Retention Of Crowns Research Articles

An In vitro Comparison of Retention of Provisional Crowns Cemented with Provisional Cement Enriched with Three Different Additives

Introduction: Dental caries remains a constant problem in clinical practice. The rates of recurrent caries around long-term provisional restorations may be even higher due to poor marginal adaptation and less stable materials. Since provisional crowns luted with provisional cement are susceptible to bacterial infiltration and caries, antibacterial and anticariogenic agents have been added to provisional cement, and retention of the provisional crown has been evaluated in this study. Materials and Methods: Ten extracted maxillary first premolar teeth were selected. Standardised tooth preparation was done. A total of 40 provisional crowns were fabricated using tooth-coloured auto-polymerising acrylic resin. The prepared provisional crowns were divided into four groups of 10 crowns each. Crowns were cemented on the prepared teeth after enriching with the three solutions individually. All specimens were stored in 100% humidity at 37°C for 1 h, thermocycler 100 times between 5°C and 55°C with a dwell time of 10 s and then stored at 100% humidity at 37°C. Cemented crowns were subjected to tensile dislodgement force using a universal testing machine with a crosshead speed of 5 mm/min. Results: Provisional cement enriched with Profluorid Varnish has shown properties of the highest tensile dislodgement force, with chlorhexidine-reduced retention. Conclusion: The present study concluded that Profluorid Varnish, as an additive in non-eugenol provisional cement (Provicol), is more effective in increasing retention.

Clinical evaluation and parental and child satisfaction with restoration of primary teeth using zirconia and stainless steel crowns: A randomised clinical study

Introduction: Full-coronal restoration is the choice of treatment for restoring pulpally treated tooth or tooth with multiple surface involvement. In paediatric dentistry, semi-permanent stainless steel crowns (SSCs) are considered gold standard, but with increasing need of aesthetics, zirconia crowns have started gaining importance. Hence, this study was conducted to evaluate the clinical performance of SSCs and zirconia crowns and to compare the child satisfaction and parental ratings of impact of treatment using these preformed crowns. Materials and Methodology: This study was a part of randomised controlled trial performed on 60 children of 4–8 years old. The primary molars were cemented with either SSCs or zirconia crowns and were evaluated clinically at baseline, 6-month and 12-month follow-up for crown retention, crown fracture, gingival and debris index, wear, marginal integrity and recurrent caries. The trials also evaluated parental satisfaction and child satisfaction based on five-point Likert scale at the end of 12-month follow-up. The data were analysed using Chi-square test for categorical data and independent sample t-test for quantitative data. Results: Both the crowns were 100% retentive at 12-month follow-up. Fair debris score and mild gingivitis were reported in 3% with SSC at 6–12 months. One zirconia crown fractured at 12 months. Fifty-four per cent of parents in zirconia and 57% in SSC stated that the crowns improved masticatory function. Children reported a mean Likert score of 3.0 for SSC and 4.89 for zirconia which was highly significant. Conclusion: Both the crowns increased the overall health of crowned tooth and were fully retentive for the studied duration. However, zirconia crowns were more gingival friendly and had an edge over SSC in terms of aesthetics.

The Effect of the Digital Manufacturing Technique, Preparation Taper, and Cement Type on the Retention of Aged Anterior Provisional Crowns: An In Vitro Study

