Time of day-dependent deviations in dynamic and static occlusion: A prospective clinical study.

STATEMENT OF PROBLEM: The registration of dental occlusion is essential for prosthodontic treatment. However, studies on time-dependent changes of static and dynamic occlusion that may affect definitive restorations are lacking. PURPOSE: The purpose of this prospective clinical study was to use conventional and digital occlusal registration techniques to evaluate time-dependent fluctuations in static and dynamic occlusion. MATERIAL AND METHODS: The static and dynamic occlusion of 19 healthy individuals (14 women and 5 men with a mean ±standard deviation age of 30.8 ±4.8 years) was examined 3 times a day using occlusal foil (12-µm occlusion foil) and a digital sensor (T-Scan III). The procedure was repeated after 14 days. The statistical analysis covered all registrations referencing the first measurement point to assess occurring differences, and changes per tooth and arch were determined (α=.05). Potential influencing factors were calculated by using mixed logistic regression. Marginal probabilities were calculated considering the registration technique and the time of measurement. RESULTS: Significant differences were found between registered occlusal patterns and the different registration techniques. Occlusal changes per maxillary dental arch were observed with static foil registration (P<.001; 98.8%), left laterotrusion foil registration (P=.001; 29.6%), right laterotrusion foil registration (P=.001; 29.6%), static sensor registration (P<.001; 20.3%), left laterotrusion sensor registration (P=.001; 71.7%), and right laterotrusion sensor registration (P=.005; 67.7%). None of the techniques showed higher probabilities of occlusal changes at a given time of day with respect to time-dependent changes. CONCLUSIONS: The study revealed that occlusion cannot be considered constant and that the topography and intensity of the contact points vary. Circadian occlusion variance can be assumed without preferring a specific time of the day. This differentiated view of occlusion as a changing system helps to clarify the challenge of dental restorations for both the patient and the practitioner.

Cytotoxicity of 3D-printed, milled, and conventional oral splint resins to L929 cells and human gingival fibroblasts.

OBJECTIVES: Evidence on the biocompatibility of three-dimensional (3D)-printed and milled resins for oral splints is limited. This in vitro study assessed the influence of the manufacturing method on the cytotoxicity of oral splint resins on L929 cells and human gingival fibroblasts (GF1). MATERIALS AND METHODS: Standardized specimens of four 3D-printed, two-milled, one-thermoformed, and one-pressed splint resin were incubated with L929 and GF1 cells for 24 h. Immunofluorescence and WST-8 assay were performed to evaluate cytotoxic effects. One-way analysis of variance and Tukey's multiple comparison test were applied with the variables "splint resin" and "manufacturing method" (p < .05). RESULTS: Immunofluorescence showed attachment of L929 and GF1 cells to the splint resins. Irrespective of the manufacturing method, the WST-8 assay revealed significant differences between splint resins for the viability of L929 and GF1 cells. L929 cells generally showed lower viability rates than GF1 cells. The evaluation of cell viability by the manufacturing method showed no significant differences between 3D printing, milling, and conventional methods. CONCLUSIONS: The cytotoxic effects of 3D-printed, milled, and conventional oral splint resins were similar, indicating minor influence of the manufacturing method on biocompatibility. Cytotoxicity of the resins was below a critical threshold in GF1 cells. The chemical composition might be more crucial than the manufacturing method for the biocompatibility of splint resins.

Retrospective evaluation of extended glass-ceramic ceramic laminate veneers after a mean observational period of 10 years.

