Prosthetic outcome of cement-retained implant-supported fixed dental restorations: a systematic review

New Radiological Corticalization Index as an Indicator of Implant Success Rate Depending on Prosthetic Restoration-5 Years of Follow-Up

The new Radiological Corticalization Index (CI) is an indicator that describes bone remodeling near the dental implant's neck at the pixel level and is not visible to the naked eye. The aim of this research was to evaluate the correlation between the CI and bone remodeling using only radiographic (RTG) images. RTG samples were divided into groups depending on prosthetic restoration; the implant neck area around dental implants was examined, and texture features of the RTG images were analyzed. The study also investigated the type of prosthetic restoration and its influence as a factor on bone structure. The statistical analysis included evaluating feature distribution, comparing means (t-test) or medians (W-test), and performing a regression analysis and one-way analysis of variance or the Kruskal-Wallis test, as no normal distribution or between-group variance was indicated for the significant differences in the investigated groups. Differences or relationships were considered statistically significant at p < 0.05. The research revealed correlations between single crowns, overdenture restoration, bridge restoration, platform switching, prosthetic fracture, CI, and also marginal bone loss where p was lower than 0.05. However, the corticalization phenomenon itself has not yet been fully explored. The findings suggest that, depending on the type of prosthetic restoration, the corticalization index may correlate with marginal bone loss or not. Further research is necessary, as the index is suspected to not be homogeneous.

Full-Mouth Rehabilitation of a Patient with Sjogren's Syndrome with Maxillary Titanium-Zirconia and Mandibular Monolithic Zirconia Implant Prostheses Fabricated with CAD/CAM Technology: A Clinical Report

Dental implants have become a well-established treatment modality for the management of complete and partial edentulism. Recent advancements in dental implant systems and CAD/CAM technologies have revolutionized prosthodontic practice by allowing for the predictable, efficient, and faster management of complex dental scenarios. This clinical report describes the interdisciplinary management of a patient with Sjogren's syndrome and terminal dentition. The patient was rehabilitated using dental implants and zirconia-based prostheses in the maxillary and mandibular arches. These prostheses were fabricated using a combination of CAD/CAM and analog techniques. The successful outcomes for the patient demonstrate the importance of appropriate use of biomaterials and the implementation of interdisciplinary collaboration in treating complex dental cases.

A novel method of 3D printing locating guide for abutment screw removal in cement-retained implant-supported prostheses

Background/purpose

Cement-retained restorations have the advantages of passive fit, less complexity of clinical and laboratory methods, cost, esthetics, and dimensional stability over screw-retained restorations, especially in multiple abutment implant-supported prostheses. A common and difficult technical problem with cement-retained implant prostheses is abutment screw loosening. Three-dimensional (3D) printing is a technology that has been rapidly developed and has become widely accepted in dentistry. The aim of this study was to establish a novel method of using 3D implant planning guide to locate the abutment screw in cement-retained implant prosthesis.

Materials and methods

Six standard gypsum complete denture models were used to locate the abutment screw. An implant analog (4.5 mm in diameter and 12 mm in length) was placed in the drilling hole (5 mm in diameter and 14 mm in depth). After scanning with a 3D scanner, the 3D printing software was used to design the abutment screw location guide, which was printed by a resin-based 3D printer.

Results

A total of 30 abutment screws were located and removed using the guide. The locating guide's actual diameter was 2.4 mm. The drilling point was accurate and precise, and no excessive loss of the abutment was noticed.

Conclusion

The guide would help the dentist in locating the abutment screw access channel, resulting in a more precise and accurate drilling point. The guide for locating the abutment screw enhances the accuracy of screw channel access and reduces damage to the crown and abutment.

Impact of cement type and abutment height on pull-off force of zirconia reinforced lithium silicate crowns on titanium implant stock abutments: an in vitro study

Background

Pull-off forces of cement-retained zirconia reinforced lithium silicate (ZLS) in implant-supported single crowns on stock titanium abutments with respect to abutment height and implant cement were evaluated and compared.

Methods

Pull-off force of ZLS crowns on stock titanium abutments was evaluated concerning dental cement and abutment height. A total sample size of 64 stock abutments with heights of 3 mm (n = 32) and 5 mm (n = 32) was used. The ZLS crowns were cemented with four different types of cement (one temporary, two semi-permanent, and one permanent). After cementation, water storage, and thermocycling each sample was subjected to a pull-off test using a universal testing machine.

Results

The temporary cement showed the least pull-off force regardless of abutment height (3/5 mm: means 6 N/23 N), followed by the semi-permanent methacrylate-infiltrated zinc oxide cement (28 N/55 N), the semi-permanent methacrylate-based cement (103 N/163 N), and the permanent resin composite cement (238 N/820 N). Results of all types of cement differed statistically significantly from each other (p ≤ .012). The type of implant cement has an impact on the pull-off force of ZLS crowns and titanium abutments.

Conclusions

Permanent cements present higher retention than semi-permanent ones, and temporary cements present the lowest values. The abutment height had a subordinate impact.

