Food impaction on three-dimensional printed models with periodontal ligament simulation.

OBJECTIVE: This study aims to evaluate food impaction on three-dimensional (3D) printed models with periodontal ligament simulation. MATERIALS AND METHODS: Based on a commercial typodont pair, 3D maxillary and mandibular models were created with no teeth and with tooth sockets that were 1 mm wider than the original ones from 24 to 27 or 34 to 37 for periodontal ligament simulation with vinyl polysiloxane impression material. In total, 35 pairs of 7 combinations, including maxillary/mandibular typodonts in occlusion with maxillary/mandibular 3D models with/without a distal gap of canines on 3D models (tooth 23 or 33) were mounted on hinge articulators and divided into seven groups (n = 5). Each sample experienced the same manual chewing simulation on a customized device. The proximal surfaces were photographed to measure the percentage of food impaction area using ImageJ software. RESULTS: Group with fixed maxillary and mandibular teeth showed more food impaction than other groups with significant differences in the average of maxilla and the average of all proximal areas. CONCLUSION: The flexibility of the periodontal ligament and the degree of freedom of the teeth in their sockets may contribute to the extent of food impaction in proximal spaces.

Food Impaction in Dentistry: Revisited.

PURPOSE: This review aimed to highlight the aetiology and risk factors of food impaction along with the treatment in each case. MATERIALS AND METHODS: A search was conducted in PubMed from 1947 to March 28, 2023. The search terms utilised included (food impaction) OR (interdental impaction). No filter was applied. Articles related to the classification, aetiology, treatment, and associated factors of food impaction in dentistry and published in English or with an abstract in English were selected. RESULTS: A total of 72 articles were included in the review, which revealed the variety and complexity of aetiological factors and treatment of food impaction in dentistry, as well as the heterogeneity of previous studies. Based on the aetiology, different treatment plans and management should be considered. CONCLUSION: This review indicated the need to identify the pathology of food impaction before treatment. Considering the causal factors of food impaction - including proximal contact loss, occlusal disharmony, morphological deformity, positional abnormality, and interdental papillae loss - different management approaches such as restoration, occlusal adjustment, orthodontic, nonsurgical or surgical treatment could be applied. Further clinical and experimental research is warranted to address the prevention and treatment of food impaction in dentistry.

Clinical Outcomes of Posterior Implants with Surveyed Crowns for Implant-Assisted Removable Partial Dentures: A Retrospective Study.

Purpose: To evaluate the clinical outcomes of posterior implants with surveyed crowns in implant-assisted removable partial dentures (IARPDs). Materials and Methods: Internal-connection implants were inserted and restored with surveyed crowns at the most posterior molar regions of Kennedy class I or II in partially edentulous patients between 2007 and 2018. IARPDs were fabricated and functioned with or without clasps on the surveyed implant crowns. Clinical outcomes of biologic problems, mechanical problems, and marginal bone loss (MBL) through periapical and panoramic views were recorded and measured. The effects of sex, Kennedy classification, opposing dentition, and clasp existence on MBL were analyzed using Mann-Whitney test, and the implant length, crown-to-implant (C/I) ratio, and function period on MBL were analyzed using a multiple regression analysis at α = .05. Results: A total of 32 posterior implants were restored with a surveyed crown for IARPDs in 16 patients (7 men, 9 women; mean age: 69.3 ± 6.0 years). A total of 15 IARPDs were for the mandible (1 maxilla), and 13 were Kennedy class I (3 class II) before implant insertion. All internal-connection implants (15 bone-level and 17 tissue-level) with 7-mm (n = 12), 8.5-mm (n = 18), and 9-mm (n = 2) lengths were restored for 3 surveyed premolar crowns and 29 molar crowns (15 first molar and 14 second molar). The mean C/I ratio was 1.48. The mean function period of the implants was 60.9 ± 40.2 months (range: 14 to 155), and the mean MBL was 0.11 ± 0.36 mm. Only Kennedy class II showed significantly more MBL (P = .002). The implant survival and success rates were 96.9% and 90.6%, respectively. Conclusion: Within the limitations of this retrospective clinical study, mainly in mandibular IARPDs, implants with surveyed crowns showed high survival and success rates during short- to medium-term functions. Posterior implants with surveyed crowns appear to be a reliable alternative for free-end removable partial denture (RPD) patients.

