Dental Alloy Adhesive Primers and Bond Strength at Alloy-Resin Interface: A Systematic Review and Meta-analyses

AIM

The present systematic review aimed to report the studies concerning the primers in improving bond strength and identifying pertinent primers for a particular dental alloy by adhering to PRISMA precepts.

MATERIALS AND METHODS

PubMed and Semantic Scholar databases were scoured for articles using 10 search terms. In vitro studies satisfying the inclusion criteria were probed which were meticulously screened and scrutinized for eligibility adhering to the 11 exclusion criteria. The quality assessment tool for in vitro studies (QUIN Tool) containing 12 criteria was employed to assess the risk of bias (RoB).

RESULTS

A total of 48 studies assessing shear bond strength (SBS) and 15 studies evaluating tensile bond strength (TBS) were included in the qualitative synthesis. Concerning SBS, 33.4% moderate and 66.6% high RoB was observed. Concerning TBS, 26.8% moderate and 73.2% high RoB was discerned. Seventeen and two studies assessing SBS and TBS, respectively, were included in meta-analyses.

CONCLUSIONS

Shear bond strength and TBS increased for the primed alloys. Cyclic disulfide primer is best-suited for noble alloys when compared with thiol/thione primers. Phosphoric acid- and phosphonic acid ester-based primers are opportune for base alloys.

CLINICAL SIGNIFICANCE

The alloy-resin interface (ARI) would fail if an inappropriate primer was selected. Therefore, the selection of an appropriate alloy adhesive primer for an alloy plays a crucial role in prosthetic success. This systematic review would help in the identification and selection of a congruous primer for a selected alloy.

Formulation, Configuration, and Physical Properties of Dental Composite Resin Containing a Novel 2π + 2π Photodimerized Crosslinker - Cinnamyl Methacrylate: An In Vitro Research

AIM

To formulate and characterize the chemical structure of a new dental composite with photodimerized cinnamyl methacrylate (PD-CMA) photo-crosslinking comonomer and to evaluate the monomer-to-polymer conversion (MPC) and glass transition temperature (Tg) of the new composite copolymers.

MATERIALS AND METHODS

CMA was PD by ultraviolet C-type (UVC) irradiation. The research groups were a control group C0 without PD-CMA and two trial groups: E10 (10 wt. % PD-CMA substituted in the base comonomers (B) and diluent (D) mixture); E20 (20 wt.% PD-CMA completely replacing the diluent (D) monomer). Infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies were employed for ascertaining copolymerization (CP). The surface features and composition of the copolymers were explained by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopy, respectively. The MPC and Tg of the copolymers were assessed using FTIR and differential scanning calorimetry, respectively. Statistical tests were used to compare the groups.

RESULTS

The configuration of the new copolymers P (BD-Co-CMA) and P(B-Co-CMA) was confirmed. The MPC% and T g of the copolymers were better than the control. PD-CMA at 20 wt. % in the P (B-Co-CMA) copolymer exhibited the highest MPC% and Tg.

CONCLUSION

The incorporation of PD-CMA in the composite resin resulted in new P (BD-Co-CMA) and P (B-Co-CMA) copolymers with improved MPC% and Tg.

CLINICAL SIGNIFICANCE

The substitution with PD-CMA offset the shortcomings of the conventional BD comonomers concerning the mechanical properties and biocompatibility of the restorative composite resin. This might ameliorate the restorations in vivo longevity and serviceability.

Portraiture and Double Bond Conversion of a Monomethacrylate-based Oral Prosthetic Resin Substituted with a Novel Tri(azine-acrylate) Cross-linker

AIM

To formulate, design, and chemically characterize a novel denture base resin (DBR) copolymer containing triazine-based antimicrobial comonomer and also to evaluate the double bond conversion (DC) in the copolymer with various concentrations of the comonomer by fourier transform infrared (FTIR) spectroscopy.

MATERIALS AND METHODS

The study groups comprise a control group G0 in which the specimens (n = 10) were polymerized without the triazine comonomer and trial groups G10 and G20 where the polymerized specimens (n = 10 each) contained 10 and 20% triazine comonomer, respectively. FTIR was employed to ascertain and evaluate copolymerization (CP) and DC. The obtained DC values were subjected to statistical analysis.

RESULTS

A new denture base copolymer containing antimicrobial triazine comonomer was formed with ascertained copolymerization and higher DC than the control group. Twenty percent triazine comonomer in the copolymer exhibited the maximum DC.

CONCLUSION

Incorporation of the antimicrobial comonomer copolymerized with DBR to form a novel denture base copolymer exhibiting high DC.

CLINICAL SIGNIFICANCE

The novel denture base copolymer may prevent the microbial adhesion on the denture surface thereby preventing denture-induced stomatitis in the edentulous patients. Nonetheless, this novel copolymer may enhance the other necessary properties of the DBR and would ameliorate the living quality of the senile geriatric population with good in vivo serviceability.

