Publications by authors named "Samir Abou-Ayash"

27 Publications

  • Page 1 of 1

Influence of cyclic loading on load-to-failure of different ceramic CAD-CAM implant-supported single crowns.

Int J Prosthodont 2021 Feb 26. Epub 2021 Feb 26.

Purpose: To compare the load to failure values of different ceramic CAD/CAM implant crown materials with drilled screw access holes with and without cyclic loading applied.

Materials And Methods: Forty zirconia abutments with a titanium base were pre-loaded onto implants to support maxillary right first premolar crowns that were milled from four different CAD/CAM ceramic materials (zirconia reinforced lithium silicate, hybrid ceramic, lithium disilicate, and zirconia; n = 10 each). After cementing the crowns, screw access channels were prepared by drilling through occlusal surfaces. Half of the specimens were subjected to cyclic loading for 5 million cycles at 2 Hz (n = 5/material). After cyclic loading, vertical loads were applied to failure, and the load to failure values of all crowns were recorded and statistically analyzed. Two-way analysis of variance was used with restricted maximum likelihood estimation and Tukey-Kramer adjustments (α = .05).

Results: During cyclic loading, the zirconia abutment in one lithium disilicate specimen cracked at 2 million cycles, as well as a zirconia-reinforced lithium silicate crown. Results for the load to failure test series showed statistical differences between the materials. Zirconia resulted in significantly higher failure loads when compared to the other materials (P < .001). Cyclic loading did not significantly affect the load to failure values.

Conclusion: Cyclic loading did not significantly influence the load to failure of any of the materials tested. Zirconia crowns with drilled screw access channels cemented on zirconia abutments with a titanium base had higher load to failure values compared to the other ceramic crown materials.
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http://dx.doi.org/10.11607/ijp.6510DOI Listing
February 2021

The effect of scanned area on the accuracy and time of anterior single implant scans: an in vitro study.

J Dent 2021 Feb 26:103620. Epub 2021 Feb 26.

Department of Reconstructive Dentistry and Gerodontology, University of Bern, Freiburgstrasse 7, 3007 Bern, Switzerland. Electronic address:

Objectives: To investigate the effect of scanned area on the accuracy and scan time of intraoral scans of an anterior implant.

Materials And Methods: Three operators experienced in intraoral scanning (at least 2-year experience) performed partial and complete-arch scans (n = 10) of a dentate resin model with an implant at left central incisor site by using an intraoral scanner (Trios3; 3Shape, Copenhagen, Denmark). Each partial- or complete-arch scan was superimposed to a reference scan from a laboratory scanner (Ceramill Map 600; Amann Girrbach AG). Mean distance (selected 7 points) and angular (mesiodistal and buccolingual) scanbody deviations in test scans (trueness) and their variance (precision) were calculated. Linear-regressions (trueness), two-sided F-tests with a Bonferroni correction (precision), and multiple linear regressions (scan time), with the operator as a covariate were applied (alpha = .05).

Results: Interactions were found between the scanned area and the operator for their effect on trueness of all points and angles, except for point 6 at implant-abutment connection in mesiodistal plane (p < .05). No significant difference was found between the precision of partial and complete-arch scans for all operators (p > .05). Partial-arch scan times were significantly shorter, overall, and for each operator (p < .001). No significant effect of scan time was found on the trueness of partial- and complete-arch scans (p > .05).

Conclusions: Partial and complete-arch scans of anterior single implants with an intraoral scanner resulted in similar accuracies, and were not influenced by the operator or the scan time. Scan times of partial-arch scans were significantly shorter.

Clinical Significance: Partial-arch scans can be used for the fabrication of monolithic anterior single implant crowns because the scans can be completed in shorter times without compromising the accuracy.
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http://dx.doi.org/10.1016/j.jdent.2021.103620DOI Listing
February 2021

Management of a partially edentulous patient with idiopathic root resorption by using digital and conventional implant planning technologies.

J Prosthet Dent 2021 Feb 23. Epub 2021 Feb 23.

Senior Lecturer, Section for Digital Implant- and Reconstructive Dentistry [DIRecD], Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland. Electronic address:

This clinical report describes the rehabilitation of the maxillary arch of a partially edentulous patient with idiopathic root resorption, limited interarch distance, and a high smile line. Four implants were placed to provide a screw-retained fixed partial denture. The esthetic and functional challenges of a high smile line and limited interarch distance were addressed by using a combination of conventional and digital implant treatment technologies.
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http://dx.doi.org/10.1016/j.prosdent.2021.01.011DOI Listing
February 2021

O-Ring Attachments on One-Piece Mini Dental Implants: In-Vitro Analysis of Retention Force Reproducibility Using Different Pristine Matrix-O-Ring Combinations.

Int J Prosthodont 2021 Feb 23. Epub 2021 Feb 23.

Purpose: To analyze the influence of pristine matrix and O-ring dimensions on retention force and reproducibility in single one-piece mini dental implants (MDIs) with ball patrices under in vitro conditions.

Materials And Methods: Three different matrix and O-ring combinations (MH1-MH3) were evaluated (n = 50 per group) on 1.8-mm-diameter implants. The matrices were manually mounted on the implants and were subsequently removed in a vertical linear manner using a metal pin with two strain gauges, recording the maximum force during disconnection. After five disconnections, the O-rings were exchanged, and the mean retention force was calculated, resulting in 50 values for each matrix and O-ring combination. Mean retention forces, SDs, and 95% CI were calculated. Analysis of variance was used to test the global differences, and post hoc pairwise comparisons were subsequently applied. The level of significance was set to P < .05.

