Handling Uncertainty in Cost-Effectiveness Analysis: Budget Impact and Risk Aversion.

Methods to handle uncertainty in economic evaluation have gained much attention in the literature, and the cost-effectiveness acceptability curve (CEAC) is the most widely used method to summarise and present uncertainty associated with program costs and effects in cost-effectiveness analysis. Some researchers have emphasised the limitations of the CEAC for informing decision and policy makers, as the CEAC is insensitive to radial shifts of the joint distribution of incremental costs and effects in the North-East and South-West quadrants of the cost-effective plane (CEP). Furthermore, it has been pointed out that the CEAC does not incorporate risk-aversion in valuing uncertain costs and effects. In the present article, we show that the cost-effectiveness affordability curve (CEAFC) captures both dimensions of the joint distribution of incremental costs and effects on the CEP and is, therefore, sensitive to radial shifts of the joint distribution on the CEP. Furthermore, the CEAFC also informs about the budget impact of a new intervention, as it can be used to estimate the joint probability that an intervention is both affordable and cost-effective. Moreover, we show that the cost-effectiveness risk-aversion curve (CERAC) allows the analyst to incorporate different levels of risk-aversion into the analysis and can, therefore, be used to inform decision-makers who are risk-averse. We use data from a published cost-effectiveness model of palbociclib in addition to letrozole versus letrozole alone for the treatment of oestrogen-receptor positive, HER-2 negative, advanced breast cancer to demonstrate the differences between CEAC, CEAFC and CERAC, and show how these can jointly be used to inform decision and policy makers.

Prevalence of Missing Values and Protest Zeros in Contingent Valuation in Dental Medicine.

BACKGROUND: The number of contingent valuation (CV) studies in dental medicine using willingness-to-pay (WTP) methodology has substantially increased in recent years. Missing values due to absent information (i.e., missingness) or false information (i.e., protest zeros) are a common problem in WTP studies. The objective of this study is to evaluate the prevalence of missing values in CV studies in dental medicine, to assess how these have been dealt with, and to suggest recommendations for future research. METHODS: We systematically searched electronic databases (MEDLINE, Web of Science, Cochrane Library, PROSPERO) on 8 June 2021, and hand-searched references of selected reviews. CV studies in clinical dentistry using WTP for valuing a good or service were included. RESULTS: We included 49 WTP studies in our review. Out of these, 19 (38.8%) reported missing values due to absent information, and 28 (57.1%) reported zero values (i.e., WTP valued at zero). Zero values were further classified into true zeros (i.e., representing the underlying preference of the respondent) or protest zeros (i.e., false information as a protest behavior) in only 9 studies. Most studies used a complete case analysis to address missingness while only one study used multiple imputation. CONCLUSIONS: There is uncertainty in the dental literature on how to address missing values and zero values in CV studies. Zero values need to be classified as true zeros versus protest zeros with follow-up questions after the WTP elicitation procedure, and then need to be handled differently. Advanced statistical methods are available to address both missing values due to missingness and due to protest zeros but these are currently underused in dental medicine. Failing to appropriately address missing values in CV studies may lead to biased WTP estimates of dental interventions.

Incorporating Portfolio Uncertainty in Decision Rules for Healthcare Resource Allocation.

Cost-effectiveness analysis is widely adopted as a means to inform policy and decision makers in setting priorities for healthcare resource allocation. In resource-constrained settings, decision makers are confronted with healthcare resource reallocation decisions, e.g., moving funds from one or more existing healthcare programs to fund new healthcare programs. The decision-making plane (DMP) has been developed as a means to graphically present the results of reallocating available healthcare resources when healthcare program costs and effects are uncertain. Mapping a value function over the DMP allows the analyst to value all possible combinations of net costs and net effects that may result from reallocating available healthcare resources under conditions of uncertainty. In this paper, we extend this approach to include a change in portfolio risk, stemming from a change in the portfolios of funded healthcare programs, as an additional source of uncertainty, and demonstrate how this can be incorporated into the value function over net costs and net effects for a risk-averse decision maker. The methodology presented in this paper is of particular interest to decision makers who are risk averse, as it will help to better incorporate their preferences in the process of deciding how to best allocate scarce healthcare resources.

