Multicenter Prospective Clinical Study on Chairside-Fabricated Partial Crowns: 5-Year Results for Lithia-Zirconia Glass-Ceramic Restorations.

OBJECTIVES: Clinical evaluation of chairside-fabricated lithia-zirconia glass-ceramic (LZGC) partial crowns (CCPCs) in a multicenter practice-based study. MATERIALS AND METHODS: Seventy-one patients were restored with 92 adhesively luted CCPCs (Cerec SW 4.2/Cerec MC XL/Celtra Duo) in three private dental clinics (C1-C3). Time-dependent (Kaplan-Meier) survival rates (SVR) and success rates (SCR) were calculated. The following possible covariates of SVRs and SCRs were evaluated in a Cox regression model: Restoration position (premolar/molar), luting material (Variolink/Calibra), and operator (C1-C3). RESULTS: Seventy-three CCPCs were placed in 59 patients and were included in the study (mean observational period: 58.0 ± 15 months). Four complete failures (two tooth fractures, one restoration fracture, and one endodontic failure) were recorded. All failures and interventions occurred in one of the three centers (5-year SCR: C1 + C2: 100%; C3: 71%; 95% confidence interval: [0.55; 0.87]). Additionally, three biological, and two technical complications required clinical intervention to maintain function, and all occurred in C3. Restorations placed in C1 and C2 showed a significantly reduced risk for failure/intervention (hazard ratio = 0.103, p = 0.026) compared with restorations placed in C3. CONCLUSIONS: LZGC CCPCs showed good five-year clinical performance. However, SVRs and SCRs were significantly influenced by the operator. Additional clinical data are required for a more detailed investigation of this effect.

Clinical evaluation of chairside-fabricated partial crowns composed of zirconia-reinforced lithium silicate ceramics: 3-year results of a prospective practice-based study.

OBJECTIVES: Prospective practice-based clinical evaluation of chairside fabricated monolithic partial crowns composed of zirconia-containing lithium silicate (ZLS) ceramic material. MATERIALS AND METHODS: Between October 2013 and September 2014, 71 patients were restored with 92 partial crowns on vital or sufficiently endodontically treated teeth. The monolithic restorations were fabricated chairside (Cerec SW 4.2/Cerec MC XL) from a glaze-fired ZLS ceramic material (Celtra Duo, Dentsply Sirona, Bensheim, Germany). Adhesive cementation was performed using the total-etch technique with one of two dual-curing composite materials. Modified United States Public Health Service parameters were evaluated annually; moreover, the parameters "time-dependent survival" (in situ criterion) and "success rates" (event-free restorations) were evaluated according to Kaplan-Meier analysis. RESULTS: Sixty-nine patients with 17 premolar and 71 molar partial crowns attended annual follow-up examinations (observational period: 36.0 ± 5.7 months). Two complete failures were recorded and were caused by a tooth fracture (at 30 months) and a restoration fracture (at 38 months), (3-year survival rate: 99%; 95% confidence interval (CI 95%): [0.97;1]). One clinical intervention was necessary (endodontic treatment) to maintain function (3-year success rate: 98%; (CI95%: [0.95:1]). CONCLUSIONS: Chairside-fabricated ZLS partial crowns show a good initial clinical performance. However, to further evaluate this new material, clinical data from studies with longer observational periods are required. CLINICAL SIGNIFICANCE: Based on this mid-term evaluation, ZLS ceramics appear to be a promising alternative material for the chairside fabrication of adhesively luted monolithic posterior restorations with a low risk of material-related complications.

Technical and biological complications of single-molar implant restorations.

OBJECTIVES: Retrospective evaluation of the biological and technical complications in implant-supported single-tooth molar restorations performed in a private practice after functional periods of ≥4 years. MATERIAL AND METHODS: Sixty-five patients (34 females, age 51.7 ± 10.6 years) with 112 implants received annual follow-up examinations and participated in a maintenance program. The survival (in situ) and success (complication-free) rates of implants and superstructures were evaluated. Time-dependent peri-implantitis rates were calculated, and the influencing factors were identified using a multiple Cox regression. RESULTS: The implant survival rate was 100%. Three of 112 crowns required replacement (prosthetic survival rate = 98.1%). Thirty technical complications were observed: loss of retention (16), ceramic fracture (10), and screw loosening (4). The success rate of the superstructures was 79.0% after 7 years. Overall, 9.2% of the patients developed peri-implantitis (probing depth ≥5 mm, BOP, suppuration, bone loss ≥3.5 mm); (smokers: 41.6%, non-smokers: 1.8%). After 7 years, the time-dependent implant success rate (free of peri-implantitis) was 100% for non-smokers and 58.6% for smokers. Multiple analysis showed a significant effect of smoking (hazard ratio, 19.5; P = 0.008) on peri-implantitis. CONCLUSIONS: Implants with cemented single-tooth restorations in the molar region constitute a reliable treatment in private practice. Smokers have a significantly increased peri-implantitis rate.

