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

Prolonged post-washing in ethanol decreases bond strength of additively manufactured crown materials

OBJECTIVES

This study aimed to investigate the effect of post-washing duration and crown thickness on the bond strength between additively manufactured crown materials and dental cement in vitro.

METHODS

Rectangular-shaped specimens of two thicknesses (1.5 and 2.0 mm) were additively manufactured from permanent VarseoSmile Crown (VC) and long-term temporary NextDent (ND) materials. The specimens were post-washed (n = 160) in ethanol for 5 min, 10 min, 1 h, and 8 h then cemented with dual-cure resin cement. Twenty PMMA (TC) were milled as a control. A chevron-notch test was performed to measure the maximum load until failure (N). Interfacial bond strength (J/m2) was calculated and statistically analysed. The mode of failure was analysed by scanning electron microscopy (SEM).

RESULTS

There was a significant difference in the bond strength between all groups (p < 0.01). VC at 1.5mm thickness post-washed for 10 min showed the highest mean bond strength (1.77 ±0.96 J/m2) while VC at 2.0mm thickness post-washed for 8 h showed the lowest (0.22 ±0.10 J/m2). Exposure to ethanol for 8 h resulted in lower bond strength. Within the type of material, there were no differences in bond strength between the thicknesses when post-washed for the same duration.

CONCLUSIONS

Prolonged post-washing of AM crown materials can significantly decrease the bond strength to resin cement. There were no differences between the permanent and long-term temporary AM materials. When post-washed for 5 min, AM materials observed comparable or higher bond strength values compared to PMMA.

CLINICAL SIGNIFICANCE

The output of this research serves as a guide for dental practitioners, emphasising the importance of adhering to correct post-washing procedures for optimal bond strength of additively manufactured crown materials.

Evaluation of the effect of surface roughness and modification of implant abutment axial wall on the retention of zirconium oxide copings before and after thermocycling

Background

The purpose of this study was to determine the effect of one-wall elimination of the abutment and also the surface treatment of the abutment on the retention of cement-retained, implant-supported zirconium oxide copings.

Material and Methods

In this experimental study, four straight abutments were connected to four implant analogs (DIO, UF, Busan, Korea) with 35 Ncm torque. They are mounted vertically in resin blocks. Abutments were prepared as following groups: A) abutment was used in its intact standard form as a control group. B) 4 mm of the flat wall was removed to produce an abutment with 3 walls. C) The abutment surface was abraded with 50 µm AL2O3 powder. D) 4 mm of a flat wall of the abutment was removed, then the abutment surface was abraded with 50 µm AL2O3 airborne particle.10 zirconium oxide copings were made. Samples were cemented with temp bond NE to abutments. The retention of copings was measured before and after incubation using the universal testing machine. T-test, one-way ANOVA, and Post Hoc Tukey Test were used for statistical analysis of data.

Results

In all groups, retention was decreased after thermocycling (P ≤0.001). 3 wall abutments had less retention than the control group before thermocycling. A significant difference was detected between 3 wall abutments and 4 walls of sandblasted abutments before thermocycling. After thermocycling, no difference in retention was seen between groups.

Conclusions

Thermocycling significantly reduces the retention of implant-supported ceramic copings. Sandblasting abutments with 50 µm AL2O3 air-borne particles did not increase the retention of ziconium oxide copings which were cemented with temp bond NE. One wall elimination of abutment decreased the retention of zirconia copings. Key words:Retention, crown, abutment, zirconia coping, sandblasting.

Association of Age, Gender, and Site of Implant Placement: An Institution-Based Retrospective Study

Tooth loss is an undesirable condition that leads to functional, esthetic and social damage, having an impact on an individual's quality of life. Dental implants are man-made tooth root replacements that are increasingly used to replace a missing tooth. It is important to gather demographic data in order to take precautions before the possible failures. Hence the objective of this study was to retrospectively determine the association between age, gender, and site of implant placement in patients reporting to a private dental institution. This study was carried out from the data obtained from the case records of 1281 patients who had undergone implant therapy. Chi-square test was applied to see associations of gender, age and implant site. The results show that a maximum number of 348 implants (27.7%) were placed in patients aged between 41-50 years. The patient pool consisted of 705 (55%) females and 576 (45%) males. A maximum of 228 implants (17.80%) were placed in region 46 and 224 implants (17.49%) in region 36. Only 2 implants (0.2%) were placed in region 41. There was a positive association between age, gender and site of implant. In those aged 20-30 years, 20.53% of implants were placed, 26.23% in 31-40 years, 27.1% in 41-50 years, 17.95% in 51-60 years and 8.11% in 61-70 years of age. In male, a maximum of 124 implants (54.4%) were placed in region 46 and only 1 implant (50%) in region 41. In females, region 36 had a maximum of 110 implants (49.1%), and the least number of implants were placed in regions 31 and 41. In this study, it can be concluded that general factors such as age and gender had a significant effect on the site of implant placement.

