Stock Versus CAD/CAM Customized Zirconia Implant Abutments - Clinical and Patient-Based Outcomes in a Randomized Controlled Clinical Trial

Metal-Free Custom-Made Zirconia Implants-A Prospective 5-Year Follow-Up Single-Arm Clinical Trial

BACKGROUND

Dental implants made of zirconia (ZrO2) are a potential alternative for titanium implants in dentistry because of their good biocompatibility, mechanical properties and excellent aesthetic results. However, solid long-term scientific data to prove clinical success of ZrO2 implants are scarce.

AIM

The aim of this study was to describe and to examine the clinical performance of custom-made two-piece ZrO2 implants, to identify possible influencing factors: a) manipulation of the implant after placement and b) the occlusal scheme on the survival rate, and to evaluate the performance of the implant-supported crown. This follow-up study collected and examined the 5-year data to answer the main question: What are the survival and the success rates of custom-made ZrO2 implants in the maxillary premolar region after 5 years?

MATERIAL AND METHODS

Of the 31 included patients in this prospective 5-year follow-up single-arm clinical trial, 30 received a custom-made ZrO2 implant to replace a missing single maxillary premolar, which was subsequently restored with a lithium disilicate crown. Parameters regarding clinical performance, marginal bone-level (MBL) changes, and patient-related outcome measures (PROMs) were assessed preoperatively, at the baseline, as well as 1 and 5 years after crown placement. Chances of survival and success of the implant were calculated and displayed using Kaplan-Meier statistics. Kaplan-Meier survival analysis was also performed with stratification based on the variables "manipulation of the implant prior to impression taking" and "occlusal scheme" and compared using log-rank tests. Bone-level moderation in time was compared using a paired samples t-test. Patient's expectations and satisfaction after 5 years were compared as a measure of fulfilled expectations, using a Wilcoxon signed-rank test. Performance of the implant-supported crowns was evaluated using validated criteria.

RESULTS

Survival and success probabilities after 5 years were, respectively, 75.8% (95% CI [60.0%; 91.0%]) and 71.0% (95% CI [54.0%; 88.0%]) for the custom-made ZV3 implants. No significant differences in survival rate were found after stratification on "manipulation of the implant" and on "occlusal scheme." Mean bone-level alteration between baseline and the first follow-up was +0.06 mm (95% CI [-0.23 mm; 0.12 mm]; SD = 0.42 mm) and between baseline and the second follow-up was +0.04 mm (95% CI [-0.35 mm; 0.26 mm]; SD = 0.54 mm). Patients' satisfaction for patients with implants still in function after 5 years was 91.7% (IQR = [90.5%-97.3%]), indicating satisfaction with the treatment. Pooled satisfaction in patients with successful implants after 5 years was significantly higher than patients' expressed expectations before treatment. None of the crowns failed, and no interventions were required.

CONCLUSION AND CLINICAL IMPLICATIONS

Survival rate of these particular ZV3 implants in our study was lower than expected and clinically not acceptable. Hence, ZV3 implant placement as applied in this study cannot be recommended for clinical practice. Further research on the different appearances of mechanical failure in ZrO2 implants would be highly recommended before a larger prospective randomized clinical trial is conducted to evaluate treatment with custom-made ZrO2 dental implants.

Clinician preferences for single-unit implant restoration designs and materials: A survey of the membership of the Pacific Coast Society for Prosthodontics

STATEMENT OF PROBLEM

Clinical research has difficulty keeping pace with the rapid evolution of materials, protocols, and designs of single-unit implant restorations. The clinical design preferences of prosthodontics for different clinical scenarios are lacking.

PURPOSE

The purpose of this cross-sectional survey was to determine the current prevalence of usage of various treatment options and materials for single-unit implant-supported restorations.

MATERIAL AND METHODS

From August to September of 2022, a survey invitation was sent to members of the Pacific Coast Society for Prosthodontics (PCSP). The survey was hosted online and asked 37 questions related to the materials, protocols, and design preferences for single-unit implant-supported restorations in various clinical scenarios. The prompts included the suggestion that answers should be based on preferences for the "ideal" treatment of a hypothetical patient seeking implant treatment for the replacement of a single missing tooth.

RESULTS

Of 133 questionnaires sent via email, 35 were returned. The results are presented with histograms that use color coding as an experience proxy metric. A total of 87% of respondents was in private practice, and 60% reported having restored more than 1000 single-unit implant restorations. For the replacement of a single maxillary central incisor under ideal conditions and angulation through the palatal surface, respondents preferred bone level implants (93%) and screw-retained restorations (80%), with 50% of those being zirconia with a titanium abutment and 21% being cast metal-ceramic. For an identical scenario, except that the angulation would be through the facial surface, respondents preferred the angled screw system (55%) and cemented (41%) restorations. For the replacement of a single missing mandibular molar under ideal conditions, respondents preferred bone level implants (79%) and screw-retained restorations (79%), with 70% of those being zirconia with a titanium abutment and 17% being cast metal-ceramic.

CONCLUSIONS

While a wide range of protocols, designs, and materials exist for the replacement of a single missing tooth, these results provide a snapshot of current single-unit implant prosthodontic preferences in the Western United States and Canada.

A randomized clinical trial on zirconia versus titanium implants in maxillary single tooth replacement

OBJECTIVES

This RCT aimed to compare zirconia and titanium dental implants in the maxillary premolar region. The comparison was based on marginal bone level (MBL) changes, clinical parameters, aesthetic outcomes, and patient related outcome measures (PROMs) 1 year after prosthetic loading.