Risk factors for technical and biological complications with zirconia single crowns.

OBJECTIVES: This practice-based study evaluated the clinical performance and risk factors for biological and technical complications with conventionally luted zirconia crowns. MATERIALS AND METHODS: Sixty-eight patients (39 female) with a total of 323 restorations placed on 219 vital teeth, 69 endodontically treated teeth (ETT), and 41 implants (incisors, 96; premolars, 89; molars, 138; observational period, 79.7 ± 14.2 months) underwent a clinical follow-up examination and were included in the study. Time-dependent survival (in situ), success (event free), and veneering ceramic fracture (VCF) rates were calculated and analyzed relative to the following risk factors: smoking status, location of the crown, and type of abutment. RESULTS: Fifty-three complete failures were recorded. A significant influence of the abutment type on survival could be detected (p = 0.033): ETT demonstrated a significantly (p = 0.029) lower 7-year survival rate (73.8%, 95% confidence interval [95% CI] 0.600-0.876) than crowns placed on implants (90.0%, 95% CI 0.814-0.990). The success rate of the crowns was significantly influenced by the location of the restoration (p = 0.0058). A total of 75.6% (95% CI 0.648-0.864) of the anterior crowns remained event free, compared to 50.4% (95% CI 0.388-0.621) of the molar crowns. Furthermore, the location of the crowns affected the VCF rate (p = 0.018, event-free anterior teeth 95.2% (95% CI 0.880-1), event-free molars 80.9% (95% CI 0.706-0.913)). CONCLUSIONS: Survival and success rates were significantly influenced by the type of abutment and the location of the restoration. CLINICAL RELEVANCE: More complete failures should be expected for crowns placed on ETT, while crowns on molars demonstrated more biological and technical complications than anterior zirconia crowns.

Clinical outcome of double crown-retained implant overdentures with zirconia primary crowns.

PURPOSE: This retrospective study aims at the evaluation of implant-supported overdentures (IODs) supported by ceramo-galvanic double crowns (CGDCs: zirconia primary crowns + galvano-formed secondary crown). MATERIALS AND METHODS: In a private practice, 14 patients were restored with 18 IODs (mandible: 11, maxilla: 7) retained by CGDCs on 4 - 8 implants and annually evaluated for technical and/or biological failures/complications. RESULTS: One of the 86 inserted implants failed during the healing period (cumulative survival rate (CSR) implants: 98.8%). During the prosthetic functional period (mean: 5.9 ± 2.2 years), 1 implant demonstrated an abutment fracture (CSR-abutments: 98.2%), and one case of peri-implantitis was detected. All IODs remained in function (CSR-denture: 100%). A total of 15 technical complications required interventions to maintain function (technical complication rate: 0.178 treatments/patients/year). CONCLUSION: Considering the small sample size, the use of CGDCs for the attachment of IODs is possible without an increased risk of technical complications. However, for a final evaluation, results from a larger cohort are required.

Implant-supported overdentures with different bar designs: A retrospective evaluation after 5-19 years of clinical function.