A retrospective analysis of autotransplanted teeth including an evaluation of a novel surgical technique.

OBJECTIVES: To assess survival rates and frequency of complications for immature and mature autotransplanted teeth after at least 1 year in function. MATERIALS AND METHODS: All consecutive patients who had undergone tooth autotransplantation between 2000 and 2018 were invited to a clinical and radiographic follow-up examination. First, survival rates were calculated on the basis of a phone inquiry. A clinical follow-up examination allowed for the calculation of the success rate, i.e., absence of any potentially adverse clinical and radiographic findings of the autotransplanted teeth. Moreover, the effect of demographic, dental, and surgical variables on survival/success was analyzed statistically. RESULTS: Thirty-eight teeth in 35 patients were transplanted during the study period. Three teeth in 3 patients were excluded due to missing records. All other patients were successfully contacted and interviewed by phone. Out of these 35 transplants, 32 were still in function, and 3 had been extracted, yielding a 91.4% survival probability after a median follow-up of 3.4 years. Of the 32 teeth qualifying for the success analysis, 20 (62.5%) showed absence of potentially adverse findings, while 3 (9.4%) required root canal treatment (RCT). Out of the 9 mature, root-end resected transplants, 4 exhibited ongoing pulp canal obliteration, all with a single root canal. Postoperative and potentially adverse findings or failures were found more frequently in the group of mature transplants (55.6%) than immature transplants (30.4%) and for molars (72.7%) than premolars (17.6%) or canines (25%). None of the potential predictors had a statistically significant effect on survival or success. CONCLUSION: Autotransplanted teeth yielded a satisfying midterm survival rate regardless of their stage of development. An additional, extraoral root-end resection of mature transplants may lead to rates of revascularization and postoperative pulp canal obliteration higher than the data reported on unmodified mature transplants. CLINICAL RELEVANCE: Extraoral root-end resection of mature teeth shows promising outcomes for transplants especially with a single root canal and uncomplicated root morphology.

Dealing with Bad Risk in Cost-Effectiveness Analysis: The Cost-Effectiveness Risk-Aversion Curve.

Cost-effectiveness analysis has been advocated and is widely used to inform policy and decision makers in setting priorities for resource allocation. Since the costs and effects of health care interventions are uncertain, much research interest has focused on handling uncertainty in cost-effectiveness analysis. The most widely used method to summarize uncertainty in cost-effectiveness analysis is the cost-effectiveness acceptability curve, which estimates the probability that an intervention is cost effective for a wide range of threshold ratios. However, by estimating the uncertainty associated with incremental costs and effects, information about the uncertainty associated with the costs and effects of the individual programs is lost, which may be important to inform risk-averse decision makers. In the present paper, we suggest to penalize the expected net monetary benefit (NMB) of a program for its downside risk (i.e. bad risk), which preserves the uncertainty of the individual programs and rank orders programs according to their risk-adjusted NMB. The cost-effectiveness risk-aversion curve (CERAC) is introduced, which estimates the net benefit-to-risk ratio for a wide range of threshold rations. The CERAC is a helpful additional tool to inform decision and policy makers who are risk averse, and can easily be constructed using the results of a cost-effectiveness analysis.

A Systematic Review of WTA-WTP Disparity for Dental Interventions and Implications for Cost-Effectiveness Analysis.

Cost-effectiveness analysis is widely adopted as an analytical framework to evaluate whether health care interventions represent value for money, and its use in dentistry is increasing. Traditionally, in cost-effectiveness analysis, one assumes that the decision maker's maximum willingness to pay (WTP) for health gain is equivalent to his minimum willingness to accept (WTA) monetary compensation for health loss. It has been documented in the literature that losses are weighted higher than equivalent gains, i.e., that WTA exceeds WTP for the same health condition, resulting in a WTA/WTP ratio greater than 1. There is a knowledge gap of published WTA/WTP ratios for dental interventions in the literature. We therefore conducted a (i) systematic review of published WTA-WTP estimates in dentistry (MEDLINE, Web of Science, Cochrane Library, London, UK) and (ii) a patient-level analysis of WTA/WTP ratios of included studies, and (iii) we demonstrate the impact of a WTA-WTP disparity on cost-effectiveness analysis. Out of 55 eligible studies, two studies were included in our review. The WTA/WTP ratio ranged from 2.58 for discontinuing water fluoridation to 5.12 for mandibular implant overdentures, indicating a higher disparity for implant rehabilitations than for dental public health interventions. A WTA-WTP disparity inflates the cost-effectiveness of dental interventions when there is a substantial risk of both lower costs and health outcomes. We therefore recommend that in these cases the results of cost-effectiveness analyses are reported using different WTA/WTP ratios in a sensitivity analysis.

