Influence of plasma pretreatment on shear bond strength of self-adhesive resin cements to polyetheretherketone.

OBJECTIVES: The aim of this study is to evaluate the adhesion between PEEK and two self-adhesive resin cements after plasma treatment. METHODS: Eight hundred sixty-four polyetheretherketone (PEEK) disks were cut and polished to silicon carbide (SIC) P4000. One half of the specimens were randomly selected and pretreated with plasma, whereas the remaining 432 specimens remained untreated. Subsequently, specimens were randomly allocated to four groups (n = 108/group): Visio.link (Bredent), Signum PEEK Bond (Heraeus Kulzer), Ambarino P60 (Creamed), and a control group without additional treatment. Half of the specimens of each group (n = 54) were then cemented with either RelyX Unicem Automix 2 (3 M ESPE) or with Clearfil SA (Kuraray). All specimens were stored in water for 24 h (37 °C). Afterwards, specimens were divided into three groups (n = 18) for different aging levels: (1) no aging (baseline measurement), (2) thermal aging for 5,000 cycles (5/55 °C), and (3) thermal aging for 10,000 cycles (5/55 °C). Thereafter, shear bond strengths (SBS) were measured, and failure types (adhesive, mixed, and cohesive) were assessed. Data were analyzed using descriptive statistics, four- and one-way ANOVA followed by a post hoc Scheffé test (p < 0.05). RESULTS: No adhesion could be established without adhesive pretreatment, irrespectively, whether plasma was applied or not. Also, no bond strength was measured when Ambarino P60 was applied. In contrast, adhesive pretreatment resulted in SBS ranging between 8 and 15 MPa. No significant differences were found between the resin cements used. In general, no cohesive failures were observed. Groups without plasma treatment combined with Visio.link or Signum PEEK Bond showed predominantly mixed failure types. Control groups, plasma treated, or treated using Ambarino P60 groups fractured predominantly adhesively. CONCLUSION: The use of methyl methacrylate (MMA)-based adhesives allows bonding between PEEK and self-adhesive resin cements. Plasma treatment has no impact on bond to resin cements. CLINICAL SIGNIFICANCE: PEEK reconstructions can be cemented using self-adhesive resin cements combined with pretreatment with MMA-based adhesives.

The randomized shortened dental arch study: oral health-related quality of life.

OBJECTIVES: Although the shortened dental arch (SDA) concept is a widely accepted strategy to avoid overtreatment, little is known on its impact on oral health-related quality of life (OHRQoL). This multicenter randomized controlled trial aimed to investigate the OHRQoL for removable partial dental prostheses (RPDP) with molar replacement versus the SDA concept. MATERIAL AND METHODS: In both groups, missing anterior teeth were replaced with fixed dental prosthesis. Two hundred fifteen patients with bilateral molar loss in at least one jaw were included. The Oral Health Impact Profile (OHIP-49) was completed before; 6 weeks (baseline), 6 months, and 12 months after treatment; and thereafter annually until 5 years. RESULTS: Of the initial cohort, 81 patients were assigned to the RPDP group and 71 to the SDA group (age, 34 to 86 years). Before treatment, the median OHIP score was similar in both groups (RPDP, 38.0; SDA, 40.0; n.s.). Results indicate marked improvements in OHRQoL in both groups between pretreatment and baseline (RPDP, 27.0; SDA, 19.0; p ≤ 0.0001) which continued in the RPDP group until the 1-year follow-up (p = 0.0002). These significant reductions in OHIP scores are reflected in its subscales. No further differences were seen within and between groups during the remainder observation period. CONCLUSION: Both treatments show a significant improvement in OHRQoL which continued in the RPDP group until the 1-year follow-up. No significant differences were seen between groups. CLINICAL RELEVANCE: For improving OHRQoL, it is not necessary to replace missing molars with a RPDP.

The randomized shortened dental arch study: tooth loss over five years.

