Publications by authors named "Michael Stimmelmayr"

54 Publications

Short communication: In vitro pilot study: Are monolithic 3Y-TZP zirconia crowns too strong for titanium Implants?

Int J Prosthodont 2021 Mar 3. Epub 2021 Mar 3.

Purpose: To report on pilot tests for a planned study on single implant-supported crowns made from different restorative materials using finite element analysis (FEA) and in vitro load-to-failure testing.

Materials And Methods: Within this pilot study, FEA was conducted using Ansys 2019 R2 to simulate stress and deformation for implant-supported crowns made of lithium disilicate ceramic (LiS2) and zirconia (3Y-TZP). Additionally, an in vitro load to failure test was conducted using two specimens per group to evaluate the failure mode and to confirm the findings from the FEA.

Results/conclusion: FEA revealed stress areas at the palatal cervical areas of the crowns. In the load to failure test, both hybrid abutment crowns made of LiS2 fractured (410 N and 510 N) before plastic deformation of the metal implant components occurred. The monolithic hybrid abutment crowns made of 3Y-TZP did not fracture until tests were interrupted at 646-N and 690-N occlusal force, when plastic deformation of the metal implant components was visually observed.
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http://dx.doi.org/10.11607/ijp.7322DOI Listing
March 2021

Mechanical stability of all-ceramic abutments retained with three different screw materials in two-piece zirconia implants-an in vitro study.

Clin Oral Investig 2020 May 3;24(5):1801-1806. Epub 2019 Sep 3.

Department of Prosthodontics, University of Munich, Goethestr 70, 80336, Munich, Germany.

Objectives: To measure the abutment rotation and fracture load of two-piece zirconia implants screwed with three different abutment screw materials.

Material And Methods: Thirty-six zirconia implants with 36 zirconia abutments were distributed into 3 test groups: group G connected with gold screws, group T with titanium screws, and group P with peek screws. In the first part of the study, the rotation angle of the abutments was measured. The second part of the study measured the maximum fracture force of adhesively bonded lithium disilicate crowns after artificial aging and fracture modes were reported.

Results: In group G, the median rotation angle was 8.0°, in group T 11.6°, and in group P 9.5°. After artificial aging, no screw loosening, crown, abutment, or implant fracture occurred. The median fracture force in group G was 250 N, in group T 263 N, and in group P 196 N.

Conclusions: Rotation angles and fracture loads of two-piece zirconia implants with gold, titanium, or peek screws showed no significant differences; however, fracture loads showed inferior results for group P.

Clinical Relevance: The indication for the material peek as an abutment screw is still questionable and should be considered carefully.
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http://dx.doi.org/10.1007/s00784-019-03043-3DOI Listing
May 2020

Advances in materials and concepts in fixed prosthodontics: a selection of possible treatment modalities.

Br Dent J 2019 May;226(10):739-748

Associate Professor, Department of Prosthetic Dentistry, University Hospital, LMU, Munich, Germany.

The introduction of adhesive techniques in combination with translucent restorative materials has greatly influenced treatment concepts in fixed prosthodontics. Modern production technologies offer access to new polymer materials that provide innovative pre-treatment options for complex prosthetic rehabilitations. Additionally, computer-aided design and manufacturing (CAD/CAM) provides access to new ceramic types and thus extends the range of indications for metal-free restorative options. With these developments, important changes of treatment concepts in fixed prosthodontics have occurred which affect the professional life of dental practitioners with a focus on prosthetic dentistry. This article gives an overview of the advances in selected fields of fixed prosthodontics and provides support in material selection for different kinds of indications, from single-tooth restorations to fixed dental prostheses.
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http://dx.doi.org/10.1038/s41415-019-0265-zDOI Listing
May 2019

Metal-free implant-supported single-tooth restorations. Part II: Hybrid abutment crowns and material selection.

Quintessence Int 2019 ;50(4):260-269

In many areas of restorative dentistry, metal-free materials offer an alternative to metal-based restorations while ensuring high levels of biocompatibility and esthetics. Rapidly evolving CAD/CAM technology has significantly expanded the range of materials available, providing access to materials classes and their combinations not previously available within conventional manufacturing, such as zirconia ceramics and hybrid ceramics. In addition, digital methods offer previously unavailable options in diagnostics, greater planning reliability, better material quality through standardization of the manufacturing process, and reproducibility - significant benefits that can be used to advantage, especially in oral implantology. Even though technological progress in the field of metal-free materials has given rise to considerable improvements in their mechanical properties over the decades, their clinical long-term success is still very much dependent on an appropriate indication and proper material selection, on the knowledge and skills of the dental practitioner and dental technician, and on an adequate occlusion concept. The high rate of innovation - both with regard to the materials themselves and to CAD/CAM technology - therefore requires an adequate level of prior knowledge to sensibly and successfully implement the wide range of possibilities. It is becoming more and more puzzling for users to find their way around the many different new techniques and materials. This review article provides an up-to-date overview of the possibilities and limitations of metal-free implant-supported single-tooth restorations. This second part discusses hybrid abutment crowns and materials selection. Resultant treatment concepts are presented and evaluated based on clinical examples.
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http://dx.doi.org/10.3290/j.qi.a42099DOI Listing
November 2019

Metal-free implant-supported single-tooth restorations. Part I: Abutments and cemented crowns.