PURPOSE: A retrospective evaluation of extended anterior ceramic laminate veneers (EACVs) after a mean observational period of 10 years. METHODS: Thirty-one patients (20 females/11 males) underwent restoration with 101 adhesively luted, heat-pressed EACVs (maxilla, n = 65; mandible, n = 36). RESULTS: The 10 year survival rate was 91.8% (95% confidence interval [95%-CI]: 0.87;0.97). Eight ceramic fractures, one biological failure, and one change in treatment plan caused the observed failures. Seventy-seven of the 101 restorations remained intervention-free in service (success rate: 78.6% [95%-CI: 0.70;0.88]). Fourteen interventions were needed (nine recementations, two endodontic treatments, two composite fillings, and one fracture polishing). The jaw position (maxilla/mandible, survival P = .578/success P = .056) had no influence on the clinical performance. EACVs covering large areas of exposed dentin (>50%) were associated with a significantly increased risk (hazard ratio 2.98, P = .019) of needing a clinical intervention (success rate: 68.0% [95%-CI: 0.52; 0.84]). However, the degree of dentin exposure had no effect on the survival rate (P = .761). CONCLUSIONS: After a mean observational period of 10 years, mandibular and maxillary EACVs exhibited survival and success rates that were comparable. Significantly lower success rates were associated with large areas of exposed dentin (>50%). CLINICAL SIGNIFICANCE: Mandibular and maxillary EACV revealed 10-year survival rates comparable to those published for anterior metal-ceramic and glass-ceramic full-coverage crowns. Precaution should be taken not to expose dentin, and when large areas of dentin are exposed, different conditioning/luting strategies should be used.

Overdentures borne on less than four abutments with telescopic crowns: 5-year results of a retrospective clinical study.

OBJECTIVE: Retrospective evaluation of the clinical performance of tooth-supported overdentures retained by resilient telescopic crowns with occlusal clearance fit (ODRTC) in severely reduced dentition (1-3 remaining teeth). MATERIALS AND METHODS: A total of 313 ODRTCs were inserted in an undergraduate prosthodontic program (University Medical Center, Goettingen, Germany) between 2000 und 2012. Data regarding 263 ODRTCs in 221 patients were reevaluated (observational period: 64.5 ± 34.8 months), and time-dependent survival and success rates (Kaplan-Meier-Estimator) were calculated. The number of the abutment teeth was analyzed as an influencing factor (Cox regression model (p < 0.05)). RESULTS: The 5- and 8-year overdenture survival rates were 62% [CI: 0.55; 0.69] and 38% [CI: 0.30; 0.45]. The 5- and 8-year success-rates (biologically and technically event-free restorations) were 13% [CI: 0.09; 0.17] and 3% [CI: 0.01; 0.05]. On the abutment level, the 5- and 8-year survival rates were 55% [CI: 0.48; 0.62], and 34% [CI: 0.27; 0.42]. The number of abutment teeth significantly influenced the overdenture and abutment survival rates. Restorations with 1 or 2 abutments were significantly associated with an increased number of technical and biological complications (decementation of the primary crown, abutment fracture) compared to ODRTCs with 3 abutments. CONCLUSIONS: The survival and success rates of ODRTCs are significantly influenced by the number of abutments. CLINICAL RELEVANCE: For ODRTCs, reduced survival and success rates are expected, especially when only 1 or 2 abutment teeth are included.

Removal forces of adhesively and self-adhesively luted implant-supported zirconia copings depend on abutment geometry.

This in vitro study evaluated the effects of different abutment axial heights on the retentiveness of adhesively and self-adhesively luted zirconia copings. Ankylos implants were embedded in resin blocks. Two groups of titanium abutments ("long", height: 6.79 mm, taper: 4.8°; "short", height: 4.31 mm, taper: 4.8°; Compartis-ISUS, DeguDent) were used for the luting of CAD/CAM-fabricated zirconia copings (Compartis, DeguDent) with an adhesive (Multilink Automix; Ivoclar Vivadent) and a self-adhesive (RelyX Unicem; 3M ESPE) composite. After water storage and 5000 thermocycles (5 °C/55 °C), retention forces were evaluated using a universal testing machine (Zwick). Significant differences were determined via two-way ANOVA and t-tests with Bonferroni-Holm correction. Significant interactions between abutment geometry and luting agents were observed. RelyX Unicem showed the highest levels of retentiveness, irrespective of the varying abutment geometries (mean values long/short: 487.7 N/447.9 N). When Multilink Automix was used, removal forces were significantly lower (311.7 N/101.1 N) and negatively affected by the use of the shorter abutments. Customized long abutments supported better retention forces than customized short abutments for both luting agents.

