Relining Materials Research Articles

Influence of Diode and Nd:YAG laser irradiation on shear bond strength between soft relining material and conventional, thermoplastic, and CAD/CAM denture resins

Influence of Diode and Nd:YAG laser irradiation on shear bond strength between soft relining material and conventional, thermoplastic, and CAD/CAM denture resins

Comparison of Bond Strength of Soft Denture Liner on the Denture Base Materials Produced by Different Methods and Effect of Thermocycling

Aim: This study set out to determine the tensile bond strength between denture bases (produced by 3D printing technology, conventional technique, and computer-aided design and computer-aided manufacturing [CAD/CAM] milled) and silicone-based soft lining material. The consequence of thermocycling on the bonding strength was also investigated. Materials and Methods: The bonding between denture foundation materials produced through three distinct techniques (conventional, CAD/CAM milled, and 3D printed) and silicone-based soft lining material was examined. Before tensile testing, half of the samples underwent thermocycling (5–55°C, 5,000 cycles) in 37°C distilled water for 48 hours. A universal testing apparatus employed a crosshead speed of 5 mm/min. The failure type was identified visually, and the maximum tensile strength was noted. The Shapiro-Wilk test and analysis of variances ( P = .05) were used to assess the statistics. Results: CAD/CAM milled denture base material (1.56 ± 0.62/1.36 ± 0.16 MPa) showed higher bond strength values than the other denture bases in the tensile test conducted before and after thermocycling ( P < .001). The denture base material made conventionally had the lowest bond strength (1.02 ± 0.24/0.77 ± 0.1 MPa) ( P < .001). The tensile bond strength values of the conventional and 3D printing groups showed a statistically significant drop before and after thermocycling ( P = .001). Regardless of thermocycling, adhesive failure was primarily seen in all groups (76.6%). Conclusion: Compared to conventionally produced denture bases, the bond strength of soft relining materials to CAD/CAM milled and 3D printed denture base is different. In denture base materials that are conventionally, CAD/CAM and 3D printed, the thermocycling method reduced bonding strength values.

Effect of adhesives and mechanical surface treatments on the hard relining of CAD-CAM denture bases.

The aim of this study was to evaluate the impact of mechanical roughening, adhesive applications, and aging on the bonding between CAD-CAM denture base materials with distinct chemical contents and hard relining material. A total of 300 denture base specimens were produced by additive, subtractive, and conventional heat-polymerization techniques (N=100). The specimens have been classified into five subgroups based on the particular surface treatments administered (n=20): (1) Hard relining material's adhesive application (control); (2) Tungsten carbide bur application for 1min, and hard reline material's adhesive application; (3) Airborne-particle abrasion (APA) with 110 μm Al2O3, and hard reline material's adhesive application; (4) Scotchbond Universal application; and (5) Visio.link application. Representative specimens from each subgroup were examined under a Scanning Electron Microscope (SEM). Subsequently, self-cure hard relining material was condensed in the center of the specimens. Half of the specimens were thermally aged with 5000 cycles at 5°C-55°C. The shear bond strength (SBS) test was performed, and failure loads were recorded. The data was evaluated by Robust ANOVA and Bonferroni test (p<0.05). No statistically significant difference was obtained between the production techniques (p = 0.051). The lowest SBS was observed in the control group among surface treatments, while mechanical surface treatments and universal adhesive showed the highest SBS for both aged and non-aged groups. Aging caused a significant decrease for all test groups (p=0.001). Mechanical surface treatments and universal adhesive applications are more effective for maintaining adhesion across all production techniques.

Bond Strength of Nanocomposite Hard Liner to CAD-CAM Milled, 3D Printed, and Conventionally Fabricated Denture Base Resins.

