Hikaru Arakawa

Quality of life assessment of bone-anchored fixed partial denture patients with unilateral mandibular distal-extension edentulism

STATEMENT OF PROBLEM Dental implants are expanding their use among partially edentulous patients. However, whether implants can promote the quality of life (QOL) of these patients has not been sufficiently examined. PURPOSE This study compared the QOL level among implant denture, removable partial denture, and no restoration patients with distal extension type unilateral mandibular edentulism. MATERIAL AND METHODS Three groups (n = 12 each) of subjects with unilateral mandibular distal-extension edentulism who were matched for age, sex, and missing teeth were studied. The groups were (1) implant denture, (2) removable partial denture, and (3) no restoration. QOL levels of these 3 groups were compared using a self-administered questionnaire with 3 major subscales: oral condition, general condition, and dental treatment. RESULTS The implant denture group showed higher oral condition related QOL score than the other groups. There was no significant difference in oral condition-related QOL scores between the removable partial denture and no restoration groups. There was no significant difference in the general condition related QOL score and dental treatment-related score among the 3 groups. CONCLUSION In unilateral mandibular distal extension edentulous patients, oral-condition-related QOL levels for dental implant patients were higher than those of removable partial denture or no restoration patients. The QOL levels of the removable partial denture patients were almost identical to those of no restoration patients.

Response shift in oral health-related quality of life measurement in patients with partial edentulism

The purposes of this study were to determine whether a response shift was observable after partial denture treatment and to identify the predictors that influenced the response shift magnitude and direction. A total of 173 consecutive patients with no more than eight missing teeth who received implant-supported, fixed or removable partial dentures at Okayama University Dental Hospital were asked to complete a full-version Oral Health-Related Quality of Life (OHRQoL) questionnaire before (pre-test) and after treatment (post-test). Additionally, a short form (then-test) consisting of seven questions selected from the full version had its reliability verified and was utilised to retrospectively assess the pre-treatment OHRQoL status. The difference between the summary scores of the then-test and the pre-test determined the response shift magnitude and direction. The then-test mean score (22·9 ± 6·6) was significantly lower (worse OHRQoL) than that of the pre-test (26·4 ± 5·2). The response shift effect size was of moderate magnitude and negative direction (d = -0·78). A multiple regression analysis showed that age (younger patients) (P < 0·01), number of replaced teeth (fewer) (P < 0·01) and pre-test scores (lower) (P < 0·01) were the significant predictors for response shift. In conclusion, a response shift phenomenon with negative and moderate effect size was observed after partial denture treatment. The significant predictor variables were young age, fewer numbers of replaced teeth and lower pre-test scores.

A longitudinal retrospective study of the analysis of the risk factors of implant failure by the application of generalized estimating equations

PURPOSE Many studies have identified risk factors for dental implant failure, although few have investigated the correlation among implant fixtures within single patients. A better analytical method may include repeated measures analysis including generalized estimating equations (GEE). This retrospective cohort study aimed to (1) identify the risk factors for failure of dental implantation and (2) evaluate an analytical method using GEE analysis. METHODS We analyzed data on early and late implant failures in 296 patients providing 721 rough surface dental implants (2.44 implants per patient). Potential predictors of implant failure included age, gender, smoking, location of implant, use of bone augmentation, number of remaining teeth, opposing tooth condition, fixture length, fixture diameter and type of suprastructure (fixed or removable partial denture). The likelihood of early and late implant failure was estimated by GEE. RESULTS The early failure rate was 1.5% (11/721 implants, 7/296 patients) and the 10-year cumulative survival rate was 94.0% (7/710 implants, 5/293 patients). The GEE analysis revealed that a significant risk factor for early implant failure was smoking (p<0.01), whereas significant risk factors for late failure were maxillary implant (p=0.02), posterior implant (p<0.01), number of remaining teeth (≥20) (p<0.01), opposing unit being a removable partial denture or nothing (p=0.04) and having a removable type suprastructure (p<0.01). CONCLUSIONS GEE analysis showed that smoking was a risk factor for early implant failure, and several risk factors were identified for late implant failure.

