Comparative analyses of time efficiency and cost in fabricating fixed implant-supported prostheses in digital, hybrid, and conventional workflows: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Economic considerations affect whether new technologies are adopted in dental practice. Limited evidence exists regarding the time and cost efficiency of different workflows for fabricating implant-supported restorations.

PURPOSE

The purpose of this systematic review and meta-analysis was to compare the time and cost involved in fabricating fixed implant-supported prostheses using digital, hybrid, and conventional methods throughout the entire prosthetic treatment by analyzing both clinical and laboratory steps.

MATERIAL AND METHODS

A systematic review was conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA)-P 2015 guidelines. The methods and inclusion criteria were specified in a protocol registered with the International Prospective Register of Systematic Reviews (PROSPERO) (registration number CRD42023458734). The databases PubMed, Cochrane, and PROSPERO were searched using keywords: (Prosthodontic OR restorative dentistry OR denture) AND (CAD CAM OR Digital workflow OR Computer Dentistry OR Digital Design) AND (Economic OR cost OR Financial OR time efficiency). Two investigators selected articles independently.

RESULTS

A qualitative synthesis of 12 articles published from 2010 to 2023 showed that digital scans took less time than conventional impressions (P<.05) in 7 out of 9 articles. Additionally, 8 articles revealed significant reductions in laboratory working time with digital workflows, intermediate times with hybrid workflows, and longer times with conventional workflows (P<.001). Meta-analysis confirmed the time efficiency of digital scanning over conventional impressions (Hedges g=1.65, 95% CI [0.33, 2.98]) and a substantial reduction in laboratory time with digital workflows compared with other workflows (Hedges g=6.55, 95% CI [2.69; 10.42]). However, no significant difference was found in adjustment time between digital and other workflows (Hedges g=0.91, 95% CI [-0.72; 2.55]). Direct laboratory costs were observed to be higher in conventional workflows compared with hybrid or digital workflows, with hybrid workflows also showing elevated costs compared with digital workflows (P<.05).

CONCLUSIONS

The digital workflow demonstrates potential benefits in reducing scan time, laboratory processing time, and direct laboratory costs for implant-supported restorations in partial edentulism. Further research is needed to validate these findings, particularly for long-span implant-supported fixed partial prostheses.

The Influence of Cement Thickness within the Cap on Stress Distribution for Dental Implants

The purpose of this finite element analysis (FEA) was to evaluate the stress distribution within the prosthetic components and bone in relation to varying cement thicknesses (from 20 to 60 μm) utilized to attach a zirconia crown on a conometric cap. The study focused on two types of implants (Cyroth and TAC, AoN Implants, Grisignano di Zocco, Italy) featuring a Morse cone connection. Detailed three-dimensional (3D) models were developed to represent the bone structure (cortical and trabecular) and the prosthetic components, including the crown, cement, cap, abutment, and the implant. Both implants were placed 1.5 mm subcrestally and subjected to a 200 N load at a 45° inclination on the crown. The results indicated that an increase in cement thickness led to a reduction in von Mises stress on the cortical bone for both Cyroth and TAC implants, while the decrease in stress on the trabecular bone (apical zone) was relatively less pronounced. However, the TAC implant exhibited a higher stress field in the apical area compared to the Cyroth implant. In summary, this study investigated the influence of cement thickness on stress transmission across prosthetic components and peri-implant tissues through FEA analysis, emphasizing that the 60 μm cement layer demonstrated higher stress values approaching the material strength limit.

Influencing Factors Regarding the Severity of Peri-Implantitis and Peri-Implant Mucositis

The scientific literature is increasingly focused on peri-implant mucositis and peri-implantitis, which are biological outcomes of dental implant treatment.

BACKGROUND/OBJECTIVES

The present study aimed to evaluate the two most critical complications of dental implantation, peri-implant mucositis and peri-implantitis, through the prism of different influencing factors.

METHODS

We followed 40 patients, with a total number of 92 dental implants, divided into three age groups: under 35 years, between 35 and 55 years, and older than 55 years. Patients were also divided into groups according to the time since implant placement: 1-3 years, 4-7 years, and more than 7 years. The patients were examined, and periodontal pocket depth, peri-implant pocket depth, Löe-Silness gingival index, mucosal thickness, and keratinized mucosal width were recorded; bone resorption was measured on radiographs using a 2D image analysis method; and a questionnaire was also conducted.

RESULTS

Bone resorption was highest in the 35-55 age group (3.09 ± 0.04 mm) and for implants placed 4-7 years ago (3.39 ± 0.12 mm). Females had a mean bone resorption of 3.4 ± 0.15 mm and males of 2.45 ± 0.07 mm. Statistically, there was a significant difference only in the Löe-Silness index: the 35-55 age group had the highest values (p = 0.04).

CONCLUSIONS

There were no statistically significant differences between the time since implant placement and the degree of bone resorption, nor between sexes. Peri-implant inflammation may occur at any age, regardless of the lifetime of the implants.

Effect of supracrestal tissue height on marginal bone level changes at platform-switching dental implants placed crestally and subcrestally: A randomized clinical-trial

OBJECTIVES

The presence of insufficient peri-implant supracrestal tissue height (STH) may increase marginal bone resorption. This study aims to evaluate the effect of STH on marginal bone level changes (ΔMBC) in platform-switching posterior implants placed crestally and subcrestally.

METHODS

A total of 80 implants were included in this study. There were two main groups in the study; STH≤2 mm (A) and STH> 2 mm (B) and four subgroups according to the implant placement level, crestally (I) and subcrestally (II): A-I, A-II, B-I, and B-II. Intraoperatively, STH and placement depths of implants were measured from mesial and distal aspects. The mesial and distal peri-implant marginal bone levels were measured on periapical radiographs at immediately (T0), 6 months (T1), 9 months (T2), and 12 months (T3) after functional loading, and the difference between the marginal bone levels was calculated as the ΔMBC.

RESULTS

Statistically significantly more mesial ΔMBC was detected in the A-I than in the B-I at the time of T0-T1. In the group with STH greater than 2 mm, the difference in ΔMBC between the crestally and subcrestally placements was not statistically significant.

CONCLUSIONS

This study was found that STH is effective at protecting the marginal bone in the early period, and in cases where the STH is insufficient, subcrestally placement may increase long-term implant success by preventing marginal bone loss from occurring beyond the implant shoulder. The clinical trial number is NCT05595746.

CLINICAL SIGNIFICANCE

In this study, it was demonstrated that an STH greater than 2 mm is important for marginal bone stabilization, regardless of crestal and subcrestal levels, and that subcrestally placement is beneficial in cases of insufficient STH.

Clinical performance and risk factors of all-ceramic screw-retained implant crowns in the posterior region based on a retrospective investigation

OBJECTIVES

Clinical data on all-ceramic screw-retained implant crowns (SICs) luted on titanium base abutments (TBAs) over more than 3 years are sparse. This study aimed to evaluate the clinical performance and potential risk factors for these restorations.

MATERIALS AND METHODS

Analysis took place based on the medical patient-records of three dental offices. Implant survival and prosthetic complications over time were evaluated. The study included SICs in premolar and molar regions made from monolithic lithium disilicate ceramic (M_LiDi) or veneered zirconia (V_ZiO) luted on a TBA documented over an observation time of at least 3 years. Survival and complication rates were calculated and compared by a log-rank test. Cox-Regressions were used to check potential predictors for the survival (p < .05).

RESULTS

Six hundred and one crowns out of 371 patients met the inclusion criteria and follow-up period was between 3.0 and 12.9 (mean: 6.4 (SD: 2.1)) years. Over time, six implants had to be removed and 16 restorations had to be refabricated. The estimated survival rates over 10 years were 93.5% for M_LiDi and 95.9% for V_ZiO and did not differ significantly among each other (p = .80). However, V_ZiO showed significantly higher complication rates (p = .003). Material selection, sex, age, and implant diameter did not affect the survival of investigated SICs but crown height influences significantly the survival rate (hazard ratio, HR = 1.26 (95%CI: 1.08, 1.49); p = .043).

CONCLUSIONS

Screw-retained SICs luted on TBAs that were fabricated from monolithic lithium disilicate ceramic or veneered zirconia showed reliable and similar survival rates. Increasing crown heights reduced survival over the years.

Effect of treatment with implant-supported fixed partial dentures on oral health-related quality of life in patients with unilateral shortened dental arch

Background/purpose

Implant-supported fixed partial dentures (IFPDs) are a treatment option for partially edentulous dentition with missing posterior-most molars despite the concept of a shortened dental arch (SDA). This study aimed to evaluate the effect of IFPD treatment on oral health-related quality of life (OHRQoL) in patients with unilateral SDA missing two adjacent molars and to compare the effects of single- and two-unit IFPDs.

Materials and methods

Forty patients with unilateral SDA missing two adjacent molars (Kennedy Class II) participated in this study; 11 patients received one implant placement in the first molar and were treated with a single-unit IFPD (single-unit group), and 29 received two implant placements and were treated with a two-unit IFPD (two-unit group). The Oral Health Impact Profile (OHIP) questionnaire for OHRQoL assessment and the gummy jelly test for objective masticatory performance were administered before and after IFPD treatment. The Wilcoxon signed-rank test for all patients and Mann-Whitney U test were performed for pre- and post-treatment comparisons and between-group comparisons, respectively.

Results

The OHIP summary score and gummy jelly glucose concentration in all patients showed significant improvements after treatment (all P < 0.05). No significant differences were observed between the single- and two-unit groups for any of the items. Using the minimal important difference in the OHIP summary score, 63.6 % and 58.6 % of patients in the single- and two-unit groups, respectively, showed improvement by 6 points or more.

