Five-year retrospective study on success, survival and incidence of complications of single crowns supported by dental implants

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Marginal Bone Loss in Posterior Implants Placed at Different Levels and Different Prosthetic Designs: A Retrospective Study With a Minimum of 1-Year Follow-Up

Various factors influence marginal bone loss after implant placement. This study explored the association between marginal bone loss and posterior implants positioned at different bone levels. Computer records and radiographs of patients with at least 2 adjacent implants were retrieved. Cases were categorized into nonsplinted prosthesis and splinted prosthesis groups. Radiographic measurements were conducted at the time of abutment placement (T0), 1-3 years follow-up (T1), and the last visit (T2), measuring the vertical distance between adjacent implants. Multilevel linear regression models using generalized estimating equations were employed, with a significance level set at 5% (α = 0.05). Fifty-six patient records were included, comprising 120 implants: 84 nonsplinted (70%) and 36 splinted (30%). In the nonsplinted group, marginal bone loss progression significantly depended on crestal height differences. For the mesial sides of posterior implants, marginal bone loss measured 1.0 ± 0.6 mm from T0 to T1, 2.4 ± 1.1 mm from T1 to T2, and 3.4 ± 1.2 mm from T0 to T2. Similarly, the distal sides of the most anteriorly placed implant exhibited marginal bone loss of 1.0 ± 0.7 mm from T0 to T1, 2.4 ± 1.0 mm from T1 to T2, and 3.5 ± 1.2 mm from T0 to T2. Nonsplinted implants demonstrated a higher progression of marginal bone loss. This study suggests that nonsplinted implants may lead to a more pronounced progression of marginal bone loss, particularly concerning crestal height differences, underscoring the need for further research.

Risk factors impacting the survival of implants replaced following failure: A retrospective study

AIM

This study aimed to investigate factors influencing the survival of replaced dental implants.

MATERIALS AND METHODS

Charts from 2005 to 2021 were reviewed. Replaced implants after removal for the first time were identified. Depending on their survival, the replaced group was divided into the surviving and second-removal groups. Risk factors affecting survival of replaced implants were evaluated considering clustering of multiple implants within patients.

RESULTS

The present study included 464 replaced implants of 370 patients, of which 429 and 35 implants were categorized into the surviving group and the second-removal group. The 5-year survival rate was 90.2 ± 0.18% in replaced implants at sites with a periodontitis history and 97.0 ± 0.15% at sites without a periodontitis history (p = 0.008). The 5-year survival rate was 89.1 ± 0.27% in replaced implants with guided bone regeneration (GBR) at first implant placement and 93.9 ± 0.14% at non-GBR (p = 0.032). The 5-year survival rate was 97.6 ± 0.13% in replaced implants with GBR and 90.3 ± 0.17% in replaced implants without GBR (p = 0.026). In the multivariable analysis adjusted for clinical variables, periodontitis history (adjusted hazard ratio [aHR] = 3.417; 95% confidence interval [CI] = 1.161-10.055), GBR at first implant placement (aHR = 2.152; 95% CI = 1.052-4.397) and non-GBR at primary implant replacement (aHR = 0.262; 95% CI = 0.088-0.778) were identified as independent risk factors for second implant removal.

CONCLUSIONS

Periodontitis history, GBR at first implant placement and non-GBR at primary implant replacement were identified as risk factors affecting the survival of replaced implants.

Retention of zirconia crown to oxidized titanium base abutment: Experimental research

STATEMENT OF PROBLEM

To separate the crown from the titanium base abutment, by using heat, caused oxidization of the titanium base abutment. The effect of this procedure on the retention of a crown is unclear.

PURPOSE

To compare the resin bond strength and failure type between zirconia crowns and titanium base abutments utilizing four different surface treatments. Surface roughness and morphology of each surface treatment were also investigated.

MATERIAL AND METHODS

Forty titanium base abutments (Variobase®) were divided into four groups, 1. Control, 2. Air abraded, 3. Oxidized, and 4. Oxidized-air abraded. Oxidized and oxidized-air abraded groups were debonded from zirconia crowns using constant dry heat at 500 ˚C. For air abraded and oxidized-air abraded groups (after oxidization), the titanium base abutments were air abraded with Al3O2. After cleaning, one specimen of each group was investigated under a non-contact profilometer (50x), then the same samples were investigated under SEM at 25,300,500,1000 magnification and EDS at 30kV of accelerated voltage. All specimens were then cemented (RelyX Ultimate). After aging, with thermocycling under 5C° to 55C°,120 seconds dwell time for 5,000 cycles, bond strength was tested and statistical differences were calculated with One-way ANOVA (p-value <0.05) follow by Tukey test. All separated crowns and titanium base abutments were investigated under a light microscope (20x), using fisher's exact test for correlation of the failure types.

