Drilling- and withdrawing-related thermal effects of implant site preparation for ceramic and stainless steel twist drills in standardized bovine bone.

INTRODUCTION: Excessive surgical trauma is believed to be among the most important causes for early implant losses. As thermal injury to the bone is not only dependent on the amount of generated heat but also on the tissue exposure time, and the greatest temperature increase was found within the withdrawing period, the entire osteotomy procedure with the parameters contributing to thermal damage is of particular clinical relevance. The aim of this study was to investigate the thermal performance of metal-based and ceramic implant drills regarding the temperature exposure time during the whole osteotomy process. MATERIALS AND METHODS: This investigation consisted of 240 individual preparations in total, comprising two different drilling depths (10 and 16 mm), two irrigation methods (external and without irrigation), two implant drill materials (stainless steel and zirconia), and three consecutive drill diameters per material (2.0/2.2, 2.8, and 3.5 mm) with 10 identical repetitions. Real-time multichannel temperature measurement was conducted during automated drilling procedures in standardized bovine bone specimens. RESULTS: The maximum temperature changes were highly associated with the time period of passive drill withdrawing (p ≤ 0.05), irrespective of drill material, drilling depth, or drill diameter. Statistically significant differences in temperature generation between stainless steel and ceramic drills were observed in irrigated testing sites at both drilling depths with smaller drill diameters (2.0/2.2 and 2.8 mm, p ≤ 0.05). CONCLUSION: Results of this in vitro study could demonstrate a strong association between the highest temperature increase and the passive withdrawing time period in both investigated drill materials. Considering these findings and the resulting thermal bone damage due to the whole surgical procedure, high overall temperatures in combination with a prolonged heat exposure time may impact the future osseointegration process.

Thermal effects of various drill materials during implant site preparation-Ceramic vs. stainless steel drills: A comparative in vitro study in a standardised bovine bone model.

OBJECTIVES: The aim of this study was to evaluate thermal effects of ceramic and metal implant drills during implant site preparation using a standardised bovine model. MATERIAL AND METHODS: A total of 320 automated intermittent osteotomies of 10- and 16-mm drilling depths were performed using zirconium dioxide-based and stainless steel drills. Various drill diameters (2.0/ 2.2, 2.8, 3.5, 4.2 mm ∅) and different cooling methods (without/ with external saline irrigation) were investigated at room temperature (21 ± 1°C). Temperature changes were recorded in real time using two custom-built multichannel thermoprobes in 1- and 2-mm distance to the osteotomy site. For comparisons, a linear mixed model was estimated. RESULTS: Comparing thermal effects, significantly lower temperatures could be detected with steel-based drills in various drill diameters, regardless of drilling depth or irrigation method. Recorded temperatures for metal drills of all diameters and drilling depths using external irrigation were below the defined critical temperature threshold of 47°C, whereas ceramic drills of smaller diameters reached or exceeded the harmful temperature threshold at 16-mm drilling depths, regardless of whether irrigation was applied or not. The results of this study suggest that the highest temperature changes were not found at the deepest point of the osteotomy site but were observed at subcortical and deeper layers of bone, depending on drill material, drill diameter, drilling depth and irrigation method. CONCLUSIONS: This standardised investigation revealed drill material and geometry to have a substantial impact on heat generation, as well as external irrigation, drilling depth and drill diameter.

Guided Osteotomy and Guided Autotransplantation for Treatment of Severely Impacted Teeth: A Proof-of-Concept Report.

INTRODUCTION: The aim was to present a novel surgical technique using virtually preplanned 3-dimensional (3D)-printed templates for guided osteotomies. These were to ensure atraumatic uncovering of a severely impacted donor tooth including guided drilling of the recipient alveolus followed by a secure autotransplantation procedure. METHODS: This report presents an autotransplantation procedure of a 14-year-old patient with a severely impacted second premolar and extensive contact to the roots of the adjacent teeth and the inferior alveolar nerve. Autotransplantation of the impacted premolar was virtually performed using modified methods from guided implant surgery in order to prefabricate 3D-printed templates with the aid of a fully digital workflow. RESULTS: Satisfactory treatment could be achieved using surgical templates for guided osteotomies of the surgical access, guided drilling of the recipient site, and occlusal reference template ensuring autotransplantation in the appropriate 3D location of the graft. An atraumatic approach could be ensured with an extraoral time of 46 seconds by 1 fitting attempt; no injuries or altered sensation of the inferior alveolar nerve were present. A vital natural tooth could be observed. CONCLUSIONS: This innovative technique uses for the first time a fully implemented digital workflow for guided osteotomies, guided drilling, and guided autotransplantation of a severely impacted tooth. 3D-printed templates could ensure a guided atraumatic approach and facilitate highly complex treatments by virtually implementing recommended guidelines in future autotransplantations.

