Retrospective clinical study of 842 clasp-retained removable partial dentures with a metal framework: survival, maintenance needs, and biologic findings.

OBJECTIVES: To evaluate clasp-retained removable partial dentures (C-RPDs) with a metal framework for survival, maintenance requirements, and biological implications. METHOD AND MATERIALS: C-RPDs were retrospectively analyzed based on patient records. Treatment failure was defined as fracture of a framework component (metal base or connector) or loss of an abutment tooth. Other outcome variables included factors that might conceivably impact C-RPD survival (maxilla vs. mandible, Kennedy classes, opposing dentitions, treatment by students vs. certified dentists), mobility and caries of abutment teeth (in relation to clasp designs), and maintenance requirements (relining, clasp or resin fractures). Differences were evaluated by appropriate statistical tests at the P ≤ .05 level. RESULTS: A total of 612 patients (339 men, 273 women) 60.0 ± 11.5 years old at delivery were included, covering 842 C-RPDs and a mean observation period of 42.1 ± 33.2 months. Kaplan-Meier C-RPD survival was 76.2% after 5 years and 49.5% after 10 years. Biological complications (i.e. loss of abutment teeth) accounted for the vast majority (95.6%) of C-RPDs failures, and Kaplan-Meier C-RPD survival was significantly better in the mandible (P = .015). Some clasp designs contributed significantly to caries and removal of abutment teeth (both P < .05). No other significant differences were noted. CONCLUSION: Tooth loss both emerges as the main cause of C-RPDs failure and might be amenable to careful selection of clasp designs. Overall, better C-RPD survival should be expected in the mandible. A non-contributory role of Kennedy classes and opposing dentitions is tentatively suggested based on numerically heterogeneous subgroups.

Changes in the arch width and buccal corridor after fixed orthodontic treatment with Damon self-ligating system: premolar extraction vs. non-extraction.

INTRODUCTION: Extraction vs. non-extraction is a crucial decision in orthodontic therapy. OBJECTIVE: The aim of the present study was to investigate the changes in the dental arch width and buccal corridor after orthodontic treatment using extraction and non-extraction therapy with Damon self-ligating system. MATERIAL AND METHODS: This retrospective study consisted of 35 patients (20 female and 15 male patients with median age of 12.5 years), treated by extracting 4 or 2 premolars, and 37 patients (16 female and 21 male patients with the median age of 12.8 years), treated without premolar extraction. Both groups were treated with Damon self-ligating system. Plaster models before (T0) and after (T1) treatment were measured, and the arch width values were determined at the level of the first molars, second premolars, canines and palatal rugae. Buccal corridor width was measured using the extraoral images at T0 and T1. Paired t-test was used for the analysis of the normally distributed data, and Wilcoxon Mann-Whitney U test was used for the data with non-normal distribution. Values of p<0.05 were set as statistically significant. RESULTS: The upper intercanine width increased significantly in both groups (p<0.01). In the non-extraction group, the arch width increased significantly in the maxillary second premolar and first molar region (p<0.01) as well as in the region of the canines (p=0.04), second premolars (p=0.01) and first molars (p<0.01) of the mandible. The buccal corridor decreased significantly in the non-extraction group (p<0.01). CONCLUSION: Premolar extraction in combination with Damon self-ligating system did not lead to reduction of the dental arch width in the maxilla, nor did it increase the size of the buccal corridors.

Impact of two different patient decision aids in prosthodontic consultations: a prospective randomized controlled study.

OBJECTIVES: Different approaches to prosthodontic consultation, all involving a strong focus on shared decision-making, were analyzed from the perspective of patients by inter-group comparisons. No patient decision aid (PDA) was used in the control group, a paper-based PDA in test group 1, and a software-based PDA in test group 2. MATERIALS AND METHODS: Seventy-five patients were prospectively randomized to the control group or a test group. All patients then rated the consultation on a questionnaire, six key items of which were analyzed, along with the time spent on each consultation. RESULTS: Overall satisfaction was highest in test group 2, with a significant difference from the control group (p = 0.015). Test group 2 showed the most favorable ratings for all six questionnaire items, which invariably was significant compared to the control group (p = 0.032). Test group 1 significantly differed from test group 2 based on two items (consultation was adequately intelligible: p = 0.011; consultation was adequately comprehensive: p = 0.034) but not from the control group based on any item (p = 0.070). CONCLUSIONS: Within the limitations of this study, the use of a software-based PDA, in particular, can be recommended based on patient satisfaction and was associated with the shortest sessions for consultation. CLINICAL RELEVANCE: Patients are routinely faced with a wealth of information in dental offices and may be overwhelmed especially by prosthetic treatment options and decision requirements. Our findings shed some light on the nature of aids that may truly be helpful in the process of shared decision-making. TRIAL REGISTRATION: ClinicalTrials.gov.Identifier: ISRCTN11472465.