Quintessence Int 2019 ;50(3):176-184

In many areas of restorative dentistry, metal-free materials offer an alternative to metal-based restorations while ensuring high levels of biocompatibility and esthetics. Rapidly evolving CAD/CAM technology has significantly expanded the range of materials available, providing access to materials classes and their combinations not previously available within conventional manufacturing, such as zirconia ceramics and hybrid ceramics. In addition, digital methods offer previously unavailable options in diagnostics, greater planning reliability, better material quality through standardization of the manufacturing process, and reproducibility - significant benefits that can be used to advantage, especially in oral implantology. Even though technological progress in the field of metal-free materials has given rise to considerable improvements in their mechanical properties over the decades, their clinical long-term success is still very much dependent on an appropriate indication and proper material selection, on the knowledge and skills of the dental practitioner and dental technician, and on an adequate occlusion concept. The high rate of innovation - both with regard to the materials themselves and to CAD/CAM technology - therefore requires an adequate level of prior knowledge to sensibly and successfully implement the wide range of possibilities now open. It is becoming more and more puzzling for users to find their way around the many different new techniques and materials. This review article provides an up-to-date overview of the possibilities and limitations of metal-free implant-supported single-tooth restorations. This first part discusses abutments and cemented crowns. Resultant treatment concepts are presented and evaluated based on clinical examples.
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http://dx.doi.org/10.3290/j.qi.a41906DOI Listing
November 2019

Implant health and factors affecting peri-implant marginal bone alteration for implants placed in staged maxillary sinus augmentation: A 5-year prospective study.

Clin Implant Dent Relat Res 2019 Feb 4;21(1):32-41. Epub 2019 Jan 4.

Prosthodontics, Dental School, Ludwig-Maximilian University, Munich, Germany.

Purpose: Evaluating the extent of and the factors affecting marginal bone level (MBL) alterations and consecutively implant success and implant health for implants placed in staged maxillary sinus floor (SF) augmentation.

Materials And Methods: A 5-year prospective, cohort study was conducted on 85 patients with 124 maxillary sinus augmentation procedure and 295 implants placed. Peri-implant MBL alterations (reductions) were evaluated radiographically at the first year, third year, and fifth year postloading follow-ups and were considered to patient-related risk factors (age, gender, diabetes mellitus, smoking, rheumatic disorders, and history of periodontal disease [PD]), to clinican/surgically related risk factors (membrane perforations, sinus site, and residual ridge height), to implant/prosthesis-related features (implant length, diameter, location, keratinized gingiva, and restoration gap), and to the plaque score. Additionally, implant and prostheses survival/success rate and peri-implant health (mucositis/peri-implantitis) were assessed.

Results: About 267/295 implants (drop-out:n9 pat; 28 implants: 9%) were followed for 5 years (survival/success: 99.3%/96.5%), presenting significant (P < .001) differences of MBL alterations (-1.45 ± 0.38 mm) over time. The univariate analysis demonstrated differences of MBL alterations for smokers versus nonsmokers (P = .005), for patients with versus without history of PD (P = .001), and presence versus absence of plaque (P = .041). In the 5-year multivariate analysis, MBL alteration was influenced by time (P = .001) and was related to risk factors as smoking (P = .001; odds ratio [OR] = 6.563) and history of PD (P = .015; OR = 4.450). Significant ORs for MBL alterations were also found for a restoration gap used for a full-arch dentures (P = .001; OR = 8.275) associated with reduced (≤3 mm) residual ridge height (P = .015; OR = 1.365). The overall 5 year incidence of peri-implant mucositis and peri-implantitis was 25.3% and 3.7% at implant level and 30.3% and 6.6% at patient level, respectively.

Conclusions: Apart from the high success rate and healthy status of implant placed in staged SF seen, MBL alteration increased over time and was negatively affected predominately by patient-specific risk factors such as smoking status and previous history of periodontitis.
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http://dx.doi.org/10.1111/cid.12684DOI Listing
February 2019

Clinical Outcome of Implants Placed in Staged Maxillary Sinus Augmentation Using Bovine Bone Mineral Mixed with Autogenous Bone at Three Different Ratios: A 5-Year Prospective Follow-up Study.

Int J Oral Maxillofac Implants 2018 Nov/Dec;33(21):1351-1361

Purpose: To evaluate the 5-year clinical outcomes for implants placed in a staged sinus floor elevation (SFE) procedure and to compare three patient groups with sinus grafts with three different ratios of bovine bone mineral (BBM) and autogenous bone (AB) mixture.

Materials And Methods: A 5-year prospective cohort study was conducted on 81 patients with 119 staged SFEs non-randomly distributed to three groups based on the origin of the AB and the mixture ratio with BBM: group 1 (locally harvested AB [LHB] from osteotomy sites + BBM, ratio: 1:10), 31 patients, 37 SFEs; group 2: (LHB + intraorally harvested peripheral AB [IHPB] from retromolar/chin region + BBM, ratio: 1:4), 22 patients, 29 SFEs; and group 3 (LHB + extraorally harvested peripheral AB [EHPB] from iliac crest/tibia + BBM, ratio 1:1), 28 patients, 53 SFEs. After graft healing (5 to 7 months), 284 dental implants (group 1: 76, group 2: 61, group 3: 147 [overall: 2.3 implants/sinus]) were placed. After an additional healing period (5 to 7 months), all implants placed were functionally loaded and prospectively followed by clinical and radiographic evaluations assessing implant survival/success rate as well as peri-implant marginal bone level (MBL) alteration at 1, 3, and 5 years postloading.

Results: A total of 76/81 patients with 267/284 implants were followed for up to 5 years (dropouts: 5 patients/15 implants; implant loss = 2). The 5-year implant survival and implant success rate (group 1: 100%/98.6%; group 2: 98.3%/96.6%; group 3: 99.3%/95.7%) did not differ between the three graft mixture groups. The peri-implant marginal bone alteration (reduction) averaged over all 5 years was 1.40 ± 0.29 mm for group 1, 1.41 ± 0.22 mm for group 2, and 1.46 ± 0.46 mm for group 3 (P = .187). However, over time, a continual and significant MBL reduction (P = .045) was noted for all groups presenting peri-implant MBL changes between 1 year and 5 years of -0.17 mm (group 1), -0.12 mm (group 2), and -0.24 mm (group 3), respectively.