Guided Lateral Sinus Lift Procedure Using 3-Dimensionally Printed Templates for a Safe Surgical Approach: A Proof-of-Concept Case Report.

The purpose of this article was to present a guided lateral window sinus lift procedure with the aid of a fully digital workflow using surgical templates for window osteotomy preparation and implant placement. A 22-year-old patient with insufficient residual bone height in the posterior maxilla was treated with a maxillary sinus augmentation procedure with a lateral window technique and simultaneous implant installation using 3-dimensionally printed surgical guides. The surgical guides, used for the preparation of both the lateral window and the implant site according to the optimal prosthodontic and anatomic position, were based on a fully digital workflow and virtual pre-planning with modified implant-planning software. Successful functional and esthetic rehabilitation of the patient was accomplished using standard surgical techniques and instruments but an innovative method for the production and application of surgical templates ensured a precise and safe approach for the lateral window osteotomy preparation. This guided lateral window sinus lift technique may reduce the incidence of surgical complications and failures and enhance patient-related outcomes.

Association between maxillary lateral incisors' root volume and palatally displaced canines: An instrumental variables approach to the guidance theory.

OBJECTIVES:: To evaluate association and causation between maxillary lateral incisors' (MxI2) apical root volume (ARV) and palatally displaced canines (PDC). MATERIALS AND METHODS:: In a retrospective cross-sectional study, computed tomography scans of 179 patients with unilateral PDC were analyzed. MxI2 root length and volume on the impaction and eruption side were measured. A mixed logit model was used to infer the association between ARV and PDC and an instrumental variables approach to interpret causality. RESULTS:: MxI2 root length on the impaction side was shorter in 42%, equal in 33% and longer in 25% of the patients. ARV amounted for 13.5% of total root volume on the impaction and 14.9% on the eruption side. Reduced ARV was significantly associated with the impaction side ( P < .001). The causal effect of ARV on PDC in the instrumental variable approach amounted to less than half of the association in a standard noncausal approach. CONCLUSIONS:: An association between PDC and reduced MxI2 root length and volume was confirmed. However, the lack of causality did not allow the researchers to draw a conclusion as to whether a reduced ARV is causing PDC or resulting from it; this should be considered in etiologic theories.

Impacted and transmigrated mandibular canines: an analysis of 3D radiographic imaging data.

OBJECTIVES: Impacted and transmigrated mandibular canines differ greatly in incidence, etiopathology, associated anomalies, and treatment prospects, when compared to their maxillary counterparts. The aim of this study was to provide a detailed analysis of 3D radiographic imaging data of impacted mandibular canines. MATERIALS AND METHODS: In a retrospective cross-sectional study, CT/CBCT data of 88 patients with a total of 94 impacted mandibular canines were analysed. Evaluated parameters included location, morphology, neighbouring structures, associated anomalies, the influence of those factors on mandibular canine transmigration, as well as applied treatment. RESULTS: Transmigration was found to occur in 40.4% of impacted mandibular canines. Transmigrated canines were located significantly more basally and horizontally angulated. Further, transmigration was significantly associated with a lack of contact to adjacent teeth and the canine's apex not contacting the mandibular cortical bone. The overall incidence of root resorptions of adjacent teeth related to impacted mandibular canines was 7.3% and was more likely, if the canine was lingually impacted. While about half of the non-transmigrated impacted canines were orthodontically aligned, half of the transmigrated canines were surgically removed. Monitoring was the second most applied treatment strategy for both groups, and no canines were autotransplantated. CONCLUSIONS: Root resorption of adjacent teeth and transmigration are commonly occurring phenomena related to impacted mandibular canines. CLINICAL RELEVANCE: Treatment often entails the surgical removal of the canine-especially in cases of transmigration. The findings emphasise the importance of early diagnosis and CT/CBCT imaging for further diagnostics and future research of impacted mandibular canines.

Survival rate of autotransplanted teeth after 5 years - A retrospective cohort study.

