Tactile misfit detection ability at the implant-abutment interface of internal connection dental implants: an in-vitro study.

OBJECTIVE: The aim of this in-vitro study was to investigate the tactile assessment ability at the implant impression-taking stage. METHODS: Thirty clinicians (18 novices, 12 experts) were included for a tactile fit assessment by using a used/new probe (tip diameter 100 µm/20 µm). Six implant replicas and related impression copings of two internal connection implant systems were used, each with a perfect fit (0 µm) and defined vertical micro gaps of 8, 24, 55, 110 and 220 µm at the interface. Statistical analysis was performed using descriptive methods and non-parametric tests with a focus on specificity (ability to detect perfect fit), sensitivity (ability to detect misfit), and predictive values. P-values <5% were considered statistically significant. RESULTS: The tactile assessment showed a mean total sensitivity for the Straumann and Nobel Biocare systems of 83% and 80% with a used probe, and 91% and 92% with a new probe, respectively. The mean total specificities were 33% and 20% with a used probe and 17% and 3% with a new probe, respectively. No statistical significance was observed between novice and expert clinicians concerning their tactile assessment ability. CONCLUSIONS: The ability to detect a perfect fit (specificity) with a probe was very poor for both implant systems and impaired with the use of a new probe. The use of a new probe improved the gap detection ability (sensitivity) significantly at the expense of the specificity. A combination of additional chairside techniques with training and calibration could improve clinicians' ability to correctly assess the fit/misfit at the implant-abutment interface.

Zirconia bars for mandibular implant overdentures: A 1-year clinical and radiographic pilot study.

PURPOSE: To evaluate the clinical performance of zirconia bars with distal extensions supporting mandibular implant overdentures based on biological and prosthodontic outcomes. MATERIALS AND METHODS: Fifteen edentulous patients (seven women and eight men) were included in a pilot study. Each patient received two interforaminal implants and a mandibular implant overdenture supported by a CAD/CAM zirconia bar with distal extensions, giving a total of 30 implants. The bar design, biological outcomes (implant survival and peri-implant conditions), peri-implant bone level changes recorded on a panoramic radiograph and prosthodontic maintenance (bar fracture and maintenance of the attachment system) were assessed at a 1-year follow-up. RESULTS: After 1 year, all 15 zirconia bars with their corresponding prostheses and implants were successfully in situ with no prosthodontic maintenance required and no biological complications. One patient showed moderate mucosal hyperplasia around the bar. The peri-implant radiographic measurements revealed a stable marginal bone level, with a mean of 0.20 ± 0.67 mm. The mean total length of the bar segments was 41.9 mm (range 35.0 to 51.0 mm), 8.6 mm (range 7.2 to 10.6 mm) of which came from the length of the distal extension, resulting in a mean increase in rigid support of 71% (range 60% to 99%). The mean distal bar connector area was 9.7 mm2 (range 6.8 to 18.7 mm2). CONCLUSION: Zirconia bars with distal extensions for implant overdentures appear to be a reliable option for the prosthodontic rehabilitation of edentulous mandibles. A survival rate of 100% was observed for implants, bars and prostheses, with stable peri-implant bone levels, no biological complications and a low risk of prosthodontic maintenance being required.

Single versus splinted short implants at sinus augmented sites: A systematic review and meta-analysis.