[ZApprO versus ZÄPrO: results of a first comparative study]. / ZApprO versus ZÄPrO: Ergebnisse einer ersten Vergleichsstudie.

BACKGROUND: More than 60 years after the enactment of the first Licensing Regulations for Dentists (ZÄPrO), a new Licensing Regulations for Dentists, the ZApprO, was implemented in 2020. The aims of this study were to evaluate and compare the "Course in Technical Propaedeutics" (TPK) with the course "Dental Propaedeutics with a Focus on Dental Technology" (ZPDT), which are based on different legal foundations. METHODS: The following parameters were compared after completion of the courses: (1) theoretical and practical knowledge, (2) regular department-internal learner evaluation, and (3) special evaluation of learning conditions by the learners and (4) by the instructors. The theoretical and practical exams and the questionnaires were analyzed in terms of their test-statistical characteristics (difficulty, discrimination index, internal consistency). Group comparisons between TPK and ZPDT were conducted using t­tests for independent groups. RESULTS: Significant differences were only detected in the students' evaluation of their learning conditions, with theoretical and practical knowledge transfer being rated lower in the TPK than in the ZPDT. DISCUSSION: The comparable results of the knowledge assessments and the regular learner evaluation, triangulated with the comprehensive learner and instructor evaluation, allowed a broad assessment of both courses. The significant differences identified provide opportunities for optimization of the newly implemented ZPDT course.

Ball versus Locator® Attachments: A Retrospective Study on Prosthetic Maintenance and Effect on Oral-Health-Related Quality of Life.

Locator® and ball attachments are well-established systems to attach overdentures to two inter-foraminal implants. This study aimed to evaluate differences between the two systems regarding prosthetic maintenance and patients' oral-health-related quality of life (OHRQoL). Dental records of patients with a mandibular implant-retained overdenture were retrospectively analyzed. Prosthetic maintenance measures involving the denture suprastructure and attachment matrix and patrix were analyzed. Furthermore, the Oral Health Impact Profile-G14 (OHIP-G14) was used to evaluate OHRQoL. Results were analyzed by means of Kaplan-Meier analysis and Student's t- and log-rank tests. The records of 122 patients were evaluated. Kaplan-Meier survival analysis revealed a significant difference between ball attachments (Group B; n patients = 47) and Locator® attachments (Group L; n patients = 75) regarding the occurrence of denture fractures (p < 0.001) and events affecting the matrix (p = 0.028) and patrix (p = 0.030). Group L had a significantly lower total OHIP-G14 score than Group B (p = 0.002). The most common maintenance events were matrix-related and denture relining for both attachment systems. Group B required more maintenance measures than Group L. Moreover, patients in Group L had better OHRQoL than patients in Group B.

Influence of different agents on the preload force of implant abutment screws.

STATEMENT OF PROBLEM: Screw loosening is a common problem in implant dentistry; however, information is sparse on the influence of different fluids on the screw threads. PURPOSE: The purpose of this in vitro study was to investigate the influence of 4 different fluids and agents (saliva, blood, chlorhexidine [CHX] gel, and special sealing silicone) on the preload force of abutment screws. MATERIALS AND METHODS: The test specimens (N=50) consisted of a thread sleeve resembling the implant, an abutment analog, and an abutment screw. The tightening of the screw with a torque wrench was performed in 5 steps (15 Ncm, 20 Ncm, 25 Ncm, 30 Ncm, and 35 Ncm). Each agent was applied in the lumen of the thread sleeve of 10 specimens. Ten dry thread sleeves served as the control. Comparisons between 2 independent groups were performed with the t test or Wilcoxon-Mann-Whitney test, as appropriate. The Bonferroni correction was used for multiple comparisons (α=.05). RESULTS: Preload forces increased linearly with the applied tightening torque for dry implant lumina, as well as for saliva, blood, silicone, and CHX gel in the implant lumina or thread sleeves. In general, none of the tested agents resulted in significantly higher preload forces compared with the dry control. CONCLUSIONS: The agents investigated did not have any lubricant action on implant abutment screws.

