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.

Molecular and cellular cues of diet-associated oral carcinogenesis--with an emphasis on areca-nut-induced oral cancer development.

In modern times, potent dietary carcinogens are key contributors for neoplastic development. For oral squamous cell carcinoma (OSCC), one of the leading cancer types in developing countries, main oncogenic inducers/enhancers, including areca nut chewing, tobacco smoking, and alcohol consumption, were shown to promote cancer initiation/progression. Over decades, studies from different laboratories have identified underlying cellular and molecular mechanisms for carcinogen-induced OSCC. In this review, we will give an overview of where we are in understanding potential oral carcinogenic factors stimulated OSCC tumorigenesis, especially those associated with areca nut chewing in Asians, aiming to provide future scope of possible interception.

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.

Development of digital shade guides for color assessment using a digital camera with ring flashes.

Digital photographs taken with cameras and ring flashes are commonly used for dental documentation. We hypothesized that different illuminants and camera's white balance setups shall influence color rendering of digital images and affect the effectiveness of color matching using digital images. Fifteen ceramic disks of different shades were fabricated and photographed with a digital camera in both automatic white balance (AWB) and custom white balance (CWB) under either light-emitting diode (LED) or electronic ring flash. The Commission Internationale d'Éclairage L*a*b* parameters of the captured images were derived from Photoshop software and served as digital shade guides. We found significantly high correlation coefficients (r² > 0.96) between the respective spectrophotometer standards and those shade guides generated in CWB setups. Moreover, the accuracy of color matching of another set of ceramic disks using digital shade guides, which was verified by ten operators, improved from 67% in AWB to 93% in CWB under LED illuminants. Probably, because of the inconsistent performance of the flashlight and specular reflection, the digital images captured under electronic ring flash in both white balance setups revealed less reliable and relative low-matching ability. In conclusion, the reliability of color matching with digital images is much influenced by the illuminants and camera's white balance setups, while digital shade guides derived under LED illuminants with CWB demonstrate applicable potential in the fields of color assessments.

Shear bond strength of provisional restoration materials repaired with light-cured resins.

This study evaluated the repair bond strengths of light-cured resins to provisional restoration materials with different chemical compositions and polymerization techniques. Fifty discs (10 mm in diameter and 1.5 mm thick) were fabricated for each provisional resin base material, including a self-cured methacrylate (Alike), self-cured bis-acrylate (Protemp 3 Garant), light-cured bis-acrylate (Revotek LC) and a heat-cured methacrylate (Namilon). All specimens were stored in distilled water at 37 degrees C for seven days before undergoing repair with one of four light-cured resins, including AddOn, Revotek LC, Dyractflow and Unifast LC and a self-cured resin (Alike), according to the manufacturers' instructions, for a total of 200 specimens. After 24 hours of storage in 37 degrees C water, the shear bond strengths were measured with a universal testing machine and fracture surfaces were examined under a stereomicroscope. Two-way ANOVA revealed that provisional resin-base material (p < 0.001), repair material (p < 0.001) and their interactions (p < 0.001) significantly affected the repair strength. Tukey's multiple comparisons showed that the lowest bonding strengths were found in specimens of heat-cured methacrylate resin materials repaired with bis-acryl resins, with their failure modes primarily being of the adhesive type. The highest bond strengths were recorded when the provisional resin-base materials and repairing resins had similar chemical components and the failure modes tended to be of the cohesive type.

Triple immediate therapy (ridge expansion, soft tissue augmentation, and provisional restoration) of maxillary anterior single implant.