Tensile Bond Strength and Marginal Integrity of a Self-adhering and a Self-etch Adhesive Flowable Composite after Artificial Thermomechanical Aging

Aim

This study aims to compare the self-etch adhesive (SEA) and self-adhesive flowable composite (SAF) concerning tensile bond strength (TBS) and marginal integrity by microleakage (µ LK) test in deciduous molars after artificial thermomechanical aging.

Materials and methods

120 extracted primary molars were collected. Sixty teeth were mounted for testing TBS. Teeth were restored using SAF (n = 30) and SEA-conventional flowable (CF) composite (n = 30) and subjected to artificial thermal aging. Half the teeth (n = 15) from each material were subjected to mechanical loading (SEA-TBS-L and SAF-TBS-L). The specimens with no-load (NL) served as control (SEA-TBS-NL and SAF-TBS-NL). Class V cavity prepared and restored with SAF (n = 30) and SEA-CF (n = 30) to test µ LK after thermal aging. The subgroups were as same as the TBS based on with or without mechanical loading (SEA-µ LK-L, SEA-µ LK-NL, SAF-µ LK-L, SAF-µ LK-L; n = 15 each). µ LK was determined by employing the dye immersion technique.

Results

Concerning TBS, there is a significant difference between SEA and SAF with load or no load. Concerning µ LK, there is a significant difference between the materials under loading and no difference was found when not mechanically loaded. Also, concerning both TBS and µ LK, a significant difference was observed between the load and no-load subgroups within each material.

Conclusion

SAF exhibited higher TBS than the SEA. Mechanical loading not only adversely affected the TBS but also increased the µLK of the compared materials.

Clinical Significance

Restoring the primary teeth with SAF not only shortens the laborious operatory time but also yields good clinical serviceability with the good bond strength and minimal µ LK, thus preventing premature loss of teeth and consequential malocclusion.

How to cite this article

Kamatchi M, Ajay R, Gawthaman M, et al. Tensile Bond Strength and Marginal Integrity of a Self-adhering and a Self-etch Adhesive Flowable Composite after Artificial Thermomechanical Aging. Int J Clin Pediatr Dent 2022;15(2):204-209.

Effect of Triazine Comonomer Substitution on the Structure and Glass Transition Temperature of Monomethacrylate-based Resin Polymer: An In Vitro Study

AIM AND OBJECTIVES

The present research aimed to characterize and deduce the structure of a novel denture base copolymer containing antimicrobial triazine comonomer by nuclear magnetic resonance (NMR) and energy-dispersive X-ray (EDX) spectroscopies. Also, it aimed to evaluate the glass transition temperature (Tg) with the addition of TATA at different concentrations.

MATERIALS AND METHODS

The trial groups G10 and G20 were thermo-polymerized with triazine comonomer, whereas the control group G0 was polymerized without the triazine. NMR and EDX spectroscopies assessed copolymerization along with deducing elemental composition in 
mass %. The surface topographies were observed through field-emission scanning electron microscopy (FESEM). The Tg of the resultant copolymer was examined by differential scanning calorimetry. Pertinent statistical tests with relevant multiple comparison tests were exercised to compare the mean Tg of the groups.

RESULTS

The configuration of a new copolymer containing triazine comonomer was manifested with additional protons and carbon atoms. Nitrogen was detected in the EDX spectroscopy of the trial groups. The Tg of the new copolymer was higher than the G0. The triazine comonomer in the copolymer at 20% concentration exhibited the highest Tg.

CONCLUSION

The triazine comonomer substitution produced a novel denture base copolymer with enhanced Tg.

CLINICAL SIGNIFICANCE

The novel denture base copolymer may possess enhanced biomechanical properties due to the TATA's cross-linking capability. Nevertheless, the antimicrobial property of the triazine comonomer incorporated in the denture base composition might be beneficial in inhibiting the microbial colonization on the denture's surface.

Histocompatibility of Thermopolymerized Denture Base Copolymer Processed with a Novel Ring-opening Oxaspiro Comonomer: A Histomorphometric Investigation in Rats

AIM AND OBJECTIVE

The aim of the research was to evaluate the histocompatibility of thermopolymerized (TP) novel denture copolymer containing 3,9-dimethylene-1,5,7,11-tetraoxaspiro[5,5]undecane (DMTOSU) comonomer in rats' palatine tissue.

MATERIALS AND METHODS

The rats were randomly categorized into four groups (n = 6 per group). G_CW: Denture base appliance (DBA) fabricated by short polymerization cycle in a water bath without DMTOSU; G_TW: DBA with 20 wt.% DMTOSU polymerized at 70°C for 2 hours followed by short polymerization cycle in a water bath; G_TA: DBA with 20 wt.% DMTOSU polymerized at 60°C for 45 minutes followed by 130°C for 20 minutes in an autoclave; and Group NC (negative control): rats with no DBA. The rats were euthanized after 2 weeks and the palatal tissues were subjected to histological examination. Epithelial thickness (ET), connective tissue thickness (CT), and keratin layer thickness (KT) were measured.

RESULTS

G_CW exhibited greater ET, CT, and KT than the other groups. The ET and KT of G_TA were significantly lesser than G_TW. Multiple comparisons exhibited significant differences between the groups, except for G_TW and G_TA concerning the CT.