Results: ANOVA (global P < .0001) and pairwise comparisons (all P < .0001) demonstrated statistically significant differences among the three different matrix and O-ring combinations, with mean values of 5.18 N (MH 1), 6.73 (MH 2), and 9.08 (MH 3). Within each combination, retention force variations of > 1 N could not be demonstrated; ie, by exchanging O-rings, a similar retention force can be reestablished.

Conclusion: Matrix and O-ring dimensions have a significant influence on retention forces in one-piece MDIs. Pristine O-rings demonstrated highly reproducible initial retention forces in all matrices.
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http://dx.doi.org/10.11607/ijp.7055DOI Listing
February 2021

Effect of Complete Dentures on Facial Soft Tissue Volume: A 3D Comparative Study.

Int J Prosthodont 2021 Feb 19. Epub 2021 Feb 19.

Purpose: To investigate the volumetric facial soft tissue changes associated with wearing complete dentures using 3D face scans.

Materials And Methods: Forty volunteers, 20 men and 20 women, were recruited for the study and treated with maxillary and mandibular complete dentures. Six facial scans were taken of each subject. Three scans were wearing a complete denture, and three without them. The 3D face scans were captured with the volunteers in three mouth positions: closed, relaxed, and smiling. Each scan was superimposed in order to analyze and quantify the linear measurements of 14 soft tissue landmarks and the total volume that the subject gained with the prosthesis.

Results: Three variables were evaluated in each analysis: gender, mouth attitude, and age category. In the analysis of the soft tissue landmarks, there was a significant effect of age, with patients older than 75 years showing the greatest changes (P < .05). The landmarks that showed the most changes were those located around the mouth. In the volume analysis, the variable with the highest influence was gender, with men gaining more volume than women (P < .05).

Conclusion: Complete dentures have a significant effect on volumetric change in perioral tissues. These changes are marked in patients older than 75 years. Compared to women, men depicted greater volumetric changes with complete dentures. These results open a new avenue for clinicians and developers using face scans to design future restorations for edentulous patients.
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http://dx.doi.org/10.11607/ijp.7057DOI Listing
February 2021

Clinical outcomes and costs of conventional and digital complete dentures in a university clinic: A retrospective study.

J Prosthet Dent 2021 Feb 17. Epub 2021 Feb 17.

Senior lecturer, Extra muros, Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland; Professor, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland. Electronic address:

Statement Of Problem: Scientific data analyzing the clinical outcomes and costs of complete dentures fabricated by using conventional and computer-aided design and computer-aided manufacturing (CAD-CAM) processes are lacking.

Purpose: The purpose of this retrospective study was to compare the treatment duration, financial costs, and postdelivery adjustments of CAD-CAM and conventional removable complete dentures.

Material And Methods: Thirty-two edentulous participants (16 women, 16 men; age 35-85 years) who had received either CAD-CAM (n=16) or conventional (n=16) maxillary and mandibular removable complete dentures provided by prosthodontists with a minimum of 2 years of experience were evaluated. The CAD-CAM denture systems were either DDS-AV (AvaDent Digital Dental Solutions) (n=11) or DD-IV (Wieland Digital Denture) (n=5). The total treatment period (days) was recorded at 3 different time points (T0: preliminary alginate impression; T1: denture delivery; T2: last scheduled postdelivery adjustment). Adjustments during the follow-up (after T2) were noted and included the removal of areas of excessive pressure, relining, or repairs. The costs of the dental treatment and the laboratory fees were calculated. The Wilcoxon rank sum tests were used for statistical analysis (α=.05).

Results: No statistically significant difference regarding the treatment duration between digitally and conventionally fabricated removable complete dentures was found: T-T (P=.889); T-T (P=.675); T- T (P=.978). No significant difference was found in the number adjustments for areas of excessive pressure, relines, or repairs (P=.757, P=1.000, P=1.000) during the period. Laboratory costs of CAD-CAM removable complete dentures were significantly lower than those of conventional removable complete dentures (P<.001), but clinical fees were similar between groups (P=.596), resulting in a reduction in the overall total costs for the CAD-CAM removable complete dentures (P=.011). Regarding the number of clinical visits, neither the group (conventional/CAD-CAM (P=.945)/DDS-AV/DD-IV [P=.848]) nor the interaction group (conventional/CAD-CAM and DDS-AV/DD-IV)/period (P=.084/P=.171) showed any significant differences.

Conclusions: CAD-CAM removable complete dentures can be considered a viable alternative to conventional removable complete dentures regarding treatment duration, clinical and follow-up visits, adjustments, and maintenance requirements.
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http://dx.doi.org/10.1016/j.prosdent.2020.12.014DOI Listing
February 2021

Attitudes of dental students towards treating elderly patients. Dental students’ attitudes on geriatric patients

Swiss Dent J 2021 01 21;131(2). Epub 2021 Jan 21.

Clinic of General, Special Care and Geriatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.

The purpose of this questionnaire-based survey was to evaluate the attitudes of the undergraduate dental students towards elders. The 14-item Geriatric attitudes scale (GAS) questionnaire, along with a 9-item questionnaire with specific questions on the current geriatric dental curriculum, confidence, and preference in treating the elderly patients were administered to the undergraduate dental students (3rd bachelor, 1st master, and 2nd master) in the four Swiss university dental schools. Mean GAS scores were calculated and inter- and intra-group differences were analyzed with ANOVA and post hoc tests (level of significance set at α=0.05). Responses to the 9-item questionnaire were reported descriptively. Further analyses were performed to evaluate the effect of demographic factors on the GAS scores. 305 students (meanage: 25.8±4.0y) participated in this study. The mean overall GAS score of the students was 3.5±0.4. There were no significant differences in the GAS scores between the centers [F(3, 300)=2.266, p=0.081] or between the year of training [F(2, 301)=1.884, p=0.154]. Demographic factors did not influence the GAS scores. Students considered geriatric dentistry as an important part of their dental undergraduate education. The current geriatric curriculum was perceived to be on an adequate level. Hands-on experience in treating geriatric patients in the undergraduate curriculum was positively opinionated, and mobile dental services for elders with limited access to care was considered a good solution. In conclusion, the attitudes of the Swiss undergraduate dental students towards an elderly patient seem acceptable but could still be improved.
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January 2021

Exploring Older Swiss People's Preferred Dental Services for When They Become Dependent.

