Accuracy of implant surgical guides fabricated using computer numerical control milling for edentulous jaws: a pilot clinical trial.

BACKGROUND: To evaluate the accuracy of a computer numerical control (CNC) milled surgical guide for implant placement in edentulous jaws. METHODS: Edentulous patients seeking implants treatment were recruited in this prospective cohort study. Radiographic guides with diagnostic templates were fabricated from wax-up dentures. Patients took cone-beam computed tomography (CBCT) wearing the radiopaque radiographic guides. Implant positions were virtually designed in the planning software based on the CBCT data, and the radiographic templates were converted into surgical guides using CNC milling technique. Forty-four implants were placed into 12 edentulous jaws following guided implant surgery protocol. Post-surgery CBCT scans were made for each jaw, and the deviations between the planned and actual implant positions were measured. Deviation of implant position was compared between maxilla and mandible, and between cases with and without anchor pins using independent t-test. RESULTS: Nine patients (3 males and 6 females) with 12 edentulous jaws were recruited. The mean age of patients was 59.2 ± 13.9 years old. All 44 implants was placed without complication and survived, the mean three dimensional linear deviation of implant position between virtual planning and actual placement was 1.53 ± 0.48 mm at the implant neck and 1.58 ± 0.49 mm at the apex. The angular deviation was 3.96 ± 3.05 degrees. No significant difference was found in the deviation of implant position between maxilla and mandible (P = 0.28 at neck, 0.08 at apex), nor between cases with and without anchor pins (P = 0.87 at neck, 0.06 at apex). CONCLUSIONS: The guides fabricated using the CNC milling technique provided comparable accuracy as those fabricated by Stereolithography. The displacement of the guides on edentulous arch might be the main contributing factor of deviation. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR-ONC-17014159 (July 26, 2017).

Retention force of removable partial dentures with different double crowns.

OBJECTIVES: The aim of the study was to compare the retentive behaviors of double crowns with different designs and material compositions before and after artificial aging. MATERIALS AND METHODS: Six pairs of double crowns were fabricated: telescopic crowns 0° made of high-noble metal (group A) or non-precious metal (group B), telescopic zirconia copings with secondary crowns made of electroplated gold 2° (group C), crowns with friction pins 2° made of non-precious metal (group D) or zirconia (group E), and conical crowns 6° made of high-noble metal (group F). Retention forces were assessed before and after artificial aging, and after axial and non-axial loading. RESULTS: Initially, specimens in group D (13.9 N), B (12.5 N), and E (12.2 N) exhibited the highest retention forces. Retention forces in groups A (9.6 N), C (7.4 N), and F (6.0 N) were statistically significantly lower than those of the other groups (p < 0.05). After artificial aging, double crowns with additional retention elements exhibited the highest retention forces. The largest retention force losses were evident in groups A (70%), B (64%), C (39%), and F (47%). CONCLUSIONS: Double crowns with different designs and made of different materials exhibited different retention forces and different long-term retentive behavior. The highest retention force losses were evident in double crowns with more extended surface contact, such as telescopic crowns. CLINICAL SIGNIFICANCE: Telescopic crowns with additional retention elements were more resistant to wearing than double crowns without additional retention elements. An additional clinical benefit might be the quick and easy possibility of enhancing retention.

Accuracy of CAD-CAM-fabricated removable partial dentures.

STATEMENT OF PROBLEM: The conventional fabrication of removable partial dentures (RPDs) is a complex, error-prone, time-consuming, and expensive process. The use of computer-aided design and computer-aided manufacturing (CAD-CAM) techniques, especially rapid prototyping, promises a more effective method for fabricating RPD frameworks. PURPOSE: The purpose of this in vitro study was to evaluate the fit of RPD clasps fabricated by means of 4 different CAD-CAM-systems and to compare those fittings with that of the conventional lost-wax casting technique (LWT). MATERIAL AND METHODS: A master model of a partially edentulous maxilla with the canines and second molars as the remaining teeth was fabricated. After the model was optically scanned, we designed a quadrangularly supported RPD with 4 clasps and a palatal strap major connector. A standard tessellation language data set was used to fabricate 12 identical RPDs by using 4 different CAD-CAM techniques: indirect rapid prototyping (wax inject printing combined with LWT), direct rapid prototyping (selective laser melting), indirect milling (wax milling with LWT), and direct milling (resin milling [polyetheretherketone]). Three conventionally cast RPDs (LWT) served as the control group. The fit accuracy of the clasps (n=12 for each group) was determined in both the horizontal and vertical dimensions by using light microscopy. RESULTS: Indirectly milled RPDs (117 ±34 µm horizontal and 45 ±21 µm vertical) and directly milled RPDs (43 ±23 µm horizontal, and 38 ±21 µm vertical) showed significantly better (P<.05) fit than did conventionally fabricated LWT RPDs (133 ±59 µm horizontal; 73 ±25 µm vertical). The worst fit was found for RPDs fabricated using indirect rapid prototyping (323 ±188 µm horizontal and 112 ±60 µm vertical) or direct rapid prototyping (365 ±205 µm horizontal and 363 ±133 µm vertical), which were unstable on the master model, making them unsuitable for clinical use. Most RPDs exhibited smaller vertical measuring distances. CONCLUSIONS: Compared with the LWT, milling techniques enabled fabrication of RPDs with comparable or better fit. However, RPDs fabricated with rapid prototyping techniques showed distinct fitting irregularities.

