Brigitte Ohlmann

Clinical performance of extended zirconia frameworks for fixed dental prostheses: two-year results

The purpose of this prospective cohort study was to assess the performance of tooth-supported, extended zirconia, fixed dental prostheses (FDPs). Thirty FDPs with span-lengths between 36 and 46 mm (mean: 40.33 mm), four to seven units and with connector dimensions of approximately 9 mm(2) were inserted (19 in the posterior region, 11 including anterior teeth) using glass-ionomer cement and assessed (aesthetic evaluation, failures, hypersensitivity/tooth vitality, secondary caries, pocket depth, decementation and chipping) at baseline and after 2 years. Differences between baseline and 2-year recall were analysed using the Wilcoxon signed-rank test for matched pairs. There were five failures. One FDP revealed a core fracture at the base of the connector, probably caused by a damage induced during fabrication. Two FDPs had to be recemented, one abutment tooth had to be treated endodontically and one cohesive failure of the veneer was observed. There were no significant changes of pocket depth and hypersensitivity between baseline and 2-year recall. The aesthetics were rated as excellent by the patients at both baseline and recall. Two year clinical results of extended zirconia based FDPs with 9 mm(2) connectors are promising.

All-ceramic inlay-retained fixed partial dentures: Preliminary results from a clinical study

OBJECTIVES The objective of this study was to evaluate the clinical performance of zirconia-based all-ceramic fixed partial dentures anchored by inlays. METHODS A total of thirty FPDs, manufactured using a zirconia frame and veneered with press ceramic, were anchored by use of inlay retainers. All FPDs were designed to replace one missing molar and were adhesively luted by use of one of two different resin cements. Documentation included failures and other complications, plaque accumulation, and aesthetic and functional performance. Statistical analysis was performed using a cox-regression model. RESULTS During the 12 months observation period a total of thirteen clinically relevant complications occurred-four delaminations of the veneer and six decementations. Three FPDs had to be replaced because of a fracture of the framework. The cement chosen, the location, and the design of the retainer had no statistically significant effect on the occurrence of complications. During the observation period, accumulation of plaque on the abutment teeth was not significantly greater than on reference teeth. Postoperative sensitivity did not differ significantly between the different luting cement groups. The aesthetic and functional performance of the FPDs was acceptable. CONCLUSIONS Improved adhesion between resin cement and inlay retainer is desirable before general recommendation of all-ceramic inlay-retained FPDs. Use of different luting cements seems to have no effect on the occurrence of complications.

Research Diagnostic Criteria for Temporomandibular Disorders: A Calibration and Reliability Study

Abstract The aim of this study was to investigate the reliability between different examiners when using the axis I of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). The hypothesis was that the standardized RDC/TMD examination protocol enables calibrated examiners to evaluate all examination items reliably. After calibration training by the RDC/TMD calibration team including the calibration of palpation pressure and the performance of the standardized examination protocol, four examiners, blinded to the patients’ medical histories examined 24 subjects in a randomized sequence. One experienced examiner was the standard (hierarchical calibration). The recorded measurements strictly followed the RDC/TMD. Intraclass correlation coefficients (ICC), bias and precision were calculated to estimate interrater reliability. Acceptable (0.75≥ICC>0.4) to excellent (ICC>0.75) reliability was found for 20 of the 23 (87%) examinations. Only sub-retromandibular muscle palpation and joint sound vibration recordings on lateral excursion showed poor-results (ICC≤0.4). The RDC/TMD examination protocol enables calibrated examiners to perform most (87%) examination items with satisfactory reliability. Therefore multi-site studies based on the RDC/TMD examination protocol may become feasible, keeping in mind the unsatisfactory reliability of 13% of the items (clicking during laterotrusion to the ipsilateral side, palpation of the posterior and submandibular region).

