Cornelius Dirk

Clinical and radiological investigations of mandibular overdentures supported by conventional or mini-dental implants: A 2-year prospective follow-up study

Statement of problem Conventional dental implants are not applicable in the mandibular interforaminal region if bone volume is limited. Mini‐dental implants offer an alternative means of supporting mandibular overdentures in a narrow residual ridge, without additional surgery. Purpose The purpose of this nonrandomized clinical trial was to compare the ability of mini‐dental implants with that of conventional dental implants in supporting mandibular overdentures during a 2‐year clinical follow‐up. Bone quality, bone resorption, implant stability, and oral health were assessed radiographically. Material and methods A total of 32 participants with edentulism were included. Twenty‐two participants (99 implants) received 4 to 5 mini‐dental implants (diameter: 1.8‐2.4 mm; length: 13‐15 mm, study group), and 10 participants (35 implants) received 2 to 4 conventional dental implants (diameter: 3.3‐3.7 mm; length: 11‐13 mm, control group). The selection of the participants in the study or control group was based on the available bone volume in the mandible. The selection was not randomized. The density of cortical bone thickness was measured in Hounsfield units (HU) from computed tomography data, and patients were followed for 2 years. The participants were examined 3, 6, 12, and 24 months after surgery. Primary stability immediately after the insertion of dental implants (Periotest), secondary stability 6 months after implantation, modified plaque, bleeding on probing indices, and probing depth were measured and analyzed statistically (&agr;=.05). Results The mean HU value 6 months after implantation in the participants who received mini‐dental implants was significantly (P=.035) higher (1250 HU) than that in the participants who received conventional dental implants (1100 HU). The probing depths around the conventional dental implants (1.6 and 1.8 mm, respectively) were significantly higher than those around the mini‐dental implants (1.3 and 1.2 mm, respectively) 12 and 24 months after surgery, respectively (P<.001). The mean primary and secondary stability values for conventional dental implants were −4.0 and −4.9, respectively. The primary and secondary stability values for the mini‐dental implants were −0.3 and −1.4, respectively. The Periotest values of the primary (measured immediately after implant insertion) and secondary implant stabilities (measured 6 months after implant insertion) were significantly higher for the conventional dental implants than for the mini‐dental implants (P<.001). Conclusions Based on this 2‐year clinical trial, patients receiving mini‐dental implants had clinical outcomes similar to those of patients receiving conventional dental implants to support overdenture prostheses.

Changes in biting forces with implant-supported overdenture in the lower jaw: A comparison between conventional and mini implants in a pilot study.

The biting ability of patients improves noticeably after receiving implant-supported overdentures in comparison to conventional complete dentures. However, the change of biting with such treatment concepts has been quantitatively investigated in only a limited number of studies. The aim of the present study has been to measure the biting forces of edentulous patients with complete dentures and after receiving implant-supported overdentures. A total of 26 edentulous patients were included. Ten patients received two to four conventional implants (control group, Ø3.3-3.7mm, L11-13mm) and 16 patients received four to five mini implants (study group, Ø1.8-2.4mm, L13-15mm) inserted in the mandibular interforaminal region. All patients received a lower overdenture with ball/rubber ring attachments and a complete denture for the maxilla. The biting forces were measured using Prescale pressure sheets type low before the insertion of implants and after receiving implant-supported overdenture. The measured sheets were later scanned and analysed using FPD-8010E software. The range of biting forces before the insertion of implants was 80N-122N for the control group and 66-88N for the study group. After the insertion of implants, the range of biting forces increased to 167N-235N for the control group and to 81N-138N for the study group. However, the increase in biting forces after the insertion of implants was not significant for either group. No significant difference was obtained between the two implant systems. The biting forces improved after insertion of implants regardless of which implant system was used. However, the degree of improvement is noticeably related to the original bone quality of the mandible at the insertion regions of implants.