The repeatability of digital shade measurement--a clinical study.

OBJECTIVES: The intraoral VITA Easyshade spectrophotometer is a shade measurement system that provides for objective determination of the shade of natural teeth and of dental materials. Over a period of 2.5 years, this clinical study assessed the repeatability of VITA Easyshade measurement, using metal ceramic restorations and based on L*a*b* parameters. MATERIALS AND METHODS: Shade tests of 25 metal ceramic crowns were carried out objectively in 19 patients using VITA Easyshade and subjectively by a dentist. The measurements were taken using a separate positioning device at the time of insertion, after 14 days (baseline), after 6 months, after 1.5 years and after 2.5 years. RESULTS: ∆E was calculated from ∆L*, ∆a*, ∆b* data as a measure of the differences in shade. The average values during the follow-up controls were ∆E 2 = 2.2 (6 months), ∆E 3 = 2.3 (1.5 years) and ∆E 4 = 2.0 (2.5 years). Subjective shade analysis during the follow-up controls did not reveal any changes in the ceramic veneer. CONCLUSIONS: The average of ∆E = 2.1 represented the difference in color. The examiner could not detect any difference in color over the evaluation period of 2.5 years. CLINICAL RELEVANCE: Good results in terms of the repeatability and accuracy of VITA Easyshade measurements were reported in previous in vitro studies. Objective assessment under clinical conditions is required in order to evaluate the shade stability of tooth-colored restorative materials in the oral cavity. For this purpose, the quality and handling of VITA Easyshade must be verified from a clinical perspective.

Frictional telescopic crowns in severely reduced dentitions: a 5-year clinical outcome study.

Clinical outcomes for frictional telescopic crowns supporting removable prostheses in patients with severely reduced dentitions with one to three remaining teeth per arch have been inadequately documented. Seventy-four patients with severely reduced dentitions received 82 telescopic removable partial dentures that were supported by 173 frictional telescopic crowns. The recorded individual telescopic abutment survival rate over a 60-month period was 80.6%. This observation was significantly influenced by sex and tooth vitality and mobility (Kaplan-Meier). The risk of loss of telescopic crowns was significantly influenced by sex, arch, vitality, and abutment tooth distribution (Cox regression). Telescopic removable partial dentures were proven to be a favorable treatment concept for severely reduced dentitions in the selected group of patients.

Estimating costs for shade matching and shade corrections of fixed partial dentures for dental technicians in Germany: a pilot investigation.

AIMS: To evaluate the additional operating expenses caused by shade matching by dental technicians in the dental practice and by color changes of fixed partial dentures. METHODS: A questionnaire was handed out to visitors of the 2010 ADT dental technician congress in Germany. Thirty-one completed questionnaires were evaluated. RESULTS: Mean costs caused by shade matching and shade correction per month were 1269$ (SD = 1278$; n = 25) and per unit of FPD 9.32$ (SD = 8.89$). CONCLUSIONS: An improvement of shade matching, shade communication and reproduction should be made in order to minimize the considerable economic damage for dental laboratories.

Longevity of frictional telescopic crowns in the severely reduced dentition: 3-year results of a longitudinal prospective clinical study.

