Single Dental Implant Restoration: Cemented or Screw-Retained? A Systematic Review of Multi-Factor Randomized Clinical Trials

Abstract

Background: Dental implant rehabilitation has significantly advanced prosthodontics by providing a reliable, long-lasting solution for missing teeth. This systematic review compares the clinical, technical, and biological outcomes of cemented versus screw-retained single dental implant restorations based on randomized clinical trials (RCTs). Materials and Methods: This review included recent human and in vitro studies focusing on the keywords “cemented vs. screw-retained” and “dental implant”. Eight studies met the inclusion criteria, which investigated parameters, including implant survival rate, bleeding on probing (BOP), probing depth, plaque index, marginal bone loss (MBL), cytokine concentrations, mechanical complications, esthetic outcomes, patient satisfaction, treatment time, and technical failures. Results: The primary outcomes, BOP and MBL, did not statistically differ between cemented and screw-retained implants (p-values for MBL and BOP are 0.5813 and 0.8093, respectively). The reviewed studies, including RCTs, split-mouth studies, and clinical evaluations, demonstrated comparable clinical, technical, and biological outcomes between the two restoration methods. Conclusions: Screw-retained and cemented dental implant restorations exhibit similar clinical, technical, and biological outcomes. Screw-retained restorations offer advantages such as retrievability, ease of repair, and predictable passive fit, while cemented restorations provide superior esthetics. The risk of peri-implant complications due to residual cement in cemented restorations must be considered. Future research should explore long-term stability and the impact of different prosthetic protocols on peri-implant health.

1. Introduction

1.1. Rationale

Dental implant rehabilitation has revolutionized the field of prosthodontics, providing a reliable and long-term solution for the replacement of missing teeth. The history of dental implants dates back thousands of years, with evidence of early attempts to restore missing teeth found in ancient civilizations. However, in the 20th century, significant advancements were made in implantology, leading to the development of modern dental implant systems. The concept of osseointegration, pioneered by Professor Per-Ingvar Brånemark in the 1950s, laid the foundation for the success of dental implants. Through his research, Brånemark discovered that titanium implants could fuse with the surrounding bone, providing a stable foundation for tooth replacement. This discovery marked a turning point in implant dentistry, and titanium became the material of choice for dental implant fixtures [1].

Over the years, different types of dental implant-supported prosthodontics have been developed to meet the varying needs of patients [2]. Single-tooth implant restorations are commonly used to replace missing teeth. These restorations consist of a dental implant fixture that serves as the artificial root and a crown that mimics the appearance and function of a natural tooth. Single-tooth implant restorations offer excellent esthetics and function, providing a durable and long-lasting solution. In cases where multiple adjacent teeth are missing, implant-supported fixed partial dentures, also known as implant bridges, can be utilized [3]. Choosing between a screwed or cemented prosthesis is crucial in dental implant rehabilitation. Both options have advantages and limitations, and the decision depends on various factors, including clinical requirements, esthetic demands, and patient preferences [4,5].

Screw-retained restorations involve the direct attachment of the prosthesis to the dental implant fixture using a screw. This method offers several benefits, such as retrievability, ease of repair, and predictable passive fit. Screw-retained restorations allow straightforward maintenance and facilitate access to the implant site for cleaning and assessment. Additionally, they eliminate the potential risks associated with residual cement, which can lead to peri-implant complications and tissue inflammation. On the other hand, cemented restorations are affixed to the dental implant abutment using dental cement. This technique provides superior esthetics as the cemented prosthesis can seamlessly integrate with the surrounding natural dentition. Cemented restorations offer better access for creating lifelike contours and surface characteristics, enhancing esthetic outcomes. However, residual cement can pose significant risks, such as peri-implant inflammation, tissue complications, and increased susceptibility to infection [6,7,8].

In recent years, a hybrid approach combining both screw-retained and cemented components has gained popularity. This technique, known as the screw–cement-retained prosthesis, balances retrievability and esthetics. The prosthesis is secured to the dental implant abutment using a screw, while the superstructure is cemented onto the framework. This hybrid approach allows easier retrievability while maintaining optimal esthetic results [9].

1.2. Objectives

The objective of this systematic review is to evaluate the impact of different dental prosthesis protocols, cemented single-tooth dental implant rehabilitation and screwed ones, on the primary outcomes of bleeding on probing (BOP) and marginal bone level (MBL) following dental implantation procedures. The review also aims to assess secondary effects such as implant survival rates, patient satisfaction, esthetic outcomes, and complications, including peri-implantitis and prosthetic failures. This review aims to comprehensively understand the effectiveness and long-term stability of dental prostheses and cementation techniques in promoting peri-implant health by synthesizing available evidence in randomized clinical trials.