Low Bone Density Predictability of CBCT and Its Relation to Primary Stability of Tapered Implant Design: A Pilot Study.

Research regarding bone density assessment using cone beam computed tomography in low bone density regions is sparse. This in vitro study aimed to evaluate the predictability of cone beam computed tomography for low bone density regions and its correlations with primary implant stability when placing tapered design implants with a stepped osteotomy. Eighteen porcine mandibular condyles were used as simulated low bone density regions. Hounsfield units (HU), obtained via multislice computed tomography, and gray values (GV), obtained via cone beam computed tomography, were measured three times at one-month intervals. The maximum implant insertion torque (MIT) and implant stability quotient (ISQ) were recorded as the taper design implants were placed using a stepped osteotomy. HU and GV were measured as 335.05-803.07 and 389.98-906.40, respectively. For repeated measurements of HU and GV, the intraclass correlation coefficients were 0.989 and 0.980; the corresponding value for mean HU and GV was 0.768. Bland-Altman plots showed a mean difference between HU and GV of -78.15. Pearson correlation coefficients revealed a strong correlation between HU and GV (r=0.91, p<0.01). The mean ± standard deviation values for MIT and ISQ were 36.44 ± 6.64 Ncm and 80.85 ± 2.03, respectively, but no statistically significant correlations were found with GV and HU. Within the study's limitations, GV showed similar bone density estimation compared to HU in soft bones. Tapered implant placement with a stepped osteotomy achieved stable primary implant stability in soft bones. However, these in vitro results need to be approved in further clinical studies.

Long term clinical result of implant induced injury on the adjacent tooth.

The purpose of the retrospective study was to investigate the long-term result of implant-induced injury on the adjacent tooth. The subjects of this retrospective study were patients who had received implants and had tooth injury; direct invasion of root (group I), root surface contact (group II), or < 1 mm distance of the implant from the root (group III). Clinical and pathological changes were periodically examined using radiographs and intra-oral examinations. Paired t-tests and chi-square tests were used to evaluate the implant stability quotient (ISQ) of implant and tooth complications, respectively (α = 0.05). A total of 32 implants and teeth in 28 patients were observed for average 122.7 (± 31.7, minimum 86) months. Seven teeth, three of which were subsequently extracted, needed root canal treatment. Finally, 90.6% of the injured teeth remained functional. Complications were significant and varied according to the group, with group I showing higher events than the others. The ISQs increased significantly. One implant in group I resulted in osseointegration failure. The implant survival rate was 96.9%. In conclusion, it was found even when a tooth is injured by an implant, immediate extraction is unnecessary, and the osseointegration of the invading implant is also predictable.

Corrigendum: Clinical evaluation of ridge augmentation using autogenous tooth bone graft material: case series study.

[This corrects the article on p. 156 in vol. 39, PMID: 24471036.].

Evaluation of adjacent tooth displacement in the posterior implant restoration with proximal contact loss by superimposition of digital models.

PURPOSE: This study was conducted to investigate patterns of adjacent tooth displacement in the posterior implant with interproximal contact loss (ICL) by 3-D digital superimposition method. MATERIALS AND METHODS: Posterior partially edentulous patients, restored with implant fixed partial prostheses before 2011 and suffered from food impaction of ICL between 2009 and 2011, were included. Two dental casts, at the time of delivery and at the time of food impaction in a same patient, was converted into 3-D digital models through scanning and superimposition was performed to assess chronologic changes of the dentition. Directions of tooth displacement were evaluated and the amount of ICL was calculated. Correlations between the amount of ICL and elapsed time, or between the amount of ICL and age after function, were assessed at a significance level of P<.05. RESULTS: A total number of 13 patients (8 males, 5 females) with a mean age of 65.76 ± 9.94 years and 17 areas (4 maxillae, 13 mandibles) were included in this retrospective study. Teeth adjacent to the implant restoration showed complex displacements but characteristic tendency according to the location of the arch. The mean amount of ICL was 0.33 ± 0.14 mm. Elapsed time from function to ICL was 61.47 ± 31.27 months. There were no significant differences between the amount of ICL and elapsed time, or age (P>.05). CONCLUSION: Natural teeth showed various directional movements to result in occlusal change in the arch. The 3-D superimposition of chronologic digital models was a helpful method to analyze the changes of dentition and individual tooth displacement adjacent to implant restoration.