OBJECTIVE: This review primarily evaluated the success, survival and failure rates of implants shorter than 10 mm restored with single-unit or splinted fixed dental prostheses in maxillary sinus augmented sites. MATERIAL AND METHODS: Two reviewers independently performed the systematic search of electronic databases, including MEDLINE, EMBASE and CENTRAL, up to September 2019 with no language restriction. A supplemental hand search consisted of screening 13 journals. The inclusion criteria were: primary studies reporting implant, prosthetic and patient-reported outcome measures (PROMs) of extra-short and short implants placed in conjunction with sinus floor elevation in partially dentate patients, restored with single- and splinted-crowns for direct comparison, with a minimal 1-year follow-up. Weighted arithmetic mean (WAM) of the implant survival was performed according to the type of prosthesis. This was confirmed by using Review Manager software to perform meta-analysis. RESULTS: Two observational studies reporting on 106 tapered, press-fit, sintered porous-surfaced implants with a length ranging from 5 mm to 9 mm were included in this systematic review. Of these, 20 and 86 implants were restored with single and splinted prostheses, respectively. The risk ratio (RR) was 1.16 (95% CI: .31-4.30, p = .58, I² = 0%) for individually restored implants failure when compared to splinted implants, indicating that short dental implants restored with single crowns could have a 16% higher possibility of failure if compared to implants with splinted crowns. The heterogeneity value was not statistically significative (p = .58). No statistical difference in the implant survival rate of the two types of analysed prostheses was observed after WAM (p= .923). The level of evidence for the included studies ranged from low (4) to fair (2B). CONCLUSION: Similar clinical outcomes up to a 9-year follow-up were observed in single and splinted porous-surfaced implants shorter than 10 mm located in sites with sinus lift. However, the conclusion shall be interpreted with caution due to the level of evidence and limited number of included studies included in this systematic review.

Antibiotics in reconstructive dentistry / Antibiotikarichtlinien Rekonstruktive Zahnmedizin

These guidelines concern the administration of systemic antibiotics in reconstructive dentistry. While the general guidelines for antibiotic prophylaxis apply to patients at risk, the prophylactic administration of antibiotics is only indicated in very rare cases in healthy patients: chamber-preserving measures with autologous grafts during extractions in the hygiene phase and implantation with controlled bone regeneration in the surgical phase.

Computer-assisted, template-guided immediate implant placement and loading in the mandible: a case report.

BACKGROUND: Computer-assisted implant planning has become an important diagnostic and therapeutic tool in modern dentistry. This case report emphasizes the possibilities in modern implantology combining virtual implant planning, guided surgery with tooth and implant supported templates, immediate implant placement and loading. CASE PRESENTATION: A straight forward approach was followed for the mandible presenting with hopeless lower incisors. Diagnosis, decision making and treatment approach were based on clinical findings and detailed virtual three-dimensional implant planning. Extractions of the hopeless mandibular incisors, immediate and guided implant placement of six standard implants, and immediate loading with a provisional fixed dental prosthesis (FDP) were performed fulfilling patient's functional and esthetic demands. The final computer assisted design / computer assisted manufacturing (CAD/CAM) FDP with a titanium framework and composite veneering was delivered after 6 months. At the 1-year recall the FDP was free of technical complications. Stable bony conditions and a healthy peri-implant mucosa could be observed. CONCLUSIONS: Computer assisted implantology including three-dimensional virtual implant planning, guided surgery, and CAD/CAM fabrication of provisional and final reconstructions allowed for a concise treatment workflow with predictable esthetic and functional outcomes in this mandibular full-arch case. The combination of immediate implant placement and immediate loading was considerably more complex and required a high level of organization between implantologist, technician and patient. After the usage of a first tooth-supported surgical template with subsequent extraction of the supporting teeth, a second surgical template stabilized on the previously inserted implants helped to transfer the planned implant position in the extraction sites with a guided approach.

Influence of Crown-to-Implant Ratio on Long-Term Marginal Bone Loss Around Short Implants.