Different Treatment Modalities Using Dental Implants in the Posterior Maxilla: A Finite Element Analysis

The objective of this study was to compare the biomechanical behavior of peri-implant bone tissue and prosthetic components in two modalities of treatment for posterior region of the maxilla, using short implants or standard-length implants associated with bone graft in the maxillary sinus. Four 3D models of a crown supported by an implant fixed in the posterior maxilla were constructed. The type of implant: short implant (S) or standard-length implant with the presence of sinus graft (L) and type of crown retention: cemented (C) or screwed (S) were the study factors. The models were divided into SC- cemented crown on a short implant; SS- screwed crown on the short implant; LC- cemented crown on a standard-length implant after bone graft in the maxillary sinus and LS- crown screwed on a standard-length implant after bone graft in the maxillary sinus. An axial occlusal loading of 300 N was applied, divided into five points (60N each) corresponding to occlusal contact. The following analysis criteria were observed: Shear Stress, Maximum and Minimum Main Stress for bone tissue and von Mises Stress for the implant and prosthetic components. The use of standard-length implants reduced the shear stress in the cortical bone by 35.75% and the medullary bone by 51% when compared to short implants. The length of the implant did not affect the stress concentration in the crown, and the cement layer acted by reducing the stresses in the ceramic veneer and framework by 42%. Standard-implants associated with cemented crowns showed better biomechanical behavior.

Bond Integrity of Titanium Surface to Resin Cement After Conditioning with Different Photobiomodulataion Therapy (PBT)

The aim of the present study was to evaluate the efficacy of interfacial bonding between resin cement and titanium alloy conditioned with different Photobiomodulataion Therapy (PBT) in comparison with conventional regimes. Seventy-five samples of titanium bar were segmented polished; and based on conditioning regime divided into five groups (15 each specimens). Group 1: No treatment (control), Group 2: Sand blasting with 120 µm Al2O3, Group 3: Er,Cr:YSGG (ECL), Group 4: Er:YAG laser (EYL), Group 5: Nd:YAG laser (NYL). After different conditioning regimes, resin cement was mixed and applied. All specimens were thermocycled for 500 cycles and positioned on universal testing machine for shear bond strength testing. Modes of failure was assessed by a single examiner using stereomicroscope at 40× magnification. Three pairs of specimens in each group were sputter coated and scanning electron microscope (SEM) images were taken at 1000× magnification using 20 Kv. The highest SBS values were observed in group 2 (14.25±2.29 MPa) and the lowest bond values were displayed in group 1 (6.98 ±0.59 MPa). Titanium alloy abutments conditioned with different laser prototypes ECL (11.22±1.40 MPa), EYL (9.29±1.22 MPa) and NYL (9.12 ±1.84 MPa) exhibited comparable SBS (p > 0.05). Adhesive failures were primarily dominant among all experimental groups. Photo-biomodulation in the form of ECL lasers has the potential to be used as a supplement to sandblasting procedure in conditioning of cement retained titanium alloy implant abutments.

Predictable immediate implant placement and restoration in the esthetic zone

This article describes a comprehensive step-by-step protocol for immediate implant placement and restoration in the esthetic zone. Clinical Considerations Immediate implant placement into fresh extraction sockets and immediate restoration have become widely accepted, demonstrating long-term success rates that are comparable with traditional delayed implant protocols. However, they are technique sensitive and require proper treatment planning as well as meticulous execution to be predictable and successful in the long term. This is particularly important in the esthetic zone, where even minor aberrations and mistakes can have devastating consequences, and especially in younger patients, where esthetic and functional outcomes should remain stable for years and possibly decades to come. The eight critical steps for predictable immediate implant placement include: provisional restoration of the failing tooth and presurgical phase, atraumatic tooth extraction, initial implant osteotomy, 3D bone graft packing, guided implant placement with a surgical guide, customized abutment insertion, provisional crown relining, and placement of a connective tissue graft from tuberosity. Immediate implant protocols in the esthetic zone require thorough planning and execution in the proper sequence. Each one of the critical steps discussed in this article has its own importance and challenges, which are critically assessed based on current scientific evidence.

Knowledge and Attitudes of Dental Interns and Dentists on Implants and Implant-Retained Restorations in Jeddah, Saudi Arabia

Objectives:

This cross-sectional study aimed to assess the knowledge and attitudes of dental interns and dentists in Jeddah, Saudi Arabia, about Cement-Retained Restoration (CRR), Screw Retained Restoration (SRR), and implant restoration.

Methods:

A total of 530 dentists and students participated in the study. Data were collected using a self-administrated questionnaire modified from previous studies. The collected data were analyzed using SPSS software for t-test, linear regression, and ANOVA.

Results:

Participants had a mean score of 5.01 (SD = 1.50) for a total of nine implant-retained restoration (IRR)knowledge questions (lowest score = 0, highest score = 9), and general implant knowledge had a mean score of 3.12 (SD = 1.25) for five questions with scores of 0 to 5. The participants’ knowledge about implants significantly differed in relation to gender, place of work, and work status. Also, participant knowledge about IRR showed significant differences in relation to participants' knowledge, age, gender and place of work. The dental interns and dentists were in agreement in considering SRR to be better than CRR for six out of nine factors. Those factors were cost effectiveness, expertise required for provision, retrievability, retention, fracture resistance, and passivity of fit.

Conclusion:

The overall knowledge of dental interns and dentists regarding implants and IRR was fair and needs to be improved, given the tendency of general dentists to engage in implant dentistry. Both dentists and interns considered CRR to be aesthetically superior, easier to fabricate, and requiring comparatively less expertise in comparison to SRR.

Retrospective comparison of posterior fixed dental prostheses supported by two different titanium abutments on tissue level implants

STATEMENT OF PROBLEM

Clinical studies comparing compatible computer-aided design and computer-aided manufacturing (CAD-CAM) titanium abutments (CAs) and original prefabricated 1-piece titanium abutments (PAs) for posterior fixed dental prostheses (FDPs) on Straumann Tissue Level (STL) implants are sparse.

PURPOSE

The purpose of this retrospective clinical study was to compare the performance of posterior FDPs supported by CAs and PAs on STL implants after a mean observation period of 7.2 years.