Matrix metalloproteinase-8 is the major potential collagenase in active peri-implantitis

PURPOSE Current clinical procedures to control or regenerate bone loss due to peri-implantitis are not predictable neither accomplish complete resolution. Therefore, early detection of the onset and the active periods of bone loss are crucial for prevention of extensive peri-implant bone resorption. This study aimed to determine a possible association between the presence of collagenases (MMP-1, MMP-8 and MMP-13) in peri-implant sulcular fluid (PISF) and active periods of bone loss by annually adjusted vertical bone loss (AVBL) measurements. METHODS Intended sample consisted of 76 consecutive patients who received oral implant treatment at the Fixed Prosthodontic Clinic of Okayama University Hospital from 1990 to 2000. Twelve subjects were lost to follow-up or refused to participate. Consequently, the actual sample consisted of 64 patients who were followed-up for at least one year. Those patients with AVBL>0.6mm were included in the severe peri-implantitis group, and randomly selected, age-, gender- and implantation site-matched healthy patients (AVBL<0.3mm) comprised the control group. PISF samples were collected from both groups and further analyzed by western blot for detection of collagenases. RESULTS Four patients presented severe peri-implantitis. MMP-8 was the only collagenase detected in peri-implant sites with ongoing bone loss. PISF samples from control group showed no positive reactions to any collagenase. CONCLUSION This study showed MMP-8 as a possible marker for progressive bone loss in peri-implantitis.

Retrospective investigation of the remaining teeth status of patients with implant-supported fixed partial dentures in unilateral free-end edentulism

PURPOSE This study aimed to compare the various complication-free rates and survival rates of remaining teeth among implant-supported fixed dentures (IFDs), removable partial dentures (RPDs) and no-restoration (NR) patients with unilateral free-end edentulism. MATERIAL AND METHODS The study subjects were selected among those who received prosthodontic treatment at Okayama University Dental Hospital for their unilateral free-end edentulism (2 or 3 missing teeth). Thirty-three patients were included in the IFD group, 41 matched patients in the RPD group, and 10 patients who received RPDs but refused their use were regarded as NR group. The remaining dentition was classified into five subcategories in relation to the missing portion: adjacent teeth to the missing portion (AD), contralateral posterior dentition in the same jaw (CS) and in the opposite jaw (CO), ipsilateral opposing posterior dentition (IO), and anterior dentition (AN). Complications were defined as tooth extraction, periodontal lesions, periapical lesions or loss of retention of the prosthesis and were assessed by one examiner based on the hospital chart records. RESULTS The cumulative complication-free rates in the remaining teeth were significantly different among each of the three groups (p<0.01), with a significantly lower incidence rate in the IFD group. Regarding the cumulative survival rate of the remaining teeth, there was a significant difference only between IFD and NR group (p=0.01), especially in the CO region (p=0.04). CONCLUSIONS Stable posterior occlusal support obtained with IFD treatment for unilateral free-end edentulism may reduce the incidence of complications in the remaining teeth, by decreasing the adverse mechanical stress.

Identification of risk factors for fracture of veneering materials and screw loosening of implant‐supported fixed partial dentures in partially edentulous cases

This retrospective study identified the risk factors for fracture of veneering materials and screw loosening of implant-supported fixed partial dentures in partially edentulous cases. The study group included a total of 182 patients who were installed 219 suprastructures at the Fixed Prosthodontic Clinic of Okayama University Dental Hospital between February 1990 and March 2005 and were subdivided in two subgroups: 120 patients (149 facing suprastructures) were included in the subgroup to investigate the risk factors of fracture of veneering materials, and 81 patients (92 suprastructures) were included in the subgroup to identify the risk factors of abutment screw loosening. Each patient was followed up from the day of suprastructure installation until March, 2005. A Cox proportional hazards regression model was used to identify the risk factors related to technical complications, and eight factors were regarded as candidate risk factors. Screw retention was the significant risk factor for fracture of veneering materials, whereas connection of suprastructures with natural tooth was the significant risk factor for screw loosening. It was suggested that screw retention was a significant risk factor for the fracture of veneering materials, and connection of suprastructures with natural tooth was a significant risk factor for screw loosening. Future studies, involving dynamic factors (e.g. bruxism) as predictors as well, are more helpful to discuss the risk factor of fracture of veneering materials and screw loosening.

