Additive Manufacturing: A Comparative Analysis of Dimensional Accuracy and Skin Texture Reproduction of Auricular Prostheses Replicas.

PURPOSE: The use of computer-aided design/computer-aided manufacturing (CAD/CAM) and additive manufacturing in maxillofacial prosthetics has been widely acknowledged. Rapid prototyping can be considered for manufacturing of auricular prostheses. Therefore, so-called prostheses replicas can be fabricated by digital means. The objective of this study was to identify a superior additive manufacturing method to fabricate auricular prosthesis replicas (APRs) within a digital workflow. MATERIALS AND METHODS: Auricles of 23 healthy subjects (mean age of 37.8 years) were measured in vivo with respect to an anthropometrical protocol. Landmarks were volumized with fiducial balls for 3D scanning using a handheld structured light scanner. The 3D CAD dataset was postprocessed, and the same anthropometrical measurements were made in the CAD software with the digital lineal. Each CAD dataset was materialized using fused deposition modeling (FDM), selective laser sintering (SLS), and stereolithography (SL), constituting 53 APR samples. All distances between the landmarks were measured on the APRs. After the determination of the measurement error within the five data groups (in vivo, CAD, FDM, SLS, and SL), the mean values were compared using matched pairs method. To this, the in vivo and CAD dataset were set as references. Finally, the surface structure of the APRs was qualitatively evaluated with stereomicroscopy and profilometry to ascertain the level of skin detail reproduction. RESULTS: The anthropometrical approach showed drawbacks in measuring the protrusion of the ear's helix. The measurement error within all groups of measurements was calculated between 0.20 and 0.28 mm, implying a high reproducibility. The lowest mean differences of 53 produced APRs were found in FDM (0.43%) followed by SLS (0.54%) and SL (0.59%)--compared to in vivo, and again in FDM (0.20%) followed by SL (0.36%) and SLS (0.39%)--compared to CAD. None of these values exceed the threshold of clinical relevance (1.5%); however, the qualitative evaluation revealed slight shortcomings in skin reproduction for all methods: reproduction of skin details exceeding 0.192 mm in depth was feasible. CONCLUSION: FDM showed the superior dimensional accuracy and best skin surface reproduction. Moreover, digital acquisition and CAD postprocessing seem to play a more important role in the outcome than the additive manufacturing method used.

First clinical experiences with CAD/CAM-fabricated PMMA-based fixed dental prostheses as long-term temporaries.

OBJECTIVE: The clinical performance of polymethylmethacrylate (PMMA)-based fixed dental prostheses (FDP) was evaluated in the indication of long-term temporaries. MATERIALS AND METHODS: In the current indication of the applied machinable PMMA-based material (Vita CAD-Temp), i.e. temporary crowns and FDPs, 27 patients with compromised dentitions (uncertain dental prognosis or postponement of a removable treatment option) were recruited and 45 FDPs (3 or 4 units, 37 terminal-retained, 8 cantilevered) were inserted. Frameworks were computer-aided design (CAD)/computer-aided manufacturing (CAM)-manufactured after conventional impression taking and labside scanning of stone master casts. A resin-modified hybrid cement material (RelyX Unicem) was used for luting in a conventional protocol. Clinical follow-up was performed biannually. RESULTS: Over an observation time from 2 to 26 months (median 13 months), 11 complications were found in 9 out of 45 PMMA restorations: 4 losses of retention, 5 complete fractures; two of these subsequent to a trepanation for endodontic treatment. Thereby, 3 out of 8 cantilevered FDPs had to be removed within 8 months. Thus, the statistical evaluation included FDPs with abutment at end, only. These standard design FDPs (n = 37) showed a 90.4 % survival rate with a complication-free rate of 88.3 % estimated for an observation time of 16 months. CONCLUSION: Cantilevered FDPs and reconstructions on abutment teeth with markedly reduced biological prognosis or endodontic intervention yielded a high-failure rate. Terminal-retained FDPs performed clinically well in cases without compromised abutment teeth. CLINICAL RELEVANCE: PMMA-based material might be used successfully for long-term temporization with 3- to 4-unit FDPs in a standard design over at least one year.