CONCLUSION

The novel denture copolymer containing 20 wt.% of DMTOSU comonomer is histocompatible with rats' palatine tissue.

CLINICAL SIGNIFICANCE

As DMTOSU is a double-ring-opening antishrinking oxaspiro monomer, its incorporation in TP-DBR would result in dimensionally accurate and stable dentures without endangering the biocompatibility in the prospective years.

Histocompatibility of Dental Restorative Composite Resin Photopolymerized with a Novel Multifunctional Comonomer: A Histopathological Analysis in Rats

BACKGROUND

Restorative dentistry is impossible without composite resins. Toxicity of these resins is common though possessing favorable properties. Modifications of the resin matrix are being executed to improve the properties of the material. Dipentaerythritol penta-/hexa-acrylate (DPEPHA) monomer has been recently identified as a cross-linking comonomer with the conventional resin matrix.

PURPOSE

This study aimed to investigate the histocompatibility of DPEPHA comonomer in photopolymerized resin at 20 and 40 wt.% concentrations in rats.

MATERIALS AND METHODS

Eighteen male Wister rats were subjected to subcutaneous implantation of conventional resin specimens without DPEPHA (G0) and with DPEPHA at 20 wt.% (G20) and 40 wt.% (G40) concentrations. Then, the rats were subdivided according to the time of resection of the implantation sites at 1, 2, and 4 weeks (n = 6 rats). Tissue specimens were submitted to histopathological analysis.

RESULTS

Except for 4 weeks' time interval, there were significant differences (P < 0.05) in the inflammation among the groups at each time interval. The order of inflammation was NC <G40 ≤G20 <G0. Concerning the fibrous capsule thickness, significant difference existed among the groups at each time interval and within the groups at all 3 time intervals (P < 0.05).

CONCLUSION

Composite resin specimens with DPEPHA comonomer exhibited good histocompatibility in rats at 40 wt.% concentration.

Effect of Novel Cycloaliphatic Comonomer Incorporation on the Color Stability of Thermo-polymerized Denture Base Resin

BACKGROUND

Denture during its in vivo service encounters myriad food pigments and numerous physico-mechanical dynamic changes. Denture discoloration is one of the unresolved problems that should be unraveled to satisfy the esthetic demands of the patients.

AIM

This study aims to evaluate the color stability of a novel denture base copolymer with 10% and 20% (vol/vol) concentration of cycloaliphatic comonomer.

MATERIALS AND METHODS

Control group (G0) comprises specimens made without cycloaliphatic comonomer. The specimens of trial groups G10 and G20 were fabricated with 10% and 20% cycloaliphatic comonomer, respectively. For each group, thirty specimens (n = 30) were made. The specimens (n = 10) were immersed in three food colorant solutions (erythrosine, tartrazine, sunset yellow) for 56 days after artificial thermal aging. Ultraviolet-visible spectrophotometer was employed to measure the tristimulus values and calculate the color change (ΔE) of the specimens prior to and following rapid thermal aging or immersion of the specimens in the food colorants.

RESULTS

G0 showed the highest ΔE and G20 exhibited the least with each colorant. G10 had an intermediate imperceptible ΔE with each colorant. Also, significant differences (P = .000) existed between the food colorants within each group. The highest ΔE value was observed with sunset yellow and the lowest ΔE with tartrazine with each group.

CONCLUSION

The addition of cycloaliphatic comonomer in denture base acrylic resins improved the color stability. The new copolymer with 20 Vol.% comonomer exhibited the highest color stability with all the food colorants.

Bond Strength of Acrylic Denture Tooth to a Novel Thermo-Polymerized Denture Base Copolymer Containing Cycloaliphatic Comonomer after Mechanical and Thermal Aging

BACKGROUND

There are numerous artificial denture tooth materials available of which acrylic resin teeth were used widely. The resin teeth bond chemically to the denture base resin, and this bonding is affected by numerous intrinsic and extrinsic factors. The type of cross-linker in the denture base monomer is one such factor which has a questionable influence on the bond strength. Recently, cycloaliphatic comonomer was added in the methyl methacrylate monomer and the resultant novel copolymer possessed good physico-mechanical and biological properties.

PURPOSE

The purpose of this study was to evaluate the shear bond strength (SBS) between acrylic denture tooth and resultant novel copolymer after cyclic loading and thermal aging.

MATERIALS AND METHODS

Sixty central incisor denture teeth were bonded to three types of acrylic denture base resin groups (n = 20 per group) categorized based on the presence of the cycloaliphatic comonomer - Control group (G0): denture bases without cycloaliphatic comonomer and trial groups G10 and G20 contain 10 vol.% and 20 vol.% comonomer, respectively, substituted in the denture base monomer component. The specimens were processed and subjected to cyclic loading and thermal aging which was then followed by SBS testing.

RESULTS

G20 possessed the highest SBS followed by G10. G0 had the least SBS. All the specimens of the control and trial groups exhibited adhesive-cohesive mixed failure at the resin tooth-base resin interface.

CONCLUSION

The addition of cycloaliphatic comonomer increased the SBS between the resultant novel copolymer and the resin teeth after cyclic loading and thermal aging.