OBJECTIVES: The longevity of frictional telescopic crowns (FTC) in severely reduced dentitions with 1 to 3 remaining teeth per jaw has not yet been studied prospectively and exclusively. Aims of this study were to estimate risks of telescope loss and abutment tooth loss and to determine abutment tooth mobility over time. METHOD AND MATERIALS: A total of 74 patients with severely reduced dentitions received 82 telescopic removable partial dentures (TRPDs) retained with 173 FTCs. Dentures were reexamined after 1 week and 3, 6, 12, 18, 24, 30, and 36 months. Tooth mobility was monitored with Periotest values. Adjuvant therapies were carried out if necessary. Survival probabilities of telescopes and abutment teeth as well as the influence of clinical factors (age, sex, jaw, vitality, opposing dentition, axis inclination, end Periotest value, crown length, crown margin quality, wearing mode, tooth types, abutment distribution, number of telescopes) were calculated with Kaplan-Meier estimators. The relative risks for telescope loss were calculated with Cox regression. RESULTS: The survival rate was 93.9% for abutment teeth and 87.5% for telescopes. Number of telescopes, abutment distribution, vitality, and gender as factors influenced the survival rates (Kaplan-Meier). In combination with the jaw as a factor, these affected the risk for telescope loss (Cox regression). Periotest values (mean of abutment teeth per examination) decreased significantly (P < .0001). Altogether, 11% of teeth fractured and 4.6% of teeth were extracted. Patients were mostly very satisfied. CONCLUSION: TRPDs proved to be a favorable treatment concept for severely reduced dentitions. FTCs can be considered as elements with a good benefit-maintenance relation. A general increase of abutment tooth mobility could not be verified.

Prospective observation of CAD/CAM titanium ceramic single crowns: a three-year follow up.

STATEMENT OF PROBLEM: Computer-aided design/computer-aided manufacturing (CAD/CAM) titanium ceramic restorations were developed with the potential for replacing expensive, high noble metal ceramic restorations. However, there is a lack of information about the clinical performance of CAD/CAM titanium ceramic single crowns. PURPOSE: The purpose of this study was to evaluate CAD/CAM titanium ceramic single crowns after 3 years in function. MATERIAL AND METHODS: A total of 41 crowns were fabricated for 21 patients. The titanium copings were CAD/CAM milled (Everest CAD/CAM system) with an even thickness of 0.5 mm, and low-fusing veneering porcelain (Vita Titanium Porcelain) was added incrementally. The crowns were cemented using zinc phosphate cement after confirming that there were no mechanical and biological complications. The patients were recalled at 12, 24, and 36 months after cementation to examine the presence of any complications and measure periodontal parameters such as probing depth (PD), bleeding on probing (BOP), and plaque index (PI). The success and survival rates were estimated using the Kaplan-Meier analysis. RESULTS: The success rate of CAD/CAM titanium ceramic crowns with regard to mechanical complications was 82.3% (95% confidence interval: 71.2% to 95.1%). The cumulative survival rate of the crowns was 94.9% (95% confidence interval: 88.3% to 100%) after 3 years. No biological complications were observed. At the end of the follow up, PD was 2.93 mm, percentile of surface with BOP was 29.2, and PI was 0.31. CONCLUSIONS: The clinical performances of the CAD/CAM titanium ceramic crowns for 3 years were acceptable, with no biologic complications and a high cumulative survival rate.

Effect of Cisplatin on parotid gland function in concomitant radiochemotherapy.

PURPOSE: To determine the influence of concomitant radiochemotherapy with cisplatin on parotid gland tissue complication probability. METHODS AND MATERIALS: Patients treated with either radiotherapy (n = 61) or concomitant radiochemotherapy with cisplatin (n = 36) for head-and-neck cancer were prospectively evaluated. The dose and volume distributions of the parotid glands were noted in dose-volume histograms. Stimulated salivary flow rates were measured before, during the 2(nd) and 6(th) weeks and at 4 weeks and 6 months after the treatment. The data were fit using the normal tissue complication probability model of Lyman. Complication was defined as a reduction of the salivary flow rate to less than 25% of the pretreatment flow rate. RESULTS: The normal tissue complication probability model parameter TD(50) (the dose leading to a complication probability of 50%) was found to be 32.2 Gy at 4 weeks and 32.1 Gy at 6 months for concomitant radiochemotherapy and 41.1 Gy at 4 weeks and 39.6 Gy at 6 months for radiotherapy. The tolerated dose for concomitant radiochemotherapy was at least 7 to 8 Gy lower than for radiotherapy alone at TD(50). CONCLUSIONS: In this study, the concomitant radiochemotherapy tended to cause a higher probability of parotid gland tissue damage. Advanced radiotherapy planning approaches such as intensity-modulated radiotherapy may be particularly important for parotid sparing in radiochemotherapy because of cisplatin-related increased radiosensitivity of glands.

