Undetected residual cement on standard or individualized all-ceramic abutments with cemented zirconia single crowns - a prospective randomized pilot trial

Long-term retention and survival of cemented implant-supported zirconia and metal-ceramic single crowns: A retrospective study

OBJECTIVES

To evaluate the effect of different cement types on the incidence of failure and loss of retention of zirconia and metal-ceramic single crowns (SCs) cemented on implant abutments.

METHODS

We placed 567 implant-supported SCs in 358 patients and retrospectively evaluated long-term retention for up to 12.8 years. The frameworks were made from metal alloy (n = 307) or zirconia (n = 260). SCs were cemented with permanent (glass-ionomer cement; n = 376) or semipermanent cement (zinc oxide non-eugenol cement; n = 191) on standardized (n = 446) or customized (n = 121) abutments. Kaplan-Meier curves were used to calculate the incidence of decementation. Differences between survival curves were assessed with log-rank tests. Cox-regression analysis was performed to evaluate multiple risk factors.

RESULTS

Of the 567 SCs, 22 failed because of technical complications and four because of implant loss. Loss of retention was observed in 50 SCs. Analysis revealed a 7% probability of loss of retention for zirconia and 16% for metal-ceramic SCs after 10 years (p = .011). After 5 years, loss of retention was higher for standardized abutments than for customized abutments (p = .014). The probability of loss of retention was higher with semipermanent than with permanent cement (p = .001). Cox-regression analysis revealed semipermanent cement as the only significant risk factor for SC failure (p = .026).

CONCLUSIONS

In contrast to semipermanent cement, permanent cement provides acceptable long-term retention of cemented implant-supported SCs. These possible positive effects of customized abutments have to be controlled with larger sample sizes.

Mechanical stability of angulated zirconia abutments supporting maxillary anterior single crowns on narrow-diameter implants

OBJECTIVES

To investigate the fracture strength of angulated hybrid abutments supporting anterior single crowns on narrow-diameter implants (NDIs).

MATERIAL AND METHODS

Zirconia abutment with angulations of labial inclination 0° (TZ0Z), 15° (TZ15Z), 30° (TZ30Z) and palatal inclination 15° (TZ - 15Z) was designed on 3.3-mm titanium-zirconium (Ti-Zr) NDIs. Titanium abutment connected with Ti-Zr implant (TZ0T) and 0° zirconia abutment connected with pure titanium (Ti) implant (T0Z) were control groups. Thirty-six un-restored abutments and 36 abutments restored with highly translucent zirconia (HTZ) crowns were tested. Failure loads were compared among 6 groups, and bending moments were calculated for comparison between un-restored and restored abutments.

RESULTS

Failure loads of un-restored abutments were affected by the abutment angle. Sixty-seven percent samples in TZ30Z and 83% samples in TZ - 15Z group fractured at the thinnest part of the zirconia abutment and exhibited lower failure load (p < .05). Failure loads of restored abutments were close to or exceeded the maximum bite force of anterior teeth, and no differences were found among six groups (p > .05). Except TZ15Z and TZ0T group, the bending moment increased with the crown construction, especially for TZ30Z and TZ - 15Z groups (p < .001).

CONCLUSIONS

The fracture strength of hybrid abutments restored with HTZ crown on Ti-Zr NDIs exceeded the bite forces of anterior teeth for all the groups and were not affected by the abutment angle.

CLINICAL RELEVANCE

In terms of fracture strength, Ti-Zr NDIs combined with angulated hybrid abutments and HTZ crowns can be used in the anterior region.

Abutment margin levels and residual cement occurrence in cement-retained implant restorations: An observational study

OBJECTIVES

To evaluate the association between different vertical levels of the abutment margin and residual cement prevalence in cement-retained implant restorations with customized abutments.

METHODS

One hundred and nine single-unit cement-retained implant restorations with a screw-access channel were included. The crowns were intraorally cemented on the abutments, and excess cement was removed. The abutment-crown complex was unscrewed, and the abutment-crown complex and peri-implant tissue were photographed. Residual cement presence was recorded by dividing the abutment-crown complex and peri-implant tissue into four quadrants: mesial, distal, buccal, and lingual. The prevalence of residual cement was compared according to the height of the custom abutment margin of the corresponding quadrant. A multilevel model was used for statistical analysis (α = .05).