Comparison of histomorphometry and microradiography of different implant designs to assess primary implant stability.

OBJECTIVES: To contribute toward optimizing the long-term stability of dental implants. Our working hypothesis was that the degrees of immediate implant-bone contact, and hence of primary stability, would demonstrably differ between implant systems due to their different external geometries and thread designs (macro-design). This demonstration was provided in a bovine model (ex vivo) by employing and comparing histomorphometry and microradiography as evaluation methods. MATERIALS AND METHODS: A total of 120 implants, representing six different implant thread designs, were inserted following the recommended surgical protocol in ribs of freshly slaughtered cattle. Twenty specimens of implants with surrounding bone were prepared per system and were divided into two equally sized groups of 60 specimens for analysis by either histomorphometry or micro-computed tomography. Data were analyzed by Mann-Whitney U test (P ≤ .05). RESULTS: One of the implant systems, featuring a slight tapered external geometry and a progressive thread design, consistently revealed the most favorable bone-implant contacts in both histomorphometric and microradiographic evaluations. Overall, consistently higher values of bone-implant contact were obtained with the microradiographic than the histomorphometric approach, and this difference reached statistical significance in three of the six implant systems tested. CONCLUSIONS: Progressive threads offering a bone-condensing effect can significantly help to maximize implant-bone contact percentages. Compared to histomorphometry, microradiography is likewise a suitable method to evaluate bone-implant contact, offering the additional benefits of being noninvasive and less time consuming.

Clinical evaluation of laboratory-made and CAD-CAM-fabricated occlusal devices to treat oral parafunction.

STATEMENT OF PROBLEM: The demand for occlusal devices to treat oral parafunction is rising. Conventionally, these occlusal devices are produced in the dental laboratory, which requires impressions and gypsum casts. Computer-aided design and computer-aided manufacturing (CAD-CAM) require fewer production steps and may offer greater comfort. Whether this is an improvement on conventional procedures is unclear. PURPOSE: The purpose of this crossover clinical study was to examine whether a digital workflow is feasible for fabricating occlusal devices to treat oral parafunction and to compare CAD-CAM-fabricated occlusal devices with conventionally produced ones to determine whether the digital method provides better results. MATERIAL AND METHODS: Thirty participants wore digitally fabricated occlusal devices for 3 months and then conventionally produced occlusal devices for another 3 months or vice versa. The main target parameter was the participant's preference for 1 of the device types. RESULTS: Both types had specific advantages and disadvantages, but the differences in participants' preference were not statistically significant. After completing the 2 testing periods, 16 participants preferred the laboratory-made device, whereas 12 participants preferred the digital occlusal device. Two participants dropped out during the study. CONCLUSIONS: Given the absence of statistically significant differences, the digitally fabricated device can be considered a suitable alternative to laboratory-made devices. Laboratory-made occlusal devices are now the gold standard. However, given the savings in terms of cost and treatment time, they may be replaced, particularly if the production process can be improved.

Prospective clinical study of bilateral balanced occlusion (BBO) versus canine-guided occlusion (CGO) in complete denture wearers.