Conclusion: According to the clinical results obtained, dental implants inserted in grafted (staged) SFE using a mixture of BBM with a minimal amount of AB harvested from local sites provide for similarly high 5-year implant/augmentation success rates as graft mixtures with AB harvested from peripheral intraoral or extraoral donor sites, confirming no need for additional bone harvesting.
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http://dx.doi.org/10.11607/jomi.6765DOI Listing
December 2018

Temporary Single Palatal Implant for Denture Stabilization During Augmentation and Implant Procedure: A Case Report.

Int J Periodontics Restorative Dent 2018 Nov/Dec;38(6):e105-e111

This case report introduces a temporary denture with reduced extension stabilized in the edentulous maxilla as a possible treatment method for patients with a severe gag reflex, allowing them to test the function, esthetics, and tolerance of the denture prior to hard tissue augmentation and implant placement. A 4-mm implant was placed in the central anterior palate and allowed to heal for 3 months. During the complete treatment period, a denture with reduced extension can be delivered on a fixed Locator abutment. This method was successfully applied in three patients, and the palatal implant remained stable until the final removable prosthesis could be delivered.
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http://dx.doi.org/10.11607/prd.3600DOI Listing
April 2019

Anterior restorations: The performance of ceramic veneers.

Quintessence Int 2018 ;49(2):89-101

Adhesive bonding techniques in combination with tooth-colored restorative materials are one of the greatest achievements of restorative dentistry. Adhesively bonded veneers made from various silicate ceramic materials have contributed significantly to this. Ceramic veneers had long been considered to be only esthetic implements. However, their range of indications has been steadily increasing, making ceramic veneers a highly viable alternative to classic, far more invasive forms of restorative treatment. Today these veneers are used to restore the biomechanics of the dentition, to establish adequate function, to mask highly discolored endodontically treated teeth, and for many other purposes. The present article explains the principles of modern veneer technology based on clinical examples, with special emphasis on collaboration with the dental laboratory and communication within the dental team. This includes analyzing the case, defining the treatment goal, determining the right shade, selecting the most suitable ceramic material, finding the best preparation design, and choosing the most appropriate adhesive concept. The article will also explore the long-term prognosis of ceramic veneers as reported by a number of scientific studies.
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http://dx.doi.org/10.3290/j.qi.a39509DOI Listing
October 2018

Virtual Simulation of Periodontal Surgery Including Presurgical CAD/CAM Fabrication of Tooth-Colored Removable Splints on the Basis of CBCT Data: A Case Report.

Int J Periodontics Restorative Dent 2017 Nov/Dec;37(6):e310-e320

Innovative digital diagnostic, design, and manufacturing technologies combined with high-performance polymers offer new possibilities to facilitate complex interdisciplinary treatment procedures. This article reports on the interaction of different digital technologies, from presurgical digital simulation of periodontal surgery to final prosthodontic rehabilitation, in a case of amelogenesis imperfecta in a 17-year-old girl. The aim was to digitally determine the treatment outcome by three-dimensional simulation of the soft tissue removal and to create computer-aided design/computer-assisted manufacture tooth-colored splints before the clinical treatment. The case report shows the synergy of the combination of multiple digital technologies for a predictable periodontal and prosthetic treatment outcome.
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http://dx.doi.org/10.11607/prd.2769DOI Listing
July 2018

Load bearing capacity, fracture mode, and wear performance of digitally veneered full-ceramic single crowns.

Int J Comput Dent 2017;20(3):245-262

Objectives: Computer-aided technologies can help to minimize clinical complications of zirconia-based restorations such as veneering porcelain fractures. The aim of this study was to evaluate different veneering approaches for zirconia single crowns regarding contact wear, fracture strength, and failure mode.

Methods: Six different types of computer-aided design (CAD) crowns were manufactured and conventionally cemented on 10 metal dies each: three groups with a zirconia framework and a CAD/CAM-fabricated veneering cap ("digital veneering system": DVS, CAD-on, Infix CAD), zirconia-based crowns with pressed veneering caps (Infix Press), zirconia framework containing the dentin layer with only the incisal enamel material added (dentin-core), and conventional substructure with powder buildup veneering porcelain (layering technique). All specimens were submitted to artificial aging (120,000 mechanical cycles, 50 N load, 0.7-mm sliding movement, 320 thermocycles). After contact wear was measured with a laser scanning system, fracture resistance and failure mode were examined using a universal testing machine and a scanning electron microscope. Statistical analysis was performed at a significance level of 5%.

Results: No statistical difference was revealed regarding the contact wear of the restorations (P = 0.171; ANOVA). No significant difference was found regarding the fracture resistance of the crowns (P = 0.112; ANOVA). Failure analysis revealed three different failure patterns: cohesive veneering fracture, adhesive delamination, and total fracture, with a characteristic distribution between the groups.

Significance: All tested specimens survived artificial aging and exhibited clinically acceptable wear resistance and fracture resistance. Digital veneering techniques offer a promising, time- and cost-effective manufacturing process for all-ceramic restorations and may usefully complement the digital workflow.
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November 2017

Fracture resistance of different implant abutments supporting 
all-ceramic single crowns after aging.

Int J Comput Dent 2017;20(1):53-64

Objective: To test the mechanical properties of three different restorative materials for implant abutments supporting all-ceramic single crowns.

Materials And Methods: Thirty implants with butt-joint connections were distributed into three test groups: Group A with 10 one-piece zirconia abutments, Group U with 10 titanium abutments, and Group T with 10 titanium-zirconia hybrid abutments. Monolithic zirconia single crowns were cemented and artificially aged. The crowns were loaded at a 30-degree angle in a universal testing machine until fracture or bending. Additionally, after removal of the restorations, the implant-abutment interface of the fixtures was inspected using a scanning electron microscope (SEM).

