Efficacy of customized crown-level position jig in measuring peri-implant crestal bone level on periapical radiographs: An in vitro study.

Background/purpose: Accuracy of using implant length on periapical radiographs as calibration reference for measurements has not been verified. This study aimed to verify the measurements of peri-implant crestal bone level (piCBL) on periapical radiographs taken by the paralleling technique and using the implant length for calibration; and to propose a customized crownlevel position (CLP) jig to improve the measurement accuracy of piCBL. Materials and methods: A typodont installed an implant and a screw-retained crown at maxillary central incisor was used. To simulate piCBL, a metal post was placed near the implant at the same height of implant platform. The CLP jig was designed and 3-dimensionally printed out to allow implant projected orthogonally on periapical film. Thirty periapical radiographs were taken using paralleling technique with and without the jig by three examiners. The implant axis and implant length on radiographs were acquired by image segmentation. The discrepancy of piCBL determination (ΔD) from these measurements were compared and further analyzed when using the implant length for calibration. Results: The piCBL measurement errors were smaller when the jig was used for all examiners (P < 0.001). The inter-rater differences were insignificant. After calibration, ΔD with and without jig were 0.09 (0.07-0.11) and 0.43 (0.38-0.49) mm, respectively. Conclusion: Conventional long-cone paralleling technique using true implant length for calibration demonstrated imprecise piCBL measurement on periapical radiographs. Transferring the implant axis to the CLP jig allowed orthogonal projection of radiography which provided reliable measurements of piCBL with an accuracy of less than 0.1 mm.

Long-term evaluation of peri-implant keratinized mucosa stability after free epithelialized graft and keratinized mucosa shifting procedures: A retrospective study up to 13 years.

OBJECTIVES: This study aimed to assess the risk of less than 2 mm keratinized mucosa (KM) width occurrence after free epithelialized graft (FEG) and keratinized mucosa shifting (KMS) procedures using survival analysis. In addition, KM dimensional changes were evaluated. MATERIALS AND METHODS: This study included 76 implants in 36 patients with insufficient KM (<2 mm). The implants underwent either FEG or KMS procedures. The mid-buccal KM width was measured from surgery to the end of a one 13-year follow-up period. RESULTS: Mean follow-up durations were 9.2 ± 3.9 years for FEG and 6.3 ± 4.2 years for KMS. Two implants in FEG and nine implants in KMS exhibited a KM width of less than 2 mm during follow-up. The hazard ratios for KMS compared to FEG were 6.48 (crude) and 6.54 (adjusted), both statistically significant (p < .05). The incidence rate of KMS (4.06%) was higher than that of FEG (0.63%), with an average incidence time of 3.38 years for KMS and 8.82 years for FEG post-surgery. FEG showed a significant shrinkage within 6 months (33% ± 22%), whereas KMS demonstrated a gradual decrease over 13 years (34% ± 25%). FEG exhibited significantly greater width change than KMS during a 5-year follow-up (p < .05). CONCLUSIONS: FEG and KMS enhanced PIKM but exhibited different long-term reduction patterns. FEG demonstrated rapid shrinkage, while KMS displayed gradual and continuous reduction. Moreover, KMS presented a higher risk and incidence of KM width less than 2 mm compared to FEG.

Risk assessment of interproximal contact loss between implant-supported fixed prostheses and adjacent teeth: A retrospective radiographic study.

STATEMENT OF PROBLEM: Studies of interproximal contact loss (ICL) associated with implant-supported fixed prostheses (ISFPs) have typically used dental floss or metal strips to determine ICL and have shown a high prevalence of 34% to 66%, which does not match the authors' experience. Moreover, the implant prosthetic factors contributing to ICL have seldom been reported. PURPOSE: The purpose of this clinical study was to examine follow-up radiographs of ISFPs to determine the prevalence of open contacts between the ISFP and adjacent teeth and to assess the risk factors associated with ICL at patient, implant prosthesis, and adjacent tooth levels. MATERIAL AND METHODS: Patients treated with ISFPs at a single clinical center were included. Digital radiographs obtained at the time of ISFP delivery and subsequent follow-up were assessed, and a total of 180 ISFPs with 296 interproximal contacts in 147 patients were screened for analyses. The prevalence and risk factors of ICL at the levels of patient (age, sex, diabetes, smoking, and bruxism), implant prosthesis (follow-up period, arch location, splinting, ceramic or metal materials, screw or cement-retained, and abutment-fixture connection), and adjacent tooth (mesial or distal side, contact with unrestored tooth, composite resin restoration, or fixed prosthesis, vitality, bone height, and contralateral spacing) were analyzed with logistic regressions and generalized estimating equation (GEE) analyses (α=.05). RESULTS: The onset of ICL was from 6 to 96 months after ISFP delivery. The prevalence of ICL at the patient level was 15.0%, at the implant prosthesis level 13.3%, and at the adjacent tooth levels 8.8%. Twenty-six of the participants had 2 or more ISFPs. The multivariable GEE analysis reported that sex at patient level; longer follow-up period and implant prostheses with external hexagonal and internal octagonal connections at implant prosthesis level; and contralateral spacing, contact with composite resin filling and mesial side of ISFP at adjacent tooth level were significant risk factors of ICL, where contralateral spacing had the highest adjusted odds ratio of 20.88 (P=.002). CONCLUSIONS: Most of the ICL were found at the mesial side of ISFPs, and the odds of ICL was significant in participants with longer follow-up periods. Internal hexagonal connections reported relatively lower risk than others. Factors relevant to the anterior component of occlusal force, such as male sex, contralateral spacing at adjacent tooth, and proximal contact of ISFP with resin filling, seem to be high risk factors for ICL.