PURPOSE: To evaluate the influence of the crown-to-implant ratio (CI) on marginal bone loss (MBL) around short dental implants placed in the posterior mandible. MATERIALS AND METHODS: All patients treated with short implants (7 mm length) in the posterior mandible between 1994 and 2003 at the Dental Clinic of the Department of Neuroscience of the University of Padua (Italy) were retrospectively included in the analysis. MBL and clinical CI (cCI) were measured on the radiographs. Implant characteristics including implant diameter, prosthetic type, retention mode, antagonist type, veneering material, and implant surfaces were retrieved from local medical records. A generalized linear mixed model was estimated to identify the predictors of MBL. RESULTS: A total of 108 dental implants placed in 51 patients were included in the analysis. Mean follow-up was 16 years (range: 11 to 20 years). Mean cCI was 2.21 (SD = 0.31) with a mean crown height of 10.86 mm (SD = 0.99). Mean MBL was 1.42 mm (SD = 0.38). At multivariable analysis, cCI ≥ 2 was associated with higher MBL (regression coefficient: 0.27; 95% CI: 0.15 to 0.40), while implant characteristics, follow-up, and site were not associated with MBL. The effect of a cCI ≥ 2 was estimated in an increase of 0.28 mm in MBL (95% CI: 0.14 to 0.43 mm). CONCLUSION: Higher cCI was associated with greater MBL of implant-supported fixed dental prostheses in short dental implants placed in the posterior mandible, while implant characteristics, follow-up, and site were not associated with MBL. However, the increase of 0.28 mm of MBL in patients with a cCI ≥ 2 may be not clinically relevant.

Masticatory Performance and Maximum Bite and Lip Force Depend on the Type of Prosthesis.

PURPOSE: The aim of this cross-sectional study was to assess maximum restraining lip force (MLF), maximum voluntary bite force (MBF), and patient-related parameters to evaluate their influence on masticatory function in four groups of participants with different dental states. METHODS: Participants were recruited and assigned to one of four different groups depending on dental status: complete removable dental prostheses (CRDP group); edentulous with two-implant overdentures (IOD group); Kennedy Class I partial removable dental prostheses (PRDP group); or fully dentate (control group). A dental examination was performed and history taken. MLF was measured as the maximum withstood pulling force with three sizes of oral screens, MBF was evaluated using a digital force gauge, and masticatory performance was assessed using a two-color mixing ability test. Linear regression was used to determine the predictive effects of covariates on masticatory performance. Global and pairwise comparisons were also carried out. RESULTS: A total of 68 participants with an average age of 69.3 ± 7.7 years were recruited. MLF depended on the screen size (P = .0004; Kruskal-Wallis) and increased with CRDP use, especially in challenging tasks, such as restraining the smallest screen. The highest MBF was found in dentate participants (P < .0001; Mann-Whitney). Analysis of variance (ANOVA) showed a global significant difference in masticatory performance between groups, with PRDP patients chewing better than CRDP patients. Dental state, time lapse since last tooth loss, and MBF predicted masticatory function. CONCLUSION: Tooth loss significantly affects MBF and masticatory performance. Free-end saddles with a rotational axis in two-implant IODs and Kennedy Class I PRDPs may limit MBF and consequently masticatory performance. CRDP design should facilitate perioral muscular function.

Misfit of implant prostheses and its impact on clinical outcomes. Definition, assessment and a systematic review of the literature.

BACKGROUND AND AIM: Compromised fit between the contact surfaces of screw-retained implant-supported fixed dentures (IFDs) is thought to create uncontrolled strains in the prosthetic components and peri-implant tissues, thus evoking biological and technical complications such as bone loss, screw loosening, component fractures and, at worst, loss of implants or prostheses. The aim of this systematic review was to evaluate the impact of marginal misfit on the clinical outcomes of IFDs, and to elucidate definition and assessment methods for passive fit. MATERIALS AND METHODS: A systematic review of the literature was conducted with a PICO question: "For partially or complete edentulous subjects with screw-retained IFDs, does the marginal misfit at the implant-prosthesis interfaces have an impact on the clinical outcomes?". A literature search was performed electronically in PubMed (MEDLINE) with the help of Boolean operators to combine key words, and by hand search in relevant journals. English written in vivo studies published before August 31, 2016 that reported on both clinical outcome and related implant prosthesis misfit (gap, strains, torque) were selected using predetermined inclusion criteria. RESULTS: The initial search yielded 2626 records. After screening and a subsequent filtering process, five human and five animal studies were included in the descriptive analysis. The selected studies used different methods to assess misfit (linear distortion, vertical gap, strains, screw torque). While two human studies evaluated the biological response and technical complications prospectively over 6 and 12 months, the animal studies had an observation period < 12 weeks. Four human studies analysed retrospectively the 3 to 32 years' outcomes. Screw-related complications were observed, but biological sequelae could not be confirmed. Although the animal studies had different designs, bone adaptation and implant displacement was found in histological analyses. Due to the small number of studies and the heterogenic designs and misfit assessment methods, no meta-analysis of the data could be performed. CONCLUSIONS: The current literature provides insufficient evidence as to the effect of misfit at the prosthesis-implant interface on clinical outcomes of screw-retained implant-supported fixed dentures. Marginal gaps and static strains due to screw tightening were not found to have negative effects on initial osseointegration or peri-implant bone stability over time. Based on two clinical studies, the risk for technical screw-related complications was slightly higher. While the degree of tolerable misfit remains a matter of debate, the present data do not imply that clinicians neglect good fit, but aim to achieve the least misfit possible. Conflict of interest statement: The authors declare no conflict of interest. The review was conducted as part of the 2016 Foundation of Oral Rehabilitation Consensus Conference on "Prosthetic Protocols in Implant-based Oral Rehabilitation".