MATERIALS AND METHODS

Fifty patients were randomly assigned to receive either a zirconia (ZrO2, n = 25) implant or a titanium (Ti, n = 25) bone-level implant. Implants were provided with a lithium disilicate crown 3 months after placement. Follow-up was at 1 month and after 1 year. The primary outcome pertained to changes in MBL. Reported secondary outcomes consisted of implant survival, peri-implant tissue health, aesthetics, and PROMs.

RESULTS

Mean MBL change after 1 year was 0.01 mm (SD = 0.45; min = 0.72, max = 0.86) for ZrO2 and -0.09 mm (SD = 0.34; min = 0.53, max = -1.06) for Ti (p = .439). Scores for the other clinical outcome parameters and PROMs were generally favorable, with no significant differences. However, significant differences were found for the aesthetic outcomes regarding two criteria: (a) level of facial mucosa (p = .022), in favor of Ti, and (b) root convexity/soft tissue color and texture (p = .005) in favor of ZrO2.

CONCLUSION AND CLINICAL IMPLICATIONS

The ZrO2 and Ti implant types used in this study, replacing a single missing maxillary premolar, show a comparable outcome in terms of MBL change after 1 year. Clinical and aesthetic parameters, as well as PROMs, are favorable and similar between both implant types after 1 year of prosthetic loading. These short-term study results suggest that both are suitable for clinical use.

Evaluation of marginal bone level, technical and biological complications between screw-retained and cement-retained all-ceramic implant-supported crowns on zirconia abutment: A systematic review and meta-analysis

PURPOSE

The purpose of this study was to evaluate the difference in marginal bone level, technical and biological complications between screw-retained and cemented all-ceramic implant-supported crowns fabricated on zirconia abutment at different follow-up periods.

MATERIALS AND METHODS

Independent search was conducted in Cochrane Library, EBSCO, and PubMed/PubMed Central/MEDLINE databases and the Google Scholar search engine for prospective studies and randomized controlled trials published between January 2014 and June 2023 evaluating the marginal bone level, technical and biological complications between screw-retained and cemented all-ceramic implant-supported crowns fabricated on zirconia abutment. Meta-analysis was conducted to assess the quantitative data on the marginal bone level and biological complications.

RESULTS

A total of eight studies were included for qualitative synthesis and six studies for quantitative synthesis. For marginal bone level, no statistically significant difference was observed (P = 0.83 and P = 0.69, respectively) during the follow-up period of 3 years and 5 years. For probing depth, the cemented group showed more amount of probing depth than the screw-retained group at a follow-up period of 3 years (P < 0.05) whereas no statistically significant difference was observed at a follow-up period of 5 years (P = 0.73). For bleeding on probing, the cemented group showed more probing depth than the screw-retained group at a follow-up period of 5 years (P = 0.10).

CONCLUSION

The evidence suggests that the screw-retained group showed no statistically significant difference in marginal bone level, comparatively fewer biological complications, and relatively higher technical complications than the cemented group at different follow-up periods.

Clinical outcome of narrow diameter dental implants: a 3-year retrospective study

BACKGROUND

This study aimed to analyze the clinical outcome and complications of narrow-diameter dental implants (NDIs) (diameter ≤3.5 mm).

METHODS

The 274 NDIs that met the selection criteria from 2013 to 2018 were included in the retrospective study, and the survival rates (SVR) were compared. Mechanical complications included screw loosening and fractures of the implant components, such as the implant fixture, abutment, and prosthesis. In addition, marginal bone loss (MBL) was measured immediately after surgery and 1 year after loading.

RESULTS

The 3-year cumulative SVR was 92.4%. Nineteen fixtures failed during the follow-up. The failure rate was significantly higher (OR=4.573, p<0.05) in smokers and was significantly higher in osteoporosis patients (OR=3.420, p<0.05). The vertical and horizontal values of MBL were 0.33±0.32 mm and 0.18±0.17 mm, respectively. Mechanical complications included screw loosening (5.5%) and porcelain fracture (2.2%), but no fractures of the fixture or components were observed. The choice of titanium and zirconium (TiZr) alloy implant was significantly more frequent in the posterior region. Bone graft was significantly more frequently done in the anterior region.

CONCLUSIONS

According to the high SVR and stability of NDIs, the findings of the study suggest that NDIs may be a replacement for regular diameter dental implants (RDIs) and the use of TiZr alloy could extend the indication of NDIs. In the esthetic area, contour augmentation may be a reason for increasing the frequency of bone grafts.

CAD/CAM Abutments in the Esthetic Zone: A Systematic Review and Meta-Analysis of Soft Tissue Stability

Computer-aided design and computer-aided manufacturing customized abutments are increasingly used in everyday clinical practice. Nevertheless, solid scientific evidence is currently lacking regarding their potential advantages in terms of soft tissue stability. The main aim of this systematic review and meta-analysis was to compare the soft tissue outcomes of prefabricated versus customized (CAD/CAM) abutments. The present review was registered with PROSPERO (CRD42020161875) and the protocol was developed according to the PRISMA statement. An electronic search was performed on three databases (PubMed, Embase and Cochrane Central) up to May 2023. Data extraction was followed by qualitative and quantitative analysis of the included studies. Three randomized controlled clinical trials and three controlled clinical trials (number of patients = 230; number of dental implants = 230) with a follow-up of between 12 and 36 months were included. No significant differences were observed between prefabricated versus customized (CAD/CAM) abutments regarding midfacial mucosal recession, interproximal papillae and pink aesthetic score (PES) after 12 months. Conclusion: The potential benefits of CAD/CAM abutments on soft tissues should be better clarified in future investigations. The usage of customized CAD/CAM abutments in everyday clinical practice should be based on a careful case-by-case evaluation (CRD42020161875).