MATERIAL AND METHODS

Patients who received STL implants and posterior FDPs by using CAs or PAs between January 2002 and December 2012 and returned for follow-up between January 2017 and September 2018 were included in this study. Technical and biological complications of FDPs were examined and recorded. Radiographs were used for the measurement of marginal bone loss (MBL) of each implant. Variables, complication rates, and MBL of the 2 groups were analyzed by using a generalized estimating equation and multivariable linear mixed model.

RESULTS

Ninety-nine patients with 195 implants in the CA group and 75 patients with 143 implants in the PA group were included. The mean functional time of FDPs was 6.5 ±1.1 years for the CA group and 8.1 ±2.6 years for the PA group. No implant failure was noted in either group. The technical complication rate was 20.8% in the CA group and 26.3% in the PA group. Abutment screw loosening (ASL) was noted in the CA group (8.5%). The decementation rate was significantly higher in the PA group (14.1%) than that in the CA group (3.1%) (adjusted odds ratio=4.40, confidence interval=1.41 to 13.69, P=.011). No significant differences were found between the 2 groups in terms of the rates of ceramic chipping, peri-implantitis, peri-implant mucositis, or mean MBL.

CONCLUSIONS

Using CAs or PAs to support posterior FDPs on STL implants has no significant effect on the incidence rate of biological complications. However, a higher ASL rate and a lower decementation rate were noted with CAs than with PAs.

Fabricating a screw-retained, complete arch, fixed implant prosthesis using selective metal laser sintering: A clinical report

In contemporary prosthodontic practice, implant-supported therapy has consistently resulted in high success rates, with satisfactory and predictable outcomes for completely edentulous patients. Of the several options, complete-arch, fixed screw-retained solutions are generally considered to be the preferred treatment solution. Screw retention offers advantages such as predictable retrievability and potentially easy prosthodontic maintenance, as well as excess cement not being a concern. However, implant mispositioning and malalignment may often necessitate the use of cement-retained prostheses. This clinical report describes a method of fabricating a complete-arch, implant screw-retained, double framework metal-ceramic prosthesis, despite the unfavorable implant positioning, by using selective direct metal laser sintering technology.

Factors associated with abutment screw loosening in single implant supported crowns: A cross-sectional study

Background

Implant restorations are considered an ideal treatment option for replacement of missing teeth in partially edentulous patients. Abutment screw loosening is one of the frequently observed technical complications of implant-supported prosthesis. This study aimed to determine the prevalence and factors associated with the abutment screw loosening in cement-retained single-implant crowns.

Methods

Enrolment criteria included partially edentulous patients who have been rehabilitated with one or more cement-retained single-implant crowns with minimum postcementation period of 1 year. They were recalled and evaluated for the presence or absence of screw loosening both clinically and radiographically. They were further evaluated for the presence or absence of factors associated with screw loosening such as parafunctional habits, wider occlusal table, steep cuspal inclines, non-axial loading and cantilevering of the pontic.

Results

Twenty-six cement-retained single-implant crowns out of 280 showed screw loosening, making the overall prevalence rate of 10.77%. Among the factors evaluated, parafunctional habits were associated with three cases, wider occlusal table in four, steep cuspal inclines in three, non-axial loading in nine and cantilevering of the pontic in three cases. Exact reasons could not be ascertained in four cases.

Conclusion

Abutment screw loosening seems to be a significant prosthetic complication of cement-retained single-implant crowns. Factors evaluated significantly affect the functional durability of the prosthesis. These factors should be considered while restoring to enhance the longevity of such restorations.

Fracture loads of screw-retained implant-supported zirconia prostheses after thermal and mechanical stress

PURPOSE

The objective of the present study was to evaluate fracture loads of screw-retained implant-supported zirconia prostheses after artificial aging.

METHODS

Four types of screw-retained implant-supported prostheses were fabricated (n=11 each); porcelain-veneered zirconia prosthesis (PVZ), indirect composite-veneered zirconia prosthesis (IVZ), porcelain-fused-to-metal prosthesis (PFM), and monolithic zirconia prosthesis (ML). The specimens were subjected to 10,000 thermocycles and cyclic loading for 1.2 million cycles. Fracture loads were measured, and the data were analyzed with the Kruskal-Wallis and Steel-Dwass tests (α=0.05).

RESULTS

All specimens survived the artificial aging procedures. The fracture loads for the PVZ (1.52kN), IVZ (1.62kN), and PFM groups (1.53kN) did not significantly differ; however, the fracture load for the ML group (6.61kN) was significantly higher than those for the other groups. The fracture load for the IVZ group was comparable to those for the PVZ and PFM groups.

CONCLUSIONS

The monolithic zirconia prostheses exhibited significantly higher fracture loads than the bilayered prostheses. All the investigated types of screw-retained implant-supported zirconia prostheses appear sufficient to resist posterior masticatory forces during long-term clinical use.