RESULTS

Cement remnants were discovered on 72.48% of the dental implants. When the restoration quadrants were compared, cement remnants were present on 51.38%, 39.45%, 20.18%, and 17.43% of the mesial, distal, buccal, and lingual surfaces, respectively (p < .01). Regarding the abutment margin level, cement residues were found in 60.22% and 61.4% of the 0.5 mm subgingival and ≥1 mm subgingival margin groups, respectively, which were significantly more than those in the supragingival (23.65%) and equigingival (26.59%) margin groups (p < .01). After adjustment for confounding factors, the adjusted odds ratio (with 95% confidence interval) for residual cement in the subgingival margin groups was 3.664 (1.71, 7.852) when compared to the supragingival and equigingival margin groups.

CONCLUSIONS

The risk of residual cement occurrence was 3.66-fold higher with a subgingival abutment margin than with supragingival and equigingival abutment margins.

Effect of abutment neck taper and cement types on the amount of remnant cement in cement-retained implant restorations: an in vitro study

PURPOSE

The present study aims to analyze the effect of abutment neck taper and types of cement on the amount of undetected remnant cement of cement-retained implant prostheses.

MATERIALS AND METHODS

Three neck taper angles (53°, 65°, 77°) and three types of cement (RMGI: resin-modified glass ionomer, ZPC: zinc phosphate cement, ZOE: zinc oxide eugenol cement) were used. For each group, the surface percentage was measured using digital image and graphic editing software. The weight of before and after removing remnant cement from the abutment-crown assembly was measured using an electronic scale. Two-way ANOVA and Duncan & Scheffe’s test were used to compare the calculated surface percentage and weight of remnant cement (α = .05).

RESULTS

There were significant differences in remnant cement surface percentage and weight according to neck taper angles (P < .05). However, there were no significant differences in remnant cement surface percentage and weight on types of cement. No interaction was found between neck taper angles and types of luting cement (P > .05). The wide abutment with a small neck taper angle showed the most significant amount of remnant cement. And the types of luting cement did not influence the amount of residual cement.

CONCLUSION

To remove excess cement better, the emergence profile of the crown should be straight to the neck taper of the abutment in cement-retained implant restoration.

[Comparison of residual cement between CAD/CAM customized abutments and stock abutments via digital measurement in vitro]

OBJECTIVE

To compare the residual cement between computer aided design/computer aided manufacturing customized abutments (CCA) and stock abutments (SA), and to evaluate the feasibility of digital measurement for residual cement volume by three-dimensional scanning.

METHODS

Twenty master models needed in this study were all taken from one 47-year-old patient with arrested periodontitis, who had already had an implant placed at his right upper central incisor site in the Department of Periodonto-logy, Peking University School and Hospital of Stomatology. After 4 weeks of soft tissue conditioning by means of customized healing abutment, the height of peri-implant soft tissue was measured, from the implant platform to mucosal margin, as 5 mm. Using customized impression coping, the impression was taken and twenty models were fabricated and allocated to 4 groups according to the type of abutments: CCA1 (5 mm transmucosal height CCA, with margin at tissue level), CCA2 (4 mm transmucosal height CCA, with 1 mm submucosal margin), SA1 (3 mm transmucosal height SA, with 2 mm submucosal margin) and SA2 (1 mm transmucosal height SA, with 4 mm submucosal margin). Crowns were cemented to the abutments, which were seated on the working models. Excess cement was removed by a prosthodontic specialist. Thereafter, the volume of residual cement was evaluated by using three-dimensional scanning technique. The area proportion of residual cement was calculated on photographs taken by a single lens reflex camera. The weight of residual cement was weighed by an analytical balance. And the correlation of residual cement volume data with residual cement area proportion or weight of residual cement acquired by traditional methods was analyzed.

