The International Journal of Prosthodontics, 01/2025

This review focuses on the progressive role of 3D printing in dentistry, particularly emphasizing the use of zirconia-based and lithium disilicate (LS2)–based ceramic materials. Celebrated for their biocompatibility and esthetic resemblance to natural teeth, these materials have shown promising results with high success rates. Digital light processing (DLP) and stereolithography (SLA) have been noted for producing superior 3D-printed ceramic products. Despite facing challenges such as surface defects, mechanical strength limitations, and esthetic inconsistencies, active research is dedicated to refining the quality and esthetics of 3D-printed zirconia-based and LS2-based ceramics. This review acknowledges the need to mitigate the steep costs of this manufacturing form and recognizes the current shortfall in clinician and technician awareness of these advanced techniques. Addressing these issues through focused research on improving surface quality, dimensional accuracy, and mechanical properties of 3D-printed dental prostheses is crucial, as is enhancing the dental community’s understanding and acceptance of this innovative technology.

Purpose: To investigate the effect of immediate provisionalization of single-tooth implants at healed sites for peri-implant soft-tissue conditions, focusing on papilla formation around single implants. Materials and Methods: In total, 12 patients received a total of 12 implants in the incisor, canine, or premolar region of the maxilla or mandible at healed sites with immediate chairside provisionalization. After 4 months, the temporary crown was replaced with the permanent crown. After 40 ± 13.1 months, clinical follow-up was conducted, assessing probing pocket depth (PPD), bleeding on probing (BoP), mucosal recession (MR), and width of keratinized mucosa (KM). Papilla index (PI) was determined immediately after implant placement (t0), before removing the temporary crown (t1), 4 weeks after delivery of the definitive crown (t2), and at the final follow-up examination (t3) to evaluate papilla formation and its change over time. Results: None of the implants were lost. The mean PPD was 2.5 ± 0.39 mm, and BoP of 25% and 3.5 mm of KM were observed at the final follow-up. No implants showed MR. PI increased in all patients from 1.5 ± 0.45 at t0 to 2.4 ± 0.56 at t1, 2.6 ± 0.47 at t2, and 3.0 ± 0 at t3. The increase in PI between t0 and each individual timepoint from t1 to t3 showed statistical significance. Conclusions: The present results indicate the suitability and benefit of immediate provisionalization to achieve favorable peri-implant soft tissue conditions and papilla formation.

Purpose: To investigate the prosthetic parameters, clinical indices, crestal bone levels, and inflammatory biomarkers in peri-implant crevicular fluid (PICF) as influenced by two different implant restorative materials—metal-ceramic and monolithic zirconia—at baseline, 1 year, and 2 years. Materials and Methods: A total of 20 patients with bilateral implants placed in the same arch were selected. A monolithic zirconia (Mono-ZrO₂; 4Y-PSZ) crown was placed on one side, and a metal-ceramic crown was placed on the contralateral side after randomization. Interproximal marginal bone level, clinical parameters, MMP-8 levels in PICF, and prosthetic characteristics (as determined by modified United States Public Health Service [USPHS] criteria) were evaluated at baseline and at 1-year and 2-year follow-ups. Data were descriptively examined. The results were evaluated using chi-square test, ANOVA, and Student t test. At P < .05, statistical significance was determined. Results: A total of 20 metal-ceramic crowns and 20 Mono-ZrO₂ crowns were delivered. A 100% survival of the implants and prosthetic crowns was achieved across all patients, with no instances of failure noted throughout the 2-year follow-up period. The periodontal changes observed in the participants were analyzed and demonstrated statistically insignificant alterations. Prosthetic alterations were assessed according to USPHS criteria, revealing minor ceramic chippings and instances of screw loosening within the metal-ceramic group during both the 1- and 2-year follow-up periods. These incidents were collectively categorized as technical issues. Regarding anatomical form and color match to the surrounding dentition, Mono-ZrO₂ crowns obtained much lower evaluations when compared to metalceramic crowns. However, when evaluating the loss of marginal bone and level of inflammatory markers, there were no discernible variations between the groups. Conclusions: The null hypothesis that there would be no similarity in the survival rates and interactions at the peri-implant interface between the two types of restorations was rejected. Mono-ZrO₂ and metal-ceramic crowns demonstrated no statistical differences across all parameters examined in the present prospective investigation.