Bone substitute material composition and morphology differentially modulate calcium and phosphate release through osteoclast-like cells

The aim of this study was to determine the material composition and cell-mediated remodelling of different calcium phosphate-based bone substitutes. Osteoclasts were cultivated on bone substitutes (Cerabone, Maxresorb, and NanoBone) for up to 5 days. Bafilomycin A1 addition served as the control. To determine cellular activity, the supernatant content of calcium and phosphate was measured by inductively coupled plasma optical emission spectrometry. Cells were visualized on the materials by scanning electron microscopy. Material composition and surface characteristics were assessed by energy-dispersive X-ray spectroscopy. Osteoclast-induced calcium and phosphate release was material-specific. Maxresorb exhibited the highest ion release to the medium (P = 0.034; calcium 40.25mg/l day 5, phosphate 102.08 mg/l day 5) and NanoBone the lowest (P = 0.021; calcium 8.43 mg/l day 5, phosphate 15.15 mg/l day 5); Cerabone was intermediate (P = 0.034; calcium 16.34 mg/l day 5, phosphate 30.6 mg/l day 5). All investigated materials showed unique resorption behaviours. The presented methodology provides a new perspective on the investigation of bone substitute biodegradation, maintaining the material-specific micro- and macrostructure.

Retrospective investigation of gingival invaginations@@@Retrospektive Untersuchung der Gingivaduplikatur: Part II: microbiological findings and genetic risk profile@@@Teil II: Mikrobiologische Befunde und genetisches Risikoprofil

Background and objectiveGingival invaginations are a frequent finding during tooth extraction and following orthodontic space closure. Based on the interdental localization and sometimes pronounced depth, it has been suggested that a gingival invagination may impede oral hygiene. In Part I of this series, the time until active tooth movement and the localization of extraction were identified as potential risk factors for the development of gingival invagination. The aims of the present study were the analysis of the microbial spectrum of a gingival invagination in comparison with pool samples of the sulcus of Ramfjord teeth, on the one hand, and the importance of genetic variations of the pro-inflammatory mediator interleukin-1 (IL-1) and its receptor antagonist (IL-1-RN), on the other hand. In addition, a possible role of smoking as a risk factor was evaluated.Subjects and methodsA total of 30 patients with (n=16) and without (n=14) gingival invagination were examined for the presence of eleven periodontal pathogen bacterial species with a commercially available test (micro-IDent®Plus, Hain Lifescience, Nehren, Germany). The genetic evaluation was performed with the GenoType® IL-1 test (Hain Lifescience).ResultsThe results of the microbiological analysis of gingival invaginations showed that the bacterial flora might differ or even be higher than the pool sample from sulcus regions. The genetic evaluation demonstrated that in the group without gingival invagination only 14% showed an IL-1 polymorphism, whereas this value was twice as high (35%) in the group with gingival invagination. In addition, a combination of both polymorphisms IL-1 and IL-1-RN was only found in patients with gingival invagination (25%). Interestingly, smoking patients showed a significant increase of the severity of the gingival invagination.ConclusionThis retrospective study demonstrated that gingival invagination might be accompanied with an altered microbiological bacterial spectrum and a genetic IL-1 polymorphism. In addition, smoking was identified as another potential risk factor for the severity of gingival invaginations.ZusammenfassungHintergrund und FragestellungDie Gingivaduplikatur ist eine häufig auftretende Veränderung nach Zahnextraktion und kieferorthopädischem Lückenschluss. Aufgrund ihrer interdentalen Lokalisation und bisweilen ausgeprägten Tiefenentwicklung wurde sie mit einer erschwerten Mundhygienefähigkeit in Verbindung gebracht. Im Teil I dieser Artikelserie konnten der zeitliche Faktor und die Lokalisation der Extraktion als potenzielle wichtige Einflussfaktoren für die Entstehung der Gingivaduplikatur identifiziert werden. Ziele der vorliegenden Studie waren einerseits die Analyse des mikrobiologischen Keimspektrums einer Gingivaduplikatur im Vergleich zu Poolproben aus dem Sulkus von Ramfjord-Zähnen und andererseits, ob ein Zusammenhang zwischen einer genetischen Variation des spezifischen proinflammatorischen Markers Interleukin-1 (IL-1) und dessen Rezeptorantagonisten (IL-1-RN) sowie einer positiven Raucheranamnese und der Entstehung einer Duplikatur besteht.Probanden und MethodikDreißig Patienten mit (n=16) und ohne (n=14) Gingivaduplikatur wurden mit Hilfe eines kommerziell erhältlichen Testverfahrens (micro-IDent®Plus, Hain Lifescience, Nehren) auf das Vorhandensein von elf parodontal pathogenen Bakterienstämmen untersucht. Die genetische Evaluation erfolgte durch das GenoType® IL-1 Testverfahren (Hain Lifescience).ErgebnisseDie Ergebnisse der mikrobiologischen Untersuchung ergaben, dass Gingivaduplikaturen in Einzelfällen ein verändertes Keimspektrum bzw. höhere Werte einiger Bakterienspezies aufweisen können als die jeweilige Poolprobe. In der Gruppe ohne Gingivaduplikatur lag nur bei etwa 14% ein IL-1-Polymorphismus vor, wohingegen der Wert mehr als doppelt so hoch war (35%) in der Gruppe mit einer Gingivaduplikatur. Eine Kombination beider Polymorphismen, IL-1 und seines Rezeptorantagonisten, wurde nur bei Patienten mit Gingivaduplikatur (25%) detektiert. Interessanterweise wurde bei einer positiven Raucheranamnese ein statistisch signifikanter Anstieg der Ausprägung einer Gingivaduplikatur diagnostiziert.SchlussfolgerungDie vorliegende retrospektive Studie lässt die Hypothese zu, dass eine Gingivaduplikatur mit einem veränderten mikrobiologischen Keimspektrum und genetischen IL-1-Polymorphismus vergesellschaftet sein kann. Darüber hinaus wurde der Tabakkonsum als weiterer Einflussfaktor für die Ausprägung einer Duplikatur identifiziert.