A well-made provisional fixed prosthesis must present as a preview of the future prosthesis and may also augment the health of the abutments and periodontium. Provisional restorations have been prepared chairside with polymethyl methacrylate (PMMA) since time immemorial. CAD/CAM additive and subtractive technologies have revolutionized the fabrication of interim restorations in dental clinics. The current literature lacks substantial data about retention of provisional crowns manufactured using Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) additive and subtractive techniques with various temporary cements. This in vitro study aims to assess and compare the retention of temporary/provisional anterior crowns based on the combined effect of different digital manufacturing techniques, preparation tapers, and the temporary cements used for cementation. Two maxillary right central incisor typodont teeth were prepared to receive all-ceramic crowns, one with a 10-degree taper and the other with a 20-degree taper. Forty 3D-printed working models with the 10° taper and forty working models with the 20° taper were prepared to receive the temporary crowns. Forty temporary crowns were 3D-printed and forty crowns were milled (20 from each taper group). Kerr Temp-Bond NE conventional cement and Kerr Temp-Bond clear cement were used for cementation in the two groups. The number of samples per test group was 10. All samples were thermocycled and subjected to a universal testing machine to measure the pull-off force until retention loss (N) under tension with a crosshead speed of 5 mm/min. The pull-off force was highest for group 8, i.e., 3D-printed crowns with a 20° taper and cemented with Kerr Temp-Bond clear cement, followed by groups 6, 7, 4, 5, 3, and 2. Group 1, i.e., milled crowns with 10° taper cemented with Kerr Temp-Bond NE conventional cement, exhibited the lowest pull-off retentive force. The clinical selection of long-term provisional crowns fabricated using 3D-printing technology, prepared with 10° or 20° tapers, and cemented with clear cement, is the most favorable in terms of the retention of provisional crowns. 3D-printed provisional crowns can be used as an alternative to conventional and CAD/CAM-milled crowns for long-term provisionalization.

The effect of die spacer on retention and fitting of complete cast crowns

Purpose: The aim of this study was to determine the influence of multiple layers of die relief agent and different cement thickness on the retention of cast restorations using two different cements.
 Materials and Methods: 144 standard stainless steel dies were divided into two groups. Each of them includes 72 dies. These groups were divided into 12 equal subgroups as well. In both groups, die spacer was applied to dies in 0, 3, 4, 5, 6 and 7 layers (each layer=5µ). In the first group, crowns were cemented with Zinc Phosphate and in the second group, Polycarboxylate was used for cementing. After that, the strength required for separating the castings from the dies was measured.
 Results: The difference among 12 subgroups analyzed by one-way ANOVA regarding Polycar- boxylate cement did not reach statistical significance. (P=0.95). A similar result was obtained with zinc phosphate cement (P=0.616). Likewise, the two-way ANOVA was carried out between the zinc phosphate and polycarboxylate groups. There was a significant difference between the average of two groups (P<0.001).
 Conclusion: Range of cement layer thickness that used in this study didn’t statistically signifi- cantly affect the force required to remove cemented cast copings. Although the castings cemented with Zinc Phosphate needed higher force to be dislodged from dies.

Comparative evaluation of retention of lithium disilicate crowns with four different cementation systems- An in-vitro Study

AIM OF THE STUDY: This in vitro study was performed to compare the retention of pressable lithium disilicate crowns cemented with four different cementation systems.METHODS: Eighty single rooted maxillary 1st premolars were collected after excluding teeth with caries and/or previous restorations. Preparation of the samples was standardized by using a diamond bur mounted onto a surveyor. An anatomic crown was waxed on each tooth and then hot pressed using lithium disilicate ceramic (IPS e.max PRESS, IvoclarVivadent). The samples were randomly divided into 4 groups (n = 20) according to different cementation systems. Each group sample was subjected to a seating force of 50N using universal testing machine. Each upper block was pulled along the path of insertion of the crown with a crosshead speed of 1mm/min.RESULTS: Self adhesive resin cement showed the maximum tensile strength among all adhesive luting cements (2.65 MPa). Self etch resin cement group showed mean tensile strength of (1.78 MPa) that was marginally less than total etch resin cement (1.86 MPa). Glass ionomer cement exhibited least tensile strength (1.41 MPa) compared to the other three luting cements.CONCLUSION: Within the limitations of this in vitro study, it was concluded that lithium disilicate full coverage crowns cemented with self adhesive resin cement showed higher bond strength followed by total etch resin cement, self etch resin cement and glass ionomer cement.