A Comparative Study of Laser Irradiation Versus Sandblasting in Improving the Bond Strength of Titanium Abutments

Objective: The purpose of this study was to evaluate the effects of Er,Cr:YSGG laser irradiation with different energy powers versus sandblasting for enhancing the tensile bond strength (TBS) between titanium implant abutments (IAs) and resin cements. Background data: Clinical decementation of prosthetic restorations often occurs, particularly on short IAs. Increasing the bonding area on the IA surface can enhance the function and longevity of the superstructure. Materials and methods: Fifty dental IAs were used in solid form and randomly assigned to five groups (n = 10 each) for the following different pretreatments: control group was left untreated, a laser operating at 2.78 μm wavelength with different energy powers (1, 2, and 3 W) was used for three laser groups, and 50 μm alumina particles were applied to the abutment surface for the sandblasting group. Fifty metal substructures that had an occlusal metal O-ring were cast and cemented to all abutments using dual-cure resin cement. Test specimens were then subjected to thermal cycling. TBS tests were performed with a universal testing machine. The specimens' surface topography and roughness were evaluated with scanning electron microscope, and energy dispersive spectroscopy (EDS) was used to measure the elemental profiles of each specimen. Data were analyzed using a one-way analysis of variance/Kruskal-Wallis test at a significance level of p < 0.05. Results: Surface treatments affected the surface roughness and TBS of the IA. The sandblasting group showed the highest bond strength values (510.77 ± 60.86 N) and followed by the 2 W group (279.07 ± 37.9 N). In EDS analysis, no elemental components other than titanium and oxygen were observed, except for in the sandblasting group. Conclusions: Sandblasting and 2 W laser treatment increased the surface roughness of the IA, which could contribute to the increased interfacial bond strength between the IA and resin cement.

What is the Best Available Luting Agent for Implant Prosthesis?

Cement-retention is a viable option in restoring dental implants. A wide range of dental cements with different properties are commercially available for use in the cementation of implant prostheses. The selection of a dental cement for proper clinical application can be challenging. This article overviews the commercially available dental cements used in cement-retained implant-supported prostheses. Guidelines for cement selection are presented according to abutment and prosthetic material. Cementation techniques to reduce excess cement in peri-implant tissues are also mentioned.

Removal torque pattern of a combined cone and octalobule index implant-abutment connection at different cyclic loading: an in-vitro experimental study

Background

Despite the high survival rate of dental implants, screw loosening is frequently reported. Screw loosening can cause a misfit of the implant-abutment connection leading to peri-implantitis or abutment screw fracture. Therefore, studies about related factors and mechanism of screw loosening are needed. The aim of this study was to evaluate the decreasing pattern of removal torque values (RTVs) of a combined cone and octalobule index implant-abutment connection under different numbers of mechanical loading cycles.

Materials and methods

The study was performed in accordance with ISO 14801:2007. Eighty-four implants with the combined cone and octalobule index implant-abutment connection (PW Plus dental implant system, PW Plus Company) were used. All abutment screws were tightened 30 N cm twice with a 10-min interval. The control group was without cyclic loading and the experimental groups underwent different numbers of loading cycles until 2,000,000 cycles. Then, the abutment screws of all samples were untightened to measure the RTVs. The data were analyzed using ANOVA and Tukey’s HSD test.

Results

The RTVs of the control group decreased 7.78% compared to the insertion torque. All experimental groups from 50,000 to 2,000,000 cycles showed significant decreases in RTVs compared to the control group (P < 0.05). RTVs in the group of 50,000 cycles to 1,800,000 cycles did not change significantly, but there was a significant reduction of RTVs in the group of 2,000,000 cycles when compared to the group of 50,000 cycles (P < 0.05).

Conclusions

According to the setting condition for the fatigue test complied to ISO 14801:2007, the RTVs of the combined cone and octalobule index implant-abutment connection reduced significantly after 50,000 cycles and did not change significantly until 2,000,000 cycles.

A Prosthetic Solution to Poorly Placed Implants in the Posterior Mandible

The objective of the present study is to find a solution for patients who have multiple implants that are poorly placed in the posterior mandible and require a solution to be rehabilitated, taking into account some diagnostic principles such as maintenance of the occlusal plane, maintenance of correct dental arch inclination, and adequate vertical dimension.

Shear bond strength of luting cements to fixed superstructure metal surfaces under various seating forces

PURPOSE

In this study, the shear bond strengths (SBS) of luting cements to fixed superstructure metal surfaces under various seating forces were investigated.

MATERIALS AND METHODS

Seven different cements [Polycarboxylate (PCC), Glass-Ionomer (GIC), Zinc phospahate (ZPC), Self-adhesive resin (RXU), Resin (C&B), and Temporary cements ((RXT) and (TCS))] were bonded to a total number of 224 square blocks (5×5×3 mm) made of one pure metal [Titanium (CP Ti) and two metal alloys [Gold-Platinum (Au-Pt) and Cobalt-Chrome (Co-Cr)] under 10 N and 50 N seating forces. SBS values were determined and data were analyzed with 3-way ANOVA. Pairwise comparisons and interactions among groups were analyzed with Tukey's simultaneous confidence intervals.

RESULTS

Overall mean scores indicated that Co-Cr showed the highest SBS values (1.96±0.4) (P<.00), while Au-Pt showed the lowest among all metals tested (1.57±0.4) (P<.00). Except for PCC/CP Ti, RXU/CP Ti, and GIC/Au-Pt factor level combinations (P<.00), the cements tested under 10 N seating force showed no significantly higher SBS values when compared to the values of those tested under 50 N seating force (P>.05). The PCC cement showed the highest mean SBS score (3.59±0.07) among all cements tested (P<.00), while the resin-based temporary luting cement RXT showed the lowest (0.39±0.07) (P<.00).

CONCLUSION

Polycarboxylate cement provides reliable bonding performance to metal surfaces. Resin-based temporary luting cements can be used when retrievability is needed. GIC is not suitable for permanent cementation of fixed dental prostheses consisting of CP Ti or Au-Pt substructures.

Influence of abutment height and convergence angle on the retrievability of cement-retained implant prostheses with a lingual slot

PURPOSE

Cement-retained implant prostheses can lack proper retrievability during repair, and residual cement can cause peri-implantitis. The purpose of this in vitro study was to evaluate the influence of abutment height and convergence angle on the retrievability of cement-retained implant prostheses with lingual slots, known as retrievable cement-type slots (RCS).

