Implant-supported Crowns Research Articles

Fabrication of three implant-supported crowns using a digital workflow: a case report.

Accurate working impression is an essential requirement for the fabrication of implant prosthesis, and digital impressions have recently become more popular. In this case report, a completely digital workflow is introduced for the fabrication of three single-unit screw-retained implant crowns on the posterior maxilla by a dental student, under supervision. This approach involved the use of an intraoral scanner to capture a digital impression of the three implants and their surrounding mucosa, the opposing arch, and occlusion. The use of intraoral scanners and digital impressions illustrated an efficient and patient-friendly method of capturing the necessary data to fabricate a well-fitted prothesis. The aim of this case report is to examine a fully digital approach in the production of multiple single-unit implant crowns.

Options for replacing a single lost anterior tooth in a dentition with reduced periodontal health

To restore comfort, function, and esthetics while maintaining occlusal stability, restoring a single missing anterior tooth in a periodontally impaired dentition is a significant task. An implant-supported crown, traditional three-unit fixed partial denture (FPD), cantilever FPD, resin-bonded FPD, or removable partial denture can be considered in a normal, healthy dentition; however, problems with mobility and poor periodontal support of the remaining dentition may make these procedures unfeasible options as it might be difficult to avoid overloading of the implant in periodontal compromised adjacent teeth, difficult to achieve proper esthetics with conventional FPD, to maintain the stability of dental arch with acrylic resin removable partial dentures is not possible and incidences of frequent debonding of resin bonded FPD are high when abutments are mobiles. Fiber-reinforced composite resin FPD is often effective in these clinical situations to provide a conservative therapy option to restore the patient’s ease and esthetics by limiting mobility.

Impact of liner treatment on the translucency of CAD/CAM multi-colored lithium disilicate and multi-layered zirconia implant-supported crowns, and evaluation of fracture strength of ceramic crowns.

This study aimed to evaluate the optical properties of liner-treated CAD/CAM Multi-colored lithium disilicate (Amber Mill Direct; AMD) and multi-layered zirconia (Omega multi; OM) implant-supported crowns, as well as their effect on the fracture strength of Ti or Zr abutments to which they were applied. After sintering AMD and OM ceramic blocks, they were classified into three groups: untreated, liner-treated, and liner-treated with added color. Optical properties were evaluated by analyzing color differences using background materials to assess translucency and the masking ability of liner-treated ceramics. Subsequently, the fracture strength of implant-supported crowns applied to Ti or Zr abutments was measured, and statistical analysis was conducted using Weibull statistics. Untreated AMD exhibited the highest translucency. Liner treatment reduced translucency in both ceramics, while color-added liner treatment increased translucency. Liner-treated AMD showed greater color difference compared to OM, whereas color-added liner treatment reduced the color difference. Fracture strength was highest in Ti abutment-OM crowns (548.03 N) and lowest in Zr abutment-AMD crowns (283.58 N). Additionally, the Weibull coefficient was over twice as high in Ti abutment-AMD crowns (m = 17.500). Color liners can adjust the high translucency of lithium disilicate ceramics to block discoloration, providing natural tooth-like color and enabling the creation of esthetic restorations. Furthermore, lithium disilicate ceramic crowns applied to Ti abutments exhibited high Weibull coefficients and fracture strengths.

Comparative Evaluation of Fracture Strength of Implant Supported Crown Fabricated from CAD/CAM and 3D Printed Resin Matrix Ceramic

Objective: To compare fracture strength of screw-retained implant-supported crown of resin matrix ceramic when fabricated using CAD/CAM and 3D printing Material and method: vericom Mazic® Duro (CAD/CAM Nano Hybrid Ceramic) was used as particle-filled composite CAD/CAM material, saremco Print Crowntec (3D printable resins-based) as 3D printed composite material, and the control group was composed of IPS e.max. ZirCAD ivoclar vivadent (zirconia) was used to fabricate mandibular first molar screw-retained, implant-supported crowns. After the fabrication, the crowns were cemented with the Rely X U200 self-adhesive resin cement (3M ESPE, Germany) on stock abutments tightened to analogs embedded in acrylic resin. Finally, all crowns were subjected to a fracture resistance test. fracture strength was evaluated by using one–way ANOVA with Chi-square used for the association between the modes of fracture. Result: The results showed that there were significant differences between all the groups used, the control group (Group zirconia) was significantly higher, as the mean was equal to 6391 N. Followed by Group vericom (cad/cam) with a mean of 2558 N, then Group seramco (3D printing) with a mean of 817.92 N. Dunnett T3 test showed statistically significant differences in fracture resistance between the three groups. There was no significant difference between the modes of fracture and the methods. Conclusion: Screw-retained implant-supported crowns manufactured by CAD/CAM technique had better fracture resistance value than those of the 3D printed technique. Clinical Relevance: resin matrix ceramic is a possible substitute for zirconia in an implant-supported crown