Swiss Dent J 2020 11 3;130(11):876-884. Epub 2020 Nov 3.

Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland

The objective of this study was to explore the preferred dental services of older people for when they become dependent. It aimed to assess their preferred type of health care professional and location of dental service, and relate their preferences to their willingness to pay (WTP) and willingness to travel (WTT). Older people aged 65 years or older were invited to participate in a questionnaire-based discrete choice experiment (DCE), to measure preferences for dental examinations and treatment, defined by two attributes: type of professional and location of the activity. Hypothetical scenarios based attributes were displayed in a projected visual presentation and participants noted their personal preference using a response sheet. Data was analyzed using a random-effects logit model. Eighty-nine participants (mean age 73.7 ± 6.6 years) attended focus group sessions. Respondents preferred that the family dentist (β: 0.2596) or an auxiliary (β: 0.2098) undertake the examination and wanted to avoid a medical doctor (β: –0.469). The preferred location for dental examination was at a dental practice (β: 0.2204). Respondents preferred to avoid treatments at home (β: –0.3875); they had a significant preference for treatment at the dental office (β: 0.2255) or in a specialist setting (β: 0.1620, ns). However, the type of professional did not have a significant influence on overall preference. Participants with a low WTP preferred examination at home (β: 0.2151) and wanted to avoid the dental practice (β: –0.0235), whereas those with a high WTP preferred the dental office (β: 0.4535) rather than home (β: –0.3029). WTT did not have a significant influence on preference. The study showed that older people generally preferred receiving dental services in a dental practice or specialist setting, and would prefer not to be treated at home. Continuity of dental services provided by the family dentist should therefore be prioritized where possible and further studies should examine the role of domiciliary care at home.
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November 2020

Biological and technical complications in root cap-retained overdentures after 3-15 years in situ: a retrospective clinical study.

Clin Oral Investig 2020 Sep 7. Epub 2020 Sep 7.

Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Objectives: This retrospective clinical study investigates the frequency of biological and technical complications in patients rehabilitated by natural root-retained overdentures (RODs) with cast post-and-cores (root caps) wearing precision attachments and analyses factors influencing complication rates (e.g. oral hygiene routines).

Materials And Methods: Patients formerly treated with RODs were invited for a cost-free clinical visit to evaluate their intraoral status. Furthermore, they were interviewed and patient records were screened for complications occurring since denture delivery. Statistical models include descriptive analyses, Fisher's exact test, odds ratios, and a multivariate regression model.

Results: A total of 114 patients wearing 128 RODs with a total of 280 abutment teeth were evaluated (mean service time: 7.9 years). Technical complications occurred in 68.8% of the RODs, with matrix loosening being the most frequent complication (50.1%). Biological complications occurred in 53.9% of all RODs, with the presence of denture stomatitis being the most common biological complication (38.3%). The presence of denture stomatitis was significantly higher in the maxilla relative to the mandible (p = 0.0029), in subjects cleaning their dentures less than twice a day (p < 0.001), in subjects regularly using CHX-containing products (p = 0.036) and in subjects with a plaque index > 40% (p < 0.001).

Conclusions: Root cap-retained overdentures with precision attachments are a viable treatment option in partially dentate subjects, even over long-term periods. However, high complication rates should be expected.

Clinical Relevance: Establishing good oral hygiene is a decisive factor in preventing complications in RODs. Furthermore, CHX-containing products may not be recommended for routine domestic use.
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http://dx.doi.org/10.1007/s00784-020-03555-3DOI Listing
September 2020

Accuracy of intraoral scanning in completely and partially edentulous maxillary and mandibular jaws: an in vitro analysis.

Clin Oral Investig 2020 Aug 19. Epub 2020 Aug 19.

Section for Digital Implant- and Reconstructive Dentistry [DIRecD], Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Objectives: New generation intraoral scanners are promoted to be suitable for digital scans of long-span edentulous spaces and completely edentulous arches; however, the evidence is lacking. The current study evaluated the accuracy of intraoral scanning (IOS) in partially and completely edentulous arch models and analyzed the influence of operator experience on accuracy.

Materials And Methods: Four different resin models (completely and partially edentulous maxilla and mandible) were scanned, using a new generation IOS device (n = 20 each). Ten scans of each model were performed by an IOS-experienced and an inexperienced operator. An industrial high-precision scanner was employed to obtain reference scans. IOS files of each model-operator combination, their respective reference scan files (n = 10 each; total = 80), as well as the IOS files from each model generated by the same operator, were superimposed (n = 45; total = 360) to calculate trueness and precision. An ANOVA for mixed models and post hoc t tests for mixed models were used to assess group-wise differences (α = 0.05).

Results: The median overall trueness and precision were 24.2 μm (IQR 20.7-27.4 μm) and 18.3 μm (IQR 14.4-22.1 μm), respectively. The scans of the inexperienced operator had significantly higher trueness in the edentulous mandibular model (p = 0.0001) and higher precision in the edentulous maxillary model (p = 0.0004).