Results: In Group A, the abutments failed on average at 336.78 N, in Group U at 1000.12 N, and in Group T at 1296.55 N. The mean values between Groups T and U (P = 0.009), and between Group A and Groups T and U (P < 0.001) were significantly different. The abutments in Group A failed early due to fractures of the internal parts and parts close to the implant neck. In Groups T and U, failures occurred due to bending of the implant neck.

Conclusion: This experimental study proves that hybrid and titanium abutments have similar mechanical properties. One-piece abutments made of zirconia showed significantly lower fracture resistance.
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June 2017

Accuracy and reproducibility of four cone beam computed tomography devices using 3D implant-planning software.

Int J Comput Dent 2017;20(1):21-34

Objective: To measure the deviations of four different cone beam computed tomography (CBCT) devices in three dimensions by means of a three-dimensional (3D) implant-planning program.

Materials And Methods: A master radiographic template with two vertical, two transverse, and two sagittal radiopaque markers was fabricated for a human dry skull. The lengths of the markers were measured with a high-precision caliper. The skull and the template were scanned in each of the four CBCT devices (1. Gendex GXCB-500; 2. Sirona Galileos Comfort; 3. Sirona Orthophos XG 3D; 4. Carestream CS 9300) 19 times (10 scans without moving the skull, and 9 scans with repeated repositioning of the skull in the device, according to the manufacturers' instructions). A 3D implant-planning program was used to measure the lengths of the six markers digitally. Actual and digital measurements were compared to determine device-specific errors. The repositioning of the skull examined the reproducibility of the CBCT devices. Linear measurements were analyzed statistically (P < 0.05).

Results: Mean deviations without moving the skull (vertical/sagittal/transverse) for device 1 were 0.023 mm/
0.000 mm/0.025 mm (0.07%/0.19%/0.24%), for device 2 were 0.410 mm/0.115 mm/0.080 mm (-1.75%/0.32%/
0.88%), for device 3 were -0.665 mm/-0.215 mm/
-0.675 mm (-2.71%/-1.82%/-4.42%), and for device 4 were -0.045 mm/-0.135 mm/-0.410 mm (-0.45%/
-1.54%/-2.57%). The overall mean deviation for device 1 was 0.028 mm (0.16%), for device 2 was 0.072 mm (-0.95%), for device 3 was 0.518 mm (-2.97%), and for device 4 was -0.197 mm (-1.53%). The mean deviation after repositioning for device 1 was 0.004 mm (-0.65%), for device 2 was -0.250 mm (0.95%), for device 3 was 0.496 mm (-2.66%), and for device 4 was -0.265 mm (-1.92%). Thus, apart from device 3, the deviations increased.

Conclusion: Deviations from the actual measurements were detected with each device. Therefore, respecting safety distances when placing implants is crucial.
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June 2017

CAD/CAM splints for the functional and esthetic evaluation of newly defined occlusal dimensions.

Quintessence Int 2017 ;48(3):181-191

Pretreatment with occlusal splints is a crucial step in a structured treatment approach for a complex rehabilitation that changes the vertical dimension of occlusion. Meticulous patient compliance is one of the essential prerequisites for overall treatment success. However, patient compliance is all too often insufficient due to esthetic, phonetic, and functional limitations when using conventional occlusal splints in one arch. Modern production technologies now allow the use of tooth-colored occlusal splints made of polycarbonate, whose quality and material properties are quite distinct from those of conventionally manufactured splints made of transparent polymethyl methacrylate (PMMA). These materials, produced under standardized polymerization conditions, are extremely homogenous, which provides benefits such as a greater accuracy of fit by eliminating the polymerization shrinkage, greater long-term stability of shapes and shades, better biocompatibility, less wear, and a more favorable esthetic appearance. In addition, tooth-colored polycarbonate splints can be fabricated very thin without significantly increasing the fracture risk, thanks to the flexibility of the material. The improved wearing comfort combined with acceptable esthetics result in significantly improved patient compliance in terms of a "23-hour splint."

Conclusion: By providing separate splints for the maxilla and mandible in the case of major alterations of the vertical dimension of occlusion, the esthetic and functional aspects defined by the wax-up can be completely transferred to the removable splints for a "test drive" by the patient, reversibly, and under realistic conditions. This dual-splint approach additionally facilitates segmental transfer into the definitive restoration.
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http://dx.doi.org/10.3290/j.qi.a37641DOI Listing
February 2018

Accuracy and mechanical performance of passivated and conventional fabricated 3-unit fixed dental prosthesis on multi-unit abutments.

J Prosthodont Res 2017 10 7;61(4):403-411. Epub 2017 Feb 7.

University of Munich, Department of Prosthodontics, Goethestr. 70, 80336 Munich, Germany.

Purpose: The aim of this study was to evaluate the fit and mechanical stability of conventional versus passive fitting 3-unit fixed dental prosthesis (FDP) screw-retained on implants.

Methods: Twenty acrylic models, each with two embedded implants, were fabricated and functioned as patient-models. Impressions were taken and 20 all-ceramic FDPs were pre-fabricated on the plaster casts. Respectively 10 FDPs were fixed on the plaster casts (group 1) and on the patient-models for passive fitting (group 2). The fit of each FDP was checked on the patient-model by means of visual control (grades 1-10) and microscopic examination. Furthermore, specimens were artificially aged for possible prosthodontic failures, followed by a fracture strength test.

Results: Group 2 [1.4 (±0.3)] showed significantly (p<0.001) better results in the visual examination of the marginal fit compared to group 1 [6.3 (±2.4)]. The microscopic marginal misfit was 160μm (±80μm) at the abutment margin and 150μm (±80μm) at the axial wall of the abutment for group 1, respectively, 0μm and 0μm up to 17μm for group 2 (p<0.001). No failure of the FDPs could be observed during artificial aging in both groups. The fracture load showed no significant difference (p=0.60) between group 1 [2583N (±664N)] and group 2 [2465N (±238N)].