Conclusion

IFPD treatment for patients with SDA missing two adjacent molars may provide clinically meaningful improvements in OHRQoL.

Fracture resistance of hybrid ceramic abutments with different restoration lengths: A pilot study

AIM

In this pilot study, the fracture resistance of hybrid abutments with different restoration lengths was investigated.

MATERIALS AND METHODS

Sixteen monolithic zirconia restorations of an upper right incisor were designed to fit a titanium base abutment. Eight central incisors had a crown length of 8 mm (T1) and the other half a length of 12 mm (T2). All crowns were cemented on the titanium base using a resin cement. After cementation, the samples were placed in a thermocycler for 5000 cycles. Fracture strength was measured using a universal test machine. Deformations and fractures of the samples were investigated.

RESULTS

The mean fracture resistance of T1 was 515 N (SD 96 N, 339-650) and 305 N (SD 57 N, 234-408) for T2 (p < 0.001). Both groups showed deformation of the titanium base, with no significant difference between both groups (p = 0.200). A difference in fracture type (p = 0.013) was observed, with significantly more screw fractures occurring in group T1 (p = 0.026).

CONCLUSION

Within the limitations of this study, hybrid restorations with standard titanium base abutments can withstand forces that have been associated with chewing, irrespective of the crown length. However, the shorter crowns demonstrated more fatal fractures.

Fracture resistance of cement-retained lithium disilicate implant-supported crowns: Effect of material used for two-piece abutments

PURPOSE

This study compared the fracture strength of single lithium disilicate implant-supported crowns fabricated on two-piece abutments with various materials: ceramic-reinforced PEEK, zirconia, and lithium disilicate.

MATERIALS AND METHODS

Thirty-six implants were embedded in acrylic cylinders. A two-piece abutment and a crown were designed following a pre-operation scan for a maxillary left central incisor. The designed crown was used to fabricate 36 lithium disilicate crowns. The designed abutment was used to manufacture 36 abutments from 3 materials, 12 each: (A) zirconia; (B) lithium disilicate; and (C) ceramic-reinforced PEEK. Abutments were surface treated and bonded on the titanium base abutments with resin cement. Then, lithium disilicate crowns were bonded on the assigned abutments. Specimens were then subjected to dynamic loading for 1,200,000 cycles. The fracture strength (N) of the assembly was assessed using a universal testing machine. One-way ANOVA followed by multiple comparison tests was used to evaluate the effect of abutment material on the fracture strength of single implant-supported restorations at a significance of .05.

RESULTS

The average fracture strength for the groups with zirconia, PEEK, and lithium disilicate two-piece abutments were 1362N ± 218N, 1235N ± 115N, and 1472N ± 171N, respectively. There was a significant (p < 0.05) difference in fracture strength among the groups. The lithium disilicate group had significantly higher fracture strength (p = 0.0058) than the group with PEEK; however, there was no significant (p > 0.05) difference between the other groups.

CONCLUSIONS

Two-piece abutments restored with lithium disilicate crowns investigated in the study have the potential to withstand the average physiological occlusal forces in the anterior region.

A conservative approach to localize loose implant screw through cemented crown: an in vitro experimental study

BACKGROUND

Retrieval of cement-retained implant-supported restorations is intriguing in cases of screw loosening. Detecting the estimated size of the screw access hole (SAH) could decrease destruction to the prosthesis and preserve the crown.

OBJECTIVES

To precisely localize loose implant screws through cemented crowns to reduce crown damage after screw loosening.

MATERIALS AND METHODS

In this in vitro study, 60 cement-retained implants supported 30 zirconia-based, and 30 ceramics fused to metal (CFM) lower molar crowns were invented, and each was subdivided into three subgroups (10 each). In group I (AI/BI) (control), SAH was created with the aid of orthopantomography (OPG). In contrast, in group II (zirconia-crown), SAH was created with the aid of CBCT + 3D printed surgical guide with a 2 mm metal sleeve in subgroups IIA/IIIA and CBCT + MAR was used to develop SAH in subgroups IIB/IIIB. SEM and Micro-CT scanned the SAH openings to determine the diameter of the hole, cracking, chipping, and chipping volume.

RESULTS

Regarding the effect of plane CBCT and CBCT + MAR on prepared crowns, a highly significant association between group I with group II (p = 0.001) and group III (p = 0.002) was detected. Regarding the cracking of SAH, significant differences between the zirconium crown and CFM restoration (p = 0.009) were found, while for the chipping, no significant association was seen between groups (p = 0.19).

CONCLUSIONS

CBCT, either as a plane CBCT or with MAR, significantly improved the accuracy of drilling the screw channel and decreased injury to the existing restoration and abutment, aiding in better localization of SAH in loosened implant abutment screws.

Survey of screw-retained versus cement-retained implant restorations used in both education and private dental practices

AIMS

In the literature, it is still unclear if the decisions for selecting the type of implant crown-retaining system are based on scientific-based research or if the Universities' choices, Implant marketing trends, or finances could have a major influence on the private dentists' decisions.

OBJECTIVES

Therefore, this study aimed to evaluate the crown-retaining system (cement- or screw-retained) used in dental schools and private dental practices.

METHODS

A 13-item questionnaire was sent to Canadian dental schools (n = 10) and dental offices in London (n = 298), Canada. The questionnaire included demographic questions and questions to reveal the dentists' perspectives on prosthetic implant treatment between the two-retaining systems. Results were analyzed using descriptive statistics and multinomial logistic regression (p = 0.05).

RESULTS

Twenty-four private dentists and five dental schools responded to the survey - 62.5% of private practitioners and 60% of universities reported using both systems. A trend was observed in using screw-retained systems by dentists who graduated 5-10 years ago. Straumann, Astra, and Nobel Biocare were the private practices and dental schools' preferred implant systems. The use of platform switching for all cases was selected by 54.2% of the private practitioners and 40% of the dental schools. Resin cement was the private practice's preferred cementation method; the dental schools used glass ionomer and zinc phosphate cement. The multinomial logistic regressions showed no statistical difference between the crown-retaining system chosen and the decision factors. The laboratory technician's recommendations and cost influenced the decision-making process for private dentists. For the universities, perio-restorative outcome, implant position, survival rates, institute preferences, and evidence-based research influenced the crown-retaining system's decision-making process.  CONCLUSION: The Canadian dental schools and private practice reported using both screw- and cement-retaining systems. However, there was a difference in the selection criteria as the universities showed a tendency towards a more research-based approach in their decision, while for the private practices, the technicians' recommendations and cost played a major role in the decision process. It was noted that the implant systems preconized by the Universities were observed to be used in private practices.

Prediction of excess cement residues using a regression model to avoid peri-implant diseases: An in vitro study

Dental implant restorations attached to cement can potentially result in peri-implant mucositis and peri-implantitis if cement residues are present. Effectively predicting and eliminating such dental cement residues is crucial for preventing complications. This study focuses on creating a regression model using the pixel values to predict the Excess Cement Residues (ECR) by employing an octagonal surface imaging approach. A model featuring gingival imitation, ten abutments, and ten crowns was created, and the cemented implants underwent thorough photographic and analytical assessment. The ECR was determined through two distinct approaches: the Computerized Planimetric Method (CPM) and the weighing method. Across ten implants in this in vitro study, ECR varied from 0.3 to 21 mg, with an average of 5.69 mg. The findings reveal a higher amount of ECR on the distal, mesiobuccal, and mesial sides. Utilizing Pearson's correlation, a coefficient value of r = 0.786 signifies a strong correlation between CPM and the weighing method. The regression model further aids in predicting ECR based on pixel values. The octagonal surface imaging approach not only vividly captures information about ECR in the implant cementation region but also emphasizes the feasibility of ImageJ as an effective tool for detecting ECR. The congruence between CPM and the weighing method results supports the application of the regression model for precise ECR prediction.

Screw-retained ceramic-veneered/monolithic zirconia partial implant-supported fixed dental prostheses: A 5 to 10-year retrospective study on survival and complications

PURPOSE

To assess the clinical performance of screw-retained, ceramic-veneered, monolithic zirconia partial implant-supported fixed dental prostheses (ISFDP) over 5-10 years and to evaluate implant- and prosthesis-related factors influencing treatment failure and complications.

MATERIALS AND METHODS

Partially edentulous patients treated with screw-retained all-ceramic ISFDPs with 2-4 prosthetic units with a documented follow-up of ≥5 years after implant loading were included in this retrospective study. The outcomes analyzed included implant/prosthesis failure and biological/technical complications. Possible risk factors were identified using the mixed effects Cox regression analysis.

RESULTS

A screened sample of 171 participants with 208 prostheses (95% of the restorations were splinted crowns without a pontic) supported by 451 dental implants were enrolled in this study. The mean follow-up duration after prosthesis delivery was 82.4 ±17.2 months. By the end of the follow-up period, 431 (95.57%) of the 451 implants remained functional at the implant level. At the prosthesis level, 185 (88.94%) of the 208 partial ISFDPs remained functional. Biological complications were observed in 67 implants (14.86%), and technical complications were observed in 62 ISFDPs (29.81%). Analysis revealed only emergence profiles (over-contoured) as a significant risk factor for implant failure (P<0.001) and biological complications (P<0.001). Full-coverage ceramic-veneered zirconia prostheses had a significantly greater chance of chipping (P<0.001) compared with buccal-ceramic-veneered or monolithic zirconia prostheses.