Clinical outcomes of single implant supported crowns utilising the titanium base abutment: A 7.5-year prospective cohort study

ObjectiveTo assess radiographic, clinical and patient-reported outcomes of single zirconia implant-supported crowns on titanium base abutments (TBA) over a 7.5-year period. MethodsTwenty-four patients received bone-level titanium implants and screw-retained zirconia implant crowns utilising TBA. Marginal bone level (MBL), clinical parameters (probing depth-PD, bleeding on probing-BoP, plaque control record-PCR), technical complications (USPHS criteria) and patient satisfaction were assessed at crown delivery (baseline), 1 year (FU-1) and at 7.5 years (FU-7.5) of follow-up. ResultsEighteen patients were available for re-examination at 7.5 years. The mean MBL at FU-7.5 (0.35 ± 0.20mm) did not significantly change compared to baseline (0.54 ± 0.39, p=.352) and to FU-1 (0.54 ± 0.45mm, p=0.524). From baseline to 7.5 years, the mean PD increased significantly, from 3.0 ± 0.6mm to 3.7 ± 0.8mm (p=0.005). However, BoP and PCR did not significantly change; (BOP: from 27.1 ± 20.7% to 25.0 ± 20.0%, p=0.498; PCR: from 11.1 ± 21.2% to 25.0 ± 25.1%, p=0.100). Nine patients presented with more than one bleeding site. This denoted a peri-implant mucositis prevalence of 50%, whilst none of the implants presented peri-implantitis. One incidence of minor and major ceramic chipping were reported on 2 out of the 18 crowns, resulting in a prosthetic survival rate of 94.4%. Seventeen patients were highly satisfied with their result. ConclusionSingle implant-supported zirconia crowns on TBA displayed: (i) minor number of technical complications, (ii) high prosthetic survival rate, (iii) stable marginal bone level and (iv) high patient satisfaction at 7.5 years. Clinical implicationsTitanium base abutments despite their high use in clinical practice, lacked medium- and long-term studies. The presented findings highlight their clinical performance at 7.5 years as they display satisfying radiographic, clinical and patient-related outcomes. TBA appear to be a suitable abutment choice for medium-term implant-supported restorations.

Detection of the Fixed Prostheses on Panoramic Images: An Artificial Intelligence Based Study.

To investigate the effectiveness of using YOLO-v5x in detecting fixed prosthetic restoration in panoramic radiographs. Descriptive study. Place and Duration of the Study: Department of Oral and Maxillofacial Radiology, Eskisehir Osmangazi University, Eskisehir, Turkiye from November 2022 to April 2023. For the labelling of fixed prosthetic restorations, 8,000 panoramic radiographs were evaluated using the YOLO-v5x architecture. In creating the dataset for this study, fixed prosthetic restorations were categorised as dental implant, pontic, crown, and implant-supported crown on dental panoramic radiographs. The labelled images were then randomly split into three groups: 80% for training, 10% for validation, and 10% for testing. The labelled panoramic images constituted the model's training dataset, and leveraging the knowledge acquired during this learning stage, the model generated predictions in the testing phase. The majority of labelling data were dedicated to crown restorations. The precision and sensitivity values of YOLOv5x were 0.99 and 0.98 for crowns, 0.98 and 0.99 for implants, 0.99 and 0.99 for pontics, and 0.99 and 0.99 for implant-supported crowns, respectively. The results obtained in this study demonstrate a satisfactory success rate of YOLO-v5x in detecting dental prosthetic restorations. The high precision and sensitivity of the model indicate its strong potential to enhance clinical professional performance and contribute to the development of more efficient dental health services. Artificial intelligence, Dentistry, Dental prosthesis, Panoramic radiography.