OBJECTIVES: The study was designed to provide clinical outcome data for two treatments of the shortened dental arch (SDA). MATERIAL AND METHODS: In a multicenter randomized controlled clinical trial, patients with complete molar loss in one jaw were provided with either a partial removable dental prosthesis (PRDP) retained with precision attachments or treated according to the SDA concept preserving or restoring a premolar occlusion. No implants were placed. The primary outcome was tooth loss. RESULTS: Of 152 treated patients, 132 patients reached the 5-year examination. Over 5 years, 38 patients experienced tooth loss. For the primary outcome tooth loss, the Kaplan-Meier survival rates at 5 years were 0.74 (95% CI 0.64, 0.84) in the PRDP group and 0.74 (95% CI 0.63, 0.85) in the SDA group. For tooth loss in the study jaw, the survival rates at 5 years were 0.88 (95% CI 0.80, 0.95) in the PRDP group and 0.84 (95% CI 0.74, 0.93) in the SDA group. The differences were not significant. No Cox regression models of appropriate fit explaining tooth loss on the patient level could be found. CONCLUSIONS: The overall treatment goals of a sustainable oral rehabilitation and the avoidance of further tooth loss over longer periods were not reliably achievable. The influence of the type of prosthetic treatment on tooth loss might have been overestimated. CLINICAL RELEVANCE: Regarding our results, the patient's view will gain even more importance in the clinical decision between removable and fixed restorations in SDAs.

The randomized shortened dental arch study: 5-year maintenance.

The scientific evidence concerning prosthodontic care for the shortened dental arch (SDA) is sparse. This randomized multicenter study aimed to compare two common treatment options: removable partial dental prostheses (RPDPs) for molar replacement vs. no replacement (SDA). One of the hypotheses was that the follow-up treatment differs between patients with RPDPs and patients with SDAs during the 5-year follow-up period. Two hundred and fifteen patients with complete molar loss in one jaw were included in the study. Molars were either replaced by RPDPs or not replaced according to the SDA concept. A mean number of 4.2 (RPDP) and 2.8 (SDA) treatments for biological or technical reasons occurred during the 5-year observation time per patient. Concerning the biological aspect, no significant differences between the groups could be shown, whereas treatment arising from technical reasons was significantly more frequent for the RPDP group. When the severity of treatment was analyzed, a change over time was evident. When, at baseline, only follow-up treatment with minimal effort is required, over time there is a continuous increase to moderate and extensive effort observed for both groups (Controlled-trials.com number ISRCTN97265367).

Two-body wear of occlusal splint materials.

This study investigates the wear resistance of four different types of occlusal splint materials based on two-body wear simulations under wet and dry conditions. Twenty specimens of each splint material (Dentalon Plus, Orthoplast, Biocryl C, and Eclipse), each with a diameter of 16 mm and a thickness of 3 mm, were tested, half under wet and half under dry conditions. Each wear test was performed using a device called chewing simulator CS-4 (n=10; test load: 50 N; number of cycles: 10000, 20000, and 30000; continuous rinsing with 30°C water for wet conditions); the antagonists were simulated using steel balls. Wear was determined using a 3D laser scanner and a surface analysis program. To detect significant statistical differences, wear data after 10000; 20000; and 30000 cycles were compared using the Kruskal-Wallis test and the Mann-Whitney U-test. The level of significance was set at 5%. Significant differences were found between the groups of different materials tested under wet conditions (P<0.05), whereas no differences between them were found under dry conditions (P>0.05). No significant difference was found between the wet and dry conditions for all materials and cycles (P>0.05). For groups of different materials tested under wet conditions, the degree of volume loss generated in the Chewing Simulator CS-4 was found to differ significantly for different numbers of cycles. The presence of water had no effect on the volume loss in the different material groups that were tested.

Description and evaluation of a new approach on pre-clinical implant dentistry education based on an innovative simulation model.