Histopathological Verification of Osteoimmunological Mediators in Peri-Implantitis and Correlation to Bone Loss and Implant Functional Period.

Peri-implantitis (PI) is characterized by inflammation and bone resorption eventually leading to implant failure, but the characteristic pathologic determinants are undefined to date. This study aims to elucidate the parameters involved in PI pathogenesis, including intraoral implant retention time, extent of bone loss, smoking history, and identification of osteoimmunological markers for inflammation and bone loss. Peri-implant tissues (n = 21) displaying clinically diagnosed PI from patients with vertical bone loss ranging from 0-12 mm and implant function period between 1 and 60 months were evaluated by histochemistry and immunohistochemistry for TRAP, CD3, RANK, RANKL, OPG, and TNF-α. Statistical analyses were performed with the Welch test and correlation coefficients were calculated. Most bone resorption occurred during the first 12 months of implant function and correlated with the extent of inflammation, although histological signs of inflammation strongly varied between samples from minimal appearance of inflammatory cells to extended infiltrates. Implant function period and smoking history did not significantly affect the degree of inflammation. Higher RANK levels emerged in the first 12 months of implant function compared to longer retention times and were negatively correlated to the occurrence of RANKL. Additionally, histological signs of inflammation were about two-fold higher in specimens with bone resorption up from 5 mm compared to under 5 mm. CD3(+) cells were more prevalent in extensive inflammatory infiltrates and samples derived from smokers. Our analyses proved that PI-induced bone loss is differentially influenced by the parameters evaluated in this study, but a distinct interconnection between disease severity and implant retention time can be established.

Comparison of the force levels among labial and lingual self-ligating and conventional brackets in simulated misaligned teeth

Background/objective The aim of this study was to evaluate force levels exerted by levelling arch wires with labial and lingual conventional and self-ligating brackets. Materials/methods The tested orthodontic brackets were of the 0.022-in slot size for labial and 0.018-in for lingual brackets and were as follows: 1. Labial brackets: (i) conventional bracket (GAC-Twin, Dentsply), (ii) passive self-ligating (SL) brackets (Damon-Q®, ORMCO; Ortho classic H4™, Orthoclassic; FLI®SL, Rocky Mountain Orthodontics) and (iii) active SL brackets (GAC In-Ovation®C, DENTSPLY and SPEED™, Strite). 2. Lingual brackets: (i) conventional brackets (Incognito, 3M and Joy™, Adenta); (ii) passive SL bracket (GAC In-Ovation®LM™, Dentsply and (iii) active SL bracket (Evolution SLT, Adenta). Thermalloy-NiTi 0.013-in and 0.014-in arch wires (Rocky Mountain Orthodontics) were used with all brackets. The simulated malocclusion represented a maxillary central incisor displaced 2 mm gingivally (x-axis) and 2 mm labially (z-axis). Results Lingual bracket systems showed higher force levels (2.4 ± 0.2 to 3.8 ± 0.2 N) compared to labial bracket systems (from 1.1 ± 0.1 to 2.2 ± 0.4 N). However, the differences between SL and conventional bracket systems were minor and not consistent (labial brackets: 1.2 ± 0.1 N for the GAC Twin and 1.1 ± 0.1 to 1.6 ± 0.1 N for the SL brackets with 0.013-in thermalloy; lingual brackets: 2.5 ± 0.2 to 3.5 ± 0.1 N for the conventional and 2.7 ± 0.3 to 3.4 ± 0.1 N for the SL brackets with 0.013-in Thermalloy). Limitations This is an in vitro study with different slot sizes in the labial and lingual bracket systems, results should be interpreted with caution. Conclusions/implications Lingual bracket systems showed higher forces compared to labial bracket systems that might be of clinical concern. We recommend highly flexible nickel titanium arch wires lower than 0.013-in for the initial levelling and alignment especially with lingual appliances.