Impact of smoking on cost-effectiveness of 10-48 years of periodontal care.

The study aims were (1) to explore whether "periodontal treatment" consisting of surgical therapy (flap, resective, or regenerative) or scaling and root planing treatment with long-term periodontal maintenance treatment, is cost-effective in terms of preventing periodontitis-attributable tooth extraction and replacement by implant-supported crowns ("extraction/replacement"); (2) to assess the effect of cigarette smoking on this cost-effectiveness. Data for this observational retrospective study were collected from dental charts of patients who had received periodontal therapy and at least annual follow-up visits for >10 years were analyzed by linear regression generalized estimating equations and generalized linear models. Among 399 adults (199 males, 200 females), those with the least mean annual treatment cost experienced the greatest mean annual costs for extraction/replacement, indicating general cost-effectiveness. Cigarette smoking adversely impacted this cost-effectiveness, with current heavy smokers experiencing no cost-effectiveness. Former smokers with Grade C periodontitis benefitted most, whereas smoking did not influence cost-effectiveness for Grade B periodontitis. Assessed by mean annual costs of "extraction/replacement," periodontal treatment was cost-effective, which decreased in a dose-response manner by former and current smoking intensity. Cigarette smoking should be factored into treatment planning and cost-effective analyses of periodontal treatment. Smoking cessation should be encouraged.

Comparison of fatigue lifetime of new generation CAD/CAM crown materials on zirconia and titanium abutments in implant-supported crowns: a 3D finite element analysis.

Due to the dynamic character of the stomatognathic system, fatigue life experiments simulating the cyclic loading experienced by implant-supported restorations are critical consideration. The aim of this study was to examine the effect of different crown and abutment materials on fatigue failure of single implant-supported crowns. Models were created for 10 different designs of implant-supported single crowns including two zirconia-reinforced lithium silicates (crystallized and precrystallized), monolithic lithium disilicate, polymer-infiltrated ceramic networks, and polyetheretherketone supported by zirconia and titanium abutments. A cyclic load of 179 N with a frequency of 1 Hz was applied on palatal cusp of a maxillary first premolar at a 30° angle in a buccolingual direction. In the models with titanium abutments, the polymer-infiltrated ceramic network model had a lower number of cycles to fatigue failure values in the implant (5.07), abutment (2.30), and screw (1.07) compared to others. In the models with zirconia abutments, the crystallized zirconia-reinforced lithium silicate model had a higher number of cycles to fatigue failure values in the abutment (8.52) compared to others. Depending on the fatigue criteria, polyetheretherketone implant crown could fail in less than five year while the other implant crowns exhibits an infinite life on all models. The type of abutment material had an effect on the number of cycles to fatigue failure values for implants, abutments, and screws, but had no effect on crown materials. The zirconia abutment proved longer fatigue lifetime, and should thus be considered for implant-supported single crowns.

Comparison of digital study model superimposition methods using implant-supported crowns and best-fit algorithms

Research regarding orthodontic changes using the superimposition of digital study models (DSMs) is commonplace. Information regarding the accuracy of data processing by superimposition software is limited. The study aimed to compare different methods of superimposing DSMs using implant-supported crowns (ISC) as a stable reference structure. DSMs containing ISCs were sourced from a database of patients treated with clear aligner therapy. The DSM representing the planned treatment outcome was superimposed on the pretreatment DSM. Three tooth points were selected for comparison on the contralateral side of each ISC. Differences in Cartesian coordinates for each tooth point for each arch superimposition method, used by the Geomagic Control X(3D systems, Rock Hill, NC) software system, were recorded. Paired t tests for the reference standard superimposition method best-fit high-resolution using the entire dental arch compared with initial, best-fit low-resolution, and best-fit high-resolution using the ISC only were calculated. The DSMs of 54 dental arches containing ISCs were evaluated. All mean differences for displacements of selected points on the contralateral side to the ISC in the 3 Cartesian planes were<0.05 mm (P<0.05) and below the threshold of clinical significance. In addition, the standard superimposition techniques (initial, best-fit low-resolution, and best-fit high-resolution) resulted in nonstatistically significant and nonclinically significant differences in the position of the ISC. Researchers can be confident that the described superimposition methodologies, with and without ISCs as a stable reference structure, are a valid method for accurately assessing most intraarch dental changes.

