Comparative Evaluation of Lateral Condylar Guidance Angle Measured Using Hanau’s Formula & Lateral Interocclusal Records

Abstract

BACKGROUND The goal of registering condylar guidance is to program the articulator for simulating the patient’s condylar movements as accurately as possible to save chairside time involved in adjusting the occlusal interferences at the time of fit in. The use of Hanau’s formula (L = H / 8 +12) was advocated by Sir Rudolph Hanau in 1930 which he used to calculate lateral condylar guidance (LCG) for adjusting his articulators. But due to the ease of application, the formula is widely used by dentists till date. Jack Stern, Hanau's longterm partner, confided in 1960 that the 'Formula' was never considered to be precise, after 10 years of study (1920 - 1930). Rather it was a point of approximation. There is a lack of uniformity in the literature regarding average condylar inclinations and its comparison to the Hanau formula, therefore a study was undertaken to evaluate and compare the 2 methods used to determine the lateral condylar guidance. METHODS 24 completely dentulous participants were included in the study. Two methods were used to obtain the lateral condylar guidance, the first method was obtaining the calculated lateral condylar guidance using the hanau’s formula and the second was obtaining the measured lateral condylar guidance using the interocclusal records. Impressions of each participant were made. Protrusive and lateral records were made using interocclusal recording medium (MAARC® Perfect Bite Registration). After completion of facebow transfer, programming of the articulator was done using protrusive record and the horizontal condylar guidance was recorded. The calculated lateral condylar guidance was recorded using the Hanau’s formula & the measured condylar guidance was recorded using right and left lateral records. Both the values obtained were evaluated and compared. RESULTS Mean LCG values obtained using Hanau’s formula was 16 degrees for the left side (SD - 1.404) and for the right side it was 16.17 degrees. (SD - 1.694). Mean LCG values obtained using lateral interocclusal records were 20 degrees for the left side (SD - 6.691) and 20.08 degrees (SD - 4.926) for the right side.There was a statistically significant difference between lateral condylar guidance records obtained using Hanau’s formula and lateral interocclusal records. CONCLUSIONS Application of Hanau formula is helpful to estimate Bennett angle. No doubt the formula is easy to apply and less cumbersome, but when we are working on high precision demanding cases we should try and find better options to record LCG. Making a lateral interocclusal record and then programming the articulator is a more reliable method. KEY WORDS Hanau’s Formula, Bennet Angle, Condylar Guidance, Articulators, Interocclusal Records, Lateral Condylar Guidance