| ObjectiveMany oral surgeries,such as implant surgery,extraction of impacted teeth,crown lengthening,guided tissue regeneration,and jaw cyst resection,all face the problem of bone tissue removal or postoperative bone tissue growth.How to cut bone tissue with minimal trauma and efficiently promote bone tissue repair has always been a hot issue that scholars have paid attention to.Er: YAG laser produces less heat when cutting bone tissue,and the thermal damage area to hard tissue is narrow,so it is a good instrument for cutting bone tissue.Low level laser therapy(LLLT)is a non-invasive treatment method with osteoinductive ability,which can effectively promote the growth and repair of bone tissue under appropriate parameters and irradiation time.In this study,by establishing an animal experimental model of rat skull defect,the Er:YAG laser and the traditional stainless steel drill were used to compare the bone repair of the rat skull after cutting the skull,and at the same time observe the dual laser(Er:YAG laser combined with Nd:YAG laser)on the osteogenesis and angiogenesis of rat skull defects,and provide an experimental basis for the clinical use of laser-assisted alveolar surgery and the promotion of bone regeneration.MethodsTwenty 6-week-old male SD rats with an average body weight of 200 g were selected.Ten rats(20 bone defects)were divided into one group,and the 20 bone defects were randomly divided into five subgroups(n=4):Group A: A traditional stainless-steel trephine was installed on a dental handpiece at a speed of 1000rpm/min,and a circular full-thickness bone defect with a diameter of 4mm was prepared.Group B: A circular full-thickness bone defect with a diameter of 4 mm was prepared using Er:YAG laser(MSP,150 mj,15Hz,2.25W).Group C: A circular full-thickness bone defect with a diameter of 4 mm was prepared using Er:YAG laser(MSP,150 mj,15Hz,2.25W).A 320 μm-diameter fiber optic Nd:YAG laser(MSP,15 Hz,1.5W)was used to irradiate the entire bone defect area vertically in non-focus mode at a distance of 3cm from the bone surface.The spot area was 0.44cm2 when irradiated,and the irradiation was 60s/d for a total of 7 d.Group D: Er:YAG laser(MSP,150 mj,15Hz,2.25W)was used to prepare circular full-thickness bone defects with a diameter of 4mm.A 320 μm diameter fiber optic Nd:YAG laser(MSP,15 Hz,1.5W)was used to irradiate the entire bone defect area vertically in non-focus mode at a distance of 3cm from the bone surface.The spot area is 0.44 cm2 when irradiated,irradiated 120s/d,a total of 7d.Group E: A circular full-thickness bone defect with a diameter of 4 mm was prepared using Er:YAG laser(MSP,150 mj,15Hz,2.25W).A320-μm-diameter fiber optic Nd:YAG laser(MSP,15 Hz,1.5W)was used to irradiate the entire bone defect area vertically in non-focus mode at a distance of 3cm from the bone surface.The spot area is 0.44 cm2 when irradiated,irradiated 180s/d,a total of 7d.The osteogenic effect of dual laser on bone tissue was analyzed by gross observation,Micro-CT image analysis and histomorphological observation.Result1.General tissue observation:Immediately after operation,the margin of the skull defect in group A was smooth and continuous.The edge of the skull defect in group B was obviously rough and uneven,and the amount of bleeding was less than that in group A.In group C,the wound margin of the bone tissue was rough and uneven,and there were multiple small areas of blood clots.In group D,a complete blood clot was seen attached to the surface of the bone defect,and the color was bright red.Group E blood clot color dark red and ill-defined.Four weeks after operation,the color of soft tissue in group A was normal,and the defect of bone tissue was obvious;the color of soft tissue in group B was normal,and the defect of bone tissue was obvious;the soft tissue of group C healed well,the texture was tough,and the scope of skull defect was reduced;in group D,a small amount of blood clots could be seen in soft tissue The block was not absorbed,and the scope of the skull defect was reduced;in group E,the soft tissue completely covered the bone surface,a large number of red areas could be seen,there were many residual blood clots,and a large scale of the skull defect