Comparative Evaluation of the Effect of Degree of Convergence and Surface Area on the Retentive Force of Titanium Crowns Cemented with Various Adhesive Luting Agents on Extracted Human Teeth – A Laboratory Study

Introduction: The retention of base metal crowns and noble metal crowns cemented with various luting agents is well documented. However, little emphasis was given to the degree of convergence and surface area of tooth preparation. Aim and Objective: A study was planned to analyze the effect of the degree of convergence and surface area of the tooth preparation on the retention of titanium crowns with various adhesive luting agents. Materials and Methods: Forty-five caries-free extracted human premolars were obtained. They were divided into three groups according to the degree of convergence and further subdivided based on the type of luting agents used. The teeth were prepared with an angle of convergence of 5°, 10°, and 15° with a flat occlusal surface using K9 crown finishing installation, complete. Light body copper band impressions were made to determine the surface area. Titanium crowns thus obtained were sandblasted, ultrasonically cleaned, and cemented using Panavia F, Calibra, and Glass Ionomer Cement. Results: Results showed that Panavia F was the best luting agent exhibiting maximum retentive force to dislodge the crown in a vertical direction using the universal tensile testing machine at a cross-head speed of 1 mm/min. Conclusion: The force required to dislodge the titanium crown from the prepared tooth was maximum for Panavia F on 5°, 10°, and 15° angle of convergence at 65.23 kgf, 48.52 kgf, and 40.14 kgf. Retentive force values drastically reduced as the degree of convergence increased. There was a reduction in the surface area due to an increase in the taper.

Influence of Pre-Treatment and Artificial Aging on the Retention of 3D-Printed Permanent Composite Crowns.

The aim of this in vitro study is to investigate the bonding properties of a 3D-printable permanent composite material in comparison to milled composite materials. The tested materials are 3D-printed BEGO VarseoSmile Crown plus (VA1_ab, VA1_nt, VA2_ab, VA2_nt), Vita Enamic (EN1, EN2), and 3M Lava Ultimate (UL1, UL2) (N = 64; n = 8). For this purpose, all crowns are luted to polymer tooth stumps #46 (FDI) using dual-curing luting composite, strictly according to the manufacturer’s instructions. VA1_ab and VA2_ab are additionally airborne-particle abraded. 4 groups (VA2_ab, VA2_nt, EN2, UL2) are artificially aged (1,200,000 cycles, 50 N, 10,000 thermocycles), whereby no specimen has failed. All 64 specimens undergo pull-off testing until retention loss. The mean forces of retention-loss is 786.6 ± 137.6 N (VA1_nt, *), 988.6 ± 212.1 N (VA2_nt, *, Ɨ), 1223.8 ± 119.2 N (VA1_ab, Ɨ, ǂ), 1051.9 ± 107.2 N (VA2_ab, *, Ɨ), 1185.9 ± 211.8 N (EN1, Ɨ, ǂ), 1485.0 ± 198.2 N EN2, ǂ), 1533.8 ± 42.4 N (UL1, ǂ), and 1521.8 ± 343.4 N (UL2, ǂ) (one-way ANOVA (Scheffé method); p < 0.05; *, Ɨ, ǂ: group distribution). No characteristic failure modes can be detected. In conclusion, all of the pull-off forces reflect retention values that seem to be sufficiently high for clinical use. Additional airborne-particle abrasion of VA does not result in significantly better retention but can be recommended.

Factors influencing retention of resin-based luting systems on implants: A systematic review