BACKGROUND: Immediate restoration during implant placement in the premaxillary area can achieve a favorable esthetic result. However, the treatment always poses a great challenge to clinicians, especially for patients with preexisting soft and hard tissue deficiencies. The aim of this clinical report was to present a protocol for a multidisciplinary approach to provide an immediate implant restoration for patients with ridge deficiency. METHODS: A 21-year-old female presented with a mesial shift of the maxillary right canine due to loss of a lateral incisor at an early age. The treatment protocol included orthodontic space redistribution to open a canine space for implant placement. Subsequently, ridge expansion and implant placement combined with connective tissue grafting for the reconstruction of the soft tissue profile were performed, and an immediate provisional prosthesis was delivered simultaneously. A definitive University of California at Los Angeles-style ceramometal crown was completed 6 months later with periodical clinical maintenance. RESULTS: The 18-month postoperative follow-up revealed that the implant was stable, and the buccal depression of the surgical area was reconstructed. Papillae were augmented, and a harmonious soft tissue margin was achieved in the esthetic zone. Radiographs demonstrated a normal vertical osseous height and excellent osseointegration of the implant. CONCLUSIONS: The combination technique of ridge expansion and soft tissue augmentation can be applied to immediate implant restoration cases without the need for complicated bone grafting surgeries in atrophic ridges. This triple immediate strategy enabled us to reduce the number of surgeries, which simplified the overall procedure without compromising the esthetic results.

Reconstruction of the severely resorbed atrophic edentulous ridge of the maxilla and mandible for implant rehabilitation: report of a case.

We describe a case with a severely resorbed atrophic edentulous ridge in both the maxilla and mandible. The maxilla was reconstructed using a sinus-lifting procedure and onlay bone graft. The mandible was reconstructed by anterior osteotomy with an interpositional sandwich iliac bone graft at the symphysis area, subperiosteally with iliac bone chips mixed with hydroxylapatite bilaterally at the posterior atrophic ridge, and vestibuloplasty with a split thickness skin graft (STSG). After full-mouth implant rehabilitation, a 5-year follow-up of this case shows a satisfactory result.

Transpositioned flap vestibuloplasty combined with implant surgery in the severely resorbed atrophic edentulous ridge.

The use of transpositioned flap (lipswitch) vestibuloplasty combined with implant surgery in patients with severely resorbed atrophic edentulous ridges is reviewed. The cases of 17 patients with severely resorbed atrophic edentulous ridges at the mandible undergoing implant rehabilitation were reviewed. Lipswitch vestibuloplasty was followed immediately by the implant surgery. Postoperative follow-up consisted of clinical and radiographic examinations. Seventeen patients with atrophic ridges (12 class II and 5 class III) each had 2 implant fixtures placed in the mandible as abutments for a clip and bar overdenture. The average time of follow-up was 6 years. Before surgery, all patients had severely atrophic ridges with a compromised shallow vestibule of varying degrees. Satisfactory results were observed in regard to the immediate and long-term morphology of the vestibule, the health of the peri-implant tissue, the stability of implant fixtures, and the functionality of the prostheses. The lipswitch vestibuloplasty offers a safe and convenient method of surgical access for implant fixture installation, with the advantage of rebuilding the vestibule of a compromised atrophic ridge in the anterior mandible.

Effects of implant neck design on primary stability and overload in a type IV mandibular bone.

This study investigates the effect of implant neck design on primary stability and overload using 3D finite element analysis. Four commercial dental implants and mandibular segments are created. Various parameters including the osseointegration condition (non-osseointegration and full osseointegration), force direction (vertical and horizontal), and cortical bone thickness (Tc = 0.3, 0.5, and 1 mm) are considered. The vertical and horizontal forces, 500 N and 250 N, are statically applied at the top of the platform, respectively. Micromotion and von Mises stress are employed to evaluate the risk of osseointegration and bone fatigue before osseointegration condition. After osseointegration, the principal stress is used to analyze the bone overload. Maximal von Mises stress and micromotion of the peri-implant bone decreased as cortical bone thickness increased. Horizontal force induces stress concentration in the bone around the implant neck easier than that of vertical force, and it may result in crestal bone loss. Thinner cortical bone should avoid dental implantation because it causes a noteworthy larger micromotion and stress concentration in cortical bone in particular Tc less than 0.3 mm.

Finite element analysis of dental implant neck effects on primary stability and osseointegration in a type IV bone mandible.