Monolithic zirconia reconstructions supported by teeth and implants: 1- to 3-year results of a case series.

OBJECTIVE: Today, only scarce information is available on monolithic zirconia reconstructions. The objective of this study was to evaluate the performance of monolithic zirconia for tooth- and implant-borne reconstructions. METHOD AND MATERIALS: Monolithic zirconia single crowns (SCs) and fixed dental prostheses (FDPs) supported by implants or teeth were included in this study. Implant placement and prosthetic treatment were done in the same clinical setting. One technician performed all laboratory work using the same CAD/CAM workflow (DentalDesigner, Ceramill Motion 2, Amann Girrbach). The endpoints were technical outcome, color match, marginal adaptation, anatomical form, and biologic aspects. The modified United States Public Health Service (USPHS) criteria and periodontal parameters were applied for the clinical evaluation by two independent examiners. Descriptive statistics and nonparametric tests were used for statistical comparisons. RESULTS: Forty patients (17 men, 23 women, mean age 59.1 ±â€¯14.7 years) with 109 reconstructions (74 SCs, 35 FDPs) supported by 38 implants and 71 teeth were assessed, resulting in a total of 238 monolithic zirconia units (including 62 pontics and 18 cantilevers). Median follow-up time was 23.8 months (12 to 36 months). No technical failures were observed. The total prosthesis survival rate was 99.6% (teeth, 100%; implants, 98.4%) due to the loss of one implant. The periodontal/peri-implant parameters stand for healthy tissue, and caries was not detected. The records obtained by the USPHS revealed good clinical outcomes. CONCLUSION: These short-term results indicate that monolithic zirconia reconstructions for teeth and implants may be a satisfactory treatment option, particularly in the posterior region.

Impact of digital intraoral scan strategies on the impression accuracy using the TRIOS Pod scanner.

OBJECTIVES: Little information is available on the impact of different scan strategies on the accuracy of full-arch scans with intraoral scanners. The aim of this in-vitro study was to investigate the trueness and precision of full-arch maxillary digital impressions comparing three scan strategies. METHOD AND MATERIALS: Three scan strategies (A, B, and C) were applied each five times on one single model (A, first buccal surfaces, return from occlusal-palatal; B, first occlusal-palatal, return buccal; C, S-type one-way). The TRIOS Pod scanner (3shape, Copenhagen, Denmark) with a color detector was used for these digital impressions. A cast of a maxillary dentate jaw was fabricated and scanned with an industrial reference scanner. This full-arch data record was digitally superimposed with the test scans (trueness) and within-group comparison was performed for each group (precision). The values within the 90/10 percentiles from the digital superimposition were used for calculation and group comparisons with nonparametric tests (ANOVA, post-hoc Bonferroni). RESULTS: The trueness (mean ± standard deviation) was 17.9 ± 16.4 µm for scan strategy A, 17.1 ± 13.7 µm for B, and 26.8 ± 14.7 µm for C without statistically significant difference. The precision was lowest for scan strategy A (35.0 ± 51.1 µm) and significantly different to B (7.9 ± 5.6 µm) and C (8.5 ± 6.3 µm). CONCLUSIONS: Scan strategy B may be recommended as it provides the highest trueness and precision in full-arch scans and therefore minimizes inaccuracies in the final reconstruction.

