An in vivo study to record bite force until denture dislodgement of an existing and new maxillary denture with and without use of denture adhesive

INTRODUCTION

Adequate retention is a basic requirement for the acceptance of complete dentures. Since there are several factors involved in the retention of dentures, in many occasional situations it is not possible to obtain the desirable optimal retention. In these instances, different mechanical aids to retention like springs, suction chambers, suction rubber discs and magnets are used. Since, these mechanical aids cause some ill effects to the surrounding tissues, many patients frequently resort to the use of denture adhesives.^1,3,4,5

There are many methods to measure retention in a complete denture like using hydraulic pulley, radio telemetry, cineradiography and gnathodynamometry, etc. Because of their technique sensitivity and limitations, the introduction of customized autoclavable “Gnathometer” instrument facilitates simple measurement of retention of the maxillary dentures, which allows the patient to bite on a small rubber pad with the central and lateral incisors of the maxillary and mandibular denture teeth.^{3,6- 8}

Hence, this in - vivo study was planned to record the BFDD of an existing and new maxillary complete denture without and with the use of a denture adhesive in subjects, with the help of customized autoclavable gnathometer which facilitates simple measurement of BFDD of the maxillary denture with the following objectives:

• To measure BFDD in an existing denture without and with use of denture adhesive.

• To measure BFDD in new denture without and with use of denture adhesive.

• To compare BFDD between an existing and new denture without and with use of denture adhesive.

Methodology

Before starting the procedure, the patients were explained about the procedure and aim of the study and informed consent was obtained from all the patients. Ethical clearance was obtained from the ethical clearance committee of the institution.

A. Materials and armamentarium used in the study.

Materials and instruments which were available and used routinely for the fabrication of complete denture in the department were used for the studyalong with customized autoclavable ‘Gnathometer’ and fittydent denture adhesive cream as shown in Figures 1 & 2.

B. Fabrication of a customized autoclavable ‘Gnathometer’.

A customized autoclavable Gnathometer was planned to be fabricated under the guidance of mechanical engineer, with the help of a schematic representation of the instrument. The stainless steel sheets were cut into the desired shapes. The spring thickness of 0.65mm was selected. An arm of a gnathometer with needle to show the deflections and spring were attached to the instrument with the help of screws. Rubber pads were attached to help the patient to bite on it. Instrument was then graduated from 1 to 10 units (Figure 3)

C. Patient selection and Grouping of the study subjects.

A total of twenty edentulous subjects 14 male and 6 female age ranged from 50 to 76 years who were in normal health, without systemic problems, not under any medication, non-fasting, having class I ridge relationship were randomly selected for the study. All the selected subjects were not satisfied with the retention of their existing complete dentures and treated for new set of complete dentures.

For the study purpose, following groups were made:

Group I – Subjects who’s BFDD recorded with existing complete denture.

Group II – Subjects who’s BFDD recorded with new complete denture.

Methods:

A – Without use of denture adhesive (base line). B – With use of denture adhesive (at different time intervals).

D. Measurement of an intaglio surface area of the maxillary complete denture

Tissue fitting surface area of a complete denture is one of the important factors which can affect its retention. The retentive force is proportional to the square of the surface area, which indicates the importance of maximum tissue coverage for dentures. To measure the surface area an aluminum foil was adapted over an intaglio surface of a maxillary complete denture and was cut along markings made with a marker over the borders of the denture (Figure 4). Care was taken to avoid any folds on the surface. Adopted aluminum foil was then spread over a flat paper to facilitate measuring surface area using a ‘Planimeter’ (FIgures 5 & 6).

E. Method employed for recording the BFDD in Group I-A and Group II-A subjects.

As a baseline, the BFDD was recorded for Group-I A subjects The recordings were made by using the newly fabricated customized autoclavable “Gnathometer”. Whereas, for Group II- A subjects after insertion of new set of complete denture, they were allowed for 2 weeks of adjustment period for the denture to settle. When the subjects were problem free, BFDD of the new maxillary dentures were recorded without the use of denture adhesive by following the same procedures as for existing denture as baseline.

F.Method employed for recording the BFDD in Group I-B and Group II-B subjects.

At the start of study, all the subjects were given instructions about the use of denture adhesive and demonstrations were given following manufacturer’s instruction.

Application of denture adhesive

For the Group I-B and Group II-B subjects, prior to the application of denture adhesive the dentures were removed, cleaned and dried. The selected study material “Fittydent” denture adhesive which is in the form of cream was then applied to the maxillary denture on the fitting surface. Each strip of approximately 1cm adhesive was placed at the anterior, posterior, right and left areas on intaglio surface of maxillary complete denture (Figure 7). The excess lengths of the denture adhesive strip was cut and removed with a sharp instrument. Then dentures were placed in the oral cavity and allowed for initial one hour for the denture adhesive to attain its properties.

For each subject BFDD measurements were recorded thrice for every time interval of 1st, 2nd, 4th, 6th and 8th hours following the application of denture adhesive i.e. at 11am, 12pm, 2pm, 4pm and 6pm. After the 2nd hour following the application of denture adhesive i.e. after 12pm, the patients were allowed for intake of food and water. On each occasion, the subjects were allowed for 3 minutes to reseat their denture by bringing their mandibular denture into occlusion with maxillary denture teeth between recordings (Figures 8 &9).

Using pre designed Proforma individual patient information was recorded. The data obtained were statistically analyzed using ANOVA for different time intervals and student’s t-test for group wise comparison.

RESULTS

The results were expressed as Mean & Standard Deviation (SD) values. The changes in BFDD values were tested by Student paired t- test and repeated ANOVA. The obtained values were tabulated and statistically analyzed. In statistical analysis for significance, probability (p) was considered.