MATERIALS AND METHODS

We fabricated six types of titanium abutments (10 of each type) with two different heights (4 mm and 6 mm), three different convergence angles (8°, 10°, and 12°), a sloped shoulder margin (0.6 mm depth), a rectangular shape (6 mm × 6.5 mm) with rounded edges, and a rectangular ledge (2 mm × 1 mm) for the RCS. One monolithic zirconia crown was fabricated for each abutment using a dental computer-aided design/computer-aided manufacturing system. The abutments and crowns were permanently cemented together with dual-curing resin cement, followed by 24 hours in demineralized water at room temperature. Using a custom-made device with a slot driver and torque gauge, we recorded the torque (N·cm) required to remove the crowns. Statistical analysis was conducted using multiple regression analysis and Mann-Whitney U tests (α=.05).

RESULTS

Removal torques significantly decreased as convergence angles increased. Multiple regression analysis showed no significant interaction between the abutment height and the convergence angle (Durbin-Watson ratio: 2.186).

CONCLUSION

Within the limitations of this in vitro study, we suggest that the retrievability of cement-retained implant prostheses with RCS can be maintained by adjusting the abutment height and convergence angle, even when they are permanently cemented together.

A Prosthesis Retention System for Full-Arch, Fixed, Implant-Supported Prosthesis

Full-arch, fixed, implant-supported prostheses can be designed to be cement- or screw-retained. Both retention mechanisms have a few inherent disadvantages. A fixed attachment system has been introduced to circumvent the disadvantages of both screw and cement retention. This system eliminates the screw access holes and the use of cement. The number of intraoral procedures required is also reduced. The purpose of this article is to report a case using the Locator F-Tx Attachment System to facilitate fabrication of an esthetic, clinician-retrievable, full-arch implant-supported fixed dental prosthesis.

The current considerations in the fabrication of implant prostheses and the state of prosthetic complications: A survey among the dental technicians

PURPOSE

To investigate the current considerations in the fabrication of dental implant prostheses (DIP) and the state of prosthetic complications from the dental technicians (DT) perspective.

METHODS

A self-designed pretested questionnaire and an informed consent were distributed to 150 certified DT working in dental laboratories of Riyadh, KSA. The demographic data, questions related to the implant fixed/removable prostheses and questions on the prosthetic complications related to the DIP were collected. Descriptive statistics and Chi-square test were used for statistical analysis, considering a P-value of <0.05 using SPSS.

RESULTS

130 responses (response rate 83.6%) were received. 53% (n = 69) of the DT received job orders for DIP from >20 dentists. 49% (n = 64) of dentists took the leading role in the treatment planning/designing. 48% (n = 62) and 52% (n = 68) of requests were for Cement and Screw retained DIP respectively. Custom abutments 37% (n = 49) choice of abutments. Porcelain fused to metal (PFM) 34% (n = 44) and PFM with metal occlusal surface 55% (n = 71) were material of choice. 49% (n = 64) designing of implant overdentures were according to the dentist's instructions with Ball and Socket 48% (n = 63) to be the most common attachment. DT regarded poor implant location/orientation 38% (n = 49) and inaccuracies in impression/bite-registration 40% (n = 52) as the obstacles to success. Half 50% (n = 65) of the repairs were for facing damage/chipping of ceramic. Fracture of the denture base/tooth detachment 50% (n = 65) was common with implant over dentures.

CONCLUSIONS

DT played a role and took decisions regarding the DIP. Frequent problems found by DT were poor implant location, discrepancies in impression/bite-registration, facing damage/chipping and damage/fracture of the denture base/prosthetic teeth. The frequency of these complications can be minimized by an increase in the prosthetic knowledge of the dentists and establishing clear protocols for communication between the dentist and the DT.

Influence of Luting Materials on the Retention of Cemented Implant-Supported Crowns: An In Vitro Study

The retention force of cemented crowns on implant abutments with various luting materials was evaluated. Cobalt⁻chromium crowns were cemented onto tapered titanium abutments (Camlog) with eugenol-free temporary cement (RelyX TempBond NE), composite-based temporary cement (Bifix Temp), zinc phosphate cement (Harvard Cement), glass-ionomer cements (Meron, Fuji I), and resin-modified glass-ionomer cements (Fuji II, Fuji Plus, Ketac Cem Plus). Specimen aging via hydrostress was performed in artificial saliva at 37 °C for 14 days (S1), followed by hydrothermal stress with thermocycling (S2). The crowns were removed, and the force was recorded (T1). Subsequently, the crowns were recemented, aged, and removed, and the force was recorded (T2, T3). The retention forces differences were statistically significant according to the storage conditions at T1 (p = 0.002) and T3 (p = 0.0002). After aging (S1), Ketac Cem Plus had the highest retention force median value difference (T3 versus T1) (-773 N), whereas RelyX TempBond NE had the lowest (-146 N). After aging (S2), Meron had the highest retention force median value difference (-783 N), whereas RelyX TempBond NE had the lowest (-168 N). Recementation decreased the retention force of the implant-supported cobalt⁻chromium crowns cemented and recemented with the same luting materials. Luting materials (at T1) and aging conditions significantly impacted the retention force.