Bone resorption in different parts of the mandible in patients restored with an implant overdenture. A retrospective radiographic analysis.

AIM: This study investigated the pattern of resorption of the mandibular ridge under implant-supported overdentures. MATERIAL AND METHODS: Files of 60 patients were available for analysis (45 women and 15 men, mean age at the time of the follow-up 76.5 ± 8.5 years, 54 patients restored with bars, 6 with ball anchors). A baseline was defined by different stable landmarks and quartered. Linear measurements from this baseline at different clinical relevant sites approximately at: (i) the area close to the mental foramen/close to the implant, (ii) the chewing center, and (iii) the distal edge of the denture flange were carried out on rotational tomograms (OPTs). The OPTs were taken after prosthetic restoration and at an individual follow-up time (mean 11 ± 4.75 years). The known implant length served to scale each measurement to avoid any distortion errors. RESULTS: The resorption rate showed a high individual variation, but among the three sites, the difference was highly significant. Median values of site (i) left = -0.07 mm/right = +0.05 mm, site (ii) left = -0.60 mm/right = -0.55 mm, and site (iii) left = -1.58 mm/right = -2.01 mm. CONCLUSIONS: The load of the distal flange of a mandibular implant overdenture increases bone resorption as a local factor, whereas implants may help to prevent resorption in the neighboring bone. An individual-adapted follow-up protocol should be established for each patient restored with an implant overdenture.

Clinical Fitting and Adjustment Time for Implant-Supported Crowns Comparing Digital and Conventional Workflows.

PURPOSE: The aim of this prospective cohort study was to investigate clinical and laboratory performance of implant-supported reconstructions comparing the digital to the conventional workflow. MATERIALS AND METHODS: Twenty study participants were treated in a cross-over design for single-tooth replacement in posterior sites, each with a customized titanium abutment plus computer-assisted design and computer-assisted manufacturing (CAD/CAM)-zirconia-suprastructure (test: digital workflow; n = 20) and a standardized titanium abutment plus PFM-crown (control: conventional pathway; n = 20). Evaluation of the 40 reconstructions included: 1) feasibility of laboratory cross-mounting of each abutment-crown-connection, and 2) assessment of adaptation time for clinical adjustments of interproximal and occlusal surfaces. Statistical analyses were performed using the exact Wilcoxon rank sum tests. RESULTS: Laboratory cross-mounting was feasible for three reconstruction pairings revealing a 15% vice versa transfer success rate. All implant crowns could be provided successfully within two clinical appointments, independently of the workflow used. The mean clinical adjustment time was significantly lower (p < .001) for test reconstructions from the digital workflow with 2.2 min (standard deviation [SD] ± 2.1) compared with the ones from the conventional pathway with 6.0 min (SD ± 3.9). CONCLUSIONS: The digital workflow was almost threefold more efficient than the established conventional pathway for fixed implant-supported crowns. Clinical fitting could be predictably achieved with no or minor adjustments within the digital process of intraoral scanning plus CAD/CAM technology.

Mucosal Manifestations in the Edentulous Maxilla with Implant Supported Prostheses: Clinical Results from a Well-Maintained Patient Cohort.

BACKGROUND: Prostheses in the edentulous maxilla affect the mucosa. PURPOSE: To evaluate mucosal alterations with implant supported fixed prostheses (FDP) and overdentures (IOD). MATERIAL AND METHODS: Patients receiving prostheses during a time period of 10 years were recruited. Maxillary mucosal conditions in relation to FDPs, IODs were analyzed. Peri-implant parameters were measured and the Oral Health Impact Profile (OHIP) was administered. RESULTS: One hundred seven patients wearing 74 IODs and 33 FDPs were identified with a total of 519 implants, the mean observation time was 6.5 ± 2.7. Cumulative implant survival was 93%. Erythema and hyperplastic tissue were identified in 71% of the IOD wearers, but were mostly absent with FDPs. The peri-implant parameters demonstrated healthy peri-implant mucosa. Medication and smoking had no effect on mucosal alteration (OR = 1.065 and 1.568). The average OHIP value was 3.73 ± 4.12. A lower value (p < 0.0048) was found for FDPs and one type of IOD. CONCLUSIONS: A rigorous maintenance program did not prevent IOD mucosal alterations in IOD wearers, but the health of the peri-implant mucosa was maintained and was comparable for all types of prostheses.