2. Materials and Methods

2.1. Eligibility Criteria

The inclusion criteria are as follows:

• Recent studies (last 20 years) have to avoid running into drugs or formulations that are no longer used and safe;
• Randomized clinical trials;
• Single-implant restoration type (screwed or cemented);
• Follow-up time of at least 12 months.

The exclusion criteria are as follows:

• Studies on subjects with absolute contraindications to dental implant therapy (heart disease, cardiomyopathies, ciliopathies or recent heart attack, ongoing oncological diseases, bone diseases such as rickets or decalcification, bisphosphonate therapy for the treatment of intravenous osteoporosis, psychiatric illness, or alcohol and/or drug abuse [10]);
• In vitro or silica studies;
• Case reports.

2.2. Information Sources

The research sources are the most common and reliable scientific research channels according to the scientific community:

• Scopus Elsevier;
• Web of Science;
• Google Scholar;
• Pubmed.

2.3. Search Strategy and Selection Process

The search strategy planned to insert the following word string in the information sources, according to the previous paragraphs (1 June 2023):

“(cemented) AND/OR (screw-retained) AND (dental implant)”.

Furthermore, by inclusion and exclusion criteria, recent works were considered, and only some types of studies were selected using the filters already present in the scientific information sources.

Subsequently, once the studies were obtained, they were subjected to a first screening through independent reading by the authors of “title” and “abstract”, and then the full text was read (logically, if they were not discarded earlier as they did not meet the inclusion criteria already when reading “title” or “abstract”).

The revision method is based on the PRISMA statement, with methodology and subdivision in the manuscript according to their parameters and the presence of the PRISMA flow chart [11,12,13]. Keywords for this systematic review were selected using medical subject headings (MeSHs). In the process of identifying the study objective, the PICO (Population, Intervention, Comparison, Outcome) system was utilized [14], with the following question:

Are there different outcomes in single-tooth cement-retained or screwed-retained dental implant restorations?

2.4. Data Items

The parameters considered are all those extrapolated from the individual articles as outcomes (

Table 1. Main investigated outcomes.

Clinical And Periodontal Outcomes	BOP: Bleeding On Probing PI: Plaque Index Mpi: Modified Plaque Index PES/WES KM: Keratinized Mucosa MT: Mucosal Thickness PPD: Probing Depth Msbi: Modified Sulcus Bleeding Index
Instrumental Or Radiographical Outcomes	Spectrophotometry MBL: Marginal Bone Level
Biological, Laboratory, and Microbiological Outcomes	TNF-A: Tumor Necrosis Factor Alpha IL-6: Interleukina-6 Bacterial Counts
Technical and Prosthetic Outcomes	Technical Failure
Patient-Related Outcomes	OHIP: Oral Health Impact Profile Proms: Patient-Reported Outcome Measures Patient Satisfaction Treatment Time
Others	FIPS: Functional Implant Prosthodontic Score Treatment Time

):

2.5. Study Risk of Bias Assessment

Addressing the risk of bias is essential in a systematic review. Considering factors such as study design, quality, population, intervention, and outcomes helps minimize bias and enhance the overall quality and reliability of the evidence. Continued research and vigilance in evaluating bias are necessary to ensure accurate and dependable results in systematic reviews. The Risk of Bias 2 (RoB 2) tool, developed by the Cochrane Collaboration, assessed the randomized clinical trials (RCTs) included in this review. This tool evaluates bias across five domains: randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome, and selection of the reported result. Each study was rated as having “low risk”, “some concerns”, or “high risk” of bias for each domain. The comprehensive assessment allowed for a rigorous evaluation of potential biases affecting the included studies, contributing to the reliability of the review’s conclusions [15] (

Table 2. Risk of bias definition according to RoB2 Tool (Green: Low; Yellow: Medium or Some Concerns; Red: High or Not definite (ND)).

	Naumann et al. [16]	Lv et al. [17]	Weigl et al. [18]	Kraus et al. [19]	Thoma et al. [20]	Amorfini et al. [21]	Cacaci et al. [22]	Thoma et al. [23]
Clearly stated aims/objectives	Low	Low	Low	Low	Low	Low	Low	Low
Detailed explanation of sample size calculation	Low	Low	Low	Low	Low	Low	Low	Low
Detailed explanation of sampling technique	Low	Low	Low	Low	Low	Low	Low	Low
Details of comparison group	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns
Detailed explanation of methodology	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns
Operator details	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns
Randomization	Low	Low	Low	Low	Low	Low	Low	Low
Method of measurement of outcome	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns
Outcome assessor details	Low	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns
Blinding	ND	ND	ND	ND	ND	ND	ND	ND
Statistical analysis	Low	Low	Low	Low	Low	Low	Low	Low
Presentation of results	Low	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns	Some Concerns

).