A retrospective comparative 8-year study of cumulative complications in teeth adjacent to both natural and implant-supported fixed partial dentures.

PURPOSE To compare the complication rate of natural teeth adjacent to implant supported dentures (IFDs) with that of teeth serving as abutments for fixed partial dentures (FPDs). The second goal was to assess the risk factors for complications in teeth adjacent to bounded edentulous spaces. MATERIALS AND METHODS The study subjects were selected from patients who received prosthodontic treatment for their bounded edentulous space not exceeding two missing teeth between February 1990 and March 2007. Sixty-one patients were included in the IFD group and 66 patients were included in the FPD group. Tooth complications were defined as tooth extraction, periodontal lesion, periapical lesion, and loss of prosthesis and were assessed by one examiner based on dental records. RESULTS The 8-year cumulative complication rate for the IFD group (7.9%) was significantly lower than for the FPD group (40.7%). Additionally, the 8-year cumulative complication rate of vital teeth (6%) was significantly lower than that of nonvital teeth (45.9%). A cox proportional hazard analysis revealed that nonvitality of dental pulp was a significant risk factor for tooth complications, whereas treatment modality was not. CONCLUSIONS Teeth adjacent to IFD-treated edentulous spaces presented fewer complications than natural teeth serving as abutments for FPDs. Conservation of teeth adjacent to edentulous spaces as vital teeth was the key finding to limit further tooth loss.

A retrospective comparative ten-year study of cumulative survival rates of remaining teeth in large edentulism treated with implant-supported fixed partial dentures or removable partial dentures

PURPOSE This study aimed to compare the survival rates of remaining teeth between implant-supported fixed dentures (IFDs) and removable partial dentures (RPDs) in patients with large edentulous cases. The second goal was to assess the risk factors for remaining tooth loss. MATERIALS AND METHODS The study subjects were selected among those who received prosthodontic treatment at Okayama University Dental Hospital for their edentulous space exceeding at least four continuous missing teeth. Twenty-one patients were included in the IFD group and 82 patients were included in the RPD group. Survival rates of remaining teeth were calculated in three subcategories: (1) whole remaining teeth, (2) adjacent teeth to intended edentulous space, and (3) opposing teeth to intended edentulous space. RESULTS The ten-year cumulative survival rate of the whole remaining teeth was significantly higher in the IFD group (40.0%) than in the RPD group (24.4%). On the other hand, there was no significant difference between two groups in the survival rate of teeth adjacent or opposing to intended edentulous space. A Cox proportional hazard analysis revealed that RPD restoration and gender (male) were the significant risk factors for remaining tooth loss (whole remaining teeth). CONCLUSIONS These results suggest that IFD treatment can reduce the incidence of remaining tooth loss in large edentulous cases.

Planning for Prosthodontic Clinical Researches-Predictor and Outcome Variables and Statistical Analysis-

臨床疫学研究を遂行する際に, 統計方法の選択と結果の解釈は頭を悩ます事項である. 特に, 臨床研究の遂行に十分慣れていない初心者にとっては, 統計の難しさがハードルになって, 臨床研究に苦手意識を持つ場合がある. しかし, 臨床疫学研究の本質は, 仮説の設定と研究デザインであり, これらが決まれば, 予測因子と結果因子, 統計方法はある程度自動的に決定される. 本論文では, 前回の研究デザインを中心にした内容に引き続いて, 各種変数, 統計方法などこれから臨床研究を行うための必須の知識を概説した.