RESULTS

There was a significant difference in the mean value of tensile bond strength among the control and test groups. Comparisons between control(237.6±46.3N) and oxidized(241.7±46.3N) showed statistically different values from air abraded(372.9±113.2N) when assembled using different surface treatments of the titanium-based abutments. (p-value<0.005) As for failure type, there were statistically significant differences between control versus air abraded, control versus oxidized-air abraded, oxidized versus air abraded, and oxidized versus oxidized-air abraded. (p-value<0.001) The titanium surface morphology shown from the profilometer and SEM was coordinated. Control (Ra 333.8nm) and oxidized (Ra 321.0nm) groups surfaces showed smooth, corrugated surfaces, meanwhile air abraded (Ra 476.0nm) and oxidized-air abraded (Ra 423.8nm) groups showed rough, rugged surfaces.

CONCLUSION

Heat oxidization of titanium-based abutments did not adversely affect tensile bond strength or the failure mode and surface roughness between titanium base abutments and zirconia crowns. However, air abrasion of the titanium surface increased surface roughness and retentive strength.

CLINICAL IMPLICATIONS

The titanium base abutments that were oxidized under heat treatment did not have an effect on crown retention. Thoroughly air abraded the titanium abutment prior to cementation can increase cement bond strength.

What is the prevalence of peri-implantitis? A systematic review and meta-analysis

Background

Peri-implantitis is a usual finding but estimates of its prevalence fluctuate very much. This may be due to the wide variety of disease definitions. This systematic review aims to estimate the overall prevalence of peri-implantitis and the effect of different study designs, function times and use of probing depth on prevalence rate.

Methods

Following electronic and manual searches of the literature published from January 2005 to December 2021, data were extracted from the studies fitting the study criteria. Fifty-seven articles were included in this study.

Results

Prevalence of peri-implantitis was 19.53% (95% CI 12.87–26.19) at the patient-level, and 12.53% (95% CI 11.67–13.39) at the implant-level and it remains highly variable even following restriction to the clinical case definition. The use of probing depth like diagnostic criteria affected the prevalence data.

Conclusion

The results indicate that it remains essential the identification of the diagnostic markers for more accurate disease classification.

Association between IL-1A, IL-1B and IL-1RN Polymorphisms and Peri-Implantitis: A Systematic Review and Meta-Analysis

Recent studies report that individuals with polymorphisms in the genes that encode for interleukin (IL)-1α and IL-1β (IL-1A and IL1B, respectively) and for IL-1 receptor antagonist (IL-1RN) may be more susceptible in developing peri-implantitis. Therefore, the current systematic review evaluates what is reported about the role of genetics, more specifically of single nucleotide polymorphisms (SNP) on IL-1 and variable number of tandem repeats (VNTR) on IL-1RN, in the development of peri-implantitis. This systematic review was carried out by screening PubMed, B-on, Cochrane and Scopus databases, for articles English, Spanish, and Portuguese, with no limit regarding the publication year. Eight articles were selected for systematic review and four for meta-analytic syntheses. Our results show that although there is a lack of consensus in the literature, there seems to be an association between IL-1A, IL-1B, and IL-1RN polymorphisms with peri-implantitis. The results of the meta-analysis showed that patients who have the polymorphic allele at position +3954 of the IL-1B gene have on average almost twice the risk of developing peri-implantitis (odds ratio = 1.986, 95% confidence interval).

Titanium Nanosurface with a Biomimetic Physical Microenvironment to Induce Endogenous Regeneration of the Periodontium

The periodontium supports the teeth by dentoalveolar fibrous joints that serve unique oral functions. Endogenous regeneration of the periodontium around artificial teeth (dental implants) provides a cost-effective solution for the extension of healthy life expectancy but remains a challenge in regenerative medicine. Biomimetics can create smart biomaterials that tune endogenous cells at a tissue-material interface. Here, we created a smart titanium nanosurface mimicking the surface nanotopography and micromechanical properties of the tooth root cementum (TRC), which is essential for the induction of dentoalveolar fibrous joints to regenerate the periodontium. After transplantation into the rat renal capsule, only the titanium artificial tooth with the TRC-mimetic nanosurface formed a complex dentoalveolar fibrous joint structure, with bone tissue, periodontal ligament (PDL), and TRC, in the decellularized jawbone matrix. TRC-mimetic titanium implants induce the formation of functional periodontium, even in a jawbone implantation model, which generally causes osseointegration (ankyloses). In human PDL cells, TRC analogousness in the surface mechanical microenvironment regulates matrix mineralization through bone sialoprotein expression and phosphorus metabolism, which are critical for cementogenesis. Therefore, the titanium nanosurfaces with nanotopographical and mechanical microenvironments mimicking the TRC surface induce dentoalveolar fibrous joints for periodontal regeneration by interfacial tuning of endogenous cells.

Clinical and radiographical performance of implants placed with simultaneous guided bone regeneration using resorbable and nonresorbable membranes after 22-24 years, a prospective, controlled clinical trial

Aim

The aim was to evaluate the performance of implants placed with simultaneous guided bone regeneration (GBR) using resorbable or nonresorbable membranes compared to implants placed in pristine bone without bone regeneration after an observation period of 22–24 years.

Material and Methods

The patient cohort of this clinical trial was treated from 1994 to 1996. Dehiscence defects were treated with GBR by either using resorbable collagen membranes (BG) or nonresorbable ePTFE membranes (GT). Implants placed in pristine bone served as a control (CT). Clinical parameters, marginal bone levels, and technical outcomes were evaluated following restoration placement and at the present follow‐up. A 3D radiographic analysis was conducted in order to assess buccal and oral bone dimensions. Implant survival was assessed with Kaplan–Meier analysis and a frailty model (level of significance 5%).