CONCLUSIONS

Screw-retained ceramic-veneered, monolithic partial ISFDPs have a favorable long-term survival rate. Over-contoured emergence profile is a significant risk factor associated with implant failure and biological complications. Buccal-ceramic-veneered and monolithic zirconia partial ISFDPs lower the initial prevalence of chipping compared with a full-coverage veneered design.

CEMENTED AND SCREW-RETAINED IMPLANT-SUPPORTED RESTORATIONS MAY HAVE A COMPARABLE RISK FOR PERI-IMPLANT MUCOSITIS AND PERI-IMPLANTITIS

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION

Reis INRD, Fukuoka GL, Nagay BE, Pannuti CM, Spin-Neto R, Silva EVFD. Incidence of peri-implant disease associated with cement- and screw-retained implant-supported prostheses: A systematic review and meta-analysis. J Prosthet Dent. 2023 Oct 2:S0022-3913(23)00563-2. doi:10.1016/j.prosdent.2023.08.030. Epub ahead of print. PMID: 37793953.

SOURCE OF FUNDING

None declared.

TYPE OF STUDY/DESIGN

Systematic review and meta-analysis.

Clinical performance of implant-supported single hybrid abutment crown restoration: A systematic review and meta-analysis

PURPOSE

To investigate survival rates and technical and biological complications of one-piece screw-retained hybrid abutments in implant-supported single crowns (SCs).

STUDY SELECTION

An electronic search was performed on five databases for clinical studies involving implant-supported single hybrid abutment crowns constructed using titanium-base (Ti base) abutments, with at least 12 months of follow-up. The RoB 2, Robins-I, and JBI tools were used to assess the risk of bias for the different study types. Success, survival, and complication rates were calculated, and a meta-analysis was performed to obtain a pooled estimate. Peri-implant health parameters were extracted and analyzed.

RESULTS

22 records (20 studies) were included in this analysis. Direct comparisons between screw-retained hybrid abutment SCs and cemented SCs showed no significant differences in the 1-year survival and success rates. For SCs using a hybrid abutment crown design, their 1-year survival rate was 100% (95% CI: 100%-100%, I2 = 0.0%, P = 0.984), and a success rate of 99% (95% CI: 97%-100%, I2 = 50.3%, P = 0.023) was calculated. No confounding variables significantly affected the estimates. The individual technical complication rate was low at 1-year follow-up. The estimated incidence of all types of complications in hybrid abutment SCs is less than 1%.

CONCLUSIONS

Within the limitations of this study, implant-supported SCs using a hybrid abutment crown design showed favorable short-term clinical outcomes. Additional well-designed clinical trials with at least a 5-year observation period are required to confirm their long-term clinical performance.

The effect of three dental cement types on the corrosion of dental implant surfaces

Statement of problem

One of the main challenges facing dental implant success is peri-implantitis. Recent evidence indicates that titanium (Ti) corrosion products and undetected-residual cement are potential risk factors for peri-implantitis. The literature on the impact of various types of dental cement on Ti corrosion is very limited.

Purpose

This study aimed to determine the influence of dental cement on Ti corrosion as a function of cement amount and type.

Materials and methods

Thirty commercially pure Ti grade 4 discs (19 × 7mm) were polished to mirror-shine (Ra ≈ 40 nm). Samples were divided into 10 groups (n = 3) as a cement type and amount function. The groups were no-cement as control, TempBond NE (TB3mm, TB5mm, and TB8mm), FujiCEM-II (FC3mm, FC5mm, and FC8mm), and Panavia-F-2.0 (PC3mm, PC5mm, and PC8mm). Tafel's method estimated corrosion rate (icorr) and corresponding potential (Ecorr) from potentiodynamic curves. Electrochemical Impedance Spectroscopy (EIS) data was utilized to obtain Nyquist and Bode plots. An equivalent electrical circuit estimated polarization resistance (Rp) and double-layer capacitance (Cdl). Inductively coupled plasma mass spectrometry (ICP-MS) analysis was conducted to analyze the electrolyte solution after corrosion. pH measurements of the electrolyte were recorded before and after corrosion tests. Finally, the corroded surface was characterized by a 3D white-light microscope and scanning electron microscope. Statistical analysis was conducted using either one-way ANOVA followed by Tukey's Post Hoc test or Kruskal-Wallis followed by Dunn's test based on data distribution.

Results

Based on cement amount, FC and PC significantly increased icorr in higher amounts (FC8mm-icorr = 8.22 × 10-8A/cm2, PC8mm-icorr = 5.61 × 10-8A/cm2) compared to control (3.35 × 10-8A/cm2). In contrast, TB3mm decreased icorr significantly compared to the control. As a function of cement type, FC increased icorr the most. EIS data agrees with these observations. Finally, corroded surfaces had higher surface roughness (Ra) compared to non-corroded surfaces.

Conclusion

The study indicated that cement types FC and PC led to increased Ti-corrosion as a function of a higher amount. Hence, the implant stability could be impacted by the selection, excessive cement, and a potentially increased risk of peri-implantitis.

Retrieval of cement-retained zirconia implant-supported crowns with an Er,Cr:YSGG laser

STATEMENT OF PROBLEM

Cement-retained implant-supported crowns can be challenging to retrieve from the abutment once technical or biological issues arise. Removal traditionally requires sectioning the crown with rotary instruments, which causes irreversible damage to the crown and potential damage to the periodontal apparatus stabilizing the implant.

PURPOSE

The purpose of this in vitro study was to evaluate an erbium, chromium-doped yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser as a minimally invasive alternative for the retrieval of zirconia implant-supported crowns from titanium abutments. Time, temperature, and structural changes to the crown after retrieval were assessed. Appropriate laser parameters were established for this method of crown retrieval.

MATERIAL AND METHODS

Twenty zirconia crowns were milled for a maxillary left second premolar based on a CAD-CAM implant analog cast. Ten of these crowns were cemented with a noneugenol zinc oxide dental cement (group Temp) (n=10). The remaining 10 were cemented with a self-adhesive universal resin cement (group Resin) (n=10). Er,Cr:YSGG laser irradiation was performed with the Waterlase iPlus for 1-minute cycles. An attempt was made to remove the crown with a mechanical instrument after each cycle. A type K thermocouple continuously recorded temperature at the level of the abutment. For statistical comparison of decementation time and temperature, the Mann-Whitney test was used (α=.05). Scanning electron microscopy of the nonirradiated and the irradiated crowns was used for analysis of structural and dimensional changes.

RESULTS

A significant difference (P<.001) was found in the time ±standard deviation required to retrieve the crowns between group Temp (02:40 ±00:18 minutes:seconds) and group Resin (05:26 ±00:36 minutes:seconds). A significant difference (P<.001) was found in the mean ±standard deviation temperature recorded between group Temp (24.0 ±1.19 °C) and group Resin (25.7 ±0.66 °C). No structural changes to crowns were observed after irradiation.

CONCLUSIONS

Retrieval of cement-retained zirconia implant-supported crowns with an Er,Cr:YSGG laser is safe and efficient. Crowns luted with zinc oxide dental cement were retrieved significantly faster while maintaining a significantly lower average temperature than those luted with resin cement. Laser irradiation for decementation did not cause structural changes to zirconia implant-supported crowns.

Conometric Connection for Implant-Supported Crowns: A Prospective Clinical Cohort Study

BACKGROUND

Traditional screw or cemented connections in dental implants present limitations, prompting the exploration of alternative methods. This study assesses the clinical outcomes of single crowns and fixed partial prostheses supported by conometric connections after one year of follow-up.

METHODS

Twenty-two patients received 70 implants, supporting 33 rehabilitations. Biological responses and prosthodontic complications were evaluated at baseline, 6 months, and 12 months.

RESULTS

All implants exhibited successful osseointegration, with no losses or peri-implant inflammation. Marginal bone levels showed minimal changes, well below pathological thresholds. The difference in marginal bone loss (MBL) was -0.27 ± 0.79 mm between T0 and T1, and -0.51 ± 0.93 mm between T0 and T2. No abutment screw loosening or crown chipping occurred. However, coupling stability loss was observed in nine cases.

CONCLUSIONS

The conometric connection demonstrated successful integration and minimal complications after one year. This alternative shows promise, particularly in simplifying handling and improving marginal adaptation. Further research with larger sample sizes and longer follow-up is warranted for comprehensive validation.

Clinical effect of Nobel Biocare angulated screw channel crown compared with cement crown in the aesthetic area: A retrospective cohort study with a mean 32 months follow-up (range 12 to 70 months)

OBJECTIVE

The objective of this study is to compare the clinical efficacy of angulated screw channel abutment applied in the anterior area with regular cemented crowns.

MATERIALS AND METHODS

Forty-eight patients were included and divided into two groups: the angulated screw channel group (ASC) and regular cemented group (RC) in this retrospective cohort study. The evaluation criteria included implant/restoration survival rate, keratinized mucosa width (KMW), bleeding on probing rate (BOP%), probing depth (PD), pink aesthetic score (PES), mechanical/biological complications, emergence angle (EA), the site of implant axis penetrate (SA), marginal bone loss (MBL), and buccal bone thickness (BBT) at 0 mm, 1 mm, 3 mm, 5 mm below the implant shoulder were evaluated in immediate postoperative (T0) and follow-up period (T1).

RESULTS

This retrospective cohort study included a total of 48 patients, with a mean 32 months follow-up period range from 12 months to 70 months. The study did not find any cases of implant failure or restoration failure. EA was significantly wider in the RC group than ASC group (RC: 33.53° ± 8.36° vs ASC: 27.43° ± 8.08°, p = 0.016*). While the BOP% was statistically significant higher in the RC group than ASC group (RC: 28.35% ± 22.92% vs ASC: 13.18% ± 20.00%, p = 0.027*). No significant differences were observed in the other measurements of comparison.