The effect of ultrafast fiber laser application on the bond strength of resin cement to titanium

The purpose of this study was to investigate the effect of ultrafast fiber laser treatment on the bond strength between titanium and resin cement. A total of 60 pure titanium discs (15 mm × 2 mm) were divided into six test groups (n = 10) according to the surface treatment used: group (1) control, machining; group (2) grinding with a diamond bur; group (3) ultrafast fiber laser application; group (4) resorbable blast media (RBM) application; group (5) electro-erosion with copper; and group (6) sandblasting. After surface treatments, resin cements were applied to the treated titanium surfaces. Shear bond strength testing of the samples was performed with a universal testing machine after storing in distilled water at 37 °C for 24 h. One-way ANOVA and Tukey's HSD post hoc test were used to analyse the data (P < 0.05). The highest bond strength values were observed in the laser application group, while the lowest values were observed in the grinding group. Sandblasting and laser application resulted in significantly higher bond strengths than control treatment (P < 0.05). Ultrafast fiber laser treatment and sandblasting may improve the bond strength between resin cement and titanium.

A finite element analysis of novel vented dental abutment geometries for cement-retained crown restorations

Recent literature indicates that the long-term success of dental implants is, in part, attributed to how dental crowns are attached to their associated implants. The commonly utilized method for crown attachment - cementation, has been criticized because of recent links between residual cement and peri-implant disease. Residual cement extrusion from crown-abutment margins post-crown seating is a growing concern. This study aimed at (1) identifying key abutment features, which would improve dental cement flow characteristics, and (2) understanding how these features would impact the mechanical stability of the abutment under functional loads. Computational fluid dynamic modeling was used to evaluate cement flow in novel abutment geometries. These models were then evaluated using 3D-printed surrogate models. Finite element analysis also provided an understanding of how the mechanical stability of these abutments was altered after key features were incorporated into the geometry. The findings demonstrated that the key features involved in improved venting of the abutment during crown seating were (1) addition of vents, (2) diameter of the vents, (3) location of the vents, (4) addition of a plastic screw insert, and (5) thickness of the abutment wall. This study culminated in a novel design for a vented abutment consisting of 8 vents located radially around the abutment neck-margin plus a plastic insert to guide the cement during seating and provide retrievability to the abutment system.Venting of the dental abutment has been shown to decrease the risk of undetected residual dental cement post-cement-retained crown seating. This article will utilize a finite element analysis approach toward optimizing dental abutment designs for improved dental cement venting. Features investigated include (1) addition of vents, (2) diameter of vents, (3) location of vents, (4) addition of plastic screw insert, and (5) thickness of abutment wall.

Current status of implant prosthetics in Japan: a survey among certified dental lab technicians

Background

There are many implant cases in which dental technicians take initiative with regard to the design of implant prostheses, and to a certain extent, this area of care is one in which dentists do not necessarily play the leading role. Moreover, inadequate communication between dental technicians and dentists and insufficient instructions for technicians has been highlighted as issues in the past. The purpose of this questionnaire is to improve the quality of implant prostheses and thereby contribute to patient service by clarifying, among other aspects of treatment, problem areas and considerations in the fabrication of implant prostheses, conceptual-level knowledge, and awareness of prosthodontics on the part of the dentists in charge of treatment and methods for preventing prosthetic complications.

Methods

A cross-sectional survey was given to 120 certified dental technicians. To facilitate coverage of a broad range of topics, we classified the survey content into the following four categories and included detailed questions for (1) the conditions under which implant technicians work, (2) implant fixed prostheses, (3) implant overdentures, and (4) prosthetic complications.

Results

Out of 120 surveys sent, 74 technicians responded resulting in a response rate of 61.6%.

Conclusions

This survey served to clarify the current state of implant prosthodontics, issues, and considerations in the fabrication of implant prostheses, and the state of prosthetic complications and preventive initiatives, all from a laboratory perspective. The results of this survey suggested that, to fabricate prostheses with a high level of predictability, functional utility, and aesthetic satisfaction, it is necessary to reaffirm the importance for dentists to increase their prosthetic knowledge and work together with dental technicians to develop comprehensive treatment plans, implement an organized approach to prosthesis design, and accomplish occlusal reconstruction.

Retention Strength after Compressive Cyclic Loading of Five Luting Agents Used in Implant-Supported Prostheses

The purpose of this study was to evaluate and compare the retention strength of five cement types commonly used in implant-retained fixed partial dentures, before and after compressive cyclic loading. In five solid abutments screwed to 5 implant analogs, 50 metal Cr-Ni alloy copings were cemented with five luting agents: resin-modified glass ionomer (RmGI), resin composite (RC), glass ionomer (GI), resin urethane-based (RUB), and compomer cement (CC). Two tensile tests were conducted with a universal testing machine, one after the first luting of the copings and the other after 100,000 cycles of 100 N loading at 0.72 Hz. The one way ANOVA test was applied for the statistical analysis using the post hoc Tukey test when required. Before and after applying the compressive load, RmGI and RC cement types showed the greatest retention strength. After compressive loading, RUB cement showed the highest percentage loss of retention (64.45%). GI cement recorded the lowest retention strength (50.35 N) and the resin composite cement recorded the highest (352.02 N). The type of cement influences the retention loss. The clinician should give preference to lower retention strength cement (RUB, CC, and GI) if he envisages any complications and a high retention strength one (RmGI, RC) for a specific clinical situation.

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

OBJECTIVE

To determine the survival and the incidence of biologic and technical complications of implant-supported single crowns after 5 years of function.

MATERIAL AND METHODS

Patients treated with dental implants at the National Dental Centre, Singapore, from 2006 to 2010 were recruited from the Implant Registry and evaluated by two clinicians. One hundred and ninety-four patients, with 266 implant single crowns (SCs), were examined clinically for biologic and technical parameters. Digital radiographs were also obtained. Failure and complication rates were calculated based on the person-time at risk.