The large variety in materials makes it difficult for dentists to select the right material for appropriate retention of single crowns on implants. An assessment of the retentive force and influencing parameters is lacking. The aim of this systematic review is to provide an overview of the retention values of resin-based luting materials of single tooth crowns on implants. Influencing factors, such as the abutment geometry, different pretreatment options, or the application of resin-based systems, are taken into account. A Pubmed-Medline library search was conducted, supported by manual searching, to collect available studies between the years 2005 to 2020. The following MeSH terms were used: “dental AND implant AND crown AND cementation AND retention”, as well as other combinations to identify as many studies as possible. After setting the filters and deleting the duplicates, 269 studies were identified. Finally, 23 studies were considered eligible for this review. Resin-based adhesive luting materials in combination with a primer showed the highest retention values. The retention is significantly influenced by a small cement gap, high loading during cementation, and pretreatment of the abutment. A low bias risk was shown for all included studies. The large number of available resin-based luting materials offer dentists the possibility to influence the individual retention of single-tooth crowns on implants. According to the present study, retentive strength can be clinically influenced not only by the choice of luting material. A pretreatment using sandblasting and an appropriate primer influences retention positively. Exerting pressure on the restoration after cementation also leads to increased retention. However, clinical studies would be desirable for the future to further investigate the results of this review.

Longevity of metal-ceramic single crowns cemented onto resin composite prosthetic cores with self-adhesive resin cement: an update of a prospective analysis with up to 106months of follow-up.

To evaluate the longevity of metal-ceramic single crowns cemented onto resin composite prosthetic cores using a self-adhesive resin cement in a prospective clinical descriptive study. A total of 152 teeth were endodontically treated and received resin composite prosthetic cores and metal-ceramic crowns cemented with a self-adhesive resin cement. The patients included in the sample were recalled for clinical and radiography evaluation in an up-to-106-month period after the final cementation procedures, with an average of 62months of follow-up. 91.5% of the sample (142 teeth) were evaluated regarding the treatment survival rate, analyzed considering the loss of crown retention (crown debonding)and tooth loss as the primary outcome. In addition, post debonding, androot fracture occurrences were also recorded as secondary outcomes to evaluate the success rate of the prosthetic treatment. The aesthetic parameters were also evaluated according to the FDI criteria. The Kaplan-Meier method and Cox regression with 95% confidence interval were applied for the statistical analysis. Regarding the primary outcome, the metal-ceramic crowns cemented with self-adhesive resin cement presented a high survival rate (91.5%), with 8 crown debondingsand 3 tooth losses (1 due to caries and 2 due to periodontal disease) occurring after the evaluation period. For secondary outcomes, 9 root fracturesand 4 post debondings occurred, generating a success rate of 72%. All crowns had a score 1 on the FDI criteria, indicating that they were clinically excellent or very good regarding the aesthetic parameters. The metal-ceramic crowns luted with a self-adhesive resin cement presented a survival rate of 91.5% after an average of 62months of follow-up. Furthermore, the restorations remained aesthetically satisfactory over time, without changes that would indicate prosthetic retreatment. A success rate of 72% was obtained considering the secondary outcome, mainly related to intraradicular retainer failures (root fractures or post debonding). The self-adhesive resin cement is clinically indicated for cementation of metal-ceramic crowns onto resin composite prosthetic cores.

Laboratory Fracture Resilience of Hybrid Abutments Used in Oral Rehabilitation: A Systematic Review.

When implants are required in prosthodontics treatment, one of the most important decisions is the choice of the final crown and the type of connection to the implant through the abutment. Hybrid abutments are becoming a primary choice. They are projected and produced with materials whose properties guarantee the required mechanical features (including resistance) and take advantage of the hybrid abutment crown retention between screw and cement. However, a review of the mechanical resistance of the different abutment types and associated materials is still lacking. This review aimed to study the in vitro mechanical efficiency of the hybrid abutments used in oral rehabilitation. Methods: A systematic review was conducted using the PubMed, B-on, and Google Scholar databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: 75 articles were identified from all databases, and 33 were selected after abstract screening. Thus, 21 studies were included in the review after full-text reading. Among the materials used for crowns, lithium disilicate was, aesthetically, the primary choice for its aesthetic and moderate strength. On the other hand, zirconia showed the best fracture resistance. Regarding the different kinds of abutments, there is still some lack of knowledge about the best design. Conclusions: Within the limitations of this systematic review, we can conclude that hybrid pillars are an excellent choice for oral rehabilitation through implants, showing improved resistance when including materials such as zirconia and lithium disilicate.