Influence of Material Selection on the Marginal Accuracy of CAD/CAM-Fabricated Metal- and All-Ceramic Single Crown Copings.

This study evaluated the marginal accuracy of CAD/CAM-fabricated crown copings from four different materials within the same processing route. Twenty stone replicas of a metallic master die (prepared upper premolar) were scanned and divided into two groups. Group 1 (n = 10) was used for a pilot test to determine the design parameters for best marginal accuracy. Group 2 (n = 10) was used to fabricate 10 specimens from the following materials with one identical CAD/CAM system (GAMMA 202, Wissner GmbH, Goettingen, Germany): A = commercially pure (cp) titanium, B = cobalt-chromium alloy, C = yttria-stabilized zirconia (YSZ), and D = leucite-reinforced glass-ceramics. Copings from group 2 were evaluated for the mean marginal gap size (MeanMG) and average maximum marginal gap size (AMaxMG) with a light microscope in the "as-machined" state. The effect of the material on the marginal accuracy was analyzed by multiple pairwise comparisons (Mann-Whitney, U-test, α = 0.05, adjusted by Bonferroni-Holmes method). MeanMG values were as follows: A: 46.92 ± 23.12 µm, B: 48.37 ± 29.72 µm, C: 68.25 ± 28.54 µm, and D: 58.73 ± 21.15 µm. The differences in the MeanMG values proved to be significant for groups A/C (p = 0.0024), A/D (p = 0.008), and B/C (p = 0.0332). AMaxMG values (A: 91.54 ± 23.39 µm, B: 96.86 ± 24.19 µm, C: 120.66 ± 32.75 µm, and D: 100.22 ± 10.83 µm) revealed no significant differences. The material had a significant impact on the marginal accuracy of CAD/CAM-fabricated copings.

Retrospective evaluation of extended heat-pressed ceramic veneers after a mean observational period of 7 years.

OBJECTIVES: Retrospective evaluation of extended anterior glass-ceramic veneers 7 years after placement in a private practice. MATERIALS AND METHODS: A total of 31 patients (20 females/11 males) underwent restoration with adhesively luted extended veneers that were fabricated using heat-pressed glass-ceramic (Cergo, Dentsply Sirona). A single dentist restored 101 teeth (maxilla, n = 65; mandible, n = 36). Adhesive cementation was performed using an etch-and-rinse adhesive (OptibondFL, Kerr Corporation), and two different dual-curing composite cements (Variolink, Ivoclar Vivadent/Calibra, Dentsply Sirona). RESULTS: After 7 years, the Kaplan-Meier survival rate (in situ criteria) was 93.6% (95% CI: 0.89; 0.98). The observed failures were caused by ceramic fractures for seven restorations and biological failure for one restoration. In total 80 of the 101 restorations were still in service and did not require any clinical intervention (7-year success rate: 84.3% [95% CI]: 0.76; 0.93). Interventions were necessary in 13 cases (8 recementations, 2 endodontic treatments, 2 composite fillings (caries), and 1 polishing of minor fractures). The clinical performance was not influenced by the veneer position (maxilla/mandible, survival P = .56/success P = .30). The veneers that covered large areas of exposed dentin (>50%) exhibited a significantly increased risk (hazard ratio 3.71, P = .0041) for requiring a clinical intervention; however, no effect on the survival rate was observed for these veneers (P = .35). CONCLUSIONS: Following 7 years of clinical service, extended anterior ceramic veneer restorations exhibited comparable survival and success rates for the upper and lower jaw. Large areas of exposed dentin (>50%) were associated with significantly lower success rates. CLINICAL SIGNIFICANCE: Dentin exposure (more than 50% of the preparation surface) during preparation significantly affects the clinical performance of extended heat-pressed glass-ceramic veneers.

Prospective Evaluation of Posterior Fixed Zirconia Dental Prostheses: 10-Year Clinical Results.