To investigate the effect of zirconium dioxide nanoparticles (ZrO2NPs) on the shear bond strength (SBS) of hard denture lines bonded to different denture base resins. Five different denture bases were used in this study: conventional heat-cured resin, IvoCad, AvaDent, NextDent, and FormLabs, in acrylic specimens of 10 × 10 × 2.5 mm3 (N = 150, n = 10). Specimens were centered at the bottom of a silicon mold to create an auto-polymerized holder. Three major groups of reline material were used: no ZrO2NPs (control), 2 wt.%, and 4 wt.% ZrO2NPs. Reline was bonded to the resin surface using a customized jig. After polymerization, specimens were stored in distilled water, and 5000 thermal cycles were performed. Each specimen was fixed to an Instron machine, and SBS was tested using a blade loaded (1 mm/min) at the resin interface until failure. Data was collected and analyzed using two-way ANOVA and post hoc Tukey test (α = 0.05). AvaDent showed the highest SBS when compared with other denture base materials (p < 0.001) except for IvoCad. The addition of ZrO2NPs significantly decreased the SBS of AvaDent (p = 0.003) and IvoCad (p = 0.001), while heat polymerized resin, Formlabs, and NextDent showed no significant change in SBS (p > 0.05). CAD-CAM milled denture base resin showed higher SBS with pure denture reline. The addition of ZrO2NPs decreased the SBS of reline with CAD-CAM milled denture base resins but did not change bond strength with 3D printed and conventional denture base resins.

Rehabilitation of Combined Hard and Soft Palate Defects with a Soft Relining Prosthesis: A Clinical Report.

It remains a significant challenge in prosthetic rehabilitation for combined hard and soft palate defects on account of two primary reasons. At first, conventional impressions can hardly get an accurate analogue and usually bring about a terrible experience for the patients. Secondly, conventional hard denture base resins used in obturator prostheses exhibit limitations in marginal sealing, undercut retention, and elastic buffering when in contact with the soft palate. This article presents a case where combined hard and soft palate defects were successfully and rapidly reconstructed by using digital intraoral impression technology and denture soft reline material.

Effect Of Air-Abrasion And Er:Yag Laser On The Bond Strength Between The Metal Housing Of An Overdenture Attachment System And The Hard Relining Material

Objective. This study investigated the effect of air-abrasion and erbium:yttrium-aluminum-garnet (Er:YAG) laser treatments on push-out bond strength (PBS) between hard relining material and metal housing of an overdenture attachment system. Material and Methods. A total of 36 metal housings were randomly divided into 3 subgroups according to surface pretreatments (n=12): Control (no surface treatment; C), air-abrasion (A), and Er:YAG laser (L). Surface roughness (Ra) of specimens was determined using a profilometer. One additional specimen per group was evaluated by scanning electron microscopy (SEM). The hard relining material was bonded to metal housings, and a PBS test was performed using a universal testing machine. Data were statistically analyzed using 1-way analysis of variance (ANOVA), Tukey’s honestly significant difference (HSD), and Tamhane’s T2 tests (α=.05). Results. C and L groups showed the lowest and highest Ra values, respectively. The mean Ra of the A group was statistically different from the mean values of the C and L groups (P&amp;lt;.001). The L group showed higher PBS values than the C group (P&amp;lt;.05), whereas the A group exhibited statistically similar PBS values to both C and L groups (P&amp;gt;.05). Conclusions. Air-abrasion did not significantly increase the bond strength between the metal housing and hard relining material. Er:YAG laser irradiation noticeably improved the PBS but caused surface microcracks.

Assessment of occlusion changes during laboratory phase of relining: An in vitro study.