INTRODUCTION: Predominantly theoretical courses are employed to teach German dental students in implant dentistry at pre-clinical stage. As implant dentistry is an important part of the clinical treatment spectra, practical implementation of this field at an early stage of education seems to be appropriate. By a newly developed interdisciplinary implant dentistry course, students should assess an improved competence level as well as first practical experiences in the field of implant dentistry at the pre-clinical stage of their education. MATERIALS AND METHODS: Interdisciplinary implant dentistry education was integrated in the final pre-clinical course Phantom II at the Department of Prosthodontics, LMU, Munich. In total 120 pre-clinical students participated at the implant dentistry education course. After theoretical introduction into implant surgery and implant prosthetics, 30 simulation units were employed for the practical training of the participants. All important treatment steps were carried out by the students under instruction by the supervisors, including interdisciplinary planning, the use of the drilling template, the template guided insertion of two implants, as well as the integration of two ball attachments into a pre-existing full denture. After the course participants were asked by questionnaire about the quality of the course and their personal opinion. RESULTS: The course received an extraordinary positive feedback. In total 108 students evaluated the course with the overall grade of 1.68 according to the German school-mark system (1 = excellent, 6 = unsatisfactory). Also the single parts of the course were voted constantly positively. CONCLUSION: The aim of this first interdisciplinary course for pre-clinical students was to enhance competence level and practical implementation of implant dentistry at an early stage of education. Participants' comments and suggestions on the questionnaires demonstrated the positive response and the general interest in this form of dental education, as well as the demand for further development of training in this field.

Reconstruction of the vertical jaw relation using CAD/CAM.

There can be severe loss of the vertical dimension of occlusion due to chemical, mechanical and traumatic causes. This can give rise to both esthetic and functional problems for the patient. Restoration is possible usually only by redesigning the occlusal surfaces. The prosthetic readjustment of the vertical jaw relation represents a considerable intervention in the stomatognathic system, requiring predictable, minimally invasive methods. Long-term provisional solutions clearly superior to pure splint therapy can be produced by means of new CAD/CAM techniques. They are inserted permanently and only in this way can the patient test the new occlusal situation and the success of treating functional disorders be verified. A further major advantage then becomes apparent when the final restoration is produced. The previously adjusted and tested occlusion is retained and every tooth can be treated and restored individually. Long treatment sessions are thus a thing of the past.

Axial condyle morphology and horizontal condylar angle in patients with internal derangement compared to asymptomatic volunteers.

The purpose of this study was to evaluate the possible structural variations of axial condyle morphology and horizontal condylar angle between patients with internal derangement and asymptomatic volunteers. Forty-five symptomatic patients and 31 asymptomatic volunteers (AV) were included in this study. All subjects had bilateral high-resolution magnetic resonance imaging scans. Axial condyle morphology was evaluated using these images and classified into four diagnostic groups: convex, flat, and concave anterior surfaces, and tapered form. The angulation between the condylar long axis and the transversal plane was then measured. A Wilcoxon-Whitney-Mann-U-test demonstrated no significant differences in the horizontal angulation of the patients with disk displacement with reduction (DDR) (24.35+/-9.31) as compared to patients with displacement without reduction (DDN) (25.61+/-10.11) and asymptomatic volunteers (25.68+/-9.31) (AV). Eighty percent of the flat type condyles and 73.3% of the tapered type condyles belonged to the symptomatic patients with disk displacement with reduction (DDR) and without reduction (DDN). Chi-square test demonstrated significant differences between the diagnostic groups of condyle types (p<0.01). A comparison of the angular difference of right and left joints of asymptomatic volunteers and patients using the Wilcoxon-Whitney-Mann-U test showed that the results of the asymptomatic volunteers were significantly lower (p = 0.05). The conclusion that an increase in the horizontal condylar angle is a predisposing factor for the development of internal derangement or that the derangement develops during the prognosis of the disorder could not be clearly stated based on the results of this study. It is proposed that the difference between condyle morphology in patients with disk displacement and asymptomatic volunteers may be a result of the remodeling or degeneration caused by the disorder.

Morphology of the mandibular fossa and inclination of the articular eminence in patients with internal derangement and in symptom-free volunteers.