Results

Out of the originally 72 patients (mean age 75.4 ± 15.70 years) with 265 implants, 39 patients with 147 implants were included in the study after a median period of 23.5 years. Implant survival was 89.3% in group BG (n = 100), 90.2% in group GT (n = 37), and 93.8% in group CT (n = 105), without significant differences (Frailty proportional hazard model p = .79). Smoking had a negative effect on survival (p = .0122). Mean vertical marginal bone levels were −2.3 ± 1.4 mm (BG, n = 59), −3.0 ± 1.5 mm (GT, n = 21), and −2.3 ± 1.6 mm (CT, n = 52). The vertical buccal bone levels were −3.0 ± 1.9 mm (BG, n = 57), −3.5 ± 2.2 mm (GT, n = 21), and −2.6 ± 1.8 mm (CT, n = 49), without significant differences.

Conclusion

Implant placement with GBR procedures provides treatment outcomes with favorable implant survival rates (89.3%–93.8%) after 23.5 years. Smoking, however, affected implant survival negatively.

Surface attrition of zirconia and hybrid composite resin superstructure during implant therapy

PURPOSE

The purpose of this study was to examine morphological changes in the superstructure of implants in relation to the degree of attrition of the implant superstructure and its antagonists.

METHODS

Thirty-three patients participated. The implant superstructures of the first molar and its antagonists were scanned with an intraoral scanner every 3 months. The amount of attrition was calculated in relation to the various materials used for the superstructure, and differences were analyzed statistically (P < 0.05).

RESULTS

Attrition of the implant superstructure was 110 ± 30 µm for monolithic zirconia and 105 ± 27 µm for resin-veneered metal after 12 months. No statistically significant difference was found between the two groups. In contrast, attrition of the antagonists was 75 ± 25 µm for zirconia and 105 ± 20 µm for resin-veneered metal after 12 months. A statistically significant difference in the attrition levels between the two groups was observed after 9 and 12 months.

CONCLUSION

During the 12-month observation period, there was no difference in superstructure attrition between zirconia and resin-veneered metal. Attrition of the antagonists was higher for hybrid composite resin-veneered metal than for zirconia, suggesting that surface roughness affected the degree of attrition.

Assessment of Trabecular Bone During Dental Implant Planning using Cone-beam Computed Tomography with High-resolution Parameters

Background:

Cone-Beam Computed Tomography (CBCT) with high-resolution parameters may provide an acceptable resolution for bone assessment.

Objectives:

The purpose of this study is to assess trabecular bone using two cone-beam computed tomography (CBCT) devices with high-resolution parameters in comparison to micro-computed tomography (µCT).

Methods:

Bone samples (n=8) were acquired from dry mandibles and scanned by two CBCT devices: 1) VV (Veraview R100, Morita; FOV 4x4, 75kV, 9mA, voxel size 0.125µm); and PR (Prexion 3D, Prexion; FOV 5x5, 90kV, 4mA, 37s, voxel size 108µm). Gold-standard images were acquired using µCT (SkyScan 1272; Bruker; 80kV, 125mA, voxel size 16µm). Morphometric parameters (BvTv- Bone Volume Fraction, BsBv- Trabecular specific surface, TbTh- Trabecular thickness and TbSp- Trabecular separation) were measured. Statistical analysis was performed within ANOVA, Spearman Correlation test and Bland-Altmann plots with a statistical significance level at p=0.05.

Results:

CBCT devices showed similar BvTv values in comparison to µCT. No statistical difference was found for BvTv parameters assessed by CBCT devices and µCT. BsBv values were underestimated by CBCT devices (p<0.01), whereas TbTh and TbSp values were overestimated by them (p<0.01). Positive correlations were found between VV and µCT measurements for BvTv (r2= 0.65, p=0.00), such as between PR and µCT measurements for TbSp (r2= 0.50, p=0.04). For BsBv measurements, PR was negatively correlated with µCT (r2= -0.643, p=0.01).

Conclusion:

The evaluated CBCT device was able to assess trabecular bone. However, bone parameters were under or overestimated in comparison to µCT.

Marginal Adaptation and Microbial Leakage at Conometric Prosthetic Connections for Implant-Supported Single Crowns: An In Vitro Investigation