Conclusion: The accuracy of IOS for partially and completely edentulous arches in in vitro settings was high. Experience with IOS had small influence on the accuracy of the scans.

Clinical Relevance: IOS with the tested new generation intraoral scanner may be suitable for the fabrication of removable dentures regardless of clinician's experience in IOS.
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http://dx.doi.org/10.1007/s00784-020-03486-zDOI Listing
August 2020

Variability in tongue pressure among elderly and young healthy cohorts: A systematic review and meta-analysis.

J Oral Rehabil 2020 Aug 16. Epub 2020 Aug 16.

Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Objectives: Tongue pressure (TP) is used for the diagnosis of oral hypofunction; however, the impact of several variables on TP is unclear. Therefore, the current systematic review and meta-analysis aimed to analyse the variability in tongue pressure among healthy individuals aged ≥60 years vs <60 years. Secondary outcomes were the influence of gender and the type of measuring device (Iowa Oral Performance Instrument (IOPI) vs JMS tongue pressure measurement device (JMS)).

Methods: PubMed and the Japanese database Ichushi-Web were searched systematically by two independent reviewers for studies reporting TP values in healthy populations. Clinical studies published between 1959 and June 2020 with more than 10 participants, written in English, German or Japanese, were included. A random-effects meta-regression for aggregate-level data was applied (α < 0.05).

Results: Sixty-eight studies reported TP for a total of 13 773 subjects aged <60 years (n = 3265) and ≥60 years (n = 10 508). TP was significantly higher in subjects <60 years (estimated weighted mean (EWM) ± standard error = 51.9 ± 1.28 kPa; 95% CI = 49.4-54.4) relative to those ≥60 (EWM = 34.7 ± 0.94 kPa; 95% CI = 32.8-36.5) (P < .001), men (EWM = 45.9 ± 2.09 kPa; 95% CI = 41.8-50.0) relative to women (EWM = 39.3 ± 1.68 kPa; 95% CI = 36.0-42.6) (P = .015) and when assessed with the IOPI (EWM = 51.9 ± 1.32 kPa; 95% CI = 49.3-54.5) compared to the JMS (EWM = 33.5 ± 0.63 kPa; 95% CI = 32.2-34.7) (P < .001). In terms of gender, there was no significant difference in TP among subjects ≥60 years (P = .282). However, in subjects younger than 60, a significant difference was observed (P = .004).

Conclusions: Healthy populations aged <60 years showed significantly higher TP than those aged ≥60 years. TP values ascertained by the IOPI are significantly higher than those obtained with the JMS.
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http://dx.doi.org/10.1111/joor.13076DOI Listing
August 2020

Platform switching in two-implant bar-retained mandibular overdentures: 1-year results from a split-mouth randomized controlled clinical trial.

Clin Oral Implants Res 2020 Oct 8;31(10):968-979. Epub 2020 Aug 8.

Department of Reconstructive Dentistry and Gerodontology, University of Bern, Bern, Switzerland.

Objectives: The concept of platform switching is widely applied in current implant dentistry; however, the influence on peri-implant bone-level alterations (ΔIBL), especially in the field of implant overdentures (IODs), remains inconclusive. Therefore, the present study aimed to test the alternative hypothesis that there is an equivalent ΔIBLs at platform-switching and platform-matching implant abutments in 2-implant bar-retained IODs.

Materials And Methods: Two interforaminal implants were placed in 32 subjects, who were randomly assigned to either an immediate- or a 3-month post-placement loading group. Furthermore, one implant in each subject was randomly assigned to receive a platform-switched abutment (test), and one a platform-matching abutment (control). The implants were splinted with prefabricated, chairside customized bars. ΔIBL was recorded by using customized radiograph holders at implant placement, implant loading, 3 months, 6 months, and 12 months after loading.

Results: After 1 year, equivalent ΔIBL could be identified (test: -0.51 mm ± 0.49 versus control: -0.56 mm ± 0.52; p < .001). ΔIBL increased over time and was more pronounced in the delayed-loaded implants (-0.87 mm ± 0.61) relative to the immediately loaded implants (-0.35 mm ± 0.43; p = .022).

Conclusions: The prosthetic concept of platform switching does not necessarily lead to reduced bone loss. Immediate-loading of implants, primarily splinted with a bar, might be beneficial regarding peri-implant bone-level alterations over a short-term period.
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http://dx.doi.org/10.1111/clr.13640DOI Listing
October 2020

Root-retained overdentures: Survival of abutment teeth with precision attachments on root caps depends on overdenture design.

J Oral Rehabil 2020 Oct 3;47(10):1254-1263. Epub 2020 Aug 3.

Department of Reconstructive Dentistry and Gerodontology, University of Bern, Bern, Switzerland.

Background: Root-retained overdentures (OD) are one treatment option for partially edentulous patients. However, the available evidence regarding factors influencing abutment survival in root-retained ODs is limited.

Purpose: This retrospective study included clinical examinations and evaluated the survival rate of roots restored with precision attachments soldered to post-and-core (gold cap) retained ODs, analysed with respect to various patient- and prosthesis-related factors.

Methods: Patients receiving at least one OD with gold caps in the past were invited for comprehensive clinical examinations. The primary outcome parameter was the abutment survival rate over the observation period (2002-2016). Possible contributing factors (eg closed vs open OD design) were analysed. Analyses included Kaplan-Meier estimators, Cox regressions and hazard ratios (HR).