Comparative Study of Dental Custom CAD-CAM Implant Abutments and Dental Implant Stock Abutments

The implementation of CAD-CAM systems in dentistry has significantly influenced the evolution of dental implantology and implant-supported prosthetics within the past three decades. Implant-supported prostheses are comfortable and aesthetic. The prosthetic abutment has also faced a rapid design evolution, from the individualization of standard stock abutments offered by various manufacturers to a modern customization process using CAD-CAM technology. This paper presents a comparative study between 20 dental custom CAD-CAM implant abutments and 20 dental implant stock abutments, based on a set of measurements performed on the digital casts obtained from 24 cases of prosthetic rehabilitation on implants. The statistical analysis (Mann–Whitney U test) revealed significant differences between these two types of abutments: the incisal margin line diameter dimensions for custom abutments were significantly improved compared to standard abutments at the cervical level (U = 343.00, z = 3.868, p < 0.0005) and the incisal/occlusal level (U = 352.00, z = 4.112, p < 0.0005), while the inclination angle of the custom abutments relative to the 0-axis was significantly smaller than that of standard abutments (U = 115.50, z = −2.286, p = 0.022). The use of custom abutments leads to an increase in the final size of the abutment, an improvement in the retention of the prosthetic work, and reduces the angulation of the abutment in relation to the implant axis, thus decreasing the risk of unscrewing or fracturing the dental screw.

Marginal Bone Level and Biomechanical Behavior of Titanium-Indexed Abutment Base of Conical Connection Used for Single Ceramic Crowns on Morse-Taper Implant: A Clinical Retrospective Study

The goal of this retrospective clinical study was to evaluate the behavior of Morse-taper indexed abutments by analyzing the marginal bone level (MBL) after at least 12 months of function. Patients rehabilitated with single ceramic crowns between May 2015 and December 2020 received single Morse-taper connection implants (DuoCone implant) with two-piece straight abutment baseT used for at least 12 months, presenting periapical radiograph immediately after crown installation were enrolled. The position of the rehabilitated tooth and arch (maxilla or mandible), crown installation period, implant dimensions, abutment transmucosal height, installation site (immediate implant placement or healed area), associated with bone regeneration, immediate provisionalization, and complications after installation of the final crown were analyzed. The initial and final MBL was evaluated by comparing the initial and final X-rays. The level of significance was α = 0.05. Seventy-five patients (49 women and 26 men) enrolled had a mean period of evaluation of 22.7 ± 6.2 months. Thirty-one implant-abutment (IA) sets had between 12–18 months, 34 between 19–24 months, and 44 between 25–33 months. Only one patient failed due to an abutment fracture after 25 months of function. Fifty-eight implants were placed in the maxilla (53.2%) and 51 in the mandible (46.8%). Seventy-four implants were installed in healed sites (67.9%), and 35 were in fresh socket sites (32.1%). Thirty-two out of these 35 implants placed in fresh sockets had the gap filled with bone graft particles. Twenty-six implants received immediate provisionalization. The average MBL was −0.67 ± 0.65 mm in mesial and −0.70 ± 0.63 mm in distal (p = 0.5072). The most important finding was the statistically significant difference comparing the values obtained for MBL between the abutments with different transmucosal height portions, which were better for abutments with heights greater than 2.5 mm. Regarding the abutments’ diameter, 58 had 3.5 mm (53.2%) and 51 had 4.5 mm (46.8%). There was no statistical difference between them, with the following means and standard deviation, respectively, −0.57 ± 0.53 mm (mesial) and −0.66 ± 0.50 mm (distal), and −0.78 ± 0.75 mm (mesial) and −0.746 ± 0.76 mm (distal). Regarding the implant dimensions, 24 implants were 3.5 mm (22%), and 85 implants (78%) had 4.0 mm. In length, 51 implants had 9 mm (46.8%), 25 had 11 mm (22.9%), and 33 implants were 13 mm (30.3%). There was no statistical difference between the abutment diameters (p > 0.05). Within the limitations of this study, it was possible to conclude that better behavior and lesser marginal bone loss were observed when using abutment heights greater than 2.5 mm of transmucosal portion and when placed implants with 13 mm length. Furthermore, this type of abutment showed a little incidence of failures within the period analyzed in our study.

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.

Relation of CAD/CAM zirconia dental implant abutments with periodontal health and final aesthetic aspects; A systematic review

Background

Using dental implants to replacing missing teeth and satisfy both functional and aesthetic needs is one of the mainstream dental treatments. New approaches including computer-aided design and computer-assisted manufacture (CAD/CAM) have been introduced to improve these elements. This systematic review aimed to compare CAD/CAM zirconia (Zr) implant abutments with other available abutments in terms of peri-implant health and aesthetics.

Material and Methods

Five electronic databases (PubMed, Web of Science, Scopus, ProQuest, and Embase) were scoured for clinical studies evaluating Zr abutments reporting on the outcomes of interest including interproximal papilla stability (PS), papilla recession (REC), pink and white esthetic score (PES, WES), marginal bone level (MBL), color, and soft tissue contour. A hand searches in English language journals until September 2020 complemented the search. Two tools of Joanna Briggs Institute and Jaded Score calculation were used for the risk of bias assessment. No quantitative synthesis of the data was done due to high heterogeneity.

Results

A total of six studies from the 412 ones obtained from the search were included. The study designs were either prospective cohort (n=3) or randomized clinical trial (n=3). Papilla fill, WES, PES, and the distance from the bone crest of adjacent teeth to the contact point (CPB) and inter-tooth-implant distance (ITD) was not significantly different between Zr CAD/CAM and Zr stock abutments. However, soft tissue stability and REC index were better in Zr CAD/CAM abutments.

