Long-term clinical outcome of three-unit fixed-fixed posterior zirconia ceramic inlay-retained FDPs with a modified design.

OBJECTIVES: To assess the long-term clinical outcome of posterior inlay-retained fixed dental prostheses (IRFDPs) with a modified design made from zirconia ceramic. METHODS: In 30 patients thirty 3-unit IRFDPs were placed to replace 7 premolars (4 in the maxilla, 3 in the mandible), and 23 first molars (15 in the maxilla, 8 in the mandible). Preparations were accomplished in agreement with the general principles for ceramic inlay restorations and modified with a short retainer-wing bevel preparation within the enamel at the buccal and oral sides. The frameworks were milled from 3Y-TZP ceramic, and the pontics were veneered with feldspathic ceramic. All IRFDPs were bonded with a phosphate monomer containing luting resin after air-abrasion of the intaglio surfaces. The patients were recalled 6-12 months after placement, and then annually. Kaplan-Meier analysis was used to calculate the survival and complication rates of the IRFDPs. RESULTS: The mean observation time was 10.6 ± 1.5 years. The 10-year cumulative survival rate was 89% with 4 failures, two of them were due to deep secondary caries with loss of retention, one due to repeated debonding with enamel fractures, and one due to generalized progressive periodontitis. The most common complication was chipping of the veneering ceramic (20.1%). Eighteen IRFDPs were free of any type of complication up to 15.4 years, which corresponds to a 10-year cumulative success rate of 70.4%. CONCLUSION: The long-term clinical performance of modified IRFDPs made of veneered zirconia ceramics was favorable after 10 years, therefore, they represent a treatment alternative to replace posterior single missing teeth. CLINICAL SIGNIFICANCE: Zirconia-based IRFDPs fabricated in the modified design may represent a substance-preserving alternative to conventional posterior FDPs to replace posterior single missing teeth, particularly in cases where implants cannot be placed, and when the adjacent teeth already have small restorations or defects.

The Single Midline Implant in the Edentulous Mandible-Current Status of Clinical Trials.

The single midline implant in the edentulous mandible is a treatment concept that has often been controversially discussed. Nearly 30 years ago, the first available clinical results revealed high implant survival rates and remarkable improvements in oral comfort, function, patient satisfaction and oral health-related quality of life for edentulous patients compared to the situation with no implant. However, the clinical trials were predominantly conducted with a small number of patients over a short to medium follow-up period. Today, numerous clinical investigations on the single midline implant in the edentulous mandible, which increasingly include longer-term observation periods, are available. It is the aim of this overview to present the current literature and to highlight the clinical problems. This article is a 2023 update of a review published by the authors in the German language in 2021 in the German journal Implantologie. In total, 19 prospective clinical trials with a follow-up period of 0.5-10 years were analyzed. Over this observation period, single implants with modern rough implant surfaces in the edentulous mandible reveal high implant survival rates of between 90.9 and 100% when a conventional delayed loading protocol was applied.

Influence of the number of implants in the edentulous mandible on chewing efficacy and oral health-related quality of life-A within-subject design study.

OBJECTIVES: To investigate the chewing efficiency and oral health-related quality of life of edentulous patients wearing complete dentures, successively supported by one, two, and three implants in the mandible. METHODS: Thirteen (13) edentulous patients of at least 50 years of age received three implants in the mandible. After a conventional submerged healing period, the central implant was uncovered and connected to the denture base using a stud attachment. Two months later, chewing efficacy was evaluated, and the two lateral implants were uncovered and connected to the denture base. The central retention element was replaced by a short healing abutment with no connection to the denture base. Chewing efficiency was evaluated two months later. Afterward, the healing abutment of the central implant was replaced by a stud attachment and again connected to the denture base. Two months later, chewing efficacy was evaluated again. Oral health-related quality of life (OHRQoL) was measured at each recall visit using the summary score of the oral health impact profile. For statistical analysis of chewing efficacy, the changes from baseline (with no implants) to one, two, and three implants were used and tested by analysis of variance with repeated mesurements. RESULTS: Chewing efficacy clearly increased after implant loading, with a significant increase when two implants were loaded (p ≤ .05), compared to the chewing efficacy with no implants. OHRQoL also significantly improved after implant loading. CONCLUSIONS: Within the limitations of the present clinical trial regarding the number of patients, chewing efficacy as well OHRQoL of edentulous patients improve after implant placement in the mandible, irrespective of the number of implants. The best chewing efficacy was achieved with two implants.

