The International Journal of Prosthodontics, 05/2019

Purpose: To investigate changes in oral health prior to and after conversion of fractured abutment teeth in double crown-retained removable dental protheses (DC-RDPs) into root-anchored ball attachments. Materials and Methods: Twenty patients were supplied with one root-anchored ball attachment after abutment tooth fracture. The Oral Health Impact Profile (OHIP-49) was completed by the patients prior to and after treatment to assess changes in perceived oral health. Results: Changes in OHIP were statistically and clinically significant (28.90 points prior to treatment and 13.80 points after treatment), especially in cases with a minor number of remaining double crowns. Conclusion: The conversion of fractured abutment teeth in DC-RDPs into root-anchored ball attachments can be an effective strategy for improving perceived oral health.

Purpose: To compare oral function and health-related quality of life (HRQoL) in patients reconstructed with either a reconstruction plate or a free vascularized bone flap with or without 3D planning. Materials and Methods: Patients from the Institute for Reconstructive Sciences in Medicine, University Medical Center Utrecht, and Radboud University Medical Center were included. This cross-sectional study assessed objective masticatory performance with the mixing ability test (mixing ability index [MAI]), maximum bite force, maximum mouth opening, and HRQoL. Differences between groups were analyzed using analysis of variance or Kruskal-Wallis test for continuous variables and chi-square test for categorical variables. Results: Six patients with digitally planned resections and reconstructions were included. For comparison, five patients treated with freehand bone reconstruction and four patients treated with plate reconstruction were also included. Mixing ability was superior in 3D-planned reconstructions (MAI: 20.7 ± 6.7) compared to plate reconstructions (MAI: 30.0 ± 0.1, P = .017) and freehand reconstructions (MAI: 29.5 ± 1.1, P = .017). Maximum mouth opening, bite force, and HRQoL differences did not reach statistical significance. Conclusion: This study indicated a possible benefit to masticatory performance of adequate surgical planning for one-phase reconstruction using 3D technology. A larger prospective study is necessary to gain more evidence regarding this finding.

Purpose: To evaluate the challenges of the direct filling technique, the use of dental chairside CAD/CAM milling, the use of 3D printing, and the attitudes toward 3D printing-based applications for restorative treatments among Finnish dentists. Materials and Methods: An electronic questionnaire was sent to 3,777 Finnish dentists. Background information, challenges linked to the direct filling technique, use of dental chairside CAD/CAM milling, use of 3D printing, and attitudes toward 3D printing-based applications in restorative dentistry were asked in the questionnaire with multiple-choice questions. The number of replies was 760, and the response rate was 20.1%. Results: Poor survival rates and moisture sensitivity were the main reported challenges associated with the direct filling technique. Use of chairside CAD/CAM milling was reported by 271 (35.7%) respondents. Use of 3D printing technique was reported by 54 (7.1%) respondents. Most respondents answered that they would consider using 3D printing for manufacturing tooth fillings in the future. Conclusion: If dental chairside CAD/CAM technology can provide a solution for manufacturing long-lasting indirect restorations with good esthetic properties and an effective cost-benefit ratio, the wider use of chairside CAD/CAM systems might be indicated, especially in the public sector. New 3D printing- based applications used for restorative treatments are attracting interest among Finnish dentists, but also indicate a need for further development of 3D printing techniques for cost-effective restorative treatment.

Purpose: To study the complication and success rates of root-filled teeth restored with zirconia posts in a critical review. Materials and Methods: An electronic literature search in the MEDLINE, Cochrane Library, Ovid-EMBASE, and Chinese National Knowledge Infrastructure (CNKI) databases was undertaken in December 2018. Other databases were also searched for gray literature, and the electronic search was complemented by a manual search in the related reviews and references of full-text articles. Initial screening of the titles and abstracts of eligible studies was conducted by two independent reviewers in duplicate. Complication and success rates were extracted from the included studies and then pooled using a random- or fixed-effects model. Poisson regression was used to study the effect of core materials (resin vs composite). Results: Among 431 screened articles, 2 prospective and 3 retrospective studies met the eligibility criteria and were included. The pooled data showed that zirconia posts had a favorable 3-year success rate of 97.4% (95% confidence interval [CI] 95.7% to 98.8%). The estimated 3-year catastrophic complication (ie, tooth extraction) rate was 0.09% (95% CI 0% to 1.67%), and the estimated 3-year noncatastrophic complication rates were 0.24% (95% CI 0% to 1.16%) for post complications, 0.78% (95% CI 0% to 4.29%) for crown complications, and 0.03% (95% CI 0% to 0.63%) for endodontic failures. Conclusion: Based on the limited number of clinical cohort studies, zirconia posts appear to be suitable for use in post-and-core systems. However, the studies included in this critical review had a relatively high risk of bias, and further well-designed clinical studies, especially long-term randomized controlled trials, are required to confirm these findings.

Purpose: To assess whether particles from metal and other alloplastic materials detected in tissues surrounding dental implants could have other sources of origin besides biotribocorrosion or detachment from the implant surface. Materials and Methods: A total of 52 prostheses were randomly tested at various stages of manufacture. Identification of the detached microparticles was performed using light field microscopy and comparison with previously obtained microscopic images. Results: Microparticles of metallic, ceramic, plaster, polishers, or unidentifiable origin were detected in 49 prostheses (94%). Conclusion: Without an exhaustive decontamination protocol, prostheses and abutments carry metal microparticles and microparticles of other origins that could contribute to the development of peri-implant pathologies.