Evaluating Maxillary Sinus Septa Using Cone Beam Computed Tomography: Is There a Difference in Frequency and Type Between the Dentate and Edentulous Posterior Maxilla?

PURPOSE: To analyze and compare the frequency, type, and location of maxillary sinus septa in patients with a dentate and an edentulous posterior maxilla using cone beam computed tomography (CBCT) imaging. MATERIALS AND METHODS: The study consisted of 100 maxillary sinuses: 50 from patients with a dentate and 50 from patients with an edentulous posterior maxilla. The aim was to assess the frequency, morphology, and location of maxillary sinus septa in axial, sagittal, and coronal CBCT images. Images were only included in this study provided that patients were older than 30 years of age, at least one maxillary sinus was completely visible in the field of view (FOV), and the sinus membrane exhibited a mucosal thickening of a maximum 4 mm. Differences regarding age, sex, side, septa location, and type of dentition (dentate/edentulous posterior maxilla) were analyzed. RESULTS: The mean age of the 100 patients (66 women, 34 men) was 58.3 years. A total of 60 sinus septa were found in exactly half of the evaluated sinuses. The major part of the septa was found on the floor of the maxillary sinus (n = 34/56.7%). Of these, the majority was located in the posterior maxilla in the region of the second molars (n = 27/79.4%). The most common orientation of the septa was coronal (63.3%), followed by septa in relation to the infraorbital canal (23.3%). Regarding the status of the dentition in the posterior maxilla in relation to the distribution of sinus septa, septa were present in 26 (52%) dentate and in 24 (48%) edentulous regions. Thus, for a potential influence of the status of the dentition in the posterior maxilla on the frequency of sinus septa, no significant impact was found (P = .69). CONCLUSION: Sinus septa are frequent anatomical structures, and are found equally often in patients with a dentate and an edentulous posterior maxilla. This is of clinical relevance, as patients with missing teeth in the posterior area of the maxilla are often in need of a sinus floor elevation (SFE) procedure when dental implant placement is intended. As sinus septa are reported to be an important reason for surgical complications during SFE, a three-dimensional radiographic examination using CBCT prior to surgery might be helpful for diagnostic evaluation and treatment planning.

Measuring the Monetary Value of Dental Implants for Denture Retention: A Willingness to Pay Approach.

PURPOSE: Two interforaminal dental implants in is a common treatment option for denture retention in edentulous patients. Economic methods to assess the patient's quality of life include the willingness to pay (WTP) for implant treatment and willingness to accept (WTA) to forgo implant treatment. The purpose of this study was to assess the monetary value of implant retained complete dentures using WTP and WTA. METHODS: We included a convenience sample of 16 patients from a previously published cohort study on the survival of immediately loaded implants in edentulous patients to assess WTP and WTA for this treatment option. RESULTS: The average maximum WTP for implant treatment was 4606 (95% CI: 2991-6222) Swiss Francs. Out of the 16 patients, only 5 were willing to trade their implants for money, with a mean WTA of CHF 33'500 (range: 3000-100'000).All patients would agree to undergo the implant surgery procedure again. CONCLUSION: The results of the present study show that most patients are not willing to trade the increase in quality of life after implant surgery against money, suggesting that WTA exceeds by large WTP for the same health condition.

Comparison between Radiographic (2-dimensional and 3-dimensional) and Histologic Findings of Periapical Lesions Treated with Apical Surgery.

