Effects of the Implant Design on Peri‐Implant Bone Stress and Abutment Micromovement: Three‐Dimensional Finite Element Analysis of Original Computer‐Aided Design Models

Background: Occlusal overloading causes peri‐implant bone resorption. Previous studies examined stress distribution in alveolar bone around commercial implants using three‐dimensional (3D) finite element analysis. However, the commercial implants contained some different designs. The purpose of this study is to reveal the effect of the target design on peri‐implant bone stress and abutment micromovement. Methods: Six 3D implant models were created for different implant–abutment joints: 1) internal joint model (IM); 2) external joint model (EM); 3) straight abutment (SA) shape; 4) tapered abutment (TA) shapes; 5) platform switching (PS) in the IM; and 6) modified TA neck design (reverse conical neck [RN]). A static load of 100 N was applied to the basal ridge surface of the abutment at a 45‐degree oblique angle to the long axis of the implant. Both stress distribution in peri‐implant bone and abutment micromovement in the SA and TA models were analyzed. Results: Compressive stress concentrated on labial cortical bone and tensile stress on the palatal side in the EM and on the labial side in the IM. There was no difference in maximum principal stress distribution for SA and TA models. Tensile stress concentration was not apparent on labial cortical bone in the PS model (versus IM). Maximum principal stress concentrated more on peri‐implant bone in the RN than in the TA model. The TA model exhibited less abutment micromovement than the SA model. Conclusion: This study reveals the effects of the design of specific components on peri‐implant bone stress and abutment displacement after implant‐supported single restoration in the anterior maxilla.     

Toothache Caused by Trigeminal Neuralgia Secondary to Vestibular Schwannoma: A Case Report

Introduction

Vestibular schwannoma, also called acoustic neuroma, is a tumor composed of Schwann cells that most commonly involves the vestibular division of the 8th cranial nerve. A thorough medical and dental history and properly conducted diagnostic testing and radiographic evaluation are essential in differentiating odontogenic tooth pain from tooth pain of a nonodontogenic origin.

Methods

This report discusses a case of acoustic neuroma mimicking odontogenic pain. A 61-year-old man presented with pain in the lower left quadrant. Medical history revealed peripheral neuropathy and prior exposure to Agent Orange. Diagnostic testing on teeth #19, #20, and #21 ruled out an odontogenic cause for the pain. Brushing of a specific region of the face elicited pain that resembled the patient's chief concern. The patient was referred to a craniofacial pain center with the tentative diagnosis of trigeminal neuralgia. Treatment for trigeminal neuralgia was not successful, prompting referral to the neurosurgery department where magnetic resonance imaging was performed.

Results

Magnetic resonance imaging revealed a moderate-size, lobular, left cerebellopontine angle mass lesion consistent with acoustic neuroma with compression of the left trigeminal nerve secondary to the lesion.

Conclusions

Acoustic neuroma can cause tooth pain secondary to compression of the trigeminal nerve.     

Micromorphology of the Dental Pulp Is Highly Preserved in Cancer Patients Who Underwent Head and Neck Radiotherapy

Introduction

Teeth are often included in the radiation field during head and neck radiotherapy, and recent clinical evidence suggests that dental pulp is negatively affected by the direct effects of radiation, leading to impaired sensitivity of the dental pulp. Therefore, this study aimed to investigate the direct effects of radiation on the microvasculature, innervation, and extracellular matrix of the dental pulp of patients who have undergone head and neck radiotherapy.

Methods

Twenty-three samples of dental pulp from patients who finished head and neck radiotherapy were analyzed. Samples were histologically processed and stained with hematoxylin-eosin for morphologic evaluation of the microvasculature, innervation, and extracellular matrix. Subsequently, immunohistochemical analysis of proteins related to vascularization (CD34 and smooth muscle actin), innervation (S-100, NCAM/CD56, and neurofilament), and extracellular matrix (vimentin) of the dental pulp was performed.

Results

The morphologic study identified preservation of the microvasculature, nerve bundles, and components of the extracellular matrix in all studied samples. The immunohistochemical analysis confirmed the morphologic findings and showed a normal pattern of expression for the studied proteins in all samples.