Retention Strength of Zirconia Crowns Cemented onto PEEK Abutments Using Two Different Types of Resin Cement With or Without Primer Application-An In Vitro Study.

To evaluate the retention of zirconia crowns on polyetheretherketone (PEEK) abutments using different luting agents, with and without PEEK primer. A total of 100 PEEK abutment replicas were fabricated, airborne particle-abraded with aluminum oxide, and divided into four groups (n = 25). A total of 100 zirconia crowns were fabricated and cemented using either adhesive resin cement or self-adhesive resin cement with and without PEEK primer; thus, the groups were: group AA-P (adhesive cement with primer); group AA-N (adhesive cement without primer); group SA-P (self-adhesive cement with primer); and group SA-N (self-adhesive cement without primer). The specimens were thermocycled and subjected to crown pull-out tests. The values were recorded and analyzed using analysis of variance and post hoc analysis (α = .05). The mode of failure of debonded surfaces was evaluated using scanning electron microscopy. The pull-out force values were 3.13 ± 0.31 MPa for group AA-P, 1.77 ± 0.20 MPa for group AA-N, 2.10 ± 0.12 MPa for group SA-P, and 1.49 ± 0.18 MPa for group SA-N. Statistically significant differences were found between all four groups (P < .001). The specimens with PEEK primer applied showed higher values compared to nonprimed specimens for both cements tested. Scanning electron microscopy analysis showed more mixed failures for adhesive cement and more adhesive failures for self-adhesive resin cement. The maximum pull-out forces were recorded for zirconia crowns bonded to PEEK abutments with adhesive cement. The use of PEEK primer increased the pull-out values for both resin cements.

Effect of Indented Structures on the Retention of Cement-Retained Implant-Supported Crowns by Provisional Cement

Purpose: The objective of this study was to investigate the effect of indented structures, such as dimples and retention groove formations, on the retention of titanium abutment walls when cementing cobalt-chromium (Co-Cr) alloy crowns with zinc oxide-eugenol cement. Materials and Methods: Forty-eight titanium abutments (n = 6) were prepared, of which 24 abutments were 4.0 mm and the other 24 were 6.0 mm in height. These 4.0 mm and 6.0 mm abutments were organized into eight groups: no-dimple, 2-dimple, 4-dimple, and axial retention groove groups. The position and dimensions of the dimples and axial retention grooves were the same for all prepared abutments. Laser-sintered cobalt-chromium (Co-Cr) alloy crowns were cemented using a provisional cement. After thermocycling, a retention test was performed using a universal testing machine. Statistical analysis was performed using the nonparametric Kruskal–Wallis test and post-hoc Mann–Whitney U test (𝛼= .05) to compare the mean retentive force. Results: The lowest retentive force recorded was from the 4.0 mm no-dimple group (112.03 ± 20.30). Forming dimples and retention grooves increased the retentive force for the 4.0 mm groups, but the difference was not statistically significant (p > .05). A statistically significant difference was displayed by the 6.0 mm abutment with the 4-dimple group compared to the 6.0 mm no-dimple group (p < .05). Conclusion: Within the limitations of this in vitro study, the mean retentive force was higher with dimples and axial retention grooves for 4.0 mm titanium abutments but was statistically insignificant (p > .05). An increase in abutment height was statistically correlated with an increase in retentive force within the same number of dimple-groups (p < .05).