Results: 114 patients with 128 ODs originally retained by 280 abutments, with a cumulative total exposure time of 2035.4 years, were examined. Twenty-seven abutment teeth (9.6%) were lost after a mean observation period of 7.9 ± 3.4 years. Significant factors associated with abutment loss were a closed, compared to an open OD design (HR 8.38 (95% CI 1.11-63.59), P = .040), which was independent of the number of abutments per OD. Furthermore, the loss rate was higher when the denture was not worn day-and-night (HR 3.52 (95% CI 1.32-9.40), P = .012). Oral hygiene behaviour was associated with higher HRs.

Conclusions: ODs remain a viable treatment option for patients with few teeth remaining in the dental arch. It is advisable to choose an open design for the OD, irrespective of the number of abutment teeth. Furthermore, gold cap-retained ODs should not be removed overnight.
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http://dx.doi.org/10.1111/joor.13060DOI Listing
October 2020

Reliability and comparability of methods for assessing oral function: Chewing, tongue pressure and lip force.

J Oral Rehabil 2020 Jul 21;47(7):862-871. Epub 2020 Apr 21.

Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Background: Quantitative clinical assessment tests for oral function have become popular in patient assessment; however, their comparability remains unclear.

Objective: To assess the reliability and comparability of pairs of different instruments for measuring maximum tongue pressure (MTP), chewing function (CF) and maximum lip force (MLF), and to analyse the influence of subjects' characteristics on the applied instruments.

Methods: Each pair of instruments, as well as a single device measuring the maximum voluntary bite force (MBF), was assessed across 26 healthy volunteers. The respective pairs of devices were compared using Bland-Altman plots and linear regression analysis. Furthermore, the influence of age, occlusal support zones, number of functional occlusal units, MBF, MTP and MLF were investigated as predictors on CF using a generalised estimating equation model.

Results: Neither the two assessments of CF, nor of MLF were correlated to each other, but there was a significant correlation between the assessments of MTP. Hue-Check Gum was able to demonstrate a significantly higher CF in younger compared to older individuals (P = .004) and individuals with high numbers compared to low numbers of occlusal units (P < .001). Those differences could not be demonstrated with the Vivident chewing gum.

Conclusion: The absolute values of MTP assessed by the two applied devices cannot directly be compared, although normalised values may be directly comparable. Moreover, our observations suggest that the Hue-Check Gum was able to discriminate the effects of age and the number of occlusal units on CF. Our observations suggest that the two gums cannot be used interchangeably.
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http://dx.doi.org/10.1111/joor.12976DOI Listing
July 2020

Clinical outcomes and bone-level alterations around one-piece mini dental implants retaining mandibular overdentures: 5-year follow-up of a prospective cohort study.

Clin Oral Implants Res 2020 Jun 9;31(6):549-556. Epub 2020 Mar 9.

Department of Reconstructive Dentistry and Gerodontology, University of Bern, Bern, Switzerland.

Objectives: To report on the clinical outcomes of one-piece mini dental implants (MDIs) retaining mandibular implant overdentures (IODs), including marginal bone-level alterations (ΔMBLs), clinical peri-implant parameters, and technical- and biological complications during a 5-year follow-up. The null hypothesis was that ΔMBLs would be equal in subjects older than 65 years relative to younger subjects.

Materials And Methods: Four 1.8-mm diameter one-piece MDIs with ball attachments were placed in the interforaminal region of 20 edentulous subjects. The existing complete dentures were converted to IODs. Standardized radiographs of each implant were taken at implant placement (baseline) and during the five-year follow-up. ΔMBLs and potential influencing factors were evaluated, and peri-implant parameters, and biological and technical complications were recorded.

Results: The implant and prosthetic survival rates were both 100%. IODs fractured in seven participants. The overall mean ΔMBL after 5 years was -1.18 mm (standard deviation: 0.79 mm). ΔMBLs per month were most pronounced within the first 3 months after implant placement. ΔMBLs were not influenced by the implant location, the presence of keratinized mucosa, or gender. However, ΔMBLs were significantly smaller in subjects older than 65 years (p = .007).

Conclusions: One-piece MDIs retaining mandibular IODs with O-ring attachments are a predictable treatment option, providing stable peri-implant bone and soft tissue conditions over a mid-term follow-up. Incorporating a metal reinforcement can prevent denture fracturing when converting a complete denture into an IOD. The presence of keratinized mucosa does not necessarily lead to decreased bone-level changes. Advanced age might be beneficial in terms of peri-implant bone stability.
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http://dx.doi.org/10.1111/clr.13591DOI Listing
June 2020

Use of an attachment system with angulated abutments and polyetheretherketone inserts to retain a maxillary overdenture: A clinical report.

J Prosthet Dent 2020 Aug 29;124(2):129-134. Epub 2019 Nov 29.

Professor, Division of Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; Privat Docent, Division of Gerodontology and Removable Prosthodontics, University of Geneva, Geneva, Switzerland.

This clinical report describes the rehabilitation of a maxillary edentulous arch with a current overdenture attachment system with angulated prefabricated abutments and polyetheretherketone (PEEK) inserts. Prefabricated angulated abutments were used on previously and recently placed diverging implants, which enabled a common path of insertion for the overdenture to be established during fabrication.
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http://dx.doi.org/10.1016/j.prosdent.2019.07.013DOI Listing
August 2020

A digital cast-free clinical workflow for oral rehabilitation with removable partial dentures: A dental technique.

J Prosthet Dent 2020 May 2;123(5):680-685. Epub 2019 Aug 2.