Purpose: To evaluate radiographic changes around six implants (two posterior zygomatic implants and four conventional implants) used with fixed detachable restorations in patients with severe maxillary posterior resorption with either polyether ether ketone (PEEK) or titanium frameworks. Materials and Methods: In total, 12 maxillary edentulous patients were rehabilitated with six implants, including two posterior zygomatic and four conventionally placed implants for each patient following All-on-6 distribution and opposing a mandibular All-on-4 implant-retained fixed detachable prosthesis. A two-stage surgical unloaded healing protocol was performed. According to framework and teeth materials, there were two groups: group 1— CAD/CAM–milled framework from modified BioHPP PEEK bonded to PMMA crowns; and group 2—screwretained CAD/CAM–milled framework from titanium bonded to zirconia crowns. Bone loss evaluation for six implants was performed using CBCT at the time of delivery (T0), after 1 year (T1), and after 3 years (T2). Results: There was a statistically significant difference in bone loss between the PEEK and titanium groups. There was less bone loss in the PEEK group around anterior conventional implants at buccal (P = .01), mesial (P < .001), and distal surfaces (P < .001) and for zygomatic implants at buccal (P = .004) and palatal surfaces (P = .003). Conclusions: Within the limitations of the study, the full-arch PEEK and titanium frameworks of fixed-detachable prostheses used with an All-on-6 distribution using zygomatic implants for rehabilitation of maxillary edentulous atrophied posterior arches was a promising treatment approach. Less bone loss was observed with the PEEK framework restorations combined with the PMMA crowns group.

Purpose: To evaluate the effect of cheek retractors on the accuracy of capturing peripheral borders in totally edentulous digital scans by comparing the conventional impression technique to digital scans made using two different cheek retractors. Materials and Methods: In total, 16 edentulous maxillary impressions were made using three techniques: (1) the conventional impression technique, using modeling thermoplastic compound and zinc oxide eugenol paste; (2) the digital intraoral scanning technique, using the DIO scan retractor (DIO); and (3) the digital intraoral scanning technique, using the Brånemark lip retractor (BRAN). The control impressions of each patient were poured, scanned using a desktop scanner, and transferred into a 3D-analysis software. DIO and BRAN groups were scanned using an intraoral scanner, imported, and superimposed, using best-fit algorithm on the corresponding control. The root mean square for the whole surface and for particular regions of interest were calculated to assess the degree of trueness. Patient perception of the impression techniques was the secondary outcome. Statistical analyses were performed using one-sample t test and Wilcoxon test (α = .05). Results: Significant discrepancies were found for BRAN and DIO compared to the control. No significant discrepancies were found when comparing RMS of BRAN and DIO at different regions. Scan retractors had a significant impact on patient satisfaction, with patients preferring DIO. Conclusions: Edentulous intraoral scans made using cheek retractors had similar deviations when compared to each other but diverged from the conventional impression in the edentulous maxilla. Patient preference for intraoral scans over conventional impressions was confirmed. The use of different retraction methods during intraoral scanning of totally edentulous maxillary arches does not affect the peripheral border registration.

Purpose: To evaluate the prevalence of biologic and technical/mechanical complications in an edentulous older population rehabilitated with complete removable dental prostheses (CDs) and overdentures (toothretained [ODs], implant-retained [IODs]). Materials and Methods: Patient records of adults (> 60 years) rehabilitated with CDs, ODs, and IODs were included. Demographic information (age, sex), information on the prostheses type, number and type of biologic/prosthetic complications, and the number and time of the complications were extracted. Kaplan-Meier model was used for statistical analyses. Results: A total of 162 patients (mean age: 74.5 ± 9.45 years; n = 224 prostheses: CD = 172, OD = 21, IOD = 31) were included. The average period of function in situ was 19.70 ± 27.66, 32.72 ± 27.84, and 31.73 ± 32.67 months for the CDs, ODs, and IODs, respectively. Five prostheses failed. Survival analysis revealed an overall survival rate (SR) of 97.8%, with individual 5-year cumulative survival probability of 96.1% for CDs, 94.1% for ODs, and 100.0% for IODs. There were no significant survival differences between maxillary and mandibular prostheses within each type of rehabilitation. In the maxilla, no significant differences were found in maintenance visit times due to prosthodontic complications among the different types of prostheses. Patients with mandibular CDs required maintenance visits earlier compared to mandibular ODs (P < .001) and IODs (P < .001). Patients with mandibular ODs also required maintenance visits earlier than those with mandibular IODs (P = .005). Conclusions: Rehabilitation of the edentulous arches, whether with CDs, ODs, or IODs, is a predictable treatment modality with high SRs. Differences in maintenance visit times were observed, with CDs and ODs in the mandible requiring earlier visits compared to IODs.