INTRODUCTION: The aim of this study was to evaluate the concordance of 2- and 3-dimensional radiography and histopathology in the diagnosis of periapical lesions. METHODS: Patients were consecutively enrolled in this study provided that preoperative periapical radiography (PR) and cone-beam computed tomographic imaging of the tooth to be treated with apical surgery were performed. The periapical lesional tissue was histologically analyzed by 2 blinded examiners. The final histologic diagnosis was compared with the radiographic assessments of 4 blinded observers. The initial study material included 62 teeth in the same number of patients. RESULTS: Four lesions had to be excluded during processing, resulting in a final number of 58 evaluated cases (31 women and 27 men, mean age = 55 years). The final histologic diagnosis of the periapical lesions included 55 granulomas (94.8%) and 3 cysts (5.2%). Histologic analysis of the tissue samples from the apical lesions exhibited an almost perfect agreement between the 2 experienced investigators with an overall agreement of 94.83% (kappa = 0.8011). Radiographic assessment overestimated cysts by 28.4% (cone-beam computed tomographic imaging) and 20.7% (periapical radiography), respectively. Comparing the correlation of the radiographic diagnosis of 4 observers with the final histologic diagnosis, 2-dimensional (kappa = 0.104) and 3-dimensional imaging (kappa = 0.111) provided only minimum agreement. CONCLUSIONS: To establish a final diagnosis of an apical radiolucency, the tissue specimen should be evaluated histologically and specified as a granuloma (with/without epithelium) or a cyst. Analysis of 2-dimensional and 3-dimensional radiographic images alike results only in a tentative diagnosis that should be confirmed with biopsy.

The effect of tooth loss on gait stability of community-dwelling older adults.

OBJECTIVE: To investigate the effects of tooth loss on gait stability in a healthy elderly population. METHODS: A case-control study was conducted among healthy and prosthetically well-restored seniors over the age of 65 years. The test group comprised 24 edentulous participants who were restored with complete dentures in the upper jaw and an overdenture fixed on two implants in the lower jaw. The control group comprised 25 dentate participants who either still had their natural teeth or were restored with conventional fixed partial dentures. Gait stability was evaluated by measuring the parameters 'gait velocity' and 'cycle-time variability' during self-selected normal walking speed and under dual-task performance conditions. Measurements were conducted using the GAITRite(®) electronic walkway system. RESULTS: Dentated and fixed restored participants (the control group) had a significantly higher gait velocity compared with denture wearers (the test group) under both normal walking (p = 0.03) and dual-task performance conditions (p = 0.01). In each test condition, among edentulous participants, gait velocity did not significantly differ according to whether the participant wore their dentures. CONCLUSION: The present results suggest that tooth loss in healthy seniors is associated with lower gait velocity and therefore may have a negative impact on gait stability.

Dacryocystography using cone beam CT in patients with lacrimal drainage system obstruction.

PURPOSE: To assess the usefulness of cone beam CT (CBCT) for dacryocystography (DCG) using either direct syringing or passive application of contrast medium. METHODS: Ten consecutive patients with epiphora who had CBCT-DCG in a sitting position were retrospectively analyzed. CBCT-DCGs were performed using 2 techniques: direct syringing with contrast medium or using the passive technique, where patients received 3 drops of contrast medium into the conjunctival sac before CBCT-DCG. Clinical and radiologic diagnoses were compared for both groups. RESULTS: The 10 patients (men = 3) had a mean age of 63.2 years. Both techniques proved to be simple procedures with good delineation of the bone, soft tissue, and the contrast medium in the lacrimal system. No side effects were noted. CONCLUSIONS: CBCT-DCG is a useful alternative to determine the localization of stenosis in patients with chronic epiphora.

Assessment of smoking behaviour in a dental setting: a 1-year follow-up study using self-reported questionnaire data and exhaled carbon monoxide levels.

