CT-based dentulous mandibular alveolar ridge measurements as predictors of crown-to-implant ratio for short and extra short dental implants

Feasibility of implant placement in healed mandibular molar sites: A retrospective cone beam computed tomography study

STATEMENT OF PROBLEM

Implant placement in the mandibular molar sites plays a crucial role in the restoration of edentulous mandibles. However, the evaluation of bone quantity before implant surgery using cone beam computed tomography (CBCT) is lacking.

PURPOSE

The purpose of this clinical study was to evaluate CBCT images of edentulous patients to analyze the feasibility of implant placement in healed mandibular molar sites.

MATERIAL AND METHODS

The CBCT data of 138 patients were analyzed in the sagittal plane for measurements of mandibular bone height (MBH), superior bone height (SBH), inferior bone height (IBH), buccal bone width (BBW), lingual bone width (LBW), and alveolar bone widths (ABWs). The edentulous sites were categorized according to the bone quantity and complexity of the implant surgery. Multivariate analysis of variance (MANOVA) was used to analyze the site, sex, and age-related variations. An independent t test was used to compare the difference of bone dimension in different sites and between sexes. One-way ANOVA followed by post hoc tests were used to analyze the difference between different age groups. Categorical variables were presented as number of events and percentages. The chi-squared test was used to compare categorical variables (α=.05).

RESULTS

A total of 534 sites of interest were recorded, including 274 hemimandibles. A significant difference in BBW was found between the first and second molar sites. Men had higher MBH, SBH, IBH, and BBW than women. The distribution of implant surgical complexity in the conventional group was 63.5%, while the buccolingual tilted implant group accounted for 17.0%, and the complicated group accounted for 19.5%. Of the 274 hemimandibles, an implant could be placed directly at molar sites in 88% of situations.

CONCLUSIONS

The BBW at the mandibular second molar site was greater than that at the first molar site. The amount of available bone in the SBH and BBW was greater in men than in women at the healed molar sites. Age did not significantly affect the complexity of the implant surgery. Implants can be placed directly in healed mandibular molar sites in most patients who require a complete arch mandibular implant-supported restoration.

Effects of Thermoforming on the Mechanical, Optical, Chemical, and Morphological Properties of PET-G: In Vitro Study

The effectiveness of clear aligners in correcting malocclusions is closely linked to the properties of the materials used to make them. The polymers used in the manufacture of clear aligners have well-established properties. However, the process of manufacturing clear aligners, known as thermoforming, involves thermal and mechanical shocks that may alter these properties. The objective of this study was to evaluate the effects of thermoforming on the mechanical, optical, chemical, and morphological properties of sixty PET-G specimens. The study compared the thickness, weight, absorbance, chemical structure, surface roughness, elastic modulus, yield strength, and breaking load of thirty thermoformed specimens with thirty non-thermoformed specimens. The study introduces a new approach by using standardized samples to analyze both chemical and physical properties. The results showed statistically significant differences in thickness (-15%), weight (-11%), and surface roughness (+1233% in roughness average; +1129% in RMS roughness) of the material. Additionally, a correlation was found between reduction in thickness and increase in opalescence. There was no significant change in the functionality of the aligners after thermoforming, as no significant mechanical changes were found. However, the increase in surface roughness may lead to plaque and fluid accumulation and worsen the fit of the aligners.

Analysis of ultra-short implants with different angulations: a retrospective case-control study with 2 to 9 years of follow-up

OBJECTIVES

Does the angulation of ultrashort implants influence the stability of the peri-implant bone? The present study aimed to evaluate the effectiveness of non-axial ultrashort implants after 2 to 9 years of follow-up in resorbed alveolar ridges.

MATERIALS AND METHODS

All partially edentulous patients with ultrashort implants (< 6 mm) used in the posterior region of an atrophic mandible or maxilla, to support partial dentures in conjunction with standard implants, were included in this study. Peri-implant bone loss, success and survival rates, crestal bone levels, crown-to-implant ratio and implant angulation were measured for each implant. Implants were divided into two groups: straight implants with angulation < 17° (control group) and tilted implants with angulation > 17° (test group). Statistical analysis was used to find any significant differences between the two study groups and to investigate significant linear correlations among all the variables (p = 0.05).

RESULTS

A total of 42 ultrashort implants with a mean of 4 years of follow-up were included: 20 ultrashort axially loaded implants and 22 tilted implants. Mean crestal bone levels from baseline loading to maximum follow-up did not reveal statistical differences in regard to PBL; mean success and survival rates were 100% in all groups.

CONCLUSIONS

PBL, success and survival rates of axial ultrashort implants and tilted ultrashort implants are comparable to those of conventional implants.

CLINICAL RELEVANCE

This retrospective study revealed that ultrashort implants, even when placed with an angulation > 17°, can safely be used to support partial fixed prostheses. Further prospective clinical studies with larger samples and prospective design are needed to confirm these findings.

Evaluation of the clinical efficacy and safety of modified alveolar cleft bone graft with cone-beam CT digital imaging in children

BACKGROUND

Cone-beam computed tomography (CBCT) is used to observe the bone density and bone height in children with modified alveolar bone graft (ABG) at different times after operation. In this study, the changes of labial-palatal bone mass in the stable period of bone union and in the bone graft area were investigated to provide reference for subsequent treatment.