Hydroxyapatite-coated implant: Clinical prognosis assessment via a retrospective follow-up study for the average of 3 years.

PURPOSE: This research evaluated clinical outcomes of two types of hydroxyapatite (HA)-coated implants: OT (Osstem TS III-HA, Osstem implant Co., Busan, Korea) and ZM (Zimmer TSV-HA, Zimmer dental, Carlsbad, USA). MATERIALS AND METHODS: The research was conducted on 303 implants (89 of OT, 214 of ZM), which were placed from January 16, 2010 to December 20, 2012. The prognosis was evaluated in terms of success rates, survival rates, annual marginal bone loss, and implant stability quotients (ISQ). The samples were classified into immediate, early, conventional, and delayed groups according to the loading time. RESULTS: Overall, there were no significant differences between OT and ZM in success rates, survival rates, and annual marginal bone loss, except for the result of secondary stability. OT showed 77.83 ± 8.23 ISQ, which was marginally higher than 76.09 ± 6.90 ISQ of ZM (P<.05). In terms of healing periods, only immediate loading showed statistically significant differences (P<.05). Differences between OT and ZM were observed in terms of two indices, the annual marginal bone loss (0.17 ± 0.58 mm/year < 0.45 ± 0.80 mm/year) and secondary stability (84.36 ± 3.80 ISQ > 82.48 ± 3.69 ISQ) (P<.05). OT and ZM did not have any statistically significant differences in early, conventional, and delayed loading (P>.05). CONCLUSION: OT (97.75%) and ZM (98.50%) showed relatively good outcomes in terms of survival rates. In general, OT and ZM did not show statistically significant differences in most indices (P>.05), although OT performed marginally better than ZM in the immediate loading and 1-stage surgery (P<.05).

Conservative interdisciplinary treatment of a case with multiple facial and condyle fractures.

The purpose of this case report is to describe an interdisciplinary approach for a 51-year-old male who underwent multiple facial fractures including bilateral condyle fractures. The patient underwent emergency surgery, which included open reduction of the maxilla and mandibular symphysis and closed reduction of the bilateral condyle fractures. Although the patient recovered a comfortable range of mouth opening and alleviation of the temporomandibular joint (TMJ) symptoms after surgery, he suffered from a large anterior-posterior discrepancy due to less stability on the condyle-fossa relationships and from open bite with contacts only on both second molars and right second premolars. In this case, first, to increase the occlusal contact, comprehensive orthodontic treatment was completed. Second, occlusal equilibration was selectively performed to relieve the interferences and establish a stable range of mandibular movement without any changes in the vertical dimension. Third, both the upper central incisors and left lateral incisor were minimally restored with splinted and single zirconia crowns, which had modified lingual contours to provide adequate anterior guidance permitting the anterior-posterior discrepancy of the posterior teeth during protrusion. This conservative interdisciplinary treatment, including open and closed reduction, orthodontic treatment, occlusal adjustment, and minimal prosthetic restorations, resulted in a stable mandibular position and recovery of mastication function.

Prospective randomized clinical trial of hydrophilic tapered implant placement at maxillary posterior area: 6 weeks and 12 weeks loading.