Head of Section for Digital Implant- and Reconstructive Dentistry [DIRecD], Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland. Electronic address:

The present report describes a technique for a digital cast-free clinical workflow for the fabrication of a combined tooth-implant-supported removable partial denture. This technique comprises digital intraoral scanning, computer-aided design, and subtractive computer-aided manufacturing for the denture base, denture teeth, and crowns and additive computer-aided manufacturing for the denture framework (CAD-CAM).
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http://dx.doi.org/10.1016/j.prosdent.2019.05.008DOI Listing
May 2020

Evolution of in vivo assessed retention forces in one-piece mini dental implant-retained mandibular overdentures: 5-Year follow-up of a prospective clinical trial.

Clin Implant Dent Relat Res 2019 Oct 16;21(5):968-976. Epub 2019 Jul 16.

Division of Gerodontology, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Switzerland.

Background: The evolution of retention forces in one-piece mini dental implants (MDIs) retaining implant overdentures (IODs) is of major importance, as the male parts cannot be exchanged, due to the implant design.

Purpose: To report the evolution of retention forces of one-piece MDIs, retaining mandibular IODs with ball/ O-ring attachments during 5 years assessed in vivo.

Materials And Methods: Four MDIs were installed in the interforaminal region and immediately loaded using the existing mandibular complete denture. Directly post-op, at the 1-year and the 5-year follow-up, the retention forces were assessed with a validated strain gauge at each implant site separately.

Results: At the male part, changes could only be observed at implant site 34: During the first year, there was a statistically significant increase, whereas the retention forces were decreased at the 5-year follow-up. At the female part, retention forces decreased significantly over time. Baseline values could be reestablished by exchanging the O-rings. The changes of the retention forces were more obvious in the posterior, compared to the anterior implants.

Conclusions: Retention forces at the female part decrease significantly over time, when retaining mandibular IODs by MDIs with ball/ O-ring attachments. Baseline values can be reestablished by exchanging the O-rings. At the male part, changes of retention forces depend on the implant location.
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http://dx.doi.org/10.1111/cid.12816DOI Listing
October 2019

A digital intraoral implant scan technique using a combined healing abutment and scan body system.

J Prosthet Dent 2020 Feb 12;123(2):206-209. Epub 2019 Jul 12.

Senior Lecturer, Section for Digital Implant and Reconstructive Dentistry [DIRecD], Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland. Electronic address:

Multiple clinical appointments are generally needed after implant placement for the delivery of definitive implant-supported crowns. Digital and conventional workflows are accompanied by the frequent connection and disconnection of prosthetic components such as healing abutments, interim crowns, impression posts, and definitive abutments before the placement of definitive crowns. Repetitive removal of these components may result in trauma on the component-peri-implant soft tissue interface. This report describes a technique for the fabrication of an implant-supported crown by using a combined healing and scan body abutment in a digital workflow. This technique reduces the number of appointments and allows the formation of a soft tissue emergence profile similar to that of the definitive crown, which can help minimize patient discomfort during placement of an implant crown.
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http://dx.doi.org/10.1016/j.prosdent.2019.01.016DOI Listing
February 2020

Stabilizing mandibular complete dentures by a single midline implant-influence on quality of life: 2-year results from a randomized clinical trial comparing different loading protocols.

Clin Oral Investig 2020 Feb 27;24(2):927-935. Epub 2019 Jun 27.

Department of Prosthodontics, Propaedeutics and Dental Materials, Christian-Albrechts University of Kiel, Kiel, Germany.

Objectives: The knowledge about the influence of dental treatment on health-related quality of life (HRQoL) is still limited. The aim of this multicenter randomized controlled clinical trial was to assess the effect of stabilizing an existing complete denture, by means of a single mandibular implant, on HRQoL. Furthermore, the impact of the loading protocol, i.e., immediate or delayed loading, in edentulous patients was evaluated.

Methods: One hundred fifty-eight participants aged 60-89 years were randomly assigned to study group A (immediate loading; n = 81) and to group B (delayed loading; n = 78). All participants received a single midline implant in the mandible. The implants were either immediately loaded (group A) or after a closed healing period of 3 months (group B) by connecting the existing mandibular complete dentures to ball attachments. HRQoL was assessed with the Short Form-36 questionnaire of health (SF-36) at baseline, 4 months, and 24 months after implant loading.

Results: Improvement of HRQoL by means of a single implant-retained mandibular overdenture could not be demonstrated after 4 and 24 months of implant loading. Furthermore, the application of two different loading protocols did not influence HRQoL ratings of study participants.

Conclusion: The loading protocol is not a factor, influencing HRQoL in patients treated by a single midline implant in the edentulous mandible.

Clinical Relevance: A single midline implant in the edentulous mandible, stabilizing a mandibular complete denture, cannot be recommended for improving HRQoL.
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http://dx.doi.org/10.1007/s00784-019-02969-yDOI Listing
February 2020

The influence of prosthetic material on implant and prosthetic survival of implant-supported fixed complete dentures: a systematic review and meta-analysis.

J Prosthodont Res 2019 Jul 11;63(3):251-265. Epub 2019 Mar 11.

Department of Prosthodontics, Tufts University School of Dental Medicine, Boston, MA, United States. Electronic address:

Purpose: Evaluating the impact of the prosthetic material on implant- and prosthetic survival of implant-supported fixed complete dentures.

Study Selection: Electronic and hand searches were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) to identify clinical studies including at least 10 patients restored with implant-supported dentures. The primary outcome was to evaluate the implant survival rate according to the applied restorative materials. The prosthetic survival rate was evaluated as secondary outcomes.