RESULTS

Residual cement was observed on all the experiment samples. The residual cement volume of CCA was significantly less than that of SA [(0.635 3±0.535 4) mm³ vs. (2.293 8±0.943 8) mm³, P < 0.001]. Consistently, CCA had less residual cement area proportion and weight than those of SA [area proportion: 7.57%±2.99% vs. 22.68%±10.06%, P < 0.001; weight: (0.001 5±0.001 0) g vs. (0.003 7±0.001 4) g, P < 0.001]. The residual cement volume was strongly correlated with the residual cement area proportion and residual cement weight (r>0.75, P < 0.001).

CONCLUSION

These in vitro results suggest that CCA minimized the residual cement more effectively than SA. The method to digitally evaluate the residual cement volume is feasible, but its validity and reliability need to be further studied.

Comparison of peri-implant clinical outcomes of digitally customized and prefabricated abutments: A systematic review and meta-analysis

BACKGROUND

Digitally customized abutments are increasingly used in contemporary implant prosthodontics.

PURPOSE

This systematic review and meta-analysis aimed at comparing the peri-implant clinical outcomes of digitally customized and prefabricated abutments.

MATERIALS AND METHODS

The search strategies included electronic databases (PubMed, Embase, Scopus, and Cochrane clinical trials database) and related journals up to September, 2020. A qualitative and quantitative synthesis was performed on data extracted from the included studies.

RESULTS

Three RCTs (number of patients = 120; number of dental implants = 120) and two prospective cohort studies (number of patients = 144; number of dental implants = 144) with one to three-year follow-up periods were included. The quantitative analyses did not demonstrate a significant difference between digitally customized and prefabricated abutments for peri-implant pocket depth (P = 0.62), plaque index (P = 0.67), bleeding on probing (P = 0.43), keratinized mucosa width (P = 0.75), and pink aesthetic score (P = 0.30) at one-year follow-up visit. The qualitative analyses for marginal bone level change, calculus accumulation, implant survival rate, implant success rate, white aesthetic score, and patient-reported outcomes did not demonstrate a significant difference between two groups during 1 to 3-year follow-up visits.

CONCLUSION

The current data do not provide evidence of significant differences between two abutment fabrication methods in terms of peri-implant clinical outcomes within short-term period (CRD42020170807).

Bone Remineralization around Dental Implants following Conservative Treatment after Peri-Implantitis

The aim of this case report is to show that bone remineralization around dental implants with a history of peri-implantitis is possible after irritant factors are removed and only conservative treatment is performed. Patient came to the clinic after three years of dental implant placement complaining about swelling, sensitivity and gingiva color changes at the posterior part of the maxilla. During radiographic and intraoral examinations peri-implantitis of the #24 implant site was diagnosed. The surgical treatment method was rejected and performed conservative treatment instead. The outcome is promising; periapical radiographs three months later showed bone remineralization as well as stable bone after 10 years. A key clinical message: Bone remineralization around dental implants with a history of peri-implantitis is possible after irritant factors are removed and conservative treatment performed.

Effects of precementation on minimizing residual cement around the marginal area of dental implants

STATEMENT OF PROBLEM

Residual cement is detrimental to the long-term success of dental implants with a cement-retained restoration. The complete elimination of excess cement remains a challenge.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of precementation technique on minimizing the residual cement and retention of restorations.

MATERIAL AND METHODS

Four custom cobalt-chromium alloy (Co-Cr) abutments were manufactured by computer-aided design and computer-aided manufacturing (CAD-CAM) as precementation abutments with height and radius reductions of 25 μm (A25), 50 μm (A50), 75 μm (A75), and 100 μm (A100). Fifty CAD-CAM-fabricated standard Co-Cr abutments and corresponding crowns were randomly matched and treated as follows: 10 specimens were cemented with the conventional cementation procedure with glass ionomer cement (G0), and 40 were precemented with precementation abutments (n=10) before the definitive cementation with standard abutments (G25, G50, G75, G100). The weight of the cement in the cement space was calculated, and the marginal sealing was evaluated by using a stereoscopic microscope. The effects of precementation with resin cement on minimizing residual cement around the marginal area of dental implants were further evaluated extraorally. The influence of precementation with glass ionomer and resin cement on the retention force was analyzed by using a universal testing machine at a crosshead speed of 0.5 mm/min. One-way ANOVA was used to analyze cement mass and marginal sealing values. Two-way ANOVA was used to compare the retention forces (α=.05).