OBJECTIVES: This study analyses the changes in smoking habits over the course of 1 year in a group of patients referred to an oral medicine unit. MATERIALS AND METHODS: Smoking history and behaviour were analysed at baseline and after 1 year based on a self-reported questionnaire and on exhaled carbon monoxide levels [in parts per million (ppm)]. During the initial examination, all smokers underwent tobacco use prevention and cessation counselling. RESULTS: Of the initial group of 121 patients, 98 were examined at the follow-up visit. At the baseline examination, 33 patients (33.67 %) indicated that they were current smokers. One year later, 14 patients (42.24 % out of the 33 smokers of the initial examination) indicated that they had attempted to stop smoking at least once over the follow-up period and 15.15 % (5 patients) had quit smoking. The mean number of cigarettes smoked per day by current smokers decreased from 13.10 to 12.18 (p = 0.04). The exhaled CO level measurements showed very good correlation with a Spearman's coefficient 0.9880 for the initial visit, and 0.9909 for the follow-up examination. For current smokers, the consumption of one additional cigarette per day elevated the CO measurements by 0.77 ppm (p < 0.0001) at the baseline examination and by 0.84 ppm (p < 0.0001) at the 1-year follow-up. CONCLUSIONS: In oral health care, where smoking cessation is an important aspect of the treatment strategy, the measurement of exhaled carbon monoxide shows a very good correlation with a self-reported smoking habit. CLINICAL RELEVANCE: Measurement of exhaled carbon monoxide is a non-invasive, simple and objective measurement technique for documenting and monitoring smoking cessation and reduction.

Location and dimensions of the mental foramen: a radiographic analysis by using cone-beam computed tomography.

INTRODUCTION: The mental foramen (MF) is an important landmark in dentistry. Knowledge of its position is central to perform block anesthesia of the mental nerve or to avoid nerve damage during surgical procedures in the premolar area of the mandible. The present radiographic study aimed at evaluating the location and dimension of the MF and measuring distances to neighboring structures by using limited cone-beam computed tomography (CBCT). METHODS: Sagittal, axial, and coronal CBCT images of 142 patients (26 bilateral and 116 unilateral cases) were retrospectively screened to determine the location of the MF with respect to adjacent teeth and to take linear measurements of the size of the MF and its distances to the upper and lower borders of the mandible. In addition, the course and angulation of the mental canal exiting the MF were assessed. RESULTS: The majority of MF (56%) were located apically between the 2 premolars, and another 35.7% of MF were positioned below the second premolar. On average, the MF was localized 5.0 mm from the closest root of the adjacent tooth (range, 0.3-9.8 mm). The mean size of the MF showed a height of 3.0 mm and a length of 3.2 mm; however, individual cases showed large differences in height (1.8-5.1 mm) and in length (1.8-5.5 mm). All mental canals exiting the MF demonstrated an upward course in the coronal plane, with 70.1% of the mental canal presenting an anterior loop (AL) in the axial view. The mean extension of AL in cases with an AL was 2.3 mm. CONCLUSIONS: This study is consistent with previous radiographic studies regarding size and location of MF and distances between MF and adjacent anatomic structures. The assessed bilateral cases showed a high intraindividual concordance for certain features when comparing right and left sides.

Anatomical characteristics and dimensions of edentulous sites in the posterior maxillae of patients referred for implant therapy.

The purpose of this study was to analyze the width and height of edentulous sites in the posterior maxilla using cone beam computed tomography (CBCT) images from patients referred for implant therapy. A total of 122 CBCT scans were included in the analysis, resulting in a sample size of 252 edentulous sites. The orofacial crest width was measured in coronal slices, perpendicular to the alveolar ridge. The bone height was analyzed in the respective sagittal slices. Additionally, the following secondary outcome parameters were evaluated: the morphology of the sinus floor, the presence of septa in the maxillary sinus, and the thickness of the sinus membrane. The mean crest width for all analyzed sites was 8.28 mm, and the mean bone height was 7.22 mm. The percentage of patients with a crest width of less than 6 mm was 27% in premolar sites and 7.8% in molar sites. The bone height decreased from premolar to molar areas, with a high percentage of first and second molar sites exhibiting a bone height of less than 5 mm (54.12% and 44.64%, respectively). Regarding the morphology of the sinus floor, 53% of the edentulous sites exhibited a flat configuration. A septum was present in 67 edentulous sites (26.59%). Analysis of the sinus membrane revealed 88 sites (34.9%) with increased mucosal thickness (> 2 mm). For the crest width, the location of the edentulous site and the morphology of the sinus floor were both statistically significant variables. For the crest width and mean bone height, the location of the edentulous site and the morphology of the sinus floor were both statistically significant variables. The study confirmed that a high percentage of edentulous sites in the posterior maxilla do require sinus floor elevation to allow the placement of dental implants. Therefore, a detailed three-dimensional radiograph using CBCT is indicated in most patients for proper treatment planning.

