Early histological, microbiological, radiological, and clinical response to cemented and screw-retained all-ceramic single crowns

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

STATEMENT OF PROBLEM

Recent 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.

PURPOSE

The 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 METHODS

A 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).

RESULTS

In 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.

CONCLUSIONS

Airborne-particle abrasion significantly increased the bond strength of all 3 cements after thermocycling and long-term aging.

Implant prosthodontic design as a predisposing or precipitating factor for peri-implant disease: A review

Over the past decade, emerging evidence indicates a strong relationship between prosthetic design and peri-implant tissue health. The objective of this narrative review was to evaluate the evidence for the corresponding implant prosthodontic design factors on the risk to peri-implant tissue health. One of the most important factors to achieve an acceptable implant restorative design is the ideal implant position. Malpositioned implants often result in a restorative emergence profile at the implant-abutment junction that can restrict the access for patients to perform adequate oral hygiene. Inadequate cleansability and poor oral hygiene has been reported as a precipitating factors to induce the peri-implant mucositis and peri-implantitis and are influenced by restorative contours. The implant-abutment connection, restorative material selection and restoration design are also reported in the literature as having the potential to influence peri-implant sort tissue health.

Clinical performance of lithium disilicate and zirconia CAD/CAM crowns using digital impressions: A systematic review

PURPOSE

The purpose of this systematic review was to compare the clinical performance of lithium disilicate (LDS) and zirconia (Z) single crowns manufactured by computer-aided design/computer-aided manufacturing (CAD/CAM) systems using intraoral optical scanners (IOS).

MATERIALS AND METHODS

An electronic search for articles published between January 2012 and January 2022 in the English language was performed with the Medline/Pubmed database under the guidelines of Preferred Reporting Items for Systemic Reviews and Meta-analysis (PRISMA). The specific search terms used were "zirconia", "lithium disilicate", "CAD/CAM", "intraoral optical scanner", and "survival".

RESULTS

The initial electronic search resulted in 278 articles. Most of the resulting articles were excluded, six clinical studies addressing the clinical outcomes of Z and LDS crowns fitted the inclusion criteria and were selected for review. Of these six studies, three were randomised controlled trials, two were retrospective studies, and one was a prospective study. To quantify the clinical performance of the crowns several parameters were recorded, including fractures, endodontic complications, periodontal complications, technical complications, aesthetic complications, and biological complications. It was noted that the most common technical complication of Z and LDS crowns was chipping at a rate of 1.4% and 5% respectively. Regarding Z crowns, aesthetic concerns were the most frequently observed complication.

CONCLUSION

The outcomes of this systematic review indicate that Z and LDS crowns display a similar incidence of periodontal and endodontic complications when compared to metal-ceramic crowns, suggesting that these all-ceramic materials are viable alternatives. The incidence of chipping was higher in LDS crowns compared to other materials, while Z crowns were inferior in terms of aesthetics.

A five-year randomised controlled trial comparing zirconia-based versus metal-based implant-supported single-tooth restorations in the premolar region

OBJECTIVES

To compare 5-year biological, technical, aesthetic, and patient-reported outcomes of single-tooth implant-supported all-ceramic versus metal-ceramic restorations.

MATERIALS AND METHODS

Thirty patients with 63 premolar agenesis participated in the 5-year follow-up. The prosthetic treatment on single-tooth implants were randomly assigned to all-ceramic crowns on zirconia abutments (AC=31) or metal-ceramic crowns on metal abutments (MC=32). All patients were recalled to clinical examinations at baseline, 1, 3, and 5 years after prosthetic treatments. Biological, technical, and aesthetic outcomes including complications, were clinically and radiographically registered. The patient-reported outcomes were recorded using OHIP-49 questionnaire before treatment and at each follow-up examination.

RESULTS

At 5-year examination, the survival rate was 100% for implants and 100 % for AC and 97% for MC crowns and abutments. The marginal bone loss after 5-years was minor and not significantly different (p= 0.056) between AC (mean: 0.3, SD: 1.1) and MC restorations (mean: -0.1, SD: 0.4). The success rate of the implants based on marginal bone loss was 77.4% for AC- and 93.7% for MC-restorations. The marginal adaptation was significantly better for MC than for AC restorations (p=0.025). The aesthetic outcomes and patient-reported outcomes between AC and MC restorations were not significantly different.

CONCLUSIONS

The biological, aesthetic and patient-reported outcomes for implant-supported AC and MC restorations were successful and with no significant difference after 5-years. The marginal adaptation of the MC crowns cemented on titanium abutments showed significantly better fit than restorations based on zirconia crowns cemented on zirconia abutments.