OBJECTIVES: Previous studies have often discussed occlusal concepts for complete dentures without formulating a recommendation. Various options are available, the most common ones being canine-guided occlusion (CGO) and bilateral balanced occlusion (BBO). We designed a prospective randomized study to compare these two schemes with the goal of formulating a recommendation. MATERIALS AND METHODS: Forty patients could be evaluated. In a crossover design, they were randomized to a CGO>BBO group and a BBO>CGO group, each starting out by wearing their dentures with the first occlusal scheme for 3 months, followed by a first investigator- and patient-centered assessment. Then, each patient was transitioned to the other occlusal scheme by replacing the denture setup in the dental laboratory, followed by another 3 months of intraoral use and a second assessment. Wilcoxon-Mann-Whitney and marginal homogeneity tests were used for statistical analysis. RESULTS: All statistically significant differences favored the CGO concept. Based on patient ratings, the CGO>BBO group preferred its esthetics (p = 0.02) and the BBO>CGO group its mandibular retention (p = 0.05), phonetics (p = 0.03), and masticatory function (p = 0.01). Based on investigator assessments, maxillary denture retention was found to significantly improve among the BBO>CGO patients after transition to CGO (p = 0.01). CONCLUSIONS: Within the limitations of this study, canine guidance can be recommended as a comfortable alternative to bilateral balanced occlusion for complete dentures. CLINICAL RELEVANCE: This recommendation can reduce the time requirements for the fabrication of complete dentures in dental laboratories.

Conical zirconia telescoping into electroformed gold: A retrospective study of prostheses supported by teeth and/or implants.

BACKGROUND: Telescopic prostheses are an evidence-based treatment modality, and conical zirconia crowns and electro-formed gold copings have been used for dentures supported by teeth and/or implants. PURPOSE: We aimed to evaluate the survival rates of zirconia-based tooth/implant restorations. MATERIALS AND METHODS: A total of 126 telescopic overdentures, all retained by conical zirconia crowns and electro-formed gold copings, were retrospectively evaluated and failures analyzed for abutment configurations. Survival rates and modifying factors were evaluated by Kaplan-Meier analysis, log-rank testing, and Cox regression analysis. RESULTS: We evaluated observation periods of up to 11.5 years (mean: 45.25 ± 25.11 months). Five-year prosthesis survival was 96.9 ± 2.2% (95% CI: 92.6-100). Six dentures had been lost, and these failures were significantly associated with specific abutment configurations. CONCLUSIONS: Within the limitations of this retrospective study, the concept of conical zirconia telescoping into electro-formed gold provides a viable alternative to other telescopic designs used for removable dental prostheses. The concept is well suited especially for tooth/implant-supported prosthetic rehabilitation.

IPS e.max for All-Ceramic Restorations: Clinical Survival and Success Rates of Full-Coverage Crowns and Fixed Partial Dentures.

The IPS e.max system by Ivoclar Vivadent, offering a variety of products and indications, is widely used for all-ceramic restorations. We analyzed the clinical track record of these products in daily clinical practice, associating their restorative survival rate with various parameters to define recommendations for long-term stability. A total of 1058 full-coverage crowns and fixed partial dentures (FPDs) were evaluated retrospectively over up to 66.48 (37.05 ± 18.4) months. All were made of IPS e.max Press, IPS e.max CAD, IPS e.max Ceram or IPS e.max ZirPress and had been delivered by a private dental practice within three years. Uses not recommended by the manufacturer were also deliberately included. The five-year cumulative survival was 94.22% (i.e., 94.69% or 90.58% for glass-ceramic crowns or FDPs and 100% or 90.06% for zirconia-based crowns or FDPs). Significantly superior outcomes emerged for conventional vs. adhesive cementation and for vital vs. non-vital abutment teeth, but not for recommended vs. non-recommended uses. Caution is required in restoring non-vital teeth, but the spectrum of recommended uses should generally be reconsidered and expanded, given our finding of high survival and success rates for IPS e.max ceramics, even for uses not currently recommended by the manufacturer.

Locator® versus ceramic/electroplated double-crown attachments: a prospective study on the intraindividual comparison of implant-supported mandibular prostheses.

OBJECTIVES: Implant-supported overdentures are an established dental treatment mode. The aim of this prospective study was and interindividual comparison of patient satisfaction with restorations retained by a prefabricated and thus inexpensive attachment system (Locator®) or with a technologically complex and thus expensive attachment system (ceramic/electroplated double crowns) with similar retentive performance. MATERIALS AND METHODS: Twelve patients received a Locator and a double-crown prosthesis in a crossover study for test periods of 3 months each. The main target parameter was the patient's final decision in favor of one of the two prosthesis types. RESULTS: After completing both test phases, seven patients opted for the Locator prosthesis and five patients opted for the double-crown prosthesis. CONCLUSION: Given the predominant lack of statistically significant differences, the two types of prostheses can be described as equivalent. A recommendation in favor of the Locator prosthesis can be motivated by its lower cost. CLINICAL RELEVANCE: The results of the study show that the more cost-effective variant was comparable to the more expensive double-crown prosthesis under the conditions prevailing in the study. Depending on the indication, this may influence the decision-making process in daily clinical practice and support the clinician's patient information and consultation efforts.