Characteristics and dimensions of the sinus membrane in patients referred for single-implant treatment in the posterior maxilla: a cone beam computed tomographic analysis.

PURPOSE: The purpose of the present study was to evaluate the thickness and anatomic characteristics of the sinus membrane using cone beam computed tomography (CBCT) in patients evaluated for implant surgery in the posterior maxilla. MATERIALS AND METHODS: The study included 131 consecutive patients referred for dental implant placement in the posterior maxilla. A total of 138 CBCT images was obtained using fields of view of 4 × 4 cm, 6 × 6 cm, or 8 × 8 cm. Reformatted sagittal CBCT slices were analyzed with regard to the thickness and characteristics of the sinus membrane at single-tooth gaps in the posterior maxilla. Factors that might influence the dimensions of the sinus membrane, such as age, sex, endodontic status, and the season, were analyzed. RESULTS: The mean thickness of the maxillary sinus mucosa varied between 2.1 and 2.69 mm in the three locations analyzed. Fewer than half of the evaluated sinuses exhibited a healthy mucosa (49 of 138, or 35.51%). Most of the pathologic findings were flat, shallow thickenings (63 of 138, or 45.65%). Sex did not influence the thickness of the sinus membrane at the root tips of the premolars or at single-tooth gaps, but there was a statistically significant correlation in the region of the maxillary molars. No other evaluated factors had a statistically significant effect on the dimensions of the antral mucosa. CONCLUSIONS: In the present study, sex was the only factor influencing the dimension of the sinus membrane, whereas patient age, season, and the endodontic status of neighboring teeth had no significant effect on the thickness of the antral mucosa. Future studies should address which types of mucosal thickening require interdisciplinary therapy.

Assessment of bone channels other than the nasopalatine canal in the anterior maxilla using limited cone beam computed tomography.

PURPOSE: The anterior maxilla, sometimes also called premaxilla, is an area frequently requiring surgical interventions. The objective of this observational study was to identify and assess accessory bone channels other than the nasopalatine canal in the anterior maxilla using limited cone beam computed tomography (CBCT). METHODS: A total of 176 cases fulfilled the inclusion criteria comprising region of interest, quality of CBCT image, and absence of pathologic lesions or retained teeth. Any bone canal with a minimum diameter of 1.00 mm other than the nasopalatine canal was analyzed regarding size, location, and course, as well as patient gender and age. RESULTS: A total of 67 accessory canals ≥1.00 mm were found in 49 patients (27.8%). A higher frequency of accessory canals was observed in males (33.0%) than in females (22.7%) (p = 0.130). Accessory canals occurred more frequently in older rather than younger patients (p = 0.115). The mean diameter of accessory canals was 1.31 ± 0.26 mm (range 1.01-2.13 mm). Gender and age did not significantly influence the diameter. Accessory canals were found palatal to all anterior teeth, but most frequently palatal to the central incisors. In 56.7%, the accessory canals curved superolaterally and communicated with the ipsilateral alveolar extension of the canalis sinuosus. CONCLUSIONS: The study confirms the presence of bone channels within the anterior maxilla other than the nasopalatine canal. More than half of these accessory bone canals communicated with the canalis sinuosus. From a clinical perspective, studies are needed to determine the content of these accessory canals.

Markov models in dentistry: application to resin-bonded bridges and review of the literature.

Markov models are mathematical models that can be used to describe disease progression and evaluate the cost-effectiveness of medical interventions. Markov models allow projecting clinical and economic outcomes into the future and are therefore frequently used to estimate long-term outcomes of medical interventions. The purpose of this paper is to demonstrate its use in dentistry, using the example of resin-bonded bridges to replace missing teeth, and to review the literature. We used literature data and a four-state Markov model to project long-term outcomes of resin-bonded bridges over a time horizon of 60 years. In addition, the literature was searched in PubMed Medline for research articles on the application of Markov models in dentistry.