Effect of Cementation Technique on Retention of All Ceramic Crowns Cemented to Zirconia and Titanium Implant Abutments: A Comparative in Vitro Study

Objective: The aim of this study is to evaluate the retention of lithium disilicate crowns cemented by resin cement on zirconia and titanium implant abutments coated with glycerin and eugenol. Materials and Methods: Forty implant analogs were embedded in forty blocks of epoxy resin. Twenty implant analogs received a zirconia implant abutment to which 20 IPS e.max press crowns were cemented. The other twenty implant analogs received a titanium implant abutment to which 20 IPS e.max press crowns were cemented. According to the cementation technique, the samples were subdivided into two groups, 10 samples each. In Gp A, zirconia implant abutments’ surfaces were coated with a single coat of eugenol before cementing crowns with the permanent resin luting cement. In Gp B, same as in Gp B with replacement of eugenol with single coat of glycerin. In Gp C, Titanium implant abutments’ surfaces were coated with a single coat of eugenol before cementing crowns with the permanent resin luting cement. In Gp D, same as in Gp C with replacement of eugenol with single coat of glycerin. Each sample was subjected to a pull-out test. Loads required to remove the crowns were recorded, and mean values for each group determined. Data were statistically analyzed. Results: The mean values ±SD of loads at failure (n -10) for each group were as follows in Newton (N): Group(A) 141.9±17.9, Group(B) 134±14.5, Group(C) 140.5±17, Group(D) 143.6±12.4. All groups showed statistically insignificant difference in retention (p&lt;0.05). Conclusions: There was no significant difference between eugenol and glycerin coated zirconia implant abutments in retention of lithium disilicate crowns. There was no significant difference between eugenol and glycerin coated titanium implant abutments in retention of lithium disilicate crowns.

Clinical Performance and Parental Satisfaction with Composite Strip Crown and Prefabricated Zirconia Crown for Primary Anterior Teeth: A Randomized Clinical Trial

To compare clinical performance and parental satisfaction with composite strip crown and prefabricated zirconia crown for primary anterior teeth. The study compares clinical evaluation and parental satisfaction of two different crowns for primary anterior teeth. A total of 102 teeth in each group selected between ages 3 and 6 years, who met the inclusion criteria, were randomly allocated into two groups for further evaluation. Group A for strip crowns (55 teeth) and group B for zirconia crowns (47 teeth). The crowns were evaluated clinically with various criteria like-color match, crown retention, gingival health, crown contour, opposing tooth wear, marginal integrity, and recurrent caries. The samples were also evaluated for parental satisfaction based on 5-point Likert scale and child liking was also recorded with Smiley face Likert scale at baseline, 3 and 9 months. Statistical analysis was done using Chi-square test (p <0.05). Zirconia crowns showed better color match, crown retention, crown contour, and gingival health. Strip crowns showed more discoloration and chipping of material over a period of time. None of the samples showed opposing tooth wear, open margins, and recurrent caries in strip and zirconia crown group. Parents and children both were highly satisfied with zirconia crowns. Clinically zirconia crowns showed higher success rate as compared to strip crowns and parental overall satisfaction was higher for zirconia crowns. Zirconia crowns exhibited a higher clinical performance and parental satisfaction; hence, if affordability is out weighted, zirconia crown stands better with esthetics of the child.

Effect of Surface Modifications on the Retention of Implant-supported Cement-retained Crowns with Short Abutments: An In Vitro Study

The study aimed to evaluate and compare the effect of incorporating one circumferential groove and bur modification on retention of cast copings on implant abutment cemented with glass ionomer cement. Fifteen straight shoulder implant abutments casted of height 6 mm used with corresponding 12 mm long stainless steel implant analog. The abutments were divided into three groups of five abutments in each group. Group I: Control group, without any surface modification, Group II: Milling of a circumferential groove, and Group III: Bur modification by creating punches of size whole round bur diameter 5 per axial surfaces. Glass ionomer definitive cement was used to adhere the cast copings to each group of abutments. After thermocycling, the specimens were evaluated for retention using the Instron Universal Testing Machine's pull-out test. The data were analyzed using One-way ANOVA, followed by the Tukey post-hoc test to compare the load among the three groups. According to the findings, the inclusion of a circumferential groove (Group II) increased the retention of glass ionomer cement maintained implant-supported crowns by 44.58%. The bur modification (Group III) boosted glass ionomer cement maintained implant-supported crown retention by 110.69% while retaining retrievability. Results were statistically significant. Bur modification revealed more retention when compared to the groove and control group. Short abutments are used in the clinical situation where interarch space is less. To achieve adequate retention of the implant crowns, surface modification of the abutments is necessary while selecting a cement-retained prosthesis.