Clinical performance of long-span zirconia frameworks for fixed dental prostheses: 5-year results

The purpose of this prospective cohort study was to assess the performance of tooth-supported, long-span, zirconia fixed dental prostheses (FDPs). Thirty FDPs with span lengths from 36 to 46 mm (mean 40·33 mm), with 4-7 units and with connector dimensions ∼9 mm(2) were inserted (19 in the posterior region, 11 including anterior teeth) using glass-ionomer cement. The performance of the FDPs was assessed (aesthetic evaluation, failures, hypersensitivity/tooth vitality, secondary caries, pocket depth, decementation, and chipping) at baseline and after 5 years. Cox regression analysis was performed to identify risk factors. There were 16 failures after 5 years. Framework fracture occurred for two FDPs, four FDPs had to be re-cemented, one abutment tooth had to be treated endodontically, one abutment tooth fractured and cohesive failure of the veneer occurred for eight. Four FDPs had to be replaced, so survival was 82%. The aesthetics were rated as excellent by the patients at baseline and good at the 5-year recall. Cox regression analysis showed that both length [P = 0·05, exp(B) = 1·22] and location [P = 0·019, exp(B) = 4·09] of the FDP were risk factors for failure. Compared with the previously published 2-year results, the incidence of complications increased dramatically. Additionally, it was shown that long-span FDPs in the molar region are at greater risk of failure than FDPs in the anterior region.

The prevalence of myofascial pain and its association with occlusal factors in a threshold country non-patient population

The objective of the study is to assess the prevalence of myofascial pain in a threshold country and to isolate occlusal risk factors. One hundred and seventy-one randomized selected women were examined by a trained examiner in accordance with the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) examination procedure. Subscales of the SCL 90-R, graded chronic pain status, and anamnestic questionnaires were also used. Logistic regression was performed to compute the odds ratios for six common occlusal features with regard to the presence of myofascial pain, in accordance with the RDC/TMD criteria. Fifteen subjects (15 / 151 = 9.93%) suffered from myofascial pain. Results from logistic regression analysis showed that non-occlusion (posterior teeth, at least one side) and open bite increased the risk of myofascial pain. The prevalence of myofascial pain in this study is comparable with that in another study, in a highly industrialized environment, in which the RDC/TMD was used. The role of occlusion in a non-patient population seems to be restricted to serious alterations of normality. This article presents the prevalence of myofascial pain and its association with occlusal factors. This issue will help the clinicians to assess the influence of occlusion in myofascial pain patients and to send the patient to the appropriate specialist.

Optimizing preparation design for metal-free composite resin crowns

STATEMENT OF PROBLEM Although composite resin materials are used for posterior crown restorations, the influence of preparation design, material thickness, convergence angle, and method of cementation on fracture resistance remains unclear. PURPOSE The purpose of this in vitro study was to test the hypothesis that minimal preparation designs provide an acceptable level of fracture resistance for posterior composite resin crowns. MATERIAL AND METHODS Nonreinforced Artglass composite resin crowns (n=128) were fabricated on human molars in 16 test groups (n=8). Axial tooth preparation included a 1-mm-deep shoulder or a 0.5-mm chamfer preparation, whereas occlusal reduction was either 0.5 mm or 1.3 mm. The total angle of convergence was 4 or 11 degrees and the crowns were cemented either with glass ionomer cement (Ketac Cem) or resin cement (2bond2). After 10,000 thermal cycles, crowns were vertically loaded until failure occurred; load was measured in newtons. Statistical analysis was performed by a 4-way ANOVA (alpha=.05). RESULTS Statistical analysis revealed significant effects of occlusal thickness (P<.001), cement (P<.001), preparation design (P=.011), and convergence angle (P=.001) on the fracture resistance of the composite crowns. For composite resin crowns with an occlusal thickness of 0.5 mm, the resistance to fracture was lower than for crowns with a 1.3-mm thickness. Fracture resistance was greater when resin cement was used, and greater for the chamfer finish line than for the shoulder finish line. Use of a greater total convergence angle reduced fracture resistance. CONCLUSIONS Fracture resistance of composite resin crowns was significantly improved by increasing the occlusal thickness of the crowns, by using resin cement, and by reducing the total convergence angle.