PURPOSE: To investigate the clinical survival and success rates of conventionally luted three- and four-unit fixed dental prostheses (FDPs) with zirconia frameworks (Cercon Smart Ceramics, DeguDent) after a mean observation period of 119 ± 36 months. MATERIALS AND METHODS: A total of 75 patients were treated in the Department of Prosthodontics at the University of Goettingen, Germany, and a total of 99 posterior FDPs were inserted and luted with zinc phosphate cement. Time-dependent survival and success rates were calculated using Kaplan-Meier curves, and their relationships with the type of veneer (ceramic), location (maxilla vs mandible), and span length (three-unit vs four-unit) were analyzed with a Cox regression model (P < .05). RESULTS: Of the 99 inserted FDPs, 24 were lost to follow-up, 51 remained functional and passed the 10-year examination (overall survival rate: 75.0%; 95% confidence interval [CI]: 0.64, 0.85), and 13 were absolute failures caused by technical events (technical survival rate: 84%; 95% CI: 0.64, 0.85). In 50 FDPs, relative failure required a clinical intervention to maintain function (overall success rate: 40%; 95% CI: 0.29, 0.52). For 35 of these FDPs, the relative failure was caused by technical events (technical success rate: 61%; 95% CI: 0.49, 0.73). None of the evaluated factors showed an association with overall or technical survival or success. CONCLUSION: Zirconia-based posterior FDPs produced with a first-generation computer-assisted manufacturing (CAM) system revealed high rates of absolute and relative failure, mainly due to technical events, after a mean observational period of 10 years. Further clinical studies with updated computer-assisted design (CAD)/CAM systems are needed to determine the long-term performance of zirconia-based FDPs.

Fitting accuracy of zirconia single crowns produced via digital and conventional impressions-a clinical comparative study.

OBJECTIVES: This study focused on the clinical investigation of the internal and marginal fit of CAD/CAM-fabricated zirconia single crowns produced via conventional and digital impression techniques. MATERIALS AND METHODS: In a private practice, 20 molar teeth, one from each of 20 patients, were prepared with a circumferential 1.0-mm deep chamfer and an occlusal reduction of 1.5 mm. Conventional impression (CI) taking with a polyvinylsiloxane material (Aquasil Monophase + Aquasil XLV; Dentsply, Konstanz, Germany) and intraoral scanning (IS) (Cara TRIOS; Heraeus, Hanau, Germany) of each of the preparations was performed, and then two respective zirconia copings per tooth were produced (20 crowns per group). The marginal and internal fit of the restorations was evaluated employing a replica technique. For statistical analysis, a pairwise comparison (Wilcoxon rank test) was performed. RESULTS: Zirconia single crowns produced with the IS technique revealed a statistically significant better precision of internal fit only in specific areas (chamfer area/occlusal area). The evaluation of marginal fit showed no significant differences between the two groups. All restorations of both groups offered internal and marginal gaps within the postulated clinical tolerance ranges. CONCLUSIONS: CAD/CAM-fabricated zirconia single crowns produced with CI and IS techniques offer adequate marginal and internal precision. However, the IS technique provides lower internal gaps in some specific areas. CLINICAL RELEVANCE: The clinical precision of fit of restorations produced with a CI and an IS technique appeared to be equivalent. Therefore, the IS technique can be rated as a suitable alternative for the manufacturing of single crowns.

Chairside Fabrication of an All-Ceramic Partial Crown Using a Zirconia-Reinforced Lithium Silicate Ceramic.

The chairside fabrication of a monolithic partial crown using a zirconia-reinforced lithium silicate (ZLS) ceramic is described. The fully digitized model-free workflow in a dental practice is possible due to the use of a powder-free intraoral scanner and the computer-aided design/computer-assisted manufacturing (CAD/CAM) of the restorations. The innovative ZLS material offers a singular combination of fracture strength (>370 Mpa), optimum polishing characteristics, and excellent optical properties. Therefore, this ceramic is an interesting alternative material for monolithic restorations produced in a digital workflow.

Fabrication of Zirconia-Reinforced Lithium Silicate Ceramic Restorations Using a Complete Digital Workflow.