A Comparative Evaluation of Lateral Condylar Guidance by Clinical and Radiographic Methods - Hanau's Formula Revisited

Background

Various clinical methods for recording the condylar guidance (CG) are the intraoral check bite method, graphic tracings, and functional recordings. Accuracy of graphic tracings is affected by patient-related factors such as neuromuscular control of the individual, stability of record bases as well as stability of recording media. The current recommended average settings using Hanau's formula questionable, and thus reassessment is needed.

Purpose

The purpose of this study is to use radiographic technique to determine the lateral CG and compare these values with those obtained using Hanau's formula and to evaluate whether there are differences between the right and left paths of the condyles.

Materials and Methods

Twenty completely edentulous patients were selected. Articulator was modified with sectioned protractor for obtaining per degree interval calibration. With the protrusive records, the horizontal CG (H) was adjusted and the Bennett's angle (LCG-C) was calculated using the formula. With the tracing device in the mouth, sub-mento vertex projection radiographs were obtained. Each radiograph was traced and superimposed for Bennett angle determination (LCG-M).

Results

The median (interquartile range [IQR]) of right and left LCG-C were 15.45 (0.8) and 15.50 (0.7), respectively. The median (IQR) of right and left LCG-M were 37.00 (6.0) and 36.50 (6.8), respectively. A statistically significant difference exists between LCG-C and LCG-M. Both LCG-C and-M values exhibited no variations on both sides.

Conclusions

Radiographic technique yielded an amplified LCG when compared to the value obtained by Hanau's formula.

Synthesis and Characterization of a Ring-Opening Oxaspiro Comonomer by a Novel Catalytic Method for Denture Base Resins

Background:

3,9-Dimethylene-1,5,7,11-tetraoxaspiro[5,5]undecane (DMTOSU) is a double ring-opening monomer that exhibits expansion upon polymerization and may be used as a denture base resin's comonomer to offset or minimize polymerization shrinkage. It's synthesis by transesterification reaction (TE) catalyzed by distannoxane is not reported in the literature. The synthesis became the prime concern because this monomer is hardly available commercially.

Purpose:

The purpose is to confirm the DMTOSU synthesis and compare the synthesized monomers obtained by two different catalytic processes through Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies.

Materials and Methods:

Scheme I synthesis was by TE catalyzed by dichlorotetrabutyl distannoxane (DCBS) yielding M1 monomer. Scheme II synthesis was catalyzed by dibutyltin oxide-carbon disulfide (DBTO-CS₂) yielding M2 monomer.

Results:

The appearance of a characteristic peak at 1212 cm⁻¹ in FTIR spectrum, a doublet at δ 4.95 in ¹H-NMR spectrum and a peak at δ 117.12 in ¹³C-NMR spectrum confirmed the synthesis of DMTOSU-M1catalyzed by DCBS, which is not significantly different from DMTOSU-M2 catalyzed by DBTO-CS₂.

Conclusion:

The catalytic action of DCBS is a successful alternative to the DBTO-CS₂ catalysis in DMTOSU synthesis.

Copolymerization of Ring-Opening Oxaspiro Comonomer with Denture Base Acrylic Resin by Free-Radical/Cationic Hybrid Polymerization

BACKGROUND

Polymerization shrinkage is an innate characteristic of thermo-polymerized denture base acrylic resin. Volumetric shrinkage is still a problem, although myriad material modifications. Ring-opening oxaspiro monomers have promising volumetric expansions of about 7%. These monomers have diminished the shrinkage in dental filling resins through copolymerization (CP). However, their CP with denture base resins is not reported yet.

PURPOSE

The aim is to confirm the CP of an oxaspiro monomer with methyl methacrylate (MMA) by radical-cationic hybrid polymerization and to assess the degree of conversion (DC) of the formed copolymer.

MATERIALS AND METHODS

The oxaspiro monomer was synthesized by a transesterification reaction. The study groups were based on the composition and thermo-polymerization method. The control and E1 groups were thermo-polymerized in water-bath, whereas the E2 group in a laboratory autoclave. Both E1 and E2 groups contained the oxaspiro monomer and cationic initiator. E2 group had an additional radical initiator. The CP and DC were confirmed and assessed by infrared spectroscopy.

RESULTS

Accentuation of carbonyl peak, the disappearance of the spiro-carbon peak, and the appearance of ether linkages in experimental groups confirmed the ring-opening. E2 group had the highest DC.

CONCLUSION

The oxaspiro monomer successfully copolymerized with MMA and had good DC.

Chemical Characterization and Physical Properties of Dental Restorative Composite Resin with a Novel Multifunctional Cross-linking Comonomer

AIM AND OBJECTIVE

To chemically characterize restorative composite resin polymerized with 20 wt.% and 40 wt.% dipentaerythritol penta-/hexaacrylate (DPEPHA) comonomer. Furthermore, this study aimed to evaluate the conversion degree (DC) and glass transition temperature (T_g) of the newly formed copolymer.