Assessment of occlusion changes during laboratory phase of relining is essential to evaluate the occlusal discrepancies that could get incorporated in the denture with the use of different relining materials. Since the long term stability and functional success of the denture is heavily influenced by occlusion, an In-vitro study to assess these changes after relining is warranted. The aim of the study is to evaluate the changes in occlusion during laboratory phase of relining procedure. This is an in vitro study with a total of 30 specimen. A total of 30 maxillary standardized dentures were fabricated after mounting on a semi adjustable articulator. These samples will be divided into three groups based on the relining material used (Autopolymerizing resin, Heat-cure resin, Tissue conditioner). The vertical dimension, Centric contact points and eccentric contact points were measured before and after relining. The variables were tested to see if they had a normal distribution using the Shapiro-Wilk test. Parametric distribution was seen for ECP leading to further comparison using one way analysis of variance (ANOVA). Non-parametric distribution was found while testing the VD, CCP leading to adoption of Kruskal-wallis test for comparison of groups. Dunn Bonferroni test was done for VD since results were significant. The results of this in-vitro study showed statistically significant difference with respect to change in vertical dimension in all groups pre and post relining (P = 0.005). The centric contact points showed lesser variation in position when comparing the pre to the post relining phase with the use of autopolymerising resins, whereas heat cure resins and tissue conditioners showed statistically significant difference in the centric point contacts post relining. No statistically significant changes were seen in eccentric occlusion post relining in all groups. Tissue conditioners showed minimum mean changes in eccentric contacts. Within the limitations of this study, the use of autopolymerising resins depicted the most stable results with respect to occlusion, for relining of dentures.

Effect of Air-abrasion and Er:YAG Laser on the Bond Strength Between the Metal Housing of an Overdenture Attachment System and the Hard Relining Material

Effect of Air-abrasion and Er:YAG Laser on the Bond Strength Between the Metal Housing of an Overdenture Attachment System and the Hard Relining Material

Effect of various surface treatments on relining bond strength of CAD-CAM denture base materials.

The aim of this study was to analyze the impact of various surface treatments and production methods on the shear bond strength (SBS) between reline material and denture base resins. One-hundred-twenty specimens were produced using conventional heat-polymerization, subtractive, and additive techniques. Each group consisted of 40 specimens. The specimens were divided into four subgroups, each with 10 samples, for surface treatments. These subgroups were: (1) Control-only monomer application, (2) 50 μm airborne-particle abrasion, (3) 110 μm airborne-particle abrasion, and (4) Roughening with tungsten carbide bur. Representative specimens from each subgroup were examined under SEM. Then, auto-polymerized resin was condensed in the center of the specimens. Specimens were subjected to thermal aging (5000 cycles at 5-55°C). The SBS test was conducted and failure loads were recorded. The data were evaluated by two-way ANOVA and Tukey pairwise multiple comparisons method (p < 0.05). The additively produced group showed significantly lower SBS than conventional and subtractive groups (p < 0.001), with no significant differences between the subtractive and conventional groups. Specimens that underwent monomer application only showed the lowest SBS among surface treatments, while 50 μm airborne-particle abrasion showed the highest SBS. Based on the partial eta-squared analysis results, the surface treatment mainly impacted SBS. Among the surface treatment methods, treating denture bases with 50 μm airborne-particle abrasion is more effective for maintaining adhesion, especially in the additive technique.

Effect of soft denture liners on complete denture treatments: A systematic review.

This systematic review examined the effectiveness of soft denture relining (SDR) materials. A comprehensive search of MEDLINE, Cochrane Library, and ICHUSHI was conducted up to July 26, 2020. Target outcomes were patient satisfaction, oral health-related quality of life (OHRQOL), masticatory ability (MA), denture functional duration, residual ridge resorption (RRR), and microbial contamination. An organization specializing in literature searches performed the reference searches, and two reviewers independently selected the literature sources, extracted the data, and assessed the risk of bias. The reviewers resolved any disagreements concerning the assortment of literature sources through discussion. SDR included acrylic- and silicone-based materials, which were evaluated separately. Reviewers selected 7, 5, 11, 1, 4, and 6 studies to assess patient satisfaction, OHRQOL, MA, functional duration, RRR, and microbial contamination, respectively. The results confirmed that SDR improved patient satisfaction, OHRQOL, MA, and RRR. However, the functional duration of SDR material is shorter than that of hard denture relining (HDR) or acrylic resin material. Furthermore, SDR material is more susceptible to microbial contamination in the long term. The risk of bias for the included studies tended to be high because of specific issues (difficulty in blinding SDR versus HDR). For patients who wear complete dentures, SDR often provides beneficial outcomes such as pain reduction and recovery from MA. However, caution should be exercised regarding their use owing to insufficient functional duration and the possibility of microbial contamination during long-term use.