Immediate loading of two unsplinted mandibular implants in edentulous patients with an implant-retained overdenture: an observational study over two years.

OBJECTIVES: Immediate loading of two unsplinted mandibular implants by means of an overdenture may be a viable and cost-effective treatment option to improve the patient's oral health-related quality of life. We therefore conducted a prospective observational study to estimate implant survival and patient satisfaction after an immediate loading protocol in edentulous patients. MATERIALS AND METHODS: Twenty edentulous patients who received two interforaminal implants (Straumann Standard implant, length 12 mm) were included in our study. Immediately after implant placement, ball attachments with a diameter of 2.25 mm were placed on the implants and the respective matrices were directly incorporated in the existing complete denture. Clinical recalls were scheduled 1 week, 1, 3, 6 months, and 1 and 2 years after implant placement. The following clinical parameters were assessed: gingival bleeding index (GBI), visual plaque index (VPI), and soft tissue overgrowth. In addition, we also assessed radiological bone level change (RBLC) using panoramic radiographs, and patient satisfaction using a visual analogue scale at baseline, after 6 months and 2 years. RESULTS: No implant failures occurred during the 2-year observation period, resulting in a survival rate of 100%. The mean RBLC was 0.67 mm (95% Confidence Interval [95% CI]: 0.47-0.86 mm) two years after surgery. The GBI and VPI after two years were 24 (95% CI: 9-38)% and 36 (95% CI: 19-53)%, respectively. Soft tissue overgrowth was 1.6 mm (95% CI: 1.1-2.1) on average after two years. In a multivariate regression model, patients with a GBI ≥50% on average showed an increased RBLC (-0.6 mm, p = 0.007). High patient ratings were recorded for overall satisfaction. Overall patient satisfaction measured on a scale between one and ten was 5.2 (95% CI: 2.1-8.5) before implant placement and 9.5 (95% CI: 9.1-10) after 2 years. CONCLUSION: Immediate loading of two unsplinted interforaminal implants in overdenture patients using ball attachments is a clinically viable treatment option that leads to a high survival rate and oral health-related quality of life.

Wear of ceramic and titanium ball attachments in subjects with an implant-retained overdenture: a controlled clinical trial.

STATEMENT OF PROBLEM: Loss of retention of implant-retained overdentures due to wear of the patrix or matrix of the attachment system is a common clinical problem. PURPOSE: The purpose of this controlled clinical trial was to compare the wear of ceramic and titanium ball attachments and their corresponding gold matrices after 1 year of clinical function in subjects with implant-retained mandibular overdentures. MATERIAL AND METHODS: Forty subjects who had been treated with a 2-implant-retained overdenture received either 2 ruby ball attachments (20 subjects) or 2 titanium ball attachments (20 subjects). The diameter of the ball attachments and the thickness of the matrix were measured optically before insertion and after 1 year of clinical function. Differences among groups were then compared with the Wilcoxon rank sum test (α=.05). To estimate any correlation between clinical parameters and wear, the Spearman rank test was used. RESULTS: There was no significant difference (P=.73) in the median wear of ball attachments for the titanium group (5.3 µm; median 1.3 µm) and for the ceramic group (1.3 µm; median 1.3 µm). In the ceramic group, a fracture rate of 30% was observed. The mean wear of the matrices in the titanium group was 3.1 µm (median 6.8 µm) and in the ceramic group 2.1 µm (median 3.4 µm), P=.01. No correlation was found between ball attachment wear and matrix insert wear (Spearman rank test). Wear of matrices was weakly correlated with an increase in divergence between implant axes in the sagittal plane (P=-.28 and P=.021). Ball attachment wear was associated with an increase in divergence between matrix axes in the sagittal plane (P=-.34 and P=.047). CONCLUSIONS: Matrices on ceramic ball attachments showed less wear than those placed on titanium ball attachments. However, the use of ruby ball attachments cannot be recommended because of a high fracture rate.