Conclusions

Higher soft tissue stability can be achieved for Zr compared to titanium abutments with either stock or CAD/CAM abutments. Key words:Dental implants, Dental abutment, Computer-Assisted Design, Computer-Aided Manufacturing, Zirconia abutment, Soft tissue stability.

Clinical assessment of different implant-supported esthetic crown systems fabricated with semi-digital workflow: Two-year prospective study

OBJECTIVE

To assess the clinical outcome of three esthetic implant-supported crown systems fabricated with semi-digital workflow and their influence on the clinical outcome of dental implants.

MATERIAL AND METHODS

A total of 30 participants had received dental implants restoring missing maxillary first/second premolars. After 6 weeks, customized zirconia abutments were early loaded. Two months later, the definitive crowns were fabricated using semi-digital workflow and cemented. According to the crown material, 3 groups were randomly allocated; group (Z): ultrahigh-translucent monolithic zirconia, group (C): resin-matrix ceramic and group (P): polyetherketoneketone veneered with light-cured composite resin. Clinical outcomes including the survival and success rates were evaluated at baseline, 6, 12, 18, and 24 months.

RESULTS

The survival rate for all studied groups was 100%, while their success rate was 100% for group (Z) and 90% for group (C) and group (P). Based on the functional implant prosthodontic score, a statistically significant difference was detected between group (Z) and group (P) (p < 0.001) as well as between group (C) and group (P) (p = 0.01).

CONCLUSIONS

The zirconia group had the most favorable clinical behavior, while the polyetherketoneketone had the least. All crown systems had comparable success rates with similar values of the peri-implant marginal bone loss.

CLINICAL SIGNIFICANCE

Using semi-digital workflow, ultrahigh-translucent monolithic zirconia, resin-matrix ceramic and polyetherketoneketone veneered with light-cured composite resin can be considered as favorable implant-supported crowns. The implant-supported crown system based on polyetherketoneketone veneered with light-cured composite resin is counted as a promising esthetic and restorative option.

Mechanical properties and marginal fit of prefabricated versus customized dental implant abutments: A comparative study

INTRODUCTION

Dental implant abutments play an important role in the health and aesthetics of soft and hard tissues around implants.

PURPOSE

To compare mechanical properties and marginal fit of prefabricated and customized dental implant abutments and provide references to evaluate the relationship between abutment choice and clinical indications.

METHODS

Titanium abutments were randomly divided into prefabricated and customized abutments. Static and dynamic loads were applied according to ISO14801:2016. Mechanical properties, including fracture strength, fatigue strength, rotational torque value, and torque loss rate, were measured. The biological properties of the implant abutments were assessed using an internal marginal fit. The samples were sliced, and the internal marginal fit was examined using a scanning electron microscope before and after cyclic loading. The length of the tight contact was calculated at the level of the conical connection, lower internal connection, and screw threads. Microleakage was evaluated by immersing the samples in 1% methylene blue and measuring the absorbance.

RESULTS

The fracture strengths of the prefabricated abutments were greater than those of the customized abutments before and after cyclic loading. The average fatigue strengths of the prefabricated and customized abutments were 350 and 300 N, respectively. The removal torque loss of the customized abutments was significantly greater than that of the prefabricated abutments. Significant differences were found in conical connection before loading, while the screw threads showed substantial differences between the two groups after loading. Microleakage in the customized abutments was significantly higher than that in the prefabricated abutments before and after loading.

CONCLUSIONS

Prefabricated abutments showed superior mechanical and biological properties compared with customized abutments in vitro, suggesting a greater risk of mechanical and biological complications occurring with the use of customized abutments. This study provides a reference for the clinical selection of implant abutments.

CAD/CAM Abutments versus Stock Abutments: An Update Review

With the evolution of CAD/CAM technology, custom titanium and/or zirconia abutments are increasingly being used, leading to several comparisons in the literature, both mechanical and aesthetic, to evaluate performance differences between these two types of abutments. Therefore, the aim of this comprehensive review is to present the most recent data on the latest comparisons between CAD/CAM and stock abutment applications. The PICO model was used to perform this review, through a literature search of the PubMed (MEDLINE) and Scopus electronic databases. CAD/CAM abutments allow individualization of abutment parameters with respect to soft tissue, allow increased fracture toughness, predict the failure mode, show no change in the fracture toughness over time, reduce the prosthetic steps, and reduce the functional implant prosthesis score and pain perceived by patients in the early stages. The advantages associated with the use of stock abutments mainly concern the risk of corrosion, time spent, cost, and fit, evaluated in vitro, in the implant–abutment connection. Equal conditions are present regarding the mechanical characteristics during dynamic cycles, screw loss, radiographic fit, and degree of micromotion. Further randomized controlled clinical trials should be conducted to evaluate the advantages reported to date, following in vitro studies about titanium and/or zirconia stock abutments.

An esthetic evaluation of different abutment materials in the anterior Maxilla: A randomized controlled clinical trial using a crossover design

PURPOSE

To assess the effect of implant abutment material and soft tissue thickness on the peri-implant soft tissue color using spectrophotometry and to evaluate gingival esthetics and patient satisfaction with three different abutments.

MATERIALS AND METHODS

Twenty-five patients with a missing maxillary tooth in the esthetic area received an endosseous implant using a two-stage protocol. Grey titanium, pink anodized titanium, and hybrid zirconia custom abutments were fabricated for each participant and inserted for one week with a cross-over design in a randomized manner. Color measurements were made using a spectrophotometer comparing midfacial peri-implant soft tissue and marginal gingiva of the contralateral tooth. CIE Lab color scale was employed following the formula: ΔE = [(∆L)² +(∆a)² +(∆b)² ] ^½ . PES scores were recorded, and patient satisfaction questionnaires were completed at each abutment change visit and at 1-year follow-up. Statistical analysis was performed using Friedman's test and the Wilcoxon signed-rank test with Bonferroni correction as well as the Mann-Whitney U test (α = 0.05).