RESULTS

The mean biologic time in function was 5.9 ± 1.3 years. None of the implants had been lost, resulting in a 5-year survival of 100%. The corresponding success (complication-free) rate was 92.9% (95% CI: 89.2, 95.4). The mean prosthetic time in function was 5.2 ± 1.5 years, with a 5-year survival of implant-supported SCs of 98.2% (95% CI: 95.8, 99.3). The corresponding success rate was 88.9% (95% CI: 84.8, 92.0). The 5-year incidence of biologic complications, defined as PPD ≥6 mm with bleeding on probing/suppuration, in the presence of ≥2.5 mm of radiographic bone loss, was 7.1% (95% CI: 4.6, 10.9). The 5-year incidence of technical complications was 6.5% (95% CI: 3.9, 10.7) for fracture of the veneering material, 4.3% (95% CI: 2.4, 7.7) for loss of retention, 2.1% (95% CI: 1.0, 4.7) for abutment screw loosening and 0.4% (95% CI: 0.1, 2.5) for abutment fracture.

CONCLUSIONS

High survival rates (98.4%) for both the single tooth implants and the respective single crowns were demonstrated after 5.2 ± 1.5 years. However, the success rates were considerably lower (84.9%), indicating that biologic and technical complications were frequent.

Effects of crown retrieval on implants and the surrounding bone: a finite element analysis

PURPOSE

The aim of this study was to observe stress concentration in the implant, the surrounding bone, and other components under the pull-out force during the crown removal.

MATERIALS AND METHODS

Two 3-dimensional models of implant-supported conventional metal ceramic crowns were digitally constructed. One model was designed as a vertically placed implant (3.7 mm × 10 mm) with a straight abutment, and the other model was designed as a 30-degree inclined implant (3.7 mm × 10 mm) with an angled abutment. A pull-out force of 40 N was applied to the crown. The stress values were calculated within the dental implant, the abutment, the abutment screw, and the surrounding bone.

RESULTS

The highest stress concentration was observed at the coronal portion of the straight implant (9.29 MPa). The stress concentrations at the cortical bone were lower than at the implants, and maximum stress concentration in bone structure was 1.73 MPa. At the abutment screws, the stress concentration levels were similiar (3.09 MPa and 3.44 MPa), but the localizations were different. The stress at the angled abutment was higher than the stress at the straight abutment.

CONCLUSION

The pull-out force, applied during a crown removal, did not show an evident effect in bone structure. The higher stress concentrations were mostly observed at the implant and the abutment collar. In addition, the abutment screw, which is the weakest part of an implant system, also showed stress concentrations. Implant angulation affected the stress concentration levels and localizations.

CLINICAL IMPLICATIONS

These results will help clinicians understand the mechanical behavior of cement-retained implant-supported crowns during crown retrieval.

The selection criteria of temporary or permanent luting agents in implant-supported prostheses: in vitro study

PURPOSE

The use of temporary or permanent cements in fixed implant-supported prostheses is under discussion. The objective was to compare the retentiveness of one temporary and two permanent cements after cyclic compressive loading.

MATERIALS AND METHODS

The working model was five solid abutments screwed to five implant analogs. Thirty Cr-Ni alloy copings were randomized and cemented to the abutments with one temporary (resin urethane-based) or two permanent (resin-modified glass ionomer, resin-composite) cements. The retention strength was measured twice: once after the copings were cemented and again after a compressive cyclic loading of 100 N at 0.72 Hz (100,000 cycles).

RESULTS

Before loading, the retention strength of resin composite was 75% higher than the resin-modified glass ionomer and 2.5 times higher than resin urethanebased cement. After loading, the retentiveness of the three cements decreased in a non-uniform manner. The greatest percentage of retention loss was shown by the temporary cement and the lowest by the permanent resin composite. However, the two permanent cements consistently show high retention values.

CONCLUSION

The higher the initial retention of each cement, the lower the percentage of retention loss after compressive cyclic loading. After loading, the resin urethane-based cement was the most favourable cement for retrieving the crowns and resin composite was the most favourable cement to keep them in place.

Screw- vs. Cement-retained Implant-supported Prosthesis in Partially Edentulous Patients: An Oral Health Technology Assessment Report

Understanding the morbidity events, incidence, and cost associated with each type of retention system used for implant supported prosthesis will help the clinician in better decision making. This study assessed the clinical and cost-effectiveness of the screw- and cement-retained implant-supported single crown and fixed partial denture for the replacement of teeth in partially edentulous jaws, from a health services perspective. A systematic literature search conducted in 10 databases, complemented by 4 journal databases and International Association for Dental Research abstracts, identified 92 studies on the single crown and 40 studies on the fixed partial denture. Minor and major technical complication events, as well as failure events, were extracted from strong- and medium-quality studies. Studies based on similar designs were pooled with a random-effects Poisson regression model. A decision tree was developed to estimate the cost-effectiveness over a 15-y period posttreatment. The initial and maintenance costs to treat technical complication events were based on an American Dental Association survey of 2011 to 2012. Probabilistic sensitivity analysis was used to examine the uncertainty in the data input parameters. Clinical evidence generated from the meta-analysis suggested no statistical difference between the 2 retention systems. The cost-effectiveness is presented as an incremental cost-effectiveness ratio. The evidence from this report suggests that cement retention is the more cost-effective strategy as compared with screw retention prosthesis. Knowledge Transfer Statement: Evidence generated by this study will help clinicians make an appropriate cost-effective treatment decision in choosing the retention system for partially edentulous patients.