Conclusions: Visual and microscopic examination detected huge differences in marginal fit between groups 1 and 2. However, no statistically verifiable differences could be detected in long-term stability of implant-supported FDPs irrespective of the fit.
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http://dx.doi.org/10.1016/j.jpor.2016.12.011DOI Listing
October 2017

Precise Placement of Single-Retainer Resin-Bonded Fixed Dental Prostheses with an Innovative Splint Design.

J Prosthodont 2017 Jul 26;26(5):359-363. Epub 2016 Oct 26.

Department of Prosthodontics, University of Munich, Germany.

Single-retainer resin-bonded fixed dental prostheses (RBFDPs) are difficult to position due to the pressure of soft tissue at the pontic area and the single-retainer design. This clinical report describes an innovative technique for the insertion of single-retainer RBFDPs. An incisal inserting splint is used to position the RBFDPs reliably. With the help of grooves in the buccal and incisal area of the splint, the precise positioning of the splint on the adjacent teeth and the RBFDP can be controlled. Also, a hole in the retainer wing region of the splint gives access for pressure application on the wing during the bonding process. With the aid of this method, 25 single-retainer FBFDPs were inserted in the correct position in a case series. The splint described here allows the precise insertion of single-retainer RBFDPs and simplifies delivery.
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http://dx.doi.org/10.1111/jopr.12562DOI Listing
July 2017

Accuracy of five intraoral scanners compared to indirect digitalization.

Clin Oral Investig 2017 Jun 12;21(5):1445-1455. Epub 2016 Jul 12.

Department of Prosthodontics, Ludwig-Maximilians University Munich, Goethestraße 70, 80336, Munich, Germany.

Objectives: Direct and indirect digitalization offer two options for computer-aided design (CAD)/ computer-aided manufacturing (CAM)-generated restorations. The aim of this study was to evaluate the accuracy of different intraoral scanners and compare them to the process of indirect digitalization.

Material And Method: A titanium testing model was directly digitized 12 times with each intraoral scanner: (1) CS 3500 (CS), (2) Zfx Intrascan (ZFX), (3) CEREC AC Bluecam (BLU), (4) CEREC AC Omnicam (OC) and (5) True Definition (TD). As control, 12 polyether impressions were taken and the referring plaster casts were digitized indirectly with the D-810 laboratory scanner (CON). The accuracy (trueness/precision) of the datasets was evaluated by an analysing software (Geomagic Qualify 12.1) using a "best fit alignment" of the datasets with a highly accurate reference dataset of the testing model, received from industrial computed tomography.

Results: Direct digitalization using the TD showed the significant highest overall "trueness", followed by CS. Both performed better than CON. BLU, ZFX and OC showed higher differences from the reference dataset than CON. Regarding the overall "precision", the CS 3500 intraoral scanner and the True Definition showed the best performance. CON, BLU and OC resulted in significantly higher precision than ZFX did.

Conclusions: Within the limitations of this in vitro study, the accuracy of the ascertained datasets was dependent on the scanning system. The direct digitalization was not superior to indirect digitalization for all tested systems.

Clinical Relevance: Regarding the accuracy, all tested intraoral scanning technologies seem to be able to reproduce a single quadrant within clinical acceptable accuracy. However, differences were detected between the tested systems.
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http://dx.doi.org/10.1007/s00784-016-1902-4DOI Listing
June 2017

Mandibular Full-Arch Fixed Prostheses Supported on 4 Implants with Either Axial Or Tilted Distal Implants: A 3-Year Prospective Study.

Clin Implant Dent Relat Res 2016 Dec 28;18(6):1119-1133. Epub 2016 Apr 28.

Professor, Dental School, Prosthodontics, Ludwig-Maximilian University (LMU) Munich, Germany.

Purpose: This prospective study evaluated the clinical and radiographic outcome of distally cantilevered 4-implant-supported fixed mandibular prostheses (4-ISFMP) with distal implants either in axial or distally tilted direction.

Material And Methods: Forty-one mandibulary edentulous patients received acrylic veneered 4-ISFMP with casted framework. Based on distal implant placement direction patients were assigned to 2 groups: 21 patients with four (2 anterior/2 posterior) axial implants (axial-group I) and 20 patients with 2 anterior axial/2 distal tilted implants (tilted-group II). Patients were prospectively followed for 3 years by annual examinations of implants and prosthetic survival rates including assessment for biological and mechanical complications. Additionally, peri-implant marginal bone resorption [MBR], pocket depth [PD], plaque index [PI], bleeding index [BI] and gingival index [GI], and calculus index [CI] were evaluated at each annual follow-up.

Results: 37/41 patients (19 axial-group I, 18 tilted-group II) and 148/164 implants were followed at the 1-, 2-, and 3-year evaluation (dropout rate: 11.8%) presenting no implant and denture loss (100% survival). The overall, MBR at year 1, 2, and 3 was 1.11 ± 0.4 mm, 1.26 ± 0.42 mm, and 1.40 ± 0.41 mm, respectively, representing a significant (p < .001) continuing time depending annual reduction. MBR and PD did not differ between anterior and posterior regions in both groups or for anterior and posterior regions between the groups. PI and CI were significantly (p < .001) higher for implants in anterior regions than for posterior regions in both groups. Moreover, posterior implant regions showed significantly (p < .001) higher PI and CI for axial-group I than for tilted-group II over time. Biological and mechanical complications as well as GI and BI did not differ between the groups over a 3-year follow-up period.

Conclusion: For clinical implant and prosthesis outcome no statistical significant mean differences were noted for distally cantilevered 4-ISFMP supported by distal implants placed in tilted or axial direction.
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http://dx.doi.org/10.1111/cid.12419DOI Listing
December 2016

[Dental biocorrosions - etiology, diagnostic, prevention and treatment options].