Masticatory function and nutrition in old age.

Nowadays, many people retain their natural teeth until late in life as a result of the large success of preventive strategies. However, there is still a very high prevalence of edentulism especially in elderly patients and many of these patients are provided with inadequate dental prostheses. In addition, many elderly citizens suffer from systemic diseases leading to increased drug prescription with age. This may have direct or indirect negative effects on the health and integrity of oral tissues like teeth, mucosa or muscles. There is growing evidence that a close interaction between the general medical condition and oral health exists. From a dental point of view, the chewing ability and capacity and its interaction with the nutritional status seem to be especially important. For example, complete denture wearers present a significant oral disability, which often leads to a gradual deterioration of their individual dietary habits. The improvement of maximum bite force and chewing efficiency may be an important prerequisite for an adequate nutrition. Those functional parameters can often be improved by providing functional dental prostheses or by stabilizing complete dentures with endosseous implants. Nevertheless, an improvement of the nutritional status can only be achieved through a close collaboration with dieticians or clinical nutritionists.

In Vitro Implant Impression Accuracy Using a New Photopolymerizing SDR Splinting Material.

PURPOSE: The study aims to evaluate three-dimensionally (3D) the accuracy of implant impressions using a new resin splinting material, "Smart Dentin Replacement" (SDR). MATERIALS AND METHODS: A titanium model of an edentulous mandible with six implant analogues was used as a master model and its dimensions measured with a coordinate measuring machine. Before the total 60 impressions were taken (open tray, screw-retained abutments, vinyl polysiloxane), they were divided in four groups: A (test): copings pick-up splinted with dental floss and fotopolymerizing SDR; B (test): see A, additionally sectioned and splinted again with SDR; C (control): copings pick-up splinted with dental floss and autopolymerizing Duralay® (Reliance Dental Mfg. Co., Alsip, IL, USA) acrylic resin; and D (control): see C, additionally sectioned and splinted again with Duralay. The impressions were measured directly with an optomechanical coordinate measuring machine and analyzed with a computer-aided design (CAD) geometric modeling software. The Wilcoxon matched-pair signed-rank test was used to compare groups. RESULTS: While there was no difference (p = .430) between the mean 3D deviations of the test groups A (17.5 µm) and B (17.4 µm), they both showed statistically significant differences (p < .003) compared with both control groups (C 25.0 µm, D 19.1 µm). CONCLUSIONS: Conventional impression techniques for edentulous jaws with multiple implants are highly accurate using the new fotopolymerizing splinting material SDR. Sectioning and rejoining of the SDR splinting had no impact on the impression accuracy.

Retrievability of implant-supported crowns when using three different cements: a controlled clinical trial.

PURPOSE: The purpose of this study was to analyze the removal of implant-supported crowns retained by three different cements using an air-accelerated crown remover and to evaluate the patients' response to the procedure. MATERIALS AND METHODS: This controlled clinical trial was conducted with 21 patients (10 women, 11 men; mean age: 51 ± 10.2 years) who had received a total of 74 implants (all placed in the posterior zone of the mandible). Four months after implant surgery, the crowns were cemented on standard titanium abutments of different heights. Three different cements (two temporary: Harvard TEMP and Improv; and one definitive: Durelon) were used and randomly assigned to the patients. Eight months later, one blinded investigator removed all crowns. The number of activations of the instrument (CORONAflex, KaVo) required for crown removal was recorded. The patients completed a questionnaire retrospectively to determine the impact of the procedure and to gauge their subjective perception. A linear regression model and descriptive statistics were used for data analysis. RESULTS: All crowns could be retrieved without any technical complications or damage. Both abutment height (P = .019) and cement type (P = .004) had a significant effect on the number of activations, but the type of cement was more important. An increased total number of activations had no or only a weak correlation to the patients' perception of concussion, noise, pain, and unwillingness to use the device. CONCLUSIONS: Cemented implant crowns can be removed, and the application of an air-accelerated device is a practicable method. A type of cement with appropriate retention force has to be selected. The impact on the patients' subjective perception should be taken into account.

