JOURNAL CLUB ON INTEROCCLUSAL

RECORDING MATERIALS

DEPT OF PROSTHODONTIADr.REVATHY GOUNDER

Aim:to evaluate the linear dimensional change,compressive resistance and effect of varying thickness on the compresive resistance of four elastomeric interocclussal recording materials.

Introduction:Many materials are available for interocclusal

records .these includes waxes ,metallic pastes,acrylic resins and elastomeric materials .patients interocclusal records are made and sent along the cast to the laboratory.this requires that the records must be dimensionally stable for a given period of time before they are used to

used to articulate the casts.each of these interocclusal recording materials exhibits a degree of deformation when compressed under a load .the deformation may vary with the thickness and the properties of the recording materials used.

Materials and methods: Four types of interocclusal recording media

were used in this study.Three were addition silicones,and one a polyether material.

A cylindrical brass master cylindrical die was machine tooled for this study.three brass trays of 10mm internal diameter were machine tooled to fit snugly over the cylindrical master die in the form of hollow cylinders,open at the ends.

When the custom trays were snugly positioned over the die,the difference in the heights of the trays and that of the die varied 2mm,4mm and 6mm depending upon the tray used.

30 samples for each of the four materials were fabricated with 10 samples of 2mm,4mm and 6mm thickness each

Evaluated the linear dimensional change using a universal measuring machine.

Results:linear dimensional changes of the samples

were tested by measuring the length of line C-D imprinted on the test samples by means of a universal measuring machine

The compressive resistance was measured by finding out the compression distance on an instron testing machine under a constant compressive force of 25 newton.

The compression resistance decreased as the thickness increased.

Each of the test samples was loaded on an instron testing machine and subjected to a constant compressive force of 25 newton for a duration of 1 minute.

Linear dimensional change and compression distances between interocclusal recording materials were analysed by using one way and two way analysis.

AIM: A CLINICAL EVALUATION OF INTEROCCLUTIOL REGISTRATION IN CENTRIC RELATION

MATERIAL AND METHODS :The study casts were obtained from a patient with

partial lower edentulousness,without a free end saddle.

Casts were manually articulated a maximum intercuspation position

Measurements performed with a double cooardinate ZKM 0.2-250 travelling microscope with a precision of 0.2 micrometer.Draft paper was glued to the base of upper and lower casts.

Two reference points were selected at random on each cast ,duly aligned for the measurement of vertical distance .

The measurement were calculated as the difference between the readings reffering to the two obtained points on the microscope dial. A jig was made on the upper cast with duralay acrylic resin.

At each closure ,the interposition of carbon paper indicated the site in the jig to be filled .

On this basis, a separation of the posterior teeth was defined to guarantee the elimination of any interference on closure and created a space for

the positioning of the registration materials.Registration with wax :Ten registrations were obtained with wax 7 sheets

previously cut along the extension of the arches.the registrations were obtained on double thickness wax to compensate the posterior space created by the jig.

Registration with wax plus zinc oxide eugenol paste:

The registrations with wax were obtained in the same manner mentioned above and a small portion of zoe paste was then added in the region of the firt molars,both on the upper and lower part of the wax sheet.

Registrations with wax plus Duralay acrylic resin:

after the registrations with wax were obtained as cited above ,two small perforations were made in the wax sheet for the addition of small portions of the resin.during the plastic phase of the resin,the registration was repositioned in the mouth until full polymerization .

Registration with condensation silicone :The silicone was divided into two parts and placed on

the right and left sides on the occlusal surface of the molars.with the jig in position,the mandible was placed in centric relation.

Results: Because the distribution of sample was

normal,the analysis of variance and tukey test were used,showing the right side to be statistically different at the level of 1%.on the left side,wax and silicone were the materials with the highest standard deviation.

Discussion: In this study,we evaluated the materials in the

centric relation because this is the position of choice for diagnosis and planning of oral rehabilitation.lucia jig was used because it allowed obtention of a rigid and defined stopping point in the anterior region,which ensured the CR position and allowed the evaluation of registration materials used in the posterior region of the arch during measurement with the microscope.

Conclusion: Silicone and wax were the materials that

provided the highest standard deviations and the highest range of variation.

On the right side,silicone was significantly different at the level of 1%compared to the other materials tested.