5-year randomized multicenter clinical trial on single dental implants placed in the midline of the edentulous mandible.

OBJECTIVES: This multicenter randomized controlled clinical trial was conducted to investigate whether the loading protocol of single dental implants placed in the midline of edentulous mandibles will influence the implant survival or prosthetic maintenance. MATERIALS AND METHODS: In total, 158 patients were randomly assigned either to the immediate loading group (n = 81) or to the delayed loading group (n = 77). All implants were loaded with an overdenture retained by a ball attachment. RESULTS: After 5 years, 102 patients attended the follow-up investigation. Immediately loaded single implants in the midline of the edentulous mandible revealed a statistically significant lower survival rate than implants loaded conventionally over an observation period of 5 years. In the immediate loading group, 9 implants failed within the first three months of implant loading. No further implant loss was recorded for this group. Two implants failed in the delayed loading group, whereas one implant had to be removed during second-stage surgery and the second five years after implant loading. Non-inferiority of the survival rate of the midline implant of the immediate loading group, compared with the delayed loading group, could not be shown (p = .79, CI immediate loading: 74.9%; 100.0%, CI delayed loading: 73.0%; 100.0%). The observed difference in implant survival between the two treatment groups over time was statistically significant. CONCLUSIONS: The results of the present study indicate that immediate loading of a single mandibular implant in the edentulous mandible should be considered only in exceptional cases.

Retention and wear of resin matrix attachments for implant overdentures.

OBJECTIVES: The aim of the present laboratory study was to investigate the retentive properties and the wear of three different resin matrix attachments for implant overdentures as well as to assess the effects of implant angulation. METHODS AND MATERIALS: Three attachment systems with either polyetheretherketone inserts (PEEK; Novaloc, Straumann, Basel, Switzerland), polyetherketoneketone inserts (PEKK; CM Loc, Cendres + Métaux, Biel, Switzerland) or nylon inserts (Locator R-Tx, Zest Dental Solutions, Escondido, California, USA) were evaluated. The patrices were connected to their implant analogues and fixed in a resin cast at implant angulations of 0° and 15°. The corresponding matrices with inserts were fixed in a stylized unilaterally removable dental prothesis. To simulate masticatory forces 30,000 insertion and removal cycles with an eccentric load of 100 N at a distance of 12 mm were performed in a chewing simulator. The retention forces were measured. The wear patterns were examined using a scanning electron microscope (SEM). The statistical analysis was performed using a one-way ANOVA followed by a Games-Howell test and a Friedman test. RESULTS: All attachment systems revealed a significant decrease in retention after testing, except PEEK 0°/0° and PEEK 15°/15°. PEEK and PEKK attachment systems showed significantly higher retentive forces than the nylon attachment system between 5000 and 30,000 cycles. The implant angulation did not significantly influence the retention behavior for any of the three attachment systems. Patrices showed no signs of wear, whereas the matrix inserts displayed signs of deformation. CONCLUSION: Within the limitations of the present study, attachments with PEEK and PEKK inserts combined with titanium patrices are favorable for long-term use, both for orthogonal and tilted implants. All three attachment systems showed a high variability of the retentive forces at baseline and for subsequent cycles. This should be taken into consideration for clinical use.

Long-term clinical outcome of posterior metal-ceramic crowns fabricated with direct metal laser-sintering technology.