Deep learning-designed implant-supported posterior crowns: Assessing time efficiency, tooth morphology, emergence profile, occlusion, and proximal contacts

ObjectivesTo compare implant supported crowns (ISCs) designed using deep learning (DL) software with those designed by a technician using conventional computer-aided design software. MethodsTwenty resin-based partially edentulous casts (maxillary and mandibular) used for fabricating ISCs were evaluated retrospectively. ISCs were designed using a DL-based method with no modification of the as-generated outcome (DB), a DL-based method with further optimization by a dental technician (DM), and a conventional computer-aided design method by a technician (NC). Time efficiency, crown contour, occlusal table area, cusp angle, cusp height, emergence profile angle, occlusal contacts, and proximal contacts were compared among groups. Depending on the distribution of measured data, various statistical methods were used for comparative analyses with a significance level of 0.05. ResultsISCs in the DB group showed a significantly higher efficiency than those in the DM and NC groups (P ≤ 0.001). ISCs in the DM group exhibited significantly smaller volume deviations than those in the DB group when superimposed on ISCs in the NC group (DB–NC vs. DM–NC pairs, P ≤ 0.008). Except for the number and intensity of occlusal contacts (P ≤ 0.004), ISCs in the DB and DM groups had occlusal table areas, cusp angles, cusp heights, proximal contact intensities, and emergence profile angles similar to those in the NC group (P ≥ 0.157). ConclusionsA DL-based method can be beneficial for designing posterior ISCs in terms of time efficiency, occlusal table area, cusp angle, cusp height, proximal contact, and emergence profile, similar to the conventional human-based method. Clinical significanceA deep learning-based design method can achieve clinically acceptable functional properties of posterior ISCs. However, further optimization by a technician could improve specific outcomes, such as the crown contour or emergence profile angle.

Aesthetic assessment of maxillary lateral and canine implant-supported crowns by laypersons and orthodontists.

The objectives of this study were to evaluate how laypersons and orthodontists evaluate and rank aesthetic parameters of an implant-supported crown (ISC) on the canine position (ISC-C) and lateral position (ISC-L). A digital survey of 11 cases, 5 ISC-C, 5 ISC-L and 1 control case without ISC, was distributed to 207 laypersons and 296 orthodontists. All cases included one extraoral photograph and three intraoral photographs. The respondents were asked to identify the ISC and to evaluate the aesthetic parameters regarding colour of the implant (CI), shape of the implant (SI) and gingival colour around ISC (GCI). Differences within and between the groups were tested using Chi-2-test and Independent-Samples t-test. All invited laypersons and 184 orthodontists (62% response rate) answered the survey. Orthodontists (89%) more correctly identified the ISC, regardless of its position, than laypersons (50%) (p < 0.001). Both laypersons (54%) and orthodontists (23%) rated higher proportions of acceptance of CI, SI and GCI in favour for the ISC-L than ISC-C (laypersons: 40%, orthodontists: 10%) (p < 0.001). Assessing each parameter separately, orthodontists rated higher for ISC-L, compared to the ISC-C (p < 0.001). In general, laypersons and orthodontist ranked tooth colour (mean, standard deviation [SD]:8.0,1.5 and 9.0, 1.0) and tooth shape (mean, SD: 8.0, 1.7 and 8.8, 1.2) as aesthetically higher than the gingival colour (mean, SD: 7.2, 2.2 and 8.0, 1.7) (p > 0.001). Conclusion: Laypersons and orthodontists consider the ISC-L as aesthetically more preferable, compared to the ISC-C.

Finite Element Analysis of the Stress and Deformation in Bone Caused by CFR-PEEK, Titanium, and Zirconia Ceramic Implants.