MMW Fortschr Med 2016 Apr;158(8):64-7

Poliklinik für Zahnärztliche Prothetik, Ludwig-Maximilians-Universität, München, Deutschland.

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http://dx.doi.org/10.1007/s15006-016-8151-yDOI Listing
April 2016

Minimally invasive treatment options in fixed prosthodontics.

Quintessence Int 2016 Mar;47(3):207-16

Minimally invasive treatment options have become increasingly feasible in restorative dentistry, due to the introduction of the adhesive technique in combination with restorative materials featuring translucent properties similar to those of natural teeth. Mechanical anchoring of restorations via conventional cementation represents a predominantly subtractive treatment approach that is gradually being superseded by a primarily defect-oriented additive method in prosthodontics. Modifications of conventional treatment procedures have led to the development of an economical approach to the removal of healthy tooth structure. This is possible because the planned treatment outcome is defined in a wax-up before the treatment is commenced and this wax-up is subsequently used as a reference during tooth preparation. Similarly, resin- bonded FDPs and implants have made it possible to preserve the natural tooth structure of potential abutment teeth. This report describes a number of clinical cases to demonstrate the principles of modern prosthetic treatment strategies and discusses these approaches in the context of minimally invasive prosthetic dentistry.
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http://dx.doi.org/10.3290/j.qi.a35115DOI Listing
March 2016

Transmission of light in the visible spectrum (400-700 nm) and blue spectrum (360-540 nm) through CAD/CAM polymers.

Clin Oral Investig 2016 Dec 26;20(9):2501-2506. Epub 2016 Feb 26.

Department of Prosthodontics, Dental School of the Ludwig-Maximilian University of Munich, Goethestraße 70, 80336, Munich, Germany.

Objectives: CAD/CAM-fabricated long-term temporary restorations from high-density polymers can be applied for a wide range of indications. Milled from monolithic, mono-colored polymer blocks, the translucency of the material plays an important role for an esthetically acceptable result. The aim of this study was to compare the transmittance through visible light and blue light of CAD CAM polymers to a glass-ceramic material of the same color.

Materials And Methods: Ambarino High-Class (AM), Telio-CAD (TC), Zenotec PMMA (ZT), Cercon base PMMA (CB), CAD Temp (CT), Artbloc Temp (AT), Polycon ae (PS), New Outline CAD (NC), QUATTRO DISK Eco PMMA (GQ), Lava Ultimate (LU), and Paradigm MZ 100 (PA) were employed in this study using the feldspathic glass-ceramic Vita Mark II (MK) as control group. Using a spectrophotometer, the overall light transmittance was measured for each material (n = 40) and was calculated as the integration (t (λ) dλ [10]) of all t values for the wavelengths of blue light (360-540 nm). Results were compared to previous data of the authors for visible light (400 to 700 nm).

Results: Wilcoxon test showed significant differences between the light transmittance of visible and blue light for all materials.

Conclusion: CAD/CAM polymers showed different translucency for blue and visible light. This means clinicians may not conclude from the visible translucency of a material to its permeability for blue light. This influences considerations regarding light curing.

Clinical Relevance: CAD/CAM polymers need to be luted adhesively; therefore, clinicians should be aware about the amount of blue light passing through a restoration.
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http://dx.doi.org/10.1007/s00784-016-1755-xDOI Listing
December 2016

Factors affecting peri-implant bone resorption in four Implant supported mandibular full-arch restorations: a 3-year prospective study.

J Clin Periodontol 2016 Jan 26;43(1):92-101. Epub 2016 Jan 26.

Department of Statistics, Johannes Kepler University (JKU) Linz, Austria.

Background: Peri-implant marginal bone-level (MBL) alteration represents one of the parameters included in the criteria for determining implant health.

Objective: Factors affecting peri-implant MBL alteration for 4-implant-supported fixed mandibular prostheses (4-ISFMP) were assessed.

Material & Methods: A 3-year prospective, cohort study was conducted on 44 mandibularly edentulous patients treated with 4-ISFMP. Peri-implant MBL alteration was evaluated radiographically at the 12-, 24- and 36-month follow-ups considering to patient-related risk factors [age, gender, diabetes mellitus, smoking, cardiovascular disease (CVD), rheumatic disorders (RD)] and implant/prosthesis-related features (implant location, keratinized gingiva, denture cantilever length, prosthesis supporting zone, opposing dentition) as well as to peri-implant biological parameters (plaque-, bleeding-, calculus index).

Results: 148/176 implants (37 patients, drop-out: 15%) were followed for 3 years showing significant (p < 0.001) annual differences of MBL alterations over time. The univariate analysis demonstrated differences of MBL alterations for smokers (p = 0.014), for patients with CVD (p = 0.001) and RD (p = 0.011). In the 3-year multivariate analysis, MBL alteration was influenced by time (p < 0.001) and showed relationship with risk factors as smoking (p < 0.002; OR = 18.965), CVD (p < 0.021; OR = 5.172), RD (p < 0.006; OR = 50.171) and plaque-index (p = 0.034; OR = 3.252).

Conclusions: Although peri-implant MBL alteration increased annually, significant odds ratios, were found for patients-related risk factors identifying them potentiating the alterations.
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http://dx.doi.org/10.1111/jcpe.12469DOI Listing
January 2016

Tooth-implant-supported posterior fixed dental prostheses with zirconia frameworks: 3-year clinical result.

Clin Oral Investig 2016 Jun 24;20(5):1079-86. Epub 2015 Sep 24.

, Josef-Heilingbrunner-Str. 2, 93413, Cham, Germany.

Objectives: This case series compared the clinical survival of tooth-implant-supported (TI-S) and tooth-supported (T-S) three-unit fixed dental prostheses (FDPs) with zirconia frameworks and described the incidence of biological and technical complications.