RESULTS

Abutment material type significantly affected the ΔΕ values of the peri-implant mucosa when compared to the contralateral teeth. At baseline, the highest ΔΕ means ± standard deviation (SD) values were obtained with grey titanium (11.25 ±2.98), followed by pink anodized titanium (9.90 ±2.51), and zirconia abutments (6.46 ±1.43). Differences were statistically significant irrespective of soft tissue thickness. The highest PES values were obtained with zirconia abutments (10.88 ±0.88), followed by pink anodized titanium (10.12 ±1.13) and the lowest with grey titanium (9.68 ±1.41). PES differences were significant only for the thin soft tissue group. Regarding patient satisfaction, VAS scores for the pink anodized and zirconia hybrid abutment groups were higher than the grey titanium group for each question.

CONCLUSION

The color difference between soft tissues around teeth and implants was significant in all groups regardless of tissue thickness. The hybrid zirconia abutments resulted in the least color difference, followed by pink anodized and grey titanium. Significantly different PES values were recorded only for the thin tissue group. There was no significant difference in patient satisfaction between zirconia and pink anodized abutments at the 1-year follow up. Pink anodized abutments represent a good esthetic alternative to zirconia hybrid abutments especially in mechanically challenging situations. This article is protected by copyright. All rights reserved.

Early crestal bone loss around implants placed at previously failed sites compared with initially integrated implants: A retrospective cohort study

BACKGROUND

There is minimal information on early crestal bone loss (CBL) associated with implants placed at failed sites.

PURPOSE

This retrospective cohort study aimed to evaluate CBL of surviving and restored implants placed at previously failed sites (replaced implants [RIs]) compared to that of implants initially integrated and restored (pristine implants [PIs]), within the same subjects from implant placement to 17 months post-delivery of restoration.

METHODS

Subjects who had both PI(s) and RI(s) were recruited. The following data were retrieved: patient demographics, implant locations, types of implant failure, use of bone graft procedure(s), and intraoral radiographs at implant placement (T0), restoration delivery (T1), and the post-restoration follow-up (T2). A blinded evaluator measured crestal bone levels at T0, T1, and T2.

RESULTS

Forty-four implants (22 in the RI and 22 in the PI group) from the 22 subjects were reviewed. The 22 implants in the RI group were placed either at early failure (17) or late failure (5) sites. There was a 4.6 times higher likelihood of bone graft procedures performed in association with RIs compared to PIs when using a generalized linear mixed model. Differences in crestal bone levels were compared between the two groups at each time point. There were no significant differences in the mesial and mean crestal bone levels between the PI and RI groups. The RI group exhibited lower crestal bone levels on the distal side compared to the PI group at all time points. However, this difference was due to crestal bone level at T0 (p = 0.039) not due to implant replacement (p = 0.413) or bone graft procedure (p = 0.302) when using mixed regression modeling.

CONCLUSION

The effect of replacements of implants at failed sites on CBL was not significant. RIs, once integrated, exhibited the same pattern of CBL as pristine implants.

Screwmentable implant-supported prostheses: A systematic review

STATEMENT OF PROBLEM

Screwmentable prostheses were developed to combine the benefits of screw retention and cement retention. However, data are limited on the clinical performance of this type of prosthesis.

PURPOSE

The purpose of this systematic review was to collect scientific evidence on screwmentable prostheses and evaluate their long-term clinical behavior.

MATERIAL AND METHODS

An electronic search was conducted by 2 independent reviewers for articles published in scientific dental journals in English from 2004 to April 2020. The search strategy followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Inclusion criteria were scientific studies concerning the screwmentable type of prosthesis.

RESULTS

The search provided 494 records. Of these, 24 studies fulfilled the inclusion criteria and were included in the review. The included articles presented significant heterogeneity concerning the manufacturing process and the materials used. One randomized clinical trial, 2 prospective clinical studies, 14 in vitro studies, 3 protocol descriptions, 1 case series, and 3 case reports were included.

CONCLUSIONS

Based on the systematic search of the literature, it is concluded that the screwmentable prosthesis combines advantages of both cement-retained and screw-retained restorations, including passive fit, retrievability, excess cement control, tissue-friendly emergence profile, and improved esthetics. Nevertheless, data from well-designed clinical trials are limited, and further research is required to provide evidence on their long-term clinical behavior.

A review on patient-specific facial and cranial implant design using Artificial Intelligence (AI) techniques

INTRODUCTION

Researchers and engineers have found their importance in healthcare industry including recent updates in patient-specific implant (PSI) design. CAD/CAM technology plays an important role in the design and development of Artificial Intelligence (AI) based implants.The across the globe have their interest focused on the design and manufacturing of AI-based implants in everyday professional use can decrease the cost, improve patient's health and increase efficiency, and thus many implant designers and manufacturers practice.

AREAS COVERED

The focus of this study has been to manufacture smart devices that can make contact with the world as normal people do, understand their language, and learn to improve from real-life examples. Machine learning can be guided using a heavy amount of data sets and algorithms that can improve its ability to learn to perform the task. In this review, artificial intelligence (AI), deep learning, and machine-learning techniques are studied in the design of biomedical implants.

EXPERT OPINION

The main purpose of this article was to highlight important AI techniques to design PSIs. These are the automatic techniques to help designers to design patient-specific implants using AI algorithms such as deep learning, machine learning, and some other automatic methods.