Parotid-gland-sparing 3D conformal radiotherapy in patients with bilateral radiotherapy of the head and neck region--results in clinical practice.

The aim was to improve the prediction rate of hyposalivation after using a modern 3D-conformal-radiotherapy-technique (3D-CRT) by sparing of the contralateral parotid gland. Between June 2002 and October 2006, 107 patients (90 male, 17 female, average age: 58 years) with squamous cell carcinoma of the head and neck were included in a prospective, non-randomized study. All patients were treated using 3D-CRT. Parotid function was assessed by measuring stimulated salivary flow before, during and at the end of radiotherapy, as well as 1, 6 and 12 months after radiotherapy. Measurements were converted to flow rates and normalized relative to that before treatment. Mean doses (D(mean)) were calculated from dose-volume histograms (DVHs) based on computed tomographies (CTs) for the left and right parotid gland separately. Patients were grouped according to the D(mean) of the lowest irradiated parotid gland. Group I included all patients who received a D(mean)<26Gy (n=23), group II D(mean) 26-40Gy (n=38) and group III D(mean)>40Gy (n=46). By the time of 6 months after irradiation, salivary flow rates decreased continuously during the therapy. In group I the flow rate decreased to 59%, in group II to 40% and in group III to 14%, p<0.05. One year after irradiation a recovery effect could be measured in all groups. A sufficient saliva flow rate can be proven if one parotid gland is spared with a D(mean) dose <26Gy. Approximately, one quarter of the participants showed a significant improvement.

The influence of different disinfectants on primary impression materials.

OBJECTIVE: To investigate the dimensional changes and the surface quality of dental impression materials after disinfection with 3 chemically different agents. METHOD AND MATERIALS: Four alginate impression materials and 1 addition silicone material were selected. The impressions were made from a brass model simulating a 3-unit fixed partial denture. The chemical disinfection was performed with 3 different disinfectants for 10 minutes. Three samples of each impression material and disinfectant agent were investigated. As a control, 3 impressions of each material were made without any disinfection. The casts were made with a type IV dental stone. For each cast, 6 diameters and 3 distances were measured. To evaluate the dimensional stability, measurements were taken at a magnification of 34X with a light microscope. The surface quality was recorded using a profilometer. RESULTS: The dimensional change and surface quality differed minimally; however, statistically significant differences were found between alginate and addition silicone impression materials (ANOVA, P < .05). Casts from the silicone impressions were more accurate than the casts from alginate impressions. CONCLUSION: Different impression disinfection methods have only a marginal influence on dimensional stability and surface quality of dental casts. To achieve a higher precision, the use of an addition silicone can be recommended.

Specialisation and specialist education in prosthetic dentistry in Europe.

This presentation reports on the results of a meeting of prosthodontists from selected European countries. The aim of the meeting was to analyse and promote specialisation and specialist education in Prosthetic Dentistry in Europe. Representatives for Europe were selected from the European Prosthodontic Association (EPA) board, the Education and Research Committee of International College of Prosthodontists (ICP), countries with a legally recognised speciality, countries without a recognised speciality but organised training programmes and countries with neither of these situations. Data about specialisation and specialist training in Prosthodontics in Europe was scrutinised and discussed. The programmes for countries with specialist training had relatively similar content, mostly of three years duration. There was strong agreement that a recognised speciality raises the level of care within the discipline for both specialists and non-specialists. In several of the countries where a speciality had been introduced it had been initiated by pressure from public health planning authorities. The conclusions are that from a professional viewpoint an advancement of the speciality over Europe would develop the discipline, improve oral health planning and quality of patient care. A working group for harmonisation was recommended.

The significance of marginal gap and overextension measurement in the evaluation of the fit of complete crowns.