Effect of hemispherical dimples at titanium implant abutments for the retention of cemented crowns

PURPOSE

The aim of this study was to assess the effect of hemispherical dimple structures on the retention of cobalt-chromium (Co-Cr) crowns cemented to titanium abutments, with different heights and numbers of dimples on the axial walls.

MATERIALS AND METHODS

3.0-mm and 6.0-mm abutments (N = 180) and Co-Cr crowns were prepared. The experimental groups were divided into two and four dimple groups. The crowns were cemented by TempBond and PANAVIA F 2.0 cements. The retention forces were measured after thermal treatments. A two-way Analysis of Variance (ANOVA) and post-hoc Tukey HSD test were conducted to analyze change in retention forces by use of dimples between groups, as well as t test for the effect of abutment height change (α = .05).

RESULTS

Results of the two-way ANOVA showed a statistically significant difference in retention force due to the use of dimples, regardless of the types of cements used (P < .001). A significantly higher mean retention forces were observed in the groups with dimples than in the control group, using the post hoc Tukey HSD test (P < .001). Results of t test displayed a statistically significant increase in the retention force with 6.0-mm abutments compared with 3.0-mm abutments (P < .001). The groups without dimples revealed adhesive failure of cements, while the groups with dimples showed mixed failure of cements.

CONCLUSION

Use of hemispherical dimples was effective for increasing retention forces of cemented crowns.

Biomechanical Testing of Two-Unit Bridges and a Comparison of Replacement Retention Depending on a Cementation Medium, Replacement Position, and Gap Size

Dental replacements are placed between the abutment teeth. The exceptions are two-unit bridges, as they are supported by a single tooth prepared only on one side of the missing tooth. The presented study deals with an analysis of a pressure force action on two-unit bridges placed in the frontal part (20 samples), where the pressure action is lower, and in the distal part (20 samples), where the pressure action is higher. A CAD program by 3Shape was used for digital designing with two different gap settings, 10 μm (20 samples) and 30 μm (20 samples). Two-unit bridges were attached to the prepared tooth using two types of dental cement (20/20 samples), which were selected for their physical and bioactive properties. All two-unit bridges (a total of 80 samples) were fabricated from CoCr alloys on Mlab cusing R by applying the Selective Laser Melting (SLM) technology. Mechanical testing was performed using the Inspekt5 table blue. The obtained data were used to verify the hypotheses-a difference between both types of cement (A ≠ B), a difference between the frontal and distal two-unit bridges (F ≠ D) and a difference between the gap sizes (10 ≠ 30). To confirm the given theories, data were statistically evaluated using the F-test and subsequent t-tests. The resulting p-value was compared with the level of significance (α = 0.05). A statistical evaluation revealed a significant difference between the compared groups; however, no explicit correlation between the individual groups of specimens was identified.

Dentists' Preference toward Fixed Versus Removable Implant Prosthesis on Edentulous Jaws to Improve Quality of Life

Implants that can be used in the prosthetic rehabilitation of full and partial edentulous patients are now frequently used due to advances in dentistry. The aim of the study is to find the prevalence of implant supported fixed vs. removable prosthesis and associated quality of life evaluation. A cross-sectional, descriptive study was conducted in an institution, on randomly selected individuals. The study group consisted of adult patients who attended the outpatient Department of Prosthodontics from June 2019-March 2020. Eighty-six thousand (86,000) case sheets were evaluated and Chi-square test, independent t-test and frequency analysis were used to explore the relationship between two variables. Out of the patients, 76.5% preferred fixed prosthesis while 23.5% chose removable prosthesis. Females preferred fixed prosthesis over removable. The young-old age group had more removable prosthesis compared to the middle- and elderly age group. Patients with implant supported fixed dental prosthesis had a better quality of life compared with patients with implant supported overdentures. Esthetic and functional rehabilitation is a preferred option females generally care more about their teeth and looks so wanted more fixed options. The young-old age group preferred removable prosthesis over fixed prosthesis. Patients with implant supported fixed dental prosthesis have a better quality of life compared with patients with implant supported overdentures.

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.

Osseointegration of Hafnium when Compared to Titanium - A Structured Review

Aim:

This systematic review was conducted to analyse osseointegration of hafnium over conventional titanium.