2.6. Synthesis Methods

Synthesizing the data collected from multiple studies is a crucial step in a systematic review. The synthesis methods used in a systematic review can vary depending on the specific objectives of the review and the type of data being analyzed; in this case, the authors have performed a narrative synthesis. A narrative synthesis is a method of summarizing the findings of multiple studies in a narrative format. This method is appropriate when the studies included in the review are heterogeneous and cannot be easily compared [24].

2.7. Registration

Details of the protocol for this systematic review were registered in the Prospective International Register of Systematic Reviews (PROSPERO) with ID 435028 on 13 June 2023. The final registration number is CRD42023435028. PROSPERO serves as a global repository of systematically documented evaluations in healthcare, social well-being, public welfare, educational advancements, criminal justice, and worldwide progress, encompassing outcomes associated with well-being.

3. Results

3.1. Study Selection

From a first search on the scientific search engines, as explained in Section 3.2, 208 results were obtained, some of which date back to 1980. Only full texts from the last 20 years were considered, and several 14 results were obtained. Following an analysis of the results by first reading titles and abstracts, and in the event of the uncertainty of the full text by two independent authors, the results selected and compatible with the review criteria are 14. This review presents the method used (see Section 2) and the PRISMA flow chart (Figure 1).

3.2. Study Characteristics

The main characteristics of the selected studies are included in

Table 3. Study characteristics.

Authors	Year	Dental Implant Position
Naumann et al. [16]	2023	ND
Lv et al. [17]	2021	Anterior region
Weigl et al. [18]	2019	Bilateral premolar or molar
Kraus et al. [19]	2019	Anterior and posterior
Thoma et al. [20]	2018	Anterior region
Amorfini et al. [21]	2018	Anterior region
Cacaci et al. [22]	2017	Premolar and molar
Thoma et al. [23]	2016	Anterior region

below according to the following parameters (Table 3):

• Authors—Authors of the single study;
• Year—Year of publication of the study;
• Dental implant position—Position of rehabilitation.

3.3. Results of Individual Studies

Naumann et al.’s [16] manuscript investigated the differences between screw-retained and cemented crowns in single-tooth monolithic lithium disilicate cases. They evaluated a monolithic hybrid abutment for dental implants; in particular, they considered 20 subjects and randomly assigned them to the test or control group. They used only titanium implants with internal conic connections. They evaluated different parameters like Functional Implant Prosthetic Score (FIPS), Oral Health Impact Profile (OHIP) score, and patient satisfaction using patient-reported outcome measures (PROMS). One restoration failed after six months due to loss of adhesion between the Ti base and individual abutment; it was the only early failure.

Lv et al. [17] evaluated clinical, radiographic, and immunological outcomes of angulated screw-retained and cemented single-implant crowns. In their RCT, the authors randomly assigned each of the 56 subjects to a group; after that, they evaluated different parameters like implant survival rate, bleeding on probing rate (BOP), probing depth (PD), modified plaque index (mPI), marginal bone loss (MBL), concentrations of cytokines (TNF-α and IL-6) in crevicular fluid, mechanical complications, and pink esthetic score/white esthetic score (PES/WES). Weigl et al. [18] compared the clinical performance of screw-retained and cement-retained dental implant crowns. They used zirconia monolithics for screw ones and porcelain fused to metal for cemented ones. In this split-mouth study, 22 patients received two dental implants in the premolar/molar region. The authors evaluated clinical parameters (BOP, plaque index (PI)), soft-tissue health, crestal-bone-level changes (MBL), technical complications, and the patient’s subjective feelings. They reported no implant loss and minor technical failures in both groups during the follow-up period. Kraus et al. [19], in their RCT, tested the use of cemented dental implant restoration vs. screwed ones and evaluated clinical, technical, and biological outcomes in the aesthetic zone. Forty-four patients underwent dental implant surgery and prosthodontic restoration and were followed up for three years. The authors evaluated biological and radiographical aspects at every recall, and technical outcomes were assessed using the United States Public Health Service (USPHS) criteria. They recorded one implant loss and some reconstruction loss. Thoma et al. analyzed the clinical, microbiological, and histological outcomes of cemented or screw-retained veneers on 44 patients in the anterior region. They evaluated the previous parameters in four different groups: cement-retained with submucosal veneering, cement-retained without submucosal veneering, screw-retained with submucosal veneering, and screw-retained without submucosal veneering, in all cases with a zirconia abutment. Amorfini et al. [21] compared clinical outcomes of screw-retained and cemented single crowns on zirconia abutment of dental implants. Thirty-two patients received a dental implant in the anterior area. Prosthetic (prosthetic crown (PC) and tooth crown (TC) indexes) and biological complications like MBL, mPI, PPD, PI, mucosal recession, and PES/WES score were followed up to 10 years. They did not record any implant failure in this period. Cacaci et al. [22], in their clinical study, evaluated the performance of zirconia crowns considering the type of retention screw vs. cement. They performed this study using 114 dental implants in the molar and premolar regions on 58 patients. The authors evaluated mPI and sulcus bleeding index (mSBI); technical failure as fractures and surface qualities of marginal fitting were assessed—a previous study by Thoma et al. [23] tested the esthetic outcome and mucosal quality of veneering or not zirconia abutments on dental implants. They randomly assigned one of the 44 single-tooth dental implant restorations to one of the four groups: cemented, screw-retained, a reconstruction based on white zirconia abutments, and ones on pink-veneered zirconia abutments. Esthetic outcomes have been considered based on a spectrophotometric evaluation of peri-implant mucosal color; they measured the mucosal thickness, too.