Accuracy of a Template-Guided Implant Surgery System with a CAD/CAM-Based Measurement Method: An In Vitro Study.

PURPOSE: The aim of this in vitro study was to evaluate the accuracy of template-guided implantation planned with implant-planning software (Implant Studio), comparing computer-aided design/computer-assisted manufacture (CAD/CAM)-based measurements with measurements via cone beam computed tomography (CBCT). MATERIALS AND METHODS: Thirty template-guided implantations were planned and performed on acrylic-resin models. The implant positions were detected with an intraoral scanner, evaluated with CAD quality-control software, and compared with the planned positions in the test group. Preliminary deviations were measured via CBCT in the control group of the first 10 samples and compared with the first 10 samples of the test group. RESULTS: When directly compared, measurements obtained using CBCT (control group) showed a trend toward greater deviations. In the CAD/CAM-based evaluation of the 30 samples, the mean ± SD deviation of the insertion axis from the planned implant axis was 2.011 ± 0.855 degrees. The mean deviations of the implant shoulders in the horizontal direction and at the implant apices were 0.725 ± 0.142 mm and 0.990 ± 0.244 mm, respectively. In the vertical direction, the mean deviation was 0.541 ± 0.129 mm. CONCLUSION: CAD/CAM-based measurements are more accurate than CBCT measurements. Therefore, this radiation-free measurement method is a viable diagnostic alternative. Implant planning with planning software and subsequent placement using surgical templates appears to be a reliable and precise therapeutic option in vitro. However, these findings will still have to be supported by in vivo studies.

In vivo study for tooth colour determination-visual versus digital.

OBJECTIVES: Tooth colour determination is an essential component in the preservative and prosthetic workflow during production of tooth-coloured restorations. The aim of the study was to compare the clinical suitability of conventional, visual tooth colour determination and digital methods. MATERIALS AND METHODS: Tooth colour of vital, natural central incisors among a total of 107 subjects was determined visually by a dentist (VD) and dental technician (VDT) using VITA Toothguide 3D-MASTER®, digitally by the spectrophotometer VITA Easyshade Advance 4.0 (reference instrument) and Trios®Color intra-oral scanner (test subject). Reliability was examined by repeating the digital measurements of 20 teeth three times. The analysis was based on the recorded 3D-MASTER values and L*a*b/L*C*h parameters. RESULTS: The measuring accuracy was 43.9% with the Trios®Color scanner, 35.5% for VD and 34.6% for VDT. In 25.5% of cases, the scanner's results corresponded with VD and in 33.6% with VDT. The visual methods corresponded with 45.8%. All mean values of the recorded colour differences fell within the clinically acceptable range of ΔE ≤ 6.8. The intra-oral scanner attained repeatability of 78.3% and the VITA Easyshade system of 76.6%. CONCLUSIONS: The Trios®Color intra-oral scanner appears to be a good alternative to the current standard of visual tooth colour determination. The new module attains better results than the visual method and is comparable to the reference instrument. CLINICAL RELEVANCE: Dentistry becomes increasingly digitalized and tooth colour determination devices have generally to be improved. Therefore, the investigation of a new digital device is important for future developments.

Digital process for an implant-supported fixed dental prosthesis: A clinical report.

A digital process is presented for an implant-supported single-tooth and a 3-unit fixed dental prosthesis (FDP) with customized abutments and monolithic prosthetic zirconia restorations. The digital impression on the implant level was made with a TRIOS intraoral scanner (3Shape). This process included the fabrication of an implant cast with the fused deposition modeling technique and a 3-dimensional printing process with integrated implant analogs. The process enabled the FDPs to be designed with CAD/CAM on the cast before patient contact. Designing a printed implant cast expands the use of the digital workflow in the dental field.