Glass or carbon fiber-reinforced polyetheretherketone (CFR-PEEK) composites and zirconia ceramic have been offered as more modern implant biomaterials. This study examined the effects of zirconia ceramic implants, titanium, and CFR-PEEK on bone stress and deformation. A geometric model of a mandibular molar replaced with an implant-supported crown was created for this in vitro finite element analysis investigation. The dimensions of the implant employed in the study are 11.0 mm in length and 4.5 mm in diameter. Using finite element analysis, three implant assemblies composed of zirconium, titanium, and CFR-PEEK were produced. 150 N loads were applied both vertically and obliquely on the long axis of the implant. The von-Mises stresses and deformation were compared using ANSYS Workbench 18.0 and finite element software, with a significance threshold of P < 0.05. All three implant assemblies-zirconia, titanium, and CFR-PEEK-showed comparable stresses and deformation in bone with no appreciable variations. Zirconia and PEEK reinforced with carbon fibers (CFR-PEEK) have been found to be viable replacements for titanium in implant biomaterials.

IMMEDIATE RESTORATION CUSTOM-MADE BY ADDITIVE MANUFACTURING ABOUT DENTAL IMPLANTS: PREDICTABLE RESULTS FOR PINK AND WHITE ESTHETICS

The definition of dental implant failure has evolved from focusing solely on lack of osseointegration to encompass broader concerns such as aesthetics. However, the criteria for aesthetic failure in implant dentistry are not well defined. Although several aesthetic indices have been validated to objectively evaluate clinical outcomes, including failure of an implant-supported crown. In this sense, aesthetic flaws in implant dentistry can be categorized into pink and white tissue flaws. This study aims to describe an extensive rehabilitation protocol where implants were placed using printed surgical guides and adaptations for bone and tissue grafts, facilitating restoration in the aesthetic zone. Key clinical stages and aspects are illustrated through the case of a fractured upper left central incisor, where an implant system was used for immediate patient rehabilitation. By highlighting these crucial steps and considerations, this study underscores the effectiveness of immediate implantation and restoration techniques in achieving optimal aesthetic and functional outcomes in dental rehabilitation

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

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. 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. 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. 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.

Single missing molar with wide mesiodistal length restored using a single or double implant-supported crown: A self-controlled case report and 3D finite element analysis.

Based on a self-controlled case, this study evaluated the finite element analysis (FEA) results of a single missing molar with wide mesiodistal length (MDL) restored by a single or double implant-supported crown. A case of a missing bilateral mandibular first molar with wide MDL was restored using a single or double implant-supported crown. The implant survival and peri-implant bone were compared. FEA was conducted in coordination with the case using eight models with different MDLs (12, 13, 14, and 15 mm). Von Mises stress was calculated in the FEA to evaluate the biomechanical responses of the implants under increasing vertical and lateral loading, including the stress values of the implant, abutment, screw, crown, and cortical bone. The restorations on the left and right sides supported by double implants have been used for 6 and 12 years, respectively, and so far have shown excellent osseointegration radiographically.The von Mises stress calculated in the FEA showed that when the MDL was >14 mm, both the bone and prosthetic components bore more stress in the single implant-supported strategy. The strength was 188.62-201.37 MPa and 201.85-215.9 MPa when the MDL was 14 mm and 15 mm, respectively, which significantly exceeded the allowable yield stress (180 MPa). Compared with the single implant-supported crown, the double implant-supported crown reduced peri-implant bone stress and produced a more appropriate stress transfer model at the implant-bone interface when the MDL of the single missing molar was ≥14 mm.

Auxiliary occlusal devices for IO scanning in a complete digital workflow of implant-supported crowns: a randomized controlled trial