OBJECTIVE: The purpose of this study was to evaluate temporomandibular joint morphology and to compare possible structural variations in the temporomandibular joint anatomy of symptomatic anterior disk displacement patients with possible structural variations in the temporomandibular joint anatomy of symptom-free volunteers. STUDY DESIGN: Fifty-six symptomatic patients and 25 symptom-free volunteers were included in this study. All subjects had bilateral high-resolution magnetic resonance imaging scans performed in the sagittal (closed and open) positions. Disk positions were evaluated with these images, and the patients were accordingly classified into 4 diagnostic groups. The angulation between the Frankfort horizontal plane and the posterior slope of the articular eminence, as well as the width and depth of the glenoid fossa and the articular tuberculum, were automatically measured with the aid of a computer. RESULTS: The Mann-Whitney U test demonstrated significant differences in the angular and linear values obtained in disk displacement with reduction patients in comparison with the values obtained in patients with disk displacement without reduction and in symptom-free volunteers. CONCLUSION: It is proposed that a steeper posterior slope and higher tuberculum articulaire are predisposing factors for the development of disk displacement with reduction. Flattening of the eminence may progress in time, leading to the onset of disk displacement without reduction.

Variability of disk position in asymptomatic volunteers and patients with internal derangements of the TMJ.

This study determined the variability of temporomandibular joint (TMJ) disk position in medial, central, and lateral aspects of the joint using magnetic resonance imaging (MRI). Subjects had clinical evidence of reciprocal TMJ clicking (N = 123) or restricted mandibular motion (N = 52). Eighty-nine asymptomatic volunteers provided a control group. Disk position was quantified on MRI by measuring the angle formed by a line through the middle of the condyle and perpendicular to the Frankfort plane and a line through the same midpoint of the condyle and tangential to the posterior-most aspect of the disk. The disk position in asymptomatic TMJs varied considerably with a tendency toward farther anterior placement in more lateral images. In 47 TMJs from a total of 52 TMJ5 (90%), restricted mobility was associated with anterior disk displacement (ADD) without reduction. The disk position demonstrated a mean displacement of 77 degrees without significant differences at the medial and lateral aspects of the condyle. One hundred TMJs from a total of 123 TMJs (81%) with reciprocal clicking demonstrated ADD with reduction. Tomograms revealed larger lateral displacements or rotational displacements in these joints, whereas medial images frequently showed similar ranges of disk positions as compared with asymptomatic TMJs. The results suggest that disk positions of up to +15 degrees on medial tomograms and +30 degrees on lateral tomograms should be regarded as normal variations. Furthermore, multisection analysis of all parasagittal images improved the separation between disk displacement and asymptomatic TMJs.

Evaluation of diagnostic criteria from computerized axiography to detect internal derangements of the TMJ.

Objective of this study was to evaluate the diagnostic value of 3-D computed axiography to detect anterior disk displacements (ADD) of the TMJ. 65 patients with MRI confirmed ADD with reduction and 27 patients with ADD without reduction were examined by 3-D computed axiography. 44 healthy volunteers with normal disk position and joint function served as controls. A descriptive analysis of the axiographic opening/closing cycle revealed significantly higher rates of abrupt deviations, accelerations/decelerations, and crossings for ADD with reduction compared to healthy volunteers. A new axiographic index reduced the number of false positive to 10% and false negative to 14% of the diagnosis. ADD without reduction was characterized by significantly shorter opening curves. The optimum split point at 11 mm, resulted in 10% false positive and 20% false negative diagnosis. However, the diagnostic value of computed axiography was reduced by the significant influence of the clicking or limited joint on the contralateral TMJ.

All-ceramic resin-bonded bridges. A 3-dimensional finite-element analysis study.

Resin-bonded fixed partial dentures (FPD) with a metal framework have some disadvantages: a grey shimmer of the metal wings through the abutment teeth, a higher corrosion rate, and an allergenic potential of the non-precious alloys used. The Al2O3 ceramic In-Ceram seems to be strong enough to serve as a framework for resinbonded all-ceramic FPDs. Because of the fact that ceramic wings often don't have enough inter-occlusal space, a new preparation design was developed. The objective of this study was to determine the influence of load orientation (45 degrees and 60 degrees) and the design of the interproximal connector on the stress distribution in the bridges. A 3-dimensional finite-element model was developed to simulate the anatomical situation. The biting force was assumed as 250 N and oriented in oro-buccal direction. The loading-point was palatal 1.5 mm beneath the incisal edge. It was found that stress generally increased with an angle of the biting force of 60 degrees. A small interdental connector (3 mm height) and/or strong interdental separation resulted in stresses of up to 455 MPa (45 degrees) or 534 MPa (60 degrees). Less separation with rounded edges and a higher connector (4 mm) reduced the stress to 122 MPa (45 degrees) and 143 MPa (60 degrees). Due to an average tensile strength of In-Ceram at 340-400 MPa, an all-ceramic resin-bonded FPD may only be recommended if the height of the connector could be minimum 4 mm. Rounded edges and little interdental separation are significant for stress reduction.