The peri-implant health in patients attending an annual recall program. A clinical and microbiological study in 74 patients from the Tübingen Implant Registry.

OBJECTIVES: To describe the peri-implant condition of unselected implant recall patients, to relate it to relevant features from the patient medical history, and to look at associations across these findings. PATIENTS AND METHODS: Prior to their most recent recall appointment, 74 individuals underwent a clinical and microbiological (PCR) investigation. RESULTS: Signs of a serious peri-implantitis condition were not encountered in this patient cohort. However, a high prevalence of moderate plaque and bleeding on probing (60% and 78%, respectively) and PCR proof of periodonto-pathogenic bacteria (43% positive for one or more target species) was apparent. The mean pocket probing depth was 2.9 mm. The by far most prominent co-morbidity belonged to the group of patients with cardiovascular diseases (CVD; 27%). CVD were statistically significantly associated with the prevalence and concentration of Prevotella intermedia in the peri-implant sulcus (P = 0.022). Age was positively associated with plaque load (P < 0.001). The Tanerella forsythensis score and prevalence was higher in implants supporting fixed than removable restorations (P = 0.025). Four of the five bacteria species assessed showed a high association with each other (exception: Aggregatibacter actinomycetemcomitans), but not to other hygiene findings. CONCLUSIONS: A considerable number of individuals exhibited peri-implant findings that would require anti-infective treatment. Prevalence and concentrations of periodonto-pathogenic bacteria seemed to be associated with a variety of other variables from the patients' history, but not to clinical findings in this patient group.

Thirteen-year follow-up study of resin-bonded fixed partial dentures.

OBJECTIVE: The technique of resin-bonded fixed partial dentures (RBFPD) is a well-accepted clinical technique to replace missing teeth. The survival rates reported in the literature vary widely, and the conclusions are sometimes conflicting. This study presents the clinical long-term performance of silicoated RBFPDs and also determines the main cause of failure. METHOD AND MATERIALS: Sixty-one patients with a total of 74 RBFPDs were either examined or requested to complete a questionnaire regarding their fixed partial dentures. Sixty-four were placed in the anterior region, and 10 in the posterior region. No more than one missing tooth in the posterior area and two missing teeth in the anterior region were replaced with RBFPDs. A retentive preparation was made on the abutment teeth. All the RBFPDs were adhesively seated. RESULTS: Eighteen RBFPDs failed after a mean observation time of 7.8 years (nine retention losses of one or more retainers, six carious lesions, and three veneer fractures occurred). Seven RBFPDs were rebonded, whereas the remaining 11 failures had to be replaced with conventional FPDs. Fifty-six RBFPDs were primary restorations, and seven secondary RBFPDs were used after the loss of the primary restoration. A mean survival rate better than 69% after a 13-year observation period was calculated. Including the rebonded restorations, a mean functional survival rate of 83% was estimated. A total of 18 failures (24.3%) of all restorations were observed, the main cause being loss of retention. CONCLUSION: Silicoated RBFPDs are a viable treatment means with an acceptable success expectancy.

Assessing the reliability of a digital preparation assistant system used in dental education.

Use of a digital preparation assistant system may improve considerably the quality of preclinical dental education, provided the system works reliably. Thus, the purpose of this pilot study was to quantitatively assess the reliability of a new preclinical digital preparation assistant system (PREPassist, KaVo, Germany). The system was used to repeatedly scan four different unprepared and four different prepared teeth both with and without repositioning. Corresponding measurements were made to quantify accuracy, repeatability, and reproducibility. This was done by estimating the measurement error. Based on this estimation, respective limits of agreement were calculated. We used these ranges, along with assessments of the measurement's accuracy, to judge whether the results satisfy our expectations for clinically acceptable measurements. For preclinical laboratory instruction, the results indicate an acceptable accuracy (mean accuracy of 89 microm) of the measurements. This assessment applies as well to repeatability, given by the range of the respective limits of agreement (range <200 microm). However, in the case of reproducibility, the limits revealed discrepancies of practical importance (range >200 microm). Reproducibility of tooth repositioning in the available mounting device is unacceptable for preclinical laboratory instruction because of the observed range >200 microm. Thus, there is a need for the manufacture of new and more reliable mounting devices because reproducibility procedures are mostly encountered in preclinical instruction in restorative techniques. In contrast to reproducibility, accuracy and repeatability are acceptable for practical purposes. Balancing advantages and disadvantages, we conclude that, in general, the PREPassist system delivers reliable results.