Encouraging clinical results were reported on a novel cone-in-cone coupling for the fixation of dental implant-supported crowns (Acuris, Dentsply Sirona Implants, Mölndal, Sweden). However, the presence or absence of a microgap and a potential bacterial leakage at the conometric joint has not yet been investigated. A misfit and a resulting gap between the conometric components could potentially serve as a bacterial reservoir that promotes plaque formation, which in turn may lead to inflammation of the peri-implant tissues. Thus, a two-fold study set-up was designed in order to evaluate the bidirectional translocation of bacteria along conometrically seated single crowns. On conometric abutments filled with a culture suspension of anaerobic bacteria, the corresponding titanium nitride-coated (TiN) caps were fixed by friction. Each system was sterilized and immersed in culture medium to provide an optimal environment for microbial growth. Positive and negative controls were prepared. Specimens were stored in an anaerobic workstation, and total and viable bacterial counts were determined. Every 48 h, samples were taken from the reaction tubes to inoculate blood agar plates and to isolate bacterial DNA for quantification using qrt-PCR. In addition, one Acuris test system was subjected to scanning electron microscopy (SEM) to evaluate the precision of fit of the conometric coupling and marginal crown opening. Throughout the observational period of one week, blood agar plates of the specimens showed no viable bacterial growth. qrt-PCR, likewise, yielded a result approaching zero with an amount of about 0.53 × 10⁻⁴ µg/mL DNA. While the luting gap/marginal opening between the TiN-cap and the ceramic crown was within the clinically acceptable range, the SEM analysis failed to identify a measurable microgap at the cone-in-cone junction. Within the limits of the in-vitro study it can be concluded that the Acuris conometric interface does not allow for bacterial translocation under non-dynamic loading conditions.

Influence of abutment angulation on loss of prosthetic abutment torque under mechanical cycling

STATEMENT OF PROBLEM

Internal conical connections provide mechanical stability for the prosthetic abutment and implant connection. However, some clinical situations require the use of angled prosthetic abutments that may increase stress on supportive implants by difference force vectors under cyclic loading.

PURPOSE

The purpose of this in vitro study was to measure the screw loosening values of prosthetic abutments with internal conical connections (indexed and nonindexed) having different angles under mechanical cycling.

MATERIAL AND METHODS

Thirty-six implants (4.0×13 mm, Titamax) with internal conical connections and their respective universal prosthetic abutments (n=36, 3.5×3.3 mm) were divided into indexed and nonindexed groups (n=18) with abutment inclinations of 0 (straight), 17, and 30 degrees. An insertion torque of 15 Ncm was applied according to the manufacturer's specifications. The specimens underwent fatigue testing of 500 000 cycles at a frequency of 2 Hz with a dynamic compressive load of 120 N at an angle of 30 degrees. The detorque values were measured by using a digital torque meter and tabulated for statistical analyses.

RESULTS

The specimens with indexed abutments had mean ±standard deviation detorque values of 6.72 ±2.29 Ncm under mechanical cycling, whereas those with nonindexed abutments had values of 8.98 ±1.84 Ncm. In the indexed group, the lowest detorque value was observed for abutments at 30 degrees compared with the straight group (P<.05). As for nonindexed abutments, similar detorque values were observed after increasing the abutment inclination (P>.05).

CONCLUSIONS

A decrease in detorque values in the indexed abutments related to their inclination was found under mechanical cycling, whereas the prosthetic abutments with 30 degrees of angulation had the lowest values. No decrease was found in the nonindexed abutments.

Early Loading of Mandibular Molar Single Implants: 1 Year Results of a Randomized Controlled Clinical Trial

The purpose of this study was to compare the implant survival, peri-implant marginal bone level, and peri-implant soft tissue of three different types of implants. This was performed with an early loading protocol, using a complete digital workflow, for one year of follow-up. Twenty-four patients with a single missing tooth in the mandibular posterior region were randomly assigned to the control group (SLActive Bone level implant; Institut Straumann AG, Basel, Switzerland), experiment group 1 (CMI IS-III Active implant; Neobiotech Co., Seoul, Korea), and experiment group 2 (CMI IS-III HActive implant; Neobiotech Co., Seoul, Korea). For each patient, a single implant was installed using the surgical template, and all prostheses were fabricated using a computer-aided design/computer-aided manufacturing system on a 3-dimensional model. A provisional prosthesis was implanted at 4 weeks, and a definitive monolithic zirconia prosthesis was substituted 12 weeks following the implant placement. The implant stability quotient (ISQ) and peri-implant soft tissue parameters were measured, and periapical radiographs were taken at 1, 3, 4, 8, 12, 24, 36, and 48 weeks after implant placements. Seven implants in the control group, nine implants in the experiment 1 group, and eight implants in the experiment 2 group were analyzed. There were no significant differences among the three groups in terms of insertion torque, ISQ values between surgery and 8 weeks of follow-up, marginal bone loss at 48 weeks of follow-up, and peri-implant soft tissue parameters (P > 0.05). Statistically significant differences in ISQ values were observed between the control and experiment 1 groups, and the control and experiment 2 groups at the 12 to 48 weeks' follow-ups. Within the limits of this prospective study, an early loading protocol can be applied as a predictable treatment modality in posterior mandibular single missing restorations, achieving proper primary stability.

Primary Stability of Dental Implants in Low-Density (10 and 20 pcf) Polyurethane Foam Blocks: Conical vs Cylindrical Implants

Background: The aim of the present study was to compare, in low-density polyurethane blocks, the primary implant stability values (micromobility) and removal torque values of three different implant geometries in two different bone densities representing the structure of the human posterior jaws. Methods: A total of 60 implants were used in the present investigation: twenty implants for each of three groups (group A, group B, and group C), in both polyurethane 10 pcf and 20 pcf densities. The insertion torque, pull-out torque, and implant stability quotient (ISQ) values were obtained. Results: No differences were found in the values of Group A and Group B implants. In both these groups, the insertion torques were quite low in the 10 pcf blocks. Better results were found in the 20 pcf blocks, which showed very good stability of the implants. The pull-out values were slightly lower than the insertion torque values. High ISQ values were found in Group A and B implants. Lower values were present in Group C implants. Conclusions: The present investigation evaluated implants with different geometries that are available on the market, and not experimental implants specifically created for the study. The authors aimed to simulate real clinical conditions (poor-density bone or immediate post-extraction implants) in which knowledge of dental implant features, which may be useful in increasing the primary stability, may help the oral surgeon during the surgery planning.

