Peter Rehmann

Sinus lift augmentation using autogenous bone grafts and platelet-rich plasma: radiographic results.

OBJECTIVES Autologous bone grafting and sinus floor elevation is a widely accepted method for reconstruction of the atrophic maxilla. The aim of this investigation was to examine the influence of platelet-rich plasma (PRP) on bone grafting in sinus floor augmentation. STUDY DESIGN A prospective, controlled, randomized study including 34 patients undergoing sinus augmentation before implant placement was designed. The intervention group had additional treatment with PRP. Radiographic imaging was performed by computerized tomography (CT) and panoramic radiography 4 months after augmentation and before implant placement. RESULTS Bone density showed no significant increase when PRP was used in combination with autologous bone grafting compared with autologous bone alone. CONCLUSIONS This study showed no positive effect of PRP on bone density in CT evaluation when used in sinus floor augmentation. Bone density in the CT showed no correlation to histomorphometric evaluation.

Effect of different retraction and impression techniques on the marginal fit of crowns

OBJECTIVES Periodontal conditions in restored teeth are strongly influenced by the marginal fit of the restoration which is closely related to the quality of the impression. However, the influence of the retraction and impression technique on the outcome of the impression has only sparsely been investigated. Thus, it was the objective of this study to compare the marginal fit in fixed restorations using two modes of gingival retraction and two different impression techniques in an animal model. METHODS To simulate clinical conditions, 6 teeth in each of 10 lower jaws of freshly slaughtered cows were prepared with subgingival finish lines. Two different retraction techniques were used to expose the finish line: retraction cords containing epinephrine (Surgident) and electro-surgery were applied contra-laterally at 3 teeth per quadrant. Two impressions per jaw were taken in a two-step putty-wash technique (TPW) and a one-step putty-wash technique (OPW), respectively. On the casts, measurement copings were fabricated and seated on the extracted original tooth. In each coping the marginal discrepancy was assessed at 8 reference marks. Since the data was normally distributed, results were subjected to parametric statistics (T-test; p=0.05). RESULTS Overall marginal discrepancies ranged between 0 and 200 microm. There was a small but not significant difference between electro-surgery and the retraction cords whereas TPW produced significantly better results than OPW (p<0.05). CONCLUSIONS Within the limits of the study it can be concluded that the use of gingival retraction cords as well as electro-surgery lead to acceptable results. The difference between TPW and OPW concerning the marginal discrepancies can be regarded as clinically insignificant.

Treatment outcomes with removable partial dentures: a retrospective analysis.

PURPOSE This retrospective clinical study aimed to evaluate the long-term outcomes of clasp-retained, metal-framework removable partial dentures (RPDs) and their clasped teeth, the influencing factors on survival, and the type and number of repairs needed during the observation period. MATERIALS AND METHODS The study is based on a convenience sample of 52 patients who received 65 RPDs with a total of 207 clasped teeth. The mean observation period was 3.11 ± 0.29 years (maximum: 10 years). Patient gender, prosthesis location (maxilla/mandible), number and distribution (Kennedy class) of abutment teeth, and impact of a continuous follow-up program on a favorable outcome probability were analyzed. Statistical analysis was performed using the Kaplan-Meier method (P < .05) in combination with Cox regression analysis. RESULTS During the observation period, 9.2% of the RPDs ceased to function and 5.8% of the abutment teeth were extracted. Mean RPD survival time was 8.07 ± 0.66 years, with a positive outcome probability of 90% after 5 years. Prosthesis location was the only parameter that significantly (P < .05) impacted this probability. CONCLUSION Overall, the high survival probability and low extraction rate of the abutment teeth reported in this study indicate that RPDs designed according to hygienic pronciples are clinically successful.