PURPOSE: This retrospective study evaluated the outcome of implant-retained overdentures (IODs) after 5-19 years of clinical function. MATERIALS AND METHODS: A retrospective analysis of patient files was performed referring to 27 patients who received 36 IODs with 3 different bar designs (group A=prefabricated round bars, n=7; group B=one-piece anterior milled bars, n=20; and group C=two bilaterally placed milled bars, n=9) in the mandible (n=24) and/or in the maxilla (n=12). The analysis focused on the survival and success rates (according to Kaplan-Meier) of the implants and prostheses. Technical complication rates for each type of restoration were analyzed and compared via one-way ANOVA and the Chi-squared test. The prevalence of peri-implantitis (radiographic bone loss ≥3.5 mm) was evaluated by digital analysis of panoramic radiographs taken post-operative (baseline) and after 5-19 years of clinical function (follow-up). RESULTS: The mean observational time was 7.3 years. The survival rates of the prostheses and implants were 100% and 97.7%, respectively. Technical complications occurred more frequently in group A (mean: 3.5 during observational time) than in the other two groups (B: 0.8; C: 1.0). However, this difference was not statistically significant (P=0.58). Peri-implantitis was diagnosed for 12.4% of the implants in 37% of the patients. CONCLUSION: Bar-retained IODs are an adequate treatment option for edentulous jaws. These restorations may exhibit high implant/prosthesis survival rates (>97%), and a limited incidence of technical complications after a mean observational period of >7 years. Nevertheless, peri-implantitis was identified as a frequent and serious biological complication for this type of reconstruction.

Prospective evaluation of zirconia posterior fixed partial dentures: 7-year clinical results.

PURPOSE: The clinical performance of three- and four-unit fixed partial dentures (FPDs) with frameworks made of yttria partially stabilized zirconia was determined after a mean observational period of 84 months. MATERIALS AND METHODS: Seventy-five patients were treated with 99 posterior FPDs. Fifty-one specimens were veneered with an experimental ceramic suitable for titanium and zirconia frameworks; 48 restorations were veneered with a commercially available low-fusing ceramic optimized for zirconia frameworks. All restorations were luted with zinc-phosphate cement. Statistical analysis was performed according to Kaplan-Meier; potential risk factors were analyzed using the Cox regression analysis. RESULTS: Nineteen restorations failed completely: 12 due to technical complications, 6 due to biologic complications, and 1 for unknown reasons. The overall survival rate after 84 months was 83.4%. Thirty-two events required clinical intervention for restoration maintenance, resulting in a time-dependent success rate of 57.9% after 84 months. Nineteen dropouts occurred during the follow-up time. None of the evaluated factors showed an association with survival or success of the restorations. CONCLUSIONS: After a mean observational period of 7 years, the survival and success rates of zirconia-based posterior FPDs were inferior to those published for metal-ceramic FPDs. The majority of failures were caused by technical complications (material fractures). The main reasons for clinical intervention to maintain function were fractures of the veneering ceramic and decementations.

Multifactorial analysis of the impact of different manufacturing processes on the marginal fit of zirconia copings.

This study evaluated the effect of different parameters on the marginal precision of CAD/CAM-fabricated zirconia copings. Specimens(n=60) were fabricated with two different scanners and two milling systems. The copings were evaluated with respect to their mean and average maximum marginal gaps. A two-way analysis of variance (ANOVA) (α=0.05) was used to evaluate the effect of different parameters (scanner, milling process) on marginal accuracy. The mean (averaged maximum) marginal gaps ranged from 57.9 (112.2 µm) to 71.0 (144.6 µm) in the "as machined" state. After manual adaptation, the respective values ranged from 54.6 (98.0 µm) to 59.9(107.7 µm). The system and manual adaptation variables were found both to have multiple significant effects on the marginal gap size and to have a complex interaction. Thus, synchronized/validated processing chains should be preferentially used to guarantee optimal fitting accuracy for CAD/CAM zirconia restorations.

An 18-year retrospective evaluation of glass-infiltrated alumina crowns.

OBJECTIVE: To evaluate the long-term performance of conventionally luted In-Ceram crowns with a maximum follow-up period of 18.6 years. METHOD AND MATERIALS: Eighty patients (39 females and 41 males) were treated at the University of Göttingen with a total of 272 In-Ceram restorations (163 anterior and 109 posterior). All participated in a clinical follow-up examination (mean observational period, 13.5 ± 3.6 years). Time-dependent crown survival (in situ criteria) and success rates (event-free restorations) were calculated according to Kaplan-Meier and analyzed in relation to the crown position (anterior vs posterior crowns) using a Cox regression model. RESULTS: Forty-three complete failures (overall survival, 80.5%) were recorded; 73.4% remained event-free after 15 years. Of the 163 anterior restorations, 18 crowns failed (9 fractures and 9 biologic reasons), resulting in a survival rate of 87.5% after 15 years (success rate, 82.7%). The remaining complete failures (10 fractures, 8 biologic reasons, and 7 changes of treatment plan) were recorded for posterior crowns (survival rate, 68.3%; success rate, 56.9%). Cox regression revealed a significant difference in survival (P = .00523) and success rates (P = .000297) of anterior and posterior crowns. CONCLUSION: The survival and success rates of anterior In-Ceram crowns at 15 years are comparable to those published for metal-ceramic crowns. Significantly lower survival rates and an increased rate of complications should be expected if In-Ceram crowns are placed on premolars and molars. Chipping of the veneering material was the most frequent technical complication in the posterior area.