Purpose: To observe the effect of the cavity design of the direct composite restoration on a real case of the patient’s tooth structures after applying mandibular kinematics with finite element analysis. Materials and Methods: Four complex maxillomandibular models of the maxillary right second molar and mandibular right second molar were constructed from the patient’s CBCT acquisition, and the patient’s kinematic data recorded with Modjaw were added. Different shapes and sizes of mesio-occluso-distal (MOD) composite restorations were simulated, including the polymerization shrinkage of this material. Finite element analyses were used to observe the von Mises stresses occurring during polymerization and mastication. Results: The stresses were observed at the cavity margin, and the amplitude of the stresses was higher when the enamel volume was lower. The reduction in occlusal enamel volume with the open-angle vestibular and palatal walls resulted in a greater increase in stresses observed on the structures. Conclusions: The occlusal enamel is the area that bears the maximum masticatory stress, and the loss of this enamel volume generates a much greater concentration of stress on the underlying structures. It is important to preserve as much enamel tissue as possible when designing a cavity for a direct composite restoration.

Purpose: To develop a system for assessment of the status of a tooth to receive a full coverage crown and depict it on a measurable scale, and to validate its use by assessing examiner reproducibility. Materials and Methods: The index was developed based on the inputs from experts in the field with a consensus on factors (four periodontal, two endodontic, and four prosthodontic), stages of severity (stage 1 to stage 4), assigned scores, and relative weights pertaining to varied clinical scenarios. Based on the selection of factor-stage combinations, an overall tooth crownability index (TCI) score along with three-factor scores were computed. The validation study included clinical and radiologic assessment of cases based on the index criteria by four independent examiners (periodontist, prosthodontist, endodontist, and general practitioner). Results: A total of 40 teeth were assessed. The distribution of repeated selection by the examiners was very similar to the initial distribution (kappa = 0.93). There was no statistically significant difference in the mean scores of examiners in TCI and factorial scores. An excellent agreement between the measurements was observed among the examiners (ICC = 0.993; Crohnbach α = .993). Conclusions: TCI with excellent agreement and good reproducibility among the examiners has been developed for a tooth to receive a full-coverage crown. TCI will serve as a baseline tool in treatment plan decision-making based on the status of the teeth and in research for evaluating the efficacy of various treatment options available (standard criteria for outcome assessment).

Purpose: To investigate the influence of three post-and-core systems and two crown materials on stresses in restored premolars using finite element analysis (FEA). Materials and Methods: A maxillary second premolar 3D model was created in SolidWorks 2014 (Dassault Systémés). Severe loss of tooth structure was simulated with six restorative options: (1) glass-fiber-reinforced composite post and composite core (GFRC) + CAD/CAM leucite-reinforced glass-ceramic crown (LRC); (2) carbon-fiberreinforced composite post and composite core (CFRC) + LRC; (3) metal cast post-and-core (MPC) + LRC; (4) GFRC + CAD/CAM composite resin crown (CC); (5) CFRC + CC; and (6) MPC + CC. Three-point occlusal loading (150 N) was simulated and von Mises and maximum principal stresses were calculated. Results: Although maximum von Mises stresses in the crown and dentin were similar across groups (137.9 to 139.2 MPa crown; 17.2 to 19.6 dentin), there were important differences in stress distribution in dentin. Maximum stresses were on the bottom of the post preparation cavity only in the MPC + CC group. Stress values for the posts were CFRC (4.8 MPa) > GFRC (6.7 MPa) > MPC (10.3 MPa). CC-restored models presented higher von Mises stresses for the post-and-core compared to the LRC groups. Maximum principal stresses were lower compared to von Mises stresses, following the same trend, and were distributed similarly in all groups. Conclusions: Both GFRC and CFRC showed favorable stress distribution in the dentin and restorative materials, while MPC increased stresses in the core, post, and post cement. The more rigid crown material seems to transmit less stress to the underlying core and crown cement compared to CC.