PURPOSE: Early loading of implant can be determined by excellent primary stability and characteristic of implant surface. The implant system with recently improved surface can have load application 4-6 weeks after installing in maxilla and mandible. This study evaluated the effect of healing period to the stability of hydrophilic tapered-type implant at maxillary posterior area. MATERIALS AND METHODS: This study included 30 patients treated by hydrophilic tapered-type implants (total 41 implants at maxilla) and classified by two groups depending on healing period. Group 1 (11 patients, 15 implants) was a control group and the healing period was 12 weeks, and Group 2 (19 patients, 26 implants) was test group and the healing period was 6 weeks. Immediately after implant placement, at the first impression taking, implant stability was measured using Osstell Mentor. The patients also took periapical radiographs after restoration delivery, 12 months after restoration and final followup period. The marginal bone loss around the implants was measured using the periapical radiographs. RESULTS: All implants were survived and success rate was 97.56%. The marginal bone loss was less than 1mm after 1 year postoperatively except the one implant. The stabilities of the implants were not correlated with age, healing period until loading, insertion torque (IT), the diameter of fixture and the location of implant. Only the quality of bone in group 2 (6 week) was correlated with the stability of implant. CONCLUSION: Healing period of 6 weeks can make the similar clinical prognosis of implants to that of healing period of 12 weeks if bone quality is carefully considered in case of early loading.

Retrospective clinical study of ultrawide implants more than 6 mm in diameter.

BACKGROUND: The prognosis of wide implants tends to be controversial. While wider implants were initially expected to result in a larger osseointegration area and have higher levels of primary stability, they were reported to have a relatively high rate of failure. The clinical outcome of ultrawide implants of more than 6 mm in diameter was evaluated through a retrospective study. METHODS: The investigation was conducted on patients who had received ultrawide implant (≥6 mm diameter) placements in Seoul National University Bundang Hospital from January 2008 to December 2013. Complications were investigated during the maintenance period, and marginal bone loss was measured using periapical radiography. Primary stability immediately after the implant placement and second stability after second surgery or during impression were measured using Osstell® Mentor (Osstell, Sweden) as an implant stability quotient (ISQ). RESULTS: Fifty-eight implants were placed in 53 patients (30 male, 23 female), and they were observed for an average of 50.06 ± 23.49 months. The average ISQ value increased from 71.22 ± 10.26 to 77.48 ± 8.98 (P < 0.005). The primary and secondary stability shows significantly higher at the mandible than at the maxilla (P < 0.001). However, mean survival rate shows 98.28 %. Average marginal bone loss of 0.018 and 0.045 mm were measured at 12 and 24 months after the loading and 0.14 mm at final follow-up date (mean 46.25 months), respectively. Also in this study, the bone loss amount was noticeably small compared to regular implants reported in previous studies. CONCLUSIONS: The excellent clinical outcome of ultrawide implants was confirmed. It was determined that an ultrawide implant can be used as an alternative when the bone quality in the posterior teeth is relatively low or when a previous implant has failed.

The clinical prognosis of implants that are placed against super-erupted opposing dentition.

OBJECTIVES: If teeth are missing, super-eruption of teeth in the opposing arch can occur in the area and can change the occlusal plane. When missing teeth are replaced with implants, the oral surgeon must determine whether or not the super-erupted teeth need to be treated in order to normalize the occlusal plane. In this study, we evaluated the clinical prognosis of dentition after implant placement and prosthetic treatment were completed in an occlusal plane altered by super-erupted teeth in the opposing arch without additional treatment of the super-erupted teeth. MATERIALS AND METHODS: Twenty-two patients (9 males, 13 females) were treated with implants and prosthetics without addressing the super-erupted opposing dentition from April 2004 to August 2012 at Seoul National University Bundang Hospital. A total of 33 implants were placed. Values of crestal bone loss, survival rates, and surgical and prosthetic complications for an average of 29.6 months after prosthetic loading were recorded. RESULTS: In one case, the cover screw was exposed after implant surgery. The mean crestal bone loss was 0.09±0.30 mm. Of the 33 implants, 31 survived, a survival rate of 93.94%. A prosthetic complication occurred in one case but functioned well after correction. CONCLUSION: Favorable clinical results from prosthetic complications, crestal bone loss, and implant survival rates were exhibited in implants next to a super-erupted opposing tooth.