Materials and Methods:

Search methodology was comprehended using PICO analysis and a comprehensive search was initiated in PubMed Central, Medline, Cochrane, Ovid, Science Direct, Copernicus and Google Scholar databases to identify the related literature. Randomised control trials, clinical studies, case control studies and animal studies were searched for osseointegration of hafnium coated titanium implants versus conventional titanium implants. Timeline was set to include all the manuscripts published till December 2018 in this review.

Clinical Significance:

Hafnium is a very promising surface coating intervention that can augment osseointegration in titanium implants. If research could be widened, including in vivo studies on hafnium as a metal for coating over dental implants or as a dental implant material itself to enhance better osseointegration, it could explore possibilities of this metal in the rehabilitation of both intra and extra oral defects and in medically compromised patients with poor quality of bone.

Results:

Out of the 25 articles obtained from the PICO based keyword search, 5 studies were excluded based on title and abstract. Out of the remaining 20 studies, 16 were excluded based on the inclusion and exclusion criteria of our interest and finally, 4 were included on the basis of core data.

Conclusion:

This systematic review observed hafnium metal exhibited superior osseointegration than titanium. Owing to its biocompatibility, hafnium could be an alternative to titanium, in the near future.

Effectiveness of Antianxiety Drugs on Postoperative Pain Perception After Implant Placement: An In Vivo Study

Aim:

To evaluate the effectiveness of midazolam and zolpidem on postoperative pain perception in patients undergoing implant placement.

Materials and Methods:

In the present in vivo study 60 patients undergoing implant placement were selected based on the inclusion criteria framed and were randomly allocated using sequentially numbered, opaque, and sealed envelope (SNOSE) method into 3 groups with 20 patients each after obtaining informed consent. Group A was the control group, Group B received midazolam 7.5 mg 30 minutes before the procedure. Group C received zolpidem 5 mg 30 minutes before the procedure. The anxiety level of patients was recorded using the Corah scale and postoperative pain was recorded after 2 hours of implant placement using the VAS scale. Statistical analysis was done using analysis of variance (ANOVA), one-way multivariate analysis of variance (one-way MANOVA), and then Tukey’s Honestly Significant Difference (HSD) test for comparison among groups at the 0.05 level of significance.

Results:

Group A had a mean anxiety level of 16 ± 1.451, Group B had a mean anxiety level of 11.2 ± 2.858, and Group C had a mean anxiety level of 13 ± 2.9019 and a statistically significant difference between the groups was observed ( P < .05). The mean for the postoperative pain perception for Group A was 6.8 ± 1.1965, for Group B was 3.8 ± 1.3611, and Group C was 5 ± 1.451 and a statistically significant difference between the groups was observed ( P < .05).

Conclusion:

This study concluded that both midazolam and zolpidem significantly reduced anxiety levels and postoperative pain in patients undergoing implant placement.

Effect of different surface treatments on the shear bond strength of luting cements used with implant-supported prosthesis: An in vitro study

PURPOSE

The aim of this study was to investigate the shear bond strength of luting cements used with implant retained restorations on to titanium specimens after different surface treatments.

MATERIALS AND METHODS

One hundred twenty disc shaped specimens were used. They were divided into three groups considering the surface treatments (no treatment, sandblasting, and oxygen plasma treatment). Water contact angle of specimens were determined. The specimens were further divided into four subgroups (n=10) according to applied cement types: polycarboxylate cement (Adhesor Carbofine-AC), temporary zinc oxide free cement (Temporary Cement-ZOC), non eugenol provisional cement for implant retained prosthesis (Premier Implant Cement-PI), and non eugenol acrylic-urethane polymer based provisional cement for implant luting (Cem Implant Cement-CI). Shear bond strength values were evaluated. Two-way ANOVA test and Regression analysis were used to statistical analyze the results.

RESULTS

Overall shear bond strength values of luting cements defined in sandblasting groups were considerably higher than other surfaces (P<.05). The cements can be ranked as AC > CI > PI > ZOC according to shear bond strength values for all surface treatment groups (P<.05). Water contact angles of surface treatments (control, sandblasting, and plasma treatment group) were 76.17° ± 3.99, 110.45° ± 1.41, and 73.80° ± 4.79, respectively. Regression analysis revealed that correlation between the contact angle of different surfaces and shear bond strength was not strong (P>.05).

CONCLUSION

The retentive strength findings of all luting cements were higher in sandblasting and oxygen plasma groups than in control groups. Oxygen plasma treatment can improve the adhesion ability of titanium surfaces without any mechanical damage to titanium structure.

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.