DISCUSSION

Surface area of a complete denture is one of the important factors which affect its retention. The retentive force is proportional to the square of the surface area, which indicates the importance of maximum tissue coverage for dentures. In the present study, the measured intaglio surface area values for existing maxillary complete dentures ranged from highest value of 47.7cm² to lowest value of 28.8cm2 and for new maxillary complete dentures ranged from highest value of 51.5cm² to lowest value of 31.5 cm.²

Since the units obtained with the Customized autoclavable Gnathometer used in this study can be interpreted in terms of Newton (N), a direct correlation with previous studies can be made and the results of the present study showed that at the 1st and 2nd time intervals i.e. at T1 and T2, BFDD of existing dentures was improved nearly 4 to 6 times (45 N and 60 N respectively) when compared with the baseline values (11 N) followed by a decline till T8 to 3 times (31 N) in one of the subject. This increase in BFDD values till T2 followed by decline till T8 was observed for more than 60% of the subjects in group I and II. But in nearly 40% of subjects in Group I and II, an increase in BFDD values was seen till T6, followed by a decline at T8.

Authors9-20 have proved the diurnal variations in retention by using different denture base materials which showed increased retention at morning than afternoon due to changes in palatal tissue morphology which results from change in tissue form and thickness, related to fluid distribution, gravity and posture. In the present study also, all the subjects showed increased BFDD values during morning hours followed by a gradual decline after 12 Noon till evening.

Grasso et al showed that ‘Fixodent’ cream denture adhesive enabled patients to generate significantly greater incisal bite force up to 8 hours after application. The ‘Fittydent’ cream denture adhesive tried in this study was effective for up to 8 hours. Due to its solubility, one can anticipate that the intake of food and beverages and the daily hygienic care of the dentures might decrease the adhesive properties and, eventually the retention and BFDD. Since this study was performed on non-fasting subjects, normal clinical function was tested, but not the pure effect of denture adhesive, as subjects were allowed for intake of food and beverages.⁷

Other adhesives with different chemical compounds and an extended period of testing (e.g. 10 to 12 hours) could be compared in future studies. The finding of the present study demonstrates that using denture adhesive increased BFDD not only for the existing, but also for the new dentures. Maximum BFDDs of existing dentures with adhesive were significantly lower than forces with new dentures and adhesive. This could be probably due to loss of adhesive from the under extended denture borders and decreased retention of existing dentures when compared to the new complete dentures having properly contoured borders.

The results of the present study showed that consistent improvement was observed in BFDD mean values when an denture adhesive was used for all time intervals from the baseline (mean 5.76N and 9.88N) to maximum during T2 (mean 39.89N and 46.11N) followed by a gradual decline from T4 (mean 33.78N and 38.65N) to minimum during T8 (mean 19.16N and 21.78N) respectively for Group-1 and Group-II subjects as shown in Table 6 & 7.

The t-value showed variable changes with range of 4.9(at T8) to 17.7(at T2) and p-value was highly significant (p<0.001hs) at all time intervals with F-value of 39.13N when a comparison was made for BFDD values recorded in Group-I subjects between methods A and B i.e. mean difference.

The t-value showed variable changes with range of 6(at T8) to 12.2(at T4) and p-value was highly significant (p<0.001HS) at all time intervals with F-value of 58.86N when a comparison was made for BFDD values recorded in Group-II subjects between methods A and B i.e. mean difference.

Also, when a comparison was made for BFDD values recorded in Group- I and Group-II subjects between method I-A & II-A and method I-B& II-B, the p-values were significant only at baseline (t-value 2.7) and T4 (t-value 2.3) with mean difference of -4.12 to -4.87 respectively and not significant at T1 (t-value 1.2), T2 (t-value1.7), T6 (t-value 1.5) and T8 (t-value 1.2) with mean difference of -4.77, -6.21, -3.53& -2.62 respectively as shown in Table-10.

In the present study, all the 6 female subjects showed a decreased BFDD values when compared to 14 male subjects at all time intervals from base line to T8. In the present study the denture adhesive was applied only to the maxillary dentures. However, the subjects frequently complained problems with their mandibular dentures. Techniques and devices should be developed in order to measure the retention in the mandibular dentures and to evaluate the effect of adhesives in preventing displacement of the mandibular dentures.

Since, the instrument used for this study was custom made; further research is needed to determine its reproducibility and predictability and to interpret the BFDD units in comparison to the universal unit like Newton (standardization).

SUMMARY AND CONCLUSION

In the present study, when an evaluation was made in Group-I and group-II subjects, between method A and B, consistent improvement in BFDD values seen in method B at all different time of intervals with a gradual increase from time intervals T1 to T2 followed by decline till T8.

This increase in BFDD values till T2 followed by decline till T8 was observed for more than 60% of the subjects in Group-I and Group-II. But in nearly 40% of subjects in Group-1 and Group-II, an increase in BFDD values was seen till T6, followed by a decline at T8. The cream denture adhesive tried in this study was effective for up to 8 hours. Due to its solubility, one can anticipate that the intake of food and beverages and the daily hygienic care of the dentures might decrease the adhesive properties and, eventually the retention and BFDD. Since this study was performed on non-fasting subjects, normal clinical function was tested, but not the pure effect of denture adhesive, as subjects were allowed for intake of food and beverages.

The results of the present study demonstrated that the use of denture adhesive enhanced increased BFDD not only for the existing, but also for the new dentures. Maximum BFDDs recorded by the existing dentures with adhesive were significantly lower than the forces in new dentures with use of a denture adhesive. This could be explained by the loss of adhesive from the denture borders and decrease in retention of existing dentures when compared to new ones. Also, 6 female subjects showed a decreased BFDD values compared to 14 male subjects at all time intervals from base line to T8.