Results: Forty-one of 2254 studies were finally selected. A statistically significant difference (p = 0.0337) was found between implant survival rates in the main restorative groups (metal-ceramic:97%(95%CI [0.96;0.98]), all-ceramic:99%(95%CI [0.98;1.00]), metal-resin:97%(95%CI [0.96;0.98])). Prosthetic survival rates were: (metal-ceramic:95%(95%CI [0.89;0.97]), all-ceramic:97%(95%CI [0.92;0.99]), metal-resin:97%(95%CI [0.95;0.98]), with no statistically significant difference (p = 0.3796) between the groups. Chipping incidence rates were as follows: metal-ceramic:8%(95%CI[0.03;0.20]), all-ceramic:15%(95%CI [0.06;0.32]), and metal-resin:22%(95%CI [0.13;0.33]). Five types of exact restorative materials were identified (porcelain-fused-to-non-precious alloy, porcelain-fused-to-zirconia, precious-metal-acrylic-resin, non-precious-metal-acrylic resin, and PMMA). Again, implant survival rates were statistically significantly influenced by the applied restorative materials (p = 0.0126), whereas, no significant differences were reported regarding prosthetic survival rate.

Conclusions: Prosthetic material selection seems to have no clinically relevant influence on implant- and prosthetic survival rate in implant-supported fixed complete dentures. Due to the high chipping rate, quantifying prosthetic survival alone does not seem to be a reliable tool for evaluating the outcome of the restorations and providing recommendations. These results, along with the obvious lack of evidence, suggest that clinicians must exercise caution whenever porcelain-fused-to-zirconia or metal-resin restorations are considered.
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http://dx.doi.org/10.1016/j.jpor.2019.02.001DOI Listing
July 2019

Group 3 ITI Consensus Report: Patient-reported outcome measures associated with implant dentistry.

Clin Oral Implants Res 2018 Oct;29 Suppl 16:270-275

Universidad Inter Continental, Mexico City, Mexico.

Objectives: The aim of Working Group 3 was to focus on three topics that were assessed using patient-reported outcome measures (PROMs). These topics included the following: (a) the aesthetics of tooth and implant-supported fixed dental prostheses focusing on partially edentulous patients, (b) a comparison of fixed and removable implant-retained prostheses for edentulous populations, and (c) immediate versus early/conventional loading of immediately placed implants in partially edentate patients. PROMs include ratings of satisfaction and oral health-related quality of life (QHRQoL), as well as other indicators, that is, pain, general health-related quality of life (e.g., SF-36).

Materials And Methods: The Consensus Conference Group 3 participants discussed the findings of the three systematic review manuscripts. Following comprehensive discussions, participants developed consensus statements and recommendations that were then discussed in larger plenary sessions. Following this, any necessary modifications were made and approved.

Results: Patients were very satisfied with the aesthetics of implant-supported fixed dental prostheses and the surrounding mucosa. Implant neck design, restorative material, or use of a provisional restoration did not influence patients' ratings. Edentulous patients highly rate both removable and fixed implant-supported prostheses. However, they rate their ability to maintain their oral hygiene significantly higher with the removable prosthesis. Both immediate provisionalization and conventional loading receive positive patient-reported outcomes.

Conclusions: Patient-reported outcome measures should be gathered in every clinical study in which the outcomes of oral rehabilitation with dental implants are investigated. PROMs, such as patients' satisfaction and QHRQoL, should supplement other clinical parameters in our clinical definition of success.
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http://dx.doi.org/10.1111/clr.13299DOI Listing
October 2018

Patient-reported outcome measures focusing on aesthetics of implant- and tooth-supported fixed dental prostheses: A systematic review and meta-analysis.

Clin Oral Implants Res 2018 Oct;29 Suppl 16:224-240

Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Objectives: The aim of this systematic review and meta-analysis was to summarize the existing evidence on patient-reported aesthetic outcome measures (PROMs) of implant-supported, relative to tooth-supported fixed dental prostheses.

Material And Methods: In April 2017, two reviewers independently searched the Medline (PubMed), EMBASE, and Cochrane electronic databases, focusing on studies including patient-reported aesthetic outcomes of implant- and tooth-supported fixed dental prostheses (FDPs). Human studies with a mean follow-up period of at least 1 year, a minimum of ten patients, and English, German, or French publication were included. For the comparison of subgroups, random-effects meta-regression for aggregate-level data was used.

Results: The systematic search for implant-supported prostheses focusing on patient-reported outcomes identified 2,675 titles, which were screened by two independent authors. Fifty full-text articles were analyzed, and finally, 16 publications (including 19 relevant study cohorts) were included. For tooth-supported prostheses, no studies could be included. A total of 816 implant-supported reconstructions were analyzed by patients. Overall aesthetic evaluation by the patients' visual analogue scale (VAS) rating was high in implant-supported FDPs (median: 90.3; min-max: 80.0-94.0) and the surrounding mucosa (median: 84.7; min-max: 73.0-92.0). Individual restorative materials, implant neck design (i.e., tissue or bone level type implants), and the use of a fixed provisional had no effect on patients' ratings of the definitive implant-supported FDPs.

Conclusions: Aesthetics is an important patient-reported measure, which lacks in standardized methods; however, patients' satisfaction was high for implant- supported FDPs and the surrounding mucosa.
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http://dx.doi.org/10.1111/clr.13295DOI Listing
October 2018

Computer-Aided Design/Computer-Assisted Manufacture Monolithic Restorations for Severely Worn Dentition: A Case History Report.

Int J Prosthodont 2017 November/December;30(6):530–532. Epub 2017 Oct 30.