Cemented versus screw-retained zirconia-based single implant restorations: 5-year results of a randomized controlled clinical trial

Objectives

To compare cemented and screw‐retained one‐piece zirconia‐based restorations in terms of clinical, radiographic, and technical outcomes 5 years after insertion.

Materials and methods

Thirty‐four patients with single‐tooth implants were randomly restored with either a cemented lithium disilicate crown on a one‐piece customized zirconia abutment (CEM, 17 patients) or a screw‐retained crown based on a directly veneered one‐piece customized zirconia abutment (SCREW, 16 patients). All patients were recalled for a baseline examination (7–10 days after crown insertion) and then annually up to 5 years. The following outcomes were assessed: marginal bone level (changes), technical, and clinical (bleeding on probing, plaque control record, probing depth, and keratinized tissue) parameters. The Mann–Whitney U‐test was used to assess differences between the two groups.

Results

At 5 years, 26 patients (13 in each group) were re‐examined. The survival rates on the implant and restorative levels were 100% and 82.4% (equally for both groups), respectively. At 5 years, the median marginal bone level was located at −0.15 mm (IQR: −0.89 mm; 0.27 mm) (CEM) and −0.26 mm (IQR: −0.38 mm; 0.01 mm) (SCREW) below the implant shoulder (intergroup p = .9598). The median changes between baseline and the 5‐year follow‐up amounted to −0.23 mm (CEM; intragroup p = .0002) and −0.15 mm (SCREW; intragroup p = .1465) (intergroup p = .1690). The overall technical complication rate at 5 years was 15.4% (CEM) and 15.4% (SCREW) (intergroup p = 1.00). Clinical parameters remained stable over time (baseline to 5 years).

Conclusions

At 5 years, screw‐retained and cemented restorations rendered largely the same clinical, technical, and radiographic outcomes. Technical complications were frequent in both groups.

Esthetic, mechanical, and biological outcomes of various implant abutments for single-tooth replacement in the anterior region: a systematic review of the literature

Background

The choice of the appropriate implant abutment is a critical step for a successful outcome. Titanium abutments have demonstrated high survival rates, due to their excellent biocompatibility and high mechanical strength, although they often result in a grayish discoloration of the peri-implant mucosa. This esthetic concern culminated in the introduction of ceramic abutments. The aim of this review was to assess the esthetic, mechanical, and biological outcomes as well as the survival of the different types of abutments used for single-implant restorations in the anterior area.

Material and methods

An electronic search was conducted in Medline, Embase, and Cochrane Central databases using the appropriate Mesh terms and predetermined eligibility criteria. The quality of the studies was assessed using the ROB 2 tool. The last search was conducted on 18th of March 2020.

Results

From the 2074 records initially identified, 23 randomized controlled trials (32 publications) were included for qualitative analysis. Data were classified based on study information, specific characteristics of the intervention and comparator, and information related to the outcome measures. Seven studies exhibited an overall low risk of bias, while twelve studies raised some concerns.

Conclusions

The rate of abutment failure was low and was associated with the ceramic abutments, especially those with internal connection. Limited correlation was noted between soft tissue thickness and color difference. Titanium abutments caused significantly more discoloration to the soft tissues than ceramic abutments, while hueing (gold or pink) slightly improved their color performance. Zirconia allowed a better color match than titanium or gold abutments, still discolored slightly the soft tissues. The submucosally modified zirconia abutments exhibited encouraging results. No significant difference was reported between materials or different types of retention on recession, papillary fill, and biological outcomes.

Peri-implant and esthetic outcomes of cemented and screw-retained crowns using zirconia abutments in single implant-supported restorations-A systematic review and meta-analysis

OBJECTIVES

To evaluate the peri-implant tissue changes and esthetic outcomes of cemented and screw-retained crowns of single-tooth implants in the esthetic zone using zirconia abutments.

MATERIAL AND METHODS

An electronic search was performed on nine databases. The risk-of-bias was assessed by the revised Cochrane risk-of-bias tool for randomized (RoB 2) and non-randomized (ROBINS-I) clinical trials. Marginal bone level change, soft tissue thickness, bleeding on probing, probing depth, survival rates of implants and crowns, complications, plaque and papilla indexes, and pink esthetic score data were extracted and analyzed. The certainty of evidence was accessed through the GRADE approach.

RESULTS

Nine records were included and 7 were used in the meta-analyses. Screw-retained crowns presented greater marginal bone level change (MD -0.04 [-0.08, -0.00] p = 0.04, I²  = 0%) compared to cemented crowns up to 1-year. At 3 and 4 years no significant differences (p > 0.05) were observed. Soft tissue thickness did not differ between groups (p > 0.05). The bleeding on probing was higher in cemented group than in screw-retained crowns at 1-year (MD 0.17 [0.08, 0.27] p = 0.0005, I²  = 0%), at medium-term periods (3 and 4 years) no statistically significant differences (p > 0.05) were observed for this outcome. Probing depth, survival rates of implants and crowns, complications, and plaque index, as well as esthetic analysis using the papilla index and pink esthetic score did not differ statistically (p > 0.05) between both retention systems at short and medium-term periods.