CONCLUSION

Within the limitations of the study, angulated screw channel (Nobel Biocare) crowns might allow the implant axis aim at incisal edge to reduce the emergence angle in the anterior area and benefit the soft-tissue during the 12-70 months follow-up period.

Effect of Restoration Design on the Removal Torque Loss of Implant-supported Crowns after Cyclic Loading

AIM

To compare the removal torque loss (RTL) percentage of screw-retained, cement-retained, and combined screw- and cement-retained implant-supported crowns after cyclic loading and measure the impact of cyclic loading on removal torque.

MATERIALS AND METHODS

Thirty-two dental implants (4.0 × 10 mm) in resin blocks and abutments were divided into four groups (n = 8) based on restoration design: combined screw- and cement-retained group (SC), two cement-retained groups: cemented with adhesive resin cement (AR) (Panavia V5) or provisional cement (PR) (RelyX Temp NE), and screw-retained one-piece titanium group (TI). Removal torques were measured in Newton-centimeter (Ncm) before and after 500,000-cycle cyclic loading with forces ranging from 20 to 200 N at 15 Hz. The RTL percentage in each group was calculated. The paired t-test was used to detect the difference between pre-loading (RT1) and post-loading removal torque (RT2) in each group and 1-way ANOVA was used to detect the difference of RTL percentage between groups.

RESULTS

The post-loading removal torques in all groups were significantly lower than their pre-loading removal torques (p < 0.001). The 1-way ANOVA test found no significant difference in the RTL% between the study groups. The PR group exhibited the lower RTL% (30.74 ± 7.3%), followed by the TI (30.78 ± 5.6%), AR (32.12 ± 2.5%), and SC (35.71 ± 5.1%) groups.

CONCLUSION

Combined screw- and cement-retained restorations exhibited similar RTL compared with other restoration designs, and cyclic loading significantly affected the removal torque.

CLINICAL SIGNIFICANCE

Combined screw- and cement-retained restorations can be utilized in single-tooth situations, offering a comparable impact on screw joint stability while providing benefit of retrievability. Cyclic loading significantly influences joint stability, periodic checkup for screw loosening is recommended. How to cite this article: Jongsiri S, Arksornnukit M, Homsiang W, et al. Effect of Restoration Design on the Removal Torque Loss of Implant-supported Crowns after Cyclic Loading. J Contemp Dent Pract 2023;24(12):951-956.

Effects of cyclic loading on loss of abutment screw torque of angled screw channel single implant crowns on narrow diameter implants

STATEMENT OF PROBLEM

Screw access channels that emerge on the facial aspect of anterior screw-retained implant crowns can compromise esthetics. Recently, angled screw channels (ASCs) have been developed that can alter screw access channel angulations to improve esthetics. While ASCs can be used on narrow-diameter implants, information is limited on the loss of abutment screw torque on narrow-diameter implants with ASCs.

PURPOSE

The purpose of this in vitro study was to compare the loss of abutment screw torque after thermocycling and the cyclic loading of ASCs from 3 different companies connected to narrow-diameter implants.

MATERIAL AND METHODS

A total of 40 narrow-diameter implants (NobelReplace Conical Connection 3.5×11.5 mm) were mounted individually in acrylic resin blocks and divided equally into 4 groups. The first group, NB-0 (Control), consisted of screw-retained zirconia crowns fabricated on ASCs at 0-degree angulation (n=10). The other 3 groups consisted of a total of 30 screw-retained zirconia crowns fabricated on ASCs at 20-degree angulation: NB-20 (Angulated Screw Channel Solutions), ATL-20 (Atlantis Custom Base Solution with angulated screw access), and DA-20 (Dynamic TiBase). Each crown was secured on the mounted implant with its corresponding titanium base insert and screw and then tightened to the manufacturer's recommended torque with a digital torque gauge. The initial reverse torque value (RTVI) was obtained and recorded at baseline. Subsequently, a new set of screws were tightened to recommended values, and each specimen underwent thermocycling and then cyclic loading at 0 to 100 N at 10 Hz for 1 million cycles to simulate 1year of functional loading. After cyclic loading, the final reverse torque values (RTVF) were recorded and compared with the RTVI to evaluate the percentage torque loss (PTLF). Statistical analysis was performed using the Kruskal-Wallis analysis, Rank base analysis of covariance (ANCOVA), and the Tukey HSD post hoc comparisons (α=.05).

RESULTS

Significant differences were found for the PTLF among all groups after cyclic loading (P<.001). The PTLF in ATL-20 (51.4%) was significantly higher than in NB-0 (22.2%) (P<.001) and NB-20 (29.2%) (P=.010). No significant difference was found in the PTLF among other groups (P>.05).

CONCLUSIONS

The abutment screw torque loss after cyclic loading of the ASCs on narrow diameter implants among the 4 groups did not perform comparably. The largest percentage torque loss was recorded for the ATL-20 group. The NB-20 group demonstrated the lowest percentage torque loss. DA-20 showed percentage torque loss less than ATL-20; however, its RTVF was the lowest.

Incidence of peri-implant disease associated with cement- and screw-retained implant-supported prostheses: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Implant-supported fixed dental prostheses can be cement- or screw-retained on the implant or abutment, with advantages and disadvantages for each method. Cemented prostheses have been associated with peri-implant disease because cement remnants act as a reservoir for bacteria and hinder biofilm control. However, contrasting evidence has been presented regarding this association based on studies with varying designs, and a systematic review and meta-analysis is required.

PURPOSE

The purpose of this systematic review and meta-analysis was to answer the focused question: In patients who received implant-supported prostheses, is the incidence of peri-implant diseases higher in cemented implant-supported prostheses than in screw-retained ones?

MATERIAL AND METHODS

The search was conducted using the National Library of Medicine (MEDLINE-PubMed), SCOPUS, EMBASE, and ISI Web of Science databases. Randomized clinical trials (RCTs) that assessed the incidence of peri-implant disease in cement- and screw-retained prostheses were included. Two authors independently screened the titles and abstracts, and analyzed the full texts, extracted data, and assessed the risk of bias. The findings were summarized using meta-analyses with random effects, and the level of certainty of the evidence was determined using the grading of recommendations, assessments, development, and evaluations (GRADE) approach.

RESULTS

The search yielded 4455 articles that met the inclusion criteria based on the title and/or abstract selection. A total of 6 RCTs were included for analysis. The meta-analysis revealed no significant difference between cement- and screw-retained prostheses for the risk of peri-implant mucositis (RR: 1.36, 95% CI: 0.42-4.38, P=.61). Similarly, no significant difference was observed between cement- and screw-retained prostheses for the incidence of peri-implantitis (RR: 1.00, 95% CI: 0.23-4.31, P=1.00).

CONCLUSIONS

Moderate certainty evidence suggests that cement- and screw-retained prostheses present a similar risk for peri-implant mucositis and peri-implantitis.

Clinical performance of immediately placed and immediately loaded single implants in the esthetic zone: A systematic review and meta-analysis

OBJECTIVES

The aim of this study was to assess the following PIO question: In adult patients treated with an indication for single tooth extraction in the maxillary esthetic zone (15-25), what is the influence of an immediate implant placement and immediate loading protocol on the clinical performance (primary aim) and esthetic outcomes (secondary aim) focusing on investigations published after 2010.

MATERIAL AND METHODS

An electronic search in Medline (PubMed), the Cochrane Central Register of Controlled Trials, and EMBASE databases up to April 2022 was performed to identify clinical studies investigating the outcome of single implants subjected to immediate placement with immediate restoration/loading (Type 1A).

RESULTS

Sixty-three studies (10 randomized controlled trials, 28 prospective and 25 retrospective cohort studies) were included with a follow-up ranging from 12 to 96 months. One thousand nine hundred sixty-one implants reported survival rates of 99.2 (98.6-99.5) % at 1 year, 97.5 (95.9-98.4) % after 3 years, and 95.8 (93.3-97.4) % after 5 years; 1064 immediately loaded restorations presented survival rates of 98.9 (97.8-99.5) % after 1 year, 96.8 (93.6-98.4) % after 2 years, and 94.8 (89.6-97.4) % after 5 years. Comparing baseline to 12-month data using the Hedges' g effect size (95% CI), papilla height presented an overall effect size of -0.71 (-1.25, -0.1) mm, midfacial recession change of -0.15 (-0.66, 0.36) mm, and a 0.82 (0.37, 1.28) gain in PES.

CONCLUSIONS

Immediate implant placement and immediate loading can be considered a predictable and safe treatment option for single maxillary anterior restorations with adequate survival rates and favorable esthetics outcomes for up to 5 years.

Three-Dimensional Peri-Implant Tissue Changes in Immediately vs. Early Placed Tapered Implants Restored with Two Different Ceramic Materials-1 Year Results

BACKGROUND

A prospective multi-center randomized controlled clinical trial was performed to digitally analyze tissue volume changes in immediately and early placed implants with simultaneous bone augmentation restored with two different all-ceramic materials.

METHODS

A total of 60 patients received 60 bone-level tapered implants (BLT, Straumann AG) immediately (n = 30) or early placed, 8-10 weeks after tooth extraction, (n = 30). Implants were restored with all-ceramic single crowns fabricated out of zirconia (Lava Plus, 3M), or lithium disilicate (E.max CAD, Ivoclar Vivadent AG) bonded to titanium base abutments (Variobase for Cerec, Straumann AG). Impressions were taken at baseline (BL), 6 and 12 months, and STL data were used to define an area of interest (AOI) to analyze peri-implant volume changes and midfacial recessions.