Purpose: To update data on the transfer accuracy of digital implant impressions using a coordinate-based analysis, the latest intraoral scanners (IOS) were investigated in an established clinical close model setup. Materials and Methods: An implant master model (IMM) of the maxilla with four implants in the posterior area (maxillary first premolars and first molars) and a reference cube were scanned 10 times each with four different IOS: i700 (i7; Medit), Primescan (PS; Dentsply Sirona), and Trios 4 (T4) and Trios 5 (T5; 3Shape). Datasets were compared to a reference dataset of IMM that was generated with x-ray computed tomography in advance. 3D deviations for the implant-abutment interface points (IAIPs) were calculated. Statistical analysis was performed by multifactorial ANOVA (P < .05). Results: Overall deviations for trueness (mean) ± precision (SD) of the IAIPs ranged from 88 ± 47 μm for PS, 112 ± 57 μm for i7, 121 ± 42 μm for T4, and 124 ± 43 μm for T5 with decreasing accuracy along the scan path. For trueness, a significant difference between the PS and the T4 was detected for one implant position. For precision, no significant differences were noticed. Conclusions: Although the latest IOS showed a significant improvement in transfer accuracy, the accumulating deviation along the scan path is not yet resolved. Considering the Trios system, the innovation seems to be limited because no improvement could be detected between T4 and T5.

Purpose: To evaluate the color alterations, flexural strength, and microhardness properties of two different 3D-printed permanent crown resins. Materials and Methods: Samples were produced from two different 3D-printed permanent crown resins: Group 1 (Saremco Crowntec, Saremco Dental) and Group 2 (P-crown V2, Senertek). Color changes (ΔE values), flexural strength, and Vickers hardness number (VHN) of the samples were calculated. Data were analyzed with Shapiro-Wilk normality test, independent t test, and Mann-Whitney U tests. The significance level was accepted as P < .05. Results: ΔE values for red wine were found to be significantly higher in Group 1 (6.43 ± 2.26; P < .001). The flexural strength values (MPa) of Group 1 were significantly higher than Group 2 in all three solutions (P < .001). There was no significant difference between the VHN values of the samples kept in wine and coffee solutions (P = .271; .827). Conclusions: 3D-printing resins are affected at different levels by coloring solutions. Microhardness and flexural strength of 3D-printed samples kept in different coloring agents are different. In the use of 3D-printing resins, product selection should be made by taking into account the individual factors such as the eating and drinking habits of the patient and the physical properties expected from the sample.

Immediate nonfunctional loading of an implant in the anterior region is a documented treatment modality with high success rates. This therapeutic approach is frequently used to overcome esthetic and functional problems during the provisionalization period but also because it provides better support of peri-implant soft tissues. For that purpose, an implant-supported resin restoration, either traditionally or digitally made, is used. This clinical report describes the modification of a patient’s natural tooth, which was previously fractured, to be used as an implant-supported provisional restoration to obtain better esthetics and preservation of the soft tissues in their original, pre-extraction position.

Additive manufacturing (AM), also known as 3D printing, has become one of the pillars of digital technology in the dental field of prosthodontics. With the burgeoning development in preexisting AM technology and the evolution of new techniques, which are concurrent with the development of printable biomaterials, the application range of the technology has broadened from the construction of diagnostic models to more complex applications such as maxillofacial prosthetics and implant planning. A full understanding of the technology and its related fabrication parameters will enable the maximum benefit from such technology. Therefore, the aim of this review is to represent a range of AM technologies so that prosthodontists and dental technicians can evaluate more closely the advantages and disadvantages of each technique, the application of technology in the field of prosthodontics, areas of current research in the field, and recommendations for areas of future research.

Multiple disconnection and reconnection of abutments has been known to affect the mucosal barrier around implants, leading to marginal bone loss (MBL). This clinical report describes a novel technique that amalgamates the benefits of digital technologies including the fabrication of surgical guides for implant placement, customized hybrid zirconia abutments, and all-ceramic lithium disilicate crowns prior to implant placement. Correct 3D implant positioning, along with immediate placement of the definitive hybrid customized abutment and a lithium disilicate crown, have the potential to reduce treatment time, visits, and costs while delivering optimal esthetic outcomes.