Effects of Computer-Aided Manufacturing Technology on Precision of Clinical Metal-Free Restorations.

PURPOSE: The purpose of this study was to investigate the marginal fit of metal-free crowns made by three different computer-aided design/computer-aided manufacturing (CAD/CAM) systems. MATERIALS AND METHODS: The maxillary left first premolar of a dentiform was prepared for all-ceramic crown restoration. Thirty all-ceramic premolar crowns were made, ten each manufactured by the Lava system, Cercon, and Cerec. Ten metal ceramic gold (MCG) crowns served as control. The marginal gap of each sample was measured under a stereoscopic microscope at 75x magnification after cementation. One-way ANOVA and the Duncan's post hoc test were used for data analysis at the significance level of 0.05. RESULTS: The mean (standard deviation) marginal gaps were 70.5 (34.4) µm for the MCG crowns, 87.2 (22.8) µm for Lava, 58.5 (17.6) µm for Cercon, and 72.3 (30.8) µm for Cerec. There were no significant differences in the marginal fit among the groups except that the Cercon crowns had significantly smaller marginal gaps than the Lava crowns (P < 0.001). CONCLUSIONS: Within the limitation of this study, all the metal-free restorations made by the digital CAD/CAM systems had clinically acceptable marginal accuracy.

A case report about the reconstruction procedures of the previously failed cylinderical implants site using distraction osteogenesis.

We report the eventually successful treatment of a huge bone defect and peri-implantitis following reconstruction of a previously failed intra-mobile cylinder implant system (IMZ) implant site using distraction osteogenesis (DO). In the anterior mandible, two IMZ implants failed and surgical debridement was performed in accordance to the patient's needs. Thereafter, mobility and suppuration were decreased and the patient visited the dental clinic on a regular basis for oral health maintenance. However, the inflammation did not resolve, and the bone destruction around the implants progressed for 4 years. Finally, the implants failed and a severe bone defect remained after implant removal. To reconstruct the bone defects, we attempted bone graft procedures. Titanium mesh was unsuccessfully used to obtain bone volume regeneration. However, DO subsequently was used to obtain sufficient bone volume for implant placement. The new implants were then installed, followed by prosthetic procedures. In conclusion, progression of peri-implantitis could not be arrested despite surgical intervention and repeated maintenance care for 3 years. Reconstruction of the peri-implantitis site was complicated due to its horizontal and vertical bone defects. Lesions caused by implant failure require an aggressive regenerative strategy, such as DO. DO was successful in reconstruction of a peri-implantitis site that was complicated due to horizontal and vertical bone defects.

Prospective comparative study of tapered implants with SLA surfaces in the maxillary posterior area according to 3- and 6-month loading time.

The purpose of this study was to demonstrate clinical outcomes of sandblasted, large-grit, acid-etched (SLA)-surfaced tapered implants when early loaded in partially edentulous spaces in the maxilla. SLA-surfaced implants were placed in participants in the maxillary posterior edentulous area. At the time of definitive restoration, participants were allocated either to group 1 (3-month loading group) or group 2 (6-month loading group). A total of 36 participants (18 people [35 implants] in group 1 and 18 [33 implants] in group 2) were analyzed. Clinical outcomes, including survival rate and peri-implant parameters such as marginal bone loss were measured 1 year after loading. The survival rate was 97.0% in group 1 and 100% in group 2. Marginal bone loss was 0.22 ± 0.34 mm in group 1 and 0.17 ± 0.25 mm in group 2 at 1 year after loading (P = .488). There were no significant differences between groups in keratinized mucosal width (P = .206), Plaque Index (P = .677), or Gingival Index (P = .558). With adequate remaining bone height and primary implant stability achieved, the 3-month early loading of SLA-surface tapered implants may be a viable choice when restoring posterior maxillary edentulous areas.

Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.