Proposal and In-Depth Analysis of Emergency Treatment Procedures for Removing Fractured Abutments in Implants With Tapped-In Connections: Case Report

In implant-supported prostheses, the most frequently reported mechanical complications after implant restoration are loosening or fracture of abutments or screws. Such complications have serious consequences, and removal of fractured abutments or screws is difficult. There are various methods to remove fractured abutment screws in implants with screwed-in connections. However, no approach has been reported to retrieve solid abutments in implants with a locking-taper implant-abutment connection, which are rarely observed in clinical settings. This study presents the case of a 62-year-old male patient with a fractured abutment in an upper-right second premolar implant. Abutment fracture is a common mechanical complication after dental implantation. Parafunctional habits and occlusal overloading may generate excessive occlusal forces, which increase the risk of mechanical complications. This report presents a series of emergency procedures for removing a fractured solid abutment and fabricating a new prosthesis to restore the edentulous area. In this retrospective analysis, the authors deeply consider the whole treatment, through which the deficiencies of the treatment are noted, and corresponding future directions are discussed. This case report presents a convenient approach to removing a solid abutment in a sudden emergency, discusses possible reasons for solid abutment fractures, designs a new rescue kit for easy retrieval of such abutments and summarizes a valid solution for removing fractured solid abutments.

Long-term performance of implant-supported metal-ceramic and all-ceramic single crowns

PURPOSE

To evaluate failure rates and incidence of chipping for metal-ceramic and all-ceramic implant-supported single crowns (SCs).

METHODS

Six hundred and fifty-two implant-supported SCs placed in 404 patients (mean age: 57.8 years; 193 male; mean SCs per patient: 1.6) were evaluated up to 12.8 years. The frameworks of the SCs were made from Au alloys (n = 319), CoCr (n = 37), zirconia (n = 286), or lithium disilicate (n = 10). Full-coverage ceramic veneers were placed on 319 Au SCs, 34 CoCr SCs, and 92 zirconia SCs. One hundred and fifty-two monolithic zirconia SCs were not veneered. A partial veneer was placed on the buccal surface only of a further 42 zirconia SCs.

RESULTS

A total of 26 failures were caused by loss of implants (n = 6), ceramic fractures and chipping (n = 15), loosening of the abutment (n = 4), or swallowing of a de-cemented SC (n = 1). Kaplan-Meier analysis revealed a probability of survival of 96% after five years and 92% after 10 years. A greater incidence of failure was observed for lithium disilicate and zirconia SCs than for metal-ceramic SCs (p < .05). Separate analysis of the most frequent complication, chipping (n = 61), revealed that zirconia and lithium disilicate frameworks were significant risk factors for chipping (p < 0.05). Furthermore, a significantly greater incidence of chipping was observed for SCs with full-coverage veneers than for monolithic zirconia SCs and for SCs with partial veneers (p < .05).

CONCLUSION

Avoidance of full-coverage veneers significantly improves the clinical performance of implant-supported crowns, primarily reduces the incidence of chipping.

Randomized Controlled Trials in Implant Dentistry: Assessment of the Last 20 Years of Contribution and Research Network Analysis

The aim of this study was to evaluate the characteristics of randomized controlled trials (RCTs) regarding implant-supported single tooth or fixed partial dentures. We performed searches (PubMed/MEDLINE and Web of Science) to identify all RCTs published from 1996 to 2016 and assessed publication details, study characteristics, international collaboration networks, and characteristics related to the implant-supported treatment. Two reviewers independently screened the titles/abstracts and selected full texts. A total of 122 RCTs were included, and most of the authors were from Europe (72%). Most trials did not report a trial registering number (89.9%) or sample size calculation (58.2%). The use of the CONSORT Statement increased over the past 9 years. Trials were mostly conducted at universities (54.9%), and only 13.1% compared 2 or more implant brands. Loading protocol was the most prevalent main comparison among the included studies, and most of the RCTs did not clearly report whether they excluded patients with known risk factors. The studies reviewed here presented different methodological and publication characteristics, and many did not show aspects aligned with current research practices.

A systematic review of the survival and complication rates of zirconia-ceramic and metal-ceramic single crowns

OBJECTIVES

The aim of the present systematic review was to analyze the survival and complication rates of zirconia-based and metal-ceramic implant-supported single crowns (SCs).

MATERIALS AND METHODS

An electronic MEDLINE search complemented by manual searching was conducted to identify randomized controlled clinical trials, prospective cohort and retrospective case series on implant-supported SCs with a mean follow-up time of at least 3 years. Patients had to have been clinically examined at the follow-up visit. Assessment of the identified studies and data extraction was performed independently by two reviewers. Failure and complication rates were analyzed using robust Poisson's regression models to obtain summary estimates of 5-year proportions.

