Search

Objectives To assess clinical, radiological and esthetic outcomes of prosthodontic rehabilitations supported by root-analogue implants (RAIs) or roots of severely damaged teeth after forced orthodontic extrusion (FOE). Materials and Methods Clinical data regarding RAIs and FOE were recorded and retrospectively evaluated for 40 patients by two independent investigators. Functional and esthetic outcomes were assessed for n = 20 pre-molars and n = 20 anterior teeth via comparison of radiographic and digital images applying the novel Functional Implant Prosthodontic Score (FIPS). Krippendorff’s alpha coefficient was calculated to assess inter-rater reliability. Mann-Whitney-U-Test was used to compare the assessed parameters. Level of significance was set to p

The outcome in the treatment of furcation defects is often unsatisfactory. The reasons are morphologic and pathologic peculiarities as well as extensive changes in shape caused by resective treatment of periodontal lesions in multi-rooted teeth. Therefore, augmentative strategies are suggested to improve the prognosis. However, the success rate decreases with increasing severity of the disease. In contrast, if the affected roots are not extracted but are extruded after hemi- or trisection, this leads to a coronal displacement of the disease process and a significantly improved situation for hygiene. At the same time, the resection of inflammatory tissue of the periodontal pockets is accompanied by vertical and horizontal bone apposition. The results are predictable and stable in the long term. The burden for the patient is low. ((Quintessence Int 2022;53: 884-891; Originally published (in German) in Quintessenz Zahnmedizin 2020; 71(9): 1024-1032; doi: 10.3290/j.qi.b3418205).

The restoration of severely damaged teeth challenges dental practitioners because defects are often located at the subcrestal level. In these cases, surgical crown lengthening or orthodontic extrusion procedures are deemed necessary to maintain the biologic width and respect a sufficient ferrule design after preparation. Considering the negative effects of invasive surgical therapy-such as the reduction of alveolar bone support of the neighboring teeth-forced extrusion might be a valid therapeutic alternative. This clinical case report illustrates forced orthodontic extrusion with a minimally invasive appliance that is applicable in daily clinical routine.

Maintaining and restoring teeth exhibiting subgingival or even subcrestal defect extensions represent a common problem in daily practice. Such teeth are often deemed "unrestorable" due to a significant hard tissue loss and defect locations violating the biologic width. In order to achieve a sufficient 2-mm-ferrule design and reestablish the biologic width, both surgical crown lengthening and orthodontic extrusion have been suggested. However, surgical crown lengthening has a negative effect on the attachment level of adjacent teeth as well as esthetic disadvantages particularly in the esthetic zone. Therefore, orthodontic extrusion might be considered as a valid therapeutic alternative since gingival architecture is maintained. While most orthodontic appliances are too complex for daily application, forced orthodontic extrusion by means of the Tissue Master Concept might be a cos t- and time -effective approach due to advances in adhesive and computer-assisted dentistry. This clinical case series illustrates the methodology of the rather straightforward Tissue Master Concept in specific clinical situations that may occur in clinical routine.

In cases of severely compromised teeth, dental practitioners are confronted with the therapeutic decision of whether to restore a tooth or replace it with an implant. Comparative scientific evidence on patient perception of both treatment approaches is scarce. The subject of this prospective clinical study was to compare oral health-related quality of life (OHRQoL) between two treatment groups: restoration of severely destroyed teeth after orthodontic extrusion (FOE) versus tooth extraction and implant-supported single crown restoration (ISC). A self-selected trial was performed with 21 patients per group. OHRQoL was assessed with the aid of the Oral Health Impact Profile (OHIP-G49) at different time intervals: before treatment (T1), after treatment (T2), after restoration (T3) and at recall (T4). Overall, OHIP scores improved from baseline to follow-up for both concepts with no significant differences between groups. There were no significant differences in subscales between FOE and ISC at T1, T3 and T4. In terms of functional limitations (p = 0.003) and physical disability (p = 0.021), patients in the FOE group temporarily exhibited lower OHRQoL at T2 in comparison to the ISC group. However, at baseline, after final restoration and at recall, the study demonstrates the same level of OHRQoL for both treatment concepts.

Frequency tuned parametric amplifiers may experience changes in both the two-to-one frequency ratio between the parametric and the direct excitation, and between the direct excitation frequency and the systems natural frequency. These effects are investigated theoretically using a Duffing-Mathieu equation as the model system, and investigated experimentally using a macro cantilever beam as the model object. The approximate analytical steady-state vibration amplitudes are derived using the method of varying amplitudes, and compared with results of direct numerical integration, showing good agreement. Theoretical predictions reveal that for detuned superthreshold parametric amplification some of the amplitude-frequency curves appear to collapse. Experiments show that a drop in the maximum steady-state vibration amplitude occurs for specific areas in the amplitude-excitation detuning domain, whereas for other areas frequency detuning may yield an increased maximum steady-state vibration amplitude. Thus frequency detuning is a feature which can purposefully be avoided or utilized, dependent on the usage e.g. for sensors or energy harvesters. We report experimentally obtained bistable amplified steady-state responses, which also support theoretical findings.

This study investigates the frequency detuning effects of parametric and direct excitation for near-resonant nonlinear structural vibrations. Specifically, the detuning effects of a two-to-one frequency ratio between the parametric and direct excitation, and of a drift in natural frequency, are studied. These effects are investigated theoretically using a Duffing- Mathieu equation as the model system, and experimentally using a cantilever beam as the model object. The approximate analytical responses are derived using the method of varying amplitudes, and compared with results of direct numerical integration and experiments showing good agreement. For frequency detuned superthreshold parametric excitation some of the theoretical frequency-amplitude solution branches appear to merge. For some ranges of parametric excitation frequency a drop in experimental steady-state vibration amplitude was found, indicating performance degradation whereas for other frequency ranges, frequency detuning may yield an increased steady-state vibration amplitude. This makes frequency detuning a feature which can purposefully be avoided or utilized, dependent on the application.

Parametric amplification is realized by adding parametric excitation to externally driven near-resonant oscillations. The effect of specific cubic nonlinearities on the parametrically amplified steady-state vibrations and gain is investigated theoretically. Here, gain is defined as the ratio of steady-state vibration amplitude of the directly and parametrically excited system, to vibration amplitude of the directly excited only system. The nonlinear effect of midplane stretching is compared to the effects of nonlinear inertia and curvature. An approximate analytical expression for the vibration amplitude is derived. For a given small level of transverse displacement for both the cantilever and doubly clamped beam, the effect of midplane stretching is dominant compared to those caused by nonlinear inertia and curvature. It was found that the beam slenderness ratio can be used as an effective design parameter for parametric amplifiers.