ObjectivesTo compare the crown accuracy and time efficiency of a complete digital workflow, utilizing an auxiliary occlusal device and IO scanning, with a conventional workflow, for multiple implant-supported single crowns.Materials and methods24 patients with two adjacent posterior implants were included. 12 patients were randomly assigned to digital workflow group, involving intra-oral scanning with an auxiliary occlusal device and manufacture of customized abutments and zirconia single crowns (test group). The other 12 were assigned to the conventional workflow (control group), involving conventional impression and CAD-CAM crowns based on stone casts. Crown scanning was done before and after clinical adjustment using an intraoral scanner. Two 3D digital models were overlapped to assess dimension changes. Chair-side and laboratory times for the entire workflow were recorded and a linear mixed model and Independent-sample t tests were used for the statistical analysis.ResultsThe maximum occlusal deviation was 279.67 ± 112.17 μm and 479.59 ± 203.63 μm in the test and control group, respectively (p < 0.001). The sizes of the occlusion adjustment areas were 12.12 ± 10.51 mm2 and 25.12 ± 14.14 mm2 in the test and control groups, respectively (p = 0.013). The mean laboratory time was 46.08 ± 5.45 and 105.92 ± 6.10 min in the test and control groups, respectively (p < 0.001).The proximal contact adjustment and mean chair-side time showed no statistically significant difference between two groups.ConclusionsA digital workflow for two implants-supported single crowns using an auxiliary device required fewer occlusal crown adjustments, and less laboratory time compared to conventional workflow.Clinical RelevanceThe use of auxiliary occlusal devices in IOS enhances the accuracy of virtual maxillomandibular relationship in extended edentulous spans. Consequently, employing a digital workflow for multiple implants-supported crowns using IO scanning and an auxiliary occlusal device proves to be a feasible, accurate and efficient approach.

Patient-reported outcome measures (PROMs) of digital and conventional impression methods for fixed dentures.

Digital impression technique or computer-aided impression (CAI) has been recently concluded as a clinically acceptable alternative to conventional impression method (CIM) in the fabrication of crowns, short fixed partial dentures (FPDs), and implant-supported crowns. The purpose of this study was to investigate the patients' opinion and subjective perception of two different ways of impression - digital and conventional. A total of 45 patients were treated with CAI and CIM for the fabrication of tooth or implant-supported crowns. They fulfilled a questionnaire including 11 questions regarding the treatment time, gag reflex, discomfort related to manipulation, and other aspects of treatment. CAI was considered the preferential method for future treatment in 53% of patients, whereas 28.9% of the respondents preferred CIM. The preference for the impression method was influenced by the total time spent with the procedure, discomfort during manipulation with the tray or scanning head, size of the tray or scanning head, maximal opening discomfort, and (the tendency towards) gag reflex. CAI was considered a more comfortable and preferential method. Discomfort or difficulties during CAI negatively affected the patients' attitude to CAI, whereas the difficulties associated with CIM did not have any influence on the preferred method.

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

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

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

Statement of problemCement-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. PurposeThe 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 methodsTwenty 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. ResultsA significant difference (P<.001) was found in the time ±standard deviation required to retrieve the crowns between group Temp (02:40 ±00:18 min:sec) and group Resin (05:26 ±00:36 min:sec). 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. ConclusionsRetrieval 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. CLINICAL IMPLICATIONSWhen a complication arises with a cement-retained implant-supported restoration, the restoration can be retrieved safely with an Er,Cr:YSGG laser without incurring structural changes. The restoration may then be recemented, avoiding the need to remake the restoration.

The Role of Digital Facebow for CAD/CAM Implant-Supported Crowns Workflow.

Recent advancements in digital technologies have transformed clinical workflows in dentistry, ensuring precise restorations. Custom-made crowns and fixed partial dentures (FPDs) now rely on virtual articulation. The digital facebow provides individualized data for CAD settings, streamlining the fabrication via digital workflow. For the purpose of demonstrating the differences observed during fabrication, we present a case report involving a 68-year-old patient seeking a replacement for missing teeth 24, 25, 26, and 27. The treatment plan involved the fabrication of an implant-supported FPD using monolithic zirconia (ZrO2). However, technical hurdles emerged during the planning phase, primarily due to spatial limitations posing a risk of mechanical failure over time. Consequently, we pivoted approach towards a porcelain fused to metal (PFM) FPD. For the PFM FPD, individual values from the digital facebow adjusted both virtual and conventional articulators. For comparison, two ZrO2 FPDs were milled-individual settings and average settings. All restorations underwent assessment for occlusion in maximal intercuspal position and eccentric mandible movements. In conclusion, the case report showed that individualized PFM FPD required minimal adjustments compared to milled ZrO2 restorations, whether using individual or average values. Utilizing individual values from the digital facebow reduced operator working time and minimized the intraoral adjustments.