METHODS

A total of 140 pediatric patients with unilateral complete alveolar cleft were selected and routinely underwent iliac bone grafting. The original data obtained by ProMax 3D (Planmeca) examination were stored in DICOM format at 3 and 6 months postoperatively, and the images were reconstructed by Simplant software (Dentsply Sirona). The bone density of the healthy side was measured at 3 months and 6 months, and the results were expressed as Hounsfield units (HU). The labial and palatal bone height at the bone graft site at 3 and 6 months postoperatively was classified according to the modified Bergland classification method, and was compared with panoramic film classification.

RESULTS

Mean bone density at 3 months after surgery (385.4800±78.39770 HU) was not significantly different from that at 6 months (356.1875±73.67164 HU; P>0.05). There were significant differences between the classification of lip and palatal bone height 3 months after operation and that of the classification of panorama film in the same month (P<0.05); between the classification of lip and palatal bone height 6 months after surgery compared with that of panorama film of the same month (P<0.05); and between the classification of bone height degree in labial, palatal, and panoramic slices at 3 months after operation and that at 6 months after operation (P<0.05).

CONCLUSIONS

The labial and palatal classification is different, and the bone height classification 6 months after surgery is lower than that 3 months after surgery, indicating the persistence of bone resorption. CBCT can objectively evaluate the bone quality in the bone graft area, which has clinical application value for surgical evaluation value and posttreatment guidance.

Influence of direct prostheses on the condition of the alveolar processes during dental implantation

OBJECTIVE

The purpose of this article is to study of the processes accompanying osseointegration of the dental implants using various plate prostheses as temporary constructions, as well as to compare the dynamics of changes in the state of the jaw alveolar processes.

MATERIALS AND METHODS

The effect of dentures on the condition of the alveolar processes was studied in all patients according to the technique developed by L. Chulak on the 7th, 14th, 30th day and in 3, 6 months. To verify the results, the degree of atrophy of the alveolar processes was also determined by the second method the authors have chosen at the same time as indicated above.

RESULTS

The measurement results confirm linear changes in the height of the alveolar processes of the jaws with a decrease in the tissues of the prosthetic area. Throughout the duration of the examination, atrophy of the tissues of the alveolar processes is observed. Judging by the results obtained during the patients' study, it can be concluded that when applied as a temporary prosthesis with a dental delayed implantation of a partial denture made of polypropylene, the results of the state of the hard tissues of the mandible alveolar process show a better adaptation of the mucous membrane and slowing of atrophy of the jaw alveolar processes with this type of prosthetics.

Effect of Variable Implant Tip Distances on Stress Distribution around the Mental Foramen: A Finite Element Analysis

AIM: This study aimed to evaluate the effect of gap between traditional implant tip and mental nerve using finite element analysis. METHODS: Four finite element models (FEM) were prepared for dummy crowns that were supported by traditional implants that were placed vertically in laser scanned mandibular bone geometry. Where gap distance were designed to be 1.5, 2.0, 2.5, and 3.0 mm. Dummy crown, 50 μm cement layer, and implant complex models’ components were modeled in 3D on engineering computer-aided design (CAD)/CAD (computer-aided manufacturer) software formerly collected in Finite Element Analysis package. Each model was subjected to two loading cases as 150N compressive load at central fossa, and 50N Oblique (45º) load at central fossa of the dummy crown. RESULTS: Good agreement of the FEM was obtained when compared to similar studies. Under applied study loads, all resulting values of stresses and deformations of the four models were within physiological limits. The obtained data showed no effect on cortical bone, implant complex, cement layer, and dummy crown to changing of gap distance. In addition, the cancellous bone, especially around the mental canal, was considerably affected by the variation in that gap distance. CONCLUSION: Increasing the gap distance between the dental implant tips may reduce the stress and deformation around the mental canal. Minimum gap distance of order 2.5 mm is recommended to reduce stresses and deformations around canal to favorable limits, while more gap distance is also recommended with larger bone geometries.

Histological and Histomorphometric Evaluation of New Bone Formation after Maxillary Sinus Augmentation with Two Different Osteoconductive Materials: A Randomized, Parallel, Double-Blind Clinical Trial

This study aimed to investigate the histological features of deproteinized equine bone mineral (DEBM) and anorganic bovine bone (ABB) after human sinus augmentation with the lateral approach. Twenty-three sinus augmentations were performed in 16 patients (male: 10/female: 6) using DEBM or ABB in a randomized fashion. Healing took place over the next 6 months. Bone core biopsies (N = 23) were obtained for each subject prior to placing the dental implants. The biopsies were processed for both histological descriptions and histomorphometric analysis. Statistical analyses were applied as appropriate, defining statistical significance as p < 0.05. Core bone biopsies revealed no differences in terms of newly formed bone between groups, or differences in terms of tissue inflammation. Both DEBM and ABB appear to be suitable biomaterials for bone augmentation in sinus lift surgery in the short term. However, dedicated studies are required to confirm these results and their stability in the long term.