MATERIALS AND METHODS

The trial groups were photo-polymerized with DPEPHA comonomer, whereas the control group was photo-polymerized only with the propriety resin monomers. Infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies were used for establishing copolymerization. The characteristics and composition (mass %) of the surface were explained by field-emission scanning electron microscopy (FESEM) and energy-dispersive X-ray (EDX) spectroscopy, respectively. The DC and T_g of the resultant copolymers were evaluated through FTIR and differential scanning calorimetry, respectively. Appropriate statistical tests with corresponding post hoc tests were employed to compare the medians and means of DC and T_g, respectively.

RESULTS

The formation of a new copolymer P(GEU-Co-DPEPHA) was evident. The DC and T_g of the P(GEU-Co-DPEPHA) copolymer were greater than the control. DPEPHA in the copolymer at 40 wt.% concentration showed the highest DC and T_g.

CONCLUSION

DPEPHA comonomer addition leads to the formation of a new P(GEU-Co-DPEPHA) copolymer with improved DC and T_g.

CLINICAL SIGNIFICANCE

The novel P(GEU-Co-DPEPHA) copolymer may improve the physico-mechanical and biological properties of the restorative composite resin. This would improve the quality of restoration and its in vivo serviceability, thereby imparting a good living quality to the entailed population.

Histocompatibility of Novel Cycloaliphatic Comonomer in Heat-cured Denture Base Acrylic Resin: Histomorphometric Analysis in Rats

Background:

Prosthodontics is impossible without denture base resins. Allergic reactions to these resins are not uncommon, albeit favorable properties. Monomeric modifications are being done to improve the properties of the material. Tricyclodecane dimethanol diacrylate (TCDDMDA) monomer has been recently identified and experimented as a comonomer with methyl methacrylate (MMA).

Aim:

This study aimed to investigate the histocompatibility of TCDDMDA comonomer in polymerized resin at 10% and 20% (vol/vol) concentrations in rats by histomorphometric analysis.

Materials and Methods:

Twenty-four male Wistar rats were randomly divided into the following four groups: NP group (control; n = 6), with no palatal appliance, Groups P0, P10, and P20 were fixed with palatal appliances fabricated of 100% MMA, 10% TCDDMDA + 90% MMA, and 20% TCDDMDA + 80% MMA, respectively. Weights of the animals were recorded just before the appliance placement and after 14 days. The animals were sacrificed, and the palatal tissues were processed for histopathological analysis. Histomorphometric parameters assessed were total epithelial (ET), connective tissue (CT), and keratin layer (KT) thicknesses.

Results:

No significant difference was observed regarding body weight. Group P0 showed increased ET, CT, and KT when compared to other groups. Bonferroni multiple comparison tests showed a statistically significant difference between all the groups except between P10 and P20 for all the three morphometric parameters.

Conclusion:

Palatal appliances with TCDDMDA comonomer showed good histocompatibility in rats up to 20% (vol/vol) concentration.

Effect of Novel Cycloaliphatic Comonomer on Surface Roughness and Surface Hardness of Heat-cure Denture Base Resin

Background:

Polymethyl methacrylate (PMMA) is a widely used resin in the field of prosthodontics for fabricating myriad orofacial prostheses. Albeit several advantages, it possesses certain lacunae concerning physicomechanical properties.

Purpose:

This in vitro research aimed to evaluate the surface roughness (SR) and hardness (SH) of heat-cured PMMA processed with a cycloaliphatic monomer, tricyclodecane dimethanol diacrylate (TCDDMDA), in methyl methacrylate at various concentrations.

Materials and Methods:

Groups have been divided into control (SRC and SHC) and experimental groups (SR10 and 20; SH10 and 20). Forty-five PMMA disc specimens were prepared. SR was assessed using a nanomechanical testing machine and the arithmetic roughness (Ra) was recorded. The same specimens were then subjected to Vicker’s microhardness testing and Vicker’s hardness number (VHN) was obtained. Data were compared using one-way analysis of variance (ANOVA) and post hoc Bonferroni tests (α=0.05).

Results:

The mean (standard deviation [SD]) of SRC, SR10, and 20 groups were 111.415 nm (0.789), 62.666 nm (0.482), and 41.004 nm (0.561), respectively. The mean (SD) VHN of SHC, SH10, and 20 groups were 21.003 (0.252), 23.975 (0.207), and 34.622 (0.079), respectively.

Conclusion:

The addition of TCDDMDA markedly decreased the SR and increased the SH of the experimental groups.

Comparative Evaluation of pH and In Vitro Cytotoxicity of Zinc Oxide-Ozonated Eugenol and Conventional Zinc Oxide Eugenol as Endodontic Sealers

Background:

Eugenol released from zinc oxide eugenol (ZOE)–based sealants may cause irritation to the periapical tissues and has cytotoxic potential. Ozone therapy has numerous clinical applications with humans because of its bactericidal action, detoxifying effect, stimulation of angiogenesis, and wound-healing capacity. Therefore ozone can be incorporated in ZOE sealer to exploit these properties.