Analysis of impact of desensitizing agents on the retention of crowns cemented with luting agents

The present study was undertaken for assessing the impact of desensitizing agents on the retention of crowns cemented with luting agents. 40 freshly extracted mandibular molar teeth were selected. Two study groups were made: Group C: Control group-Glass ionomer cement; and Group G: Study group-GC Tooth Mousse desensitizer. Crowns were fabricated and were subjected under universal force testing machine. All the results were recorded in Microsoft excel sheet and were analyzed by SPSS software. Mean tensile bond strength of group C specimens was 49.1 Kg while mean tensile strength of Group 2 specimens was 47.1 Kg respectively. While comparing statistically, non-significant results were obtained. Application of desensitizing agents may be designated during fabrication of crowns as it will not affect the retentive ability of the luting cements.

Effect of surface pretreatment and artificial aging on the retention of lithium disilicate crowns cemented to zirconia implant abutments

Statement of problemRecent advancements in restorative dentistry have seen an increase in the use of ceramic restorations and zirconia implant abutments. However, how the pretreatment of a zirconia abutment and different artificial aging protocols affect the bond strength of a cemented, monolithic lithium disilicate crown is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of surface pretreatment on the retentive strength of milled lithium disilicate crowns bonded to custom zirconia implant abutments with different resin cements after thermocycling and long-term aging. Material and methodsA total of 144 crowns (n=8) were milled and bonded to 144 abutments. In the experimental groups, 72 abutments were airborne-particle abraded with 50-μm aluminum oxide before bonding. All specimens were stored at 37 °C in 100% humidity for 24 hours. Forty-eight specimens were subjected to thermocycling, and another 48 were subjected to aging for 6 months. Retentive strength was measured by using a pull-off test with a universal testing machine. Retentive strength values were calculated and compared with 3-way analysis of variance and a Tukey-Kramer post hoc test (α=.05). ResultsIn the 24-hour aging group, retention for all experimental groups was significantly higher (P<.05) than for the control group, except for Panavia 21 with Clearfil Ceramic Primer. In the thermocycling and long-term aging groups, all cements in the experimental group displayed significantly higher retention than the control. The airborne-particle abrasion of custom zirconia implant abutments with 50-μm aluminum oxide before bonding to lithium disilicate crowns significantly increased the bond strength of the Multilink Hybrid Abutment with Monobond Plus and RelyX Ultimate with Scotchbond Universal cements after 24-hour aging, but not of Panavia 21 with Clearfil Ceramic Primer. ConclusionsAirborne-particle abrasion significantly increased the bond strength of all 3 cements after thermocycling and long-term aging.

Clinical Evaluation of Stainless Steel Crown versus Zirconia Crown in Primary Molars: An In Vivo Study.

AimThe objective of this clinical trial was to evaluate and compare two full-coronal restoration [stainless steel crowns (SSCs) and zirconia crown] in carious primary posterior teeth.Materials and methodsForty endodontically treated primary teeth in children within the age-group of 3-9 years were selected and divided into two equal groups (20 SSCs and 20 zirconia crown). The two crowns were evaluated for retentivity of crown, temporomandibular joint (TMJ) problem, gingival response, plaque accumulation, and tooth wear in opposing teeth after 1st and 3rd month follow-up.ResultsBoth the crowns showed 100% results regarding TMJ problems, but SSCs performed better in terms of retention of crown, gingival response, plaque accumulation, and tooth wear in opposing teeth. The statistics showed significant result by using Mann-Whitney U test and Wilcoxon signed-rank test.ConclusionStainless steel crowns performed better among both the full-coronal restoration for posterior primary teeth.Clinical significanceStainless steel crowns remain “Gold Standard”, for posterior full coverage restorations in primary molars as compared to zirconia crowns.How to cite this articleAgrawal R, Khanduja R, Singhal M, et al. Clinical Evaluation of Stainless Steel Crown versus Zirconia Crown in Primary Molars: An In Vivo Study. Int J Clin Pediatr Dent 2022;15(1):15-19.