RESULTS

For immediate placement, a mean volume loss of -5.56 mm3 (±5.83 mm3) was found at 6 months, and of -6.62 mm3 (±6.56 mm3) at 12 months. For early placement, a mean volume loss of -1.99 mm3 (±5.82 mm3) at 6 months, and of -3.7 mm3 (±5.62 mm3) at 12 months was found. The differences in volume loss at 12 months between the two implant placement protocols were significant (p = 0.005). In both groups, mean midfacial recessions of 0.48 mm (±0.52) occurred.

CONCLUSIONS

A more pronounced peri-implant volume loss can be expected 12 months after immediate implant placement compared with early placement.

Changes in Peri-implant Marginal Bone Level by Jaw Location: A Systematic Review and Meta-Analysis of 4970 Implants

The purpose of this study was to evaluate the current evidence on marginal bone-level changes (ΔMBL) around internal connection implants with fixed prostheses by jaw location over time. An electronic literature search for ΔMBL (change in marginal bone level) was conducted in 6 databases. The data from the included manuscripts were categorized by jaw sextant of the implants and duration of follow-up (<2 years, 2-5 years, and >5 years). Meta-analyses were performed on groups with at least 5 studies. A total of 1270 records were screened. Full-text review of 413 papers resulted in a total of 46 studies (representing 2259 patients with 4970 implants) included for quantitative synthesis and analysis. The ΔMBL was summarized at 2 time intervals with the following results: <2 years (anterior maxilla = 0.393 mm [95% confidence interval {CI}, 0.172, 0.613], posterior maxilla = 0.468 mm [95% CI, 0.288, 0.648], and posterior mandible 0.559 mm [95% CI, 0.397, 0.72]), 2 to 5 years (anterior maxilla = 0.683 mm [95% CI, 0.224, 1.142], posterior maxilla = 0.645 mm [95% CI, 0.42, 0.87], and posterior mandible 0.563 mm [95% CI, 0.278, 0.849]). There were insufficient studies in the anterior mandible and with follow-up data over 5 years for quantitative synthesis. Within the limitations of this study, location within the maxillary and mandibular jaws does not seem to influence ΔMBL around internal connection bone level implants with fixed restorations. Although there may be a tendency for greater initial remodeling in the posterior mandible followed by long-term stability, additional studies are needed to evaluate this further.

Comparative evaluation of biological, mechanical, and patient-reported outcomes of angulated screw channel abutments versus multi-unit abutment-retained single-unit implant restorations in the anterior esthetic zone: An-in vivo study

Aims

The study aimed to evaluate biological, mechanical, and patient reported parameters associated with ASC abutments and MU abutments for the fabrication of screw retained implant crowns in the anterior esthetic zone.

Setting and Design

For the study, 20 patients were selected and implants were placed within the constraints of prosthetic envelope. Later, the screw retained crown was fabricated.

Materials and Methods

Biological parameters (including implant survival rate, marginal bone levels using cone beam computed tomography, and soft tissue assessment using periodontal indices) were measured at the time of crown placement and 1 year follow up. Mechanical parameter (screw loosening) was calculated using removal torque loss (RTL) values obtained at the time of crown placement and 1 year follow up. Patient reported parameters were evaluated using a questionnaire at 1 year follow up.

Statistical Analysis Used

All data were tabulated, statistically analyzed, and compared using SPSS version 23 IBM Corporation, Armonk, NY, USA.

Results

Implant survival was found 100% in both the groups. The marginal bone level reduced considerably in both the groups from baseline to 1 year follow up. The MU abutment group had slightly less marginal bone loss than the ASC abutment group. Additionally, there was no statistically significant difference between the two groups' periodontal indices at baseline and 1-year follow-up values. At baseline, the RTL value was substantially lower (P <0.003) in the ASC abutment group than in the MU abutment group, however at the 1-year follow-up, there was no statistically significant difference in RTL or screw loosening between the two groups. Patient-reported data showed no statistically significant difference.

Conclusion

Within the constraints of this study, it was suggested that both ASC and MU abutments provide equally promising results in terms of biological, mechanical, and patient-reported parameters in the anterior esthetic region for single screw-retained crowns.

Influence of Periodontal Status and Prosthetic Treatment on Survival and Success Rates in Implant Therapy: A 5-Year Retrospective Follow-Up Study

The objective of the present study was to evaluate the 5-year outcome of dental implant therapy and assess the survival, success, and biological and technical complications. A periodontal and prosthetic-oriented evaluation was conducted on the variables that can influence the long-term predictability of implant therapy. A total of 615 patients and 1427 dental implants from a private clinic (MedArtis Dent, Cluj-Napoca, Romania) were enrolled in the study. The study was a longitudinal cohort with data collected retrospectively from physical/digital dental records in combination with a cross-sectional clinical/radiological examination. Results showed that periodontal diagnosis at baseline had a significant impact on the marginal bone loss prediction. Data showed that the cylindrical implant with an internal 45° medium taper connection experienced a higher rate of bone resorption compared to the tapered implant with the 5° internal connection. Screw-retained restorations and overdentures showed a statistical decrease in the marginal bone level height when compared to the cemented restorations. Data from our study suggest that not only is there a powerful association between recall visits and the rate of complications in dental implant treatment, but a lack of professional maintenance predicts a higher bone level loss during the 5-year interval.

Fracture strength of implant-supported hybrid abutment crowns in premolar region fabricated using different restorative CAD/CAM materials

The present study investigated the fracture strength of hybrid abutment crowns (HACs) in the premolar region that were fabricated with different restorative computer-aided design/computer-aided manufacturing (CAD/CAM) materials. The abutment-implant structures were randomly assigned into four groups (n=11 per group): bi-layered zirconia restorations (BL), translucent zirconia (4Y-PSZ) restorations (TZ), lithium disilicate ceramic restorations (LD), and dispersed nanoparticle-filled composite resin restorations (CM). All restorations were adhesively bonded to the titanium abutments. After the restoration-abutment complex was tightened onto the implant, the fracture strength was measured. The TZ (2.06 kN) and LD (1.87 kN) groups had significantly higher median fracture strengths than the BL (1.12 kN) and CM (1.10 kN) groups. In terms of fracture resistance, the 4Y-PSZ and lithium disilicate ceramic monolithic restorations would be superior to bi-layered 3Y-TZP and composite resin monolithic restorations for HACs in the premolar region.

Application of 3D-printed guide for locating screw access channels in cement-retained complete arch implant-supported zirconia restorations

Removal of cement-retained complete arch implant-supported zirconia restorations can be challenging. A predictable and minimally invasive technique combining cone beam computed tomography (CBCT) and intraoral scans with a virtual implant planning software program is described to identify the location of the screw access channels during the retrieval, thus minimizing damage to the existing restoration and allowing reuse.

An assessment of the passivity of the fit of multiunit screw-retained implant frameworks manufactured by using additive and subtractive technologies

STATEMENT OF PROBLEM

The lack of passive fit in implant-supported restorations can lead to mechanical and biological complications and compromise the longevity of the prosthesis. The manufacturing technique and evaluation site are factors that may affect the passive fit of multiunit screw-retained implant frameworks. However, scientific information regarding this issue is lacking.

PURPOSE

The purpose of this in vitro study was to investigate the effect of manufacturing technique and evaluation site on the passive fit of multiunit screw-retained implant frameworks.

MATERIAL AND METHODS

Two multiunit implant analogs were placed into the right second premolar and second molar sites of a mandibular typodont model. A total of 50 3-unit Co-Cr frameworks were fabricated with 3 indirect (conventional technique, polymethyl methacrylate milling, stereolithography) and 2 direct techniques (selective laser melting and soft alloy milling). The patterns obtained by indirect techniques were subsequently cast. The Sheffield test was used for the assessment. Digital images of the sites were obtained by using a stereomicroscope at ×40 magnification, and the measurement points (n=10 for each site) were examined to record the vertical marginal discrepancy values (μm) with the aid of a measuring software program. The collected data were subjected to the 2-way ANOVA and Tukey honestly significant difference test (α=.05).

RESULTS

The influence of the manufacturing technique (variable 1) on the vertical marginal discrepancy values was statistically significant (P<.001). However, the evaluation site (variable 2) (P=.097) and the interaction of the variables (P=.960) were not statistically significant. The lowest misfit values were observed for selective laser melting (74.2 ±20.5 μm) followed by stereolithography (92.8 ±23.9 μm), soft alloy milling (108.4 ±12.0 μm), polymethyl methacrylate milling (116.7 ±17.0 μm), and conventional technique (137.5 ±18.9 μm). The vertical marginal discrepancy values of the selective laser melting group were significantly lower than those of all other groups (P<.05).

CONCLUSIONS

The manufacturing technique significantly affected the passive fit. selective laser melting-fabricated frameworks demonstrated superior fitting accuracy. Among the indirect techniques, stereolithography-fabricated frameworks revealed the lowest misfit values. The vertical marginal discrepancy values of all manufacturing groups were within the range of clinical acceptability (<150 μm).

Comparison between Distal Extension Attachment-retained Removable Partial Prostheses with Integrated and Conventional Reciprocation Designs: A Clinical Trial

AIM

To compare marginal bone level (MBL) around the abutments in integrated and conventional reciprocation designs in attachment-retained removable partial prosthesis (A-RPP).