Purpose: To assess the influence of a screw access hole (SAH) and mechanical cycling on the fracture load of implant-supported crowns (ISCs) manufactured with screw-retained (s) or cement-retained (c) abutments with either metal (M) or zirconia (Z) infrastructure. Materials and Methods: Six groups of restorations were made based on type of infrastructure (M or Z), fixation (s or c), and whether they underwent aging (a) with mechanical cycling: Zc, Zs, Zsa, Mc, Ms, and Msa. All ISCs were porcelain veneered and tested for compression to failure in distilled water (37°C) using a universal testing machine. ISCs from groups Zsa and Msa were mechanically cycled (106 cycles; 2 Hz, 100 N) in distilled water before compressive testing. Fractographic principles were followed to assess the fracture surfaces. The fracture load data were statistically analyzed using one-way analysis of variance and Tukey test (α = .05). The relationships between experimental group and failure mode were analyzed using chi-square test (α = .05). Results: Regardless of the infrastructure material, cement-retained ISCs (Zc and Mc) showed higher fracture load values than screw-retained ISCs (Zs, Zsa, Ms, and Msa) (P .001), which were statistically similar to each other (P > .05). Aging had no effect on the fracture load of ISCs. There was a significant relationship between failure mode and experimental group (P .001). Catastrophic fractures were found only in Zc and Zs. All metal-based ISCs failed from chipping reaching the metal infrastructure. Conclusion: Cement-retained ISCs showed higher fracture resistance than screw-retained prostheses. No catastrophic failures were found for metal-based ISCs. Aging did not affect the fracture load, but did affect the failure mode of ISCs.

Purpose: To assess the manufacturing tolerances of three different intraoral scanbodies (ISBs) and their possible influence on the transfer of the intraoral implant position to the digital cast. Materials and Methods: Three different ISBs were measured using x-ray computed tomography. The length, diameter, angle, and target volume deviation were analyzed, and the data were subjected to a univariate analysis of variance. Results: There were significant differences between all three ISBs in length, diameter, and target volume deviations (P .05). Conclusion: Manufacturing tolerances of ISBs have the potential to decisively affect the transfer accuracy of the implant position from the recorded intraoral position to the digital cast, which needs to be considered.

Purpose: To investigate the effects of different combinations of self-adhesive resin cements and surface treatments on the microtensile bond strength (μTBS) of different CAD/CAM resin-matrix ceramics. Materials and Methods: Two different types of CAD/CAM resin-matrix ceramics (LAVA Ultimate [LU] and Vita Enamic [VE]) were used. Slices 5 mm in thickness were obtained from each CAD/CAM material. Samples of each ceramic were randomly separated into the following surface treatment groups: (1) Control group with no surface treatment; (2) 9.5% hydrofluoric acid (HF) + universal adhesive (UA, Single Bond Universal, 3M ESPE); and (3) Sandblasting with 50-μm aluminum oxide particles (SN) + UA. Two different types of recently developed resin cement (RelyX U200, 3M ESPE; SET PP, SDI Dental Limited) were applied to the treated ceramic slices in each group. After 24 hours, parallel sections were removed from the specimens, and microbeam-shaped sticks (1.0 × 1.0 × 10 mm) were prepared. The μTBS test was performed, and the data were statistically analyzed. Results: Statistical analyses revealed differences among the study groups (P .05). The control groups of each resin cement exhibited lower μTBS values than the groups that received surface treatment (P .05). The effect of surface treatment on μTBS (partial eta-squared [ηp2] = 0.381) was more significant than the effects of ceramic (ηp2 = 0.267) and self-adhesive resin cement (ηp2 = 0.184). Conclusion: Surface treatment is the most important factor affecting the μTBS of resin cement to CAD/CAM materials, followed by the type of resin-matrix ceramic and the type of resin cement, respectively.

Purpose: To evaluate the physical and mechanical properties of zirconia ceramic manufactured with stereolithography and to quantitatively analyze the internal and marginal adaptation of the zirconia ceramic dental crowns. Materials and Methods: A resin-based zirconia suspension with a solid content of 45 vol% was prepared. Zirconia dental crowns (n = 5) for the maxillary right first molar were designed and manufactured. Physical and mechanical properties-including density, sintering shrinkage, flexural strength, Weibull parameters, phase composition, and microstructure-of the stereolithography-manufactured zirconia crowns were evaluated. A three-dimensional subtractive analysis technique was used to evaluate the internal and marginal adaptation. Results: The stereolithography-manufactured zirconia (n = 22) achieved a flexural strength of 812 ± 128 MPa and a Weibull modulus of 7.44. Quantitative analysis of the fabricated zirconia crowns showed a cement space of 63.40 ± 6.54 μm in the occlusal area, 135.08 ± 10.55 μm in the axial area, and 169.58 ± 18.13 μm in the marginal area. Conclusion: Within the limits of this study, the strength of the stereolithography-manufactured zirconia was adequate for fabricating dental crowns. However, internal and marginal adaptation are not yet ideal for clinical application.

Fixed dental prostheses are the standard treatment option for replacing missing teeth when adjacent teeth require crowns or are already restored with crowns. Divergent abutment teeth axes may require invasive teeth preparation to achieve a common path of insertion, which substantially weakens residual tooth structure and increases the risk of pulpal problems. In selected cases with divergent abutment teeth in the buccal-lingual direction, the use of a rotational path of insertion might overcome these problems. This concept is presented via a clinical case history report.

Leiomyosarcoma is a rare malignant condition occurring in the maxillofacial region in which the mandible may be affected. Management of this tumor in the mandible may include segmental mandibulectomy, osteocutaneous fibula free-flap reconstruction, endosseous implants, and postoperative radiotherapy. Posttreatment malocclusion can be managed with an overpartial mandibular resection prosthesis. The purpose of this report is to describe the expeditious oral rehabilitation of an oncologic patient with posttreatment malocclusion, demonstrating the utility of an overpartial mandibular resection prosthesis.