RESULTS

The search provided 5,263 titles and 455 abstracts, full-text analysis was performed for 240 articles, resulting in 35 included studies on implant-supported crowns. Meta-analysis revealed an estimated 5-year survival rate of 98.3% (95% CI: 96.8-99.1) for metal-ceramic implant supported SCs (n = 4,363) compared to 97.6% (95% CI: 94.3-99.0) for zirconia implant supported SCs (n = 912). About 86.7% (95% CI: 80.7-91.0) of the metal-ceramic SCs (n = 1,300) experienced no biological/technical complications over the entire observation period. The corresponding rate for zirconia SCs (n = 76) was 83.8% (95% CI: 61.6-93.8). The biologic outcomes of the two types of crowns were similar; yet, zirconia SCs exhibited less aesthetic complications than metal-ceramics. The 5-year incidence of chipping of the veneering ceramic was similar between the material groups (2.9% metal-ceramic, 2.8% zirconia-ceramic). Significantly (p = 0.001), more zirconia-ceramic implant SCs failed due to material fractures (2.1% vs. 0.2% metal-ceramic implant SCs). No studies on newer types of monolithic zirconia SCs fulfilled the simple inclusion criteria of 3 years follow-up time and clinical examination of the present systematic review.

CONCLUSION

Zirconia-ceramic implant-supported SCs are a valid treatment alternative to metal-ceramic SCs, with similar incidence of biological complications and less aesthetic problems. The amount of ceramic chipping was similar between the material groups; yet, significantly more zirconia crowns failed due to material fractures.

How do peri-implant biologic parameters correspond with implant survival and peri-implantitis? A critical review

Objectives

The aim of this critical review was to evaluate whether commonly used biologic diagnostic parameters correspond to implant survival and peri‐implantitis prevalence.

Materials and methods

Publications from 2011 to 2017 were selected by an electronic search using the Pubmed database of the US National Library of Medicine. Prospective and retrospective studies with a mean follow‐up time of at least 5 years and reporting prevalence of peri‐implantitis as well as mean bone loss and standard deviation were selected. The correlation between reported prevalence of peri‐implantitis and reported implant survival, mean follow‐up time, mean bone loss, mean probing depth, and mean bleeding on probing was calculated. Mean bone loss and standard deviation were used for estimation of proportion of implants with bone loss exceeding 1, 2, and 3 mm.

Results

Full‐text analysis was performed for 255 papers from 4,173 available ones, and 41 met all the inclusion criteria. The overall mean weighted survival rate was 96.9% (89.9%–100%) and the reported prevalence of peri‐implantitis ranged between 0% and 39.7%, based on 15 different case definitions. The overall weighted bone loss was 1.1 mm based on 8,182 implants and an average mean loading time ranging from 5 to 20 years. No correlation was found between mean bone loss and the reported prevalence of peri‐implantitis. The estimated prevalence of implants with bone loss above 2 mm was 23%. The overall weighted mean probing depth was 3.3 mm, and mean weighted bleeding was 52.2%. Only a weak correlation was found between survival and function time (r = −0.49). There was no relation between the probing depth or bleeding and the mean bone loss, mean follow‐up time, and reported prevalence of peri‐implantitis.

Conclusion

Biologic parameters mean probing depth and mean bleeding on probing do not correlate with mean bone loss and this irrespective of follow‐up. Case definition for peri‐implantitis varied significantly between studies indicating that an unambiguous definition based on a specified threshold for bone loss is not agreed upon in the literature.

[Criteria for success in dental implants]

With the comprehensive application and development of implant dentistry in recent years, multi-institutional data have supported a large number of clinical research findings. A consensus was gradually reached on the evaluation of the state and effect of implants and types of indicators that were selected after restoration. This study aims to examine the frequently used criteria to define treatment success in implant dentistry.

Long-term follow-up of single crowns supported by short, moderately rough implants-A prospective 10-year cohort study

OBJECTIVES

To evaluate prospectively the clinical and radiographic outcomes after ten years of short (6 mm) implants with a moderately rough surface supporting single crowns in the posterior region.

MATERIAL AND METHODS

Forty 6 mm modified sandblasted large-grit acid-etched (mod-SLA), soft tissue level implants were installed in the distal segments of 35 consecutive patients. After 6 weeks of healing, abutments were tightened, and single porcelain-fused-to-metal crowns were cemented. Implant survival, marginal bone loss, and clinical crown/implant ratio were evaluated at various time intervals up to 10 years after loading.

RESULTS

Two out of the 40 implants were lost before loading, one implant was lost after 7 years because of peri-implantitis. One patient with two implants died and was excluded from analysis. Two patients did not come at the 10-year follow-up and were considered as drop out (2 implants). The survival rate was 91.7% (n = 36). Thirty-three implants were available for marginal bone loss evaluation. A mean marginal bone loss after 10 years of function was 0.8 ± 0.7 mm. Between 5 and 10 years, the loss was 0.2 ± 0.4 mm. No technical complications were registered during the 10-year period. The clinical crown/implant ratio increased with time from 1.6 at the delivery of the prosthesis to 2.0 after 10 years of loading with no increase between 5 and 10 years.