CAD/CAM fabrication accuracy of long- vs. short-span implant-supported FDPs.

OBJECTIVE: To compare the precision of fit of long-span vs. short-span implant-supported screw-retained fixed dental prostheses (FDPs) made from computer-aided-design/computer-aided-manufactured (CAD/CAM) titanium and veneered with ceramic. The null hypothesis was that there is no difference in the vertical microgap between long-span and short-span FDPs. MATERIALS AND METHODS: CAD/CAM titanium frameworks for an implant-supported maxillary FDP on implants with a flat platform were fabricated on one single master cast. Group A consisted of six 10-unit FDPs connected to six implants (FDI positions 15, 13, 11, 21, 23, 25) and group B of six 5-unit FDPs (three implants, FDI positions 21, 23, 25). The CAD/CAM system from Biodenta Swiss AG (Berneck, Switzerland) was used for digitizing (laser scanner) the master cast and anatomical CAD of each framework separately. The frameworks were milled (CAM) from a titanium grade V monobloc and veneered with porcelain. Median vertical distance between implant and FDP platforms from the non-tightened implants (one-screw test on implant 25) was calculated from mesial, buccal, and distal scanning electron microscope measurements. RESULTS: All measurements showed values <40 µm. Total median vertical microgaps were 23 µm (range 2-38 µm) for group A and 7 µm (4-24 µm) for group B. The difference between the groups was statistically significant at implant 21 (P = 0.002; 97.5% CI -27.3 to -4.9) and insignificant at implant 23 (P = 0.093; -3.9 to 1.0). CONCLUSIONS: CAD/CAM fabrication including laboratory scanning and porcelain firing was highly precise and reproducible for all long- and short-span FDPs. While all FDPs showed clinically acceptable values, the short-span FDPs were statistically more precise at the 5-unit span distance.

Space requirement of a prefabricated bar on two interforaminal implants: a prospective clinical study.

OBJECTIVES: This clinical study measured the dimensional changes of existing lower complete dentures due to the integration of a prefabricated implant bar. Additionally, the impact of this dimensional change on patient satisfaction and oral function was analyzed. METHODS: Twenty edentulous patients (10 men/10 women; aged 65.9 ± 11.8 years) received two interforaminal implants. Subsequent to surgery, a chair side adapted, prefabricated bar (SFI Bar(®), C+M, Biel, Switzerland) was inserted, and the matrix was polymerized into the existing lower denture. The change of the denture's lingual dimension was recorded by means of a bicolored, silicone denture duplicate that was sectioned in the oro-vestibular direction in the regions of the symphysis (S) and the implants (I-left, I-right). On the sections, the dimensional increase was measured using a light microscope. Six months after bar insertion, patients answered a standardized questionnaire. RESULTS: All dentures exhibited increased lingual volume, more extensively at S than at I (P = 0.001). At S, the median diagonal size of the denture was doubled (+4.33 mm), and at I, the median increase was 50% (I-left/-right = +2.66/+2.62 mm). The original denture size influenced the volume increase (P = 0.024): smaller dentures led to a larger increase. The amount of denture increase did not have negative impact on either self-perceived oral function or patient satisfaction. Approximately, 95% of the patients were satisfied with the treatment results. CONCLUSIONS: The lingual size of a lower denture was enlarged by the integration of a prefabricated bar without any negative side effects. Thus, this attachment system is suitable to convert an existing full denture into an implant-supported overdenture.

Zirconia-Based Screw-Retained Prostheses Supported by Implants: A Retrospective Study on Technical Complications and Failures.