Bias Evaluation of the Accuracy of Two Extraoral Scanners and an Intraoral Scanner Based on ADA Standards

The spread and application of computer-aided design/computer-aided manufacturing (CAD/CAM) technology have contributed to the rapid development of digitalization in dentistry. The accuracy of scan results is closely related to the devising subsequent treatment plans and outcomes. Professional standards for evaluating scanners are specified in the American National Standard/American Dental Association Standard 132 (ANSI/ADA No. 132). The aims of this study were to use the three samples mentioned in ANSI/ADA No. 132 and evaluate the accuracy and reproducibility of two extraoral scanners and an intraoral scanner based on the inspection standards recommended by ANSI/ADA No. 132. In this study, two trained operators used two extraoral scanners (E4, 3Shape, Denmark & SHINING DS100+, Shining, China) and an intraoral scanner (TRIOS SERIES3, 3Shape, Denmark) to perform 30 scans of each of the three samples at a temperature of 25 ± 2°C and export standard tessellation language files and used reverse engineering software to perform measurements and iterative nearest point matching experiments. The measured values obtained were compared with the reference values measured by a coordinate measuring machine (NC8107, Leader Metrology, USA). We performed a normal distribution test (Shapiro-Wilk test), the nonparametric Kruskal-Wallis test, and an independent-samples t-test to analyze the reproducibility of each scan for different models. The experimental results indicate that the trueness and precision of the two extraoral scanners and the intraoral scanner had a slight mean deviation. The trueness and precision of the three scanners on the curved surface and groove areas are poor. The accuracy and reproducibility of E4 outperformed SHINING and TRIOS. The iterative closest point matching experiment also showed good matching results. The two extraoral scanners and the intraoral scanner in this study can meet the basic clinical requirements in terms of accuracy, and we hope that digital technology will be more widely used in dentistry in the future.

[Prosthetic intermediaries in oral implantology: Literature review]

Prosthetic intermediaries in oral implantology are attachments that allow connection between the implant and the prosthesis itself. Although this rehabilitation has a high success rate; the selection of the prosthetic abutment represents is important in implant treatment. Currently, there is a great variety of intermediate abutments, corresponding to various techniques and materials. Prosthetic intermediaries can be classified according to the type of connection, their retention to the prosthesis, their axial relationship with the implant body, the manufacturing material and type of manufacture, or whether rehabilitation is single or multiple. This scenario can lead to doubts as to the selection of the ideal implant attachment in each case in order to achieve satisfactory rehabilitation, as well as functional and aesthetic requirements and the preservation of biological principles. Indeed, oral implantology has revolutionized dentistry and will continue to expand the range of possibilities; therefore, it is important to classify the prosthetic options available. The present literature review aims to demonstrate the different alternatives and options available for the intermediate abutments most used in implant prostheses.

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).

Anatomical Shaping for Zirconia Custom Implant Abutment to Enhance Anterior Esthetic: A Clinical Technique

Abutments are used in dentistry to attach dental crowns to dental implant. Currently, zirconia custom abutment is the one which is mostly used in restorations, since it offers several advantages, especially better esthetics and prevention from infection. Several innovations are done in the implant designs and procedures to achieve better esthetics. Computer-aided design & computer-aided manufacturing (CAD/CAM) system is widely used innovative technology in dentistry. This technology offers custom implants that help to achieve better esthetics and good internal fit. This procedure used a novel technique of anatomical modification of the final abutment incisal edge from straight anatomical edge to irregular one with a mamelon-incisal effect to enhance esthetic, shade matching, and anatomical replication of incisal structure that resembles the natural incisor. Usually, dental technicians will perform facial and incisal cut-back and apply porcelain layers to the crown in order to reproduce the translucency and the other optical effects that most closely match that of natural dentin and enamel, especially at the incisal edge. These optical effects will make the prosthetic crown look more natural and esthetically pleasant. By this presented technique will help the dental technician to achieve highly esthetic crown with completely digital workflow without the need for porcelain layering. The procedure was also followed up to 3, 6, and 12 months after the surgery and found no complications or complaints from the patient and esthetically satisfied.

Artificial intelligence in fixed implant prosthodontics: a retrospective study of 106 implant-supported monolithic zirconia crowns inserted in the posterior jaws of 90 patients

Background

Artificial intelligence (AI) is a branch of computer science concerned with building smart software or machines capable of performing tasks that typically require human intelligence. We present a protocol for the use of AI to fabricate implant-supported monolithic zirconia crowns (MZCs) cemented on customized hybrid abutments.

Methods

The study protocol consisted of: (1) intraoral scan of the implant position; (2) design of the individual abutment and temporary crown using computer-aided design (CAD) software; (3) milling of the zirconia abutment and the temporary polymethyl-methacrylate (PMMA) crown, with extraoral cementation of the zirconia abutment on the relative titanium bonding base, to generate an individual hybrid abutment; (4) clinical application of the hybrid abutment and the temporary PMMA crown; (5) intraoral scan of the hybrid abutment; (6) CAD of the final crown with automated margin line design using AI; (7) milling, sintering and characterisation of the final MZC; and (8) clinical application of the MZC. The outcome variables were mathematical (quality of the fabrication of the individual zirconia abutment) and clinical, such as (1) quality of the marginal adaptation, (2) of interproximal contact points and (3) of occlusal contacts, (4) chromatic integration, (5) survival and (6) success of MZCs. A careful statistical analysis was performed.