BACKGROUND: Autotransplantation of teeth (TX) is a predictable treatment option, although this type of therapy is often overlooked compared to other types of restorations. PURPOSE: As current literature contains few long-term studies concerning the outcome of autotransplanted immature molars, the aim was to evaluate results after a follow-up period of 5 years. MATERIAL AND METHODS: This retrospective study enrolled all patients treated with immature autotransplanted molars after a follow-up period of 5 years. In order to ensure comparable results, survival rate was investigated as well as clinical and radiological parameters. Contralateral teeth (TC) were used as controls for further assessments and for ensuring comparable future results. RESULTS: 52 patients with 66 TX were examined. Mean age at the time of surgery was 19.64 years. Tooth survival rate after 5 years was 89.39%. The results for parameters such as PPD, BOP, mobility, dental caries, periapical pathologies and endodontic treatments showed no differences. In contrast, dental restorations (p < 0.001), occlusal contacts (p = 0.003) and sensitivity (p < 0.001) differed significantly between TX and TC. CONCLUSIONS: The current findings clearly confirm that TX is an effective alternative treatment option to fixed prosthodontic restorations and dental implants, and provides for results equivalent to those with the patients' natural teeth.

Guided Modern Endodontic Surgery: A Novel Approach for Guided Osteotomy and Root Resection.

INTRODUCTION: Continuous improvements in techniques, instruments, and materials have established modern endodontic microsurgery as a state-of-the-art treatment method. The purpose of this approach was to introduce a new surgical endodontic technique by using a three-dimensional printed template for guided osteotomy and root resection. METHODS: A 38-year-old patient was diagnosed with periapical lesions of teeth #3 and #4 and extruded gutta-percha material. Three-dimensional radiographic and optical scan files were imported into surgical planning software designed for guided implant surgery. Within the adapted software program the periapical lesions and the extruded gutta-percha were visualized and marked. With the aid of virtually positioned surgical pins and piezoelectric instruments, the osteotomy size, the apical resection level, and the bevel angle were defined before treatment. Three-dimensional surgical templates for each tooth were designed within the software program for a guided treatment approach. RESULTS: This approach comprised the treatment of periapical lesions of teeth #3 and #4 with root-end fillings and the detection and complete removal of the extruded gutta-percha material without perforation of sinus membrane. There were no postoperative complications, and clinical and radiologic assessments verified complete healing of the teeth. CONCLUSIONS: The guided microsurgical endodontic treatment presented appears to be a viable technique that allows for predefined osteotomies and root resections.

Guided Autotransplantation of Teeth: A Novel Method Using Virtually Planned 3-dimensional Templates.

INTRODUCTION: The aim of this study was to introduce an innovative method for autotransplantation of teeth using 3-dimensional (3D) surgical templates for guided osteotomy preparation and donor tooth placement. METHODS: This report describes autotransplantation of immature premolars as treatment of an 11-year-old boy having suffered severe trauma with avulsion of permanent maxillary incisors. This approach uses modified methods from guided implant surgery by superimposition of Digital Imaging and Communications in Medicine files and 3D data sets of the jaws in order to predesign 3D printed templates with the aid of a fully digital workflow. RESULTS: The intervention in this complex case could successfully be accomplished by performing preplanned virtual transplantations with guided osteotomies to prevent bone loss and ensure accurate donor teeth placement in new recipient sites. Functional and esthetic restoration could be achieved by modifying methods used in guided implant surgery and prosthodontic rehabilitation. The 1-year follow-up showed vital natural teeth with physiological clinical and radiologic parameters. CONCLUSIONS: This innovative approach uses the latest diagnostic methods and techniques of guided implant surgery, enabling the planning and production of 3D printed surgical templates. These accurate virtually predesigned surgical templates could facilitate autotransplantation in the future by full implementation of recommended guidelines, ensuring an atraumatic surgical protocol.

Influence of repeat surgery on treatment time in the interdisciplinary management of impacted maxillary canines: A retrospective cohort study.