OBJECTIVES: To evaluate the long-term clinical outcome of posterior metal-ceramic crowns fabricated with CAD/CAM-based laser-sintering technology (BEGO Medical, Bremen, Germany). MATERIALS AND METHODS: Sixty posterior crowns were placed in 39 patients. After tooth preparation, impression taking and model casting, the stone dies were scanned to create STL data, followed by manufacturing of crown frameworks with laser-sintering technology. A base metal alloy (CoCr) and a precious alloy (AuPt) were used for 31 and 29 posterior crowns, respectively, which were veneered using the layering technique. All crowns were cemented using glass-ionomer cement. RESULTS: The mean observation period was 10.5 ±â€¯3.9 years. Six patients with 10 crowns were regarded as dropout. Nine crowns had been removed, three of them were intact but they were removed due to a new prosthetic treatment plan. The cumulative survival rate of all crowns was 81% after 14.7 years. When comparing the survival rates related to the alloy used, the Gehan-Wilcoxon test showed no significant differences between both alloys. Biological complications were most commonly reported, while technical complications did not affect the function of the crowns. CONCLUSION: The long-term clinical outcome of posterior metal-ceramic crowns fabricated with CAD/CAM-based laser-sintering technology is very promising, so that this novel technique could be an alternative to the traditional lost wax casting process.

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.

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.

Three-Dimensional Reconstruction of the Genial Spinal Canal.

The aim of this anatomical study was to investigate the genial spinal canal histologically and to reconstruct it three-dimensionally to improve understanding of its anatomy and to reveal any differences between dentate and edentulous specimens. Two tissue blocks from the mandible between the left and right second incisors, one dentate and one edentulous, were fixed in 4.5% formaldehyde, decalcified and embedded in paraffin. Serial histological sections were prepared, stained with Azan and examined microscopically. Additionally, three-dimensional models of the blocks were reconstructed using microphotographs of the sections. The genial spinal canal in the dentate specimen contained a neurovascular bundle, which branched into a nerve innervating the incisor and a neurovascular bundle, whereas that in the edentulous specimen contained some nerves for vestibular gingival innervation and a vascular bundle. The results suggest differences in the genial spinal canal between dentate and edentulous mandibles. Further research is needed to confirm this finding. Clin. Anat., 33:1102-1108, 2020. © 2019 Wiley Periodicals, Inc.

Rotational Path of Insertion in Fixed Prosthodontics when Abutment Axes Do Not Match: A Case History Report.

Fixed dental prostheses are the standard treatment option for replacing missing teeth when adjacent teeth require crowns or are already restored with crowns. Divergent abutment teeth axes may require invasive teeth preparation to achieve a common path of insertion, which substantially weakens residual tooth structure and increases the risk of pulpal problems. In selected cases with divergent abutment teeth in the buccal-lingual direction, the use of a rotational path of insertion might overcome these problems. This concept is presented via a clinical case history report.

Outcome of posterior fixed dental prostheses made from veneered zirconia over an observation period of up to 13 years.

OBJECTIVES: It was the aim of this clinical study to evaluate the long-term outcome of 3- to 4-unit posterior all-ceramic fixed dental prostheses (FDPs) made from veneered zirconia ceramic. METHODS: Between June 2003 and February 2005, 48 patients received 58 restorations. Twenty-four FDPs had a fixed-to-fixed design (FF) and thirty-four FDPs had a cantilever design (CA). Frameworks were scanned and milled out of 3 mol% yttrium-oxide partially-stabilized zirconia ceramic (CerconBase30, Degudent) and were veneered with feldspathic ceramic (CerconCeramS, Degudent). All FDPs were cemented with glass-ionomer cement (Ketac-Cem, 3 MEspe) after air-abrading the inner crown surfaces. RESULTS: The mean observation period was 85.4 ±â€¯54 (FF) and 91.7 ±â€¯50 (CA) months, respectively. Ten cantilever FDPs and 5 fixed FDPs were lost due to biological problems of the abutment teeth. Two cantilever FDPs and 4 fixed-to-fixed FDPs were lost due to technical failures of the ceramic materials. The cumulative 13-year survival rate was 43.2% (FF) (CI: 22.8-66.2%) and 52.5% (CA) (CI: 32.5-71.8), respectively. In 13 cases, intraoral repair or polishing of the fractured feldspathic ceramic veneers was needed (7 in group FF, 6 in CA). Eight abutments of six restorations (4 in FF, 4 in CA) had to be treated endodontically and caries therapy was needed in 6 abutment teeth (4 in group FF, 2 in CA). The cumulative 13-year success rate was 29.5% (FF) (CI: 12.1-55.9%) and 22.5% (CA) (CI: 7.9-49.3%). CONCLUSIONS: Within the limitations of the present investigation, posterior fixed dental prostheses made from veneered zirconia with either a fixed-to fixed or a cantilever design show comparable survival and success rates after 13 years of clinical observation. CLINICAL SIGNIFICANCE: FDPs made from veneered zirconia ceramic present high failure and complication rates, irrespective of the design (fixed-to-fixed or cantilevered).