BACKGROUND: Little information is yet available on zirconia-based prostheses supported by implants. PURPOSE: To evaluate technical problems and failures of implant-supported zirconia-based prostheses with exclusive screw-retention. MATERIAL AND METHODS: Consecutive patients received screw-retained zirconia-based prostheses supported by implants and were followed over a time period of 5 years. The implant placement and prosthetic rehabilitation were performed in one clinical setting, and all patients participated in the maintenance program. The treatment comprised single crowns (SCs) and fixed dental prostheses (FDPs) of three to 12 units. Screw-retention of the CAD/CAM-fabricated SCs and FDPs was performed with direct connection at the implant level. The primary outcome was the complete failure of zirconia-based prostheses; outcome measures were fracture of the framework or extensive chipping resulting in the need for refabrication. A life table analysis was performed, the cumulative survival rate (CSR) calculated, and a Kaplan-Meier curve drawn. RESULTS: Two hundred and ninety-four implants supported 156 zirconia-based prostheses in 95 patients (52 men, 43 women, average age 59.1 ± 11.7 years). Sixty-five SCs and 91 FDPs were identified, comprising a total of 441 units. Fractures of the zirconia framework and extensive chipping resulted in refabrication of nine prostheses. Nearly all the prostheses (94.2%) remained in situ during the observation period. The 5-year CSR was 90.5%, and 41 prostheses (14 SCs, 27 FDPs) comprising 113 units survived for an observation time of more than 5 years. Six SCs exhibited screw loosening, and polishing of minor chipping was required for five prostheses. CONCLUSIONS: This study shows that zirconia-based implant-supported fixed prostheses exhibit satisfactory treatment outcomes and that screw-retention directly at the implant level is feasible.

In vitro precision of fit of computer-aided designed and computer-aided manufactured titanium screw-retained fixed dental prostheses before and after ceramic veneering.

OBJECTIVE: To compare the precision of fit of full-arch implant-supported screw-retained computer-aided designed and computer-aided manufactured (CAD/CAM) titanium-fixed dental prostheses (FDP) before and after veneering. The null-hypothesis was that there is no difference in vertical microgap values between pure titanium frameworks and FDPs after porcelain firing. MATERIALS AND METHODS: Five CAD/CAM titanium grade IV frameworks for a screw-retained 10-unit implant-supported reconstruction on six implants (FDI tooth positions 15, 13, 11, 21, 23, 25) were fabricated after digitizing the implant platforms and the cuspid-supporting framework resin pattern with a laser scanner (CARES(®) Scan CS2; Institut Straumann AG, Basel, Switzerland). A bonder, an opaquer, three layers of porcelain, and one layer of glaze were applied (Vita Titankeramik) and fired according to the manufacturer's preheating and fire cycle instructions at 400-800 °C. The one-screw test (implant 25 screw-retained) was applied before and after veneering of the FDPs to assess the vertical microgap between implant and framework platform with a scanning electron microscope. The mean microgap was calculated from interproximal and buccal values. Statistical comparison was performed with non-parametric tests. RESULTS: All vertical microgaps were clinically acceptable with values <90 µm. No statistically significant pairwise difference (P = 0.98) was observed between the relative effects of vertical microgap of unveneered (median 19 µm; 95% CI 13-35 µm) and veneered FDPs (20 µm; 13-31 µm), providing support for the null-hypothesis. Analysis within the groups showed significantly different values between the five implants of the FDPs before (P = 0.044) and after veneering (P = 0.020), while a monotonous trend of increasing values from implant 23 (closest position to screw-retained implant 25) to 15 (most distant implant) could not be observed (P = 0.169, P = 0.270). CONCLUSIONS: Full-arch CAD/CAM titanium screw-retained frameworks have a high accuracy. Porcelain firing procedure had no impact on the precision of fit of the final FDPs. All implant microgap measurements of each FDP showed clinically acceptable vertical misfit values before and after veneering. Thus, the results do not only show accurate performance of the milling and firing but show also a reproducible scanning and designing process.