CONCLUSION

The connection system considering zirconia abutments presented no influence on peri-implant parameters and esthetics evaluation for medium-term periods (3 and 4 years).

Retention of different temporary cements tested on zirconia crowns and titanium abutments in vitro

Purpose

The aim of the present study was to examine the retention force of monolithic zirconia copings cemented with various temporary cements on implant abutments in vitro.

Methods

Sixty exercise implants with pre-screwed implant abutments were embedded in resin. Subsequently, 60 CAD/CAM manufactured zirconia copings were divided into three main groups [Harvard Implant Semi-permanent (HAV), implantlink semi Forte (IMP), Temp Bond NE (TBNE)]. The zirconia copings were cemented on the implant abutments and loaded with 35 N. Specimens were stored in distilled water (37 °C) for 24 h. Half of the test specimens of each group were subjected to a thermocycling (TC) process. Retention force was measured in a universal testing machine. Using magnifying glasses, the fracture mode was determined. Statistical analysis was performed applying the Kruskal-Wallis test, the post hoc test according to Dunn-Bonferroni and a chi-square test of independence.

Results

Without TC, IMP showed the highest retention of the three temporary luting agents (100.5 ± 39.14 N). The measured retention forces of IMP were higher than those of HAV (45.78 ± 15.66 N) and TBNE (61.16 ± 20.19 N). After TC, retention was reduced. IMP showed the greatest retentive strength (21.69 ± 13.61 N, three fail outs). HAV and TBNE showed pull-off forces of similar magnitude (17.38 ± 12.77 N and 16.97 ± 12.36 N, two fail outs). The fracture mode analysis showed different results regarding the tested cements before and after TC (facture type before/after TC): IMP (III+II/III), HAV (I/II) and TBNE (III/III). There were clear differences of the fracture modes regarding the examination before and after TC.

Conclusions

Within the limits of this study, IMP showed the highest pull-off forces under the chosen test conditions. All three temporary luting agents showed lower retention forces after TC. Retention values in the individual cement classes were very heterogeneous. Easy cement removal in the crown lumen favours the dominance of adhesive cement fractures on the abutment and adhesive/cohesive cement fractures on the abutment with HAV appears advantageous in case of recementation of the superstructure.

Clinical and histological comparison of the soft tissue morphology between zirconia and titanium dental implants under healthy and experimental mucositis conditions-A randomized controlled clinical trial

OBJECTIVES

To analyse the soft tissue morphology under healthy and experimental mucositis conditions comparing zirconia and titanium implants.

METHODS

Forty-two patients with two adjacent missing teeth received one zirconia (Zr) and one titanium (Ti) implant, with the mesial and distal position randomized. At 3 months, half of the patients were instructed to continue (healthy; h) and the other half to omit (experimental mucositis; m) oral hygiene around the implants for 3 weeks. Clinical parameters were evaluated before and after the experimental phase, and a soft tissue biopsy was harvested. Mixed model analyses were performed to analyse the data.

RESULTS

The plaque control record increased significantly for the two mucositis groups, reaching 68.3 ± 31.9% (mean ± SD) for Zr-m and 75.0 ± 29.4% for Ti-m (p < .0001), being also significantly lower for Zr-m than for Ti-m. Bleeding on probing remained stable in group Zr-m and amounted to 21.7 ± 23.6%, but increased significantly in group Ti-m (p = .040), measuring 32.5 ± 27.8%. The number of inflammatory cells and the length of the junctional epithelium did not significantly differ between the groups.

CONCLUSION

Both implants rendered similar outcomes under healthy conditions. Lower plaque and bleeding scores were detected for zirconia implants under experimental mucositis conditions. Histologically, only minimal differences were observed.

Peri-Implant Diseases and Biologic Complications at Implant-Supported Fixed Dental Prostheses in Partially Edentulous Patients

PURPOSE

This is a single center, retrospective study to assess the prevalence of peri-implant disease and biologic complications in a cohort of partially edentulous subjects in relation to selected prosthetic factors.

MATERIALS AND METHODS

Subjects previously treated with one or more implant-supported fixed dental prosthesis (ISFDPs) were recalled for a comprehensive examination. Clinical and radiographic records were taken and questionnaires were administered. The prevalence of implant failure, peri-implant disease and other biologic complications were correlated with selected prosthetic, clinical and patient-related factors using chi-square and multiple regression analyses.