MATERIALS AND METHODS

Around 14 participants were indiscriminately selected and separated into two groups. For every group, an A-RPP with one of the studied reciprocation types was fabricated and assessed. Group I received A-RPP with integrated reciprocation and group II received A-RPP with conventional reciprocation. MBL around the crowned primary and secondary abutments was assessed on the day of A-RPP insertion, at 6 and at 9 months of denture use.

RESULTS

Comparison of MBL values at the primary and secondary abutments within each group showed no statistical difference from time of delivery and throughout the study. After using the A-RPP for 6 and 9 months, group I revealed lower mean values of MBL than group II which were statistically significant.

CONCLUSION

Distal extension A-RPP with integrated and conventional reciprocation designs were associated with raise in bone loss. Integrated reciprocation design revealed a lesser amount of bone loss than the conventional reciprocation design and therefore, it is considered as more preferable to be used.

CLINICAL SIGNIFICANCE

Distal extension A-RPP with integrated reciprocation is superior in terms of periodontium preservation around abutment teeth as compared to distal extension A-RPD with conventional reciprocation.

Soft-Tissue Augmentation around Dental Implants with a Connective Tissue Graft (CTG) and Xenogeneic Collagen Matrix (CMX)-5-Year Follow-Up

Proper horizontal and vertical thickness of the gingival connective tissue has been proven to be one of the success criteria in dental implant and reconstructive surgery. When thin tissue is found, gingiva augmentation methods can be used to increase the quality and volume of the tissue. Many methods have been described, among them pedicle soft-tissue flaps or autogenic tissue grafts. As an alternative to patients' own tissue, xenogenic materials can be used for grafting. The fundamental issue is to choose a material that will ensure the maximum therapeutic effect, while also minimizing the negative influence on the patient's health. The aim of this study was to compare gingival augmentation procedures using a palatal connective tissue graft (CTG) and an xenogenic soft-tissue substitute, Geistlich Mucograft (xenogeneic collagen matrix; CMX), and assess whether the timing of the graft surgery influences the clinical outcomes. The original study was a randomized control trial with a total of 75 implants placed. The patients received the soft-tissue thickening 3 months before the implant placement or 3 months after the implant placement (depending on the group). A connective tissue graft (CTG) or Geistlich Mucograft were used (depending on the group). For both the CTG and Geistlich Mucograft, better clinical outcomes were observed for maintaining the alveolar bone level and the thickness of the attached gingiva compared to the control group with no gingival augmentation. The Geistlich Mucograft showed good clinical performance in comparison to the control. Soft-tissue augmentation with the CTG before the implant placement was found to be most efficient method in terms of a stable increase of the tissue thickness since, throughout the entire observation period, the greatest increase of 1.035 mm (SD = 0.73 mm) in thickness was observed. Statistically important differences in the tissue thickness baseline compared after 5 years were observed for groups G1 vs. G2b (no augmentation vs. CTG before), G1 vs. G3b (no augmentation vs. CTG after) and for groups G2b vs. G3a (CTG before vs. CMX after).

Implant prosthodontic design as a predisposing or precipitating factor for peri-implant disease: A review

Over the past decade, emerging evidence indicates a strong relationship between prosthetic design and peri-implant tissue health. The objective of this narrative review was to evaluate the evidence for the corresponding implant prosthodontic design factors on the risk to peri-implant tissue health. One of the most important factors to achieve an acceptable implant restorative design is the ideal implant position. Malpositioned implants often result in a restorative emergence profile at the implant-abutment junction that can restrict the access for patients to perform adequate oral hygiene. Inadequate cleansability and poor oral hygiene has been reported as a precipitating factors to induce the peri-implant mucositis and peri-implantitis and are influenced by restorative contours. The implant-abutment connection, restorative material selection and restoration design are also reported in the literature as having the potential to influence peri-implant sort tissue health.

Implant angulation and fracture resistance of one-piece screw-retained hybrid monolithic zirconia ceramic restorations

OBJECTIVE

This study aimed to investigate the fracture resistance of one-piece screw-retained hybrid monolithic zirconia ceramic restorations in different implant angulations.

MATERIALS AND METHODS

Three implant fixtures were embedded in acrylic resin blocks with 0°, 15°, and 25° angulations. For each group of implant angulations, 11 screw-retained one-piece monolithic zirconia restorations were made and bonded to the titanium inserts with a dual-cure self-adhesive resin. The complexes were screwed to the implant fixtures with titanium screws. The samples were thermocycled, subjected to compressive load, and fracture modes were recorded. One-way ANOVA and post hoc Tukey's test were used for statistical analyses (α = 0.05).

RESULTS

One-way ANOVA showed the fracture resistance to be significanltly different among the study groups (P = 0.036). The 15° group was significantly more resistant than 0° (P = 0.031). However, the 25° group was not significantly different from the 15° (P = 0.203) and 0° groups (P = 0.624). Fractures occurred only on the restorations, not at the screw levels.

CONCLUSIONS

Tilting the implant up to 15° improves the fracture resistance of one-piece screw-retained hybrid monolithic zirconia restorations; however, increasing the tilt to 25° would not yield restorations with significantly better fracture strength than the straight implants. Accordingly, when angulated implants are indicated in the esthetic zones, one-piece screw-retained hybrid monolithic zirconia ceramic restorations can be used with acceptable fracture strength.

Full-Mouth Rehabilitation of a Patient with Gummy Smile-Multidisciplinary Approach: Case Report

The impairment of aesthetic function leads to a decreased quality of life. An unaesthetic smile due to excessive gingival exposure demands, most of the time, a complex treatment in which the objective is the vertical reduction of the amount of exposed fixed gingiva by obtaining a complete exposure of the anatomical crown of the teeth and restoring the ideal dimensions of the biological width. This paper presents a case of a 48-year-old female patient who was unsatisfied with her aesthetics and had disturbed masticatory function due to the absence of some posterior teeth. The cone beam computed tomography was performed to evaluate the facial and dental morphology. The treatment plan included diode laser and piezo-surgery utilization for the frontal area of the upper arch and implants to restore the distal area of the lower and upper arch. Zirconia ceramic was used for the final restorations. This complex and multidisciplinary full-mouth rehabilitation lasted for two years, and the patient was pleased with the result. This case showed that a well-established treatment plan is necessary to obtain long-lasting results. The use of adequate procedures and equipment ensures a predictable result.

Computer-Aided Design and Computer-Aided Modeling (CAD/CAM) for Guiding Dental Implant Surgery: Personal Reflection Based on 10 Years of Real-Life Experience

Traditional dental implant surgery has been challenged by the phenomenal progression in computer-assisted surgery (CAS) that we have been witnessing in recent years. Among the computer-aided technologies, computer-aided design and computer-aided manufacturing (CAD/CAM) techniques represent by far the most attractive and accepted alternatives over their dynamic counterpart, navigational assistance. Based on many years of experience, we have determined that CAD/CAM technology for guiding dental implant surgery is valuable for rehabilitation of the anterior maxillary region and the management of complete or severe partial edentulism. The technology also guarantees the 3D parallelism of implants. The purpose of the present report is to describe indications for use of CAD/CAM dental implant guided surgery. We analyzed the clinical and radiological data of thirteen consecutive edentulous patients treated using CAD/CAM techniques. All of the patients had stable cosmetic results with a high rate of patient satisfaction at the final follow-up examination. No intra- and/or postoperative complications were encountered during any of the steps of the procedure. The application of CAD/CAM techniques produced successful outcomes in the patients presented in this series.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Maintenance issues of elderly patients requiring nursing care with implant treatments in dental visiting: position paper

PURPOSE

Japan, with an increasing number of elderly people needing long-term care in a super-aged society, urgent needs to develop the clinical guidelines on implant maintenance for elderly people with declining independence. The purpose is to categorize the troubles encountered in the care of patients with dental implants and to indicate actual practices and points of note.

METHODS

From the members of the Japanese Society of Oral Implantology, 12 expert panelists who were experienced with many problems of implant maintenance during dental visits and were familiar with their solutions were selected. Through repeated discussions in the many panel meetings, the problems of implant maintenance during dental visits were distilled.

RESULTS

During a dental visit, the oral cavity, general conditions, and background of elderly patients who cannot orally care for themselves must be grasped, and medical staff, care managers, and patients should understand the changes in these factors as time goes by. The solutions and responses that can be made differ greatly depending on the medical care facilities, the environment, differences in the experience of medical staff, and the patient's background. Thus, it is necessary to select safe treatments appropriate to each situation.

CONCLUSIONS

This paper features many opinions based on clinical experiences. However, clinical guidelines on implant management during dental visits should be formulated in the future based on the accumulation of evidence through the implementation of clinical research.

Immediate Functional Loading with Full-Arch Fixed Implant-Retained Rehabilitation in Periodontal Patients: Clinical Study

(1) Background. The immediate functional loading of implants is a clinical procedure used for treating periodontal edentulous patients. This clinical study aimed to evaluate the clinical outcomes of the immediate functional loading of implants with fully fixed rehabilitations in compromised periodontal patients. (2) Methods. Three hundred and five implants IPX screw implants were placed in 27 periodontal patients using an immediate functional loading protocol with fixed rehabilitations. All patients had a previous history of periodontitis, four patients (14.8%) were smokers and seven patients (25.9%) suffered from chronic medical conditions. (3) Results. Implant and prosthetic clinical findings were evaluated during a mean period of 41.3 ± 19.6 months. No implants were lost during the clinical follow-up. The cumulative survival rate for all implants was 100%. Regarding the prostheses designed, a total of 54 fixed prostheses were placed in the 27 patients immediately after the surgery. Forty-four hybrid fixed prostheses (81.5%) and 10 fixed rehabilitations (18.5%) were placed in the patients. The mean marginal bone loss was 1.51 ± 1.16 mm, ranging from 0 to 3.5 mm during the follow-up evaluation. Thirty-one implants (10.2%) in 10 patients (37%) were associated with peri-implantitis. Five patients (18.5%) showed some kind of technical complications (loss/fracture of the prosthetic screw, acrylic resin fracture, ceramic chipping). (4) Conclusions. The clinical outcomes of this study demonstrate that fixed rehabilitation by immediate functional loading of implants is considered a predictable procedure.