Clinical evaluation of an improved cementation technique for implant-supported restorations: a randomized controlled trial

BACKGROUND

Cement remnants were frequently associated with peri-implantitis. Recently, a shoulderless abutment was proposed, raising some concern about cement excess removal.

AIM

To compare different cementation techniques for implant-supported restorations assessing the amount of cement remnants in the peri-implant sulcus. Additional aim was to compare the effect of these cementation techniques using two different abutment designs.

MATERIAL & METHODS

Forty-six patients requiring double implant-supported restoration in the posterior maxilla were randomly divided in two groups according to the cementation modality: intraoral and extraoral. According to the abutment finishing line, implants in each patient were randomly assigned to shoulderless or chamfer subgroup. In the intraoral group, crowns were directly seated onto the titanium abutment. In the extraoral group, crowns were firstly seated onto a resin abutment replica and immediately removed, then cleansed of the cement excess and finally seated on the titanium abutment. After cement setting, in both groups, cement excess was carefully tried to remove. Three months later, framework/abutment complexes were disconnected and prepared for microscopic analysis: surface occupied by exposed cement remnants and marginal gaps were measured. Additionally, crown/abutment complexes were grinded, and voids of cement were measured at abutment/crown interface. Related-samples Friedman's two-way analysis of variance by ranks was used to detect differences between groups and subgroups (P ≤ 0.5).

RESULTS

At the end of the study, a mean value of 0.45 mm² (±0.80), 0.38 mm² (±0.84), and 0.065 mm² (±0.13) and 0.07 mm² (±0.15) described surface occupied by cement remnants in shoulderless and chamfer abutment with intraoral cementation and shoulderless and chamfer abutment with extraoral cementation, respectively. A mean value of 0.40 mm² (±0.377), 0.41 mm² (±0.39) and 0.485 mm² (±0.47) and 0.477 mm² (±0.43) described cement voids at the abutment/crown interface; a mean value of 0.062 mm (±0.03), 0.064 mm (±0.35), 0.055 mm (±0.016) and 0.054 mm (±0.024) described marginal gaps. Statistics showed tendency of intraoral cementation to have significantly higher cement remnants compared with abutments with extraoral cementation groups. At the same time, the presence of voids was significantly higher in case of extraoral cementation. No significant differences between groups for the variable "gap".

CONCLUSIONS

Despite the presence of more voids, extraoral cementation reduces cement excess. However, using low adhesivity cement and careful cement removal, a very limited quantity of cement remnants was observed also in the intraoral cementation.

Cemented and screw-retained implant-supported single-tooth restorations in the molar mandibular region: A retrospective comparison study after an observation period of 1 to 4 years

Objectives: The aim of this study was to evaluate the survival and compare the appearance of different mechanical and biological complications, in screw-retained and cemented-retained single-tooth implant-supported restorations localized in the molar mandibular region, over a period of 1 to 4 years. Material and Methods: A retrospective study was carried out with a total of eighty implant-supported restorations, which were placed in eighty patients for prosthetic rehabilitation of a mandibular molar. Forty patients were rehabilitated with a cemented-retained restoration and the other forty with a screw-retained restoration. The presence of the following complications was recorded for both types of prostheses: Fractures of the ceramic veneering, loosening screws, mucositis and peri-implantitis. Debonding of the restoration was analyzed in the cemented-retained restoration group. The clinical survival of crowns was analyzed with a Kaplan-Meier test and the clinical complications were compared, using a Student t test and Log-rank test. Results: 27 patients registered some complication. The average rate of complications was 37,5% for cemented-retained restorations and 30% for screw-retained restorations. The complications more common in the cemented-retained restoration were the presence of mucositis (14,87%), while in the screw-retained restorations was the loosening screw (20%). Student t test and Log-Rank test found significant differences (p=0,001) between the screw loosening and presence of mucositis. Conclusions: The cemented-retained restorations seem to prevent screw loosening, but the presence of cement seem to increase the complications around the soft tissues, however in the screw-retained restorations the presence of mucositis and peri-implantitis are lower than cemented-retained restorations. The incidence of fracture of ceramic veneering was similar in both groups.

Key words:Screw-retained restorations, cemented-retained restorations, screw loosening, peri-implant diseases and fracture ceramic veneering.

Fixed restorations supported by Morse-taper connection implants: a retrospective clinical study with 10-20 years of follow-up

OBJECTIVES

Rehabilitation with implant-supported fixed prostheses is a predictable modality to restore lost function and esthetics; however, fixed restorations are subject to biological and prosthetic complications, which may represent a problem in the long-term. The aim of this study was to evaluate the long-term survival and complication rates of fixed restorations supported by Morse-taper connection implants.

MATERIALS AND METHODS

Between January 1992 and December 2002, 49 patients (age range 22-70 years), were included in this study. The restorations involved 58 fixed reconstructions (15 single crowns [SCS], 29 partial prostheses, 14 full-arches), supported by 178 Morse-taper connection implants with a follow-up ranging from 10 to 20 years. Outcomes such as implant survival, marginal bone loss, frequency of biological and prosthetic complications as well as "complication-free" survival of restorations were investigated.

RESULTS

The 20-year overall cumulative implant survival was 97.2%. A few biological (3.4%) and prosthetic (10.3%) complications were reported. The "complication-free" survival rate of restorations was 85.5%. No statistically significant differences were observed among patients' gender, age, smoking or parafunctional habits, prosthesis site and type.

CONCLUSIONS

Satisfactory "complication-free" survival rates can be achieved after 20 years for fixed restorations supported by Morse-taper connection implants, with minimal marginal bone loss and complications.