Clinical factors affecting adhesive fixed partial dentures: a 6-year study.

One hundred forty-one adhesive fixed partial dentures were placed under controlled conditions for a 6-year longitudinal study. The influence of location (anterior/posterior, maxilla/mandible), tooth preparation techniques (retentive/less invasive), and four different methods of metal conditioning (sandblasting/electrolytic etching and/or pyrolytic/tribochemical silane coating) on the survival rate was investigated. Failures (23 of 24) were caused by loss of adhesion at the metal-cement interface. The retentive tooth preparation reduced the risk of failure to almost one twentieth, but the intraoral location did not influence survival time. The effect of silane-coating on longevity was extremely positive and was not reflected by successful retainers.

[Clinical comparison of bonded bridges as a function of preparation and metal conditioning. Statistical analysis of failures]. / Klinischer Vergleich von Adhäsivbrücken in Abhängigkeit von Präparationsform und Gerüstkonditionierung.

A total of 107 bonded bridges could be re-evaluated after a mean period of 2.3 years and a maximum of 5 years. The preparation of mechanical retentive aids, such as grooves and bores resulted in a significant reduction of failure rates after one year. Electrolytical etching or silicoating of the CoCr restorations failed to have any effect on the failure rates of those bridges that were provided with adequate mechanical retention.

[Success of implantation depending on the type of prosthetic superstructure]. / Implantationserfolg in Abhängigkeit von der prothetischen Suprakonstruktion.

53 patients with 120 endosseous implants could be re-evaluated after a mean period of 2.7 years (maximum 5 years). Using casts from the upper with transfer posts and lower jaw, we measured the deviation of the implant axes from their ideal direction and localisation. Furthermore, we tried to find out, whether an unfavourable localisation compromised the prognosis of osseointegrated implants. Ideal, axial load by the prosthetic construction was often impossible because of unfavourable localisation of the implants. In a rank correlation analysis we found a significant influence of unfavourable localisation on prognosis in the group of hinge bars. Further weak correlations were revealed between loss of attachment and gingiva index which in turn was correlated with the plaque index.

[Optimized pin geometry for improved retention of parapulpal pins in amalgam]. / Verbesserte Retention parapulpärer Stifte im Amlagam durch Formoptimierung.

The retentive part of parapulpal pins is often very bulky, and this may compromise the strength of the amalgam restoration. This in turn may considerably limit the range of applications of parapulpal pins. For this reason the geometry of the retentive pin portion was optimized with the aid of a finite element analysis. This manoeuvre resulted in a better stress distribution and improved retention, although the pin size was reduced. In clinical terms this implies a wider range of possible applications, because these pins allow safe anchorage of extensive amalgam restorations and do not affect the strength of the restoration.

[Differential diagnosis of reciprocal joint clicking using electronic axiography (SAS)]. / Zur Differentialdiagnose reziproker Knackphänomene mit Hilfe der electronischen Achsiographie (SAS).

25 patients with reciprocal clicking in one or both temporomandibular joints were examined clinically and with an electronic axiographic system (SAS-System). Studying the direction of the sudden change of the condylar path during clicking, we established a tentative differential diagnosis of "centric anterior dislocations" of the disc and "eccentric posterior dislocations". Interpreting the axiographic pathways we found an eccentric posterior dislocation of the disc in 20 TMJs. But in at least 11 cases, which could be re-evaluated by magnetic resonance tomography (CMR), the diagnosis "eccentric posterior dislocation" was false. As we found several variations of anterior dislocations with a cranial and lateral deviation of the condylar path during opening clicking, the diagnosis of "eccentric disc dislocations" established by axiography was not reliable.