The purpose of this study is to investigate the effect of implant neck design and cortical bone thickness by means of 3-D linearly elastic finite element analysis and to analyze primary and secondary stability of clinical evidence based on micromotion and principal stress. Four commercial dental implants, comparable in size, for a type IV bone and mandibular segments were created. Various parameters were considered, including the osseointegration condition (non- and full bonded), force direction (vertical and horizontal) and cortical bone thickness (0.3, 0.5 and 1mm). The force was considered a static load applied at the top of the platform. The magnitudes of the vertical and horizontal loading direction were 500 N and 250 N. Micromotion and principal stresses were employed to evaluate the failure of osseointegration and bone overloading, respectively. The results show that Maximum stress of the peri-implant bone decreased as cortical bone thickness increased. The stress concentration regions were located at the implant neck between the cortical bone and cancellous bone. The micromotion level in full osseointegration is less than that in non-osseointegration and it also decreases as a increasing of cortical bone thickness. Consequently, cortical bone thickness is a key factor for primary stability.

Areca nut extracts increased the expression of cyclooxygenase-2, prostaglandin E2 and interleukin-1α in human immune cells via oxidative stress.

BACKGROUND AND OBJECTIVES: Areca nut has been identified as a carcinogen. Inflammation reveals a strong link with tumourigenesis. The aim of this study was to investigate the effects of areca nut on the expression of the key pro-inflammatory mediators involved in malignancy, cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), interleukin (IL)-1α and nuclear factor-κB (NF-κB), by human immune cells. The role of oxidative stress was also examined. MATERIALS AND METHODS: Human peripheral blood mononuclear cells (PBMCs) were treated with extracts of ripe areca nut (rANE) or tender areca nut (tANE). Expression of pro-inflammatory mediators was assayed using Western blotting, reverse transcription-polymerase chain reaction, competitive enzyme immunoassay or enzyme-linked immunosorbent assay (ELISA). Activity of NF-κB was evaluated using an ELISA-based method. RESULTS: Both rANE and tANE enhanced the expression of COX-2, PGE2 and IL-1α by PBMCs. The secretion of PGE2 was induced by rANE (≤20-40µgml(-1)) and tANE (≤160µgml(-1)) significantly in a dose- and time-dependent manner. However, the above enhancing effects of ANEs could be attenuated by antioxidants. ANEs also increased the nuclear expression of the redox-sensitive factor NF-κB. CONCLUSIONS: The results demonstrate that ANEs induced the expression of pro-inflammatory mediators mainly through the induction of oxidative stress and implicate the possibility of using antioxidants for disease prevention.

Effects of light attenuation by fibre posts on polymerization of a dual-cured resin cement and microleakage of post-restored teeth.

OBJECTIVES: The influence of light transmitting ability of different fibre posts on the polymerization of a dual-cured resin cement, and the further microleakage of the post-restored endodontically treated teeth were examined. METHODS: An LED curing light was used as light source and the measurements of 470 nm irradiances were made at 1mm intervals along the posts (P-Lux, P-White, and P-Steel). The polymerization of a dual-cured resin cement surrounding the posts at five depths (0, 2, 5, 8, and 10mm) from the top was evaluated using micro-Raman spectra after 40s light-curing. Meanwhile, 36 human single-rooted endodontically treated teeth were randomly divided into three groups and restored with these posts and the cement according to the manufacturers' instructions. Microleakages of the post-restored teeth were compared using an electrochemical measurement system on three consecutive days, and statistically analysed using nonparametric tests. RESULTS: Light transmission through fibre posts was exponentially reduced as the depth increased (p<0.05, R(2)>0.95), and the polymerization of the resin cement beyond the depth of 5mm significantly declined for all specimens (p<0.05). Fibre posts displayed higher value of light transmission, exhibited a higher polymerization rate of surrounding resin cement, and also demonstrated less microleakage; whilst P-Steel posts had the lowest polymerization rate and produced higher microleakage (p<0.017). CONCLUSIONS: The effective radiance along the post was diminished exponentially, which features the insufficient polymerization of a dual-cured resin cement surrounding the posts at apical region and might therefore influence the microleakage of post-restored teeth.