Antimicrobial hard denture reliners using quaternary ammonium methacryloxy silicate (K18 QAMS) and K18-functionalized filler

Objective: To determine the effects of adding a quaternary ammonium methacryloxy silicate (K18) and K18-functionalized filler (K18-Filler) on the material and antimicrobial properties of a hard denture reline material. Materials and methods: 30% K18 in methyl methacrylate (K18-MMA; 0–20 wt% of reliner) and K18-Filler (0–30 wt% of reliner) were incorporated into KoolinerTM hard denture reliner. KoolinerTM served as the control. The cure (Shore A hardness), hydrophilicity (contact angles), mechanical (3-point bend test), water sorption, and antimicrobial properties against Streptococcus mutans, S. sanguinis, and Candida albicans were determined. Results: Most K18 groups cured well and had comparable Shore A hardness values (range ~52 to 70 DHN) to that of controls (67.2 ± 1.8 DHN; Bonferroni corrected p &gt; 0.0003). Even the softest group had hardness values within the range of commercial products. Half of the K18 groups had comparable contact angles to that of controls (range ~75° to 80° vs 83.41° ± 2.66°; Bonferroni corrected p &gt; 0.0003), and most were within the range of commercial liners. K18-MMA and K18-Filler increased modulus but decreased ultimate transverse strength (UTS). All experimental groups had comparable or higher moduli than controls (range ~966 to 2069 MPa vs 1340 ± 119 MPa; Bonferroni corrected p &lt; 0.0003), but only half of the experimental groups had comparable UTS to that of controls (range ~41 to 49 MPa vs 55.8 ± 1.5 MPa; Bonferroni corrected p &gt; 0.0003). The 15% and 20% K18-MMA with 30% K18-Filler groups had significant antimicrobial activity against all three microbes ( p &lt; 0.05). However, the 15% and 20% K18-MMA with 30% K18-Filler groups had significantly higher water sorption at early time points ( p &lt; 0.05). After 8 weeks, they were comparable to each other ( p &gt; 0.05). Conclusions: K18-MMA and K18-Filler are promising antimicrobial additives that produce hard denture liners with material properties within the range of commercial products and significant antimicrobial properties against S. mutans, S. sanguinis, and C. albicans. Further development is needed to reduce water sorption.

PROSTHETIC TREATMENT OF A PATIENT WITH RESECTION OF THE HARD PALATE WITH AN OBTURATOR WITH A SILICONE BASE

The most commonly used treatment method for maxillary resection patients is with an obturator, closing the communication between the oral and nasal cavity. Prosthetic methods and means with different types of materials are used for its fabrication. The purpose of the described clinical case is to track the opportunity for treatment of a patient with resection of the hard palate, with an obturator with a silicon base.The clinical case tracks the treatment of a patient with maxillary carcinoma. Preliminary alginate impressions were taken from the jaws. A custom tray with which a functional impression with a silicone material was taken, was fabricated for the mandible. The height and the central position of the mandible were determined with record bases with wax rims. The dentures were finished with heat cured resin. The upper denture was used as a custom tray for taking a functional impression of the prosthetic field with silicone cream material. After packing in the laboratory, the impression material was replaced with permanent soft relining material Molloplast B (Detax). The finished dentures were adjusted and articulated until bilaterally balanced occlusion was achieved. Treatment results showed good retention and stability of the prosthetic construction. Functional impression shaping and subsequent replacing with silicon material ensured a good and tight hermetic seal in the area of the defect. The use of permanent soft relining material allowed a trauma-free transmission of masticatory pressure and a stable connection with the plastic base of the obturator. The patient’s eating and speech as well as the fluid intake were successfully restored. The achieved results improved the quality of life of the patient and his self-esteem. Prosthetic treatment with an obturator with a silicon base provides good retention and stability of the prosthetic construction which allows successful restoration of the patient`s eating and speech.