Materials and Methods:

Eugenol was ozonated using ozonator machine and the samples were divided into two groups: Group I: zinc oxide eugenol (n = 10) and Group II: zinc oxide–ozonated eugenol (OZOE; n = 10). The pH of the fresh sealer samples and the set samples was measured using calibrated pH meter after predetermined time intervals. Cytotoxicity of the set sealer was evaluated on mouse L929 fibroblasts using cellular metabolic assay.

Results:

pH of the samples in Group II was higher when compared to Group I. Group II showed higher cell viability than the Group I.

Conclusion:

OZOE sealers can be used as an alternative to the conventional ZOE sealers.

Chemical Structure and Physical Properties of Heat-cured Poly(methyl methacrylate) Resin Processed with Cycloaliphatic Comonomer: An In Vitro Study

AIM

The purpose of this in vitro research is to chemically characterize polymethyl methacrylate (PMMA) processed with 10% and 20% (v/v) tricyclodecane dimethanol diacrylate (TCDDMDA) comonomer. It also aimed to assess the degree of conversion (DC) and glass transition temperature (T_g) of the formed copolymers.

MATERIALS AND METHODS

The experimental groups were processed with the TCDDMDA comonomer (10% and 20% v/v), whereas the control group was processed only with the methyl methacrylate monomer. The copolymerization was studied by nuclear magnetic resonance (NMR) spectroscopy. The surface characteristics and composition (wt%) were studied by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopy (cuboidal specimen; 5 mm × 5 mm × 3 mm), respectively. The DC and T_g of the formed copolymers (powdered form) were analyzed by Fourier transform infrared spectroscopy and differential scanning calorimetry, respectively. One-way analysis of variance with post hoc Bonferroni test was used to compare the mean values of DC% and T_g among the groups.

RESULTS

The newly formed copolymer [P(MMA-co-TCDDMDA)] was chemically characterized by NMR and FESEM-EDX. The DC and T_g of the experimental groups were higher than the control. Tricyclodecane dimethanol diacrylate at 20% (v/v) concentration showed the highest DC and T_g.

CONCLUSION

The addition of TCDDMDA comonomer improved the DC and T_g of the formed copolymer.

CLINICAL SIGNIFICANCE

The P(MMA-co-TCDDMDA) copolymer is expected to improve the mechanical properties and biocompatibility of the denture base acrylic resin. This would result in improved denture quality and durability, thereby, imparting a better quality of life to the geriatric population.

Effect of Implant Abutment Acid Etching on the Retention of Crowns Luted with Different Cements: An In Vitro Comparative Evaluation

Background:

Air abrasion of the implant abutment surface improves the bond strength of luting agents. However, the effect of acid etching and combination of air abrasion and acid etching on the bond strength of various luting agents under masticatory load is yet to be documented.

Purpose:

The purpose of this study was to evaluate the effect of implant abutment surface modifications on the tensile bond strength (TBS) of cast metal copings (CMCs) luted with different luting agents, subjected to cyclic fatigue loads.

Materials and Methods:

A total of 150 Ni-Cr CMCs were made on commercially pure titanium (Cp-Ti) laboratory analogues. The samples were categorized into three groups based on surface modifications and five subgroups for luting agents. The CMCs were cemented to the respective surface-modified groups, stored in distilled water at 37°C for 24 hours, and then subjected to load cycling, followed by tensile loading. One-way analysis of variance (ANOVA) was used to compare the mean bond strength between luting agents.

Results:

Self-adhesive resin cement showed the highest TBS followed by resin-modified glass ionomer cement, zinc polycarboxylate, and zinc phosphate cement. Non-eugenol temporary cement showed least TBS values on all modified abutment surfaces.

Conclusion:

Air abrasion + acid etching (HY) provided the greatest TBS followed by acid-etched (AE) surface only. Air-abraded (AA) surface yielded the least TBS for luting agents.

Correlation of vertical dimension of occlusion in parents and their offspring: A cephalometric study

Background:

Establishment of optimal vertical dimension of occlusion (VDO) for prosthetic patients, either complete denture or fixed full mouth rehabilitation, is a vital step to discern at a pleasing esthetics and harmonious function. None of the experiments in the literature studied the hopeful inheritance of the VDO from a parent to offspring.

Purpose:

The aim of this study was to establish the dominant mode of inheritance of VDO from parents to offspring using cephalometric landmarks.

Materials and Methods:

Following the inclusion criteria, 20 families were selected and explained about the study design. Individual cephalograph of father, mother, and offspring were traced out of bony landmarks. The reference planes were delineated for the measurements from maxillary incisal (I) tip and mesio-palatal cusp tip of maxillary first molar (M) to palatal (PP) and inter-foramina (IFP) planes.

Results:

In all the distances measured, there exists a statistically significant difference between both father and son and mother and son. For the measured IPP, MPP, and IIFP distances, there is no statistically significant difference existed between father and daughter. However, in MIFP distance, there is a significant difference between father and daughter. Except for the IIFP distance between mother and daughter (P = 0.08), in all other measured distances, there existed a statistically significant difference.

Conclusion:

There is no dominant mode of inheritance from the parent to the son with respect to the measured parameters. Inheritance was observed to be stronger between father and daughter than between mother and daughter.

