A soft liner is an elastic or viscoelastic material applied to the fitting surface of denture or obturator for the purpose of reducing and more evenly distributing occlusal loads on the underlying oral tissues. Resilient liners may be regarded as an analogue of the periodontal ligament and compressible healthy muco-periosteum in edentulous persons [1,2].

Resilient lining materials have taken their place in complete denture prosthodontics since their first reported clinical application by Tylman [3]. Some complete denture wearers suffer prolonged discomfort under their dentures despite all possible prosthetic adjustment. This may be because of poor patient tolerance, low pain threshold, thin mucosa or irregular bony contour. Tissue underneath the lower denture usually receives more masicatory pressure per unit area than the upper [4]. Resilient lining materials are mainly used for patients who cannot tolerate these pressures, acts as shock absorber and reduces the effect of transferred force to the basal seat of the denture [5-7].

Obturator is the prosthesis that is used to close and rehabilitate congenital and/or acquired maxillary defect and reestablishes a barrier between the oral cavity and nasal cavities [8-11].

Severe resorption of the mandibular ridge contributes to instability and resultant discomfort of a conventional acrylic resin denture [12]. In this case, the dentures can be made functional and comfortable with a resilient liner [13].

Soft lining materials are used to absorb and distribute masticatory forces through elastic deformation of the denture, thereby minimizing the direct load transmitted to atrophied supporting tissues. In addition, the soft-lining produces an equal amount of pressure over the bone of the ridge and, thereby avoids resistance from the prominent spicules to a larger amount of applied force [14,15].

The liners enable change to occur in the shape of abused oral tissues in response to functional loading [16]. And then assist in producing an even distribution of functional load over the entire denture bearing area. In this way, the oral mucosa underneath the removable denture is less lightly to be traumatized by the presence of denture [16-18], Thus resilient liners are considered to be an analog of mucopenosteum[7] .The present study was conducted to compare retention stability and support of the patients wearing dental prosthesis with and without soft liners.

This prospective longitudinal study was conducted in the Department of Prosthodontics of Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh from January 2008 to December 2010.A total 60 patients of both sexes were evaluated in this study; of them 30 patients were treated with soft-lined denture and obturator (Group-A) and 30 patients were treated without soft lined conventional denture and obturator (Group-B). Each of the patients was selected by a thorough medical and dental history as well as clinical examination, diagnostic model analysis and radiographic investigations. Treatment plan was explained to the patients mentioning the proposed procedure. Being assured of patient's full cooperation, they were finally selected. Before starting the procedure, every patient signed the informed consent form. Standard clinical and laboratory procedures were maintained in an asepsis environment for fabrication of conventional denture and obturator. After remounting the prosthesis on articulator, proper cleaning, finishing and polishing were done, then the prosthesis was inserted into patient's mouth (group-B). On the other hand, the denture or obturator fabricated with soft-lining materials (Group-A) needed further procedures. After insertion the existing centric occlusion and intercuspation were used as a means to seat the denture bearing area into the patient mouth. The borders are reduced 1-2 mm except the posterior border of maxillary denture and remolded to their functional contours by using low-fusing compound. A close mouth impression with zinc oxide eugenol paste was taken asking the patient to close the denture teeth lightly into the intercuspal position. The impression was poured with dental stone. The cast with denture was invested into a flask with counterpart. When plaster was set completely, the flask was opened and the impression material from the denture was removed by warm water. Reduction of tissue surface of denture/obturator then all over the area was done about 1-3 mm by a grinding stone and few undercuts were prepared to lock the materials perfectly. Separating medium on plaster surface and bonding agent on resin surface was applied. Then the soft lining material Molloplast-B was rolled and placed on the denture base and packing was done with standard method. The final closer of the flask was achieved with metal to metal contact between the halves of the flask before placing it for curing process. Standard curing cycle as per manufacturer's instructions was followed for curing. After curing and bench cooling, deflasking and retrieval of the denture was done with care. The denture was cleaned ultrasonically in a plaster and stone remover solution. The bulk of the flashed materials was trimmed from denture, borders and contoured with a No. 60 LG grinding wheel. Silicone rubber resilient liners were trimmed, at slow speeds with disks and rubber wheels. Then polishing and finishing was done properly. The Molloplast-B lined denture or obturator was then inserted into patient's mouth and instructions for use the denture or obturator were given to the patient (Group-A)10,20. Having the denture or obturator inserted into mouth, retention, stability and support were checked and these baseline data for both groups were recorded properly and advised to come for follow visits after 1st week, 3rd week, 5th week and 5th month for evaluation. On each follow up visit retention, stability and support of the patients of both groups were checked and the data were recorded for formulation of results.