Full-arch rehabilitation of patients with severe tooth wear due to parafunctional behavior is a challenge for dentists and dental technicians, especially when a highly esthetic outcome is desired. A variety of different treatment options and prosthetic materials are available for such a clinical undertaking. The ongoing progress of computer-aided design/computer-assisted manufacture technologies in combination with all-ceramic materials provides a predictable workflow for these complex cases. This case history report describes a comprehensive, step-by-step treatment protocol leading to an optimally predictable treatment outcome for an esthetically compromised patient.
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http://dx.doi.org/10.11607/ijp.5500DOI Listing
February 2018

Impact of prosthetic material on mid- and long-term outcome of dental implants supporting single crowns and fixed partial dentures: A systematic review and meta-analysis.

Eur J Oral Implantol 2017;10 Suppl 1:47-65

Aim: The impact of prosthetic material selection on implant survival is not clear. The current criteria for choosing a prosthetic material seem to be based on clinician preferences. This systematic review aims to evaluate the impact of restorative materials on the mid- and long-term survival of implants supporting single crowns and fixed partial dentures.

Materials And Methods: Hand and MEDLINE searches were performed to identify relevant literature for single crowns (SC) and fixed partial dentures (FPD). Further inclusion criteria were a mean follow-up period of at least 3 years, the inclusion of at least 10 patients in a relevant study cohort, and a clear description of prosthesis type and prosthetic material.

Results: A total of 63 studies for the SC group and 11 studies for the FPD group were included. Full arch restorations were not included. The materials utilised in the SC group were metal-ceramic (precious and non-precious), lithium-disilicate, veneered zirconia, veneered alumina, and nanoceramics. The materials used in the FPD group were metal-ceramic (precious), veneered titanium, metal-resin (precious), and veneered zirconia. No significant impact on the prosthetic material relating to mid- or long-term implant survival was identified. Furthermore, there were no statistically significant differences between the survival rates of the dental prostheses made from different materials (SC and FPD group). Single crowns made of nanoceramics showed a higher risk for decementation relative to other materials (0.80, 95% CI [0.67; 0.89]; P < 0.0001), whereas metal-resin FPDs showed a higher risk for chipping (0.36, 95% CI [0.23; 0.52]; P = 0.0072).

Conclusion: The current evidence suggests that prosthetic material selection has no influence on mid- and long-term survival of implants restored with single crowns and fixed partial dentures. Similarly, the prosthetic material seems to have no significant impact on prosthetic survival rates. Further research is required to provide more evidence regarding the impact of the prosthetic material on long-term outcome. Conflict-of-interest statement: The authors declare that they have no conflict of interest.
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March 2018

Single mandibular implant study (SMIS) - masticatory performance - results from a randomized clinical trial using two different loading protocols.

J Dent 2017 Oct 10;65:64-69. Epub 2017 Jul 10.

Department of Prosthodontics, Propaedeutics and Dental Materials, Christian-Albrechts University at Kiel, Kiel, Germany.

Objectives: This multi-centre randomized controlled trial was conducted to investigate, whether the masticatory performance of elderly edentulous patients is improved by placement of a single implant in the midline of the edentulous mandible, and whether improvements differ with respect to the loading protocol, i.e., implant is loaded either directly or three months later after second stage surgery.

Methods: Edentulous seniors aged 60-89 years were screened according to inclusion and exclusion criteria and 163 underwent implant placement. Of those, 158 were randomly assigned either to the direct loading group A (n=81) or the conventional loading group B (n=77). Chewing efficacy was obtained before treatment, one month after implant placement during the submerged healing phase (only group B) and 1 and 4 months after implant loading.

Results: The masticatory performance increased over time in both groups. Four months after loading, a significant increase was observed for both groups compared to the baseline data without implant (p≤0.05). However, between the two groups, chewing efficiency did not differ significantly at any point in time (p>0.05).

Conclusions: A single midline implant in the edentulous mandible increases masticatory performance significantly, independently from the loading protocol.

Clinical Significance: A single midline implant in the edentulous mandible increases masticatory performance. The loading protocol has no influence.
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http://dx.doi.org/10.1016/j.jdent.2017.07.005DOI Listing
October 2017

Single Mandibular Implant Study: Recruitment Considerations.

Int J Prosthodont 2017 Jan/Feb;30(1):43-46

Purpose: The aim of this multicenter single mandibular implant study was to compare the clinical outcome of an immediately loaded implant placed in the midline of an edentulous mandible with the clinical outcome when closed healing and delayed loading is chosen. Here, the patient recruitment period and the main reasons for exclusion were analyzed.

Materials And Methods: Patient recruitment was performed at nine German universities. Rather conservative inclusion and exclusion criteria, including denture satisfaction, denture status, a psychologic symptom checklist, and a defined bone height in the posterior mandible, had to be fulfilled. It was initially calculated that 230 persons would have to be screened within 13 months to include 180 persons in the trial.

Results: Within 13 months (December 2012 to December 2013), 201 patients were screened for possible inclusion in the trial and 148 met the inclusion criteria. Finally, after the recruitment period was extended by 2.5 months, 224 patients were screened and 169 were included. Of those screened, 55 (24.6%) did not meet the inclusion criteria and were excluded. Another 4 patients (1.8%) were excluded based on their psychologic symptom checklist score, while 5 others (2.8%) showed signs of noncompliance. A further 8 patients (4.4%) decided not to participate and withdrew their informed consent, and another 3 (1.3%) were no longer available after screening. Another 2 patients were excluded due to medical contraindications and 1 due to an insufficient mandibular denture. In 34 cases (15.2%), the residual bone height did not comply with McGarry type II or III.

Conclusion: Within the limitations of this patient recruitment period, it can be concluded that residual bone height is the most important factor when considering elderly edentulous patients for implant therapy. The psychologic symptom checklist score was less important.
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http://dx.doi.org/10.11607/ijp.4975DOI Listing
March 2017