Results

90 patients (35 males, 55 females; mean age 53.3 ± 13.7 years) restored with 106 implant-supported MZCs were included in the study. The follow-up varied from 6 months to 3 years. The quality of the fabrication of individual hybrid abutments revealed a mean deviation of 44 μm (± 6.3) between the original CAD design of the zirconia abutment, and the mesh of the zirconia abutment captured intraorally at the end of the provisionalization. At the delivery of the MZCs, the marginal adaptation, quality of interproximal and occlusal contacts, and aesthetic integration were excellent. The three-year cumulative survival and success of the MZCs were 99.0% and 91.3%, respectively.

Conclusions

AI seems to represent a reliable tool for the restoration of single implants with MZCs cemented on customised hybrid abutments via a full digital workflow. Further studies are needed to confirm these positive results.

Standard vs customized healing abutments with simultaneous bone grafting for tissue changes around immediate implants. 1-year outcomes from a randomized clinical trial

BACKGROUND

Immediate implants have shown risks of esthetic complications. The hypothesis was that a customized healing abutment could improve the peri-implant tissue healing.

PURPOSE

To evaluate and compare the soft and hard tissue healing around immediate implants that received bone grafting and a customized vs a standard healing abutment.

MATERIALS AND METHODS

Patients, who required tooth extraction and who received an immediate implant (with an alloplastic graft material) were randomly assigned to a customized or a standard healing abutment group. Clinical and radiographic examinations were taken at baseline, at 4 and 12 months.

RESULTS

Twenty-five patients out of 61 were excluded from the study because unsuitable for immediate implantation. In total, 36 patients were randomized in the two groups. There were 17 females and 19 males (age range 23-77). No prosthetic or implant failure was registered during the study period. The Papilla Index was significantly higher in the customized than in the standard group at 4 and 12 months (P = .0002). The bone loss at mesial sites was significantly higher in the control than in the test group (P = .0014).

CONCLUSION

The customized healing abutment group showed the most favorable outcomes (in terms of PI and MBL) in case of immediate implant that received a peri-implant bone grafting procedure.

Two-part implant abutments with titanium and ceramic components: Surface modification affects retention forces-An in-vitro study

OBJECTIVES

Two-part abutments consist of titanium base and ceramic coping. Their long-term success is largely determined by the mechanical stability. The aim of the present study was to investigate the retention forces of two-part implant abutments. The study included zirconia and lithium disilicate ceramics copings, with different surface treatments and resin-based luting agents.

MATERIAL AND METHODS

The analysis of retention forces was based on a total of 70 test specimens. Seven surface modifications and three resin-based luting agents were employed for the bonding of components in the seven groups (n = 70). All surfaces of titanium bases-except for a control-were pretreated with aluminum oxide blasting, either alone or in combination with surface activating primers. Surfaces of ceramic copings were also treated mechanically by sandblasting, either alone or with acid etching or different primers. All specimens underwent thermal aging (10⁴ cycles, 5°C/55°C). The retention forces between the two parts were measured with a pull-off test. The results were analyzed by two-way ANOVA statistics. Fracture patterns were evaluated by light and scanning electron microscopy.

RESULTS

No mechanical pretreatment of the titanium (group 2) base resulted in the lowest retention. The combination with Monobond plus leads to the highest pull-off forces for both ceramic materials.

CONCLUSIONS

Surface modifications and resin-based agents influence the retention of components of two-part abutments. Lithium disilicate ceramic copings reached comparable results of retention to the typically used zirconia copings.

Correlation Between Conditional Approval and Customized Bone Implant Devices

This report aims to summarize key concerns regarding customized devices and conditional approval during the premarket evaluation of bone implants, and to explore the correlation between them. Based on the experience of approval of the first domestic custom-designed bone implant, we consider the process of gaining conditional approval for urgently-needed medical devices and medical devices for rare diseases, as well as the guidance available for clinical investigation. We also streamlined the scientifically administrative concept of this unique device, from the design and development of premarket technical evaluation to continuous post-market study. The present study found that those two aspects have certain connections, but they are not directly correlated to each other. In contrast to the USA, Canada, Australia and the EU, where regulations and guidelines have been established for the use of customized devices, in this regard, China is still it its infancy. Thus, there is considerable potential for China to develop and perfect the policies relating to customized devices and to develop relevant strategies to ensure their efficacy with the aid of conditional approval. Appropriate scientific conditional approval for mass production of individualized anatomy-matching bone implants could become a valuable approach for precision medicine.

Mechanical Outcomes, Microleakage, and Marginal Accuracy at the Implant-Abutment Interface of Original versus Nonoriginal Implant Abutments: A Systematic Review of In Vitro Studies

Purpose

Instead of original abutments, compatible abutments are often selected for financial reasons. The present study aimed to evaluate mechanical outcomes, microleakage, and marginal accuracy at the implant-abutment interface of original versus nonoriginal implant abutments.

Study Selection

Search strategy encompassed literature from 1967 up to March 2017 to identify relevant studies meeting the inclusion criteria. The following electronic databases were consulted: PubMed database of the U.S. National Library of Medicine, Embase (Excerpta Medica dataBASE), and the Grey Literature Database (New York Academy of Medicine Grey Literature Report). Quality assessment of the full-text articles selected was performed. Abutments were classified in original (produced by the same implant manufacturer), nonoriginal certified (produced by a third-party milling center, certified by implant companies), and nonoriginal compatible (produced by a third-party milling center for similar connections).

Results

A total of 16 articles fulfilled inclusion criteria and quality assessment and were selected for the qualitative analysis. All of the included studies were in vitro research with high or moderate risk of bias and reported data from 653 implant abutments. Original and nonoriginal certified abutments showed better results in terms of mechanical outcomes, microleakage, and marginal accuracy compared to nonoriginal compatible abutments.