Influence of implant geometry on primary insertion stability and simulated peri-implant bone loss: an in vitro study using resonance frequency analysis and damping capacity assessment.

PURPOSE: To investigate the influence of implant geometry on primary stability and on peri-implant bone loss in an in vitro model using the Periotest and Osstell devices. MATERIALS AND METHODS: Screw-type implants of various diameters and lengths were inserted into bovine bone blocks of different densities, and the primary insertion stability was recorded. To study the influence of implant geometry on implant stability with different levels of peri-implant bone loss, implants were inserted into acrylic resin blocks to mimic osseointegration, and different amounts of the peri-implant acrylic resin were removed. Measurements with both devices at each millimeter step yielded the threshold for the least detectable attachment loss. RESULTS: The predominant factors influencing implant stability were bone quality and attachment loss. Implant type and length exerted some influence on implant stability values, while variations in implant diameter produced only minor alterations in the measurements. In simulations of peri-implant attachment loss, implant stability decreased more dramatically for the shorter and narrower implants. The inclusion of more variables in the analyses resulted in less focused measurements. CONCLUSIONS: The results of this study clearly show that the outcome of implant stability assessment depends on environmental factors such as bone quality and implant geometry. While the authors do not recommend the use of the Periotest or Osstell devices for a comparison of the stability of two individual implants, both should be useful to monitor the state of an individual implant over time.

A comparison of implant-supported, bar- or ball-retained mandibular overdentures: a retrospective clinical, microbiologic, and immunologic study of 10 edentulous patients attending a recall visit.

PURPOSE: Clinical, microbiologic, and immunologic comparisons of the peri-implant health in edentulous volunteers wearing long-standing implant-supported ball- or Dolder bar-retained mandibular overdentures were performed. MATERIALS AND METHODS: Ten age- and gender-matched individuals (mean age, 71 years) with either ball- or bar-retained complete mandibular overdentures, scheduled for an annual implant recall examination, were investigated an average of 7 years after implant placement. Plaque and gingival crevicular fluid samples were obtained from the peri-implant sulcus. The groups were compared with regard to peri-implant probing depth; plaque and bleeding on probing scores; sulcular fluid flow rates; implant stability measurements (Periotest device); relative concentrations of Actinobacillus actinomycetemcomitans, Prevotella intermedia, Fusobacterium nucleatum, Porphyromonas gingivalis, Tannerella forsythensis, and Treponema denticola assessed by polymerase chain reaction analysis; and sulcular concentrations of interleukin-1beta and prostaglandin E2, assessed by enzyme-linked immunosorbent assay. RESULTS: No statistically significant differences were found for any of the examined parameters between both study groups. CONCLUSION: Within the limitations of this study, both ball attachments and Dolder bars can be recommended for overdenture retention, with either one showing satisfying clinical, microbiologic, and immunologic findings in the peri-implant tissues after several years of service in healthy recall patients with good oral hygiene habits.

Associations between peri-implant crevicular fluid volume, concentrations of crevicular inflammatory mediators, and composite IL-1A -889 and IL-1B +3954 genotype. A cross-sectional study on implant recall patients with and without clinical signs of peri-implantitis.