This case report describes the fabrication of monolithic all-ceramic restorations using zirconia-reinforced lithium silicate (ZLS) ceramics. The use of powder-free intraoral scanner, generative fabrication technology of the working model, and CAD/CAM of the restorations in the dental laboratory allows a completely digitized workflow. The newly introduced ZLS ceramics offer a unique combination of fracture strength (>420 MPa), excellent optical properties, and optimum polishing characteristics, thus making them an interesting material option for monolithic restorations in the digital workflow.

Evaluation of removal forces of implant-supported zirconia copings depending on abutment geometry, luting agent and cleaning method during re-cementation.

PURPOSE: To evaluate the effects of different abutment geometries in combination with varying luting agents and the effectiveness of different cleaning methods (prior to re-cementation) regarding the retentiveness of zirconia copings on implants. MATERIALS AND METHODS: Implants were embedded in resin blocks. Three groups of titanium abutments (pre-fabricated, height: 7.5 mm, taper: 5.7°; customized-long, height: 6.79 mm, taper: 4.8°; customized-short, height: 4.31 mm, taper: 4.8°) were used for luting of CAD/CAM-fabricated zirconia copings with a semi-permanent (Telio CS) and a provisional cement (TempBond NE). Retention forces were evaluated using a universal testing machine. Furthermore, the influence of cleaning methods (manually, manually in combination with ultrasonic bath or sandblasting) prior to re-cementation with a provisional cement (TempBond NE) was investigated with the pre-fabricated titanium abutments (height: 7.5 mm, taper: 5.7°) and SEM-analysis of inner surfaces of the copings was performed. Significant differences were determined via two-way ANOVA. RESULTS: Significant interactions between abutment geometry and luting agent were observed. TempBond NE showed the highest level of retentiveness on customized-long abutments, but was negatively affected by other abutment geometries. In contrast, luting with Telio CS demonstrated consistent results irrespective of the varying abutment geometries. Manual cleaning in combination with an ultrasonic bath was the only cleaning method tested prior to re-cementation that revealed retentiveness levels not inferior to primary cementation. CONCLUSION: No superiority for one of the two cements could be demonstrated because their influences on retentive strength are also depending on abutment geometry. Only manual cleaning in combination with an ultrasonic bath offers retentiveness levels after re-cementation comparable to those of primary luting.

Anisotropic local physical properties of human dental enamel in comparison to properties of some common dental filling materials.

OBJECTIVE: A major aspect in evaluating the quality of dental materials is their physical properties. Their properties should be a best fit of the ones of dental hard tissues. Manufacturers give data sheets for each material. The properties listed are characterized by a specific value. This assumes (but does not prove) that there is no direction dependence of the properties. However, dental enamel has direction-dependent properties which additionally vary with location in the tooth. The aim of this paper is to show the local direction dependence of physical properties like the elastic modulus or the thermal expansion in dental hard tissues. With this knowledge the 'perfect filling/dental material' could be characterized. MATERIALS AND METHOD: Enamel sections of ∼400-500 µm thickness have been cut with a diamond saw from labial/buccal to palatal/lingual (canine, premolar and molar) and parallel to labial (incisor). Crystallite arrangements have been measured in over 400 data points on all types of teeth with x-ray scattering techniques, known from materials science. RESULTS: X-ray scattering measurements show impressively that dental enamel has a strong direction dependence of its physical properties which also varies with location within the tooth. Dental materials possess only little or no property direction dependence. Therefore, a mismatch was found between enamel and dental materials properties. CONCLUSION: Since dental materials should possess equal (direction depending) properties, worthwhile properties could be characterized by transferring the directional properties of enamel into a property 'wish list' which future dental materials should fulfil. Hereby the 'perfect dental material' can be characterized.

Early loading of surface modified implants in the posterior mandible - 5 year results of an open prospective non-controlled study.