could be touched.At 8 weeks,only a small amount of bone defect was repaired in group A;the soft tissue in group B grew well,and a small amount of new bone formation was palpable;the soft tissue in group C healed well,and the palpable bone defect range was significantly reduced;the soft tissue color of group D was darker than that of group A,B and C,and the scope of bone defect was significantly reduced;in group E,the soft tissue was dark red,adhered to the surface of bone tissue,and obvious bone tissue depression could be touched.2.Micro-CT imaging analysis:?2.1 New bone volume(NBV): At 4 weeks,the new bone volume(NBV)of group C was significantly higher than that of groups A,B and E(p<0.001),but there was no significant difference between group D and group C(p>0.05).The NBV of group E was the lowest,and that of group A was lower than that of group B(p<0.01).At 8 weeks,the new bone volume(NBV)in group C was significantly higher than that in groups A,B and E(p<0.001),but no significant difference was found between group D and group C(p>0.05),and group A had the lowest NBV(p<0.001).2.2 Trabecular thickness(Tb.TH): At 4 and 8 weeks,the trabecular thickness(Tb.TH)of group A was lower than that of the other groups(p<0.05),and the Tb.TH values of groups C and D were the closest and higher than those of the other groups(p<0.05),and there was no statistical significance between the two groups(p>0.05).2.3 Number of bone trabeculae(Tb.N): As time went by,the number of bone trabeculae(Tb.N)increased in all groups.At 4 and 8 weeks,Group C and group D had the most Tb.N,and the difference between the two groups was not statistically significant(p>0.05);group A had the least Tb.N compared with other groups,and the difference was significant with group C and group D(p<0.001),and the difference was significant with group B(p<0.01),but the difference was not statistically significant with group E(p>0.05).2.4 Bone Mineral density(BMD): Bone mineral density(BMD)is an important index to evaluate the quality of mature bone.At 4 and 8 weeks,the BMD of group E was the lowest(p<0.001),group D was the highest(p<0.001),group C was second only to group D,and there was no significant difference between the two groups(p>0.05),and group A was lower than group B(p<0.001)3.Histomorphological observation:3.1 H&E staining observation: At 4w,the inflammatory tissue in groups B,C,and D was significantly lower than that of the other groups.At 8w,no obvious inflammatory cell infiltration was seen in the bone tissue of each group.There were more new blood vessels in groups C and D than in other groups,and the amount of new blood vessels in group B was higher than that in group A.The thickness of trabecular bone in group C and group D was the thickest,better than that of other groups,and group B was better than that of group A and group E.3.2 Masson staining analysis: At 4w,only a small amount of bluestained new bone was seen in groups A,B,and E;there were more bluestained new bone at the defect edge in groups C and D;at 8w,the new bone in groups C and D The bone mass increases.Group A was partially covered by fibrous connective tissue;group B only saw a small amount of fibrous tissue,and the bone formation speed and new bone mass were better than those in group A.Conclusion1.Compared with the bone trepaning group,Er: YAG laser cutting of bone tissue had rougher bone wound edges,promoted the coagulation effect in the operative area,and accelerated the repair of bone tissue and blood vessels.2.Under appropriate laser parameter selection,the combined application of dual laser can reduce the inflammatory reaction at the wound site and promote the mineral deposition of bone tissue,and the osteogenic effect is better than that of Er: YAG laser group with the same parameter setting alone.3.Using Er: YAG laser(MSP,150 mJ,15 Hz,2.25 W,water: 6,gas: 4)to prepare rat skull defect,and combined with Nd: YAG laser(MSP,15 Hz,1.5W)to irradiate 3cm from bone surface,Nd: Different YAG laser irradiation time can produce different osteogenic effects.When the irradiation time is 60s/d and 120s/d,the effect of promoting bone repair is similar and better than 180s/d. |
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