Influence of hydrothermal aging on the shear bond strength of 3D printed denture-base resin to different relining materials

ObjectivesThis study evaluated the repairability of three-dimensional printed (3DP) denture bases based on different conventional relining materials and aging. Material and methodsThe groups for surface characterization (surface-roughness and contact-angle measurements) were divided based on the denture base and surface treatment. Shear bond strength test and failure-mode analysis were conducted by a combination of three variables: denture base, relining materials, and hydrothermal aging (HA). The initial characterization involved quantifying the surface roughness (n = 10) and contact angle (n = 10) of denture base specimens with and without sandblasting (SB) treatment. Four relining materials (Kooliner [K], Vertex Self-Curing [V], Tokuyama Rebase II (Normal) [T], and Ufi Gel Hard [U]) were applied to 3DP, heat-cured (HC), and self-cured (SC) denture-base resin specimens. Shear bond strength (n = 15) and failure-mode analyses (n = 15) were performed before and after HA, along with evaluations of the fractured surfaces (n = 4). Statistical analyses were performed using a two-way analysis of variance (ANOVA) for surface characterization, and a three-way ANOVA was conducted for shear bond strength. ResultsThe surface roughness peaked in HC groups and increased after SB. The 3DP group displayed significantly lower contact angles, which increased after treatment, similar to the surface roughness. The shear bond strength was significantly lower for 3DP and HC denture bases than for SC denture bases, and peaked for U at 10.65 ± 1.88 MPa (mean ± SD). HA decreased the shear bond strength relative to untreated samples. Furthermore, 3DP, HC, and SC mainly showed mixed or cohesive failures with V, T, and U. K, on the other hand, trended toward adhesive failures when bonded with HC and SC. ConclusionThis study has validated the repairability of 3DP dentures through relining them with common materials used in clinical practice. The repairability of the 3DP denture base was on par with that of conventional materials, but it decreased after aging. Notably, U, which had a postadhesive application, proved to be the most effective material for repairing 3DP dentures.

Evaluation The Effect of Incorporation of Different Herbal Extract Powders (Either Neem or Aloe Vera) On Thermal Conductivity and Shear Bond Strength of Acrylic Soft Denture Liner Material

The main drawbacks of the soft liners were poor thermal conductivity and poor bonding between denture base and soft lining. The purpose of this study was to analysis the influence of incorporating either Neem or Aloe Vera on thermal conductivity and shear bond strength of heat cure acrylic soft liner. Sixty heat cure acrylic soft liner specimens were prepared and classified as two major groups based on tests that evaluated (thermal conductivity and shear bond strength), each major group sub classified for three groups based on incorporated material: The control group (10) specimens, (10) specimens with 10% by weight of Neem powder; (10) specimens with 10% by weight of Aloe Vera powder. Thermal conductivity specimens were fabrication with dimensions of (40 mm diameter × 2.5 mm thickness). Two acrylic block of shear bond strength specimens with dimensions (75mm × 25mm × 5 mm length, width, depth respectively) was fabrication. The reline material application on space between two acrylic blocks. The (Lee disc) equipment was used to assess thermal conductivity. With a crosshead speed of 0.5mm/min, a shear bond strength was measured. Data statically analyzed by One-way ANOVA and LSD tests. The results showed the Neem group had highest mean value of thermal conductivity and shear bond strength than aloe Vera and control groups at p&lt;0.01. Either Neem or Aloe Vera increased thermal conductivity and shear bond strength of soft liner.

Bond Strength of Reline Materials to 3D-Printed Provisional Crown Resins.