Materials And Methods: Forty-four patients received 27 TI-S FDPs and 22 T-S FDPs. Twenty-seven titanium screw implants were inserted at the dislodged position of two missing posterior teeth. All implants were provided with customized zirconia abutments. Zirconia frameworks were fabricated by a CAD/CAM system and veneered in powder build-up technique. All restorations were cemented with glass ionomer. Baseline evaluation was performed 2 weeks after cementation with recall examinations performed at 6, 12, 24 and 36 months by calibrated investigators. Survival probabilities according to Kaplan-Meier were calculated. Gingival parameters and bone loss were assessed and statistically evaluated.

Results: The mean service time of the FDPs was 35 months (±6). Two technical complications (fracture of veneering porcelain) were observed. One biological complication was recorded. The Kaplan-Meier survival probability was 93.9 % for all types of complications and 100 % related to restorations in service. The type of abutment support (TI-S vs. T-S) had no significant influence on the survival probability (p = 0.412, log rank test). No difference of the gingival parameters was detected between implants and natural teeth.

Conclusions: Tooth-implant-supported zirconia-based FDPs showed similar clinical performance compared to tooth-supported zirconia-based FDPs.

Clinical Relevance: Within the limitations of this case series, tooth-implant-supported FDPs with zirconia frameworks seem to be a reliable treatment option.
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http://dx.doi.org/10.1007/s00784-015-1594-1DOI Listing
June 2016

Fit of 4-unit FDPs from CoCr and zirconia after conventional and digital impressions.

Clin Oral Investig 2016 Mar 30;20(2):283-9. Epub 2015 Jun 30.

Department of Prosthodontics, Dental School of the Ludwig-Maximilian University of Munich, Goethestrasse 70, 80336, München, Germany.

Objectives: To evaluate the marginal and internal fit of CAD/CAM-generated frameworks for 4-unit, fixed dental prostheses (FDPs) from zirconia (Z) and cobalt-chromium alloy (C) made with conventional (CI) and digital impressions (DI).

Materials And Methods: A titanium model was digitized with an intraoral scanner (DI, LAVA™ C.O.S.; 3M ESPE; Seefeld, Germany; n = 12). Additionally, 12 conventional impressions were taken, and referring plaster casts were digitized by a laboratory-scanner (CI, LAVA™ Scan ST; 3M ESPE; n = 12). Frameworks were fabricated (3M ESPE) from cobalt-chromium (DI-C, n = 12; CI-C, n = 12) and zirconia (DI-Z, n = 12; CI-Z, n = 12) from the same datasets. A replica technique was applied to measure the accuracy. The Mann-Whitney U statistical test was applied to detect statistical differences between each material and methodology groups in terms of fit.

Results: Frameworks from DI-C (median 19.07 μm) showed significantly better marginal fit than CI-C (median 64.64 μm, p < 0.001). Frameworks from DI-Z (median 52.50 μm) showed significantly better marginal fit than CI-Z (median 72.94 μm, p = 0.001). Additionally, frameworks from DI-C showed a significantly better marginal fit than DI-Z (p < 0.001).

Conclusions: CI and DI led to a clinically acceptable marginal fit of 4-unit FDPs from cobalt-chromium and zirconia. DI leads to better marginal fit of the cobalt-chromium frameworks; however, no effect on zirconia was found.

Clinical Relevance: The results indicate that DI is suitable for fabricating 4-unit, cobalt-chromium and zirconia frameworks with regard to fit requirements.
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http://dx.doi.org/10.1007/s00784-015-1513-5DOI Listing
March 2016

Implant Impression Techniques for the Edentulous Jaw: A Summary of Three Studies.

J Prosthodont 2016 Feb 1;25(2):146-50. Epub 2015 Jun 1.

University of Munich, Department of Prosthodontics, Munich, Germany.

Purpose: Precise implant-supported restorations require accurate impressions. Transfer, pick-up, and splinted pick-up are commonly used techniques. Several in vitro studies have compared these impression techniques; however, all studies used mechanical evaluation methods. The purpose of this study was to compare the discrepancies of these impression techniques digitally in vitro and in vivo.

Materials And Methods: Four dental implants were inserted in ten polymer mandibular models bilaterally in the regions of the first molars and canines. Three different impressions were made of each model and the models (original and stone casts) were scanned and digitized. Clinically, four implants were inserted in ten edentulous jaws; transfer and splinted pick-up impressions were made. With inspection software, discrepancies between the different impressions were calculated.

Results: The mean discrepancies in the in vitro study of the original polymer model to stone casts were 124 ± 34 μm for the transfer type, 116 ± 46 μm for the pick-up type, and 80 ± 25 μm for the splinted pick-up type, resulting in a mean discrepancy between the transfer and splinted pick-up type of 44 μm (124 - 80 μm). Clinically, the mean discrepancy between these two impression techniques was 280 μm.

Conclusions: The differing results between the transfer and splinted pick-up techniques of in vitro and in vivo data showed the need for clinical data; however, splinted pick-up impressions seemed to produce the most precise results.
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http://dx.doi.org/10.1111/jopr.12305DOI Listing
February 2016

Light transmittance by a multi-coloured zirconia material.

Dent Mater J 2015 23;34(3):310-4. Epub 2015 Apr 23.

Comprehensive Dental Care, Oral Implant Center, Niigata Hospital, Nippon Dental University.