INTRODUCTION: An important criterion for the success of a crown is marginal fit. However, in the patient's mouth fit can only be evaluated by subjective methods. This study describes the correlation between objective marginal fit and its subjective evaluation by dentists and dental technicians. MATERIALS AND METHODS: Thirty human premolars and molars were randomly divided into six groups and prepared with a shoulder. For each of the six groups, complete crowns were made of different alloys and technologies (casting: AuAgCu, AuPdPt, PdAgAu, CoCrMo, and Ti; milling: Ti). The crowns were cemented with provisional cement. Ten dentists and 10 technicians were asked to evaluate the fit of the crowns with a new dental explorer. The crowns were then cleaned and cemented with a zinc-oxide-phosphate-cement. The marginal gap and a possible overextended margin of the crowns were examined under a special 4x light microscope with a magnification level of 560 X. The means of the gaps and the overextended margins were calculated for each group. Significances were detected by analysis of variance (ANOVA) and the post-hoc-test (Bonferroni, p<0.05). Correlations between objective measuring and subjective evaluation were evaluated using the Pearson test. The influence of the measured values on the subjective evaluation was determined by regression analyses. RESULTS: Crowns made from different alloys and technologies showed partly significantly (p<0.05) different marginal gaps (mean ranging from 35 microm to 92 microm) and significantly (p<0.05) different overextended margins (mean ranging from 40 microm to 149 microm). There were significant correlations (p<0.05) between subjective findings and objective data. Significant correlations (p<0.01) were also found between the subjective findings of dentists and technicians. Compared to the marginal gap, only the overextended margin had a significant influence (p=0.00) on the subjective evaluations of the clinicians. CONCLUSION: Crowns from different alloys and technologies showed differences in marginal fit. Marginal gap and the overextension of the crowns significantly correlated with the subjective evaluation of their fit by dentists and dental technicians. For the decision of the clinicians, whether a crown is acceptable, overextension was more important than marginal gap.

Problems reported by patients before and after prosthodontic treatment.

PURPOSE: This study sought to investigate problems reported by patients before and after prosthodontic treatment. MATERIALS AND METHODS: Patient-reported problems were studied using the item list contained in the German version of the Oral Health Impact Profile in a convenience sample of 107 prosthodontic patients before (T0), 1 month after (T1), and 6 to 12 months after treatment (T2). "Frequently reported" problems were defined as impacts experienced fairly often or very often. The prevalence of frequently reported problems was compared among treatment groups and across appointments. RESULTS: At baseline, the most prevalent frequently reported problems were "difficulty chewing" (31%), "take longer to complete a meal" (28%), "food catching" (26%), "uncomfortable to eat" (24%), and "unable to eat (because of dentures)" (23%). At T2, the most prevalent frequently reported problems were "sore spots" (5%), "painful gums" (4%), "discomfort (because of dentures)" (3%), and "sore jaw" (2%). The number of reported problems decreased from 18.0 (T0) to 7.5 (T1), and further to 4.5 (T2). The decrease was the fastest in fixed partial denture wearers and the slowest in removable partial denture wearers. Some problems emerged during or after prosthodontic treatment. The kind of pre- and posttreatment problems differed substantially. CONCLUSION: The number of problems decreased substantially after prosthodontic treatment. Fixed partial dentures more effectively influenced the problems reported before treatment than did removable partial or complete dentures.

Oral health-related quality of life in patients treated with fixed, removable, and complete dentures 1 month and 6 to 12 months after treatment.

PURPOSE: This study described oral health-related quality of life (OHRQoL) before and after treatment in patients with fixed, removable, and complete dentures. MATERIALS AND METHODS: OHRQoL was measured using the German version of the Oral Health Impact Profile (OHIP-G) in a convenience sample of 107 prosthodontic patients at baseline and 1 and 6 to 12 months after treatment. The sum of OHIP-G item responses (OHIP-G49, range 0 to 196) characterized OHRQoL impairment in 42 patients treated with fixed prosthodontics, 31 patients treated with removable dentures, and 34 patients treated with complete dentures. OHIP-G49 medians were compared with the OHRQoL level in a general population sample (n = 2,026). A multivariable binomial regression analysis, controlling for the effects of baseline OHRQoL and follow-up wave, was used to compare the level of impaired OHRQoL in different prosthodontic treatment groups at follow-ups. RESULTS: OHRQoL improved in 96% of the subjects. OHIP-G49 medians reached the level of OHRQoL in the general population 1 month after treatment (fixed prosthodontics patients 6 OHIP-G units; general population subjects 5 units; removable denture patients 23 units, 15 units in general population subjects; complete denture patients 13 units, 23 units in general population subjects). OHIP-G49 medians were below population norms 6 to 12 months after treatment. In patients treated with removable/complete dentures, the expected posttreatment OHIP-G49 problem rate was 1.9 times the problem rate in patients treated with fixed prosthodontics, holding baseline OHIP-G49 and follow-up wave constant. CONCLUSION: OHRQoL changed substantially comparing pretreatment scores with 1 and 6 to 12 months of follow-up in patients treated with fixed, removable, and complete dentures.