Ten-year clinical outcome of single implant-retained mandibular overdentures-A prospective pilot study.

OBJECTIVES: The aim of this prospective pilot study was to evaluate the concept of one single implant placed in the edentulous mandible to retain a complete denture with regard to implant survival and prosthodontic maintenance over an observation period of 10 years. MATERIALS AND METHODS: Eleven edentulous patients were included and received one implant in the midline of the mandible. Five implants healed submerge and were uncovered 2 months later. The other six healed un-submerged and were provided with a healing abutment 4 mm in height thus moderately loaded. All denture bases were temporarily relined during the healing period and two months later provided with a ball attachment for implant retention. Implant related parameters and prosthodontic maintenance interventions were assessed four weeks after implant loading and then annually. RESULTS: Over a mean observation period of 108.9 months (35-136 months), no implant was lost. The most frequent prosthetic maintenance intervention was activation of the matrix due to loss of retention, followed by exchange of the female part. Fracture of the denture base in the attachment area was a frequent complication and occurred in 8 cases. Two denture bases fractured twice. CONCLUSION: Within the limitations of this prospective pilot study, the concept of a single midline implant to retain a mandibular complete denture is promising over ten years for edentulous patients. Regular recall visits should be scheduled due to frequent maintenance interventions. Further research on this topic with a larger study cohort is needed.

The single mandibular implant study - Short-term effects of the loading protocol on Oral Health-related Quality of Life.

PURPOSE: A single implant can be placed to retain an overdenture in the edentulous mandible. This study aimed at the development of Oral Health-related Quality of Life comparing immediate and delayed implant loading, i.e., loading after 3 months of submerged healing. METHODS: In a randomized controlled trial, 158 participants received a single mandibular implant in the midline. Quality of life was measured using the summary score of the German 49-item Oral Health Impact Profile at baseline, one month after implant placement (direct loading group) as well as one and four months after loading. RESULTS: Mean scores at baseline were comparable. Four months after implantation, a decrease of mean scores was recognized for both groups, indicating a significantly enhanced quality of life after treatment. When comparing the groups after both 1 and 4 months of loading, quality of life was insignificantly higher in the delayed loading group (1 month: 42.1 vs. 32.3; 4 months: 33.6 vs. 27.7). For immediate loading, an insignificant tendency to an earlier improvement was recognized (Δ1month-baseline: 9.7, compared to Δ1month-baseline: 6.4). CONCLUSIONS: The single mandibular implant concept was associated with a positive impact on quality of life. However, no statistically significant influence of implant loading on quality of life was found.

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

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.

Ten-year outcome of zirconia ceramic cantilever resin-bonded fixed dental prostheses and the influence of the reasons for missing incisors.