Fracture resistance of the veneering on inlay-retained zirconia ceramic fixed partial dentures

Aims. The aim of this in vitro study was to evaluate the fracture load of zircon frames veneered with a polymer glass holding box inlay-retained fixed partial dentures (FPDs). The influence of the position of the frame and the span length was tested. Additionally, the fracture load values of zircon frames veneered with a press ceramic were evaluated. Material and methods. Box inlay cavities were prepared on mandibular molars and premolars. Forty-eight FPDs were manufactured using industrially prefabricated zircon frames veneered with the polymer glass Artglass®. Sixteen FPDs received individually manufactured CAD/CAM zircon frames veneered with a press ceramic. All FPDs underwent thermal cycling and mechanical loading (ML). The load to fracture was measured and fracture sites were evaluated. Results. Four polymer veneered FPDs showed fractures in the veneering material after ML. The mean fracture resistance ranged from 531 N to 727 N. No significant influence of frame localization could be observed. Significantly greater fracture resistance values were found in the ceramic veneered FPDs (1276 N to 1413 N). There was no significant effect of span length in the polymer veneered group or in the all-ceramic group, with the exception of a significant peak in fracture load value for intermediate span lengths in the polymer group with a localized occlusal zircon frame. Conclusions. Polymer veneered FPDs with Y-TZP frames showed acceptable fracture resistance values, but they cannot yet be unreservedly recommended for clinical use. Fracture values for CAD/CAM manufactured Y-TZP frames combined with a press ceramic deserve further clinical investigation.

Fracture behaviour of zirconia ceramic cantilever fixed dental prostheses in vitro.

Objective. Evaluation of the fracture resistance of all-ceramic cantilever fixed dental prostheses (FDPs) manufactured from zirconia frameworks and veneered with a press ceramic. Material and Methods. Two mandibular premolars were prepared either with a box inlay cavity or with a full crown chamfer preparation and then duplicated. 40-three-unit cantilever FDPs replacing one premolar, with a group size of eight for each design, were manufactured. In group i-i the cantilever FDPs were retained by two inlays, in group i-c by an inlay–crown combination, and in group c-c by two crowns. The frameworks in groups i-c-R and c-c-R were reinforced by an additional shoulder on the oral side of the zirconia frameworks. All FDPs were subjected to thermal cycling (TC) and 600,000 cycles of mechanical loading (ML) with 50 N. The load to fracture was measured and fracture sites were evaluated. Results. The mean fracture values ranged from 172 N to 792 N. Fracture-strength values were significantly lower for the i-i retained FDPs than for the i-c and c-c combinations. There was no significant effect of the reinforcing shoulder in groups i-c-R and c-c-R. For FDPs with a crown on the terminal tooth, fractures were usually within the distal wall of the distal crown. Conclusions. Inlay–inlay retained cantilever FDPs cannot withstand the mastication forces expected. Fracture load values for inlay–crown and crown–crown-retained FDPs encourage further clinical investigation. The mode of fracture indicates that reinforcement of the distal crown wall might enhance fracture resistance.

Psychosocial behaviour and health care utilization in patients suffering from temporomandibular disorders diagnosed on the basis of clinical findings and MRI examination

The aim of this study was to evaluate psychosocial behaviour and differences in health care utilization between subgroups of patients suffering from temporomandibular disorders, using both clinical examination and magnetic resonance imaging (MRI).

Temporomandibular disorders in association with scuba diving.

Objective:To determine the prevalence of temporomandibular disorders (TMD) in scuba divers and to identify the risk factors for the development of pain in the stomatognathic system before and after diving by the use of a questionnaire. Design:Retrospective cohort study based on questionnaires. Participants:A total of 296 active divers, aged 18 to 65 years, participating in scuba diving meetings in Heidelberg, Germany. Interventions:Each diver answered a questionnaire containing 29 questions, predominantly on symptoms of TMD. Main Outcome Measures:The data collected from the divers were calculated by the use of logistic regression tests. Risk factors for the development of TMD were evaluated. Results:Clenching seemed to be the greatest risk factor for pain while holding the mouthpiece and for pain in the masticatory muscle system after diving. Limited mouth opening and clenching were responsible for the development of pain in the temporomandibular joint after the dive. The prevalence of TMD-related symptoms was higher in women before, during, and after the dive. Conclusions:Individuals exhibiting TMD-related symptoms seem to be at the greatest risk of developing pain in the masticatory muscle system and/or the temporomandibular joint during or after the dive.