The results present in these selected studies will be listed below in

Table 4. Selected studies: individual results.

Authors	Sample Size	Type of Groups	Outcomes	Main Outcomes	Follow-Up	Dental Implant	Statistic
Naumann et al. [16]	20 patients	Monolithic hybrid abutment crowns (screw-retained) vs. monolithic hybrid abutments with adhesively cemented monolithic single-tooth crowns	FIPS; OHIP; treatment time; PROMs		36 months	CONELOG SCREW-LINE; Camlog Biotechnologies, Basel, Switzerland, implants with in internal conical connection, beveled implant shoulder angle 45° platform switching	No differences, p > 0.05
Lv et al. [17]	56 patients	Angulated screw-retained vs. cemented single-implant crowns	BOP; PD; mPI; MBL; TNF-α; IL-6; PES/WES	BOP; MBL	1 year	Nobel Replace Conical Connection Implants and Nobel Active Internal implants 3.5 mm in diameter and 8–15 mm in length (Nobel Biocare, AB, Goteborg, Sweden)	BOP lower in screwed group, p = 0.018; TNF-α higher in screwed group p = 0.019; no significant differences in other groups
Weigl et al. [18]	22 patients with 44 dental implants	Screw-retained, monolithic, zirconia, and cemented porcelain-fused-to-metal (PFM) implant crowns	BOP; PI; MBL; technical failure; patient satisfaction	BOP; MBL	1 year	Ankylos® implants of 3.5 mm diameter (Dentsply Sirona Implants, York, PA, USA	BOP higher in cemented group, p = 1.000; PI higher in cemented group, p = 0.240; no statistical differences in other parameters
Kraus et al. [19]	44 patients	Cemented restoration vs. screw-retained restoration	Clinical parameters, radiographical parameters, MBL, biological parameters, technical parameters	MBL	3 years	OsseoSpeed, DENTSPLY Implants, Mölndal, Sweden	MBL, no differences, p = 0.864; no differences for the other outcomes
Thoma et al. [20]	44 patients	Cement-retained with submucosal veneering vs. cement-retained without submucosal veneering vs. screw-retained with submucosal veneering vs. screw-retained without submucosal veneering	Clinical parameters: BOP; PD; PI; KM; MT; microbiological parameters (bacterial count); histological parameters (inflammatory cell count)	BOP	1 year	OsseoSpeed, ASTRA TECH Implant System, DENTSPLY Implants, Mölndal, Sweden	BOP was lower in screwed groups, p < 0.02; Tannerella forsythia and Peptostreptococcus micro counts were higher in cemented groups; no statistical differences for other outcomes, p > 0.05
Amorfini et al. [21]	32 patients	Ceramic veneer fused directly on the zirconia abutment vs. a porcelain-fused-to-zirconia crown cemented on a customized zirconia abutment	PPD; mPI; BOP; papilla index; MBL; PES/WES; prosthetic complications; mechanical complications; biological complications	BOP; MBL	10 years	Tissue Level implants (Straumann AG)	MBL after 10 years was higher in cemented group, p < 0.05; papilla grew in both groups in the first 2 years, p < 0.05; No statistical differences in other outcomes, p > 0.05
Cacaci et al. [22]	58 patients with 114 dental implants	Screw-retained vs. cement-retained single crowns	mPI; mSBI; technical failures (fractures, surface qualities, marginal fitting)		36.9 months	Camlog Promote/Promote Plus; Conelog, Wimsheim, Germany	No statistical difference for outcomes, p > 0.05
Thoma et al. [23]	44 patients	Cemented vs. screw-retained reconstructions (based on white zirconia abutments or pink-veneered zirconia abutments)	Spectrophotometry; mucosal thickness		Not specified (allocation after implant healing)	OsseoSpeed, DENTSPLY Implants, Mölndal, Sweden	Higher mucosal thickness value in nonveneered abutment, p < 0.032

and divided as follows:

• Authors—Authors of the single study;
• Sample size—Sample size of the study (number of implants if not otherwise specified);
• Types of groups—a subdivision of the groups and types;
• Outcomes—principal data results of the study;
• Main outcomes—Data about the main outcomes of this study;
• Follow-up—maximum follow-up;
• Dental implant—the type of dental implant used;
• Statistic—statistical data (respectively, for “main outcome results” and separated by semicolon);

The results present in these selected studies will be listed below in

Table 5. Selected studies: individual results.

Outcome	Author	Difference between Data
		Screwed	Cemented
PI	Weigl et al. [18], Thoma et al. [20]	No visible plaque: 86.4% Thin film of plaque: 9.1% Moderate plaque: 4.5%; 4.85 ± 15.15	No visible plaque: 72.7% Thin film of plaque: 27.3% Moderate plaque: 0; 5.65 ± 24.1
mPI	Amorfini et al. [21], Cacaci et al. [22], Lv et al. [17]	0.1 (0.2); 0.6 ± 0.1; 0.19 ± 0.32	0.1 (0.3); 0.5 ± 0.6; 0.30 ± 0.47
PES/WES	Amorfini et al. [21], Lv et al. [17]	PES 7.7 WES ND: PES 12.42 ± 1.28 WES 9.29 ± 0.75	PES 7.9 WES 8: PES 12.24 ± 1.69 WES 9.40 ± 0.65

and divided as follows:

• Outcome—Results considered, only comparable data have been considered in this table;
• Authors—Authors of the single study;
• Difference between data—Separated by numbers and semicolon, respectively, in order of author names;

  ○

  Screwed—Data at 12 months;

  ○

  Cemented—Data at 12 months.

3.4. Results of Syntheses

Naumann et al. [16], in their RCT, showed no statistical differences in investigated parameters between screw-retained monolithic hybrid abutment crowns and cemented ones using lithium disilicate. Lv et al. [17], in their RCT, showed no dental implant failure in the esthetic region after one year of examination. BOP was significantly lower in the screw-retained group but with a higher value of TNF-α; no other significant differences were evaluated between groups.

Weigl et al. [18] showed a higher value of BOP in cemented restoration (double) with higher plaque presence. According to the authors, the restoration type is independent of MBL. Patients reported higher satisfaction in both groups despite three technical failures in the screwed group and four in the cemented one. Kraus et al. [19], in their RCT, evaluated different biological, clinical, technical, and radiographical parameters. They did not record statistical differences between groups’ biological, technical, and radiographic outcomes. One merit to be reported in this context is that a cemented crown had to be removed because of peri-implant disease. Thoma et al. [20] showed minimal differences between their four examined groups except for one value, BOP. BOP was higher in the two cemented groups compared to the screwed ones. Descriptive and quantitative histological examination showed a higher inflammatory reaction in cemented groups with more inflammatory cells. Microbiological analysis showed similar values except for two species, Tannerella forsythia and Peptostreptococcus micros, found in the cemented groups with a higher count. Amorfini et al. [21] showed no prosthetic complications in both groups or significant differences in biological parameters such as PPD, mPI, BOP, or PES/WES. Still, there was some data to report about MBL and PI. MBL ranged between 0 and 1.75 mm in both groups; after ten years, the median value was 0.82 mm and 0.95 mm for screwed and cemented groups, respectively (in the Section 3, this manuscript reports erroneously published inverted data).

The papilla index fluctuated between 1 and 3 from the prosthesis to all periods; the peri-implant papilla grew in both groups in the first two years. Cacaci et al. [22], after a mean follow-up period of 36.9 months, reported just 1.8% of porcelain veneering fractures and chipping in just two cemented cases. Despite the lower value of bleeding in screw-retained restoration, this and all the other outcomes did not show any statistical difference in this study. Thoma et al. [23] obtained interesting data about esthetic outcomes; a pink veneered abutment seems to have a better impact from an esthetical point of view despite thinking the mucosal thickness was sacrificed. They did not highlight differences between screw- and cemented-retained restorations.