Full-contour zirconia restorations are gaining in popularity. Highly translucent zirconia materials and multi-coloured zirconia blocks might help to overcome the aesthetic drawbacks of traditional zirconia. This study evaluated the transmittance of visible light (400-700 nm) through the four different layers (Enamel Layer EL, Transition Layer 1 TL1, Transition Layer 2 TL2, Body Layer BL) of a multi-coloured zirconia block (KATANA™ Zirconia Multi-Layered Disc (ML)) using a spectrophotometer. Forty specimens (thickness of 1±0.05 mm) from each layer were examined and statistically evaluated at a confidence-level of 5%. Light transmittance was expressed as a percentage of the through-passing light. The following mean values (SD) were found: EL 32.8% (1.5), TL1 31.2% (1.3), TL2 25.4% (1.3) and BL 21.7% (1.1). Significant differences were found between all groups (ANOVA, Student-Newman-Keuls). This multi-coloured zirconia block showed four layers with different light transmittance capabilities. It might therefore be useful for enhancing the aesthetic appearance of full-contour zirconia restorations made from this material.
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http://dx.doi.org/10.4012/dmj.2014-238DOI Listing
February 2017

The Digital One-Abutment/One-Time Concept. A Clinical Report.

J Prosthodont 2015 Oct 5;24(7):580-585. Epub 2015 Jan 5.

Department of Prosthodontics, Munich Dental School, Munich, Germany.

The digital fabrication of dental restorations on implants has become a standard procedure during the last decade. Avoiding changing abutments during prosthetic treatment has been shown to be superior to the traditional protocol. The presented concept for implant-supported single crowns describes a digital approach without a physical model from implant placement to final delivery in two appointments. A 54-year-old man was provided with a single-tooth implant on his left mandibular first molar. Before wound closure, the implant position was captured digitally with an intraoral scanning device. After bone healing at the time of second-stage surgery the final screw-retained crown fabricated without a physical model was inserted. Soft tissue healing took place at the definitive restoration, avoiding abutment changes or changes of the healing cap. These led to stable soft tissues with a minimum of surgery. The benefits of digital fabrication and the unique way to scan the implant right after placement give an additional value that would not be achieved by analog techniques. In addition to financial benefits it represents a biologically advantageous, one-abutment/one-time approach with customized screw-retained, full-contour crowns or cemented crowns on custom abutments.
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http://dx.doi.org/10.1111/jopr.12256DOI Listing
October 2015

Vertical ridge augmentation using the modified shell technique--a case series.

Br J Oral Maxillofac Surg 2014 Dec 26;52(10):945-50. Epub 2014 Sep 26.

University of Munich, Department of Prosthodontics, Goethestr. 70, 80336 Munich, Germany.

Vertical defects of the alveolar crest often restrict the placement of implants. The outcome of vertical augmentation is unpredictable so we aimed to develop a technique that has predictable results. We used autogenous grafts trimmed to shells less than 1mm thick to rebuild the vertical dimensions of the alveolar ridge. The shells were fixed with microscrews and the vertical space between the shell and the residual bone was filled with autogenous particulate bone. Vertical dimensions before and after augmentation were measured and descriptive statistics calculated. A total of 17 patients (10 female, 7 male, mean (SD) age 46 (17) years) had 18 sites augmented (2 sites in one patient). In 2 cases the wound dehisced and healing was by secondary intention. The rest healed uneventfully. The mean (SD) vertical defect was 4.7 (1.4) mm and mean (SD) resorption during consolidation was 0.5 (0.7) mm. All 30 previously planned implants were placed, and none failed during the first year. Loading was monitored for a mean (SD) period of 14.6 (10.5) months. The technique showed promising results and could be an alternative to procedures that use extraoral donor sites.
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http://dx.doi.org/10.1016/j.bjoms.2014.08.009DOI Listing
December 2014

Epithelial attachment and downgrowth on dental implant abutments--a comprehensive review.

J Esthet Restor Dent 2014 Sep-Oct;26(5):324-31. Epub 2014 Mar 11.

Oral Surgery Office, Bahnhofstrasse 20, 87700, Memmingen, Germany.

Unlabelled: The soft tissues around dental implants are enlarged compared with the gingiva because of the longer junctional epithelium and the hemidesmosonal attachments are fewer, suggestive of a poorer quality attachment. Inflammatory infiltrates caused by bacterial colonization of the implant-abutment interface are thought to be one of the factors causing epithelial downgrowth and subsequent peri-implant bone loss. Gold alloys and dental ceramics as well as the contamination of the implant surface with amino alcohols, appear to promote epithelial downgrowth. Physical manipulaton of the abutment surfaces, including concave abutment designs, platform switching, and microgrooved surfaces are believed to inhibit epithelial downgrowth and minimizes bone loss at the implant shoulder. This paper reviews the factors that are believed to influence the migration of epithelial attachment the dental implant and abutment surfaces. Exploration of innovative computer-aided design/computer-aided manufacturing-based concepts such as "one abutment-one time" and their effect on epithelial downgrowth are discussed.

Clinical Significance: Based on the review of current literature, the authors recommend inserting definitive abutments at the time of surgical uncovering. To implement this concept, registration of the implant position should to be taken at the time of surgical implant placement.
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http://dx.doi.org/10.1111/jerd.12097DOI Listing
September 2016

Two-stage horizontal bone grafting with the modified shell technique for subsequent implant placement: a case series.

Int J Periodontics Restorative Dent 2014 Mar-Apr;34(2):269-76

This case series evaluated the graft stability and resorption of a modified shell technique for horizontal ridge augmentation. Autogenous bone shells of 1-mm thickness were fixed with microtitanium screws with the gaps between the shells and ridge filled with autogenous bone chips. In 22 patients, 30 cases were performed to augment 50 regions. Forty-two implants were inserted after a healing period of 5.5 (± 1.0) months. Preoperatively, the mean width of the crest was 2.7 mm (± 0.9), after bone grafting, 6.7 mm (± 0.8), and during implant placement, 5.9 mm (±0.7), and the mean resorption was 0.8 mm (± 0.5) (P < .001). This technique showed promising results. However, due to slight resorption, the ridge should be over contoured.
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http://dx.doi.org/10.11607/prd.1374DOI Listing
February 2016