Influence of Anterior Guidance on the Inclination of Horizontal Condylar Guidance in Dentulous Subjects - A Clinical Study

BACKGROUND One of the most widely used methods to record horizontal condylar guidance is the use of protrusive interocclusal records. Therefore, this study was done to evaluate the reliability of protrusive interocclusal record with and without the influence of anterior determinant on horizontal condylar guidance among dentulous patients. METHODS Diagnostic impressions of 21 participants were made and casts were poured. Facebow record were obtained and transferred to semi-adjustable articulator. Protrusive interocclusal records were made using Alu-wax. In group 1, protrusive interocclusal records were obtained at incisal edge to edge position (conventional method). In group 2, 3 and 4 protrusive interocclusal records were obtained at a distance of 4 mm, 6 mm and at incisal edge to edge position respectively using a customized flat anterior jig. Programming of the Hanau articulator were done for all the 4 groups. One-way ANOVA test and Pearson’s correlation tests were done to compare and correlate horizontal condylar guidance. RESULTS The mean values obtained for flat anterior jig at incisal edge to edge position, at 4 mm and 6 mm provided good Pearson correlation values for the right (R = 0.773, R = 0.779, R = 0.632) as well as the left side (R = 0.631, R = 0.601, R = 0.545) respectively, on comparison with the conventional incisal edge to edge values. This indicated a positive correlation which was statistically significant. CONCLUSIONS The horizontal condylar guidance is influenced by anterior determinant. Therefore, the reliability of protrusive records is dependent on eliminating the influence of anterior determinant. KEY WORDS Horizontal Condylar Guidance, Anterior Determinant, Protrusive Interocclusal Records

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

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

Interocclusal Records in Fixed Prosthodontics

An accurate interocclusal record is essential for the successful delivery of fixed prosthodontic restorations. There are various materials and techniques used to obtain an interocclusal record in order to facilitate mounting of the dental casts on an articulator. The interocclusal record describes the vertical and horizontal relationship of the maxillary and mandibular teeth. In circumstances where the vertical relationship is not supported through a tripod of widely spaced opposing contacts, the interocclusal record will be needed to restore this vertical support to prevent inaccurate mounting. The clinician should understand when an interocclusal record is required and have an awareness of the different materials and techniques available to record an interocclusal registration.

A Review of Occlusal Registration Materials Utilized in Recording Various Occlusal Relations

The success of any prosthetic rehabilitation depends on several factors; most important factor is precisely recording of centric relation and transferring the same to the articulator. When partial or completely edentulous arches are present, cast mounting is considerably more complex. Interocclusal records are the means by which the interarch relationships are transferred from mouth to an articulator. The purpose of this review is to evaluate the accuracy and stability of the materials used in routine clinical practice to obtain interocclusal records.

A Comparative study to measure the horizontal condylar guidance obtained by protrusive interocclusal records and panoramic radiographic images in completely edentulous patients

Background & Objectives:The study was conducted with objective to compare the horizontal condylar guidance (HCG) obtained by protrusive interocclusal records and panoramic radiographic images in completely edentulous patients.Materials & Methods:The horizontal condylar guidance was measured in 25 completely edentulous patients by protrusive interocclusal records using zinc oxide eugenol paste through a face bow transfer (HanauTM Spring bow, Whip Mix Corporation, USA) to a semi-adjustable articulator (HanauTM Wide-Vue Articulator, Whip Mix Corporation, USA). In the same patients, HCG was traced in the panoramic radiograph. The angles formed by the intersection of two lines: Frankfurt’s horizontal plane and posterior slope of articular eminence was measured using protractor to represent the horizontal condylar guidance angle on each side.Results:The mean difference between the horizontal condylar guidance angles values obtained using protrusive interocclusal record and panoramic radiograph was 2.68 degrees and 3.40 degrees for the right and the left side respectively, with the panoramic radiograph values being higher. This difference between the values was found to be highly significant between the two methods for the right side (t = 2.70, p = 0.012) and left side (t = 3.69, p = 0.001). A significant positive correlation was found between the horizontal condylar guidance obtained from protrusive interocclusal record and panoramic radiograph for the right (r = 0.643, p = 0.001) and left sides (r = 0.622, p = 0.001) separately.Conclusion:The panoramic radiographic tracing can be used to calculate the mean horizontal condylar guidance in the completely edentulous patients and these values can be used to programme semi-adjustable articulators avoiding the cumbersome process of obtaining protrusive interocclusal records.