Certainty of Evidence

Present assessments of certainty (or confidence) in the body of evidence for each outcome assessed in this manuscript vary depending on the specific study and the available data. The following assessments provide a general overview:

• Bleeding on Probing (BOP): The evidence for BOP outcomes is moderately sure. This assessment is based on including randomized clinical trials (RCTs), split-mouth studies, and clinical evaluations in the review. These study designs contribute to a relatively robust body of evidence. However, some limitations regarding study quality, potential biases, and heterogeneity among the included studies may still exist.
• Marginal Bone Level (MBL): The body of evidence for MBL outcomes is also moderately certain. Like BOP, the evidence is derived from various study designs, including RCTs, split-mouth studies, and clinical evaluations. While these studies provide valuable information, variations in methodologies, sample sizes, and follow-up periods may impact the overall certainty of the evidence.
• Implant Survival Rate: The certainty in the body of evidence for implant survival rate outcomes is relatively high. Implant survival is a well-documented and commonly reported outcome in dental implant research. Including multiple studies investigating this parameter contributes to a robust body of evidence, enhancing the certainty of the findings.
• Patient Satisfaction and Esthetic Outcomes: The certainty in the evidence for patient satisfaction and esthetic outcomes could be much higher. These outcomes are often subjective and influenced by individual preferences and perceptions. The available studies may have variations in assessment methods, follow-up periods, and sample sizes, leading to potential heterogeneity and lower certainty for the evidence.
• Technical Failures and Complications: The certainty of the evidence for technical failures and complications is variable. While the studies in the review provide insights into these outcomes, there may be variations in definitions, reporting methods, and follow-up periods. Consequently, the certainty of the evidence may range from low to moderate, depending on the specific outcome and available data.

It is important to note that these assessments are generalizations and may not apply uniformly to all studies included in the review. The overall certainty in the body of evidence should be interpreted cautiously, considering the specific characteristics of each study and the limitations inherent in the available data.

This study’s decision to focus on a statistical analysis of MBL (marginal bone loss) and BOP (bleeding on probing) was driven by specific research objectives, clinical relevance, and comparability. Among the available parameters, MBL and BOP were the only ones directly comparable across different groups or time points, allowing for meaningful statistical comparisons. Additionally, these two parameters are widely recognized as essential indicators of periodontal health and disease progression, further justifying their selection for analysis in this study. This targeted approach ensured that the analysis captured the most relevant and comparable data to draw accurate conclusions about the intervention’s effects on periodontal outcomes. Only manuscripts that contain enough data to perform a statistical analysis have been considered in these tables. (

Table 6. MBL ×100 multiplied sample chi-square test: the chi-square is 1.0849. The p-value is 0.581319. The results are not significant at p < 0.05. “Cemented” and “Screwed” columns show the median data obtained, “Row Totals” are the total of these data, and “Sample Size” represents the number of dental implant restorations investigated. The first column indicates the type of statistical analysis up to the authors’ column.

MBL Chi-Square (×100)	Cemented	Screwed	Row Totals	Sample Size (Number of Dental Implants)
Amorfini et al. [21]	1 (2.02) [0.51]	3 (1.98) [0.52]	4	32
Kraus et al. [19]	50 (50.38) [0.00]	50 (49.62) [0.00]	100	44
Weigl et al. [18]	82 (80.61) [0.02]	78 (79.39) [0.02]	160	17
Total	133	131	264	93

and

Table 7. BOP chi-square test: the chi-square is 0.4232. The p-value is 0.809304. Results are not significant at p < 0.05. “Cemented” and “Screwed” columns show the median data obtained, “Row Totals” are the total of these data, and “Sample Size” represents the number of dental implant restorations investigated. The first column indicates the type of statistical analysis up to the authors’ column.

BOP Chi-Square	Cemented	Screwed	Row Totals	Sample Size (Number of Dental Implants)
Lv et al. [17]	37 (38.66) [0.071]	22 (20.34) [0.131]	59	56
Thoma et al. [20]	30 (28.83) [0.05]	14 (15.17) [0.09]	44	44
Weigl et al. [18]	0 (8 52) [0.03]	4 (4.48) [0.05]	13	17
Total	76	40	116	117

, and Figure 2) [25].

4. Discussion

4.1. Discussion

Several factors come into play when considering the choice between screw-retained and cemented restorations. The retrievability of the restoration is an essential consideration. Screw-retained restorations allow easy retrieval, enabling repair or maintenance without damaging the prosthesis or implant. This is particularly important when access to hygiene or peri-implant assessment is a priority. Complications associated with each technique should also be evaluated [26,27].

