups of subjects: 1) Dentulous 2) Edentulous group having sample size of 30 for each group with equal gender distribution (15 males, 15 females each). Downs analysis was used for base value. Lateral cephalographs were taken for all selected subjects. Three points were marked on tragus as Superior (S), Middle (M), and Inferior (I) and were joined with ala (A) of the nose to form ala-tragus lines. The angle formed by each line (SA plane, MA plane, IA plane) with Frankfort Horizontal (FH) plane was measured by using custom made device and modified protractor in all dentulous and edentulous subjects. Also, in dentulous subjects angle between Frankfort Horizontal plane and natural occlusal plane was measured. The measurements obtained were subjected to the following statistical tests; descriptive analysis, Student's unpaired t-test and Pearson's correlation coefficient. RESULTS: The results demonstrated, the mean angle COO (cant of occlusal plane) as 9.76degrees, inferior point on tragus had given the mean angular value of IFH [Angle between IA plane (plane formed by joining inferior point-I on tragus and ala of nose- A) and FH plane) as 10.40degrees and 10.56degrees in dentulous and edentulous subjects respectively which was the closest value to the angle COO and was comparable with the values of angle COO value in Downs analysis. Angulations of ala-tragus line marked from inferior point with occlusal plane in dentulous subject had given the smallest value 2.46degrees which showed that this ala-tragus line was nearly parallel to occlusal plane. CONCLUSION: The inferior point marked on tragus is the most appropriate point for marking ala-tragus line.