Tooth preparation for full-coverage restorations—a literature review

ObjectivesThe objective of this review was to assess the current knowledge about tooth preparation for full-coverage restorations regarding the following aspects: biological parameters, preparation geometry, and technical conditions.MethodsA systematic literature search was conducted using three electronic databases (MEDLINE, DIMDI, and Cochrane databases) in order to identify relevant citations; additionally, the process was augmented by a hand search.ResultsA number of 117 citations were relevant; 11 of these were reviews, 23 were clinical studies, 82 were in vitro investigations, and one was animal research.ConclusionThe basic form of a preparation has not changed substantially over the years, although new materials like all-ceramic systems have their own demands with regard to the details of the preparation’s geometry. Estimating how much of the tooth structure can be removed without harming the tooth remains one of the biggest problems, if not the main difficulty, during tooth preparation. As the periodontal tissues may be affected by the restoration margin, a supragingival position of the margin should be preferred whenever possible. No finish line design has yet proven to be superior with regard to the marginal accuracy of the subsequent restoration. Instead, good detectability of the margin for the dental technician or intraoral scanning devices appears to be of primary importance in order to achieve a good fitting restoration.Clinical significanceA detailed look at the covered aspects regarding tooth preparations can help to improve clinical outcomes in daily practice.

Effects of implant system, impression technique, and impression material on accuracy of the working cast.

PURPOSE This in vitro study aimed to identify the effects of the implant system, impression technique, and impression material on the transfer accuracy of implant impressions. The null hypothesis tested was that, in vitro and within the parameters of the experiment, the spatial relationship of a working cast to the placement of implants is not related to (1) the implant system, (2) the impression technique, or (3) the impression material. MATERIALS AND METHODS A steel maxilla was used as a reference model. Six implants of two different implant systems (Standard Plus, Straumann; Semados, Bego) were fixed in the reference model. The target variables were: three-dimensional (3D) shift in all directions, implant axis direction, and rotation. The target variables were assessed using a 3D coordinate measuring machine, and the respective deviations of the plaster models from the nominal values of the reference model were calculated. Two different impression techniques (reposition/pickup) and four impression materials (Aquasil Ultra, Flexitime, Impregum Penta, P2 Magnum 360) were investigated. In all, 80 implant impressions for each implant system were taken. Statistical analysis was performed using multivariate analysis of variance. RESULTS The implant system significantly influenced the transfer accuracy for most spatial dimensions, including the overall 3D shift and implant axis direction. There was no significant difference between the two implant systems with regard to rotation. Multivariate analysis of variance showed a significant effect on transfer accuracy only for the implant system. CONCLUSIONS Within the limits of the present study, it can be concluded that the transfer accuracy of the intraoral implant position on the working cast is far more dependent on the implant system than on the selection of a specific impression technique or material.

A new method for assessing the accuracy of full arch impressions in patients

OBJECTIVE To evaluate a new method of measuring the real deviation (trueness) of full arch impressions intraorally and to investigate the trueness of digital full arch impressions in comparison to a conventional impression procedure in clinical use. METHODS Four metal spheres were fixed with composite using a metal application aid to the lower teeth of 50 test subjects as reference structures. One conventional impression (Impregum Penta Soft) with subsequent type-IV gypsum model casting (CI) and three different digital impressions were performed in the lower jaw of each test person with the following intraoral scanners: Sirona CEREC Omnicam (OC), 3M True Definition (TD), Heraeus Cara TRIOS (cT). The digital and conventional (gypsum) models were analyzed relative to the spheres. Linear distance and angle measurements between the spheres, as well as digital superimpositions of the spheres with the reference data set were executed. RESULTS With regard to the distance measurements, CI showed the smallest deviations followed by intraoral scanners TD, cT and OC. A digital superimposition procedure yielded the same order for the outcomes: CI (15±4μm), TD (23±9μm), cT (37±14μm), OC (214±38μm). Angle measurements revealed the smallest deviation for TD (0.06°±0,07°) followed by CI (0.07°±0.07°), cT (0.13°±0.15°) and OC (0.28°±0.21°). CONCLUSION The new measuring method is suitable for measuring the dimensional accuracy of full arch impressions intraorally. CI is still significantly more accurate than full arch scans with intraoral scanners in clinical use. CLINICAL SIGNIFICANCE Conventional full arch impressions with polyether impression materials are still more accurate than full arch digital impressions. Digital impression systems using powder application and active wavefront sampling technology achieve the most accurate results in comparison to other intraoral scanning systems (DRKS-ID: DRKS00009360, German Clinical Trials Register).