(1) Purpose: The aim of the present study was to compare the bond strength between two 3D-printed resins designed for long-term provisional crowns and three different reline materials. (2) Materials and Methods: Rectangular specimens were prepared from two 3D-printed resins (Envision Tech and NextDent C&B) and a conventional self-cure PMMA. Transparent tubes filled with three different reline materials including composite resin, Bis-acryl, and PMMA were bonded to the 3D-printed specimens (n = 11 per group, total of 6 study groups). Tubes filled with PMMA were bonded to the prepared PMMA specimens which served as the control group (n = 11, control group). The specimens were subjected to a shear bond strength (SBS) test, and mode of failure was recorded using light microscopy. Statistical analysis was performed using a one-way ANOVA and post hoc Tukey's tests (alpha = 0.05). (3) Results: The highest SBS value was achieved to both 3D-printed materials with the PMMA reline material. The bond to both 3D-printed materials was lower with Bis-acrylic or composite resin relines in comparison to that with PMMA (p-value < 0.05). No significant difference was found between the control PMMA group and either 3D-printed material when relined with PMMA (p-value > 0.05). (4) Conclusion: The tested 3D-printed resins achieved a clinically acceptable bond strength when relined with PMMA.

Antifungal effects of eugenol on Candida albicans adherence to denture polymers.

The study's objective is to assess the adherence of C. albicans in different types of denture polymers and the effectiveness of eugenol and commercialized denture cleansers in the removal of C. albicans. Three types of denture base polymers (Lucitone® 199 (High-Impact PMMA), Impact® (conventional PMMA) and Eclipse® (UDMA)) and two hard denture reline materials (Kooliner® and Tokuyama® Rebase II Fast) were used in this study. Three hundred samples were prepared (6 × 2 mm disc shape) and divided into five groups of denture polymers (n=60) and further subjected into five treatment groups (Polident®, Steradent, distilled water, eugenol 5-minutes, and eugenol 10-min). Three samples were extracted from each treatment group for baseline data (n=12). Baseline data were used to calculate the initial number of C. albicans adherence. A 0.5 ml immersion solution from each specimen was cultured on YPD agar and incubated for 48 h at 37 °C. Visible colonies were counted using a colony counter machine (ROCKER Galaxy 230). The result showed that the denture base polymer significantly affected the initial adherence (p=0.007). The removal of C. albicans was also considerably affected by the denture base polymers and denture cleansers (p<0.05). Lucitone®, Tokuyama®, and Kooliner® denture base polymers immersed for 3 min in eugenol showed the best results of removal. This study's overall results showed that all denture polymers used as denture bases had an effect on C. albicans initial adherence and removal from the denture base, and eugenol is comparable to commercialised denture cleansers in reducing the number of attached C. albicans on denture base polymers.

Comparison of shear bond strength between hard relining material and 3D-printing denture base resin containing silica micro-gel

Comparison of shear bond strength between hard relining material and 3D-printing denture base resin containing silica micro-gel

The Effect of Disinfection Methods on C. Albicans in Three Types of Denture Base Materials

This study aimed to evaluate the efficacy of disinfectant solutions on Candida albicans (C. albicans) for different types of denture materials. A total of 144 specimens (10x10x2 mm) were obtained from three different materials: autopolymerized acrylic resin, heat-cured acrylic resin, and hard relining material (n = 6). Three disinfectant solutions were used: 100% white vinegar, 2% chlorhexidine digluconate (Saver) and denture cleaning tablets (Corega). The specimens were placed on Eliza plates and 1.5 mL of Yeast Extract Peptone (YPD) was added to each well. Then, 30�L of candida culture was added to the wells. Next, the specimens were incubated at 37�C at 80 rpm for 48 h. Disinfectants were added to the Eliza plates. For all specimens, the disinfectants were replaced with 2 mL of sterile water and kept at 100 rpm for 30 min. Then, 0.1 mL of the liquid was taken and inoculated into the pads containing YPD medium. After incubation, the candida colony growth on the pads was measured. Scanning electron microscope (SEM) images were taken from randomly selected specimens from each group. Statistically significant differences (𝑃 [ 0.05) were found between the disinfectant method groups and the control group for the three types of denture materials. The 2% chlorhexidine gluconate (Saver) disinfectant was the most effective for C. Albicans ATCC 60193 and oral isolate of C. Albicans for all three of the tested denture materials. The effect of cleaning of tabs (Corega) and white vinegar was found to be similar.