PURPOSE: To evaluate the effect of repeat surgery on treatment time in the interdisciplinary management of impacted maxillary canines. MATERIAL AND METHODS: This retrospective cohort study enrolled patients referred for computed tomographic examination for impacted maxillary canines within a 5-year observational period. The occurrence of repeat surgery was analysed with regard to treatment time, canine location, and surgical exposure technique. RESULTS: A total of 55 patients with 79 impacted maxillary canines were analysed. Of those, 83.6% did not present with complications that would have prompted repeat surgery during their treatment. For patients requiring repeat surgery, time until clinically visible movement of the canine was significantly longer (p < 0.001), whereas time between initial movement and eruption into the oral cavity was significantly shorter (p < 0.001). Overall treatment time did not differ significantly (p = 0.13). An open surgical exposure technique was associated with a significantly lower occurrence of repeat surgeries (p = 0.03). Bilateral impaction of canines significantly prolonged overall treatment time (p = 0.01). CONCLUSIONS: In the event of initial treatment failure during the interdisciplinary management of impacted maxillary canines, repeat surgery should be considered, which has limited effect on overall treatment time. An open surgical exposure technique is preferable.

Drilling- and withdrawing-related thermal changes during implant site osteotomies.

BACKGROUND: Intrabony temperature increase is not only dependent on shearing energy and mechanical friction between bone and surgical drill but is also related to heat capacity and thermal conductivity of the surrounding bone and the applied surgical instrument. Thus time of occurrence of the highest temperature rise can be expected after the shearing process of the osteotomy, potentially affecting the process of osseointegration. PURPOSE: The aim of this study was to evaluate temperature changes during the shearing and withdrawing processes during osteotomies. MATERIALS AND METHODS: An overall 160 automated intermittent osteotomies (10/16 mm drilling depth) with 2 mm diameter twist drills and 3.5 mm diameter conical drills and different irrigation methods (without/external/internal/combined) were performed on standardized bone specimens. The drilling cycles were operated by a computer-controlled surgical system, while a linear motion potentiometer and multichannel temperature sensors in various intrabony levels ensured the real-time documentation of temperature changes during the shearing and withdrawing processes. RESULTS: The highest temperature changes were invariably recorded during the process of withdrawal. Significantly lower temperature changes (p < .02) could be recorded at maximum drilling depths during the shearing process regardless of drilling depth, diameter or irrigation method. During coolant supply, 2 mm diameter twist drills showed higher temperatures (10 mm, p < .01/16 mm, p < .03) compared with 3.5 mm diameter conical implant drills. Internal (10 mm, p < .01) or combined irrigation (16 mm, p < .01) was associated with significantly lower temperatures compared with external irrigation by the use of conical implant drills. CONCLUSIONS: Considering that heat generation during osteotomies is a multifactorial scenario, this study could demonstrate that the highest temperature rise during implant osteotomies occurs during the withdrawing process and that the time of occurrence is influenced by predominant factors such as osteotomy depth and mode of irrigation.

A novel standardized bone model for thermal evaluation of bone osteotomies with various irrigation methods.

OBJECTIVES: Based on a novel standardized bovine specimen, the aim of this study was to investigate thermal effects of different irrigation methods during intermittent and graduated drilling. MATERIAL AND METHODS: Temperature changes during implant osteotomies (n = 320) of 10 and 16 mm drilling depths with various irrigation methods were investigated on manufactured uniform bone samples providing homogenous cortical and cancellous areas and analogous thermal conductivity comparable to human bone. Automated sequences were performed with surgical twist drills of 2 mm ∅ and conical drills of 3.5, 4.3 and 5 mm ∅. Real-time recording of temperature increase was done using two custom-built multichannel thermoprobes with 14 temperature sensors at a predefined distance of 1 and 2 mm to the final osteotomy. The effects of drilling depth, drilling diameter and irrigation methods on temperature changes were investigated by a linear mixed model. RESULTS: Using this uniform bone specimen, the greatest temperature rise was observed without any coolant supply with 29.87°C, followed by external with 28.47°C and then internal with 25.86°C and combined irrigation with 25.68°C. Significant differences (P ≤ 0.0156) between drill depths of 10 vs. 16 mm could be observed with all irrigation methods evaluated. With each of the irrigation methods, significantly higher temperature changes (P < 0.0001) during osteotomies could be observed between twist drills of 2 mm ∅ and conical drills of 3.5, 4.3 and 5 mm ∅. During 10 and 16 mm drilling osteotomies, external irrigation showed significantly higher temperatures (P < 0.05) for all conical drills compared with internal or combined irrigation, respectively. Significantly lower temperatures (P < 0.05) could be detected with internal or combined irrigation for the use of conical drills with various diameters and drilling depths. CONCLUSIONS: This fully standardized bone model provides optimized comparability for the evaluation of bone osteotomies and resulting temperature changes. As regards the efficiency of the various irrigation methods, it could be demonstrated that internal and combined irrigation appears to be more beneficial than external irrigation.