Conclusions

Direct effects of radiotherapy are not able to generate morphologic changes in the microvasculature, innervation, and extracellular matrix components of the dental pulp in head and neck cancer patients.     

Improvement in the repair of defects in maxillofacial soft tissue in irradiated minipigs by a mixture of adipose-derived stem cells and platelet-rich fibrin

To find out if adipose-derived stem cells (ASC) and platelet-rich fibrin (PRF), alone or combined, had any effect on the repair of maxillofacial soft tissue defects in irradiated minipigs, ASC were isolated, characterised, and expanded. Twenty female minipigs, the right parotid glands of which had been irradiated, were randomly divided into 4 groups of 5 each: those in the first group were injected with both ASC and PRF (combined group), the second group was injected with ASC alone (ASC group), the third group with PRF alone (PRF group), and the fourth group with phosphate buffer saline (PBS) (control group). Six months after the last injection, the size and depth of each defect were assessed, and subcutaneous tissues were harvested, stained with haematoxylin and eosin, and examined immunohistologically and for apoptosis. Expanded cells were successfully isolated and identified. Six months after injection the defects in the 3 treated groups were significantly smaller (p<0.001) and shallower (p<0.001) than those in the control group. Those in the combined group were the smallest and shallowest. Haematoxylin and eosin showed that the 3 treated groups contained more subcutaneous adipose tissue than the control group, and also had significantly greater vascular density (p<0.001) and fewer apoptotic cells (p<0.001). Both ASC and PRF facilitate the repair of defects in maxillofacial soft tissue in irradiated minipigs, and their combined use is more effective than their use as single agents.     

Significance of occlusal force for dietary fibre and vitamin intakes in independently living 70-year-old Japanese: from SONIC Study

Objectives

The number of teeth has frequently been used as an indicator of oral health in investigations of food intake; however, this measure does not represent the efficacy of the masticatory performance. Masticatory performance may be more important for food selection and avoidance than number of remaining teeth. The aim of this study was to investigate the association of occlusal force with habitual dietary intakes in independently living older Japanese.

Methods

The study population was 757 community-dwelling people aged 69–71 years old. Bilateral maximal occlusal force in the intercuspal position was measured with pressure-sensitive sheets. Removable denture wearers kept their dentures in place during the measurements. Dietary habits during the preceding month were assessed using a brief-type self-administered diet history questionnaire that measures consumption frequencies of selected food commonly consumed and calculates energy-adjusted dietary intakes. Linear trends of food and nutrient intakes with decreasing occlusal force were tested after adjusting for gender and socioeconomic factors.

Results

After adjusting for socioeconomic status and the number of remaining teeth, decline of occlusal force was significantly associated with lower intakes of vegetables, vitamins A, C, B₆, folate, and dietary fibre (P for trend < 0.05). In contrast, number of teeth was significantly associated only with calcium and zinc, controlling for occlusal force.

Conclusions

It is concluded that occlusal force was significantly associated with intakes of vitamins and dietary fibre rather than number of remaining teeth in independently living older Japanese.     

Evaluation of Efficacy of Microwave Irradiation in Disinfecting Dental Gypsum Casts: An Ex Vivo Study

The aim of this study is to assess the efficacy of microwave irradiation in disinfecting gypsum casts and also to compare its efficacy with validated method of chemical disinfection. The present study is an ex vivo study conducted on a sample of five irreversible hydrocolloid impressions in vitro and on ten patients gypsum casts in vivo following standard impression techniques to check the efficacy of microwave oven irradiation and compare its efficacy with standard chemical method of disinfection. Results were analysed using Mann–Whitney test and Wilcoxon signed rank test. Untreated gypsum casts showed cfu/ml counts with a median log value of 6, while microwave-irradiated ones had median cfu/ml counts of 0. Casts poured from chemically disinfected impressions demonstrated cfu/ml counts with a median log value of 5. Microwave irradiation was found to be effective in disinfecting gypsum casts when compared to chemical disinfectant in disinfecting dental impressions.