Indirect repair of saliva-contaminated materials using veneering ceramics

PURPOSE

To analyze the in vitro efficacy of a surface conditioning liquid facilitating ceramic repairs of saliva-contaminated metal-ceramic and all-ceramic restorations.

MATERIALS AND METHODS

Specimens constructed from non-precious alloy (NPA), precious alloy (PA), lithium-disilicate (LD), zirconia (ZI), veneering ceramics for zirconia (VZI), veneering ceramics for lithium-disilicate (VLD), and veneering ceramics for metal alloys (VM) were manufactured (total: n = 168; each material n = 24). Veneering ceramic cylinders (thickness: 2mm) were hand-layered on top of the specimens. Shear bond strength (SBS) tests were performed, measuring the maximum bond strength (MBS) of the cylinders on the specimens. Following this, the specimens were artificially aged and stored in artificial saliva for 30 days at 37°C. After physical cleaning using aluminum oxide air abrasion, a new surface conditioning liquid was applied (test, n = 84) or not (control, n = 84). New ceramic cylinders were hand-layered followed by a second SBS test. Descriptive statistics, linear regression analyses, and a one-sample t-test (α = 0.05) were used to ascertain the differences within (pre- vs. post-repair) and between the groups.

RESULTS

All specimens in the test group could be repaired, whereas 18 repairs in the control group failed. After the repairs, an MBS decrease was observed for the NPA specimens of the control group (-15.5MPa, p = 0.004) but not among any of the test groups. Comparing the change in MBS between the test and control groups, the reduction was significantly higher in the repaired NPA specimens of the control group (mean difference 11.8 MPa, p = 0.017).

CONCLUSIONS

Using the analyzed surface conditioning liquid, metal-ceramic and all-ceramic materials can be repaired, while some repairs failed without the liquid. The initial bond strengths between core and veneering materials could be restored in all specimens when the new surface conditioning liquid was applied. This article is protected by copyright. All rights reserved.

Clinical Evaluation of Cement-Retained Implant-Supported CAD/CAM Monolithic Zirconia Single Crowns in Posterior Areas: Results of a 6-Year Prospective Clinical Study

Background: Different technologies and materials can be used for implant-supported restorations in posterior areas. Our study aimed to evaluate the clinical performance of CAD/CAM implant-supported monolithic zirconia single crowns (ZrSCs) cemented onto titanium abutments with a dual-curing resin cement after 6 years of use. Methods: Fifty patients in need of one single crown in posterior regions were enrolled. The patients were recalled for a follow-up after 6 months and then yearly for a total observation period of 6 years. The biological and technical complications were examined using criteria set by the United States Public Health Service (USPHS), whereas visual analogue scales (VASs) were used to evaluate the patients’ aesthetic and functional satisfaction. Results: No patient was lost at follow-up; both the survival and success rates were 100%. No fractures, decementation, peri-implantitis, or soft tissue inflammation were recorded. Forty-six restorations were rated Alpha in each evaluated parameter of the USPHS’s criteria. According to the patients’ VASs assessments, the overall function of the ZrSCs was 8.4 (±2.1), whereas the overall aesthetic was 8.7 (±0.7). Conclusions: Monolithic zirconia single crowns cemented with dual-curing resin cements onto titanium abutments can be considered an effective clinical option in posterior regions after 6 years of function.

Narrow diameter implants to replace congenital missing maxillary lateral incisors: a 1-year prospective, controlled, clinical study

OBJECTIVES

To report the clinical, radiographic, aesthetic and patient-reported outcomes after placement of a newly developed Narrow-Diameter Implant (NDI) in patients with congenitally Missing Lateral Incisors (MLIs).

MATERIALS AND METHODS

Patients with MLIs with a mesio-distal distance between the canine and the central incisor of 5.9-6.3mm received a dental implant with a diameter of 2.9mm (Test), while a diameter of 3.3mm (Control) was used when the distance was 6.4-7.1mm. After healing, a cement-retained bi-layered zirconia crown was fabricated. At the 1-year follow-up (T2), implant survival rate, marginal Crestal Bone Level (CBL) changes, biological and technical complications were registered. The aesthetic outcome was assessed by using the Copenhagen Index Score, and the patient-reported outcomes were recorded using the OHIP-49 questionnaire.

RESULTS

One-hundred patients rehabilitated with 100 dental implants Ø2.9mm (n = 50) or Ø3.3mm (n = 50) were included. One Ø3.3mm implant was lost and 7 patients dropped out of the study, yielding an implant survival rate of 99% (p = 1.000). At T2 a CBL of -0.19 ± 0.25 mm (Test) and -0.25 ± 0.31 mm (Control) was detected, with no statistically significant difference between the groups (p = 0.342). Good to excellent aesthetic scores (i.e. 1-2) were recorded in most of cases. Technical complications (i.e. loss of retention, abutment fracture, chipping of veneering ceramic) occurred once in three patients with no statistically significant difference between the groups (p > 0.05). OHIP scores did not differ significantly at follow-ups between groups (p = 0.110).

CONCLUSION

The use of Ø2.9mm diameter implants represents as reliable a treatment option as Ø3.3mm implants, in terms of CBL changes, biological and technical complications. Favorable aesthetics and patient-reported outcomes were recorded for both groups.

Immediate Maxillary Full-Arch Rehabilitation of Periodontal Patients with Terminal Dentition Using Tilted Implants and Bone Augmentation: A 5-Year Retrospective Cohort Study

Background: All-on-four protocols with tilted implants in the maxilla are used to rehabilitate the terminal dentition of the severe generalized periodontitis patients. Data on long-term biological complications are scarce. Methods: Eighty-four axial and forty-six tilted immediate implants have been placed in the extraction sockets of 23 patients according to a four–six implants protocol combined with ridge augmentation. Within 72 h, a provisional prosthesis was cemented to the implants; after 6 months, a cemented ceramic–metallic prosthesis was delivered. The patients were followed for up to 5 years. Results: The 5-year survival rate of the straight and tilted implants was 100% and 97.8, and the prosthetic one was 100%. Marginal bone loss (MBL) of the straight implants was 0.42 ± 0.67 and 0.59 ±1.01 mm on the mesial and distal sides; for the tilted, it was 0.37 ± 0.68 and 0.34 ±0.62 mm, and the differences were not statistically significant. Implant position, smoking, keratinized mucosal width, and cantilever did not affect MBL. Peri-implant mucositis involved 29.4% and 22.2% of the straight and tilted implants, respectively; peri-implantitis involved 5.8% and 4.4% of the straight and tilted implants, respectively, without statistical significance. Conclusions: This immediate loading protocol’s 5-year survival and success rates were high. No difference between the straight and tilted implants was found regarding survival, success rates, and MBL.

The Mechanical Behavior of a Screwless Morse Taper Implant-Abutment Connection: An In Vitro Study

The use of screwless Morse taper implant−abutment connections (IAC) might facilitate the clinician’s work by eliminating the mechanical complications associated with the retention screw. The aim of this study is to evaluate the effect of artificial chewing on the long-term stability of screwless Morse taper IACs. Thirty-two implant abutments restored with an upper central incisor zirconia crown were used and divided into four groups according to the implant−abutment assembling manner (C1,H: screw retained (20 Ncm); C2: tapped; or C3: torqued (20 Ncm; the screws were removed before the dynamic loading)). All specimens were subjected to a cyclic loading (98 N) for 10 million chewing cycles. The survived samples were exposed to a pull-off force until failure/disassembling of the connection. All the samples revealed a 100% survival. Regarding the pull-off test, the screw-retained internal hexagonal IAC revealed significantly higher resistance to failure/disassembling (769.6 N) than screwless conical IACs (171.6 N−246 N) (p < 0.0001). The retention forces in the Morse taper groups were not significantly different (p > 0.05). The screw-retained hexagonal IAC showed the highest retention stability. The screw preload/retention in the conical IAC was lost over time in the group where the screws were kept in place during loading. Nevertheless, the screwless Morse taper IACs were stable for an extended service time and might represent a valid form of treatment for single-tooth replacement.

Misfit simulation on implant prostheses with different combinations of engaging and nonengaging titanium bases. Part 1: Stereomicroscopic assessment of the active and passive fit

STATEMENT OF PROBLEM

Little is known about whether the misfit level of implant-supported screw-retained prostheses can be tolerated when different combinations of engaging and nonengaging titanium bases are used.

PURPOSE

The purpose of this in vitro study was to simulate prosthetic workflow distortions (horizontal and vertical) and to evaluate the fit (passive and active) of 2-implant-supported screw-retained zirconia frameworks with 3 different combinations of abutments: both engaging, engaging and nonengaging, and both nonengaging.