Impact Strength and Dimensional Accuracy of Heat-Cure Denture Base Resin Reinforced With ZrO2 Nanoparticles: An In Vitro Study

Background:

Polymerization shrinkage and fracture are the two common trouble shoots with denture base resins. Polymerization shrinkage affects the dimensional accuracy and fit of the prosthesis. The effect of zirconia (ZrO₂) nanoparticles on polymerization shrinkage is not documented yet.

Purpose:

The aim and objective of this study were to evaluate the impact strength and dimensional accuracy of heat-cured poly methyl methacrylate (PMMA) on reinforcement with ZrO₂ nanoparticles.

Materials and Methods:

Conventional heat-cure denture base resin (control) and the polymer reinforced with 3, 5, and 7 wt% of ZrO₂ nanoparticles were prepared and used in this study. Forty bar-shaped specimens were prepared and tested for impact strength using Charpy’s type impact tester. Forty denture bases were fabricated and checked for dimensional accuracy by measuring the distance between the denture base and the cast in two different sections using the travelling microscope.

Results:

The impact strength decreased with increased concentration of ZrO₂ and found to be least at 7 wt% concentration (2.01 ± 0.26 J/mm²). The distance between the denture base and the cast significantly decreased both in the posterior palatal seal region (0.060 ± 0.007 cm) and mid-palatine section region (0.057 ± 0.006 cm) with ZrO₂ nanoparticles reinforcement and was found to be least at 7 wt% concentration.

Conclusion:

Reinforcement of heat-cured PMMA with ZrO₂ nanoparticles significantly increased the dimensional accuracy and decreased the impact strength.

Monomer Modifications of Denture Base Acrylic Resin: A Systematic Review and Meta-analysis

Background:

Methyl methacrylate monomer of denture base resins was modified with several monomers to achieve better physico-mechanical properties without compromising the biocompatibility. However, there are no consensuses on the best strategy to achieve best modified monomer.

Purpose:

To identify and evaluate the differences in the properties between conventional and modified monomers and to verify the influence of several variables on the properties of denture base acrylic resin.

Materials and Methods:

This study was executed by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. In-vitro studies that investigated the properties of conventional and modified monomers were selected. Searches were carried out in the Ebscohost, PubMed, Semantic scholar and J-stage databases. The search commenced from the year 1995 and the last search was done till November 2018. A comparison was performed between modified and unmodified monomers. The analyses were carried out using fixed-effect models.

Results:

The meta-analysis results showed high heterogeneity in all aspects, and higher flexural strength for monomers modified with 20% methacrylic acid.

Conclusion:

Although the articles included in this meta-analysis showed high heterogeneity and high risk of bias, the in-vitro literature seems to suggest that use of modified monomers could improve the properties of denture base resins. Other variants of monomer modifications and their tested parameters were discussed in this systematic review as well. Dimensional accuracy is an unexplored variable to be evaluated extensively in the future researches.

Effect of Surface Modifications on the Retention of Cement-retained Implant Crowns under Fatigue Loads: An In vitro Study

Background:

Masticatory forces cause fatigue to the dental luting agents, adversely affecting the retention of these cement-retained crowns. Sandblasting (SB) and diamond abrading the abutment surface improves the bond strength of luting agents. However, the effect of acid etching (AE) on the implant abutment surface and the effect of other surface modifications under masticatory load are yet to be documented.

Purpose:

The aim of the study was to evaluate the effect of abutment surface modifications on the retention of cement-retained restorations subjected to cyclic fatigue loads.

Materials and Methods:

Forty Ni-Cr copings were made on Cp-titanium laboratory analogs. The specimens were divided into two groups as Group I: Uniaxial tensile loading (UTL) and Group II: Offaxial cyclic loading followed by uniaxial tensile loading [CTL]. Further subgrouped as, subgroup I: Control (C), subgroup II: SB, subgroup III: AE, and subgroup IV: SB + AE. The copings were luted with Zn₂(PO₄)₃ and subjected to uniaxial tensile loading. Copings were recemented, and CTL was conducted. Two-way analysis of variance was used as the statistical test of significance.

Results:

In relation to the subgroups, the bond strength of Zn₂(PO₄)₃ was higher in Group I than in Group II. The bond strength in subgroup IV was superior in both Group I and Group II (547.170 N ± 5.752 and 531.975 N ± 6.221 respectively).

Conclusions:

For both UTL and CTL, abutment SB + AE elicited maximum coping retention followed by AE. Off-axial cyclic loading adversely affected the retention irrespective of the surface modifications.

Color Stability Assessment of Two Different Composite Resins with Variable Immersion Time Using Various Beverages: An In vitro Study

Purpose of the Study:

The aim of the study was to evaluate the difference in the color of microhybrid (MH) and nanofilled (NF) composite resins after 24 and 48 h in beverages such as red wine (RW), Coca-Cola, and distilled water. The specific objective of this study was to investigate the cumulative effect of the colorant solutions on the dental composites.