RESULTS

A convenience sample of 71 subjects with 100 prostheses supported by 222 dental implants were enrolled in the study. The mean follow-up time after prosthesis delivery was 3.3 ± 1.5 years (range of 1-9 years). The cumulative implant survival rate was 99.1%. Peri-implantitis was the most frequent major biologic complication (5% of implants), while the most frequent minor biologic complication was peri-implant mucositis (84.10% of implants). A diagnosis of peri-implant mucositis was more likely associated with cement-retained prostheses compared to screw-retained prostheses (OR 6.8, 95% CI 1.1-78.6, p = 0.045) and for short-span prostheses (≤3 prosthetic units) (OR 2.3, 95% CI 1.1-5.0, p = 0.034). Subject-reported quality of life measures were high regardless of the existence of major and/or minor complications, but decreased with increasing number of minor and total biologic complications.

CONCLUSIONS

Peri-implant mucositis and other minor biologic complications were highly prevalent. The distribution of the observed complications differed based on the method of prosthesis retention and the number of prosthetic units replaced.

Interdisciplinary treatment with implant-supported prostheses for an adolescent with ectodermal dysplasia: A clinical report

This clinical report describes interdisciplinary treatments for a 17-year-old girl with ectodermal dysplasia. The treatment was initiated with orthodontic therapy. After the remaining primary teeth had been extracted, 6 implants were placed in the maxilla with bilateral sinus floor elevations, and 6 implants were placed in the mandible. Immediate restorations were provided. Definitive restorations included screw-retained partial dental prostheses and ceramic crowns.

Influence of margin location and luting material on the amount of undetected cement excess on CAD/CAM implant abutments and cement-retained zirconia crowns: an in-vitro study

Background

The flexibility in designing the submucosal part of CAD/CAM customized implant abutments and the individual positioning of its shoulder line has been suggested to reduce the risk of leaving undetected cement residues, thus preventing adverse effects on peri-implant tissues. A high correlation between excess cement left in the soft tissues and the occurrence of increased biofilm accumulation with sulcular bleeding and/ or suppuration has been reported. This in turn may cause peri-implant inflammation and peri-implant marginal bone loss. The aim of this study was to assess the frequency of cement remnants after the luting of zirconia crowns on CAD/CAM custom molar abutments with different margin levels and to evaluate the impact of the luting material.

Material and methods

A total of 20 titanium molar CAD/CAM implant abutments (BEGO Medical GmbH) with internal taper connection/ internal hex anti-rotation protection, and a convex emergence profile with different margin positions (0, 1, 2 and 3 mm below the mucosa), were virtually designed (Implant Studio, 3Shape) and manufactured. A master cast was scanned, duplicated by a 3D printer and individual gingival masks were produced to simulate peri-implant soft tissues. 20 corresponding zirconia crowns were designed (Cerec 3D, Dentsply Sirona), produced and cemented to the abutments with two different luting materials; a zinc oxide non-eugenol cement (Temp Bond NE) or a methacrylate cement (Panavia V5). To ensure retrievability of the crown/abutment connection, occlusal openings providing access to the abutment screws were designed. Excess cement was thoroughly removed and the crown/abutment units were unscrewed to evaluate the occurrence of cement residues. All the quadrants of each specimen were evaluated for calculation of the ratio between the cement remnant area and the total specimen area using Adobe Photoshop. Spearman analysis was performed to detect correlations between different variables. A two-sided t-test, ANOVA, Mann–Whitney, and Kruskal–Wallis tests were applied to detect differences between the groups.

Results

Cement remnants were found in every depth of the crown abutment complex and in almost every area investigated. The amount of cement residues increased as the crown-abutment margin was located more submucosally. Lingual areas were more prone to cement remnants than other surface areas (p = 0.0291). Excess cement was not only found at the margins of the crown-abutment complex, but also underneath (basal) the abutment itself, where cleaning was impossible. No statistical difference in the effect of zinc oxide non-eugenol- and methacrylate cement on the frequency of excess material at the lateral abutment surfaces could be demonstrated in vitro. The proportion of basal abutment aspects covered with cement residues was, however, significantly smaller in Panavia V5 samples with an average of 4.9 ± 3.7% compared to Temp Bond samples with an average of 8.6 ± 5.5%.

Conclusions

Given the results obtained in the present investigation the margin of CAD/CAM molar abutments should be located as coronally as possible to minimize the amount of cement remnants. If an epigingival or supragingival margin location is not feasible due to esthetic concerns, it cannot be recommended to place the margin of molar CAD/CAM abutments deeper than 1.5 mm in the proximal and oral regions.