CAD-CAM complete denture resins: Effect of relining on the shear bond strength

ObjectivesThe aim of this study was to compare the shear bond strength of relined CAD-CAM complete removable dental prosthesis (CRDP) resins with conventional heat-polymerized polymethylmethacrylate (PMMA) resin. MethodsA total of 96 resin specimens in identical dimensions of 10 mm × 10 mm × 11 mm were fabricated for four study groups [#1- Conventional heat-polymerized group: n=24 (ProBase); #2- Milled#1: n=24 (Ivobase); #3- Milled#2: n=24 (Ivotion); #4- 3D-printed: n=24, (NextDent Denture 3D+)]. Twelve specimens in each group were sectioned in the middle to produce a 3 mm defect and then were relined using a conventional denture relining material. All specimens underwent thermocycling (5-55°C) for 10,000 cycles. The shear bond tests were carried out in a universal testing machine. One-way ANOVA and Tukey's test were used for statistical analysis (p<0.05). The two-parameter Weibull distribution values were calculated. ResultsRelined 3D-printed specimens had a significantly lower shear bond strength when compared with conventional (p=0.0003) and milled groups (Milled#1: p=0.0004; Milled#2: p<0.0001). There were no differences in the shear bond strengths between the milled and conventional groups. Weibull distribution presented the highest shape value for the non-relined Milled#1 (22.83) group and the lowest values for the 3D-printed relined group (4.001). ConclusionThe findings of this study conclude that the shear bond strength of the conventionally-relined 3D-printed resins used for fabricating CRDPs was inferior to the shear bond strength of conventionally-relined resins employed for manufacturing CRDPs using CAD-CAM milling and conventional heat-polymerization techniques. Clinical significanceWhen considering 3D-printing for the fabrication of CRDPs, it is recommended to employ it in clinical situations where a frequent need for denture relining is not expected.

Tensile bond strength of auto-polymerizing and heat-polymerizing denture reliners on the conventional and CAD-CAM denture base materials.

The study aimed to compare the tensile bond strength (TBS) of auto-polymerizing and heat-polymerizing denture reliners on the conventional (compression-molding and injection-molding) and computer-aided design and computer-aided manufacturing (milled and 3D-printed) denture base materials. Eighty standard dogbone-shaped specimens were fabricated from four materials: compression-molding, injection-molding, milled, and 3D-printed denture base materials. A 3-mm cutoff was removed from each specimen at the midsection, and all specimens were reattached with either auto-polymerizing (n=10) or heat-polymerizing (n=10) reliner. The TBS was measured on the universal testing machine. A scanning electron microscope (SEM) was used to examine the fractured surfaces at cross sections to determine the dominant failure mode in each group. Two-way ANOVA was used to examine the effects of denture base material and reliner on the TBS (α=0.05). Weibull survival analysis was also used to determine the survival probability curves. Heat-polymerizing reliner led to a higher TBS than the auto-polymerizing reliner, except in the compression-molding (p=0.573) groups. Compression-molding denture base material connected with a heat-polymerizing reliner showed the highest TBS (29.8±6.9MPa), whereas 3D-printed denture base material connected with an auto-polymerizing reliner showed the lowest TBS (7.2±0.9MPa). The survival probability based on the Weibull model demonstrated that the compression-molding denture base material connected with either auto-polymerizing or heat-polymerizing reliners had the longest survival time to failure, whereas 3D-printed denture base material relined with auto-polymerizing reline material showed the shortest survival time to failure. Under the SEM, the compression-molding groups demonstrated that the failure modes were mixed but predominantly cohesive. The injection-molding and milled groups showed predominantly adhesive failures at the denture base-reline material interfaces. The dominant mode of failure in the 3D-printed groups was cohesive failures within the bonding adhesive. Although the heat-polymerizing reliner led to a higher TBS than the auto-polymerizing reliner in most denture base materials, the compression-molding denture base material can achieve high TBS with both reliners. When the auto-polymerizing reliner is used with 3D-printed denture base material, clinicians should be aware of lower TBS value and possible cohesive failures, and the detachment of the reliner from the denture base.