Impact of radiation history, gender and age on bone quality in sites for orthodontic skeletal anchorage device placement.

AIMS Stability of orthodontic miniscrew implants is prerequisite to their success and durability in orthodontic treatment. As investigations revealed a positive correlation of miniscrew stability to periimplant bone quality, it has been the aim of this study to analyze the bone structure of resection preparations of human mandibles histologically by investigating the samples according to age, gender and exposure to radiotherapy. METHODS Inflammation- and tumor-free alveolar bone sections from human mandibles (n = 31) with previously diagnosed carcinoma, chronic osteomyelitis or cysts were analyzed histomorphologically and histomorphometrically as to the dimension of trabeculae in cancellous areas. Group A investigated the impact of a history of radiation therapy, group B of gender and group C contrasted biopsies from individuals aging under 60 or over 60 years. Statistics were performed using the Kruskal-Wallis-test. RESULTS Radiation, gender and age did not significantly influence bone density. The mean bone density averaged 40.7 ± 15.0% of spongiosa for the total collective with a median age of 58.4 years ± 14.7 years. CONCLUSIONS Our findings provide new information on bone quality, thus contributing to a more precise evaluation of the parameters affecting and those not affecting miniscrew implant stability. On the basis of these results, the formulation of clinical guidelines for risk assessment of therapeutic approaches in patients prior to insertion of orthodontic skeletal anchorage devices seems to be conceivable.

Time-dependent behavior of porcine periodontal ligament: A combined experimental, numeric in-vitro study

Introduction: The aim of this study was to analyze the time‐dependent in‐vitro behavior of the periodontal ligament (PDL) by determining the material parameters using specimens of porcine jawbone. Time‐dependent material parameters to be determined were expected to complement the results from earlier biomechanical studies. Methods: Five mandibular deciduous porcine premolars were analyzed in a combined experimental‐numeric study. After selecting suitable specimens (excluding root resorption) and preparing the measurement system, the specimens were deflected by a distance of 0.2 mm at loading times of 0.2, 0.5, 1, 2, 5, 10, and 60 seconds. The deflection of the teeth was determined via a laser optical system, and the resulting forces and torques were measured. To create the finite element models, a microcomputed tomography scanner was used to create 3‐dimensional x‐ray images of the samples. The individual structures (tooth, PDL, bone) of the jaw segments were reconstructed using a self‐developed reconstruction program. A comparison between experiment and simulation was conducted using the results from finite element simulations. Via iterative parameter adjustments, the material parameters (Youngs modulus and Poissons ratio) of the PDL were assessed at different loading velocities. Results: The clinically observed effect of a distinct increase in force during very short periods of loading was confirmed. Thus, a force of 2.6 N (±1.5 N) was measured at the shortest stress duration of 0.2 seconds, and a force of 1.0 N (±0.5 N) was measured at the longest stress duration of 60 seconds. The numeric determination of the material parameters showed bilinear behavior with a median value of the first Youngs modulus between 0.06 MPa (2 seconds) and 0.04 MPa (60 seconds), and the second Youngs modulus between 0.30 MPa (10 seconds) and 0.20 MPa (60 seconds). The ultimate strain marking the transition from the first to the second Youngs modulus remained almost unchanged with a median value of 6.0% for all loading times. Conclusion: A combined experimental‐numeric analysis is suitable for determining the material properties of the PDL. Microcomputed tomography allows high‐precision recordings with only minimum effort. This study confirms the assumption of time dependency and nonlinearity of previous studies. HighlightsTime‐dependent behavior of the PDL was evaluated with an experimental numeric method.Combined analysis was suitable for determining material properties of the PDL.Time‐dependency and nonlinearity and results from previous studies were confirmed.