RESULTS

The cement weight of G50 (7.2 ±0.6 mg) was significantly higher than that of G25 (6.0 ±1.1 mg, P<.05), while no significant differences in cement weights were found among G50, G75, and G100. Consistently, the G50, G75, and G100 had higher marginal sealing values than that of the G25 (P<.01). Extraoral experiments showed that the precementation with A50 reduced subgingival residual cement without affecting retention.

CONCLUSIONS

These in vitro results suggest that precementation with a precisely manufactured precementation abutment minimized the residual cement around implant abutments, and 50 μm could be a preferable precementation space.

Detection of Residual Excess Zinc Oxide–Based Cement With Laser Fluorescence (DIAGNOdent): In Vitro Evaluation

Because of its importance in the development of peri-implant mucositis and peri-implantitis, detection of residual excess cement (REC) is often the focus of studies addressing cement-retained implant-supported restorations. The purpose of this study was to evaluate the sensitivity and specificity of laser fluorescence (DIAGNOdent) for detecting residual excess zinc oxidebased cement around dental implants. In this in vitro study, 15 tissue-level implants were embedded in acrylic resin. To simulate gingiva around the implants, the transgingival part of each implant was covered with a gingival mask silicon material. Cement (Tempobond; 1 × 1 × 1 mm) was applied to 30 areas, 4 mm below the gingival-mimicking line using a custom-made template. A DIAGNOdent laser device was used by 2 independent examiners to evaluate the presence or absence of cement in a selected area. The examiners were allowed to probe the gingival sulcus (2-mm depth) 2 times with a 5-minute interval between tests. The residual cement was recognized by gently walking the device tip around the implant. A detection score less than 16 indicated an absence of cement, and scores of 16 or greater indicated the presence of excess luting agent in the implant sulcus. The sensitivity and specificity of DIAGNOdent to detect REC in the sulcus were 100% and 96.67%, respectively. Based on our findings, we propose that DIAGNOdent could be used to detect REC in the sulcus of cement-retained implant supported restorations.

A systematic review of the influence of the implant-abutment connection on the clinical outcomes of ceramic and metal implant abutments supporting fixed implant reconstructions

OBJECTIVES

The objective of this systematic review was to assess the influence of implant-abutment connection and abutment material on the outcome of implant-supported single crowns (SCs) and fixed dental prostheses (FDPs).

METHODS

An electronic Medline search complemented by manual searching was conducted to identify randomized controlled clinical trials, prospective and retrospective studies with a mean follow-up time of at least 3 years. Patients had to have been examined clinically at the follow-up visit. Failure and complication rates were analyzed using robust Poisson regression, and comparisons were made with multivariable Poisson regression models.

RESULTS

The search provided 1511 titles and 177 abstracts. Full-text analysis was performed for 147 articles resulting in 60 studies meeting the inclusion criteria. Meta-analysis of these studies indicated an estimated 5-year survival rate of 97.6% for SCs and 97.0% for FDPs supported by implants with internal implant-abutment connection and 95.7% for SCs and 95.8% for FDPs supported by implants with external connection. The 5-year abutment failure rate ranged from 0.7% to 2.8% for different connections with no differences between the types of connections. The total number of complications was similar between the two connections, yet, at external connections, abutment or occlusal screw loosening was more predominant. Ceramic abutments, both internally and externally connected, demonstrated a significantly higher incidence of abutment fractures compared with metal abutments.

CONCLUSION

For implant-supported SCs, both metal and ceramic abutments with internal and external connections exhibited high survival rates. Moreover, implant-supported FDPs with metal abutments with internal and external connections for also showed high survival rates.