CONCLUSION

Short (6 mm) implants with a moderately rough surface supporting single crowns in the posterior region and loaded after 6-7 weeks maintained full function for at least 10 years with low marginal bone resorption.

Comparison of a Novel Ultrasonic Scaler Tip vs. Conventional Design on a Titanium Surface

The aim of this in vitro study was to evaluate the alterations of a titanium surface after treatment with two different types of ultrasonic tips: conventional steel versus an innovative copper alloy silver-plated one. Twenty smooth-surface, grade IV unalloyed titanium discs were divided into two groups. The discs were ultrasonically instrumented and the scaler was connected with a loading machine. The surface morphology was examined using scanning electron microscopy (SEM) and fractal analysis of lacunarity was calculated to highlight the alteration of the surface using the two different tips. The SEM analysis showed different degrees of surface roughness between the two types of scaler tips. Moreover, these observations demonstrated that the new tip showed fewer irregularities on the disc’s surface than the conventional steel tip. The statistical and fractal analysis showed a statistically significant difference between the two groups. Surface alterations of titanium induced by the conventional ultrasonic tips were much greater than those made by copper alloy silver plated tips. The presented results suggest that the use of this new ultrasonic tip may reduce the alterations on the implant surface during its use in dental practice.

The micromechanical behavior of implant-abutment connections under a dynamic load protocol

BACKGROUND

The implant-abutment connection (IAC) is known to be a key factor for the long-term stability of peri-implant tissue.

PURPOSE

The aim of the present in vitro study was to detect and measure the mechanical behavior of different IACs by X-ray imaging.

MATERIALS AND METHODS

A total of 20 different implant systems with various implant dimensions and IACs (13 conical-, 6 flat-, and 1 gable-like IAC) have been tested using a chewing device simulating dynamic and static loading up to 200 N. Micromovements have been recorded with a high-resolution, high-speed X-ray camera, and gap length and gap width between implant and abutment have been calculated. Furthermore, X-ray video sequences have been recorded to investigate the sealing capacity of different IACs.

RESULTS

Out of the 20 implant systems, eight implant systems with a conical IAC showed no measurable gaps under static and dynamic loading (200 N). By contrast, all investigated implant systems with a flat IAC showed measurable gaps under dynamic and static loading. X-ray video sequences revealed that a representative conical IAC had sufficient sealing capacity.

CONCLUSION

Within the limits of the present in vitro study, X-ray imaging showed reduced formation of microgaps and consecutive micromovements in implants with conical IAC compared to flat IACs.

The Use of a Novel Porcine Derived Acellular Dermal Matrix (Mucoderm) in Peri-Implant Soft Tissue Augmentation: Preliminary Results of a Prospective Pilot Cohort Study

Objective

Over the years, several techniques have been proposed for soft tissue augmentation around dental implants in order to improve keratinized mucosa width (KMW). Recently, a porcine derived acellular dermal matrix (Mucoderm®) has been proposed as autogenous graft substitute in order to avoid palatal harvesting and obtain comparable results to connective tissue grafts, in terms of aesthetics and function. The aim of this study is to present the one-year follow-up results of this matrix in peri-implant soft tissue augmentation procedures.

Material and Methods

Twelve patients were enrolled in this pilot prospective study: a dental implant was placed in the upper premolar area and, at implant uncovering after eight weeks, the matrix was inserted. KMW gain was considered as primary outcome variable.

Results

After one month from matrix insertion, mean KMW was 7.86±3.22 mm (100%), with no statistically significant intragroup variations (p>0.05). No membrane exposures or wound healing complications occurred during postoperative phase and, after one year, mean KMW was 5.67±2.12 mm (72.13%).

Conclusions

The results of the present pilot study indicate that by placing a Mucoderm membrane during implant surgery the keratinized tissue width can be augmented, and the width remains stable for the assessment period of 12 months. Further studies with greater power and longer investigation period are needed to confirm the suggestion for clinical use. Clinical trial registration number is EudraCT number 2018-000147-16.

Incidence and pattern of implant fractures: A long-term follow-up multicenter study

BACKGROUND

Currently, there is incomplete understanding of the fracture patterns in the implant and their association with clinical factors.

PURPOSE

The aim of this study was to investigate the incidence and pattern of implant fracture (IF) by using 9-year, long-term multicenter follow-up data.

MATERIALS AND METHODS

The association of the incidence and differences in fracture patterns with clinical factors (based on patient variables and implant variables) was assessed for statistical significance using the Chi-square and Fisher exact test, as appropriate.

RESULTS

Among a total of 19 087 implants in 8501 patients (7838 male and 663 female) placed over 9 years, fractures were observed in 70 implants (0.4%) in 57 patients (50 male and 7 female). Cases with less than 50% bone loss had a higher incidence of horizontal and vertical IFs limited to the crest module, which are defined as Type I fractures (n = 13, 18.6%). In contrast, cases with ≥50% severe bone loss exhibited a higher incidence of Type II vertical fractures (n = 22, 31.4%), extending beyond the crestal portion (P = .001). Type III fractures (n = 5, 7.1%), defined as a horizontal fracture beyond the crestal module, were also observed.