Materials and Methods:

MH and NF composite resins (A2 shade) were used in this current study. Sixty disk-shaped material specimens (10 mm in diameter × 2 mm in thickness) were prepared using a fiber mold (ring), with the desired dimensions. The specimen surfaces were polished using super-snap polishing system. Sixty specimens were divided into two groups of 30 each (Group I: MH resin composite; Group II: NF resin composite). Both the groups divided into six subgroups (Subgroup I: RW for 24 h [RW-24]; Subgroup II: RW for 48 h; Subgroup III: Coca-Cola for 24 h [CC-24]; Subgroup IV: Coca-Cola for 48 h [CC-48]; Subgroup V: Distilled water for 24 h [DW-24]; Subgroup VI: Distilled water for 48 h [DW-48]). All the samples were immersed in respective drinks for a period of 24 h, and color differences were measured using ultraviolet spectrophotometer. Once again, all the samples were immersed for another 24 h in the same drinks. After 48 h, the color change of the samples was measured. Measurements were made according to the CIE L × a × b × color space relative to the CIE standard illuminant D65. The color changes of the specimens were evaluated using the following formula: Statistical analysis was performed. The data were analyzed using the one-way ANOVA and t-test at a significance level of 0.05.

Conclusion:

Color stability of MH composite resin was found to be inferior than the NF resin composite irrespective of immersion medium and time. In RW, the color change observed was maximum for both composite resins followed by Coca-Cola. Immersing the resin composites in distilled water for 24 and 48 h had negligible color change. A 48-h immersion of both composite resins in all three immersion mediums showed greater color change than 24 h immersion.

A comparative evaluation of microleakage of restorations using silorane-based dental composite and methacrylate-based dental composites in Class II cavities: An in vitro study

Aim:

The aim of this in vitro study was to evaluate and compare the microleakage of restorations using low shrinkage silorane-based dental composite and methacrylate-based dental composites in Class II cavity at the occlusal and gingival margins.

Materials and Methods:

Sixty mandibular molars were collected and divided into three experimental groups and one negative control group. Class II slot cavity was prepared on the mesial surface. Experimental groups were restored with Group I: silorane-based microhybrid composite, Group II: methacrylate-based nanohybrid composite, and Group III: Methacrylate-based microhybrid composite, respectively. Group IV: negative control. The samples were thermocycled, root apices were sealed with sticky wax and coated with nail varnish except 1 mm around the restoration. This was followed by immersion in 2% Rhodamine-B dye solution under vacuum at room temperature for 24 h. Then, the samples were sectioned longitudinally in the mesiodistal direction and evaluated under stereomicroscope ×40 magnification. Scoring was done according to the depth of dye penetration in to the cavity. Statistical analysis of the data was done.

Results:

The results were that no statistically significant difference in the microleakage at the occlusal margin for all the restorative materials, whereas at the gingival margin, silorane-based microhybrid composite showed less microleakage than the methacrylate-based nano- and micro-hybrid composites.

Conclusion:

In general, silorane-based microhybrid composite had less microleakage among the other materials used in this in vitro study.

A simple method of enhancing retention in interim hollow bulb obturator in a case of an acquired palatal defect

Maxillary defects occur either as a result of surgical resection of malignant tumors of the nasal cavity and paranasal sinuses or of the congenital causes. Rehabilitation of the patients with maxillectomy defects presents a challenge in restoring the lost form, function and speech. Maxillary interim obturators in prosthetic reconstruction of the defects are often complicated with lack of adequate retention, stability, and support. This case report presents the simplified approach, to rehabilitate a case of sub-total maxillectomy due to squamous cell carcinoma of maxillary sinus, using a closed hollow bulb obturator prosthesis fabricated with a "U" loop and a modified buccal flange for enhanced retention of the prosthesis.

Exudative pleural effusions in patients over forty years of age--an analysis of seventy-six patients

A prospective study of 76 consecutive patients over the age of 40 years, with exudative pleural effusion, was undertaken to determine the common causes of such a clinical condition. Malignant pleural effusions were the most common in this series, found in 49 patients (64.47%), all but one being metastatic from elsewhere. Forty were secondary to a carcinoma of the bronchus, 3 from carcinoma of the breast, 1 each from carcinoma of the ovary, oesophagus, and larynx; lymphoma accounted for the remaining 2. Infective causes accounted for 24 of the effusions (31.57%). Of the infections, tuberculosis was the most common, accounting for 17 of the 24. Other infective causes included bacterial empyemas in 4, ruptured amoebic liver abscess in 2, and actinomycosis in 1. Pancreatitis, pulmonary thromboembolism, and a post-cardiotomy syndrome were diagnosed in 1 patient each, while the diagnosis remained unknown in the remaining 5 patients. In 2 patients the diagnosis was made on autopsy.

Percutaneous visceral pleural biopsy with fenestrated cup biopsy forceps

When there is an exudative pleural effusion often both the parietal and the visceral pleura are affected, but the usual practice is to perform a percutaneous parietal pleural biopsy alone for diagnosis. Percutaneous visceral pleural biopsy was carried out in 20 patients with exudative pleural effusions with fenestrated cup biopsy forceps. In all 20 biopsies pleural tissue was obtained and it was diagnostic in 19 cases. The procedure is painless and appears safe.