OBJECTIVES: This clinical study evaluated the long-term outcome and survival rate of all-ceramic cantilever resin-bonded fixed dental prostheses (RBFDPs) made of zirconia-ceramic with a single-retainer design to replace missing incisors. In addition, whether the reason for missing incisors has an influence on the longevity of RBFDPs was analyzed. MATERIALS AND METHODS: One hundred and eight zirconia ceramic cantilever RBFDPs were provided for 87 patients. Seventy-five RBFDPs replaced maxillary incisors and 33 mandibular incisors. The restorations were subsequently categorized into 3 groups according to the reasons for missing teeth (congenitally missing, trauma and other reasons). The patients were followed up annually, and the restorations were assessed for function and aesthetics. The mean observation time of the RBFDPs was 92.2±33months. RESULTS: Six debondings and 1 loss of restoration were recorded. The lost restoration was removed at the patient's request after a small chip occurred on the mesial edge of the pontic. Three of the 6 observed debondings were caused by traumatic incidents. All debonded RBFDPs were rebonded successfully with no further complications. Zirconia ceramic RBFDPs yielded a 10-year survival rate of 98.2% and a success rate of 92.0%. CONCLUSIONS: Anterior zirconia ceramic cantilever RBFDPs provided excellent clinical longevity. The reasons for missing incisors did not influence the longevity of the cantilever RBFDPs.

Single Mandibular Implant Study: Recruitment Considerations.

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.

Bond strength of a new generation of universal bonding systems to zirconia ceramic.

The purpose of this laboratory study was to evaluate the tensile bond strength of a new generation of universal bonding systems to zirconia ceramic and to compare the results with the bond strength of a clinically-established bonding system. Eighty zirconia ceramic test specimens (e.max ZirCAD) were air-abraded and bonded to Plexiglas tubes, filled with an aliphatic dimethacrylate filling material (Clearfil F II), using three so called universal bonding systems of a new generation with different compositions (Monobond Plus/MultilinkAutomix, NX3, Scotchbond Universal/RelyX Ultimate). The latter was used also without the phosphate monomer containing primer Scotchbond Universal. A clinically established phosphate monomer containing adhesive cement served as control group (Panavia F2.0). The specimens were stored in water at 37°C for 3 or 150 days and the long-term storage series were additionally thermal cycled between 5 and 55°C for 37,500 times to simulate oral conditions. All specimens underwent tensile bond strength testing. The statistical analysis was performed using Kruskal-Wallis and Wilcoxon-Test with a Bonferroni-Holm correction for multiple testing. After 150 days the median bond strength of RelyX Ultimate, with and without Scotchbond Universal, and Panavia F2.0 did not differ statistically (range: 21.7-28.8MPa), while the bond strength of Monobond Plus/Multilink Automix was significantly lower (15.4MPa), and that of NX3 the lowest (6.6MPa). After 150 days of water storage with thermal cycling, all adhesive system showed significantly reduced tensile bond strengths compared to that after 3 days. Only RelyX Ultimate was comparable to the established bonding system Panavia F2.0. The additional use of Scotchbond Universal did not result in a significant effect.

Long-term retention behaviour of resin matrix attachment systems for overdentures.

OBJECTIVES: The purpose of this laboratory study was to evaluate the long-term retention behaviour of two resin matrix attachment systems for overdentures and the influence of the implant angulation. METHODS: Sixteen titanium patrices of each attachment system were connected to their corresponding implant analogues and fixed in an auto curing resin either orthogonally (n=8) or 20° tilted (n=8). The corresponding matrices, one made from polyetherketoneketone (PEKK; CM LOC, Cendres+Métaux, Biel, Switzerland), one made from polyethylene (PE; Locator, Zest Anchors, Escondido, California, USA), were fixed in a stylised unilaterally removable dental prosthesis resulting in 4 groups with 8 specimens in each group. Overall, 30,000 joining and separating cycles of the matrix were performed in a chewing simulator. After each joining movement, the unilaterally removable dental prosthesis was loaded eccentrically with 100N at a distance of 12mm from the attachment to simulate clinical loading conditions. Retentive forces were measured during the test using force transducers. The statistical analysis was performed using Tukey-HSD. RESULTS: Both attachment systems showed a significant decrease in retention over time, which occurred earlier in the tilted groups than in the orthogonal groups. After 5000-30,000 joining and separating cycles the PE matrix attachment provided significantly lower retention than the PEKK matrix attachment system. CONCLUSION: Within the limitations of this investigation, the combination of a titanium patrix and a matrix made from polyetherketoneketone seems to be a promising material combination for long-term retention, also on tilted implants.