CONCLUSION

Peri-implantitis-induced marginal and vertical bone loss and manufacturing-induced defects were considered to be major factors in IF. Therefore, using clinically verified implant systems and striving to minimize bone loss by preventing and actively treating peri-implantitis is essential to reduce IFs.

Evaluation of implant screw loosening by resonance frequency analysis with triaxial piezoelectric pick-up: in vitro model and in vivo animal study

OBJECTIVE

The aim of this study was to evaluate implant screw loosening using resonance frequency (RF) analysis with triaxial piezoelectric pick-up in vitro and in vivo.

METHODS

For the in vitro experiment, a titanium implant was inserted into a mandibular model. The abutment screws were tightened to 10 N torque and loosened from 0 to 90° for RF measurement using 13 different screw conditions. In the in vivo experiment, three titanium implants were installed in each tibia of a New Zealand white rabbit, and the RF values were recorded after 8 weeks. For the RF analyses, a small 3D accelerometer was mounted rigidly onto the implant abutment, and impulsive vibration was directly applied to the abutment to vibrate the implant in a direction perpendicular to the tibia and implant (x-axis). The y-axis was defined as parallel to the tibia. The RF values of the x- and y-axis directions (RF-X and RF-Y) were used for evaluation.

RESULTS

The RF values significantly decreased according to the degree of screw loosening (p < 0.05, ANOVA). In the in vitro model, RF-Y with x- and y-axis vibrations (RF-Yx and RF-Yy) significantly differed from the initial value at 10 and 15°, respectively (p < 0.05, Dunnett's test). In the in vivo experiment, the RF-Yy significantly differed from the initial value between 5 and 20° (p < 0.05).

CONCLUSION

The results suggest that RF analysis with triaxial piezoelectric pick-up can be used to detect implant screw loosening.

CLINICAL RELEVANCE

RF analysis with the triaxial piezoelectric pick-up can be used to detect screw loosening after mounting the superstructure.

Randomized Controlled Clinical Trial to Compare Posterior Implant-Supported Modified Monolithic Zirconia and Metal-Ceramic Single Crowns: One-Year Results

PURPOSE

The purpose of this randomized controlled clinical trial was to investigate the prosthetic outcomes of posterior implant-supported single crowns (SCs) with a modified monolithic zirconia or metal-ceramic design at 1 year of loading.

MATERIALS AND METHODS

Forty participants with 73 dental implants in need of at least 1 maxillary or mandibular posterior implant-supported SC were consecutively selected for this study. The included participants were randomly divided into modified monolithic zirconia (MMZ) and metal-ceramic (MC) groups. The implant-supported SCs were examined after 1 year for survival and technical complications. Descriptive statistics were used to illustrate the data, and the association associated risks of complications were estimated using the logistic regression model with Firth's approach for rare outcome (α = 0.05).

RESULTS

During the observation period, 2 participants in the MC group were lost to follow-up. A total of 38 participants with 70 posterior implant-supported SCs (36 and 34 SCs in the MMZ and MC groups respectively) completed the 1-year follow-up examination. One implant failed in the MMZ group. The 1-year survival rates for implants and crowns were both 97.2% in the MMZ group. The survival rates for implants and crowns were both 100% in the MC group. One screw loosening event was observed in one screw-retained SC in the MMZ group; however, 8 complication events occurred in 7 SCs in the MC group. Therefore, the complication-free rates were 97.1% and 79.4% in the MMZ and MC SCs respectively. The most common complication in the MC group was screw loosening (14.7%), followed by loss of retention (5.9%), and ceramic fracture (2.9%). Significantly more technical complications were observed in the MC SCs than MMZ SCs (p = 0.0432).

CONCLUSION

The modified monolithic zirconia design applied to the posterior implant-supported SCs had a significantly lower technical complication rate than did the metal-ceramic one.

Analysis and management of implant-prosthetic complications: Description of a diagnostic and therapeutic algorithm with a clinical case

PATIENT

A 65-year-old non-smoker man with stabilized chronic periodontitis and in good general health conditions presented to our observation. The patient reported crown mobility, gingival inflammation and localized pain, corresponding to the mandibular right first molar rehabilitated with a cement-retained implant crown. This clinical situation suspected a fracture of an implant-prosthetic component. Through the described diagnostic algorithm, an abutment hexagon fracture was revealed. Thus, a minimally invasive treatment was carried out in order to use the residual implant-prosthetic components for a new implant-prosthetic rehabilitation.

DISCUSSION

Fractures of implant-prosthetic components are clinical occurrences that may result in irreversible failures. The main causes of a possible fracture are dependent on biomechanical considerations and production processes of implant-prosthetic components. The respect of the rigorous planning and the employment of the implant-prosthetic devices of the same manufacturer are recommended.

CONCLUSIONS

Specific employments and protocols have to be offered in order to manage the fractures of implant-prosthetic components. This work showed that through the described diagnostic and therapeutic algorithm, the clinician can be guided towards a proper diagnosis and a correct management of the cases where a fracture of implant-prosthetic components may occur.