OBJECTIVES: The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. MATERIALS AND METHODS: The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. RESULTS: The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p < 0.05). However, the mean bond strengths significantly decreased in the connector groups (CE and CV) after thermal cycling (p < 0.05). The elemental analysis suggested diffusion of ceramic substances into the zirconia surface. CONCLUSIONS: A glass-ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

One-Year Prospective Study of 7-mm-Long Implants in the Mandible: Installation Technique and Crown/Implant Ratio of 1.5 or Less.

This study prospectively evaluated the clinical prognoses of short implants (7-mm long) in the mandible. We investigated the clinical prognosis of short implants in 20 patients (46 implants) according to the installation technique (submerged or nonsubmerged), installation depth (5.5-mm depth, 7-mm depth), and crown/implant ratio. We investigated the marginal bone loss and peri-implant soft-tissue index 12 months after the final prosthetic delivery. Twelve months after prosthetic delivery, no statistically significant differences were observed in bone loss in relation to the type of installation technique, installation depth, or crown/implant ratio. The plaque index and pocket depth indexes were not influenced by the installation technique, installation depth, or crown/implant ratio. We observed marginal bone loss of 3.3 mm in 1 implant from the nonsubmerged group. The total 1-year success rate was 97.83%. Based on this 1-year success rate, short implants had a good clinical prognosis, regardless of the installation technique, installation depth, or crown/implant ratio.

Effect of surface treatment and liner material on the adhesion between veneering ceramic and zirconia.

Fully sintered zirconia blocks, each with one polished surface, were treated with one of the followings: 1) no treatment, 2) airborne-particle abrasion with 50µm alumina, and 3) airborne-particle abrasion with 125µm alumina. Before veneering with glass ceramic, either liner Α or liner B were applied on the treated surfaces. All veneered blocks were subjected to shear force in a universal testing machine. For the groups with liner A, irrespective of the particle size, air abrasion on Y-TZP surfaces provided greater bond strength than polishing. Application of liner B on an abraded zirconia surface yielded no significant influence on the adhesion. In addition, specimens with liner A showed higher bond strength than those with liner B, if applied on roughened surfaces. Fractured surfaces were observed as mixed patterns in all groups. For the liner A, surface treatment was helpful in bonding with veneering ceramic, while it was ineffective for the liner B.

Prospective observational study of the early loading of nanostructured calcium phosphate-coated tapered implants in the mandible and maxilla.

The purpose of this study was to evaluate the prospective clinical results of early loading. Implants were inserted in 11 maxillae (group I, 23 implants) and 12 mandibles (group II, 19 implants). Six months after prosthetic loading, several factors were investigated. Significant differences between the primary and secondary stability were not observed in groups I and II. The primary stability in the mandible was 81.1 implant stability quotient (ISQ), which was significantly higher than the 73.3 ISQ value observed in the maxilla (P = .003). The survival rates were 100% in group I and 94.7% in group II for 9 and 10.4 months, respectively. The marginal bone loss was 0.07 mm in group I and -0.07 mm in group II. After the placement of nanostructured calcium phosphate- coated implants, excellent primary and second stability was obtained.

Evaluation of subjective satisfaction of dental implant patients.

OBJECTIVES: The goal of this study was to estimate the overall satisfaction level of dental implant patients and further evaluate factors influencing satisfaction. MATERIALS AND METHODS: Self-administered questionnaires were mailed to patients who received dental implant therapy at Seoul National University Bundang Hospital (Seongnam, Korea) from October 2003 to April 2005. The main portion of the questionnaire was shared to evaluate the level of satisfaction with implant therapy. The questionnaires contained evaluations of influencing factors, which were classified as pain-related, service-related, and complication-related. RESULTS: The responses from 93 patients (41 males, 52 females) with a total of 325 implants were included in the analysis, and the mean score for overall satisfaction level with implant therapy was 8.26. Female patients showed higher visual analogue scale (VAS) scores for both pain during (P=0.000) and after implant surgery (P=0.016). Male patients showed more 'negative' values for the reasonability of treatment cost (P=0.008) and the adequacy of the treatment period (P=0.022). CONCLUSION: The subjective satisfaction of patients was influenced by various factors, especially complication-related factors.