Conclusions

Following the clear warnings coming from the present systematic review, clinical suggestions regarding the effect of a nonoriginal abutment can be drawn. However, in vivo, long-term, randomized controlled trials are needed to provide definitive clinical conclusion about the long-term clinical outcomes of original and nonoriginal abutments.

Histological and micro-CT analysis of peri-implant soft and hard tissue healing on implants with different healing abutments configurations

OBJECTIVE

The aim of this study was to assess the effect of different abutment configurations on peri-implant soft and hard tissue healing.

MATERIALS AND METHODS

Two-piece dental implants, 3.5 mm in diameter and 8 mm in length, were placed in four beagle dogs. Two different transmucosal healing abutment configurations were randomly selected: one with a wide emergence profile (WE) (45° angulation with implant long axis) and the other with a narrow emergence profile (NE) (15° angulation with implant long axis). After four months of healing, the animals were sacrificed. Micro-CT scans were taken for mesio-distal analysis; subsequently, the biopsies were prepared for bucco-lingual histometric analyses. Several measurements were taken using the following reference points: marginal mucosal level (MML), apical barrier epithelium (aBE), implant shoulder (IS), marginal bone crest (BC), and first bone-to-implant contact (fBIC).

RESULTS

In the micro-CT analysis, the distance from IS-fBIC was 1.11 ± 0.66 mm for WE and 0.12 ± 0.21 mm for NE (p = 0.004). The IS-BC of WE was -0.54 ± 0.80 mm, whereas NE presented 0.76 ± 0.48 mm (p = 0.002). The histometric analysis showed that both groups presented comparable dimensions of peri-implant biologic width (p > 0.05). However, in the distance from IS to BC, the WE showed a mean distance of -0.66 ± 0.78 mm while NE was 0.06 ± 0.42 mm (p = 0.039); the IS to fBIC was 0.89 ± 0.68 mm for WE while NE was 0.30 ± 0.30 mm (p = 0.041).

CONCLUSION

The design of the transmucosal component can influence the establishment of the peri-implant biologic width. The flat and wide emergence profile induced an apical displacement of the peri-implant biologic width and more bone loss.

Impact of different placement depths on the crestal bone level of immediate versus delayed placed platform-switched implants

PURPOSE

The preservation of peri-implant bone is one requirement for long-term success of dental implants. The purpose of this study was to evaluate the impact of subcrestal placement on the crestal bone level of immediate versus delayed placed implants after loading.

MATERIALS AND METHODS

In this retrospective study, data of 159 patients who received 330 implants was analyzed. Implants were placed subcrestally, crestally or supracrestally into fresh sockets or healed sites. Vertical bone level height was assessed radiographically and implants were followed up annually. The influence of patient and implant related risk factors for peri-implant bone loss was evaluated using a linear mixed model.

RESULTS

Depth of implant placement was significantly correlated with peri-implant bone loss (P = 0.001, 95% CI). Least effective loss of crestal bone was determined when implants were placed between 1 mm and 1.99 mm subcrestally. Smoking significantly enhanced the risk of peri-implant bone loss (P = 0.04, 95% CI). Immediate implant placement was not positively correlated with peri-implant bone loss (P = 0.51, 95% CI).

CONCLUSION

Within the limits of this study, implant placement 1.08 mm subcrestally may be recommendable in order to avoid supracrestal expositions of platform-switched titanium implants over time.

Fractographic analyses of failed one-piece zirconia implant restorations

BACKGROUND

Promising results of initial clinical trials with yttria-stabilized zirconia have led to more extensive use of zirconia in dental implant superstructures. The applications have extended to abutments and complex individually designed crown-abutment one-piece structures. Little is known about their clinical success and the primary cause of failures.

PURPOSE

The aim of this study was to identify the cause of fracture of retrieved implant-retained one-piece prostheses that failed during clinical use.

METHODS

Nine fractured restorations were analyzed with fractographic methods and their fracture origins were identified.

RESULTS

All but two of the fractures originated in an area of tight contact between the implant or titanium screw and the abutment base. Results of the evaluation showed that zirconia-based implant restorations with very thin walls in the region connecting the prosthesis to the implant are vulnerable to damage from the screw retaining process and fracture from non-axial loads. Two restorations failed due to veneer fractures.

SIGNIFICANCE

The findings suggest that large crowns on narrow implants or implants with internal fixation should preferably not be made with zirconia abutments, or that a new design approach should be considered.

Fractography of clinically fractured, implant-supported dental computer-aided design and computer-aided manufacturing crowns

Today, a substantial part of the dental crown production uses computer-aided design and computer-aided manufacturing (CAD/CAM) technology. A recent step in restorative dentistry is the replacement of natural tooth structure with pre-polymerized and machined resin-based methacrylic polymers. Recently, a new CAD/CAM composite was launched for the crown indication in the load-bearing area, but the clinical reality forced the manufacturer to withdraw this specific indication. In parallel, a randomized clinical trial of CAD/CAM composite crowns luted on zirconia implant abutments revealed a high incidence of failure within the first year of service. Fractured crowns of this clinical trial were retrieved and submitted to a fractographic examination. The aim of the case series presented in this article was to identify failure reasons for a new type of CAD/CAM composite crown material (Lava Ultimate; 3M Oral Care, St. Paul, Minnesota, USA) via fractographic examinations and analytical assessment of luting surfaces and water absorption behavior. As a result, the debonding of the composite crowns from the zirconia implant abutments was identified as the central reason for failure. The adhesive interface was found the weakest link. A lack of silica at the zirconia surface certainly has compromised the bonding potential of the adhesive system from the beginning. Additionally, the hydrolytic stress released from swelling of the resin-based crown (water absorption) and transfer to the luting interface further added to the interfacial stress and most probably contributed to a great extend to the debonding failure.