OBJECTIVES: To assess possible relationships between peri-implant crevicular fluid (PICF) volumes, biochemical markers of the peri-implant immune response, and periodontitis-associated genotype. MATERIAL AND METHODS: PICF samples from 29 implant maintenance patients, 24 wearing overdentures, five having single crowns and bridgework (11 patients with peri-implantitis and 18 individuals with healthy peri-implant conditions), were analyzed for per site and per crevicular-fluid-volume concentrations of interleukin-1beta, plasminogen activator inhibitor type 2, and prostaglandin E2 by ELISA. Associations between the three substance concentrations and to crevicular fluid flow rate were analyzed by linear regression analysis. The possible differentiating influence of the composite interleukin-1A and -1B genotype on the patients' peri-implant health and biochemical inflammatory status was checked formally with t-test statistics and the Wilcoxon' test. One implant per patient was chosen for analysis. RESULTS: In patients with healthy peri-implant conditions, genotype-positive individuals showed elevated crevicular fluid flow rates and at the same time reduced mediator concentrations. In patients with an implant affected from peri-implantitis, no statistically significant influence of the periodontitis-associated genotype around the fixture can be stated. There was no statistical difference between per site and per crevicular-fluid-volume concentration analyses. All three mediator concentrations were positively related to each other, while there was a strong negative correlation between crevicular fluid volume and plasminogen activator inhibitor 2 or prostaglandin E2. CONCLUSIONS: The Interleukin-1 polymorphism investigated exerted only little influence on the peri-implant crevicular immune response, and this influence appeared to be of limited impact in sites with established peri-implantitis lesions.

Reliability of findings around healthy implants in association with oral hygiene measures: a clinical, microbiological, and immunological follow-up in edentulous patients.

OBJECTIVES: To assess the performance of clinical, microbiological, and immunological diagnosis of peri-implant health and the influence of professional hygiene measures on them. MATERIAL AND METHODS: Twenty-one edentulous patients with oral implants supporting a lower overdenture were followed up over 3 months beginning 1 week before their annual recall visit. Hygiene scores, probing depth, bleeding on probing (BOP), implant stability, gingival crevicular fluid (GCF) volume, sulcular interleukin-1beta (IL-1beta) and prostaglandin E2 (PGE2) concentrations, and relative concentrations of five bacterial species (polymerase chain reaction) were investigated. Measurement variation was assessed as a function of (a) intra- and (b) inter-examiner reliability, (c) inter-implant variation in each patient, (d) time, and (e) effect of hygiene measures by accuracy, repeatability, reproducibility, and visualization with the Bland and Altman Plot. RESULTS: Measurement means and accuracy (in parentheses) were as follows: GCF volume 1.5 microl (1.5), Interleukin-1beta 8 ng/ml (26), PGE2 63 ng/ml (185), bacteria sum score 0.2 (0.7), plaque score 1 (1), BOP score 0 (1), Periotest value -4 (3), resonance frequency analysis ISQ 66 (11), and pocket probing depth 2.3 mm (0.7). No finding exhibited any statistically significant measurement variation as explained by accuracy, repeatability, or reproducibility. Bland and Altman Plots revealed insufficient agreement for replicated BOP assessments. A short post-treatment reduction in plaque and BOP scores was visually apparent. Still, professional oral hygiene measures exerted no sustained influence on the clinical and biochemical appearance of the peri-implant tissues. CONCLUSION: All findings except BOP showed statistically acceptable repeatability and moderate vulnerability to influences present 'chairside' in clinical practice.

Resonance frequency analysis and damping capacity assessment. Part I: an in vitro study on measurement reliability and a method of comparison in the determination of primary dental implant stability.

OBJECTIVES: The aims of this in vitro study were to evaluate reliability of the Osstell and Periotest devices in the assessment of implant stability and to perform a method comparison. MATERIAL AND METHODS: Commercial dental implants were inserted into bovine rib segments of different anatomical origins and densities. Repeated measurements were performed, varying (a) the torque-in force of the devices' attachment screw (the Osstell transducer and the ball attachment, insert for the Periotest device), (b) the insertion site bone quality, and (c) the thread exposure in simulated peri-implant bone defects. RESULTS: Both methods were comparably reliable and showed a strong association to each other in the classification of implant stability. As opposed to torque-forced screw attachment, the variations in bone composition, differences in inter-implant stability of adjacent implants, and peri-implant bone reduction were statistically significant for both methods. CONCLUSIONS: Both non-invasive diagnostic devices seem to be useful in the long-term follow-up of implant integration.