AIM: The aim of the present study was to evaluate an early loading protocol for surface modified implants placed in the posterior mandible. MATERIAL AND METHODS: A total of 134 implants with a TiO(2) blasted, fluoride modified surface were inserted into the posterior mandibles of 44 patients. The implants were functionally loaded after 7 weeks of healing. Implant stability quotient (ISQ) values (during the first year), bleeding on probing (BOP), plaque accumulation and marginal bone level (MBL) were assessed until the end of the observation period of 5 years. A total of 41 patients with 123 implants completed the study. RESULTS: No implants were lost. ISQ values decreased significantly from the time of insertion to 2 weeks and increased significantly until the 1-year follow up. BOP varied until the end of the observation period between 7.9% and 13.0%. Plaque accumulation decreased from the time of early loading to the end of the study. MBL changed from 0.59 mm at the time of implant placement to 0.80 mm at the time of early loading. Thereafter, only slight variations in MBL occurred until the end of the observation period. CONCLUSIONS: The results confirm that early loading is a promising option also in posterior edentulism of the mandible.

Organic anion transporter 3 (OAT3) and renal transport of the metal chelator 2,3-dimercapto-1-propanesulfonic acid (DMPS).

Recent investigations involving intact rabbit renal proximal tubules indicated that organic anion transporter 3 (OAT3) may be involved in the transport of 2,3-dimercapto-1-propanesulfonic acid (DMPS). Therefore, we evaluated the interaction of OAT3 with DMPS to determine the effect of OAT3 on basolateral DMPS uptake. We used stably transfected HEK293 cells expressing human and rabbit orthologs of the exchanger OAT1 and OAT3. Using 6-carboxyfluorescein (6-CF) as a substrate, the IC50 determinations for reduced DMPS (DMPSH) revealed a stronger interaction with OAT1 than with OAT3 (rbOAT1, 123.3 +/- 13.7; hOAT1, 85.1 +/- 8.8; rbOAT3, 171.7 +/- 22.3; and hOAT3, 172.2 +/- 36.4 micromol/L). However, inhibition of 6-CF uptake by the oxidized form of DMPS (DMPSS), the main form of DMPS in the blood, showed a greater affinity for OAT3 (rbOAT1, 237.4 +/- 23; hOAT1, 104.6 +/- 13.1; rbOAT3, 52.4 +/- 7.6; and hOAT3, 31.6 +/- 6.6 micromol/L). To determine whether DMPSH and DMPSS are substrates for OAT3, we performed efflux studies with [14C]glutarate and inwardly directed gradients of glutarate. The inhibitors trans-stimulated the efflux of [14C]glutarate, suggesting that OAT3 may be able to transport both forms of DMPS. On the basis of the substantial interaction of OAT3 with DMPSS, we conclude that OAT3 represents the dominant basolateral player in renal detoxification processes resulting from use of DMPS.

Relative contribution of OAT and OCT transporters to organic electrolyte transport in rabbit proximal tubule.

We compared the characteristics of several cloned rabbit organic electrolyte (OE) transporters expressed in cultured cells with their behavior in intact rabbit renal proximal tubules (RPT) to determine the contribution of each to basolateral uptake of the weak acid ochratoxin A (OTA) and the weak base cimetidine (CIM). The activity of organic anion transporters OAT1 and OAT3 proved to be distinguishable because OAT1 had a high affinity for PAH (K(t) of 20 microM) and did not support estrone sulfate (ES) transport, whereas OAT3 had a high affinity for ES (K(t) of 4.5 microM) and a weak interaction with PAH (IC(50) > 1 mM). In contrast, both transporters robustly accumulated OTA. Intact RPT also accumulated OTA, with OAT1 and OAT3 each responsible for approximately 50%: ES and PAH each reduced uptake by approximately 50%, and the combination of the two eliminated mediated OTA uptake. The weak base CIM was transported by OAT3 (K(t) of 80 microM) and OCT2 (K(t) of 2 microM); OCT1 had a comparatively low affinity for CIM, and CIM uptake by OAT1 was equivocal. Intact RPT accumulated CIM, with TEA and ES reducing CIM uptake by 20 and 75%, respectively, suggesting that OAT3 plays a quantitatively more significant role in CIM uptake in the early proximal tubule than OCT1/2. In single S2 segments of RPT, ES and TEA each blocked approximately 50% of CIM uptake. Thus the fractional contribution of different OE transporters to renal secretion is influenced by their affinity for substrate and relative expression level in RPT.