Screw-retained restorations may carry the risk of screw loosening, leading to instability and potential implant damage. Cemented restorations, on the other hand, have a higher risk of residual cement, which, if not thoroughly removed, can cause peri-implant inflammation and tissue complications. The potential danger of residual cement in cement-retained restorations compared to screw-retained restorations on dental implants has been a concern in implant dentistry. Cementation has been widely used for its advantages in achieving a passive fit and esthetic outcome. However, residual cement can pose significant risks to peri-implant tissues and implant stability. One primary danger of residual cement is its potential to cause peri-implant inflammation and tissue complications. If not thoroughly removed, cement remnants can lead to chronic inflammation of the surrounding soft tissues, resulting in peri-implant mucositis or even peri-implantitis. These inflammatory conditions can compromise the health and longevity of the implant and its supporting structures. Residual cement can also be foreign, attracting bacterial colonization and biofilm formation. This creates a favorable microbial growth environment and increases the infection risk around the implant site. Bacteria and their by-products can contribute to peri-implant tissue breakdown and bone loss, further jeopardizing the implant’s stability and oral health [28]. The challenges of detecting and removing residual cement additionally emphasize its potential danger. Cement remnants can be challenging to identify clinically, as they may hide beneath the gingival margin or become embedded within the soft tissues. This makes thorough removal during maintenance procedures difficult, increasing the likelihood of leaving residual cement behind. In contrast, screw-retained restorations eliminate the risk of residual cement. The absence of cement eliminates the potential complications associated with its presence, providing a more favorable environment for peri-implant tissues [29].

Moreover, the retrievability of screw-retained restorations allows easy access during maintenance visits, enabling thorough cleaning and inspection of the implant site. Various preventive measures have been proposed to mitigate the potential dangers of residual cement in cement-retained restorations. These include using a controlled cementation technique, techniques such as cementation for provisional restoration, or temporary abutments [30]. These techniques can facilitate the removal of excess cement before final restoration placement, minimizing the risk of residual cement. Esthetics play a significant role in decision-making, especially in the anterior region. Screw-retained restorations avoid screw access holes, which can compromise the final aesthetic outcome. When adequately executed, cemented restorations can integrate seamlessly with the natural dentition, resulting in superior esthetic results. Ramon-Morales et al.’s [31] study investigated individuals with peri-implant mucositis and peri-implantitis, focusing on the microbiota of implants and neighboring teeth. Using mass spectrometry, Gram-negative enteric rods/Pseudomonas were significantly higher in cemented restored implants than screw-restored implants. The association between Gram-negative enteric rods/Pseudomonas and cemented fixed implants remained significant even after adjusting for confounding factors at the implant and patient levels [32].

Furthermore, peri-implantitis was also significantly associated with cemented restored implants. These findings suggest a potential link between microbial presence and implant restoration type, highlighting the importance of considering restoration techniques in peri-implantitis management. Freitas et al. [33], in an in vitro study, aimed to investigate the mechanical performance and failure modes of cemented and screw-retained implant-supported crowns with internal and external implant–abutment connections. Eighty-four implants were divided into four groups based on the retention method and connection type. Accelerated life testing was performed, and the reliability and failure modes of the crowns were evaluated. The results showed that fatigue and damage accumulation contributed to the failure of all groups, as indicated by the beta values. The cement-retained crowns with internal connections demonstrated the highest reliability, while the screw-retained crowns with external connections had the lowest reliability. Screw-retained restorations primarily experienced abutment fractures, while cement-retained restorations exhibited screw fractures in the external connection group and implant/screw fractures in the internal connection group. Cicciù et al.’s [34] experimental study compared two dynamic virtual models of an implant–prosthesis system: one with a single-bonded prosthetic crown cemented on the implant and the other with a single prosthetic crown screwed onto the system. The study evaluated the resistance to a static axial load of 400 N in both systems and analyzed mechanical stress’s distribution and dissipation using finite element analysis. The results showed that the cemented prosthesis had a more uniform stress distribution than the screwed prosthesis. The stress concentration was observed around the access hole of the screw connection, which could lead to a fracture in the screwed prosthesis. The study concluded that the cemented prosthesis was more durable and less prone to fracture than the screwed prosthesis. However, the study acknowledged several limitations, including the simplified mathematical model, little consideration of loading forces, and the need for further analysis of dynamic fatigue loading [35]. Overall, the study provided qualitative insights into the biomechanical behavior of the two implant–prosthesis connections but emphasized the need for more comprehensive and realistic models to validate the findings in a clinical context [36].