Resonance frequency analysis and damping capacity assessment. Part 2: peri-implant bone loss follow-up. An in vitro study with the Periotest and Osstell instruments.

OBJECTIVE: We compared the performance of damping capacity assessment (Periotest device) to resonance frequency analysis (Osstell device) in the assessment of peri-implant bone loss in an in vitro experiment. MATERIAL AND METHODS: Screw-type oral implants were polymerized into acrylic blocks. Peri-implant bone loss was simulated by successively removing defined portions of material surrounding the implants in millimeter increments. Measurement values of both devices were compared by assessing the associated measurement errors, by calculating correlation analyses and drawing scatterplots, and by means of regression analysis referring to increasing bone loss. RESULTS: Both devices produced comparable results suggesting agreement of the measured implant stability values to the actual loss of peri-implant resin. There was a noticeable correlation of the Periotest and Osstell implant stability values. CONCLUSION: The results of this experiment suggest agreement in predicting the actual implant stability with both the instruments with the Osstell instrument being the more precise device.

Radiographic study of changes in the mandibular condyle after implant prosthodontic rehabilitation.

PURPOSE: The aim of this follow-up investigation was to assess the influence of clinical variables after implant prosthodontic rehabilitation in patients without temporomandibular disorders on alterations of condylar morphology as seen radiographically. MATERIALS AND METHODS: In 167 patients, the condylar findings of flattening, erosion, osteophytes, and sclerosis were scored according to severity on rotational panoramic radiographs. Findings were followed up on images taken before and on average 5 years after implant prosthodontic rehabilitation. Changes were analyzed in relation to age, gender, initial radiologic status, and occlusal support pre- and posttreatment, according to Eichner groups, by logistic regression analysis. RESULTS: The majority of patients did not show structural alterations over the follow-up period, regardless of whether the condyle was already affected at the outset of the investigation. Condyles unaffected at the time of the first radiograph made up the majority of increases in radiographic score. Flattening and sclerosis were cumulative, whereas erosions and osteophytes had a more transient character. There was no influence of the mentioned clinical or radiographic findings on the development of changes. CONCLUSION: Over the investigated period, the incidence of all four noted findings doubled. However, the statistical methods employed could not detect any influence of patient variables or the insertion of implant-retained prosthodontics on the development of condylar changes in this specific patient group. Both assertions reflect the complexity of the topic.

Implant-supported laser-welded titanium and conventional cast frameworks in the partially edentulous law: a 5-year prospective multicenter study.

PURPOSE: This study evaluated and compared the clinical performance of laser-welded titanium fixed partial implant-supported prostheses with that of conventional cast frameworks in the partially edentulous jaw. MATERIALS AND METHODS: Forty-two patients provided with Brånemark system implants were arranged into two groups. Twenty-one patients (group A) were provided with a conventional cast ceramometal framework in one side of the jaw and a laser-welded titanium framework with low-fusing porcelain in the other side. In group B, 21 patients received a titanium framework prosthesis to replace a conventional implant prosthesis. Clinical and radiographic data were collected for 5 years. RESULTS: Four implants and one titanium framework were lost during the follow-up period. The two framework designs did not show any significant differences with regard to implant or prosthesis survival (P > .05). Few clinical complications were observed. In group A, marginal bone loss after 5 years was similar for both prosthesis designs, with an average of 0.1 mm and 0.3 mm in the maxilla and mandible, respectively. Basically, no bone loss was observed on average in group B. Furthermore, no significant relationship was observed between marginal bone loss and placement of prosthesis margin or prosthesis design. CONCLUSION: Except for an insignificant tendency toward a slightly higher incidence of small chips of porcelain veneers, laser-welded titanium frameworks presented an overall similar clinical performance as conventional cast frameworks in partial implant situations after 5 years.