Using a Modified Neutral Zone Technique to Improve the Stability of Mandibular Complete Dentures: A Prospective Clinical Study

PURPOSE The aim of this study was to evaluate the improvement in mandibular complete dentures (MCD) stability using a modified neutral zone technique (MNZT). MATERIALS AND METHODS For 21 patients who were dissatisfied with their primary MCD, MCDs were fabricated using the MNZT. RESULTS Nearly all of the patients showed considerable improvement in oral health-related quality of life, and 85.7% of the patients stated an improvement in general denture stability and while chewing. A masticatory function test showed no significant changes. CONCLUSION This MNZT seems to improve MCD function, especially in patients who cannot be treated with implants.

Pilot Study on the Influence of Nutritional Counselling and Implant Therapy on the Nutritional Status in Dentally Compromised Patients.

Objectives To investigate the impact of implant-prosthetic rehabilitation combined with nutritional counseling on the nutritional status of patients with severely reduced dentitions. Design An explorative intervention study including an intra-individual comparison of 20 patients with severely reduced dentitions in terms of nutrition- and quality of life-related parameters recorded at baseline and at six and twelve months after implant-prosthetic rehabilitation. Participants Twenty patients from the Department of Prosthetic Dentistry of Justus-Liebig University of Giessen, with an mean age of 63 years, who had fewer than ten pairs of antagonists. Measurements The baseline data collection included dental status, a chewing ability test, laboratory parameters, anthropometric data (body mass index), energy supply, a 3-day dietary record, an analysis of the oral health-related quality of life (OHRQoL) with the OHIP-G14, the Mini-Mental Status (MMS) and Mini Nutritional Assessment (MNA). Six months after implantation and prosthetic rehabilitation, individual nutritional counseling was performed by a dietician. Data were again collected and analyzed. A final follow-up was conducted 12 months after prosthetic rehabilitation. Results Despite the highly significant improvement in masticatory ability and OHRQoL after implant-prosthetic rehabilitation, no significant changes were observed regarding MNA, anthropometric data or energy supply. Except for cholinesterase (p = 0.012), ferritin (p = 0.003), folic acid (p = 0.019) and vitamin A (p = 0.004), no laboratory parameter changed significantly during the investigation period. In addition, no general significant differences were observed for nutrient intake or food choice. Conclusion The present study does not confirm the assumption that the implant-prosthetic rehabilitation of patients with severely reduced residual dentitions with or without an individual nutritional counseling influences nutritional status.

Treatment Outcomes of Cantilever Fixed Partial Dentures on Vital Abutment Teeth: A Retrospective Analysis.

PURPOSE This retrospective clinical study evaluated the long-term outcomes of cantilever fixed partial dentures (CFPDs) and the factors influencing their survival probability. MATERIALS AND METHODS The study is based on a convenience sample of 57 patients who received 71 CFPDs on a total of 176 vital abutment teeth. The mean survival time of the CFPDs was calculated using a Kaplan-Meier estimate. The following variables were analyzed as covariates of the survival function (logrank test, P < .05): sex, denture location, number and distribution (Kennedy Class) of the abutment teeth, dentition in the opposing arch (removable dentures, fixed partial dentures, or natural dentition), position of the cantilever unit (mesial or distal), and participation in follow-up visits. RESULTS The mean observation period was 3.2 ± 2.8 years (maximum 10.7 years). During the observation period, 22.5% (n = 16) of the CFPDs ceased functioning. The calculated outcome probability was 93.0% after 5 years and 84.5% after 8 years. The number of abutment teeth was the only parameter that significantly (P < .05) impacted this probability. CONCLUSION The survival rate of CFPDs on vital abutment teeth is comparable to that of conventional fixed partial dentures. Thus, CFPDs on vital abutments are an acceptable alternative to removable dentures.

Do Sealing Materials Influence Superstructure Attachment in Implants

PURPOSE This study aimed to evaluate the possible effect of sealing materials on superstructure attachment (ie, tightening/loosening torque and implant-abutment gap) in two different implant systems. MATERIALS AND METHODS A silicone, a chlorhexidine gel, and an industrial lubricant were tested. A 3D microscope was used for assessment of the implant-abutment gap, and the abutment screw was tightened and loosened with a digital torque screwdriver. A total of 20 implants per test group (10 BEGO Semados RI and 10 Nobel Biocare Replace Select Straight) were evaluated. RESULTS The tested sealing materials did not influence the gap between implant and abutment, but the force necessary for loosening the abutment screws decreased significantly. CONCLUSION Sealing materials may be useful against bacteria, but probably influence torque negatively.