The studies included in this discussion compared the outcomes of screw-retained and cemented crowns in dental implant restorations. Naumann et al. [16] found no significant differences in functional and patient-reported outcomes between screw-retained monolithic hybrid abutment crowns and cemented crowns using lithium disilicate. Lv et al. [17] reported no implant failures in the esthetic region, with lower bleeding on probing in the screw-retained group but higher levels of TNF-α. Weigl et al. [18] observed higher plaque presence and bleeding on probing in cemented restorations, with no significant difference in marginal bone loss [37,38].

Overall, the evidence suggests that screw-retained and cemented crowns can provide satisfactory outcomes, with slight differences in specific clinical parameters. Tonella et al. [39] aimed to evaluate the stress distribution in three-unit implant-supported fixed partial dentures using different retention systems (screwed or cemented) and prosthetic connections (external hexagon, internal hexagon, and Morse taper) through photoelasticity.

Six models were created with different configurations, and axial and oblique loads were applied to analyze stress patterns. The results showed that the screwed retention system exhibited higher stress levels than the cemented system under axial and oblique loads. The internal hexagon implant demonstrated better stress distribution for cemented and screwed prostheses. Oblique loading increased stress levels in all models. The cemented retention system showed a more favorable stress distribution overall. From a biomechanical perspective, the internal hexagon implant was considered more advantageous. Notably, oblique loading increased stress levels in all tested systems and connections. Pellizzer et al. [40] aimed to evaluate the stress distribution of different retention systems (screwed and cemented) for implant-supported fixed partial dentures using the photoelastic method. Two photoelastic resin models were created, each containing two implants with varying retention systems. The fixed partial dentures were standardized and made of Ni-Cr alloy. Axial and oblique forces were applied on the occlusal surface using a Universal Testing Machine, and the results were observed and photographed using a circular polariscope. The screw retention system consistently exhibited higher fringes under axial and oblique loads, indicating higher stress levels than the cemented retention system. The study concluded that cemented implant-supported dentures had better stress distribution and lower stress magnitude than screw-retained dentures under axial and oblique loads [28,41]. Implant design variations, such as thread geometry, tapering, and platform switching, can influence primary stability and load distribution. Brands offering implants with advanced design features may perform better in challenging clinical scenarios [9]. Moreover, the compatibility and precision of prosthetic components, such as abutments and crowns, provided by different brands can affect the final restoration’s fit, aesthetics, and functional longevity. Brands with precise and well-integrated prosthetic systems may reduce technical complications and improve overall clinical outcomes [42,43]. The position of dental implants within the oral cavity plays a crucial role in determining clinical outcomes. Anatomical considerations, functional demands, and esthetic requirements vary significantly across different mouth regions, influencing implant success. Implants placed in the anterior region, especially the esthetic zone, require careful consideration of esthetics, soft tissue management, and bone quality. Anterior implants must achieve optimal gingival contour and color match, making cemented restorations preferred for superior esthetics (Table 3). Conversely, posterior implants prioritize functional load-bearing capabilities, whereas screw-retained restorations are favored for their retrievability and ease of maintenance [44].

Furthermore, oblique loads resulted in increased stress concentrations in all the models. Choosing between screw-retained and cemented restorations in dental implant treatments depends on various factors. Screw-retained repairs offer easy retrievability and secure connection but carry the risk of screw loosening. Cemented restorations provide esthetic advantages and passive fit but have a higher risk of residual cement and associated complications. The selection should consider factors such as retrievability, esthetics, biomechanics, and clinician expertise. Further research is needed to understand better the long-term outcomes of different restoration techniques in implant dentistry.

4.2. Limitations

This study has several limitations that should be considered. The small sample size, potential selection bias, and heterogeneity among the included studies limit the generalizability and validity of the findings. Additionally, the study’s retrospective or observational design, possible publication bias, and lack of long-term follow-up introduce uncertainty and bias into the results. These limitations emphasize the need for caution when interpreting the study’s findings and highlight areas for future research improvement. It is recognized that determining whether all included articles utilize the same brand and identical implant characteristics, as well as the specific positioning of implants within the oral cavity, is essential for a comprehensive analysis. Further studies are necessary to perform this analysis and obtain enough data for a systematic review.

5. Conclusions

Screw-retained restorations offer advantages such as retrievability, ease of repair, and predictable passive fit, while cemented restorations provide superior esthetics. However, residual cement in cemented restorations poses a risk of peri-implant complications. Bleeding on probing and marginal bone loss were the main investigated outcomes, and they did not statistically differ between cemented or screwed groups. The choice between screw-retained and cemented restorations should be made considering the specific clinical requirements, esthetic demands, and patient preferences. Further research is needed to explore long-term stability and the impact of different prosthetic protocols on peri-implant health.