Table I shows the distribution of patient's, it was found that among group-A patients, 60% had retention and stability of denture, whereas among group-B patients, it was 86.7% different was statistically significant (p>0.05). After treatment no patient had complaint in retention and stability in Group A. Whereas in Group B patients, it decreased to 33.3% and different was statistically significant (p<0.05)

Table I: Distribution of patients by retention and stability for denture during different study period (n=30)

Chi-square test is done to determine the p value, Group-A (n=30): Patients treated with soft lining material, Group-B (n=30): Patients treated without soft lining material.

Table II showed that among group-A patients, 13.3% had retention and stability of obturator, whereas among group-B patients, it was 80% and different was statically significant (p<0.05). After treatment no patient had complaint of retention and stability in group-A patients, whereas in group-B patients, it decreased to 33.3% and different was statistically significant(p<0.05).

Table II: Distribution of patients by retention and stability for obturator during study period (n=30)

Chi-square test is done to determine the p value, Group-A (n=30): Patients treated with soft lining material, Group-B (n=30): Patients treated without soft lining material

Table III was found that among group-A 13.3% patients had support for denture, whereas among group-B patients, it was 6.7% and difference was not statistically significant (p>0.05). After treatment no patient had complaint of support in group-A patients whereas in group-B patients, it increased to 33.3% and different was statistically significant (p<0.05).

Table III: Distribution of patients by support for denture during study period (n=30)

Chi-square test is done to determine the p value, Group-A (n=30): Patients treated with soft lining material, Group-B (n=30): Patients treated without soft lining material.

Table IV was found that among group-A 20% patients had support for obturator, whereas among group-B patients, it was 13.3% and different was not statistically significant (p>0.05). After treatment no patient had complaint of support in group-A patients whereas in group-B patients, it was increased to 40% and difference was statistically significant (<0.05).

Table IV: Distribution of patients support for obturator during different stud period (n=30)

Chi-square test is done to determine the p value Group-A (n=30): Patients treated with soft lining material Group-B (n=30): Patients treated without soft lining material.

This study demonstrates that soft lining material significantly enhances denture retention and stability. Following treatment, 100% of patients in Group A reported satisfactory outcomes, compared to 33.3% in Group B, highlighting the superior clinical efficacy of the soft liner. These results align with previous research indicating that soft liners improve denture adaptation and load distribution, while increasing retention and stability through a resilient interface with oral tissues. Furthermore, the improved adaptation and reduction of interfacial gaps associated with these materials contribute to superior clinical performance [19,20].

This study demonstrated that the use of soft lining materials significantly improved obturator retention and stability. Following treatment, Group A achieved a 100% satisfaction rate, significantly outperforming Group B at 33.3%, which confirms the superior efficacy of soft liners. These findings align with previous research indicating that resilient liners enhance masticatory function and prosthesis stability through improved adaptation and a cushioning effect [21].

The current study demonstrated a significant improvement in denture support within the soft-lining group. Following treatment, Group A achieved 100% satisfactory support, compared to 33.3% in Group B, highlighting the superior efficacy of soft liners. These findings align with existing literature, which suggests that resilient liners and suitable denture base materials enhance stress distribution and overall denture support [22,23].

This study demonstrated a significant improvement in obturator support when using soft lining materials. Following treatment, Group A achieved a 100% satisfaction rate regarding support, compared to 40% in Group B, underscoring the superior efficacy of soft liners. These findings align with existing prosthodontic literature, which indicates that resilient soft liners enhance stress distribution, improve adaptation, and provide superior support for removable prostheses. Furthermore, the use of these materials is reported to increase patient comfort and functional efficiency by minimizing tissue trauma and enhancing overall denture stability [24,25].

Overall, Soft lining materials greatly enhance the retention, stability, and support of dentures and obturators, outperforming conventional methods in clinical practice.

Based on the results of the present study it can be concluded that soft lining materials used in denture and obturator increase retention, stability and support in denture and obturator wearer rather than the patients wearing the prostheses without soft liner.

ACKNOWLEDGEMENT

We gratefully acknowledge all the patients and their attendances participated in this study. We would also like to acknowledge the Department of Prosthodontics, BSMMU where the study was carried out.

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