Tissue distribution of the laminin beta1 and beta2 chain during embryonic and fetal human development.

Laminins are the major glycoproteins present in all basement membranes. Previously, we showed that perlecan is present during human development. Although an overview of mRNA-expression of the laminin beta1 and beta2 chains in various developing fetal organs is already available, a systematic localization of the laminin beta1 and beta2 chains on the protein level during embryonic and fetal human development is missing. Therefore, we studied the immunohistochemical expression and tissue distribution of the laminin beta1 and beta2 chains in various developing embryonic and fetal human organs between gestational weeks 8 and 12. The laminin beta1 chain was ubiquitously expressed in the basement membrane zones of the brain, ganglia, blood vessels, liver, kidney, skin, pancreas, intestine, heart and skeletal system. Furthermore, the laminin beta2 chain was present in the basement membrane zones of the brain, ganglia, skin, heart and skeletal system. The findings of this study support and expand upon the theory that these two laminin chains are important during human development.

Prospective evaluation of zirconia posterior fixed partial dentures: four-year clinical results.

PURPOSE: In this prospective clinical study, the performance of three- and four-unit fixed partial dentures (FPDs) with frameworks fabricated of yttria partially stabilized zirconia was determined after a mean observation period of 50 months. The study focused on the survival of the restoration (in situ criterion) and the success of the ceramic veneers (no defect). MATERIALS AND METHODS: Seventy-five patients with a maximum of two missing teeth and an antagonistic dentition were treated at the Department of Prosthodontics, University of Goettigen, with 99 posterior FPDs. Fifty-one specimens (experimental group) were veneered with an experimental ceramic suitable for titanium and zirconia frameworks (thermal expansion coefficient [TEC]: 8.5 microm/m*K); 48 restorations (Ceram-S group) were veneered with a commercially available low-fusing ceramic optimized for zirconia frameworks (TEC: 9.5 microm/m*K). All restorations were luted with zinc-phosphate cement. Statistical analysis was performed according to the Kaplan-Meier method; time-dependent success rates of the different types of ceramic veneers were analyzed using the log-rank test. RESULTS: Seven restorations were lost: 4 due to technical complications and 3 due to biologic complications. The overall survival rate after 48 months was 94% (Kaplan-Meier analysis). Twenty-three events required clinical intervention for restoration maintenance: 13 ceramic veneer chippings (polishing), 6 losses of retention (recementation), 3 caries lesions (filling therapy), and 1 loss of vitality (endodontic treatment). Between the two groups of veneering materials, no significant difference in the probability for success was determined (log-rank test, P=.81). CONCLUSIONS: Within a mean observation period of 4 years, sufficient survival rates for zirconia-based posterior FPDs could be verified. The main complications included fracture of the ceramic veneering material and decementation, which occurred mainly in the mandible.

Tissue distribution of perlecan domains III and V during embryonic and fetal human development.

A major component of basement membranes (BMs) is perlecan, a five-domain heparan sulphate proteoglycan. During murine embryogenesis, nearly all BMs of mesenchymal origin express perlecan, and it is believed to participate in the supramolecular assembly of BMs. However, the distribution of perlecan in human embryonic and fetal tissues is widely unknown, except for cartilage anlagen of developing extremities and the fetal spine. Clinical syndromes, caused by perlecan-associated mutations or gene-defects, suggest its multifunctional involvement during human development. Here we reveal the immunohistochemistry of perlecan domains III and V during human development from gestational weeks (gw) 6 to 12 in basement membrane zones (BMZs) of the developing brain, nervous system, blood vessels, skin, lung, heart, kidney, liver, intestine and skeletal system. Interestingly, a difference in the distribution of the two perlecan domains was found in the endoneurium of ganglia. Domain III is strongly present from gw 6 onwards, while domain V shows attenuated expression at this stage and has been detected abundantly only from gw 8 onwards, possibly indicating vascularization of the endoneurium during this early stage. We found perlecan to be present particularly at those stages of human development where epithelial-mesenchymal interactions occur.