MATERIAL AND METHODS

The fit of both engaging (n=10), engaging and nonengaging (n=10), and both nonengaging (n=10) 2-implant-supported zirconia frameworks was evaluated on control and definitive casts simulating 50-, 100-, and 150-μm vertical and 35-, 70-, 100-μm horizontal misfit levels. Stereomicroscopy was used to assess the passive fit (1 screw tightened) and active fit (both screws tightened) of the zirconia frameworks. Vertical deviations in the implant and abutment connection (the implant-abutment gap measured vertically) between the implant platform and reference line on the titanium base were measured. The Kruskal-Wallis and Mann-Whitney U tests (α=.05) were used to compare different implant-supported zirconia specimens on each definitive cast.

RESULTS

When 1 screw was tightened, both engaging specimens had higher vertical deviations (ranging from 40.1 to 131.1 μm) in 35- and 70-μm horizontal misfit levels, as compared with engaging and nonengaging (19.8 to 85.1 μm) and both nonengaging (6.6 to 14.3 μm) specimens. Comparing medians of the 100-μm misfit in horizontal (engaging and nonengaging 140.4 μm; both nonengaging 151.6 μm) and vertical (engaging and nonengaging 49.8 μm; both nonengaging 42.6 μm) directions, the horizontal misfits caused larger vertical deviations. When both screws were tightened in 50-, 100-, and 150-μm vertical misfit groups, the vertical gap increase in the engaging and nonengaging specimens was significantly higher than that in both the nonengaging specimens (P<.001).

CONCLUSIONS

As the level of simulated misfit increased, the vertical gap between the implant and abutment increased. Horizontal misfits were less tolerated than vertical ones and may be more detrimental. Both nonengaging 2-implant-supported zirconia frameworks were found to tolerate the different misfit levels better, followed by engaging and nonengaging and both engaging frameworks.

Screw-and-cement–retained prosthesis versus cement-retained prosthesis: Which is more appropriate for the upper premolar area?

Background/purpose

The narrow alveolar ridge in the maxillary premolars area limits the angle of implant placement and the shape of the prosthesis. The aim of this study was to evaluate which implant prosthesis, screw-and-cement-retained prosthesis (SCRP) or cement-retained prosthesis (CRP), was more suitable for the maxillary premolar area.

Materials and methods

We conducted virtual implantation on 58 implant images from 47 patients obtained using cone beam computed tomography (CBCT). The width and buccal inclination of the alveolar bone, the angulation of the implant fixture, and the angulation of abutment were measured and calculated.

Results

We determined that SCRP was feasible in 52% and 78.8% of first and second premolar areas, respectively. There was a positive relationship between the feasibility of SCRP and the premolar region in general (P = 0.031), although SCRP was more likely to be a possibility in the second premolar area. On multiple logistic regression analysis, the difference in the angle between the axis of the prosthesis and the axis of the alveolar bone (RA) was significantly associated with the type of prosthesis (P = 0.001). The RA was significantly higher for CRP implants (OR = 1.885; 95% CI: 1.31 to 2.70).

Conclusion

SCRP is not always feasible in the maxillary premolar area, especially in the first premolar area. If the difference between the angle of the axis of the prosthesis and the axis of the alveolar bone is large, it may be necessary for the clinician to consider CRP in the treatment planning stage.

Comparative Study by Systematic Review and Meta-Analysis of the Peri-Implant Effect of Two Types of Platforms: Platform-Switching versus Conventional Platforms

OBJECTIVE

The aim of the systematic review and meta-analysis carried out was to evaluate the effects of changing the prosthetic platform on peri-implant tissue after 1 year of prosthetic loading.

MATERIAL AND METHODS

In November 2020, an electronic search was carried out in PubMed, EMBASE, Web of Science, and Scopus databases with the aim of obtaining all the randomized clinical trials that had been published in the preceding 10 years comparing the effects on the peri-implant tissue of implants with a prosthetic platform change and implants with a conventional platform for at least 1 year after prosthetic loading. Randomized model meta-analyses of the selected studies were performed to compare the results of the two implant groups in terms of vertical maintenance of bone level and increased probing depth.

RESULTS

Nine studies were included, summing up a total of 475 implants with prosthetic platform exchange and 462 implants with a conventional platform. Implants with prosthetic platform exchange had less peri-implant bone loss than implants with a conventional platform (mean difference of 0.255 mm, statistically significant) but suffered a greater increase in probing depth (mean difference of 0.082 mm, not statistically significant). However, the probing depth from One Study Remove revealed a statistically significant increase of 0.190 mm in the prosthetic platform exchange group compared to the conventional platform group.

CONCLUSION

Implants with platform switching suffer less peri-implant bone loss after 1 year of loading than implants with a conventional platform. Further long-term studies are required to observe how these differences vary over time.

Assessment of Preload Loss after Cyclic Loading in the OT Bridge System in an “All-on-Four” Rehabilitation Model in the Absence of One and Two Prosthesis Screws

The aim of this study was to evaluate the stability of prosthetic screws after applying cyclic loadings in an “all-on-four” rehabilitation model with the OT Bridge system. The model was tested both with and without anterior screws. Four implant analogues following the “all-on-four” concept were inserted in an edentulous mandibular resin model. An OT Bridge system with a Cr–Co prosthetic framework was fabricated. Depending on the presence or absence of one or two anterior screws on the implant analogues, three groups were created, i.e., Gr.1: three tightening screws, Gr.2: two tightening screws, Control Group: four tightening screws. Each single group underwent subsequent 400,000 cyclic loads, simulating approximately a year of chewing by using a dynamometer machine. This cycle was repeated five times for each group, and preload loss values were evaluated on each prosthetic screw after each cycle. All the data obtained were analyzed by one-way ANOVA and Student’s t-test. No statistically significant differences after intragroup analysis were found. A statistically significant difference within the Gr.1 between the screws in positions 33 and 36, equal to 15.2% (p-value = 0.0176), was found. The OT Bridge seems a useful system to maintain the retention of a prosthesis during mechanical stress conditions even in the absence of one screw in an “all-on-four” rehabilitation. This could represent a good solution to solve the esthetic problem of the screw buccal access hole for fixed solutions.

A Systematic Review of Cementation Techniques to Minimize Cement Excess in Cement-Retained Implant Restorations

Background: The most used types of retention of implant-supported prostheses are screw-retained or cement-retained restorations. The advantages and disadvantages of both have been identified by various authors over the years. However, cement-retained implant crowns and fixed partial dentures are among the most used types of restorations in implant prostheses, due to their aesthetic and clinical advantages. When cemented prostheses are made on implants, the problem of cement residues is important and often associated with biological implant pathologies. The objective of this research was to establish to what extent the techniques to reduce excess cement really affect the volume of cement residues. Materials and Methods: This review was written following the PRISMA statement; a detailed search was carried out in three different electronic databases—PubMed, Scopus, and Cochrane Library. The inclusion criteria were prospective clinical studies, with at least 10 participants per group, and with at least 6 months of the follow-up period. Results: There have been many proposals for techniques supposed to reduce the amount of excess cement in the peri-implant sulcus and on the prosthetic components, but of these, which are exceptional in their in vitro capabilities, very few have been clinically validated, and this represents the real limitation and a great lack of knowledge regarding this topic. Three articles met the inclusion criteria, which were analyzed and compared, to obtain the information necessary for the purposes of the systematic review. Discussion: Extraoral cementation can reduce the excess cement, which, after a normal excess removal procedure, is, nevertheless, of such size that it does not affect the possibility of peri-implant pathologies developing. All these studies concluded that a small amount of cement residue is found in the gingival sulcus, and using eugenol-free oxide cements, the residues were only deposited on the metal surfaces, with a better peri-implant tissues health. Conclusion: Despite the limitations of this study, it was possible to carefully analyze these characteristics and obtain valuable suggestions for daily clinical practice. Resinous cements are considered, due to the free monomers present in them, toxic for the soft tissues. The provisional zinc-oxide cements, also eugenol-free, represent the ideal choice. The different grades of retentive forces provided by these cements do not seem to have clinical effects on the decementation of restorations.

Application of Semipermanent Cements and Conventional Cement with Modified Cementing Technique in Dental Implantology

Objectives

The aim of this study was to evaluate the influence of artificial ageing on the retention force of original semipermanent cements, as well as the possibility of using conventional cements for semipermanent cementation with adequate modification of the cementing protocol.

Materials and methods

Forty CoCrMo alloy crowns were divided in four groups (each group n=10) and fixed with two semipermanent cements (resin-based and glass ionomer-based cements) and one conventional (zinc phosphate), using conventional and modified cementation techniques on titanium abutments. The samples were stored in humid conditions for 24 hours at 37°C and subjected to thermocycling (500 cycles) and mechanical cyclic loading (7 days, 3, 6, 9 and 12 months function simulation). The cast crowns were removed and the retention force was recorded.

Results

The highest initial retention force measured was for zinc-phosphate cement - conventional cementing (198,00±61,90 N), followed in descending order by zinc-phosphate cement - modified cementing technique (152,00±45,42 N), long term temporary cement - GC Fuji Temp LT (57,70±20,40 N), and semipermanent cement - Telio CS Cem Implant (56,10±18,68 N). After 12 months, the highest retention force measured was for zinc-phosphate cement - conventional cementing (88, 90±14, 45 N), followed by zinc-phosphate cement - modified cementing (48, 15±14,41N), semipermanent cement GC Fuji Temp LT (16,55±3,88 N) and Telio CS Cem Implant (15,55±5,52 N).

Conclusions

Zinc-phosphate cement - modified cementing technique and original semipermanent cements can be recommended for conditional permanent cementing of implant supported crowns.

Clinical relevance

The use of semipermanenet cements and zinc-phosphate cement - modified cementing technique provides a predictable retrievability of implant-supported crowns.