Selection of 1-mm venting or 2.5-mm screw access holes on implant crowns based on cement extrusion and retention capacity

BackgroundThis in vitro study aimed to provide evidence regarding the selection of hole diameters of implant crowns to reduce excess cement extrusion at the abutment margin, and to examine the maintenance of their retention capacity in anterior and posterior cement-retained implant crowns.MethodsSix groups of implant crowns were prepared according to the position of the teeth and the size of their holes as follows: anterior crown without hole (ANH), anterior crown with 1-mm mini venting hole (AMH), anterior crown with 2.5-mm regular screw access hole (ARH), posterior crown without hole (PNH), posterior crown with 1-mm mini venting hole (PMH), and posterior crown with 2.5-mm regular screw access hole (PRH). Temporary cement was used to bond the crowns to the abutments. The mean amount of excess cement extrusion among the different groups at the abutment margin was calculated. Retentive strength under different hole designs was measured as the dislocation force of the crown using a universal testing machine. One-way ANOVA and Welch’s t-test were used to analyze the results.ResultsThe average amounts of extruded excess cement were 18.96 ± 0.64, 1.78 ± 0.41, and 1.30 ± 0.41 mg in the ANH, AMH, and ARH groups, respectively, and 14.87 ± 0.36, 1.51 ± 0.40, and 0.82 ± 0.22 mg in the PNH, PMH, and PRH groups, respectively. The hole opening in the crowns could significantly reduce residual cement regardless of its size (p < 0.001). The mean retentive strengths were 54.16 ± 6.00, 47.63 ± 13.54, and 31.99 ± 7.75 N in the ANH, AMH, and ARH groups, respectively, and 57.84 ± 10.19, 53.22 ± 6.98, and 39.48 ± 5.12 N in the PNH, PMH, and PRH groups, respectively. The retention capacity of the implant crown deteriorated rapidly as the holes on the crown surface enlarged.ConclusionsThe presence of a hole on the implant crown reduced the amount of excess cement. The retention ability of the implant crowns deteriorated as the size of the hole increased. Considering the esthetic effect of the crown and the possible influence on crown retention, an implant crown with a 1-mm mini venting hole is a better clinical choice than the one with a 2.5-mm regular screw access hole.

Effects of variable retention harvesting on canopy transpiration in a red pine plantation forest

BackgroundVariable Retention Harvesting (VRH) is a forest management practice applied to enhance forest growth, improve biodiversity, preserve ecosystem function and provide economic revenue from harvested timber. There are many different forms and compositions in which VRH is applied in forest ecosystems. In this study, the impacts of four different VRH treatments on transpiration were evaluated in an 83-year-old red pine (Pinus Pinus resinosa) plantation forest in the Great Lakes region in Canada. These VRH treatments included 55% aggregated crown retention (55A), 55% dispersed crown retention (55D), 33% aggregated crown retention (33A), 33% dispersed crown retention (33D) and unharvested control (CN) plot. These VRH treatments were implemented in 1-ha plots in the winter of 2014, while sap flow measurements were conducted from 2018 to 2020.ResultsStudy results showed that tree-level transpiration was highest among trees in the 55D treatment, followed by 33D, 55A, 33A and CN plots. We found that photosynthetically active radiation (PAR) and vapor pressure deficit (VPD) were major controls or drivers of transpiration in all VRH treatments. Our study suggests that dispersed or distributed retention of 55% basal area (55D) is the ideal forest management technique to enhance transpiration and forest growth.ConclusionsThis study will help researchers, forest managers and decision-makers to improve their understanding of water cycling in forest ecosystem and adopt the best forest management regimes to enhance forest growth, health and resiliency to climate change.